JP2022044257A - Piezoelectric film element and piezoelectric film vibrator - Google Patents

Abstract

To provide novel piezoelectric film element and piezoelectric film vibrator including an electrode whose conductivity decreases less easily even after heating under an oxidative atmosphere and a PZT piezoelectric film with high orientation and the excellent piezoelectric characteristic.SOLUTION: A piezoelectric film element includes a substrate, a first electrode layer including ruthenium and/or ruthenium oxide disposed on the substrate, an oxide layer with a perovskite structure oriented on a (100) surface disposed on the first electrode layer, and a piezoelectric film with a perovskite structure containing zinc, zirconium, and titanium disposed on the oxide layer.SELECTED DRAWING: Figure 1

Description

The present invention relates to a piezoelectric membrane element and a piezoelectric membrane oscillator.

Piezoelectric membrane oscillators having a piezoelectric film and electrodes formed on the upper and lower surfaces of the piezoelectric film are used in various piezoelectric devices such as vibration power generation elements, sensors, actuators, inkjet heads, and autofocus. As the piezoelectric film, a PZT-based piezoelectric film having a perovskite crystal containing lead (Pb), zirconium (Zr), and titanium (Ti) is widely used. As a method for producing this PZT-based piezoelectric film, a CSD method (chemical solution deposition: also referred to as a chemical solution volume method or a sol-gel method) is known (Patent Document 1).

The CSD method is a method in which a precursor solution (or a sol-gel solution) containing a metal element having a target composition is applied to the surface of a substrate, and the obtained coating film is heated in an oxidizing atmosphere to form a piezoelectric film. be. The CSD method is an advantageous method in that a piezoelectric film can be manufactured by using a relatively small device without requiring a high vacuum as compared with the sputtering method.

The production of the PZT-based piezoelectric membrane oscillator using the CSD method is performed, for example, as follows. First, the precursor solution is applied onto the first electrode layer, and the obtained coating film is heated in an oxidizing atmosphere at a temperature at which a PZT-based piezoelectric film is formed. As a result, a piezoelectric film element including the first electrode layer and the PZT-based piezoelectric film is obtained. Next, a second electrode layer is formed on the PZT-based piezoelectric film of the piezoelectric film element to obtain a PZT-based piezoelectric film oscillator. In the manufacture of this PZT-based piezoelectric membrane oscillator, it is necessary that the first electrode layer does not easily lose its conductivity when heated in an oxidizing atmosphere. Therefore, as the material of the first electrode layer, platinum, which is less likely to be oxidized when heated in an oxidizing atmosphere, is used. Platinum has the effect of promoting nucleation when the PZT-based piezoelectric film is formed by heating, and also has the effect of forming a PZT-based piezoelectric film having high orientation and excellent piezoelectric characteristics.

Japanese Unexamined Patent Publication No. 2018-148113

In order to broaden the range of electrode material selection, an electrode material that does not easily lose its conductivity even when heated in an oxidizing atmosphere and can generate a PZT-based piezoelectric film having the same orientation as when platinum is used. It is desirable if can be developed. However, the electrode material whose conductivity does not easily decrease even when heated in an oxidizing atmosphere has a low effect of promoting the formation of nuclei of the PZT-based piezoelectric film, and depending on the CSD method, it is possible to generate a PZT-based piezoelectric film having high orientation. It tends to be difficult.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is an electrode whose conductivity does not easily decrease even when heated in an oxidizing atmosphere, and a PZT-based piezoelectric material having high orientation and excellent piezoelectric characteristics. It is an object of the present invention to provide a novel piezoelectric film element having a film and a piezoelectric film oscillator.

In order to solve the above problems, the piezoelectric film element of the present invention is placed on a substrate, a first electrode layer containing ruthenium and / or ruthenium oxide arranged on the substrate, and the first electrode layer. It includes an oxide layer having a perovskite structure oriented on the arranged (100) plane, and a piezoelectric film having a perovskite structure containing lead, zirconium and titanium arranged on the oxide layer.

According to the piezoelectric film element of the present invention, since the first electrode layer contains ruthenium and / or ruthenium oxide, the conductivity is unlikely to decrease even when heated in an oxidizing atmosphere. Further, since an oxide layer containing an oxide having a perovskite structure oriented in the (100) plane is arranged on the first electrode layer, lead, zirconate and titanium are contained on the oxide layer by the CSD method. When a PZT-based piezoelectric film having a perovskite structure is formed, it becomes possible to generate a PZT-based piezoelectric film having high orientation of the (100) plane and excellent piezoelectric characteristics.

