Corrosion-resistant member

Abstract

Provided is a corrosion-resistant member in which a corrosion-resistant coating film is less likely to be detached from a base material even when the corrosion-resistant member experiences a thermal history. The corrosion-resistant member comprises: a metal-made base material (10); and a corrosion-resistant coating (30) formed on a surface of the base material (10). The corrosion-resistant coating film (30) comprises a magnesium fluoride layer (31) and an aluminum fluoride layer (32) laminated in this order as observed from the base material (10) side. The aluminum fluoride layer (32) has a first crystalline region (32A) and a second crystalline region (32B) in each of which aluminum fluoride contained therein has a crystalline form. The first crystalline region (32A) is a region in which a regular array of diffraction spots is observed in an electron beam diffraction image obtained by the irradiation with an electron beam having a beam diameter of 10 to 20 nm, inclusive. The second crystalline region (32B) is a region in which a plurality of diffraction spots are observed but a regular array of diffraction spots is not observed in an electron beam diffraction image obtained by the irradiation with the electron beam.

Description

Technical Field

[0001] The present invention relates to a corrosion-resistant member.

Background Art

[0002] In a semiconductor manufacturing process, corrosive gases such as chlorine gas and fluorine gas may be used. Therefore, members constituting a semiconductor manufacturing apparatus are required to have corrosion resistance. Examples of members constituting a semiconductor manufacturing apparatus include a chamber, piping, a gas storage device, a valve, a susceptor, a shower head, and the like. Patent Document 1 discloses a member such as a shower head used in a semiconductor manufacturing process. This member has an aluminum surface coated with a corrosion-resistant film composed of at least one of aluminum fluoride and magnesium fluoride.

[0003] Further, Patent Document 2 discloses a vacuum chamber member in which a corrosion-resistant film is formed on the surface of a base material. The surface side of the corrosion-resistant film is a layer mainly composed of aluminum oxide or a layer mainly composed of aluminum oxide and aluminum fluoride, and the base material side of the corrosion-resistant film is a layer mainly composed of magnesium fluoride or a layer mainly composed of magnesium fluoride and aluminum oxide.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the members disclosed in Patent Documents 1 and 2 had a problem that the corrosion-resistant coating was likely to peel off from the base material due to the heat history. An object of the present invention is to provide a corrosion-resistant member in which the corrosion-resistant coating is less likely to peel off from the base material even when subjected to a heat history.

Means for Solving the Problems

[0006] To solve the above problems, one aspect of the present invention is as follows [1] to [5]. [1] A corrosion-resistant member comprising a metal base material and a corrosion-resistant coating formed on the surface of the base material, The corrosion-resistant coating is a laminate in which a magnesium fluoride layer containing magnesium fluoride and an aluminum fluoride layer containing aluminum fluoride are laminated in this order from the base material side, The aluminum fluoride layer has a first crystalline region and a second crystalline region in which the contained aluminum fluoride is crystalline, The first crystalline region is a region in which a row of diffraction spots having regularity is observed in an electron diffraction image obtained by irradiating an electron beam having a beam diameter of 10 nm or more and 20 nm or less, The second crystalline region is a region in which a plurality of diffraction spots are observed in an electron diffraction image obtained by irradiating the electron beam, but a row of diffraction spots having regularity is not observed.

[0007] [2] The corrosion-resistant member according to [1], wherein the first crystalline region is arranged adjacent to or in the vicinity of the magnesium fluoride layer. [3] The corrosion-resistant member according to [1] or [2], wherein the metal base material is made of aluminum or an aluminum alloy.

[0008] [4] The corrosion-resistant member according to any one of [1] to [3], wherein the thickness of the magnesium fluoride layer is 0.1 μm or more and 20 μm or less. [5] The corrosion-resistant member according to any one of [1] to [4], wherein the thickness of the aluminum fluoride layer is 0.2 μm or more and 50 μm or less.

