JP2002265224A - Blt ferroelectric thin film, manufacturing method therefore and application liquid therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a concentrated application liquid having a high concentration which does not deteriorate electrical properties of BLT ferroelectric thin films. SOLUTION: The application liquid for forming the BLT ferroelectric thin film is prepared in such a manner that a solution including respective metal alkoxides of Bi, La and Ti as solutes in organic solvents is heated, at the same time, is vaporized under a reduced pressure and is concentrated until the total concentration of the metallic elements becomes 0.1-1.0 mol/L.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the, Bi, La and comprising a Ti La-substituted bismuth titanate-based, i.e. BLT system ferroelectric _{(Bi (4-x) y} La x y Ti
₃ O ₁₂ ).

[0002]

2. Description of the Related Art A BLT-based ferroelectric has a P (accumulated charge).
-E (electric field) Hysteresis has a small coercive electric field so that it can be stored in a low electric field, stored charges are not easily discharged even when the temperature rises, and it is hard to be fatigued by repeated storage and erasure. There are various materials that are expected to be applied.

Accordingly, various methods for producing a BLT-based ferroelectric thin film have been studied, and among them, a method of forming a BLT-based ferroelectric thin film on a substrate by applying a coating solution to the substrate and firing it. Is considered promising. in this case,
A solution in which an alkoxide containing each metal of Bi, La and Ti is dissolved in an organic solvent is used as a coating liquid. In particular,
The cycle of applying the coating solution on the substrate by a method such as spin coating, drying and pre-baking is repeated until a BLT-based ferroelectric thin film having a desired thickness is obtained.

[0004]

In this case, in particular, B
The solubility of the alkoxide of i or La is low, and it is difficult to increase the metal ion concentration in the coating solution. For this reason, the number of cycles (the number of coatings) required until a BLT-based ferroelectric thin film having a desired thickness is obtained is extremely large, and the film formation efficiency is low.

In order to increase the concentration of metal ions in the coating solution, a method has been proposed in which the coating solution is concentrated by distillation under reduced pressure (see Japanese Patent Application Laid-Open No. H10-258252). When a coating solution concentrated to / L or more is used, a phenomenon that the leak current characteristic of the formed BLT-based ferroelectric thin film becomes poor frequently occurs. This is because during the concentration, a very small and minute solute component precipitates, and the precipitate component is contained in the coated thin film, and in the subsequent drying and calcination stage, abnormal grain growth occurs with the precipitate component as a nucleus. It is presumed that the cause is that surface irregularities in such a portion become severe. Such minute and trace amounts of precipitated components cannot be completely removed even by filtering.

Therefore, even when the coating solution is concentrated, if the concentration of the total metal ions is reduced to 0.1 mol / L, abnormal grain growth occurs, the crystallinity is reduced, and the electrical characteristics and
Above all, deterioration of the leak current characteristic is caused. The currently available coating liquid has a total metal ion concentration of 0.1.
It is a concentrated solution of less than 1 mol / L and has a desired thickness of BLT.
The number of cycles (the number of applications) required until a ferroelectric thin film is obtained is still large, and the film formation efficiency is low.

Accordingly, the present invention has been developed to realize a technique capable of further increasing the metal ion concentration of such a coating solution.
It is possible to obtain a concentrated coating solution having a high concentration without deteriorating the electrical characteristics of the LT-based ferroelectric thin film, and to reduce the number of times of application.

[0008]

Means for Solving the Problems and Embodiments of the Invention A concentrated solution realized by the present invention is used for forming a La-substituted bismuth titanate-based ferroelectric thin film containing Bi, La and Ti. It is a coating solution and contains Bi and La in an organic solvent.
And a solution containing the respective metal alkoxides of Ti and Ti as a solute is concentrated by distillation under reduced pressure while heating. The total concentration of these metal elements is concentrated to 0.1 to 1.0 mol / L. Here, preferred organic solvents include alcohol-based organic solvents, ether-based organic solvents, ketone-based organic solvents, and the like. For example, as an alcohol organic solvent, methanol, ethoxymethanol, ethanol, propanol, butanol, amyl alcohol, cyclohexanol, methylcyclohexanol,
Ethylene glycol monomethyl ether (2-methoxyethanol), ethylene glycol monoacetoester,
Examples thereof include diethylene glycol monomethyl ether, diethylene glycol monoacetate, propylene glycol monoethyl ether, propylene glycol monoacetate, dipropylene glycol monoethyl ether, and methoxybutanol. Examples of ether organic solvents include methylal, diethyl ether, dipropyl ether, dibutyl ether, diamyl ether, diethyl acetal, dihexyl ether, trioxane, and dioxane. Further, as a ketone organic solvent, acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl amyl ketone, methyl cyclohexyl ketone, diethyl ketone,
Ethyl butyl ketone, trimethyl nonanone, acetonitrile acetone, dimethyl oxide, holon, cyclohexanone, diacetone alcohol and the like can be mentioned. Among these organic solvents, alcohol-based organic solvents are particularly preferred.

