Simulation Research of Tapered Sidewall Trench Superjunction MOSFETs

Abstract

This paper studied the relationship of breakdown voltage and charge imbalance of 600V tapered sidewall trench superjunction MOSFETs. Simulation structures including three types of structures: 600V vertical sidewall trench superjunction MOSFET (Type1) and 600V tapered sidewall trench superjunction MOSFET (Type2 and Type3). Under the condition of P-column and N-column uniform doping, Type1 structure has the highest peak breakdown voltage. Type2 structure has the lowest peak breakdown voltage under the condition of P-column doping concentration slightly lower than N-column doping concentration. The peak breakdown voltage of structure Type3 is higher than Type2, but the sensitivity of breakdown voltage in the charge imbalance state is the highest. The Gaussian dopant profile in P-column can make the peak breakdown voltage of the tapered sidewall trench superjunction MOSFET achieved the same level of the peak breakdown voltage of the vertical sidewall trench superjunction MOSFET. It is concluded that the sensitivity of breakdown voltage in the charge imbalance state is related to the structure: Type2 structure under the condition of P-column undercompensation and Type3 structure under the condition of P-column overcompensation are both beneficial to the process control.