JP2012119347A - Piezoelectric module, piezoelectric device, and piezoelectric module manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric module which can prevent reduction in piezoelectric displacement and restrict occurrence of cracks in a piezoelectric thin film due to stress concentration at the time of piezoelectric deformation and which exhibits excellent piezoelectric characteristics.SOLUTION: The structure of a piezoelectric module 10 is such that, since a buffer layer LB is provided in an extension area EA, not only is it possible to realize electrical insulation between an upper electrode layer LU and a lower electrode layer LL, it is also possible to have a piezoelectric thin film LP localized in only a drive area MV within a window space WS1. This makes it possible to prevent reduction in piezoelectric displacement, as well as to restrict occurrence of cracks in the piezoelectric thin film LP due to stress concentration at the time of piezoelectric deformation. Furthermore, since an insulation material of the buffer layer LB has the same kind of crystalline structure as that of a piezoelectric material which forms the piezoelectric thin film LP formed on the buffer layer LB, it is possible to increase adhesion properties and also restrict reduction in piezoelectric characteristics.

Description

  The present invention relates to a piezoelectric module, a piezoelectric device, and a method for manufacturing a piezoelectric module.

  In recent years, various piezoelectric modules that deform an elastic film with a piezoelectric thin film have been proposed. As a piezoelectric module, for example, a piezoelectric actuator used in an ink jet printer head or the like forms a window space by removing a part of a substrate, and an elastic film (diaphragm) covers a ceiling portion of the window space. ) Is provided. On the diaphragm, a lower electrode, an island-shaped piezoelectric body (piezoelectric thin film), and an upper electrode are stacked in this order.

  In the piezoelectric actuator having such a configuration, a voltage is applied between the upper and lower electrodes to elastically deform the piezoelectric body. The deformation of the piezoelectric body at that time is transmitted to the diaphragm, and the diaphragm is deformed, thereby producing a required mechanical action. Each of the upper and lower electrodes is electrically connected to the drive circuit, but it is necessary to prevent an electrical short circuit between the wirings.

  Therefore, for example, in the configuration disclosed in Patent Document 1, the extending portion of the piezoelectric body is used for insulating the upper and lower electrodes by extending not only the upper electrode but also the piezoelectric body in the lead-out portion of the upper electrode. The configuration is taken. In the configuration disclosed in Patent Document 2, an insulating layer is formed in a region of the substrate surface where the piezoelectric body is not provided, and an insulating slope that covers the side surface of the piezoelectric body is formed by a part of the insulating layer. A wiring layer provided along the insulating slope is connected to the upper electrode. Further, in the configuration disclosed in Patent Document 3, the lower electrode is formed smaller than the piezoelectric body, and the upper electrode is formed from the substrate surface to the upper portion of the piezoelectric body over the step of the piezoelectric body. By providing the insulating layer so as to cover the electrodes, a configuration is adopted in which the occurrence of a short circuit between the upper and lower electrodes is suppressed.

JP-A-8-116684 JP 2008-227144 A JP 2007-006620 A JP 2008-87471 A

  However, in the configuration as in Patent Document 1, the piezoelectric body extends not only to the movable region on the window space but also to the peripheral region surrounding the movable region, but the substrate is not removed in the peripheral region. A restraining force from the substrate to the piezoelectric body acts on the substrate. As a result, the amount of piezoelectric displacement in the piezoelectric body has been a factor. Further, since the stress of the piezoelectric body is concentrated on the boundary portion between the movable region and the peripheral region, there is a problem that damage such as a crack occurs in a portion of the piezoelectric body on the boundary portion.

