JP2964893B2 - Preparation method of oxide thin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an oxide ferroelectric thin film or an oxide paraelectric thin film which can be used for a thin film capacitor, a piezoelectric material, a pyroelectric material or the like.

[0002]

2. Description of the Related Art Ferroelectric thin films are used in many fields of electronics due to many properties of ferroelectrics such as ferroelectricity, piezoelectricity, pyroelectricity, and electro-optic effect. Application to memory cells is receiving attention with the rapid development of integration. Of these, barium strontium titanate has a higher dielectric constant than strontium titanate, and can change the Curie temperature depending on the composition ratio of barium and strontium, and can be used as a paraelectric at the operating temperature of the device. A particularly promising material. Conventionally, as a method of manufacturing an oxide thin film, a method of forming a film by a dry process such as a sputtering method or a vacuum evaporation method, or a method of forming a film by a wet process such as a sol-gel method has been adopted.

However, in the case of film formation by a dry process, the equipment used is very expensive and the vapor pressure differs for each element, so that a thin film having excellent stoichiometry cannot be stably manufactured. However, they have disadvantages such as poor crystallinity, low productivity and high cost, and are far from practical use. On the other hand, when a film is formed by a wet process, for example, a sol-gel method using an organometallic compound is required to precisely control chemical composition, uniformity at a molecular level,
There are advantages in terms of lowering the temperature of the process, increasing the area, and reducing equipment costs. However, since the conventional sol-gel method mainly uses methanol or a lower alcohol such as ethanol as a solvent, the solution of the organometallic compound is extremely unstable, and absorbs atmospheric moisture and is easily hydrolyzed. Therefore, it was difficult to produce a uniform thin film. Further, since these lower alcohols have a high vapor pressure, the film after coating is dried quickly in spin coating or the like, and it has been difficult to produce a thin film having a uniform thickness. In recent years, for example, J.I. Am. Ceram. So
c. , 71, (5), C-280 (1988), etc.
The use of ethylene glycol monomethyl ether in the production of a ferroelectric thin film such as lead titanate has been described, which is represented by the general formula (Ba _x Sr _1-x ) TiO ₃ (0
When it is used as a solvent for synthesizing an oxide thin film represented by ≦ x ≦ 1), there has been a problem that an organometallic compound of Ba and an organometallic compound of Ti selectively react and precipitate. Further, Advanced Ceramic M
materials, 3, (2), 183 (1988), etc., describe that barium acetate is dissolved in an aqueous acetic acid solution and mixed with titanium isopropoxide. In this method, titanium isopropoxide and acetic acid are used. Reacts easily to form precipitates. In addition, in order to achieve precise control of composition and uniformity, it is necessary to synthesize a composite alkoxide having a controlled metal atomic ratio as a precursor, but since water is added to the raw material, a solution of the precursor is required. Was unstable, and it was difficult to control the chemical composition of the precursor.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances. That is, an object of the present invention is to provide a uniform and highly stoichiometric oxide ferroelectric thin film or oxide which can be used for a thin film capacitor, a piezoelectric substance, a pyroelectric substance, etc. on a substrate using an organometallic compound. An object of the present invention is to provide a method for stably producing a paraelectric thin film.

[0005]

The present inventors have studied and found that the general formula (Ba _x Sr _1-x ) TiO ₃ (0 ≦ x ≦ 1)
In the method for producing an oxide thin film represented by
r, dissolve the organometallic compound containing each Ti component in a specific solvent, or dissolve them in a specific solvent in a specific order, apply the resulting mixed solution on a substrate to form a thin film, Then by crystallization following pyrolysis,
It has been found that oxide thin films that are uniform and have excellent stoichiometry can be prepared.

A first aspect of the present invention is a compound represented by the general formula (Ba _x S)
r _1-x ) TiO ₃ (0 <x ≦ 1), and relates to a method for producing an oxide thin film, which is represented by the following general formula (IA)
R ^{1 ′} OR ² OH (IA) wherein R ^{1 ′} represents an aliphatic hydrocarbon group having 2 or more carbon atoms, and R ² may have an ether bond. Represents a divalent aliphatic hydrocarbon group.) The following general formulas (II) and (III)
) Or three kinds of metal alkoxide compounds represented by the general formulas (II) to (IV) are converted to Ba (OR ³ ) ₂ (II) Ti (OR ⁴ ) ₄ (III) Sr (OR ⁵ ) ₂ (IV) (In the formula, R ³ , R ⁴ and R ⁵ each represent an aliphatic hydrocarbon group.) Simultaneously or in an arbitrary order, and after mixing, the mixture is heated and reacted. The obtained mixed solution is applied on a substrate to form a thin film, and then heat-treated.

