Analysis of 1.2 kV 4H-SiC Trench-Gate MOSFETs with Thick Trench Bottom Oxide

The 1.2 kV-rated trench-gate SiC power MOSFET with thick trench bottom oxide is analyzed and compared with previous trench-gate SiC power MOSFET structures. Specific on-resistance (R_{on, sp}), breakdown voltage (BV), threshold voltage (V_TH), gate-drain capacitance (C_{gd, sp}) and gate charge (Q_gd) were extracted using numerical simulations for trench bottom oxide thickness between 500 A and 8000 A. It was found that the electric field in the trench bottom oxide was below 4 MV/cm for oxide thickness beyond 4000 A. An analytical model is proposed to allow estimation of the electric field in the trench bottom oxide. The R_{on, sp} for the thick bottom oxide structure was 1.9 m Ω - cm²(at Vgs of 20 V), Cgd, sp (at Vds= 1000 V) was 417 pF/cm² and Qgd, sp (at Vgs =20 V, R_g=10 Ω, Vds=800V) was 671 nC / cm², which is significantly better than most planar-gate devices. This structure has superior specific on-resistance compared with previous trench-gate and planar-gate structures.