JP2008177353A - Piezoelectric element and ink jet head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To sufficiently relax a stress generated between a substrate and a piezoelectric film by arranging an adequate intermediate layer for fulfilling a proper condition. <P>SOLUTION: The piezoelectric element comprises a substrate consisting mainly of a silicon (Si) or an oxide silicon (SiO<SB>2</SB>), the intermediate layer formed on the substrate, a first electrode layer formed on the intermediate layer, a piezoelectric layer formed on the first electrode layer by a lead-based piezoelectric material, and a second electrode layer formed on the piezoelectric layer. The thickness of the intermediate layer plus the first electrode layer is not less than 15% of that of the piezoelectric layer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a piezoelectric element that mutually converts electrical energy and mechanical energy, and more particularly, to a piezoelectric element that includes a film-like piezoelectric body (piezoelectric film). The present invention also relates to an inkjet head to which such a piezoelectric element is applied.

  In recent years, in the field of micro electrical mechanical systems (MEMS), certain functions are manifested by applying an electric or magnetic field, such as dielectrics, piezoelectrics, magnetics, pyroelectrics, and semiconductors. Research has been actively conducted to manufacture elements including functional materials such as electronic ceramics using various film forming techniques.

  For example, in order to enable high-definition and high-quality printing in an inkjet printer, it is necessary to make the ink nozzles of the inkjet head fine and highly integrated. Therefore, miniaturization and high integration are also required for the piezoelectric elements (piezoelectric actuators) that drive the ink nozzles. Therefore, it has been studied to produce a piezoelectric element using a film formation technique that can form a layer thinner than a bulk material and can form a fine pattern.

  By the way, when the piezoelectric element is formed by a film forming technique, heat treatment is usually performed after the piezoelectric film is formed on the substrate in order to improve the crystallinity of the piezoelectric film. Alternatively, the piezoelectric film may be formed while the substrate is heated. However, since the thermal expansion coefficient is generally different between the substrate and the piezoelectric film, cracks occur in the substrate or the piezoelectric film during the heat treatment, during the cooling after the heat treatment, or when the heated substrate is cooled during the film formation. Or the substrate and the piezoelectric film are separated from each other.

For example, a ceramic substrate such as zirconium oxide, alumina, or magnesium oxide is often used as the substrate. Recently, due to the spread of semiconductor processes, silicon (Si) substrates and SOI substrates (Silicon on Insulator substrates: substrates having a structure in which silicon oxide (SiO ₂ ) is inserted between the Si substrate and the surface Si layer) are used. In addition, an attempt has been made to use a substrate mainly composed of silicon and silicon oxide. However, in any case, the thermal expansion coefficient is considerably different between these substrates and piezoelectric ceramics such as PZT.

  As a related technique, Patent Document 1 discloses a substrate, a first electrode formed on the substrate, a piezoelectric thin film formed by heating the substrate on the first electrode, and a piezoelectric thin film on the piezoelectric thin film. A piezoelectric thin film element including a formed second electrode is disclosed. In this piezoelectric thin film element, the thermal expansion coefficient of the piezoelectric thin film is made smaller than the thermal expansion coefficient of the substrate, and the piezoelectric thin film is used as a compression film by the substrate when the temperature is lowered after the piezoelectric thin film is formed. The mechanical strength of the body thin film is maintained (pages 2 and 5). Patent Document 1 also discloses a piezoelectric thin film element in which an intermediate layer is further provided between a substrate and a first electrode (second page).

  However, examples of the substrate having a higher thermal expansion coefficient than that of the piezoelectric film include zirconium oxide, alumina, and magnesium oxide. Generally, such a substrate is not excellent in processing accuracy, so that a fine device is manufactured. It is not suitable for. On the other hand, when attention is paid to processing accuracy, it is desirable to use a Si substrate or an SOI substrate. However, since the thermal expansion coefficient of these substrates is smaller than the thermal expansion coefficient of the piezoelectric film, tensile stress is generated on the piezoelectric film. I can't avoid it.

  On the other hand, when the piezoelectric film contains lead (lead-based piezoelectric film), such as PZT (lead zirconate titanate), the following problems also occur. That is, when a piezoelectric film is formed on a substrate directly or via an electrode, components in the piezoelectric film diffuse to the substrate side. In particular, when a silicon substrate is used, lead diffused from the piezoelectric film easily reacts with silicon to produce lead glass. As a result, in the piezoelectric film, lead is insufficient and lattice defects occur, and sufficient piezoelectric performance cannot be obtained. In addition, in a silicon substrate, there is a problem that the substrate becomes brittle when lead is mixed. Therefore, in order to prevent the diffusion of components at the interface where materials having different components are adjacent to each other, it is necessary to provide an intermediate layer (diffusion prevention layer) between these materials.

