Mirror-Patterned SRAM Array Layout for Better Exposure Quality
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Solution Overview
Problem
Current SRAM architectures face challenges in producing desirable patterns as the gap of the exposure process decreases, making it difficult to enhance exposure quality.
Innovation Solution
A static random access memory (SRAM) array pattern is designed with a substrate and four regions, where each region partially overlaps, and SRAM cells share elements like contact plugs, simplifying the manufacturing process and reducing cell area by using a 2X2 array layout with mirror-patterned SRAM cells along a horizontal axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the exposure process gap is reduced to increase memory density, then the storage capacity is improved, but the exposure quality and manufacturing precision deteriorate
Solution Approach 1:
The patent applies asymmetry by using mirror-patterned layouts where adjacent SRAM cells have inverted orientations. This asymmetric arrangement within a symmetric framework allows the exposure process to maintain precision even as gap distances are reduced, because the alternating patterns create self-aligning features that are less sensitive to exposure variations.
Solution Approach 2:
The SRAM array is segmented into repeating units of four cells arranged in a 2x2 block pattern. This segmentation allows each small unit to be optimized independently while maintaining overall array functionality. The segmented mirror-patterned design enables better control over exposure processes at reduced gap dimensions.
2Area of stationary object
If the SRAM cell area is reduced to increase array density, then the storage density is improved, but the manufacturing complexity increases
Solution Approach 1:
Adjacent SRAM cells are merged to share common elements such as contact plugs, word lines, and bit lines. In the mirror-patterned 2x2 array, cells share boundary elements, reducing the total number of discrete components. This merging reduces cell area while the regular repeating pattern maintains manufacturing simplicity through standardization.
Solution Approach 2:
The patent implements universality by using identical or mirrored layouts for all SRAM cells in the array. Each cell type serves multiple functions: storage, sharing contact plugs with neighbors, and providing self-aligned patterns for exposure. This universal design simplifies manufacturing by reducing the number of unique layout rules that must be followed.
3Productivity
If the exposure gap is decreased to increase integration density, then the array density is improved, but the pattern formation quality worsens
Solution Approach 1:
The mirror-patterned asymmetric layout within symmetric 2x2 blocks creates self-aligning features that maintain pattern formation quality even at reduced exposure gaps. The alternating orientations produce complementary patterns that are more robust to exposure process variations, allowing higher array density without sacrificing pattern quality.
Solution Approach 2:
The patent changes the layout parameter arrangement by using mirror images instead of identical repetitions. This parameter transformation (from translation-only symmetry to reflectional symmetry) improves pattern formation robustness at reduced gap dimensions, as the mirror patterns create self-correcting alignment features that maintain quality despite smaller exposure margins.
Data Source
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AI summary
The invention provides a static random access memory (SRAM) array pattern, which comprises a substrate, a first region, a second region, a third region and a fourth region are defined on the substrate and arranged in an array, each region partially overlaps with the other three regions, and each region contains a SRAM cell, the layout of the SRAM cell in the first region is the same as that in the third region, the layout of the SRAM cell in the second region is the same as that in the fourth region, and the layout of the SRAM cell in the first region and the layout of the SRAM cell in the fourth region are mirror patterns along a horizontal axis.