JP2008163401A - Chemical liquid for forming oxide coating film, method of forming oxide coating film using the same , layered body and method of manufacturing the same and metal oxide film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a high grade oxide coating film free from pin holes and roughened surface and having a smooth surface on the surface of a material-to-be-treated consisting essentially of a metal by anodization. <P>SOLUTION: The chemical liquid used for forming the oxide coating film on the surface of the material-to-be-treated consisting essentially of the metal by the anodization contains water and a proton-philic solvent. The proton-philic solvent is preferably an aprotic polar solvent and is more preferably a cyclic compound, particularly N-alkyl pyrrolidone. The method of forming the oxide coating film includes a step for anodization the material-to-be-treated consisting essentially of the metal in the chemical liquid. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a chemical conversion liquid for forming an oxide film by anodic oxidation on the surface of a material to be processed mainly containing a metal, and a material to be processed mainly containing a metal by anodic oxidation using the chemical conversion liquid. A method of forming an oxide film on the surface of the metal (hereinafter, the treatment for forming the oxide film may be referred to as “chemical conversion treatment”), metal oxidation formed by anodization using this chemical conversion liquid The present invention relates to a laminate having a material film and a method for producing the same, and a metal oxide film formed on the surface of a material to be treated by anodization using this chemical conversion liquid. Chemical liquid for efficiently forming a high quality oxide film having no pinholes and excellent surface smoothness, a method for forming an oxide film using the same, a laminate, a method for producing the same, and metal oxidation It relates to material films.

  The present invention can be suitably applied to a material to be processed mainly containing a valve metal such as aluminum or tantalum.

  Valve metal is a metal that has a so-called valve action (rectifying action), in which the oxide layer on the metal conducts current only in one direction and hardly conducts current in the opposite direction (metal surface technology association, metal surface technology). Handbook (Revised New Edition), p.712, (1976)), and the oxide film formed on the surface of the treated material mainly composed of valve metal is on other noble metals or transition metals. It differs in many respects compared to the oxide film to be produced, and is used for many purposes by taking advantage of its unique properties.

  For example, it is used as various electronic components or elements, particularly dielectric thin films used for capacitors and semiconductor elements, gate insulating films for thin film transistors, oxide films used for reflectors for flat displays and switching elements, and the like.

  Such oxide films used as dielectric thin films of capacitors and semiconductor elements, and gate insulating films of thin film transistors must be thin and dense, have no pinholes, and have a smooth (flat) surface. However, the oxide film obtained by chemical conversion of the material to be treated mainly of the valve metal has a feature that, in principle, pinholes cannot be formed at the time of film formation and it is dense. Therefore, it has been conventionally useful for these applications.

  Various chemical conversion liquids used for these chemical conversion treatments have been conventionally proposed. For example, in Japanese Patent Application Laid-Open No. 2000-328293, by using a chemical conversion solution in which an aromatic carboxylate is dissolved using ethylene glycol and water as a solvent, an oxide film having high insulation and high hillock resistance is shortened. Forming in time.

  However, recently, with the miniaturization of various elements, there is a demand for forming an oxide film that is denser and has higher surface smoothness than before. In addition, there is a demand for reducing the amount of non-aqueous solvent in the chemical conversion liquid and increasing the amount of water from the viewpoint of facilitating waste liquid treatment in consideration of the environment. In addition, since ethylene glycol is subject to the “Act on Understanding of the Release of Specific Chemical Substances to the Environment and Promotion of Improvement in Management (PRTR Law)”, it is preferable to avoid the use of ethylene glycol if possible.

  Furthermore, when water is included in the chemical conversion liquid, there is a problem that the film quality of the oxide film to be formed changes due to fluctuations in the amount of moisture in the liquid, and it is desired to reduce the effects of fluctuations in the amount of moisture. There is also a demand.

  Various electrical conditions for anodization in chemical conversion treatment have also been proposed.

