JPH08157260A - Production of thin ferroelectric film - Google Patents

Abstract

PURPOSE: To suppress the occurrence of lattice defects due to the release of Pb or PbO and to reduce deviation in compsn. and a leakage current by polycondensing organometallic compds. or inorg. salts of the constituent elements of a Pb-contg. perovskite type ferroelectric by heating in an org. acid solvent. CONSTITUTION: Organometallic compds. or inorg. salts of the constituent elements of a Pb-contg. perovskite type ferroelectric represented by the formula (where 1 > y >=0, 1 > x > 0, A is La or Er and each of B and C is Zr, Ti, Mg or Nb) are polycondensed by heating and stirring at 115-125 deg.C for 2-3hr in an org. acid solvent in a nitrogen atmosphere and the resultant product is cooled to room temp. and diluted with other solvent capable of dissolving the organometallic compds. or inorg. salts to prepare a soln. of a precursor of a Pb-contg. perovskite type compd. This soln. is dropped on a substrate and spin coating, drying and heat treatment are carried out. These processes are repeated three times and then annealing is carried out at 650 deg.C for 15sec in a 100% oxygen atmosphere to form the objective thin Pb-contg. perovskite type ferroelectric film on the substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a ferroelectric thin film used for memory elements, pyroelectric elements, piezoelectric elements, electro-optical elements and the like.

[0002]

2. Description of the Related Art Conventionally, ferroelectrics have been variously applied in the field of electronics by utilizing their unique electrical characteristics. For example, an infrared linear array sensor utilizing its pyroelectricity, an ultrasonic sensor utilizing its piezoelectricity, or a waveguide type optical modulator utilizing its electro-optical effect. Used in various ways.

A DRAM (Dynamic Random Access M
Since its appearance as a charge storage solid-state memory with a simple structure and manufacturing method in 1970, it has been widely used while increasing its degree of integration. In particular, since 1972, so-called 1Tr-1C DRAM in which one memory cell includes one capacitor and one transistor has been most widely used because of its simple shape and small size. In this DRAM, it is a dielectric thin film capacitor that stores charges, and a transistor made of a semiconductor is used as a switch for separating the capacitors from each other.

Although the chip area is gradually increasing with the integration of DRAM, the cell area is decreasing at a rate higher than that. On the other hand, the cell capacity (capacitance of the capacitor) required for the DRAM is required to be about 30 fF even from the point of view of the sensitivity of the sense amplifier, the bit line capacity, etc. even if the integration is advanced. Therefore, in order to keep the capacitance C of the capacitor at a certain level, it is necessary to increase the effective area S of the capacitor or decrease the thickness d of the capacitor thin film.
It is necessary to increase the relative permittivity ε _r of the capacitor material. As a method of increasing the integration of DRAMs up to the present, a method of increasing S and decreasing d such as a stack type cell or a trench type capacitor cell has been adopted. However, in such a three-dimensional structure, the increase in the number of steps due to the complication of the process and the decrease in the yield due to the increase in steps are regarded as problems, and the thinning has already reached its limit. Therefore, it has become necessary to deposit a dielectric thin film having a large relative permittivity ε _r on Si.

On the other hand, as nonvolatile semiconductor memory elements, ROM (Read Only Memory) and PROM (Programmabl
e ROM), EPROM (Erasable PROM), EEPROM (E
lectrically Erasable PROM), especially EEPR
The OM is promising because it can electrically rewrite the stored contents. In this EEPROM, MI
A method is known in which a trap region or a floating gate in a gate insulating film of an S (Metal Insulator Semiconductor) field effect transistor is charged by injecting charges from a silicon substrate and the surface conductivity of the substrate is modulated by the electrostatic induction. ing.

As a non-volatile memory of a method completely different from this EEPROM, there is a ferroelectric non-volatile memory utilizing spontaneous polarization of a ferroelectric. This ferroelectric non-volatile memory contains MFS (Metal Ferroelectric Semiconduct).
or) -FET (Field Effect Transistor) structure and capacitor structure.

In the MFS-FET structure, the gate insulating film of the MIS-FET is a ferroelectric thin film, and the semiconductor surface is adapted to compensate the spontaneous polarization depending on the direction and size of the spontaneous polarization of the ferroelectric. The contents of the memory are read out by utilizing the fact that the conductivity of the semiconductor surface is modulated by the electric charges induced in the memory.

