JP2003063825A - Coating liquid for forming ferrodielectric thin film, method for manufacturing the same, and ferrodielectric thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coating liquid capable of forming a ferrodielectric thin film by sintering at low temperature having excellent storage stability and reproducibility containing effective components capable of dissolving in general- purpose organic solvents. SOLUTION: This coating liquid is characterized by containing organic solvents and a reacted product which is obtained by reacting (A) organic metal compounds and (B) compounds selected from carboxylic acids, alcohols, ethers, ketones, and esters without organic solvents.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a coating liquid for forming a ferroelectric thin film, a method for producing the same, and a ferroelectric thin film.
More specifically, a coating solution for forming a ferroelectric thin film, which contains an active ingredient soluble in a general-purpose organic solvent, has excellent storage stability and reproducibility, and can form a ferroelectric thin film even by firing at low temperature, The present invention relates to a ferroelectric thin film produced by using the manufacturing method and the coating solution.

[0002]

_2. Description of the Related Art In recent years, the formula (Bi ₂ O ₂ ) ²⁺ (A _m-1 B _m O
_{3m + 1} ) ²⁻ has a layered structure of Bi-based ferroelectric (BL
SF) thin films are drawing attention. In the above formula, A is 1,
A few or three valent ions (eg Bi, Pb, Ba, Sr,
Ca, Na, K, and ions of rare earth elements) or a combination of these ions, and B is 4, 5, 6
Valent ions (eg Ti, Nb, Ta, W, Mo, F
e, an ion of a metal element such as Co or Cr) or a combination of these ions, and m is an integer of 1 to 5. Bi-based ferroelectrics (BL having such a layered structure)
SF) thin film has a small coercive electric field of PE hysteresis,
It has been spotlighted as a material for semiconductor memories and sensors because it has characteristics such as less fatigue of the film due to polarization reversal (Tasung Takenaka "Bismuth Layer Structure Ferroelectrics and Particle Orientation" (Company) Application Report of Applied Electronic Property Subcommittee of the Physical Society of Japan, November 22, 1994, pp. 1-8; "Ceramics" Vol. 30, No. 6, pp. 499-
503 (1995)). Among them, SrBi ₂ Ta ₂ O
₉ system, ^{_{i.e., (Bi 2 O 2) 2+}} (SrTa 2 O 7) 2 - are of particular interest as a material BLSF films exhibiting these properties significantly for.

As a method for forming these BLSF thin films,
The sputtering method, the CVD method, the coating type film forming method and the like can be mentioned, but the thin film forming method by the sputtering method or the CVD method requires an expensive apparatus because it contains a large amount of metal oxide as a constituent component of the thin film. There are problems that it is costly and that it is difficult to control and manage the composition of the dielectric film, and in particular, it is difficult to apply it to a large-diameter substrate. On the other hand, the coating type film forming method is promising because it does not require expensive equipment, the film forming cost is relatively low, and the dielectric film composition control and its management are easy. BL used in this coating type film forming method
As the SF-based coating liquid, a carboxylic acid salt of Sr or Bi (for example, 2-ethylhexanoate) and an alkoxide compound of Ta are dissolved in acetic acid ester to prepare a coating liquid (12th ferroelectric substance). Application Conference Proceedings; Mitsubishi Materials Corporation; 24-TP-11 (pp.57-58); 1
995.5.24-27, "Jpn. J. Appl. P."
hys. "Vol. 34 (1995) pp. 5096-
5099) and 2-such as Sr, Bi, Ta, Nb, and Ti.
Ethyl hexanoate was dissolved in xylene and MOD (Me
tallo-Organic Decompositi
on) type coating liquid (the same collection of proceedings; Olympus Optical Co., Ltd., Symmetrix Corporation; 26-
TC-10, pp. 139-140, 1995.5.2
4-27) etc. have been reported. However, when a thin film is formed using these coating liquids, in order to obtain appropriate electric characteristics, it is necessary to bake twice at a high temperature of about 800 ° C. in an oxygen atmosphere. High-temperature heating in oxygen has a large thermal effect on the substrate, and Pt / SiO ₂ and Pt / Ta / SiO ₂ used for manufacturing ferroelectric nonvolatile memory and the like.
In a / Si substrate or the like, damage such as oxidation of the Pt film occurs. In addition to this, there is a problem that the surface of the thin film is roughened due to the growth of crystal grains, and as a result, the electrical characteristics are deteriorated such as an increase in leak current. Further, it has not always been sufficiently satisfactory in terms of productivity of the semiconductor manufacturing process. Further, Japanese Patent Application Laid-Open No. 10-259007 discloses that a coating liquid for forming a Bi-based ferroelectric thin film includes Bi and A metal elements (where A is Bi, Pb and B).
a, Sr, Ca, Na, K and at least one metal element selected from rare earth elements), and B metal element (where B is Ti, Nb, Ta, W, Mo, F).
e, Co and Cr), which is at least one metal element selected from the group consisting of e, Co and Cr), and two or more of them form complex metal alkoxides. Bi, which contains water or an organic metal compound obtained by hydrolysis with water and a catalyst, and which is 1 to 1.1 mole times the theoretical value
A coating solution containing is proposed. It is described that this coating solution has no precipitation of particles of an excess metal element, has a small leak current, is excellent in hydrogen heat treatment resistance and pressure resistance, and can form a dense film, and is excellent in storage stability. ing. However, in the specific example described in the above publication, in order to obtain appropriate electric characteristics, when forming the ferroelectric thin film, the ferroelectric thin film is baked twice at a high temperature of 800 ° C. in an oxygen atmosphere. High-temperature heating in oxygen is not always satisfactory as a coating solution, because of problems such as thermal influence on the substrate and roughening of the thin film surface due to growth of crystal grains.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the problems of the prior art as described above, and contains an active ingredient soluble in a general-purpose organic solvent, and has storage stability and reproducibility during use. It is an object of the present invention to provide a coating liquid for forming a ferroelectric, which is excellent in forming a thin film even by firing at low temperature, a method for producing the same, and a ferroelectric thin film produced by using the excellent coating liquid. .

