JP2008258638A - Method for manufacturing ferrodielectric film and material solution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing highly reliable ferrodielectric film containing no lead, and to provide a ferroelectric capacitor and a dielectric memory. <P>SOLUTION: The method for manufacturing the ferrodielectric film 101 includes the steps of: (a) mixing polycarboxylate containing niobium element, polycarboxylate containing bismuth element, polycarboxylic acid or polycarboxylic acid ester, and organic solvent; and (b) applying the mixed solution on a base and then heat treating it to form the ferrodielectric film composed of BiNbO<SB>4</SB>. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a ferroelectric film and a method for manufacturing the same.

  Ferroelectric materials such as PZT are used for various applications such as ferroelectric memories, piezoelectric elements, and infrared sensors, and their research and development are actively conducted.

  In particular, the ferroelectric memory is non-volatile and is expected as a next-generation memory having an operation speed equivalent to that of a DRAM. Furthermore, the ferroelectric memory has a feature of low power consumption compared to other memories.

However, a ferroelectric material such as PZT is not preferable for mass production because it contains a large amount of lead that is harmful to the human body. Moreover, in PZT, since lead is easily volatilized, oxygen having a low binding energy with lead is easily lost.
JP 2001-261611 A

  An object of the present invention is to provide a highly reliable ferroelectric film that does not contain lead, a method for manufacturing the same, a ferroelectric capacitor, and a dielectric memory.

The ferroelectric film according to the present invention is made of BiNbO ₄ .

In the ferroelectric film according to the present invention, the BiNbO ₄ may have a Bi layered perovskite structure.

  The ferroelectric film according to the present invention may further contain Si or Si and Ge.

A method for manufacturing a ferroelectric film according to the present invention includes:
(A) a step of mixing a polycarboxylate containing a niobium element, a polycarboxylate containing a bismuth element, a polycarboxylic acid or a polycarboxylic acid ester, and an organic solvent;
(B) forming a ferroelectric film made of BiNbO ₄ by applying the mixed solution on the substrate and then performing a heat treatment.

A method for drawing a ferroelectric film according to the present invention includes:
(A) A sol-gel raw material containing a hydrolysis / condensation product of a metal alkoxide containing a niobium element, a sol-gel raw material containing a hydrolysis / condensation product of a metal alkoxide containing a bismuth element, a polycarboxylic acid or a polycarboxylic acid ester, and an organic By mixing with a solvent, the polycarboxylic acid derived from the polycarboxylic acid or the polycarboxylic acid ester is subjected to an esterification reaction between the metal alkoxide containing the niobium element and the metal alkoxide containing the bismuth element to produce a ferroelectric. Producing a body precursor composition;
(B) a step of forming a ferroelectric film made of BiNbO ₄ by applying the precursor composition onto a substrate and then performing a heat treatment;
including.

  In the method for manufacturing a ferroelectric film according to the present invention, the organic solvent may be an alcohol.

  In the method of manufacturing a ferroelectric film according to the present invention, in the step (a), a sol-gel raw material further containing Si or Si and Ge can be mixed. In particular, Si or Si and Ge are preferably added to the precursor composition in a proportion of 1 to 3 mol%.

  The ferroelectric raw material solution according to the present invention includes a polycarboxylate containing a niobium element, a polycarboxylate containing a bismuth element, a polycarboxylic acid or a polycarboxylic acid ester, and an organic solvent.

  A ferroelectric raw material solution according to the present invention includes a sol-gel raw material containing a hydrolysis / condensation product of a metal alkoxide containing a niobium element, a sol-gel raw material containing a hydrolysis / condensation product of a metal alkoxide containing a bismuth element, and a polycarboxylic acid. An acid or polycarboxylic acid ester and an organic solvent are included.

  The ferroelectric capacitor according to the present invention has any one of the ferroelectric films described above.

  A ferroelectric memory according to the present invention has the above-described ferroelectric capacitor.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

1. Ferroelectric Film and Ferroelectric Capacitor FIG. 1 is a cross-sectional view schematically showing a ferroelectric capacitor 100 using a ferroelectric film 101 according to the present embodiment.

  As shown in FIG. 1, the ferroelectric capacitor 100 is formed on the substrate 10, the first electrode 102, the ferroelectric film 101 formed on the first electrode 102, and the ferroelectric film 101. The second electrode 103 is formed.

  The thicknesses of the first electrode 102 and the second electrode 103 are, for example, about 50 to 150 nm.

