High-Temperature Electrical and Thermal Aging Performance and Application Considerations for SiC Power DMOSFETs

TLDR

The study measured the temperature dependence and stability of three commercially available unpackaged SiC DMOSFETs. The devices exhibited 6–7× higher on‑state resistance at 350 °C, threshold voltages that nearly doubled under positive gate stress at 300 °C but recovered with negative bias, negligible drain‑current change, a threshold that approaches zero at high temperature, leakage that rises sharply once the threshold falls below ~150 mV, and a sudden shift from linear to nonlinear output after 24–100 h air or 570–1000 h N₂ aging at 300 °C due to nickel‑oxide growth, yet remain operable at temperatures far above their rated limits.

Abstract

The temperature dependence and stability of three different commercially-available unpackaged SiC Dmosfets have been measured. On-state resistances increased to 6 or 7 times their room temperature values at 350 °C. Threshold voltages almost doubled after tens of minutes of positive gate voltage stressing at 300 °C, but approached their original values again after only one or two minutes of negative gate bias stressing. Fortunately, the change in drain current due to these threshold instabilities was almost negligible. However, the threshold approaches zero volts at high temperatures after a high temperature negative gate bias stress. The zero gate bias leakage is low until the threshold voltage reduces to approximately 150 mV, where-after the leakage increases exponentially. Thermal aging tests demonstrated a sudden change from linear to nonlinear output characteristics after 24-100 h air storage at 300 °C and after 570-1000 h in N2 atmosphere. We attribute this to nickel oxide growth on the drain contact metallization which forms a heterojunction p-n diode with the SiC substrate. It was determined that these state-of-the-art SiC mosfet devices may be operated in real applications at temperatures far exceeding their rated operating temperatures.