  On the other hand, in the configuration as in Patent Document 2 in which the lower electrode is formed larger than the piezoelectric body, it is necessary to insulate the upper electrode from the lower electrode, but it is difficult to say that the structure ensures complete insulation. Further, in Patent Document 3, since the piezoelectric body is formed smaller than the upper electrode, there is no problem with insulation between the upper electrode and the lower electrode. However, in order to realize this configuration, the piezoelectric body is patterned after the lower electrode is patterned. Need to form. However, in this method, the central portion of the piezoelectric body is formed on the patterned lower electrode, while the outer peripheral portion of the piezoelectric body is formed directly on the substrate. In general, when a piezoelectric body is formed in a heated state, the characteristics of the formed piezoelectric body are easily affected by the formation temperature of the piezoelectric body. When the piezoelectric material is formed so as to extend over both the lower electrode and the substrate surface as in the invention of Patent Document 3, the temperature distribution at the time of forming the piezoelectric material tends to be particularly uneven, and the in-plane uniformity is It becomes difficult to form a good piezoelectric body.

  Therefore, as in Patent Document 4, an insulating film is provided so as to cover the substrate surface widely, the lower electrode is disposed below the insulating film, and the extending portion of the piezoelectric body and the upper electrode is disposed on the insulating film. Attempts have been made to improve the uniformity of the formation temperature of the piezoelectric body by arranging and electrically insulating. However, the actual situation is that a piezoelectric thin film excellent in crystal orientation and piezoelectric characteristics cannot be formed on a normal insulating film such as a silicon oxide film.

  The present invention has been made in view of such circumstances, and it is possible to prevent the piezoelectric displacement from being lowered, to suppress generation of cracks in the piezoelectric thin film due to stress concentration during piezoelectric deformation, and to provide excellent piezoelectricity. It is an object to provide a piezoelectric module, a piezoelectric device, and a method for manufacturing the piezoelectric module.

  In order to solve the above-mentioned problems, a first aspect of the present invention is a piezoelectric conversion module that performs conversion between voltage and mechanical deformation using a piezoelectric body disposed on a diaphragm, wherein the diaphragm layer is formed on the support layer. And the support layer is provided with a window space, and the presence of the window space allows the first area corresponding to the window space and the window space to be planarly formed as a planar expansion range. A composite substrate in which a surrounding second region is defined; a lower electrode layer formed on the diaphragm layer and extending over both the first and second regions; a drive area defined in the first region; An insulating buffer layer formed on the lower electrode layer so as to cover both the extended area extending from the drive area onto the second region, and formed on the buffer layer in the drive area A piezoelectric thin film, and an upper electrode layer formed from the driving area on the piezoelectric thin film to the extending area on the buffer layer, and having the same crystal structure as the piezoelectric material forming the piezoelectric thin film The buffer layer is formed of an insulating material.

  The invention of claim 2 is the piezoelectric module according to claim 1, wherein both the piezoelectric material and the insulating material have a perovskite structure.

  The invention according to claim 3 is the piezoelectric module according to claim 2, wherein the piezoelectric material is mainly composed of a PZT (lead zirconate titanate) system.

  The invention of claim 4 is the piezoelectric module according to claim 2, wherein the insulating material is BTO (barium titanate), STO (strontium titanate), PLT (lanthanum lead titanate), PT ( The main component is any one selected from the group consisting of lead titanate), BST (barium strontium titanate), and SRO (strontium ruthenate).

  According to a fifth aspect of the present invention, there is provided the piezoelectric module according to any one of the first to fourth aspects, wherein the piezoelectric module converts between an electrical signal and a mechanical displacement.

  The invention according to claim 6 is the piezoelectric device according to claim 5, wherein the piezoelectric device is configured as an ink jet head by including the piezoelectric module as an ink ejection drive mechanism.

  The invention of claim 7 is a method of manufacturing a piezoelectric module in which a surface shape of the diaphragm is deformed by applying a voltage to a piezoelectric thin film disposed on the diaphragm, wherein (a) the diaphragm layer is formed on the support layer. Providing a composite substrate material in which a first region and a second region surrounding the first region as a planar area are defined as a planar spreading range; and (b) on the diaphragm layer, the first region Forming a lower electrode layer extending over both the first region and the second region; and (c) both a drive area defined in the first region and an extended area extending from the drive area onto the second region. Forming an insulating buffer layer having a perovskite structure formed on the lower electrode layer so as to cover the surface; and (d) a perovskite on the buffer layer in the driving area. Forming a piezoelectric thin film made of a piezoelectric material having a structure; (e) forming an upper electrode layer from the drive area on the piezoelectric thin film to the extending area on the buffer layer; and (f) the above A step of selectively removing the first region of the support layer of the composite material to form a window space, and exposing the diaphragm in the window space.

