Threshold voltage instability of SiC MOSFETs under very-high temperature and wide gate bias

Abstract

Threshold voltage (V_TH) instability affects the reliability of silicon carbide (SiC) MOSFETs. In this article, the influence of gate bias (V_GS) and high temperature on V_TH instability is investigated under wide V_GS and very-high temperature range (150°C to 275°C). The degradation mechanism of gate oxide under coupling of different electrical and thermal stress is revealed. When the device is subjected to +V_GS, the relationship between V_TH shift and temperature is not monotonic and there is a temperature turning point. This is mainly related to the capture/release and generation of electron traps. However, the V_TH shift increases sharply and gate oxide breakdown for the device bias at +35 V, which is related to Fowler–Nordheim (F–N) tunnelling effect. For a large −V_GS, the V_TH shift is very small. Moreover, when the negative V_GS decreases, the V_TH shift is positively correlated with temperature, which may result from the activation and charge exchange of hole traps. However, the influence of moving ions changes the temperature dependence of V_TH shift for the device bias at −30 V. Finally, the devices of different manufacturers are studied and similar change patterns are found. This finding provides guidance for the further application of SiC MOSFETs under high temperatures and different voltages.