Large-size synthetic quartz glass substrate, evaluation method, and manufacturing method
AssigneeShin-Etsu Chemical Co., Ltd.
InventorsYoko Ishitsuka, Atsushi Watabe, Daijitsu Harada, Masaki Takeuchi
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Abstract
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.
Claims7
A method for evaluating the flatness of a large-size synthetic quartz glass substrate having front and back surfaces, the method comprising the steps of:
- partitioning an effective range into a plurality of evaluation regions such that the evaluation regions partly overlap each other, the effective range defined on one or both of the front and back surfaces of the large-size synthetic quartz glass substrate;
- measuring a flatness within each evaluation region;
- and
- computing a difference between the flatness in one evaluation region and the flatness in another evaluation region overlapping the one evaluation region, wherein
- the large-size synthetic quartz glass substrate has a diagonal length of at least 1,000 mm, and a thickness of 5 to 30 mm.
Dependencies are inferred from the claim text.