  If the oxidation current density during anodic oxidation is increased, the growth of the oxide film is too fast and the film tends to be rough with respect to the film thickness, and an oxide film having a smooth surface may not be formed. Therefore, in order to solve this problem, a two-step anodizing process of a constant current anodizing process and a constant voltage anodizing process is generally performed. That is, first, an oxide film is formed by anodizing at a constant current until a voltage corresponding to a desired film thickness is obtained. After that, in order to repair the roughness of the formed oxide film, the voltage is kept at a constant voltage until the current is sufficiently reduced.

  However, even in such a two-step anodizing process, if the current density in the constant current anodizing process is excessively increased, or if the time of the subsequent constant voltage anodizing process is too short, the surface roughness of the oxide film to be formed is reduced. There is a problem that happens.

Japanese Patent Application Laid-Open No. 6-216389 describes that the film quality of an oxide film formed by performing anodization by alternating current containing a direct current component is improved. There is a problem that an expensive power supply is required. Japanese Patent Application Laid-Open No. 9-138420 discloses that constant current anodization is performed at a very high current density to obtain a flat film without waviness. However, even if the undulation is eliminated, fine roughness cannot be avoided, and it is difficult to apply to a reflector or an element that requires finer and higher surface smoothness.
JP 2000-328293 A JP-A-6-216389 JP-A-9-138420

  The present invention meets the above-mentioned requirements, and a chemical conversion liquid for forming a high-quality oxide film having a smooth surface free from pinholes and surface roughness by anodic oxidation on the surface of a material to be treated mainly containing metal. An object of the present invention is to provide a method for forming an oxide film using the above.

  Furthermore, it aims at providing the laminated body which consists of a to-be-processed material which has such a high quality metal oxide film and metal oxide film on the surface, and its manufacturing method.

  The present invention also provides a chemical conversion liquid that can form a high-quality film even when the amount of water is increased, and that changes in film quality due to fluctuations in the amount of water are reduced, and a method for forming an oxide film using the same. The purpose is to do. It is another object of the present invention to provide a chemical conversion liquid that can stably form such a high-quality oxide film regardless of specific electrical conditions, and a method for forming an oxide film using the same. Furthermore, it aims at providing the formation method of the chemical conversion liquid which uses the nonaqueous solvent which does not conflict with PRTR method, and can reduce the amount of the nonaqueous solvent in a chemical conversion liquid, and this. .

  As a result of intensive studies, the present inventors have found that the above problems can be solved by using a specific nonaqueous solvent as the main solvent of the chemical conversion liquid, and have reached the present invention.

  That is, the gist of the present invention is a chemical conversion liquid used for forming an oxide film on the surface of a material containing metal as a main component by anodic oxidation, comprising a water and a protic solvent, Exist.

  The protic solvent in the present invention is preferably an aprotic polar solvent, more preferably a cyclic compound, for example, a solvent having a lactam structure, and particularly preferably N-alkylpyrrolidone. Among N-alkylpyrrolidones, inexpensive N-methylpyrrolidone is most preferable. In addition, the chemical liquid for forming an oxide film of the present invention contains water. In this case, the content of water in the chemical liquid is preferably 10% by mass or more, more preferably 20% by mass or more, and still more preferably. It is 30% by mass or more, preferably less than 80% by mass, more preferably less than 60% by mass, and still more preferably less than 50% by mass.

  Another gist of the present invention resides in a method for forming an oxide film including a step of anodizing a material to be treated mainly containing a metal in the chemical conversion solution.

  Another gist of the present invention is a laminate comprising a metal oxide film on the surface of a material to be treated whose main component is a metal, wherein the metal oxide film comprises water and a protic solvent. The layered product is a film formed by anodic oxidation on the surface of the material to be treated using a chemical conversion solution containing.

  Another gist of the present invention is a method for producing a laminate having a metal oxide film on the surface of a material to be treated containing a metal as a main component, the composition comprising water and a protic solvent. The present invention resides in a method for manufacturing a laminate, which includes a step of forming a metal oxide film by anodizing the surface of the material to be processed using a liquid.

  Another gist of the present invention is a metal oxide film, which is formed by anodic oxidation on the surface of a material to be treated with a metal as a main component, using a chemical liquid containing water and a protic solvent. A metal oxide film characterized by being a film.

