Method for manufacturing a piezoelectric element, piezoelectric element, and droplet dispensing head

Abstract

To provide a method for manufacturing a piezoelectric element having excellent piezoelectric properties and a piezoelectric element.SOLUTION: A method for manufacturing the piezoelectric element 44 comprises the steps of forming a first conductive film 441a on a diaphragm 36 as a substrate; etching the first conductive film 441a; forming a second conductive film 441b on the first conductive film 441a; etching the second conductive film 441b to form the first electrode 441 having a step region S as a step comprising the second conductive film 441b and the first conductive film 441a at the edge; forming a seed layer 442 as an orientation control layer covering the first electrode 441 by a liquid phase method; forming a piezoelectric film 443a on the seed layer 442; forming a piezoelectric body 443 by etching the piezoelectric film 443a; and forming a second electrode 444 covering the piezoelectric body 443.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a piezoelectric element, a piezoelectric element, and a droplet ejection head.

Background Art

[0002] As a droplet ejection head, which is one of the devices using a piezoelectric element, for example, a droplet ejection head used in an inkjet printer described in Patent Document 1 is known. The droplet ejection head includes a flow path forming substrate in which a pressure chamber communicating with a nozzle is formed, and a piezoelectric element provided via a diaphragm on one surface side of the flow path forming substrate. By causing a pressure change in the ink in the pressure chamber by the piezoelectric element, ink droplets are ejected from the nozzle. In addition, the piezoelectric element has an orientation control layer formed so as to cover the first electrode between the first electrode and the piezoelectric layer in order to control the crystal orientation of the piezoelectric layer. In Patent Document 1, the orientation control layer is formed by an inkjet method in which a precursor solution of the orientation control layer is dropped.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the film thickness of the orientation control layer is increased, the thickness of the piezoelectric layer disposed between the first electrode and the second electrode becomes relatively thin, so that the piezoelectric characteristics of the piezoelectric element may deteriorate. On the other hand, when the film thickness of the orientation control layer is decreased, if the orientation control layer is formed by a liquid phase method, there is a risk that the corner portions at the ends of the first electrode may become too thin or may not be formed. Furthermore, if an orientation control layer is not deposited on the corners of the first electrode, the piezoelectric layer may grow in an unintended crystal orientation, potentially causing cracks or other defects in the piezoelectric layer and degrading its piezoelectric properties. [Means for solving the problem]

[0005] A method for manufacturing a piezoelectric element according to one aspect of the present invention includes the steps of: forming a first conductive film on a substrate; etching the first conductive film; forming a second conductive film on the first conductive film; etching the second conductive film to form a first electrode having a step at its end consisting of the second conductive film and the first conductive film; forming an orientation control layer covering the first electrode by a liquid phase method; forming a piezoelectric film on the orientation control layer; etching the piezoelectric film to form a piezoelectric body; and forming a second electrode covering the piezoelectric body.

[0006] A method for manufacturing a piezoelectric element according to one aspect of the present invention includes the steps of: forming a first conductive film on a substrate; forming a first electrode by etching the edge of the first conductive film so as to have a step; forming an orientation control layer covering the first electrode; forming a piezoelectric film on the orientation control layer; forming a piezoelectric body by etching the piezoelectric film; and forming a second electrode covering the piezoelectric body.

[0007] A piezoelectric element according to one aspect of the present invention comprises a first electrode, an orientation control layer provided on the first electrode, a piezoelectric body provided on the orientation control layer and containing potassium, sodium, and niobium, and a second electrode provided on the piezoelectric body, wherein the first electrode has a flat region and an inclined region, and the first electrode has a stepped region between the flat region and the inclined region.

[0008] A droplet dispensing head according to one aspect of the present invention includes the aforementioned piezoelectric element, a voltage application unit for applying a voltage to the piezoelectric element, a pressure chamber substrate provided with a pressure chamber whose volume changes due to the piezoelectric element, a flow path substrate provided with a communication flow path communicating with the pressure chamber, and a nozzle plate provided with a nozzle communicating with the communication flow path. [Brief explanation of the drawing]

[0009] [Figure 1] A schematic diagram showing the general configuration of a droplet dispensing device. [Figure 2] Exploded perspective view of the droplet dispensing head. [Figure 3] Cross-sectional view along line III-III in Figure 2. [Figure 4] Plan view of a piezoelectric element. [Figure 5] Figure 4 shows a cross-sectional view along the VV line. [Figure 6] Enlarged cross-sectional view of region VI in Figure 5. [Figure 7] Enlarged cross-sectional view of region VII in Figure 6. [Figure 8] An enlarged cross-sectional view of the first electrode according to Embodiment 2 of Figure 7. [Figure 9] Flowchart relating to the method for manufacturing a piezoelectric element 1. [Figure 10A] A cross-sectional view showing one step in manufacturing method 1. [Figure 10B] A cross-sectional view showing one step in manufacturing method 1. [Figure 10C] A cross-sectional view showing one step in manufacturing method 1. [Figure 10D] A cross-sectional view showing one step in manufacturing method 1. [Figure 10E] A cross-sectional view showing one step in manufacturing method 1. [Figure 10F] A cross-sectional view showing one step in manufacturing method 1. [Figure 10G] A cross-sectional view showing one step in manufacturing method 1. [Figure 10H] A cross-sectional view showing one step in manufacturing method 1. [Figure 11] Flowchart relating to the second method for manufacturing a piezoelectric element. [Figure 12] A cross-sectional view showing one step in manufacturing method 2.

