Lithography Mask Contour Rounding for Nanoscale Precision
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Solution Overview
Problem
Current lithographic techniques face challenges in accurately reproducing small features due to the limitations of mask manufacturing, where real manufactured masks have rounded corners instead of sharp corners, leading to model errors and inconsistencies, especially at the nanoscale.
Innovation Solution
A method is developed to generate rounded contours for lithographic mask patterns by converting contour representations into 1D representations, applying filters to distinguish and smooth corner types, and updating contour points to create continuous and smooth rounded contours, supporting anamorphic cases and varying rounding behaviors at inner and outer corners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sharp corners are used in mask pattern design, then design precision is improved, but manufacturing accuracy deteriorates due to rounded corners in real manufactured masks
Solution Approach 1:
The patent applies preliminary action by pre-rounding the corners in the mask pattern design before manufacturing. The rounding radius is carefully selected to match the actual manufacturing rounding behavior, so that the designed rounded corners produce the intended sharp features in the final printed pattern. This anticipates the manufacturing distortion and compensates for it in advance.
Solution Approach 2:
The patent changes the geometric parameters of the mask pattern by introducing controlled rounding radii at corners. Instead of using sharp 90-degree corners, the design incorporates rounded corners with specific radii that compensate for manufacturing-induced rounding, thereby maintaining the intended feature dimensions and shapes in the final product.
2Manufacturing precision
If rounded contours are applied to mask patterns, then manufacturing accuracy is improved, but model consistency deteriorates due to inconsistencies in rounding behavior at different corner types
Solution Approach 1:
The patent applies local quality by treating different corner types (inner corners, outer corners, re-entrant corners) differently in the rounding model. Each corner type is assigned a specific rounding radius based on its geometric characteristics and manufacturing behavior. This localized approach ensures that each corner is rounded appropriately while maintaining overall model consistency and predictability.
3Reliability
If continuous mask patterns are generated, then manufacturing robustness is improved, but computational complexity increases due to sophisticated filtering and contour updating
Solution Approach 1:
The patent applies segmentation by dividing the contour processing into discrete segments between corners. The filtering and rounding operations are applied segment-by-segment rather than to the entire contour at once. This segmented approach ensures continuous mask patterns while managing computational complexity through localized processing.
Data Source
AI summary
A methods and systems for determining rounded contours of target contours or other lithography related contour for mask design. The method includes converting a contour representation to (i) a first set of contour point locations in a first dimension (e.g., x) and (ii) a second set of contour point locations in a second dimension (e.g., y). A signal function is determined based on the first and second sets of contour point locations, the signal function indicative of different segments of the contour representation. The first set of contour point locations is updated based on a first filter function and the signal function, and the second set of contour point locations is updated based on a second filter function and the signal function. Based on the updated contour point locations, a rounded contour of the contour representation is generated.