JP2001261338A - Raw material solution for forming titanium-containing metal oxide thin film, method of forming the same, and titanium-containing metal oxide thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a raw material solution capable of forming a thick film in a single coating operation, free of striations after being applied, excellent in stability with the lapse of time, causing no cracks in the resultant metal oxide thin film, affording a sufficiently densified metal oxide thin film with on voids, and free of film thickness unevenness after being applied for coating. SOLUTION: In this raw material solution comprised of such a solution that a partial hydrolyzate and/or partial polycondensate thereof of the corresponding alkoxy group-bearing organometallic compounds of component metals is (are) contained in an organic solvent, propylene glycol is used as the organic solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a titanium oxide thin film,
Alternatively, a metal oxide containing Ti for forming a Ti-based oxide thin film such as barium titanate, barium strontium titanate, strontium titanate, bismuth titanate, lead titanate, and lead zirconate titanate by a sol-gel method or the like The present invention relates to a raw material solution for forming a thin film, a method for forming the metal oxide thin film containing Ti, and a metal oxide thin film containing Ti.

[0002]

2. Description of the Related Art Ti-containing metal oxide thin films are made of Ti.
Applications in a wide range of fields are expected due to the properties of the metal itself or the combination of its component metals. For example, a titanium oxide film is used as a high refractive index film and a photocatalyst. Further, barium titanate, barium strontium titanate, strontium titanate, bismuth titanate, lead titanate, lead zirconate titanate, and the like have attracted attention as high dielectric constant films, ferroelectric films, and the like.

[0003] By the way, not only a metal oxide thin film containing Ti but also a general method of forming a metal oxide thin film includes the following.
Although there are a sputtering method, an MOCVD method, and the like, a sol-gel method of applying an organometallic solution to a substrate is a relatively inexpensive and simple method for forming a thin film.

In the sol-gel method, a raw material solution containing a hydrolyzable compound of each component metal as a raw material, a partial hydrolyzate thereof and / or a partial polycondensate thereof is applied to a substrate, and the coating film is dried. Thereafter, the film is heated, for example, to about 400 ° C. in the air to form a metal oxide film, and then fired at a temperature equal to or higher than the crystallization temperature of the metal oxide (eg, about 700 ° C.) to crystallize the film. This is a method of forming a ferroelectric thin film.

As a method similar to the sol-gel method, there is an organic metal decomposition (MOD) method. In the MOD method, a raw material solution containing a thermally decomposable organometallic compound, for example, a metal β-diketone complex (for example, metal acetylacetonate) or a carboxylate (for example, acetate) is applied to a substrate, Heating in air or an oxygen-containing atmosphere, etc., causes evaporation of the solvent in the coating film and thermal decomposition of the metal compound to form a metal oxide film, which is then fired (annealed) at a crystallization temperature or higher. Crystallize the film. Therefore, the film forming operation is almost the same as that of the sol-gel method except for the type of the starting compound.

As described above, since the sol-gel method and the MOD method have the same film forming operation, a method using both of them is also possible. That is, the raw material solution may contain both a hydrolyzable metal compound and a thermally decomposable metal compound. In this case, hydrolysis and thermal decomposition of the raw material compound occur during heating of the coating film, and the metal Oxide forms.

Accordingly, the sol-gel method, MO
The D method and the method using these methods in combination are referred to as “sol-gel method”, and the raw material solution used in such a method is referred to as “sol-gel liquid”.

[0008] The sol-gel method and the like have the advantages of being inexpensive, simple, and suitable for mass production.
An excellent feature is that the film thickness is relatively uniform. Therefore, it can be said that this is the most advantageous film forming method for forming a ferroelectric thin film on a relatively flat substrate.

Metal alkoxides or organic acid salts are generally used as an organic metal raw material for the sol-gel method or the like. As the organic solvent for dissolving these organometallic raw materials, alcohols, ethylene glycol derivatives, xylene, toluene and the like can be used.
As the organic solvent, ethylene glycol derivatives are considered to be good, and in particular, ethylene glycol monomethyl ether (2
-Methoxyethanol) has been widely used (for example, Jpn. J. Appl. Phys. Vol. 33 (1994) pp. 5196-5200,
JP-A-9-28415, etc.).

However, in general, when a film is formed by a sol-gel method using a sol-gel solution using 2-methoxyethanol as an organic solvent, the thickness of a crack-free thin film formed by one coating is at most 0. .About.1 μm (film thickness after annealing), which caused a reduction in production efficiency and an increase in film formation cost.

Therefore, as a method of increasing the film formation throughput by increasing the film thickness which can be formed by one application and lowering the film formation cost, 1,3-propanediol is used as an organic solvent of the sol-gel liquid. (Journal of Materials Science 30 (1995) pp.2507-
2516).

