JPH06117977A - Gas collecting device - Google Patents

Abstract

PURPOSE:To collect ammonium in a clean atmosphere such as a clean room efficiently since the total amount of atmosphere related to collection can be grasped accurately and ammonium can be collected efficiently. CONSTITUTION:In a gas collecting device, for example, containers 1 (first and second-stages) consisting of a styrol 1 are aligned in series and a pump 4 is laid out at the rearstream side of the second-stage container 1. Each container 1 is provided with gas introducing ports 6 and 8 and gas delivery ports 7 and 9. Also, the container 1 is constituted closedly other than the gas delivery ports 7 and 9, the pure water of an absorption liquid 2 is housed up to approximately 1/4-3/4, and a space for circulating an introduction gas is formed between the upper part of the absorption liquid and the inner wall of the container 1. When the pump 4 is operated, the atmosphere gas flows into the container 1 and contacts the absorption liquid 2 and ammonium in the gas is collected in the absorption liquid 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas trapping device for trapping impurities in an atmosphere of a target region, and more particularly to a trapping device for ammonia in a clean room.

[0002]

2. Description of the Related Art In a semiconductor factory, various chemicals are used in a clean room.
Gas may evaporate from the chemical solution. The volatilized gas may diffuse in the clean room when there is no exhaust facility or when the gas is exhausted to the outside by the exhaust facility or the like but partly leaks. This gas becomes an impurity in the atmosphere in the clean room. Further, among these gases, molecular or ionic ones cannot be removed by the current filter, and there are many impurities which adversely affect the semiconductor. The target elements are all metals and hydrofluoric acid,
It is an ionic impurity that volatilizes from hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, ammonia, etc., and these have some adverse effects on semiconductors. Therefore, it is important to accurately evaluate the amount of these impurities, but for that purpose, it is necessary to reliably collect the impurities in the atmosphere.

First, in the method of directly analyzing the atmospheric gas, the atmospheric gas is collected, and API-MS (Atmosp) is used.
heric Pressure Ionizatio
n Mass Spectrometer; atmospheric pressure ionization mass spectrometer). However, since this method is a method for collecting and analyzing impurities in a high-purity gas online, it is very difficult to handle the collected gas directly to the collecting device. Further, this method is not compatible with all samples and impurities, and there is a combination of main components and impurities so that the ion-molecule reaction, which is a characteristic of API-MS, does not proceed.

Next, there is a dissolution method in which an atmosphere is collected in a solution (absorption solution) and then impurities dissolved in the solution are analyzed. This dissolution method is a method in which a sample atmosphere is ventilated through an absorption tube containing an absorption liquid to collect a target component. Absorption tubes of various shapes are used in order to obtain high collection efficiency without decomposing the target component. Generally, a midget impinger or a frit gas bubbler is used for the absorption tube.
The sample is collected in the arrangement as shown in FIG.
That is, in FIG. 3, 20 is an impinger, and 2
1 is a silicon stopper for sealing the open end of the impinger 20, 23 is a silicon tube, 2 is an absorbing liquid, 4 is a suction pump, and 5 is a flowmeter. In the collection device of FIG. 3, the suction pump 4 causes a negative pressure in the impinger 20 to introduce an atmosphere into the absorbent 2 through the silicon tube 23, and the atmosphere is made into bubbles to be absorbed in the absorbent 2. Dissolve impurities. Hereinafter, the impurity collection method using this collection device is referred to as a bubbling method.

