Investigations of p-Shielded SiC Trench IGBT with Considerations on IE Effect, Oxide Protection and Dynamic Degradation

Abstract

This work investigates the design of gate structure for the SiC trench IGBTs. The conventional trench IGBT structure established in silicon is not suitable for SiC IGBT, since it suffers from high oxide field. The grounded p-shield concept developed for SiC trench MOSFET cannot be readily transferred to SiC trench IGBT, since it counteracts the injection enhancement (IE) effect and nullifies the purpose of a trench gate structure. The floating p-shield structure has been found to cause severe dynamic degradation in SiC trench MOSFETs due to the charge storage effect. However, this dynamic degradation is effectively suppressed in the SiC trench IGBT, since the holes injected from the collector neutralize the stored negative charges in the floating p-shield. In the meanwhile, the floating p-shield is found to effectively suppress the high oxide field while maintains the IE effect. Thus, the floating p-shield solves the key issues and proves a promising solution for SiC trench IGBTs.