Semiconductor Layout Structure for SRAM Dummy Contact Isolation
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Solution Overview
Problem
In the fabrication of high-density small-sized SRAM cell arrays, the pattern density effect and optical proximity correction (OPC) lead to enlarged metal contact holes, causing electrical shorts between dummy gates and contacts, which are detrimental to circuit devices.
Innovation Solution
A semiconductor layout structure is introduced where dummy contact and gate patterns are alternately arranged with sectioned dummy contacts and gates, including inner and outer contacts/gates, and gaps are used to isolate potential short circuits formed by outer contacts/gates during enlargement due to pattern density or OPC effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dummy contact patterns are placed in the dummy region to maintain pattern density, then manufacturing uniformity is improved, but optical proximity correction enlarges the contact holes causing electrical shorts with dummy gates
Solution Approach 1:
The dummy contact pattern is segmented into multiple sections along the first direction, creating separate contact regions. This segmentation prevents the entire dummy contact from enlarging uniformly due to OPC, reducing the risk of electrical shorts while maintaining pattern density benefits.
Solution Approach 2:
Different sections of the dummy contact pattern are positioned at different distances from the cell edge region, creating local variations in their susceptibility to enlargement effects. The sectioned structure allows certain regions to accommodate controlled enlargement without causing electrical shorts.
2Stability of the object's composition
If metal contact holes are enlarged by OPC to compensate for pattern density effects, then pattern density uniformity is improved, but the enlarged contacts contact the dummy gate causing electrical shorts
Solution Approach 1:
By dividing the dummy contact pattern into multiple sections, the patent allows controlled enlargement of individual sections without causing complete contact with the dummy gate. This maintains pattern density uniformity while preventing electrical shorts.
Solution Approach 2:
The sectioned dummy contact structure acts as an intermediary between the need for pattern density uniformity and the prevention of electrical shorts. The segmented design mediates the conflict by allowing localized enlargement while maintaining overall separation from the dummy gate.
3Productivity
If the SRAM cell array is designed with high density and small size, then integrated density is improved, but pattern density effects and line-end effects cause spontaneous enlargement of metal contact holes
Solution Approach 1:
The dummy contact pattern is divided into multiple sections, which prevents uncontrolled enlargement across the entire contact structure. This segmentation maintains manufacturing precision for high-density SRAM cell arrays by limiting the propagation of enlargement effects.
Solution Approach 2:
Different sections of the dummy contact are positioned with varying characteristics, allowing local adaptation to pattern density effects and line-end effects while maintaining overall contact hole size control in high-density configurations.
Data Source
AI summary
A semiconductor layout structure includes a substrate comprising a cell edge region and a dummy region abutting thereto, a plurality of dummy contact patterns disposed in the dummy region and arranged along a first direction, and a plurality of dummy gate patterns disposed in the dummy region and arranged along the first direction. The dummy contact patterns and the dummy gate patterns are alternately arranged. Each dummy contact pattern includes an inner dummy contact proximal to the cell edge region and an outer dummy contact distal to the cell edge region, and the inner dummy contact and the outer dummy contact are arranged along a second direction perpendicular to the first direction and spaced apart from each other by a first gap.