JP3601635B2 - Switching device for gas analyzer - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a gas analyzer switching device that is mounted on a gas analyzer and is used to selectively switch a gas flow path when selectively analyzing a plurality of measurement gases.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, when measuring gas concentration in a clean room or the like, air at a measurement point in the clean room is introduced into a gas analyzer through a fluid introduction pipe, and the concentration of ammonia gas or the like is measured to a sub-ppb level. ing. Generally, there are a plurality of measurement points, air is introduced from a plurality of points by a plurality of fluid introduction pipes, the fluid introduction pipes are switched using a switching device, and a selected measurement gas is introduced into the gas analyzer. It has become.
[0003]
[Problems to be solved by the invention]
The gas analyzer is generally arranged at a position distant from the measurement point, and is connected by a fluid introduction pipe between them, and in some cases, is separated by about 50 m. When the measurement point and the analyzer are separated in this way, the previously measured gas may remain in the fluid introduction pipe that sends the measurement gas, or the previously measured gas component may adhere to the wall of the fluid introduction pipe. This causes a problem of being affected by the gas measured last time. For example, considering the case where the concentration of ammonia gas at a measurement point at a certain time is relatively high and the concentration at the next time is lower than the previous time, the influence of the residual gas in the fluid introduction pipe at the previous time is Contamination occurs, causing errors in measured values at the next time point.
[0004]
Such a contamination has been a major problem when measuring low-concentration gases, such as ammonia gas measurement in a clean room, but no effective solution has been proposed. .
[0005]
The present invention has been made in view of the above-described drawbacks of the conventional example, and has an object to provide a gas analyzer switching device for suppressing contamination and enabling accurate measurement of a low concentration gas. I do.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, in the present invention, a switching means having a plurality of fluid introduction paths and selectively conducting at least one of the fluid introduction paths to a gas analyzer, and a measuring means connected to each of the fluid introduction paths. The switching device for the gas analyzer was constituted by the suction means for sucking the gas.
[0007]
Each fluid introduction path can be connected to the suction means via a valve, and these valves can be controlled independently.
[0008]
The control is such that, for example, when one of the fluid introduction paths is selected, a valve connected to the selected fluid introduction path is closed, and the other valves are opened.
[0009]
BEST MODE FOR CARRYING OUT 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 device for measuring ammonia gas in a clean room will be described. In a semiconductor device manufacturing process, it is known that a gaseous contaminant such as ammonia causes a pattern defect. To prevent such a problem, it is required to accurately measure the ammonia concentration in a clean room. . Since the concentration of the ammonia component in the clean room is extremely low, suppression of contamination in the ammonia gas measuring device is strongly required.
[0010]
FIG. 1 is an explanatory view of 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 the processing chambers A, B,..., N provided in each manufacturing process of the semiconductor device and the air in the clean room 2 are supplied through the fluid introduction pipes a, b,. It is introduced into the gas measuring device 1.
[0011]
As shown in FIG. 2, the ammonia gas measuring device 1 includes a gas analyzer 21 for measuring ammonia gas, a switching device 22 for selectively introducing a measurement gas into the gas analyzer 21, and a gas analyzer 21 and a switching device. A control device 23 (sequencer, personal computer, etc.) for controlling the device 22, 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 result. I have.
[0012]
On the upstream side of the switching device 22, suction pipes 51z, 51a, 51b,..., 51n are connected in the middle of the fluid introduction pipes z, a, b,. , 52a, 52b,..., 52n are connected to the suction pump 53. The solenoid valves 52z, 52a, 52b,..., 52n are independently controlled to open and close according to commands from the controller 23. The drive of the suction pump 53 is also controlled by the controller 23.
[0013]
The suction flow rate of the suction pump 53 is higher than the suction flow rate of the pump 26 described later, and is about 10 to 20 liters / minute (the pump 26 is about 1 liter / minute).
[0014]
FIG. 3 shows a rotary valve unit as an example of the switching device 22. This unit includes a plurality of fluid inlets 31 and one fluid outlet 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 outlet 32 to communicate with any one of the fluid inlets 31. The rotating plate 33 is rotated by a geared motor 35, and by this rotation, a fluid inlet which is communicated with the fluid outlet 32 is selected. The switching device 22 may be, for example, a "Rotary valve unit" manufactured by Leodyne or an "Automatic valve unit 401 series" manufactured by From.
[0015]
The gas analyzer 21 includes a diffusion scrubber 25 and an ion chromatograph 28 as shown in FIG. The diffusion scrubber 25 includes a porous hollow tube 25a made of a fluorine-based porous film, and pure water as an absorbing liquid is introduced outside the hollow tube 25a, and a fluid introduction tube is provided inside the hollow tube 25a. It is connected to the fluid outlet 32 of the switching device 22 by p. A pump 26 is arranged on the outlet side of the diffusion slab 25 to suck in the measurement gas, and the ammonia component in the measurement gas is absorbed by the absorbing liquid while passing through the hollow tube 25a. On the other hand, the moisture in the measurement gas is discharged through the valve 27. The absorbing solution having absorbed the ammonia component is sent to the ion chromatograph 28, where the ammonia is separated and analyzed. This analysis result is sent to the output device 24 via the control device 23 and output (displayed) as the ammonia concentration.