The ferroelectric film 101 is made of BiNbO ₄ and has a Bi layered perovskite structure. The ferroelectric film 101 further contains Si, or Si and Ge. The addition of Si or Si and Ge will be described in detail later.

Bi layered perovskite has a crystal structure as shown in FIG. A plurality of octahedrons having oxygen as a vertex are arranged between layers formed of Bi. Nb is located inside the octahedron. A ferroelectric film 101 according to the present invention is made of α-phase (ferroelectric phase) BiNbO ₄ . The thickness of the ferroelectric film 101 is, for example, about 50 to 150 nm.

2. Method for Manufacturing Ferroelectric Film and Ferroelectric Capacitor Next, a method for manufacturing a ferroelectric film and a ferroelectric capacitor in the present embodiment will be described.

  (1) First, the substrate 10 is prepared. As the substrate 10, for example, silicon can be used.

  (2) Next, the first electrode 102 is formed on the substrate 10. The first electrode 102 can be formed by, for example, a laser ablation method. That is, a target including a desired electrode material is prepared. Then, the target is irradiated with laser light, and atoms including oxygen atoms and metal atoms are knocked out of the target to generate plumes. Then, the plume is emitted toward the substrate 10 and brought into contact therewith. As a result, the first electrode 102 is formed by epitaxial growth on the substrate 10.

The material of the first electrode 102 is not particularly limited, and is not limited to Pt, Ir, IrO 2 _X , SrRuO ₃ , Nb—SrTiO ₃ , La—SrTiO ₃ , Nb— (La, Sr) CoO ₃ , LaNiO ₃ , or PbBaO ₃ or the like can be used. Here, Nb—SrTiO ₃ is obtained by doping SrTiO ₃ with Nb, La-SrTiO ₃ is obtained by doping SrTiO ₃ with La, and Nb— (La, Sr) CoO ₃ is represented by (La, Sr). CoO ₃ is doped with Nb.

  Further, as a method for forming the first electrode 102, an ion beam assist method, a sputtering method, a vacuum deposition method, or the like may be used instead of the laser ablation method.

  (3) Next, the ferroelectric film 101 is formed on the first electrode 102.

  First, a polycarboxylate containing a niobium element, a polycarboxylate containing a bismuth element, a polycarboxylic acid or a polycarboxylic acid ester, and an organic solvent are mixed.

  As the polycarboxylate containing the niobium element, for example, niobium octylate can be used. As shown in FIG. 3, niobium octylate has a structure in which Nb is covalently bonded by two atoms and an octyl group is present in the other part.

  Carboxylic acid and niobium octylate form a network mainly through an alcohol exchange reaction. Reaction occurs between the carboxylic acid and the octyl group (alcohol exchange reaction), and esterification of R—COO—Nb proceeds. Thus, in the present embodiment, niobium octylate can be esterified to bind the niobium octylate molecule to the precursor network by condensation of niobium octylate and alkoxide.

  As a polycarboxylate containing a bismuth element, for example, bismuth octylate can be used. Similarly to niobium octylate, bismuth octylate undergoes network formation mainly through an alcohol exchange reaction.

  In this embodiment mode, an alcohol can be used as the organic solvent. When alcohol is used as the solvent, both the sol-gel raw material and the polycarboxylic acid or polycarboxylic acid ester can be dissolved well.

  Although it does not specifically limit as alcohol, Monovalent alcohols, such as butanol, methanol, ethanol, and propanol, or a polyhydric alcohol can be illustrated. Examples of such alcohols include the following.

Monohydric alcohols;
As propanol (propyl alcohol), 1-propanol (boiling point 97.4 ° C), 2-propanol (boiling point 82.7 ° C),
As butanol (butyl alcohol), 1-butanol (boiling point 117 ° C.), 2-butanol (boiling point 100 ° C.), 2-methyl-1-propanol (boiling point 108 ° C.), 2-methyl-2-propanol (melting point 25.4) ℃, boiling point 83 ℃),
As pentanol (amyl alcohol), 1-pentanol (boiling point 137 ° C.), 3-methyl-1-butanol (boiling point 131 ° C.), 2-methyl-1-butanol (boiling point 128 ° C.), 2,2 dimethyl-1 -Propanol (boiling point 113 ° C), 2-pentanol (boiling point 119 ° C), 3-methyl-2-butanol (boiling point 112.5 ° C), 3-pentanol (boiling point 117 ° C), 2-methyl-2-butanol (Boiling point 102 ° C.),
Polyhydric alcohols;
Ethylene glycol (melting point −11.5 ° C., boiling point 197.5 ° C.), glycerin (melting point 17 ° C., boiling point 290 ° C.).

