JP2005302933A - Piezoelectric element, piezoelectric actuator, ink jet recording head, ink jet printer, surface acoustic wave device, frequency filter, oscillator, electronic circuit, thin film piezoelectric resonator, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric element provided with a piezoelectric film having high piezoelectric constant; and to provide a piezoelectric actuator, an ink jet recording head, an ink jet printer, a surface acoustic wave device, a frequency filter, an oscillator, electronic circuit, a thin-film piezoelectric resonator, and an electronic apparatus which use the piezoelectric element. <P>SOLUTION: The piezoelectric element 1 is provided with a seed layer 5 formed on a substrate, and the piezoelectric film 6 formed on the seed layer 5. The seed layer 5 consists of a bismuth laminar compound, and oriented preferentially to a (c) axis (001). The piezoelectric film 6 is perovskite and consists of relaxer material oriented preferentially to pseudo cubic (100). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a piezoelectric element having a piezoelectric film, a piezoelectric actuator, 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, and performs printing by ejecting ink droplets from the nozzle while scanning the head. As a head actuator in such an ink jet recording head for 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.
In recent years, relaxor materials have attracted attention as materials having high piezoelectric characteristics (piezoelectric constant). However, although this relaxor material exhibits high piezoelectric properties as a bulky bulk, it does not become a clean film when it is formed as a thin film, and thus it is difficult to make it function as a piezoelectric film.

  The present invention has been made in view of the above circumstances, and an object thereof is a piezoelectric element including a piezoelectric film having a high piezoelectric constant, a piezoelectric actuator using the piezoelectric element, an ink jet recording head, an ink jet printer, To provide a surface acoustic wave device, a frequency filter, an oscillator, an electronic circuit, a thin film piezoelectric resonator, and an electronic device.

The present inventors obtained the following knowledge as a result of intensive studies to achieve the above object.
As a method of forming a clean thin film from a relaxor material and causing it to function as a piezoelectric film, for example, it is conceivable to form a relaxor material on an electrode made of SrRuO ₃ .
On the other hand, as a condition for the relaxor material to exhibit higher piezoelectric properties, it must have a rhombohedral structure and be preferentially oriented to pseudo cubic (100).

Therefore, when the relaxor material is used for the piezoelectric film of the piezoelectric element, the pseudo-cubic (100) -oriented relaxor material is formed on the pseudo-cubic (100) -oriented as the lower electrode layer. This is preferable. However, in order to orient (100) the SrRuO ₃ , it is necessary to use the ion beam assist method. However, in this case, a new problem such as an increase in manufacturing cost arises.

On the other hand, in order to make the ion beam assist method unnecessary, it is conceivable to form a (100) orientation film of PZT as a seed layer on the lower electrode and orient the relaxor material on the (100) orientation.
However, not only the (100) orientation but also the (111) or (110) oriented material is mixed in on the Pt or Ir that is easily deposited as the lower electrode. As a result, not only (100) but also the orientation of (111) or (110) is easily mixed into the relaxor material formed thereon, and the resulting piezoelectric film has its piezoelectric properties ( The piezoelectric constant may not be sufficiently high.
Based on such knowledge, the present inventor completed the present invention as a result of further research.

That is, the piezoelectric element of the present invention comprises a seed layer formed on a substrate and a piezoelectric film formed on the seed layer,
The seed layer has the general formula Bi ₂ A _m-1 B _m O _{3m + 3} (where m = 2, 3, 4, A is a metal element selected from Ba, Ca, Sr, La, Bi, and B is Fe, Ga) , Ti, Ta, Nb, V, Mo, W, Zr, Hf) and a preferentially oriented c axis (001).
The piezoelectric film is made of a relaxor material of perovskite type and preferentially oriented to pseudo cubic (100).

According to this piezoelectric element, since the bismuth layered compound is used as the seed layer, this bismuth layered compound easily becomes c-axis orientation, that is, (001) orientation even on an electrode made of, for example, Pt or Ir. . Since a relaxor material oriented in pseudo cubic (100) is easily formed on the (001) oriented bismuth layered compound, the piezoelectric film made of the relaxor material is a perovskite type. This is preferentially oriented to pseudo cubic (100). Therefore, since this piezoelectric film has ferroelectricity, that is, has high piezoelectric characteristics, the piezoelectric constant is high and the applied voltage is more greatly deformed.
In the present invention, the term “preferentially oriented” means that most (eg, 90% or more) is oriented to (100) which is a desired orientation, and the rest is other orientation (eg (111) orientation). Of course, the case where 100% is the desired orientation (100) is also included.

In the piezoelectric element, the relaxor material is preferably a perovskite type having a rhombohedral structure and preferentially oriented to pseudo cubic (100).
If it becomes like this, since a relaxor material shows a higher piezoelectric characteristic, a piezoelectric material film will function more favorably.

In the piezoelectric element, it is preferable that the seed layer is made of at least one of materials represented by the following formulas.
_{· SrBi 2 (Ta 1-x} Nb x) 2 O 9 ( where, 0 ≦ x ≦ 1.0)
・ (Bi _1-x La _x ) ₄ Ti ₃ O ₁₂ (where 0 ≦ x ≦ 0.4)
SrBi ₄ Me ₄ O ₁₅ (where Me is at least one of Ti, Zr, and Hf)
By doing so, the bismuth layered compound is more easily c-axis oriented on the electrode made of, for example, Pt or Ir, and becomes (001) oriented. 100).

Moreover, it is preferable that the said relaxer material consists of at least 1 type of the material shown by the following formula | equation.
_{· (1-x) Pb (} Sc 1/2 Nb 1/2) O 3 -xPbTiO 3
(Where x is 0.10 <x <0.42)
_{· (1-x) Pb (} In 1/2 Nb 1/2) O 3 -xPbTiO 3
(However, x is 0.10 <x <0.37)
_{· (1-x) Pb (} Ga 1/2 Nb 1/2) O 3 -xPbTiO 3
(However, x is 0.10 <x <0.50)
(1-x) Pb (Sc _1/2 Ta _1/2 ) O ₃ -xPbTiO ₃
(Where x is 0.10 <x <0.45)
(1-x) Pb (Mg _1/3 Nb _2/3 ) O ₃ —xPbTiO ₃
(However, x is 0.10 <x <0.35)
_{· (1-x) Pb (} Fe 1/2 Nb 1/2) O 3 -xPbTiO 3
(Where x is 0.01 <x <0.10)
(1-x) Pb (Zn _1/3 Nb _2/3 ) O ₃ —xPbTiO ₃
(Where x is 0.01 <x <0.11)
(1-x) Pb (Ni _1/3 Nb _2/3 ) O ₃ —xPbTiO ₃
(However, x is 0.08 <x <0.38)
_{· (1-x) Pb (} Co 1/2 W 1/2) O 3 -xPbTiO 3
(Where x is 0.10 <x <0.42)
In this way, the piezoelectric constant is sufficiently high, and thus the piezoelectric film is deformed better.

The piezoelectric element may be an ink jet recording head having a cavity whose inner volume changes, and the inner volume of the cavity may be changed by deformation of the piezoelectric film.
Thus, if the piezoelectric element (head actuator) for an ink jet recording head is used, the ink can be discharged well with good piezoelectric characteristics.

A piezoelectric actuator according to the present invention includes the above-described piezoelectric element.
According to this piezoelectric actuator, it functions well due to the piezoelectric characteristics as described above.

