JPH0694733A - Switching method for gas and analyzer using same - Google Patents

Abstract

PURPOSE:To obtain a method for switching gases and a gas analyzer using the same in which a measurement at a ppb or ppt level can be accurately conducted by one analyzer particularly in the case of measuring impurities in the gases to be introduced through a plurality of gas tubes. CONSTITUTION:A gas analyzer switches two types of gases to be introduced through gas tubes and measures impurities of the respective gases, and comprises a nitrogen gas tube 13 for introducing nitrogen gas up to a gas analyzing unit 12 of the analyzer 11, and an oxygen gas tube 14 for introducing oxygen gas in such a manner that the tubes 13, 11 are separately laid. In the measurement of the impurities at a ppb or ppt level, a structure in which the nitrogen gas and the oxygen gas are switched so that the two types of gases do not flow in the same tube is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas switching technique, and particularly for measuring impurities in a gas introduced through a plurality of gas pipes, a ppb (part
per billion), and a technology effective when applied to a gas switching method that enables accurate measurement at a ppt (part per trillion) level and a gas analyzer using the same.

[0002]

2. Description of the Related Art Conventionally, in measuring impurities in a gas introduced through a plurality of gas pipes, for example, as shown in FIG. 3, two kinds of gases, a nitrogen (N ₂ ) gas and an oxygen (O ₂ ) gas, are contained. When measuring impurities with one analyzer, a method of joining the sampling lines of two kinds of gas on the way is conceivable.

That is, on the way to the gas analysis section 2 of the analyzer 1, a nitrogen gas pipe 3 for introducing nitrogen gas and an oxygen gas pipe 4 for introducing oxygen gas are connected via a block valve 5, The block valve 5 switches the gas to be introduced into the gas analysis unit 2.

[0004]

However, in the prior art as described above, there is no problem in measuring impurities up to about ppm (part per million), but ppb and ppt levels using piping and parts of ultra clean specifications are used. In the impurity measurement of (1), the rest of the gas that has flowed first becomes impurities in the gas that has been switched next, causing a problem that an accurate amount of impurities cannot be measured.

For example, the amount of H ₂ O (water) and O ₂ (oxygen) in nitrogen gas and the amount of H ₂ O (water) in oxygen gas present at ppb to ppt levels are combined into one analyzer. Considering the case where the measurement is performed in step 3, the result when the method of FIG. 3 is performed is as shown in FIG. In the figure, the horizontal axis is time and the vertical axis is H.
The impurity concentrations of ₂ O and O ₂ are set.

That is, when nitrogen gas is first flowed, impurities H ₂ O and O ₂ are stably detected. Next, when the nitrogen gas is switched to the oxygen gas, the O ₂ concentration is greatly increased, and the H ₂ O concentration is also increased to and stabilized at the actual H ₂ O level in the oxygen gas.

After that, when the gas is switched to nitrogen gas again, the substitution proceeds to some extent and the concentrations of O ₂ and H ₂ O decrease. However, it does not reach the original concentration as it did when nitrogen gas was first passed.

The reason for this is that the relationship of adsorption and desorption of molecules to and from the inner wall of the pipe occurs at the merging portion t in FIG. That is, the inside of the pipe at the confluence portion t is as shown in FIG. 5, and when oxygen gas first flows in the pipe, a large amount of O ₂ molecules are adsorbed on the inner wall of the pipe. Here, even if the gas is switched to nitrogen, the flowing gas becomes nitrogen, but the O ₂ molecules adsorbed on the inner wall of the pipe are gradually desorbed and detected.

Therefore, even if the oxygen gas is returned to the nitrogen gas again, not the oxygen concentration as an impurity contained in the nitrogen gas but the amount of oxygen desorbed from the pipe of the joining portion t is measured. However, there is a problem that accurate impurity measurement cannot be performed by switching the introduced gas.

Therefore, an object of the present invention is to measure impurities in a gas introduced through a plurality of gas pipes.
It is an object of the present invention to provide a gas switching method and a gas analyzer using the same, which enables accurate measurement at the ppb or ppt level with a single analyzer.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0012]

Among the inventions disclosed in the present application, a brief description will be given to the outline of typical ones.
It is as follows.

That is, the gas switching method of the present invention is a gas switching method for switching a plurality of types of gases introduced through a plurality of gas pipes and measuring impurities contained in these plurality of types of gases. Therefore, a plurality of gas pipes are separately installed up to the gas analysis unit for measuring impurities.

Further, the gas analyzer of the present invention uses the above-mentioned gas switching method, and ppb or ppt by one device.
Impurity measurement at the level is performed.

[0015]

According to the above-described gas switching method and the gas analyzer using the same, it is possible to prevent plural kinds of gases from flowing in the same pipe by laying gas pipes separately up to the gas analysis unit. You can

With this, it is possible to prevent mixing of other molecules on the inner wall of the gas pipe due to adsorption and desorption, and it is possible to accurately measure impurities in the gas in a short time.

[0017]

FIG. 1 is a schematic configuration diagram showing a gas analyzer and peripheral piping according to an embodiment of the present invention, and FIG. 2 is a gas analyzer of the present embodiment in which nitrogen gas and oxygen gas are switched to change the gas content. It is a characteristic view which shows the result of having measured the impurity.

First, the configuration of the gas analyzer of this embodiment and its peripheral piping will be described with reference to FIG.

