JP2016103579A - Manufacturing method of substrate with piezoelectric thin film, manufacturing method of piezoelectric actuator, manufacturing method of ink jet head, substrate with piezoelectric thin film, piezoelectric actuator, ink jet head and ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the occurrence of device failure by recognizing whether or not a piezoelectric thin film has such film quality that device failure occurs due to reduction in adhesion and piezoelectric characteristics before device manufacture.SOLUTION: A manufacturing method of a substrate with piezoelectric thin film comprises a piezoelectric thin film forming step (S4) and an inspection step (S5). The film forming step forms a piezoelectric thin film having the perovskite structure on a ground layer including a substrate. The inspection step irradiates the piezoelectric thin film with light, and determines the quality of the piezoelectric thin film on the basis of the measurement result of diffusion light reflected on the piezoelectric thin film.SELECTED DRAWING: Figure 4

Description

  The present invention includes a substrate with a piezoelectric thin film in which a piezoelectric thin film having a perovskite structure is formed on an underlayer including the substrate, a method for manufacturing the substrate, a piezoelectric actuator having the substrate with a piezoelectric thin film, a method for manufacturing the piezoelectric actuator, and the piezoelectric actuator. The present invention relates to an inkjet head, a method for manufacturing the same, and an inkjet printer having the inkjet head.

In recent years, as electromechanical conversion elements for application to driving elements and sensors, lead-based piezoelectric materials such as lead zirconate titanate (Pb (Zr, Ti) O ₃ ), potassium sodium niobate ((K, Lead-free piezoelectric materials such as Na) NbO ₃ ) are used. Such a piezoelectric body is expected to be applied to a MEMS (Micro Electro Mechanical Systems) element by being formed as a thin film on a substrate such as silicon (Si).

  In manufacturing a MEMS element, since high-precision processing using a semiconductor process technology such as photolithography can be applied, the element can be reduced in size and density. In particular, the cost can be greatly reduced by manufacturing the elements at a high density on a relatively large Si wafer having a diameter of 6 inches or 8 inches, compared to single wafer manufacturing in which the elements are individually manufactured. it can.

  In addition, the piezoelectric material has been made thinner and the device has been converted to MEMS, thereby improving the sensitivity of the sensor and the characteristics of the driving element by improving the conversion efficiency of the mechanical electricity. For example, in a thermal sensor, it is possible to increase measurement sensitivity by reducing thermal conductance due to MEMS, and in an inkjet head for a printer, high-definition patterning can be achieved by increasing the density of nozzles.

When a material containing Pb is used as the piezoelectric body, a crystal made of Pb, Zr, Ti, and O called PZT is often used. Since PZT exhibits a good piezoelectric effect when it has the perovskite structure shown in FIG. 11, it needs to be a perovskite single phase. Here, the perovskite structure ideally has a cubic unit cell, and is disposed at each vertex (A site) of the cubic crystal (for example, Pb) and at the body center (B site). This is an ABO ₃ type crystal structure composed of a metal (for example, Zr or Ti) to be formed and oxygen O arranged at each face center of a cubic crystal. Crystals having a perovskite structure include tetragonal crystals, orthorhombic crystals, rhombohedral crystals and the like in which cubic crystals are distorted. In particular, in PZT, there is a layer boundary called MPB (Morphotropic Phase Boundary) when the molar ratio of Zr and Ti located at the B site is around 52:48. In this MPB composition, since the maximum of the piezoelectric characteristics such as the piezoelectric constant, the polarization value, and the dielectric constant can be obtained, the piezoelectric body having the MPB composition is actively used.

  When a piezoelectric body is used for a MEMS drive element such as an ink jet head, the piezoelectric body must be formed on a substrate of Si or the like with a thickness of 1 to 5 μm in order to satisfy a necessary displacement generating force. As a method for forming such a piezoelectric thin film (hereinafter also referred to as a piezoelectric thin film) on a substrate, a chemical film forming method such as a CVD method (Chemical Vapor Deposition), a physical method such as a sputtering method or an ion plating method is used. A liquid phase growth method such as a conventional method or a sol-gel method is known.

  By the way, as an important film characteristic of the piezoelectric thin film in the MEMS driving element, there is adhesion with an underlayer including a substrate. In the case of an ink jet head, a piezoelectric thin film to which an electric signal is applied is driven by a reverse piezoelectric effect to apply a force to a chamber (pressure chamber) filled with liquid to discharge the liquid. A large force acts on the interface. Also, in order to realize high-resolution drawing, in order to arrange the channels with high density, it is necessary to reduce the thickness of the piezoelectric thin film, and therefore, the piezoelectric thin film is easily peeled off. Therefore, it is necessary to maintain the adhesion between the piezoelectric thin film and the underlayer.

In addition, the piezoelectric constant, which is one of the parameters indicating the electromechanical conversion characteristics, is also important as the film characteristics of the piezoelectric thin film. The higher the piezoelectric constant, the more efficiently it can be driven with respect to the input voltage. For example, in an ink jet head, in order to enable high-speed injection by utilizing a quick response with an optimum design, the piezoelectric constant | d ₃₁ | of the piezoelectric thin film has a value of, for example, 140 pm / V or more, preferably 160 pm / V or higher is required.

  In mass production of piezoelectric elements, for example, a piezoelectric thin film is continuously formed on a silicon wafer having a diameter of 6 inches or 8 inches. Therefore, the above-mentioned characteristics such as adhesion and piezoelectric constant are not only in the wafer surface but also between wafers, that is, batch. Even between, it is required to meet the specifications.

  On the other hand, it is generally very difficult to form a piezoelectric thin film stably for a long period of time, and after a stable film formation of a piezoelectric thin film on a dozen wafers, there is a defective film that does not meet the specifications suddenly. Sometimes formed. As described above, in the formation of a piezoelectric thin film, it is important to obtain a crystal having a perovskite structure, but it is a metastable phase due to slight variations in composition and disturbance of the environment during crystallization. This is probably because crystals of a pyrochlore structure and amorphous regions are easily formed, and their heterogeneous phases increase, thereby causing deterioration in adhesion and piezoelectric characteristics. Therefore, at the time of mass production, it is required to inspect films formed on as many substrates as possible instead of inspection by sampling.

  Here, in the conventional general film inspection, methods such as X-ray fluorescence analysis (XRF) and Raman spectroscopy are available as non-destructive methods for inspecting a composition correlated with film quality. . However, in the former method, since the film is irradiated with X-rays having a certain energy or more, damage to the film is large. In the latter method, the intensity of Raman scattered light generated by laser irradiation on the film is very weak with respect to incident light, and the measurement accuracy is low. Furthermore, both methods are expensive to install the apparatus and are not suitable for low-cost inspection.

  Further, as a method for measuring the crystallinity of the film, there is a method using X-ray diffraction (XRD). However, with XRD, it is difficult to perform measurement without contamination and without contamination of particles or the like. Further, the XRD measurement itself does not correspond to the measurement of film adhesion and piezoelectric constant.

