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Tantalum pentoxide, a non conventional gate insulator for MOS devices Eguizabal-Rivas, Antonio L. 1984

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TANTALUM PENTOXIDE, GATE  INSULATOR  A NON  CONVENTIONAL  FOR MOS  DEVICES  by  ANTONIO L. Ingeniero  EGUIZABAL-RIVAS  Civil-Electrico,  Universidad  (Santiago,  A THESIS SUBMITTED  Chile,  Tecnica  d e l Estado  1970)  IN PARTIAL FULFILMENT OF  THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE  THE FACULTY OF GRADUATE STUDIES Department  We  accept to  of E l e c t r i c a l  this  Thesis  the r e q u i r e d  Engineering  as c o n f o r m i n g standard  THE UNIVERSITY OF BRITISH COLUMBIA November 1984 © Antonio  L.  E g u i z a b a l R i v a s , 1984  In  presenting  requirements  this thesis f o r an  of  British  it  freely available  agree for  that  understood for  I agree  Library  shall  for reference  and  study.  I  for extensive  that  h i s or  her  copying or  f i n a n c i a l gain  be  shall  copying of  g r a n t e d by  not  be  Electrical  The U n i v e r s i t y o f B r i t i s h 2075 Wesbrook P l a c e V a n c o u v e r , Canada V6T 1W5 Date  DE-6  (2/79)  November 6 t h ,  19 84  of  Engineering Columbia  make  further this  thesis  head o f  this  It  my  is  thesis  a l l o w e d w i t h o u t my  permission.  Department of  the  representatives. publication  the  University  the  p u r p o s e s may by  the  that  permission  department or  f u l f i l m e n t of  advanced degree at  Columbia,  scholarly  in partial  written  i i  ABSTRACT Non  c o n v e n t i o n a l gate  generally classic  dielectrics  Si0  presented existing  here  that  extensively reflects 2  grown  over  suitable  gate  for  methods.  High  advantage  classic  were  temperature. developed  A method  using  successfully transistors. f o r m o f MOS  structure of  was  this  class  account  the  successful  of  The  oxide  using  both  (^26-28)  dioxide (100  being  to  gate 1000  insulators,  times g r e a t e r )  samples  at  room  technique,  was  t o b o t h MOS  capacitors  devices  which Vgs  as  as g a t e  devices  a  Si,  was  in fabricating  low  l e a k a g e c u r r e n t s and  MOS  and  it  field  effect  fabricated  i n the  good  dielectric  Id  Ta 0 2  vs.  Gate 5  leakage oxidation  that  over  takes  current. of  Capacitors that  Vds  leakage  A small signal  presented,  gate  and  parameter.  insulator.  is  zero  were  exhibited  technique, i n t e r f a c i a l  used  gate  dielectrics  obtained  Capacitor  as a d o u b l e  non  a  liftoff  with  used  an  was  Transistors,  c u r r e n t s were low,  of  pentoxide, o f f e r s considerable  silicon  Furthermore,  characteristics,  work  f o r p r o c e s s i n g the tantalum metal  the  applied  the  from p u r e s p u t t e r e d  permittivity  MOS  as  Succesful  were  higher leakage c u r r e n t s in  The  transistors.  anodically  tantalum  encountered  and  are  from  development  application  wafers.  relative of  however  technology.  insulators  characteristic over  in this  capacitors  silicon  devices  considerably  its  b o t h t h e r m a l l y and  tantalum metal  MOS  depart  and  5  f o r b o t h MOS  for  t h e r e s e a r c h and  compound, T a 0 ,  insulator is  used  2  insulators  Si0  2  model into  Another  Ta 0 2  5  yielded  high s p e c i f i c capacitances.  over also  The the  purpose  of t h i s  University  insulator Silicon  T h e s i s i s to report  of  British  Columbia  MOSFET t e c h n o l o g y b a s e d  Dioxide  (Ta 0 /Si0 ) 2  5  2  on  the of  development the  the Tantalum  heteromorphic  double  at gate  Pentoxide-  structure.  TABLE  OF  CONTENTS  ABSTRACT TABLE  i i  OF  CONTENTS  iv  LIST  OF  TABLES  v i i  LIST  OF  FIGURES  x  ACKOWLEDGEMENTS CHAPTER  x i i  1  INTRODUCTION CHAPTER AN  1  2  OVERVIEW  CHAPTER  OF  NON C O N V E N T I O N A L  INSULATORS  6  3  THE  THEORY  OF  THE  Ta 0 -Si0 2  5  DOUBLE  2  DIELECTRIC  STRUCTURE  29  3.1  STEADY  3.2  TRANSIENT  ANALYSIS  3.3  EFFECT  THE DOUBLE  ON 3.4  OF  ANALYSIS  THE MOSFET EFFECT  THE 3.5  STATE  OF  MOSFET  ENERGY  ,  36 38  DIELECTRIC  GATE  INSULATOR  PERFORMANCE  A  HIGH  41  PERMITTIVITY  GATE  INSULATOR  ON  PERFORMANCE  BANDS  OF  THE  46  TANTALUM PENTOXIDE  INSULATOR 50  3.6  DOUBLE  CHAPTER  MOSFET  STRUCTURE  52  4  FABRICATION 4.1  DIELECTRIC  MOS 4.1.1  AND  PROCESSING  CAPACITORS  WITH  THICKNESS  OF  SCRIBING  CAPACITOR  THERMAL T a 0 2  AND  MEASUREMENTS 4.1.2  MOS  5  SHEET  AS  DEVICES  INSULATOR  54 .54  RESISTIVITY 55  AND M A R K I N G  55  V  4.1.3  PEROXIDE  ACID  4.1.4  RF  4.1.5  THERMAL  4.1.6  ALUMINIUM  4.1.7  PHOTOLITHOGRAPHY  59  4.1.8  CONTACT  60  57  SPUTTERING  57  OXIDATION  57  DEPOSITION  59  METALLIZATION  4.2  MOS  4.3  PROCESS  4.4  THE  LIFTOFF  4.5  MOS  CAPACITORS  4.5.1  CLEANING  CAPACITORS  WITH  DOUBLE  AND F A B R I C A T I O N TECHNIQUE WITH  ANODIZATION  DIELECTRIC  60  COMMENTS  ON  61  TANTALUM FILMS  ANODIC IN  STRUCTURE  Ta 0 2  CITRIC  5  AS  64  INSULATOR  ACID  ..65  ELECTROLYTE  SOLUTION 4.5.2 4.6  69  ANODIZATION  INTERFACIAL  CHAPTER  IN  H PO„ 3  OXIDATION  MOS  ELECTROLYTE  SOLUTION  .72  CAPACITORS  73  5  RESULTS  AND M E A S U R E M E N T S  ON MOS  CAPACITORS  76  5.1  ELLIPSOMETRY  7 6  5.2  C-V  MEASUREMENTS  77  5.3  I-V  MEASUREMENTS  81  5.4  HILLOCK  5.5  DISCUSSION  FORMATION OF  INVESTIGATION  85  RESULTS  93  5.5.1  ELLIPSOMETRY  93  5.5.2  C-V  CURVES  99  5.5.3  I-V  CURVES  5.6 CHAPTER  INTERFACIAL  OXIDATION  114 MOS  CAPACITORS  121  6  FABRICATION TRANSISTORS  AND  PROCESSING  OF  MTAOS  FIELD  EFFECT 123  vi  6.1  SHEET  RESISTIVITY  DETERMINATION  125  6.2  SILICON  6.3  THICK  OXIDE  6.4  BORON  PREDEPOSITION  128  6.5  BORON  DRIVE-IN  128  6.6  GATE  PHOTOLITHOGRAPHY  6.7  THIN  OXIDE  6.8  PREPARATION  6.9  PEROXIDE-ACID  THERMAL OXIDATION  126  PHOTOLITHOGRAPHY  PROCESS OF  127  129  SIMULATION  DEVICE  WAFERS  CLEANING  OF  USING FOR  ALL  SUPREM  ANODIZATION  WAFERS  129 ...132 133  6.10  ALUMINIUM EVAPORATION  6.11  PHOTOLITHOGRAPHY  6.12  MICROSCOPE  6.13  DETERMINATION  6.14  PRELIMINARY  RF  6.15  PRELIMINARY  THERMAL OXIDATION  137  6.16  PRELIMINARY  ANODIC  138  6.17  RF  6.18  THERMAL OXIDATION  6.19  ANODIC  6.20  PRELIMINARY  6.21  LIFTOFF  6.22  MICROSCOPE  6.23  PEROXIDE-ACID  6.24  SOURCE  6.25  MICROSCOPE  6.26  ALUMINIUM DEPOSITION  6.27  DRAIN  6.28  ETCHING  FOR  133 LIFTOFF  EXAMINATION  SPUTTERING  OF  THE  AFTER  SWELLING  SPUTTERING  OF  OXIDATION  OF  133 LIFTOFF FACTOR  134 S  TANTALUM  OXIDATION  TANTALUM OF OF  139  TANTALUM  140  EXAMINATION  PATTERNING  AND ON  AFTER  LIFTOFF  CLEANING THIN GATE  BACK  FOR  CONTACT OF  WAFER  144 145  OXIDE  REMOVAL  PHOTOGRAPHY  SOURCE  143 143  EXAMINATION  AND D R A I N  136  139  TANTALUM  MICROSCOPE  134  145 145  CONTACTS  146  PHOTOLITHOGRAPHY  147  AND A u  147  DEPOSITION  6.29  FINAL  CHAPTER  MICROSCOPE  EXAMINATION  148  7  RESULTS  AND  MEASUREMENTS  ON  MTAOS  FIELD  EFFECT  TRANSISTORS  154  7.1  TESTING  AND MEASUREMENT PROCEDURE  7.2  DISCUSSION  OF  154  RESULTS  163  7.2.1  C-V  CURVES  ON D O U B L E  7.2.2  I-V  CURVES  ON T H E  DIELECTRIC  DOUBLE  INSULATOR  DIELECTRIC  GATE  INSULATOR  169  7.2.3  GATE  7.2.4  THE OUTPUT  7.2.5  THE TRANSFER  7.2.6  PULSE  RESPONSE  7.2.7  SPICE  SIMULATION  7.3  DOUBLE  CHAPTER  THRESHOLD VOLTAGE  169  CURVES  DIELECTRIC  170  CURVES  173  OF T H E DD M O S F E T s OF MOSFET  MOSFET  CHARACTERISTICS  EQUIVALENT  CIRCUIT  174 175 181  8  SUMMARY  AND CONCLUSIONS  183  REFERENCES APPENDIX C-V  .163  187  I  _  AND I - V  APPENDIX  SOURCE  SPICE  &ee—Add&adum. •ti'ru^e-F—s-epa-F-a-t-e—e-O'V-e'i?  PROGRAMS  195  III  LABORATORY APPENDIX  O F MOS C A P A C I T O R S  II  COMPUTER APPENDIX  CURVES  PROCESSING  DETAILS  212  IV AND S U P R E M S I M U L A T I O N  RESULTS  222  „  viii  L I S T OF TABLES 3.1 D o u b l e D i e l e c t r i c  MOSFET P a r a m e t e r s  45  3.2 S i n g l e D i e l e c t r i c  MOSFET P a r a m e t e r s  47  3.3 MOS C a p a c i t o r  Insulator Figure  Of M e r i t  ..49  4.1 S i n g l e D i e l e c t r i c  T h e r m a l MOS C a p a c i t o r s  56  4.2 T h e r m a l O x i d a t i o n  Of T a n t a l u m On S i l i c o n  58  4.3 D o u b l e D i e l e c t r i c  MOS C a p a c i t o r s  61  4.4 S i n g l e D i e l e c t r i c  A n o d i c MOS C a p a c i t o r s  73  4.5 I n t e r f a c i a l 5.1 S p u t t e r i n g  Oxidation  Of Ta On G l a s s  5.2 O x i d e T h i c k n e s s 5.3  Resume  Of T a n t a l u m On S i l i c o n  Of  Samples  Determination  Thermal  75 88  By E l l i p s o m e t r y  Oxide  MOS-SD  99  C a p a c i t o r s C-V  Curves  105  5.4 Resume  Of  Thermal  Oxide  MOS-DD  Capacitors  C-V  Curves  106  5.5 Resume Of A n o d i c O x i d e MOS-SD C a p a c i t o r s  C-V C u r v e s 107  5.6  Calculated Relative Dielectric Ta 0 2  2  5.8  1 08 Constant  Of  Anodic 1 09  5  Flatband  Voltage,  Single Dielectric 5.9 F l a t b a n d  Voltage,  Double D i e l e c t r i c 5.10  Of T h e r m a l  5  5.7 C a l c u l a t e d R e l a t i v e D i e l e c t r i c Ta 0  Constant  Flatband  Anodic  Ta 0  5.11 Resume  2  Ta 0 2  Of  5  And F i x e d  MOS C a p a c i t o r s  Capacitance  And F i x e d  C h a r g e Of : Charge  110 Of  MOS C a p a c i t o r s  Voltage, 5  Capacitance  Capacitance  111 And F i x e d  C h a r g e Of  MOS C a p a c i t o r s Schottky  I-V  112 Curves  And  Calculated  ix  Optical For  Value  Thermal  5.12 Resume Optical For 5.13  Of  Ta 0 2  Of  Of  Ta 0 2  Constant 116  5  Schottky  Value  Anodic  The R e l a t i v e D i e l e c t r i c  I-V  Curves  And  Calculated  The R e l a t i v e D i e l e c t r i c  Constant 117  5  Photoconduction  In Tantalum  Oxide  MOS  Capacitors  .120  5.14 I n t e r f a c i a l  Oxidation  MOS  C a p a c i t o r s , C-V R e s u l t s  122  5.15  Oxidation  MOS  Capacitors,  122  Interfacial  6.1 D e v i c e  Substrate  6.2 SUPREM S i m u l a t i o n 6.3 D r y T h e r m a l  Marking  And M e a s u r e d R e s i s t i v i t y  .126  Results  Oxidation  7.1 Summary Of D o u b l e  I-V R e s u l t s  Of S i 0  Dielectric  130 131  2  MOSFET C h a r a c t e r i s t i c s 1 74  X  L I S T OF FIGURES 3.1 The G e n e r a l D o u b l e 3.2 E q u i v a l e n t  Dielectric  Permittivity  3.3 E n e r g y  Band D i a g r a m  3.4 D o u b l e  Dielectric  Structure  Of A D o u b l e  31  Insulator  .....44  Of The A l - T a 0 - n S i S t r u c t u r e 2  5  MOSFET S t r u c t u r e  .50 53  4.1 A n o d i z a t i o n  Cell  And Equipment  68  4.2 A n o d i z a t i o n  Cell  V o l t a g e Under C o n s t a n t C u r r e n t ...70  4.3 A n o d i z a t i o n  Cell  C u r r e n t Under C o n s t a n t V o l t a g e ...71  5.1 C-V M e a s u r i n g  System  F o r MOS C a p a c i t o r s  79  5.2 I-V M e a s u r i n g  System  F o r MOS C a p a c i t o r s  83  5.3 Dark  Field  Photograph  Glass(sample 5.4  Dark  5.5 Dark Si0 5.6  2  Si0  2  5.7 Dark Si0  2  5.8 Dark Si0  2  Field  (sample  (sample  Photograph  On S i l i c o n  5.9 E l l i p s o m e t r i c  (560X),  500  On  A Ta MES On  (140X),  200 A Ta RFS On  (sample. 4T6)  Photograph  On S i l i c o n Field  RFS  90  Photograph  On S i l i c o n Field  Ta  BNR500)  Photograph  On S i l i c o n  Dark  A  90  Photograph  (sample  Field  500  G500)  Field  Silicon  (560X),  (sample  91  (140X),  50 A Ta RFS On T h i n  2T6) (140X),  Thin  91 500 A Ta RFS On  Thin  3T7) (140X),  92 1000 A Ta RFS On T h i n  4T7)  92  D a t a V s . Time, Sample BNR500  5.10  Ellipsometric  D a t a V s . T i m e , Sample BNR1000  5.11  Transient  Ellipsometry,  Sample  5.12 T r a n s i e n t  Ellipsometry,  Sample BNR1000  BNR500  94 95 97 98  6.1 MTAOS A n o d i c O x i d a t i o n  Under C o n s t a n t C u r r e n t  141  6.2 MTAOS A n o d i c O x i d a t i o n  Under C o n s t a n t V o l t a g e  142  xi  6.3  MTAOS T r a n s i s t o r ;  Drain,  6.4  MTAOS T r a n s i s t o r ,  C o n t a c t Window A r e a D e t a i l  6.5  Overall  6.6  MTAOS T r a n s i s t o r  6.7  R-S  Flip  6.8  MOS  Capacitor  6.9  Overall  View  Showing  MOSFET And  R-S  Flip  Metallization  ..149 149  Flop  150  Details  ....150  Windows  151  Area, Contact M e t a l l i z a t i o n Showing  6.10  Contact  Pads And  6.11  NOR  6.12  Interconnection  G a t e And  Gate D e t a i l s  Contact M e t a l l i z a t i o n  Flop Contact  View  S o u r c e And  R-S  MOSFET And  Diffused  151 Resistor  .152  Alignment Markers  152  Flip  153  And  F l o p O v e r a l l View  Contact  Pad D e t a i l  7.1  System  For P l o t t i n g  7.2  Static  Output  C u r v e , Sample MTAOS3 T h e r m a l  157  7.3  Static  Output  C u r v e , Sample MTAOS4 A n o d i c  158  7.4  Static  Transfer  C u r v e , Sample MTAOS3 T h e r m a l  159  7.5  Static  Transfer  C u r v e , Sample MTAOS4 A n o d i c  160  7.6  System  F o r M e a s u r i n g The MOSFET P u l s e R e s p o n s e  7.7  C-V  C u r v e On D o u b l e D i e l e c t r i c  MOSCTest 7.8  C-V  C-V  Curves  T e s t Wafer  156  (sample 165  Dielectric  Test  Wafer  (sample  200A A n o d i c  166  C u r v e Of MOSFET G a t e , T h e r m a l  Sample MTAOS3  ...167  C u r v e Of MOSFET G a t e , A n o d i c Sample MTAOS5  ...168  7.10  C-V  7.11  I-V C u r v e On MOSFET G a t e , T h e r m a l  7.12  I-V C u r v e On MOSFET G a t e , A n o d i c Sample MTAOS4  7.13  ....162  200A T h e r m a l  C u r v e On D o u b l e  MOSCTest 7.9  MOSFET S t a t i c  153  Double  Dielectric  MOSFET  Sample MTAOS3  Output  Curves,  ..171 ...172  Sample  MTAOS 3 7.14  Double  MTAOS3  176 Dielectric  MOSFET  Saturated  Test,  Sample 176  7.15  Double  D i e l e c t r i c . MOSFET  Pulse  Test  (Turn On),  Sample MTAOS3 7.16  177  Double D i e l e c t r i c  MOSFET P u l s e  Test  (Turn O f f ) ,  Sample MTAOS3 7.17  Double  177  Dielectric  MOSFET  Output  Curves,  Sample  MTAOS4 7.18  178  Double D i e l e c t r i c  MOSFET  Saturated  Test,  Sample  MTA0S4 7.19  Double  178 Dielectric  MOSFET  Pulse  Test  (Turn On),  Sample MTAOS4 7.20  179  Double D i e l e c t r i c  MOSFET P u l s e  Test  (Turn O f f ) ,  Sample MTAOS4 7.21  Leaky Gate  7.22 L e a k y G a t e  179 In MOSFET, A n o d i c T a 0 , 2  In MOSFET, T h e r m a l  5  Ta 0 , 2  5  Sample MTAOS4 Sample  180  MTAOS3 180  7.23  Double D i e l e c t r i c  MOSFET E q u i v a l e n t C i r c u i t  182  xiii  ACKNOWLEDGEMENTS I his  wish  t o thank my S u p e r v i s o r ,  guidance  Thesis.  and encouragement  conversations  to Dr. Peter most  valued  preparing Ahmed the  (Solid  assistance  (now  with  State  initial  Laboratory  (now  with  expression  Northern  Dr.  Technique  Jamil  Ballard  on t a n t a l u m Research)  metal;  for his  Research  My  thanks  Division, Assisted  i n Ottawa, samples  to  Mr.  for  supplying  software.  the  James  Search  Henderson  for  of  Magnetron  in  obtaining  the the the  The a s s i s t a n c e of Ms. A n g e l a R u n n a l s , Ms.  Lyons-Lamb and Mr. J o n N i g h t i n g a l e acknowledged, as they  of B e l l  f o r MOS c a p a c i t o r s .  Main L i b r a r y , f o r h i s a s s i s t a n c e ' Library  material.  interfacing  o f g r a t i t u d e t o Ms. C a r l a M i n e r  Enhanced S p u t t e r i n g  made  using  t h e FMT e d i t o r under  I  also  wish t o acknowledge  Science Computer reference Victoria  o f t h e Computer C e n t r e i s  possible  Thesis  these  to  and i n  a s s i s t a n c e and h e l p on t h e s u b j e c t , and f o r a l l o w i n g  My  my w i f e  indebted  Research) f o r suggesting  t h e use o f some o f h i s computer  also  I am  details,  o x i d a t i o n samples;  Microtel Pacific  Smith  in this  a t UBC) f o r h i s  i n many p r o c e s s i n g  p o s s i b l e use of t h e L i f t o f f  for  P u l f r e y f o r h i s i n t e r e s t and  on t h e s u b j e c t . A l s o  the i n t e r f a c i a l  to Dr. David  me  Janega  Young  on t h e work p r e s e n t e d  My t h a n k s t o D r . D a v i d  enlightning  D r . Lawrence  to  compose  t h e MTS o p e r a t i n g the i n f i n i t e  this  system.  patience  that  B r e n d a and o u r c h i l d r e n have d e m o n s t r a t e d d u r i n g a l l years  of  encouragement my mother  and  of  hard other  brother,  work  and  members o f my this  work  study.  Without  the  family, i n p a r t i c u l a r would  have  not  been  xiv  possible.  To  dedicate t h i s life,  a l l them,  I e x p r e s s my d e e p i n d e b t e d n e s s . I  work t o a man  but h e r o i c a l l y  lost  that  the l a s t  fought o n e : my  many  battles  father.  in  1  CHAPTER 1  INTRODUCTION The  term  non-conventional  describe  those  Si0  in  used  2  isolation,  which  MOS  depart  as  masking,  gate  the  silicon  research  in alternate  devices.  In  insulators either metal  dioxide,  the p r e s e n t is  used,  obtained  by  t o form MOS  namely thermal  insulators,  device  resist  authors  suitable  work, one  of  or a n o d i c  c a p a c i t o r s and  and  general  advantages  have f o l l o w e d  for  such  Tantalum  to  classic  the n a t u r a l  numerous  dielectrics  used the  implant  surface p a s s i v a t i o n . Notwithstanding of  is  c o n s i d e r a b l y from  technology  diffusion  dielectrics  use  in  MOS  non-conventional  Pentoxide  (Ta 0 ),  o x i d a t i o n of  tantalum  field  effect  2  devices  5  on  silicon substrates. Large Ultra  Scale,  Large  Scale  technologies down t o the  and  1 micron  large  Very  Integrated  f e a t u r e s and of  i s t o be  (early  major  resolved  yet,  induced  failures,  namely  the in  lines  the extremely  w i n d " , of t y p i c a l l y  order  dice At  areas  which  transported  the  in  solution  metal  and  per  problem  will  of p e r f o r m i n g  successful.  interconnecting  "electron  Circuits  beyond,  devices  microtechnology  by  S c a l e I n t e g r a t e d and  devices capable  number  1984),  Large  the  future require  when to  scaled achieve  (>300,000) i f t h i s this  present  seem t o have not to  time been  electromigration  ions  (usually  that  form  Aluminium)  the are  high current d e n s i t i e s , i . e . , 10,000  subthreshold conduction  i n MOS  A/cm  2  [Black,  transistors,  1969]; i n which  2  the  device  drain  current  applied is  does  gate  scale  required.  [Dennard  reduction  of  attaining  The gate  the  of  al.,  1974].  insulator and  d e p e n d s on  gm:  former  dielectric  which  is  is  a  constant) be  more  in  used  Field  that  and  said  on  A  then,  close  relate  (which  the  drain  relation  with  A  on  similar  the  Another  complicated  the  Effect  device  p r o p o r t i o n a l to  the  in  and  by  about  The  of  increases  threshold voltage  the MOS  channel  change,  that a general  the  important  design  applications.  capacitance  the  ULSI.  constant.  i s reduced  crucial  (linear)  insulator  I t can  and  1969]  constant.  small  importance  advantages.  important,  threshold voltage,  both  great  i s in direct  dielectric  not  consequence,  presently  i t is also directly  suffers  dielectric  decreases).  the  do  for very  i t s geometry, t h r e s h o l d v o l t a g e  f o r analog  conductance,  [Sze,  condition)  currents  Oxide Semiconductor  p e r h a p s t h e most  factor,  where  i s of  dielectrics  relative  insulator  of c i r c u i t s  a  f o r VLSI  the  latter  a problem As  of  1 9 7 4 ] . The  c u t o f f or OFF  effect  equations  reveals that  transistors  the  presents  for Metal  with  parameter, the same  this  non-zero  efforts  subthreshold  subthreshold  the  transconductance gate  operation  i s i n the  The  the  (MOSFET's) have d e f i n i t i v e  current  effect,  of  [Troutman,  successful devices  examination  voltage,  so  to the  high p e r m i t t i v i t y  Transistors  the  et  insulators  drain  despite  (the d e v i c e  and  o f f , i . e . , a s m a l l , but  t o do  critical  properly  devices  turn  flows  voltage  leakage  c u r r e n t s are  in  still  particularly  low  not  as  it with  (which  improvement  3  on  t h e MOSFET d e v i c e p e r f o r m a n c e  use  of h i g h p e r m i t t i v i t y  ( T a 0 ) has a r e l a t i v e 2  in  times  larger  insulators.  dielectric  5  seven  gate  c a n be a c c o m p l i s h e d  than  silicon  in  Because of i t s n e g a t i v e  Ta 0  help  can  voltage  [Seki  further  promising  field,  either  down  thickness the  in  and  voltage.  This  silicon a  tantalum  voltage the  gate  higher  layer  is  pentoxide.  a  lower  density, threshold  constant  the  be  As  the  charge  K,  of a  device  the gate  is  insulator  hence  limiting  used  instead  material  the  insulator  avoided,  if  breakdown a  double  a thin silicon  fields,  as  a c r o s s t h e compound d i e l e c t r i c material,  the  layer,  1978],  constant material  (i.e.,  breakdown  turn-on  of the s i n g l e  [ A n g l e and T a l l e y ,  i s d e p o s i t e d over  permittivity  fixed  bound,  can  insulator  i s p r o t e c t e d from  higher  gate  be  v o l t a g e by o x i d e breakdown. The  of h i g h d i e l e c t r i c  pentoxide)  drop  oxide.  bound,  situation  structure  dielectric latter  a  d i o x i d e gate  thick  should  by t h e a p p l i c a t i o n  dimensions,  v o l t a g e has then  voltage,  dielectric  Therefore,  charge  internal  by t h e same f a c t o r  applied  gate  the  gate  i t s three  i s reduced  maximum  applied  the  about  i s i n a v o i d i n g the gate  o r t h e one c a u s e d  gate v o l t a g e t o the c l a s s i c scaled  reducing  application  breakdown by  generated  27,  performance  interface  pentoxide  e t a l . , 1984]  Another insulator  in  of 2  expected. 5  constant  dioxide (Si0 ).  theory, a sevenfold increase  2  Tantalum  by t h e  layer  If  (i.e., of  low  d i o x i d e ) , the most  of  the  will  appear i n  thicker  tantalum  4  In  the  double  pinholes small,  insulator  coinciding thus  Amorphous  in  the  producing  silicon  a  permeability  ions.  By a p p l y i n g a s e c o n d  one,  these e f f e c t s  much  denser  used  to  much  and  proved  to  MOS  It  and f a s t  i s quite  possible  insulator  direct  onto  inner  pentoxide  has a  insulating  gate  found  Random A c c e s s Memory  single  and t h e d o u b l e in  use  with  moderate  in  a  VLSI  [Ohta  The MOS  currents.  dielectric  future  both  devices  dielectric  VLSI  high  structure and  constant  256/512 k b i t  (RAM), w h i c h a i m s t o w a r d s  memory I n t e g r a t e d C i r c u i t  for  switching pulse response.  the  ion  structure i s  insulator  transistors,  application  has  the  d e v i c e s . The s u c c e s s f u l  that  has  the  retards  t e c h n o l o g i e s . Already, the high d i e l e c t r i c pentoxide  and  and m i g r a t i o n o f a l k a l i  have good C-V c u r v e s and low l e a k a g e  permittivity have  the  insulator.  porous  Tantalum  dielectric  of  vanishingly  quality  possibly  functional  transconductance capacitors  vapour  and  capacitor  be  better  is  outer d i e l e c t r i c  i n t h e p r e s e n t work a s  MOSFET  probability  location  c a n be r e d u c e d .  double  the  structurally  water  structure, The  same  dioxide i s  high  migration.  structure,  the  ULSI  tantalum dynamic 1  Mbit  e t a l . , 1980].  i  The  purpose  measurements and Capacitors  of results  fabricated  p e n t o x i d e ; and from double the  this  dielectric  tantalum  obtained  with  anodic  the experimental  ( T a 0 ) gate  oxide  Thesis  2  5  was  is  from and  present  the  experimental  MOS  thermal  MOSFET's  insulator  obtained  to  by  tantalum  utilizing  structure, thermal  a  i n which  and a n o d i c  5  processes. This  Thesis  is  appendices. previous third is  The  work  chapter,  presented,  as l a t e r  the  information  chapter, and  the  results  measurements devices)  eight  second c h a p t e r  the theory  technology.  and  into  The  of t h e d o u b l e  on a d e v i c e  related  to  the  are presented.  dielectric  will  chapters  device.  The s e v e n t h  dielectric  obtained.  summary and c o n c l u s i o n s of t h i s  work  In are  the  insulator  of  around  the  the  MOS fifth  capacitors  contains  MOSFET's  chapter  of t h e  contain a l l  In  chapter  four  In  be d e v e l o p e d  p e r f o r m e d on t h e MOS  on t h e d o u b l e  and t h e r e s u l t s  and  field.  processing  dielectric  measurements  made  in this  f o u r t h and s i x t h  double  chapters  c o n t a i n s an o v e r v i e w  done by s e v e r a l a u t h o r s  this  capacitor  divided  (MTAOS  eight,  presented.  the  the  6  CHAPTER 2  AN  OVERVIEW OF  NON  CONVENTIONAL  A l a r g e number of a u t h o r s properties I  of  non  have a t t e m p t e d  the  to present  s u b j e c t . These cover  compounds u s e d as  Despite electrode were  first  value  and  thick  i n a non  by  [Berry  of  and  s u b s t r a t e s . Thin  aluminium  1959],  s i n c e A l metal  same  formation  was  used  [Huber and  A detailed  study  "valve  metals",  Ta,  Al,  Nb,  concisely attention  Zr, in  oxides.  as Haas,  Hf,  W, form  t o be  the  contact  counter  used  films  in  low  capacitance  of  30  nF  with  f o r s a m p l e s made  anodically  oxidized  same a p p l i c a t i o n tantalum  evaporated  and  version  was  instead sputtered  and  for anodic  a  and  dielectric  1960].  of t h e  i . e . , the  book  devoted  was  f o r the over  way.  sputtered  Typical  of  on  several  thin  of  capacitances  films  simplicity  of  pentoxide  were o b t a i n e d  were a l s o p r o d u c e d  d e g r e e of  claimed,  10-100 nA  films  oxidation  Sloan,  and  2  chapter,  i n o b t a i n i n g good  anodic  nF/mm  c u r r e n t s of  ceramic  certain  10  In t h i s  conventional  capacitors for printed c i r c u i t s .  leakage  film  thin  difficulties  obtained  metal  densities  the  dielectrics.  different  a summary of p u b l i s h e d works  dielectrics  early  have r e p o r t e d many  c o n t a c t s , s u c c e s s f u l tantalum  tantalum  on  conventional  INSULATORS  anodic  oxides  of  electrolytically Bi, by  to tantalum  Sb  and  Young and  the  in  the  so  called  formed o x i d e s  of  others,  was  given  1961,  with  great  p r o p e r t i e s of  i t s thin  7  Anodically aluminium  oxide  zirconium  (60  films  (Al 0 ), 2  oxide  fabricated, their  grown t h i n 3  (Zr0 )  and  2  using  of  silicon  devices,  although  (SiO),  tantalum  pentoxide  (Ta 0 ),  titanium  oxide  2  evaporation  techniques  c o n d u c t i o n and n e g a t i v e r e s i s t a n c e Hz);  oxide  the a p p l i c a t i o n  2  (Ti0 )  were  for evaluating  a t low  frequencies  was n o t i n t e n d e d  but r a t h e r i n s w i t c h i n g and  5  rectifying  f o r MOS  [Hickmott,  1962]. A study of  the  transport fields type  done on a M e t a l - I n s u l a t o r - M e t a l (MIM) s t r u c t u r e  form  Ta-Ta 0 -Au 2  revealed  5  mechanism o b e y s an  and  that  at high  Ohmic  fields  (i.e.  77K),  gave  an a c t i v a t i o n  energy  o x i d e p r o p e r t i e s was n o t e d A rather unusual observed prepared thermal be  as t h i n  At h i g h  type  negative  resistance  around  50 nm  [Mead,  and  their  oxides  Tunnel  is  i n the  1962]. was  o x i d e s , when  obtained  resistance  by  the  a r e found t o  to the voltage (Esaki)  low  Measurements  characteristics  and t a n t a l u m  as opposed  of the  low  conduction  emission.  p r o c e s s . Regions of n e g a t i v e  current controlled,  at  of 0.1 eV. A d i s c o n t i n u i t y  titanium  f i l m s and  fields  electronic  current-voltage  f o r niobium,  electronic  i t follows a Poole-Frenkel  the  g o v e r n e d by a F o w l e r - N o r d h e i m  the  characteristic  e m i s s i o n a t room t e m p e r a t u r e s .  temperatures  that  controlled  diode  [Chopra,  1963]. Thin nitride were  film  circuits  using  resistors  (TaN) a n d c a p a c i t o r s made o f a n o d i c  successfully  circuits,  applied  i . e . , incorporating  in  creating  discrete  made o f t a n t a l u m tantalum the  bipolar  first  oxide hybrid  transistors  8  to  a  common  digital  circuits  high value in  a  ceramic [Berry,  resistors  partial  for  resistors metal  1963], L a t e r a method  was d e v e l o p e d ,  atmosphere  1963]. F u r t h e r m o r e , system  s u b s t r a t e , i n making b o t h  of argon  a production  deposition  by  sputtering  style  open  films  was r e p o r t e d t o make 4 m i l l i o n  film  per  year-shift  f o r producing  and oxygen  of tantalum  a n a l o g and  [Balde,  tantalum  [Pendergast, ended  vacuum  f o r manufacturing square  inches  of  C h a r s c h a n and D i n e e n ,  1 964] . Reactive  sputtering  subatmospheric deposit  films  (Ta 0 ), 2  partial  ( T i N ) and o x i d e s for  the  tantalum  pressure  of tantalum  tantalum  5  of  nitride  carbide  (Ti0 ), 2  metal  gas p r e s s u r e s (TaN),  Niobium N i t r i d e s  that the i n t r o d u c t i o n  reactive  component,  pressure,  were o b t a i n e d .  sputtered  superconducting  NbN,  has  [Gerstenberg, The sparked  the  highest  Nb N); 2  film  o f Oxygen a s  a  i n the e l e c t r i c a l controlling  of sheet  its  resistivity  and  carbides  and t h a t n i o b i u m  nitride,  transition  temperatures  1964].  interest  i t s predecessors.  temperature  By  and  hybrid thin  t h a t most n i t r i d e s  tantalum  [Read a n d A l t m a n n , 1965]  i n the r e s e a r c h of t h i n  t h i s m a t e r i a l , as i t o f f e r e d over  films.  properties  d i s c o v e r y of beta more  effect  reproducible values  I t was f o u n d  of  dimensional  had a d r a s t i c  have  one  two  (NbN  I t was n o t e d  partial  nitride  2  circuits.  the  pentoxide  (TaC and T a C ) t i t a n i u m  of  of  was u s e d t o  tantalum  fabrication  properties  with  improved e l e c t r i c a l  I t has h i g h e r  coefficient  f i l m s made o f  of  resistivity,  resistance  properties a smaller and  its  9  superconducting  transition  temperature  tantalum  i s formed  of  i s introduced at a p a r t i a l  argon  mTorr  and  other  gases  normal  750  the t o t a l  pressure  (body  tantalum  films  of  10  to  vacuum q u a l i t y ) that  a  30  of the  conversion  to  centered cubic s t r u c t u r e ) takes place,  ( t e t r a g o n a l ) i s heated  made  of p h o t o e l e c t r i c of N b 0 2  over  5  t h e c o n d u c t i o n mechanism  i n vacuum t o about  by  Electronic  photoconduction  Ta 0 ,  irradiated current  using  sharp  with  was  intensity  found  that  light  measurements  indicated.  in  thin  metal,  relation  can  films  film  has been  as  cells.  exists  between p h o t o c u r r e n t  a characteristic and Bobb,  Chemical  conventional  F o r Ta and T i a n o d i c  fabricated, between  response  oxides a l i n e a r  in a  the  type  relation  although  practical  is  i s two  junction  and p h o t o v o l t a g e ,  i s not d e s i r a b l e  to the  photocell,  (50-100 s e c ) and t h e c o n v e r s i o n e f f i c i e n c y the  in  experimental  However, t h e t r a n s i e n t  o f m a g n i t u d e below  of  c u r r e n t when  proportional  exists  be  1966].  the i n c r e a s e  A thin  intensity,  silicon  [Chopra  film  [Hickmott,  i n which  1961].  niobium  oxide  conduction  light,  a linear  and  orders  of  [Young,  photocurrent  slow  found  t o be a p p r o x i m a t e l y  of the l i g h t  i t was f o u n d  the  i s also  ultraviolet  found f o r  s u b s t r a t e s , a s knowledge o f  studies  increases  thermally oxidized  very  metal  photoresponse  with  5  p r o p e r t i e s has been  through  obtained  and  when an a t m o s p h e r e  pressure  (i.e.,  Beta  C. Evidence  2  system  i s 10 u T o r r . i t was f o u n d  tantalum  when b e t a  in a sputtering  i s much l e s s .  such  photocell  1963].  vapour  deposition techniques  (CVD) have been  10  applied  t o the  of T i 0 , T a 0 2  2  appropiate  5  fabrication and  Nb 0 2  Vidicons.  platinum  was  A used  compound.  using  wide  the  Lead  and  (Bi„Ti 0 ) 3  problems  the  control  compound. H i g h d i s s i p a t i o n  1971 ] .  Takei,  Tantalum  pentoxide  for  Integrated  Circuits  microwave  frequencies.  (Ta 0 ) 2  for  later  o x i d a t i o n on  The size the  MIC's  g u i d e w a v e l e n g t h Xg reduction  as  larger.  This  constant  e e f f , which  dielectric  is  high  based  can  size  er  be  er  the this  of the  by  Q  (=100)  the be  of  2  at  System  degree  and  of  increased, i f  the  is  5  a  larger  can  be  achieved  made  dielectric relative  s u b s t r a t e . H e n c e , by  (i.e. Ta 0 ), reduction  'relative  technologies.  effective  function  been  sputtering  substrate  the  the  have  high  on m e t a l  i n t e g r a t i o n can  on  [Szedon  Tantalum  r e d u c e d , and  constant  of  called  in  f o r Microwave  alumina substrate  is a direct  constant  and  moderately  are  determined  substrates with large integration  its  so  an  films  to  The  w e l l as  relative dielectric  of  s p u t t e r i n g of  dielectrics due  to  high  f o r use  spite  thin  5  as  and  dielectrics  use  very  c u r r e n t s were f o u n d  (MIC's),  constant  for  f a c t o r s which depend s t r o n g l y  application  dielectric  anodic  in  heavy c o n d u c t i o n  considered  a  (=160) h a v e been r e p o r t e d  stoichiometry  films  1970].  with  1 2  in  and  (PbO)  the  from s i l i c o n  Duffy,  capacitors,  and  oxide  films  of  techniques,  Metal-Insulator-Metal  frequency  pyrolysis  substrates,  [Wang, Z a i n i n g e r  permittivity  by  same CVD  range of  Bismuth t i t a n a t e f i l m s relative  c a p a c i t o r s , i n which  were o b t a i n e d  5  organo-metal  were a l s o d e p o s i t e d , in  of MOS  using  degree  of  [Caulton,  11  1971]. A rather insulator the  gate  was a p p l i e d  approach  t o a MOSFET v o l t a g e d i v i d e r ,  with  the  a capacitive  position  [Okamoto and U g a i ,  silicon  placed  of  N /0 2  2  interface  with  i t  is  technologically  and  aluminium  metal  heat  drain  metal  over  of a S i - T a and S i - T a -  treatment  in  different  2  an  It  approximate  was  reported  that  the  that  with the S i l i c o n  the  when  thin  Ta-Si  annealed.  films  System. T h i s  the S i - S i 0  temperature  root  process used  tantalum  shown by s i l i c o n , at this  square  interdiffusion  low t e m p e r a t u r e  compatible  to the s t a b i l i t y  MOSFET  tantalum  i n t h e form  negligible  due  This  movable g a t e e l e c t r o d e  sputtered  show  said  o i l (later  underneath.  with the  the  2  Because of the r e l a t i v e l y C),  being  which  and N / H 0 m i x t u r e s . The k i n e t i c s o f  time.  exhibited  silicone  in  gate  1971].  under  incorporation  dependence  oxide  of  of  was made f e a s i b l e  atmospheres oxygen  function  oxidation  structures,  over  voltage divider,  being  Thermal  a  gate  current  Al  to a non-conventional  e l e c t r o d e i s made t o s l i d e  glycerine), formed  unorthodox  2  (525 are is  interface  [ C r o s e t and V e l a s c o ,  1971 ] . A  thin  pentoxide was The  film  capacitor  h a s been  s p u t t e r e d over  of s i l i c o n  successfully  fabricated,  anodized T a 0  capacitance density  d i o x i d e over  2  5  over  i s dominated  because  of i t s s m a l l e r d i e l e c t r i c  with  anodic  tantalum  reproducibility,  as the d e s i r e d  This  which  Si0  2  a ceramic s u b s t r a t e .  by t h e s i l i c o n  film,  oxide.  in  tantalum  dioxide  c o n s t a n t a s compared  gave  a h i g h degree of  capacitance density  of  the  12  Si0 /Ta 0 2  2  thin  5  thickness  of  the  coefficient  of  compensate  the  resistance networks  film  capacitor  silicon  is  dioxide  capacitance  film.  (TCC)  negative  controlled  can  (TCR) o f t a n t a l u m n i t r i d e  dioxide thickness [Sato,  the  temperature  adjusted  to  coefficient  of  resistors  b a s e d on t h e T a n t a l u m S y s t e m ) ,  of t h e s i l i c o n  The  be  temperature  by  (used  by p r o p e r Sato  in  RC  selection  and  Okamoto,  1973]. Thermal  oxidation  of  tantalum  e l e c t r o n beam e v a p o r a t i o n on s i l i c o n , order  t o study the Si-Ta-{Ta  o f a maxima used  in  i n the oxide's  deciding  the  m e t a l . The e l a p s e d  time  oxidation  time  interaction oxidation  of  with of  the  for  Ta  Si  by  have been p r e p a r e d  in  refractive  maximum  It  Si-Ta  namely  oxidation the  f a s h i o n as the S i - S i 0  This  t h a t some  during  the  interaction  at  into the S i c r y s t a l ,  interface  2  i s the  when  thermal  t a k e s p l a c e . I t was c l a i m e d t h a t t h e p r o p e r t i e s o f  oxide  film  and  the  Si-{Ta  c o n t r o l l e d by t h e S i / T a r a t i o Allison,  was  the c o - o x i d a t i o n of a  i n t e r f a c e h a s a c t u a l l y moved  in a s i m i l a r  value  ocurred  s m a l l , b u t n o n - z e r o amount o f s i l i c o n . the  index  was c o n c l u d e d  substrate  film,  criteria  o x i d a t i o n of the tantalum  this  film.  deposited  s t r u c t u r e . The  apparent  complete  the the  oxide}  films  in  K i r k e n d a l l and R e y n o l d s ,  An  interesting  evaporated  oxide films  insulator of  oxide} the  oxide  i n t e r f a c e c a n be film  [Revesz,  1974]. structure  tungsten  (W0 ) 3  is and  made  using  molybdenum  (Mo0 ) o x i d e s , sandwiched between o r t h o g o n a l l y e v a p o r a t e d A l 3  electrodes.  I t was e s t a b l i s h e d t h a t a S c h o t t k y t y p e  barrier  1 3  exists  between t h e  linearity  of  concluded  that  adjacent  to  film  and  the  2.3  space  use  coatings  quantum  yield  the  of  desired  junction  also  2.37,  Reynolds,  similar close  insulating between  solar  The  cells,  of  optimum  value  thermal o x i d a t i o n  that  results  oxide]  in  in  a  structure  of  if  its  a  with  high  as w i t h a  surroundings  recombination.  t o t h e optimum  1975].  since i t s  at s h o r t wavelengths,  properties  oxide  field  importance  without  was  layer  the  the  to the  generated  it  Sathianandan,  process  great  and  the  a  Niobium  refractive  [Revesz,  Allison  and  1976].  MOS  capacitance  measurements  techniques are h e l p f u l semiconductor-  interface  states  particular oxidized  of  verifying  is in  application.  the c a r r i e r s  n-p  has  pentoxide  for s i l i c o n  This i s is  interface,  pentoxide  it  exists  oxide with a S i l i c o n - { T a  high p e r f e c t i o n .  for  i . e . , an  layer  temperature  by  voltage plot  (2.23) i s v e r y c l o s e  i s a low  noncrystalline  the  charge  of t a n t a l u m  index  tantalum  index  versus applied  2  required in this  reach  oxide  t h e e l e c t r o d e [Padmanabhan and  refractive  good  and  a compound b a r r i e r ,  antireflection  of  1/C  a  Another  of  contacts  by  the  that  and  as  obtained  in  method  [Sze,  of t h e o r i g i n a l  annealing  in  density  interface  of  interface,  o b s e r v i n g the  forming  gas  states  (N /H 2  by a  C-V  the  plot  final  of  ways,  in  1969].  Thermally  been  prepared  oxide t h i c k n e s s ,  I t was  mixture),  factor  of  of  density  various  have  film. 2  the  the c h a r a c t e r i s t i c s  sputtered tantalum  purpose,  gave t w i c e  be  Terman  s a m p l e s of  this  in determining  oxide can  using  4,  noted  that  reduced  the  while  the  1 4  oxide  charge  Allison,  remained  thermally  oxidized  gradient  in  the  substrate-oxide increases  observations Ta 0 2  of  the  oxide.  and  multilayer  its  have  that  (=10  nm)  layer  measured  by  the  on  R e y n o l d s and  (and  substrate  Allison,  Chemical  its  of  towards  this as  etched  slope e x i s t s ,  of  are  at  a  using  a  substrate  as  compared  gradient  t h e Ta  they  oxide  grown  in  Deposition  organo-metallic assistance  depends [Revesz,  compound  of  a  (CVD)  is  a technique  i s deposited  carrier  gas,  by  temperature  oxides  with  grown  tantalum  are  mainly  equipment organic  using  this  usually a  method, w i t h  (300-500 C)  process,  amorphous s t r u c t u r e s , s i m i l a r  in and  oxides. the the  compound.  vast  The  mixture  complexity  Films  of  deposited  of a by  results  the of  of in  thermally  this  the  approach  deposition  suitable CVD  films  advantage  that  to  disadvantages  availability  the  by  pyrolysis  w h i c h c o n t a i n s oxygen among o t h e r s . T a n t a l u m p e n t o x i d e  a low  the  1976].  Vapour  have been d e p o s i t e d  the  refractive  a GaAs  Hence, t h e  the  in i t s actual  was  on  at  a  actually  ellipsometry  slope)  were  exists  boundary  5  that  index  of o x i d e  opposite  shown  the  existence  substrate case.  largely  being  and  p r o p e r t i e s of  index  m o d e l . Measurements p e r f o r m e d  index  the  silicon  2  The  index  refractive  with  [Revesz  optical  i s somewhat c o n t r o v e r s i a l ,  silicon  w h i c h an  the  its Si-Ta 0  show t h a t a g r a d i e n t w i t h the  of  and  from  measurement, a t h i n  with  negative  refractive  interface  gradient  time,  on  5  optical  slightly  end  index  and  1976].  Ellipsometric  outer  fixed  show  tantalum smooth  15  s u r f a c e s and close  to  good a d h e s i o n ,  2.3  and  with  an o p t i c a l  m e a s u r e m e n t s gave a r e l a t i v e and  C-V  three  plots  indicated  different  substrates, t h e C-V  curves  conduction limited,  with  densities  a  and  Schottky plot a two-slope  optical  bandgap of 4.4  eV.  Capacitance  to fast  DC  was  show  constant  emission  from the o f 5.3  linear  was but  not  saturation,  Frohman-Bentchkowsky, research  temperature  or s i l i c o n  work  2  of  incorporates  the in  is  of  oxide  the  Ta  on  the  This  process.  one  thermally  oxidized Ta 0  of s i l i c o n  and  2  the  5  A  revealed slope)  fits  the  obtained  t h e CVD  Si0  by  films  2  currents  [Kaplan,  the S i - T a 0 2  Balog  metal It  film, is  well  silicide  in  this  gradient  show  films contain a significant  r e s u l t s g i v e a r a t i o of 0.85  the  silicon  that  index  analysis  below 2  to which  claimed  has  (TaSi )  occurs  refractive  Gravimetric  interface  5  occurs  phenomenon  the cause f o r the film.  which  films  5  interaction  tantalum  the  interaction  bulk  current  portion (first  r e q u i r e d t o form t a n t a l u m  dioxide (Si0 ).  deposition  The  be  low  of  1976].  revealed that a s i g n i f i c a n t the  to  b u t a t much l o w e r 2  Further  states.  at  obtained,  ( s i x o r d e r s of m a g n i t u d e ) t h a n T a 0 and  p-silicon  v s . Square Root V o l t a g e )  value,  current  of  surface  c a p a c i t a n c e measurements. I n t e r e s t i n g l y , also  22-25  charge l i m i t e d at higher d e n s i t i e s .  (log Current  constant  of  no d i f f e r e n c e among  established  Poole-Frenkel  space  constant  no h y s t e r e s i s . Some d i s t o r t i o n  at  c u r v e , and  a dielectric  refraction  orientations  attributed  mechanism  of  t h a t t h e r e was  showing  was  index  dielectric  crystal  a l l  an  that amount  Si-Atom/Ta-  1 6  atom  i n the  (SIMS) in  a  oxide  analysis  by  incorporation  Secondary  sense.  The  assuming of  formation  Ion  seem t o s t r e n g t h e n  qualitative  explained  the  film.  silicon of  this  oxygen  grain  Spectroscopy  hypothesis at  interface  that by  Mass  interaction  is  facilitates  the  boundary d i f f u s i o n  s t r o n g S i - 0 bonds  least  [Revesz  and  due  to  Kirkendall,  1976]. The has  R u t h e r f o r d B a c k s c a t t e r i n g (RBS)  been a p p l i e d  characteristics analysis,  to study  of  light  the and  p o s i t i v e , i o n s w i t h an the  s u r f a c e t o be  elastic  knowledge of  the  energy  i s then loss.  significant  oxide high  energy  (i.e.  are  of  MeV)  a r e used  to  effects  tantalum  is  boundary  no  sharp  pentoxide  varies  with  layer.  to  1976). be  in  The  from  on  of  high they  for  show the  purity  source.  In  exhibit  substantial  with  that  of S i - O - T a this  energy  during  anodic  the  Ta 0 , 2  and  the  slightly  Revesz et bonds has  effect,  5  refractive  thickness, decreasing  formation  be  inelastic  between t h e Ta m e t a l found  can  films  to g e t t e r i n g  the  spectrum,  the  Ta  r e p o r t e d p r e v i o u s l y by  responsible  bombard  from  energy  ions rate  contrast  I t was  the oxide  t h i n n e r o x i d e s , as  a  oxides,  there  pointed  profile  due  from  data  RBS  helium  surface composition  technique  and  and  back)  this  incorporation,  (1974  collecting  near  oxygen  with  by  R e s u l t s from  thermal  index  1-5  the  the  (typical  t h e He  partial  In  ions  from  beam d e p o s i t i o n  b o u n d a r y and  itself.  obtained  impurity  technique  energy  concentration  electron  tantalum  layer  bounced  s u r f a c e and  o b t a i n e d . A depth spectra  the T a { o x i d e } - S i  s t u d i e d , and  scattered  analysis  and  al been the  1  incorporation interaction  silicon  capacitor  structures,  by  method.  The  films  titanium  and  the  the t a n t a l u m  of  Ta 0 2  Kirkendall,  results  increasing  at  fractions  an  prepared  for  into  symmetry  of  anodization  of t a n t a l u m  increased  tantalum the  temperature  to  reliability  as compared  Furthermore,  agents  room  this  and  reverse bias,  capacitors.  the  characteristic  sputtering  gave  under  alloying  for  1976].  have been  v a r y i n g atom  rate)  i s noted  5  (tantalum-tantalum-oxide/metal)  standard  had  oxide  that  TM  the  failure  proposed  the  titanium-tantalum films  in  (lower  to  [ H i r v o n e n , R e v e s z and  Anodic use  of  7  it  with  has  have t h e DC  been effect  conductance  [ P e t e r s and  Schwartz,  1977].' A  conduction  insulator  film,  mechanism  vanadium p e n t o x i d e  both  forward  and  under  forward  bias)  combination that in  no  the  single  one  (log  I  between 0.4-0.7 V; 1.25  I-V  V and  then  For  an Ohmic  one  and  exists  under  another  (V 0 ) 2  the gate  characteristic  exhibited  under  proportional  t o the  and  a S q u a r e Law  area  a Schottky  t o a S q u a r e Law  forward b i a s ,  and  bias  measurements showed t h a t  region exists;  a Schottky  square  root  one.  with d i f f e r e n c e s  in  V)  above  region in  relation,  A similar  at  type of  for voltages  type  a  transport  reverse  for higher voltages, a t r a n s i t i o n  then  for  emission e f f e c t s  is  from  that  is positive  f o r the c a r r i e r  example, I-V  potential  indicated  5  (i.e.,  c o u l d account  which the c u r r e n t passes linear  of  c o n d u c t i o n and  the e x p e r i m e n t a l  v o l t a g e s (0.4 V)  relation  the  structure.  conditions, low  reverse bias  of d i f f e r e n t  MOS  study  to a  situation  the  region  18  e x t e n s i o n s and  s l o p e s of  measurements, C-V with  voltage  certain  independent, An  frequency,  whereas  voltage.  A  with  certain  relationship  was  curve  which  ordinate  film  metal  over  oxide  by  the  capacitor  area  frequency  reverse bias c o n d i t i o n s . dominates forward  the or  C-V  reverse  capacitance decreases  with  reverse  bias,  with  of  it  increases  deviation  from  this  at v o l t a g e s c l o s e to zero. A p l o t  a s l o p e , such gives  of  vs.  Voltage  gave  t h a t when i n t e r s e c t e d a  value  frequency  Vb  (the  [Mackus, S u l i ,  capacitors, fabricated  glass  annealing  substrates anodization  of  determination  at  of a the  barrier Torok  0.1  of  mm , 2  t h e AC  and  and  s p u t t e r i n g tantalum  then  method, were  by  producing  which  used  in  p r o p e r t i e s of  tantalum  gave a the  finished  experimental  t h e s e . The  effect  the c a p a c i t o r s i n n i t r o g e n at temperatures  250-350 C was improved  s t u d i e d , and  capacitance  temperature the  coefficient  the a u t h o r s  stability,  established  lower  of c a p a c i t a n c e  n i t r o g e n a n n e a l i n g . The  losses (TCC)  metal  films,  of  lower  DC  leakage,  between that  and  was  of  an  better  obtained  deposition process,  M a g n e t r o n E n h a n c e d S p u t t e r i n g (MES), p r o v e d quality  became  1977].  Thin  after  capacitance  the C a p a c i t a n c e  independent  t h a t above a  b i a s the  (voltage) axis,  height), Hevesi,  has  of  found  s l o p e s under  degree  found  i n v e r s e square  relationships  was  and  Capacitance  complex  characteristic  forward  voltage,  the  the  with d i f f e r e n t  i . e . , with  It  forward  law  characteristic.  indicate  frequency.  square  relationship,  I-V  also  under b o t h  inverse  bias,  plots,  and  critical  the  than  to those  give  better  prepared  by  19  the  conventional  Bill  and G e r s t e n b e r g , Capacitors  (TaN), u s i n g been  Diode  sputter  thin  film on  technology glazed followed  deposited  showed  performance  superior  were  treatment and  metal  and i m p r o v e d  Kamei,  properties,  have been  optical  2  l o s s of of  substrates  This  oxide  5  capacitors  the previous  and  dissipation  endurance  [Ooken,  at  t o heat  Ohwada,  Okamoto  nonvolatile formed over  a  surface  acoustic  loss,  refractive  by  1.5-2.0  z i n c oxide  wave  conventional  dB/cm,  a  in a thin  film  index  surface  have  memory  been  waveguide  analyzed  devices.  g l a s s or s i l i c o n  Anodic  wave  l o s s o f 7.0-7.5 on  silicon  incorporate  potential  and  substrates,  o f 2.15, an  1978].  which for  than For  acoustic  made  and R i c h a r d ,  structures,  and g l a s s )  techniques.  refractive  RF  group  indices greater  3500-3700 m/s, and an a c o u s t i c  2  acousto-optic  i s r e p r e s e n t a t i v e of a nitride,  dielectric  and S i 0  exhibits  silicon  [ H i c k e r n e l l , Davis  Double 2  using  had an o p t i c a l  5  dB/cm, when u s e d  Ta 0  These  with  f a b r i c a t e d f o r use i n i n t e g r a t e d o p t i c a l  (namely  Ta 0  velocity  Reactive  oxidation,  TCC  high  also  and c a n be d e p o s i t e d  example,  Lower  reliabilty  w h i c h have low o p t i c a l 2  anodic  a s compared w i t h  with  and B r a g g c e l l s  materials  Si0  successfully  substrates.  by e v a p o r a t i o n .  pentoxide  spectrum a n a l y z e r s . of  also  nitride  1978].  Tantalum  (SAW)  by  capacitors.  obtained,  have  ceramic  counterelectrodes  factors  [Rottersman,  1978].  o f TaN i s  (Ta-oxide)  equipment  made o f a n o d i c a l l y o x i d i z e d t a n t a l u m  fabricated  sputtering  DC  both  use  in  thermal T a 0  is  and t h e n  2  5  aluminium  20  electrodes of  the  insulator  voltage can  be  this  are d e p o s i t e d f o r d e t e r m i n i n g the film.  between stored  the gate  at the  structure  device,  is  the presence  voltage  of  the as  charge  define  conduction  "write" cycle), temperature Only  MOS  usual  of t h i s  the  or  ohmic  threshold  the  the  can  Ta 0 /Si0 2  5  conditions  The  double  2  (i.e.,  fields,  that  be  interface  the d e v i c e .  the  i t i s the  predominates.  i n the e x p e r i m e n t a l  transistors,  3  and  fabricated  have been d e v e l o p e d , e l i m i n a t e d the  anodization  tantalum  the  gate  of  electrode.  temperature  gate  This  coefficients The  relative  resultant  work  [Angle  for  gate  which  insulator  was  oxynitride,  between  constant  w h i c h was  gate  of  transistors  pentoxide which  of masks from  used  as  matched  had  and a  produced  eliminating  [ K a l f a s s and  5  the  insulator  22,  thus  2  developed  produced  tantalum  Ta 0  replaced  frequent cleaning  transconductance,  double  with anodized  combination  anodic  dielectric  devices with high  1979].  of  MOS  of M e t a l - T a { o x i d e } - S i ( o x i d e } - S i l i c o n  the  necessity  state  component  The  high  the  If  in a  memory c e l l of  field  during manufacturing.  electrode.  a  absence  through high  insulator  a  charge  insulators.  affects  Hence,  applying  1978].  insulator 2  charge  logical  were u s e d  film  Al 0  gate  P o o l e - F r e n k e l . At m o d e r a t e  dependent  Talley,  gate  the  capacitors  Thin as  used  as  by  substrate, a  between b o t h  under  (MTOS) s t r u c t u r e and  e l e c t r o d e and  the presence  is,  that  interface  mechanism  dielectric  predicts  transistor.  constructed, can  Theory  characteristics  the  Lueder,  21  Experimental GaAs  substrates  obtained  f o r both  properties  of  interaction similar  pentoxide  showed  that  good  thermal  and  anodic  these  films  the  interaction  oxides.  indicate  on s i l i c o n  due t o l e s s  film-substrate  incorporation  pentoxide  film.  grown films  The  that  p r o p e r t i e s were o b t a i n e d w i t h  T a , as a r e d u c e d  films  insulating  takes p l a c e d u r i n g the thermal  to  insulating of  work o f t a n t a l u m  a  were  optical  pronounced  g r o w t h of  Ta 0 , 2  anodic  of Ga a n d / o r As i n t o  processing was  claimed,  the  tantalum  However,  i t was  not p o s s i b l e  to obtain  capacitance-voltage curves  [Nishi  and R e v e s z ,  1979].  2  developed of  f o r p r o d u c t i o n of l o c a l i z e d  the f i b r e  as  the  interface  implanted The the  bundles  silicon advance to  between  the  of  and  inertness  from  each  w i t h an  overall  the  and e l e c t r i c a l  continous  fluids  of t a n t a l u m  electrical  without  metal  and i t s o x i d e s  was  serves  and  the  prosthesis.  insulated  other  This provided a structure  i n the mechanical  system  system  metal,  by  from  anodically  passivation with  of  significant  stability  required  stimulation  dissolution  MOS  excitation  The a r r a y  an a u d i t o r y c o c h l e a r  pentoxide,  nitride.  survive  nervous  medium  sapphire,  electrical  nervous  e l e c t r o d e s a r e made of t a n t a l u m  formed t a n t a l u m  on  i n the a u d i t o r y nerve.  electronics  conducting  5  5  substrates. Better  interaction  A microelectrode array, using T a 0  on  due  i n the to  the  [May, Shamma a n d W h i t e ,  1979]. Capacitors were u s e d rate  made  with  thin  f o r studying the e f e c t s  of t h e s e . Two  distinct  film  anodic  of h u m i d i t y  failure  modes were  tantalum on t h e  oxide  failure  established:  22  point  breakdown  resulting  from  failures  which  Melroy, A  are  Self  memory  word  line  Random  Aligned  capacitor  the  using  uses which  required  small  at  there  is  they  2  a  is  as  5  a  in realizing 7.4 ixm .  of  was  small  of  Ta 0 .  Heat  2  high  phenomena i n  treatment  permittivity  that  it  integrated  [Ohta,  tantalum  that  at  samples  high  fields  using  conductivity  i s decreased  again. A shift  Poole-  in  anodic  anodic tantalum  takes  o r vacuum, and i f t h i s treatment  However  an anomalous  i n oxygen heat  films  t h e o r y a t low f i e l d s , and  10  second  have  Yamada,  pentoxide  after  minutes  time.  1980].  an i n c r e a s e i n c o n d u c t i v i t y  a  d i d not  circuits  and T a r u i ,  on  current  nor i t s h o l d  reveals that  in  storage  The l e a k a g e  cell,  evidence  of  high  the c a p a c i t a n c e  enough  memory  takes place  the  process.The  A l . The  films,  exceeded  using  stacked  u s i n g t h e same t e c h n o l o g y  experimental  conduction  5  [Adolt  t h e P o o l e - F r e n k e l model p r e v a i l s .  Frenkel 2  Ta 0  obey t h e S c h o t t k y  fields,  (DRAM)  and  line  Nakamura, S h i m i z u  conduction  higher  edge o f t h e  i n t h e c o n s t r u c t i o n o f a 256  512 k b i t s and 1 M b i t  Shiraki,  that  Memory  MOSFET  area  operation  been d e s i g n e d  shows  (QSA)  is crucial  the  Experimental  Access  anodic  affect  The  the exposed  edge  subjected to reverse bias  and t h e b i t  the i n s u l a t o r  Saitoh,  spots  and  1.5 um d o u b l e - p o l y s i l i c o n - S i  through  also  at  was d e v e l o p e d  i s polySi  insulator,  localized  defects,  weak  1980].  storage capacitor kbit  processing  when o n l y  Dynamic  Quadruply  by r a n d o m l y d i s t r i b u t e d  material  counterelectrode and  caused  place time i s  in  oxygen,  the  from  t h e anomalous  23  Poole-Frenkel changes to  into  were  trap  the  attributed  density  ratio  [Matsumuto, S u s u k i A  new  rather  n o r m a l one  and  kind  novel  of  gate  the  MIS  insulator  semiconductor instability slow d r i f t is  an  density  and  donor  level  energy  i n the  in  film  a  a  by  over  (TFT)  was  organic gun  However, weeks of  o v e r a CdSe f i l m ,  device  fabricated,  deteriorated  the  in a  few  days  Vos  The a  Te  caused  interface.  quite  [De  to  showed  fabricated  w h i c h was  on  by  This  with  the  instable and  a of  insulators.  semiconductor  same p o l y m e r  film  evaporation  p r e v i o u s TFT  uses  fabricated  the  been  that  polymer  teflon)  electron  the  device  thin  using  insulator-  improvement  transistor  (i.e.,  few  the 1980].  insulator,  substrate. after  These  donor  thin  applied  observed.  i n the  structure  was  then  to v a r i a t i o n s  Yabumoto,  polytetrafluoroethylene study  is  and  Hindryckx,  1980]. The  optical  o x i d e s have silicon The  been  substrates  oxidation  time  and  electrical  determined by for  the  by  examination  and  Delta  as  a  had  a  function very  complete c o n v e r s i o n further  change  annealing contrast  by  slow  tantalum  of of  the  and  rate  slow  After of  to  in dry  a  transition  thermal  films  I-V  be  on  methods.  oxygen  was  parameters  Psi  amount,  indicating  o x i d e had  that  a  taken p l a c e .  Any  attributed  to  in stoichiometry.  Revesz et  layer,  Ta  certain  change,  changes  w i t h a p r e v i o u s work by index  and  ellipsometric  time.  from m e t a l  films  of the  C-V  in these parameters could  effects  refractive  analyzing  ellipsometric,  obtained  they  properties  al.,  represented  a  In  tapered by  five  24  layers  o f 1.5 nm t h i c k  refractive  index  indicated  the  flatband,  was  through  found,  the oxide  presence  of  a  instead  The I-V c u r v e s  is  typical  of  the  negative  oxide  dielectric  pentoxide  films  curves  charge  at  constant  of  r e v e a l e d a two s l o p e S c h o t t k y  tantalum  graded  t h i c k n e s s . The C-V  h y s t e r e s i s and a r e l a t i v e  26.  of  plot,  [Smith  which  and Young,  1981]. Metal-Insulator-Metal for  ( L C D s ) . A MIM d e v i c e , u s i n g T a 0 2  was o p t i m i z e d  for this  s p u t t e r e d metal program Frenkel MIM  was  Miner films  are important,  wide  range  (less  than  substrate.  the parameters  of  nitrogen  for  and S t r e a t e r , prepared  refractive  doping  better  since this  anodizing a A  computer  i n the Poole-  with class  index  C0  laser  produces  to  2%. T h i s d e c r e a s e  a decrease  process  exposed t o i n t e n s e l a s e r permittivity  of  the  from  radiation.  tantalum  the  enhanced  the  [Baraff,  1981]. tantalum of  with  thin  pentoxide films  to  over  has  low p r o p a g a t i o n Irradiation  i n the r e f r a c t i v e  i s considered  crystallization  of  multiplexing  1 dB/cm a t 633 nm w a v e l e n g t h ) .  a  5  as the i n s u l a t o r ,  5  by p a r t i a l l y  glass  to determine  parameter  Waveguide  Ta 0  a  .Furthermore,  Long, M a c L a u r i n ,  2  on  Crystal  c o n d u c t i o n model t o o p t i m i z e t h e p e r f o r m a n c e  switch.  2  application,  film  used  conductivity  2  developed  use a s n o n - l i n e a r d e v i c e s i n m u l t i p l e x i n g L i q u i d  Displays  Si0  (MIM) d e v i c e s have been  be  a  loss using  i n d e x , up  related  to  i t s amorphous s t a t e ,  the when  This i n turn a f f e c t s the  oxide  [Terui  and  Kobayashi,  1981]. Bismuth oxide  i s another  insulator  material  that  has  25  been  used  in  Semiconductor reactive  for  (MIS)  yielded  (loss  production  hysteresis When  produces  its  [Lalevic  tantalum  films  are  sputtering,  cell  kHz,  a stress  It  was  large  in  the  changes  recombination  making  with  field  gate  and  circuit  Murty,  insulator  o x i d e had  low  required  hysteresis  GaAs  of  found  Ateff,  InP,  C-V  was  curves small  silicon  as  fill  which  d e v i c e was  effect  induced  stress  the the  used  stress  carrier  diffusion  recombination short  factor  anodically  state  o r I-V in  circuit  were  oxidized  reduced  mm. 1500  The  a gate  to  2  of h i g h q u a l i t y  The as  r e p o r t e d , and  the  reduce  C-V  estimated  the 500  oxide  um  and  electron  Uemura,  Integrated  tantalum  form  used  [Yamamoto and  Microwave  t o be  l e n g t h of  measured  cm /Vs for  d a t a was  to  mode d e v i c e .  density  order  d e v i c e had  technology  (MICs) makes use  C-V  i s induced,  the  minority  v o l t a g e and  annealing  was  and  useful  over  the  that  t i m e , as w e l l  interface  No  2  The  3  it  relatively  i n a MOSFET a c c u m u l a t i o n  l o o p . The  width  2  1981].  enough  insulator.  mobility,  to study  c a p t u r e c r o s s s e c t i o n . Moreover, open  Bi 0  c o n s t a n t of 25,  deposited  in order  Indium p h o s p h i d e ,  a gate  i n a i r . The  by  1981].  performance.  current,  oxide  35  deposited  frequency c a p a c i t o r s .  Talwai,  and  and  gate  was  annealed  i n the n e g a t i v e d i r e c t i o n  by  Metal-Insulator-  film  dielectric  of 0.002 a t low  of  a c u r v a t u r e of t h e s u b s t r a t e . A MIS  produced  an  The  later  a relative  of  as a p h o t o v o l t a i c  time  and  [ R a j u and  substrates  length  capacitors.  factor)  show a s h i f t  in  fabrication  ion sputtering  capacitor a tan5  the  1981],  Circuits capacitors  26 i  in  interstage  capacitor they  of  microwave  has a M e t a l - I n s u l a t o r - M e t a l  were  integrally  insulating by  coupling  sputtered  and  150 nm,  a relative  factor  (tan5)  exponential  patterning.  Typical  dielectric  with  o f 0.03 a t 1 MHz.  relation  Anodization  with  applied  merit  permittivity  and  erE,  the  formed  capacitances  i n the  t h i c k n e s s of  o f 20-25 and  a  loss  current  had an  [Elta,  Chu,  voltage  1982],  o f a l u m i n i u m has a l s o p r o d u c e d  o f 30 pF, and a r e l a t i v e of  on t h e s e m i -  i s then  The l e a k a g e  f o r MIC c a p a c i t o r s , i n t h e form o f  quality  and  an o x i d e  constant  C e r r e t a n i and C o u r t n e y ,  figure  structure  (MIM)  (reactively)  r a n g e o f 50-200 pF were o b t a i n e d ,  value  The  GaAs s u b s t r a t e . A s t a i r c a s e shape  lift-off  Mahoney,  amplifiers.  Al 0 , 2  the  product  dielectric  with  3  dielectric  a  constant of  strength,  i n t e r m s o f b a n d w i d t h and a r e a  dielectrics typical o f 8. The  the  relative  indicates  f o r a given  the  material  [Binet,1982 ] . Further a two s t a g e 2.8 GHz  of  these  Ion  an i n s e r t i o n [Chu,  and D o n n e l l e y , Sensitive  fabricated  process  2  with  with  pentoxide  Field  SOS  loss  Mahoney,  i n t h e 1.2 t o  elements,  produced  a  good q u a l i t y  i s quite  capacitance dielectric  o f 1 dB a t 16 GHz Elta  Courtney,  for  a  Finn,  1983]. Effect  (silicon  as gate  operating  as c o u p l i n g  1500 pF/mm , and a v e r y  capacitor  Piacentini  MIC c a p a c i t o r s i n d i c a t e s t h a t  5  IF a m p l i f i e r ,  The r e a c t i v e MIM  pF  tantalum  2  monolithic  was o b t a i n e d 29  i n the T a 0  r a n g e and u s i n g  feasible. density  work  Transistors  on s a p p h i r e )  insulator  produced  (iSFET's),  technology the highest  and pH  27  sensitivity have  a  among t h r e e  metal  which they making  very  useful  It  s o l u t i o n pH, was  as  concluded  sensing  with that  [Akiyama, U j i h i r a ,  by  the  The  2  f i l m s are  a  the  Niki,  substrate  solution  and  i n the  of  a  CH  suitable  ion FET  bond  using  many  [Pitt,  Further substrates the  oxide  of  a high the  1983;  analysis  show t h a t depends  tantalum  metal  reduced,  less  be  by  film  L-B  l a y e r not  dielectric  a i r . The  relative  A  techniques only  breakdown  is  Roberts,  Ta 0  5  the  silicon  residual  evaporation. of  2  As  silicon  the is  film  as  an  ideal  gate  silicon  incorporated  vacuum  and  1983]  f i l m s on  pressure  gate  pinhole  strength  and  on  choosing  thin  Lloyd,  amount of  acid,  aqueous  of  thermal  an  aluminium fatty  characteristics  of  from  substituting a divalent  L-B  Petty  layers,  s e l e c t e d by  and  the  amount  measurements  i n the  hydrophilic termination.  d e v e l o p e d . The  a l s o has  insulator.  l e n g t h and  amorphous s i l i c o n was  but  exhibits  chain  2  f o r f o r the  insulator free  s u c h a m o l e c u l e can  and  suitable  (i.e.,  immersed  permittivity  most  i s a simple  end  gate  5  seconds.  molecule  a hydrophilic termination hydrophobic  2  molecular  w h i c h has  a  Ta 0  1982].  single  molecule  in  electrode,  few  activity  a amphiphilic  polar  amphiphilic  was  not  voltage  t i m e of a  hydrogen  of  gate  between o u t p u t  film  5  do  electrolyte  d e t e c t o r s . The  Okabe Sugano and  removal  the  response  Ta 0  for  aqueous s o l u t i o n w i t h oxide).  90%  the  Langmuir-Blodgett formed  pH  relation a  material  as  ISFETs  i t i s the  immersed w h i c h a c t s as  ISFET e x h i b i t s a l i n e a r the  dielectrics.  g a t e e l e c t r o d e , and  are  them  other  during quality  incorporated  to  to the is the  28  oxide. Also, constant Si  i t was f o u n d  and  interesting  dielectric producing  layer,  substrate  quality  2  dielectric  a s t h e amount of  [Hasegawa, Ogawa,  of  Si  fabricated  i s based  Wada  and  of  this  Nakamura and I s h i k a w a , A thin  film  Sputtering channel  was u s e d threshold  to  Ta 0 2  5  layer.  Ta  Si. A  and  and a h i g h  thus  avoiding cell  Ito,  (TFT) w i t h tantalum  deposited  by  being developed.  and d r a i n  fabrication  of  625C,  fused  quartz  Magnetron  tantalum pentoxide  is  Taguchi,  Enhanced  The d e v i c e has a psubstrate  the  Ta 0 . 2  compatible  [Seki,  and  Al  r e g i o n s . R e a c t i v e Ion E t c h i n g (RIE) 5  The  device  o f t h e d e v i c e a l l o w e d a maximum  which  was  pentoxide as  exhibits  v o l t a g e o f - 2 . 5 V and a t r a n s c o n d u c t a n c e  The  silicon  interfacial  memory  [Kato,  dynamic  of a  The  produced,  with a  pattern  for a VLSI  for  1983],  has r e c e n t l y  source  developed  i n the o x i d a t i o n  technique  and  structure,  was  i s then  transistor  insulator  2  heteromorphic  p l a c e by wet o x i d a t i o n ,  dielectric  using  Si0 ,  storage capacitors  takes  oxidations  f o r growing a  over  5  covered with a thin  double  separate  Ta 0  technique  oxidation  doped  film.  technique  high q u a l i t y  The  gate  relative  1983].  An  RAM.  the the  the leakage c u r r e n t decrease  i n c r e a s e s i n the oxide  Nakano,  that  with  glass  a  o f 70MS.  temperature  s u b s t r a t e s and  Unagami and T s u j i y a m a ,  1984],  29  CHAPTER 3  THE THEORY OF THE T a 0 - S i 0 2  DIELECTRIC  Considerable dielectric  amount  insulators,  Nitride-Oxide-Silicon such  as  of  work were  dynamic  (1969),  and  the  MNOS a n d MTAOS b e h a v i o u r They  immediately  above t h e s u b s t r a t e .  similar,  devices  and  could  also  which had s u p e r i o r The  double  structure on  large  has  be  (1976)  (EPROMs). The and  Scott  ( 1 9 7 0 ) . The  importance, as  layer  established  not  of S i 0 , 2  performances that  MTAOS  t h e MNOS  Ta{ox}/Si{ox}  memory  technology, device. dielectric  as a r e s u l t of i n v e s t i g a t i o n s films  for applications  1976], memory d e v i c e s  1978] a n d more r e c e n t l y Random A c c e s s M e m o r i e s  in  s i m i l a r , although  f a b r i c a t e d using  been d e v e l o p e d  devices-  cells  The e l e c t r i c a l  permittivity insulating thin  Talley,  Metal-  Wallmark  c h a r a c t e r i s t i c s over  [Angle,  the  static  i n common a t h i n  heteromorphic  i n MOS C a p a c i t o r s  dynamic  have  Angle  double  i n memory  have g r e a t  i s quite  identical.  are  by  in  Frohman-Bentchkowsky  aspects of t h i s device  also  on  Read O n l y Memories  was s t u d i e d  theoretical  done  based  and  MNOS Memory T r a n s i s t o r (1969)  was  (MNOS) s y s t e m - u s e d  Programmable  Ross  DOUBLE  2  STRUCTURE  which  non-volatile  Electrically  5  [Angle  and  s t o r a g e MOS c a p a c i t o r s f o r  o f VLSI p r o p o r t i o n s  [Ohta  et  al.,1982]. Generally (MDIS)  speaking, structures  theMetal-Double have  similar  Insulator-Semiconductor properties,  namely  a  30  dissimilar  field  electronic certain  distribution  conduction  conditions,  a charge  1)  i n double  insulator,  (emission)  S e v e r a l a r e a s of common research  i n each  insulating  The LSI and VLSI  mechanisms  retention  interest  different  o r memory  and  effect.  to microelectronics  structures  densities  under  and t h e  are i d e n t i f i a b l e :  require  increase^device  sealing. 2)  Further  o x i d e s and 3)  Device  scaling  scaling  to insulator  4)  Insulators  in  decreases  devices  requires  thinner  the  maximum  gate  voltage  breakdown.  of l a r g e  capacitance  most  MOS  insulators.  due  required  in  cases  an  dielectric  constant  in proportionally increase  in  produce the  less  leakage  area, current  but is  observed. 5)  Breakdown o f a t h i n  if  a larger  itself 6)  and t h e g a t e  be  high  7) of  dielectric  constant the  Dioxide,  w i t h a breakdown  permittivity level  insulator  with  of S i l i c o n  dielectric  oxide  of leakage  In t h e double pinholes  negligible,  down o x i d e c a n be a v o i d e d is  placed  between  electrode.  combined  properties  low  permittivity  The l a r g e  can  scaled  of Tantalum excellent  Pentoxide insulating  thus producing  voltage  thickness,  governed  a double by  the  while maintaining a  current.  insulator coinciding  structure, in  the  thus producing a b e t t e r  the same  quality  probability location  is  insulator.  31  8)  Amorphous S i l i c o n  it  has h i g h  of  alkali  has  permeability ions.  dielectric  9)  i s s t r u c t u r a l l y p o r o u s and  t o water v a p o u r and  The  application  reduces these  a much d e n s e r  migration  Dioxide  effects.  structure,  of  migration  a second  Tantalum  possibly  outer  Pentoxide  retarding  the i o n  through i t .  Double d i e l e c t r i c  stuctures  hence t h e y c a n be u s e d  as  e x h i b i t memory e f f e c t s ,  memory  cells  if  properly  designed.  In  this  work,  o u r main e f f o r t  development  of  applications  as opposed  DRAMs.  a  The MOSFET  pentoxide-si1 icon Tantalum{0xide}structure.  Ta 0 /Si0 2  that  dioxide  gate  inner  electrode.  Figure  is  insulator  3.1 g i v e s t h e main  features  and t o a l e s s e r d e g r e e ,  (gate) e l e c t r o d e  5  al.,  1964; G r o v e e t a l . , 1965; G r a y ,  Of transport  MTAOS  above t h e  the gate  contact  of such a double shown. The  the T a 0 2  5  and S i 0  2  t h e i n t e r f a c e between t h e  Si0  analyzed  and the s i l i c o n  tantalum  or  and d i m e n s i o n s  the  2  device,  section  and t h e T a 0 . 2  MOSFET  i s termed a M e t a l -  i s below  a cross  the  immediately  a r e a s a r e t h e i n t e r f a c e s between  insulators top  insulator  for  i n the  f o r e i t h e r RAMs o r  incorporates  insulator  and t h e o u t e r  critical  t o a memory c e l l  device  substrate,  with  insulator  2  Si1 icon{Oxide}-Si1 icon  The  dielectric,  5  i s concentrated  substrate  The  interface  i s well 1969]  between  known [Grove e t and  i t  i s not  here. great under  importance steady  i s t h e p h y s i c a l model  state  and t r a n s i e n t  forcarrier  conditions.  The  Gate Contact  Substrate The Al-Ta 0 -Si02-nSi Structure 2  5  gure 3.1 The General Double D i e l e c t r i c Structure  33  differences exact  i n the c o m p o s i t i o n  analysis  transient  case.  insulator  that  transport electrode  limited  [Lenzlinger  and  the  is  insulator  [Mead,  low, is  1962;  is  Angle,  example,  ( a s compared w i t h  anomalous P o o l e - F r e n k e l oxide  seems  thermal  to  tantalum  oxide  on  explained  this  complex  positive  gate  bias,  under  negative  determines formed a t effect  the  the  lowering  conduction  emission  of  of  Ta 0 ,  the  Poole-Frenkel  type  and  by  n o r m a l P-F  current  the  takes  2  5  1978],  density  p l a c e , but  more  by  charge  tantalum  interface.  