JP2000351623A - Raw material solution for forming perovskite oxide thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a perovskite oxide thin film having a uniform surface shape and excellent uniformity of electric characteristics by using a raw material solution for forming a perovskite oxide thin film not using an ethylene glycol derivative. SOLUTION: In this raw material solution for forming a perovskite oxide thin film containing Ti and/or Zr, the raw material solution comprises a solution of a metal compound containing each component metal or two or more component metals, its partial hydrolyzate or its partial polycondensate in an organic solvent. The solution contains one or more kinds of butanol solvents selected from the group consisting of 1-butanol, 2-butanol, 2-methyl-1-propanol and 2- methyl-2propanol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a metal oxide-based perovskite oxide thin film which can be expected to be applied to various dielectric devices due to its electrical and / or optical properties.
The present invention relates to a raw material solution for forming a perovskite oxide thin film to be formed by a sol-gel method or the like.

[0002]

2. Description of the Related Art Metal oxide thin films, in particular, lead zirconate titanate (PZT) and lanthanum-doped (PLZT)
_{ZT: Pb x La 1-x} (Zr y Ti 1-y) 1-X / 4 O 3) is their high dielectric constant, is applied from the excellent ferroelectric characteristics to the various dielectric device it has been expected. As a method of forming these metal oxide thin films, there are a sputtering method, an MOCVD method, and the like. As a relatively inexpensive and simple method of forming a thin film, there is a sol-gel method of applying an organic metal solution to a substrate.

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 at a crystallization temperature or higher to crystallize the film. To 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, in the following, the sol-gel method, MO
The D method and methods using these methods in combination are referred to as “sol-gel method”.

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 an organic solvent for the raw material solution for forming a perovskite oxide thin film, an ethylene glycol derivative is considered to be good, and in particular, ethylene glycol monomethyl ether (2-methoxyethanol) has been widely used (for example, Jp.
nJAppl.Phys.Vol.33 (1994) pp.5196-5200, JP-A-9
-28415 publication).

[0009]

However, recently, the harmfulness of ethylene glycol derivatives such as ethylene glycol monomethyl ether and the like, particularly the influence on the reproductive function, has become a problem (for example, JP-A-9-28415).
Accordingly, development of a raw material solution for forming a perovskite oxide thin film without using an ethylene glycol derivative has been strongly desired.

In addition, PZT prepared by a conventional sol-gel method
In general, it is known that the surface morphology of a system thin film is uneven, and the particle size of the film-forming particles is non-uniform (for example,
Jpn.J.Appl.Phys.Vol.33 (1994) pp.5159-5166, J.Mate
r. Res., vol 11, No. 10, Oct. 1996, pp. 2556-2564). That is, the PZT-based thin film generally has an uneven surface morphology divided into coarse perovskite particles having a particle diameter of about 1000 nm and fine zirconia particles. If the surface morphology is non-uniform, the electrical characteristics will also be non-uniform depending on the location, which will be an obstacle to producing a fine capacitor.

The present invention solves the above-mentioned conventional problems, and is a raw material solution for forming a perovskite-type oxide thin film without using an ethylene glycol derivative, wherein the perovskite has a uniform surface morphology and excellent uniformity of electric characteristics. It is an object of the present invention to provide a raw material solution for forming a perovskite-type oxide thin film that can form a type oxide thin film.

[0012]

The raw material solution for forming a perovskite oxide thin film of the present invention is a raw material solution for forming a perovskite oxide thin film containing Ti and / or Zr. A raw material solution comprising a solution containing one or more metal compounds selected from the group consisting of a metal or a metal compound containing two or more component metals, a partial hydrolyzate thereof and a partial polycondensate thereof in an organic solvent In the solution, 1-butanol, 2-butanol,
It is characterized by containing one or more butanol solvents selected from the group consisting of 2-methyl-1-propanol and 2-methyl-2-propanol.

