Wiring board, method for producing wiring board, and composition for forming barrier film

Abstract

This wiring board comprises a barrier film disposed directly or indirectly on a substrate including copper wiring, and the barrier film contains flaky titanium oxide or a flaky titanium-metal composite oxide.

Description

Wiring board, method for producing wiring board, and composition for forming barrier film

[0001] The present invention relates to a wiring board, a method for producing a wiring board, and a composition for forming a barrier film.

[0002] As semiconductor devices become more highly integrated, there is a demand for further miniaturization of wiring. In order to suppress an increase in wiring resistance due to miniaturization of wiring, Cu (copper), which has higher conductivity, is being used as the wiring material instead of Al (aluminum), which has been used conventionally.

[0003] Because fine patterning of Cu by dry etching or the like is difficult, Cu wiring is formed by the so-called damascene method. In this damascene method, fine wiring grooves corresponding to a predetermined wiring pattern are first formed using SiO2 (silicon oxide) or the like. Next, a Cu film is formed by depositing Cu in the wiring grooves by plating. The Cu film is formed to a thickness that fills the wiring grooves and covers the entire substrate surface. The Cu film is then polished by CMP (Chemical Mechanical Polishing). This polishing of the Cu film continues until all of the Cu film outside the wiring grooves is removed and the surface of the silicon oxide film outside the wiring grooves is exposed. As a result, the Cu film remains only in the wiring grooves, resulting in Cu wiring embedded in the wiring grooves.

[0004] Cu has a higher diffusibility into silicon oxide films than Al, so if Cu wiring (Cu film) is formed directly on a silicon oxide film, Cu may diffuse into the silicon oxide film, potentially causing short circuits between the wiring.

[0005] Furthermore, with the recent trend toward finer wiring and multilayer wiring using Cu, an increase in the resistance of the wiring due to oxidation of the Cu surface has become a problem.

[0006] Therefore, Cu wiring requires a barrier film to prevent Cu diffusion and oxidation of the Cu surface. A method for forming this barrier film is, for example, to form an alloy film made of an alloy of Cu and Mn (manganese) on the silicon oxide in which the wiring groove is formed prior to the formation of the Cu film, and then to perform a heat treatment after the formation of the Cu film, thereby diffusing Mn in the alloy film to the interface with the silicon oxide film, and forming Mn at the interface. ｘ Si ｙ O ｚ A method for forming a barrier film consisting of (x, y, z: numbers greater than 0) has been proposed (see Japanese Patent Laid-Open Publication No. 2005-277390).

[0007] Japanese Patent Application Laid-Open No. 2005-277390

[0008] However, this proposed method leaves unnecessary Mn that does not contribute to the formation of a barrier film in the Cu wiring, which increases the resistance of the Cu wiring.Furthermore, the formation of such an alloy film takes time, which reduces the throughput of the wiring board performance.

[0009] Therefore, an object of the present invention is to provide a wiring board provided with a barrier film that can suppress oxidation of the surface of a copper film (copper wiring), a method for producing the same, and a composition for forming a barrier film.

[0010] The invention made to solve the above problems is a wiring substrate having a barrier film directly or indirectly on a substrate having copper wiring, the barrier film containing flaky titanium oxide or flaky titanium-metal composite oxide.

[0011] Another invention made to solve the above-mentioned problems is a method for manufacturing the above-mentioned wiring board, which includes a step of applying a barrier film-forming composition directly or indirectly onto a substrate having copper wiring, wherein the barrier film-forming composition contains flaky titanium oxide or flaky titanium-metal composite oxide, or flaky titanic acid, flaky titanium-metal acid, or a salt thereof, and a solvent (hereinafter, this may be referred to as "wiring board manufacturing method (I)").

[0012] Yet another invention made to solve the above-mentioned problems is a method for manufacturing the above-mentioned wiring board, which comprises the steps of forming a polymer film directly or indirectly on a substrate having copper wiring, applying a barrier film-forming composition onto the polymer film, and removing the polymer film, wherein the barrier film-forming composition contains flaky titanium oxide or flaky titanium-metal composite oxide, or flaky titanic acid, flaky titanium-metal acid, or a salt thereof, and a solvent (hereinafter, this may be referred to as "wiring board manufacturing method (II)").

[0013] Yet another invention made to solve the above-mentioned problems is a barrier film-forming composition used to manufacture the above-mentioned wiring board, which contains flaky titanium oxide, or flaky titanium-metal composite oxide, or flaky titanic acid, flaky titanium-metal acid, or a salt thereof, and a solvent.

[0014] According to the present invention, it is possible to provide a wiring board provided with a barrier film that can suppress oxidation of the surface of a copper film (copper wiring), a method for producing the same, and a composition for forming a barrier film.

[0015] Fig. 1 is a schematic diagram showing a wiring board according to one embodiment of the present invention. Fig. 2 is a schematic diagram showing a wiring board according to one embodiment of the present invention. Fig. 3 is a cross-sectional photograph of Cu wiring in Example 1. Fig. 4 is a cross-sectional photograph of Cu wiring in Example 4. Fig. 5 is a cross-sectional photograph of Cu wiring in Comparative Example 1. Fig. 6 is a cross-sectional photograph of Cu wiring in Example 9. Fig. 7 is a cross-sectional photograph of Cu wiring in Example 13.

[0016] The wiring board, the method for producing a wiring board (I), the method for producing a wiring board (II), and the composition for forming a barrier film of the present invention will be described in detail below.

[0017] <Wiring Board> The wiring board will be described with reference to Fig. 1. The wiring board 1 includes a barrier film 4 directly or indirectly on a substrate 2 having copper wiring 3. Fig. 1 illustrates an embodiment in which the barrier film 4 is provided directly on the substrate 2 having copper wiring 3. As shown in Fig. 2, the wiring board 1 may include an insulating film 5 between the substrate 2 having copper wiring 3 and the barrier film 4.

[0018] The substrate 2 may be made of, for example, a silicon substrate.

[0019] The copper wiring 3 can be formed by, for example, a CVD method, a PVD method, an electrolytic plating method, an electroless plating method, etc. The wiring width, wiring spacing, and wiring height of the copper wiring 3 are not particularly limited, and examples thereof include a wiring width and wiring spacing of 20 μm each, and a wiring height of 7 to 8 μm.

[0020] The substrate 2 having the copper wiring 3 can be fabricated by a known method. For example, wiring grooves are formed on a silicon substrate by a damascene method using a silicon oxide film, copper is embedded in the grooves, and the silicon oxide film is then removed to fabricate an exposed copper wiring pattern. The wiring grooves and exposed copper wiring pattern can be formed by known photolithography and etching techniques.

[0021] The barrier film 4 contains flaky titanium oxide or flaky titanium-metal composite oxide. The barrier film 4 can be formed by the method described below using a barrier film-forming composition described below. When the barrier film 4 contains flaky titanium oxide, it preferably has an absorption peak in the wavelength range of 250 to 280 nm and no absorption peak in the wavelength range of 300 to 800 nm in its ultraviolet-visible light absorption spectrum measured in the wavelength range of 200 to 800 nm using a spectrophotometer (Hitachi, Ltd.'s "U-3300"). When the barrier film 4 contains flaky titanium-metal composite oxide, it preferably has an absorption peak in both the wavelength range of 250 to 280 nm and the wavelength range of 300 to 800 nm in its ultraviolet-visible light absorption spectrum measured in the wavelength range of 200 to 800 nm using the spectrophotometer.

