| 摘要 |
PURPOSE:To permit detection with high accuracy by determining an oxygen concn. from the measurement of the number of dust obtd. by bringing oxygen into chemical reaction with a monosilane. CONSTITUTION:The inside of a chamber 12 is evacuated by a vacuum system 17 and a gaseous mixture composed of gaseous N2 and SiH4 is supplied at a prescribed flow rate into the chamber 12. Laser light 23 is irradiated from a pipe 13 into the chamber 12. The O2 contained in the gaseous N2 and the SiH4 cause the chemical reaction when the gaseous SiH4 is mixed with the gaseous N2. The gas which consists of the gaseous mixture composed of the gaseous N2 and the gaseous H2 and in which the dust of the resulted product of reaction of SiO2 is suspended is thus supplied into the chamber 12. Laser light 23 is irregularly reflected by the dust and part of the scattered light is made incident on a photodetector 15 when the laser light 23 is irradiated to such SiO2 dust. The pulse signals corresponding to the number of dust are outputted from the detector 15 and are counted 24. The number of dust per unit volume in the gas flowing in the chamber 12 is determined from the count value per unit time of the counter 24 and the concn. of O2 in the gaseous N2 is counted back 25. |
