JP2971116B2 - Noble gas purification method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for purifying a rare gas, and more particularly to a method for purifying a rare gas such as helium, neon, argon, krypton, xenon, etc. containing a halogen-based gas as an impurity. The present invention relates to a method for purifying a rare gas for efficiently removing and purifying a zero-group element, that is, impurities in a rare gas using a getter metal.

Since noble gases have similar chemical properties, it is customary to purify any noble gas using a getter.

Helium and argon are rarely used in the semiconductor manufacturing industry, which has been developing remarkably in recent years, and there is an increasing demand for improving their purity. Further, neon, krypton, and xenon are indispensable gases for producing special lamps and the like, and these gases are particularly expensive, and thus often used gas is circulated and used. In this case, it is also necessary to remove impurities in the circulating gas to purify the circulating gas to high purity.

There are nitrogen, hydrocarbons, carbon monoxide, carbon dioxide, oxygen, hydrogen and water vapor as impurities generally contained in rare gases, and it is desirable to remove them to the order of ppb and purify them to high purity. It is rare.

On the other hand, recently, a demand for removing halogen-based impurities contained in a rare gas simultaneously with these impurities has been expanding mainly in the semiconductor manufacturing industry, and in particular, gases for excimer laser and semiconductor manufacturing. There is a strong demand for high-purity purification in a circulation system for rare gases used in the process and expensive rare gases used in the manufacture of special lamps.

[Prior art] There are two types of getters, evaporating type using barium and the like and non-evaporating type such as titanium type and zirconium type.
In general, non-evaporable getter agents are often used for purifying rare gases.

Conventionally, using a non-evaporable getter agent to remove impurities such as nitrogen, hydrocarbons, carbon monoxide, carbon dioxide, oxygen, hydrogen and water vapor in the rare gas, and purify the rare gas as a getter agent A method of using titanium and a titanium-based alloy and contacting it with a rare gas at a high temperature of about 1000 ° C., a method of using zirconium or a zirconium-based alloy as a getter agent and contacting the rare gas at a temperature of about 300 to 700 ° C. Commonly used. These getter agents include, for example, Zr-
V-Fe ternary alloy, Zr-Al-V disclosed in JP-A-2-18045
Ternary alloy, Zr-Ti-Ni ternary alloy of British Patent 1370208,
Journal of the Less Common Metal, Vol. 53 (1977)
Zr (CO _x , V _1-x ) ₂ and Zr (Fe
_(x , V _1-x ) ₂ , and a binary alloy getter such as a Zr—Ti alloy is known from US Pat. No. 2,926,981 as a binary alloy getter.

[Problems to be solved by the invention]

However, as mentioned above, all of these getters are intended to remove hydrogen, moisture, nitrogen, hydrocarbons, carbon monoxide, carbon dioxide or oxygen,
It is not intended to remove impurities such as halogens or halogen-based compounds.

If a halogen compound is removed using these getters, not only a high temperature such as 900 ° C. or more is required, but also a titanium or zirconium halide generated by the reaction has a high vapor pressure. It cannot be used because of the drawbacks that it evaporates and desorbs from the getter and mixes into the purified gas, or condenses in a low-temperature portion of the apparatus such as a pipe to block the gas flow path.

As described above, a method of efficiently purifying a rare gas including removal of halogen-based impurities has not yet been known.

Means and Solution for Solving the Problems The present inventors have conducted intensive studies to efficiently remove impurities in a rare gas including halogen-based impurities and obtain a highly purified purified rare gas. Using calcium or magnesium as a getter, and if necessary,
It has been found that the object can be achieved by using a titanium or zirconium-based getter agent in combination, and the present invention has been achieved.

