Determination of threshold energy for hot electron interface state generation

Abstract

A detailed understanding of hot electron nMOSFET degradation, necessary for predictive device lifetime estimation, requires both a realistic hot carrier distribution function (DF) model and an accurate microscopic interface state (IFS) generation model. Attempts to extract the latter have always been clouded by uncertainties in the former. This work addresses both aspects of this problem. First, a physics-based, two-part DF model which can successfully explain all observed bias dependencies for substrate, I/sub B/, and gate current, I/sub G/, in nMOSFETs is presented. In addition, a new back-gate bias, V/sub BS/, effect on IFS generation is identified. Then, combining Monte Carlo (MC) simulations with extensive measurements, a powerful technique is demonstrated which can for the first time probe the energy dependence of hot electron IFS generation in nMOSFETs. Although appropriate for use with more sophisticated IFS generation models, results based on a simple threshold model provide an estimate of 3-3.5 eV for IFS generation.