JP2016143806A - Mn-DOPED PZT-BASED PIEZOELECTRIC FILM - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Mn-doped PZT-based piezoelectric film formed by CSD method, having a thickness of 0.8 μm or more, excellent in stability after polarization processing, and the piezoelectric characteristics of which do not deteriorate.SOLUTION: A PZT-based piezoelectric film is composed of a Mn-doped composite oxide, and formed by CSD method. When the total mol number of Zr and Ti in the composite oxide is 1 mol, the mole ratio of Mn is in a range of 0.01-0.045, and the PZT-based piezoelectric film crystal oriented to the (100) plane or (001) plane preferentially has a thickness of 0.8-3 μm. The orientation of the (100) plane or (001) plane by X-ray diffraction is preferably 95% or more, and deviation D of the hysteresis loop of the polarization-electric field characteristics is preferably at least 8.8 kV/cm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a PZT-based piezoelectric film doped with Mn used for gyro sensors, infrared sensors, piezoelectric sensors, inkjet heads, autofocus, and the like. More specifically, the present invention relates to a Mn-doped PZT-based piezoelectric film excellent in stability after polarization treatment suitable for the use of the sensor.

  Conventionally, a CSD (Chemical Solution Deposition) method represented by a sol-gel method and a sputtering method are well known as methods for producing a PZT film for use in a piezoelectric MEMS (Micro Electro Mechanical Systems) device. In general, a PZT-based film manufactured by the CSD method has a high dielectric breakdown voltage and is suitable for a high voltage driving device such as an ink jet head. On the other hand, PZT-based films produced by sputtering often have compressive stress due to the implantation effect during film formation, and a film excellent in low-voltage driving can be formed by being oriented in the (001) plane. It is also possible to develop a spontaneous polarization phenomenon that aligns the polarization direction immediately after film formation by devising the film formation method.

  When a ferroelectric thin film such as PZT is produced as a sensor element such as a gyro sensor by sputtering, the polarization state may be lost due to heat treatment for soldering in a reflow process after packaging. However, since a film having a spontaneous polarization phenomenon has an internal bias in the film, this heat treatment is advantageous in that the polarization state is not lost.

  On the other hand, when a ferroelectric thin film such as PZT is produced by the CSD method, the produced ferroelectric thin film is excellent in characteristic reproducibility and in-plane characteristic uniformity due to its film formation properties. In addition, since the CSD method does not use a vacuum, the apparatus cost is significantly lower than the sputtering method. In order to take advantage of such merits, there is a demand for a PZT film that has excellent temperature characteristics even in the CSD method and does not lose the polarization state.

  Conventionally, it has been disclosed that a spontaneous polarization phenomenon appears in a PZT film even in the CSD method (see Non-Patent Document 1). This document explains that this phenomenon is due to the fact that the film is distorted by the influence of distortion due to lattice mismatch at the substrate interface at the thin film level, and the spontaneous polarization phenomenon is induced.

  A method for manufacturing a ferroelectric thin film in which an orientation control layer having a crystal orientation of (100) plane is formed on a lower electrode, which will be described later, is described in Patent Document 1. A method for manufacturing a ferroelectric thin film for forming an orientation control layer having a crystal orientation of (110) plane on a lower electrode, which will be described later, is described in Patent Document 2.

JP2012-256850 (Claims 1 to 3) JP2012-256851A (Claims 1 to 3)

A. L. Kholkin, K. G. Brooks, D. V. Taylor, S. Hiboux and N. Setter: "Self-Polarization Effect in Pb (Zr, Ti) O3 Thin Films", Integrated Ferroelectrics, 1998, vol. 22, pp. 525-533.

  However, Non-Patent Document 1 shows that when the film is formed by the CSD method, the spontaneous polarization phenomenon disappears as the thickness of the PZT film increases. Specifically, in a PZT film with a film thickness of 0.7 μm or less, the polarization does not change significantly, but when it exceeds 0.7 μm, the effect of strain is eliminated and the spontaneous polarization phenomenon disappears. Is explained to be very small. For this reason, in order to produce a film having a spontaneous polarization phenomenon with a thickness of 0.8 μm or more that can be practically used by the CSD method, there is still a problem to be solved.

  An object of the present invention is to provide a Mn-doped PZT-based piezoelectric film that is formed by the CSD method, has a film thickness of 0.8 μm or more, has excellent stability after polarization treatment, and does not deteriorate piezoelectric characteristics. It is in.

  By adding Mn to the PZT-based material and increasing the degree of crystal orientation of the (100) plane or (001) plane of the film, the present inventors have practically sufficient even if the film thickness is 0.8 μm or more. It was found that a PZT film having a spontaneous polarization phenomenon can be obtained, and the present invention has been achieved.

  A first aspect of the present invention is a PZT-based piezoelectric film formed by a CSD method made of a Mn-doped composite oxide, wherein the total number of moles of Zr and Ti in the composite oxide is 1 mole. When the molar ratio of Mn is in the range of 0.01 to 0.045, the PZT-based piezoelectric film is preferentially crystallized in the (100) plane or (001) plane, and the film thickness is 0.8 to It is a Mn-doped PZT-based piezoelectric film characterized by being 3 μm.

  A second aspect of the present invention is an invention based on the first aspect, and is an Mn-doped PZT-based piezoelectric film having an orientation degree of (100) plane or (001) plane of 95% or more by X-ray diffraction It is.

A third aspect of the present invention is an invention based on the first or second aspect, wherein the deviation D of the hysteresis loop of the polarization-electric field characteristic obtained by the following formula (1) is at least 8.8 kV / cm. This is a certain Mn-doped PZT piezoelectric film.
D = E _C ⁺ − [(E _C ⁺ + E _C ⁻ ) / 2] (1)
Where E _C ⁺ is the absolute value of the positive electric field value from 0 kV / cm when the polarization is 0 μC / cm ² , and E _C ⁻ is the negative value from 0 kV / cm when the polarization is 0 μC / cm ^2. The absolute value of the electric field value on the side.

In the Mn-doped PZT-based piezoelectric film according to the first aspect of the present invention, in the PZT material having a perovskite structure represented by ABO ₃ containing Pb, Zr and Ti, by adding Mn, A part of certain Ti and Zr is substituted with Mn, and spontaneous polarization phenomenon appears. As a result, even if the film is 0.8-3 μm, it has excellent temperature stability in the polarization state, and after packaging this film It is possible to suppress the disappearance of the polarization state by the heat treatment of the soldering in the reflow process. The specific technical reason is that, as shown in the following formula (2), oxygen vacancies are generated, and the domain wall is pinned, whereby a spontaneous polarization phenomenon appears.
Pb _{1 + y / 2} Zr _x Ti _(1-x) O ₃ + yMn ³⁺ →
Pb _{1 + y / 2} (Zr _x Ti _(1-x) Mn _y ) (O _{3-y / 2} V ^·· _{y / 2} ) (2)

  Secondly, when Mn is doped by the CSD method, a composition gradient of Mn is formed in which the concentration of Mn ions decreases in the film thickness direction from the lower surface side of the film toward the upper surface side of the film, and a gradient of oxygen vacancies is simultaneously generated. . It is presumed that the concentration gradient of oxygen defects creates a bias in the film and the spontaneous polarization phenomenon appears more reliably.

  Third, since the crystal orientation is preferentially oriented to the (100) plane or the (001) plane, the polarization direction is aligned upward immediately after film formation, so that the spontaneous polarization phenomenon is maintained and the polarization stability is improved. be able to. Even if Mn is doped, the piezoelectric characteristics of the piezoelectric film do not deteriorate.

