A novel superjunction MOSFET with improved ruggedness under unclamped inductive switching

The ruggedness of a superjunction metal-oxide semiconductor field-effect transistor （MOSFET） under unclamped inductive switching conditions is improved by optimizing the avalanche current path. Inserting a P-island with relatively high doping concentration into the P-column, the avalanche breakdown point is localized. In addition, a trench type P＋ contact is designed to shorten the current path. As a consequence, the avalanche current path is located away from the N＋ source/P-body junction and the activation of the parasitic transistor can be effectively avoided. To verify the proposed structural mechanism, a two-dimensional （2D） numerical simulation is performed to describe its static and on-state avalanche behaviours, and a method of mixed-mode device and circuit simulation is used to predict its performances under realistic unclanlped inductive switching. Simulation shows that the proposed structure can endure a remarkably higher avalanche energy compared with a conventional superjunction MOSFET.