Best Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, in order to make each member recognizable, the scale of each member may be different from the actual one. In each drawing, the X-axis, Y-axis, and Z-axis orthogonal to each other are appropriately indicated. The direction along the X-axis is the X-direction, the direction along the Y-axis is the Y-direction, and the direction along the Z-axis is the Z-direction. When specifying the directions of the X-direction, Y-direction, and Z-direction, the positive direction is indicated as "+", the negative direction is indicated as "-", and the positive and negative signs are used together in the direction notation.

[0011] In addition, in the present embodiment, when the plane including the X-axis and the Y-axis is defined as the XY plane, viewing the XY plane in the Z-direction is referred to as a plan view or planar, and viewing a cross-section including the Z-axis from a direction perpendicular to the cross-section is referred to as a cross-sectional view or cross-sectional. Furthermore, in the following description, for example, the description "Element B is provided on Element A" includes cases where Element B is provided in contact with Element A, cases where Element B is provided with another element C or the like interposed therebetween with respect to Element A, or cases where a part of Element B is provided in contact with Element A and the remaining part of Element B is provided with another element C or the like interposed therebetween with respect to Element A. In addition, in the following description, the specific dimensions of each described configuration are shown as preferred application examples, but the configuration of the present invention is not limited to the described dimensions.

[0012] 1. Configuration of Droplet Discharging Device The configuration of the droplet discharging device 100 will be described with reference to FIG. 1. FIG. 1 is a schematic diagram showing a schematic configuration of the droplet discharging device in the embodiment. The droplet discharging device 100 is an inkjet printing device that performs printing by discharging droplets of ink as a liquid onto a medium 12. The medium 12 can adopt a printing target of any material such as resin film or cloth in addition to printing paper.

[0013] The droplet dispensing device 100 comprises a droplet dispensing head 26, a head moving mechanism 20, a liquid storage section 14, a transport mechanism 16, and a control unit 80. The primary scanning direction, which is the direction in which the droplet ejection head 26 moves, is the X direction; the secondary scanning direction, which is the direction in which the medium 12 is fed, is the Y direction; and the ink ejection direction of the droplet ejection head 26 is the -Z direction.

[0014] The liquid storage section 14 stores the ink that will be supplied to the droplet ejection head 26. The liquid storage section 14 can be a liquid pack in the shape of a bag made of a flexible film, an ink tank that can be refilled with ink, or a removable ink cartridge.

[0015] The droplet ejection head 26 has a plurality of nozzles N for ejecting ink. Multiple nozzles N are arranged in the Y direction. The droplet ejection head 26 ejects ink supplied from the liquid storage section 14 from the multiple nozzles N toward the medium 12.

[0016] The head movement mechanism 20 includes a conveyor belt 21 and a carriage 22 that houses the droplet dispensing head 26. The carriage 22 is connected to the conveyor belt 21 and reciprocates in the X direction as the conveyor belt 21 is driven. The transport mechanism 16 transports the medium 12 in the Y direction.

[0017] The control unit 80 includes processing circuits such as a CPU (Central Processing Unit) and an FPGA (Field Programmable Gate Array), as well as storage circuits such as semiconductor memory, and controls the overall operation of the droplet dispensing device 100. The control unit 80 is electrically connected to the transport mechanism 16, the head moving mechanism 20, and the droplet ejection head 26, and controls each of these parts. Under the control of the control unit 80, the transport mechanism 16 transports the medium 12, and the droplet ejection head 26 ejects ink from the nozzle N, thereby printing the desired image on the medium 12.

[0018] 2. Configuration of the droplet dispensing head Next, the configuration of the droplet ejection head 26 will be described with reference to Figures 2 and 3. Figure 2 is an exploded perspective view of the droplet ejection head 26, and Figure 3 is a cross-sectional view taken along line III-III in Figure 2. As shown in Figure 2, the droplet discharge head 26 includes a nozzle plate 62, two vibration absorbers 64, a flow path substrate 32, a pressure chamber substrate 34, a diaphragm 36 as a substrate, a wiring substrate 46, a drive circuit 50 as a voltage application unit, and a housing 48.

[0019] The nozzle plate 62, vibration absorber 64, flow path substrate 32, pressure chamber substrate 34, diaphragm 36, and wiring substrate 46 are plate-shaped members that are elongated in the Y direction. The nozzle plate 62, the flow path substrate 32, the pressure chamber substrate 34, and the diaphragm 36 have a structure that is substantially symmetrical with respect to their respective centerlines in the X direction.

[0020] The planar dimensions of the pressure chamber substrate 34, the diaphragm 36, and the wiring substrate 46 are smaller than the planar dimensions of the flow path substrate 32 and the housing portion 48. The nozzle plate 62, the two vibration absorbers 64, the flow path substrate 32, the pressure chamber substrate 34, the diaphragm 36, the wiring substrate 46, and the housing 48 are assembled together, for example, via adhesive.

