JP2013187207A - Piezoelectric actuator, method for manufacturing the same, liquid injection head, method for manufacturing the same, and liquid injection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric actuator which is low in environmental load, suppresses rupture, and exhibits a large amount of displacement, and to provide a liquid injection head provided with the piezoelectric actuator.SOLUTION: The piezoelectric actuator includes a first electrode, a piezoelectric layer provided on the first electrode, and a second electrode provided on the piezoelectric layer. The piezoelectric layer is made of a composite oxide having a perovskite structure containing Bi, Fe, Ba, and Ti. The second electrode is formed of an iridium film having a film thickness of 30-50 nm inclusive and a compressive stress of 0.4-1.0 GPa inclusive.

Description

  The present invention relates to a piezoelectric actuator having a piezoelectric layer made of a piezoelectric material and an electrode, and a method for manufacturing the piezoelectric actuator, a liquid ejecting head that includes the piezoelectric actuator and ejects droplets from nozzle openings, a method for manufacturing the liquid ejecting head, and a liquid ejecting apparatus. .

  As a typical example of a liquid ejecting head, for example, a part of a pressure generation chamber communicating with a nozzle that ejects ink droplets is configured by a vibration plate, and the vibration plate is deformed by a piezoelectric actuator to add ink in the pressure generation chamber. There is an ink jet recording head that presses and ejects ink droplets from a nozzle. A piezoelectric actuator used in an ink jet recording head is configured by sandwiching a piezoelectric layer (piezoelectric film) made of a piezoelectric material exhibiting an electromechanical conversion function, for example, a crystallized dielectric material, between two electrodes. There is something.

A piezoelectric material used as a piezoelectric layer constituting such a piezoelectric actuator is required to have high piezoelectric characteristics, and a typical example of the piezoelectric material is lead zirconate titanate (PZT) (Patent Document 1, etc.). reference). However, from the viewpoint of environmental problems, there is a demand for a piezoelectric material with reduced lead or lead content. For example, there is a BiFeO ₃ -based piezoelectric material containing Bi and Fe (see, for example, Patent Document 2). .

JP 2001-223404 A JP 2007-287745 A

However, in the case of a piezoelectric actuator having a piezoelectric layer made of such a BiFeO ₃ composite oxide, there is a problem that the piezoelectric actuator may break due to an increase in the amount of deflection toward the pressure generating chamber. There is. Further, since the amount of displacement is not sufficient as compared with lead zirconate titanate, an improvement in the amount of displacement is required. Such a problem exists not only in the ink jet recording head, but of course in other liquid ejecting heads that eject droplets other than ink, and also in piezoelectric actuators used for other than liquid ejecting heads. Exist as well.

  In view of such circumstances, the present invention has a piezoelectric actuator that has a small environmental load, is suppressed in breakage, and has a large amount of displacement, a liquid ejecting head and a liquid ejecting apparatus including the piezoelectric actuator, a method for manufacturing the piezoelectric actuator, and a liquid It is an object of the present invention to provide a method for manufacturing an ejection head.

An aspect of the present invention that solves the above problem includes a first electrode, a piezoelectric layer provided on the first electrode, and a second electrode provided on the piezoelectric layer, wherein the piezoelectric layer comprises: An iridium film comprising a complex oxide having a perovskite structure containing Bi, Fe, Ba and Ti, wherein the second electrode has a film thickness of 30 nm to 50 nm and a compressive stress of 0.4 GPa to 1.0 GPa The piezoelectric actuator is characterized by comprising:
In this embodiment, the piezoelectric layer is made of a complex oxide having a perovskite structure containing Bi, Fe, Ba and Ti, and the second electrode has a thickness of 30 nm to 50 nm and 0.4 GPa to 1.0 GPa. By using an iridium film having a compressive stress, it is possible to obtain a piezoelectric actuator that is prevented from being broken and has a large displacement. Furthermore, since the content of non-lead or lead can be suppressed, the burden on the environment can be reduced.

  According to another aspect of the invention, there is provided a liquid ejecting head including a pressure generating chamber communicating with a nozzle opening for ejecting a liquid and the piezoelectric actuator for causing a pressure change in the pressure generating chamber. According to this, since the piezoelectric actuator having a large amount of displacement that is prevented from being broken, a liquid ejecting head that is excellent in reliability and piezoelectric characteristics (displacement amount) can be obtained. Furthermore, since the content of non-lead or lead can be suppressed, the burden on the environment can be reduced.

  According to another aspect of the invention, a liquid ejecting apparatus includes the liquid ejecting head. According to this aspect, it is possible to realize a liquid ejecting apparatus that reduces the load on the environment and is excellent in reliability and piezoelectric characteristics.

