CN116782744A

CN116782744A - Piezoelectric element

Info

Publication number: CN116782744A
Application number: CN202310237641.8A
Authority: CN
Inventors: 大桥幸司; 滨田泰彰; 北田和也; 矢野凯己; 浅川勉; 竹内正浩; 堀场靖央; 板山泰裕
Original assignee: Seiko Epson Corp
Current assignee: Seiko Epson Corp
Priority date: 2022-03-17
Filing date: 2023-03-13
Publication date: 2023-09-19
Also published as: JP2023136544A

Abstract

The invention provides a piezoelectric element which suppresses the generation of cracks in a piezoelectric layer. The piezoelectric element (44) is provided with: a contact layer (445) which is formed on the vibration plate (36) and contains titanium; a lower electrode (441) formed on the adhesion layer (445); a diffusion suppression layer (447) which is formed on the lower electrode (441) and contains iridium; a seed layer (442) formed on the diffusion suppression layer (447) and comprising bismuth; a piezoelectric layer (443) which is formed on the seed layer (442) and contains potassium, sodium, and niobium; an upper electrode (444) formed on the piezoelectric layer (443).

Description

Piezoelectric element

Technical Field

The present invention relates to a piezoelectric element.

Background

Conventionally, piezoelectric elements using a non-lead piezoelectric material have been developed in place of lead piezoelectric materials such as lead zirconate titanate. For example, patent document 1 discloses a piezoelectric element including a potassium sodium niobate (KNN) -based piezoelectric layer. In the piezoelectric element, an adhesion layer is formed between the first electrode and the vibration plate to improve adhesion between the first electrode and the vibration plate. Titanium, titanium oxide, or the like is used for the adhesion layer.

However, the piezoelectric element described in patent document 1 has a problem that if the piezoelectric layer is formed relatively thick, cracks are likely to occur in the piezoelectric layer. In detail, KNN is a complex oxide having a perovskite structure. If titanium or titanium oxide is used for the adhesion layer, titanium is easily diffused into the piezoelectric layer by heat treatment or the like in the manufacturing process. If titanium diffuses, the growth of grains of KNN oriented on the (111) plane occurs in addition to grains of original KNN oriented preferentially on the (100) plane. Therefore, if the piezoelectric layer is formed relatively thick, internal stress tends to concentrate on grain boundaries due to a difference in shrinkage, and cracks may occur in the piezoelectric layer.

In addition, if the adhesion layer is omitted or zirconium is used in the adhesion layer, cracks are likely to occur in the piezoelectric layer regardless of the crystal orientation. This is because, although the diffusion of titanium is reduced, residual stress in the piezoelectric layer, which is generated due to the difference in linear expansion coefficient and/or the difference in lattice spacing between the piezoelectric layer and the vibration plate, is difficult to relax. That is, a piezoelectric element is intended to suppress the occurrence of cracks in a piezoelectric layer.

Patent document 1: japanese patent application laid-open No. 2018-133458

Disclosure of Invention

The piezoelectric element is provided with: a contact layer formed on the substrate and containing titanium; a lower electrode formed on the adhesion layer; a diffusion suppression layer formed on the lower electrode and including iridium; a seed layer formed on the diffusion suppression layer and including bismuth; a piezoelectric layer formed on the seed layer and including potassium, sodium, and niobium; and an upper electrode formed on the piezoelectric layer.

Drawings

Fig. 1 is a schematic diagram showing a schematic configuration of a recording apparatus including a droplet ejection head according to a first embodiment.

Fig. 2 is an exploded perspective view of the droplet ejection head.

Fig. 3 is a schematic cross-sectional view along the XZ plane, including line A-A in fig. 2.

Fig. 4 is a plan view showing the structure of the piezoelectric element.

Fig. 5 is a cross-sectional view taken along the YZ plane and including line E-E of fig. 4.

Fig. 6 is an X-ray diffraction intensity curve of the examples and comparative examples.

Fig. 7 is an X-ray diffraction intensity curve of the examples and comparative examples.

Fig. 8 is an X-ray diffraction intensity curve of the examples and comparative examples.

Fig. 9 is a cross-sectional SEM photograph of the piezoelectric layer of example 1.

Fig. 10 is a plan SEM photograph of the piezoelectric layer of example 1.

Fig. 11 is a cross-sectional SEM photograph of the piezoelectric layer of comparative example 1.

Fig. 12 is a plan SEM photograph of the piezoelectric layer of comparative example 1.

Fig. 13 is a diagram showing a depth direction profile of example 1 based on SIMS measurement.

Fig. 14 is a diagram showing a depth direction profile of comparative example 1 based on SIMS measurement.

Fig. 15 is a diagram showing a depth direction profile of comparative example 2 based on SIMS measurement.

Fig. 16 is a schematic cross-sectional view showing a state of diffusion of titanium in the piezoelectric layer of example 1.

Fig. 17 is a schematic cross-sectional view showing a state of diffusion of titanium in the piezoelectric layer of comparative example 1.

Fig. 18 is a cross-sectional view showing a configuration of a droplet ejection head according to a second embodiment.

Detailed Description

1. First embodiment

In the embodiments described below, a piezoelectric element using a non-lead piezoelectric material, a droplet discharge head to which the piezoelectric element is applied, and a recording apparatus are exemplified, and will be described with reference to the accompanying drawings. In the following drawings, XYZ axes are marked as coordinate axes as needed, and the direction in which the arrow mark points is set as the +direction, and the direction opposite to the +direction is set as the-direction. The +z direction is sometimes referred to as upper, the-Z direction is sometimes referred to as lower, and the case of viewing from the +z direction is sometimes referred to as top view or planar view. In addition, for convenience of illustration, the sizes of the respective components are made different from actual ones.

1.1. Recording device

As shown in fig. 1, a recording apparatus 100 as an inkjet printer includes a droplet ejection head 1. The liquid droplet ejection head 1 includes a piezoelectric element 44 according to the present embodiment described later.

In the recording apparatus 100, printing such as recording is performed by causing droplets of ink to adhere to the recording medium 2 from the droplet discharge head 1. The recording apparatus 100 includes a head moving mechanism 5, a medium conveying mechanism 6, an ink storage unit 7, and a control unit 18 in addition to the droplet ejection head 1.

The head moving mechanism 5 includes a carriage 4 and a timing belt 8. The liquid droplet ejection head 1 is mounted on the carriage 4. The carriage 4 is connected to a timing belt 8. The timing belt 8 is driven by a motor, not shown, and moves the carriage 4 in a direction along the X axis, which is the main scanning direction. Thus, the droplet discharge head 1 can reciprocate in the X-axis direction relative to the recording medium 2.