[0005]

The present invention comprises (A) an organometallic compound and (B) a compound selected from carboxylic acids, alcohols, ethers, ketones and esters in the absence of an organic solvent. It is intended to provide a coating liquid for forming a ferroelectric thin film, which contains a reaction product obtained by the reaction and an organic solvent, a method for producing the same, and a ferroelectric thin film.

Component (A) In the present invention, the organometallic compound is Li, Na, K,
Mg, Ca, Sr, Ba, La, Ti, Zr, Hf,
V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co,
A metal selected from Ni, Cu, Zn, Pb and Bi (hereinafter referred to as “specific metal”), preferably Na or C
a, Sr, Ba, La, Ti, Zr, Hf, Nb, T
It is a compound of a metal selected from a, Mo, W, Pb and Bi, and metal alkoxide and metal carboxylate are preferable.

The metal alkoxide is a compound obtained by reacting a metal atom with an alcohol and is represented by the following general formula (1). M ^a (OR ¹ ) _a (1) (In the formula (1), M is Li, Na, K, Mg, Ca,
Sr, Ba, La, Ti, Zr, Hf, V, Nb, T
a, Cr, Mo, W, Mn, Fe, Co, Ni, Cu,
Represents an atom selected from Zn, Pb and Bi,
a is a positive number of 1-7 according to the valence of the metal M, and R
¹ is a residue excluding the OH group of alcohol. )

As the alcohol forming the above-mentioned metal alkoxide, for example, the alcohol represented by the following formula (2) can be mentioned as a preferable example. R ¹ OH (2) (In the formula (2), R ¹ is a saturated or unsaturated hydrocarbon group having 1 to 6 carbon atoms or a hydrocarbon group further substituted with an alkoxyl group having 1 to 6 carbon atoms. In the above general formula (2), when R ¹ is a saturated or unsaturated hydrocarbon group having 1 to 6 carbon atoms, the alcohol may be, for example, methanol, ethanol, 1-propanol, 2-propanol, Butanol, amyl alcohol, cyclohexanol, etc. can be mentioned. When R ¹ is a hydrocarbon group further substituted with an alkoxyl group having 1 to 6 carbon atoms, as an alcohol,
Examples thereof include methoxymethanol, methoxyethanol, ethoxymethanol, ethoxyethanol, methoxypropanol, ethoxypropanol, and propoxypropanol.