The gas analyzer of the present embodiment is a gas analyzer for switching between two kinds of gas introduced through, for example, a gas pipe and measuring impurities in each of these gases. Up to 12, a nitrogen gas pipe 13 for introducing nitrogen gas and an oxygen gas pipe 14 for introducing oxygen gas are separately laid.

In the impurity measurement at the ppb or ppt level, the nitrogen gas and the oxygen gas are switched so that the two kinds of gas do not flow in the same pipe.

Next, the operation of this embodiment will be described.

For example, as in an atmospheric pressure ionization mass spectrometer, H ₂ O in nitrogen gas existing at the ppb level is present.
Amount of (water) and O ₂ (oxygen) and H ₂ O in oxygen gas
Consider a case where the amount of (water) is measured by the analyzer 11.

First, when nitrogen gas is first passed through the nitrogen gas pipe 13, impurities H ₂ O and O ₂ are stably detected. Next, when the nitrogen gas is switched to the oxygen gas through the oxygen gas pipe 14, the O ₂ concentration is significantly increased and H 2
_{The 2} O concentration also increases and stabilizes up to the actual H ₂ O level in oxygen gas.

After that, when the gas is switched to the nitrogen gas through the nitrogen gas pipe 13 again, in the prior art, the substitution proceeds to some extent as shown in FIG. 4, and the concentrations of O ₂ and H ₂ O decrease, but the nitrogen gas is first discharged. It does not fall back to the original concentration as when flowing gas.

However, in this embodiment, as shown in FIG. 2, the O ₂ and H ₂ O concentrations are rapidly replaced in a short time to the same level as when nitrogen gas was first passed. As a result, two kinds of impurities of nitrogen gas and oxygen gas can be accurately measured by one analyzer 11 in a short time.

This is because, even if the gas molecules adsorbed on the inner wall of the nitrogen gas pipe 13 or the oxygen gas pipe 14 are desorbed, the nitrogen gas or the oxygen gas does not flow in the same pipe unlike the conventional case. In addition, it does not affect the measured concentration of impurities.

Therefore, according to the analyzer 11 of this embodiment, different kinds of nitrogen gas pipes 13 and oxygen gas pipes 14 are provided.
Since the and are separately installed up to the gas analysis unit 12 of the analyzer 11, even if the oxygen gas is measured and then the impurity measurement of the nitrogen gas is performed again, the concentration of the impurity contained in the nitrogen gas can be accurately measured. It is possible to measure the impurities in the oxygen gas with high accuracy.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say.

For example, in the gas analyzer of this embodiment, the case where two kinds of gases, nitrogen gas and oxygen gas, are switched to analyze impurities has been described, but the present invention is not limited to the above embodiments. However, the present invention can be widely applied to the case where a larger number of plural kinds of gases are introduced and further the case where gases other than nitrogen gas and oxygen gas are introduced.

Further, in the present embodiment, more accurate impurity measurement can be performed by, for example, baking the piping, and impurities in the piping are removed in advance, especially when clean piping is used. The measurement accuracy can be improved. This is because the molecules adsorbed on the inner wall of the pipe as shown in FIG. 5 can be forcibly removed by baking at about 200 ° C.

In the above description, the case where the invention made mainly by the present inventor is applied to the gas switching method used in the gas analyzer which is the field of application of the invention has been described, but the present invention is not limited to this and the ppb Or pp
It can be widely applied to other devices that require t-level measurement accuracy and that require switching of a plurality of types of gases.

[0032]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows.
It is as follows.

That is, by separately laying a plurality of gas pipes up to the gas analysis unit for measuring impurities, it is possible to prevent a plurality of kinds of gas from flowing in the same pipe, so that the gas pipes It is possible to prevent mixing of other molecules on the inner wall due to adsorption and desorption, and to accurately measure impurities in the gas in a short time.

As a result, particularly in the measurement of impurities in the gas introduced through a plurality of gas pipes, the measurement at the ppb or ppt level can be accurately performed by one analyzer, and the gas line measurement of the semiconductor device manufacturer can be performed. An excellent gas switching method and gas analyzer can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a gas analyzer and peripheral piping according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a gas analyzer of the present embodiment.
It is a characteristic view which shows the result of having measured the impurity in gas by switching oxygen gas.

FIG. 3 is a schematic configuration diagram showing a gas analyzer and peripheral piping, which is an example of a conventional technique.

FIG. 4 shows a gas analyzer which is an example of a conventional technique,
It is a characteristic view which shows the result of having measured the impurity in gas by switching nitrogen gas and oxygen gas.

FIG. 5 shows a gas analyzer which is an example of a conventional technique,
It is explanatory drawing which shows the inside of piping when it switches from oxygen gas to nitrogen gas.

[Explanation of symbols]

 1 analyzer 2 gas analyzer 3 nitrogen gas pipe 4 oxygen gas pipe 5 block valve 11 analyzer 12 gas analyzer 13 nitrogen gas pipe 14 oxygen gas pipe

Claims (2)

[Claims] 1. A gas switching method for switching a plurality of kinds of gases introduced through a plurality of gas pipes and measuring impurities contained in the plurality of kinds of gases, wherein the plurality of gas pipes are connected to each other. A gas switching method comprising laying separately up to a gas analysis unit for performing the impurity measurement so that the plurality of types of gas do not flow in the same pipe. 2. A gas analyzer, wherein the gas switching method according to claim 1 is used to measure impurities at a ppb or ppt level with a single device.