  In Patent Document 2, an electro-mechanical conversion element unit composed of an upper and lower electrode and a piezoelectric material layer exhibiting an electro-mechanical conversion effect sandwiched between the electrodes is arranged on a Si substrate, and according to an applied electric signal. In a piezoelectric actuator that deforms a part of a substrate, one or more intermediate layers are formed between the substrate and the electromechanical conversion element portion, and the intermediate layer is formed into an adhesion functional layer, a reaction preventing layer, a film stress with the substrate. It is disclosed that it is composed of a single layer or a plurality of layers having a relaxation function layer.

Patent Document 3 discloses a laminated structure comprising a Si substrate, an intermediate layer having a function of preventing reaction to lead atoms on the Si substrate, and a piezoelectric ceramic containing lead on the intermediate layer. ing. Among them, the piezoelectric ceramic film is formed by an aerosol gas jet deposition method in which an ultrafine particle material is sprayed and deposited on a Si substrate through a nozzle to form a fine shape.
As described above, in Patent Documents 2 and 3, by providing an intermediate layer composed of a single layer or a plurality of layers, both lead diffusion prevention and stress relaxation are achieved.

Patent Document 4 discloses a piezoelectric actuator in which a piezoelectric element including a lower electrode, a piezoelectric film, and an upper electrode is formed on a diaphragm. The piezoelectric film has a close contact area in close contact with the diaphragm. The diaphragm includes at least a first insulating film and a second insulating film that is formed closer to the piezoelectric element than the first insulating film and has a diffusion preventing function. In the second insulating film, at least a portion corresponding to the adhesion region has an amorphous structure. As the second insulating film, a material mainly containing any one of zirconium oxide, aluminum oxide, and titanium oxide is used.
That is, in Patent Document 4, by forming amorphous zirconia or the like as the second insulating film on the diaphragm, lead is prevented from diffusing from the piezoelectric film to the diaphragm side, and the piezoelectric film and the diaphragm To improve the adhesion.

Patent Document 5 discloses an actuator device including a vibration plate and a piezoelectric element including a lower electrode, a piezoelectric layer, and an upper electrode on the vibration plate, and the vibration plate is an insulation made of zirconium oxide (ZrO ₂ ). An actuator device is disclosed that includes at least a body film, and the crystal of the insulator film has a (−111) plane preferentially oriented.
That is, in Patent Document 5, the adhesion between the diaphragm and the piezoelectric layer is enhanced by providing a columnar zirconia layer on the diaphragm.

  Further, Patent Document 6 discloses a step of forming a diaphragm film on a substrate, a step of forming a lower electrode on the diaphragm film, and a piezoelectric film formation for forming a piezoelectric film on the lower electrode. The first step, the step of patterning the piezoelectric film and the lower electrode formed in the first step of forming the piezoelectric body into a predetermined shape, and the vibration on the piezoelectric film left by the patterning and the piezoelectric film removed A method of manufacturing a piezoelectric film element comprising a second piezoelectric film forming step of forming a piezoelectric film on the plate film and a step of forming an upper electrode on the piezoelectric film is disclosed.

Patent Document 7 discloses a piezoelectric element including a lower electrode formed on a ZrO ₂ film, a piezoelectric film formed on the lower electrode, and an upper electrode formed on the piezoelectric film. In the piezoelectric film, a piezoelectric element having a degree of orientation on the 100 plane measured by an X-ray diffraction wide angle method of 40% or more and 70% or less is disclosed.
JP 2004-146640 A (2nd and 5th pages) JP 11-204849 A (first page) JP 2000-328223 A (page 2) JP 2005-168172 A (first and second pages) JP 2005-176433 A (first page) JP 2002-314163 A (2nd page) JP 2001-274472 A (2nd page)

  The inventor of the present application conducted an experiment to insert an intermediate layer under various conditions in order to improve the element diffusion prevention function and the stress relaxation function between the substrate and the piezoelectric film. Then, simply providing a diffusion prevention layer or a stress relaxation layer may cause cracks without obtaining a sufficient stress relaxation effect, or cause piezoelectric distortion without applying a sufficient electric field to the piezoelectric body. It has been found that the problem of not being able to occur arises.

Regarding the material and thickness of the intermediate layer, in Patent Document 6, when forming a piezoelectric film of about 1500 nm (1.5 μm) (paragraph 0038), a ZrO ₂ film of 200 nm to 800 nm is provided (paragraph 0034). It is disclosed that an adhesion layer made of titanium or chromium is provided (paragraph 0035). However, if the ZrO ₂ film or the adhesion layer is made too thick with respect to the piezoelectric film, the expansion and contraction of the piezoelectric film cannot be used efficiently, and the manufacturing cost and time are increased. Therefore, it is desirable to clarify an appropriate thickness that can ensure the functions of the intermediate layer (diffusion prevention, stress relaxation, etc.).

