Coating Method

Abstract

The film forming method of the present invention comprises: a first step of coating a first solution containing polysilazane on the surface (2a) of a metal substrate (2) and heating the first solution to form a first film (1) on the surface (2a) of the metal substrate (2); and a second step of coating a second solution containing polysilazane on the surface (1a) of the first film (1) and heating the solution at a temperature lower than the heating temperature of the first step to form a second film (3) on the surface (1a) of the first film (1), wherein the density of the first film is less than 2.00 g / cm3 and the density of the second film is greater than 2.00 g / cm3.

Description

Technical Field

[0001] The present invention relates to a method for forming a film having corrosion resistance. Background Art

[0002] Some structural members of semiconductor or flat panel display manufacturing equipment or equipment based on these equipment are exposed to corrosive gas or plasma of corrosive gas.

[0003] These structural members are usually formed using metal materials such as aluminum alloys or stainless steel, but metal materials such as aluminum alloys or stainless steel have low corrosion resistance to halogen-based corrosive gases or plasmas of these gases. Therefore, in order to impart corrosion resistance to these members, for example, a silica-based film using perhydropolysilazane is sometimes used for coating. The silica-based film is very dense and has high corrosion resistance to halogen-based corrosive gases or plasmas. Therefore, by forming a silica-based film on the surface of the structural member, the surface of the structural member can be shielded from the external environment, thereby suppressing the corrosion of the structural member.

[0004] In addition, the silica film formed using perhydropolysilazane is dense but fragile, and its linear expansion coefficient is extremely small compared to that of metal materials. Therefore, cracks are generated in the film during the film formation process, and in order to suppress the generation of the cracks, the film is formed into a thin film and cannot fully cover the structural member, which reduces the effect of shielding the structural member from the external environment, thereby reducing the anti-corrosion effect of the structural member.

[0005] To address such a problem, Patent Document 1 discloses forming a silica-based film using a solution containing perhydropolysilazane and polyorganosilazane.

[0006] In Patent Document 1, polyorganosilazane is contained in the solution to form a film more flexible than a silica-based film formed using only perhydropolysilazane, thereby preventing cracks from occurring in the film (for example, refer to Patent Document 1).

[0007] [Prior art literature]

[0008] [Patent Document]

[0009] Patent Document 1: Japanese Patent Application Publication No. 2002-105676 Summary of the invention

[0010] [Problems to be solved by the invention]

[0011] In Reference 1, since the heat treatment temperature after the solution is applied is set to a relatively low temperature (about 300°C), the film contains unconverted materials in addition to the silicon dioxide obtained by silicon dioxide conversion. The inclusion of unconverted materials in the film contributes to the flexibility of the film, but reduces the density of the film, so a sufficiently dense silicon dioxide-based film cannot be obtained. In addition, since the heat treatment temperature is 300°C, it is difficult to obtain a film with sufficient corrosion resistance for raw materials with a large linear expansion coefficient, especially aluminum alloys.

[0012] Thus, in the silica-based film described in Citation 1, although cracks generated in the film can be prevented, a sufficiently dense film cannot be obtained, and thus the corrosion resistance may be poor.

[0013] [Technical means to solve the problem]

[0014] (1) The film forming method of the present invention comprises:

[0015] In a first step, a first solution containing polysilazane is applied to a surface of a metal substrate, and the first solution is heated to form a first film on the surface of the metal substrate; and

[0016] In a second step, a second solution containing polysilazane is applied to the surface of the first film, and the second solution is heated at a temperature lower than the heating temperature in the first step to form a second film on the surface of the first film.

[0017] The density of the first film is less than 2.00 g / cm3,

[0018] The density of the second film is 2.00 g / cm3 or more.

[0019] According to the film forming method of the structure, the density of the second film is 2.00 g / cm3 or more, and the second film is obtained as a dense film in which silicon dioxide is fully converted. On the other hand, the density of the first film is less than 2.00 g / cm3, and the first film contains unconverted materials in addition to silicon dioxide. By including unconverted materials in the first film, the first film can be given flexibility.

[0020] Furthermore, in the second step, since heating is performed at a temperature lower than the heating temperature in the first step, the first film is not heated at a temperature higher than that in the first step due to heating in the second step.

[0021] This can suppress the conversion of the unconverted product of the first film into silicon dioxide due to heating of the first film and the densification of the first film accompanying this, thereby maintaining the flexibility of the first film.

[0022] In this way, since the second film is formed on the surface of the flexible first film, even if the second film is formed into a sufficiently dense film, the stress acting on the second film due to the difference in linear expansion coefficient between the second film and the metal substrate can be alleviated, thereby preventing cracks from occurring on the surface of the second film.

[0023] As a result, a decrease in the anticorrosion effect due to cracks can be prevented, and a sufficiently dense film can be obtained, thereby forming a film having high corrosion resistance.

[0024] (2) In the above film forming method, the second solution preferably contains at least one of an organic metal, a metal compound, and an amine compound.