Advantages of the Invention

[0009] The corrosion-resistant member according to the present invention has a corrosion-resistant coating that is difficult to peel from the base material even when subjected to a heat history.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0011] One embodiment of the present invention will be described below. Note that this embodiment shows an example of the present invention, and the present invention is not limited to this embodiment. Also, various changes or improvements can be made to this embodiment, and forms with such changes or improvements can also be included in the present invention.

[0012] As shown in Fig. 1, the corrosion-resistant member according to this embodiment includes a metal base material 10 and a corrosion-resistant film 30 formed on the surface of the base material 10. This corrosion-resistant film 30 is a laminate of a magnesium fluoride layer 31 containing magnesium fluoride (MgF2) and an aluminum fluoride layer 32 containing aluminum fluoride (AlF3) in order from the base material 10 side.

[0013] Further, as shown in Fig. 1, the aluminum fluoride layer 32 has a first crystalline region 32A in which the contained aluminum fluoride is crystalline and a second crystalline region 32B in which the contained aluminum fluoride is crystalline. The first crystalline region 32A is a region where a row of diffraction spots having regularity is observed in an electron diffraction image obtained by irradiating an electron beam with a beam diameter of 10 nm or more and 20 nm or less. Further, the second crystalline region 32B is a region where a plurality of diffraction spots are observed in an electron diffraction image obtained by irradiating an electron beam with a beam diameter of 10 nm or more and 20 nm or less, but a row of diffraction spots having regularity is not observed.

[0014] A TEM image of the cross section of the corrosion-resistant member according to this embodiment is shown in Fig. 2. Note that Figs. 1 and 2 are cross-sectional views when the corrosion-resistant member is cut in a plane along the lamination direction of the magnesium fluoride layer 31 and the aluminum fluoride layer 32. As shown in Fig. 2, the aluminum fluoride layer 32 has a first crystalline region 32A and a second crystalline region 32B. In the corrosion-resistant member of Fig. 2, portions A, B, and C on the magnesium fluoride layer 31 side of the aluminum fluoride layer 32 are the first crystalline region 32A, and portions D and E on the surface side of the aluminum fluoride layer 32 are the second crystalline region 32B.

[0015] The electron diffraction image shown in Fig. 3 is an electron diffraction image obtained by irradiating portion A of the aluminum fluoride layer 32 of the corrosion-resistant member of Fig. 2 with the above electron beam. Similarly, the electron diffraction images shown in Figs. 4 to 7 are electron diffraction images obtained by irradiating portions B to E of the aluminum fluoride layer 32 of the corrosion-resistant member of Fig. 2 with the above electron beam.

[0016] As can be seen from the electron diffraction images of FIGS. 3 to 5, in the electron diffraction images obtained by irradiating portions A, B, and C of the aluminum fluoride layer 32 with an electron beam having a beam diameter of 10 nm or more and 20 nm or less, rows of diffraction spots having regularity are observed. Further, as can be seen from the electron diffraction images of FIGS. 6 and 7, in the electron diffraction images obtained by irradiating portions D and E of the aluminum fluoride layer 32 with an electron beam having a beam diameter of 10 nm or more and 20 nm or less, a plurality of diffraction spots are observed, but rows of diffraction spots having regularity are not observed.

[0017] Since the corrosion-resistant member according to the present embodiment includes the corrosion-resistant coating 30, it has excellent corrosion resistance even in a strongly corrosive gas or plasma. Further, since the magnesium fluoride layer 31 is interposed between the aluminum fluoride layer 32 and the base material 10, the adhesion between the aluminum fluoride layer 32 and the base material 10 is high. Furthermore, since the aluminum fluoride layer 32 has the first crystalline region 32A and the second crystalline region 32B, the corrosion-resistant coating 30 is less likely to peel from the base material 10 and less likely to crack even when subjected to a thermal history. For example, even when subjected to a thermal history of repeating temperature increase and decrease, peeling or cracking of the corrosion-resistant coating 30 is less likely to occur. As a result, the corrosion-resistant member according to the present embodiment has excellent corrosion resistance even when subjected to a thermal history, and the generation of particles derived from the peeling of the corrosion-resistant coating 30 is suppressed.