  In the Mn-doped PZT-based piezoelectric film according to the second aspect of the present invention, the degree of orientation of the (100) plane or (001) plane by X-ray diffraction is 95% or more, so that the polarization stability is further improved. Can do.

  The Mn-doped PZT piezoelectric film according to the third aspect of the present invention has a hysteresis loop shift D immediately after the film formation, and D is at least 8.8 kV / cm. can get.

It is a figure which shows the hysteresis curve of each piezoelectric material film when doped with Mn of the present invention (shown by a solid line) and when not doped with Mn (shown by a broken line). It is a schematic diagram showing the behavior of the piezoelectric film when a voltage is applied to the Mn-doped PZT piezoelectric film of the embodiment of the present invention.

  Next, the form for implementing this invention is demonstrated.

[Mn-doped PZT piezoelectric film]
The Mn-doped PZT piezoelectric film of the present invention is a piezoelectric film in which a Mn element is added (doped) to a composite oxide having a Pb-containing perovskite structure such as lead zirconate titanate (PZT). This piezoelectric film is a Mn-doped PZT piezoelectric film, a Mn-doped PNbZT piezoelectric film, a Mn-doped PLaZT piezoelectric film, or the like. In this specification, these piezoelectric films are called PZT-based piezoelectric films. This Mn-doped PZT piezoelectric film is formed by the CSD method and is made of a Mn-doped composite oxide. When the total number of moles of Zr and Ti in this composite oxide is 1 mole, the molar ratio of Mn is in the range of 0.01 to 0.045, and this PZT-based piezoelectric film has a (100) plane or Crystal orientation is preferentially performed on the (001) plane, and the film thickness is 0.8 to 3 μm. The preferential orientation refers to a state in which an arbitrary peak intensity is relatively higher than other peak intensities as compared with a bulk X-ray diffraction pattern.

  In the case of a PZT-based film formed by a wet coating method such as a sol-gel method that does not dope Mn, piezoelectric properties are not exhibited immediately after the film formation, and a polarization treatment is necessary. On the other hand, in a film doped with Mn and preferentially crystallized in the (100) plane or (001) plane, the vertical axis is the amount of polarization and the horizontal axis is an electric field. Has an imprint phenomenon that shifts to the positive electric field side, and the film as a whole becomes a film whose polarization direction is aligned upward immediately after film formation. In addition, such a film has excellent polarization stability due to the imprint phenomenon caused by Mn doping, and does not deteriorate the piezoelectric characteristics, so that the film is more suitable as a piezoelectric body. If the film is not preferentially crystallized in the (100) plane or the (001) plane, the imprint phenomenon does not occur and the spontaneous polarization phenomenon does not occur. Further, when the film thickness is less than 0.8 μm, there is a problem that a sufficient amount of displacement cannot be obtained, and when it exceeds 3 μm, there is a problem that the film formation takes time and productivity is lowered. A preferred film thickness is 1 to 2 μm.

In the Mn-doped PZT type piezoelectric film, it is preferable that the deviation D of the hysteresis loop of the polarization-electric field characteristic shown in the following formula (1) is at least 8.8 kV / cm. When the deviation D is less than 8.8 kV / cm, the polarization state is not sufficiently aligned and sufficient piezoelectric characteristics are not exhibited. The deviation D is preferably large, but the hysteresis loop deviation that can be achieved in practice is 22 kV / cm. The hysteresis loop indicated by the solid line in FIG. 1 is that of the PZT-based piezoelectric film doped with Mn of the present invention, and the hysteresis loop indicated by the broken line in FIG. 1 is that of the PZT-based piezoelectric film not doped with Mn. . In FIG. 1, E _C ⁺ is an absolute value of the electric field value on the positive side from 0 kV / cm when the polarization is 0 μC / cm ² , and E _C ⁻ is from 0 kV / cm when the polarization is 0 μC / cm ^2. Is the absolute value of the electric field value on the negative side.
^{_{D = E C + - [(}} E C + + E C -) / 2] (1)

[Mn-doped PZT-based piezoelectric film forming composition]
The composition for forming the Mn-doped PZT-based piezoelectric film includes a PZT-based precursor, a diol as a main solvent, polyvinylpyrrolidone as a liquid viscosity modifier, and the like. The PZT-based precursor contained in the composition is a raw material for constituting the composite oxide and the like in the formed PZT-based piezoelectric film, and the total number of moles of Zr and Ti in the composite oxide is 1 When molar, the molar ratio of Mn is in the range of 0.01 to 0.045. When the molar ratio of Mn is less than 0.01, the imprint phenomenon does not occur in the formed PZT-based piezoelectric film, and the spontaneous polarization phenomenon does not occur. If it exceeds 0.045, the piezoelectric properties of the piezoelectric film are deteriorated.

More specifically, when the PZT-based piezoelectric film-forming composition is a PMnZT piezoelectric film-forming composition, the metal atomic ratio (Pb: Mn: Zr: Ti) in the composition is (1.00 to 1.00). 1.20): (0.01 to 0.045): (0.40 to 0.55): (0.45 to 0.60) is satisfied, and the total ratio of the metal atomic ratio of Zr and Ti is 1. It is included in the ratio. Thereby, in the piezoelectric film after formation, when the general formula of the PZT piezoelectric film is represented by Pb _z Mn _x Zr _y Ti _1-y O ₃ , x, y, and z in the general formula are 0.01 ≦ It can be controlled to a desired composition satisfying x ≦ 0.045, 0.40 ≦ y ≦ 0.55 and 0.95 ≦ z ≦ 1.10.

When the PZT-based piezoelectric film-forming composition is a PMnNbZT piezoelectric film-forming composition, the metal atomic ratio (Pb: Mn: Nb: Zr: Ti) in the composition is (1.00-1.20) : (0.01 to 0.045): (0.01 to 0.045): (0.40 to 0.55): (0.45 to 0.60) and Zr, Ti and Mn The total proportion of Nb metal atom ratios is included at a rate of 1. Thereby, in the formed piezoelectric film, when the general formula of the PNbZT piezoelectric film is represented by Pb _z Mn _x Nb _1-x Zr _y Ti _1-y O ₃ , x, y, and z in the general formula are The composition can be controlled so as to satisfy 0.01 ≦ x ≦ 0.045, 0.40 ≦ y ≦ 0.55, and 0.95 ≦ z ≦ 1.10.

When the PZT-based piezoelectric film-forming composition is a PMnLaZT piezoelectric film-forming composition, the metal atomic ratio (Pb: La: Mn: Zr: Ti) in the composition is (1.00-1.20) : (0.01 to 0.05): (0.01 to 0.045): (0.40 to 0.55): (0.45 to 0.60), and metal atoms of Pb and La The total ratio is included at a ratio of 1. Thus, in the piezoelectric film after forming, when referring to the general formula of the PLaZT piezoelectric film with _{Pb z La t Mn x Zr y} Ti 1-y O 3, x in the general formula, y, is z and t It can be controlled to a desired composition satisfying 0.01 ≦ x ≦ 0.045, 0.40 ≦ y ≦ 0.55, 0.01 ≦ t ≦ 0.05, and 1.00 ≦ z ≦ 1.20. .

