Method of making a fracture-resistant calcium fluoride single crystal and its use

US6740159B2 · kind B2 · utility

Assignees

• Schott Glas · DE
• Carl Zeiss SMT GmbH · DE

Inventors

• Joerg Kandler · Cospeda, DE
• Ewald Moersen · Mainz, DE
• Burkhard Speit · Mainz, DE
• Harry J. Bauer · Aalen, DE
• Thure Boehm · Aalen, DE
• Eric Eva · Aalen, DE
• Michael Thier · Heubach, DE
• Hexin Wang · Los Altos, US
• Frank Richter · Frankfurt, DE
• Hans-Josef Paus · Stuttgart, DE

Key dates

• Filing date: Aug 28, 2002
• Grant date: May 25, 2004
• Expiry date: Sep 18, 2022

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C30B29/12
• WIPO field: Surface technology, coating
• WIPO sector: Chemistry

Abstract

A method of making a fracture-resistant large-size calcium fluoride single crystal is described, which is suitable for an optical component for radiation in the far UV range. The calcium fluoride raw material for the single crystal is first melted and subsequently solidified by cooling the melt to form a single crystal. However the calcium fluoride raw material is doped with from 1 to 250, preferably 1 to 100, ppm of strontium, preferably added as strontium fluoride, and contains from 1 to 10 ppm of sodium as well as up to 100 ppm of other impurities.