A 4H-SiC Trench MOSFET with the vertical field plate coupled floating island and two epi-layers

A novel silicon carbide (SiC) U-shape trench MOSFET(UMOSET) with the vertical field plate coupled floating island structure (VFF-UMOSFET) is proposed. Double epitaxial layer is adopted. Simulations study is performed using Sentaurus TCAD. The effect of the field plate and floating island on the electric field distribution, breakdown voltage and specific ON-resistance (sRON, sp) are studies and the relationship between doping concentration and breakdown voltage in the first drift zone and the second drift zone is discussed respectively. The simulation results show that the VFF-UMOSFET with the vertical field plate coupled floating island structure exhibits a higher figure of merit related to the breakdown voltage and the specific on-resistance, which is improved by 37.5% and 65%, respectively, with comparison to the state-of-the-art source trench(ST-MOSFET) and reduce the peak of the electric field at the trench-gate bottom by 60%, compared with the standard UMOSFET, while effectively reducing the electric field at the field plate bottom. Finally, the optimization of parameters (field plate depth, floating island geometry) is discussed.