  Another aspect of the present invention is a method of manufacturing a piezoelectric actuator comprising a first electrode, a piezoelectric layer provided on the first electrode, and a second electrode provided on the piezoelectric layer. Forming a piezoelectric layer made of a composite oxide having a perovskite structure containing Bi, Fe, Ba and Ti on the first electrode, and a film thickness of 30 nm to 50 nm on the piezoelectric layer, And it exists in the manufacturing method of the piezoelectric actuator characterized by having the process of forming the 2nd electrode which consists of an iridium film | membrane which has a compressive stress of 0.4 GPa or more and 1.0 GPa or less. A first iridium film having a compressive stress of 30 nm to 50 nm and 0.4 GPa to 1.0 GPa on a piezoelectric layer made of a composite oxide having a perovskite structure containing Bi, Fe, Ba, and Ti. By forming the two electrodes, it is possible to manufacture a piezoelectric actuator that is prevented from being broken and has a large displacement. Furthermore, since the content of non-lead or lead can be suppressed, the burden on the environment can be reduced.

  Another aspect of the present invention is a method of manufacturing a liquid ejecting head including a pressure generation chamber communicating with a nozzle opening and a piezoelectric actuator that causes a pressure change in the pressure generation chamber. The method of manufacturing a liquid ejecting head includes a step of manufacturing the piezoelectric actuator by a manufacturing method. According to this, it is possible to manufacture a liquid jet head that reduces the load on the environment and is excellent in reliability and piezoelectric characteristics (displacement amount).

FIG. 3 is an exploded perspective view illustrating a schematic configuration of the recording head according to the first embodiment. FIG. 3 is a plan view of the recording head according to the first embodiment. FIG. 3 is a cross-sectional view of the recording head according to the first embodiment. FIG. 3 is a cross-sectional view illustrating a manufacturing process of the recording head according to the first embodiment. FIG. 3 is a cross-sectional view illustrating a manufacturing process of the recording head according to the first embodiment. FIG. 3 is a cross-sectional view illustrating a manufacturing process of the recording head according to the first embodiment. FIG. 3 is a cross-sectional view illustrating a manufacturing process of the recording head according to the first embodiment. FIG. 3 is a cross-sectional view illustrating a manufacturing process of the recording head according to the first embodiment. The figure which shows the drive waveform used by the test example. 1 is a diagram illustrating a schematic configuration of a recording apparatus according to an embodiment of the present invention.

(Embodiment 1)
FIG. 1 is an exploded perspective view showing a schematic configuration of an ink jet recording head which is an example of a liquid ejecting head according to Embodiment 1 of the invention, FIG. 2 is a plan view of FIG. 1, and FIG. 2 is a cross-sectional view taken along line AA ′ of FIG. As shown in FIGS. 1 to 3, the flow path forming substrate 10 of the present embodiment is made of a silicon single crystal substrate, and an elastic film 50 made of silicon dioxide is formed on one surface thereof.

  A plurality of pressure generating chambers 12 are arranged in parallel in the width direction of the flow path forming substrate 10. In addition, a communication portion 13 is formed in a region outside the longitudinal direction of the pressure generation chamber 12 of the flow path forming substrate 10, and the communication portion 13 and each pressure generation chamber 12 are provided for each pressure generation chamber 12. Communication is made via a supply path 14 and a communication path 15. The communication part 13 communicates with a manifold part 31 of a protective substrate, which will be described later, and constitutes a part of a manifold that becomes a common ink chamber for each pressure generating chamber 12. The ink supply path 14 is formed with a narrower width than the pressure generation chamber 12, and maintains a constant flow path resistance of ink flowing into the pressure generation chamber 12 from the communication portion 13. In this embodiment, the ink supply path 14 is formed by narrowing the width of the flow path from one side. However, the ink supply path may be formed by narrowing the width of the flow path from both sides. Further, the ink supply path may be formed by narrowing from the thickness direction instead of narrowing the width of the flow path. In the present embodiment, the flow path forming substrate 10 is provided with a liquid flow path including the pressure generation chamber 12, the communication portion 13, the ink supply path 14, and the communication path 15.

  Further, on the opening surface side of the flow path forming substrate 10, a nozzle plate 20 having a nozzle opening 21 communicating with the vicinity of the end of each pressure generating chamber 12 on the side opposite to the ink supply path 14 is provided with an adhesive. Or a heat-welded film or the like. The nozzle plate 20 is made of, for example, glass ceramics, a silicon single crystal substrate, stainless steel, or the like.

