Storage method for gas-filled containers and (E)-1,1,1,4,4,4-hexafluoro-2-butene

Abstract

Provided is a gas-filled container which is filled with (E)-1,1,1,4,4,4-hexafluoro-2-butene and in which the purity thereof is unlikely to decrease for a long period of time. The gas-filled container is obtained by filling a container with (E)-1,1,1,4,4,4-hexafluoro-2-butene. The part of the container that is in contact with the (E)-1,1,1,4,4,4-hexafluoro-2-butene, with which the container is filled, is made of metal having a copper concentration of less than 0.5 mass%.

Description

Technical Field

[0001] The present invention relates to a filled container filled with a gas and a method for storing (E)-1,1,1,4,4,4-hexafluoro-2-butene.

Background Art

[0002] In order to stably perform fine processing in dry etching, it is required that the dry etching gas be of high purity (for example, 99.9% by volume or more). Further, since the dry etching gas is stored until use in a filled container, it is necessary to maintain high purity over a long period in the filled container. Patent Document 1 discloses a technique for storing 2-fluorobutane, 2-fluoro-2-methylpropane, and 2-fluoropentane, which can be used as dry etching gases, while maintaining high purity over a long period. In the technique disclosed in Patent Document 1, by filling a filled container made of manganese steel with a small amount of aluminum adhering to the inner surface with 2-fluorobutane, 2-fluoro-2-methylpropane, or 2-fluoropentane, a decrease in purity is suppressed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The use of (E)-1,1,1,4,4,4-hexafluoro-2-butene as a dry etching gas for semiconductor manufacturing is being considered. However, because (E)-1,1,1,4,4,4-hexafluoro-2-butene has a double bond in its molecule, it is less stable than 2-fluorobutane, 2-fluoro-2-methylpropane, and 2-fluoropentane, and is prone to reactions such as isomerization, polymerization, and decomposition during storage. Therefore, when the technology disclosed in Patent Document 1 was applied to (E)-1,1,1,4,4,4-hexafluoro-2-butene, reactions such as isomerization, polymerization, and decomposition sometimes occurred during long-term storage, resulting in a decrease in purity. The object of the present invention is to provide a gas-filled container in which the purity of the filled (E)-1,1,1,4,4,4-hexafluoro-2-butene does not easily decrease over a long period of time, and a method for storing (E)-1,1,1,4,4,4-hexafluoro-2-butene. [Means for solving the problem]

[0005] To solve the aforementioned problems, one aspect of the present invention is as follows [1] to

[13] . [1] A gas-filled container in which (E)-1,1,1,4,4,4-hexafluoro-2-butene is filled into the container, A gas-filled container in which the portion of the filled container in contact with the (E)-1,1,1,4,4,4-hexafluoro-2-butene is made of a metal in which the copper concentration is less than 0.5% by mass.

[0006] [2] The gas-filled container according to [1], wherein the portion of the filled container in contact with the (E)-1,1,1,4,4,4-hexafluoro-2-butene is made of a metal in which the copper concentration is less than 0.4% by mass. [3] The gas-filled container according to [1] or [2], wherein the metal is steel. [4] The gas-filled container according to [1] or [2], wherein the metal is at least one of manganese steel and chromium-molybdenum steel. [5] The concentration of copper is measured by X-ray photoelectron spectroscopy. [1] to [4] A gas-filled container as described in any one of these items.

[0007] [6] The gas-filled container according to any one of [1] to [5], wherein the filled container comprises a cylinder containing the (E)-1,1,1,4,4,4-hexafluoro-2-butene and a valve for opening and closing a flow path for the (E)-1,1,1,4,4,4-hexafluoro-2-butene inside the cylinder to the outside. [7] A gas-filled container according to any one of the following [1] to [6], wherein the purity of the (E)-1,1,1,4,4,4-hexafluoro-2-butene to be filled is 99.90% by volume or higher.

[0008] [8] A method for storing (E)-1,1,1,4,4,4-hexafluoro-2-butene, which is stored in a filled container, A method for storing (E)-1,1,1,4,4,4-hexafluoro-2-butene, wherein the portion of the filled container that comes into contact with the filled (E)-1,1,1,4,4,4-hexafluoro-2-butene is made of a metal with a copper concentration of less than 0.5% by mass.

[0009] [9] The method for storing (E)-1,1,1,4,4,4-hexafluoro-2-butene according to [8], wherein the portion of the filled container that comes into contact with the filled (E)-1,1,1,4,4,4-hexafluoro-2-butene is made of a metal in which the copper concentration is less than 0.4% by mass.