In the present invention, the metal includes an alloy.
Preferably, the material to be treated has a valve metal as a main component, more preferably one or more selected from the group consisting of aluminum, tantalum, titanium, niobium, zirconium and hafnium, more preferably aluminum and / Or tantalum as a main component, particularly preferably aluminum as a main component.

  In the present invention, the material to be treated containing a metal as a main component means that an element contained in the largest mass in the material to be treated is a metal. Preferably, the metal is contained in an amount of 50% by mass to 100% by mass. The to-be-processed material which has a valve metal as a main component means that the element contained in mass most in a to-be-processed material is a valve metal. Preferably, the total amount of the valve metal in the material to be processed (the total amount when a plurality of valve metals are included) is 50% by mass or more and 100% by mass or less. When importance is attached to the properties as a valve metal, the material to be treated contains the valve metal in a total amount of 85% by mass to 100% by mass.

  According to the chemical liquid for forming an oxide film and the method for forming an oxide film using the same according to the present invention, there is an advantage that a high quality oxide film having no pinholes or surface roughness and having high surface smoothness can be obtained. The present invention can be suitably used for forming almost all dense and smooth oxide films such as thin film transistors, ceramic capacitors, MIM diodes, and MIM field emission devices.

  Further, according to the chemical liquid for forming an oxide film of the present invention and the method of forming an oxide film using the same, it is possible to obtain a high-quality oxide film without adopting conventional control of electrical conditions. Therefore, there is no need to use an expensive special device, and there is an advantage that the cost can be reduced.

  Further, according to the chemical liquid for forming an oxide film and the method for forming an oxide film using the same according to the present invention, a high quality film is formed even if the amount of water in the chemical liquid is increased. The amount of non-aqueous solvent in the medium can be reduced, the amount of water can be increased, and a non-aqueous solvent that does not conflict with the PRTR method can be used. Furthermore, since the change in film quality due to fluctuations in moisture content can be reduced, the liquid components can be easily controlled and the convenience is increased. It is also suitable for use in an environment where the amount of moisture tends to fluctuate.

  Furthermore, according to the present invention, there is an advantage that a laminated body in which a high-quality metal oxide film having a smooth surface with no pinholes or surface roughness is formed on a material to be treated can be obtained. A laminate made of a material to be processed on which such a high-quality metal oxide film is formed can be used for various purposes. For example, a thin film transistor, a ceramic capacitor, an MIM type diode, an MIM type field emission device, a reflection of a flat display, etc. It can be suitably used as a plate.

  In addition, according to the present invention, there is an advantage that a high-quality metal oxide film having a smooth surface without a pinhole or surface roughness can be obtained. Such a high-quality metal oxide film can be used for various applications. For example, it can be suitably used as a thin film transistor, a ceramic capacitor, an MIM type diode, an MIM type field emission device, and a reflection plate for a flat display.

  Hereinafter, preferred embodiments of a chemical conversion solution for forming an oxide film of the present invention, a method for forming an oxide film using the same, a laminate and a method for producing the same, and a metal oxide film will be described in detail.

  In the present invention, water and a parent proton are used as a chemical conversion solution used for forming an oxide film on the surface of a material to be treated mainly containing a metal, preferably a material to be treated mainly containing a valve metal, by anodization. A chemical conversion solution containing an organic solvent is used.

[Treatment materials mainly composed of metals]
As described above, the valve metal to be treated in the present invention is one in which the oxide layer on the metal conducts current only in one direction and hardly conducts current in the opposite direction. The valve metal used in the present invention is not particularly limited as long as a dense and smooth oxide film can be formed. Aluminum, tantalum, titanium, niobium, zirconium, hafnium, tungsten, molybdenum, vanadium, and silicon 1 type or 2 types or more chosen from the group which consists of can illustrate. Preferably, it is one or more selected from the group consisting of aluminum, tantalum, titanium, niobium, zirconium and hafnium, more preferably one or more selected from the group consisting of aluminum, tantalum and niobium. More preferably, it is aluminum and / or tantalum.