  According to the first to seventh aspects of the invention, since the buffer layer is responsible for the electrical insulation of the upper and lower electrode layers in the extension area, the piezoelectric thin film can be localized in the drive area in the window space. It has become. Thereby, it is possible to prevent the piezoelectric displacement from being lowered and to suppress the occurrence of cracks in the piezoelectric thin film due to the stress concentration during the piezoelectric deformation.

  In addition, since the insulating material constituting the buffer layer is the same type of crystal structure as the piezoelectric material constituting the piezoelectric thin film, it is possible to increase the crystallinity of the piezoelectric thin film when forming the piezoelectric thin film on the buffer layer. Thus, it is possible to suppress a decrease in piezoelectricity due to the provision of the buffer layer, and it is possible to maintain high adhesion between the buffer layer and the piezoelectric thin film.

It is the figure which showed the external appearance of the inkjet head manufactured by embodiment of this invention. It is the figure which showed the structure of the piezoelectric module manufactured by embodiment of this invention. It is one sectional view showing the important section composition of the piezoelectric module manufactured by the embodiment of the present invention. It is the figure which showed one process in embodiment of this invention. It is the figure which showed one process in embodiment of this invention. It is the figure which showed one process in embodiment of this invention. It is the figure which showed one process in embodiment of this invention. It is the figure which showed one process in embodiment of this invention. It is the figure which showed one process in embodiment of this invention. It is the figure which showed one process in embodiment of this invention. It is the figure which showed one process in embodiment of this invention. It is the figure which showed one process in embodiment of this invention. It is the figure which showed one process in embodiment of this invention. It is the figure which showed one process in embodiment of this invention. It is the figure which showed one process in embodiment of this invention. It is the figure which showed one process in embodiment of this invention. It is the figure which showed one process in embodiment of this invention. It is the figure which showed one process in embodiment of this invention.

<1. Overview of Piezoelectric Devices and Piezoelectric Modules>
The embodiment of the present invention is configured as a piezoelectric module built in an ink jet head and used as an ink ejection drive mechanism.

  In this specification, a functional structure that includes a piezoelectric element and is integrated is called a “piezoelectric module”, and a device that is completed by combining a piezoelectric module with another component independent of the piezoelectric module is called a “piezoelectric module”. It is called “device”.

<1-1. Basic configuration>
FIG. 1 is a perspective view showing an inkjet head 100 to which a piezoelectric module 10 according to an embodiment of the present invention is applied. 2 is a view showing the vicinity of the piezoelectric module 10 in the inkjet head 100, in which FIG. 2 (a) is a top view and FIG. 2 (b) is a view of FIG. 2 (a). It is sectional drawing cut | disconnected by the II line.

  In FIG. 1, an ink jet head 100 is mounted on an ink jet printer (not shown), and one or a plurality of piezoelectric modules (piezoelectric conversion modules) manufactured by a process described later in a substantially rectangular housing HS. 10, circuit components such as a driver circuit and an interface circuit, and mechanical components such as an ink main tank are built in. In response to a print control signal from the ink jet printer main body, the piezoelectric module 10 serving as an ink ejection drive mechanism performs scanning while ejecting ink onto a predetermined recording medium, thereby printing or recording an image on the recording medium. I do. The piezoelectric module 10 discharges ink by performing conversion between the voltage applied to the piezoelectric body arranged on the diaphragm and the mechanical deformation of the piezoelectric body (and the diaphragm).

  As shown in FIG. 2B, the piezoelectric module 10 is roughly divided into a nozzle plate L1, a glass substrate L2, and a body plate L3, which are stacked in this order from the bottom.

  The nozzle plate L1 has a thickness of about 100 to 300 μm and is formed from a flat Si (silicon) substrate. A plurality of nozzle openings 11 that eject ink droplets are formed side by side through holes that pass through the Si substrate in the direction perpendicular to the surface (however, only one is shown in FIG. 2B). The nozzle opening 11 is a two-stage hole including a discharge tip port 11a having a diameter of about 20 μm and a discharge introduction port 11b having a diameter of about 50 μm connected thereto.

