Lithography Substrate Holder Sealing to Limit Immersion Liquid Intrusion
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Solution Overview
Problem
In lithographic apparatuses, the immersion liquid can contaminate the underside of the substrate and apply thermal loads due to evaporation, which affects the flatness and cleanliness of the substrate.
Innovation Solution
A substrate holder with a main body, main burls, first and second seal members, and extraction openings is designed to restrict the passage of liquid radially inward and facilitate the removal of fluid, thereby maintaining substrate cleanliness and flatness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the immersion liquid is allowed to reach the substrate edge, then the substrate can be properly supported and cooled, but the liquid contaminates the substrate underside and causes thermal loads from evaporation
Solution Approach 1:
The substrate holder is segmented into multiple functional zones: a main body for support, seal members for liquid restriction, and extraction openings for fluid removal. This segmentation allows different regions to perform specialized functions - supporting the substrate while preventing and removing liquid contamination
Solution Approach 2:
The patent extracts the harmful liquid from the substrate environment by providing extraction openings that actively remove fluid from between the substrate and holder. This takes out the contaminant before it can cause significant damage, resolving the contradiction between needing liquid presence for cooling/support and preventing contamination
2Object-affected harmful factors
If seal members are added to restrict liquid passage, then substrate cleanliness improves, but device complexity increases
Solution Approach 1:
Instead of making the entire substrate holder complex, seal members are applied locally at specific positions where liquid restriction is needed. The seal members are positioned to restrict liquid radially inward past them, providing targeted protection without unnecessary complexity elsewhere in the structure
Solution Approach 2:
The patent merges multiple functions into integrated components: seal members both restrict liquid passage and provide structural support, while extraction openings serve both cooling and contamination removal functions. This merging reduces overall device complexity compared to having separate components for each function
3Object-affected harmful factors
If extraction openings are provided to remove fluid, then substrate cleanliness improves, but device complexity increases
Solution Approach 1:
The extraction openings enable the substrate holder to self-regulate fluid removal. The system uses the natural pressure differential and flow dynamics to extract liquid without requiring complex active pumping mechanisms, achieving contamination removal through passive self-service
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The substrate holder achieves an acceptable compromise between substrate flatness and cleanliness while minimizing the passage of immersion liquid along the substrate's underside, reducing contamination and thermal loads.
Implementation Method 1
a first seal member projecting from the main body surface and having an upper surface, the first seal member surrounding the plurality of main burls and configured to restrict the passage of liquid between the substrate and the main body surface radially inward past the first seal member
Implementation Method 2
a plurality of extraction openings formed in the main body between the first seal member and the second seal member for the extraction of fluid into the main body from between the main body and the substrate
Data Source
AI summary
A substrate holder for use in a lithographic apparatus and configured to support a substrate, the substrate holder having a main body having a main body surface, a plurality of main burls projecting from the main body surface, wherein each main burl has a distal end surface configured to support the substrate, a first seal member projecting from the main body surface and having an upper surface, the first seal member surrounding the plurality of main burls and configured to restrict the passage of liquid between the substrate and the main body surface radially inward past the first seal member, and a plurality of minor burls projecting from the upper surface of the first seal member, wherein each minor burl has a distal end surface configured to support the substrate.