Piezoelectric element application device

Abstract

To provide a piezoelectric element application device capable of improving a displacement magnitude of a diaphragm.SOLUTION: A piezoelectric element application device comprises: a diaphragm made of an oxidation silicon; a first electrode formed above the diaphragm; a seed layer that is formed above the first electrode and the diaphragm; a piezoelectric layer that is formed on the seed layer, and contains potassium, natrium, and niobium; and a second electrode that is formed on the piezoelectric layer. The diaphragm further contains potassium and natrium. In a secondary ion mass spectrometry in the diaphragm and the piezoelectric layer, a strength of potassium in the diaphragm is lower than that of potassium in the piezoelectric layer, and the strength of natrium in the diaphragm is lower than that of natrium in the piezoelectric layer.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a piezoelectric device. [Background technology]

[0002] A piezoelectric element generally has a substrate, a piezoelectric layer having electromechanical conversion properties, and two electrodes sandwiching the piezoelectric layer. In recent years, devices using such piezoelectric elements as a driving source (piezoelectric element application devices) have been actively developed. Examples of piezoelectric element application devices include liquid ejection heads such as ink jet recording heads, MEMS elements such as piezoelectric MEMS elements, ultrasonic measurement devices such as ultrasonic sensors, and further piezoelectric actuator devices.

[0003] Lead zirconate titanate (PZT) is known as the material for the piezoelectric layer of piezoelectric elements (piezoelectric material). However, in recent years, with a view to reducing the environmental impact, development of lead-free piezoelectric materials with reduced lead content has been progressing.

[0004] As one of the lead-free piezoelectric materials, for example, potassium sodium niobate (KNN; (K,Na)NbO3) has been proposed as disclosed in Patent Document 1. Specifically, Patent Document 1 discloses a piezoelectric element including a first electrode, a second electrode, and a thin-film piezoelectric layer (KNN-based piezoelectric layer) made of a perovskite-type composite oxide containing potassium, sodium, and niobium, provided between the first and second electrodes. Patent Document 1 also discloses a diaphragm composed of an elastic film made of silicon dioxide formed on a substrate, and an insulating film made of zirconium oxide formed on the elastic film. The insulating film made of zirconium oxide disclosed in Patent Document 1 has a function of suppressing the diffusion of components such as potassium constituting the piezoelectric layer to the substrate side. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2018-133458 A Summary of the Invention [Problem to be solved by the invention]

[0006] As mentioned above, piezoelectric elements using KNN (KNN-based piezoelectric elements) have been proposed as one of the lead-free piezoelectric materials. However, it is known that the displacement characteristics of KNN-based piezoelectric layers are smaller than those of conventional lead-based piezoelectric layers (e.g., PZT piezoelectric layers), and in piezoelectric elements in which part of the substrate is an elastic film and piezoelectric application devices (piezoelectric devices) equipped with such piezoelectric elements, simply replacing the PZT piezoelectric layer with a KNN piezoelectric layer reduces the amount of displacement of the diaphragm, and there are cases in which the required specifications for a piezoelectric device cannot be met.

[0007] Under these circumstances, there is a demand for a KNN-based piezoelectric element that can improve the amount of displacement of the diaphragm.

[0008] It should be noted that such problems are not limited to piezoelectric actuators mounted on liquid ejecting heads such as ink jet recording heads, but also exist in other devices using piezoelectric elements. [Means for solving the problem]

[0009] In order to solve the above problems, according to one embodiment of the present invention, there is provided a piezoelectric element application device comprising: a vibration plate made of silicon oxide; a first electrode formed above the vibration plate; a seed layer formed above the first electrode and the vibration plate; a piezoelectric layer formed on the seed layer and containing potassium, sodium and niobium; and a second electrode formed on the piezoelectric layer, wherein the vibration plate further contains potassium and sodium, and in secondary ion mass spectrometry of the vibration plate and the piezoelectric layer, the intensity of potassium in the vibration plate is lower than the intensity of potassium in the piezoelectric layer, and the intensity of sodium in the vibration plate is lower than the intensity of sodium in the piezoelectric layer. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view showing a schematic configuration of a recording apparatus according to a first embodiment. [Diagram 2] FIG. 2 is an exploded perspective view of a recording head of the recording apparatus of FIG. [Diagram 3] FIG. 2 is a plan view of a recording head of the recording apparatus of FIG. [Figure 4] 4 is a cross-sectional view taken along line AA′ in FIG. [Diagram 5] FIG. 5 is an enlarged cross-sectional view taken along line BB' in FIG. [Figure 6] FIG. 2 is a diagram showing the measurement results of secondary ion mass spectrometry in Example 1. [Figure 7] FIG. 11 is a diagram showing the measurement results of secondary ion mass spectrometry in Example 2. [Figure 8] FIG. 1 is a diagram showing the measurement results of secondary ion mass spectrometry in Comparative Example 1. [Figure 9] 1 is a scanning electron microscope (SEM) image of Comparative Example 2. [Figure 10] FIG. 4 is a diagram showing the measurement results of the piezoelectric element of the first embodiment by secondary ion mass spectrometry. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The following description shows one aspect of the present invention, and can be modified as desired without departing from the scope of the present invention. In addition, in each drawing, the same reference numerals indicate the same members, and the description is omitted as appropriate. The numbers following the letters constituting the reference numerals are used to distinguish between elements that are referred to by the reference numerals containing the same letters and have similar configurations. When it is not necessary to distinguish between elements indicated by reference numerals containing the same letters, these elements are referred to by reference numerals containing only letters.

[0012] In each drawing, X, Y, and Z represent three mutually orthogonal spatial axes. In this specification, the directions along these axes are respectively referred to as the first direction X (X direction), the second direction Y (Y direction), and the third direction Z (Z direction), and the direction indicated by the arrow in each drawing is described as the positive (+) direction, and the opposite direction to the arrow is described as the negative (-) direction. The X and Y directions represent the in-plane directions of the plate, layer, and film, and the Z direction represents the thickness direction or lamination direction of the plate, layer, and film.

