JP2010187003A - Precursor composition and method of manufacturing piezoelectric element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite oxide laminated body excelling in an insulation property, and a method of manufacturing the same. <P>SOLUTION: This composite oxide laminated body includes: a substrate 20; a first composite oxide layer 24 formed on the substrate 20 and represented by general formula ABO<SB>3</SB>; and a second composite oxide layer 26 formed on the first composite oxide layer 24 and represented by general formula AB<SB>1-x</SB>C<SB>x</SB>O<SB>3</SB>, wherein the element A comprises at least Pb, the element B comprises at least one of Zr, Ti, V, W and Hf, and the element C comprises at least one of Nb and Ta. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a composite oxide laminate using a Pb-based perovskite oxide, a method for producing the composite oxide laminate, and a device using the composite oxide laminate of the present invention.

Pb-based perovskite oxides such as PZT (Pb (Zr, Ti) O ₃ ) have excellent ferroelectric characteristics or piezoelectric characteristics. Therefore, for example, it has attracted attention as a ferroelectric film of a ferroelectric memory (see Patent Document 1) or as a piezoelectric element (see Patent Document 2).

JP 2001-139313 A JP 2001-223404 A

  An object of the present invention is to provide a composite oxide laminate having excellent insulating properties and a method for producing the same.

  Another object of the present invention is to provide a device including the complex oxide laminate according to the present invention.

The composite oxide laminate according to the present invention is
A substrate,
A first composite oxide layer formed above the substrate and represented by the general formula ABO ₃ ;
A second complex oxide layer formed above the first complex oxide layer and represented by the general formula AB _1-x C _x O ₃ ;
A element consists of at least Pb,
B element consists of at least one of Zr, Ti, V, W and Hf,
C element consists of at least one of Nb and Ta.

  According to the composite oxide laminate of the present invention, by having the specific second composite oxide layer above the first composite oxide layer, the occurrence of crystal defects in the first composite oxide layer is prevented, Excellent ferroelectric and piezoelectric properties can be exhibited.

In the composite oxide laminate of the present invention,
The B element is Zr and Ti,
The C element may be Nb.

In the composite oxide laminate of the present invention,
The second complex oxide layer may be composed of a complex oxide containing Nb in a range of 0.1 ≦ x ≦ 0.3.

In the composite oxide laminate of the present invention,
Furthermore, the second complex oxide layer may include at least one of 0.5 mol% or more of Si and Ge.

In the composite oxide laminate of the present invention,
The second complex oxide layer may be smaller in thickness than the first complex oxide layer.

In the composite oxide laminate of the present invention,
The substrate may have an electrode layer.

In the composite oxide laminate of the present invention,
A buffer layer for controlling the crystal orientation of the first composite oxide layer may be provided below the first composite oxide layer.

The method for producing a composite oxide laminate according to the present invention includes:
Forming a first composite oxide layer represented by the general formula ABO ₃ above the substrate;
Forming a second composite oxide layer represented by the general formula AB _1-x C _x O ₃ above the first composite oxide layer,
A element consists of at least Pb,
B element consists of at least one of Zr, Ti, V, W and Hf,
C element consists of at least one of Nb and Ta.

  According to the manufacturing method of the present invention, the specific second complex oxide layer is formed above the first complex oxide layer, thereby preventing the occurrence of crystal defects in the first complex oxide layer, which is excellent. A composite oxide laminate having ferroelectric characteristics and piezoelectric characteristics can be produced.

In the production method of the present invention,
The second composite oxide layer is subjected to heat treatment after applying a precursor composition containing a precursor for forming an insulating composite oxide represented by the general formula AB _1-x C _x O _3. Can be formed.

In the method for producing a composite oxide laminate of the present invention,
The precursor composition may include a precursor containing at least the B element and the C element, and partially having an ester bond.

In the method for producing a composite oxide laminate of the present invention,
The precursor may further include at least one of Si and Ge.

  The device according to the present invention includes the composite oxide laminate according to the present invention.

  The device in the present invention means one including the complex oxide laminate of the present invention, and includes a component having the complex oxide laminate and an electronic apparatus having the component. A specific example of the device will be described later.

Sectional drawing which shows the complex oxide laminated body concerning this embodiment. The figure which shows the change of the Raman vibration mode of A site ion at the time of adding Si in lead titanate in this embodiment. The figure which shows the carboxylic acid containing lead used in this embodiment. The figure which shows the polycarboxylic acid or polycarboxylic acid ester used in this embodiment. The figure which shows the polycarboxylic acid or polycarboxylic acid ester used in this embodiment. The figure which shows the polycarboxylic acid or polycarboxylic acid ester used in this embodiment. The figure which shows the polycarboxylic acid or polycarboxylic acid ester used in this embodiment. The figure which shows the production | generation reaction of the precursor in the precursor composition which concerns on this embodiment. The figure which shows the production | generation reaction of the precursor in the precursor composition which concerns on this embodiment. (A) is a figure which shows the hysteresis of the complex oxide laminated body of Example 1, (B) is a figure which shows the hysteresis of the complex oxide laminated body of the comparative example 1. FIG. The figure which shows the change of the amount of polarization of Example 1 and Comparative Example 1. FIG. (A), (B) is a figure which shows the semiconductor device concerning this embodiment. 1 is a cross-sectional view schematically showing a 1T1C type ferroelectric memory according to an embodiment. FIG. 11 shows an equivalent circuit of the ferroelectric memory shown in FIG. 10. Sectional drawing which shows typically the piezoelectric element which concerns on the application example of this embodiment. FIG. 3 is a schematic configuration diagram of an ink jet recording head according to an application example of the embodiment. FIG. 3 is an exploded perspective view of an ink jet recording head according to an application example of the embodiment. 1 is a schematic configuration diagram of an inkjet printer according to an application example of the present embodiment. Sectional drawing which shows the surface acoustic wave element which concerns on the application example of this embodiment. The perspective view which shows the frequency filter which concerns on the application example of this embodiment. The perspective view which shows the oscillator which concerns on the application example of this embodiment.

  Hereinafter, embodiments of the present invention will be described in detail.

1. Composite Oxide Stack FIG. 1 is a cross-sectional view schematically showing a composite oxide stack 100 according to the present embodiment.

