Storage method for fluoro-2-butene

Abstract

This invention provides a method for storing fluoro-2-butene that minimizes the progression of isomerization reactions during storage. [Solution] General formula C4H x F y Fluoro-2-butene, represented by the general formula where x is between 0 and 7, y is between 1 and 8, and x+y is 8, may or may not contain hydrogen chloride as an impurity. When this fluoro-2-butene contains hydrogen chloride, the concentration of hydrogen chloride in the gas phase is kept below 100 ppm by volume and stored in a container.

Description

Technical Field

[0001] The present invention relates to a method for storing fluoro-2-butene.

Background Art

[0002] Unsaturated fluorocarbons disclosed in Patent Documents 1, 2, etc. may be used as etching gases for dry etching. Among unsaturated fluorocarbons, fluoro-2-butene has attracted attention as an etching gas that can be used in the most advanced dry etching processes.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, fluoro-2-butene has geometric isomers of Z-form and E-form, and there was a risk that the isomerization reaction would proceed during long-term storage. An object of the present invention is to provide a method for storing fluoro-2-butene in which the isomerization reaction hardly proceeds during storage.

Means for Solving the Problems

[0005] To solve the above problems, one aspect of the present invention is as follows [1] to [3]. [1] A method for storing fluoro-2-butene represented by the general formula C4H x F y where x in the general formula is 0 or more and 7 or less, y is 1 or more and 8 or less, and x + y is 8, A method for storing fluoro-2-butene, wherein the fluoro-2-butene may or may not contain hydrogen chloride as an impurity, and in the case where it contains hydrogen chloride, the concentration of hydrogen chloride in the gas phase is 100 ppm by volume or less, and the fluoro-2-butene is stored in a container.

[0006] [2] A method for storing fluoro-2-butene according to [1], wherein the fluoro-2-butene is at least one selected from (Z)-1,1,1,4,4,4-hexafluoro-2-butene, (E)-1,1,1,4,4,4-hexafluoro-2-butene, (Z)-1,1,1,2,4,4,4-heptafluoro-2-butene, (E)-1,1,1,2,4,4,4-heptafluoro-2-butene, (Z)-1,1,1,2,3,4,4,4-octafluoro-2-butene, and (E)-1,1,1,2,3,4,4,4-octafluoro-2-butene. [3] The method for storing fluoro-2-butene as described in [1] or [2], which involves storing it at a temperature between -20°C and 50°C. [Effects of the Invention]

[0007] According to the present invention, the isomerization reaction of fluoro-2-butene is less likely to proceed during storage. [Modes for carrying out the invention]

[0008] 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.

[0009] The storage method for fluoro-2-butene according to this embodiment is based on the general formula C4H x F yA method for storing fluoro-2-butene, which is represented by the general formula where x is between 0 and 7, y is between 1 and 8, and x+y is 8, wherein the fluoro-2-butene may or may not contain hydrogen chloride (HCl) as an impurity, and in the case where it contains HCl, the concentration of hydrogen chloride in the gas phase is 100 ppm by volume or less, and the fluoro-2-butene is stored in a container.

[0010] If fluoro-2-butene contains hydrogen chloride as an impurity, the isomerization reaction of fluoro-2-butene is accelerated by the catalytic action of hydrogen chloride. Therefore, fluoro-2-butene containing hydrogen chloride may undergo isomerization during storage, potentially leading to a decrease in purity.

[0011] Fluoro-2-butene stored by the storage method according to this embodiment does not contain hydrogen chloride, or if it does, the amount is small. Therefore, isomerization reactions are less likely to proceed even during long-term storage, and a decrease in purity is less likely to occur. Thus, fluoro-2-butene can be stored stably for a long period of time.

[0012] The techniques disclosed in Patent Documents 1 and 2 do not take into account the concentration of hydrogen chloride in the unsaturated fluorocarbon. Therefore, when fluoro-2-butene was stored using the techniques disclosed in Patent Documents 1 and 2, the isomerization reaction of fluoro-2-butene was sometimes accelerated by hydrogen chloride. As a result, the isomerization reaction of fluoro-2-butene progressed during storage, and its purity sometimes decreased.

[0013] The storage method for fluoro-2-butene according to this embodiment will be described in more detail below. [Fluoro-2-butene] The fluoro-2-butene according to this embodiment has the general formula C4H x F y It is represented by the formula and satisfies the following three conditions: x is between 0 and 7 in the general formula, y is between 1 and 8, and x+y is 8. The type of fluoro-2-butene is not particularly limited as long as it satisfies the above requirements.

