JP2012054560A - Method of manufacturing piezoelectric element, method of manufacturing ink jet recording head, and method of manufacturing ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel environment-friendly piezoelectric material having excellent piezoelectric characteristics.SOLUTION: The piezoelectric material having a perovskite-type structure is represented by a general formula (1). (BiBa)(FeTi)O...(1), where 0<x<1. x is a Ba composition in the A site of a perovskite-type structure, and a Ti composition in the B site. The piezoelectric material is extremely useful because it contains no environmentally problematic lead (Pb). The piezoelectric material is lead-free, and yet ensures good piezoelectric characteristics, e.g. a sufficient amount of the lattice distortion.

Description

  The present invention relates to a piezoelectric material and a piezoelectric element.

A piezoelectric element used for an ink jet printer head or the like has a piezoelectric layer made of a piezoelectric material. A typical example of this piezoelectric material is Pb (Zr, Ti) O ₃ (PZT) (see, for example, JP-A-2001-223404). However, since PZT and the like contain lead (Pb), there is a very environmental problem.

JP 2001-223404 A

An object of the present invention is to provide a novel piezoelectric material that is environmentally friendly and excellent in piezoelectric characteristics, and a piezoelectric element having a piezoelectric layer made of the piezoelectric material.

The piezoelectric material according to the present invention is
It is represented by the following general formula (1).
(Bi _1-x Ba _x ) (Fe _1-x Ti _x ) O ₃ (1)

  However, 0 <x <1.

This piezoelectric material is extremely useful because it does not contain lead (Pb) which causes environmental problems. Furthermore, this piezoelectric material can obtain a good piezoelectric characteristic, for example, a sufficient lattice strain amount, while being lead-free.

In the piezoelectric material according to the present invention,
0 <x ≦ 0.50 may be satisfied.

In the piezoelectric material according to the present invention,
It can be oriented to (100) in a pseudo cubic display.

In the present invention, for example, “oriented to (100)” means that all crystals are oriented to (100) and that most crystals (eg, 90% or more) are oriented to (100). And the case where the remaining crystals not oriented to (100) are oriented to (110) or the like. That is, “orientation at (100)” can also be referred to as “priority orientation at (100)”. This is the same in the present invention when, for example, “oriented to (110)”.

In the piezoelectric material according to the present invention,
It can be oriented to (110) in a pseudo cubic display.

In the piezoelectric material according to the present invention,
The polarization direction can be the [111] direction in pseudocubic representation.

In the present invention, “the polarization direction is the [111] direction in the pseudo-cubic crystal display” means that the polarization direction is completely in the [111] direction in the pseudo-cubic crystal display. And the case in which the polarization direction is slightly deviated from the [111] direction in the pseudo-cubic crystal display but is substantially in the [111] direction. The case where the polarization direction is substantially [111] direction in the pseudo cubic crystal display, for example, the polarization direction is the pseudo cubic crystal display in the <111> direction and <1.
For example, the angle between the polarization direction and the <111> direction is 10 ° or less.

The first piezoelectric element according to the present invention is:
A substrate;
A lower electrode formed above the substrate;
A piezoelectric layer formed above the lower electrode;
An upper electrode formed above the piezoelectric layer,
The piezoelectric layer is made of a piezoelectric material represented by the following general formula (1).
(Bi _1-x Ba _x ) (Fe _1-x Ti _x ) O ₃ (1)

  However, 0 <x <1.

In the description of the present invention, the word “upper” is, for example, “specific (hereinafter“
Other specific things (hereinafter referred to as “B”) formed in “above” of “A”). In the description of the present invention, in the case of this example, there are a case where B is directly formed on A and a case where B is formed on A via another. The word “above” is used as included.

In the piezoelectric element according to the present invention,
An elastic layer may be formed above the base and below the lower electrode.

In the description according to the present invention, the word “downward” is, for example, “specific (hereinafter“
Other specific things (hereinafter referred to as “B”) formed in “below” of “A”). In the description according to the present invention, in the case of this example, the case where B is formed directly under A and the case where B is formed under other via A The word “downward” is used as an expression including “.”.