The metal carboxylate is a compound obtained by reacting a metal atom with a carboxylic acid, and is represented by the following general formula (3). M in _{^{a (OOCR 2) a (3}} ) ( the formula (3), M is, Li, Na, K, Mg , Ca,
Sr, Ba, La, Ti, Zr, Hf, V, Nb, T
a, Cr, Mo, W, Mn, Fe, Co, Ni, Cu,
Represents an atom selected from Zn, Pb and Bi,
a is a positive number of 1-7 according to the valence of the metal M, and R
² is a residue excluding the COOH group of carboxylic acid. )

Suitable examples of the carboxylic acid forming the metal carboxylate include those represented by the following formula (4). R ² COOH (4) (In the formula (4), R ² represents a hydrocarbon group substituted with a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms.) In the general formula (4), When R ¹ is a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms, examples of the carboxylic acid include acetic acid, 2-methylpropionic acid, pentanoic acid, 2,2, -dimethylpropionic acid, butanoic acid. , Hexanoic acid, 2-ethylhexanoic acid, octylic acid, nonanoic acid, decanoic acid, acetic acid, propionic acid, butyric acid, valeric acid and the like.

The specific metal contained in the organometallic compound is one or more kinds in total, preferably 1 to 5 kinds, more preferably 2 kinds.
~ 3 types. The organometallic compound may be a compound having two or more specific metals, or two or more organometallic compounds may be used in combination, but the metals present in the organometallic compound may be Pb, Zr, Ti and 1 to 4 kinds selected from La or Sr, Bi, Ti, Ta
And 1 to 4 selected from Nb are more preferable.

Component (B) The component (B) of the present invention comprises carboxylic acids, alcohols,
At least one organic compound selected from ethers, ketones, and esters (hereinafter, "specific organic compound")
That is).

Examples of the carboxylic acids include compounds represented by the following formula (5). R ³ COOH (5) [In the formula (5), R ³ represents a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms. ] Specific carboxylic acids include, for example, acetic acid, 2-methylpropionic acid, pentanoic acid, 2,2, -dimethylpropionic acid, butanoic acid, hexanoic acid, 2-ethylhexanoic acid, octylic acid, nonanoic acid, decanoic acid. , Acetic acid, propionic acid, butyric acid, valeric acid and the like.

Examples of alcohols include compounds represented by the following formula (6). R ⁴ —OH (6) [In the formula (6), R ³ represents a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms. ] As specific alcohols, R ⁴ has 1 to 6 carbon atoms.
In the case of the saturated or unsaturated hydrocarbon group of, for example, methanol, ethanol, 1-propanol, 2-propanol, butanol, amyl alcohol, cyclohexanol and the like can be mentioned. When R ⁴ is a hydrocarbon group further substituted with an alkoxyl group having 1 to 6 carbon atoms, alcohols such as methoxymethanol, methoxyethanol, ethoxymethanol,
Examples thereof include ethoxyethanol, methoxypropanol, ethoxypropanol, propoxypropanol and the like.

Examples of ethers include compounds represented by the following formula (7). R ⁵ OR ⁶ (7) [In the formula (7), R ⁵ and R ⁶ represent a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms. Specific examples of ethers include methylal, diethyl ether, dipropyl ether, dibutyl ether, diamyl ether, diethyl acetal, dihexyl ether, trioxane and dioxane.

Examples of the ketones include compounds represented by the following formula (8). R ⁷ R ⁸ C = O (8) [In the formula (8), R ⁸ and R ⁸ represent a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms. Specific examples of the ketones include acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl amyl ketone, methyl cyclohexyl ketone, diethyl ketone, ethyl butyl ketone, trimethylnonanone, acetonitrile acetone, dimethyl oxide, holone, Examples thereof include cyclohexanone and diacetone alcohol.

Examples of the esters include compounds represented by the following formula (9). R ⁹ COOR ¹⁰ (9) [In the formula (9), R ⁹ and R ¹⁰ represent a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms. ] Specific esters include, for example, ethyl formate, methyl acetate, ethyl acetate, butyl acetate, cyclohexyl acetate, methyl propionate, ethyl butyrate, ethyl oxyisobutyrate, ethyl acetoacetate, ethyl lactate, methoxybutyl acetate, oxalic acid. Examples thereof include diethyl and diethyl malonate.

In the present invention, the amount of the specific organic compound used is not more than 5 times the mol of the organometallic compound, preferably 0.5.
~ 3 times the molar amount. Reaction product In the present invention, the component (A) and the component (B) are reacted in the absence of an organic solvent to form a reaction product (hereinafter, referred to as "specific reaction product"). is there. Here, the reaction temperature of the (A) component and the (B) component is usually 0 to
250 ° C., preferably 25 to 150 ° C., the reaction time is 0.
It is 5 to 6 hours, preferably 1 to 4 hours.