  The glass substrate L2 provided on the nozzle plate L1 is also formed with a communication hole penetrating in the direction perpendicular to the surface, and communicates with the upper part of the inlet 11b of the nozzle opening 11. By selectively removing the lower surface of the support layer LS (23), which will be described later, an individual flow path 12 is formed on the glass substrate L2 to send ink to the discharge introduction port 11b of the nozzle.

The body plate L3 is configured such that the diaphragm layer LD (21) is supported by the support layer LS (23). Three layers constituting an SOI (Silicon on Insulator) substrate having a three-layer structure, that is, the support layer LS (Si), the box layer LX (SiO ₂ ), and the active layer LD (Si) from the bottom are supported layers. By selectively removing the LS and the box layer LX, window spaces WS1 and WS2 are formed in the support layer LS and the box layer LX. The presence of the window space WS1 conceptually defines a first area A1 corresponding to the window space WS1 and a second area A2 that planarly surrounds the window space WS1 as a planar expansion range.

  Further, the portion of the active layer LD mainly on the window space WS1 can be relatively easily deformed by losing support from below, and functions as the diaphragm layer LD.

The piezoelectric conversion drive unit of the piezoelectric thin film module 10 is
(1) a lower electrode layer LL (52) formed on the diaphragm layer LD and extending over both the first and second regions A1, A2.
(2) Insulating property formed on the lower electrode layer LL so as to cover both the drive area MV defined in the first area A1 and the extending area EA extending from the drive area MV to the second area A2. Buffer layer LB (53a) of
(3) In the drive area MV defined in the first region A1, the piezoelectric thin film LP (54a) formed on the buffer layer LB;
(4) an upper electrode layer LU (57a) formed in the area of the extending area EA on the buffer layer LB from the drive area MV on the piezoelectric thin film LP;
Is provided.

  Here, the window space WS 1 functions as the pressure generation chamber 14, and the window space WS 2 functions as the common ink chamber 13. The pressure generation chamber 14 and the common ink chamber 13 communicate with each other via the individual flow path 12.

  An electrical wiring connection portion is provided above the upper electrode layer LU, and is electrically connected to the circuit board through the wiring.

  In the piezoelectric module 10 having such a structure, the upper electrode layer LU and the lower electrode layer LL are insulated and separated by the buffer layer LB. The piezoelectric thin film LP exists only in the first region A1 corresponding to the window space WS1, and does not extend to the second region A2. For this reason, the stress at the boundary between the first region and the second region is not applied to the piezoelectric thin film LP.

  Further, corresponding to the feature of the present invention, the buffer layer LB is formed of an insulating material having the same kind of crystal structure as that of the piezoelectric material forming the piezoelectric thin film LP. Specifically, the piezoelectric thin film LP is formed by PZT (lead zirconate titanate) having a perovskite structure as a crystal structure, and the buffer layer LB is formed by PLT (lead lanthanum titanate) having the same perovskite structure as a crystal structure. Is formed. By having the same kind of crystal structure, the crystallinity of the piezoelectric thin film LP formed on the buffer layer LB is improved, and the piezoelectric characteristics are also improved. This point will be mentioned later in the explanation of the manufacturing method.

<1-2. Basic operation>
A voltage is applied between the lower electrode layer LL and the upper electrode layer LU in accordance with a print control signal from the ink jet printer main body, whereby the piezoelectric thin film LP is deformed so as to shrink in the in-plane direction. Due to the deformation force, the diaphragm layer LD is deformed so as to protrude downward, and the volume of the pressure generating chamber 14 is reduced. As a result, the ink supplied into the pressure generating chamber 14 is ejected from the nozzle opening 11 as ink droplets. By reversing the polarity of the voltage applied between the lower electrode layer LL and the upper electrode layer LU, the piezoelectric thin film LP and the diaphragm layer LD are deformed so as to protrude upward, and the volume of the pressure generating chamber 14 is increased. Thus, the ejection of ink droplets is stopped and the replenishment of ink is introduced into the pressure generating chamber 14.

