Mask Pattern Assistant Structures for Lithography Proximity Correction
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Solution Overview
Problem
In high-integration integrated circuits, the optical proximity effect leads to corner rounding and end-cap shortening during pattern transfer in photolithography, causing electrical performance issues and complicating mask pattern design with additional assistant patterns.
Innovation Solution
A mask pattern design featuring continuous patterns with assistant patterns that form closed openings, where the assistant patterns' dimensions are smaller than the photolithography tool's minimum resolution, connecting first and second patterns to reduce corner rounding and end-cap shortening, and increasing the process window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If assistant patterns are added between device patterns on the mask to reduce end-cap shortening and corner rounding, then pattern distortion is reduced, but mask pattern complexity increases and database storage space increases
Solution Approach 1:
The patent introduces assistant patterns as intermediary elements between device patterns on the mask. These assistant patterns serve as optical mediators that modify the light distribution during photolithography exposure, thereby reducing end-cap shortening and corner rounding effects on the actual device patterns without requiring changes to the device pattern geometry itself.
Solution Approach 2:
The patent applies parameter changes by adjusting the dimensions, positions, and geometries of assistant patterns relative to device patterns. By varying these parameters, the optical proximity effects are optimized to minimize pattern distortion while maintaining a manageable mask complexity level.
2Productivity
If device size is reduced and distance between devices is reduced to increase integration, then device integration increases, but optical proximity effect causes more severe pattern distortion
Solution Approach 1:
The patent segments the mask pattern into device patterns and assistant patterns, where assistant patterns are specifically placed between adjacent device patterns. This segmentation allows independent optimization of each element's geometry and position to address optical proximity effects that become more severe as device spacing decreases.
Solution Approach 2:
Assistant patterns act as optical intermediaries that modify the light field distribution between closely-spaced device patterns. By introducing these intermediary elements, the patent compensates for the increased optical proximity effects that occur when device size and spacing are reduced for higher integration.
3Manufacturing precision
If line width of transferred pattern is expanded to compensate for end-cap shortening, then pattern dimension accuracy improves, but patterns may bridge each other causing short circuits
Solution Approach 1:
The patent applies local quality by making assistant patterns have different geometries and dimensions compared to device patterns. The assistant patterns are specifically designed with dimensions smaller than the photolithography resolution limit, creating localized optical effects that compensate for end-cap shortening without causing unwanted bridging between adjacent patterns.
Solution Approach 2:
The patent uses parameter changes by setting the assistant pattern dimensions below the resolution limit of the photolithography tool. This parameter selection allows the assistant patterns to influence the optical field and compensate for pattern distortion while remaining invisible in the final transferred pattern, thus preventing short circuits.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design effectively reduces corner rounding and end-cap shortening, enhances electrical stability, and simplifies database storage by preventing assistant patterns from being printed in the photoresist or material layer, thereby improving the photolithography process.
Implementation Method 1
the deviation occurs as the pattern is transferred from the mask to the material layer in the photolithography process. That is, when a pattern on a mask is transferred onto a wafer by using the photolithography process, the corner rounding and end-cap shortening usually happen on the transferred pattern and the line width of the pattern is either increased or decreased. This kind of phenomenon is so-called optical proximity effect (OPE).
Data Source
AI summary
The invention provides a mask pattern. The mask pattern comprises at least a continuous pattern. Each of the continuous patterns has a first pattern, a second pattern and a set of assistance patterns. The assistant patterns are located between the first pattern to the second pattern. The first pattern, the assistant patterns and the second pattern together form a closed opening.