The second piezoelectric element according to the present invention is
A substrate;
A piezoelectric layer formed above the substrate;
A first electrode formed above the piezoelectric layer;
A second electrode formed above the piezoelectric layer and spaced apart from the first electrode,
The piezoelectric layer is made of a piezoelectric material represented by the following general formula (1).
(Bi _1-x Ba _x ) (Fe _1-x Ti _x ) O ₃ (1)

  However, 0 <x <1.

In the piezoelectric element according to the present invention,
0 <x ≦ 0.50 may be satisfied.

In the piezoelectric element according to the present invention,
The piezoelectric material may be oriented to (100) in a pseudo cubic display.

In the piezoelectric element according to the present invention,
The piezoelectric material may be oriented to (110) in a pseudo cubic display.

In the piezoelectric element according to the present invention,
The polarization direction of the piezoelectric material may be a [111] direction in a pseudo cubic display.

In the piezoelectric element according to the present invention,
The piezoelectric material may have a rhombohedral structure.

In the piezoelectric element according to the present invention,
The piezoelectric material may have a monoclinic structure.

Sectional drawing which shows the 1st piezoelectric element which concerns on this embodiment. Sectional drawing which shows the 2nd piezoelectric element which concerns on this embodiment.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

1.1. First, the piezoelectric material according to this embodiment will be described. The piezoelectric material according to the present embodiment is represented by the following general formula (1).
(Bi, Ba) (Fe, Ti) O ₃ (1)

The piezoelectric material according to this embodiment has a perovskite structure. The piezoelectric material is preferably oriented in (100) or (110) in pseudocubic display. The polarization direction of the piezoelectric material is desirably a [111] direction in pseudo cubic display. In pseudo cubic display (
A piezoelectric material that is oriented in (100) or (110) and has a polarization direction in the [111] direction in a pseudo cubic crystal display can have good piezoelectric characteristics. The piezoelectric material according to this embodiment desirably has a rhombohedral structure or a monoclinic structure. The valence of each element in the piezoelectric material is as follows: Bi is +3 valence, Ba is +2 valence, Fe is +3 valence, Ti is +4
The valence and O are preferably -2 values. Thereby, the piezoelectric material can be charge neutral.

The general formula (1) can also be represented by the following general formula (1 ′) or (1 ″).
(Bi _1-x Ba _x ) (Fe _1-x Ti _x ) O ₃ (1 ′)
(1-x) BiFeO ₃ —xBaTiO ₃ (1 ″)

However, 0 <x <1 and preferably 0 <x ≦ 0.50. x is the Ba composition at the A site of the perovskite structure, and the Ti composition at the B site.

1.2. The piezoelectric material according to the present embodiment is extremely useful because it does not contain lead (Pb) that causes environmental problems. Furthermore, the piezoelectric material according to the present embodiment can obtain good piezoelectric characteristics, for example, a sufficient lattice strain amount, while being lead-free. This has been confirmed in experimental examples described later.

2.1. Next, the first piezoelectric element 100 according to this embodiment will be described. FIG.
It is sectional drawing which shows typically an example of the 1st piezoelectric element 100 which has the piezoelectric material layer 6 which consists of a piezoelectric material which concerns on this embodiment.

The piezoelectric element 100 is formed on the base 2, the lower electrode 4 formed above the base 2, the piezoelectric layer 6 formed on the lower electrode 4 and made of the above-described piezoelectric material, and the piezoelectric layer 6. And an upper electrode 7. The piezoelectric element 100 can further include an elastic layer 3 formed on the base 2 and below the lower electrode 4. The lower electrode 4 can be formed on the elastic layer 3. Note that the piezoelectric element 100 may not have the elastic layer 3.

As the substrate 2, for example, a (110) -oriented single crystal silicon substrate can be used, and is not particularly limited. The substrate 2 may be a single substrate or a laminate in which other layers are laminated on the substrate. The elastic layer 3 can be applied as an elastic plate in an ink jet recording head, for example. As the elastic layer 3, for example, a film in which silicon oxide and zirconium oxide are laminated in this order can be used, and the elastic layer 3 is not particularly limited. The thickness of the elastic layer 3 is, for example, about 1 μm. The substrate 2 can have, for example, a cavity 20 below the elastic layer 3 and opened in the substrate 2.

