The “Permanent” Component of NBTI Revisited: Saturation, Degradation-Reversal, and Annealing

While the defects constituting the recoverable component R of NBTI have been very well analyzed recently, the slower defects forming the more “permanent” component P are much less understood. Using a pragmatic definition for P, we study the evolution of P at elevated temperatures in the range 200◦C to 350◦C to accelerate these very slow processes. We demonstrate for the first time that P not only clearly saturates, with the saturation value depending on the gate bias, but also that the degradation at constant gate bias can also slowly reverse. Furthermore, at temperatures higher than about 300◦C, a significant amount of additional defects is created, which are primarily uncharged around Vth but contribute strongly to P at higher VG. Our new data are consistent with our recently suggested hydrogen release model which will be studied in detail using newly acquired long-term data.