The composite oxide laminate 100 according to this embodiment includes a substrate 20, a first composite oxide layer 24 formed above the substrate 20, represented by a general formula ABO ₃ , and a first composite oxide layer 24. And a second composite oxide layer 26 formed above and represented by the general formula AB _1-x C _x O ₃ . Here, the element A can be composed of at least Pb, the element B can be composed of at least one of Zr, Ti, V, W, and Hf, and the element C can be composed of at least one of Nb and Ta.

  As the substrate 20, various types can be used depending on the type and application of the complex oxide laminate 100 of the present embodiment. For example, when the composite oxide stack 100 is used for a capacitor such as a ferroelectric memory, the substrate 20 having an electrode layer (lower electrode) can be used. When the composite oxide laminate 100 is used for a surface acoustic wave device, a sapphire substrate or the like can be used as the substrate 20.

In the example shown in FIG. 1, the composite oxide stack 100 constitutes a capacitor and has an electrode layer. That is, in this example, the substrate 20 has the first electrode layer 22 and the second electrode layer 23 formed in order on the base material 21. The first electrode layer 22 is made of, for example, a platinum group metal such as platinum. The second electrode layer 23 is composed of a conductive oxide layer having a perovskite structure such as LaNiO ₃ . The second electrode layer 23 can function as a buffer layer for controlling the crystal orientation of the first composite oxide layer 24. By having the second electrode layer 23 functioning as such a buffer layer, the first complex oxide layer 24 can be epitaxially grown on the second electrode layer 23. In this case, the first complex oxide layer 24 grows with the same plane orientation as that of the second electrode layer 23.

  The film thicknesses of the first composite oxide layer 24 and the second composite oxide layer 26 are appropriately selected depending on the device to which this embodiment is applied. The first composite oxide layer 24 mainly constitutes a ferroelectric film or a piezoelectric film of the device. The second composite oxide layer 26 has a function of suppressing characteristic deterioration of the first composite oxide layer 24. Therefore, the film thickness of the second composite oxide layer 26 is set so as to cover at least the surface of the first composite oxide layer 24 and absorb the foreign phase formed on the outermost surface of the first composite oxide layer 24. The For example, in the example of the capacitor shown in FIG. 1, the film thickness of the second composite oxide layer 26 can be set to 100 to 1000 nm.

In the present embodiment, in the first composite oxide layer 24 represented by the general formula ABO ₃ , the A element can be at least Pb, the B element can be Zr and Ti, and the C element can be Nb. In the second composite oxide layer 26 represented by the general formula AB _1-x C _x O ₃ , the A element is at least Pb, the B element is Zr and Ti, and the C element is Nb. it can. In this case, Nb can be included in the range of 0.1 ≦ x ≦ 0.3. That is, in the present embodiment, the second composite oxide layer 26 can be Pb (Zr, Ti, Nb) O ₃ (PZTN) in which Nb is doped at the Ti site.

Nb is substantially the same size as Ti (the ionic radius is the same, and the atomic radius is the same), is twice as heavy, and it is difficult for atoms to escape from the lattice by collisions between atoms due to lattice vibration. Further, the valence is +5 and stable, and even if Pb is lost, the valence of Pb loss can be compensated by Nb ⁵⁺ . Further, even if Pb loss occurs during crystallization, it is easier to enter small Nb than large O loss.

Moreover, since Nb also has a +4 valence, Ti ⁴⁺ can be sufficiently replaced. Furthermore, in fact, Nb has a very strong covalent bond, and Pb is considered to be difficult to escape (H. Miyazawa, E. Natori, S. Miyashita; Jpn. J. Appl. Phys. 39 (2000). 5679).

  By constituting the second composite oxide layer 26 with PZTN and containing Nb at a specific ratio, the adverse effects due to Pb deficiency are eliminated, and the composition controllability is excellent. As a result, PZTN has extremely good hysteresis characteristics, leakage characteristics, reduction resistance, insulation properties, and the like compared to normal PZT.

  Until now, Nb doping to PZT has been mainly performed in the Zr-rich rhombohedral region, but the amount is 0.2-0.025 mol% (J. Am. Ceram. Soc, 84). (2001) 902; Phys. Rev. Let, 83 (1999) 1347) and so on. It is considered that the reason why Nb could not be doped in a large amount as described above was that the crystallization temperature increased to 800 ° C. or more when Nb was added at, for example, 10 mol%.

Accordingly, it is preferable to add PbSiO ₃ silicate to the precursor composition of the second composite oxide layer 26 at a ratio of 0.5 to 10 mol%, for example. Thereby, the crystallization energy of PZTN can be reduced. That is, when PZTN is used as the material of the composite oxide layer, the crystallization temperature of PZTN can be reduced by adding PbSiO ₃ silicate together with Nb. In addition, silicate and germanate can be mixed and used instead of silicate. The inventors of the present application have confirmed that Si, after acting as a sintering agent, constitutes part of the crystal as A site ions (see FIG. 2). That is, as shown in FIG. 2, when silicon was added to lead titanate, a change was observed in the Raman vibration mode E (1TO) of the A site ion. The change in the Raman vibration mode was observed when the Si addition amount was 8 mol% or less. Therefore, it was confirmed that Si was present at the A site of the perovskite with a slight addition of Si.

  In the present invention, Ta can be used instead of Nb or together with Nb. Even when Ta is used, there is a tendency similar to that of Nb described above.

As described above, in this embodiment, the composite oxide laminate represented by the general formula AB _1-x C _x O ₃ is preferably at least one of Si and Ge of 0.5 mol% or more, more preferably 0.5 to 10 mol% Si or Si and Ge can be included.

In the present embodiment, on the second composite oxide layer 26, a third electrode layer 28 made of the same material (LaNiO ₃ ) as the second electrode layer 23 and a material (platinum) similar to the first electrode layer 22 are used. The fourth electrode layer 30 is sequentially formed. The third electrode layer 28 and the fourth electrode layer 30 constitute an upper electrode of the capacitor.

  The third electrode layer 28 is not necessarily provided, but providing the third electrode layer 28 has an advantage of improving the reliability of the element by being isolated from moisture in the atmosphere.

  In the present embodiment, the protective layer 30 can be further provided on the surface as necessary. The protective layer 30 is made of an insulating film such as silicon oxide, silicon nitride, or alumina. The protective layer 30 has a function of preventing the first composite oxide layer 24 and the second composite oxide layer 26 from being deteriorated by a reducing gas (for example, hydrogen).