  The PZT-based precursor has an organic group on each metal atom of Pb, Mn, Zr and Ti, each metal atom of Pb, Mn, Nb, Zr and Ti, or each metal atom of Pb, Mn, La, Zr and Ti. A compound in which is bonded via its oxygen or nitrogen atom is preferred. For example, one kind selected from the group consisting of metal alkoxide, metal diol complex, metal triol complex, metal carboxylate, metal β-diketonate complex, metal β-diketoester complex, metal β-iminoketo complex, and metal amino complex Or 2 or more types are illustrated. Particularly suitable compounds are metal alkoxides, partial hydrolysates thereof, and organic acid salts.

Specifically, examples of the Pb compound include acetates such as lead acetate: Pb (OAc) ₂ and alkoxides such as lead diisopropoxide: Pb (OiPr) ₂ . Examples of the Mn compound include organic acid salts such as manganese 2-ethylhexanoate, manganese naphthenate and manganese acetate, and metal β-diketonate complexes such as acetylacetone manganese. Further, as the Ti compound, titanium tetraethoxide: Ti (OEt) ₄ , titanium tetraisopropoxide: Ti (OiPr) ₄ , titanium tetra n-butoxide: Ti (OnBu) ₄ , titanium tetraisobutoxide: Ti (OiBu) ₄ , alkoxides such as titanium tetra-t-butoxide: Ti (OtBu) ₄ and titanium dimethoxydiisopropoxide: Ti (OMe) ₂ (OiPr) ₂ . Moreover, as a Zr compound, the alkoxides similar to the said Ti compound are preferable. Further, examples of the Nb compound include alkoxides and organometallic acid salts such as niobium pentaethoxide and niobium 2-ethylhexanoate, and examples of the La compound include organic metal acid salts such as lanthanum acetate hemihydrate. It is done. Although the metal alkoxide may be used as it is, a partially hydrolyzed product thereof may be used in order to promote decomposition.

  The Pb compound, Mn compound, Ti compound and Zr compound, or Nb compound or La compound are contained in the composition in such a ratio as to give the desired metal atom ratio. Here, the reason for controlling the Mn ratio in the composition to be in the above range is that if the Mn ratio in the composition is less than the lower limit, x in the above general formula indicating the film composition after film formation is the lower limit. As described above, the imprint phenomenon does not occur in the PZT piezoelectric film after formation, and the spontaneous polarization phenomenon does not occur. On the other hand, if the ratio of Mn in the composition exceeds the upper limit, x in the above general formula indicating the film composition after film formation exceeds the upper limit, and as described above, the piezoelectric characteristics of the piezoelectric film deteriorate. It is. The reason for controlling the ratio of Zr and Ti in the composition to be in the above range is that if the ratio of Zr and Ti in the composition is out of the above range, This is because y of y is out of the above desired range and the piezoelectric constant of the piezoelectric film cannot be sufficiently improved. Moreover, the reason for controlling the ratio of Pb in the composition to be in the above range is that if the ratio of Pb in the composition is less than the lower limit, z in the above general formula indicating the film composition after film formation is the lower limit. This is because a large amount of pyrochlore phase is contained in the film, and electrical characteristics such as piezoelectric characteristics are remarkably deteriorated. On the other hand, if the ratio of Pb in the composition exceeds the upper limit value, z in the above general formula indicating the film composition after film formation exceeds the upper limit value, and a large amount of PbO remains in the film after baking. This is because the current increases and the electrical reliability of the film decreases. That is, excess lead tends to remain in the film, and the leak characteristics and insulation characteristics are deteriorated.

  When the composition for forming a PZT-based piezoelectric film is a composition for forming a PZT piezoelectric film, the metal atomic ratio (Pb: Mn: Zr: Ti) in the composition is (1 .05 to 1.15): (0.02 to 0.042): (0.45 to 0.55): (0.45 to 0.55) and the sum of the metal atomic ratios of Zr and Ti The ratio is preferably set to 1.

  When the PZT-based piezoelectric film-forming composition is a PNbZT piezoelectric film-forming composition, the metal atomic ratio (Pb: Mn: Nb: Zr: Ti) in the composition is (1.00-1.20) : (0.01 to 0.045): (0.01 to 0.045): (0.40 to 0.55): (0.45 to 0.60) and Zr, Ti and Mn It is preferable that the total ratio of the metal atom ratio of Nb is 1.

  When the PZT-based piezoelectric film forming composition is a PLaZT piezoelectric film forming composition, the metal atomic ratio (Pb: La: Mn: Zr: Ti) in the composition is (1.00 to 1.20). : (0.01 to 0.045): (0.01 to 0.045): (0.40 to 0.55): (0.45 to 0.60), and metal atoms of Pb and La It is preferable to set the ratio so that the total ratio is 1. In the present specification, the magnitude (high and low) of the piezoelectric constant means the magnitude (high and low) of the absolute value of the piezoelectric constant.

  The concentration of the PZT precursor in 100% by mass of the composition is 17 to 35% by mass in terms of oxide concentration. The reason why the concentration of the PZT precursor is limited to this range is that a sufficient film thickness cannot be obtained if the concentration is less than the lower limit value, whereas cracks are likely to occur if the upper limit value is exceeded. Among these, it is preferable that the density | concentration of the PZT type | system | group precursor which occupies in 100 mass% of compositions is 20-25 mass% in an oxide density | concentration. In addition, the oxide concentration in the concentration of the PZT-based precursor in the composition occupies 100% by mass of the composition calculated on the assumption that all metal atoms contained in the composition have become the target oxide. The concentration of metal oxide.

  Examples of the main solvent diol contained in the composition include propylene glycol, ethylene glycol, and 1,3-propanediol. Of these, propylene glycol or ethylene glycol is preferred. By using diol as a solvent component, the storage stability of the composition can be enhanced.

  The ratio of the said diol in 100 mass% of compositions is 16-56 mass%. The reason why the ratio of the diol is limited to this range is that if it is less than the lower limit value, a problem that precipitates are generated occurs. On the other hand, if it exceeds the upper limit value, voids (micropores) are easily generated when the film is thickened. Among these, it is preferable that the ratio of diol shall be 28-42 mass%.

  Other solvents include carboxylic acids, alcohols (for example, polyhydric alcohols other than ethanol, 1-butanol and diol), esters, ketones (for example, acetone, methyl ethyl ketone), ethers (for example, dimethyl ether, diethyl ether). , Cycloalkanes (for example, cyclohexane, cyclohexanol), aromatics (for example, benzene, toluene, xylene), other tetrahydrofuran, etc., and mixed solvents in which one or more of these are further added to a diol It can also be.

  Specific examples of the carboxylic acid include n-butyric acid, α-methylbutyric acid, i-valeric acid, 2-ethylbutyric acid, 2,2-dimethylbutyric acid, 3,3-dimethylbutyric acid, 2,3-dimethylbutyric acid, 3-methylpentanoic acid, 4-methylpentanoic acid, 2-ethylpentanoic acid, 3-ethylpentanoic acid, 2,2-dimethylpentanoic acid, 3,3-dimethylpentanoic acid, 2,3-dimethylpentanoic acid, 2- It is preferable to use ethylhexanoic acid or 3-ethylhexanoic acid.

  As the ester, ethyl acetate, propyl acetate, n-butyl acetate, sec-butyl acetate, tert-butyl acetate, isobutyl acetate, n-amyl acetate, sec-amyl acetate, tert-amyl acetate, isoamyl acetate are used. As the alcohol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, iso-butyl alcohol, 1-pentanol, 2-pentanol, 2-methyl-2-pentanol, 2-methoxy It is preferred to use ethanol.

