Lithography Source Mask Optimization with Selective OPC Constraints
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Solution Overview
Problem
Existing methods for optimizing sources and masks in lithography using Source Mask Optimization (SMO) and Optical Proximity Correction (OPC) perform these techniques independently, leading to suboptimal results, particularly in regions with dense or complex patterns, where collaborative use of SMO and OPC is not effectively utilized.
Innovation Solution
A method that selectively applies the OPC restriction rule during SMO to optimize the source and mask pattern, allowing for synergistic use of SMO and OPC, by restricting edge shifts in certain patterns and applying different processing methods to different pattern types, including the use of sub-resolution assist features and wavefront engineering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If SMO and OPC are performed independently, then the computation is simpler and faster, but the optimization effect is insufficient and the source and mask are not synergistically optimized
Solution Approach 1:
The patent combines SMO and OPC into a unified collaborative optimization framework where the source optimization in SMO considers OPC restriction rules, and the mask optimization in OPC uses the optimized source. This merging allows both techniques to work synergistically rather than independently, improving the overall optimization effect while maintaining computational efficiency through shared data structures and iterative refinement.
Solution Approach 2:
The patent implements a dynamic optimization process where the optimization approach adapts based on pattern characteristics. For hotspot patterns (dense/complex regions), collaborative SMO-OPC optimization is applied. For non-hotspot patterns, independent optimization is used. This dynamic selection of optimization strategies resolves the contradiction by applying the more computationally intensive collaborative method only where necessary.
2Adaptability or versatility
If SMO is performed without OPC restriction rules, then the source optimization is more flexible, but the correction effect of OPC is not reflected and the final mask pattern is not optimally optimized
Solution Approach 1:
The patent applies different optimization strategies to different regions of the mask pattern. OPC restriction rules are applied selectively to hotspot patterns (dense/complex regions) where collaborative optimization is beneficial, while non-hotspot patterns use independent SMO without restriction rules. This local differentiation maintains flexibility where needed while ensuring optimal optimization where collaborative approach is applied.
Solution Approach 2:
The patent performs preliminary source optimization using SMO with OPC restriction rules before executing the final OPC process. This preliminary action ensures that the source is optimized in advance with consideration of OPC constraints, so that when OPC is applied subsequently, the correction effect is maximized and the final mask pattern achieves optimal optimization.
3Manufacturing precision
If OPC restriction rules are applied to all patterns, then the collaborative optimization is maximized, but the computation time increases and the efficiency of SMO is reduced
Solution Approach 1:
The patent segments the mask pattern into hotspot regions (dense/complex patterns) and non-hotspot regions. OPC restriction rules are applied only to hotspot patterns during SMO, while non-hotspot patterns use independent SMO without restriction rules. This segmentation allows collaborative optimization to be applied selectively, maximizing the collaborative optimization effect where needed while minimizing the additional computation time required.
Data Source
AI summary
A system and method for optimizing (designing) a mask pattern, in which SMO and OPC are collaboratively used to exert a sufficient collaborative effect or are appropriately used in different manners.The method for designing a source and a mask for lithography includes a step (S1) of selecting a set of patterns; a step of performing source mask optimization (SMO) using the set of patterns, under an optical proximity correction (OPC) restriction rule which is used for selectively restricting shifting of an edge position of a polygon when OPC is applied to the set of patterns; and a step (S3, S4) of determining a layout of the mask for lithography, by applying OPC to all patterns constituting the mask for lithography using the source optimized through the SMO.