A simplified post-soft-breakdown current model for MOS devices

Based on the tunneling current model, a simplified current model is developed for MOS devices after soft breakdown (SBD). The post-soft-breakdown current consists of modified direct tunneling current and Fowler Nordheim (FN) tunneling current. Considering the change of gate oxide after soft breakdown, impacts of soft breakdown on the dielectric constant, and effective electron mass of the gate oxide are discussed, and their values are obtained by fitting simulation results to experimental data. It is found that the effective electron mass is decreased after soft breakdown due to damaged oxide, while the dielectric constant is increased after soft breakdown due to interface distortion. In this way, the leakage current after soft breakdown can be accurately calculated. The validity of the proposed model is confirmed by experimental results. Z.L. Li currently is with the Department of Electrical and Electronic Engineering, University of Hong Kong.