[0025] Organic metals, metal compounds, and amine compounds are catalysts for lowering the silica conversion temperature of polysilazane. By containing these in the first solution and the second solution, the silica conversion temperature of polysilazane can be lowered, and silica conversion can be performed even at a lower temperature.

[0026] (3) The silica film formed using a solution containing polyorganosilazane contains organic silica having an organic component such as methyl group. When such a silica film containing organic silica is exposed to a halogen gas, the organic portion is selectively corroded, and the corrosion resistance may be poor.

[0027] Therefore, in the above-mentioned film forming method, the polysilazane contained in the second solution is preferably perhydropolysilazane.

[0028] More preferably, both the polysilazane contained in the first solution and the polysilazane contained in the second solution are perhydropolysilazane.

[0029] In this case, compared with the case of polysilazane having an organic group such as polyorganosilazane, a dense film can be obtained, and a film having higher corrosion resistance can be formed.

[0030] (4) In the above film forming method, the first film and the second film each preferably have a film thickness of 0.01 μm or more and 10.0 μm or less, and more preferably 0.05 μm or more and 5.0 μm or less.

[0031] When the thickness of the first film is less than 0.05 μm, the stress acting on the second film may not be sufficiently relieved. When the thickness of the first film exceeds 5.0 μm, the entire film formed by combining the first film and the second film may be fragile. By making the thickness of the first film greater than 0.05 μm and less than 5.0 μm, a film that can appropriately relieve the stress acting on the second film can be obtained.

[0032] Furthermore, when the film thickness of the second film is less than 0.05 μm, there is a possibility that the surface of the first film cannot be sufficiently shielded from the external environment.

[0033] When the film thickness of the second film exceeds 5.0 μm, the film may peel off, break or the like due to the internal stress of the second film itself.

[0034] By setting the film thickness of the second film to be 0.05 μm or more and 5.0 μm or less, it is possible to obtain a film that can appropriately shield the surface of the metal substrate from the external environment.

[0035] (5) In the above-mentioned film forming method, the first step may be performed by repeatedly applying the first solution on the metal substrate and heating the first solution a predetermined number of times to form the first film.

[0036] In this case, the first film can be thickened and can sufficiently cover the surface of the metal substrate.

[0037] (6) In the film forming method, the second step may be performed by repeatedly applying the second solution on the first film and heating the second solution at a temperature lower than the heating temperature of the first step a predetermined number of times to form the second film.

[0038] In this case, the surface of the flexible first film, which has not been sufficiently converted into silicon dioxide, can be fully covered with the second film.

[0039] [Effects of the Invention]

[0040] According to the present invention, a film having high corrosion resistance can be formed. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a partial cross-sectional view of the metal substrate and the film after the second film is formed in the second step.

[0042] Figure 2 This is an electron microscope photograph of a cross section of a film of a comparative example.

[0043] Figure 3 This is an electron microscope photograph of a cross section of the film of Example 1.

[0044] Figure 4 This is an electron microscope photograph of a cross section of the film of Example 2.

[0045] Figure 5 This is an electron microscope photograph of a cross section of the film of Example 3.

[0046] Explanation of symbols

[0047] 1: First skin film

[0048] 1a: Surface

[0049] 2: Metal substrate

[0050] 2a: Surface

[0051] 3: Second membrane DETAILED DESCRIPTION

[0052] Hereinafter, a film forming method according to an embodiment of the present invention will be described.

[0053] The film forming method of the present embodiment is a method for forming a silica-based film using polysilazane.

[0054] The silicon dioxide-based film obtained by this embodiment is formed on structural components such as chambers or piping exposed to halogen-based corrosive gases or corrosive gas plasma in an etching device or a film forming device such as chemical vapor deposition (CVD) or physical vapor deposition (PVD) used in the manufacture of semiconductors or flat panel displays.

[0055] The film forming method of this embodiment includes: a first step of applying a first solution containing polysilazane on the surface of a metal substrate and heating the first solution to form a first film on the surface of the metal substrate; and a second step of applying a second solution containing polysilazane on the surface of the first film and heating it at a temperature lower than the heating temperature of the first step to form a second film on the surface of the first film. In addition, the density of the first film is less than 2.00 g / cm 3 The density of the second film is 2.00 g / cm 3 above.

[0056] Hereinafter, each step will be described.

[0057] (1) Regarding the first step

[0058] (1-1) Application of the first solution

[0059] In the first step, as described above, the first solution is applied to the surface of the metal substrate.

[0060] The first solution is a polysilazane-containing solution obtained by dissolving polysilazane in an organic solvent.

[0061] As the polysilazane, as the chain polysilazane, perhydropolysilazane, polymethylhydrosilazane, poly(N-methylsilazane), polyN-(triethylsilyl)allylsilazane, polyN-(dimethylamino)cyclohexylsilazane, phenylpolysilazane, etc. can be used. Among these, perhydropolysilazane having an average molecular weight of 300 to 5000 is particularly preferred.