An ink jet recording head of the present invention includes the above-described piezoelectric element as a piezoelectric element that changes the internal volume of the cavity by deformation of a piezoelectric film in an ink jet recording head having a cavity whose internal volume changes. It is characterized by that.
According to this ink jet recording head, as described above, ink can be ejected satisfactorily due to good piezoelectric characteristics. In addition, since the piezoelectric constant of the piezoelectric film is particularly high and the deformation is greater with respect to the applied voltage, the area (volume) of the cavity required to eject a predetermined amount of ink is larger than the conventional one. It is small and therefore allows high density nozzles.

An ink jet printer according to the present invention includes the ink jet recording head described above.
According to this ink jet printer, since the ink jet recording head having high performance and high nozzle density is provided, high speed printing is possible.

A surface acoustic wave device according to the present invention is characterized in that the piezoelectric element according to claim 1 or 2 is formed on a substrate.
According to this surface acoustic wave element, the surface acoustic wave element itself has high performance because the piezoelectric film of the piezoelectric element has good piezoelectric characteristics.

The frequency filter of the present invention is formed on the piezoelectric film included in the surface acoustic wave element, on the piezoelectric film, and applied to the first electrode. And a second electrode that resonates with a specific frequency of a surface acoustic wave generated in the piezoelectric film by an electric signal or a frequency in a specific band and converts it into an electric signal.
According to this frequency filter, since the piezoelectric characteristics of the piezoelectric film are good, and the electromechanical coupling coefficient of the piezoelectric film is high, the specific band width is good.

The oscillator of the present invention is formed on the piezoelectric film included in the surface acoustic wave element, and generates an electric signal applying electrode on the piezoelectric film by an applied electric signal, and the piezoelectric An oscillation circuit that is formed on the body film and includes a resonance electrode and a transistor that resonates a specific frequency component of a surface acoustic wave generated by the electrode for applying an electric signal or a frequency component of a specific band. It is characterized by that.
According to this oscillator, since the piezoelectric characteristic of the piezoelectric film is good and the electromechanical coupling coefficient of the piezoelectric film is high, the extension coil can be omitted, and the circuit configuration becomes simple. In addition, since an oscillation circuit composed of a transistor or the like is provided, the size is reduced by integration with the transistor.

The electronic circuit of the present invention includes the oscillator and an electric signal supply element that applies the electric signal to the electric signal applying electrode provided in the oscillator, and the frequency component of the electric signal. A function of selecting a specific frequency component from or converting to a specific frequency component, or applying a predetermined modulation to the electric signal, performing a predetermined demodulation, or performing a predetermined detection It is said.
According to this electronic circuit, the piezoelectric film of the surface acoustic wave device provided in the oscillator has good piezoelectric characteristics, and thus the piezoelectric film has a high electromechanical coupling coefficient and can be integrated with the oscillation circuit. Because it is possible, it is small and has high performance.

The thin film piezoelectric resonator of the present invention is characterized in that a resonator comprising the above piezoelectric element is formed on a substrate.
According to this thin film piezoelectric resonator, since the piezoelectric film of the resonator has a high electromechanical coupling coefficient, it can be used in a high frequency region such as a GHz band.
In such a thin film piezoelectric resonator, if a via hole is formed on the side of the substrate opposite to the side where the resonator is formed, a diaphragm type thin film piezoelectric resonator is obtained.
If an air gap is formed between the substrate and the resonator, an air gap type thin film piezoelectric resonator is obtained.

An electronic apparatus according to the present invention includes at least one of the frequency filter, the oscillator, the electronic circuit, and the thin film piezoelectric resonator.
According to this electronic apparatus, the piezoelectric film has good piezoelectric characteristics, and therefore, since the piezoelectric film has a high electromechanical coupling coefficient, it is small and has high performance.

The present invention will be described in detail below.
(Piezoelectric element)
First, the piezoelectric element of the present invention will be described.
FIG. 1 is a view showing an embodiment in which the piezoelectric element of the present invention is applied to a piezoelectric element that is a head actuator for an ink jet recording head. In FIG. 1, reference numeral 1 denotes a piezoelectric element.

The piezoelectric element 1 is formed on 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 lower part A seed layer 5 formed on the electrode 4, a piezoelectric film 6 formed on the seed layer 5, and an upper electrode 7 formed on the piezoelectric film 6. is there. Here, in the present invention, the substrate 2 to the lower electrode 4 are referred to as a base.
As the substrate 2, a (100) -oriented single crystal silicon substrate, a (111) -oriented single crystal silicon substrate, a (110) -oriented Si substrate, or the like can also be used. Of course, an amorphous silicon oxide film such as a thermal oxide film or a natural oxide film can be used on the surface.

The elastic film 3 formed on the substrate 2 is a film that functions as an elastic plate in a piezoelectric element serving as a head actuator for an ink jet recording head, and is made of SiO ₂ , ZrO _2, etc., and has a thickness of, for example, about 1 μm. It is formed thick. With respect to the elastic film 3, as described later, when the substrate 2 is etched to form a cavity therein, the elastic film 3 functions as an etching stopper layer so that the elastic film 3 functions as an etching stopper layer with Si such as SiO ₂ or ZrO _2. It is preferable to use a material having a sufficient selection ratio. The elastic film 3 may be formed as a common elastic plate when a plurality of piezoelectric elements are formed on the substrate 2 serving as 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. For example, as shown in FIG. 1, the lower electrode 4 is formed in the same size as the piezoelectric film 6, that is, in the same shape as the upper electrode 7. It has been done. The lower electrode 4 has a common elastic plate so as to function as a common electrode when a plurality of piezoelectric elements are formed on the substrate 2 serving as an ink chamber substrate in an ink jet recording head to be described later. You may form in the same magnitude | size as the elastic film 3 as. The lower electrode 4 is made of Pt (platinum), Ir (iridium), IrO _x (iridium oxide), Ti (titanium), or the like, and has a thickness of about 100 nm to 200 nm.

The seed layer 5 has a general formula Bi ₂ A _m-1 B _m O _{3m + 3} (where m = 2, 3, 4 and A is a metal element selected from Ba, Ca, Sr, La, Bi, and B is Fe, Ga , Ti, Ta, Nb, V, Mo, W, Zr, and Hf), and is preferentially oriented in the c-axis (001) with a bismuth layered compound (hereinafter referred to as a Bi layered compound). It will be. Specifically, it is preferably made of at least one material selected from the following formulas.
_{· SrBi 2 (Ta 1-x} Nb x) 2 O 9
(However, 0 ≦ x ≦ 1.0) (m = 2)
(Bi _1-x La _x ) ₄ Ti ₃ O ₁₂
(However, 0 ≦ x ≦ 0.4) (m = 3)
SrBi ₄ Me ₄ O ₁₅
(However, Me is at least one of Ti, Zr, and Hf) (m = 4)

  Such a Bi layer compound is formed on the lower electrode 4 by a liquid phase method or a gas phase method. When the film is formed in this way, the Bi layered compound is easily preferentially oriented to the c-axis orientation on the lower electrode 4 made of, for example, Pt or Ir, and thereby becomes (001) orientation. In particular, the three types of Bi layered compounds represented by the above formulas are more easily c-axis oriented on the lower electrode 4 (preferentially oriented to c-axis orientation) and (001) oriented. Here, “preferentially oriented” includes the case where most are oriented in the c-axis orientation, which is the desired orientation, as described above, but the rest are in other orientations. Thus, if most are oriented in the c-axis orientation which is the desired orientation, when the piezoelectric film 6 is formed thereon as will be described later, the piezoelectric film 6 is better due to the pseudo cubic (100). In other words, that is, the preferred orientation is (100).

