JP4605348B2 - Piezoelectric element, piezoelectric actuator, piezoelectric pump, ink jet recording head, ink jet printer, surface acoustic wave element, frequency filter, oscillator, electronic circuit, thin film piezoelectric resonator, and electronic device - Google Patents

Description

  The present invention relates to a piezoelectric element having a piezoelectric film, a piezoelectric actuator, a piezoelectric pump, an ink jet recording head, an ink jet printer, a surface acoustic wave element, a frequency filter, an oscillator, an electronic circuit, a thin film piezoelectric resonator, and an electronic apparatus.

Inkjet printers are known as printers that enable high image quality and high-speed printing. The ink jet printer includes an ink jet recording head having a cavity whose internal volume changes. An ink jet printer performs printing by ejecting ink droplets from its nozzles while scanning an ink jet recording head. As a head actuator in an ink jet recording head for such an ink jet printer, a piezoelectric element using a piezoelectric film represented by PZT (Pb (Zr, Ti) O ₃ ) has been conventionally used (for example, Patent Document 1).

In addition, since surface acoustic wave elements, frequency filters, oscillators, electronic circuits, and the like are desired to have improved characteristics, it is desired to provide good products using new piezoelectric materials.
JP 2001-223404 A

  By the way, in the ink jet printer, higher image quality and higher speed have been demanded. In order to meet such demands, it has become an indispensable technique to increase the density of nozzles in an ink jet recording head. For this purpose, it is necessary to improve the characteristics of the piezoelectric film, that is, the piezoelectric constant, particularly for the piezoelectric element (head actuator) laminated on the cavity.

  An object of the present invention is to provide a piezoelectric element having good piezoelectric characteristics. Another object of the present invention is to provide a piezoelectric actuator, a piezoelectric pump, an ink jet recording head, an ink jet printer, a surface acoustic wave element, a frequency filter, an oscillator, an electronic circuit, a thin film piezoelectric resonator, and an electronic apparatus using the piezoelectric element. Is to provide.

The piezoelectric element according to the present invention is
A substrate;
A buffer layer formed above the substrate;
A piezoelectric film formed above the buffer layer,
The buffer layer is made of perovskite _{Pb ((Zr 1-a Ti} a) 1-b X b) O 3,
X consists of at least two of V, Nb, and Ta,
a is in the range of 0.15 ≦ a ≦ 0.8,
b is in the range of 0.05 ≦ b ≦ 0.4;
The piezoelectric film is made of a perovskite type relaxor material.

  In the present invention, the substrate includes one layer and a plurality of layers.

  In the present invention, other specific objects (hereinafter referred to as “B”) above a specific object (hereinafter referred to as “A”) are B formed directly on A, A on A, And B formed through the others.

According to this piezoelectric element, the buffer layer made of Pb ((Zr _{1 -a} Ti _a ) _{1 -b} X _b ) O ₃ (hereinafter also referred to as “PZTX”) formed above the base body, And a piezoelectric film made of a relaxor material formed above the buffer layer. With respect to PZTX, a dense thin film can be formed above the substrate while controlling the orientation. Furthermore, the relaxor material can be easily laminated as a dense thin film above the dense PZTX once formed. Therefore, this piezoelectric element can have a piezoelectric film with good piezoelectric characteristics. In other words, this piezoelectric element has a high piezoelectric constant and undergoes greater deformation with respect to the applied voltage.

The piezoelectric element according to the present invention is
A substrate;
A buffer layer formed above the substrate;
A piezoelectric film formed above the buffer layer,
The buffer layer is made of perovskite _{Pb ((Zr 1-a Ti} a) 1-b X b) O 3,
X consists of at least one of V and Ta,
a is in the range of 0.15 ≦ a ≦ 0.8,
b is in the range of 0.05 ≦ b ≦ 0.4;
The piezoelectric film is made of a perovskite type relaxor material.

  According to this piezoelectric element, the buffer layer made of PZTX formed above the substrate and the piezoelectric film made of a relaxor material formed above the buffer layer are included. With respect to PZTX, a dense thin film can be formed above the substrate while controlling the orientation. Furthermore, the relaxor material can be easily laminated as a dense thin film above the dense PZTX once formed. Therefore, this piezoelectric element can have a piezoelectric film with good piezoelectric characteristics. In other words, this piezoelectric element has a high piezoelectric constant and undergoes greater deformation with respect to the applied voltage.

The piezoelectric element according to the present invention is
A substrate;
A buffer layer formed above the substrate;
A piezoelectric film formed above the buffer layer,
The buffer layer is made of perovskite type Pb _{1- (b / 2)} ((Zr _1−a Ti _a ) _1−b X _b ) O ₃ ,
X consists of at least one of V, Nb, and Ta,
a is in the range of 0.15 ≦ a ≦ 0.8,
b is in the range of 0.05 ≦ b ≦ 0.4;
The piezoelectric film is made of a perovskite type relaxor material.

According to this piezoelectric element, from Pb _{1- (b / 2)} ((Zr _1-a Ti _a ) _1-b X _b ) O ₃ (hereinafter also referred to as “PZTX”) formed above the substrate. The buffer layer, and a piezoelectric film made of a relaxor material formed above the buffer layer. With respect to PZTX, a dense thin film can be formed above the substrate while controlling the orientation. Furthermore, the relaxor material can be easily laminated as a dense thin film above the dense PZTX once formed. Therefore, this piezoelectric element can have a piezoelectric film with good piezoelectric characteristics. In other words, this piezoelectric element has a high piezoelectric constant and undergoes greater deformation with respect to the applied voltage.

In the piezoelectric element according to the present invention,
a is in the range of (a _MPB −0.05) ≦ a ≦ a _MPB ,
a _MPB can indicate the value of a at the phase boundary of the crystal structure of the buffer layer.

In the piezoelectric element according to the present invention,
The buffer layer may have a at the phase boundary of the crystal structure of the buffer layer.

In the piezoelectric element according to the present invention,
The buffer layer may have a rhombohedral structure and be preferentially oriented to pseudo cubic (100).

  In the present invention, the “preferential orientation” means that when 100% of crystals are pseudo-cubic crystals (100) having a desired orientation, and most crystals (pseudo-cubic crystals (100) having a desired orientation ( For example, 90% or more) are oriented and the remaining crystals are in other orientations (for example, (111) orientation).

In the piezoelectric element according to the present invention,
The buffer layer may have a pseudo cubic structure and be preferentially oriented to pseudo cubic (100).

In the piezoelectric element according to the present invention,
The piezoelectric film may have a rhombohedral structure and be preferentially oriented to pseudo cubic (100).

In the piezoelectric element according to the present invention,
The relaxor material can be made of at least one of materials represented by the following formulas (1) to (9).

_{(1-x) Pb (Sc} 1/2 Nb 1/2) O 3 -xPb (Zr 1-y Ti y) O 3 ··· Equation (1)
(Where x is 0.10 <x <0.42, y is 0 ≦ y ≦ 1)
_{(1-x) Pb (In} 1/2 Nb 1/2) O 3 -xPb (Zr 1-y Ti y) O 3 ··· Equation (2)
(Where x is 0.10 <x <0.37, y is 0 ≦ y ≦ 1)
_{(1-x) Pb (Ga} 1/2 Nb 1/2) O 3 -xPb (Zr 1-y Ti y) O 3 ··· Equation (3)
(Where x is 0.10 <x <0.50, y is 0 ≦ y ≦ 1)
_{(1-x) Pb (Sc} 1/2 Ta 1/2) O 3 -xPb (Zr 1-y Ti y) O 3 ··· Equation (4)
(Where x is 0.10 <x <0.45, y is 0 ≦ y ≦ 1)
(1-x) Pb (Mg _1/3 Nb _2/3 ) O ₃ -xPb (Zr _1-y Ti _y ) O ₃ Formula (5)
(Where x is 0.10 <x <0.35, y is 0 ≦ y ≦ 1)
_{(1-x) Pb (Fe} 1/2 Nb 1/2) O 3 -xPb (Zr 1-y Ti y) O 3 ··· Equation (6)
(Where x is 0.01 <x <0.10, y is 0 ≦ y ≦ 1)
(1-x) Pb (Zn _1/3 Nb _2/3 ) O ₃ -xPb (Zr _1-y Ti _y ) O ₃ Formula (7)
(Where x is 0.01 <x <0.10, y is 0 ≦ y ≦ 1)
(1-x) Pb (Ni _1/3 Nb _2/3 ) O ₃ -xPb (Zr _1-y Ti _y ) O ₃ Formula (8)
(Where x is 0.10 <x <0.38, y is 0 ≦ y ≦ 1)
_{(1-x) Pb (Co} 1/2 W 1/2) O 3 -xPb (Zr 1-y Ti y) O 3 ··· Equation (9)
(Where x is 0.10 <x <0.42, y is 0 ≦ y ≦ 1)

In the piezoelectric element according to the present invention,
The buffer layer may include 5 mol% or less of Si, or Si and Ge.

In the piezoelectric element according to the present invention,
A lower electrode formed above the substrate;
The buffer layer formed above the lower electrode;
And an upper electrode formed above the piezoelectric film.

In the piezoelectric element according to the present invention,
At least one of the lower electrode and the upper electrode may be made of a material mainly containing Pt.

  The piezoelectric actuator according to the present invention can have the above-described piezoelectric element.

  The piezoelectric pump according to the present invention can have the above-described piezoelectric element.

  The ink jet recording head according to the present invention can have the above-described piezoelectric element.

  The ink jet printer according to the present invention can have the ink jet recording head described above.

  The surface acoustic wave device according to the present invention may be formed by forming the above-described piezoelectric element above a substrate.

The frequency filter according to the present invention includes a first electrode formed above the piezoelectric film included in the surface acoustic wave element,
And a second electrode formed above the piezoelectric film.

An oscillator according to the present invention includes a first electrode formed above the piezoelectric film included in the surface acoustic wave element,
A second electrode formed above the piezoelectric film;
And an oscillation circuit having a transistor.

  The electronic circuit according to the present invention can include the oscillator described above.

  The thin film piezoelectric resonator according to the present invention can be formed by forming a resonator having the above-described piezoelectric element above a substrate.

  The electronic device according to the present invention can include at least one of the above-described piezoelectric pump, the above-described frequency filter, the above-described oscillator, the above-described electronic circuit, and the above-described thin film piezoelectric resonator.

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

1-1. Piezoelectric Element FIG. 1 is a view showing an embodiment in which the piezoelectric element according to the present invention is applied to a piezoelectric element 1 that is a head actuator for an ink jet recording head.

  The piezoelectric element 1 includes a substrate 2 made of silicon (Si), an elastic film 3 formed on the substrate 2, a lower electrode 4 formed on the elastic film 3, and a buffer layer formed on the lower electrode 4. 5, a piezoelectric film 6 formed on the buffer layer 5, and an upper electrode 7 formed on the piezoelectric film 6. In the present embodiment, the substrate 2 to the lower electrode 4 are referred to as a base.

  As the substrate 2, for example, a (100) -oriented single crystal silicon substrate, a (111) -oriented single crystal silicon substrate, a (110) -oriented silicon substrate, or the like can be used. Alternatively, a silicon substrate having an amorphous silicon oxide film such as a thermal oxide film or a natural oxide film formed on the surface thereof can be used.

The elastic film 3 is a film that functions as an elastic plate in a piezoelectric element that serves as a head actuator for an ink jet recording head. The thickness of the elastic film 3 is, for example, about 1 μm. As will be described later, the elastic film 3 has a sufficient selection ratio with the substrate 2 so that the elastic film 3 functions as an etching stopper layer when the substrate 2 is etched to form a cavity. Can be made of material. That is, for example, when the substrate 2 is made of silicon, the elastic film 3 can be made of, for example, SiO ₂ or ZrO ₂ . The elastic film 3 can be formed as an elastic plate common to the plurality of piezoelectric elements 1 when the plurality of piezoelectric elements 1 are formed on the substrate 2 which is an ink chamber substrate in an ink jet recording head described later.

The lower electrode 4 serves as one electrode for applying a voltage to the piezoelectric film 6. The lower electrode 4 can be formed in the same planar shape as the piezoelectric film 6 and the upper electrode 7, for example. For the lower electrode 4, when a plurality of piezoelectric elements 1 are formed on the substrate 2, which is an ink chamber substrate in an ink jet recording head described later, a common elasticity is used so as to function as an electrode common to the plurality of piezoelectric elements 1. It can be formed in the same planar shape as the elastic film 3 as a plate. The lower electrode 4 can be made of, for example, platinum (Pt), iridium (Ir), iridium oxide (IrO _x ), titanium (Ti), or the like. The thickness of the lower electrode 4 is, for example, about 100 nm to 200 nm.