  According to the composite oxide laminate 100 according to the present embodiment, a specific second composite oxide layer (PZTN layer) 26 is formed on the first composite oxide layer 24 (PZT layer), as will be described later. In addition, the first composite oxide layer 24 has a very high insulating property and can have excellent ferroelectric characteristics and piezoelectric characteristics.

  That is, the PZT layer is likely to be deficient due to the lead and oxygen being removed from the PZT layer by heat treatment. In particular, when oxygen vacancies are formed, oxygen atoms move more easily than other elements, and oxygen atoms diffuse. Furthermore, the balance of charges is lost due to oxygen deficiency, and Pb, Zr, and Ti of PZT become unstable, so that the diffusion coefficient of these elements also increases. On the other hand, in the PZTN layer, there are very few defects in the crystal, and particularly oxygen vacancies can be prevented, so that diffusion of oxygen elements in the PZT layer can be suppressed. Therefore, generation of PZT crystal defects due to heat treatment can be suppressed, and the insulation can be maintained high.

2. Manufacturing method of complex oxide laminated body The manufacturing method of the complex oxide laminated body concerning embodiment of this invention has the following processes at least.

(1) A step of forming a first composite oxide layer represented by the general formula ABO ₃ above the substrate.

(2) A step of forming a second composite oxide layer represented by the general formula AB _1-x C _x O ₃ above the first composite oxide layer.

  Here, the element A can be composed of at least Pb, the element B can be composed of at least one of Zr, Ti, V, W, and Hf, and the element C can be composed of at least one of Nb and Ta.

  Hereinafter, the manufacturing method according to the present embodiment will be specifically described with reference to FIG.

(1) Formation of First Composite Oxide Layer 24 First, the first composite oxide layer 22 represented by the general formula ABO ₃ is formed on the substrate 20. In the example shown in FIG. 1, the A element can be Pb and the B element can be Pb (Zr, Ti) O _{3 made} of Zr and Ti.

The first composite oxide layer 24 can be formed by epitaxial growth on the substrate 20. In this case, the first complex oxide layer 22 grows with the same plane orientation as the substrate 20. As described above, the substrate 20 may be a single crystal substrate, or a substrate in which a so-called buffer layer having crystal controllability is formed on a base material as shown in FIG. That is, in the substrate 20 shown in FIG. 1, the first electrode layer 22 and the second electrode layer 23 are sequentially formed on the base material 21. The first electrode layer 22 is made of, for example, a platinum group metal such as platinum. The second electrode layer 23 is composed of a conductive oxide layer having a perovskite structure such as LaNiO ₃ . The second electrode layer 23 can function as a buffer layer for controlling the crystal orientation of the first composite oxide layer 24. For example, when the first composite oxide layer 24 has a (100) crystal orientation, LaNiO ₃ , SrRuO _3, or the like can be used as the second electrode layer 23. When the first composite oxide layer 24 has a (111) crystal orientation, a platinum group such as Pt, Ir, or Ru can be used as the second electrode layer 23. In this case, the first electrode layer 22 may not be provided.

  The formation method of the 1st complex oxide layer 24 is not specifically limited, A well-known film-forming method can be used. As such a film forming method, a liquid phase method such as a sol / gel method or a MOD method, or a vapor phase method such as a CVD method, a sputtering method, or a laser ablation method can be used, but a liquid such as a sol / gel method is preferable. It can be formed using a phase method.

  In the case of using the sol-gel method, a sol-gel raw material for forming the first composite oxide layer is applied on the substrate 20, and then the coating film is subjected to a heat treatment for drying and degreasing. Heat treatment is performed. This coating and heat treatment can be repeated a plurality of times depending on the film thickness of the first composite oxide layer 24. The heat treatment temperature for crystallization varies depending on the type and crystal orientation of the first composite oxide, but for example, in the case of PZT, it can be performed at 650 ° C. to 700 ° C.

(2) Formation of Second Composite Oxide Layer 26 The second composite oxide layer 26 is formed of a precursor for forming an insulating composite oxide represented by, for example, the general formula AB _1-x C _x O _3. It can form by performing the heat processing, after apply | coating the precursor composition containing.

  Below, a precursor composition and its manufacturing method are explained in full detail.

(2) -1: Precursor composition The precursor composition used in the present production method is used for forming the second composite oxide layer 26. Here, the second composite oxide layer is represented by the general formula AB _1-x C _x O ₃ , the A element is composed of at least Pb, and the B element is composed of at least one of Zr, Ti, V, W, and Hf. And the C element can be composed of at least one of Nb and Ta. Furthermore, the second composite oxide layer 26 is represented by the general formula AB _1-x C _x O ₃ , and the A element can be made of Pb, the B element can be made of Zr and Ti, and the C element can be made of Nb. . And in this embodiment, a precursor contains at least B element and C element, and has an ester bond in part.

  In the precursor composition, the precursor may be dissolved or dispersed in an organic solvent. Alcohol can be used as the organic solvent. 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 the alcohol 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.),
As described in detail later, the precursor composition has an ester bond formed by esterification of a polycarboxylic acid and a metal alkoxide and can be reversibly reacted. It can be decomposed into a metal alkoxide. Therefore, this metal alkoxide can be reused as a precursor raw material.

  In addition, the precursor composition used in the present invention has the following advantages. In a commercially available PZT sol-gel solution, lead acetate is generally used as a lead raw material. However, lead acetate is unlikely to bind to other Ti or Zr alkoxides, and lead is difficult to be incorporated into the precursor network. In the present invention, for example, of the two carboxyl groups of succinic acid, which is a divalent polycarboxylic acid, the acidity of one of the first carbolsyl groups that initially act as an acid is pH = 4.0 and the pH of acetic acid = Lead acetate binds to succinic acid because it is smaller than 4.56 and stronger than acetic acid. That is, the salt of weak acid + strong acid → strong acid salt + weak acid. Further, since the remaining second carbolsyl group of succinic acid is bonded to another MOD molecule or alkoxide, it is easy to network with the precursor of Pb, which has been difficult until now.

(2) -2; Method for Producing Precursor Composition The method for producing a precursor composition used in the present embodiment is a sol-gel raw material containing at least the B element and the C element, Ester by esterification of polycarboxylic acid or polycarboxylic acid derived from polycarboxylic acid ester and metal alkoxide by mixing sol-gel raw material containing condensate, polycarboxylic acid or polycarboxylic acid ester, and organic solvent Forming a precursor having a bond.