Here, in the piezoelectric film element of the present invention, it is preferable that the thickness of the first electrode layer is in the range of 50 nm or more and 400 nm or less.
In this case, since the withstand voltage characteristic of the first electrode layer is improved, the piezoelectric membrane oscillator using this piezoelectric membrane element has a high dielectric breakdown withstand voltage.

Further, in the piezoelectric film element of the present invention, it is preferable that the oxide layer contains an oxide nanosheet having a lanthanum nickelate or a perovskite structure.
In this case, the oxide nanosheet having a lanthanum nickate and a perovskite structure has a high orientation of the (100) plane. Therefore, the oxide layer contains these oxides, so that the orientation of the (100) plane of the PZT-based piezoelectric film is high. The property is more reliably improved, and the piezoelectric characteristics are further improved.

The piezoelectric membrane oscillator of the present invention includes the above-mentioned piezoelectric film element and a second electrode arranged on the piezoelectric film of the piezoelectric film element.

According to the piezoelectric film transducer of the present invention, since the second electrode is arranged on the piezoelectric film of the above-mentioned piezoelectric film element, the conductivity of the first electrode layer is lowered even when heated in an oxidizing atmosphere. It is difficult, and the PZT-based piezoelectric film has high orientation. Therefore, the piezoelectric membrane oscillator of the present invention has excellent piezoelectric characteristics.

According to the present invention, a novel piezoelectric membrane element and a piezoelectric membrane oscillator having an electrode whose conductivity does not easily decrease even when heated in an oxidizing atmosphere and a PZT-based piezoelectric membrane having high orientation and excellent piezoelectric characteristics can be obtained. It will be possible to provide.

It is a schematic sectional drawing of the PZT-based piezoelectric membrane oscillator which concerns on one Embodiment of this invention. It is an X-ray diffraction pattern of the PZT piezoelectric film of the PZT piezoelectric film element obtained in Example 1 of this invention and the PZT piezoelectric film element obtained in Comparative Example 1. It is an SEM photograph of the PZT piezoelectric film element obtained in Example 1 of the present invention, (a) is an SEM photograph of a cross section, and (b) is an SEM photograph of the surface of a PZT piezoelectric film. It is the SEM photograph of the PZT piezoelectric film element obtained in the comparative example 1, (a) is the SEM photograph of the cross section, and (b) is the SEM photograph of the surface of the PZT piezoelectric film.

Hereinafter, the PZT-based piezoelectric membrane element and the PZT-based piezoelectric membrane oscillator according to the embodiment of the present invention will be described with reference to the attached drawings.

FIG. 1 is a schematic cross-sectional view of a PZT-based piezoelectric membrane oscillator according to an embodiment of the present invention.
As shown in FIG. 1, the PZT-based piezoelectric film transducer 10 includes a substrate 11, a first electrode layer 12 arranged on the substrate 11, and an oxide layer 13 arranged on the first electrode layer 12. A PZT-based piezoelectric film 14 arranged on the oxide layer 13, and a second electrode layer 16 arranged on the PZT-based piezoelectric film 14 are included. The substrate 11, the first electrode layer 12, the oxide layer 13, and the PZT-based piezoelectric film 14 constitute the PZT-based piezoelectric film element 15.

As the substrate 11, a silicon substrate, a stainless steel substrate, an alumina substrate, or the like can be used. When a silicon substrate is used, a thermal oxide film (SiOx film) is formed on the surface of the silicon substrate by thermally oxidizing the surface of the silicon substrate in order to suppress the diffusion of the constituent elements (particularly lead) of the PZT-based piezoelectric film 14. ) Is desirable. The heat-resistant substrate may further have an adhesion layer in order to improve the adhesion with the first electrode layer 12. As the adhesion layer, a titanium film or a titanium oxide film (diox film) can be used. The titanium film can be formed by, for example, a sputtering method. The titanium oxide film can be formed, for example, by holding the titanium film in an atmospheric atmosphere at a temperature of 700 ° C. or higher and 800 ° C. or lower for 1 to 3 minutes and firing it.

