Compensation of Long-Term Drift Effects of SiC MOSFETs under Power Cycling Like Gate Conditions

Inhalt:
When switching SiC MOSFETs with a bipolar gate voltage, a long-term Vth shift occurs leading to an increase of RDS;on and thus affecting power cycling (P/C) tests as well as the device behaviour during application. Within this work, a compensation approach is presented, allowing to adjust VGS;on in accordance with the measured Vth shift. This way an additional drift effect, not related to DeltaVth and triggered by exceeding a certain negative VGS;off is identified and investigated. A comparison with more application-like switching further reveals that one P/C-like switching event adds much more to DeltaVth than one switching event during application, while the additional drift component is also present during application. Finally, a novel concept for nearly drift free P/C tests based on preconditioning is introduced, whereby first P/C results indicate a substantial impact on P/C lifetime.