That is, the present invention provides (1) at least
A rare gas containing one or more of halogen, hydrogen halide, halogenated carbon and halogenated hydrocarbon is brought into contact with calcium or magnesium to remove impurities contained in the rare gas. And (2) one or more of halogen, hydrogen halide, carbon halide, and halogenated hydrocarbon, and nitrogen, hydrocarbon, carbon monoxide, carbon dioxide, oxygen, After contacting a rare gas containing one or two or more of hydrogen and water vapor with calcium or magnesium, zirconium, a zirconium-based alloy, titanium or a titanium-based alloy is contacted to remove impurities contained in the rare gas. This is a method for purifying a rare gas, which is characterized in that it is removed.

In the present invention, the halogen-based impurities to be mainly removed include, for example, fluorine, chlorine, halogen gas such as bromine, hydrogen fluoride, hydrogen chloride, trifluoromethane,
Examples thereof include compounds in which part or all of hydrogen in a hydrocarbon is replaced with halogen, such as tetrafluoroethane, trichloromethane, and tetrachloroethane.

Calcium and magnesium used as a getter agent for removing impurities including a halogen-based substance (hereinafter referred to as getter agent A) include metal calcium and metal magnesium, and may be commercially available products. It can be easily obtained. These metals are usually used as the getter agent A in the form of granules or in the form of pellets formed of fine particles of about 100 mesh.

The getter agent A can be used as it is, but it is preferable to carry out an activation treatment in advance in a vacuum or a rare gas at, for example, about 400 to 700 ° C. for 10 to 200 minutes before the purification of the rare gas.

The getter agent A is filled in a rare gas purifying cylinder,
Used at a temperature of 0 ° C. or higher, preferably 550 ° C. or higher, and by flowing a raw material rare gas into a purification cylinder, impurities such as halogen, hydrogen halide, halogenated carbon, and halogenated hydrocarbon in the rare gas are used. Is captured by the getter agent A by a reaction with other impurities, and is removed from the rare gas, and the rare gas is continuously purified to a high purity.

In the present invention, impurities such as hydrogen, moisture, nitrogen, carbon monoxide, carbon dioxide, and oxygen are removed by the getter agent A at the same time as halogens and halogen compounds in the rare gas, but the concentration of these impurities is reduced. In the case of high purity and further complete purification, a titanium or zirconium-based getter agent (hereinafter referred to as a getter agent B) is provided downstream of the getter agent A, and a rare gas is brought into contact with the getter agent A to obtain a halogen-based getter agent. After removing the impurities of the getter agent B, the impurities such as nitrogen, hydrocarbons, carbon monoxide, carbon dioxide, oxygen, hydrogen and water vapor that could not be sufficiently removed by the getter agent A are successively removed. It can be completely removed.

Examples of the getter agent B include zirconium, a zirconium-containing alloy, titanium, and a titanium-containing alloy.For example, zirconium sponge, titanium sponge, and Zr-Fe, Zr-Ti, Zi-Ni binary alloys and Zr
-V-Fe, Zr-Al-V multi-component alloys and other conventionally known getter agents, Zr-V binary alloys by the present inventors, Zr-V-Cr
And multi-element alloys such as Zr-V-Ni (Japanese Patent Application No. 02-242586)
No.) is preferred.

Next, the present invention will be specifically described with reference to the drawings.

FIG. 1 is a flow sheet of a rare gas purifying apparatus used in the present invention.

In FIG. 1, a gas inlet 1 and an outlet 2 are provided,
A source rare gas supply pipe 6 is connected to an inlet 1 of a purification cylinder 5 in which a getter agent 3 is filled and a heating heater 4 is disposed, and a cooling pipe 7 is connected to an outlet 2. .
Further, a purified gas extraction pipe 8 is connected downstream of the cooling pipe 7.

As the getter agent 3, the getter agent A alone or both getter agents A and B are filled depending on conditions. When the getter agents A and B are used at the same time, the getter agent A is charged into the gas inlet side of the purifying cylinder and the getter agent B is charged into the gas outlet side.

