JP7399752B2 - Piezoelectric film, piezoelectric laminate, piezoelectric element, and piezoelectric laminate manufacturing method - Google Patents

Description

The present invention relates to a piezoelectric film, a piezoelectric laminate, a piezoelectric element, and a method for manufacturing a piezoelectric laminate.

Piezoelectric bodies are widely used in functional electronic components such as sensors and actuators. As a material for the piezoelectric body, lead-based materials, particularly PZT-based ferroelectrics represented by the composition formula Pb(Zr _1-x Ti _x )O ₃ are widely used. Since PZT-based piezoelectric bodies contain lead, they are not preferred from the viewpoint of pollution prevention. Therefore, potassium sodium niobate (KNN) has been proposed as a lead-free piezoelectric material (see, for example, Patent Documents 1 and 2). In recent years, there has been a strong demand to further improve the performance of piezoelectric bodies made of lead-free materials such as KNN.

Japanese Patent Application Publication No. 2007-184513 Japanese Patent Application Publication No. 2008-159807

An object of the present invention is to further extend the life of a piezoelectric film made of potassium sodium niobate.

According to one aspect of the invention,
It is a polycrystalline film made of potassium sodium niobate,
Contains Mn,
A piezoelectric film in which more Mn exists in the grain boundaries of a crystal than in a parent phase of the crystal, and its related technology are provided.

According to the present invention, it is possible to further extend the life of a piezoelectric film made of potassium sodium niobate.

1 is a diagram showing an example of a cross-sectional structure of a piezoelectric laminate according to an embodiment of the present invention. It is a figure which shows the modification of the cross-sectional structure of the piezoelectric laminated body concerning one embodiment of this invention. 1 is a diagram showing an example of a schematic configuration of a piezoelectric device according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of a cross-sectional structure of an intermediate body (a laminate before heat treatment) when producing a piezoelectric laminate according to an embodiment of the present invention. It is a figure showing a modification of the schematic structure of the piezoelectric device concerning one embodiment of the present invention.

<One embodiment of the present invention>
Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

(1) Configuration of Piezoelectric Laminate As shown in FIG. A piezoelectric film (piezoelectric thin film) 3 is formed on the lower electrode film 2, and an upper electrode film 4 is formed on the piezoelectric film 3.

The substrate 1 is a single crystal silicon (Si) substrate 1a on which a surface oxide film (SiO ₂ film) 1b such as a thermal oxide film or a CVD (Chemical Vapor Deposition) oxide film is formed, that is, a Si substrate having a surface oxide film. can be suitably used. Further, as the substrate 1, as shown in FIG. 2, a Si substrate 1a having an insulating film 1d formed of an insulating material other than SiO ₂ on its surface can also be used. Further, as the substrate 1, a Si substrate 1a having an exposed Si (100) plane or Si (111) plane or the like on the surface, that is, a Si substrate without the surface oxide film 1b or the insulating film 1d can also be used. The substrate 1 may be formed of a metal material such as an SOI (Silicon On Insulator) substrate, a quartz glass (SiO ₂ ) substrate, a gallium arsenide (GaAs) substrate, a sapphire (Al ₂ O ₃ ) substrate, or stainless steel (SUS). It is also possible to use a metal substrate. The thickness of the single crystal Si substrate 1a can be, for example, 300 μm or more and 1000 μm or less, and the thickness of the surface oxide film 1b can be, for example, 1 nm or more and 4000 nm or less.

The lower electrode film 2 can be formed using platinum (Pt), for example. The lower electrode film 2 is a single crystal film or a polycrystalline film (hereinafter also referred to as a Pt film). It is preferable that the crystals constituting the Pt film are preferentially oriented in the (111) plane with respect to the surface of the substrate 1. That is, it is preferable that the surface of the Pt film (the surface that becomes the base of the piezoelectric film 3) is mainly composed of a Pt (111) plane. The Pt film can be formed using techniques such as sputtering and vapor deposition. In addition to Pt, the lower electrode film 2 is made of various metals such as gold (Au), ruthenium (Ru), or iridium (Ir), alloys containing these as main components, strontium ruthenate (SrRuO ₃ , abbreviation: SRO), or The film can also be formed using a metal oxide such as lanthanum nickelate (LaNiO ₃ , abbreviation: LNO). Further, the lower electrode film 2 may be a single layer film formed using the above-mentioned various metals or metal oxides, or a laminated film of a Pt film and a film made of SRO provided on the Pt film. It may also be a laminate of a Pt film and a film made of LNO provided on the Pt film. Note that in order to improve the adhesion between the substrate 1 and the lower electrode film 2, for example, titanium (Ti), tantalum (Ta), titanium oxide (TiO ₂ ), nickel (Ni), ruthenium oxide, etc. An adhesion layer 6 mainly composed of (RuO ₂ ), iridium oxide (IrO ₂ ), or the like may be provided. The adhesive layer 6 can be formed using a method such as a sputtering method or a vapor deposition method. The thickness of the lower electrode film 2 can be, for example, 100 nm or more and 400 nm or less, and the thickness of the adhesive layer 6 can be, for example, 1 nm or more and 200 nm or less.

The piezoelectric film 3 includes, for example, potassium (K), sodium (Na), and niobium (Nb), and is made of an alkali niobium oxide represented by the composition formula (K _1-x Na _x ) _y NbO ₃ , that is, niobic acid. A film can be formed using potassium sodium (KNN). The coefficient x [=Na/(K+Na)] in the above-mentioned composition formula has a size within the range of 0<x<1. The coefficient y [=(K+Na)/Nb] is preferably set within the range of 0.7≦y≦1.50, for example. The piezoelectric film 3 is a KNN polycrystalline film (hereinafter also referred to as KNN film 3). The crystal structure of KNN is a perovskite structure. The KNN film 3 can be formed using a method such as a sputtering method, a PLD (Pulsed Laser Deposition) method, or a sol-gel method. The thickness of the KNN film 3 is, for example, 0.5 μm or more and 5 μm or less.

The crystals constituting the KNN film 3 have priority over the (001) plane orientation with respect to the surface of the substrate 1 (for example, the Si substrate 1a if the substrate 1 is a Si substrate 1a having a surface oxide film 1b or an insulating film 1d). It is preferable that it is oriented. That is, it is preferable that the surface of the KNN film 3 (the surface that becomes the base of the upper electrode film 4) is mainly constituted by the KNN (001) plane orientation. By directly forming the KNN film 3 on the Pt film that is preferentially oriented in the (111) plane with respect to the surface of the substrate 1, the crystals constituting the KNN film 3 are oriented in the (001) direction with respect to the surface of the substrate 1. ) It becomes easy to achieve preferential orientation in the plane direction. That is, 80% or more of the crystal groups constituting the KNN film 3 are oriented in the (001) plane with respect to the surface of the substrate 1, and 80% or more of the surface of the KNN film 3 is oriented in the KNN (001) direction. ) surface.