A second aspect of the present invention is a compound represented by the general formula (Ba _x S)
r _1-x ) TiO ₃ (0 <x <1) and relates to a method for producing an oxide thin film represented by the following general formula (IB)
In a solvent represented by the following formula, CH ₃ OR ^{2 ′} OH (IB) (wherein R ^{2 ′} represents a divalent aliphatic hydrocarbon group.) A barium alkoxide compound represented by the following general formula (II) Ba (OR ³ ) ₂ (II) (wherein R ³ represents an aliphatic hydrocarbon group) and then two kinds of compounds represented by the following general formulas (III) and (IV) A metal alkoxide compound is added and reacted to obtain Ti (OR ⁴ ) ₄ (III) Sr (OR ⁵ ) ₂ (IV) (wherein R ⁴ and R ⁵ each represent an aliphatic hydrocarbon group). The mixed solution is applied on a substrate to form a thin film, and then heat-treated.

A third aspect of the present invention relates to a method for producing an oxide thin film represented by SrTiO ₃ , wherein R ¹ is a compound represented by the following general formula (I): R ¹ OR ² OH (I) Represents an aliphatic hydrocarbon group, and R ² represents a divalent aliphatic hydrocarbon group which may have an ether bond.) Two metal alkoxides represented by the following general formulas (III) and (IV) The compounds are added at the same time or in any order and mixed, and then reacted by heating. Ti (OR ⁴ ) ₄ (III) Sr (OR ⁵ ) ₂ (IV) (wherein R ⁴ and R ⁵ are fats, respectively) Represents a group hydrocarbon group.) The obtained mixed solution is applied on a substrate to form a thin film, and then heat-treated.

Hereinafter, the present invention will be described in detail. In the present invention, the metal alkoxide compound used is selected from those represented by the following general formulas (II), (III) and (IV). Ba (OR ³ ) ₂ (II) Ti (OR ⁴ ) ₄ (III) Sr (OR ⁵ ) ₂ (IV) (wherein, R ³ , R ⁴ and R ⁵ each represent an aliphatic hydrocarbon group. In general formulas (II), (III) and (IV), R ³ , R ⁴ and R ⁵ are preferably an alkyl group having 1 to 4 carbon atoms, and specific metal alkoxide compounds include barium dimethoxide. , Barium diethoxide,
Barium dipropoxide, barium dibutoxide, strontium dimethoxide, strontium diethoxide, strontium dipropoxide, strontium dibutoxide, titanium tetramethoxide, titanium tetraethoxide, titanium tetrapropoxide, titanium tetrabutoxide, etc. can be exemplified. However, the present invention is not limited to these.

The solvent used in the present invention is represented by the following general formula (I). ^{R 1 OR 2 OH (I)} ( wherein, R ¹ represents an aliphatic hydrocarbon group, R ² represents a divalent aliphatic hydrocarbon group which may have an ether bond.) Of R ¹ As the aliphatic hydrocarbon group, an alkyl group having 1 to 4 carbon atoms is preferable, and R ² is an alkylene group having 2 to 4 carbon atoms as the divalent aliphatic hydrocarbon group which may have an ether bond. And a divalent group having 4 to 8 carbon atoms in which an alkylene group having 2 to 4 carbon atoms is bonded by an ether bond. Specifically, for example, monoalkyl ethers of ethylene glycol such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl Monoalkyl ethers of diethylene glycol such as ethers,
1,2-propylene glycol monoalkyl ethers such as 1,2-propylene glycol monomethyl ether, 1,3-propylene glycol monomethyl ether, 1,3-propylene glycol monoethyl ether, 1,3-propylene glycol monopropyl ether, and the like Monoalkyl ethers of 1,3-propylene glycol, and the like, but are not limited thereto. These may be used alone or in combination of two or more. Among them, examples of the solvent represented by the above general formula (IB) include ethylene glycol monomethyl ether, 1,3-propylene glycol monomethyl ether and the like.

