Components for forming metal oxide films

Abstract

To provide a metal oxide film-forming composition that provides a metal oxide film with a low etching rate, a metal oxide film manufacturing method using the same, and an etching method.SOLUTION: A metal oxide film-forming composition contains metal oxide nanoclusters (A) and a solvent (S). In the composition, a capping agent (B) containing a carboxylic acid ester compound with a specific structure is bonded to a surface of the metal oxide nanocluster (A), and a size of metal oxide nanocluster (A) is set to 5 nm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a metal oxide film-forming composition, a method for producing a metal oxide film using the metal oxide film-forming composition, and an etching method. [Background technology]

[0002] In general, in etching processes for manufacturing semiconductor devices and the like, a patterned resist film formed by photolithography using a resist material such as a photoresist or an electron beam resist is used as an etching mask. In order to perform etching processing well, it is desirable that the etching rate of the etching mask be significantly lower than the etching rate of the object to be etched when compared to the same type of etchant.

[0003] However, when a resist film formed using the above-mentioned resist material is used as an etching mask, depending on the combination of the etchant and the object to be etched, there may be little difference between the etching rate of the object to be etched and the etching rate of the etching mask. In such cases, an etching mask called a hard mask, which generally exhibits a low etching rate against various etchants, is often used. Known hard masks include, for example, hard masks made of a metal oxide film containing metal oxide nanoparticles such as zirconium oxide nanoparticles (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2020-503409 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventional metal oxide films containing metal oxide nanoparticles are formed by heating a coating film made of a composition containing metal oxide nanoparticles. However, the inventors have found that the etching rate of conventional metal oxide films is not necessarily sufficiently low, and there is a need for a method for forming metal oxide films with a lower etching rate.

[0006] The present invention has been made in view of the above-described conventional circumstances, and aims to provide a metal oxide film-forming composition that provides a metal oxide film with a low etching rate, a method for producing a metal oxide film using the same, and an etching method. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above-mentioned problems. As a result, they have discovered that the above-mentioned problems can be solved by bonding a capping agent (B) containing a carboxylic acid ester compound of a specific structure to the surface of the metal oxide nanocluster (A) in a metal oxide film-forming composition containing the metal oxide nanocluster (A) and a solvent (S), thereby reducing the size of the metal oxide nanocluster (A) to 5 nm or less, and have completed the present invention. Specifically, the present invention provides the following.

[0008] A first aspect of the present invention is a method for producing a metal oxide nanocluster (A) containing a metal oxide nanocluster (A) and a solvent (S), The size of the metal oxide nanocluster (A) is 5 nm or less, A capping agent (B) is bonded to the surface of a metal oxide nanocluster (A), The capping agent (B) is represented by the following formula (b1): R 1 -(CH2) n -CO-OR 2 (b1) (In formula (b1), R 1 is a carboxy group, a phosphono group, or a phosphate group, and R 2 is a saturated aliphatic hydrocarbon group, and n is an integer of 2 or greater. The metal oxide film-forming composition contains one or more compounds represented by the following formula:

[0009] A second aspect of the present invention is forming a coating film made of the metal oxide film-forming composition according to the first aspect; Heating the coating; Including, A method for producing a metal oxide film.

[0010] A third aspect of the present invention is an etching method for etching an etching object having an etching mask, comprising: The method includes heating a coating film formed on an object to be etched, the coating film being made of the metal oxide film-forming composition according to the first aspect, to form an etching mask. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a metal oxide film-forming composition that gives a metal oxide film with a low etching rate, a method for producing a metal oxide film using the same, and an etching method. DETAILED DESCRIPTION OF THE INVENTION

[0012] <Composition for forming metal oxide film> The metal oxide film-forming composition contains metal oxide nanoclusters (A) and a solvent (S). The size of the metal oxide nanoclusters (A) is 5 nm or less. A capping agent (B) is bonded to the surface of the metal oxide nanoclusters (A). The capping agent (B) contains a carboxylic acid ester compound represented by the formula (b1) described below. The metal oxide film formed by heating a coating film made of the above-mentioned metal oxide film-forming composition exhibits an etching rate with various etchants that is sufficiently lower than the etching rates for objects to be etched made of various materials. Therefore, the metal oxide film formed by heating a coating film made of the above-mentioned metal oxide film-forming composition is suitably used as an etching mask.

