JP3646389B2 - Switching device for gas analyzer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a switching device for a gas analyzer used for switching a gas flow path when selectively analyzing a plurality of sample gases or the like attached to a gas analyzer.
[0002]
[Prior art]
FIG. 5 is an explanatory diagram showing a conventional example of a gas analyzer switching device. In this figure, a plurality of measurement gas flow paths are selectively switched by a switching device 51 and connected to a gas analyzer 52. A control device (such as a microcomputer) 53 controls the operations of the gas analyzer 52 and the switching device 51.
[0003]
The switching device 51 includes a plurality of gas inlets 54 and one measurement gas outlet 55, and any one of the gas inlets 54 is measured via the common channel 58 by switching the electromagnetic valve 56. Conducted to the gas outlet 55. The opening / closing of the electromagnetic valve 56 is controlled via a drive circuit 57 based on a command from the control device 53.
[0004]
[Problems to be solved by the invention]
However, in the switching device 51 having the above-described configuration, each measurement gas flows to the gas outlet 55 via the common flow path 58, and thus has a drawback of being affected by the gas measured immediately before. . That is, taking the measurement of ammonia gas as an example, the concentration of ammonia gas measured immediately before is relatively high, and then when another measurement gas having a relatively low ammonia gas concentration is introduced from another gas inlet 54, There is a drawback that contamination (contamination) occurs due to the influence of residual gas in the common flow path 58, and a large error occurs in the measured value of the low-concentration ammonia gas.
[0005]
Such contamination has been a major problem especially when measuring low concentration gas (for example, measuring ammonia gas in a clean room for manufacturing semiconductor devices), but no effective solution has been proposed in the past. It was.
[0006]
The present invention has been made in view of the drawbacks of the conventional example as described above, and it is an object of the present invention to provide a switching device for a gas analyzer for suppressing contamination and accurately measuring a low concentration gas. To do.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the present invention has a plurality of fluid inlets, and includes switching means for selectively connecting at least one of them to the gas analyzer, for cleaning the measurement gas flow path. In the gas analyzer switching device for introducing a cleaning liquid into at least one of the fluid inlets , the cleaning liquid is pure water stored in a container, and the pure water is circulated by a pump and an ion exchange resin device. It is characterized by being configured to reproduce .
[0008]
When the measurement gas in the gas analyzer is an acidic gas or a basic gas, water can be used as the cleaning liquid.
[0009]
The cleaning liquid may be flowed every time the sample gas is switched.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
Here, an example in which the embodiment of the present invention is used as an ammonia gas measuring apparatus for measuring ammonia gas in a clean room will be described. In semiconductor device manufacturing processes, gaseous contaminants such as ammonia are known to cause pattern defects, and it is required to accurately measure the ammonia concentration in a clean room as a countermeasure. . And since the ammonia component in a clean room is very low concentration, suppression of the contamination in an ammonia gas measuring device is calculated | required strongly.
[0011]
FIG. 1 is a diagram for explaining the configuration of an embodiment of the present invention. In this figure, an ammonia gas measuring device 1 is arranged at a corner in a clean room 2. The air in each of the processing chambers A, B,..., N provided for each manufacturing process of the semiconductor device and the air in the clean room 2 are ammonia by the fluid introduction pipes a, b,. It is introduced into the gas measuring device 1.
[0012]
As shown in FIG. 2, the ammonia gas measuring device 1 includes a gas analyzing unit 21 that measures ammonia gas, a switching device 22 that selectively introduces the measuring gas into the gas analyzing unit 21, a gas analyzing unit 21, and a switching device. And an output device 24 (CRT, LCD, printer, etc.) for receiving the output of the ion chromatograph 28 via the control device 23 and outputting the measurement results. Yes.
[0013]
FIG. 3 shows a rotary valve unit as an example of the switching device 22, and this unit includes a plurality of fluid introduction ports 31 and one fluid discharge port 32. A rotatable disk-shaped rotating plate 33 is disposed inside the unit, and a groove 34 is formed in the rotating plate 33. The groove 34 allows the fluid discharge port 32 and any one of the fluid introduction ports 31 to communicate with each other. The rotating plate 33 is rotated by a geared motor 35, and a fluid introduction port communicating with the fluid discharge port 32 is selected by this rotation. As the switching device 22, for example, “Rotary valve unit” manufactured by Leodyne, “Automatic valve unit 401 series” manufactured by Frome, etc. can be used.
[0014]
As shown in FIG. 2, the gas analyzer 21 includes a diffusion scrubber 25 and an ion chromatograph 28. The diffusion scrubber 25 includes a porous hollow tube 25a formed of a fluorine-based porous membrane, and pure water as an absorbing liquid is introduced to the outside of the hollow tube 25a, and the inside of the hollow tube 25a is a fluid introduction tube. The fluid outlet 32 of the switching device 22 is connected by p. A pump 26 is arranged on the outlet side of the diffusion rubber 25 to suck in the measurement gas, and the ammonia component in the measurement gas is absorbed by the absorption liquid while passing through the hollow tube 25a. On the other hand, moisture in the measurement gas is discharged through the valve 27. The absorption liquid that has absorbed the ammonia component is sent to the ion chromatograph 28 where the ammonia is separated and analyzed. The analysis result is sent to the output device 24 via the control device 23 and output (displayed) as the ammonia concentration.
[0015]