The lower electrode 4 is one electrode for applying a voltage to the piezoelectric layer 6. The film thickness of the lower electrode 4 is, for example, 100 nm to 300 nm. The lower electrode 4 is not particularly limited. For example, a film in which a conductive oxide having a perovskite structure (for example, LaNiO ₃ or SrRuO ₃ ) is stacked on a metal film such as platinum (Pt) is used. it can. For example, it is desirable that the film made of the conductive oxide is oriented to (100) or (110) in the pseudo cubic crystal display as in the piezoelectric layer 6 made of the piezoelectric material. Thereby, the crystal structure and orientation of the conductive oxide film are succeeded, and the lower electrode 4 has a perovskite structure and is oriented to (100) or (110) in a pseudo cubic crystal display. The piezoelectric layer 6 made of a piezoelectric material can be easily obtained.

The piezoelectric layer 6 is made of the piezoelectric material according to the present embodiment described above. The film thickness of the piezoelectric layer 6 is not particularly limited, but is, for example, 200 nm to 1.5 μm.

The upper electrode 7 is the other electrode for applying a voltage to the piezoelectric layer 6. As the upper electrode 7, for example, a single layer of platinum (Pt), iridium (Ir), iridium oxide (IrOx), a conductive oxide having a perovskite structure (for example, LaNiO ₃ , SrRuO _3, etc.), or these A laminate can be used and is not particularly limited. The film thickness of the upper electrode 7 is
For example, it is 100 nm to 200 nm.

The lower electrode 4, the piezoelectric layer 6, and the upper electrode 7 can be patterned as shown in FIG. 1, for example, to form a columnar deposit (columnar portion) 50.

2.2. Next, a method for manufacturing the first piezoelectric element 100 according to this embodiment will be described with reference to FIG.

(A) First, the elastic layer 3 is formed on the substrate 2. The elastic layer 3 can be formed by, for example, a thermal oxidation method, a chemical vapor deposition (CVD) method, a sputtering method, a vapor deposition method, or the like.

(B) Next, the lower electrode 4 is formed on the elastic layer 3. The lower electrode 4 can be formed, for example, by sputtering, spin coating, CVD, laser ablation, or the like.

(C) Next, a piezoelectric layer 6 made of the piezoelectric material according to the present embodiment is formed on the lower electrode 4. The piezoelectric layer 6 can be formed using, for example, a sol-gel method, a MOD (Metal Organic Decomposition) method, or the like. The method for forming the piezoelectric layer 6 when using the sol-gel method or the MOD method is specifically as follows.

First, a precursor solution for forming the piezoelectric layer 6 is applied onto the lower electrode 4 by using, for example, a spin coating method (precursor solution applying step). For the precursor solution, for example, an organometallic compound containing each of the constituent metals of the piezoelectric material to be the piezoelectric layer 6 is mixed so that each constituent metal has a desired molar ratio, and the mixture is mixed with an organic solvent such as alcohol. It can be prepared by dissolving or dispersing using As an organometallic compound containing a constituent metal of a piezoelectric material,
For example, metal alkoxides, organic acid salts, β-diketone complexes, and the like can be used. Examples of the organometallic compound containing the constituent metals (Bi, Ba, Fe, Ti) of the piezoelectric material include the following.

Examples of the organometallic compound containing bismuth (Bi) include bismuth isopropoxide. Examples of the organometallic compound containing barium (Ba) include barium ethoxide. Examples of the organometallic compound containing iron (Fe) include iron acetate. Examples of the organometallic compound containing titanium (Ti) include titanium isopropoxide. The organometallic compound containing the constituent metal of the piezoelectric material is not limited to these.

Various additives such as a stabilizer can be added to the precursor solution as necessary. When hydrolysis and polycondensation are caused in the precursor solution, together with an appropriate amount of water in the precursor solution,
An acid or base can be added as a catalyst. Examples of the additive to the precursor solution include diethanolamine and acetic acid.

