# SRAM Reliability Sign-Off

SRAM yield sign-off needs per-cell failure probabilities of 10⁻⁶ to 10⁻¹² at every PVT condition, and running importance sampling at each one is expensive. The method transfers each failure lobe's design point across PVT, corrects it with one SPICE run per lobe, and adds split-conformal margins computed from importance sampling on a random subset of sign-off conditions, escalating undecided conditions to importance sampling. Across all 242 unseen conditions of a SkyWater 130-nm cell and an ASAP7 7-nm cell, no calibrated decision was unsafe, the minimum operating voltage read from the conformal upper limit lay −1 to +34 mV from importance sampling, and a 1-Mb macro delivered at least 99.88% yield.

SRAM yield sign-off needs per-cell failure probabilities of 10⁻⁶ to 10⁻¹² at every PVT condition, and running importance sampling at each one is expensive. The method transfers each failure lobe's design point across PVT, corrects it with one SPICE run per lobe, and adds split-conformal margins computed from importance sampling on a random subset of sign-off conditions, escalating undecided conditions to importance sampling. Across all 242 unseen conditions of a SkyWater 130-nm cell and an ASAP7 7-nm cell, no calibrated decision was unsafe, the minimum operating voltage read from the conformal upper limit lay −1 to +34 mV from importance sampling, and a 1-Mb macro delivered at least 99.88% yield.