[0014] Specific examples of fluoro-2-butene include (Z)-CHF2-CF=CF-CF3, (E)-CHF2-CF=CF-CF3, (Z)-CF3-CH=CF-CF3, (E)-CF3-CH=CF-CF3, (Z)-CH2F-CF=CF-CF3, (E)-CH2F-CF=CF-CF3, (Z)-CHF2-CH=CF-CF3, (E)-CHF2-CH=CF-CF3, (Z)-CHF2-CF=CF-CHF2, (E)-CHF2-CF=CF-CHF2, (Z)-CF3-CH=CH-CF3, (E)-CF3-CH=CH-CF3, (Z)-CH3-CF=CF-CF3, (E)-CH3-CF=CF-CF3, (Z)-CH2F-CH=CF-CF3, (E)-CH2F-CH=CF-CF3, (Z)-CH2F-CF=CH-CF3, (E)-CH2F-CF=CH-CF3, (Z)-CH2F-CF=CF-CHF2, (E)-CH2F-CF=CF-CHF2, (Z)-CHF2-CH=CH-CF3, (E)-CHF2-CH=CH-CF3, (Z)-CHF2-CF=CH-CHF2, (E)-CHF2-CF=CH-CHF2, (Z)-CH3-CH=CF-CF3, (E)-CH3-CH=CF-CF3, (Z)-CH3-CF=CH-CF3, (E)-CH3-CF=CH-CF3, (Z)-CH3-CF=CF-CHF2, (E)-CH3-CF=CF-CHF2, (Z)-CH2F-CH=CH-CF3, (E)-CH2F-CH=CH-CF3, (Z)-CH2F-CH=CF-CHF2, (E)-CH2F-CH=CF-CHF2, (Z)-CH2F-CF=CH-CHF2, (E)-CH2F-CF=CH-CHF2, (Z)-CH2F-CF=CF-CH2F, (E)-CH2F-CF=CF-CH2F, (Z)-CHF2-CH=CH-CHF2, (E)-CHF2-CH=CH-CHF2, (Z)-CH3-CH=CH-CF3, (E)-CH3-CH=CH-CF3, (Z)-CH3-CH=CF-CHF2, (E)-CH3-CH=CF-CHF2, (Z)-CH3-CF=CH-CHF2, (E)-CH3-CF=CH-CHF2, (Z)-CH3-CF=CF-CH2F, (E)-CH3-CF=CF-CH2F, (Z)-CH2F-CF=CH-CH2F, (E)-CH2F-CF=CH-CH2F, (Z)-CH2F-CH=CH-CHF2,(E)-CH2F-CH=CH-CHF2, (Z)-CH3-CH=CH-CHF2, (E)-CH3-CH=CH-CHF2, (Z)-CH3-CH=CF-CH2F, (E)-CH3-CH=CF-CH2F, (Z)-CH3-CF=CH-CH2F, (E)-CH3-CF=CH-CH2F, (Z)-CH3-CF= Examples include CF-CH3, (E)-CH3-CF=CF-CH3, (Z)-CH2F-CH=CH-CH2F, (E)-CH2F-CH=CH-CH2F, (Z)-CH3-CH=CH-CH2F, (E)-CH3-CH=CH-CH2F, (Z)-CH3-CH=CF-CH3, and (E)-CH3-CH=CF-CH3. ,

[0015] These fluoro-2-butenes may be used individually or in combination of two or more. Furthermore, as described above, E / Z geometric isomers exist for the above-mentioned fluoro-2-butenes, and any of these geometric isomers of fluoro-2-butene can be used in the storage method for fluoro-2-butene according to this embodiment.

[0016] When storing fluoro-2-butene in a container, either a gas consisting solely of fluoro-2-butene may be stored in the container, or a mixed gas containing fluoro-2-butene and a diluent gas may be stored in the container. As the diluent gas, at least one selected from nitrogen gas (N2), helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe) can be used. The content of the diluent gas is preferably 90% by volume or less, and more preferably 50% by volume or less, relative to the total amount of gas stored in the container.

[0017] 〔container〕 The container for storing fluoro-2-butene is not particularly limited in shape, size, or material, as long as it can contain and seal the fluoro-2-butene. The container material can be metal, ceramic, resin, etc. Examples of metals include manganese steel, chromium-molybdenum steel, stainless steel, Hastelloy®, and Inconel®.