  Among them, aluminum anodic oxide coatings have various specificities in their geometric structure and physical, chemical and optical properties, and they can be precisely controlled by changing the anodic oxidation conditions. It is particularly preferable because it can be used for various applications utilizing the functionality of the anodic oxide film.

  The material to be treated according to the present invention may preferably be an alloy containing two or more of these valve metals as long as it contains these valve metals as a main component, or an alloy with other elements. May be. The other elements to be alloyed are not particularly limited. For example, when the valve metal is aluminum, neodymium and yttrium are preferable, and neodymium is particularly preferable. In addition, the valve metal as a main component means that the valve metal is contained in an amount of 50% by mass to 100% by mass as described above.

  In addition, the to-be-processed material made into a process target by this invention may contain materials other than a metal within the range which does not have trouble with the anodic oxidation which concerns on this invention. Here, examples of materials other than metals include, but are not limited to, silicon, carbon, boron, phosphorus, and the like.

[Chemical conversion liquid]
<Solute>
Although there is no restriction | limiting in particular as a solute anion contained in the chemical conversion liquid used for the anodic oxidation of this invention, The anion derived from aromatic carboxylic acid or hydroxycarboxylic acid is preferable.

  As the aromatic carboxylic acid, a compound having a benzene ring, a condensed benzene ring, a non-benzene aromatic ring, a heteroaromatic ring and the like and a carboxyl group can be used. Examples of aromatic carboxylic acids containing no hetero atom that can be used in the present invention include salicylic acid, phthalic acid, benzoic acid, γ-resorcinic acid, toluic acid, cumyl acid, t-butylbenzoic acid, anisic acid, 2,4 -Cresotic acid, cinnamic acid, N-methylanthranilic acid, gentisic acid, gallic acid and p-hydroxybenzoic acid. Examples of the heteroaromatic carboxylic acid include nicotinic acid, 2-furoic acid, 2-thenoic acid, and hydrazylbenzoic acid. Furthermore, an aromatic carboxylic acid having a functional group other than a carboxyl group can be used as long as the desired effect of the present invention is not impaired. For example, aromatic carboxylic acids having a nitro group or an amino group such as nitrobenzoic acid, anthranilic acid, monomethylaminobenzoic acid and dimethylaminobenzoic acid can also be used. These aromatic carboxylic acids may be used individually by 1 type, and may be used in combination of 2 or more type. Among these aromatic carboxylic acids, salicylic acid, phthalic acid, benzoic acid, and γ-resorcinic acid are preferable, and salicylic acid is particularly preferable.

  Hydroxycarboxylic acid has an optical isomer, and its type is not particularly limited, and any of L-type, D-type, and DL-type may be used. Moreover, a meso body may be sufficient. Natural or synthetic materials may be used. Specific examples of the hydroxycarboxylic acid include, for example, glycolic acid, lactic acid, α-oxy-n-butyric acid, α-oxyisobutyric acid, α-oxy-n-valeric acid, α-oxyisovaleric acid, and α-oxyacid. -Oxy-2-methylbutyric acid, α-oxyacrylic acid, β-oxyacid, hydroacrylic acid, β-oxybutyric acid, β-oxyisobutyric acid, β-oxy-n-valeric acid, β-oxyisovaleric acid, α -Ethylhydroacrylic acid, oxypivalic acid, and oxydicarboxylic acids such as tartronic acid, methyltartronic acid, ethyltartronic acid, hydroxymethylmalonic acid, malic acid, citramalic acid, α-oxy-α'-methylsuccinic acid, etc. And monohydroxycarboxylic acid such as tartaric acid and the like. Further, a C2-C5 hydroxycarboxylic acid having a functional group other than an alcoholic hydroxyl group or a carboxyl group can be used as long as the desired effect of the present invention is not impaired. These hydroxycarboxylic acids may be used alone or in combination of two or more. Of these hydroxycarboxylic acids, lactic acid, malic acid and tartaric acid are preferred.

In addition, you may include 1 or more types of aromatic carboxylic acid and 1 or more types of hydroxycarboxylic acid.
Preferably, one or more aromatic carboxylic acids are contained.