The capacitor structure has a structure in which a ferroelectric thin film is sandwiched by electrodes, and the presence or absence of a reversal current due to the polarization reversal of the spontaneous polarization of the ferroelectric is detected to read the memory contents.

The method of manufacturing such a ferroelectric thin film includes
Physical methods such as vacuum deposition method, sputtering method and laser ablation method, and sol-gel method and MOD (Metal Organic Deposition) method using organic metal compounds as starting materials to thermally decompose and oxidize them to obtain oxide ferroelectrics. , CV
A chemical method such as D (Chemical Vapor Deposition) method is used.

Examples of such a ferroelectric thin film material include PZT (lead zirconate titanate) and PbTi.
O ₃ (lead titanate), BaTiO ₃ (barium titanate)
PZT-based materials are being actively studied as the most promising materials at present. However, in order to be used in various electronic devices, it is necessary to satisfy many specifications such as excellent environmental characteristics, little change over time, and good temperature characteristics.

As a film forming method suitable for such an actual situation, it is possible to perform homogeneous mixing at the atomic level, easy composition control and excellent reproducibility, and it is possible to form a large area film at normal temperature and normal pressure. The sol-gel method or the MOD method, which has advantages such as that and is industrially low in cost, is suitable.

Next, the reference J. J. Appl. Of K. Samesima (ROHM) et al.
Phys. Vol. 32 (1993) pp.4144-4146 etc.,
An example of a conventional process will be described.

In this film forming method, a solution of an organometallic compound such as lead acetate, titanium tetraisopropoxide, zirconium tetraisopropoxide, etc. is treated with methanol, ethanol, propanol, butanol, methoxyethanol,
Prepared by mixing in an alcohol solvent such as ethoxyethanol, for example, (1)

[0014]

[Equation 1]

A step of purifying a complex alkoxide sol having a two-dimensional chain structure as described above, (2) a step of applying the same on a substrate by a spin coating method, a dip coating method or the like, (3) in air After being hydrolyzed by the water of

[0016]

[Equation 2]

A step of forming a gel having a three-dimensional mesh structure as described above, (4) a step of removing the reaction-purified alcohol and residual water not taken into the mesh structure from the film,
(5) A step of heat treatment for crystallizing from a gel state to an amorphous state.

Although the MOD method basically comprises the same steps as the sol-gel method, it does not go through the step of forming a complex alkoxide having a two-dimensional chain structure by partial hydrolysis in the above step (1). In addition, it is a method of directly obtaining an oxide by heating and baking.

[0019]

However, the conventional method using an alcohol solvent as a solvent for the above-mentioned precursor solution is such that when heat treatment is carried out at a high temperature, a component having a high saturated vapor pressure is the main composition, for example, In a Pb-based ferroelectric thin film such as PZT, Pb or PbO was evaporated and desorbed from the film, and the film composition sometimes deviated from the stoichiometric ratio. If the composition morphology deteriorates the surface morphology or a thin film with many lattice defects is formed,
The electrical characteristics are significantly affected, and the phenomenon that the ferroelectricity is lowered or the leak current is increased occurs. In such a ferroelectric thin film containing Pb as a main composition, reduction of leak current and improvement of ferroelectric characteristics are required. In order to improve these electrical characteristics, for example, a method of first producing a thin film containing Pb in a stoichiometric ratio and then obtaining a thin film having a stoichiometric composition after heat treatment has been attempted. The characteristics have not been sufficiently improved yet.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a method of manufacturing a ferroelectric thin film having excellent electric characteristics such as leak current and fatigue characteristics. To do.

[0021]

According to the method of the invention described in claim 1, an organometallic compound or an inorganic salt of each element constituting a lead-based perovskite type ferroelectric is heated and stirred in an organic acid solvent. After that, a ferroelectric thin film is prepared by using a precursor solution prepared by diluting with another solvent capable of dissolving the above-mentioned organometallic compound or inorganic salt.

The method according to the second aspect of the invention is characterized in that acetic acid is used as the organic acid solvent.

The method according to the third aspect of the present invention is characterized in that the heating temperature is in the range of 115 ° C. to 125 ° C. and the stirring time is 2 hours to 3 hours.

