IC Layout With Asymmetric Tap Spacing for Latch-Up Immunity
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Solution Overview
Problem
As integrated circuits (ICs) miniaturize, they face challenges such as latch-up, a type of short circuit, due to the closer proximity of transistors, which can lead to reliability issues and increased chip size from the use of tap cells to prevent latch-up.
Innovation Solution
A layout is generated for ICs that strategically places tap cells and transistors in an arrangement less likely to induce latch-up, with high-risk regions identified and either increased tap cell placement or voltage adjustments made to prevent latch-up, while optimizing chip area usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tap cells are placed closer to transistors to prevent latch-up, then reliability improves, but chip area increases
Solution Approach 1:
The patent applies local quality by differentiating tap cell placement strategies based on regional latch-up risk assessments. High-risk regions receive enhanced tap cell protection, while low-risk regions use minimal or no tap cells, optimizing the balance between reliability and chip area utilization.
Solution Approach 2:
The patent implements preliminary action through pre-characterization of latch-up risk across different chip regions before final tap cell placement. This allows the design process to proactively identify high-risk areas and allocate tap cells accordingly, rather than using uniform placement throughout the chip.
2Productivity
If transistors are placed closer together to increase functional density, then productivity improves, but latch-up risk increases
Solution Approach 1:
The patent enables high transistor density in low-risk regions by implementing region-specific design rules. Different minimum spacing requirements are applied based on the latch-up risk characterization of each region, allowing maximum density where safe and adequate spacing where necessary.
Solution Approach 2:
The patent performs preliminary latch-up risk characterization and establishes region-specific design rules before transistor placement. This allows the placement tool to optimize transistor density in each region according to pre-determined safety margins, achieving high overall density while maintaining reliability.
3Ease of manufacture
If uniform tap cell placement is used across the chip, then manufacturing simplicity improves, but chip area increases
Solution Approach 1:
The patent replaces uniform tap cell placement with localized placement based on region-specific latch-up risk. This maintains manufacturing simplicity through automated tools while significantly reducing the number of tap cells required compared to uniform placement across the entire chip.
Data Source
AI summary
An integrated circuit includes a semiconductor substrate, first tap regions, second tap regions, and first gate structures. The semiconductor substrate includes a first active region. The first and second tap regions in the semiconductor substrate and on opposite sides of the first active region. The first gate structures are over the first active region. A distance between the first tap region and a first one of the first gate structures adjacent the first tap region is greater than a distance between the second tap region and a second one of the first gate structures adjacent the second tap region.