The first electrode layer 12 contains ruthenium and / or ruthenium oxide. The first electrode layer 12 may be a ruthenium single layer, a ruthenium oxide single layer, or a laminated body in which a ruthenium layer and a ruthenium oxide layer are laminated. Ruthenium has conductivity even in the form of an oxide. Therefore, the conductivity of the first electrode layer 12 is unlikely to decrease even when heated in an oxidizing atmosphere. The thickness of the first electrode layer 12 is preferably in the range of 50 nm or more and 400 nm or less.

The oxide layer 13 contains an oxide having a perovskite structure oriented in the (100) plane. The oxide layer 13 preferably contains an oxide nanosheet having a lanthanum nickelate or a perovskite structure. The oxide nanosheet is preferably a single crystal nanosheet of an oxide having a perovskite structure, and particularly preferably a calcium niobate nanosheet. The thickness of the oxide layer 13 is not particularly limited, but is generally in the range of 10 nm or more and 50 nm or less.

The PZT-based piezoelectric film 14 is a film having a perovskite structure containing lead (Pb), zirconium (Zr), and titanium (Ti). Examples of the PZT-based piezoelectric film 14 include a PZT (lead zirconate titanate) piezoelectric film, a PNbZT (lead niob-doped lead zirconate titanate) piezoelectric film, and a PLZT (lead lanthanate-doped lead zirconate titanate) piezoelectric film. .. The PZT-based piezoelectric film 14 is preferably oriented on the (100) plane. The thickness of the PZT-based piezoelectric film 14 is not particularly limited, but is generally in the range of 200 nm or more and 5000 nm or less.

The material of the second electrode layer 16 is not particularly limited. The second electrode layer 16 may contain ruthenium and / or ruthenium oxide in the same manner as the first electrode layer 12. Further, the second electrode layer 16 may contain a metal used as an electrode of a piezoelectric membrane oscillator such as platinum. The thickness of the second electrode layer 16 is preferably in the range of 50 nm or more and 400 nm or less.

Next, a method for manufacturing the PZT-based piezoelectric membrane oscillator 10 of the present embodiment will be described.
The method for manufacturing the PZT-based piezoelectric film oscillator 10 includes a step of manufacturing the PZT-based piezoelectric film element 15 and a second electrode that forms a second electrode layer 16 on the PZT-based piezoelectric film 14 of the PZT-based piezoelectric film element 15. Includes a layer forming step. The manufacturing process of the PZT-based piezoelectric film element 15 includes a first electrode layer forming step of forming the first electrode layer 12 on the substrate 11 and an oxide layer forming the oxide layer 13 on the first electrode layer 12. It includes a forming step and a PZT-based piezoelectric film forming step of forming the PZT-based piezoelectric film 14 on the oxide layer 13.

In the first electrode layer forming step, the first electrode layer 12 is formed on the substrate 11 to produce a substrate with electrodes. The method for forming the first electrode layer 12 is not particularly limited. For example, when the first electrode layer 12 contains ruthenium, a DC sputtering method using a ruthenium target can be used. When the first electrode layer 12 contains ruthenium oxide, for example, a method of heating and oxidizing a ruthenium film formed by a DC sputtering method using a ruthenium target in an oxidizing atmosphere can be used. The oxidizing atmosphere is in oxygen or a gas containing oxygen (eg, air).

In the oxide layer forming step, the oxide layer 13 is formed on the first electrode layer 12 of the substrate with electrodes. The method for forming the oxide layer 13 is not particularly limited. For example, when the oxide layer 13 contains lanthanum nickelate, the sol-gel method can be used. The sol-gel method is a method in which a lanthanum nickel acid solution is applied onto the first electrode layer 12 of a substrate with an electrode, and the obtained coating film is heated in an oxidizing atmosphere. As a method for applying the lanthanum nickel acid solution, a spin coating method or a dip method can be used. When the oxide layer 13 contains an oxide nanosheet having a perovskite structure, a coating method or an electrodeposition method can be used. The coating method is a method in which an oxide nanosheet dispersion liquid in which oxide nanosheets are dispersed is coated on a first electrode layer 12 of a substrate with an electrode, and the obtained coating film is heated in an oxidizing atmosphere. As a method for applying the oxide nanosheet dispersion liquid, a spin coating method or a dip method can be used. In the electrodeposition method, first, a substrate with an electrode and a counter electrode are immersed in an oxide nanosheet dispersion. Next, a DC power supply is connected to the first electrode layer 12 and the counter electrode of the substrate with electrodes, a voltage is applied with the first electrode layer 12 as the positive electrode and the counter electrode as the negative electrode, and the oxide nanosheet is formed on the first electrode layer 12. Electrode electrodeposition. Then, the substrate with electrodes on which the oxide nanosheets are electrodeposited is heated to bake the oxide nanosheets on the first electrode layer 12. The oxide nanosheet dispersion can be prepared by using a known method. For example, as a method for preparing a calcium niobate nanosheet dispersion, the method described in Solid State Ionics, 151, 177 (2002) can be used.

