Accumulation-Mode Device: New Power MOSFET Breaking Superjunction Silicon Limit by Simulation Study

Abstract

In this article, new structures are proposed with an extra electrode for accumulation-mode vertical double-diffused metal-oxide semiconductor (VDMOS) (EA VDMOS) and a gate electrode for accumulation-mode VDMOS (GA VDMOS). For accumulation-mode VDMOS, the drift region is lightly doped to support drain voltage in the OFF-state. A large density of electrons is accumulated to modulate the conductivity of the drift region in the ON-state. It is contradictory to obtain high breakdown voltage (BV) and low specific ON-resistance ( ${R}_{ \mathrm{\scriptscriptstyle ON},\text {sp}}$ ) in the conventional VDMOS, because both of them depend on the doping concentration of the drift region. This contradictory relationship between the BV and ${R}_{ \mathrm{\scriptscriptstyle ON},\text {sp}}$ is eliminated for EA and GA VDMOS, thereby breaking the superjunction (SJ) silicon limit. Simulation results indicate that ${R}_{ \mathrm{\scriptscriptstyle ON},\text {sp}}$ of the accumulation-mode VDMOS devices are significantly reduced. The ${R}_{ \mathrm{\scriptscriptstyle ON},\text {sp}}$ of EA and GA VDMOS can be reduced by 60% (0.85 $\text{m}\Omega ~ \cdot $ cm2) and 30% (1.68 $\text{m}\Omega ~ \cdot $ cm2) compared with the SJ VDMOS (2.41 $\text{m}\Omega ~ \cdot $ cm2) at the BV of 600 V, respectively. In addition, the performance of the accumulation-mode VDMOS is independent of charge balance which is necessary for the SJ VDMOS.