Also, getters A and B are used in the present invention.
Are used at the same time, as shown in FIG.
Although two purifying cylinders may be filled, getter agents A and B may be filled in separate cylinders, and both getter agents A may be on the upstream side of the gas and the getter agent B may be on the downstream side of the gas. May be connected as a two-cylinder purifier.

When purifying the rare gas, the raw material rare gas is supplied from the supply pipe 6 into the purification cylinder 5 via the inlet 1 while the purification heater 5 is heated to a predetermined temperature by the heater 4 for heating. Purification cylinder 5
The rare gas that has entered comes into contact with the getter agent 3,
The impurities react with the getter agent 3 and are removed. The gas from which the impurities have been removed enters the cooling pipe 7 via the outlet 2, where it is cooled to a predetermined temperature and then used through the purified gas extraction pipe 8.

[Effects of the Invention] According to the present invention, impurities such as halogens, hydrogen halides, halogenated carbons, and halogenated hydrocarbons in a rare gas, which are difficult to remove by a conventional method, can be efficiently removed. It became.

In addition, by using a titanium or zirconium-based getter agent together, other impurities are completely removed,
An extremely high purity purified rare gas can be obtained.

In addition, during purification, the getter agent halide does not evaporate or condense and block the gas flow path in low-temperature parts such as pipes, and the purification equipment is relatively small. It can be easily installed in a place where the cost is large, such as in a clean room of a manufacturing factory.

Example 1 Example 1 An apparatus having the same configuration as that shown in FIG.
A getter agent A having a mesh size of 4 to 10 obtained by sifting commercially available granular calcium (purity: 99%) is filled into a purification tube made of a stainless steel tube having an inner diameter of 14 mm and sifted by 600 mm, and then activated at 720 ° C. for 3 hours in a helium stream. Treatment was performed.

Then, while adjusting the temperature of the purification cylinder to 600 ° C., using a mass flow controller as an impurity, helium gas added so that it becomes 10 ppm of carbon tetrafluoride, 10 ppm of carbon tetrachloride, and 10 ppm of hydrogen chloride, 0.89 / min, pressure 4k
Purification was performed continuously by supplying at gf / cm ² , and the outlet gas of the purification cylinder was analyzed by TCD gas chromatography.

As a result, breakthrough of carbon tetrafluoride was observed after a lapse of 1300 hours from the start of gas flow. During this time, no breakthrough of other impurities was observed, and no clogging of the pipe of the gas at the outlet of the purifying cylinder occurred.

Example 2 A commercially available shaved magnesium (purity: 97% or more) was used as a getter agent A and charged in the same purification cylinder as used in Example 1, and the activation temperature was 600 ° C. for 3 hours and the purification temperature was 500 ° C. Purification was performed in the same manner as in Example 1 except for the above, and the gas at the outlet of the purification cylinder was analyzed.

As a result, breakthrough of tetrafluorocarbon was recognized 1000 hours after the start of gas flow. During this time, no breakthrough of other impurities was observed, and no clogging of the pipe due to the gas at the outlet of the purification cylinder was observed.

Example 3 An apparatus having a configuration similar to that shown in FIG.
A commercially available 4-10 mesh getter agent A obtained by sifting commercially available granular calcium (purity: 99%) into a quartz purification cylinder having an inner diameter of 19 mm is filled with 600 mm, and further downstream, Zr 80% by weight and Fe 20% by weight are filled. After the getter agent B having a mesh size of 6 to 14 mesh was filled with 200 mm of the alloy consisting of, an activation treatment was performed at 720 ° C. for 3 hours in a helium stream.

