JP2005069803A - Carbonyl fluoride sensing material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simply measure a gas of carbonyl fluoride of which the concentration is below an environmental standard concentration. <P>SOLUTION: The carbonyl fluoride detecting material comprises a carrier with a development of a color indicator which has a discoloration region within a hydrogen ion concentration range of 3.1-4.4 and a humectant. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a gas detection material that detects carbonyl fluoride at an environmental standard concentration.

In the cleaning process of the CVD process, perfluorocarbon (PFC), nitrogen trifluoride (NF3), etc. have been used in the past. It is starting to be used.
However, it is highly toxic, and it is desired that the environmental standard concentration (TLV) is set to 2 ppm and detected at a concentration lower than this.
In order to detect carbonyl fluoride (COF2), hydrogen fluoride (HF) is generated by hydrolysis by bubbling or the like, and this hydrogen fluoride may be detected using an electrochemical gas sensor. There is a problem that the structure is complicated by requiring another means for decomposition, and the detection sensitivity is low.

  The present invention has been made in view of such problems, and its object is to provide a gas detection material capable of detecting carbonyl fluoride at an environmental standard concentration or less without requiring a special hydrolysis means. Is to provide.

  In order to solve such a problem, in the present invention, a color indicator having a color change range at a hydrogen ion concentration of 3.1 to 4.4 and a moisturizing agent are developed on a carrier.

The carbonyl fluoride in the atmosphere is once taken into the moisture previously absorbed in the moisturizing agent, and this moisture causes COF2 + H2O → CO2 + O2 + 2HF.
To generate hydrogen fluoride (HF).
This hydrogen fluoride reacts with a color indicator having a color change range at a hydrogen ion concentration of 3.1 to 4.1 dissolved in the humectant, thereby causing a change in optical density.

  Of course, the amount of carbonyl fluoride taken into the moisturizer is proportional to the sampling time, so by adjusting the sampling time according to the concentration of carbonyl fluoride to be detected, carbonyl fluoride below the environmental standard concentration is detected. can do.

Therefore, details of the present invention will be described below based on examples.
A color indicator having a color change range in an acidic range of 3.1 to 4.4, for example, methyl orange 0.02 v / v%, glycerin 15 v / v% as a humectant, and methanol 85 v as a solvent. / V% is mixed to prepare a color reaction solution.

  Preferably, a carrier having air permeability, for example, a filter paper made of cellulose or the like is immersed in the color reaction solution, and the carrier is impregnated with the color reaction solution. After a predetermined time, the carrier is pulled up from the color reaction solution, the excess color reaction solution is squeezed with a rubber roller, and the solvent is evaporated at a temperature of about 40 ° C. Thereby, a sheet-like gas detection material is completed.

  FIG. 1 shows an example of an apparatus suitable for automatically measuring a gas detection material of the present invention in a tape shape. In the figure, reference numeral 1 denotes a conveyance path of the gas detection material 2. A through-hole 3 having a diameter of about 1 centimeter is formed on the surface facing the detection material 2 in the gas suction portion disposed so as to be opposed to the negative pressure from the suction pump 5 through the pipe 4. It is working.

  Reference numeral 6 denotes a measurement head unit which is disposed on the other surface side of the gas detection material 2 facing the through hole 3 of the gas suction unit 1 and is to be detected at a position facing the through hole 3 of the suction unit 1. 7 is configured as a light shielding container in which 7 is formed. The measurement head unit 6 includes a light emitting diode 8 that generates a wavelength at which a reaction mark can be detected, for example, a peak wavelength of 555 nm, and a pin type photodiode 9 having a maximum sensitivity at a detection wavelength, for example, a wavelength of 560 nm, reflected from the reaction mark. Are arranged so as to have an incident / reflection relationship so that reaction marks formed on the gas detection material 2 can be detected.

  When the above-described detection material 2 is cut into a tape shape and set on the reels 10 and 11, the suction part 1 is elastically contacted with the measuring head 6 and the suction pressure of the pump 5 is applied to the suction part 1. The test gas is sucked into the measurement head unit 6 from the inlet 12. The test gas passes through the detection material 2 from the through hole 7 and is discharged to the outside.

The test gas is taken into the moisture retained by the glycerin on the detection material 2 in the process of passing through the detection material 2, and the carbonyl fluoride contained in the test gas is
COF2 + H2O → CO2 + O2 + 2HF
To generate hydrogen fluoride (HF).
Hydrogen fluoride reacts with methyl orange originally present on the carrier, changes the color density corresponding to the density, and produces reaction traces.

  In this way, when a predetermined sampling time, for example, about 15 seconds elapses, the suction of the test gas is stopped, and the process moves to the step of measuring the optical density of the reaction trace.

That is, the light from the light emitting diode 8 is absorbed according to the optical density of the reaction mark formed on the surface of the detection material 2, so that the optical density before the start of measurement, that is, the optical density of the background of the detection material. By obtaining the difference between the concentration and the optical density of the reaction trace, the concentration of carbonyl fluoride that has passed through the detection material 2 or the accumulated passage amount can be known.
When the measurement for one sampling is completed, the paper feed mechanism 13 and the winding reel 11 are driven to move the unused portion of the detection material to the measurement region.

  This gas detection material 2 was set in the above-described measuring apparatus, its sampling time was set to 15 seconds, and a standard gas containing carbonyl fluoride up to 6 ppm in increments of 1 ppm to 1 ppm was shown in FIG. A calibration curve with high linearity could be obtained.

  In the above embodiment, a porous carrier such as filter paper is used to pass (permeate) the test gas through the carrier. Even if a carrier is used, the same effect is obtained. In this case, the test gas is allowed to flow down along the surface of the carrier, and in a simple measurement, it can be used as it is exposed to the atmospheric air.

It is sectional drawing which shows one Example of a suitable measuring apparatus when shape | molding the carbonyl fluoride detection material of this invention on a tape. It is a diagram which shows the calibration curve of the carbonyl fluoride detection material of this invention.

Explanation of symbols

    2 Gas Detection Material 5 Suction Pump 6 Measuring Head 7 Detected Gas Inlet 8 Light-Emitting Diode 9 Photodiode

Claims (4)

  A carbonyl fluoride detecting material obtained by developing a color indicator having a color change range at a hydrogen ion concentration of 3.1 to 4.4 and a humectant on a carrier.   The carbonyl fluoride detecting material according to claim 1, wherein the color indicator is methyl orange.   The carbonyl fluoride detecting material according to claim 1, wherein the humectant is glycerin.   The carbonyl fluoride detecting material according to claim 1, wherein the carrier has gas permeability.

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