Temperature-Independent Gate-Oxide Degradation Monitoring of SiC MOSFETs Based on Junction Capacitances

Gate-oxide degradation has been one of the major reliability challenges of SiC MOSFETs and should be monitored carefully to avoid unexpected power converter failures. Various precursors have been introduced in the literature for gate-oxide degradation monitoring. However, those proposed precursors are temperature dependent and it is highly challenging to eliminate temperature effects. In this article, two new temperature-independent precursors (Miller capacitance and gate-source capacitance changes) are proposed for gate-oxide degradation monitoring of SiC MOSFETs. During the accelerated aging tests under high electric field and high temperature, a consistent change in Miller capacitance and gate-source capacitance is reported for both common source and Kelvin source SiC MOSFETs. Also, the temperature sensitivity of each precursor is investigated. The proposed precursors enable the monitoring of gate-oxide degradation without decoupling the impact of package degradation. Based on the findings, a simple early warning in situ circuit is proposed to monitor gate-oxide aging. A comprehensive precursor comparison is provided to show the merits of the proposed precursors. Finally, the experimental results are presented to validate the efficacy of the in situ monitoring circuit.