In the case of a sol-gel solution using this 1,3-propanediol solvent, a high-quality film having a fine structure equivalent to that of a sol-gel solution using a 2-methoxyethanol solvent can have a maximum thickness of 1 μm in a single application. Degree (film thickness after annealing)
It can be formed with a film thickness up to. However, this one
The sol-gel solution of 3-propanediol solvent has a boiling point of 21
Since the temperature is as high as 3.5 ° C. and the film is not dried immediately after the application, the film thickness changes before the drying step after the application, and there is a disadvantage that the film thickness differs between the film center portion and the film end portion. (Journa
l of Materials Science 30 (1995) pp. 2507-2516). In addition, even during drying, since the solvent has a high boiling point, the evaporation occurs smoothly, so that the film thickness becomes uneven due to the evaporation after the evaporation. Furthermore, since 1,3-propanediol is expensive, when 1,3-propanediol is used as a solvent, there is also a problem that the cost of the sol-gel liquid increases.

On the other hand, it has been proposed to use propylene glycol as a solvent as a sol-gel solution having excellent long-term storage properties and easy quality control (JP-A-4-342).
422). However, Japanese Patent Application Laid-Open No. 4-342422 discloses
The publication discloses that metal alkoxide is used only for one component Ti of the multi-component system raw material. Since only one kind of metal alkoxide is used, the hydrolysis characteristics are easily controlled and quality control is performed. Although it is easy, the metal-O-metal bond due to hydrolysis and condensation polymerization is small due to the small amount of alkoxide, and most of the ceramics are formed by thermal decomposition, so the obtained ferroelectric thin film is not dense. In addition, there is a problem that a low-quality film having many voids is formed and the crystallization temperature is high. Further, in order to produce a thick film, it is necessary to increase the concentration of the sol-gel solution. However, since the alkoxide is small, the amount of the composite alkoxide generated is also small, and it is difficult to increase the concentration.

[0014]

As described above, conventionally, a relatively thin film having a relatively large thickness can be formed by a single coating without unevenness of the film thickness, and it is inexpensive, has excellent storage stability, and has a high density. In fact, no sol-gel solution capable of easily forming a thin film has been provided.

The present invention solves the above-mentioned conventional problems, and it is possible to form a thick film having a thickness of 0.2 μm or more by one coating. No striations after application. Excellent stability over time. No cracks occur in the metal oxide thin film. There are no voids in the metal oxide thin film and the metal oxide thin film is sufficiently densified. In addition, there is no unevenness in film thickness after coating. It is an object of the present invention to provide a Ti-containing metal oxide thin film forming raw material solution having the above effects.

[0016]

The raw material solution for forming a metal oxide thin film containing Ti according to the present invention is a raw material solution for forming a metal oxide thin film containing Ti, which has an alkoxy group. In a raw material solution comprising a solution containing a partial hydrolyzate of an organometallic compound of a component metal and / or a partial polycondensate thereof in an organic solvent, propylene glycol is contained in the solution.

That is, the present inventors have conducted intensive studies to realize a sol-gel solution having the above-mentioned characteristics, and as a result, using propylene glycol as a main solvent, an organometallic compound of a component metal having an alkoxy group, particularly The present inventors have found that a sol-gel solution satisfying the above properties can be obtained by condensation polymerization of all metal compounds as those containing an alkoxy group of propylene glycol or an alkoxy group of propylene glycol and a β-diketone group. Was completed.

According to the present invention, by including propylene glycol, the viscosity of the solution is increased due to the high viscosity of propylene glycol, and some of the alkoxy groups of the organometallic compound are substituted with the alkoxy groups of propylene glycol. This enables a thick film to be formed (characteristics).

The film thickness can be further increased by subjecting the organometallic compound to polycondensation to include an alkoxy group of propylene glycol or an alkoxy group of propylene glycol and a β-diketone group. This is because the alkoxy group of propylene glycol or the organometallic compound containing the alkoxy group of propylene glycol and β-diketone group has high solubility in alcohol and propylene glycol, and partial hydrolysis and polycondensation in solution. It is conceivable that a large number of metal-oxygen bonds due to are generated.

When it is desired to reduce the film thickness, the film may be diluted with a low-viscosity organic solvent or the like (eg, ordinary alcohol).

The boiling point of propylene glycol is 18
Since the temperature is relatively low at 7.4 ° C., the film thickness becomes uniform, and no film thickness unevenness occurs due to evaporation (characteristic).

Further, as compared with the case where a 1,3-propanediol solvent is used, precipitation and gelation are prevented, and the aging stability of the sol-gel solution is improved due to the stability of the metal alkoxide in propylene glycol. Presumed to be high. (Characteristic).

In particular, by subjecting the organometallic compound to polycondensation as containing an alkoxy group of propylene glycol, the stability over time can be further improved as compared with a sol-gel solution containing only propylene glycol. This is presumably because the substitution of propylene glycol with the alkoxy group of the organometallic compound proceeds with time. Further, when the organometallic compound has a β-diketone group in addition to the alkoxy group of propylene glycol, the stability over time can be further improved.