  Images and characters are printed on the recording medium by relatively scanning the recording medium and the inkjet head and repeating such operations while turning on / off the print control signal.

<2. Manufacturing method of piezoelectric module>
In describing the method for manufacturing a piezoelectric module according to the present invention, the piezoelectric module 10 to be manufactured has a function of deforming the surface shape of the diaphragm by applying a voltage to the piezoelectric thin film LP disposed on the diaphragm as described above, and is an inkjet printer. It is assumed that it is used as a thin film actuator head for use.

  FIG. 3 is a cross-sectional view of the piezoelectric module 10 cut along the line II-II in FIG. 2A, which is produced by the method for manufacturing a piezoelectric module according to the embodiment of the present invention. 4-18 is sectional drawing which shows each step of embodiment of the manufacturing method of the piezoelectric module by this invention cut | disconnected by the II-II line | wire of Fig.2 (a).

  Hereinafter, a method of manufacturing the piezoelectric module 10 of FIG. 3 will be described with reference to FIGS.

<2-1. Preparation of composite substrate material>
First, an SOI substrate 1 is prepared as a composite substrate material including a semiconductor as shown in FIG. In this SOI substrate 1, thermal oxide films 20a and 20b are formed on both main surfaces MS1 and MS2, and an active layer 21 (about 5 μm thick) is formed between the thermal oxide films 20a and 20b from above. Diaphragm layer LD), box layer 22 (LX) having a thickness of about 0.2 μm, and support layer 23 (LS) having a thickness of about 100 to 600 μm.

  As shown in FIG. 2, the SOI substrate 1 includes a first area A1 corresponding to the expansion of the window space WS1 and a second area A2 that surrounds the first area A1 as a planar expansion range. Is included.

<2-2. Manufacturing process on the first main surface side>
Next, a manufacturing process on the first main surface (upper surface in FIG. 4) MS1 on which the piezoelectric thin film LP is formed of both main surfaces of the SOI substrate 1 will be described in order with reference to FIGS.

  (First Step) The lower electrode layer LL that uniformly spreads over the entire surface of the diaphragm layer LD (and therefore over both the first region A1 and the second region A2) is formed.

First, as shown in FIG. 5, Ti (titanium) is uniformly formed on the surface of the thermal oxide film 20a on the first main surface MS1 side by a sputtering method so as to have a thickness of 20 nm, and then in an oxygen atmosphere. Oxidized with TiO _x (titanium oxide). Subsequently, Pt (platinum) is uniformly formed by sputtering so as to have a thickness of 100 nm. TiO _x is formed on the surface of the adhesion layer 51, Pt is the lower electrode layer 52 first main surface MS1 side of the thermal oxide film 20a of the SOI substrate 1 in this order in the purpose is to function as a (lower electrode layer LL) To do.

  (Second Step) As shown in FIG. 6, an insulating buffer layer LB having a perovskite structure is formed uniformly over the lower electrode layer LL. Therefore, the buffer layer LB covers both the drive area MV (FIG. 2) defined in the first area A1 and the extending area EA (also FIG. 2) extending from the drive area MV to the second area A2. It will be.

  Specifically, the buffer layer 53 is formed by sputtering using PLT (lead lanthanum titanate), which is known to easily form a stable and high-quality thin film having a perovskite structure, so as to have a film thickness of 100 nm. To form uniformly. As the film forming method, an organic metal thermal decomposition method (MOD method) or a chemical vapor deposition method (CVD method) may be used in addition to the sputtering method.

  (Third Step) In the drive area MV of FIG. 2, a piezoelectric thin film LP made of a piezoelectric material having a perovskite structure is formed on the buffer layer LB.