[0022] Because the barrier film 4 contains flaky titanium oxide or flaky titanium-metal composite oxide, it can suppress oxidation of the surface of the copper film (copper wiring). The reason for this is not entirely clear, but is presumed to be as follows: A barrier film containing flaky titanium oxide or flaky titanium-metal composite oxide has a structure in which flaky titanium oxide particles or flaky titanium-metal composite oxide particles are arranged without gaps, and is therefore thought to have superior gas barrier properties compared to titanium oxide films formed by, for example, a sputtering method.

[0023] Moreover, the barrier film 4 can be easily removed by dry etching.

[0024] The thickness of the barrier film 4 can be set to any desired value by appropriately selecting the coating method, and can be set to, for example, 1 nm or more and 50 nm or less.

[0025] A preferred embodiment of the barrier film 4 is a titanium oxide film with a high substrate coverage, in which flaky titanium oxide particles or flaky titanium-metal composite oxide particles are oriented parallel to the substrate, specifically a titanium oxide film with a coverage of 90% or more, preferably 95% or more. A film with a coverage of 90% or more is called a dense film, and the coverage can be determined by image analysis of scanning probe micrographs. Furthermore, a monolayer film in which there is little overlap between the flaky titanium oxide particles or flaky titanium-metal composite oxide particles is formed, specifically a monolayer film in which the film is formed to a thickness of one particle with no particle overlap in some areas, and the remaining portion is formed to a thickness of at most 2 to 3 particles overlapping each other, is preferred. A monolayer film with a density comparable to that of a dense monolayer film prepared by the Langmuir-Blodgett method is more preferred. The absorbance of the titanium oxide film can be measured and compared with the theoretical absorbance of the titanium oxide film to confirm that it is a monolayer film. Specifically, in this specification, a monolayer film is defined as a film that exhibits an absorbance of 80 to 120%, preferably 90 to 110%, of the theoretical absorbance (0.05) of a monolayer film of flaky titanium oxide. Such a dense monolayer film of flaky titanium oxide is a transparent film with no absorption in the visible light region, and has an absorption peak in the wavelength range of 250 to 280 nm in the ultraviolet-visible light absorption spectrum, but does not have an absorption peak in the wavelength range of 300 to 800 nm. A dense monolayer film of flaky titanium-metal composite oxide is a film that has absorption peaks in both the wavelength range of 250 to 280 nm and the wavelength range of 300 to 800 nm in the ultraviolet-visible light absorption spectrum. When the barrier film 4 is a monolayer film of flaky titanium oxide, its thickness can be appropriately set depending on the thickness of the flaky titanium oxide particles, and can be, for example, 1 nm to 2 nm.

[0026] The barrier film 4 is preferably a laminated film in which the above-mentioned single-layer films are stacked. The laminated film has a multilayer structure in which single-layer films are stacked. Since the flaky titanium oxide particles or flaky titanium-metal composite oxide particles remain oriented in each single-layer film, the properties of the single-layer film are maintained. Furthermore, since the multilayer structure contains a large number of flaky titanium oxide particles or flaky titanium-metal composite oxide particles, the properties of the flaky titanium oxide particles or flaky titanium-metal composite oxide particles can be further enhanced. Specifically, a laminated film can more effectively suppress oxidation of the surface of the copper film (copper wiring) compared to a single-layer film. Each layer of the laminated film is preferably the dense single-layer titanium oxide film. Therefore, specifically, the laminated film is transparent and has no absorption in the visible light region. In the ultraviolet-visible light absorption spectrum, a film having an absorption peak in the wavelength range of 250 to 280 nm and no absorption peak in the wavelength range of 300 to 800 nm is preferred. The thickness of the laminated film can be appropriately adjusted, for example, by the number of laminations, and can be 1 nm to 50 nm, preferably 2 nm to 40 nm. When the thickness of the laminated film is 2 nm or more, oxidation of the surface of the copper film (copper wiring) can be more effectively suppressed. When the thickness of the laminated film is 40 nm or less, the peelability of the barrier film 4 by dry etching can be further improved.

[0027] The insulating film 5 is provided to prevent short circuits between the copper wirings 3 or between wirings in multilayer wiring. As the insulating film 5, an inorganic film such as silicon oxide or an organic film formed from a curable resin composition is used.

[0028] The curable resin composition is not particularly limited, but from the viewpoint of excellent heat resistance, mechanical properties, etc., curable resin compositions containing polyimide-based resins or polybenzoxazole-based resins are preferred. Among them, positive-type photosensitive resin compositions that can improve the properties of the cured product are preferred. Examples of positive-type photosensitive insulating resin compositions include those described in Japanese Patent No. 4853155 and Japanese Patent No. 4692219. The positive-type photosensitive resin composition may contain other additives such as phenolic compounds, crosslinking agents, crosslinking aids, crosslinked fine particles, adhesion aids, solvents, sensitizers, and leveling agents, as needed.

[0029] The insulating film 5 formed from the positive photosensitive resin composition is formed by curing the positive photosensitive resin composition, and therefore has excellent resolution, thermal shock resistance, adhesion, electrical insulation, etc., and further exhibits little change in shape before and after a heating step. Therefore, it can be suitably used particularly as an interlayer insulating film or a planarizing film for a circuit board.

[0030] The insulating film 5 can be formed, for example, by coating the substrate 2 with a positive photosensitive resin composition and drying it to volatilize the solvent, etc., to form a coating film. The coating is then exposed to light through a desired mask pattern, and developed with an alkaline developer to dissolve and remove the exposed areas, thereby obtaining the desired pattern. Furthermore, the insulating film can be formed by performing a heat treatment after development to develop insulating film properties.

[0031] <Method for manufacturing wiring board (I)> The method for manufacturing wiring board (I) is a method for manufacturing the wiring board described above. The method for manufacturing wiring board (I) includes a step of applying a barrier film-forming composition directly or indirectly onto a substrate having copper wiring (hereinafter also referred to as “coating step (I)”).

[0032] The method for manufacturing a wiring board may include a step of heating or exposing the coating film formed in the coating step (hereinafter also referred to as a "film forming step").

[0033] [Coating Step (I)] In this step, a barrier film-forming composition is applied directly or indirectly onto a substrate having copper wiring. The substrate having copper wiring is described above in the section <Wiring Substrate>. The barrier film-forming composition will be described later. The barrier film can be formed by removing the solvent from the coating film formed in this step.

[0034] Examples of the case where the barrier film-forming composition is indirectly applied to a substrate having copper wiring include the case where the barrier film-forming composition is applied to the insulating film described above, and the case where the barrier film-forming composition is applied to a primer film formed to ensure adhesion between the substrate or insulating film and the barrier film. An example of a method for forming the insulating film is described above in the section <Wiring substrate>. Examples of the primer film include the polymer film described below in the section <Wiring substrate manufacturing method (II)>.

[0035] The coating method is not particularly limited, and examples thereof include spin coating, spray coating, roller coating, dip coating, flow coating, knife coating, electrostatic coating, bar coating, die coating, brush coating, and dropwise application of liquid.