The coating solution is applied by a spin coating method or the like, but is usually carried out at room temperature. For this reason, it is required that the coating solution does not precipitate at room temperature and can be used at room temperature. For this purpose, a step of concentrating the coating solution by distillation under reduced pressure is also performed at room temperature (see Japanese Patent Application Laid-Open No. H10-258252). Even if the coating solution is heated and concentrated in a state where it is difficult to precipitate, since it is meaningless if it is precipitated when used at room temperature thereafter, it must be used within a temperature range that does not precipitate at the operating temperature. Concentrated.

The present inventors have conducted intensive studies and have found that even if the coating solution is heated and concentrated in a state where it is difficult to precipitate, it is meaningless if it is subsequently precipitated when used at room temperature. Conventional recognition that concentration at the use temperature is contrary to the fact, in fact, if the coating solution is heated and concentrated in a state where it is difficult to precipitate, then it does not precipitate even when cooled to room temperature,
It has been found that when this concentrated solution is applied and fired, the electrical characteristics of the ferroelectric thin film are not deteriorated. Based on this finding, we succeeded in increasing the enrichment. That is, the total concentration of Bi, La and Ti metal elements contained in the coating solution is 0.1 to 1.0 mol / L while using a predetermined organic solvent and metal alkoxide and hardly depositing by heating.
When the solution was concentrated until, the precipitate did not precipitate even when cooled thereafter, and it was confirmed that the electric characteristics of the ferroelectric thin film baked using the coating solution were maintained well.

Particularly, an organic solvent (preferably an alcoholic organic solvent) is selected from those having a boiling point of 50 ° C. or higher,
Further, it is preferable to prepare a concentrated coating solution by distillation under reduced pressure at a temperature of 40 ° C. or higher and at least 10 ° C. lower than the boiling point (standard boiling point) of the selected organic solvent. In particular, organic solvents having a boiling point of 100 ° C. or higher (such as 2-methoxyethanol and 2-ethoxyethanol) are preferable.
The temperature condition of the distillation under reduced pressure is 50 ° C. or more (particularly preferably 80 ° C.).
C. or higher).

Further, the present invention can be concentrated to a high concentration.
Preferred coating solutions are metal ions of Bi, La and Ti
The concentration ratio (Bi: La: Ti) is (4-x) y: xy: 3
Where x is in the range of 0.2 ≦ x ≦ 1.0,
And y is a coating liquid in the range of 0.9 ≦ y ≦ 1.1.
You. Therefore, when preparing the solution to be subjected to the above-mentioned vacuum distillation,
Is a metal alkoxide of Bi, La and Ti
At an appropriate compounding ratio to achieve the metal ion concentration ratio,
Add to organic solvent (preferably alcoholic organic solvent)
Preferably. Metal alkoxide used here
Is typically represented by the general formula “M (OR) _x: M in the formula
Is Bi, La or Ti, x is M valence, R is alkyl
Wherein the R moiety is lower alkyl
(Eg C_TwoH_Five, C_ThreeH₇, C_FourH₉, C _FiveH₁₁)
Is preferred. Also, as the metal alkoxide used
Means that Bi, La and Ti are each a single constituent metal element
And various alkoxides,
Metal complex comprising two or more complex metal alkoxides
Lucoxide may be used.

The method of adding these metal alkoxides to an organic solvent is not particularly limited. The metal alkoxides to be used may be individually or simultaneously dropped in a predetermined organic solvent. After the dropping and mixing, it is preferable to reflux under a high temperature condition close to the boiling point of the used organic solvent to completely dissolve the solute. The reflux treatment is preferably performed in a flow of an inert gas such as nitrogen gas. The solution containing the metal alkoxide as a solute may contain a small amount of water or a catalyst in addition to the organic solvent in order to promote hydrolysis of the metal alkoxide.