For example, the spin rotation speed in spin coating is initially set to about 500 rpm, and then the rotation speed can be increased to about 2000 rpm so that coating unevenness does not occur.

Next, heat treatment is performed at a temperature, for example, about 10 ° C. higher than the boiling point of the solvent used in the precursor solution using a hot plate or the like in an air atmosphere (dry heat treatment step).

Next, in order to decompose and remove the ligand of the organometallic compound used in the precursor solution, heat treatment is performed, for example, at about 300 ° C. to 400 ° C. using a hot plate or the like in the atmosphere (degreasing heat treatment step).

In addition, a series of processes of the precursor solution coating process, the drying heat treatment process, and the degreasing heat treatment process described above can be repeated as appropriate according to the desired film thickness.

Next, the piezoelectric layer 6 is obtained by performing a crystallization annealing, that is, a firing step for crystallization.
The crystallization annealing can be performed at about 550 ° C. to 650 ° C. in an oxygen atmosphere by, for example, RTA (Rapid Thermal Annealing).

The piezoelectric layer 6 can be formed using not only a liquid phase method such as a sol-gel method or a MOD method, but also a vapor phase method such as a laser ablation method or a sputtering method.

(D) Next, the upper electrode 7 is formed on the piezoelectric layer 6. The upper electrode 7 can be formed by, for example, sputtering, spin coating, chemical vapor deposition (CVD), laser ablation, or the like.

(E) Next, post-annealing can be performed as necessary. Thereby, a good interface between the piezoelectric layer 6 and the upper and lower electrodes can be formed, and the crystallinity of the piezoelectric layer 6 can be improved. The post-annealing can be performed in an oxygen atmosphere by, for example, RTA.

(F) Next, if necessary, each member can be patterned by etching to form, for example, the columnar portion 50 and the cavity 20.

Through the above steps, the first piezoelectric element 100 according to the present embodiment can be manufactured.

2.3. In the first piezoelectric element 100 according to this embodiment, the piezoelectric layer 6 is made of the above-described piezoelectric material. As described above, this piezoelectric material can have good piezoelectric characteristics while being lead-free. Therefore, according to the present embodiment, it is possible to provide a piezoelectric element that is environmentally friendly and has excellent piezoelectric characteristics.

  2.4. Next, experimental examples will be described.

  An experimental sample of the first piezoelectric element 100 according to the present embodiment was obtained by the following method.

First, an SiO ₂ film having a thickness of 500 nm, Zr on a (110) oriented silicon substrate (base 2).
An elastic layer 3 was obtained by laminating O ₂ films with a thickness of 500 nm. A SiO ₂ film was formed by a thermal oxidation method, and a ZrO ₂ film was formed by a sputtering method. Next, as a lower electrode 4, a Pt film having a thickness of 200 nm and a LaNiO ₃ film having a thickness of 100 nm were sequentially stacked on the ZrO ₂ film by sputtering. The power for sputtering the Pt film and the LaNiO ₃ film was 200 W. The orientation of the obtained LaNiO ₃ film was confirmed to be oriented to (100) in the pseudo cubic crystal display.

Next, a piezoelectric layer 6 made of the above-described piezoelectric material was formed on the LaNiO ₃ film. In this experimental example, as the piezoelectric material, the above-described general formula (1 ′):
(Bi _1-x Ba _x ) (Fe _1-x Ti _x ) O ₃ (1 ′)
In this example, x was changed from 0.05 to 0.05 in increments of 0.05.

  Specifically, the piezoelectric layer 6 was obtained as follows.

First, reagents for organometallic compounds (bismuth isopropoxide, barium ethoxide, iron acetate, titanium isopropoxide) containing the constituent metals of the piezoelectric material were prepared. Next, they were mixed so as to have a molar ratio corresponding to the composition of the desired piezoelectric material, and dissolved (dispersed) in butyl cellosolve. Furthermore, diethanolamine was added as a stabilizer for this solution. Thus, the precursor solution of the piezoelectric material described above was prepared.