potential  barrier,  the  Angle  (1976)  that  under  takes  limited  or  behaviour,  observing  conduction  is  if it  compensated  complex  place,  but  conduction  to surface s t a t e s The  increase in e l e c t r i c a l  the Coulombic  5  e x i s t e n c e of  trapping  flow, a t t r i b u t e d  the A l ( g a t e } - T a 0  2  Talley,  the a p p l i e d b i a s .  behaviour  space  into  c o n s i d e r a t i o n s , however a  be  conduction  dominates. Anodic  these  sign  r e p r e s e n t s the  Angle  i f the  exhibits  bias  by  to  the b a r r i e r  t h e donor d e n s i t y ) ,  follow  depending  1976;  current  emission  of  case  limited  the  f o r the  established  type  influenced  normal P o o l e - F r e n k e l  high  This  band. In t h e  greatly  c e n t r e s . For  been  double  however,  dominant  t u n n e l i n g through  bulk  the  Fowler-Nordheim  1969].  is  for  i s a p p l i e d to the  d i o x i d e . The  to  by  the  are q u i t e d i f f e r e n t  has  2  due  conduction  emission  trapping  for S i 0  caused  transport  it  silicon  makes  particularly  c u r r e n t s flow,  these  Snow,  carrier  although  voltage  conduction  and  mechanism  mechanism  a  governs  pentoxide  each d i e l e c t r i c  complicated,  When  structure,  mechanism tantalum  quite  of  Poole-Frenkel c o n d u c t i v i t y by  when i t i n t e r a c t s  34  with  an  electric  carriers  field.  Space c h a r g e c o n d u c t i o n  injected into  compensation  charge  Considering  the  contributions  the  by  v i r t u e of  currents  expressed  as:  W  -t-  d  W  the  5  Ta 0 2  are Si0  thicknesses;  in  insulator  term  j t ( z ) i s the  pentoxide, the  conduction  determined the  given  by  2  +  and  and the  conduction by  the  In  the  can  be  along  current  V  no  current  - i -  Si0  theorem,  i n s u l a t o r s can  2  j  t  (  z  )  d  z  the be  O. la)  )  rs J  °  j  s  (  z  )  d  z  constants; are  the  (3.1b)  )  s e c t i o n areas;  Vs  density  et and t and  s are  resulting  density effect,  i n the  a current  time.  i n the and  the  The  tantalum js(z)  is  dioxide  and  dependency  on  silicon  t u n n e l i n g . The  are  voltages  variable r represents current  es  density  distribution  axis.  Poole-Frenkel expressed  fo  density  Fowler-Nordheim  that  -r  Poole-Frenkel  v a r i a b l e z i n d i c a t e s that  exists  is  4-  n  +  cross  Vt  and  5  dielectric  2  insulator each  Ta 0  dV  the  conduction  1  s^37f  and  there  Ramo-Shockley  1 -  ITdT e  As  V  and  the  f o r the  C  and  where  from  present.  displacement  terminal  Where At  insulator  results  emission,  the  current  density  as:  c  f t E  P  e x p (  " iJ-tV^V^i^  (3  -  2)  usually  35  Where E t i s t h e e l e c t r i c $  field  represents  i n t h e t a n t a l u m p e n t o x i d e and  the  quantity  the b a r r i e r  For  the Fowler-Nordheim emission,  height.  the  current  density  is  expressed as:  J  Where  Es  is  characteristic mass  and  current  in  E e x p ( - E /E ) fn s ^ o s  the  field  constants  in  \  the  silicon  3.3)  dioxide.  C f n and Eo depend on t h e  height.  Notice  that  functions  effective  of the a p p l i e d  i n s u l a t o r s t r u c t u r e , an e l e c t r i c  voltage field  the  insulators  shall  displacement  the  field. Va  to  i s created  i n d i v i d u a l i n s u l a t o r . G a u s s ' Law p r e s c r i b e s of  The  i n both cases,  upon t h e a p p l i c a t i o n o f a g a t e  continuity  o \  /o  2  d e n s i t i e s are strong  double each  =  barrier  Furthermore, the  s  that the  D a t t h e i n t e r f a c e between  be m a i n t a i n e d :  O. '"X  e.E^ - e E = t t s s  (3 4) 0  Qi the the  i s the charge per u n i t area voltage total  drops across  applied  each d i e l e c t r i c  voltage.  s e m i c o n d u c t o r work f u n c t i o n  V = - t E ^ -sE a  t  a t t h e i n t e r f a c e . The sum  s  Then,  considering  0ms, we  +  y  lb  s  +  T  h a s t o be e q u a l the  have:  <b  ms  (3 5)  vo.jy  of to  metal  36  The  silicon  surface potential  conventional  definition  i s r e p r e s e n t e d by  of p o t e n t i a l  difference  \ps and  the  (drop)  is  used. Finally,  the  electric  charge  has  t o be  conserved  at a l l  times:  (3.6)  In g e n e r a l , an dielectrics, interface  interface at  the  charge  structure,  charge  interface.  upon t i m e  can  be  Equations  3.4,  3.5,  emission  and  the  Qi w i l l  and  F-N  The  by  and  of  the  i n the  both  of  this  insulating  simultaneous  considering  mechanism  between  dependence  geometry  obtained 3.6,  appear  solution  the  P-F  Si0 ;  not  2  of  Ta 0 2  an  5  easy  task!  {3.1}  STEADY STATE ANALYSIS: The  current for  different  c o n d u c t i o n mechanisms r e s p o n s i b l e f o r t h e  t r a n s p o r t i n the S i 0  creating  an  accumulation  between d i e l e c t r i c s . field,  caused  following  by  Upon t h e the  Ta 0 2  d i o x i d e and  place  in  different,  the  of c a r r i e r s application  gate  following  pentoxide.  at  the  cause  at the  interface  of  external  takes  an  conduction  place  in  the  Poole-Frenkel  takes  These  quite  create a current discontinuity,  accumulation  the  voltage, electronic  conduction tantalum  are a l s o  5  the Fowler-Nordheim e m i s s i o n  silicon  charge  and  2  which  interface.  being  leads to This  a  charge  37  accumulation, distribution, The  in  turn,  until  current  solution  the  electric  field  the  charge  at  conditions, therefore, substituting  the  currents  Js  at  E t and E s , a s w e l l  Qi. and  in  Under  Jt  steady  are  as  state  equal,  and  Equations  3.4  and  3.5  Es i n t h e S i 0 : 2  (V  )/s  -<J>  2—§—ms  E = s  gives  t h e i n t e r f a c e i s n e g l i g i b l e . By  conditions  the f i e l d  field  by s t e a d y s t a t e a n a l y s i s  interface  charge  electric  continuity i s established.  obtained  these  a b o v e , we o b t a i n  the  i n each d i e l e c t r i c  both the  adjusts  . 1 + _t  3  ? )  e s_  e  s  t  (3.8) 1 +  This  last  electric thickness es=3.8,  equation  field  represents  the  reduction  i n the S i 0  2  due t o t h e a d d i t i o n o f a s e c o n d d i e l e c t r i c o f  t and r e l a t i v e p e r m i t t i v i t y e t .  Using  et=27, s=200 A, a n d t = l 0 0 0 A, a r e d u c t i o n  values  of  f a c t o r of  0.587 i s o b t a i n e d . By  s i m i l a r r e a s o n i n g we o b t a i n  E,t =  the f i e l d  Et i n the T a 0 : 2  F~~  5  (3.9)  1 + -2  On t h e o t h e r h a n d , i f t h e i n t e r f a c e c h a r g e Q i  is  non-zero,  38  the  internal  calculated For  electric  fields  i n each i n d i v i d u a l  the T a 0 2  due  to t h i s  c h a r g e , can be  dielectric:  insulator:  5  e E = °  For  the S i 0  2  s s  o  1 e. + t  E =  TRANSIENT  +  insulators  will  (V  =  o f change  at  solution  this  the  detailed  t  ms  e.t  of a sudden v o l t a g e a t certain  fields  f l o w as p r e s c r i b e d  J 4 v_ ( V .T T )  V a' '  the  gate,  applied  and  b e f o r e . The  Law  that:  -  J  u  variables  V  (3.12)  be  density  directly for  g a t e v o l t a g e and t i m e .  differential  c a n be o b t a i n e d  c o n d u c t i o n mechanisms  ,T)  T ;  charge w i l l  i n current  a given applied partial  (V  " s^ a'  i n the i n t e r f a c e  t o the d i f f e r e n c e  dielectrics,  independent  +<j> )  ,T.) Ct  dT  to  s  of C h a r g e r e q u i r e s  X  proportional  - J -  have  currents w i l l  Conservation  rate  t t  — £ - ( I Jr J  ANALYSIS:  Upon t h e a p p l i c a t i o n  The  +  (3.11)  es  dQ  o  +  s  of  (3.10)  /  I  conduction  ms'  insulator:  Q./e  both  v  t —=— e s s  £  {3.2}  s  Y  equation  of  both The two  i f more i n f o r m a t i o n of  is available.  F o r example  39  Ross  and Wallmark,  a MNOS s t r u c t u r e , the  interface  between d i e l e c t r i c s ,  of  silicon,  when a f i e l d  level,  the  donor  derivation,  tunneling  insulator.  These  transferred applied  solution  E =  fc  duration  E =F 8  fact  ms  instant Then  g i v e n by:  if  the  )  Q  i  / £  general  the  on t h e  on  charge  electric  the  +  £  ± / e  is  varying  o  —  °  isa  fields:  (  t  3.4  time  3  <  1  3  )  s  °  -  + s  for  Equation  +  a-V*ms> 5  composite  relation  the i n t e r f a c e  insulator  e  (3.14)  -§- e. + e t  Qi=Qi(Va,t)  of gate v o l t a g e  the  that  3.5,  +  relation  the  trap  through  exponentially  v o l t a g e and t i m e ,  s  their  gate p u l s e .  f o r both  t — —  Where t h e  and  in  be  logarithmically  s  (V  states  to  depended  that  Equation  a  assumed  a  (V -U, -«  t  the  t h e y assumed a m o n o e n e r g e t i c  obtained  the  i s found  In  authors  of a p p l i e d in  with  trap  of the a p p l i e d  substituted  communicate  to the s t r u c t u r e .  was  at  of t r a p p i n g  between  pulse  Considering function  b e h a v i o u r of  as a f u n c t i o n  which  transfer  charge,  gate  amplitude  type  i s applied  and t h e c h a r g e  direct  the t r a n s i e n t  and e x p l a i n e d , t h e c o n d u c t i o n mechanism  centres  mathematical  studied  (1969)  t  is  s  valid  for  t>to,  the  application.  c o r r e s p o n d i n g v o l t a g e s a c r o s s each  d i e l e c t r i c are  40 (V  -<J> )  -Til  (3.15) {1  s t  +  e  }  {e / s +  e /t> t  s  (V -ip -<J> ) a s ms r  V = s {1  Very  little  f o r Equation  case  and  tunneling  transition  analyzed  Following  by  the  obtaining  filled  last  no  details.  trap  a  i  o  o  The  function  and  X i s quite  close  In  the case  of  knowledge  are  at  i n a better defining  using  rectangular  i  (3.17)  o  r a p i d l y t o zero  f o r t>to,  t o 1 Angstrom.  the composite  h a s t o be  mechanisms 3.12  E i ( - t / t o ) converges  a MNOS  we h a v e :  Q (x)=qXN (x ,0){0.5 7 7 + l n ( t / t ) - E ( - t / t ) } i  Ross  states  through  authors,  term  a computer  a solution considering  probabilities  these  f o r the  Frohman-Bentchkowsky  3.12, b u t he g i v e s  (1969) o b t a i n e d  structure  on a s o l u t i o n  conditions.  t h e MNOS  Wallmark  barrier.  published  under t r a n s i e n t  analyzed  solution and  t s  +  h a s been  Qi=Qi(Va,t) (1970)  (3.16)  +  acquired  dielectric  of  the  the i n t e r f a c e , i n order way. Once a g a i n ,  the o v e r a l l behaviour  the  Ta 0 -Si0 , 2  intimate  5  2  conduction  to evaluate interface  o f a MDIS  more  Equation properties  system.  41  {3.3}  EFFECT OF THE DOUBLE DIELECTRIC GATE INSULATOR ON THE  MOSFET  PERFORMANCE:  In  the  insulator  double  insulator  structure,  an  equivalent  t h i c k n e s s d i c a n be d e f i n e d :  e d  s = s + — — t  ±  T h i s c a n be v e r i f i e d in  series,  (3.18)  by c o n s i d e r i n g t h e c a p a c i t o r s C t and Cs  and c a l c u l a t i n g  the t o t a l  capacitance  C : T  C C, s t C  =  T  (3.19) C  Also,  an  reflects  + C. t  s  equivalent  capacitance  the combination  of both  Ci  per  dielectrics  unit  area  c a n be  that  written  as: s o C.  =  (3.20) d . a.  Therefore, gate  the t o t a l  insulator  capacitance. This represented of  capacitance  is  less  per unit  than  i s quite obvious,  each  per  unit  area  i n the double  single  insulator  as t h e i n s u l a t o r s  by two c a p a c i t o r s i n s e r i e s ,  capacitance  area  each w i t h  corresponding  c a n be  a to  value each  dielectric. Of  interest  are  the  equivalent  capacitance  to  Si0  2  42  capacitance  ratio: C. C  This  ratio  compared values  of s=200 A,  reduced,  the  e  s  the  the s i l i c o n  0.587. T h e r e f o r e ,  same  1 +  s  represents  with  t  (3.21 )  s  e  t  reduction  in  capacitance  dioxide capacitance.  t=1000  A,  es=3.8 and  as the e l e c t r i c  field  equivalent capacitance  For  as  typical  et=27, t h e r a t i o i s across  the  Si0  2  is  i s a l s o r e d u c e d by t h e  factor.  Conversely, the  an e q u i v a l e n t p e r m i t t i v i t y  capacitor  units.  From  is  considered  to  can  have  the e q u i v a l e n t capacitance  be  defined,  if  a t h i c k n e s s o f t+s  expression,  Equation  3.20:  C. = 'i  t+s  s +—  e — t  (3.22) t  e  Then, t h e e q u i v a l e n t p e r m i t t i v i t y  ej  ,  =  t+s  s/e  g  (3.23)  +t/e  t  A g r a p h of i t s f u n c t i o n i s shown curves for  given  for different  a large ratio  permittivity  c a n be d e f i n e d a s :  insulator  of i n s u l a t o r  approaches  in Figure  that  with  several  compounds. N o t i c e  thicknesses, of  3.2,  the  the  outer  that  equivalent (and l a r g e r )  43  insulator The  dielectric  constant.  f o l l o w i n g Equations  using  thes i m p l i f i e d  d  x  Notice  that  define  model  "TT ^ i c  =  {  the operation  insulator  The  threshold voltage  V  a  MOSFET,  [ S z e , 1969]:  (  V V  v  d  -  *a  I d , the d r a i n c u r r e n t ,  the  of  v  <- >  }  3 24  i s proportional to C i ,  capacitance.  T  =  2  *b  +  V  i s given by:  fb  +  ^A,D( V 2  { 2 £ S  } %  / i „ C  O  R  l  IcT  Notice  that  thethreshold voltage V ^  t o C i , which  = —  x  device  (3.26)  d.  transconductance i s :  L1-uC.Vj. i d  Which In  i s directly  the case  slightly  related  i s i s given by:  C.  The  i s inversely  more  of  (3.27)  proportional to C i . the channel  complicated:  conductance,  thes i t u a t i o n i s  44  CP cn  CM cn  CM  >-  ri >  -  Zr0 e =30 Ta 0 e=27  tTM-  2  r  ri  2  a. LU  r  ru-  2  5  *=» «=*  cr. > n «3  -  e =8 A l 0 r  2  er «I r  S i  3N4  r=6 A l 0 2  a .00  S-00 RflTID  10.00 DT  IS.00  INCULPTDR  £0.00  ZS.00  THICKNESSES  Figure 3.2 Equivalent P e r m i t t i v i t y of a Double Insulator Structure  3  3  50 . 0 0  45  g  The c h a n n e l since Based  d  =  -E-  y  C  i  (  conductance  V  " V  g  (3.28)  remains  approximately  C i has i n c r e a s e d , but V h a s T  on  obtained  the using  above r e a s o n i n g , the S i 0  same,  decreased.  Table  insulator  2  the  3.1 g i v e s t h e r e s u l t s  c a p a c i t a n c e as r e f e r e n c e .  TABLE 3.1 DOUBLE DIELECTRIC MOSFET PARAMETERS Tantalum  Pentoxide  on S i l i c o n  Dioxide  t/s=5.0  t/s=2.0  t/s=1.0  Idi/Ids  0.587  0.780  0.877  V i/V s  = 1 .704  =1.282  =1.140  Ci/Cs  0.587  0.780  0.877  gmi/gms  0.587  0.780  0.877  gdi/gds  =1  =1  =1  i ' refer  to  T  T  The s u b s c r i p t s s ' x  equivalent of  insulator  the tantalum  and  x  parameters,  pentoxide  the  Si0  2  and  t and s a r e the t h i c k n e s s  and s i l i c o n  dioxide,  respectively.  46  Notice  that the channel  constant  as t h e r a t i o  conductance  t/s i s varied.  insulator  capacitance  diminishing  t / s . The g a t e  is  gd r e m a i n s  and  drain  The  increase  threshold voltage decreases  with as t / s  reduced.  MOSFET  which  has  of a s i n g l e  high  relative  i s valid  exception  t h a t the r e l a t i v e  o f et t o es i s t h e n  nitride  2  dielectric  ON  THE  oxide,  t h e same  previous  relations,  with the  of the T a 0  these  2  values  5  the  7.11.  quantities,  as comparison,  of gate  constant  i s 3.8. U s i n g  f o r tantalum  (er=7.6) and a l u m i n i u m  insulator  layer  f o r t h e MOSFET d e v i c e  27, and t h a t o f t h e S i 0  calculated  dielectric  permittivity,  reasoning  ratio  INSULATOR  PERFORMANCE:  In t h e c a s e  The  transconductance,  current  {3.4} EFFECT OF A HIGH PERMITTIVITY GATE  is  approximately  oxide  pentoxide,  (er=8) u s i n g  a r e shown i n T a b l e  3.2.  silicon  the  Si0  2  47  TABLE  3.2  SINGLE DIELECTRIC MOSFET Tantalum  Pentoxide,  Silicon  Ta 0 /Si0 2  5  2  et/es=7.11  PARAMETERS  N i t r i d e and A l u m i n i u m  Si N / S i 0 3  a  en/es=2.0  2  Al 0 /Si0 2  3  ea/es=2.11  7.11  2.0  =0.141  =0.500  Ci/Cs  7.11  2.0  2.11  gmi/gms  7.11  2.0  2.11  gdi/gds  =1  =1  =1  Idi/Ids  2  2.11  =0.475  Oxide  48  It  quite  insulator  as  remaining  gate  voltage  and  is  conductance The  reduced  of  v o l t a g e and of m e r i t  c erE,  same  largest.  bandwidth The  circuits effects  due  system  is  to p a r a s i t i c  i s t h e maximum  Binet  Table  several  widely  field  insulator  has  the  aluminium  oxide  The  use  structure design 5  3.3  used  (breakdown)  silicon  can  in  (breakdown)  storage  it  is  factor  based  fact  that  the  ratio for  impedance  voltage. figure which  The  figure  the  on best  er/t is coupling shunting with  of  tantalum merit,  Following  of m e r i t the  by  for  maximum pentoxide  followed  by  nitride.  single  transistor  insulator  the  applied.  o b j e c t i v e s . In t h e o r y , gate  the  i s s m a l l compared  applied  gives  highest  of e i t h e r  i n a MOS  i s measured by  thickness t i s limited  insulators, is  and  an  (used  i n which the  t=E/Va, were Va (1982),  the  capacitor  impedance. However, t h e  channel  withstand  maximum  when  capacitances  threshold  The  to  1982],  and  insulator  same.  the  obtained  MIC's) i s t h a t  parameters  the  factor.  charge  Binet,  b a n d w i d t h of a  in  the  is  f l a t p l a t e capacitor equation  capacitor  that  i s the c a p a c i t o r charge 1977;  constant  other  Capacitor  were E  0  all  Notice  the  MOS  dielectric  transconductance,  store a given  Subak-Sharpe,  2  with  the  by  the  [Glaser,  Ta 0  high  remains approximately  f i e l d . This  the  will,  drain current.  electric  the  the  increase  ability  applied  that  oxide  equal,  capacitance  figure  clear  offer  insulator will the  be  or d o u b l e a  single,  function high  insulator of  the  permittivity  c o n s i d e r a b l e advantages  over  49  t h e compound chapters, impose  structure,  the e l e c t r o n i c  a  serious  monoinsulator. immediately the  electronic  insulator  double  to  layer  conduction, (typically  CAPACITOR  Dioxide, S i l i c o n  MATERIAL  3  a  er  with  nm)  thickness that  of  Si0  2  Field,  3.3  E  7.6  8  Ta 0  5  27  FIGURE OF MERIT A l u m i n i u m O x i d e and  erE [MV/cm]  this  t u n n e l i n g through  Pentoxide  4  3  2  tantalum  insulator,  Nitride,  3.8  A1 0 2  pentoxide  >10  [MV/cm]  Si N  the  the  INSULATOR  Tantalum  2  currents,  i s avoided.  MOS  Si0  ( i . e . leakage)  if  TABLE  Silicon  see i n t h e f o l l o w i n g  the S i s u b s t r a t e , can reduce c o n s i d e r a b l y  i s such  the b a r r i e r  shall  conduction  limitation  The  over  b u t as we  e erE 0  [pfV/mm ] 2  15.2  1 3458  1 0  76  67290  1 0  80  70832  4  108  95623  50  {3.5}  ENERGY BANDS OF An  effort  insulator  as  is available parameters barrier tool  was  insulators  TANTALUM PENTOXIDE INSULATOR:  made t o c o m p i l e  t o p r o d u c e an in  the  such  is  energy  electron Internal  used  to  [Goodman,  enough  regarding  affinity  obtain  the  1968]. However,  unavailability  of  published  p r o v i d e s no  tantalum  details  pentoxide  metal-insulator one  given  by  by  (4.2  previous authors  1973;  Revesz  Angle,  an  et  energy  for  an  gate  potential  band  barrier  Young  bandgap e n e r g y  of T a 0  no  2  1984], w h i c h  on  (1976)  Thesis,  h i s source  d a t a . The  eV.  for  value eV)  ones  Kaplan  the d a t a  i s presented  in  structure in equilibrium  but the  of h i s  with  A l s o the v a l u e the  5  confirms  Angle  i n h i s Ph.D.  a l . , 1976], B a s e d  powerful  i n the case  [ Z a i n i n g e r e t a l . , 1969;  applied).  a  of  i s c o i n c i d e n t with  band d i a g r a m 5  is  h e i g h t c o i n c i d e s (0.72  eV)  essential  affinity  structure  0.71  data  electron  r e f e r e n c e s on  (1961) of  Al-Ta 0 -nSi 2  or  this  and m e t a l - i n s u l a t o r  figures.  p r o v i d e s a s k e t c h of a band d i a g r a m he  from  the  photoemission  measurements have been made [Goodman, the  data  band d i a g r a m . L i t t l e  literature  as  potentials.  that  THE  the  of  the  obtained et  al.,  provided Figure  by 3.3,  (no e x t e r n a l  51  Vacuum Level  qXj=3.38eV  —Al S^mJ2-S Xj  :  H—Ta 0 —I-—n Si 2  Metal-Insulator Barrier Silicon-Insulator Barrier : Insulator Electron  5  Potential Potential  Affinity  [j"g; I n s u l a t o r Bandgap E n e r g y A  ; Voltage  across  Insulator with  zero gate  voltage  Figure 3.3 Energy Band Diagram of the A l - T a 0 - n S i Structure 2  5  52  {3.6}  DOUBLE D I E L E C T R I C MOSFET STRUCTURE: The  3.4.  cross  s e c t i o n of t h i s d e v i c e  I t s dimensions are t y p i c a l  this  work.  The  transistor  j u n c t i o n s on a n - S i oxide  to provide  gate  metal  gate,  proper The gold  in  Figure  t h e ones used i n  has t h e d r a i n and source  p-type  s u b s t r a t e , w i t h windows c u t i n t h e f i e l d area  contains  s t r u c t u r e , b o u n d e d by t h e s u b s t r a t e a n d  contact.  formed under t h e g a t e , the  and r e f l e c t  a d e q u a t e c o n t a c t s . The g a t e  the double i n s u l a t o r the  i s shown  An  inversion  when a n e g a t i v e  thus p r o v i d i n g  enhancement  operation, the drain-source  s u b s t r a t e or b u l k , has a c o n t a c t metallization.  *  p-type channel i s  voltage mode  i s applied to  operation.  For  b i a s h a s t o be n e g a t i v e . provided  by  a  bottom  53  l  IIIIIIIIIIUIIIIIIIIIIIIIII  t-SiOo  B  n Si Typical Gate  Au  Dimensions:  6  L e n g t h : 10 ym  Gate O x i d e  Thickness:  S i 0 : 200 2  T a  2°5  Substrate  Field  Junction  A  : 1000  A  Proposed Symbol G o-  Figure  3.4  Double D i e l e c t r i c  O x i d e : 600  -o B  MOSFET S t r u c t u r e .  Depth:  nm 1  ym  54  CHAPTER 4  FABRICATION  Before  t h e f i n a l MTAOS s t r u c t u r e c o u l d be d e v e l o p e d , i t  was n e c e s s a r y processing  AND PROCESSING OF MOS CAPACITOR DEVICES  t o study  of  i n great d e t a i l  tantalum  c a p a c i t o r s . Then a s t e p Ta 0 -Si0 2  5  these  double  2  were  further  dielectric  fabrication  and  single  dielectric  MOS  into  the  MOS C a p a c i t o r f a b r i c a t i o n .  When  established  t e c h n o l o g i e s , the double then  pentoxide  the  could  as  be  successful  dielectric  processing  MTAOS d e v i c e c o u l d  only  be f a b r i c a t e d .  {4.1}  MOS CAPACITORS WITH THERMAL T a O 2  Considerable  amount  of  time  AS INSULATOR:  s  was  p r o c e s s i n g o f MOS C a p a c i t o r s w i t h a s i n g l e of T a 0 , a n d s e v e r a l t e c h n i q u e s 2  were  made  5  used.  The  following  devoted  to the  insulating  film  f o r p a t t e r n i n g t h e Ta m e t a l  general  processing  steps  were  followed: Thickness  and f o u r p o i n t r e s i s t i v i t y  measurements,  S c r i b i n g and m a r k i n g . P e r o x i d e - A c i d c l e a n i n g u s i n g t h e RCA p r o c e s s . RF S p u t t e r i n g o f t a n t a l u m  metal.  Thermal O x i d a t i o n i n d r y oxygen. Aluminium evaporation  f o r gate e l e c t r o d e s .  P a t t e r n i n g of aluminium metal Back c o n t a c t by a l u m i n i u m  by p h o t o l i t h o g r a p h y ,  evaporation.  55  {4.1.1} THICKNESS AND SHEET R E S I S T I V I T Y  MEASUREMENTS:  T h i c k n e s s measurements were p e r f o r m e d DGS-E  Gauge  dial  caliper.  Four  with  Point  measurements were done u s i n g a H e w l e t t - P a c k a r d Source,  a Fluke  Kulicke an  8000A  or  and S o f f a Model  8050A  Digital  3007, No.130,  a  Mitutoyo  resistivity 6186C C u r r e n t  Voltmeter  and  four p o i n t probe  a  with  i n t e r p r o b e s p a c i n g o f 0.025 i n c h e s .  {4.1.2} SCRIBING AND MARKING: Scribing pen,  on  special  the code  individual made e a s y . in  and m a r k i n g wafer's and  wafer,  date so  was done w i t h a  back, was that  standard  immediately  above t h e f l a t .  inscribed,  unique  future identification  A l a r g e amount o f s a m p l e s was p r e p a r e d ,  T a b l e 4.1.  diamond  to  A  each  c o u l d be as  shown  TABLE SINGLE SAMPLE  DIELECTRIC NAME  Ta  4.1  THERMAL  MOS  THICKNESS  CAPACITORS  [A]  SUBSTRATE  NL  500  n  Type  N2  1 000  n  Type  500  P  Type  BNR1000  1000  P  Type  SampleA  500  P  Type  SampleB  1 000  P  Type  500  P  Type  1000  P  Type  MOSC1  500  n  Type  MOSC2  1000  n  Type  MOSC3  500  n  Type  MOSC4  1 000  n  Type  MOSC5  500  n  Type  MOSC6  500  n  Type  MOSC7  1 000  n  Type  MOSC8  1000  n  Type  BNR500  500ALift 1OOOALift  57  {4.1.3} PEROXIDE ACID CLEANING: Cleaning  of t h e w a f e r s  p e r o x i d e p r o c e s s [ K e r n and the  Appendix  step,  which  {4.1.4} RF  3140  Si  single Valve  shiny  Sputtering  performed  The  vacuum s y s t e m  acid-  detailed  water  followed  and v e r y c l e a n  of Ta m e t a l on  accomplished using  target  i n Argon,  by  system,  mounted  in each  surface.  with a p a r t i a l  the b a s e p l a t e I o n i z a t i o n and  Consolidated  Vacuum  sputtering  rate  determined  by  Gage).  was D.  Young,  15  Smith  using  to Gauge  these  nm/min,  already  on  a  The  NRC  which  10"  6  (CHA Corp.  703  sputtering  p r e s s u r e of 26  Vacuum  Under  the  a Perkin-Elmer  H i g h Vacuum S y s t e m .  e v a c u a t e d t h e chamber  IG-101P Ion Tube Ionization  was  Control  was  [ S m i t h and  SSEE-100  SPUTTERING:  Randex  monitored  in deionized  p r o d u c e d a smooth,  substrates,  Automatic  t h e RCA  P u o t i n e n , 1970], as  I I I . Rinsing  Radio Frequency clean  followed  mTorr.  Torr,  as  Industries G1C-110A  conditions, was  the  previously  the S l o a n Angstrometer  method  1981].  {4.1.5} THERMAL OXIDATION: Thermal Thermco tube  oxidation  Products  (5 cm)  temperature difference loss,  thus  oxygen  was  Corp. Mini  furnace, in  o f t h e Ta  centre  at the edges, obtaining manually  Lock  was  in order a  "flat"  regulated  was  performed  Brute r e s i s t a n c e  w i t h a Ana  the  films  by  set to  201 to  500  C,  compensate  Brooks  a  heated quartz  Controller.  temperature a  in  The  w i t h +5 for  profile. R-2-15-A  C  heat Dry tube  58  flowmeter, reading  and  of  parameter,  set  9.4 was  to  cm). varied  order  t o determine  oxide  quality.  a flow  The  o f 1.0 l / m i n  oxidation  considerably  i t s optimum  value  (a B r o o k s  time,  a  as d e s c r i b e d in  tube  critical below, i n  function  of the  TABLE 4.2 THERMAL OXIDATION OF TANTALUM ON SILICON SAMPLE NAME N1 N2 BNR500 BNR1000  Ta THICKNESS  TEMPERATURE  TIME  A  500  C  60 min  1 000 A  500  C  120 min  A  500  C  93 min  1 000 A  500  C  187 min  500  500  SampleA  500  A  500  C  3.5 h r s  SampleB  1000  A  500  C  3.5 h r s  500  A  500  C  6.5 h r s  1 000 A  500  C  10  hrs  500ALift 1OOOALift MOSC1  500  A  400  C  5  hrs  MOSC2  1000  A  400  C  7  hrs  MOSC3  500  A  600  C  5  hrs  MOSC4  1000  A  600  C  7  hrs  MOSC5  500  A  MOSC6  500  A  600  C  5  MOSC7  1000  A  400  C  1 week  MOSC8  1000  A  600  C  7  Broken  under p r o c e s s i n g hrs  hrs  59  {4.1.6} ALUMINIUM DEPOSITION: Initially, using  a  some s a m p l e s had  Veeco  model  metal  before  deposition  the  d e s c r i b e d below,  introducing radiation oxide, either  mask. The  an  or  the  Aluminium metal Electron  the  Beam,  that  namely could  would be  ALA  1793,  and  hung on  10"  6  High  0.045" d i a . ) was the  tungsten  Torr, before  thickness  any  ranged  Inficon  Model  density  of  321  2.73  evaporation  Quartz used  aluminium  600  Crystal  took and  by  existed  of  energy in  the  2  In  1981].  opposed  to  using a  CHA  Auto  i n t o hoops of  Torr  5  interface.  (as  a  a  replaced  [Miner,  with  f i l a m e n t s . The  10"  Al  energy p r o c e s s )  silicon  cut  between  was  deposited  high  at the  evaporated  i s a high  p u r i t y . 1%  the  affected  I n d u s t r i e s Model SE-600-RP E v a p o r a t o r controller.  to  implant  substrate  thermally  which  evacuated  possibility  factor,  Si  results  j a r was  s i n c e the  E-Beam  was  gate  p l a c e . T h i s method was  unknown  damage  case,  bell  took  from t h e  aluminium  VE-400 E l e c t r o n Beam equipment and  stencil  one  an  Tech  II  wire  (Cominco  cm  lengths,  chamber p r e s s u r e p l a c e . The  1000  nm,  Film Thickness  was  evaporated  as  given Monitor  by  a (a  for aluminium).  {4.1.7} PHOTOLITHOGRAPHY: Photolithography electrodes,  a dot  photoresist The  dots  process  have an  rings provide  and  area  was  used  ring  to  mask was  as d e s c r i b e d of  electrical  pattern used  with  in detail  0.7854 mm  2  isolation.  (1 mm  the  aluminium  a  negative  i n Appendix I I I .  diameter),  and  the  60  {4.1.8} BACK CONTACT METALLIZATION: The metal,  back c o n t a c t using  the  e l e c t r o d e s . Again the  metal  large  be  thermal  alternative  in  this  thus with  double  dielectric  to evaluate  fabrication  aluminium  layer. by  marking,  the  Then  a dry  a  the  processing  of  Dry  b)  T a n t a l u m RF s p u t t e r i n g .  e)  Back c o n t a c t  be  an  STRUCTURE:  of a  in  number  T h i s method thin  metal  After  a  of  silicon  is applied,  cleaning  and  follows:  metallization.  oxidation  above. E x p e r i m e n t a l l y ,  flow  very of  for  accomplished  described  r a t e was  used  was  furnace  oxygen  to  cost  photolithography.  resistance  an  the  evaporation.  Patterning using  oxidation  the  o x i d a t i o n i n oxygen.  d)  thermal  as  however  techniques.  used  tantalum  steps are  is  proved  was  oxidation.  a)  c) Aluminium  2  formation  layer  thermal  thermal  5  gate  Gold  that  known p r o c e s s i n g  2  f o r the  application,  indicated  Ta 0 -Si0  aluminium  favored.  its characteristics.  requires f i r s t  followed  for  was  CAPACITORS WITH DOUBLE DIELECTRIC  samples  oxide  evaporating  evaporation  used  prohibitive,  MOS The  The  by  same method d e s c r i b e d above  usually  economical  of  made  amount of w a f e r s p r o c e s s e d  would  {4.2}  was  small  the  tantalum i t was  [Tarr,  1 l/min.  The  in  the  oxidation,  determined  1980], a b o u t additional  that 1  steps  same as the  A/min., used i n  61  this  procedure  using  this  a r e t h e same a s b e f o r e . The samples  prepared  technique a r e :  TABLE 4.3 DOUBLE DIELECTRIC MOS SAMPLE  The  2,  THICKNESS  20S50T  20 A  50 A  20S100T  20 A  100 A  20S200T  20 A  200 A  50S100T  50 A  100 A  50S200T  50 A  200 A  50S500T  50 A  500 A  50S1000T  50 A  1000 A  metal  when  f u l l y converted  values film  5  f a c t o r ) as d e t a i l e d  on t h e l a s t  column w i l l  into  Capacitors film  f o r the i n i t i a l  on s i l i c o n  Ta 0 -Si 5  will  of a p p r o x i m a t e l y  i n Chapter  6.  Hence,  produce a c o r r e s p o n d i n g  COMMENTS: produced  the  required  e v a l u a t i o n of the thermal  s u b s t r a t e s . The s t r u c t u r e  then  has  MOS Ta 0 2  5  a Al-  configuration.  conversion  rather  i t s oxide,  t h i c k n e s s twice as l a r g e .  T h i s method o f f a b r i c a t i o n  The  THICKNESS 20 A  {4.3} PROCESS AND FABRICATION  2  Ta  an i n c r e a s e i n t h i c k n e s s , by a f a c t o r  the 2  2  20 A  (the"swelling"  Ta 0  Si0  20S20T  tantalum  show  NAME  CAPACITORS  of  the tantalum  metal  film  l e n g t h y p r o c e s s , and a l t h o u g h p r e v i o u s  into  oxide  authors  is a gave  62  some  indication  oxidation Young,  1981],  i t was  a  characteristics. produced, a  few  Ta  400  and  gold-yellow  case  quite  final  was  quite  striking.  in  attempt this this  would  project.  In  two  to  obtain  cases  Sputtering  Ta  for  was  of  the  increased  nm  samples.  in identifying  Si substrate  was  nm  each are  intense  i n most c a s e s  of t h e A l - T a o x i d e - S i  have v a s t l y  t h e amount o f  films  (MES),  time  BNR500 and deposited  in  order  BNR1000), by  to  required  type,  possible  orientations,  to  i t was  Magnetron evaluate  n  and  capacitors.  substrate  hence t h e t o t a l  color  sample, i f  in order to e s t a b l i s h  increased  samples,  This  made t o use d i f f e r e n t  (samples  to  characteristics.  100  used,  days.  temperature  p u r p l e - b l u e f o r t h e 50  also  few  i n some c a s e s r e d u c e d  the e f f e c t  helpful  from  hours ( f o r  a  temperature  was  varied  to several  case  and  terms  samples  t i m e s , which  In b o t h c a s e s , t h e c o l o r s  The  work, and  the  of  was  i n the q u a l i t y was  amount  one  in  (leakage) current  I-V  the  and  Capacitance-Voltage  films)  C,  Smith  time  and  for  required.  differences  as  in  C t o 600  color  however p t y p e was  No  large  oxidation  and  t h e C-V  film  difference  and  Ta  thermal  some e x p e r i m e n t a t i o n s h o u l d  i n some c a s e s , t h e  The  the  a  (for very thin  on  et al.,1974;  as c o n d u c t i o n  i n order to determine  variations  f o r complete  t h e optimum o x i d a t i o n  Hence,  t h e u s u a l 500 C,  that  voltage,  films),  Furthermore, from  felt  with d i f f e r e n t  minutes  thicker  [Revesz  parameters  given  required  film  to determine  more c r i t i c a l  for  the time  of the metal  take p l a c e of  of  any  variables complete  possible Enhanced possible  63 differences  in  the  capacitors.  Silicon  performance wafers  were  L a b o r a t o r i e s of B e l l Northern and  processed  as  in  difference,  Appendix  the  entire  to the S o l i d  State  Ottawa,  c l e a n i n g method was u s e d ,  followed  this  f o r MOS  the  t h e MOS C a p a c i t o r s  Al  i f the  processing  Ta{oxide}  film  technology  was t o be  had  in trying  Ta m e t a l o r Ta o x i d e used  experiencies  film  on  Si  of concentrated  even  "pirahna  H2SO4  HNO3  2  and  ants, results damage  and H 0 ) 2  NH F), a  which were  names d e r i v e d  devour very  resulted,  substrate,  and "marabunta e t c h "  everything  in particular  to  The  etch"  hot  HF,  and  (a h o t s o l u t i o n  (a h o t  solution  upon  the  their  passage.  a n d i n most c a s e s photoresist  of  or  The severe  to  the  when t h e " A m a z o n i a n " s o l u t i o n s were  u s e d . I t was a m a z i n g t o o b s e r v e b o t h Ta a n d T a 0 2  u n t o u c h e d by s u c h s t r o n g  chemical  from a s p e c i e s of Amazonian  unsatisfying, either  author  10% HF a n d B u f f e r e d  HF, t o more s t r o n g e r m i x t u r e s like  The  was  to pattern the  substrates.  went f r o m t h e c l a s s i c a l  dangerous mixtures  oxide  g a t e e l e c t r o d e , and not over t h e  present  frustrating  films  5  with the  o f MOSFETs.  of  Capacitors  2  f u r t h e r extended t o the f a b r i c a t i o n  solutions  initial  t h e Ta a n d T a 0  s u b s t r a t e . E t c h i n g o f t h e Ta o r  many  Ontario;  was e x a c t l y t h e same a s i n d i c a t e d b e f o r e .  under  mandatory,  MOS  I I I . Besides  process  i n a way t h a t w o u l d y i e l d only  finished  Research i n  S e v e r a l a t t e m p t s were made t o p r o c e s s  film  the  sent  by MES. A d i f f e r e n t  detailed  fabrication,  of  chemicals.  5  films  rest  64  {4.4} THE L I F T O F F TECHNIQUE ON TANTALUM A the  better processing  Liftoff  metal  films.  etching) over of  technique It  a thin  was d e v e l o p e d  is  based  the r e q u i r e d  final  shape.  Then  positive  pattern  the  is  the  2.  negative  Then  RF S p u t t e r i n g  evaporation  a b o v e . The f i n a l  but  wafer's  attacked  by  a negative  image  tantalum  film  aluminium,  the  Aluminium  is  the f i n a l vary  metal  was RF s p u t t e r e d , steps  s t e p mentioned  was using were  before:  m e t a l by p h o t o l i t h o g r a p h y ,  with  etching  tantalum  as  by a l u m i n i u m  usual,  required considerable on t h e o r i g i n a l  1000  after surface, the  metal. etching.  i . e . , the  Al  f o r gate e l e c t r o d e s , e x a c t l y as d e s c r i b e d  from 600 t o  noticed,  first  for l i f t o f f .  was c o n t i n u e d  90 m i n u t e s , d e p e n d i n g  varied  (i.e.,  The d e p o s i t i o n methods  metal  of tantalum  o f unwanted  the p r o c e s s i n g  metal  Al  tantalum  deposited  a b o v e . The f o l l o w i n g  evaporation of  with  image.  4. L i f t o f f  the  case,  tantalum  Patterning  3.  the  t h e RCA SSEE100 c l e a n i n g  1. A l u m i n i u m  to  obtained.  same methods d e s c r i b e d  used, a f t e r  with  the u n d e r l y i n g  but i n t h i s  and  metal,  patterned  a n d by e t c h i n g  use  removing c h e m i c a l l y  then  deposited  evaporated  on  i n need, and t h e use o f for  l a y e r of aluminium  the S i s u b s t r a t e ,  considerably,  method was  FILMS:  nm.  