Degradation and recovery of variability due to BTI

In this paper we investigate the increase (degradation) of variability due to NBTI and the statistical behavior of Vth after end of stress (recovery). Furthermore we analyze the dependency of the additional variability of Vth on the transistor size and geometry. For the necessary statistical relevance we perform NBTI experiments with a special smart array test-structure at a large amount of pMOSFETs with various geometries. We prove our results for a second technology node with a different oxide thickness. We demonstrate for the first time that also the induced additional variability recovers. Furthermore we show that the variability of pMOSFETs after NBTI depends not only on the size of the active area (w × l) but also on its geometry (w/l).