A Novel MOS-Channel Diode Embedded in a SiC Superjunction MOSFET for Enhanced Switching Performance and Superior Short Circuit Ruggedness

Jongwoon Yoon,Kwangsoo Kim

doi:10.3390/electronics10212619

Abstract

In this study, a novel MOS-channel diode embedded in a SiC superjunction MOSFET (MCD SJ-MOSFET) is proposed and analyzed by means of numerical TCAD simulations. Owing to the electric field shielding effect of the P+ body and the P-pillar, the channel diode oxide thickness (tco) of MCD can be set to very thin while achieving a low maximum oxide electric field (EMOX) under 3 MV/cm. Therefore, the turn-on voltage (VF) of the proposed structure was 1.43 V, deactivating the parasitic PIN body diode. Compared with the SJ-MOSFET, the reverse recovery time (trr) and the reverse recovery charge (Qrr) were improved by 43% and 59%, respectively. Although there is a slight increase in specific on-resistance (RON), the MCD SJ-MOSFET shows very low input capacitance (CISS) and gate to drain capacitance (CGD) due to the reduced active gate. Therefore, significantly improved figures of merit RON × CGD by a factor of 4.3 are achieved compared to SJ-MOSFET. As a result, the proposed structure reduced the switching time as well as the switching energy loss (ESW). Moreover, electro-thermal simulation results show that the MCD SJ-MOSFET has a short circuit withstand time (tSC) more than twice that of the SJ-MOSFET at various DC bus voltages (400 and 600 V).

Highlights

Using the charge balance concept, superjunction (SJ) MOSFETs are considered as a promising approach to improve the trade-off between specific on-resistance (RON) and breakdown voltage (BV) beyond silicon’s (Si) limit [1]
It can be seen that the proposed structure has about 46% lower saturation current at VDS = 600 V compared to the SJ-MOSFET
The results show that the peak reverse recovery current IRRM of the MOS-channel diode (MCD) SJ-MOSFET is 206 A/cm2, which is much lower than that of SJ-MOSFET (324 A/cm2)

Summary

Introduction

Using the charge balance concept, superjunction (SJ) MOSFETs are considered as a promising approach to improve the trade-off between specific on-resistance (RON) and breakdown voltage (BV) beyond silicon’s (Si) limit [1]. The parasitic PIN body diode of the SiC MOSFET features a relatively higher turn-on voltage (~3 V) than its Si MOSFET counterpart (~0.7 V), owing to the wide band gap properties, which further deteriorates the reverse recovery characteristics. Research was conducted to improve the reverse recovery characteristics by embedding a p-type SBD in the drain side of a SiC SJ-MOSFET [11,12]. Several studies demonstrated that integrating an MOS-channel diode (MCD) is another option for enhancing reverse recovery characteristics [17,18]. Due to the low VF of the MCD, the MCD SJ-MOSFET can greatly improve the reverse recovery characteristics compared with the SJ-MOSFET, while deactivating the parasitic body diode. Electro-thermal simulation results show that the MCD SJ-MOSFET boasts superior short circuit performance compared to the SJ-MOSFET

Device Structures and Simulation Background

Electrical Characteristics

Conclusions