CN106233480B - Piezoelectric element, the manufacturing method of piezoelectric element, piezoelectric actuator, ink gun and ink-jet printer - Google Patents
Piezoelectric element, the manufacturing method of piezoelectric element, piezoelectric actuator, ink gun and ink-jet printer Download PDFInfo
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- CN106233480B CN106233480B CN201580021126.XA CN201580021126A CN106233480B CN 106233480 B CN106233480 B CN 106233480B CN 201580021126 A CN201580021126 A CN 201580021126A CN 106233480 B CN106233480 B CN 106233480B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/14—Structure thereof only for on-demand ink jet heads
- B41J2/14201—Structure of print heads with piezoelectric elements
- B41J2/14233—Structure of print heads with piezoelectric elements of film type, deformed by bending and disposed on a diaphragm
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/16—Production of nozzles
- B41J2/1607—Production of print heads with piezoelectric elements
- B41J2/161—Production of print heads with piezoelectric elements of film type, deformed by bending and disposed on a diaphragm
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/16—Production of nozzles
- B41J2/1621—Manufacturing processes
- B41J2/1623—Manufacturing processes bonding and adhesion
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/16—Production of nozzles
- B41J2/1621—Manufacturing processes
- B41J2/1626—Manufacturing processes etching
- B41J2/1628—Manufacturing processes etching dry etching
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/16—Production of nozzles
- B41J2/1621—Manufacturing processes
- B41J2/1626—Manufacturing processes etching
- B41J2/1629—Manufacturing processes etching wet etching
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/16—Production of nozzles
- B41J2/1621—Manufacturing processes
- B41J2/164—Manufacturing processes thin film formation
- B41J2/1646—Manufacturing processes thin film formation thin film formation by sputtering
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/01—Manufacture or treatment
- H10N30/07—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base
- H10N30/074—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by depositing piezoelectric or electrostrictive layers, e.g. aerosol or screen printing
- H10N30/076—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by depositing piezoelectric or electrostrictive layers, e.g. aerosol or screen printing by vapour phase deposition
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/01—Manufacture or treatment
- H10N30/07—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base
- H10N30/074—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by depositing piezoelectric or electrostrictive layers, e.g. aerosol or screen printing
- H10N30/079—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by depositing piezoelectric or electrostrictive layers, e.g. aerosol or screen printing using intermediate layers, e.g. for growth control
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/20—Piezoelectric or electrostrictive devices with electrical input and mechanical output, e.g. functioning as actuators or vibrators
- H10N30/204—Piezoelectric or electrostrictive devices with electrical input and mechanical output, e.g. functioning as actuators or vibrators using bending displacement, e.g. unimorph, bimorph or multimorph cantilever or membrane benders
- H10N30/2047—Membrane type
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/704—Piezoelectric or electrostrictive devices based on piezoelectric or electrostrictive films or coatings
- H10N30/706—Piezoelectric or electrostrictive devices based on piezoelectric or electrostrictive films or coatings characterised by the underlying bases, e.g. substrates
- H10N30/708—Intermediate layers, e.g. barrier, adhesion or growth control buffer layers
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/80—Constructional details
- H10N30/85—Piezoelectric or electrostrictive active materials
- H10N30/853—Ceramic compositions
- H10N30/8548—Lead-based oxides
- H10N30/8554—Lead-zirconium titanate [PZT] based
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Abstract
Piezoelectric element (27) has piezoelectric body layer (such as piezoelectric membrane (25)) on basal layer (such as lower electrode (24)).Piezoelectric body layer has orientation characteristic identical from the basal layer and the orientation characteristic different with the basal layer.On the thickness direction of the piezoelectric body layer, orientation characteristic identical with the basal layer is biased to the basal layer side.
Description
Technical Field
The present invention relates to a piezoelectric element in which a piezoelectric layer is formed on a base layer, a method for manufacturing the piezoelectric element, a piezoelectric actuator, an ink jet head, and an ink jet printer including the piezoelectric element.
Background
In recent years, lead zirconate titanate (Pb (Zr, Ti) O) has been used3) And the like, or lead-free piezoelectric materials containing no lead, are used as electromechanical conversion elements applied to driving elements, sensors, and the like. Since such a piezoelectric body is formed as a thin film on a substrate such as silicon (Si), it is expected to be applied to MEMS (Micro Electro Mechanical Systems) elements.
In the manufacture of MEMS devices, high-precision processing using semiconductor process technology such as photolithography can be employed, and therefore, the devices can be miniaturized and densified. In particular, compared to monolithic fabrication in which elements are fabricated individually, by performing high-density fabrication on Si wafers having a diameter of 6 inches or 8 inches at a time, the cost can be significantly reduced.
Further, by making the piezoelectric body thin or the device MEMS, the electromechanical conversion efficiency is improved, and a new added value such as improvement of the sensitivity or the characteristics of the device can be obtained. For example, in the thermal sensor, the measurement sensitivity can be improved by the reduction of the thermal conductivity due to the MEMS formation, and in the inkjet head used for the printer, the high-precision patterning due to the high density of the nozzles can be realized. In addition, in such devices it is necessary toIn the piezoelectric layer (piezoelectric film) provided therein, a high piezoelectric constant d is desired31。
When the piezoelectric layer is used as an MEMS driving element, although reference is also made to a device of design, the piezoelectric layer must be formed to a thickness of, for example, 3 to 5 μm in order to satisfy a necessary displacement generating force. When a piezoelectric layer is formed on a substrate such as Si, a chemical film formation method such as a cvd (chemical Vapor deposition) method, a physical method such as a sputtering method or an ion plating method, a growth method in a liquid phase such as a sol-gel method, and the like are known, and according to these film formation methods, it is important to find film formation conditions under which a film having necessary properties can be obtained.
PZT, i.e., a crystal composed of lead (Pb), zirconium (Zr), titanium (Ti), and oxygen (O), is often used as a material for the piezoelectric layer. The PZT is used as the ABO shown in FIG. 83Since a perovskite structure has a good piezoelectric effect, it is necessary to have a perovskite single phase. Conversely, if the crystallinity of the piezoelectric layer is deteriorated and the crystalline or amorphous region of the pyrochlore structure is increased, the piezoelectric characteristics are lowered. Since Pb is likely to evaporate during PZT film formation, it is necessary to carefully set film formation conditions to obtain a perovskite crystal.
By ABO3The unit cell shape of a PZT crystal of the perovskite structure of the type varies depending on the ratio of Ti and Zr as atoms entering the site B. That is, when Ti is large, the crystal lattice of PZT is tetragonal, and when Zr is large, the crystal lattice of PZT is rhombohedral. When the molar ratio of Zr and Ti is about 52:48, these two crystal structures coexist, and a Phase Boundary line adopting such a composition ratio is referred to as MPB (Morphotropic Phase Boundary). In the composition of the MPB, the maximization of piezoelectric characteristics such as piezoelectric constant, polarization intensity, and dielectric constant can be obtained, and thus the piezoelectric body of the MPB composition is actively utilized.
In addition to utilizing perovskite crystallinity or MPB composition, it is also important to appropriately control the crystal orientation of the piezoelectric body to increase the piezoelectric constant. For exampleThe orientation directions of Pb-based perovskite crystals include (100), (110), and (111), but the piezoelectric constant d is increased31In this case, when comparing the normal piezoelectric strain △ X1 in the case where an electric field is applied in the (001) direction to the region having the polarization in the (001) direction of tetragonal crystals and the piezoelectric strain △ X2 in the case where the same electric field is applied in the (100) direction to the region having the polarization in the (100) direction of tetragonal crystals, the piezoelectric strain △ X2 generated by 90 ° rotation from the (100) direction to the (001) direction domain is larger than the normal piezoelectric strain △ X1.
