Modulation of Ciss of a 4H-SiC Planar MOSFET with a Shorter Sidewall and a Thicker Gate

In this study, reducing the sidewall width of the 1200 V 4H-SiC planar power Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) by 6.9% increases the input capacitance, C_iss, by approximately 6%, which is contributed by the increase of 13.5% in Q_GS directly. In order to increase the accuracy of calculation and dynamic characteristics, the equation of C_iss,sp might be counted in the sidewall capacitance, C_swall, when the width is different from the interlayer dielectric thickness on the top of the gate. Then, the modified calculation result of 7% is almost consistent with the measured result of 6% and simulation result of 6.8% for C_iss,sp. In addition, the poly gate thickness between 400 nm and 800 nm can contribute extra change in C_iss,sp by 2-3% as well. Because of the reduction in the sidewall width, the die size is also reduced. The specific-on resistance is decreased by 17%, while exhibiting no significant change in reverse breakdown voltage.