The buffer layer 5 can be made of perovskite Pb ((Zr _1-a Ti _a ) _1-b X _b ) O ₃ (hereinafter also referred to as “PZTX”). X may consist of at least two of V, Nb, and Ta. Alternatively, X can consist of at least one of V and Ta. The buffer layer 5 has a rhombohedral structure or a pseudo cubic structure, and can be preferentially oriented to pseudo cubic (100).

  Here, the “pseudocubic structure” includes, for example, a rhombohedral structure, a tetragonal structure, and a monoclinic structure. The buffer layer 5 is formed on the lower electrode 4 by a liquid phase method or a gas phase method. The buffer layer 5 can be preferentially oriented to the pseudo-cubic crystal (100) by appropriately controlling the temperature condition (heating condition) and the like during film formation. Here, the “preferential orientation” means that all the crystals are oriented in the pseudo-cubic crystal (100) having a desired orientation, and most crystals are oriented in the pseudo-cubic crystal (100) having the desired orientation. And the case where the remaining crystals that are not oriented in the pseudo cubic (100) are in other orientations. Thus, if most crystals are oriented in the desired orientation of pseudocubic crystal (100), when the piezoelectric film 6 is formed on the buffer layer 5 as will be described later, the piezoelectric film 6 becomes the buffer layer. 5 is succeeded, and the same crystal structure, that is, pseudo cubic (100) is preferentially oriented.

A in Pb ((Zr _1-a Ti _a ) _1-b X _b ) O ₃ has a certain range. The upper limit of a is the value of a at the phase boundary (MPB: Morphotropic Phase Boundary) of the crystal structure of the buffer layer 5 (hereinafter also referred to as “a _MPB ”). The value of a (a _MPB ) at the phase boundary is a value indicating the composition ratio of Ti when the rhombohedral structure and the tetragonal structure undergo phase transition. The range of “a” is smaller than the composition ratio at the time of phase transition, and thus the range becomes a rhombohedral structure. Here, the piezoelectric constant (d ₃₁ ) takes a local maximum near the phase boundary. Therefore, a value close to the value of a (a _MPB ) at the phase boundary is selected as the lower limit value of a. Therefore, as the range of a, although a relatively small value can be allowed in configuring the present invention, in order to obtain a higher piezoelectric constant (d ₃₁ ), a preferable value of a, that is, a value at the phase boundary. A value closer to (a _MPB ) is selected. Therefore, the lower limit value of the range of a is the value of a when the piezoelectric element 1 is operated and the lower limit value of the allowable piezoelectric constant (d ₃₁ ). When the above-mentioned content is expressed by a formula, for example, a is
(A _MPB −0.05) ≦ a ≦ a _MPB
Can range. a _MPB is about 0.5, for example. Note that a _MPB is not particularly limited because it can change depending on the film stress, etc.
0.2 ≦ a _MPB ≦ 0.8
Can range. Therefore, a
0.15 ≦ a ≦ 0.8
Can range.

If a is in the above-mentioned range, the buffer layer 5 can be easily controlled to a rhombohedral structure, and high piezoelectric characteristics can be exhibited. The buffer layer 5 can also have a (a _MPB ) at the phase boundary of the crystal structure of the buffer layer 5. Thereby, the piezoelectric constant (d ₃₁ ) can be set to the maximum value.

Note that the range of a is actually related to measurement errors and the like. That is, for example, a takes into account a measurement error, for example a measurement error of about 2 percent,
(A _MPB −0.05) −0.02 ≦ a ≦ a _MPB +0.02
It is preferable that it is the range of these. The same applies to all numerical ranges described below.

A Pb-based perovskite structure, such as PZT, has a high vapor pressure of Pb, so that Pb located at the A site of the perovskite structure is likely to evaporate. In the above-described PZTX, the case where the composition formula is represented by Pb ((Zr _1−a Ti _a ) _1−b X _b ) O ₃ has been described. However, the composition formula of PZTX is Pb _{1− (b / 2)} (( Zr _1-a Ti _a) can also _1-b X _b) be represented by _{O 3.} In this case, X can be composed of at least one of V, Nb, and Ta. In the composition formula of PZTX, (b / 2) represents the amount of deficiency of Pb.

  When Pb escapes from the A site, oxygen is simultaneously lost due to the principle of charge neutrality. This phenomenon is called a Schottky defect. For example, when oxygen is lost in PZT, the band gap of PZT decreases. Due to the reduction of the band gap, the band offset at the electrode interface is reduced, and the insulating property of the piezoelectric film made of PZT is reduced.

  However, according to the present embodiment, the entire crystal structure is obtained by substituting X (+5 valence) higher in valence than Zr and Ti (+4 valence) with the element (Zr, Ti) at the B site. The neutrality can be maintained, and oxygen deficiency can be prevented. As a result, the insulating property of the buffer layer 5 becomes good, and current leakage can be prevented.

  For example, when X is made of Nb, Nb is almost the same size as Ti (the ionic radius is close and the atomic radius is the same) and the weight is twice, so collisions between atoms due to lattice vibrations. Makes it difficult for atoms to escape from the lattice. Also, even if Pb loss occurs during crystallization, it is easier to enter small Nb than large O (oxygen). Therefore, O (oxygen) escape can be effectively prevented. Furthermore, it is considered that Nb has a strong covalent bond with oxygen and is difficult to escape from the system (H. Miyazawa, E. Natori, S. Miyashita; Jpn. J. Appl. Phys. 39 (2000) 5679. ). Although an example in which X is Nb has been described here, the case where X includes at least one of V and Ta has the same or similar effect.

The deficiency of Pb is preferably approximately half of the addition amount b of X. That is, the loss amount of Pb is indicated by b / 2. Thereby, PZTX can maintain neutrality electrically. And the addition amount b of X is:
0.05 ≦ b ≦ 0.4
It is preferable that it is the range of these. If the added amount b of X is less than 0.05, the current leakage preventing effect due to the addition of X is not good. On the other hand, even if the added amount b of X exceeds 0.4, the current leak preventing effect is not exceeded. I cannot expect much improvement.

  The buffer layer 5 can contain 5 mol% or less of silicon (Si), or silicon and germanium (Ge). Details will be described in the section of a method for manufacturing a piezoelectric element.

  Since the buffer layer 5 is a piezoelectric material, it affects the piezoelectric characteristics of the piezoelectric film 6 described later (helps the piezoelectric characteristics). The buffer layer 5 is not particularly limited as long as the buffer layer 5 has a film thickness that can provide an effect and effect as a buffer layer described later. Specifically, the film thickness of the buffer layer 5 can be, for example, about 10 nm to 1.0 μm.

  The buffer layer 5 can also be composed of a plurality of layers. For example, when the buffer layer 5 is composed of two layers, the buffer layer 5 can be composed of a first PZTX and a second PZTX. Here, the first PZTX and the second PZTX differ in at least one of X, the composition ratio a, and the composition ratio b.

  The piezoelectric film 6 is made of a relaxor material having a perovskite type and a rhombohedral structure and preferentially oriented to pseudo cubic (100), and has a thickness of about 500 nm to 1000 nm. The typical film thickness of the piezoelectric film 6 is 300 nm to 3.0 μm. With respect to the upper limit of the thickness, the thickness can be increased within a range that maintains the denseness and crystal orientation of the thin film, and the thickness is allowed to be about 10 μm.

  As a relaxer material, the material shown by the following formula | equation (1)-(9) is mentioned, for example. One or a plurality of types selected from these are formed by a liquid phase method or a gas phase method as described later, whereby the piezoelectric film 6 is obtained.

_{(1-x) Pb (Sc} 1/2 Nb 1/2) O 3 -xPb (Zr 1-y Ti y) O 3 ··· Equation (1)
(Where x is 0.10 <x <0.42, preferably 0.20 <x <0.42, y is 0 ≦ y ≦ 1)
_{(1-x) Pb (In} 1/2 Nb 1/2) O 3 -xPb (Zr 1-y Ti y) O 3 ··· Equation (2)
(Where x is 0.10 <x <0.37, preferably 0.20 <x <0.37, y is 0 ≦ y ≦ 1)
_{(1-x) Pb (Ga} 1/2 Nb 1/2) O 3 -xPb (Zr 1-y Ti y) O 3 ··· Equation (3)
(Where x is 0.10 <x <0.50, preferably 0.30 <x <0.50, y is 0 ≦ y ≦ 1)
_{(1-x) Pb (Sc} 1/2 Ta 1/2) O 3 -xPb (Zr 1-y Ti y) O 3 ··· Equation (4)
(Where x is 0.10 <x <0.45, preferably 0.20 <x <0.45, y is 0 ≦ y ≦ 1)
(1-x) Pb (Mg _1/3 Nb _2/3 ) O ₃ -xPb (Zr _1-y Ti _y ) O ₃ Formula (5)
(Where x is 0.10 <x <0.35, preferably 0.20 <x <0.35, more preferably X = 0.3, y is 0 ≦ y ≦ 1)
_{(1-x) Pb (Fe} 1/2 Nb 1/2) O 3 -xPb (Zr 1-y Ti y) O 3 ··· Equation (6)
(Where x is 0.01 <x <0.10, preferably 0.03 <x <0.10, y is 0 ≦ y ≦ 1)
(1-x) Pb (Zn _1/3 Nb _2/3 ) O ₃ -xPb (Zr _1-y Ti _y ) O ₃ Formula (7)
(Where x is 0.01 <x <0.10, preferably 0.03 <x <0.09, more preferably X = 0.09, y is 0 ≦ y ≦ 1)
(1-x) Pb (Ni _1/3 Nb _2/3 ) O ₃ -xPb (Zr _1-y Ti _y ) O ₃ Formula (8)
(Where x is 0.10 <x <0.38, preferably 0.20 <x <0.38, more preferably X = 0.3, y is 0 ≦ y ≦ 1)
_{(1-x) Pb (Co} 1/2 W 1/2) O 3 -xPb (Zr 1-y Ti y) O 3 ··· Equation (9)
(Where x is 0.10 <x <0.42, preferably 0.20 <x <0.42, y is 0 ≦ y ≦ 1)

A relaxor material is a material that shows a broad (wide) peak in the temperature dependence of the dielectric constant in a bulk solid as shown in FIG. 2, and the temperature at which the dielectric constant reaches a maximum is shifted by frequency measurement. Say. The relaxor material is a material that exhibits a broad (wide) peak in temperature dependence of the piezoelectric constant. On the other hand, a piezoelectric material which is a non-relaxer material such as Pb (Zr, Ti) O ₃ (hereinafter also referred to as “PZT”) has a very high temperature dependence of dielectric constant and piezoelectric constant as shown in FIG. Shows a sharp peak. Therefore, by using a relaxor material as the piezoelectric film 6, the obtained piezoelectric element 1 exhibits good piezoelectric characteristics in a wide temperature range, which makes the characteristics highly reliable and stable. However, when the film thickness of the relaxor material is about 100 nm to 1 μm, the clear peak shown in FIG. 2 is not always shown. Some relaxor materials having a film thickness of about 100 nm to 1 μm exhibit a more gentle change in dielectric constant between room temperature and 100 ° C.

The piezoelectric film 6 is a perovskite type having a rhombohedral structure and preferentially oriented to pseudo cubic (100), and is called an engineered domain arrangement. Therefore, the piezoelectric film 6 has a high piezoelectric constant (d ₃₁ ). Here, as described above, the “preferential orientation” means that all the crystals are oriented in the pseudo-cubic crystal (100) having the desired orientation, and that most crystals are in the pseudo-cubic crystal (100) having the desired orientation. The case where the remaining crystals that are oriented and not oriented to pseudo cubic (100) are in other orientations can be included. Similarly, the piezoelectric film 6 is formed on the preferentially oriented buffer layer 5 and has a crystal structure that inherits the crystal structure of the buffer layer 5. Therefore, like the buffer layer 5, the piezoelectric film 6 is also preferentially oriented to pseudo cubic (100).

In the material for forming the piezoelectric film 6 (relaxer material), as described above, the range of x representing the composition ratio on the Pb (Zr _1-y Ti _y ) O ₃ (hereinafter also referred to as “PZT”) side between the materials. In particular, the upper limit thereof is the value of x at the phase boundary (MPB) of the crystal structure of the piezoelectric film 6 (hereinafter also referred to as “x _MPB ”). The value of x at the phase boundary (x _MPB ) is a value indicating the composition ratio on the PZT side when the rhombohedral structure and the tetragonal structure undergo phase transition. The range of x is smaller than the composition ratio at the time of phase transition, and is thus a range in which a rhombohedral structure is obtained. Here, the piezoelectric constant (d ₃₁ ) takes a local maximum near the phase boundary. Therefore, a value close to the value of x (x _MPB ) at the phase boundary is selected as the lower limit value of x. Therefore, as a range of x, although a relatively small value can be allowed in constructing the present invention, in order to obtain a higher piezoelectric constant (d ₃₁ ), a preferable value of x, that is, a value of x at the phase boundary. A value closer to (x _MPB ) is selected. Therefore, the lower limit value of the range of x is the value of x when the piezoelectric constant (d ₃₁ ) is allowed when the piezoelectric element 1 is operated. When the above content is expressed by an equation, for example, x is
(X _MPB −0.05) ≦ x ≦ x _MPB
Can range. If x is in the above-mentioned range, the piezoelectric film 6 can be easily controlled to a rhombohedral structure, and high piezoelectric characteristics can be expressed. The piezoelectric film 6 can also have x (x _MPB ) at the phase boundary of the crystal structure of the piezoelectric film 6. Thereby, the piezoelectric constant (d ₃₁ ) can be set to the maximum value.