[0013] That is, the present inventors have considered that in order to achieve the above object, first, as the organometallic compound as a raw material, a metal alkoxide is desirable. This is because in the sol-gel method using a metal alkoxide as a central raw material, a metal-oxygen bond is formed by hydrolysis and condensation polymerization, and as a result, a dense film is generally easily obtained. On the other hand, the MOD method using a thermally decomposable organometallic compound as a raw material is generally considered to be a porous thin film and easy to have a rosette structure because the raw material does not undergo condensation polymerization. Therefore, as an organometallic compound as a raw material, a lead raw material compound is lead acetate trihydrate and / or lead acetate anhydride, a titanium raw material compound is titanium alkoxide, and a Zr raw material compound is zirconium alkoxide. And proceeded with the research. Where Pb
The reason why lead acetate was selected as the raw material compound is that lead alkoxides did not dissolve and the stability with time was poor.

The present inventors have conducted intensive studies on such a raw material system to find a raw material solution for forming a perovskite oxide thin film satisfying the following conditions.

The solvent used is a low-toxic organic solvent. It has excellent coating properties (no striation). It has stability over time. It has good surface morphology and a dense film. As a result, butanol, i.e., 1-butanol, 2-butanol, 2-methyl-1-propanol,
By using 2-methyl-2-propanol as a main solvent, coating properties are remarkably improved, and a drastic improvement in the surface morphology of the obtained thin film is observed. Further, β-diketones are required as a stabilizer. The present inventors have found that by adding a fixed amount, it is possible to suppress the rate of hydrolysis and the rate of polycondensation of the raw material solution and to improve the stability over time, without impairing the effect of improving the applicability and surface morphology. Was completed.

Organic solvents other than butanol satisfying the condition of a low-toxic organic solvent have high solubility and few precipitates do not occur during synthesis, and have good coating properties even in a raw material solution using a solvent that does not precipitate during synthesis. In many cases, good surface morphology could not be satisfied even if the coating characteristics were satisfied. Butanol was most suitable as the organic solvent satisfying the above conditions.

Further, other stabilizers other than β-diketones (β-ketoesters, alkanolamines, polyhydric alcohols, esters, long-chain carboxylic acids, long-chain alcohols, and others) have coating properties, Some of them were effective in improving the stability over time, but none of them could satisfy the surface morphology.

On the other hand, selection of the starting organometallic compound was also studied. Previously, a film was formed using butanol (Journal of Materials Science 19 (1984) 595-5
98), but the starting organometallic compounds used here were lead 2-ethylhexanoate, zirconium acetyl acetate, and titanium tetrabutoxide. Then, when the raw material system used here was examined, as a raw material organometallic compound, 2-Pb raw material compound was used.
When lead ethylhexanoate was used, the above conditions were satisfied, but the conditions were not satisfied, and a porous thin film having many voids was obtained. On the other hand, when lead acetate trihydrate and / or anhydrous lead acetate were used, a dense thin film structure was obtained, and not only the surface morphology but also the surface morphology was good.

When zirconium acetyl acetate is used as the Zr raw material compound, the above conditions are satisfied, but striation occurs, and there is also a problem in stability over time. (Eg, 15% PLZT (120/1/52/48)). Further, the above conditions were not satisfied, and a porous thin film having many voids was obtained. On the other hand, when the zirconium alkoxide was used, the amount of lead was increased by 15% PL by optimizing the amount of acetylacetone.
A solution free of ZT (130/1/52/48) precipitation could be obtained, and a dense thin film structure was obtained, and the surface morphology was good. This is because, when zirconium acetyl acetate is used as a raw material, the amount of β-diketones such as acetylacetone cannot be optimized, so that a precipitate is generated, whereas in the case of zirconium alkoxide, the amount of β-diketones such as acetylacetone is reduced. It is considered that the solution can be optimized, so that a solution without precipitation can be obtained by this optimization, and that other conditions are satisfied.

