Method of preserving an inflated container and e-1,1,1,4,4,4-hexafluoro-2-butene

Abstract

An inflated container filled with E-1,1,1,4,4,4-hexafluoro-2-butene is provided, which is less likely to decrease in purity over a long period of time. The inflated container is obtained by filling E-1,1,1,4,4,4-hexafluoro-2-butene in a container. A portion of the container in contact with the filled E-1,1,1,4,4,4-hexafluoro-2-butene is formed of a metal having a copper concentration of less than 0.5 mass%.

Description

Technical Field

[0001] This invention relates to a method for pre-filled gas-filled containers and for preserving E-1,1,1,4,4,4-hexafluoro-2-butene. Background Technology

[0002] In dry etching, high purity (e.g., 99.9% by volume or higher) is required for stable micro-machining. Furthermore, the dry etching gas is stored in a filled container until use, necessitating long-term maintenance of high purity within the container.

[0003] Patent Document 1 discloses a technique for maintaining the high purity of 2-fluorobutane, 2-fluoro-2-methylpropane, and 2-fluoropentane, which can be used as dry etching gases, over a long period. In the technique disclosed in Patent Document 1, purity reduction is suppressed by filling a manganese steel filling container with 2-fluorobutane, 2-fluoro-2-methylpropane, or 2-fluoropentane into the container, which has a low aluminum content attached to its inner surface.

[0004] Existing technical documents

[0005] Patent Document 1: International Publication No. 2016 / 117464 Summary of the Invention

[0006] Research has been conducted on using E-1,1,1,4,4,4-hexafluoro-2-butene as a dry etching gas for semiconductor manufacturing. However, due to the presence of double bonds within the molecule, E-1,1,1,4,4,4-hexafluoro-2-butene exhibits lower stability compared to 2-fluorobutane, 2-fluoro-2-methylpropane, and 2-fluoropentane, and is prone to isomerization, polymerization, and decomposition reactions during storage.

[0007] Therefore, if the technology disclosed in Patent Document 1 is applied to E-1,1,1,4,4,4-hexafluoro-2-butene, isomerization, polymerization, decomposition and other reactions will occur during long-term storage, resulting in a decrease in purity.

[0008] The objective of this invention is to provide a gas-filled container in which the purity of E-1,1,1,4,4,4-hexafluoro-2-butene is not easily reduced over a long period of time, and a method for preserving E-1,1,1,4,4,4-hexafluoro-2-butene.

[0009] In order to solve the above-mentioned problems, one aspect of the present invention is as described below in [1] to

[13] .

[0010] [1] An inflatable filling container is obtained by filling a filling container with E-1,1,1,4,4,4-hexafluoro-2-butene.

[0011] The portion of the filling container that comes into contact with the E-1,1,1,4,4,4-hexafluoro-2-butene is formed of a metal with a copper concentration of less than 0.5% by mass.

[0012] [2] According to the gas-filled container of [1], the portion of the container in contact with the E-1,1,1,4,4,4-hexafluoro-2-butene is formed of a metal with a copper concentration of less than 0.4% by mass.

[0013] [3] The metal is steel in the inflated container as described in [1] or [2].

[0014] [4] The inflated container according to [1] or [2], wherein the metal is at least one of manganese steel and chromium-molybdenum steel.

[0015] [5] In any one of [1] to [4], the concentration of copper in the gas-filled container is determined by X-ray photoelectron spectroscopy.

[0016] [6] The gas-filled container according to any one of [1] to [5], the filling container comprising: a gas 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 gas cylinder to flow to the outside.

[0017] [7] The gas-filled container according to any one of [1] to [6] is filled with E-1,1,1,4,4,4-hexafluoro-2-butene having a purity of 99.90% by volume or more.

[0018] [8] A method for preserving E-1,1,1,4,4,4-hexafluoro-2-butene, comprising filling E-1,1,1,4,4,4-hexafluoro-2-butene into a filling container for preservation.

[0019] The portion of the filling container that comes into contact with the E-1,1,1,4,4,4-hexafluoro-2-butene being filled is formed of a metal with a copper concentration of less than 0.5% by mass.

