Critical discussion on unified 1/f noise models for MOSFETs

Abstract

Recently, unified noise models, like BSIM3, have been proposed in literature to describe the 1/f noise of n- and p-type MOSFETs in all operating regimes. These models combine carrier number fluctuations and correlated mobility fluctuations. The latter are induced by the Coulomb scattering of free carriers at trapped interface charge. The unified 1/f noise models assume implicitly that the mobility, limited by Coulomb scattering, does not depend on the inversion carrier density. However, this assumption is not correct in view of theoretical calculations and recent experimental results. In this paper, we show that the correlated mobility fluctuations are negligible, if the correct dependence on inversion carrier density is taken into account for the Coulomb scattering limited mobility. Consequently, the unified 1/f noise models cannot predict the 1/f noise observed experimentally in p-type MOSFETs, except if nonphysical fitting parameters are used. This paper serves as a critical discussion on the unified 1/f noise models for MOSFETs. Here it is not our intention to propose a new 1/f noise model.