The medium conveyance mechanism 6 conveys the recording medium 2 in the +y direction, which is the sub-scanning direction. Thereby, the recording medium 2 moves in the +y direction relative to the droplet discharge head 1.

The ink storage unit 7 stores ink ejected from the droplet ejection head 1. The ink stored in the ink storage portion 7 is supplied to the droplet ejection head 1 via an ink pipe, not shown. The ink storage unit 7 may be arranged in a plurality of ways corresponding to a plurality of types of ink exhibiting colors such as black, cyan, magenta, and yellow, for example. The liquid droplets ejected from the liquid droplet ejection head 1 are not limited to ink, and may be other than ink, such as a processing liquid or a cleaning liquid.

The liquid droplet ejection head 1 is disposed on a side of the carriage 4 facing the recording medium 2. The droplet ejection head 1 includes a nozzle surface, not shown, on a surface facing the recording medium 2. The nozzle surface is provided with a plurality of nozzles N. The plurality of nozzles N are arranged in a row corresponding to the type of ink described above.

The ink in the ink storage portion 7 is supplied to the droplet discharge head 1, and is discharged as droplets from the plurality of nozzles N by actuators described later of the droplet discharge head 1. The droplets of the ejected ink are ejected and adhere to the recording medium 2.

The control unit 18 includes a plurality of processing circuits such as a CPU (Central Processing Unit: central processing unit) and an FPGA (Field Programmable Gate Array: field programmable gate array), and a memory circuit such as a semiconductor memory. The control unit 18 controls the operation of the entire recording apparatus 100. The head moving mechanism 5, the medium conveying mechanism 6, the droplet ejection head 1, and the like are electrically connected to the control unit 18, and are comprehensively controlled by the control unit 18.

According to the above-described aspect, the movement of the droplet discharge head 1 in the main scanning direction and the conveyance of the recording medium 2 in the sub-scanning direction are made to correspond to each other, and the ink is attached to the recording medium 2 at a predetermined timing, whereby an image or the like can be printed on the recording medium 2.

Although a serial printer is exemplified as the recording apparatus 100 in the present embodiment, the recording apparatus to which the droplet discharge head 1 is applied is not limited to this. For example, the recording apparatus may be a line head printer. The device on which the droplet discharge head 1 is mounted is not limited to the recording device 100, and may be, for example, a device for manufacturing a color filter such as a liquid crystal display, an electrode forming device such as an organic electroluminescent display or a field emission display, a biochip manufacturing device, or the like.

1.2. Liquid drop ejection head

As shown in fig. 2, the droplet ejection head 1 includes: the nozzle plate 62, the two vibration absorbers 64, the flow path formation substrate 32, the pressure chamber substrate 34, the plurality of piezoelectric elements 44, the vibration plate 36 as a substrate, the wiring substrate 46, the driving circuit 50, and the housing portion 48. The piezoelectric device 40 is constituted by a plurality of piezoelectric elements 44.

The nozzle plate 62, the vibration absorbing body 64, the flow path forming substrate 32, the pressure chamber substrate 34, the vibration plate 36, and the wiring board 46 are substantially rectangular plate-like members, and the longitudinal direction thereof is along the Y axis in a plan view. In manufacturing the liquid droplet ejection head 1, the nozzle plate 62 and the two vibration absorbing bodies 64, the flow path forming substrate 32, the pressure chamber substrate 34, the vibration plate 36, the wiring substrate 46, and the housing portion 48 are stacked in this order, and are bonded to each other by, for example, an adhesive.

The nozzle plate 62, the flow path formation substrate 32, the pressure chamber substrate 34, and the diaphragm 36 have a structure substantially line-symmetrical with respect to a center line in a direction along the respective X-axis. In plan, the sizes of the pressure chamber substrate 34, the diaphragm 36, and the wiring substrate 46 are smaller than the sizes of the flow path forming substrate 32 and the housing 48.

A plurality of nozzles N are formed in the nozzle plate 62. The nozzle N is a through hole penetrating the nozzle plate 62, and is substantially circular in plane. The plurality of nozzles N are arranged along the Y axis, and are arranged in two rows in the direction along the X axis. The two vibration absorbing bodies 64 are arranged so as to sandwich the nozzle plate 62 in the X-axis direction. The two shock-absorbing bodies 64 are flexible films.

The flow path forming substrate 32 has two first openings 32a, a plurality of second openings 32b, and a plurality of third openings 32c. The first opening 32a is substantially rectangular in a plane along the Y axis in the longitudinal direction. The first opening 32a is provided along a long side of the flow path forming substrate 32 along the long side of the Y axis in a plan view.

The plurality of second openings 32b are arranged in two rows in the direction along the Y axis. Similarly, the plurality of third openings 32c are also arranged in two rows in the direction along the Y axis. In the direction along the X axis, the first openings 32a, the second openings 32b, the third openings 32c, the second openings 32b, and the first openings 32a are arranged in this order. Further, the second opening 32b and the third opening 32c adjacent in the direction along the X axis are arranged in substantially the same manner as the positions in the direction along the Y axis.

The pressure chamber substrate 34 is provided with a plurality of openings 34a. The opening 34a is substantially rectangular in a plane along the X axis in the longitudinal direction. The plurality of openings 34a are arranged in two rows in the direction along the Y axis. Two rows of the plurality of openings 34a are arranged side by side in the direction along the X axis. Each opening 34a is provided at a position overlapping the second opening 32b and the third opening 32c adjacent to the flow path forming substrate 32 on a plane.

A plurality of piezoelectric elements 44 are formed on the vibration plate 36. Specifically, a plurality of piezoelectric elements 44 are disposed on the upper main surface of the vibration plate 36. The piezoelectric elements 44 are provided at positions overlapping the opening portions 34a of the pressure chamber substrate 34 in a plan view. The openings 34a of the pressure chamber substrate 34 form pressure chambers C described later together with the lower surface of the vibration plate 36.

The driving circuit 50 drives the plurality of piezoelectric elements 44. Specifically, the driving circuit 50 is an IC (Integrated Circuit: integrated circuit) chip that outputs a driving signal for driving each piezoelectric element 44 and a reference voltage. The driving circuit 50 is mounted on the upper main surface of the wiring board 46. The wiring board 46 is provided with wiring for inputting signals to the drive circuit 50, driving signals outputted from the drive circuit 50, and a reference voltage.

Terminals, not shown, of the wiring board 46 and the piezoelectric elements 44 are bonded via bumps B described later. The input signal to the drive circuit 50 is input to the above-described terminal via, for example, an FPC (Flexible Printed Circuits: flexible printed circuit).

