Analog Standard Cell Parasitic Capacitance Reduction
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Solution Overview
Problem
Existing analog standard cell designs face challenges in reducing parasitic capacitance, which affects the operational bandwidth of amplifiers, due to densely packed conductive features leading to increased parasitic capacitance and reduced device speed.
Innovation Solution
An analog standard cell template is introduced, featuring two active regions with a specific arrangement of conductive lines and power rails in the first metal layer, along with gate structures and contact vias, which reduces parasitic capacitance by strategically placing source/drain contacts and power rail contact vias, and utilizing a 'same-potential grouping' technique in subsequent metal layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conductive features are densely packed to increase functional density, then the number of interconnected devices per chip area increases, but parasitic capacitance increases which reduces device speed
Solution Approach 1:
The patent applies same-potential grouping by connecting contacts to the same potential node (e.g., all source contacts to ground) through shared conductive lines. This minimizes potential differences between adjacent conductive features, thereby reducing parasitic capacitance while maintaining dense packing for high functional density
Solution Approach 2:
The patent implements separate conductive line systems for different signal types: power rails for power delivery, signal lines for data transmission, and ground lines for reference potential. Each line type is optimized locally for its specific function, reducing unnecessary capacitive coupling between dissimilar signals while maintaining overall density
2Ease of manufacture
If standard cell methodology is applied to analog circuits to improve design convenience, then design efficiency increases, but cell height and feature size uniformity becomes difficult to maintain
Solution Approach 1:
The patent creates a universal analog standard cell template that can be instantiated multiple times with different functions (amplifiers, oscillators, etc.) while maintaining consistent cell height and feature size. The template includes standardized power rail locations, ground contact positions, and active region dimensions that work across different analog circuit implementations
Solution Approach 2:
The patent divides the analog standard cell into distinct functional regions: input stage, output stage, and biasing networks, each with standardized dimensions. This segmentation allows each region to be independently optimized while maintaining overall cell uniformity when instantiated in arrays
3Productivity
If scaling down is continued to increase production efficiency, then production costs decrease, but RC delay becomes more significant affecting circuit performance
Solution Approach 1:
The patent moves power delivery to the first metal layer instead of relying solely on planar scaling. By utilizing vertical dimension (multiple metal layers) for power distribution, the patent reduces the impact of horizontal scaling on RC delay, maintaining performance while benefiting from continued scaling for production efficiency
Data Source
AI summary
An analog standard cell is provided. An analog standard cell according to the present disclosure includes a first active region and a second active region extending along a first direction, and a plurality of conductive lines in a first metal layer over the first active region and the second active region. The plurality of conductive lines includes a first conductive line and a second conductive line disposed directly over the first active region, a third conductive line and a fourth conductive line disposed directly over the second active region, a middle conductive line disposed between the second conductive line and the third conductive line, a first power line spaced apart from the middle conductive line by the first conductive line and the second conductive line, and a second power line spaced apart from the middle conductive line by the third conductive line and the fourth conductive line.