  The counter ion of the solute anion is not particularly limited. For example, ammonium ions, alkali metal ions, 1, 2, 3 and quaternary alkyl ammonium ions, phosphonium ions and sulfonium ions can be used. Among them, it is preferable to use ammonium ions or 1, 2, 3 or quaternary alkyl ammonium ions. The carbon number of the alkyl group in the case of using an alkylammonium ion can be selected in consideration of solubility in a solvent, but usually an alkyl group having 1 to 4 carbon atoms is selected.

  These solutes may be used alone or in combination of two or more. Moreover, you may use combining said solute and arbitrary arbitrary solutes other than the above.

  Particularly preferable as the solute of the chemical conversion liquid of the present invention is an ammonium salt of an aromatic carboxylic acid and / or an ammonium salt of tartaric acid, and among them, an ammonium salt of an aromatic carboxylic acid is most preferable, and ammonium salicylate is most preferable. It is.

  The concentration of these solutes in the chemical conversion solution of the present invention is not particularly limited as long as it is in a range where it is stably dissolved, but is usually 0.01% by mass or more, preferably 0.1% by mass or more, particularly preferably. It is 1 mass% or more, usually 30 mass% or less, preferably 25 mass% or less, particularly preferably 15 mass% or less. In order to increase the electrical conductivity of the chemical conversion liquid and facilitate oxidation at normal current density, it is desirable that the concentration of the solute is not too low. In order to suppress dissolution of the generated oxide film, it is desirable that the solute concentration is not too high.

<solvent>
The chemical conversion liquid of the present invention contains water and a protic solvent.
In the present invention, the solvent classification is in accordance with the Kolthoff classification (IM Kolthoff, Analytical Chemistry, 46 (13), 1992 (1974)).

Examples of the protic solvent include amphoteric solvents such as ethylenediamine, ammonia and formamide, and aprotic polar solvents such as dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, hexamethylphosphoramide, pyridine and tetrahydrofuran. The prophilic solvent is preferable because it releases an proton like a proton-donating solvent or a neutral solvent, so that it becomes an anion, and the amount taken into the oxide film increases, which causes a rough surface. This is because it is suppressed. For the same reason, the aprotic solvent is more preferable than the amphoteric solvent among the protic solvents, and among them, the aprotic polar solvent is more preferable in consideration of miscibility with water. In aprotic polar solvents, cyclic compounds that are less likely to be incorporated into the oxide film due to steric hindrance are preferred over chain compounds. From the viewpoint of safety and workability, N-methylpyrrolidone and N-ethyl are preferred. N-alkylpyrrolidones such as pyrrolidone are particularly preferred.
These protic solvents may be used alone or in combination of two or more.

  In the chemical conversion liquid of the present invention, the protophilic solvent is preferably contained in the total solvent of the chemical conversion liquid in an amount of 50% by mass or more, particularly 60% by mass or more and 80% by mass or less, particularly 70% by mass or less. . In order to form a high-quality oxide film, it is desirable that the amount of the protophilic solvent in the chemical conversion liquid is large. However, in order to increase the electrical conductivity of the chemical conversion liquid and facilitate oxidation at a normal current density, it is desirable that the amount of the prophilic solvent in the chemical conversion liquid is not too large.

The chemical conversion liquid of the present invention contains water in addition to the protic solvent.
The content of water in the chemical conversion liquid of the present invention is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 25% by mass or more, particularly preferably 30% by mass or more, and preferably 80%. It is less than mass%, more preferably less than 60 mass%, still more preferably less than 50 mass%, particularly preferably less than 40 mass%. In order to obtain high electrical conductivity, it is desirable that the chemical conversion liquid contains water to some extent. In order to form a particularly high quality oxide film, it is desirable that the amount of water in the chemical conversion liquid is not too large.

  The chemical conversion liquid of the present invention can be used by mixing a solvent other than the protic solvent and water as a sub-solvent, but it is desirable that the content is lower than both the protic solvent and water. This subsolvent may be used individually by 1 type, and may be used in combination of 2 or more type. The sub-solvent preferably contains one or more solvents selected from the group consisting of a solvent having an alcoholic hydroxyl group and an aprotic organic solvent.

