| CPC C30B 35/002 (2013.01) [C30B 15/12 (2013.01); C30B 29/06 (2013.01)] | 9 Claims |

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1. A CZ crucible for growing a single crystal silicon ingot by a CZ method, wherein
the CZ crucible comprises a closed-end cylindrical graphite crucible and a closed-end cylindrical quartz glass crucible disposed inside the graphite crucible,
the CZ crucible includes a gap between an inner surface of a bottom portion of the graphite crucible and an outer surface of a bottom portion of the quartz glass crucible on a central axis of the CZ crucible, the gap keeping the inner surface of the bottom portion of the graphite crucible and the outer surface of the bottom portion of the quartz glass crucible contactless with each other,
the outer surface of the bottom portion of the quartz glass crucible has a concave surface shape, and
an inner surface of the bottom portion of the quartz glass crucible at a central axis of the quartz glass crucible has a curved concave surface shape.
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