JP2017077708A - Mems device, liquid jetting head, and liquid jetting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a MEMS device in which breakage such as burning, in an end part of an upper electrode layer 39 stacked on a piezoelectric layer 38 is suppressed, and to provide a liquid jetting head and a liquid jetting device.SOLUTION: A MEMS device comprises a drive area 35 having a laminate structure in which a lower electrode layer 37, a piezoelectric layer 38, and an upper electrode layer 39 are stacked in this order. The lower electrode layer 37, piezoelectric layer 38, and upper electrode layer 39 are extended from the drive area 35 to a non-drive area 36 outside the drive area 35. In the upper electrode layer 39 in at least the non-drive area 36 and on the opposite side of the piezoelectric layer 38, a common metal layer 40b electrically connected to the piezoelectric layer 38 is formed. In the extending direction of the upper electrode layer 39, the end of the common metal layer 40b on the opposite side of the drive area 35 is formed more on the drive area 35 side from the end of the upper electrode layer 39 on the opposite side of the drive area 35.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a MEMS device including a first electrode layer, a second electrode layer, and an insulator layer sandwiched between these electrode layers, a liquid ejecting head including the MEMS device, and a liquid ejecting apparatus It is about.

  A MEMS device including a first electrode layer, a second electrode layer, and an insulator layer sandwiched between these electrode layers is applied to various apparatuses (for example, a liquid ejecting apparatus and a sensor). . For example, in a liquid ejecting apparatus, a MEMS device including a piezoelectric layer as a kind of insulator layer is incorporated in a liquid ejecting head that ejects liquid. As such a liquid ejecting apparatus, for example, there are image recording apparatuses such as an ink jet printer and an ink jet plotter. Recently, there are various kinds of liquid ejecting apparatuses taking advantage of the feature that a very small amount of liquid can be accurately landed on a predetermined position. It is also applied to manufacturing equipment. For example, a display manufacturing apparatus for manufacturing a color filter such as a liquid crystal display, an electrode forming apparatus for forming an electrode such as an organic EL (Electro Luminescence) display or FED (surface emitting display), a chip for manufacturing a biochip (biochemical element) Applied to manufacturing equipment. The recording head for the image recording apparatus ejects liquid ink, and the color material ejecting head for the display manufacturing apparatus ejects solutions of R (Red), G (Green), and B (Blue) color materials. The electrode material ejecting head for the electrode forming apparatus ejects a liquid electrode material, and the bioorganic matter ejecting head for the chip manufacturing apparatus ejects a bioorganic solution.

  In the liquid jet head, a piezoelectric layer sandwiched between the first electrode layer and the second electrode layer is driven by applying a voltage (electric signal) to both electrode layers. And it is comprised so that a pressure fluctuation may be produced in the liquid in a pressure chamber by this drive, and a liquid may be ejected from a nozzle using this pressure fluctuation. That is, both electrode layers and the portion sandwiched between them function as a piezoelectric element that causes pressure fluctuation in the pressure chamber. Here, a voltage from the control unit is supplied to each electrode layer via a wiring and a bump formed on the wiring board. For this reason, pads (electrodes) connected to bumps formed on the wiring substrate are stacked at least at the end of the second electrode layer stacked above the piezoelectric layer of both electrode layers. . And such a connection of a bump and a pad is performed on a piezoelectric material layer (refer patent document 1).

JP 2004-136663 A

  By the way, when the piezoelectric layer is damaged due to externally applied force or deformation of the piezoelectric layer itself due to driving of the piezoelectric element, the second end formed above the end of the pad, that is, the piezoelectric layer. There is a possibility that leakage current flows between the end of the electrode layer and the electrode such as the first electrode layer formed below the piezoelectric layer, and the piezoelectric layer and the second electrode layer are destroyed. there were. Specifically, there was a risk of burning out at the end of the second electrode layer.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a MEMS device, a liquid jet, in which damage such as burning at the end of the second electrode layer laminated on the insulator layer is suppressed. A head and a liquid ejecting apparatus are provided.

The MEMS device of the present invention has been proposed to achieve the above object, and includes a drive region having a stacked structure in which a first electrode layer, an insulator layer, and a second electrode layer are stacked in this order. With
The first electrode layer, the insulator layer, and the second electrode layer extend from the driving region to a non-driving region outside the driving region,
A third electrode layer electrically connected to the second electrode layer is formed at least on the side of the second electrode layer opposite to the insulator layer in the non-driving region,
In the extending direction of the second electrode layer, the end of the third electrode layer on the side opposite to the driving region is more driven than the end of the second electrode layer on the side opposite to the driving region. It is formed on the region side.

  According to this configuration, the electrical resistance in the second electrode layer formed outside the end opposite to the driving region of the third electrode layer is such that the second electrode layer and the third electrode layer are Since the height is higher than the stacked region, the current flowing through the second electrode layer outside the third electrode layer can be suppressed. Thereby, the rise in voltage at the end portion of the second electrode layer can be suppressed, and damage to the insulator layer and the second electrode layer due to leakage current flowing through the end portion can be suppressed. As a result, the reliability of the MEMS device is improved.

  In the above configuration, the film thickness of the second electrode layer formed outside the end of the third electrode layer opposite to the driving region is the thickness of the region where the third electrode layer is formed. It is desirable that the thickness of the second electrode layer is smaller.

