Recycling Large Photomask Substrates via Sandblasting and Repolishing
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Solution Overview
Problem
The recycling of large-size photomask substrates for TFT liquid crystal panels is hindered by the need for high flatness and accuracy, as existing methods fail to efficiently remove material while minimizing deformation and material loss, leading to reduced exposure accuracy and increased costs due to the wastage of expensive synthetic quartz substrates.
Innovation Solution
A method involving the removal of a light-shielding film from used photomask substrates, followed by sandblasting and repolishing to create a regenerated substrate with a concave surface shape, which reduces material removal and deformation, thereby improving flatness and parallelism, and allowing for efficient reuse in exposure processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the photomask substrate is repolished to remove damages and stains, then the surface quality is improved, but the substrate thickness is reduced and deflection increases
Solution Approach 1:
The substrate is pre-heated before polishing to reduce thermal strains and prevent stepped surface formation. This preliminary thermal treatment allows effective strain elimination while minimizing material removal and maintaining substrate thickness
Solution Approach 2:
The polishing process parameters are optimized by controlling substrate temperature and polishing conditions to eliminate thermal strains effectively while removing minimal material, thereby preventing excessive deflection
2Shape
If more material is removed during polishing to improve flatness, then the flatness is improved, but the substrate becomes thinner and more prone to deflection
Solution Approach 1:
The substrate temperature is changed and controlled during polishing to reduce thermal strains, allowing effective flatness improvement with minimal material removal. This parameter control prevents the need for excessive polishing that would thin the substrate
3Ease of repair
If the substrate is reused after polishing, then cost is reduced, but exposure accuracy deteriorates due to deflection variations
Solution Approach 1:
The substrate is pre-heated before polishing to eliminate thermal strains that cause stepped surfaces and deflection variations. This preliminary treatment ensures that reused substrates maintain consistent flatness and deflection characteristics, preserving exposure accuracy
Solution Approach 2:
Polishing parameters are optimized by controlling substrate temperature to minimize material removal while achieving required flatness. This ensures reused substrates maintain uniform thickness and deflection, preventing exposure accuracy deterioration
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 method enhances exposure accuracy and reduces the burden on exposure correction, increasing production yield and allowing for the reuse of substrates, thereby reducing costs and improving the efficiency of large-size panel exposure.
Implementation Method 1
resurfacing the glass substrate stock using a processing tool of sand blasting
Implementation Method 2
repolishing the resurfaced glass substrate stock
Data Source
AI summary
A used large-size photomask substrate having a patterned light-shielding film is recycled by (i) removing the light-shielding film from the used substrate to provide a photomask-forming glass substrate stock, (ii) resurfacing the glass substrate stock by sand blasting, (iii) repolishing the resurfaced glass substrate stock to yield a regenerated glass substrate stock, (iv) applying a light-shielding film onto the regenerated glass substrate stock to yield a regenerated photomask-forming blank, and (v) processing the light-shielding film of the blank into a pattern corresponding to the desired exposure of a mother glass, yielding a regenerated photomask substrate.