[0018] Such a corrosion-resistant member according to the present embodiment is suitable as a member that requires corrosion resistance and heat resistance. For example, it is suitable as a member constituting a semiconductor manufacturing apparatus (particularly, a film forming apparatus using a chemical vapor deposition method). As a specific example, it is suitable as a susceptor or a shower head of a film forming apparatus that forms a thin film on a wafer in a state where plasma is generated. If the corrosion-resistant member according to the present embodiment is used as a member constituting a semiconductor manufacturing apparatus, the generation of particles is suppressed, so that a semiconductor can be manufactured with a high yield.

[0019] Hereinafter, the corrosion-resistant member according to the present embodiment will be described in more detail. 〔Base material〕 The metal constituting the base material 10 is not particularly limited and may be a single metal (including inevitable impurities) or an alloy. For example, it may be aluminum or an aluminum alloy.

[0020] Magnesium fluoride layer The thickness of the magnesium fluoride layer 31 is preferably 0.1 μm or more and 20 μm or less, more preferably 0.15 μm or more and 10 μm or less, and even more preferably 0.2 μm or more and 7 μm or less. If the thickness of the magnesium fluoride layer 31 is 0.1 μm or more, the adhesion between the aluminum fluoride layer 32 and the base material 10 becomes higher. Therefore, the corrosion-resistant film 30 is less likely to peel off from the base material 10 even when subjected to a heat history. Also, if the thickness of the magnesium fluoride layer 31 is 20 μm or less, the magnesium fluoride layer 31 is less likely to crack even when subjected to a heat history.

[0021] The method for measuring the thickness of the magnesium fluoride layer 31 is not particularly limited, and examples include methods such as a transmission electron microscope (TEM), a scanning transmission electron microscope (STEM), and a scanning electron microscope (SEM). For example, a TEM image is obtained using a transmission electron microscope, and the thickness of the magnesium fluoride layer 31 can be measured by confirming the boundary between the magnesium fluoride layer 31 and the adjacent layer in the TEM image based on the image contrast. The thicknesses of the aluminum fluoride layer 32, the first crystalline region 32A, and the second crystalline region 32B can also be measured by the same methods as described above.

[0022] Also, the method for quantitative analysis of each element such as fluorine and magnesium contained in the magnesium fluoride layer 31 is not particularly limited, and for example, it can be analyzed by energy dispersive X-ray analysis (EDS analysis) or electron probe microanalyzer analysis (EPMA analysis).

[0023] Aluminum fluoride layer The aluminum fluoride contained in the aluminum fluoride layer 32 may be at least one selected from aluminum fluoride (AlF3), aluminum fluoride hydrate (AlF3·nH2O), aluminum fluoride containing some hydroxyl groups (AlF 3-x (OH) x ), aluminum fluoride hydrate containing some hydroxyl groups (AlF 3-X (OH) X ·nH2O), aluminum fluoride containing some oxygen (AlF 3(1-X) O 3 / 2X ), and aluminum fluoride hydrate containing some oxygen (AlF 3(1-X) O 3 / 2X ·nH2O).

[0024] The thickness of the aluminum fluoride layer 32 is preferably 0.2 μm or more and 50 μm or less, more preferably 0.3 μm or more and 40 μm or less, and even more preferably 0.5 μm or more and 30 μm or less. If the thickness of the aluminum fluoride layer 32 is within the above range, the corrosion resistance of the corrosion-resistant coating 30 is more excellent and the aluminum fluoride layer 32 is less likely to crack even when subjected to a heat history. The measuring method of the thickness of the aluminum fluoride layer 32 is as described above in the section of the magnesium fluoride layer.

[0025] In addition, the quantitative analysis method of each element such as fluorine and aluminum contained in the aluminum fluoride layer 32 is not particularly limited, but for example, it can be analyzed by energy dispersive X-ray analysis or electron probe microanalyzer analysis (EPMA analysis).