In the PZT-based piezoelectric film forming step, the PZT-based piezoelectric film 14 is formed on the oxide layer 13 of the substrate with electrodes. The PZT-based piezoelectric film 14 can be formed by using the CSD method. The CSD method is a method of forming a PZT-based piezoelectric film by applying a PZT-based piezoelectric precursor solution on the oxide layer 13 of a substrate with electrodes and heating the obtained coating film in an oxidizing atmosphere. Is. The PZT-based piezoelectric precursor solution is a liquid that produces a PZT-based piezoelectric substance by heating in an oxidizing atmosphere. Since the oxide layer 13 contains an oxide having a perovskite structure oriented on the (100) plane, the PZT-based piezoelectric film oriented on the (100) plane is formed by heating the coating film of the PZT-based piezoelectric precursor solution. 14 can be formed. As a method for applying the PZT-based piezoelectric precursor solution, a spin coating method or a dip method can be used. Further, in the PZT-based piezoelectric film forming step, the step of applying the PZT-based piezoelectric precursor solution and the obtained coating film are heated in an oxidizing atmosphere until the PZT-based piezoelectric film 14 having a desired thickness is obtained. The process may be repeated. In this way, the PZT-based piezoelectric film element 15 is obtained.

In the second electrode layer forming step, the second electrode layer 16 is formed on the PZT-based piezoelectric film 14 of the PZT-based piezoelectric film element 15, and the PZT-based piezoelectric film oscillator 10 is manufactured. The method for forming the second electrode layer 16 is not particularly limited. For example, when the second electrode layer 16 contains ruthenium and / or ruthenium oxide, it can be formed in the same manner as in the case of the first electrode layer 12 described above. When the second electrode layer 16 contains platinum, for example, a DC sputtering method using a platinum target can be used.

According to the PZT-based piezoelectric film element 15 of the present embodiment having the above configuration, since the first electrode layer 12 contains ruthenium and / or ruthenium oxide, the conductivity is high even when heated in an oxidizing atmosphere. Hard to drop. Further, since the oxide layer 13 containing an oxide having a perovskite structure oriented in the (100) plane is arranged on the first electrode layer 12, the PZT-based piezoelectric film is placed on the oxide layer 13 by the CSD method. When the film 14 is formed, it becomes possible to form the PZT-based piezoelectric film 14 having high orientation of the (100) plane and excellent piezoelectric characteristics.

Further, in the PZT-based piezoelectric film element 15 of the present embodiment, when the thickness of the first electrode layer 12 is within the range of 50 nm or more and 400 nm or less, the withstand voltage characteristic of the first electrode layer 12 is improved. Therefore, the PZT-based piezoelectric membrane oscillator 10 using the PZT-based piezoelectric membrane element 15 has a high dielectric breakdown withstand voltage.

Further, in the PZT-based piezoelectric film element 15 of the present embodiment, when the oxide layer 13 contains an oxide nanosheet having a lanthanum nickelate or a perovskite structure, the orientation of the (100) plane of the oxide layer 13 becomes high. .. Therefore, when the oxide layer 13 contains these oxides, the orientation of the (100) plane of the PZT-based piezoelectric film 14 is more reliably increased, and the piezoelectric characteristics are further improved.

According to the PZT-based piezoelectric film transducer 10 of the present embodiment, the PZT-based piezoelectric film element 15 and the second electrode layer 16 arranged on the PZT-based piezoelectric film 14 of the PZT-based piezoelectric film element 15 are provided. The first electrode layer 12 does not easily lose its conductivity even when heated in an oxidizing atmosphere, and the PZT-based piezoelectric film 14 has high orientation. Therefore, the PZT-based piezoelectric membrane oscillator 10 of the present embodiment has excellent piezoelectric characteristics.

Although the embodiments of the present invention have been described above, the present invention is not limited to this, and can be appropriately changed without departing from the technical idea of the invention.