[0013] In addition, the components shown in each drawing, i.e., the shape and size of each part, the thickness of the plate, layer and film, the relative positional relationship, the repeating unit, etc., may be exaggerated in order to explain the present invention. Furthermore, the term "above" in this specification does not limit the positional relationship of the components to "directly above". For example, the expressions "first electrode on the substrate" and "piezoelectric layer on the first electrode" described later do not exclude other components between the substrate and the first electrode, or between the first electrode and the piezoelectric layer.

[0014] (First embodiment) (Piezoelectric device) First, an ink jet recording apparatus, which is an example of a liquid ejecting apparatus including a recording head, which is an example of a piezoelectric application device according to a first embodiment of the present invention, will be described with reference to the drawings. Fig. 1 is a perspective view showing a schematic configuration of the ink jet recording apparatus.

[0015] In an ink jet recording apparatus (recording apparatus) I, as shown in Fig. 1, an ink jet recording head unit (head unit) II is detachably mounted on cartridges 2A and 2B. The cartridges 2A and 2B constitute an ink supplying means. The head unit II has a plurality of ink jet recording heads (recording heads) 1 (see Fig. 2, etc.) described later, and is mounted on a carriage 3. The carriage 3 is mounted on a carriage shaft 5 attached to a device main body 4 so as to be movable in the axial direction. The head unit II and carriage 3 are configured to be capable of ejecting, for example, a black ink composition and a color ink composition, respectively.

[0016] The driving force of the drive motor 6 is transmitted to the carriage 3 via a number of gears and a timing belt 7 (not shown), and the carriage 3 mounting the head unit II is moved along the carriage shaft 5. Meanwhile, the device body 4 is provided with a transport roller 8 as a transport means, and a recording sheet S, which is a recording medium such as paper, is transported by the transport roller 8. Note that the transport means for transporting the recording sheet S is not limited to the transport roller, and may be a belt, a drum, or the like.

[0017] A piezoelectric element 300 (see FIG. 2, etc.), which will be described in detail later, is used as a piezoelectric actuator device in the recording head 1. By using the piezoelectric element 300, it is possible to prevent deterioration of various characteristics (durability, ink ejection characteristics, etc.) of the recording device I.

[0018] Next, an ink jet recording head (recording head) 1, which is an example of a liquid ejection head mounted on a liquid ejection device, will be described with reference to the drawings. Fig. 2 is an exploded perspective view showing a schematic configuration of the recording head 1. Fig. 3 is a plan view showing a schematic configuration of the recording head 1. Fig. 4 is a cross-sectional view taken along line AA' in Fig. 3. Note that Figs. 2 to 4 each show a part of the configuration of the recording head 1, and have been omitted as appropriate.

[0019] As shown in the figure, the flow path forming substrate (substrate) 10 contains silicon (Si) For example, the substrate 10 is made of a silicon (Si) single crystal substrate.

[0020] The substrate 10 is formed with pressure generating chambers 12 (hereinafter also referred to as "pressure chambers 10") partitioned by a plurality of partition walls 11. The pressure chambers 12 are arranged side by side along a direction (+X direction) in which a plurality of nozzle openings 21 that eject ink of the same color are arranged side by side.

[0021] An ink supply path 13 and a communication path 14 are formed on one end side (+Y direction side) of the pressure chamber 12 in the substrate 10. The ink supply path 13 is configured so that the area of ​​the opening on one end side of the pressure chamber 12 is small. Furthermore, the communication path 14 has approximately the same width as the pressure chamber 12 in the +X direction. A communication section 15 is formed on the outside (+Y direction side) of the communication path 14. The communication section 15 constitutes a part of a manifold 100. The manifold 100 serves as a common ink chamber for each pressure chamber 12. In this way, a liquid flow path consisting of the pressure chamber 12, the ink supply path 13, the communication path 14, and the communication section 15 is formed on the substrate 10.

[0022] A nozzle plate 20 made of, for example, SUS is bonded onto one surface (the surface on the -Z direction side) of the substrate 10. Nozzle openings 21 are arranged in the nozzle plate 20 along the +X direction. The nozzle openings 21 communicate with each pressure chamber 12. The nozzle plate 20 can be bonded to the substrate 10 by an adhesive, a heat-welded film, or the like.

[0023] A diaphragm 50 is formed on the other surface (the surface on the +Z direction side) of the substrate 10. The diaphragm 50 is made of silicon oxide, for example, silicon dioxide (SiO2). The diaphragm 50 does not have to be a separate member from the substrate 10. For example, a part of the surface layer (including the surface) on the +Z direction side of the substrate 10 made of silicon may be transformed into silicon oxide by thermal oxidation, and this may be used as the diaphragm 50. FIG. 5, which will be described later, shows an example in which the diaphragm 50 is laminated on the surface of the other face (the face on the +Z direction side) of the substrate 10, but the substrate 10 and the diaphragm 50 may be integrated.

[0024] A first electrode 60, a seed layer (orientation control layer) 57, a piezoelectric layer 70, and a second electrode 80 are formed on the diaphragm 50. A lead electrode 90 is connected to one end side of the first electrode 60 (the side opposite to the communication path 14).

[0025] The details of the configurations, materials, etc. of the first electrode 60, the seed layer (orientation control layer) 57, the piezoelectric layer 70, and the second electrode 80 will be described later.

[0026] In this embodiment, the vibration plate 50 and the first electrode 60 are displaced by the displacement of the piezoelectric layer 70 having electromechanical conversion characteristics. That is, the vibration plate 50 and the first electrode 60 substantially function as a vibration plate. However, in reality, the second electrode 80 is also displaced by the displacement of the piezoelectric layer 70, so that the region in which the vibration plate 50, the first electrode 60, the piezoelectric layer 70, and the second electrode 80 are sequentially stacked functions as a movable part (also called a vibration part) of the piezoelectric element 300. In this specification, the region of the vibration plate 50 that functions as the vibration part, i.e., the region that forms a part of the wall surface of the pressure chamber 12, is referred to as the "first region R1" and described.

