Method for producing a liquid composition for forming a BCTZ film, and a method for producing a BCTZ film

Abstract

To provide a liquid composition for forming a BCTZ film, which can control the crystal particle size and form a BCTZ film with stable properties, a method for producing the liquid composition for forming a BCTZ film, and a BCTZ film, and a method for producing the BCTZ film.SOLUTION: A liquid composition for forming a BCTZ film is provided, in which barium carboxylate, calcium carboxylate, a titanium alkoxide and a zirconium alkoxide are mixed in an organic solvent in a molar ratio of Ba:Ca:Ti:Zr=(1-X):X:(1-Y):Y (0.03≤X≤0.20, 0.05≤Y≤0.25) and a stabilizer is added. The barium carboxylate and calcium carboxylate are metal salts of carboxylic acids represented by the general formula CnH2n+1COOH (5≤n≤7). The organic solvent is a mixed solvent containing a carboxylic acid and an acetate.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention is used in forming a BCTZ film made of a mixed oxide of barium, calcium, titanium, and zirconium, which is used in thin film capacitors and capacitors. B Method for producing a CTZ film-forming liquid composition, and BCTZ film It is related to. [Background technology]

[0002] For example, (Ba 1-X Ca X )(Ti 1-Y Zr Y A BCTZ film made of a mixed oxide of barium, calcium, titanium, and zirconium, such as SiO3, has a high dielectric constant and is therefore used as a dielectric film for forming multilayer ceramic capacitors, etc., as shown in Patent Documents 1 to 5, for example. The above-mentioned BCTZ film is formed by sintering BCTZ powder, for example, in Patent Documents 1 to 5. A method of forming a BCTZ film by sputtering using a sputtering target has also been proposed.

[0003] Recently, there has been a demand for thinner and larger capacitance electronic components such as multilayer ceramic capacitors, and this has led to demand for thinner and larger-area BCTZ films. However, when a BCTZ film is formed by sintering BCTZ powder, it is difficult to make the BCTZ film thin because the particle size of the powder is relatively large. Furthermore, when BCTZ films are formed by sputtering using a sputtering target, it is difficult to form uniform, large-area BCTZ films, and there is a risk of many oxygen defects occurring in the formed BCTZ films.

[0004] Therefore, as a method for making the BCTZ film thinner and larger in area, it is conceivable to apply a sol-gel method, as disclosed in Patent Documents 6 to 8, for example. In the sol-gel method, a BCTZ film is formed by applying a sol-gel liquid to a predetermined thickness and then baking it, which makes it possible to form a thin, large-area BCTZ film relatively stably. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-022890 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-173473 [Patent Document 3] Republished WO2013 / 022064 [Patent Document 4] Japanese Patent Application Laid-Open No. 2016-017028 [Patent Document 5] Japanese Patent Application Laid-Open No. 2016-213297 [Patent Document 6] Japanese Patent Application Publication No. 2019-220571 [Patent Document 7] Japanese Patent Application Publication No. 2019-220572 [Patent Document 8] Japanese Patent Application Publication No. 2019-220573 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the BCTZ films described in Patent Documents 6 to 8 have an oriented layered structure, and the manufacturing method is complicated, making it impossible to stably form BCTZ films with uniform properties. In particular, there is a risk that the properties of large-area BCTZ films will vary greatly. Furthermore, in the BCTZ films described in Patent Documents 6 to 8, the crystal grain size is not controlled, and therefore the leakage current cannot be suppressed to a low level, resulting in insufficient insulation resistance and reduced tunability characteristics, and there is a risk that stable characteristics as a dielectric film cannot be obtained.

[0007] The present invention has been made in view of the above-mentioned circumstances, and provides a method for controlling the crystal grain size and forming a BCTZ film with stable characteristics. B Method for producing a CTZ film-forming liquid composition, and BCTZ film The purpose is to provide the following. [Means for solving the problem]

[0008] In order to solve the above problems, the present inventors have conducted extensive research and have found that a BCTZ film-forming liquid composition contains barium carboxylate and calcium carboxylate, and the barium carboxylate and calcium carboxylate are represented by the general formula C n H 2n+1 By adjusting the n (number of carbon atoms) in the general formula of the carboxylic acid, which is a metal salt of a carboxylic acid represented by COOH, and adjusting the chain length of the carboxylic acid, the decomposition temperature can be adjusted. Here, it was discovered that by heating the BCTZ film-forming liquid composition in two stages, a first heating step and a second heating step, it is possible to adjust nucleation in the first heating step and nucleus growth in the second heating step, and thus control the crystal grain size of the formed BCTZ film.