Next, this precursor solution was applied onto the lower electrode 4 by a spin coat method (precursor solution application step). Next, about 10 ° C from the boiling point of the solvent (about 170 ° C in the case of butyl cellosolve)
Heat treatment (drying) was performed at a high temperature to remove the solvent and cause gelation (dry heat treatment step). Next, by heating to about 400 ° C., organic components other than the solvent remaining in the film were decomposed / removed (degreasing heat treatment step) to form an amorphous film having a thickness of 100 nm. The above process was repeated 5 times. Next, the piezoelectric layer 6 having a film thickness of 500 nm was formed by crystallization by heating at 600 ° C. for 1 minute in an oxygen atmosphere by RTA.

It was confirmed that the crystal structure of the piezoelectric material constituting the obtained piezoelectric layer 6 was a perovskite type structure, which was a rhombohedral structure or a monoclinic structure. Therefore, it is estimated that the polarization direction of the piezoelectric material is the [111] direction in the pseudo cubic crystal display. The piezoelectric material was confirmed to be oriented to (100) in the pseudo cubic display. X-ray θ-2θ measurement and Raman scattering were used to identify the crystal structure, polarization direction, and orientation of the piezoelectric material.

Next, a 200 nm-thick P film is formed on the piezoelectric layer 6 as the upper electrode 7 by sputtering.
A t film was formed.

Each experimental sample of the piezoelectric element 100 was obtained as described above. Table 1 shows the strain amount of the lattice of the piezoelectric material when an electric field of 100 kV / cm is applied from the upper and lower electrodes to the piezoelectric layer 6 of these experimental samples. The strain amount of the lattice was determined from θ-2θ measurement by electric field X-ray.

As shown in Table 1, in the experimental sample having a Ba composition (Ti composition) x of 0.05 to 0.50, the strain amount of the lattice was 0.15% or more, and good piezoelectric characteristics were confirmed. As a reference example, an experimental sample in which x is 0 (zero) was also produced. In this case, the lattice strain was 0.07%, as shown in Table 1.

From the above experimental results, it was confirmed that the piezoelectric material according to the present embodiment has good piezoelectric characteristics.

3.1. Next, the second piezoelectric element 200 according to this embodiment will be described. FIG.
It is sectional drawing which shows typically an example of the 2nd piezoelectric element 200 which has the piezoelectric material layer 6 which consists of a piezoelectric material which concerns on this embodiment. The same members as those of the first piezoelectric element 100 described above are denoted by the same reference numerals, and detailed description thereof is omitted.

The piezoelectric element 200 is formed on the substrate 2, the piezoelectric layer 6 formed above the substrate 2 and made of the above-described piezoelectric material, the first electrode 40 formed on the piezoelectric layer 6, and the piezoelectric layer 6. Formed second
An electrode 70. The piezoelectric element 200 can have a buffer layer 30 formed on the substrate 2. The piezoelectric layer 6 can be formed on the buffer layer 30.

The buffer layer 30 can have a function of controlling the crystal orientation of the piezoelectric layer 6. For example, when the substrate 2 has this function, the buffer layer 30 may not be provided. The buffer layer 30 has, for example, a perovskite structure and is displayed in a pseudo cubic (100
) Or (110). As a result, the crystal structure and orientation of the buffer layer 30 are inherited, and the piezoelectric material has a perovskite structure on the buffer layer 30 and is oriented to (100) or (110) in the pseudo cubic crystal display. The piezoelectric layer 6 can be easily obtained. As an oxide constituting the buffer layer 30,
Examples thereof include LaNiO ₃ and SrRuO ₃ .

The first electrode 40 and the second electrode 70 are electrodes for applying a voltage to the piezoelectric layer 6.
Examples of the first electrode 40 and the second electrode 70 include platinum (Pt) and iridium (Ir).
, Iridium oxide (IrOx), conductive oxide having a perovskite structure (for example, LaNi
A single layer such as O ₃ , SrRuO ₃ , or the like, or a laminate thereof can be used, and is not particularly limited. The film thicknesses of the first electrode 40 and the second electrode 70 are, for example, 100 nm to 200 n.
m.

