Impact of Bias Temperature Instabilities on the Performance of Power Electronics Employing SiC MOSFETs

Abstract

In this work a reliability study of SiC power MOSFETs working as switching elements in a DC-DC Boost converter circuit is discussed. A critical parameter for a high-performance operation is the stable characteristics of the transistors employed. However, charge trapping effects such as bias temperature instabilities can affect e.g. the threshold voltage of transistors and thus lead to a variation in circuit behavior and efficiency. Furthermore, a time-dependent drift of the threshold voltage (∆Vth) of the MOSFET over time can cause an increase of the on-resistance (RDS(ON)) too, and thus affect the static on-state power losses accordingly (PON). In this work, we use our physical reliability simulator Comphy to extract the threshold voltage drift of the transistor over time for various mission profiles for gate biases under device operation. Using the extracted ∆Vth values from the simulator, we can reproduce the measured behavior of the DC-DC boost converter circuit. With the calibrated toolset, we can obtain the ∆Vth values over a long operation time to predict the aged behavior of the circuit parameters employing Spice simulations, which could be beneficial for circuit design and lifetime prediction of the system.