[0009] The present invention has been made based on the above-mentioned findings, and the BCTZ film-forming liquid composition of the present invention is a BCTZ film-forming liquid composition used when forming a BCTZ film composed of a mixed oxide of barium, calcium, titanium, and zirconium, wherein barium carboxylate, calcium carboxylate, titanium alkoxide, and zirconium alkoxide are mixed in an organic solvent so as to satisfy a molar ratio of Ba:Ca:Ti:Zr=(1-X):X:(1-Y):Y (where 0.03≦X≦0.20, 0.05≦Y≦0.25), and a stabilizer is added, and the barium carboxylate and the calcium carboxylate are compounds represented by the general formula C n H 2n+1 The metal salt is a carboxylic acid represented by COOH (where 5≦n≦7), and the organic solvent is a mixed solvent containing a carboxylic acid and an acetic acid ester.

[0010] According to this BCTZ film-forming liquid composition, the molar ratio is Ba:Ca:Ti:Zr=(1-X):X:(1-Y):Y (where 0.03≦X≦0.20, 0.05≦Y≦0.25), making it possible to form a BCTZ film with excellent dielectric properties. The barium carboxylate and the calcium carboxylate are represented by the general formula C n H 2n+1 It is a metal salt of a carboxylic acid represented by COOH, and because n (the number of carbon atoms) in the general formula of the carboxylic acid is 5 or more, the crystal grain size of the BCTZ film does not become too small, and deterioration of the tunability characteristics of the BCTZ film can be suppressed. On the other hand, because n (the number of carbon atoms) in the general formula of the carboxylic acid is 7 or less, the crystal grain size of the BCTZ film does not become too large, and the leakage current of the BCTZ film can be kept low, ensuring insulation resistance. Furthermore, since the organic solvent is a mixed solvent containing a carboxylic acid and an acetic acid ester, it is possible to improve long-term storage stability.

[0011] In the BCTZ film-forming liquid composition of the present invention, the carboxylic acid contained in the organic solvent is preferably the same as the carboxylic acid that forms the barium carboxylate and the calcium carboxylate. In this case, since the carboxylic acid contained in the organic solvent is the same as the carboxylic acid forming the barium carboxylate and the calcium carboxylate, it is possible to further improve long-term storage stability.

[0012] The method for producing a BCTZ film-forming liquid composition of the present invention is the same as the method for producing a BCTZ film-forming liquid composition described above, and is characterized by comprising: a first mixing step of mixing a barium compound, a calcium compound, and a carboxylic acid in an amount of 3 to 8 times the total number of moles of Ba and Ca; a first reflux step of refluxing the first mixture obtained in the first mixing step to prepare an organic barium-calcium compound; a second mixing step of mixing the organic barium-calcium compound, a titanium alkoxide, a zirconium alkoxide, and a stabilizer in an amount of 0.5 to 4.0 times the total number of moles of Ti and Zr; and a second reflux step of mixing the second mixture obtained in the second mixing step with an acetic acid ester and refluxing the mixture.

[0013] According to this method for producing a BCTZ film-forming liquid composition, an organic barium-calcium compound is formed by mixing a barium compound, a calcium compound, and a carboxylic acid in an amount that is 3 to 8 times the total molar amount of Ba and Ca, and refluxing the mixture. This allows the barium compound and calcium compound to react sufficiently with the carboxylic acid. Furthermore, the organic barium calcium compound, titanium alkoxide, zirconium alkoxide, and a stabilizer in an amount of 0.5 to 3.0 times the total number of moles of Ti and Zr are mixed together, and this mixture is mixed with acetic acid ester and refluxed, thereby making it possible to produce the above-mentioned BCTZ film-forming liquid composition.

[0014] Here, the method for producing a BCTZ film-forming liquid composition of the present invention preferably includes a distillation step of performing reduced pressure distillation after the first reflux step.

[0015] The BCTZ film of the present invention is a BCTZ film composed of a mixed oxide of barium, calcium, titanium, and zirconium, and is characterized in that the crystal grain size in a cross section along the thickness direction is in the range of 30 nm to 50 nm.

[0016] In the BCTZ film with this configuration, the crystal grain size in the cross section along the thickness direction is 30 nm or more, which can suppress the deterioration of tunability characteristics, while the crystal grain size in the cross section along the thickness direction is 50 nm or less, which can suppress leakage current and ensure insulation resistance.