[0013] Essential and optional components that may be contained in the metal oxide film-forming composition will be described below.

[0014] [Metal oxide nanoclusters (A)] In this specification, the term "metal oxide nanocluster" refers to an aggregate of metal oxides, which is an aggregate composed of multiple surfaces formed from metal oxides. A capping agent (B), which will be described later, is bonded to the surface of the metal oxide nanocluster (A). Note that the metal oxide nanocluster (A) is made of a metal oxide, and the capping agent (B) is not included in the components that make up the metal oxide nanocluster.

[0015] X-ray diffraction measurement of the metal oxide nanocluster (A) detects diffraction peaks corresponding to the above planes. The metal oxide nanocluster (A) may be crystalline, microcrystalline, or amorphous. Depending on the components contained in the metal oxide nanocluster (A), peaks resulting from metal atom planes (crystal planes), broad peaks, or broad halo patterns are detected in the X-ray diffraction pattern of the metal oxide nanocluster (A). In this specification, if not only peaks but also broad peaks or broad halo patterns are not detected in the X-ray diffraction pattern of a certain sample, the sample is deemed to not contain the metal oxide nanocluster (A).

[0016] The size of the metal oxide nanocluster (A) is 5 nm or less, preferably 4 nm or less, and more preferably 3 nm or less. The lower limit of the size of the metal oxide nanocluster is not particularly limited, and may be, for example, 0.5 nm or more, 1 nm or more, or 2 nm or more. By using metal oxide nanoclusters (A) of such a size, it is possible to form a metal oxide film that exhibits a low etching rate with various etchants. In this specification, the size of the metal oxide nanocluster (A) refers to the value calculated by the Halder-Wagner method from the half-width of the scattering peak in the spectrum detected by X-ray scattering intensity distribution measurement.

[0017] There are no particular limitations on the metal elements constituting the metal oxide contained in the metal oxide nanocluster (A). Note that boron, silicon, germanium, arsenic, antimony, and tellurium, which are often distinguished from metal elements as semimetal elements, are also considered to be metal elements in the present application. Examples of metal elements include zinc, yttrium, hafnium, zirconium, lanthanum, cerium, neodymium, gadolinium, holmium, lutetium, tantalum, titanium, silicon, aluminum, antimony, tin, indium, tungsten, copper, vanadium, chromium, niobium, molybdenum, ruthenium, rhodium, rhenium, iridium, germanium, gallium, thallium, and magnesium. Among these, hafnium, zirconium, and titanium are preferred from the viewpoints of the excellent film-forming properties of the metal oxide film-forming composition, the ease of forming metal oxide films that exhibit low etching rates with various etchants, and the stability of the metal oxide nanocluster (A). The metal oxide nanocluster (A) may contain one type of metal oxide, or may contain two or more types of metal oxides.

[0018] The content of the metal oxide nanoclusters (A) in the metal oxide film-forming composition is not particularly limited. Preferably, the metal oxide nanocluster (A) is used in an amount such that the solids concentration of the metal oxide film-forming composition is 0.5 mass % or more and 5 mass % or less. In this specification, the ratio of the total mass of the components of the metal oxide film-forming composition other than the solvent (S) to the mass of the metal oxide film-forming composition is defined as the "solids concentration." By using a metal oxide film-forming composition having a solid content concentration within the above range, it is possible to form a metal oxide film having a high metal oxide filling rate and a low etching rate with various etchants.

[0019] [Capping agent (B)] In the metal oxide film-forming composition, a capping agent (B) is bound to the surface of a metal oxide nanocluster (A). The capping agent (B) may be bound to the metal oxide nanocluster (A) so as to cover a part of the surface of the metal oxide nanocluster (A), or may be bound to the metal oxide nanocluster (A) so as to cover the entire surface of the metal oxide nanocluster (A). By bonding the capping agent (B) to the surface of the metal oxide nanocluster (A), the metal oxide nanocluster (A) is dispersed uniformly and stably in the metal oxide film-forming composition.

