Cleaning method of high-pressure gas container

Abstract

Provided is a method for cleaning a high-pressure gas container capable of suppressing the generation of water inside the high-pressure gas container. This method for cleaning a high-pressure gas container is provided with: a pressure reduction step for reducing the pressure inside the high-pressure gas container until the internal pressure becomes 5 Pa or less; and a cleaning step for cleaning the inside of the high-pressure gas container after the pressure reduction step. The cleaning step includes a hydrogen halide supply stage in which hydrogen halide is supplied to the high-pressure gas container subjected to the pressure reduction step, a metal oxide removal stage in which hydrogen halide is discharged from the high-pressure gas container subjected to the hydrogen halide supply stage, and a discharge stage in which hydrogen halide is discharged from the high-pressure gas container subjected to the metal oxide removal stage. And a hydrogen halide supply step for reacting the metal oxide present on the inner surface of the high-pressure gas container with the hydrogen halide supplied by the hydrogen halide supply step to generate water, and a discharge step for discharging the water generated in the metal oxide removal step and the hydrogen halide supplied by the hydrogen halide supply step from the high-pressure gas container.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a cleaning method of a high-pressure gas container. BACKGROUND

[0002] Hydrogen halide (HX) used in a semiconductor manufacturing process is preferably anhydrous, and the moisture concentration needs to be, for example, 1.0 volume ppm or less. However, if a metal oxide (for example, ferrous oxide (FeO)) is present on the inner surface of a high-pressure gas container filled with hydrogen halide, the filled hydrogen halide and the metal oxide react to generate a metal halide (for example, ferrous chloride (FeCl2)) and water (H2O). Furthermore, as a cause of the presence of the metal oxide on the inner surface of the high-pressure gas container, it is considered that, for example, in an opening inspection performed at the time of purchase or pressure resistance inspection of the high-pressure gas container, a metal contained in the material of the high-pressure gas container is oxidized by atmospheric oxygen to generate the metal oxide.

[0003] As a method of removing the metal oxide present on the inner surface of the high-pressure gas container, a method of reacting the hydrogen halide and the metal oxide has been adopted. For example, Patent Literature 1 discloses a method of supplying liquefied hydrogen chloride to the high-pressure gas container, causing the metal oxide on the inner surface of the high-pressure gas container and the liquefied hydrogen chloride to react to generate water at a temperature of 30°C or higher and 50°C or lower, and thereafter discharging the liquefied hydrogen chloride containing the generated water from the high-pressure gas container.

[0004] PRIOR ART DOCUMENTS

[0005] Patent Literature 1: Japanese Patent Publication No. 2002-54799 SUMMARY

[0006] However, the technology disclosed in Patent Literature 1 can not be able to sufficiently suppress the generation of water depending on the temperature at which the metal oxide on the inner surface of the high-pressure gas container and the liquefied hydrogen chloride are caused to react, and thus there is room for improvement.

[0007] An object of the present disclosure is to provide a cleaning method of a high-pressure gas container capable of suppressing the generation of water inside the high-pressure gas container.

[0008] To solve the foregoing object, one embodiment of the present disclosure is as shown in the following [1] to

[10] .

[0009] [1] A cleaning method of a high-pressure gas container, comprising: a depressurization step of depressurizing an inside of the high-pressure gas container until an internal pressure becomes 5 Pa or less, and a cleaning step of cleaning the inside of the high-pressure gas container on which the depressurization step is performed,

[0010] The cleaning step includes a hydrogen halide supply stage, a metal oxide removal stage, and a discharge stage,

[0011] In the hydrogen halide supplying stage, hydrogen halide is supplied to the high-pressure gas container in which the pressure reducing process is performed,

[0012] In the metal oxide removing stage, a metal oxide present on an inner surface of the high-pressure gas container and the hydrogen halide supplied through the hydrogen halide supplying stage are caused to react to generate water in an inside of the high-pressure gas container in which the hydrogen halide supplying stage is performed.

[0013] In the discharging stage, the water generated in the metal oxide removing stage and the hydrogen halide supplied through the hydrogen halide supplying stage are discharged from the high-pressure gas container.

[0014] [2] The cleaning method of a high-pressure gas container according to [1], wherein an inner surface of the high-pressure gas container is not coated with a coating material, and a maximum height Rz of the inner surface of a main body portion of the high-pressure gas container is 5 μm or less.

[0015] [3] The cleaning method of a high-pressure gas container according to [1] or [2], wherein the pressure reducing process is a process of performing degassing until an internal pressure becomes 5 Pa or less while the high-pressure gas container is maintained at a temperature of 50°C or higher and 200°C or lower.

[0016] [4] The cleaning method of a high-pressure gas container according to any one of [1] to [3], wherein the hydrogen halide is at least one of hydrogen fluoride, hydrogen chloride, hydrogen bromide, and hydrogen iodide.

[0017] [5] The cleaning method of a high-pressure gas container according to any one of [1] to [4], wherein the hydrogen halide supplying stage is a process of supplying hydrogen halide to the high-pressure gas container until the hydrogen halide is liquefied in the high-pressure gas container.

[0018] [6] The cleaning method of a high-pressure gas container according to any one of [1] to [5], wherein the metal oxide removing stage is a process of leaving the high-pressure gas container to which the hydrogen halide is supplied through the hydrogen halide supplying stage at a temperature of lower than 30°C for 1 day or more.

[0019] [7] The cleaning method of a high-pressure gas container according to any one of [1] to [6], wherein, in a case where a volume of the high-pressure gas container is 10 L or more and 50 L or less, the discharging stage is a process of discharging the water and the hydrogen halide from the high-pressure gas container by inverting the high-pressure gas container upside down.

[0020] [8] The cleaning method of a high-pressure gas container according to any one of [1] to [6], wherein, in a case where the volume of the high-pressure gas container is more than 50 L and 1000 L or less, the discharging stage is a step of discharging the water and the hydrogen halide in the liquid phase from the high-pressure gas container using an inner tube inserted into the inside of the high-pressure gas container.

[0021] [9] The cleaning method of a high-pressure gas container according to any one of [1] to [8], wherein the cleaning step is repeatedly performed 2 or more times after the pressure-reducing step.

[0022]

[10] The cleaning method of a high-pressure gas container according to any one of [1] to [9], wherein the metal oxide is at least one of iron oxide, chromium oxide, molybdenum oxide, and manganese oxide.

[0023] If the inside of a high-pressure gas container is cleaned by the cleaning method of a high-pressure gas container of the present disclosure, generation of water in the inside of the high-pressure gas container can be suppressed. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a schematic view showing an example of an apparatus that performs a hydrogen halide supplying stage and a discharging stage in the cleaning method of a high-pressure gas container of an embodiment of the present disclosure.