[0017] In the BCTZ film of the present invention, the crystal orientation is preferably randomly oriented. In this case, the crystal orientation is random and not oriented in a specific direction, resulting in stable characteristics in the thickness direction and in the plane direction.

[0018] The method for producing a BCTZ film of the present invention is a method for producing a BCTZ film composed of a mixed oxide of barium, calcium, titanium, and zirconium, and is characterized by comprising: a coating step of coating the above-mentioned BCTZ film-forming liquid composition; a first heating step of heating the coated BCTZ film-forming liquid composition at a temperature in the range of 200°C to 500°C to form a BCTZ gel film; and a second heating step of repeatedly performing the coating step and the first heating step to obtain a BCTZ gel film of a predetermined thickness, and then heating the BCTZ gel film at a temperature in the range of 600°C to 800°C.

[0019] According to this method for producing a BCTZ film, sufficient crystal nuclei can be generated in the first heating step, in which the applied BCTZ film-forming liquid composition is heated at a temperature in the range of 200°C to 500°C to form a BCTZ gel film. As a result, in the subsequent second heating step, in which the BCTZ gel film is heated at a temperature in the range of 600°C to 800°C, nucleus growth is suppressed, making it possible to adjust the crystal grain size of the BCTZ film. [Effects of the Invention]

[0020] According to the present invention, it is possible to control the crystal grain size and form a BCTZ film with stable characteristics. B Method for producing a CTZ film-forming liquid composition, and BCTZ filmcan be provided. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a flow diagram showing a method for producing a BCTZ film-forming liquid composition according to one embodiment of the present invention. [Figure 2] FIG. 1 is a flow diagram showing a method for producing a BCTZ film according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] The BCTZ film-forming liquid composition, the method for producing the BCTZ film-forming liquid composition, the BCTZ film, and the method for producing the BCTZ film, which are embodiments of the present invention, will be described below. The BCTZ film-forming liquid composition of this embodiment is used, for example, as a dielectric film for a multilayer ceramic capacitor (Ba 1-X Ca X )(Ti 1-Y Zr Y It is used to form a BCTZ film made of a mixed oxide of barium, calcium, titanium, and zirconium, such as SiO3.

[0023] The BCTZ film-forming liquid composition of this embodiment is prepared by mixing barium carboxylate, calcium carboxylate, titanium alkoxide, and zirconium alkoxide in an organic solvent in a molar ratio of Ba:Ca:Ti:Zr=(1-X):X:(1-Y):Y (where 0.03≦X≦0.20, 0.05≦Y≦0.25), and further adding a stabilizer.

[0024] And barium carboxylate and calcium carboxylate are represented by the general formula C n H 2n+1 It is considered to be a metal salt of a carboxylic acid represented by COOH (where 5≦n≦7). The organic solvent is a mixed solvent containing a carboxylic acid and an acetic acid ester. As the carboxylic acid, 2-ethylhexanoic acid, ethylbutyric acid, 2-ethylpentanoic acid, etc. can be used. In this embodiment, it is preferable that the carboxylic acid contained in the organic solvent and the carboxylic acid constituting the barium carboxylate and calcium carboxylate are the same carboxylic acid.

[0025] As the acetate ester, for example, isoamyl acetate, amyl acetate, ethyl acetate, etc. can be used. In this embodiment, in the organic solvent, the ratio A / B of the number of moles A of carboxylic acid to the number of moles B of acetate ester is preferably within the range of 0.05 or more and 0.30 or less.

[0026] As the stabilizer, for example, β-ketoesters such as acetylacetone, propylene glycol, etc. can be used. Furthermore, the ratio C / E of the total number of moles C of barium carboxylate, calcium carboxylate, titanium alkoxide and zirconium alkoxide to the total number of moles E of the stabilizer is preferably within the range of 0.5 or more and 4 or less.

[0027] Next, the method for producing the BCTZ film-forming liquid composition of this embodiment will be described with reference to the flow diagram of FIG.

[0028] As shown in FIG. 1, the method for producing a BCTZ film-forming liquid composition according to this embodiment includes a first mixing step S01 in which a barium compound, a calcium compound, and a carboxylic acid in an amount between 3 and 8 times the total number of moles of Ba and Ca are mixed; a first reflux step S02 in which the first mixture obtained in the first mixing step S01 is refluxed; a distillation step S03 in which, after the first reflux step S02, the organic barium calcium compound is prepared by vacuum distillation; a second mixing step S04 in which the organic barium calcium compound, a titanium alkoxide, a zirconium alkoxide, and a stabilizer in an amount between 0.5 and 3.0 times the total number of moles of Ti and Zr are mixed; and a second reflux step S05 in which the second mixture obtained in the second mixing step S04 is mixed with an acetic ester and refluxed.

