Correlation of Dynamic and Static Metrics of SRAM Cell under Time-Zero Variability and After NBTI Degradation

Static metrics are often used to characterize read stability and write-ability of an SRAM cell. In this paper, two major dynamic SRAM metrics: critical read stability (TREAD) and critical writeability (TWRITE) are discussed and correlated with static metrics. For correlation between dynamic and static metrics, variability analysis is carried out at time-zero and after NBTI degradation of the SRAM cell. Shift in correlation factor is compared for before and after NBTI degradation. Assessment of correlation between dynamic and static metrics is used to identify those static metrics which best capture the dynamic behavior of the cell.