Gate Structure Design of SiC Trench IGBTs for Injection-Enhancement Effect

The trench gate structure is widely employed in silicon IGBTs because of the injection-enhancement effect (IE-effect) that reduces the conduction loss. However, the conventional trench gate structure cannot readily be transferred to SiC IGBT, since it would suffer from a high oxide field that severely threatens the device reliability. In this paper, the gate structure design of SiC trench IGBT is investigated through comprehensive numerical TCAD simulations. The grounded p-shield trench gate is widely adopted for oxide protection in SiC MOSFET but it counteracts the IE-effect in the SiC trench IGBT by extracting holes, thus nullifying the purpose of a trench gate. The floating p-shield trench gate is much easier to be implemented and more area effective. It is found that the floating p-shield provides similar oxide protection in the SiC trench IGBT as the grounded p-shield does, while a strong IE-effect is maintained. The dynamic degradation caused by a floating p-shield, as observed in SiC trench MOSFET, is effectively suppressed in the SiC trench IGBT, owing to the injected holes from collector that compensates the negative charge storage in the floating p-shield. Therefore, the floating p-shield structure is a promising solution for realizing high-performance SiC trench IGBTs.