  Regardless of the type of the solvent having an alcoholic hydroxyl group that can be used as a secondary solvent, both aliphatic alcohols and aromatic alcohols can be used. An aliphatic alcohol is preferred. For example, monohydric alcohols such as methanol, ethanol, propanol, and isopropanol; dihydric alcohols such as ethylene glycol and propylene glycol; trihydric or higher polyhydric alcohols, and the like. A solvent having a functional group other than an alcoholic hydroxyl group in the molecule can also be used as long as the desired effect of the present invention is not impaired. For example, a solvent having an alkoxy group such as methyl cellosolve or cellosolve can also be used.

As the aprotic solvent, a polar solvent or a nonpolar solvent may be used. Examples of polar solvents include lactone solvents such as γ-butyrolactone, γ-valerolactone, and δ-valerolactone; carbonate solvents such as ethylene carbonate, propylene carbonate, and butylene carbonate; N-methylformamide, N-ethylformamide, N, Amide solvents such as N-dimethylformamide, N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-methylpyrrolidinone; Nitrile solvents such as 3-methoxypropionitrile and glutaronitrile; Examples thereof include phosphoric ester solvents such as trimethyl phosphate and triethyl phosphate.
Moreover, as a nonpolar solvent, hexane, toluene, silicon oil, etc. can be illustrated.

[anodization]
In the present invention, the anodizing method is not particularly limited, but it is preferable to first perform a constant current anodizing step at a constant current density and then perform a constant voltage anodizing step at a constant voltage. In this case, the constant current anodizing step is usually performed by direct current, but an alternating current component or a fluctuation component may be added, and the current density may be gradually decreased or gradually increased.

  Alternatively, a method of anodizing at a low current density and then anodizing at a high current density as proposed in Japanese Patent Application Laid-Open No. 2005-320623 may be used. By using this method in combination, there is a possibility of obtaining a smooth oxide film with less surface roughness.

Current density at a constant current anodic oxidation process is not particularly limited, preferably, 5 .mu.A / cm ² or more, more preferably 50 .mu.A / cm ² or more, more preferably 0.1 mA / cm ² or more, and particularly preferably 0. 5 mA / cm ² or more, preferably less than 100 mA / cm ² , more preferably less than 50 mA / cm ² , still more preferably less than 10 mA / cm ² , and particularly preferably less than 5 mA / cm ² .

  The treatment after the constant current anodization is not particularly limited, but normally, after reaching a predetermined formation voltage (Vf) by anodization at a constant current density, the voltage is maintained for a certain period of time. Constant voltage anodic oxidation is performed. The ultimate voltage Vf at this time is not particularly limited as long as a sufficient oxide film is formed, but is usually 500 V or less, preferably 200 V or less, more preferably 150 V or less, and particularly preferably 100 V or less. Further, it is preferably 1 V or higher, more preferably 2 V or higher, particularly preferably 3 V or higher.

  The temperature at the time of such anodization is a temperature range in which the chemical conversion liquid exists stably as a liquid, and is usually −20 ° C. or higher, preferably 0 ° C. or higher, and usually 150 ° C. or lower, preferably 100 ° C. or lower.

  In the present invention, the anodic oxidation may be performed over the entire surface of the material to be processed, or may be performed only on a part thereof. When an oxide film is formed only on a part of the material to be processed, a part to be anodized can be selected in advance by photolithography using a photoresist.

  The oxide film thus obtained has no pinholes and is excellent in surface smoothness. For example, it is possible to reduce the average surface roughness (Ra) or the root mean square surface roughness (RMS) to 50 to 80% as compared with the case of using a conventional chemical conversion liquid.

  The method for obtaining the metal oxide film from the material to be treated having the metal oxide film formed as described above is not particularly limited and may be performed according to a conventional method. For example, an acid or alkali solution such as sulfuric acid or sodium hydroxide may be used. A method of dissolving and removing the material to be processed by, for example, is mentioned. For example, after pasting another metal substrate such as platinum on the metal oxide film formed on the aluminum substrate that is the material to be treated, the aluminum substrate that is the material to be treated is removed, and further the other metal substrate such as platinum. By bonding together, an unconventional laminate such as platinum / aluminum anodic oxide film / platinum can be formed (because it is impossible to form an oxide film on platinum by anodic oxidation).

