A Novel 4H-SiC MOSFET With High-K/Low-K Dielectric for Improved Frequency Characteristics

Abstract

Split-Gate MOSFET (SG-MOSFET) is promising in power-switching circuits due to the fast turn-on/off speed and low switching loss. However, in higher-frequency applications, the gate architecture needs to be changed to obtain the improved high-frequency figure of merit (HF-FOM) over the SG-MOSFET. In this paper, a planar split-gate SiC MOSFET with Low-K (nanoporous SiCOH) gate-source dielectric and High-K (HfO₂) source field-plate dielectric (named LHK-MOSFET) is proposed and investigated by numerical simulations. As for the proposed MOSFET, the High-K field-plate dielectric helps reduce semiconductor bulk capacitance (C_SiC), thereby reducing the gate-drain capacitance (C_GD). Besides, the Low-K gate-source dielectric helps to reduce the gate-source insulation layer capacitance (C_IL). When compared to the SG-MOSFET with a source field plate (SFP-SG-MOSFET) and SG-MOSFET, the gate-drain capacitance (C_GD) of the proposed MOSFET is reduced by 35.8% and 73.0%, and the gate-drain charge (Q_GD) is reduced by 26.9% and 62.3%, respectively. It is calculated that the HF-FOM ($C_{GD}\times R_{onsp}$) of the proposed MOSFET is reduced by 35.2% and 71.0% compared to SFP-SG-MOSFET and SG-MOSFET, respectively. The improved performance indicates that the proposed device is a competitive choice for high-frequency power electronic systems.