Power MOSFET RDSon under repetitive avalanche cycling

In this paper, a low voltage vertical power MOSFET is submitted to repetitive avalanche cycles under very high current (≫400A) at high temperature (≫150°C). Electrical characteristics such as B<inf>VDSS</inf>, I<inf>GSS</inf>, I<inf>DSS</inf>, V<inf>F</inf>, V<inf>GSth</inf> and R<inf>DSon</inf> are systematically tested along cycling. After a large number of avalanche pulses well above products requirements measurements show that R<inf>DSon</inf> decreases with the number of avalanche cycles whereas other parameters stay constant. With a simple model of R<inf>DSon</inf> measurement and new measurements such as the resistance of the metallization between two bonding wires we can connect this unexpected drop of R<inf>DSon</inf> measurement to MOSFET source electrode evolution.