  Therefore, in view of the above points, an object of the present invention is to sufficiently relieve stress generated between the two by disposing an intermediate layer satisfying an appropriate condition between the substrate and the piezoelectric film.

In order to solve the above problems, a piezoelectric element according to one aspect of the present invention includes a substrate mainly composed of silicon (Si) or silicon oxide (SiO ₂ ), an intermediate layer formed on the substrate, A first electrode layer formed on the intermediate layer, a piezoelectric layer formed of a lead-based piezoelectric material on the first electrode layer, and a second electrode layer formed on the piezoelectric layer The total thickness of the intermediate layer and the first electrode layer is 15% or more of the thickness of the piezoelectric layer.

An inkjet head according to one aspect of the present invention includes a substrate mainly composed of silicon (Si) or silicon oxide (SiO ₂ ), an intermediate layer formed on one surface of the substrate, and the intermediate A first electrode layer formed on the layer; a piezoelectric layer patterned on the first electrode layer with a lead-based piezoelectric material; and a second electrode layer formed on the piezoelectric layer A plurality of pressure chambers formed on the other surface of the substrate and filled with a liquid, and a flow path for supplying the liquid to the plurality of pressure chambers, the intermediate layer and the first electrode layer Is 15% or more of the thickness of the piezoelectric layer.

  According to the present invention, the intermediate layer and the first electrode layer (lower electrode layer) are formed so that the total thickness is 15% or more of the piezoelectric layer between the substrate and the piezoelectric film (piezoelectric layer). ), The stress generated in the substrate and the piezoelectric layer can be sufficiently relaxed. As a result, cracks in the substrate or the piezoelectric layer can be suppressed, and the two can be prevented from being separated from each other. Therefore, a high-quality piezoelectric element and an inkjet head including the same can be provided with high yield. become.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, the same reference number is attached | subjected to the same component and description is abbreviate | omitted.
FIG. 1 is a cross-sectional view showing a part of a piezoelectric element according to an embodiment of the present invention.
As shown in FIG. 1, the piezoelectric element includes a substrate 1, an intermediate layer 2, a lower electrode layer 3, a piezoelectric layer (piezoelectric film) 4, and an upper electrode layer 5. In such a structure, an electric field is applied to the piezoelectric layer 4 through the lower electrode layer 3 and the upper electrode layer 5. Thereby, the piezoelectric layer 4 expands and contracts due to the piezoelectric effect. Such a piezoelectric element is applied to, for example, an actuator that drives an inkjet head that ejects ink in an inkjet printer. Or you may utilize as an ultrasonic transducer which transmits / receives an ultrasonic wave in the probe for ultrasonic waves of an ultrasonic diagnosing device.

The substrate 1 is a substrate that can be processed by a semiconductor process, such as a silicon (Si) substrate or an SOI substrate. In the present embodiment, the substrate 1 includes a silicon layer 11 and a silicon thermal oxide (SiO ₂ ) film 12 formed on the surface thereof. The thickness of the substrate 1 varies depending on the application of the piezoelectric element. For example, the thickness of the substrate 1 is about 500 μm to 600 μm, and the thickness of the silicon thermal oxide film 12 is about 500 nm. is there.
In this embodiment, the silicon substrate 1 is used because a pattern such as a fine electrode can be highly integrated on the substrate 1 by using a semiconductor process.

  The intermediate layer 2 prevents the diffusion of elements between the silicon substrate 1 and the piezoelectric layer 4 and relaxes the stress generated in the substrate 1 and the piezoelectric layer 4. In the present embodiment, the intermediate layer 2 has a two-layer structure including a metal oxide layer 21 and an adhesion layer 22 from the silicon substrate 1 side.

The metal oxide layer 21 has a thickness of about 100 nm to 1000 nm, for example. As the metal oxide, it is desirable to use a material having a columnar crystal structure. In this embodiment, zirconium oxide (zirconia: ZrO _x , X≈2) is used. The metal oxide layer 21 mainly has a stress relaxation function and a diffusion prevention function.

  The adhesion layer 22 has, for example, a thickness of about 50 nm, and zirconium (Zr), titanium (Ti), chromium (Cr), nickel (Ni), tantalum (Ta), niobium ( Nb) and a metal or metal oxide containing at least one element. The adhesion layer 22 mainly has a stress relaxation function and a function of improving the adhesion between the metal oxide layer 21 and the lower electrode layer 3.

  Here, the metal oxide layer 21 and the adhesion layer 22 may be formed of different materials. For example, if the former is a metal oxide (for example, zirconium oxide) and the latter is a metal (for example, zirconium), both may contain the same element. Further, both of them may be formed of a metal oxide (for example, zirconium oxide and titanium oxide) as long as they contain different metal elements.