It is preferable that more than half of the crystals in the crystal group constituting the KNN film 3 have a columnar structure. It is preferable that the boundaries between the crystals constituting the KNN film 3, that is, the crystal grain boundaries existing in the KNN film 3, penetrate in the thickness direction of the KNN film 3. For example, in the KNN film 3, there are more crystal grain boundaries that penetrate in the thickness direction than crystal grain boundaries that do not penetrate in the thickness direction of the KNN film 3 (for example, crystal grain boundaries parallel to the plane direction of the substrate 1). is preferred.

The average grain size of the crystals (crystal group) constituting the KNN film 3 (hereinafter also referred to as "average crystal grain size of the KNN film 3") is preferably, for example, 100 nm or more. The average crystal grain size of the KNN film 3 herein refers to the average crystal grain size in a cross section of the KNN film 3 in the planar direction of the substrate 1. The average crystal grain size of the KNN film 3 can be obtained by analyzing the field of view of an image taken with a scanning electron microscope (for example, a SEM image) or an image taken with a transmission electron microscope (for example, a TEM image). As the image analysis software, for example, "ImageJ" manufactured by Wayne Rasband can be used.

By increasing the average crystal grain size of the KNN film 3, it is possible to lower the grain boundary density in the KNN film 3. The grain boundary density here is the value obtained by dividing the total length of the grain boundaries of the crystals in the cross section of the KNN film 3 in the plane direction of the substrate 1 by the cross-sectional area (=total length of the grain boundaries of the crystal grains/ cross-sectional area).

From the viewpoint of lowering the grain boundary density of the KNN film 3, it is preferable that the average crystal grain size of the KNN film 3 is as large as possible. However, if the average crystal grain size of the KNN film 3 becomes larger than the thickness of the KNN film 3, the in-plane uniformity of piezoelectric properties may deteriorate. Therefore, from the viewpoint of suppressing deterioration of in-plane uniformity of piezoelectric properties, the average crystal grain size of the KNN film 3 is preferably smaller than the thickness of the KNN film 3.

The KNN film 3 contains manganese (Mn). In addition, in the KNN film 3, Mn exists at the grain boundaries, and the Mn present at the grain boundaries (for example, the number of Mn particles existing at the grain boundaries) is the parent phase of the crystals constituting the KNN film 3. (for example, the number of Mn particles present in the matrix). Therefore, when an electric field is applied to the piezoelectric element 20 (piezoelectric device 30), which will be described later, it is possible to suppress the movement of oxygen vacancies present in the grain boundaries of the KNN film 3.

Oxygen vacancies (oxygen vacancies) exist at a predetermined ratio inside the crystals (crystal grains) constituting the KNN film 3 and at the grain boundaries. Among these oxygen vacancies, the oxygen vacancies that exist in the grain boundaries of the KNN film 3 in particular occur when an electric field is applied to a piezoelectric element 20 (piezoelectric device 30), which will be described later, which is manufactured by processing the piezoelectric laminate 10. may move to. When the oxygen vacancies move and reach the electrode film (lower electrode film 2 or upper electrode film 4), the oxygen vacancies react with the metal in the electrode film, resulting in a short circuit. Therefore, the inventors of the present application conducted extensive studies on suppressing the movement of oxygen vacancies present at the grain boundaries of the KNN film 3. As a result, when Mn exists at the grain boundaries of the KNN film 3, this Mn becomes a pair with the oxygen vacancies existing at the grain boundaries of the KNN film 3, that is, the Mn existing at the grain boundaries becomes oxygen vacancies. It was found that it is possible to trap oxygen vacancies and suppress the movement of oxygen vacancies present at grain boundaries. In addition, although such an effect of suppressing the movement of oxygen vacancies is obtained by Mn present in the grain boundaries, Mn present in the parent phase (inside the crystal) of the crystals constituting the KNN film 3 (for example, Mn constituting the KNN film 3) It was also found that it is difficult to obtain Mn depending on the Mn incorporated in the lattice of the crystal. These findings were discovered for the first time as a result of intensive studies by the inventors of the present application.

The content of Mn in the KNN film 3 is preferably within a range of, for example, 0.2 at% or more and 2.0 at% or less with respect to the amount of niobium in the KNN film 3 (polycrystalline film). That is, the Mn concentration of the KNN film 3 is preferably 0.2 at% or more and 2.0 at% or less. The Mn concentration here is the total concentration of Mn present in the grain boundaries and Mn present in the parent phase.

If the Mn concentration in the KNN film 3 is 0.2 at% or more, even if the Mn content in the KNN film 3 is a small amount, a certain amount or more of Mn can be present in the grain boundaries, and It becomes possible to increase the amount of Mn present in the matrix compared to the amount of Mn present in the matrix. As a result, the above-mentioned effect of suppressing oxygen vacancy movement can be obtained. By setting the Mn concentration of the KNN film 3 to 2.0 at % or less, the relative dielectric constant of the KNN film 3 can be set to a size suitable for applications such as sensors and actuators.

The KNN film 3 does not impair the effect of adding elements other than K, Na, Nb, and Mn, such as copper (Cu), lithium (Li), Ta, and antimony (Sb), with Mn within the above-mentioned range. It may be contained within a range, for example, within a range of 5 at % or less (if multiple types of the above-mentioned elements are added, the total concentration is 5 at % or less).

The upper electrode film 4 can be formed using various metals such as Pt, Au, aluminum (Al), and Cu, or alloys thereof. The upper electrode film 4 can be formed using a method such as a sputtering method, a vapor deposition method, a plating method, or a metal paste method. The upper electrode film 4 does not have a large influence on the crystal structure of the KNN film 3 unlike the lower electrode film 2. Therefore, the material, crystal structure, and film forming method of the upper electrode film 4 are not particularly limited. Note that an adhesion layer containing, for example, Ti, Ta, TiO ₂ , Ni, RuO ₂ , IrO ₂ or the like as a main component is provided between the KNN film 3 and the upper electrode film 4 in order to improve their adhesion. It may be. The thickness of the upper electrode film 4 can be, for example, 100 nm or more and 5000 nm or less, and when an adhesive layer is provided, the thickness of the adhesive layer can be, for example, 1 nm or more and 200 nm or less.

