Tap Cell Pitch Layout for Latch-Up-Immune Integrated Circuits
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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 size, necessitating the use of tap cells to reduce substrate resistance and positive feedback, but these cells can enlarge the IC.
Innovation Solution
A layout is generated for ICs by strategically placing tap cells, transistors, and interconnect metallization patterns to minimize latch-up risk, with high-risk regions receiving more tap cells or adjusted operating voltages, and using a scoring system to determine risk areas and optimize tap cell placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If transistors are placed closer together to miniaturize the IC, then functional density increases and power consumption decreases, but latch-up risk increases due to shorter distances between transistors
Solution Approach 1:
The patent introduces tap cells as intermediary structures between transistors. These tap cells include substrate taps that extend into the substrate and are connected to power rails, acting as mediators to provide alternative current paths and reduce the direct coupling between adjacent transistors, thereby preventing latch-up while maintaining miniaturization
Solution Approach 2:
The patent segments the substrate by inserting tap cells at regular intervals between transistors. Each tap cell divides the substrate region into smaller segments, creating isolation zones that prevent the propagation of latch-up currents across the entire IC while maintaining compact dimensions
2Reliability
If tap cells are added to reduce substrate resistance and prevent latch-up, then reliability improves, but IC size increases
Solution Approach 1:
The patent applies partial action by strategically placing tap cells only in critical regions where latch-up risk is highest, rather than uniformly across the entire IC. The spacing between tap cells is optimized to provide sufficient protection while minimizing the total number of tap cells required, thus reducing area overhead
Solution Approach 2:
The patent changes the parameter of tap cell spacing to optimize the balance between reliability and size. By adjusting the distance between adjacent tap cells, the design achieves adequate latch-up protection with minimal area penalty, adapting the spacing parameter based on specific IC layout requirements
Data Source
AI summary
An integrated circuit includes a semiconductor substrate, devices, first tap regions, and second tap regions. The devices are over the semiconductor substrate. The first tap regions are over the semiconductor substrate along a first direction. The second tap regions are over the semiconductor substrate along the first direction. A first pitch between adjacent two of the first tap regions in the first direction is greater than a second pitch between adjacent two of the second tap regions in the first direction.