  Moreover, the liquid viscosity modifier contained in the composition has a large effect of suppressing cracks in the formed piezoelectric film. As this liquid viscosity adjusting agent, polyvinylpyrrolidone (PVP) which is a polymer compound is suitable for adjusting the relative viscosity. It is preferable that k value of polyvinylpyrrolidone contained in the composition of this invention is 30-90. The ratio of the polyvinyl pyrrolidone is 0.005 to 0.25 mol in terms of monomer with respect to 1 mol of the PZT precursor.

  Moreover, in the composition of this invention, it is preferable to add C6-C12 linear monoalcohol, and the addition ratio is 0.6-10 mass% in 100 mass% of compositions. It is preferable. When an appropriate amount of linear monoalcohol is included in the composition, a gel film capable of effectively releasing organic substances out of the film at the time of calcination can be formed, and even if the film thickness exceeds 100 nm, the fine and high characteristic Mn A doped PZT piezoelectric film is obtained.

  In addition to the above components, β-diketones (for example, acetylacetone, heptafluorobutanoylpivaloylmethane, dipivaloylmethane, trifluoroacetylacetone, benzoylacetone, etc.), β Ketone acids (for example, acetoacetic acid, propionylacetic acid, benzoylacetic acid, etc.), β-ketoesters (for example, lower alkyl esters of the above ketone acids such as methyl, propyl, butyl, etc.), oxyacids (for example, lactic acid, glycolic acid) , Α-oxybutyric acid, salicylic acid, etc.), lower alkyl esters of the above oxyacids, oxyketones (eg, diacetone alcohol, acetoin, etc.), diols, triols, higher carboxylic acids, alkanolamines (eg, diethanolamine, triethanol) Amine, monoeta Ruamin), a polyvalent amine or the like may be added from 0.2 to 3 approximately at (stabilizer number of molecules) / (number of metal atoms). Of these, β-diketone acetylacetone is preferred as the stabilizer.

[Method for producing Mn-doped PZT-based piezoelectric film forming composition]
Next, a method for producing the Mn-doped PZT piezoelectric film-forming composition of the present invention will be described. First, PZT-based precursors such as the Pb compound described above are prepared, and these are weighed so as to have a ratio that gives the desired metal atomic ratio. The above-mentioned weighed PZT precursor and diol are put into a reaction vessel and mixed, and a synthetic solution is preferably prepared by refluxing and reacting at a temperature of 130 to 175 ° C. for 0.5 to 3 hours in a nitrogen atmosphere. To do. After the reflux, it is preferable to remove the solvent by a method of atmospheric distillation or vacuum distillation. Moreover, when adding stabilizers, such as acetylacetone, when inject | pouring the above-mentioned PZT type | system | group precursor and diol in a reaction container, it introduces and mixes with these. Alternatively, it is preferable to add these to the synthesis solution after desolvation and perform reflux at a temperature of 130 to 175 ° C. for 0.5 to 5 hours in a nitrogen atmosphere. Then, the synthetic liquid is cooled to room temperature (about 25 ° C.) by allowing to cool at room temperature. After cooling, by adding a solvent other than the diol, the concentration of the PZT precursor contained in the synthesis solution is adjusted to a desired concentration. The amount of the PZT precursor and diol used is such that the concentration of the PZT precursor in the finally obtained composition of 100% by mass is 17 to 35% by mass in terms of oxide concentration, and the concentration of diol is 16 to 56% by mass. Adjust as follows.

  A sol-gel solution is preferably prepared by adding linear monoalcohol to the cooled synthesis solution. When adding linear monoalcohol, when adding solvents other than the above-mentioned diol to the synthetic liquid after cooling, these are added together to prepare a sol-gel liquid.

  And the polyvinyl pyrrolidone of the quantity from which the ratio with respect to 1 mol of PZT type | system | group precursors is 0.005-0.25 mol in monomer conversion is added to the said sol-gel liquid, and it is made to disperse | distribute uniformly by stirring. As a result, the Mn-doped PZT-based piezoelectric film forming composition of the present invention is obtained.

  After the preparation of the composition, the particles are removed by filtration or the like, and the number of particles having a particle size of 0.5 μm or more (particularly 0.3 μm or more, especially 0.2 μm or more) is 50 or less per milliliter of the composition. It is preferable to do this. If the number of particles having a particle size of 0.5 μm or more in the composition exceeds 50 particles per milliliter of the composition, the long-term storage stability becomes poor. The number of particles having a particle size of 0.5 μm or more in the composition is preferably as small as possible, and particularly preferably 30 or less per milliliter of the composition.

[Method of forming Mn-doped PZT-based piezoelectric film]
Next, a method for forming the Mn-doped PZT piezoelectric film of the present invention will be described. This forming method is a method of forming a piezoelectric film by a sol-gel method, and uses the above-described composition for forming a PZT-based piezoelectric film of Mn dope as a raw material solution.

First, the Mn-doped PZT-based piezoelectric film forming composition is applied on a substrate to form a coating film (gel film) having a desired thickness. The coating method is not particularly limited, and examples thereof include spin coating, dip coating, LSMCD (Liquid Source Misted Chemical Deposition) method, and electrostatic spraying method. As the substrate on which the piezoelectric film is formed, a heat resistant substrate such as a silicon substrate or a sapphire substrate on which a lower electrode is formed is used. The lower electrode formed on the substrate is formed of a material that has conductivity such as Pt, TiO _x , Ir, and Ru and does not react with the piezoelectric film. For example, the lower electrode can have a two-layer structure of a TiO _X film and a Pt film in order from the substrate side. Further, when a silicon substrate is used as the substrate, an SiO ₂ film can be formed on the substrate surface.

Further, on the lower electrode on which the piezoelectric film is formed, an orientation control film in which the crystal orientation is preferentially controlled is formed on the (100) plane or the (001) plane before the piezoelectric film is formed. It is desirable. This is because a Mn-doped PZT-based piezoelectric film can be formed into a film having a uniform polarization direction immediately after film formation by strongly orienting it to the (100) plane or (001) plane. Examples of the orientation control film include an LNO film (LaNiO ₃ film), a PZT film, and a SrTiO ₃ film whose crystal orientation is controlled preferentially on the (100) plane or the (001) plane.

  As a method of setting the preferential crystal orientation of the orientation control layer to the (100) plane, for example, this lower portion of the substrate having the lower electrode in which the crystal plane described in Patent Document 1 is oriented in the (111) axis direction. When a composition for forming a ferroelectric thin film is applied, calcined, and fired on an electrode to form an orientation control layer, a crystal grain size control layer is formed on the lower electrode. The coating amount of the composition for forming a ferroelectric thin film on the control layer is set so that the layer thickness after crystallization of the orientation control layer is in the range of 35 nm to 150 nm, and the temperature during the calcination Can be included in the range of 150 ° C. to 200 ° C. or 285 ° C. to 315 ° C. (hereinafter referred to as the first method).

  Further, as a method of setting the preferential crystal orientation of the orientation control layer to the (110) plane, for example, this lower portion of the substrate having the lower electrode in which the crystal plane described in Patent Document 2 is oriented in the (111) axis direction. When a composition for forming a ferroelectric thin film is applied, calcined, and fired on an electrode to form an orientation control layer, a crystal grain size control layer is formed on the lower electrode. The application amount of the composition for forming a ferroelectric thin film on the control layer is set so that the layer thickness after crystallization of the orientation control layer is in the range of 5 nm to 30 nm, and the temperature during the calcination Can be included in the range of 180 ° C. to 300 ° C. (hereinafter referred to as the second method).

