Carrier backscattering characteristics of strained silicon-on-insulator n-MOSFETs featuring silicon–carbon source/drain regions

This work investigates for the first time, the physics of carrier transport in a sub-90 nm strained silicon-on-insulator (SOI) n-MOSFET with silicon–carbon (Si:C) source/drain (S/D) regions. The insertion of Si:C in the S/D exerts a lateral tensile strain in the transistor channel, leading to appreciable drive current enhancement. Significant improvement in both carrier backscattering r_sat and source injection velocity υ_inj were observed, accounting for the large drive current I_Dsat enhancement in Si:C S/D transistors. This improvement becomes more appreciable as the gate length is reduced. The reduction in r_sat is related to a shorter critical length ℓ₀ for carrier backscattering. On the other hand, the splitting of six-fold degenerate conduction band valleys due to strain-induced effects results in a reduced in-plane transport mass and thus contributes to significant υ_inj enhancement. In addition, the dependence of drive current performance on source injection velocity and ballistic efficiency in a short channel MOSFET is also discussed.