The housing 48 is a container for storing ink, and has a frame shape. When the droplet ejection head 1 is assembled, the pressure chamber substrate 34, the diaphragm 36, and the wiring board 46 are disposed in the internal space of the housing 48. At both sides of the housing 48 in the X-axis direction, through holes 48a are formed.

As shown in fig. 3, the wiring board 46, the diaphragm 36, and the pressure chamber substrate 34 are housed inside the frame-like shape of the housing 48. The outer edge of the frame shape of the housing 48 is in contact with the upper side of the flow path forming substrate 32. A nozzle plate 62 and two vibration absorbing bodies 64 are connected to the lower side of the flow path forming substrate 32. Here, the droplet discharge head 1 has a structure symmetrical to the left and right in fig. 3. Therefore, in the following description, the structure in the-X direction, which is the left direction, will be described, and the description of the structure in the +x direction will be omitted.

A space Rb is formed near the end of the housing 48 in the-X direction. The space Rb communicates with the through hole 48a at the upper side and communicates with the first opening 32a of the flow path forming substrate 32 at the lower side. The space Rb corresponds to the shape on the plane of the first opening portion 32a and extends in the direction along the Y axis.

The flow channel forming substrate 32 is provided with a space Ra, a partition wall 32d, a supply flow channel 26b, and a communication flow channel 26c. The space Ra is an internal space formed by the first opening 32 a. The partition wall 32d is provided between the first opening 32a and the second opening 32 b. The lower end of the partition wall 32d is located above the lower surface of the flow path forming substrate 32, and is recessed in the +z direction. The lower end of the partition wall 32d and the upper surface of the shock absorber 64 form the liquid supply chamber 26a. The supply flow passage 26b is an internal space formed by the second opening 32 b.

The pressure chamber C is formed by the opening 34a of the pressure chamber substrate 34, the lower surface of the diaphragm 36, and the upper surface of the flow path formation substrate 32. That is, the diaphragm 36 forms a wall surface above a part of the wall surface of the pressure chamber C. The pressure chamber C communicates with the supply flow passage 26b at a position below the end in the-X direction.

The communication flow passage 26c is an internal space formed by the third opening 32 c. The pressure chamber C communicates with the communication flow passage 26C at a position below the end in the +x direction, and communicates with the nozzles N of the nozzle plate 62 via the communication flow passage 26C.

According to the above-described embodiment, the through-hole 48a communicates with the spaces Rb and Ra, the supply liquid chamber 26a, the supply flow path 26b, the pressure chamber C, the communication flow path 26C, and the nozzle N in this order, thereby forming the flow path of the ink. In the above-described structure for forming the ink flow path, the supply liquid chamber 26a to the communication flow path 26c are provided so as to correspond to the plurality of nozzles N, respectively.

The through-hole 48a is supplied with ink from the ink storage portion 7. The spaces Ra and Rb function as liquid storage chambers for storing ink supplied into the pressure chamber C. The space Rb communicates with a plurality of spaces Ra arranged along the Y axis. The ink supplied from the through hole 48a is stored in the space Ra through the space Rb. The ink stored in the space Ra is supplied to the pressure chamber C through the supply liquid chamber 26a and the supply flow path 26 b.

The piezoelectric element 44 is disposed so as to overlap the pressure chamber C in a planar surface. That is, the respective piezoelectric elements 44 are provided in correspondence with the plurality of pressure chambers C. The piezoelectric element 44 includes an active portion 440 described later. A wiring board 46 is disposed above the piezoelectric element 44, and a driving circuit 50 is disposed above the wiring board 46. The wiring board 46 and the piezoelectric element 44 are electrically connected by the bump B.

A drive signal and a reference voltage are input from the wiring board 46 to the piezoelectric element 44 via the bump B. The piezoelectric element 44 is deformed by applying a voltage to the input of a drive signal and a reference voltage. The vibration plate 36 vibrates in association with the deformation of the piezoelectric element 44. In this way, the ink is ejected from the nozzles N by pressure fluctuation in the pressure chamber C.

The diaphragm 36 is driven by the piezoelectric element 44. The drive circuit 50 applies a voltage to the piezoelectric element 44. The piezoelectric element 44, the diaphragm 36 serving as a driving section, and the driving circuit 50 serving as a voltage applying section constitute an actuator for ejecting liquid droplets.

1.3. Piezoelectric element

The arrangement on the plane of the piezoelectric element 44 will be described. As shown in fig. 4, the plurality of piezoelectric elements 44 are arranged adjacent to each other in the direction along the Y axis. The piezoelectric element 44 includes a lower electrode 441, a seed layer 442, a piezoelectric layer 443, an upper electrode 444, and the like. Although the details will be described later, the lower electrode 441, the seed layer 442, the piezoelectric layer 443, and the upper electrode 444 are stacked in this order from the vibration plate 36 upward in the direction along the Z axis. In the following description with reference to fig. 4, unless otherwise specified, a state in a plan view will be described.

The plurality of upper electrodes 444 are arranged so as to overlap each pressure chamber C in the direction along the Z axis. The upper electrode 444 extends from a substantially rectangular region overlapping the pressure chamber C to be drawn out in the +x direction. Although not shown, each of the upper electrodes 444 is electrically connected to the drive circuit 50 at a tip extending in the +x direction.

In the process of manufacturing the piezoelectric element 44, the seed layer 442 and the piezoelectric layer 443 are formed to have a substantially entire surface shape by covering the lower electrode 441, and then only the region S is etched. That is, in the region S, the seed layer 442 and the piezoelectric layer 443 are not disposed. The region S is substantially hexagonal elongated in the direction along the X axis, and is provided between the upper electrodes 444 adjacent in the direction along the Y axis.

The lower electrode 441 is formed in a whole surface shape so as to cover the insulator layer 362. The lower electrode 441 is electrically connected to the drive circuit 50 through a terminal not shown. An independent voltage is applied to each upper electrode 444, whereas a common voltage is applied to the lower electrode 441.

The detailed structure of the piezoelectric element 44 will be described. As shown in fig. 5, the plurality of piezoelectric elements 44 are formed so as to contact the upper surface of the vibration plate 36. A region S is arranged between two piezoelectric elements 44 adjacent in the direction along the Y axis. In fig. 5, the diaphragm 36, the flow path formation substrate 32, and the pressure chamber substrate 34 are illustrated in addition to the two piezoelectric elements 44.