(2) Configuration of piezoelectric device FIG. 3 shows a schematic configuration diagram of a device 30 (hereinafter also referred to as piezoelectric device 30) having a KNN film 3 in this embodiment. The piezoelectric device 30 is connected to an element 20 (element 20 having the KNN film 3, hereinafter also referred to as piezoelectric element 20) obtained by molding the piezoelectric laminate 10 described above into a predetermined shape, and the piezoelectric element 20. It includes at least a voltage applying section 11a or a voltage detecting section 11b. The voltage applying section 11a is a means for applying a voltage between the lower electrode film 2 and the upper electrode film 4 (between the electrodes), and the voltage detecting section 11b is a means for applying a voltage between the lower electrode film 2 and the upper electrode film 4. This is a means for detecting the voltage generated between the electrodes (between the electrodes). Various known means can be used as the voltage applying section 11a and the voltage detecting section 11b.

By connecting the voltage application section 11a between the lower electrode film 2 and the upper electrode film 4 of the piezoelectric element 20, the piezoelectric device 30 can function as an actuator. The KNN film 3 can be deformed by applying a voltage between the lower electrode film 2 and the upper electrode film 4 using the voltage applying section 11a. Through this deformation operation, various members connected to the piezoelectric device 30 can be operated. In this case, examples of uses of the piezoelectric device 30 include heads for inkjet printers, MEMS mirrors for scanners, and vibrators for ultrasonic generators.

By connecting the voltage detection section 11b between the lower electrode film 2 and the upper electrode film 4 of the piezoelectric element 20, the piezoelectric device 30 can function as a sensor. When the KNN film 3 deforms due to a change in some physical quantity, a voltage is generated between the lower electrode film 2 and the upper electrode film 4 due to the deformation. By detecting this voltage with the voltage detection section 11b, the magnitude of the physical quantity applied to the KNN film 3 can be measured. In this case, applications of the piezoelectric device 30 include, for example, an angular velocity sensor, an ultrasonic sensor, a pressure sensor, an acceleration sensor, and the like.

(3) Method for manufacturing piezoelectric laminate, piezoelectric element, and piezoelectric device A method for manufacturing the piezoelectric laminate 10, piezoelectric element 20, and piezoelectric device 30 described above will be described with reference to FIG. 4.

As shown in FIG. 4, first, a substrate 1 is prepared, and an adhesion layer 6 (Ti layer) and a lower electrode film 2 (Pt film) are formed in this order on one of the main surfaces of the substrate 1 by, for example, sputtering. To form a film. Note that the substrate 1 may be prepared on which the adhesive layer 6 and the lower electrode film 2 are formed in advance on one of the main surfaces.

The following conditions are exemplified as conditions for providing the adhesive layer 6.
Temperature (substrate temperature): 100°C or more and 500°C or less, preferably 200°C or more and 400°C or less Discharge power: 1000W or more and 1500W or less, preferably 1100W or more and 1300W or less Atmosphere: Argon (Ar) gas atmosphere Atmospheric pressure: 0.1 Pa or more 0.5 Pa or less, preferably 0.2 Pa or more and 0.4 Pa or less Formation time: 30 seconds or more and 3 minutes or less, preferably 45 seconds or more and 2 minutes or less

The following conditions are exemplified as conditions for forming the lower electrode film 2.
Temperature (substrate temperature): 100°C or more and 500°C or less, preferably 200°C or more and 400°C or less Discharge power: 1000W or more and 1500W or less, preferably 1100W or more and 1300W or less Atmosphere: Ar gas atmosphere Atmospheric pressure: 0.1Pa or more and 0.5Pa Below, preferably 0.2 Pa or more and 0.4 Pa or less Film forming time: 3 minutes or more and 10 minutes or less, preferably 4 minutes or more and 8 minutes or less, and more preferably 5 minutes or more and 6 minutes or less

Subsequently, a layer containing Mn is provided on the lower electrode film 2, that is, at a position that will be in contact with the lower surface of the KNN film 3. Examples of the layer containing Mn include a KNN layer containing Mn (KNN film containing Mn). Hereinafter, the layer containing Mn provided on the lower electrode film 2 will also be referred to as the first Mn layer 7. The first Mn layer 7 is a single crystal layer or a polycrystalline layer. The first Mn layer 7 can be provided using a method such as a sputtering method or a vapor deposition method. The thickness of the first Mn layer 7 can be, for example, 1 nm or more and 200 nm or less. The Mn concentration in the first Mn layer will be described later.

When forming a KNN layer containing Mn as the first Mn layer 7 by, for example, a sputtering method, the composition ratio of the first Mn layer 7 can be adjusted, for example, by controlling the composition of the target material used during sputtering film formation. The target material can be produced by mixing and firing K ₂ CO ₃ powder, Na ₂ CO ₃ powder, Nb ₂ O ₅ powder, Mn powder (or MnO powder), or the like. The composition of the target material can be controlled by adjusting the mixing ratio of K ₂ CO ₃ powder, Na ₂ CO ₃ powder, Nb ₂ O ₅ powder, Mn powder (or MnO powder), etc.

The following conditions are exemplified as conditions for providing the KNN layer containing Mn as the first Mn layer 7 by, for example, a sputtering method. Note that the film forming time is appropriately set depending on the thickness of the first Mn layer.
Discharge power: 2000 W or more and 2400 W or less, preferably 2100 W or more and 2300 W or less Atmosphere: Ar gas + oxygen (O ₂ ) gas atmosphere Atmospheric pressure: 0.2 Pa or more and 0.5 Pa or less, preferably 0.2 Pa or more and 0.4 Pa or less O ₂ Partial pressure of Ar gas to gas (Ar/O ₂ partial pressure ratio): 30/1 to 20/1, preferably 27/1 to 22/1
Film forming temperature: 500°C or more and 600°C or less, preferably 500°C or more and less than 600°C, more preferably 550°C or more and less than 600°C Film forming rate: 0.5 μm/hr or more and 2 μm/hr or less, preferably 0.75 μm/hr hr or more and 1.5μm/hr or less

A KNN film not containing Mn (Mn-free KNN film) 3A is formed on the first Mn layer 7. When forming the Mn-free KNN film 3A by, for example, a sputtering method, the composition ratio of the Mn-free KNN film 3A can be adjusted, for example, by controlling the composition of the target material used during sputtering film formation. The target material can be produced by mixing K ₂ CO ₃ powder, Na ₂ CO ₃ powder, Nb ₂ O ₅ powder, etc. and firing the mixture. The composition of the target material can be controlled by adjusting the mixing ratio of K ₂ CO ₃ powder, Na ₂ CO ₃ powder, Nb ₂ O ₅ powder, etc. The conditions for forming the Mn-free KNN film 3A can be the same as the conditions for forming the first Mn layer 7 described above.

