Evaluation and robustness of wide bandgap semiconductor devices

Wide bandgap semiconductor devices were evaluated using forms of reliability and robustness testing. This was performed to determine the devices’ limitations through robustness testing and investigate their operation over time through reliability testing. Robustness testing was performed via short circuit testing on SiC (silicon carbide) MOSFET devices and surge current testing on SiC JBS (junction barrier Schottky) didoes while reliability testing occurred using HTOL testing on SiC JBS diodes. Short circuit testing was divided into two forms: to investigate the oxide thickness on the short circuit response of the devices and the effect of varying on- state resistance on the short circuit response of the device. Results yielded that thinner oxide devices failed at higher short circuit energies than the standard oxide devices. Higher on- state resistance yielded higher short circuit energy released due to larger IDS. Surge current testing was performed on JBS diodes of varying substrate thicknesses to determine whether this parameter affects the surge current limits of the devices. Devices of 110 mm, 175 mm and 375 mm were tested and the majority of devices failed at the 150- 159 A testing level. There was a positive correlation to the amount of surge current energy generated and the size of the N+ substrate of the JBS diode. HTOL testing was performed on JBS diodes. Using high temperature testing at 175 °C for 520 hours with a 25% IF constant current applied bias, accelerated testing was performed mirroring 70°C operation at 15.1 years. As the test progressed, there was a shift in the breakdown voltage for each of the devices due to charge trapping between the P+ and N- region. None of the devices degraded as breakdown voltage stayed within 10% of the initial value.

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