JP4059596B2 - Perfluorocarbons measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a measuring device for detecting perfluorocarbons by pyrolysis.
[0002]
[Prior art]
Perfluorocarbons used as a working gas for dry etching of silicon wafers have a low global warming effect coefficient and are toxic to the human body. Since such low-concentration perfluorocarbons cannot be directly detected by existing sensors, they are usually pyrolyzed at a temperature of several hundred degrees or more to generate an acid gas, and this acid gas is converted into a colored reaction sheet. It is detected by the tape type gas detector used or the electrochemical gas sensor.
[0003]
[Problems to be solved by the invention]
In a clean room of a semiconductor factory where such a gas is used, a fluorine-based cleaning agent is used when cleaning equipment. Such a fluorine-based cleaning agent has a problem that it contains a large error in the measurement of perfluorocarbon because an acid gas component is generated by thermal decomposition at a temperature necessary for thermally decomposing perfluorocarbons.
The present invention has been made in view of such problems, and the object of the present invention is a perfluorocarbon capable of measuring perfluorocarbons having a management concentration with high accuracy regardless of the presence or absence of a fluorine-based cleaning agent. It is to provide a fluorocarbons measuring device.
[0004]
[Means for Solving the Problems]
In order to solve such a problem, in the present invention, the first reactor, the water scrubber means, the moisture permeation conduit, the second reactor, and the acid gas detection means are connected in series. The heating temperature of the first reactor is set to 700 to 850 ° C. in which the fluorine-based cleaning agent can be thermally decomposed and the perfluorocarbons are not modified as much as possible, and the heating temperature of the second reactor is perfluorocarbon compound is to set the temperature you pyrolysis.
[0005]
[Action]
In the first reactor 1, only the fluorine-based cleaning agent is thermally decomposed into acidic gases and removed by the water scrubber means. The perfluorocarbons that have passed through the water scrubber means are subjected to thermal decomposition into acid gas in the second reactor after the excess water is removed, and the concentration thereof is measured by the acid gas detection means.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Therefore, details of the present invention will be described below based on the illustrated embodiment.
FIG. 1 shows an embodiment of the present invention. A first reactor 1 is configured by winding a heater 3 around a reaction tube 2 having an inlet 2a connected to a sampling region. 2 b is connected to the inlet 4 a of the water scrubber means 4.
[0007]
In this embodiment, the water scrubber means 4 includes a water permeable tube 5 (product name: Nafion tube) in which a material that selectively permeates water is formed into a tubular shape, and a water absorption cylinder 7 containing a granular moisture absorbent 6 such as silica gel. Are connected in series so that the tube 5 is located on the upstream side.
[0008]
The outlet 4b of the water scrubber means 4 is connected to the second reactor 9 through a moisture permeable tube 8 similar to the aforementioned moisture permeable tube 5. The second reaction furnace 9 is configured by winding a heater 11 around a reaction tube 10 having an inflow port 10a connected to the moisture permeable tube 5, and an acid gas detection means, in this embodiment, in the outflow port 10b. A detection paper type gas detection device 12 is connected via a conduit 13.
[0009]
The detection paper type gas detection device 12 includes a tape transport mechanism 18 that transports the detection paper 14 processed into a tape shape to a measurement head 17 including a light emitting element 15 and a light receiving element 16 at regular intervals, and a sampling pump 20. The suction head 19 is configured to receive the negative pressure from the gas and to bring the test gas into contact with the detection paper 14 in cooperation with the measurement head 17.
[0010]
The detection paper 14 may be any color as long as it reacts with an acidic gas such as HF, for example, methyl red 0.22 wt%, buffer solution 17.5 ml, and a humectant such as glycerin or ethylene glycol. It can be produced by impregnating a filter paper made of cellulose into a color developing solution prepared by dissolving 15 ml of a polyhydric alcohol in a readily evaporable organic solvent so that the total amount becomes 100 ml, and volatilizing the organic solvent.
[0011]