Further, when all the organometallic compounds contain an alkoxy group or an alkoxy group and a β-diketone group, an oxide thin film with few voids can be obtained (characteristic). This densification is considered to be due to the formation of a large number of metal-oxygen bonds due to partial hydrolysis and partial polycondensation in the alkoxy groups of propylene glycol of all the organometallic compounds in the sol-gel liquid.

Such a raw material solution for forming a metal oxide thin film containing Ti according to the present invention includes a Ti oxide thin film (titanium oxide thin film), a composite oxide thin film containing Ti and another metal, for example, Ti and Ba. And / or perovskite metal oxide thin film containing Sr, perovskite metal oxide thin film containing Ti and Pb, Bi containing Ti and Bi
It is suitable as a raw material solution for forming a layered perovskite-type metal oxide thin film.

In the present invention, the content of propylene glycol with respect to the organic solvent present in the raw material solution is preferably at least 10% by weight, and the concentration of the metal compound in the raw material solution in terms of oxide is preferably at least 10% by weight. Preferably, there is.

In the present invention, β-diketones are used in an amount of 0.1 to the total number of metal elements present in the raw material solution.
It is preferable that the compound is contained with a molecular number of up to 5 times, whereby a more excellent effect can be obtained.

The raw material solution for forming a Ti-containing metal oxide thin film and the method for forming a Ti-containing metal oxide thin film according to the present invention comprise the steps of: A method for forming a metal oxide thin film containing Ti by applying the film to a conductive substrate and then heating the film to a temperature equal to or higher than its crystallization temperature, wherein the film contains Ti having a film thickness of 0.2 μm or more in one coating step. It is characterized by forming a metal oxide thin film.

The Ti-containing metal oxide thin film of the present invention is formed by such a method of forming a Ti-containing metal oxide thin film of the present invention.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

The Ti-containing metal oxide thin film formed in the present invention may be a Ti oxide thin film (titanium oxide thin film) or a composite oxide thin film containing Ti and another metal, for example, Ti and Ba and / or perovskite-type metal oxide thin film, perovskite-type metal oxide thin film, Bi layered perovskite-type metal oxide thin film containing Ti and Bi _{(Bi 4} Ti _{3 O 12} based metal oxide containing Ti and Pb containing Sr Material thin film).

This oxide material can contain a small amount of a doping element. Examples of doping elements include P
b, Zr, Ca, Sr, Ba, Hf, Sn, Th, Y,
Sm, Dy, Ce, Bi, Sb, Nb, Ta, W, M
o, Cr, Co, Ni, Fe, Cu, Si, Ge, U,
Sc, V, Pr, Nd, Eu, Gd, Tb, Ho, E
Examples thereof include r, Tm, Yb, Lu, and La, and the content is preferably 0.1 or less in terms of the atomic fraction of metal atoms in the thin film.

In the present invention, propylene glycol is used as the organic solvent, but may be a single solvent of propylene glycol or a mixed solvent of propylene glycol and another organic solvent. When a mixed solvent of propylene glycol and another organic solvent is used, the ratio of propylene glycol to all organic solvents in the raw material solution is 10% by weight or more, particularly 15% by weight or more, in order to achieve the above-mentioned properties. It is preferred that

Other organic solvents that can be used in combination include:
Alcohols other than propylene glycol, carboxylic acids,
Esters, ketones, ethers, cycloalkanes, aromatic solvents, etc., among which alcohols include ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1
-Propanol, 2-methyl-2-propanol, 1-
Alkanols such as pentanol, 2-pentanol and 2-methyl-2-pentanol, cycloalkanols such as cyclohexanol, and alkoxy alcohols such as 2-methoxyethanol and 1-ethoxy-2-propanol can be used.

Examples of the carboxylic acid solvent include n-
Butyric acid, α-methylbutyric acid, i-valeric acid, 2-ethylbutyric acid,
2,2-dimethylbutyric acid, 3,3-dimethylbutyric acid, 2,3
-Dimethylbutyric acid, 3-methylpentanoic acid, 4-methylpentanoic acid, 2-ethylpentanoic acid, 3-ethylpentanoic acid, 2,2-dimethylpentanoic acid, 3,3-dimethylpentanoic acid, 2,3-dimethylpentane Acid, 2-ethylhexanoic acid, 3-ethylhexanoic acid and the like.

Examples of the ester solvents include ethyl acetate, propyl acetate, n-butyl acetate, sec-butyl acetate, tert-butyl acetate, isobutyl acetate, n-amyl acetate, sec-amyl acetate, tert-amyl acetate, and isoamyl acetate. And the like.

The ketone solvents include acetone, methyl ethyl ethone and methyl isobutyl ketone, and the ether solvents include chain ethers such as dimethyl ether and diethyl ether, and cyclic ethers such as tetrahydrofuran and dioxane. As the cycloalkane-based solvent, cycloheptane,
Cyclohexane and the like, and aromatic solvents include toluene, xylene and the like.

