JP2019091917A - Piezoelectric film and piezoelectric element and ink jet print head using the same - Google Patents

Abstract

To provide a piezoelectric film having stable piezoelectric characteristics.SOLUTION: A piezoelectric film 8 includes an adhesion layer 101 formed on the surface of a lower electrode 7, a first seed layer 102 formed on the adhesion layer 101, a plurality of PZT layers 103 to 106 in units of main firing stacked on the first seed layer 102, a second seed layer 107 formed on the surface of the PZT 106 in units of main firing, and a plurality of PZT layers 108 to 112 in units of main firing formed on the surface of the second seed layer 107. The seed layers 102 and 107 are made of, for example, a PZT seed layer made of PZT or a TiO seed layer made of TiO.SELECTED DRAWING: Figure 10

Description

  The present invention relates to a piezoelectric film using lead zirconate titanate (PZT), a piezoelectric element using the same, and an ink jet print head.

  An ink jet print head is known as an actuator using a piezoelectric film. An example of such an ink jet print head is disclosed in US Pat. The inkjet print head disclosed in Patent Document 1 includes a nozzle substrate, a pressure chamber substrate, a vibrating film, and a piezoelectric element bonded to the vibrating film. In the pressure chamber substrate, a pressure chamber into which the ink is introduced is formed, and a diaphragm faces this pressure chamber. The piezoelectric element is configured by laminating a lower electrode, a piezoelectric film and an upper electrode from the vibrating film side.

Lead zirconate titanate (PZT: PbZr _x Ti _1-x O ₃ ) is a velovskite _- type ferroelectric substance, and sensors and actuators utilizing its excellent piezoelectric properties have been proposed. The piezoelectric film using PZT is formed by a sputtering method or a sol-gel method. The formation of a PZT film by the sol-gel method is described, for example, in Patent Document 2. In the sol-gel method, a coating step of applying a precursor solution containing PZT to form a coating film, a drying step of drying the coating film, and heating the coating film after the drying step cause gelation of the coating film. A firing step and a main firing step of heat-treating and sintering the gelled coating film are included. Usually, the PZT film is formed by repeatedly performing the process including the application process, the drying process, and the pre-baking process a plurality of times and then performing the main baking process. Then, a piezoelectric film having a target film thickness is formed by repeatedly performing such a series of steps. Therefore, the piezoelectric film includes a plurality of stacked PZT layers.

JP, 2013-215930, A Unexamined-Japanese-Patent No. 6-40727

  An object of the present invention is to provide a piezoelectric film having stable piezoelectric characteristics, and a piezoelectric element and an ink jet print head using the same.

The piezoelectric film according to the present invention is a piezoelectric film including PZT layers of a plurality of main firing units stacked, and is a first seed layer present on the lower surface side of the PZT layer of the lower main firing unit. And a second seed layer interposed between the PZT layers of two adjacent main firing units at an intermediate position between the PZT layer of the lower main firing unit and the PZT layer of the uppermost main firing unit. .
The “PZT layer of the main firing unit” is a coating step of applying a precursor solution containing PZT, a drying step of drying the coating film, and a pre-baking step of heating the coating film after the drying step to gelate The PZT layer is formed by performing the main baking step of subjecting the gelled coating film to heat treatment and sintering after the gelled film formation step consisting of the above is performed one or more times.

  In this configuration, the seed layer is provided not only on the lower surface side of the bottom main firing unit PZT layer but also at an intermediate position between the bottom main firing unit PZT layer and the top main firing unit PZT layer. Exists. For this reason, as compared with the piezoelectric film in which the seed layer is formed only on the lower surface side of the bottom main PZT unit of the main firing unit, the crystal direction of the PZT layer of each main firing unit is easily aligned. Thus, a piezoelectric film having stable piezoelectric characteristics can be obtained.

In one embodiment of the present invention, the first seed layer and the second seed layer are made of the same material. In this configuration, the manufacturing efficiency of the piezoelectric film can be improved.
In one embodiment of the present invention, the first seed layer and the second seed layer are composed of a PZT seed layer made of PZT.
In one embodiment of the present invention, the first seed layer and the second seed layer are composed of a TiO seed layer made of titanium oxide.

In one embodiment of the present invention, the first seed layer and the second seed layer are made of different materials.
In one embodiment of the present invention, the first seed layer is composed of a TiO seed layer composed of titanium oxide, and the second seed layer is composed of a PZT seed layer composed of PZT.

In one embodiment of the present invention, the first seed layer is composed of a PZT seed layer composed of PZT, and the second seed layer is composed of a TiO seed layer composed of titanium oxide.
In one embodiment of the present invention, the PZT seed layer heats and gels the coating film after the application step of applying a precursor solution containing PZT, the drying step of drying the coating film, and the drying step. After the gelled film forming process including the pre-baking process is performed once, the gelled coating film is formed by performing a main baking process of heat treatment and sintering.

A piezoelectric element according to the present invention comprises a lower electrode, the piezoelectric film according to any one of claims 1 to 8 formed on the lower electrode, and an upper electrode formed on the piezoelectric film. Including. In this configuration, a piezoelectric element having stable piezoelectric characteristics can be obtained.
An ink jet print head according to the present invention includes a cavity, a vibrating film disposed on the cavity and defining a top surface portion of the cavity, and the piezoelectric element formed on the vibrating film. In this configuration, by using a piezoelectric element having stable piezoelectric characteristics, it is possible to provide an ink jet print head capable of realizing stable driving characteristics.

FIG. 1 is a schematic plan view of an ink jet print head to which a piezoelectric film utilization apparatus according to an embodiment of the present invention is applied. FIG. 2 is a schematic enlarged cross-sectional view along the line II-II in FIG. FIG. 3 is a schematic enlarged cross-sectional view along the line III-III in FIG. FIG. 2 is a schematic perspective view of the inkjet print head. FIG. 5 is a partially enlarged plan view of FIG. FIG. 6 is a process diagram showing an example of a manufacturing process of the ink jet print head. FIG. 7 is a plan view for explaining the configuration of an ink jet print head according to another embodiment of the present invention. FIG. 8 is a cross-sectional view for explaining the configuration of the inkjet print head of FIG. FIG. 9 is a plan view for explaining the configuration of an ink jet print head according to still another embodiment of the present invention. FIG. 10 is a schematic cross-sectional view of a piezoelectric film.

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.
FIG. 1 is a schematic plan view of an ink jet print head to which a piezoelectric film utilization apparatus according to an embodiment of the present invention is applied. FIG. 2 is a schematic enlarged cross-sectional view along the line II-II in FIG. FIG. 3 is a schematic enlarged cross-sectional view along the line III-III in FIG. FIG. 4 is a schematic perspective view of an ink jet print head. However, in FIG. 1 and FIG. 4, the hydrogen barrier film indicated by reference numeral 13 in FIGS. 2 and 3 and the insulating film indicated by reference numeral 14 are omitted.

  Referring to FIG. 2, the inkjet print head 1 includes a silicon substrate 2 and a nozzle substrate 3 having a discharge port 3 a for discharging ink. The vibrating film forming layer 10 is stacked on the silicon substrate 2. A pressure chamber (cavity) 5 as an ink flow path (ink reservoir) is formed in a laminate of the silicon substrate 2 and the vibrating membrane forming layer 10. The pressure chamber 5 is formed in the silicon substrate 2 and is formed in the space 5A penetrating the silicon substrate 2 in the thickness direction, and on the back surface (surface on the silicon substrate 2 side) of the vibrating membrane forming layer 10 and in the space 5A. It is comprised from the continuous recessed part 5B.