On the other hand, the elastic film 50 is formed on the side opposite to the opening surface of the flow path forming substrate 10 as described above. On the elastic film 50, for example, titanium oxide having a thickness of about 30 to 50 nm or the like. An adhesion layer 56 for improving adhesion between the first electrode 60 such as the elastic film 50 and the like is provided. In the present embodiment, titanium oxide is used as the adhesion layer 56, but the material of the adhesion layer 56 varies depending on the first electrode 60 and the type of the underlying layer, but for example, an oxide or nitride containing zirconium or aluminum, , SiO ₂ , MgO, CeO ₂ or the like. Note that an insulator film made of zirconium oxide or the like may be provided on the elastic film 50 as necessary.

  Further, on the adhesion layer 56, a first electrode 60, a piezoelectric layer 70 which is a thin film having a thickness of 3 μm or less, preferably 0.3 to 1.5 μm, and a second electrode 80 are laminated. Thus, a piezoelectric actuator 300 is configured as pressure generating means for causing a pressure change in the pressure generating chamber 12. Here, the piezoelectric actuator 300 refers to a portion including the first electrode 60, the piezoelectric layer 70, and the second electrode 80. In general, one electrode of the piezoelectric actuator 300 is used as a common electrode, and the other electrode and the piezoelectric layer 70 are patterned for each pressure generating chamber 12. In the present embodiment, the first electrode 60 is used as a common electrode for the piezoelectric actuator 300 and the second electrode 80 is used as an individual electrode for the piezoelectric actuator 300. However, there is no problem even if this is reversed for the convenience of the drive circuit and wiring. In the above-described example, the elastic film 50, the adhesion layer 56, the first electrode 60, and the insulator film provided as necessary function as a vibration plate. However, the present invention is not limited to this. For example, the elastic film 50 and the adhesion layer 56 may not be provided. Further, the piezoelectric actuator 300 itself may substantially serve as a diaphragm.

In the present embodiment, the piezoelectric material constituting the piezoelectric layer 70 is a complex oxide having a perovskite structure including bismuth (Bi), iron (Fe), barium (Ba), and titanium (Ti). In the A site of the perovskite structure, that is, the ABO ₃ type structure, oxygen is 12-coordinated, and in the B site, oxygen is 6-coordinated to form an octahedron. Bi and Ba are located at the A site, and Fe and Ti are located at the B site.

  Such a composite oxide having a perovskite structure containing Bi, Fe, Ba and Ti is a composite oxide having a perovskite structure of a mixed crystal of bismuth ferrate and barium titanate, or bismuth ferrate and barium titanate. Is also expressed as a solid solution in which the solid solution is uniformly dissolved. In the X-ray diffraction pattern, bismuth ferrate and barium titanate are not detected alone.

Here, bismuth ferrate and barium titanate are known piezoelectric materials each having a perovskite structure, and those having various compositions are known. For example, as bismuth ferrate or barium titanate, in addition to BiFeO ₃ or BaTiO ₃ , some elements (Bi, Fe, Ba, Ti, O) are partially lost or excessive, or some of the elements are other elements However, in the present invention, when expressed as bismuth ferrate or barium titanate, as long as the basic characteristics are not changed, those that deviate from the stoichiometric composition due to deficiency or excess Those in which some of the elements are substituted with other elements are also included in the ranges of bismuth ferrate and barium titanate. The ratio of bismuth ferrate to barium titanate can also be changed variously.

The composition of the piezoelectric layer 70 made of a complex oxide having such a perovskite structure is represented, for example, as a mixed crystal represented by the following general formula (1). Moreover, this formula (1) can also be represented by the following general formula (1 ′). Here, the description of the general formula (1) and the general formula (1 ′) is a composition notation based on stoichiometry, and as described above, as long as a perovskite structure can be taken, it is inevitable due to lattice mismatch, oxygen deficiency, etc. Of course, a partial substitution of elements is allowed as well as a slight compositional deviation. For example, if the stoichiometric ratio is 1, the range of 0.85 to 1.20 is allowed. In addition, even when the general formulas are different as described below, those having the same ratio of the A-site element to the B-site element may be regarded as the same composite oxide.
(1-x) [BiFeO ₃ ] -x [BaTiO ₃ ] (1)
(0 <x <0.40)
(Bi _1-x Ba _x ) (Fe _1-x Ti _x ) O ₃ (1 ′)
(0 <x <0.40)

  Further, the complex oxide constituting the piezoelectric layer 70 may further contain an element other than Bi, Fe, Ba, and Ti. Examples of other elements include Mn, Co, and Cr. Of course, even a complex oxide containing other elements needs to have a perovskite structure.