The Environmental Agency's guideline for measurement methods stipulates the JIS (Japanese Industrial Standard) method for collecting each of the following components, and all of them basically adopt the above-mentioned dissolution method. ing. Component: Collection method (HCl: JIS K0107, HF:
JIS 0105, NO _x : JIS K0104)

Using this bubbling method, it is possible to analyze impurities in the atmosphere quite easily and accurately by selecting a solution suitable for impurities (a solution having a high impurity collection efficiency) as the absorbing solution. . When the target element is a metal, a 1% nitric acid aqueous solution is used as the absorption liquid, and when it is an ionic impurity, pure water is used as the absorption liquid. In addition, as a method of collecting impurities in the atmosphere with an absorbing solution, there is another very simple method of collecting pure aqueous solution by simply leaving it in the atmosphere, which is called a solution leaving method. . Here, Table 1 shows a comparison of the collection amount when the ionic impurities in the atmosphere are collected by the dissolution method (bubbling method) and the solution standing method by the collection device shown in FIG.

[0007]

[Table 1] In this case, the atmosphere was simultaneously collected for 8 hours by the bubbling method and the solution leaving method in different places A and B (in the clean room). The analysis of each ionic impurity was performed by an ion chromatograph analyzer.

As can be seen from the analysis results of Table 1, the bubbling method has a larger collection amount except ammonia, and the collection efficiency is more than 90%, and good results are obtained. However, regarding ammonia (ammonia ion: NH ₄ ⁺ ), although there is a smell of ammonia at location A than at location B, there is no difference between locations A and B by the bubbling method, and the collection efficiency is 60. % Is bad. On the other hand, regarding ammonia, the solution standing method is considered to show better results.

It is considered that the reason why the amount of collected ammonia is low in the bubbling method is that the ammonia is a molecule which is easily volatilized, and the ammonia once dissolved is volatilized by bubbling.

Here, the JIS method (JIS K0099)
The method of analyzing ammonia in exhaust gas is 0.5%
Although a boric acid solution is used (ammonia is fixed by boric acid), about 1700 ng of ammonia is contained in 100 ml of a 0.5% boric acid solution, and about 10 times more ammonia than pure water is produced. Contained (Pure water 10
It is 160 ng in 0 ml), and a trace amount of ammonia cannot be measured. Therefore, this JIS method is a method suitable when the amount of ammonia is considerably large, and cannot be applied to an atmosphere such as a clean room where the amount of impurities is very small.

[0011]

As described above, although the amount of the solution left to collect is considerably large, the total amount of the atmosphere involved in the collection within the standing time is unknown, and therefore the amount per unit volume as in the bubbling method is not known. There is a problem that the weight of ammonia cannot be calculated. Further, in the bubbling method, ammonia is volatilized and the collection amount is deteriorated.
When the absorbing solution is a boric acid solution, there is a problem that ammonia as an impurity in boric acid interferes with microanalysis.

The present invention has been made in view of the above problems, and the total amount of the atmosphere involved in the collection can be accurately grasped, and the target impurities such as ammonia in the gas can be efficiently used as the absorbing liquid. An object of the present invention is to provide a gas collecting device that can collect well.

[0013]

DISCLOSURE OF THE INVENTION The present invention relates to a gas collecting apparatus for introducing a gas in a target region and collecting a target impurity in the introduced gas, except for the gas inlet and outlet. Is closed, and a collection container containing an absorption liquid of a target impurity so that a space communicating with the inlet and the outlet is formed inside, and the gas introduced from the inlet is The problem is solved by allowing the liquid to circulate in the space so as to come into contact with the surface of the liquid and discharge the liquid from the discharge port. Further, in the present invention, the target impurity may be ammonia and the absorbing liquid may be water.

[0014]