In the present invention, the specific reaction product obtained as described above may be further hydrolyzed and condensed to give a hydrolysis-condensation product (hereinafter referred to as "specific hydrolysis-condensation product"). In this hydrolysis, water or water and a catalyst are added to a specific reaction product, and the reaction is performed at 20 to 100 ° C. for several hours to
It can be performed by stirring for several days. Water is usually 100 mol% based on 100 mol% of the specific reaction product.
Below, it is preferably used in an amount of 50 to 5 mol%.

The catalyst that can be used here is, for example,
Inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid; acid catalysts such as acetic acid, propionic acid, butyric acid, maleic acid and other organic acids, sodium hydroxide, potassium hydroxide, ammonia, monoethanolamine, diethanolamine, tetramethylammonium hydroxide Inorganic / organic alkali catalysts such as Of these, it is more preferable to use an acid catalyst. In an inorganic alkali such as sodium hydroxide or potassium hydroxide, metal ions such as sodium or potassium may remain in the coating solution to affect the electrical characteristics of the coating film. This is because the nitrogen-based alkali may form a nitrogen compound having a high boiling point after the hydrolysis reaction, which may affect the densification of the coating film during the firing step. In addition,
The conditions of the hydrolysis condensation can be appropriately selected depending on the use of the coating.

By further hydrolyzing the specific reaction product in this way, the content of organic components in the entire coating film after the drying step can be reduced, and
Metalloxane bond of each metal (Bi-O-Bi, Bi-O
-Ta, Bi-O-Sr, Ta-O-Bi-O-Sr and the like) can be promoted.

Preparation of Coating Liquid for Forming Ferroelectric Thin Film In the present invention, a coating liquid for forming a ferroelectric thin film is prepared by dissolving or dispersing a specific reaction product and / or a specific hydrolysis-condensation product in an organic solvent. Is obtained. Here, two or more kinds of the specific reaction product and the specific hydrolysis-condensation product can be mixed.

Further, an organometallic compound other than the specific reaction product (hereinafter referred to as "other organometallic compound") can be used in combination. Other organometallic compounds include
The metal alkoxide, metal carboxylate, etc. of (A) component used for manufacture of a specific reaction product can be mentioned.

Examples of the organic solvent that dissolves or disperses such a specific reaction product include alcohol solvents and
Examples thereof include polyhydric alcohol solvents, ether solvents, ketone solvents, ester solvents, lower carboxylic acid solvents and the like. Examples of alcohol solvents include methanol, ethanol, propanol, butanol, amyl alcohol, cyclohexanol, and methylcyclohexanol. As the polyhydric alcohol solvent, ethylene glycol monomethyl ether, ethylene glycol monoacetate, diethylene glycol monomethyl ether, diethylene glycol monoacetate, propylene glycol monoethyl ether,
Propylene glycol monoacetate, dipropylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monopropyl ether, methoxybutanol and the like can be mentioned. Examples of the ether solvent include methylal, diethyl ether, dipropyl ether, dibutyl ether, diamyl ether, diethyl acetal, dihexyl ether, trioxane and dioxane. As the ketone solvent, acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl amyl ketone, methyl cyclohexyl ketone, diethyl ketone, ethyl butyl ketone, trimethylnonanone, acetonitrile acetone, dimethyl oxide, phorone, cyclohexanone, diacetone alcohol Etc. can be mentioned. As the ester solvent,
Ethyl formate, methyl acetate, ethyl acetate, butyl acetate, cyclohexyl acetate, methyl propionate, ethyl butyrate,
Examples thereof include ethyl oxyisobutyrate, ethyl acetoacetate, ethyl lactate, methoxybutyl acetate, diethyl oxalate and diethyl malonate. Examples of the lower carboxylic acid solvent include acetic acid, propionic acid, butyric acid, valeric acid and the like. The above solvents may be used alone or in combination of two or more. In the present invention, the concentration of the total amount of the specific reaction product and the specific hydrolysis-condensation product and the organometallic compound used as necessary in the coating solution is 1 to 20% by weight of solid content in terms of metal oxide. %, Preferably 5 to 15% by weight.

