Fabrication of 0.12 μm pMOSFETs on high Ge fraction Si/Si_(1-x)Ge_x/Si(100) heterostructure with ultrashallow source/drain formed using B-doped SiGe CVD

摘要

High Ge fraction Si/Si_(1-x)Ge_x/Si heterostructures (x = 0.5) are processed into the super self-aligned ultrashallow junction electrode (S~3E) pMOSFETs. The ultrashallow junction is made from the selective epitaxial B-doped Si_(0.5)Ge_(0.5) on source/drain grown by chemical vapor deposition (CVD) and subsequent thermal diffusion of B from B-Si_(0.5)Ge_(0.5) into the substrate. The Ge fraction in the S~3EMOSFETs' buried layer changes to 0.35 after the B diffusion at 750℃ due to the interdiffusion between Si and Ge. The B diffusion depth in Si/SiGe/Si is shallower compared to that in Si. Compared to Si-channel S3EMOSFET, the maximum linear transconductance of the 0.12 μm gate Si_(0.65)Ge_(0.35)-channel S~3EMOSFET increases by approximately 45%. The threshold voltage shift and the S factor degradation in the short channel region are well suppressed compared to the Si-channel S~3EMOSFETs. It is suggested that the suppression of short channel effects is caused by the ultrashallow source/drain and the valence band discontinuity at the Si_(1-x)Ge_x/buffer Si interface.