[0026] 〔First Crystalline Region and Second Crystalline Region〕 The first crystalline region 32A is a region in which a row of diffraction spots having regularity is observed in an electron diffraction image obtained by irradiating an electron beam with a beam diameter of 10 nm or more and 20 nm or less. The "row of diffraction spots having regularity" will be described in detail below. That is, a plurality of rows of diffraction spots are arranged so as to form a point-symmetric figure with the diffraction spot located at the center of the electron diffraction image as the center of point symmetry, and the electron diffraction image is constituted. This row of diffraction spots is a row in which three or more diffraction spots are arranged linearly at equal intervals. The "row of diffraction spots having regularity" in the present invention means the row of diffraction spots arranged as described above.

[0027] Figs. 3 to 5 are electron diffraction images obtained by irradiating portions A, B, and C of the aluminum fluoride layer 32 of the corrosion-resistant member of Fig. 2 with an electron beam having a beam diameter of 10 nm or more and 20 nm or less. A row in which three or more diffraction spots are arranged linearly at equal intervals is arranged in three parallel rows. Then, with the diffraction spot located at the center of the electron diffraction image (the diffraction spot located at the center of the central row) as the center of point symmetry, each diffraction spot constituting the two outer rows sandwiching the central row is arranged so as to form a point-symmetric figure. Therefore, portions A, B, and C of the aluminum fluoride layer 32 are the first crystalline region 32A.

[0028] The second crystalline region 32B is a region in which a plurality of diffraction spots are observed in an electron diffraction image obtained by irradiating an electron beam with a beam diameter of 10 nm or more and 20 nm or less, but a row of diffraction spots having the regularity like that of the first crystalline region 32A is not observed. Figs. 6 and 7 are electron diffraction images obtained by irradiating portions D and E of the aluminum fluoride layer 32 of the corrosion-resistant member of Fig. 2 with an electron beam having a beam diameter of 10 nm or more and 20 nm or less. Although a plurality of diffraction spots are observed, a row of diffraction spots having regularity is not observed. Therefore, portions D and E of the aluminum fluoride layer 32 are the second crystalline region 32B.

[0029] The observation of such a point-symmetric figure in an electron beam diffraction image means that a single crystal or a polycrystal consisting of multiple crystals aligned in the same direction exists within an area corresponding to the beam diameter of the electron beam. In contrast, when multiple diffraction spots are observed in an electron beam diffraction image but such a point-symmetric figure is not observed, this means that a polycrystal consisting of multiple crystals aligned in different directions exists within an area corresponding to the beam diameter of the electron beam.

[0030] In other words, the first crystalline region 32A contains a single crystal or a polycrystal consisting of multiple crystals arranged in the same direction, while the second crystalline region 32B contains a polycrystal consisting of multiple crystals arranged in different directions. The method for analyzing the first crystalline region 32A and the second crystalline region 32B is not particularly limited as long as it is a method that can obtain an electron beam diffraction image by irradiating with an electron beam having a beam diameter of 10 nm to 20 nm. The electron beam irradiation conditions include irradiation with a transmission electron microscope HF-2200 manufactured by Hitachi High-Tech Corporation at an acceleration voltage of 230 kV.

[0031] The first crystalline region 32A and the second crystalline region 32B may each be in the form of a layer, or may be laminated within the aluminum fluoride layer 32. Alternatively, one of the first crystalline region 32A and the second crystalline region 32B may be in the form of a mass and dispersed within the other (i.e., the aluminum fluoride layer 32 may have an island structure made up of the first crystalline region 32A and the second crystalline region 32B). However, the first crystalline region 32A is preferably disposed adjacent to or close to the magnesium fluoride layer 31. With this configuration, the adhesion between the magnesium fluoride layer 31 and the aluminum fluoride layer 32 becomes higher.

[0032] The ratio of the thickness (length in the stacking direction) of the first crystalline region 32A to the thickness of the aluminum fluoride layer 32 is preferably 5% or more and 95% or less, more preferably 10% or more and 90% or less, and even more preferably 15% or more and 80% or less. With such a configuration, the adhesion between the magnesium fluoride layer 31 and the aluminum fluoride layer 32 becomes higher. The method for measuring the thickness of the first crystalline region 32A is as described above in the section on the magnesium fluoride layer.

