Photomask Dummy Feature Retargeting for Proximity Correction
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Solution Overview
Problem
Conventional photolithography methods face difficulties in implementing target patterns at nanometer scales due to spatial bandwidth constraints, leading to complex design rules and increased challenges in proximity correction and mask manufacturing, making it hard to maintain intended functionality and efficiency in circuit design.
Innovation Solution
A method that involves generating mask pattern data with dummy features having initial and retargeted patterns, allowing for downstream adjustments to achieve optimal photomask patterns, which simplifies the design process and improves communication between circuit designers and mask makers by separating critical and non-critical feature dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photolithography methods are used to implement target patterns at nanometer scales, then spatial bandwidth constraints are encountered, but manufacturing precision and design complexity increase significantly
Solution Approach 1:
The patent segments the photomask pattern into two distinct components: critical dimensions (CDs) that define device functionality and dummy features that are retargeted for manufacturing optimization. This segmentation allows independent optimization of each component, resolving the contradiction by maintaining CD precision while simplifying overall pattern complexity through selective retargeting of non-critical dummy features
Solution Approach 2:
The patent applies local quality by treating critical dimensions and dummy features differently. Critical dimensions maintain their original design specifications to preserve device functionality, while dummy features are locally retargeted to simplify manufacturing. This differential treatment allows manufacturing precision to be improved in critical areas without unnecessarily complicating the overall design
2Manufacturing precision
If complex design rules are applied to maintain target pattern functionality, then manufacturing precision is maintained, but proximity correction and mask manufacturing become more difficult
Solution Approach 1:
By segmenting the pattern into critical dimensions and retargetable dummy features, the patent enables simplified mask manufacturing. The segmentation allows proximity correction to focus only on critical areas while dummy features are pre-optimized, reducing the overall complexity of mask fabrication and improving ease of manufacture without sacrificing target pattern fidelity
Solution Approach 2:
The patent applies preliminary action by retargeting dummy features before mask fabrication. This pre-processing step optimizes dummy feature dimensions and positions to account for anticipated manufacturing variations and proximity effects, thereby simplifying the subsequent mask manufacturing process and reducing the need for complex real-time corrections
3Ease of manufacture
If dummy features are retargeted downstream, then mask manufacturing is simplified, but communication between circuit designers and mask makers must be improved
Solution Approach 1:
The patent introduces an intermediary data structure that preserves the relationship between original design intent and retargeted dummy features. This intermediary representation allows automated software to perform retargeting while maintaining traceability to the original design specifications, preventing loss of design intent information even as manufacturing simplicity is improved
Solution Approach 2:
The patent implements feedback mechanisms where retargeted dummy feature patterns are verified against original design specifications. This feedback loop ensures that retargeting operations do not compromise design intent, allowing manufacturing simplification while maintaining accurate communication between designers and mask makers through automated verification
Data Source
AI summary
The present disclosure is directed a method for preparing photomask patterns. The method comprises receiving drawn pattern data for a design database, the drawn pattern data describing device circuit features and dummy features. The dummy features have first target patterns. Mask pattern data is generated for the dummy features, wherein one or more of the dummy features have second target patterns that are different from the first target patterns. The mask pattern data is corrected for proximity effects.