3.2. Next, a method for manufacturing the second piezoelectric element 200 according to this embodiment will be described with reference to FIG.

(A) First, the buffer layer 30 is formed on the substrate 2. The buffer layer 30 can be formed by, for example, sputtering, spin coating, CVD, laser ablation, or the like.

(B) Next, the piezoelectric layer 6 is formed on the buffer layer 30. Since this process is the same as the one manufacturing process of the first piezoelectric element 100 described above, detailed description thereof is omitted.

(C) Next, the first electrode 40 and the second electrode 70 are formed on the piezoelectric layer 6. The first electrode 40 and the second electrode 70 can be formed by, for example, a sputtering method, a spin coating method, a CVD method, a laser ablation method, or the like. The first electrode 40 and the second electrode 70 can be patterned by a known method.

(D) Next, post-annealing can be performed as necessary. Since this process is the same as the one manufacturing process of the first piezoelectric element 100 described above, detailed description thereof is omitted.

Through the above steps, the second piezoelectric element 200 according to the present embodiment can be manufactured.

3.3. Like the first piezoelectric element 100, the second piezoelectric element 200 according to this embodiment is environmentally friendly and can have excellent piezoelectric characteristics.

4). Although the embodiments of the present invention have been described in detail as described above, those skilled in the art will readily understand that many modifications are possible without substantially departing from the novel matters and effects of the present invention. Accordingly, all such modifications are intended to be included in the scope of the present invention.

For example, the above-described piezoelectric element according to the embodiment of the present invention includes, for example, an ink jet recording head, an actuator, a gyro sensor, and an FB used in an ink jet printer.
BAW (bulk acoustic wave) filter such as AR (film bulk acoustic resonator) type and SMR (so lid mounted resonator) type, SAW (surface acoustic wave) filter,
It can be applied to an ultrasonic motor or the like. The piezoelectric element according to the embodiment of the present invention has excellent piezoelectric characteristics and can be suitably applied to various applications.

2 Base, 3 Elastic layer, 4 Lower electrode, 6 Piezoelectric layer, 7 Upper electrode, 20 Cavity, 30 Buffer layer, 40 1st electrode, 50 Columnar part, 70 2nd electrode, 100 1st
200, the second piezoelectric element.

Claims (11)

A piezoelectric material represented by the following general formula (1).
(Bi _1-x Ba _x ) (Fe _1-x Ti _x ) O ₃ (1)
However, 0 <x <1. In claim 1,
Piezoelectric material where 0 <x ≦ 0.50. In claim 1 or 2,
Piezoelectric material that is oriented to (100) in pseudo cubic form. In claim 1 or 2,
Piezoelectric material oriented in (110) on a pseudocubic display. A substrate;
A lower electrode formed above the substrate;
A piezoelectric layer formed above the lower electrode;
An upper electrode formed above the piezoelectric layer,
The piezoelectric layer is a piezoelectric element made of a piezoelectric material represented by the following general formula (1).
(Bi _1-x Ba _x ) (Fe _1-x Ti _x ) O ₃ (1)
However, 0 <x <1. A substrate;
A piezoelectric layer formed above the substrate;
A first electrode formed above the piezoelectric layer;
A second electrode formed above the piezoelectric layer and spaced apart from the first electrode,
The piezoelectric layer is a piezoelectric element made of a piezoelectric material represented by the following general formula (1).
(Bi _1-x Ba _x ) (Fe _1-x Ti _x ) O ₃ (1)
However, 0 <x <1. In claim 5 or 6,
Piezoelectric element where 0 <x ≦ 0.50. In any of claims 5 to 7,
The piezoelectric material is a piezoelectric element having a pseudo cubic crystal orientation (100). In any of claims 5 to 7,
The piezoelectric material is a piezoelectric element oriented in a (110) pseudo-cubic crystal display. In any one of Claims 5 thru | or 9,
The piezoelectric material has a rhombohedral structure. In any one of Claims 5 thru | or 9,
The piezoelectric material has a monoclinic structure.

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