Further, a pyrochlore phase, which is a metastable layer of a Pb-based perovskite phase, is likely to be generated by a change in film forming conditions, resulting in a decrease in piezoelectric constant. Therefore, it is desirable to minimize the pyrochlore phase.
For example, in patent document 1, in a structure in which a perovskite phase of a piezoelectric layer is mainly oriented at (100), a proportion of a pyrochlore phase is suppressed to be low, thereby suppressing a decrease in piezoelectric characteristics. The lower electrode serving as the base layer of the piezoelectric layer contains (111) -oriented platinum (Pt).
Documents of the prior art
Patent document
Patent document 1: japanese unexamined patent application publication No. 2010-50388 (see claims 1 and 2, paragraphs [0010] to [0012], [0030], FIG. 14, FIG. 15, etc.)
Disclosure of Invention
Problems to be solved by the invention
When a piezoelectric layer having an orientation characteristic different from that of the underlying layer is formed on the underlying layer, strain is likely to occur in the piezoelectric layer because these orientation characteristics are different from each other. As a result, it becomes difficult to secure adhesion between the piezoelectric layer and the base layer, and film peeling of the piezoelectric layer is likely to occur. In this regard, in patent document 1, no condition is specified for improving the adhesion between the piezoelectric layer and the base layer.
The present invention has been made to solve the above-described problems, and an object thereof is to provide a piezoelectric element, a method for manufacturing the piezoelectric element, a piezoelectric actuator, an ink jet head, and an ink jet printer including the piezoelectric element, which can improve adhesion between the piezoelectric layer and the base layer and suppress film peeling even when the piezoelectric layer having an orientation characteristic different from that of the base layer is formed on the base layer.
Means for solving the problems
In the piezoelectric element according to one aspect of the present invention, the piezoelectric layer is formed on the base layer, and has the same orientation characteristics as the base layer and the orientation characteristics different from the base layer, and the orientation characteristics same as the base layer are biased toward the base layer side in the thickness direction of the piezoelectric layer.
Effects of the invention
According to the above configuration, even when a piezoelectric layer having an orientation characteristic different from that of the underlying layer is formed on the underlying layer, adhesion between the piezoelectric layer and the underlying layer can be improved, and film peeling of the piezoelectric layer can be suppressed.
Drawings
Fig. 1 is an explanatory diagram showing a schematic configuration of an inkjet printer according to an embodiment of the present invention.
Fig. 2 is a cross-sectional view showing a schematic configuration of a piezoelectric actuator of an ink jet head provided in the ink jet printer.
Fig. 3 is a sectional view showing the structure of the ink jet head.
Fig. 4 is an enlarged cross-sectional view of the piezoelectric element of the piezoelectric actuator.
Fig. 5 is a cross-sectional view showing a manufacturing process of the piezoelectric actuator.
Fig. 6 is a graph showing a spectrum obtained by 2 θ/θ measurement of XRD on the piezoelectric thin film of the piezoelectric actuator.
Fig. 7 is a cross-sectional view showing another structure of the piezoelectric element.
Fig. 8 is an explanatory view schematically showing the crystal structure of PZT.
Fig. 9 is an explanatory view schematically showing the difference in piezoelectric strain generated by the difference in crystal orientation of the piezoelectric body.
Detailed Description
Hereinafter, one embodiment of the present invention will be described with reference to the drawings. In the present specification, when a numerical range is expressed as a to B, the numerical range includes values of the lower limit a and the upper limit B.
[ ink jet printer configuration ]
Fig. 1 is an explanatory diagram showing a schematic configuration of an ink jet printer 1 according to the present embodiment. The ink jet printer 1 is an ink jet recording apparatus of a so-called line-head type in which an ink jet head 21 is linearly provided in an ink jet head 2 in a width direction of a recording medium.
The inkjet printer 1 includes: the ink jet head 2, the feed roller 3, the take-up roller 4, the two rear rollers (backing rollers) 5 and 5, the intermediate tank 6, the liquid feed pump 7, the reservoir tank 8, and the fixing mechanism 9 are described above.
The ink jet head 2 discharges ink from the ink jet head 21 toward the recording medium P, performs image formation (drawing) based on image data, and is disposed in the vicinity of one of the rear rollers 5. The structure of the inkjet head 21 will be described later.
The feed roller 3, the take-up roller 4, and each of the rear rollers 5 are cylindrical members that are rotatable around an axis. The feed roller 3 is a roller that feeds out a long recording medium P wound around a plurality of layers on the peripheral surface thereof toward an opposing position facing the ink jet head 2. The feed roller 3 is rotated by a driving unit, not shown, such as a motor, and feeds and conveys the recording medium P in the X direction of fig. 1.
The winding roller 4 winds the recording medium P fed by the feeding roller 3 and discharged with ink by the ink jet head 2 around the circumferential surface.
Each rear roller 5 is disposed between the delivery roller 3 and the take-up roller 4. The rear roller 5 positioned on the upstream side in the transport direction of the recording medium P transports the recording medium P toward the opposing position facing the ink jet head 2 while winding the recording medium P fed by the feed roller 3 around a part of the peripheral surface and supporting the recording medium P. The other rear roller 5 winds the recording medium P around a part of the peripheral surface from a facing position facing the ink jet head 2 toward the winding roller 4, supports the recording medium P, and conveys the recording medium P.
The intermediate tank 6 temporarily stores ink supplied from the storage tank 8. The intermediate tank 6 is connected to the ink tube 10, adjusts the back pressure of the ink in each inkjet head 21, and supplies the ink to each inkjet head 21.
The liquid feed pump 7 supplies the ink stored in the storage tank 8 to the intermediate tank 6, and is disposed in the middle of the supply pipe 11. The ink stored in the storage tank 8 is drawn up by the liquid-sending pump 7 and supplied to the intermediate tank 6 through the supply pipe 11.
The fixing mechanism 9 fixes the ink discharged from the ink jet head 2 onto the recording medium P. The fixing mechanism 9 is configured by a heater for heating and fixing the discharged ink on the recording medium P, a UV lamp for curing the ink by irradiating UV (ultraviolet) to the discharged ink, and the like.
In the above configuration, the recording medium P fed from the feed roller 3 is conveyed to the facing position facing the ink ejecting head 2 by the rear roller 5, and ink is ejected from the ink ejecting head 2 to the recording medium P. Thereafter, the ink discharged onto the recording medium P is fixed by the fixing mechanism 9, and the recording medium P on which the ink is fixed is wound by the winding roller 4. In this way, in the line head type ink jet printer 1, the ink is discharged while the recording medium P is conveyed in a state where the ink jet head 2 is stationary, and an image is formed on the recording medium P.
The inkjet printer 1 may be configured to form an image on a recording medium by a serial head method. The serial header mode is as follows: while the recording medium is being conveyed, the inkjet head is moved in a direction (width direction) orthogonal to the conveyance direction to eject ink, thereby forming an image. In this case, the ink jet head moves in the width direction of the recording medium while being supported by a structure such as a carriage.
