Lithography Assist Features for Across Slit Asymmetry Compensation
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Solution Overview
Problem
Current lithographic projection technologies face challenges in reproducing patterns with features smaller than the classical resolution limit, leading to difficulties in achieving desired electrical functionality and performance due to across slit asymmetry during multifocal imaging, which affects the symmetry and placement of target features on substrates.
Innovation Solution
The introduction of assist features in the design layout, placed based on different focus positions, to reduce the shift caused by across slit asymmetry, achieved by shifting the design layout and optimizing numerical aperture, sigma, best focus, and wavelength peak separation, thereby enhancing target feature symmetry and placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multifocal imaging is used to pattern substrates, then manufacturing productivity is improved, but across slit asymmetry causes image shift that deteriorates target feature symmetry and placement precision
Solution Approach 1:
The patent applies asymmetry by introducing assist features with asymmetric patterns (such as asymmetric line widths, spacing, or positions) that specifically compensate for the across-slit asymmetry caused by multifocal imaging. These asymmetric assist features are strategically placed to counterbalance the image shift, thereby restoring target feature symmetry and placement accuracy while maintaining the productivity benefits of multifocal imaging.
Solution Approach 2:
The patent employs parameter changes by adjusting optical parameters (such as numerical aperture, wavelength, or focus positions) and assist feature parameters (such as size, position, and pattern geometry) to optimize the compensation effect. By varying these parameters, the system achieves better control over the image shift while maintaining high manufacturing productivity through multifocal imaging.
2Manufacturing precision
If assist features are added to compensate for image shift, then target feature placement precision is improved, but design layout complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the assist feature compensation into discrete, modular elements that can be independently designed and positioned. Rather than implementing a complex global adjustment, the system uses multiple simple assist features placed at specific locations around target features, making the design layout more manageable while achieving precise target feature placement compensation.
Solution Approach 2:
The patent uses assist features as intermediary elements that mediate between the imaging system's inherent asymmetry and the desired symmetric target feature placement. These assist features act as intermediate structures that absorb and compensate for the image shift, simplifying the overall design by providing a straightforward mechanism to achieve placement precision without requiring complex direct adjustments to the target features themselves.
Data Source
AI summary
Enhancing target features of a pattern imaged onto a substrate. This may include adding one or more assist features to a patterning device pattern in one or more locations adjacent to one or more target features in the patterning device pattern. The one or more assist features are added based on two or more different focus positions in the substrate. This can also include shifting the patterning device pattern and/or a design layout based on the two or more different focus positions and the one or more added assist features. This may be useful for improving across slit asymmetry. Adding the one or more assist features to the pattern and shifting the pattern and/or the design layout enhances the target features by reducing a shift caused by across slit asymmetry for a slit of a multifocal lithographic imaging apparatus. This may reduce the shift across an entire imaging field.