Novel designs of 4H-SiC trench gate metal-oxide-semiconductor field effect transistors (UMOSFETs) with low on-resistance

In this paper novel 4H-SiC UMOSFETs structures with n-type wrapping region and superjunctions are proposed to reduce on-resistance while maintaining breakdown voltage. In the proposed 4H-SiC UMOSFETs structure an n-type region is created to wrap the p+ shielding region at the bottom of the trench gate. The on-resistances of the optimized 4H-SiC UMOSFETs and the conventional one are 2.31mΩ-cm² and 3.56 mΩ-cm² at VGS=15 V and VDS=10 V respectively. The on-resistance and the FOM (figure of merit = VBR²/Ron) improve by 35.1% and 37.3% respectively. By introducing a current spreading layer (CSL)the on-resistance of the optimized 4H-SiC UMOSFETs with superjunctions is 6.03mΩ-cm² compared with 17.36 mΩ-cm² for the conventional structure. The FOM of the optimized device with CSL is improved by 110.4% compared with the conventional one with same doping concentration.