Context-Aware Signal Delay Adjustment for IC Timing Accuracy
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Solution Overview
Problem
Existing timing analysis methods for integrated circuit designs are inaccurate due to variations in device performance caused by placement relative to other devices, leading to incorrect delay calculations and operating speed issues.
Innovation Solution
The method involves automatically identifying cells in a standard cell library, assigning alignment contexts based on physical relationships, adjusting signal delay times using delay multiples, and performing a timing analysis to account for strain changes in transistor processing speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard delay times from library are used, then timing analysis is simple and fast, but timing accuracy is incorrect due to placement variations
Solution Approach 1:
The patent applies local quality by assigning different alignment contexts to different cells based on their specific placement relationships with adjacent cells. Each cell's delay is adjusted according to its local alignment context (e.g., same-width alignment, different-width alignment, corner alignment), rather than applying a uniform delay value to all cells. This localized adjustment approach improves timing accuracy while maintaining computational efficiency.
Solution Approach 2:
The patent changes the delay parameter from a fixed standard library value to a dynamic value that varies based on alignment context. By introducing alignment context as a parameter and associating it with delay multiples (e.g., 1.0x, 1.1x, 1.2x), the system adjusts delay times according to placement conditions, thereby improving timing analysis accuracy without requiring complete redesign of the timing analysis process.
2Reliability
If placement variations are ignored, then standard cell library delays can be used, but device performance differences are not captured
Solution Approach 1:
The patent segments the continuous variation in placement relationships into discrete alignment context categories. By dividing placement variations into specific types (same-width alignment, different-width alignment, corner alignment, etc.), the system can systematically handle each category with appropriate delay adjustments. This segmentation approach makes the complex problem of placement variations manageable while improving reliability.
Solution Approach 2:
The patent performs preliminary action by pre-establishing alignment context tables that map placement relationships to delay multiples before timing analysis. These pre-computed alignment contexts and their associated delay factors are stored and readily available during timing analysis, eliminating the need for complex real-time calculations and improving both reliability and efficiency.
3Measurement precision
If alignment contexts are assigned to all cells, then delay accuracy improves, but processing time increases
Solution Approach 1:
The patent performs preliminary action by pre-computing and storing alignment contexts and their associated delay multiples in lookup tables before timing analysis. During actual timing analysis, the system simply queries these pre-computed values based on cell placement relationships, avoiding complex real-time calculations. This approach maintains high delay calculation precision while minimizing additional processing time.
Solution Approach 2:
The patent uses copying by creating alignment context representations from placement geometry and storing them in pre-computed tables. These copied alignment context data structures can be efficiently referenced multiple times during timing analysis without requiring repeated geometric calculations, thereby improving delay precision while reducing processing time through efficient data reuse.
Data Source
AI summary
Methods and systems assign an alignment context to each of the cells within an integrated circuit layout, from previously established alignment contexts, based on how the different cell widths cause each of the cells to align with adjoining cells. Also, such methods and systems retrieve standard signal delay times for each of the cells from a standard cell library. This allows these methods and systems to adjust the signal delay times for each of the cells based on which alignment context has been assigned to each of the cells, to produce adjusted delay times for each of the cells. Following this, the methods and systems perform a timing analysis of the layout using the adjusted delay times for each of the cells, and output the results of the timing analysis.