pMOSFET Performance Enhancement With Strained Si1 - xGeₓ Channels

The inversion-layer hole mobility in MOSFETs with thin silicon-germanium (Si1-xGex) channels grown pseudomorphically on Si is calculated using a self-consistent 6 × 6k·pPoisson-Schrödinger mobility simulator calibrated to experimental and simulation data. The addition of uniaxial compressive stress to the inherent biaxial compressive strain of the pseudomorphic Si1-xGexlayer is found to further enhance hole mobility by up to 2.5×. Two-dimensional device simulations are used to assess the benefit of the Si1-xGexheterostructure channel for boosting the ON-state current (Ion) of p-channel MOSFETs with a gate length (Lg) of 18 nm; the results show a moderate (10%-40%) improvement over a bulk-Si MOSFET.