[0020] The capping agent (B) contains one or more compounds represented by the following formula (b1): R 1 -(CH2) n -CO-OR 2 (b1) (In formula (b1), R 1 is a carboxy group, a phosphono group, or a phosphate group, and R 2 is a saturated aliphatic hydrocarbon group, and n is an integer of 2 or greater. The compound represented by formula (b1) is susceptible to thermal decomposition due to its structure. Therefore, when a coating film made of a metal oxide film-forming composition containing metal oxide nanoclusters (A) to which a compound represented by formula (b1) is bonded as a capping agent (B) is heated, the capping agent (B) is thermally decomposed satisfactorily, and a metal oxide film in which the metal oxide nanoclusters (A) are densely packed is formed. A metal oxide film in which the metal oxide nanoclusters (A) are densely packed exhibits a low etching rate with various etchants.

[0021] In formula (b1), R 1is a carboxy group, a phosphono group, or a phosphate group. The compound represented by formula (b1) binds to the surface of the metal oxide nanocluster (A) through the interaction between the carboxy group, the phosphono group, or the phosphate group and the surface of the metal oxide nanocluster (A).

[0022] In formula (b1), R 2 is a saturated aliphatic hydrocarbon group. 2 However, if the capping agent (B) is an unsaturated aliphatic hydrocarbon group, the unsaturated bonds react with each other during the formation of the metal oxide film by heating, which is thought to inhibit the successful decomposition of the capping agent (B).If the capping agent (B) is not successfully thermally decomposed, the filling rate of the metal oxide nanoclusters (A) in the metal oxide film decreases, and the etching rate of the metal oxide film with various etchants increases.

[0023] R 2 The structure of the saturated aliphatic hydrocarbon group as the aryl group may be linear, cyclic, or a combination of a linear structure and a cyclic structure. The linear saturated aliphatic hydrocarbon group may be linear or branched. R 2 The number of carbon atoms in the saturated aliphatic hydrocarbon group R is not particularly limited. 2 The saturated aliphatic hydrocarbon group as the alkyl group preferably has 1 or more and 10 or less carbon atoms, more preferably 1 or more and 6 or less carbon atoms, and even more preferably 1 or more and 4 or less carbon atoms. R 2 Specific examples of the saturated aliphatic hydrocarbon group as include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, and an n-decyl group.

[0024] In formula (b1), n ​​is an integer of 2 or more. There is no particular upper limit for n. n is preferably an integer of 2 or more and 10 or less, more preferably an integer of 2 or more and 6 or less, even more preferably an integer of 2 or more and 4 or less, and particularly preferably 2 or 3.

[0025] Preferable specific examples of the compound represented by formula (b1) include: succinic acid monomethyl ester, succinic acid monoethyl ester, succinic acid mono-n-propyl ester, succinic acid monoisopropyl ester, succinic acid mono-n-butyl ester, succinic acid mono-tert-butyl ester, adipic acid monomethyl ester, adipic acid monoethyl ester, adipic acid mono-n-propyl ester, adipic acid monoisopropyl ester, adipic acid mono-n-butyl ester, adipic acid mono-tert-butyl ester, Glutaric acid monomethyl ester, Glutaric acid monoethyl ester, Glutaric acid mono-n-propyl ester, Glutaric acid monoisopropyl ester, Glutaric acid mono-n-butyl ester, and Carboxylic acid esters such as glutaric acid mono-tert-butyl ester; 2-(methoxycarbonyl)ethylphosphonic acid, 2-(ethoxycarbonyl)ethylphosphonic acid, 2-(n-propyloxycarbonyl)ethylphosphonic acid, 2-(isopropyloxycarbonyl)ethylphosphonic acid, 2-(n-butyloxycarbonyl)ethylphosphonic acid, 2-(tert-butyloxycarbonyl)ethylphosphonic acid, 3-(methoxycarbonyl)propylphosphonic acid, 3-(ethoxycarbonyl)propylphosphonic acid, 3-(n-propyloxycarbonyl)propylphosphonic acid, 3-(isopropyloxycarbonyl)propylphosphonic acid, 3-(n-butyloxycarbonyl)propylphosphonic acid, 3-(tert-butyloxycarbonyl)propylphosphonic acid, 4-(methoxycarbonyl)butylphosphonic acid, 4-(ethoxycarbonyl)butylphosphonic acid, 4-(n-propyloxycarbonyl)butylphosphonic acid, 4-(isopropyloxycarbonyl)butylphosphonic acid, 4-(n-butyloxycarbonyl)butylphosphonic acid, and Alkylphosphonic acids such as 4-(tert-butyloxycarbonyl)butylphosphonic acid; 2-(methoxycarbonyl)ethyl phosphate, 2-(ethoxycarbonyl)ethyl phosphate, 2-(n-propyloxycarbonyl)ethyl phosphate, 2-(isopropyloxycarbonyl)ethyl phosphate, 2-(n-butyloxycarbonyl)ethyl phosphate, 2-(tert-butyloxycarbonyl)ethyl phosphate, 3-(methoxycarbonyl)propyl phosphate, 3-(ethoxycarbonyl)propyl phosphate, 3-(n-propyloxycarbonyl)propyl phosphate, 3-(isopropyloxycarbonyl)propyl phosphate, 3-(n-butyloxycarbonyl)propyl phosphate, 3-(tert-butyloxycarbonyl)propyl phosphate, 4-(methoxycarbonyl)butyl phosphate, 4-(ethoxycarbonyl)butyl phosphate, 4-(n-propyloxycarbonyl)butyl phosphate, 4-(isopropyloxycarbonyl)butyl phosphate, 4-(n-butyloxycarbonyl)butyl phosphate, and Examples include phosphate esters such as 4-(tert-butyloxycarbonyl)butyl phosphate.

