Statistical model for subthreshold current considering process variations

In this paper, an analytical technique for modeling the statistical distribution of the sub-threshold leakage variation is presented. The technique focuses on the subthreshold leakage variation induced by the within-die channel length variations. The threshold voltage variations due to the channel length variations are also included in the model. The spatial correlations between the parameters as well as the stacking effects in complex gates are considered in the technique. To assess the accuracy of the technique, we compare the results of the model for basic gates and a 1-bit full adder with those of the Monte-Carlo method. The comparison shows a small error of less than 1% for the mean and 10% for the standard deviation for the technologies considered. The same approach may be applied to other parameter variations including temperature, supply voltage, oxide thickness and threshold voltage.