  According to this configuration, the electrical resistance of the second electrode layer formed outside the end of the third electrode layer opposite to the driving region can be further increased. Thereby, damage to the insulator layer and the second electrode layer at the end of the second electrode layer can be further suppressed.

  In each of the above structures, it is preferable that the second electrode layer includes a plurality of conductive layers.

  According to this configuration, it is possible to easily form the second electrode layer having an increased electrical resistance outside the end opposite to the driving region of the third electrode layer.

Moreover, the liquid jet head of the present invention includes the MEMS device having the above-described configuration,
A pressure chamber at least partially partitioned by the drive region;
A nozzle communicating with the pressure chamber,
The insulator layer is a piezoelectric layer.

  According to this configuration, the reliability of the liquid jet head is improved by improving the reliability of the MEMS device.

  In the above-described configuration, it is preferable that a bump substrate that contacts the third electrode layer is formed, and a wiring board that is spaced apart from the MEMS device is provided.

  According to this configuration, the wiring board can be arranged so as to protect the piezoelectric element. Accordingly, it is not necessary to separately provide a protective substrate for protecting the piezoelectric element, and the configuration of the liquid ejecting head is simplified.

  In the above configuration, it is preferable that the bump includes a resin portion protruding from the wiring substrate and a conductive layer formed on the surface of the resin portion.

  According to this configuration, when the bump is bonded to the third electrode layer, the resin portion is elastically deformed to secure a bonding area between the third electrode layer and the bump (conductive layer), thereby making the both more reliable. Can be conducted.

  Further, in the above configuration, it is preferable that the bumps are formed of conductive portions protruding from the wiring board.

  According to this configuration, the bump can be easily formed.

  According to another aspect of the invention, a liquid ejecting apparatus includes the liquid ejecting head having the above-described configuration.

FIG. 3 is a perspective view illustrating a configuration of a printer. FIG. 3 is a cross-sectional view illustrating a configuration of a recording head. It is sectional drawing explaining the structure of a piezoelectric device. It is a top view explaining the structure of a piezoelectric device. It is sectional drawing to which the principal part of the piezoelectric device was expanded. It is sectional drawing explaining the structure of the piezoelectric device in 2nd Embodiment. It is sectional drawing explaining the structure of the piezoelectric device in 3rd Embodiment. It is sectional drawing explaining the structure of the piezoelectric device in 4th Embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. In the embodiments described below, various limitations are made as preferred specific examples of the present invention. However, the scope of the present invention is not limited to the following description unless otherwise specified. However, the present invention is not limited to these embodiments. In the following, an ink jet recording head (hereinafter referred to as a recording head) which is a kind of a liquid ejecting head including a piezoelectric device which is a kind of MEMS device according to the present invention, and a kind of a liquid ejecting apparatus equipped with the ink jet recording head. An ink jet printer (hereinafter referred to as a printer) will be described as an example.

  The configuration of the printer 1 will be described with reference to FIG. The printer 1 is an apparatus that records an image or the like by ejecting ink (a type of liquid) onto the surface of a recording medium 2 (a type of landing target) such as a recording paper. The printer 1 includes a recording head 3, a carriage 4 to which the recording head 3 is attached, a carriage moving mechanism 5 that moves the carriage 4 in the main scanning direction, a conveyance mechanism 6 that transfers the recording medium 2 in the sub scanning direction, and the like. Yes. Here, the ink is stored in an ink cartridge 7 as a liquid supply source. The ink cartridge 7 is detachably attached to the recording head 3. It is also possible to employ a configuration in which the ink cartridge is disposed on the main body side of the printer and supplied from the ink cartridge to the recording head through the ink supply tube.

  The carriage moving mechanism 5 includes a timing belt 8. The timing belt 8 is driven by a pulse motor 9 such as a DC motor. Therefore, when the pulse motor 9 operates, the carriage 4 is guided by the guide rod 10 installed on the printer 1 and reciprocates in the main scanning direction (width direction of the recording medium 2). The position of the carriage 4 in the main scanning direction is detected by a linear encoder (not shown) which is a kind of position information detecting means. The linear encoder transmits the detection signal, that is, the encoder pulse (a kind of position information) to the control unit of the printer 1.

  Next, the recording head 3 will be described. FIG. 2 is a cross-sectional view illustrating the configuration of the recording head 3. FIG. 3 is an enlarged sectional view of the main part of the recording head 3, that is, a sectional view of the piezoelectric device 14. FIG. 4 is an enlarged plan view of a main part (left end part in FIG. 3) of the piezoelectric device 14. FIG. 5 is an enlarged cross-sectional view of the main part of the piezoelectric device 14. In addition, the white arrow in FIG. 5 represents the flow of electric current. For convenience, the stacking direction of the members constituting the piezoelectric device 14 will be described as the vertical direction. As shown in FIG. 2, the recording head 3 in this embodiment is attached to the head case 16 in a state where the wiring substrate 33, the piezoelectric device 14, and the flow path unit 15 are stacked.

  The head case 16 is a box-shaped member made of synthetic resin, and a liquid introduction path 18 for supplying ink to each pressure chamber 30 is formed therein. The liquid introduction path 18 is a space for storing ink common to a plurality of formed pressure chambers 30 together with a common liquid chamber 25 described later. In the present embodiment, two liquid introduction paths 18 are formed corresponding to the rows of pressure chambers 30 arranged in two rows. An accommodation space 17 that is recessed in a rectangular parallelepiped shape from the lower surface to the middle of the height direction of the head case 16 is formed on the lower surface side of the head case 16. When the flow path unit 15 described later is joined in a state of being positioned on the lower surface of the head case 16, the piezoelectric device 14 and the wiring board 33 stacked on the communication substrate 24 are accommodated in the accommodation space 17. It is configured.