[0029] Here, examples of the barium compound that can be used include barium carbonate and barium hydroxide. As the calcium compound, for example, calcium carbonate, calcium hydroxide, etc. can be used. The conditions for the first reflux step S02 are preferably an inert gas atmosphere such as nitrogen gas or argon gas, a holding temperature in the range of 130°C to 170°C, and a holding time in the range of 0.5 hours to 5.0 hours.

[0030] The conditions for the reduced pressure distillation in the distillation step S03 are an absolute pressure in the range of 0.01 MPa to 0.05 MPa, a temperature in the range of 130° C. to 170° C., and a holding time in the range of 30 minutes to 5 hours. Note that the distillation step S03 may be omitted.

[0031] Examples of titanium alkoxides that can be used include titanium tetraisopropoxide, titanium butoxide, and titanium ethoxide. As the zirconium alkoxide, for example, zirconium isopropoxide, zirconium butoxide, zirconium ethoxide, etc. can be used. The conditions for the second reflux step S05 are preferably an inert gas atmosphere such as nitrogen gas or argon gas, a holding temperature in the range of 130°C to 170°C, and a holding time in the range of 1.0 hour to 5.0 hours.

[0032] By the steps described above, it is possible to produce the BCTZ film-forming liquid composition of this embodiment.

[0033] Next, the BCTZ film of this embodiment will be described. The BCTZ film of this embodiment is formed using the BCTZ film-forming composition of this embodiment described above, and (Ba 1-X Ca X )(Ti 1-Y Zr Y )O3, etc., is composed of mixed oxides of barium, calcium, titanium, and zirconium. The BCTZ film preferably has a composition of Ba:Ca:Ti:Zr=(1-X):X:(1-Y):Y (where 0.03≦X≦0.20, 0.05≦Y≦0.25).

[0034] In the BCTZ film of this embodiment, the crystal grain size in the cross section along the thickness direction is set to be within the range of 30 nm to 50 nm. Here, the crystal grain size in a cross section of the BCTZ film along the thickness direction can be measured as follows. In this embodiment, in cross-sectional observation of a BCTZ film using FE-SEM, the particle diameters (major diameters) of three particles randomly selected when observing crystals in a cross-section of one field of view are measured.

[0035] In addition, in the BCTZ film of this embodiment, it is preferable that the crystal orientation is randomly oriented, that is, it is preferable that the crystal orientation is not oriented in a specific preferred orientation. Whether the deposited BCTZ film has a random orientation can be measured using the following method. Measurements are carried out using a focusing method with an XRD device. In the range of 2θ / θ = 10 to 90°, when the (110) peak intensity is taken as 100, the PDF (Powder Diffraction Data) indicates that the (100) peak intensity is 10 to 30 and the (111) peak intensity is 15 to 40, which is considered to be "random orientation."

[0036] Next, the method for producing a BCTZ film according to this embodiment will be described with reference to the flow chart of FIG.

[0037] As shown in FIG. 2, the method for producing a BCTZ film according to this embodiment includes a coating step S11 in which the BCTZ film-forming liquid composition according to this embodiment is applied; a first heating step S12 in which the applied BCTZ film-forming liquid composition is heated within a temperature range of 200°C to 500°C to form a BCTZ gel film; and a second heating step S13 in which the coating step S11 and the first heating step S12 are repeated to form a BCTZ gel film of a predetermined thickness, and then the BCTZ gel film is heated within a temperature range of 600°C to 800°C.

[0038] In the coating step S11, the BCTZ film-forming liquid composition of this embodiment is coated onto a substrate, for example, a Si wafer having an adhesion layer made of Ti or TiO formed thereon and an electrode made of Pt or Au formed thereon. Spin coating, dip coating, or the like is preferably used as the coating method.

[0039] In the first heating step S12, the applied BCTZ film-forming composition is heated to a temperature range of 200° C. to 500° C. using a heating device such as a hot plate to form a BCTZ gel film. At this time, crystal nuclei are generated in the formed BCTZ gel film. The lower limit of the heating temperature in the first heating step S12 is preferably 100° C. or higher, and more preferably 150° C. or higher. The upper limit of the heating temperature in the first heating step S12 is preferably 400° C. or lower, and more preferably 350° C. or lower.