  Since the seed layer 5 is a piezoelectric material, it does not function as the lower electrode 4 but rather functions as a piezoelectric film 6 to be described later, and affects the piezoelectric characteristics of the piezoelectric film 6. (Helps piezoelectric properties). Therefore, if the thickness of the seed layer 5 becomes too thick, the influence on the piezoelectric characteristics of the piezoelectric film 6 becomes large. Therefore, the thickness of the seed layer 5 is set so that this influence does not become larger than necessary. Is preferably 100 nm or less, and more preferably 50 nm 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), and has a thickness of about 300 nm to 3000 nm, preferably about 500 nm to 1000 nm, desirably It is formed to about 500 nm. However, the upper limit value of the film thickness of the piezoelectric film 6 can be made thicker as long as the denseness and crystal orientation as a thin film can be maintained, and specifically, it can be allowed to be about 10 μm. it can.

As a relaxor material, the material shown by the following formula | equation 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 -xPbTiO 3
(Where x is 0.10 <x <0.42, preferably 0.20 <x <0.42)
_{· (1-x) Pb (} In 1/2 Nb 1/2) O 3 -xPbTiO 3
(Where x is 0.10 <x <0.37, preferably 0.20 <x <0.37)
_{· (1-x) Pb (} Ga 1/2 Nb 1/2) O 3 -xPbTiO 3
(Where x is 0.10 <x <0.50, preferably 0.30 <x <0.50)
(1-x) Pb (Sc _1/2 Ta _1/2 ) O ₃ -xPbTiO ₃
(Where x is 0.10 <x <0.45, preferably 0.20 <x <0.45)
(1-x) Pb (Mg _1/3 Nb _2/3 ) O ₃ —xPbTiO ₃
(Where x is 0.10 <x <0.35, preferably 0.20 <x <0.35)
_{· (1-x) Pb (} Fe 1/2 Nb 1/2) O 3 -xPbTiO 3
(Where x is 0.01 <x <0.10, preferably 0.03 <x <0.10)
(1-x) Pb (Zn _1/3 Nb _2/3 ) O ₃ —xPbTiO ₃
(Where x is 0.01 <x <0.11, preferably 0.03 <x <0.11)
(1-x) Pb (Ni _1/3 Nb _2/3 ) O ₃ —xPbTiO ₃
(Where x is 0.08 <x <0.38, preferably 0.09 <x <0.38)
_{· (1-x) Pb (} Co 1/2 W 1/2) O 3 -xPbTiO 3
(Where x is 0.10 <x <0.42, preferably 0.20 <x <0.42)

  Here, as shown in FIG. 2A, the relaxor material indicates a material having a broad (wide) peak of the dielectric dependency, and the temperature at which the dielectric constant is maximized is shifted by frequency measurement. Say material. At the same time, the temperature dependence of the piezoelectric constant shows a broad (wide) peak. On the other hand, a piezoelectric material which is a non-relaxer material such as PZT has a very sharp peak in temperature dependence of dielectric constant and piezoelectric constant as shown in FIG. 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.

The piezoelectric film 6 is a perovskite type, has a rhombohedral structure, is preferentially oriented to pseudo cubic (100), has an engineered domain arrangement, and therefore has a high piezoelectric constant (d ₃₁ ). It has become. Here, “preferentially oriented” includes a case where most of the pseudo-cubic crystals (100) having a desired orientation are oriented as described above, but the rest are in other orientations. That is, it is formed on the seed layer 5 similarly preferentially oriented, and this seed layer 5 is preferentially oriented to the c-axis orientation and thereby has a (001) orientation, so that the piezoelectric film 6 made of a relaxor material is also formed. The perovskite type is preferentially oriented to pseudo cubic (100). Here, since the seed layer 5 is preferentially oriented to the c-axis orientation and has the (001) orientation, the obtained Bi layered compound has almost no contamination of the (111) or (110) orientation, Therefore, the relaxor material formed thereon is hardly mixed with the (111) or (110) orientation.

Further, in the material for forming the piezoelectric film 6 (relaxer material), as described above, regarding the range of x representing the composition ratio on the PbTiO ₃ (PT) side between the materials, the upper limit thereof is particularly the phase boundary ( MPB), that is, a value indicating the composition ratio on the PbTiO ₃ (PT) 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 d constant (d ₃₁ ), which is a piezoelectric constant, takes a maximum value near the phase boundary (MPB). Therefore, a value close to the value of x at the time of this MPB is selected as the lower limit value of x. Therefore, as described above, the range of x is a preferable range in order to obtain a d constant (d ₃₁ ) that is a higher piezoelectric constant, although a relatively small value can be allowed in configuring the present invention. Value, that is, a value closer to the value of x at the time of the MPB.

Thus, the piezoelectric film 6 made of the relaxor material having the perovskite type and the rhombohedral structure and preferentially oriented to the pseudo-cubic crystal (100), as described above, has conventionally had a complicated method for forming it. It was necessary. For example, a buffer layer is formed by using a laser ablation method and a complicated method such as an ion beam assist method, and a base is formed by forming a perovskite-type lower electrode on the buffer layer. A piezoelectric film was formed on the base. The reason for adopting such a method is that the manufacturing margin for forming a dense thin film of relaxor material on a conventional electrode material such as Pt or Ir is small, whereas it is relatively easy on a perovskite type electrode such as SrRuO _3. This is because a thin film can be obtained, and a laser ablation method or an ion beam assist method is required to control the orientation of the SrRuO ₃ electrode.

  However, such a method has a problem in that the process is complicated, and thus the cost is high, and the piezoelectric characteristics of the obtained piezoelectric film are not sufficiently stable. On the other hand, the Bi layered compound is preferentially oriented in the c-axis (001) on the lower electrode 4 such as Pt or Ir as described above, and becomes a dense thin film. A relaxor material such as PMN-PT can be easily laminated as a dense thin film on the Bi layered compound. Therefore, in the present invention, as described above, the seed layer 5 made of the Bi layered compound is formed in advance, and the piezoelectric film 6 made of the relaxor material is formed on the seed layer 5 so that the gas phase method can be used as described later. In addition, the piezoelectric film 6 having excellent piezoelectric characteristics can be easily obtained by the liquid phase method.

The upper electrode 7 serves as the other electrode for applying a voltage to the piezoelectric film 6. Like the lower electrode 4, for example, Pt (platinum), Ir (iridium), IrO _x (iridium oxide), Ti ( Titanium), SrRuO _3, etc., with a thickness of about 100 nm.
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. If the seed layer 5 made of a Bi layer compound is sandwiched between the lower electrode 4 made of SrRuO ₃ and the piezoelectric film 6 made of a relaxor material, the pseudo-cubic crystal (100) of the piezoelectric film 6 is manufactured in the manufacturing process. The orientation can be controlled more easily.

Next, a method for manufacturing the piezoelectric element 1 having such a configuration will be described.
First, as the substrate 2, a (110) or (100) -oriented single crystal Si substrate, a (111) -oriented single crystal Si substrate, or an amorphous silicon oxide film that is a natural oxide film is formed (100) or (110 ) An oriented Si substrate is prepared.
Next, the elastic film 3 is formed on the substrate 2 as shown in FIG. 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.
Next, as shown in FIG. 3B, the lower electrode 4 made of, for example, Pt is formed on the elastic plate 3. Since this Pt can be (111) preferentially oriented relatively easily, it can be easily oriented and grown on the elastic film 3 by adopting a relatively simple method such as sputtering.

