| 摘要 |
PROBLEM TO BE SOLVED: To stably produce a large single crystal of metal fluoride such as calcium fluoride having physical properties which allow it to be used as an optical material in photolithography technology by suppressing occurrence of crystal break during crystal pulling and any mixing of air bubbles. SOLUTION: In a crystal pulling apparatus in which a melt of metal fluoride in a crucible is brought into contact with a seed crystal and a single crystal is pulled up, the crucible is a double structured crucible composed of an outer crucible (4) and an inner crucible (5) accommodated in the outer crucible. An opening shielding member (21) is provided at an opening (20) of a gap space formed by an internal surface of the outer crucible and an external surface of the inner crucible in the double structured crucible. Since volatilization of metal fluoride from the gap space (20) can be suppressed, it is possible to significantly suppress temperature change of the melt associated with the volatilization and troubles associated with solidification of a volatile component occurred by its contact with a low temperature part in a furnace followed by falling again thereof into the melt. COPYRIGHT: (C)2007,JPO&INPIT
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