[0021] The nozzle plate 62 is a plate-shaped member on which multiple nozzles N are formed. Each nozzle N is a through-hole with a substantially circular planar shape. The multiple nozzles N are arranged along the Y direction. The multiple nozzles N are arranged in two rows along the X direction. The two vibration absorbers 64 are flexible films and are positioned in the X direction, flanking the nozzle plate 62.

[0022] The flow channel substrate 32 has two first openings 32a, a plurality of second openings 32b, and a plurality of third openings 32c. The shape of the first opening 32a is a rectangle that is elongated in the Y direction when viewed from above. Multiple second openings 32b are arranged in the Y direction. Multiple third openings 32c are arranged in the Y direction. In the X direction of the flow channel substrate 32, the first opening 32a, the second opening 32b, the third opening 32c, the third opening 32c, the second opening 32b, and the first opening 32a are provided in this order. Furthermore, the second opening 32b and the third opening 32c, which are adjacent in the X direction, are provided so that their positions in the Y direction are approximately the same.

[0023] Multiple openings 34a are formed in the pressure chamber substrate 34. The shape of the opening 34a is a rectangle that is elongated in the X direction when viewed from above. The multiple openings 34a are arranged adjacent to each other in the Y and X directions. In addition, the openings 34a are positioned to overlap with the adjacent second opening 32b and third opening 32c of the flow channel substrate 32 in a plan view.

[0024] A piezoelectric element 44 is provided on the diaphragm 36. The piezoelectric element 44 is positioned so as to overlap with the opening 34a of the pressure chamber substrate 34 in a plan view. The opening 34a constitutes part of the pressure chamber, which will be described later.

[0025] The drive circuit 50 drives the piezoelectric element 44. The drive circuit 50 is implemented as an integrated circuit (IC) chip that outputs a drive signal and a reference voltage for driving the piezoelectric element 44. The drive circuit 50 is mounted on a wiring board 46.

[0026] The wiring board 46 is provided with terminals and wiring for input signals to the drive circuit 50 and drive signals and reference voltages output from the drive circuit 50.

[0027] As shown in Figure 3, the terminals of the wiring board 46 are connected to the piezoelectric element 44 via the wiring on the bump B and the diaphragm 36. In addition, FPCs (Flexible Printed Circuits) and the like (not shown) are connected to the terminals of the wiring board 46, and input signals are supplied to the drive circuit 50.

[0028] The housing 48 is a case that houses the circuit board and ink. The pressure chamber circuit board 34, the diaphragm 36, and the wiring circuit board 46 are arranged in the internal space of the housing 48. At both ends of the housing portion 48 in the X direction, through holes 48a and a space Rb that communicates with the through holes 48a and extends in the Y direction are provided. The space Rb of the housing portion 48 constitutes part of the liquid storage chamber for storing ink.

[0029] The flow channel substrate 32 is provided with a space Ra, a supply liquid chamber 26a, and a supply channel 26b. Space Ra is the internal space of the first opening 32a of the flow channel substrate 32, and the supply channel 26b is the internal space of the second opening 32b. The supply liquid chamber 26a is a space that communicates with space Ra and the supply channel 26b, and is enclosed by the partition wall 32d of the flow channel substrate 32 and the vibration absorber 64.

[0030] A pressure chamber C is provided in the pressure chamber substrate 34. The pressure chamber C is a space enclosed by the opening 34a of the pressure chamber substrate 34, the diaphragm 36, and the flow path substrate 32. The pressure chamber C is in communication with the supply flow path 26b and the communication flow path 26c of the flow path substrate 32. The communication channel 26c is the internal space of the third opening 32c. The communication channel 26c communicates with the pressure chamber C and the nozzle N of the nozzle plate 62.

[0031] Spaces Ra and Rb function as liquid storage chambers that store the ink supplied to pressure chamber C. Space Rb is in communication with multiple spaces Ra aligned in the Y direction, and the ink supplied through the through hole 48a is stored in the multiple spaces Ra via space Rb. The ink stored in space Ra is supplied to the pressure chamber C via the supply liquid chamber 26a and the supply channel 26b.

[0032] The piezoelectric element 44 is positioned so as to overlap with the pressure chamber C in the +Z direction. The wiring board 46 and the drive circuit 50 are arranged so as to cover the two piezoelectric elements 44. The piezoelectric element 44 is supplied with a drive signal and a reference voltage from the drive circuit 50 via the bump B and the wiring board 46. When the piezoelectric element 44 receives the drive signal and reference voltage, it deforms. The diaphragm 36 vibrates in conjunction with the deformation of the piezoelectric element 44, causing the pressure in the pressure chamber C to fluctuate, and ink is ejected from the nozzle N.

[0033] 3. Configuration of the piezoelectric element Next, the configuration of the piezoelectric element 44 will be described with reference to Figures 4 and 5. Figure 4 is a plan view of the piezoelectric element 44, and Figure 5 is a cross-sectional view of Figure 4 along line VV. As shown in Figure 4, the piezoelectric element 44 is positioned to overlap with a plurality of pressure chambers C arranged in the Y direction in a plan view. The piezoelectric element 44 includes a first electrode 441, a seed layer 442 as an orientation control layer, a piezoelectric body 443, and a second electrode 444.

[0034] The first electrode 441 is provided in one-to-one correspondence with the pressure chamber C. The first electrode 441 is connected to wiring drawn out in the +X direction and is electrically connected to the drive circuit 50 via bump B. The piezoelectric element 443 has a through hole 443b between two adjacent first electrodes 441, where the piezoelectric element 443 is not provided.

