A Bias-Dependent Model for the Impact of Process Variations on the SRAM Soft Error Immunity

Nanometer SRAM cells are more susceptible to the particle strike soft errors and the increased statistical process variations, in advanced nanometer CMOS technologies. In this paper, an analytical model for the critical charge variations accounting for both die-to-die (D2D) and within-die (WID) variations, over a wide range of bias conditions, is proposed. The derived model is verified and compared to Monte Carlo simulations by using industrial hardware-calibrated 65-nm CMOS technology. This paper shows the impact of the coupling capacitor, one of the most common soft error mitigation techniques, on the critical charge variability. It demonstrates that the adoption of the coupling capacitor reduces the critical charge variability. The derived analytical model accounts for the impact of the supply voltage, from 0.1 to 1.2 V, on the critical charge and its variability.