The piezoelectric element 44 includes: an adhesion layer 445, a lower electrode 441, a diffusion suppression layer 447, a seed layer 442, a piezoelectric layer 443, and an upper electrode 444. In the piezoelectric element 44, the adhesion layer 445, the lower electrode 441, the diffusion suppression layer 447, the seed layer 442, the piezoelectric layer 443, and the upper electrode 444 are stacked in this order. That is, the lamination direction of the layers of the piezoelectric element 44 is a direction along the Z axis.

The area where the planar adhesion layer 445, the lower electrode 441, the seed layer 442, the diffusion suppression layer 447, the piezoelectric layer 443, and the upper electrode 444 overlap is defined as the active portion 440. The active portion 440 is a region where the piezoelectric layer 443 is deformed when a voltage is applied between the lower electrode 441 and the upper electrode 444. The movable portion 440 faces the pressure chamber C through the diaphragm 36 in the direction along the Z axis.

Here, the diffusion suppressing layer 447 is formed in a whole surface shape. The diffusion suppressing layer 447 may be formed so as to be discontinuous in the plane of the region S, for example.

The seed layer 442 corresponding to each of the plurality of piezoelectric elements 44 is formed so as to be continuous in a region other than the region S in the plane. The piezoelectric layer 443 corresponding to each of the plurality of piezoelectric elements 44 is formed so as to be continuous in a region other than the region S on the plane.

The vibration plate 36 has a silicon (Si) substrate 361 and an insulator layer 362. The silicon substrate 361 is made of single crystal silicon. Although not shown, the silicon substrate 361 includes a silicon layer and a silicon oxide layer (SiO ₂ ). A silicon oxide layer is disposed over the silicon layer, and the silicon oxide layer is in contact with the insulator layer 362. Instead of the silicon substrate 361, an SOI (Silicon on Insulator: silicon on insulator) substrate, a glass substrate, or the like may be used. The insulator layer 362 contains zirconia (ZrO ₂ )。

The adhesion layer 445 is formed on the vibration plate 36, specifically, at a position overlapping with the plane of the active portion 440 so as to contact the upper surface of the insulator layer 362. The adhesion layer 445 contains titanium (Ti). The titanium included in the adhesion layer 445 may be titanium oxide (TiO ₂ ) Titanium of (c) a).

Here, residual stress may occur in the piezoelectric layer 443 due to a difference in linear expansion coefficient or a difference in lattice spacing between the piezoelectric layer 443 and the vibration plate 36. In contrast, by including titanium in the adhesion layer 445, the residual stress described above is easily relaxed. In addition, zirconium or zinc (Zn) may be used in place of titanium in the adhesion layer 445.

The lower electrode 441 is formed on the adhesion layer 445, and is formed so as to contact the surface above the adhesion layer 445 in detail. The lower electrode 441 includes platinum (Pt). The lower electrode 441 is not limited to a single layer of platinum, and may be formed of IrO, for example _x 、LaNiO ₃ 、SrRuO ₃ Such as a single layer of a conductive oxide film, a structure in which two or more layers are stacked with the single layer of the above material may be employed.

The diffusion suppressing layer 447 is formed in a whole surface shape so as to cover the lower electrode 441. More specifically, the adhesion layer 445 and the lower electrode 441 are formed so as to cover both sides of the lower electrode 441 and a part of the upper side of the vibration plate 36 on both sides of the adhesion layer 445. In other words, the diffusion suppressing layer 447 is interposed between the adhesion layer 445 and the lower electrode 441, and the seed layer 442 and the piezoelectric layer 443. Therefore, even at the interface between the diffusion suppression layer 447 and the vibration plate 36, the diffusion of titanium can be suppressed.

The diffusion suppression layer 447 contains iridium (Ir). This suppresses diffusion of titanium contained in the adhesion layer 445 with respect to the piezoelectric layer 443. The diffusion-suppressing layer 447 may also comprise iridium oxide (IrO) _x ). Iridium oxide may be generated by oxidation of iridium during a heating process or the like in the manufacturing process of the piezoelectric element 44.

Although the thickness of the diffusion suppression layer 447 is not particularly limited, it is set to, for example, 3nm to 50nm.

The seed layer 442 is formed on the diffusion suppressing layer 447, specifically, is formed so as to cover the diffusion suppressing layer 447. The seed layer 442 is controlled so that the crystal orientation of the composite oxide in the piezoelectric layer 443 is uniform. The seed layer 442 promotes preferential orientation of the crystal of the piezoelectric layer 443 to the (100) plane.

The seed layer 442 is a complex oxide having a perovskite structure and containing bismuth (Bi), titanium (Ti), iron (Fe), and lead (Pb). Although the seed layer 442 contains titanium that may cause growth of crystal grains of KNN oriented to the (111) plane in the piezoelectric layer 443, as a result of studies by the applicant, it was found that the crystal orientation to the (100) plane was promoted in the composite oxide of the piezoelectric layer 443. Therefore, the occurrence of cracks due to grain boundaries can be further suppressed, and the electrical characteristics of the piezoelectric element 44 are improved.

The composition of each element of the seed layer 442 is not particularly limited, but for example, lead is set to 0.1, bismuth is set to 1.1, iron is set to 0.5, titanium is set to 0.5, and oxygen (O) is set to 3.0 in terms of the molar ratio of each element. These components are adjusted, for example, by the molar ratio of the individual elements in the precursor solution of the seed layer 442 at the time of making the seed layer 442. Since the dielectric constant of the seed layer 442 is relatively high, the displacement efficiency expressed by the displacement amount of the piezoelectric layer 443 with respect to the applied voltage is good. The method of manufacturing the piezoelectric element 44 will be described below.

The seed layer 442 has a thickness of 20nm or less. Accordingly, since the seed layer 442 contains bismuth, iron, titanium, and lead, the effect of aligning the crystal orientation of the composite oxide can be ensured even when the thickness is 20nm or less. Further, since the thickness described above becomes thinner, diffusion of titanium contained in the seed layer 442 is reduced with respect to the piezoelectric layer 443.

The seed layer 442 is not limited to the perovskite structure. The seed layer 442 may have a structure similar to a perovskite structure, and thus may have an octahedral crystal structure in which six oxygen atoms are coordinated to iron or titanium.

The piezoelectric layer 443 is a main portion of the piezoelectric element 44 having piezoelectricity, and is deformed by application of voltage. The piezoelectric layer 443 is formed on the seed layer 442 so as to contact with it, and covers the seed layer 442. The piezoelectric layer 443 contains potassium (K), sodium (Na), and niobium (Nb), and will have the general formula ABO ₃ The perovskite structure composite oxide is mainly represented. Specifically, the composite oxide can be represented by the following formula (1).