  The flow path unit 15 joined to the lower surface of the head case 16 includes a nozzle plate 21 having a plurality of nozzles 22 arranged in a row, and a communication substrate 24 provided with a common liquid chamber 25 and the like. A plurality of nozzles 22 (nozzle rows) arranged in a row are provided at equal intervals from the nozzle 22 on one end side to the nozzle 22 on the other end side at a pitch corresponding to the dot formation density. The common liquid chamber 25 is formed in a long shape along the direction in which the pressure chambers 30 are arranged side by side (nozzle row direction) as a flow path common to the plurality of pressure chambers 30. Each pressure chamber 30 and the common liquid chamber 25 communicate with each other through an individual communication passage 26 formed in the communication substrate 24. That is, the ink in the common liquid chamber 25 is distributed to each pressure chamber 30 via the individual communication passage 26. Further, the nozzle 22 and the pressure chamber 30 corresponding to the nozzle 22 communicate with each other via a nozzle communication passage 27 that penetrates the communication substrate 24 in the plate thickness direction.

  As shown in FIGS. 2 and 3, the piezoelectric device 14, which is a kind of MEMS device, includes a pressure chamber forming substrate 29, a diaphragm 31, and a piezoelectric element 32 that are stacked in this order. A wiring substrate 33 is disposed on the upper surface of the piezoelectric device 14 with an interval that does not hinder the driving of the piezoelectric element 32. In addition, the piezoelectric device 14 and the wiring board 33 in this embodiment are accommodated in the accommodation space 17 in a united state by being bonded by an adhesive 48.

  The pressure chamber forming substrate 29 is a hard plate material made of silicon, for example, made of a silicon single crystal substrate whose surface (upper surface and lower surface) has a (110) plane. A part of the pressure chamber forming substrate 29 is removed in the plate thickness direction by etching, and a plurality of spaces to be the pressure chambers 30 are formed along the nozzle row direction. This space is partitioned by the communication substrate 24 on the lower side and partitioned by the diaphragm 31 to constitute the pressure chamber 30. In addition, this space, that is, the pressure chamber 30 is formed in two rows corresponding to the nozzle rows formed in two rows. Each pressure chamber 30 is formed in an elongated shape in a direction orthogonal to the nozzle row direction, the individual communication passage 26 communicates with one end portion in the longitudinal direction, and the nozzle communication passage 27 communicates with the other end portion. . Note that the sidewall of the pressure chamber 30 in the present embodiment is inclined with respect to the upper surface or the lower surface of the pressure chamber forming substrate 29 due to the crystallinity of the silicon single crystal substrate.

The diaphragm 31 is a thin film member having elasticity, and is laminated on the upper surface of the pressure chamber forming substrate 29 (surface opposite to the communication substrate 24). The diaphragm 31 seals the upper opening of the space to be the pressure chamber 30. In other words, the upper surface which is a part of the pressure chamber 30 is partitioned by the diaphragm 31. A region defining the upper surface of the pressure chamber 30 in the diaphragm 31 functions as a displacement portion that deforms (displaces) in a direction away from or in the direction of approaching the nozzle 22 as the piezoelectric element 32 is bent and deformed. That is, a part of the pressure chamber 30 in the diaphragm 31, specifically, a region defining the upper surface is a drive region 35 in which bending deformation is allowed. On the other hand, a region outside the upper opening of the pressure chamber 30 in the diaphragm 31 (a region outside the driving region 35) is a non-driving region 36 in which bending deformation is inhibited. The diaphragm 31 is, for example, an elastic film made of silicon dioxide (SiO ₂ ) formed on the upper surface of the pressure chamber forming substrate 29 and an insulator made of zirconium dioxide (ZrO ₂ ) formed on the elastic film. And a membrane. And the piezoelectric element 32 is laminated | stacked in the position corresponding to the drive area | region 35 on this insulating film (surface on the opposite side to the pressure chamber 30 side of the diaphragm 31), respectively.

  The piezoelectric element 32 of the present embodiment is a so-called flexure mode piezoelectric element. The piezoelectric elements 32 are arranged in two rows corresponding to the rows of pressure chambers 30 arranged in two rows. As shown in FIG. 3, each piezoelectric element 32 is a piezoelectric body that is a kind of a lower electrode layer 37 (corresponding to the first electrode layer in the present invention) and an insulating layer (dielectric layer) on the diaphragm 31. The layer 38 and the upper electrode layer 39 (corresponding to the second electrode layer in the present invention) are sequentially laminated. That is, the piezoelectric element 32 is a kind of a laminated structure including the lower electrode layer 37, the piezoelectric layer 38, and the upper electrode layer 39. In this embodiment, the lower electrode layer 37 is an individual electrode formed independently for each piezoelectric element 32, and the upper electrode layer 39 is a common electrode formed continuously across the plurality of piezoelectric elements 32. It has become. That is, as shown in FIG. 4, the lower electrode layer 37 and the piezoelectric layer 38 are formed for each pressure chamber 30. On the other hand, the upper electrode layer 39 is formed across the plurality of pressure chambers 30. In this embodiment, as shown in FIG. 3, since the rows of pressure chambers 30 are arranged in two rows, the lower electrode layer 37 and the piezoelectric layer 38 are arranged in two rows correspondingly. Has been. Further, the upper electrode layer 39 is formed from a position corresponding to one row of pressure chambers 30 to a position corresponding to the other row of pressure chambers 30.