The concentration of the solution before concentration under reduced pressure (solution before concentration) is the total concentration of Bi, La and Ti in the concentrated solution (coating solution of the invention) finally obtained in the practice of the present invention. When the concentration is 0.1 to 1.0 mol / L, the total concentration of Bi, La, and Ti in the pre-concentration liquid is 1/5 to 1/10 of the concentration in the concentrated liquid, typically 0.01. It is preferable to set to 0.1 mol / L.
It is particularly preferable to set this concentration to 0.05 to 0.08 mol / L.

The preferred embodiment of the coating solution of the present invention has been described above. As will be understood from this description, the present invention provides, as another aspect, a method for producing the coating solution of the present invention. I do. That is, the method for producing a coating liquid for forming a La-substituted bismuth titanate-based ferroelectric thin film of the present invention comprises the steps of preparing Bi, La in an organic solvent (preferably an alcohol-based organic solvent).
And a solution containing each metal alkoxide of Ti and Ti as a solute is distilled under reduced pressure while heating to concentrate the total concentration of these metal elements to 0.1 to 1.0 mol / L. Further, as a preferable method for producing a coating solution of the present invention, the organic solvent (preferably an alcohol-based organic solvent) is selected from those having a boiling point of 50 ° C. or higher, and the vacuum distillation is performed at a temperature of 40 ° C. or higher. At least 10 ° C. below the boiling point of the selected organic solvent
This method is performed under low temperature conditions.
Particularly preferred as the method is a method in which an organic solvent having a boiling point of 100 ° C. or higher is used and / or the temperature condition of the vacuum distillation is 50 ° C. or higher (particularly preferably 80 ° C. or higher). Another preferred method for producing a coating liquid of the present invention is to adjust the total concentration of Bi, La and Ti in the solution before concentration to 0.01 to 0.1 mol / L (particularly preferably 0.05 to 0.08 mol). / L). Another preferable production method is a method in which the above-mentioned suitable raw materials and conditions are appropriately adopted.

Next, a BLT-based ferroelectric thin film obtained by using the coating solution of the present invention and a method for producing the same will be described. The BLT-based ferroelectric thin film provided by the present invention is a film characterized by being formed from the above-described coating film of the present invention. Therefore, the BLT according to the present invention
The ferroelectric thin film can be obtained by applying the coating solution of the present invention to a substrate and baking it. A preferred BLT-based ferroelectric thin film is a BLT-based ferroelectric thin film obtained by applying the coating solution of the present invention having any one of the above-mentioned constitutions to a substrate and firing the same, wherein the metal ion concentration ratio of Bi, La and Ti is ( 4-
x) y: xy: 3, 0.2 ≦ x ≦ 1.0,
In addition, it is characterized in that 0.9 ≦ y ≦ 1.1. The method of applying the coating liquid of the present invention to various general substrate materials and the method of baking are not particularly limited, and various conventionally known methods are employed. Therefore, BL
The method for producing the T-based ferroelectric thin film is not particularly limited.
In view of the feature of the coating liquid of the present invention that the metal ion concentration of i, La and Ti is higher than before, the coating liquid of the present invention having any one of the above structures is applied to a substrate and pre-baked. The cycle is repeated a plurality of times to stack the layers to a predetermined thickness, and after the layers are stacked to the predetermined thickness, the main firing is performed and BLT is performed.
A method of producing a ferroelectric thin film is preferred. in this case,
The coating solution has a high metal ion concentration and does not require a large number of cycles.

[0017]

EXAMPLES The present invention will be described in more detail with reference to the following examples. The present invention is not limited to these examples.

