Effect of interface-roughness scattering on mobility degradation in SiGe p-MOSFETs with a high-k dielectric/SiO₂ gate stack

A physical model for mobility degradation by interface-roughness scattering and Coulomb scattering is proposed for SiGe p-MOSFET with a high-k dielectric/SiO_2 gate stack. Impacts of the two kinds of scatterings on mobility degradation are investigated. Effects of interlayer (SiO_2) thickness and permittivities of the high-k dielectric and interlayer on carrier mobility are also discussed. It is shown that a smooth interface between high-k dielectric and interlayer, as well as moderate permittivities of high-k dielectrics, is highly desired to improve carriers mobility while keeping a low equivalent oxide thickness. Simulated results agree reasonably with experimental data.