Effects of Pulsed and DC Body-Diode Current Stress on the Stability of 1200-V SiC MOSFET I-V Characteristics

Abstract

1,200-V and 1,700-V SiC power MOSFETs from multiple suppliers were subject to dc and pulsed-current stress of the body-diode. Three of the five suppliers of 1,200-V devices evaluated showed no significant bipolar degradation, but the other two supplier’s devices showed varying degrees of degradation due this bipolar phenomenon. Electrical results of newly released 1,700-V devices from two suppliers showed significant degradation in the body-diode and MOSFET I-V characteristics following both dc and pulsed-current stress of their body-diodes. The electrical results presented in this work are consistent with basal plane dislocations (BPDs) that form stacking faults during forward conduction of the body-diode. Significant drift in the body-diode forward voltage and MOSFET on-resistance indicates that a much higher BPD density may be present in 1,700-V devices in comparison to the more mature 1,200-V device offerings. The likely presence of BPDs can lead to significant reliability issues in some modern SiC power MOSFETs, and their distribution seems to vary across suppliers and among devices with the same rating and from the same supplier. These differences are likely due to variations in wafer and device processing among suppliers and within a given product line from a single supplier.