Function The gas generated in the semiconductor factory has some adverse effects on the semiconductor. It is known that among the gases, ammonia can be easily and efficiently collected by bringing it into contact with pure water. Therefore, if impurities in the atmosphere are collected using pure water, the atmosphere in the semiconductor factory can be analyzed for ammonia.
However, even if pure water is used, the conventional bubbling method and solution leaving method have drawbacks, respectively, and sufficient analysis results cannot be obtained as they are. On the contrary,
The inventor has conducted various studies in order to construct a gas collection device that does not have the drawbacks of each collection method. That is, in order to prevent volatilization of ammonia in the solution caused by the bubbling method, it is convenient to use the solution standing method. However, in the solution standing method, the total amount of atmosphere involved in the collection is unknown. Therefore, the present invention is configured and a space is formed in the collection container to seal the absorbing liquid, and the gas in the target region is circulated in the space so as to be in contact with the surface of the absorbing liquid. Therefore, the total amount of the atmosphere involved in the collection can be accurately grasped, and the target impurities in the gas can be efficiently collected in the absorbing liquid. Incidentally, for example, ammonia is suitable as the target impurity, and water (particularly pure water) is suitable as the absorbing liquid.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of a gas collecting apparatus according to an embodiment. This gas collecting device introduces a gas in an atmosphere in a clean room and collects ammonia in the introduced gas. For example, a container 1 made of styrene (first stage, second stage) 2 The pumps 4 are arranged in series, and a pump 4 is disposed on the downstream side of the second-stage container 1.
The first and second container 1 are provided with gas inlets 6 and 8 and gas outlets 7 and 9. Also, each container 1
In detail, as shown in FIGS. 2 (a) and 2 (b), except for the gas inlets 6 and 8 and the gas outlets 7 and 9, it is configured to be hermetically sealed, and the pure water of the absorbing liquid is about 1 / A space a is formed between the upper part of the absorbing liquid and the inner wall of the container 1 for accommodating the introduced gas up to about 4 to 3/4. The discharge port 7 of the first-stage container 1 and the introduction port 8 of the second-stage container 1 are connected by a tube 3 made of silicon, and between the discharge port 9 of the second-stage container 1 and the pump 4. Are connected by a tube via a flow meter 5. Since the pump 4 is the same as that shown in FIG. 3, the description thereof will be omitted. A liquid film flowmeter can be used as the flowmeter 5.

The container 1 will be described in more detail. Container 1
In the embodiment, as shown in FIG. 2, it has a short prismatic shape, and the top and bottom surfaces are substantially square with one side of about 14 cm, and are made of styrene having a height of 3.5 cm.
The container 1 also has a structure in which a lid 1a covers the main body 1b on the upper surface. Initially, the container 1 is in a state where the lid 1a is removed. In the configuration of the container 1, first, the main body 1b of the container 1 is
The inside is washed with pure water and 100 ml of pure water as the absorbing liquid 2 is put into the main body 1b. Then, the lid 1 is attached to the main body 1b.
After carrying out a, the side surface is covered with a sealing tape so as not to leak from the container 1 and sealed. In addition, in each container 1, as the inlet port 8 (for introducing and discharging the atmosphere and for connecting the tube 3) and the outlet ports 7 and 9, a hole having a diameter of 5 mm is formed at both ends on the diagonal of the container lid 1a. Keep it. The introduction port 6 of the first-stage container 1 is formed by appropriately opening ten through holes having a diameter of about 1 mm on the gas introduction side. In addition, the tube 3 connects the first-stage outlet 7 and the second-stage inlet 8, and the second-stage outlet 9 and the pump 4 are connected via the flow meter 5 to collect gas. The device configuration is complete.

Next, the operation of the embodiment will be described. When the ammonia in the atmosphere in the clean room is collected by the gas collecting apparatus of the embodiment, first, the pump 4 is operated so that the gas in the atmosphere is sequentially introduced into the first and second container 1. Then, the absorbing liquid is circulated so that the gas comes into contact with the absorbing liquid. The flow rate of the pump 4 at this time is 0.5 l / min. The flow rate is monitored by the flow meter 5. When the collection for a predetermined time is completed, the absorption liquid 2 is transferred to a clean and clean 100 ml container made of polyethylene, and ammonia in the absorption liquid is analyzed by the concentration column method of an ion chromatograph analyzer.