  5 and 6 schematically show the precursor formation reaction.

  The precursor generation reaction can be broadly divided into a first-stage alkoxy group substitution reaction as shown in FIG. 5 and a second-stage esterification reaction as shown in FIG. including. 5 and 6 show an example in which dimethyl succinate is used as a polycarboxylic acid ester and n-butanol is used as an organic solvent for convenience. Dimethyl succinate is nonpolar but dissociates in alcohol to form dicarboxylic acid.

  In the first-stage reaction, as shown in FIG. 5, both are ester-bonded by esterification of dimethyl succinate and a 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. The first and second stage reactions occur similarly in other alcohols.

  In the second stage reaction, as shown in FIG. 6, 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 occurs, A reaction product in which the carboxyl group is esterified 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. In addition, since dimethyl succinate dissociates in two steps and the first carboxyl group has a larger acid dissociation constant than the second carboxyl group, the first stage reaction has a higher reaction rate than the second stage reaction. Therefore, the second stage reaction proceeds more slowly than the first stage reaction.

  In the present embodiment, the following method can be employed to promote the esterification reaction described above.

  (A) Increase the concentration or reactivity of the reactants. Specifically, the reactivity is increased by increasing the degree of dissociation of the polycarboxylic acid or polycarboxylic acid ester by increasing the temperature of the reaction system. The temperature of the reaction system depends on the boiling point of the organic solvent, but is preferably higher than room temperature and lower than the boiling point of the organic solvent. As temperature of a reaction system, it can be 100 degrees C or less, for example, Preferably it is 50-100 degreeC.

  (B) The reaction by-product is removed. Specifically, esterification further proceeds by removing water and alcohol generated together with esterification.

  (C) Physically accelerate the molecular motion of the reactants. Specifically, the reactivity of the reactant is enhanced by irradiating energy rays such as ultraviolet rays.

  As described above, the organic solvent used in the method for producing the precursor composition can be an alcohol. 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.

  In the method for producing a precursor composition, the polycarboxylic acid or the polycarboxylic acid ester may be divalent or higher. The following can be illustrated as polycarboxylic acid used for this invention. 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. Examples of the above polycarboxylic acids or esters thereof are shown in FIGS. 4A to 4D. In addition, the present invention is characterized in that the 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.

  In the method for producing a precursor composition, the divalent carboxylic acid ester is 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.

  The molecular weight of the polycarboxylic acid ester may be 150 or less. If the molecular weight of the polycarboxylic acid ester is too large, the film tends to be damaged when the S L volatilizes during heat treatment, and a dense film may not be obtained.

  The polycarboxylic acid ester may be a liquid at room temperature. If the polycarboxylic acid ester is solid at room temperature, the liquid may gel.

  The amount of polycarboxylic acid or polycarboxylic acid ester used depends on the composition ratio of the sol-gel raw material and the composite oxide laminate, but the total of, for example, PZT sol-gel raw material, PbNb sol-gel raw material, and PbSi sol-gel raw material to which the polycarboxylic acid is bonded. The molar ion concentration and the molar ion concentration of the polycarboxylic acid can be preferably 1 ≧ (the molar ion concentration of the polycarboxylic acid) / (the total molar ion concentration of the raw material solution), more preferably 1. The addition amount of polycarboxylic acid can be 0.35 mol, for example.

  The amount of polycarboxylic acid or polycarboxylic acid ester added is desirably equal to or greater than the total number of moles of raw material solutions to be combined. The ratio of the molar ion concentration of the two is 1: 1, and all the raw materials are bonded, but since the ester exists stably in the acidic solution, in order to make the ester exist stably, the total number of moles of the raw material solution It is preferable to add a large amount of polycarboxylic acid. Here, the number of moles of polycarboxylic acid or polycarboxylic acid ester is a valence. That is, in the case of a divalent polycarboxylic acid or polycarboxylic acid ester, one molecule of polycarboxylic acid or polycarboxylic acid ester can bind two molecules of raw material molecules. If it is polycarboxylic acid ester, it will be 1: 1 with 0.5 mol of polycarboxylic acid or polycarboxylic acid ester with respect to 1 mol of raw material solutions. In addition, the polycarboxylic acid or the polycarboxylic acid ester is not an acid from the beginning, but dissociates the ester of the polycarboxylic acid in the alcohol to form a polycarboxylic acid. In this case, the number of moles of alcohol to be added is preferably 1 ≧ (number of moles of alcohol / number of moles of polycarboxylic acid ester). This is because, in order to sufficiently dissociate all the polycarboxylic acid esters, the larger the number of moles of alcohol, the more stable dissociation. Here, the number of moles of alcohol also means the so-called molar ion concentration divided by the valence of alcohol.

  In the manufacturing method of a precursor composition, the raw material which consists of metal carboxylates can further be included. Typical examples of such metal carboxylates include lead acetate and lead octylate, which are the lead carboxylates described above.

  In the method for producing a precursor composition, an organometallic compound (MOD raw material) can be used together with the sol-gel raw material. As such an organometallic compound, 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. In this case, Nb—Nb has two atoms bonded to each other, but since no more networks exist, it is treated as a MOD raw material.

  Formation of a network of carboxylic acid and MOD raw material proceeds mainly by an alcohol exchange reaction. For example, in the case of niobium octylate, it reacts between a carboxylic acid and an octyl group (alcohol exchange reaction), and esterification of R—COO—Nb proceeds. Thus, in this embodiment, by esterifying the MOD raw material, the molecules of the MOD raw material can be bonded to the precursor network by condensation of the MOD raw material and the alkoxide.

Furthermore, in the method for producing a precursor composition of the present 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 crystallization temperature can be lowered.

In the method for producing a precursor composition of the present embodiment, in order to obtain PZTN, a mixture of at least a sol-gel solution for PbZrO ₃ , a sol-gel solution for PbTiO ₃ , and a sol-gel solution for PbNbO _{3 is} used as the sol-gel solution. be able to. Also in this case, the above-described sol-gel raw material containing Si or Si and Ge can be further mixed.

When Ta is introduced instead of Nb, a sol-gel solution for PbTaO ₃ can be used as the sol-gel raw material.