  When the piezoelectric layer 70 includes Mn, Co, and Cr, Mn, Co, and Cr are complex oxides having a structure located at the B site. For example, when Mn is included, the composite oxide constituting the piezoelectric layer 70 has a structure in which part of Fe in a solid solution in which bismuth ferrate and barium titanate are uniformly dissolved, is substituted with Mn, or ferric acid It is expressed as a composite oxide having a perovskite structure of mixed crystals of bismuth manganate and barium titanate, and the basic characteristics are the same as those of a composite oxide having a perovskite structure of mixed crystals of bismuth ferrate and barium titanate. However, it has been found that the leakage characteristics are improved. Further, when Co or Cr is included, the leakage characteristics are improved in the same manner as Mn. In the X-ray diffraction pattern, bismuth ferrate, barium titanate, bismuth iron manganate, bismuth iron cobaltate, and bismuth iron chromate are not detected alone. Further, although Mn, Co and Cr have been described as examples, it has been found that leakage characteristics are similarly improved when two other transition metal elements are included at the same time. In addition, other known additives may be included to improve the properties.

The piezoelectric layer 70 made of a complex oxide having a perovskite structure including Mn, Co, and Cr in addition to Bi, Fe, Ba, and Ti is, for example, a mixed crystal represented by the following general formula (2). is there. Moreover, this formula (2) can also be represented by the following general formula (2 ′). In General Formula (2) and General Formula (2 ′), M is Mn, Co, or Cr. Here, the description of the general formula (2) and the general formula (2 ′) is a composition notation based on the stoichiometry, and as described above, as long as the perovskite structure can be taken, it is unavoidable due to lattice mismatch, oxygen deficiency, etc. Such a composition deviation is allowed. For example, if the stoichiometry is 1, one in the range of 0.85 to 1.20 is allowed. In addition, even when the general formulas are different as described below, those having the same ratio of the A-site element to the B-site element may be regarded as the same composite oxide.
(1-x) [Bi (Fe _1-y M _y ) O ₃ ] -x [BaTiO ₃ ] (2)
(0 <x <0.40, 0.01 <y <0.10)
_{(Bi 1-x Ba x)} ((Fe 1-y M y) 1-x Ti x) O 3 (2 ')
(0 <x <0.40, 0.01 <y <0.10)

  Note that the piezoelectric layer 70 of the present embodiment may be oriented in any of the (110) plane, the (100) plane, and the (111) plane, and is not particularly limited.

  In the piezoelectric actuator 300 included in the ink jet recording head of the present embodiment, the second electrode 80 is formed of an iridium film having a film thickness of 30 nm to 50 nm and a compressive stress of 0.4 GPa to 1.0 GPa. It will be. In other words, the second electrode 80 is an iridium film formed by a manufacturing method having a thickness of 30 nm to 50 nm and an internal stress of compressive stress of 0.4 GPa to 1.0 GPa.

  Thus, in the piezoelectric actuator 300, the piezoelectric layer 70 is made of a complex oxide having a perovskite structure containing Bi, Fe, Ba, and Ti, and the second electrode 80 on the piezoelectric layer 70 is formed with a film thickness. Is an iridium film formed so as to have a compressive stress of not less than 30 nm and not more than 50 nm and not less than 0.4 GPa and not more than 1.0 GPa, so that the piezoelectric actuator 300 bends before being applied with a voltage. (Initial deflection) is reduced to, for example, 200 nm or less, and breakage of the piezoelectric actuator 300 caused by an increase in the amount of deflection toward the pressure generation chamber can be suppressed. Further, even when driven at a high voltage or when driven for a long period of time, the piezoelectric actuator 300 is prevented from being broken due to deflection, and the piezoelectric actuator 300 is excellent in durability. Therefore, an ink jet recording head excellent in reliability in which breakage of the piezoelectric actuator 300 is suppressed is obtained. Further, since the piezoelectric actuator 300 has a large amount of displacement, it becomes an ink jet recording head having excellent piezoelectric characteristics.

  Each second electrode 80, which is an individual electrode of the piezoelectric actuator 300, is drawn from the vicinity of the end on the ink supply path 14 side and extends to the elastic film 50 or an insulator film provided as necessary. For example, a lead electrode 90 made of gold (Au) or the like is connected.

