Low-Field Mobility in Strained Silicon Inversion Layers and UTB MOSFETs for Different Substrate Orientations

To continue improvement of CMOS device performance process induced uniaxial stress is widely adopted in logic technologies starting from the 90 nm technology generation. In this work we model stress induced electron mobility enhancement in ultra thin body (UTB) MOSFETs for (001) and (110) substrate orientation using the Monte Carlo method. Uniaxial stress effects on the band structure are incorporated by adapting the non-local empirical pseudopotential method including spin-orbit interaction for arbitrary strain conditions. Stress induced change of the electron effective mass is found to be very important to explain mobility enhancement in UTB MOSFETs. Simulation results of electron mobility are in good agreement to recent experimental data.