[0035] Figure 5 shows the cross-sectional configuration of a piezoelectric element 44 provided in relation to one pressure chamber C. As shown in Figure 5, the piezoelectric element 44 is provided on the diaphragm 36 in a position that overlaps with the pressure chamber C. The diaphragm 36 has a silicon substrate 361 and an insulating layer 362. The piezoelectric element 44 has a structure in which a first electrode 441, a seed layer 442, a piezoelectric body 443, and a second electrode 444 are stacked on the diaphragm 36 in this order. Here, in the piezoelectric element 44, the portion in which the first electrode 441, the seed layer 442, the piezoelectric body 443, and the second electrode 444 overlap in the Z direction is referred to as the active portion 440. The active portion 440 is the portion in which the piezoelectric body 443 deforms when a voltage is applied between the first electrode 441 and the second electrode 444.

[0036] The insulating layer 362 is made of zirconium oxide (ZrO2). The first electrode 441 consists of a titanium (Ti) layer and a platinum (Pt) layer. The first electrode 441 is not limited to multiple layers of Ti and Pt, but may consist of a single layer of a metallic material such as Ti, Pt, iridium (Ir), aluminum (Al), nickel (Ni), gold (Au), or copper (Cu), or it may be formed by laminating multiple layers of these metallic materials.

[0037] The seed layer 442 functions as an orientation control layer for controlling the orientation of the piezoelectric body 443 in the process of forming the piezoelectric body 443, which will be described later. As the material for the seed layer 442, for example, polycrystalline nickel lanthanate (LaNiO3), or a composite oxide having a perovskite-type structure in which the A site contains bismuth (Bi) and the B site contains iron (Fe) and titanium (Ti) and is self-oriented on the (100) plane, or bismuth manganate can be used.

[0038] Preferably, lead-free piezoelectric materials are used as the material for the piezoelectric element 443. Examples of lead-free piezoelectric materials include bismuth ironate (BiFeO3), barium titanate (BaTiO3), potassium sodium lithium niobate ((K,Na,Li)NbO3), potassium sodium lithium tantalate niobate ((K,Na,Li)(Nb,Ta)O3), potassium bismuth titanate ((Bi1 / 2K1 / 2)TiO3), sodium bismuth titanate ((Bi1 / 2Na1 / 2)TiO3), and bismuth manganese (Bi You can use MnO3, or a composite oxide containing bismuth (Bi), K, Ti, and iron (Fe) ((Bi,K)(Ti,Fe)O3), or a composite oxide containing Bi, Fe, barium (Ba), and Ti ((Bi,Ba)(Fe,Ti)O3), or a composite oxide obtained by adding metals such as Mn, cobalt (Co), or chromium (Cr) to the aforementioned composite oxides ((Bi,Ba)(Fe,Ti,M)O3) (where M is Mn, Co, or Cr).

[0039] The second electrode 444 is made of Ir. However, the second electrode 444 is not limited to Ir, and may be a single layer of a metallic material such as Pt, Al, Ni, Au, or Cu, or it may be formed by laminating multiple layers of such metallic materials. The second electrode 444 is provided in common to multiple active parts 440.

[0040] A separate voltage is applied to each active unit 440 from the drive circuit 50 as a drive signal to the first electrode 441, and a reference voltage is applied to the second electrode 444 from the drive circuit 50 as a voltage common to the multiple active units 440.

[0041] 4. Configuration of the first electrode Next, the configuration of the first electrode 441 of the piezoelectric element 44 will be described with reference to Figures 6 to 8. Figures 6 and 7 show the first electrode 441 according to Embodiment 1, and Figure 8 shows the first electrode 441 according to Embodiment 2.

[0042] 4A. Embodiment 1 Figure 6 is an enlarged cross-sectional view of region VI, indicated by the dashed line in Figure 5, and Figure 7 is an enlarged cross-sectional view of region VII, indicated by the dashed line in Figure 6. As shown in Figure 6, the first electrode 441 according to Embodiment 1 has stepped edges at both ends in the Y direction, and in cross-sectional view, it has a shape like two trapezoids stacked on top of each other in two stages. The first electrode 441 has a flat region F corresponding to the upper base of the upper trapezoid, an inclined region T corresponding to the hypotenuse of the lower trapezoid, and a stepped region S as a step between the flat region F and the inclined region T.

[0043] As shown in Figure 7, the stepped region S further includes a secondary inclined region ST corresponding to the hypotenuse of the upper trapezoid and a secondary flat region SF corresponding to the upper base of the lower trapezoid.

[0044] In the seed layer 442 provided on the first electrode 441, if the thickness in the normal direction of the flat region F is defined as thickness H1, the thickness in the normal direction of the corner C2 between the flat region F and the sub-inclined region ST is defined as thickness H2, and the thickness in the normal direction of the corner C3 between the sub-flat region SF and the inclined region T is defined as thickness H3, then the thickness H2 of corner C2 is thinner than the thickness H1 of the flat region F. Similarly, the thickness H3 of corner C3 is thinner than the thickness H1 of the flat region F. In addition, regarding the thickness of the seed layer 442, thickness H2 is the thickness in the direction perpendicular to the tangent line L2 that is in contact with the corner C2 between the flat region F and the sub-inclined region ST, and thickness H3 is the thickness in the direction perpendicular to the tangent line L3 that is in contact with the corner C3 between the sub-flat region SF and the inclined region T.

