Retractable Bridge for Immersion Lithography Substrate Tables
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Solution Overview
Problem
In immersion lithography, swapping substrates underneath the projection system without draining the liquid supply system is challenging due to the risk of drying stains on the final element and contamination, which reduces throughput and increases the risk of contamination.
Innovation Solution
A lithographic apparatus with moveable substrate tables that have a retractable bridge to maintain the liquid supply system intact during substrate swapping, ensuring that the top surfaces of the tables are close enough to prevent liquid leakage and allowing for simultaneous movement under the projection system without draining the liquid supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the liquid supply system is drained to swap substrate tables, then substrate swapping can be performed, but drying stains appear on the final element and contamination risk increases
Solution Approach 1:
The substrate table is designed with a moveable protrusion that can dynamically change position between a first position (forming an outer edge) and a second position (not forming an outer edge). This dynamic reconfiguration allows the table to adapt its geometry to prevent liquid leakage during swapping while maintaining proper liquid confinement during operation.
Solution Approach 2:
The substrate table is divided into functional segments including the moveable protrusion and the main table body. The protrusion can be independently positioned to either define the liquid confinement boundary or be retracted, allowing selective control over liquid containment without draining the entire supply system.
2Productivity
If the liquid supply system remains active during substrate swapping, then throughput improves, but liquid leakage occurs between substrate tables
Solution Approach 1:
The moveable protrusion dynamically adjusts its position during the swapping process. When substrate tables need to be positioned close together, the protrusion is in the first position to form a seal and prevent leakage. During normal operation, it can be retracted to the second position.
Solution Approach 2:
The moveable protrusion acts as an intermediary element between the substrate table and the liquid supply system. It creates a temporary seal or barrier that prevents liquid from leaking into the gap between tables during swapping, while allowing the liquid supply to remain active.
3Reliability
If substrate tables are moved close together under the projection system, then liquid leakage is prevented, but the tables cannot be easily swapped
Solution Approach 1:
The moveable protrusion provides dynamic adaptability in the table configuration. During swapping operations, the protrusion can be positioned to not form an outer edge, allowing tables to be moved close together without permanent structural modification, thus maintaining ease of operation while enabling liquid confinement when needed.
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 method enables faster substrate swapping without liquid leakage, reducing the risk of contamination and improving throughput by maintaining the liquid supply system active during the swapping process.
Implementation Method 1
It has been proposed to immerse the substrate in the lithographic projection apparatus in a liquid having a relatively high refractive index, e.g. water, so as to fill a space between the final element of the projection system and the substrate. The point of this is to enable imaging of smaller features since the exposure radiation will have a shorter wavelength in the liquid.
Implementation Method 2
the substrate table includes a moveable protrusion which, in a use position, exposes a top surface which is substantially in the same plane as a top surface of the substrate table and presents, in plan, an outer edge of the substrate table
Data Source
AI summary
A moveable member is provided which extends the top surface of a substrate table, in plan, beyond a bumper which protects the substrate table during collision. The moveable member may be retracted to a retracted position in which it no longer extends beyond the bumper. In this way it is possible to move two substrate tables together and to allow the retractable member to pass under a liquid supply system which normally provides liquid between the projection system and a substrate without turning off of the liquid supply system.