Immersion Lithography Substrate Holder for Edge Sealing and Liquid Extraction
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Solution Overview
Problem
In lithographic apparatuses, the immersion liquid can contaminate the substrate's under surface and cause thermal issues due to evaporation, especially near the edge, affecting the substrate's flatness and cleanliness.
Innovation Solution
A substrate holder with a main body, main burls, and multiple seal members is designed to restrict the passage of liquid radially inward, featuring extraction openings and inlet openings to manage fluid and gas flow, ensuring the substrate's edge is supported and minimizing liquid contact with the under surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the immersion liquid is allowed to reach the under surface of the substrate, then the substrate edge can be supported, but the substrate becomes contaminated and experiences thermal loads
Solution Approach 1:
The substrate holder is segmented into multiple functional zones: an outer region with an outer seal member for substrate edge support, and an inner region with an inner seal member and extraction openings for liquid management. This segmentation allows different parts of the substrate holder to perform different functions - supporting the substrate edge while preventing liquid contamination in the imaging area.
Solution Approach 2:
Extraction openings are provided in the inner region of the substrate holder to actively remove immersion liquid from between the substrate and the holder. This extraction mechanism prevents liquid from reaching the under surface of the substrate in the imaging area, thereby eliminating contamination and thermal load issues while still allowing liquid presence in the outer support region.
2Object-affected harmful factors
If seal members are added to restrict liquid passage, then substrate cleanliness is improved, but device complexity increases
Solution Approach 1:
Different regions of the substrate holder are given different sealing properties: the outer seal member in the outer region provides a first level of sealing for substrate support, while the inner seal member in the inner region provides a second level of sealing for liquid restriction. Each seal member is positioned and configured to address specific local requirements, optimizing cleanliness without unnecessary complexity throughout the entire structure.
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
This design enhances the substrate's flatness and cleanliness by reducing liquid contact and thermal loads, facilitating easier substrate removal and maintaining imaging quality.
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.