[ ink jet head Structure ]
Next, the structure of the inkjet head 21 will be described. Fig. 2 is a sectional view showing a schematic configuration of the piezoelectric actuator 21a of the inkjet head 21. Fig. 3 is a cross-sectional view of the inkjet head 21 in which the nozzle substrate 31 is joined to the piezoelectric actuator 21a of fig. 2.
The inkjet head 21 includes a thermal oxide film 23, a lower electrode 24, a piezoelectric thin film 25 (piezoelectric layer), and an upper electrode 26 in this order on a support substrate 22 having a plurality of pressure chambers 22a (openings).
The support substrate 22 is formed of a semiconductor substrate made of a single crystal Si (silicon) material having a thickness of, for example, about 300 to 750 μm or an soi (silicon on insulator) substrate, and supports a piezoelectric element 27 described later. Fig. 2 shows a case where the support substrate 22 is formed of an SOI substrate. The SOI substrate is a substrate in which two Si substrates are bonded via an oxide film. The upper wall of the pressure chamber 22a in the support substrate 22, that is, the wall on the piezoelectric thin film 25 side in the pressure chamber 22a constitutes a vibration plate 22b as a driven film. That is, the diaphragm 22b is formed in the support substrate 22 so as to cover the pressure chamber 22 a. The vibrating plate 22b vibrates by the driving of the piezoelectric element 27, and applies pressure to the ink in the pressure chamber 22 a.
The thermal oxide film 23 is made of, for example, SiO with a thickness of about 0.1 μm2The (silicon oxide) structure is formed for the purpose of protecting and insulating the support substrate 22.
The lower electrode 24 is a common electrode provided in common to the plurality of pressure chambers 22a, and is formed by laminating a Ti (titanium) layer and a Pt (platinum) layer. The Ti layer is formed to improve adhesion between the thermal oxide film 23 and the Pt layer. The Ti layer has a thickness of, for example, about 0.02 μm, and the Pt layer has a thickness of, for example, about 0.1 μm.
The piezoelectric film 25 is made of ABO3The perovskite dielectric thin film is formed of PZT in the present embodiment. The piezoelectric film 25 is provided corresponding to each pressure chamber 22 a. The thickness of the piezoelectric thin film 25 is, for example, 1 μm to 5 μm.
The upper electrode 26 is a separate electrode provided corresponding to each pressure chamber 22a, and is configured by laminating a Ti layer and a Pt layer. The Ti layer is formed to improve adhesion between the piezoelectric thin film 25 and the Pt layer. The Ti layer has a thickness of about 0.02 μm, for example, and the Pt layer has a thickness of about 0.1 to 0.2 μm, for example. The upper electrode 26 is provided so as to sandwich the piezoelectric thin film 25 between the upper electrode 26 and the lower electrode 24 in the film thickness direction. Instead of the Pt layer, a layer made of gold (Au) may be formed.
The lower electrode 24, the piezoelectric thin film 25, and the upper electrode 26 constitute a piezoelectric element 27 for discharging ink in the pressure chamber 22a to the outside. The piezoelectric element 27 is driven based on a voltage (drive signal) applied from the drive circuit 28 to the lower electrode 24 and the upper electrode 26. The inkjet head 21 is formed by arranging the piezoelectric elements 27 and the pressure chambers 22a vertically and horizontally.
A nozzle substrate 31 is bonded to the support substrate 22 on the side opposite to the piezoelectric element 27. The nozzle substrate 31 is provided with discharge holes (nozzle holes) 31a for discharging ink stored in the pressure chambers 22a to the outside as ink droplets. The pressure chamber 22a contains ink supplied from the intermediate tank.
In the above-described configuration, when a voltage is applied from the drive circuit 28 to the lower electrode 24 and the upper electrode 26, the piezoelectric thin film 25 expands and contracts in a direction perpendicular to the thickness direction (a direction parallel to the surface of the support substrate 22) in accordance with the potential difference between the lower electrode 24 and the upper electrode 26. Then, a curvature is generated in the diaphragm 22b due to a difference in length between the piezoelectric film 25 and the diaphragm 22b, and the diaphragm 22b is displaced (bent, vibrated) in the thickness direction.
Therefore, if ink is contained in the pressure chamber 22a, the pressure wave is propagated to the ink in the pressure chamber 22a by the vibration of the vibration plate 22b, and the ink in the pressure chamber 22a is discharged as ink droplets from the discharge hole 31a to the outside.
As described above, since the upper electrode 26 is formed on the piezoelectric thin film 25 and the piezoelectric thin film 25 is sandwiched between the lower electrode 24 and the upper electrode 25, a voltage can be applied to these electrodes to expand and contract the piezoelectric thin film 25. In the piezoelectric element 27 of the present embodiment, as will be described later, even when the piezoelectric thin film 25 having the orientation characteristic different from that of the lower electrode 24 is formed on the lower electrode 24, film peeling of the piezoelectric thin film 25 can be suppressed. Therefore, in the piezoelectric actuator 21a including the piezoelectric element 27, a drive failure due to film peeling of the piezoelectric thin film 25 can be reduced.
Further, since the ink jet head 21 of the present embodiment includes the piezoelectric actuator 21a described above, it is possible to reduce ejection failure of ink caused by film peeling of the piezoelectric thin film 25. In addition, in the inkjet printer 1 including the inkjet head 21, it is possible to avoid a decrease in the quality of an image formed on a recording medium due to an ejection failure of ink caused by film peeling of the piezoelectric thin film 25.
[ detailed description of piezoelectric element ]
Next, the orientation characteristics of the lower electrode 24 and the piezoelectric thin film 25 will be described. Fig. 4 is an enlarged cross-sectional view of the piezoelectric element 27 of the piezoelectric actuator 21 a. In the same drawing, for convenience, the respective layers are not shown in hatching, and the thermal oxide film 23 is not shown. As described above, the piezoelectric element 27 has the piezoelectric thin film 25 on the lower electrode 24 as the base layer. The lower electrode 24 has a (111) -oriented platinum (Pt) layer on the adhesion layer (not shown).
As described above, the piezoelectric thin film 25 is composed of PZT. Here, when Pb (Zr) is usedxTi1-x)O3In the present embodiment, x is 0.50 to 0.55 and represents an MPB composition or a composition close thereto in the case of PZT. Thereby, higher piezoelectric characteristics (e.g., high piezoelectric constant d) than the composition other than MPB can be obtained31). In particular, it is desirable that the molar ratio of Zr to Ti is in the vicinity of 52:48 which becomes the composition of MPB.
The piezoelectric thin film 25 has a (111) orientation, with the (100) orientation of the perovskite phase being the main orientation. That is, the piezoelectric thin film 25 has the same orientation characteristic ((111) orientation) as the lower electrode and has an orientation characteristic ((100) orientation) different from that of the lower electrode 24.
Here, "having the (100) orientation as the main orientation" means: in the piezoelectric thin film 25, the ratio of the peak intensity of the (100) orientation of the perovskite phase to the sum of the peak intensities of the (100) orientation, the (110) orientation, and the (111) orientation of the perovskite phase, which is obtained by 2 θ/θ measurement by X-ray diffraction (XRD: X-ray diffraction), is 95% or more. In addition, strictly speaking, the (100) orientation of the perovskite phase needs to be distinguished from the (001) orientation, but in the vicinity of the MPB composition, the positions of occurrence of peak intensities obtained by XRD measurement are close to each other, and such separation is difficult, and therefore, the (100) orientation is not particularly distinguished, but is uniformly regarded.
