Investigation of Forward Voltage Degradation due to Process-Induced Defects in 4H-SiC MOSFET

Abstract

We investigated process induced defects at various ion implantation conditions, and evaluated forward voltage degradation of body diode in 3.3 kV SiC MOSFET. First, by using photoluminescence (PL) observation, we evaluated the formation level of Basal Plane Dislocations (BPD) induced by Al implantation and anneal process with various Al implantation dose. Second, 3.3 kV double-diffused SiC MOSFETs were fabricated and forward current stress tests were performed to body diodes in SiC MOSFETs. Then, electrical characteristics of SiC MOSFETs before and after the stress test were measured, and expanded Stacking faults (SFs) in SiC epitaxial layer after the stress test were observed by PL imaging method. These results indicate that low dose or high temperature Al implantation conditions can suppress the formation of BPDs, and SiC MOSFETs fabricated using optimized Al implantation conditions show high reliability under current stress test.