Substrate Centering in Immersion Lithography Chucks
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Solution Overview
Problem
In immersion lithographic apparatuses, determining and correcting for the offset between the center of a substrate and the center of a depression in a chuck is crucial to prevent liquid seepage and ensure precise substrate placement, as inaccuracies can lead to instability in the gas seal and hinder the manufacturing process.
Innovation Solution
A method involving the use of a test substrate to measure the offset between the substrate's center and the chuck's center, utilizing optical systems and prealigners to determine the gap and center positions, and calibrating the substrate handler to correct for these offsets, ensuring precise substrate positioning and minimizing the gap between the substrate and chuck edges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the substrate is immersed in a liquid bath for lithography, then imaging resolution is improved due to shorter wavelength in liquid, but liquid turbulence and instability occur during substrate scanning
Solution Approach 1:
The patent extracts the liquid from the entire substrate area and confines it only to the exposure area between the final element and the substrate. This is achieved through a localized liquid supply system with inlets and outlets positioned to provide liquid only where needed during scanning, eliminating liquid turbulence while maintaining immersion lithography benefits in the exposure zone.
2Quantity of substance
If liquid is supplied along the direction of substrate movement, then localized liquid supply is achieved, but liquid flow instability and turbulence may occur
Solution Approach 1:
The patent applies local quality by providing liquid only in the specific region between the final element and the substrate during scanning, rather than across the entire substrate. The liquid supply system uses strategically positioned inlets and outlets to create localized liquid presence only where optical immersion is required, maintaining stability elsewhere.
3Manufacturing precision
If the substrate center is misaligned with the chuck depression center, then substrate placement error occurs, but liquid seepage and gas seal instability result
Solution Approach 1:
The patent applies preliminary action by measuring the offset between substrate center and chuck depression center using a test substrate with alignment marks before actual production. The measured offset is stored and used to pre-correct substrate handler positioning, ensuring substrates are accurately centered in the depression during normal operation, preventing liquid seepage and maintaining gas seal stability.
Data Source
AI summary
A method for determining an offset between a center of a substrate and a center of a depression in a chuck includes providing a test substrate to the depression, the test substrate having a dimension smaller than a dimension of the depression, measuring a position of an alignment mark of the test substrate while in the depression, and determining the offset between the center of the substrate and the center of the depression from the position of the alignment mark.