[10] The method for storing (E)-1,1,1,4,4,4-hexafluoro-2-butene according to [8] or [9], wherein the metal is steel.

[11] The method for storing (E)-1,1,1,4,4,4-hexafluoro-2-butene according to [8] or [9], wherein the metal is at least one of manganese steel and chromium-molybdenum steel.

[0010]

[12] The copper concentration is measured by X-ray photoelectron spectroscopy. [8] to

[11] A method for storing (E)-1,1,1,4,4,4-hexafluoro-2-butene as described in any one of these items.

[13] A method for storing (E)-1,1,1,4,4,4-hexafluoro-2-butene according to any one of the items [8] to

[12] , wherein the purity of the (E)-1,1,1,4,4,4-hexafluoro-2-butene to be filled is 99.90% by volume or higher. [Effects of the Invention]

[0011] According to the present invention, the purity of the filled (E)-1,1,1,4,4,4-hexafluoro-2-butene is less likely to decrease over a long period of time. [Modes for carrying out the invention]

[0012] One embodiment of the present invention is described below. This embodiment is merely an example of the present invention, and the present invention is not limited to this embodiment. Furthermore, various modifications or improvements can be made to this embodiment, and such modified or improved forms may also be included in the present invention.

[0013] (E)-1,1,1,4,4,4-Hexafluoro-2-butene is being considered for use as a dry etching gas in semiconductor manufacturing, but because it is not widely used industrially, its physical properties are not fully understood, and there are currently very few reports on its long-term storage stability or compounds that act as decomposition catalysts.

[0014] As a result of diligent research, the inventors of the present invention have found that when (E)-1,1,1,4,4,4-hexafluoro-2-butene comes into contact with metallic copper, copper alloys, or copper compounds, it undergoes reactions such as isomerization, polymerization, and decomposition, resulting in a decrease in purity, and have completed the present invention. The present invention specifies the material of the filling container for filling (E)-1,1,1,4,4,4-hexafluoro-2-butene in order to suppress reactions such as isomerization, polymerization, and decomposition of (E)-1,1,1,4,4,4-hexafluoro-2-butene.

[0015] In other words, the gas-filled container according to this embodiment is a gas-filled container in which (E)-1,1,1,4,4,4-hexafluoro-2-butene is filled into the container, and the portion of the container in contact with the filled (E)-1,1,1,4,4,4-hexafluoro-2-butene is made of a metal in which the copper concentration is less than 0.5% by mass.

[0016] Furthermore, the storage method for (E)-1,1,1,4,4,4-hexafluoro-2-butene according to this embodiment is a method of storing (E)-1,1,1,4,4,4-hexafluoro-2-butene by filling it into a filled container, wherein the portion of the filled container that comes into contact with the filled (E)-1,1,1,4,4,4-hexafluoro-2-butene is made of a metal with a copper concentration of less than 0.5% by mass.

[0017] In the filled container, the portion that comes into contact with the filled (E)-1,1,1,4,4,4-hexafluoro-2-butene is made of a metal with a copper concentration of less than 0.5% by mass. Therefore, reactions such as isomerization, polymerization, and decomposition are unlikely to occur in the filled (E)-1,1,1,4,4,4-hexafluoro-2-butene. As a result, even if the gas-filled container according to this embodiment is stored for a long period of time, the purity of the filled (E)-1,1,1,4,4,4-hexafluoro-2-butene is unlikely to decrease. Thus, if a gas-filled container is filled with high-purity (E)-1,1,1,4,4,4-hexafluoro-2-butene, its high purity is likely to be maintained even after long-term storage.

[0018] Note that the above-mentioned copper means copper element. When the metal forming the portion of the filling container that comes into contact with the filled (E)-1,1,1,4,4,4-hexafluoro-2-butene contains copper, the copper may be metallic copper, a copper alloy, or a copper compound such as a copper salt.

[0019] Also, the concentration of copper contained in the above-mentioned metal needs to be less than 0.5% by mass, preferably 0.4% by mass or less. And in order to further suppress reactions such as isomerization, polymerization, and decomposition of (E)-1,1,1,4,4,4-hexafluoro-2-butene, it is more preferably 0.1% by mass or less, and even more preferably 0.01% by mass or less. There is no particular lower limit for the concentration of copper, but it may be 0.001% by mass or more. The method for measuring the concentration of this copper is not particularly limited, but it can be measured by X-ray photoelectron spectroscopy (XPS analysis).