[0036] This step may be performed once or multiple times. When performed once, a single layer film of flaky titanium oxide can be formed. When performed multiple times, a laminated film of the single layer film can be formed. When this step is performed multiple times, the number of times is not particularly limited, and can be, for example, from 2 to 50 times. When performed 40 times or less, a barrier film with high peelability by dry etching can be formed.

[0037] Furthermore, when this process is carried out multiple times, if a single coating process is carried out to a thickness of 0.1 nm or more and 2 nm or less, the flaky titanium oxide particles will be arranged in a regular pattern, making it possible to form a highly transparent barrier film.

[0038] [Film Formation Step] In this step, the coating film formed in the coating step is heated or exposed to light. When this step is included, removal of the solvent from the coating film can be promoted, and the barrier film can be formed efficiently.

[0039] The coating film can be heated at a temperature of 5°C or higher and 500°C or lower. The upper limit of the heating temperature is preferably 200°C, more preferably 150°C, and even more preferably 100°C. The lower limit of the heating temperature is preferably room temperature. The film may also be formed while maintaining a humidity of approximately 50% or higher and 100% or lower, preferably approximately 60% or higher and 95% or lower. By appropriately setting the film formation conditions, such as the concentration of flaky titanium oxide and the like in the barrier film-forming composition and the film formation temperature, and by appropriately controlling the film formation rate and the evaporation rate of the organic solvent, a barrier film with a high coverage of the substrate with flaky titanium oxide particles or flaky titanium-metal composite oxide can be formed.

[0040] The coating film can be exposed to light having a wavelength with energy equal to or greater than the band gap of titanium oxide, for example. This is a film-forming method that utilizes the photocatalytic activity of titanium oxide.

[0041] <Method for manufacturing wiring board (II)> The method for manufacturing wiring board (II) is a method for manufacturing the above-mentioned wiring board. The method for manufacturing wiring board (II) includes a step of forming a polymer film directly or indirectly on a substrate having copper wiring, and applying a barrier film-forming composition onto the polymer film (hereinafter also referred to as a “coating step (II)”), and a step of removing the polymer film (hereinafter also referred to as a “removing step”).

[0042] [Coating Step (II)] In this step, a polymer film is first formed directly or indirectly on a substrate having copper wiring, which is described above in the section <Wiring Substrate>.

[0043] An example of a method for forming a polymer film indirectly on a substrate having copper wiring is to coat the barrier film-forming composition on the insulating film described above. An example of a method for forming the insulating film is described above in the section on <Wiring substrate>.

[0044] Examples of methods for forming the polymer film include a method in which a polymer solution of a cationic polymer such as poly(ethyleneimine), polydiallyldimethylammonium chloride, or polyallylamine hydrochloride is applied to a substrate.

[0045] The thickness of the polymer film to be formed can be set appropriately, for example, to 0.5 nm or more and 20 nm or less.

[0046] In this step, a barrier film-forming composition is then applied onto the polymer film. The barrier film-forming composition will be described later.

[0047] The method for applying the barrier film-forming composition is not particularly limited, and examples thereof include spin coating, spray coating, roller coating, dip coating, flow coating, knife coating, electrostatic coating, bar coating, die coating, brush coating, and a method of dropping droplets.

[0048] This step may be performed once or multiple times. When performed once, a single layer film of flaky titanium oxide can be formed. When performed multiple times, a laminated film of the single layer film can be formed. When this step is performed multiple times, the number of times is not particularly limited, and can be, for example, from 2 to 50 times. When performed 40 times or less, a barrier film with high peelability by dry etching can be formed.

[0049] Furthermore, when this step is carried out multiple times, if a single coating step is carried out to a film thickness of 0.1 nm or more and 2 nm or less, the flaky titanium oxide particles or flaky titanium-metal composite oxide particles will be arranged in a regular pattern, making it possible to form a highly transparent barrier film.

[0050] In this process, polymer films and barrier films are laminated alternately, which corresponds to a method called layer-by-layer deposition. This method has the advantage that a thick barrier film can be easily formed because flaky titanium oxide particles or flaky titanium-metal composite oxide particles are adsorbed onto the polymer layer.

[0051] [Removal Step] In this step, the polymer film is removed, and a barrier layer is formed.

[0052] The method for removing the polymer film is not particularly limited, and examples thereof include a method of removing the film by heating and a method of removing the film by exposure. When removing the film by heating, for example, a method of heating at 400° C. is used. When removing the film by exposure, for example, ultraviolet light with a wavelength of 300 nm or less (intensity: 1 mW / cm ２ ) for 12 hours.

[0053] <Barrier Film-Forming Composition> The barrier film-forming composition is used to produce the above-mentioned wiring board. In other words, the barrier film-forming composition is used to produce a wiring board having a barrier film directly or indirectly provided on a substrate having copper wiring, the barrier film containing flaky titanium oxide or flaky titanium-metal composite oxide. Furthermore, the barrier film-forming composition is used in the coating step in the above-mentioned method for producing the wiring board.

[0054] In one embodiment, the barrier film-forming composition contains flaky titanium oxide or flaky titanic acid or a salt thereof (hereinafter also referred to as "flaky titanium oxide compound") and a solvent.

[0055] The flaky titanium oxide compound is easily swollen by water, and in some cases, the layers are peeled off and dispersed. Examples of the flaky titanium oxide compound include flaky titanium oxide, flaky titanic acid, and flaky titanate.

[0056] The flaky titanate is a layered TiO ２ It is thought to have a structure composed of crystals and cations (interlayer ions) between the layers, and TiO ２ It also includes those in which part of the Ti in the crystal is replaced by other cations or lattice defects. For example, Japanese Patent No. 3062497 discloses the structural formula and production method of flaky titanate.

[0057] According to Japanese Patent No. 3062497, flaky titanate can be obtained, for example, by a method in which raw materials are a metal that forms interlayer ions, a cationic metal that replaces part of the Ti in the crystal, and an oxide of Ti or a compound that becomes said oxide by heating, and a halide or sulfate of an alkali metal or alkaline earth metal is used as a flux, and the mixture is mixed so that the mass ratio of flux to raw materials is 0.2 to 1.3, and then heated and fired at 700 to 1200°C.

[0058] Examples of metals that form interlayer ions include alkali metals such as potassium, rubidium, cesium, etc. Furthermore, examples of metals of cations that substitute for a portion of Ti in the crystal include metals with a valence of 1 to 3 that are different from the above metals, such as those selected from alkaline earth metals, Li, Zn, Cu, Fe, Al, Ga, Mn, and Ni.

[0059] Examples of the flaky titanate include those obtained by reacting the following flaky titanic acid with a basic organic compound, in which the interlayer ions are organic cations. The basic organic compound is preferably a basic organic compound having an interlayer swelling effect, and examples thereof include alkylamines such as methylamine, ethylamine, propylamine, diethylamine, triethylamine, butylamine, dodecylamine, stearylamine, dipentylamine, dioctylamine, trioctylamine, and 2-ethylhexylamine, and salts thereof; alkanolamines such as ethanolamine, diethanolamine, triethanolamine, isopropanolamine, diisopropanolamine, triisopropanolamine, and 2-amino-2-methyl-1-propanol; quaternary ammonium hydroxides such as tetramethylammonium hydroxide and tetrabutylammonium hydroxide, and salts thereof; quaternary ammonium salts such as dodecyltrimethylammonium salt, cetyltrimethylammonium salt, stearyltrimethylammonium salt, and benzyltributylammonium salt; 3-methoxypropylamine, 3-ethoxypropylamine, polyethyleneimine, polydiallyldimethylammonium chloride; and phosphonium salts such as dodecyltributylphosphonium salt and octadecyltributylphosphonium salt.

