Clock Tree Line Width Optimization for Electromigration and Capacitance
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Solution Overview
Problem
Integrated circuit designs face challenges in managing electromigration in metal interconnect layers, which can lead to voids and circuit failure, particularly due to varying current loads in clock tree structures, where default rule lines may not adequately address routing efficiency and capacitance concerns.
Innovation Solution
The solution involves setting non-default-rule (NDR) line widths in clock trees based on expected output current levels, with thicker lines for higher current paths and thinner lines for lower current paths, optimizing routing efficiency while mitigating electromigration risks and minimizing routing area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If default rule line widths are used in clock trees, then manufacturing simplicity is maintained, but routing efficiency and capacitance optimization are insufficient
Solution Approach 1:
The patent applies different line width rules to different clock tree regions based on their specific current loading characteristics. High-current paths receive thicker lines while low-current paths use thinner lines, optimizing each region's performance rather than applying a uniform default rule across the entire clock tree.
Solution Approach 2:
The invention changes the line width parameter dynamically based on current magnitude. By calculating expected current levels for each clock buffer output and adjusting line widths accordingly, the patent optimizes routing efficiency and capacitance while maintaining manufacturing feasibility through automated design rules.
2Reliability
If thicker lines are used for high current paths, then electromigration assurance is improved, but routing area increases
Solution Approach 1:
Thicker line widths are applied only to specific high-current paths where electromigration is a concern, while thinner lines are used in low-current regions. This localized approach maintains reliability where needed without unnecessarily increasing overall routing area.
Solution Approach 2:
The patent applies electromigration protection (thicker lines) partially, only where current levels exceed certain thresholds. This avoids the excessive action of thickening all clock tree lines uniformly, thereby reducing total routing area while maintaining adequate reliability.
3Area of stationary object
If thinner lines are used for low current paths, then routing area is reduced, but electromigration protection may be insufficient
Solution Approach 1:
The patent dynamically adjusts line width parameters based on calculated current levels for each clock buffer output. Thinner lines are applied to low-current paths to reduce area, while the system automatically increases line widths for paths where current exceeds electromigration thresholds, ensuring adequate protection.
Solution Approach 2:
The design process incorporates feedback loops where current levels are calculated for each clock buffer, and line width rules are adjusted accordingly. This feedback mechanism ensures that electromigration protection is applied appropriately - neither excessive nor insufficient - based on actual electrical loading conditions.
4Device complexity
If uniform line widths are used across all clock buffers, then design simplicity is maintained, but capacitance optimization is lost
Solution Approach 1:
The patent applies different line width characteristics to different clock tree regions based on their specific capacitance requirements. By matching line widths to local current and capacitance demands, the invention reduces overall clock tree capacitance and energy consumption while maintaining manageable design complexity through automated rule-based assignment.
Solution Approach 2:
The system changes line width parameters based on calculated capacitance and current requirements for each clock buffer output. This parameter optimization reduces total clock tree capacitance and energy loss while maintaining design simplicity through automated, rule-based line width assignment rather than manual optimization.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for improved routing efficiency, reduced capacitance, and enhanced electromigration assurance by tailoring line widths to current demands, thereby balancing reliability and area utilization in integrated circuit designs.
Implementation Method 1
Electromigration is the transport of atoms within a conductive material, which is caused by collisions that transfer momentum between electrons passing through the conductive material (i.e., current) and the atoms of the conductive material.
Data Source
AI summary
In some embodiments, an initial circuit arrangement is provided. The initial circuit arrangement includes cells that include default-rule lines and non-default-rule lines. Line widths of the default-rule lines are selectively increased for a first cell in the initial circuit arrangement, thereby providing a first modified circuit arrangement. A first maximum capacitance value is calculated for the first cell of the first modified circuit arrangement. A second modified circuit arrangement is provided by selectively increasing line widths of the non-default-rule lines in the first modified circuit arrangement. A second maximum capacitance value is calculated for the first cell of the second modified circuit arrangement. A line width of a first non-default-rule line is selectively reduced based on whether the first maximum capacitance value adheres to a predetermined relationship with the second maximum capacitance value. The second modified circuit arrangement is manufactured on a semiconductor substrate.