  Next, a seed layer 5 is formed on the lower electrode 4 as shown in FIG. As a method for forming the seed layer 5 (film formation method), for example, a liquid phase method such as a sol-gel method using a precursor solution of the Bi layer compound is employed. In this liquid phase method, the seed layer 5 is formed by disposing the precursor solution on the lower electrode 4 by a known coating method such as a spin coating method or a droplet discharge method, and then performing a heat treatment such as firing. obtain. That is, the seed layer 5 is formed by repeating a series of steps of the precursor solution coating step, the drying heat treatment step, and the degreasing heat treatment step as appropriate according to the desired film thickness, and then performing crystallization annealing. Specific conditions are shown below.

As a precursor solution (precursor material) of the Bi layered compound constituting the seed layer 5, each constituent metal of this compound (oxide) (for example, [SrBi ₂ (Ta _1-x Nb _x ) ₂ O ₉ ]) , Sr, Bi, Ta, Nb) -containing metal alkoxides or metal salts such as carbonates are prepared and used for each metal element.
Specifically, as the organic acid salt, strontium 2-ethylhexanoate (Sr), bismuth ethylhexanoate (Bi), tantalum ethylhexanoate (Ta), niobium ethylhexanoate (Nb), etc. are used. All are used by dissolving in a solvent such as octane, butoxyethanol, or xylene.

And, in the case of the molar ratio of each element constituting the Bi layer compound (for example, [SrBi ₂ (Ta _1-x Nb _x ) ₂ O ₉ ]), these metal compounds are converted into Sr: Bi: (Ta, Nb) = 1: 2: 2) is mixed. For the precursor compound mixed in this way, for example, an appropriate solvent or dispersion medium such as alcohols is provided in order to provide physical properties suitable for the coating method employed (for example, spin coating method or droplet discharge method). It is preferable to prepare a sol-like liquid material by adding, for example.

Subsequently, the sol-like liquid (precursor solution) prepared in this way is applied onto the lower electrode 4. For example, when the spin coating method is employed for the coating process, first, the precursor solution is dropped on the lower electrode 4. Then, 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.

The degreasing heat treatment step is performed by heating to about 350 ° 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 is performed by heating to, for example, about 600 ° C. using rapid thermal annealing (RTA) or the like in an oxygen atmosphere.
In this way, the Bi layer compound is formed on the lower electrode 4 made of (111) -oriented Pt so as to be preferentially oriented in the c-axis (001), whereby the seed layer 5 can be formed.

  For the formation of the seed layer 5 made of the Bi layered compound, a droplet discharge method can be used instead of the spin coating method as a coating method, and a laser ablation method can be used as a film forming method instead of the liquid phase method. Alternatively, a vapor phase method such as sputtering can be employed. When the seed layer 5 is formed by sputtering, rapid thermal annealing (RTA) is performed once at, for example, 700 ° C. after the formation. The power during sputtering is set to 200 W, for example.

Next, a piezoelectric film 6 is formed on the seed layer 5 as shown in FIG. As a method for forming the piezoelectric film 6 (film forming method), for example, a liquid phase method such as a sol-gel method using a precursor solution of the relaxor material is employed. In this liquid phase method, the precursor solution is disposed on the seed layer 5 by a known coating method such as a spin coating method or a droplet discharge method, and then a heat treatment such as baking is performed, whereby the piezoelectric film 6 Get. Specifically, in the same manner as the formation of the seed layer 5, a series of steps including a precursor solution coating step, a solvent removal step, a drying heat treatment step, and a degreasing heat treatment step are repeated as appropriate according to the desired film thickness, Thereafter, crystallization annealing is performed to form the piezoelectric film 6. Conditions in each process are almost the same as the formation of the seed layer 5.
The piezoelectric film 6 formed in this way is c-axis oriented and formed on the seed layer 5 preferentially oriented to (001), so that it becomes easy to orient to pseudo cubic (100), resulting in And a perovskite type having a rhombohedral structure and preferentially oriented to pseudo cubic (100).

Here, with respect to the precursor solution that is a material for forming the seed layer 5 and the piezoelectric film 6, an organic metal containing a constituent metal of the piezoelectric material or the relaxor material that becomes the seed layer 5 or the piezoelectric film 6, respectively. That is, it is produced by mixing organic metals such as metal alkoxides and organic acid salts so that each metal has a desired molar ratio, and further dissolving or dispersing them using an organic solvent such as alcohol. In addition, various additives such as stabilizers may be added to the precursor solution as necessary. Further, when hydrolysis / polycondensation is caused in the solution, an appropriate amount of water is added. An acid or a base may be added as a catalyst.
Although the piezoelectric film 6 is also formed by the liquid phase method, it may be formed by using a vapor phase method such as a laser ablation method or a sputtering method as with the seed layer 5.

  Thereafter, an upper electrode 7 made of Pt is formed on the piezoelectric film 6 as shown in FIG. The upper electrode 7 can be formed by sputtering or the like, similar to the lower electrode 4.

In the piezoelectric element 1 obtained in this way, the piezoelectric film 6 made of the relaxor material is formed on the seed layer 5 which is c-axis oriented and preferentially oriented to (001). The body film is also well preferentially oriented to pseudo-cubic crystal (100), and thus has a high piezoelectric constant and a greater deformation with respect to the applied voltage.
The piezoelectric element of the present invention can be used not only as a head actuator for the ink jet recording head described above but also as another piezoelectric actuator.

(Example)
Based on the manufacturing method shown in FIGS. 3A to 3E, the piezoelectric element 1 was manufactured as follows.
First, the lower electrode 4 made of (111) -oriented Pt was formed on the substrate 2 through the elastic film 3 to a thickness of 100 nm by sputtering. The power during sputtering was 200 W.
Next, precursor solutions of three kinds of compounds represented by the following formulas were prepared as follows.
_{· SrBi 2 (Ta 1-x} Nb x) 2 O 9 ( where, x = 0.1) (m = 2)
(Bi _1-x La _x ) ₄ Ti ₃ O ₁₂ (where x = 0.1) (m = 3)
・ SrBi ₄ Ti ₄ O ₁₅ (m = 4)
The constituent metal diethylhexanoate in each compound was used and dissolved in a solvent such as octane, butoxyethanol, or xylene to obtain a precursor solution.

  And these precursor solutions are each apply | coated on the said lower electrode 4 by the spin coat method (application process of a precursor solution), Then, it heat-processes at the temperature about 10 degreeC higher than a solvent (dry), and removes a solvent ( Drying heat treatment step), and further decomposing / removing the organometallic ligand by heating to about 350 ° C. (degreasing heat treatment step), and then using rapid thermal annealing (RTA) in an oxygen atmosphere to about 600 ° C. Three types of seed layers 5 were formed by heating and crystallization. The film thickness of each seed layer 5 was 20 nm.

