| 摘要 |
A circulation duct with a blow fan and a shutter is provided to form gas flows in a transfer chamber below a heat treatment furnace, and a dust removing filter unit is provided in a blowout port of the circulation gas passage. Three, for example, gas supply pipes with a number of blowout holes are provided on the front side of the filter unit at set heights, and a clean air source is connected to the proximal end of the air supply pipes through an opening/closing valve. Clean gas is fed into the transfer chamber from the clean air source from the start of an unloading of the wafers to the time of the dismounting of the wafers from a wafer boat with the circulation of gas flows in the circulation gas passage stopped. A filter material of the dust removing filter is PTFE, which can reduce the amount of impurities scattered from the dust removing filter that attach on the wafers.
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