Actuator, liquid ejection head, liquid ejection device, wearable terminal device, eye tracking device, and method for manufacturing the same

Abstract

To provide a highly reliable actuator.SOLUTION: An actuator according to the present invention includes a vibration plate, an electrode layer formed integrally with the vibration plate, and a substrate having a piezoelectric layer, the substrate includes a silicon material, the piezoelectric layer includes potassium sodium niobate, the electrode layer includes a Pt film, and the average particle diameter in the plane direction of the Pt particles forming the Pt film is larger than the thickness of the Pt film.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an actuator, a liquid ejection head, a liquid ejection device, a wearable terminal device, an eye tracking device, and a manufacturing method thereof. [Background technology]

[0002] Patent Document 1 discloses a liquid ejection head including a drive unit that vibrates a piezoelectric portion by an actuator having a piezoelectric portion made of a lead-free piezoelectric material whose main component is sodium potassium niobate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-126445 Summary of the Invention [Problem to be solved by the invention]

[0004] The objective is to provide a highly reliable actuator. [Means for solving the problem]

[0005] The actuator of the present invention is an actuator comprising a vibration plate, an electrode layer formed integrally with the vibration plate, and a substrate having a piezoelectric layer, wherein the substrate contains a silicon material, the piezoelectric layer contains potassium sodium niobate, the electrode layer contains a Pt film, and the average particle diameter in the planar direction of the Pt particles constituting the Pt film is larger than the thickness of the Pt film. Effect of the Invention

[0006] It is possible to provide a highly reliable actuator. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram (top view) of a first embodiment. [Diagram 2] 1 is a schematic diagram (a longitudinal cross-sectional view of a piezoelectric element) of a first embodiment. [Diagram 3] 1 is a schematic diagram (a cross-sectional view in the short direction of a piezoelectric element) of a first embodiment. [Figure 4] FIG. 1 is a schematic diagram (cross-sectional view of a heating part) of a first embodiment. [Diagram 5] FIG. 2 is a functional block diagram of the first embodiment. [Figure 6] FIG. 4 is a sequence diagram illustrating a manufacturing method according to the first embodiment. [Figure 7] 2A to 2C are diagrams illustrating a manufacturing method according to the first embodiment. [Figure 8] 1 is an electron microscope photograph of the first embodiment. [Figure 9] FIG. 4 is a schematic diagram of a second embodiment. [Figure 10] FIG. 4 is a schematic diagram (cross-sectional view) of a second embodiment. [Figure 11] FIG. 13 is a conceptual diagram (cross-sectional view) illustrating the function of the third embodiment. [Figure 12] FIG. 13 is a conceptual diagram (plan view) illustrating the function of the third embodiment. [Figure 13] FIG. 13 is a schematic diagram of a third embodiment. [Figure 14] FIG. 11 is a schematic diagram (cross-sectional view) of a third embodiment. [Figure 15] FIG. 13 is a schematic diagram (cross-sectional view) of a fourth embodiment. [Figure 16] FIG. 13 is a conceptual diagram (cross-sectional view) illustrating the function of the fifth embodiment. [Figure 17] FIG. 13 is a schematic diagram of a sixth embodiment. [Figure 18] FIG. 13 is a diagram illustrating an optical system according to a sixth embodiment. [Figure 19] 13 is an example of a movable device according to the sixth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are given the same reference numerals, and duplicated description will be omitted.

[0009] <First embodiment> An overview of this embodiment is shown in Fig. 1 to Fig. 4. Fig. 1 is a plan view. Fig. 2 shows a longitudinal cross section of the piezoelectric layer 18 along line A-A' in Fig. 1. Fig. 3 shows a lateral cross section of the piezoelectric layer 18 along line B-B' in Fig. 1. Fig. 4 shows a cross section of the heating unit 12 along line CC' in Fig. 1.

[0010] A nozzle plate 36 is bonded to the underside of an individual liquid chamber substrate 10, which has a vibration plate 38, a piezoelectric layer 18, and a metal layer laminated on the upper part (upper electrode layer 16), and a holding substrate 44 and a common liquid chamber substrate (not shown) are laminated on top of the individual liquid chamber substrate 10 to form an ink flow path, thereby forming an inkjet head.

[0011] Ink is supplied to the ink supply port 26, fluid resistance portion, and individual liquid chamber 42 that open into the individual liquid chamber substrate 10 via a common liquid chamber (common liquid chamber substrate / holding substrate 44) that communicates with an ink tank not shown, and ink is ejected from the nozzle 34 that communicates with the individual liquid chamber 42 by the pressure generated by driving the piezoelectric element 19 (composed of a piezoelectric layer 18, upper electrode layer 16, and lower electrode 14) formed on the vibration plate 38 of the individual liquid chamber 42.

[0012] The piezoelectric element 19 is driven by a voltage applied to the upper electrode layer 16 and the lower electrode 14, with the upper electrode layer 16 being drawn out using individual wiring 28 and connected to a driving IC 32 and an FPC 50 (Flexible Printed Circuit), and the lower electrode 14 being connected to the FPC 50 using a common wiring 30. The FPC 50 and the common wiring 30 are connected by wires 48 made of a metal such as Au or Al. The wires have a diameter of a dozen micrometers to a few hundred micrometers, and are formed by a typical wire bonding process.

[0013] The present embodiment is characterized in that it includes a resistance temperature detector 20 and a heating unit 12, heats the ink, and controls the temperature. Another feature is the piezoelectric layer 18, which does not lose its piezoelectric properties even at high temperatures.

[0014] The technical problems involved in heating the ink and a method for solving the problems by improving the piezoelectric layer 18 will be described below.

[0015] Piezoelectric inkjet heads use strong mechanical force to eject ink, so they have a wide selection of inks and are widely used for industrial purposes. Many of the inks used in industrial applications, such as functional inks such as UV inks, are highly viscous. High-viscosity inks require a large force to eject, which leads to larger actuators and higher costs. Therefore, since viscosity decreases as temperature increases, it is common to heat the ink to lower its viscosity.

[0016] As functional inks for industrial applications become more diverse, there is an increasing demand for inks with higher viscosity. This has led to a demand for inks to be heated to higher temperatures to reduce their viscosity. Currently, the piezoelectric material used in piezoelectric elements, a typical component of inkjet printer actuators, is PZT (Pb(Zr,Ti)O 3 Commonly used materials are lead zirconate titanate (PZT), and PZT-based materials in which impurities are added to PZT. Piezoelectric layers have the property that as the temperature rises, depolarization occurs and the displacement characteristics begin to deteriorate, and when depolarization or depolarization occurs, the displacement characteristics of the piezoelectric element deteriorate, causing a decrease in the ink ejection performance and poor print quality. (JP Patent Publication 9-141865)

[0017] It has been reported that depolarization occurs at temperatures below the Curie point (about half the Curie point), at which point the polarization disappears and the piezoelectricity is lost (depolarization), resulting in deterioration of the characteristics. (Journal of the Japan Society for Precision Engineering Vol.83, p411-414, No.5, 2017)

[0018] When the ink chamber is heated, the heat is also transferred to the piezoelectric element above the ink chamber, so the temperature of the piezoelectric element also reaches the heating temperature. Therefore, if a piezoelectric element is used whose Curie point is not sufficiently secured against the heating temperature, there is a risk of depolarization occurring. When depolarization occurs, the displacement characteristics of the piezoelectric element deteriorate, which reduces the ink ejection performance and causes problems such as poor print quality.

[0019] Perovskite-structured potassium sodium niobate ((K,Na)NbO 3 (hereinafter referred to as KNN) has a relatively high Curie temperature and is said to have good piezoelectric properties among lead-free piezoelectric materials, and is therefore attracting attention.

[0020] KNN is a piezoelectric material with a high Curie temperature, good temperature stability, and a wide operating range with respect to temperature. In general, KNN has a higher Curie temperature than PZT (JP 2022-126445 A). Therefore, by using KNN, the piezoelectric characteristics can have better temperature stability than PZT, so that the temperature operating range as an inkjet can be widened. Therefore, the ink can be heated to a higher temperature to reduce the viscosity, so that an ink with a higher viscosity can be used.