  The shape of each layer 37, 38, 39 will be described in detail below. As shown in FIG. 4, the lower electrode layer 37 in the present embodiment extends along the longitudinal direction of the pressure chamber 30 with a width narrower than the width (dimension in the nozzle row direction) of the drive region 35 (pressure chamber 30). Has been. In the present embodiment, the width of the lower electrode layer 37 extending from the end of the drive region 35 to the non-drive region 36 is narrower (smaller) than the width of the lower electrode layer 37 formed at the center of the drive region 35. Is formed. In other words, the width at the end of the lower electrode layer 37 is narrower than the width at the center. Note that the width of the end portion of the lower electrode layer 37 is narrower than the width of a common bump 42a described later. Further, both ends of the lower electrode layer 37 in the extending direction (longitudinal direction) are extended from the driving region 35 to the non-driving region 36. Specifically, the end on one side of the lower electrode layer 37 (outside in the piezoelectric device 14) in the present embodiment is extended to the outside of the end of the piezoelectric layer 38 on the same side as shown in FIG. ing. An individual metal layer 40c, which will be described later, is laminated on the lower electrode layer 37 outside the end of the piezoelectric layer 38, and has the same potential as the individual metal layer 40c. Further, the end on the other side (the inner side in the piezoelectric device 14) in the extending direction of the lower electrode layer 37 is between the end of the drive region 35 and the end of the piezoelectric layer 38 on the same side as shown in FIG. It extends to the non-driving area 36.

  In addition, as shown in FIG. 4, the piezoelectric layer 38 in the present embodiment extends along the longitudinal direction of the pressure chamber 30 with a width narrower than the width of the drive region 35. Both ends in the extending direction (longitudinal direction) of the piezoelectric layer 38 are extended from the drive region 35 to the non-drive region 36 as shown in FIG. Specifically, one end of the piezoelectric layer 38 in this embodiment is a non-driving region 36 between the end of the driving region 35 and the end of the lower electrode layer 37 on the same side, as shown in FIG. It is extended to. An individual metal layer 40 c extending from a position overlapping the lower electrode layer 37 is laminated at the end of the piezoelectric layer 38 in the non-driving region 36. Further, the other end in the extending direction of the piezoelectric layer 38 extends to the outside of the end of the lower electrode layer 37 on the same side, as shown in FIG.

  Furthermore, as shown in FIG. 4, the upper electrode layer 39 in the present embodiment extends in the nozzle row direction to the outside of the region where both ends thereof overlap the row of the group of pressure chambers 30. Further, as shown in FIG. 3, the upper electrode layer 39 is formed from the non-driving region 36 on one end side to the non-driving region 36 on the other end side in the piezoelectric device 14 in the longitudinal direction of the pressure chamber 30. . Specifically, one end in the extending direction of the upper electrode layer 39 is an area that overlaps one of the piezoelectric layers 38 arranged in parallel in one row, and is one driving area. It extends to the non-driving area 36 outside 35. More specifically, one end in the extending direction of the upper electrode layer 39 extends to a region between the outer end of one drive region 35 and the outer end of one piezoelectric layer 38. . The other end in the extending direction of the upper electrode layer 39 is a region overlapping the other piezoelectric layer 38 of the piezoelectric layers 38 arranged in two rows, and is more than the other driving region 35. It extends to the outer non-drive region 36. More specifically, the other end in the extending direction of the upper electrode layer 39 extends to a region between the outer end of the other drive region 35 and the outer end of the other piezoelectric layer 38. .

  A region where all of the lower electrode layer 37, the piezoelectric layer 38 and the upper electrode layer 39 are laminated, in other words, a region where the piezoelectric layer 38 is sandwiched between the lower electrode layer 37 and the upper electrode layer 39, It functions as the piezoelectric element 32. That is, when an electric field corresponding to the potential difference between the two electrodes is applied between the lower electrode layer 37 and the upper electrode layer 39, the piezoelectric layer 38 bends and deforms in a direction away from or close to the nozzle 22, thereby driving region The 35 diaphragms 31 are deformed. In the present embodiment, both ends of the piezoelectric element 32 extend to the non-driving area 36 outside the driving area 35 in the longitudinal direction of the piezoelectric element 32. It should be noted that deformation (displacement) of the portion of the piezoelectric element 32 that overlaps the non-drive region 36 is inhibited by the pressure chamber forming substrate 29.

  As the above-described lower electrode layer 37 and upper electrode layer 39, iridium (Ir), platinum (Pt), titanium (Ti), tungsten (W), nickel (Ni), palladium (Pd), gold (Au) And various metals such as these, alloys thereof, and alloys such as LaNiO 3 are used. As the piezoelectric layer 38, a ferroelectric piezoelectric material such as lead zirconate titanate (PZT), niobium (Nb), nickel (Ni), magnesium (Mg), bismuth (Bi) or yttrium is used. A relaxor ferroelectric or the like to which a metal such as (Y) is added is used. In addition, non-lead materials such as barium titanate can also be used.