[0045] The reason why the thickness of the seed layer 442 is thinner than that of the flat region F at corners C2 and C3 is because the seed layer 442 is formed by the liquid phase method.

[0046] In this embodiment, as a liquid-phase method, a solution method is used in which the seed layer 442 is formed from a precursor solution. In the solution method, the precursor solution of the seed layer 442 is spin-coated onto the first electrode 441. Due to the fluidity of the precursor solution, the spin-coated seed layer 442 precursor solution tends to flow easily at the corners of the first electrode 441, and the liquid film of the precursor solution becomes thinner at the corners of the first electrode 441. Subsequently, the film thickness of the seed layer 442 formed by firing in a heating furnace also becomes thinner at the corners of the first electrode 441.

[0047] In this embodiment, a stepped region S is provided on the first electrode 441 so that the liquid film of the precursor solution in the seed layer 442 does not become too thin at the corners of the edge of the first electrode 441. Therefore, according to the configuration of this embodiment 1, it is possible to prevent the liquid film of the precursor solution of the seed layer 442 from becoming too thin at the corners C2 and C3 of the first electrode 441. Therefore, problems such as the seed layer 442 not being formed and becoming disconnected, or the thickness of the seed layer 442 becoming too thin to function as an orientation control layer, are avoided.

[0048] In this embodiment, since defects in the seed layer 442 are suppressed, the occurrence of defects in the piezoelectric element 443 caused by defects in the seed layer 442 is also suppressed. Therefore, the growth of the piezoelectric element 443 in an unintended crystal orientation and the occurrence of cracks in the piezoelectric element 443 are suppressed, making it possible to provide a piezoelectric element 443 with excellent piezoelectric properties.

[0049] In this embodiment, a configuration is shown in which one set of sub-sloping areas ST and sub-flat areas SF are provided in the stepped area S. However, two or more sets of sub-sloping areas ST and sub-flat areas SF may be provided in the stepped area S. In other words, the stepped area S may be configured to have multiple steps.

[0050] 4B. Embodiment 2 Figure 8 is an enlarged cross-sectional view of the first electrode 441 according to Embodiment 2. As shown in Figure 8, in the first electrode 441 according to Embodiment 2, the stepped region S is composed only of a secondary inclined region ST. The angle θ1 between the secondary inclined region ST and the flat region F of the first electrode 441 is smaller than the angle θ2 between the secondary inclined region ST and the inclined region T.

[0051] The secondary inclined region ST is provided such that angles θ1 and θ2 have the relationship described above. The secondary inclined region ST may also be a case where a large number of pairs of secondary inclined regions ST and secondary flat regions SF, as shown in Embodiment 1, are arranged in the stepped region S; in other words, a large number of stepped structures are arranged to form an inclined shape.

[0052] The seed layer 442 is formed by a liquid-phase method, similar to Embodiment 1. Therefore, the thickness of the seed layer 442 is thinner in the direction of the corner C2 between the flat region F and the sub-inclined region ST than in the thickness H1 in the direction of the flat region F. Similarly, the thickness of the seed layer 442 is thinner in the direction of the corner C4 between the sub-inclined region ST and the inclined region T than in the thickness H1 in the direction of the flat region F. Furthermore, thickness H2 is the thickness perpendicular to the tangent line L2 that touches the corner C2 between the flat region F and the secondary inclined region ST, and thickness H4 is the thickness perpendicular to the tangent line L4 that touches the corner C4 between the secondary inclined region ST and the inclined region T.

[0053] The configuration of Embodiment 2 is similar to that of Embodiment 1 in that it avoids problems such as the seed layer 442 not being formed and becoming disconnected, or the thickness of the seed layer 442 becoming so thin that it cannot function as an orientation control layer. Therefore, similar to Embodiment 1, the growth of the piezoelectric element 443 in an unintended crystal orientation and the occurrence of cracks in the piezoelectric element 443 are suppressed, and a piezoelectric element 443 with excellent piezoelectric properties can be provided.

[0054] 5. Method for manufacturing piezoelectric elements Next, the manufacturing method of the piezoelectric element 44 will be described with reference to Figures 9 to 12. Figures 9 and 10A to 10H are diagrams illustrating manufacturing method 1, and Figures 11 and 12 are diagrams illustrating manufacturing method 2.

[0055] 5A. Manufacturing method 1 Figure 9 is a flowchart relating to the piezoelectric element manufacturing method 1, and Figures 10A to 10H are cross-sectional views showing one step of the manufacturing method 1, respectively.

[0056] In step S1, as shown in Figure 10A, a first conductive film 441a constituting the first electrode 441 is formed on the diaphragm 36. For example, sputtering or vapor deposition can be used to form the first conductive film 441a.

[0057] In step S2, as shown in Figure 10B, the first conductive film 441a is etched to pattern the portion corresponding to the lower trapezoid of the first electrode 441. The lower base of the lower trapezoid of the first electrode 441, i.e., the length in the Y direction, is, for example, 50 μm. Photolithography can be used, for example, to pattern the first conductive film 441a.