In the present invention, the compounds represented by the above general formulas (II) and (II)
The metal alkoxide compounds represented by I) and (IV) are added or dissolved in the solvent represented by the above general formula (I) simultaneously or in an arbitrary order, and reacted by heating. In this case, when R ¹ in the general formula (I) represents a methyl group, that is, when the solvent represented by the general formula (IB) is used, attention should be paid to the order of adding the metal alkoxide. There must be. That is, first, a barium alkoxide compound represented by the general formula (II) is added, dissolved, and reacted by heating. Thereby, the ligand of Ba is replaced with a solvent. Next, a metal alkoxide compound containing Ti represented by the general formula (III) and a metal alkoxide compound containing Sr represented by the general formula (IV) are added to the solution. If the order of addition is not such, precipitation occurs in the solution, and a homogeneous mixed solution cannot be obtained. In the case of producing an oxide thin film represented by BaTiO ₃ , two kinds of metal alkoxide compounds represented by the general formulas (II) and (III) are used, and SrTiO ₃ is used.
In the case of producing an oxide thin film represented by the formula (2), two kinds of metal alkoxide compounds represented by the above general formulas (III) and (IV) may be used. It is effective that the mixed solution obtained as described above is further treated by distillation or reflux to form a complex alkoxide as a precursor.

The mixed solution obtained by reacting the metal alkoxide compound as described above is coated on a substrate to form a thin film, and then heat-treated. In this case, it is also possible to apply the mixed solution on a substrate after hydrolysis. As the substrate, any substrate can be used as long as it can be applied to a target element.
ITO / SiO ₂ glass, Pt / Ti / SiO ₂ / Si
Etc. can be used. Methods for applying this solution on a substrate include spin coating, dipping, spraying,
A screen printing method, an inkjet method, or the like can be used.

The coated substrate is heated. That is, the substrate is heated at a heating rate of 0.1 to 500 ° C./sec, and the coating layer is thermally decomposed in a temperature range of 100 ° C. to 500 ° C. where crystallization does not occur, and then 0.1 to 500 ° C./sec. The substrate is heated at a temperature rising rate of 300 ° C., and the oxide thin film is crystallized in a temperature range of 300 ° C. to 1200 ° C. When the application is repeated, after the application, the substrate is heated at a heating rate of 0.1 to 500 ° C./sec, and the applied layer is thermally decomposed in a temperature range of 100 ° C. to 500 ° C. where crystallization does not occur. After repeating this application and thermal decomposition a predetermined number of times, the oxide thin film is crystallized in a temperature range of 300 ° C to 1200 ° C. By this heat treatment, an oxide thin film is formed.

The heat treatment temperature during the film formation is 500 to 12
When the temperature is in the range of 00 ° C., the mixed solution obtained as described above is applied to a substrate in a state where water or a catalyst is not added (that is, in a state where it is not hydrolyzed), and heat treatment is performed. Is preferred. The reason for this is that it is more preferable to use the non-hydrolyzed state in terms of electric characteristics, particularly leak current characteristics.

[0015]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples. Example 1 Ba (OC ₂ H ₅ ) ₂ was dissolved in ethylene glycol monomethyl ether dehydrated with a molecular sieve to obtain a 0.6 M solution. The solution is stirred for 1 hour.
Distilled at 25 ° C. for 2 hours, refluxed for further 22 hours,
a (OC ₂ H ₄ OCH ₃ ) ₂ was obtained. Sr (OC ₂ H ₅ ) ₂ and Ti (O-i-C ₃ H ₇ ) ₄ are added to the solution so that the molar ratio of Ba, Sr, and Ti is 0.5: 0.5: 1, and 0 is added. A solution having a concentration of 0.6 M was obtained. Next, this solution was distilled at 125 ° C. for 2 hours while stirring, and further refluxed for 22 hours to obtain a composite alkoxide: (Ba _0.5 Sr _0.5 ) Ti
(OC ₂ H ₄ OCH ₃ ) ₆ was obtained. This alcohol substitution reaction was confirmed by a ¹ H NMR spectrum. This solution was a homogeneous, light brown, transparent liquid without any precipitate. This solution was spin-coated on an ITO / SiO ₂ glass substrate, and then heated at a rate of 10 ° C./sec.
Hold at 0 ° C for 2 minutes and 700 ° C for 1 hour. (Ba _0.5 Sr _0.5 ) T consisting of the obtained perovskite single phase
The surface of the iO ₃ thin film was optically smooth and transparent.