  The nozzle substrate 3 is formed of, for example, a silicon plate, is bonded to the back surface of the silicon substrate 2, and defines the pressure chamber 5 together with the silicon substrate 2 and the vibrating film forming layer 10. The nozzle substrate 3 has a recess 3 b facing the pressure chamber 5, and the ink discharge passage 3 c is formed on the bottom of the recess 3 b. The ink discharge passage 3 c penetrates the nozzle substrate 3 and has a discharge port 3 a on the opposite side to the pressure chamber 5. Therefore, when the volume change of the pressure chamber 5 occurs, the ink stored in the pressure chamber 5 passes through the ink discharge passage 3c and is discharged from the discharge port 3a.

  The pressure chamber 5 is formed by digging the silicon substrate 2 and the vibrating film forming layer 10 from the back surface side of the silicon substrate 2. In the silicon substrate 2 and the vibrating membrane forming layer 10, an ink supply path 4 (see FIG. 1 and FIG. 3 together) communicating with the pressure chamber 5 is further formed. The ink supply path 4 is in communication with the pressure chamber 5 and is formed to guide the ink from the ink tank (for example, an ink cartridge) which is an ink supply source to the pressure chamber 5.

The pressure chamber 5 is formed to elongate along the ink flow direction 21 which is the left and right direction in FIG. The top wall portion of the pressure chamber 5 in the vibrating film forming layer 10 constitutes a vibrating film 10A. The vibrating film 10A (the vibrating film forming layer 10) is made of, for example, a silicon oxide (SiO ₂ ) film formed on the silicon substrate 2. The vibrating film 10A (the vibrating film forming layer 10) is formed, for example, on a silicon (Si) layer formed on the silicon substrate 2, a silicon oxide (SiO ₂ ) layer formed on the silicon layer, and a silicon oxide layer It may be composed of a laminated body with a silicon nitride (SiN) layer. In this specification, the vibrating membrane 10A means a top wall portion which divides the pressure chamber 5 in the vibrating membrane forming layer 10. Therefore, in the vibrating membrane forming layer 10, the portion other than the top wall portion of the pressure chamber 5 does not constitute the vibrating membrane 10A.

  The thickness of the vibrating membrane 10A is, for example, 0.4 μm to 2 μm. When the vibrating film 10A is formed of a silicon oxide film, the thickness of the silicon oxide film may be about 1.2 μm. When the vibrating film 10A is formed of a laminate of a silicon layer, a silicon oxide layer and a silicon nitride layer, the thicknesses of the silicon layer, the silicon oxide layer and the silicon nitride layer are each about 0.4 μm It is also good.

  The pressure chamber 5 is divided by the vibrating film 10A, the silicon substrate 2, and the nozzle substrate 3. In this embodiment, the pressure chamber 5 is formed in a substantially rectangular parallelepiped shape. The length of the pressure chamber 5 may be, for example, about 800 μm, and the width thereof may be about 55 μm. The ink supply path 4 is formed to communicate with one end in the longitudinal direction of the pressure chamber 5 (in this embodiment, the end located on the opposite side to the discharge port 3 a). The discharge port 3 a of the nozzle substrate 3 is disposed in the vicinity of the other end in the longitudinal direction of the pressure chamber 5 in this embodiment.

The piezoelectric element 6 is disposed on the surface of the vibrating membrane 10A. The piezoelectric element 6 includes a lower electrode 7 formed on the vibrating film forming layer 10, a piezoelectric film 8 formed on the lower electrode 7, and an upper electrode 9 formed on the piezoelectric film 8. There is. In other words, the piezoelectric element 6 is configured by sandwiching the piezoelectric film 8 between the upper electrode 9 and the lower electrode 7 from above and below.
The lower electrode 7 has, for example, a two-layer structure in which a Ti (titanium) layer and a Pt (platinum) layer are sequentially stacked from the vibrating film 10A side. Besides, the lower electrode 7 can be formed of a single film such as an Au (gold) film, a Cr (chromium) layer, or a Ni (nickel) layer. The lower electrode 7 has a main electrode portion 7A in contact with the lower surface of the piezoelectric film 8 and an extension 7B extending to an outer region of the piezoelectric film 8 (see also FIGS. 1 and 4). .

The piezoelectric film 8, for example, _PZT formed by a sol-gel method or a sputtering method _{(PbZr x Ti 1-x O} 3: lead zirconate titanate) can be applied membrane. Such a piezoelectric film 8 is made of a sintered body of metal oxide crystal. The thickness of the piezoelectric film 8 is preferably 1 μm to 5 μm. The total thickness of the vibrating film 10A is preferably about the same as the thickness of the piezoelectric film 8 or about 2/3 of the thickness of the piezoelectric film.

The upper electrode 9 is formed in substantially the same shape as the piezoelectric film 8 in a plan view. The upper electrode 9 has a three-layer structure in which, for example, an IrO ₂ (iridium oxide) layer and an Ir (iridium) layer are sequentially stacked from the piezoelectric film 8 side, and a Pt layer or an Au layer is further stacked.
The hydrogen barrier film 13 covers the surface of the vibrating film forming layer 10, the surface of the piezoelectric element 6, and the surface of the extension of the lower electrode 7. The hydrogen barrier film 13 is covered with, for example, Al ₂ O ₃ (alumina). Thereby, the characteristic deterioration of the piezoelectric film 8 due to hydrogen reduction can be prevented. An insulating film 14 is stacked on the hydrogen barrier film 13. The insulating film 14 is made of, for example, SiO ₂ . Wirings 15 are formed on the insulating film 14. The wiring 15 is made of a metal material containing Al (aluminum).

  One end of the wiring 15 is disposed above one end of the upper electrode 9. A through hole 16 which penetrates the hydrogen barrier film 13 and the insulating film 14 continuously is formed between the wiring 15 and the upper electrode 9. One end of the wiring 15 enters the through hole 16 and is connected to the upper electrode 9 in the through hole 16. In addition, the hydrogen barrier film 13 and the insulating film 14 have a cutting portion 17 at a position corresponding to a region surrounded by the peripheral portion on the surface of the upper electrode 9. The cut portion 17 is a portion where the hydrogen barrier film 13 and the insulating film 14 are cut.

  In addition, an opening 18 which penetrates the hydrogen barrier film 13 and the insulating film 14 continuously is formed at a position corresponding to a predetermined region on the extension of the lower electrode 7, and the surface of the lower electrode 7 is an opening. Exposed through 18 o'clock. The exposed portion constitutes a pad portion 7 d for connecting the lower electrode 7 to the outside. On the surface of the vibrating film forming layer 10, on the upstream side of the upstream end of the ink flow direction 21 of the piezoelectric element 6, viewed from the direction orthogonal to the ink flow direction 21 (direction along the surface of the silicon substrate 2) The hydrogen barrier film 13 and the insulating film 14 are formed only in the region near the upstream end of the piezoelectric element 6, and the hydrogen barrier film 13 and the insulating film 14 are not formed on the upstream side thereof.

  The piezoelectric element 6 is formed at a position facing the pressure chamber 5 with the vibrating film 10A interposed therebetween. That is, the piezoelectric element 6 is formed to be in contact with the surface of the vibrating film 10A opposite to the pressure chamber 5. The pressure chamber 5 is filled with ink supplied from an ink tank (not shown) through the ink supply path 4. The vibrating membrane 10 </ b> A defines the top surface of the pressure chamber 5 and faces the pressure chamber 5. The vibrating membrane 10A is supported by the portion around the pressure chamber 5 in the laminated body of the vibrating membrane forming layer 10 and the silicon substrate 2, and in the direction facing the pressure chamber 5 (in other words, the thickness direction of the vibrating membrane 10A) ) Is flexible.

  The wiring 15 and the pad portion 7 d of the lower electrode 7 are connected to the drive circuit 20. The drive circuit 20 may be formed in a region different from the pressure chamber 5 of the silicon substrate 2 or may be formed outside the silicon substrate 2. When a drive voltage is applied from the drive circuit 20 to the piezoelectric element 6, the piezoelectric film 8 is deformed by the reverse piezoelectric effect. As a result, the vibrating film 10A is deformed together with the piezoelectric element 6, whereby the volume change of the pressure chamber 5 is brought about, and the ink in the pressure chamber 5 is pressurized. The pressurized ink passes through the ink discharge passage 3c, and is discharged as fine droplets from the discharge port 3a.

