JP2747753B2 - Method and apparatus for removing trace impurity gas components in inert gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently removing nitrogen, oxygen, carbon dioxide and other impurity gas components present in a trace amount in an inert gas and an apparatus therefor.

[0002]

2. Description of the Related Art In many manufacturing processes, an inert gas such as helium, neon, argon, krypton, or xenon is often required to have a high purity. An inert gas is required.

[0003] All industrial inert gases are used after being pumped through a pipe, but contain impurities such as nitrogen, oxygen and carbon dioxide. Therefore, these impurities must be removed to achieve high purity. Must.

[0004] In addition, rare gases such as neon, krypton and xenon are very expensive compared to other industrial gases and are often recovered and used. There is a demand for an inexpensive and high-performance device for removing odor.

As one method of purifying an inert gas containing an impurity gas component such as nitrogen, a method using a metal or alloy getter mainly comprising titanium and zirconium has been developed. The reaction tube filled with the getter can remove nitrogen, oxygen, carbon dioxide, carbon monoxide, and the like at a high temperature.

For example, Japanese Patent Application Laid-Open No. Sho 62-3008 discloses an apparatus and method for removing nitrogen and other impurity gas components in argon gas using a getter alloy composed of zirconium-vanadium-iron. I have. Although the temperature is set to 20 to 400 ° C., preferably 200 to 350 ° C., the embodiment mainly employs a temperature condition of 350 ° C. The getter may be in the form of a powder or a small lump, but it is preferable to use a pellet obtained by compressing an alloy powder.

[0007] In Japanese Patent Application Laid-Open No. 2-116607, nitrogen, oxygen, moisture, methane, carbon monoxide and carbon dioxide which are impurities other than hydrogen in an inert gas are removed by a first-stage getter cylinder. A method of removing only hydrogen by a second-stage getter cylinder is shown, and zirconium-vanadium-iron or zirconium-iron is used in the first-stage getter cylinder, and zirconium- is used in the second-stage getter cylinder.
Aluminum is used. In this case, both the first-stage getter tube and the second-stage getter tube have a temperature of 35 ° C.
Maintain at 0-450 ° C.

In Japanese Unexamined Patent Publication (Kokai) No. 2-293310, hydrocarbons, nitrogen, oxygen, water, methane, carbon monoxide, and carbon dioxide, which are impurities other than hydrogen in a rare gas at high temperature, are obtained by a first-stage getter cylinder. The carbon is removed, and then hydrogen is converted to water at 40 ° C. or less by a nickel-based catalyst filled in the upper part of the second-stage filling cylinder, and water is removed by molecular sieves filled in the lower part of the second-stage filling cylinder. Is to be adsorbed. As the getter, metals such as titanium and zirconium, titanium and zirconium are mainly used, and alloys obtained by combining nickel, aluminum, iron and vanadium are used. Among them, titanium sponge, titanium-zirconium and zirconium are used. -Vanadium-iron is preferred, and titanium sponge is used in the embodiment. The getter is filled in a reaction tube, and is heated to 400 to 1200 ° C. (970 in the example).
(° C).

[0009]

As the degree of integration of semiconductors increases, the purity level required in the manufacture of VLSIs is required to be each impurity concentration of 1 ppb or less.

The above-mentioned titanium or zirconium-based getters are generally sponge-shaped or prepared by sintering a powder of 10 to 100 μm in granular form. In order to obtain the performance suitable for the above, it is necessary that impurities reacted on the surface diffuse in the solid.

However, in order to promote the diffusion in the solid, the reaction tube must be operated at a high temperature of 300 to 800 ° C., so that if a large amount of an inert gas containing nitrogen or oxygen is erroneously introduced. The reaction is accelerated, and in the worst case, the temperature exceeds the heat resistance temperature of the filling cylinder, which may lead to the destruction of the filling cylinder.

In addition, in the reaction with an impurity gas component at a low temperature of 300 ° C. or less, the diffusion rate in the solid is reduced and the diffusion is limited to the surface layer portion, so that there is a disadvantage that many unused portions remain.

[0013] Under such a background, the present invention provides a method for producing a trace amount of nitrogen, oxygen, carbon dioxide, and the like contained in an inert gas.
It is an object of the present invention to provide an industrial method capable of removing other impurity gas components at a low temperature and further reducing the cost for gas purification by increasing the use efficiency of the filler.

[0014]

According to the present invention, there is provided a method for removing a trace impurity gas component in an inert gas, comprising the steps of:
An inert gas containing a trace amount of an impurity gas component is brought into contact with the filler (P) on which a metal thin film has been formed by the VD method.

Further, the apparatus for removing trace impurity gas components in an inert gas according to the present invention has a gas inlet (2) and a gas outlet (3), and forms a metal thin film on an inorganic porous substrate by a PVD method. A reaction tube (1) filled with the formed filler (P);
A heating mechanism (4) for heating the filler (P) filled in (1) is provided.

