Single-Pulse Short-Circuit Ruggedness of Different 650V SiC MOSFET Cell Designs

Abstract:
The short-circuit withstand capability of SiC MOSFETs is critical for ensuring robust and reliable performance in automotive and industrial applications under high-stress transient conditions. This study investigates the ruggedness and failure mechanisms of 650V Silicon Carbide (SiC) MOSFETs under single-pulse short-circuit, focusing on three gate channel designs: asymmetrical trench, symmetrical trench, and planar. Multiple samples from five manufacturers were tested to ensure statistical significance. Failed devices were analyzed via electrical measurement and front side decapsulations. Results reveal that planar gate structures due to thinner gate oxides and lower threshold voltage, exhibit lower short circuit robustness compared to trench-based designs. This is primarily due to higher saturation drain current, higher energy dissipation and elevated gate oxide temperatures that leads to early gate oxide rupture. Increased gate threshold voltage (VGS(th)) and thicker gate oxide (dGOX) in asymmetric trench SiC MOSFETs boost gate oxide reliability by lowering electric field intensity and improving shortcircuit (SC) ruggedness. In contrast, symmetric trench structures provide strong SC resilience due to uniform current and heat spread but demand a much larger chip area.