  Referring to FIGS. 1 to 4, in the laminate of the silicon substrate 2 and the vibrating membrane forming layer 10, a plurality of pressure chambers 5 extend in parallel with each other and are formed in a stripe shape. The plurality of pressure chambers 5 are formed at equal intervals at small intervals (for example, about 30 μm to 350 μm) in their width direction. Each pressure chamber 5 has a rectangular shape elongated in the ink flow direction 21 from the ink supply passage 4 to the discharge passage 3 c in a plan view. That is, the top surface portion of the pressure chamber 5 has two side edges 5 c and 5 d along the ink flow direction 21 and two edge 5 a and 5 b along the direction orthogonal to the ink flow direction 21. The ink supply passage 4 is divided into two passages at one end of the pressure chamber 5 and is in communication with the common ink passage 19. The common ink passage 19 is in communication with the ink supply passage 4 corresponding to the plurality of pressure chambers 5 and is formed to supply the ink from the ink tank to the ink supply passage 4.

  The piezoelectric element 6 is formed so that the length in the ink flow direction 21 (the same direction as the longitudinal direction of the vibrating membrane 10A) is shorter than the length in the longitudinal direction of the vibrating membrane 10A, and has a rectangular shape in plan view . Then, as shown in FIG. 1, both end edges 6a and 6b along the lateral direction of the piezoelectric element 6 open a predetermined distance d1 (for example, 5 μm) with respect to the corresponding end edges 10Aa and 10Ab of the vibrating membrane 10A. Is located inside. Further, the piezoelectric element 6 has a width in the short side direction (direction parallel to the main surface of the silicon substrate 2) orthogonal to the longitudinal direction of the vibrating membrane 10A is the short side of the vibrating membrane 10A (the top surface portion of the pressure chamber 5). It is formed narrower than the width of the direction. The both side edges 6c and 6d along the longitudinal direction of the piezoelectric element 6 are disposed inside the corresponding side edges 10Ac and 10Ad of the vibrating membrane 10A at predetermined intervals d2 (for example, 5 μm).

  The lower electrode 7 is a flat plate having a predetermined width in a direction along the ink circulation direction 21 in plan view and extending across the plurality of pressure chambers 5 in a direction orthogonal to the ink circulation direction 21. It is a common electrode shared by the piezoelectric elements 6. The first side 7 a of the lower electrode 7 along the direction orthogonal to the ink flow direction 21 is aligned with a line connecting one edge 6 a of the plurality of piezoelectric elements 6 in plan view. The second side 7b opposite to the first side 7a of the lower electrode 7 is outside the edge 10Ab of the vibrating membrane 10A corresponding to the other edge 6b of the plurality of piezoelectric elements 6 (downstream of the ink flow direction 21 Side).

  In the lower electrode 7, on the downstream side of the ink flow direction 21 of each piezoelectric element 6, a cutout 7 c having a rectangular shape in a plan view and penetrating the lower electrode 7 is formed. Each cutout 7 c has two side edges (short sides) along the ink circulation direction 21 and two edges (long sides) along the direction orthogonal to the ink circulation direction 21 in plan view. . One edge of the cut-out portion 7c is disposed at a position aligned with the edge 6b of the piezoelectric element 6 with respect to the ink flow direction 21, and the other edge is outside the edge 10Ab of the vibrating membrane 10A (in the ink flow direction 21 Located downstream). One side edge of the excising part 7c is disposed outside the one side edge 10Ac of the vibrating membrane 10A, and the other side edge of the excising part 7c is disposed outside the other side edge 10Ad of the vibrating membrane 10A. There is. Therefore, in plan view, the end on the edge 10Ab side of the vibrating membrane 10A is disposed inside the cutout 7c. In a region between the second side 7 b of the lower electrode 7 and the plurality of cut-out portions 7 c, a rectangular pad portion 7 d elongated in the direction perpendicular to the ink flow direction 21 is formed.

  Lower electrode 7 is drawn from main electrode portion 7A constituting piezoelectric element 6 and in a direction along the surface of vibrating membrane forming layer 10 from main electrode portion 7A, and the peripheral edge of the top surface portion (vibration membrane 10A) of pressure chamber 5 And an outwardly extending extension 7B of the peripheral edge of the top surface of the pressure chamber 5 in a straddling manner. The main electrode portion 7A is formed shorter than the vibrating membrane 10A along the longitudinal direction of the vibrating membrane 10A, and the both end edges thereof are predetermined as described above with respect to the corresponding both end edges 10Aa and 10Ab of the vibrating membrane 10A. It is arranged inside with an interval d1. Further, the width of the main electrode portion 7A along the widthwise direction of the vibrating membrane 10A is formed narrower than the width in the widthwise direction of the vibrating membrane 10A, and both side edges thereof correspond to corresponding both sides of the vibrating membrane 10A. With respect to the edges 10Ac and 10Ad, the gap d2 is opened and disposed inside.

  The extension 7B straddles the corresponding side edges 5c and 5d of the top surface of the pressure chamber 5 from the side edges of the main electrode 7A in plan view, and the outside of the side edges 5c and 5d of the top surface of the pressure chamber 5 It extends to the side. The extension 7B is a region excluding the main electrode portion 7A in the entire region of the lower electrode 7. Referring to FIG. 5, in the extension 7B, a portion straddling the peripheral edge (in this embodiment, the side edges 5c and 5d in this embodiment) of the top surface portion of the pressure chamber 5 may be referred to as "crossing region 7C" in plan view. . Further, in the lower electrode 7, a region inside the peripheral edges 5 a to 5 d of the top surface portion of the pressure chamber 5 in plan view is referred to as “inner electrode region” and outside the peripheral edges 5 a to 5 d of the top surface portion of the pressure chamber 5. A region may be referred to as an "outer electrode region".

  The main electrode portion 7A in the lower electrode 7 is included in the inner electrode region. The extension 7B of the lower electrode 7 is composed of an area other than the main electrode portion 7A in the inner electrode area and an external electrode area. A region in the vicinity of the boundary between the inner electrode region and the outer electrode region is a crossing region 7C. In this embodiment, the boundary between the inner electrode region and the outer electrode region has two boundary lines corresponding to the middle portions of the side edges 5 c and 5 d of the top surface of the pressure chamber 5. Therefore, in this embodiment, the lower electrode 7 has two straddle regions 7C straddling the middle portions of the side edges 5c and 5d of the top surface portion of the pressure chamber 5 in plan view.

  In this embodiment, the thickness of the bridging region 7C of the lower electrode 7 and the portion of the inner electrode region excluding the bridging region 7C is thinner than the thickness of the other regions. That is, in this embodiment, the lower electrode 7 corresponds to the thin portion corresponding to the crossing region 7C, the thin portion corresponding to the region excluding the crossing region 7C in the inner electrode region, and the regions other than these regions. And a thick portion. The thin portion of the lower electrode 7 is shown in FIG. 5 by a dot area. In this embodiment, the width of the region belonging to the inner electrode region in each crossing region 7C is between the corresponding side edge of the inner electrode region in the inner electrode region and the corresponding side edge of the main electrode portion 7A. It is set to the same width as the area width. Therefore, in this embodiment, lower electrode 7 has a thin portion corresponding to straddle region 7C, a thin portion corresponding to main electrode portion 7A, and a thick portion corresponding to regions other than these regions. There is. The width of the region belonging to the inner electrode region in each crossing region 7C is greater than the width of the region between the corresponding side edge of the inner electrode region in the inner electrode region and the corresponding side edge of the main electrode portion 7A. It may be set to a short width.