In the present embodiment, the orientation characteristic of the piezoelectric thin film 25 in the thickness direction is shifted toward the base layer side as compared with the base layer (lower electrode 24). More specifically, the orientation (111) of the piezoelectric thin film 25, which shows the same orientation characteristics as the lower electrode 24, is shifted toward the lower electrode 24 side in the thickness direction of the piezoelectric thin film 25 (more toward the lower electrode 24 side than the side of the piezoelectric thin film 25 opposite to the lower electrode 24), and particularly, is present in a large amount in a thickness portion of 50nm or less from the lower electrode 24 side.
In this way, since the orientation characteristic of the piezoelectric thin film 25 in the thickness direction is biased toward the base layer side as in the base layer, the orientation characteristic is almost matched in one kind in the vicinity of the interface between the piezoelectric thin film 24 and the base layer, and thus the strain of the piezoelectric thin film 25 is relaxed. Therefore, even when the piezoelectric thin film 25 having the orientation characteristic different from that of the underlying layer is formed on the underlying layer, the adhesion between the piezoelectric thin film 25 and the underlying layer is improved, and the film peeling of the piezoelectric thin film 25 can be suppressed.
Specifically, the underlayer is the lower electrode 24 having the (111) orientation, and the piezoelectric thin film 25 has the (111) orientation with the (100) orientation of the perovskite phase as the main orientation. In this way, the piezoelectric thin film 25 has the (111) orientation while having the (100) main orientation, and the (111) orientation is biased toward the lower electrode 24 side, so that the orientation characteristics can be matched to the (111) orientation identical to the lower electrode 24 in the vicinity of the interface between the piezoelectric thin film 25 and the lower electrode 24. Therefore, even when the piezoelectric thin film 25 having the (100) main orientation is formed on the lower electrode 24 having the (111) orientation, the strain of the piezoelectric thin film 25 is relaxed, the adhesion between the piezoelectric thin film 25 and the lower electrode 24 is improved, and the film peeling of the piezoelectric thin film 25 is suppressed.
In addition, since the piezoelectric thin film 25 has the same orientation characteristic ((111) orientation) as that of the base layer in the thickness portion of 50nm or less from the base layer side, the orientation characteristic can be reliably matched in one direction near the interface between the piezoelectric thin film 25 and the base layer. This can reliably relax the strain of the piezoelectric thin film 25, and can reliably improve the adhesion between the piezoelectric thin film 25 and the base layer.
The distribution of the (111) orientation in such a piezoelectric thin film having a (100) main orientation can be controlled by adjusting the surface roughness (roughness) of the lower electrode 24. The surface state of the lower electrode 24 strongly affects the crystallinity of the piezoelectric thin film 25 to be formed later, and it is difficult to obtain the piezoelectric thin film 25 of the present embodiment by forming only the lower electrode 24 having high (111) orientation. One of the factors affecting the crystallinity of the piezoelectric thin film 25 is the roughness of Pt constituting the lower electrode 24, and by adjusting the roughness of Pt, the piezoelectric thin film 25 having the same orientation characteristics ((111) orientation) as the lower electrode 24 can be obtained. Iridium (Ir) may be used as the lower electrode 24 instead of Pt, but even in this case, the same piezoelectric thin film 25 as in the present embodiment can be obtained by controlling the roughness of the Ir surface.
[ method for manufacturing piezoelectric actuator ]
Next, fig. 5 is a cross-sectional view showing a manufacturing process of the piezoelectric actuator 21a, regarding the method of manufacturing the piezoelectric actuator 21a having the piezoelectric element 27 described above. The thickness of each layer shown below is an example, and is not limited to this value.
First, an soi (silicon on insulator) substrate as the support substrate 22 is prepared. The SOI substrate is a substrate in which a support layer 22c (thickness 600 μm) made of silicon, an intermediate oxide film layer 22d (thickness 0.5 μm) made of silicon oxide, and a device layer 22e (thickness 5 μm) made of silicon are laminated in this order. The thickness of the support layer 22c may be changed according to the design of the piezoelectric actuator 21a or the inkjet head 21. The support substrate 22 may be a single silicon substrate. Then, the support substrate 22 was thermally oxidized to form a thermally oxidized film 23 (thickness: 0.1 μm) on the surface.
Subsequently, Ti (thickness 20nm) and Pt (thickness 100nm) were formed on the surface of the thermal oxide film 23 by sputtering, thereby forming the lower electrode 24. In addition, titanium oxide (TiO) may also be formedx) Instead of Ti. Pt has self-orientation and is oriented in the (111) direction with respect to the support substrate 22. As described above, Ir may be used instead of Pt.
Subsequently, the PZT layer 25a constituting the piezoelectric thin film 25 is formed on the lower electrode 24 by sputtering. Subsequently, Ti (thickness: 0.1 μm) and Au (thickness: 0.2 μm) were sequentially formed on the layer 25a by sputtering, thereby forming a layer 26a constituting the upper electrode 26. Then, a photoresist is applied to the layer 26a, and exposure and development are performed to form a mask pattern of the upper electrode 26. Then, the layer 26a is wet-etched using the photoresist as a mask, and patterned to form the upper electrode 26.
Further, a photoresist pattern (diameter 180 μm) for patterning the layer 25a by wet etching was formed on the upper electrode 26. Thereafter, the layer 25a is wet-etched with a mixed etching solution of hydrofluoric/nitric acid, hydrogen peroxide water, hydrofluoric acid, or the like, and patterned to form the piezoelectric thin film 25 of PZT having a diameter of 180 μm.
Next, a photoresist is applied to the support layer 22c side of the support substrate 22, and exposed and developed to form a photoresist pattern. Then, the intermediate oxide film layer 22d is used as an Etching stopper layer, and a BOSCH process (using SF) using a deep reactive Ion Etching apparatus (DRIE: deep reactive Ion Etching) is performed6、 C4F8As an etching gas) is subjected to a deep reactive ion etching process for the support layer 22 c. By wet etching with HF, or with CHF3The exposed intermediate oxide film layer 22d was removed by dry etching with an equal gas, thereby forming a pressure chamber 22a having a diameter of 200 μm, i.e., a movable portion of the diaphragm. The device layer 22e exposed by the etching of the intermediate oxide film layer 22d serves as a diaphragm 22 b. Thereby, the piezoelectric actuator 21a is completed.
When the piezoelectric actuator 21a is used for the ink head 21, a nozzle substrate having nozzle holes may be bonded to the support substrate 22 on the side opposite to the piezoelectric thin film 25 with an adhesive or the like. Further, the piezoelectric actuator 21a may also be used for devices other than the ink jet head 21, such as an ultrasonic sensor, an infrared sensor, a frequency filter, and the like.
In each of the above steps, the cleaning is performed by rinsing with ultrapure water as necessary. In particular, since foreign matter in the ink flow path is a cause of clogging of the nozzle hole, careful cleaning is required. When the rinsing with ultrapure water alone is insufficient, ultrasonic waves may be added to the rinsing with ultrapure water, and isopropyl alcohol or acetone may be used. In addition, when stubborn stains are present, RCA cleaning with an aqueous hydrogen peroxide solution of ammonia or an aqueous hydrogen peroxide solution of sulfuric acid is effective for protecting the PZT layer surface side.