Regarding the content of each metal element component in the coating liquid for forming such a ferroelectric thin film, for example, the content of Bi metal element component, Sr metal element component and Ta metal element component, the kind of applicable device ( DRA for FRAM
M, MFS, MFIS, MFMIS, etc.), the type and thickness of the upper and lower electrodes to be used, the combination, the type and thickness of the barrier layer, and the presence or absence of a seed layer (alignment film), etc. It may be appropriately selected depending on the situation.

The coating liquid for forming a ferroelectric thin film and the method for producing the coating liquid of the present invention can be applied to the formation of any ferroelectric thin film. In particular, it can be preferably applied to the formation of a Bi-based ferroelectric thin film. For example, the formula (Bi ₂ O ₂ ) ²⁺ (A _m-1
B _m O _{3m + 1} ) ²⁻ , where A is a mono-, di-, or trivalent ion (for example, Bi, Pb, Ba, Sr, Ca, Na, K, and an ion of a rare earth element), or these B is a combination of four, five, and six valent ions (for example,
Ti, Nb, Ta, W, Mo, Fe, Co, Cr, and other metal element ions), or a combination of these ions, and m is an integer of 1 to 5. ] A ferroelectric thin film having a structure shown in the following, specifically, SrBi ₂ Ta ₂ O ₉ system;
(Bi ₂ O ₂ ) ²⁺ (SrTa ₂ O ₇ ) ² -based ferroelectric thin film and the like, and the formula (Bi ₂ O ₃ ) (M ¹ _l M ² _m O _x ) [wherein M ¹ is
A divalent metal ion, M ^2, is a pentavalent metal ion, 1 and m are positive numbers from 0.5 to 5, and x is M ^1.
And a positive number calculated from the valence of M ² . ] A ferroelectric thin film or the like having a structure shown in FIG.

Ferroelectric thin film and method for producing the same In the present invention, in order to form a ferroelectric thin film composed of a plurality of kinds of metal elements, preferably three or more kinds of metal elements, a specific reaction product and another organometallic compound are used. It is preferable to form a coating solution by mixing and dissolving a coating solution for forming a ferroelectric thin film (hereinafter referred to as "coating solution") on a substrate and drying it as necessary.

The above various solvents are LSM-CV for open spin coating, closed spin coating, and mist coating.
The most preferable one can be appropriately used according to the difference in the coating conditions such as the D method and the dipping method. Examples of the substrate to which the coating solution is applied include silicon wafers. An electrode made of a silicon oxide film, a metal such as Pt, Ir, Ru, and a conductive metal oxide which is a metal oxide thereof may be formed on the silicon wafer.

The coating solution is applied onto the substrate by a known coating method such as a spinner method or a dipping method, usually 50 to 40.
Drying is performed at a temperature of 0 ° C, preferably 150 to 250 ° C. Furthermore, the calcination may be performed at a temperature of 250 to 500 ° C. It is preferable to set a desired film thickness by repeating a series of operations such as coating of the coating liquid, drying and calcination several times.

The ferroelectric thin film has a thickness of 10 to 200 nm.
The film thickness is preferably Next, 500-800
Main firing is performed at a temperature of about 60 ° C., preferably about 600 to 700 ° C. to form a ferroelectric thin film having a crystal structure. In the main firing step, room temperature (25 ° C) to 5 to 20 ° C / m
Furnace method in which the temperature is raised to the main firing temperature at a heating rate of about in, and then the main firing temperature is maintained for about 30 to 80 minutes, and the main firing temperature is from room temperature to about 30 to 300 ° C./sec. It is possible to select various firing methods such as the RTP method in which the temperature is raised to 1.0 and then the main firing temperature is maintained and firing is performed for about 0.5 to 10 minutes.

In the present invention, as the substrate, a silicon wafer on which an electrode (lower electrode) made of a metal such as Pt, Ir, Ru or the like and a conductive metal oxide which is a metal oxide thereof is formed is used. After forming the ferroelectric thin film on the ferroelectric thin film by the method of the present invention, an electrode (upper electrode) is formed on the ferroelectric thin film, whereby a ferroelectric memory can be manufactured. Here, as the upper electrode, it is possible to use the metals, metal oxides, etc. listed as the material for the lower electrode, and to form these materials on the ferroelectric thin film by a known method such as a sputtering method or a vapor deposition method, Ferroelectric memory is manufactured by annealing under the same conditions as those at the time of firing.

[0032]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited to these examples.

