A Trench and Field Limiting Rings Co-Assisted JTE Termination With N-P-N Sandwich Epitaxial Wafers for 4H-SiC Devices

In this letter, a trench and field limiting rings co-assisted JTE termination with N-P-N sandwich epitaxial wafers for 4H-SiC devices is proposed and experimentally demonstrated for the first time. The formation of an N-enrich region by ion implantation at the bottom of the trench prevents the generation of leakage current along the P+ buried layer. The P+ buried layers on both sides and the P-shield region at the bottom of the trench can together modulate the electric field near the N-enrich region and improve the breakdown characteristics of the proposed termination. Meanwhile, it is found that the electric field on both sides of the P+ buried layer is similar to that near the P-shield region, indicating that a good modulation effect is formed. Further, it is verified that the proposed termination is less sensitive to the ring width and the initial ring spacing of the field limiting rings, and better electrical characteristics can be obtained with appropriate trench width and enough field limiting rings. Moreover, the over etching effect is found in the fabrication process, and simulation is used to verify that deeper over etching depth will lead to lower breakdown voltage. The breakdown characteristics of the proposed termination can be improved by increasing the dose and energy of ion implantation in the P-shield region.