Next, precursor solutions of three kinds of relaxer materials represented by the following formulas were prepared as follows.
(1-x) Pb (Mg _1/3 Nb _2/3 ) O ₃ —xPbTiO ₃
(However, x = 0.3)
(1-x) Pb (Zn _1/3 Nb _2/3 ) O ₃ —xPbTiO ₃
(However, x = 0.1)
(1-x) Pb (Ni _1/3 Nb _2/3 ) O ₃ —xPbTiO ₃
(However, x = 0.1)
Prepare metal reagents such as lead acetate, titanium isopropoxide, magnesium acetate, niobium ethoxide, as well as zinc, nickel acetate or alkoxide, and have molar ratios corresponding to the compounds (relaxer materials) that form them. These were mixed and dissolved (dispersed) in butyl cellosolve, and diethanolamine was added as a solution stabilizer to prepare a precursor solution.
Then, these precursor solutions are respectively applied onto the three seed layers 5 by the spin coating method (precursor solution applying step), and then heat-treated (dried) at a temperature about 10 ° C. higher than the solvent to obtain a solvent. Is removed (dry heat treatment step) and further heated to about 350 ° C. to decompose / remove the organometallic ligand (degreasing heat treatment step), and then using rapid thermal annealing (RTA) in an oxygen atmosphere. Three types of piezoelectric films 6 were formed on each seed layer 5 by heating to about 600 ° C. and crystallization.

Thereafter, an upper electrode 7 made of Pt was formed on each piezoelectric film 6 by sputtering, and nine types of piezoelectric elements 1 were obtained.
When the piezoelectric film 6 in each piezoelectric element 1 obtained in this way was examined by X-ray diffraction (XRD), it was confirmed that it was preferentially oriented to (100), and it had a rhombohedral structure. It was also confirmed.
Further, when the piezoelectric constant (d ₃₁ ) of the piezoelectric film 6 was measured, as shown in the following table, all were as high as 400 pC / N or more, and the leak current was 10 ⁻⁵ A / cm at 100 kV / cm. It was less than cm ^2.
Furthermore, were examined repetition durability during 300 kV / cm is applied in the piezoelectric element 1 was provided with high durability can guarantee 10 ⁹ times.

"table"
Sample No. Seed layer Piezoelectric film Piezoelectric constant d ₃₁ (pC / N)
(1) A D 450
(2) A E 410
(3) A F 430
(4) BD 420
(5) B E 460
(6) B F 470
(7) CD 440
(8) CE 480
(9) C F 410
However, A, B, and C in the “seed layer” column are Bi layer compounds shown in the following formula, respectively, and D, E, and F in the “piezoelectric film” column are relaxor materials shown in the following formulas, respectively. is there.
_{A; SrBi 2 (Ta 1-} x Nb x) 2 O 9
(However, x = 0.1) (m = 2)
B; (Bi _1-x La _x ) ₄ Ti ₃ O ₁₂
(However, x = 0.1) (m = 3)
C; SrBi ₄ Ti ₄ O ₁₅ (m = 4)
D; (1-x) Pb (Mg _1/3 Nb _2/3 ) O ₃ —xPbTiO ₃
(However, x = 0.3)
E; (1-x) Pb (Zn _1/3 Nb _2/3 ) O ₃ —xPbTiO ₃
(However, x = 0.1)
F; (1-x) Pb (Ni _1/3 Nb _2/3 ) O ₃ —xPbTiO ₃
(However, x = 0.1)

(Inkjet recording head)
Next, an ink jet recording head using the piezoelectric element shown in FIG. 1 will be described. FIG. 4 is a side sectional view showing a schematic configuration of an ink jet recording head using the piezoelectric element shown in FIG. 1, and FIG. 5 is an exploded perspective view of the ink jet recording head. Note that FIG. 4 is shown upside down from a normally used state. In these drawings, reference numeral 50 denotes an ink jet recording head (hereinafter referred to as a head). As shown in FIG. 4, the head 50 includes a head main body 57 and a piezoelectric element 54 provided on the head main body 57. 4 includes the lower electrode 4, the seed layer 5, the piezoelectric film 6 and the upper electrode 7 in the piezoelectric element 1 shown in FIG. 1 (see FIG. 5). 4 is an elastic plate 55 in FIG. The substrate 2 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. 56 is housed. 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 Si substrate 2 described above, and includes a plurality of cavities (ink cavities) 521 by a nozzle plate 51, side walls (partition walls) 522, and an elastic plate 55 described later. A reservoir 523 for temporarily storing ink supplied from the ink cartridge 631 and a supply port 524 for supplying ink from the reservoir 523 to each cavity 521 are partitioned.

These cavities 521 are arranged corresponding to the respective nozzles 511 as shown in FIG. 4, and the volume of each of these cavities 521 is variable due to vibration of an elastic plate 55 described later. It is comprised so that it may do.
As a base material for obtaining the ink chamber substrate 52, that is, the substrate 2, for example, 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.

  On the other hand, an elastic plate 55 is provided on the side of the ink chamber substrate 52 opposite to the nozzle plate 51, and a plurality of piezoelectric elements 54 are provided on the side of the elastic plate 55 opposite to the ink chamber substrate 52. Yes. As described above, the elastic plate 55 is formed by the elastic film 3 in the piezoelectric element 1 shown in FIG. 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 as shown in FIG. The communication hole 531 supplies ink from an ink cartridge 631 described later to the reservoir 523.

Each piezoelectric element 54 is configured by inserting the piezoelectric film 6 between the lower electrode 4 and the upper electrode 7 as described above, and each piezoelectric element 54 corresponds to a substantially central portion of each cavity 521. It is arranged. 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), and the elastic plate 55 vibrates (deflects) due to vibration (deflection) of the piezoelectric element 54, so that the internal pressure of the cavity 521 is reduced. It functions to increase instantaneously.
The base 56 is formed of, for example, various resin materials, various metal materials, and the like, and the ink chamber substrate 52 is fixed and supported on the base 56 as shown in FIG.

  In the head 50 having such a configuration, a voltage is applied between the lower electrode 4 and the upper electrode 6 of the piezoelectric element 54 in a state where a predetermined ejection signal is not input via the piezoelectric element driving circuit. In the absence, 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 6 of the piezoelectric element 54, As shown in FIG. 6B, the piezoelectric film 6 is bent and deformed in the minor axis direction. As a result, the elastic plate 55 bends, for example, by 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 displacement (absolute value) of the piezoelectric film 6 in the minor axis direction of the cavity 521, the greater the amount of flexure of the elastic plate 55, making it possible to eject ink droplets more efficiently. . In the present invention, as described above, since the piezoelectric constant (d ₃₁ ) of the piezoelectric film 6 of the piezoelectric element 54 (1) is high and the applied voltage is more deformed, it is elastic. The amount of bending of the 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 in this way, 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 its original shape, 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 ink chamber 521 from the nozzle 511, and an amount of ink corresponding to the ink discharge 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.

  In order to manufacture the head 50 having such a configuration, first, the base material to be the ink chamber substrate 52, that is, the substrate 2 made of the above-described (110) -oriented silicon single crystal substrate (Si substrate) is prepared. Then, as shown in FIG. 3, the elastic film 3 is formed on the substrate 2, and the lower electrode 4, the seed layer 5, the piezoelectric film 6, and the upper electrode 7 are sequentially formed thereon. The elastic film 3 formed here becomes the elastic plate 55 as described above.

Next, the upper electrode 7, the piezoelectric film 6, the seed layer 5, and the lower electrode 4 are patterned corresponding to the individual cavities 521 to be formed, and the number corresponding to the number of cavities 521 as shown in FIG. 4. The piezoelectric element 54 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 set at predetermined positions. A recess is formed.

  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, and then, for example, a parallel plate type reactive ion etching, an inductively coupled method, an electron cyclotron resonance method, Dry etching such as helicon wave excitation method, magnetron method, plasma etching method, ion beam etching method, etc., or wet etching with high concentration alkaline aqueous solution such as potassium hydroxide, tetramethylammonium hydroxide, etc. Do.

