Lithographic Illumination Correction Device Using Displaced Rod Stops
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Solution Overview
Problem
Current illumination intensity correction devices for lithographic projection exposure apparatuses face challenges in achieving precise correction accuracy due to the influence of field curvatures and telecentricity errors, which affect the uniformity of illumination intensity across the illumination field.
Innovation Solution
The introduction of a novel illumination intensity correction device featuring rod-shaped individual stops with adjustable displacement along their axes, allowing for precise positioning to minimize the impact of field curvatures and maintain telecentricity, utilizing a displacement drive to set intensity correction positions and employing a cooling unit to manage thermal loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the free ends of individual stops are positioned close to the arrangement plane of the illumination field, then the correction device structure is compact, but the correction accuracy is reduced due to increased influence of field curvatures and telecentricity errors
Solution Approach 1:
The patent introduces a new degree of freedom by allowing the free ends of individual stops to be positioned at different distances from the arrangement plane along the optical axis (z-direction), rather than constraining them to a single plane. This spatial dimensionality change enables independent optimization of correction accuracy while maintaining compact structure, as the distance parameter becomes an additional correction variable that can compensate for field curvature and telecentricity effects.
2Reliability
If individual stops are positioned at different distances from the arrangement plane, then field curvature influence is reduced, but the device structure becomes more complex
Solution Approach 1:
The correction device is segmented into multiple groups of individual stops, where each group consists of stops with different distances from the arrangement plane. This segmentation allows each group to address specific field curvature variations, thereby improving illumination uniformity across the field while keeping each individual stop group relatively simple in structure.
Solution Approach 2:
Different regions of the correction device have different local qualities in terms of stop positioning. Stops in different groups are positioned at different distances from the arrangement plane, creating local variations in correction strength and characteristics. This local quality differentiation enables optimized correction for different field regions while maintaining overall device functionality.
3Measurement precision
If the correction device is positioned closer to the illumination field, then the correction effect is stronger, but telecentricity errors increase
Solution Approach 1:
The patent utilizes parameter changes by varying the distance parameter of individual stops from the arrangement plane. This parameter variation allows the correction device to achieve strong correction effectiveness at close distances while compensating for telecentricity errors through the different distance positioning of stops in different groups, effectively decoupling correction strength from telecentricity error introduction.
Data Source
AI summary
An illumination intensity correction device can specify an illumination intensity over an illumination field of a lithographic projection exposure apparatus. The correction device has a plurality of rod-shaped individual stops arranged next to one another. A displacement drive can displace at least some of the individual stops at least along their respective rod axis. Free ends of the individual stops are individually displaceable using the displacement drive into a specified displacement position to specify an intensity correction of an illumination of the illumination field. The intensity correction acts along a correction dimension transverse with respect to the rod axes.