[0060] The action of the basic compound can be achieved by adding the basic compound to a suspension of flaky titanic acid dispersed in an aqueous medium under stirring.

[0061] The flaky titanic acid can be prepared by treating the flaky titanate with an acid or hot water to form an interlayer ion and / or TiO ２ Examples include those in which the cations that partially substituted for Ti in the crystal are replaced with hydrogen and / or hydronium ions.

[0062] The acid treatment can be carried out, for example, by adding an acid to an aqueous dispersion of the flaky titanate while stirring. Examples of the acid include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and boric acid, as well as organic acids. The hot water treatment can be carried out, for example, by dispersing the flaky titanate in hot water at 60°C or higher and stirring the mixture.

[0063] Flake-like titanium oxide can be obtained by treating the titania sol obtained by reacting the flaky titanic acid with a basic organic compound as described above, followed by heat treatment to remove the base and water. This process is described, for example, in Japanese Patent Publication No. 2979132. Flake-like titanic acid is a layered crystal of titanic acid. By treating it with a basic organic compound that has an interlayer swelling effect, the interlayers swell or peel, and then re-aggregate upon drying, resulting in a stack of titanium oxide layers with a thickness of 1 nm or less. Amines and water are sandwiched between these layers, and it is believed that heating this product at 100 to 350°C causes the water and amines to desorb from between the layers, resulting in the layers peeling off, yielding flaky titanic acid.

[0064] It is preferable for the flaky titanium oxide particles to contain an organic cation, as described below, because charge repulsion between the organic cations facilitates dispersion of the flaky titanium oxide particles. However, an excessively high organic cation content may result in aggregation of the flaky titanium oxide particles. Therefore, the organic cation content is preferably in the range of 0.05 to 3 equivalents relative to the titanium (Ti) contained in the flaky titanium oxide, more preferably 0.1 to 3 equivalents, and even more preferably 0.9 to 1.5 equivalents. The organic cation is preferably a quaternary ammonium ion, more preferably a quaternary ammonium ion having a total carbon number of 9 or more, such as tetrabutylammonium ion. The inclusion of a quaternary ammonium ion having a total carbon number of 9 or more enables dispersion in many organic solvents. Furthermore, the surface of the flaky titanium oxide particles may be coated with conventional organic compounds such as surfactants and coupling agents, or inorganic compounds such as silica and alumina, from the viewpoints of dispersibility in organic solvents and affinity for resins.

[0065] The content of the flaky titanium oxide particles in the barrier film-forming composition can be adjusted as appropriate. ２ The content is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, more preferably 0.02% by mass or more, still more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, calculated as a percentage. If the content is too high, the volume that can be occupied by each flaky titanium oxide particle becomes small, causing aggregation and making it prone to settling. ２The amount is preferably 10% by mass or less, more preferably 1.0% by mass or less, calculated as TiO. ２ In terms of mass conversion, 0.001 to 10 mass% is more preferable, 0.01 to 10 mass% is more preferable, 0.02 to 10 mass% is more preferable, 0.05 to 10 mass% is even more preferable, 0.05 to 1.0 mass% is even more preferable, and 0.1 to 1.0 mass% is even more preferable.

[0066] The organic solvent can be appropriately selected depending on the application, but organic solvents with a dielectric constant of 5 or more are preferred because they facilitate dispersion of flaky titanium oxide particles, and organic solvents with a dielectric constant of 10 or more are more preferred. As such organic solvents, at least one selected from the group consisting of acetonitrile (dielectric constant 37, boiling point 82°C), methanol (dielectric constant 33, boiling point 65°C), dimethyl sulfoxide (dielectric constant 47, boiling point 189°C), ethanol (dielectric constant 24, boiling point 78.3°C), 2-propanol (dielectric constant 18, boiling point 82.5°C), γ-butyrolactone (dielectric constant 39, boiling point 205°C), N,N-dimethylformamide (dielectric constant 38, boiling point 153°C), methyl ethyl ketone (dielectric constant 18.5, boiling point 80°C), 1-butanol (dielectric constant 17.8, boiling point 118°C), and formamide (dielectric constant 109, boiling point 210°C) is more preferred.

[0067] The barrier film-forming composition contains almost no water, and the water content is preferably 10% by mass or less, more preferably 5% by mass or less, more preferably 1% by mass or less, even more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less. The barrier film-forming composition may contain various additives such as a resin binder, a dispersant, a surface conditioner (a leveling agent, a wettability improver), a pH adjuster, an antifoaming agent, an emulsifier, a colorant, an extender, an antifungal agent, a curing aid, a thickener, or a filler as a third component, provided that the effect of the present invention is not impaired.

[0068] The barrier film-forming composition is produced by (1) centrifuging an aqueous dispersion of flaky titanium oxide particles containing organic cations, and mixing and dispersing the resulting precipitate with an organic solvent; (2) freeze-drying an aqueous dispersion of flaky titanium oxide particles containing organic cations, and then mixing and dispersing the resulting freeze-dried product with an organic solvent; or (3) removing water from an aqueous dispersion of flaky titanium oxide particles containing organic cations using an evaporator, and mixing and dispersing the resulting dried product with an organic solvent.

[0069] To produce the aqueous dispersion of flaky titanium oxide particles containing organic cations, for example, the method described in WO99 / 11574 can be used. Specifically, WO 99 / 11574 discloses that (1) a layered metal titanate such as cesium titanate, lithium potassium titanate, or potassium magnesium titanate is synthesized, the resulting layered metal titanate is suspended in an aqueous solvent, and then an acid such as hydrochloric acid, sulfuric acid, or nitric acid is added to extract the metal ions, thereby obtaining titanic acid having a layered structure; (2) the layered titanic acid produced by the method (1) is suspended in a liquid medium, and then a basic compound that serves as an organic cation source, such as an amine compound or an ammonium compound, is added to obtain flaky titanium oxide particles having a swollen interlayer structure and containing organic cations; and (3) the flaky titanium oxide particles whose interlayers have been swollen by the method (2) are shaken or otherwise subjected to delamination to obtain flaky titanium oxide nanosheets. The aqueous dispersion in which the flaky titanium oxide particles of (2) are dispersed and the aqueous dispersion in which the delaminated flaky titanium oxide nanosheets of (3) are dispersed can be suitably used.