Comparative Example 1 Ba (OC ₂ H ₅ ) ₂ , Sr (OC ₂ H ₅ ) ₂ and Ti
(OiC ₃ H ₇ ) ₄ was simultaneously dissolved in ethylene glycol monomethyl ether dehydrated with a molecular sieve such that the molar ratio of Ba: Sr: Ti was 0.5: 0.5: 1. The solution was distilled at 125 ° C. for 2 hours with stirring, and refluxed for 22 hours. When this solution was allowed to stand at room temperature for a while, a precipitate was formed, and the solution did not become a uniform solution. As a result of the analysis, a large amount of Ba and Ti was detected in the precipitate, and a large amount of Sr was detected in the solution as compared with the composition ratio of the charge. From this analysis result, it was found that a precursor having excellent stoichiometry could not be synthesized by the method of this comparative example.

Example 2 Ti (OiC ₃ H ₇ ) ₄ was dissolved in ethylene glycol monoethyl ether dehydrated with a molecular sieve to obtain a 0.6M concentration solution.
Distilled at 35 ° C. for 2 hours. Ba, Sr and Ti
Is adjusted so that the molar ratio of Ba (O-
Add i-C ₃ H ₇ ) ₂ and Sr (OC ₂ H ₅ ) ₂ and add 0.6
M solution was obtained. The solution is then stirred at 135 ° C.
And refluxed for 22 hours to obtain a composite alkoxide: (Ba _0.6 Sr _0.4 ) Ti (OC ₂ H ₄ O).
C ₂ H ₅ ) ₆ was obtained. This alcohol substitution reaction is ¹ H
Confirmed by NMR spectrum. This solution was a uniform, light brown, transparent liquid without any precipitate. This solution was spin-coated on an ITO / SiO ₂ glass substrate, then heated at a rate of 10 ° C./sec and kept at 300 ° C. for 2 minutes and 700 ° C. for 1 hour. The resulting film thickness of 0.1 μm
The (Ba _0.6 Sr _0.4 ) TiO ₃ thin film was composed of a single perovskite phase, and its surface was optically smooth and transparent.

Comparative Example 2 Ba (OC ₂ H ₅ ) ₂ , Sr (OC ₂ H ₅ ) ₂ and Ti
(OiC ₃ H ₇ ) ₄ was simultaneously dissolved in ethylene glycol monomethyl ether dehydrated with a molecular sieve such that the molar ratio of Ba: Sr: Ti was 0.6: 0.4: 1. Then, a solution having a concentration of 0.6 M was obtained, distilled at 125 ° C. for 2 hours with stirring, and refluxed for 22 hours. When this solution was allowed to stand at room temperature for a while, a metal-colored precipitate was formed, and the solution did not become a uniform solution. As a result of the analysis, a large amount of Ba and Ti was detected in the precipitate, and a large amount of Sr was detected in the solution as compared with the composition ratio of the charge. From this analysis result, it was found that a precursor having excellent stoichiometry could not be synthesized by the method of this comparative example.

Example 3 Ti (OiC ₃ H ₇ ) ₄ was dissolved in ethylene glycol monoethyl ether dehydrated with a molecular sieve to obtain a 0.6 M concentration solution. The solution is stirred for 1 hour.
Distilled at 35 ° C. for 2 hours. The molar ratio of Ba and Ti in the solution is 1: 1 so as to _{Ba (O-i-C 3} H 7) 2 was added to obtain a solution of 0.6M concentration. Next, this solution was distilled at 135 ° C. for 2 hours with stirring, and further refluxed for 18 hours to obtain a composite alkoxide: BaTi (OC ₂ H ₄ OC _2).
Were obtained H _{5) 6.} This alcohol substitution reaction is ¹ H NM
Confirmed by R spectrum. This solution was a uniform, light brown, transparent liquid without any precipitate. Further, water was added to this solution so that the molar ratio with Ba was 1: 1 to obtain a uniform partial hydrolysis solution. This solution was converted to Pt / Ti /
Spin coating on SiO ₂ / Si substrate followed by 10 ° C.
/ Second at 350 ° C. for 2 minutes and 700
C. for 30 minutes. The obtained ferroelectric thin film BaTiO ₃ having a thickness of 0.1 μm is composed of a single phase of perovskite,
The surface was optically smooth and transparent.