[0040] In the second heating step S13, the BCTZ gel film is heated and fired in a temperature range of 600° C. to 800° C. using a firing furnace such as a muffle furnace or an RTA. During firing, the crystal nuclei generated in the first heating step grow. The lower limit of the heating temperature in the second heating step S13 is preferably 650° C. or higher, and the upper limit of the heating temperature in the second heating step S13 is preferably 800° C. or lower.

[0041] In the BCTZ film-forming liquid composition of this embodiment, the barium carboxylate and the calcium carboxylate are represented by the general formula C n H 2n+1 The metal salt of carboxylic acid is represented by COOH, and n (the number of carbon atoms) in the general formula of the carboxylic acid is set to a value within the range of 5 to 7. This adjusts the decomposition temperature, allowing sufficient crystal nuclei to be generated in the first heating step S12 and suppressing nucleus growth in the second heating step S13. This prevents the crystal grains from becoming coarse. Therefore, it is possible to form a BCTZ film in which the crystal grain size in the cross section along the thickness direction is controlled to be within the range of 30 nm to 50 nm.

[0042] According to the BCTZ film-forming liquid composition of this embodiment having the above-described configuration, barium carboxylate and calcium carboxylate are represented by the general formula C n H 2n+1 It is a metal salt of a carboxylic acid represented by COOH, and because n (the number of carbon atoms) in the general formula of the carboxylic acid is 5 or more, the crystal grain size of the BCTZ film does not become too small, and deterioration of the tunability characteristics of the BCTZ film can be suppressed. On the other hand, because n (the number of carbon atoms) in the general formula of the carboxylic acid is 7 or less, the crystal grain size of the BCTZ film does not become too large, and the leakage current of the BCTZ film can be kept low, ensuring insulation resistance.

[0043] Furthermore, the molar ratio of Ba:Ca:Ti:Zr is (1-X):X:(1-Y):Y (where 0.03≦X≦0.20, 0.05≦Y≦0.25), making it possible to form a BCTZ film with excellent dielectric properties. Furthermore, since the organic solvent is a mixed solvent containing a carboxylic acid and an acetic acid ester, it is possible to improve the long-term storage stability.

[0044] In the BCTZ film-forming liquid composition of this embodiment, if the carboxylic acid contained in the organic solvent and the carboxylic acid that forms the barium carboxylate and calcium carboxylate are the same carboxylic acid, it is possible to further improve the long-term storage stability.

[0045] The method for producing a BCTZ film-forming liquid composition of this embodiment includes a first mixing step S01 in which a barium compound, a calcium compound, and a carboxylic acid in an amount between three and eight times the total moles of Ba and Ca are mixed together, a first reflux step S02 in which the first mixture obtained in the first mixing step S01 is refluxed, and a distillation step S03 in which an organic barium-calcium compound is prepared by vacuum distillation after the first reflux step S02, thereby allowing the barium compound and calcium compound to react sufficiently with the carboxylic acid.

[0046] The method also includes a second mixing step S04 in which an organic barium calcium compound, a titanium alkoxide, a zirconium alkoxide, and a stabilizer in an amount of 0.5 to 3.0 times the total number of moles of Ti and Zr are mixed, and a second reflux step S05 in which the second mixture obtained in the second mixing step S04 is mixed with an acetic acid ester and refluxed, thereby making it possible to produce the above-mentioned BCTZ film-forming liquid composition.

[0047] In the BCTZ film of this embodiment, the crystal grain size in the cross section along the thickness direction is 30 nm or more, which can suppress the deterioration of the tunability characteristics. On the other hand, the crystal grain size in the cross section along the thickness direction is 50 nm or less, which can suppress the leakage current and ensure the dielectric strength. Furthermore, in the BCTZ film of this embodiment, when the crystal orientation is randomly oriented, the crystal orientation is not oriented in a specific direction, and therefore the characteristics in the thickness direction and in the plane direction are stable.

[0048] According to the method for producing a BCTZ film of this embodiment, in the first heating step S02, in which the applied BCTZ film-forming liquid composition is heated in a temperature range of 200°C to 500°C to form a BCTZ gel film, sufficient crystal nuclei can be generated. As a result, in the second heating step S03, in which the BCTZ gel film is heated in a temperature range of 600°C to 800°C, nucleus growth is suppressed, making it possible to adjust the crystal grain size of the BCTZ film.

[0049] Although the embodiment of the present invention has been described above, the present invention is not limited to this and can be modified as appropriate within the scope of the technical idea of ​​the invention. [Example]

[0050] The results of the evaluation test for evaluating the effects of the present invention will be described below.

