A Method for the Measurement of the Threshold-Voltage Shift of SiC MOSFETs During Power Cycling Tests

The application of established test routines like power cycling to wide bandgap devices may be not as straightforward as it seems: When power cycling silicon carbide MOSFETs, the original purpose of triggering package related degradations under application-like and accelerated conditions might be influenced by device related changes during the test, such as carrier trapping, which may lead to a shift in the threshold-voltage V-th and, thus, in the operating point. With the aim to track the V-th shift during power cycling in order to separate themechanisms-i.e., to indicate and quantify the different overlapping effects-a novel inline Delta V-th measurement approach is proposed, which can be integrated in existing power cycling test benches with only minor adaptions. First power cycling results with Delta V-th monitoring reveal a shift in the operating point leading to an early failure detection in conjunction with a V-th shift.