Comparative Example 3 Ba (OC ₂ H ₅ ) ₂ and Ti (OiC ₃ H ₇ ) ₄ were converted to B
a and Ti were simultaneously dissolved in ethylene glycol monomethyl ether dehydrated with a molecular sieve so as to have a molar ratio of 1: 1 to form a 0.6 M solution, and distilled at 125 ° C. for 2 hours with stirring. Reflux for an additional 22 hours. When this solution was allowed to stand at room temperature for a while, a large amount of precipitate was formed, and the solution did not become a uniform solution.

Example 4 Sr (OC ₂ H ₅ ) ₂ and Ti (OiC ₃ H ₇ ) ₄ were converted to S
r and Ti were simultaneously dissolved in ethylene glycol monomethyl ether dehydrated with molecular sieves so as to have a molar ratio of 1: 1 to form a 0.5 M concentration solution, and distilled at 125 ° C. for 2 hours while stirring, After refluxing for another 22 hours, the composite alkoxide: SrTi (OC ₂ H ₄ OC
H ₃ ) ₆ was obtained. This alcohol substitution reaction is ¹ H NM
Confirmed by R spectrum. This solution was a uniform, light brown, transparent liquid without any precipitate. This solution is
The substrate was spin coated and subsequently heated at a rate of 10 ° C./sec and held at 300 ° C. for 2 minutes and at 700 ° C. for 1 hour. The obtained 0.1 μm-thick SrTiO ₃ thin film was composed of a single perovskite phase, and its surface was optically smooth and transparent.

Example 5 Complex alkoxide obtained in Example 4: SrTi
A solution containing (OC ₂ H ₄ OCH ₃ ) ₆ was spin-coated on an ITO / glass substrate, subsequently heated at a rate of 10 ° C./sec, and held at 300 ° C. for 2 minutes and at 600 ° C. for 30 minutes. . Further, when Pt was adhered to the thin film and the leak current was measured, it was found that the applied current was about 1 at an applied voltage of 2 V.
× 10 ⁻⁶ A / cm ² .

Example 6 Complex alkoxide obtained in Example 4 above: Sr
Water was added to the solution containing Ti (OC ₂ H ₄ OCH ₃ ) _{6 so} that the molar ratio with Ti was 1: 1 to obtain a uniform partial hydrolysis solution. This solution was spin-coated on an ITO / glass substrate, and then heated at a rate of 10 ° C./sec.
It was kept at 00 ° C for 2 minutes and at 600 ° C for 30 minutes. Further, when Pt was adhered on the thin film and the leak current was measured, at an applied voltage of 2 V, about 1 × 10 ⁻⁵ A /
cm ² .

Example 7 Sr (OC ₂ H ₅ ) ₂ and Ti (O-i-C ₃ H ₇ ) ₄ were converted to S
r and Ti were dissolved simultaneously in ethylene glycol monoethyl ether dehydrated with molecular sieves so that the molar ratio of r and Ti became 1: 1 to form a 0.6 M solution, and distilled at 135 ° C. for 2 hours with stirring. The mixture was further refluxed for 22 hours to obtain a composite alkoxide: SrTi (OC ₂ H ₄ OC
It was obtained ₂ H _{5) 6.} This alcohol substitution reaction is ¹ H N
Confirmed by MR spectrum. This solution was a uniform, light brown, transparent liquid without any precipitate. This solution is
Spin-coated on TO / glass, followed by heating at a rate of 10 ° C / sec, 300 ° C for 2 minutes and 600 ° C for 3 minutes.
Hold for 0 minutes. Furthermore, when Pt was adhered on the obtained thin film and the leak current was measured, it was about 5 × 10 ⁻⁷ A / cm ² at an applied voltage of 2 V.

