| 摘要 |
PURPOSE:To form a grown up membrane with a uniform membrane thickness as well as to enhance mass productivity, by also flowing a gas impurity into a vapor growth reaction tube from the end part of the gas outflow side thereof. CONSTITUTION:In a horizontal reaction tube 1 wherein a carrier gas accompanying a reactive gas and gaseous impurity is flowed thereinto from an inlet 5 and discharged from an outlet 6, a gas reverse inflow port 7 is provided in the vicinity of the outlet 6 to flow the gaseous inpurity into said reaction tube 1. By this structure, the gas is reversely permeated to the upstream side and reverse diffusion effect replenishing reduced impurity amount is realized while a grown membrane with uniform membrane thickness is formed and, at the same time, mass productivity is enhanced.
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