The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 12, 2011
Filed:
Jun. 23, 2008
Masabumi Ito, Tokyo, JP;
Hiroshi Kojima, Fukushima, JP;
Masabumi Ito, Tokyo, JP;
Hiroshi Kojima, Fukushima, JP;
Asahi Glass Company, Limited, Tokyo, JP;
Abstract
The present invention aims at providing a glass substrate required to have a surface polished with extremely high accuracy as in glass substrates for reflective masks for use in EUVL; and a polishing method for producing the glass substrate. The present invention provides a glass substrate for mask blank, which is a glass substrate comprising SiOas a main component and having a polished main surface, wherein concave defects and convex defects on the main surface have a depth of 2 nm or smaller and a height of 2 nm or smaller, respectively, and have a half-value width of 60 nm or smaller, so that the concave defects and/or the convex defects do not cause phase defects when the glass substrate is used to produce a mask for exposure and the mask is used. Also disclosed are a polishing method for producing the glass substrate, and a mask blank and a mask for exposure using the glass substrate.