OPC Corner Correction via Rectangular Pattern Adjustment
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Solution Overview
Problem
Current OPC methods for pattern corner correction, such as rule-based and model-based OPC, fail to effectively address corner rounding distortion in semiconductor fabrication, leading to overlay errors and coverage shortages due to the limitations of serif correction and model-based OPC in small pattern sizes and complex corner geometries.
Innovation Solution
An OPC method that involves adding or removing rectangular correction patterns from the photomask layout, specifically using rectangular patterns with diagonal lines on angle bisectors and vertices positioned relative to the target patterns, to modify the layout and improve corner correction, combined with model-based OPC for enhanced accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If rule-based OPC with serif correction is used, then corner rounding is improved for larger patterns, but it becomes inapplicable and causes overcompensation or undercompensation for smaller patterns
Solution Approach 1:
The patent changes the correction approach from fixed serif patterns to variable rectangular patterns whose dimensions and positions are adjusted based on pattern size and corner curvature characteristics. This allows the same correction method to adapt to both large and small patterns by modifying parameters such as rectangular pattern size, position, and shape factors.
Solution Approach 2:
The correction method transitions from static serif patterns to dynamic rectangular patterns that can be adjusted in size, position, and shape based on the specific corner characteristics. The correction amount and rectangular pattern dimensions are determined dynamically through calculation rather than using fixed empirical values.
2Adaptability or versatility
If model-based OPC is used, then correction can be applied under different conditions, but the correction effect is limited by the correction segment and calculation time
Solution Approach 1:
The patent segments the correction problem by focusing specifically on corner regions rather than treating the entire pattern uniformly. Rectangular patterns are added or removed at specific corner locations based on calculated shape factors, allowing precise local correction without requiring fine segmentation of the entire pattern boundary.
Solution Approach 2:
Instead of applying full model-based OPC to the entire pattern boundary, the patent applies correction selectively only at corner regions where rounding distortion is most critical. This partial action approach achieves effective corner correction while reducing calculation complexity and time requirements.
3Manufacturing precision
If corner distortion is greatly reduced, then corner rounding is improved, but it causes undulation of the straight line and worse correction results
Solution Approach 1:
The patent applies different correction strategies to different regions: rectangular patterns are added or removed specifically at corner regions to address rounding distortion, while the straight line portions maintain their original geometry. This local quality approach ensures corner correction without introducing undulation to straight line segments.
Data Source
AI summary
The present invention discloses an OPC method for a pattern corner, comprising the following steps of: S01: providing a photomask which has an original layout containing target patterns, wherein the target patterns have at least one convex corner at a vertex of two first adjacent sides with an angle of 90-degree therebetween and at least one concave corner at a vertex of two second adjacent sides with an angle of 270-degree; S02: modifying the original layout to obtain a modified layout by adding at least one first rectangular correction pattern from outside of the convex corner and/or removing at least one second rectangular correction pattern from inside of the concave corner; S03: performing a model-based OPC correction to the modified layout to obtain a corrected photomask.