Example 1 Titanium isopropoxide (T
i (OC ₃ H ₇ ) ₄ ) was dissolved in methoxyethanol by dropping and stirring to prepare a solution. To this solution, a solution obtained by stirring bismuth ethoxide (Bi (OC ₂ H ₅ ) ₃ ) in methoxyethanol was mixed, and refluxed at 124 ° C. for 1 hour in a nitrogen stream. After this,
It was left to cool slowly to room temperature. Further, a solution obtained by dropping and stirring lanthanum isopropoxide (La (OC ₃ H ₇ ) ₃ ) in methoxyethanol was refluxed at 124 ° C. for 1 hour in a nitrogen stream, and then left to cool slowly to room temperature. . The bismuth ethoxide-titanium propoxide solution thus prepared and the lanthanum propoxide solution were mixed, stirred for 1 hour at room temperature in a nitrogen stream, and further heated for 1 hour while heating to 80 ° C. . The solution was left to cool slowly to room temperature, and Bi: La: Ti = 3.25: 0.75: 3
With the composition ratio, the concentration of all metal ions in the solution is 0.07 m
ol / L sol-gel stock solution 1 was prepared. The sol-gel stock solution 1 was further heated to 80 ° C. under reduced pressure to remove an appropriate amount of the solvent, thereby preparing a sol-gel solution 2 in which the concentration of all metal ions in the solution was 0.56 mol / L. Using this sol-gel solution 2, a La-substituted bismuth titanate thin film was prepared by a process of spin coating, drying, calcining, and firing. Using a silicon wafer as the substrate, a thermal oxide film is formed on the surface at a thickness of 0.8 μm, a Ti thin film is stacked thereon by 5 nm sputtering, and a Pt thin film is further stacked thereon by 200 nm sputtering. Was used. After dropping an appropriate amount of the sol-gel solution 2 on this substrate,
3 seconds at 1000 rpm, then 30 at 3000 rpm
Coating was performed by rotation for 2 seconds, followed by drying at 200 ° C. for 10 seconds and further calcination at 350 ° C. for 10 minutes.
After repeating this operation twice, 750 ° C. in an oxygen stream
For 10 minutes to perform crystallization by firing. By repeating the above steps twice, a La-substituted bismuth titanate thin film having a thickness of about 0.2 μm was formed.

(Comparative Example 1) After preparing a sol-gel stock solution 1 by the method shown in Example 1, the sol-gel stock solution 1 was depressurized at room temperature to remove an appropriate amount of the solvent, whereby all metal ions in the solution were removed. A sol-gel comparative solution 3 having a concentration of 0.56 mol / L was prepared. A La-substituted bismuth titanate thin film was prepared by spin-coating, drying, calcining, and firing using the sol-gel comparative solution 3 thus prepared. The method of forming the La-substituted bismuth titanate thin film is the same as that of the first embodiment.

(Comparison between Mika Example 1 and Comparative Example 1) X-ray diffraction charts of the La-substituted bismuth titanate thin films produced in Example 1 and Comparative Example 1 are shown in FIG. In Example 1, a stronger diffraction intensity was obtained than in Comparative Example 1. FIG. 2 shows the leakage current characteristics of the La-substituted bismuth titanate thin films produced in Example 1 and Comparative Example 1, respectively. A metal mask having a hole having a diameter of 200 μm was brought into close contact with each of the La-substituted bismuth titanate thin films to form a Pt thin film of 0.1 μm.
The thickness of the Pt thin film formed on the substrate side of each of the La-substituted bismuth titanate thin films is determined by depositing the Pt thin film thus formed on the substrate side with the dots of the Pt thin film thus formed as an upper electrode. As a lower electrode, measurement was performed by applying a voltage between the two electrodes. In comparison with Comparative Example 1, Example 1 shows that the leakage current characteristics are improved and the amount of current is reduced by several orders of magnitude.

Example 2 Titanium isopropoxide
(Ti (OC ₃ H ₇ ) ₄ ) is dropped into methoxyethanol.
The solution was dissolved by stirring to prepare a solution. To this solution, a solution obtained by stirring bismuth ethoxide (Bi (OC ₂ H ₅ ) ₃ ) in methoxyethanol was mixed, and refluxed at 124 ° C. for 1 hour in a nitrogen stream. After this,
It was left to cool slowly to room temperature. Further, a solution obtained by dropping and stirring lanthanum isopropoxide (La (OC ₃ H ₇ ) ₃ ) in methoxyethanol was refluxed at 124 ° C. for 1 hour in a nitrogen stream, and then left to cool slowly to room temperature. . The bismuth ethoxide-titanium propoxide solution thus prepared and the lanthanum propoxide solution were mixed, stirred for 1 hour at room temperature in a nitrogen stream, and further heated for 1 hour while heating to 80 ° C. . The solution was left to cool slowly to room temperature, and the concentration of all metal ions in the solution was 0.07 mol at a composition ratio of Bi: La: Ti = 3.3: 1.1: 3.
/ L sol-gel stock solution 4 was prepared. Here, in order to promote hydrolysis, a solution obtained by adding 0.02 ml of pure water to 20 ml of methoxyethanol was dropped into the sol-gel solution, and the sol-gel stock solution 4 was further reduced under reduced pressure to 6
By heating to 0 ° C. and removing an appropriate amount of the solvent, a sol-gel solution 5 in which the concentration of all metal ions in the solution was 0.42 mol / L was prepared. Using this sol-gel solution 5, La is spin-coated, dried, calcined, and fired to produce La.
A substituted bismuth titanate thin film was prepared. Example for substrate
The one prepared by the same method as that prepared in 1 was used. After dropping an appropriate amount of the sol-gel solution 5 on this substrate, 1
The coating was performed by spinning at 3,000 rpm for 3 seconds and then at 3,000 rpm for 30 seconds, followed by drying at 200 ° C. for 10 seconds and further calcination at 350 ° C. for 10 minutes. After repeating this operation twice, crystallization was performed by firing at 750 ° C. for 10 minutes in an oxygen stream. The above steps were repeated three times to form a La-substituted bismuth titanate thin film having a thickness of about 0.2 μm.