[0058] In step S3, as shown in Figure 10C, a second conductive film 441b is formed on the patterned first conductive film 441a. In step S4, as shown in Figure 10D, the second conductive film 441b is etched to pattern the portion corresponding to the upper trapezoid of the first electrode 441.

[0059] In step S4, a first electrode 441 consisting of a two-layer structure of a first conductive film 441a and a second conductive film 441b is formed on the diaphragm 36. The first electrode 441 has a flat region F corresponding to the upper base in the second conductive film 441b, which corresponds to the upper trapezoid, a sloped region T corresponding to the hypotenuse in the first conductive film 441a, which corresponds to the lower trapezoid, and a stepped region S between the flat region F of the second conductive film 441b and the sloped region T of the first conductive film 441a.

[0060] The length of the stepped region S of the first electrode 441 in the Y direction is approximately 50 nm. The thickness of the first conductive film 441a, i.e., the length in the Z direction, is approximately 50 nm, and the thickness of the second conductive film 441b is approximately 50 nm. Therefore, the sub-flat region SF of the stepped region S is located at a height of approximately 50% of the thickness of the first electrode 441. The sub-flat region SF should be located at a height of approximately 30-70% of the thickness of the first electrode 441. Furthermore, if multiple steps are provided in the stepped region S, i.e., if multiple sub-flat regions SF are provided in the stepped region S, each sub-flat region SF should be located at an appropriate height in the thickness of the first electrode 441, according to the number of sub-flat regions SF.

[0061] In step S5, as shown in Figure 10E, a seed layer 442 is formed on the first electrode 441 by a liquid-phase method. In step S5, a precursor solution of a seed layer 442 (not shown) is spin-coated onto the first electrode 441 to form a liquid film of the precursor solution on the first electrode 441. Then, it is fired in a heating furnace to form the seed layer 442.

[0062] As described above, the thickness of the seed layer 442 is thinner at the corner C2 than at the flat region F. Similarly, the thickness of the seed layer 442 is thinner at the corner C3 than at the flat region F. However, since the first electrode 441 has a step region S between the flat region F and the inclined region T, it is possible to avoid the seed layer 442 not being deposited at the corners C2 and C3 of the first electrode 441. Furthermore, it is possible to avoid the seed layer 442 becoming so thin as to be unable to function as an orientation control layer.

[0063] In step S6, as shown in Figure 10F, a piezoelectric film 443a constituting the piezoelectric body 443 is formed on the seed layer 442. The piezoelectric film 443a can be formed in the same manner as the seed layer 442. The piezoelectric film 443a may consist of multiple layers. A piezoelectric film 443a consisting of multiple layers can be formed by repeating the process from spin coating to firing multiple times.

[0064] In step S7, as shown in Figure 10G, the piezoelectric film 443a is etched to form the piezoelectric body 443. In step S8, a second electrode 444 is formed on the piezoelectric element 443, as shown in Figure 10H.

[0065] 5B. Manufacturing method 2 Figure 11 is a flowchart relating to the piezoelectric element manufacturing method 2, and Figure 12 is a cross-sectional view showing one step of the manufacturing method 2. In the manufacturing method 2, the first conductive film 441a is etched to form the first electrode 441.

[0066] In step S11, a first conductive film 441a constituting the first electrode 441 is formed on the diaphragm 36.

[0067] In step S12, the first conductive film 441a is etched to pattern the first electrode 441 having a step at the edge of the first conductive film 441a. As a result of step S12, the first electrode 441 is patterned to have a shape having a flat region F, a stepped region S, and a sloped region T, as shown in Figure 12.

[0068] Step S12 includes two steps. In the first step, the first conductive film 441a is patterned. In the second step, the edges of the first electrode 441 are etched to form a stepped region S. Thus, in manufacturing method 2, there is no step of forming the second conductive film 441b, so the first electrode 441 having a stepped region S can be formed in fewer steps than in manufacturing method 1.

[0069] In step S13, a seed layer 442 is formed on the first electrode 441 by a liquid-phase method. In step S14, a piezoelectric film 443a constituting the piezoelectric body 443 is formed on the seed layer 442. In step S15, the piezoelectric film 443a is etched to form the piezoelectric body 443. In step S16, a second electrode 444 is formed on the piezoelectric element 443.

[0070] 5C. Variation 1 of Manufacturing Method 2 Next, we will describe a modified example of manufacturing method 2. In Modification 1, a photolithography method using a halftone mask is used in step S12 of manufacturing method 2. By using a halftone mask, two different thicknesses of resist can be formed on the first conductive film 441a. Therefore, the first electrode 441 having a stepped region S can be patterned in a single etching step.

[0071] Thus, in this modified example 1 of manufacturing method 2, the etching step of the first conductive film 441a is completed in just one step, so the first electrode 441 having a stepped region S can be formed in fewer steps than in manufacturing method 2.

[0072] 5D. Variation 2 of Manufacturing Method 2 Next, we will explain a modified example of manufacturing method 2, part 2. In the modified example 2, a photolithography method using a gradient mask is used in step S12 of the manufacturing method 2. By using a gradient mask, a resist having a tapered shape can be formed on the first conductive film 441a. Therefore, the first electrode 441 having the stepped region S shown in Figure 8 can be patterned in a single etching step.