Initially,  10-20 m i n u t e s , indicating  etchant  from 60  A l thickness, no  reaction  which was  g a s b u b b l e s a p p e a r e d on  that  solution.  time,  the  Al  metal  was  Towards t h e e n d o f t h i s  65  process,  i t was  changed  from  texture.  The  in  a  is  Interestingly, Q  scratch  the  optical  a  leave  the  sold  swab  tantalum  sample(s)  result  metal, then  made  cotton  naked e y e .  Bay  seen  S h o r e , New  etching  a clean,  no  process  film.-  (i.e.,  a  standard  foam swab  York) I t was  (Sof-  proved  defined  damage t o t h e could  to 30-  from  the  pattern  of  silicon  continue  to  necessary  r e s i d u a l Al/Ta  well  a  severely  s o l u t i o n for another  remove t h e  was  A  swab.  Ta  would  under  free surface.  to  with the  one  rinsed  foam  was  even  i n the  a soft  wrinkled  this  wrinkled  removed,  unwanted of  surface  and  the  or  in order  end  rubbed with  as  scratch  metal  to a coarse  surface,  Room P r o d u c t s ,  this,  tantalum  in drugstores),  tantalum  minutes,  After  i f the  clean,  w a f e r . The  gently  remove  microscope,  leave  45  to  tip  Swab, C l e a n  the  smooth a p p e a r a n c e  water and  done  common  that  s a m p l e ( s ) t h e n were c a r e f u l l y  de-ionized  This  noticed  substrate.  as  described  before.  {4.5}  MOS  CAPACITORS WITH ANODIC T a 0 2  Another films  i s by  Several Young, that  anodic  authors 1961;  than  previous  Ta)  have  the  dry  which  of a t h i n  superior  AS  producing  as  tantalum  d e a l t with  of  method a very  q u a l i t y and,  thermal o x i d a t i o n  of  Ta  of  pentoxide Ta  metal.  [Berry,  1959;  reliable  one  course,  much  films.  However,  insulating substrates  a l u m i n a ) or c o n d u c t i v e further  INSULATOR:  layer  this  e t a l . , 1971]  work o n l y or  of  reported  f i l m s of  example g l a s s or  way  oxidation  Dell'Oca  produces  faster the  possible  5  simplified  the  ones  (a p l a t e of  problem  of  (for Al  making  66  electrical silicon, found  contact  t o i t . In t h i s  case,  the  a s e m i c o n d u c t o r , and a p r a c t i c a l  f o r making a good e l e c t r i c a l  substrate  was  s o l u t i o n had t o be  contact  t o t h e Ta f i l m  on  Si . A  possible s o l u t i o n i s to allow  the  cross  type  s e c t i o n of t h e s i l i c o n  i s c h o s e n . By t a k i n g the substrate,  the  anode, t h e e l e c t r o n i c c u r r e n t substrate  make t h e T a - p S i  good the  strip  close  thin  anodic  oxide  the already  detected cell,  will  of the constant  a  f a c e . Under oxidize  on t h e s i l i c o n  taken  Ta 0 . 2  5  NOT t o grow an  the  through  the voltage current  be  across  source.  At  anodization  current  i n c r e a s e dV/dt  density  2  T h i s c o n d i t i o n c a n be  across  e t a l . , 1971], The m e t a l w i l l when  by e t c h i n g  w h i c h would p r o d u c e a l a y e r o f S i 0  constant  Vlimit  be  Hence, a  surface, i f  to a n o d i c a l l y  a f u n c t i o n o f t i m e , when a c o n s t a n t  i t s oxide,  will  reversed  be b l o c k e d .  previously deposited  for  into  then  i n the wafer's  the voltage  current  a p-Si  as t h i s  to the s i l i c o n  feasible  i t . The r a t e o f v o l t a g e  [Dell'Oca  is  was a c c o m p l i s h e d  through a  electrode i s  If a n-Si substrate i s  current  shold  proper  direction  d i c t a t e s that  diode  formed a n o d i c  by m o n i t o r i n g  as  biased.  This  care  of s i l i c o n ,  flow  Ta-nSi  i t i s then  However,  the tantalum  through  the  the c u r r e n t  possible choice,  to the f l a t ,  l a y e r o f Ta m e t a l  substrate.  if  must e x i s t  i s p type.  conditions,  under  the  contact  substrate  small  a  forward  is,  substrate,  that  only  and t h e a n o d i z a t i o n direct  these  the  diode  used as t h e case biased  and n o t i n g  is  t o flow  i n t o account  in  type  the current  is  flows  constant  the e l e c t r o l y t e fully  converted  the c e l l this  reaches  point  the  67  process anode  is  interrupted.  ( u s u a l l y oxygen),  taking  place  on  layer.  It i s also  to  cell,  the  possible  "healing" oxide  and  film are  shown  2.  m o n i t o r e d as 4.  the  5.  Rinsing  a  oxide  evidence  film  that  and  2  it  is  [Young,  a certain  or a r e a s  cell  Si0  voltage  process,  in  the  associated  f o r both constant  f o l l o w i n g steps  on  silicon  of by  tantalum  current  were u s e d  substrates,  after  in the  metal.  aluminium at  f u n c t i o n of  current,  voltage  time. voltage  f u n c t i o n of  in de-ionized  evaporation.  constant  A p p l i c a t i o n of c o n s t a n t  m o n i t o r e d as  is  process:  oxidation a  change  a constant  weak s p o t s  4.1,  the  g r o w t h of a  current  anodization  tantalum  Sputtering  Anodic  the  from  processes.  Back c o n t a c t  3.  escaping  further  quality  on  in Figure  SSEE100 c l e a n i n g  1. RF  place  a  applying  experimental  principles,  anodic  by  better  The  voltage  these  producing RCA  itself.  constant  B a s e d on  a  takes  gas  surface:  constant  i s b a s e d on  effect  equipment  silicon  the  obtain  any  indicates that  known, t h a t  after  to  1961]. T h i s  the  Also,  to the  cell,  current  time. water  t o remove a l l t r a c e s  of  electrolyte solution.  The  processing  evaporation 4.4  gives  used.  then  continues  as  before,  f o r gate e l e c t r o d e s , being  further details  of  the  the  wafers  with  next and  the  step.  Al  Table  electrolytes  68  Constant Current Phase  Figure  4. 1 A n o d i z a t i o n  C e l l and Equ ipment  69  {4.5.1} ANODIZATION A Al  good  IN CITRIC ACID ELECTROLYTE SOLUTION:  contact  contact performs  density  of  process,  a value  films  wafer  to  20  voltage  3-5  2  used  Autograph  a  films  film  of  sharp  of the c e l l contrast with  hours. color  It  in  tantalum process  with metal  the time  under  first  across  with  the  a chart  Recorder). fast  is fully  cell  recorder  The  anodic  process, in  converted  from  thermal  to observe  few s e c o n d s .  set  the  to i t s  rate  oxidation, a  of  i sin few  t h e sudden change i n  the formation The f i n a l  o f an  color  oxide  was  light  Constant  this  Dell'Oca  the  thermal  oxide  t h i c k n e s s . At t h i s  films,  for  the  p o i n t the Constant  same  Current  i s i n t e r r u p t e d , t o be f o l l o w e d by t h e a p p l i c a t i o n o f  corresponds in  source  f o r a 50 nm Ta sample, and g o l d f o r a 100 nm sample, i n  agreement  a  2 inch  v o l t a g e , as e x p l a i n e d b e f o r e . T h i s  i s q u i t e amazing  the  quality  6186C) w i t h a maximum  i s determined  o f t h e Ta s u r f a c e , d e n o t i n g  film, blue  nm  Current  good  and a c u r r e n t  Chart  current  of a s t a n d a r d  is a relatively 100  A  the Constant  The v o l t a g e  7100BM S t r i p  of t a n t a l u m  well.  t o form  a f u n c t i o n of time,  o x i d e . The o x i d a t i o n t i m e change  for  (Hewlett-Packard  o f 100 v o l t s . as  minutes  used  c l o s e t o 20 cm ,  was  recorded  oxidation  was  2  quite  1 9 6 1 ] . The s u r f a c e a r e a  setting  (Moseley  function  t h a t h a s been p r o v e n  i s very mA  this  mA/cm  [Young,  Si  was  1  i s r e q u i r e d t o t h e anode, and t h e back  Voltage  for a certain  time.  The a p p l i e d v o l t a g e  to the o p e r a t i n g v o l t a g e of the  case  n o t more t h a n  e t a l . (1971),  20 v o l t s .  1-3 h r s . ,  process. Therefore, a constant  MOS  Capacitor,  B a s e d on d a t a  g i v e n by  i s the u s u a l time  for this  v o l t a g e o f 20 V  was  applied  70  Sample M05C10 .1M Citric Acid J=1mA/cm2 Vcell • (V) 60-  t (min) 0  1  2  3  A  Figure 4.2 Anodization C e l l Voltage under Constant  Current  71  Sample MOSC10 .1 M Citric Acid V= 15 Volts Icell* (mA)  6-I  54  AH  34  H T  5  ~T"~  10  15  —r—  20  F i g u r e 4.3 A n o d i z a t i o n C e l l Current under Constant  t (min) 25  Voltage  72  to  the  with,  cell  an  1 hr.,  electrometer  recorder. Figures  for  The  4.2  4.3.  constant  current  constant  voltage.  and  classic  tantalum 1959  has  and  decided order  to  capacitor (1965),  the  Solutions  of  and  anodic  remove boiled  3  for  1961;  traces  were  charts  of  oxidation  be  given  film, that  acid  by  it  was  used  in  resulting  MOS  also  the  of  [Berry,  Randall  et  use  tantalum  in both cases, for previous  solutions  once  the  i t r e d u c e s the  results  the  (constant  III gives  as  prepared good  in isopropyl alcohol  w a f e r s . Appendix  under  1966], however  q u a l i t y and  devices  s a m p l e s were t h e n  all  under  al.  aqueous s o l u t i o n of p h o s p h o r i c  apparent  the V ( t )  voltage  anodic  should  results  produced  were  shown i n  leakage current  McLean,  quality  M  chart  ELECTROLYTE SOLUTION:  film  an  MOS  had  a  driving  measurements a r e  electrolyte the  0.1  602)  s h a r p change of  1961]. B o t h e l e c t r o l y t e  differences  The  another  better  concentration  place  H PO„  Young,  in  monitored  diminishing  p e r f o r m a n c e . The  a  leakage current  a q u e o u s s o l u t i o n of c i t r i c  compare  conductivity  [Young,  been an  i n d i c a t e that  produces  these  electrolyte  1963;  that  of  Note the  {4.5.2} ANODIZATION IN The  the  (Keithley  results  and  and  were  anodic  current)  ionic  oxides. as  authors and  oxidation  took  compared. water,  electrolyte  s o l u t i o n s , and  to  any  these  in further  this  used,  rinsed in de-ionized  remove  acid  water detail.  in  to then the  73  4.4  TABLE  SINGLE DIELECTRIC ANODIC MOS SAMPLE NAME  Ta  THICKNESS [A] 500  Citric  Acid  MOSC10  500  Citric  Acid  MOSC11  1 000  Phosphoric  Acid  MOSC12  500  Phosphoric  Acid  MOSC13  500  Citric  MOSC14  500  Phosphoric  000  Citric  MOSC16  500  Phosphoric  MOSC17  500  Citric  Acid  000  Citric  Acid  1  MOSC18  1  INTERFACIAL OXIDATION A  new  fabricating silicon  technique, MOS  a  previous  authors  tantalum  pentoxide  behind  this  travel  interface paper  an  a  2  is  that  However,  structure  insulator  thermally from  oxidation  2  on t h e t a n t a l u m  outer  wet  the  i s then  of T a 0 2  5  5  grown one  Acid  used i n  substrates,  film  and grow a f i l m  a double  and an  was  gases  given  will at the  in their  i t s origins. dielectric  inner insulator  and  principle  oxidizing  and  by  i n which a f i l m of  the  film  of  tantalum  reported  a t 800C. The  no i n d i c a t i o n  pentoxide  Acid  allows the o x i d a t i o n  a l . , 1983],  the outer T a 0  of S i 0 .  insulating  et  Acid  O x i d a t i o n , was  was d e p o s i t e d on s i l i c o n  procedure  through  of  departed  [Kato  by  as t h i s  film  Acid  CAPACITORS:  Interfacial  This process  followed  MOS  capacitors,  through  pentoxide.  then  ELECTROLYTE  M0SC9  MOSC15  {4.6}  CAPACITORS  The  one, w i t h of  Si0 . 2  74  The  procedure  slightly thermal steps  followed  different oxides  are  as  metal  and  Si.  processing  and  four  point  of  5.  T h e r m a l o x i d a t i o n of  6.  Wet  7.  Aluminium e v a p o r a t i o n  8.  Patterning  9.  Back c o n t a c t  oxidation  are  the  RCA  process.  metal.  tantalum  i n dry  oxygen.  silicon. for gate  gold  electrodes.  photolithography.  evaporation.  have a l r e a d y  500  given  flow  c o l o r was  was  properly  A of  Ta  been d i s c u s s e d  metal deposited  f o l l o w i n g the  i n Appendix  of  1.5  furnace  cycles, t i m e on Table  in the  4.5  only  1/min, i n s t e a d of  o x i d i z e d . The  previously,  the  indicating  800C, f o r  order  to of  summarizes  the  the  and  as  that  1  the  being 1/min.  Ta  metal  introduced  varying the  double  results.  were  described  usual  determine  quality  RFS  difference  w a f e r s were t h e n  at  by  same method  I I I , the  deep p u r p l e - b l u e ,  oxidation  structure.  tantalum  of  by  steps  had  The  oxidation  using  of A l m e t a l by  thermally,  and  measurements.  d e t a i l e d i n Appendix I I I .  wafers  wet  resistivity  marking.  Sputtering  five  oxygen  The  growing  follows:  RF  and  was  of  4.  before  Janega,  advantage  cleaning  oxidized  P.  the  Peroxide-Acid  they  Dr.  has  3.  and  time  it  S c r i b i n g and  first  the  and  w r i t e r and  2.  The  an  this  f o r b o t h Ta  1. T h i c k n e s s  The  by  into  periods effect  of of  dielectric  75  TABLE  4.5  INTERFACIAL OXIDATION OF TANTALUM ON SAMPLE  The  OXIDATION CYCLE 3-54-3 m i n .  MTJ 2  500 A  3-114-3 m i n .  MTJ 3  500 A  3-54-3 m i n .  MTJ 4  500 A  3-24-3 m i n .  MTJ 5  300 A  digit  and t h e l a s t  o f t h e samples during  on  the  using wafers  o f oxygen  annealed  in  nitrogen  ones had no a n n e a l i n g  flow,  I I I , the  t h e second of  only. the  Ta{oxide}  film  t h e wet o x i d a t i o n . A l u m i n i u m technique  positive back  using  e q u i p m e n t . The sample marked MTJ1, w i t h was  i n Appendix  showed t h a t  by use o f t h e E-Beam  photolithography  deposited  are given  i n d i c a t e s t h e t i m e o f oxygen  not d e t e r i o r i a t e  deposited  None  o x i d a t i o n gas f l o w s  Examination  by  WET  500 A  oxygen + h y d r o g e n  did  THICKNESS  MTJ 1  wet  first  Ta  SILICON  and l a t e r  patterned  p h o t o r e s i s t . Gold also  the  was  was  E-Beam  electrodes  in place,  a t 500C f o r 3 m i n . The  remaining  treatment.  76  CHAPTER 5  RESULTS AND MEASUREMENTS ON MOS  Once proper  CAPACITORS  t h e MOS c a p a c i t o r s and d e v i c e s were set  implemented.  of  systematic  In the case  mesurement  fabricated, procedures  o f MOS c a p a c i t o r s  these  a was  consisted  of:  1) E l l i p s o m e t r i c  Determination  2) C a p a c i t a n c e - V o l t a g e 3) C u r r e n t - V o l t a g e  {5.1}  Thickness.  (C-V) C u r v e s .  (I-V) Curves.  ELLIPSOMETRY: The  Rudolf  oxide  thickness  M o d e l 43603-200E  Digital disc  of O x i d e  Equipment  drive,  running  techniques software  under  was  done u s i n g a  Ellipsometer controlled  Corporation  magnetic  OS/8  determination  tape real  minicomputer;  unit, time  by a  A/D  and  w i t h a RL-01  D/A  converters,  and u s i n g p r e v i o u s l y r e p o r t e d  [Hopper e t a l . , 1975; C o r n i s h e t a l . , developed  by  D.  PDP8/E  Smith  (1980).  A Spectra Physics  Model  133 h e l i u m - n e o n  laser,  beam  of  a t 632.8 nm. The e l l i p s o m e t e r a n g l e o f  incidence The  red  color  equations,  light  was 70° and measurements made i n z o n e s  ellipsometric  thickness  provided the  1973] and  using given  parameters the  * and. A were  transparent  the r e f r a c t i v e  measurements a r e u s u a l l y  taken,  then  single  index  source,  a  I and I I I . converted to  layer  model  of t h e f i l m .  Several  and t h e s e a r e then  averaged.  77  The  software  residing  of  a  of  pair  i n t h e computer c o n t r o l s t h e  small  through  reducing  optics  of  the  stepper  gear  boxes  by  two  coupled  via  Polarizer  motor d r i v e n u n i t s .  position  feedback  type  computer  attempts  to  output  reducing  light  performed  starting  point  gear  find  optics.  the  the p o s i b i l i t y  measurement  time.  obtained  71A  the  to  balance  Capacitance-Voltage also  measuring  by a computer system  Capacitance  electrically  to  control  then  of  a  the  p l a c e d at the or balance i s give  a good  software,  and a l s o  thus  reducing the  method  to  The  voltage  offset adjusted  voltage  f o r negative  and e x p e n s i v e  gate  optically  were 1981]. Model and  the capacitance  interfacing  unit.  by a D/A c o n v e r t e r a n d i t source,  w h i c h c a n be  to a desired value. This allows  C-V p l o t  special  i s provided  by an o p p o s i n g  an  j i g box p r o v i d e d  t o t h e c o m p u t e r , v i a t h e A/D  biasing  [Boyd,  i n F i g u r e 5.1. A Boonton  connected  shielded test  measurements  controlled  i s shown  Meter,  (C-V)  information  a  is  and  r e s i d e n t i n the  null  order  o f an e r r o r  Analyzer  (null)  An i n i t i a l in  encoders),  system  software  of these  C-V MEASUREMENTS: The  The  boxes  computer  minimizing  {5.2}  (shaft  drive,  Polarizer  position  by a p h o t o d e t e c t o r  manually,  to  and  resolvers  the a  in turn  Analyzer  The c o n t r o l  and  as sensed  of the A n a l y z e r  initially  the  E l l i p s o m e t e r . The a n g u l a r  are a c c u r a t e l y given  transmitted  motors, which  rotation  the user  v o l t a g e s , without  to  is  manually obtain  resorting to  D/A c o n v e r t e r s . The b i a s i n g  voltage i s  78  monitored turn  by  a Dana Model  serves  as  5900 D i g i t a l  a f e e d b a c k A/D  commands from  t h e computer,  incremented  and  software The  program  a  theoretical  capacitance thickness, curves  of C-V  a  obtained.  The  the  area  and  the  by  Houston  and  efficient  layer  can  indicate "fast"  fb  =  origin,  "  as  amount each  can  the  The  Q  f  /  i n f o r m a t i o n can  By  ox  calculated  irregularities of  follow  M e t e r . The  surface the  comparing  with  sweep  hysteresis,  r e v e a l the presence  flatband  be  i f the c a p a c i t o r  of  an  capacitance  flatband voltage  C  be  presence they  Capacitance  insulator.  V s  the  kind,  obtained.  V  XY  which  i s known. The  usually  i t s orientation  be  Complot  arrangement  samples,  capacitance,  permittivity  and  voltage  The  of  t h i c k n e s s can  the  1981].  vast  (oxide)  if  around  oxide  t o o b t a i n the  insulator  i n the  flatband of  Instrument  amount of  a p p l i e d t o the  curve  the  capacitors.  component  charge  way  curves.  experimental  [Boyd,  a great  the  mobile  etc.  be  resident  C-V  values  curves,  curve  any,  calculated  can  A  the  calculating  density,  accumulation  of  measured.  plotting  curve,  a  voltage  t h e PDP8/E m i n i c o m p u t e r . T h i s  insulator  states,  for  from a l a r g e amount  C-V  bias  in  appropiate  i n o b t a i n i n g the  state  s e v e r a l MOS  the  from  fast  curves  contained  in  surface  gate  used  provides  d r i v e n by  provided  From  and  were p l o t t e d  plotter,  the  allows  which  c o n v e r t e r . Then by  capacitance  module, CV.PG was  source  data,  the  Voltmeter,  i s given  (5.1)  the  ideal and by:  79  PDP8/E BUS  Bias BOONTON 71A o C-Meter  PDP8/E BUS  and Ox ~ 0 9  •-Capacitance  Tungsten Wire PDP8/E BUS to vac pump — Voltage  Shielded Test Box  Figure 5.1 C-V Measuring System for MOS Capacitors.  rass Block  80  Where t h e m e t a l  to semiconductor  0ms a n d Qf i s t h e n e t c h a r g e 1969].  Then,  the f l a t b a n d  work f u n c t i o n  at flatband  per u n i t  c a p a c i t a n c e c a n be  ox ~~ e +  is  given  by  area [Sze,  calculated:  £  C  fb t  The  slope  "fast"  of  o  ox  the  C-V  (5.2)  /kT/e N  x  q  s  curve  _  A,D  c a n be used  t o c a l c u l a t e the  surface state density: C OX N  ss(fast)  —cTcT—  =  ( A V  a  "  2  The  q u a n t i t y AVa r e p r e s e n t s t h e a c t u a l  and  q<p =Eg/2 + k T l n {ni/Na} . F  The  "slow"  insulator the  surface  states,  and mobile  ionic  caused  charges,  C-V c u r v e . A good e s t i m a t e  M  <  (5.3)  slope  of  the  by p o l a r i z a t i o n  produces  of these  curve  of the  hysteresis  i s g i v e n by  in  [North,  1980]: C N  i  n  \  ss(slow)  =  —  —  —  _ , 3qcj)  (5 4) \o..t>  AV, h  F  Where t h e h y s t e r e s i s  width  around  flatband  i s r e p r e s e n t e d by  AVh. The the V).  C-V d a t a  c a n be r e p l o t t e d  capacitance Linear  squared  extrapolation  i n t h e form  v s . the gate of  the  of the i n v e r s e  bias voltage  replotted  data  of  ( 1 / C vs 2  to  the  81  voltage  axis gives  1969].  T h i s method was  in  work on  {5.3}  I-V  2  data the  p r o g r a m was  written  increment  i n the  by  has  plot  o r a so c a l l e d  the  source  the  system  in turn  (buffer)  option  are  is  which  [Sze, (1975)  (19*77)  in  resident  software  Dana  provided  Model  converter.  resistor  placed  usually  set  i n the  directly  to  measurements.  100  current  temporarily  of  i n FORTRAN  runs  in  a linear  IV w h i c h  Appendix 5.2. the  D/A  is a the  II.  the  converter,  protective output  arrangement  of  I-V  it  both  Isolating  404  DVM-A/D  The  driven is  gate by  t h e D/A  a negligible use  the  monitored  indicating  current  allows  current,  399  computer.  as  the  The  leakage  and  in  A K e i t h l e y Model  a Tyco Model  minicomputer,  at  the  details  ohms, w h i c h has  This  read  ( l o g I v s . i/V) . The  5900, w h i c h s e r v e s There  source  sequentially  i s stored  measure  a  (Al  V)  i t feeds  by  current  positive  would  t o a K e i t h l e y Model  Then  DC  A computer  then  in Figure  to  the  (I v s .  i s i n t e r f a c e d with  is  and  data  given  i s connected  that  of p l o t t i n g  shown  i s used  voltage  the  Makus  both  voltage..  Then the  Schottky  Amplifier.  converter,  A/D  by  measuring  author,  program w r i t t e n  Electrometer  and  and  Padmanahban  under  bias voltage  PDP/8E m i n i c o m p u t e r , measuring  by  gate  this  circuit.  the  a  films,  capacitors,  gate  and  by  3  obtained  negative  the  user  was  MOS  and  which  i n p a p e r s by  potential  5  electrode)  602  Mo0  built-in  V 0 .  I-V  through  flowing  used  or  MEASUREMENTS:  The flow  diffusion  W O 3 and  r e l a t ion with  their  the  DVM  limiting converter, effect of  on the  82  computer  and  interfacing  fast  and  user  chooses the  number  efficient  of  increments, into  the d a t a ,  w i t h and  is  The  the  s h e e t ) , and  scales,  which  without  axes  the axes  All  measurements were made i n an  to  avoid  currents  ground  i n the  l o s s c a b l e s was isopropyl taken.  loops nA  made and  alcohol,  before  This ensured  conductors  (due  t h a t any  to dust,  test  graph.  keyboard plotting in  the  A l l scaling  according  test each  and  j i g . Care  the  use  jig batch  of  was  was  taken leakage  shielded cleaned  low with  of mesurements were  surface leakage  contamination  optically  t h e measured  Extensive  the  and  values.  n o i s e , as  range.  voltage  i s a c h o i c e of  electrically  the  and  the  via  labelled  recorded  which c o n t a i n e d  were  entered  in a  that  (for s e v e r a l curves  of p l o t  box,  data  w r i t t e n so  of a L i n e a r or S c h o t t k y  range of  I-V  maximum g a t e  are  type  shielded  was  computer. There  done a u t o m a t i c a l l y and and  to acquire  software  instrument  commands  same  way.  circuits  of  the  exposed  or water v a p o u r )  was  minimal. The  intention  Schottky of  the  form  I-V  providing  i s i n the  characteristic  information, I  of  of  the  (high  permittivity. conduction  and  one,  I-V  case  i n the by  i t is  frequency)  mechanism  first,  error  a factor  of  Linear  idea  second  to  obtain  more  the  s l o p e of  value  to  calculate  of  question  the of  seen  er(°°) from  log the  insulator whether  or P o o l e - F r e n k e l has  be  or  overall  the c a l c u l a t e d  2. T h i s can  in  t o g i v e an  possible  i s Schottky  otherwise  data  examining  However, t h e c l a s s i c  answered by  first  insulator,  v s . i/V. From t h i s  optical  the  will the  the to  be  be in  expression  83  Shielded Test Box  PDP67E BUS  PDP8/E BUS  PDP8/E BUS  Isolating Amp, Keithley 399  Figure 5.2 I-V Measuring System for MOS  Capacitors  84  of  the  P-F  conduction:  J = quN P  When  this  the p l o t Frenkel  E expC-qA  is plotted  straight  line,  lowering constant  0  = {  permittivity  ( 5  g )  2  can  i n the Schottky  its  slope  gives  form,  the  and  Poole-  /3pf :  (5.6)  2 f  o The  /E) /kT  f P  expression  is a  + 3  r  then  be  calculated  from:  2  TT B e (oo) r  e On  the  is  given  other  f  E - g —  =  (  7  )  a o  hand, t h e  Schottky  exp(-qcf)  = A*T  s  Where A*  i s the  Schottky  plot  Frenkel  mechanism.  conduction  current density  Richardson  is a straight  + J23 /E)/kT  s  constant. line,  Unfortunately,  examination  of a s t r a i g h t  line  plot  information  from  the  and  it  the c o n d u c t i o n  has  been  photoemission  measurements  Frenkel  Schottky  vs.  slope,  half  there  of  i s no  i s P-F  or  i n the  form  [Dell'Oca, can  that et be  if  the easy  S,  conduction  suggested  dilemma  The  i s then  whether  More  (5.8)  pf  determining  required,  <  by:  J  i/V.  5  Pooleway  from  of  of the  log I vs.  process  from  the  is  internal  a l . , 1971],  the  solved.  The  85  photoemission  t h r e s h o l d energy  v o l t a g e a c r o s s the metal  and  [Goodman, Talley  insulator, 1 9 6 8 ] . In  (1978)  mechanism can positive) If  the  and  intercept,  reverse are  and  and  now  interface  that by  the  and  reverse  kind  the  the  conduction  bias Schottky  plots.  nearly  the  bias,  same Poole-  i . e . , the c o n d u c t i o n If Schottky  differences  of  and  (gate  in  Si substrates w i l l  currents  emission  forward  forward  electrode limited.  then  the  Angle  of  the  have  and  type  paper,  examining  same  the a p p l i e d between  Schottky  classic  i s taking place;  t h e A l and  reverse  the  not  responsible,  the  (gate n e g a t i v e )  both  conduction  between  their  determined  under  bulk-limited is  be  at  hence d e f i n i n g  indicated  slopes  Frenkel  insulator,  i s a f u n c t i o n of  several  is  emission  work f u n c t i o n s  lead  orders  to of  forward magnitude  different. As  i t can  be  measured the  plots  later,  straight  real  already  seen  line  conduction proposed  have  not  a l l  Schottky  mechanism  is  the  2  plots, more  ones. Furthermore,  large  Ta 0  samples  5  which suggests elaborate  forward  current differences  have  of  and  that  than  the  reverse  bias  several orders  of  magnitude.  {5.4}  HILLOCK FORMATION T h r o u g h our  Ta  metal  was  or  "measles"  protuberances thermal  INVESTIGATION:  experimental  RF  Sputtered  appeared are  s t r e s s e s on  on  formed  on  work,  i t was  found  that  when  clean Si substrates, hillocks the  surface.  probably  t h e Ta m e t a l  as  a  d u r i n g and  These  small  consequence  of  after deposition  86  [Miner, dark  1981]. C l o s e  field  "milky  (Figures  way"  density quite  pattern,  of  5.3  of  RF  Westwood  possible  hillocks  and  possibly  to n o t i c e  that  i n the  exhibits  hillocks  are  small,  quite  pinhole  et  similar  surface  Ta,  Hillock  growth  unwanted  source  defects  in  height  times  very to  of  10  serious cover  they the  problem  them  have  deposited  i f the  [Jakson  and  L i , 1982], the  thin  films  (1  um  substrates the  to  hillocks  by  kinetics grain  will  are  and  however a c e r t a i n d e g r e e of cycling In  promotes  order  to  but  to  a  on  these  typical  appears Al  as  over  Si a  creates  a  void  fails recent  growth  relatively  on  massive  stresses  a bulk process,  and as  observation,  with temperature exists,  an  typically  This  Under  a  silicon  photoresist  and  diffusion.  hysteresis  niobium  1971]. In more  c o n t r o l l e d by  shrink  levels,  in  is  thermal compressive  boundary  grow  or  hillock  less) deposited  i s governed  growth  opposed  or  A  thickness.  Tolliver,  work  made t o  al.,  dimensions,  passivation  [ S a n t o r o and  al.,  indicated that  also  is  is interesting  evaporated  large  this  was  that  100  or area  et  condition,  reported  s e e n . They  c a s e of  high  contamination  Galeener  by  under sky"  that  attempt  It  dimension.  and  "star  [Galeener  formation.  lateral  substrates,  a  found  an  between  were not  of  was  1975], and  paper  i n the  reveals  it  d e g r e e . These a u t h o r s a l s o  nitride,  microscope  tantalum  link  a  the  indicates a relatively  al.,  a  lesser  5.8)  Sputtered  et  with  However,  establish  pentoxide  to  which  hillocks.  typical  1980,  examination  as  changes, repeated  growth.  quantify  the  possible  e f f e c t of  contamination  87  (mainly  dust  (Corning  7059)  Sputtering argon  was  power of  of  at 120  1-2X10~  6  a  followed. of  Results  and  Only the  are  a  Torr,  relative  number of given  rate  W.  25-30 m T o r r . M i c r o s c o p e  count  and  prepared  atmosphere  RF  pressure  were  clean  "dirty"  the  was 100  measure  5.1.  per  samples  to done  RF  in  an  indicated  argon p a r t i a l under  i s given, unit  the  A/min., under  gases  examination  hillocks  in Table  of  Residual and  glass  introduced  equipment. Tantalum d e p o s i t i o n  gas  forward  particles),  area  a  pressure  dark as  a  field  no  actual  was  done.  TABLE RF  S P U T T E R I N G OF  Ta  5.1 ON G L A S S  SAMPLES  CONDITION  THICKNESS  G1 0 0  Clean  100  A  Normal  G500  Clean  500  A  Normal  Dirty  500  A  High  IG500  Clean  500  A  Normal  3 1 0 18 1C  Clean  500  A  Normal  3 1 0 1 8 1D  Dirty  500  A  Normal  040281C  Clean  500  A  (*)  Low  040281D  Dirty  500  A  (*)  Low  110281Cl  Clean  500  A  (#)  Very  Low  110281C2  Clean  500  A  (#)  Very  Low  180281C1  Clean  500  A  ($)  Low  180281C2  Clean  500  A  ($)  Low  180281C1  Clean  1 000 A  (fc)  High  180281C2  Clean  1 000 A  (&)  High  SAMPLE  G500D  NAME  .  HILLOCK  Notes: (*)  0.22  (#)  RFS  ($)  Vacuum  10"  (&)  Sample  sputtered  nm  f i l t e r  Equipment 7  installed thoroughly  Torr. again.  in  Argon  cleaned.  line.  DENSITY  89  It  is  not  sample is  whether  i s r e l a t e d t o the  some  correlation  equipment effect  and  the  of  submicron effects, also  conclusive  density  beteween  amount of  cleaning,  filter as  the  some  the of the  Ar  hillock  hillocks.  gas  line  with  sputtering. Experimentally,  plasma  behaved  evidence  could  low,  the  erratic  way,  growth  was  hillock be  found,  randomness  accurately  of  described,  noticeable  effect.  conditions  show  transmission  correlation  MeC-3Bi) i n a t t e m p t i n g  count  the  (10-20)  over  the  " s t a r sky"  Silicon  s a m p l e s , and  samples  although the RFS Ta  the  to  (BNR  all  pattern  pinholes.  the  that  No  when  the  moving  conclusive  samples  is  cannot  cases  was  too be  there  dark  The  a  field  done  in a  have  samples  little  pinhole  Ta-RFS  5.3  to  glass  hillock  is less  i n d i c a t e s perhaps a b e t t e r  the  density,  Upon e x a m i n a t i o n  density  5.8 and  It appears that  less  i s higher. pinhole  glass  wafer. F i g u r e s  silicon.  samples.  be  plasma  arcs  u n i t gave v e r y  Ta-MES on  samples, which again  positive  seems t o  of  under  a  O p t i c a l , m e t a l l u r g i c a l , Model  several  u n i t , the  the  observations  for  supplied)  f o r the MES  with  that  secondary a r c s  number of  in  e n t i r e 2"  magnification  transmission  film  find  transmission  show t h e  MES  (Union  There  secondary  not  RFS  some  affected.  the  the  and  microscope  examined with  as  with  there  installing  observed  Microscope examination no  and  stability we  glass  of. t h e  appears  produced  the  during  the  It  the  however  contamination  growth d i m i n i s h e d .  correlation  randomly,  hillocks,  decontaminating  i n the  i n an  c l e a n l i n e s s of  under  than  the  quality  Figure  5.4  Dark  Enhanced  Field  Photograph  Sputtered  ( 5 6 0 X ) , 500  on S i l i c o n  (sample  A Ta  Magnetron  BNR500).  Figure  5.5  Dark  Sputtered  Figure  5.6  Sputtered  on  Dark on  Field thin  Photograph Si0  Field thin  2  on S i l i c o n  Photograph  Si0  2  (140X),  (sample  (140X),  on S i l i c o n  200  A Ta 4T6).  50 A Ta  (sample  RF  2T6).  RF  Figure  5.7  Dark  Sputtered  on  Field thin  Photograph Si0  2  on  (140X),  Silicon  500  (sample  A Ta  RF  3T7).  •  Figure  5.8  Dark  Sputtered  on  Field thin  Photograph Si0  2  (140X),  on S i l i c o n  1000  (sample  A Ta 4T7).  RF  93  {5.5}  DISCUSSION OF  RESULTS:  {5.5.1} ELLIPSOMETRY: Data  obtained  from  t h e s a m p l e s BNR500 and  which the e l l i p s o m e t r i c  parameters  measured d u r i n g t h e d r y  thermal  form  in Figure  thickness) at  min  and  exhibits  15 min,  60  5.9  as o p p o s e d  oxidation  thickness).  The  increasing  t i m e . The  is  due  to  themselves It  after  is  360  2n  the  of  time,  that  long time.  properties this into  is  interpreted  that  of t h i s  work a r e  similar  report  parameter, oxidized.  changes  "P and  in  A  Ta  with curves  they-  repeat  after  and  attributed  a  from  curves period  ellipsometric Young  being e n t i r e l y to  (1981), converted  changes  in  annealing. It i s interesting  published  a s h a r p peak o f 46 d e g r e e s  A similar  at  the A  i n the  the  A c u r v e s v s . time  t o t h e ones  f o r a 400  (1000  are apparent  that,  place  the metal  structural  the  but  assume a c o n s t a n t  a trend i s given  take  as  slow  and  observe  They  i.e.,  of t h e o x i d e . F o l l o w i n g S m i t h  stoichiometry  of  Ta  for *  monotonically  both parameters  Indications  changes  oxide, with  A  degrees  BNR1000  discontinuity  sample BNR1000. T h i s i n d i c a t e s slow  graph  (500  50 d e g r e e s  property,  t h e BNR500 sample c u r v e s , and for  48  in  degrees.  expected  value a f t e r  peak o f  decreases  apparent  modulo  BNR500  f o r sample  A  periodically  i s shown  s h a r p peak of  for  parameter  its  Sample  t o a broad  time  A were  oxidation,  5.10.  a rather  * and  BNR1000, i n  A thick  tantalum  situation  exists  by  these  a t 20 min.  film for  obtained in  that A,  in  to  this  authors. f o r the  *  i s thermally which  the  94  360  r-  n  Time(min)  Figure 5.9 Ellipse-metric Data vs. Time, Sample BNR500  80  95  Figure 5.10 Ellipsometric Data vs. Time, Sample BNR1000  96  starting  value  is  follows a similar compared time  with  close  130  s h a p e . The s h i f t  metal.  oxidize a  We c a n t h e n  degrees,  thicker  be f u l l y  o x i d i z e d i n t h e above s e n s e  that  a longer  time,  a 1000 A Ta f i l m  Finally,  a  plot  grown  i n both  5.12  a r e computer p l o t s  termed  i.e.,  the "steady  that a  grown  place  with  peculiar should  to  their  film final  or  and t h a t  be f u r t h e r  was  refractive  index  and  Young,  used  t o perform [Boyd,  75 m i n . , and  grows,  the  value after  permanent"  5.11  and  ellipsometric  a certain  condition.  values  rest  time, It i s  on a l o c u s  shape o f t h e A-* c u r v e s  for  l a r g e changes of A take  This  g r o w t h of t h e r m a l  could  be  tantalum  a  property  pentoxide  that  investigated.  made  on  of t a n t a l u m several 2  5  the t h i c k n e s s computation runing  in In  [Young,  1981] w i t h a s u b s t r a t e i n d e x  1981],  oxide  samples.  o f 2.22 f o r t h e T a 0  i s based  to  d a t a . T h e s e g r a p h s c a n be  initially  determination  substrates  program  of a c t u a l  t o the general  the  film  A v s . * was made, a s t h e f i l m i s  s m a l l changes of  Thickness  ANALYS  of  state  oxide,  of  t o be 120 m i n . i s r e q u i r e d  t o n o t i c e that the f i n a l  corresponds  film  sample.  as the  approach  interesting  after  BNR500 and BNR1000 s a m p l e s . F i g u r e s  "transient",  parameters  (twice)  s a y t h a t a 500 A Ta  will  oxidize  as  represents the a d d i t i o n a l  safely  estimated  and t h e c u r v e  i n t h e BNR1000 c u r v e ,  t h e BNR500 sample,  required to f u l l y  tantalum  to  silicon  these,  1961;  layer,  Smith  o f 3 . 8 6 - J 0 . 0 2 5 was using the  program  i n t h e PDP8/E m i n i c o m p u t e r .  on t h e s i n g l e  a  optically  This  transparent  97  a?  •=*  * 20  v  *25  45  c-  60  <0  •»• 30 35 * 40 50 *65 75  CM"  LU  Q  as  LU  c  a  *T=0 min  os-  *  10  15  0.00  IS. 00  T  1~  30.00  ^S.00  PSI  / DECKCeC  T  CO.00  T  7S.00  Figure 5.11 Transient Ellipsometry, Sample BNR500  1  30.00  98  CT *60 * VO  65 * 75  rvi"  to  QL  LU •  CO  en -I  IT)  * x=0  *  min  10 20 25  30 35  •^40 45 ^ 55*  B . BE  1S.H0  30.BB PSI  5  0  T"  T  1S.BB /  T-  CB.BB  —I  7 S . BB  DEGREES  Figure 5.12 Transient Ellipsometry, Sample BNR1000  —1  30 . BB  99  model and no a l l o w a n c e s the  interface  al.,  between  a r e made f o r t h e t r a n s i t i o n  t h e T a { o x i d e } and s u b s t r a t e [Revesz e t  1974 and 1976 ( f o r t h e g r a d e d  Smith  and Young, 1981  are given  i n Table  refractive  model);  The  results  5.2.  