In the present invention, it is preferable to mix β-diketones as a stabilizer in the raw material solution.
By adding a stabilizer, the rate of accelerated decomposition and the rate of polycondensation of the raw material solution are suppressed, and the storage stability is improved. In this case, the amount of β-diketones added as a stabilizer is β-diketone relative to the total number of metal elements present in the raw material solution.
The amount is preferably 0.1 to 5 times, more preferably 0.2 to 3 times, the number of molecules of the diketones. If the amount of the β-diketone is too large, the stability may be reduced. If the amount is too small, the effect of the β-diketone cannot be sufficiently obtained. As the β-diketones to be used, acetylacetone, benzoylacetone, dibenzoylacetone, diisobutylmethane, dipivaloylmethane, 3-methylpentane-2,4
-Dione, 2,2-dimethylpentane-3,5-dione, heptafluorobutanoylpivaloylmethane, trifluoroacetylacetone and the like, among which economicalness, denseness of the film, and halides are included. Acetylacetone is desirable from the viewpoint that there is no acetylacetone.

The β-diketone as a stabilizer may be added at any stage in the production process of the raw material solution. However, when performing azeotropic distillation described later, it is preferable to add it after this distillation. In the case where the metal alkoxide is partially hydrolyzed, it is preferable to add β-diketones before the partial hydrolysis because the hydrolysis rate can be easily controlled. When β-diketones are added, a small amount of water may be added to the raw material solution in order to promote hydrolysis after coating.

In the raw material solution for forming a metal oxide thin film containing Ti according to the present invention, propylene glycol is used as an organic solvent, and preferably, an alkoxy group of propylene glycol or β-
It can be prepared according to a conventional method except that a compound having a diketone group is used, and β-diketones are further compounded as a stabilizer.

As the starting organometallic compound, a component metal or a metal compound containing two or more component metals, a partial hydrolyzate thereof and a partial polycondensate thereof can be used.
Particularly preferred organometallic compounds are hydrolyzable or thermally decomposable organometallic compounds. For example, alkoxides, organic acid salts, β-diketone complexes and the like are typical examples, but various other complexes such as amine complexes can be used for metal complexes. Here, examples of the β-diketone include acetylacetone (= 2,4-pentanedione), heptafluorobutanoylpivaloylmethane, dipivaloylmethane, trifluoroacetylacetone, and benzoylacetone.

Specific examples of suitable organometallic compounds as raw materials include, as the lead compound and the lanthanum compound, organic acid salts such as acetates (lead acetate and lanthanum acetate) and alkoxides such as diisopropoxy lead. Examples of the titanium compound include tetraethoxy titanium, tetra isopropoxy titanium, tetra n-butoxy titanium, tetra i
Alkoxides such as -butoxytitanium, tetra-t-butoxytitanium and dimethoxydiisopropoxytitanium are preferred, but organic acid salts or organometallic complexes can also be used. The zirconium compound is the same as the above-mentioned titanium compound.

Examples of the bismuth compound include carboxylate salts such as bismuth acetate and bismuth 2-ethylhexanoate, bismuth hydroxide, bismuth nitrate, bismuth carbonate, and other alkoxides of bismuth. Examples of the strontium compound include strontium acetate. And carboxylate salts such as strontium 2-ethylhexanoate, strontium hydroxide, strontium nitrate, strontium carbonate, and other strontium alkoxides.

The starting metal compound may be a complex metal compound containing two or more component metals in addition to the compound containing one kind of metal as described above. Examples of such composite metal compounds include PbO
₂ [Ti (OC ₃ H ₇ ) ₃ ] ₂ , PbO ₂ [Zr (OC
₄ H _{9) 3] 2} and the like.

In the present invention, for the above-mentioned reasons, it is particularly preferable that the total organometallic compound is an alkoxide group of propylene glycol or a compound having the alkoxide group and a β-diketone group.
Examples of the Ti raw material compound having a diketone group include titanium diisopropoxide bisacetyl acetate.

In the present invention, a metal compound used as a raw material for each of these component metals is dissolved in propylene glycol or an organic solvent containing propylene glycol,
Preferably, a β-diketone is added as a stabilizer to contain a titanium oxide of a metal oxide thin film containing Ti or a precursor of a composite metal oxide (oxide containing two or more metals). A raw material solution is prepared.

The ratio of the metal compound contained in the raw material solution may be substantially the same as the metal atomic ratio of the metal oxide thin film containing Ti to be formed. However, lead compounds generally have high volatility, and lead deficiency may occur due to evaporation during heating for changing to a metal oxide or during firing for crystallization. Therefore, in anticipation of this deficiency, lead may be present in a slight excess (for example, a 2 to 20% excess).
The degree of lead deficiency varies depending on the type of lead compound and film forming conditions, and can be determined in advance by experiments.