  Referring to FIGS. 1 to 4, upper electrode 9 is formed shorter than vibrating membrane 10A along the longitudinal direction of vibrating membrane 10A, and both end edges thereof correspond to corresponding both end edges 10Aa of vibrating membrane 10A. , 10Ab, with the predetermined spacing d1 open. The upper electrode 9 is formed such that the width along the width direction of the vibrating membrane 10A is narrower than the width in the width direction of the vibrating membrane 10A, and the side edges thereof correspond to the corresponding side edges of the vibrating membrane 10A. The interval d2 is opened with respect to 10Ac and 10Ad, and they are arranged inside.

  The piezoelectric film 8 is formed in the same pattern as the upper electrode 9. That is, the piezoelectric film 8 is formed shorter than the vibrating film 10A in the longitudinal direction of the vibrating film 10A, and both end edges thereof are predetermined with respect to corresponding both end edges 10Aa and 10Ab of the vibrating film 10A. The interval d1 between the The piezoelectric film 8 is formed such that the width along the width direction of the vibrating film 10A is narrower than the width in the width direction of the vibrating film 10A, and both side edges thereof correspond to corresponding both sides of the vibration film 10A. With respect to the edges 10Ac and 10Ad, the gap d2 is opened and disposed inside. The lower surface of the piezoelectric film 8 is in contact with the upper surface of the portion constituting the piezoelectric element 6 in the lower electrode 7, and the upper surface of the piezoelectric film 8 is in contact with the lower surface of the upper electrode 9.

  The wiring 15 is connected at one end to one end of the upper electrode 9 (an end on the one end 6a side of the piezoelectric element 6) and extends in the direction opposite to the ink flow direction 21 in plan view. The pad portion 15B is integrated with the lead-out portion 15A, and is connected to the tip of the lead-out portion 15A. The lead-out portion 15A is one end portion of the upper surface of the piezoelectric element 6 (an end portion on one edge 6a side of the piezoelectric element 6) and an end surface of the piezoelectric element 6 connected thereto except for a portion connected to the upper electrode 9. It is formed on the surface of the insulating film 14 covering the surface of the vibrating film forming layer 10. The pad portion 15B is formed on the surface of the vibrating film forming layer 10 where the hydrogen barrier film 13 and the insulating film 14 are not formed.

  An annular region (peripheral annular region elongated in the ink flow direction 21 in this embodiment) between the peripheral edge 10Aa to 10Ad of the diaphragm 10A and the peripheral edge 6a to 6d of the piezoelectric element 6 in the diaphragm 10A is the piezoelectric element 6 or It is an area which is not constrained by the peripheral wall of the pressure chamber 5 and is an area where large deformation occurs. That is, the peripheral portion of the vibrating membrane 10A is a region where large deformation occurs. Therefore, when the piezoelectric element 6 is driven, the peripheral edge of the vibrating membrane 10A is bent so that the inner peripheral side of the peripheral edge of the vibrating membrane 10A is displaced in the thickness direction of the pressure chamber 5 (downward in this embodiment). As a result, the entire central portion surrounded by the peripheral portion of the vibrating membrane 10A is displaced in the thickness direction of the pressure chamber 5 (downward in this embodiment).

  Portions inside the top surface portion peripheral edges 5a to 5d of the pressure chamber 5 in the straddle region 7C of the lower electrode 7 (in this embodiment, the side edges 5c and 5d of the top surface portion) are formed on the peripheral portion of the vibrating membrane 10A. It is done. Therefore, the straddle region 7C of the lower electrode 7 may prevent the deformation of the vibrating membrane 10A. In this embodiment, since the lower electrode 7 has a thin portion corresponding to the straddle region 7C, the deformation of the vibrating membrane 10A is less likely to be impeded compared to the case where the entire lower electrode 7 is thick. Further, in this embodiment, the lower electrode 7 has a thin portion corresponding to the area (in this embodiment, the main electrode portion 7A in the present embodiment) other than the thin-walled portion corresponding to the straddle region 7C, of the inner electrode region. Because of the presence of the parts, the deformation of the vibrating membrane 10A is less likely to be impeded.

  Further, in this embodiment, the lower electrode 7 is a thick portion corresponding to a region excluding the crossing region 7C and a region (the main electrode portion 7A in this embodiment) excluding the crossing region 7C in the inner electrode region. The resistance value of the lower electrode 7 can be reduced as compared with the case where the entire thickness of the lower electrode 7 is thin. That is, according to this embodiment, the resistance value of the lower electrode 7 can be reduced, and the displacement of the diaphragm 10A can be increased.

FIG. 6 is a process diagram showing an example of a manufacturing process of the ink jet print head 1.
First, the vibrating film forming layer 10 is formed on the surface of the silicon substrate 2 (S1). Specifically, a silicon oxide layer (for example, 1.2 μm thick) is formed on the surface of silicon substrate 2. When the vibrating film forming layer 10 is formed of a laminate of a silicon layer, a silicon oxide layer and a silicon nitride layer, a silicon layer (for example, 0.4 μm thick) is formed on the surface of the silicon substrate 2 A silicon oxide layer (for example, 0.4 μm thick) is formed thereon, and a silicon nitride layer (for example, 0.4 μm thick) is formed on the silicon oxide layer. For example, an underlying oxide film such as Al ₂ O ₃ , MgO, or ZrO ₂ may be formed on the surface of the vibrating film forming layer 10. These base oxide films prevent the metal atoms from coming out of the piezoelectric film 8 to be formed later. If the metal electrons come out, the piezoelectric characteristics of the piezoelectric film 8 may be deteriorated. In addition, if the removed metal atoms are mixed into the silicon layer constituting the vibrating film 10A, the durability of the vibrating film 10A may be deteriorated.

  Next, a lower electrode film which is a material layer of the lower electrode 7 is formed on the vibrating film forming layer 10 (on the base oxide film when the base oxide film is formed) (S2) . The lower electrode film is made of, for example, a Pt / Ti laminated film having a Ti film (for example, 100 Å to 400 Å thick) as a lower layer and a Pt film (eg, 100 Å to 4000 Å thick) as an upper layer. Such lower electrode film may be formed by sputtering.

  Next, a thin portion of the lower electrode film is formed (S3). That is, a resist mask is formed to cover the region other than the region to be the thin portion of the lower electrode 7 (the region excluding the crossover region 7C of the crossover region 7C of the lower electrode 7 and the inside electrode region) by photography. By using the mask as a mask, the lower electrode film is etched to form a thin portion of the lower electrode 7. The thickness of the thin portion is, for example, about 1000 Å, and the thickness of the portion (thick portion) other than the thin portion is, for example, about 2000 Å.

Next, a material film (piezoelectric material film) of the piezoelectric film 8 is formed on the entire surface of the lower electrode film (S4). Specifically, for example, a PZT film having a thickness of 1 μm to 5 μm is formed by a sol-gel method. Such a PZT film is made of a sintered body of metal oxide crystal grains.
Next, an upper electrode film which is a material of the upper electrode 9 is formed on the entire surface of the piezoelectric material film (step S5). The upper electrode film is made of, for example, Ir / Ir0 ₂ laminated film for an upper layer of Ir film (e.g. 500Å~2000Å thick) and lower the IrO ₂ film (e.g. 400Å~1600Å thickness). Such upper electrode film may be formed by sputtering.

  Next, patterning of the upper electrode film, the piezoelectric material film, and the lower electrode film is performed (S6-S12). First, a resist mask of the pattern of the lower electrode 7 is formed by photography (S6), and the upper electrode film, the piezoelectric material film and the lower electrode film are etched in the same pattern using the resist mask as a mask. A lower electrode film of a predetermined pattern is formed (steps S6-S9). More specifically, the upper electrode film is patterned by dry etching (step S7), the piezoelectric material film is patterned by wet etching (S8), and the lower electrode film is patterned by dry etching (step S9). Thus, the lower electrode 7 is formed. The etchant used for the wet etching of the piezoelectric material film may be acids mainly composed of hydrochloric acid.

