| 摘要 |
PURPOSE:To minimize unnecessary oxide-film thickness with excellent reproducibility, and to produce a semiconductor element, a crystal defect of which by oxygen is reduced, in an impurity diffusion process by introducing a gas in a core tube while automatically controlling the flow rate of a substitute gas in proportional to the magnitude of oxygen concentration in the gas. CONSTITUTION:When semiconductor wafers 3 are stored in a core tube 1, a second flow valve 11 is closed, and a first flow valve 8 and a third flow valve 13 are opened, and residual oxygen in the core tube 1 is introduced to an oxygen concentration detector 12 through the first flow valve 8 and the core tube 1 by a substitute gas through a gas introducing tube 7. The oxygen concentration detector 12 compares oxygen partial pressure in a sample gas and a reference gas having specified oxygen partial pressure, and output voltage takes a value inversely proportional to the logarithm of oxygen concentration. Accordingly, the formation of an unnecessary oxide film to the semiconductor wafer can be minimized while reproducibility is improved, and crystal defects due to oxygen are decreased in an impurity diffusion process, thus enhancing the performance of a semiconductor element.
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