  At least a part of the manifold 100 is formed on the flow path forming substrate 10 on which such a piezoelectric actuator 300 is formed, that is, on the first electrode 60, the elastic film 50, the insulator film provided as necessary, and the lead electrode 90. A protective substrate 30 having a manifold portion 31 constituting the above is joined via an adhesive 35. In this embodiment, the manifold portion 31 penetrates the protective substrate 30 in the thickness direction and is formed across the width direction of the pressure generating chamber 12. As described above, the communication portion 13 of the flow path forming substrate 10. The manifold 100 is configured as a common ink chamber for the pressure generation chambers 12. Alternatively, the communication portion 13 of the flow path forming substrate 10 may be divided into a plurality of pressure generation chambers 12 and only the manifold portion 31 may be used as a manifold. Further, for example, only the pressure generation chamber 12 is provided in the flow path forming substrate 10 and a member (for example, an elastic film 50, an insulator film provided as necessary, etc.) interposed between the flow path forming substrate 10 and the protective substrate 30 ) May be provided with an ink supply path 14 for communicating the manifold 100 and each pressure generating chamber 12.

  A piezoelectric actuator holding portion 32 having a space that does not hinder the movement of the piezoelectric actuator 300 is provided in a region facing the protective substrate 30 piezoelectric actuator 300. The piezoelectric actuator holding part 32 only needs to have a space that does not hinder the movement of the piezoelectric actuator 300, and the space may be sealed or unsealed.

  As such a protective substrate 30, it is preferable to use substantially the same material as the coefficient of thermal expansion of the flow path forming substrate 10, for example, glass, ceramic material, etc. In this embodiment, the same material as the flow path forming substrate 10 is used. The silicon single crystal substrate was used.

  The protective substrate 30 is provided with a through hole 33 that penetrates the protective substrate 30 in the thickness direction. The vicinity of the end of the lead electrode 90 drawn from each piezoelectric actuator 300 is provided so as to be exposed in the through hole 33.

  A drive circuit 120 for driving the piezoelectric actuators 300 arranged in parallel is fixed on the protective substrate 30. For example, a circuit board or a semiconductor integrated circuit (IC) can be used as the drive circuit 120. The drive circuit 120 and the lead electrode 90 are electrically connected via a connection wiring 121 made of a conductive wire such as a bonding wire.

  In addition, a compliance substrate 40 including a sealing film 41 and a fixing plate 42 is bonded onto the protective substrate 30. Here, the sealing film 41 is made of a material having low rigidity and flexibility, and one surface of the manifold portion 31 is sealed by the sealing film 41. The fixing plate 42 is formed of a relatively hard material. Since the area of the fixing plate 42 facing the manifold 100 is an opening 43 that is completely removed in the thickness direction, one surface of the manifold 100 is sealed only with a flexible sealing film 41. Has been.

  In such an ink jet recording head I of this embodiment, ink is taken in from an ink introduction port connected to an external ink supply means (not shown), and the interior from the manifold 100 to the nozzle opening 21 is filled with ink, and then driven. In accordance with a recording signal from the circuit 120, a voltage is applied between each of the first electrode 60 and the second electrode 80 corresponding to the pressure generating chamber 12, and the elastic film 50, the adhesion layer 56, the first electrode 60, the piezoelectric body. By bending and deforming the layer 70, the pressure in each pressure generation chamber 12 is increased, and ink droplets are ejected from the nozzle openings 21.

  Next, an example of a method for manufacturing the ink jet recording head of the present embodiment will be described with reference to FIGS. 4 to 8 are cross-sectional views in the longitudinal direction of the pressure generating chamber.

First, as shown in FIG. 4A, a silicon dioxide film made of silicon dioxide (SiO ₂ ) or the like constituting the elastic film 50 is formed by thermal oxidation or the like on the surface of a flow path forming substrate wafer 110 that is a silicon wafer. To do. When an insulator film (not shown) made of zirconium oxide or the like is provided on the elastic film 50 or the like, it can be formed by, for example, a reactive sputtering method or thermal oxidation.

  Next, as shown in FIG. 4B, an adhesion layer 56 made of titanium oxide or the like is sputtered on the elastic film 50 (silicon dioxide film) or on the insulator film when an insulator film is provided. It is formed by the method or thermal oxidation.

  Next, as shown in FIG. 5A, a first electrode 60 made of platinum, iridium, iridium oxide, or a laminated structure thereof is formed on the entire surface of the adhesion layer 56 by sputtering, vapor deposition, or the like. . Next, as shown in FIG. 5B, patterning is performed simultaneously on the first electrode 60 so that the side surfaces of the adhesion layer 56 and the first electrode 60 are inclined using a resist (not shown) having a predetermined shape as a mask.