In this embodiment, the heating temperature of the first reactor 1 is controlled by the temperature control means 21 so that the fluorine-based cleaning agent can be thermally decomposed and the perfluorocarbons such as C5F8 are not denatured as much as possible. The heating temperature of the second reaction furnace 9 is adjusted to 700 to 850 ° C. and the temperature at which the perfluorocarbons can be pyrolyzed, for example, 900 to 1000 ° C.
[0012]
When the sampling pump 20 is operated in this state, a test gas containing a fluorine-based cleaning agent flows from the inlet 2a of the first reactor 1, and only the fluorine-based cleaning agent is acidic in the first reactor 1. It is thermally decomposed into gases, and perfluorocarbons flow into the water scrubber means 4 in an undecomposed state. In the water scrubber means 4, since the moisture in the air that has passed through the moisture permeable tube 5 is supplied to the saturated state in advance, only the acidic gas having extremely high solubility in water is removed by the water scrubber means 4. The
[0013]
On the other hand, perfluorocarbons are hardly absorbed and flow into the moisture permeable tube 8 to release excess moisture into the atmosphere by the water scrubber means 4 and into the second reaction furnace 9 to enter hydrogen fluoride (HF). ) And other acidic gases. The acidic gas generated in the second reaction furnace 9 flows into the detection paper type gas detection device 11 and reacts with the reagent of the detection paper 14 to generate reaction traces having an optical concentration corresponding to the concentration of the acidic gas. Since this reaction proceeds in proportion to the integrated concentration of perfluorocarbons, it is possible to arbitrarily set the detection sensitivity by adjusting the sampling time.
[0014]
Thereby, even if the fluorine-based cleaning agent is mixed in the test gas, perfluorocarbons having a low concentration can be measured with high accuracy. Further, since excess water is removed in advance by the water scrubber means 4, perfluorocarbons can be reliably pyrolyzed without incurring waste of heat energy due to heating of water in the second reactor 9. In addition, it is possible to prevent occurrence of errors in the acid gas detection means due to excessive moisture.
[0015]
In the above-described embodiment, the water scrubber means 4 is constituted by a water absorption tube containing a moisture permeable tube and a hygroscopic agent. However, as shown in FIG. Even if a bubbling device provided such that the lower end of the inflow side pipe 32 is located below the water surface and the lower end of the outflow side pipe 33 is located in the space 34 is used, the same effect can be obtained.
[0016]
In the above-described embodiments, the gas generated by the thermal decomposition of the perfluorocarbons is detected by the color reaction of the detection paper, but the electrochemical type capable of detecting the thermal decomposition gas of the perfluorocarbons. Obviously, other types of gas sensors such as a gas sensor can be used to achieve the same effect.
[0017]
【The invention's effect】
As described above, according to the present invention , in the first reactor, only the fluorine-based cleaning agent can be thermally decomposed into acidic gases and removed by the water scrubber means, and the excess of perfluorocarbons that have passed through the water scrubber means. After removing excessive moisture, it is reliably pyrolyzed into an acidic gas in the second reactor, and perfluorocarbons can be detected with high accuracy without being affected by impurities.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an embodiment of the present invention.
FIG. 2 is a view showing another embodiment of the water scrubber means.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 1st reactor 4 Water scrubber means 5 Moisture permeable tube 7 Water absorption cylinder 8 Moisture permeable tube 9 Second reactor 12 Acid gas detection means

Claims (2)

The first reaction furnace, the water scrubber means, the moisture permeation conduit, the second reaction furnace, and the acid gas detection means are connected in series, and the heating temperature of the first reaction furnace is set to a fluorine-based cleaning agent. pyrolysis possible, and perfluorocarbon ethers to as much as possible denatured no 700 to 850 ° C, also the perfluorocarbon such a heating temperature of the second reactor is set to that temperature C to pyrolysis Perfluorocarbons measuring device.  The perfluorocarbons measurement according to claim 1, wherein the water scrubber means is configured by connecting a moisture permeable tube and a water absorbing cylinder containing a hygroscopic agent so that the moisture permeable tube is on the upstream side. apparatus.

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