Here, particularly when a (110) -oriented silicon substrate is used as the base material (substrate 2), the above-described wet etching (anisotropic etching) using a high-concentration alkaline aqueous solution is preferably employed. In this case, the elastic film 3 can function as an etching stopper during the wet etching with the high-concentration alkaline aqueous solution, so that the ink chamber substrate 52 can be formed more easily.
In this manner, the ink chamber substrate 52 is formed by etching away the base material (substrate 2) in the thickness direction until the elastic plate 55 (buffer layer 3) is exposed. At this time, the portion that remains without being etched becomes the side wall 522, and the exposed elastic film 3 is in a state in which 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 bonding of the nozzle plate 51, for example, an adhesive method using an adhesive or a fusion method can be used.
Thereafter, the ink chamber substrate 52 is attached to the base body 56, whereby the ink jet recording head 50 is obtained.

  In the ink jet recording head 50 obtained as described above, since the piezoelectric element 54 has good piezoelectric characteristics, it is possible to perform efficient ejection. Accordingly, high-density printing and high-speed printing are possible, and further, the entire head can be miniaturized.

(inkjet printer)
Next, an ink jet printer provided with the ink jet recording head 50 will be described. In the present invention, an inkjet printer includes not only printers that print on paper or the like, but also industrially used droplet discharge devices.

FIG. 7 is a schematic configuration diagram showing an embodiment in which the ink jet printer of the present invention is applied to a general printer that prints on paper or the like, and reference numeral 600 in FIG. 7 denotes the ink jet printer. In the following description, the upper side in FIG. 7 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. The ink jet printer 600 has a tray 621 for placing the recording paper P in the upper rear, a discharge port 622 for discharging the recording paper P in the lower front, and an operation panel on the upper surface. 670.

The operation panel 670 is composed of, for example, a liquid crystal display, an organic EL display, an LED lamp, and the like. A display unit (not shown) for displaying an error message and the like, and an operation unit (not shown) including various switches and the like. Z)).
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 reciprocates the head unit 63 in response to the rotation of the carriage motor 641. .
The head unit 630 includes the ink jet recording head 50 including a large number of nozzles 511, an ink cartridge 631 that supplies ink to the ink jet recording head 50, and the ink jet recording head 50 and the ink cartridge 631. A carriage 632.

  Note that full-color printing can be performed by using an ink cartridge 631 filled with ink of four colors of yellow, cyan, magenta, and black (black). 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 be able to reciprocate and is fixed to a part of the timing belt 644.
When the timing belt 644 travels forward and backward via a pulley by the operation of the carriage motor 641, the head unit 63 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 as a driving source and a sheet feeding roller 652 that rotates by the operation of the sheet feeding motor 651.
The paper feed roller 652 is composed of a driven roller 652a and a drive roller 652b that are vertically opposed to each other with a feeding path (recording paper P) of the recording paper P interposed therebetween. The drive roller 652b is a paper feed motor 651. It is connected to. 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 640. Instead of the tray 621, a configuration in which a paper feed cassette that stores the recording paper P can be detachably mounted may 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 that stores a control program for controlling each unit, a piezoelectric element driving circuit that drives the piezoelectric element (vibration source) 54 to control the ink ejection timing, A driving circuit for driving the printing device 640 (carriage motor 641), a driving circuit for driving the paper feeding device 650 (paper feeding motor 651), and a communication circuit for obtaining print data from the host computer, and electrically connected thereto And a CPU for performing various controls in each unit.

In addition, for example, various sensors capable of detecting a printing environment such as the remaining amount of ink in the ink cartridge 631, the position of the head unit 63, temperature, and humidity 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.

Such an ink jet printer 600 includes the ink jet recording head 50 capable of high-performance and high-density nozzles as described above, so that high-density printing and high-speed printing are possible.
In addition, the inkjet printer 600 of the present invention can be a droplet discharge device used industrially as described above. In this case, as the ink (liquid material) to be ejected, various functional materials are adjusted to an appropriate viscosity with a solvent or a dispersion medium and used.

In addition, the piezoelectric element of the present invention can be applied not only to the ink jet recording head 50 and the ink jet printer 600 described above, but also to various devices.
Hereinafter, embodiments of a surface acoustic wave element, a frequency filter, an oscillator, an electronic circuit, a thin film piezoelectric resonator, and an electronic apparatus according to the present invention will be described with reference to the drawings.

(Surface acoustic wave device)
FIG. 8 shows an embodiment of a surface acoustic wave device including the piezoelectric element of the present invention, that is, a piezoelectric element having the seed layer 5 and the piezoelectric film 6 shown in FIG.
This surface acoustic wave device includes a single crystal silicon substrate 11, an oxide thin film layer 12, a seed layer 13, a piezoelectric film 14, a protective layer 15 made of oxide or nitride as a protective film, and an electrode 16. It consists of and. The electrode 16 is an inter-digital electrode (Inter-Digital Transducer: hereinafter referred to as “IDT electrode”). When viewed from above, for example, the inter-digital electrodes 141, 142, 151 shown in FIG. 9 and FIG. , 152, and 153.

In order to manufacture the surface acoustic wave device having such a configuration, first, a (100) single crystal silicon substrate is prepared as the single crystal silicon substrate 11.
Next, a thin film of, for example, IrO ₂ or TiO ₂ is formed on the single crystal silicon substrate 11 using a laser ablation method or the like to form an oxide thin film layer 12.

Next, a seed layer 13 is formed on the oxide thin film layer 12 by a liquid phase method in the same manner as in the formation of the piezoelectric element 1, and a piezoelectric film 14 is further formed thereon by a liquid phase method.
Next, a SiO ₂ film is formed as a protective film 15 on the piezoelectric film 14 by, for example, a laser ablation method. The protective film 15 protects the piezoelectric film 14 from the atmosphere to prevent the influence of moisture and impurities in the atmosphere, for example, and also serves to control 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 SiO ₂ .

Thereafter, 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.
In the surface acoustic wave device thus obtained, the surface acoustic wave device itself has high performance because the piezoelectric film 14 has good piezoelectric characteristics.

(Frequency filter)
FIG. 9 shows an embodiment of the frequency filter of the present invention.
As shown in FIG. 9, 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. 8 is formed is used. That is, an oxide thin film layer 12, a seed layer 13, a piezoelectric film 14, and a protective layer 15 made of oxide or nitride as a protective film are stacked in this order on a (100) single crystal silicon substrate 11. It is a substrate.

  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.

  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.

(Oscillator)
FIG. 10 shows an embodiment of the oscillator of the present invention.
As shown in FIG. 10, the oscillator has a substrate 150. As the substrate 150, for example, a substrate on which the surface acoustic wave element shown in FIG. That is, an oxide thin film layer 12, a seed layer 13, a piezoelectric film 14, and a protective layer 15 made of oxide or nitride as a protective film are stacked in this order on a (100) single crystal silicon substrate 11. It is a substrate.

  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 application 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.

  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 and the surface acoustic wave that propagates to the IDT electrode 153 side are generated. The surface acoustic wave velocity is about 5000 m / s. Of these surface acoustic waves, the surface acoustic waves having a specific frequency component are 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. When the surface acoustic wave having the specific frequency component is repeatedly reflected by the IDT electrodes 152 and 153, 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.