  In addition, an inspection device (for example, manufactured by Axact Corporation) that measures the electric charge by providing an electrode portion in an arbitrary minute area in the wafer surface while measuring the charge and measuring the displacement by laser measurement is also available. Proposed. However, this inspection apparatus has drawbacks that the electrode portion cannot be used as a device, the introduction cost of the apparatus is high, and the quality of adhesion cannot be determined.

  Therefore, in each of the above methods, even if it is determined as a non-defective product at the film inspection stage, a defect may be found after device fabrication.

  On the other hand, methods for measuring the film thickness and surface roughness of a piezoelectric thin film are disclosed in Patent Documents 1 and 2, for example. In Patent Document 1, the film thickness of a piezoelectric thin film is measured in a non-contact manner by an optical thin film measuring apparatus. And it is discriminate | determined as follows whether the measured value of the film thickness by said optical measurement is a reliable value. In other words, light is applied to the surface of the piezoelectric thin film, and is obtained by interference between the light reflected by the surface of the piezoelectric thin film and the light transmitted through the piezoelectric film and reflected by the surface of the lower electrode. The reflectance is measured from the reflected light. And, based on the measured reflectance, whether the measured value of the film thickness by optical measurement is close to the film thickness value (actual value) in the cross section of the piezoelectric thin film measured by a scanning electron microscope (SEM) Whether or not it is a highly reliable value is determined. In Patent Document 2, the surface smoothness (surface roughness) of a piezoelectric thin film is measured using an atomic force microscope (AFM).

JP 2013-197553 A (refer to claim 1, paragraphs [0011], [0020], [0022], [0031] to [0038], FIG. 2, FIG. 4 etc.) JP 2011-181776 A (see paragraph [0046] etc.)

  However, the methods disclosed in Patent Documents 1 and 2 measure (inspect) the external parameters of the piezoelectric thin film, such as the film thickness and surface roughness of the piezoelectric thin film, as described above. It does not inspect the state, nor does it inspect the film quality of the piezoelectric thin film that affects the adhesion and piezoelectric properties. For this reason, in a device manufactured thereafter, a device defect may occur due to a decrease in the adhesion and piezoelectric characteristics of the piezoelectric thin film. Conventionally, such a device failure has been found after the device is manufactured, and it has not been possible to recognize whether or not the film is a device failure before the device is manufactured.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to form a piezoelectric thin film having a film quality that causes a device failure due to a decrease in adhesion and piezoelectric characteristics. Of manufacturing a substrate with a piezoelectric thin film capable of suppressing the occurrence of device defects, and a method of manufacturing a piezoelectric actuator using the manufacturing method and an inkjet head. A manufacturing method and a substrate with a piezoelectric thin film, a piezoelectric actuator, an inkjet head, and an inkjet printer are provided.

  According to one aspect of the present invention, there is provided a method of manufacturing a substrate with a piezoelectric thin film, a film forming step of forming a piezoelectric thin film having a perovskite structure on an underlayer including the substrate, irradiating the piezoelectric thin film with light, And an inspection step for determining the quality of the piezoelectric thin film based on the measurement result of the diffused light reflected by the piezoelectric thin film.

  If a crystal phase (for example, pyrochlore structure) different from the perovskite structure exists in the film of the piezoelectric thin film having the perovskite structure, the adhesion to the underlayer of the piezoelectric thin film and the piezoelectric characteristics are deteriorated. By irradiating the piezoelectric thin film with light and measuring the resulting diffused light (diffuse reflected light), it is possible to investigate the cloudiness of the piezoelectric thin film due to the different crystal phases, thereby improving adhesion and piezoelectric properties. It is possible to determine the quality of the piezoelectric thin film that has an effect.

  As described above, the quality of the piezoelectric thin film is judged based on the measurement result of the diffused light obtained by irradiating the piezoelectric thin film with light. It is possible to recognize whether or not the formed piezoelectric thin film is a film that causes a device failure due to a decrease in adhesion and piezoelectric characteristics. Thereby, a device can be produced using a substrate having a piezoelectric thin film with good film quality (substrate with a piezoelectric thin film), and the occurrence of device defects can be suppressed.

  In the inspection step, the quality of the film quality may be determined based on the measurement result of the diffused light excluding regular reflected light. Regardless of whether or not the different crystal phases exist in the film, the specularly reflected light is generated by specular reflection on the surface of the piezoelectric thin film. Therefore, when such specularly reflected light is included in the diffused light, There is a possibility that noise due to specularly reflected light is included in the measurement result of diffused light. By determining the quality of the film based on the measurement result of the diffused light excluding the specularly reflected light, the influence of noise due to the specularly reflected light is reduced and the accuracy of determining the quality of the film based on the measurement result of the diffused light is improved. be able to.

  In the inspection step, it may be determined that the film quality is good when the reflectance of the diffused light is 11% or less. If the reflectance of diffused light is 11% or less, it is considered that there are few crystallized phases in the film that cause a decrease in adhesion and piezoelectric characteristics because there are few white turbid portions in the piezoelectric thin film. Therefore, it is possible to realize highly reliable film quality determination with respect to adhesion and piezoelectric characteristics.

  In the inspection step, when the diffused light reflectance is 6% or less, the film quality may be determined to be good. If the reflectance of diffused light is 6% or less, it is considered that there are very few crystal turbidities in the film that cause a decrease in adhesion and piezoelectric properties because there are very few white turbid portions in the piezoelectric thin film. Therefore, the film quality can be judged more reliably with respect to the adhesion and the piezoelectric characteristics.

  A method for manufacturing a piezoelectric actuator according to another aspect of the present invention is a method for manufacturing a piezoelectric actuator using the above-described method for manufacturing a substrate with a piezoelectric thin film, wherein the method for manufacturing a substrate with a piezoelectric thin film includes the film forming step. A step of forming a lower electrode as an outermost layer of the base layer, and the method of manufacturing the piezoelectric actuator includes a step of forming an upper electrode on the piezoelectric thin film determined to have a good film quality in the inspection step And a step of forming a pressure chamber in the substrate on which the upper electrode is formed.

  A lower electrode is formed as the outermost layer of the underlayer, and after forming the piezoelectric thin film, an upper electrode is formed on the piezoelectric thin film determined to have good film quality, and a pressure chamber is formed on the substrate on which the upper electrode is formed. A piezoelectric actuator is obtained. Since the piezoelectric actuator is configured using a piezoelectric thin film that has been judged to have good film quality, the piezoelectric actuator reduces the occurrence of defects (for example, drive failure as an element) due to the deterioration of the adhesion and piezoelectric characteristics of the piezoelectric thin film. can do.

