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UBC Theses and Dissertations

A molecular dynamics approach to studying gate oxides in Ge-MOSFETs Heydari Haratameh, Amirsalar


As silicon-based transistors are reaching their performance limit, a growing need for a new semiconductor material has arisen. Germanium has been suggested as the potential substitute for silicon-based Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs). This dissertation is focused on the source of reliability issues of MOSFETs fabricated on germanium and offers several solutions to cope with MOSFETs reliability issues. Due to the miniaturization of electronic devices, especially MOSFETs, some reliability challenges have arisen, such as the higher threshold voltage and increased gate leakage current. This device downscaling has led to a poor interface quality at the dielectric/substrate interface of Ge-MOSFETs. I employed Molecular Dynamics (MD) tools to investigate the nature of the dielectric material structure on the germanium substrate and the type of defects responsible for electrical degradation. This dissertation is dedicated to proposing several solutions which enable the semiconductor industry to mitigate the associated reliability issues of Ge-MOSFETs which leave behind the commercialization of these MOSFETs. A reactive molecular dynamics force field was employed in this research, enabling the simulation of ongoing bond breaking and formation. In addition to finding the effect of oxidation temperature on the density of interfacial defects, this research has shed light on the effect of oxide thickness on interface quality. The need for stabilizing the native oxide of germanium leads to proposing a novel approach to improve both interface quality and dielectric constant. Dilute concentrations of aluminum were doped into the oxide network, and as a result, improved dielectric constant and enhanced dielectric/substrate interface quality were obtained.

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