The concentration of the organometallic compound in the raw material solution is not particularly limited, and varies depending on the coating method used and the presence or absence of partial hydrolysis. In general, the total metal content in terms of the organometallic compound is 10 to 40% by weight. In particular, the range is preferably from 15% by weight to 40% by weight. By using such a relatively high-concentration raw material solution, 0.2% can be obtained in one application.
A thick film having a thickness of not less than μm can be formed.

The organic metal compound is propylene glycol,
Alternatively, a solution dissolved in an organic solvent containing propylene glycol can be used as it is as a raw material solution for film formation by a sol-gel method or the like. Alternatively, in order to promote film formation, this solution may be heated to promote partial hydrolysis or partial polycondensation of a hydrolyzable organometallic compound (for example, alkoxide).

The heating for the partial hydrolysis is controlled by controlling the temperature and time so that the hydrolysis does not proceed completely.
When the hydrolysis is completely performed, the stability of the raw material solution is remarkably reduced, gelation is easily caused, and uniform film formation is difficult. The heating conditions are as follows: a temperature of 50 to 200 ° C .;
Time is appropriate. During the hydrolysis, the hydrolyzate
Polycondensation may occur partially due to the MO-bond (M = metal), but such polycondensation is acceptable if it is partial.

When the raw material solution contains both the metal alkoxide and the metal carboxylate, the water of crystallization accompanying the metal carboxylate may be removed before mixing with the metal alkoxide. The removal of the water of crystallization can be carried out by first dissolving only the metal carboxylic acid in a solvent, distilling the solution and dehydrating the solution by azeotropic distillation with the solvent. Therefore, in this case, a solvent that can be azeotropically distilled with water is used. When mixed with a metal alkoxide without removing the water of crystallization of the metal carboxylate, the hydrolysis of the metal alkoxide may progress excessively or may be difficult to control, and when precipitation may occur after partial hydrolysis. Alternatively, water of crystallization may be removed.

According to such a raw material solution for forming a Ti-containing metal oxide thin film of the present invention, a Ti-containing metal oxide thin film can be formed according to the following procedure in the same manner as in a conventional sol-gel method or the like. A film can be formed.

First, the material solution for forming a metal oxide thin film containing Ti of the present invention is applied on a heat-resistant substrate. Coating is generally performed by spin coating, but roll coating, spraying, dipping, curtain flow coating,
Other coating methods, such as a doctor blade, are also applicable. After application, the coating is dried and the solvent is removed. The drying temperature varies depending on the type of the solvent, but is usually 50 to 200.
℃, preferably in the range of 100 to 180 ℃. However, the solvent is removed during the heating in the next step for converting the metal compound in the raw material solution into the metal oxide, so that the step of drying the coating film is not necessarily required.

Thereafter, as a calcining step, the coated substrate is heated, and the metal compound is completely hydrolyzed or thermally decomposed to be converted into a metal oxide, thereby forming a film made of the metal oxide. This heating is generally performed in an atmosphere containing steam in the sol-gel method requiring hydrolysis, for example, in an air or steam-containing atmosphere (for example, a nitrogen atmosphere containing steam), and in the MOD method for thermal decomposition, oxygen-containing is used. It takes place in an atmosphere. The heating temperature varies depending on the type of the metal compound, but is usually in the range of 150 to 550 ° C, preferably 300 to 450 ° C. The heating time is selected so that hydrolysis and thermal decomposition proceed completely, but usually 1 hour.
It takes about a minute or two hours.

In the case of the sol-gel method, etc.
Since it is often difficult to obtain a film thickness required for a metal oxide thin film containing i, the above coating and (drying) calcination are repeated as necessary to obtain a metal oxide film having a desired film thickness. To obtain a film. The film obtained in this way is either amorphous or crystalline, but has insufficient crystallinity. Therefore, finally, as a crystallization annealing step, firing is performed at a temperature equal to or higher than the crystallization temperature of the metal oxide to obtain a crystalline metal oxide thin film having a crystal structure such as a perovskite type. The firing for crystallization may not be performed once at the end, but may be performed after the above-described calcination for each applied coating film, but it is necessary to repeat firing at a high temperature many times. Therefore, it is economically advantageous to perform the operation at the end.

The firing temperature for this crystallization is usually 50
A relatively low temperature of 0 to 1000 ° C. may be sufficient, for example, 550
７００700 ° C. Therefore, a substrate having heat resistance enough to withstand this firing temperature is used. The baking (annealing) time for crystallization is usually 1 minute to 2 minutes.
It is about time, and the firing atmosphere is not particularly limited, but is usually air or oxygen.

