Photomask Assist Pattern Layout for Boundary Necking Control
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Solution Overview
Problem
The semiconductor manufacturing process faces the necking problem in photoresist patterns near the boundary between low and high pattern density regions, which affects pattern fidelity and process window.
Innovation Solution
A photomask structure with assist patterns on the sidewalls of layout patterns, where the lengths of these assist patterns decrease away from the boundary between low and high pattern density regions, ensuring spacings meet or exceed design rules, thereby improving pattern fidelity and process window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photomask structure is used, then manufacturing process is simple, but necking problem occurs in photoresist pattern near boundary between low and high pattern density regions
Solution Approach 1:
The photomask structure is segmented into multiple functional regions: first region with low pattern density, second region with high pattern density, and transition region with assist patterns. This segmentation allows each region to be optimized independently while preventing necking at the boundary through controlled pattern density gradients.
Solution Approach 2:
Different regions of the photomask are assigned different pattern densities locally. The first region has low pattern density, the second region has high pattern density, and the transition region has intermediate density with assist patterns. This local quality variation prevents necking by creating a gradual transition rather than a sharp boundary.
2Manufacturing precision
If assist patterns are added to prevent necking, then pattern fidelity improves, but device complexity increases
Solution Approach 1:
Assist patterns are introduced as intermediary elements between the first and second regions. These assist patterns have intermediate pattern density and act as a mediator to bridge the transition between low and high density regions, preventing necking while maintaining overall structure integrity.
Solution Approach 2:
The solution moves from a one-dimensional pattern density transition to a two-dimensional structure by adding assist patterns in the transition region. This dimensional expansion allows for controlled gradient transition that prevents necking without requiring complex three-dimensional structures.
Data Source
AI summary
A photomask structure having a first region and a second region is provided. The layout pattern density of the first region is smaller than the layout pattern density of the second region. The photomask structure includes a first layout pattern, a second layout pattern, and first assist patterns. The first layout pattern is located in the first region and the second region. The second layout pattern is located in the second region. The second layout pattern is located on one side of the first layout pattern. The first assist patterns are located on the first sidewall of the first layout pattern and separated from each other. The first sidewall is adjacent to the second layout pattern. The first assist patterns are adjacent to a boundary between the first region and the second region. The lengths of two adjacent first assist patterns decrease in the direction away from the boundary.