Example 1 1.14 g of Sr (OiC ₃ H ₇ ) ₂ and Ta (OC ₂ H ₅ )
₅ 5.00 g and 5.23 g of 2-ethylhexanoic acid were mixed and stirred at 150 ° C. for 4 hours. After completion of the reaction, the mixture was cooled to room temperature to obtain an organometallic compound reacted with SrTa metal alkoxides. The obtained organometallic compound is heated at room temperature to 50.
The mixture was stirred under reduced pressure at 0 ° C for 1 hour to remove low boiling point alcohol, which was designated as (a) specific reaction product. Bi (OtC
₅ H ₁₁ ) ₃ 7.00 g was mixed with 0.99 g of butyric acid to give 100
The mixture was stirred at 0 ° C for 2 hours. After the reaction was completed, the mixture was cooled to room temperature, and B
An organometallic compound reacted with the i alkoxide was obtained. The obtained organometallic compound was stirred at room temperature to 50 ° C. under reduced pressure for 1 hour to remove low boiling point alcohol, which was used as (b) specific reaction product. → Is this compound also a specific reaction product? ↑ Yes, this is also a "specific organometallic compound". In this example, two types of "specific organometallic compounds" are combined. The above (a) specific reaction product and (b) specific reaction product were mixed so as to be Sr: Bi: Ta = 0.9: 2: 2, and the concentration was converted to a metal oxide concentration of 10 with propylene glycol monopropyl ether. The mixture was diluted to give a weight percentage to obtain a coating liquid for ferroelectric thin film (coating liquid 1).

Example 2 1.14 g of Sr (OiC ₃ H ₇ ) ₂ and Ta (OC ₂ H ₅ )
₅ 5.00 g and 5.23 g of 2-ethylhexanoic acid were mixed and stirred at 150 ° C. for 4 hours. After completion of the reaction, the mixture was cooled to room temperature to obtain an organometallic compound reacted with SrTa metal alkoxides. The obtained organometallic compound is heated at room temperature to 50.
The mixture was stirred under reduced pressure at 0 ° C for 1 hour to remove low boiling point alcohol, which was used as a specific reaction product. Using the specific reaction product and Bi (OtC ₅ H ₁₁ ) ₃ as another organometallic compound, Sr: Bi: Ta = 0.9: 2: 2 was mixed, and propylene glycol monopropyl ether was added. The mixture was diluted to a concentration of 10% by weight in terms of metal oxide to obtain a ferroelectric thin film forming coating liquid (coating liquid 2).

Comparative Example 1 Sr (OiC ₃ H ₇ ) ₂ 3.70 g, Bi (OtC ₅ H ₁₁ ) ₃
18.82 g, Ta (OC ₂ H ₅ ) ₅ 16.25 g and propylene glycol monopropyl ether 355.0
After mixing g and stirring at 25 ° C. for 1 hour, 393.7 g of a mixed solution of Sr metal alkoxide, Bi metal alkoxide and Ta metal alkoxide was obtained. 9.0 g of water and 885.6 g of propylene glycol monopropyl ether
And mixed with the above Sr metal alkoxide, Bi
After adding 393.7 g of a mixed solution of a metal alkoxide and a Ta metal alkoxide, the temperature was raised to 60 ° C., the mixture was heated and stirred for 4 hours, and after completion of the reaction, cooled to room temperature, and Sr
A solution of a hydrolyzed condensate obtained by hydrolyzing and condensing BiTa metal alkoxides was obtained. To the resulting solution of the hydrolyzed condensate, 44.71 g of 2-ethylhexanoic acid was added,
After stirring at 25 ° C. for 30 minutes to exchange the functional groups of the hydrolyzed condensate, this solution was heated to 40 to 50 ° C. and stirred under reduced pressure for 30 minutes to remove 100 g of a solution from which the low boiling point alcohol was removed. Obtained. Next, the solution from which the low boiling point alcohol has been removed is cooled to room temperature and then diluted with propylene glycol monopropyl ether to a concentration of 10% by weight in terms of metal oxide, and a coating liquid for forming a ferroelectric thin film (coating) Liquid 3) was prepared.