[0025] Figure 2 is a schematic view showing an example of an apparatus that performs a pressure-reducing step in the cleaning method of a high-pressure gas container of an embodiment of the present disclosure.

[0026] Figure 3 is a cross-sectional view showing an example of a high-pressure gas container that can be used in the cleaning method of a high-pressure gas container of an embodiment of the present disclosure.

[0027] Figure 4 is a cross-sectional view showing an example of a high-pressure gas container that can be used in the cleaning method of a high-pressure gas container of an embodiment of the present disclosure.

[0028] Figure 5 is a graph showing a relationship between the number of times of performing a cleaning step and the amount of water discharged in a discharging stage.

[0029] Figure 6 is a graph showing a relationship between the number of days elapsed after filling with hydrogen chloride and the moisture concentration of hydrogen chloride. DETAILED DESCRIPTION

[0030] The following describes one embodiment of this disclosure. Furthermore, this embodiment illustrates one example of this disclosure, and this disclosure 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 this disclosure.

[0031] The cleaning method for a high-pressure gas container according to this embodiment includes: a decompression step of reducing the internal pressure of the high-pressure gas container until the internal pressure is below 5 Pa, and a cleaning step of cleaning the internal pressure of the high-pressure gas container after the decompression step. The cleaning step includes a hydrogen halide supply stage, a metal oxide removal stage, and a discharge stage. In the hydrogen halide supply stage, hydrogen halide is supplied to the high-pressure gas container after the decompression step. In the metal oxide removal stage, inside the high-pressure gas container after the hydrogen halide supply stage, the metal oxide present on the inner surface of the high-pressure gas container reacts with the hydrogen halide supplied in the hydrogen halide supply stage to generate water. In the discharge stage, the water generated in the metal oxide removal stage and the hydrogen halide supplied in the hydrogen halide supply stage are discharged from the high-pressure gas container.

[0032] The cleaning method for a high-pressure gas container according to this embodiment includes: a decompression step of reducing the internal pressure of the high-pressure gas container until the internal pressure is below 5 Pa, and a cleaning step of cleaning the internal pressure of the high-pressure gas container after the decompression step.

[0033] The cleaning process comprises a hydrogen halide supply stage, a metal oxide removal stage, and a discharge stage. The hydrogen halide supply stage involves supplying hydrogen halide to the high-pressure gas container, which has undergone a depressurization process. The metal oxide removal stage occurs inside the high-pressure gas container after the hydrogen halide supply stage, where the metal oxides present on the inner surface of the container react with the hydrogen halide supplied during the hydrogen halide supply stage to generate water. The discharge stage involves discharging the water generated during the metal oxide removal stage and the hydrogen halide supplied during the hydrogen halide supply stage from the high-pressure gas container.

[0034] The cleaning method for the high-pressure gas container of this embodiment includes the above-described decompression step and the above-described cleaning step. Therefore, if the cleaning method for the high-pressure gas container of this embodiment is used to clean the inside of the high-pressure gas container, the metal oxides that are the source of water generation are removed, and the generation of water inside the high-pressure gas container can be suppressed.

[0035] Such a cleaning method of the high-pressure gas container of the present embodiment is suitable as a method of cleaning a high-pressure gas container for filling and storing a hydrogen halide used in a semiconductor manufacturing process. The high-pressure gas container cleaned by the cleaning method of the high-pressure gas container of the present embodiment can maintain the moisture concentration of the filled hydrogen halide at a low concentration (e.g., 1.0 volume ppm or less) because water is less likely to be generated inside. That is, if a high-pressure gas container cleaned by the cleaning method of the high-pressure gas container of the present embodiment is used, a high-quality hydrogen halide can be obtained.

[0036] In addition, with respect to the hydrogen halide used in the semiconductor manufacturing process, the concentration of hydrogen molecules (H2) is also limited, and for example, is required to be reduced to 10 volume ppm or less. However, it is known that ferrous chloride and hydrogen molecules are generated by the reaction of the 0-valent metal (e.g., iron) present on the inner surface of the high-pressure gas container and the hydrogen halide. The generation reaction of hydrogen molecules is an endothermic reaction, and thus proceeds easily as the reaction temperature increases. Therefore, for example, the method described in Patent Document 1 is a method of heating the high-pressure gas container after the hydrogen halide is supplied, and thus there is a concern that the generation of hydrogen molecules will be promoted.

[0037] The cleaning method of the high-pressure gas container of the present embodiment can also suppress the generation of hydrogen molecules because it does not require heating the high-pressure gas container after the hydrogen halide is supplied. Thus, the deterioration of the hydrogen molecule concentration in the hydrogen halide can be suppressed, and it can also be maintained at 10 volume ppm or less.

[0038] As the high-pressure gas container becomes larger, the heating treatment of the high-pressure gas container becomes difficult to perform, but the cleaning method of the high-pressure gas container of the present embodiment does not require the heating treatment of the high-pressure gas container, and can remove the metal oxide from the inside of the high-pressure gas container under mild conditions.

[0039] In addition, with respect to the hydrogen halide used in the semiconductor manufacturing process, the concentration of phosphorus atoms (P) is also limited, and for example, is required to be reduced to 2 volume ppb or less. As a method of suppressing the reaction of the above-described hydrogen halide and the metal oxide, a method of coating the inner surface of the high-pressure gas container with a coating material is known. For example, a method of plating the inner surface of the high-pressure gas container with a nickel-phosphorus alloy is known, but if the hydrogen halide is filled in the high-pressure gas container, there is a concern that phosphorus atoms from the nickel-phosphorus alloy will mix into the hydrogen halide.

[0040] If the inside of the high-pressure gas container is cleaned by the cleaning method of the high-pressure gas container of the present embodiment, even a high-pressure gas container whose inner surface is not coated with a coating material can suppress the generation of water inside the high-pressure gas container. Thus, the deterioration of the phosphorus atom concentration in the hydrogen halide can be suppressed, and it can also be maintained at 2 volume ppb or less.

[0041] Further, the high-pressure gas container cleaned by the cleaning method of the high-pressure gas container of the present embodiment is not limited to a hydrogen halide, and can be filled with various gases.

[0042] Hereinafter, the cleaning method of the high-pressure gas container of the present embodiment will be described in more detail.

[0043] [High-pressure gas container]

[0044] The high-pressure gas container used in the cleaning method of the high-pressure gas container of the present embodiment is a container that discharges and fills a gas via a flow path of the gas. The kind of the high-pressure gas container used in the cleaning method of the high-pressure gas container of the present embodiment is not particularly limited, and, for example, the size and the shape are not particularly limited. The material of the high-pressure gas container is also not particularly limited, and, as an example, a metal material containing at least one of iron (Fe), chromium (Cr), molybdenum (Mo), and manganese (Mn) can be listed.