[0062] Examples of the organic solvent include ethers (ethyl ether, isopropyl ether, ethyl butyl ether, dibutyl ether, 1,2-dioxyethane, dioxane, dimethyldioxane, tetrahydrofuran, tetrahydropyran, etc.), or hydrocarbons (pentane, hexane, isohexane, methylpentane, heptane, isoheptane, octane, isooctane, cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, benzene, toluene, xylene, ethylbenzene, etc.). One or a mixture of two or more of these ethers and hydrocarbons may be used as the organic solvent.

[0063] The concentration of polysilazane in the first solution is preferably 0.05% by mass or more and 40% by mass or less. If the concentration of polysilazane is less than 0.05% by mass, it is possible that the first film of sufficient film thickness cannot be obtained. If the concentration of polysilazane exceeds 40% by mass, the viscosity of the first solution becomes high, and the thickness of the first film is likely to become uneven. The concentration of polysilazane in the first solution is more preferably 1% by mass or more and 25% by mass or less.

[0064] The first solution may contain a catalyst in addition to the polysilazane. The catalyst has the effect of relatively lowering the temperature at which the polysilazane is converted into silicon dioxide, or accelerating the speed of silicon dioxide conversion.

[0065] Examples of the catalyst include metal catalysts (organic metals or metal compounds) and amine catalysts (amine compounds).

[0066] Examples of the metal catalyst include organic metals or metal compounds containing at least one metal selected from nickel, titanium, platinum, rhodium, cobalt, iron, ruthenium, osmium, palladium, iridium, and aluminum. Metal carboxylates are particularly preferred in terms of solubility, stability, and reactivity in a polysilazane-containing solution.

[0067] Examples of the amine catalyst include amine compounds such as monoamines, diamines, triamines, tetraamines, hydroxy compounds containing chain amine residues, and hydroxy compounds containing cyclic amine residues.

[0068] Furthermore, the hydroxy compound containing an amine residue reacts with polysilazane to be modified into polysilazane containing an amine residue.

[0069] In the case where the first solution contains a catalyst (at least one of an organic metal, a metal compound, and an amine compound), the weight ratio of the catalyst (total amount) relative to polysilazane is preferably 0.0001 or more and 1 or less. If the weight ratio of the catalyst relative to polysilazane is less than 0.0001, it is possible that the effect as a catalyst cannot be fully obtained. If the weight ratio of the catalyst relative to polysilazane exceeds 1, the thickening (gelation) of the first solution becomes significant, and the film thickness of the first film is likely to become uneven. The weight ratio of the catalyst relative to polysilazane is more preferably 0.001 or more and 0.2 or less. By making the weight ratio of the catalyst relative to polysilazane less than 0.2, the thickening of the first solution can be effectively suppressed.

[0070] Here, the conditions for converting the polysilazane contained in the first solution and the second solution into silicon dioxide (silicon dioxide conversion conditions) include parameters such as heating temperature, heating time, heating environment, the presence or absence of the catalyst, or the type of the catalyst.

[0071] The heating temperature (silica conversion temperature) is determined based on other parameters included in the silica conversion conditions, that is, the presence or absence of the catalyst, the type of the catalyst, the heating time, and the heating environment.

[0072] In addition, in the following description, the silica conversion condition of the polysilazane in the first solution is also referred to as the first silica conversion condition, and the silica conversion temperature of the polysilazane in the first solution is also referred to as the first silica conversion temperature. In addition, the silica conversion condition of the polysilazane in the second solution is also referred to as the second silica conversion condition, and the silica conversion temperature of the polysilazane in the second solution is also referred to as the second silica conversion temperature.

[0073] When the first solution does not contain a catalyst, the first silica conversion temperature is, for example, 300°C to 550°C.

[0074] When the first solution contains a metal catalyst, the first silica conversion temperature is, for example, 120°C to 350°C.

[0075] When the first solution contains an amine-based catalyst, the first silica conversion temperature is, for example, room temperature to 250°C.

[0076] The first silica conversion conditions including the first silica conversion temperature can be obtained by measuring the first solution by the following method.

[0077] The first silicon dioxide conversion conditions are measured by forming a film using the first solution on a silicon wafer.

[0078] First, measure the weight of the silicon wafer using an electronic balance or the like. After coating the first solution on the silicon wafer by spin coating, heat it in the atmosphere at a specified heating temperature and for a specified heating time to form a silica-based film, and then measure the weight of the silicon wafer with the silica-based film formed thereon. Next, find the difference in weight of the silicon wafer before and after the formation of the silica-based film, and use this value as the film weight. Then, measure the film thickness using a known method. Preferably, measure it from the film cross-section using a field emission-scanning electron microscope (FE-SEM) device or the like to obtain a more accurate film thickness. Using the obtained film weight and film thickness, calculate the film density according to the following formula.

[0079] In this method, set multiple combinations of heating temperature and heating time, and find the film density for each combination. In each combination, use the combination with a film density of 2.0 g / cm 3 or more as the first silica conversion condition.