[0024]

According to the method of the present invention as set forth in claim 1, a solution containing an organic metal compound or inorganic salt of a part of the elements constituting the ferroelectric thin film and an organic acid is prepared, and the solution is mixed with another strong acid. After adding an organometallic compound or an inorganic salt of a part of the elements constituting the dielectric thin film, this solution is preferably heated, stirred or the like to carry out polycondensation to obtain a desired precursor solution. By producing a ferroelectric thin film using this precursor solution, lattice defects due to the release of Pb and PbO from the film are suppressed, and composition shift is reduced. Further, the leak current is reduced and the electrical fatigue characteristics are excellent.

According to the method of the invention described in claim 2, a desired precursor solution is obtained by using acetic acid as the organic acid solvent.
By producing a ferroelectric thin film using this precursor solution, lattice defects due to the release of Pb and PbO from the film are suppressed, and composition shift is reduced. Further, the leak current is reduced and the electrical fatigue characteristics are excellent.

According to the method of the invention described in claim 3, the desired precursor solution is obtained by heating the solution at a temperature of 115 ° C. to 125 ° C. and stirring it for 2 hours to 3 hours.
By producing a ferroelectric thin film using this precursor solution, lattice defects due to the release of Pb and PbO from the film are suppressed, and composition shift is reduced. Further, the leak current is reduced and the electrical fatigue characteristics are excellent.

[0027]

EXAMPLES The perovskite type ferroelectric material of the present invention complies with the following chemical formula, for example.

(Pb _1-y A _y ) (B _x C _1-x ) O ₃ where 1> y ≧ 0, 1>x> 0, and A is La or Er.
And B and C are different elements selected from the group consisting of Zr, Ti, Mg and Nb.

In the present invention, examples of the organic acid solvent include saturated aliphatic monocarboxylic acids such as acetic acid, formic acid and propionic acid, and saturated aliphatic dicarboxylic acids such as oxalic acid, malonic acid and succinic acid. Further, the other solvent is not particularly limited as long as it is a solvent capable of dissolving the above-mentioned organometallic compound or inorganic salt, but for example, alcohols (eg: ethanol, propanol, ethylene glycol, Acetylene etc.), ketones (eg acetone, ethyl methyl ketone etc.), esters (eg methyl acetate, ethyl acetate etc.), ethers (eg diethyl ether, ethyl methyl ether etc.),
Cycloalkanes (cyclohexane, cyclohexanol, etc.), carboxylic acids (eg formic acid, acetic acid, benzoic acid, etc.)
Examples include toluene and xylene.

In the method of manufacturing the ferroelectric thin film of the present invention, the sol-gel method or the MOD method is used. As the precursor solution preparation process by the sol-gel method or the MOD method, first, as described above, a solution containing an organometallic compound or inorganic salt of some elements constituting the ferroelectric thin film and an organic acid as a solvent is prepared. After adding an organometallic compound or an inorganic salt of some other element constituting the ferroelectric thin film to this solution, the solution is subjected to polycondensation, preferably by heating or stirring, to obtain a desired precursor. Obtain body solution. That is, when a perovskite-type ferroelectric thin film represented by (Pb _1-y A _y ) (B _x C _1-x ) O ₃ is prepared, Pb and A are first dissolved in a solution, and then B and A mixture of C is added, or Pb and A previously dissolved are mixed with B and then C to prepare a non-aqueous solution. Then, a certain amount of water is added to the non-aqueous solution to carry out hydrolysis and polycondensation to obtain a precursor solution. The solvent may be added to adjust the concentration of the non-aqueous solution before adding water.

The mixing amount of the organometallic compound of each element, the inorganic salt, the solvent and the like when preparing the precursor solution is not particularly limited, and depends on the composition of the finally formed ferroelectric thin film. It can be appropriately prepared, and the mixing amount usually used when preparing a precursor solution by the sol-gel method / MOD method can be used.

When the solution containing the organometallic compound or the inorganic salt is heated and stirred, the temperature is from 115 ° C to 12 ° C.
It is preferable to stir at a heating temperature of 5 ° C. for 2 hours to 3 hours. Here, as the heating temperature, an appropriate temperature may be selected depending on the solvent. The stirring time is 2 hours to 3 hours, since it is necessary to stir until the reaction is completed.