  Next, after peeling off the resist mask, a resist mask of the pattern of the piezoelectric film 8 is formed by photolithography (S10), and the upper electrode film and the piezoelectric material film are etched to the same pattern using this resist pattern (S11-S12). More specifically, the upper electrode film is patterned by dry etching (S11), and the piezoelectric material film is patterned by wet etching (S12). Thus, the piezoelectric film 8 and the upper electrode 9 are formed.

Thereafter, the resist mask is peeled off, and a hydrogen barrier film 13 covering the entire surface is formed (S13). The hydrogen barrier film 13 may be an Al ₂ O ₃ film formed by sputtering, and the film thickness may be 400 Å to 1600 Å.
Further, the insulating film 14 covering the hydrogen barrier film 13 is formed (S14). The insulating film 14 may be a SiO ₂ film, and its film thickness may be 2500 Å to 10000 Å.

Next, back surface grinding is performed to thin the silicon substrate 2 (S15). For example, the silicon substrate 2 having a thickness of about 670 μm in the initial state may be thinned to a thickness of about 300 μm.
Then, the pressure chamber 5 is formed by performing etching (dry etching or wet etching) from the back surface of the silicon substrate 2 on the laminated body of the silicon substrate 2 and the vibrating film forming layer 10, and at the same time, the vibrating film 10A is formed. It is formed. The underlying oxide film formed on the surfaces of the hydrogen barrier film 13 and the vibrating film forming layer 10 prevents the metallic element (Pb, Zr, Ti in the case of PZT) from coming off from the piezoelectric film 8 during this etching. The piezoelectric characteristics of the piezoelectric film 8 are kept good. Further, as described above, the base oxide film formed on the surface of the vibrating film forming layer 10 contributes to the maintenance of the durability of the silicon layer forming the vibrating film 10A.

Thereafter, the hydrogen barrier film 13 and the insulating film 14 are patterned, the wiring 15 is formed, and the like, whereby the ink jet print head 1 shown in FIGS. 1 to 4 is obtained.
In the embodiment described above, the thickness of the bridging region 7C of the lower electrode 7 and the region of the inner electrode region excluding the bridging region 7C (the main electrode portion 7A in this embodiment) is greater than the thicknesses of the other regions. It is thinly formed. However, as shown in FIGS. 7 and 8, even if the thickness of the area (main electrode portion 7A in this embodiment) excluding the crossing area 7C in the inner electrode area is formed to be thicker than the thickness of the crossing area 7C. Good. In other words, only the straddle region 7C of the lower electrode 7 may be thinner than the other regions. That is, the lower electrode 7 may have a thin portion corresponding to the crossing region 7C and a thick portion corresponding to a region other than the crossing region 7C. The thin-walled portion of the lower electrode 7 in this case is shown by a dot area in FIG.

Also in such a configuration, the resistance value of the lower electrode 7 can be reduced, and the displacement of the diaphragm 10A can be increased. Moreover, in such a configuration, the thickness of the main electrode portion 7A is formed thicker than the thickness of the thin portion corresponding to the straddle region 7C, so the resistance value of the lower electrode 7 can be further reduced.
Also in the configuration as shown in FIGS. 7 and 8, the width of the region belonging to the inner electrode region in each crossover region 7C corresponds to the correspondence between the corresponding side edge of the inner electrode region in the inner electrode region and the main electrode portion 7A. The width may be set shorter than the width of the area between the side edges. In such a case, the thickness of the region between the main electrode portion 7A and the straddle region 7C in the inner electrode region may be formed as thin as the straddle region 7C or the thickness of the main electrode portion 7A. It may be formed thick.

  In the above-described embodiment, the entire crossing region 7C is formed to be thin. However, it is not necessary that the entire crossing region 7C is formed thin, and only a part of the crossing region 7C in the longitudinal direction (direction along the side edges 5c and 5d of the top surface portion of the pressure chamber 5) It may be formed. In other words, the thickness of only a part of the bridging region 7C in the lower electrode 7 may be formed thinner than the thickness of the other regions. For example, as shown in FIG. 9, in the straddle region 7C, a rectangular thin portion and a thick portion alternately having a longitudinal direction along the side edges 5c and 5d of the top surface portion of the pressure chamber 5 along the longitudinal direction. It may be configured to be formed. In FIG. 9, a rectangular thin portion in the straddle region 7C is shown as a halftone dot region.

  Furthermore, the lower electrode 7 is a pressure chamber in addition to or in place of a straddle region (hereinafter referred to as a "first straddle region 7C") straddling the side edges 5c and 5d of the top surface portion of the pressure chamber 5 in plan view. It may have a straddle region (hereinafter, referred to as "second straddle region 7C") straddling the edges 5a and 5b of the top surface portion 5 of 5. When the lower electrode 7 has the second straddle region in addition to the first straddle region, the peripheral edges 5a to 5d of the top surface portion of the pressure chamber 5 in the first straddle region and the second straddle region The thickness of at least a part in the direction along is formed thin. When lower electrode 7 has a second straddle region instead of the first straddle region, at least the direction along edges 5a and 5b of the top surface portion of pressure chamber 5 in the second straddle region A part of the thickness is formed thin. Also in these cases, the thickness of the region excluding the straddle region 7C in the portion (inner electrode region) of the lower electrode 7 arranged inside the top surface peripheral edge 5a to 5d of the pressure chamber 5 in plan view is thin You may form.

Next, a configuration example of the piezoelectric film 8 used in the ink jet print head 1 will be described.
FIG. 10 is a schematic cross-sectional view of the piezoelectric film 8. The piezoelectric film 8 is formed in contact with the surface of the lower electrode (metal film) 7 formed on the silicon substrate 2. More specifically, the vibrating film forming layer 10 is formed on the surface of the silicon substrate 2, the lower electrode 7 is formed on the surface of the vibrating film forming layer 10, and the piezoelectric film is formed on the surface of the lower electrode 7. 8 are formed. In this embodiment, the lower electrode 7 is a Pt / Ti laminated film having a Ti film as a lower layer and a Pt film as an upper layer. An upper electrode 9 is formed on the upper surface of the piezoelectric film 8. Upper electrode 9, in this embodiment, consists of Ir / Ir0 ₂ laminated film for an upper layer of Ir film and a lower layer of IrO ₂ film.

  The piezoelectric film 8 includes an adhesion layer 101 formed on the surface of the lower electrode 7, a first seed layer 102 formed on the adhesion layer 101, and a plurality of main layers stacked on the first seed layer 102. The PZT layers 103 to 106 of the firing unit, the second seed layer 107 formed on the surface of the PZT 106 of the main firing unit, and the PZTs of a plurality of main firing units formed on the surface of the second seed layer 107 And layers 108-112.

  The “PZT layer of the main firing unit” is a coating step of applying a precursor solution containing PZT, a drying step of drying the coating film, and a pre-baking step of heating the coating film after the drying step to gelate The PZT layer is formed by performing the main baking step of subjecting the gelled coating film to heat treatment and sintering after the gelled film formation step consisting of the above is performed one or more times. That is, the PZT layer of the present fired unit is formed by the sol-gel method.

  The precursor solution contains a solvent in addition to PZT. In the application step, for example, a precursor solution is spin-coated. The drying step is performed, for example, in a temperature environment of 140 ° C. The drying step may be natural drying. In the pre-baking step, heat treatment at a temperature (eg, 400 ° C.) higher than the melting point (327.5 ° C.) of lead is performed on the coated film after the drying step. In the pre-baking step, heat treatment may be performed at a temperature (eg, 300 ° C.) less than the melting point of lead. In this firing step, a heat treatment at, for example, 700 ° C. is performed on the gelled coating film. The firing process may be performed by rapid thermal annealing (RTA).