[0027] A protective substrate 30 is bonded by an adhesive 35 onto the substrate 10 (diaphragm 50) on which the piezoelectric elements 300 are formed. The protective substrate 30 has a manifold portion 32. The manifold portion 32 constitutes at least a part of the manifold 100. The manifold portion 32 of this embodiment penetrates the protective substrate 30 in the thickness direction (Z direction), and is further formed across the width direction (+X direction) of the pressure chambers 12. The manifold portion 32 communicates with the communication portion 15 of the substrate 10. With this configuration, the manifold 100 is constituted as a common ink chamber for each pressure chamber 12.

[0028] A piezoelectric element holding portion 31 is formed in the protective substrate 30 in a region including the piezoelectric element 300. The piezoelectric element holding portion 31 has a space that does not hinder the movement of the piezoelectric element 300. This space may be sealed or not. The protective substrate 30 is provided with a through hole 33 that penetrates the protective substrate 30 in the thickness direction (Z direction). An end of the lead electrode 90 is exposed in the through hole 33.

[0029] Examples of materials for the protection substrate 30 include Si, SOI, glass, ceramic materials, metals, and resins, but it is more preferable for the protection substrate 30 to be made of a material having approximately the same thermal expansion coefficient as the substrate 10.

[0030] A drive circuit 120 that functions as a signal processing unit is fixed on the protective substrate 30. The drive circuit 120 can be, for example, a circuit board or a semiconductor integrated circuit (IC: Integrated Circuit). The drive circuit 120 and the lead electrodes 90 are electrically connected via connection wiring 121 made of a conductive wire such as a bonding wire that is inserted through a through hole 33. The drive circuit 120 can be electrically connected to a printer controller 200 (see FIG. 1). Such a drive circuit 120 functions as a control means for the piezoelectric actuator device (piezoelectric element 300).

[0031] In addition, a compliance substrate 40 consisting of a sealing film 41 and a fixed plate 42 is bonded onto the protective substrate 30. The sealing film 41 is made of a material with low rigidity, and the fixed plate 42 can be made of a hard material such as metal. The region of the fixed plate 42 facing the manifold 100 is an opening 43 that is completely removed in the thickness direction (Z direction). One surface of the manifold 100 (the surface on the +Z direction side) is sealed only by the sealing film 41 which is flexible.

[0032] Such a recording head 1 ejects ink droplets in the following manner. First, ink is taken in from an ink inlet connected to an external ink supply means (not shown), and the inside is filled with ink from the manifold 100 to the nozzle opening 21. Then, in accordance with a recording signal from the drive circuit 120, a voltage is applied between the first electrode 60 and the second electrode 80 corresponding to each pressure chamber 12, causing the piezoelectric element 300 to bend and deform. This increases the pressure inside each pressure chamber 12, and ink droplets are ejected from the nozzle opening 21.

[0033] (Piezoelectric element) Next, the configuration of the piezoelectric element 300 used as the piezoelectric actuator device of the recording head 1 will be described in detail with reference to the drawings. Fig. 5 is an enlarged cross-sectional view taken along line BB' in Fig. 4.

[0034] As shown in FIG. 5, the piezoelectric element 300 includes a substrate 10, a vibration plate 50 formed on the substrate 10, a first electrode 60 formed on the vibration plate 50, a piezoelectric layer 70 formed on the first electrode 60 and containing potassium, sodium and niobium, and a second electrode 80 formed on the piezoelectric layer 70.

[0035] The substrate 10 is provided with pressure chambers 12 partitioned by a plurality of partition walls 11. With this configuration, the movable portion of the piezoelectric element 300 is formed.

[0036] A diaphragm 50 is formed on the other surface (the surface on the +Z direction side) of the substrate 10. The diaphragm 50 is made of silicon oxide, for example, silicon dioxide (SiO2).

[0037] The thickness of the diaphragm 50 is, for example, not less than 200 nm and not more than 10,000 nm.

[0038] Conventional piezoelectric elements often use a laminated structure consisting of a silicon oxide film and a zirconium oxide (Zr2O) film laminated thereon as the diaphragm. However, the recording head 1 of this embodiment is characterized in that a silicon oxide film is used as the diaphragm 50, and a first electrode 60 is provided on the silicon oxide film. In other words, the recording head 1 of this embodiment does not use a zirconium oxide film as the diaphragm. This makes it possible to reduce the rigidity of the diaphragm 50, and to improve the displacement of the diaphragm 50 even in the case of a KNN-based piezoelectric layer with a relatively low piezoelectric constant.

[0039] On the other hand, if the zirconium oxide film is simply omitted from the diaphragm, the constituent elements of the piezoelectric layer may diffuse too far toward the diaphragm, which may disrupt the composition balance of the entire piezoelectric layer. Furthermore, if the amount of diffused elements in the diaphragm increases, the adhesion between the diaphragm and the piezoelectric layer or between the diaphragm and the first electrode layer may decrease, which may cause the layers to peel off.

[0040] Therefore, in this embodiment, the vibration plate 50 is a single layer made of silicon oxide. If the material of the vibration plate 50 is a material other than silicon oxide, there is a risk that element diffusion from the piezoelectric layer 70 cannot be sufficiently suppressed. Therefore, the vibration plate 50 is made of silicon oxide.