  Since the precursor of the precursor composition obtained in this embodiment has an appropriate ester bond between a plurality of molecular networks, a reversible reaction is possible. Therefore, in the precursor, the polymerized precursor (polymer network) can be decomposed into a metal alkoxide condensate by proceeding the reaction in the left direction shown in FIG.

  The method for producing a precursor composition and the precursor composition used in the present embodiment have the following characteristics.

  According to the method for producing a precursor composition, a polymer network in which hydrolysis / condensation products (a plurality of molecular networks) of metal alkoxide as a sol-gel raw material are polycondensed by an ester bond in an organic solvent with a polycarboxylic acid. can get. Therefore, this polymer network has moderate ester bonds between a plurality of molecular networks derived from the hydrolysis / condensation product. The esterification reaction can be easily performed by temperature control or the like.

  Moreover, since the precursor composition has an appropriate ester bond between a plurality of molecular networks, a reversible reaction is possible. Therefore, in the composition remaining after the formation of the composite oxide multilayer film, the polymerized precursor (polymer network) can be decomposed into a metal alkoxide (or a molecular network composed of a condensate thereof). it can. Such metal alkoxides (or molecular networks composed of condensates thereof) can be reused as precursor raw materials, so that harmful substances such as lead can be reused, and there are great advantages from the environmental viewpoint. .

(3) Formation of Upper Electrode When using the complex oxide laminate according to the present embodiment as a capacitor, an upper electrode is formed on the second complex oxide layer 26. In the example shown in FIG. 1, the third electrode layer 28 is formed on the second complex oxide layer 26, and the fourth electrode layer 30 is formed on the third electrode layer 28. The third electrode layer 28 can be composed of a conductive complex oxide layer having the same perovskite structure as the second complex oxide layer 28. As the third electrode layer 28, for example, LaNiO ₃ can be used similarly to the second electrode layer 23. As the fourth electrode layer 30, for example, a platinum group metal such as Pt can be used similarly to the first electrode layer 22. The third electrode layer 28 can be formed by a laser ablation method, a sputtering method, a CVD method, or the like. The fourth electrode layer 30 can be formed by a sputtering method or the like.

  When the first and second composite oxide layers 24 and 26 are used as surface acoustic wave elements, an interdigital electrode (IDT) having a predetermined pattern is formed on the second composite oxide layer 26 as described later. Electrode) can be formed.

(4) Formation of Capacitor When the composite oxide multilayer body according to this embodiment is used as a capacitor, the first and second composite oxide layers 24 and 26 and the third and fourth electrode layers 28 and 30 are publicly known. Patterning is performed by lithography and etching.

  Further, a protective layer 30 made of oxide (silicon oxide), nitride (silicon nitride), alumina or the like is publicly known on the exposed surfaces of the substrate 20, the composite oxide layers 24 and 26 and the electrode layers 28 and 30 as necessary. It can be formed by the method (CVD method etc.).

  According to the manufacturing method of the present embodiment, by forming the second composite oxide layer 26 on the first composite oxide layer 24, the following operational effects are obtained. That is, by forming the second composite oxide layer (for example, PZTN layer) 26 on the first composite oxide layer (for example, PZT layer) 24, the generation of crystal defects in the PZT layer can be suppressed, and It is possible to prevent the atoms of the PZT layer from diffusing. As a result, the composite oxide laminate of the present embodiment can exhibit excellent ferroelectric characteristics and piezoelectric characteristics without deterioration of the insulating properties of the PZT layer.

  Hereinafter, the above-described effects will be specifically described with respect to an example of the combination of the PZTN layer 24 and the PZTN layer 26.

  In the composite oxide layer, crystal defects are likely to be concentrated on the top of the layer. In particular, in the case of PZT, although the crystallization temperature is as low as about 500 ° C. and suitable for device application, lead deficiency tends to occur at the top of the layer due to the high vapor pressure of lead (Pb). When a defect due to lead deficiency occurs, oxygen deficiency occurs simultaneously due to the principle of charge neutrality (Schottky defect). As a result, PZT is known to exhibit a high leakage current. For this reason, when the piezoelectric drive is performed, the PZT layer easily escapes as a leak current with a large applied electric field, and thus the actual piezoelectric constant cannot be increased. Further, if a high electric field is continuously applied while ignoring the leakage current, the PZT layer generates heat due to the leakage current, and eventually has a problem of destruction. As described above, when a PZT layer is formed, it is relatively easy to obtain a good PZT crystal film at a low crystallization temperature, but a large leak is caused by a different phase including lead deficiency and oxygen deficiency occurring at the top of the PZT layer. Current is likely to be generated. Therefore, it is difficult for the PZT layer to obtain a large piezoelectric constant. Therefore, theoretically, although thinning the PZT composite oxide to about 1 μm is advantageous in order to derive a large piezoelectric constant, PZT is actually 10 μm or more in consideration of the large leakage current. Used as a thick film (bulk).

  On the other hand, PZTN is a complex oxide that can prevent oxygen vacancies by utilizing the high covalent bonding property and the multivalent element of niobium even when defects are formed by the high vapor pressure of lead. As a result, it has already been confirmed by the present inventor that PZTN exhibits a leakage current of about 1 / 10,000 of PZT. However, the crystallization temperature tends to be slightly higher than that of PZT.

  The present invention adds the merits of both PZT and PZTN and complements the demerits. For example, a PZT crystal layer having a film thickness (for example, 1 μm) is first formed. At this time, since PZT has a low crystallization temperature, it is relatively easy to obtain a good crystal film. Next, a thin layer (for example, 100 nm) of PZTN is formed as the uppermost layer. When the PZTN layer is crystallized, the crystal orientation of PZT can be effectively utilized, and the PZTN layer can be crystallized at a low temperature by so-called epitaxial growth. In addition, when the PZTN layer is crystallized, the top phase of the PZT layer is absorbed. As described above, since the PZTN layer is a ceramic that hardly generates a heterogeneous phase, a heterogeneous phase is hardly generated in the uppermost layer of the laminate. For these reasons, the composite oxide laminate of the present invention has high insulating properties, and has excellent ferroelectric characteristics and piezoelectric characteristics, as will be apparent from Examples described later.

3. Example 1
Examples of the present invention will be described below, but the present invention is not limited thereto.

3.1. Example 1
The composite oxide laminate according to Example 1 was obtained as follows. In Example 1, a PZT layer was used as the first composite oxide layer, and a PZTN layer was used as the second composite oxide layer. The reference numerals of the members are the same as those shown in FIG.