[0073] Thus, in this modified version 2 of manufacturing method 2, the etching step of the first conductive film 441a is completed in just one step, so the first electrode 441 having the stepped region S shown in Figure 8 can be formed in fewer steps than in manufacturing method 2.

[0074] As described above, the following effects can be obtained according to this embodiment. A method for manufacturing a piezoelectric element 44 according to one aspect of the present invention includes the steps of: forming a first conductive film 441a on a diaphragm 36 as a substrate; etching the first conductive film 441a; forming a second conductive film 441b on the first conductive film 441a; etching the second conductive film 441b to form a first electrode 441 having a step region S at its end, which is a step made of the second conductive film 441b and the first conductive film 441a; forming a seed layer 442 as an orientation control layer covering the first electrode 441 by a liquid phase method; forming a piezoelectric film 443a on the seed layer 442; etching the piezoelectric film 443a to form a piezoelectric body 443; and forming a second electrode 444 covering the piezoelectric body 443.

[0075] Thus, this embodiment includes the step of providing a first electrode 441 having a stepped region S. Therefore, in the process of forming the seed layer 442 by the liquid phase method, the liquid film of the precursor solution of the seed layer 442 can be prevented from becoming too thin at the corners C2 and C3 of the first electrode 441. This prevents problems such as the seed layer 442 not being formed and becoming disconnected, or the thickness of the seed layer 442 becoming so thin that it cannot function as an orientation control layer.

[0076] In this embodiment, since defects in the seed layer 442 are suppressed, defects in the piezoelectric body 443 caused by defects in the seed layer 442 are also suppressed during the process of forming the piezoelectric body film 443a. Therefore, the growth of the piezoelectric element 443 in an unintended crystal orientation and the occurrence of cracks in the piezoelectric element 443 are suppressed, making it possible to provide a piezoelectric element 443 with excellent piezoelectric properties.

[0077] A method for manufacturing a piezoelectric element 44 according to one aspect of the present invention includes the steps of: forming a first conductive film 441a on a diaphragm 36 as a substrate; forming a first electrode 441 by etching the first conductive film 441a so that it has a step region S as a step at its edge; forming a seed layer 442 as an orientation control layer covering the first electrode 441; forming a piezoelectric film 443a on the seed layer 442; forming a piezoelectric body 443 by etching the piezoelectric film 443a; and forming a second electrode 444 covering the piezoelectric body 443.

[0078] Thus, this embodiment includes the step of providing a first electrode 441 having a stepped region S. Therefore, in the process of forming the seed layer 442, problems such as the seed layer 442 not being formed and being interrupted at the corners C2 and C3 of the first electrode 441, or the thickness of the seed layer 442 becoming too thin to function as an orientation control layer, are avoided.

[0079] In this embodiment, since defects in the seed layer 442 are suppressed, defects in the piezoelectric body 443 caused by defects in the seed layer 442 are also suppressed during the process of forming the piezoelectric body film 443a. Therefore, the growth of the piezoelectric element 443 in an unintended crystal orientation and the occurrence of cracks in the piezoelectric element 443 are suppressed, making it possible to provide a piezoelectric element 443 with excellent piezoelectric properties.

[0080] A method for manufacturing a piezoelectric element 44 according to one aspect of the present invention further includes, in the step of forming the first electrode 441, a step of patterning the first conductive film 441a and a step of forming a step in the first conductive film 441a. Therefore, according to the manufacturing method of the piezoelectric element 44 of this embodiment, a first electrode 441 having a stepped region S can be formed from the first conductive film 441a, and thus the effects of reducing the number of processes, such as reducing manufacturing costs and shortening manufacturing time, can be enjoyed.

[0081] A method for manufacturing a piezoelectric element 44 according to one aspect of the present invention further includes a step of forming a step of creating a step in the first conductive film 441a using a halftone mask in the step of forming the first electrode 441. Therefore, according to the manufacturing method of the piezoelectric element 44 of this embodiment, the first electrode 441 having a stepped region S can be formed in fewer steps, thus enabling the enjoyment of reduced manufacturing costs and shorter manufacturing times due to the reduction in the number of steps.

[0082] A piezoelectric element 44 according to one aspect of the present invention comprises a first electrode 441, a seed layer 442 as an orientation control layer provided on the first electrode 441, a piezoelectric body 443 provided on the seed layer 442 and containing potassium, sodium and niobium, and a second electrode 444 provided on the piezoelectric body 443, wherein the first electrode 441 has a flat region F and a sloped region T, and the first electrode 441 has a stepped region S between the flat region F and the sloped region T.

[0083] Thus, the piezoelectric element 443 is composed of a material containing potassium, sodium, and niobium. In other words, the piezoelectric element 443 is composed of a lead-free piezoelectric material. Furthermore, the first electrode 441 has a stepped region S between a flat region F and an inclined region T. Therefore, even if the seed layer 442 is formed from a lead-free piezoelectric material, problems such as the seed layer 442 not being deposited at the corners of the ends of the first electrode 441, or the thickness of the seed layer 442 becoming too thin to function as an orientation control layer, can be avoided.

[0084] In this embodiment, since defects in the seed layer 442 are suppressed, the occurrence of defects in the piezoelectric element 443 caused by defects in the seed layer 442 is also suppressed. Therefore, the growth of the piezoelectric element 443 in an unintended crystal orientation and the occurrence of cracks in the piezoelectric element 443 are suppressed, making it possible to provide a piezoelectric element 443 with excellent piezoelectric properties.

