JPH09318609A - Switching device for gas analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform accurate measuring by suppressing contamination (pollution) in a gas analyzer. SOLUTION: An ammonia gas measuring device 1 includes a gas analyzing part 21 for measuring ammonia gas, a switching device 22 for selectively introducing a plurality of measured gases to the gas analyzing part 21, a controller 23 for controlling the gas analyzing part 21 and the switching device 22, an output device 24 for outputting measuring results an a suction pump 23 for sucking a great amount of measured gas. For measuring the gas from an introducing pipe (a), a solenoid valve 52a is closed while other solenoid valves are opened. The switching device 22 selects the fluid introducing pipe (a). Then, only the gas from the introducing pipe (a) is sent through the switching device 22 to the gas analyzing part 21. The gases from the other introducing pipes are all sucked by the suction pump 23. Since a gas flow rate is increased by the sucking of the suction pump 23, the influence of gas remaining in the fluid introducing pipe or stuck gas is prevented and accurate measuring is performed with little contamination.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas analyzer switching device which is mounted on a gas analyzer and is used for switching gas passages when selectively analyzing a plurality of measurement gases.

[0002]

2. Description of the Related Art Conventionally, when measuring a 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 to measure the concentration of ammonia gas or the like to a sub ppb level. Is being done. Generally, there are a plurality of measurement points, air is introduced from the plurality of points by a plurality of fluid introduction pipes, the fluid introduction pipes are switched by using a switching device, and the selected measurement gas is introduced to the gas analyzer. It is like this.

[0003]

The gas analyzer is generally arranged at a position distant from the measuring point, and is connected by a fluid introducing pipe between them, and in some cases it may be separated by about 50 m. If the measurement location and the analyzer are separated from each other 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. However, this causes a problem of being affected by the previously measured gas. For example, consider the case where the concentration of ammonia gas at a measurement point at a certain time point was relatively high, and the concentration at the next time point was lower than that at the previous time point, so it was affected by the residual gas in the fluid introduction pipe at the previous time point. Contamination occurs, which causes an error in the measured value at the next time point.

Such contamination is particularly
It was a big problem when measuring low concentration gas such as ammonia gas measurement in a clean room.
So far, no effective solution has been proposed.

The present invention has been made in view of the above-mentioned drawbacks of the conventional example, and provides a gas analyzer switching device for suppressing contamination and enabling accurate measurement of a low-concentration gas. Is an issue.

[0006]

In order to solve the above-mentioned problems, in the present invention, a switching means having a plurality of fluid introduction passages for selectively conducting at least one of the fluid introduction passages to a gas analyzer, and the fluid. The gas analyzer switching device was constituted by the suction means connected to each of the introduction paths and sucking the measurement gas.

Each fluid introducing passage may be connected to a suction means via a valve, and these valves may be independently controlled.

The above-mentioned control is performed, for example, so that when one of the fluid introducing passages is selected, the valve connected to the selected fluid introducing passage is closed and the other valves are opened.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below 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 the manufacturing process of semiconductor devices, it is known that gaseous contaminants such as ammonia cause pattern defects, and as a countermeasure against this, it is required to accurately measure the ammonia concentration in the clean room. . And
Since the ammonia component in the clean room has an extremely low concentration, suppression of contamination in the ammonia gas measuring device is strongly required.

FIG. 1 is an explanatory view of the configuration of the embodiment of the present invention.
In this figure, the ammonia gas measuring device 1 is arranged at a corner in the clean room 2. The air in each of the processing chambers A, B, ...
, N and the fluid introducing pipe z are introduced into the ammonia gas measuring device 1, respectively.

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 the measurement gas to the gas analysis unit 21, a control device 23 (sequencer, personal computer, etc.) for controlling the gas analysis unit 21 and the switching device 22, and a control device for controlling the output of the ion chromatograph 28. Two
Output device 24 (CR
T, LCD, printer, etc.).

On the upstream side of the switching device 22, a suction pipe 51 is provided in the middle of each fluid introduction pipe z, a, b, ..., N.
, 51n are connected, and these suction pipes 51 have solenoid valves 52z, 52a, 52b ,.
It is connected to the suction pump 53 via n. Solenoid valve 5
.., 52n are controlled to be opened and closed independently by a command from the control device 23. The suction pump 53 is also driven and controlled by the control device 23.

The suction flow rate of the suction pump 53 is higher than the suction flow rate of the pump 26, which will be described later, and is about 10 to 20 liters / minute (the pump 26 is about 1 liter / minute).

FIG. 3 shows a rotary valve unit as an example of the switching device 22, and this unit includes a plurality of fluid inlets 31 and one fluid outlet 32. A rotatable disc-shaped rotary plate 33 is arranged inside the unit, and a groove 34 is formed in the rotary plate 33. The groove 34 connects the fluid discharge port 32 and any one of the fluid introduction ports 31. The rotating plate 33 is rotated by the geared motor 35, and this rotation selects the fluid inlet port communicating with the fluid outlet port 32. As the switching device 22, for example, a "rotary valve unit" manufactured by Rheodyne Co., Ltd. or an "automatic valve unit 401 series" manufactured by From Co., Ltd. may be used.