  The polycarboxylic acid or the polycarboxylic acid ester is preferably a divalent carboxylic acid or a polycarboxylic acid ester.

  The following can be illustrated as polycarboxylic acid. Examples of the trivalent carboxylic acid include Trans-aconitic acid, trimesic acid, and examples of the tetravalent carboxylic acid include pyromellitic acid and 1,2,3,4-cyclopentanetetracarboxylic acid. Polycarboxylic acid esters that dissociate in alcohol and act as polycarboxylic acids include divalent dimethyl succinate, diethyl succinate, dibutyl oxalate, dimethyl malonate, dimethyl adipate, dimethyl maleate, and diethyl fumarate. Examples include trivalent tributyl citrate, triethyl 1,1,2-ethanetricarboxylate, tetraethyl 1,1,2,2-ethanetetracarboxylate, trimethyl 1,2,4-benzenetricarboxylate, and the like. . These polycarboxylic acid esters are dissociated in the presence of an alcohol and function as a polycarboxylic acid. In addition, the present invention is characterized in that a network is connected by esterification using a polycarboxylic acid. For example, in a single carboxylic acid such as acetic acid or methyl acetate and its ester, the ester network does not grow. It is not included in the invention.

  The divalent carboxylic acid ester can be preferably at least one selected from succinic acid esters, maleic acid esters and malonic acid esters. Specific examples of these esters include dimethyl succinate, dimethyl maleate, and dimethyl malonate.

Furthermore, in the method for manufacturing a ferroelectric film of this embodiment, a sol-gel raw material containing Si or Si and Ge can be used as a sol-gel raw material containing a hydrolyzed / condensed product of metal alkoxide. As such a sol-gel solution may be used alone sol-gel solution for PbSiO _3, or both the sol-gel solution and PbGeO ₃ sol-gel solution for PbSiO _3. By using such a sol-gel raw material containing Si or Ge, the temperature during film formation can be lowered, and the ferroelectric can be crystallized from about 450 ° C.

Thus, by adding Si or Si and Ge, α-phase BiNbO ₄ that is a ferroelectric phase can be obtained more reliably.

  The ferroelectric film 101 can be formed by applying the mixed solution on the substrate and then crystallizing it by applying heat treatment or the like.

  Specifically, a series of steps including a mixed solution coating step, an alcohol removal step, a drying heat treatment step, and a degreasing heat treatment step are performed a desired number of times, and then baked by crystallization annealing to form the ferroelectric film 101. The conditions in each process are as follows, for example.

  In the mixed solution coating step, the mixed solution is coated by a coating method such as spin coating. First, the mixed solution is dropped on the first electrode 102. Spin is performed for the purpose of spreading the dropped solution over the entire surface of the substrate. The rotation speed of the spin is, for example, about 500 rpm. Next, the mixed solution is applied onto the first electrode 102 by performing spinning for a desired time at a reduced rotational speed. The number of rotations at this time is, for example, 50 rpm or less. The drying heat treatment step is performed at 150 to 180 ° C. The drying heat treatment is performed using a hot plate or the like in an air atmosphere. Similarly, the degreasing heat treatment step is performed in an air atmosphere on a hot plate maintained at 300 ° C to 350 ° C. Firing for crystallization is performed using thermal rapid annealing (RTA) or the like in an oxygen atmosphere.

  The thickness of the sintered ferroelectric film 101 can be about 50 to 150 nm. The ferroelectric film 101 can also be formed by using, for example, a sputtering method, a molecular beam epitaxy method, or a laser ablation method.

  Instead of polycarboxylates containing niobium elements and polycarboxylates containing bismuth elements, sol-gel raw materials containing hydrolysis / condensation products of metal alkoxides containing niobium elements, and hydrolysis of metal alkoxides containing bismuth elements A sol-gel raw material containing a decomposition / condensation product may be used. A sol-gel raw material containing a hydrolysis / condensation product of a metal alkoxide containing niobium element, a sol-gel raw material containing a hydrolysis / condensation product of a metal alkoxide containing bismuth element, a polycarboxylic acid or a polycarboxylic acid ester, and an organic solvent By mixing, the polycarboxylic acid derived from the polycarboxylic acid or the polycarboxylic acid ester, the metal alkoxide containing the niobium element, and the metal alkoxide containing the bismuth element are esterified to produce a precursor of the ferroelectric substance. A body composition can be made.