A layer containing Mn or a layer made of Mn is provided on the Mn-free KNN film 3A, that is, at a position in contact with the upper surface of the Mn-free KNN film 3A. Examples of the layer containing Mn include a KNN layer containing Mn (KNN film containing Mn). Hereinafter, the layer containing Mn or the layer made of Mn provided on the Mn-free KNN film 3A will also be referred to as the second Mn layer 8. The second Mn layer 8, unlike the first Mn layer 7, does not have a large effect on the crystal structure of the Mn-free KNN film 3A. Therefore, the material, crystal structure, and film forming method of the second Mn layer 8 are not particularly limited. The second Mn layer 8 can be provided using a method such as a sputtering method, a vapor deposition method, or a metal paste method. The thickness of the second Mn layer 8 can be, for example, 1 nm or more and 200 nm or less. The Mn concentration in the second Mn layer 8 when the second Mn layer 8 is a layer containing Mn will be described later.

The conditions for providing the layer containing Mn as the second Mn layer 8 by, for example, sputtering can be the same as the conditions for providing the first Mn layer 7 described above.

Moreover, the following conditions are exemplified as conditions for forming a layer made of Mn as the second Mn layer 8.
Temperature (substrate temperature): Room temperature or more and 300°C or less, preferably room temperature or more and 100°C or less Discharge power: 100W or more and 500W or less, preferably 150W or more and 300W or less, more preferably 200W or more and 250W or less Atmosphere: Ar gas atmosphere Atmospheric pressure: 0 .05 Pa or more and 0.5 Pa or less, preferably 0.05 Pa or more and 0.2 Pa or less Formation time: 30 seconds or more and 3 minutes or less, preferably 45 seconds or more and 2 minutes or less

The Mn concentration in the first Mn layer 7 and the Mn concentration in the second Mn layer 8 when the second Mn layer 8 is a layer containing Mn are as follows: The Mn concentration in the KNN film 3 after heat treatment is adjusted to be within the range of 0.2 at % to 2.0 at % by diffusion of Mn from the KNN film 3 .

Then, the upper electrode film 4 is formed on the second Mn layer 8 by, for example, a sputtering method. The conditions for forming the upper electrode film 4 can be similar to the conditions for forming the above-described lower electrode film 2. As a result, as shown in FIG. 4, a laminate 12 having the substrate 1, the lower electrode film 2, the first Mn layer 7, the Mn-free KNN film 3A, the second Mn layer 8, and the upper electrode film 4 is obtained.

Thereafter, the laminate 12 is subjected to heat treatment under predetermined conditions. As a result, Mn in the first Mn layer 7 and the second Mn layer 8 diffuses into the Mn-free KNN film 3A. As a result, the Mn-free KNN film 3A is a film containing Mn at a predetermined concentration, and is a KNN film in which Mn exists in the grain boundaries and in which the Mn present in the grain boundaries is larger than the Mn present in the matrix. It becomes 3.

The following conditions are exemplified as the heat treatment conditions.
Annealing temperature (temperature of laminate): 600°C or higher, preferably 600°C or higher and 800°C or lower, more preferably 650°C or higher and 750°C or lower Annealing time: 0.5 hours or more and 12 hours or less, preferably 1 hour or more and 6 hours Annealing atmosphere: air or nitrogen atmosphere, more preferably 2 hours or more and 3 hours or less

By performing the heat treatment, Mn in the first Mn layer 7 and the second Mn layer 8 diffuses into the Mn-free KNN film 3A, so that the first Mn layer 7 and the second Mn layer 8 almost disappear. As a result, a piezoelectric laminate 10 (see FIG. 1) having a substrate 1, a lower electrode film 2, a KNN film 3, and an upper electrode film 4, which contains Mn and exists in the grain boundaries, becomes the parent phase. A piezoelectric laminate 10 is obtained having more KNN film 3 than Mn present. Although it is preferable that the first Mn layer 7 and the second Mn layer 8 disappear by performing the heat treatment, the first Mn layer 7 and the second Mn layer 8 may remain.

Then, by forming this piezoelectric laminate 10 into a predetermined shape by etching or the like (performing fine processing into a predetermined pattern), a piezoelectric element 20 as shown in FIG. 11a or the voltage detection section 11b, the piezoelectric device 30 is obtained. As the etching method, for example, a dry etching method such as reactive ion etching, or a wet etching method using a predetermined etching solution can be used.

When forming the piezoelectric laminate 10 by dry etching, a photoresist pattern as an etching mask for dry etching is formed on the piezoelectric laminate 10 (for example, the upper electrode film 4) by a photolithography process or the like. As an etching mask, a noble metal film (metal mask) such as a chromium (Cr) film, nickel (Ni) film, platinum (Pt) film, or Ti film may be formed by sputtering. Then, dry etching is performed on the piezoelectric laminate 10 (upper electrode film 4, KNN film 3, etc.) using a gas containing a halogen element as an etching gas. Note that the halogen element includes chlorine (Cl), fluorine (F), and the like. As the gas containing the halogen element, BCl ₃ gas, SiCl ₄ gas, chlorine (Cl ₂ ) gas, CF ₄ gas, C ₄ F ₈ gas, etc. can be used.

When forming the piezoelectric laminate 10 by wet etching, a silicon oxide (SiO _x ) film or the like is formed on the piezoelectric laminate 10 (for example, the upper electrode film 4) as an etching mask for wet etching. Then, the piezoelectric laminate 10 is immersed in, for example, an etching solution containing an alkaline aqueous solution of a chelating agent and not containing hydrofluoric acid, and wet etching is performed on the piezoelectric laminate 10 (upper electrode film 4, KNN film 3, etc.). Note that as the etching solution containing an alkaline aqueous solution of a chelating agent and not containing hydrofluoric acid, an etching solution that is a mixture of ethylenediaminetetraacetic acid as a chelating agent, aqueous ammonia, and aqueous hydrogen peroxide can be used.

(4) Effects obtained by this embodiment According to this embodiment, one or more of the following effects can be obtained.