5.2  OXIDE THICKNESS DETERMINATION Ta  index  ( f o r the t a p e r e d m o d e l ) ] .  TABLE  SAMPLE  layer at  BY ELLIPSOMETRY  THICKNESS  PROCESS  N2  400 A  Thermal  1173.3 A  N3  400 A  Thermal  1173.2 A  MOSC17  500 A  Anodic  890.5 A  MOSC 1 8  1 000 A  Anodic  1530.1 A  MTEST.T  500 A  Thermal  792.4 A  MTEST.A  500 A  Anodic  893.3 A  OXIDE THICKNESS  {5.5.2} C-V CURVES These  curves  described,  using  these v a r i e d , the o x i d e  were  obtained  t h e p r o g r a m CV  a to  Surface  distort  region.  method  1981].  parameters  i s anodic  appear  i t s shape,  I t was n o t i c e d t h a t  accumulation  region  as  of thermal a  factor.  also  plays  i n some c u r v e s , and t h e y  tend  particularly  solution  such  or thermal,  of o x i d a t i o n i s a l s o  oxides, the e l e c t r o l y t e states  already  The shape of  p r o c e s s i n g , a n d a n n e a l i n g . In t h e c a s e  the anodic  role.  [Boyd,  the oxide  grown o x i d e s , t h e t e m p e r a t u r e With  the  and i t d e p e n d e d on s e v e r a l  t h i c k n e s s , whether  substrate,  by  around  i n the A l - T a 0 - S i  was d i f f i c u l t  2  5  to obtain,  the i n v e r s i o n samples,  the  independently  100  of  t h e s u b s t r a t e t y p e . T h i s was n o t t h e c a s e  dielectric  samples,  structure.  However,  encountered curve  in  i . e . , those in  obtaining  i s quite "noisy",  surface  some  states  a  with  defined  indicating  ramp). The f a c t  that  accumulation  obtain  in  This  correlates  the double layer  dielectric  prevents  examination this  MOS  Another  interesting  capacitors,  understood,  decrease  i n apparent  leakage  currents  the  is  some c a s e s , probably  dielectric.  insulator.  itself a weak  in  that  flowing. region in  which  and  at  the  the  Si0  2  F o r example,  and  reduction  approaching  T h i s phenomena i s related  due  to  an  increase  of  accumulation.  two a n o d i c  1984],  C-V  (ionic)  oxide charge i n  of  indicates a  in  i n the  lack  not  to a  Similar  researchers [Nishioka,  the  of the  be  onset  large hysteresis,  the  to  due t o t h e m o b i l e However,  a  of  seems  large hysteresis  dependent  9 and 10) show  when  it  by o t h e r  that  inversion.  curves with h y s t e r e s i s  process  indicates  characteristic  is  capacitance  were o b s e r v e d  obtaining  capacitors,  to  corroborates  r e g i o n from  observed,  gate  o f t h e I-V c u r v e s , a s shown l a t e r ,  accumulation  In  slow  Furthermore,  manifests  results  slow  (leakage) c u r r e n t s are  excessive electronic  dielectric  well  samples,  of  difficult  the obtainable accumulation  capacitance  not  is  was  conduction.  analysis.  single  with  2  i . e . , the  the r e l a t i v e l y  dielectric  large conduction  5  presence  voltage  double  difficulty  the  follow  relatively  2  inversion;  they  single  the  Al-Ta 0 -Si0 -Si  cases,  (since  the  in  curve  was  consistency that  this  in  effect  d e f i n e d p r o p e r t y of the grown T a O  b u t upon  samples  (MOSC  fabricating  more  2  s  101  samples w i t h hysteresis double  V,  i s observed  dielectric  thickness 5  t h e same c i t r i c  over  capacitors increase was  total  the c r y s t a l to  currents. This  crystalline  like  than  a conductor Ta 0 2  sputtered  thermally  effect  range  an i n s u l a t o r .  was  at  i n nitrogen observed  [Kimura  reasonable  i n c a p a c i t a n c e was  The  C-V  5.3  results  the  Dielectric  MOS  are presented  is  MOS  at  change range  Then  re-  b e h a v e s more indicates  for  reactively  et a l . , MOSC  (MOSC6, except  recorded  and v e r y  3 and 4  500  that  1983].  A  a  accumulation  Ta) large and  high. i n a summary Single  Double D i e l e c t r i c  form  i n Tables  Dielectric  (MOS-SD)  (MOS-DD) and MOS S i n g l e  Capacitors.  using the value  which  curve,  c u r r e n t s were a l s o  5.4 and 5.5, f o r t h e  thermal  By  C-V  500C),  work  f o r sample  a  (an  short  order).  650-700C  produced  leakage  of  (i.e.,  MOS  5  600C  due t o a  Previous  a t 600C. However, one sample  that  2  temperature  processed  decrease  Ta 0  at  p l a c e and t h e i n s u l a t o r  f i l m s annealed  field  single  amorphous  (large  obtained  memory c a p a c i t o r s .  i s possibly  from  recrystallizes  5  ( 4 T 7 , 1000 A Ta  large h y s t e r e s i s curves  processed  structure,  no  a l a r g e h y s t e r e s i s of  p e r t i n e n t to the  were  takes  No  exhibits  (1978) f o r t h e i r  crystallization  that  sample  a b s e n c e o f MOS c a p a c i t o r b e h a v i o u r  large conduction  order)  the very  little,or  MOSC 13, 15, 17 and 18). One  capacitor  pecularity which  process, very  o f 100C above t h e " n o r m a l "  the  in  MOS  2  and T a l l e y  Another  (samples  50 A of S i 0 )  approaching  by A n g l e  acid  the  of  oxide  capacitance capacitance  in Cox,  deep  accumulation,  i t i spossible to  102  calculate  the  relative C e  dielectric t  ox  =  constant  from:  ox  (5.9)  A £ 0  The  area  A  i n most c a s e s  diameter  dot.  ellipsometer  The  thickness  measurements or  swelling  factor.  from  C-V  the  i s 0.7854x10"  The  curves  i s given  t h a t of a  2  tox,  from  calculated  m,  6  was  obtained  calculations  relative  in Tables  mm from  using  dielectric  5.6  1  the  constant  (thermal)  and  5.7  (anodic). The  value  makes t h e is  of  flatband  surface potential  obtained  flatband  the  from t h e  Debye l e n g t h  [Sze,  c  Cfb  1969;  -  R  \//s=0, t h u s  C-V  capacitance  voltage Vfb  plot with  by  the  producing  first  equation  the  value  four point  This  value  possible [Sze,  involves  Vfb  is  Na  or Nd  entered  obtained. the  fixed  into With  i s obtained Irvin's  t h e C-V the  charge  curve  latter i n the  C = —22E_(d> rc q rtis  v  „  ) ID  n type  fc  =  q  ( V  fb  +  W  p type  (5.12)  and it  oxide  (5.11)  C Q  from  charts.  p.468]:  Q  the  (5.io)  measurements and  i s then  calculate  1969;  the  1 1  s u b s t r a t e doping  of C f b  to  that  ZIZZZZ  resistivity  corresponding  flatbands),  calculating  1/C +(/kT/e N,/a) ' ox ' s AD '  the  which  1  fb  of  that  p.435]:  v  The  (i.e.,  a is  Qfc  1 03  This  i s a straightfoward  the  metal-semiconductor  However, i n s u f f i c i e n t function  by  "  ( x  +  E  g  /  2  q  *ms  =  *  "  ( x  +  E  g  /  2  q  [Sze,  0ms MIS  " V  from band  the  F  i>j?  It is  expression  diagram  [Glaser,  V  +  P type  (5.13a)  (5.13b)  the  silicon  [Angle,  1976]  f o r the  the f o l l o w i n g v a l u e s are  q0m=4.1  eV  qx=4.45  eV  1.12  impurity  eV.  The  last  semiconductor  quantity  is  = — —  concentration:  =  kT  — —  I n (.n-/tog)  ln(N /n ) A  ±  n type  p  taken  \pF i s a f u n c t i o n  kT  ^  work  1969]:  be  substrate  structures.  n type  b a n d g a p e n e r g y Eg o f t h e s i l i c o n to  i s known.  r e s p e c t i v e l y . I n t h e band d i a g r a m  structure  5  the  5  x a r e t h e m e t a l work f u n c t i o n and  affinity  0ms,  of  1969]:  *m  Al-Ta 0 -Si  here  Sze,  =  electron  The  of  ^ms  Where 0m and  used  2  1977;  m  value  difference  o f m e t a l s on T a 0 - S i  analysis  Suback-Sharpe,  2  work f u n c t i o n  t o compute t h e v a l u e o f  obtained  i f the  d a t a o r none i s a v a i l a b l e on t h e  properties  possible  calculation  type  (5.14a)  (5.14b)  of  104  Were \//F i s t h e d i f f e r e n c e between semiconductor average  doping  intrinsic value  and  concentration  concentration  of  With  these  Fermi  i t sintrinsic of  4.5xl0 * 1  1 . 8x10  cm" ,  10  o f \pF i s -0.263 V f o r n t y p e  substrates. and  substrate  the  3  level  of  v a l u e . U s i n g an cm""  3  and  an  the c a l c u l a t e d  and +0.263 V f o r  quantities,  the  the values  p  type  o f 0ms  forn  fixed  oxide  p m a t e r i a l c a n be c a l c u l a t e d :  0ms=-O.647 V n - S i s u b s t r a t e 0ms=-1.173  Finally, charge  V p-Si substrate  the f l a t b a n d v o l t a g e , capacitance i s given  i n Tables  5.8  (thermal)  and  and 5.9 ( a n o d i c ) .  1  TABLE RESUME  OF  THERMAL  SAMPLE/THICKNESS  5.3  OXIDE MOS-SD  TEMP/TIME  CAPACITORS  C-V  ACCUMULATION CAP.  CURVES  COMMENTS  57500  pF/cm  2  Acc.Diff.  8500  pF/cm  2  A c c . D i f f.  500C/93min  76250  pF/cm  2  Low  BNR1000/1000A  500C/187min  94063  pF/cm  2  Acc.Diff.  SampleA/500A  500C/21Omin  160000  pF/cm  2  Acc.Diff.  SampleB/1000A  500C/21Omin  84000  pF/cm  2  Acc.Diff.  1000AMOS/1000A  500C/360min  120000  pF/cm  2  Peak  500ALift/500A  500C/390min  175000  pF/cm  2  Acc.Diff.  MOSC1/500A  400C/300min  n/a  n/a  No  MOS  Cap.  MOSC2/1000A  400C/420min  n/a  n/a  No  MOS  Cap.  MOSC3/500A  600C/300min  n/a  n/a  No  MOS  Cap.  MOSC4/1000A  600C/420min  n/a  n/a  No  MOS  Cap.  MOSC6/500A  600C/300min  130000  pF/cm  2  Peak  Acc.  MOSC7/1000A  400C/1wk  150000  pF/cm  2  Peak  Acc.  MOSC8/1000A  600C/420min  98750  pF/cm  2  Peak  Acc.  N2/400A  500C/80min  N3/400A  500C/320min  BNR500/500A  Notes: 1.  Acc.  Diff.:  2.  Hyst.:  Accumulation  Hysterisis.  D i f f i c u l t .  Hyst.  Acc.  1 06  TABLE RESUME  OF  THERMAL  SAMPLE/THICKNESS  5.4  OXIDE MOS-DD CAPACITORS  TEMP/TIME  ACCUMULATION CAP.  COMMENTS  1T6/20S20T  A  500C/3min  33875  pF/cm  2  Inv.  2T6/20S50T  A  500C/7.5min  27032  pF/cm  2  Smooth  SS  3T6/20S100T  A  500C/15min  28438  pF/cm  2  Low  4T6/20S200T  A  500C/30min  28750  pF/cm  2  Inv.  SS  1T7/50S100T  A  500C/15min  13375  pF/cm  2  Inv.  SS  2T7/50S200T  A  500C/30min  24000  pF/cm  2  Peak  Acc.  3T7/50S500T  A  500C/75min  20000  pF/cm  2  Low  500C/150min  20500  pF/cm  4T7/50S1000T  A  Notes: 1.  C- •V C U R V E S  Inv.  SS:  Inversion  with  Surface  States.  :  Hyst.  Hyst.  Large  Hyst  TABLE 5.5 RESUME OF ANODIC OXIDE MOS-SD CAPACITORS C-V CURVES SAMPLE/THICKNESS  PROCESS  ACCUMULATION CAP.  COMMENTS  MOSC9/500 A  Citric  Ac i d  25000 pF/cm  2  Large  Hyst  MOSC10/500 A  Citric  Ac i d  1 5000 pF/cm  2  Large  Hyst  MOSC11/1000 A  Phosp . Ac i d  76875 pF/cm  2  Peak A c c .  MOSC12/500 A  Phosp . A c i d  87500 pF/cm  2  Peak A c c .  Ac i d  431 25 pF/cm  2  Acc.Diff.  Phosp . A c i d  70000 pF/cm  2  Acc.Diff.  Ac i d  51875 pF/cm  2  Smooth  Phosp . Ac i d  88750 pF/cm  2  Peak A c c .  MOSC13/500 A MOSC14/500 A MOSC15/1000 A MOSC16/500 A  Citric  Citric  MOSC17/500 A  Citric  Ac i d  77000 pF/cm  2  Low  Hyst.  MOSC18/1000 A  Citric  Ac i d  82750 pF/cm  2  Peak A c c .  TABLE CALCULATED  RELATIVE DIELECTRIC  SAMPLE  Ta  THICKNESS  5.6 CONSTANT  OF  THERMAL  TEMP/TIME  Ta er  N2  400  A  500C/80min  5 .57  N3  400  A  500C/320min  0 .82  BNR500  500  A  500C/93min  9 .24  BNR1000  1000  A  500C/187min  22 . 7 8  SampleA  500  A  500C/21Omin  1 9.38  SampleB  1 000 A  500C/21Omin  20 . 3 4  1000AMOS  1 000 A  500C/360min  29 . 0 6  500  A  500C/390min  21 . 2 0  500  A  600C/300min  1 5.75  500ALift MOSC6 MOSC7  1 000 A  400C/1  week  36 . 3 2  MOSC8  1 000 A  600C/420min  23 .91  2  TABLE CALCULATED SAMPLE  RELATIVE Ta  DIELECTRIC  THICKNESS  5.7 CONSTANT  OF  PROCESS  ANODIC  Ta  er  MOSC9  500  A  Citric  Acid  3 .03  MOSC10  500  A  C i t r i c  Acid  1 .82  MOSC11  1 000 A  MOSC12  500  A  MOSC13  500  A  MOSC14  500  A  MOSC15  1 000 A  Phosp.Acid  18 . 6 2  Phosp.Ac id  1 0 .60  Acid  5 .22  Phosp.Ac id  8 .48  C i t r i c  C i t r i c  Acid  1 0 .75  MOSC16  500  A  MOSC17  500  A  C i t r i c  Acid  9 .33  1 000 A  C i t r i c  Acid  20 . 0 4  MOSC18  Phosp.Acid  1 2 .56  TABLE FLATBAND  VOLTAGE,  SINGLE SAMPLE  TYPE  CAPACITANCE  DIELECTRIC Cfb  5.8  Ta 0 2  [pf/cm ] 2  5  AND F I X E D  C H A R G E OF  MOS  CAPACITORS  Vfb  [V]  Qfc  [e/cm ] 2  N2  n  28595  + 1 .85  -8.96X10  N3  n  7395  -1  +5.43x10 °  BNR500  P  32295  + 0.56  - 2 . 9 2 X 1 0  BNR500  P  35111  + 1 .35  + 8 . 2 2 X 1 0  SampleA  P  41 4 9 4  -6.57  -7.73X10  SampleB  P  33608  -6.49  - 4 . 0 2 X 1 0  1000AMOS  n  381 92  500ALift  P  42437  MOSC6  n  MOSC7 MOSC8  .67  -10.24  1 1  1  1  1  1  0  1  1  2  2  +7 . 18x10  1 2  -8.03  -1  1 3  3 9 1 51  -2.00  + 1.10x10  n  40789  -1  + 6 . 0 2 X 1 0  n  35744  -5.00  .29  .01X10  +2.68x10  1  1  2  1  1  2  111  TABLE FLATBAND  VOLTAGE, DOUBLE  SAMPLE  TYPE  CAPACITANCE  DIELECTRIC  Cfb  5.9  [pf/cm ] 2  AND F I X E D  CHARGE  OF  MOS C A P A C I T O R S Vfb  [V]  Qfc  [e/cm ] 2  1T6  n  21231  -2.95  +4.87x10  2T6  n  18324  - 4 . 37  +6 . 2 8 X 1 0  3T6  n  18863  -9.17  +1.51x10  1 2  4T6  n  18931  -7.67  +1.25X10  1 2  1T7  n  1 3375  -3.33  +2.24X10  1  1  2T7  n  1 6741  -8.26  + 1.13x10  1  2  3T7  n  1 6053  -0.24  -5.71X10  4T7 .  n  1 4941  -5.63  +6 . 3 4 X 1 0  1 1  1  1  1 0  1  1  TABLE FLATBAND  VOLTAGE, ANODIC  SAMPLE  TYPE  Cfb  5.10  CAPACITANCE Ta 0 2  MOS  5  [pf/cm ] 2  AND F I X E D CHARGE OF CAPACITORS Vfb  [V]  Qfc  [e/cm ] 2  MOSC9  n  1 7286  -5.35  + 7 . 3 4 X 1 0  MOSC9  n  17286  +2.28  - 4 . 5 6 x 1 0  MOSC10  n  1 1 832  -1.13  MOSC10  n  1 1 832  MOSC 1 1  n  32406  MOSC 1 2  n  341  MOSC 1 3  n  MOSC 1 4  '  1  1  1  1  - 4 . 5 2 X 1 0  1  0  + 2.16  - 2 . 6 3 X 1 0  1  1  -2.24  + 7 . 6 4 X 1 0  1  1  -2.05  + 7 . 6 6 X 1 0  1  1  24367  + 0.51  - 3 . 1 1x10  1  1  n  31118  -0.39  -1.12x10  1  1  MOSC 1 5  n  26935  + 1.61  - 7 . 3 0 X 1 0  MOSC 1 6  n  34343  -3.66  +2 . 1 7 x 1 0  MOSC17  n  32428  -2.21  +7 . 5 1 X 1 0  1  1  MOSC18  n  33406  -4.02  + 1 . 7 4 X 1 0  1  2  55  1  1  1  2  113  I t can and  be c o n c l u d e d  calculations  t h e n , t h a t from that  operational  f a b r i c a t e d u s i n g t h e r m a l and tantalum  pentoxide.  the  anodic  above  MOS  c a p a c i t o r s can  processes  Furthermore,  measurements  double  for  be  obtaining  dielectric  MOS  c a p a c i t o r s a l s o show g o o d o p e r a t i o n a l c h a r a c t e r i s t i c s . In p a r t i c u l a r , 5.10, 1.  i t can The  from  be  the r e s u l t s p r e s e n t e d  said  i n Tables  5.6  that:  calculated  value  of  the  relative  dielectric  c o n s t a n t v a r i e s a c c o r d i n g t o t h e t h i c k n e s s of t h e Ta 0 2  f i l m and  5  i n the case  of t h e t h e r m a l With  short  oxidation  the v a l u e of  effect  i s a l s o n o t i c e d by p r e v i o u s a u t h o r s  1984],  very t h i n (1974)  and  i t was  l a y e r of S i 0  reported  tantalum  times,  oxide  attributed 2  at the  that at  thin  oxide,  w i t h the o x i d a t i o n time.  al.,  with  films  and  er i s l e s s .  This  anodic  oxide  higher  the  value  Young Ta and  (1981)  of  T a 0 , and 2  the  Ta 0  as a  5  film  thermal  oxide  2  constant t o an  the  increase in  for a  of 26  These  than  r e p o r t e d by Young ( 1 9 6 1 ) of 27, (MIM)  film.  5  less  capacitor;  by  Smith  f o r a p-MOS c a p a c i t o r w i t h  o x i d e ; but h i g h e r than Allison  the  are  Metal-Insulator-Metal  i n the  to  with co-oxidation  p o s s i b l y due  p o r o s i t y or inhomogeneity than  index  dielectric  samples,  [ N i s h i o k a et  incorporates  t h e o x i d e t h i c k n e s s . The  samples g i v e a  varies  t o t h e f o r m a t i o n of a  interface,  consequence, the r e f r a c t i v e  final  i n t e r f a c e . Revesz et a l .  silicon  the  oxide  i t e r a c t i o n d u r i n g t h e g r o w t h of t h e r m a l  decreased  to  (1976) of  t h e ones o b t a i n e d  11.4  for thermal  and  thermal  by  tantalum  Revesz oxide  11 4  on 2.  silicon  The  substrates.  f l a t b a n d v o l t a g e s are  vary  in  magnitude  substrate. highest the  lowest.  thermal  The  charge  and  sign,  depending  oxide.  i n the  The  on  the  a positive  charge  mostly  a negative  charge,  range  of  dielectric  samples, Qfc  range  2.2X10  2  of  exhibits  5  was  formed  charge  substrate compared 4.5X10 oxide  1 1  as  Allison, charge  type. with to  These  Its  the  reported  i n the  and  by  i n the  oxide  and the  samples  c a p a c i t o r s have  n type  p type its  mostly  samples  magnitude In t h e  acid,  and  acid,  with  with  charges/cm . 2  previous  when made on 6x10  1 1  -5x10  negative same as  range  of  a  tantalum  [Revesz  1981], has p type  oxide  smaller  Thermal  authors  Young,  a  a  anodic  the  i s somewhat  oxides,  double  the  mostly  the  with  2  if  have  in  positive,  charge  of  exhibit  c h a r g e s / c m . The  1 2  citric  range  nature  samples  2  1.5X10  i n magnitude  the  charges/cm .  1 3  is  S m i t h and  oxide  the  magnitude  1 2  process  varies  on  5  with  thermal  2.2X10  1976;  2  a positive  in  they  exhibited  MOS  Qfc,  Ta 0  phosphoric  formed  m a g n i t u d e was  {5.5.3} I-V  mostly  in  if  to  1 1  sample  s u b s t r a t e and  1X10  to  of  and  these.  thermal  11  type  the anodic  oxide,  mostly  2.9x1U  negative,  dielectric  v o l t a g e s between  fixed  Ta 0  the oxide  double  The  the  with  f l a t b a n d v o l t a g e s , and  flatband 3.  The  mostly  a  and  negative  substrates. Its 1 2  .  CURVES: curves  were  obtained  by  the  method  already  11 5  described. obtain  From  the  constant,  the  value  of  which  refraction.  Schottky  is  the  graphs,  optical  equal  to  i s possible  relative  the  By u s i n g t h e S c h o t t k y  it  dielectric  square of the  emission  is  can a  straight  line.  l i n e can  several  slopes  be  I n most c a s e s o b t a i n e d . In  denoting  Schottky  models.  calculate  the S c h o t t k y  l " 2 {—^ l n J , - l n J E  The  a  other  complex  following  in l o g  in Table  1 0  straight  ,l n E„h ) 2  I  plot  f i t to a  there  are  phenomena,  the P o o l e - F r e n k e l  expression  was  used  or to  2  2  -SL-  {  5  #  1  5  )  2  0  v s . /V  were d o n e , a s our form.  lines, be  most  indicating  represented  Schottky  plots  A summary of r e s u l t s  is  are  given  optical  the emission  are a l s o given al.,  of T a 0 2  5  departs  Smith  that  s l o p e can  relative  i n Table  1976;  of the S c h o t t k y the  p l o t s are  emission  on S i l i c o n  model.  i n t e r p r e t e d as a  permittivity.  The  p l o t s p r o v i d e an  from t h e s e  5.11.  and  be  classical  substrates i s a  indication  of of  models. These  the t y p i c a l two  value  number  From p r e v i o u s a u t h o r s  Young, 1981],  not  mechanism  by a P o o l e - F r e n k e l o r S c h o t t k y  s l o p e changes i n the S c h o t t k y  plot  cases,  2.  mentioned,  of c o n s t a n t  et  the  conduction  (kT)  E a c h p o r t i o n of c o n s t a n t  how  curves,  5.11.  already  cannot  -  0  Appropriate conversions  As  by  slope:  , „h }(lnE^  E  1  given  and  however, a best  w h i c h d e p a r t s c o n s i d e r a b l y from e i t h e r  =  of  be c a l c u l a t e d . T h i s a s s u m e s t h a t t h e S c h o t t k y  straight  e  index  model,  o b t a i n i n g t h e s l o p e 31nJ/3v/E i n t h e e x p e r i m e n t a l er(«)  to  slope  [Kaplan Schottky curve,  11 6  w i t h a somewhat a  slope  that  dielectric that  k n e e . In i t , t h e h i g h  i s close  t o the o p t i c a l  c o n s t a n t . However,  some samples e x h i b i t  provides different ohmic  sharp  in this  r e g i o n a t low  fields,  when  Schottky  form.  the  In  v a l u e of t h e work  two and t h r e e s l o p e s . Mead  (1962)  s a m p l e s and t h e y  work, he n o t e s  and a exp(i/V)  conduction  TABLE  THE FOR  SAMPLE/TYPE  that  have  three  there  i s an  region  characteristic  at  higher  i s plotted in  5.11  RESUME OF SCHOTTKY I-V CURVES AND OPTICAL VALUE OF  we  relative found  his  fields  r e g i o n has  have  i n f o r m a t i o n of h i s MIM slopes.  field  CALCULATED  RELATIVE DIELECTRIC CONSTANT THERMAL T a 0  PROCESS  2  5  er (o>)  COMMENTS  N2/n  Thermal/500C  3.032  Curve  N3/n  Thermal/500C  1 .925  Two  Slopes  Nl/n  Thermal/500C  5.455  Two  Slopes  BNR500/p  Thermal/500C  8.523  Curve  BNR1000/p  Thermal/500C  21.056  Two  Slopes  SampleA/p  Thermal/500C  2.424  Two  Slopes  SampleB/p  Thermal/500C  3.867  Two  Slopes  1OOOAMOS/n  Thermal/500C  1.895/1.213 T h r e e  Slopes  500ALift/p  Thermal/500C  1.364/1.435 T h r e e  Slopes  lOOOALift/p  Thermal/500C  1.213  M0SC6/n  Thermal/600C  50.928  Two  Slopes  MOSC7/n  Thermal/400C  174.643  Two  Slopes  MOSC8/n  Thermal/600C  3.564  Two  Slopes  w/null  w/null  Curve  1 17  TABLE RESUME OPTICAL  VALUE  OF OF  SCHOTTKY THE  5.12  I-V  RELATIVE  CURVES  DIELECTRIC  Ta 0 2  SAMPLE/TYPE  AND  CALCULATED CONSTANT  FOR  ANODIC  5  PROCESS  er  (co)  COMMENTS  MOSC9/n  Citric  Ac i d  3 . 491  Two  Slopes  MOSC10/n  Citric  Ac i d  18. 334  Str.  MOSC13/n  Citric  Ac i d  2 5 . 047  MOSC14/n  Phosp.  Ac i d  17. 240  Three  Slope  MOSC15/n  Citric  Ac i d  4 . 378  Three  Slope  MOSC16/n  Phosp.  Ac i d  12. 732  Curve  MOSC17/n  Citric  Ac i d  6. 734  Curve  MOSCl8/n  Citric  Ac i d  17. 055  Curve  Line  f:  Curve  1 18  In some s a m p l e s , the  Schottky  the  fact  can  conduction  at  for  three  mechanisms:  at  fields  trapped  and low  at  high  is field  temperatures,  electrons Frenkel  into type  fields,  current of  that  thermal  is  band,  a  forward  oxides  under  limited  attributed  to  i s responsible for type  emission; the c u r r e n t of  producing  Balog  and  limited  trapped a PooleFrohman-  P-F e m i s s i o n a t  towards a space  and T a l l e y  experimental  charge  limited  (1978) a r g u e t h a t t h e i n the anodic  data,  P-F t y p e c o n d u c t i o n  forward  mechanism  surface  they  and  concluded  takes place f o r  b i a s and under  conduction the  of  They p r o v i d e an e m p i r i c a l r e l a t i o n  Angle  bias,  prevails;  ionization  excitation  mechanisms a r e q u i t e d i f f e r e n t  charge  interface  reverse bias, a  dominates,  s t a t e s at the  which  Al-Ta{oxide}  formed d u r i n g p r o c e s s i n g .  A clear MOS  2  band  Kaplan,  fields.  JaV ' .  field  temperatures,  thermal  conduction  o x i d e s . From t h e i r  under  space  by  and a t r a n s i t i o n  form  conduction  and h i g h  (1976) c o n s i d e r a b u l k  at higher  the  thermal  the  respective  v o l t a g e s and h i g h  a Fowler-Nordheim  emission.  Bentchkowsky low  -fields  enhanced  c u r r e n t s . Mead  their  applied  emission  an ohmic c h a r a c t e r i s t i c  the c u r r e n t flow, y i e l d i n g  flow  low  from  reinforces  Schottky  with  e l e c t r o n s i n the conduction  finally  or  er(°°)  This  the conduction  regions  room) t e m p e r a t u r e s ,  high  of  are q u i t e unreasonable.  account  proposed  (i.e.,  values  that neither a Poole-Frenkel  mechanisms (1962)  plots  the c a l c u l a t e d  evidence  capacitors.  illuminated,  It  of photoconduction  was  was n o t i c e d t h a t when  large variations  found  in  the  t h e samples were  i n * conduction  current  took  1 19  place,  as d e t e c t e d  leakage the  c u r r e n t . Some s a m p l e s  incident light  Westinghouse exactly  given  Heat  25 cm above  exhibited and  by t h e e l e c t r o m e t e r  than  conduction stepping  band,  stones  source  250 W,  but r e l a t e d  of p h o t o c u r r e n t that  this  Some  t o which photo generated i n the i n s u l a t o r  bandgap.  that  a  samples others,  i n c r e a s e , as  phenomena  to the traps  was  115 V, p l a c e d  t o the a p p l i e d l i g h t  5.11, i t s u g g e s t s  dependent,  light  of t h e sample.  from t h e c a l c u l a t e d r a t i o s  process  The  Ray ( i n f r a r e d ) lamp, the centre  i n measuring the  e x h i b i t e d more s e n s i t i v i t y t o  others.  more s e n s i t i v i t y  i n Table  used  i s not  i n the oxide's  electrons  use  as  TABLE PHOTOCONDUCTION SAMPLE  IN  5.13  TANTALUM  PROCESS  OXIDE  MOS  PHOTOCURRENT  N2  Thermal/500C  3.5  1T6  Thermal/500C  3.7  2T6  Thermal/500C  15.8  3T6  Thermal/500C  2.3  4T6  Thermal/500C  1 .0  1T7  Thermal/500C  133.3  2T7  Thermal/500C  2.0  3T7  Thermal/500C  3.2  4T7  Thermal/500C  1 .3  N1  Thermal/500C  8.0  BNR.500  Thermal/500C  6.3  SampleA  Thermal/500C  1 .0  SampleB  Thermal/500C  5.6  1000AMOS  Thermal/500C  3.5  500ALift  Thermal/500C  1 .2  1OOOALift  Thermal/500C  2.0  MOSC6  Thermal/600C  1 .5  MOSC 7  Thermal/400C  32.0  MOSC8  Thermal/600C  3.2  MOSC14  Anodic/Phosp.  5.5  MOSC15  Anodic/Citric  20.5  MOSC16  Anodic/Phosp.  MOSC17  Anodic/Citric  MOSC18  Anodic/Ci tr ic  1 .3 11.0 1 .8  CAPACITORS  121  {5.6}  INTERFACIAL OXIDATION MOS Both  samples.  C-V  and  I t was  excellent  I-V  noted  inversion  regions.  towards  difficulties  that  visible This  indicates  structure  is  Si0  under  2  layer The  process  i s quite  2  from  current  magnitude  than  b o t h C-V  5.12 and  and I-V  the  5  the  as  a  smooth of  dielectric is of  of and  the Ta 0 2  5  also  without  surface  states.  dielectric  t h e method o f g r o w i n g  the  successful.  the  small,  had  double  curves also  previous  5.13 data.  that  I-V  i s quite  the  of  these  curves are  none  region  i s quite  successful,  (leakage)  Tables  good and  the T a 0  with  the presence  for  accumulation  sample  single  acumulation  the q u a l i t y  very  results  the  i n the  indicate  that  obtained  defined  accumulation,  The  bumps, t h a t  well first,  appeared  capacitors.  were  i n g e n e r a l t h e C-V  with  In t h e  transition  MOS  curves  that  quality,  CAPACITORS:  indicate  electronic of c o m p a r a b l e  double  summarize t h e  dielectric  that  this  conduction or  smaller process.  results obtained  from  1 22  TABLE INTERFACIAL SAMPLE  WET  O X I D A T I O N MOS  OX.TIME  MTJ 1  3-54-3  min  MTJ 1  3-54-3  min  MTJ 2  3-114-3 min  MTJ 2  3-114-3 min  MTJ 3  3-54-3  min  MTJ 3  3-54-3  min  MTJ 4  3-24-3  min  MTJ 4  3-24-3  min  MTJ 5  CAPACITORS ,  Ta 0 /Si0 2  5  Si0  2  5  Si0  2  2  s  Si0  Ta 0 /Si0 2  5  Si0  2  2  2  OXIDATION  2  2  Ta 0  INSULATOR  2  Ta O /Si0  N/A  INTERFACIAL  2  Ta 0 /Si0 2  C-V  RESULTS  ACCUMULATION C A P .  INSULATOR  TABLE  SAMPLE  5.14  5  51875  pF/cm  2  46500  pF/cm  2  76750  pF/cm  2  56563  pF/cm  2  88750  pF/cm  2  75000  pF/cm  2  106250  pF/cm  2  117500  pF/cm  2  175000  pF/cm  2  5.15  MOS C A P A C I T O R S ,  LEAKAGE  CURRENT  I-V  RESULTS  SCHOTTKY  MTJ 1  Double  0.52  nA a t  10 V  Two  MTJ 2  Double  0.30  nA a t  10 V  Two  MTJ 3  Double  0.52  nA a t  10 V  Two  MTJ 4  Double  13  MTJ 5  Ta 0 2  5  14.5  nA a t MA  at  10 V 10 V  Two Three  SLOPES  1 23  CHAPTER 6  FABRICATION AND PROCESSING OF MTAOS F I E L D EFFECT TRANSISTORS  The  MTAOS a c t i v e  already  developed  particular  the  liftoff  on s i l i c o n  modified  version  Solid  fabricate  at a  Enhancement as Two  this  in  dedicated  two  dielectric  Further reveal  o f t h e MOS  were  of  C-V  the  structure, processed and  following general 1) T h i c k n e s s  used i n  Engineering  objective  the  its  thermal  tantalum  n-type  Si  was  to  p-Channel feasibility  and  anodic  pentoxide.  substrates,  This each  p r e p a r a t i o n method. In o r d e r t o quality  several  of  the  final  substrates  f o r dot and  ring  I-V measurements o f t h e s e  the insulator  i s b a s e d on a  insulator  for preparing groups  of  family.  followed:  verify  simultaneously  oxidation  MOSFET, and t o d e m o n s t r a t e  t o the i n d i v i d u a l  independently  anodic  The  double  2  the  MOS c a p a c i t o r s , i n  Electrical  University.  5  using  p-MOS t e c h n o l o g y  Laboratory,  methods  resulted  and  the standard  a new a c t i v e d e v i c e  oxidation  The  of  2  main a v e n u e s  f o r the  process  Ta 0 /Si0 type  fabricated  s u b s t r a t e s . The p r o c e s s i n g  State  Department,  were  techniques  tantalum  the  devices  were  double also  MOS  capacitors.  will  accurately  performance. processing  and f o u r p o i n t  2)  S c r i b i n g and m a r k i n g .  3)  Peroxide-acid  4)  Thermal o x i d a t i o n of  steps  were  followed:  resistivity  cleaning using  t h e RCA  substrates,  measurements.  process.  using  t h e "wet"  1 24  hydrogen600 5)  oxide  thickness target:  nm. Photolithography  field 6)  oxygen method. F i e l d  of  source  and  drain  windows  on  predeposition  and  oxide.  S o u r c e and  d r a i n boron d i f f u s i o n s :  dr i v e - i n . 7) G a t e p h o t o l i t h o g r a p h y , 8)  Thermal  oxidation,  for  the  Si0  9)  thin  gate  2  window using  in f i e l d  the  "dry"  Aluminium  thermal  oxygen  method,  insulator.  Peroxide-acid cleaning, excluding  10)  oxide.  t h e HF  evaporation  in  for  step.  preparation  for  liftoff. 11)  Photolithography  of a l u m i n i u m  12)  RF  tantalum  13)  T h e r m a l o x i d a t i o n of  14)  Anodic  15)  Liftoff  16)  I n s p e c t i o n of a l l w a f e r s under  17)  Peroxide-Acid  S p u t t e r i n g of  18)  Drain  gate  oxide.  19)  o x i d a t i o n of  and  metal.  first second  p a t t e r n i n g of  group i n dry  I n s p e c t i o n and  tantalum  acid.  pentoxide. microscope. t h e HF  photolithography  photography  oxygen.  group i n c i t r i c  cleaning, excluding source  liftoff.  of  all  step.  t o remove  wafers  thin  under  microscope. 20) 21)  Peroxide-Acid Aluminium  cleaning, exluding  evaporation  for  source,  22)  Photolithography  gate  d r a i n and  contacts.  gate of  by  t h e HF  step.  e l e c t r o n beam  technique  contacts.  aluminium  source,  drain  and  125  23)  Thick  oxide  for  substrate  24)  Gold  back  e t c h i n g on w a f e r ' s back,  (back)  evaporation  preparation  contact. by  Electron  Beam  technique  for  contact.  25)  Final  microscope  inspection  of  a l l wafers.  Photography.  The under  first  three  Chapter  4, and t h e y  were s c r i b e d w i t h easily  wafers,  {6.1}  identified.  together  with  three  so  here.  that  detail  A l l wafers  they  S i x MTAOS d e v i c e general  in  could  be  w a f e r s were  and one S i 0  2  control  a t o t a l ' of t e n s u b s t r a t e s .  SHEET R E S I S T I V I T Y The  four point  procedure impurity wafers steps.  described  a r e not repeated  a code a n d d a t e ,  and u n i q u e l y  processed,  s t e p s were a l r e a d y  to  resistivity  verify  the  sheet  concentration v i aIrvin were  cleaned  The s u b s t r a t e s  following  using used  measurements  are  r e s i s t i v i t y and o b t a i n t h e curves  for silicon. A l l  t h e RCA p r o c e d u r e were  standard  n-type  with  silicon,  a l l its of the  characteristics:  Manufacturer: Lot  DETERMINATION:  Monsanto  No. 4002, S e r i a l ' No. D i - 4 5 6 4 0 , Date  Dopant: Phosphorous, N Resistivity: Thickness:  3/5/76  type.  8-10 ohm-cm.  11-12 m i l s ; D i a m e t e r :  1.98-2.02  inches.  126  Two  groups  of wafers  will  have t h e t a n t a l u m  a r e used pentoxide  in  which t h e oxide  will  in  Table  the sheet  6.1, w i t h  in this  stage:  t h e ones t h a t  t h e r m a l l y grown  be grown a n o d i c a l l y . resistivity  and  those  These a r e g i v e n  results.  TABLE 6.1 DEVICE SUBSTRATE MARKING AND MEASURED R E S I S T I V I T Y TYPE  MARKING  {6.2}  [ohm-cm]  MTAOS1  Thermal  9.337  MTAOS2  Thermal  10.171  MTAOS3  Thermal  9.528  MTAOS4  Anodic  9.438  MTAOS5  Anodic  9.856  MTAOS6  Anodic  9.221  MOS I  Control  9.976  MOS I I  Control  9.259  MOS I I I  Control  9.044  Si02 I  Si0  2  9.472  SI02 I I  Si0  2  10.637  SILICON THERMAL OXIDATION: The  cleaned  conditioned Coleman value: aid  RESISTIVITY  wafers  were t h e n  o x i d a t i o n furnace  temperature  of  internal  a  previous regulating  (Fairchild  controllers)  600 nm). The t e m p e r a t u r e  for  with thick  Wheelco/Barber oxide  (target  was s e t t o 1100°C±5 w i t h t h e  thermocouple system.  introduced to a previously  The  temperature gas  flows  profile were  and  s e t as  1 27  described  i n Appendix  were removed, c o o l e d checked  against  ellipsometric before  III. After for a  the  Color  measurements,  in Chapter  4.  The  Sample  The  few  2 hrs.  m i n u t e s and  Chart using  results  the are  *  the  their  for s i l i c o n  the  samples  thickness  oxides  equipment  and  described  Thickness  [nm]  15.72  122.72  591.1  Si02II  19.27  108.06  602.8  of  the  grown Color  as  {6.3}  THICK OXIDE PHOTOLITHOGRAPHY: mask s e t u s e d  available,  and  it  passive  devices,  it.  devices  a)  A  b)  A MOS  c)  A Logic  throughout  contains  hence t h e  resistor,  application,  inspected etching. resolution  this  n a k e d eye to  process  600  nm.  was  already  several active  "Smorgasbord"  was  attached  and to  p-n  diode  and  MOS  capacitor.  Transistor. Inverter,  through  are  corresponds  a sample of  name  by  are:  Photolithography windows  Chart  observed  Which,  The  from t h e  film  by  following:  A  pink.  details  min.,  Si02I  color,  The  45  was  the  under  used  field  exposure, given  2 I n p u t NOR  g a t e and  to etch  oxide.  the  RS  source  Negative  development, e t c h i n g ,  and  III.  a microscope  f o r r e s o l u t i o n and  gave  excellent  and  proper  etching.  results  wafers  with  and  drain  photoresist  i n Appendix  They  The  Flip-Flop.  stripping were  then  under/over good  line  128  {6.4}  BORON PREDEPOSITION: The  and  diffusion  drive-in  type,  we  drain  Boron  which  3  Appendix  together  III).  temperature  The  other  furnace the  was measured, u s i n g  At  point,  encountered, achieved.  Initilly,  resistivity  6.8  {6.5}  step,  of  fi-cm,  and  and t h e  four point  probe  finally  o f 2.6-2.8 fi-cm. The  measured  the  and c o o l i n g i t s p r o b e method.  difficulty  test  was  not  gave  iteration  a third  test  before  o f 2.0 ohm-cm c o u l d  (8-11 fl-cm), a s e c o n d  1.95-1.99 ohm-cm, v e r y was  degree  see  ("predoped")  introduced,  the four point  certain  the  temperature  (for details  After cycling  as the t a r g e t value  were t o o h i g h of  a  are  i n the  predeposition  Coleman  the p r e d e p o s i t i o n  w a f e r s were i n t r o d u c e d .  this  the  gases  f o r the  t o 1090±5°C. A h a l f - s l i c e ,  resistivity  value  a r e n-  impurity,  i s preconditioned  slices  set  t o check  through  Wheelco/Barber  with  carefully  w a f e r was u s e d  passed  with  one hour b e f o r e  that  the substrates  i s used as a c c e p t o r  is  (Faichild,  controllers)  device  the predeposition  a r e i n t e r e s t e d i n c r e a t i n g two p+ r e g i o n s  form o f B B r ,  for  h a s two s t e p s :  of the i m p u r i t i e s . Since  and s o u r c e .  furnace  process  be  values gave  a  one gave a  sheet  resistivity  was  close to the target value.  Total  time  23 m i n .  BORON DRIVE-IN: Before  the  drive-in  formed d u r i n g  the previous  It  that  was n o t e d  ("wetting") before  of i m p u r i t i e s , t h e "boron g l a s s " , predeposition  by p l a c i n g t h e w a f e r s etching  in  HF,  step,  was  removed.  in de-ionized  the  results  water  improved  129  considerably. slows  to  that  reaction,  the proper  furnace  w i t h a Pt-Rd  allowed  into  Appendix  I I I . Total  typical  green  The  the time  was  The l a t t e r  conditioning,  furnace  and c y c l e d  2  hrs.  a mask a l i g n m e n t  Model  source  Kulicke  Mask  and  was  and  17A  The  Soffa  data  this was  Si0  2  slices  as d e t a i l e d i n samples  showed  be  this  seen.  layer  equipment  process  simulation  over  in a  an  exposure  developed  Kasper  ultraviolet  time.  Negative  automatically  693 P h o t o r e s i s t  as d e t a i l e d  available  photolithography.  with  Spray  in  a  Developer,  i n Appendix I I I .  SIMULATION USING SUPREM:  step, the gate o x i d a t i o n  furnace  to  Aligner,  and  Model  {6.7} THIN OXIDE PROCESS After  was i n  the  step, performed  adjustable  used,  e t c h e d and s t r i p p e d  used  After  g a t e window now c a n be c u t u s i n g  photoresist  thick  thermocouple.  and  PHOTOLITHOGRAPHY:  Instruments  No  initial  t r a c k s when e x a m i n e d w i t h naked e y e . A t  required  light  water  allowed to s e t t l e  no smears o r e v i d e n c e o f c o n t a m i n a t i o n c o u l d  {6.6} GATE  This  surface  t h e r e i s a slow  (1090±1°C),  agreement w i t h t h e s e t t i n g .  