  The total thickness of the intermediate layer 2 is preferably 6% or more of the thickness of the piezoelectric layer 4. This ratio corresponds to the thickness of the intermediate layer 2 being 180 nm (or 900 nm) or more when the thickness of the piezoelectric layer 4 is 3 μm (or 15 μm), for example. The reason for this is that if the intermediate layer 2 is thinned to less than 6% of the thickness of the piezoelectric layer 4, a sufficient stress relaxation effect cannot be obtained, and cracks are generated in the substrate 1 or the piezoelectric layer 4, This is because peeling may occur between the intermediate layer 2 and the lower electrode layer 3.

  In addition, although the boundary of the metal oxide layer 21 and the contact | adherence layer 22 is shown clearly in FIG. 1, these boundaries do not necessarily need to be clear. Even if there is a layer in which the metal oxide layer 21 and the adhesion layer 22 are mixed, it is sufficient if the thickness of the intermediate layer 2 as a whole satisfies the above condition (6% or more of the piezoelectric layer). A stress relaxation effect can be obtained.

  The lower electrode layer 3 has a thickness of about 400 nm to about 1000 nm, and is formed of a metal such as platinum (Pt), gold (Au), iridium (Ir), or ruthenium (Ru). The lower electrode layer 3 is used together with an upper electrode layer 5 to be described later when an electric field is applied to the piezoelectric layer 4 and also has a function of preventing element diffusion between the substrate 1 and the piezoelectric layer 4. Yes.

  In the present embodiment, the total thickness of the intermediate layer 2 and the lower electrode layer 3 is desirably 15% or more of the thickness of the piezoelectric layer 4. This ratio corresponds to the total thickness of the intermediate layer 2 and the lower electrode layer 3 being 450 nm (or 2250 nm) or more when the thickness of the piezoelectric layer 4 is 3 μm (or 15 μm), for example. To do. The reason is that if the thickness of the intermediate layer 2 and the lower electrode layer 3 is made too thin, a sufficient stress relaxation effect cannot be obtained.

  On the contrary, it is not very desirable to make the total thickness of the intermediate layer 2 and the lower electrode layer 3 larger than 50% of the thickness of the piezoelectric layer 4. This is because the expansion and contraction of the piezoelectric layer 4 cannot be used efficiently in a device to which the piezoelectric element is applied. For example, in an inkjet head, there is a risk that the amount of deformation of the substrate with respect to expansion and contraction of the piezoelectric element is small.

  In FIG. 1, the boundary between the intermediate layer 2 and the lower electrode layer 3 is clearly shown, but these boundaries are not necessarily clear. For example, there is no problem even if the adhesion layer 22 and the lower electrode layer 3 are mixed with each other at the boundary between them.

The piezoelectric layer 4 is made of a lead-based piezoelectric ceramic such as PZT (lead zirconate titanate). The upper electrode layer 5 is made of, for example, platinum (Pt) having a thickness of about 500 nm.
The thickness of the piezoelectric layer 4 is desirably about 3 μm or more in order to obtain a sufficient displacement when the piezoelectric layer is expanded and contracted. When the piezoelectric element according to this embodiment is used as a fine device like an actuator for an ink jet head, it is sufficient that the thickness of the piezoelectric layer 4 is about 10 μm at the maximum.

The appropriate thickness ranges of the intermediate layer 2 and the lower electrode layer 3 in such a piezoelectric element are defined based on experiments conducted by the inventors of the present application. The experiment will be described below.
FIG. 2 is a flowchart showing a manufacturing method of the piezoelectric element shown in FIG. FIG. 3 is a table showing the results of this experiment.

First, a method for manufacturing a piezoelectric element will be described.
In step S1 of FIG. 2, a silicon substrate is prepared. Normally, a substrate is formed so as to have a desired shape and thickness depending on the use of the piezoelectric element (for example, an actuator for an inkjet head). In the experiment, a silicon substrate having a thickness of about 525 μm was prepared. . A thermal oxide film having a thickness of about 300 nm is formed on the surface of the silicon substrate.

Next, in step S2, a zirconium oxide (ZrO _x ) layer is formed as a metal oxide layer on the silicon substrate. As a film forming method, for example, a reactive sputtering method using a metal zirconium target and a mixed gas of argon (Ar) and oxygen (O ₂ ) as a sputtering gas is employed. As shown in FIG. 3, in the experiment, the thickness of the zirconium oxide layer was changed in the range of 150 nm to 1000 nm. Here, in FIG. 3, X≈2.

