Impact of BTI-Induced Threshold Voltage Shifts in Shoot-Through Currents From Crosstalk in SiC MOSFETs

In this article, a method for evaluating the implications of threshold voltage (VTH) drift from gate voltage stress in SiC MOSFETs is presented. By exploiting the Miller coupling between two devices in the same phase leg, the technique uses the shoot-through charge from parasitic turn-on to characterize the impact of bias temperature instability (BTI)-induced VTH shift. Traditional methods of BTI characterization rely on the application of a stress voltage without characterizing the implication of the VTH shift on the switching characteristics of the device in a circuit. Unlike conventional methods, this method uses the actual converter environment to investigate the implications of VTH shift and should therefore be of more interest to applications engineers as opposed to device physicists. Furthermore, a common problem is the underestimation of the VTH shift since recovery from charge detrapping can mask the true extent of the problem. The impact of temperature, the recovery time after stress removal, and polarity of the stress has been studied for a set of commercially available SiC MOSFETs.