(1) Formation of First Composite Oxide Layer First, a 90 nm Pt layer (first electrode layer) 22 and a 60 nm LaNiO ₃ layer (second electrode layer) 23 are sequentially formed on a silicon substrate (base material) 21. The formed substrate 20 was prepared. The Pt layer and the LaNiO ₃ layer are each formed by sputtering.

  Next, a first composite oxide layer (hereinafter also referred to as “PZT layer”) 24 made of PZT was formed on the substrate 20 by a known sol-gel method. The precursor composition used in this step was obtained by the following method.

In this example, the first and second raw material solutions containing at least one of Pb, Zr and Ti were used as the precursor composition for the PZT layer. As the first raw material solution, a solution obtained by dissolving a condensation polymer for forming a PbZrO ₃ perovskite crystal with Pb and Zr in an n-butanol solvent in an anhydrous state was used. As the second raw material solution, a solution obtained by dissolving a condensation polymer for forming PbTiO ₃ perovskite crystals of Pb and Ti in an n-butanol solvent in an anhydrous state was used.

When a composite oxide layer made of PbZr _0.52 Ti _0.48 O ₃ (PZT) is formed using the first and second raw material solutions, (first raw material solution) :( second raw material solution) = 52 : 48 ratio.

  The sol-gel raw material thus obtained was applied onto the substrate 20 by spin coating, and the coating film was dried at 150 to 180 ° C. and then subjected to a degreasing heat treatment at 350 to 350 ° C. Thereafter, the coating film was baked at 650 ° C. by the RTA method to obtain a 100 nm PZT layer.

  The above coating film formation, drying, degreasing heat treatment, and firing steps were repeated 10 times to form a PZT layer 24 having a thickness of about 1 μm.

(2) Formation of Second Composite Oxide Layer Next, a precursor composition was prepared, and a second composite oxide layer (hereinafter also referred to as “PZTN layer”) 26 made of PZTN was formed using the precursor composition. The precursor composition used in this step was obtained by the following method.

  A precursor composition for a PZTN film includes first to third raw material solutions containing at least one of Pb, Zr, Ti, and Nb, dimethyl succinate as a polycarboxylic acid ester, and an organic solvent as an organic solvent. It was obtained by mixing with n-butanol. The mixed solution is obtained by dissolving the sol-gel raw material and dimethyl succinate in n-butanol at a ratio of 1: 1.

As the first raw material solution, a solution obtained by dissolving a condensation polymer for forming a PbZrO ₃ perovskite crystal with Pb and Zr in an n-butanol solvent in an anhydrous state was used.

As the second raw material solution, a solution obtained by dissolving a condensation polymer for forming PbTiO ₃ perovskite crystals of Pb and Ti in an n-butanol solvent in an anhydrous state was used.

As the third raw material solution, a solution obtained by dissolving a polycondensation polymer for forming a PbNbO ₃ perovskite crystal with Pb and Nb in an n-butanol solvent in an anhydrous state was used.

In the case where a composite oxide layer made of PbZr _0.33 Ti _0.47 Nb _0.2 O ₃ (PZTN) is formed using the first, second and third raw material solutions, (first raw material solution): (second (Raw material solution): (Third raw material solution) = 33: 47: 20. Furthermore, for the purpose of lowering the crystallization temperature of the composite oxide layer, as a fourth raw material solution, a solution obtained by dissolving a condensation polymer for forming PbSiO ₃ crystals in an n-butanol solvent in an anhydrous state is 2 It added to the said mixed solution in the ratio of mol%, and the precursor composition was obtained.

  The precursor composition thus obtained was applied onto the first composite oxide layer 24 by spin coating, the coating film was dried at 150 to 180 ° C., and then subjected to a degreasing heat treatment at 350 to 350 ° C. . Thereafter, the coating film was baked at 700 ° C. by the RTA method to obtain a PZTN layer of about 100 nm.

(3) Formation of upper electrode and protective layer Next, a 60 nm LaNiO ₃ layer (third electrode layer) 28 and a 50 nm Pt layer (third layer) are formed on the second composite oxide layer (PZTN layer) 24 by sputtering. A fourth electrode layer) 30 was sequentially formed. Further, the fourth electrode layer 30, the third electrode layer 28, the second complex oxide layer 26, and the first complex oxide layer 24 were patterned by known lithography and dry etching to form a capacitor. Next, a protective layer (silicon oxide layer) 32 was formed by a CVD method using trimethylsilane.

  The hysteresis of the capacitor of Example 1 obtained in this way was determined. The result is shown in FIG. Further, the relationship between the voltage and the amount of polarization (2Pr) obtained for the capacitor of Example 1 is indicated by a in FIG.

  From FIG. 7A, it was confirmed that the capacitor of Example 1 was excellent in ferroelectric characteristics and had good hysteresis. From FIG. 8, it was found that according to the capacitor of Example 1, a large amount of polarization stable over a wide voltage range can be obtained.

3.2. Comparative Example 1
A comparative capacitor was obtained in the same manner as in Example 1 except that the second composite oxide layer 26 was not formed. When the hysteresis was obtained for this comparative capacitor, the result of FIG. 7B was obtained. From FIG. 7B, it was confirmed that the hysteresis characteristics could not be obtained at a certain voltage in the comparative capacitor.

  Further, the relationship between the voltage and the polarization amount (2Pr) obtained for the comparative capacitor of Comparative Example 1 is indicated by a symbol b in FIG. From FIG. 8, it can be seen that according to the capacitor of Comparative Example 1, the amount of polarization is smaller than that of the capacitor of Example 1, and the capacitor is destroyed at a voltage higher than about 50 V, so that the ferroelectric characteristics cannot be obtained. It was.

  As described above, according to the present example, having the PZTN layer on the PZT layer has an extremely high insulating property and excellent ferroelectricity as compared with Comparative Example 1 that does not have the PZTN layer. It was confirmed to have characteristics. The remanent polarization value of Example 1 was about twice that of Comparative Example 1. Since the remanent polarization value reflects the piezoelectric constant, this example shows that a piezoelectric constant nearly twice as large as that of the comparative example can be obtained.

4). Device The device of the present invention includes a component having the composite oxide laminate of the present invention and an electronic apparatus having the component. Examples of the device of the present invention are described below.

