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 rsat and source injection velocity υinj were observed, accounting for the large drive current IDsat enhancement in Si:C S/D transistors. This improvement becomes more appreciable as the gate length is reduced. The reduction in rsat 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 υinj enhancement. In addition, the dependence of drive current performance on source injection velocity and ballistic efficiency in a short channel MOSFET is also discussed.