IC Cell Density Redistribution for Layout Area Reduction
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Solution Overview
Problem
Integrated circuit (IC) layout optimization faces challenges in reducing congestion regions and minimizing layout area, as existing CAD-based development processes struggle to efficiently redistribute cell densities, leading to increased manufacturing costs and inefficient die size management.
Innovation Solution
A method involving initial cell density distribution flattening, identification of high routing density regions, cell size adjustments through expansion and shrinkage, and a recalibration process to redistribute cell densities, utilizing electronic design automation tools and computer-aided design procedures to optimize IC layout and reduce congestion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If initial placement is performed without density redistribution, then placement process is simple and fast, but congestion regions increase and layout area expands
Solution Approach 1:
The patent applies preliminary action by performing density flattening and cell redistribution before final placement and routing. The method calculates target density distributions and redistributes cells in advance to prevent congestion regions from forming, thereby reducing the overall layout area before the actual manufacturing process begins
Solution Approach 2:
The patent changes the density parameter distribution across the layout by calculating target density values for different regions and redistributing cells to achieve uniform density. This parameter transformation converts non-uniform initial density distributions into uniform target density distributions, optimizing layout area utilization
2Reliability
If cell densities are flattened to specific density value, then congestion regions are reduced, but additional processing steps are required
Solution Approach 1:
The patent applies local quality by identifying different density regions within the layout and applying specific redistribution operations to each region. The method calculates local density values and target density distributions for different areas, allowing customized cell movement strategies for high-density versus low-density regions rather than uniform treatment across the entire layout
Solution Approach 2:
The patent implements feedback by calculating current density distributions, comparing them against target density values, and using this information to guide subsequent cell redistribution operations. The method iteratively adjusts cell positions based on density feedback until convergence to the target uniform density distribution is achieved
3Productivity
If routing density is considered in redistribution, then routing congestion is minimized, but calculation complexity increases
Solution Approach 1:
The patent applies preliminary action by performing routing density analysis and incorporating routing constraints into the cell redistribution process before actual routing occurs. The method calculates routing density distributions in advance and uses this information to guide cell placement optimization, preventing routing congestion before it occurs
Solution Approach 2:
The patent changes the optimization parameters by incorporating routing density as an additional constraint parameter alongside cell density. The method transforms the optimization problem to consider both cell density uniformity and routing density distribution, adjusting cell positions to satisfy multiple parameter requirements simultaneously
Data Source
AI summary
A method for redistributing cell densities in layout of IC is provided. Initial cell density distribution and routing density distribution are obtained in an initial placement of the IC. White space is inserted into the initial placement according to a specific density value, so as to flatten the initial cell density distribution to the specific density value and obtain a flat cell density distribution. The specific density value is larger than a maximum cell density value within the initial cell density distribution. Cell densities of a first region are increased in the IC according to the routing density distribution and the flat cell density distribution, so as to obtain a modified cell density distribution. The modified cell density distribution is smoothed to obtain a calibrated cell density distribution. The white space is removed from the calibrated cell density distribution to obtain a final placement.