Lithographic Substrate Table Thermal Drift Control
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Solution Overview
Problem
Lithographic processes face inaccuracies due to thermal drift of substrates between alignment measurement and exposure, causing misalignment and overlay errors.
Innovation Solution
Applying heat to the substrate table between alignment measurement and exposure to stabilize and maintain temperature, reducing thermal drift through controlled heating elements and feedback loops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the substrate table is cooled by the cooling system, then the substrate table temperature is reduced, but thermal drift occurs causing misalignment between alignment measurement and lithographic exposure
Solution Approach 1:
The patent applies heat to the substrate table in advance between alignment measurement and lithographic exposure to counteract the cooling effect. This preliminary heating action ensures that the substrate table temperature stabilizes before exposure, preventing thermal drift and maintaining alignment accuracy despite the cooling system being active during the process
2Manufacturing precision
If heat is applied to the substrate table to reduce thermal drift, then alignment accuracy is improved, but the cooling system effectiveness is reduced
Solution Approach 1:
The patent implements periodic heating cycles where heat is applied to the substrate table at specific intervals between alignment measurement and exposure. This periodic heating compensates for thermal drift only when necessary, allowing the cooling system to remain effective during other periods, thus balancing alignment accuracy with cooling efficiency
3Stability of the object's composition
If the substrate table temperature is stabilized through heat application, then thermal drift is reduced, but process complexity increases due to additional heating control
Solution Approach 1:
The patent employs a feedback control system that monitors substrate table temperature and automatically adjusts heating power accordingly. Temperature sensors detect thermal drift, and the control system modulates heating element power to maintain temperature stability, eliminating the need for complex manual intervention while ensuring consistent alignment 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 enhances the accuracy of lithographic exposures by maintaining alignment marks closer to their measured positions, reducing thermal drift and overlay errors.
Implementation Method 1
applying heat to the substrate table to reduce cooling of the substrate table provided by the cooling system
Implementation Method 2
the substrate table comprising a cooling system operative to cool the substrate table
Data Source
AI summary
A method of performing a lithographic exposure of a substrate, the substrate being held on a substrate table, the substrate table comprising a cooling system operative to cool the substrate table, the method comprising performing an alignment measurement of the substrate, applying heat to the substrate table to reduce cooling of the substrate table provided by the cooling system, the heat being applied between a time at which the alignment measurement is performed and a time at which the lithographic exposure is performed and performing the lithographic exposure of the substrate.