A new remote Coulomb scattering model for ultrathin oxide MOSFETs

We studied the effect of the depletion charge in the polysilicon gate on electron mobility in ultrathin oxide MOSFETs. An improved theory for remote-charge-scattering-limited mobility in silicon inversion layers has been developed. It is shown that if the oxide is thin enough, the remote Coulomb scattering (RCS) due to the depletion charge in the polygate becomes an effective scattering mechanism, whose effect is comparable to those of the main scattering mechanisms that control the movement of the carriers in the MOSFET channel. The model is implemented in a Monte Carlo simulator, where the effects of the ionized impurities charge in the substrate, the interface trapped charge and the contribution of other scattering mechanisms are taken into account simultaneously. Our results show that RCS cannot be neglected for oxide thicknesses below 2 nm, but that its effects for t/sub ox/>5 nm are negligible. Good agreement with experimental results was obtained.