Next, in step S3, a zirconium (Zr) layer or a titanium oxide (TiO _Y ) layer is formed as an adhesion layer on the metal oxide layer.
When forming the zirconium layer, for example, the film is formed by a sputtering method using a metal zirconium target and argon gas as a sputtering gas. In this case, steps S2 and S3 may be performed continuously by changing the type of sputtering gas from argon / oxygen mixed gas to argon gas. In that case, since the composition gradually changes from the zirconium oxide layer (metal oxide layer) to the zirconium layer (adhesion layer), the boundary between the two becomes ambiguous, but there is no problem in the function of the intermediate layer.

On the other hand, when the titanium oxide layer is formed as the adhesion layer, for example, the film is formed by a reactive sputtering method using a metal titanium target and a mixed gas of argon (Ar) and oxygen (O ₂ ) as a sputtering gas. . In the experiment, the thickness of the zirconium layer and the titanium oxide layer was set to 50 nm (see FIG. 3). Here, in FIG. 3, Y≈2.

  Next, in step S5, a platinum (Pt) layer is formed on the adhesion layer as a lower electrode layer. As a film forming method, for example, a sputtering method using a platinum target and argon gas as a sputtering gas is employed. As shown in FIG. 3, in the experiment, the thickness of the platinum layer was set to 500 nm to 800 nm.

  Next, in step S6, a PNN-PZT layer is formed as a piezoelectric layer. In the experiment, a PZT layer was formed by an aerosol deposition (AD) method. The AD method is a film forming method in which a film forming material is deposited on a substrate by spraying an aerosol in which raw material powder (for example, ceramic raw material powder) is dispersed in a gas from a nozzle toward the substrate. The aerosol refers to solid or liquid fine particles floating in a gas.

  FIG. 4 is a schematic diagram showing a film forming apparatus using the AD method. This film forming apparatus includes a gas cylinder 101 provided with a pressure adjusting unit 102, transfer pipes 103 and 106, an aerosol generating chamber 104 provided with a container driving unit 105, and a film forming chamber 107 provided with an exhaust pump 108. And a nozzle holder 109 and a substrate holder 110 provided with a substrate holder driving unit 111.

The gas cylinder 101 is filled with nitrogen (N ₂ ), oxygen (O ₂ ), helium (He), argon (Ar), dry air, or the like used as a carrier gas. The pressure adjustment unit 102 adjusts the flow rate of the carrier gas supplied to the aerosol generation chamber 104 via the transport pipe 103. Raw material powder is disposed in the aerosol generation chamber 104, and the raw material powder is blown up and dispersed by introducing a carrier gas into the aerosol generation chamber 104. The container driving unit 105 agitates the raw material powder by applying vibration or the like to the aerosol generation chamber 104. The aerosol generated in this way is supplied to the injection nozzle 109 via the transport pipe 106.

  The inside of the film forming chamber 107 is maintained at a predetermined degree of vacuum by an exhaust pump 108. The injection nozzle 109 has an opening having a predetermined shape and size, and injects the aerosol supplied from the aerosol generation chamber 104 at a high speed. The substrate holder driving unit 111 moves the substrate holder 110 three-dimensionally. Thereby, the relative position and relative speed between the spray nozzle 109 and the substrate are controlled.

In the film forming apparatus shown in FIG. 4, the raw material powder (PNN-PZT powder) is disposed in the aerosol generation chamber 104 and the substrate 1 on which the intermediate layer (metal oxide layer and adhesion layer) and the lower electrode layer are formed is used. Then, the lower electrode layer side is set on the substrate holder 110 with the nozzle facing. Then, the substrate is maintained at a predetermined film formation temperature (for example, 500 ° C. to 800 ° C.), and the film formation apparatus is driven to spray aerosol from the nozzle 109. Thereby, the raw material powder accelerated at high speed collides with a lower layer such as a substrate or a deposit formed earlier. Thereby, the raw material powder bites into the lower layer, and the raw material powder is crushed at the time of a collision to generate a new crushed surface. When this crushing surface adheres to and bonds to the lower layer, a strong film is formed. In the meantime, the substrate holder 110 is moved at a predetermined speed and repeatedly scanned, whereby a PZT layer having a desired thickness can be formed in a desired region.
According to such an AD method, a film forming mechanism (called a mechanochemical reaction can be used to form a strong and dense film, and a thick film (for example, a thick film that cannot be obtained by a sol-gel method or the like). It is also possible to form a film having a thickness of 3 μm or more.

  Next, in step S7, a platinum (Pt) layer is formed as an upper electrode layer on the piezoelectric layer by a sputtering method or the like. The upper electrode layer may be formed after heat treatment of the piezoelectric layer described later. In the experiment, in order to observe the state of the piezoelectric layer, a sample in which the upper electrode layer was not formed was prepared.