  An inkjet head manufacturing method according to still another aspect of the present invention is an inkjet head manufacturing method using the above-described piezoelectric actuator manufacturing method, and supports the substrate on which the pressure chamber of the piezoelectric actuator is formed. The substrate includes a step of bonding a nozzle substrate having ink ejection holes to the surface of the support substrate opposite to the piezoelectric thin film formation side with respect to the pressure chamber.

  An ink jet head is obtained by attaching a nozzle substrate to the surface of the support substrate of the piezoelectric actuator opposite to the piezoelectric thin film forming side with respect to the pressure chamber. Since an inkjet head is configured using a piezoelectric thin film that has been determined to have good film quality, the occurrence of defects (for example, ink ejection defects) due to a decrease in the adhesion and piezoelectric characteristics of the piezoelectric thin film is reduced in this inkjet head. Can do.

  A substrate with a piezoelectric thin film according to still another aspect of the present invention is a substrate with a piezoelectric thin film in which a piezoelectric thin film having a perovskite structure is formed on an underlayer including the substrate, and the piezoelectric thin film is irradiated with light, When diffuse light except regular reflection light reflected by the piezoelectric thin film is measured, the reflectance of the diffuse light is 11% or less.

  If a crystal phase (for example, pyrochlore structure) different from the perovskite structure exists in the film of the piezoelectric thin film having the perovskite structure, the adhesion to the underlayer of the piezoelectric thin film and the piezoelectric characteristics are deteriorated. However, by irradiating the piezoelectric thin film with light and measuring the obtained diffused light (diffuse reflected light), it is possible to investigate the cloudiness of the piezoelectric thin film caused by the different crystal phases. When the diffused light reflectance is 11% or less, it is considered that there are few different crystal phases that cause white turbidity in the film of the piezoelectric thin film, so that good adhesion and piezoelectric characteristics can be obtained in the piezoelectric thin film. At this time, since the diffused light does not include specularly reflected light, the reflectance of the diffused light is hardly affected by noise due to the specularly reflected light.

  Thus, it can be recognized that the piezoelectric thin film is a film having good adhesion and piezoelectric characteristics before the fabrication of devices such as piezoelectric actuators and inkjet heads. Therefore, it is possible to produce a device using such a substrate having a piezoelectric thin film with good film quality (substrate with a piezoelectric thin film), and to suppress the occurrence of device defects due to the adhesion of the piezoelectric thin film and the deterioration of the piezoelectric characteristics. .

  The reflectance of the diffused light may be 6% or less. In this case, it is considered that the different crystal phases causing white turbidity are very small in the film of the piezoelectric thin film, so that good adhesion and piezoelectric characteristics can be reliably obtained in the piezoelectric thin film. Therefore, it is possible to manufacture a device using a substrate having such a piezoelectric thin film with good film quality and reliably suppress the occurrence of device defects.

The ABO ₃ type perovskite structure A site element contains at least one of lead, barium, lanthanum, strontium, bismuth, lithium, sodium, calcium, cadmium, magnesium, potassium, and the B site element is zirconium. And titanium, and may further include at least one of vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, scandium, cobalt, copper, indium, tin, gallium, cadmium, iron, and nickel.

  In the configuration in which the piezoelectric thin film has a perovskite structure containing any one of the above elements, the above-described effects can be obtained.

  A piezoelectric actuator according to still another aspect of the present invention includes the above-described substrate with a piezoelectric thin film, and an upper electrode and a lower electrode formed so as to sandwich the piezoelectric thin film from the film thickness direction, and the piezoelectric thin film is formed. A pressure chamber is formed in the substrate.

  Since a piezoelectric actuator is formed using a piezoelectric thin film having good adhesion and piezoelectric characteristics, defects (for example, defective driving as an element) due to a decrease in the adhesion and piezoelectric characteristics of the piezoelectric thin film occur in this piezoelectric actuator. Can be reduced.

  An ink jet head according to still another aspect of the present invention includes the above piezoelectric actuator and a nozzle substrate having ink discharge holes, and the nozzle on which the pressure chamber of the piezoelectric actuator is formed is a support substrate. The substrate is bonded to the surface of the support substrate opposite to the piezoelectric thin film forming side with respect to the pressure chamber.

  Since the inkjet head is configured using a piezoelectric thin film with good adhesion and piezoelectric characteristics, the occurrence of defects (for example, ink ejection defects) due to the deterioration of the adhesion and piezoelectric characteristics of the piezoelectric thin film is reduced in this inkjet head. can do.

  An ink jet head according to still another aspect of the present invention includes a piezoelectric actuator in which a lower electrode and a piezoelectric thin film having a lead-based perovskite structure are formed in this order on an underlayer including a substrate, and an ink discharge hole. And a nozzle substrate having a pressure chamber is formed on the substrate on which the piezoelectric thin film is formed, and the piezoelectric thin film is irradiated with light and reflected by the piezoelectric thin film. When the diffused light excluding regular reflected light is measured, the diffused light has a reflectance of 11% or less.

  By irradiating the piezoelectric thin film used for the piezoelectric actuator constituting the inkjet head with light, and measuring the diffused light (diffuse reflected light) obtained, the crystal phase (for example, pyrochlore structure) different from the lead-based perovskite structure is obtained. The resulting clouded state of the piezoelectric thin film can be examined. When the diffused light reflectance is 11% or less, it is considered that there are few different crystal phases that cause white turbidity in the film of the piezoelectric thin film, so that good adhesion and piezoelectric characteristics can be obtained in the piezoelectric thin film. At this time, since the diffused light does not include specularly reflected light, the reflectance of the diffused light is hardly affected by noise due to the specularly reflected light. Therefore, in an inkjet head configured using a piezoelectric substrate having a lead-based perovskite structure with a good adhesion and piezoelectric characteristics on the lower electrode and a nozzle substrate, the adhesion of the piezoelectric thin film and It is possible to suppress the occurrence of device defects due to the deterioration of the piezoelectric characteristics.

  The thickness of the piezoelectric thin film is preferably 2 μm or more and 6 μm or less. In this case, in the inkjet head, ink can be reliably discharged using the piezoelectric thin film in the above-mentioned film thickness range.

  An ink jet printer according to still another aspect of the present invention includes the above ink jet head, and ejects ink from the ink jet head toward a recording medium. As a result, in an image formed by ink ejection on the recording medium, it is possible to suppress deterioration in image quality due to ink ejection failure.

  Prior to fabrication of devices such as piezoelectric actuators and inkjet heads, the film quality of the piezoelectric thin film that affects adhesion and piezoelectric properties can be recognized. Therefore, it is possible to manufacture a device using a substrate having a piezoelectric thin film with good film quality, and to suppress the occurrence of device defects due to the deterioration of the adhesion and piezoelectric characteristics of the piezoelectric thin film.