[0045] In addition, the high-pressure gas container used in the cleaning method of the high-pressure gas container of the present embodiment can be a new (unused) high-pressure gas container, or a used high-pressure gas container. Further, it can be a high-pressure gas container that is open to the atmosphere, or a high-pressure gas container that is not open to the atmosphere.

[0046] The state of the inner surface of the high-pressure gas container is also not particularly limited, and the inner surface of the high-pressure gas container can be coated with a coating material, or can not be coated. As an example of the coating material coated on the inner surface of the high-pressure gas container, a nickel (Ni) plating layer, a nickel-phosphorus alloy (Ni-P) plating layer, a zinc (Zn) plating layer, a gold (Au) plating layer, and a silver (Ag) plating layer can be listed.

[0047] In addition, the roughness of the inner surface of the high-pressure gas container is also not particularly limited, but the maximum height Rz of the inner surface of the main body portion of the high-pressure gas container is preferably 5 μm or less. The inner surface of the high-pressure gas container can not be coated with a coating material, and the maximum height Rz of the inner surface of the main body portion of the high-pressure gas container is 5 μm or less. If the inner surface of the high-pressure gas container is made to have a small roughness (smooth), the quality of the hydrogen halide filled after cleaning can be maintained at a high quality even if the cleaning method of the high-pressure gas container is simplified. In addition, the quality of the hydrogen halide can be improved compared to the conventional cleaning method of the high-pressure gas container.

[0048] More preferably, the maximum height Rz of the inner surface of the main body portion of the high-pressure gas container is 1 μm or more and 5 μm or less, and the maximum height Rz of the inner surface of the portion other than the main body portion of the high-pressure gas container is 15 μm or more and 20 μm or less, further preferably, the maximum height Rz of the inner surface of the main body portion of the high-pressure gas container is 1 μm or less, and the maximum height Rz of the inner surface of the portion other than the main body portion of the high-pressure gas container is 15 μm or more and 20 μm or less, particularly preferably, the maximum height Rz of the inner surface of the main body portion of the high-pressure gas container is 1 μm or less, and the maximum height Rz of the inner surface of the portion other than the main body portion of the high-pressure gas container is 1 μm or less.

[0049] Further, the "main body portion" of the high-pressure gas container in the present disclosure refers to the central portion in the longitudinal direction of the high-pressure gas container except for both end portions in the longitudinal direction. Also, the end portion is a portion having a volume of 5% of the volume of the high-pressure gas container.

[0050] For example, in the case where the high-pressure gas container is cylindrical or square cylindrical, the main body portion refers to the central portion of the cylinder or square cylinder except for both end portions in the height direction (length direction). In addition, in the case where the high-pressure gas container is spherical, the main body portion refers to the central portion except for both end portions in the radial direction of the sphere.

[0051] The method of reducing the maximum height Rz of the inner surface of the main body portion of the high-pressure gas container is not particularly limited, and a method of polishing the inner surface of the main body portion of the high-pressure gas container can be exemplified. As the method of polishing the inner surface of the main body portion of the high-pressure gas container, for example, sand blasting polishing, barrel polishing, electrolytic polishing can be exemplified.

[0052] The method of measuring the maximum height Rz of the inner surface of the main body portion of the high-pressure gas container is not particularly limited, and for example, the method described in Japanese Industrial Standard JIS B0601-2013 can be used.

[0053] The measuring machine for measuring the maximum height Rz of the inner surface of the main body portion of the high-pressure gas container is not particularly limited, and for example, a stylus-type surface roughness measuring machine such as a small surface roughness measuring machine SURFTEST SJ-210 series manufactured by Mitutoyo Corporation can be used.

[0054] Further, the cleaning method of the high-pressure gas container of the present embodiment can be applied to cleaning of various high-pressure gas containers, but is particularly suitable for cleaning of a high-pressure gas container in which a coating material is not applied to the inner surface and the maximum height Rz of the inner surface of the main body portion is 5 μm or less.

[0055] Next, an example of the cleaning method of the high-pressure gas container of the present embodiment will be described with reference to Figure 1 and Figure 2 the drawings.

[0056] 〔decompression process〕

[0057] The high-pressure gas container for the cleaning process needs to remove the water inside by a decompression process of decompressing the inside of the high-pressure gas container to an internal pressure of 5 Pa or less. Figure 2 is a diagram showing an example of an apparatus for performing a decompression process on a high-pressure gas container having a volume of 10 L or more and 50 L or less. With reference to Figure 2 The decompression process will be described.

[0058] The inside of the high-pressure gas container 19, for example, having a volume of 47 L is brought to a decompressed state by the decompression process. That is, the water and other gases inside the high-pressure gas container 19 are exhausted using the vacuum pump 17. The decompression process is preferably performed while the high-pressure gas container 19 is maintained at a temperature of 50°C or more and 200°C or less, more preferably at a temperature of 100°C or more and 200°C or less, and still more preferably at a temperature of 150°C or more and 200°C or less, until the internal pressure becomes 5 Pa or less. The temperature of the high-pressure gas container 19 can be adjusted, for example, by heating the high-pressure gas container 19 using the heater 20 provided in a manner covering the high-pressure gas container 19.

[0059] When the high-pressure gas container 19 is heated, in order to inactivate the dissolvable plug installed on the valve of the high-pressure gas container 19, it is preferable to blow air from the dissolvable plug cooling air supply source 23 to the dissolvable plug to cool the dissolvable plug.

[0060] Further, the internal pressure of the high-pressure gas container 19 after the decompression process is performed needs to be 5 Pa or less, preferably 1 Pa or less, more preferably 0.01 Pa or less, and still more preferably less than 0.01 Pa. The vacuum pump 17 is preferably a dry vacuum pump.

[0061] Furthermore, before the decompression process is performed, it is preferable to remove the water inside the piping by circulating an inactive gas in the piping. The type of the inactive gas is not particularly limited, and nitrogen (N2), helium (He), argon (Ar), xenon (Xe), and the like can be mentioned. Figure 2 is an example in which nitrogen is used as the inactive gas, and the inactive gas can be circulated from the nitrogen supply source 13 to the piping.

[0062] The moisture concentration of the inactive gas such as nitrogen used herein is preferably 1 volume ppm or less, more preferably 0.1 volume ppm or less, and still more preferably 0.05 volume ppm or less.

[0063] 〔cleaning process〕

[0064] After the decompression process is completed, a cleaning process of cleaning the inside of the high-pressure gas container is performed.Figure 1 is a view showing an example of the device which performs the cleaning process. Referring to Figure 1 The cleaning process will be described.

