Semiconductor Edge Cell Layout for Pattern Uniformity
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Solution Overview
Problem
The existing methods for improving pattern uniformity in semiconductor device arrays through buffer zones result in significant area overhead, as dummy devices are structurally identical but not electrically active, leading to increased chip space usage.
Innovation Solution
A nearly buffer zone free layout methodology is proposed, where edge cells with shape tolerance stress due to pattern density gradients are reconfigured from a square to a rectangular shape aspect ratio, with the long axis oriented parallel to the stress, to alleviate variability and reduce area overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a buffer zone of dummy devices is added around the array to mitigate density gradient effects, then pattern uniformity between active devices is improved, but area overhead increases significantly
Solution Approach 1:
The patent extracts only the essential function of the buffer zone (mitigating density gradient effects at array edges) while removing the dummy devices themselves. Instead, it uses reconfigured active edge cells that perform both the buffer function and the active device function, eliminating the need for separate dummy structures and reducing area overhead.
Solution Approach 2:
The edge cells are reconfigured to serve dual purposes: they maintain the array's active functionality while simultaneously providing the buffer zone effect by adjusting their pattern density. This multi-functionality eliminates the need for separate dummy buffer devices, as the edge cells themselves become the buffer.
2Area of stationary object
If edge cells are reconfigured from square to rectangular shape to reduce shape tolerance stress, then area efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies different shape configurations to different locations within the array. Edge cells are reconfigured to rectangular shapes with aspect ratios optimized for their specific position and orientation, while center cells maintain their original square configuration. This localized adaptation optimizes area efficiency at edges without unnecessarily complicating the entire array layout.
Data Source
AI summary
In some embodiments, an integrated circuit includes a central array region having a first layout feature density. A background region surrounds the central array region and has a second layout feature density, which is different from the first density. A peripheral array region surrounds the central array region and separates the central array region from the background region. The peripheral array region has a third layout feature density between the first and second layout feature densities.