In the way they cope with variability, present-day methodologies are onerous, pessimistic and risky, all at the same time! Dealing with variability is an increasingly important aspect of highperformance digital integrated circuit design, and indispensable for first-time-right hardware and cutting-edge performance. This invited paper discusses the methodology, analysis, synthesis and modeling aspects of this problem. These aspects of the problem are compared and contrasted in the ASIC and custom (microprocessor) domains. This paper pays particular attention to statistical timing analysis and enumerates desirable attributes that would render such an analysis capability practical and accurate.

Uncertainty in circuit performance due to manufacturing and environmental variations is increasing with each new generation of technology. It is therefore important to predict the performance of a chip as a probabilistic quantity. This paper proposes three novel algorithms for statistical timing analysis and parametric yield prediction of digital integrated circuits. The methods have been implemented in the context of the -42660 static timing analyzer. Numerical results are presented to study the strengths and weaknesses of these complementary approaches. Across-the-chip variability continues to be accommodated by 39516 's "Linear Combination of Delay (LCD)" mode. Timing analysis results in the face of statistical temperature and V dd variations are presented on an industrial ASIC part on which a bounded timing methodology leads to surprisingly wrong results.

We present a new method for mismatch analysis and automatic yield optimization of analog integrated circuits with respect to global, local and operational tolerances. Effectiveness and efficiency of yield estimation and optimization are guaranteed by consideration of feasibility regions and by performance linearization at worst-case points. The proposed methods were successfully applied to two example circuits for an industrial fabrication process.

Towards predictable deep-submicron manufacturing

Abstract—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 103 samples. Index Terms—Analog/RF circuits, MAXoperator, parametric yield.

As VLSI technology moves to the nanometer scale for transistor feature sizes, the impact of manufacturing imperfections result in large variations in the circuit performance. Traditional CAD tools are not well-equipped to handle this scenario, since they do not model this statistical nature of the circuit parameters and performances, or if they do, the existing techniques tend to be over-simplified or intractably slow. We draw upon ideas for attacking parallel problems in other technical fields, such as computational finance, machine learning and hydrology, and synthesize them with innovative attacks for our problem domain of integrated circuits, to develop novel solutions to problems of efficient statistical analysis of circuits in the nanometer regime. In particular, this thesis makes three contributions: 1) SiLVR, a nonlinear response surface modeling (RSM) and performance-driven dimensionality reduction strategy, that uses the concepts of projection pursuit and latent variable regression to obtain an absolute improvement in modeling error of up to 34% over the best quadratic RSM method. SiLVR also captures the designer’s insight into the circuit behavior, by automatically extracting quantitative measures of relative