(Comparative Example 2) After preparing a sol-gel stock solution 4 by the method shown in Example 2, the sol-gel stock solution 4 was depressurized at room temperature to remove an appropriate amount of the solvent, thereby obtaining all metal ions in the solution. A sol-gel comparative solution 6 having a concentration of 0.42 mol / L was prepared. Using the sol-gel comparative liquid 6 thus prepared, a La-substituted bismuth titanate thin film was prepared by a process of spin coating, drying, calcining, and firing. The method of forming the La-substituted bismuth titanate thin film is the same as that of the second embodiment.

(Comparison between Example 2 and Comparative Example 2) Example 2
FIG. 3 shows an X-ray diffraction chart of the La-substituted bismuth titanate thin films prepared in Comparative Example 2 and Comparative Example 2, respectively. In Example 2, a stronger diffraction intensity was obtained than in Comparative Example 2. FIG. 4 shows the leakage current characteristics of the La-substituted bismuth titanate thin films produced in Example 2 and Comparative Example 2, respectively. The measuring method is the same as in the case of Example 1 and Comparative Example 1. Comparative Example 2
On the other hand, in Example 2, it is shown that the leakage current characteristic is improved and the amount of current is reduced by several orders of magnitude.

Example 3 Titanium isopropoxide
(Ti (OC ₃ H ₇ ) ₄ ) is dropped into methoxyethanol.
The solution was dissolved by stirring to prepare a solution. To this solution, a solution obtained by stirring bismuth ethoxide (Bi (OC ₂ H ₅ ) ₃ ) in methoxyethanol was mixed, and refluxed at 124 ° C. for 1 hour in a nitrogen stream. After this,
It was left to cool slowly to room temperature. Further, a solution obtained by dropping and stirring lanthanum isopropoxide (La (OC ₃ H ₇ ) ₃ ) in methoxyethanol was refluxed at 124 ° C. for 1 hour in a nitrogen stream, and then left to cool slowly to room temperature. . The bismuth ethoxide-titanium propoxide solution and the lanthanum propoxide solution thus prepared were mixed, stirred at room temperature for 1 hour in a nitrogen stream, and further heated at 80 ° C. for 1 hour. The solution was left to cool slowly to room temperature, and the concentration of all metal ions in the solution was 0.07 mol / L at a composition ratio of Bi: La: Ti = 3.42: 1.8: 3.
A sol-gel stock solution 7 was prepared. Here, 20 ml of methoxyethanol was added to 0.0 ml of pure water to promote hydrolysis.
After adding 2 ml of the solution dropwise to the sol-gel solution,
The sol-gel stock solution 7 was further heated to 60 ° C. under reduced pressure to remove an appropriate amount of the solvent, thereby preparing a sol-gel solution 8 in which the concentration of all metal ions in the solution was 0.42 mol / L. Using this sol-gel solution 8, a La-substituted bismuth titanate thin film was prepared by spin coating, drying, calcining, and firing processes. A substrate manufactured by the same method as that manufactured in Example 1 was used.
After dropping an appropriate amount of the sol-gel solution 8 on this substrate, 1000
coating for 3 seconds at rpm, then 30 seconds at 3000 rpm, then drying at 200 ° C. for 10 seconds,
Further, calcination was performed at 350 ° C. for 10 minutes. After repeating this operation twice, crystallization was performed by firing at 750 ° C. for 10 minutes in an oxygen stream. The process up to this point is 3
This was repeated twice to form a La-substituted bismuth titanate thin film having a thickness of about 0.2 μm.

Comparative Example 3 After preparing a sol-gel stock solution 7 by the method shown in Example 3, the sol-gel stock solution 7 was depressurized at room temperature to remove an appropriate amount of the solvent, whereby all metal ions in the solution were removed. A sol-gel comparative solution 9 having a concentration of 0.42 mol / L was prepared. Using the sol-gel comparative liquid 9 thus prepared, a La-substituted bismuth titanate thin film was prepared by a process of spin coating, drying, calcining, and firing. The method of forming the La-substituted bismuth titanate thin film is the same as that of the third embodiment.

