Support Table Pressure Control for Lithography Unloading
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Solution Overview
Problem
In lithographic apparatuses, there is a challenge in efficiently unloading objects from support tables while minimizing the amount of immersion liquid that remains on the substrate and support table, which can lead to residue and contamination issues.
Innovation Solution
A method and system involving a support table with pressure channels and a seal member to control liquid retention and removal, where a first pressure is applied to the central region and a second pressure to the peripheral region, allowing for controlled liquid management during unloading by increasing pressures towards ambient levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If vacuum pressure is applied uniformly across the support table to unload the substrate, then the substrate can be released from the support table, but immersion liquid remains trapped between the substrate and seal member causing residue and contamination
Solution Approach 1:
The support table is divided into two distinct pressure zones: a first pressure zone (central region) and a second pressure zone (peripheral region). This segmentation allows different pressure levels to be applied simultaneously to different areas, enabling the substrate to be unloaded while preventing liquid trapping at the seal member interface.
Solution Approach 2:
Different pressure characteristics are applied to different regions of the support table. The central region receives a first pressure that facilitates substrate release, while the peripheral region receives a second pressure that prevents liquid entrapment at the seal member. This local differentiation of pressure quality resolves the contradiction between easy unloading and liquid residue prevention.
2Productivity
If vacuum pressure is reduced to ambient pressure to release the substrate, then the substrate can be removed from the support table, but liquid is trapped between the substrate and seal member
Solution Approach 1:
The pressure control system is segmented into two independent control channels: one for the central region and one for the peripheral region. This allows the central region pressure to be reduced for rapid substrate release while the peripheral region maintains higher pressure to prevent liquid loss at the seal member interface.
Solution Approach 2:
The peripheral region pressure is maintained at a higher level before substrate removal to pre-prevent liquid entrapment. This preliminary action ensures that when the central pressure is reduced for quick unloading, the liquid is already positioned to drain away from the seal member, preventing both residue and contamination.
3Reliability
If high vacuum is applied to clamp the substrate securely, then the substrate is held firmly on the support table, but immersion liquid is trapped between the substrate and seal member
Solution Approach 1:
The clamping function is segmented between two pressure zones: the central region provides strong vacuum clamping for substrate security, while the peripheral region maintains higher pressure to prevent liquid trapping at the seal member. This spatial segmentation allows both reliable clamping and contamination prevention to occur simultaneously.
Solution Approach 2:
Different vacuum qualities are applied locally to different regions. The central region experiences high vacuum for secure substrate holding, while the peripheral region experiences reduced vacuum or positive pressure to maintain liquid drainage pathways clear of the seal member, preventing contamination.
4Object-affected harmful factors
If pressure is increased uniformly to remove liquid from the support table, then liquid residue is reduced, but the substrate cannot be properly released from the support table
Solution Approach 1:
The pressure application is segmented into two independent zones with opposite pressure trends during unloading: the central region pressure decreases to enable substrate release, while the peripheral region pressure increases to remove liquid residue. This segmentation allows both objectives to be achieved without conflict.
Solution Approach 2:
Different pressure qualities are applied locally during the unloading process. The central region receives reduced pressure (or overpressure) to facilitate substrate release, while the peripheral region receives increased pressure to actively remove liquid residue. This local differentiation resolves the contradiction between substrate release and liquid removal.
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 approach effectively reduces liquid residue on the substrate and support table, enhancing the unloading process and preventing contamination, which improves substrate quality and reduces wear on support table components.
Implementation Method 1
applying a first pressure to a central region of the support table under a central portion of the object; and applying a second pressure to a peripheral region of the support table under a peripheral portion of the object
Data Source
AI summary
A method of unloading an object from a support table, the object clamped to the support table during an exposure process by: applying a first pressure to a central region of the support table under a central portion of the object; and applying a second pressure to a peripheral region of the support table under a peripheral portion of the object, wherein during clamping the first pressure and the second pressure are controlled such that liquid is retained between the object and a seal member that is positioned radially between the central region and the peripheral region at an upper surface of the support table and protrudes towards the object, the method including: increasing the first pressure towards ambient pressure; removing at least some of the liquid retained between the object and the seal member by decreasing the second pressure; and increasing the second pressure towards the ambient pressure.