NBTI-Related Variability Impact on 14-nm Node FinFET SRAM Performance and Static Power: Correlation to Time Zero Fluctuations

A Monte Carlo SPICE framework is proposed to evaluate the impact of negative bias temperature instability (NBTI) variability on performance and static power ( ${P}_{\text {S}}$ ) of static random access memory (SRAM) array on 14-nm node FinFETs. Gamma distribution is found to be applicable for NBTI-induced threshold voltage ( $\Delta {V}_{T}$ ) and subthreshold slope ( $\Delta $ SS) shifts by using data set from different sources. A compact variability model is proposed for the time evolution of mean and variance of NBTI distribution, considering any possible correlation between time zero and NBTI variability. The relative sensitivity of device and SRAM degradation are evaluated, by correlating SRAM static noise margin degradation to transistor level ${V}_{T}$ shift. The impact of $\Delta $ SS on ${P}_{\text {S}}$ improvement due to NBTI is also evaluated.