[0065] First, the high-pressure gas container 19, which has been brought to a vacuum state by the pressure-reducing process, is removed from the device shown in Figure 2 and installed in the device shown in Figure 1 Further, in Figure 1 , the "high-pressure gas container 19" is denoted as "high-pressure gas container 7". Next, the hydrogen halide supply stage of supplying hydrogen halide to the high-pressure gas container 7 is performed, but before the hydrogen halide supply stage is performed, the following operation is preferably performed. That is, hydrogen halide is supplied to the pipe located on the upstream side of the high-pressure gas container 7 in the device shown in Figure 1 , pressurized to a pressure of 0.1 MPaG or more, and then the operation of repeatedly reducing the pressure to the degree of atmospheric pressure using the discharge unit 12 is performed, and the air and water in the device shown in Figure 1 are removed in advance.

[0066] After the above operation is performed, the hydrogen halide supply stage is performed. The hydrogen halide supply stage preferably supplies hydrogen halide to the high-pressure gas container until the hydrogen halide is liquefied in the high-pressure gas container. That is, hydrogen halide can be supplied from the hydrogen halide supply source 5 to the high-pressure gas container 7, and the supply of hydrogen halide is continued until the hydrogen halide exists in two phases of gas phase and liquid phase in the high-pressure gas container 7 (until a part of the hydrogen halide is liquefied). The mass of the hydrogen halide supplied to the high-pressure gas container 7 can be measured by weight. Further, the mass of the hydrogen halide supplied to the high-pressure gas container 7 having a volume of 47 L is preferably 5 kg or more and 30 kg or less.

[0067] The kind of the hydrogen halide is not particularly limited, and can be at least one of hydrogen fluoride (HF), hydrogen chloride (HC1), hydrogen bromide (HBr), and hydrogen iodide (HI). Figure 1 is an example in which hydrogen chloride is used as the hydrogen halide.

[0068] In addition, the moisture concentration of the hydrogen halide supplied from the hydrogen halide supply source 5 to the high-pressure gas container 7 is preferably 0.2 vol ppm or less, more preferably 0.1 vol ppm or less, and further preferably 0.05 vol ppm or less.

[0069] Further, the purity of the hydrogen halide supplied from the hydrogen halide supply source 5 to the high-pressure gas container 7 is preferably 3N or more (99.9 vol % or more), more preferably 4N or more (99.99 vol % or more), and further preferably 5N or more (99.999 vol % or more).

[0070] Here, it is preferable to perform the operation of removing the air and water in the high-pressure gas container 7 before the high-pressure gas container 7, from which the hydrogen halide has been supplied, is removed from the device shown in Figure 1 .Figure 1 Hydrogen halide is removed from the apparatus shown. Specifically, it is preferable to remove it from the purification helium cylinder 1. Figure 1 The device shown is supplied with helium, which will Figure 1 After the device is pressurized to a pressure of 1.0 MPaG or higher, the pressure is repeatedly reduced to atmospheric pressure using the discharge unit 12 to remove pre-existing pressure. Figure 1 Hydrogen halide inside the device shown.

[0071] from Figure 1 The high-pressure gas container 7 is removed from the apparatus shown, and a metal oxide removal stage is performed. That is, inside the high-pressure gas container 7, which has undergone the hydrogen halide supply stage, the metal oxides present on the inner surface of the high-pressure gas container 7 react with the hydrogen halide supplied through the hydrogen halide supply stage to generate water.

[0072] There is no particular limitation on the types of metal oxides; at least one of iron oxides, chromium oxides, molybdenum oxides, and manganese oxides can be cited as examples.

[0073] The metal oxide removal stage can be performed by allowing the high-pressure gas container 7, which has undergone the hydrogen halide supply stage, to stand at a predetermined temperature for a predetermined time. The temperature during the metal oxide removal stage is preferably below 30°C. Furthermore, the time during the metal oxide removal stage is preferably 1 day or more, more preferably 10 days or more, and even more preferably 60 days or more. That is, the metal oxide removal stage can also involve allowing the high-pressure gas container, which has been supplied with hydrogen halide during the hydrogen halide supply stage, to stand at a temperature below 30°C for 1 day or more.

[0074] There are no particular limitations on the method of setting the high-pressure gas container 7 to a temperature below 30°C; for example, using air conditioning equipment such as an air conditioner can be cited. Furthermore, during the metal oxide removal stage, it is believed that the room temperature and external air temperature of the environment in which the high-pressure gas container 7 is located will have some influence on the reaction rate of the metal oxides and hydrogen halides, but in the temperature range below 30°C, this influence is negligible. Therefore, in the temperature range below 30°C, the number of cleaning steps required to achieve the necessary cleaning effect will not increase with the temperature. Additionally, during the metal oxide removal stage, the interior of the high-pressure gas container 7 is a sealed space, and therefore is almost unaffected by the humidity and air pressure outside the high-pressure gas container 7.

[0075] Next, the water generated by the reaction of the metal oxide and the hydrogen halide in the metal oxide removal stage is discharged from the high-pressure gas container 7 in the discharge stage together with the remaining hydrogen halide that is supplied in the hydrogen halide supply stage and is not consumed by the reaction in the metal oxide removal stage. In this discharge stage, the metal halide generated by the reaction of the metal oxide and the hydrogen halide in the metal oxide removal stage can also be discharged from the high-pressure gas container 7.

[0076] Using Figure 3 The water and the hydrogen halide are discharged from the high-pressure gas container 7 in the apparatus shown in the drawing, but if the distribution coefficient of the water with respect to the hydrogen halide is taken into account, the hydrogen halide containing the water is more effectively discharged to the outside of the high-pressure gas container 7 from the liquid phase side than from the gas phase side.

[0077] Therefore, for example, in the case where the volume of the high-pressure gas container is 10 L or more and 50 L or less, it is preferable that the discharge stage discharge the water and the hydrogen halide from the high-pressure gas container by inverting the high-pressure gas container upside down. That is, in the case of a small high-pressure gas container having a volume of 10 L or more and 50 L or less, since only one container valve is provided, in order to discharge the hydrogen halide from the liquid phase side, it is preferable that the high-pressure gas container be disposed in a posture in which the container valve faces downward in the vertical direction, and the liquefied hydrogen halide be discharged from the high-pressure gas container.

[0078] Further, the small high-pressure gas container having a volume of 10 L or more and 50 L or less is preferably disposed in a posture in which the container valve faces downward in the vertical direction, but it is not necessary to make it stand straight, and as long as the container valve faces downward in the vertical direction, it is not a problem even if it is in an inclined posture. The inclination angle is not particularly limited, and for example, it is preferably 45° or more and less than 90°.