1 is an explanatory diagram illustrating a schematic configuration of an inkjet printer according to an embodiment of the present invention. FIG. It is the figure which showed together the top view which shows the schematic structure of the actuator of the inkjet head with which the said inkjet printer is provided, and the A-A 'arrow sectional drawing in the top view. It is sectional drawing of the said inkjet head. It is a flowchart which shows the flow of the process at the time of manufacture of the said inkjet head. It is sectional drawing which shows the manufacturing process of the said inkjet head. It is sectional drawing of the board | substrate with a piezoelectric thin film which formed the piezoelectric thin film on the base layer containing a board | substrate. It is explanatory drawing which shows typically light quantity distribution of the diffused light obtained by irradiating light to a measurement object. It is sectional drawing which shows the manufacturing process of the said board | substrate with a piezoelectric thin film. It is explanatory drawing which shows the relationship between the reflectance of a diffused light, the adhesiveness of a piezoelectric thin film, and evaluation of a piezoelectric characteristic. It is a graph which shows the reflectance spectrum of the diffused light about three piezoelectric thin films from which film quality differs. It is explanatory drawing which shows the crystal structure of a piezoelectric material. It is explanatory drawing shown typically.

  An embodiment of the present invention will be described below with reference to the drawings. In the present specification, when the numerical range is expressed as A to B, the numerical value range includes the values of the lower limit A and the upper limit B.

[Configuration of inkjet printer]
FIG. 1 is an explanatory diagram illustrating a schematic configuration of an inkjet printer 1 according to the present embodiment. The ink jet printer 1 is a so-called line head type ink jet recording apparatus in which an ink jet head 21 is provided in a line shape in the width direction of a recording medium in the ink jet head unit 2.

  The ink jet printer 1 includes an ink jet head unit 2, a feed roll 3, a take-up roll 4, two back rolls 5 and 5, an intermediate tank 6, a liquid feed pump 7, a storage tank 8, and a fixing tank. And a mechanism 9.

  The ink jet head unit 2 ejects ink from the ink jet head 21 toward the recording medium P to perform image formation (drawing) based on image data, and is disposed in the vicinity of one back roll 5. Details of the inkjet head 21 will be described later.

  The feed roll 3, the take-up roll 4 and the back rolls 5 are members each having a cylindrical shape that can rotate about its axis. The feeding roll 3 is a roll that feeds the long recording medium P wound around the circumferential surface toward the position facing the inkjet head unit 2. The feeding roll 3 is rotated by driving means (not shown) such as a motor, thereby feeding the recording medium P in the X direction in FIG.

  The take-up roll 4 is taken out from the take-out roll 3 and takes up the recording medium P on which the ink is ejected by the inkjet head unit 2 around the circumferential surface.

  Each back roll 5 is disposed between the feed roll 3 and the take-up roll 4. One back roll 5 located on the upstream side in the conveyance direction of the recording medium P is opposed to the inkjet head unit 2 while winding the recording medium P fed by the feeding roll 3 around and supporting the recording medium P. Transport toward The other back roll 5 conveys the recording medium P from a position facing the inkjet head unit 2 toward the take-up roll 4 while being wound around and supported by a part of the peripheral surface.

  The intermediate tank 6 temporarily stores the ink supplied from the storage tank 8. The intermediate tank 6 is connected to a plurality of ink tubes 10, adjusts the back pressure of ink in each inkjet head 21, and supplies ink to each inkjet head 21.

  The liquid feed pump 7 supplies the ink stored in the storage tank 8 to the intermediate tank 6 and is disposed in the middle of the supply pipe 11. The ink stored in the storage tank 8 is pumped up by the liquid feed pump 7 and supplied to the intermediate tank 6 through the supply pipe 11.

  The fixing mechanism 9 fixes the ink ejected to the recording medium P by the inkjet head unit 2 on the recording medium P. The fixing mechanism 9 includes a heater for heat-fixing the discharged ink on the recording medium P, a UV lamp for curing the ink by irradiating the discharged ink with UV (ultraviolet light), and the like. Yes.

  In the above configuration, the recording medium P fed from the feeding roll 3 is transported to a position facing the inkjet head unit 2 by the back roll 5, and ink is ejected from the inkjet head unit 2 to the recording medium P. Thereafter, the ink ejected onto the recording medium P is fixed by the fixing mechanism 9, and the recording medium P after ink fixing is taken up by the take-up roll 4. As described above, in the line head type inkjet printer 1, ink is ejected while the recording medium P is conveyed while the inkjet head unit 2 is stationary, and an image is formed on the recording medium P.

  The ink jet printer 1 may be configured to form an image on a recording medium by a serial head method. The serial head method is a method of forming an image by ejecting ink by moving an inkjet head in a direction orthogonal to the transport direction while transporting a recording medium.

[Configuration of inkjet head]
Next, the configuration of the inkjet head 21 will be described. FIG. 2 is a plan view showing a schematic configuration of an actuator 21a (piezoelectric actuator) of the inkjet head 21 and a cross-sectional view taken along the line AA ′ in the plan view. FIG. 3 is a cross-sectional view of the inkjet head 21 in which the nozzle substrate 31 is joined to the actuator 21a of FIG.

  The inkjet head 21 has a thermal oxide film 23, a lower electrode 24, a piezoelectric thin film 25, and an upper electrode 26 in this order on a substrate 22 having a plurality of pressure chambers 22a (openings). The substrate 22, the thermal oxide film 23, and the lower electrode 24 constitute an underlayer that becomes an underlayer when the piezoelectric thin film 25 is formed. However, the underlayer is not limited to these and may be changed as appropriate. Is possible.

  The substrate 22 is configured by a semiconductor substrate or a SOI (Silicon on Insulator) substrate made of a single crystal Si (silicon) alone having a thickness of about 300 to 750 μm, for example. Note that FIG. 2 shows a case where the substrate 22 is configured by an SOI substrate. The SOI substrate is obtained by bonding two Si substrates through an oxide film. The upper wall of the pressure chamber 22a in the substrate 22 (the wall positioned closer to the piezoelectric thin film 25 than the pressure chamber 22a) constitutes a vibration plate 22b serving as a driven film. Displacement (vibration) applies pressure to the ink in the pressure chamber 22a. The substrate 22 on which the pressure chamber 22a is formed is also referred to as a support substrate for supporting the piezoelectric element 27 formed thereon.

The thermal oxide film 23 is made of, for example, SiO ₂ (silicon oxide) having a thickness of about 0.1 μm, and is formed for the purpose of protecting and insulating the substrate 22.

  The lower electrode 24 is a common electrode provided in common to the plurality of pressure chambers 22a, and is configured by laminating a Ti (titanium) layer and a Pt (platinum) layer. The Ti layer is formed in order to improve the adhesion between the thermal oxide film 23 and the Pt layer. The thickness of the Ti layer is, for example, about 0.02 μm, and the thickness of the Pt layer is, for example, about 0.1 μm. A layer made of TiOx (titanium oxide) may be used instead of the Ti layer.

