Clock Tree Synthesis With Decoupling Capacitor Fillers
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Solution Overview
Problem
Conventional clock tree synthesis methods fail to ensure sufficient space between clock cells and other elements, leading to potential electromigration and IR drop issues, which can cause circuit failures in integrated circuits.
Innovation Solution
A clock tree synthesis method that involves setting a keep-out margin for clock cells, generating reserved spaces adjacent to them, and inserting decoupling capacitor filler cells with related area and capacitance, ensuring sufficient space and mitigating electromigration and IR drop risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If clock cells are arranged closer together to increase integration density, then productivity is improved, but reliability deteriorates due to electromigration and IR drop issues
Solution Approach 1:
The patent applies preliminary action by setting keep-out margins and reserving spaces around clock cells during the clock tree synthesis phase, before physical implementation. This advance planning ensures that sufficient spacing is maintained between clock cells to prevent electromigration and IR drop issues, while still achieving high integration density through optimized layout strategies.
Solution Approach 2:
The patent applies local quality by differentiating the treatment of different regions in the circuit layout. Clock cells with strong driving strength are assigned larger keep-out margins and surrounded by reserved spaces, while other regions follow standard spacing rules. This localized approach ensures critical areas have adequate spacing for reliability without unnecessarily reducing overall integration density.
2Reliability
If keep-out margin is increased to ensure sufficient space between clock cells, then reliability is improved, but area utilization deteriorates
Solution Approach 1:
The patent applies local quality by setting different keep-out margin sizes based on the specific characteristics of each clock cell. Clock cells with strong driving strength receive larger keep-out margins to prevent electromigration and IR drop, while clock cells with weaker driving strength use smaller margins. This differentiated approach ensures reliability for critical cells without unnecessarily reducing area utilization across the entire design.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the keep-out margin parameter based on clock cell driving strength. The keep-out margin is not a fixed value but varies according to the specific requirements of each clock cell, allowing optimization of both reliability and area utilization through parameter adaptation rather than uniform constraints.
3Reliability
If decoupling capacitor filler cells are added to reserved spaces, then reliability is improved through voltage stabilization, but device complexity increases
Solution Approach 1:
The patent applies self-service by using decoupling capacitor filler cells that serve dual purposes: they provide voltage stabilization and IR drop mitigation for the clock tree, while also filling unused reserved spaces in the layout. This self-service approach allows the circuit to benefit from additional decoupling capacitance without requiring separate dedicated capacitor structures, thereby improving reliability while minimizing the increase in device complexity.
Solution Approach 2:
The patent applies universality by designing decoupling capacitor filler cells that perform multiple functions simultaneously. These filler cells provide decoupling capacitance for voltage stabilization, fill unused layout spaces to improve area utilization, and serve as part of the clock tree structure. This multi-functionality reduces the need for separate components, improving reliability while limiting the increase in device complexity.
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
The method effectively reduces the likelihood of electromigration and IR drop, improving the circuit's reliability and stability by ensuring adequate spacing and reducing voltage drops, making it easier to pass tests and extend the service life of the circuit.
Implementation Method 1
disposing a decoupling capacitor filler cell in the reserved space, wherein an area and/or capacitance of the decoupling capacitor filler cell are/is related to the keep-out margin
Data Source
AI summary
The invention discloses a clock tree synthesis method including steps of: determining a driving strength of a clock cell; determining a reserved space corresponding to the clock cell according to the driving strength; generating the clock cell and the reserved space, wherein the reserved space is adjacent to the clock cell; setting a decoupling capacitor filler cell in the reserved space, wherein the area and/or capacitance of the decoupling capacitor filler cell are/is associated with the driving strength; and fixing the attribute(s) of the clock cell and the attribute(s) of the decoupling capacitor filler cell.