Substrate Table Fluid Extraction for Bubble-Free Immersion Lithography
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Solution Overview
Problem
The formation of bubbles within the immersion fluid in lithographic apparatuses can introduce defects into the image formed on substrates, as these bubbles may float into the space between the substrate and the projection system, affecting the performance of the immersion lithographic apparatus.
Innovation Solution
A substrate table with a recess and a fluid extraction system that extracts fluid from the gap between the edge of the substrate and the edge of the recess, where the rate of fluid extraction is greater in localized sections to minimize bubble formation and prevent bubbles from rising into the immersion fluid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the substrate is submersed in a large body of liquid for immersion lithography, then the refractive index is improved to enable imaging of smaller features, but turbulence and bubble formation occur leading to defects in the image
Solution Approach 1:
The patent divides the immersion liquid into two distinct regions: a first immersion liquid in contact with the substrate surface, and a second immersion liquid above it with a free surface. This segmentation prevents bubbles from forming in the critical first region while maintaining the high refractive index benefits of immersion lithography in the second region.
Solution Approach 2:
The patent extracts and removes bubbles from the immersion liquid using a bubble removal device that detects and eliminates bubbles before they can reach the substrate surface. This extraction process prevents bubbles from entering the critical imaging region while maintaining the immersion liquid's optical properties.
2Speed
If the substrate table is accelerated during scanning exposure in immersion lithography, then the exposure speed is improved, but additional motors are required and turbulence occurs leading to unpredictable effects
Solution Approach 1:
The patent introduces a gas layer as an intermediary between the substrate table and the immersion liquid. This gas cushion reduces direct contact and friction, allowing for smoother acceleration and deceleration of the substrate table without causing turbulence in the immersion liquid, thereby enabling high-speed scanning exposure with reduced device complexity.
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 enhanced fluid extraction system effectively reduces the likelihood and impact of bubbles forming in critical areas, thereby improving the performance and defectivity of the immersion lithographic apparatus by ensuring a bubble-free environment between the substrate and the projection system.
Implementation Method 1
a fluid extraction system, configured to extract fluid from a gap between the edge of the substrate and the edge of the recess
Data Source
AI summary
A substrate table for an immersion lithographic apparatus is disclosed having a recess, configured to receive a substrate of a given size, and a fluid extraction system, configured to extract fluid from a gap between the edge of the substrate and the edge of the recess, the fluid extraction system configured such that the rate of flow of fluid extracted from a localized section of the gap is greater than the rate of flow of fluid extracted from another section of the gap.