Immersion Lithography Liquid Removal Device
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Solution Overview
Problem
In lithographic apparatuses, efficiently removing liquid from the gap between a substrate and the substrate table is challenging, especially when the whole top surface of the substrate is covered in immersion liquid, leading to liquid accumulation and turbulence issues during scanning exposure.
Innovation Solution
A liquid removal device with an elongated extractor connected to an under-pressure source, configured to move relative to the substrate table, generates a gas flow along the gap towards the outlet by orienting its tangent at an angle between 20° and 90° relative to the gap's tangent, enhancing liquid extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If liquid is supplied to fill the space between the final element and substrate during immersion lithography, then imaging resolution is improved due to shorter wavelength in liquid, but liquid accumulation in the gap between substrate and substrate table causes turbulence and operational instability
Solution Approach 1:
The patent extracts and removes liquid from the gap between the substrate and substrate table using a liquid removal device with suction outlets, preventing liquid accumulation while maintaining immersion liquid in the imaging space, thus resolving the contradiction between improved imaging resolution and operational stability
Solution Approach 2:
The patent uses a liquid removal device with suction outlets connected to a vacuum source to create negative pressure and remove liquid from the gap, applying pneumatic principles to control liquid distribution and eliminate turbulence without affecting the immersion lithography process
2Productivity
If the substrate is scanned during exposure, then productivity is improved, but liquid turbulence increases due to acceleration of the large body of liquid
Solution Approach 1:
The liquid removal device continuously extracts liquid from the gap between substrate and substrate table during scanning, preventing turbulence caused by substrate acceleration while maintaining steady liquid levels, enabling high-speed scanning without compromising operational stability
Solution Approach 2:
The patent changes the liquid level parameter by actively removing liquid from the gap, transforming the liquid state from a large accelerated body causing turbulence to a controlled thin layer that remains stable during high-speed substrate scanning
3Reliability
If a liquid confinement system is used to supply liquid only on localized area, then device complexity increases, but liquid accumulation is reduced
Solution Approach 1:
The liquid removal device with multiple suction outlets automatically removes liquid from the gap based on liquid accumulation, providing self-regulating liquid level control without requiring complex confinement systems, thus improving reliability while maintaining simplicity
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 effectively removes liquid from the gap between the substrate and the substrate table, minimizing turbulence and ensuring efficient drying of the substrate surface, thereby improving the operational stability and precision of the lithographic process.
Implementation Method 1
generates a gas flow along the gap towards the outlet
Implementation Method 2
connected to an under-pressure source
Data Source
AI summary
A method of removing liquid from a substrate supported on a substrate table and from a gap between the substrate and the substrate table includes: providing a liquid removal device with at least one outlet connected to an under pressure source, the outlet forming an elongated extractor of a predetermined geometry; relatively moving the substrate table and the liquid removal device such that the extractor is adapted to pass over all of the substrate and gap and such that substantially at any given time any local part of the extractor at the edge of a non-dried portion of the gap has, in a plane, its local tangent orientated at an angle of between about 35° and 90° to the local tangent of the gap.