(K _m ，Na _1-m )NbO ₃ …(1)

Wherein, the formula (1) satisfies that m is more than or equal to 0.1 and less than or equal to 0.9.

The potassium-sodium niobate-based composite oxide of formula (1) is a non-lead-based piezoelectric material in which the content of lead or the like is suppressed, and is a so-called KNN-based composite oxide. The KNN-based composite oxide is advantageous in reducing environmental load, and has excellent piezoelectric characteristics as compared with other non-lead-based piezoelectric materials. Further, the KNN-based composite oxide is advantageous for use at high temperatures because it has a curie temperature higher than that of other non-lead-based piezoelectric materials such as BNT-BKT-BT and is less likely to cause depolarization due to a temperature rise.

In the formula (1), the content of potassium is preferably set to be relative to the constituent ABO ₃ The total amount of metal elements in the A site is 30% to 70% by mole. That is to say,preferably, m satisfies 0.3.ltoreq.m.ltoreq.0.7. More preferably, the content of potassium is 40% by mole or more and 60% by mole or less relative to the total amount of metal elements constituting the a site. That is, m is more preferably 0.4.ltoreq.m.ltoreq.0.6. Accordingly, the piezoelectric characteristics of the piezoelectric layer 443 are improved.

The piezoelectric layer 443 may contain lithium and other metal elements such as the first transition element, in addition to the KNN-based composite oxide of formula (1). The piezoelectric layer 443 may include a piezoelectric material having a general formula ABO including potassium, sodium, and niobium ₃ Complex oxide having perovskite structure represented by general formula ABO ₃ A mixed crystal of other complex oxides of the perovskite structure is shown. The piezoelectric material included in the piezoelectric layer 443 may include an element having a partially defective component, an element having a partially excessive component, or the like among the above elements.

The piezoelectric layer 443 is crystal-oriented in the {100} azimuth. That is, the piezoelectric layer 443 is preferentially oriented on the (100) plane. Thus, the piezoelectric characteristics of the piezoelectric element 44 can be further improved. In the present specification, the term "preferential alignment" means that 50% or more, preferably 80% or more of crystals are aligned on a predetermined crystal plane. Specifically, the term "preferentially oriented on the (100) plane" includes a case where all crystals of the piezoelectric layer 443 are oriented on the (100) plane and a case where at least 50% or more of the crystals are oriented on the (100) plane. The crystal orientation of the piezoelectric layer 443 can be known by analyzing an X-ray diffraction intensity curve by an X-ray diffraction (XRD) method.

The thickness of the piezoelectric layer 443 is not particularly limited, but is set to, for example, 500nm to 2000nm.

Here, in the piezoelectric layer 443, when the element concentration in the depth direction is measured from above by secondary ion mass spectrometry (SIMS: secondary Ion Mass Spectrometry), the strength of the detected titanium slightly increases on the side of the adhesion layer 445 as the lower side. In this embodiment, diffusion of titanium is suppressed by the diffusion suppressing layer 447. Therefore, in the piezoelectric layer 443, in a region where the distance from the seed layer 442 in the stacking direction, that is, the distance along the Z-axis direction is 240nm or more, the titanium strength measured by SIMS is 300cps or less. This can further suppress the orientation of the crystal in the piezoelectric layer 443 to a plane other than the (111) plane.

The upper electrode 444 is formed on the piezoelectric layer 443. The upper electrode 444 is disposed on the piezoelectric layer 443. The upper electrode 444 is composed of a platinum layer. The upper electrode 444 is not limited to be formed of a platinum layer, and may be a single layer of a metal material such as aluminum, nickel, gold, or copper, or may be a structure in which two or more layers are stacked on a single layer of the metal material.

In the present embodiment, the piezoelectric element 44 in which the lower electrode 441, the seed layer 442, the piezoelectric layer 443, the upper electrode 444, and the like are sequentially stacked on the vibration plate 36 is illustrated, but the present invention is not limited thereto. The piezoelectric element of the present invention may be, for example, a longitudinal vibration type piezoelectric element in which piezoelectric materials, electrode forming materials, and the like are alternately laminated so as to expand and contract in the axial direction.

1.4. Method for manufacturing piezoelectric element

First, the diaphragm 36 is manufactured. Specifically, the silicon plate is thermally oxidized, thereby forming silicon oxide on the upper surface. Thereby, a silicon substrate 361 including a silicon layer and a silicon oxide layer is formed. Next, after a silicon oxide layer is covered with a zirconium layer by a sputtering method, the zirconium layer is thermally oxidized, thereby forming a zirconium oxide layer as the insulator layer 362.

Next, the adhesion layer 445 and the lower electrode 441 are formed. Specifically, a titanium layer, a platinum layer, and then a layer containing iridium are stacked in this order over the upper surface of the insulator layer 362 by a sputtering method to form a whole surface.

Next, a layer to be the seed layer 442 is formed by a MOD (Metal Organic Decomposition: metal organic decomposition) method. Specifically, as a precursor solution of the seed layer 442, a propionic acid solution of lead, bismuth, iron, titanium is prepared. At this time, the molar ratio of each element is, for example, lead: bismuth: iron: titanium = 10:110:50:50. the above propionic acid solution is coated over the diffusion suppressing layer 447 by spin coating.

After drying and degreasing were performed at 350 ℃ using a hot plate, and then heat treatment was performed at 650 ℃ for three minutes under an oxygen atmosphere by RTA (Rapid Thermal Annealing: rapid thermal annealing) performed by an infrared lamp or the like. Thus, a layer including the seed layer 442 in the entire surface is formed.

Next, a layer to be the piezoelectric layer 443 is formed by the MOD method. First, a precursor solution of the above layer is prepared. The precursor solution contains, as a solute, metal complexes of elements contained in the piezoelectric layer 443 described above, such as potassium, sodium, and niobium. The solvent of the precursor solution is an organic solvent capable of dissolving or dispersing each metal complex.

Specifically, potassium 2-ethylhexanoate, sodium 2-ethylhexanoate, niobium 2-ethylhexanoate, and the like are used as the metal complex. For example, an organic solvent monomer such as 2-n-butoxyethanol or n-octane or a mixed solution is used as the solvent. The content of each metal complex in the precursor solution corresponds to a desired molar ratio of each element of the piezoelectric layer 443.

The precursor solution is coated on the layer including the seed layer 442 by spin coating. Next, after drying was performed at 180 ℃ and degreasing was performed at 380 ℃ using a hot plate, heating treatment was performed at 750 ℃ for three minutes under an oxygen atmosphere by RTA. This promotes crystallization of the composite oxide of the piezoelectric layer 443. Then, a layer including the entire surface of the piezoelectric layer 443 is formed. In order to secure the thickness of the piezoelectric layer 443, the process from the application of the precursor solution to the heating process by RTA is repeatedly performed.