The precursor solution prepared in the present invention can be formed on a substrate or an electrode to form a desired element such as a capacitor. The substrate used is not particularly limited, and a silicon substrate, a compound semiconductor substrate, an insulating substrate such as polycarbonate, or the like can be used. In the case of forming a capacitor, for example, a ferroelectric thin film is formed on a desired insulating film, an oxide film, etc. and an electrode formed on a silicon substrate, and an upper electrode is formed on the ferroelectric thin film. You can The upper and lower electrodes can be formed by a known method such as a sputtering method or a vapor deposition method. A known material can be used as the electrode material, and it is not particularly limited, but Pt, Ti, Ta, Pt / Ti, Pt.
/ Ta or the like can be used. The film thickness of the electrode at that time is not particularly limited. When forming a ferroelectric thin film on a substrate, an electrode, or the like, the precursor solution prepared as described above can be formed by, for example, a spin coating method. The conditions at that time are not particularly limited, and a desired rotation speed and the like can be set appropriately. When the precursor solution is applied on a substrate, an electrode, etc., its film thickness is not particularly limited, but it is 100Å to 1000
Å is preferable. Further, the coating liquid O ₂ atmosphere,
30 minutes to 1 in the temperature range of 400 ℃ to 700 ℃
A desired ferroelectric thin film can be formed by heat treatment for about 20 minutes. Here, the heat treatment temperature is 700
If the temperature exceeds ℃, there is a problem that unevenness of the film surface becomes large due to grain growth and composition deviation occurs.
If the temperature does not reach ℃, there is a problem that organic substances remain in the film. Further, if the heat treatment time exceeds 120 minutes, there is a problem that the unevenness of the film surface becomes large due to grain growth or composition shift occurs, and if it does not reach 30 minutes, organic matter remains in the film. . The above-described operation can be repeated a plurality of times to form a ferroelectric thin film having a desired film thickness and a desired orientation. In addition, during heat treatment, the treatment temperature is not limited to the crystallization temperature, but the treatment is performed at a temperature sufficient to burn organic substances without raising the temperature to the crystallization temperature, and after the amorphous film is formed, crystallization is performed at the final stage. You may heat-process by temperature.

The first and second embodiments of the method for producing a ferroelectric thin film according to the present invention will be described below with reference to the drawings.

First, the first embodiment will be described. FIG. 1 is a cross-sectional view for explaining a ferroelectric thin film element manufactured by the method for manufacturing a ferroelectric thin film according to the present invention. n
Thermally-oxidized film 2 with a film thickness of 2000Å on the surface of the silicon substrate
And a Ti film 3 with a film thickness of 300Å is formed on the thermal oxide film 2.
Is formed by a sputtering method, and a film thickness of 2000 is formed on the Ti film 3.
The Pt film 4 of Å was similarly formed by the sputtering method and used as a substrate.

Next, as shown in FIG. 2, a precursor solution for preparing the PZT thin film on the substrate was synthesized.
First, 0.1 [mol] lead acetate in 1 [mol] acetic acid
Was added and the mixture was heated and stirred at 100 [° C.] in a nitrogen atmosphere for about 1 hour. In addition to this, titanium isopropoxide (Ti
36 [ml] of a solution of (OCH (CH ₃ ) ₂ ) ₄ ) prepared in 2-methoxyethanol to 1 [mol / l] and zirconium isopropoxide (Zr (OCH (C)
H ₃ ) ₂ ) ₄ ) with 2-methoxyethanol at 1 [mol /
64 ml of the prepared solution was added to
Heat and stir in a nitrogen atmosphere at [° C] for about 3 hours,
After cooling to room temperature, 0.5 with 2-methoxyethanol
It was adjusted to [mol / l]. Furthermore, add 0.2 to this solution.
After adding [mol] water and stirring for about 1 hour, diethanolamine was added, and this was used as a PZT precursor solution.

This precursor solution was dropped on the above substrate and, as shown in FIG. 3, 350 rpm × 3 seconds, 5000 rpm.
Spin coat under conditions of × 20 seconds and dry gel at 100 ° C.
After producing by heat treatment for 15 minutes, the thermal decomposition of organic matter is 40
It was carried out at 0 ° C for 60 minutes. By repeating this process three times, a thin film 5 having a film thickness of about 2000 Å was obtained.