  Next, after peeling off the resist, the piezoelectric layer 70 is laminated on the first electrode 60. The method for manufacturing the piezoelectric layer 70 is not particularly limited. For example, a MOD (Metal film) that obtains a piezoelectric layer (piezoelectric film) made of a metal oxide by coating and drying a solution containing a metal complex and firing at a high temperature. The piezoelectric layer 70 can be manufactured by using a chemical solution method such as an —Organic Decomposition ”method or a sol-gel method. In addition, the piezoelectric layer 70 is manufactured by a vapor phase method, a liquid phase method, or a solid phase method such as a laser ablation method, a sputtering method, a pulse laser deposition method (PLD method), a CVD method, an aerosol deposition method, or the like. be able to.

  As a specific example of the formation procedure when the piezoelectric layer 70 is formed by the chemical solution method, first, as shown in FIG. 5C, a metal complex, specifically Bi, is formed on the first electrode 60. The piezoelectric precursor film 71 is formed by applying a piezoelectric film forming composition (precursor solution) made of a MOD solution or a sol containing a metal complex containing Fe, Ba and Ti using a spin coating method or the like. Form (application process).

  The precursor solution to be applied is obtained by mixing a metal complex capable of forming a composite oxide containing Bi, Fe, Ba and Ti by firing, and dissolving or dispersing the mixture in an organic solvent. When forming the piezoelectric layer 70 made of a complex oxide containing Mn, Co, and Cr, a precursor solution containing a metal complex containing Mn, Co, and Cr is further used. What is necessary is just to mix the mixing ratio of the metal complex which each contains Bi, Fe, Ba, and Ti, and the metal complex which has Mn, Co, and Cr mixed as needed so that each metal may become a desired molar ratio. As a metal complex containing Bi, Fe, Ba, Ti, Mn, Co, and Cr, for example, an alkoxide, an organic acid salt, a β-diketone complex of each metal can be used. Examples of the metal complex containing Bi include bismuth 2-ethylhexanoate and bismuth acetate. Examples of the metal complex containing Fe include iron 2-ethylhexanoate, iron acetate, and tris (acetylacetonato) iron. Examples of the metal complex containing Ba include barium isopropoxide, barium 2-ethylhexanoate, barium acetylacetonate, and the like. Examples of the metal complex containing Ti include titanium isopropoxide, titanium 2-ethylhexanoate, titanium (di-i-propoxide) bis (acetylacetonate), and the like. Examples of the metal complex containing Mn include manganese 2-ethylhexanoate and manganese acetate. Examples of the organometallic compound containing Co include cobalt 2-ethylhexanoate and cobalt (III) acetylacetonate. Examples of the organometallic compound containing Cr include chromium 2-ethylhexanoate. Of course, as the metal complex to be contained in the precursor solution, a metal complex containing Bi, Fe, Ba, Ti, or one kind of Mn, Co, or Cr contained as necessary may be used. A metal complex containing more than one species may be used. Examples of the solvent for the precursor solution include propanol, butanol, pentanol, hexanol, octanol, ethylene glycol, propylene glycol, octane, decane, cyclohexane, xylene, toluene, tetrahydrofuran, acetic acid, octylic acid, and the like.

Next, the piezoelectric precursor film 71 is heated to a predetermined temperature (for example, 150 to 200 ° C.) and dried for a predetermined time (drying step). Next, the dried piezoelectric precursor film 71 is degreased by heating it to a predetermined temperature (for example, 350 to 450 ° C.) and holding it for a certain time (degreasing process). The degreasing referred to here is to release the organic component contained in the piezoelectric precursor film 71 as, for example, NO ₂ , CO ₂ , H ₂ O, or the like. The atmosphere of the drying step or the degreasing step is not limited, and may be in the air, in an oxygen atmosphere, or in an inert gas. In addition, you may perform an application | coating process, a drying process, and a degreasing process in multiple times.

  Next, as shown in FIG. 6A, the piezoelectric precursor film 71 is crystallized by heating to a predetermined temperature, for example, about 600 to 850 ° C., and holding it for a certain time, for example, 1 to 10 minutes. A piezoelectric film 72 made of a composite oxide having a perovskite structure containing Bi, Fe, Ba and Ti is formed (firing step). Also in this firing step, the atmosphere is not limited, and may be in the air, in an oxygen atmosphere, or in an inert gas. Examples of the heating device used in the drying step, the degreasing step, and the firing step include an RTA (Rapid Thermal Annealing) device that heats by irradiation with an infrared lamp, a hot plate, and the like.

  Next, the above-described coating process, drying process, degreasing process, coating process, drying process, degreasing process, and firing process are repeated a plurality of times in accordance with a desired film thickness and the like, and the piezoelectric layer 70 composed of a plurality of piezoelectric films 72 As shown in FIG. 6B, a piezoelectric layer 70 having a predetermined thickness composed of a plurality of layers of piezoelectric films 72 is formed. For example, when the film thickness of the coating solution per one time is about 0.1 μm, for example, the entire film thickness of the piezoelectric layer 70 composed of the ten piezoelectric films 72 is about 1.1 μm. In the present embodiment, the piezoelectric film 72 is provided by being laminated, but only one layer may be provided.