  Next, in step S8, in order to promote crystal grain growth in the piezoelectric layer and improve crystallinity, the laminated body (metal oxide layer to upper electrode layer) including the piezoelectric layer is subjected to heat treatment (post). Anneal). Thereafter, the substrate and the laminate are left to cool at room temperature to complete the piezoelectric element. In the experiment, heat treatment was performed in an atmosphere of about 800 ° C.

The piezoelectric element samples thus manufactured (Examples 1 to 7 and Comparative Examples 1 to 3 in FIG. 3) were evaluated as follows.
First, a laminate including a substrate and a piezoelectric layer was observed, and it was observed whether peeling or cracking occurred in any of the layers.

  Next, about the sample which can observe a cross section, the cross section was observed with the scanning electron microscope (SEM: Scanning Electron Microscope), and the thickness of each layer was measured. In this experiment, since the heat treatment was performed in the atmosphere (step S8), there is a possibility that a part of the layer formed by the metal has been oxidized, but in the microscopic observation, the boundary of all the layers should be confirmed. I was able to. On the other hand, for samples that cannot be observed in a cross section (those that cannot maintain the shape of the sample), the cross section of the sample prepared separately before heat treatment (up to step S7) was observed, and the thickness of each layer was measured. It has been confirmed that the thickness of each layer does not change much before and after the heat treatment.

Furthermore, the following two values were calculated based on the measured thickness of each layer.
(1) Ratio of the thickness of the intermediate layer to the thickness of the piezoelectric layer (%)
= Thickness of intermediate layer (metal oxide layer + adhesion layer) / thickness of piezoelectric layer x 100
(2) Ratio of the thickness of the intermediate layer and the lower electrode layer to the thickness of the piezoelectric layer (%)
= (Metal oxide layer + adhesion layer + lower electrode layer) thickness / piezoelectric layer thickness × 100

Referring to the experimental results in FIG. 3, no cracks were observed in the piezoelectric layer and the substrate in the samples of Examples 1 to 3. In the samples of Examples 4 to 6, cracks were observed at some end portions of the piezoelectric layer, but at other portions, the shape of the sample was maintained to such an extent that it could be sufficiently used as a piezoelectric element. It was. Furthermore, no cracks were observed in the sample of Example 7 in which the material of the adhesion layer was changed to titanium oxide (TiO _Y ).

On the other hand, in the samples of Comparative Examples 1 and 2, the piezoelectric layer was cracked as much as the piezoelectric layer was shattered during the movement of the sample. In Comparative Example 7 in which the material of the adhesion layer was changed to titanium oxide (TiO _Y ), many cracks were generated in the entire piezoelectric layer.

  Pay attention to such results, (1) the ratio of the thickness of the intermediate layer to the thickness of the piezoelectric layer, and (2) the ratio of the thickness of the intermediate layer and the lower electrode layer to the thickness of the piezoelectric layer. Then, when the intermediate layer or the intermediate layer and the lower electrode layer are sufficiently thick with respect to the piezoelectric layer (specifically, the intermediate layer is 6% or more of the piezoelectric layer, or the piezoelectric layer On the other hand, when the intermediate layer and the lower electrode layer are 15% or more), it has been clarified that the piezoelectric layer can be prevented from cracking or peeling from the substrate.

Next, an inkjet head to which a piezoelectric element according to an embodiment of the present invention is applied will be described.
FIG. 5 is a cross-sectional view showing a partial structure of the inkjet head according to the first embodiment of the present invention.
As shown in FIG. 5, the inkjet head includes a substrate 1 and a plurality of piezoelectric elements (a lower electrode layer 3, a piezoelectric layer 4, and an upper electrode layer 5) disposed on the substrate 1 via an intermediate layer 2. And a partition plate 42 that partitions the space on the nozzle plate 41 into a plurality of regions corresponding to the arrangement of the piezoelectric elements. The substrate 1 is an arrangement surface of the piezoelectric elements 3 to 5 and operates as a vibration plate that vibrates (deforms) when the piezoelectric element expands and contracts due to the piezoelectric effect. A plurality of pressure chambers 43 filled with ink are formed by the substrate 1, the nozzle plate 41, and the partition walls 42. A plurality of discharge ports (nozzle portions) 44 are formed in the surface of the nozzle plate 41 so as to correspond to the plurality of pressure chambers 43. In FIG. 5, a mechanism for supplying ink to each pressure chamber 43 is omitted for the sake of simplicity. The intermediate layer 2 includes a metal oxide layer and an adhesion layer (see FIG. 1).