[0026] Among these, succinic acid monomethyl ester, succinic acid monoethyl ester, succinic acid mono-n-propyl ester, succinic acid monoisopropyl ester, succinic acid mono-n-butyl ester, succinic acid mono-tert-butyl ester, adipic acid monomethyl ester, adipic acid monoethyl ester, adipic acid mono-n-propyl ester, adipic acid monoisopropyl ester, adipic acid mono-n-butyl ester, adipic acid mono-tert-butyl ester, Glutaric acid monomethyl ester, Glutaric acid monoethyl ester, Glutaric acid mono-n-propyl ester, Glutaric acid monoisopropyl ester, Glutaric acid mono-n-butyl ester, and Carboxylic acid esters such as glutaric acid mono-tert-butyl ester are preferred.

[0027] The mass ratio of the compound represented by formula (b1) to the total mass of the capping agent (B) is not particularly limited as long as the desired effect is not impaired. The ratio of the mass of the compound represented by formula (b1) to the total mass of the capping agent (B) is preferably 50 mass% or more, more preferably 70 mass% or more, even more preferably 80 mass% or more, particularly preferably 90 mass% or more, and most preferably 100 mass%.

[0028] As described above, the capping agent (B) may contain other compounds in addition to the compound represented by formula (b1). Examples of the capping agent (B) that can be used together with the compound represented by formula (b1) include at least one selected from the group consisting of alkoxysilanes, phenols, alcohols, carboxylic acids, and carboxylic acid halides.

[0029] Specific examples of the capping agent (B) include n-propyltrimethoxysilane, n-propyltriethoxysilane, n-octyltrimethoxysilane, n-octyltriethoxysilane, n-dodecyltrimethoxysilane, n-dodecyltriethoxysilane, n-hexadecyltrimethoxysilane, n-hexadecyltriethoxysilane, n-octadecyltrimethoxysilane, n-octadecyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenethylphenyltrimethoxysilane, and phenyltriethoxysilane. Ethylethyltriethoxysilane, 3-{2-methoxy[poly(ethyleneoxy)]}propyltrimethoxysilane, 3-{2-methoxy[poly(ethyleneoxy)]}propyltriethoxysilane, 3-{2-methoxy[tri(ethyleneoxy)]}propyltrimethoxysilane, 3-{2-methoxy[tri(ethyleneoxy)]}propyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane, allyltriethoxysilane, 1-hexenyltrimethoxysilane, 1-hexenyltrimethoxysilane Cetyltriethoxysilane, 1-octenyltrimethoxysilane, 1-octenyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-acryloylpropyltriethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, 3-isocyanatopropyl Alkoxysilanes such as propyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropyltriethoxysilane; phenols or alcohols such as ethanol, n-propanol, isopropanol, n-butanol, n-heptanol, n-hexanol, n-octanol, oleyl alcohol, n-dodecyl alcohol, n-octadecanol, benzyl alcohol, phenol, and triethylene glycol monomethyl ether;Examples of the acid include acids such as octanoic acid, acetic acid, propionic acid, 2-[2-(methoxyethoxy)ethoxy]acetic acid, oleic acid, lauric acid, stearic acid, benzoic acid, 2-acryloyloxyethyl succinic acid, and 2-acryloyloxyethyl phthalic acid; and acid halides of these acids, such as acid chlorides of these acids, preferably phenols, alcohols, or the compounds listed as acids.

