Method for manufacturing single-crystal silicon
View Patent ↗The success rate of multi-pulled single crystal growth by the Czochralski method is enhanced by the use of a melt crucible having an amount of barium on an inner surface thereof which varies inversely with the diameter of the crucible. At least one single crystal is separated from the melt by a free span method.
1. A method for manufacturing single-crystal silicon using a multi-pulling method for sequentially pulling up a plurality of pieces of single-crystal silicon from a material melt in an identical crucible within a chamber by a Czochralski method, the method comprising the steps of:
forming a layer containing barium on an inner wall of a crucible having a nominal diameter of 18 inches or of a crucible having a nominal diameter of 32 inches,
wherein the amount of barium is 1.4×10 16 atoms·cm −2 or more and 5.4×10 16 atoms·cm −2 or less in case the diameter of the crucible is 18 inches, or 1.4×10 15 atoms·cm −2 or more and 5.4×10 15 atoms·cm −2 or less in case the diameter of the crucible is 32 inches;
selecting one of the crucibles having the nominal diameters of 18 inches or 32 inches;
preparing the material melt in the selected crucible;
pulling up a single-crystal silicon from the material melt;
additionally charging further polycrystalline material into the material melt remaining after pulling up the single-crystal silicon and melting the further polycrystalline material in said material melt while continuing heating of the material melt; and
pulling up a next single-crystal silicon from said material melt containing the further polycrystalline material additionally charged and melted therein, wherein
the step of additionally charging and melting the polycrystalline material and the step of pulling up a next single-crystal silicon are repeated one or more times, and wherein at least one of the steps of pulling up a single-crystal silicon and pulling up a next single-crystal silicon, which is repeated one or more times, includes a step of omitting at least a part of formation of a tail part of the single-crystal silicon and separating the single-crystal silicon from the material melt.
2. The method for manufacturing single-crystal silicon using a multi-pulling method of claim 1 , wherein the layer containing barium is prepared by spraying an aqueous solution of a barium salt onto the inside of the previously formed crucible.
3. The method of claim 2 , wherein the crucible is heated to a temperature of from 200 to 300° C. during spraying.
4. The method of claim 2 , wherein the aqueous solution of a barium salt is an aqueous solution of barium carbonate or barium hydroxide.
5. The method of claim 2 , wherein the aqueous solution of a barium salt is an aqueous solution of barium hydroxide.
6. The method of claim 2 , wherein the amount of barium is varied at different portions of the inner crucible walls by varying the amount of the aqueous solution of barium salt sprayed onto the inside of the crucible at different portions of the inner crucible walls.
7. The method of claim 2 , wherein the crucible rotates during spraying.