Polarity-Dependent Electric Field Modulation via Depletion Region Punchthrough in IGBTs Under Gate-Collector Coupled Stress

Le résumé fourni par la source

Insulated gate bipolar transistors (IGBTs) are subjected to critical combined gate-collector voltage stress under extremeoff-state blocking andon-state saturation conditions, presenting serious reliability challenges. This study identifies a severe degradation mode under such conditions and clarifies its physical origin. Electrical measurements and TCAD simulations reveal that under negative gate voltage with positive collector bias, the IGBT exhibits a strong positive threshold voltage shift and parallel rightward drift in capacitance–voltage characteristics. Both degradation features intensify with increasing collector voltage, far exceeding the effects observed under single stress conditions. The underlying mechanism is attributed to depletion region punchthrough modulated gate oxide field: high collector voltage causes full depletion layer penetration across the drift region, reshaping and amplifying the vertical electric field in the gate oxide. This enhanced field substantially increases electron injection from the polysilicon gate through Fowler–Nordheim (F–N) tunneling, resulting in significant charge trapping and device degradation. TCAD simulations validate this mechanism by demonstrating the depletion behavior, field distribution, and trap accumulation. Crucially, IGBTs with thicker drift regions show minimal degradation in both threshold voltage and$C$–$V$characteristics under identical stress, as punchthrough is prevented, providing further confirmation of the proposed mechanism. These findings uncover a critical reliability concern in IGBTs under high-voltage coupled stress and offer valuable guidance for robust power device design.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.