A New SiC Trench MOSFET Structure With Protruded p-Base for Low Oxide Field and Enhanced Switching Performance

Abstract

The high OFF-state oxide field in the SiC trench MOSFET is a threat for its long term reliability, and thus hinders the wide acceptance of the SiC trench MOSFETs. In this paper, an SiC trench MOSFET with protruded p-bases (PB-MOS) is proposed, which features protruded p-bases to shield the gate oxide at the trench bottom against the high OFF-state drain voltage. Numerical device simulations based on Sentaurus TCAD verify the benefits of the structure. The OFF-state oxide field ( ${ {E}}_{\text {ox-m}}$ ) in the PB-MOS is 1.7 MV/cm, which is dramatically lower compared to the high ${ {E}}_{\text {ox-m}}$ of 8.6 MV/cm in the conventional trench MOSFET (C-MOS). The above benefit is achieved without sacrificing device performances. The reverse transfer capacitance ( ${ {C}}_{\text{rss}}$ ) of the PB-MOS is around ten times lower than that in the C-MOS. Both the gate charge ( ${ {Q}}_{\text{G}}$ ) and the gate-to-drain charge ( ${ {Q}}_{\text{GD}}$ ) of the PB-MOS are significantly improved compared to the C-MOS. A low specific ON-resistance ( ${ {R}}_{\text{ON}}$ ) is maintained in the PB-MOS by using additional JFET doping to compensate the JFET effect. As a result, the PB-MOS presents much better figures of merit ${ {Q}}_{\text{G}} \cdot { {R}}_{\text{ON}}$ and ${ {Q}}_{\text{GD}} \cdot { {R}}_{\text{ON}}$ than those of the C-MOS. The PB-MOS achieves a much faster switching speed than the C-MOS, and consequently exhibits an appreciable reduction in the switching energy loss.