[0070] The metal titanate salt produced in the above step (1) is preferably a mixed alkali metal titanate salt produced, for example, as follows: ２ O and M' ２ O (M and M' are different alkali metals) or M ２ O and M' ２Each compound that decomposes to O and titanium dioxide or a compound that generates titanium dioxide upon heating are mixed preferably in a molar ratio of M / M' / Ti of 3 / 1 / 5 to 3 / 1 / 11, and the mixture is fired at a temperature of 500 to 1100°C, more preferably 600 to 900°C. The above temperature range is preferred to ensure sufficient reaction to reduce the amount of residual raw material composition and to prevent the formation of substances with different compositions. The mixed alkali metal titanate obtained above has a Ti in the host skeleton. ４＋ A compound represented by the formula M in which a part of the sites is substituted with an alkali metal ion different from the interlayer alkali metal. ｘ [M' ｘ／３ Ti ２－ｘ／３ ]O ４ This compound has an orthorhombic layered structure (a lepidocrocite-type crystal structure) represented by the formula (where M and M' are different alkali metals, and x is 0.50 to 1.0). The alkali metal ions represented by M and M' in this substance are active and undergo exchange reactions with other cations or incorporation through intercalation of organic matter. Therefore, when contacted with an acidic aqueous solution, the alkali metal ions (M) between the layers and (M') in the host skeleton are exchanged with hydrogen ions (present in the form of hydronium ions) in a short period of time, resulting in an efficient, low-cost flaky titanium oxide dispersion for industrial production. The value of x in the composition formula can be controlled by varying the mixing ratio of the starting materials. To obtain a uniform, single-phase compound, thorough mixing is preferred during the synthesis process, and the raw material powders are preferably ground and mixed using an automatic mortar or similar. In addition, by appropriately selecting the firing temperature when producing the layered metal titanate or by adopting the so-called flux method in which a flux is added during firing, the particle size of the layered metal titanate can be appropriately adjusted, thereby making it possible to appropriately control the particle size of the flaky titanium oxide.

[0071] In the above-mentioned step (2), a basic compound serving as an organic cation source is preferably mixed in a liquid medium in an amount of preferably 0.05 to 3 neutralization equivalents relative to the hydrogen (H) contained in the layered titanic acid, thereby eliminating the hydrogen contained in the layered titanic acid and inserting the basic compound between the layers. Then, as described in step (3), the layers are preferably peeled off to produce flaky titanium oxide particles. If the amount of basic compound is less than the above-mentioned range, hydrogen ions are not sufficiently eliminated, while if it is too much, swelling occurs, making peeling between the layers more difficult. A more preferred amount is 0.1 to 3 neutralization equivalents, and even more preferred is 0.9 to 1.5 neutralization equivalents. The amount of basic compound is preferably 0.05 to 3 equivalents relative to the titanium (Ti) contained in the layered titanic acid, more preferably 0.1 to 3 equivalents, and even more preferably 0.9 to 1.5 equivalents. It is preferable that the amount of basic compound satisfy both the above-mentioned preferred range for hydrogen (H) and the preferred range for titanium (Ti). A part of such basic compounds is contained as organic cations in the flaky titanium oxide, preferably on the particle surface.

[0072] Examples of basic compounds include (1) quaternary ammonium hydroxide compounds (e.g., tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide), (2) alkylamine compounds (e.g., propylamine, diethylamine), and (3) alkanolamine compounds (e.g., ethanolamine, aminomethylpropanol). Among these, quaternary ammonium hydroxide compounds are preferred due to their excellent reactivity. Quaternary ammonium hydroxide compounds with a total carbon number of 9 or more, such as tetrabutylammonium hydroxide, are more preferred because they function effectively as dispersants for flaky titanium oxide particles even when dispersed in an organic solvent. The liquid medium used in step (2) can be water, an organic solvent such as alcohol, or a mixture thereof. Industrially, an aqueous liquid medium primarily composed of water is preferred. The order in which the layered titanic acid and the basic compound are added to the liquid medium is not particularly limited. For example, the layered titanic acid and the basic compound can be added to water and then stirred to mix. Alternatively, the basic compound can be added to a slurry in which the layered titanic acid is dispersed in water, or the layered titanic acid can be added to an aqueous solution of the basic compound. Next, by continuing stirring, the layer of layered titanic acid peels off, yielding flaky titanium oxide particles. While there are no particular limitations on the reaction temperature, it is preferable to carry out the reaction at room temperature for 1 to 20 days to prevent decomposition of the layered titanic acid. To further enhance the degree of delamination, the container containing the solution may be shaken, as in step (3) above. This shaking produces nanosheets with a length and width of approximately 0.1 to 30 μm, and a thickness of approximately 0.5 to 10 nm, preferably approximately 0.5 to 2 nm, and more preferably approximately 0.5 to 1 nm. A shaker, paint conditioner, shaker, or the like may be used for shaking.

[0073] The flaky titanium oxide particles preferably have the composition formula Ti ２－ｘ／３ O ４ （４ｘ／３）－ (where x is 0.57 to 1.0), specifically Ti １．８１ O ４ ０．７６－ ~Ti １．６７ O ４ １．３３－The flaky titanium oxide particles are represented by TiO ６ The octahedra are linked by edge sharing to form a two-dimensional framework structure. ４＋ Since 9.5 to 17% of the sites are defective, the flaky particles have a structure with a large negative charge.

[0074] Next, this dispersion of flaky titanium oxide particles containing an organic cation, preferably an aqueous dispersion, is centrifuged to separate the precipitate and the liquid medium. A conventional centrifuge can be used for the centrifugation. Centrifugation may be repeated two or more times to adjust the water content to the desired level. The separated precipitate is mixed with an organic solvent and dispersed to obtain an organic solvent dispersion. To disperse the flaky titanium oxide particles in an organic solvent, a conventional dispersing machine such as a stirrer, colloid mill, ball mill, or bead mill, a shaker, a paint conditioner, or a shaker can be used, and the third component described above can be added at this time.

[0075] Alternatively, a dispersion, preferably an aqueous dispersion, of flaky titanium oxide particles containing an organic cation is freeze-dried to obtain a freeze-dried product. A conventional freeze-dryer can be used for freeze-drying. The resulting freeze-dried product may be subsequently sublimated under vacuum to adjust the water content to the desired level. The freeze-dried product is then mixed with an organic solvent and dispersed. To disperse the flaky titanium oxide particles, the same conventional agitators, colloid mills, ball mills, bead mills, and other dispersing machines, shakers, paint conditioners, shakers, and the like can be used, and the third component described above can be added at this time.

[0076] In another embodiment, the barrier film-forming composition contains a flaky titanium-metal composite oxide or a flaky titanium-metal acid or its salt (hereinafter also referred to as a "flaky titanium-metal compound") and a solvent.

[0077] Examples of the metal in the flaky titanium-metal composite oxide include iron, cobalt, nickel, manganese, and combinations thereof. Among these, iron is preferred. In this specification, when the metal is iron, the flaky titanium-iron composite oxide may be referred to as "flaky titanium iron oxide."

[0078] When the barrier film-forming composition contains flaky titanium oxide iron, it can exhibit higher barrier properties than when it contains flaky titanium oxide. That is, the number of coating cycles can be reduced compared to when flaky titanium oxide is contained, and sufficient effects of preventing oxidation of wiring can be obtained even with a thin film thickness.

[0079] The following description will be given taking the case where the metal is iron as an example.

[0080] The flaky titanium-iron compound is easily swollen with water, and in some cases, the layers are peeled off and dispersed. Examples of the flaky titanium-iron compound include flaky titanium iron oxide, flaky titanic acid, and flaky titanic ferrate.

