Thermal Stability of SiC-MOSFETs at High Temperatures

Thanks to the superior electrical properties of silicon carbide (SiC), the active area of SiC-MOSFETs is significantly smaller than that of the silicon-based counterparts. Consequently, the thermal impedance is increased, which leads to higher operating temperatures when exposed to high power dissipation. This work investigates the thermal stability under these operating conditions by means of high-temperature characterization, measurements up to destruction, and electro-thermal simulations. The temperature dependence of the threshold voltage ${V}_{\text {th}}{(}{T}{)}$ was found to diminish at high temperatures, which allows thermally stable operation at elevated temperatures. At low ${V}_{\text {GS}}$ , however, the nonuniform current distribution and the formation of hot spots are still a concern. A special setup using pulses of constant power is applied for the investigation of the thermal stability via the behavior of ${V}_{\text {GS}}$ . The results are confirmed by postfailure optical inspection of the dies and by simulated temperature distributions.