US 6,982,001 B2 | ||
Dehydroxylation and purification of calcium fluoride materials using a halogen containing plasma | ||
Robert A. Bellman, Painted Post, N.Y. (US); Dana C. Bookbinder, Corning, N.Y. (US); Kishor P. Gadkaree, Big Flats, N.Y. (US); and Cynthia B. Giroux, Corning, N.Y. (US) | ||
Assigned to Corning Incorporated, Corning, N.Y. (US) | ||
Filed on May 28, 2004, as Appl. No. 10/856,633. | ||
Prior Publication US 2005/0263064 A1, Dec. 01, 2005 | ||
Int. Cl. C30B 11/00 (2006.01); C30B 11/12 (2006.01) |
U.S. Cl. 117—11 | 11 Claims |
1. A method for growing a metal fluoride single crystal, said method comprising the steps of:
placing a metal fluoride material of formula MF2 in a vessel;
placing the vessel in a crystal growth furnace;
reducing a pressure in the crystal growth furnace to a pressure of less than 10−3 mm Hg;
exposing the fluoride material and surfaces in the furnace to a halogen containing plasma at a pressure in the range of 0.1–150
mm Hg at temperature in the range 200–800° C. for a selected time in the range of 1–120 hours;
stopping the flow of plasma and reducing the pressure in the furnace to less than 10−3 mm Hg;
heating the fluoride material to a temperature above its melting point; and
cooling the melted fluoride material, using a selected time and temperature cycle to form a metal fluoride single crystal
suitable for below 200 nm optical lithography
wherein M is selected from the group consisting of calcium, barium, magnesium and strontium, and mixtures thereof.
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