Optimization method of field-limiting ring structure for 1200 V 4H-SiC PiN diodes

This paper presents a study on the field limiting ring (FLR) termination of a 1200 V 4H-SiC PiN diode. Through simulations, the effects of ring number, ring width, and ring spacing on the electric field distribution and reverse breakdown characteristics are investigated. The simulations reveal that increasing the number of FLRs effectively mitigates edge field crowding within a certain range, although the improvement tends to saturate. Enlarging the ring width mainly extends the depletion region of a single ring, while its impact on overall field uniformity is limited. Ring spacing proves to be the critical factor: excessive spacing disrupts the stepwise field-sharing mechanism, leading to field crowding at the main junction and premature breakdown. Based on these findings, an optimized termination design is proposed by slightly increasing the ring width and reducing the ring spacing towards the chip edge. Simulation results demonstrate that the optimized design improves the breakdown voltage from 1332 V to 1452 V (an 8.26% enhancement), without causing additional reverse leakage issues. This work clarifies the role of FLR structural parameters in determining breakdown performance and provides a feasible optimization approach for designing high-voltage SiC power device terminations.