[0079] On the other hand, for example, in the case where the volume of the high-pressure gas container exceeds 50 L and is 1000 L or less, the discharge stage preferably inserts an internal pipe into the inside of the high-pressure gas container, and uses the internal pipe to discharge the water and the hydrogen halide in the liquid phase from the high-pressure gas container. Figure 4 The volume 440 L high-pressure gas container 124 shown in the drawing and Figure 2 The volume 900 L high-pressure gas container 132 shown in the drawing has the gas phase side siphon tube 121, 128 and the liquid phase side siphon tube 122, 129 inserted into the inside of the high-pressure gas container (the gas phase side siphon tube 121, 128 and the liquid phase side siphon tube 122, 129 correspond to the internal pipe as a constitutional element of the present disclosure). Therefore, it is possible to use the liquid phase side siphon tube 122, 129 facing the lower side to discharge the liquefied hydrogen halide from the liquid phase side to the outside of the high-pressure gas container 124, 132, and thus it is possible to efficiently discharge the water contained in the hydrogen halide to the outside of the high-pressure gas container 124, 132.

[0080] Such a cleaning step can be performed once after the pressure reduction step, or can be performed repeatedly two or more times after the pressure reduction step.

[0081] After the cleaning step, the moisture concentration, hydrogen molecule concentration, and phosphorus atom concentration of the halogen hydride discharged through the discharging stage can be measured, respectively. The moisture concentration of the halogen hydride can be measured using a moisture meter. As the moisture meter, an analysis device of a cavity ring-down spectroscopy (CRDS) system can be used. In addition, the hydrogen molecule concentration of the halogen hydride can be measured, for example, by gas chromatography (GC). As the detector of the gas chromatography, a pulsed discharge type photo-ionization detector can be used. The phosphorus atom concentration of the halogen hydride can be measured by, for example, inductively coupled plasma atomic emission spectrometry (ICP-AES).

[0082] The high-pressure gas container cleaned as described above can be used as a high-pressure gas container for filling and storing a halogen hydride. That is, if a halogen hydride is filled in the high-pressure gas container cleaned as described above (for example, if a halogen hydride is filled in the high-pressure gas container after the cleaning step without opening the high-pressure gas container to the atmosphere), the moisture concentration of the filled halogen hydride can be maintained at a low concentration (for example, 1.0 volume ppm or less). The kind of the filled halogen hydride is not particularly limited, and can be at least one of hydrogen fluoride, hydrogen chloride, hydrogen bromide, and hydrogen iodide.

[0083] Example

[0084] The following shows examples and comparative examples, and more specifically describes the present disclosure.

[0085] [Example 1]

[0086] A high-pressure gas container made of metal having a volume of 47 L was prepared. The inner surface of the high-pressure gas container was polished, and the maximum height Rz of the inner surface of the main body portion was set to 1 μm, and the maximum height Rz of the inner surface of the portion other than the main body portion was set to 20 μm. The inner surface of the high-pressure gas container was not coated with a coating material.

[0087] The high-pressure gas container was installed on the device shown in Figure 2 , and a pressure reduction step was performed. That is, a pressure reduction step was performed in which the temperature was maintained at 145°C or higher and 155°C or lower, and the inner pressure of the high-pressure gas container was reduced to 0.01 Pa or lower.

[0088] Next, after the temperature of the high-pressure gas container after the pressure reduction step became room temperature, the high-pressure gas container was removed from the device shown in Figure 1 , and was installed on the device shown in Figure 1 . Then, the container valve of the high-pressure gas container was set to a closed state, and a cleaning step was performed in which the temperature was maintained at 145°C or higher and 155°C or lower, and the inner surface of the high-pressure gas container was cleaned. Figure 1The hydrogen chloride was supplied in the apparatus as shown until the pressure became 1.80 MPaG, and then the pressure was reduced until the residual pressure became 0.1 MPaG, and the above operation was repeated a total of 5 times.

[0089] Next, a cleaning process was performed on the high-pressure gas container. That is, the container valve of the high-pressure gas container was brought to an open state, and 25 kg of hydrogen chloride having a moisture concentration of 0.2 volume ppm or less was filled into the high-pressure gas container (hydrogen halide supply stage), and then, in a state where the temperature was maintained in a range of 15°C or higher and 25°C or lower, the high-pressure gas container was left to stand for 24 hours (metal oxide removal stage). Thereafter, the high-pressure gas container valve was brought to a closed state, and the hydrogen chloride was discharged from the high-pressure gas container until the residual pressure became 0.11 MPa (discharge stage). The cleaning process as described above was repeated a total of 4 times. Figure 3 The high-pressure gas container was removed from the apparatus as shown, and the high-pressure gas container was inverted upside down (the container valve was brought to a posture in which it faced downward in the vertical direction), and the container valve was brought to an open state, and the hydrogen chloride was discharged from the high-pressure gas container until the residual pressure became 0.11 MPa (discharge stage). The cleaning process as described above was repeated a total of 4 times.

[0090] In the high-pressure gas container after the cleaning process was performed, 25 kg of hydrogen chloride having a moisture concentration of 0.2 volume ppm or less was again filled. Then, the moisture concentration of the hydrogen chloride filled into the high-pressure gas container was measured with an analysis apparatus of a cavity ring-down spectroscopy (CRDS) system, and the hydrogen molecule concentration was measured with a gas chromatography (GC), and the phosphorus atom concentration was measured with an inductively coupled plasma atomic emission spectrometry (ICP-AES). As a detector of the gas chromatography, a pulsed discharge type photo-ionization detector was used. As a result, the moisture concentration of the hydrogen chloride was 0.6 volume ppm, the hydrogen molecule concentration was 0.1 volume ppm or less, and the phosphorus atom concentration was 0.5 volume ppb. The results are shown in Table 1.

[0091] [Example 2]

[0092] The cleaning of the high-pressure gas container was performed in the same manner as in Example 1, except that the maximum height Rz of the inner surface of the main body portion and the inner surface of the portion other than the main body portion was 1 μm, and the number of times of performing the cleaning process was 1.

[0093] In the high-pressure gas container after the cleaning process was performed, 25 kg of hydrogen chloride having a moisture concentration of 0.2 volume ppm or less was again filled. Then, the moisture concentration of the hydrogen chloride filled into the high-pressure gas container was measured with an analysis apparatus of a cavity ring-down spectroscopy (CRDS) system, and the hydrogen molecule concentration was measured with a gas chromatography (GC), and the phosphorus atom concentration was measured with an inductively coupled plasma atomic emission spectrometry (ICP-AES). As a detector of the gas chromatography, a pulsed discharge type photo-ionization detector was used. As a result, the moisture concentration of the hydrogen chloride was 0.6 volume ppm, the hydrogen molecule concentration was 0.1 volume ppm or less, and the phosphorus atom concentration was 0.5 volume ppb. The results are shown in Table 1.