[0021] The industrial manufacturing method of KNN has been improved, and the piezoelectric properties have been improved. In a KNN piezoelectric thin film element, good piezoelectric properties are obtained by having a specific crystal structure, and the piezoelectric constant can be further improved by improving the crystallinity and controlling the composition. For example, high piezoelectric properties can be obtained and long-term reliability can be improved by optimizing the film formation conditions of a film formation device such as sputtering or CVD for forming a piezoelectric thin film and controlling the average crystal grain size of the piezoelectric thin film within an appropriate range (JP Patent Publication 2008-159807).

[0022] By using MEMS technology, it is possible to miniaturize elements and increase their integration, and to fabricate elements with multiple functions on a substrate at the same time. In inkjet heads, it is possible to increase the density of piezoelectric thin film elements and the nozzle density, which allows for higher image resolution.

[0023] In this way, piezoelectric thin film elements using KNN thin films have a high Curie temperature and good temperature stability, allowing stable ejection at high temperatures. Because they are piezoelectric thin film elements, they can also be used in conjunction with MEMS technology, making it possible to provide a heater and a temperature detection sensor on the same substrate at low cost.

[0024] On the other hand, in inkjet heads with a heating mechanism, it is important to suppress depolarization and depolarization, and to have good temperature detection and heater performance. For temperature detection performance, it is necessary to improve the TCR (temperature coefficient of resistance), and for heaters, it is necessary to stabilize the temperature characteristics taking into account deterioration over time (e.g. suppression of migration). For thin-film piezoelectric elements, the actuator, heater, and temperature sensor can be integrated on the same silicon substrate by using the MEMS process. This allows for lower product costs. By using thin-film formation technology to create a unimorph actuator in which a vibration plate, electrodes, piezoelectric bodies, etc. are laminated in individual liquid chambers, high density can be achieved by patterning individual piezoelectric elements, electrodes, and wiring using semiconductor device manufacturing processes (photolithography, etc.).

[0025] In the MEMS process, silicon semiconductor processes are generally used, but the silicon substrate is a material with high thermal conductivity and good heating efficiency, so the ink can be heated efficiently. Pt material has thermal and chemical stability as a heater. Pt material is also generally used as the upper and lower electrodes of piezoelectric thin film elements.

[0026] It was found that in order to improve the performance as a microheater and a temperature detection sensor, it is effective to increase the Pt crystal grain size and form the film at a high temperature. By increasing the Pt crystal grain size, the TCR (temperature coefficient of resistance) can be increased as a temperature detection performance, and deterioration over time (e.g., migration suppression) can be suppressed as a heater, so that a heating mechanism with excellent overheat controllability can be realized. In addition, by making the average grain size in the lateral direction larger than the film thickness, it is possible to suppress the increase in surface roughness and the occurrence of voids while increasing the Pt crystal grain size. It is possible to suppress the diffusion of voids to cause deterioration over time (increase in electrical resistance and disconnection). In this embodiment, the average grain size is used almost synonymously with the crystal grain size. In principle, there is a possibility that the above functions will not be satisfied when an amorphous layer is significantly present on the surface of the crystal grain. In this embodiment, most of the average grain size is crystalline.

[0027] By increasing the Pt crystal grain size of the lower electrode layer 14, the average crystal grain size of the KNN thin film can be increased, resulting in high piezoelectric properties and improved long-term reliability. Crystallization of the piezoelectric thin film occurs from the lower electrode side, so the interface between the lower electrode layer 14 and the piezoelectric thin film is important. If the Pt crystal grain size of the lower electrode layer 14 is small, the grain boundaries will hinder the lateral crystal growth of the piezoelectric thin film formed on top, making it impossible to ensure a sufficient grain size for the piezoelectric thin film. It is important to increase the grain size of the lower electrode, which serves as the base film.

[0028] It is easier to improve the crystallinity of the lower electrode layer 14 than the upper electrode layer 16. For example, after the piezoelectric thin film is formed, temperature constraints in the process may arise due to changes in the material properties and characteristics caused by the thermal history of the piezoelectric thin film material.

[0029] In this way, by increasing the grain size in the lower electrode layer 14 made of Pt material, the performance of the microheater and the temperature detection sensor can be improved, and the thin film piezoelectric element can obtain high piezoelectric performance. In addition, the long-term reliability of both the heating mechanism and the piezoelectric thin film can be improved.

[0030] Finally, it is possible to provide an inkjet head having a piezoelectric thin film element using a KNN thin film, which has good heating controllability, can eject high viscosity ink with high precision at low cost, and has improved reliability. The optimal size of the Pt particle diameter will be described later.

[0031] The actuator according to this embodiment is an actuator including a vibration plate 38, a substrate having a lower electrode layer 14, a piezoelectric layer, and an upper electrode layer 16 formed integrally with the vibration plate 38, a heating resistor 12 formed on the substrate, and a resistance temperature detector 20 formed on the substrate, the substrate being made of a silicon material, and the piezoelectric layer being made of potassium sodium niobate. This allows operation at high temperatures. A highly reliable actuator can be provided.

[0032] The actuator according to this embodiment is characterized in that the lower electrode layer 14, the thermal resistor, and the temperature sensor contain the same material, which makes it possible to simultaneously deposit each layer, thereby reducing manufacturing costs.

[0033] Next, the main components of this embodiment, in which the heating means, the resistance temperature detector 20, and the lower electrode layer 14 of the piezoelectric layer 18 are made of Pt, will be described below.

[0034] (Nozzle plate 36) The nozzle plate 36 is a substrate on which the nozzles 34 for ejecting ink are arranged, and any material can be used depending on the required rigidity and processability. Examples include metals or alloys such as SUS and nickel, inorganic materials such as silicon and ceramics, and resin materials such as polyimide. The nozzle processing method can be selected based on the characteristics of the material and the required precision and processability, and examples include electroforming plating, etching, pressing, laser processing, photolithography, etc. The nozzle opening diameter, number of arrangements, and arrangement density can be set to the optimal combination according to the specifications required for the ink head.

[0035] (Individual liquid chamber substrate 10) The individual liquid chamber substrate 10 has individual liquid chambers 42, fluid resistance portions, and ink supply ports 26 formed therein. Any substrate material can be used in consideration of processability and physical properties, but a silicon substrate that can be used with photolithography is used for 300 dpi (approximately 85 μm pitch) or more. Any method can be used to process the liquid chambers, but when using the above-mentioned photolithography method, either wet etching or dry etching can be used. In either method, the liquid chamber side of the vibration plate can be made into a silicon dioxide film or the like to serve as an etch stop layer, so that the liquid chamber height can be controlled with high precision.

[0036] The individual liquid chamber 42 has the function of applying pressure to the ink, causing droplets to be ejected from the nozzle 34. A vibration plate 38 is formed above the individual liquid chamber 42, and a piezoelectric element 19 is formed on the vibration plate 38, in which a lower electrode 14, a piezoelectric layer 18, and an upper electrode layer 16 are laminated. Any material can be used for the vibration plate 38, but it is preferable to use a highly rigid material such as silicon, nitride, oxide, or carbide. It may also be a laminate structure of these materials. When using a laminate film, it is preferable to use a structure with little residual stress, taking into account the internal stress of each material. For example, Si 3 N 4 and SiO 2 In the case of the laminate, the Si 3 N 4 and SiO 2 For example, a structure in which these are alternately laminated to relieve stress can be given.

[0037] The thickness of the vibration plate 38 can be selected according to the desired characteristics, but is preferably in the range of about 0.5 μm to 10 μm, and more preferably in the range of 1.0 to 5.0 μm. If the vibration plate 38 is too thin, it is easily damaged by cracks, etc., and if it is too thick, the amount of displacement is small and the ejection efficiency is reduced. In addition, if it is too thin, the natural frequency of the vibration plate 38 is reduced, and there is a problem that the driving frequency cannot be increased.

[0038] The lower electrode 14 and the upper electrode layer 16 can be made of any conductive material. Examples include metal, alloy, and oxide electrode films. These materials may be single-layered or multi-layered. If necessary, an adhesive layer may be formed in consideration of adhesion to the diaphragm 38. Examples of electrode materials that are highly stable include Pt, Ir, Ir oxide, and Ru. As an oxide electrode film, SrRuO 3 , LaNiO 3 , IrO 2 , RuO 2 , SrO, etc. are used. The adhesion layer with the diaphragm 38 is made of a titanium layer, a titanium oxide layer, a titanium tungsten layer, an alumina layer, a zirconium oxide layer, etc. The adhesion layer is generally thin, about several tens of nm, and has a small contribution to rigidity. As will be described later, when an electrode material is used as the resistance temperature sensor or heating means, Pt is preferable. A laminated film containing Pt may also be used.