[0041] In this manner, in this embodiment, by using the diaphragm 50 made of silicon oxide, it is possible to further suppress the diffusion of potassium, sodium, and the like from the piezoelectric layer 70 to the diaphragm 50 side. Specifically, in secondary ion mass spectrometry (SIMS analysis) of the diaphragm 50 and the piezoelectric layer 70, the intensity of potassium in the diaphragm 50 is lower than the intensity of potassium in the piezoelectric layer 70, and the intensity of sodium in the diaphragm 50 is lower than the intensity of sodium in the piezoelectric layer 70. Note that in this specification, "intensity" in secondary ion mass spectrometry means the average intensity within each element.

[0042] As described above, in order to improve the amount of displacement of the diaphragm 50 while ensuring the adhesion between the diaphragm 50 and the piezoelectric layer 70, it is effective to make the diaphragm 50 a single layer of silicon oxide (i.e., omitting the conventional ZrO2 film) to reduce the rigidity of the entire diaphragm 50 and suppress the diffusion of potassium, sodium, and the like into the diaphragm 50. Therefore, in this embodiment, the amount of diffusion of potassium and sodium in the diaphragm 50 is specified by the intensity (SIMS intensity) by SIMS analysis as described above. That is, by making the intensity of each of potassium and sodium in the diaphragm 50 lower than the intensity of each of potassium and sodium in the piezoelectric layer 70, the amount of displacement of the diaphragm 50 can be improved without reducing the piezoelectric constant of the piezoelectric layer 70.

[0043] As specific means for reducing the amount of potassium and sodium diffused into the vibration plate 50, in addition to the above-mentioned method of making the vibration plate 50 a single layer of silicon oxide, optimizing the material of the seed layer 57 and optimizing the conditions for depositing the piezoelectric layer 70 are effective.

[0044] Precious metals such as platinum (Pt) and iridium (Ir) or oxides of these metals are suitable as the material of the first electrode 60. Any material may be used as the material of the first electrode 60 as long as it has electrical conductivity. The thickness of the first electrode 60 is not particularly limited, but is, for example, 10 nm to 200 nm.

[0045] The first electrode 60 may be formed via an adhesion layer 56. In this case, the adhesion layer may be made of, for example, titanium oxide (TiO X ). Other examples of the adhesion layer 56 include a layer containing titanium (Ti) and a layer containing silicon nitride (SiN). The adhesion layer has a function of improving adhesion between the piezoelectric layer 70 and the diaphragm 50. The adhesion layer 56 also functions as a stopper that reduces the excessive penetration of potassium and sodium, which are constituent elements of the piezoelectric layer 70, into the substrate 10 through the first electrode 60 when forming the piezoelectric layer 70, which will be described later. The adhesion layer can be omitted.

[0046] The potassium intensity at the first electrode 60 may be lower than the potassium intensity at the diaphragm 50 , and the sodium intensity at the first electrode 60 may be lower than the sodium intensity at the diaphragm 50 .

[0047] The first electrode 60 may be provided for each pressure chamber 12. In other words, the first electrode 60 may be configured as an individual electrode independent for each pressure chamber 12. In this case, the first electrode 60 is formed to be smaller than the width of the pressure chamber 12 in the ±X directions.

[0048] Moreover, the first electrode 60 is formed wider than the width of the pressure chamber 12 in the ±Y directions. That is, in the ±Y directions, both ends of the first electrode 60 are formed to extend beyond the region (first region R1) of the vibration plate 50 that faces the pressure chamber 12. In other words, when viewed from the thickness direction (±Z directions) of the piezoelectric layer 70, the first electrode 60 is formed so as to cover the first region R1.

[0049] By providing the first electrode 60 so as to cover the first region R1, which is the movable region of the vibration plate 50, it is possible to suppress the diffusion of potassium, sodium, and the like constituting the piezoelectric layer 70 toward the vibration plate 50. If potassium, sodium, and the like diffuse excessively into the vibration plate 50, the embrittlement of the vibration plate 50 progresses, and may lead to brittle fracture with repeated driving. Therefore, by covering the first region R1 of the vibration plate 50 with the first electrode 60 so as to suppress the diffusion of potassium and sodium, it is possible to improve the life of the piezoelectric device. The width of the first electrode 60 may be the same as the width of the pressure chamber 12 in the ±Y direction, but from the viewpoint of further suppressing the diffusion of each of the above elements, it is preferable that the width of the first electrode 60 is formed wider than the width of the pressure chamber 12.

[0050] Fig. 10 shows the results of SIMS analysis of the piezoelectric element of this embodiment. The SIMS analysis results shown in Fig. 10 were performed on the vibration plate 50, the first electrode 60, and the piezoelectric layer 70, and the seed layer was omitted. As shown in Fig. 10, in the vibration plate 50 below the first electrode 60, i.e., in the first region R1, it can be seen that the intensity of sodium and potassium increases once near the interface between the first electrode 60 and the vibration plate 50, but then the intensity drops sharply. From this, it can be seen that the diffusion of potassium, sodium, etc. to the first region R1 can be suppressed by providing the first electrode 60 so as to cover the first region R1.

[0051] Moreover, when the first electrode 60 is provided so as to cover the first region R1, the average value of the potassium intensity in the first region R1 is lower than the average value of the potassium intensity in the region other than the first region R1 (the second region R2), and the average value of the sodium intensity in the first region R1 is lower than the average value of the sodium intensity in the second region R2. This is clear from a comparison between FIG. 10 and FIG. 6 of (Example 1) described later, and is because the diffusion of potassium, sodium, etc. advances in the second region R2 where the piezoelectric layer exists on the diaphragm without the first electrode (corresponding to Example 1). That is, the diffusion of potassium and sodium is more suppressed in the first region R1 covered by the first electrode 60 than in the second region R2 not covered by the first electrode 60, so that the intensities of potassium and sodium in the first region R1 are lower than those in the second region R2.

[0052] By thus lowering the strength of each of the potassium and sodium in the first region R1, which is the movable region, embrittlement of the first region R1 can be further suppressed, and the life of the piezoelectric device can be further improved.

