Probability calculation of read failures in nano-scaled SRAM cells under process variations

In this paper, we present an accurate method for predicting the read failure probability of SRAM cells. First, using a simple I–V model for transistors, analytical expressions for the Vread and Vtrip of SRAM cells are obtained. These expressions are subsequently used to derive a fairly accurate model for the read margin of SRAM cells. Then, using Jacobian determinant, the joint probability density function for the Vread and Vtrip is calculated without assuming any specific distribution function for its probability. The accuracy of the approach is studied by comparing its results with those of previous techniques and standard Monte Carlo simulations for 32 and 45 nm CMOS technologies. Compared to these techniques, our approach has a considerably lower error at the price of slightly increasing the computation time or is much faster at the cost of marginally decreasing the accuracy. In addition, the method has the advantage of not being restricted to a specific probability distribution form.