According to the present invention, there is provided a raw material solution for forming a perovskite-type oxide thin film, which has low toxicity, excellent coating properties, excellent stability over time, and a dense film having a good surface morphology. .

When the raw material solution for forming a perovskite oxide thin film of the present invention is formed into a film, a good surface morphology is obtained. Specifically, the crystal grains become finer and the particle size becomes smaller throughout the film. The mechanism of the effect of eliminating the variation other than perovskite such as the zirconia phase or the pyrochlore phase in addition to the fact that it becomes almost uniform and the dispersion disappears is presumed as follows.

That is, the organometallic complex of Ti and / or Zr to which butanol (or butanol and β-diketones) present in the raw material solution is coordinated is a conventional organometallic complex,
For example, since the crystallization temperature is lower than that of an organometallic complex to which an ethylene glycol derivative (or an ethylene glycol derivative and a stabilizer) is coordinated, during calcination of the film and / or crystallization annealing (firing), First, a large number of TiO ₂ or ZrO ₂ crystals are generated unevenly on the substrate. Then, since these crystals become initial nuclei and grow, crystal oxide thin films composed of uniform and fine crystal grains are formed. As described above, since the crystal grains are fine and uniform, and no phase other than perovskite is generated, the electrical characteristics are also uniform throughout the film,
Even if a device is manufactured from any part of the ferroelectric thin film, a product of almost the same quality can be obtained, and the reliability of the product is improved.

In the present invention, the content of the butanol solvent with respect to the organic solvent present in the raw material solution is 30% by weight.
It is preferable that it is above.

In the present invention, β-diketones are added in an amount of 0.1 to the total number of metal elements present in the raw material solution.
To 5 times the number of molecules, in particular, the content of 1-butanol with respect to the organic solvent present in the raw material solution is 30% by weight or more and based on the total number of metal elements present in the raw material solution. It is preferable that acetylacetone is contained in a molecular number of 0.1 to 5 times, whereby a more excellent effect can be obtained.

The raw material solution for forming a perovskite type oxide thin film of the present invention is particularly suitable as a raw material solution for forming a perovskite type oxide thin film containing Pb and Zr and / or Ti.

As described above, in the present invention, titanium alkoxide is used as the Ti raw material compound, zirconium alkoxide is used as the Zr raw material compound, and lead acetate trihydrate and / or anhydrous lead acetate are used as the Pb raw material compound. Preferably, it is used.

[0027]

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

The perovskite-type oxide thin film formed in the present invention is an oxide material containing one or both of Ti and Zr. As an example of such a perovskite oxide thin film, a perovskite oxide thin film (lead zirconate titanate: PZT thin film) composed of Pb and Zr and / or Ti can be mentioned.

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

In the present invention, as the organic solvent, butanol, ie, 1-butanol, 2-butanol, 2-butanol,
One or two or more butanol solvents of methyl-1-propanol and 2-methyl-2-propanol are used,
In consideration of economy, melting point, and handling property depending on flash point, it is most preferable to use 1-butanol. As the organic solvent, a mixed solvent of these butanol solvents and another organic solvent may be used.In this case, in order to obtain excellent surface morphology, the ratio of the butanol solvent to the total organic solvent in the raw material solution is required. Is 30% by weight or more, especially 4%
It is preferable that the content be 0% by weight or more.

Other organic solvents that can be used in combination include:
Alcohols other than butanol, carboxylic acids, esters,
Ketones, ethers, cycloalkanes, aromatic solvents and the like can be mentioned, and among them, alcohols include ethanol, 1-propanol, 2-propanol, 1-pentanol, 2-pentanol, 2-methyl-2-pen Alkanols such as tanol, 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 solvent 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. 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.

The raw material solution for forming a perovskite oxide thin film of the present invention uses a butanol solvent as an organic solvent,
Preferably, it can be prepared according to a conventional method except that a β-diketone is blended as a stabilizer.