The upper electrode 7 serves as the other electrode for applying a voltage to the piezoelectric film 6. The upper electrode 7 can be made of, for example, platinum (Pt), iridium (Ir), iridium oxide (IrO _x ), titanium (Ti), SrRuO ₃ or the like. The thickness of the upper electrode 7 can be about 100 nm.

  In the above-described example, the case where the piezoelectric element 1 is used as a head actuator for an ink jet recording head has been described. However, the piezoelectric element 1 can be used as a piezoelectric actuator other than the head actuator for an ink jet recording head.

As for the lower electrode 4, the use of a perovskite electrode such as SrRuO ₃ does not depart from the spirit of the present invention. By sandwiching the PZTX buffer layer 5 between the lower electrode 4 made of SrRuO ₃ and the piezoelectric film 6 made of the relaxor material, the pseudo-cubic (100) orientation of the piezoelectric film 6 is further improved in the manufacturing process. It can be easily controlled.

1-2. Next, a method for manufacturing the piezoelectric element 1 according to the present embodiment will be described.

  (1) First, a (110) or (100) oriented single crystal silicon substrate, a (111) oriented single crystal silicon substrate, or an amorphous silicon oxide film as a natural oxide film is formed as the substrate 2 (100). Alternatively, a (110) oriented silicon substrate is prepared.

  (2) Next, as shown in FIG. 4, the elastic film 3 is formed on the substrate 2. For the elastic film 3, a vapor phase method such as a CVD method, a sputtering method, or a vapor deposition method is appropriately determined and adopted according to the material to be formed.

  (3) Next, as shown in FIG. 5, the lower electrode 4 made of, for example, platinum (Pt) is formed on the elastic plate 3. Platinum has a (111) preferred orientation relatively easily. Therefore, for example, by adopting a relatively simple method such as a sputtering method, the alignment growth can be easily performed on the elastic film 3.

(4) Next, as shown in FIG. 6, the buffer layer 5 is formed on the lower electrode 4. _{Specifically, Pb ((Zr 1-a} Ti a) 1-b X b) O 3, _{or, Pb 1- (b / 2)} ((Zr 1-a Ti a) 1-b X b) O ₃ (hereinafter also referred to as “PZTX”) is placed on the lower electrode 4 by a coating method such as a spin coating method or a droplet discharge method. Next, the buffer layer 5 is obtained by performing a heat treatment such as baking. More specifically, for example, as follows.

  The buffer layer 5 prepares a mixed solution (precursor solution) composed of first to third raw material solutions containing at least one of Pb, Zr, Ti, and X, and heat-treats the oxide contained in the mixed solution It can be obtained by crystallization by the like.

  About the raw material solution which is a forming material of the buffer layer 5, the organic metals each containing the constituent metal of PZTX are mixed so that each metal may become a desired molar ratio, and these are further mixed using organic solvents, such as alcohol. It is prepared by dissolving or dispersing. An organic metal such as a metal alkoxide or an organic acid salt can be used as the organic metal containing each constituent metal of PZTX. Specifically, examples of the carboxylate or acetylacetonate complex containing the constituent metal of PZTX include the following.

  Examples of the organic metal containing lead (Pb) include lead acetate. Examples of the organic metal containing zirconium (Zr) include zirconium butoxide. Examples of the organic metal containing titanium (Ti) include titanium isopropoxide. Examples of the organic metal containing vanadium (V) include vanadium oxide acetylacetonate. Examples of the organic metal containing niobium (Nb) include niobium ethoxide. Examples of the organic metal containing tantalum (Ta) include tantalum ethoxide. Note that the organic metal containing the constituent metal of PZTX is not limited to these.

  Various additives such as a stabilizer can be added to the raw material solution as necessary. Furthermore, when hydrolysis / polycondensation is caused in the raw material solution, an acid or a base can be added as a catalyst together with an appropriate amount of water to the raw material solution.

For example, as the first raw material solution, a solution in which a polycondensation polymer for forming a PbZrO ₃ perovskite crystal composed of Pb and Zr among constituent metal elements of PZTX is dissolved in a solvent such as n-butanol in an anhydrous state is used. It can be illustrated.

For example, as the second raw material solution, a solution obtained by dissolving a polycondensation polymer for forming a PbTiO ₃ perovskite crystal of Pb and Ti among the constituent metal elements of PZTX in a solvent such as n-butanol in an anhydrous state. It can be illustrated.

For example, as the third raw material solution, a solution obtained by dissolving a polycondensation product for forming a PbXO ₃ perovskite crystal by Pb and X in a constituent metal element of PZTX in a solvent such as n-butanol in an anhydrous state. It can be illustrated. In addition, when X consists of 2 or more types of elements, the 3rd raw material solution can consist of a several raw material solution. For example, when X consists of three kinds of V, Nb, and Ta, the third raw material solution can consist of three kinds of raw material solutions. Specifically, for example, the third raw material solution includes a solution obtained by dissolving a polycondensation product for forming a PbVO ₃ perovskite crystal with Pb and V in a solvent such as n-butanol in an anhydrous state, and Pb and Nb. A solution obtained by dissolving a polycondensation polymer for forming a PbNbO ₃ perovskite crystal in an anhydrous state in a solvent such as n-butanol, and a polycondensation polymer for forming a PbTaO ₃ perovskite crystal by Pb and Ta, And a solution dissolved in an anhydrous state in a solvent such as butanol.

  Using the first, second, and third raw material solutions, the first, second, and third raw material solutions are mixed at a desired ratio so that the buffer layer 5 has a desired composition ratio. The buffer layer 5 can be formed by crystallizing the mixed solution by heat treatment or the like.

  Specifically, the buffer solution 5 is formed by performing a series of steps of a mixed solution coating step, an alcohol removing step, a drying heat treatment step, and a degreasing heat treatment step a desired number of times, and then firing by crystallization annealing. The conditions in each process are as follows, for example.

  In the mixed solution coating step, the mixed solution is coated by a coating method such as spin coating. First, the mixed solution is dropped on the lower electrode 4. Spin is performed for the purpose of spreading the dropped solution over the entire surface of the substrate. The rotation speed of the spin is, for example, about 500 rpm in the initial stage, and then the rotation speed is increased to about 2000 rpm so that coating unevenness does not occur, thereby completing the coating. The drying heat treatment step is performed by heat treatment (drying) 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. About a degreasing heat treatment process, in order to decompose | disassemble / remove the organometallic ligand used for the precursor solution, it carries out by heating at about 350 to 400 degreeC using a hotplate in air | atmosphere atmosphere. The crystallization annealing, that is, the firing step for crystallization is performed by heating to, for example, about 600 ° C. using rapid thermal annealing (RTA) or the like in an oxygen atmosphere.

  The film thickness of the buffer layer 5 after sintering can be, for example, about 10 nm to 1.0 μm. The buffer layer 5 can also be formed by using, for example, a sputtering method, a molecular beam epitaxy method, or a laser ablation method.

When forming the buffer layer 5, it is preferable to further add PbSiO ₃ silicate at a ratio of, for example, 1 to 5 mol%. Thereby, the crystallization energy of PZTX can be reduced. That is, when PZTX is used as the buffer layer 5, the crystallization temperature of PZTX can be reduced by adding PbSiO ₃ silicate together with the addition of X. Specifically, in addition to the first to third raw material solutions described above, a fourth raw material solution can be used. Examples of the fourth raw material solution include a solution obtained by dissolving a condensation polymer in a solvent such as n-butanol in an anhydrous state in order to form a PbSiO ₃ crystal. As an additive for promoting crystallization, germanate can also be used. When the buffer layer 5 is formed, the buffer layer 5 can contain 5 mol% or less of Si or Si and Ge by adding PbSiO ₃ silicate or germanate.

  In this way, by forming the buffer layer 5 on the lower electrode 4 made of (111) -oriented platinum (Pt), the perovskite-type, rhombohedral or pseudo-cubic PZTX has a pseudo-cubic (100) Formed in a preferentially oriented state.

  (5) Next, as shown in FIG. 7, the piezoelectric film 6 is formed on the buffer layer 5. Specifically, first, a precursor solution of a relaxor material is disposed on the buffer layer 5 by a known coating method such as a spin coating method or a droplet discharge method. Next, the piezoelectric film 6 is obtained by performing a heat treatment such as firing.

  More specifically, first, in the same manner as the formation of the buffer layer 5, the precursor solution coating step, the solvent removal step, the drying heat treatment step, and the degreasing heat treatment step are appropriately repeated according to the desired film thickness. repeat. Next, the piezoelectric film 6 is formed by performing crystallization annealing. Conditions in each step are almost the same as the formation of the buffer layer 5.

  The piezoelectric film 6 is formed on the buffer layer 5 preferentially oriented to (100), so that it inherits the crystal structure of the buffer layer 5, that is, its orientation, and takes precedence over the same crystal structure, that is, pseudo-cubic crystal (100). It is formed by orientation.

  For the precursor solution that is a material for forming the piezoelectric film 6, organic metals each containing a constituent metal of the relaxor material that becomes the piezoelectric film 6 are mixed so that each metal has a desired molar ratio, and alcohol These are dissolved or dispersed using an organic solvent such as An organic metal such as a metal alkoxide or an organic acid salt can be used as the organic metal containing the constituent metals of the relaxor material. Specifically, examples of the carboxylate or acetylacetonate complex containing the constituent metal of the relaxor material include the following.

  Examples of the organic metal containing lead (Pb) include lead acetate. Examples of the organic metal containing zirconium (Zr) include zirconium butoxide. Examples of the organic metal containing titanium (Ti) include titanium isopropoxide. Examples of the organic metal containing magnesium (Mg) include magnesium acetate. Examples of the organic metal containing niobium (Nb) include niobium ethoxide. Examples of the organic metal containing nickel (Ni) include nickel acetylacetonate. Examples of the organic metal containing scandium (Sc) include scandium acetate. Examples of the organic metal containing indium (In) include indium acetylacetonate. Examples of the organic metal containing zinc (Zn) include zinc acetate. Examples of the organic metal containing iron (Fe) include iron acetate. Examples of the organic metal containing gallium (Ga) include gallium isopropoxide. Examples of the organic metal containing tantalum (Ta) include tantalum ethoxide. Examples of the organic metal containing tungsten (W) include tungsten hexacarbonyl. The organic metal containing the constituent metal of the relaxor material is not limited to these.

  Various additives such as a stabilizer can be added to the precursor solution as necessary. Furthermore, in the case where hydrolysis / polycondensation is caused in the precursor solution, an acid or a base can be added as a catalyst together with an appropriate amount of water to the precursor solution.

  In the present embodiment, an example in which both the buffer layer 5 and the piezoelectric film 6 are formed by a liquid phase method has been described. However, the buffer layer 5 and the piezoelectric layer 6 are formed by using a gas phase method such as a laser ablation method or a sputtering method. The piezoelectric film 6 can also be formed.

  (6) Next, as shown in FIG. 8, an upper electrode 7 made of, for example, platinum (Pt) is formed on the piezoelectric film 6. The formation of the upper electrode 7 can be performed by sputtering or the like, similarly to the lower electrode 4.

  Through the above steps, the piezoelectric element 1 according to the present embodiment can be manufactured.

1-3. Action / Effect Conventionally, in order to form a piezoelectric film made of a relaxor material having a perovskite type and a rhombohedral structure and preferentially oriented to pseudo cubic (100), a complicated method has been required. Specifically, for example, it is as follows.

  First, a buffer layer is formed by using a laser ablation method and a complicated method such as an ion beam assist method. Next, a base is formed by forming a perovskite-type lower electrode on the buffer layer. Next, a piezoelectric film is formed on the base. The reason for taking such a complicated method is as follows.

The manufacturing margin for forming a dense thin film of relaxor material on a conventional electrode material such as platinum (Pt) or iridium (Ir) is small. On the other hand, a dense thin film can be obtained relatively easily on a perovskite electrode such as SrRuO ₃ . In order to control the orientation of a perovskite electrode such as SrRuO ₃ , a laser ablation method or an ion beam assist method is required. The result is a complex approach. However, in such a conventional method, there are problems that the process is complicated, the cost is high, and the piezoelectric characteristics of the obtained piezoelectric film are not sufficiently stable.