(a) Mn (for example, Mn particles) is present at the grain boundaries of the KNN film 3, and Mn present at the grain boundaries of the KNN film 3 is present in the parent phase of the crystals constituting the KNN film 3. By being larger than Mn, when an electric field is applied to the piezoelectric element 20 (piezoelectric device 30) produced by processing the piezoelectric laminate 10, the movement of oxygen vacancies present in the grain boundaries of the KNN film 3 is suppressed. It becomes possible to do so. This makes it possible to reduce oxygen vacancies reaching the electrode film (lower electrode film 2 or upper electrode film 4) and to lengthen the time it takes oxygen vacancies to reach the electrode film. As a result, the life of the KNN film 3 can be extended. For example, a Highly Accelerated Life Test (abbreviation) is performed in which a positive or negative electric field of 300 kV/cm is applied to the upper electrode film 4 while the piezoelectric laminate 10 is heated to a temperature of 200° C. :HALT), it is possible to make the time from the start of electric field application to the dielectric breakdown of the KNN film 3 under at least one of the electric field (positive or negative electric field) application conditions to 7600 seconds or more. Note that in this embodiment, it is assumed that the KNN film 3 has reached dielectric breakdown when the leakage current density flowing through the KNN film 3 exceeds 30 mA/cm ² .

For each of Samples 1 to 5 of the KNN film 3, in which the Mn content is 0.5 at% (wt%), and the Mn present in the grain boundaries is greater than the Mn present in the matrix, the inventors of the present application , HALT was performed under the above conditions. Samples 1 to 5 were produced under the same conditions within the range of conditions described in the above embodiment. The HALT measurement results were: Sample 1: 24334.3 seconds, Sample 2: 16080.0 seconds, Sample 3: 22045.7 seconds, Sample 4: 15831.4 seconds, and Sample 5: 7602.9 seconds. These HALT values are the average of values measured at seven locations within 0.5 mmφ for each sample.

For each of Samples 6 to 10 of KNN film 3 in which the Mn content is 1.0 at% (wt%) and the Mn present in the grain boundaries is greater than the Mn present in the matrix, the inventors of the present application , HALT was performed under the above conditions. Samples 6 to 10 are the same as Samples 1 to 5 described above, except that the Mn content (for example, the thickness of the first Mn layer and the second Mn layer, the Mn concentration in the first Mn layer and the second Mn layer) was adjusted. Manufactured under the same conditions. The HALT measurement results were: Sample 6: 30737.1 seconds, Sample 7: 25465.7 seconds, Sample 8: 9822.9 seconds, Sample 9: 24274.3 seconds, and Sample 10: 36154.3 seconds. These HALT values are the average of values measured at seven locations within 0.5 mmφ for each sample.

In addition, the inventors of the present application under the above conditions for each of KNN film samples 11 to 15 in which the Mn content is 0.5 at% and the Mn present in the grain boundaries is smaller than the Mn present in the matrix. I performed HALT below. Note that in samples 11 to 15, K ₂ CO ₃ powder, Na ₂ CO ₃ powder, Using a target material prepared by mixing Nb ₂ O ₅ powder and MnO powder and firing, a KNN film was formed on the lower electrode film, an upper electrode film was formed on the KNN film, and piezoelectric A laminate was produced. Further, samples 11 to 15 were not subjected to the heat treatment described in the above embodiment. The HALT measurement results were: Sample 11: 6171.4 seconds, Sample 12: 5648.6 seconds, Sample 13: 4705.7 seconds, Sample 14: 5284.3 seconds, and Sample 15: 3428.6 seconds. These HALT values are the average of values measured at seven locations within 0.5 mmφ for each sample.

In addition, the inventors of the present application under the above conditions for each of KNN film samples 16 to 20, in which the Mn content is 1.0 at%, and the Mn present in the grain boundaries is smaller than the Mn present in the matrix. I performed HALT below. Note that Samples 16 to 20 were manufactured under the same conditions as Samples 11 to 15 described above, except that the mixing ratio of MnO powder was changed. The HALT results were sample 16: 5220.0 seconds, sample 17: 4311.4 seconds, sample 18: 7491.4 seconds, sample 19: 4782.9 seconds, and sample 20: 4050.0 seconds. These HALT values are the average of values measured at seven locations within 0.5 mmφ for each sample.

As described above, the inventors of the present application have found that even if the Mn content is within a predetermined range, if the Mn present in the grain boundaries is less than the Mn present in the matrix, the life of the HALT is less than 7600 seconds. I confirmed that it would happen.

(b) Since the average crystal grain size of the KNN film 3 is larger than the average crystal grain size of a conventional KNN film, for example, 100 nm or more, it is possible to lower the grain boundary density of the KNN film 3. As a result, for example, the ratio (= This makes it possible to reduce oxygen vacancies present at grain boundaries (oxygen vacancies/total oxygen vacancies). As a result, oxygen vacancies in the KNN film 3 that move when an electric field is applied to the piezoelectric device 30 can be reliably reduced, and the life of the KNN film 3 can be further extended.

(c) Since the amount of Mn present in the grain boundaries of the KNN film 3 is larger than that of Mn present in the parent phase, and the average crystal grain size of the KNN film 3 is large (for example, 100 nm or more), the KNN film 3 This makes it possible to further extend the lifespan of the Note that since the amount of Mn present in the grain boundaries of the KNN film 3 is greater than the amount of Mn present in the matrix, even if the average grain size of the KNN film 3 is not large (for example, even if it is less than 100 nm) ), it is possible to obtain at least the above-mentioned effect (a), that is, the above-mentioned effect of suppressing oxygen vacancy movement.

(d) By including Mn in the KNN film 3 at a concentration of, for example, 0.2 at% or more and 2.0 at% or less, the relative dielectric constant of the KNN film 3 can be It is possible to prevent the dielectric constant from becoming excessively high and to make the dielectric constant suitable for applications such as sensors and actuators.

(5) Modifications This embodiment is not limited to the above-mentioned aspects, but can also be modified as follows. Moreover, these modifications can be combined arbitrarily. In addition, in the description of the following modified examples, etc., the term "KNN film 3" includes cases where it means a KNN film containing Mn, a case where it means a KNN film not containing Mn, and cases where it means both of these. .

(Modification 1)
At least one of the first Mn layer 7 and the second Mn layer 8 may be provided. In this case, the Mn concentration, etc. in the first Mn layer 7 or the second Mn layer 8 is adjusted so that the Mn concentration in the KNN film 3 after heat treatment is 0.2 at % or more and 2.0 at % or less. In this modification as well, it is possible to obtain a KNN film 3 in which the amount of Mn present in the grain boundaries is greater than the amount of Mn present in the matrix, and the same effects as in the above-described embodiment can be obtained. However, from the viewpoint of uniformly diffusing Mn over the thickness direction of the KNN film 3, it is preferable to provide both the first Mn layer 7 and the second Mn layer 8.

