Feasibility of SiC threshold voltage drift characterization for reliability assessment in production environments

We reviewed the practical challenges of assessing the threshold voltage drift of SiC MOSFETs in the context of a commercial production environment and qualification standards. Stress bias interruption is a key challenge owing to the rapid recovery of threshold following the removal of bias and the necessity of delays and bias interruptions when qualifying device lots. The test standards in use proscribe how such interruptions should be handled using a re-application of the stress once the device is ready for characterization, but these turn out to be completely inadequate when dealing with the trapping mechanics of SiC MOS. Our data indicates that a relatively short stress re-application can be successful at restoring a majority of the threshold voltage drift at room temperature, scaling with the square root of the interruption time. Additionally, it is important to re-apply the stress bias even for brief interruptions since the threshold recovers so quickly (as opposed to the 96-hour interrupt window allowed before reapplication is necessary in JESD22 A-108D).