Understanding SRAM High-Temperature-Operating-Life NBTI: Statistics and Permanent vs Recoverable Damage

The paper shows using deconvolution, SRAM V_min shift statistics yield a spread that follows Poisson area scaling and a time- and voltage-dependence of t^1/6 and V³, respectively. This is demonstrated to be consistent with permanent NBTI shift (Si-H bond breaking) relevant for end-of-life extrapolation. In contrast recoverable NBTI shift (hole trapping/detrapping) is shown to be only a function of stress duty and can be very small for realistic product duties.