(Modification 2)
When providing an adhesive layer between the KNN film 3 and the upper electrode film 4, it is preferable to provide the second Mn layer 8 before providing the adhesive layer. The second Mn layer 8 is preferably provided between the KNN film 3 and the adhesive layer, that is, in contact with the upper surface of the KNN film 3. This is because if the second Mn layer 8 is provided between the adhesion layer and the upper electrode film 4, the adhesion layer may inhibit the diffusion of Mn from the second Mn layer 8 to the KNN film 3. Note that the conditions for providing the adhesive layer between the KNN film 3 and the upper electrode film 4 can be the same as the conditions for providing the adhesive layer 6 described above. Also in this modification, the same effects as in the above-described embodiment can be obtained.

(Modification 3)
When forming the KNN film 3, a KNN film doped with Mn (Mn-containing KNN film) may be formed using a target material mixed with Mn powder (or MnO powder, etc.). The mixing ratio of Mn powder (or MnO powder, etc.) in the target material is determined by considering the Mn diffused from the first Mn layer 7 and the second Mn layer 8 into the Mn-containing KNN film, and the Mn in the KNN film 3 after heat treatment. The ratio is such that the concentration is 0.2 at% or more and 2.0 at% or less. The conditions for forming the Mn-containing KNN film can be the same as those in the above embodiment. Also in this modification, the same effects as in the above-described embodiment can be obtained.

(Modification 4)
The piezoelectric laminate 10 does not need to include the lower electrode film 2. That is, the piezoelectric laminate 10 includes a substrate 1, a KNN film (piezoelectric film) 3 formed on the substrate 1, in which Mn present in the grain boundaries is larger than Mn present in the matrix, and The upper electrode film 4 (electrode film 4) may be formed.

In the piezoelectric laminate 10 according to this modification, a Mn-free KNN film 3A is formed on a substrate 1, and a layer containing Mn or a layer made of Mn, that is, a second Mn layer 8, is formed on the Mn-free KNN film 3A. The electrode film 4 is formed on the second Mn layer 8 to produce a laminate 12, and the laminate 12 is heat-treated. The conditions for forming (providing) each film (layer) can be the same as the conditions for each film (layer) shown in the above embodiment. In addition to or in place of the second Mn layer 8, a layer containing Mn (i.e., the first Mn layer 7) may be provided between the substrate 1 and the KNN film 3 (Mn-free KNN film 3A). good.

FIG. 5 shows a schematic configuration diagram of a piezoelectric device 30 manufactured using the piezoelectric laminate 10 according to this modification. The piezoelectric device 30 includes at least a piezoelectric element 20 obtained by molding the piezoelectric laminate 10 into a predetermined shape, and a voltage applying section 11a and a voltage detecting section 11b connected to the piezoelectric element 20. . In this modification, the piezoelectric element 20 has a patterned electrode formed by forming the electrode film 4 into a predetermined pattern. For example, the piezoelectric element 20 includes a pair of positive and negative pattern electrodes 4p ₁ on the input side and a pair of positive and negative pattern electrodes 4p ₂ on the output side. An example of the pattern electrodes 4p ₁ and 4p ₂ is a comb-shaped electrode (Inter Digital Transducer, abbreviation: IDT).

By connecting the voltage applying section 11a between the pattern electrodes _4p1 and the voltage detecting section 11b between the pattern electrodes _4p2 , the piezoelectric device 30 can be used as a filter such as a surface acoustic wave (SAW) filter. It can function as a device. SAW can be excited on the surface of the KNN film 3 by applying a voltage between the pattern electrodes _4p1 by the voltage applying section 11a. The frequency of the SAW to be excited can be adjusted by, for example, adjusting the pattern pitch of the pattern electrode _4p1 . For example, the shorter the pitch of the IDTs as the pattern electrodes _4p1 , the higher the SAW frequency, and the longer the pitch, the lower the SAW frequency. Among the SAWs excited by the voltage application unit 11a, propagating through the KNN film 3, and reaching the pattern electrode _4p2 , the SAW has a predetermined frequency (frequency component) determined according to the pitch of the IDT as the pattern electrode _4p2 , etc. As a result, a voltage is generated between the pattern electrodes _4p2 . By detecting this voltage by the voltage detection unit 11b, it is possible to extract a SAW having a predetermined frequency from among the excited SAWs. Note that the term "predetermined frequency" herein may include not only a predetermined frequency but also a predetermined frequency band whose center frequency is a predetermined frequency.

Also in this modification, the same effect as in the above-described embodiment can be obtained because in the KNN film 3, the amount of Mn present in the grain boundaries is greater than the amount of Mn present in the matrix.

(Modification 5)
An orientation control layer for controlling the orientation of crystals constituting the KNN film 3 may be provided between the lower electrode film 2 and the KNN film 3. When providing the first Mn layer 7, it is preferable to provide an orientation control layer between the lower electrode film 2 and the first Mn layer 7. In addition, when the lower electrode film 2 is not provided as described in Modification 4, between the substrate 1 and the KNN film 3 (when the first Mn layer 7 is provided, between the substrate 1 and the first Mn layer 7). Preferably, an orientation control layer is provided. The orientation control layer is, for example, a metal oxide such as SRO, LNO, strontium titanate (SrTiO ₃ , abbreviation: STO), and can be formed using a material different from the material constituting the lower electrode film 2. can. It is preferable that the crystals constituting the orientation control layer are preferentially oriented in the (100) plane with respect to the surface of the substrate 1.

(Modification 6)
In the above-described embodiments and modifications, the first Mn layer 7 and the second Mn layer 8 are provided, and heat treatment is performed to diffuse Mn into the Mn-free KNN film 3A (KNN film 3). However, the present invention is not limited to the above-described embodiments and modifications. For example, instead of providing the first Mn layer 7 and the second Mn layer 8, or in addition to providing at least one of the first Mn layer 7 and the second Mn layer 8, the lower electrode film 2 and the upper electrode film 4 ( At least one of the electrode films 4) may contain Mn. At this time, Mn is included in the side close to the upper surface of the lower electrode film 2 (the surface in contact with the KNN film 3), preferably the uppermost surface of the lower electrode film 2, and the lower surface of the upper electrode film 4 (the surface in contact with the KNN film 3) ), preferably the lowermost surface of the upper electrode film 4, preferably contains Mn. The Mn concentration contained in the lower electrode film 2 and the upper electrode film 4 is such that the Mn concentration in the KNN film 3 after the heat treatment can be, for example, 0.2 at % or more and 2.0 at % or less. Note that when Mn is included in the upper electrode film 4 in this modification, it is preferable that no adhesive layer be provided between the KNN film 3 and the upper electrode film 4. This is because, as described above, the adhesion layer may inhibit the diffusion of Mn into the KNN film 3. The other configurations are the same as those of the above-described embodiment and modification.