  The generation reaction of the precursor composition is broadly classified into a first-stage alkoxy group substitution reaction and a second-stage esterification reaction to form a polymer network.

  In the first stage reaction, both are ester-bonded by esterification of dimethyl succinate and metal alkoxide of the sol-gel raw material. That is, dimethyl succinate dissociates in n-butanol, and a proton is added to one carbonyl group (first carbonyl group). A substitution reaction of the first carbonyl group and the alkoxy group of the metal alkoxide occurs, and a reaction product in which the first carboxyl group is esterified and an alcohol are generated. Here, the “ester bond” means a bond (—COO—) between a carbonyl group and an oxygen atom.

  In the second stage reaction, a substitution reaction between the other carboxyl group (second carboxyl group) remaining in the first stage reaction and the alkoxy group of the metal alkoxide occurred, and the second carboxyl group was esterified. A reaction product and an alcohol are produced.

  Thus, a polymer network in which the hydrolysis / condensation products of metal alkoxide contained in the sol-gel raw material are ester-bonded is obtained by the two-stage reaction. Therefore, this polymer network has ester bonds in a moderately orderly manner in the network.

(4) Next, the second electrode 103 is formed on the ferroelectric film 101. The second electrode 103 can be formed by, for example, a sputtering method or a vacuum deposition method. As the upper electrode, it is preferable to use a material mainly made of Pt. The second electrode 103 is not limited to Pt, and Ir, IrO _x , SrRuO ₃ , Nb—SrTiO ₃ , La—SrTiO ₃ , Nb— (LaSr) CoO ₃ , LaNiO ₃ , PbBaO _3, etc. These known electrode materials can also be used.

  (5) Next, post-annealing can be performed in an oxygen atmosphere using RTA or the like, if necessary. As a result, a good interface between the second electrode 103 and the ferroelectric film 101 can be formed, and the crystallinity of the ferroelectric film 101 can be improved.

  Through the above steps, the ferroelectric film 101 and the ferroelectric capacitor 100 according to the present embodiment can be manufactured.

  According to the ferroelectric capacitor 100 of the present embodiment, the crystallization temperature can be lowered and the squareness of hysteresis can be improved. Further, the improvement in the squareness of hysteresis by the ferroelectric capacitor 100 is effective in the stability of disturbance, which is important for driving a simple matrix ferroelectric memory device.

3. Ferroelectric Memory FIGS. 4A and 4B are diagrams showing the configuration of a simple matrix ferroelectric memory device 300 in the embodiment of the present invention. 4A is a plan view thereof, and FIG. 4B is a cross-sectional view taken along the line AA of FIG. 4A. As shown in FIGS. 4A and 4B, the ferroelectric memory device 300 has a predetermined number of word lines 301 to 303 arranged on the substrate 308 and a predetermined number of the word lines. Bit lines 304 to 306. The ferroelectric film 307 described in the above embodiment is inserted between the word lines 301 to 303 and the bit lines 304 to 306, and strong in the intersection region between the word lines 301 to 303 and the bit lines 304 to 306. A dielectric capacitor is formed.

  In the ferroelectric memory device 300 in which memory cells configured by this simple matrix are arranged, writing to and reading from the ferroelectric capacitors formed in the intersecting regions of the word lines 301 to 303 and the bit lines 304 to 306 are as follows: This is performed by a peripheral drive circuit, a read amplifier circuit (not shown) or the like (referred to as “peripheral circuit”). This peripheral circuit may be formed by a MOS transistor on a substrate different from the memory cell array and connected to the word lines 301 to 303 and the bit lines 304 to 306, or a single crystal silicon substrate may be used as the substrate 308. By using the peripheral circuit, it is possible to integrate the peripheral circuit on the same substrate as the memory cell array.

  FIG. 5 is a cross-sectional view showing an example of a ferroelectric memory device 400 in which the memory cell array is integrated with the peripheral circuit on the same substrate in the present embodiment.

  In FIG. 5, a MOS transistor 402 is formed on a single crystal silicon substrate 401, and this transistor formation region becomes a peripheral circuit portion. The MOS transistor 402 includes a single crystal silicon substrate 401, source / drain regions 405, a gate insulating film 403, and a gate electrode 404. The ferroelectric memory device 400 includes an element isolation oxide film 406, a first interlayer insulating film 407, a first wiring layer 408, and a second interlayer insulating film 409.