FIG. 11 is a diagram showing an example in which the oscillator (surface acoustic wave device) of the present invention is applied to a VCSO (Voltage Controlled SAW Oscillator), and (a) is a side perspective view. b) 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. As shown in FIG. 8, the substrate 64 is formed on the (100) single crystal silicon substrate 11, the oxide thin film layer 12, the seed layer 13, the piezoelectric film 14, and the protective film. This is a substrate in which a protective layer 15 made of oxide or nitride as a film is laminated in this order.
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, and the oscillator 63 and the wiring 66 are connected by a wire line 68 such as a gold wire, so that the IC 62 and the oscillator 63 are electrically connected via the wiring 66. It is connected to the.

The VCSO may be formed by integrating the IC 62 and the oscillator (surface acoustic wave element) 63 on the same substrate.
FIG. 12 shows a schematic diagram of a VCSO in which an IC 62 and an oscillator 63 are integrated. In FIG. 10, the oscillator 63 has a structure in which the formation of the second oxide thin film layer 13 is omitted in the surface acoustic wave device shown in FIG.
As shown in FIG. 12, the VCSO is formed by sharing the single crystal silicon substrate 61 (11) in the IC 62 and the oscillator 63. Although not shown, the IC 62 and the electrode 65a (15) provided in the oscillator 63 are electrically connected. In the present embodiment, in particular, a TFT (thin film transistor) is employed as the transistor constituting the IC 62.

  By adopting a TFT as a transistor constituting the IC 62, in this embodiment, first, an oscillator (surface acoustic wave element) 63 is formed on the single crystal silicon substrate 61, and then different from the single crystal silicon substrate 61. 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. 11 and 12 is used, for example, as a VCO (Voltage Controlled Oscillator) of the PLL circuit shown in FIG. Here, the PLL circuit will be briefly described.
FIG. 13 is a block diagram showing the basic configuration of the PLL circuit. As shown in FIG. 13, 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 voltage whose value is set according to the difference. A 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 that continuously changes within a certain range according to an input voltage value.

  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. The frequency of the output signal 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.

(Electronic circuit and electronic equipment)
FIG. 14 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. 14 is, for example, a circuit provided in the mobile phone 100 illustrated in FIG. Here, the cellular phone 100 shown in FIG. 15 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. 14 has a basic configuration of the 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, and a transmission power amplifier. 84, transmitter / receiver demultiplexer 85, antennas 86a and 86b, low noise amplifier 87, reception filter 88, reception mixer 89, reception signal processing circuit 90, receiver 91, frequency synthesizer 92, control circuit 93, and input / display circuit 94 It is prepared. 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 transmission / reception 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). Note that the frequency synthesizer 92 includes a PLL circuit that transmits at an oscillation frequency of, for example, 760 MHz, divides the 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. 15 and inputting an instruction from the operator. This corresponds to the unit 104 and the operation button unit 105.

  In the electronic circuit having the above configuration, the frequency filter shown in FIG. 9 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 in the signal output from the transmission mixer 82 and the frequency required by the reception mixer 89. Has been. The PLL circuit provided in the frequency synthesizer 92 is provided with the oscillator shown in FIG. 11 or the oscillator (VCSO) shown in FIG. 12 as the VCO 74 of the PLL circuit shown in FIG.

(Thin film piezoelectric resonator)
FIG. 16 shows an embodiment of the thin film piezoelectric resonator of the present invention. Reference numeral 30 in FIG. 16 denotes a diaphragm-type thin film piezoelectric resonator particularly used as a communication element or a communication filter. The thin film piezoelectric resonator 30 has an elastic plate 32 on a base 31 made of a single crystal silicon substrate. A resonator 33 is formed through the gap.
The base 31 is made of a (110) -oriented single crystal silicon substrate having a thickness of about 200 μm, and penetrates from the bottom side to the top side of the base 31 on the bottom side (the side opposite to the resonator 32). A via hole 34 is formed.

  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 seed 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 part (portion excluding the base 2) of the piezoelectric element 1 shown in FIG.

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

The lower electrode 4 is made of (111) -oriented Pt, and the thickness thereof is about 200 nm.
The seed layer 5 is made of a Bi layered compound and is preferentially oriented with respect to the c-axis (001). Specifically, the seed layer 5 is made of a Bi layered compound or the like represented by the following formula and has a thickness of 0.1 μm. It is formed as follows.
_{· SrBi 2 (Ta 1-x} Nb x) 2 O 9
(However, 0 ≦ x ≦ 1.0) (m = 2)
(Bi _1-x La _x ) ₄ Ti ₃ O ₁₂
(However, 0 ≦ x ≦ 0.4) (m = 3)
SrBi ₄ Me ₄ O ₁₅
(However, Me is at least one of Ti, Zr, and Hf) (m = 4)
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 0.9 μm.
The upper electrode 7 is made of Pt, like the lower electrode 4. However, the upper electrode 6 is formed to a thickness of about 700 nm in this embodiment.
The upper electrode 6 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.

  In order to manufacture the thin film piezoelectric resonator 30 having such a configuration, first, a base material to be the base 31, that is, the above-described (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 seed 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 buffer layer 3 is employed as the elastic plate 32, silicon nitride and silicon dioxide are formed in this order on the Si substrate prior to the formation of the elastic film 3. deep.

Next, the upper electrode 7, the piezoelectric film 6, the seed layer 5, and the lower electrode 4 are patterned corresponding to the via holes 34 to be formed, thereby forming 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.
Thereafter, the pad 36 and the wiring 37 that connect the upper electrode 7 and the electrode 35 are formed, and the thin film piezoelectric resonator 30 is obtained.

  In the thin film piezoelectric resonator 30 obtained in this manner, the piezoelectric characteristics of the piezoelectric film of the resonator are good, and thus have a high electromechanical coupling coefficient. Therefore, for example, in a high frequency region such as the GHz band. In addition, it can function well even though it is small (thin).

FIG. 17 is a view showing another embodiment of the thin film piezoelectric resonator of the present invention, and reference numeral 40 in FIG. 17 denotes a thin film piezoelectric resonator. The main difference between the thin film piezoelectric resonator 40 and the thin film piezoelectric resonator 30 shown in FIG. 16 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, this thin film piezoelectric resonator 40 is obtained by forming a resonator 42 on a base body 41 made of a (110) -oriented single crystal silicon substrate. The resonator 42 includes the lower electrode 4, the seed layer 5, the piezoelectric film 6, the lower electrode 44 made of the same material as the upper electrode 7, the piezoelectric material layer 45 made of the seed layer and the piezoelectric film, and the upper electrode 46. In particular, the lower electrode 44, the piezoelectric material layer 45, and the upper electrode 46 are stacked on the air gap 43.

  Here, in the present embodiment, the elastic film 3 is formed under the lower electrode 44 so as to cover the air gap 43, and this elastic film 3 becomes the elastic plate 47 as in the previous example. Yes. 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 layer 3 is formed thereon. These laminated films may be formed as the elastic plate 47. Alternatively, the elastic plate 47 may be formed from a laminated film of silicon nitride and silicon dioxide, or silicon dioxide alone, without forming the elastic film layer 3.

In order to form the thin film piezoelectric resonator 40 having such a configuration, first, for example, germanium (Ge) is formed on the substrate 41 by vapor deposition or the like, and further patterned into the same shape as the air gap forming the same. As a result, a sacrificial layer is formed.
Next, the elastic film 3 is formed covering the sacrificial layer. Prior to this, silicon nitride and silicon dioxide may be formed, or only silicon dioxide may 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 film 3 and further patterned by dry etching or the like to form the lower electrode 44.
Next, a seed layer and a piezoelectric film are formed in this order so as to cover the lower electrode 44, a layer that becomes the piezoelectric material layer 45 is formed from these laminated films, and further, this is patterned by dry etching or the like, whereby a piezoelectric material layer is formed. 45 is formed.
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 way, by forming the elastic film 3, 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.
Thereafter, 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, thereby obtaining the thin film piezoelectric resonator 40.