[0039] The piezoelectric material of the piezoelectric layer 18 is potassium sodium niobate ((K,Na)NbO 3 KNN (hereinafter referred to as KNN) is used. KNN has a relatively high Curie temperature, and among lead-free piezoelectric materials, it has good piezoelectric properties. KNN is a piezoelectric material with a high Curie temperature, good temperature stability, and a wide operating range for temperature. In general, KNN has a higher Curie temperature than PZT. Therefore, by using KNN, the piezoelectric properties can be made more stable in temperature than PZT, and the temperature operating range for inkjet can be widened.

[0040] Therefore, the ink can be heated to a higher temperature to reduce the viscosity, allowing a higher viscosity to be used. Any method can be used to form the KNN thin film, and various methods such as sputtering, PLD, CVD, and chemical solution deposition (CSD) can be appropriately selected. The upper electrode layer 16 and the piezoelectric layer 18 must be patterned for each individual liquid chamber 42. For patterning, a normal photolithography method can be used.

[0041] The actuator according to this embodiment is characterized in that the Curie temperature of the piezoelectric layer is 350° C. or higher. By using potassium sodium niobate, the Curie temperature can be made higher than that of PZT, which is a commonly used piezoelectric material. This improves the reliability of high-temperature operation.

[0042] The piezoelectric element 19, which is composed of the piezoelectric layer 18 and the upper and lower electrodes, needs to be formed above the individual liquid chamber 42. If it is formed on the partition wall that separates the individual liquid chamber 42, it will hinder the deformation of the vibration plate 38, which will cause a decrease in ejection efficiency and damage to the piezoelectric element 19 due to stress concentration.

[0043] The individual liquid chamber substrate 10 is formed with a fluid resistance portion (not shown) that communicates with the individual liquid chamber 42. The fluid resistance portion has a function of supplying ink from the common liquid chamber to the individual liquid chamber 42, and at the same time, has a function of preventing the ink from flowing backwards and ejecting the ink from the nozzle by the pressure generated in the individual liquid chamber by driving the piezoelectric element 19. Therefore, it is necessary to reduce the cross-sectional area of ​​the individual liquid chamber in the ink flow direction and increase the fluid resistance. When silicon is used for the individual liquid chamber substrate 10 and the individual liquid chamber 42 and the fluid resistance portion are formed by photolithography and etching, there is an advantage that they can be processed under the same conditions as the individual liquid chamber 42. In order to increase the fluid resistance by making the height of the fluid resistance portion lower than the individual liquid chamber, the amount of over-etching of the individual liquid chamber needs to be controlled by time management, so the fluid resistance cannot be made uniform due to variations in the etching rate. As a result, the ejection uniformity is deteriorated.

[0044] The fluid resistance portion communicates with the common liquid chamber through an ink supply port that opens through the vibration plate 38. The individual liquid chambers are divided by partitions, and a piezoelectric element is formed corresponding to each of them. The height of the individual liquid chambers can be set arbitrarily based on the head characteristics, but it is preferable to set it in the range of 20 to 100 μm. The partitions between the individual liquid chambers can be set arbitrarily based on the arrangement density, but it is preferable to set the partition width to 10 to 30 μm. If the partition width is narrow, mutual interference between adjacent liquid chambers occurs when the piezoelectric elements of adjacent individual liquid chambers are driven, resulting in large variations in ejection. The partition width can be narrowed by lowering the liquid chamber height.

[0045] (Holding board 44) As mentioned above, since the individual liquid chamber substrate 10 is thin, at 20 to 100 μm, a holding substrate is bonded to the side facing the nozzle plate in order to ensure the rigidity of the individual liquid chamber substrate. Any material can be used as the holding substrate material, but it is necessary to select a material with a similar thermal expansion coefficient to prevent warping of the individual liquid chamber substrate 10. For this reason, glass, silicon, SiO 2 , ZrO 2 , Al 2 O 3 However, a silicon substrate made of the same material as the individual liquid chamber substrate 10 is preferable.

[0046] The holding substrate 44 must have an opening that forms a part of the ink supply port 26. Furthermore, a holding substrate recess is formed in an area facing the individual liquid chamber. It is necessary to secure a space in which the piezoelectric element 19 can be driven and the vibration plate 38 can be displaced. The holding substrate recess is preferably partitioned for each individual liquid chamber 42 and bonded on the individual liquid chamber partition. This can increase the rigidity of the thin individual liquid chamber substrate, making it possible to reduce mutual interference between adjacent liquid chambers when the piezoelectric element is driven. For this purpose, the holding substrate 44 is preferably made of a high rigidity material such as silicon, rather than a low rigidity material such as resin. Furthermore, since the recess of the holding substrate 44 is partitioned for each individual liquid chamber, high processing accuracy is required for high density printing, and it is desirable for the width of the partition wall of the holding substrate 44 to be 5 to 20 μm in a 300 dpi head.

[0047] (20 resistance thermometers) Since the viscosity of ink changes depending on the temperature, it is necessary to accurately detect the temperature of the head. In the present invention, in order to detect a temperature close to that of the ink, a temperature sensor, a resistance temperature detector 20, is formed on the individual liquid chamber substrate 10. The layer structure is the lower electrode layer 14 and the piezoelectric layer 18 of the piezoelectric element 19 that pressurizes the individual liquid chamber 42. Since there is no need to add a material or process dedicated to the resistance temperature detector 20, there is no increase in cost. In addition, since a dedicated area is not required, it is possible to prevent the head from becoming large. Electrode wiring is drawn out from the lower electrode layer 14 and connected to an external circuit. Here, the number of the resistance temperature detector 20 is only one in FIG. 1, but it is not limited to one, and multiple resistors may be arranged.

[0048] The temperature can be estimated from the voltage value when a constant current is applied from an external circuit to the lower electrode layer 14. Although Pt, Ir, Ir oxide, Ru, etc. have been given as examples of the electrode material in the above, Pt is preferable for the resistance temperature detector 20. The Pt resistance temperature detector 20 is used in standard thermometers of the international temperature scale, and is therefore most suitable as a temperature sensor because it has the highest accuracy of the resistance temperature detector 20, high linearity, excellent corrosion resistance and stability over time.

[0049] As is well known, the resistance of a resistor is proportional to the resistivity and the pattern length, and inversely proportional to the width and height of the cross section, and in the above case, the width and height can be realized with high precision, so the variation in resistance is also small. Therefore, since the variation in resistance is small, the variation in the detected temperature is also small, making it possible to perform high-precision ejection control as an inkjet printer.

[0050] (Heating part 12) In order to eject highly viscous ink such as UV ink, a heating means is provided near the individual liquid chamber. Here, the heating means is formed on the individual liquid chamber substrate 10. The individual liquid chamber substrate is in contact with the ink in the individual liquid chamber, and the individual liquid chamber substrate 10 is made of silicon or the like, which has a very high thermal conductivity. Therefore, by providing the heating means on the individual liquid chamber substrate 10, it becomes possible to heat the ink in the individual liquid chamber 42 very efficiently.

[0051] Pt material has thermal and chemical stability as a heater. There is no need to add materials or processes for the heating means, so there is no increase in costs. In addition, no dedicated area is required, so the head can be prevented from becoming larger. The above-mentioned electrode wiring is drawn out from the lower electrode 14 and connected to an external circuit. By applying a current or voltage to the lower electrode, the individual liquid chambers can be heated by Joule heat generated by resistance heating.

[0052] (operation) FIG. 5 is a functional block diagram of this embodiment. Inkjet control is performed by a driving IC (inkjet control unit) 32. It is wired to the upper electrode layer 16 by individual wiring 28. All piezoelectric elements 19 have an upper electrode layer 16, a piezoelectric layer 18, and a lower electrode 14. The upper electrode layer 16 and the piezoelectric layer 18 are formed independently for each individual liquid chamber 42. The lower electrode layer 14 is formed in common with other piezoelectric elements and is at the same potential by a common wiring 30. The lower electrode 14 is formed on the individual liquid chamber substrate 10 together with the heating unit 12 and the resistance temperature detector 20. The resistance temperature detector 20 is formed of Pt as described above, and the resistance value is calculated from the current and voltage control in the temperature arithmetic unit 60. The calculated resistance value is converted into a temperature, and the information is provided to the temperature control unit 58. The difference between the provided temperature and the set temperature is calculated, and the current and voltage are controlled by the current and voltage control unit 56 so that the temperature becomes the set temperature, and the current and voltage are supplied to the heating unit 12. This causes the heating portion 12 made of Pt to generate heat. The temperature change caused by this heat generation is detected by the resistance temperature detector 20, so that the temperature can be precisely controlled to a set temperature.

