Modeling Surface Scattering Effects in the Solution of the BTE based on Spherical Harmonics Expansion

The effect of surface scattering mechanisms, which are responsible for mobility degradation in field effect transistors, has been incorporated into the solution of the Boltzmann transport equation based on spherical harmonics expansion [1]. The collision mechanisms to be considered when a Si-SiO2 interface is present are: surface roughness, collisions with ionized impurities trapped at the interface and surface phonons. The models associated with these scattering mechanisms have been applied to the simulation of MOS devices and they were able to show the same effect of mobility degradation as semi-empirical mobility models [2]. Moreover, the experimentally-detected universal mobility behavior of inversion layers [3] is also quantitatively reproduced by our model.