Even in the thin film piezoelectric resonator 40 obtained in this way, the piezoelectric characteristics of the piezoelectric film of the resonator are good, and thus have a high electromechanical coupling coefficient. Therefore, for example, in a high frequency region such as the GHz band. In addition, it can function well even though it is small (thin).
Further, in the above-described thin film piezoelectric resonators 30 and 40, an appropriate inductive filter is configured by appropriately combining with circuit components such as an inductance and a capacitor.

As described above, the surface acoustic wave device, the frequency filter, the oscillator, the electronic circuit, the thin film piezoelectric resonator, and the electronic device (the mobile phone 100) according to the embodiment of the present invention have been described, but the present invention is not limited to the above embodiment, Modifications can be made freely within the scope of the present invention.
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 example of an electronic circuit has been described. However, the present invention is not limited to a mobile phone, and various movements are possible. It can be applied to a body 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.

It is sectional drawing which shows one Embodiment of the piezoelectric element of this invention. (A), (b) is a graph for demonstrating a relaxor material. (A)-(e) is a manufacturing-process figure of a piezoelectric element. 1 is a schematic configuration diagram of an ink jet recording head. 2 is an exploded perspective view of an ink jet recording head. FIG. (A), (b) is a figure for demonstrating operation | movement of a head. It is a schematic block diagram of the inkjet printer of this invention. 1 is a side sectional view showing a surface acoustic wave device according to the present invention. It is a perspective view which shows the frequency filter which concerns on this invention. It is a perspective view which shows the oscillator which concerns on this invention. It is the schematic which shows an example which applied the said oscillator to VCSO. It is the schematic which shows an example which applied the said oscillator to VCSO. It is a block diagram which shows the basic composition of a PLL circuit. It is a block diagram which shows the structure of the electronic circuit which concerns on this invention. It is a perspective view which shows the mobile telephone as embodiment of an electronic device. It is a sectional side view which shows the thin film piezoelectric resonator which concerns on this invention. It is a sectional side view which shows the thin film piezoelectric resonator which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric element, 2 ... Substrate, 3 ... Elastic film, 4 ... Lower electrode, 5 ... Seed layer, 6 ... Piezoelectric film,
7 ... Upper electrode, 11 ... Single crystal silicon substrate (single crystal substrate), 14 ... Piezoelectric film,
50: Inkjet recording head (head), 54: Piezoelectric element,
60 ... Inkjet printer, 521 ... Cavity

Claims (14)

A seed layer formed on the substrate, and a piezoelectric film formed on the seed layer,
The seed layer has the general formula Bi ₂ A _m-1 B _m O _{3m + 3} (where m = 2, 3, 4, A is a metal element selected from Ba, Ca, Sr, La, Bi, and B is Fe, Ga) , Ti, Ta, Nb, V, Mo, W, Zr, Hf) and a preferentially oriented c axis (001).
The piezoelectric film is made of a relaxor material preferentially oriented to pseudo cubic (100) in a perovskite type.   2. The piezoelectric element according to claim 1, wherein the relaxor material is a perovskite type, has a rhombohedral structure, and is preferentially oriented to pseudo cubic (100). The piezoelectric element according to claim 1, wherein the seed layer is made of at least one of materials represented by the following formulas.
_{· SrBi 2 (Ta 1-x} Nb x) 2 O 9 ( where, 0 ≦ x ≦ 1.0)
・ (Bi _1-x La _x ) ₄ Ti ₃ O ₁₂ (where 0 ≦ x ≦ 0.4)
SrBi ₄ Me ₄ O ₁₅ (where Me is at least one of Ti, Zr, and Hf) The piezoelectric element according to claim 1, wherein the relaxor material is made of at least one of materials represented by the following formulas.
_{· (1-x) Pb (} Sc 1/2 Nb 1/2) O 3 -xPbTiO 3
(Where x is 0.10 <x <0.42)
_{· (1-x) Pb (} In 1/2 Nb 1/2) O 3 -xPbTiO 3
(However, x is 0.10 <x <0.37)
_{· (1-x) Pb (} Ga 1/2 Nb 1/2) O 3 -xPbTiO 3
(However, x is 0.10 <x <0.50)
(1-x) Pb (Sc _1/2 Ta _1/2 ) O ₃ -xPbTiO ₃
(Where x is 0.10 <x <0.45)
(1-x) Pb (Mg _1/3 Nb _2/3 ) O ₃ —xPbTiO ₃
(However, x is 0.10 <x <0.35)
_{· (1-x) Pb (} Fe 1/2 Nb 1/2) O 3 -xPbTiO 3
(Where x is 0.01 <x <0.10)
(1-x) Pb (Zn _1/3 Nb _2/3 ) O ₃ —xPbTiO ₃
(Where x is 0.01 <x <0.11)
(1-x) Pb (Ni _1/3 Nb _2/3 ) O ₃ —xPbTiO ₃
(However, x is 0.08 <x <0.38)
_{· (1-x) Pb (} Co 1/2 W 1/2) O 3 -xPbTiO 3
(Where x is 0.10 <x <0.42)   5. The piezoelectric element according to claim 1, wherein the piezoelectric element is an ink jet recording head having a cavity whose inner volume changes, and the inner volume of the cavity is changed by deformation of the piezoelectric film. The piezoelectric element described in 1.   The piezoelectric actuator provided with the piezoelectric element as described in any one of Claims 1-5. In an ink jet recording head having a cavity whose internal volume changes,
An ink jet recording head comprising the piezoelectric element according to any one of claims 1 to 5 as a piezoelectric element that changes the internal volume of the cavity by deformation of the piezoelectric film.   An ink jet printer comprising the ink jet recording head according to claim 7.   A surface acoustic wave device, wherein the piezoelectric device according to any one of claims 1 to 4 is formed on a substrate. A first electrode formed on the piezoelectric film included in the surface acoustic wave device according to claim 9;
An electric signal that is formed on the piezoelectric film and resonates with a specific frequency or a specific frequency of a surface acoustic wave generated in the piezoelectric film by an electric signal applied to the first electrode, and converts it into an electric signal. A frequency filter comprising: a second electrode. An electric signal applying electrode that is formed on the piezoelectric film included in the surface acoustic wave device according to claim 9 and generates a surface acoustic wave in the piezoelectric film by an applied electric signal;
An oscillation circuit formed on the piezoelectric film and including a resonance electrode and a transistor for resonating a specific frequency component or a specific frequency component of a surface acoustic wave generated by the electric signal application electrode; An oscillator comprising: An oscillator according to claim 11;
An electrical signal supply element that applies the electrical signal to the electrical signal application electrode provided in the oscillator;
Select a specific frequency component from the frequency components of the electrical signal or convert it to a specific frequency component, or apply predetermined modulation to the electrical signal, perform predetermined demodulation, or perform predetermined detection An electronic circuit characterized by having a function.   A thin film piezoelectric resonator, wherein a resonator comprising the piezoelectric element according to any one of claims 1 to 4 is formed on a substrate. An electronic apparatus comprising at least one of the frequency filter according to claim 10, the oscillator according to claim 11, the electronic circuit according to claim 12, and the thin film piezoelectric resonator according to claim 13.

Images