  The piezoelectric thin film 25 is composed of a ferroelectric thin film having a perovskite structure, such as lead zirconate titanate (PZT), and is provided corresponding to each pressure chamber 22a. The film thickness of the piezoelectric thin film 25 can be, for example, 1 μm or more and 10 μm or less. However, as a piezoelectric actuator for an ink jet head, the film thickness is 2 μm or more and 6 μm or less. Desirable from. In addition, in the ink jet head, a piezoelectric thin film 25 having lead (Pb), that is, having a lead-based perovskite structure is desirable in terms of obtaining good piezoelectric characteristics.

  The upper electrode 26 is an individual electrode provided corresponding to each pressure chamber 22a, and is configured by laminating a Ti layer and a Pt layer. The Ti layer is formed in order to improve the adhesion between the piezoelectric thin film 25 and the Pt layer. The thickness of the Ti layer is about 0.02 μm, for example, and the thickness of the Pt layer is about 0.1 to 0.2 μm, for example. The upper electrode 26 is provided so as to sandwich the piezoelectric thin film 25 from the film thickness direction with the lower electrode 24. Note that a layer made of gold (Au) may be formed instead of the Pt layer.

  The lower electrode 24, the piezoelectric thin film 25, and the upper electrode 26 constitute a piezoelectric element 27 for discharging ink in the pressure chamber 22a to the outside. The piezoelectric element 27 is driven based on a voltage (drive signal) applied from the drive circuit 28 to the lower electrode 24 and the upper electrode 26. The inkjet head 21 is formed by arranging the piezoelectric element 27 and the pressure chamber 22a vertically and horizontally.

  A nozzle substrate 31 is bonded to the substrate 22 on which the pressure chamber 22a is formed on the side opposite to the piezoelectric thin film 25 forming side. The nozzle substrate 31 is formed with an ink discharge hole (nozzle hole) 31a for discharging the ink stored in the pressure chamber 22a to the outside as ink droplets. Ink supplied from the intermediate tank 6 is stored in the pressure chamber 22a.

  In the above configuration, when a voltage is applied from the drive circuit 28 to the lower electrode 24 and the upper electrode 26, the piezoelectric thin film 25 is in a direction perpendicular to the thickness direction (substrate) according to the potential difference between the lower electrode 24 and the upper electrode 26. (Direction parallel to the surface of 22). Then, due to the difference in length between the piezoelectric thin film 25 and the diaphragm 22b, a curvature is generated in the diaphragm 22b, and the diaphragm 22b is displaced (curved or vibrated) in the thickness direction.

  Therefore, if ink is accommodated in the pressure chamber 22a, a pressure wave is propagated to the ink in the pressure chamber 22a by the vibration of the vibration plate 22b described above, and the ink in the pressure chamber 22a is ejected from the ejection hole 31a. Is discharged to the outside.

[Inkjet head manufacturing method]
Next, the manufacturing method of the inkjet head 21 of this embodiment is demonstrated below. FIG. 4 is a flowchart showing the flow of processing when manufacturing the inkjet head 21. In this embodiment, a substrate preparation step (S1), a thermal oxide film formation step (S2), a lower electrode formation step (S3), a piezoelectric thin film formation step (S4), an inspection step (S5), an upper electrode formation step ( The inkjet head 21 is manufactured by performing the pressure chamber forming step (S7) and the nozzle substrate bonding step (S8) in this order. Among these, S1 to S5 correspond to the manufacturing process of the substrate with the piezoelectric thin film, and S1 to S7 correspond to the manufacturing process of the piezoelectric actuator. Hereinafter, the details of each step will be described with reference to FIG. FIG. 5 is a cross-sectional view showing the manufacturing process of the inkjet head 21.

(S1; substrate preparation process)
First, the substrate 22 is prepared. As the substrate 22, crystalline silicon (Si) often used in MEMS (Micro Electro Mechanical Systems) can be used. Here, two Si substrates 22 c and 22 d are bonded via an oxide film 22 e. An SOI structure is used.

(S2: thermal oxide film formation step)
The substrate 22 is put in a heating furnace and held at about 1500 ° C. for a predetermined time, and thermal oxide films 23a and 23b made of SiO ₂ are formed on the surfaces of the Si substrates 22c and 22d, respectively.

(S3; lower electrode forming step)
Next, Ti and Pt layers are sequentially formed on one thermal oxide film 23a by a sputtering method to form the lower electrode 24. As a result, a base layer composed of the substrate 22, the thermal oxide film 23a, and the lower electrode 24 is formed. That is, the lower electrode 24 is located in the outermost layer on the side opposite to the substrate 22 in the base layer.

(S4: Piezoelectric thin film forming step)
Subsequently, a piezoelectric thin film 25 having a perovskite structure such as PZT is formed on the substrate 22. More specifically, the substrate 22 is reheated to about 600 ° C., and a PZT layer 25a serving as a displacement film is formed by sputtering. Next, a photosensitive resin 35 is applied to the substrate 22 by a spin coating method, and unnecessary portions of the photosensitive resin 35 are removed by exposure and etching through a mask, and the shape of the piezoelectric thin film 25 to be formed is transferred. . Thereafter, using the photosensitive resin 35 as a mask, the shape of the layer 25 a is processed using a reactive ion etching method to form the piezoelectric thin film 25.

(S5: Inspection process)
The film quality of the piezoelectric thin film 25 formed on the substrate 22 is inspected. Details of the inspection process will be described later. In addition, the process demonstrated below is performed only with respect to the board | substrate 22 which has the piezoelectric thin film 25 determined to be film quality with the test | inspection process of S5.

(S6; upper electrode forming step)
Next, Ti and Pt layers are sequentially formed on the lower electrode 24 by a sputtering method so as to cover the piezoelectric thin film 25, thereby forming a layer 26a. Subsequently, a photosensitive resin 36 is applied onto the layer 26a by a spin coating method, and unnecessary portions of the photosensitive resin 36 are removed by exposure and etching through a mask, and the shape of the upper electrode 26 to be formed is transferred. To do. Thereafter, using the photosensitive resin 36 as a mask, the shape of the layer 26a is processed using a reactive ion etching method to form the upper electrode 26.

(S7: pressure chamber forming step)
Next, a photosensitive resin 37 is applied to the back surface (thermal oxide film 23b side) of the substrate 22 by a spin coat method, and unnecessary portions of the photosensitive resin 37 are removed by exposure and etching through a mask. The shape of the pressure chamber 22a to be formed is transferred. Then, using the photosensitive resin 37 as a mask, the substrate 22 is removed using a reactive ion etching method to form a pressure chamber 22a to be an actuator 21a.

(S8; nozzle substrate bonding step)
Thereafter, the substrate 22 of the actuator 21a and the nozzle substrate 31 having the ink discharge holes 31a are bonded using an adhesive or the like. Thereby, the inkjet head 21 is completed. The intermediate glass having a through hole at a position corresponding to the ink discharge hole 31a is used, the thermal oxide film 23b is removed, and the substrate 22 and the intermediate glass, and the intermediate glass and the nozzle substrate 31 are anodically bonded. May be. In this case, the three parties (substrate 22, intermediate glass, nozzle substrate 31) can be joined without using an adhesive.