  The ferroelectric memory device 400 includes a memory cell array including ferroelectric capacitors 420. The ferroelectric capacitor 420 includes a lower electrode (first electrode or second electrode) 410 serving as a word line or a bit line, From a ferroelectric film 411 including a ferroelectric phase and a paraelectric phase, and an upper electrode (second electrode or first electrode) 412 formed on the ferroelectric film 411 and serving as a bit line or a word line Composed.

  Further, the ferroelectric memory device 400 includes a third interlayer insulating film 413 on the ferroelectric capacitor 420, and the memory cell array and the peripheral circuit portion are connected by the second wiring layer 414. In the ferroelectric memory device 400, a protective film 415 is formed on the third interlayer insulating film 413 and the second wiring layer 414.

  According to the ferroelectric memory device 400 having the above configuration, the memory cell array and the peripheral circuit portion can be integrated on the same substrate. The ferroelectric memory device 400 shown in FIG. 5 has a configuration in which a memory cell array is formed on the peripheral circuit portion. Of course, the memory cell array is not arranged on the peripheral circuit portion, and the memory cell array It is good also as a structure which is in contact with the circuit part planarly.

  Since the ferroelectric capacitor 420 used in the present embodiment is composed of the ferroelectric film according to the above-described embodiment, the squareness of hysteresis is very good and it has a stable disturb characteristic. Furthermore, the ferroelectric capacitor 420 has less damage to peripheral circuits and other elements due to lower process temperature, and less process damage (especially hydrogen reduction), thereby suppressing deterioration of hysteresis due to damage. Can do. Therefore, by using the ferroelectric capacitor 420, the simple matrix ferroelectric memory device 300 can be put into practical use.

  FIG. 6A shows a structural diagram of a 1T1C type ferroelectric memory device 500 as a modification. FIG. 6B is an equivalent circuit diagram of the ferroelectric memory device 500.

  As shown in FIG. 6A, the ferroelectric memory device 500 includes a capacitor 504 (1C) comprising a lower electrode 501, an upper electrode 502 connected to a plate line, and the ferroelectric film 503 of the above-described embodiment. ), And a memory element having a structure similar to that of a DRAM including a switching transistor element 507 (1T) having a gate electrode 506 connected to the data line 505 and one of the source / drain electrodes connected to the word line. . The 1T1C type memory can perform writing and reading at a high speed of 100 ns or less, and the written data is nonvolatile. Therefore, it is promising for replacement of the SRAM.

  As mentioned above, although an example of embodiment of this invention was described, this invention is not limited to these, Various aspects can be taken within the range of the summary.

4). Experimental Examples Hereinafter, experimental examples of the present invention will be described.

  The ferroelectric film according to the present embodiment was performed using the following raw material solution.

  Bismuth octylate and niobium octylate in a molar ratio of (bismuth octylate) :( niobium octylate) = 1: 1 in a solvent such as n-butanol together with Si element at a ratio of 1.5 mol% A mixed solution was made.

  Next, the said solution and dimethyl succinate were mixed and the raw material solution was produced. Further, dimethyl succinate was mixed at a ratio of 0.5 mol / l with respect to each raw material solution metal element concentration of 1 mol / l. Thereafter, each raw material solution was sealed and maintained at 90 ° C. for 30 minutes, and then cooled to room temperature to sufficiently promote esterification.

  A sample was prepared by the method shown in FIG. 7 using the prepared solution.

  That is, a lower electrode made of platinum is formed by a sputtering method, a raw material solution is applied to a platinum substrate by a spin coating method, and dried at 150 to 180 ° C. (150 ° C.) using a hot plate to remove alcohol. . Then, degreasing heat treatment was performed at 300 to 350 ° C. (300 ° C.) using a hot plate. Then, the said application | coating process, the drying process, and the degreasing heat processing were performed in multiple times (all 3 times) as needed, and the coating film of the desired film thickness was obtained. Further, a ferroelectric film sample having a film thickness of 150 nm was obtained by crystallization annealing (firing). Firing for crystallization was performed at 650 to 700 ° C. (650 ° C.) using rapid thermal annealing (RTA) in an oxygen atmosphere. Further, an upper electrode made of platinum is formed by a sputtering method, and recovery annealing is performed at 650 to 700 ° C. (650 ° C.) using RTA, whereby a ferroelectric capacitor sample (hereinafter referred to as “capacitor”). Also called “sample”).

  The following characteristics were investigated using this sample.