[0051] (Example 1 of the present invention) Barium carbonate was used as the barium raw material and calcium carbonate as the calcium raw material so that the BCTZ composition ratio was 94:6:84:16 and the BCTZ oxide equivalent concentration was 4 mass%, and the mixture was refluxed at 150°C for 4 hours together with 2-ethylhexanoic acid in an amount six times the total moles of Ba and Ca. Subsequently, titanium tetraisopropoxide was used as the titanium raw material, zirconium n-butoxide was used as the zirconium raw material, isoamyl acetate was used as the solvent, and acetylacetone in an amount one time the total moles of Zr and Ti was used as a stabilizer, and the mixture was refluxed at 150°C for 1 hour in a nitrogen atmosphere to obtain a BCTZ film-forming liquid composition. The resulting BCTZ film-forming liquid composition was applied dropwise to a Pt / Ti / Si substrate by spin coating, and the coated substrate was pre-baked at 300°C for 5 minutes on a hot plate, and then baked at 700°C for 1 minute (heating rate 10°C / sec) in an RTA to obtain a BCTZ film.

[0052] (Example 2 of the present invention) Barium carbonate was used as the barium raw material and calcium carbonate as the calcium raw material so that the BCTZ composition ratio was 94:6:84:16 and the BCTZ oxide equivalent concentration was 4 mass%, and the mixture was refluxed at 150°C for 4 hours together with 2-ethylbutyric acid in an amount six times the total moles of Ba and Ca. Subsequently, titanium tetraisopropoxide was used as the titanium raw material, zirconium n-butoxide was used as the zirconium raw material, isoamyl acetate was used as the solvent, and acetylacetone in an amount one time the total moles of Zr and Ti was used as a stabilizer, and the mixture was refluxed at 150°C for 1 hour in a nitrogen atmosphere to obtain a BCTZ film-forming liquid composition. The resulting BCTZ film-forming liquid composition was applied dropwise to a Pt / Ti / Si substrate by spin coating, and the coated substrate was pre-baked at 300°C for 5 minutes on a hot plate, and then baked at 700°C for 1 minute (heating rate 10°C / sec) in an RTA to obtain a BCTZ film.

[0053] (Example 3 of the present invention) Barium carbonate was used as the barium raw material and calcium carbonate as the calcium raw material so that the BCTZ composition ratio was 94:6:84:16 and the BCTZ oxide equivalent concentration was 4 mass%, and the mixture was refluxed at 150°C for 4 hours together with 2-ethylbutyric acid in an amount six times the total moles of Ba and Ca. Subsequently, titanium tetraisopropoxide was used as the titanium raw material, zirconium n-butoxide was used as the zirconium raw material, isoamyl acetate was used as the solvent, and acetylacetone in an amount one time the total moles of Zr and Ti was used as a stabilizer, and the mixture was refluxed at 150°C for 1 hour in a nitrogen atmosphere to obtain a BCTZ film-forming liquid composition. The resulting BCTZ film-forming liquid composition was applied dropwise to a Pt / Ti / Si substrate by spin coating, and the coated substrate was pre-baked at 200°C for 5 minutes on a hot plate, and then baked at 800°C for 1 minute (heating rate 10°C / sec) in an RTA to obtain a BCTZ film.

[0054] (Example 4 of the present invention) Barium carbonate was used as the barium raw material and calcium carbonate as the calcium raw material so that the BCTZ composition ratio was 94:6:84:16 and the BCTZ oxide equivalent concentration was 4 mass%, and the mixture was refluxed at 150°C for 4 hours together with 2-ethylbutyric acid in an amount six times the total moles of Ba and Ca. Subsequently, titanium tetraisopropoxide was used as the titanium raw material, zirconium n-butoxide was used as the zirconium raw material, isoamyl acetate was used as the solvent, and acetylacetone in an amount one time the total moles of Zr and Ti was used as a stabilizer, and the mixture was refluxed at 150°C for 1 hour in a nitrogen atmosphere to obtain a BCTZ film-forming liquid composition. The resulting BCTZ film-forming liquid composition was dropped onto a Pt / Ti / Si substrate and spin-coated. The coated substrate was pre-baked at 500°C for 5 minutes on a hot plate, and then baked at 600°C for 1 minute (heating rate 10°C / sec) in an RTA to obtain a BCTZ film.