Formation of Ferroelectric Thin Film 10 by sputtering on a 6-inch diameter silicon wafer on which 1000 nm of thermally oxidized SiO ₂ was formed.
A Pt lower electrode having a film thickness of 0 nm was formed. Next, the Pt
On the lower electrode, the coating liquid 1 obtained in Example 1 was applied at 500 rpm for 5 seconds using a spin coater, and then 3000 times.
After spin coating at rpm for 20 seconds and drying at 250 ° C. for 5 minutes, 65 ° C. at a heating rate of 25 ° C./45° C./sec.
A coating film was formed by heating to 0 ° C. and performing heat treatment for 10 minutes in an oxygen atmosphere. Then, the coating liquid 1 is applied onto this coating film in the same manner as described above, dried, heated, and heat-treated. These operations are performed twice, to form a ferroelectric thin film having a thickness of 80 nm. did. Further, instead of the coating liquid 1, the coating liquid 2 was used in the same manner as above, and 80% was formed on the Pt lower electrode.
A ferroelectric thin film having a thickness of nm was formed. Further, instead of the coating liquid 1, the coating liquid 3 was used to form a ferroelectric thin film having a thickness of 80 nm on the Pt lower electrode in the same manner as above.

Then, a diameter of 0.2 m is formed on each of the above ferroelectric thin films by a sputtering method through a metal mask.
A 200-nm-thick Pt upper electrode having a thickness of m was formed and fired at 650 ° C. for 10 minutes in an oxygen atmosphere to manufacture a ferroelectric element. A sectional view of the obtained ferroelectric element is schematically shown in FIG.

The hysteresis characteristics and the saturation characteristics of the ferroelectric element manufactured by using the coating liquid 1 of Example 1 are shown in FIG. 2 and FIG. 3 and the ferroelectric characteristics manufactured by using the coating liquid 2 of Example 2, respectively. Hysteresis characteristics and saturation characteristics of the body element are shown in FIGS. 4 and 5, respectively. Further, the hysteresis characteristics and the saturation characteristics of the ferroelectric element manufactured using the coating liquid 3 of Comparative Example 1 are shown in FIGS. 6 and 7, respectively. Note that FIG.
In FIG. 5 and FIG. 7, ■ represents the non-inversion polarization amount Pnv (μc / c
m ² ) and ♦ represent the residual polarization quantity 2Pr (μc / cm ² ).

As apparent from FIGS. 2 and 3, the implementation
His of a ferroelectric element obtained by using the coating liquid 1 of Example 1
The high-voltage side is closed and the therisis property is good. Non-anti
The amount of polarization polarization Pnv is 7 to 8 μc / c when the applied voltage is about 2V.
m²And shows a good saturation characteristic curve.
Maximum amount of 2Pr is 12μc / cm at applied voltage of 3V ²And
It can be seen that the characteristic curve is almost saturated. Example 2
Hysteresis of Ferroelectric Element Produced Using Coating Solution 2 of
The cis and saturation characteristics are shown in Fig. 4 and Fig. 5, respectively.
You As is clear from FIGS. 4 and 5, the coating of Example 2 was applied.
Hysteresis of ferroelectric element obtained by using cloth liquid 2
The characteristics are good because the high voltage side is closed. Non-inverted polarization amount
Pnv is 8-9 μc / cm when applied voltage is about 2V²Tona
Shows a good saturation characteristic curve, and the residual polarization amount is 2Pr.
Is 13 μc / cm at an applied voltage of 3 V ²And is almost saturated
It can be seen that the characteristic curve is close to.

On the other hand, as is apparent from FIGS. 6 and 7, the hysteresis characteristic of the ferroelectric element obtained by using the comparative coating solution 3 of Comparative Example 1 shows the characteristic of the leakage tendency that the high voltage side is widened. It is also shown that the non-inverted polarization amount Pnv and the residual polarization amount 2Pr do not reach saturation unless they are on the high voltage side, or do not reach saturation at all. As described above, by using the coating liquid for forming a ferroelectric thin film (Example 1 and Example 2) which contains a specific reaction product and an organic solvent, the ferroelectric substance can be used at a low temperature such as 650 ° C. A thin film can be formed, and a ferroelectric element having excellent hysteresis characteristics and saturation characteristics can be obtained. On the other hand, it is understood that the effect of the present invention cannot be obtained with the coating liquid as in Comparative Example 1.