[0081] The flaky titanate has a similar crystal structure to that of the flaky titanate, and is composed of layered TiO ２ A part of Ti in the crystal is substituted with Fe. Examples of metals that form cations (interlayer ions) in the interlayer ions include alkali metals such as potassium, rubidium, and cesium.

[0082] Examples of the flaky titanate include those obtained by reacting a basic organic compound with the flaky titanate described below, in which the interlayer ions are organic cations. Examples of the basic organic compound that can be reacted with the flaky titanate include the basic organic compounds that can be reacted with the flaky titanate described above.

[0083] The action of the basic organic compound can be achieved by adding the basic compound to a suspension of flaky titanic acid dispersed in an aqueous medium under stirring.

[0084] The flaky titanic acid can be obtained by treating the flaky titanic acid with an acid or hot water to form interlayer ions and / or TiO ２ Examples include those in which the cations that partially substituted for Ti in the crystal are replaced with hydrogen and / or hydronium ions.

[0085] The acid treatment can be carried out in the same manner as in the process carried out for the aqueous dispersion of the flaky titanate described above.

[0086] Like flaky titanium oxide, flaky titanium iron oxide can be obtained by reacting the above-mentioned flaky titanic acid with a basic organic compound to obtain a sol, which is then heat-treated to remove the base and water.

[0087] The content of the organic cation contained in the flaky titanium oxide iron particles is preferably in the range of 0.05 to 3 equivalents relative to the hydrogen (H) contained in the flaky titanium iron oxide, more preferably in the range of 0.1 to 3 equivalents, and even more preferably in the range of 0.9 to 1.5 equivalents. The organic cation is preferably a quaternary ammonium ion, and more preferably a quaternary ammonium ion having a total carbon number of 9 or more, such as a tetrabutylammonium ion. The inclusion of a quaternary ammonium ion having a total carbon number of 9 or more enables dispersion in many organic solvents. Furthermore, from the viewpoints of dispersibility in organic solvents, affinity for resins, etc., the surface of the flaky titanium iron oxide particles may be coated with a conventional organic compound such as a surfactant or a coupling agent, or an inorganic compound such as silica or alumina.

[0088] The content of the flaky titanium oxide iron particles in the barrier film-forming composition is TiO ２ In terms of conversion, 0.001 to 10 mass% is more preferable, 0.01 to 10 mass% is more preferable, 0.02 to 10 mass% is more preferable, 0.05 to 10 mass% is even more preferable, 0.05 to 1.0 mass% is even more preferable, and 0.1 to 1.0 mass% is particularly preferable.

[0089] To produce an aqueous dispersion of flaky titanium iron oxide particles containing the organic cations, (4) synthesize a layered metal titanate such as lithium potassium titanate or potassium magnesium titanate, suspend the resulting layered metal titanate in an aqueous solvent, add an acid such as hydrochloric acid, sulfuric acid, or nitric acid, and extract the metal ions to obtain layered titanium iron oxide. (5) Suspend the layered titanium iron oxide produced by the method (4) in a liquid medium, and add a basic compound that serves as an organic cation source, such as an amine compound or ammonium compound, to obtain flaky titanium iron oxide particles with a swollen interlayer structure and containing organic cations. (6) The flaky titanium iron oxide particles whose interlayers have been swollen by the method (5) are shaken or otherwise peeled to obtain flaky titanium iron oxide particles.

[0090] The metal titanate salt produced in the above step (4) is preferably a mixed alkali metal titanate salt produced, for example, as follows: ２ O and M' ２ O (M and M' are different alkali metals) or M ２ O and M' ２ O, titanium dioxide or a compound that generates titanium dioxide upon heating, and iron(III) oxide or a compound that generates iron(III) oxide upon heating are mixed preferably in a molar ratio of M / M' / Ti / Fe of 3 / 1 / 13 / 0 to 3 / 0 / 9 / 3, and the mixture is fired at a temperature of 500 to 1100°C, more preferably 600 to 1000°C. The above temperature range is preferred to ensure sufficient reaction to reduce the amount of residual raw material composition and to prevent the formation of substances with different compositions. The mixed alkali metal titanate obtained above has a Ti-containing structure in the host skeleton. ４＋ Some of the sites are alkali metal ions other than the interlayer alkali metal ions or Fe ３＋ Formula M ｘ [M' （ｘ－ｙ）／３ Ti(6-x-2y) / 3Fe ｙ ]O ４This compound has an orthorhombic layered structure (lepidocrocite-type crystal structure) represented by the formula (where M and M' are different alkali metals, x is 0.50 to 1.0, and y is 0 to 1.0). The alkali metal ions represented by M and M' in this substance are active and undergo exchange reactions with other cations or incorporation through intercalation of organic matter. Therefore, when contacted with an acidic aqueous solution, the alkali metal ions between the layers (M) and in the host skeleton (M') are exchanged with hydrogen ions (present in the form of hydronium ions) in a short time, resulting in the production of a flaky titanium iron oxide dispersion that is efficient and inexpensive to produce industrially. The values ​​of x and y in the composition formula can be controlled by varying the mixing ratio of the starting materials. Furthermore, to obtain a uniform, single-phase compound, thorough mixing is preferred during the synthesis process, and the raw material powders are preferably ground and mixed using an automatic mortar or similar. Furthermore, by appropriately selecting the firing temperature when producing the layered metal titanate, or by employing a so-called flux method in which a flux is added during firing, the particle size of the layered metal titanate can be appropriately adjusted, thereby allowing the particle size of the flaky titanium iron oxide to be appropriately controlled.

[0091] In the step (5), a basic compound serving as an organic cation source is preferably mixed in a liquid medium in an amount of preferably 0.05 to 3 neutralization equivalents relative to the hydrogen (H) contained in the layered titanate, thereby eliminating the hydrogen contained in the layered titanate and inserting the basic compound between the layers. Then, as described in step (6), the layers are peeled off to produce flaky titanium iron oxide particles. If the amount of basic compound is less than this range, hydrogen ions are not sufficiently eliminated, while if it is too much, swelling occurs, making peeling between the layers more difficult. A more preferred amount is 0.1 to 3 neutralization equivalents, and even more preferred is 0.9 to 1.5 neutralization equivalents. The amount of basic compound is preferably 0.05 to 3 equivalents relative to the titanium (Ti) contained in the layered titanate, more preferably 0.1 to 3 equivalents, and even more preferably 0.9 to 1.5 equivalents. It is preferable that the amount of basic compound satisfy both the preferred range for hydrogen (H) and the preferred range for titanium (Ti). A part of such basic compounds is contained as organic cations in the flaky titanium iron oxide, preferably on the particle surface.

[0092] The flaky titanium iron oxide particles preferably have the composition formula [Ti(6-x-2y) / 3Fe ｙ O ４ ] （４ｘ－ｙ）／３－ (where x is 0.57 to 1.0, and y is 0 to 0.80), specifically Ti ＞１．７３ Fe ＞０ O ４ ＜１．１７ー ~Ti １．２０ Fe ０．８ O ４ ０．８－ The flaky titanium iron oxide particles are represented by TiO ６ The octahedra are linked by edge sharing to form a two-dimensional framework structure. ４＋ 0-40% of seats are Fe ４＋ In addition to being substituted with Ti ４＋ Since 0 to 17% of the sites are defects, the flaky particles have a large negative charge. ４＋ by Ti ４＋ Ti according to seat replacement ４＋ The defect of the sheet is reduced, and when y = 0.8, the theoretical Ti ４＋ This results in a crystal structure with no defects.