[0018] 〔Impurities〕 The fluoro-2-butene according to this embodiment contains hydrogen chloride as an impurity or does not contain it. However, when it contains hydrogen chloride, since the concentration of hydrogen chloride in the gas phase part is set to 100 volume ppm or less and stored in a container, as described above, the isomerization reaction of fluoro-2-butene is less likely to be promoted. As a result, the isomerization reaction of fluoro-2-butene hardly proceeds during storage. In addition, if the concentration of hydrogen chloride in the gas phase part is below the above concentration, the concentration of hydrogen chloride in the liquid phase part will also be sufficiently low.

[0019] Note that hydrogen chloride may be generated in the manufacturing process of fluoro-2-butene. Also, the concentration of hydrogen chloride in fluoro-2-butene can be quantified by an infrared spectrophotometer. The phrase "does not contain it" means a case where it cannot be quantified by an infrared spectrophotometer.

[0020] In order to make the isomerization reaction of fluoro-2-butene hardly proceed during storage, the concentration of hydrogen chloride in the gas phase part needs to be 100 volume ppm or less, preferably 50 volume ppm or less, and more preferably 10 volume ppm or less. Note that the concentration of hydrogen chloride in the gas phase part may be 0.1 volume ppm or more.

[0021] 〔Method for producing fluoro-2-butene with low hydrogen chloride concentration〕 The method for producing fluoro-2-butene with a low hydrogen chloride concentration is not particularly limited. For example, a method of removing hydrogen chloride from fluoro-2-butene with a high hydrogen chloride concentration can be mentioned. The method for removing hydrogen chloride from fluoro-2-butene is not particularly limited, and a known method can be adopted. For example, a method of contacting an adsorbent to adsorb hydrogen chloride to the adsorbent, a method of contacting a reactant to react hydrogen chloride with the reactant, and a method of separating by distillation can be mentioned. Specific examples of the adsorbent include molecular sieve and activated carbon.

[0022] 〔Pressure conditions during storage〕 The storage pressure conditions in the fluoro-2-butene storage method according to this embodiment are not particularly limited as long as the fluoro-2-butene can be stored in a sealed container, but it is preferable to set the pressure to 0.05 MPa or more and 5 MPa or less, and more preferably to 0.1 MPa or more and 3 MPa or less. If the pressure conditions are within the above range, the fluoro-2-butene can be circulated without heating when the container is connected to the dry etching apparatus.

[0023] [Storage temperature conditions] The storage temperature conditions for fluoro-2-butene in the storage method according to this embodiment are not particularly limited, but it is preferably -20°C to 50°C, and more preferably 0°C to 40°C. If the storage temperature is -20°C or higher, deformation of the container is less likely to occur, so the airtightness of the container is lost and the possibility of oxygen, water, etc. entering the container is low. If oxygen, water, etc. enter, the polymerization and decomposition reactions of fluoro-2-butene may be accelerated. On the other hand, if the storage temperature is 50°C or lower, the polymerization and decomposition reactions of fluoro-2-butene are suppressed.

[0024] 〔etching〕 The fluoro-2-butene according to this embodiment can be used as an etching gas. When an etching gas containing the fluoro-2-butene according to this embodiment is used in the etching process when manufacturing a semiconductor having a silicon (Si) film, a protective film is formed on the mask and sidewalls, thereby improving the selectivity of the etching process. Furthermore, the etching gas containing fluoro-2-butene according to this embodiment can be used in both plasma etching using plasma and plasmaless etching without plasma.

[0025] Examples of plasma etching include reactive ion etching (RIE), inductively coupled plasma (ICP) etching, capacitively coupled plasma (CCP) etching, electron cyclotron resonance (ECR) plasma etching, and microwave plasma etching. Furthermore, in plasma etching, the plasma may be generated within the chamber where the workpiece to be etched is placed, or the plasma generation chamber and the chamber in which the workpiece to be etched is placed may be separated (i.e., remote plasma may be used). [Examples]

[0026] The present invention will be further described below with reference to examples and comparative examples. Fluoro-2-butene containing hydrogen chloride at various concentrations was prepared. An example of the preparation of fluoro-2-butene is described below. (Preparation Example 1) One 10L manganese steel cylinder and four 1L manganese steel cylinders were prepared. These cylinders were referred to as Cylinder A, Cylinder B, Cylinder C, and Cylinder D, respectively. 5000g of (Z)-1,1,1,4,4,4-hexafluoro-2-butene (boiling point: 33°C) was filled into the cylinder and liquefied by cooling to 0°C, forming a liquid phase and a gas phase at approximately 100kPa. Cylinders A, B, C, and D were then cooled to -78°C after the internal pressure was reduced to below 1kPa using a vacuum pump.