[0053] A seed layer (orientation control layer) 57 is provided between the first electrode 60 and the piezoelectric layer 70. When the adhesive layer 56 is formed, the seed layer 57 may be provided on the adhesive layer 56. The seed layer 57 has a function of controlling the orientation of the crystals of the piezoelectric material constituting the piezoelectric layer 70. That is, by providing the seed layer 57 on the first electrode 60, the crystals of the piezoelectric material constituting the piezoelectric layer 70 can be preferentially oriented in a predetermined plane direction (for example, the (100) plane). By increasing the crystal orientation of the piezoelectric layer 70, it is possible to efficiently utilize domain rotation and improve the displacement characteristics of the piezoelectric layer 70.

[0054] The seed layer 57 has a thickness of, for example, 1 nm or more and 50 nm or less.

[0055] Examples of the material of the seed layer 57 include compounds containing bismuth, iron, titanium, and lead, oxides of lithium and niobium (LiNbO), and zinc oxide (ZnO). Among them, compounds containing bismuth, iron, titanium, and lead are preferable. By using a compound containing bismuth, iron, titanium, and lead as the material of the seed layer 57, the crystal structure of the KNN-based piezoelectric layer 70 can be more stabilized. In other words, by forming the piezoelectric layer 70 using LiNbO as the seed layer 57, the stability of potassium and sodium in the piezoelectric layer 70 can be increased, and as a result, the diffusion of potassium and sodium to the vibration plate 50 and the substrate 19 can be more suppressed. From this viewpoint, it is preferable that the seed layer 57 is also provided between the vibration plate 50 and the piezoelectric layer 70.

[0056] The piezoelectric layer 70 is provided between the first electrode 60 and the second electrode 80. The piezoelectric layer 70 is a so-called thin-film piezoelectric body having a thickness of 500 nm or more and 3000 nm or less. Here, the "thin-film piezoelectric body" refers to a piezoelectric body formed by crystal growth on a substrate. The piezoelectric layer 70 is formed with a width wider than the width of the first electrode 60 in the ±X direction. The piezoelectric layer 70 is also formed with a width wider than the length of the pressure chamber 12 in the ±Y direction in the ±Y direction. The end of the piezoelectric layer 70 on the ink supply path 13 side (+Y direction side) is formed to the outside beyond the end of the first electrode 60 on the +Y direction side. In other words, the end of the first electrode 60 on the +Y direction side is covered by the piezoelectric layer 70. On the other hand, the end of the piezoelectric layer 70 on the lead electrode 90 side (-Y direction side) is located inside (+Y direction side) of the end of the first electrode 60 on the -Y direction side. In other words, the end of the first electrode 60 on the −Y direction side is not covered with the piezoelectric layer 70.

[0057] The piezoelectric layer 70 is preferably made of polycrystals preferentially oriented in the (100) plane. By preferentially oriented in the (100) plane in this manner, it is possible to efficiently utilize the rotation of the domains and improve the displacement characteristics.

[0058] Note that "preferentially oriented in the (100) plane" includes cases where all of the crystals in the piezoelectric layer 70 are oriented in the (100) plane, and cases where most of the crystals (50% or more, preferably 80% or more, and more preferably 90% or more) are oriented in the (100) plane.

[0059] Furthermore, when the piezoelectric layer 70 is made of polycrystal, stress is dispersed and uniform within the plane, making the piezoelectric element 300 less susceptible to stress damage, improving the reliability of the element.

[0060] The piezoelectric layer 70 is formed by a solution method (also called a liquid phase method or wet method) such as an MOD method or a sol-gel method, or a gas phase method such as a sputtering method. The piezoelectric layer 70 of this embodiment is a perovskite-type composite oxide containing potassium (K), sodium (Na), and niobium (Nb) and represented by the general formula ABO3. That is, the piezoelectric layer 70 contains a piezoelectric material made of a KNN-based composite oxide represented by the following formula (1).

[0061] (K X ,Na 1-X )NbO3 (1) (0.1≦X≦0.9)

[0062] The piezoelectric material constituting the piezoelectric layer 70 may be a KNN-based composite oxide, and is not limited to the composition represented by formula (1) above. For example, other metal elements (additives) may be contained in the A site or B site of potassium sodium niobate. Examples of such additives include manganese (Mn), lithium (Li), barium (Ba), calcium (Ca), strontium (Sr), zirconium (Zr), titanium (Ti), bismuth (Bi), tantalum (Ta), antimony (Sb), iron (Fe), cobalt (Co), silver (Ag), magnesium (Mg), zinc (Zn), and copper (Cu).

[0063] One or more of these types of additives may be included. In general, the amount of additives is 20% or less, preferably 15% or less, more preferably 10% or less, based on the total amount of the main element. By using additives, it is easy to improve various properties and diversify the structure and function, but it is preferable that KNN is present in an amount of more than 80% from the viewpoint of exerting the properties derived from KNN. In addition, even in the case of a complex oxide containing these other elements, it is preferable that it is configured to have an ABO3 type perovskite structure.

[0064] In addition, in this specification, the term "perovskite-type complex oxide containing K, Na, and Nb" refers to a "complex oxide having an ABO3-type perovskite structure containing K, Na, and Nb," and is not limited to only a complex oxide having an ABO3-type perovskite structure containing K, Na, and Nb. In other words, in this specification, the term "perovskite-type complex oxide containing K, Na, and Nb" includes a piezoelectric material represented as a mixed crystal containing a complex oxide having an ABO3-type perovskite structure containing K, Na, and Nb (for example, the KNN-based complex oxide exemplified above) and another complex oxide having an ABO3-type perovskite structure.

[0065] The other complex oxide is not limited within the scope of this embodiment, but is preferably a lead-free piezoelectric material with a lead (Pb) content of 0.1 at% or less. Moreover, the other complex oxide is more preferably a lead-free piezoelectric material with a lead (Pb) and bismuth (Bi) content of 0.1 at% or less. This results in a piezoelectric element 300 with excellent biocompatibility and low environmental impact.

