Statistical Analysis of Read Static Noise Margin for Near/Sub-Threshold SRAM Cell

Abstract

A fast statistical method for the analysis of the Read SNM of a 6 T SRAM cell in near/subthreshold region is proposed. The method is based on the nonlinear behavior of the cell. DIBL and body effects are thoroughly considered in the derivation of an accurate closed form solution for the Read Static Noise Margin (SNM) of the near/subthreshold SRAM cell. This method uses the state space equation to derive the Read SNM of the cell as a function of threshold voltage of cell transistors. This function shows the dependency of the Read SNM on sizing, VDD, temperature, and threshold voltage variations. It provides a fast reliability analysis for a cell array of a given size and a supply voltage. It also calculates the accurate value of failure probability of the cell. The analytical results are verified using Monte-Carlo simulations in 45 nm Predictive Technology Models.