[0041]

EFFECT OF THE INVENTION Obtained by reacting (A) the organometallic compound of the present invention with (B) a compound selected from carboxylic acids, alcohols, ethers, ketones and esters in the absence of an organic solvent. A coating liquid for forming a ferroelectric thin film, which contains a reaction product and an organic solvent, contains an active ingredient soluble in a general-purpose organic solvent, and has excellent storage stability and reproducibility during use. It is practical because it exists. In addition, according to the production method of the present invention, an excellent coating liquid for forming a ferroelectric thin film can be obtained. Moreover, the ferroelectric thin film can be satisfactorily formed by the coating liquid for forming a ferroelectric thin film even by firing at a low temperature.

Therefore, a ferroelectric thin film having excellent electric characteristics and an excellent ferroelectric element using the same can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a ferroelectric element.

FIG. 2 is a graph showing hysteresis characteristics of a ferroelectric element formed using coating liquid 1.

FIG. 3 is a graph showing a saturation characteristic of a ferroelectric element formed by using coating liquid 1.

FIG. 4 is a graph showing hysteresis characteristics of a ferroelectric element formed by using coating liquid 2.

FIG. 5 is a graph showing saturation characteristics of a ferroelectric element formed by using coating liquid 2.

FIG. 6 is a graph showing hysteresis characteristics of a ferroelectric element formed using coating liquid 3.

FIG. 7 is a graph showing saturation characteristics of a ferroelectric element formed by using coating liquid 3.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01L 21/316 H01L 21/316 G (72) Inventor Kinji Yamada 2-11-24 Tsukiji, Chuo-ku, Tokyo F-Terms in JSR Co., Ltd. (reference) 4G048 AA05 AB02 AB05 AC02 AD02 AE08 5F058 BA11 BC03 BF46 BH03 5G303 AA10 AB15 BA03 CA01 CB03 CB05 CB06 CB10 CB11 CB13 CB35 CB35 CB35 CB35 CB35 CB40 CB32 CB25 CB32 CB25 CB25 CB32 CB25 CB23 CB25 CB23 CB25 CB23 CB25 DA05

Claims (12)

[Claims] 1. A reaction product obtained by reacting (A) an organometallic compound with (B) a compound selected from carboxylic acids, alcohols, ethers, ketones and esters in the absence of an organic solvent. A coating liquid for forming a ferroelectric thin film, which comprises: and an organic solvent. 2. The coating liquid for forming a ferroelectric thin film according to claim 1, wherein the amount of the component (B) used is 5 times or less the mole number of the organometallic compound (A). 3. An (A) organometallic compound and a compound selected from (B) carboxylic acids, alcohols, ethers, ketones and esters in a mole number of 5 times or less the mole number of (A), A coating liquid for forming a ferroelectric thin film, comprising a reaction product obtained by reaction and an organic solvent. 4. The (A) organometallic compound is Li, Na,
K, Mg, Ca, Sr, Ba, La, Ti, Zr, H
f, V, Nb, Ta, Cr, Mo, W, Mn, Fe, C
The coating liquid for forming a ferroelectric thin film according to claim 1, which has a metal atom selected from o, Ni, Cu, Zn, Pb and Bi. 5. The (A) organometallic compound is Pb, Zr, or T.
The coating liquid for forming a ferroelectric thin film according to claim 1, which is a metal selected from i and La. 6. The (A) organometallic compound is Sr, Bi, T
The coating liquid for forming a ferroelectric thin film according to claim 1, which is a metal selected from i, Ta and Nb. 7. A reaction product is obtained by reacting (A) an organometallic compound with (B) a compound selected from carboxylic acids, alcohols, ethers, ketones and esters in the absence of an organic solvent. A method for producing a coating liquid for forming a ferroelectric thin film, which comprises mixing the reaction product with an organic solvent. 8. The method for producing a coating liquid for forming a ferroelectric thin film according to claim 7, wherein the amount of the component (B) used is 5 times or less the molar amount of the organometallic compound (A). 9. An organometallic compound (A) and a compound selected from (B) carboxylic acids, alcohols, ethers, ketones and esters in a mole number of 5 times or less the mole number of (A), A method for producing a coating liquid for forming a ferroelectric thin film, which comprises reacting to produce a reaction product and mixing the reaction product with an organic solvent. 10. The method for producing a coating liquid for forming a ferroelectric thin film according to claim 7, wherein after the reaction product is formed, the reaction product is further hydrolyzed and condensed. 11. The method for producing a coating liquid for forming a ferroelectric thin film according to claim 7, wherein after the reaction product is formed, the reaction product is further hydrolyzed and condensed. 12. A ferroelectric thin film formed from the coating liquid for forming a ferroelectric thin film according to claim 1.