[0066] The second electrode 80 is provided continuously on the piezoelectric layer 70 and the vibration plate 50 across the +X direction. That is, the second electrode 80 is configured as a common electrode common to a plurality of piezoelectric layers 70. In this embodiment, the first electrode 60 constitutes an individual electrode provided independently in correspondence with the pressure chambers 12, and the second electrode 80 constitutes a common electrode provided continuously across the arrangement direction of the pressure chambers 12, but the first electrode 60 may constitute a common electrode and the second electrode 80 may constitute an individual electrode.

[0067] The material of the second electrode 80 is preferably a precious metal such as platinum (Pt) or iridium (Ir) or an oxide thereof. The material of the second electrode 80 may be any material that has electrical conductivity. The material of the first electrode 60 and the material of the second electrode 80 may be the same or different.

[0068] According to the piezoelectric element application device (recording head 1) of the first embodiment described above, by using a vibration plate 50 made of silicon oxide and limiting the SIMS intensities of potassium and sodium in the vibration plate 50 to be lower than the SIMS intensities of potassium and sodium in the piezoelectric layer 70, it is possible to improve the displacement of the vibration plate 50 while ensuring adhesion between the vibration plate 50 and the piezoelectric layer 70.

[0069] (Other embodiments) In the above first embodiment, an inkjet recording head has been described as an example of a liquid jet head, but the present invention is applicable to liquid jet heads in general, and can also be applied to liquid jet heads that jet liquids other than ink. Other liquid jet heads include, for example, various recording heads used in image recording devices such as printers, color material jet heads used in manufacturing color filters for liquid crystal displays and the like, electrode material jet heads used in forming electrodes for organic EL displays, FEDs (field emission displays), and bioorganic matter jet heads used in manufacturing biochips.

[0070] In addition, the piezoelectric element 300 described above is not limited to a piezoelectric element mounted on a liquid ejection head, but can also be applied to a piezoelectric element mounted on other piezoelectric element application devices. Examples of piezoelectric element application devices include ultrasonic devices, motors, pressure sensors, pyroelectric elements, and ferroelectric elements. In addition, completed products using these piezoelectric element application devices, such as a liquid ejection device using the liquid ejection head, an ultrasonic sensor using the ultrasonic device, a robot using the motor as a driving source, an IR sensor using the pyroelectric element, and a ferroelectric memory using a ferroelectric element, are also included in the piezoelectric element application devices.

[0071] Furthermore, the dimensions (for example, thickness), shapes, etc. of each element listed above are merely examples and can be changed without departing from the gist of this embodiment.

[0072] (Manufacturing method for piezoelectric device) Next, an example of a method for manufacturing a piezoelectric device (recording head 1) will be described. Note that, although the following describes a case where the piezoelectric layer 70 is manufactured by a chemical solution method (wet method), the manufacturing method for the piezoelectric layer 70 is not limited to the wet method, and may be a gas phase method.

[0073] First, a substrate (hereinafter also referred to as a "wafer") containing silicon is prepared, and the substrate is thermally oxidized to form a diaphragm 50 made of silicon dioxide (SiO2) on the surface.

[0074] Next, the first electrode 60 is formed on the diaphragm 50 by a normal method (such as sputtering or vapor deposition). The first electrode 60 may be formed via an adhesion layer 56 (for example, titanium oxide). When the adhesion layer 56 is formed, the adhesion layer 56 and the first electrode 605 may be patterned simultaneously. The patterning of the adhesion layer 56 and the first electrode 60 may be performed by dry etching such as reactive ion etching (RIE) or ion milling, or wet etching using an etching solution. The shapes of the patterned adhesion layer 56 and the first electrode 60 are not particularly limited.

[0075] Next, a seed layer 57 is formed on the patterned first electrode 60 and to cover the diaphragm 50. The seed layer 57 can be formed by a chemical solution method (wet method) in which a solution (precursor solution) containing a metal complex is applied and dried, and then baked at a high temperature to obtain a metal oxide. Examples of materials for the seed layer 57 include compounds containing bismuth, iron, titanium, and lead, lithium and niobium oxide (LiNbO), and zinc oxide (ZnO).

[0076] Next, a plurality of piezoelectric films are formed on the seed layer 57 . The piezoelectric layer 70 is composed of these multiple piezoelectric films. The piezoelectric layer 70 can be formed by a solution method (chemical solution method) such as the MOD method or the sol-gel method. By forming the piezoelectric layer 70 by the solution method, the productivity of the piezoelectric layer 70 can be increased. The piezoelectric layer 70 formed by the solution method is formed by repeating a series of steps from the step of applying a precursor solution (application step) to the step of firing the precursor film (firing step) multiple times.

[0077] A specific procedure for forming the piezoelectric layer 70 by a solution method is as follows, for example. First, a precursor solution containing a predetermined metal complex is prepared. The precursor solution is prepared by dissolving or dispersing a metal complex capable of forming a composite oxide containing K, Na, and Nb by firing in an organic solvent. At this time, a metal complex containing an additive such as Mn may be further mixed.

[0078] Examples of the metal complex containing K include potassium 2-ethylhexanoate and potassium acetate. Examples of the metal complex containing Na include sodium 2-ethylhexanoate and sodium acetate. Examples of the metal complex containing Nb include niobium 2-ethylhexanoate and pentaethoxyniobium. When Mn is added as an additive, examples of the metal complex containing Mn include manganese 2-ethylhexanoate. In this case, two or more metal complexes may be used in combination. For example, potassium 2-ethylhexanoate and potassium acetate may be used in combination as the metal complex containing K. Examples of the solvent include 2-n-butoxyethanol, n-octane, or a mixed solvent thereof. The precursor solution may include an additive that stabilizes the dispersion of the metal complex containing K, Na, and Nb. Examples of such additives include 2-ethylhexanoic acid.