[0020] 〔Filling container〕 The filling container in the gas-filled filling container according to the present embodiment, and the filling container in the method for storing (E)-1,1,1,4,4,4-hexafluoro-2-butene according to the present embodiment are preferably provided with a cylinder and a valve. The cylinder is a member in which (E)-1,1,1,4,4,4-hexafluoro-2-butene is stored. This cylinder is preferably an integrally molded seamless container. Also, the valve is a member that opens and closes the flow path for flowing the (E)-1,1,1,4,4,4-hexafluoro-2-butene inside the cylinder to the outside and controls the flow of the (E)-1,1,1,4,4,4-hexafluoro-2-butene flowing through the flow path.

[0021] In the filled container, the parts that come into contact with the filled (E)-1,1,1,4,4,4-hexafluoro-2-butene, such as the cylinder (especially the inner surface of the cylinder) and the valve, are preferably made of steel. Examples of steel include at least one of stainless steel, manganese steel, and chromium-molybdenum steel.

[0022] Examples of cylinders made of manganese steel or chromium-molybdenum steel include those manufactured from steel pipes specified in JIS standard JIS G3429 (Seamless steel pipes for high-pressure gas containers), such as STH11, STH12 (manganese steel pipes) and STH21, STH22 (chromium-molybdenum steel pipes).

[0023] However, these standards do not include a copper component, and the copper concentration in manganese steel and chromium-molybdenum steel is unknown; therefore, simply meeting these standards is insufficient. Analysis of the inner surfaces of several commercially available cylinders that meet the STH12 standard revealed a mixture of cylinders with copper concentrations ranging from 1.0 mass% to less than 0.005 mass%. Therefore, when using general manganese steel and chromium-molybdenum steel in this invention, it is necessary to select cylinders with a copper concentration of less than 0.5 mass%.

[0024] Regarding the valve, it is preferable that it be made of steel, similar to the cylinder, but a valve made of brass, Monel® or other copper alloy may also be used, as long as it is plated with nickel or the like to prevent direct contact with (E)-1,1,1,4,4,4-hexafluoro-2-butene.

[0025] [(E)-1,1,1,4,4,4-Hexafluoro-2-butene] The purity of (E)-1,1,1,4,4,4-hexafluoro-2-butene to be filled into the container (purity before filling into the container) is preferably 99.90% by volume or higher, more preferably 99.95% by volume or higher, and even more preferably 99.99% by volume or higher. If high-purity (E)-1,1,1,4,4,4-hexafluoro-2-butene is filled into a container as described above, its purity will hardly decrease during storage, making it easy to maintain high purity even after long-term storage.

[0026] For example, if the purity of (E)-1,1,1,4,4,4-hexafluoro-2-butene before filling into a container is purity X, and the purity of (E)-1,1,1,4,4,4-hexafluoro-2-butene after being stored in the container at 23°C for 30 days is purity Y, then it is possible to make purity Y 99.90% by volume or higher. Furthermore, it is possible to make the difference between purity X and purity Y (purity X - purity Y) less than 0.02 percentage points.

[0027] When dry etching is performed using (E)-1,1,1,4,4,4-hexafluoro-2-butene with a purity of 99.90 volume% or higher as the dry etching gas, the reproducibility of plasma behavior and etching performance tends to be good. The method for measuring the purity of (E)-1,1,1,4,4,4-hexafluoro-2-butene is not particularly limited, but it can be measured by gas chromatography or Fourier transform infrared spectroscopy (FT-IR analysis).

[0028] The method for filling a container with (E)-1,1,1,4,4,4-hexafluoro-2-butene is not particularly limited, but one example is to fill a vacuum-filled container with (E)-1,1,1,4,4,4-hexafluoro-2-butene through a filling line that has been purged with an inert gas selected from nitrogen gas (N2), argon (Ar), and helium (He).

[0029] The purging process can be performed using either a batch purging method, which involves filling the filling line with inert gas and then evacuating it, or a flow purging method, which involves continuously flowing inert gas through the filling line. The filling line is preferably composed of piping whose inner surface has been treated by passivation or electropolishing.