  First, as shown in FIG. 7, PZT (lead zirconate titanate) is uniformly formed on the buffer layer 53 by sputtering at a temperature of 600 ° C. so as to have a film thickness of 5 μm. Although it is difficult for PZT to form a good perovskite structure with stable composition and crystal orientation with good reproducibility, a buffer layer 53 made of an insulating oxide having a perovskite structure such as PLT is formed in advance. In addition, by forming on the buffer layer 53, the PZT thin film 54 having excellent characteristics can be stably formed with good reproducibility, and the high current pressure can be secured by suppressing the leakage current. It is possible to increase the function of

  Subsequently, a resist is uniformly coated on the PZT thin film layer 54 in FIG. 7, and selectively exposed and developed to pattern the PZT thin film layer 54 as shown in FIG. A resist pattern 55 having a diameter of 200 μm is formed.

  Thereafter, as shown in FIG. 9, a PZT pattern having a diameter of 200 μm, that is, a PZT thin film layer 54a is formed by ICP dry etching using PZT using a chlorine-based or fluorine-based gas with the resist pattern 55 as a mask. Etching may be wet etching using a hydrofluoric acid solution. That is, the piezoelectric thin film LP is formed by removing a portion of the PZT thin film layer 54 outside the drive area MV by this etching. Thereby, the lateral constraint by the piezoelectric thin film LP can be released, the piezoelectric displacement of the diaphragm layer LD can be prevented from being lowered, the piezoelectric displacement can be enlarged, and the problem of cracking can be avoided.

  Thereafter, a resist is uniformly coated on the piezoelectric thin film LP and the buffer layer 53 in FIG. 9, and selectively exposed and developed to pattern the buffer layer 53 as shown in FIG. A resist pattern 55a having a diameter of 210 μm covering the driving area MV and a resist pattern 55b having a width of 60 μm covering the extending area EA (electrode lead portion) are formed.

  Then, as shown in FIG. 11, using the resist pattern 55a and the resist pattern 55b as a mask, the PLT as the buffer layer 53 is selectively etched by ICP dry etching using a chlorine-based or fluorine-based gas, The PLT pattern, that is, the buffer layer 53a (buffer layer LB) is patterned. As a result, the buffer layer LB is removed except for a portion existing inside the first region A1 and a portion belonging to the extended area EA in the second region. Etching may be wet etching using a hydrofluoric acid solution.

  The formed buffer layer LB is formed to be slightly larger than an upper electrode layer LU, which will be described later, thereby ensuring the insulation between the lower electrode layer LL and the upper electrode layer LU.

  (Fourth Step) The upper electrode layer LU is formed from the drive area MV on the piezoelectric thin film LP to the extending area EA on the buffer layer LB.

  First, as shown in FIG. 12, the resist patterns 55a and 55b in FIG. 11 are removed, and Ti is formed on the entire surface exposed by the sputtering so as to have a thickness of 20 nm, followed by Au. (Gold) is formed uniformly by sputtering so as to have a thickness of 300 nm. Here, the surface is formed in this order for the purpose of functioning as an adhesion layer 56 for Ti and an upper electrode layer 57 for Au.

  Subsequently, a resist is uniformly applied to the entire surface of the configuration formed in FIG. 12, and selectively exposed and developed to pattern the upper electrode layer 57 as shown in FIG. For this purpose, a resist pattern 58a having a diameter of 180 μm is formed in the drive area MV, and a resist pattern 58b having a width of 50 μm is formed in the extending area EA (electrode extraction portion).

  Then, as shown in FIG. 14, using the resist patterns 58a and 58b as a mask, the Au layer and the Ti layer are selectively etched to form the adhesion layer 56a and the upper electrode layer 57a (upper electrode layer LU). . Etching may be wet etching using a solution or dry etching using a chlorine-based gas or the like.

  Thus, the manufacturing process on the first main surface MS1 side of the SOI substrate 1 on which the piezoelectric thin film LP is formed is completed.

<2-3. Manufacturing process on the second main surface side>
Subsequently, a manufacturing process on the second main surface MS2 side opposite to the first main surface MS1 on which the piezoelectric thin film LP is formed on both main surfaces of the SOI substrate 1 will be described with reference to FIGS. I will explain later.

  (Fifth Step) In the composite support layer LS described above, the first region A1 is selectively removed to form the window space WS1, and the diaphragm layer LD is exposed in the window space WS1.

