JP4240680B2 - Octafluorocyclopentene measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a measuring apparatus for detecting pyrofluorooctene, a kind of 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 was made in view of such problems, it is an object regardless of whether the fluorine-based cleaning agent, octa capable of measuring the octafluorocyclopentene about control concentration with high precision It is to provide a fluorocyclopentene measuring device.
[0004]
[Means for Solving the Problems]
In order to solve such a problem, in the present invention, the first reaction furnace, the moisture absorption cylinder having the carrier supported by the moisture absorbent, the second reaction furnace, and the acid gas detection means are connected in series. At the same time, the heating temperature of the first reactor is set to a first temperature of 700 to 850 ° C. at which the fluorine-based cleaning agent can be thermally decomposed and octafluorocyclopentene is not modified as much as possible. The heating temperature of the furnace was set to a second temperature at which the octafluorocyclopentene can be pyrolyzed.
[0005]
[Action]
In the first reactor 1, only the fluorine-based cleaning agent other than octafluorocyclopentene is thermally decomposed into acidic gases and flows into the moisture absorbing cylinder, and is absorbed and removed by the moisture in the moisture absorbing agent. The octafluorocyclopentene that has passed through the moisture absorption cylinder is thermally decomposed into acidic gas in the second reactor, and its concentration is measured by the acidic 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 moisture absorption cylinder 4.
[0007]
The hygroscopic cylinder 4 is composed of a granular material such as silica gel or alumina, or a carrier 5 made of a porous cellulose granular material as described in Japanese Patent Laid-Open No. 3-231942, and a hygroscopic agent such as polyvalent glycerin. It contains a material impregnated with alcohol.
[0008]
A second reaction furnace 6 is connected to the outlet 4 b of the moisture absorption cylinder 4. The second reaction furnace 6 is configured by winding a heater 8 around a reaction tube 7 having an inlet 7a connected to the hygroscopic cylinder 4. The outlet 7b has an acid gas detection means, in this embodiment a detection paper. The gas detector 10 is connected.
[0009]
The detection paper type gas detection device 10 includes a tape transport mechanism 15 that transports the detection paper 11 processed into a tape shape to a measurement head 14 including a light emitting element 12 and a light receiving element 13 at regular intervals, and a sampling pump 16. The suction head 17 is configured to receive the negative pressure from the gas and to bring the test gas into contact with the detection paper 11 in cooperation with the measurement head 14.
[0010]
The detection paper 11 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 temperature control means 20 allows the heating temperature of the first reactor 1 to be thermally decomposed with a fluorine-based cleaning agent other than octafluorocyclopentene (C 5 F 8 ) , and octafluorocyclopentene as much as possible. The temperature of the second reactor 6 is adjusted to a temperature at which the octafluorocyclopentene can be thermally decomposed, for example, 900 to 1000 ° C.
[0012]
When the sampling pump 16 is operated in this state, a test gas containing a fluorine-based cleaning agent flows in from the inlet 2a of the first reactor 1, and a fluorine-based material other than octafluorocyclopentene is used in the first reactor 1. Only the cleaning agent is thermally decomposed into acidic gases, and octafluorocyclopentene flows into the moisture absorption cylinder 4 in an undecomposed state. Only the acidic gas is selectively absorbed and removed by the moisture retained by the moisture absorbent of the carrier 5 of the moisture absorbing cylinder 4.
[0013]
On the other hand, octafluorocyclopentene is hardly absorbed and flows into the second reactor 6 as it is, and is thermally decomposed into an acidic gas such as hydrogen fluoride (HF). The acidic gas generated in the second reaction furnace 6 flows into the detection paper type gas detection device 10 and reacts with the reagent of the detection paper 11 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 octafluorocyclopentene, it is possible to arbitrarily set the detection sensitivity by adjusting the sampling time.
[0014]
Thereby, even if a fluorine-type cleaning agent is mixed in the test gas, octafluorocyclopentene having a low concentration can be measured with high accuracy.
[0015]
In the above-described embodiment, the hygroscopic cylinder is configured to accommodate the granular material carrying the hygroscopic agent, but the belt-like body such as cellulose impregnated with the hygroscopic agent is ensured in the winding direction. Even if it is wound with a closing degree as much as possible and accommodated so that the direction of the winding axis is the gas flow direction, the same effect can be obtained.
[0016]
FIG. 2 shows a second embodiment of the present invention. In this embodiment, the moisture is formed into a tube by using a material that selectively allows moisture to permeate into the inlet 2a of the first reactor 1. A permeable tube 22 (for example, trade name Nafion tube) is connected.
According to this embodiment, the moisture in the environment permeates through the moisture permeable tube 22 and flows into the moisture absorption cylinder 4 to replenish the moisture, thereby improving the acid gas removal efficiency. In addition, since the Nafion tube has high hydrocarbon gas permeability, even if the sampled gas to be measured contains a high concentration of alcohol such as a cleaning agent, it is selectively discharged out of this system. Therefore, measurement errors can be suppressed.
[0017]
In the above-described embodiment, the gas generated by the thermal decomposition of octafluorocyclopentene is detected by the color reaction of the detection paper. However, the electrochemical formula capable of detecting the thermal decomposition gas of octafluorocyclopentene. Obviously, other types of gas sensors such as a gas sensor can be used to achieve the same effect.
[0018]
【The invention's effect】
Above, in the first reactor 1 according to the present invention as described by the fluorine-based cleaning agent other than octafluorocyclopentene is thermally decomposed is removed by moisture absorption tube acidic gases, octafluorocyclopentene is second It can be thermally decomposed into acidic gas in the reaction furnace and detected by the acidic gas detection means, and octafluorocyclopentene 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 present invention with a structure on the inflow side of the first reactor 4;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 1st reaction furnace 4 Hygroscopic cylinder 5 Carrier 6 2nd reaction furnace 10 Acid gas detection means

Claims (4)

A first reaction furnace, a moisture absorption cylinder having a moisture absorbent supported on a carrier, a second reaction furnace, and an acid gas detection means are connected in series, and the heating temperature of the first reaction furnace is set to fluorine-based. The cleaning agent can be thermally decomposed and the first temperature of 700 to 850 ° C. at which the octafluorocyclopentene is not modified as much as possible, and the heating temperature of the second reactor is the first temperature capable of thermally decomposing the octafluorocyclopentene . An octafluorocyclopentene measuring device set at a temperature of 2. The octafluorocyclopentene measuring apparatus according to claim 1, wherein the carrier is configured by winding a granular body or a band-shaped body. The octafluorocyclopentene measuring apparatus according to claim 1, wherein the hygroscopic agent is a polyhydric alcohol. The octafluorocyclopentene measuring apparatus according to claim 1, wherein a moisture permeable tube is connected upstream of the first reactor.

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