As the starting metal compound, a metal compound containing each component metal or two or more component metals, a partial hydrolyzate thereof and a partial polycondensate thereof can be used, and a particularly preferable metal compound is a hydrolyzable metal compound. Alternatively, it is a thermally decomposable organometallic compound. 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 organometallic compounds suitable 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.

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, in particular, Ti
It is preferable to use titanium alkoxide as a raw material compound, zirconium alkoxide as a Zr raw material compound, and lead acetate trihydrate and / or anhydrous lead acetate as a Pb raw material compound.

In the present invention, a metal compound used as a raw material of each of these component metals is dissolved in butanol or an organic solvent containing butanol, and preferably formed by adding a β-diketone as a stabilizer. A raw material solution containing a precursor of a composite metal oxide (an oxide containing two or more metals) of a perovskite oxide thin film is prepared.

The ratio of each metal compound contained in the raw material solution may be substantially the same as the metal atomic ratio of the perovskite oxide thin film 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 metal compound in the raw material solution is not particularly limited and varies depending on the coating method to be used and the presence or absence of partial hydrolysis. Generally, the total metal content in terms of metal oxide is 0.1 to 20% by weight. Is preferable.

A solution in which a metal compound is dissolved in butanol or an organic solvent containing butanol can be used as it is as a raw material solution for film formation by a sol-gel method or the like. Alternatively, to promote film formation, the solution is heated to produce a hydrolyzable metal compound (eg, alkoxide).
May be partially hydrolyzed or partially polycondensed and used for film formation. That is, in this case, the raw material solution contains a partial hydrolyzate and / or a partial polycondensate of at least a part of the metal compound.

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 a temperature of 80 to 200 ° C., a temperature of 0.5 to 50
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 a metal alkoxide and a metal carboxylate, it is preferable to remove crystallization water accompanying the metal carboxylate 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. If the metal carboxylate is mixed with the metal alkoxide without removing the water of crystallization, the hydrolysis of the metal alkoxide may progress too much or its control may be difficult, and precipitation may occur after partial hydrolysis.

According to such a raw material solution for forming a perovskite oxide thin film of the present invention, a perovskite 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. .

First, a raw material solution for forming a perovskite oxide thin film of the present invention is applied on a substrate. The coating is generally performed by spin coating, but other coating methods such as roll coating, spraying, dipping, curtain flow coating, and doctor blade can also be applied. 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 about 80 to 200C, and preferably in the range of 100 to 180C. However,
Since the solvent is removed during the heating in the next step for converting the metal compound in the raw material solution to the metal oxide, the drying step of the coating film is not necessarily required.

Thereafter, as a calcining step, the applied substrate is heated to completely hydrolyze or thermally decompose the organometallic compound and convert it to a metal oxide, thereby forming a film made of the metal oxide. This heating is generally performed in an atmosphere containing water vapor in a sol-gel method requiring hydrolysis, for example, air or an atmosphere containing water vapor (for example, a nitrogen atmosphere containing water vapor).
The MOD method for thermal decomposition is performed in an oxygen-containing atmosphere. The heating temperature varies depending on the type of the metal oxide, but is usually in the range of 150 to 550 ° C, preferably 300 to 450 ° C. The heating time is selected so that the hydrolysis and thermal decomposition proceed completely, but is usually about 1 minute to 2 hours.

In the case of a sol-gel method or the like, it is often difficult to obtain a film thickness required for a perovskite-type oxide thin film by one application, so that the above application and (drying) By repeating baking, a metal oxide film having a desired film thickness is obtained. The film obtained in this way is amorphous or crystalline, but the crystallinity is insufficient, so the polarization is low,
Cannot be used as a ferroelectric thin film. 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 perovskite crystal structure. 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
It is in the range of 0 to 800C, for example, 500 to 750C. Therefore, a substrate having heat resistance enough to withstand this firing temperature is used. The firing (annealing) time for crystallization is usually about 1 minute to 2 hours, and the firing atmosphere is not particularly limited, but is usually air or oxygen.