4.1. Next, a semiconductor element including the complex oxide laminate of the present invention will be described. In the present embodiment, a ferroelectric memory device including a ferroelectric capacitor, which is an example of a semiconductor element, will be described as an example.

  FIG. 9A and FIG. 9B are diagrams schematically showing a ferroelectric memory device 1000 having the complex oxide laminate of the present invention. 9A shows a planar shape of the ferroelectric memory device 1000, and FIG. 9B shows a II cross section in FIG. 9A.

  As shown in FIG. 9A, the ferroelectric memory device 1000 includes a memory cell array 200 and a peripheral circuit unit 300. The memory cell array 200 is arranged so that a lower electrode 210 (word line) for row selection and an upper electrode 220 (bit line) for column selection cross each other. The lower electrode 210 and the upper electrode 220 have a stripe shape composed of a plurality of line-shaped signal electrodes. The signal electrode can be formed so that the lower electrode 210 is a bit line and the upper electrode 220 is a word line. The peripheral circuit unit 300 includes various circuits for selectively writing information to or reading information from the memory cell array 200. For example, the peripheral circuit unit 300 is a first driving circuit for selectively controlling the lower electrode 210. 310, a second drive circuit 320 for selectively controlling the upper electrode 220, and a signal detection circuit (not shown) such as a sense amplifier.

  As shown in FIG. 9B, a ferroelectric film 215 is disposed between the lower electrode 210 and the upper electrode 220. In the memory cell array 200, a memory cell that functions as the ferroelectric capacitor 230 is formed in a region where the lower electrode 210 and the upper electrode 220 intersect. The ferroelectric capacitor 230 is constituted by the complex oxide multilayer body 100 of the present invention. That is, the ferroelectric film 215 is formed using the first and second composite oxide layers 24 and 26 of the present invention. The ferroelectric film 215 includes at least a lower electrode 210 (for example, the first and second electrode layers 22 and 23 of the present embodiment shown in FIG. 1) and an upper electrode 220 (for example, the first electrode of the present embodiment shown in FIG. 1). 3 and the fourth electrode layers 28, 30) may be disposed between the intersecting regions.

  Further, the peripheral circuit section 300 includes a MOS transistor 330 formed on the semiconductor substrate 400 as shown in FIG. 9B. The MOS transistor 330 has a gate insulating film 332, a gate electrode 334, and source / drain regions 336. The MOS transistors 330 are separated from each other by an element isolation region 410. A first interlayer insulating film 420 is formed on the semiconductor substrate 400 on which the MOS transistor 330 is formed. The peripheral circuit unit 300 and the memory cell array 200 are electrically connected by the wiring layer 51. Further, in the ferroelectric memory device 1000, a second interlayer insulating film 430 and an insulating protective layer 440 are formed.

  FIG. 10 shows a structural diagram of a 1T1C type ferroelectric memory device 500 as another example of the semiconductor device. FIG. 11 is an equivalent circuit diagram of the ferroelectric memory device 500.

  As shown in FIG. 10, the ferroelectric memory device 500 includes a lower electrode 501, an upper electrode 502 connected to a plate line, and the ferroelectric film 503 of the above-described embodiment (first and second composites of the present invention). A switching transistor element 507 (1T) having a capacitor 504 (1C) composed of oxide layers 24, 26) and one of source / drain electrodes connected to a data line 505 and a gate electrode 506 connected to a word line The memory device has a structure similar to that of a DRAM. 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.

  According to the semiconductor device of this embodiment, since it is formed using the raw material solution of the above embodiment, the ferroelectric film can be crystallized at a low temperature, and can be mixed with a semiconductor element such as a MOS transistor. can do. The semiconductor device of this embodiment is not limited to the above-described one, and can be applied to a 2T2C ferroelectric memory device and the like.

4.2. Next, an example in which the composite oxide laminate of the present invention is applied to a piezoelectric element will be described.

  FIG. 12 is a cross-sectional view showing a piezoelectric element 1 having the complex oxide laminate of the present invention. The piezoelectric element 1 is formed on a base material 2, a lower electrode 3 formed on the base material 2, a piezoelectric film 4 formed on the lower electrode 3, and the piezoelectric film 4. And an upper electrode 5. The piezoelectric film 4 is formed using the first and second composite oxide layers 24 and 26 of the present invention.

  The substrate 2 is composed of a (110) -oriented single crystal silicon substrate and a thermal oxide film formed on the surface of the single crystal silicon substrate. The base material 2 is processed to form ink cavities 521 in the ink jet recording head 50 as described later (see FIG. 13).

4.3. Inkjet Recording Head Next, an inkjet recording head in which the above-described piezoelectric element functions as a piezoelectric actuator and an inkjet printer having this inkjet recording head will be described. FIG. 13 is a side sectional view showing a schematic configuration of the ink jet recording head according to the present embodiment, and FIG. 14 is an exploded perspective view of the ink jet recording head, which is upside down from a state in which it is normally used. It is shown. FIG. 15 shows an ink jet printer 700 having an ink jet recording head according to this embodiment.

  As shown in FIGS. 13 and 14, the ink jet recording head 50 includes a head main body (base body) 57 and a piezoelectric portion 54 formed on the head main body 57. The piezoelectric element 54 shown in FIG. 12 is provided in the piezoelectric portion 54. The piezoelectric element 1 is configured by laminating a lower electrode 3, a piezoelectric film (ferroelectric film) 4, and an upper electrode 5 in this order. The piezoelectric film 4 is a film formed using the composite oxide laminate of the present invention. In the ink jet recording head, the piezoelectric unit 54 functions as a piezoelectric actuator.

  The head body (base body) 57 includes a nozzle plate 51, an ink chamber substrate 52, and an elastic film 55. And these are accommodated in the housing | casing 56, and the inkjet recording head 50 is comprised.

  Each piezoelectric element is electrically connected to a piezoelectric element drive circuit (not shown) and is configured to operate (vibrate, deform) based on a signal from the piezoelectric element drive circuit. That is, each piezoelectric part 54 functions as a vibration source (head actuator). The elastic film 55 vibrates due to the vibration (deflection) of the piezoelectric portion 54 and functions to instantaneously increase the internal pressure of the cavity 521.