[0094] [Example 3]

[0095] The cleaning of the high-pressure gas container was performed in the same manner as in Example 1, except that the maximum height Rz of the inner surface of the main body portion and the inner surface of the portion other than the main body portion was 5 μm, and the number of times of performing the cleaning step was 2.

[0096] In the high-pressure gas container after the cleaning step was performed, hydrogen chloride having a moisture concentration of 0.2 vol ppm or less was again filled at 25 kg. Then, in the same manner as in Example 1, the moisture concentration, hydrogen molecule concentration, and phosphorus atom concentration of the hydrogen chloride filled in the high-pressure gas container were measured. As a result, the moisture concentration of the hydrogen chloride was 0.8 vol ppm, the hydrogen molecule concentration was 1.0 vol ppm, and the phosphorus atom concentration was 0.7 vol ppb. The results are shown in Table 1.

[0097] [Example 4]

[0098] The cleaning of the high-pressure gas container was performed in the same manner as in Example 1, except that the halogenated hydrogen used in the cleaning step was changed from hydrogen chloride having a moisture concentration of 0.2 vol ppm or less to hydrogen bromide having a moisture concentration of 0.2 vol ppm or less, and the amount of the hydrogen bromide supplied in the halogenated hydrogen supply stage was set to 20 kg.

[0099] In the high-pressure gas container after the cleaning step was performed, hydrogen bromide having a moisture concentration of 0.2 vol ppm or less was again filled at 20 kg. Then, in the same manner as in Example 1, the moisture concentration, hydrogen molecule concentration, and phosphorus atom concentration of the hydrogen bromide filled in the high-pressure gas container were measured. As a result, the moisture concentration of the hydrogen bromide was 0.9 vol ppm, the hydrogen molecule concentration was 0.1 vol ppm or less, and the phosphorus atom concentration was 0.9 vol ppb. The results are shown in Table 1.

[0100] [Example 5]

[0101] The cleaning of the high-pressure gas container was performed in the same manner as in Example 1, except that the number of times of performing the cleaning step was 1, and the temperature in the metal oxide removal stage was changed to 35°C or higher and 40°C or lower.

[0102] In the high-pressure gas container after the cleaning step was performed, hydrogen chloride having a moisture concentration of 0.2 vol ppm or less was again filled at 25 kg. Then, in the same manner as in Example 1, the moisture concentration, hydrogen molecule concentration, and phosphorus atom concentration of the hydrogen chloride filled in the high-pressure gas container were measured. As a result, the moisture concentration of the hydrogen chloride was 0.2 vol ppm, the hydrogen molecule concentration was 12 vol ppm, and the phosphorus atom concentration was 0.5 vol ppb. The results are shown in Table 1.

[0103] [Example 6]

[0104] The cleaning of the high-pressure gas container was performed in the same manner as in Example 1, except that the pressure reduction in the pressure reduction step was performed until the internal pressure of the high-pressure gas container became 5 Pa.

[0105] After the cleaning process, 25 kg of hydrogen chloride with a moisture concentration of less than 0.2 ppm by volume was refilled into the high-pressure gas container. Then, the moisture concentration, hydrogen molecule concentration, and phosphorus atom concentration of the hydrogen chloride filled into the high-pressure gas container were measured in the same manner as in Example 1. The results showed that the moisture concentration of the hydrogen chloride was 0.9 ppm by volume, the hydrogen molecule concentration was less than 0.1 ppm by volume, and the phosphorus atom concentration was 0.6 ppb by volume. The results are shown in Table 1.

[0106] [Example 7]

[0107] The temperature of the decompression process was changed to above 50°C and below 55°C. Otherwise, the high-pressure gas container was cleaned in the same manner as in Example 1.

[0108] After the cleaning process, 25 kg of hydrogen chloride with a moisture concentration of less than 0.2 ppm was refilled into the high-pressure gas container. Then, the moisture concentration, hydrogen molecule concentration, and phosphorus atom concentration of the hydrogen chloride filled into the high-pressure gas container were measured in the same manner as in Example 1. The results showed that the moisture concentration of the hydrogen chloride was 0.5 ppm, the hydrogen molecule concentration was less than 0.1 ppm, and the phosphorus atom concentration was 0.5 ppb. The results are shown in Table 1.

[0109] [Example 8]

[0110] The temperature of the decompression process was changed to above 190°C and below 200°C. Otherwise, the high-pressure gas container was cleaned in the same manner as in Example 1.

[0111] After the cleaning process, 25 kg of hydrogen chloride with a moisture concentration of less than 0.2 ppm by volume was refilled into the high-pressure gas container. Then, the moisture concentration, hydrogen molecule concentration, and phosphorus atom concentration of the hydrogen chloride filled into the high-pressure gas container were measured in the same manner as in Example 1. The results showed that the moisture concentration of the hydrogen chloride was 0.2 ppm by volume, the hydrogen molecule concentration was less than 0.1 ppm by volume, and the phosphorus atom concentration was 0.8 ppb by volume. The results are shown in Table 1.

[0112] [Example 9]

[0113] Prepare a 440L metal high-pressure gas container (refer to...) Figure 4 The inner surface of the high-pressure gas container was ground so that the maximum height Rz of the inner surface of the main body was 1 μm, and the maximum height Rz of the inner surface of the parts other than the main body was 20 μm. No coating material was applied to the inner surface of the high-pressure gas container.

[0114] The high-pressure gas container was changed from a 47L container to a 440L container as described above. The temperature of the decompression process was changed to 50°C or higher and 55°C or lower. The decompression process was carried out until the internal pressure of the high-pressure gas container reached 3Pa. The amount of hydrogen chloride supplied in the hydrogen halide supply stage was set to 250kg. The number of cleaning processes was set to 1. Otherwise, the high-pressure gas container was cleaned in the same way as in Example 1.

[0115] After the cleaning process, 250 kg of hydrogen chloride with a moisture concentration of less than 0.2 ppm was refilled into the high-pressure gas container. Then, the moisture concentration, hydrogen molecule concentration, and phosphorus atom concentration of the hydrogen chloride filled into the high-pressure gas container were measured in the same manner as in Example 1. The results showed that the moisture concentration of the hydrogen chloride was 0.6 ppm, the hydrogen molecule concentration was less than 0.1 ppm, and the phosphorus atom concentration was 0.4 ppb. The results are shown in Table 1.