Pure water 41 as a cleaning liquid is supplied to one of the plurality of fluid introduction ports 31 of the switching device 22 shown in FIG. Further, the pure water 41 is circulated and regenerated through the ion exchange resin device 43 by the pump 42 of FIG.
[0016]
Next, the operation of the embodiment of the present invention will be described with reference to the timing chart of the embodiment of the present invention shown in FIG. 4 and FIG.
[0017]
First, the control device 23 drives the geared motor 35 of FIG. 3 to rotate the rotating plate 33 and controls the switching device 22 so that the measurement gas in the A chamber flows (FIG. 4A). The measurement gas from the chamber A is sucked by the pump 26 in FIG. 2, the ammonia component contained in this measurement gas is collected in the absorption liquid of the diffusion scrubber 25 in FIG. 2, and the absorption liquid is sent to the gas analysis unit 21. It is analyzed (FIG. 4 (e)). After a predetermined time (for example, 20 minutes) has elapsed, the fluid introduction port of the switching device 22 is switched to the cleaning liquid side, and a trace amount (for example, 0.1 cc) of cleaning liquid is introduced into the switching device 22 (FIG. 4B). As a result, the ammonia component remaining in the switching device 22 is collected in the cleaning liquid (water), and contamination is suppressed. The cleaning liquid is pushed out by the pressure of the pump 42, passes through the hollow tube 25 a of the diffusion scrubber through the switching device 22, and is discharged through the valve 27.
[0018]
Next, the switching device 22 introduces the measurement gas in the B chamber (FIG. 4C), and thereafter repeats the same operation until the measurement gas is introduced into the N chamber (FIG. 4D).
[0019]
If the gas analyzer of the present invention as described above is used, contamination in the switching device can be minimized. According to the experiments of the present inventor, the contamination can be greatly suppressed as compared with the case where the conventional apparatus is used. Specifically, when the conventional switching device shown in FIG. 5 and the switching device of the above-described embodiment of the present invention (using an 8-way rotary valve) were subjected to a comparative test, contamination when using the device of FIG. Was 23%. In other words, when a measurement gas containing 20 ppb of ammonia flows from one fluid inlet and then a measurement gas of 0 ppb of ammonia flows from another fluid inlet, the measured value should be 0 ppb if there is no contamination. It was 4.6 ppb (20 × 0.23 ppb). When the switching device of the above example was tested in the same manner, the contamination was 4.0% when there was no cleaning liquid and 0.9% when the cleaning liquid was introduced.
[0020]
When a rotary valve is used as the switching device, the common flow path (see 58 in FIG. 5) can be shortened, so that contamination can be significantly suppressed. Furthermore, when the flow path of the rotary valve is washed with a washing solution, contamination can be suppressed almost.
[0021]
In the above apparatus, the timing of introducing the cleaning liquid is arbitrary. For example, the cleaning liquid may be introduced only after the measurement gas having a particularly high concentration is measured, or the cleaning liquid may be cleaned every time the measurement gas is switched. Good. If cleaning is performed every time the measurement gas is switched, it is possible to obtain accurate measurement values while suppressing contamination in the measurement of all measurement gases.
[0022]
As the switching device of the present invention, an electromagnetic valve type device as in the conventional device (FIG. 5) may be used, but the use of the rotary valve as in the above embodiment has a great effect of suppressing contamination. In addition, the switching cycle can be shortened.
[0023]
In the embodiments of the present invention, pure water is used as the cleaning liquid. However, the cleaning liquid is not limited thereto, and a fluid such as an organic solvent may be used according to the property of the measurement gas.
[0024]
【The invention's effect】
As described above, according to the present invention, there are provided a plurality of fluid introduction ports, including switching means for selectively conducting at least one of them to the gas analyzer, for cleaning the measurement gas flow path. In the gas analyzer switching device for introducing a cleaning liquid into at least one of the fluid inlets , the cleaning liquid is pure water stored in a container, and the pure water is circulated by a pump and an ion exchange resin device. Since it is configured to regenerate, it is possible to prevent the degradation of pure water, and to obtain an effect that accurate measurement can be performed while suppressing contamination.
[Brief description of the drawings]
FIG. 1 is a diagram showing an arrangement of a clean room ammonia gas measuring apparatus using a gas analyzer switching device according to the present invention in a clean room.
FIG. 2 is a configuration explanatory view of an embodiment of the present invention showing a configuration of an ammonia gas measuring device.
FIG. 3 is a perspective view of a rotary valve unit as a switching device.
FIG. 4 is a timing chart showing the operation of the embodiment.
FIG. 5 is a configuration explanatory diagram of a conventional example showing a conventional switching device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Ammonia gas measuring device 21 Gas analysis part 22 Switching apparatus 31 Fluid inlet 41 Cleaning liquid

Claims (3)

A switching means having a plurality of fluid inlets, selectively switching at least one of the fluid inlets to the gas analyzer, and having at least one of the fluid inlets as a cleaning liquid for cleaning the measurement gas channel In the gas analyzer switching device to be introduced into the gas , the cleaning liquid is pure water stored in a container, and the pure water is circulated and regenerated by a pump and an ion exchange resin device. Switching device for analyzer.   The switching device according to claim 1, wherein the cleaning liquid is introduced each time the switching means is switched.   The switching device according to claim 1 or 2, wherein the switching means is a rotary valve.

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