First, as shown in FIG. 15, TEOS (Tetraethoxysilane: Si (OC ₂ H ₅ ) ₄ ) − is formed on the second main surface MS 2 of the SOI substrate 1 so that the SiO ₂ (silicon dioxide) layer 60 has a thickness of 2 μm. It is uniformly formed by the CVD method.

Next, a resist is uniformly coated on the SiO ₂ layer 60, and selectively exposed and developed to obtain a resist pattern 61 as shown in FIG. An area not protected by the resist pattern 61 is a processing area of the window space WS1. A suitable processing area for the window space WS1 is about 220 μm in diameter.

Subsequently, using the resist pattern 61 as a mask pattern, the SiO ₂ layer 60 and the thermal oxide film 20b in an area not protected by the resist pattern 61 shown in FIG. 16 (an area where the window space WS1 is formed) are formed by RIE (Reactive Ion). Etching) is selectively dry-etched with CHF ₃ gas to form a pattern of SiO ₂ layer 60a and thermal oxide film 20b ′ as shown in FIG.

Then, using the pattern of the SiO ₂ layer 60a formed as described above as a mask, the SOI substrate 1 is selectively deep-digged in a direction perpendicular to the second main surface MS2 by a Bosch process of an ICP (Inductively Coupled Plasma) apparatus. As shown, the window space WS1 (pressure generation chamber 14) is created.

Further, in a state where the structure on the first main surface MS1 side is protected with a resist, the SiO ₂ of the exposed box layer LX in the WS1, the SiO ₂ layer 60a on the surface on the second main surface MS2, and the thermal oxide film 20b ′ are formed. Remove by wet etching with dilute hydrofluoric acid.

  Thereafter, the glass substrate L2 of FIG. 2 and the nozzle plate L1 in which the two-step holes 11 are formed are assembled on the second main surface MS2 side to form a piezoelectric module (see FIG. 3).

  The piezoelectric module 10 as shown in FIG. 3 can be manufactured by the manufacturing process including the first to fifth steps described above.

  When the inkjet head 100 is manufactured, the piezoelectric module 10 is incorporated in the housing HS as shown in FIG. 1 together with other parts such as a main tank of ink and a control circuit board, so that electrical wiring and a structural package are obtained. Inkjet head 100 is manufactured by performing the process.

<3. Performance verification of piezoelectric module according to this embodiment>
In order to verify the performance of the piezoelectric module 10 according to the present embodiment described above, a comparative example in which the piezoelectric thin film LP is formed without providing the buffer layer LB in the extending area EA is compared with the piezoelectric module 10 manufactured according to the present embodiment. While evaluating.

  As a result, in the comparative example, a crack is generated in the piezoelectric thin film LP at the boundary between the driving area MV and the extending area EA during driving, and the piezoelectric displacement of the diaphragm layer LD is lower than that in the present embodiment. It was. On the other hand, when the piezoelectric module 10 according to the present embodiment was applied, the above-described crack did not occur, and the piezoelectric displacement was improved by 20% compared to the comparative example.

  As can be seen from the above performance verification, the piezoelectric module 10 according to the embodiment is superior to the comparative example in the following points.

  First, in the structure of the piezoelectric module 10 manufactured as described above, since the electrical insulation between the upper electrode layer LU and the lower electrode layer LL in the extending area EA can be realized by the buffer layer LB, the driving in the window space WS1 is performed. It is possible to localize the piezoelectric thin film LP in the area MV (that is, it is not necessary to extend the piezoelectric thin film beyond the window space WS1), and it is possible to prevent the piezoelectric displacement from being lowered and at the time of piezoelectric deformation. It is possible to suppress generation of cracks in the piezoelectric thin film LP due to stress concentration.

  In addition, since the insulating material constituting the buffer layer LB has the same kind of crystal structure as that of the piezoelectric material constituting the piezoelectric thin film LP, the crystallinity of the piezoelectric thin film LP is increased when the piezoelectric thin film LP is formed on the buffer layer LB. Accordingly, it is possible to suppress a decrease in piezoelectricity due to the provision of the buffer layer LB, and it is possible to maintain high adhesion between the buffer layer LB and the piezoelectric thin film LP.