point  so t h a t  adhered  (Thermco P a c e s e t t e r I I ) was f i r s t s e t  temperature  profiled  were  the  rate.  drive-in  then  appears  the i n i t i a l  etching The  It  for accurately the  available  silicon in  can  be  growing  performed. a thin  substrate,  the  Solid  p r o g r a m , SUPREM, r u n i n g  s i m u l a t e the growth of t h e s i l i c o n  using  State  under  200 A  Lab. A  MTS,  dioxide  the  was  at high  130  temperatures  in  combinations  of  an  oxidizing  temperatures  oxygen a t m o s p h e r e were u s e d . (details  atmosphere.  and The  oxidation results  Several  time  are  i n a dry  as  follows  i n Appendix I V ) :  TABLE  6.2  SUPREM SIMULATION RESULTS Time  For min. the  the  [min]  5  1000  200  3  1090  224  3  1090  224  10  1090  349  38.5  1090  754  60  1090  998  80  1090  1198  85  1090  1244  90  1090  1290  gate  d e v i c e wafers  oxide,  The A  above  determining  test  Color for  SUPREM  the process s e l e c t e d  furnace temperature  were  using  measurements c o u l d The  T h i c k n e s s [A] 140  thin  500  Oxide  1000  i n d r y oxygen,  cleaned.  [°C]  3  was c h e c k e d  below  Temperature  a t 1000  i s then 5 C.  Before  introduced i n the furnace, the c y c l e samples  Chart silicon,  previously  available so  that  prepared  and  does n o t p r o v i d e d a t a only  ellipsometric  be c a r r i e d o u t . results  the r i g h t  cycle  were u s e d conditions  as a s t a r t i n g for  a  point in  target  Si0  2  131  thickness prepared  of  200  fora  measurements,  for  Test  sequence until  When t h e s e l e c t e d used,  A.  this  the  oxidations  proper  SUPREM v a l u e  application.  oxidation cycle  a) 5 m i n . 0 , 2  b) Samples c)  It used  then and  ellipsometric  target value  of 5  min.  c l e a n e d and  was o b t a i n e d .  at  1000  C  was  is  important  consists  t o note  of f i v e  that the  steps:  Purge.  Introduced.  3 min. 0 , P a s s i v a t i o n . 2  d) X m i n . 0 + H C l ,  Slow O x i d a t i o n .  2  e) 20 m i n . N , 2  Annealing.  step d ) , the actual  test  of  were  t h e m e a s u r e d t h i c k n e s s was 110-120 A, w h i c h i s t o o low  actual  In  wafers  wafer  time  was v a r i e d  ( g i v e n by t h e l e t t e r  m e a s u r e d . The r e s u l t s  are given  TABLE  X ) , a n d then  i n Table  0 +HCl 2  individual  i t s thickness  6.3.  6.3  DRY THERMAL OXIDATION OF WAFER  f o r each  Time  [min]  Si0  2  Thickness  [nm]  TEST 200A  2  13.74  TEST 200A  5  17.47  TEST 200A  7  20.72  TEST 200A  (etched)  7  17.12  TEST 200A  (etched)  10  23.95  TEST 200A  (etched)  8  21.04  1 32  Based on t h e s e acceptable.  results,  The m o d i f i e d  a) 5 m i n . 0 , b) Samples  i s quite  c y c l e i s then:  3 min. 0 , P a s s i v a t i o n . 2  2  e) 20 min. N ,  The d e v i c e  and c o n t r o l  previously  Slow  Oxidation.  Annealing.  2  wafers  were  c o n d i t i o n e d and p r o f i l e d  Wheelco/Barber  Coleman  then  introduced  furnace  Controllers),  at  to  (Fairchild  a  a  with  temperature  of  C.  {6.8}  PREPARATION OF DEVICE At  this  anodic quite  different. thin  oxide,  the  oxidation  anodic  MOS  Photolithography small  straight  flat  yield,  edge  groups,  Since  so t o have a d i r e c t anodic  WAFERS FOR  p o i n t the d e v i c e  and t h e r m a l  overall  the  6.3  Introduced.  d) 8 m i n . 0 + H C l ,  1000  e n t r y on T a b l e  Purge.  2  c)  the l a s t  the  w a f e r s were  a s t h e next anodic  i t i s necessary contact  (this  to  the  separated  processing  device  wafers  t o remove silicon  i s t h e same p r o c e s s  capacitor with  ANODIZATION:  processing  negative  i s no  developed  used  an  area, for  during  Chapter  p h o t o r e s i s t was  alternative.  have  a small  i n the d e v i c e wafer. T h i s s l i g h t l y  but t h e r e  steps are  substrate  in  p i e c e o f a diamond c u t w a f e r  i n t o the  4).  u s e d , and a to  cover  reduces  the  1 33  {6.9} PEROXIDE-ACID CLEANING OF ALL WAFERS: All  control  modified etch,  otherwise  Aluminium  the t h i n  Evaporator, described  the  s a m p l e s were c l e a n e d  oxide  thermal  which e x c l u d e s  will  the  HF  be removed.  evaporation  for Liftoff.  previously  i n Chapter  loaded  Al  followed,  This with  was high  4. The m o n i t o r e d  t o 500 nm. E x p e r i m e n t a l l y , liftoff  using a  EVAPORATION:  in preparation  close  device  v e r s i o n o f t h e RCA p r o c e s s ,  {6.10} ALUMINIUM  step  and  was t o o t h i c k  done  in  purity  final  this  as the a  CHA  A l wire,  thickness  w r i t e r found  (around  first  1000 nm)  as was  that  when  the e t c h i n g  t i m e was q u i t e l o n g and u n d e r e t c h i n g  took p l a c e , a s compared  with  nm)  a thinner  Smaller  layer  values  required,  can  (around  500  be u s e d , and l e s s  however t h e r e s o l u t i o n  can  of  deposited  etching be  Al.  time w i l l  impaired  due  be to  over-etching.  {6.11} PHOTOLITHOGRAPHY The  Liftoff  photolithography careful did  pattern new  with  an  negative  exact  discovered version) evaporated  with  the  a  delineated  using  p h o t o r e s i s t . At t h i s  point, a  opposite  considerable  Gate  aluminium  (negative  application.  t h a t by c o m b i n i n g with  was  o f t h e a v a i l a b l e masks was done. The s e t  f o r our s p e c i f i c  one,  LIFTOFF:  pattern  examination  n o t have  FOR  delay  be  mask,  mask  the  removed.  image)  of d e s i g n i n g a  involved,  a Gate Contact  Window  could  Instead  mirror  (negative  exact  This  i t was  area  required  of a  1 34  critical  double  the q u a l i t y  alignment  and  exposure,  o f our Mask A l i g n e r ,  "guinea  pig"  wafer  quality  o f our  was  used  confirmed  technique  was  processed  with  a  our  good  this  was  not  to  verify  device that good  the  e x p e c t a t i o n s and  revealed that  this  one.  device wafers  were  close  examination  Only  the  microscope  excellent  around  LIFTOFF:  alignment,  revealed good  t e c h n i q u e worked the  gate  edge  very  straight.  of u n d e r e t c h i n g of t h e  evident normal.  on  the  Except  edges  (tweezer  a l l  very  well,  and with  a r e a . Some " r a g g i n g "  This Al  that  resolution  under h i g h e r m a g n i f i c a t i o n , w h i c h w i l l  liftoff degree  the  exposure  definition  visible  good  had  the double  A  under  A  the  step.  method.  under  wafers  easy  and  {6.12} MICROSCOPE EXAMINATION AFTER Inspection  an  considering  results  procedure.  microscope  which  was  not make  suggests  the  perhaps  some  flaws  were  h a n d l i n g ) , which are  quite  metal.  Some  f o r t h e s e , the d e v i c e wafers  exhibited  very  quality.  {6.13} DETERMINATION OF Before sputtering, required  the  the o x i d a t i o n (ideally)  into  a  SWELLING FACTOR  tantalum  i t was  for  THE  necessary target  process, oxide,  to  could  be  determine  the  metal  will  i n d e p e n d e n t l y of whether  o r a n o d i c . The  original  metal  and  final it  oxide w i l l can  be  be  said  deposited the  t h i c k n e s s of t a n t a l u m all  thermal  film,  metal  S: by  thickness  pentoxide. be  In  converted  t h e method i s  thicker that  that  the  "swelling"  1 35  takes  place.  calculated areas  Hence a s w e l l i n g  considering  and  the  thickness  factor  S can  molecular  of  the  be  defined,  weights,  initial  metal  and  and  densities, final  oxide  f i1ms: m  Ta 0  6  2  5  Ta 0 2  (A  5  t  = 6  the areas  m{Ta}=l80.88 obtained.  value  CRC  and  by  using  weight  the  tantalum  swelling  pentoxide t  S  2  and  5  Rubber  Young  Company,  57th  Handbook, t h e d e n s i t y (1961)  the  T  5{Ta 0 }=7.95  3  2  factor  5  S i s d e f i n e d as  t h i c k n e s s to the  gr/cm  the  tantalum  factor  two  atoms  2 ° 5  a  (6.2)  2 i n the denominator a r i s e s of  stoichiometry figures,  the  tantalum  are  i s r i g h t . By S factor  m  the  tantalum t h i c k n e s s :  =  The  3  r a t i o of  2 t^ Ta  Ta 0 2  s  gr  m { T a 0 } = 4 4 1 . 7 6 gr i s  Chemistry  from  m{0}=16  density are:  6{Ta}=16.6 g r / c m  Then,  Ta  6  ]  (Chemical  P h y s i c s and  tantalum  pentoxide  Ta  fc  a r e e q u a l , and  the  1977)  of  A  gr, the molecular  From  Edition,  Ta  (  ( .D  L2.—  £_2  ^ a Clearly,  )  r e q u i r e d t o form  fact  Ta 0 , 2  weight  Ta. =2.55 5  Ta 0 2  5  ( 6 > 3  that i f the  5  u s i n g t h e above m o l e c u l a r  =  -Ta  the  i s then: 6  5  from  )  136  It  is  important  t o compare t h i s  value with  measured ones. Revesz e t a l . (1976), tantalum an  oxides,  initial  then  metal  2.14.  theoretical expect fully  value  experience, used:  yield  2.55.  the  It  the  S  favourably  quite  original  thermal  t h i c k n e s s o f 60 nm f o r  quite  factor with  reasonable  metal  is the  then  to  t h i c k n e s s v a l u e , when  to oxide.  RF SPUTTERING OF  work,  and  two s t a n d a r d  from  gate  oxide  pentoxide.  values  of t a n t a l u m when  thickness  In t h i s  TANTALUM:  previous  500 and 1000 A, w h i c h  a  tantalum  oxide  compares  of  PRELIMINARY this  i n h i s work on  t h i c k n e s s o f 28 nm;  This  converted  In  be  film  doubling  {6.14}  are  gave a f i n a l  experimentally  case  MOS  Capacitor  metal  thickness  fully  oxidized  will  o f 1000 and 2000 A f o r t h e only  500 A o f Ta f i l m  will  used.  Previously Sputtering through low  clean  e q u i p m e n t . A good  for  possiblity  of  impurities.  We  This  10-15  were i n t r o d u c e d i n t o  recommended  also  practice,  min.,  in  recommend  order due that  to  under  possiblity  functions:  the  roughing  from  under  holds  pump  the wafer;  due t o v i b r a t i o n  is  any  chamber/target  clean  glass  samples  ( p r e f e r a b l y two). the  the c e n t r e of the t a r g e t , thus  o f movement  followed  eliminate  to  be p l a c e d s i d e by s i d e t o t h e w a f e r two  t h e RF  work, was t o p r e l i m i n a r y s p u t t e r a t  contamination,  accomplishes  place,  wafers  our e x p e r i m e n t a l  power  should  test  substrate  in  e l i m i n a t i n g any  (particularly  when  i n a c t i o n ) and by a i r b e i n g removed  secondly  the g l a s s r e c e i v e s  an  equal  1 37  amount  of  deposited  microscope count,  (dark  and  density)  a  metal,  field  the  Sloan Angstrometer  forward  RF  more  gives  power of  using  the  one  can  be  hillock  will  several fairly  films  seem  determined and 160  film  reveal  W  to  be  thickness  imaginary quite  reflects  or  microscope  most of  the  D.  etch  of  by  the  used  for  or  measle  the  pinhole  Smith  taking  (using  method).  Ta  W),  At  the  rate be  measurements a t  two  angles.  metal  Westwood  (1975),  f i l m s , a l l complex  component. F u r t h e r m o r e ,  reflective,  and  requires.  shows a  incident  not  like  these  transparent  Examination  "mirror"  a  can  for t r i o d e sputtered  e l l i p s o m e t r i c technique  naked eye  by  ( r e f l e c t e d power <5  ellipsometer  values large  before  stepwise  ellipsometry,  different  with a  the  r a t e was  A/min. The  determined or  show  these  examination.  sputtering  294  will  transmission  The  is  hence  as  either  surface,  by  which  light.  {6.15} PRELIMINARY THERMAL OXIDATION: A  single  test  wafer  Oxygen a t m o s p h e r e a t  500  C,  was in  stabilized  furnace  Analock  C o n t r o l l e r s ) . The  and  201  at  the  above t h e MOS  capacitor  optimum was  centre.  for  then  intense  full  The  ends,  clean  with  Thermco P r o d u c t s C o r p . ,  with  the  temperature  was  t i m e was  of m e t a l  no  dry and  flow  allowed  in a  conditioned  a t i m e of  conversion  oxidized  gas  oxidation  work, and  removed and blue,  previously  (Minibrute,  furnace  thermally  90  set  to was  based  min  was  1  l/min,  set  on  to  previous  decided  into oxide.  +5C  to  be  The  wafer  t o c o o l . I t s c o l o r was  bright  traces  of  contamination.  1 38  Ellipsometric value  of  80  determination  of  the  film  thickness  gave a  nm.  {6.16} PRELIMINARY ANODIC OXIDATION: Anodic with  Al  o x i d a t i o n was  deposited  good c o n t a c t . acid as  The  u s e d and  Chapter  a current  cell.  its  back b r a s s  oxidized,  B e c a u s e of  the  contact,  Ta  that  the  water  exposed area. and  dryed  medium d a r k evident. part  Also,  100  V,  areas  i s too  high  (weak  spots  and  electric  fields  beyond  will  was  of  the  same  set-up  was  wafer  against  perimeter the  i s not wafer,  distributed  rinsed in d . i .  deterioration  noticed during  the  i n d i c a t e s breakdown by our  and  as  procedure was  set  the  probably  oxide  was  pinholes)  breakdown.  This  w a f e r s . The  film  thickness,  determined  as  revealed  to a voltage  processing  nm.  citric  through  the  carefully  a  passed  uniformly  successfully  90  was  around  for  of  was  the  invaluable  gave a v a l u e  cell  holds  be  traces  power s u p p l y  which  back, t o a s s u r e  isopropyl alcohol. Its color  some b u b b l i n g  Current  that  wafer,  s o l u t i o n of  2  conductor  some  1961]. A n a l y s i s of  Constant  test  same equipment  1 mA/cm  w a f e r was  which  M  metal at  current  The  and  of a n o d i z a t i o n ,  [Young,  a  in b o i l i n g  blue,  of  the  thus a s s u r i n g the  of  ring  a c t s as  i n the  a 0.1  the  0  this  another  anodization  4,  density  and  on  was  w a t e r . The  in  the  evaporation  electrolyte  in de-ionized described  by  p e r f o r m e d on  was were  latter  "sparking" that  the  limit  grown,  some  were s u b j e c t experience  the  anodic  of  to was  device  ellipsometrically,  1 39  {6.17}  RF  SPUTTERING  After wafers  could  each  wafer  two  or  due  to  this  processed.  individually, wafers  Each  previously (Corning partial  2947).  pressure sputtering  rate  reflected  power.  thickness surface  of  is  not  be  mT.  than  10~  gradient  is  294  accomplished  from  done gases  Under  samples  conditions  forward  samples  had  an  estimated  and  and  a  the  <5  W  deposited  examination  indicates  free  contamination  from  two  measured  W  m i r r o r - l i k e  by  a  160  eye  target  with  at  Naked  Ta,  argon,  had  these  that  the  glass in  on  with  accompanied  is  Torr.  covered  labeled  Residual  A/min  A l l  500 A .  and  device  indicated  away  introduced  6  was  uniformly  sputtering  26  remaining  experience  (RCA p r o c e s s )  of  better  our  was  The  pressure  as  the  sputtering  thickness  wafer  cleaned  experiment, RF  could  noticeable  centre.  TANTALUM:  preliminary  be  more a  OF  that  the and  impurities.  {6.18}  THERMAL  A l l  OXIDATION  thermal  conditioned  500  with  and  oxidation  time  removed  and  oxidized  Ta  areas  were  transparent, bluish  film  a  dry  was  surface  as is  oxygen at  to  cool  had  a  Al the  samples  furnace  90 m i n ,  left  the  TANTALUM:  device  previously C,  OF  was Al  can  everywhere.  (already  flow  rate  which  introduced  described of  point  before  deep  1  the  further  seen  The quite  to  before)  1/min.  blue-purple  etched. be  were  a at  The  total  wafers  were  handling. color  in  film  seems  to  well,  although  The the be the  1 40  {6.19} ANODIC OXIDATION OF Before thermally The  CHA  the  anodic  evaporated  e q u i p m e n t was  deposited  as  anodization  process  The  onto  indicated  Current  b)  Constant Voltage  Constant  avoids  the  a chart  Mode:  anodization  to  cell.  intense  color  blue.  change  constant  current  The  basic  that  most of not  1971], but electronic constant min.,  the  the very  has  the  and  of  set  The  15 V was  current  the  and  will  into  be  wafer finally  to  through  this under it  oxide. mode, i s "healed",  [Dell'Oca  the  the  when  voltage  verified  this  to observe  6.1,  on  usual,  g r a p h of V ( t )  constant  I(t)  of  converted  current)  as  across  yellow  Figure  a p p l i e d to  flow  50 V,  color  at  limit  {6.16}. As  understood process  (leakage  to  V(t)  the  pinholes  been e x p e r i m e n t a l l y  conduction  the  in  is fully  under  well  min.  solution  voltage  interesting  shown  metal  The  spots.  Acid  voltage  to pale  2-3  weak s p o t s  was  point,  is quite  assumption  voltage  and  Ta  was  Monitor.  weak  in Section  tantalum,  is  of  2  the  of  A  steps:  1 mA/cm . The  this  It  mode  main  M Citric  Power S u p p l y  i n a matter  reaches V l i m i t ,  a  i n a 0.1  At  from m e t a l l i c  two  sample.  7500  Thickness  Mode: H e a l i n g  monitored  of  was  Anodization.  problems encountered  recorder  changed  the  of  each anodic  a thickness  by  density  Current  proceed, A l metal  back of  c o n s i s t e d of  Constant  current  the  u s e d , and  w a f e r s were a n o d i z e d  the  in  oxidation could  a)  a constant  TANTALUM:  et a l . ,  reduce the  cell,  monitored with  the  film. for a  A 60  chart  141 Sample MTA0S6 .1M Citric Acid J=1mA/cm2  Figure 6.1 MTAOS Anodic Oxidation under Constant Current.  142  Sample MTAOS6 .1M Citric Acid V=10Volts I cell (uA)  i  600 -  500  H  400 H  300 H  200 1  100 H  0  Figure 6.2 MTAOS Anodic Oxidation under Constant Voltage.  1 43  recorder, time  is  After  shown  anodization  took  in  {6.20}  de-ionized  a  N  with The  Ta{oxide}  areas,  formation  of  {6.21} A  gate  in  5 min.,  a  the  hour,  cloud  the  actually  with  thoroughly alcohol  and  under  the  features  are  The  was  Al  contamination  sky" under  or  deep  "milky  dark  field Some  due  exists f i r s t  wafers  ones  Al  It  was  the  revealing  the was  underetching noticed  the  show  blue-purple  on  "ragging"  to  between  way"  free  a  or  that  anodic  a  and  blue/light-blue  color.  PATTERNING:  order  beaker  and  "measles".  difference  a  a l l  photoresist.  was  introduced  phosphoric  temperature  isopropyl  delineated  probably  the  wafer  of  ratio),  area,  latter,  device  or  wafers.  LIFTOFF  well  obtained  of  color  the  solution  were  of  "star  hillocks  oxide  and  wafers in  current  EXAMINATION:  resolution  was  underdeveloping  thermal  that  typical  the  significant  of  boiled  examination  good  surfaces.  in  A decrease  a l l  water,  revealed  visible,  evident  place,  MICROSCOPE  preliminary  microscope  6.2.  jet.  2  PRELIMINARY  A  in  Figure  noticed.  in  color  in  clearly  rinsed dryed  as  to  of  check  gas  containing shows The  the  bubbles  closely  wrinkled.  acid  and  formed  of  wafer  was  of  hot  the  above  with  solution  signs  a  (70  de-ionized  quality  monitored the  into  a  and  etching  water  (1:1  process.  After  the  wafer.  The  thermometer wafer.  deterioration allowed  C)  another  placed  After and 30  one  it  has  min.  in  1 44  the  solution,  after  w a t e r . A Sof-Swab was  used  to  T a { o x i d e } on is  taken,  of  the  ( C l e a n Room P r o d u c t s ,  as  quickly  rinsing  s p o t s can  be  be and  required. A l l  w i t h no lines,  drains,  a l l  wafer not  For  in  reveal  the  "star  e x a m i n e d under dark  sky"  field.  t h e d e p o s i t i o n of t a n t a l u m a  pattern.  done  as  sources  the  the  or  5.  back  in  for  3-4  thermal)  way.  show a c l e a n features  are very Dark  sky"  tantalum  " m i l k y way"  well field  pattern  of  metal  was  sample of  processed  silicon  ones)  did  p a t t e r n , when  I t i s then q u i t e c o n c l u s i v e , t h a t metal  on  silicon  A more e x t e n s i v e d i s c u s s i o n  i n Chapter  and  Al/Ta{oxide},  a c l e a n , bare  ( o f same c h a r a c t e r i s t i c s  Any  wafers  "star  which  comparison,  Sof-Swab.  LIFTOFF:  resolution.  typical  use  in a similar  and  shows  If  liberal  perhaps  gates  examination  i n the a r e a s  the  (anodic  liftoff  good  by  4.  the wafer  device  indicating the  of  15 min.,  device  successfully  t r a c e s of  cleaned,  placing  f o r another  field,  in Chapter  the a c t i o n  removed by  solution  bright  oxidized.  York)  s u r f a c e can  delineated,  hillocks,  New  care  {6.22} MICROSCOPE EXAMINATION AFTER  such  Shore,  d.i.  mentioned  were p r o c e s s e d  surface,  Bay  in  top, procedure  the  Under  rinsed  with  or u n t i l  wafers  removed,  g r e a t c a r e , the w r i n k l e d A l  etching  times  was  remove, w i t h  d . i . water  stubborn  which  on  originates this  subject  such was  1 45  {6.23} PEROXIDE-ACID CLEANING: A m o d i f i e d RCA hydrofluoric attacked  cleaning process  acid  (HF)  s t e p was  the very  thin  (200  {6.24} SOURCE AND Since  the  A)  not gate  was  used,  used,  as  Si  i n which  this  DRAIN THIN GATE OXIDE REMOVAL: thin  gate  oxide  was  grown e v e r y w h e r e on  surface, i t i s necessary  t o remove  i t from  and  drain,  to  reliable  contact.  accomplished  by  solution  have  oxide.  wafer  photoresist  would  the  provide  a  photolithography  p r o c e s s . E t c h i n g was  a t a r a t e of  850  A/min,  using  performed for  a  the  the  source  This  a  was  negative  in a buffered  total  time  of  HF 30  sees.  {6.25} MICROSCOPE PHOTOGRAPHY: Examination wafers  were  obtain  a  under  the  in excellent set  of  microscope  c o n d i t i o n . I t was  color  negative  i n c o n j u n c t i o n w i t h a Model M20  6.5  excellent  show t h e  Notice  the  for microphotography  different blue-green  devices color  pink-orange  b a c k g r o u n d of  yellow  the  quite  of  striking  ( A l ) has  source  the  and  considering  been a p p l i e d y e t .  Film  Microscope.  of  thick  of  then  the  to  devices  camera was The  used  combination  work. F i g u r e s 6.3  captured the  that a l l  decided  pictures  f a b r i c a t e d . A W i l d Model MPS20 N e g a t i v e  proved  revealed  by  tantalum field  the  drain  diffusions.  that  no  contact  camera.  pentoxide,  oxide The  to  and colors  the pale are  metallization  1 46  {6.26} ALUMINIUM DEPOSITION The  final  high p u r i t y Previous  contact  considerable evaporation  [Solomon,  amount  i n Tungsten  sodium  is  V  the  final  measured  V  in  the  W  indicates mobile The  those  in with  the  the  the h i g h l y  high mobile  Experimental  the t h r e s h o l d v o l t a g e identically, [Janega,  devices  except  1983]. The  with  thermally  E-Beam d e p o s i t e d m e t a l ;  of a charge  that  thermal  under  filaments.  metallization  higher  the presence  i n the gate  oxide  which  ,due t o  ions.  thoroughly acetone  Beam  and c l e a n e d  unit  users  was  Previously  a good vacuum  was  deposited  satisfactory processed introduced  had d e p o s i t e d  i n hot  carriers o f HC1  were  and HN0 , 3  t i t a n i u m and n i c k e l .  (using the m o d i f i e d  (<4X10  as i n d i c a t e d  same  cleaned  was  The  and t e s t e d f o r p o s s i b l e l e a k s .  obtained  the  VE400)  wafer  i n t h e E-Beam e q u i p m e n t  inspection, in  The  i n a h o t 5% s o l u t i o n  samples  were p l a c e d  Model  sandblasted,  alcohol.  reassembled  clean  (Veeco  i t shearth  isopropyl  previous  6.22)  equipment  cleaned,  and  inspected  entire  contact  A l than  Electron  since  using  i s melted  by m e a s u r i n g  method.  1983] i n d i c a t e d  filaments. Apparently,  evident  was  evaporated  was  1974; J a n e g a ,  o f c o n v e n t i o n a l MOSFET's f a b r i c a t e d  for  in  was  done by d e p o s i t i n g  t h e E l e c t r o n Beam  i n which A l metal  present  confirmation  using  was  o f Na c a n be d e p o s i t e d  method,  vacuum  CONTACTS:  metallization  aluminium metal  work  FOR  6  Torr),  way,.  the  t o t h e E-Beam e q u i p m e n t ,  of  as  metal  Monitor.  remaining  Control  process  carousel. After  1000 nm  by t h e T h i c k n e s s  then  RCA  wafers  t o monitor  Upon a  wafers  were  were  also  the  quality  1 47  of  the f i n a l  double  {6.27} DRAIN AND This  of  the f i n a l  in  SOURCE  step  mask t o g e t h e r  insulator structure.  CONTACT  required  with  a  mask a l i g n m e n t ,  steps,  close  to  metallization  (contact)  photolithography  using  given  i n Appendix  etching The  the  those  very  with  surface  at a  pattern. This  on t h e v e r y  fine  i s wanted. rate,  i s probably  due t o  pattern,  This  device  details  monitor the  gas b u b b l e s  surface.  by  faster  f o r t h e d o t and r i n g ones. A l s o ,  top  patterned  to c l o s e l y  ( d o t and r i n g ) e t c h e d  the device  effect  The  under o r o v e r e t c h i n g  as  ( H ) form 2  has  a  features,  more  slowing  r a t e of e t c h i n g .  {6.28} ETCHING ON BACK OF WAFER AND Before  t h e Au back c o n t a c t  wafer's back,  Au DEPOSITION:  could  be e v a p o r a t e d  i t s back h a s t o be e t c h e d  remove  the  Nalgene  beaker, with  t h i c k oxide  wafer  was  handled  a diameter  beaker  f o r 60 s e e s .  sufficient  very  very  grown i n t h e i n i t i a l  w a f e r was u s e d . The e t c h i n g  are  was  As one  exercized  alignment.  layer  q u i c k l y a t the exposed A l  pronounced  before.  p o s i t i v e p h o t o r e s i s t , as per  the device  l a r g e r exposed  compared  the  with  the contact  a t t e n t i o n was  perfect  as n e i t h e r  c o n t r o l wafers  than  great  I I I . C a r e was t a k e n  process,  using  t h e Mask A l i g n e r d e s c r i b e d  processing  obtaining  PHOTOLITHOGRAPHY:  slightly  s o l u t i o n was carefully,  placed  The fumes from t h e  t o remove by e t c h i n g  carefully steps. A  smaller 48%  strong  onto the  than  HF,  to  small t h e 2"  and  the  on t o p o f t h e HF  solution  the t h i c k oxide  on t h e  148  wafer's back. Thorough r i n s i n g by  boiling  in  isopropyl  in d . i .  alcohol  water  was  followed  t o remove any  t r a c e s of  water. Gold  was  thermal Beam  deposited  equipment. 320  Thickness was  of  a Au  good was  that annealing  because  gate  of  each  option available  After nm  back  wafer  using  the  i n t h e V e e c o VE400  vacuum  (<10~  d e p o s i t e d as  Torr)  5  Ewas  indicated  by  the  was  to  be  Monitor.  decided  done, the  the  evaporation  obtained,  It  on  from our  leakage  in  Nitrogen  previous  c u r r e n t would  work  not  indications  i n c r e a s e by  were t h a t  several orders  of  magnitude.  {6.29} FINAL MICROSCOPE EXAMINATION: All under  d e v i c e and  the  microscope.  were o b t a i n e d contact  light  The The  aluminium  are field  shown  can  be  in l i g h t  alignment  film  are  shown  The  source, source  p u r p l e , and  t h e mask, namely t h e RS  is  using  the  the  same  described in  in Figures  clearly  6.6  visible  d r a i n and and  etched  resolution.  camera a r r a n g e m e n t  metallization  seen.  and  accomplished  obtained  ( t h i c k ) o x i d e . The  Transistor.  good  under w h i c h t h e  windows a r e a s  examined  showed t h a t e x c e l l e n t r e s u l t s  samples was  negative  pictures  grey,  carefully  that a l l wafers e x h i b i t e d p r o p e r l y  of most  m i c r o s c o p e and  6.12.  and  w a f e r s were  This  metallization,  Photography  6.24.  control  gate  drain  diffusions  background c o l o r  2 Input  NOR  as  contact  i s the  p i c t u r e s a l s o show s e v e r a l a r e a s Flip-Flop,  to  gate  and  of MOS  149  Figure  6.4  MTAOS  T r a n s i s t o r , C o n t a c t Window  area d e t a i l .  150  Figure  Figure  6.5  6.6  O v e r a l l view  showing MOSFET and R-S  Flip  Flop.  MTAOS T r a n s i s t o r C o n t a c t M e t a l l i z a t i o n d e t a i l s .  Figure  6.8  MOS C a p a c i t o r  Area,  contact  metallization.  152  Figure 6.10  Contact pads and alignment markers.  1 53  Figure  6.12  Interconnection  and  contact  pad  detail.  1 54  CHAPTER 7  RESULTS AND MEASUREMENTS ON MTAOS F I E L D EFFECT TRANSISTORS  The  devices  Chapters,  fabricated  as d e s c r i b e d i n the preceding  were t e s t e d u s i n g c o n v e n t i o n a l methods,  to  determine  their  overall  and  importance  i n MOS t e c h n o l o g y  in  p e r f o r m a n c e . Of g r e a t are  the  order  interest  following  device  parameters:  1) The C-V a n d I-V c u r v e s 2)  The G a t e T h r e s h o l d  3)  of the gate  voltage.  The D r a i n C u r r e n t - V o l t a g e  Voltage 4)  insulator.  (output)  curves  with  Gate  as a parameter.  The  Drain  Current  vs.  Gate  Voltage  (transfer)  curves. 5) The d e v i c e 6) The p u l s e output  {7.1}  transconductance response,  voltage  rise  and c h a n n e l  and f a l l  times  conductance. of the D r a i n  waveform.  TESTING AND MEASUREMENT PROCEDURE: The  C-V  and  equipment  was  the  a n d I-V c u r v e s  d e s c r i b e d i n Chapter use  (Micromanipulator Model  were o b t a i n e d  of Model  570 m i c r o s c o p e ) .  contact  t o the A l metal  proper  mask  quadrant.  the  5.  The  Wafer  u s i n g t h e method only  Probing  1800 AO P r o b e r  with  AO  difference Microscope Instruments  T h i s made i t p o s s i b l e t o make a good pads The  i n the dice, latter  and t o s e l e c t  the  i s a consequence of the  1 55  mask o r g a n i z a t i o n , a s t h e y their  number,  printed and  at  the  a r e made i n s u c h a way t o  expense of y i e l d .  the remaining gate  three are scrambled.  t h r e s h o l d v o l t a g e was o b t a i n e d  of t h e I d v s . Vds c u r v e ,  This  is a  drain current a l s o be  standard  explained The  by  t o the  t o t h e Vds a x i s g i v e s t h e  i n d u s t r y t e s t on MOS d e v i c e s . The  f o l l o w s then t h e r e l a t i o n  obtained  by i n s p e c t i o n  when t h e g a t e i s c o n n e c t e d  d r a i n . The p r o j e c t i o n o f t h e c u r v e T  Four p a t t e r n s a r e  i n t h e same mask, h e n c e o n l y one d i c e i s f u n c t i o n a l  The  V .  reduce  inspecting  the  I d = 0 V d s . The V  can  2  transfer  curves  as  with a Tektronix  577  below. output  curves  T r a n s i s t o r Curve Tracer  were o b t a i n e d and  they  provide  the q u a s i s t a t i c  c h a r a c t e r i s t i c s w i t h the gate v o l t a g e v a r y i n g as a s t a i r c a s e f u n c t i o n . P i c t u r e s were o b t a i n e d they  a r e shown i n F i g u r e s  to obtain the s t a t i c circuit with  of F i g u r e  the  of t h e v a r i o u s d e v i c e s , and  7.13 t o 7.22. An a t t e m p t was made  output curves.  T h i s was done u s i n g  7.1. The g a t e v o l t a g e was a c c u r a t e l y  attenuator  the fixed  ( f o r p r e c i s e gate v o l t a g e c o n t r o l ) and  t h e n t h e d r a i n v o l t a g e was s l o w l y swept m a n u a l l y . The r e s u l t i s a s e t of p a r a m e t r i c ones o b t a i n e d  curves,  with the curve  which are q u i t e c l o s e t o the  t r a c e r , a s shown i n F i g u r e s  7.2  and 7.3. The  transfer  measurements, u s i n g Figure  7.1.  By  curves  were  obtained  t h e t e s t equipment arranged  keeping  the  drain  voltage  by  static  a s shown fixed  as  in a  p a r a m e t e r , t h e g a t e v o l t a g e was swept m a n u a l l y a n d t h e d r a i n c u r r e n t m e a s u r e d . The r e s u l t a n t c u r v e s  a r e shown i n  Figures  1 56  1/2  Anatek  —  25D  Vsupply 6  HP70A4A XY Plotter  9  *  J  [mA  Id!  $ Rl 500\rv  Decade Voltage Divider (GRI^AAH)  (GR1A32K)  Figure 7.1 System for Plotting MOSFET Static Curves.  -v (v) ds  158  igure 7.3 Static Output Curve, Sample MTAOS4 Anodic.  159  Figure  7.4  Static  Transfer  Curve,  Sample  MTAOS3 T h e r m a l .  160  cn  > i  f-o  F i g u r e 7.5  S t a t i c T r a n s f e r Curve, Sample MTAOS4 Anodic.  161  7.4  and  7.5. The g a t e  inspecting  these  curves  falls  to a negligible  this  threshold,  it,  the c u r r e n t  threshold voltage a t t h e p o i n t where  value,  shown  Generator  i s very  used at  to  10 and  with  gate  and/or  1  a  gate  as  trigger  measurements  falling  were  to minimize  pulse  a  the  Function  Tektronix  5440  C-5C)  as  any  the  of  wave,  was  can  be  stray  results.  inductance Tests  were  (carbon) load  resistor  -5 V p e a k . By  correctly  examine voltage  s e l e c t e d . . Delayed  in observing  e d g e s and shape a t t h e  repetition  the l e a d lengths at  edge o f t h e d r a i n o u t p u t  helpful  using  (Tektronix  square  affact  polarity  and below  Model F210B  the o s c i l l o s c o p e , i t i s p o s s i b l e to  and  pulse  cycle  Vdd=-6 V, a r e s i s t i v e  k f l , and  Above  waveform. Measurements were made  taken  can  flows,  obtained  and  attachment  the output  capacitance  rising  the  source  and d r a i n c o n n e c t i o n s ,  triggering  the  camera  C a r e was  performed with of  7.6. A M i c r o d o t  pulse  point.  zero.  r e s p o n s e was  100 kHz, 50% d u t y  frequencies. both  the  record  the c u t o f f  s m a l l or near  in Figure  was  Oscilloscope  i.e.  by  the d r a i n c u r r e n t  appreciable drain current  The t r a n s i e n t or p u l s e circuit  c a n be o b t a i n e d  output.  with  greater  the  pulse, time detail  162  Anatek 25D Vsupply  2?  -6to-8V  CbypassT" 22uF TT tant. ^7 Rl 1kn. DUT  10X Probe (TekP6062B)  PULSE Generator Microdot F210B  Oscilloscope: Tektronix 5440 with 5A48 Dual Trace Amp. 5B42 Delayed Time Base  F i g u r e 7.6 System f o r Measuring the MOSFET Pulse Response.  163  {7.2}  DISCUSSION OF RESULTS  {7.2.1} C-V CURVES ON DOUBLE DIELECTRIC As  mentioned  in  s a m p l e s were p r e p a r e d the  double  Figures  from 7.8  accumulation  and i n v e r s i o n  insulator  a smooth c u r v e  i s essential  the  double  curves only  obtained  but  f o r both  that  significantly  for  the  tantalum porous the less  on  anodic  dielectric oxide  definitive quality. connected  as  well defined and  performance.  technology Similar  Ta 0 2  i s not  samples,  5  with  due t o a  C-V  results are  capacitance  compared  of the f i l m  high q u a l i t y  except  i s obtained the  thermal  inhomogeneous  or  5. As a c o n s e q u e n c e ,  i s reduced,  i s interpreted  resulting in  i n t h e C-V  plot  to the capacitance i n accumulation. was  made  i n t h e MOSFET  indication  of  The C-V p l o t t i n g to  the  d i s c u s s e d i n Chapter  constant  attempt  characteristic  and  l e s s accumulation  i s probably  that a  hysteresis,  insulator  that the  as  shown  and s u c c e s s f u l o p e r a t i o n o f  and t h e r m a l  process,  are  that surface s t a t e s  successful.  c a p a c i t a n c e which  to correspond An  also  anodic  oxide. This film,  the  MOSFET,  obtained are indicative feasible,  indicates  f o r the proper  dielectric  with  of  evaluated  i t can be seen  i s obtained,  that  be  The c u r v e s  regions, l i t t l e  have s m a l l o r no i n f l u e n c e This  could  7.9. From them,  double  additional  so t h a t t h e q u a l i t y  the device wafers. and  chapter,  insulator  good q u a l i t y  generally  previous  and p r o c e s s e d ,  dielectric  independently in  the  INSULATOR:  the  wafer  to  obtain  devices. the  double  equipment probing  This  the would  dielectric  already  C-V be  the  insulator  described,  microscope,  gate  with  was  special  1 64  attention  given to stray  Capacitance  Meter  c a p a c i t a n c e s and l e a d  was  successful  C-V  substrate  f o r the thermal  7.9.  plot  carefully  In t h e case  hysteresis  was o b t a i n e d wafer,  approached  those  by A n g l e  notice  that  similar  that  Ta 0 2  5  (Figure  the of  and  that  Talley  usually  small  If  possibilities:  AC  the  low  place  for large  high  frequency  channel provide  are  is  curve  interesting  are  C-V  have  r a t e . The C-V superimposed change  with  to  of  be  pairs. plot  on a  is  linear  capacitance  r a t e c a n be such generated;  or a  t o form  that  an  inversion  o f a MOSFET, i n  connection f o r  which  the  case, a  inversion  defined inversion the  not  sufficient  v o l t a g e . In t h e s e c o n d a  plot  i s c o n s t a n t , we have two  are generated  gate  to  sample i s  electron-hole  bounded by t h e s o u r c e and d r a i n  an e l e c t r i c a l  fora  insulator  capacitor  i s o b t a i n e d , and no  positive  In t h e c a s e  that  t h e sweep v o l t a g e . In t h e f i r s t  f r e q u e n c y C-V p l o t  obtained.  