Implications of Imperfect Interfaces and Edges in Ultra-small MOSFET Characteristics

Abstract

We use 3D statistical simulations to analyze the influence of imperfect interfaces and edges in sub-100 nm MOSFET characteristics. In particular, we focus on the impact of gates deformed by line edge roughness, and of oxide thickness variations resulting from a rough Si/SiO2 interface. The 3D simulations are based on a very efficient 3D drift-diffusion framework, which can introduce quantum mechanical corrections via the density gradient formalism. Random features at the gate edges and at the Si/SiO2 interface have similar statistical descriptions, but use different parameter sets in accordance with measurements. In MOSFETs, both line edge roughness and oxide thickness variations result in intrinsic parameter fluctuations, which are comparable in magnitude to random dopant effects. We simulate the dependence of intrinsic fluctuations on the statistical model parameters of the roughness. We also consider the scaling of devices with rough gate edges and rough SiO2 interfaces. Our results highlight the importance of including realistic geometry features in the design and analysis of MOSFETs below 50 nm regime.