[0080] Film density [g / cm 3 =

[0081] Film weight [g] / (Film thickness [μm] × Silicon wafer surface area [cm 2 × 0.0001)

[0082] The silica-based film obtained by heating polysilazane under conditions that do not satisfy the silica conversion conditions (heating at a temperature lower than the silica conversion temperature or for a heating time shorter than the silica conversion conditions) contains unreacted substances and thus is not a dense silica film. The unreacted substances are intermediate substances in the conversion of polysilazane to silica.

[0083] The silica-based film obtained by heating the first solution under the first silica conversion conditions does not contain unreacted substances. That is, the first silica conversion conditions represent the heating conditions for completely converting polysilazane containing the first solution into silica, and a sufficiently dense silica film can be obtained.

[0084] As the metal substrate for coating the first solution, as described above, an etching device, or a chamber or pipe of a film-forming device can be cited. These chambers or pipes are formed of stainless steel or aluminum alloy.

[0085] The surface of the metal substrate formed of stainless steel or aluminum alloy is cleaned and degreased. After that, the first solution is coated on the surface of the metal substrate.

[0086] In addition, as a pretreatment before applying the first solution, the surface of the metal substrate may be modified by a known method such as irradiation with an ultraviolet (UV) lamp, an excimer lamp, or plasma.

[0087] The first solution is applied by a known coating method such as spin coating, roll coating, flow coating, spray coating, or dip coating.

[0088] (1-2) Formation of the first film

[0089] Furthermore, in the first step, the first solution applied to the metal substrate is heated in the atmosphere or in an environment containing water vapor, so that a portion of the polysilazane contained in the first solution is converted into silicon dioxide to form a first film. The first film is a silicon dioxide-based film (inorganic siliceous film) obtained by converting a portion of the polysilazane contained in the first solution into silicon dioxide. The first solution applied to the metal substrate is heated under conditions that do not meet the prescribed first silicon dioxide conversion conditions.

[0090] The heating temperature in the first step is set to a temperature lower than the first silica conversion temperature under the specified first silica conversion conditions. For example, when the specified first silica conversion conditions are a heating time of 1 hour and a first silica conversion temperature T (T is a certain value), when the heating time of the first step is set to 1 hour, the heating temperature of the first step is set to a temperature lower than the first silica conversion temperature T.

[0091] The first film obtained by heating the polysilazane in the first solution contains unconverted substances in addition to silicon dioxide.

[0092] When the heating temperature in the first step is equal to or higher than the first silica conversion temperature, the silica conversion of the polysilazane in the first solution proceeds sufficiently, resulting in the first film becoming dense and failing to ensure flexibility.

[0093] By setting the heating temperature in the second step to a temperature lower than the first silica conversion temperature, the progress of the silica conversion of the polysilazane in the first solution can be suppressed, so that the amount of unconverted matter contained in the first film can be maintained relatively large. Thus, the proportion of unconverted matter in the first film can be appropriately maintained, and as a result, the densification of the first film is suppressed, and the first film can be given flexibility.

[0094] In addition, the density of the first film is less than 2.00 g / cm 3 This means that the first film contains unconverted substances and the conversion to silicon dioxide is not complete.

[0095] In addition, the heating temperature in the first step is preferably above the boiling point of the organic solvent. The heating based on the first step is performed for the following purposes: reacting a portion of the polysilazane of the first solution to perform silicon dioxide conversion, and removing the organic solvent of the first solution. Therefore, when the heating temperature in the first step is less than the boiling point of the organic solvent, it is possible that the organic solvent of the first solution cannot be effectively removed. By making the heating temperature in the first step above the boiling point of the organic solvent, the organic solvent of the first solution can be effectively removed.

[0096] The heating time in the first step needs to be set to: while suppressing the insufficient silicon dioxide conversion of the polysilazane in the first solution, it is allowed to react to a certain extent and form a film on the metal substrate, for example, preferably more than 0.5 hours and within 5 hours. If it is shorter than 0.5 hours, the reaction of the perhydropolysilazane in the first solution is insufficient, and the adhesion between the metal substrate and the first film may be insufficient. If it exceeds 5 hours, the silicon dioxide conversion of the polysilazane is excessively carried out, and the softness of the first film may not be ensured.

[0097] In addition, the first step can form the first film by repeatedly performing the step of applying the first solution and the step of heating the first solution a predetermined number of times.

[0098] In this case, the first film can be thickened and can sufficiently cover the surface of the metal substrate.

[0099] (2) Regarding the second step

[0100] (2-1) Application of the Second Solution

[0101] In the second step, the second solution is applied to the surface of the first film.

[0102] The second solution is a polysilazane-containing solution obtained by dissolving polysilazane in an organic solvent.

[0103] As the polysilazane, as the chain polysilazane, perhydropolysilazane, polymethylhydrosilazane, poly(N-methylsilazane), polyN-(triethylsilyl)allylsilazane, polyN-(dimethylamino)cyclohexylsilazane, phenylpolysilazane, etc. can be used. Among these, perhydropolysilazane having an average molecular weight of 300 to 5000 is particularly preferred.

