Advanced materials and structures for nanoscale CMOS devices.

摘要

Technological innovations have accomplished the continued scaling of CMOS devices well into nanometer regime. Short channel effects have been suppressed by the use of thinner gate oxide, shallower junction depth, and sophisticated channel doping profile without changing its basic structure. However, further CMOS scaling will be much more intricate due to fundamental materials and process limitations. The advanced thin-body transistor structures can effectively suppress the short channel effects, separating the need of heavy channel doping and the state-of-the-art thin gate oxide. This dissertation investigates the integration of advanced materials in front-end processes with advanced thin-body transistor structures.; Two essential processes in molybdenum (Mo) metal gate technology are developed: damage-free sputtering and high-selectivity dry etching. The physical origin of Mo gate work function engineering is simultaneous modification of the microstructure and chemistry at the gate dielectric interface, as discussed in chapter 2.; The impact of gate process technology on hafnium oxide (HfO2) gate dielectric is explored. The increase in equivalent oxide thickness and leakage current is resulted from the generation of oxygen vacancy, which causes silicon interfacial layer formation and gate electrode Fermi-level pinning in MOS devices, as discussed in chapter 3.; Tunable work function Mo gate is demonstrated for adjusting threshold voltages of ultra-thin body MOSFETs for the first time. Integration of metal gate and high-k gate dielectric employing FinFETs is demonstrated for the first time; Mo-gated HfO2 CMOS FinFETs reduce gate leakage current over 3 orders-of-magnitude for inversion equivalent oxide thickness (1.72 nm) with comparable carrier mobility, as discussed in chapter 4.