[0033] In addition, for the first crystalline region 32A and the second crystalline region 32B, at least a part of the contained aluminum fluoride being crystalline is sufficient, and it is not necessary for all of it to be crystalline. Further, this crystal preferably has a crystal unit with an aligned crystal orientation and a long side of 300 nm or more. If the long side is 300 nm or more, the adhesion between the magnesium fluoride layer 31 and the aluminum fluoride layer 32 becomes higher. This crystal unit may be a single crystal or a polycrystal.

[0034] [Method for manufacturing a corrosion-resistant member] The method for manufacturing the corrosion-resistant member according to the present embodiment is not particularly limited. For example, a method of forming an aluminum fluoride layer on the surface of a substrate made of an aluminum alloy containing magnesium by a method such as vapor deposition and then performing heat treatment can be mentioned. The aluminum fluoride layer before heat treatment contains crystalline aluminum fluoride, but all of the contained crystalline substances correspond to the crystalline substances in the second crystalline region and do not contain crystalline substances corresponding to the crystalline substances in the first crystalline region.

[0035] When heat treatment is performed in an atmosphere such as a fluorine gas atmosphere, a magnesium fluoride layer is formed between the substrate and the aluminum fluoride layer, and at the same time, a first crystalline region is formed in the aluminum fluoride layer, resulting in a state where the first crystalline region and the second crystalline region coexist in the aluminum fluoride layer.

[0036] The holding temperature during the heat treatment is preferably 200°C or higher and 500°C or lower, more preferably 300°C or higher and 475°C or lower, and still more preferably 350°C or higher and 450°C or lower. If the holding temperature during the heat treatment is 200°C or higher, the magnesium fluoride layer is likely to be formed. Also, the first crystalline region is likely to be formed in the aluminum fluoride layer. If the holding temperature during the heat treatment is 500°C or lower, cracks are less likely to occur in the aluminum fluoride layer. The holding time during the heat treatment is preferably 1 hour or longer and 250 hours or shorter, more preferably 3 hours or longer and 150 hours or shorter, and still more preferably 5 hours or longer and 100 hours or shorter. If the holding time during the heat treatment is 1 hour or longer, the magnesium fluoride layer is likely to be formed. Also, the first crystalline region is likely to be formed in the aluminum fluoride layer. If the holding time during the heat treatment is 250 hours or shorter, productivity is likely to be good.

Examples

[0037] Examples and comparative examples are shown below to more specifically explain the present invention. 〔Example 1〕 First, the substrate was pretreated, and then vacuum deposition was performed to form an aluminum fluoride layer on the surface of the substrate. Thereafter, heat treatment was performed to form a magnesium fluoride layer between the substrate and the aluminum fluoride layer and to form a first crystalline region in the aluminum fluoride layer, thereby obtaining a corrosion-resistant member.

[0038] The metal constituting the substrate is aluminum alloy A5052 containing 2.55% by mass of magnesium. Also, the substrate is in the shape of a plate with a length of 50 mm, a width of 30 mm, and a thickness of 3 mm. The pretreatment of the substrate was performed as follows. First, 50 g of U Cleaner UA68 (manufactured by Uemura Kogyo Co., Ltd.), which is an alkaline degreasing solution containing sodium borate, carbonate, phosphate, and surfactant, was dissolved in 1 L of water and the temperature was set to 50°C to obtain a degreasing solution. The substrate was immersed in this degreasing solution for 10 minutes for degreasing and then washed with pure water.

[0039] Next, 500 g of the escreen AL-5000 (manufactured by Sasaki Chemical Co., Ltd.) heated to 70°C was used as the etching solution. The degreased substrate was immersed in this etching solution for 1 minute for etching, and then washed with pure water. Thereafter, 200 g of Smart Clean (manufactured by Raiki Co., Ltd.) containing nitric acid dissolved in 400 g of water and adjusted to a temperature of 25°C was used as the smut removal solution. The etched substrate was immersed in this smut removal solution for 30 seconds for smut removal, and then washed with pure water. Then, the smut-removed substrate was vacuum dried to complete the pretreatment.