[0079] Then, the precursor solution is applied onto the vibration plate 50 on which the first electrode 60 has been formed, to form a precursor film (application step).

[0080] Next, this precursor film is heated to a predetermined temperature, for example, about 150°C to 250°C, and dried for a certain period of time (drying step). The average temperature rise rate in the drying step is preferably 50°C to 100°C / sec. By firing the piezoelectric film at such a temperature rise rate using a solution method, a piezoelectric layer 70 that is not a pseudocubic crystal can be realized.

[0081] Next, the dried precursor film is heated to a predetermined temperature, for example, 300° C. to 450° C., and is degreased by maintaining it at this temperature for a certain period of time (degreasing step).

[0082] The heating temperature in the degreasing step is preferably 450°C or less from the viewpoint of suppressing the diffusion of elements in the precursor film to the diaphragm side. More preferably, it is 400°C or less. On the other hand, if the heating temperature in the degreasing step is too low, there is a risk of orientation abnormality due to residual C (carbon). Therefore, the heating temperature is preferably 350°C or more.

[0083] The heating time in the degreasing step is preferably 10 minutes or less from the viewpoint of suppressing the diffusion of elements in the precursor film to the vibration plate side. More preferably, it is 5 minutes or less. On the other hand, if the heating time in the degreasing step is too short, there is a risk of insufficient degreasing. Therefore, the heating time is preferably 2 minutes or more.

[0084] Finally, the degreased precursor film is heated to a relatively high temperature, for example, about 650° C. to 750° C., and crystallized by maintaining it at this temperature for a certain period of time, thereby completing the piezoelectric film (firing process).

[0085] The heating temperature in the baking process is preferably 750°C or less from the viewpoint of suppressing the diffusion of elements in the precursor film to the vibration plate side. More preferably, it is 700°C or less. On the other hand, if the heating temperature in the baking process is too low, the baking may be insufficient and the crystallization may be insufficient. Therefore, the heating temperature is preferably 650°C or more.

[0086] The heating time in the firing step is preferably 10 minutes or less from the viewpoint of suppressing the diffusion of elements in the precursor film to the substrate side. More preferably, it is 5 minutes or less. On the other hand, if the heating time in the firing step is too short, firing failure and insufficient crystallization may occur. Therefore, the heating time is preferably 2 minutes or more.

[0087] Examples of heating devices used in the drying, degreasing and baking processes include an RTA (Rapid Thermal Annealing) device that heats by irradiating with an infrared lamp, a hot plate, etc. The above processes are repeated multiple times to form a piezoelectric layer 70 made of multiple piezoelectric films. In the series of processes from the coating process to the baking process, the baking process may be performed after the coating process to the degreasing process are repeated multiple times.

[0088] Furthermore, before or after forming the second electrode 80 on the piezoelectric layer 70, a reheating treatment (post-annealing) may be performed as necessary in a temperature range of 600° C. to 800° C. By performing post-annealing in this manner, a good interface between the piezoelectric layer 70 and the first electrode 60, and a good interface between the piezoelectric layer 70 and the second electrode 80 can be formed, and the crystallinity of the piezoelectric layer 70 can be improved.

[0089] After the firing process, the piezoelectric layer 70 made up of a plurality of piezoelectric films is patterned into a shape as shown in Fig. 5. The patterning can be performed by dry etching such as reactive ion etching or ion milling, or wet etching using an etching solution.

[0090] Thereafter, the second electrode 80 is formed on the piezoelectric layer 70. The second electrode 80 can be formed by a method similar to that for forming the first electrode 60.

[0091] Through the above steps, the piezoelectric element 300 including the first electrode 60, the piezoelectric layer 70, and the second electrode 80 is manufactured.

[0092] Thereafter, a protective substrate 30 is provided on the substrate 10 (vibration plate 50) on which the piezoelectric elements 300 are formed by a standard method (see FIG. 2), and then various elements are formed, such as pressure chambers 12 corresponding to each piezoelectric element 300, as well as ink supply paths 13, communicating paths 14, and communicating portions 15 (see FIG. 2). The above steps complete an assembly of chips for the piezoelectric device (recording head 1). By dividing this assembly into individual chips, the piezoelectric device (recording head 1) is obtained. EXAMPLES

[0093] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0094] Example 1 First, the surface of a silicon substrate (6 inches) was thermally oxidized, and a diaphragm made of silicon dioxide was formed on the substrate to obtain a base substrate.

[0095] Next, a piezoelectric layer was formed on the base substrate in the following manner. First, a precursor solution consisting of potassium 2-ethylhexanoate, sodium 2-ethylhexanoate, lithium 2-ethylhexanoate, niobium 2-ethylhexanoate, and manganese 2-ethylhexanoate was applied onto the base substrate by spin coating to form a precursor film (application process).

[0096] Thereafter, the precursor film was dried at 180° C. (drying step), and then degreasing was performed at 380° C. for 3 minutes (degreasing step). Next, the degreased precursor film was subjected to a heating treatment at 700°C for 3 minutes using RTA (Rapid Thermal Annealing) to form a piezoelectric film (firing process). The process from the coating process to the firing process was repeated multiple times until cracks were confirmed, and a KNN-based piezoelectric layer consisting of multiple piezoelectric films was produced.

[0097] Example 2 In the preparation of the base substrate, no thermal oxidation was performed, and a piezoelectric layer was formed on the substrate. The rest was the same as in Example 1. The diaphragm was made of a silicon dioxide film formed by oxidizing a part of the surface layer of the substrate through a heat treatment such as a baking process.

[0098] Comparative Example 1 A Zr film was formed on the substrate by sputtering, and the surface of the Zr film was thermally oxidized to form a diaphragm made of zirconium dioxide (ZrO2) on the substrate, thereby obtaining a base substrate. The rest was the same as in Example 1.