[0053] The resistance temperature detector 20 has a Pt particle size of 300 nm or more and a high TCR (temperature coefficient of resistance). This enables highly accurate measurements and allows for highly accurate ink temperature control. This makes it possible to suppress problems such as depolarization of the piezoelectric layer 18 (KNN) that occur when a high temperature setting is maintained for a long period of time. High temperature control makes it possible to ensure the reliability of the piezoelectric element 19 over a long period of time.

[0054] (Manufacturing method) Next, a manufacturing method of this embodiment will be described. A sequence diagram is shown in Fig. 6. Also, cross-sectional views for explaining the manufacturing process are shown in Fig. 7. The manufacturing method will be described below in order using the sequence and cross-sectional views.

[0055] SiO on a silicon wafer with a diameter of 6 inches and a thickness of 600 μm 2 0.3μm, Si 1.0μm, SiO 2 The three-layer diaphragm 38 was formed by laminating each layer with a thickness of 0.3 μm (step S1) (FIGS. 7(a) and 7(b)). At this time, titanium oxide (TiO 2 ) layer may be formed as an adhesive layer. 2 A titanium film is formed on the insulating film by sputtering (step S2), and then, using an RTA (Rapid Thermal Annealing) device, it is annealed at 650 to 800 °C for 1 to 10 minutes with O 2 The titanium film is thermally oxidized in the atmosphere to form a titanium oxide film (step S3).

[0056] As a result, a titanium oxide adhesive layer made of a titanium oxide film is formed on the film-formed diaphragm. At this time, the thickness of the titanium film is preferably 5 to 50 nm. To form the titanium oxide film, reactive sputtering may be used, but a thermal oxidation method using high temperatures for the titanium film is preferable. The lower electrode layer 14 is formed, for example, by sputtering platinum (Pt) to a thickness of 50 to 300 nm. This configuration is the lower electrode layer formation step (FIG. 7(b)). It is preferable to form the film by heating the substrate at a film formation temperature of 500° C. or higher (Step S4).

[0057] 8 is an SEM image of the platinum surface when the lower electrode layer 14 is formed to a thickness of 150 nm by sputtering at a film formation temperature of 550° C. An average particle diameter of about 350 nm is achieved. By setting the film formation temperature at 500° C. or higher, the average Pt particle diameter can be set to 300 nm or more.

[0058] The cross section of the piezoelectric ceramic layer was observed with a scanning electron microscope (SEM). SEM particle size observation was performed at a magnification of 50,000 times or more and a resolution of 252 pixels / inch, and the image was saved. After adjusting the contrast and brightness with image processing software (Photoshop), the image was expanded and measured. Pretreatment was performed using dilute hydrochloric acid at a temperature of 60°C and an immersion time of 120 seconds or less. More than 50 samples were taken by SEM photography and the photo intercept method, and the arithmetic average was calculated. The average platinum particle size was calculated from this.

[0059] A KNN film was formed on the lower electrode layer 14 by sputtering to a thickness of 2 μm (FIG. 7(c)) (step S5). After that, a Pt film was formed on the KNN thin film by sputtering to a thickness of 200 nm to serve as the upper electrode layer 16 (FIG. 7(d)) ​​(step S6).

[0060] After the upper electrode layer 16 is formed, the upper electrode layer 16 is patterned by dry etching (FIG. 7(e)) (step S7), the piezoelectric layer 18 is patterned by dry etching (FIG. 7(f)) (step S8), and the lower electrode 14 is patterned by dry etching (FIG. 7(g)) (step S9). In this step of patterning the lower electrode 14, the lower electrode 12, the heating portion 12, and the resistance temperature detector 20 can be formed simultaneously. Since they can be formed in a single step, they can be manufactured at low cost.

[0061] The actuator according to this embodiment is characterized in that the lower electrode layer 14, the thermal resistor, and the resistance temperature detector 20 contain the same material. This makes it possible to simultaneously deposit each layer, thereby reducing the manufacturing cost.

[0062] The arrangement pitch of the piezoelectric elements 19 was 85 μm, and the width of the piezoelectric elements 19 was 40 μm. The length of the piezoelectric elements 19 in the longitudinal direction was 1000 μm. The number of arranged piezoelectric elements 19 was 300. The width of the temperature sensor 20 was 50 μm. The width of the heating means was also 50 μm. As described above, the thickness of the heating means was 200 nm for the Pt thickness and 60 mm for the length, and 1 W could be output by applying a current of 40 mA.

[0063] Next, the interlayer insulating film 40 shown in FIG. 4 is formed by plasma CVD (step S10), and the individual wiring 28 contact hole (step S11) and the common wiring 30 contact hole are formed on the upper electrode layer 16 in the interlayer insulating film, and then 50 nm of Ti and 2 μm of Al are laminated on top of that (step S12). Then, a metal layer is formed by dry etching, and the individual wiring, the common wiring, and the metal layer around the ink supply port 26 are formed. The width of the common wiring 30 is set to 300 μm. Here, contact holes are similarly formed on the lower electrodes of the temperature detector 20 and the heating unit 12, and wiring is drawn out in the same manner as above (step S13). Then, the vibration plate 38 in the ink supply port 26 portion is removed by dry etching, and the ink supply port 26 is formed in the individual liquid chamber substrate (step S14), and the individual liquid chamber substrate 10 is completed.

[0064] Next, a holding substrate 44 having a holding substrate recess and a holding substrate opening was formed using a φ6 inch silicon wafer. First, the wafer was polished to a thickness of 400 μm, and an oxide film or the like was formed on the liquid chamber side. Then, the oxide film was photolithographically patterned so that the holding substrate recess and the holding substrate opening were opened (step S15). A resist was further formed on top of that, and the resist was photolithographically patterned so that only the holding substrate opening was opened. Then, an opening was formed through from the liquid chamber substrate side by ICP etching (step S16). Then, only the resist on the liquid chamber substrate side was removed, and the substrate side was half-etched by ICP etching using the initially patterned oxide film pattern as a mask. Finally, the oxide film was removed, and the recess and the through opening on the liquid chamber substrate side could be formed.

[0065] The prepared holding substrate is bonded. Of the individual liquid chamber substrate, the temperature sensor 20, the heating means, and the metal layer around the ink supply port (not shown) are mainly bonded to the holding substrate. As the layer thicknesses are made equal as described above, bonding can be performed without any problems.

[0066] After that, a driving IC was mounted on the substrate by flip chip bonding (step S17). After that, the 600 μm individual liquid chamber substrate was polished to 80 μm, and then the individual liquid chambers and fluid resistance parts were formed by ICP dry etching.

[0067] The width of the individual liquid chamber was 60 μm, the width of the fluid resistance portion was 30 μm, and the length was 300 μm. Etching of the fluid resistance portion and the individual liquid chamber was performed until it reached the vibration plate 38, so that they were at the same height (step S18). Also, since the vibration plate 38 of the ink supply port portion was etched in advance, a through hole could be formed. After cutting the wafer into chips by dicing, the nozzle plate and the individual liquid chamber substrate 10 were bonded in the same manner as for the holding substrate. The nozzle plate was made of SUS material with a thickness of 30 μm, and had nozzles of φ20 μm formed at a pitch of 85 μm by pressing.

[0068] An inkjet head was completed by bonding a common liquid chamber substrate made of SUS (not shown) onto the holding substrate, connecting it to an ink tank, and bonding an FPC to the connection pad portion by wire bonding.

[0069] In this inkjet head, the temperature of the resistance temperature detector 20 is detected by an external circuit to the head, and the current or voltage applied to the heating means is adjusted according to the detected temperature, thereby making it possible to achieve an appropriate ink viscosity and drive the piezoelectric element with high precision via the driving IC.

[0070] The actuator according to this embodiment is characterized in that the lower electrode is made of a Pt film, and the average particle size in the plane direction of the Pt particles constituting the Pt film is 300 nm or more. By increasing the Pt crystal grain size, the piezoelectric constant of potassium sodium niobate can be improved, and the sensitivity when measuring temperature can be improved, thereby improving the reliability of high-temperature operation.