[0040] The conditions for vacuum evaporation when forming the aluminum fluoride layer are as follows. First, after placing the pretreated substrate in the vacuum chamber, the inside of the vacuum chamber was evacuated until the degree of vacuum reached 3×10 -4 Pa. An aluminum fluoride sintered body material was used as the evaporation material, and this sintered body material was irradiated with an electron beam. The shutter was opened, and an aluminum fluoride layer with a thickness of 1.1 μm was formed on the pretreated substrate. At this time, the input power of the electron beam was about 40 mA at an acceleration voltage of 5 kV, the degree of vacuum during evaporation was 7×10 -4 Pa, and the treatment time was 120 sec. This aluminum fluoride layer does not have a first crystalline region and has only a second crystalline region.

[0041] The conditions for heat treatment are as follows. The substrate on which the aluminum fluoride layer was formed was heated to 450°C in a mixed gas atmosphere of 20% by volume of fluorine gas and 80% by volume of nitrogen gas, and heat-treated for 50 hours. By this heat treatment, a magnesium fluoride layer with a thickness of 0.5 μm was formed between the substrate and the aluminum fluoride layer, and a first crystalline region was formed in the aluminum fluoride layer. The aluminum fluoride layer was in a state where the first crystalline region and the second crystalline region coexisted. The thickness of the aluminum fluoride layer remained 1.1 μm after heat treatment. Also, the ratio of the thickness (length in the stacking direction) of the first crystalline region to the thickness of the aluminum fluoride layer was 60%.

[0042] Each element such as magnesium and aluminum present in the formed magnesium fluoride layer and aluminum fluoride layer was analyzed by energy-dispersive X-ray analysis. Specifically, for a sample processed to a thickness of 40 nm or more and 100 nm or less with an ion slicer, point analysis of each layer was performed at an acceleration voltage of 200 kV to analyze each element such as magnesium and aluminum.

[0043] The presence of the first crystalline region and the second crystalline region in the aluminum fluoride layer was confirmed by electron beam diffraction method. Specifically, for a sample processed to a thickness of 40 nm or more and 100 nm or less with an ion slicer, an electron beam with a beam diameter of 10 nm or more and 20 nm or less was irradiated, and an electron beam diffraction image was obtained with a TEM. The electron beam diffraction images of the first crystalline region and the second crystalline region are shown in FIGS. 3 to 7, respectively.

[0044] The electron beam diffraction image shown in FIG. 3 is an electron beam diffraction image obtained by irradiating the above electron beam to the A portion of the aluminum fluoride layer 32 of the corrosion-resistant member of FIG. 2. This A portion is a portion at a laminated direction position corresponding to 13% of the thickness from the substrate 10 side with respect to the thickness of the aluminum fluoride layer 32. The electron beam diffraction images shown in FIGS. 4 to 7 are electron beam diffraction images obtained by irradiating the above electron beam to the B portion to the E portion of the aluminum fluoride layer 32 of the corrosion-resistant member of FIG. 2. Similar to the case of the A portion, the B portion is a portion at a laminated direction position corresponding to 29% of the thickness, the C portion is 44%, the D portion is 72%, and the E portion is 92%.

[0045] A heating test was performed on the obtained corrosion-resistant member of Example 1, and the state of peeling of the corrosion-resistant coating was evaluated. The conditions of the heating test are such that one cycle is a process of holding at 350 ° C. for 300 min in a nitrogen gas atmosphere and then naturally cooling to room temperature, and this is performed 10 cycles.

[0046] After the heating test was completed, the corrosion-resistant coating of the corrosion-resistant member was observed with a scanning electron microscope, and the degree of peeling was evaluated. The results are shown in Table 1. In Table 1, when the area of the peeled part of the corrosion-resistant coating was less than 1% of the area of the corrosion-resistant coating, it was indicated as "SA", when it was 1% or more and less than 5%, it was indicated as "A", when it was 5% or more and less than 30%, it was indicated as "B", and when it was 30% or more, it was indicated as "C".