In the conventional piezoelectric element, diffusion of titanium is advanced by heat treatment of the precursor solution of the piezoelectric layer. If the application of the precursor solution to the heat treatment is repeatedly performed, the diffusion of titanium is further advanced. In contrast, in the piezoelectric element 44 of the present embodiment, diffusion of titanium into the piezoelectric layer 443 is suppressed by the diffusion suppressing layer 447.

The method for producing the seed layer 442 and the piezoelectric layer 443 is not limited to the MOD method. For the production of the piezoelectric layer 443, a known method such as a vapor phase method can be applied.

Next, a layer to be the upper electrode 444 is formed. Specifically, the platinum layer is formed in a planar shape on the upper surface of the layer serving as the piezoelectric layer 443 by sputtering.

Next, the region S is set by patterning. Specifically, the seed layer 442, the piezoelectric layer 443, and the upper electrode 444 are formed by removing a region corresponding to the region S from the layer including the seed layer 442, the layer serving as the piezoelectric layer 443, and the layer serving as the upper electrode 444. Examples of the method of forming the pattern include dry etching such as reactive ion etching and ion polishing, wet etching using an etching solution, and the like. In the above manner, the piezoelectric element 44 can be manufactured.

According to the present embodiment, the following effects can be obtained.

In the piezoelectric layer 443, the occurrence of cracks can be suppressed. Specifically, the diffusion suppression layer 447 including iridium can suppress diffusion of titanium in the adhesion layer 445 into the piezoelectric layer 443. Therefore, in the piezoelectric layer 443, grains oriented on a plane other than intended become difficult to grow. In addition, the difference in linear expansion coefficient between the piezoelectric layer 443 and the vibration plate 36 is easily relaxed as compared with the case where the adhesion layer containing no titanium is formed or the case where the adhesion layer 445 is omitted. In this way, even if the piezoelectric layer 443 is formed relatively thick, cracks are less likely to occur. Accordingly, the piezoelectric element 44 that suppresses the occurrence of cracks in the piezoelectric layer 443 can be provided.

2. Examples and comparative examples

Hereinafter, examples and comparative examples are shown, and effects of the above embodiments are described more specifically. Regarding example 1 and comparative examples 1 to 4, the structure and evaluation results of the piezoelectric elements are shown in table 1.

TABLE 1

In the structure of the piezoelectric element in table 1, the thickness of the layers is shown in brackets () in the layers other than the piezoelectric layers, and the number of stacked layers is shown in brackets < > in the piezoelectric layers. In the column of Ti diffusion of the evaluation results of table 1, a layer having a titanium strength exceeding 200cps by SIMS measurement is shown.

2.1. Fabrication of piezoelectric element

In the piezoelectric elements of example 1 and comparative examples 1 to 4, the molar ratio of each element contained in the seed layer was set to bismuth: iron: titanium: lead = 110:50:50:10. the molar ratio of each element contained in the piezoelectric layer was set to potassium: sodium=51: 49, and is set as an element arranged at the a site: element configured at B site = 107:100. the main element disposed at the a site is potassium or sodium, and the main element disposed at the B site is niobium.

In example 1, the insulator layer 362, the adhesion layer 445, the diffusion suppressing layer 447, and the seed layer 442 of the diaphragm 36, and the piezoelectric layer 443 were laminated and fabricated by the above-described fabrication method. The piezoelectric layer 443 is formed by repeatedly applying a precursor solution until heat treatment, whereby 10 layers are stacked. In this evaluation, the formation of the upper electrode 444 is omitted because measurement of electrical characteristics and the like is not performed.

In comparative example 1, an additional layer made of titanium was formed between the diffusion suppression layer and the seed layer by the same method as that for the adhesion layer 445, relative to example 1. The piezoelectric layers are repeatedly laminated after the heat treatment until cracks are generated. The repetition of lamination is the same as in comparative examples 2, 3 and 4 below.

In comparative example 2, the same procedure was used as in example 1 except that the adhesion layer 445 was omitted. In comparative example 3, the same procedure was used as in example 1 except that the diffusion suppression layer 447 was omitted. In comparative example 4, the same procedure was used as in comparative example 3 except that the adhesion layer was a zirconium layer and the thickness was 10 nm.

2.2. Evaluation of piezoelectric element

2.2.1. Crack generation

The surface above the piezoelectric layer was observed by a metal microscope to check whether or not cracks were generated. As a result, in example 1, no crack was generated even when 10 layers were laminated on the piezoelectric layer 443 and the thickness was 790 nm. In comparative example 1, when 10 piezoelectric layers were laminated and the thickness was 790nm, cracks were generated. In comparative example 2, when 7 piezoelectric layers were laminated and the thickness was set to 540nm, cracks were generated. In comparative example 3, when 9 piezoelectric layers were laminated and the thickness was 670nm, cracks were generated. In comparative example 4, when 6 layers were laminated on the piezoelectric body layer and the thickness was set to 450nm, cracks were generated. In example 1, even when 15 layers were laminated on the piezoelectric layer 443, and the thickness was set to 1200nm, no crack was generated.

From the above, in example 1, it is shown that even if the piezoelectric layer 443 is formed to be thick, the occurrence of cracks can be suppressed. In contrast, in comparative examples 1 to 4, it is found that cracks are likely to occur if the piezoelectric layer is formed thicker.

2.2.2. Analysis of Crystal orientation

The respective piezoelectric layers were measured by an X-ray diffraction method. Thus, the orientation of the (100), (111) and (110) planes was examined by the X-ray diffraction intensity curve. Specifically, D8 DISCOVER with GADDS of Bruker corporation was used as an X-ray diffraction apparatus. In the measurement conditions, the tube voltage was set to 50kV, the tube current was set to 100mA, the detector distance was set to 15cm, the collimator diameter was set to 0.3mm, and the measurement time was set to 120 seconds. The (111) plane was measured by tilting the silicon substrate by 54.74 °.

For the obtained two-dimensional data, the 2 θ range was set to 20 ° to 50 °, the X range was set to-95 ° to-85 °, the step length was set to 0.02 °, and the intensity normalization method was set to Bin normalized by software attached to the apparatus, thereby converting into an X-ray diffraction intensity curve. The range of KNN corresponding to the (100) plane is shown enlarged in fig. 6, the range corresponding to the (111) plane is shown enlarged in fig. 7, and the range corresponding to the (110) plane is shown enlarged in fig. 8. In fig. 6 to 8, the horizontal axis represents 2θ (degree) which is the diffraction angle of the X-ray, and the vertical axis represents the diffraction Intensity (Intensity).