[0020] [9] According to the preservation method of E-1,1,1,4,4,4-hexafluoro-2-butene described in [8], the portion of the filling container in contact with the filled E-1,1,1,4,4,4-hexafluoro-2-butene is formed of a metal with a copper concentration of less than 0.4% by mass.

[0021]

[10] The metal is steel, according to the preservation method of E-1,1,1,4,4,4-hexafluoro-2-butene as described in [8] or [9].

[0022]

[11] The metal is at least one of manganese steel and chromium-molybdenum steel, according to the preservation method of E-1,1,1,4,4,4-hexafluoro-2-butene as described in [8] or [9].

[0023]

[12] The concentration of copper in the E-1,1,1,4,4,4-hexafluoro-2-butene according to any one of [8] to

[11] is determined by X-ray photoelectron spectroscopy.

[0024]

[13] The E-1,1,1,4,4,4-hexafluoro-2-butene prepared according to any one of [8] to

[12] has a purity of 99.90% by volume or more.

[0025] According to the present invention, the purity of the filled E-1,1,1,4,4,4-hexafluoro-2-butene is not easily reduced over a long period of time. Detailed Implementation

[0026] Hereinafter, one embodiment of the present invention will be described. Furthermore, this embodiment illustrates one example of the present invention, and the present invention is not limited to this embodiment. In addition, various modifications or improvements can be made to this embodiment, and such modifications or improvements are also included in the present invention.

[0027] E-1,1,1,4,4,4-hexafluoro-2-butene has been studied as a dry etching gas for semiconductor manufacturing, but it has not been widely used in industry. As a result, its physical properties have not been fully elucidated, and there are almost no reports to date on its long-term storage stability and its use as a decomposition catalyst.

[0028] Through in-depth research, the inventors discovered that if E-1,1,1,4,4,4-hexafluoro-2-butene comes into contact with metallic copper, copper alloys, or copper compounds, isomerization, polymerization, and decomposition reactions occur, leading to a decrease in purity. This led to the completion of this invention. To suppress the isomerization, polymerization, and decomposition reactions of E-1,1,1,4,4,4-hexafluoro-2-butene, this invention specifies the material of the filling container for E-1,1,1,4,4,4-hexafluoro-2-butene.

[0029] That is, the gas-filled container of this embodiment is a gas-filled container obtained by filling a filling container with E-1,1,1,4,4,4-hexafluoro-2-butene. The part of the filling container that is in contact with the filled E-1,1,1,4,4,4-hexafluoro-2-butene is formed of a metal with a copper concentration of less than 0.5% by mass.

[0030] Furthermore, the method for preserving E-1,1,1,4,4,4-hexafluoro-2-butene in this embodiment is to fill E-1,1,1,4,4,4-hexafluoro-2-butene into a filling container for preservation. The portion of the filling container that comes into contact with the filled E-1,1,1,4,4,4-hexafluoro-2-butene is formed of a metal with a copper concentration of less than 0.5% by mass.

[0031] In the filling container, the portion in contact with the filled E-1,1,1,4,4,4-hexafluoro-2-butene is formed by a metal with a copper concentration of less than 0.5% by mass. Therefore, it is less likely to undergo isomerization, polymerization, or decomposition reactions with the filled E-1,1,1,4,4,4-hexafluoro-2-butene. Thus, even with long-term storage of the gas-filled container of this embodiment, the purity of the filled E-1,1,1,4,4,4-hexafluoro-2-butene is not easily reduced. Therefore, if a gas-filled container is filled with high-purity E-1,1,1,4,4,4-hexafluoro-2-butene, its high purity can be easily maintained even after long-term storage.

[0032] Furthermore, the copper mentioned above refers to the element copper. When the metal in the portion of the filling container that comes into contact with the E-1,1,1,4,4,4-hexafluoro-2-butene contains copper, the copper can be metallic copper, a copper alloy, or a copper compound such as a copper salt.

[0033] Furthermore, the concentration of copper in the aforementioned metal needs to be less than 0.5% by mass, preferably less than 0.4% by mass. Moreover, to further suppress isomerization, polymerization, decomposition, and other reactions of E-1,1,1,4,4,4-hexafluoro-2-butene, it is more preferably less than 0.1% by mass, and even more preferably less than 0.01% by mass. The lower limit of the copper concentration is not particularly limited and may be 0.001% by mass or more.