(A) The crystallinity of the sample ferroelectric film was examined by X-ray diffraction. FIG. 8 is a diagram showing the crystallinity of a sample ferroelectric film. According to FIG. 8, (141) and (211) peaks derived from BiNbO ₄ were observed, and it was confirmed that crystals having a bismuth layered perovskite structure were formed.

  (B) FIG. 9 shows the hysteresis obtained for the capacitor sample. From FIG. 9, it was confirmed that all the capacitor samples have good hysteresis characteristics.

Sectional drawing which shows the ferroelectric capacitor concerning embodiment. Explanatory drawing of Bi layered perovskite crystal structure. The figure which shows the niobium octylate used in this Embodiment. 1A and 1B are a plan view and a cross-sectional view schematically showing a simple matrix ferroelectric memory device in an embodiment. 1 is a cross-sectional view showing an example of a ferroelectric memory device in which a memory cell array is integrated on a same substrate together with peripheral circuits in an embodiment. Sectional drawing which shows typically the 1T1C type ferroelectric memory in the modification of embodiment, and its equivalent circuit schematic. The figure which shows the formation method of the sample of the Example concerning this Embodiment. The figure which shows the crystallinity of the ferroelectric film of the sample in an Example. The figure which shows the hysteresis characteristic of the sample in an Example.

Explanation of symbols

10 Substrate, 100 Ferroelectric capacitor, 101 Ferroelectric film, 102 First electrode, 103 Second electrode, 300 Ferroelectric memory device, 301, 302, 303 Word line, 304, 305, 306 Bit line, 307 Strong Dielectric film, 308 substrate, 400 ferroelectric memory device, 401 single crystal silicon substrate, 402 MOS transistor, 403 gate insulating film, 404 gate electrode, 405 source / drain region, 406 oxide film for element isolation, 407 first Interlayer insulating film, 408 first wiring layer, 409 second interlayer insulating film, 410 lower electrode, 411 ferroelectric film, 412 upper electrode, 413 third interlayer insulating film, 414 second wiring layer, 415 protection Film, 420 ferroelectric capacitor, 500 ferroelectric memory device, 501 bottom electrode, 502 on Electrode, 503 ferroelectric film, 504 a capacitor, 505 data lines, 506 a gate electrode, 507 a transistor element

Claims (11)

A ferroelectric film made of BiNbO ₄ . In claim 1,
The BiNbO ₄ is a ferroelectric film having a Bi layered perovskite structure. In claim 1 or 2,
Further, a ferroelectric film containing Si or Si and Ge. (A) a step of mixing a polycarboxylate containing a niobium element, a polycarboxylate containing a bismuth element, a polycarboxylic acid or a polycarboxylic acid ester, and an organic solvent;
(B) forming a ferroelectric film made of BiNbO ₄ by applying a heat treatment after applying the mixed solution on the substrate, and then manufacturing the ferroelectric film. (A) A sol-gel raw material containing a hydrolysis / condensation product of a metal alkoxide containing a niobium element, a sol-gel raw material containing a hydrolysis / condensation product of a metal alkoxide containing a bismuth element, a polycarboxylic acid or a polycarboxylic acid ester, and an organic By mixing with a solvent, the polycarboxylic acid derived from the polycarboxylic acid or the polycarboxylic acid ester is subjected to an esterification reaction between the metal alkoxide containing the niobium element and the metal alkoxide containing the bismuth element to produce a ferroelectric. Producing a body precursor composition;
(B) a step of forming a ferroelectric film made of BiNbO ₄ by applying the precursor composition onto a substrate and then performing a heat treatment;
A method for manufacturing a ferroelectric film, comprising: In claim 4 or 5,
The method for producing a ferroelectric film, wherein the organic solvent is alcohol. In any of claims 4 to 6,
In the step (a), a ferroelectric film manufacturing method in which Si or a sol-gel raw material containing Si and Ge is further mixed.   A ferroelectric raw material solution containing a polycarboxylate containing a niobium element, a polycarboxylate containing a bismuth element, a polycarboxylic acid or a polycarboxylic acid ester, and an organic solvent.   A sol-gel raw material containing a hydrolysis / condensation product of a metal alkoxide containing a niobium element, a sol-gel raw material containing a hydrolysis / condensation product of a metal alkoxide containing a bismuth element, a polycarboxylic acid or a polycarboxylic acid ester, an organic solvent, A ferroelectric raw material solution containing   A ferroelectric capacitor comprising the ferroelectric film according to claim 1.   A ferroelectric memory comprising the ferroelectric capacitor according to claim 10.

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