Timing Yield Computation via Correlated Sample Generation

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Solution Overview

Problem

Current methods for predicting parametric timing yield in VLSI chip designs are inadequate due to challenges in capturing topological correlations between different timing paths, leading to inefficient brute-force full-chip Monte Carlo analysis with high runtime impacts.

Innovation Solution

The method employs correlated sample generation and efficient statistical simulation to accurately compute timing yield by identifying yield-critical timing paths, pruning them to 6-sigma corners, and using Monte Carlo simulations to generate random delay samples, accounting for correlations between paths through common timing arcs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If brute-force full-chip Monte Carlo analysis is used to capture topological correlations between timing paths, then timing yield prediction accuracy is improved, but runtime increases significantly

Engineering Contradiction:
Improvetiming yield prediction accuracyVSAvoidruntime
Core Design Contradiction:
Measurement precisionVSLoss of time

Solution Approach 1:

The patent segments the full-chip timing analysis by identifying and isolating yield-critical timing paths from the complete design. Instead of analyzing all timing paths simultaneously, the method extracts only the critical paths that contribute most to timing yield variations, performing Monte Carlo simulations on these segmented paths only. This segmentation reduces the computational burden while maintaining prediction accuracy for timing yield.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent extracts yield-critical timing paths from the full chip design by analyzing path sensitivity and correlation characteristics. The method identifies and separates the most influential timing paths that drive yield variations, removing them from the full-chip analysis set. This extraction allows focused computational resources on the critical subset of paths, significantly reducing runtime while preserving timing yield prediction accuracy.

Inventive Principle:
Principle #2Taking out (Extraction)

2Measurement precision

If correlated sample generation is used to model topological correlations between timing paths, then timing yield computation accuracy is improved, but computational complexity increases

Engineering Contradiction:
Improvetiming yield computation accuracyVSAvoidcomputational complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies local quality by generating correlated samples selectively for timing arcs that are shared by multiple critical paths. Instead of applying correlation modeling uniformly across all timing paths, the method identifies local regions (timing arcs) where correlations are most impactful and applies correlated sample generation only to these specific locations. This localized approach reduces overall computational complexity while maintaining accuracy where it matters most.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent uses partial action by performing correlated sample generation only for the subset of timing arcs that are common to multiple critical paths, rather than exhaustively analyzing all timing arcs in the design. This partial application of correlation modeling achieves sufficient accuracy for yield prediction while significantly reducing computational complexity compared to full-chip correlation analysis.

Inventive Principle:
Principle #16Partial or excessive action

3Productivity

If yield-critical timing paths are identified and pruned to 6-sigma corners, then analysis efficiency is improved, but timing yield prediction completeness may be reduced

Engineering Contradiction:
Improveanalysis efficiencyVSAvoidtiming yield prediction completeness
Core Design Contradiction:
ProductivityVSMeasurement precision

Solution Approach 1:

The patent applies parameter changes by transforming the analysis focus from all possible timing paths to specifically the 6-sigma corners of yield-critical paths. The method identifies paths with the most significant yield impact and concentrates analysis on the extreme corners (±6 sigma) of their timing distributions, where yield-determining variations occur. This parameter-focused approach maintains prediction completeness for yield-related variations while dramatically improving analysis efficiency.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentUS20250077752A1Method to compute timing yield and yield bottleneck using correlated sample generation and efficient statistical simulation
Publication Date: 2025.03.06 SYNOPSYS INC
  • US20250077752A1 patent drawing
  • US20250077752A1 patent drawing
  • US20250077752A1 patent drawing

AI summary

Various embodiments of a method and apparatus for determining parametric timing yield and bottlenecks are disclosed which take into account correlation between electrical circuit paths through common timing arcs of an integrated circuit chip under design. Monte Carlo samples of timing arc delays are generated and used in computing timing yield and identify yield bottlenecks.