Crucible and method for pulling a single crystal

1. A crucible for pulling a silicon single crystal, the crucible having a double structure comprising a silica crucible and a graphite crucible covering an outside portion of the silica crucible, wherein the silica crucible comprises, at an opening end portion, an inward falling prevention means configured to impart a radially outward force on a body portion of the silica crucible, wherein the inward falling prevention means is constructed at the opening end portion of the silica crucible as a diameter-expanded portion with a taperingly inclined part extending at an angle of 5° to 40° with respect to an upwardly extending direction of an inner surface of the body portion in the silica crucible at a point of separating from an opening end of the graphite crucible, and wherein the diameter-expanded portion has a protruding portion protruding in the radially outward direction at an angle with respect to the diameter-expanded portion.

2. A crucible for pulling a silicon single crystal according to claim 1 , wherein an outer diameter of the body portion in the silica crucible is gradually increased in a direction from a lower portion to an upper portion.

3. A crucible for pulling a silicon single crystal according to claim 2 , wherein an outer diameter of the body portion at the upper portion of the silica crucible is larger by 1 to 10 mm than that of the body portion at the lower portion.

4. A crucible for pulling a silicon single crystal according to claim 1 , wherein the silica crucible is produced by an arc method.

5. A method for pulling a silicon single crystal, comprising pulling a silicon single crystal from a crucible for pulling a silicon single crystal of claim 1 .

6. A crucible for pulling a silicon single crystal, the crucible having a double structure comprising a silica crucible and a graphite crucible covering an outside portion of the silica crucible, wherein the silica crucible comprises, at an opening end portion, an inward falling prevention means configured to impart a radially outward force on a body portion of the silica crucible, wherein the inward falling prevention means is constructed at the opening end portion of the silica crucible as a diameter-expanded portion with a taperingly inclined part extending at an angle of 5° to 40° with respect to an upwardly extending direction of an inner surface of the body portion in the silica crucible at a point of separating from an opening end of the graphite crucible, and wherein the diameter-expanded portion has a protruding portion having a thickness in the radially outward direction that is greater than a thickness of the diameter-expanded portion.

7. A crucible for pulling a silicon single crystal according to claim 6 , wherein an outer diameter of the body portion in the silica crucible is gradually increased in a direction from a lower portion to an upper portion.

8. A crucible for pulling a silicon single crystal according to claim 7 , wherein an outer diameter of the body portion at the upper portion of the silica crucible is larger by 1 to 10 mm than that of the body portion at the lower portion.

9. A crucible for pulling a silicon single crystal according to claim 6 , wherein the silica crucible is produced by an arc method.

10. A method for pulling a silicon single crystal, comprising pulling a silicon single crystal from a crucible for pulling a silicon single crystal of claim 6 .

11. A crucible for pulling a silicon single crystal, the crucible having a double structure comprising a silica crucible and a graphite crucible covering an outside portion of the silica crucible, wherein the silica crucible comprises, at an opening end portion, an inward falling prevention means configured to impart a radially outward force on a body portion of the silica crucible, wherein the inward falling prevention means is constructed at the opening end portion of the silica crucible as a diameter-expanded portion with a taperingly inclined part extending at an angle of 5° to 40° with respect to an upwardly extending direction of an inner surface of the body portion in the silica crucible at a point of separating from an opening end of the graphite crucible, and wherein the diameter-expanded portion terminates in a protruding portion curving in the radially outward direction.

12. A crucible for pulling a silicon single crystal according to claim 11 , wherein an outer diameter of the body portion in the silica crucible is gradually increased in a direction from a lower portion to an upper portion.

13. A crucible for pulling a silicon single crystal according to claim 12 , wherein an outer diameter of the body portion at the upper portion of the silica crucible is larger by 1 to 10 mm than that of the body portion at the lower portion.

14. A crucible for pulling a silicon single crystal according to claim 11 , wherein the silica crucible is produced by an arc method.

15. A method for pulling a silicon single crystal, comprising pulling a silicon single crystal from a crucible for pulling a silicon single crystal of claim 11 .