[0030] The method for bonding the capping agent (B) to the surface of the metal oxide nanocluster (A) is not particularly limited as long as it is a method that can bring the metal oxide nanocluster (A) into contact with the capping agent (B). For example, the capping agent (B) or a solution of the capping agent (B) may be added dropwise or sprayed onto the powdered metal oxide nanocluster (A), and then the two may be mixed uniformly. Alternatively, the metal oxide nanocluster (A) may be dispersed in an organic solvent that does not fall under the category of the capping agent (B), and then the metal oxide nanocluster (A) and the capping agent (B) may be mixed together.

[0031] The amount of the capping agent (B) is not particularly limited as long as the desired effect is not impaired. The amount of the capping agent (B) is preferably 10% by mass or more and 300% by mass or less, and more preferably 40% by mass or more and 200% by mass or less, relative to the mass of the metal oxide nanocluster (A). By using the capping agent (B) in the above range, it is possible to obtain the desired effects of using the capping agent (B) and to form a metal oxide film that exhibits a low etching rate with various etchants.

[0032] Solvent The metal oxide film-forming composition contains a solvent for the purpose of adjusting the coating property and viscosity. An organic solvent is typically used as the solvent. The type of organic solvent is not particularly limited as long as it can uniformly dissolve or disperse the components contained in the metal oxide film-forming composition.

[0033] Suitable examples of organic solvents that can be used as the solvent (S) include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol-n-propyl ether, ethylene glycol mono-n-butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-n-butyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-n-butyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-n-butyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-n-butyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-n-butyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-butyl ... (Poly)alkylene glycol monoalkyl ethers such as dipropylene glycol monomethyl ether and tripropylene glycol monoethyl ether; (poly)alkylene glycol monoalkyl ether acetates such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate; other ethers such as diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol diethyl ether, and tetrahydrofuran; ketones such as methyl ethyl ketone, cyclohexanone, 2-heptanone, and 3-heptanone; alkyl lactate esters such as methyl 2-hydroxypropionate and ethyl 2-hydroxypropionate;Other esters such as ethyl 2-hydroxy-2-methylpropionate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, methyl 3-ethoxypropionate, ethyl 3-ethoxypropionate, ethyl ethoxyacetate, ethyl hydroxyacetate, 2-hydroxy-3-methyl methyl carbonate, 3-methyl-3-methoxybutyl acetate, 3-methyl-3-methoxybutylpropionate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl formate, isopentyl acetate, n-butyl propionate, ethyl butyrate, n-propyl butyrate, isopropyl butyrate, n-butyl butyrate, methyl pyruvate, ethyl pyruvate, n-propyl pyruvate, methyl acetoacetate, ethyl acetoacetate, and ethyl 2-oxobutanoate; aromatic hydrocarbons such as toluene and xylene; and amides such as N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide. These organic solvents may be used alone or in combination of two or more kinds.

[0034] The amount of the solvent (S) contained in the metal oxide film-forming composition is not particularly limited as long as the desired effect is not impaired. Since the formed metal oxide film exhibits a low etching rate with various etchants, for example, the solvent (S) is preferably used so that the solids concentration of the metal oxide film-forming composition is 0.5 mass % or more and 5 mass % or less.

[0035] [Other ingredients] The metal oxide film-forming composition may contain additives such as surfactants, dispersants, thermal polymerization inhibitors, antifoaming agents, silane coupling agents, colorants (pigments, dyes), inorganic fillers, organic fillers, crosslinking agents, and acid generators, as needed. Any of these additives may be conventionally known. Examples of surfactants include anionic, cationic, and nonionic compounds. Examples of thermal polymerization inhibitors include hydroquinone and hydroquinone monoethyl ether. Examples of antifoaming agents include silicone and fluorine-based compounds.

[0036] The method for producing the metal oxide film-forming composition is not particularly limited as long as it can uniformly mix the metal oxide nanoclusters (A) having the capping agent (B) bonded to their surfaces with the solvent (S). Specifically, the metal oxide film-forming composition can be produced, for example, according to the method shown in the Examples below.