sweep r a t e  carriers  follows  large  T h i s i s due t o t h e f a c t  t o measure t h e  number m i n o r i t y c a r r i e r s that  signal  the recombination  minority  layer  It  from  a  voltage.  and  in Figure  double  region, minority c a r r i e r s  obtained  i s used  gate  f o r t h e t h e r m a l Ta o x i d e  recombine a t a c e r t a i n  enough  the  (1978).  However t h e s e  sweep, w h i c h  the  a curve with  o f a low f r e q u e n c y MOS  thermally,  by  adjusted. A  7.10) , i n d i c a t i n g of  The  a memory d e v i c e s , a s d e s c r i b e d i n t h e  i n the i n v e r s i o n  with  between  1967; Penney and L a u , 1979].  generated  and  d e v i c e s , a s shown  quality  t h e C-V c u r v e  of  [Grove,  obtained  of t h e a n o d i c T a { o x i d e } ,  particular  paper  was  nulled  lengths.  takes case, a  region i s gate  and  regions, these  inversion  layer,  165  GATE  VDLTflGE  Figure 7.7 C-V Curve on Double D i e l e c t r i c Test Wafer (sample MOSCTest 2 0 0 A thermal).  166  F i g u r e 7.8  C-V Curve on Double D i e l e c t r i c Test Wafer MOSCTest 2 0 0 A a n o d i c ) .  (sample  167  Figure  7.9  C-V  Curve  of  MOSFET G a t e ,  Thermal  Sample  MTAOS3.  168  CATC  Figure  7.10  G-V Curve  of  MOSFET  Gate,  VDLTPCC  Anodic  Sample  MTAOS5.  169  acting  as  external is  a  sink  circuit.  produced  source  Thus,  and  accumulation,  or  of m i n o r i t y c a r r i e r s  f o r l a r g e gate  the  capacitance  interpreted  as the gate  v o l t a g e , no  inversion  is  that  then  insulator  I-V  (leakage) curves  measurements  c u r r e n t of the gate  were o b t a i n e d  any  capacitive  7.11  for a typical  for  an a n o d i c  currents more  are  position  of  the  effects. thermal  consistent  A standard  current  i s to perform  to  source  circuit.  a plot  ensures  saturated,  thus  Vds  From t h e c u r v e  that  curve. which  current,  counterpart.  and  below  conduction  7.12,  the leakage o x i d e has  Also,  the  d e p e n d s on t h e case  i n w h i c h a s m a l l , but  flows.  t o determine of the d r a i n  the t h r e s h o l d v o l t a g e current  Id  the gate  connected  the  transistor  that  the square  above  a r e shown i n F i g u r e s  that the anodic  samples,  v o l t a g e Vds, with This  to avoid  VOLTAGE:  procedure  V ,  i n order  The  v o l t a g e , V d s . T h i s was n o t t h e  Ta{oxide}  leakage  operation.  sample and i n F i g u r e  i t s thermal  {7.2.3} GATE THRESHOLD  T  oxide  indicating  to drain  thermal  way,  results  of the t h r e s h o l d of gate source  normal  w a f e r . D i f f e r e n c e s between  large, than  under  The  INSULATOR:  an i d e a o f t h e c o n d u c t i o n  in a quasistatic  process  leakage  applied  gave  of  capacitance.  {7.2.2} I-V CURVES ON THE DOUBLE DIELECTRIC GATE The  t o the  law c h a r a c t e r i s t i c obtained,  i t , there i t , there  vs. drain  t o the d r a i n is  of the Ids v s .  the t h r e s h o l d voltage i s  i s a p p r e c i a b l e flow is  fully  very  little.  of d r a i n This  is  1 70  obtained the  by  latter  are  {7.2.4} THE The  i n s p e c t i o n of shown  drain current vs. Drain  obtained  both  and  tracer  of  indicating and  circuit.  In  7.22.  gate  insulator  by  source  were  wafers,  the  An  example  yield  the  gate  the  least  s e c o n d and  spikes  ( p u l s e s of  short duration)  yield:  f o r example, t h e Wafer P r o b i n g  spite  breakdown. and  electrically  like  if  connected  in a  low  some  and  probably  to  due  7.21  damage  damage was  to and  sensitive  i n t h e Wafer  then  tracer,  discharge  in Figures  probes  was  ( F i g u r e s 7.13  was  q u i t e easy  be  it  in  static  leakage,  i s given  i t was  connecting  first,  curve  T a { o x i d e } w a f e r s were v e r y  i s a l s o important:  probe  gain  and  could  oxide  behave  present  gate  no  curve  however  the  obtained  they  excessive  faults.  results,  was  circuit,  method. T h i s was  t h a t the d e v i c e s  had  gate  the  responses  than  a p p l i e d v o l t a g e s and  equipment  improper  to ensure  that  of  i n the  taken  A l s o , the anodic  order  pulse  the  (Tektronix  because  were damaged u s i n g  curves  some  transistors  The  the  v o l t a g e , with  characteristics)  is  methods gave s i m i l a r  quality  MOSFET's  to source  This  t h e manual q u a s i s t a t i c  damaging  processing  way.  a staircase  a l l precautions  7.17)  7.18.  the T r a n s i s t o r Curve T r a c e r  t h a t more d e v i c e s  Excellent  and  (output  e x i s t e d whether  Both  with  was  to  with  generates  created.  than  parameter  in a quasistatic  some c o n c e r n  found  i n . F i g u r e s 7.14  curves,  OUTPUT CURVES:  G a t e v o l t a g e as a  577)  t h e T r a n s f e r or S a t u r a t e d  them. Probing  with  the  the d r a i n . V o l t a g e  a l s o c o n t r i b u t e to a Microscope  is  lower  equipped  171  igure 7.11 I-V Curve on MOSFET Gate, Thermal Sample MTAOS3.  172  0) >  I-CO  > to i  > LO CN II  I  > o  h LO  co  O >>  cn<  —rto  T" LO  I  CO  r~ CM  Figure 7.12 I-V Curve on MOSFET Gate, Anodic Sample MTAOS4.  173  w i t h a f l u o r e s c e n t lamp and beautiful few  disasters,  its An  s p i k e when t h e we  ballast  lamp  simply  i s switched  disconnected  on  the  generates  a  or o f f . A f t e r  lamp and  a  grounded  leads. examination  for  low  not  of F i g u r e s 7.3,  v a l u e s of Vds,  have a l i n e a r  variation.  effect  channel  c o n d u c t a n c e does not  with  Vds  origin  and  are  this  Ids,  known, but  reasons  behind  related  TRANSFER  with  the  the  curves  gate  drain  gives  indicate  summarized  both  behaviour  changes  7.1.  thermal  are  channel  t r a p p i n g i n the  silicon.  of  Again,  method,  manually  the d r a i n  current,  the  curves  Ta{oxide}  This  is  probably  due  to  as d e s c r i b e d b e f o r e . The and  7.5.  the  channel  s l o p e of  these  device.  These  t h e d e v i c e s e x h i b i t e d m o d e r a t e v a l u e s of  and  the  in  transconductance  latter.  7.4  has  c l o s e to the  unusual  measuring  a smaller transconductance  Figures  to  the q u a s i s t a t i c  presented  capacitance,  voltage  relationship  the c u r v e s  this  c u r r e n t does  shows t h a t  v o l t a g e as a p a r a m e t e r . The  in Table  anodic  gate  that  CURVES:  v o l t a g e , and  the  that  drain  usual  equal  to e l e c t r o n  T h e s e were o b t a i n e d by adjusting  f o l l o w the  and  indicates  which  i t i s p o s s i b l e t h a t the  conductance are  {7.2.5} THE  7.17  Moreover, the  s l o p e of  distinct  The  and  phenomenon,  i . e . the  quite  conductance. not  on  7.13  the c o r r e s p o n d i n g  little  as  (!), w h i c h  were o b t a i n e d  s a m p l e s . The as  compared a  reduced  curves  are  gm, for  first  ones  with  the  insulator shown  in  1 74  {7.2.6} PULSE RESPONSE OF  the  Another  important  device,  characterized  corresponding transistor. used, and  as  to  shown  the  accurately between  time  the  to  and  ON  fast  Short  s w i t c h i n g time  ton  turn  and  i n F i g u r e 7.6.  at  the  100  kHz  toff  and  square  measure t o n and  the  and  the  v e r s i o n i s slower  when  used  in  the  scope  t r a c e s are  Table  7.1  Some  at  and  10  kHz  sweep was  used  Ta{oxide}  differences  the  thermal  same c i r c u i t .  The  pictures  results  exist  oxide  the  7.19  7.16,  obtained  of  in  samples, actual  and  the  7.20. MOSFET  measurements.  TABLE SUMMARY OF  Cox  185000 p f / c m  Gate Leakage  7.1  DOUBLE DIELECTRIC MOSFET CHARACTERISTICS  THERMAL Sample MTAOS3  1 nA  Gate T h r e s h o l d  2  a t Vgs=-5 V  - 2.0  V  to  samples. G e n e r a l l y ,  than  the  device,  switching p o i n t s , in order  shown i n F i g u r e s 7.15,  summarizes  were  capacitance  waves. D e l a y e d  toff.  thermal  the  oscilloscope  stray  of  times,  t u r n OFF  l e a d s around  a minimum of  t r a c e around  the anodic  the anodic  as  i s the  S e v e r a l measurements were made, one  another expand  MOSFET's:  parameter  good g r o u n d s a s s u r e d  and  DD  A pulse generator  inductance.  to  THE  ANODIC Sample MTAOS4 84000  pf/cm  2  4 MA a t Vgs=-5 V - 2.5  V  gm  a t Vgs=-3 V  300  juS  475  MS  gm  a t Vgs=-6 V  1750  MS  1125  MS  ton  400  ns  500  ns  toff  220  ns  250  ns  175  {7.2.7} SPICE SIMULATION OF In  order  dielectric  to  verify  devices,  conjunction  with  the  the  components.  This  used  actual  i n the  capacitances. from t h e length The  indicate the  p a r a m e t e r s and  inspection d r a i n and and  o f f i n 70  device  than  the  overlap  ns.  has  and  The  combined  for  the  the  small  of  these  measured d e v i c e .  i n Appendix  the  were not  effect  IV.  of  the  the  source  fast  simulated  were not  cables  given  The  capacitances  wires  plus  used  values  circuit  and  obtained (channel  perimeters).  parameter DC  turn  device  internal taken  on  Transfer  in  into account  i n the  result  i n slower  of  the  ns  of  were Curves V  and  and  much  junction  included  Results  10  i s then  stray inductances  as  stray  devices  areas  in  circuit  a t h r e s h o l d c l o s e t o -2.5  as  Also,  same c i r c u i t  v a l u e s . The  a c t u a l one,  simulation.  double  external  transconductance  T r a n s i e n t A n a l y s i s shows a  turn  the  test;  experimental the  the  MOSFET g e o m e t r y p a r a m e t e r s were  width,  that  of  s i m u l a t i o n p r o g r a m SPICE was  pulse  The  from  performance  was-done u s i n g  threshold voltage  obtained  the  device  microscope and  MOSFET CHARACTERISTICS:  a  faster  and  gate  during  the  connecting  simulated pulse  model.  response  SPICE s i m u l a t i o n  are  176  Figure  7.13 D o u b l e D i e l e c t r i c  MTAOS 3 (Vgs s t e p  Figure  MOSFET O u t p u t C u r v e s ,  0.5 V, H o r . 1 V / d i v . ,  7.14 D o u b l e D i e l e c t r i c  Vert.  MOSFET S a t u r a t e d  MTAOS 3 (Vgs=Vds, H o r . 1 V / d i v . ,  Vert.  0.2  0.1  Sample  mA/div.)  Test,  Sample  mA/div.)  1 77  Figure  7.15 D o u b l e D i e l e c t r i c  Sample MTAOS 3 ( t o p t r a c e  Figure  i s Vgs i n p u t ,  7.16 D o u b l e D i e l e c t r i c  Sample MTAOS 3 ( t o p t r a c e  MOSFET P u l s e  lower  MOSFET P u l s e  i s Vgs i n p u t ,  Test  i s Vds o u t p u t )  Test  lower  (Turn On),  (Turn O f f ) ,  i s Vds o u t p u t )  178  Figure  7.17 D o u b l e D i e l e c t r i c  MTAOS4 (Vgs s t e p  Figure  0.5 V, H o r . 1 V / d i v . ,  7 . 1 8 Double D i e l e c t r i c  MTAOS4  MOSFET O u t p u t C u r v e s , Vert  0.1  MOSFET S a t u r a t e d  (Vgs=Vds, H o r . 1 V / d i v . ,  Vert.  0.1  Sample  mA/div.)  Test,  Sample  mA/div.)  1 79  Figure  7.19  Double  Sample  MTAOS4  Figure  7.20  Sample  MTAOS4  (top  Double (top  Dielectric trace  is  Vgs  Dielectric trace  is  MOSFET P u l s e input,  lower  MOSFET P u l s e  Vgs  input,  Test is  Test  lower  is  (Turn Vds  (Turn Vds  On), output)  Off), output)  180  Figure MTAOS4  Figure MTAOS3  7.21 L e a k y Gate (Vgs s t e p  2  0.5 V, H o r . 1 V / d i v . ,  7.22 L e a k y Gate (Vgs s t e p  i n MOSFET, A n o d i c T a 0 , Vert.  5  0.2  i n MOSFET, T h e r m a l T a 0 ,  0.5 V, H o r . 1 V / d i v . ,  2  Vert.  5  0.2  Sample mA/div.)  Sample mA/div.)  181  {7.3}  DOUBLE DIELECTRIC MOSFET EQUIVALENT CIRCUIT: Based  on t h e e x p e r i m e n t a l  transistor, circuit single  a Small  is  shown  dielectric  the  i n c r e a s e d gate  to  the  double  permittivity of is  Figure  MOSFET model  the a d d i t i o n  of a f i n i t e leakage  dielectric  7.23, and i t i s b a s e d [Millman  modify  due t o M i l l e r  and H a l k i a s ,  input conductance  MTAOS  gate  insulator  1972],  (Ggs) due t o  with  ( C g s ) . The c a p a c i t a n c e Cgd a p p e a r s and g a t e  t h e i n p u t and o u t p u t effect.  on t h e  and an t h e i n p u t c a p a c i t a n c e due  t h e o v e r l a p between t h e d r a i n to  of t h e  S i g n a l model c a n be made. The e q u i v a l e n t in  with  characteristics  areas.  admittances  increased as a  result  Its  effect  Y i n and Yout  182  MTAOS  FET  Small Signal Equivalent Circuit  After Y  Y  = g gs  gs  ds  Miller  + jo){C gs  J  =  3ds  Transformation:  J  +  +  ( l - A ) C ,} gd  J^d-A)/A}C  Where A i s t h e c i r c u i t  C T d  gain  Figure 7.23 Double D i e l e c t r i c MOSFET Equivalent C i r c u i t .  183  CHAPTER 8  SUMMARY AND  In  this  work, we  development insulator, initial  of  MOS  Circuits  and  of thus  development  f o r an  of  f o r today's  standards  new  devices,  aimed  t o w a r d s t h e VLSI  conduction  currents,  still  thus  and  authors, for  Photoconduction  our  not  quite  e x p l o r e d nor  capac i t o r s .  the  Devices.  We  feasible,  to Integrated  without of  excessive  research  t h e MOS  of our  and  family.  final  this  No  devices, length  f a m i l y of  w e l l w i t h i n the except  i n gate  area  was  The  double  insulators  quite evident  High  i n the  the  (conduction)  of p o s s i b l e  understood.  range  perhaps  small leakage  (50000 p f / c m ) were o b t a i n e d 2  for  is  devices.  phenomena  i t i s another  The  ULSI t e c h n o l o g i e s .  r e n d e r i n g them u s e f u l  d e v i c e s , and  densities  previous  road  f u t u r e work on  devices e x h i b i t e d very  MOSFET's. these  p a r t of  characteristics  dielectric  size  c a p a c i t o r p e r f o r m a n c e was  r e p o r t e d work by  structure.  are q u i t e l a r g e (channel  will  of  gate  extended  member of  the  This  MOS  be  avenues  =*lO/im).  The  be  dielectric  Effect  nature,  new  were made t o r e d u c e  the  Field  I t can  entirely  and  technology  complex  opening  design  insulator  2  paved  this  theory,  double  MTAOS  reliable.  the  a  5  work,  that  more  hardships,  which  2  development  reproducible,  with  the T a 0 / S i 0  capacitor  demonstrated  attempts  have p r e s e n t e d  MOSFET  utilizing  successful have  a  CONCLUSIONS  for for  research, capacitance  single  (Ta 0 ) 2  5  184  The  Double D i e l e c t r i c  output  and  transfer  transconductance current  was  devices,  and  threshold the y i e l d  MOSFET  and  very  switching  for  the  somewhat h i g h e r  voltage  was  o b t a i n e d was  presented  characteristics,  fast low  devices  for  2-2.5  times.  thermal the  V.  The  compatible  moderate  Gate  tantalum  anodic  good  leakage pentoxide  version.  The  d e v i c e s were s t a b l e  with  and  laboratory production  levels. From t h i s  work, t h e  following  1.  tantalum  pentoxide  The  dielectric 2.  Both anodic thin with  3.  The  films  6.  on  silicon  s u b s t r a t e s . They a r e  and  C-V  MOS  pentoxide  developed,  feasible  University  of B r i t i s h  interfacial  processing  can I-V  the c o n d u c t i o n MOS  5  grown  as  compatible  be  derived  plots  provide  mechanisms.  capacitors  Al-Ta 0 -Si0 -Si  tantalum  pentoxide  film  c u r v e s . The  2  be  using  the  structures  2  are  practical.  Double D i e l e c t r i c  The  feasible  fabrication.  insulating  Double d i e l e c t r i c  and  o x i d e s can  p r o c e s s i n g and  S i n g l e and  possible 5.  tantalum  i n f o r m a t i o n on  5  a  technology.  additional  2  is  thermal  capacitor  Al-Ta 0 -Si  concluded:  insulator  i n MOS  p r o p e r t i e s of an MOS  be  and  s t a n d a r d MOS  from  4.  f o r use  can  proved  Field over  and  Transistors,  silicon  successful  dioxide  technology  using are at  a the  Columbia.  oxidation t o be  of d o u b l e  Effect  of  silicon  a successful  dielectric  MOS  below  technique capacitors.  tantalum in  the  185  7.  B o t h MOS  c a p a c i t o r s and  better  processing  particular  the  t r a n s i s t o r s can  and  patterning  be  improved  fabrication  methods,  of  tantalum  and  once a g a i n  that  by in  tantalum  oxides. 8.  That  this  Edison  author was  has  verified  absolutely  "everything  takes  correct  10%  in  Thomas  stating  inspiration  A.  that  and  90%  perspi rat ion".  If  future  work  development  1.  are  A b e t t e r and  3.  formation  Ta  metal  of h i l l o c k s  on  silicon  as  this  and  film  should  havoc  in s i l i c o n  alkali  ions  quality  of  A compatible has  the  is quite  dioxide,  the  ( i . e . sodium) Ta 0 2  5  study  should  pinholes  of  the  made  the  for  RF  technique.  tantalum  ions are  other  on  deposited  In p a r t i c u l a r  question or  be  on  a popular  s t u d i e d and Ion  m e t a l and  pentoxide  known t o  i s then:  cause  Do  ions a f f e c t  i t s oxides  developed. A  towards  Reactive  etching  equipment, which o f f e r s  [Seki  of  the the  insulator?  p a t t e r n i n g of Ta t o be  areas  refined:  addressed. A l k a l i  the  following  substrates.  p r o b l e m of c o n t a m i n a t i o n  silicon  4.  t o be  more s c i e n t i f i c  the  The  attempted,  recommended  sputtering, 2.  is  Etching  (RIE),  with  trend e x i s t s  using  interesting  plasma  solutions.  e t a l . , 1983].  Besides  the  standard  RFS  d e p o s i t i o n method, o t h e r s  such  186  as  Electron  Beam and R e a c t i v e  developed. the  In  tantalum pentoxide  damage, s h o u l d Little  should  Memory  should can  the substrate,  Barrier  structure.  w i t h minimum  of  Work  tantalum  i s the s i t u a t i o n i n  Energy  i f a better  should  MOSFET,  be  Band  diagram  u n d e r s t a n d i n g of  with  investigated. very  built  using  a  thin  single  Dynamic Random A c e s s Memories the  directly  Affinity,  Height  Even worse  e x h i b i t enough h y s t e r e s i s  be  deposits  be  i s required.  devices  dielectric  and  be c o m p i l e d ,  insulator  should  to i d e a l .  silicon.  double d i e l e c t r i c  data this  on  one t h a t  e x i s t s on t h e E l e c t r o n  differences  pentoxide  over  be c l o s e  o r no d a t a  Function  the  particular,  RF s p u t t e r i n g  The  silicon  so t h a t  double dioxide,  a memory  cell  t r a n s i s t o r . Ideal f o r  (DRAM's), and  amount o f i n t e r e s t on t h e 1 M b i t  RAM,  considering  i t should  be  worthwhile. The  interfacial  pentoxide  should  interesting processing  oxidation be  technique  of  further that  silicon  developed.  below  tantalum  This  o f f e r s many s o l u t i o n s  of the Double D i e l e c t r i c  structure.  i s an i n the  187  REFERENCES  Adolt, A.R., and M e l r o y , D.O., 1980, " H u m i d i t y E f f e c t s on R e v e r s e B i a s T e s t i n g of Ta F i l m C a p a c i t o r s " , P r o c e e d i n g s of the 18th A n n u a l C o n f e r e n c e on R e l i a b i l i t y P h y s i c s , pp. 3943. A n g l e , R.L., 1976, "Charge S t o r a g e P r o p e r t i e s of t h e MetalT a n t a l u m O x i d e - S i l i c o n D i o x i d e - S i l i c o n (MTOS) D e v i c e " , Ph.D. D i s s e r t a t i o n , U n i v e r s i t y of K a n s a s , U.S.A. 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ED-25, no. 3,  Terui, H., and Kobayashi, M.,1981, "Refractive index decrease phenomena in Si0 -Ta 0 waveguide f i l m s by C0 l a s e r i r r a d a d i a t i o n " , J o u r n a l of A p p l i e d P h y s i c s , vol. 52, no. 9, pp. 5442-5447. 2  2  5  2  Troutman, R.R., 1974, "Subthreshold Design f o r I n s u l a t e d Gate F i e l d - E f f e c t T r a n s i s t o r s " , of S o l i d S t a t e C i r c u i t s , v o l . SC-9, no. 2, pp.  Considerations IEEE Journal 55-60.  W a l l m a r k , J.T., and S c o t t , J.H.,1969, " S w i t c h i n g and S t o r a g e C h a r a c t e r i s t i c s of MIS Memory T r a n s i s t o r s " , RCA Review, v o l . 30, pp. 335-365. Wang, C.C., Z a i n i n g e r , K.H., and D u f f y , M.T., 1970, D e p o s i t i o n and C h a r a c t e r i z a t i o n of M e t a l Oxide Thin for Electronic Applications", RCA Review, v o l . 31, pp. 729-741 . Westwood, W.D. "Tantalum Thin  ,Waterhouse, N., and F i l m s " , Academic P r e s s ,  Yamamoto, A., Gate I n s u l a t o r 18, no. 2, pp.  and Uemura, C , f o r InP MOSFETs", 62-64.  Young, L.,  1961,  "Vapor Films no. 4,  Wilcox, P.S., 1975, 1975, pp. 289 f f .  1982, " A n o d i c O x i d e F i l m as Electronic Letters, vol.  "Anodic Oxide F i l m s " ,  Academic P r e s s ,  1961.  Z a i n i n g e r , K.H., and Wang, C.C., 1969, "Thin F i l m D i e l e c t r i c Materials for Microelectronics", P r o c e e d i n g s of t h e I E E E , v o l . 57, no. 9, pp. 1564-1570.  195  APPENDIX  COMPUTER  {A2.1}  FORTRAN  The in  of  The the  routines  provided  the  operating  1 81 6 7 5 9 11 12 8  the  code,  code  and  system  I-V  the  source  code  to  obtain  the  plots,  in  either  Linear  and  system by  octal its  of  CURVES:  used  program  were  source  C C  is  operating  This  FOR O B T A I N I N G I - V  l i s t i n g  OS/8  assembler  of  a  which  main  OS/8  graph  is  Current-Voltage  graphs. under  IV,  SOURCE PROGRAMS  PROGRAM  following  FORTRAN  form  IV  II  D.  its in  addressing  callable  with  the  data or  assembler  the  Smith,  I-V  PDP8/E.  they and  are RALF  subroutines  required  written in  the  Schottky  routines Some written  run  of  the  in  the  mnemonics. runing  hardware,  under  produces  a  data:  F I L E LEAKY MOSIV I N M STEPS ( L E S S THAN 150) REAL VOLT,CINC,TIME,SVOLT,TVOLT DIMENSION VOLT(160),CINC(160),TIME(160) DIMENSION SVOLT(160),TVOLT(160),SPANN(160),STROM(160) CALL PLOTS(.005,0) IFST=2048 WRITE(4,1) F O R M A T ( I X , ' T H I S I S AN I V MEASUREMENT PROGRAM') WRITE(4,6) F O R M A T ( 1 H O , ' N U M B E R OF I N C R E M E N T S : ',$) READ(4,7)M FORMAT(F1 0 . 0 ) WRITE(4,5) FORMAT(IX,'MAXIMUM VOLTAGE [VOLTS]: ',$) READ(4,9)VMAX FORMAT(F10.5) WRITE(4,11) FORMAT(1X,'KEITHLEY SCALE: ',$) READ(4,12)SKEITH FORMAT(E7.0) WRITE(4,8) FORMAT(1X,'TYCO SCALE: ',$) READ(4,2) TYCOSC  196  2  FORMAT(F6.0) WRITE(4,4) TYCOSC FORMAT(1XTYCO S C A L E : ' , F 6 . 0 , ' V ) . WRITE(4,3) FORMAT(3X,'I',3X,'TIME',5X,'VOLT',5X,'SVOLT',8X,'TVOL I N I T I A L I Z E ARRAY TO ZERO DO 6 6 1=1,M VOLT(I) =0 CONTINUE OLVOLT=0 CALL RESET DO 6 0 1 = 1 , M CINC(I)=VMAX/M VOLT(I)=OLVOLT+CINC(I) OLVOLT=VOLT(l) CALL DAC16(VOLT(I))  4 3 C  66  10 60 C  C  ' 29 30 28  C 26 24  22 20 40 C 32 56 48  CALL TIMEX(TIME(I),SVOLT(I),IFST) CALL TYCO(TVOLT(I)) TVOLT(I)=(TVOLT(l)*TYCOSC*SKEITH)/10000 WRITE(4,10) I,TIME(I),VOLT(I),SVOLT(I),TVOLT(I) FORMAT(1X,I3,F9.4,F10.6,F10.6,E15.5) CONTINUE S E T DAC O U T P U T TO Z E R O WHEN F I N I S H E D VOLT(M+1)=0 CALL DAC16(VOLT(M+1)) DATA Y E S , N O / ' Y ' , ' N ' / ASK I F GRAPH IS REQUIRED CONTINUE WRITE(4,30) F O R M A T ( 1 X , ' P L O T GRAPH? Y / N : ',$) READ(4,28)ANSW FORMAT(A1 ) IF(ANSW.EQ.NO) GO T O 4 2 A S K WHAT K I N D OF P L O T WRITE(4,26) F O R M A T ( 1 X , ' L I N E A R PLOT? Y / N : ',$) READ(4,24)SWAN F O R M A T ( A 1) IF (SWAN.EQ.YES) GO T O 4 0 WRITE(4,22) FORMAT(1X,'SCHOTTKY PLOT? Y / N : ',$) READ(4,20)REPLY FORMAT(Al) I F ( R E P L Y . E Q . Y E S ) GO T O 3 4 CONTINUE L I N E A R PLOT WRITE(4,56) FORMAT(1X,'PLOT AXES? Y / N : ',$) READ(4,48) RESP FORMAT(AI) IF(RESP.EQ.NO) GO T O 5 2 C A L L P S C A L E ( S V O L T , 6 , M , 1) CALL PSCALE(TVOLT,8,M,1) X0=SVOLT(M+1) XINC=SVOLT(M+2) Y0=TVOLT(M+1)  1 97  YINC=TV0LT(M+2) CALL A X I S ( 0 , 0 , ' V O L T A G E [ V O L T S ] ' , - 1 5 , 6 , 0 , X O , X I N C ) CALL A X I S ( 0 , 0 , ' C U R R E N T [ A M P S ] ' , 1 4 , 8 , 9 0 , Y 0 , Y I N C ) CALL S Y M B O L ( 1 . 5 , 8 . 5 , . 1 7 5 , ' L I N E A R IV PLOT',0,14) CONTINUE CALL L I N E ( S V O L T , T V O L T , M , 1 , 0 , 0 ) CALL X Y P L O T ( 0 , 0 , 3 ) GO T O 4 2 CONTINUE SCHOTTKY PLOT C A L C U L A T E SQRT V O L T A G E AND LOG C U R R E N T DO 7 0 1=1,M SPANN(I)=SQRT(ABS(SVOLT(I))) STROM(I)=-ALOG10(ABS(TVOLT(I))) CONTINUE WRITE(4,79) FORMAT(1X,'PLOT AXES? Y / N : ',$) READ(4,58)REPON FORMAT(A1) I F ( R E P O N . E Q . N O ) GO TO 6 2 CALL PSCALE(SPANN,6,M,1) C A L L P S C A L E ( S T R O M , 8 , M , - 1) XS0=SPANN(M+1) XSINC=SPANN(M+2) YS0=STROM(M+1) YSINC=STROM(M+2) CALL A X I S ( 0 , 0 , ' S Q R T VOLTAGE [ S Q R T ( V O L T S ) ] ' , - 2 6 , 6 , 0 , X S C A L L A X I S ( 0 , 0 , ' - L O G 10 C U R R E N T [ L O G 1 0 ( A M P S ) ] ' , 2 8 , 8 , 9 0 , CALL SYMBOL(1.50,8.5,.175,'SCHOTTKY IV PLOT',0,16) CONTINUE CALL L I N E ( S P A N N , S T R O M , M , 1 , 0 , 0 ) CALL X Y P L O T ( 0 , 0 , 3 ) CONTINUE WRITE(4,71) F O R M A T ( 1 X , ' C O N T I N U E GRAPH? Y / N : ',$) READ(4,80)WORD ' FORMAT(A 1 ) I F ( W O R D . E Q . N O ) G O T O 81 GO T O 2 9 END  52  34 C C  70 79 58  62  42 71 80  {A2.2}  FORTRAN CALLABLE  These  are  Clock,  operate  acquire  data  SUBROUTINES:  subroutines  from  the the  16  bit  Dana  that  interface  Digital and  Tyco  to  to  Analog  Digital  the  Real  Converter, Voltmeters:  Time and  /  *******************************  / / / y  * * * *****  SUBROUTINE SUBROUTINE SUBROUTINE ***********  SW(I,J) RELAY(I) DAC16(V) **************  * * * *  / / /THESE FORTRAN C A L L A B L E SUBROUTINES WILL READ / T H E C O N S O L E S W I T C H R E G I S T E R OR O P E N A R E L A Y . /CALLING SEQUENCE: / CALL SW(I,J) / I=SWITCH R E G I S T E R NUMBER ( 0 - 1 1 ) / J=1 I F SWITCH IS S E T , 0 OTHERWISE / CALL RELAY(I) / I=RELAY NUMBER (0-3) / CALL DAC16(V) / V = V O L T A G E WORD (0-65535)  / / T H E ARGUMENTS /OR INTEGER.  / /  /  SETUP,  RELAY,  OF  SW(I,J)  SECT  SW  EXTERN EXTERN EXTERN EXTERN EXTERN  SW8 RELAY8 W1 DAC8 A8  BASE JSA TRAP4 STARTD SETX FLDA% FSTA SETX STARTF XTA FSTA% FLDA JAC  0 SETUP SW8  0;0 STARTD SETX FLDA% FSTA SETX STARTF FLDA% ATX JA ENTRY JSA  #IR 0,2 3 W1 0 3 30  AND  RELAY(I)  BE  / G E T ARGUMENT AND RTN / C A L L 8 MODE R O U T I N E /SET /GET /AND  I N D E X TO T H I S P T R TO ANSWER STORE IT  REAL  PTR'S  ROUTINE  / G I V E A N S TO C A L L E R / R T N TO C A L L E R  /  /RETURN #IR 0,1 3 W1  /SET /GET /AND  3 0 SETUP  /USER /PASS  RELAY SETUP  CAN  GOES  HERE  TO R O U T I N E ' S P T R TO ARG STORE IT  INDEX  A R G TO F A C TO 8 MODE  /  /OPEN A RELAY / G E T ARG FROM  CALLER  199  / / DAC16,  / / #IR, #64K, #25,  TRAP4  RELAY8  FLDA JAC  30  ENTRY JSA FLDA% FMUL FDIV  DAC 1 6 SETUP 3 #64K #2 5  ALN FSTA TRAP4 FLDA JAC  0 A8 DAC8 30  OOOO 0001 0002 F 6553. 5 F 25.0  SECT8  / /  / /  / / / / / DEC 8  /CALL 8 MODE ROUTINE /ARG IS IN FPP XR3 /RTN TO CALLER  /GET ARG AND RTN PTR'S /GET THE VOLTAGE WORD /AND SCALE TO THE DAC RANGE /DIVIDE BY THE GAIN OF /THE DAC (ASSUMED TO BE 25) /MAKE I T AN INTEGER /PASS TO 8-MODE /CALL 8-MODE ROUTINE /GET RETURN ADDRESS /RETURN TO CALLER /THIS ROUTINE'S INDEX /XR1 /XR2 /FULL SCALE FOR DAC /GAIN OF THE DAC  DECOD  SUBROUTINE ENTRY NAME ENTRY DEC8 ENTRY SW8 ENTRY RELAY8 L I S T OF ENTRY ENTRY ENTRY ENTRY ENTRY ENTRY  DATA ENTRY POINTS V8A RANG 8 SGN W3 W2 W1  DECODE VOLTAGE WORDS TO DECIMAL START WITH VOLTAGE WORD 3 n u W3 /GET VOLTAGE WORD 3 TAD AND K17 /MASK BITS 8-11 DCA V8A /AND STORE W3 /GET THE WORD AGAIN TAD RTR /ROTATE RIGHT 4 TIMES RTR AND K17 /MASK BITS 8-1 1 DCA V8B /AND STORE  200  TAD RAL RTL RTL AND DCA  / /  / /  / /  POS,  / / /  RANG,  / RO,  /  R1 ,  W3  / G E T T H E WORD /ROTATE LEFT /5 TIMES  K1 7 V8C  /MASK B I T S 8-1 1 /AND STORE  UNPACK TAD AND DCA TAD RTR RTR AND DCA  VOLTAGE W 2 K1 7 V8D W2  UNPACK TAD RTL AND DCA  VOLATGE W1  K1 7 V8E  K1 V8F  AGAIN  WORD 2 / G E T V O L T A G E WORD 2 /MASK B I T S 8-1 1 /AND STORE / G E T T H E WORD A G A I N /ROTATE RIGHT 4 TIMES /MASK BITS /AND STORE WORD 1 /GET VOLTAGE /ROTATE LEFT /MASK BIT 11 /AND STORE  8-11  WORD 1 2 TIMES  DETERMINE POLARITY TAD W1 / G E T V O L T A G E WORD 1 AND K400 /MASK AC03 SNA /IS IT ZERO? JMP POS /YES. SIGN IS POSITIVE TAD K1 / N O . S E T S I G N CODE=1 DCA SGN JMP RANG / G O TO R A N G E T E S T CLA CLL /SET SIGN CODE=0 DCA SGN DETERMINE VOLTAGE RANGE S T A R T BY T E S T I N G FOR . I V RANGE TAD W2 / G E T V O L T A G E WORD 2 AND K6000 /MASK A C 0 0 AND AC01 SZA /AC=0? JMP RO / N O . TRY NEXT RANGE DCA RANG8 / Y E S . S E T R A N G E CODE= 0 JMP OUT /RETURN TRY IV RANGE CLA CLL W 2 TAD / G E T V O L T A G E WORD 2 AND K5400 / M A S K A C 0 0 , A C 0 2 , AND A C 0 3 SZA /AC=0? JMP R1 / N O . TRY NEXT RANGE TAD K1 / Y E S . S E T R A N G E CODE= DCA RANG 8 JMP OUT /RETURN T R Y 1 OV R A N G E CLA CLL TAD W 2 / G E T V O L T A G E WORD 2 /MASK A C 0 0 AND A C 0 2 AND K5000 SZA /AC=0?  201  /  R2,  /  R3 ,  '  OUT,  JMP TAD DCA JMP TRY 100V CLA CLL TAD AND SZA JMP TAD DCA JMP MUST BE CLA CLL TAD DCA CDF C I F JMP% 1  R2 K2 RANG8 OUT RANGE  / N O . TRY N E X T RANGE /YES. SET RANGE CODE=2  W2 K4400  / G E T V O L T A G E WORD 2 / M A S K A C 0 0 AND A C 0 3 /AC=0? / N O . TRY N E X T RANGE /YES. SET RANGE CODE=3  /RETURN  R3 K3 RANG8 OUT /RETURN 1 0 0 0 V RANGE K4 RANG8 0 DEC8  /SET  RANGE  / R E T U R N TO /ROUTINE  CODE=4 CALLING  / / / / / SW8,  READ THE SWITCH XR3=1 I F B I T I S 0 LAS DCA RANG8 W 1 TAD CMA C L L CML DCA W 1 RAR ISZ W 1 JMP .-2 AND RANG8 SZA CLA ISZ W1 C I F CDF 0 JMP% SW8  REGISTER SET  AND  RETURN  WITH  /READ THE REGISTER WORD /AND STORE IT /GET BIT POINTER / S E T UP FOR MASKING /ROTATE /XR3=0  LINK  UNTIL  /MASK SWITCH WORD / I F BIT IS SET,SET /RTN  TO  XR3=1  CALLER  / / / / RELAY8,  E N E R G I Z E THE S P E C I F I E D RELAY 0 CLA CLL TAD W 1 AND K3 / M A S K I T TO M A K E S U R E 6354 / E N E R G I Z E THE RELAY CLA CLL C I F CDF 0 / R T N TO C A L L E R JMP% RELAY8  / K1 , K2, K3, K4, K17 ,  1 2 3 4 T7  202  K400, K4400, K5000, K5400, R6000, V8A, V8B, V8C, V8D, V8E, V8F, RANG8, SGN, W 3 , W 2 , W l ,  400 4400 5000 5400 6000 0 0 0 0 0 0 0 0 0 0 0  SECT8  / /  / /  / / / / PHOT8,  PA,  / / / / /  / L I S T OF /VOLTAGE  / R A N G E C O D E WORD / S I G N C O D E WORD / C O D E D V O L T A G E WORDS /FROM CALLING ROUTINE  PH08  L I S T OF S U B R O U T I N E ENTRY PHOT8 ENTRY GAN8 ENTRY CLOK8 ENTRY RCLK8 ENTRY STEP L I S T OF ENTRY ENTRY ENTRY ENTRY ENTRY ENTRY  DECODED WORDS  NAMES  DATA ENTRY P O I N T S T8L V2 V3 ERR8 FAST8 G8L  R E A D P H O T O D E T E C T O R A N D S T O R E D A T A WORD 0 CLA CLL TAD CHAN /GET CHANNEL SELECT 6323 / O U P U T TO D E V I C E 32 6321 /CONVERSION DONE? JMP PA / N O . TRY A G A I N 6324 / L O A D T H E D A T A WORD CMA /COMPLEMENT IT /AND STORE IT DCA ERR8 / R E T U R N TO C A L L I N G CDF C I F 0 /ROUTINE JMP% PHOT8  G E T T H E G A I N WORD, STORE I N CHAN  ADD  CHANNEL  NUMBER  IN  AND  ERR8  203  / / /  GAN8  / / / /  CLOK8  /  / /  FLG,  / / / / TEST,  / / /  G A I N WORD I S ANALOG INPUT 0 CLA TAD RAL RTL TAD DCA TAD 6323 CDF C I F JMP%  CLL G8L  I N THE RANGE 0 - 7 ON. C H A N N E L #17  / G E T T H E G A I N WORD ( 0 - 7 ) / S H I F T L E F T TO B I T S 6- 8  K7 CHAN CHAN  /ADD THE ANALOG CHAN /AND STORE I T / S E L E C T T H E NEW G A I N  0 GAN8  / R E T U R N TO /ROUTINE  #  CALLING  READ CLOCK AND DANA 0 I N I T I A L I Z E S Y S T E M D I R E C T COMMAND CLA CLL TAD FAST8 / G E T S U P E R F A S T CODE TAD K2000 /ADD A C 0 1 ( 1 ) TAD CHAN /ADD THE CHANNEL SELECT 6323 / O U T P U T TO D E V I C E 32 TEST CLA 631 1 AND SZA JMP  FOR  SYSTEM RDY--GROUND TRUE,AC06 CLL / L O A D F R O M D E V I C E 31 /MASK AC06 K40 /IS I T ZERO? FLG /NO. TEST AGAIN  GET T I M E , THEN START C O N V E R S I O N - - S E T SYS D I R TO 0 , W A I T , T H E N B R I N G H I G H A G A I N . READ CLOCK WHILE WAITING TAD / G E T S U P E R F A S T CODE FAST8 TAD CHAN /ADD CHANNEL S E L E C T CODE 6371 /CLOCK READY? JMP TEST / N O . TRY A G A I N 6323 / Y E S . O U T P U T D A T A WORD / L O A D LOW O R D E R C L O C K WORD 6361 DCA T8L /AND STORE I T 6362 / L O A D H I G H O R D E R C L O C K WORD DCA T8H /AND STORE I T NOP /WAIT BEFORE BRINGING SYSTEM / D I R E C T COMMAND H I G H A G A I N NOP NOP NOP TAD / L O A D S U P E R F A S T WORD FAST8 TAD CHAN / A D D C H A N N E L S E L E C T WORD TAD K2000 /ADD A C 0 1 ( 1 ) / O U T P U T TO D E V I C E 32 6323 W H I L E W A I T I N G FOR END OF C O N V E R S I O N , S I G N B I T F R O M T H E 1 2 - B I T T I M E WORDS  STRIP  OFF  204  CLA TAD RAR DCA RAL DCA TAD RAR DCA RAL DCA  / / / DFLG,  / / /  / / / / RCLK8,  CLL T8L  / G E T LOW O R D E R T I M E WORD / R O T A T E 1 B I T TO T H E R I G H T / A N D STORE AC /GET BIT 11 /AND STORE IT / R E P E A T W I T H H I G H O R D E R WORD  T8L ST8L T8H T8H ST8H  C H E C K FOR END OF C O N V E R S I O N DATA R E A D Y — G R O U N D TRUE,AC04 CLA CLL 631 1 /LOAD FROM D E V I C E AND K200 /MASK AC04 SZA /IS IT ZERO? JMP DFLG , / N O . TRY A G A I N READ I N V1,V2,V3 631 4 DCA 631 2 DCA 631 1 DCA CDF C I F JMP%  RESET n  BCD  VOLTAGE  V2  VI 0 CLOK8  100 M I C R O S E C O N D  6374 CDF C I F 0 JMP% RCLK8  / / / / / / STEP,  BACK,  AND  STORE  / L O A D V O L T A G E WORD /AND STORE IT / L O A D V O L T A G E WORD /AND STORE IT / L O A D V O L T A G E WORD /AND STORE IT / R E T U R N TO C A L L I N G /ROUTINE  V3  THE  WORD  /RESET  31  IN 3 2 1  CLOCK  PULSE  S T E P T H E S P E C I F I E D S T E P P I N G MOTOR AND WAIT FOR THE S P E C I F I E D T I M E B E F O R E :R E T U R N I N G n u CLL CLA TAD M2 / G E T MOTOR S E L E C T CODE 6332 / S E L E C T T H E MOTOR 6334 / S T E P T H E MOTOR CLA CLL TAD SLO / G E T T H E W A I T T I M E WORD CIA /GET ITS NEGATIVE I AC /INCREMENT ACCUMULATOR SZA /AC IS ZERO? BACK JMP / N O . J U M P TO B A C K CDF C I F 0 / Y E S . R E T U R N TO C A L L I N G 1  205  JMP%  STEP  /ROUTINE  / / / / K40, K200 , K2000, CHAN, K7, ERR8 , T8L, ST8L, T8H, ST8H, V1 , V2, V3, FAST8, G8L, SLO, M2,  TABLE 40 200 2000 7 7 0 0 0 0 0 0 0 0 0 0 0 0  OF  SECT8  / / / / / / / / READ8  CONSTANTS  /CHANNEL  WORDS  SELECT  CODE  /PHOTODETECTOR ERROR / L O W O R D E R C L O C K WORD /HIGH  ORDER  CLOCK.WORD  /DANA  VOLTAGE  WORDS  / S U P E R F A S T C O D E WORD / G A I N S E L E C T WORD / D E L A Y WORD F O R S T E P / M O T O R S E L E C T WORD  REA8  SUBROUTINE ENTRY ENTRY READ8 ENTRY DAC8 L I S T OF ENTRY ENTRY  AND DATA  DATA A8 D8  NAME  ENTRY  POINTS  S U B R O U T I N E TO R E A D AND D E C O D E S H A F T ENCODERS 0 CLA CLL TAD ISC8 / G E T E N C O D E R S E L E C T WORD 6332 /AND OUTPUT IT / W A I T FOR MUX TO NOP /SETTLE NOP NOP NOP NOP NOP NOP CLA CLL 6302 / G E T H I G H ORDER A N G L E DCA ANGH /AND STORE IT 6304 / G E T LOW O R D E R A N G L E DCA ANGL /AND STORE IT TAD ANGL / G E T LOW O R D E R WORD  206  AND DCA TAD RTR RTR AND DCA TAD RTL RTL RAL AND DCA TAD AND DCA TAD RTR RTR AND DCA CDF C I F JMP%  / / / / / DAC8,  / / /  K1 7 E8 ANGL  / M A S K B I T S 8-1 1 /AND STORE DECODED BCD / G E T LOW O R D E R WORD A G A I N  K1 7 D8 ANGL  /ROTATE RIGHT 2 TIMES /MASK BITS 8-11 /AND STORE DECODED BCD / G E T LOW O R D E R A G A I N /ROTATE  LEFT  5  TIMES  K1 7 C8 ANGH K1 7 B8 ANGH  /MASK /AND /GET /MASK /AND /GET  K1 7 A8 0 READ8  /ROTATE RIGHT 2 TIMES /MASK B I T S 8-11 /AND STORE DECODE BCD / R E T U R N TO C A L L I N G /ROUTINE  BITS 8-11 STORE DECODED BCD H I G H O R D E R WORD BITS 8-11 STORE DECODED BCD H I G H ORDER A G A I N  S U B R O U T I N E T O O U T P U T A V O L T A G E WORD T O T H E 1 6 - B I T D/A CONVERTER 0 CLA CLL TAD B8 / G E T M O S T S I G WORD K1 7 AND / M A S K LOW 4 B I T S RAR RTR RTR /ROTATE INTO HIGH 4 BITS DCA ANGH /AND SAVE IT TAD C8 / G E T L E A S T S I G WORD RTR RTR /ROTATE RIGHT 4 BITS AND K377 / M A S K 8 LOW O R D E R TAD ANGH /GET HIGH BITS CMA /COMPLEMENT 61 7 3 / A N D O U T P U T TO T H E DAC TAD C8 / G E T L E A S T S I G WORD A G A I N AND K1 7 / M A S K LOW O R D E R 4 B I T S RAR RTR RTR /ROTATE INTO HIGH 4 BITS CMA /COMPLEMENT 6423 / A N D O U T P U T TO T H E DAC CLA CLL CDF C I F 0 / R E T U R N TO C A L L I N G JMP% /ROUTINE DAC8  207  K1 7 , K377, ANGH, ANGL, A8, B8, C8, D8 , E8, ISC8 ,  1 7 377 0 0 0 0 0 0 0 0  /  FILE:  / H I G H O R D E R A N G L E WORD / L O W O R D E R A N G L E WORD / L I S T OF D E C O D E D A N G L E /WORDS I N BCD  /ENCODER  SELECT  CODE  ( VOLT  )  TYCO  / /  *  /  *  /  / / /  *  SUBROUTINE  TYCO  /  * * *  *  READ THE VOLTAGE FROM THE TYCO V O L T M E T E R AND R E T U R N T H E V O L T A G E TO T H E C A L L I N G R O U T I N E .  / / / / / / /  * * * * * * *  NOTE:  /  *  T H E V O L T A G E I S NOT S C A L E D TO T H E V O L T A G E R A N G E OF THE VOLTMETER. SCALING MUST B E DONE BY T H E C A L L I N G ROUTINE. ALSO, THE VOLTAGE WORD I S A L W A Y S A POSITIVE QUANTITY.  / / /  CALLING  / /  SEQUENCE: CALL  TYCO(VOLT)  / / /  WHERE:  VOLT  = VOLTAGE READ FROM TYCO VOLTMETER.  THE  / / / / / / / / /  SECT8 ENTRY  DVM88 TYCO  READ THE V O L T A G E FROM THE TYCO D V M , D E C O D E T H E V O L T A G E , AND R E T U R N TO T H E RALF CALLING ROUTINE.  / DVM8, FLAG,  0 CLA 6324  /PDP8  MODE R O U T I N E  CLL /GET  THE  FLAG  WORD  ENTRY  * * * * *  * * * *  *  208  /  /  /  / / / /  K1 7 , K37, K2000,  / /  DVML, DVMH, VH1 , VH2 , VL1 , VL2, VL3,  / / /  AND SZA JMP 6301  K2000  DCA 631 1  DVML  AND DCA TAD AND DCA TAD RTR RTR AND DCA  K37 DVMH DVMH K1 7 VH2 DVMH  /MASK THE FLAG B I T / I F DVM READY, CONTINUE / E L S E , CHECK FLAG AGAIN / G E T T H E LOW O R D E R V O L T A G E /WORD /AND SAVE I T / G E T T H E H I G H ORDER V O L T A G E /WORD / M A S K T H E LOW O R D E R B I T S / A N D S A V E T H E WORD / G E T T H E WORD /MASK THE PROPER B I T S /AND SAVE THEM / G E T T H E WORD A G A I N  R1 7 VH1  /ROTATE RIGHT 4 TIMES /MASK THE FIRST B I T /AND SAVE I T  TAD AND DCA  DVML K1 7 VL3  / G E T T H E LOW O R D E R WORD A G A I N /MASK THE F I R S T BCD D I G I T /AND SAVE I T  TAD RTR RTR AND DCA  DVML  /GET  K1 7 VL2  / R O T A T E 4 T I M E S TO T H E R I G H T /MASK NEXT BCD D I G I T /AND SAVE I T  DVML  /GET  K1 7 VL1  / R O T A T E 5 T I M E S TO T H E L E F T /MASK F I N A L BCD D I G I T /AND SAVE I T  TAD RAL RTL RTL AND DCA CDF C I F JMP%  FLAG  0  DVM8  T H E F U L L WORD  T H E F U L L WORD  AGAIN  AGAIN  / R E T U R N TO R A L F /ROUTINE  17 37 2000  0000 0000 0000  0000 0000  0000 0000  / L O W O R D E R V O L T A G E WORD / H I G H O R D E R V O L T A G E WORD / D E C O D E D V O L T A G E WORDS  209  /  #BASE, #XR #VOLT, #TEMP, #TEN1, r  /  F F F F F  BASE STARTD FLDA FSTA FLDA SETX SETB BASE LDX FSTA FLDA% FSTA  TYCO,  / /  #GOBAK,  {A2.3}  a  30 #GOBAK 0 #XR #BASE #BASE 1, 1 #BASE #BASE,1 #VOLT  DVM8 VH1 0 #TEN 1 #TEMP 1 #TEMP #TEN 1 #TEMP 2 #TEMP #TEN 1 #TEMP 3 #TEMP #TEN 1 #TEMP 4 #TEMP #VOLT  FORTRAN  This  IV  /PUT 1 INTO INDEX /SAVE POINTER /AND  SAVE  REG  1  IT  /START FLOATING POINT / C A L L T H E P D P 8 MODE R O U T I N E / S E T I N D E X R E G TO P D P 8 MODE A R E A / G E T MOST S I G DIGIT / M U L T I P L Y BY 10 /AND SAVE THE RESULT /GET NEXT D I G I T / A D D TO T E M P / M U L T I P L Y BY 10 /AND SAVE THE RESULT /GET NEXT D I G I T / A D D TO T E M P / M U L T I P L Y BY 10 /AND SAVE THE RESULT /GET NEXT D I G I T / A D D TO T E M P / M U L T I P L Y BY 10 /AND SAVE THE RESULT /GET LEAST SIG DIGIT / A D D TO T E M P / P A S S TO T H E C A L L I N G R O U T I N E / R E T U R N TO T H E C A L L I N G /ROUTINE  PROGRAM  FOR  OBTAINING  EQUIVALENT  equivalent  permittivity  CURVES:  source double  dielectric  / U S E C A L L E R S B A S E P A G E F O R NOW / S T A R T OF R A L F R O U T I N E /GET RETURN ADDRESS /AND SAVE IT / G E T P O I N T E R TO A R G / S E T I N D E X R E G TO T H I S P A G E / S A M E FOR B A S E REG  0  STARTF TRAP 4 SETX XTA FMUL FSTA XTA FADD FMUL .FSTA XTA FADD FMUL FSTA XTA FADD FMUL FSTA XTA FADD FSTA% JA  PERMITTIVITY  of  / B A S E PAGE REG /INDEX REG'S 0-2 / P O I N T E R TO ARG /TEMPORARY STORAGE  0.0 0.0 0.0 0.0 10.0  code  calculates  insulator  constant  of  the  the  stucture. inner  and  Given  outer  the  relative  dielectrics  and  210  their  ratio  equivalent thickness  of  thicknesses,  permittivity ratio.  The  as  a  number  it  produces  function of  of  a the  increments  plot  of  the  insulator has  to  be  supplied.  C C C  1 2 3 4 14 5 6 7 8 C  9  10 C  11 12  F I L E PERMIQ T H I S PROGRAM C A L C U L A T E S AND P L O T S THE E Q U I V A L E N T PERM OF A D O U B L E I N S U L A T O R S T R U C T U R E , W I T H T / S A S A P A R A M E REAL A , B , X , Y DIMENSION X(200),Y(200),TINC(200) CALL PLOTS(0.005,0) WRITE(4,1) F O R M A T ( 1 X , ' N U M B E R OF I N C R E M E N T S : ',$) READ(4,2)M FORMAT(F10.0) WRITE(4,3) F O R M A T ( 1 X , ' M A X . T H I C K N E S S R A T I O OF I N S U L A T O R I I TO I: READ(4,4)R FORMAT(F10.0) CONTINUE WRITE(4,5) F O R M A T ( 1 X , ' P E R M I T T I V I T Y OF I N S U L A T O R I : ',$) READ(4,6)B FORMAT(F10.0) WRITE(4,7) F O R M A T ( 1 X , ' P E R M I T T I V I T Y OF I N S U L A T O R I I : ',$) READ(4,8 )A FORMAT(F10.0) I N I T I A L I Z E A R R A Y TO Z E R O DO 9 I = 1 , M X(l)=0 Y(l)=0 TINC(I)=0 CONTINUE OLDT=0 DO 10 1=1,M TINC(I)=R/M X(I)=OLDT+TINC(l) OLDT=X(l) Y(I)=B*((1+X(I))/(1+X(I)*(B/A))) CONTINUE ASK I F GRAPH IS REQUIRED DATA Y E S , N O / ' Y ' , ' N ' / WRITE(4,11) FORMAT I [ 1 X , ' P L O T A X E S ? Y / N : ',$) READ(4,12)RESP FORMAT(A1)  21 1  13  I F ( R E S P . E Q . N O ) GO T O 13 CALL PSCALE(X,6,M,1) CALL PSCALE(Y,8,M,1) X0=X(M+1) XINC=X(M+2) Y0=Y(M+1) YINC=Y(M+2) C A L L A X I S ( 0 , 0 , ' R A T I O OF I N S U L A T O R T H I C K N E S S E S ' , - 3 0 , 6 , CALL A X I S ( 0 , 0 , ' E Q U I V A L E N T PERMITTIVITY', 23,8,90,Y0,Y CONTINUE CALL LINE(X,Y,M,1,0,0) CALL XYPLOT(0,0,3) GO T O 14 END  212  APPENDIX I I I  LABORATORY PROCESSING DETAILS  Some f u r t h e r processes  are  details  now  given  followed  through  devices.  In some c a s e s ,  requirements  of  concentrations H 0 2  2  ,  i n the  30%;  of  of  the  state  in greater d e t a i l .  fabrication they  of  laboratory  T h e s e have been  MOS  capacitors  are m o d i f i e d to s u i t  the  films  the  various  NH„OH,  solid  and  substrates.  chemicals  28-30%; HF,  48%;  HC1,  compatible  The  are  and  reagent  as  37-38%;  follows: ,  U SO 2  lt  95-  96%.  {A3.1}  THE  RCA  SSEE100  CLEANING  PROCEDURE  FOR  SILICON  SUBSTRATES: This Solid  is  a  State  Engineering  standard Laboratory,  a t UBC  [Kern  acid  c l e a n i n g process  1.  Prepare  water  hydroxide that  2.  Immerse  3.  Rinse in  (NH„OH). fits  Puotinen,  i n a 5:1:1 hydrogen Typical  very well  the w a f e r s / s l i c e s water c a s c a d e ,  cascade.  f o l l o w e d i n the of  1970].  Electrical The  peroxide-  follows:  ratio  of hot  peroxide amounts a r e  i n a 500  the w a f e r s / s l i c e s  first  water  :  Departement  and  i s as  a solution  ionized  ml,  cleaning process  ml  i n above  (60  (H 0 ) 2  2  300  de-  : ammonium  ml:60  ml:60  beaker. solution  i n d e - i o n i z e d water then  C)  f o r 8 min.  f o r 10 for 2  i n the  min. min.  second  213  4.  P r e p a r e a 10% HF s o l u t i o n i n amounts a r e 450 ml H 0 Immerse  6.  Rinse  7.  Prepare a s o l u t i o n  the w a f e r s / s l i c e s  the w a f e r s / s l i c e s  water  :  beaker.  Typical  and 50 ml HF.  2  5.  Nalgene  i n s o l u t i o n 4) f o r 30  in d . i .  i n a 5:1:1  hydrochloric  water p e r 3) a b o v e .  ratio  acid  o f h o t (60 C)  (HC1) : h y d r o g e n  T y p i c a l amounts a r e 300 ml:60 ml:60 m l .  8.  Immerse  the w a f e r s / s l i c e s  9.  Rinse  10.  Immerse w a f e r s / s l i c e s hot  {A 3.2}  2  the w a f e r s / s l i c e s  (60 C) i s o p r o p y l  i n s o l u t i o n 7) f o r 10 m i n .  in d . i .  water p e r 3) a b o v e .  (stirring)  i n beaker  with  400  ml  alcohol.  PHOTOLITHOGRAPHY:  Negative  (Waycoat HR200) and p o s i t i v e  photoresists  are  used  Exposure  t o UV l i g h t  process.  Development  negative  photoresist  {A3.2.1}  Negative  a)  d.i.  peroxide  (H 0 ). 2  sees.  Place  in  different  i s normally is  and m a n u a l l y  HPR204)  processing  part  usually  (Waycoat  o f t h e mask  done  steps. alignment  automatically  for  f o r the p o s i t i v e ones.  Photoresist:  wafer/slices  200 C. L e t samples c o o l  in drying in clean  oven  tray  f o r 30 m i n . before  at  applying  photoresi st. b) S p i n  wafers/slices  15 s e e s . c)  without  o n c e , a t 5000 rpm f o r  photoresist.  C a r e f u l l y apply  1b) a b o v e .  in spinner,  photoresist  with eyedropper,  repeat  214  d)  Prebake a l l wafers  i n oven  e)  Place  one a t a t i m e  expose  wafer/slices  in  mask  aligner,  f o r 8 sees.  f) Develop g)  f o r 15 m i n . , a t 60 C.  in automatic  Postbake  i n oven  developer.  f o r 15 m i n .  a t 135 C. L e t samples  cool. {A3.2.2} P o s i t i v e a)  Place  Let  Photoresist:  wafers  samples  in drying  oven  cool  clean  in  for 2 hrs. tray  at  before  300  C.  applying  photoresist. b)  Spin  wafers/slices  20 s e c . c) 2b) d) e)  without  o n c e , a t 5000 rpm f o r  photoresist.  C a r e f u l l y apply  photoresist  with eyedropper,  repeat  above. Prebake a l l wafers Place  expose  i n oven  wafer/slices  f o r 30 m i n .  one a t a t i m e  a t 105 C.  i n mask  aligner,  f o r 12 s e e s .  f) Develop Developer g)  in spinner,  i n 1:3  solution  and d e - i o n i z e d  Postbake  i n oven  of  water  Waycoat f o r 60  f o r 30 m i n .  Positive  LSI  sees.  a t 125 C. L e t samples  cool. {A3.2.3}  Etching:  {A3.2.3.1} S i l i c o n a)  Dip a l l  etching,  Dioxide:  wafer/slices  this  will  in  assure  d. i . that  water no  before  HF  gas b u b b l e s a r e  formed. b)  Pour  beaker.  450 ml  of  buffered  HF  solution  in  Nalgene  215  c)  Slowly  Etching d)  immerse  rate  Rinse  is  a l l  a l l  wafer/samples  approximately samples  for  850  in  solution.  A/min.  2+8  min.  in  de-ionized  etched  areas  water. e)  Inspect  dull  gray  under  and  f)  Etch  again  g)  Place  a l l  over  beaker  {A3.2.3.2} a)  if  in  water,  required.  samples in  in  they  Rinse  boiling  alcohol  are  be  hydrophobic.  thoroughly. isopropyl  vapours.  should  If  alcohol.  required  use  N  Dry jet.  2  Aluminium:  Prepare  in  also  microscope,  a  solution  de-ionized  maintain  of  water,  1:1  of  phosphoric  carefully  temperature,  an  s t i r r .  immersion  acid  Heat  to  (H PO„) 3  60  C  thermometer  and is  recommended. b)  Carefully  movements Etching  min.,  or  remaining Rinse  d)  varies  f)  takes  place. can  over  a l l  beaker  in  as  is  quite  solution  experimetation  etches  very  be  is  on  test  the  sample  advised.  (500  fast  (500  nm  in  nm  2-3  surface is  Slow  viscous.  is  slowly  Al  form  If  when  succesful,  treated. for  2+8  under  if  solution.  bubbles  samples  again  in  deposited  Gas  ones  wafer/slice  some  Al  less).  a l l  Place  and  E-Beam  Inspect  Etch  test  evaporated  under/overetching, e)  a  required  min.),  etching  c)  are  rate  Thermally 10-15  place  min.  required.  alcohol  de-ionized  microscope,  resolution,  samples  in  in  Do  weak not  boiling  vapours.  spots  water.  check  for  etc.  overetch. isopropyl  If  required  alcohol. use  N  2  Dry jet.  216  {A3.2.4} S t r i p p i n g {A3.2.4.1} Two  the P h o t o r e s i s t :  Negative:  possibilities  metal  and  that  exist,  one  that  i s incompatible,  i s compatible  i.e.  it will  with A l  remove i t  by e t c h i n g . • These  are:  {A3.2.4.1.1} M i c r o s t r i p a)  process: Al  P l a c e wafer/samples  i n hot  compatible. (60-70C) M i c r o s t r i p  for 5  min. b)  Immerse w a f e r / s a m p l e s  i n hot  xylene  I  (60-70C) f o r 5  min. c ) P l a c e samples d) 5  Immerse w a f e r s  xylene  i n hot  II  (60-70C) f o r 5  isopropyl  alcohol  min.  (60-70C) f o r  min.  e) Dry  blow  in nitrogen j e t .  {A3.2.4.1.2} C h r o m i c a)  i n hot  Acid  Pour c a r e f u l l y  beaker, heat  add  up  deadly  400  ml  of  incompatible with A l .  sulfuric  3 s p o o n f u l l s of c h r o m i c  to  and  process:  60C,  stirr  i t s h o u l d be  acid  (H SO«)  in  trioxide  (Cr0 )  and  thoroughly.  handled  with  2  3  T h i s mixture great  care  is and  respect. b)  Prepare  c) S l o w l y 2  min.  solution d) G i v e e)  a  beaker  with  d e - i o n i z e d water.  immerse t h e w a f e r / s a m p l e s Alternate  a  and  water.  d.  final  i .  beaker  total  rinse  P l a c e a l l samples  over  fresh  of  i n the  three times  i n d e - i o n i z e d water in b o i l i n g  in alcohol  vapours.  isopropyl  solution  for  between  the  f o r 2+8  min.  alcohol.  I f r e q u i r e d use  N  2  Dry jet.  217  {A3.2.4.2} a)  Positive:  Place wafer/samples  b) R i n s e  a l l samples  i n acetone  in fresh  f o r 60 m i n .  acetone.  c ) Dry i n N i t r o g e n j e t .  {A3.3} SILICON OXIDATION-FIELD OXIDE: The  thick  field  oxide  (typically  the  s u b s t r a t e by "wet" o x i d a t i o n i n a  The  gas flows a r e a d j u s t e d as f o l l o w s : 1. Oxygen: 1.0  furnace  i s grown at  from  1100±5C.  l/min.  2. H y d r o g e n :  1.6  l/min.  3. N i t r o g e n :  1.0  l/min.  4. H y d r o g e n C h l o r i d e  Cycle:  600 nm)  (HC1): 50  cc/min.  5-5-120-5-30 m i n . :  1 . 5 min. 0  2  2. 5 m i n . 0 + H C l 2  3. 120 m i n . H + 0 + H C l 2  4. 5 m i n . 0  2  2  5. 30 m i n . N  2  {A3.4} SILICON OXIDATION-GATE The substrate process  thin  gate  by was  experimental  oxide  OXIDE:  (typically  20 nm)  i s grown from t h e  " d r y " o x i d a t i o n i n a f u r n a c e a t 1000±5C. T h i s a  result  of  verification:  1. Oxygen: 1.0  l/min.  simulation  using  SUPREM  and  218  2. N i t r o g e n :  1.6  l/min.  3. H y d r o g e n C h l o r i d e  Cycle:  (HC1): 50 c c / m i n .  5-3-8-20-min.:  1. 5 m i n . 0  2  2. 3 m i n . 0  2  3. 8 m i n . 0 + H C l 2  4. 20 m i n . N  2  '5  {A3.5}  TANTALUM THERMAL  The furnace  tantalum  metal  i s o x i d i z e d by " d r y " o x i d a t i o n i n a  a t 5 0 0 ± 1 C . The gas f l o w  1. O x y g e n : 1.0 Cycle:  OXIDATION:  i s a d j u s t e d as f o l l o w s :  l/min.  45 t o 90 min.  until  fully  done,  for  50-100  nm  Ta  metal. 1. T h e r m a l l y  {A3.6}  o x i d i z e f o r 45-90 m i n . i n 0  2  SOURCE-DRAIN DIFFUSIONS:  The  diffusion  process  i s d i v i d e d i n t o p r e d e p o s i t i o n and  dr i v e - i n . {A3.6.1}  Predeposition:  a)  Prepare  per  RCA  two  half  wafers,  n-type m a t e r i a l , c l e a n e d  process.  b) S e t t h e gas f l o w s a s f o l l o w s : 1. N i t r o g e n ,  coarse:  2. Oxygen, f i n e :  2000  cc/min.  15 c c / m i n .  219  3.  Nitrogen,  c)  fine  (source):  Precondition  furnace  60  cc/min.  and  predope  boat,  without  wafer/samples. d)  Cycle:  3-18-2  1.  3 min.  N  2.  18 min.  3.  2 min.  {A3.6.2} a)  coarse  2  N N  min.:  coarse  2  + 0  2  + 0  fine.  2  + 0  fine  2  + N  fine  2  (BBr  3  source).  fine.  2  Drive-in: Set  the  gas  flows  1. Oxygen:  1.5  l/min.  2.  H y d r o g e n : 2.4  3.  Hydrogen C h l o r i d e  b)  Cycle:  5-80-30-5  1.  5 min.  0  2.  80  min.  0  2  +  HC1.  3.  30  min.  H  2  + 0  2  4.  5 min.  0  as  follows:  l/min. (HC1): 60  cc/min.  min.:  only.  2  2  +  HC1.  only.  {A3.6.3} BORON GLASS ETCHING: The stage  glassy  has  t o be  a)  Prepare  b)  Dip  c)  Immerse  for  surface  formed  removed by 400  ml  of  90  the  predeposition  etching: buffered  a l l wafer/samples samples  during  HF  solution.  in de-ionized  in etching  water.  solution  slowly.  Leave  sees.  d)  Rinse  e)  Boil  in de-ionized in  water  f o r 2+8  i s o p r o p y l a l c o h o l to  min.  remove a l l t r a c e s  of  220  water. Dry i n N  j e t i f required.  2  {A3.7} POST ANODIC OXIDATION CLEANING: After  the  anodic  wafer/samples a r e cleaned 1. in  oxidation with  Rinse wafer/sample de-ionized  2. C a r e f u l l y  takes  the following  i n anodic  cell  place,  the  process:  holder  f o r 10 min  water. remove sample and p l a c e  in  single  wafer  holder. 3.  Place  4.  sample  in boiling  Immerse sample  trichloroethylene.  in boiling  isopropyl  a l c o h o l . Dry i n  v a p o u r s on t o p o f b e a k e r . 5.  Dry i n n i t r o g e n  j e t i f requi'red.  {A3.8} THE BNR CLEANING PROCESS: As MES  some o f t h e s a m p l e s had T a n t a l u m d e p o s i t e d  technique at  following  steps  Bell  Northern  were  used  Research  in cleaning  in  using the  Ottawa,  the wafers  the  [Miner,  1981]: 1. U l t r a s o n i c  agitation  in  trichloroethylene  for  5  min. 2. U l t r a s o n i c 3.  Immersion  agitation  i n acetone  f o r 5 min.  i n Alconox and d e - i o n i z e d  water  solution  with u l t r a s o n i c a g i t a t i o n . 4. Long 5.  rinse  i n flowing  de-ionized  water  f o r 3 hours.  D i p i n HF.  6. S p r a y filtered  rinse  in isopropyl  nitrogen.  alcohol  and blow  dry  with  221  {A3.9} INTERFACIAL OXIDATION OF The  process  followed  a  SILICON: d r y o x i d a t i o n of t a n t a l u m  500C, d e p o s i t e d by RFS, and t h e n  a wet  o x i d a t i o n of  at  800C.  oxide  structure,  on  top of  T h i s c r e a t e s a double  were  Ta 0 2  5  s e t as f o l l o w s :  1.5  1/min.  2. H y d r o g e n : 2.5 used  was  1/min.  3-X-3  min., w i t h X v a r y i n g between 24 and  minutes: a) 3 m i n . :  0  b) X m i n : 0 c) The  with  2  1. Oxygen:  1 14  Silicon  Si0 •  The gas f l o w s  The c y c l e  at  3 min:  furnace  quartz  tube.  used  +  2  0  2  H  2  2  i s the P a c e s e t t e r  I I , r e s i s t a n c e heated,  2''  222  APPENDIX IV  SPICE  The  s i m u l a t i o n of the double  oxidation  was s i m u l a t e d  using  i ******.*06- 19-84 * * * * * * * * ODOUBLE D I E L E C T R I C 0****  MOSFET  INPUT L I S T I N G  dielectric  AND  SUPREM SIMULATION RESULTS  MOSFET DC and t r a n s i e n t c h a r a c t e r i s t i c s  was  accomplished  using  SPICE.  The  SUPREM.  SPICE  2G.1  (150CT80)  * * * * * * * * 20: 08 : 3 1 **** *  S P I C E SIMULATION TEMPERATURE  =  27.000 DEG C  0***********************************************************************  * T h i s i s t h e T r a n s i e n t R e s p o n s e o f a MTAOSFET, * a n d f a b r i c a t e d b y A. E g u i z a b a l (1983). * V I N 4 O PULSECO -11 50NS 2NS 2NS 200NS 1000NS) RS 4 3 6 0 0 RIN 3 O 500 C I N 3 O 10PF VDD 1 0 DC -6 CBYP 1 0 22UF  RL I 2  designed  IK  COUT 2 O 15PF ROUT 2 O 10MEG M1 O 3 2 O M0D1 L=10U W=680U AS=70000P AD=70000P PD=1600U PS=1S00U .MODEL M0D1 PMOS VT0=-2.5 KP=6.82E-3 .DC VIN 0 -11 -0.5 .PLOT DC V ( 2 ) .PLOT TRAN V ( 2 ) .TRAN 10NS 500NS ONS . END 1 ****************06-  19-84 * * * * * * * * * * * * * * * * * * * * * * * *  SPICE  2G.1  (150CT80)  ************************20:08:31 * * * * * * * * * * * * * * * *  ODOUBLE D I E L E C T R I C MOSFET S P I C E SIMULATION 0**** MOSFET MODEL PARAMETERS TEMPERATURE = 27.000 DEG C 0* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *  223  OTYPE OLEVEL OVTO OKP  M0D1 PMOS 1.OOO -2.500 6.82E-03  ^****************06~19-84 ************************  SPICE 2G.1 (150CT80)  ODOUBLE DIELECTRIC MOSFET SPICE SIMULATION 0**** DC TRANSFER CURVES  ************************20:08:31 ****************  TEMPERATURE =  27.000 DEG C  X VIN  V(2)  X  -6.000E+00  0 0 -5 OOOE-01 -1 OOOE+OO -1 500E+00 -2 OOOE+OO -2 500E+00 -3 OOOE+OO -3 500E+00 -4 OOOE+OO -4 500E+00 -5 OOOE+OO -5 500E+00 -6 OOOE+OO -6 500E+00 -7 OOOE+OO -7 500E+00 -8 OOOE+OO -8 500E+00 -9 OOOE+OO -9 500E+00 - 1 000E+01 . - 1 050E+01 - 1 100E+01  -5 999E+00 -5 999E+00 -5 999E+00 -5 999E+00 -5 999E+00 -5 999E+00 -5 999E+00 -5 999E+00 -5 999E+00 -5 999E+00 -5 999E+00 -5 999E+00 -6 583E-02 -2 927E-02 -1 918E-02 - 1 431E-02 - 1 142E-02 -9 505E-03 -8 142E-03 -7 121E-03 -6 328E-03 -5 694E-03 -5 176E-03  -4.000E+00  -2.000E+00  * * * * * * * * * * * *  0.0  * * * * * * * * * * *  Y 1 ****************06- 19-84 ************************  SPICE 2G .'1 (150CT80)  ODOUBLE DIELECTRIC MOSFET SPICE SIMULATION 0**** INITIAL TRANSIENT SOLUTION  NODE  VOLTAGE  NODE  VOLTAGE  NODE  VOLTAGE  ************************20:08:31 ****************  TEMPERATURE =  NODE  VOLTAGE  27.000 DEG C  224  (  1)  -6.0000  (  2)  -5.9994  ( 3 )  0.0  ( 4 )  0.0  VOLTAGE SOURCE CURRENTS NAME  CURRENT  VIN  0.0  VDD  5.999E-07  TOTAL POWER DISSIPATION 3.60E-06 WATTS 1****************06- 19-84 ************************  SPICE' 2G . 1 (150CT80)  ODOUBLE DIELECTRIC MOSFET SPICE SIMULATION 0**** OPERATING POINT INFORMATION  ************************20 * 08 : 3 1 *************** * TEMPERATURE =  27.000 DEG C  MOSFETS 0 M1 OMODEL M0D1 ID 0.0 VGS 5.999 VDS 5.999 VBS 5 . 999 ^************** **06- 19-84 ************************  SPICE 2G 1 (150CT8O)  ODOUBLE DIELECTRIC MOSFET SPICE SIMULATION 0**** TRANSIENT ANALYSIS  TIME  0 000E -08 000E -08 OOOE -08 000E -08 OOOE -08 OOOE -08 OOOE -08  TEMPERATURE =  27.000 DEG C  V(2) -6.OOOE+00  0 1 2 3 4 5 6 7  ************************20•08:31*************** *  -5 -5 -5 -5 -5 -5 -8 -1  999E+00 999E+00 999E+00 999E+00 999E+00 999E+00 229E-03 188E-02  * * * * * *  -4.OOOE+OO  -2.OOOE+00  0.0  8 9 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 5  Y 0 0  1  OOOE -08 OOOE -08 OOOE -07 100E -07 200E -07 300E -07 400E -07 500E -07 600E -07 700E -07 800E -07 900E -07 OOOE -07 100E -07 200E -07 300E -07 400E -07 500E -07 600E -07 700E -07 800E -07 900E -07 OOOE -07 100E -07 200E -07 300E -07 400E -07 500E -07 600E -07 700E -07 800E -07 900E -07 OOOE -07 100E -07 200E -07 300E -07 400E -07 500E -07 600E -07 700 E -07 800E -07 900E -07 OOOE -07  -9 499E-03 - 1 404E-03 -9 442E-03 -1 439E-03 -9 394E-03 - 1 475E-03 -9 348E-03 -1 511E-03 -9 303E-03 -1 546E-03 -9 258E-03 - 1 581E-03 -9 213E-03 - 1 G16E-03 -9 169E-03 - 1 650E-03 -9 126E-03 1 015E-02 - 1 788E+00 -3 835E+00 -4 890E+00 -5 425E+00 -5 710E+00 -5 855E+00 -5 927E+00 -5 963E+00 -5 981E+00 -5 990E+00 -5 995E+00 -5 997E+00 -5 998E+00 -5 999E+00 -5 999E+00 -5 999E+00 -5 999E+00 -5 999E+00 -5 999E+00 -5 999E+00 -5 999E+00 -5 999E+00 -5 999E+00 -5 999E+00 -5 999E+00  JOB CONCLUDED TOTAL JOB TIME  * * * * * * * * * * *  *  * * * * * *  0.0  226  ***  STANFORD UNIVERSITY PROCESS ***  1. 2. 3. 4 . 5. 6 . 7. 1 GATE STEP  ENGINEERING MODELS PROGRAM ***  VERSION 0-05 ***  .. . T I T L E GATE OXIDE ...GRID DYSI=0.001, DPTH=0 2 , YMAX=1.0 ...SUBST ORNT=100, E,LEM = P, C0NC=4.OE14 ...PLOT TOTL=Y ...PRINT HEAD=Y ...STEP TYPE=OXID, TIME=3, TEMP=1090, MODL=DRYO .. . END OXIDE tt  1  OXIDATION IN DRY OXYGEN TOTAL STEP TIME = 3.0 MINUTES I N I T I A L TEMPERATURE = 1090.00 DEGREES C. OXIDE THICKNESS = 2.2444E-02 MICRONS LINEAR OXIDE .GROWTH RATE PARABOLIC OXIDE GROWTH RATE OXIDE GROWTH PRESSURE I I I PHOSPHORUS SURFACE  I  OXIDE DIFFUSION COEFFICIENT  CONCENTRATION  SILICON DIFFUSION COEFFICIENT  SEGREGATION COEFFICIENT  1.22179E-03 I  I I I  10.000  I j  SHEET RESISTANCE 125136.  OHMS/SOUARE  CONCENTRATION  OXIDE CHARGE S I L I C O N CHARGE TOTAL CHARGE I N I T I A L CHARGE  CHEMICAL  I I I  = -4.375506E+14 ATOMS/CM!3  I  ACTIVE  2.492192E-03 MICRONS/MINUTE 3.647341E-04 MICRONS!2/MINUTE 1.00000 ATMOSPHERES  5.23156E-06 I  JUNCTION DEPTH  NET  = = =  = = = =  1 3 3 3  011304E+08 987205E+10 9973 18E+ 10 999999E+10  CONCENTRATION  OXIDE CHARGE S I L I C O N CHARGE TOTAL CHARGE  = = =  OF  IS IS IS  O. 253 99 . 7 99.9  % % %  OF TOTAL OF TOTAL OF I N I T I A L  0. 253 99. 7 99.9  % OF TOTAL % OF TOTAL % OF I N I T I A L  PHOSPHORUS  1.011304E+08 3.987205E+10 3.997318E+10  IS IS IS  SURFACE TRANSPORT COEFFICIENT  I I  3.95133E-02 I  227  INITIAL  CHARGE = GATE OXIDE  I STEP I DEPTH I (UM) I 14 -0.02 *-  0.0  1 .00  2 .00  3 .00  3.999999E+10  TIME  =  3.0  MINUTES.  CONCENTRATION 15  16  17  (LOG ATOMS/CC) 18  19  20  21  228  i  i  I  i i  I  4.00 1 SUPREM END . J> 1  ***  i i  STANFORD UNIVERSITY PROCESS ***  i i  ENGINEERING  I  I  i  I  I  i  MODELS PROGRAM ***  VERSION 0-05 ***  1 . . . . T I T L E GATE OXIDE 2....GRID DYSI=O.001, DPTH=0.2, YMAX=1.0 3....SUBST 0RNT=10O, ELEM=P, C0NC=4.0E14 4 . . . .PLOT TOTL = Y 5....PRINT HEAD=Y 6....STEP TYPE=OXID, TIME = 80.0, TEMP=1090, 7 . . . .END  M0DL = DRYO  1 GATE  OXIDE  'STEP tt  1  OXIDATION IN DRY OXYGEN TOTAL STEP TIME = 80.0 MINUTES I N I T I A L TEMPERATURE = 1090.00 DEGREES C. OXIDE THICKNESS = 0.1198 MICRONS LINEAR OXIDE GROWTH RATE PARABOLIC OXIDE GROWTH RATE OXIDE GROWTH PRESSURE I I I PHOSPHORUS SURFACE  I  OXIDE DIFFUSION COEFFICIENT  JUNCTION DEPTH  I I I  SILICON DIFFUSION COEFFICIENT  I I I  SEGREGATION COEFFICIENT  1.22179E-03 I  10.000  I I I I  = -4.474924E+14 ATOMS/CM!3 I  j  I  OXIDE SILICON TOTAL INITIAL  2.492192E-03 MICRONS/MINUTE 3.647341E-04 MICRONS!2/MINUTE 1.00000 ATMOSPHERES  5.23156E-06 I  CONCENTRATION  NET ACTIVE  = = =  SHEET RESISTANCE 126788.  OHMS/SQUARE  CONCENTRATION  CHARGE = CHARGE = CHARGE = CHARGE =  4.517386E+08 3.935OO2E+10 3.980176E+10 3.999999E+10  IS IS IS  1.13 98.9 99.5  % OF TOTAL % OF TOTAL % OF INITIAL  SURFACE TRANSPORT COEFFICIENT  I I  3.95133E-02 I  229  CHEMICAL OXIDE SILICON TOTAL INITIAL 1  CONCENTRATION  CHARGE = CHARGE = CHARGE = CHARGE = GATE OXIDE  I STEP = 1 I DEPTH I (UM) I 14 15 -0.12 * * I * I * I * I * I * I * I * I * I 0.0 * *  1 1 1 1 1 1 1 1  1 .00  2 .00  3.00  * * * * * * * *  1 1 1 1 1 1 1 1  OF PHOSPHORUS  4.517386E+08 3.935002E+10 3.980176E+10 3.999999E+10  TIME =  IS IS IS  1.13 98.9 99.5  % OF TOTAL % OF TOTAL % OF I N I T I A L  80.0 MINUTES.  CONCENTRATION  (LOG ATOMS/CC)  16  17  18  19  I I I I I I I I I  I I I I I I I I I  I I I I I I I I I  I I I I I I I I I  I I I I I I I I  I I I' I I I I I  I I I I I I I I  I I I I I I I I  21  230  4.00 1 SUPREM 1  END.b  ***  STANFORD U N I V E R S I T Y PROCESS ***  1. 2. 3 . 4 . 5 . 6 . 7 . 1 GATE  ENGINEERING MODELS PROGRAM ***  VERSION 0-05 ***  .. . T I T L E GATE OXIDE ...GRID DYSI=0.001, DPTH=0 2 , YMAX=1.0 ...SUBST 0RNT=100, ELEM=P, C0NC=4.0E14 ...PLOT TOTL=Y ...PRINT HEAD=Y ...STEP TYPE=OXID, TIME=3, TEMP=1000, MODL=DRYO .. . END OXIDE  STEP #  1  OXIDATION IN DRY OXYGEN TOTAL STEP TIME = .3.0 MINUTES I N I T I A L TEMPERATURE = 1000.00 DEGREES C. OXIDE THICKNESS = 1.4006E-02 MICRONS LINEAR OXIDE GROWTH RATE PARABOLIC OXIDE GROWTH RATE OXIDE GROWTH PRESSURE I I I PHOSPHORUS SURFACE  I  OXIDE DIFFUSION COEFFICIENT  = = =  7.479377E-03 MICRONS/MINUTE 1.739819E-04 MICRONS!2/MINUTE 1.00000 ATMOSPHERES  I I I  SILICON DIFFUSION COEFFICIENT  6.36610E-07 I  CONCENTRATION  JUNCTION DEPTH  SEGREGATION COEFFICIENT  1.35026E-04 I  10.000  = -4.947440E+14 ATOMS/CM!3 I 1 I  SHEET RESISTANCE 124966.  OHMS/SOUARE  I I I  SURFACE TRANSPORT COEFFICIENT  I I  1.19299E-02 I  231  NET  ACTIVE  OXIDE SILICON TOTAL INITIAL  CONCENTRATION  CHARGE = CHARGE = CHARGE = CHARGE = GATE OXIDE  I STEP I DEPTH I (UM) I 14 -0.01 *-  0.0  1 .00  2.00  6. 576280E+07 3. 9 9 2 6 5 5 E + 1 0 3, 9 9 9 2 3 1 E + 1 0 3. 9 9 9 9 9 9 E + 1 0  CHARGE = CHARGE = CHARGE = CHARGE =  CHEMICAL OXIDE SILICON TOTAL INITIAL  CONCENTRATION  1  6 3 3 3  OF  IS IS IS  0. 1G4 99 .8 100.  % % %  OF OF OF  TOTAL TOTAL INITIAL  0. 164 99.8 100.  % % %  OF OF OF  TOTAL TOTAL INITIAL  PHOSPHORUS  576280E+07 992655E+10 999231E+10 999999E+10  TIME  =  IS IS IS  3.0  MINUTES.  CONCENTRATION 15  16  17  (LOG ATOMS/CC) 18  19  21  232  3 .00  4.00 1 SUPREM 1  ***  END . o  STANFORD UNIVERSITY PROCESS ***  1. 2. 3. 4 . 5. 6 . 7. 1 GATE STEP  VERSION  ENGINEERING  MODELS PROGRAM ***  0-05 ***  .. . T I T L E GATE OXIDE ...GRID DYSI=0.001, DPTH=0 2, YMAX=1.0 ...SUBST ORNT=100, ELEM=P, C0NC=4.OE14 ...PLOT TOTL=Y ...PRINT HEAD=Y ...STEP TYPE=OXID, TIME=5, TEMP=1000, MODL=DRYO .. . END OXIDE tt  1  OXIDATION IN DRY OXYGEN TOTAL STEP TIME = 5.0 MINUTES I N I T I A L TEMPERATURE = 1000.00 DEGREES C. OXIDE THICKNESS = 2 . 0 0 7 4 E - 0 2 MICRONS LINEAR OXIDE GROWTH RATE PARABOLIC OXIDE GROWTH RATE OXIDE GROWTH PRESSURE I I I PHOSPHORUS  I  OXIDE DIFFUSION COEFFICIENT 6.36610E-07  = = -  7.479377E-03 MICRONS/MINUTE 1.739819E-04 MICRONS!2/MINUTE 1.00000 ATMOSPHERES  I I I  SILICON DIFFUSION COEFFICIENT  I  I I I  1.35026E-04 I  SEGREGATION COEFFICIENT 10.000  I I I I  SURFACE TRANSPORT COEFFICIENT  I I  1.19299E-02 I  233  SURFACE  CONCENTRATION  JUNCTION  -5.045019E+14 ATOMS/CM!3 SHEET  DEPTH  RESISTANCE  125066.  NET  ACTIVE  OXIDE SILICON TOTAL INITIAL  OXIDE SILICON TOTAL INITIAL  I I DEPTH I (UM) I 14 -0.02 *  0.0  1 .00  CONCENTRATION  CHARGE CHARGE CHARGE CHARGE  CHEMICAL  OHMS/SQUARE  9. 653334E+07 3. 9 8 9 4 3 3 E + 1 0 3. 9 9 9 0 8 6 E + 1 0 3. 9 9 9 9 9 9 E + 1 0  = = = =  CONCENTRATION  CHARGE = CHARGE = CHARGE = CHARGE = GATE OXIDE STEP  1  9 3 3 3  OF  IS IS IS  0.24 1 99.8 100/  % % %  OF OF OF  TOTAL TOTAL INITIAL  0.241 99 . 8 100.  % OF % OF % OF  TOTAL TOTAL INITIAL  PHOSPHORUS  653334E+07 989433E+10 999086E+10 999999E+ 10  TIME  =  IS IS IS  5.0  MINUTES.  CONCENTRATION 15  16  17  (LOG ATOMS/CC) 18  19  21  c "a XI  O  o  o o  o o  APPENDIX  C-V  AND  I-V  CURVES  ADDENDUM TO  TANTALUM GATE  OF  I  MOS  THE M . A . S c .  PENTOXIDE, INSULATOR  A NON FOR  MOS  CAPACITORS  THESIS  CONVENTIONAL DEVICES  by  ANTONIO  THE  L.  UNIVERSITY  EGUIZABAL  B R I T I S H COLUMBIA  OF  January © Antonio  L.  RIVAS  1984  Eguizabal Rivas  SAMPLE n  N2,  Type,  SINGLE Thermal  DIELECTRIC 500  C.  Sample N2 n Type S i l i c o n  CM •  u  CO  cm LU Q_  LL.  CL  LO  S.  tr  LU  •  CC  tr  n z  =>  a. LU  en  EL £_>  Z tr i— n u  tr a. tr  -I  IS. BB  -1  zs  SCHOTTKY  I V PLOT  pj-j  Sample N2 n Type S i l i c o n Gate n e g a t i v e  .  0.H 0  1  B.8B SORT  1  1-G0 VDLTflGE  1  Z.10  1  S.ZH  —  CSORTCVDLTS3D  1  1.B0  1  ^-S0  SAMPLE n  N3,  Type,  SINGLE Thermal  DIELECTRIC 500  C.  GATE  VDLTflGE  SORT  VDLTflGE  CSORTCVDLTSD3  SAMPLE n  1T6,  Type,  DOUBLE Thermal  DIELECTRIC 500  C.  -1"  SCHOTTKY  IV  PLOT  CO  Sample 1T6 n Type S i l i c o n Gate n e g a t i v e cp  CM  co-  at  in'  to"  CM  B . BB  T  B.SB SORT  T  l.GB  VOLTAGE  T  Z.tB  T  S.ZB  CSORTCVDLTS3D  I  1  SAMPLE n  2T6,  Type,  DOUBLE Thermal  DIELECTRIC 500  C.  S C H O T T K Y  I V  P L O T Sample 2T6 n Type S i l i c o n Gate n e g a t i v e  .00 SORT  T  1.60  VDLTflGE  Z.T0  T  3.Z0  CSORTCVDLTS7D  T  t-00  M  SAMPLE n  3T6,  Type,  DOUBLE Thermal  DIELECTRIC 500  C.  d.</  SCHDTTKT  IV  PLDT Sample 3T6 n Type S i l i c o n Gate n e g a t i v e  SORT  VDUTflGE  CSDRTCVDLTS33  SAMPLE n  4T6,  Type,  DOUBLE Thermal  DIELECTRIC 500  C.  Sample 4T6 n Type S i l i c o n  -i  1  1Z.BB GATE  -Z.BB VDLTflGE  1  6.BB  r10.BB  1  Z6.  J'9'  S C H O T T K Y  I V  P L O T  CD  Sample 4T6 n Type S i l i c o n Gate n e g a t i v e  to  CM"  «* tN  en"  to'  CM  1  — i -  0 .BB  B.SB SORT  l.GB VOLTAGE  r -  Z.1B  r  S.ZB  CSDRTCVDLTS33  1  *-BB  t. SB  SAMPLE n  1T7,  Type,  DOUBLE Thermal  DIELECTRIC 500  C.  GATE  VDLTflGE  ,22  JSC  S C H O T T K Y  I V  P L O T Sample 1T7 n Type S i l i c o n Gate n e g a t i v e  CM"  in-  to '  0.00  T  0.80 SDRT  T  1.G0  VDLTflGE  T  Z.*t0  T  S.ZB  CSORTCVDLTS33  T  1. 00  Si  SAMPLE n  2T7,  Type,  DOUBLE Thermal  DIELECTRIC 500  C.  Sample 2T7  GATE  VDLTflGE  2b°l  S C H O T T K Y  I V  P L D T Sample 2T7 n Type S i l i c o n Gate n e g a t i v e  to  CM"  CM  m"  to in-  to'  CM  B.8B SDRT  1.6B VOLTAGE  T  S.ZB CSORTCVDLTS33  T  "».BB  BB  SAMPLE n  3T7,  Type,  DOUBLE Thermal  DIELECTRIC 500  C.  GATE  VDLTAGE  2'8  S C H O T T K Y  I V  P L O T Sample 3T7 n Type S i l i c o n Gate n e g a t i v e  I  .80 SQRT  1  l.CB VDLTflGE  1  Z.*tB  1  3.ZB  CSORTCVDLTS33  1  t .B B  -1 1. 8  SAMPLE n  4T7,  Type,  DOUBLE Thermal  DIELECTRIC 500  C.  v3'0 ,  #6f  CQKT  VOLTAGE  CSORTCVDLTC33  2&  SAMPLE n  i  NI,  Type,  SINGLE Thermal  DIELECTRIC 500  C.  SORT  VOLTAGE  CSQRTf.VDL.TC3 3  SAMPLE n  S7,  Type,  SINGLE Thermal  DIELECTRIC 500  C.  3-5'  9&%  SORT  VDLTPGE  CSDKTCVDLTC33  SAMPLE p  BNR500, Type,  SINGLE  Thermal  DIELECTRIC 500  C.  GATE  VDLTAGE  SORT  VDLTflGE  CSORTCVDLTS33  SAMPLE p  BNR1000, Type,  SINGLE  Thermal  DIELECTRIC  500  C.  GATE  VDLTflGE  S C H Q T T K T  I V  CP  P L D T Sample BNR1000 p Type S i l i c o n Gate p o s i t i v e  s: ex  o  _J  CJ  0.00  T  0 . t0 SORT  ~T 0.60 VDLTflCE  T  1.Z0  1.C0  CSORTCVDLTS33  Z.00  Z.^Z  SAMPLE p  SampleA, Type,  SINGLE  Thermal  DIELECTRIC  500  C.  .4-3"  GflTE  VDLTflGE  21<  S C H O T T K Y  I V  P L D T Sample SAMP LEA p Type S i l i c o n Gate p o s i t i v e  to  CM  cr  to xn-  to"  0.00  0.60 SQRT  T  4.G0  VDLTflGE  Z.t0  T  S.Z0  CSQRTCVDLTS33  —r  1  00  t . Sf  SAMPLE p  SampleB, Type,  SINGLE  Thermal  DIELECTRIC  500  C.  Sample SAMPLEB  GATE  VOLTAGE  #7  SQRT  VOLTflCC  CCQRTCVDLTS33  SAMPLE  1000AMOS, n  Type,  SINGLE  Thermal  DIELECTRIC  500  C.  ,4-9'  Sample 1000AMDS n Type S i l i c o n  GATE  VDLTflGE  SQRT  VDLTflGE  [SQRTCVDLTS33  SAMPLE  500ALift, p  Type,  SINGLE  Thermal  DIELECTRIC  500  C.  GATE  VDLTPCE  S C H D T T K T  I V  P L D T  CD  Sample 5 0 0 A L i f t p Type S i l i c o n Gate p o s i t i v e te  I  to'  cy  0-00  H.S0 SQRT  T~  1.00 VDLTflGE  T  1-S0  T  2.00  CSORTCVDLTS33  T  Z.S0  -1  3.00  SAMPLE  lOOOALift, p  Type,  SINGLE  Thermal  500  DIELECTRIC C.  SCHOTTKY  IV  PLDT  CD  Sample l O O A L i f t n Type S i l i c o n Gate  negative  to  C\J-  CO-  CD  tO  to'  (M  0 .00  0.80 SORT  T  1.G0  VOLTAGE  T  Z.^0  T  3-ZB  CSQRTCVDLTS3 2  t . 80  SAMPLE n  MOSC Type,  6,  SINGLE  Thermal  DIELECTRIC 600  C.  S C H O T T K Y  I V  P L O T Sample MOSC6 n Type S i l i c o n Gate n e g a t i v e  I  1  .80 SQRT  1.60 VDLTflGE  1  Z.tB  1  3.Z0  CSQRTCVDLTS33  1  *-00  1  <K 6  SAMPLE n  M0SC7, Type,  SINGLE  Thermal  DIELECTRIC 400  C.  Sample MOSC7 n Type S i l i c o n  -I  3Z.00  -ZZ.BI  r  -1Z.00  -Z.00  GflTEwVDLTAGE  1  8.00  1 8 . 00  ZS  S C H D T T K T  IV  P L D T Sample MOSC7 n Type S i l i c o n Gate n e g a t i v e  SAMPLE n  MOSC8, Type,  SINGLE  Thermal  DIELECTRIC 600  C.  S C H D T T K Y  I V  P L D T Sample MOSC8 n Type S i l i c o n Gate  negative  CM"  t o 0_ s: cr •—'  ^ Q _J  — t  2 Ul  OL a: CJ  •  e» LS Q _l  1  C—  -  0.00  0.80 SORT  1.G0 VDLTflEE  T Z.tB  T 3.Z0  CSDRTCVDLTSD1  T *K00  *. 80  65'  SAMPLE n  M0SC9,  Type,  SINGLE  Anodic,  DIELECTRIC  C i t r i c  Acid.  GATE  VDLTflGE  3o(  S C H O T T K Y  I V  P L D T  Sample MOSC9 n Type Gate  Silicon  negative  tn n  s: tr CD"  C5  LU  LY CJ  CM  2  <=5  to  CD  0.00  0.80 SORT  T 1.90 VDLTflGE  Z.^0  3.20  CSQRTCVDLTS33  —1— <K 00  1 " K SI  SAMPLE n  MOSC10, S I N G L E  Type,  Anodic,  DIELECTRIC  Citric  Acid.  &9  3*3  \5o  SCHOTTKY CM" _  CO"  IV  PLDT Sample MOSC10 n Type S i ll ii ccoorn Gate n e g a t i v e  SAMPLE n  Type,  M0SC11, S I N G L E Anodic,  DIELECTRIC  Phosphoric  Acid.  Sample M0SC11  CD'  K <y  «s:  (-}  n Type S i l i c o n  <^  LO ~  CV UJ D_ U_  «=» in~  \ <^  cr LU £V cr i— ri 2 3  (V  "*"  cn~  [ | I  CL  LU z  CM  -  t-i cr cr  1  -35.00  -ZS.00  r— -15.00 GATE  1  1  -S.00 VDLTflGE  1~  5.00  1  15.00  ZS . 0 0  SAMPLE n  Type,  M0SC12, Anodic,  SINGLE  DIELECTRIC  Phosphoric  Acid.  3&r  Sample M0SC12 n Type S i l i c o n  LP  c <=»  * CM  i51  CM  CJ  ac LU  CL LU  LI-  LY  cr  CD  -  2 CY LU  a. LU CJ Z  tr  CJ  cr a. cr  CJ  CM:  ,  -3S.00  -ZS..00  1  1  -IS.00 GATE  -S.00 VDLTflGE  S. 0 0  IS.00  ZS.00  SAMPLE n  M0SC13,  Type,  SINGLE  Anodic,  DIELECTRIC  C i t r i c  Acid.  Sample M0SC13  CD'  n Type S i l i c o n  X.  (M  «s:  -  Qi  UJ CL  LL.  D_  in~  \  cr  e»  111  VL  CC i— r> Z  (V  1 1 1  cn ~  D. LU t_J Z  cr >— i-i £J  CC D_ CC  -35.00  1 -ZS.00  1 -IS.00 GATE  1 -5.00 VDLTflGE  1 5.00  -1 1SV00  1 25.  S C H D T T K Y  I V  P L O T Sample M0SC13 n Type S i l i c o n Gate n e g a t i v e  -j  1  0.80 SQRT  1.60 VDLTflGE  1  Z.ta  1  3.20  CSQRTCVOLTS3 3  1  t.00  -I  SAMPLE n  Type,  M0SC14, Anodic,  SING-LE  DIELECTRIC  Phosphoric  Acid.  :Sl3  ^7  SCHOTTKY  IV PLDT Sample M0SC14 n Type S i l i c o n Gate n e g a t i v e  1  l.GB RT  VDLTflGE  1  Z.^B  1  3.ZB  CSORTCVDLTS11  1  t.BB  SAMPLE n  M0SC15,  Type,  SINGLE  Anodic,  DIELECTRIC  Citric  Acid.  SCHDTTKT  IV  PLDT Sample M0SC15 n Type S i l i c o n Gate n e g a t i v e  CM  cn'  in-  to'  0.00  0.80 SQRT  T  1.E0  VDLTflGE  Z.50  3.Z0  CSDRTCVDLTS31  T  5.00  *8\ 3<i  SAMPLE n  Type,  M0SC16, Anodic,  SINGLE  DIELECTRIC  Phosphoric  Acid.  GATE  VOLTAGE  S C H Q T T K T  I V  P L D T  CD  Sample M0SC16 n Type S i l i c o n Gate n e g a t i v e to  cn •  to  CM  0.00  0.80 SQRT  T  1.60  VDLTflGE  T  Z.t0  T  3.Z0  CSQRTCVDLTS1D  T  5.00  I <r  . 80  ,8*7  SAMPLE n  M0SC17,  Type,  SINGLE  Anodic,  DIELECTRIC  Citric  Acid.  I  GATE  VDLTflGE  $2)  S C H D T T K T  I V  P L O T Sample MOSC17 n Type S i l i c o n Gate n e g a t i v e  CM"  0 .00  0.80 SORT  T  1.G0  VDLTflGE  —I  Z-tB  3.Z0  CSQRTCVDLTSD3  5.00  1  5.81  ^1/  SAMPLE n  M0SC18,  Type,  SINGLE  Anodic,  DIELECTRIC  Citric  Acid.  Sample M0SC18  con  GATE  VDLTflGE  S C H O T T K Y  I V  P L D T  CO  Sample MOSC18 n Type S i l i c o n Gate n e g a t i v e CO  est'  CM  cn'  to tn'  to'  CM  0.00  0.80  1.60  SQRT VDLTflGE  Z.50  T  3-20  CSORTCVDLTS33  5.00  5. 80  SAMPLE n  Type,  MTJ1,  DOUBLE D I E L E C T R I C  Interfacial  Oxidation.  9$  3  S C H O T T K Y  I V  P L O T Sample MTJ1 n Type S i l i c o n Gate n e g a t i v e  SQRT  VDLTflGE  CSORTCVDLTSJ1  SAMPLE n  Type,  MTJ2,  DOUBLE  DIELECTRIC  Interfacial  Oxidation.  &1  GATE  VDLTflGE  SCHDTTKT  IV  PLOT Sample MTJ2 n Type S i l i c o n Gate n e g a t i v e  oo  0.00  —I  0 .  SB  SQRT  1. £ 0 VDLTflGE  Z.  50  3. Z0  CSQRT£VDLTS33  I 5.00  5. SB  SAMPLE n  Type,  MTJ3,  DOUBLE  DIELECTRIC  Interfacial  Oxidation.  GATE  VOLTAGE  31  S C H D T T K T  I V  P L O T Sample MTJ3 n Type S i l i c o n Gate n e g a t i v e  to'  -r  B . SB SQRT  1.  GB  VDLTflGE  Z. t B  3. Z B  CSORTCVDLTSPD  I  "t. 0 0  "  —1 5. SB  Sample n  Type,  MTJ4,  DOUBLE D I E L E C T R I C  Interfacial  Oxidation.  .^1  Sample MTJ4 n Type S i l i c o n  00  n  a . 00  it  S C H O T T K Y  I V  P L O T  Sample MTJ4 n Type S i l i c o n Gate n e g a t i v e  T  0.S0 SORT  T  1.G0  VDLTflGE  T  Z.50  -r  3.Z0  CSQRTCVOLTS33  —1  5.00  1  5.  Sample n  Type,  MTJ5,  DOUBLE D I E L E C T R I C  Interfacial  Oxidation.  GATE  VDLTflGE  SQRT  VDLTflGE  CSDRTCVDLTS3D  

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