Optimization of SiC UMOSFET Structure for Improvement of Breakdown Voltage and ON-Resistance

Abstract

This paper proposes an optimized structure of 4H-SiC U-shaped accumulation-mode MOSFET (U-ACCUFET), which exhibits lower on-resistance and higher breakdown voltage. In this structure, an n-doped region is added underneath the gate trench, which covers the p+ shielding region. The new appended section spreads out the electrons to the bottom of the p+ shielding region and conducts the electrons in the downward direction. Output on-state characteristic curves ( ${I}_{\mathrm {DS}}$ – ${V}_{\textsf {DS}}$ ), on-resistance, transfer characteristic curves ( ${I}_{\textsf {DS}}$ – ${V}_{\textsf {GS}}$ ), threshold voltage ( ${V}_{t}$ ), subthreshold slope, and off-state characteristics of the optimized structure are observed. The proposed device shows on-resistance of 1.55 $\text{m}\Omega ~\cdot $ cm2 at ${V}_{\textsf {GS}}= \textsf {16}$ V and ${V}_{\textsf {DS}}= \textsf {1}$ V and breakdown voltage of 2624 V at ${V}_{\textsf {GS}}= \textsf {0}$ V. The simulation results indicate a superior performance of the optimized U-ACCUFET structure as the on-resistance reduces by 6% and breakdown voltage increases by 7.2% as compared with that of the conventional one. Also, the figure of merit ${V}_{\textsf {BR}}^{\textsf {2}}/{R}_{ \mathrm{\scriptscriptstyle ON}}$ is improved by 21.6%.