[Example 1 of the present invention]
A silicon substrate was prepared as the substrate. A thermal oxide film having a thickness of 500 nm was formed on the surface of the prepared silicon substrate by thermal oxidation. Next, a titanium film having a thickness of 20 nm was formed on the thermal oxide film by a sputtering method, and then the titanium film was held at 700 ° C. for 1 minute in an oxidizing atmosphere using infrared rapid heat treatment (RTA) and fired. The titanium oxide film was oxidized to form a titanium oxide film. Next, a ruthenium electrode (first electrode layer) having a thickness of 100 nm was formed on the surface of this titanium oxide film by a DC sputtering method to obtain a silicon substrate with an electrode. The thickness of the ruthenium electrode was measured using a spectroscopic ellipsometer.

A solution of lanthanum nickelate (LaNiO ₃ ) having a concentration of 4% by mass was spin-coated on the ruthenium electrode of the obtained silicon substrate with an electrode at a rotation speed of 4000 rpm for 15 seconds. A silicon substrate with electrodes coated with a lanthanum nickelate solution was tentatively fired at 400 ° C. for 5 minutes using a hot plate, and then using an infrared rapid heating furnace at a heating rate of 50 ° C./sec under an oxidizing atmosphere. After raising the temperature to 700 ° C., the mixture was fired at 700 ° C. for 1 minute. In this way, a lanthanum nickelate layer (seed layer) was formed on the ruthenium electrode of the silicon substrate with electrodes. As a result of measuring the X-ray diffraction pattern of the obtained nickel acid lanthanum layer using Cu—Kα as an X-ray light source, it was confirmed that the nickel acid lanthanum layer had a perovskite structure oriented in the (100) plane. The film thickness of the obtained lanthanum nickate layer was measured using a spectroscopic ellipsometer and found to be 15 nm.

Next, a PZT piezoelectric precursor solution (PZT-N solution, composition: 110/52/48 = Pb / Zr / Ti) manufactured by Mitsubishi Materials Corporation was applied at 2500 rpm on the nickel acid lanthanum layer of the silicon substrate with electrodes. It was applied by spin coating for 30 seconds at the rotation speed of. A silicon substrate with electrodes coated with a PZT piezoelectric precursor solution is calcined at 275 ° C. for 5 minutes using a hot plate, and then heated to 50 ° C./sec in an oxidizing atmosphere using an infrared rapid heating furnace. After raising the temperature to 700 ° C. at a rate, firing was performed at 700 ° C. for 1 minute. The PZT piezoelectric precursor solution was applied and fired 5 times. In this way, a PZT piezoelectric film element including a ruthenium electrode, a lanthanum nickelate layer, and a PZT piezoelectric film was obtained. The film thickness of the obtained PZT piezoelectric film was measured using a spectroscopic ellipsometer and found to be 1000 nm.

A platinum electrode (second electrode layer) was formed on the PZT piezoelectric film of the obtained PZT piezoelectric film element by a DC sputtering method to obtain a PZT piezoelectric film oscillator.

[Examples 2 to 5 of the present invention]
A PZT piezoelectric film element and a PZT piezoelectric film oscillator were produced in the same manner as in Example 1 of the present invention, except that the thickness of the ruthenium electrode (first electrode layer) was changed to the thickness shown in Table 1 below. ..

[Example 6 of the present invention]
A PZT piezoelectric film element and a PZT piezoelectric film oscillator were produced in the same manner as in Example 1 of the present invention, except that a nanosheet layer of calcium niobate (Ca ₂ Nb ₃ O ₁₀ ) was formed instead of the nickel acid lanthanum layer. .. The calcium niobate nanosheet layer was formed as follows.
A silicon substrate with an electrode and a counter electrode (SUS304) were immersed in a calcium niobate nanosheet dispersion. Next, a DC power supply was connected to the ruthenium electrode (first electrode layer) of the silicon substrate with an electrode and the counter electrode. A voltage of 100 V was applied with the ruthenium electrode as the positive electrode and the counter electrode as the negative electrode, and the calcium niobate nanosheet was electrodeposited on the ruthenium electrode. A silicon substrate with an electrode electrodeposited with calcium niobate nanosheets was heated at 100 ° C. for 5 minutes using a hot plate, and the calcium niobium nanosheets were baked with ruthenium electrodes. Calcium niobate nanosheet dispersions were prepared according to the method described in Solid State Ionics, 151, 177 (2002). As a result of measuring the X-ray diffraction pattern of the obtained calcium niobate nanosheet layer using Cu—Kα as an X-ray light source, the calcium niobate nanosheet layer has a perovskite structure oriented in the (100) plane. confirmed.

