SRAM Cell Layout With Oblique Metal Connection for Higher Density
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Solution Overview
Problem
The increasing complexity and reduced geometric size of integrated circuits have made it challenging to improve the density and reduce the cell size of Static Random Access Memory (SRAM) cells while maintaining efficient read and write speeds.
Innovation Solution
The implementation of oblique connections in the form of two-dimensional metal electrodes within the lowest metal layer of SRAM cells, utilizing double-patterning or multi-patterning processes, to enhance pitch and reduce cell height, thereby increasing SRAM density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional SRAM cell structures are used, then manufacturing process is simpler, but SRAM density is lower and cell size is larger
Solution Approach 1:
The patent introduces oblique connections that extend diagonally across multiple metal layers, transforming the traditional planar connection approach into a three-dimensional spatial arrangement. This dimensional change allows pitch enhancement and cell height reduction simultaneously, achieving higher SRAM density without proportionally increasing manufacturing complexity
Solution Approach 2:
The patent divides the connection path into multiple segments across different metal layers (first metal layer, second metal layer, third metal layer) with intermediate connection structures. This segmentation allows the oblique connection to achieve pitch enhancement through vertical layering while maintaining manufacturability through standardized layer-by-layer fabrication processes
2Quantity of substance
If cell size is reduced to increase density, then SRAM density improves, but read and write speeds deteriorate
Solution Approach 1:
By moving connections into the vertical dimension across multiple metal layers, the patent reduces the horizontal footprint of SRAM cells, enabling higher density. The oblique connection geometry maintains adequate current flow paths despite reduced cell dimensions, preserving read and write speeds while achieving compact cell layouts
3Shape
If oblique connections are implemented, then pitch is enhanced and cell height is reduced, but manufacturing complexity increases
Solution Approach 1:
The oblique connection is segmented into discrete portions formed in different metal layers with standardized patterning processes. Each layer uses conventional photolithography and etching steps, making the complex three-dimensional structure manufacturable through repeated application of standard fabrication techniques rather than requiring novel complex processes
Solution Approach 2:
The patent establishes the oblique connection geometry through preliminary patterning in lower metal layers before completing upper layer interconnects. This preliminary action defines the pitch-enhanced footprint early in the fabrication sequence, allowing subsequent layers to be formed using standard alignment and patterning processes
Data Source
AI summary
A memory structure is provided. The memory structure includes a first pull-up transistor in a first active region, a second pull-up transistor in a second active region parallel to and separated from the first active region, and an electrode overlapping the first and second active regions and configured to electrically connect a gate structure of the second pull-up transistor to a drain region of the first pull-up transistor. The electrode is formed in a metal layer closest to the first and second active regions.