As a heat-resistant substrate material used for forming such a perovskite-type oxide thin film, metals such as silicon (single crystal or polycrystal), platinum and nickel,
Perovskite-type conductive oxides such as ruthenium oxide, iridium oxide, strontium ruthenate (SrRuO ₃ ) or lanthanum strontium cobaltate ((La _X Sr ₁ -x) CoO ₃ ); quartz, aluminum nitride, titanium oxide, etc. Inorganic compounds. In the case of a capacitor film, the substrate is a lower electrode, and for example, Pt, Pt / Ti, Pt / Ta, R
u, RuO ₂ , Ru / RuO ₂ , RuO ₂ / Ru, Ir,
IrO ₂ , Ir / IrO ₂ , Pt / Ir, Pt / Ir
Perovskite-type conductive oxides such as O ₂ , SrRuO ₃ or (La _X Sr _1-x ) CoO ₃ (a two-layer structure using “/” means “upper layer / lower layer” ").)

The thickness of the perovskite-type oxide thin film formed in this manner varies depending on the application of the derivative device, but is generally preferably about 500 to 4000 °. Useful for derivative devices.

[0055]

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.

Pb raw material compound: lead acetate trihydrate lead acetate anhydride 2-ethylhexanoate La raw material compound: lanthanum acetate hemihydrate Ti raw material compound: titanium tetraisopropoxide Zr raw material compound: zirconium tetra n-butoxide zirconium acetyl acetate Examples 1 to 14, Comparative Examples 1 to 30 Pb raw material compounds shown in Tables 1 to 3, lanthanum acetate hemihydrate, and an alcohol solvent shown in Tables 1 to 3 were charged into a reaction vessel. Then, after azeotropically dehydrating the water of crystallization (lead acetate may precipitate after dehydration, there may be a precipitate).
It is diluted with an alcohol solvent shown in Tables 1 to 3 (lead acetate does not have to be completely dissolved), and then Z shown in Tables 1 to 3
The raw material compound and titanium tetraisopropoxide were added to prepare a metal atomic ratio shown in Tables 1 to 3 (the metal compound does not have to be completely dissolved at this time).

After the solution was refluxed for 3 hours in a nitrogen atmosphere (at this point, the metal compound was completely dissolved), the compounds shown in Tables 1 to 3 were used as stabilizers for the metal elements present in the raw material solution. It was added in such an amount that the number of molecules became 1 times the total number of atoms (however, in Example 1, Comparative Examples 1 and 29, no stabilizer was added).

After refluxing for 3 hours in a nitrogen atmosphere,
By adding a small amount of an alcohol solvent shown in Tables 1 to 3 and adjusting the concentration, a sol-gel solution containing a metal compound at a concentration of 15% by weight in terms of oxide was obtained.

In Example 3, after the addition of the stabilizer, water and the alcoholic solvent shown in Table 1 were added, and then the mixture was refluxed. At this time, the amount of water added is 0.1 to the total number of atoms of the metal elements present in the raw material solution.
25 times the number of molecules, the amount of alcohol added,
The amount was 9 times the amount of water added.

This sol-gel solution was converted to Pt (2000 °) / S
It is applied on a substrate of an iO ₂ (5000 °) / Si (100) wafer by a spin coating method (3000 rpm, 1 rpm).
(5 seconds) and calcined in air at 300 ° C. for 5 minutes. This coating and calcination are repeated four times, and then calcination annealing is performed at 700 ° C. for 1 minute in an oxygen atmosphere to obtain a thickness of about 2 mm.
An 800 ° ferroelectric thin film was formed.

An SEM photograph of the surface of the ferroelectric thin film was observed, and the average grain size of the crystals of the perovskite phase constituting the thin film, the presence or absence of variation in the grain size, and the presence or absence of a phase other than the perovskite phase were examined. 4 and 5. The average particle size was represented by an average intercept length of particles calculated from an SEM photograph of the thin film surface.