  A metal layer 40 is laminated on each of the electrode layers 37 and 39 of the piezoelectric element 32 thus formed. In the present embodiment, a metal weight layer 40a that suppresses deformation of the other end of the drive region 35, a common metal layer 40b serving as a pad to which a common bump 42a described later is connected, and an individual bump 42b described later are connected. An individual metal layer 40c to be a pad is formed. As the metal layer 40, gold (Au), copper (Cu), an alloy thereof, or the like is used. When the metal layer 40 is made of gold (Au) or the like, the adhesion layer made of titanium (Ti), nickel (Ni), chromium (Cr), tungsten (W), or an alloy thereof is used as the metal layer. You may provide below 40.

  As shown in FIG. 3, the metal weight layer 40 a is laminated on the upper electrode layer 39 constituting the piezoelectric element 32, which is an end portion on the other side in the longitudinal direction of the piezoelectric element 32 (inner side in the piezoelectric device 14). ing. As a result, the metal weight layer 40 a is electrically connected to the upper electrode layer 39. In the present embodiment, the metal weight layer 40a is non-driven outside the other end of the piezoelectric element 32 (piezoelectric layer 38) from the region overlapping the other end of the drive region 35 in the longitudinal direction of the piezoelectric element 32. It extends to a region overlapping with the region 36. That is, the metal weight layer 40 a is formed at the boundary between the drive region 35 on the other side in the longitudinal direction of the drive region 35 and the non-drive region 36. Thereby, the deformation | transformation in the boundary of the drive area | region 35 and the non-drive area | region 36 is suppressed, and the failure | damage of the piezoelectric material layer 38 in the said boundary can be suppressed. Note that both ends of the metal weight layer 40 a in the nozzle row direction are extended to the outside of the region overlapping the row of the group of pressure chambers 30, similarly to the upper electrode layer 39.

  As shown in FIG. 3, the common metal layer 40b (corresponding to the third electrode layer in the present invention) is an end portion on one side (outside of the piezoelectric device 14) in the longitudinal direction of the piezoelectric element 32, and the piezoelectric element 32 is laminated on the upper electrode layer 39 constituting 32. That is, the upper electrode layer 39 is laminated on the side opposite to the insulator layer 38. As a result, the common metal layer 40 b is electrically connected to the upper electrode layer 39. In the present embodiment, the common metal layer 40 b overlaps with the non-driving region 36 on the inner side from the end on one side of the upper electrode layer 39 from the region overlapping the one end on the driving region 35 in the longitudinal direction of the piezoelectric element 32. It is extended to. More specifically, as shown in FIGS. 4 and 5, in the longitudinal direction of the piezoelectric element 32 (the extending direction of the upper electrode layer 39), the end of the common metal layer 40b opposite to the drive region 35 is the upper side. The electrode layer 39 is formed closer to the drive region 35 than the end opposite to the drive region 35. In other words, one end of the upper electrode layer 39 is formed outside the one end of the common metal layer 40b. That is, the metal portion formed above the piezoelectric layer 38 in the piezoelectric device 14 (on the side opposite to the lower electrode layer 37 side) is outside from the region where the common bump 42a described later is connected (the drive region 35 is defined as It is formed so as to become thinner toward the opposite side. Note that both ends of the common metal layer 40b in the nozzle row direction are extended to the outside of a region overlapping the row of the group of pressure chambers 30 in the same manner as the metal weight layer 40a. Further, deformation of the boundary between the drive region 35 and the non-drive region 36 is suppressed by the metal weight layer 40a. The common bump 42a is connected to the metal weight layer 40a in the non-drive region 36.

  As shown in FIGS. 3 and 4, the individual metal layer 40 c is laminated on the piezoelectric layer 38 and the lower electrode layer 37 outside the one end in the longitudinal direction of the piezoelectric element 32. Specifically, the individual metal layer 40c is a region that is out of one end of the upper electrode layer 39 in the longitudinal direction of the piezoelectric element 32 and that overlaps with one end of the piezoelectric layer 38. It extends beyond the region to a region overlapping with one end of the lower electrode layer 37. As shown in FIG. 4, the individual metal layer 40 c in the present embodiment is formed to have a width wider than the width at the end of the lower electrode layer 37, and a plurality of individual metal layers 40 c are formed along the nozzle row direction. Note that individual bumps 42b, which will be described later, are connected on the individual metal layer 40c.

  The wiring board 33 connected to the piezoelectric device 14 is disposed with a gap from the diaphragm 31 (or the piezoelectric element 32) so as to protect the piezoelectric element 32 with a plurality of bumps 42 interposed therebetween. It is a flat plate-shaped member. This interval is set to such an extent that the deformation of the piezoelectric element 32 is not hindered. The wiring substrate 33 is made of, for example, a silicon single crystal substrate whose surface (upper surface and lower surface) is a (110) plane, and is arranged to be substantially the same as the outer shape of the pressure chamber forming substrate 29 (piezoelectric device 14) in plan view. As shown in FIG. 3, a drive circuit 46 (driver circuit) that outputs a signal (drive signal) for individually driving each piezoelectric element 32 is formed in a region facing the piezoelectric element 32 of the wiring board 33. Yes. The drive circuit 46 is formed on the surface of a silicon single crystal substrate (silicon wafer) to be the wiring substrate 33 by using a semiconductor process (that is, a film forming process, a photolithography process, an etching process, etc.).