As shown in fig. 6 to 8, in example 1, comparative example 2, and comparative example 4, no peak was found in the (111) plane and the (110) plane, and it was found that the orientation was preferentially oriented in the (100) plane. In contrast, in comparative examples 1 and 3, peaks of the (111) plane and the (110) plane were found, and the half-value width of the peak of the (100) plane was wider than that of the peaks of the (100) plane in examples 1, 2, and 4. From this, it was found that comparative example 1 and comparative example 3 are mixed crystals.

2.2.3. Observation of grain boundaries

The piezoelectric layer was observed for grain boundaries. Specifically, a cross section of the piezoelectric layer along the Z axis and the upper surface thereof were observed by SEM (scanning electron microscope) S-4700 of hitachi high-tech control company. Fig. 9 and 10 show SEM photographs of example 1, and fig. 11 and 12 show SEM photograph representations of comparative example 1.

In example 1, as shown in fig. 9 and 10, no grain boundary was found on the piezoelectric layer 443. In contrast, in comparative example 1, as shown in fig. 11 and 12, grain boundaries shown by broken lines of triangles were observed. As is clear from the results of the above-described X-ray diffraction, a triangular pyramid-shaped region oriented on the (111) plane was generated in comparative example 1. Therefore, in comparative example 1, cracks may occur along the grain boundaries. Although not shown, as a result of the same observation as described above for comparative examples 2, 3 and 4, no grain boundaries were observed in comparative examples 2 and 4, and grain boundaries were observed in comparative example 3.

2.2.4. Analysis of titanium diffusion in piezoelectric layers

The piezoelectric layers of example 1, comparative example 1, and comparative example 2 were subjected to composition analysis in the-Z direction, which is the depth direction from the upper surface of the piezoelectric layer toward the seed layer side, by SIMS.

As the SIMS device, a sector SIMS IMS-7f from CAMECA was used. In the measurement, using 15kV cesium ions (Cs+) as the primary ions, a beam current of 10nA was raster scanned at 100 μm square, and negative secondary ions were detected from the center 33 μm phi. At the time of measurement, an electron gun was used to suppress charging.

The depth-direction profile obtained is shown in fig. 13 to 15. For convenience of illustration, outlines of oxygen, zirconium, and the like are omitted for illustration. In fig. 13 to 15, the horizontal axis represents the time (s: seconds) for tunneling in the depth direction, and can be regarded as the distance in the-Z direction from the surface above the piezoelectric layer. The vertical axis represents the detection Intensity (units: cps) of each element. Fig. 16 and 17 show the diffusion state of titanium estimated by SIMS analysis for example 1 and comparative example 1. In fig. 16 and 17, the structures other than the insulator layer 362 (zirconia), the lower electrode 441 (Pt), and the piezoelectric layer 443 (KNN) are not shown.

In fig. 13 to 15, a boundary at a distance of 240nm from the stacking direction of the seed layers, i.e., in the +z direction, is shown by a broken line B. That is, in each drawing, the region to the left from the broken line B is the region having the distance of 240nm or more. Further, the titanium intensity in the broken line B is denoted by x marks.

The broken line B is determined by the number of peaks of titanium and sodium. Specifically, when the piezoelectric layers are repeatedly stacked by the MOD method, the intensity of sodium gradually decreases from the peak value in each single layer in the +z direction from the seed layer, and conversely, the intensity of potassium gradually increases from the minimum value to the peak value. Therefore, in each single layer of the piezoelectric layer, the peak position of sodium and the position of the potassium trough become the interface on the seed layer side, and the position of the sodium trough and the peak position of potassium become the interface in the +z direction. Since the thickness of each single layer is about 80nm, the interface in the +z direction of the third layer is indicated by a broken line B from the seed layer side of the piezoelectric layer to the upper side. The method for determining the boundary of the broken line B is not limited to the above method, and may be performed by, for example, cross-sectional elemental analysis, distance measurement, or the like in a piezoelectric layer manufactured by a gas phase method or the like.

As shown in fig. 13, in example 1, the rightmost peak position of sodium is the interface between the piezoelectric layer 443 and the seed layer 442, and the piezoelectric layer 443 is located to the left of the interface. In example 1, the diffusion of titanium into the piezoelectric layer 443 was slight. Specifically, the titanium strength at the broken line B is 70cps, and in the region at a distance of 240nm or more from the seed layer 442 in the stacking direction, that is, the region to the left from the broken line B, the titanium strength is 300cps or less. Fig. 16 is a graph schematically showing the above results.

As shown in fig. 16, the piezoelectric layer 443 of KNN is formed by stacking layers 443-1, 443-2, 443-3, … …, 443-10 at the time of manufacturing. In the piezoelectric layer 443, there is little diffusion of titanium from the lower electrode 441 side to the third layer 443-3 or more. Therefore, the piezoelectric layer 443 is preferentially oriented on the (100) plane, and the occurrence of cracks can be suppressed.

As shown in fig. 14, even in comparative example 1, the rightmost peak position of sodium is the interface between the piezoelectric layer and the seed layer, and the piezoelectric layer is located to the left of the interface. In comparative example 1, the diffusion of titanium into the piezoelectric layer was more remarkable than in example 1. In detail, the titanium intensity at the broken line B is 3000cps, and in the left region from the broken line B, the titanium intensity exceeds 300cps. Fig. 17 schematically shows the above structure.

As shown in fig. 17, the layer KNN as the piezoelectric layer is formed by stacking layers KNN-1, KNN-2, … …, KNN-10 at the time of manufacturing. In the KNN layer, diffusion of titanium also affects ten layers from the Pt layer side, namely, the tenth KNN-10 layer. As a result, layer KNN is not preferentially oriented on the (100) plane, resulting in region Q oriented on the (111) plane. Therefore, the crack CR is liable to occur along the grain boundary.

As shown in fig. 15, even in comparative example 2, the rightmost peak position of sodium is the interface between the piezoelectric layer and the seed layer, and the piezoelectric layer is located to the left of the interface. Although the diffusion of titanium into the piezoelectric layer of comparative example 2 was increased as compared with example 1, it was slightly smaller than that of comparative example 1. In detail, the titanium intensity at the broken line B is 300cps, and in the left region from the broken line B, the titanium intensity is 300cps or less. The titanium detected in the piezoelectric layer is derived from titanium contained in the seed layer. Although the diffusion of titanium was slight in comparative example 2, cracks were sometimes generated because the adhesion layer was not provided.