[0047]

Table 1

[0048] 〔Example 2〕 A corrosion-resistant member was manufactured and evaluated in the same manner as in Example 1, except that the metal constituting the base material was aluminum alloy A6061 containing 1.02% by mass of magnesium. The results are shown in Table 1. 〔Example 3〕 A corrosion-resistant member was manufactured and evaluated in the same manner as in Example 1, except that the processing time of vacuum evaporation when forming the aluminum fluoride layer on the pretreated base material was 70 min. The results are shown in Table 1.

[0049] 〔Example 4〕 A corrosion-resistant member was manufactured and evaluated in the same manner as in Example 1, except that the processing time of vacuum evaporation when forming the aluminum fluoride layer on the pretreated base material was 45 sec. The results are shown in Table 1. 〔Example 5〕 A corrosion-resistant member was manufactured and evaluated in the same manner as in Example 1, except that the conditions of heat treatment were a holding temperature of 470 °C and a holding time of 200 hours. The results are shown in Table 1.

[0050] 〔Example 6〕 A corrosion-resistant member was manufactured and evaluated in the same manner as in Example 1, except that the conditions of heat treatment were a holding temperature of 400 °C and a holding time of 20 hours. The results are shown in Table 1. 〔Comparative Example 1〕 Except for changing the conditions of vacuum deposition when forming the aluminum fluoride layer on the pretreated substrate as described later and not performing heat treatment after forming the aluminum fluoride layer on the surface of the substrate, a corrosion-resistant member was manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0051] Since heat treatment was not performed, the corrosion-resistant member of Comparative Example 1 does not have a magnesium fluoride layer. Also, since heat treatment was not performed, the corrosion-resistant member of Comparative Example 1 does not have a first crystalline region in the aluminum fluoride layer, and the aluminum fluoride layer consists only of a second crystalline region.

[0052] The conditions of vacuum deposition in Comparative Example 1 are as follows. First, after placing the pretreated substrate in the vacuum chamber, the inside of the vacuum chamber was evacuated until the degree of vacuum reached 2×10 -4 Pa. Then, the pretreated substrate was heated to 400°C. Using an aluminum fluoride sintered body material as the evaporation material, this sintered body material was irradiated with an electron beam, the shutter was opened, and an aluminum fluoride layer with a thickness of 1.1 μm was formed on the pretreated substrate. The input power of the electron beam at this time was about 40 mA at an acceleration voltage of 5 kV, the degree of vacuum during deposition was 5×10 -4 Pa, and the treatment time was 120 sec.

[0053] 〔Comparative Example 2〕 First, the substrate was pretreated, and then, as described later, vacuum deposition was performed to form a magnesium fluoride layer on the surface of the substrate, and further vacuum deposition was performed to form an aluminum fluoride layer on the magnesium fluoride layer to obtain a corrosion-resistant member. The type of metal constituting the substrate and the content of the pretreatment on the substrate are the same as in Example 1.

[0054] The conditions of vacuum deposition when forming the magnesium fluoride layer are as follows. First, after placing the pretreated substrate in the vacuum chamber, the degree of vacuum reached 2×10 -4The inside of the vacuum chamber was evacuated until it reached Pa. Then, the pretreated substrate was heated to 380°C. Using a magnesium fluoride sintered body material as the evaporation material, this sintered body material was irradiated with an electron beam, the shutter was opened, and a 0.5-μm-thick magnesium fluoride layer was formed on the pretreated substrate. The input power of the electron beam at this time was about 40 mA at an acceleration voltage of 5 kV, and the degree of vacuum during evaporation was 5×10 -4 Pa.