In the following, a PZT layer corresponding to each of one or a plurality of coating films simultaneously sintered in the main firing step may be referred to as a “pre-baked unit PZT layer”.
The adhesion layer 101 is a layer provided to enhance the adhesion between the piezoelectric film 8 and the lower electrode 7. In this embodiment, the adhesion layer 101 is formed of a TiO layer. The TiO layer can be formed by, for example, a sol-gel method, a sputtering method, or the like.

  The seed layers 102 and 107 are layers provided to improve the crystallinity and adhesion of PZT, and are formed of, for example, a PZT seed layer made of PZT or a TiO seed layer made of TiO. The first seed layer 102 and the second seed layer 107 may be made of the same material, or may be made of different materials. The PZT seed layer is a gelled film comprising a coating step of coating a precursor solution containing PZT, a drying step of drying the coating film, and a pre-baking step of heating and gelling the coating film after the drying step. After the formation step is performed once, the formed coating film is heat-treated and sintered to form a main baking step. The TiO seed layer can be formed, for example, by a sol-gel method, a sputtering method or the like.

In the configuration example of FIG. 10, PZT layers 103 to 106 of the main firing unit of four layers are stacked between the first seed layer 102 and the second seed layer 107, and the second seed layer 107 is formed. The PZT layers 108 to 112 of the main firing unit of five layers are stacked.
Among the PZT layers 103 to 106 and 108 to 112 of the main baking unit, the PZT layers 103 to 106 and 108 to 111 of the main baking units other than the PZT layer 112 of the main baking unit of the uppermost layer In this embodiment, the gelled film forming process is performed a plurality of times, including a coating process of coating, a drying process of drying the coated film, and a pre-baking process of heating and gelling the coated film after the drying process. It is formed by performing the main baking process which heat-processes and bakes the gelatinized coating film, after being performed repeatedly. Therefore, the PZT layers 103 to 106 and 108 to 111 of the main firing units other than the PZT layer 112 of the uppermost main firing unit include the PZT layer 100 of the temporary firing units of three layers. The thickness of the PZT layer 100 of one temporary firing unit is 0.08 μm in this embodiment.

  On the other hand, the PZT layer 112 of the uppermost baking unit of the main baking unit heats and gelates the coating film after the coating step of coating the precursor solution containing PZT, the drying step of drying the coating film, and the drying step. After the gelled film forming process including the pre-baking process is performed once, the gelled coating film is formed by performing a main baking process of heat treatment and sintering. Therefore, the PZT layer of the uppermost main firing unit includes the PZT layer 100 of one temporary firing unit.

  As the number of layers of the coating film simultaneously sintered by the main baking step increases, that is, as the number of layers of the PZT layer of the temporary baking unit contained in the PZT layer of the main baking unit increases, the total number of main baking steps decreases. So, the production efficiency will be high. However, as the number of layers of the coating film to be sintered simultaneously in the main baking step increases, the thickness of the entire coating film to be sintered in the main baking step becomes thicker. Irregularities on the surface (upper surface) of the PZT layer become large.

  In the configuration example of FIG. 10, while the PZT layers 103 to 106 and 108 to 111 of the main firing units other than the PZT layer 112 of the main firing unit of the uppermost layer are three PZT layers of temporary firing units. The PZT layer of the temporary firing unit contained in the PZT layer 112 of the main firing unit of the uppermost layer is one layer. Therefore, the unevenness of the surface of the PZT layer 112 of the uppermost main baking unit is smaller than the unevenness of the surface of the PZT layer 112 of the other main baking unit. As a result, the unevenness of the surface of the PZT layer 112 of the uppermost main baking unit is higher than the unevenness of the interface between the PZT layer 112 of the main baking unit and the PZT layer 112 of the second main baking unit adjacent thereto. small. Thereby, the piezoelectric film 8 having a smooth top surface is obtained. Thereby, the adhesion between the piezoelectric film 8 and the upper electrode 9 can be improved. Moreover, since the parallelism between the lower electrode 7 and the upper electrode 9 can be improved, the piezoelectric performance of the piezoelectric film can be improved.

  Further, in the configuration example of FIG. 10, the piezoelectric film 8 has the PZT layer 103 of the lowermost main firing unit in addition to the first seed layer 102 existing on the lower surface side of the lowermost PZT layer 103 of the main baking unit. And a second seed layer 107 interposed between the PZT layers 106 and 108 of adjacent main firing units at an intermediate position of the PZT layer 112 of the main firing unit of the top layer. Therefore, as compared with the case where the seed layer is provided only on the lower surface side of the bottom main firing unit PZT layer 103, the crystal orientations of the PZT layers 103 to 106 and 108 to 112 can be easily aligned. Become. Thereby, the piezoelectric film 8 having stable piezoelectric characteristics is obtained.

  Such a piezoelectric film 8 is formed as follows. First, the adhesion layer 101 is formed on the lower electrode 7, and the first seed layer 102 is formed on the adhesion layer 101. Next, the PZT layer 103 of the lowermost main firing unit is formed on the first seed layer 102, and the PZT layers 104 to 106 of the second to fourth main firing units are sequentially formed thereon. Form. Next, a second seed layer 107 is formed on the fourth main firing unit PZT layer 106. Next, the PZT layer 108 of the fifth main firing unit is formed on the second seed layer 107, and the PZT layers 109 to 111 of the sixth to eighth main firing units are formed thereon. Are formed sequentially. Finally, the PZT layer 112 of the uppermost firing unit (ninth layer) of the main firing unit is formed on the PZT layer 111 of the eighth main firing unit.

An embodiment of the piezoelectric film 8 will be described.
(First embodiment)
In the first embodiment, the first seed layer 102 and the second seed layer 107 are composed of a PZT seed layer made of PZT. In the first embodiment, since the first seed layer 102 and the second seed layer 107 are made of the same material, the manufacturing efficiency can be improved.
Second Embodiment
In the second embodiment, the first seed layer 102 and the second seed layer 107 are composed of a TiO seed layer made of TiO. In the second embodiment, since the first seed layer 102 and the second seed layer 107 are made of the same material, the manufacturing efficiency can be improved.
Third Embodiment
In the third embodiment, the first seed layer 102 is composed of a TiO seed layer composed of TiO, and the second seed layer 107 is composed of a PZT seed layer composed of PZT.
Fourth Embodiment
In the fourth embodiment, the first seed layer 102 is made of a PZT seed layer made of PZT, and the second seed layer 107 is made of a TiO seed layer made of TiO.

  In the configuration example of FIG. 10, the PZT layers of temporary firing units included in the PZT layers 103 to 106 and 108 to 111 of main firing units other than the PZT layer 112 of main firing unit of the uppermost layer are three layers. However, it is only necessary that the number of PZT layers of the temporary firing unit contained in the PZT layer 112 of the second main firing unit from the top adjacent to the PZT layer 111 of the uppermost main firing unit be two or more layers. The number of PZT layers of the temporary firing unit contained in the PZT layers 103 to 106 and 108 to 111 of the firing unit may be one or a plurality of layers other than three.

Further, the number of PZT layers of the main firing unit contained in the piezoelectric film 8 is not limited to the number of layers in the configuration example of FIG. 10, and may be set arbitrarily as long as it is two or more. Moreover, the thickness of the PZT layer of the temporary firing unit is not limited to the thickness of the configuration example of FIG. 10, and can be set arbitrarily.
Further, in the configuration example of FIG. 10, the second seed layer 107 is provided only at one predetermined intermediate position between the PZT layer 103 of the lower main firing unit and the PZT layer 112 of the upper main firing unit. Although provided, the second seed layer may be provided at a plurality of different intermediate positions.