[0104] As the organic solvent, the same type of organic solvent as the first solution can be used, and specific examples thereof include ethers (ethyl ether, isopropyl ether, ethyl butyl ether, dibutyl ether, 1,2-dioxyethane, dioxane, dimethyldioxane, tetrahydrofuran, tetrahydropyran, etc.), or hydrocarbons (pentane, hexane, isohexane, methylpentane, heptane, isoheptane, octane, isooctane, cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, benzene, toluene, xylene, ethylbenzene, etc.). One or a mixture of two or more of these ethers and hydrocarbons can also be used as the organic solvent.

[0105] The concentration of polysilazane in the second solution is preferably 0.05% by mass or more and 40% by mass or less. If the concentration of polysilazane is less than 0.05% by mass, it is possible that the second film of the required minimum thickness cannot be obtained. If the concentration of polysilazane exceeds 40% by mass, the viscosity of the second solution becomes high, and the thickness of the second film is likely to become uneven. The concentration of polysilazane is more preferably 1% by mass or more and 25% by mass or less.

[0106] The second solution preferably contains a catalyst in addition to polysilazane. When the second solution contains a catalyst, it is easy to set the heating temperature in the second step to a temperature lower than the heating temperature of the silica conversion condition in the first step.

[0107] As the catalyst, the same type of catalyst as that of the first solution can be used, and examples thereof include metal catalysts (organic metals or metal compounds) and amine catalysts (amine compounds).

[0108] Examples of the metal catalyst include organic metals or metal compounds containing at least one metal selected from nickel, titanium, platinum, rhodium, cobalt, iron, ruthenium, osmium, palladium, iridium, and aluminum. In terms of solubility, stability, and reactivity in a solution containing polysilazane, metal carboxylates are particularly preferred.

[0109] Examples of the amine catalyst include amine compounds such as monoamines, diamines, triamines, tetraamines, hydroxy compounds containing chain amine residues, and hydroxy compounds containing cyclic amine residues.

[0110] In the case where the second solution contains a catalyst (at least one of an organic metal, a metal compound, and an amine compound), the weight ratio of the catalyst (total amount) relative to polysilazane is preferably 0.0001 or more and 1 or less. If the weight ratio of the catalyst relative to polysilazane is less than 0.0001, it is possible that the effect as a catalyst cannot be fully obtained. If the weight ratio of the catalyst relative to polysilazane exceeds 1, the thickening (gelation) of the second solution becomes significant, and the film thickness may become uneven. The weight ratio of the catalyst relative to polysilazane is more preferably 0.001 or more and 0.2 or less. By making the weight ratio of the catalyst relative to polysilazane less than 0.2, the thickening of the second solution can be effectively suppressed.

[0111] When the second solution does not contain a catalyst, the second silica conversion temperature is, for example, 300°C to 550°C.

[0112] When the second solution contains a metal catalyst, the second silica conversion temperature is, for example, 120°C to 350°C.

[0113] When the second solution contains an amine-based catalyst, the second silica conversion temperature is, for example, room temperature to 250°C.

[0114] The silica conversion conditions including the second silica conversion temperature can be obtained by measuring the second solution in the same manner as the method for measuring the first silica conversion conditions.

[0115] In the present embodiment, the second silica conversion condition is a condition including a second silica conversion temperature having a value lower than the first silica conversion temperature included in the predetermined first silica conversion condition.

[0116] The second solution is applied by a known coating method such as spin coating, roll coating, flow coating, spray coating, or dip coating.

[0117] (2-2) Formation of the Second Film

[0118] Furthermore, in the second step, the second solution applied on the surface of the first film is heated in the air or in an environment containing water vapor to convert the polysilazane contained in the second solution into silicon dioxide, thereby forming a second film. The second film is a silicon dioxide-based film (inorganic siliceous film) obtained by converting the polysilazane contained in the second solution into silicon dioxide.

[0119] The heating temperature in the second step is set to a temperature lower than the heating temperature in the first step and equal to or higher than the second silica conversion temperature.

[0120] If the heating temperature is equal to or higher than the heating temperature of the first step, the conversion of the unconverted product of the first film to silicon dioxide and the accompanying densification of the first film proceed, thereby impairing the flexibility of the first film.

[0121] On the other hand, if the heating temperature is lower than the second silica conversion temperature, the silica conversion of the polysilazane contained in the second solution may not proceed sufficiently.

[0122] By setting the heating temperature to a temperature equal to or higher than the second silica conversion temperature, the progress of silica conversion of the polysilazane contained in the second solution is promoted. As a result, the second film can be formed to be denser than the first film.

[0123] In addition, the density of the second film is 2.00 g / cm 3 This means that the second film is sufficiently converted into silicon dioxide.

[0124] Regarding the heating time in the second step, as long as the second solution on the first film is sufficiently heated and the polysilazane in the second solution is converted into silicon dioxide, it is preferably 0.5 hours or more and within 10 hours. If it is shorter than 0.5 hours, the silicon dioxide conversion of the polysilazane in the second solution may become insufficient. If it exceeds 10 hours, it takes time unnecessarily, resulting in increased costs.

[0125] In the second step, the second film may be formed by repeating the step of applying the second solution and the step of heating the second solution at a temperature lower than the heating temperature in the first step a predetermined number of times.

