SiC trench IGBT with diode-clamped p-shield for oxide protection and enhanced conductivity modulation

In this paper, a diode-clamped p-shield is proposed as a feasible approach for SiC trench IGBT. The introduction of the p-shield effectively suppresses the high electric field in the gate oxide around the trench corner, which is a notorious feature for SiC trench gate devices. Additionally, the p-shield also results in a reduced Crss and thus better switching characteristics. The traditional grounded p-shield (widely adopted in SiC trench MOSFETs), however, significantly reduces the electron/hole density near the emitter side of the SiC trench IGBT. The diode-clamped p-shield structure proposed in this paper successfully solves this issue, since the potential of the p-shield in the on-state is elevated to near the turn-on voltage of the diode, and thus the extraction of holes from the p-shield is suppressed. Therefore, the proposed SiC trench IGBT with a diode-clamped p-shield reduces the high oxide field, improves the switching characteristics and maintains a low Kon simultaneously.