  After a coating film is formed on the substrate, the coating film is calcined and further baked to be crystallized. The calcination is performed under a predetermined condition using a hot plate or a rapid heating process (RTA). The calcination is performed in order to remove the solvent and to convert the metal compound into a composite oxide by thermal decomposition or hydrolysis, and is therefore preferably performed in air, in an oxidizing atmosphere, or in a steam-containing atmosphere. Even in heating in the air, the moisture required for hydrolysis is sufficiently secured by the humidity in the air. In addition, in order to remove a low boiling point solvent and adsorbed water molecules before calcining, low temperature heating (drying) may be performed at a temperature of 70 to 90 ° C. for 0.5 to 5 minutes using a hot plate or the like. Good.

  The calcination is preferably performed by holding at 250 to 300 ° C. for 2 to 5 minutes. However, in order to sufficiently remove the solvent and the like, and to further increase the effect of suppressing voids and cracks, or to promote the densification of the film structure For the reason, it is preferable to carry out by two-stage calcination in which the heating and holding temperature is changed. When performing the two-stage calcination, the first stage is calcination held at 250 to 300 ° C. for 3 to 10 minutes, and the second stage is calcination held at 400 to 500 ° C. for 3 to 10 minutes.

  In the process from application of the composition to calcination, the process up to calcination can be repeated a plurality of times so that the desired film thickness is obtained, and finally baking can be performed collectively. On the other hand, if the composition of the present invention described above is used as a raw material solution, stress due to film shrinkage that occurs during film formation can be suppressed. Therefore, 200 nm can be applied by one application without generating voids or cracks. A thick film up to this range can be formed. Therefore, the number of steps to be repeated can be reduced.

  Firing is a step for crystallizing the calcined coating by heat treatment at a temperature equal to or higher than the crystallization temperature, whereby a piezoelectric film is obtained. The firing atmosphere in this crystallization step is preferably O 2, N 2, Ar, H 2, or a mixed gas thereof. Firing is performed at 600 to 700 ° C. for about 1 to 5 minutes. Firing may be performed by rapid heat treatment (RTA). When firing by rapid heating treatment (RTA), the rate of temperature rise is preferably 2.5 to 100 ° C./second.

  Through the above steps, a Mn-doped PZT-based piezoelectric film can be obtained. This piezoelectric film can improve the piezoelectric constant by doping Mn, so that a larger displacement can be obtained and the dielectric constant can be lowered. Becomes larger. It is considered that this is mainly because the added Mn substituted Zr or Ti to cause oxygen deficiency. Further, as shown in FIG. 1, the hysteresis curve is greatly shifted to the positive side, and the polarization direction is aligned upward immediately after the film formation. Such a film is less prone to depolarization due to heat treatment in the reflow process after polarization treatment, and has excellent polarization stability. Therefore, the device operates stably by applying an electric field on the negative side. Can be made.

  Therefore, this film can be used as a piezoelectric body. Specifically, as shown in FIG. 2, each molecule 11 a in the piezoelectric film 11 is polarized before the DC voltage 14 is applied between the electrodes 12 and 13 disposed on both surfaces of the piezoelectric film 11. The state is maintained (FIG. 2A). As shown in FIG. 2B, when a voltage is applied between the electrodes 12 and 13 disposed on both surfaces of the piezoelectric film 11, the piezoelectric film 11 extends in the direction in which the voltage is applied, and this voltage is applied. When zero, the piezoelectric film 11 extending in the direction in which the voltage is applied contracts and returns to its original state (FIG. 2A), and can be applied to a piezoelectric element or the like.

  Next, examples of the present invention will be described in detail together with comparative examples.

<Example 1>
First, lead acetate trihydrate (Pb source) and propylene glycol (diol) were placed in a reaction vessel, refluxed at a temperature of 150 ° C. for 1 hour in a nitrogen atmosphere, and then titanium tetraisopropoxide ( (Ti source), zirconium tetrabutoxide (Zr source), manganese 2-ethylhexanoate (Mn source), and acetylacetone (stabilizer) are further added and refluxed at a temperature of 150 ° C. for 1 hour in a nitrogen atmosphere. Thus, a synthesis solution was prepared. Here, the lead acetate trihydrate (Pb source), manganese 2-ethylhexanoate (Mn source), zirconium tetrabutoxide (Zr source) and titanium tetraisopropoxide (Ti source) PZT precursors are The metal atomic ratio (Pb: Mn: Zr: Ti) in the liquid was weighed so as to be 1.11: 0.01: 0.52: 0.48. Propylene glycol (diol) is added to 37% by mass with respect to 100% by mass of the prepared composition, and acetylacetone (stabilizer) is 1 mol of PZT precursor contained in the prepared composition. Was added at a ratio of 2 moles. Then, unnecessary solvent was removed by distillation under reduced pressure so that the concentration of the PZT precursor in 100% by mass of the synthetic solution was 35% by mass in terms of oxide concentration. Here, the oxide concentration in the concentration of the PZT-based precursor in the synthesis solution is calculated assuming that all metal atoms contained in the synthesis solution are the target oxide, and is 100% by mass of the synthesis solution. It refers to the concentration of metal oxide (oxide conversion value).

  Subsequently, the synthetic liquid was cooled to 25 ° C. by allowing to cool at room temperature. By adding 1-octanol (C8 linear monoalcohol) and ethanol (solvent) to this synthetic solution, the concentration of the PZT-based precursor in 100% by mass of the sol-gel solution is reduced to the oxide concentration. A sol-gel solution of 25% by mass was obtained. The oxide concentration in the concentration of the PZT precursor in the sol-gel liquid is 100% by mass of the sol-gel liquid calculated on the assumption that all metal atoms contained in the sol-gel liquid have become the target oxide. It refers to the concentration of metal oxide (oxide equivalent value).

  Next, polyvinyl pyrrolidone (PVP: k value = 30) is added to the sol-gel solution so as to be 0.025 mol in terms of monomer with respect to 1 mol of the PZT precursor, and is added at room temperature (25 ° C.). The composition was obtained by stirring for a period of time. This composition used a commercially available membrane filter having a pore size of 0.05 μm, and was pressure-fed with a syringe and filtered, whereby the number of particles having a particle size of 0.5 μm or more was 1 per 1 ml of the solution. Moreover, the density | concentration of the PZT type precursor which occupies in the said composition 100 mass% was 17 mass% in the oxide density | concentration (oxide conversion value). In addition, the oxide concentration in the concentration of the PZT-based precursor in the composition occupies 100% by mass of the composition calculated on the assumption that all metal atoms contained in the composition have become the target oxide. It refers to the concentration of metal oxide (oxide equivalent value). Moreover, 1 mass% of 1-octanol (C8 linear monoalcohol) was contained with respect to 100 mass% of the said composition. Furthermore, 37 mass% of propylene glycol (diol) was contained with respect to 100 mass% of the composition.

On the other hand, a SiO ₂ film, a TiO _x film and a Pt film are laminated in this order from the bottom to the top, and the orientation degree of the (100) plane is 96% on the Pt film by the first method described above. A silicon substrate on which a PZT film serving as an orientation control layer was formed was prepared. Each film thickness is, SiO ₂ film is 500 nm, TiO ₂ film is 20nm and a Pt film was 100 nm. The orientation control layer had a thickness of 60 nm, and the silicon substrate had a diameter of 4 inches. After setting this silicon substrate on a spin coater, 1000 μL of the obtained composition was dropped on the orientation control layer of the silicon substrate, and spin coating was performed at a rotational speed of 1800 rpm for 60 seconds, whereby the orientation control layer was formed. A coating film (gel film) was formed.