[0071] The actuator according to this embodiment is characterized in that the lower electrode is made of a Pt film, and the thickness of the Pt film is 300 nm or less. This allows the average grain size in the lateral direction to be larger than the film thickness. By making the film thickness smaller than the average grain size, it is possible to increase the Pt crystal grain size while suppressing an increase in surface roughness and the occurrence of voids. It is possible to improve the reliability of high-temperature operation.

[0072] Next, another device to which the above-mentioned piezoelectric film is applied will be described. <Second embodiment> [Configuration of movable device]

[0073] Fig. 9 is a plan view showing an example of the configuration of the movable device according to the present embodiment. As shown in Fig. 9, the movable device 13 includes a mirror section 101 that reflects incident light, a first driving member 110a and a second driving member 110b that are connected to the mirror section and drive the mirror section around a first axis parallel to the Y axis, a first support section 120 that supports the mirror section and the first driving member 110a, a third driving section 130a and a fourth driving section 130b that are connected to the first support section and drive the mirror section and the first support section around a second axis parallel to the X axis, a second support section 140 that supports the third and fourth driving sections, and an electrode connection section 150 that is electrically connected to the first to fourth driving sections and a control device.

[0074] The movable device 13 is formed, for example, by forming a single SOI (Silicon On Insulator) substrate by etching or the like, and forming the reflecting surface 14, the first and second driving units 112a, 112b, the third driving units 131a-131f, the fourth driving units 132a-132f, the electrode connection unit 150, etc., on the formed substrate, so that each component is integrally formed. Note that the formation of each of the above components may be performed after or during the formation of the SOI substrate.

[0075] Figure 10 is a cross-sectional view of the movable device shown in Figure 9. The SOI substrate is a substrate in which a silicon oxide layer 162 is provided on a first silicon support layer 161 made of single crystal silicon (Si), and a second silicon layer made of single crystal silicon is further provided on the silicon oxide layer. Hereinafter, the first silicon layer is referred to as the silicon support layer 161, and the second silicon layer is referred to as the silicon active layer 163.

[0076] Since the silicon active layer 163 has a smaller thickness in the Z-axis direction than in the X-axis direction or the Y-axis direction, the drive section formed only of the silicon active layer 163 functions as an elastic section having elasticity.

[0077] The SOI substrate does not necessarily have to be flat, and may have a curvature, etc. Also, the driving part used to form the movable device 13 is not limited to the SOI substrate, so long as it can be integrally molded by etching or the like and can be partially made elastic.

[0078] The mirror section 101 is composed of, for example, a circular mirror base 102 and a reflecting surface 14 formed on the +Z side surface of the mirror base. The mirror base 102 is composed of, for example, a silicon active layer 163. The reflecting surface 14 is composed of, for example, a metal thin film containing aluminum, gold, silver, etc. The mirror section 101 may also have a rib formed on the -Z side surface of the mirror base 102 for reinforcing the mirror section. The rib is composed of, for example, a silicon support layer 161 and a silicon oxide layer 162, and can suppress distortion of the reflecting surface 14 caused by movement.

[0079] The first driving member 110a and the second driving member 110b have one end connected to the mirror base 102 and the other end connected to the support section 120. The first driving member 110a is composed of a torsion bar 111a, a first driving section 112a, and a support for the first driving section. Two torsion bars 111a and 111b that movably support the mirror section 101 extend in the first axial direction and are connected to the support for the first driving section 112a and the support for the second driving section 112b, and the support for the driving sections is connected to the support section 120.

[0080] As shown in FIG. 10, the torsion bars 111a and 111b are made of a silicon active layer 163. The first driving section 112a and the second driving section 112b are made by forming a lower electrode 201, a piezoelectric section 202, and an upper electrode 203 in this order on the +Z side surface of the silicon active layer 163, which is the elastic section. The upper electrode 203 and the lower electrode 201 are made of, for example, gold (Au) or platinum (Pt). The piezoelectric section 202 is made of, for example, a piezoelectric material such as PZT (lead zirconate titanate), potassium sodium niobate (KNaNbO 3 :KNN).

[0081] Returning to FIG. 9, the first support section 120 is a rectangular support body formed to surround the mirror section 101 and includes, for example, a silicon support layer 161, a silicon oxide layer 162, and a silicon active layer 163.

[0082] The third driving section 130a and the fourth driving section 130b are composed of a plurality of third driving sections 131a to 131f and fourth driving sections 132a to 132f, which are connected to each other in a folded manner, and one end of the third driving section 130a and the fourth driving section 130b is connected to the outer periphery of the first support section 120, and the other end is connected to the inner periphery of the second support section 140. At this time, the connection point between the support of the third driving section 130a and the first support section 120 and the connection point between the support of the fourth driving section 130b and the first support section 120, as well as the connection point between the support of the third driving section 130a and the second support section 140 and the connection point between the support of the fourth driving section 130b and the second support section 140 are point symmetrical with respect to the center of the reflecting surface 14.

[0083] In a meander structure in which multiple beams are connected in a folded manner, piezoelectric actuator group A 113a and piezoelectric actuator group B 113b are alternately provided on the +Z side surface of each beam. By driving only piezoelectric actuator group A 113a or only piezoelectric actuator group B 113b, it is possible to control the deflection angle of the mirror to the + side or - side without using a negative voltage. In addition, when applying voltages of opposite phase to piezoelectric actuator group A 113a and piezoelectric actuator group B 113b and switching the voltage or time domain of the applied signal, it is also possible to apply a time difference to the signal switching between piezoelectric actuator group A 113a and piezoelectric actuator group B 113b, so that the generated mechanical vibrations are in opposite phase between piezoelectric actuator group A 113a and piezoelectric actuator group B 113b and are cancelled out. This enables high-speed drawing and response to complex drive waveforms.

[0084] 10, the third driving section 130a and the fourth driving section 130b are configured by forming a lower electrode 201, a piezoelectric section 202, and an upper electrode 203 in this order on the +Z side surface of the silicon active layer 163, which is the elastic section. The upper electrode 203 and the lower electrode 201 are made of, for example, gold (Au) or platinum (Pt). The piezoelectric section 202 is made of PZT (lead zirconate titanate) or SrRuO3.

[0085] Returning to Figure 9, the second support unit 140 is a rectangular support member composed of, for example, a silicon support layer 161, a silicon oxide layer 162, and a silicon active layer 163, and is formed to surround the mirror unit 101, the first driving member 110a, the second driving member 110b, the first support unit 120, the third driving unit 130a, and the fourth driving unit 130b.

[0086] The electrode connection part 150 is formed, for example, on the surface on the +Z side of the second support part 140, and is electrically connected to the upper electrodes 203 and lower electrodes 201 of the first drive part 112a, the second drive part 112b, the third drive parts 131a-131f, and the fourth drive parts 132a-132f, and the control device 11 via electrode wiring such as aluminum (Al). Note that the upper electrodes 203 and the lower electrodes 201 may each be directly connected to the electrode connection part, or may be indirectly connected by connecting the electrodes to each other, for example.

[0087] In this embodiment, an example has been described in which the piezoelectric portion 202 is formed only on one surface (the +Z side surface) of the silicon active layer 163, which is the elastic portion. However, the piezoelectric portion 202 may be provided on another surface (for example, the -Z side surface) of the elastic portion, or may be provided on both one surface and the other surface of the elastic portion.

[0088] In addition, as long as the mirror unit can be driven around the first axis or the second axis, the shape of each component is not limited to the shape of the embodiment. For example, the torsion bars 111a and 111b, the first driving unit 112a, and the second driving unit 112b may have a shape with a curvature.

[0089] Furthermore, an insulating layer made of a silicon oxide film may be formed on at least one of the +Z side surface of the upper electrode 203 of the first driving member 110a and the second driving member 110b, the +Z side surface of the first support part, the +Z side surface of the upper electrode 203 of the third driving part 130a and the fourth driving part 130b, and the +Z side surface of the second support part. In this case, the electrode wiring is provided on the insulating layer, and the insulating layer is partially removed or not formed as an opening only at the connection spot where the upper electrode 203 or the lower electrode 201 is connected to the electrode wiring, thereby increasing the design freedom of the first driving member 110a, the second driving member 110b, the third driving part 130a, the fourth driving part 130b, and the electrode wiring, and further suppressing short circuits due to contact between the electrodes. The silicon oxide film also functions as an anti-reflection material.