Then, while adjusting the temperature of the purification cylinder to 600 ° C, use a mass flow controller to adjust the impurity concentration to 10 ppm of carbon tetrafluoride, 10 ppm of carbon tetrachloride, 10 ppm of hydrogen chloride, and 1 pp of oxygen.
m, nitrogen 5ppm, methane 1ppm, hydrogen 1ppm, carbon monoxide 1pp
Helium gas adjusted to m, carbon dioxide 1 ppm and moisture 5 ppm was supplied at 1.64 / min at a pressure of 4 kgf / cm ² to continuously purify, and the outlet gas of the purifying cylinder was analyzed. For each impurity in the gas, methane, carbon monoxide and carbon dioxide were measured by FID gas chromatography, carbon tetrafluoride, carbon tetrachloride, hydrogen chloride and nitrogen by TCD gas chromatography, and RGA3 reducing gas analyzer. Hydrogen was analyzed for oxygen by a Hirsch ppb oxygen analyzer, and water vapor was further analyzed by a panametric dew point meter.

As a result, nitrogen breakthrough was first observed after 1100 hours from the start of gas flow. During this time, no breakthrough of other impurities was observed, and no clogging of the pipe for the gas at the outlet of the purifying cylinder occurred.

Comparative Example 1 An alloy consisting of 20% by weight of Fe and 80% by weight of Zr was used as a getter agent in a purifying cylinder having the same structure as used in Example 1,
Helium gas was purified in the same manner as in Example 1 except that the mesh getter agent B was filled with 600 mm, and the gas at the outlet of the purification cylinder was analyzed.

As a result, carbon tetrafluoride was detected immediately after starting to flow the gas.

Comparative Example 2 An apparatus having the same configuration as that of Example 3 and 6 to 6
14mm mesh sponge titanium (getter agent B) 600m
The same operation as in Example 1 was performed except that m was charged, and the gas at the outlet of the purification cylinder was analyzed.

As a result, carbon tetrafluoride was detected immediately after starting to flow the gas. Subsequently, when the temperature of the purification cylinder was gradually increased from 600 ° C., when the temperature reached 950 ° C., no carbon tetrafluoride was detected in the outlet purified gas. However, when the purification was continued as it was, clogging of the analysis pipe occurred 2 hours later.

Comparative Example 3 The same operation as in Example 3 was performed, except that a purifying apparatus having the same configuration as in Example 3 was used and a sponge zirconium (getter agent B) of 6 to 14 mesh was filled as a getter agent with a thickness of 600 mm. Gas analysis was performed.

As a result, carbon tetrafluoride was detected immediately after starting to flow the gas. Subsequently, when the temperature of the purifying cylinder was gradually increased from 600 ° C., when the temperature reached 900 ° C., carbon tetrafluoride was not detected in the outlet purified gas. However, when purification was continued as it was, blockage of the analysis pipe occurred after 3 hours.

[Brief description of the drawings]

 FIG. 1 is a flow sheet of a rare gas purifying apparatus. The respective numbers in the drawings are as follows. DESCRIPTION OF SYMBOLS 1 ... Inlet 2 ... Outlet 3 ... Getter agent 4 ... Heater for heating 5 ... Purification cylinder 6 ... Raw material rare gas supply pipe, 7 ... Cooling pipe 8 ... Purified gas extraction pipe

Continuation of front page (56) References JP-A-56-78404 (JP, A) JP-A-57-156314 (JP, A) JP-A-61-101231 (JP, A) (58) Fields investigated (Int) .Cl. ⁶ , DB name) C01B 23/00 B01D 53/14

Claims (2)

(57) [Claims] A rare gas containing at least one or more of halogen, hydrogen halide, carbon halide and halogenated hydrocarbon as an impurity is brought into contact with calcium or magnesium and contained in the rare gas. A method for purifying a rare gas, comprising removing impurities to be removed. 2. As the impurities, one or more of halogen, hydrogen halide, carbon halide and halogenated hydrocarbon, and nitrogen, hydrocarbon, carbon monoxide,
After contacting a rare gas containing one or more of carbon dioxide, oxygen, hydrogen and water vapor with calcium or magnesium, zirconium, a zirconium-based alloy,
A method for purifying a rare gas, comprising contacting titanium or a titanium-based alloy to remove impurities contained in the rare gas.