A robust and area-efficient guard ring edge termination technique for 4H-SiC power MOSFETs

Abstract

A robust and area efficient adjusted multi-section guard rings (AMS) edge termination structure is employed to a 4H-SiC power MOSFET device rated at 1.7kV and fabricated without extra process steps or masks in this paper. The lightly doped p-type guard ring with adjusted multi-section spacing, which is similar with varied lateral doping technology widely used in silicon edge termination, creates a smoother and more uniform surface electric field distribution across all rings, resulting in a higher reverse blocking voltage with minimal edge termination area. The fabricated AMS-MOSFET devices with an active area of 2.5mm2 have reverse blocking voltage up to 2.5kV at room temperature. Compared to the conventional SiC MOSFETs with the uniform ring spacing, the AMS-MOSFET with the same edge termination area shows more than a 25% increase in the reverse blocking voltage. Furthermore, high-temperature reverse bias stress test is performed to verify junction and termination robustness of the AMS-MOSFET device. A small variation in the reverse blocking voltage and drain-source leakage current are achieved under 168h high-temperature reverse bias stress with the drain bias of 1360V at ambient temperature of 175°C, which suggests an expected robustness in high power application for the fabricated SiC MOSFET with the AMS structure.