[0037] <Metal oxide film manufacturing method> A metal oxide film is formed by heating a coating film made of the above-described metal oxide film-forming composition. That is, forming a coating film made of the above-mentioned metal oxide film-forming composition; and heating the coating to form a metal oxide film. The thickness of the metal oxide film is not particularly limited as long as the desired effect is not impaired. In terms of ease of forming a metal oxide film that exhibits a low etching rate with various etchants, the thickness of the metal oxide film is preferably 5 nm to 200 nm, more preferably 10 nm to 150 nm, and even more preferably 20 nm to 100 nm. The thickness of the metal oxide film can be adjusted by adjusting the thickness of the coating film made of the metal oxide film-forming composition, for example, by adjusting the solids concentration or viscosity of the metal oxide film-forming composition. A metal oxide film having a thickness within the above range has a high metal oxide filling rate and a low etching rate with respect to various etchants.

[0038] The coating film can be formed, for example, by applying the metal oxide film-forming composition to various substrates. Coating methods include methods using contact transfer coating devices such as roll coaters, reverse coaters, and bar coaters, and non-contact coating devices such as spinners (rotary coating devices, spin coaters), dip coaters, spray coaters, slit coaters, and curtain flow coaters. Alternatively, the viscosity of the metal oxide film-forming composition may be adjusted to an appropriate range, and then the metal oxide film-forming composition may be applied by a printing method such as an inkjet method or a screen printing method to form a coating film patterned into a desired shape. When the metal oxide film thus formed is used as a metal hard mask for etching, a patterned coating film is formed on the surface of an object to be etched.

[0039] The material of the substrate is not particularly limited. Suitable examples of the material of the substrate surface on which the metal oxide film is formed include metals, metal carbides, metal oxides, metal nitrides, and metal oxynitrides. Examples of the metals include silicon, titanium, tungsten, hafnium, zirconium, chromium, germanium, copper, aluminum, indium, gallium, arsenic, palladium, iron, tantalum, iridium, molybdenum, and alloys thereof. The substrate surface may have an uneven shape, and the uneven shape may be made of a patterned organic material. When the metal oxide film is used as a metal hard mask for etching, the material of the etching target portion of the etching target is preferably silicon nitride, silicon oxide, silicon oxycarbide, silicon carbide, silicon, polysilicon, diamond-like carbon, copper, ruthenium, tungsten, or cobalt, of which silicon nitride, silicon oxide, silicon oxycarbide, silicon carbide, silicon, polysilicon, and diamond-like carbon are preferred.

[0040] Next, if necessary, volatile components such as the solvent are removed to dry the coating film. The drying method is not particularly limited, and examples include a method of drying on a hot plate at a temperature of 80°C to 140°C, preferably 90°C to 130°C, for a time period of 60 to 150 seconds. Before heating on the hot plate, drying under reduced pressure at room temperature using a vacuum dryer (VCD) may be performed.

[0041] After the coating film is formed in this manner, the coating film is heated. The temperature at which the heating is performed is not particularly limited. The heating temperature is preferably 400°C or higher, more preferably 420°C or higher, and even more preferably 430°C or higher. The upper limit may be set appropriately, for example, to 600°C or lower, preferably 550°C or lower. The heating time is typically preferably 30 seconds or longer and 150 seconds or shorter, more preferably 60 seconds or longer and 120 seconds or shorter. The heating step may be performed at a single heating temperature, or may consist of multiple stages with different heating temperatures.

[0042] The metal oxide film formed as described above is suitably used as, for example, a metal hard mask for etching.

[0043] <Etching method> The etching method is an etching method for etching an etching target provided with an etching mask. Specifically, the etching method includes heating a coating film made of the above-mentioned metal oxide film-forming composition formed on an object to be etched to form an etching mask. In view of the low etching rate with respect to various etchants, the metal oxide nanocluster (A) contained in the metal oxide forming composition is preferably made of zirconium oxide.

[0044] The etching method is not particularly limited and may be appropriately selected from known etching methods depending on the material of the portion to be etched in the etching object. The etching method may be wet etching or dry etching, with dry etching being preferred. When dry etching is performed, it is preferable to use one or more etchants selected from the group consisting of CHF3, CF4, SF6, CHF3, CH3F, Cl2, BCl3, HBr, O2, N2, HBr, Ar, and He. Among these etchants, it is preferable to use one or more etchants selected from the group consisting of CHF3, CF4, SF6, CHF3, CH3F, Cl2, and BCl3.

