DEVITRIFICATION AGENT FOR QUARTZ GLASS CRUCIBLE CRYSTAL GROWING PROCESS
The present technology provides a devitrification agent for crucibles with improved efficiency over previous devitrification agents for use in various technological fields, including semiconductors and photovoltaic applications. The devitrification agent may include (a) barium, and (b) tantalum, tungsten, germanium, tin, or a combination of two or more thereof. The devitrification agent may be integrated into a crucible during construction, applied to the surface of a finished crucible, and/or added into the silicon melt used in crystal pull. The technology described herein, improves sag resistance and provides a devitrified surface for slower, more controlled dissolution of silica by liquid silicon melt during silicon crystal growth.
1 . A crucible comprising a body of vitreous silica having a bottom wall and a sidewall extending up from the bottom wall and defining a cavity for holding the molten silicon material, the sidewall formation and the bottom wall each having an inner and an outer surface, the crucible comprising a devitrification agent comprising (a) a first metal chosen from barium and (b) a second metal chosen from tantalum, tungsten, germanium, tin, or a combination of two or more thereof.
2 . The crucible of claim 1 , wherein the devitrification agent has a ratio of first metal to second metal of from about 1:1 to about 10:1.
3 . The crucible of claim 1 , wherein devitrification agent has a ratio of first metal to second metal of from about 2:1 to about 8:1.
4 . The crucible of claim 1 , wherein devitrification agent has a ratio of first metal to second metal of from about 5:2 to about 6:1.
5 . The crucible of any of claim 1 , wherein the devitrification agent is disposed as a coating on at least a portion of a surface of the crucible.
6 . The crucible of claim 5 , wherein the coating comprises the first metal in the form of an alkoxide, a hydroxide, a carbonate, a sol-gel solution, or a combination of two or more thereof, and the second metal in the form an alkoxide, a hydroxide, an acid, an oxide, a carbonate, a sol-gel solution, or a combination of two or more thereof.
7 . The crucible of claim 6 , where the devitrification agent further comprises a barium halide.
8 . The crucible of any of claim 1 , wherein the devitrification agent is disposed in the crucible body.
9 . The crucible of claim 8 , wherein the devitrification agent comprises (a) barium oxide, and (b) tantalum oxide, tungsten oxide, germanium oxide, tin oxide, or a combination of two or more thereof.
10 . A method for preparing a silicon melt for pulling a single crystal comprising:
providing silicon to a crucible comprising a body of vitreous silica having a bottom wall and a sidewall extending up from the bottom wall and defining a cavity for holding the molten silicon material, the sidewall formation and the bottom wall each having an inner and an outer surface, the crucible comprising a devitrification agent comprising (a) a first metal chosen from barium and (b) a second metal chosen from tantalum, tungsten, germanium, tin, or a combination of two or more thereof; and
melting the silicon within the crucible to form a first layer of substantially devitrified silica on the inner surface of the crucible which is in contact with the molten silicon.
11 . The method of claim 10 , wherein the devitrification agent has a ratio of first metal to second metal of from about 1:1 to about 10:1.
12 . The method of claim 10 , wherein devitrification agent has a ratio of first metal to second metal of from about 2:1 to about 8:1.
13 . The method of claim 10 , wherein devitrification agent has a ratio of first metal to second metal of from about 5:2 to about 6:1.
14 . The method of claim 10 , wherein the devitrification agent is disposed as a coating on at least a portion of a surface of the crucible.
15 . The method of claim 14 , wherein the coating comprises the first metal in the form of an alkoxide, a hydroxide, a carbonate, a sol-gel solution, or a combination of two or more thereof, and the second metal in the form an alkoxide, an acid, an oxide, a hydroxide, a carbonate, a sol-gel solution, or a combination of two or more thereof.
16 . The method of claim 1 , where the devitrification agent further comprises a barium halide.
17 . The method of claim 10 , wherein the devitrification agent is disposed in the silicon melt.
18 . The method of claim 17 , wherein the devitrification agent comprises (a) barium oxide, barium metal, an alloy compound comprising barium, or a combination of two or more thereof, and (b) the second metal in the form of a metal oxide, metal compound, an alloy compound comprising the second metal, or a combination of two or more thereof.
19 . The method of claim 10 , wherein the devitrification agent is disposed in the crucible body.
20 . The method of claim 19 , wherein the devitrification agent comprises (a) barium oxide, and (b) tantalum oxide, tungsten oxide, germanium oxide, tin oxide, or a combination of two or more thereof.