In such an ink jet head, a plurality of piezoelectric elements are formed on one surface of a substrate and a ceramic material or the like is dug on the opposite surface of the substrate in the same manner as described with reference to FIG. Thus, the partition wall 42 separately manufactured and the nozzle plate 41 manufactured by forming an opening in the metal plate can be manufactured by adhering using an adhesive.
When performing printing, the piezoelectric body 4 is expanded and contracted by applying a voltage to the lower electrode 3 and the upper electrode 5 in accordance with a control signal. Thereby, the diaphragm 43 is deformed and the volume of the pressure chamber 43 is changed. As a result, the ink filled in the pressure chamber 43 is pressurized and dropped from the discharge portion 44.

  In FIG. 5, the lower electrode layer 3 is patterned in accordance with the arrangement of the piezoelectric layer 4, but by forming the lower electrode layer 3 continuously over the plurality of piezoelectric layers 4, It may be a common electrode. In FIG. 5, the intermediate layer 2 is continuously arranged on the substrate 1, but a pattern may be formed in accordance with the arrangement of the piezoelectric layer 4.

FIG. 6 is a cross-sectional view showing a partial structure of an ink jet head according to the second embodiment of the present invention.
As shown in FIG. 6, this inkjet head supplies pressure chamber 51, ejection unit (nozzle unit) 52 for ejecting ink, and supply of ink from pressure chamber 51 to ejection unit 52 with respect to the inkjet head shown in FIG. 5. The three-dimensional structure 60 that forms the nozzle flow path 53 and the common flow path 54 for supplying ink to the pressure chamber 51 is formed into a monolithic structure. A method of manufacturing such an ink jet head will be described with reference to FIGS.

  First, as shown in FIG. 7A, a plurality of piezoelectric elements (lower electrode layers) are formed on one surface of the substrate 1 via the intermediate layer 2 in the same manner as described with reference to FIG. 3, the piezoelectric layer 4, and the upper electrode layer). In this embodiment, a silicon substrate of about 30 μm is used, and the thickness of the piezoelectric layer 4 is about 10 μm. FIG. 7 shows one of the piezoelectric layers 3 to 5. The intermediate layer 2 includes a metal oxide layer and an adhesion layer (see FIG. 1).

  Next, as shown in FIG. 7B, a first alumina layer 61 having a thickness of about 10 μm is formed on the surface of the substrate 1 opposite to where the piezoelectric elements 3 to 5 are disposed. It forms so that it may become a pattern. The first alumina layer 61 can be formed by various known methods. When using the AD method, for example, an alumina single crystal powder having an average particle diameter of about 0.3 μm is prepared as a raw material powder. A pattern is formed by using a resist mask on which a predetermined mask pattern is formed. The first alumina layer 61 defines a region of the pressure chamber 51 where the ink is disposed. Thereafter, heat treatment may be performed in order to remove thermal stress generated in the substrate 1 when the first alumina layer 61 is formed.

  Next, as shown in FIG. 7C, the dissolving material 62 is disposed as a sacrificial layer in the pressure chamber 51 by the AD method. The melting material 62 is a material having a hardness that allows film formation by the AD method thereon, and can be removed by wet etching. Specific examples include metal materials such as chromium (Cr) and titanium (Ti), and hard resin materials such as polyurethane resins, polyurethane acrylates, and epoxy resins.

  Next, as shown in FIG. 7D, a second alumina layer 63 is formed by an AD method in a region excluding the flow paths 53 and 54 on the first alumina layer 61 and the dissolved material 62. And as shown to (a) of FIG. 8, the melt | dissolution material 62 is arrange | positioned to the flow paths 53 and 54 as a sacrificial layer by AD method.

  Further, as shown in FIG. 8B, the formation of the third alumina layer 64 and the disposition of the melting material 62, the formation of the fourth alumina layer 65 and the disposition of the melting material 62, and the fifth alumina layer 66 The formation and disposition of the melting material 62, the formation of the sixth alumina layer (nozzle plate) 67 and the disposition of the melting material 62 are sequentially performed. The dissolving material 62 disposed in the third alumina layer 64 to the sixth alumina layer 67 serves as a sacrificial layer for forming ink flow paths and nozzles.

Next, the dissolved material 62 disposed in the first alumina layer 61 to the sixth alumina layer 67 is removed by wet etching. Thereby, as shown in FIG. 6, the pressure chamber 51, the discharge part 52, the nozzle flow path 53, and the common flow path 54 are formed.
In the present embodiment, since an intermediate layer having a sufficient thickness is disposed between the substrate 1 and the piezoelectric elements 3 to 5, the substrate 1 can be used even when heat treatment is performed on the alumina layer forming the pressure chamber. Or it can suppress that a crack arises in the piezoelectric material layer 4, or both peel from each other.

  The present invention relates to a piezoelectric element that mutually converts electrical energy and mechanical energy, and can be used particularly in a piezoelectric element including a film-like piezoelectric body (piezoelectric film). Further, the present invention can be used in an ink jet head to which such a piezoelectric element is applied.