[Details of inspection process]
FIG. 6 is a cross-sectional view of a substrate with a piezoelectric thin film in which a piezoelectric thin film 25 is formed on an underlayer including the substrate 22. In the piezoelectric thin film 25, if a crystal phase 41 (for example, pyrochlore structure) different from the perovskite structure exists on the interface side (substrate 22 side) with the base layer, the crystal of the piezoelectric thin film 25 is grown on the upper layer. The roughness (surface roughness) of the surface of the piezoelectric thin film 25 is changed, so that a convex portion 42 is formed on the surface, or the crystal state and composition in the vicinity of the grain boundary 25b of the columnar crystal constituting the piezoelectric thin film 25 are changed. As a result, a gap 43 is formed in the grain boundary 25b. In this case, when the piezoelectric thin film 25 is irradiated with light, the light is reflected by the different crystal phases 41, the light is reflected by the convex portions 42 on the surface of the piezoelectric thin film 25, and the light in the gap 43 of the grain boundary 25b is reflected. The reflection causes a white turbidity phenomenon in which the piezoelectric thin film 25 appears white turbid. In addition, when the crystal phase 41 different from the perovskite structure capable of obtaining good piezoelectric characteristics exists on the interface side with the underlayer, not only the piezoelectric characteristics are deteriorated, but also the adhesion with the underlayer (lower electrode 24). Cause a drop.

  Even if the piezoelectric thin film 25 is formed under the same conditions, if the different crystal phase 41 is suddenly generated in the piezoelectric thin film 25 due to slight compositional variation during film formation or disturbance of the environment during crystallization, the piezoelectric thin film 25 The film quality of the thin film 25 may change and become defective after device fabrication. It has been found that such a piezoelectric thin film 25 has a high degree of white turbidity due to the above-described white turbidity phenomenon. The degree of white turbidity is an index indicating the light scattering property, and can be quantified by the reflectance of diffused light.

  Therefore, in this embodiment, in the inspection process described above, light is irradiated to the piezoelectric thin film 25 formed on the underlayer, and diffused light (diffuse reflected light) reflected by the piezoelectric thin film 25 is measured (detected). The quality of the piezoelectric thin film 25 is determined based on the measurement result (measured reflectance). By measuring the diffused light, the cloudiness of the piezoelectric thin film 25 caused by the different crystal phases 41 can be examined. Therefore, the piezoelectric thin film 25 that affects the adhesion and the piezoelectric characteristics based on the measurement result of the diffused light. The quality of the film quality can be determined.

  For example, if the reflectance of diffused light is 11% or less, it can be determined that there is little crystal phase 41 that causes white turbidity in the film of the piezoelectric thin film 25. Also, the piezoelectric characteristics are good, and it can be judged that the film quality is good. In particular, if the reflectance of diffused light is 6% or less, the crystal phase 41 that is different in the film of the piezoelectric thin film 25 is very small. Therefore, it can be determined that the adhesion and piezoelectric characteristics of the piezoelectric thin film 25 are further improved. The basis for the reflectivity of 11% or 6% will be described later.

  As described above, by irradiating the piezoelectric thin film 25 with light and determining the quality of the piezoelectric thin film 25 based on the measurement result of the diffused light reflected by the piezoelectric thin film 25, the piezoelectric actuator 21a and the inkjet head Before manufacturing a device such as 21, it is possible to recognize whether or not the formed piezoelectric thin film 25 is a film that causes a device failure due to a decrease in adhesion and piezoelectric characteristics. As a result, devices such as the piezoelectric actuator 21a and the ink-jet head 21 described above are manufactured using the substrate 22 (substrate with piezoelectric thin film) having the piezoelectric thin film 25 with good film quality, and device defects such as defective driving and defective ink ejection are produced. Can be prevented from occurring.

  In particular, since the piezoelectric thin film 25 is irradiated with light and diffused light is measured, the film quality of the piezoelectric thin film 25 can be inspected nondestructively. Further, when measuring diffused light, an existing reflectance measuring device to be described later can be used instead of a special device, so that the film quality can be inspected at low cost.

  Here, FIG. 7 schematically shows a light amount distribution of diffused light (diffuse reflected light) when the measurement object is irradiated with light. As a method for measuring the reflectance of diffused light, there are an SCI (Specular Compenent Include) method and an SCE (Specular Compenent Exclude) method. The SCI method is a method for measuring diffused light including specularly reflected light, and the SCE method is a method for measuring diffused light excluding specularly reflected light. Each measurement method is CIE (International Commission on Illumination) No. 15, ASTM (American Society for Testing and Materials) E1164, JIS (Japanese Industrial Standards) Z8722, ISO (International Organization for Standardization) / D / S / 7724/1.

  The regular reflection light generated when the piezoelectric thin film 25 is irradiated with light is generated by regular reflection on the surface irrespective of the film quality of the piezoelectric thin film 25 (existence of the crystal phase 41). Even if the diffused light to be measured includes specularly reflected light, the quality of the piezoelectric thin film 25 can be judged based on the measurement result of the diffused light, but the specularly reflected light becomes noise and the quality of the film is good. There is a concern that the determination accuracy will be reduced.

  Therefore, in the inspection process, it is desirable to measure diffused light excluding specularly reflected light (SCE method) and determine the quality of the piezoelectric thin film 25 based on the measurement result. Thereby, the influence of the noise by specular reflection light can be reduced, and the determination accuracy of the film quality based on the measurement result of diffused light can be improved.

〔Example〕
Next, specific examples of a method for manufacturing a substrate with a piezoelectric thin film used for manufacturing a piezoelectric actuator and an inkjet head will be described. FIG. 8 is a cross-sectional view showing the manufacturing process of the substrate 50 with a piezoelectric thin film.

  First, a thermal oxide film 52 having a thickness of about 100 nm was formed on a substrate 51 made of a single crystal Si wafer having a thickness of about 625 μm. The thickness of the wafer may be 300 μm to 725 μm, and the diameter may be a standard value of a commercially available wafer such as 3 to 8 inches. The thermal oxide film 42 can be formed by exposing the Si wafer to a high temperature of about 1200 ° C. in an oxygen atmosphere using a wet oxidation furnace. The substrate 51 and the thermal oxide film 52 correspond to the substrate 22 and the thermal oxide film 23 in FIG. 2, respectively.

  Next, on the thermal oxide film 52, a layer made of titanium oxide (TiOx) having a thickness of about 20 nm is formed as an adhesion layer, and an electrode layer made of platinum (Pt) is formed in a thickness of about 10 nm to form a lower electrode. 53 was formed. As a result, a base layer composed of the substrate 51, the thermal oxide film 52, and the lower electrode 53 is formed. The titanium oxide constituting the lower electrode 53 may be formed by reactive sputtering, or after only forming titanium first, annealing in an oxidizing atmosphere is performed in an RTA (Rapid Thermal Anneal) furnace or a muffle furnace. May be.