[0034] There are no particular limitations on the method for determining the concentration of copper; X-ray photoelectron spectroscopy (XPS) can be used.

[0035] [Fill the container]

[0036] The filling container in the pre-filled container of this embodiment, and the filling container in the method for storing E-1,1,1,4,4,4-hexafluoro-2-butene of this embodiment, preferably includes a gas storage bottle and a valve. The gas storage bottle is a component for storing E-1,1,1,4,4,4-hexafluoro-2-butene. This gas storage bottle is preferably a seamless container formed in one piece.

[0037] In addition, the valve is a component that opens and closes the flow path of E-1,1,1,4,4,4-hexafluoro-2-butene inside the gas cylinder to the outside, and controls the flow of E-1,1,1,4,4,4-hexafluoro-2-butene flowing in the flow path.

[0038] The portions of the filling container that come into contact with the E-1,1,1,4,4,4-hexafluoro-2-butene, such as the gas cylinder (particularly the inner surface of the gas cylinder) and the valve, are preferably made of steel. Examples of steel include stainless steel, manganese steel, and chromium-molybdenum steel.

[0039] Gas cylinders made of manganese steel or chromium-molybdenum steel include those manufactured from steel pipes specified in JIS G3429 (seamless steel pipes for high-pressure gas containers) as STH11, STH12 (manganese steel pipes) and STH21, STH22 (chromium-molybdenum steel pipes).

[0040] However, these standards do not include copper, and the copper concentration in manganese steel and chromium-molybdenum steel is unclear; therefore, simply meeting these standards is insufficient. Analysis of the inner surfaces of several commercially available gas cylinders that meet the STH12 standard revealed a mixture of portions with copper concentrations of 1.0% by mass and portions less than 0.005% by mass. Therefore, in the case of using common manganese steel and chromium-molybdenum steel in this invention, it is necessary to screen for steels with copper concentrations less than 0.5% by mass.

[0041] Furthermore, regarding the valve, it is preferable to make it from steel, just like the gas cylinder. However, if a plating such as nickel plating is applied so that it does not come into direct contact with E-1,1,1,4,4,4-hexafluoro-2-butene, a valve made of copper alloy such as brass or Monel (a registered trademark) can also be used.

[0042] [E-1,1,1,4,4,4-hexafluoro-2-butene]

[0043] The purity of E-1,1,1,4,4,4-hexafluoro-2-butene (purity before filling into the filling container) is 99.90% by volume or more, more preferably 99.95% by volume or more, and even more preferably 99.99% by volume or more.

[0044] If the high-purity E-1,1,1,4,4,4-hexafluoro-2-butene described above is filled into the filling container, the purity will hardly decrease during storage, and therefore it is easy to maintain high purity even after long-term storage.

[0045] For example, if the purity of E-1,1,1,4,4,4-hexafluoro-2-butene before being filled into the filling container is set as purity X, and the purity of E-1,1,1,4,4,4-hexafluoro-2-butene after being stored in the filling container at 23°C for 30 days is set as purity Y, then purity Y can be made to be 99.90% by volume or higher. Furthermore, the difference between purity X and purity Y (purity X - purity Y) can be made to be less than 0.02 percentage points.

[0046] If E-1,1,1,4,4,4-hexafluoro-2-butene with a purity of 99.90% by volume or higher is used as the dry etching gas for dry etching, the behavior of the plasma and the reproducibility of the etching performance can easily become good.

[0047] There are no particular limitations on the method for determining the purity of E-1,1,1,4,4,4-hexafluoro-2-butene. For example, gas chromatography or Fourier transform infrared spectroscopy (FT-IR) can be used.

[0048] There is no particular limitation on the filling method of E-1,1,1,4,4,4-hexafluoro-2-butene into the filling container. For example, one method is to fill the vacuumed filling container by passing E-1,1,1,4,4,4-hexafluoro-2-butene through a filling pipeline that has been purified by an inert gas selected from nitrogen (N2), argon (Ar) and helium (He).

[0049] Purification can be any of the following methods: batch purification by filling the filling pipeline with inert gas and then evacuating it, or flow purification by continuously allowing inert gas to flow into the filling pipeline.