  Further, the wiring substrate 33 is a region that is out of the region facing the driving region 35 (the region facing the non-driving region 36), and is formed on the common metal layer 40b and the individual metal layer 40c formed on the piezoelectric layer 38. Bumps 42 projecting toward the pressure chamber forming substrate 29 are formed in the opposing regions. As shown in FIGS. 3 and 5, the bump 42 is electrically connected to an elastic resin portion 43 projecting from the wiring board 33 and a corresponding wiring in the drive circuit 46. And a conductive layer 44 formed on the surface. In the present embodiment, the individual bumps 42b connected to the individual metal layers 40c of the piezoelectric elements 32 formed in two rows are formed in two rows. In addition, common bumps 42a connected to the common metal layers 40b of the piezoelectric elements 32 formed in two rows are formed in two rows. For example, a resin such as a polyimide resin is used as the resin portion 43. As the conductive layer 44, a metal made of gold (Au), copper (Cu), nickel (Ni), titanium (Ti), tungsten (W), or an alloy thereof is used.

  More specifically, the resin portion 43 of the individual bump 42b is formed in a protruding shape along the nozzle row direction in a region facing the individual metal layer 40c on the surface of the wiring board 33. A plurality of conductive layers 44 of the individual bumps 42b are formed along the nozzle row direction corresponding to the piezoelectric elements 32 arranged in parallel along the nozzle row direction. That is, a plurality of individual bumps 42b are formed along the nozzle row direction. Each individual bump 42 b is connected to a corresponding individual metal layer 40 c on the piezoelectric layer 38. Thereby, each individual bump 42b is electrically connected to the lower electrode layer 37 via the individual metal layer 40c.

  In addition, the resin portion 43 of the common bump 42 a is formed in a ridge along the nozzle row direction in a region facing the common metal layer 40 b on the surface of the wiring substrate 33. In the present embodiment, a plurality of conductive layers 44 of the common bump 42a are formed along the nozzle row direction corresponding to the piezoelectric elements 32 arranged in parallel along the nozzle row direction. As shown in FIG. 4, the width (dimension in the nozzle row direction) of each common bump 42a (conductive layer 44) is the lower electrode layer 37 (that is, the end portion of the lower electrode layer 37) in the region overlapping the common bump 42a. It is wider (larger) than the width of. Each common bump 42 a is connected to the common metal layer 40 b at a plurality of locations along the nozzle row direction on the piezoelectric layer 38. Thereby, each common bump 42a is electrically connected to the upper electrode layer 39 via the common metal layer 40b. Note that the conductive layer 44 of the common bump 42 a may not be formed for each piezoelectric element 32. For example, it may be formed over a plurality of piezoelectric elements 32.

  The wiring substrate 33 and the MEMS device 14 (the pressure chamber forming substrate 29 on which the vibration plate 31 and the piezoelectric element 32 are laminated) are joined together by an adhesive 48 with each bump 42 interposed. As the adhesive 48, a resin having photosensitivity is preferably used. In addition, as such resin, resin which has an epoxy resin, an acrylic resin, a phenol resin, a polyimide resin, a silicone resin, a styrene resin etc. as a main component is desirable, for example. Such an adhesive 48 is applied onto the wiring substrate 33 or the vibration plate 31 in a state before being cured, and is then accurately formed at a predetermined position through an exposure process and a development process. Then, the adhesive 48 is fully cured in a state where the wiring substrate 33 and the MEMS device 14 are bonded with the adhesive 48 interposed therebetween.

  In the recording head 3 configured as described above, ink from the ink cartridge 7 is introduced into the pressure chamber 30 through the liquid introduction path 18, the common liquid chamber 25, the individual communication path 26, and the like. In this state, when a signal from the drive circuit 46 is supplied to the piezoelectric element 32 via each bump 42, the piezoelectric element 32 is driven and pressure fluctuation occurs in the pressure chamber 30. The recording head 3 uses this pressure fluctuation to eject ink droplets from the nozzles 22 via the nozzle communication path 27.

  As described above, in the recording head 3 according to this embodiment, the end of the common metal layer 40 b opposite to the drive region 35 in the extending direction of the upper electrode layer 39 is the drive region of the upper electrode layer 39. In the upper electrode layer 39 formed outside the end opposite to the drive region 35 of the common metal layer 40b because it is formed closer to the drive region 35 than the end opposite to the end 35 (see FIG. 5). The electric resistance becomes higher than the region where the upper electrode layer 39 and the common metal layer 40b are laminated. Thereby, the electric current which flows into the upper electrode layer 39 outside this common metal layer 40b can be suppressed. That is, as indicated by the white arrow in FIG. 5, a relatively large current flows from the upper electrode layer 39 and the common metal layer 40b to the common bump 42a, while the comparison is made to the upper electrode layer 39 outside the common metal layer 40b. Only small current flows. For this reason, an increase in voltage at the end of the upper electrode layer 39 is suppressed, and the piezoelectric layer 38 and the upper electrode layer 39 are damaged due to leakage current flowing from the end of the upper electrode layer 39 toward the piezoelectric layer 38. (Burnout etc.) can be suppressed. As a result, the reliability of the piezoelectric device 14 is improved, and the reliability of the recording head 3 is improved. Such an effect can be further enhanced particularly in the recording head 3 that performs pulse driving in which the voltage changes drastically. That is, in the pulse drive, since the current flowing through the upper electrode layer 39 and the common metal layer 40b (charge charge / discharge) is severe, even if a constant voltage is applied to the upper electrode layer 39 and the common metal layer 40b. In the end portion of the upper electrode layer 39 where current is difficult to flow, a rise in voltage is suppressed.

