Optical gas concentration measuring method, and method for monitoring gas concentration by said method

Abstract

To provide a concentration measurement method with which the concentrations of predetermined chemical components can be measured non-destructively, accurately, and rapidly by a simple means, up to the concentrations in trace amount ranges, as well as a concentration measurement method with which the concentrations of chemical components in a measurement target can be accurately and rapidly measured in real time up to the concentrations in nano-order trace amount ranges, and which is endowed with a versatility that can be realized in a variety of embodiments and modes. In the present invention, a measurement target is irradiated, in a time sharing manner, with light of a first wavelength and light of a second wavelength that have different optical absorption rates with respect to the measurement target. The light of each wavelength, arriving optically via the measurement target as a result of irradiation with the light of each wavelength, is received at a shared light-receiving sensor. A differential signal is formed, the differential signal being of a signal pertaining to the light of the first wavelength and a signal pertaining to the light of the second wavelength, the signals outputted from the light-receiving sensor upon receipt of the light. The concentration of a chemical component in the measurement target is derived on the basis of the differential signal.

Description

technical field [0001] The present invention relates to an optical gas concentration measurement method related to the concentration of a predetermined chemical component in gas, and a gas concentration monitoring method based on the method. Background technique [0002] In the semiconductor manufacturing process, the mixed gas is often supplied from the same line into the processing chamber of the semiconductor manufacturing apparatus. When supplying the mixed gas, it is necessary to keep the mixing ratio of the component gases constant or to change it purposefully and instantaneously during the treatment process. Therefore, a flow control device such as a flow control system unit (FCSC) provided with a gas flow measurement mechanism and a gas flow adjustment mechanism is arranged in the gas supply line. In this FCSC, it is important to be able to accurately measure the flow rate per unit time of each component gas constituting the mixed gas (hereinafter sometimes referred...

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Problems solved by technology

[0020] In Patent Document 1, the flow measurement and feedback are only performed on the upstream side of the processing chamber, so the problem of whether the measured mixing ratio is the same as the actual mixing ratio has not yet been resolved

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