	US 7,476,274 B2
	Method and apparatus for making a highly uniform low-stress single crystal by drawing from a melt and uses of said crystal
Gunther Wehrhan, Jena (Germany); Lutz Parthier, Kleinmachnow (Germany); Daniel Rytz, Herborn (Germany); Klaus Dupre, Idar-Oberstein (Germany); and Lothar Ackermann, Idar-Oberstein (Germany)
Assigned to Schott AG, Mainz (Germany)
Filed on Sep. 11, 2006, as Appl. No. 11/519,603.
Claims priority of application No. 10 2005 043 623 (DE), filed on Sep. 13, 2005.
Prior Publication US 2007/0056505 A1, Mar. 15, 2007
Int. Cl. C30B 15/20 (2006.01)

U.S. Cl. 117—15 [117/13; 117/16]

10 Claims

1. A method of making highly uniform, low-stress single crystals in a particular orientation from a melt, said melt having a melt surface and comprising melted crystal raw material, said method comprising the steps of:

a) dipping a single crystal held at a temperature under a melting point of the crystal raw material in the melt so as to form a solid-liquid phase boundary surface;

b) drawing said single crystal dipped into the melt in step a) out from the melt vertically with respect to the melt surface so as to grow the single crystal in the particular orientation;

c) conducting heat away during the drawing of the single crystal in step b);

d) during the drawing of the single crystal in step b), rotating the single crystal and the melt relative to each other with a controllable rotation speed;

e) detecting at least one characteristic surface temperature of the melt surface and/or of a crystal surface of the single crystal close to the melt surface by measuring heat energy radiated therefrom; and

f) when temperature fluctuations of the at least one characteristic surface temperature are detected, increasing or decreasing said rotation speed in order to control said at least one characteristic surface temperature and to adjust said phase boundary surface between the single crystal and the melt so that said phase boundary surface is planar.