[0045] Since there is a large difference between the etching rate of the etching mask and the etching rate of the object to be etched, the following combinations of the material of the object to be etched and the etchant are preferred: a combination of silicon nitride with a mixed gas of CHF3, CF4, CH3F, or SF6 and O2; a combination of silicon oxide with a mixed gas of CHF3, CF4, CH3F, or SF6 and O2; and a combination of polysilicon with BCl3, Cl2, or HBr. [Example]

[0046] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0047] [Preparation of Metal Oxide Film-Forming Composition] The following dispersions were prepared with reference to the description in paragraph

[0223] of JP 2018-193481 A.

[0048] [Examples 1 to 3 and Comparative Examples 1 to 3] In the examples and comparative examples, the following capping agents B1 to B6 were used. B1: succinic acid mono-tert-butyl ester B2: Adipic acid monoethyl ester B3: Glutaric acid monoethyl ester B4: 2-Acryloyloxyethyl succinic acid B5: Lauric acid B6: Malonic acid monoethyl ester

[0049] Preparation of zirconium oxide nanocluster dispersion Based on the description in paragraph

[0223] of JP 2018-193481 A, zirconium(IV) isopropoxide isopropanol (Zr(OCH(CH3)2)4(HOCH(CH3)2)) was used as the raw zirconium compound. The raw zirconium compound was reacted with water in a molar ratio of 3:1 to form a ZrO2 slurry. The ZrO2 slurry was cooled to room temperature and centrifuged to obtain wet cake A. A capping agent in an amount 1.4 times the weight of wet cake A was added to wet cake A and stirred. The types of capping agents used were those listed in Table 1. After reprecipitation, wet cake B was obtained by centrifugation. Wet cake B was dried under reduced pressure overnight to obtain a powder. Propylene glycol monomethyl ether acetate (hereinafter referred to as "PGMEA") was added to the obtained dried powder so that the solids concentration became 10% by mass, and the powder was redispersed. The mixture was then filtered to obtain a zirconium oxide nanocluster dispersion. The size (crystallite size) of the obtained zirconium oxide nanoclusters was 2.5 nm, and the size of the zirconium oxide nanoclusters was confirmed by the method described below.

[0050] -Metal oxide nanocluster size measurement Using zirconium oxide nanocluster dispersions, titanium oxide nanocluster dispersions, and hafnium oxide nanocluster dispersions as samples, XRD measurements were carried out using an X-ray diffractometer (SmartLab, manufactured by Rigaku Corporation). The results were analyzed using the accompanying software PDXL, and the size (crystallite size) of the metal oxide nanoclusters was determined using the Halder-Wagner method.

[0051] Metal oxide films were formed using the metal oxide film-forming compositions of each Example and Comparative Example obtained by the above method, and the etching selectivity, thickness of the metal oxide film, and filling rate of the metal oxide in the metal oxide film were measured according to the following methods. The measurement results are shown in Table 1.

[0052] (Method for measuring etching selectivity) The metal oxide film-forming compositions of each Example and Comparative Example were applied to a silicon nitride substrate using a spin coater. The metal oxide film-forming compositions applied to the substrate were baked at 100°C for 2 minutes to form a coating. The formed coating was then fired at 450°C for 90 seconds to form a metal oxide film. The thickness of the formed metal oxide film was measured under the following conditions using a rotary compensator-type high-speed spectroscopic ellipsometer (Woollam M-2000, manufactured by J.A. Woollam Japan Co., Ltd.). The measurement results are shown in Table 1. Measurement angles: 65°, 70°, 75° Fitting model: B-Spline

[0053] The obtained metal oxide film was subjected to dry etching under the following conditions. The thickness of the metal oxide film before and after dry etching was measured using a rotary compensator-type high-speed spectroscopic ellipsometer (Woollam M-2000, manufactured by J.A. Woollam Japan Co., Ltd.) according to the method described above. The etching rate of the metal oxide film, which is the amount of film thickness reduction per unit time, was calculated from the etching time and the change in thickness of the metal oxide film before and after etching. Furthermore, dry etching was performed on the silicon nitride substrate under the above conditions, and the etching rate of silicon nitride was calculated from the etching time and the change in thickness of silicon nitride before and after etching.

