Charge storage effect in SiC trench MOSFET with a floating p-shield and its impact on dynamic performances

A p-shield region under the gate trench is typically adopted in a SiC trench MOSFET for achieving lower oxide field and Crss. In this work, we comprehensively studied the impact of a floating termination at the p-shield region on device performance. The SiC trench MOSFET's internal dynamics is revealed with numerical simulations. It is found that a lloating p-shield can effectively reduce the OFF-state electric-field in the bottom gate oxide of a SiC trench MOSFET without degrading its static performance. However, during switching operation, holes would be emitted out of the floating p-shield which then becomes a region that stores negative charges. The charge storage effect could then dramatically elevate the ON-state oxide field after the device is switched from the OFF-state, and also result in slower switching speed. The stored negative charges would also narrow the ON-state current path, and consequently, the dynamic äon would be degraded.