(Comparison between Example 3 and Comparative Example 3) Example 3
FIG. 5 shows an X-ray diffraction chart of the La-substituted bismuth titanate thin films prepared in Comparative Example 3 and Comparative Example 3, respectively. In Example 3, as compared with Comparative Example 3, a higher diffraction intensity was obtained. FIG. 6 shows the leakage current characteristics of the La-substituted bismuth titanate thin films produced in Example 3 and Comparative Example 3, respectively. The measuring method is the same as in the case of Example 1 and Comparative Example 1. Comparative Example 3
On the other hand, in Example 3, it is shown that the leakage current characteristics are improved and the amount of current is reduced by several orders of magnitude.

[0027]

As is clear from the above examples, the La-substituted bismuth titanate ferroelectric thin film formed by the coating solution (concentrated solution) of the present invention has improved crystallinity and large leakage current characteristics. Be improved. As described above, according to the present invention, the fine structure of the La-substituted bismuth titanate ferroelectric thin film and, consequently, its electrical characteristics can be greatly improved.

[Brief description of the drawings]

FIG. 1 shows X-ray diffraction charts of La-substituted bismuth titanate thin films produced in Example 1 and Comparative Example 1, respectively.

FIG. 2 shows the leakage current characteristics of the La-substituted bismuth titanate thin films prepared in Example 1 and Comparative Example 1, respectively.

FIG. 3 shows X-ray diffraction charts of La-substituted bismuth titanate thin films prepared in Example 2 and Comparative Example 2, respectively.

FIG. 4 shows the leakage current characteristics of the La-substituted bismuth titanate thin films produced in Example 2 and Comparative Example 2, respectively.

FIG. 5 shows X-ray diffraction charts of La-substituted bismuth titanate thin films produced in Example 3 and Comparative Example 3, respectively.

FIG. 6 shows the leakage current characteristics of the La-substituted bismuth titanate thin films produced in Example 3 and Comparative Example 3, respectively.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tomoyuki Yoshida 41-cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central Research Laboratory Co., Ltd. (72) Inventor Koichi Mitsushima, Nagakute-machi, Aichi-gun, Aichi Prefecture 41 Chugaku-ji Yokomichi No. 1 within Toyota Central Research Laboratory Co., Ltd. (72) Inventor Kazumi Kato 2-15-15 Wagagaoka, Togo-cho, Aichi-gun, Aichi Prefecture (72) Inventor Kazuyuki Suzuki Kita-ku, Nagoya-shi, Aichi 2-109, Yatsushirocho Yatsushiro Dormitory Room 203 F-term (reference) 4D075 AE06 BB28Y BB28Z BB92Z CA21 DA06 DC21 EA12 EB01 EB60 4G048 AA03 AB02 AC02 AD02 AE08 5F038 AC15 AC18 EZ20 5F083 JA17 JA38 PR23 ZA21

Claims (5)

[Claims] 1. An L containing Bi, La and Ti
a coating solution for forming an a-substituted bismuth titanate-based ferroelectric thin film, wherein a solution containing each of metal alkoxides of Bi, La and Ti in an organic solvent as a solute is distilled under reduced pressure while heating; Coating solution concentrated to a total concentration of 0.1 to 1.0 mol / L. 2. The organic solvent is selected from those having a boiling point of 50 ° C. or higher, and the vacuum distillation is performed at a temperature of 40 ° C. or higher and at least 10 ° C. lower than the boiling point of the selected organic solvent. 2. The coating solution according to claim 1, wherein the coating is performed under conditions. 3. The metal ion concentration ratio of Bi, La and Ti is (4-x) y: xy: 3, and 0.2 ≦ x ≦ 1.
3. The coating liquid according to claim 1, wherein 0 and 0.9 ≦ y ≦ 1.1. 4. A BLT-based ferroelectric thin film obtained by applying the coating liquid according to claim 1 to a substrate and baking it.
The metal ion concentration ratio of i, La and Ti is (4-x)
BLT characterized by y: xy: 3, 0.2 ≦ x ≦ 1.0, and 0.9 ≦ y ≦ 1.1
Ferroelectric thin film. 5. A BLT-based ferroelectric thin film, wherein a cycle of applying the coating solution according to claim 1 to a substrate and temporarily baking is repeated a plurality of times. How to make.