Suppressing channel-conduction during dynamic avalanche to improve high density power MOSFET ruggedness and reverse recovery softness

This paper demonstrates a new phenomenon for the state-of-the-art ultra-high density trench power MOSFET: channel conduction during dynamic avalanche even when gate voltage is well below the nominal threshold voltage. In particular, a comprehensive study has been done through mixed-mode 2D device simulation and measurement, showing that the channel conduction during avalanche can not only strongly influence body diode reverse recovery behavior, but also impact device ruggedness during Unclamped Inductive Switching (UIS). Results show that by suppressing the channel conduction, diode reverse recovery softness can be improved by 23% for the same reverse peak current, and the UIS avalanche current can be improved by 7%, which is significant for the harsh automotive DC-DC converter and hybrid vehicle motor inverter applications.