Impact of fast-recovering NBTI degradation on stability of large-scale SRAM arrays

This paper presents stability analysis of large-scale SRAM arrays directly after terminating NBTI stress. While the impact of static NBTI is well examined for cells and arrays, the fast-recovering component was not yet measured on SRAM arrays. The novel method presented here analyzes the flipping of cells directly after the supply voltage was lowered to a specific value where the structure is most sensitive for NBTI induced cell flips. Thus, read margin criterion is used to characterize the decreasing cell stability due to NBTI degradation with a resolution down to 1 ms. Applying this method, the impact of static and dynamic NBTI is measured in a 65 nm low power CMOS technology. Between 1 ms and 10.000 s after stress, the NBTI induced number of cell flips decreases by almost one half.