The film forming conditions for forming titanium oxide by reactive sputtering are substrate temperature: 350 ° C., Ar flow rate: 20 sccm, O ₂ : flow rate 1 sccm, pressure: 0.4 Pa, and RF power applied to the target: 200 W. . In the case where only titanium is formed first and annealing is performed after the film formation, instead of reactive sputtering, the substrate temperature in the oxygen atmosphere is about 730 ° C. and the heating time is 30 minutes.

  The sputtering conditions for Pt are Ar flow rate: 20 sccm, pressure: 0.4 Pa, RF power applied to the target: 150 W, and substrate temperature: 530 ° C. The lower electrode 53 corresponds to the lower electrode 24 in FIG. Pt becomes a film having (111) orientation due to its self-orientation, but Pt crystallinity affects the film quality of the PZT thin film formed on Pt, so it is desirable that Pt has high crystallinity. .

Subsequently, the Si wafer with Pt was put into a dielectric thin film forming apparatus, and a piezoelectric thin film 54 made of PZT having a thickness of 5 μm was formed by sputtering. The sputtering conditions at this time are Ar flow rate: 20 sccm, O ₂ flow rate: 0.6 sccm, pressure: 0.5 Pa, substrate temperature: 600 ° C., and RF power applied to the target: 500 W. Thereby, the board | substrate 50 with a piezoelectric thin film is obtained.

  Here, it is desirable to increase the amount of Pb in the PZT target in order to compensate for Pb loss during the high-temperature deposition of PZT. The amount of Pb in the target is at least 1.2 mol%, preferably 1.3 to 1.5 mol%, when the amount of Pb in the stoichiometric composition of PZT is 1 mol%.

  A plurality of PZT films were formed by such a film forming method, and the reflectance of the diffused light was measured by a reflectance measuring device. As the reflectance measuring device, a spectrocolorimeter (for example, CM-3600d manufactured by Konica Minolta or its successor) can be used. In the above apparatus, the reflectance of the diffused light was measured by the SCE method after the reflectance was normalized by the reference sample according to the above-mentioned standard. At this time, the reflectance of diffused light including regular reflection may be measured by the SCI method. However, by using the SCE method of measuring the reflectance of diffused light excluding regular reflected light, the diffused light is more sensitive. It can be measured.

  As described above, when the reflectance of diffused light is measured by irradiating the PZT thin film with light, for example, the central part and the outer peripheral part of the wafer may be measured at several places. At this time, as a measurement location of the outer peripheral portion, for example, a position of 5 to 10 mm from the outer peripheral end may be measured.

  FIG. 9 shows the relationship between the diffused light reflectance measured by irradiating a plurality of PZT thin films with light, and the evaluation of the adhesion and piezoelectric characteristics of the piezoelectric thin film. For the above-mentioned adhesion and piezoelectric characteristics, in order to evaluate all of the formed piezoelectric thin films, the device (actuator 21a) was manufactured by the method shown in FIG. And the adhesion of the piezoelectric thin film with the substrate and the piezoelectric constant of the device were investigated.

Specifically, for adhesion, the voltage applied to the upper electrode and the lower electrode sandwiching the piezoelectric thin film was increased, the amount of displacement of the piezoelectric thin film when the piezoelectric thin film was peeled off, and evaluated according to the following criteria. As a specification required for the adhesion of the piezoelectric thin film, 80 MPa is one standard as the shear stress of the film (stress in the direction perpendicular to the film thickness). In other words, if the piezoelectric thin film is peeled off from the base at a shear stress of 80 MPa or less, the specification is not satisfied and the product becomes a defective product. Since the shear stress and the displacement amount of the piezoelectric thin film are in a correspondence relationship, it is possible to determine whether the specification is satisfied, that is, whether the adhesion is good or not, by monitoring the displacement amount.
≪Adhesion evaluation criteria≫
○ The piezoelectric thin film did not peel even when the piezoelectric thin film was displaced by a displacement amount at which the shear stress was 80 MPa.
X: When the piezoelectric thin film was displaced by a displacement amount at which the shear stress was 80 MPa or less, the piezoelectric thin film was peeled off.

Regarding the piezoelectric constant, | d ₃₁ | was determined by a known method from the relationship between the applied voltage and the displacement amount of the piezoelectric thin film, and evaluated based on the following criteria.
≪Piezoelectric property evaluation criteria≫
◎ ... | d ₃₁ | is 160 pm / V or more.
O ... | d ₃₁ | is 140 pm / V or more and less than 160 pm / V.
×... | D ₃₁ | is less than 140 pm / V.

  Note that the minimum number of batches (number of lots) is desirably 10 or more in order to determine whether the product is non-defective or defective.

As a result of the evaluation, as shown in FIG. 9, when the diffused light reflectance was 11% or more, both the adhesion and the piezoelectric characteristics of the piezoelectric thin film were poor (x). However, when the diffused light reflectance is in the range of 6 to 11%, the adhesiveness of the piezoelectric thin film is good (◯), and the piezoelectric properties are also good, with | d ₃₁ | being 140 to 160 pm / V. )Met. Further, when the reflectance of diffused light is less than 6%, the adhesion of the piezoelectric thin film is good (◯), and the piezoelectric property is | d ₃₁ | is 160 to 180 pm / V, which is even better (◎ )Met.

  Therefore, from the above, when the diffused light reflectance is 11% or less, preferably 6% or less, it can be determined that the film quality is good with respect to adhesion and piezoelectric characteristics, and the film quality can be determined with high reliability.

  In addition, the reflectance of the diffused light in each piezoelectric thin film shown in FIG. 9 shows the highest value as a representative value among the reflectances measured in the wavelength range of 360 nm to 740 nm. FIG. 10 shows diffuse reflectance spectra for three piezoelectric thin films A, B and C having different film qualities as an example. It can be seen that the points A to C in FIG. 9 plot the representative values (maximum values) of the reflectance in the piezoelectric thin films A to C in FIG. 10.

  As a result of evaluating the film quality of various piezoelectric thin films, the minimum value of the diffused light reflectance was 0.5%. This is presumably because there is almost no diffuse reflection on the underlying layer below the piezoelectric thin film, and there is no diffusion on the piezoelectric thin film depending on the film conditions.

  In the above, the quality determination of the film quality of the piezoelectric thin film is performed based on the reflectance of the diffused light itself, but it may be performed based on the reflectance fluctuation rate obtained with the piezoelectric thin film of good film quality. For example, the average value of the diffuse reflectance of the piezoelectric thin film having good film quality (reflectance of 11% or less) shown in FIG. 9 is 7.7%, and its standard deviation 1σ is 2.4%. Considering the variation of the measurement system in addition to the average value of the reflectance and its variation (standard deviation), the upper limit (reference) R of the reflectance that can be determined to be good film thickness is 7.7 + 2.4 + α (%) By this formula, for example, R = 11 (%) or other values can be set.