  In the above description, an ink jet recording head that discharges ink has been described as an example. However, the present embodiment is intended for liquid ejecting heads and liquid ejecting apparatuses that use piezoelectric elements. Examples of the liquid ejecting head include a recording head used in an image recording apparatus such as a printer, a color material ejecting head used for manufacturing a color filter such as a liquid crystal display, an organic EL display, and an electrode formation such as an FED (surface emitting display). Examples thereof include an electrode material ejecting head used in manufacturing, a bioorganic matter ejecting head used in biochip manufacturing, and the like.

4.4. Surface acoustic wave device Next, an example of a surface acoustic wave device to which the composite oxide laminate of the present invention is applied will be described with reference to the drawings.

  FIG. 16 is a cross-sectional view schematically showing a surface acoustic wave device 300 according to this embodiment.

  The surface acoustic wave device 300 includes a substrate 11, a piezoelectric film 12 formed on the substrate 11, interdigital electrodes (hereinafter referred to as “IDT electrodes”) 18 and 19 formed on the piezoelectric film 12, and ,including. The IDT electrodes 18 and 19 have a predetermined pattern. The piezoelectric film 12 is configured using the first and second composite oxide layers 24 and 26 of the present invention.

  The surface acoustic wave device 300 according to the present embodiment is formed as follows using the piezoelectric film laminate according to the present invention, for example.

  First, the first and second composite oxide layers 24 and 26 shown in FIG. 1 are formed on the substrate 11 shown in FIG. 16 to form the piezoelectric film 12. Further, a conductive film is formed on the piezoelectric film 12. Next, IDT electrodes 18 and 19 are formed on the piezoelectric film 12 by patterning the conductive film using a known lithography technique and etching technique.

4.5. Frequency Filter Next, an example of a frequency filter to which the composite oxide laminate of the present invention is applied will be described with reference to the drawings. FIG. 17 is a diagram schematically illustrating the frequency filter of the present embodiment.

  As shown in FIG. 17, the frequency filter has a base 140. As the substrate 140, a laminate (see FIG. 16) similar to the surface acoustic wave element 300 described above can be used.

  IDT electrodes 141 and 142 are formed on the upper surface of the substrate 140. Further, sound absorbing portions 143 and 144 are formed on the upper surface of the base 140 so as to sandwich the IDT electrodes 141 and 142. The sound absorbing parts 143 and 144 absorb surface acoustic waves that propagate on the surface of the base 140. One IDT electrode 141 is connected to a high frequency signal source 145, and the other IDT electrode 142 is connected to a signal line. Here, the piezoelectric film can be formed using the composite oxide laminate of the present invention.

4.6. Oscillator Next, an example of an oscillator to which the composite oxide laminate of the present invention is applied will be described with reference to the drawings. FIG. 18 is a diagram schematically illustrating the oscillator according to the present embodiment.

  As shown in FIG. 18, the oscillator has a base 150. As the base 150, a laminate (see FIG. 16) similar to the surface acoustic wave element 300 described above can be used.

  An IDT electrode 151 is formed on the upper surface of the substrate 150, and IDT electrodes 152 and 153 are formed so as to sandwich the IDT electrode 151. A high frequency signal source 154 is connected to one comb-like electrode 151a constituting the IDT electrode 151, and a signal line is connected to the other comb-like electrode 151b. The IDT electrode 151 corresponds to an electric signal applying electrode, and the IDT electrodes 152 and 153 are used for resonance to resonate a specific frequency component of a surface acoustic wave generated by the IDT electrode 151 or a frequency component of a specific band. It corresponds to an electrode. Here, the piezoelectric film can be formed using the composite oxide laminate of the present invention.

  The above-described oscillator can also be applied to a VCSO (Voltage Controlled SAW Oscillator).

  As described above, the frequency filter and the oscillator according to the present embodiment include the surface acoustic wave device having a large electromechanical coupling coefficient according to the present invention. Therefore, according to the present embodiment, it is possible to reduce the size of the frequency filter and the oscillator.

  In addition, this invention is not limited to embodiment mentioned above, A various deformation | transformation is possible. For example, the present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the invention includes a configuration that achieves the same effect as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

  20 substrate 21 base material 22 first electrode layer 23 second electrode layer 24 first complex oxide layer 26 second complex oxide layer 28 third electrode layer 30 fourth electrode layer 1 piezoelectric element 2. Substrate, 3. Lower electrode, 4. Piezoelectric film, 5. Upper electrode, 50. Inkjet recording head.

Claims (12)

A substrate,
A first composite oxide layer formed above the substrate and represented by the general formula ABO ₃ ;
A second complex oxide layer formed above the first complex oxide layer and represented by the general formula AB _1-x C _x O ₃ ;
A element consists of at least Pb,
B element consists of at least one of Zr, Ti, V, W and Hf,
The composite oxide laminate, wherein the C element is composed of at least one of Nb and Ta. In claim 1,
The B element is Zr and Ti,
The composite oxide stack, wherein the C element is Nb. In claim 2,
The second complex oxide layer is a complex oxide laminate including a complex oxide containing Nb in a range of 0.1 ≦ x ≦ 0.3. In any of claims 1 to 3,
Further, the second complex oxide layer is a complex oxide laminate including at least one of Si and Ge of 0.5 mol% or more. In any of claims 1 to 4,
The second complex oxide layer is a complex oxide laminate having a smaller film thickness than the first complex oxide layer. In any of claims 1 to 5,
The substrate is a composite oxide laminate having an electrode layer. In any one of Claims 1 thru | or 6.
A composite oxide stack having a buffer layer for controlling crystal orientation of the first composite oxide layer below the first composite oxide layer. Forming a first composite oxide layer represented by the general formula ABO ₃ above the substrate;
Forming a second composite oxide layer represented by the general formula AB _1-x C _x O ₃ above the first composite oxide layer,
A element consists of at least Pb,
B element consists of at least one of Zr, Ti, V, W and Hf,
The method for producing a composite oxide laminate, wherein the C element comprises at least one of Nb and Ta. In claim 8,
The second composite oxide layer is subjected to heat treatment after applying a precursor composition containing a precursor for forming an insulating composite oxide represented by the general formula AB _1-x C _x O _3. The manufacturing method of the complex oxide laminated body formed by these. In claim 9,
The said precursor composition is a manufacturing method of complex oxide laminated body containing the precursor which contains the said B element and the said C element at least, and has an ester bond in part. In any of claims 9 and 10,
The method for producing a composite oxide laminate, wherein the precursor further includes at least one of Si and Ge.   A device comprising the composite oxide laminate according to claim 1.

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