The thin film 5 was crystallized by heat treatment using an infrared high speed annealing device to obtain a ferroelectric thin film 5. The heat treatment conditions are atmospheric pressure, 100% oxygen atmosphere, annealing temperature of 650 ° C., and annealing time of 15 seconds.

Next, the second embodiment will be described.
As shown in FIG. 4, (Pb _1-y Er _y ) (Zr _x T
A precursor solution for preparing an i _1-x ) O ₃ (hereinafter PEZT) thin film was synthesized. First, lead acetate 0.098 [mol] and erbium nitrate 0.002 in 1 [mol] acetic acid.
[Mol] was added, and the mixture was heated and stirred at 100 [° C.] in a nitrogen atmosphere for about 1 hour. To titanium isopropoxide _{(Ti (OCH (CH 3)} 2) 4) 1 with 2-methoxyethanol solution 36 was prepared in [mol / l] [ml]
And zirconium isopropoxide (Zr (OCH (CH
₃ ) ₂ ) ₄ ) with 2-methoxyethanol at 1 [mol /
64 ml of the prepared solution was added to
Heat and stir in a nitrogen atmosphere at [° C] for about 3 hours,
After cooling to room temperature, 0.5 with 2-methoxyethanol
It was adjusted to [mol / l]. Furthermore, add 0.2 to this solution.
After adding [mol] water and stirring for about 1 hour, diethanolamine was added, and this was used as a PEZT precursor solution.

Using this precursor solution, a ferroelectric thin film was prepared by the same method as in the first embodiment. However, the film thickness at this time was about 2500Å.

Next, a comparative example will be described. As shown in FIG. 5, a precursor solution was synthesized by a method using an alcohol solvent, which was also shown in the prior art, and a ferroelectric thin film was prepared by the same method as in the first embodiment. As an example.

With respect to the ferroelectric thin films 5 of the first embodiment, the second embodiment and the comparative example described above, the composition analysis before and after the heat treatment by the infrared rapid annealing apparatus was performed by EPMA. FIG. 6 is a diagram showing the Pb composition ratio before and after the heat treatment. As is apparent from FIG. 6, the reduction in Pb after the heat treatment was 0.4 mol% in the first example compared with 3.9 mol% in the comparative example by the thin film forming method using acetic acid as a solvent according to the present invention. It can be seen that the amount is suppressed to 0.3 mol% in the second example.

On the ferroelectric thin film 5 of the first embodiment, the second embodiment, and the comparative example described above, 6 is formed by the vacuum deposition method.
The Pt upper electrode 6 having a thickness of 2000 μm and a thickness of 0 μm × 60 μm was formed. FIG. 7 is a diagram showing a leak current when a DC bias of 3 V is applied to the ferroelectric thin film 5. As is clear from the figure, the thin film production method using acetic acid as the solvent according to the present invention suppressed the lattice defects due to the desorption of Pb and PbO from the film and was able to reduce the leak current.

FIG. 8 is a diagram showing a hysteresis loop showing the ferroelectricity before and after the polarization inversion of the PZT thin film of the comparative example is repeated 10 ⁸ times. FIG. 9 shows the PZ of the first embodiment.
FIG. 11 is a diagram showing a hysteresis loop showing ferroelectricity before and after repeating the polarization inversion of the T thin film 10 ⁸ times.
FIG. 8 is a diagram showing a hysteresis loop showing ferroelectricity before and after repeating the polarization inversion 10 ⁸ times of the PEZT thin film of the second example. This fatigue characteristic was measured by applying stress with the pulse shown in FIG. 11 and using the four consecutive pulses shown in FIG. Comparing FIGS. 9 and 10 with FIG. 8, it can be seen that the change in ferroelectricity before and after the repetition of polarization inversion in the example of the present invention is smaller than that in the comparative example. Therefore, it was revealed that by using the method for producing a ferroelectric thin film according to the present invention, lattice defects due to desorption of Pb and PbO from the film can be suppressed and fatigue characteristics can be significantly improved. . Here, a Zr / Ti ratio of 64/36 was taken as an example, but similar effects were obtained with other composition ratios.

