Lithographic Substrate Support Table Gas Flow Control
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Solution Overview
Problem
Lithographic apparatuses face challenges in maintaining substrate flatness and reducing wear on support tables during loading and unloading, due to uneven pressure distribution and substrate deformation, leading to overlay errors and wear on the support table surfaces.
Innovation Solution
A method involving a gas flow system with controlled pressure phases, where gas is supplied or extracted through specific regions of the support table's gas flow openings to manage pressure and prevent substrate slipping and deformation, including phases where gas is supplied or extracted through central, intermediate, and outer regions of the support table during loading and unloading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gas is extracted uniformly from the entire support table surface, then substrate clamping is achieved, but substrate deformation occurs and flatness deteriorates
Solution Approach 1:
The support table surface is divided into multiple regions (central region, intermediate region, outer region) with different gas extraction characteristics. Different regions have different numbers of gas flow openings or different extraction rates, allowing selective clamping of substrate areas to prevent deformation while maintaining overall clamping reliability.
Solution Approach 2:
Different regions of the support table are given different local properties regarding gas extraction. The central region may have fewer or no gas flow openings to avoid clamping the substrate center which would cause deformation, while outer regions have more openings for secure clamping. This local differentiation maintains flatness while achieving reliable clamping.
2Manufacturing precision
If substrate is clamped firmly to prevent movement, then positioning accuracy is improved, but wear on support table surface increases
Solution Approach 1:
Gas extraction is initiated in a controlled sequence before full substrate contact is achieved. By preliminarily extracting gas from certain regions while the substrate is still approaching, the substrate is gently guided into position without sudden slapping or impact that would cause wear, while still achieving firm clamping for positioning accuracy.
Solution Approach 2:
Gas extraction is performed in periodic phases or stages rather than continuously at full intensity. The extraction rate or active region is modulated over time during the clamping process, allowing the substrate to settle gradually onto the support table surface, reducing impact wear while maintaining final positioning accuracy.
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 improves substrate flatness and reduces wear on the support table by controlling pressure distribution, minimizing slipping and deformation, and enhancing the accuracy and efficiency of the loading and unloading processes.
Implementation Method 1
Gas is supplied or extracted through specific regions of the support table's gas flow openings to manage pressure and prevent substrate slipping and deformation
Data Source
AI summary
A method for unloading a substrate from a support table configured to support the substrate, the method including: supplying gas to a gap between a base surface of the support table and the substrate via a plurality of gas flow openings in the support table, wherein during an initial phase of unloading the gas is supplied through at least one gas flow opening in an outer region of the support table and not through any gas flow opening in a central region of the support table radially inward of the outer region, and during a subsequent phase of unloading the gas is supplied through at least one gas flow opening in the outer region and at least one gas flow opening in the central region.