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.