Remote Coulomb scattering in metal-oxide-semiconductor field effect transistors: Screening by electrons in the gate

The screening of remote Coloumb scattering (RCS) by free electrons in the polycrystalline silicon gate of a metal oxide semiconductor transistor was studied. A previous RCS model has been completed by adding the effects of screening by electrons in the gate assuming a Thomas-Fermi dielectric function. Along with photon scattering, surface roughness scattering and Coloumb scattering due to substrate impurities, a Monte Carlo simulator has been included in the model. An evaluation of the mobility curves for different values of the oxide thickness has been made, and it has been found that the weakened RCS effect is important for very thin oxide layers.