[0116] [Example 10]

[0117] Prepare a 900L metal high-pressure gas container (refer to...) Figure 5 The inner surface of the high-pressure gas container was ground so that the maximum height Rz of the inner surface of the main body was 1 μm, and the maximum height Rz of the inner surface of the parts other than the main body was 20 μm. No coating material was applied to the inner surface of the high-pressure gas container.

[0118] The high-pressure gas container was changed from a 47L container to a 900L container as described above; the temperature of the decompression process was changed to 50°C or higher and 55°C or lower; the decompression process was carried out until the internal pressure of the high-pressure gas container reached 3Pa; the amount of hydrogen chloride supplied in the hydrogen halide supply stage was set to 500kg; and the number of cleaning processes was set to 2. Otherwise, the high-pressure gas container was cleaned in the same way as in Example 1.

[0119] After the cleaning process, 500 kg of hydrogen chloride with a moisture concentration of less than 0.2 ppm by volume was refilled into the high-pressure gas container. Then, the moisture concentration, hydrogen molecule concentration, and phosphorus atom concentration of the hydrogen chloride filled into the high-pressure gas container were measured in the same manner as in Example 1. The results showed that the moisture concentration of the hydrogen chloride was 0.3 ppm by volume, the hydrogen molecule concentration was less than 0.1 ppm by volume, and the phosphorus atom concentration was 0.7 ppb by volume. The results are shown in Table 1.

[0120] [Example 11]

[0121] The maximum height Rz of the inner surface of the main body and the parts other than the main body of the high-pressure gas container is set to 20 μm, and the cleaning process is performed 5 times. Otherwise, the high-pressure gas container is cleaned in the same way as in Example 1.

[0122] In the high-pressure gas container after the cleaning process was performed, hydrogen chloride having a moisture concentration of 0.2 vol ppm or less was again filled at 25 kg. Then, the moisture concentration, hydrogen molecule concentration, and phosphorus atom concentration of the hydrogen chloride filled in the high-pressure gas container were measured in the same manner as in Example 1. As a result, the moisture concentration of the hydrogen chloride was 0.8 vol ppm, the hydrogen molecule concentration was 0.2 vol ppm, and the phosphorus atom concentration was 1.0 vol ppb. The results are shown in Table 1.

[0123] [Example 12]

[0124] The amount of hydrogen chloride supplied in the hydrogen chloride supply stage was set to 2 kg, and the number of times the cleaning process was performed was 20, and the cleaning of the high-pressure gas container was performed in the same manner as in Example 1 except for this.

[0125] In the high-pressure gas container after the cleaning process was performed, hydrogen chloride having a moisture concentration of 0.2 vol ppm or less was again filled at 25 kg. Then, the moisture concentration, hydrogen molecule concentration, and phosphorus atom concentration of the hydrogen chloride filled in the high-pressure gas container were measured in the same manner as in Example 1. As a result, the moisture concentration of the hydrogen chloride was 1.2 vol ppm, the hydrogen molecule concentration was 0.1 vol ppm or less, and the phosphorus atom concentration was 0.4 vol ppb. The results are shown in Table 1.

[0126] [Comparative Example 1]

[0127] The cleaning process was not performed, and the same treatment as in Example 1 was performed on the same high-pressure gas container as in Example 1.

[0128] In the high-pressure gas container after the cleaning process was performed, hydrogen chloride having a moisture concentration of 0.2 vol ppm or less was again filled at 25 kg. Then, the moisture concentration, hydrogen molecule concentration, and phosphorus atom concentration of the hydrogen chloride filled in the high-pressure gas container were measured in the same manner as in Example 1. As a result, the moisture concentration of the hydrogen chloride was 1.2 vol ppm, the hydrogen molecule concentration was 0.1 vol ppm or less, and the phosphorus atom concentration was 0.4 vol ppb. The results are shown in Table 1.

[0129] [Comparative Example 2]

[0130] The conditions of the temperature and pressure in the decompression process were changed, and the cleaning of the high-pressure gas container was performed in the same manner as in Example 1 except for this.

[0131] In the high-pressure gas container after the cleaning process was performed, hydrogen chloride having a moisture concentration of 0.2 volume ppm or less was filled again at 25 kg. Then, the moisture concentration, hydrogen molecule concentration, and phosphorus atom concentration of the hydrogen chloride filled in the high-pressure gas container were measured in the same manner as in Example 1. As a result, the moisture concentration of the hydrogen chloride was 2.5 volume ppm, the hydrogen molecule concentration was 1.0 volume ppm, and the phosphorus atom concentration was 0.8 volume ppb. The results are shown in Table 1.

[0132] [Comparative Example 3]

[0133] The cleaning of the high-pressure gas container was performed in the same manner as in Example 1 except that the pressure condition in the decompression process was different.

[0134] In the high-pressure gas container after the cleaning process was performed, hydrogen chloride having a moisture concentration of 0.2 volume ppm or less was filled again at 25 kg. Then, the moisture concentration, hydrogen molecule concentration, and phosphorus atom concentration of the hydrogen chloride filled in the high-pressure gas container were measured in the same manner as in Example 1. As a result, the moisture concentration of the hydrogen chloride was 1.6 volume ppm, the hydrogen molecule concentration was 2.0 volume ppm, and the phosphorus atom concentration was 0.3 volume ppb. The results are shown in Table 1.

[0135] [Reference Example 1]

[0136] A nickel-phosphorus alloy was applied to the inner surface of the high-pressure gas container as the coating material by plating treatment, and the same treatment as in Comparative Example 1 was performed on the high-pressure gas container in the same manner as in Example 1.

[0137] In the high-pressure gas container after the cleaning process was performed, hydrogen chloride having a moisture concentration of 0.2 volume ppm or less was filled again at 25 kg. Then, the moisture concentration, hydrogen molecule concentration, and phosphorus atom concentration of the hydrogen chloride filled in the high-pressure gas container were measured in the same manner as in Example 1. As a result, the moisture concentration of the hydrogen chloride was 0.8 volume ppm, the hydrogen molecule concentration was 0.2 volume ppm, and the phosphorus atom concentration was 2.1 volume ppb. The results are shown in Table 1.

[0138]

[0139] In Example 1 and Example 5, the moisture concentration of the hydrogen chloride discharged at the discharge stage was measured in the same manner as in Example 1 each time the cleaning process was performed once. Then, the amount of water (moles) discharged at the cleaning process once was calculated from the measured value of the moisture concentration. The results are shown in the coordinate graph of Figure 5 Figure 5 The coordinate graph of the cumulative value of the amount of water discharged is shown in

[0140] The cumulative value of the amount of water discharged is calculated from the cumulative value of the amount of hydrogen chloride discharged and the moisture concentration of the hydrogen chloride. Figure 6 ​From the graph of FIG. 1, it is known that the total amount of water discharged is equivalent in Example 1 and Example 5. From this result, it is known that the temperature of the metal oxide removal stage does not need to be increased, and water can be removed even if it is lower than 30°C.

