On efficient Monte Carlo-based Statistical Static Timing Analysis of digital circuits

The Monte-Carlo (MC) technique is a well-known solution for statistical analysis. In contrast to probabilistic (non-Monte Carlo) statistical static timing analysis (SSTA) techniques, which are typically derived from simple statistical or timing models, the MC-based SSTA technique encompasses complicated timing and process variation models. However, a precise analysis that involves a traditional MC-based technique requires many timing simulation runs (1000s). In this paper, the behavior of the critical delay of digital circuits is investigated by using a Legendre polynomial-based ANOVA decomposition. The analysis verifies that the variance of the critical delay is mainly due to the pairwise interactions among the principal components (PCs) of the process parameters. Based on this fact, recent progress on the MC-based SSTA, through Latin hypercube sampling (LHS), is also studied. It is shown that this technique is prone to inefficient critical delay variance and quantile estimating. Inspired by the decomposition observations, an efficient algorithm is proposed which produces optimally low L2-discrepancy quasi-MC (QMC) samples which significantly improve the precision of critical delay statistical estimations, compared with that of the MC, LHS, and traditional QMC techniques.