[0030] Products resulting from the reaction of (E)-1,1,1,4,4,4-hexafluoro-2-butene with copper include, for example, (Z)-1,1,1,4,4,4-hexafluoro-2-butene produced by cis-trans isomerization, 1,2,3,4-tetrakis(trifluoromethyl)cyclobutane produced by dimerization, and polymers of (E)-1,1,1,4,4,4-hexafluoro-2-butene produced by polymerization. [Examples]

[0031] The present invention will be described in more detail below with reference to examples and comparative examples. [Example 1] A seamless 10L container made of manganese steel with a copper concentration of 0.4 mass% was prepared as a cylinder. The inner surface of this cylinder was shot blasted, acid-cleaned, and washed with water, and then dried. After that, a valve made of SUS316L with a copper concentration of less than 0.005 mass% was attached to the cylinder to create a filled container. Then, the inside of this filled container was evacuated while heated.

[0032] This filled container was connected to a gas filling line that leads to a SUS316 tank containing (E)-1,1,1,4,4,4-hexafluoro-2-butene. The purity X of (E)-1,1,1,4,4,4-hexafluoro-2-butene in the tank, as analyzed by gas chromatography, was 99.95% by volume. The inner surface of this tank was electropolished.

[0033] Next, the gas filling line was subjected to a batch purging process, which involved filling it with nitrogen gas and then repeatedly evacuating it. Then, 1 kg of (E)-1,1,1,4,4,4-hexafluoro-2-butene was transferred from the tank to the filling container via this gas filling line, thereby obtaining a gas-filled container with (E)-1,1,1,4,4,4-hexafluoro-2-butene inside. The internal pressure (gauge pressure) of the obtained gas-filled container was 0.06 MPaG.

[0034] The gas-filled containers obtained in this manner were filled with (E)-1,1,1,4,4,4-hexafluoro-2-butene and left to stand at 23°C for 30 days. The purity Y of (E)-1,1,1,4,4,4-hexafluoro-2-butene in the gas-filled containers was then measured. The results showed no decrease in purity from the purity X before filling the containers, and the purity was 99.95% by volume. That is, the difference between purity X and purity Y (purity X - purity Y) was 0.00 percentage points. The results are shown in Table 1.

[0035] [Table 1]

[0036] After measuring the purity Y of (E)-1,1,1,4,4,4-hexafluoro-2-butene, the (E)-1,1,1,4,4,4-hexafluoro-2-butene was extracted from the gas-filled container, and a batch purging process was performed by filling it with nitrogen gas and repeatedly evacuating it. The container was then cut into 2 cm squares using a laser cutting machine, and XPS analysis of the inner surface of the container was performed using these as measurement samples to measure the copper concentration. As a result, the copper concentration remained unchanged from the initial 0.4 mass%.

[0037] The analytical equipment and conditions used for gas chromatography are as follows: Equipment: Shimadzu Corporation GC-2014s gas chromatograph Column: CarboPak B 60 / 80 SP-1000 Column temperature: 150℃ / 200℃ Injection temperature: 200℃ Carrier gas: Helium Detector: Flame ionization detector (FID)

[0038] Furthermore, the analytical instrument, analytical conditions, and sputtering conditions used for the XPS analysis are as follows. Equipment: ULVAC-PHI X-ray photoelectron spectroscopy analyzer PHI5000VersaProbeII Atmosphere: Vacuum (1.0 x 10 6 (Less than Pa) X-ray source: Monochromatic Al Ka ​​(1486.6 eV) Spectrometer: Electrostatic concentric hemispherical spectrometer

[0039] X-ray beam diameter: 100 μm (25 W, 15 kV) Signal acquisition angle: 45.0° Pass energy: 23.5 eV Measurement energy range: Cr2p 570-584eV Mn2p 632-648eV Fe2p 704-720eV Cu2p 930-945eV

[0040] Ion source for sputtering: Ar2,500+ Sputtering acceleration voltage: 10kV Sputtering area: 2mm x 2mm Spattering time: 10 minutes

[0041] [Examples 2-6 and Comparative Examples 1, 2, 4, 5] Except for the difference in the type of steel used to form the seamless container used as a cylinder (Table 1 shows the type of steel and the concentration of copper), the same procedure as in Example 1 was performed, and the purity Y of (E)-1,1,1,4,4,4-hexafluoro-2-butene in the gas-filled container was measured after standing at 23°C for 30 days. The results are shown in Table 1.

[0042] [Example 7] Except for the fact that a nickel alloy coating was formed on the inner surface of the cylinder by electroless plating, the same procedure as in Example 1 was performed, and the purity Y of (E)-1,1,1,4,4,4-hexafluoro-2-butene in the gas-filled container was measured after standing at 23°C for 30 days. The results are shown in Table 1. The copper concentration on the surface of the nickel alloy coating was confirmed to be less than 0.05% by mass by XPS analysis.