[0099] Comparative Example 2 The same procedure was followed as in Example 1, except that the material of the piezoelectric layer was an AlN film.

[0100] For each of the above-mentioned Examples and Comparative Examples, the following element diffusion and interlayer delamination were confirmed.

[0101] <Confirmation of element diffusion> The diffusion of elements into the piezoelectric layer on the diaphragm side was confirmed using a secondary ion mass spectrometry (SIMS) device ("IMS-7f sector type" manufactured by CAMECA). 15 keV Cs+ was used as the primary ion, raster-scanned over a 100 μm square with a beam current of 10 nA, and negative secondary ions were detected from the center 33 μm diameter. An electron gun was used to prevent charge-up.

[0102] <Check for delamination> The presence or absence of delamination was determined by observation using a scanning electron microscope (SEM). Specifically, observation was performed using a Hitachi S-4700 scanning electron microscope at an accelerating voltage of 10 kV and a magnification of 100 kV to confirm the state of delamination.

[0103] (Test Results) In Comparative Example 2, AlN was used as the material for the piezoelectric layer, which caused a large amount of Al to diffuse to the substrate side, resulting in delamination between the piezoelectric layer and the substrate.

[0104] Fig. 6 shows the analysis results of Example 1 in which a SiO2 film was used as the diaphragm 50, Fig. 7 shows the analysis results of Example 2 in which a SiO2 thin film was used as the diaphragm 50, and Fig. 8 shows the analysis results of Comparative Example 1 in which a ZrO2 film was used as the diaphragm. Note that Figs. 6 to 9 are all analysis results from the piezoelectric layer toward the substrate side, and the analysis results toward the substrate side are shown with the passage of analysis time (horizontal axis).

[0105] As shown in Figures 6 and 7, when only a film made of SiO2 was used as the diaphragm, the concentrations of potassium (K) and sodium (Na) that make up the piezoelectric layer tended to decrease gradually, rather than suddenly, even after passing the interface with the piezoelectric layer. From this, it is considered that when a SiO2 film is used as the diaphragm, the constituent elements of the piezoelectric layer diffuse to the diaphragm side to some extent. However, in Examples 1 and 2, no delamination occurred between the piezoelectric layer and the diaphragm, and adhesion was ensured.

[0106] On the other hand, as shown in Figure 8, when a laminated film of SiO2 film and ZrO2 film was used as the vibration plate, the concentration of potassium (K) and sodium (Na) that make up the piezoelectric layer suddenly decreased, and no element diffusion toward the vibration plate side was confirmed, and no delamination was confirmed. However, it is believed that the amount of displacement was smaller than in Examples 1 and 2 due to the increased rigidity of the entire vibration plate. From these findings, it can be seen that in order to ensure adhesion between the piezoelectric layer and the vibration plate while reducing the rigidity of the vibration plate and improving the amount of displacement, it is preferable to use a film made of SiO2 as the vibration plate. [Explanation of symbols]

[0107] I...ink jet recording apparatus (liquid ejection apparatus), II...ink jet recording head unit (head unit), 1...ink jet recording head (liquid ejection head), 10...substrate, 12...pressure chamber, 13...ink supply path, 14...connecting path, 15...connecting portion, 20...nozzle plate, 21...nozzle opening, 30...protective substrate, 31...piezoelectric element holding portion, 32...manifold portion, 40...compliance substrate, 50...diaphragm, 57...seed layer (orientation control layer), 60...first electrode, 70...piezoelectric layer, 80...second electrode, 90...lead electrode, 100...manifold, 300...piezoelectric element, R1...first region

Claims

1. a diaphragm made of silicon oxide; a first electrode formed above the diaphragm; a seed layer formed above the first electrode and the diaphragm; a piezoelectric layer formed on the seed layer and containing potassium, sodium, and niobium; a second electrode formed on the piezoelectric layer; Equipped with the diaphragm further contains potassium and sodium; In secondary ion mass spectrometry of the vibration plate and the piezoelectric layer, the intensity of potassium in the vibration plate is lower than the intensity of potassium in the piezoelectric layer; The intensity of sodium in the diaphragm is lower than the intensity of sodium in the piezoelectric layer. A piezoelectric element application device characterized by:

2. 2. The piezoelectric device according to claim 1, further comprising a layer containing titanium oxide between the vibration plate and the first electrode.

3. 2. The piezoelectric device according to claim 1, wherein the seed layer contains bismuth, iron, titanium, and lead.

4. The diaphragm is formed on a silicon substrate, the silicon substrate has a pressure chamber; When a region of the vibration plate that forms a part of the wall surface of the pressure chamber is defined as a first region, The piezoelectric device according to claim 1 , wherein the first electrode covers the first region when viewed in the thickness direction of the piezoelectric layer.

5. In secondary ion mass spectrometry in the first region and a second region other than the first region of the diaphragm, an average potassium intensity in the first region is lower than an average potassium intensity in the second region; 5. The piezoelectric device according to claim 4, wherein the average value of the sodium intensity in the first region is lower than the average value of the sodium intensity in the second region.

6. the potassium intensity at the diaphragm is higher than the potassium intensity at the first electrode; 2. The piezoelectric device according to claim 1, wherein the sodium intensity in the diaphragm is higher than the sodium intensity in the first electrode.

7. A piezoelectric element application device as described in claim 1, characterized in that the intensity of potassium in the piezoelectric layer repeatedly increases and decreases along the thickness direction of the piezoelectric layer.

8. A piezoelectric element application device as described in claim 1, characterized in that the intensity of sodium in the piezoelectric layer repeatedly increases and decreases along the thickness direction of the piezoelectric layer.

9. A piezoelectric element application device as described in claim 1, characterized in that the strength of the silicon in the piezoelectric layer repeatedly increases and decreases along the thickness direction of the piezoelectric layer.

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