[0055] (Example 5 of the present invention) Barium carbonate was used as the barium raw material and calcium carbonate as the calcium raw material so that the BCTZ composition ratio was 90:10:80:20 and the BCTZ oxide equivalent concentration was 4 mass%, and the mixture was refluxed at 150°C for 4 hours together with 2-ethylbutyric acid in an amount six times the total moles of Ba and Ca. Subsequently, titanium tetraisopropoxide was used as the titanium raw material, zirconium n-butoxide was used as the zirconium raw material, isoamyl acetate was used as the solvent, and acetylacetone in an amount one time the total moles of Zr and Ti was used as a stabilizer, and the mixture was refluxed at 150°C for 1 hour in a nitrogen atmosphere to obtain a BCTZ film-forming liquid composition. The resulting BCTZ film-forming liquid composition was applied dropwise to a Pt / Ti / Si substrate by spin coating, and the coated substrate was pre-baked at 300°C for 5 minutes on a hot plate, and then baked at 700°C for 1 minute (heating rate 10°C / sec) in an RTA to obtain a BCTZ film.

[0056] (Invention Example 6) to (Invention Example 8) A BCTZ film was obtained in the same manner as in Invention Example 1, except that the conditions were changed as shown in the table.

[0057] (Comparative Example 1) Barium di-1-propoxide, titanium n-propoxide, zirconium n-butoxide, and calcium diethoxide were used as raw materials to achieve a BCTZ composition ratio of 94:6:84:16 and a BCTZ oxide-equivalent concentration of 4 mass%, and 2-methoxyethanol was used as the main solvent, followed by refluxing for 2 hours at 100°C. 2-Ethylhexanoic acid was then added as a stabilizer in an amount twice the molar amount of the barium raw material, and the mixture was refluxed for 2 hours at 100°C to obtain a BCTZ film-forming liquid composition. The resulting BCTZ film-forming liquid composition was dropped onto a Pt / Ti / Si substrate and spin-coated. The coated substrate was pre-baked at 450°C for 5 minutes on a hot plate, and then baked at 1000°C for 1 minute (heating rate 10°C / sec) in an RTA to obtain a BCTZ film.

[0058] (Comparative Example 2) Barium carbonate was used as the barium raw material and calcium carbonate as the calcium raw material so that the BCTZ composition ratio was 94:6:84:16 and the BCTZ oxide equivalent concentration was 4 mass%, and the mixture was refluxed at 150°C for 4 hours together with n-butyric acid in an amount six times the total moles of Ba and Ca. Subsequently, titanium tetraisopropoxide was used as the titanium raw material, zirconium n-butoxide was used as the zirconium raw material, isoamyl acetate was used as the solvent, and acetylacetone in an amount one time the total moles of Zr and Ti was used as a stabilizer, and the mixture was refluxed at 150°C for 1 hour in a nitrogen atmosphere to obtain a BCTZ film-forming liquid composition. The resulting BCTZ film-forming liquid composition was applied dropwise to a Pt / Ti / Si substrate by spin coating, and the coated substrate was pre-baked at 300°C for 5 minutes on a hot plate, and then baked at 700°C for 1 minute (heating rate 10°C / sec) in an RTA to obtain a BCTZ film.

[0059] (Comparative Example 3) Barium carbonate was used as the barium raw material and calcium carbonate as the calcium raw material so that the BCTZ composition ratio was 94:6:84:16 and the BCTZ oxide equivalent concentration was 4 mass%, and the mixture was refluxed at 150°C for 4 hours together with acetic acid in an amount six times the total moles of Ba and Ca. Subsequently, titanium tetraisopropoxide was used as the titanium raw material, zirconium n-butoxide was used as the zirconium raw material, isoamyl acetate was used as the solvent, and acetylacetone in an amount one time the total moles of Zr and Ti was used as a stabilizer, and the mixture was refluxed at 150°C for 1 hour in a nitrogen atmosphere to obtain a BCTZ film-forming liquid composition. The resulting BCTZ film-forming liquid composition was applied dropwise to a Pt / Ti / Si substrate by spin coating, and the coated substrate was pre-baked at 300°C for 5 minutes on a hot plate, and then baked at 700°C for 1 minute (heating rate 10°C / sec) in an RTA to obtain a BCTZ film.

[0060] Comparative Example 4 A BCTZ film was obtained in the same manner as in Invention Example 1, except that the conditions were changed as shown in the table.

[0061] The crystal grain size and degree of X-ray orientation in a cross section along the thickness direction of the obtained BCTZ films of the invention example and comparative example were evaluated as follows.

