Multi-Layer Power Rail Layout for Electromigration Reduction
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Solution Overview
Problem
Existing semiconductor designs face challenges in reducing electromigration during the layout and design phase, leading to potential circuit failures and delays in product delivery due to electromigration rule violations, which are costly and detrimental to customer relations.
Innovation Solution
The proposed solution involves separating power and ground rails from the cells and fingers by placing them on different layers, with vias connecting them, thereby reducing electromigration by altering the evaluation criteria for electromigration rules and avoiding design errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If power rail and fingers are placed on the same layer to reduce manufacturing steps, then manufacturing complexity is reduced, but electromigration risk increases
Solution Approach 1:
The patent transitions from a two-dimensional same-layer configuration to a three-dimensional multi-layer configuration. Power rails are placed on one layer while fingers are placed on adjacent layers, connected through vertical vias. This spatial separation in the vertical dimension reduces electromigration risk by altering current distribution while maintaining manufacturing feasibility through standard multi-layer semiconductor processes.
2Reliability
If electromigration rules are enforced strictly during design review, then circuit reliability is improved, but design cycle time increases
Solution Approach 1:
The patent implements electromigration mitigation measures during the initial layout design phase rather than as a corrective action during later design review. By pre-structuring the power delivery network with separated rails and fingers connected via vias, the design inherently satisfies electromigration requirements, eliminating the need for time-consuming iterative corrections and allowing parallel processing of design and verification activities.
3Reliability
If layout redesign is performed to fix electromigration violations, then electromigration compliance is achieved, but product delivery is delayed
Solution Approach 1:
The multi-layer power finger structure is implemented as a default design template from the beginning of the design process. This preliminary structuring ensures electromigration compliance is built-in rather than added later, allowing the design team to proceed with fabrication without time-consuming redesign cycles and maintaining aggressive product delivery schedules.
4Reliability
If multiple vias are used to connect power rails to fingers on different layers, then electromigration is reduced, but device complexity increases
Solution Approach 1:
The patent segments the power delivery function into separate components: power rails on one layer, fingers on adjacent layers, and connecting vias. This segmentation distributes the current path across multiple discrete elements, reducing current density in any single conductor and mitigating electromigration. The segmentation is implemented using standard semiconductor manufacturing capabilities, avoiding excessive 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
This approach enhances semiconductor reliability and manufacturing efficiency by minimizing electromigration, allowing for faster design realization and reducing the risk of circuit failures.
Implementation Method 1
one or more power vias electrically connecting the power rail to the power finger such that the one or more power vias extending from the first layer to the second layer, and one or more ground vias electrically connecting the ground rail to the ground finger
Implementation Method 2
Electromigration is the movement of atoms based on the flow of current through a material. As the current density in a conductor increases, the heat dissipated within the material will repeatedly break atoms from the conductive structure and dislodge and move the atoms.
Data Source
AI summary
A semiconductor circuit configured to reduce electromigration. The circuit comprises a power rail and ground rail located on a first layer. A power finger and a ground finger are located on a second layer. Cells are located on the second layer, such that the one or more cells are electrically connected to a power finger and a ground finger. The circuit also includes one or more power vias electrically connecting the power rail to the power finger. The one or more power vias extend from the first layer to the second layer. One or more ground vias electrically connecting the ground rail to the ground finger, such that the one or more ground vias extend from the first layer to the second layer. The placement of the fingers on a different level than the rails establishing the fingers as non-contiguous sections thereby reducing electromigration and overcoming design analysis errors.