  After the piezoelectric layer 70 is formed in this way, the second electrode 80 made of iridium and having a compressive stress of 0.4 GPa or more and 1.0 GPa or less with a film thickness of 30 nm or more and 50 nm or less is formed on the piezoelectric layer 70. Form. The method for forming the second electrode 80 is not particularly limited, but can be formed by, for example, a sputtering method, a CVD method, or the like.

In this way, the film forming conditions for manufacturing the second electrode 80, specifically, the sputtering method, the pressure during film formation, the output power density, the film forming temperature, the target (Ir) and the piezoelectric layer The second electrode 80 manufactured in the step of forming the second electrode 80 on the piezoelectric layer 70 by adjusting the conditions such as the distance to the 70 and the thickness of the second electrode 80 to be formed. Internal stress can be adjusted. For example, the deposition conditions are as follows: Ar pressure during deposition is 0.50 to 1.0 Pa, output power density is 0.3 to 2.0 kW / m ² , deposition temperature is 20 to 300 ° C., target (Ir ) And the piezoelectric layer 70 can be 100 to 120 mm or the like. Here, since the internal stress of the second electrode 80 manufactured according to each film formation condition and thickness of the second electrode 80 changes, it is necessary to adjust the balance between the film formation conditions and thickness. In any case, the second electrode 80 formed on the piezoelectric layer 70 has a thickness in the range of 30 nm to 50 nm and a compressive stress of 0.4 GPa to 1.0 GPa. By performing the subsequent steps, it is possible to finally manufacture an ink jet recording head or the like in which the rupture of the piezoelectric actuator 300 is suppressed and the displacement amount is improved. Then, by determining the internal stress of the second electrode 80 at the stage of manufacturing the second electrode 80 that is in the process of manufacturing the ink jet recording head or the like, the piezoelectric actuator such as the ink jet recording head that is finally manufactured is obtained. Since it is possible to determine the difficulty of breaking and the amount of displacement characteristics, the yield can be improved. For example, when the second electrode is made of platinum instead of iridium, even if the film forming conditions and the film thickness are adjusted, the electrode having a compressive stress of 0.4 GPa or more and 1.0 GPa or less is formed. hard.

  After the second electrode 80 is formed in this way, as shown in FIG. 7A, the piezoelectric layer 70 and the second electrode 80 are simultaneously patterned in a region facing each pressure generating chamber 12 to obtain the first A piezoelectric actuator 300 having the electrode 60, the piezoelectric layer 70, and the second electrode 80 is formed. The patterning of the piezoelectric layer 70 and the second electrode 80 can be performed collectively by dry etching via a resist (not shown) formed in a predetermined shape. Thereafter, post-annealing may be performed in a temperature range of 600 ° C. to 800 ° C. as necessary. Thereby, a good interface between the piezoelectric layer 70 and the first electrode 60 or the second electrode 80 can be formed, and the crystallinity of the piezoelectric layer 70 can be improved.

  Next, as shown in FIG. 7B, a lead electrode 90 made of, for example, gold (Au) or the like is formed over the entire surface of the flow path forming substrate wafer 110, and then a mask pattern made of, for example, a resist or the like. Patterning is performed for each piezoelectric actuator 300 via (not shown).

  Next, as shown in FIG. 7C, a protective substrate wafer 130 which is a silicon wafer and serves as a plurality of protective substrates 30 is disposed on the side of the piezoelectric actuator 300 of the flow path forming substrate wafer 110 via an adhesive 35. After the bonding, the flow path forming substrate wafer 110 is thinned to a predetermined thickness.

  Next, as shown in FIG. 8A, a mask film 52 is newly formed on the flow path forming substrate wafer 110 and patterned into a predetermined shape.

  Then, as shown in FIG. 8B, the flow path forming substrate wafer 110 is anisotropically etched (wet etching) using an alkaline solution such as KOH through the mask film 52, whereby the piezoelectric actuator 300 is formed. Corresponding pressure generating chambers 12, communication portions 13, ink supply passages 14, communication passages 15 and the like are formed.

  Thereafter, unnecessary portions of the outer peripheral edge portions of the flow path forming substrate wafer 110 and the protective substrate wafer 130 are removed by cutting, for example, by dicing. Then, after removing the mask film 52 on the surface opposite to the protective substrate wafer 130 of the flow path forming substrate wafer 110, the nozzle plate 20 having the nozzle openings 21 formed therein is bonded, and the protective substrate wafer 130 is also formed. The compliance substrate 40 is bonded to the substrate, and the flow path forming substrate wafer 110 or the like is divided into a single chip size flow path forming substrate 10 or the like as shown in FIG. To do.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited to a following example.