[0085] In one aspect of the present invention, the piezoelectric element 44 further comprises a stepped region S of the first electrode 441 having a sub-inclined region ST and a sub-flat region SF, wherein the sub-inclined region ST is positioned between the flat region F and the sub-flat region SF, and the sub-flat region SF is positioned between the sub-inclined region ST and the inclined region T. Therefore, problems such as the seed layer 442 not being deposited at the corners of the ends of the first electrode 441, resulting in a break in the film, or the thickness of the seed layer 442 becoming too thin to function as an orientation control layer, can be avoided.

[0086] In one aspect of the present invention, the piezoelectric element 44 further has a thickness of the seed layer 442 as an orientation control layer such that the thickness H2 in the direction normal to the corner C2 between the flat region F and the sub-inclined region ST is thinner than the thickness H1 in the direction normal to the flat region F. Therefore, problems such as the seed layer 442 not being deposited at the corners of the ends of the first electrode 441, resulting in a break in the film, or the thickness of the seed layer 442 becoming too thin to function as an orientation control layer, can be avoided.

[0087] In one aspect of the present invention, the piezoelectric element 44 further has a sub-inclined region ST in the stepped region S of the first electrode 441, and the angle θ1 between the sub-inclined region ST and the flat region F is smaller than the angle θ2 between the sub-inclined region ST and the inclined region T. Therefore, problems such as the seed layer 442 not being deposited at the corners of the ends of the first electrode 441, resulting in a break in the film, or the thickness of the seed layer 442 becoming too thin to function as an orientation control layer, can be avoided.

[0088] In one aspect of the present invention, the piezoelectric element 44 further has a normal thickness H1 of the flat region F of the first electrode 441 that is greater than the normal thickness H2 of the corner C2 between the flat region F and the sub-inclined region ST of the first electrode 441. Therefore, problems such as the seed layer 442 not being deposited at the corners of the ends of the first electrode 441, resulting in a break in the film, or the thickness of the seed layer 442 becoming too thin to function as an orientation control layer, can be avoided.

[0089] A droplet dispensing head 26 according to one aspect of the present invention includes the aforementioned piezoelectric element 44, a drive circuit 50 as a voltage application unit that applies a voltage to the piezoelectric element 44, a pressure chamber substrate 34 provided with a pressure chamber C whose volume changes due to the piezoelectric element 44, a flow path substrate 32 provided with a communication flow path 26c that communicates with the pressure chamber C, and a nozzle plate 62 provided with a nozzle N that communicates with the communication flow path 26c. Since the droplet dispensing head 26 includes a piezoelectric element 44 with excellent piezoelectric properties, it can be made into a droplet dispensing head 26 with high industrial value.

[0090] Although the present invention has been described above based on preferred embodiments, the present invention is not limited to the embodiments described above. Furthermore, the configuration of each part of the present invention can be replaced with any configuration that performs a similar function to the embodiments described above, and any configuration can be added. [Explanation of symbols]

[0091] 12... Medium, 14... Liquid containment section, 16... Conveying mechanism, 20... Head movement mechanism, 21... Conveying belt, 22... Carriage, 26... Droplet dispensing head, 26a... Supply liquid chamber, 26b... Supply channel, 26c... Communication channel, 32... Channel substrate, 32a... First opening, 32b... Second opening, 32c... Third opening, 32d... Partition wall, 34... Pressure chamber substrate, 34a... Opening, 36... Diaphragm, 361... Silicon substrate, 362... Insulator layer, 44... Piezoelectric element, 440... Active part, 441... First electrode, 441a... First conductive film, 441b... Second conductive film, 442...Seed layer, 443...Piezoelectric material, 443a...Piezoelectric film, 443b...Through hole, 444...Second electrode, 46...Wiring board, 48...Housing part, 48a...Through hole, 50...Drive circuit, 62...Nozzle plate, N...Nozzle, 64...Vibration absorber, 80...Control unit, 100...Droplet ejection device, B...Bump, C...Pressure chamber, C2, C3, C4...Corner, H1, H2, H3, H4...Thickness, L2, L3, L4...Tangential, θ1, θ2...Angle, Ra, Rb...Space, F...Flat region, S...Step region, ST...Sub-inclined region, SF...Sub-flat region, T...Inclined region.

Claims

1. First electrode and, An orientation control layer provided on the first electrode, A piezoelectric material containing potassium, sodium, and niobium is provided on the orientation control layer, The piezoelectric element comprises a second electrode provided on the piezoelectric element, The first electrode has a flat region and a sloped region, The first electrode has a stepped region between the flat region and the inclined region, The stepped region of the first electrode has a secondary inclined region, The angle between the secondary inclined region and the flat region is smaller than the angle between the secondary inclined region and the inclined region. Piezoelectric element.

2. The piezoelectric element according to claim 1, A voltage application unit that applies a voltage to the piezoelectric element, A pressure chamber substrate is provided with a pressure chamber whose volume changes due to the piezoelectric element, A flow path substrate is provided with a communication channel that communicates with the pressure chamber, A nozzle plate provided with a nozzle that communicates with the aforementioned communication channel, Droplet dispensing head.

Images