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the materials, amounts used, ratios, processing contents, processing procedures, and the like shown in the following Examples are within the scope of the present invention. It can be changed as appropriate. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

(Example 1)
An Al-2 atomic% Nd thin film having a thickness of about 400 nm was deposited on an alkali-free glass substrate by sputtering. Next, this film was subjected to constant current anodization to 50 V at a current density of 0.1 mA / cm ² in an N-methylpyrrolidone solution of 1% by mass ammonium salicylate having a water content of 30% by mass, and then at a constant voltage anode at 50 V for 60 minutes. Oxidized to form an oxide film.
When the surface roughness of the obtained oxide film was measured using software attached to an SPM (Seiko Instruments Inc .: SPA-300HV) apparatus, the average surface roughness (Ra: centerline average roughness defined in JIS B0601) The three-dimensional expansion) was 0.6 nm, and the maximum height difference was 6 nm.

(Comparative Example 1)
In Example 1, an oxide film was formed in the same manner as in Example 1 except that an ethylene glycol solution of 1% by mass ammonium salicylate having a water content of 30% by mass was used.
Ra of the obtained oxide film was 1.0 nm, and the maximum height difference was 16 nm.

(Comparative Example 2)
In Example 1, an oxide film was formed in the same manner as in Example 1 except that a diethylene glycol solution of 1% by mass ammonium salicylate having a water content of 30% by mass was used.
The obtained oxide film had an Ra of 1.3 nm and a maximum height difference of 11 nm.

(Comparative Example 3)
In Example 1, an oxide film was formed in the same manner as in Example 1 except that a 1% by mass ammonium salicylate aqueous solution was used.
Ra of the obtained oxide film was 3.6 nm, and the maximum height difference was 52 nm.

The following can be understood from the above results.
As for the surface of the formed oxide film, the oxide film (Comparative Example 3) formed in a chemical conversion liquid not containing a non-aqueous solvent is the roughest. The film formed in the chemical conversion liquid containing ethylene glycol (Comparative Example 1) or in the chemical conversion liquid containing diethylene glycol (Comparative Example 2) is slightly suppressed in surface roughness, but contains the protophilic solvent according to the present invention. Compared with the oxide film formed using the chemical conversion liquid (Example 1), it is about twice as rough, and the oxide film formed using the chemical conversion liquid according to the present invention is remarkably excellent in surface smoothness. I understand.

  The chemical conversion solution and the method for forming an oxide film of the present invention are suitable for the formation of almost all oxide films that require dense and surface smoothness such as thin film transistors, ceramic capacitors, MIM diodes, and MIM field emission devices. Can be adopted.

Claims (8)

  A chemical conversion solution for forming an oxide film on the surface of a material containing metal as a main component by anodic oxidation, which comprises water and a protic solvent.   The chemical liquid for forming an oxide film according to claim 1, wherein the protic solvent is an aprotic polar solvent.   The chemical solution for forming an oxide film according to claim 1, wherein the protic solvent is a cyclic compound.   The chemical solution for forming an oxide film according to claim 3, wherein the protic solvent is N-alkylpyrrolidone.   5. A method for forming an oxide film, comprising the step of anodizing a material to be treated mainly containing a metal in the chemical conversion solution according to claim 1.   A laminate having a metal oxide film on the surface of a material to be treated mainly containing a metal, wherein the metal oxide film uses a chemical conversion liquid containing water and a protic solvent, A laminate comprising a film formed by anodic oxidation on a surface of a material to be processed.   A method for producing a laminate having a metal oxide film on a surface of a material to be treated mainly containing a metal, the surface of the material to be treated using a chemical conversion liquid containing water and a protic solvent. A process for producing a laminate comprising the step of anodizing a metal oxide film to form a metal oxide film.   A metal oxide film, which is a film formed by anodic oxidation on the surface of a material to be treated containing a metal as a main component using a chemical conversion liquid containing water and a protic solvent. Oxide film.