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

Abstract

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 / cm 2, 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.