Also in this modification, Mn in the lower electrode film 2 and the upper electrode film 4 (electrode film 4) can be diffused into the KNN film 3 by performing the same heat treatment as in the above-described embodiment. As a result, it is possible to obtain a piezoelectric laminate 10 having a KNN film 3 in which Mn exists in the grain boundaries, and the same effects as in the above-described embodiment and modification can be obtained.

(Modification 7)
In the above-described embodiments and modified examples, by providing at least one of the first Mn layer 7 and the second Mn layer 8 and performing heat treatment, the Mn present in the grain boundaries becomes stronger than the Mn present in the matrix. The explanation has been given by taking as an example a case where a KNN film 3 having a large number of KNN films is manufactured. However, the present invention is not limited to the above-described embodiments and modifications. For example, the piezoelectric laminate 10 described above can be manufactured by the manufacturing method described below without providing either the first Mn layer 7 or the second Mn layer 8 described above.

First, a KNN film 3 doped with Mn is formed on the lower electrode film 2 of the substrate 1 . The method and conditions for forming the Mn-doped KNN film 3 can be the same as those described in the embodiment and the third modification described above. Thereafter, an upper electrode film 4 is formed on the KNN film 3. Conditions for forming (providing) the adhesive layer 6, the lower electrode film 2, and the upper electrode film 4 can be the same as those in the above-described embodiment. As a result, a laminate 12 is obtained. Thereafter, the laminate 12 is subjected to heat treatment under predetermined conditions. The heat treatment conditions can be the same as those in the above embodiment. After the heat treatment, the laminate 12 is cooled over 20 minutes or more until the temperature of the laminate 12 reaches 400°C. Thereafter, the laminate 12 is cooled until the temperature of the laminate 12 reaches about room temperature (25° C.). By cooling the laminate 12 in this manner, the piezoelectric laminate 10 having the KNN film 3 in which the amount of Mn present in the grain boundaries is greater than the amount of Mn present in the matrix can be obtained. The piezoelectric laminate 10 produced by the method according to this modification also provides the same effects as the above-described embodiments.

<Other embodiments>
The embodiments of the present invention have been specifically described above. However, the present invention is not limited to the above-described embodiments, and various changes can be made without departing from the spirit thereof.

In the above-described embodiment, a case has been described in which the KNN film 3 contains Mn, and the amount of Mn present in the grain boundaries of the crystals constituting the KNN film 3 is greater than the Mn present in the parent phase of the crystals, but the present invention is not limited to this. . For example, the KNN film 3 contains Mn and copper (Cu), and the Mn and Cu present in the grain boundaries of the crystals constituting the KNN film 3 (for example, the total number of particles of Mn and Cu present in the grain boundaries) are The number of particles may be greater than the number of Mn and Cu present in the matrix (for example, the total number of particles of Mn and Cu present in the matrix). In this case, the KNN film 3 preferably contains Cu and Mn such that the total concentration of Cu and Mn is within a range of, for example, 0.2 at% or more and 2.0 at% or less. Even in this case, effects similar to those of the above-described embodiments can be obtained.

For example, in addition to or in place of Mn, the KNN film 3 may contain other metal elements that have the same effect as Mn to maintain the relative dielectric constant of the KNN film 3 while obtaining the above-mentioned oxygen vacancy migration suppressing effect. may be contained in a concentration that allows for appropriate size. Even in this case, the same effects as the above-described embodiment and modification can be obtained.

Furthermore, for example, when the piezoelectric laminate 10 described above is molded into the piezoelectric element 20, the piezoelectric device 30 produced using the piezoelectric laminate 10 (piezoelectric element 20) can be applied to a desired application such as a sensor or an actuator. As far as possible, the substrate 1 may be removed from the piezoelectric laminate 10.

<Preferred embodiments of the present invention>
Hereinafter, preferred embodiments of the present invention will be additionally described.

(Additional note 1)
According to one aspect of the invention,
It is a polycrystalline film made of potassium sodium niobate,
Contains Mn,
A piezoelectric film is provided in which the amount of Mn present in the grain boundaries of the crystal is greater than the amount of Mn present in the parent phase of the crystal.

(Additional note 2)
The piezoelectric film according to Supplementary Note 1, preferably,
When a positive or negative electric field of 300 kV/cm is applied to the electrode film provided on the piezoelectric film at a temperature of 200° C., the leakage current density is 30 mA/cm from the start of electric field application under at least one electric field application condition. The time it takes to exceed cm ² is 7600 seconds or more.

(Additional note 3)
The piezoelectric film according to appendix 1 or 2, preferably,
It is composed of crystal grains having an average grain size of 100 nm or more.

(Additional note 4)
The piezoelectric film according to any one of Supplementary Notes 1 to 3, preferably,
The content of Mn is within the range of 0.2 at% or more and 2.0 at% or less with respect to the amount of niobium in the polycrystalline film.

(Appendix 5)
According to one aspect of the invention,
A substrate and
an electrode film;
A piezoelectric film that is a polycrystalline film made of potassium sodium niobate,
The piezoelectric film contains manganese (Mn),
A piezoelectric laminate is provided in which more Mn exists in grain boundaries of crystals constituting the piezoelectric film than in a matrix of the crystals.

(Appendix 6)
According to yet another aspect of the invention,
A substrate and
a piezoelectric film that is formed on the substrate and is a polycrystalline film made of potassium sodium niobate;
an electrode film formed on the piezoelectric film,
The piezoelectric film contains Mn,
A piezoelectric element or a piezoelectric device is provided, in which more Mn exists in grain boundaries of crystals constituting the piezoelectric film than in a matrix of the crystals.

(Appendix 7)
According to yet another aspect of the invention,
A substrate and
a lower electrode film formed on the substrate;
a piezoelectric film that is formed on the lower electrode film and is a polycrystalline film made of potassium sodium niobate;
an upper electrode film formed on the piezoelectric film,
The piezoelectric film contains Mn,
A piezoelectric element or a piezoelectric device is provided, in which more Mn exists in grain boundaries of crystals constituting the piezoelectric film than in a matrix of the crystals.