[0016]
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. 3 via a fluid introduction pipe x. Further, the pure water 41 is circulated and regenerated through the ion exchange resin device 43 by the pump 42 of FIG.
[0017]
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.
[0018]
First, the control device 23 closes, for example, the solenoid valve 52a and opens all the remaining solenoid valves (FIGS. 4F, 4G, and 4H), and drives the geared motor 35 in FIG. The switching device 22 is rotated so that the measurement gas flows from the fluid introduction pipe a (FIG. 4A). The measurement gas from the chamber A is sucked by the pump 26 in FIG. 2, and the ammonia component contained in the 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 analyzer 21. It is analyzed (FIG. 4 (e)).
[0019]
While the measurement gas from the chamber A is being sent from the fluid introduction pipe a to the gas analyzer 21, a large amount of the measurement gas from the other fluid introduction pipe is sucked by the suction pump 53 via each solenoid valve 52.
[0020]
After a lapse of a predetermined time (for example, 20 minutes), the fluid inlet of the switching device 22 is switched to the cleaning liquid side, and a small amount (for example, 0.1 cc) of the cleaning liquid is introduced into the switching device 22 (FIG. 4B). Thereby, the ammonia component remaining in the switching device 22 is collected by the cleaning liquid (water) and washed. The cleaning liquid is pushed out by the pressure of the pump 42, passes through the switching device 22, passes through the hollow tube 25 a of the diffusion scrubber, and is discharged via the valve 27.
[0021]
Next, the controller 23 closes the solenoid valve 52b and opens all remaining solenoid valves (FIGS. 4 (f), (g), and (h)) so that the measurement gas flows from the fluid introduction pipe b. The switching device 22 is controlled (FIG. 4C). During this time, a large amount of the measurement gas is sucked from another fluid introduction pipe by the suction pump 53. Hereinafter, the same operation is repeated until the measurement gas is introduced into the N chamber (FIG. 4D).
[0022]
When the gas analyzer of the present invention as described above is used, even if the length of the fluid introduction pipe is long, the gas flow rate is increased by suction of the suction pump 53, so that the residual gas and the attached gas in the fluid introduction pipe are increased. And the influence of the previous measurement gas is reduced.
[0023]
According to the experiments by the inventors, in the case of the conventional type device without the suction pump 53, the response (the measured value divided by the true value of the measured amount) is obtained because the measured gas is sucked only by the pump 26. It was bad. In other words, the response was poor and about 75% even when 24 hours had passed after using a 50 m fluid introduction pipe. On the other hand, when the above apparatus was used to perform suction for 1 hour at a suction rate of 15 liters / minute by the suction pump 53 before the start of the measurement, the response at the elapse of 1 hour after the start of the measurement was 93% and 2 hours. The response at the passage of time was 97%, and a measurement result with little contamination was obtained. It should be noted that by increasing the suction time in advance, the subsequent response is improved.
[0024]
In the above embodiment, all of the fluid introduction pipes are sucked by the suction pump 53. However, only predetermined fluid introduction pipes are sucked by the suction pump 53, and other fluid introduction pipes are sucked by the pump 26. You may. Then, there is an advantage that the capacity of the suction pump 53 can be small.
[0025]
By the way, in order to increase the amount of suction from each fluid introduction pipe, it is conceivable that a large amount of suction is performed by the pump 26 in the conventional type device. However, the absorption liquid (pure water) is also sucked, and the problem that water enters the pump 26 occurs. It is also conceivable to arrange a pump upstream of the diffusion scrubber 25. However, this causes a problem that ammonia generated from inside the pump enters the diffusion scrubber 25, making it impossible to measure a small amount of ammonia. On the other hand, according to the present invention, since the suction pump 53 is disposed on the upstream side of the switching device 22, it is possible to perform accurate measurement with less contamination without causing the above-described problem. it can.
[0026]
【The invention's effect】
As described above, according to the present invention, it is possible 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 in a clean room of an ammonia gas measuring device for a clean room using a switching device for a gas analyzer according to the present invention.
FIG. 2 is a configuration explanatory view of an embodiment of the present invention showing the 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.
[Explanation of symbols]
1 Ammonia gas measuring device 21 Gas analyzer 22 Switching device 51z, 51a, 51b, ..., 51n Suction pipe 52z, 52a, 52b, ..., 52n Electromagnetic valve 53 Suction pump z, a, b, ..., n Fluid introduction pipe

Claims (1)

Switching means having a plurality of fluid introduction paths and selectively guiding at least one of the fluid introduction paths to the gas analyzer; and suction means connected to each of the fluid introduction paths via a valve for aspirating a measurement gas. Controlling the valves independently, and when one of the fluid introduction paths is selected by the switching means, closes the valve connected to the selected fluid introduction path, and opens the other valves. A switching unit for controlling the gas analyzer.

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