[Example 7 of the present invention]
The PZT piezoelectric membrane element and the PZT piezoelectric membrane oscillator were manufactured in the same manner as in Example 1 of the present invention except that the SUS304 substrate was used instead of the silicon substrate.

[Example 8 of the present invention]
The PZT piezoelectric membrane element and the PZT piezoelectric membrane oscillator were manufactured in the same manner as in Example 6 of the present invention except that the SUS304 substrate was used instead of the silicon substrate.

[Example 9 of the present invention]
The PZT piezoelectric film element and the same as in Example 1 of the present invention, except that the thickness of the ruthenium electrode (first electrode layer) is 10 nm and the ruthenium oxide electrode is formed on the ruthenium electrode with a thickness of 90 nm. A PZT piezoelectric film transducer was manufactured. The ruthenium oxide electrode was formed by an RF sputtering method targeting ruthenium oxide.

[Example 10 of the present invention]
A PZT piezoelectric film element and a PZT piezoelectric film oscillator were produced in the same manner as in Example 1 of the present invention, except that a ruthenium oxide electrode having a thickness of 100 nm was used instead of the ruthenium electrode (first electrode layer). The ruthenium oxide electrode was formed as follows.
A ruthenium film was formed by a DC sputtering method targeting ruthenium. Next, the ruthenium film was calcined at 700 ° C. for 1 hour in an oxidizing atmosphere to oxidize the ruthenium film. It was confirmed by the X-ray diffraction pattern that ruthenium oxide was produced.

[Comparative Example 1]
The same as in Example 1 of the present invention except that the lanthanum nickelate layer (seed layer) was not formed on the ruthenium electrode of the silicon substrate with the electrode, that is, the PZT piezoelectric film was directly formed on the ruthenium electrode. The PZT piezoelectric film element and the PZT piezoelectric film oscillator were manufactured.

[Reference Example 1]
A PZT piezoelectric film element and a PZT piezoelectric film oscillator were produced in the same manner as in Example 1 of the present invention, except that a platinum electrode having a thickness of 100 nm was used instead of the ruthenium electrode. The platinum electrode was formed by the DC sputtering method.

[evaluation]
For the PZT piezoelectric film elements obtained in Examples 1 to 10 of the present invention and Comparative Example 1, the X-ray diffraction pattern of the PZT piezoelectric film was measured using Cu—Kα as an X-ray light source. FIG. 2 shows the X-ray diffraction pattern of the PZT piezoelectric film of the piezoelectric film element obtained in Example 1 of the present invention and the piezoelectric film element obtained in Comparative Example 1. From the X-ray diffraction pattern of FIG. 2, the X-ray diffraction peak of the (100) plane of the perovskite structure was confirmed in the PZT piezoelectric film of the PZT piezoelectric film element obtained in Example 1 of the present invention, and the PZT piezoelectric film was (100). It can be seen that it is oriented to the surface. Similarly, in the PZT piezoelectric film elements obtained in Examples 2 to 10 of the present invention, the X-ray diffraction peak of the (100) plane of the perovskite structure was confirmed, and the PZT piezoelectric membrane was oriented to the (100) plane. confirmed. On the other hand, from the X-ray diffraction pattern of FIG. 2, in the PZT piezoelectric film of the PZT piezoelectric film element obtained in Comparative Example 1, the X-ray diffraction peak of the (100) plane of the perovskite structure was not detected, and the (100) plane was formed. It can be seen that they are not oriented.

With respect to the PZT piezoelectric film elements obtained in Examples 1 to 10 of the present invention and Comparative Example 1, the cross section and the surface of the PZT piezoelectric film were observed using an SEM (scanning electron microscope), respectively. FIG. 3 shows an SEM photograph of the PZT piezoelectric film element obtained in Example 1 of the present invention, and FIG. 4 shows an SEM photograph of the PZT piezoelectric film element obtained in Comparative Example 1.