[0090] [Controller control details] Next, details of the control by the control device that drives the first to fourth drive units of the movable device will be described.

[0091] When a positive or negative voltage is applied in the polarization direction, the piezoelectric section 202 provided in the first driving member 110a, the second driving member 110b, the third driving section 130a, and the fourth driving section 130b undergoes deformation (e.g., expansion and contraction) proportional to the potential of the applied voltage, thereby exerting the so-called inverse piezoelectric effect. The first driving member 110a, the second driving member 110b, the third driving section 130a, and the fourth driving section 130b move the mirror section 101 by utilizing the inverse piezoelectric effect.

[0092] In this case, the angle formed by the XY plane and the reflecting surface 14 when the reflecting surface 14 of the mirror section 101 is tilted in the +Z direction or the -Z direction with respect to the XY plane is called the deflection angle. In this case, the +Z direction is the positive deflection angle, and the -Z direction is the negative deflection angle.

[0093] First, the control of the control device that drives the first driving unit will be described. In the first driving member 110a and the second driving member 110b, when a driving voltage is applied in parallel to the piezoelectric unit 202 of the first driving unit 112a and the second driving unit 112b via the upper electrode 203 and the lower electrode 201, each piezoelectric unit 202 is deformed. Due to the effect of the deformation of the piezoelectric unit 202, the first driving unit 112a and the second driving unit 112b are bent and deformed. As a result, a driving force about the first axis acts on the mirror unit 101 via the twist of the two torsion bars (connecting units) 111a and 111b, and the mirror unit 101 moves about the first axis. The driving voltage applied to the first driving member 110a and the second driving member 110b is controlled by the control device 11.

[0094] Therefore, the control device 11 applies a driving voltage having a predetermined sinusoidal waveform in parallel to the first driving section 112a and the second driving section 112b of the first driving member 110a and the second driving member 110b, so that the mirror section 101 can be moved around the first axis at a period of the driving voltage having a predetermined sinusoidal waveform.

[0095] In particular, for example, when the frequency of the sinusoidal waveform voltage is set to approximately 20 kHz, which is similar to the resonant frequency of the torsion bars 111a and 111b, the mirror portion 101 can be made to resonate and vibrate at approximately 20 kHz by utilizing the mechanical resonance caused by the twisting of the torsion bars 111a and 111b.

[0096] The actuator for driving the mirror according to this embodiment is characterized by using the semiconductor substrate described in the second and third embodiments. This allows the use of a substrate with a large piezoelectric constant and a small Young's modulus, realizing a large driving range. In addition, materials with no environmental impact are used.

[0097] Next, an embodiment in which the piezoelectric film is applied to another device will be described. <Third embodiment> (Vibration principle of piezoelectric microphone) In this embodiment, a configuration in which a piezoelectric microphone is applied will be described. FIG. 11 is a diagram showing an example of the vibration principle of a piezoelectric microphone. As shown in FIG. 11, a vibration detector 400, which is an example of a piezoelectric microphone (piezoelectric MEMS microphone), detects sound waves by converting the displacement caused by sound waves into an electric signal (voltage) by the piezoelectric effect. Specifically, the vibration detector 400 is a method in which a piezoelectric film 417 that generates electric charges by distortion is directly formed on a vibration part 411 (diaphragm). Here, the directions of each part (function) constituting the vibration detector 400 in the three-dimensional coordinate axis will be described. The X direction is the direction indicating the horizontal direction when the vibration detector shown in FIG. 12 described later is viewed from above. The Y direction is the direction indicating the vertical direction when the vibration detector 400 shown in FIG. 12 is similarly viewed from above. The Z direction is the direction indicating the depth direction when the vibration detector 400 shown in FIG. 12 is similarly viewed from above (for example, the direction from bottom to top when the vibration detector is placed on a flat surface).

[0098] In this method, input of sound waves or the like causes vibration part 411 (diaphragm) to vibrate in the plus and minus Z directions as shown in FIG. 11. This generates stress, and piezoelectric film 417 detects distortion at the portion where the stress occurs. Therefore, in terms of constraints on movement in the plus and minus Z directions, piezoelectric microphones have a higher degree of freedom than capacitive microphones. Furthermore, since vibration detectors can detect distortion with a simple structure, the device fabrication process is simple and they are suitable for miniaturization. Furthermore, since vibration detectors do not require an input power source, the passive circuit is simple and they can have a wide dynamic range.

[0099] (Partial plan view of a piezoelectric microphone) Next, a partial plan view of the piezoelectric microphone will be described. Fig. 12 is a diagram showing an example of a partial plan view of the piezoelectric microphone according to the first embodiment. As shown in Fig. 12, in the vibration detector, one or more fixed end beam parts 413 (rectangular parts surrounded by dotted lines) are provided between each of one or more vibration parts 411 and the fixed part 412. In the example shown in Fig. 12, one or more vibration parts 411 are each formed into four approximately triangular shapes so as to approximately match four regions divided by diagonals in a rectangle inside the fixed part 412 included in the vibration detector.

[0100] One or more fixed end beam portions 413 (rectangular portions surrounded by dotted lines) are provided for each of the one or more vibrating portions 411, and at least one of the total length of the portions of the one or more fixed end beam portions 413 connected to the fixed portion 412 and the total length of the portions of the one or more fixed end beam portions 413 connected to the vibrating portion 411 is shorter than the length of the portion of the vibrating portion 411 that faces the fixed portion 412.

[0101] That is, each fixed end beam portion is connected to the fixed portion 412 within a range shorter than the length of the side of the vibration portion 411 formed in a substantially triangular shape that is closest to the fixed portion. This makes it possible to alleviate the constraint on the vibration portion 411 from the fixed portion 412. Here, each direction in the three-dimensional coordinate axes (X-axis, Y-axis, Z-axis) of each portion (function) constituting the vibration detector 400 will be described. The X-direction is the direction indicating the horizontal direction when the vibration detector 400 is viewed from above. The Y-direction is the direction indicating the vertical direction perpendicular to the X-direction (horizontal direction) when the vibration detector is viewed from above.

[0102] The Z direction is a direction indicating a depth direction perpendicular to the X direction and the Y direction when the vibration detector 400 is viewed from above (for example, a bottom-to-top direction when the vibration detector 400 is placed on a flat surface). Hereinafter, the three-dimensional coordinate axes in the vibration detector shown in the same positional relationship are assumed to indicate the same directions as in FIG. 12. In this embodiment, a weight part 415 formed of a support layer is added from a fixed part 412 of one or more vibration parts 411 in a direction away from the center of gravity of the one or more vibration parts (free end or tip). This results in a structure that lowers the general natural frequency and improves the sensitivity to vibration in the low-frequency band.

[0103] (Planar view of a piezoelectric microphone) Next, a plan view of a piezoelectric microphone will be described. FIG. 13 is a diagram showing an example of a plan view of a piezoelectric microphone according to the first embodiment. As shown in FIG. 13, a vibration detector, which uses a piezoelectric microphone as an example, has one or more vibration units 411, a fixed unit 412, a fixed end beam unit 413 (a rectangular portion surrounded by a dotted line), and a distortion detection unit 414. The configuration of the vibration unit 411 is the same as the shape and number described in FIG. 11. In the example shown in FIG. 13, one or more fixed end beam units 413 are arranged symmetrically on each side facing the fixed unit 412 at a predetermined interval.

[0104] Among these, one or more vibrating parts 411 are connected to the fixed part 412 via one or more fixed end beam parts 413. Here, the term "beam part" generally refers to a member that mainly supports the force of a building or the like, and is one of the structural frameworks. That is, in this embodiment, the fixed end beam part refers to a member for connecting the vibrating part 411 and the fixed part 412. Therefore, the one or more fixed end beam parts 413 are disposed between the one or more vibrating parts 411 and the fixed part 412, and have the function of connecting the one or more vibrating parts 411 and the fixed part 412.

[0105] The strain detection unit 414 has a function of detecting sound waves by converting strain accompanying vibration of one or more vibrating units 411 into an electric signal (voltage) by the piezoelectric effect of the strain detection unit 414. The strain detection unit 414 is provided in the vicinity of one or more fixed end beam units 413 or one or more fixed end beam units 413 in one or more vibrating units 411, or in the vicinity of one or more fixed end beam units 413 and one or more fixed end beam units 413 in one or more vibrating units 411. The strain detection unit 414 further comprises a piezoelectric material such as PZT (lead zirconate of titanium Pb(Zr,Ti)O 3 , potassium sodium niobate (KNaNbO 3 The electrodes are made of highly crystalline Pt(111) and the seed layer is made of SrRuO(001) oriented Pt(111). 3 This makes it possible to form a piezoelectric film with a high piezoelectric constant, improving the sensitivity of the microphone.