The piezoelectric element 1 according to the present embodiment includes the buffer layer 5 made of PZTX formed on the substrate and the piezoelectric film 6 made of a relaxor material formed on the buffer layer 5. With respect to PZTX, a dense thin film can be formed on a Pt or Ir electrode while controlling the orientation. Furthermore, a relaxor material such as (1-x) Pb (Mg _1/3 Nb _2/3 ) O ₃ -xPbTiO ₃ (hereinafter also referred to as “PMN-PT”) is densely formed on the dense PZTX once formed. As a thin film, it can be easily laminated. That is, according to the piezoelectric element 1 according to the present embodiment, the piezoelectric film 6 made of the relaxor material is formed on the buffer layer 5 preferentially oriented to pseudo cubic (100). Is also well preferentially oriented to pseudo cubic (100). Therefore, the piezoelectric element 1 according to the present embodiment can have the piezoelectric film 6 with good piezoelectric characteristics. In other words, the piezoelectric element 1 according to the present embodiment has a high piezoelectric constant and undergoes greater deformation with respect to the applied voltage.

  In addition, according to the piezoelectric element 1 according to the present embodiment, the relaxor material represented by the above-described formulas can be used as the piezoelectric film 6. As a result, the piezoelectric element 1 according to the present embodiment has a sufficiently high piezoelectric constant. Therefore, the piezoelectric element 1 according to the present embodiment, more specifically, the piezoelectric film 6 is more deformed.

  In addition, the piezoelectric element 1 according to the present embodiment has the buffer layer 5 made of PZTX. If the buffer layer 5 is not provided, that is, if the lower electrode and the piezoelectric film are in contact with each other, the piezoelectric film and the lower electrode are separated by lead (Pb) and oxygen escaping from the piezoelectric film. In some cases, material deterioration may occur at the interface. In some cases, composition deviation occurs at the interface between the lower electrode and the piezoelectric film, and a region having a low dielectric constant is formed at the interface. As a result, a sufficient voltage may not be applied to the piezoelectric film itself.

  On the other hand, the piezoelectric element 1 according to the present embodiment has the buffer layer 5 made of PZTX. Pb atoms in PZTX only diffuse into the lower electrode 4 at a depth of several tens of nm or less even under high temperature conditions. Thus, the diffusion of Pb atoms into the lower electrode 4 is extremely small. In other words, it can be said that there is almost no diffusion of Pb atoms to the lower electrode 4 as compared with the case where the buffer layer 5 is not provided. In PZTX, almost all of the Pb atoms are at the lattice positions where they should be, and the crystal lattice breakage due to the defects of the Pb atoms is hardly observed. That is, it can be said that almost all Pb atoms contained in PZTX are present at the Pb atom position of the perovskite structure. This means that not only the most easily moved Pb atoms but also other elements such as oxygen, Zr and Ti are difficult to diffuse, and the PZTX film itself has a barrier property such as a Pb barrier property or an oxygen barrier. Have sex.

  Therefore, according to the piezoelectric element 1 according to the present embodiment, a composition shift occurs at the interface between the lower electrode 4 and the buffer layer 5 made of PZTX, and a region having a low dielectric constant is formed at the interface. There is almost no. As a result, a sufficient voltage can be applied to the piezoelectric film 6 itself.

  In addition, according to the method for manufacturing the piezoelectric element 1 according to the present embodiment, the piezoelectric film 6 can be easily formed by a liquid phase method that makes the process simpler than the vapor phase method.

1-4. Experimental Example Based on the above-described method for manufacturing a piezoelectric element, the piezoelectric element 1 was manufactured as follows.

  First, the lower electrode 4 made of platinum (Pt) with (111) orientation was formed on the substrate 2 through the elastic film 3 by sputtering. The film thickness of the lower electrode 4 was 200 nm. The power during sputtering was 200 W.

Next, a precursor solution of Pb (Zr _0.3 Ti _0.5 (Nb _0.9 Ta _0.1 ) _0.2 ) O ₃ (hereinafter also referred to as “PZTX”) was prepared as follows. .

A mixed solution composed of first to fourth raw material solutions containing at least one of Pb, Zr, Ti, Nb, and Ta was prepared. As the first raw material solution, a solution obtained by dissolving a condensation polymer for forming a PbZrO ₃ perovskite crystal of Pb and Zr among the constituent metal elements of PZTX in an n-butanol solvent in an anhydrous state was used. As the second raw material solution, a solution in which a polycondensation polymer for forming a PbTiO ₃ perovskite crystal of Pb and Ti among the constituent metal elements of PZTX was dissolved in an n-butanol solvent in an anhydrous state was used. As the third raw material solution, a solution obtained by dissolving a polycondensation polymer for forming PbNbO ₃ perovskite crystals of Pb and Nb in an n-butanol solvent in an anhydrous state among the constituent metal elements of PZTX was used. As the fourth raw material solution, a solution obtained by dissolving a polycondensation polymer for forming a PbTaO ₃ perovskite crystal of Pb and Ta among the constituent metal elements of PZTX in an n-butanol solvent in an anhydrous state was used.

When the buffer layer 5 was formed, PbSiO ₃ silicate was further added at a ratio of 2 mol%. Specifically, in addition to the first to fourth raw material solutions described above, a fifth raw material solution was used. As the fifth raw material solution, a solution obtained by dissolving a condensation polymer in an n-butanol solvent in an anhydrous state to form PbSiO ₃ crystals was used.

  Using the first to fifth raw material solutions, the first to fifth raw material solutions were mixed at a desired ratio so that the buffer layer 5 had a desired composition ratio. Next, a series of steps including a mixed solution coating step, an alcohol removing step, a drying heat treatment step, and a degreasing heat treatment step were performed a desired number of times, and then fired by crystallization annealing to form the buffer layer 5.

  In the mixed solution coating step, the mixed solution was applied by spin coating. First, the mixed solution was dropped on the lower electrode 4. Spin was performed for the purpose of spreading the dropped solution over the entire surface of the substrate. The rotation speed of the spin was initially set to about 500 rpm, and then the rotation speed was increased to about 2000 rpm so that coating unevenness did not occur, thereby completing the coating. The drying heat treatment step was performed by heat treatment (drying) at a temperature 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. The degreasing heat treatment step was performed by heating to about 400 ° C. using a hot plate in an air atmosphere in order to decompose / remove the organometallic ligand used in the precursor solution. The crystallization annealing, that is, the firing step for crystallization, was performed by heating to about 600 ° C. using rapid thermal annealing (RTA) or the like in an oxygen atmosphere. The thickness of the buffer layer 5 after sintering was 300 nm.

  In this way, by forming the buffer layer 5 on the lower electrode 4 made of (111) -oriented platinum (Pt), the perovskite-type, rhombohedral or pseudo-cubic PZTX has a pseudo-cubic (100) It was formed in a preferentially oriented state.

Next, a precursor solution of 0.70 Pb (Mg _1/3 Nb _2/3 ) O ₃ -0.30 PbTiO ₃ (hereinafter also referred to as “PMN-PT”) was prepared as follows.

  First, metal reagents of lead acetate, titanium isopropoxide, magnesium acetate, and niobium ethoxide were prepared. Next, while mixing these so that it might become a molar ratio corresponding to PMN-PT to form, these were melt | dissolved (dispersed) in the butyl cellosolve. Furthermore, diethanolamine was added as a stabilizer for this solution. In this way, a precursor solution was prepared. Acetic acid can also be used in place of diethanolamine.

  And this precursor solution was apply | coated on the buffer layer 5 by the spin coat method (precursor solution application | coating process). Next, it was heat-treated (dried) at a temperature about 10 ° C. higher than the boiling point of the solvent (about 170 ° C. in the case of butyl cellosolve) to remove the solvent and gel (dry heat treatment step). Next, by heating to about 350 ° C., organic components other than the solvent remaining in the film were decomposed / removed (degreasing heat treatment step) to form an amorphous film. Next, the piezoelectric film 6 was formed by heating to about 600 ° C. using rapid thermal annealing (RTA) in an oxygen atmosphere and performing crystallization. The film thickness of the piezoelectric film 6 was 300 nm.

  Next, the upper electrode 7 made of platinum (Pt) was formed on the piezoelectric film 6 by sputtering, and the piezoelectric element 1 was obtained.

  When the piezoelectric film 6 in the piezoelectric element 1 thus obtained was examined by X-ray diffraction (XRD), it was confirmed that it was preferentially oriented to pseudo cubic (100), and a rhombohedral structure It was also confirmed.

Further, when the piezoelectric constant (d ₃₁ ) of the piezoelectric film 6 was measured, it was 400 pC / N in absolute value. Moreover, the leakage current was less than 10 ⁻⁵ A / cm ² at 100 kV / cm. Furthermore, when the repeated durability of the piezoelectric element 1 when 300 kV / cm was applied was examined, the piezoelectric element 1 had a durability capable of guaranteeing 1 × 10 ⁹ times.

In addition, when the buffer layer 5 and the piezoelectric film 6 were produced using the materials shown in Table 1 below and the piezoelectric constant (d ₃₁ ) was examined, both of d ₃₁ had a high piezoelectricity of 400 pC / N or more in absolute value. The characteristics are shown. Note that the absolute value of d ₃₁ in Table 1. The method for measuring the piezoelectric constant was as follows.

First, the displacement S of the piezoelectric body when a voltage is applied in an actual cavity is measured using a laser displacement meter. By comparing this value S with the displacement S ′ obtained by the piezoelectric displacement simulation by the finite element method, the piezoelectric constant (d ₃₁ ) of the piezoelectric film assumed by the finite element method can be adjusted. Incidentally, the physical quantities required in the piezoelectric displacement simulation by the finite element method are the Young's modulus of each film, the film stress, and the piezoelectric constant (d ₃₁ ) of the piezoelectric film.

Further, in the composition of the relaxor material, Pb (Zr _1-y Ti _y ) O ₃ may be used instead of PbTiO ₃ . Further, the value of y is preferably 0.7 ≦ y ≦ 1.

2-1. Inkjet Recording Head Next, an inkjet recording head using the piezoelectric element 1 shown in FIG. 1 will be described. 9 is a side sectional view showing a schematic configuration of an ink jet recording head using the piezoelectric element 1 shown in FIG. 1, and FIG. 10 is an exploded perspective view of the ink jet recording head. In addition, FIG. 10 is shown upside down from the state normally used.

  As shown in FIG. 9, the ink jet recording head (hereinafter also referred to as “head”) 50 includes a head main body 57 and a piezoelectric element 54 provided on the head main body 57. is there. 9 includes the lower electrode 4, the buffer layer 5, the piezoelectric film 6, and the upper electrode 7 in the piezoelectric element 1 shown in FIG. 1 (see FIG. 10). ). Further, the elastic film 3 in the piezoelectric element 1 shown in FIG. 1 is an elastic plate 55 in FIG. The substrate 2 (see FIG. 1) constitutes a main part of the head main body 57 as will be described later.

  That is, the head 50 includes a nozzle plate 51, an ink chamber substrate 52, an elastic plate 55, and a piezoelectric element (vibration source) 54 joined to the elastic plate 55 as shown in FIG. It is housed and configured. The head 50 constitutes an on-demand piezo jet head.

  The nozzle plate 51 is composed of, for example, a stainless steel rolling plate or the like, and has a large number of nozzles 511 for ejecting ink droplets formed in a line. The pitch between these nozzles 511 is appropriately set according to the printing accuracy.

  An ink chamber substrate 52 is fixed (fixed) to the nozzle plate 51. The ink chamber substrate 52 is formed by the substrate 2 described above. The ink chamber substrate 52 has a plurality of cavities (ink cavities) 521, a reservoir 523, and supply ports 524 formed by a nozzle plate 51, side walls (partition walls) 522, and an elastic plate 55 described later. It is. The reservoir 523 temporarily stores ink supplied from the ink cartridge 631 (see FIG. 15). Ink is supplied from the reservoir 523 to each cavity 521 through the supply port 524.

  The cavities 521 are each formed in a strip shape. As shown in FIGS. 11 and 12, the planar shape of the cavity 521 is a rectangular shape (parallelogram shape) having a major axis and a minor axis. Typical scales of the major axis and the minor axis of the cavity 521 are 2 mm and 60 μm, respectively. As shown in FIGS. 9 and 10, the cavity 521 is disposed corresponding to each nozzle 511. The cavities 521 each have a variable volume due to vibration of an elastic plate 55 described later. The cavity 521 is configured to eject ink by this volume change.