[ conditions for Forming Pt and PZT ]
The respective film formation conditions of Pt for the lower electrode 24 and PZT for the piezoelectric thin film 25 in the above-described method for manufacturing the piezoelectric actuator 21a will be described with reference to examples and comparative examples.
Comparative example 1
When Pt is formed by sputtering, the film forming temperature is set to 400-500 ℃, the sputtering pressure is set to 0.4Pa, the Ar flow is set to 20sccm, and the RF power is set to 150W. In this case, when the surface Roughness (Roughness) of Pt is measured, the RMS (root mean square Roughness) value is 3 to 4 nm.
Further, when PZT (layer 25a) is formed by sputtering, the film forming temperature is set to 500 ℃ or more and less than 550 ℃, and the RF power of the cathode is set to 31W/cm2The ratio of the oxygen flow rate/the argon flow rate is 1% or more and less than 2%. In addition, when PZT is formed at a high temperature, since Pb is insufficient due to evaporation of Pb, a predetermined amount (for example, 20 atm% or more and less than 40 atm%) of the amount of Pb in the PZT target is added in excess in advance compared to the stoichiometric amount (stoichiometric composition) to form PZT.
Comparative example 2
Pt was formed under the same film formation conditions as in comparative example 1. In addition, except that the RF power of the cathode was changed to 34W/cm2Except that, PZT was formed under the same film formation conditions as in comparative example 1.
Comparative examples 3 and 4
Pt was formed under the same film formation conditions as in comparative example 1. PZT was formed under the same film formation conditions as in comparative example 2, except that only the substrate temperature during film formation was changed to 550 ℃ or higher and lower than 600 ℃.
(examples 1 and 2)
The surface roughness of the lower electrode 24 is set to be RMS 3-4 nm, and the RF power of the cathode during PZT film formation is set to be 34W/cm2The film forming temperature is 550 ℃ to 600 ℃, and the ratio of oxygen flow rate/argon flow rate is 2% to 3%. The film forming rate of PZT is 1.5 μm/hr to 3 μm/hr.
(examples 3 and 4)
The surface roughness of the lower electrode 24 is set to RMS 2-3 nm. The conditions for forming PZT were the same as in examples 1 and 2.
PZT (piezoelectric thin film 25) produced under the film formation conditions of comparative examples 1 to 4 and examples 1 to 4 was evaluated by XRD. Fig. 6 shows a spectrum obtained when 2 θ/θ measurement of XRD is performed on the piezoelectric thin film 25 manufactured in example 4. The intensity (diffraction intensity, reflection intensity) on the vertical axis of fig. 6 is expressed in arbitrary units (Arbitary Unit) corresponding to the count rate per second (cps) of X-rays. The peak intensity ratio P of the (100) orientation of the perovskite phase was determined from the peak intensities obtained from the above spectra1And (110) oriented peak intensity ratio P2(111) oriented Peak intensity ratio P3The peak intensity ratio P of the pyrochlore layer4. The peak intensity ratio is specifically represented by the following formula.
Peak intensity ratio P of (100) orientation of perovskite phase1＝A1/(A1+A2+A3)
Peak intensity ratio P of (110) orientation of perovskite phase2＝A2/(A1+A2+A3)
Peak intensity ratio P of (111) orientation of perovskite phase3＝A3/(A1+A2+A3)
Peak intensity ratio P of pyrochlore phase4＝Py/(A1+A2+A3)
Wherein,
A1: peak intensity representing the (100) orientation of the perovskite phase;
A2: peak intensity representing the (110) orientation of the perovskite phase;
A3: peak intensity representing the (111) orientation of the perovskite phase;
Py: represents the peak intensity of the pyrochlore phase.
Further, the adhesiveness of the piezoelectric thin film 25 produced under the film formation conditions of comparative examples 1 to 4 and examples 1 to 4 to the lower electrode 24 was examined. Specifically, a voltage is applied to the lower electrode 24 and the upper electrode 26 of the manufactured actuator, and the diaphragm is continuously driven. At this time, a high frequency voltage of several kHz to 100kHz was applied, and the voltage was gradually increased from the initial voltage by setting the initial voltage at about 20V, and the voltage was maintained for about 1 hour in each voltage application state. Then, every time peeling of the piezoelectric film 25 was confirmed, the adhesiveness was evaluated based on the following criteria.
(evaluation criteria)
X: when a plurality of actuators are driven, peeling failure occurs before the initial voltage is increased to 20%, or failure due to peeling occurs in an assembly process before driving.
○ failure due to flaking occurs when the initial voltage is increased by 20% to 60%.
◎ failure due to flaking occurred when the initial voltage was increased by more than 60%.
Table 1 also shows the evaluation results of the peak strength and adhesion of PZT in comparative examples 1 to 4 and examples 1 to 4.
[ Table 1]
As is clear from Table 1, the piezoelectric thin films 25 of comparative examples 1 to 4 and examples 1 to 4 had a peak intensity ratio P of the perovskite phase in the (100) orientation1All above 95%, may be considered as the perovskite (100) primary orientation. Among them, in comparative examples 1 to 4, the adhesiveness of the piezoelectric thin film 25 was reduced. This is considered to be due to the following reason.
In comparative examples 3 and 4, the ratio P of the peak intensities of the pyrochlore phase in the piezoelectric thin film 254High. Although the pyrochlore phase is a metastable layer of PZT constituting the piezoelectric thin film 25, the pyrochlore phase is formed in the vicinity of the interface with the lower electrode 24 in the piezoelectric thin film 25, and is considered to cause exfoliation due to its high stress. Further, the ratio P of peak intensities of pyrochlore phase4This is considered to be caused by the fact that Pb re-evaporates from the substrate because the film forming temperature of PZT is higher than that of comparative examples 1 and 2.
In comparative example 1, although the peak intensity ratio P of the pyrochlore phase in the piezoelectric thin film 254Low, but perovskite phase peak intensity ratio P of (110) orientation2High. Due to the difference in lattice constant between the piezoelectric thin film 25 of the (100) main orientation and the lower electrode 24, even if the (110) orientation of the perovskite phase is only a small amount, strain of the piezoelectric thin film 25 is generated, and thus peeling occurs.
In comparative example 2, although the peak intensity ratio P of the pyrochlore phase in the piezoelectric thin film 254And the ratio P of the peak intensity of the (110) orientation of the perovskite phase2Low, but perovskite phase peak intensity ratio P of (111) orientation3And is also low. In the piezoelectric thin film 25 having the (100) main orientation, since the same orientation characteristics as those of the lower electrode 24 are small (111) orientation, the strain relaxation action on the piezoelectric thin film 25 having the (100) main orientation on the lower electrode 24 having the (111) orientation is small, and thus peeling occurs.
In comparative example 2, the ratio P2This is considered to be caused by the fact that the RF power of the cathode is increased during PZT molding, and the energy of the film forming particles colliding with the substrate is increased, and the growth of the (100) orientation is promoted instead of the (110) orientation. Such a stripThe material can be obtained by adjusting the energy of the film forming particles, or the same condition can be obtained by increasing the anode area of the jig around the film forming chamber or the substrate.