[0106] In this embodiment, one or more vibration parts 411 and one or more fixed end beam parts 413 constituting the vibration detector are arranged with a size as shown in FIG. 13, for example. At this time, in order to efficiently detect vibrations caused by sound as distortion, the vibration part 411 needs to be large, but the initial capacitance becomes large, and a trade-off occurs in which the load (power consumption) on the circuit side when detecting distortion, noise, etc. increase. Therefore, it is important to maintain sensitivity without widening the detection area, and it is necessary to balance the sizes of the vibration part 411 and the distortion detection part 414. In response to such a trade-off, in this embodiment, the fixed end beam parts 413 connecting one vibration part 411 and the fixed part 412 are provided at two (plural) places, and the distortion detection part 414 is provided so as to straddle the fixed end beam parts 413. As a result, the distortion detection part 414 can efficiently detect distortion while suppressing the area of ​​the distortion detection part 414 itself. Furthermore, it is possible to reduce the capacitance value in the detection circuit of the distortion detection part 414 and reduce power consumption.

[0107] (Side view of a piezoelectric microphone) Next, a side view of the piezoelectric microphone will be described. Fig. 14 is a diagram showing an example of the side of the piezoelectric microphone according to the first embodiment. Fig. 14 shows an outline of the side of the piezoelectric microphone shown in Fig. 13 with respect to side observation area 419 (pentagonal part surrounded by a dotted line). Specifically, Fig. 14 is an example of a schematic diagram that can be observed when side observation area 419 in Fig. 13 is rotated 90° about the Z axis.

[0108] As in the case shown in FIG. 11, the vibration detector 400 has a plurality of fixed end beams 413. The strain detection section 414 is provided on the plurality of fixed end beams 413 and one or more vibrating sections 411, and the strain detection section 414 provided on the plurality of fixed end beams 413 is continuous with the strain detection section 414 provided on one or more vibrating sections 411. Specifically, in the vibration detector, among the fixed section 412, one or more fixed end beams 413, one or more vibrating sections 411, and the strain detection section 414, a set of the fixed section 412, the fixed end beams 413, the vibrating section 411, and the strain detection section 414 are integrally joined to each other. More specifically, in the vibration detector 400, the fixed end beams 413 and the vibrating section 411 are integrally molded (joined) to a part of the fixed section 412 in the Y direction using a well-known semiconductor joining technique.

[0109] The material used for integral molding is, for example, silicon, SiO 2 Furthermore, the strain detection portion 414 is integrally joined to at least one of the vibration portion 411 and the fixed end beam portion 413 by a film forming process in a semiconductor process.

[0110] Moreover, the weight portion 415 is connected to one or more of the vibration portions 411, and is disposed in a direction away from the fixed portion 412 relative to the center of gravity of the one or more vibration portions 411, for example, near the tip of the vibration portion 411. By providing the weight portion 415 near the tip of the vibration portion 411, the moment of inertia of the vibration system becomes larger than before the weight portion 415 is provided. Also, the natural frequency becomes lower than before the weight portion 415 is provided. Furthermore, the displacement of the vibration portion 411 due to sound waves becomes larger than before the weight portion 415 is provided, improving the detection sensitivity.

[0111] <Fourth embodiment> The movable device and microphone shown in the second and third embodiments are used as wearable terminals because they can be made very lightly. In addition, because KNN is used as the piezoelectric material, one of the advantages is that it has good temperature characteristics in the harsh environments in which wearable terminals are used, especially at high temperatures.

[0112] FIG. 15 is a schematic diagram for explaining the external configuration of a glasses-type wearable terminal 500 as an example. The glasses-type wearable terminal 500 includes a first unit 502 and a second unit 509 as an example. The first unit 502 is arranged in a part of a glasses frame 501 as an example, and includes a controller for controlling the entire wearable terminal 500, a battery, a microphone 504, a speaker 503, and the like. The second unit 509 is also arranged in a part of the glasses frame 501, and includes a display unit 506, a camera 507, a switch 508, various sensors, and the like. The user wears the wearable terminal 500 on the head as if wearing glasses. As a result, the image displayed on the display unit realizes an augmented reality in front of the user's eyes, and provides various information. The microphone 504 uses a micro microphone with the KNN described in the third embodiment as a piezoelectric element. The display unit uses the movable device described in the second embodiment. This allows stable operation to be achieved even in a harsh environment with high temperatures.

[0113] <Fifth embodiment> In the above-described embodiment, the glasses-type wearable terminal 500 is shown as an example of a wearable terminal, but the present embodiment can be applied to other types of wearable terminals. FIG. 16(a) shows a wristwatch-type wearable terminal 600 as another example of a wearable terminal. The wearable terminal 600 includes a display unit 602 arranged on the surface of a main body unit 603, a camera 601 arranged on the side of the main body unit 603, and a band 604 that supports the main body unit 603 and is fixed to the user's arm. Although not shown, the main body unit 603 is provided with a microphone, a speaker, a switch, and the like, similar to the glasses-type wearable terminal 500. FIG. 16(b) shows a diagram of the wearable terminal 600 worn on a user's hand 606. The wearable terminal 600 is characterized by being in close contact with the wrist, and a microphone built into the main body 603 accurately measures the user's pulse. The wrist is a part where a large artery runs close to the surface, and is suitable as a part for measuring the sound waves of the pulse waves generated in the blood vessels of the artery on the skin surface. The third embodiment is optimal as a micro microphone for measuring such pulse waves. In particular, it has sensitivity to low frequencies of several hundred Hz, and the temperature characteristics of the piezoelectric material of KNN are suitable. As a wearable terminal, it is necessary to detect weak pulse sound waves in harsh environments, especially at high temperatures, so this is an application example that can take advantage of the characteristics of KNN.

[0114] Sixth embodiment Next, a case where the above-mentioned movable device 13 is applied as an eyeball tilt position detection device will be described. In this embodiment, the "eyeball tilt position" is the position of the pupil or cornea of ​​the eyeball, or the gaze direction of the user. In the following, an example will be described in which the "eyeball tilt position" is the position of the pupil or cornea, and the "eyeball tilt position detection device" is a "pupil (or cornea) position detection device." In addition, the eyeball tilt position detection device described below is synonymous with a gaze direction tracking device (eye tracking device) that detects or tracks the gaze direction of the user continuously or at time intervals.

[0115] Fig. 17 is a schematic diagram showing an eyeball tilt position detection device 1 equipped with an image display function. The arrows shown in the figure indicate the X, Y, and Z directions, and this figure shows the main parts as seen from above (+Y direction). An eyeball tilt position detection device 80 shown in Fig. 17 has a light source 82, a first light deflection unit 83, a light scanning unit 84, a second light deflection unit 85, and a light receiving unit 86.

[0116] The light source 82 has, for example, laser light sources (82r, 82g, 82b) that emit red, green, and blue laser light, and an infrared laser light source 82ir that emits infrared laser light. The laser light sources 82r, 82g, and 82b may be any one or a combination of two, and emit light for drawing an image by the reflecting surface 14 of the movable device 13. In addition, when the eyeball tilt position detection device is not provided with an image display function, the laser light sources (82r, 82g, 82b) may not be provided.

[0117] The infrared laser light source 82ir emits light for detecting the tilt position of the eyeball. The light for detecting the tilt position of the eyeball is not limited to infrared light, and may be visible light. However, from the viewpoint of improving the visibility of the drawn image, invisible light is preferable.

[0118] The first optical deflection unit 83 is, for example, a dichroic mirror, and deflects the light emitted from the light source 82 toward the reflection surface 14 of the movable device 13 while synthesizing the light. The first optical deflection unit 83 may have a plurality of first optical deflection units 83 according to the number of the laser light sources (82r, 82g, 82b) and the infrared laser light source 82ir included in the light source 82. For example, in the case of the configuration shown in Fig. 17, the first optical deflection unit 83 deflects the respective lights while synthesizing them using the first optical deflection units 83-1, 83-2, 83-3, 83-4, and 83-5.