  As a base material for obtaining the ink chamber substrate 52, that is, the above-described substrate 2, a (110) -oriented silicon single crystal substrate (Si substrate) is used. Since this (110) -oriented silicon single crystal substrate is suitable for anisotropic etching, the ink chamber substrate 52 can be formed easily and reliably. Such a silicon single crystal substrate is used such that the surface on which the elastic film 3 shown in FIG. 1 is formed, that is, the surface on which the elastic plate 55 is formed is the (110) surface.

  The average thickness of the ink chamber substrate 52, that is, the thickness including the cavity 521 is not particularly limited, but is preferably about 10 to 1000 μm, and more preferably about 100 to 500 μm. Further, the volume of the cavity 521 is not particularly limited, but is preferably about 0.1 to 100 nL, and more preferably about 0.1 to 10 nL.

  An elastic plate 55 is disposed on the side of the ink chamber substrate 52 opposite to the nozzle plate 51. Further, a plurality of piezoelectric elements 54 are provided on the side of the elastic plate 55 opposite to the ink chamber substrate 52. As described above, the elastic plate 55 is formed by the elastic film 3 in the piezoelectric element 1 shown in FIG. As shown in FIG. 10, a communication hole 531 is formed at a predetermined position of the elastic plate 55 so as to penetrate in the thickness direction of the elastic plate 55. Ink is supplied from an ink cartridge 631 to be described later to the reservoir 523 through the communication hole 531.

  Each piezoelectric element 54 is configured such that the piezoelectric film 6 is interposed between the lower electrode 4 and the upper electrode 7 as described above. As shown in FIG. 12, each piezoelectric element 54 has a rectangular shape in plan view, which is disposed corresponding to the substantially central portion of each cavity 521. Each of these piezoelectric elements 54 is electrically connected to a piezoelectric element driving circuit described later, and is configured to operate (vibrate, deform) based on a signal from the piezoelectric element driving circuit. That is, each piezoelectric element 54 functions as a vibration source (head actuator). The elastic plate 55 vibrates (deflection) by the vibration (deflection) of the piezoelectric element 54 and functions to instantaneously increase the internal pressure of the cavity 521.

  The base 56 is made of, for example, various resin materials, various metal materials, or the like. As shown in FIG. 10, the ink chamber substrate 52 is fixed and supported on the base body 56.

2-2. Operation of Inkjet Recording Head Next, the operation of the inkjet recording head 50 in the present embodiment will be described. In the head 50 according to the present embodiment, a voltage is not applied between the lower electrode 4 and the upper electrode 7 of the piezoelectric element 54 in a state where a predetermined ejection signal is not input via the piezoelectric element driving circuit. In the state, the piezoelectric film 6 is not deformed as shown in FIG. For this reason, the elastic plate 55 is not deformed, and the cavity 521 does not change in volume. Accordingly, no ink droplet is ejected from the nozzle 511.

  On the other hand, in a state where a predetermined ejection signal is input via the piezoelectric element driving circuit, that is, in a state where a constant voltage (for example, about 30 V) is applied between the lower electrode 4 and the upper electrode 7 of the piezoelectric element 54, As shown in FIG. 14, the piezoelectric film 6 is deformed by bending in the short axis direction. As a result, the elastic plate 55 bends by, for example, about 500 nm, and the volume of the cavity 521 changes. At this time, the pressure in the cavity 521 increases instantaneously, and an ink droplet is ejected from the nozzle 511.

That is, when a voltage is applied, the crystal lattice of the piezoelectric film 6 is stretched in a direction perpendicular to the plane, but is simultaneously compressed in a direction parallel to the plane. In this state, a tensile stress is acting in the plane for the piezoelectric film 6. Therefore, the elastic plate 55 is deflected and bent by this stress. The greater the amount of displacement (absolute value) of the piezoelectric film 6 in the minor axis direction of the cavity 521, the greater the amount of deflection of the elastic plate 55, making it possible to eject ink droplets more efficiently. . In the present embodiment, as described above, the piezoelectric constant (d ₃₁ ) of the piezoelectric film 6 of the piezoelectric element 54 (piezoelectric element 1) is high, and the piezoelectric element 54 (piezoelectric element 1) undergoes greater deformation with respect to the applied voltage. Yes. Thereby, the amount of deflection of the elastic plate 55 is increased, and ink droplets can be ejected more efficiently.

  Here, “efficient” means that the same amount of ink droplets can be ejected with a smaller voltage. That is, the driver circuit can be simplified and the power consumption can be reduced at the same time, so that the pitch of the nozzles 511 can be formed with higher density. Alternatively, since the length of the long axis of the cavity 521 can be shortened, the entire head can be reduced in size.

  When the ejection of one ink is completed, the piezoelectric element driving circuit stops applying the voltage between the lower electrode 4 and the upper electrode 7. Thereby, the piezoelectric element 54 returns to the original shape shown in FIG. 13, and the volume of the cavity 521 increases. At this time, the pressure (pressure in the positive direction) from the ink cartridge 631 described later toward the nozzle 511 is applied to the ink. For this reason, air is prevented from entering the cavity 521 from the nozzle 511, and an amount of ink corresponding to the ink ejection amount is supplied from the ink cartridge 631 to the cavity 521 through the reservoir 523.

  In this way, arbitrary (desired) characters and figures are printed by sequentially inputting ejection signals to the piezoelectric element 54 at the position where ink droplets are to be ejected via the piezoelectric element driving circuit. be able to.

2-3. Method for Manufacturing Inkjet Recording Head Next, an example of a method for manufacturing the inkjet recording head 50 in the present embodiment will be described.

  First, a base material to be the ink chamber substrate 52, that is, a substrate 2 made of a (110) -oriented silicon single crystal substrate (Si substrate) is prepared. Next, as shown in FIGS. 4 to 8, the elastic film 3 is formed on the substrate 2. Next, the lower electrode 4, the buffer layer 5, the piezoelectric film 6, and the upper electrode 7 are sequentially formed on the elastic film 3. The elastic film 3 formed here becomes the elastic plate 55 as described above.

  Next, the upper electrode 7, the piezoelectric film 6, the buffer layer 5, and the lower electrode 4 are patterned corresponding to the individual cavities 521 as shown in FIGS. 13 and 14, and as shown in FIG. The number of piezoelectric elements 54 corresponding to the number of cavities 521 is formed.

  Next, the base material (substrate 2) to be the ink chamber substrate 52 is processed (patterned), the concave portions to be the cavities 521 are formed at positions corresponding to the piezoelectric elements 54, and the reservoir 523 and the supply port 524 are formed at predetermined positions. Forming a recess.

  Specifically, a mask layer is formed in accordance with positions where the cavity 521, the reservoir 523, and the supply port 524 are to be formed. Next, for example, parallel plate type reactive ion etching, inductively coupled method, electron cyclotron resonance method, helicon wave excitation method, magnetron method, plasma etching method, ion beam etching method or other dry etching, or 5 to 40% by weight Wet etching is performed with a high-concentration alkaline aqueous solution such as potassium hydroxide and tetramethylammonium hydroxide.

  In the present embodiment, since a (110) -oriented silicon substrate is used as the base material (substrate 2), wet etching (anisotropic etching) using a high-concentration alkaline aqueous solution is suitably employed. In wet etching with a high-concentration alkaline aqueous solution, the elastic film 3 can function as an etching stopper as described above. Therefore, the ink chamber substrate 52 can be formed more easily.

  Thus, the ink chamber substrate 52 is formed by removing the base material (substrate 2) by etching until the elastic plate 55 (elastic film 3) is exposed in the thickness direction. At this time, a portion left without being etched becomes the side wall 522. The exposed elastic film 3 (elastic plate 55) is in a state where the function as the elastic plate 55 can be exhibited.

  Next, the nozzle plate 51 on which the plurality of nozzles 511 are formed is aligned so that each nozzle 511 corresponds to a concave portion that becomes each cavity 521, and bonded in that state. Thereby, a plurality of cavities 521, a reservoir 523, and a plurality of supply ports 524 are formed. For the joining of the nozzle plate 51, for example, an adhesive method using an adhesive or a fusion method may be used. Next, the ink chamber substrate 52 is attached to the base 56.

  Through the above steps, the ink jet recording head 50 according to the present embodiment can be manufactured.

2-4. Action / Effect According to the ink jet recording head 50 according to the present embodiment, as described above, the piezoelectric element 54 (piezoelectric element 1) has good piezoelectric characteristics, thereby enabling efficient ink ejection. Therefore, the density of the nozzles 511 can be increased. Therefore, high-density printing and high-speed printing are possible. Furthermore, the entire head can be reduced in size.

3-1. Inkjet Printer Next, an inkjet printer provided with the above-described inkjet recording head 50 will be described. FIG. 15 is a schematic configuration diagram showing an embodiment in which the inkjet printer 600 of the present invention is applied to a general printer that prints on paper or the like. In the following description, the upper side in FIG. 15 is referred to as “upper part” and the lower side is referred to as “lower part”.

  The ink jet printer 600 includes an apparatus main body 620, has a tray 621 for placing the recording paper P on the upper rear side, has a discharge port 622 for discharging the recording paper P on the lower front, and has an operation panel 670 on the upper surface. Have

  The operation panel 670 is composed of, for example, a liquid crystal display, an organic EL display, an LED lamp, and the like. )).

  Inside the apparatus main body 620, there are mainly a printing apparatus 640 provided with a reciprocating head unit 630, a paper feeding apparatus 650 for feeding the recording paper P one by one to the printing apparatus 640, the printing apparatus 640 and the paper feeding apparatus. A control unit 660 for controlling the 650 is provided.

  Under the control of the control unit 660, the paper feeding device 650 intermittently feeds the recording paper P one by one. The recording paper P that is intermittently fed passes near the lower portion of the head unit 630. At this time, the head unit 630 reciprocates in a direction substantially perpendicular to the feeding direction of the recording paper P, and printing on the recording paper P is performed. That is, the reciprocation of the head unit 630 and the intermittent feeding of the recording paper P are the main scanning and the sub-scanning in printing, and ink jet printing is performed.

  The printing apparatus 640 includes a head unit 630, a carriage motor 641 serving as a drive source for the head unit 630, and a reciprocating mechanism 642 that receives the rotation of the carriage motor 641 to reciprocate the head unit 630.

  The head unit 630 includes an ink jet recording head 50 provided with the above-described many nozzles 511, an ink cartridge 631 for supplying ink to the ink jet recording head 50, an ink jet recording head 50, and an ink cartridge 631 at a lower portion thereof. And a carriage 632 mounted thereon.

  By using an ink cartridge 631 filled with ink of four colors of yellow, cyan, magenta, and black (black), full-color printing is possible. In this case, the head unit 630 is provided with the ink jet recording head 50 corresponding to each color.

  The reciprocating mechanism 642 includes a carriage guide shaft 643 whose both ends are supported by a frame (not shown), and a timing belt 644 extending in parallel with the carriage guide shaft 643. The carriage 632 is supported by the carriage guide shaft 643 so as to reciprocate and is fixed to a part of the timing belt 644. When the timing belt 644 travels forward and backward through a pulley by the operation of the carriage motor 641, the head unit 630 reciprocates while being guided by the carriage guide shaft 643. During this reciprocation, ink is appropriately discharged from the ink jet recording head 50 and printing on the recording paper P is performed.

  The sheet feeding device 650 includes a sheet feeding motor 651 serving as a driving source thereof, and a sheet feeding roller 652 that is rotated by the operation of the sheet feeding motor 651. The paper feed roller 652 includes a driven roller 652 a and a drive roller 652 b that are opposed to each other across the feeding path (recording paper P) of the recording paper P, and the driving roller 652 b is connected to the paper feeding motor 651. Has been. With such a configuration, the paper feed roller 652 can feed a large number of recording sheets P installed on the tray 621 one by one toward the printing apparatus 6400. Note that, instead of the tray 621, a configuration in which a paper feed cassette that stores the recording paper P can be detachably mounted can be employed.

  The control unit 660 performs printing by controlling the printing device 640, the paper feeding device 650, and the like based on print data input from a host computer such as a personal computer or a digital camera.

  Although not shown in the figure, the control unit 660 mainly stores a memory for storing a control program for controlling each unit, a piezoelectric element driving circuit that drives the piezoelectric element (vibration source) 54 to control ink ejection timing, and printing. A drive circuit for driving the device 640 (carriage motor 641), a drive circuit for driving the paper feed device 650 (paper feed motor 651), and a communication circuit for obtaining print data from the host computer are electrically connected to these. And a CPU for performing various controls in each unit.

  For example, various sensors that can detect, for example, the remaining amount of ink in the ink cartridge 631, the position of the head unit 630, the printing environment such as temperature, humidity, and the like are electrically connected to the CPU. The control unit 660 obtains print data via the communication circuit and stores it in the memory. The CPU processes the print data and outputs a drive signal to each drive circuit based on the process data and input data from various sensors. The piezoelectric element 54, the printing device 640, and the paper feeding device 650 are operated by this drive signal. Thus, desired printing is performed on the recording paper P.

