Technical challenges in commercial SiC power MOSFETs

SiC power DMOSFETs offer significant reduction in switching and conduction losses over silicon IGBTs in the 1200 V or higher voltage range. However there are significant challenges in commercializing SiC power DMOSFETs. Some of these challenges will be discussed in this paper. A typical forward characteristics of a 1200 V SIC DMOSFET at 25degC are shown. The active area of this chip is 10.05 mm² and the on-resistance with a gate voltage of 15 V is approximately 100 mohm. Therefore the specific on-resistance is about 10 mohm-cm². The threshold voltage, V_T, is approximately 3 V measured at 1 mA and V_DS = 10 V. The V_T will reduce to approximately 1.5 V at a junction temperature of 150degC which is too low to reliably keep the device in off state with V_GS = 0 V. Fig. 2 shows the variation of R_DSON with temperature the R_DSON reduces with increasing temperature (25-50degC) due to the improvement in the effective inversion layer electron mobility. This presents a significant challenge for paralleling these devices.