Characteristics of ultrathin [4-7 nm] gate oxides for SiGe quantum well MOS structures

摘要

SiGe quantum well metal-oxide-semiconductor (MOS) structures were realized by the preparation of the undoped Si buffer layer, the undoped SiGe quantum well layer, and the undoped Si cap layer by molecular-beam epitaxy or low pressure chemical vapor deposition, and low thermal budget rapid thermal oxidation of the Si cap layer in dry oxygen at 1100 °C for 30-65 s. Comprehensive electrical characterization by steady state admittance spectroscopy was carried out. The relaxation of the strained SiGe layer was monitored by x-ray diffraction. The effects of the composition of the SiGe layer [Ge content, and minute C content] on the trap density and the device characteristics were investigated. Also examined were the effects of the oxidation temperature, the post-oxidation annealing [temperature and time] in nitrogen, and the post- metallization annealing [temperature and time] in forming gas, on the trap density and the device admittance characteristics.