Online Monitoring for Threshold Voltage of SiC MOSFET Considering the Coupling Impact on BTI and Junction Temperature

Gate oxide degradation can reduce the reliability of silicon carbide metal-oxide-semiconductor field-effect transistor (SiC MOSFET), which is indicated by bias temperature instability (BTI). BTI-induced threshold voltage ( V _{\text th} ) shift has an effect on ON-resistance ( R _{\text DS - ON} ) and leakage current. Meanwhile, the rising junction temperature ( T _j ) caused by power losses will affect V _{\text th} . It is of vital significance to the reliability research provided that V _{\text th} shift can be rapidly monitored when the coupling impact on BTI and T _j is sufficiently considered. In this article, the body effect in SiC MOSFET and its impact on the body diode voltage ( V _{\text SD} ) are analyzed, and the temperature dependence of V _{\text SD} is investigated. In addition, the impact mechanism of BTI in SiC MOSFET on V _{\text SD} is studied. Finally, a method for online monitoring V _{\text th} shift due to BTI and T _j is proposed employing the forward voltage of the SiC MOSFET body diode under body effect at low measuring current. Through the proposed method, V _{\text th} shift can be indirectly evaluated using V _{\text SD} . Most importantly, considering the impact of T _j , this methodology can be used in different working conditions, and the problem of difficult extraction of V _{\text th} is solved under complex working conditions.