Hereinafter, the present invention will be described in detail.

The inert gas applicable to the method of the present invention includes rare gases such as helium, neon, argon, krypton, and xenon.

An inert gas containing a trace amount of an impurity gas component includes nitrogen, oxygen, carbon dioxide,
Examples of the gas include those after removing carbon monoxide and other impurity gas components.

In the present invention, as a filler (P), a PVD method (physical vapor deposition method) is applied on an inorganic porous substrate.
A metal thin film is formed by using the method described above.

Here, examples of the inorganic porous substrate include alumina, silica, silica-alumina, diatomaceous earth, titanium oxide, zirconium sponge, and titanium sponge. In this case, if the pore diameter is less than 10 angstroms, the atomic vapor does not diffuse therein, so it is required to use one having a pore diameter of 10 angstroms or more.

Examples of the metal constituting the metal thin film include titanium, zirconium, and alloys containing these as main components. Specifically, titanium, zirconium, titanium-zirconium, titanium-nickel, zirconium-
Examples include iron, zirconium-vanadium-iron, zirconium- iron -aluminum, and the like.

The above-mentioned metal is converted into atomic vapor by using a target and an electron gun installed in a vacuum chamber, and the vapor is deposited on an inorganic porous substrate at a temperature as low as possible, thereby obtaining a filler (P). .

Atomic vapor of a metal is deposited on an inorganic porous substrate, the crystal growth state changes depending on the temperature of the substrate itself, and the characteristics of the film change. In particular, when depositing at a low temperature of about 100 ° C., a finely grown polycrystalline state is observed. With these finely grown crystals (polycrystals), a larger specific surface area can be obtained.

The contact of the thus obtained filler (P) with an inert gas containing a trace amount of an impurity gas component is carried out at a temperature of 100 to 100.
It is desirable to carry out at 300 ° C. When the temperature is too low, the removal rate of the impure gas components decreases. On the other hand, when the temperature is too high, the removal rate of the impurity gas components decreases and the heat energy is disadvantageous. However, even if the temperature is outside the above-mentioned temperature range, the degree of reduction in the removal rate of the impurity gas component does not extremely decrease, so that a slight deviation from the temperature condition is allowed.

An apparatus for carrying out the method described above comprises a gas inlet (2) and a gas outlet (3) and a filler.
An apparatus having a reaction tube (1) filled with (P) and a heating mechanism (4) for heating the filler (P) filled in the reaction tube (1) is used.

Such a reaction tube (1) may be provided in parallel, and when one of the reaction tubes has been used, it may be switched to the other and replaced.

This apparatus can also be used as a part of recovery and purification as shown in FIG. In FIG. 4, "PSA" means
It means pressure fluctuation type adsorption separation method.

[0028]

In general, zirconium and titanium are inactivated because a strong oxide film is formed on the bulk surface. Taking a zirconium-vanadium-iron alloy as an example, this alloy is formed for the purpose of preventing the formation of a strong oxide film as described above and causing diffusion in a solid at a relatively low temperature (400 to 300 ° C.). (By the way zirconium alone is 70
A temperature of from 0 to 900 ° C. is required), which has not yet been achieved.

However, when atomic vapors such as titanium and zirconium are deposited on an inorganic porous substrate in a low-temperature and high-vacuum state, a state in which an oxide film having a strong surface specific to these metals is not formed is maintained. , Nitrogen and other impurities, so that interstitial compounds with nitrogen and carbon are formed at low temperatures. In addition, since the atomic metal is crystal-growing on the surface of the inorganic porous substrate, the projections on the order of Angstrom create a large surface area, and the amount of adsorption of the impurity gas component increases.

[0030]

The present invention will be further described with reference to the following examples.

Embodiment 1 FIG. 1 is an explanatory view showing an example of the removing apparatus of the present invention.

(1) is a reaction tube having an inner diameter of 2.54 cm and a height of 1
It has dimensions of 0 mm. (2) is a gas inlet for introducing inert gas, (3) is a gas outlet for taking out gas from the reaction tube (1),
(4) is a heater for heating as an example of a heating mechanism.
(5) is a gas filter for removing particles, and (6) is a flow control device.

Using zirconium as a target and an electron gun, a zirconium sponge (manufactured by Teledyne Co., Ltd., 6 to 10) as an example of an inorganic porous base material by a PVD method.
Atomic temperature vapor of zirconium was deposited at a temperature of 100 ° C. on a mesh having a pore diameter of 20 to 40 Å. As a result, a filler (P) in which a polycrystalline zirconium thin film was formed on a zirconium sponge was obtained.

The reactor (1) was filled with 41 cc of the filler (P) and activated by heating at 300 ° C. for 2 hours with a heater (4).