3-2. Action / Effect According to the ink jet printer 600 according to the present embodiment, as described above, since the ink jet recording head 50 capable of high performance and high nozzle density is provided, high density printing and high speed printing can be performed. It becomes possible.

  The ink jet printer 600 of the present invention can also be used as a droplet discharge device used industrially. In that case, as the ink to be ejected (liquid material), various functional materials can be used by adjusting them to an appropriate viscosity with a solvent or a dispersion medium.

4-1. Next, the piezoelectric pump according to the present embodiment will be described with reference to the drawings. 16 and 17 are schematic sectional views of the piezoelectric pump 20 using the piezoelectric element 1 shown in FIG. 16 and 17 includes the lower electrode 4, the buffer layer 5, the piezoelectric film 6, and the upper electrode 7 in the piezoelectric element 1 shown in FIG. The elastic film 3 in the illustrated piezoelectric element 1 is a diaphragm 24 in FIGS. 16 and 17. The substrate 2 (see FIG. 1) serves as a base 21 that constitutes a main part of the piezoelectric pump 20. The piezoelectric pump 20 includes a base 21, a piezoelectric element 22, a pump chamber 23, a diaphragm 24, a suction side check valve 26a, a discharge side check valve 26b, a suction port 28a, and a discharge port 28b. Including.

4-2. Next, the operation of the above-described piezoelectric pump will be described. First, when a voltage is supplied to the piezoelectric element 22, the voltage is applied in the film thickness direction of the piezoelectric film 6 (see FIG. 1). And as shown in FIG. 16, the piezoelectric element 22 bends in the direction (direction of arrow a shown in FIG. 16) where the pump chamber 23 spreads. Further, the diaphragm 24 together with the piezoelectric element 22 bends in the direction in which the pump chamber 23 expands. For this reason, the pressure in the pump chamber 23 changes, and the fluid flows from the suction port 28a into the pump chamber 23 by the action of the check valves 26a and 26b (in the direction of arrow b shown in FIG. 16).

  Next, when the supply of voltage to the piezoelectric element 22 is stopped, the application of voltage in the film thickness direction of the piezoelectric film 6 (see FIG. 1) is stopped. And as shown in FIG. 17, the piezoelectric element 22 bends in the direction (direction of arrow a shown in FIG. 17) where the pump chamber 23 narrows. Further, the diaphragm 24 together with the piezoelectric element 22 bends in the direction in which the pump chamber 23 narrows. For this reason, the pressure in the pump chamber 23 changes, and the fluid is discharged from the discharge port 28b to the outside by the action of the check valves 26a and 26b (in the direction of arrow b shown in FIG. 17).

  The drive voltage of the piezoelectric pump 20 can be set to about 100 V (AC), for example. Moreover, the drive frequency of the piezoelectric pump 20 can be set to about several tens Hz to several tens kHz, for example.

  The piezoelectric pump 20 can be used as a water cooling module for electronic equipment, for example, a personal computer, preferably a notebook personal computer. The water cooling module uses the above-described piezoelectric pump 20 for driving the coolant, and has a structure including the piezoelectric pump 20 and a circulating water channel.

4-3. Action / Effect According to the piezoelectric pump 20 according to the present embodiment, as described above, the piezoelectric element 22 (piezoelectric element 1) has good piezoelectric characteristics, so that fluid can be sucked and discharged efficiently. Can do. Therefore, the piezoelectric pump 20 according to the present embodiment can have a large discharge pressure and discharge amount. In addition, the piezoelectric pump 20 can be operated at high speed. Furthermore, the overall size of the piezoelectric pump 20 can be reduced.

5-1. Surface Acoustic Wave Element Next, the surface acoustic wave element according to the present embodiment will be described with reference to the drawings. As shown in FIG. 18, the surface acoustic wave device includes a single crystal silicon substrate 11, an oxide thin film layer 12, a buffer layer 13, a piezoelectric film 14, and a protective film made of oxide or nitride as a protective film. It is composed of a layer 15 and an electrode 16. The electrode 16 is an interdigital electrode (Inter-Digital Transducer: hereinafter referred to as “IDT electrode”). When viewed from above, for example, the interdigital electrodes 141, 142, 151, shown in FIGS. 152, 153.

5-2. Method for Manufacturing Surface Acoustic Wave Element Next, an example of a method for manufacturing a surface acoustic wave element to which the present invention is applied will be described.

  First, a (100) single crystal silicon substrate is prepared as the single crystal silicon substrate 11. As the single crystal silicon substrate 11 prepared here, a semiconductor element such as a thin film transistor (TFT) may be prepared in advance. In that case, the obtained surface acoustic wave element is integrated with this semiconductor element. Will be made.

Next, an oxide thin film layer 12 is formed on the single crystal silicon substrate 11. The oxide thin film layer 12 can be formed using, for example, a laser ablation method or the like. As the oxide thin film layer 12, for example, a thin film of IrO ₂ or TiO ₂ can be used.

  Next, the buffer layer 13 is formed on the oxide thin film layer 12 by a liquid phase method in the same manner as in the case of forming the buffer layer 5 of the piezoelectric element 1 shown in FIG. Next, the piezoelectric film 14 is formed on the buffer layer 13 by a liquid phase method in the same manner as in the case of forming the piezoelectric film 6 shown in FIG.

  Next, a silicon oxide film is formed as a protective layer 15 on the piezoelectric film 14 by, for example, a laser ablation method. The protective layer 15 protects the piezoelectric film 14 from the atmosphere, prevents the influence of moisture and impurities in the atmosphere, for example, and also plays a role of controlling the temperature characteristics of the piezoelectric film 14. As long as such a purpose is satisfied, the material of the protective film is not limited to silicon oxide.

  Next, for example, an aluminum thin film is formed on the protective layer 15 and then patterned to form an electrode 16 having a desired shape called IDT, thereby obtaining the surface acoustic wave device shown in FIG. .

5-3. Action / Effect According to the surface acoustic wave device according to the present embodiment, the surface acoustic wave device itself has high performance because the piezoelectric film 14 has good piezoelectric characteristics.

6-1. Frequency Filter Next, the frequency filter according to the present embodiment will be described with reference to the drawings. FIG. 19 shows an embodiment of the frequency filter of the present invention.

  As shown in FIG. 19, the frequency filter has a substrate 140. As the substrate 140, for example, a substrate on which a surface acoustic wave element shown in FIG. 18 is formed is used. That is, it is a substrate formed by laminating the oxide thin film layer 12, the buffer layer 13, the piezoelectric film 14, and the protective layer 15 in this order on the (100) single crystal silicon substrate 11. The protective layer 15 is made of an oxide or nitride as a protective film.

  IDT electrodes 141 and 142 are formed on the upper surface of the substrate 140. The IDT electrodes 141 and 142 are made of, for example, Al or an Al alloy, and the thickness thereof is set to about 1/100 of the pitch of the IDT electrodes 141 and 142. Further, sound absorbing portions 143 and 144 are formed on the upper surface of the substrate 140 so as to sandwich the IDT electrodes 141 and 142. The sound absorbing parts 143 and 144 absorb surface acoustic waves that propagate on the surface of the substrate 140. A high frequency signal source 145 is connected to the IDT electrode 141 formed on the substrate 140, and a signal line is connected to the IDT electrode 142.

6-2. Operation of Frequency Filter Next, the operation of the above frequency filter will be described. In the above configuration, when a high frequency signal is output from the high frequency signal source 145, the high frequency signal is applied to the IDT electrode 141, thereby generating a surface acoustic wave on the upper surface of the substrate 140. The surface acoustic wave propagates on the upper surface of the substrate 140 at a speed of about 5000 m / s. The surface acoustic wave propagated from the IDT electrode 141 to the sound absorbing portion 143 side is absorbed by the sound absorbing portion 143. Of the surface acoustic waves propagated to the IDT electrode 142 side, the specific surface acoustic wave is determined according to the pitch of the IDT electrode 142 or the like. A surface acoustic wave having a frequency or a frequency in a specific band is converted into an electric signal and taken out to terminals 146a and 146b through signal lines. Note that most of the frequency components other than the specific frequency or the frequency in the specific band pass through the IDT electrode 142 and are absorbed by the sound absorbing unit 144. In this way, it is possible to obtain (filter) only a surface acoustic wave having a specific frequency or a specific band of the electric signal supplied to the IDT electrode 141 included in the frequency filter of the present embodiment.

7-1. Oscillator Next, an oscillator according to the present embodiment will be described with reference to the drawings. FIG. 20 shows an embodiment of the oscillator of the present invention.

  As shown in FIG. 20, the oscillator has a substrate 150. As the substrate 150, for example, a substrate on which a surface acoustic wave element shown in FIG. That is, it is a substrate formed by laminating the oxide thin film layer 12, the buffer layer 13, the piezoelectric film 14, and the protective layer 15 in this order on the (100) single crystal silicon substrate 11. The protective layer 15 is made of an oxide or nitride as a protective film.

  An IDT electrode 151 is formed on the upper surface of the substrate 150, and IDT electrodes 152 and 153 are formed so as to sandwich the IDT electrode 151. The IDT electrodes 151 to 153 are made of, for example, Al or an Al alloy, and each thickness is set to about 1/100 of the pitch of the IDT electrodes 151 to 153. A high frequency signal source 154 is connected to one comb-like electrode 151a constituting the IDT electrode 151, and a signal line is connected to the other comb-like electrode 151b. The IDT electrode 151 corresponds to an electric signal applying electrode, and the IDT electrodes 152 and 153 are used for resonance to resonate a specific frequency component of a surface acoustic wave generated by the IDT electrode 151 or a frequency component of a specific band. It corresponds to an electrode.

7-2. Next, the operation of the above-described oscillator will be described. In the above configuration, when a high-frequency signal is output from the high-frequency signal source 154, this high-frequency signal is applied to one comb-like electrode 151a of the IDT electrode 151, thereby propagating to the IDT electrode 152 side on the upper surface of the substrate 150. The surface acoustic wave that propagates to the IDT electrode 153 side is generated. The surface acoustic wave velocity is about 5000 m / s. Among these surface acoustic waves, the surface acoustic wave having a specific frequency component is reflected by the IDT electrode 152 and the IDT electrode 153, and a standing wave is generated between the IDT electrode 152 and the IDT electrode 153. The surface acoustic wave having the specific frequency component is repeatedly reflected by the IDT electrodes 152 and 153, whereby the specific frequency component or the frequency component in the specific band resonates and the amplitude increases. A part of the surface acoustic wave of the specific frequency component or the frequency component of the specific band is extracted from the other comb-shaped electrode 151b of the IDT electrode 151, and corresponds to the resonance frequency of the IDT electrode 152 and the IDT electrode 153. An electric signal having a frequency (or a frequency having a certain band) can be taken out to the terminals 155a and 155b.

7-3. FIG. 21 and FIG. 22 are diagrams showing an example in which the oscillator (surface acoustic wave device) of the present invention is applied to a VCSO (Voltage Controlled SAW Oscillator). FIG. 22 is a perspective view, and FIG. 22 is a top perspective view.

  The VCSO is configured to be mounted inside a metal (Al or stainless steel) housing 60. On the substrate 61, an IC (Integrated Circuit) 62 and an oscillator 63 are mounted. In this case, the IC 62 is an oscillation circuit that controls the frequency applied to the oscillator 63 in accordance with a voltage value input from an external circuit (not shown).

  In the oscillator 63, IDT electrodes 65a to 65c are formed on a substrate 64, and the configuration thereof is substantially the same as that of the oscillator shown in FIG. The substrate 64 is similar to the previous example, and as shown in FIG. 18, the oxide thin film layer 12, the buffer layer 13, the piezoelectric film 14, and the protective layer 15 are formed on the (100) single crystal silicon substrate 11. They are formed in order. The protective layer 15 is made of an oxide or nitride as a protective film.

  A wiring 66 for electrically connecting the IC 62 and the oscillator 63 is patterned on the substrate 61. The IC 62 and the wiring 66 are connected by a wire line 67 such as a gold wire, for example, and the oscillator 63 and the wiring 66 are connected by a wire line 68 such as a gold wire, whereby the IC 62 and the oscillator 63 are electrically connected via the wiring 66. Connected.

  The VCSO can also be formed by integrating the IC 62 and the oscillator (surface acoustic wave element) 63 on the same substrate.

  FIG. 23 shows a schematic diagram of a VCSO in which an IC 62 and an oscillator 63 are integrated. In FIG. 23, the oscillator 63 has a structure in which the formation of the oxide thin film layer 12 is omitted in the surface acoustic wave device shown in FIG.

