Thermomechanical behaviour of inverse diode in SiC MOSFETs under surge current stress

In this work, thermomechanical failures during single and repetitive surge current events of 40 mΩ class, 1.2 kV SiC MOSFET inverse diodes were investigated. The single event surge current was performed under different pulse length in channel-off mode. It was observed that the body diode survived 10 ms surge currents more than 11 times the application-near nominal current of 20 A. After surge current destruction a failure analysis was performed. At a high surge current event (232 A) the device failed due to the very high temperature, the aluminium metallization was melted around the bond foot and the melted metallization shorted gate and source (GS) metal. In addition to that, repetitive surge current tests, high temperature reverse bias (HTRB) tests under negative gate bias and high temperature gate bias test (HTGB) with samples exposed to repetitive surge current were performed to investigate different aging mechanisms to determine reliability aspects of the inverse diode in SiC MOSFETs.