Pupil Stop with Stop Webs for Metrology Illumination Convergence
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Solution Overview
Problem
Metrology systems face challenges in achieving accurate convergence of illumination and imaging conditions, particularly in multipole illumination settings, which affects the precision of measurements in optical production systems.
Innovation Solution
A pupil stop with at least one stop web in each pole passage opening is used to improve the convergence of metrology illumination settings to production illumination settings, where the stop web's transverse dimension is small compared to the typical stop area, and the pupil stop can be arranged as an x-dipole or C-quad to ensure precise alignment and imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a multipole illumination setting is used in metrology systems, then measurement precision can be improved, but convergence accuracy between metrology and production illumination conditions deteriorates
Solution Approach 1:
The patent applies local quality by introducing stop webs with specific properties (transverse dimensions, positions, and orientations) into specific regions (pole passage openings) of the pupil stop. Each stop web is configured with particular characteristics to locally modify the illumination pattern in its corresponding pole region, enabling precise control over the illumination conditions while maintaining overall multipole configuration. This local modification allows the metrology illumination to converge accurately with production illumination conditions.
2Manufacturing precision
If stop webs are added to pole passage openings, then illumination convergence improves, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the pupil stop into multiple pole passage openings, each containing individual stop webs. The stop webs themselves are segmented structures with specific transverse dimensions and orientations. This segmentation allows independent optimization of each pole region's illumination characteristics, enabling precise control of convergence accuracy while maintaining a modular structure that manages complexity through systematic organization.
Data Source
AI summary
A pupil stop serves for use in an illumination optical unit of a metrology system for determining, as a result of illumination and imaging under illumination and imaging conditions corresponding to those of an optical production system, an aerial image of an object to be measured. The pupil stop has two pole passage openings for specifying a respective pole of an illumination of the illumination optical unit specified by the pupil stop. In each case at least one stop web passes through the respective pole passage opening and consequently divides the pole passage opening into a plurality of partial pole openings. This yields a pupil stop with which an accuracy of a convergence of the illumination and imaging conditions of the optical production system to the illumination and imaging conditions of the optical measurement system can be improved.