Optimized design of 4H-SiC UMOSFET for high breakdown voltage

Abstract

In this work, we develop an optimized 4H-SiC U-shaped trench-gate MOSFET structure with a high breakdown voltage. In the optimized structure, a p+ shield is added under the gate oxide and the drift layer is divided into multilayers with different doping concentration. Simulation results reveal that adding a p+ shield and lowering the doping concentration around the corner of U-shape trench can effectively protect the gate oxide, resulting a significant improvement of the breakdown voltage. As a result, the breakdown voltage of the optimized structure increases by 47.7% compared with that of the conventional structure, corresponding to an improvement of 32.2% in figure of merit.