In contrast, in examples 1 to 4, the peak intensity ratio P of the pyrochlore phase in the piezoelectric thin film 254And the ratio P of the intensity of the peak of the (110) orientation of the perovskite phase2Low, ratio P of peak intensities of (111) orientation of perovskite phase3High. Since the piezoelectric thin film 25 having the (100) main orientation has many orientation characteristics (the (111) orientation) similar to those of the lower electrode 24, the strain relaxation effect on the piezoelectric thin film 25 having the (100) main orientation on the (111) oriented lower electrode 24 is large, and thus the adhesion of the piezoelectric thin film 25 to the lower electrode 24 is increased, and the peeling failure is improved. In addition, in the piezoelectric thin film 25 having the (100) main orientation, if the strain relaxation effect is to be produced, it is confirmed that the (111) orientation is present in the range of 50nm or less in thickness above the lower electrode 24 having the (111) orientation.
In addition, in the piezoelectric thin film 25 having the (100) main orientation, the peak intensity ratio P in the pyrochlore phase is determined4Is 205 × 10-6In comparative example 3, the adhesion of the piezoelectric thin film 25 was poor, and it was 190X 10-6In example 1 of (3), since the adhesiveness of the piezoelectric thin film 25 was good, it was found that the peak lightness ratio P of the pyrochlore phase, which enables obtaining good adhesiveness4Should preferably be 200 x 10 between them-6The following.
In addition, in the ratio P4Is 200X 10-6In comparative examples 1 and 2 and examples 1 to 4 described below, in the piezoelectric thin films 25 mainly oriented in (100) in examples 1 to 4, the peak intensity ratio P of the (110) orientation of the perovskite phase was set to be higher than that P of the (100) orientation of the perovskite phase2Is 1000X 10-6And a ratio P of peak intensities of (111) orientation of the perovskite phase3Is 500X 10-6As described above, however, in comparative examples 1 and 2, the ratio P2And ratio P3None of the conditions described above is satisfied. Therefore, in order to obtain good adhesion, it is considered that the ratio P is greater in the piezoelectric thin film 25 having the (100) main orientation2Must be 1000X 10-6Below and in a ratio of P3Must be 500X 10-6The above. In particular, the ratio P2117X 10 of preferred embodiment 1-6287 × 10 in comparison with comparative example 2-6200 x 10 of (A) between-6Below and in a ratio of P31364 × 10 preferred for embodiment 3-6680X 10 of comparative example 3-61000 x 10 therebetween-6The above.
In examples 1 to 4, the piezoelectric constant d31 of the piezoelectric film 25 was measured by a known cantilever method, and it was confirmed that a very high value of-180 pm/V was obtained in all cases.
[ other structures of piezoelectric elements ]
Fig. 7 is a cross-sectional view showing another structure of the piezoelectric element 27 of the present embodiment. In the figure, for convenience, the respective layers are shown without hatching, and the thermal oxide film 23 is not shown. The piezoelectric element 27 may have a seed layer 29 (buffer layer, orientation control layer) for controlling the crystal orientation of the piezoelectric thin film 25. The piezoelectric thin film 25 may be formed on the lower electrode 24 as an underlying layer via the seed layer 29.
The seed layer 29 is made of, for example, perovskite lead lanthanum titanate (PLT), and has a (111) orientation with a (100) orientation of a perovskite phase as a main orientation. The thickness of the seed layer 29 is, for example, 0.01 μm, and is 1/20 a relative to the thickness of 5 μm of the piezoelectric thin film 25.
In this way, the piezoelectric thin film 25 is formed on the lower electrode 24 via the seed layer 29 having the (100) main orientation, and the piezoelectric thin film is formed while continuing the crystal orientation of the seed layer 29, so that the piezoelectric thin film 25 having the (100) main orientation can be formed more stably and easily. Here, a direction parallel to the substrate surface (stacking surface) is referred to as a (100) direction.
The seed layer 29 has the same orientation characteristic as the base layer, that is, (111) orientation, and the different orientation characteristic from the base layer, that is, (100) orientation, but the (111) orientation exists almost in the entire thickness direction of the seed layer 29 because the seed layer 29 has a thin film thickness (0.01 μm) (see fig. 7). Therefore, in the initial stage of film formation, the piezoelectric thin film 25 is formed in the (100) orientation on the portion of the seed layer 29 formed in the (100) orientation, and is formed in the (111) orientation on the portion of the seed layer 29 formed in the (111) orientation. Therefore, the orientation characteristics of the piezoelectric thin film 25 and the seed layer 29 are matched to (100) orientation or (111) orientation in the vicinity of these interfaces. This ensures adhesion between the piezoelectric thin film 25 and the seed layer 29.
Further, since the seed layer 29 has the same (111) orientation as the orientation characteristic of the lower electrode 24, the adhesion between the seed layer 29 and the lower electrode 24 can be secured. Therefore, even when the seed layer 29 is provided between the piezoelectric thin film 25 and the lower electrode 24, film peeling of the piezoelectric thin film 25 can be suppressed.
Further, since the piezoelectric thin film 25 has the above-described orientation distribution ((111) orientation is distributed toward the base layer side in the thickness direction), the seed layer 29 preferably has a perovskite (100) main orientation, and has a (111) orientation with less (110) orientation. Such a seed layer 29 can be formed by sputtering. Although it is also related to the design of the sputtering apparatus, the seed layer 29 can be formed by optimizing the distance between the PLT target and the substrate, i.e., the T — S distance, and optimizing the crystal grain size (surface roughness) of Pt of the lower electrode. In addition, also in the high-temperature film formation of PLT, since Pb is insufficient due to the evaporation of Pb, it is necessary to add the amount of Pb in the PLT target in excess of 20 to 40 atm% in advance of the stoichiometric amount.
In addition to the PLT, the seed layer 29 may be made of Strontium Ruthenium Oxide (SRO), Strontium Titanium Oxide (STO), or magnesium oxide (MgO). Even in this case, the effects of the present embodiment described above can be obtained.
[ other structures of piezoelectric film ]
The piezoelectric film 25 may be formed of ABO3The perovskite dielectric thin film may be formed, or an additive may be added to the PZTAnd (4) obtaining. For example, ABO constituting the piezoelectric film 253In the perovskite dielectric thin film of the type, the element at the position a contains lead (Pb), and at least one of barium (Ba), lanthanum (La), strontium (Sr), bismuth (Bi), lithium (Li), sodium (Na), calcium (Ca), cadmium (Cd), magnesium (Mg), and potassium (K) may be included. The element at the position B includes zirconium (Zr) and titanium (Ti), and may include at least one of vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), scandium (Sc), cobalt (Co), copper (Cu), indium (In), tin (Sn), gallium (Ga), cadmium (Cd), iron (Fe), and nickel (Ni).
As described above, even when the piezoelectric thin film 25 is formed of a perovskite dielectric thin film to which the above-described additives are added, the above-described effects of the present embodiment can be obtained.
The piezoelectric element, the method of manufacturing the piezoelectric element, the piezoelectric actuator, the ink-jet head, and the ink-jet printer of the present embodiment described above can be described as follows, and thus the following operational effects can be exerted.
In the piezoelectric element according to the present embodiment, a piezoelectric layer having the same orientation characteristics as the base layer and different orientation characteristics from the base layer is formed on the base layer, and the orientation characteristics same as the base layer are biased toward the base layer side in the thickness direction of the piezoelectric layer.
