A Defect-Informed Phase-Field Model for Gate Oxide Breakdown in SiC MOS Structures

Abstract

Silicon carbide (SiC) MOS structures are promising for high voltage and high temperature power electronics, but gate oxide breakdown remains a major reliability concern because of its stochastic nature and the limited accessibility of the underlying failure pathway. In this work, a defect-informed phase- field framework is developed to investigate oxide breakdown in SiC MOS structures. The model is initialized using a depth- resolved pre-existing defect profile extracted from capacitance and conductance frequency response, thereby linking electrical characterization with physics-based breakdown simulation. The results show that breakdown starts from localized nucleation at defect-rich weak points near the SiO2 /SiC interface, followed by directional growth, interaction, and coalescence of degraded regions into a through-thickness conductive path. Combined analysis of the phase-field variable and electric field distribution shows that local electric field redistribution plays a key role in guiding conductive path propagation and determining the final breakdown trajectory. Post-breakdown focused ion beam scanning electron microscopy (FIB-SEM) reveals a tortuous and spatially confined channel morphology, consistent with the defect-assisted and field-driven breakdown picture predicted by the model. The proposed framework provides a useful tool for analyzing breakdown trajectories and gate oxide reliability in SiC power devices.