Next, the results of comparison between the collection device of the present invention and the solution standing method with a large collection amount shown in Table 1 will be shown. In this case, in the collection device according to the present invention (device of the present invention), as shown by a broken line 3a in FIG. 1, the container 1 in the second stage is not connected and the first stage is directly connected to the pump 4. In addition, the collecting apparatus of the solution leaving method (conventional apparatus) was constructed by placing 100 ml of pure water in a rectangular container made of styrene similar to that used in the example and without opening the lid. It was left for 16 hours (not shown).

The apparatus of the present invention is 0.5 l / min. Was collected for 16 hours at the same time as the solution standing method. as a result,
The amount of ammonia collected is 640 ng in the conventional apparatus and 21100 ng in the apparatus of the present invention. The conventional apparatus is based on the solution leaving method, which has a larger collection amount than the bubbling method, but it can be seen that the apparatus of the present invention has about 30 times more collection capacity than the conventional apparatus, and the collection efficiency is considerably good.

Next, ammonia was actually analyzed in the atmosphere in the laboratory by using the collector of the present invention. The collection device in this case was constituted by two-stage connection as shown by the solid line in FIG. 1, and the collection was performed by this. The results are shown in Table 2.

[Table 2] In this case, the material A was collected for 26.5 hours and the material B was collected for 18 hours, but the collection amount is almost constant regardless of the collection time. From these results, the results of the ammonia concentration (N) in the atmosphere, the first-stage collection rate (α ₁ ) and the total collection rate (α) were obtained based on the following equations (1) to (3). Table 3
Shown in.

The trapped ammonia concentrations in the first and second stages are N ₁ and N ₂ , respectively, and the total trapped ammonia concentration is N _T = (N ₁ +
N ₂ )

[Equation 1]

[Equation 2]

[Equation 3]

[Table 3]

Next, assuming that the collection rates of the first-stage container 1 and the second-stage container 1 are the same, the total collection rate α can be calculated by the following equation (4).

[Equation 4] The total collection rate α of A and B calculated by the equation (4) is 9
5% and 97%, which are almost the same as the total collection rate α shown in Table 2 obtained by the equations (1) to (3), and the total collection rates of the first and second stages are the same. It can be said that there is. As described above, the device of the present invention has a total collection rate of ammonia of 95%.
As described above, it is understood that the collection can be performed very efficiently. The example shown in the above embodiment is one example of the present invention, and any shape, volume, etc. of the container is within the scope of the present invention.

[0023]

As described above, according to the present invention, the total amount of the atmosphere involved in the collection can be accurately grasped and the target impurities such as ammonia can be collected efficiently, so that the clean room or the like can be cleaned. It is possible to obtain an excellent effect that ammonia can be efficiently collected in various atmospheres.

[Brief description of drawings]

FIG. 1 is a configuration explanatory diagram of an ammonia trap in an embodiment of the present invention.

FIG. 2 is a perspective view showing a detailed configuration of a container of the collection device of FIG. 1, where (a) is a first stage container and (b) is a second stage container.
It is a stage container.

FIG. 3 is a schematic explanatory view of the configuration of a conventional ammonia trap.

[Explanation of symbols]

 1 Collection Container 1a Container Lid 1b Container Body 2 Collection Liquid 3 Silicon Tube 4 Pump 5 Flow Meter 6 Inlet for Introducing First Stage Atmosphere 7 Outlet for Outgoing First Stage Atmosphere 8 Inlet for Entering Second Stage Atmosphere 9 Second-stage atmosphere outlet

Claims (2)

[Claims] 1. A gas collector for introducing a gas in a target region and collecting a target impurity in the introduced gas, the whole of which is hermetically sealed except for the gas inlet and outlet. In addition, a collection container containing the absorption liquid of the target impurities so that a space communicating with the introduction port and the discharge port is formed, and the gas introduced from the introduction port is in contact with the surface of the absorption liquid. A gas collecting device, characterized in that it is circulated in the space and discharged from an outlet. 2. The gas collecting device according to claim 1, wherein the target impurity is ammonia and the absorbing liquid is water.