Atomic-Scale Simulations of Electron Mobilities in Ultrathin SOI MOSFETs

Abstract

Carrier mobilities in metal-oxide-semiconductor field-effect transistors (MOSFETs) are conventionally modeled in a semi-classical approximation, i.e., particles are treated as classical parti-cles with a suitable effective mass or with a kinetic energy given by the crystalline energy bands. Here we review a recent method based on atomic-scale models of the Si-SiO2 interface. Carriers are described by wave functions and scattering potentials are con-structed by parameter-free quantum-mechanical calculations. The effect of primitive atomic-scale roughness (Si-Si bonds on the ox-ide side and Si-O-Si bonds on the Si side of the interface) in ultra-thin SOI MOSFETs has been investigated. It is shown that this mechanism naturally accounts for strain-induced enhancement in a quantitative way. In addition, the method has been used to deter-mine the impact of stray Hf atoms in the SiO2 interlayer in alter-nate-dielectric Si-SiO2-HfO2 structures. Finally, some features of the method are compared with the density gradient method.