  As shown in FIG. 23, the VCSO is formed by sharing the single crystal silicon substrate 61 (single crystal silicon substrate 11) in the IC 62 and the oscillator 63. Although not shown, the IC 62 and the electrode 65a (electrode 16) provided in the oscillator 63 are electrically connected. In the present embodiment, a TFT (thin film transistor) is particularly employed as the transistor constituting the IC 62.

  In this embodiment, an oscillator (surface acoustic wave element) 63 is first formed on a single crystal silicon substrate 61 and then separated from the single crystal silicon substrate 61 by adopting TFTs as transistors constituting the IC 62. The TFT formed on the second substrate can be transferred onto the single crystal silicon substrate 61 so that the TFT and the oscillator 63 can be integrated. Therefore, even if it is difficult to form the TFT directly on the substrate or it is not suitable to form the TFT, it can be suitably formed by transfer. Various methods can be adopted as the transfer method, and in particular, the transfer method described in JP-A-11-26733 can be preferably used.

  The VCSO shown in FIGS. 21 to 23 is used as a VCO (Voltage Controlled Oscillator) of the PLL circuit shown in FIG. 24, for example. Here, the PLL circuit will be briefly described.

  FIG. 24 is a block diagram showing a basic configuration of the PLL circuit. As shown in FIG. 24, the PLL circuit includes a phase comparator 71, a low-pass filter 72, an amplifier 73, and a VCO 74. The phase comparator 71 compares the phase (or frequency) of the signal input from the input terminal 70 with the phase (or frequency) of the signal output from the VCO 74, and an error whose value is set according to the difference. A voltage signal is output. The low-pass filter 72 passes only the low-frequency component at the position of the error voltage signal output from the phase comparator 71, and the amplifier 73 amplifies the signal output from the low-pass filter 72. . The VCO 74 is an oscillation circuit in which the frequency that oscillates according to the input voltage value changes continuously within a certain range.

  Under such a configuration, the PLL circuit operates so that the difference between the phase (or frequency) input from the input terminal 70 and the phase (or frequency) of the signal output from the VCO 74 is reduced. Is synchronized with the frequency of the signal input from the input terminal 70. When the frequency of the signal output from the VCO 74 is synchronized with the frequency of the signal input from the input terminal 70, the frequency thereafter matches the signal input from the input terminal 70 except for a certain phase difference, and the input signal changes. A signal that follows the signal is output.

8). Electronic Circuit and Electronic Device Next, an electronic circuit and an electronic device according to the present embodiment will be described with reference to the drawings. FIG. 25 is a block diagram showing an electrical configuration as an embodiment of the electronic circuit of the present invention. Note that the electronic circuit illustrated in FIG. 25 is, for example, a circuit provided inside the mobile phone 100 illustrated in FIG. Here, the cellular phone 100 shown in FIG. 26 is an example of the electronic apparatus of the present invention, and includes an antenna 101, a receiver 102, a transmitter 103, a liquid crystal display unit 104, an operation button unit 105, and the like. It is configured.

  The electronic circuit shown in FIG. 25 has a basic configuration of an electronic circuit provided in the mobile phone 100, and includes a transmitter 80, a transmission signal processing circuit 81, a transmission mixer 82, a transmission filter 83, a transmission power amplifier 84, A transmitter / receiver demultiplexer 85, antennas 86a and 86b, a low noise amplifier 87, a reception filter 88, a reception mixer 89, a reception signal processing circuit 90, a receiver 91, a frequency synthesizer 92, a control circuit 93, and an input / display circuit 94 are provided. It is configured. In addition, since the cellular phone currently in practical use performs frequency conversion processing a plurality of times, its circuit configuration is more complicated.

  The transmitter 80 is realized by, for example, a microphone that converts a sound wave signal into an electric signal, and corresponds to the transmitter 103 in the mobile phone 100 shown in FIG. The transmission signal processing circuit 81 is a circuit that performs processing such as D / A conversion processing and modulation processing on the electrical signal output from the transmitter 80. The transmission mixer 82 mixes the signal output from the transmission signal processing circuit 81 using the signal output from the frequency synthesizer 92. The frequency of the signal supplied to the transmission mixer 82 is about 380 MHz, for example. The transmission filter 83 passes only a signal having a frequency that requires an intermediate frequency (hereinafter referred to as “IF”) and cuts a signal having an unnecessary frequency. The signal output from the transmission filter 83 is converted into an RF signal by a conversion circuit (not shown). The frequency of this RF signal is, for example, about 1.9 GHz. The transmission power amplifier 84 amplifies the power of the RF signal output from the transmission filter 83 and outputs it to the transmission / reception duplexer 85.

  The transmitter / receiver demultiplexer 85 outputs the RF signal output from the transmission power amplifier 84 to the antennas 86a and 86b, and transmits the signals in the form of radio waves from the antennas 86a and 86b. The transmitter / receiver demultiplexer 85 demultiplexes the received signals received by the antennas 86 a and 86 b and outputs the demultiplexed signals to the low noise amplifier 87. The frequency of the reception signal output from the transmitter / receiver demultiplexer 85 is, for example, about 2.1 GHz. The low noise amplifier 87 amplifies the received signal from the transmitter / receiver demultiplexer 85. The signal output from the low noise amplifier 87 is converted to IF by a conversion circuit (not shown).

  The reception filter 88 passes only a signal having a frequency required for IF converted by a conversion circuit (not shown), and cuts a signal having an unnecessary frequency. The reception mixer 89 mixes the signal output from the transmission signal processing circuit 81 using the signal output from the frequency synthesizer 92. The intermediate frequency supplied to the receiving mixer 89 is, for example, about 190 MHz. The reception signal processing circuit 90 is a circuit that performs processing such as A / D conversion processing and demodulation processing on the signal output from the reception mixer 89. The receiver 91 is realized by, for example, a small speaker that converts an electric signal into a sound wave, and corresponds to the receiver 102 in the mobile phone 100 shown in FIG.

  The frequency synthesizer 92 is a circuit that generates a signal to be supplied to the transmission mixer 82 (for example, a frequency of about 380 MHz) and a signal to be supplied to the reception mixer 89 (for example, a frequency of 190 MHz). The frequency synthesizer 92 includes a PLL circuit that transmits, for example, at an oscillation frequency of 760 MHz. The frequency synthesizer 92 divides a signal output from the PLL circuit to generate a signal having a frequency of 380 MHz, and further divides the frequency to 190 MHz. The signal is generated. The control circuit 93 controls the overall operation of the mobile phone by controlling the transmission signal processing circuit 81, the reception signal processing circuit 90, the frequency synthesizer 92, and the input / display circuit 94. The input / display circuit 94 is for displaying the state of the device to the user of the mobile phone 100 shown in FIG. 26 and inputting an instruction from the operator. This corresponds to the display unit 104 and the operation button unit 105.

  In the electronic circuit having the above configuration, the frequency filter shown in FIG. 19 is used as the transmission filter 83 and the reception filter 88. The frequency to be filtered (frequency to be passed) is individually set by the transmission filter 83 and the reception filter 88 according to the frequency required from the signal output from the transmission mixer 82 and the frequency required by the reception mixer 89. Has been. In addition, the PLL circuit provided in the frequency synthesizer 92 includes the oscillator shown in FIG. 20 or the oscillator (VCSO) shown in FIGS. 21 to 23 as the VCO 74 of the PLL circuit shown in FIG.

9-1. First Thin Film Piezoelectric Resonator Next, a thin film piezoelectric resonator according to the present embodiment will be described with reference to the drawings. FIG. 27 shows a first thin film piezoelectric resonator according to the present embodiment. A thin film piezoelectric resonator 30 shown in FIG. 27 is a diaphragm type thin film piezoelectric resonator 30 used particularly as a communication element or a communication filter. The thin film piezoelectric resonator 30 is obtained by forming a resonator 33 on a base 31 made of a single crystal silicon substrate through an elastic plate 32.

  The base 31 is made of a (110) -oriented single crystal silicon substrate having a thickness of about 200 μm. A via hole 34 penetrating from the bottom surface side to the top surface side of the substrate 31 is formed on the bottom surface side of the substrate 31 (the side opposite to the elastic plate 32).

  In this embodiment, the elastic plate 32 is formed by the elastic film 3 in the piezoelectric element 1 shown in FIG. 1 and is formed on the (110) surface of the base 31. The resonator 33 is formed by the lower electrode 4, the buffer layer 5, the piezoelectric film 6 and the upper electrode 7 in the piezoelectric element 1 shown in FIG. Based on such a configuration, the thin film piezoelectric resonator 30 has a configuration in which the main portion (portion excluding the substrate 2) of the piezoelectric element 1 shown in FIG.

For the elastic plate 32, for example, silicon nitride (SiN) is formed on the substrate 31 to a thickness of about 200 nm, and silicon dioxide (SiO ₂ ) is further formed to a thickness of about 400 nm to 3 μm. The elastic film 3 may be formed thereon, and the laminated film of silicon nitride, silicon dioxide, and the elastic film 3 may be used as the elastic plate 32. Further, when silicon nitride and silicon dioxide are formed on the substrate 31 in this way, the elastic plate 32 can be formed only from these laminated films without forming the elastic film 3.

  The lower electrode 4 is made of, for example, (111) oriented Pt. The thickness of the lower electrode 4 is, for example, about 200 nm.

  The buffer layer 5 is made of a piezoelectric material having a perovskite type rhombohedral structure or a pseudo cubic structure, and is made of PZTX preferentially oriented to the pseudo cubic (100). The thickness of the buffer layer 5 is, for example, 0.1 μm or less.

  The piezoelectric film 6 is made of a relaxor material having a perovskite type and a rhombohedral structure and preferentially oriented to pseudo cubic (100). The thickness of the piezoelectric film 6 is, for example, about 0.9 μm.

  Similar to the lower electrode 4, the upper electrode 7 is made of Pt. In the present embodiment, the upper electrode 7 is formed to a thickness of about 700 nm. The upper electrode 7 is provided with a wiring 37 made of gold or the like via a pad 36 for electrical connection to the electrode 35 formed on the elastic plate 32.

9-2. Method for Manufacturing First Thin Film Piezoelectric Resonator Next, a method for manufacturing the above-described thin film piezoelectric resonator 30 will be described. First, a base material that becomes the base 31, that is, the aforementioned (110) -oriented single crystal silicon substrate (Si substrate) is prepared. Then, the elastic film 3 is formed on the Si substrate, and the lower electrode 4, the buffer layer 5, the piezoelectric film 6, and the upper electrode 7 are sequentially formed thereon. When a laminated film of silicon nitride, silicon dioxide, and elastic film 3 is adopted as the elastic plate 32, silicon nitride and silicon dioxide are formed in this order on the silicon substrate prior to the formation of the elastic film 3. deep.

  Next, the upper electrode 7, the piezoelectric film 6, the buffer layer 5, and the lower electrode 4 are patterned in correspondence with the via holes 34 to form the resonators 33. In particular, when the lower electrode 4 is patterned, the electrode 35 is formed simultaneously with the lower electrode 4 as shown in FIG.

  Next, the single crystal silicon substrate is processed (patterned) from the bottom side by etching or the like to form a via hole 34 penetrating therethrough. Next, a pad 36 and a wiring 37 that connect the upper electrode 7 and the electrode 35 are formed.

  Through the above steps, the first thin film piezoelectric resonator 30 according to the present embodiment can be manufactured.

9-3. Action / Effect According to the first thin film piezoelectric resonator 30 according to the present embodiment, the piezoelectric film 6 of the resonator 33 has good piezoelectric characteristics and thus has a high electromechanical coupling coefficient. Thereby, for example, it can be used in a high frequency region such as a GHz band. In addition, it functions well despite its small size (thinness).

9-4. Second Thin Film Piezoelectric Resonator FIG. 28 is a diagram showing a second thin film piezoelectric resonator according to the present embodiment. The main difference between the thin film piezoelectric resonator 40 and the thin film piezoelectric resonator 30 shown in FIG. 27 is that a via hole is not formed and an air gap 43 is formed between the substrate 41 and the resonator 42.

  That is, the thin film piezoelectric resonator 40 has a resonator 42 formed on a base body 41 made of a (110) -oriented single crystal silicon substrate. The resonator 42 is formed by a lower electrode 44, a piezoelectric material layer 45, and an upper electrode 46. The lower electrode 44 is made of the same material as the lower electrode 4 described above. The piezoelectric material layer 45 includes a buffer layer made of the same material as the buffer layer 5 described above and a piezoelectric film made of the same material as the piezoelectric film 6 described above. The upper electrode 46 is made of the same material as the upper electrode 7 described above. The resonator 42 is formed by laminating a lower electrode 44, a piezoelectric material layer 45, and an upper electrode 46, particularly on the air gap 43.