[0126] In this case, the surface of the flexible first film, which has not been sufficiently converted into silicon dioxide, can be fully covered with the second film.

[0127] Figure 1 This is a partial cross-sectional view of the metal substrate and the film after the second film is formed in the second step.

[0128] Figure 1 In the embodiment, the first film 1 is formed on the surface 2 a of the metal substrate 2 .

[0129] In addition, the second film 3 is formed on the surface 1 a of the first film 1 .

[0130] The first film 1 is formed by converting a part of the polysilazane in the first solution into silicon dioxide, and is mainly composed of silicon dioxide.

[0131] As described above, since the first film 1 contains an appropriate amount of unconverted materials, densification of the first film is suppressed, and the first film has flexibility.

[0132] In addition, as described above, the second film 3 is formed as a dense film in which polysilazane is sufficiently converted into silicon dioxide.

[0133] If the second film 3 is substantially composed of silicon dioxide, the linear expansion coefficient of the second film is an intermediate value between inorganic silicon dioxide glass and quartz, which is 0.6 to 6 (×10 -6 / ℃) approximately.

[0134] On the other hand, the metal substrate 2 is made of stainless steel or aluminum alloy. For example, Japanese Industrial Standards (JIS) SUS316L, which is stainless steel, has a thickness of 16.0 (×10 -6 / ℃), JISA6061 as aluminum alloy is 23.6 (×10 -6 / ℃).

[0135] As described above, the linear expansion coefficient of the second film 3 is extremely small compared to the metal base material 2 , and it is considered that a large stress acts on the second film 3 due to the difference in linear expansion coefficient between the second film 3 and the metal base material 2 .

[0136] On the other hand, in the present embodiment, the second film 3 is formed on the surface of the first film 1 having flexibility.

[0137] The density of the second film 3 is 2.00 g / cm 3 As described above, the second film is obtained as a dense film in which the silica conversion is sufficiently advanced. On the other hand, the density of the first film 1 is less than 2.00 g / cm 3 The first film 1 contains unconverted matter in addition to silicon dioxide. By containing unconverted matter in the first film 1, flexibility can be imparted to the first film.

[0138] Furthermore, in the second step, since heating is performed at a temperature lower than the heating temperature in the first step, the first film 1 is not heated at a temperature higher than that in the first step due to heating in the second step.

[0139] This can suppress the conversion of unconverted materials of the first film 1 into silicon dioxide due to heating of the first film 1 and the densification of the first film 1 accompanying this, thereby maintaining the flexibility of the first film 1 .

[0140] In this way, since the second film 3 is formed on the surface of the first film 1 having flexibility, even if the second film 3 is formed into a sufficiently dense film, the stress acting on the second film 3 due to the difference in linear expansion coefficient with the metal substrate 2 can be alleviated, thereby preventing the generation of cracks in the second film 3.

[0141] As a result, a sufficiently dense film can be obtained, and a film having high corrosion resistance can be formed.

[0142] In the first step and the second step, from the perspective of easily setting the second silica conversion temperature to be lower than the first silica conversion temperature, it is preferred, for example, to use a solution that does not contain a catalyst (organic metal, metal compound, and amine compound) in the first solution and to use a solution that contains a catalyst (organic metal, metal compound, and amine compound) in the second solution.

[0143] Furthermore, as the polysilazane contained in the second solution, perhydropolysilazane is particularly preferred.

[0144] In this case, compared with the case of polysilazane containing an organic group such as polyorganosilazane, a dense film can be obtained, and a second film having higher corrosion resistance can be obtained.

[0145] In the above embodiment, the first film preferably has a thickness of 0.01 μm or more and 10.0 μm or less.

[0146] When the film thickness of the first film is less than 0.01 μm, there is a possibility that the stress acting on the second film cannot be sufficiently relaxed.

[0147] When the film thickness of the first film exceeds 10.0 μm, the entire film including the first film and the second film may become fragile.

[0148] By setting the film thickness of the first film to be 0.01 μm or more and 10.0 μm or less, it is possible to obtain a film that can appropriately relax the stress acting on the second film.

[0149] The thickness of the first film is more preferably 0.05 μm or more and 5.0 μm or less.

[0150] In the above embodiment, the second film preferably has a thickness of 0.05 μm or more and 10.0 μm or less.

[0151] When the film thickness of the second film is less than 0.01 μm, there is a possibility that the surface of the first film cannot be sufficiently shielded from the external environment.

[0152] When the film thickness of the second film exceeds 10.0 μm, the film may peel off, break, or the like due to the internal stress of the second film itself.

[0153] By setting the film thickness of the second film to be 0.01 μm or more and 10.0 μm or less, it is possible to obtain a film that can appropriately shield the surface of the metal substrate from the external environment.

[0154] The thickness of the second film is more preferably 0.05 μm or more and 5.0 μm or less.

