Large-size Synthetic Quartz Glass Substrate Flatness Evaluation
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Solution Overview
Problem
Large-size synthetic quartz glass substrates used for forming masks in displays require high flatness and minimal local gradients to ensure accurate exposure, but existing methods fail to effectively evaluate and achieve uniformity across the substrate surface, leading to uneven thin film deposition and focus variations.
Innovation Solution
Defining an effective range on the substrate surface partitioned into overlapping evaluation regions, measuring flatness within each region, and determining material removal based on these measurements for local polishing to achieve high flatness and minimal local gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the substrate is divided into separated sites for flatness evaluation, then the flatness within each site can be evaluated, but the local undulation gradient between the sites cannot be evaluated
Solution Approach 1:
The substrate surface is divided into multiple evaluation regions that are arranged to overlap with each other. Each evaluation region is a smaller area where flatness can be precisely measured, and the overlapping arrangement ensures that the boundaries between regions are also evaluated, capturing the local undulation gradients that would be missed by separated non-overlapping sites.
2Manufacturing precision
If the flatness specification is determined by overall surface flatness, then the substrate can meet general requirements, but local areas with large undulation gradients cannot be detected
Solution Approach 1:
Instead of evaluating only the overall flatness of the entire substrate surface, the invention introduces evaluation regions with overlapping arrangements that enable precise measurement of local flatness variations. This allows detection of local areas with large undulation gradients while maintaining knowledge of the overall flatness, ensuring both global and local quality requirements are met.
Data Source
AI summary
A large-size synthetic quartz glass substrate has a diagonal length of at least 1,000 mm. Provided that an effective range is defined on the substrate surface, and the effective range is partitioned into a plurality of evaluation regions such that the evaluation regions partly overlap each other, a flatness in each evaluation region is up to 3 μm. From the quartz glass substrate having a high flatness and a minimal local gradient within the substrate surface, a large-size photomask is prepared.