Such a metal oxide thin film containing Ti
The heat-resistant substrate material used for forming
(Single crystal or polycrystal), metals such as platinum and nickel
, Ruthenium oxide, iridium oxide, ruthenate
Trontium (SrRuO₃) Or lanthanum cobaltate
Strontium ((La_xSr_1-x) CoO₃)Such
Perovskite-type conductive oxides such as quartz and aluminum nitride
And inorganic compounds such as minium and titanium oxide.
In the case of a capacitor film, the substrate is the lower electrode,
For example, Pt, Pt / Ti, Pt / T
a, Ru, RuO ₂, Ru / RuO₂, RuO₂/ R
u, Ir, IrO₂, Ir / IrO₂, Pt / Ir, P
t / IrO₂, SrRuO₃Or (La_xSr_1-x)
CoO₃Perovskite-type conductive oxide
(Note that a two-layer structure using "/"
Is indicated as “upper / lower”. ).

The thickness of the Ti-containing metal oxide thin film thus formed varies depending on its use, but it is usually preferably about 500 to 5 μm. The thin film is useful for various application devices such as a derivative device.

[0059]

The present invention will be described more specifically below with reference to examples and comparative examples.

The starting metal compounds used in the examples and comparative examples are as follows. Ti raw material compound: titanium diisopropoxide bisacetyl acetate Zr raw material compound: zirconium tetra n-butoxide Pb raw material compound: lead acetate trihydrate La raw material compound: lanthanum acetate hemihydrate Sr raw material compound: strontium acetate 0 .Pentahydrate Bi raw material compound: bismuth acetate Ba raw material compound: barium acetate

Example 1 A reaction vessel was charged with zirconium tetra-n-butoxide and acetylacetone as a stabilizer.
-Butoxide was added 2 mole times, and refluxed at 150 ° C for 3 hours in a nitrogen atmosphere. Titanium diisopropoxide bisacetyl acetate was added thereto, and the mixture was further added at 150 ° C. for 3 hours.
Refluxed in a nitrogen atmosphere for hours. Next, lead acetate trihydrate and lanthanum acetate hemihydrate were added, and propylene glycol as a main solvent was added in an amount of 7 mol based on the total of lead acetate trihydrate and lanthanum acetate hemihydrate. 150 ° C with double addition
For 3 hours in a nitrogen atmosphere. Thereafter, the by-product was removed by distillation under reduced pressure at 150 ° C., and propylene glycol as a main solvent was further added to adjust the concentration, whereby a liquid containing an organometallic compound at a concentration of 30% by weight in terms of oxide was obtained. Obtained. The solution was further refluxed in a nitrogen atmosphere at 150 ° C. for 3 hours, allowed to cool under stirring, and diluted with ethanol to adjust the concentration, whereby the metal atom ratio shown in Table 1 was obtained.
A sol-gel solution containing an organometallic compound at a concentration of 25% by weight in terms of oxide was obtained.

This sol-gel solution was mixed with PbTiO ₃ (40 °)
/ Pt (2000Å) / Ti (200Å) / SiO
₂ (5000 °) / Si (100 °) wafer was coated on a substrate by a spin coating method (1500 rpm, 30 seconds and 60 seconds, respectively) and dried in air at 100 ° C. for 5 minutes (hot plate). After that, it is calcined in air at 350 ° C. for 5 minutes (hot plate).
Calcination in the air for 0 minutes (hot plate), and finally RT
It was baked in an oxygen atmosphere at 700 ° C. for 5 minutes in an A furnace (rapid heat treatment furnace) for crystallization to form a metal oxide thin film.

The metal oxide thin film was examined for film properties by the following method, and the results are shown in Table 1. Table 1 also shows the results of an investigation on the presence or absence of gelation and the occurrence of precipitation when the prepared sol-gel solution was left at room temperature for six months. [Presence / absence of striation] Confirm the film after calcination by optical microscope [Presence / absence of film thickness unevenness] Visually confirm the film after calcination [Presence / absence of crack] Confirm by optical microscope after crystallization [Film thickness (nm)] ] Confirmed by SEM photograph after annealing at 700 ° C

Example 2 Titanium diisopropoxide bisacetyl acetate and lead acetate trihydrate were added to a reaction vessel, and propylene glycol as a main solvent was added in a molar amount of 7 times the lead acetate trihydrate. The mixture was refluxed at 150 ° C. for 3 hours in a nitrogen atmosphere. Thereafter, the by-product was removed by distillation under reduced pressure at 150 ° C., and propylene glycol as a main solvent was further added to adjust the concentration, whereby a liquid containing an organometallic compound at a concentration of 30% by weight in terms of oxide was obtained. Obtained. The solution was further refluxed in a nitrogen atmosphere at 150 ° C. for 3 hours, allowed to cool under stirring, and diluted with ethanol to adjust the concentration, whereby the metal atom ratio shown in Table 1 was 25% by weight as an oxide. A sol-gel solution containing an organometallic compound was obtained.

