A Cascade-Breakdown Model for Heavy-Ion-Induced Oxide Failure Mechanisms in 4H-SiC Metal-Oxide-Semiconductor (MOS) Capacitors

Abstract

Single-event gate rupture (SEGR) remains a critical limitation for deploying silicon carbide (SiC) MOSFETs in space environments, due to the comparatively poor oxide quality and a limited process window for forming a robust, defect-lean dielectric on SiC bulk. This article systematically investigates the mechanism of heavy-ion-induced oxide breakdown in 4H-SiC metal-oxide-semiconductor (MOS) capacitors. Conventional physics-based analyses of oxide breakdown typically rely on peak electric field criteria at a single point. To overcome this limitation and elucidate the local gate-oxide breakdown physics relevant to SEGR in SiC MOSFETs, we propose a novel cascade breakdown model comprising four sequential stages: electric field distortion induced by residual hole accumulation (Stage I), oxide thinning triggered by localized breakdown (Stage II), a reduction of the effective oxide thickness coupled with electric field superposition (Stage III), and ultimately, electric field runaway leading to the cascade breakdown behavior (Stage IV). An analytical expression for the peak electric field in the oxide during the thinning process is derived, yielding a refined SEGR failure criterion. In particular, by comparing the minimum peak electric field during oxide thinning with the intrinsic breakdown field, the recombination coefficient $\alpha $ was calibrated to be $3 \times 10 ^{-6}$ cm³/s. Furthermore, by incorporating energy deposition fluctuations into the proposed model, it is demonstrated that the calculated failure probability distribution of breakdown voltages agrees remarkably well with the experimental results obtained under Ta and Kr ion irradiation. Collectively, these findings deepen the microscopic understanding of the evolutionary mechanism of SEGR, providing critical insights for the radiation-hardened SiC MOS devices.