It is sectional drawing which shows the structure of the piezoelectric element which concerns on one Embodiment of this invention. It is a flowchart which shows the manufacturing method of the piezoelectric element shown in FIG. It is a table | surface which shows the result of the experiment which produced the piezoelectric element which concerns on one Embodiment of this invention. It is a schematic diagram which shows the structure of the film-forming apparatus by AD method. It is sectional drawing which shows the structure of a part of inkjet head which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the one part structure of the inkjet head which concerns on the 2nd Embodiment of this invention. It is a figure for demonstrating the manufacturing method of the inkjet head shown in FIG. It is a figure for demonstrating the manufacturing method of the inkjet head shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Intermediate layer 3 Lower electrode layer 4 Piezoelectric layer 5 Upper electrode layer 21 Metal oxide layer 22 Adhesion layer 41 Nozzle plate 42 Partition walls 43 and 51 Pressure chambers 44 and 52 Discharge part (nozzle part)
60 Three-dimensional structure 53 Nozzle flow path 54 Common flow path 61 First alumina layer 62 Dissolving material 63 Second alumina layer 64 Third alumina layer 65 Fourth alumina layer 66 Fifth alumina layer 67 Sixth Alumina layer (nozzle plate)
DESCRIPTION OF SYMBOLS 101 Gas cylinder 102 Pressure adjustment part 103,106 Transfer pipe 104 Aerosol production | generation chamber 105 Container drive part 107 Film formation chamber 108 Exhaust pump 109 Injection nozzle 110 Substrate holder 111 Substrate holder drive part

Claims (11)

A substrate mainly composed of silicon (Si) or silicon oxide (SiO ₂ );
An intermediate layer formed on the substrate;
A first electrode layer formed on the intermediate layer;
A piezoelectric layer formed of a lead-based piezoelectric material on the first electrode layer;
A second electrode layer formed on the piezoelectric layer;
Comprising
A piezoelectric element, wherein a total thickness of the intermediate layer and the first electrode layer is 15% or more of a thickness of the piezoelectric layer. A substrate mainly composed of silicon (Si) or silicon oxide (SiO ₂ );
An intermediate layer formed on the substrate;
A first electrode layer formed on the intermediate layer;
A piezoelectric layer formed of a lead-based piezoelectric material on the first electrode layer;
A second electrode layer formed on the piezoelectric layer;
Comprising
The piezoelectric element, wherein the thickness of the intermediate layer is 6% or more of the thickness of the piezoelectric layer.   The piezoelectric element according to claim 1, wherein the intermediate layer includes a metal oxide.   The said intermediate | middle layer contains the 1st layer formed with the metal oxide on the said board | substrate, and the 2nd layer formed with the metal or the metal oxide on the said 1st layer. Piezoelectric element.   The piezoelectric element according to claim 3 or 4, wherein the metal oxide has a columnar crystal structure. The piezoelectric element according to claim 4, wherein the metal oxide of the first layer contains zirconium oxide (ZrO _X ).   The second layer contains at least one element of zirconium (Zr), titanium (Ti), chromium (Cr), nickel (Ni), tantalum (Ta), and niobium (Nb). The piezoelectric element according to any one of claims 4 to 6, which is contained. The piezoelectric element according to claim 7, wherein the second layer includes zirconium (Zr) or titanium oxide (TiO _Y ).   9. The first electrode layer according to claim 1, wherein the first electrode layer includes any one of platinum (Pt), gold (Au), iridium (Ir), and ruthenium (Ru). Piezoelectric element. A substrate mainly composed of silicon (Si) or silicon oxide (SiO ₂ );
An intermediate layer formed on one side of the substrate;
A first electrode layer formed on the intermediate layer;
A piezoelectric layer patterned with a lead-based piezoelectric material on the first electrode layer;
A second electrode layer formed on the piezoelectric layer;
A plurality of pressure chambers formed on the other surface of the substrate and filled with a liquid;
A flow path for supplying liquid to the plurality of pressure chambers;
Comprising
An ink jet head, wherein a total thickness of the intermediate layer and the first electrode layer is 15% or more of a thickness of the piezoelectric layer. A substrate mainly composed of silicon (Si) or silicon oxide (SiO ₂ );
An intermediate layer formed on one side of the substrate;
A first electrode layer formed on the intermediate layer;
A piezoelectric layer patterned with a lead-based piezoelectric material on the first electrode layer;
A second electrode layer formed on the piezoelectric layer;
A plurality of pressure chambers formed on the other surface of the substrate and filled with a liquid;
A flow path for supplying liquid to the plurality of pressure chambers;
Comprising
An ink jet head, wherein the intermediate layer has a thickness of 6% or more of the thickness of the piezoelectric layer.

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