According to the above configuration, the piezoelectric layer has the same orientation characteristics as the foundation layer and has orientation characteristics different from the foundation layer, but the orientation characteristics identical to the foundation layer are shifted toward the foundation layer side in the thickness direction of the piezoelectric layer. Therefore, the orientation characteristics are substantially matched between the piezoelectric layer and the underlying layer in the vicinity of the interface between the piezoelectric layer and the underlying layer, whereby the strain of the piezoelectric layer can be relaxed. Therefore, even when a piezoelectric layer having an orientation characteristic different from that of the underlying layer is formed on the underlying layer. Adhesion between the piezoelectric layer and the base layer can be improved, and film peeling of the piezoelectric layer can be suppressed.
The base layer may be (111) oriented, and the piezoelectric layer may have (100) orientation of the perovskite phase as a main orientation and have (111) orientation. In this case, the orientation characteristic can be matched to the same (111) orientation as that of the base layer in the vicinity of the interface between the piezoelectric layer and the base layer in the piezoelectric layer. Therefore, in the structure in which the piezoelectric layer having the (100) main orientation is formed on the base layer having the (111) orientation, the strain of the piezoelectric layer is relaxed, the adhesion between the piezoelectric layer and the base layer is improved, and the film peeling of the piezoelectric layer is suppressed.
The piezoelectric layer may be composed of lead zirconate titanate, and a ratio of a peak intensity of a pyrochlore phase obtained by 2 θ/θ measurement by X-ray diffraction to a total of peak intensities of a perovskite phase in (100) orientation, (110) orientation and (111) orientation may be 200 × 10-6Hereinafter, the ratio of the peak intensity of the (110) orientation of the perovskite phase to the sum may be 1000 × 10-6Hereinafter, the ratio of the peak intensity of the (111) orientation of the perovskite phase to the sum may be 500 × 10-6The above.
The pyrochlore phase is a metastable layer composed of PZT, is formed at the interface between the underlayer and PZT, and causes film peeling due to its high stress. Further, due to the difference in lattice constant between the (111) -oriented base layer and the (100) -oriented PZT, even a small amount of (110) -oriented PZT causes strain. On the other hand, the orientation characteristics of (111) -oriented PZT are the same as those of the (111) -oriented base layer, and have a function of relaxing the strain of (100) -oriented PZT. Therefore, the ratio of the peak intensities of the pyrochlore phase was 200X 10-6The ratio of the peak intensities of the (110) orientation of the perovskite phase is 1000X 10-6The ratio of the peak intensities of the (111) orientation of the perovskite phase is 500X 10-6As described above, the adhesion between the piezoelectric layer and the base layer can be reliably improved, and the film peeling of the piezoelectric layer can be reliably suppressed.
In the piezoelectric layer, a ratio of a peak intensity of a (110) orientation of a perovskite phase to the sum may be 200 × 10-6The following. In this case, the effect of suppressing film peeling of the piezoelectric layer can be further improvedAnd (5) fruit.
In the piezoelectric body layer, a ratio of a peak intensity of a (111) orientation of a perovskite phase to the sum may be 1000 × 10-6The above. In this case, the strain of the piezoelectric layer can be further suppressed, and the effect of suppressing the film peeling of the piezoelectric layer can be further improved.
When using Pb (Zr)xTi1-x)O3When the lead zirconate titanate constituting the piezoelectric layer is represented, x may be 0.50 to 0.55. In this case, the piezoelectric layer has a so-called MPB composition or a composition close thereto, and thus can obtain high piezoelectric characteristics.
In the piezoelectric layer, the same orientation characteristic as that of the base layer may be present in a thickness portion of 50nm or less from the base layer side. In the piezoelectric layer, since the orientation characteristic similar to that of the underlying layer is surely shifted toward the underlying layer side, the orientation characteristic is almost matched in the vicinity of the interface between the piezoelectric layer and the underlying layer, and the adhesion between the piezoelectric layer and the underlying layer can be surely improved.
The piezoelectric layer may be formed of ABO3The perovskite dielectric thin film may be formed such that the element at the position A contains lead, and may contain at least one of barium, lanthanum, strontium, bismuth, lithium, sodium, calcium, cadmium, magnesium, and potassium, and the element at the position B contains zirconium and titanium, and may contain at least one of vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, scandium, cobalt, copper, indium, tin, gallium, cadmium, iron, and nickel. The above-described effects can be obtained even when the piezoelectric layer is formed of a perovskite dielectric thin film in which the above-described additive is added to PZT.
The thickness of the piezoelectric layer may be 1 to 5 μm. In this way, the above-described effects can be obtained in a structure in which the piezoelectric layer is a thin film (piezoelectric thin film).
The piezoelectric layer may be formed on the underlayer through a seed layer for controlling the orientation of the piezoelectric layer, and the seed layer may have a (111) orientation having a (100) orientation of a perovskite phase as a main orientation.
Since the seed layer has the same orientation property ((111) orientation) as the base layer and the orientation property ((100) orientation) different from the base layer, a portion whose orientation property matches (111) orientation or (100) orientation can be generated in the vicinity of the interface between the piezoelectric layer and the seed layer, and a portion whose orientation property matches (111) orientation can be generated in the vicinity of the interface between the seed layer and the base layer. Thus, even when the piezoelectric layer is formed on the base layer with the seed layer interposed therebetween, the adhesiveness of the piezoelectric layer can be improved, and the film peeling of the piezoelectric layer can be suppressed. Further, since the piezoelectric layer is formed on the seed layer having the (100) main orientation, the piezoelectric layer can be easily formed in the (100) main orientation.
The seed layer may be comprised of lead lanthanum titanate, strontium ruthenium oxide, strontium titanium oxide, or magnesium oxide. In the structure having the seed layer made of such a material, the aforementioned effects can be obtained.
The base layer may be a lower electrode. In the structure in which the piezoelectric layer is provided over the lower electrode, the aforementioned effects can be obtained.
The lower electrode may include a layer composed of platinum or iridium. In the structure in which Pt or Ir is generally used as the material of the lower electrode, the aforementioned effects can be obtained.
An upper electrode may be formed on the piezoelectric layer. Since the piezoelectric layer is sandwiched between the lower electrode and the upper electrode, a structure can be realized in which a voltage is applied to these electrodes to expand and contract the piezoelectric layer.
In the method of manufacturing the piezoelectric actuator according to the present embodiment, the base layer and the piezoelectric layer may be formed by a sputtering method. The seed layer may be formed by sputtering. By the sputtering method, a layer having desired alignment characteristics can be formed reliably.
The piezoelectric actuator according to the present embodiment may include the piezoelectric element described above, and a support substrate that supports the piezoelectric element, and the support substrate may be provided with an opening and a vibrating plate that is formed so as to cover the opening and vibrates by driving of the piezoelectric element. According to the piezoelectric element described above, even if the piezoelectric layer having the orientation characteristic different from that of the underlying layer is formed on the underlying layer, film peeling of the piezoelectric layer can be suppressed, and thus occurrence of a driving failure due to film peeling can be reduced.
The ink jet head of the present embodiment includes: the piezoelectric actuator described above; a nozzle substrate having a nozzle hole and bonded to the piezoelectric actuator on a side of the support substrate opposite to the piezoelectric element; the inkjet head ejects ink stored in the opening of the support substrate to the outside through the nozzle hole. In this case, in the inkjet head, it is possible to reduce the ink ejection failure caused by the film peeling of the piezoelectric layer.
The inkjet printer of the present embodiment includes the inkjet head described above, and ejects ink from the inkjet head toward a recording medium. In this case, it is possible to avoid a decrease in the quality of an image formed on a recording medium due to a discharge failure of ink caused by film peeling of the piezoelectric layer.
