| 摘要 |
PROBLEM TO BE SOLVED: To solve a problem of improving a joint between the flange of a reaction tube and a quartz cap in airtightness, where a large number of semiconductor wafers are loaded into the above vertical quartz reaction tube, and the silicon surface of a wafer is subjected to an oxidation treatment by the use of oxidizing gas containing hydrogen chloride gas. SOLUTION: A cap stopping up the lower end opening of a reaction tube is composed of a metal main body and a quartz cover covering the surface of a flange inside the peripheral part of the metal main body, an O ring is provided on the surface of the peripheral part of the cap to ensure airtightness for a joint between the cap and the flange, and a gap between the opposed surfaces of the cap and flange inside the O ring is purged with N2 gas to prevent hydrogen chloride gas from coming into contact with the metal and to cool down the O ring. A cooling water path is provided near to the O ring to cool down it too.
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