3 and 4A are SEM photographs of the cross section of the PZT piezoelectric film element, and FIG. 4B is an SEM photograph of the surface of the piezoelectric film of the PZT piezoelectric film element. Comparing (a) of FIG. 3 and (a) of FIG. 4, the PZT piezoelectric membrane element obtained in Example 1 of the present invention is a PZT piezoelectric membrane element as compared with the PZT piezoelectric membrane element obtained in Comparative Example 1. It can be seen that a large number of columnar crystal particles are generated. Further, comparing FIG. 3 (b) and FIG. 4 (b), the PZT piezoelectric film of the PZT piezoelectric film element obtained in Example 1 of the present invention is the PZT of the PZT piezoelectric film element obtained in Comparative Example 1. It can be seen that the surface has fewer pores and is denser than the piezoelectric film. Similarly, in the PZT piezoelectric film elements obtained in Examples 2 to 10 of the present invention, a large number of columnar crystal particles were generated in the PZT piezoelectric film, and it was confirmed that the PZT piezoelectric film had few pores on the surface and was dense. rice field.

The dielectric breakdown breakdown voltage, the dielectric constant, and d ₃₃ were measured for the PZT piezoelectric membrane oscillators obtained in Examples 1 to 10 of the present invention and Reference Example 1, respectively. The results are shown in Table 1. The dielectric breakdown breakdown voltage, the dielectric constant and d ₃₃ were measured by the following methods. In the PZT piezoelectric film element obtained in Comparative Example 1, since the X-ray diffraction peak of the (100) plane of the perovskite structure was not detected from the PZT piezoelectric film, the dielectric breakdown breakdown voltage, the dielectric constant, and d ₃₃ were measured. There wasn't.

(Measurement method of dielectric breakdown withstand voltage)
A 250 μm square platinum upper electrode (thickness 100 nm) was formed on the surface of the second electrode layer (platinum electrode) by a sputtering method. Next, a voltage is applied between the first electrode layer of the PZT piezoelectric film oscillator and the platinum upper electrode, and the voltage when the leak current density reaches 1.0 × 10 ^-4 A / cm ² is subjected to dielectric breakdown withstand voltage. And said.

(Measurement method of permittivity)
A 250 μm square platinum upper electrode (thickness 100 nm) was formed on the surface of the second electrode layer (platinum electrode) by a sputtering method. Then, the dielectric constant at a frequency of 1 kHz was measured using TFA-2000 (manufactured by AIX ACCT).

(Measuring method of d ₃₃ )
The PZT piezoelectric film element was formed into a square shape having an area of 1 mm ² to prepare an evaluation sample. The piezoelectric constant d ₃₃ of the obtained evaluation sample was measured using a DBLI system (manufactured by AIX ACCT). Piezoelectric constant d is the mechanical displacement ratio per electric field in 33 directions when an AC voltage of ± 25 V (frequency: 1 kHz) is applied between the first electrode layer and the second electrode layer of the evaluation sample by the DBLI system. It was measured as ₃₃ .

From the results shown in Table 1, the PZT piezoelectric film oscillators of Examples 1 to 10 of the present invention in which the first electrode layer contains ruthenium and / or ruthenium oxide and the oxide layer is arranged on the first electrode layer are the first. It can be seen that it has the same piezoelectric characteristics as Reference Example 1 in which platinum is used for one electrode layer. In particular, it can be seen that the PZT piezoelectric membrane oscillators obtained in Examples 1 to 4 and 6 to 10 of the present invention in which the thickness of the first electrode layer is in the range of 50 nm or more and 400 nm or less have a high dielectric breakdown withstand voltage.

10 PZT-based piezoelectric film oscillator 11 substrate 12 first electrode layer 13 oxide layer 14 PZT-based piezoelectric film 15 PZT-based piezoelectric film element 16 second electrode layer

Claims (4)

A substrate, a first electrode layer containing ruthenium and / or ruthenium oxide arranged on the substrate, and an oxide having a perovskite structure oriented on the (100) plane arranged on the first electrode layer. A piezoelectric film element including an oxide layer containing the oxide layer and a piezoelectric film having a perovskite structure containing lead, zirconium and titanium arranged on the oxide layer. The piezoelectric film device according to claim 1, wherein the thickness of the first electrode layer is in the range of 50 nm or more and 400 nm or less. The piezoelectric film element according to claim 1 or 2, wherein the oxide layer contains an oxide nanosheet having a lanthanum nickelate or a perovskite structure. A piezoelectric membrane oscillator comprising the piezoelectric membrane element according to any one of claims 1 to 3 and a second electrode arranged on the piezoelectric membrane of the piezoelectric membrane element.

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