  In the present embodiment, since the wiring substrate 33 on which the bumps 42 are formed is arranged with a space from the piezoelectric device 14, the piezoelectric element 32 can be protected by the wiring substrate 33. That is, since the wiring substrate 33 can function as a protective substrate for protecting the piezoelectric element 32, it is not necessary to separately provide a protective substrate, and the configuration of the recording head 3 is simplified. The wiring board in the present invention is not limited to the wiring board 33 provided with the driving circuit 46 as described above. For example, the driving circuit may be provided on another member different from the wiring board (for example, a driving IC provided above the wiring board), and only wiring for relaying a signal from the driving circuit may be formed on the wiring board. Good. That is, the wiring board in the present invention is not limited to a wiring board provided with a drive circuit, and includes a wiring board on which only wiring is formed. In this embodiment, the resin portion 43 is elastically deformed because the bump 42 is provided with the resin portion 43 projecting from the wiring board 33 and the conductive layer 44 formed on the surface of the resin portion 43. As a result, a bonding area between the metal layer 40 and the bump 42 (conductive layer 44) can be ensured, and both can be conducted more reliably. In addition, when bonding the piezoelectric device 14 and the wiring substrate 33, it is possible to suppress the pressure applied between the piezoelectric device 14 and the wiring substrate 33 in order to reliably connect the bump 42 and the metal layer 40. As a result, damage to the piezoelectric device 14 or the wiring board 33 can be suppressed.

  By the way, in the above-described first embodiment, the film thickness of the upper electrode layer 39 is set to be substantially constant, but is not limited thereto. In the second embodiment shown in FIG. 6, the upper electrode layer 39 is formed so as to have a thin film thickness at the end. Specifically, as shown in FIG. 6, the thickness of the upper electrode layer 39 formed outside the end of the common metal layer 40 b opposite to the driving region 35 is the same as that of the common metal layer 40 b. It is formed thinner than the film thickness of the upper electrode layer 39 formed in other regions including the region. Thereby, the electrical resistance in the upper electrode layer 39 formed outside the end of the common metal layer 40b opposite to the drive region 35 can be further increased. As a result, damage (burnout, etc.) of the piezoelectric layer 38 and the upper electrode layer 39 at the end of the upper electrode layer 39 can be further suppressed. Further, since the film thickness of the upper electrode layer 39 in other regions can be increased, the electric resistance (wiring resistance) in the path from the upper electrode layer 39 and the common metal layer 40b to the common bump 42a can be suppressed. Since other configurations are the same as those of the first embodiment described above, description thereof is omitted.

  Further, in each of the above-described embodiments, the upper electrode layer 39 made of a single layer is exemplified, but the present invention is not limited to this. A configuration in which the upper electrode layer 39 includes a plurality of conductive layers can also be employed. For example, the upper electrode layer 39 in the third embodiment shown in FIG. 7 includes a first layer 39a, a second layer 39b, a third layer 39c, and a fourth layer 39d in this order from the piezoelectric layer 38 side. Are laminated. As in the second embodiment, the upper electrode layer 39 formed on the outer side of the end of the common metal layer 40b opposite to the end opposite to the drive region 35 has an upper electrode layer formed in another region. In the region outside the common metal layer 40b, the third layer 39c and the fourth layer 39d are removed, and the first layer 39a and the second layer 39b are used so as to be thinner than the thickness of the layer 39. An electrode layer 39 is formed. The upper electrode layer 39 having such a configuration can be easily manufactured by forming the layers 39a to 39d using a semiconductor process (that is, a film forming process, a photolithography process, an etching process, and the like). . That is, it is possible to easily form the upper electrode layer 39 having an increased electrical resistance outside the end of the common metal layer 40b opposite to the drive region 35.

  Note that the first layer 39a to the fourth layer 39d may be formed of the same conductive material, or may be formed of different conductive materials. In addition, when the metal layer 40 is made of gold (Au) or the like, it is desirable to form the fourth layer 39d located on the uppermost electrode layer 39 with a conductive material that is easily in close contact with the metal layer 40. In the present embodiment, the first layer 39a and the third layer 39c are formed of iridium (Ir), and the second layer 39b and the fourth layer 39d are formed of titanium (Ti). Moreover, the layer (conductive layer) which comprises the upper electrode layer 39 is not restricted to 4 layers, What is necessary is just two or more layers. Furthermore, the electrode layer left in the area | region outside the common metal layer 40b is not restricted to two layers, What is necessary is just to form at least 1 layer or more. Since other configurations are the same as those of the first embodiment described above, description thereof is omitted.

  Furthermore, in each of the above-described embodiments, the bump 42 is formed from the resin portion 43 and the conductive layer 44, but is not limited thereto. Various configurations can be adopted as the bump 42. For example, in the fourth embodiment shown in FIG. 8, bumps 42 made of conductive portions 45 such as metal protruding from the wiring board 33 are employed. That is, metal bumps 42 having no resin inside are employed. Thereby, formation of bump 42 becomes easy. In addition, as a metal employ | adopted as such a bump 42, gold | metal | money (Au), copper (Cu), these alloys, etc. are used. In addition, the structure which welds the bump which consists of solder to a metal layer, and the structure which welds resin containing silver (Ag) to a metal layer are also employable. That is, the conductive portion in the present invention includes a resin containing a metal in addition to the above-described metal.

