Comparison of 2.3-kV 4H-SiC Accumulation-Channel Planar Power MOSFETs Fabricated With Linear, Square, Hexagonal, and Octagonal Cell Topologies

The performance of four cell topologies is compared for 2.3-kV 4H-SiC power MOSFETs fabricated in a commercial 6-in foundry. The devices were simultaneously manufactured with the same channel length (0.5 mu m), JFET width (1.1 mu m), and gate oxide thickness (55 nm) for comparison. In addition, an octagonal cell design with a JFET width of 1.5 mu m was included for comparison. The square and hexagonal cell designs had the lowest specific ON-resistance, but their breakdown voltage was found to be reduced below 2.3 kV due to sharp cell corners. The smallest reverse transfer capacitance and gate charge were observed for the octagonal cell design with significantly larger (similar to 5x) values for the square and hexagonal designs. The high-frequency figure-of-merit HF-FOM[R-ON * C-rss] for the octagonal cell design was 3.5x superior to the hexagonal and square cells and 1.5x better than the linear cell. Its high-frequency figure-of-merit HF-FOM[R-ON * Q(gd)] was 1.5x superior to the hexagonal and square cells and 1.2x better than the linear cell. This work demonstrates that the square and hexagonal cells are the best for low-frequency applications, whereas the octagonal cell design is the most suitable for achieving the best high-frequency performance of 2.3-kV 4H-SiC power MOSFETs.