As shown in FIG. 2, the gas analysis section 21 includes a diffusion scrubber 25 and an ion chromatograph 28. The diffusion scrubber 25 includes a porous hollow tube 25a made of a fluorine-based porous film, 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. fluid discharge port 3 of the switching device 22 by p
It is connected to 2. A pump 26 is arranged on the outlet side of the diffusion slubber 25 to suck 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 water content in the measurement gas is discharged via 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.

Pure water 41 as a cleaning liquid is supplied to one of the plurality of fluid introducing ports 31 of the switching device 22 shown in FIG. 3 via a fluid introducing pipe x. Further, the pure water 41 is shown in FIG.
The pump 42 of FIG.

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.

First, the controller 23 closes, for example, the solenoid valve 52a and opens all the remaining solenoid valves (see FIG. 4).
(F) (g) (h)), the geared motor 35 of FIG. 3 is driven to rotate the rotary plate 33, and the switching device 22 is controlled so that the measurement gas from the fluid introduction pipe a flows (FIG. 4).
(A)). The measurement gas from the chamber A is sucked by the pump 26 of FIG. 2, the ammonia component contained in the measurement gas is collected by the absorption liquid of the diffusion scrubber 25 of FIG. 2, and the absorption liquid is sent to the gas analysis unit 21. Analyzed (Figure 4)
(E)).

While the measurement gas from the chamber A is being sent from the fluid introduction pipe a to the gas analysis section 21, a large amount of the measurement gas from the other fluid introduction pipes is sucked by the suction pump 53 via each electromagnetic valve 52. To be done.

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. 4 (b)). ). As a result, the ammonia component remaining in the switching device 22 is collected in the cleaning liquid (water) and cleaned. The cleaning liquid is pushed out by the pressure of the pump 42,
After passing through the switching device 22, it passes through the hollow tube 25a of the diffusion scrubber and is discharged through the valve 27.

Next, the controller 23 closes the solenoid valve 52b and opens all the remaining solenoid valves (FIGS. 4 (f) (g)).
(H)), The switching device 22 is controlled so that the measurement gas from the fluid introducing pipe b flows (FIG. 4 (c)). During that time, a large amount of the measurement gas is sucked from the other 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. 4 (d)).

When the gas analyzer of the present invention as described above is used, the gas flow rate increases due to the suction of the suction pump 53 even when the length of the fluid introducing pipe is long, so that the residual gas in the fluid introducing pipe is increased. It is less likely to be affected by the adhered gas, and the effect of the previously measured gas is reduced.

According to the experiments conducted by the inventors, the suction pump 53
In the case of the conventional type device without the pump, the measurement gas is sucked only by the pump 26, so that the response (measured value divided by the true value of the measured amount) was poor. That is, the response was poor and was about 75% even after 24 hours had elapsed using a 50 m fluid introduction pipe. On the other hand, using the above-mentioned apparatus, the suction pump 53 was used to measure 15 liters /
After inhaling for 1 hour with a minute inhalation amount, 1
93% responded over time and 97 responded over 2 hours
%, And the measurement result with less contamination was obtained. It should be noted that by increasing the suction time in advance, the response after that becomes better.

In the above embodiment, the suction pump 53 sucks all the fluid introducing pipes, but only the predetermined fluid introducing pipe is sucked by the suction pump 53, and the other fluid introducing pipes are sucked by the pump 26. You may do it. This has the advantage that the capacity of the suction pump 53 can be small.

By the way, in order to increase the suction amount from each fluid introduction pipe, in the conventional type device, the pump 26
Although it is possible to inhale a large amount by this, a considerable negative pressure is applied to the diffusion scrubber 25, and not only the measurement gas but also the absorbing liquid (pure water) is sucked in, which causes water to enter the pump 26. The problem arises. It is also conceivable to arrange a pump on the upstream side of the diffusion scrubber 25. However, if this is done, ammonia generated from within the pump will enter the diffusion scrubber 25, and this will cause a problem that a trace amount of ammonia cannot be measured. 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 problems. it can.

[0026]

As described above, according to the present invention,
The effect is obtained that contamination can be suppressed and accurate measurement can be performed.

[Brief description of 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 structural explanatory view of an embodiment of the present invention showing the structure 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 analysis part 22 Switching device 51z, 51a, 51b, ..., 51n Suction pipe 52z, 52a, 52b, ..., 52n Solenoid valve 53 Suction pump z, a, b, ..., n Fluid introduction pipe

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G01N 30/26 G01N 30/26 Q 30/32 30/32 C

Claims (3)

[Claims] 1. A switching means which has a plurality of fluid introduction paths and which selectively guides at least one of them to a gas analyzer.
A switching device for a gas analyzer, comprising: a suction unit connected to each of the fluid introduction paths and configured to suction a measurement gas. 2. The switching device according to claim 1, wherein each of the fluid introduction paths is connected to the suction means via a valve, and control means for independently controlling the valve is provided. 3. The control means, when one of the fluid paths is selected by the switching means, closes a valve connected to the selected fluid introduction path and opens the other valves. The switching device according to claim 2, which is controlled.