Lithography Substrate Table Deformation Correction
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Solution Overview
Problem
Lithographic apparatuses experience focus errors due to acceleration force-induced deformation of position sensors, particularly the mirror block in interferometers, leading to differences in substrate surface level measurements between up-scan and down-scan directions, resulting in hysteretic effects and potential slip between the substrate table and the mirror block.
Innovation Solution
A method involving the determination of both up-scan and down-scan substrate maps to create a difference map, which accounts for the deformation-induced differences in substrate surface levels, allowing for correction of focus errors by adjusting the substrate table positioning during exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the substrate table is moved with large acceleration forces between exposure scans, then the substrate table can be repositioned quickly for the next exposure, but the position sensor (interferometer mirror block) deforms causing measurement errors
Solution Approach 1:
The patent applies preliminary action by performing substrate map measurements in both upward and downward scan directions before exposure. This allows the system to detect and correct for hysteresis effects and acceleration-induced deformations in advance, ensuring measurement accuracy is maintained despite the necessary large acceleration forces used during rapid table repositioning between exposures.
2Productivity
If the substrate table accelerates rapidly between scans, then productivity is improved through faster repositioning, but hysteresis effects cause different substrate surface levels to be measured in up-scan versus down-scan directions
Solution Approach 1:
The patent implements feedback by comparing substrate surface level measurements obtained from both upward and downward scan directions. The system uses this feedback information to detect hysteresis effects and correct for acceleration-induced deformations, ensuring consistent and accurate substrate leveling measurements are maintained throughout the exposure process, thereby supporting high productivity without sacrificing measurement precision.
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 mitigates focus errors by providing a deformation map that corrects for the hysteretic effects caused by acceleration forces, ensuring accurate substrate leveling and reducing positional discrepancies between up-scan and down-scan measurements.
Implementation Method 1
Typically, this type of position sensor includes an interferometer equipped with a mirror block of one or more mirrors
Implementation Method 2
Due to the large acceleration forces the position sensor associated with the substrate table may deform
Implementation Method 3
acceleration forces may cause a small amount of slip between the substrate table and the mirror block
Data Source
AI summary
A device manufacturing method in a lithographic apparatus includes determining a plurality of positions on a substrate. The plurality of positions on a measurement substrate are scanned in a first direction to determine a first substrate map of the substrate levels of the measurement substrate. The plurality of positions on the measurement substrate are scanned in a second direction to determine a second substrate map of the substrate levels of the measurement substrate. A difference map is produced that includes information of the difference in measurement substrate surface level using the first substrate map and the second substrate map.