<4. Modification>
As mentioned above, although embodiment of this invention has been described, this invention is not limited to the said embodiment, A various deformation | transformation is possible.

  * In this embodiment, PLT (lead lanthanum titanate) is used as an insulating material for forming the buffer layer LB. However, the present invention is not limited to this. For example, BTO (barium titanate), STO (strontium titanate), PT ( The main component may be selected from the group consisting of lead titanate), BST (barium strontium titanate), and SRO (strontium ruthenate).

  * In this embodiment, PZT (lead zirconate titanate) is used as the piezoelectric material for forming the piezoelectric thin film LP. However, additives may be added to PZT, and various materials based on the PZT system are also available. Available.

  * In this invention, it is only necessary that the buffer layer has electrical insulation, and the crystal structure of the buffer layer and the piezoelectric thin film are the same type (that is, the atomic arrangement rule is the same), and the crystal structure has a perovskite structure. Not limited.

10 Piezoelectric Module 100 Piezoelectric Device (Inkjet Head)
A1 1st area A2 2nd area MV drive area EA Stretching area LS Support layer LX Box layer LD Diaphragm layer (active layer)
LL Lower electrode layer LB Buffer layer LP Piezoelectric thin film LU Upper electrode layer MS1 First main surface (one main surface)
MS2 Second main surface (the other main surface)

Claims (7)

A piezoelectric conversion module that performs conversion between voltage and mechanical deformation using a piezoelectric body arranged on a diaphragm,
A diaphragm layer is formed on the support layer, a window space is provided in the support layer, and the presence of the window space allows a planar area to be expanded as a first region corresponding to the window space, and A composite substrate in which a second region surrounding the window space in a plane is defined;
A lower electrode layer formed on the diaphragm layer and extending over both the first and second regions;
An insulating buffer layer formed on the lower electrode layer so as to cover both the driving area defined in the first region and the extending area extending from the driving area onto the second region;
A piezoelectric thin film formed on the buffer layer in the driving area;
An upper electrode layer formed from the driving area on the piezoelectric thin film to the extending area on the buffer layer;
With
The piezoelectric module, wherein the buffer layer is formed of an insulating material having the same kind of crystal structure as that of the piezoelectric material forming the piezoelectric thin film. The piezoelectric module according to claim 1,
Both the piezoelectric material and the insulating material have a perovskite structure. The piezoelectric module according to claim 2,
2. The piezoelectric module according to claim 1, wherein the piezoelectric material is mainly composed of a PZT (lead zirconate titanate) system. The piezoelectric module according to claim 2,
The insulating material is from BTO (barium titanate), STO (strontium titanate), PLT (lead lanthanum titanate), PT (lead tantalum titanate), BST (barium strontium titanate), and SRO (strontium ruthenate). A piezoelectric module comprising as a main component any one selected from the group consisting of:   A piezoelectric device comprising the piezoelectric module according to claim 1, wherein the piezoelectric module performs conversion between an electric signal and a mechanical displacement.   The piezoelectric device according to claim 5, wherein the piezoelectric device is configured as an ink jet head by including the piezoelectric module as an ink ejection drive mechanism. A method of manufacturing a piezoelectric module that deforms a surface shape of the diaphragm by applying a voltage to a piezoelectric thin film disposed on the diaphragm,
(A) preparing a composite substrate material in which a diaphragm layer is formed on a support layer, and a first region and a second region surrounding the first region are defined as a planar expansion range; ,
(B) forming a lower electrode layer extending over both the first and second regions on the diaphragm layer;
(C) having a perovskite structure formed on the lower electrode layer so as to cover both the driving area defined in the first region and the extending area extending from the driving area onto the second region. Forming an insulating buffer layer;
(D) forming a piezoelectric thin film made of a piezoelectric material having a perovskite structure on the buffer layer in the driving area;
(E) forming an upper electrode layer from the driving area on the piezoelectric thin film to the extending area on the buffer layer;
(F) selectively removing the first region of the support layer of the composite material to form a window space, and exposing the diaphragm in the window space;
A method for manufacturing a piezoelectric module comprising:

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