  Here, in the present embodiment, the elastic film 3 (see FIG. 1) is formed under the lower electrode 44 so as to cover the air gap 43, and the elastic film 3 is the same as the previous example. An elastic plate 47 is provided. As for the elastic plate 47, as in the previous example, silicon nitride and silicon dioxide are formed on the substrate 41, or only silicon dioxide is formed, and the elastic film 3 is formed thereon. Thus, the laminated film can be used as the elastic plate 47. Further, the elastic plate 47 can be formed from a laminated film of silicon nitride and silicon dioxide or only silicon dioxide without forming the elastic film 3.

9-5. Method for Manufacturing Second Thin Film Piezoelectric Resonator 40 In order to form the second thin film piezoelectric resonator 40, first, for example, germanium (Ge) is formed on the substrate 41 by vapor deposition or the like, and air for forming this film A sacrificial layer is formed by patterning into the same shape as the gap.

  Next, an elastic plate 47 is formed so as to cover the sacrificial layer. Prior to this, silicon nitride and silicon dioxide can be formed, or only silicon dioxide can be formed. Subsequently, these buffer layers are patterned into a desired shape.

  Next, a layer to be the lower electrode 44 is formed so as to cover the elastic plate 47, and the lower electrode 44 is formed by patterning the layer by dry etching or the like. Next, a buffer layer and a piezoelectric film are formed in this order so as to cover the lower electrode 44. That is, a layer to be the piezoelectric material layer 45 is formed from these laminated films. Further, this is patterned by dry etching or the like to form the piezoelectric material layer 45.

Next, a layer to be the upper electrode 46 is formed so as to cover the piezoelectric material layer 45, and further, this is patterned by dry etching or the like, thereby forming the upper electrode 46. In this manner, by forming the elastic plate 47, the lower electrode 44, the piezoelectric material layer 45, and the upper electrode 46 on the sacrificial layer by patterning, the sacrificial layer is partially exposed outside. Become. Next, the sacrificial layer is removed from the substrate 41 by etching with, for example, hydrogen peroxide (H ₂ O ₂ ), thereby forming an air gap 43.

  Through the above steps, the thin film piezoelectric resonator 40 according to the present embodiment can be manufactured.

9-6. Action / Effect According to the second thin film piezoelectric resonator 40 according to the present embodiment, the piezoelectric characteristic of the piezoelectric film of the resonator 42 is good, and therefore has a high electromechanical coupling coefficient. Thereby, for example, it can be used in a high frequency region such as a GHz band. In addition, it functions well despite its small size (thinness).

  Further, in the above-described thin film piezoelectric resonators 30 and 40, an appropriate inductive filter is configured by being appropriately combined with circuit components such as an inductance and a capacitor.

  As described above, the piezoelectric element, the piezoelectric actuator, the ink jet recording head, the ink jet printer, the piezoelectric pump, the surface acoustic wave element, the frequency filter, the oscillator, the electronic circuit, the thin film piezoelectric resonator, and the electronic apparatus (mobile phone 100) according to the present embodiment. However, the present invention is not limited to the above embodiment, and can be freely changed within the scope of the present invention. The piezoelectric element according to the present invention is applicable not only to the devices described above but also to various devices.

  For example, in the above-described embodiment, a mobile phone has been described as an example of an electronic device, and an electronic circuit provided in the mobile phone as an electronic circuit has been described as an example. However, the present invention is not limited to a mobile phone, and various The present invention can be applied to a mobile communication device and an electronic circuit provided therein.

  Furthermore, the present invention can be applied not only to mobile communication devices but also to communication devices used in a stationary state such as tuners that receive BS and CS broadcasts, and electronic circuits provided therein. Furthermore, not only communication devices that use radio waves propagating in the air as communication carriers, but also electronic devices such as HUBs that use high-frequency signals propagating in coaxial cables or optical signals propagating in optical cables, and the electronics provided therein It can also be applied to circuits.

Sectional drawing which shows the piezoelectric element concerning embodiment. The graph for demonstrating a relaxor material. The graph for demonstrating a relaxor material. The manufacturing process figure of a piezoelectric element. The manufacturing process figure of a piezoelectric element. The manufacturing process figure of a piezoelectric element. The manufacturing process figure of a piezoelectric element. The manufacturing process figure of a piezoelectric element. 1 is a schematic configuration diagram of an ink jet recording head. FIG. 2 is an exploded perspective view of an ink jet recording head. The top view of a cavity. The top view of a piezoelectric element. The figure for demonstrating operation | movement of a head. The figure for demonstrating operation | movement of a head. 1 is a schematic configuration diagram of an ink jet printer according to an embodiment. The schematic sectional drawing of the piezoelectric pump using the piezoelectric element shown in FIG. The schematic sectional drawing of the piezoelectric pump using the piezoelectric element shown in FIG. 1 is a side sectional view showing a surface acoustic wave device according to an embodiment. The perspective view which shows the frequency filter concerning embodiment. The perspective view which shows the oscillator concerning embodiment. The schematic side perspective drawing which shows an example which applied the said oscillator to VCSO. FIG. 3 is a schematic top perspective view showing an example in which the oscillator is applied to VCSO. Schematic which shows an example which applied the said oscillator to VCSO. The block diagram which shows the basic composition of a PLL circuit. 1 is a block diagram showing a configuration of an electronic circuit according to an embodiment. The perspective view which shows the mobile telephone as embodiment of an electronic device. 1 is a side sectional view showing a thin film piezoelectric resonator according to an embodiment. 1 is a side sectional view showing a thin film piezoelectric resonator according to an embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piezoelectric element, 2 Substrate, 3 Elastic film, 4 Lower electrode, 5 Buffer layer, 6 Piezoelectric film, 7 Upper electrode, 11 Single crystal silicon substrate, 12 Oxide thin film layer, 13 Buffer layer, 14 Piezoelectric film, 15 Protective layer, 16 electrodes, 20 piezoelectric pump, 21 substrate, 22 piezoelectric element, 23 pump chamber, 24 diaphragm, 30 first thin film piezoelectric resonator, 31 substrate, 32 elastic plate, 33 resonator, 34 via hole, 35 electrode , 36 pad, 37 wiring, 40 second thin film piezoelectric resonator, 41 substrate, 42 resonator, 43 air gap, 44 lower electrode, 45 piezoelectric material layer, 46 upper electrode, 47 elastic plate, 50 ink jet recording head, 51 nozzle plate, 52 ink chamber substrate, 54 piezoelectric element, 55 elastic plate, 56 base, 57 head body, 61 single crystal silicon substrate, 3 oscillator, 64 substrate, 66 wiring, 67 wire line, 68 wire line, 70 input terminal, 71 phase comparator, 72 low-pass filter, 73 amplifier, 80 transmitter, 81 transmission signal processing circuit, 82 transmission mixer, 83 Transmission filter, 84 Transmission power amplifier, 85 Transmitter / receiver demultiplexer, 87 Low noise amplifier, 88 Reception filter, 89 Reception mixer, 90 Reception signal processing circuit, 91 Handset, 92 Frequency synthesizer, 93 Control circuit, 94 Display circuit, 100 Mobile Telephone, 102 Handset, 103 Transmitter, 104 Liquid crystal display, 105 Operation button, 140 Substrate, 141 electrode, 142 electrode, 143 Sound absorber, 144 Sound absorber, 145 High frequency signal source, 150 substrate, 151 electrode, 152 electrode , 153 electrode, 154 high frequency signal source, 511 nozzle, 5 21 Cavity, 522 Side wall, 523 Reservoir, 524 Supply port, 531 Communication hole, 600 Inkjet printer, 620 Device main body, 621 Tray, 622 Discharge port, 630 Head unit, 631 Ink cartridge, 632 Carriage, 640 Printing device, 641 Carriage Motor, 642 Reciprocating mechanism, 643 Carriage guide shaft, 644 Timing belt, 650 Paper feed device, 651 Paper feed motor, 652 Paper feed roller, 660 Control unit, 670 Operation panel

Claims (19)

A substrate;
A buffer layer formed above the substrate;
A piezoelectric film formed above the buffer layer,
The buffer layer is made of perovskite Pb ((Zr _1−a Ti _a ) _1−b (Nb, Ta) _b ) O ₃ ,
a is in the range of 0.15 ≦ a ≦ 0.8,
b is in the range of 0.05 ≦ b ≦ 0.4;
The piezoelectric film is Ri Do a relaxor material of a perovskite-type,
The relaxor material is a piezoelectric element made of at least one of materials represented by the following formulas (1) to (9).
_{(1-x) Pb (Sc} 1/2 Nb 1/2) O 3 -xPb (Zr 1-y Ti y) O 3
... Formula (1)
(Where x is 0.10 <x <0.42, y is 0 ≦ y ≦ 1)
_{(1-x) Pb (In} 1/2 Nb 1/2) O 3 -xPb (Zr 1-y Ti y) O 3
... Formula (2)
(Where x is 0.10 <x <0.37, y is 0 ≦ y ≦ 1)
_{(1-x) Pb (Ga} 1/2 Nb 1/2) O 3 -xPb (Zr 1-y Ti y) O 3
... Formula (3)
(Where x is 0.10 <x <0.50, y is 0 ≦ y ≦ 1)
_{(1-x) Pb (Sc} 1/2 Ta 1/2) O 3 -xPb (Zr 1-y Ti y) O 3
... Formula (4)
(Where x is 0.10 <x <0.45, y is 0 ≦ y ≦ 1)
(1-x) Pb (Mg _1/3 Nb _2/3 ) O ₃ —xPb (Zr _1-y Ti _y ) O ₃
... Formula (5)
(Where x is 0.10 <x <0.35, y is 0 ≦ y ≦ 1)
_{(1-x) Pb (Fe} 1/2 Nb 1/2) O 3 -xPb (Zr 1-y Ti y) O 3
... Formula (6)
(Where x is 0.01 <x <0.10, y is 0 ≦ y ≦ 1)
(1-x) Pb (Zn _1/3 Nb _2/3 ) O ₃ -xPb (Zr _1-y Ti _y ) O ₃
... Formula (7)
(Where x is 0.01 <x <0.10, y is 0 ≦ y ≦ 1)
(1-x) Pb (Ni _1/3 Nb _2/3 ) O ₃ —xPb (Zr _1-y Ti _y ) O ₃
... Formula (8)
(Where x is 0.10 <x <0.38, y is 0 ≦ y ≦ 1)
_{(1-x) Pb (Co} 1/2 W 1/2) O 3 -xPb (Zr 1-y Ti y) O 3
... Formula (9)
(Where x is 0.10 <x <0.42, y is 0 ≦ y ≦ 1) In claim 1 ,
a is in the range of (a _MPB −0.05) ≦ a ≦ a _MPB ,
a _MPB is a piezoelectric element showing the value of a at the phase boundary of the crystal structure of the buffer layer. In claim 1 or 2 ,
The said buffer layer is a piezoelectric element which has a in the phase boundary of the crystal structure of this buffer layer. In any one of claims 1 to 3,
The buffer layer is a piezoelectric element having a rhombohedral structure and preferentially oriented to pseudo cubic (100). In any one of Claims 1-3 ,
The buffer layer has a pseudo cubic structure and is preferentially oriented to pseudo cubic (100). In any one of Claims 1-5 ,
The piezoelectric element has a rhombohedral structure and is preferentially oriented to pseudo cubic (100). In any one of Claims 1-6 ,
The buffer layer is a piezoelectric element containing 5 mol% or less of Si, or Si and Ge. In any of the claims 1-7,
A lower electrode formed above the substrate;
The buffer layer formed above the lower electrode;
A piezoelectric element including an upper electrode formed above the piezoelectric film. In claim 8 ,
A piezoelectric element in which at least one of the lower electrode and the upper electrode is made of a material mainly containing Pt. A piezoelectric element according to any one of claims 1 to 9 piezoelectric actuator. A piezoelectric element according to any one of claims 1 to 9 piezoelectric pump. A piezoelectric element according to any one of claims 1 to 9 ink jet recording head. An ink jet printer comprising the ink jet recording head according to claim 12 . The piezoelectric element according to any one of claims 1 to 9, formed by formed above the substrate, the surface acoustic wave device. A first electrode formed above the piezoelectric film included in the surface acoustic wave device according to claim 14 ;
A frequency filter comprising: a second electrode formed above the piezoelectric film. A first electrode formed above the piezoelectric film included in the surface acoustic wave device according to claim 14 ;
A second electrode formed above the piezoelectric film;
An oscillator comprising: an oscillation circuit having a transistor. An electronic circuit comprising the oscillator according to claim 16 . A resonator having the piezoelectric element according to any one of claims 1 to 9, comprising formed above a substrate, a thin film piezoelectric resonator. Claim 11 of the piezoelectric pump, a frequency filter according to claim 15, oscillator of claim 16, the electronic circuit according to claim 17, at least one of the thin film piezoelectric resonator of claim 18 Having an electronic device.

Images