[0155] [Example]

[0156] Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

[0157] (Example 1)

[0158] As the first solution, a solution prepared by mixing a catalyst-free dibutyl ether solution containing 20% ​​by mass of perhydropolysilazane (trade name: Durazane 2200, manufactured by Merck Performance Materials) to obtain a solution containing 10% by mass of perhydropolysilazane was used.

[0159] The first silica conversion conditions in the first solution were determined to be 400° C. using the values ​​obtained by the above-described measurement method, with a heating time of 1 hour and a first silica conversion temperature of 400° C.

[0160] As the second solution, a dibutyl ether solution (manufactured by Merck Performance Materials, trade name Durazane 2400) containing a metal catalyst (palladium) and having a perhydropolysilazane content of 20 mass % was used.

[0161] The second silica conversion conditions in the second solution were determined using the values ​​obtained by the above-described measurement method, with a heating time of 1 hour and a second silica conversion temperature of 150°C.

[0162] As a metal substrate, a plate material of stainless steel (JIS SUS316L) having a size of 50 mm×50 mm and a thickness of 5 mm was prepared.

[0163] The surface of the metal substrate is degreased and cleaned, the first solution is applied by spin coating, and the surface is heated for 1 hour at 250° C., which is 150° C. lower than the first silica conversion temperature included in the first silica conversion conditions. Thus, a first film including unconverted substances is formed on the surface of the metal substrate.

[0164] Then, the second solution was applied to the surface of the first film by spin coating, and heated at the second silicon dioxide conversion temperature, i.e., 150° C., for 1 hour. Thus, the second film was formed on the surface of the first film, thereby obtaining a test piece having the first film (film thickness 0.7 μm to 0.8 μm) and the second film (film thickness 1.5 μm to 1.6 μm) formed on the metal substrate.

[0165] In addition, the density of the first film at this time was 1.82 g / cm 3 The density of the second film is 2.14 g / cm 3 The density of these films was obtained by measuring the density of films heated under the same conditions using the above-mentioned measurement method.

[0166] (Example 2)

[0167] As the first solution, a solution prepared by mixing a catalyst-free dibutyl ether solution containing 20% ​​by mass of perhydropolysilazane (trade name: Durazane 2200, manufactured by Merck Performance Materials) to obtain a solution containing 10% by mass of perhydropolysilazane was used.

[0168] The first silica conversion conditions in the first solution were determined to be 400° C. using the values ​​obtained by the above-described measurement method, with a heating time of 1 hour and a first silica conversion temperature of 400° C.

[0169] As the second solution, a dibutyl ether solution (manufactured by Merck Performance Materials, trade name Durazane 2800) containing an amine catalyst and perhydropolysilazane at a concentration of 20 mass % was used.

[0170] The second silica conversion conditions in the second solution were determined using the values ​​obtained by the above-described measurement method, with a heating time of 1 hour and a second silica conversion temperature of 130°C.

[0171] As a metal substrate, a plate material of stainless steel (JIS SUS316L) having a size of 50 mm×50 mm and a thickness of 5 mm was prepared.

[0172] The surface of the metal substrate is degreased and cleaned, the first solution is applied by spin coating, and the surface is heated for 1 hour at 250° C., which is 150° C. lower than the first silica conversion temperature included in the first silica conversion conditions. Thus, a first film including unconverted substances is formed on the surface of the metal substrate.

[0173] Then, the second solution was applied to the surface of the first film by spin coating, and heated at the second silicon dioxide conversion temperature, i.e., 130° C., for 1 hour. Thus, the second film was formed on the surface of the first film, thereby obtaining a test piece having the first film (film thickness 0.8 μm to 0.9 μm) and the second film (film thickness 1.5 μm to 1.6 μm) formed on the metal substrate.

[0174] In addition, the density of the first film at this time was 1.82 g / cm3 The density of the second film is 2.36 g / cm 3 .

[0175] (Example 3)

[0176] As the first solution, a solution prepared by mixing a catalyst-free dibutyl ether solution containing 20% ​​by mass of perhydropolysilazane (trade name: Durazane 2200, manufactured by Merck Performance Materials) to obtain a solution containing 10% by mass of perhydropolysilazane was used.

[0177] The first silica conversion conditions in the first solution were determined to be 400° C. using the values ​​obtained by the above-described measurement method, with a heating time of 1 hour and a first silica conversion temperature of 400° C.

[0178] As the second solution, a dibutyl ether solution (manufactured by Merck Performance Materials, trade name Durazane 2400) containing a metal catalyst (palladium) and having a perhydropolysilazane content of 20 mass % was used.

[0179] The second silica conversion conditions in the second solution were determined using the values ​​obtained by the above-described measurement method, with a heating time of 1 hour and a second silica conversion temperature of 150°C.

[0180] As a metal substrate, a plate of an aluminum alloy (JIS A6061) having a size of 50 mm×50 mm and a thickness of 5 mm was prepared.

[0181] The surface of the metal substrate is degreased and cleaned, the first solution is applied by spin coating, and the surface is heated for 1 hour at 250° C., which is 150° C. lower than the first silica conversion temperature included in the first silica conversion conditions. Thus, a first film including unconverted substances is formed on the surface of the metal substrate.