Next, the flow controller (6) and the gas inlet
Argon gas containing 100 ppb each of nitrogen, oxygen and carbon dioxide was introduced into the reaction tube (1) at 1.2 liter / min at 1 atm via (2), and was led out from the gas outlet (3).

The impurity gas concentration at each temperature in the purified gas derived from the gas outlet (3) was measured using an atmospheric pressure ionization mass spectrometer (UG-240-P, manufactured by Hitachi, Ltd.).
N). The results are shown in FIG.

Comparative Example 1 Next, as a control, Example 1 was repeated except that a conventionally used zirconium sponge was filled in the reaction tube (1). The results are shown in FIG.

2 and 3, the zirconium sponge conventionally used has a reduced ability to remove impurity gas components at 300 ° C. or lower, whereas the filler (P) formed with a polycrystalline zirconium thin film is used. It can be seen that even at a temperature of 300 ° C. or less, the ability to remove impurity gas components is excellent.

When the surface of the filler (P) was observed with a scanning electron microscope, zirconium crystals of about 0.06 to 0.1 μm grew on a zirconium sponge as an inorganic porous substrate as shown in FIG. Was observed. It is considered that the crystals grown in this manner increase the number of impurity adsorption sites and adsorb more impurity gas components.

Table 1 shows the measurement results of the specific surface area of the filler (P) on which the polycrystalline zirconium thin film used in Example 1 was formed and the zirconium sponge used in Comparative Example 1.
As a specific surface area measuring apparatus, “Accusorb 2100” manufactured by Micromeritics was used.

Table 1 Filler pretreatment conditions Specific surface area value Polycrystalline zirconium thin film 120 ° C., 120 minutes heating evacuation 188.7 cm ² / g Zirconium sponge 120 ° C., 120 minutes heating evacuation 0.042 cm ² / g

From Table 1, it can be seen that the specific surface area of the filler (P) on which the polycrystalline zirconium thin film was formed was significantly larger than that of the conventional zirconium sponge.

Example 2 Using titanium as a target and an electron gun, PVD
Atomic temperature vapor of titanium was deposited on alumina (Neobead MHD type, manufactured by Mizusawa Chemical Co., Ltd., pore diameter 40 Å) as an example of an inorganic porous substrate at a temperature of 100 ° C. by the method. As a result, a filler (P) in which a polycrystalline titanium thin film was formed on alumina was obtained.

When the surface of the filler (P) was observed with a scanning electron microscope, it was observed that titanium crystals of about 0.06 to 0.1 μm had grown on the alumina.

When Example 1 was repeated using this filler (P), favorable results similar to Example 1 were obtained.

[0046]

According to the present invention, nitrogen, oxygen, carbon dioxide and other trace impurity components contained in an inert gas are reduced to a temperature range of 100 to 30 which is lower than the conventional temperature range.
It can be removed at 0 ° C.

Further, since the removal is due to the reactive adsorption of the impurity gas component by the thin film portion, the filler material is removed.
(P) Adsorption is averaged in the thickness direction, and the removal amount of the impurity gas component per unit metal weight is smaller than the removal of the impurity gas component by the granular zirconium sponge or alloy zirconium getter, which is the conventional method. Has the advantage of being higher.

Therefore, the present invention is a revolutionary industrial method for removing trace amounts of nitrogen, oxygen, carbon dioxide and other impurity gas components contained in an inert gas, and is extremely useful.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an example of a removing device of the present invention.

FIG. 2 is a graph showing a relationship between an outlet impurity gas component concentration and a temperature in Example 1.

FIG. 3 is a graph showing a relationship between an outlet impurity gas component concentration and a temperature in Comparative Example 1.

FIG. 4 is a flowchart showing an example of an inert gas recovery and purification process.

FIG. 5 is a scanning electron micrograph (magnification: 5000 × ) of the surface of the filler (P) in Example 1.

[Explanation of symbols]

 (1) ... reaction tube, (2) ... gas inlet, (3) ... gas outlet, (4) ... heating mechanism, heater for heating, (5) ... gas filter, (6) ... flow control device, (P) … Filler

Claims (5)

(57) [Claims] An inert gas containing a trace amount of an impurity gas component is brought into contact with a filler (P) having a metal thin film formed on an inorganic porous substrate by a PVD method. A method for removing trace impurity gas components. 2. The method according to claim 1, wherein the metal thin film is a thin film of titanium, zirconium, or an alloy containing these as a main component. 3. The method according to claim 1, wherein the metal thin film is polycrystalline.
The described method. 4. The method according to claim 1, wherein the contacting is performed at a temperature of 100 to 300 ° C. 5. A reaction tube (1) having a gas inlet (2) and a gas outlet (3) and filled with a filler (P) having a metal thin film formed on an inorganic porous substrate by a PVD method. A heating mechanism (4) for heating the filler (P) filled in the reaction tube (1), and a device for removing trace impurity gas components in the inert gas.