[0119] The reflective surface 14 of the movable device 13 is the movable device 13 described as the optical scanning system. The reflective surface 14 of the movable device 13 scans the light deflected by the first optical deflection unit 3 in a two-dimensional direction toward the second optical deflection unit 5. At this time, the reflective surface 14 of the movable device 13 scans the light deflected by the first optical deflection unit 83 by, for example, raster scanning, to form an image.

[0120] The second optical deflection unit 85 is, for example, a holographic optical element, and deflects the light L1 scanned by the reflecting surface 14 of the movable device 13 toward the user's eyeball 87. At least a part of the light L2 deflected by the second optical deflection unit 85 is incident on the user's eyeball 87 as display image light.

[0121] The light receiving unit 86 receives the light L3 reflected by the user's eyeball 87 from the light L2 deflected by the second light deflection unit 85. The light receiving unit 86 is, for example, an imaging element capable of detecting infrared rays. In addition, a plurality of light receiving units 6 may be provided at positions capable of receiving the light L3 reflected by the user's eyeball 87. The intensity of the light received by the light receiving unit 86 changes depending on the position change of the eyeball (pupil, cornea), that is, the change in the line of sight. Therefore, the eyeball tilt position detection device 80 in this embodiment detects and estimates the eyeball tilt position based on the intensity of the light received by the light receiving unit 86. In addition, the eyeball tilt position detection device 80 may be configured to detect and estimate the eyeball tilt position based on the position of the pupil or cornea included in the image captured by the light receiving unit 86 and the reflection position of the light L2 deflected by the second light deflection unit 85.

[0122] As described above, the eyeball tilt position detection device 80 according to this embodiment can detect the eyeball tilt position while forming an image on the reflective surface 14 of the movable device 13. Furthermore, by using the movable device 13 according to the first embodiment as the reflective surface 14 of the movable device 13, optical scanning and image formation can be performed more efficiently. Furthermore, by improving the efficiency of optical scanning and image formation, image formation and eyeball tilt position detection can be achieved with lower power consumption.

[0123] The eyeball tilt position detection device 80 can also be mounted on a head mounted display as an eye tracking device to detect or track the user's gaze direction. In this case, for example, by lowering the resolution of the image displayed in the area near the user's gaze direction compared to the image displayed in the other area (foveal rendering), image processing can be speeded up compared to when a high-resolution image is displayed over the entire area.

[0124] FIG. 18 is a diagram showing in detail the optical system of the eye tracking device according to the present embodiment. The light emitted from the light source 82 is shaped by the lens 92 and the lens 93. Then, an image is formed by the image forming device 94 equipped with the movable device 13. The light that formed the image is adjusted in the direction of emission by the angle of view changing device 95. This adjustment allows the light to be appropriately projected onto the retina 32. It is also possible to intentionally adjust and switch the direction so that the light does not enter the pupil 31. The angle of view changing device can be appropriately switched upon receiving a signal St from the control unit 96. This significantly improves the accuracy of projection onto the eyeball 87 (pupil 31, retina 32), allowing the user to recognize a highly accurate image. The angle of view changing device 95 includes a movable device 13 that supports a movable part 101 at four points as shown in FIG. 19, and is suitable for vector scanning and the like, which is excellent in fine angle adjustment.

[0125] The light receiving unit 86 receives light Ls reflected by the user's eyeball 87 from the light deflected by the second light deflection unit 85. The light receiving unit 86 is, for example, an imaging element capable of detecting infrared rays. The angle of view changing device 95 accurately captures the convex portion P of the eyeball 87, thereby improving the eye tracking accuracy.

[0126] As described above, one embodiment of the present invention is as follows.

[0127] <1> The actuator according to this embodiment is an actuator including a vibration plate 38, an electrode layer 16 formed integrally with the vibration plate 38, and a substrate 10 having a piezoelectric layer 18, the substrate including a silicon material, the piezoelectric layer including potassium sodium niobate, the electrode layer including a Pt film, and the average particle diameter in the plane direction of the Pt particles forming the Pt film is larger than the thickness of the Pt film. This allows operation at high temperatures. A highly reliable actuator can be provided.

[0128] <2> In the actuator according to the present embodiment, the lower electrode layer 14 is made of a Pt film, and the average particle diameter in the surface direction of the Pt particles constituting the Pt film is 300 nm or more. <1> In this way, by increasing the Pt crystal grain size, the piezoelectric constant of potassium sodium niobate can be improved, and the sensitivity at the time of measuring the temperature can be improved, thereby improving the reliability of high-temperature operation.

[0129] <3> In the actuator according to the present embodiment, the lower electrode layer 14 is made of a Pt film, and the thickness of the Pt film is 300 nm or less. <1> ~ <2> This allows the average grain size in the lateral direction to be larger than the film thickness. By making the film thickness smaller than the average grain size, it is possible to increase the Pt crystal grain size while suppressing an increase in surface roughness and the occurrence of voids. This allows the reliability of high-temperature operation to be improved.

[0130] <4> The actuator according to this embodiment is characterized in that the Curie temperature of the piezoelectric layer 18 is 350° C. or higher. <1> ~ <3> This actuator is described in . By using potassium sodium niobate, the Curie temperature can be made higher than that of PZT, which is a commonly used piezoelectric material. This improves the reliability of high-temperature operation.

[0131] <5> The liquid ejection head according to this embodiment is <1> ~ <4> This makes it possible to maintain the ink at a high temperature, reduce the viscosity, and eject the ink even if the ink is too viscous to be ejected.

[0132] <6> The liquid ejection device according to this embodiment is <5> The present invention is characterized in that it utilizes the liquid ejection head described in 2. In this way, it is possible to provide an ejection device capable of forming an ink image using ink that is too viscous to be ejected.

[0133] <7> The manufacturing method according to the present embodiment includes the steps of forming a titanium oxide film on a silicon substrate, forming a film of Pt particles having an average particle diameter of 300 nm or more in the surface direction on the titanium oxide film at a film formation temperature of 500° C. or more, forming a potassium sodium niobate film on the Pt film, and processing the Pt film into the lower electrode 14, the heating resistor 12, and the temperature sensor 20. <1> ~ <6> This is a method for manufacturing the actuator described in 2. In this way, a potassium sodium niobate film having high piezoelectric properties can be formed, and the lower electrode layer, the thermal resistor, and the temperature sensor 20 can be simultaneously formed, thereby reducing manufacturing costs. [Explanation of symbols]

[0134] 10 Individual liquid chamber substrate (example of substrate) 12 Heating section (an example of a heating resistor) 14 Lower electrode layer 16 Upper electrode layer 18 Piezoelectric layer 19 Piezoelectric element 20 Resistance thermometer 22 Connection Pad 24 Lead wire 26 Ink supply port 28 Individual wiring 30 Common Wiring 32 Driver IC 34 Nozzle 36 Nozzle Plate 38 Diaphragm 40 Interlayer insulating film 42 Individual liquid chamber 44 Holding board 46 Contact Hole

Claims

1. A diaphragm; A substrate having an electrode layer and a piezoelectric layer formed integrally with the diaphragm. An actuator comprising: the substrate comprises a silicon material; the piezoelectric layer contains potassium sodium niobate, the electrode layer has a Pt film; The average particle size in the plane direction of the Pt particles constituting the Pt film is larger than the thickness of the Pt film. An actuator comprising:

2. The average particle size in the plane direction of the Pt particles constituting the Pt film is 300 nm or more.

2. The actuator according to claim 1 .

3. The thickness of the Pt film is 300 nm or less.

2. The actuator according to claim 1 .

4. The Curie temperature of the piezoelectric layer is 350° C. or higher.

2. The actuator according to claim 1 .

5. A liquid ejection head utilizing the actuator according to claim 1.

6. A liquid ejection device using the liquid ejection head according to claim 5.

7. A wearable terminal device having a microphone utilizing the actuator according to claim 1.

8. An eye-tracking device utilizing the actuator according to claim 1.

9. forming a silicon substrate; forming the Pt particles so that the average particle diameter in the surface direction is larger than the thickness of the Pt film; After the formation of the Pt film, a step of crystal-growing a potassium sodium niobate film as a piezoelectric layer is included. A method for manufacturing the actuator according to claim 1.

10. Further, the method includes a step of forming a titanium oxide film on the silicon substrate, The step of forming the Pt film is a step of forming a film of the Pt particles having an average particle diameter of 300 nm or more in a surface direction on the titanium oxide film at a film formation temperature of 500° C. or more. A method for manufacturing the actuator according to claim 9.

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