Back-Side Power Rail Placement for IC Reliability
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Solution Overview
Problem
The miniaturization of integrated circuits poses challenges in design and manufacturing, including stricter specifications and reliability issues, particularly in optimizing standard cell layout designs for better current resistance, electromigration, and resistance capacitance performance.
Innovation Solution
The solution involves positioning power rails and signal lines on the back-side of the substrate, which reduces the need for upper metal layer tracks, increases gate density, and enhances routing flexibility and resources by electrically coupling gates and contacts, thereby improving current resistance, electromigration, and resistance capacitance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If power rails and signal lines are positioned on the front-side using upper metal layer tracks, then routing is provided, but current resistance, electromigration, and resistance capacitance performance deteriorate
Solution Approach 1:
The patent moves power rails and signal lines from the front-side (upper metal layers) to the back-side of the substrate, utilizing the z-dimension (vertical stacking) to separate power/signal routing from logic circuit routing. This dimensional reorganization improves electrical performance by providing dedicated, lower-resistance paths while maintaining compact front-side layout.
2Area of stationary object
If upper metal layer tracks are used for power rails and signal lines, then routing is achieved, but the height and area of the layout increase
Solution Approach 1:
By relocating power rails and signal lines to the back-side of the substrate and utilizing cross-substrate vias for vertical connections, the patent eliminates the need for additional upper metal layer tracks. This reduces the overall layout height while improving electrical performance through dedicated routing paths.
3Area of moving object
If standard cell layout design is miniaturized, then device size is reduced and power consumption decreases, but design and manufacturing specifications become stricter and reliability challenges increase
Solution Approach 1:
The patent segments the routing function into two distinct domains: front-side for logic circuit interconnections and back-side for power and signal distribution. This segmentation allows each layer to be optimized independently, enabling miniaturization of the logic circuitry while maintaining robust power and signal routing that meets stringent design and manufacturing specifications.
4Adaptability or versatility
If upper metal layer tracks are used for routing, then power rails and signal lines can be implemented, but routing flexibility and resources are limited
Solution Approach 1:
The patent creates additional routing resources by utilizing the back-side of the substrate for power rails and signal lines, independent of the front-side logic routing. This vertical separation provides enhanced routing flexibility without increasing front-side layout complexity, as the two sides can be designed and optimized separately.
Data Source
AI summary
An integrated circuit includes a first power rail, a second power rail, a signal line and a first active region of a first set of transistors. The first power rail is on a back-side of a substrate, and extends in a first direction. The second power rail is on the back-side of the substrate, extends in the first direction, and is separated from the first power rail in a second direction different from the first direction. The signal line is on the back-side of the substrate, and extends in the first direction, and is between the first power rail and the second power rail. The first active region of the first set of transistors extends in the first direction, and is on a first level of a front-side of the substrate opposite from the back-side.