[0062] (crystal particle size) In the cross-sectional observation of the BCTZ film using FE-SEM, the particle size (longest diameter) of three randomly selected particles was measured when observing the crystals in one cross-section of the field of view. If the average value was within the range of 30 nm to 50 nm, it was marked as "○", and if it was outside that range, it was marked as "×", and these were recorded in the table.

[0063] (X-ray orientation degree) The deposited BCTZ film was measured using a focusing method with an XRD device. In the range of 2θ / θ = 10° to 90°, the PDF (Powder Diffraction Data) was determined to have a "random orientation" when the (100) peak intensity was 10 to 30 and the (111) peak intensity was 15 to 40, where the (110) peak intensity was 100. Cases of "random orientation" were marked with "○" and other cases with "×", and these are listed in Table 2.

[0064] (film thickness) The formed BCTZ film was measured using a spectroscopic ellipsometer (M-2000DI manufactured by JA Woollam Japan).

[0065] [Table 1]

[0066] [Table 2]

[0067] In Comparative Example 1, which did not contain barium carboxylate or calcium carboxylate, the crystal grain size of the formed BCTZ film was outside the range of 30 nm to 50 nm, and the crystals were oriented in a specific direction. In Comparative Example 2, barium carboxylate and calcium carboxylate were prepared according to the general formula C n H 2n+1 It is considered to be a metal salt of a carboxylic acid represented by COOH (n=3), and the crystal grain size of the formed BCTZ film was outside the range of 30 nm to 50 nm. In Comparative Example 3, barium carboxylate and calcium carboxylate were prepared according to the general formula C n H 2n+1 It is considered to be a metal salt of a carboxylic acid represented by COOH (n=1), and the crystal grain size of the formed BCTZ film was outside the range of 30 nm to 50 nm. In Comparative Example 4, barium carboxylate and calcium carboxylate were prepared according to the general formula C n H2n+1 It is considered to be a metal salt of a carboxylic acid represented by COOH (n=9), and the crystal grain size of the formed BCTZ film was outside the range of 30 nm to 50 nm.

[0068] In contrast, barium and calcium carboxylates are compounds of the general formula C n H 2n+1 In Examples 1-5 of the present invention, in which the metal salt of a carboxylic acid represented by COOH (5≦n≦7) was used and the organic solvent was a mixed solvent containing a carboxylic acid and an acetic acid ester, the crystal grain size of the formed BCTZ film was in the range of 30 nm to 50 nm, and further, the crystals were not oriented in a specific direction.

[0069] From the above, it was confirmed that the present invention can provide a BCTZ film-forming liquid composition that can control the crystal grain size and form a BCTZ film with stable properties, a method for manufacturing this BCTZ film-forming liquid composition, a BCTZ film, and a method for manufacturing a BCTZ film.

Claims

1. A method for producing a BCTZ film-forming liquid composition used in forming a BCTZ film composed of a mixed oxide of barium, calcium, titanium, and zirconium, comprising: mixing barium carboxylate, calcium carboxylate, titanium alkoxide, and zirconium alkoxide in an organic solvent in a molar ratio of Ba:Ca:Ti:Zr=(1-X):X:(1-Y):Y (where 0.03≦X≦0.20, 0.05≦Y≦0.25); and adding a stabilizer; the barium carboxylate and the calcium carboxylate are metal salts of carboxylic acid represented by the general formula CnH2n+1COOH (where 5≦n≦7); and the organic solvent is a mixed solvent containing a carboxylic acid and an acetate ester, a first mixing step of mixing a barium compound, a calcium compound, and a carboxylic acid in an amount of 3 to 8 times the total mole number of Ba and Ca; a first refluxing step of refluxing the first mixture obtained in the first mixing step to prepare an organic barium calcium compound; a second mixing step of mixing the organic barium calcium compound, titanium alkoxide, zirconium alkoxide, and a stabilizer in an amount of 0.5 to 4.0 times the total number of moles of Ti and Zr; a second refluxing step of mixing the second mixture obtained in the second mixing step with an acetic acid ester and refluxing the mixture; A method for producing a BCTZ film-forming liquid composition, comprising:

2. 2. The method for producing a BCTZ film-forming liquid composition according to claim 1, further comprising a distillation step of distilling under reduced pressure after the first reflux step.

3. A BCTZ film composed of a mixed oxide of barium, calcium, titanium, and zirconium, A BCTZ film characterized in that the crystal grain diameter in a cross section along the thickness direction is in the range of 30 nm to 50 nm.

4. 4. The BCTZ film according to claim 3, wherein the crystal orientation is random.

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