  The silicon substrate on which this coating film (gel film) was formed was heated and held (dried) at a temperature of 75 ° C. for 1 minute using a hot plate to remove the low boiling point solvent and water. Thereafter, the gel film was thermally decomposed by heating and holding (first-stage calcination) for 5 minutes on a 300 ° C. hot plate. Furthermore, the organic substance and adsorption water which remain | survive in a gel film were removed by heating-maintaining for 5 minutes at the temperature of 450 degreeC using another hotplate (2nd stage calcination). In this way, a calcined film (Mn-doped PZT amorphous film) having a thickness of 200 nm was obtained. This thickness of 200 nm is the thickness after firing described later.

By repeating the same operation twice as above, a calcined film having a thickness of 400 nm was obtained. This thickness of 400 nm is the thickness after firing described later. Further, the silicon substrate on which the 400 nm-thick calcined film was formed was baked by being held at 700 ° C. for 1 minute in an oxygen atmosphere by rapid heating treatment (RTA). The temperature rising rate at this time was 10 ° C./second. The MZ-doped PZT-based piezoelectric film is formed on the orientation control layer on the Pt film (lower electrode) by repeating a series of operations including application of the composition, calcination of the coating film, and baking three times. did. The measured composition of the piezoelectric film after forming the fluorescent X-ray analysis, the piezoelectric film was film composition represented by Pb1.01Mn0.01Zr _0.52 Ti _0.48 O _3. In Example 1, the following Examples 2 to 11, and Comparative Examples 1 to 4, a decrease in Pb was observed in the film after film formation. This is because the Pb source evaporated during film formation such as firing. It is because of having done.

<Example 2>
Manganese naphthenate was used in place of manganese 2-ethylhexanoate as the Mn source. PZT precursors of lead acetate trihydrate (Pb source), manganese naphthenate (Mn source), zirconium tetrabutoxide (Zr source) and titanium tetraisopropoxide (Ti source) Weighing so that (Pb: Mn: Zr: Ti) was 1.12: 0.02: 0.52: 0.48. It adjusted so that the density | concentration of the PZT type | system | group precursor which occupies in 100 mass% of compositions might be 25 mass% with an oxide density | concentration. Except for the above, a composition was prepared in the same manner as in Example 1. The same (100) plane orientation as in Example 1 was applied on the PZT orientation control layer having a 96% orientation degree in the same manner as in Example 1. A piezoelectric film was formed by repeating calcination and firing. The formed piezoelectric film was a film having a composition represented by Pb _1.02 Mn _0.02 Zr _0.52 Ti _0.48 O ₃ .

<Example 3>
Manganese acetate was used in place of manganese 2-ethylhexanoate as the Mn source. Each PZT-based precursor of lead acetate trihydrate (Pb source), manganese acetate (Mn source), zirconium tetrabutoxide (Zr source) and titanium tetraisopropoxide (Ti source) is added to a metal atomic ratio ( Pb: Mn: Zr: Ti) was weighed so as to be 1.14: 0.042: 0.55: 0.45. It adjusted so that the density | concentration of the PZT type | system | group precursor which occupies in 100 mass% of compositions might be 25 mass% with an oxide density | concentration. A PZT piezoelectric film was formed on the orientation control layer having a (100) plane orientation of 96%. Except for the above, a composition was prepared in the same manner as in Example 1, and coating, calcination, and firing were repeated in the same manner as in Example 1 to form a piezoelectric film. In this example, since the number of stacked layers is five, the last layer was fired at a thickness of 200 nm. The formed piezoelectric film was a film having a composition represented by Pb _1.03 Mn _0.042 Zr _0.52 Ti _0.48 O ₃ .

<Example 4>
As the Mn source, acetylacetone manganese was used instead of manganese 2-ethylhexanoate. Each PZT-based precursor of lead acetate trihydrate (Pb source), acetylacetone manganese (Mn source), zirconium tetrabutoxide (Zr source) and titanium tetraisopropoxide (Ti source) is added to a metal atomic ratio ( Pb: Mn: Zr: Ti) was weighed so that 1.12: 0.02: 0.45: 0.55. It adjusted so that the density | concentration of the PZT type | system | group precursor which occupies in 100 mass% of compositions might be 25 mass% with an oxide density | concentration. A PZT orientation control layer was formed on the orientation control layer having a (100) plane orientation degree of 96%. Except for the above, a composition was prepared in the same manner as in Example 1, and coating, calcination, and firing were repeated in the same manner as in Example 1 to form a piezoelectric film. The formed piezoelectric film was a film having a composition represented by Pb _1.02 Mn _0.02 Zr _0.45 Ti _0.55 O ₃ .

<Example 5>
As the Mn source, acetylacetone manganese was used instead of manganese 2-ethylhexanoate. Each PZT-based precursor of lead acetate trihydrate (Pb source), acetylacetone manganese (Mn source), zirconium tetrabutoxide (Zr source) and titanium tetraisopropoxide (Ti source) is added to a metal atomic ratio ( Pb: Mn: Zr: Ti) was weighed so as to be 1.12: 0.02: 0.60: 0.40. It adjusted so that the density | concentration of the PZT type | system | group precursor which occupies in 100 mass% of compositions might be 25 mass% with an oxide density | concentration. A piezoelectric film was formed on the PZT orientation control layer having a (100) plane orientation of 96%. Except for the above, a composition was prepared in the same manner as in Example 1, and coating, calcination, and firing were repeated in the same manner as in Example 1 to form a piezoelectric film. The formed piezoelectric film was a film having a composition represented by Pb _1.02 Mn _0.02 Zr _0.60 Ti _0.40 O ₃ .

<Example 6>
As the Mn source, acetylacetone manganese was used instead of manganese 2-ethylhexanoate. Each PZT-based precursor of lead acetate trihydrate (Pb source), acetylacetone manganese (Mn source), zirconium tetrabutoxide (Zr source) and titanium tetraisopropoxide (Ti source) is added to a metal atomic ratio ( Pb: Mn: Zr: Ti) was weighed so as to be 1.12: 0.02: 0.52: 0.48. It adjusted so that the density | concentration of the PZT type | system | group precursor which occupies in 100 mass% of compositions might be 25 mass% with an oxide density | concentration. Further, a piezoelectric film was formed on the orientation control layer having a (100) plane orientation degree of 76% by the first method described above. Except for the above, a composition was prepared in the same manner as in Example 1, and coating, calcination, and firing were repeated in the same manner as in Example 1 to form a piezoelectric film. The formed piezoelectric film was a film having a composition represented by Pb _1.02 Mn _0.02 Zr _0.52 Ti _0.48 O ₃ .

<Comparative Example 1>
As the Mn source, acetylacetone manganese was used instead of manganese 2-ethylhexanoate. Each PZT-based precursor of lead acetate trihydrate (Pb source), acetylacetone manganese (Mn source), zirconium tetrabutoxide (Zr source) and titanium tetraisopropoxide (Ti source) is added to a metal atomic ratio ( Pb: Mn: Zr: Ti) was weighed so as to be 1.15: 0.005: 0.52: 0.48. It adjusted so that the density | concentration of the PZT type | system | group precursor which occupies in 100 mass% of compositions might be 25 mass% with an oxide density | concentration. Except for the above, a composition was prepared in the same manner as in Example 1, and the same (100) plane orientation as in Example 1 was applied on the PZT orientation control layer having a 96% orientation degree in the same manner as in Example 1, A piezoelectric film was formed by repeating firing and firing. The formed piezoelectric film was a film having a composition represented by Pb _1.02 Mn _0.005 Zr _0.52 Ti _0.48 O ₃ .