[0055] The conditions for vacuum evaporation when forming the aluminum fluoride layer are as follows. First, after placing the substrate on which the magnesium fluoride layer was formed in the vacuum chamber, the inside of the vacuum chamber was evacuated until the degree of vacuum reached 2×10 -4 Pa. Then, the substrate on which the magnesium fluoride layer was formed was heated to 400°C. Using an aluminum fluoride sintered body material as the evaporation material, this sintered body material was irradiated with an electron beam, the shutter was opened, and a 1.1-μm-thick aluminum fluoride layer was formed on the magnesium fluoride layer of the substrate heated to 400°C. The input power of the electron beam at this time was about 40 mA at an acceleration voltage of 5 kV, and the degree of vacuum during evaporation was 5×10 -4 Pa. The corrosion-resistant member of Comparative Example 2 obtained does not have a first crystalline region in the aluminum fluoride layer, and the aluminum fluoride layer consists only of a second crystalline region. The corrosion-resistant member of Comparative Example 2 obtained was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0056] 〔Comparative Example 3〕 A corrosion-resistant member was manufactured and evaluated in the same manner as in Comparative Example 1, except that the metal constituting the substrate was aluminum alloy A6061 containing 1.02% by mass of magnesium. The results are shown in Table 1. 〔Comparative Example 4〕 A corrosion-resistant member was manufactured and evaluated in the same manner as in Comparative Example 2, except that the metal constituting the substrate was aluminum alloy A6061 containing 1.02% by mass of magnesium. The results are shown in Table 1.

[0057] As can be seen from Table 1, in the corrosion-resistant members of Examples 1 to 6, almost no peeling of the corrosion-resistant coating occurred even when they were subjected to the heat history by the heating test. On the other hand, in the corrosion-resistant members of Comparative Examples 2 and 4 that do not have the first crystalline region in the aluminum fluoride layer, peeling of the corrosion-resistant coating occurred due to the heating test that repeated heating and cooling. Further, in the corrosion-resistant members of Comparative Examples 1 and 3 that do not have the first crystalline region in the aluminum fluoride layer and also do not have the magnesium fluoride layer, peeling of the corrosion-resistant coating occurred due to the heating test that repeated heating and cooling, and the degree of peeling was larger than that of the corrosion-resistant members of Comparative Examples 2 and 4.

Explanation of Signs

[0058] 10 ··· Base material 30 ··· Corrosion-resistant coating 31 ··· Magnesium fluoride layer 32 ··· Aluminum fluoride layer 32A ··· First crystalline region 32B ··· Second crystalline region

Claims

1. A corrosion-resistant member comprising a metal substrate and a corrosion-resistant film formed on the surface of the substrate, wherein the corrosion-resistant film is a laminate of a magnesium fluoride layer containing magnesium fluoride and an aluminum fluoride layer containing aluminum fluoride, in that order from the substrate side, the aluminum fluoride layer has a first crystalline region and a second crystalline region in which the contained aluminum fluoride is crystalline, the first crystalline region is a region where a row of diffraction spots having regularity is observed in an electron diffraction image obtained by irradiating an electron beam having a beam diameter of 10 nm or more and 20 nm or less, a plurality of rows of diffraction spots are arranged so as to form a point-symmetric figure with the diffraction spot located at the center of the electron diffraction image as the point-symmetric center, and the electron diffraction image of the first crystalline region is constituted, and the row of diffraction spots is a row in which three or more diffraction spots are arranged linearly at equal intervals, and the row of diffraction spots constituting the electron diffraction image of the first crystalline region is the row of diffraction spots having the regularity, the second crystalline region is a region where a plurality of diffraction spots are observed in an electron diffraction image obtained by irradiating the electron beam, but the row of diffraction spots having the regularity is not observed. A corrosion-resistant member.

2. The corrosion-resistant member according to claim 1, wherein the first crystalline region is arranged adjacent to the magnesium fluoride layer.

3. The corrosion-resistant member according to claim 1 or claim 2, wherein the metal substrate is made of aluminum or an aluminum alloy.

4. The corrosion-resistant member according to any one of claims 1 to 3, wherein the thickness of the magnesium fluoride layer is 0.1 µm or more and 20 µm or less.

5. The corrosion-resistant member according to any one of claims 1 to 4, wherein the thickness of the aluminum fluoride layer is 0.2 µm or more and 50 µm or less.

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