[0093] The flaky titanium oxide iron particles have fewer defects in the crystal lattice than flaky titanium oxide particles, and therefore have improved barrier properties both as single particles and in a laminated state. Specifically, a barrier film made of flaky titanium oxide iron particles exhibits the same barrier properties as a barrier film made of flaky titanium oxide particles, even in a thinner laminated structure.

[0094] The above-mentioned flaky titanium oxide iron particles exhibit relatively higher barrier properties than flaky titanium oxide particles, and therefore, when forming a laminated structure by, for example, a spin coating method, the number of coating operations required to form a barrier film can be reduced.

[0095] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0096] <Synthesis of flaky titanium oxide> Layered titanium oxide (K ０．８ Ti １．７３ Li ０．２７ O ４ ) as a starting material, and flaky titanium oxide (Ti) was prepared by the following method. ０．８７ O ２ ) was synthesized.

[0097] The starting material, layered titanium oxide (K ０．８ Ti １．７３ Li ０．２７ O ４ ) was synthesized as follows: Potassium carbonate (K ２ CO ３ ), lithium carbonate (Li ２ CO ３ ) and titanium dioxide (TiO ２ ) were mixed in a molar ratio of 3 / 1 / 13 and thoroughly pulverized and mixed. This was placed in a platinum crucible and calcined at 800°C for 1 hour. Thereafter, the calcined raw material powder was pulverized and mixed again. Next, the pulverized and mixed raw material powder was placed in a platinum crucible and calcined at 1,000°C for 20 hours to obtain layered titanium oxide (K ０．８ Ti １．７３ Li ０．２７ O ４ ) was obtained.

[0098] 1 g of the obtained layered titanium oxide was mixed with 50 cm of 1N hydrochloric acid. ３ The mixture was added and reacted for 24 hours at room temperature while stirring using a mechanical stirrer. After the 24-hour reaction, the stirring was stopped, the mixture was left to stand for 3 hours, and the supernatant was removed by decantation. Thereafter, the amount of 1N hydrochloric acid removed by decantation was added, and the 24-hour reaction and supernatant removal were repeated twice. After that, the mixture was filtered, washed with water, and dried to obtain a hydrogen ion exchanger (H １．０７ Ti １．７３ O ４ ・H ２ Then, the hydrogen ion exchanger was heated to 1000°C, and the hydrogen ion exchanger was heated to 1000°C. ＋ The mixture was mixed at a ratio of 4 g / L with an aqueous solution in which 1 neutralization equivalent of tetrabutylammonium hydroxide was dissolved, and the mixture was allowed to react for 7 days at room temperature while stirring with a mechanical stirrer, to obtain flaky titanium oxide (Ti ０．８７ O ２ ) to obtain an aqueous dispersion (Sample 1).

[0099] <Synthesis of flaky titanium iron oxide> Layered titanium iron oxide (K ０．８ Ti １．４９ Li ０．１４ Fe ０．３７ O ４ ) as a starting material, and flaky titanium iron oxide (Ti) was prepared by the following method. １．４９ Fe ０．３７ O ４ ) was synthesized.

[0100] The starting material, layered titanium iron oxide (K ０．８ Ti １．４９ Li ０．１４ Fe ０．３７ O ４ ) was synthesized as follows: Potassium carbonate (K ２ CO ３ ), lithium carbonate (Li ２ CO ３ ), iron (III) oxide (Fe ２ O ３ ) and titanium dioxide (TiO ２) were mixed in a molar ratio of 6 / 1 / 3 / 21 and thoroughly pulverized and mixed. This was placed in a platinum crucible and calcined at 800°C for 1 hour. Thereafter, the calcined raw material powder was pulverized and mixed again. Next, the pulverized and mixed raw material powder was placed in a platinum crucible and calcined at 1,000°C for 20 hours to obtain layered titanium iron oxide (K ０．８ Ti １．４９ Li ０．１４ Fe ０．３７ O ４ ) was obtained.

[0101] 1 g of the obtained layered titanium iron oxide was mixed with 50 cm of 1N hydrochloric acid. ３ The mixture was added and reacted for 24 hours at room temperature while stirring using a mechanical stirrer. After the 24-hour reaction, the stirring was stopped, the mixture was left to stand for 3 hours, and the supernatant was removed by decantation. Thereafter, the amount of 1N hydrochloric acid removed by decantation was added, and the 24-hour reaction and supernatant removal were repeated twice. After that, the mixture was filtered, washed with water, and dried to obtain a hydrogen ion exchanger (H ０．９４ Ti １．４９ Fe ０．３７ O ４ ・H ２ Then, the hydrogen ion exchanger was heated to 1000°C, and the hydrogen ion exchanger was heated to 1000°C. ＋ The mixture was mixed at a ratio of 4 g / L with an aqueous solution containing 1 neutralization equivalent of tetrabutylammonium hydroxide dissolved therein, and the mixture was allowed to react for 7 days at room temperature while stirring with a mechanical stirrer to obtain flaky titanium iron oxide (Ti １．４９ Fe ０．３７ O ４ ) to obtain an aqueous dispersion (Sample 2).

[0102] <Preparation of Evaluation Substrate> A curable resin composition (JSR Corporation's "WPR Series") was applied to a silicon substrate having copper wiring (wiring width: 20 μm, wiring spacing: 20 μm, wiring height: 7 to 8 μm) and heated at 110°C for 5 minutes using a hot plate to form a coating film with a thickness of 10 μm on the copper wiring. The coating was then exposed to light through a desired mask pattern and developed with an alkaline developer to dissolve and remove the exposed areas, thereby forming a desired pattern. The coating film was then cured by heating at 200°C for 1 hour using a convection oven to form an insulating film, and an evaluation substrate was prepared.

[0103] <Formation of Barrier Film> A barrier film was formed on the evaluation substrate prepared above by the following method: The thickness of the barrier film was measured using an atomic force microscope (AFM; Bruker's "Dimension FastScan").

[0104] [Examples 1 to 7] In Examples 1 to 7, the barrier film was formed by layer-by-layer deposition.

[0105] (Preparation of Solution 1) Sample 1 obtained in the above <Synthesis of flaky titanium oxide> section was diluted with water to a concentration of 0.01 mass % flaky titanium oxide, and the pH was adjusted to 9 using nitric acid to prepare solution 1.

[0106] (Preparation of Solution 2) A poly(ethyleneimine) solution (Sigma-Aldrich, Mw: about 750,000, 50% by weight aqueous solution) was diluted with water to 0.25% by weight, and the pH was adjusted to 9 with nitric acid to obtain Solution 2.

[0107] (Formation of Barrier Film) The evaluation substrate prepared in the above section <Preparation of Evaluation Substrate> was immersed in the above Solution 1 for 5 minutes. Thereafter, it was washed with pure water and dried. Next, the evaluation substrate was immersed in the above Solution 2 for 5 minutes. Thereafter, it was washed with pure water and dried. The above operations were repeated until the film thickness shown in Table 1 below was obtained. Thereafter, it ... ２ ) for 12 hours to remove the resin layer formed by Solution 2, thereby forming a barrier film.