This sol-gel solution was converted to Pt (2000 °) / T
i (200 °) / SiO ₂ (5000 °) / Si (10
0 °) A wafer was coated on a substrate by a spin coating method (1500 rpm, 60 seconds) and dried in air at 100 ° C. for 5 minutes (hot plate). Then, at 350 ° C., 5
Calcined in air (hot plate) for more than 450 minutes
For 10 minutes in air (hot plate), and finally baked in an RTA furnace (rapid heat treatment furnace) at 700 ° C. for 5 minutes in an oxygen atmosphere to crystallize to form a metal oxide thin film.

The prepared sol-gel solution and this metal oxide were evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Example 3 Titanium diisopropoxide bisacetyl acetate was added to a reaction vessel, and propylene glycol as a main solvent was added 3 mol times the amount of titanium diisopropoxide bisacetyl acetate, and the mixture was added at 150 ° C. for 3 hours. Reflux in a nitrogen atmosphere. Thereafter, the by-product was removed by distillation under reduced pressure at 150 ° C., and propylene glycol as a main solvent was further added to adjust the concentration. Obtained. The solution was further refluxed in a nitrogen atmosphere at 150 ° C. for 3 hours, allowed to cool under stirring, diluted with ethanol, and adjusted in concentration to obtain a metal atom ratio shown in Table 1 at 10% by weight in terms of oxide.
A sol-gel solution containing a concentration of an organometallic compound was obtained.

Using this sol-gel solution, a film was formed in the same manner as in Example 2. The prepared sol-gel solution and this metal oxide were evaluated in the same manner as in Example 1, and the results were shown in Table 1.
It was shown to.

Example 4 Titanium diisopropoxide bisacetyl acetate and strontium acetate hemihydrate were added to a reaction vessel, and propylene glycol was used as a main solvent in an amount of 5 mol per strontium acetate hemihydrate. 3 times at 150 ° C
Refluxed in a nitrogen atmosphere for hours. Thereafter, the by-product was removed by distillation under reduced pressure at 150 ° C., and propylene glycol as a main solvent was further added to adjust the concentration. Obtained. The solution was further refluxed in a nitrogen atmosphere at 150 ° C. for 3 hours, allowed to cool under stirring, diluted with ethanol, and adjusted in concentration to obtain a metal atom ratio shown in Table 1 having a concentration of 20% by weight as oxide. A sol-gel solution containing an organometallic compound was obtained.

Using this sol-gel solution, a film was formed in the same manner as in Example 2. The prepared sol-gel solution and this metal oxide were evaluated in the same manner as in Example 1, and the results were shown in Table 1.
It was shown to.

Example 5 Titanium diisopropoxide bisacetyl acetate and barium acetate were added to a reaction vessel, and propylene glycol as a main solvent was added at 5 times the molar amount of barium acetate. At reflux. afterwards,
By-products were removed by distillation under reduced pressure at 150 ° C., and propylene glycol as a main solvent was further added to adjust the concentration to obtain a liquid containing an organometallic compound at a concentration of 25% by weight in terms of oxide. . The solution was further refluxed in a nitrogen atmosphere at 150 ° C. for 3 hours, allowed to cool under stirring, diluted with ethanol, and adjusted in concentration to obtain a metal atom ratio shown in Table 1 having a concentration of 20% by weight in terms of oxide. A sol-gel solution containing an organometallic compound was obtained.

Using this sol-gel solution, a film was formed in the same manner as in Example 2. The prepared sol-gel solution and this metal oxide were evaluated in the same manner as in Example 1, and the results were shown in Table 1.
It was shown to.

Example 6 Titanium diisopropoxide bisacetyl acetate, barium acetate and strontium acetate 0.5 were placed in a reaction vessel.
A hydrate was added, and propylene glycol as a main solvent was added at a molar ratio of 5 times the total amount of barium acetate and sulotonium acetate hemihydrate, and the mixture was refluxed at 150 ° C. for 3 hours in a nitrogen atmosphere. Thereafter, by-product distillation was performed at 150 ° C. under reduced pressure to remove by-products, and propylene glycol as a main solvent was added to adjust the concentration.
A liquid containing an organic metal compound at a concentration of 5% by weight was obtained. The solution was further refluxed in a nitrogen atmosphere at 150 ° C. for 3 hours, allowed to cool under stirring, diluted with ethanol, and adjusted in concentration to obtain a metal atom ratio shown in Table 1 having a concentration of 20% by weight as oxide. A sol-gel solution containing an organometallic compound was obtained.

Using this sol-gel solution, a film was formed in the same manner as in Example 2, and the prepared sol-gel solution and this metal oxide were evaluated in the same manner as in Example 1, and the results are shown in Table 1.
It was shown to.