[0141] In Example 1, the high-pressure gas container filled with 25 kg of hydrogen chloride after the cleaning process was left standing in a room in which the temperature was adjusted to be 20°C or higher and 25°C or lower. Then, after a predetermined time had passed, the moisture concentration of the hydrogen chloride filled in the high-pressure gas container was measured in the same manner as in Example 1. The results are shown in the graph of FIG. 1. Figure 6

[0142] In Comparative Example 1, the high-pressure gas container filled with 25 kg of hydrogen chloride after the pressure reduction process was left standing in a room in which the temperature was adjusted to be 20°C or higher and 25°C or lower. Then, after a predetermined time had passed, the moisture concentration of the hydrogen chloride filled in the high-pressure gas container was measured in the same manner as in Example 1. The results are shown in the graph of FIG. 1. Further, with respect to the test of this Comparative Example 1, three high-pressure gas containers (indicated as Comparative Example 1 A, Comparative Example 1 B, and Comparative Example 1 C in the graph of FIG. 1) were prepared, and the same test was performed for each of them. Figure 6 Figure 6 From the graph of FIG. 1, it is known that the total amount of water discharged is equivalent in Example 1 and Example 5. From this result, it is known that the temperature of the metal oxide removal stage does not need to be increased, and water can be removed even if it is lower than 30°C.

[0143] From the graph of FIG. 1, it is known that the total amount of water discharged is equivalent in Example 1 and Example 5. From this result, it is known that the temperature of the metal oxide removal stage does not need to be increased, and water can be removed even if it is lower than 30°C. ​ From the graph of FIG. 1, it is known that the total amount of water discharged is equivalent in Example 1 and Example 5. From this result, it is known that the temperature of the metal oxide removal stage does not need to be increased, and water can be removed even if it is lower than 30°C.

[0144] Explanation of Reference Numerals

[0145] 1 • • • Purified helium cylinder

[0146] 2 • • • Pressure reduction valve

[0147] 3, 4, 6, 8, 11 • • • Valves

[0148] 5 • • • Hydrogen halide supply source

[0149] 7 • • • 47L high-pressure gas container

[0150] 9 • • • Pressure gauge

[0151] 10 • • • Check valve

[0152] 12 • • • Discharge unit

[0153] 13 • • • Nitrogen supply source ​​

[0154] 14, 15, 16 ••• valve

[0155] 17 ••• vacuum pump

[0156] 18 ••• vacuum gauge

[0157] 19 ••• 47L high-pressure gas container

[0158] 20 ••• heater

[0159] 21 ••• heat insulating material

[0160] 22 ••• temperature regulator

[0161] 23 ••• soluble plug cooling air supply source

[0162] 120 ••• gas phase side container valve

[0163] 121 ••• gas phase side siphon

[0164] 122 ••• liquid phase side siphon

[0165] 123 ••• liquid phase side container valve

[0166] 124 ••• 440L high-pressure gas container

[0167] 125 ••• gas phase side container valve

[0168] 126 ••• liquid phase side container valve

[0169] 127, 130 ••• safety plug

[0170] 128 ••• gas phase side siphon

[0171] 129 ••• liquid phase side siphon

[0172] 131, 133 ••• skirt

[0173] 132 ••• 900L high-pressure gas container

Claims

1. A cleaning method of a high-pressure gas container, comprising: a depressurization process of depressurizing an inside of a high-pressure gas container until an internal pressure becomes 5 Pa or less, and a cleaning process of cleaning the inside of the high-pressure gas container subjected to the depressurization process, the cleaning process comprising a hydrogen halide supply stage, a metal oxide removal stage, and a discharge stage, in the hydrogen halide supply stage, a hydrogen halide is supplied to the high-pressure gas container subjected to the depressurization process, in the metal oxide removal stage, a metal oxide present on an inner surface of the high-pressure gas container is caused to react with the hydrogen halide supplied in the hydrogen halide supply stage to generate water inside the high-pressure gas container subjected to the hydrogen halide supply stage, and in the discharge stage, the water generated in the metal oxide removal stage and the hydrogen halide supplied in the hydrogen halide supply stage are discharged from the high-pressure gas container.

2. The cleaning method of a high-pressure gas container according to claim 1, wherein an inner surface of the high-pressure gas container is not coated with a coating material, and a maximum height Rz of an inner surface of a main body portion of the high-pressure gas container is 5 μm or less.

3. The cleaning method of a high-pressure gas container according to claim 1 or 2, wherein the depressurization process is a process of exhausting gas until the internal pressure becomes 5 Pa or less while the high-pressure gas container is maintained at a temperature of 50°C or higher and 200°C or lower.

4. The cleaning method of a high-pressure gas container according to claim 1 or 2, wherein the hydrogen halide is at least one of hydrogen fluoride, hydrogen chloride, hydrogen bromide, and hydrogen iodide.

5. The cleaning method of a high-pressure gas container according to claim 1 or 2, wherein the hydrogen halide supply stage is a process of supplying the hydrogen halide to the high-pressure gas container until the hydrogen halide is liquefied inside the high-pressure gas container.

6. The cleaning method of a high-pressure gas container according to claim 1 or 2, wherein the metal oxide removal stage is a process of leaving the high-pressure gas container to which the hydrogen halide is supplied in the hydrogen halide supply stage at a temperature of 30°C or lower for 1 day or more.

7. The cleaning method of a high-pressure gas container according to claim 1 or 2, wherein, in a case where a volume of the high-pressure gas container is 10 L or more and 50 L or less, the discharge stage is a process of discharging the water and the hydrogen halide from the high-pressure gas container by inverting the high-pressure gas container upside down.

8. The cleaning method of a high-pressure gas container according to claim 1 or 2, wherein, in a case where the volume of the high-pressure gas container exceeds 50 L and is 1000 L or less, the discharge stage is a process of inserting an inner tube into the inside of the high-pressure gas container and discharging the water and the hydrogen halide in a liquid phase from the high-pressure gas container by using the inner tube.

9. The cleaning method of a high-pressure gas container according to claim 1 or 2, wherein the cleaning process is repeatedly performed 2 or more times after the depressurization process. ​ ​ ​ ​ 10. The cleaning method of a high-pressure gas container according to claim 1 or 2, the metal oxide being at least one of iron oxide, chromium oxide, molybdenum oxide, and manganese oxide.

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