Although not shown, as a result of performing the similar SIMS analysis to the piezoelectric layer of comparative example 3, the titanium strength exceeded 200cps in the region at a distance of 240nm or more from the seed layer in the stacking direction. Therefore, the piezoelectric layer of comparative example 3 was not preferentially oriented on the (100) plane, and cracks were likely to occur along the grain boundaries.

3. Second embodiment

Although in the above-described embodiment, the lower electrode 441a is formed in a whole surface shape so as to cover the insulator layer 362 and the upper electrode 444a is arranged so as to overlap each pressure chamber C in the direction along the Z axis, in the second embodiment, the lower electrode 441a may be arranged so as to overlap each pressure chamber C in the direction along the Z axis and the upper electrode 444a may be formed in a whole surface shape so as to cover the insulator layer 362.

The detailed structure of the piezoelectric element 44a will be described. Note that, the same points as those of the first embodiment are not described. As shown in fig. 18, the plurality of piezoelectric elements 44a are formed so as to contact the upper surface of the vibration plate 36. A region S is arranged between two piezoelectric elements 44 adjacent in the Y-axis direction. In fig. 18, in addition to two piezoelectric elements 44a, the vibration plate 36, the flow path formation substrate 32, and the pressure chamber substrate 34 are illustrated.

The piezoelectric element 44a includes: an adhesion layer 445a, a lower electrode 441a, a diffusion suppression layer 447a, a seed layer 442a, a piezoelectric layer 443a, and an upper electrode 444a. In the piezoelectric element 44a, the adhesion layer 445a, the lower electrode 441a, the diffusion suppression layer 447a, the seed layer 442a, the piezoelectric layer 443a, and the upper electrode 444a are stacked in the above order. That is, the lamination direction of the layers of the piezoelectric element 44a is a direction along the Z axis.

The area where the planar adhesion layer 445a, the lower electrode 441a, the seed layer 442, the diffusion suppression layer 447a, the piezoelectric layer 443a, and the upper electrode 444a overlap is referred to as an active portion 440a. The active portion 440a is a region where the piezoelectric layer 443a is deformed when a voltage is applied between the lower electrode 441a and the upper electrode 444 a. The movable portion 440a faces the pressure chamber C through the diaphragm 36 in the direction along the Z axis.

The adhesion layer 445a is disposed so as to overlap each pressure chamber C in the direction along the Z axis. The adhesion layer 445a contacts the vibration plate 36, specifically, the surface above the insulator layer 362.

The lower electrode 441a is formed so as to cover a portion above and laterally of the adhesion layer 445a and above the insulator layer 362 on both sides of the adhesion layer 445 a. The lower electrode 441a extends so as to be drawn out in the +x direction from a substantially rectangular region overlapping the pressure chamber C. Although not shown, each of the lower electrodes 441a is electrically connected to the drive circuit 50 described above at the tip extending in the +x direction.

The diffusion suppressing layer 447a is formed so as to contact the upper surface of the lower electrode 441 a.

The seed layer 442a is formed so as to cover a portion above the diffusion suppression layer 447a, both sides of the lower electrode 441a, and above the vibration plate 36 on both sides of the lower electrode 441 a. The seed layer 442a is controlled so that the crystal orientation of the composite oxide in the piezoelectric layer 443a is uniform. By the seed layer 442a, preferential orientation of the crystal of the piezoelectric layer 443a to the (100) plane can be promoted.

The lower electrode 441a is interposed between the adhesion layer 445 and the seed layer 442a and the piezoelectric layer 443a at both sides of the adhesion layer 445 a. Therefore, diffusion of titanium is suppressed even at the interface between the piezoelectric layer 443a, the adhesion layer 445a, and the vibration plate 36.

In the case where the lower electrode of the piezoelectric element is disposed alone, in a structure in which the lower electrode does not cover the side of the adhesion layer, only the seed layer is present between the side of the adhesion layer and the piezoelectric layer. Therefore, in the piezoelectric layer 443a, grains oriented on an unintended plane may be grown. In contrast, the lower electrode 441a of the piezoelectric element 44a in the second embodiment covers the side of the adhesion layer 445a, and thus the diffusion of titanium in the adhesion layer 445a into the piezoelectric layer 443a is suppressed. Thus, even if the piezoelectric layer 443a is formed relatively thick, cracking is less likely to occur. Accordingly, the piezoelectric element 44a that suppresses the occurrence of cracks in the piezoelectric layer 443a can be provided.

4. Third embodiment

Although the liquid droplet ejection head 1 and the recording apparatus 100 to which the piezoelectric element 44 is applied are exemplified in the above-described embodiment, the application of the piezoelectric element of the present invention is not limited to this. The piezoelectric element of the present invention can be applied to an ultrasonic sensor, a piezoelectric motor, an ultrasonic motor, a piezoelectric transformer, a vibration dust removing device, a piezoelectric transducer, an ultrasonic transmitter, a pressure sensor, an acceleration sensor, and the like.

The piezoelectric element of the present invention may be mounted on a power generation device. Examples of the power generation device include a power generation device using a piezoelectric conversion effect, a power generation device using electron excitation by light, a power generation device using electron excitation by heat generation, and a power generation device using vibration.

Further, the piezoelectric element of the present invention can be applied to a pyroelectric device such as an infrared detector, a terahertz detector, a temperature sensor, and a heat sensor, or a ferroelectric element such as a ferroelectric memory.

Symbol description

36 … as a vibrating plate of the substrate; 44 … piezoelectric elements; 441 … lower electrode; 442 … seed layer; 443 … piezoelectric layers; 444 … upper electrode; 445 … cling layer; 447 … diffusion reducing layer.

Claims

1. A piezoelectric element is provided with:

a contact layer formed on the substrate and containing titanium;

a lower electrode formed on the adhesion layer;

a diffusion suppression layer formed on the lower electrode and including iridium;

a seed layer formed on the diffusion suppression layer and including bismuth;

a piezoelectric layer formed on the seed layer and including potassium, sodium, and niobium;

and an upper electrode formed on the piezoelectric layer.

2. The piezoelectric element of claim 1, wherein,

the seed layer comprises iron, titanium, and lead.

3. The piezoelectric element according to claim 2, wherein,

the thickness of the seed layer is 20nm or less.

4. The piezoelectric element according to any one of claim 1 to 3, wherein,

the diffusion-suppressing layer comprises iridium oxide.

5. The piezoelectric element of claim 1, wherein,

in the piezoelectric layer, in a region having a distance of 240nm or more from the stacking direction of the seed layer, the titanium strength measured by SIMS is 300cps or less.