| 摘要 |
PROBLEM TO BE SOLVED: To provide a low pressure CVD method in a conventional horizontal low pressure CVD apparatus for suppressing peeling off of a film formed on a dummy wafer caused by thermal stress from the wafer to thereby prevent drop of its yield. SOLUTION: A dummy wafer 9 has an average surface roughness Ra of 0.5 to 1.5μm that is 3 times larger than that of a conventional dummy wafer. The roughness of the wafer makes a CVD film deposited on the dummy wafer 9 hard to peel off. As a result, the number of particles released from the dummy wafer 9 and deposited on a wafer 8 as a product can be remarkably reduced and thus a yield can be improved. The dummy wafer 9 having a CVD film of about 1 or 2μm thick deposited thereon has been exchanged with a new one. Thus, the exchange life of the dummy wafer 9 can be prolonged to about 3 times.
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