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:
Jan. 11, 2011
Filed:
Dec. 05, 2008
Gunther Wehrhan, Jena, DE;
Lutz Parthier, Kleinmachnow, DE;
Daniel Rytz, Herborn, DE;
Klaus Dupre, Idar-Oberstein, DE;
Lothar Ackermann, Idar-Oberstein, DE;
Gunther Wehrhan, Jena, DE;
Lutz Parthier, Kleinmachnow, DE;
Daniel Rytz, Herborn, DE;
Klaus Dupre, Idar-Oberstein, DE;
Lothar Ackermann, Idar-Oberstein, DE;
Schott AG, Mainz, DE;
Abstract
The method of making uniform low-stress crystals includes immersing a seed crystal held at a temperature under its melting point in a melt in a crucible and drawing it from the melt. The crystal and/or melt are rotated relative to each other and a planar phase boundary surface is maintained between them by detecting a surface temperature of the melt and/or crystal and controlling temperature fluctuations by increasing or decreasing the rotation speed. The single crystals obtained by this method have a diameter ≧50 mm and no visible growth strips in a fishtail pattern when a 2-mm thick sample is observed between crossed polarizers. These crystals have an index of refraction uniformity Δn of <1 ppm and a stress birefringence of <1 nm/cm at 193 nm, so that optical elements suitable for DUV lithography can be made from them.