Modeling and Finite Element Simulation of Gate Leakage in Cylindrical GAA Nanowire FETs

Abstract

The gate-all-around (GAA) nanowire based devices have generated research interest in recent years for their potential in scaling beyond $10\mathrm{n}\mathrm{m}$ as they offer excellent control over channel. Reduction in gate oxide thickness and low effective mass channel material for better drive current aid gate leakage which can put limit to further scaling. In this work, we study gate leakage problem for cylindrical nanowire (NW) GAA device and present a model to accurately compute lifetime of the quasi-bound-states (QBS) in inversion region of NW. We study scattering of cylindrical waves by solving Schrodinger equation with open boundary conditions using finite element method (FEM), and thereby calculate gate leakage current for the GAA device. We conduct survey of a broad range of device materials, investigate effect of device dimensions and stress on the gate tunneling leakage. We try to bring out the conditions at which direct tunneling current through the oxide is significant and can possibly exceed the maximum permissible gate current density.