[0054] Etching equipment: RIE-200NL-101iPH (SAMCO) Etchant: CHF3 Flow rate: 70sccm Pressure: 5Pa Time: 1 minute

[0055] The etching selectivity was calculated from the etching rate of the metal oxide film and the etching rate of silicon nitride calculated by the above method using the following formula. The etching selectivity for each example and each comparative example is shown in Table 1. The higher the etching selectivity, the lower the etching rate of the metal oxide film. Etching selectivity = etching rate of silicon nitride / etching rate of metal oxide film

[0056] [Table 1]

[0057] According to the examples, it is clear that by using a composition for forming a metal oxide film, which contains metal oxide nanoclusters (A) having a size of 5 nm or less and having a capping agent (B) bonded to its surface, and which contains B1 to B3 corresponding to the compounds represented by the above-mentioned formula (b1) as capping agents (B), it is possible to form a metal oxide film with a low etching rate. On the other hand, it has been found that when a metal oxide film-forming composition is used that contains metal oxide nanoclusters (A) having a size of 5 nm or less and having a capping agent (B) bound to its surface, but that contains B4 to B6 as capping agents (B) that do not fall under the compounds represented by the above-mentioned formula (b1), a metal oxide film with a high etching rate is formed.

[0058] Comparative Example 4 A zirconium oxide nanocluster dispersion was obtained in the same manner as in Example 1, except that zirconium (IV) isopropoxide isopropanol (Zr(OCH(CH3)2)4(HOCH(CH3)2) was used as the raw zirconium compound and the raw zirconium compound was reacted with water in a molar ratio of 1.2:1, and B1: succinic acid mono-tert-butyl ester was used as the capping agent. The solids concentration of the obtained dispersion was 10 mass %. The size of the obtained zirconium oxide nanoclusters was 10 nm. Using the resulting dispersion, film formation was attempted using the method described above, but visually noticeable unevenness was observed, and a uniform film could not be obtained. There is a risk that the unevenness of the hard mask layer (metal oxide film) formed by coating may be transferred to layers below the hard mask layer during etching. For this reason, dry etching was not evaluated.

Claims

1. A method for producing a metal oxide nanocluster (A) and a solvent (S), The size of the metal oxide nanocluster (A) is 5 nm or less, a capping agent (B) is bound to the surface of the metal oxide nanocluster (A); The capping agent (B) is represented by the following formula (b1): R １ -(CH ２ ) ｎ -CO-O-R ２ ・・・(b1) (In formula (b1), R １ is a carboxy group, a phosphono group, or a phosphate group, and R ２ is a saturated aliphatic hydrocarbon group, and n is an integer of 2 or more. A metal oxide film-forming composition comprising one or more compounds represented by the following formula:

2. 2. The metal oxide film-forming composition according to claim 1, wherein the metal contained in the metal oxide nanocluster (A) is at least one metal selected from the group consisting of zinc, yttrium, hafnium, zirconium, lanthanum, cerium, neodymium, gadolinium, holmium, lutetium, tantalum, titanium, silicon, aluminum, antimony, tin, indium, tungsten, copper, vanadium, chromium, niobium, molybdenum, ruthenium, rhodium, rhenium, iridium, germanium, gallium, thallium, and magnesium.

3. The metal oxide film-forming composition according to claim 2 , wherein the metal is zirconium.

4. forming a coating film made of the metal oxide film-forming composition according to claim 1 or 2; heating the coating; A method for producing a metal oxide film, comprising:

5. The method according to claim 4, wherein the coating film is heated to a temperature of 400°C or higher.

6. The manufacturing method according to claim 4, wherein the metal oxide film is a metal hard mask.

7. An etching method for etching an etching object having an etching mask, comprising: A method for forming an etching mask, comprising heating a coating film formed on an object to be etched, the coating film being made of the metal oxide film-forming composition according to claim 1 or 2.

8. 8. The etching method according to claim 7, wherein the metal oxide nanoclusters contained in the metal oxide film-forming composition are made of zirconium oxide.

9. 8. The etching method according to claim 7, wherein the material of the portion to be etched of the object to be etched is silicon nitride, silicon oxide, silicon oxycarbide, silicon carbide, silicon, gallium nitride, polysilicon, diamond-like carbon, copper, ruthenium, tungsten, or cobalt.

10. As an etchant, CHF ３ , C.F. ４ , S.F. ６ , CHF ３ , C.H. ３ F, Cl ２ , BCl ３ , HBr, O ２ , N ２ 8. The etching method according to claim 7, wherein one or more selected from the group consisting of HBr, Ar, and He is used.

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