[0182] Then, the second solution was applied to the surface of the first film by spin coating, and heated at the second silicon dioxide conversion temperature, i.e., 150° C., for 1 hour. Thus, the second film was formed on the surface of the first film, thereby obtaining a test piece having the first film (film thickness 1.2 μm to 1.3 μm) and the second film (film thickness 1.6 μm to 1.7 μm) formed on the metal substrate.

[0183] In addition, the density of the first film at this time was 1.82 g / cm 3 The density of the second film is 2.14 g / cm 3 .

[0184] (Comparative Example)

[0185] As the first solution, a dibutyl ether solution (manufactured by Merck Performance Materials, trade name Durazane 2400) containing a metal catalyst (palladium) and perhydropolysilazane at a concentration of 20 mass% was used. The first silica conversion conditions in the first solution were based on the manufacturer's public data, with a heating time of 1 hour and a first silica conversion temperature of 250°C.

[0186] As a metal substrate, a plate material of stainless steel (JIS SUS316L) having a size of 50 mm×50 mm and a thickness of 5 mm was prepared.

[0187] The surface of the metal substrate was degreased and cleaned, the first solution was applied by spin coating, and heated at 250° C., the first silica conversion temperature, for 1 hour. Thus, a test piece having a silica film (thickness 1.2 μm to 1.3 μm) formed on the surface of the metal substrate was obtained.

[0188] 〔Observation of membrane cross section〕

[0189] The test pieces obtained in Examples 1 to 3 and the comparative examples were cut with a high-speed cutter, and the obtained cut pieces were embedded in resin and then ion milled (IM400 manufactured by Hitachi High-tech Corporation). The film cross-section was observed using a FE-SEM device (SU8020 manufactured by Hitachi High-tech Corporation).

[0190] Figure 2 This is an electron microscope photograph of a cross section of a film of a comparative example.

[0191] In the comparative example, only the first film was formed.

[0192] like Figure 2 As shown, it can be seen that there are a plurality of cracks on the surface of the first film.

[0193] Figure 3 This is an electron microscope photograph of the cross section of the membrane of Example 1. Figure 4 This is an electron microscope photograph of the cross section of the membrane of Example 2. Figure 5 This is an electron microscope photograph of a cross section of the film of Example 3.

[0194] like Figure 3 , Figure 4 ,and Figure 5 As shown, it can be seen that in Examples 1 to 3, cracks observed in the comparative example did not occur.

[0195] As seen in the comparative example, a silica-based film obtained by converting polysilazane into silica generally generates cracks when the film thickness exceeds 1.0 μm, but in Examples 1 to 3, cracks did not occur even when the total film thickness exceeded 2.0 μm.

[0196] 〔Hydrochloric acid corrosion resistance test〕

[0197] The test pieces obtained in Examples 1, 2, 3 and Comparative Example were masked so that only the surface with the film formed was exposed. The masked test pieces were immersed in a 10% hydrochloric acid solution at room temperature for 24 hours, and the corrosion state of the surface with the film formed was observed.

[0198] The results are shown in Table 1 below.

[0199] [Table 1]

[0200] Whether there is corrosion Example 1 none Example 2 none Example 3 none Comparative Example have

[0201] As shown in Table 1, in the comparative example in which cracks occurred in the first film, corrosion was observed and partial peeling occurred, but in Examples 1 to 3, corrosion was not observed.

[0202] This shows that the second film has no cracks and can prevent a decrease in the anti-corrosion effect due to cracks.

[0203] In addition, it was found that the second film had high corrosion resistance in a hydrochloric acid solution.

Claims

1. A method for forming a film, include: In a first step, a first solution containing only perhydropolysilazane as polysilazane is applied to the surface of a metal substrate, and the first solution is heated at a temperature lower than the silicon dioxide conversion temperature of the polysilazane in the first solution to form a first film on the surface of the metal substrate; as well as In a second step, a second solution containing only perhydropolysilazane as polysilazane is applied to the surface of the first film, and the second solution is heated at a temperature lower than the heating temperature of the first step and higher than the silicon dioxide conversion temperature of the polysilazane in the second solution to form a second film on the surface of the first film. The density of the second film formed by heating at a temperature lower than the heating temperature of the first step is higher than the density of the first film, and the density of the first film is less than 2.00 g / cm 3 , The density of the second film is 2.00 g / cm 3 above.

2. The film forming method according to claim 1, wherein The second solution contains at least one of an organic metal, a metal compound, and an amine compound.

3. The film forming method according to claim 1 or 2, wherein The thickness of each of the first film and the second film is 0.01 μm or more and 10.0 μm or less.

4. The film forming method according to claim 1 or 2, wherein The first step forms the first film by repeatedly performing a step of applying the first solution on the metal substrate and a step of heating the first solution a predetermined number of times.

5. The film forming method according to claim 1 or 2, wherein The second step forms the second film by repeatedly performing a step of applying the second solution on the first film and a step of heating the second solution at a temperature lower than the heating temperature in the first step a predetermined number of times.

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