Tables 4 and 5 also show the results of a survey on the presence or absence of gelation, the occurrence of precipitation, and the presence or absence of striation of the calcined film when the prepared sol-gel solution was left at room temperature for half a year. Also described.

[0064]

[Table 1]

[0065]

[Table 2]

[0066]

[Table 3]

[0067]

[Table 4]

[0068]

[Table 5]

From the above results, according to the present invention, it is possible to form a good perovskite-type oxide thin film composed of fine crystal grains having a uniform surface morphology, and to obtain β-diketones as a stabilizer. It can be seen that the stabilization of the raw material solution is improved by the addition of

On the other hand, in Comparative Examples 1 to 5 in which an organic solvent mainly composed of butanol was not used, the surface morphology was uneven, the crystal grains were large, and a good perovskite oxide thin film could not be obtained. Further, in Comparative Examples 6 to 24 and 29 in which β-diketones were not used as a stabilizer, even if 1-butanol was used as the organic solvent, the stability of the raw material solution, film formability, and the like were poor.

Further, Comparative Example 28 using lead 2-ethylhexanoate as a Pb raw material compound and Comparative Example 2 using zirconium acetyl acetate as a Zr raw material compound
In 9 and 30, 1-butanol was used as an organic solvent,
In Comparative Examples 28 and 30, although acetylacetone was used as the stabilizer, the stability of the raw material solution and the film-forming properties were poor.

[0072]

As described above in detail, according to the present invention, a raw material solution having low toxicity, excellent application properties and stability over time, has good surface morphology and excellent uniformity of surface morphology. A high-performance perovskite-type oxide thin film having excellent electrical property homogeneity is provided.

Continued on the front page (72) Inventor Masaya Matsuura 12-6 Techno Park, Mita-shi, Hyogo Mitsubishi Materials Corporation Mita Plant (72) Inventor Kensuke Kageyama 1-297 Kitabukurocho, Omiya-shi, Saitama Mitsubishi Materials Corporation 4G047 CA02 CA08 CA10 CB05 CC02 CD02 CD08 4G048 AA03 AB02 AC02 AD02 AD08 AE05 AE08

Claims (7)

[Claims] 1. A raw material solution for forming a perovskite-type oxide thin film containing Ti and / or Zr, a metal compound containing each component metal or two or more component metals, a partial hydrolyzate thereof, and In a raw material solution composed of a solution containing one or more metal compounds selected from the group consisting of the partial polycondensates in an organic solvent, 1-butanol, 2-butanol, 2-methyl-
A raw material solution for forming a perovskite oxide thin film, comprising one or more butanol solvents selected from the group consisting of 1-propanol and 2-methyl-2-propanol. 2. The raw material solution for forming a perovskite oxide thin film according to claim 1, wherein the content of the butanol solvent with respect to the organic solvent present in the raw material solution is 30% by weight or more. 3. The perovskite according to claim 1, wherein the β-diketones are contained in an amount of 0.1 to 5 times the total number of atoms of the metal elements present in the raw material solution. Raw material solution for forming oxide thin film. 4. The method according to claim 1, wherein the content of 1-butanol with respect to the organic solvent present in the raw material solution is 30% by weight or more, and the total amount of metal elements present in the raw material solution. A raw material solution for forming a perovskite-type oxide thin film, comprising acetylacetone at a molecular number 0.1 to 5 times the number of the raw materials. 5. The perovskite type material according to claim 1, which is a raw material solution for forming a perovskite type oxide thin film containing Pb and Zr and / or Ti. Raw material solution for oxide thin film formation. 6. The method according to claim 1, wherein the Ti raw material compound is a titanium alkoxide,
A raw material solution for forming a perovskite-type oxide thin film, wherein the raw material compound is a zirconium alkoxide. 7. The raw material solution for forming a perovskite oxide thin film according to claim 5, wherein the Pb raw material compound is lead acetate trihydrate and / or lead acetate anhydride.