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Elementary processes in alkane-based reactive ion etching of III-V semiconductors Meharg, Paul F. A.


Reactive ion etching (RIE) is a process used extensively in the microelectronics industry. Recently, the use of alkane-based plasmas has been developed for the etching of compound semiconductors. However, due to the complex nature of the plasma environment, relatively little is known about the etching mechanisms involved. To gain some understanding of the elementary processes involved in this technology, the interactions of some relevant ions and free radicals with these semiconductors were examined. To simulate the low energy ion bombardment that occurs in RIE using alkanes, GaAs and InP were exposed to 20-500 eV carbon ions, using a mass-separated carbon ion beam in an ultrahigh vacuum chamber. The changes induced by ion bombardment and the effects of subsequent damage-removal treatments were determined by angle-dependent X-ray photoelectron spectroscopy (XPS). To enable the effects of sputtering and ion penetration to be quantified with XPS, an InP wafer consisting of an ultrathin (4 nm) epitaxial In Player on InGaAs was used. Initially, carbon ion irradiation caused minor sputtering of the semiconductors and preferential removal of the group V constituents, with concurrent formation of carbon-semiconductor phases. The extent of the interaction increased with increasing bombardment energy. A chemically resistant, amorphous carbon residue formed after further bombardment. Whereas heating or ultraviolet light/ozone oxidation did not remove the damage, removal was effected by exposure to hydrogen ions. Similar results were observed when these semiconductors were exposed to low energy methyl ions (

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