Uniaxial Stress Induced Electron Mobility Enhancement in Silicon

Abstract

The conduction band structure of Si under uniaxial [100] stress is investigated by using the two band k·p perturbation theory. The conduction band parameters, including the conduction band minimum energy shift, split and electron effective mass change are quantitative described. Based on these band parameters, uniaxial stress induced electron mobility enhancment is systematically studied through Boltzmann transport theory. The results show that, when uniaxial [100] stress is applied to Si crystal, a gain of more than 50 % in electron mobility can be obtained. The electron mobility along the [100] increase with tensile stress and decrease with compressive stress, while does the opposite for the electron mobility along the [010] and [001]. The electron mobility along the [100], [010] and [001] tend to saturate for stress beyond a certain level. The stress induced the reduction of conductivity effective mass and the suppression of inter-valley scattering rate are responsible for the enhancement of electron mobility. The calculated results provide valuable reference for the optimum stress and orientation of the conduction channel in the uniaxial strained Si nMOS devices design. The electron mobility calculated model used in the present work is suitable for implementation in TCAD simulators.