[0045]

According to the method of the invention described in claim 1,
A solution containing an organic metal compound or an inorganic salt of some elements constituting the ferroelectric thin film and an organic acid is prepared, and an organometallic compound or inorganic of some elements constituting the other ferroelectric thin film is prepared in this solution. After the salt is added, this solution is preferably heated, stirred or the like to carry out polycondensation to obtain a desired precursor solution. By producing a ferroelectric thin film using this precursor solution, lattice defects due to the release of Pb and PbO from the film are suppressed, and composition shift is reduced. Also,
The leakage current is reduced and the electrical fatigue characteristics are excellent.

According to the method of the invention described in claim 2, a desired precursor solution is obtained by using acetic acid as the organic acid solvent.
By producing a ferroelectric thin film using this precursor solution, lattice defects due to the release of Pb and PbO from the film are suppressed, and composition shift is reduced. Further, the leak current is reduced and the electrical fatigue characteristics are excellent.

According to the method of the present invention described in claim 3, the desired precursor solution is obtained by heating the solution at a temperature of 115 ° C. to 125 ° C. and stirring it for 2 hours to 3 hours.
By producing a ferroelectric thin film using this precursor solution, lattice defects due to the release of Pb and PbO from the film are suppressed, and composition shift is reduced. Further, the leak current is reduced and the electrical fatigue characteristics are excellent.

Therefore, by using the ferroelectric thin film produced by the manufacturing method according to the present invention, a high-performance memory such as a non-volatile memory element utilizing the remanent polarization of the ferroelectric or a DRMA utilizing the high dielectric constant is used. Starting with the element, a pyroelectric element, a piezoelectric element, or an electro-optical element having excellent characteristics can be formed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a principal part showing a configuration of a ferroelectric thin film element manufactured to evaluate electric characteristics of a ferroelectric thin film manufactured by the method of the present invention.

FIG. 2 is a schematic diagram showing a flow chart of preparing a precursor solution in an example of the present invention.

FIG. 3 is a schematic view showing a flow chart for manufacturing a ferroelectric thin film by a sol-gel method in Examples and Comparative Examples of the present invention.

FIG. 4 is a schematic diagram showing a flow chart of preparing a precursor solution in an example of the present invention.

FIG. 5 is a schematic view showing a flow chart of a precursor solution preparation which has been conventionally carried out in a comparative example.

FIG. 6 is a diagram showing Pb composition ratios of a ferroelectric thin film before and after heat treatment in Examples and Comparative Examples of the present invention.

FIG. 7 is a diagram showing a leak current value when a DC bias of 3 V is applied to the ferroelectric thin film in the example of the present invention and the comparative example.

FIG. 8 is a diagram showing a hysteresis loop before and after repeating polarization inversion 10 ⁸ times of a PZT thin film in a comparative example.

FIG. 9 is a diagram showing a hysteresis loop before and after repeating 10 ⁸ polarization inversion of the PZT thin film in the first example according to the invention.

FIG. 10: PEZ in the second embodiment according to the present invention
It is a figure which shows the hysteresis loop before and after repeating the polarization inversion of the T thin film 10 ⁸ times.

FIG. 11 is a diagram showing pulses used when applying stress in the present example.

FIG. 12 is a diagram showing pulses used when performing measurement in this example.

[Explanation of symbols]

 1 n-type silicon substrate 2 silicon thermal oxide film 3 Ti film 4 Pt lower electrode film 5 ferroelectric thin film 6 Pt upper electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location H01L 29/78 41/187 41/24 9056-4M H01L 29/78 617 T 9055-4M 652 K 41 / 18 101 D 41/22 A

Claims (3)

[Claims] 1. A method of manufacturing a ferroelectric thin film, comprising heating an organometallic compound or an inorganic salt of each element constituting a lead-based perovskite ferroelectric represented by the following chemical formula in an organic acid solvent. , A ferroelectric thin film is prepared by using a precursor solution prepared by diluting with an organic solvent or another solvent capable of dissolving the above-mentioned inorganic salt after stirring. Production method. (Pb _1-y A _y ) (B _x C _1-x ) O ₃ where 1> y ≧ 0, 1>x> 0, and A is La or Er.
And B and C are different elements selected from the group consisting of Zr, Ti, Mg and Nb. 2. The method for producing a ferroelectric thin film according to claim 1, wherein acetic acid is used as the organic acid solvent. 3. The method for producing a ferroelectric thin film according to claim 1, wherein the heating temperature is in the range of 115 ° C. to 125 ° C., and the stirring time is 2 hours to 3 hours.