Example 7 Titanium diisopropoxide bisacetyl acetate and bismuth acetate were added to a reaction vessel, and propylene glycol as a main solvent was added at a molar ratio of 12 times the amount of bismuth acetate. At reflux. Thereafter, the by-product was removed by distillation under reduced pressure at 150 ° C., and propylene glycol as a main solvent was further added to adjust the concentration. Obtained. The solution was further refluxed in a nitrogen atmosphere at 150 ° C. for 3 hours, allowed to cool under stirring, diluted with ethanol, and adjusted in concentration to obtain a metal atom ratio shown in Table 1 and a concentration of 15% by weight in terms of oxide. A sol-gel solution containing an organometallic compound was obtained.

Using this sol-gel solution, a film was formed in the same manner as in Example 2, and the prepared sol-gel solution and this metal oxide were evaluated in the same manner as in Example 1, and the results were shown in Table 1.
It was shown to.

Comparative Examples 1 to 7 Examples 1 to 7, respectively, except that 1,3-propanediol was used in place of propylene glycol as the main solvent.
Preparation and film formation of the sol-gel liquid in the same manner as in 7, and evaluation of the prepared sol-gel liquid and the formed metal oxide thin film,
The results are shown in Table 1. In Table 1, ○ indicates no, and X indicates yes.

[0078]

[Table 1]

From the above results, it can be seen that the raw material solution for forming a metal oxide thin film containing Ti of the present invention is a good sol-gel solution satisfying the above-mentioned characteristics.

On the other hand, in Comparative Examples 1 to 7 using 1,3-propanediol as the main solvent alcohol,
There is unevenness in film thickness, it is difficult to increase the film thickness, and the stability of the sol-gel liquid is also poor.

[0081]

As described in detail above, according to the present invention, 1
Thick film can be formed by one application; no striation after application; excellent stability over time; no cracks in metal oxide thin film; no voids in metal oxide thin film; sufficiently dense Furthermore, a high-quality Ti-containing material solution for forming a metal oxide thin film containing Ti, which has an excellent effect such as non-uniformity of the film thickness after coating, is obtained.
Can be formed.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Satoshi Fujita 12-6 Techno Park, Mita City, Hyogo Prefecture Mitsubishi Materials Corporation Mita Plant F-term (reference) 4G047 CA02 CA05 CA07 CA08 CB06 CC02 CC03 CD02 4G048 AA03 AB02 AC02 AC08 AD02 AE05 AE08

Claims (12)

[Claims] 1. A raw material solution for forming a Ti-containing metal oxide thin film, wherein a partial hydrolyzate of an organometallic compound of a component metal having an alkoxy group and / or a partial polycondensate thereof is converted to an organic solution. 1. A raw material solution for forming a metal oxide thin film containing Ti, wherein the raw material solution comprises a solution contained in a solvent, wherein the solution contains propylene glycol. 2. The raw material solution for forming a metal oxide thin film containing Ti according to claim 1, which is a raw material solution for forming a Ti oxide thin film. 3. The raw material solution for forming a metal oxide thin film containing Ti according to claim 1, which is a raw material solution for forming a perovskite-type oxide thin film containing Ti, Ba and / or Sr. 4. The raw material solution for forming a metal oxide thin film containing Ti according to claim 1, which is a raw material solution for forming a perovskite oxide thin film containing Ti and Pb. 5. The raw material solution for forming a metal oxide thin film containing Ti according to claim 1, which is a raw material solution for forming a Bi layered perovskite oxide thin film containing Ti and Bi. 6. The method according to claim 1, wherein all of the organometallic compounds in the solution contain Ti which is characterized by having an alkoxy group of propylene glycol or having the alkoxy group and a β-diketone group. Raw material solution for forming a metal oxide thin film. 7. The metal oxide thin film containing Ti according to claim 1, wherein the content of propylene glycol with respect to the organic solvent present in the raw material solution is 10% by weight or more. Raw material solution for formation. 8. The method according to claim 1, wherein the concentration of the component metal compound in the raw material solution in terms of oxide is 1%.
A raw material solution for forming a metal oxide thin film containing Ti, which is 0% by weight or more. 9. The method according to claim 1, wherein the β-diketones have a molecular number 0.1 to 5 times the total number of atoms of the metal element present in the raw material solution. A raw material solution for forming a metal oxide thin film containing Ti, characterized in that: 10. The method according to claim 1, wherein the film is coated on a heat-resistant substrate and heated to a temperature higher than its crystallization temperature to form a film having a thickness of 0.2 μm in one coating step.
A raw material solution for forming a metal oxide thin film containing Ti, which is a raw material solution for forming the above-mentioned metal oxide thin film containing Ti. 11. A Ti-containing metal oxide thin film-forming raw material solution according to any one of claims 1 to 10, which is applied to a heat-resistant substrate and heated to a temperature higher than its crystallization temperature. A method for forming a metal oxide thin film containing Ti, comprising forming a Ti-containing metal oxide thin film having a thickness of 0.2 μm or more in one coating step. Method of forming a thin film. 12. A metal oxide thin film containing Ti formed by the method of claim 11.