Example 8 Complex alkoxide obtained in Example 7: SrTi
Water was added to the solution containing (OC ₂ H ₄ OC ₂ H ₅ ) _{6 so} that the molar ratio with Ti was 1: 1 to obtain a uniform partial hydrolysis solution. This solution was spin-coated on an ITO / glass substrate, and then heated at a rate of 10 ° C./sec.
Hold at 0 ° C for 2 minutes and at 600 ° C for 30 minutes. Further, when Pt was deposited on this thin film and the leak current was measured, the applied current was about 5 × 10 ⁻⁶ A / c at an applied voltage of 2 V.
m ² .

[0026]

The present invention uses a mixed solution prepared by adding a metal alkoxide compound containing Ba, Sr and Ti components to the solvent represented by the above general formula (I) as described above, the general formula as in the case of using those represented by (I-B), since a mixed solution was prepared by adding the metal alkoxide compound in a specific order, are formed formula (Ba _x Sr _{1 -x} ) TiO ₃ (0
The oxide thin film represented by ≦ x ≦ 1) is uniform and excellent in stoichiometry, and can be used as an oxide thin film usable for a thin film capacitor, a piezoelectric body, a pyroelectric body, and the like.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-286922 (JP, A) JP-A-1-111723 (JP, A) JP-A-63-310969 (JP, A) JP-A-1- 133967 (JP, A) Hyde, A .; R. et al. "Preparation of BaxSi (1-x) Ti03 and silica films by sol-gel techniques", Br. Ceram. Proc. (1991), Vol. 48, pp. 37-46 (58) Fields investigated (Int. Cl. ⁶ , DB name) C01G 1/00-23/08 C04B 35/42-35/49 C23C 18/00- 20/08 CA (STN) REGISTRY (STN) Patent file (PATOLIS)

Claims (3)

(57) [Claims] 1. The method according to claim 1, wherein the formula (Ba _x Sr _{1 -x} ) TiO ₃ (0
In the method for producing an oxide thin film represented by <x ≦ 1),
In a solvent represented by the following general formula (IA), R ^{1 ′} OR ² OH (IA) (wherein R ^{1 ′} represents an aliphatic hydrocarbon group having 2 or more carbon atoms, and R ² represents an ether) Represents a divalent aliphatic hydrocarbon group which may have a bond.) The following general formulas (II) and (III)
) Or three kinds of metal alkoxide compounds represented by the general formulas (II) to (IV) are converted to Ba (OR ³ ) ₂ (II) Ti (OR ⁴ ) ₄ (III) Sr (OR ⁵ ) ₂ (IV) (In the formula, R ³ , R ⁴ and R ⁵ each represent an aliphatic hydrocarbon group.) Simultaneously or in an arbitrary order, and after mixing, the mixture is heated and reacted. A method for producing an oxide thin film, comprising applying the mixed solution obtained on a substrate to form a thin film, and then performing a heat treatment. 2. The compound of the general formula (Ba _x Sr _1-x ) TiO ₃ (0
In the method for producing an oxide thin film represented by <x <1),
In a solvent represented by the following general formula (IB), CH ₃ OR ^{2 '} OH (IB) (wherein R ^2' represents a divalent aliphatic hydrocarbon group). ) Is dissolved in a barium alkoxide compound and reacted by heating, wherein Ba (OR ³ ) ₂ (II) (wherein R ³ represents an aliphatic hydrocarbon group). Then, the following general formulas (III) and (III) The two metal alkoxide compounds represented by IV) are added and reacted, and Ti (OR ⁴ ) ₄ (III) Sr (OR ⁵ ) ₂ (IV) (where R ⁴ and R ⁵ are each an aliphatic group) A hydrocarbon group.) A method for producing an oxide thin film, comprising applying the obtained mixed solution onto a substrate to form a thin film, and then performing heat treatment. 3. A method for producing an oxide thin film represented by SrTiO ₃ , wherein R ¹ OR ² OH (I) wherein R ¹ is an aliphatic hydrocarbon group And R ² represents a divalent aliphatic hydrocarbon group which may have an ether bond.) Two kinds of metal alkoxide compounds represented by the following general formulas (III) and (IV) can be used simultaneously or optionally. After mixing and heating, Ti (OR ⁴ ) ₄ (III) Sr (OR ⁵ ) ₂ (IV) (wherein R ⁴ and R ⁵ are each an aliphatic hydrocarbon group) A method for producing an oxide thin film, comprising applying the obtained mixed solution onto a substrate to form a thin film, and then performing heat treatment.