While first-order statistical static timing analysis (SSTA) techniques enjoy good runtime efficiency desired for tackling large industrial designs, more accurate second-order SSTA techniques have been proposed to improve the analysis accuracy, but at the cost of high computational complexity. Although many sources of variations may impact the circuit performance, considering a large number of inter- and intra-die variations in the traditional SSTA is very challenging. In this paper, we address the analysis complexity brought by high parameter dimensionality in SSTA and propose an accurate yet fast second-order SSTA algorithm based on novel on-the-fly parameter dimension reduction techniques. By developing a reduced rank regression (RRR)-based approach and a method of moments (MOM)-based parameter reduction algorithm within the block-based SSTA flow, we demonstrate that accurate second-order SSTA can be extended to a much higher parameter dimensionality than what is possible before. Our experimental results have shown that the proposed parameter reductions can achieve up to 10times parameter dimension reduction and lead to significantly improved second-order SSTA under a large set of process variations.

In this paper, we propose an efficient numerical algorithm for estimating the parametric yield of analog/RF circuits, considering large-scale process variations. Unlike many traditional approaches that assume normal performance distributions, the proposed approach is particularly developed to handle multiple correlated nonnormal performance distributions, thereby providing better accuracy than the traditional techniques. Starting from a set of quadratic performance models, the proposed parametric yield estimation conceptually maps multiple correlated performance constraints to a single auxiliary constraint by using a MAX operator. As such, the parametric yield is uniquely determined by the probability distribution of the auxiliary constraint and, therefore, can easily be computed. In addition, two novel numerical algorithms are derived from moment matching and statistical Taylor expansion, respectively, to facilitate efficient quadratic statistical MAX approximation. We prove that these two algorithms are mathematically equivalent if the performance distributions are normal. Our numerical examples demonstrate that the proposed algorithm provides an error reduction of 6.5 times compared to a normal-distribution-based method while achieving a runtime speedup of 10-20 times over the Monte Carlo analysis with 103samples.

The ability to account for the growing impacts of multiple process variations in modern technologies is becoming an integral part of nanometer VLSI design. Under the context of timing analysis, the need for combating process variations has sparkled a growing body of statistical static timing analysis (SSTA) techniques. While first-order SSTA techniques enjoy good runtime efficiency desired for tackling large industrial designs, more accurate second-order SSTA techniques have been proposed to improve the analysis accuracy, but at the cost of high computational complexity. Although many sources of variations may impact the circuit performance, considering a large number of inter-die and intra-die variations in the traditional SSTA analysis is very challenging. In this paper, we address the analysis complexity brought by high parameter dimensionality in static timing analysis and propose an accurate yet fast second-order SSTA algorithm based upon novel parameter dimension reduction. By developing reduced-rank regression based parameter reduction algorithms within block-based SSTA flow, we demonstrate that accurate second order SSTA analysis can be extended to a much higher parameter dimensionality than what is possible before. Our experimental results have shown that the proposed parameter reduction can achieve up to 10X parameter dimension reduction and lead to significantly improved second-order SSTA analysis under a large set of process variations.

Leakage power is becoming an increasingly important component of total chip power consumption for nanometer IC designs. Minimization of leakage power unavoidably enforces the consideration of the key sources of process variations, namely transistor channel length and threshold variations, since both have a significant impact on timing and leakage power. However, the statistical nature of chip performances often requires the use of expensive statistical analysis and optimization techniques in a leakage minimization task, contributing to high computational complexity. Further, the commonly used discrete cell libraries bring specific difficulty for design optimization and render pure continuous sizing and VT optimization algorithm suboptimal. In this paper, we present a fast yet effective approach to statistical leakage power reduction via gate sizing and multiple VT assignment. The proposed technique achieves the runtime efficiency via the use of the novel concept of equi-slack shells and performs fast leakage power reduction on the basis of shells while maintaining the timing yield. When combined with a finer grained gate-based post tuning step, the presented technique achieves Superior runtime efficiency while offering significant leakage power reduction.

Variability in process parameters leads to a significant parametric yield loss of high-performance ICs due to the large spread in leakage-power consumption and speed of chips. In this paper, we propose an algorithm for total power minimization under timing constraints in the presence of variability. The algorithm is formulated as a robust optimization program with a guarantee of power and timing yields, with both power and timing metrics being treated probabilistically. Power reduction is performed by simultaneous sizing and dual threshold-voltage assignment. An extremely fast run-time is achieved by casting the problem as a second-order conic problem and solving it using efficient interior-point optimization methods. The performance of the algorithm was evaluated on a variety of public and industrial benchmarks, with a library characterized using 70-nm Berkeley Predictive Technology Model. When compared to the deterministic optimization, the new algorithm, on average, reduces static power and total power at the 99.9th quantile by 31% and 17%, respectively, without loss of parametric yield. The run-time on the benchmarks is 30times faster than other known statistical power-minimization algorithms.

Process variations have a growing impact on circuit performance for today's integrated circuit (IC) technologies. The Non-Gaussian delay distributions as well as the correlations among delays make statistical timing analysis more challenging than ever. In this paper, we present an efficient block-based statistical timing analysis approach with linear complexity with respect to the circuit size, which can accurately predict Non-Gaussian delay distributions from realistic nonlinear gate and interconnect delay models. This approach accounts for all correlations, from manufacturing process dependence, to re-convergent circuit paths to produce more accurate statistical timing predictions. With this approach, circuit designers can have increased confidence in the variation estimates, at a low additional computation cost.

Critical path analysis is always an important task in timing verification. For todays nanometer IC technologies, process variations have a significant impact on circuit performance. The variability can change the criticality of long paths (Gattiker et al., 2002). Therefore, statistical approaches should be incorporated in critical path analysis. In this paper, we present two novel techniques that can efficiently evaluate path criticality under statistical non-linear delay models. They are integrated into a block-based statistical timing tool with the capability of handling arbitrary correlations from manufacturing process dependence and also path sharing. Experiments on ISCAS85 benchmarks as well as industrial circuits prove both accuracy and efficiency of these techniques.