[0050] The filling pipeline is preferably composed of piping whose inner surface has been passivated or electrolytically ground.

[0051] Examples of products generated by the reaction of E-1,1,1,4,4,4-hexafluoro-2-butene with copper include Z-1,1,1,4,4,4-hexafluoro-2-butene produced by cis-trans isomerization, 1,2,3,4-tetra(trifluoromethyl)cyclobutane produced by dimerization, and polymers of E-1,1,1,4,4,4-hexafluoro-2-butene produced by polymerization.

[0052] Example

[0053] The present invention will be described in more detail below with examples and comparative examples.

[0054] [Example 1]

[0055] A seamless 10L container made of manganese steel with a copper concentration of 0.4% by mass was prepared as a gas storage cylinder. The inner surface of the gas storage cylinder was sandblasted, acid-washed, and washed with water, and then dried. Then, a valve made of SUS316L steel with a copper concentration of less than 0.005% by mass was installed on the gas storage cylinder to form a filling container. Then, the inside of the filling container was evacuated under heating.

[0056] The filling container was connected to a gas filling line, which in turn was connected to an SUS316 canister containing E-1,1,1,4,4,4-hexafluoro-2-butene. The purity X of the E-1,1,1,4,4,4-hexafluoro-2-butene in the canister, analyzed by gas chromatography, was 99.95% by volume. Furthermore, the inner surface of the canister was electrolytically polished.

[0057] Next, the gas filling pipeline underwent batch purification by repeatedly evacuating after being filled with nitrogen. Then, 1 kg of E-1,1,1,4,4,4-hexafluoro-2-butene was transferred from the tank to the filling container via the same pipeline, resulting in a gas-filled container filled with E-1,1,1,4,4,4-hexafluoro-2-butene. The internal pressure (gauge pressure) of the resulting gas-filled container was 0.06 MPaG.

[0058] The resulting gas-filled container was then allowed to stand at 23°C for 30 days after filling with E-1,1,1,4,4,4-hexafluoro-2-butene. The purity Y of the E-1,1,1,4,4,4-hexafluoro-2-butene within the gas-filled container was then measured. The results showed that the purity did not decrease from the initial purity X before filling, remaining at 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.

[0059] Table 1

[0060]

[0061] After determining the purity Y of E-1,1,1,4,4,4-hexafluoro-2-butene, E-1,1,1,4,4,4-hexafluoro-2-butene was extracted from the gas-filled container and subjected to batch purification treatment involving repeated vacuuming after filling with nitrogen. Then, the container was cut into 2cm square pieces using a laser cutter and used as test samples. XPS analysis of the inner surface of the container was performed to determine the copper concentration. The results showed that the copper concentration remained unchanged compared to the initial 0.4% by mass.

[0062] Furthermore, the analytical apparatus and analytical conditions used in gas chromatography are described below.

[0063] Apparatus: Shimadzu Corporation GC-2014s gas chromatograph

[0064] Column: CarboPak B 60 / 80SP-1000

[0065] Column temperature: 150℃ / 200℃

[0066] Injection temperature: 200℃

[0067] Carrier gas: Helium

[0068] Detector: Flame Ionization Detector (FID)

[0069] In addition, the analytical apparatus, analytical conditions, and sputtering conditions used in XPS analysis are described below.

[0070] Apparatus: ULVAC-PHI Corporation X-ray photoelectron spectroscopy analyzer PHI5000 VersaProbeII

[0071] Atmosphere: Vacuum (less than 1.0 × 10⁻⁶) 6 Pa)

[0072] X-ray source: Monochromatic Al Ka ​​(1486.6 eV)

[0073] Beam splitter: Electrostatic concentric hemispherical beam splitter

[0074] X-ray beam diameter: 100μm (25W, 15kV)

[0075] Signal reception angle: 45.0°

[0076] Path energy: 23.5 eV

[0077] Measurement energy range:

[0078] Ion source for sputtering: Ar2, 500+

[0079] Acceleration voltage for sputtering: 10kV

[0080] Sputtering area: 2mm × 2mm

[0081] Sputtering time: 10 minutes

[0082] [Examples 2-6 and Comparative Examples 1, 2, 4, 5]

[0083] Except for the steel used to form the seamless container used as the gas cylinder (the steel type and copper concentration are shown in Table 1), the same procedure as in Example 1 was performed to determine the purity Y of E-1,1,1,4,4,4-hexafluoro-2-butene in the gas-filled container after standing at 23°C for 30 days. The results are shown in Table 1.