(Appendix 8)
According to yet another aspect of the invention,
A step of forming a piezoelectric film, which is a polycrystalline film made of potassium sodium niobate, on the substrate;
providing a layer containing Mn or a layer consisting of Mn on the piezoelectric film;
forming an electrode film on the layer containing Mn or the layer consisting of Mn;
a step of performing heat treatment on a laminate including the substrate, the piezoelectric film, the layer containing Mn or the layer consisting of Mn, and the electrode film,
By carrying out the step of performing the heat treatment, Mn in the layer containing Mn or the layer consisting of Mn is diffused into the piezoelectric film, and the piezoelectric film is transformed into a crystal that contains Mn and constitutes the piezoelectric film. Provided is a method for manufacturing a piezoelectric laminate in which the amount of Mn present in the grain boundaries of the piezoelectric laminate is greater than the amount of Mn present in the parent phase of the crystal.

(Appendix 9)
According to yet another aspect of the invention,
a step of forming a lower electrode film on the substrate;
forming a piezoelectric film, which is a polycrystalline film made of potassium sodium niobate, on the lower electrode film;
forming an upper electrode film on the piezoelectric film;
a step of performing heat treatment on a laminate including the substrate, the lower electrode film, the piezoelectric film, and the upper electrode film,
Before performing the step of forming the piezoelectric film, a step of providing a layer containing Mn so as to be in contact with the lower surface of the piezoelectric film, or after performing the step of forming the piezoelectric film, forming a layer of the piezoelectric film. Performing at least one of the steps of providing a layer containing Mn or a layer consisting of Mn so as to be in contact with the upper surface,
By carrying out the step of performing the heat treatment, Mn in the layer containing Mn or the layer consisting of Mn is diffused into the piezoelectric film, and the piezoelectric film is transformed into a crystal that contains Mn and constitutes the piezoelectric film. Provided is a method for manufacturing a piezoelectric laminate in which the amount of Mn present in the grain boundaries of the piezoelectric laminate is greater than the amount of Mn present in the parent phase of the crystal.

(Appendix 10)
According to yet another aspect of the invention,
A step of forming a piezoelectric film, which is a polycrystalline film made of potassium sodium niobate, on the substrate;
forming an electrode film containing Mn on the piezoelectric film;
a step of performing heat treatment on a laminate including the substrate, the piezoelectric film, and the electrode film,
By carrying out the step of performing the heat treatment, Mn in the electrode film is diffused into the piezoelectric film, and the piezoelectric film contains Mn and exists in the grain boundaries of the crystals constituting the piezoelectric film. A method of manufacturing a piezoelectric laminate is provided, in which the film contains more Mn than the mother phase of the crystal.

(Appendix 11)
According to yet another aspect of the invention,
a step of forming a lower electrode film on the substrate;
forming a piezoelectric film, which is a polycrystalline film made of potassium sodium niobate, on the lower electrode film;
forming an upper electrode film on the piezoelectric film;
a step of performing heat treatment on a laminate including the substrate, the lower electrode film, the piezoelectric film, and the upper electrode film,
Mn is included in the lower electrode film in the step of forming the lower electrode film, or Mn is included in the upper electrode film in the step of forming the upper electrode film,
By performing the step of performing heat treatment, Mn in the lower electrode film or the upper electrode film is diffused into the piezoelectric film, and the piezoelectric film becomes a crystal grain containing Mn and constituting the piezoelectric film. Provided is a method for manufacturing a piezoelectric laminate in which the amount of Mn present in the field is greater than the amount of Mn present in the matrix of the crystal.

(Appendix 12)
The method according to appendix 11, preferably,
In the step of forming the lower electrode film, Mn is included in the side closer to the upper surface of the lower electrode film, and in the step of forming the upper electrode film, Mn is included in the side closer to the lower surface of the upper electrode film. include.

1 Substrate 3 Piezoelectric film 10 Piezoelectric laminate

Claims (6)

It is a polycrystalline film made of potassium sodium niobate,
Contains Mn in a range of 0.2 at% or more and 2.0 at% or less based on the amount of niobium in the polycrystalline film ,
The crystals constituting the polycrystalline film are preferentially oriented in the (001) plane,
A piezoelectric film in which more Mn exists in grain boundaries of the crystal than in a matrix of the crystal. When a positive or negative electric field of 300 kV/cm is applied to the electrode film provided on the piezoelectric film at a temperature of 200° C., the leakage current density is 30 mA from the start of electric field application under at least one electric field application condition. 2. The piezoelectric film according to claim 1, wherein the time for exceeding / ^cm2 is 7600 seconds or more. 3. The piezoelectric film according to claim 1, wherein the piezoelectric film is composed of crystal grains having an average grain size of 100 nm or more. A substrate and
an electrode film;
A piezoelectric film that is a polycrystalline film made of potassium sodium niobate,
The piezoelectric film contains Mn in a range of 0.2 at% or more and 2.0 at% or less based on the amount of niobium in the polycrystalline film ,
The crystals constituting the piezoelectric film are preferentially oriented in the (001) plane direction,
A piezoelectric laminate in which more Mn exists in grain boundaries of the crystals constituting the piezoelectric film than in a matrix of the crystals. A substrate and
a piezoelectric film that is formed on the substrate and is a polycrystalline film made of potassium sodium niobate;
an electrode film formed on the piezoelectric film,
The piezoelectric film contains Mn in a range of 0.2 at% or more and 2.0 at% or less based on the amount of niobium in the polycrystalline film ,
The crystals constituting the piezoelectric film are preferentially oriented in the (001) plane direction,
A piezoelectric element in which the amount of Mn present in the grain boundaries of the crystal constituting the piezoelectric film is greater than the amount of Mn present in the matrix of the crystal. A step of forming a piezoelectric film, which is a polycrystalline film made of potassium sodium niobate, on the substrate;
providing a layer containing Mn or a layer consisting of Mn on the piezoelectric film;
forming an electrode film on the layer containing Mn or the layer consisting of Mn;
a step of performing heat treatment on a laminate including the substrate, the piezoelectric film, the layer containing Mn or the layer consisting of Mn, and the electrode film,
By carrying out the step of performing the heat treatment, Mn in the layer containing Mn or the layer consisting of Mn is diffused into the piezoelectric film, and the piezoelectric film is transformed into a crystal that contains Mn and constitutes the piezoelectric film. A method for producing a piezoelectric laminate, in which the amount of Mn present in the grain boundaries of the film is greater than the amount of Mn present in the parent phase of the crystal.

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