Optical Wear Detection for Lithography Support Elements
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Solution Overview
Problem
In lithographic apparatuses, the wear of support elements, such as burls, due to clamping and friction during substrate movement affects the accuracy and structural integrity, necessitating a method to detect wear without interrupting the manufacturing process.
Innovation Solution
A system comprising an illumination system, detection system, and processing circuitry that irradiates an object, receives scattered light, and compares the signal to a reference model to determine the quantity of wear on the support elements, allowing for in-situ detection and quantification of wear on the burls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If support elements are used to minimize contact area and reduce friction, then substrate positioning accuracy is improved, but wear of support elements increases
Solution Approach 1:
The patent applies preliminary action by measuring wear of support elements before it reaches critical levels that would affect substrate positioning accuracy. The optical measurement system detects wear progression in advance, allowing for proactive maintenance scheduling that prevents positioning errors while extending the operational life of support elements through planned replacements.
2Strength
If support elements are coated with thin film, then structural integrity is improved, but wear detection becomes more difficult
Solution Approach 1:
The patent replaces mechanical contact-based wear detection methods with an optical measurement system. The optical system uses light scattering properties to detect wear on coated support elements without requiring physical contact, thereby maintaining the thin film coating for structural integrity while enabling accurate wear measurement through optical property changes.
3Measurement precision
If wear measurement is performed by interrupting operation, then measurement accuracy is improved, but productivity decreases
Solution Approach 1:
The patent implements continuity of useful action by enabling wear measurements to be performed without interrupting the lithographic apparatus operation. The optical measurement system can assess support element wear while the apparatus continues its manufacturing cycle, eliminating downtime and maintaining full productivity while achieving sufficient measurement precision for wear monitoring.
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
Enables quick and efficient measurement of wear on the support elements, ensuring accurate positioning and maintaining the structural integrity of the substrate holder, thereby enhancing the precision and reliability of the lithographic process.
Implementation Method 1
receiving, using a detector, scattered light on the first side of the object
Implementation Method 2
The scattered light includes transmitted light through the object from the second side to the first side
Data Source
AI summary
A method includes irradiating an object with an illumination beam, receiving, using a detector, scattered light from a first side of the object, generating a signal based on the scattered light, comparing the signal to a reference model, and determining a quantity of wear of the first side of the object based on the comparing. The first side of the object includes a layer of a coating material, and the irradiating is from a second side of the object. The scattered light includes transmitted light through the object from the second side to the first side.