Industrial applicability
The piezoelectric element of the present invention can be used for a piezoelectric actuator, an ink jet head, and an ink jet printer.
Description of the reference numerals
1 ink jet printer
21 ink jet head
21a piezoelectric actuator
22 support substrate
22a pressure chamber (opening)
22b diaphragm
24 lower electrode (basal layer)
25 piezoelectric film (piezoelectric layer)
26 Upper electrode
27 piezoelectric element
29 seed layer
31 nozzle base plate
31a discharge hole (nozzle hole)
Claims (17)
1. A piezoelectric element is characterized in that a piezoelectric element,
a piezoelectric layer is formed on the base layer,
the piezoelectric layer has the same orientation characteristics as the base layer and different orientation characteristics from the base layer,
the orientation characteristic of the piezoelectric layer in the thickness direction is biased toward the base layer side in the same manner as that of the base layer,
the base layer is (111) oriented,
the piezoelectric layer has a (111) orientation with a (100) orientation of a perovskite phase as a main orientation,
the piezoelectric layer is formed on the base layer with a seed layer for controlling the orientation of the piezoelectric layer interposed therebetween,
the seed layer has (111) orientation with (100) orientation of perovskite phase as main orientation.
2. The piezoelectric element according to claim 1,
the piezoelectric layer is composed of lead zirconate titanate,
in the piezoelectric layer, the ratio of the peak intensity of the pyrochlore phase obtained by 2 θ/θ measurement by X-ray diffraction to the sum of the peak intensities of the perovskite phase in the (100), (110) and (111) orientations was 200 × 10-6In the following, the following description is given,
the ratio of the peak intensity of the (110) orientation of the perovskite phase to the sum is 1000X 10-6In the following, the following description is given,
the ratio of the peak intensity of the (111) orientation of the perovskite phase to the sum is 500 x 10-6The above.
3. The piezoelectric element according to claim 2,
in the piezoelectric layer, the ratio of the peak intensity of the (110) orientation of the perovskite phase to the sum is 200 × 10-6The following.
4. The piezoelectric element according to claim 2 or 3,
in the piezoelectric body layer, the ratio of the peak intensity of the (111) orientation of the perovskite phase to the sum is 1000 × 10-6The above.
5. The piezoelectric element according to claim 2 or 3,
when using Pb (Zr)xTi1-x)O3When the piezoelectric layer is composed of lead zirconate titanate, x is 0.50 to 0.55.
6. The piezoelectric element according to any one of claims 1 to 3,
in the piezoelectric layer, the same orientation characteristic as that of the base layer is present in a thickness portion of 50nm or less from the base layer side.
7. The piezoelectric element according to any one of claims 1 to 3,
the piezoelectric layer is composed of ABO3A perovskite dielectric thin film of a type,
the element at position A contains lead and at least one of barium, lanthanum, strontium, bismuth, lithium, sodium, calcium, cadmium, magnesium and potassium,
the element at position B contains zirconium and titanium, and further contains at least one of vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, scandium, cobalt, copper, indium, tin, gallium, cadmium, iron, and nickel.
8. The piezoelectric element according to any one of claims 1 to 3,
the thickness of the piezoelectric layer is 1 to 5 μm.
9. The piezoelectric element according to claim 1,
the seed crystal layer is composed of lead lanthanum titanate, strontium ruthenium oxide, strontium titanium oxide or magnesium oxide.
10. The piezoelectric element according to any one of claims 1 to 3,
the base layer is a lower electrode.
11. The piezoelectric element according to claim 10,
the lower electrode includes a layer composed of platinum or iridium.
12. The piezoelectric element according to claim 10,
an upper electrode is formed on the piezoelectric layer.
13. A method of manufacturing a piezoelectric element according to any one of claims 1 to 12,
the base layer and the piezoelectric layer are formed by sputtering.
14. A method of manufacturing a piezoelectric element according to claim 1 or 9,
and forming the seed crystal layer by a sputtering method.
15. A piezoelectric actuator, comprising:
a piezoelectric element as recited in claim 12;
a support substrate that supports the piezoelectric element;
an opening and a vibrating plate are formed in the support substrate, the vibrating plate being formed so as to cover the opening, and vibrating by driving of the piezoelectric element.
16. An ink jet head, comprising:
the piezoelectric actuator of claim 15;
a nozzle substrate having a nozzle hole and bonded to the piezoelectric actuator on a side of the support substrate opposite to the piezoelectric element;
the inkjet head ejects ink stored in the opening of the support substrate to the outside through the nozzle hole.
17. An ink-jet printer is characterized in that,
an ink jet head according to claim 16,
the inkjet printer ejects ink from the inkjet head toward a recording medium.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
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| JP2014088863 | 2014-04-23 | ||
| JP2014-088863 | 2014-04-23 | ||
| PCT/JP2015/058681 WO2015163070A1 (en) | 2014-04-23 | 2015-03-23 | Piezoelectric element, method for producing piezoelectric element, piezoelectric actuator, inkjet head, and inkjet printer |
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| Publication Number | Publication Date |
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| CN106233480A CN106233480A (en) | 2016-12-14 |
| CN106233480B true CN106233480B (en) | 2019-02-15 |
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| JP (1) | JP6274308B2 (en) |
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| EP3467890B1 (en) * | 2016-05-27 | 2021-03-31 | Konica Minolta, Inc. | Method for manufacturing piezoelectric element and method for manufacturing ink jet head |
| CN112415288B (en) * | 2020-10-22 | 2022-08-05 | 同济大学 | Measuring method of system for measuring hydrostatic pressure piezoelectric coefficient of coaxial piezoelectric cable |
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| CN101383395A (en) * | 2007-09-07 | 2009-03-11 | 富士胶片株式会社 | Piezoelectric device, liquid droplet ejecting head using the same, and process for producing the same |
| CN102790169A (en) * | 2011-05-17 | 2012-11-21 | 三菱综合材料株式会社 | Method for producing ferroelectric thin film |
| CN102787356A (en) * | 2011-05-17 | 2012-11-21 | 三菱综合材料株式会社 | Method for producing ferroelectric thin film |
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| JP5115910B2 (en) * | 2002-01-22 | 2013-01-09 | セイコーエプソン株式会社 | Printer |
| JP2007242778A (en) * | 2006-03-07 | 2007-09-20 | Seiko Epson Corp | Thin film element manufacturing method |
| US20090311417A1 (en) * | 2006-08-02 | 2009-12-17 | Ulvac, Inc. | Film forming method and film forming apparatus |
| EP2846370B1 (en) * | 2012-05-01 | 2016-07-06 | Konica Minolta, Inc. | Piezoelectric element |
| JP2015005554A (en) * | 2013-06-19 | 2015-01-08 | 株式会社リコー | Electromechanical conversion element, droplet discharge head, droplet discharge device, imaging device, and method for manufacturing electromechanical conversion element |
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| CN101383395A (en) * | 2007-09-07 | 2009-03-11 | 富士胶片株式会社 | Piezoelectric device, liquid droplet ejecting head using the same, and process for producing the same |
| CN102790169A (en) * | 2011-05-17 | 2012-11-21 | 三菱综合材料株式会社 | Method for producing ferroelectric thin film |
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| JP6274308B2 (en) | 2018-02-07 |
| WO2015163070A1 (en) | 2015-10-29 |
| CN106233480A (en) | 2016-12-14 |
| JPWO2015163070A1 (en) | 2017-04-13 |
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