<Comparative example 2>
As the Mn source, acetylacetone manganese was used instead of manganese 2-ethylhexanoate. Each PZT-based precursor of lead acetate trihydrate (Pb source), acetylacetone manganese (Mn source), zirconium tetrabutoxide (Zr source) and titanium tetraisopropoxide (Ti source) is added to a metal atomic ratio ( Pb: Mn: Zr: Ti) was weighed so as to be 1.12: 0.02: 0.52: 0.48. It adjusted so that the density | concentration of the PZT type | system | group precursor which occupies in 100 mass% of compositions might be 25 mass% with an oxide density | concentration. A piezoelectric film was formed on the orientation control layer having a (100) plane orientation of 90%. Except for the above, a composition was prepared in the same manner as in Example 1, and applied, calcined, and baked in the same manner as in Example 1 to form a piezoelectric film. The formed piezoelectric film was a film having a composition represented by Pb _1.01 Mn _0.02 Zr _0.52 Ti _0.48 O ₃ .

<Comparative Example 3>
As the Mn source, acetylacetone manganese was used instead of manganese 2-ethylhexanoate. Each PZT-based precursor of lead acetate trihydrate (Pb source), acetylacetone manganese (Mn source), zirconium tetrabutoxide (Zr source) and titanium tetraisopropoxide (Ti source) is added to a metal atomic ratio ( Pb: Mn: Zr: Ti) was weighed so as to be 1.11: 0.02: 0.52: 0.48. It adjusted so that the density | concentration of the PZT type | system | group precursor which occupies in 100 mass% of compositions might be 25 mass% with an oxide density | concentration. In addition, a piezoelectric film was formed on the orientation control layer having an orientation degree of (110) / (101) plane of 90% and an orientation degree of (100) / (001) plane of 0% by the second method described above. . Except for the above, a composition was prepared in the same manner as in Example 1, and coating, calcination, and firing were repeated in the same manner as in Example 1 to form a piezoelectric film. The formed piezoelectric film was a film having a composition represented by Pb _1.02 Mn _0.02 Zr _0.52 Ti _0.48 O ₃ .

<Comparative example 4>
The same PbT, Mn, Zr, and Ti source PZT precursors as in Example 4 had a metal atomic ratio (Pb: Mn: Zr: Ti) in the liquid of 1.15: 0.05: 0. Weighed to 45: 0.55. Except for this, a composition was prepared in the same manner as in Example 4, and coating, calcination, and firing were repeated in the same manner as in Example 1 to form a piezoelectric film. The formed piezoelectric film was a film having a composition represented by Pb _1.06 Mn _0.05 Zr _0.45 Ti _0.55 O ₃ .

<Example 7>
A composition was synthesized in the same manner as in Example 1. Lead acetate trihydrate (Pb source), acetylacetone manganese (Mn source), niobium pentaethoxide (Nb source), zirconium tetrabutoxide (Zr source) and titanium tetraisopropoxide (Ti source) PZT precursors Was weighed so that the metal atomic ratio (Pb: Mn: Nb: Zr: Ti) in the liquid was 1.14: 0.02: 0.01: 0.52: 0.48. It adjusted so that the density | concentration of the PZT type | system | group precursor which occupies in 100 mass% of compositions might be 25 mass% with an oxide density | concentration. A piezoelectric film was formed on the PZT orientation control layer having a (100) / (001) plane orientation degree of 96%. Except for the above, a composition was prepared in the same manner as in Example 1, and coating, calcination, and firing were repeated in the same manner as in Example 1 to form a piezoelectric film. The formed piezoelectric film was a film having a composition represented by Pb _1.02 Mn _0.02 Nb _0.01 Zr _0.52 Ti _0.48 O ₃ .

<Example 8>
A composition was synthesized in the same manner as in Example 1. Lead acetate trihydrate (Pb source), acetylacetone manganese (Mn source), niobium pentaethoxide (Nb source), zirconium tetrabutoxide (Zr source) and titanium tetraisopropoxide (Ti source) PZT precursors Were weighed so that the metal atomic ratio (Pb: Mn: Nb: Zr: Ti) in the liquid was 1.14: 0.02: 0.01: 0.40: 0.60. It adjusted so that the density | concentration of the PZT type | system | group precursor which occupies in 100 mass% of compositions might be 25 mass% with an oxide density | concentration. A piezoelectric film was formed on the orientation control layer having a (100) / (001) plane orientation degree of 96%. Except for the above, a composition was prepared in the same manner as in Example 1, and coating, calcination, and firing were repeated in the same manner as in Example 1 to form a piezoelectric film. The formed piezoelectric film was a film having a composition represented by Pb _1.02 Mn _0.02 Nb _0.01 Zr _0.40 Ti _0.60 O ₃ .

<Example 9>
A composition was synthesized in the same manner as in Example 1. Lead acetate trihydrate (Pb source), acetylacetone manganese (Mn source), lanthanum acetate hemihydrate (La source), zirconium tetrabutoxide (Zr source) and titanium tetraisopropoxide (Ti source) The PZT-based precursor was weighed so that the metal atomic ratio (Pb: La: Mn: Zr: Ti) in the liquid was 1.14: 0.01: 0.02: 0.55: 0.45. It adjusted so that the density | concentration of the PZT type | system | group precursor which occupies in 100 mass% of compositions might be 25 mass% with an oxide density | concentration. A piezoelectric film was formed on the PZT orientation control layer having a (100) / (001) plane orientation degree of 96%. Except for the above, a composition was prepared in the same manner as in Example 1, and coating, calcination, and firing were repeated in the same manner as in Example 1 to form a piezoelectric film. The formed piezoelectric film was a film having a composition represented by Pb _1.01 La _0.01 Mn _0.02 Zr _0.55 Ti _0.45 O ₃ .

<Example 10>
A composition was synthesized in the same manner as in Example 1. Lead acetate trihydrate (Pb source), acetylacetone manganese (Mn source), lanthanum acetate hemihydrate (La source), zirconium tetrabutoxide (Zr source) and titanium tetraisopropoxide (Ti source) The PZT precursor was weighed so that the metal atomic ratio (Pb: La: Mn: Zr: Ti) in the liquid was 1.15: 0.02: 0.02: 0.50: 0.50. It adjusted so that the density | concentration of the PZT type | system | group precursor which occupies in 100 mass% of compositions might be 25 mass% with an oxide density | concentration. A piezoelectric film was formed on the PZT orientation control layer having a (100) / (001) plane orientation degree of 96%. Except for the above, a composition was prepared in the same manner as in Example 1, and coating, calcination, and firing were repeated in the same manner as in Example 1 to form a piezoelectric film. The formed piezoelectric film was a film having a composition represented by Pb _1.011 La _0.02 Mn _0.02 Zr _0.50 Ti _0.50 O ₃ .