In the above embodiments, the present invention is applied to an ink jet print head, but the present invention relates to a microphone using a piezoelectric film, a pressure sensor, an acceleration sensor, an angular velocity sensor, an ultrasonic sensor, a speaker, an IR sensor (Thermal sensor) etc. can be applied.
In addition, various design changes can be made within the scope of matters described in the claims.

The following features can be further extracted from this specification.
A1. A diaphragm, a vibrating membrane forming layer including a vibrating membrane disposed on the cavity and defining a top surface of the cavity, and a surface of the vibrating membrane opposite to the cavity are formed in contact with the cavity. A piezoelectric element having a peripheral edge receding inward of the cavity with respect to the vibrating membrane, the piezoelectric element comprising: a lower electrode formed on the surface of the vibrating membrane-forming layer opposite to the cavity; And a piezoelectric film provided between the upper electrode and the lower electrode, the upper electrode being disposed on the side opposite to the vibrating film-forming layer with respect to the electrode, wherein the lower electrode In a plan view seen from a direction normal to the main surface of the vibrating film, the main electrode portion constituting the piezoelectric element and the main electrode portion being drawn out from the main electrode portion in the direction along the surface of the vibrating film forming layer Said cavity And an extension portion extending outward of the cavity across the top surface portion periphery, and in the plan view, the main electrode portion is an inner electrode region which is inside the top surface portion periphery of the cavity in the lower electrode The extension portion includes an outer electrode region connected to the inner electrode region and outside the upper surface peripheral edge of the cavity in the lower electrode, the lower electrode including the inner electrode region The piezoelectric film utilization apparatus which has the thin part thinly formed across the boundary line with the said outer side electrode area | region.

  The region between the peripheral edge of the vibrating film and the peripheral edge of the piezoelectric element in the vibrating film, that is, the peripheral edge of the vibrating film is a region not constrained by the peripheral wall of the piezoelectric element or the cavity, and is a region where large deformation occurs . Therefore, when the piezoelectric element is driven, the peripheral portion of the vibrating film is bent so that the inner peripheral side of the peripheral portion of the vibrating film is displaced in the thickness direction of the cavity, thereby surrounding the peripheral portion of the vibrating film. The entire central portion is displaced in the thickness direction of the cavity.

  Of the region straddling the boundary between the inner electrode region and the outer electrode region in the lower electrode in plan view, the portion inside the periphery of the top surface portion of the cavity is formed on the peripheral portion of the vibrating membrane . For this reason, there is a possibility that the region straddling the boundary between the inner electrode region and the outer electrode region in the lower electrode may prevent the deformation of the vibrating membrane. In this configuration, the lower electrode has a thin portion formed thin across the boundary between the inner electrode region and the outer electrode region. As a result, the deformation of the vibrating membrane is less likely to be impeded compared to when the entire lower electrode is thick.

  Further, in this configuration, in the lower electrode, since the thickness of the region other than the thin portion can be formed thicker than the thin portion, compared to the case where the entire thickness of the lower electrode is thin, The resistance value can be reduced. That is, according to the present invention, it is possible to provide a piezoelectric film utilization apparatus capable of reducing the resistance value of the lower electrode and increasing the displacement of the vibrating film.

A2. The piezoelectric film utilization apparatus according to “A1.”, Wherein the thin portion is formed in the entire area of a boundary between the inner electrode region and the outer electrode region in the lower electrode. In this configuration, the displacement of the diaphragm can be made larger than in the case where the thin portion is formed only in part of the boundary between the inner electrode region and the outer electrode region in the lower electrode.
A3. The piezoelectric film utilization apparatus according to "A2.", Wherein the main electrode portion is also formed in a thin thin portion having a small thickness. In this configuration, the displacement of the diaphragm can be further increased.

A4. The piezoelectric film utilization apparatus as described in "A2." Whose thickness of the area | region containing the said main electrode part in the said lower electrode is thicker than the thickness of the said thin part. In this configuration, the resistance value of the lower electrode can be further reduced.
A5. The piezoelectric film according to “A4.”, Wherein the thickness of the entire main electrode portion is thicker than the thickness of the thin portion, and the thickness of the region other than the main electrode portion in the inner electrode region is thin apparatus. In this configuration, the resistance value of the lower electrode can be further reduced, and the displacement of the diaphragm can be further increased.

A6. The piezoelectric film utilization apparatus according to “A1.”, Wherein the thin portion is formed at a part of a boundary between the inner electrode region and the outer electrode region in the lower electrode. In this configuration, the resistance value of the lower electrode can be reduced as compared to the case where the thin portion is formed in the entire boundary line between the inner electrode region and the outer electrode region in the lower electrode.
A7. The piezoelectric body according to "A6.", Wherein the thin portion includes a plurality of thin portions formed at intervals along a boundary between the inner electrode region and the outer electrode region in the lower electrode. Membrane utilization device.

A8. The piezoelectric film utilization apparatus according to "A7.", Wherein the plurality of thin portions have a rectangular shape elongated in a direction along a boundary between the inner electrode region and the outer electrode region in the lower electrode.
A9. The piezoelectric film utilization apparatus according to any one of "A6." To "A8.", Wherein the thickness of the region including the main electrode portion in the lower electrode is thicker than the thickness of the thin portion. In this configuration, the resistance value of the lower electrode can be further reduced.

A10. The piezoelectric film according to “A9.”, Wherein the thickness of the entire main electrode portion is thicker than the thickness of the thin portion, and the thickness of the region other than the main electrode portion in the inner electrode region is thin. apparatus. In this configuration, the resistance value of the lower electrode can be further reduced, and the displacement of the diaphragm can be further increased.
A11. The top surface portion of the cavity is rectangular in one direction in the plan view, and the main electrode portion has a width shorter than the width of the top surface portion of the cavity in the lateral direction and the top of the cavity in plan view. The one-side long rectangular shape having a length shorter than the longitudinal length of the surface portion, and both end edges and both side edges thereof are respectively recessed inward of the cavity than both end edges and both side edges of the top surface portion of the cavity The extension portion extends outward of the top surface side edge across the middle portion of the corresponding side edge of the top surface portion of the cavity from each side edge of the main electrode portion; The boundary between the electrode region and the outer electrode region includes two boundaries corresponding to the middle of each side edge of the top surface of the cavity, in any of "A1." To "A10." The piezoelectric film utilization apparatus of description.

A12. The piezoelectric film utilization apparatus as described in "A11." In which the said cavity is provided with two or more and these several cavities are arrange | positioned along with the transversal direction of the said cavity. In this configuration, it is possible to provide, for example, a piezoelectric film utilizing apparatus suitable for an inkjet print head.
A13. Opposite side edges of two of the main electrode parts respectively arranged on two adjacent cavities are connected by the extensions drawn from them, and two adjacent cavities of the extensions are connected. The piezoelectric film utilization device according to "A12.", Wherein the thickness of the substantially entire region between the regions is thicker than the thickness of the thin portion. In this configuration, it is possible to provide a piezoelectric film utilizing apparatus suitable for an ink jet print head and having a lower resistance value of the lower electrode.

  A14. The extension portions drawn from the plurality of main electrode portions disposed on the plurality of cavities are connected at positions outside the respective cavities than one end in the longitudinal direction of the respective cavities in the plan view. , The piezoelectric-film utilization apparatus as described in "A13." In this configuration, the lower electrode can be connected to the outside at a position outside each cavity than one longitudinal end of each cavity.

A15. The piezoelectric film according to "A14.", Wherein the lower electrode has a plurality of cut-out portions formed in a region including each of the end portions on the one end side in the longitudinal direction of each cavity in the plan view. apparatus. In this configuration, the displacement of the piezoelectric film of each piezoelectric element can be further increased.
Further, the following features can be further extracted from this specification.