  In the first embodiment described above, the upper electrode layer 39 common to the rows of the pressure chambers 30 formed in two rows is formed in one row, but the present invention is not limited to this. It is also possible to adopt a configuration in which the upper electrode layers are separately formed in regions corresponding to the respective pressure chamber rows corresponding to the rows of pressure chambers formed in two rows. Furthermore, in the above-described first embodiment, the pressure chambers 30, the piezoelectric elements 32, and the like are formed in two rows, but the present invention is not limited to this. The pressure chambers, piezoelectric elements, etc. may be formed in a single row. In the first embodiment, the common metal layer 40b is formed between one end of the drive region 35 and the non-drive region 36 outside the drive region 35. However, the present invention is not limited to this. I can't. The common metal layer may be formed at least on the upper electrode layer in the non-driving region.

  Furthermore, in the first embodiment described above, the lower electrode layer 37 is an individual electrode formed independently for each piezoelectric element 32, and the upper electrode layer 39 is a common structure formed continuously over a plurality of piezoelectric elements 32. Although it was an electrode, it is not restricted to this. It is also possible to adopt a configuration in which the lower electrode layer is a common electrode formed continuously over a plurality of piezoelectric elements, and the upper electrode layer is an individual electrode formed independently for each piezoelectric element. In this case, the upper electrode layer serving as the individual electrode is the second electrode layer in the present invention, and the individual metal layer laminated on the end of the upper electrode layer is the third electrode layer in the present invention. Even in this case, in the extending direction of the upper electrode layer, the end of the individual metal layer opposite to the driving region is formed closer to the driving region than the end of the upper electrode layer opposite to the driving region. .

  In the above description, the piezoelectric device 14 incorporated in the recording head 3 is described as an example of the MEMS device. However, the present invention is not limited to the first electrode layer, the insulator layer, and the second electrode. It can also be applied to other MEMS devices with layers and drive regions. For example, the present invention can be applied to a MEMS device that allows a drive region to function as a part of a sensor in addition to the one incorporated in a recording head. Furthermore, as the liquid ejecting head, for example, a color material discharge head used for manufacturing a color filter such as a liquid crystal display, an electrode material discharge used for forming an electrode such as an organic EL (Electro Luminescence) display, FED (surface emitting display), etc. The present invention can also be applied to bioorganic discharge heads and the like used for manufacturing heads and biochips (biochemical elements).

  DESCRIPTION OF SYMBOLS 1 ... Printer, 2 ... Recording medium, 3 ... Recording head, 4 ... Carriage, 5 ... Carriage moving mechanism, 6 ... Conveying mechanism, 7 ... Ink cartridge, 8 ... Timing belt, 9 ... Pulse motor, 10 ... Guide rod, 14 DESCRIPTION OF SYMBOLS ... Piezoelectric device, 15 ... Channel unit, 16 ... Head case, 17 ... Accommodating space, 18 ... Liquid introduction channel, 21 ... Nozzle plate, 22 ... Nozzle, 24 ... Communication substrate, 25 ... Common liquid chamber, 26 ... Individual communication Passage, 27 ... nozzle communication passage, 29 ... pressure chamber forming substrate, 30 ... pressure chamber, 31 ... vibration plate, 32 ... piezoelectric element, 33 ... wiring substrate, 35 ... drive region, 36 ... non-drive region, 37 ... lower electrode 38, piezoelectric layer, 39 ... upper electrode layer, 39a ... first layer, 39b ... second layer, 39c ... third layer, 39d ... fourth layer, 40 ... metal layer, 40a ... metal Weight layer, 40b ... Common Genus layer, 40c ... individual metal layer, 42 ... bumps, 42a ... common bumps, 42b ... individual bumps, 43 ... resin portion, 44 ... conductive layer, 45 ... conductive portion, 46 ... drive circuit, 48 ... adhesive

Claims (8)

A driving region having a laminated structure in which a first electrode layer, an insulator layer, and a second electrode layer are laminated in this order;
The first electrode layer, the insulator layer, and the second electrode layer extend from the driving region to a non-driving region outside the driving region,
A third electrode layer electrically connected to the second electrode layer is formed at least on the side of the second electrode layer opposite to the insulator layer in the non-driving region,
In the extending direction of the second electrode layer, the end of the third electrode layer on the side opposite to the driving region is more driven than the end of the second electrode layer on the side opposite to the driving region. A MEMS device formed on a region side.   The film thickness of the second electrode layer formed outside the end of the third electrode layer opposite to the drive region is the second film layer in the region where the third electrode layer is formed. The MEMS device according to claim 1, wherein the MEMS device is thinner than the film thickness of the electrode layer.   The MEMS device according to claim 1, wherein the second electrode layer includes a plurality of conductive layers. A MEMS device according to any one of claims 1 to 3,
A pressure chamber at least partially partitioned by the drive region;
A nozzle communicating with the pressure chamber,
The liquid ejecting head according to claim 1, wherein the insulator layer is a piezoelectric layer.   The liquid ejecting head according to claim 4, further comprising: a wiring board on which bumps that contact the third electrode layer are formed and spaced from the MEMS device.   The liquid ejecting head according to claim 5, wherein the bump includes a resin portion protruding from the wiring substrate and a conductive layer formed on a surface of the resin portion.   The liquid ejecting head according to claim 5, wherein the bump includes a conductive portion protruding from a wiring board. A liquid ejecting apparatus comprising the liquid ejecting head according to claim 4.

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