Failure Characterization of Discrete SiC MOSFETs under Forward Power Cycling Test

Abstract

Silicon carbide (SiC)-based metal–oxide–semiconductor field-effect transistors (MOSFETs) hold promising application prospects in future high-capacity high-power converters due to their excellent electrothermal characteristics. However, as nascent power electronic devices, their long-term operational reliability lacks sufficient field data. The power cycling test is an important experimental method to assess packaging-related reliability. In order to obtain data closest to actual working conditions, forward power cycling is utilized to carry out SiC MOSFET degradation experiments. Due to the wide bandgap characteristics of SiC MOSFETs, the short-term drift of the threshold voltage is much more serious than that of silicon (Si)-based devices. Therefore, an offline threshold voltage measurement circuit is implemented during power cycling tests to minimize errors arising from this short-term drift. Different characterizations are performed based on power cycling tests, focused on measuring the on-state resistance, thermal impedance, and threshold voltage of the devices. The findings reveal that the primary failure mode under forward power cycling tests, with a maximum junction temperature of 130 ∘C, is bond-wire degradation. Conversely, the solder layer and gate oxide exhibit minimal degradation tendencies under these conditions.

Keywords

• forward power cycling test
• on-state resistance
• discrete SiC MOSFET
• threshold voltage
• thermal impedance measurement