B1. A piezoelectric film including PZT layers of a plurality of main firing units stacked, wherein the unevenness of the surface of the PZT layer of the top main firing unit is adjacent to the PZT layer of the top main firing unit and the PZT layer of the top layer. The piezoelectric film smaller than the unevenness of the interface between the second main fired unit and the PZT layer.
The “PZT layer of the main firing unit” is a coating step of applying a precursor solution containing PZT, a drying step of drying the coating film, and a pre-baking step of heating the coating film after the drying step to gelate The PZT layer is formed by performing the main baking step of subjecting the gelled coating film to heat treatment and sintering after the gelled film formation step consisting of the above is performed one or more times. According to this configuration, a piezoelectric film having a smooth top surface can be obtained.

B2. The piezoelectric film according to "B1.", Wherein the thickness of the PZT layer of the top main firing unit is thinner than the thickness of the PZT layer of the second top main firing unit. According to this configuration, a piezoelectric film having a smooth top surface can be obtained.
B3. The PZT layer of the main baking unit of the uppermost layer applies a coating process of applying a precursor solution containing PZT, a drying process of drying the coating film, and a pre-baking of heating the coating film after the drying process. After the gelled film forming step including the step is performed once, the gelled coated film is heat-treated and sintered, and the main baking step of sintering is performed, “B1.” Or “B2. The piezoelectric film as described in "".

  In the PZT layer of the main firing unit formed by performing the main firing step after performing the gelled film forming step consisting of the application step, the drying step, and the temporary firing step once, the coating step, the drying step, and the temporary As compared with the PZT layer of the main firing unit formed by performing the main firing step after the gelled film forming step including the firing step is performed a plurality of times, the unevenness on the surface thereof becomes smaller. Therefore, in this configuration, the unevenness of the surface of the PZT layer of the main firing unit of the uppermost layer is reduced. Thereby, a piezoelectric film having a smooth top surface is obtained.

B4. The PZT layer of the second main firing unit from above is subjected to the main firing step after the gelled film forming step including the application step, the drying step, and the temporary firing step is performed a plurality of times. The piezoelectric film as described in "B3."
B5. The PZT layer of each main firing unit other than the PZT layer of the top main layer main firing unit is subjected to the gelled film formation step including the application step, the drying step, and the temporary firing step a plurality of times, The piezoelectric film as described in "B3." Formed by performing this baking process.

B6. The piezoelectric material film in any one of "B1."-"B5." Containing the 1st seed layer which exists in the lower surface side of the PZT layer of this baking unit of the lowest layer. In this configuration, the crystal orientations of the PZT layers of the main firing units are easily aligned. Thus, a piezoelectric film having stable piezoelectric characteristics can be obtained.
B7. An intermediate position between the PZT layer of the lowermost main firing unit and the PZT layer of the uppermost main layer, including a second seed layer interposed between the PZT layers of two adjacent main firing units. The piezoelectric film as described in "B6." In this configuration, the crystal orientations of the PZT layers of the main firing units are more easily aligned. Thereby, a piezoelectric film having more stable piezoelectric characteristics can be obtained.

B8. The piezoelectric film according to "B7.", Wherein the first seed layer and the second seed layer are made of the same material. In this configuration, the manufacturing efficiency of the piezoelectric film can be improved.
B9. The piezoelectric film according to "B8.", Wherein the first seed layer and the second seed layer are each composed of a PZT seed layer made of PZT.
B10. The piezoelectric film according to "B8.", Wherein the first seed layer and the second seed layer are composed of a TiO seed layer made of titanium oxide.

B11. The piezoelectric film according to "B7.", Wherein the first seed layer and the second seed layer are made of different materials.
B12. The piezoelectric film according to "B11.", Wherein the first seed layer is composed of a TiO seed layer composed of titanium oxide, and the second seed layer is composed of a PZT seed layer composed of PZT.

B13. The piezoelectric film according to "B11.", Wherein the first seed layer is composed of a PZT seed layer composed of PZT, and the second seed layer is composed of a TiO seed layer composed of titanium oxide.
B14. The PZT seed layer is a gelation comprising a coating step of coating a precursor solution containing PZT, a drying step of drying the coating film, and a pre-baking step of heating the gelation of the coating film after the drying step. After the film forming step is performed once, the gelled coating film is heat-treated and sintered to perform the main baking step, thereby forming "B9.", "B12." Or "B13." The piezoelectric film according to any one of the above.

  B15. A piezoelectric element comprising a lower electrode, the piezoelectric film according to any one of "B1." To "B14." Formed on the lower electrode, and an upper electrode formed on the piezoelectric film. In this configuration, since the uppermost surface of the piezoelectric film is smooth, the adhesion between the piezoelectric film and the upper electrode can be improved. Moreover, since the parallelism between the lower electrode and the upper electrode can be improved, the piezoelectric performance of the piezoelectric film can be improved. Thereby, the piezoelectric element excellent in piezoelectric performance can be provided.

  B16. An inkjet print head, comprising: a cavity; a vibrating membrane disposed above the cavity and defining a top surface portion of the cavity; and a piezoelectric element described in "B15." Formed on the vibrating membrane. In this configuration, it is possible to provide an ink jet print head with high ejection performance by using a piezoelectric element with excellent piezoelectric performance.

Reference Signs List 1 inkjet print head 2 silicon substrate 3 a discharge port 4 ink supply path 5 piezoelectric chamber (cavity)
5a, 5b both ends 5c, 5d of top of piezoelectric chamber 6 both sides of top of piezoelectric chamber 6 piezoelectric element 6a, 6b both ends of piezoelectric 6c, 6d both sides of piezoelectric 7 lower electrode 7A main electrode 7B extended Part 7C Crossover area 8 Piezoelectric film 9 Upper electrode 10 Vibrating film forming layer 10A Vibrating film 10Aa, 10Ab Both ends of vibrating film 10Ac, 10Ad Vibrating film on both sides 101 Adhesive layer 103 to 106, 108 to 112 Layer 102 first seed layer 107 second seed layer

Claims (10)

A piezoelectric film comprising a plurality of stacked main firing unit PZT layers,
A first seed layer existing on the lower surface side of the lowermost main firing unit PZT layer;
And a second seed layer interposed between the PZT layers of two adjacent main firing units at an intermediate position between the PZT layer of the lower main firing unit and the PZT layer of the uppermost main firing unit. , Piezoelectric film.   The piezoelectric film according to claim 1, wherein the first seed layer and the second seed layer are made of the same material.   The piezoelectric film according to claim 2, wherein the first seed layer and the second seed layer are composed of a PZT seed layer made of PZT.   The piezoelectric film according to claim 2, wherein the first seed layer and the second seed layer are composed of a TiO seed layer made of titanium oxide.   The piezoelectric film according to claim 1, wherein the first seed layer and the second seed layer are made of different materials.   The piezoelectric film according to claim 5, wherein the first seed layer is composed of a TiO seed layer composed of titanium oxide, and the second seed layer is composed of a PZT seed layer composed of PZT.   The piezoelectric film according to claim 5, wherein the first seed layer is composed of a PZT seed layer made of PZT, and the second seed layer is composed of a TiO seed layer made of titanium oxide.   The PZT seed layer is a gelation comprising a coating step of coating a precursor solution containing PZT, a drying step of drying the coating film, and a pre-baking step of heating the gelation of the coating film after the drying step. The film forming process according to any one of claims 3, 6 or 7, which is formed by performing a main baking process of heat-treating and sintering the gelled coating film after the film forming process is performed once. Piezoelectric film.   A piezoelectric element comprising: a lower electrode; the piezoelectric film according to any one of claims 1 to 8 formed on the lower electrode; and an upper electrode formed on the piezoelectric film. With the cavity,
A vibrating membrane disposed on the cavity and defining a top surface of the cavity;
An ink jet print head comprising the piezoelectric element according to claim 9 formed on the vibrating film.

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