<Example 11>
A composition was synthesized in the same manner as in Example 1. Lead acetate trihydrate (Pb source), acetylacetone manganese (Mn source), lanthanum acetate hemihydrate (La source), zirconium tetrabutoxide (Zr source) and titanium tetraisopropoxide (Ti source) The PZT-based precursor was weighed so that the metal atomic ratio (Pb: La: Mn: Zr: Ti) in the liquid was 1.14: 0.01: 0.02: 0.52: 0.48. It adjusted so that the density | concentration of the PZT type | system | group precursor which occupies in 100 mass% of compositions might be 25 mass% with an oxide density | concentration. A piezoelectric film was formed on the PZT orientation control layer having a (100) / (001) plane orientation degree of 96%. Except for the above, a composition was prepared in the same manner as in Example 1, and coating, calcination, and firing were repeated in the same manner as in Example 1 to form a piezoelectric film. The formed piezoelectric film was a film having a composition represented by Pb _1.01 La _0.01 Mn _0.02 Zr _0.52 Ti _0.48 O ₃ .

<Comparison test and evaluation>
Regarding the piezoelectric films formed in Examples 1 to 11 and Comparative Examples 1 to 4, the film thickness, the degree of orientation of the orientation control layer, the piezoelectric constant, the degree of orientation of the piezoelectric film, and the deviation of the hysteresis loop of the polarization-electric field characteristics (hereinafter referred to as the following) , Simply referred to as “hysteresis deviation”). Table 1 shows the composition and film thickness results of the piezoelectric films formed in Examples 1 to 11 and Comparative Examples 1 to 4. Table 2 below shows the results of orientation degree of the orientation control layer, piezoelectric constant, orientation degree of the piezoelectric film, and hysteresis shift.

  (i) Film thickness of piezoelectric film: The thickness (total thickness) of the cross section of the piezoelectric film was measured by SEM (manufactured by Hitachi, Ltd .: S4300).

  (ii) Piezoelectric constant: The piezoelectric constant d33 of the piezoelectric film was measured by DBLI manufactured by aix ACCT. Specifically, a capacitor structure is formed by a method similar to the method of measuring “(iv) hysteresis shift (shift amount)” described later, the amount of displacement of the film when 25 V is applied is measured, and the inclination is piezoelectric. Constant d33.

(iii) Orientation degree: Measured by a concentration method using CuKα rays using an X-ray diffraction (XRD) apparatus (manufactured by Panalytica, model name: Empyrean). From the obtained diffraction results, the peak intensity of the (100) plane or (001) plane, the peak intensity of the (110) plane or (101) plane, and the peak intensity of the (111) plane were measured, respectively, and the following formula (3 ) Was used to calculate the degree of orientation of the (100) plane or (001) plane (hereinafter abbreviated as “(100) / (001) degree of orientation”). In the PZT thin film near the MPB composition, it is difficult to separate the peaks of the (100) plane, the (001) plane, the (110) plane, and the (101) plane with CuKα rays. ), (110) / (101).
(100) / (001) degree of orientation = (100) / (001) plane strength / {(100) / (001) plane strength + (110) / (101) plane strength + (111) plane strength } (3)

(iv) Hysteresis shift (shift amount): First, a pair of electrodes of 200 μmφ was formed on the upper surface of the piezoelectric film by sputtering, and then held at 700 ° C. for 1 minute in an oxygen atmosphere using RTA. Then, annealing for recovering the damage was performed to fabricate a capacitor structure. Next, using these as test samples, a voltage of 25 V was applied at a frequency of 1 kHz with a TF analyzer 2000 to measure the hysteresis of the polarization amount of the piezoelectric film, and the coercive electric field (Ec) was obtained. Further, the deviation D of hysteresis of the obtained polarization amount was obtained from the above-described equation (1).

(A) Relationship between degree of orientation and hysteresis As shown in Table 1, in Examples 1 to 11, the hysteresis was at least 8.8 kV / cm despite the DRA treatment at 700 ° C. after film formation. Deviation occurred and it was confirmed that a strong internal bias was present in the film. On the other hand, when Example 2, Example 6, and Comparative Example 3 were compared, in Example 6 and Comparative Example 3 in which the degree of (100) / (001) orientation was inferior, the hysteresis shift was small. From this result, it was found that a high degree of orientation is necessary to obtain a larger hysteresis shift.

(b) Relationship between Mn Addition and Hysteresis Deviation When comparing Examples 1 to 11 and Comparative Example 1, the Mn content in the film is less than 0.01 when the total number of moles of Zr and Ti is 1. In Comparative Example 1), it was found that sufficient hysteresis shift was not obtained, and the amount of Mn added was required to be 0.01 or more. In Examples 7 to 11, Mn, La, and Nb are co-doped, but when the amount of Mn added is 0.01 or more, a PMnZT-based film having a large hysteresis shift is obtained as in Examples 1 to 6. I was able to. From this result, it was found that even if other elements were added to the PMnZT film, a hysteresis shift was large and a PMnZT-based film having excellent polarization temperature stability was obtained.

(c) Relationship between Mn Addition Amount and Piezoelectric Characteristics When comparing Examples 1 to 11 and Comparative Example 4, the Mn content in the film exceeds 0.045 with respect to the total number of moles of Zr and Ti being 1. It was found that the amount of Mn added must be 0.045 or less because the piezoelectric constant of Comparative Example 4) is extremely lowered and the function as a piezoelectric body is poor. In Examples 7 to 11, Mn, La, and Nb are co-doped. However, when the amount of Mn added is 0.0045 or less, the piezoelectric constant does not decrease and functions as a piezoelectric body as in Examples 1 to 6. It was found that a PMnZT-based film was obtained.

(d) Relationship between Piezoelectric Film Thickness and Piezoelectric Characteristics When comparing Examples 1 to 11 and Comparative Example 2, if the piezoelectric film thickness is less than 0.8 μm (Comparative Example 2), the piezoelectric constant is extremely high. It has been found that the film thickness of the piezoelectric film needs to be 0.8 μm or more because it becomes smaller and has a poor function as a piezoelectric body. In Examples 7 to 11, Mn, La, and Nb are co-doped. However, when the film thickness of the piezoelectric film is 0.8 μm or more, the piezoelectric constant does not decrease as in Examples 1 to 6, and the piezoelectric body It was found that a PMnZT-based film functioning as

  The Mn-doped PZT piezoelectric film of the present invention can be suitably used as a constituent material in composite electronic parts such as a gyro sensor, an infrared sensor, a piezoelectric sensor, an inkjet head, and an autofocus.

Claims (3)

  A PZT-based piezoelectric film formed by a CSD method made of a Mn-doped composite oxide, wherein the molar ratio of Mn is set to 0.1 when the total number of moles of Zr and Ti in the composite oxide is 1 mole. Mn, wherein the PZT-based piezoelectric film is preferentially crystallized in the (100) plane or the (001) plane and has a thickness of 0.8 to 3 μm. Doped PZT piezoelectric film.   The Mn-doped PZT piezoelectric film according to claim 1, wherein the degree of orientation of the (100) plane or (001) plane by X-ray diffraction is 95% or more. The Mn-doped PZT-based piezoelectric film according to claim 1 or 2, wherein a deviation D of a hysteresis loop of polarization-electric field characteristics obtained by the following formula (1) is at least 8.8 kV / cm.
^{_{D = E C + - [(}} E C + + E C -) / 2] (1)
Where E _C ⁺ is the absolute value of the positive electric field value from 0 kV / cm when the polarization is 0 μC / cm ² , and E _C ⁻ is the negative value from 0 kV / cm when the polarization is 0 μC / cm ² . The absolute value of the electric field value.

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