Retractable Bridge Immersion Lithography Liquid Loss
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Solution Overview
Problem
In immersion lithographic apparatuses, there is a challenge in maintaining the flow of immersion liquid during substrate swaps without causing temperature fluctuations or contamination, which can lead to defects and reduced throughput due to potential liquid loss and physical contact issues.
Innovation Solution
A retractable bridge system is implemented to maintain liquid flow between substrate tables during swaps, using a fluid extraction system with strategically placed extraction openings to minimize liquid loss and prevent bubble entrapment, while ensuring the bridge does not physically contact the substrate table to avoid contamination and temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If liquid is supplied to fill the space between the projection system and substrate during immersion lithography, then imaging resolution is improved, but liquid loss and turbulence occur during substrate scanning
Solution Approach 1:
A retractable bridge is introduced as an intermediary component between the substrate table and the liquid supply system. The bridge maintains the liquid seal during substrate swaps without requiring full substrate submersion, thereby preventing liquid loss while preserving imaging resolution during actual exposure operations
Solution Approach 2:
The bridge is designed to be retractable rather than fixed, allowing it to dynamically adjust its position. During substrate swaps, the bridge retracts to avoid interference, while during exposure it extends to maintain the liquid seal, thus preventing liquid loss without compromising imaging quality
2Measurement precision
If substrate is submersed in liquid bath during scanning exposure, then imaging resolution is improved, but additional motors and turbulence are required
Solution Approach 1:
The invention extracts the liquid supply function from the substrate table itself and relocates it to a separate liquid supply system with a retractable bridge. This separation eliminates the need for complex motor systems on the substrate table while maintaining liquid immersion during exposure, thus reducing device complexity without sacrificing imaging resolution
3Productivity
If liquid confinement system is used during substrate swap, then liquid flow is maintained, but physical contact causes contamination and temperature changes
Solution Approach 1:
The retractable bridge serves as a non-contact intermediary that maintains liquid flow continuity during substrate swaps. By using optical or electromagnetic fields rather than physical contact, the bridge prevents contamination and temperature changes while ensuring liquid flow is maintained for continuous substrate processing
4Loss of substance
If shutter member is positioned under liquid confinement structure, then liquid loss is prevented, but bubble entrapment and defects occur
Solution Approach 1:
The retractable bridge acts as an intermediary that maintains liquid confinement without creating the trapping conditions associated with traditional shutters. Its design allows liquid to flow smoothly beneath it during substrate swaps, preventing both liquid loss and bubble entrapment simultaneously
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 solution reduces contamination, maintains consistent temperature, and increases throughput by minimizing liquid loss and bubble entrapment during substrate swaps, enhancing the overlay performance and defectivity of the immersion system.
Implementation Method 1
a fluid extraction system configured to remove liquid from the gap through an extraction opening in a side wall surface of the shutter member and/or of the substrate table
Implementation Method 2
the liquid is distilled water, although another liquid can be used. An embodiment of the present invention will be described with reference to liquid. However, another fluid may be suitable, particularly a wetting fluid, an incompressible fluid and/or a fluid with higher refractive index than air
Data Source
AI summary
A lithographic projection apparatus is disclosed that includes a table, a shutter member, a fluid handling structure, and a fluid extraction system. The fluid handling structure may be configured to supply and confine liquid between a projection system and (i) a substrate, or (ii) the table, or (iii) a surface of the shutter member, or (iv) a combination selected from (i)-(iii). The surface of the shutter member may adjoin and be co-planar with a surface of the table. The surfaces of the shutter member and the table may be spaced apart by a gap. The fluid extraction system may be configured to remove liquid from the gap.