Non-Uniform Illumination Profiles for Lithographic Pattern Optimization
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Solution Overview
Problem
Existing lithographic projection apparatuses face challenges in accurately reproducing patterns due to high frequency non-uniformity in illumination intensity profiles, which are not adequately addressed by current optimization methods, particularly in EUV lithographic systems like NXE 3x00 and EXE 5000, impacting imaging performance.
Innovation Solution
A method utilizing a non-uniform illumination intensity profile, specifically an open slit profile, is applied for source mask or mask only optimization, accounting for beam intercepting members to mitigate high frequency non-uniformity and enhance imaging performance by adjusting patterns and projection optics until a termination condition is satisfied.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a uniform illumination intensity profile is used for optimization, then the optimization process is simpler, but high frequency non-uniformity in illumination is not adequately addressed, worsening imaging performance
Solution Approach 1:
The patent applies local quality by using a non-uniform illumination intensity profile that specifically addresses high frequency non-uniformity regions. Instead of applying uniform optimization across the entire illumination profile, the method targets and corrects localized non-uniformity issues, allowing different regions of the illumination profile to have different intensity characteristics that compensate for known non-uniformity patterns.
2Manufacturing precision
If beam intercepting members are added to mitigate high frequency non-uniformity, then imaging performance improves, but device complexity increases
Solution Approach 1:
The patent extracts and addresses the high frequency non-uniformity component separately from the overall illumination profile. By identifying and isolating the problematic high frequency non-uniformity characteristics, the optimization method specifically targets these extracted issues using beam intercepting members, rather than attempting to correct the entire illumination profile uniformly.
3Productivity
If optimization is performed without considering non-uniform illumination, then the process is faster, but pattern reproduction accuracy deteriorates
Solution Approach 1:
The patent applies preliminary action by determining the non-uniform illumination intensity profile and identifying high frequency non-uniformity characteristics before performing the optimization of the patterning device. This pre-characterization of the illumination non-uniformity allows the subsequent optimization process to account for these known factors, improving pattern reproduction accuracy without requiring excessively long optimization times.
Data Source
AI summary
A method for source mask optimization or mask only optimization used to image a pattern onto a substrate is described. The method comprises determining a non-uniform illumination intensity profile for illumination from an illumination source; and determining one or more adjustments for the pattern based on the non-uniform illumination intensity profile until a determination that features patterned onto the substrate substantially match a target design. The non-uniform illumination intensity profile may be determined based on an illumination source and the projection optics of a lithographic apparatus. In some embodiments, the projection optics comprise a slit, and the non-uniform illumination profile is a through slit non-uniform illumination intensity profile. Determining the one or more adjustments for the pattern may comprise performing optical proximity correction, for example.