Implications of gate-sided hydrogen release for post-stress degradation build-up after BTI stress

Contrary to irradiation damage, where the post-irradiation build-up of degradation is a commonly reported feature, degradation after BTI stress typically recovers monotonically. However, occasional reports on irregularities during recovery have been published. We will show here that - consistent with a gate-sided hydrogen release mechanism - additional degradation can apparently build-up during recovery also after BTI stress, which can under certain circumstances even exceed the post-stress degradation levels. This additional degradation may invalidate existing lifetime extrapolation methods and must therefore be carefully understood. Our results demonstrate that although post-stress degradation build-up is only visible under certain conditions, it is an essential feature of BTI and thus provides important clues on its microscopic origin.