[0027] A 1-inch diameter, 30cm long stainless steel tube was filled with 100mL of Molecular Sieve 5A manufactured by Union Showa Co., Ltd. This stainless steel tube was then connected to a cylinder. 500g of (Z)-1,1,1,4,4,4-hexafluoro-2-butene gas was extracted from the upper outlet of the cylinder where the gas phase was located and supplied to a stainless steel tube. The (Z)-1,1,1,4,4,4-hexafluoro-2-butene gas that passed through the stainless steel tube was then collected in cylinder A under reduced pressure.

[0028] The gas flow rate through the SUS tube was controlled to 500 mL / min using a mass flow controller. The amount of (Z)-1,1,1,4,4,4-hexafluoro-2-butene gas collected in cylinder A was 495 g. (Z)-1,1,1,4,4,4-hexafluoro-2-butene collected in cylinder A is designated as sample 1-1. The gas of (Z)-1,1,1,4,4,4-hexafluoro-2-butene collected in cylinder A was extracted from the upper outlet, and the concentration of hydrogen chloride was measured using an infrared spectrophotometer. The results are shown in Table 1. The measurement conditions for the infrared spectrophotometer are as follows. Infrared spectrophotometer: Manufactured by Thermo Fisher Scientific Corporation. Nicolet iS10 FT-IR spectrometer Total number of times: 128 Mirror speed: 0.6329 Optical path length: 3m Gas cell material: SUS316 Gas cell temperature: 100℃ Measurement wavelength range: 800~5000cm -1 Measurement wavelength for hydrogen chloride: 2945 cm² -1

[0029] [Table 1]

[0030] Next, cylinder A was heated to approximately 0°C to form a liquid phase and a gas phase. 100g of (Z)-1,1,1,4,4,4-hexafluoro-2-butene gas was extracted from the upper outlet of cylinder A, where the gas phase was present, and transferred to cylinder B under reduced pressure. Furthermore, 10g of (Z)-1,1,1,4,4,4-hexafluoro-2-butene gas was extracted from the cylinder and transferred to cylinder B under reduced pressure. Cylinder B was then heated to room temperature and allowed to stand for 24 hours. The (Z)-1,1,1,4,4,4-hexafluoro-2-butene after standing was designated as sample 1-2. The (Z)-1,1,1,4,4,4-hexafluoro-2-butene gas was extracted from the upper outlet of cylinder B, where the gas phase was present, and the concentration of hydrogen chloride was measured using an infrared spectrophotometer. The results are shown in Table 1.

[0031] Similarly, 100g of (Z)-1,1,1,4,4,4-hexafluoro-2-butene gas was extracted from the upper outlet of cylinder A, where the gas phase was present, and transferred to cylinder C under reduced pressure. Furthermore, 100g of (Z)-1,1,1,4,4,4-hexafluoro-2-butene gas was extracted from the cylinder and transferred to cylinder C under reduced pressure. Then, cylinder C was heated to room temperature and left to stand for 24 hours. The (Z)-1,1,1,4,4,4-hexafluoro-2-butene after standing was designated as sample 1-3. The (Z)-1,1,1,4,4,4-hexafluoro-2-butene gas was extracted from the upper outlet of cylinder C, where the gas phase was present, and the concentration of hydrogen chloride was measured using an infrared spectrophotometer. The results are shown in Table 1.

[0032] Similarly, 100g of (Z)-1,1,1,4,4,4-hexafluoro-2-butene gas was extracted from the upper outlet of cylinder A, where the gas phase was present, and transferred to cylinder D under reduced pressure. Furthermore, 200g of (Z)-1,1,1,4,4,4-hexafluoro-2-butene gas was extracted from the cylinder and transferred to cylinder D under reduced pressure. Then, cylinder D was heated to room temperature and left to stand for 24 hours. The (Z)-1,1,1,4,4,4-hexafluoro-2-butene after standing was designated as sample 1-4. The (Z)-1,1,1,4,4,4-hexafluoro-2-butene gas was extracted from the upper outlet of cylinder D, where the gas phase was present, and the concentration of hydrogen chloride was measured using an infrared spectrophotometer. The results are shown in Table 1.

