Optimisation of channel thickness in strained Si/SiGe MOSFETs

It is demonstrated from experimental I-V and C-V data, and confirmed by computer simulation, that strained Si/SiGe MOSFET performance severely degrades below a channel thickness of 7 nm. MOSFETs with strained Si channels of thickness 5 nm, 7 nm and 9 nm have been fabricated using a conventional high thermal budget process. The performance degradation is attributed to Ge diffusion through the strained Si layer, which causes a build up of gate oxide charge.