[0043] [Comparative Example 3] Except for using a brass valve, the same procedure as in Example 3 was followed, and the purity Y of (E)-1,1,1,4,4,4-hexafluoro-2-butene in the gas-filled container was measured after standing at 23°C for 30 days. The results are shown in Table 1. The copper concentration of the brass was 70% by mass.

[0044] [Comparative Example 6] Except for using a brass valve, the procedure was the same as in Example 6, and the purity Y of (E)-1,1,1,4,4,4-hexafluoro-2-butene in the gas-filled container was measured after standing at 23°C for 30 days. The results are shown in Table 1. The copper concentration of the brass was 70% by mass.

[0045] [Comparative Example 7] Except for using a brass valve, the procedure was the same as in Example 7, and the purity Y of (E)-1,1,1,4,4,4-hexafluoro-2-butene in the gas-filled container was measured after standing at 23°C for 30 days. The results are shown in Table 1. The copper concentration of the brass was 70% by mass.

[0046] As can be seen from the results shown in Table 1, Examples 1-7 showed no decrease in purity after storage at 23°C for 30 days, and the difference between purity X and purity Y was 0.00 percentage points. In contrast, Comparative Examples 1-7 showed a decrease in purity after storage at 23°C for 30 days. In Comparative Examples 1-7, it is thought that reactions such as isomerization, polymerization, and decomposition of (E)-1,1,1,4,4,4-hexafluoro-2-butene occurred due to copper.

Claims

1. A gas-filled container in which (E)-1,1,1,4,4,4-hexafluoro-2-butene is filled into the filled container, A gas-filled container in which the portion of the filled container in contact with the (E)-1,1,1,4,4,4-hexafluoro-2-butene is made of a metal in which the copper concentration is less than 0.5% by mass.

2. The gas-filled container according to claim 1, wherein the portion of the filled container that is in contact with the (E)-1,1,1,4,4,4-hexafluoro-2-butene is formed of a metal having a copper concentration of less than 0.4% by mass.

3. The gas-filled container according to claim 1 or claim 2, wherein the metal is steel.

4. The gas-filled container according to claim 1 or claim 2, wherein the metal is at least one of manganese steel and chromium-molybdenum steel.

5. The gas-filled container according to any one of claims 1 to 4, wherein the concentration of copper is measured by X-ray photoelectron spectroscopy.

6. The gas-filled container according to any one of claims 1 to 5, wherein the filled container comprises a cylinder containing the (E)-1,1,1,4,4,4-hexafluoro-2-butene, and a valve for opening and closing a flow path for the (E)-1,1,1,4,4,4-hexafluoro-2-butene inside the cylinder to the outside.

7. A gas-filled container according to any one of claims 1 to 6, wherein the purity of the (E)-1,1,1,4,4,4-hexafluoro-2-butene to be filled is 99.90% by volume or more.

8. A method for storing (E)-1,1,1,4,4,4-hexafluoro-2-butene by filling it into a filled container, A method for storing (E)-1,1,1,4,4,4-hexafluoro-2-butene, wherein the portion of the filled container that comes into contact with the filled (E)-1,1,1,4,4,4-hexafluoro-2-butene is made of a metal with a copper concentration of less than 0.5% by mass.

9. The method for storing (E)-1,1,1,4,4,4-hexafluoro-2-butene according to claim 8, wherein the portion of the filled container that comes into contact with the filled (E)-1,1,1,4,4,4-hexafluoro-2-butene is made of a metal in which the copper concentration is less than 0.4% by mass.

10. The method for storing (E)-1,1,1,4,4,4-hexafluoro-2-butene according to claim 8 or 9, wherein the metal is steel.

11. The method for storing (E)-1,1,1,4,4,4-hexafluoro-2-butene according to claim 8 or 9, wherein the metal is at least one of manganese steel and chromium-molybdenum steel.

12. The method for storing (E)-1,1,1,4,4,4-hexafluoro-2-butene according to any one of claims 8 to 11, wherein the concentration of copper is measured by X-ray photoelectron spectroscopy.

13. A method for storing (E)-1,1,1,4,4,4-hexafluoro-2-butene according to any one of claims 8 to 12, wherein the purity of the (E)-1,1,1,4,4,4-hexafluoro-2-butene to be filled is 99.90% by volume or more.

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