[0033] (Preparation Example 2) Samples 2-1 to 2-4 were prepared using the same procedure as in Preparation Example 1, except that (E)-1,1,1,4,4,4-hexafluoro-2-butene (boiling point 9°C) was used as the fluoro-2-butene. The hydrogen chloride concentration of each sample was then measured using an infrared spectrophotometer. The results are shown in Table 2.

[0034] [Table 2]

[0035] (Preparation Example 3) Samples 3-1 to 3-4 were prepared using the same procedure as in Preparation Example 1, except that (Z)-1,1,1,2,4,4,4-heptafluoro-2-butene (boiling point 10°C) was used as the fluoro-2-butene. The hydrogen chloride concentration of each sample was then measured using an infrared spectrophotometer. The results are shown in Table 3.

[0036] [Table 3]

[0037] (Preparation Example 4) Samples 4-1 to 4-4 were prepared using the same procedure as in Preparation Example 1, except that (E)-1,1,1,2,4,4,4-heptafluoro-2-butene (boiling point 10°C) was used as the fluoro-2-butene. The hydrogen chloride concentration of each sample was then measured using an infrared spectrophotometer. The results are shown in Table 4.

[0038] [Table 4]

[0039] (Preparation Example 5) Samples 5-1 to 5-4 were prepared using the same procedure as in Preparation Example 1, except that (Z)-1,1,1,2,3,4,4,4-octafluoro-2-butene (boiling point 1°C) was used as fluoro-2-butene. The hydrogen chloride concentration of each sample was then measured using an infrared spectrophotometer. The results are shown in Table 5.

[0040] [Table 5]

[0041] (Preparation Example 6) Samples 6-1 to 6-4 were prepared using the same procedure as in Preparation Example 1, except that (E)-1,1,1,2,3,4,4,4-octafluoro-2-butene (boiling point 8°C) was used as fluoro-2-butene. The hydrogen chloride concentration of each sample was then measured using an infrared spectrophotometer. The results are shown in Table 6.

[0042] [Table 6]

[0043] (Example 1) After leaving cylinder A standing at 20°C for 30 days, the gas of (Z)-1,1,1,4,4,4-hexafluoro-2-butene was extracted from the gas phase of cylinder A and analyzed by gas chromatography to quantify the concentration of (E)-1,1,1,4,4,4-hexafluoro-2-butene in sample 1-1. As a result, (E)-1,1,1,4,4,4-hexafluoro-2-butene, which is the product of the isomerization reaction of (Z)-1,1,1,4,4,4-hexafluoro-2-butene, was not detected.

[0044] The measurement conditions for gas chromatography are as follows: Gas chromatograph: Shimadzu Corporation GC-2014 Column: CarbopackB phase 1% sp-1000 Injection temperature: 200℃ Column temperature: 150℃ Detector: FID Detector temperature: 200℃ Carrier gas: Helium Detection limit: 1 ppm by mass

[0045] (Examples 2-18 and Comparative Examples 1-6) Table 7 shows the analytes and analysis results for Examples 2-18 and Comparative Examples 1-6, in comparison with Example 1. That is, for items other than those shown in Table 7, the analysis was performed using the same procedure as in Example 1.

[0046] [Table 7]

Claims

1. General formula C 4 H x F y A method for storing fluoro-2-butene, which is represented by the above general formula, wherein x is between 0 and 7, y is between 1 and 8, and x + y is 8, A method for storing fluoro-2-butene, wherein the fluoro-2-butene may or may not contain hydrogen chloride as an impurity, and in the case where it contains hydrogen chloride, the concentration of hydrogen chloride in the gas phase is 100 ppm by volume or less, and the fluoro-2-butene is stored in a container.

2. A method for storing fluoro-2-butene according to claim 1, wherein the fluoro-2-butene is at least one selected from (Z)-1,1,1,4,4,4-hexafluoro-2-butene, (E)-1,1,1,4,4,4-hexafluoro-2-butene, (Z)-1,1,1,2,4,4,4-heptafluoro-2-butene, (E)-1,1,1,2,4,4,4-heptafluoro-2-butene, (Z)-1,1,1,2,3,4,4,4-octafluoro-2-butene, and (E)-1,1,1,2,3,4,4,4-octafluoro-2-butene.

3. A method for storing fluoro-2-butene according to claim 1 or claim 2, wherein the fluoro-2-butene is stored at a temperature of -20°C or higher and 50°C or lower.

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