[0108] Examples 8 to 11 In Examples 8 to 11, the barrier film was formed by spin coating.

[0109] (Preparation of Solution 3) The poly(ethyleneimine) solution was diluted with PGME (propylene glycol monomethyl ether) to a concentration of 2.0% by mass, thereby obtaining Solution 3.

[0110] (Preparation of Solution 4) Sample 1 obtained in the above section <Synthesis of flaky titanium oxide> was evaporated using an evaporator and then dried in a vacuum dryer (60°C, approximately 12 hours) to obtain flaky titanium oxide powder. γ-Butyl lactone was then added so that the titanium oxide nanosheets became 0.2% by mass, to obtain Solution 4.

[0111] Solution 3 was applied to evaluation substrate 1 using a spin coater (MS-B150, manufactured by Mikasa Co., Ltd.) at 1,500 rpm for 1 minute, and then heated at 100°C for 10 minutes using a hot plate to prepare a primer film. Next, Solution 4 was applied using the spin coater. The application of Solution 4 was repeated until the film thickness shown in Table 1 below was reached, thereby forming a barrier film.

[0112] Examples 12 to 14 In Examples 12 to 14, the barrier film was formed by spin coating.

[0113] (Preparation of Solution 5) Sample 2 obtained in the above section <Synthesis of flaky titanium iron oxide> was evaporated using an evaporator and dried in a vacuum dryer (60°C, approximately 12 hours) to obtain a flaky titanium iron oxide powder. γ-Butyl lactone was then added so that the titanium iron oxide nanosheets became 0.2 mass %, to obtain Solution 5.

[0114] The above solution 3 was applied to evaluation substrate 1 using the spin coater at 1,500 rpm for 1 minute, and then heated at 100°C for 10 minutes using a hot plate to prepare a primer film. The above solution was then applied using the spin coater. The application of solution 5 was repeated until the film thickness shown in Table 1 below was reached, thereby forming a barrier film.

[0115] Comparative Example 1 In Comparative Example 1, a wiring substrate without a barrier film, that is, the evaluation substrate prepared in the above section <Preparation of Evaluation Substrate>, was used as a control.

[0116] [Comparative Example 2] As a control, a titanium oxide film was formed by sputtering in Comparative Example 2. Specifically, a titanium oxide film was formed to a thickness of 10 nm by sputtering on the evaluation substrate prepared in the above section <Preparation of Evaluation Substrate>.

[0117] <Evaluation> [Cu Wiring Oxidation Test] The wiring substrates obtained in Examples 1 to 14 and Comparative Examples 1 and 2 were heated for 120 hours at 200°C using a convection oven. After this treatment, the insulating layer and Cu wiring were cross-sectioned using a cross-section polisher ("SM-09010" manufactured by JEOL Datum Co., Ltd.), and the cross-section of the Cu wiring was observed at a magnification of 10,000 times using a scanning electron microscope ("Apreo S LoVac" manufactured by FEI Corporation). The degree of oxidation inhibition of the Cu wiring was evaluated based on the thickness of the oxide film formed on the surface of the Cu wiring. The oxide film thickness was evaluated as "A" (very good) when it was 10 nm or less; "B" (good) when it was more than 10 nm but less than 100 nm and the size of the voids generated in the Cu layer was less than 200 nm; "C" (fairly good) when it was 100 nm or more but less than 200 nm and the size of the voids generated in the Cu layer was 200 nm or more but less than 300 nm; and "D" (poor) when it was 200 nm or more and the size of the voids generated in the Cu layer was 300 nm or more. The results are shown in Table 1 below. Micrographs are also shown in Figures 3 to 7. Figure 3 is a micrograph of Example 1, Figure 4 is of Example 4, Figure 5 is of Comparative Example 1, Figure 6 is of Example 9, and Figure 7 is of Example 13.

[0118] [Barrier Film Removal Test] A barrier film was formed on a silicon substrate using the film formation method shown in Examples 1 to 14 and Comparative Example 2. The resulting barrier film was then subjected to two 10-minute etching treatments using Ar ions at 400 W. After each etching treatment, the contact angle between the surface of each substrate and water was measured to evaluate the presence or absence of barrier film residue. The evaluation criteria were as follows: a water contact angle of 40° or greater after the first etching treatment was rated "A" (very good); a water contact angle of less than 40° after the first etching treatment but 40° or greater after the second etching treatment was rated "B" (good); and a water contact angle of less than 40° after both the first and second etching treatments was rated "C" (poor). The results are shown in Table 1 below.

[0119]

[0120] The results in Table 1 show that when a barrier film containing flaky titanium oxide is provided (Examples 1 to 14), oxidation of Cu wiring can be suppressed compared to when it is not provided (Comparative Examples 1 and 2).

[0121] Furthermore, it was found that the barrier films containing flaky titanium oxide (Examples 1 to 14) could be easily peeled off by dry etching, similar to the titanium oxide film formed by sputtering (Comparative Example 2).

[0122] REFERENCE SIGNS LIST 1 Wiring substrate 2 Substrate 3 Copper wiring 4 Barrier film 5 Insulating film

Claims

1. A wiring board having a barrier film directly or indirectly on a substrate having a copper wiring, wherein the barrier film contains flaky titanium oxide or flaky titanium - metal composite oxide.

2. The wiring board according to claim 1, wherein the barrier film is a single - layer film of flaky titanium oxide or flaky titanium - metal composite oxide.

3. The wiring board according to claim 1, wherein the barrier film is a laminated film in which single - layer films of flaky titanium oxide or flaky titanium - metal composite oxide are laminated.

4. The wiring board according to claim 1, wherein the thickness of the barrier film is 1 nm or more and 50 nm or less.

5. The wiring board according to claim 1, wherein the barrier film is a laminated film in which single - layer films of flaky titanium oxide or flaky titanium - metal composite oxide are laminated, and the thickness of the laminated film is 2 nm or more and 40 nm or less.

6. The wiring board according to claim 1, wherein the metal in the flaky titanium - metal composite oxide is at least one selected from the group consisting of iron, cobalt, nickel, and manganese.

7. The wiring board according to claim 1, further comprising an insulating film between the substrate having the copper wiring and the barrier film.

8. The wiring board according to claim 6, wherein the insulating film is an organic film formed of a curable resin composition.

9. A method for manufacturing the wiring board according to any one of claims 1 to 8, comprising a step of coating a composition for forming a barrier film directly or indirectly on a substrate having a copper wiring, wherein the composition for forming a barrier film contains flaky titanium oxide or flaky titanium - metal composite oxide, or flaky titanic acid, flaky titanium - metal acid or their salts and a solvent.

10. A method for manufacturing the wiring board according to any one of claims 1 to 8, comprising a step of forming a polymer film directly or indirectly on a substrate having a copper wiring, coating a composition for forming a barrier film on the polymer film, and removing the polymer film, wherein the composition for forming a barrier film contains flaky titanium oxide or flaky titanium - metal composite oxide, or flaky titanic acid, flaky titanium - metal acid or their salts and a solvent.

11. A composition for forming a barrier film used for manufacturing the wiring board according to any one of claims 1 to 8, the composition for forming a barrier film containing flaky titanium oxide or flaky titanium-metal composite oxide, or flaky titanic acid, flaky titanium-metal acid or salts thereof, and a solvent.

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