[0084] [Example 7]

[0085] Except for the formation of a nickel alloy film obtained by electroless plating on the inner surface of the gas cylinder, the same procedure as in Example 1 was performed to determine the purity Y of E-1,1,1,4,4,4-hexafluoro-2-butene in the gas-filled container after standing at 23°C for 30 days. The results are shown in Table 1. Furthermore, XPS analysis confirmed that the copper concentration of the nickel alloy film was less than 0.05% by mass.

[0086] [Comparative Example 3]

[0087] Except for the use of a brass valve, the same procedures as in Example 3 were performed to determine the purity Y of E-1,1,1,4,4,4-hexafluoro-2-butene in the gas-filled container after standing at 23°C for 30 days. The results are shown in Table 1. Furthermore, the copper concentration of the brass was 70% by mass.

[0088] [Comparative Example 6]

[0089] Except for the use of a brass valve, the same procedures as in Example 6 were performed to determine the purity Y of E-1,1,1,4,4,4-hexafluoro-2-butene in the gas-filled container after standing at 23°C for 30 days. The results are shown in Table 1. Furthermore, the copper concentration of the brass was 70% by mass.

[0090] [Comparative Example 7]

[0091] Except for the use of a brass valve, the same procedures as in Example 7 were performed to determine the purity Y of E-1,1,1,4,4,4-hexafluoro-2-butene in the gas-filled container after standing at 23°C for 30 days. The results are shown in Table 1. Furthermore, the copper concentration of the brass was 70% by mass.

[0092] As shown in Table 1, the purity of Examples 1-7 did not decrease after being stored 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 being stored at 23°C for 30 days. It is believed that in Comparative Examples 1-7, copper-induced isomerization, polymerization, and decomposition reactions of E-1,1,1,4,4,4-hexafluoro-2-butene occurred.

Claims

1. A pre-filled gas-filled container, obtained by filling the container with E-1,1,1,4,4,4-hexafluoro-2-butene. The portion of the filling container that comes into contact with the E-1,1,1,4,4,4-hexafluoro-2-butene is formed of a metal with a copper mass concentration of less than 0.5%.

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

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

4. The inflated container according to claim 1 or 2, wherein the metal is manganese steel or chromium-molybdenum steel.

5. The gas-filled container according to claim 1 or 2, wherein the concentration of copper is determined by X-ray photoelectron spectroscopy.

6. The pre-filled container according to claim 1 or 2, wherein the container comprises: a gas 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 gas cylinder to flow to the outside.

7. The gas-filled container according to claim 1 or 2, wherein the volume purity of the E-1,1,1,4,4,4-hexafluoro-2-butene is above 99.90%.

8. A method for preserving E-1,1,1,4,4,4-hexafluoro-2-butene, comprising filling E-1,1,1,4,4,4-hexafluoro-2-butene into a filling container for preservation. The portion of the filling container that comes into contact with the E-1,1,1,4,4,4-hexafluoro-2-butene being filled is formed of a metal with a copper mass concentration of less than 0.5%.

9. The method for preserving E-1,1,1,4,4,4-hexafluoro-2-butene according to claim 8, wherein the portion of the filling container in contact with the filled E-1,1,1,4,4,4-hexafluoro-2-butene is formed of a metal with a copper mass concentration of less than 0.4%.

10. The method for preserving 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 preserving E-1,1,1,4,4,4-hexafluoro-2-butene according to claim 8 or 9, wherein the metal is manganese steel or chromium-molybdenum steel.

12. The method for preserving E-1,1,1,4,4,4-hexafluoro-2-butene according to claim 8 or 9, wherein the concentration of copper is determined by X-ray photoelectron spectroscopy.

13. The method for preserving E-1,1,1,4,4,4-hexafluoro-2-butene according to claim 8 or 9, wherein the volume purity of the filled E-1,1,1,4,4,4-hexafluoro-2-butene is 99.90% or higher.

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