Gate stack engineering of germanium mosfets with high-K dielectrics

Abstract

Germanium and high-k dielectrics are candidates that can possibly boost the performance of the metal-oxide-semiconductor field effect transistors (MOSFET) in modern integrated circuits. This dissertation mainly presents the development of gate stack formation technology on germanium with hafnium oxide as the high-k gate dielectric for MOSFET applications. Surface nitridation was first developed as a surface passivation technique on germanium for reducing the leakage current of the whole gate stack. A novel silicon passivation was then developed to achieve additional better oxide/semiconductor interface quality and gate oxide bulk properties. Consequently, both p- and n- MOSFETs were fabricated successfully on germanium. The transistor shows enhanced performance over the counterparts fabricated on silicon substrate. Finally, the reliability issue of threshold voltage instability of the Ge MOSFETs was addressed. Germanium shows promising performance of MOSFET drive current with silicon passivation for future VLSI circuits.