  As described above, by measuring the reflectivity of diffused light related to the white turbidity of the piezoelectric thin film and judging the quality of the piezoelectric thin film based on the measurement results, both adhesion and piezoelectric characteristics were excellent. Whether or not a piezoelectric thin film is formed can be grasped before device fabrication. Thereby, it is possible to eliminate in advance the defective product film that occurs suddenly when the film is repeatedly formed before the device is manufactured, and it is possible to suppress the occurrence of the device defect after the device is manufactured.

[Other materials for piezoelectric thin film]
In this embodiment, PZT has been described as an example of a piezoelectric thin film material having an ABO ₃ type perovskite structure, but is not limited to this PZT. ABO ₃ type perovskite structure A site elements are lead (Pb), barium (Ba), lanthanum (La), strontium (Sr), bismuth (Bi), lithium (Li), sodium (Na), calcium It may contain at least one of (Ca), cadmium (Cd), magnesium (Mg), and potassium (K). The B site elements include zirconium (Zr) and titanium (Ti), and vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W ), Manganese (Mn), scandium (Sc), cobalt (Co), copper (Cu), indium (In), tin (Sn), gallium (Ga), cadmium (Cd), iron (Fe), nickel (Ni ) May be included. Even when a piezoelectric thin film having a perovskite structure composed of a combination of the above metals (elements) is formed, a substrate with a piezoelectric thin film is manufactured by applying the inspection method and manufacturing method described in this embodiment, and this is used. Thus, a piezoelectric actuator, an inkjet head, and an inkjet printer can be configured.

[Others]
The substrate with a piezoelectric thin film described in the present embodiment can be applied to various devices such as an ultrasonic sensor, an infrared sensor, a frequency filter, and a nonvolatile memory in addition to a piezoelectric actuator, an inkjet head, and an inkjet printer.

  In this embodiment, the adhesion is evaluated based on the amount of displacement of the piezoelectric thin film, but the adhesion may be evaluated by a scratch test based on JIS standards. The piezoelectric constant may be measured by a conventionally known cantilever method.

  The method for manufacturing a substrate with a piezoelectric thin film according to the present invention can be used for manufacturing, for example, a piezoelectric actuator and an inkjet head.

1 Inkjet Printer 21 Inkjet Head 21a Actuator (Piezoelectric Actuator)
22 Substrate (support substrate, underlayer)
22a Pressure chamber 23 Thermal oxide film (underlayer)
24 Lower electrode (underlayer)
25 Piezoelectric thin film 26 Upper electrode 31 Nozzle substrate 31a Ink ejection hole 50 Substrate with piezoelectric thin film 51 Substrate (support substrate, underlayer)
52 Thermal oxide film (underlayer)
53 Lower electrode (underlayer)
54 Piezoelectric thin film

Claims (14)

A film forming step of forming a piezoelectric thin film having a perovskite structure on an underlayer including a substrate;
The piezoelectric thin film includes an inspection step of irradiating the piezoelectric thin film with light and determining the quality of the piezoelectric thin film based on a measurement result of diffused light reflected by the piezoelectric thin film. A method for manufacturing a substrate with a thin film.   2. The method for manufacturing a substrate with a piezoelectric thin film according to claim 1, wherein in the inspection step, the quality of the film is determined based on a measurement result of the diffused light excluding regular reflection light.   3. The method for manufacturing a substrate with a piezoelectric thin film according to claim 2, wherein in the inspection step, the film quality is determined to be good when the diffused light reflectance is 11% or less.   The method for manufacturing a substrate with a piezoelectric thin film according to claim 2 or 3, wherein in the inspection step, the film quality is determined to be good when the reflectance of the diffused light is 6% or less. A method for manufacturing a piezoelectric actuator using the method for manufacturing a substrate with a piezoelectric thin film according to claim 1,
The method for manufacturing a substrate with a piezoelectric thin film includes a step of forming a lower electrode as an outermost layer of the base layer before the film forming step,
The method for manufacturing the piezoelectric actuator includes:
Forming an upper electrode on the piezoelectric thin film determined to have good film quality in the inspection step;
And a step of forming a pressure chamber on the substrate on which the upper electrode is formed. An inkjet head manufacturing method using the piezoelectric actuator manufacturing method according to claim 5,
When the substrate on which the pressure chamber of the piezoelectric actuator is formed is a support substrate,
An inkjet head manufacturing method comprising a step of bonding a nozzle substrate having an ink discharge hole to a surface of the support substrate opposite to the piezoelectric thin film formation side with respect to the pressure chamber. Method. A substrate with a piezoelectric thin film in which a piezoelectric thin film having a perovskite structure is formed on an underlayer including a substrate,
The piezoelectric thin film is characterized in that when the diffused light excluding specularly reflected light is irradiated to the piezoelectric thin film and reflected by the piezoelectric thin film, the diffused light has a reflectance of 11% or less. With board.   The board | substrate with a piezoelectric thin film of Claim 7 whose reflectance of the said diffused light is 6% or less. ABO ₃ type A site element of the perovskite type structure includes at least one of lead, barium, lanthanum, strontium, bismuth, lithium, sodium, calcium, cadmium, magnesium, potassium,
B site elements include zirconium and titanium, and at least one of vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, scandium, cobalt, copper, indium, tin, gallium, cadmium, iron, and nickel. The substrate with a piezoelectric thin film according to claim 7 or 8, wherein the substrate has a piezoelectric thin film. A substrate with a piezoelectric thin film according to any one of claims 7 to 9,
An upper electrode and a lower electrode formed so as to sandwich the piezoelectric thin film from the film thickness direction,
A piezoelectric actuator, wherein a pressure chamber is formed on a substrate on which the piezoelectric thin film is formed. A piezoelectric actuator according to claim 10;
A nozzle substrate having ink ejection holes,
When the substrate on which the pressure chamber of the piezoelectric actuator is formed is a support substrate,
The ink jet head according to claim 1, wherein the nozzle substrate is bonded to a surface of the support substrate opposite to the piezoelectric thin film forming side with respect to the pressure chamber. A piezoelectric actuator in which a lower electrode and a piezoelectric thin film having a lead-based perovskite structure are formed in this order on an underlayer including a substrate;
An ink jet head comprising a nozzle substrate having ink ejection holes,
A pressure chamber is formed on the substrate on which the piezoelectric thin film is formed,
An inkjet head characterized in that the diffused light has a reflectivity of 11% or less when the diffused light except the specularly reflected light is irradiated onto the piezoelectric thin film and reflected by the piezoelectric thin film. .   13. The inkjet head according to claim 11, wherein the piezoelectric thin film has a thickness of 2 μm to 6 μm.   An ink jet printer comprising the ink jet head according to claim 11, wherein ink is ejected from the ink jet head toward a recording medium.

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