High Hole-Mobility Strained- P-MOSFETs With High-K/Metal Gate: Role of Strained-Si Cap Thickness

摘要

Low-field effective hole mobility of highly strained ($sim$ 2.4%, biaxial) germanium-channel (7.8 nm-thick) p-MOSFETs with high-K/metal gate stack has been experimentally investigated. Devices with various ultrathin strained-Si cap layer thicknesses, as thin as $sim!! hbox{8} hbox{rm{AA}}$, show excellent capacitance-voltage characteristics with no hysteresis or frequency dispersion and hole mobility enhancement of more than 6.5X over Si universal and 2.3X over similar devices with no strained-Si cap, at $E_{rm eff} = hbox{0.6} hbox{MV/cm}$. The influence of the strained-Si cap thickness on the hole mobility is also studied. The mobility increases with increasing Si cap thickness up to $sim$1.8 nm (with a peak mobility of 940 $hbox{cm}^{2}/hbox{Vs}$ at this cap thickness) consistent with a reduction in remote Coulombic scattering.