Example 1
First, a silicon dioxide film having a thickness of 1130 nm was formed on the surface of a single crystal silicon substrate oriented in (110) by thermal oxidation. Next, a titanium film having a thickness of 20 nm was formed on the silicon dioxide film by DC sputtering, and a titanium oxide film was formed by thermal oxidation. Next, a platinum film having a thickness of 130 nm was formed on the titanium oxide film by DC sputtering to form the first electrode 60.

  Next, a piezoelectric layer 70 made of a complex oxide having a perovskite structure containing Bi, Ba, Fe, Mn, and Ti was formed on the first electrode 60. The method is as follows. First, each n-octane solution of bismuth 2-ethylhexanoate, barium 2-ethylhexanoate, iron 2-ethylhexanoate, manganese 2-ethylhexanoate and titanium 2-ethylhexanoate in molar ratio, Bi: The precursor solution was prepared by mixing so that Ba: Fe: Mn: Ti = 0.75: 0.25: 0.7125: 0.0375: 0.25.

  Next, the precursor solution is dropped on the substrate on which the silicon dioxide film, the titanium oxide film, and the first electrode 60 are formed, and after rotating at 500 rpm for 5 seconds, the substrate is rotated at 3000 rpm for 20 seconds to perform spin coating. Thus, a piezoelectric precursor film was formed (application process). Next, the substrate was placed on a hot plate and dried at 180 ° C. for 3 minutes (drying step). Next, the substrate was placed on a hot plate and degreased at 350 ° C. for 3 minutes (degreasing step). After repeating this coating step, drying step, and degreasing step three times, firing was performed at 750 ° C. for 5 minutes in an oxygen atmosphere (RTA) (Rapid Thermal Annealing) apparatus (firing step). Next, the above process was repeated four times, and a total of 1000 nm thick piezoelectric layer 70 was formed by a total of 12 coatings.

Thereafter, an iridium film having a thickness of 50 nm was formed as the second electrode 80 on the piezoelectric layer 70 by a DC sputtering method, thereby forming the piezoelectric actuator 300. The film formation conditions of the iridium film are as follows: Ar pressure at the time of film formation 0.9 Pa, output power density 1.5 kW / m ² , film formation temperature 20 ° C., distance between target (Ir) and piezoelectric layer 70: 110 mm.

(Example 2)
The same operation as in Example 1 was performed except that the thickness of the iridium film was changed to 30 nm.

(Comparative Example 1)
Instead of forming a 50 nm-thick iridium film as the second electrode 80, a 50 nm-thick platinum film is formed by depositing an Ar pressure of 0.3 Pa, an output power density of 0.4 kW / m ² , and a deposition temperature of 330. The same operation as in Example 1 was performed except that the film was formed under the film forming condition of ° C.

(Comparative Example 2)
The same operation as in Example 1 was performed except that the film thickness of the iridium film was changed to 70 nm.

(Test Example 1)
About Examples 1-2 and Comparative Examples 1-2, the warp of the single crystal silicon substrate on which the silicon oxide film, the titanium oxide film, the first electrode 60, and the piezoelectric layer 70 were formed before the second electrode 80 was formed. The amount W1 and the warpage amount W2 of the single crystal silicon substrate after forming the second electrode 80 were measured with a stress measuring device (manufactured by KLA-Tencor). Then, the internal stress σ of the second electrode 80 in each of the piezoelectric actuators 300 of Examples 1 and 2 and Comparative Examples 1 and 2 is obtained from the difference ΔW between these warpage amounts using the following equation derived from the Stoney equation. It was. The results are shown in Table 1. Further, Table 1 also shows the direction (tensile stress or compressive stress) of the obtained internal stress σ of the second electrode 80.
Internal stress σ = (4 · E _s · T _s ² · ΔW) / [3 · I ² · (1-ν _s ) · t _f ]
E _s : Young's modulus of single crystal silicon substrate = 130 GPa
T _s : thickness of single crystal silicon substrate = 625 μm
ΔW: W1-W2
I: Scan length (range in which the amount of warpage was measured) = 110 nm
υ _s : Poisson's ratio of single crystal silicon substrate = 0.28
t _f : thickness of the second electrode 80 (nm)

The Young's modulus was measured under the following conditions using a nanoindenter (CMISRO UMIS2000).
Spherical indenter: 1 μm in diameter LA
-Initial contact overload: 0.03 mN
・ Maximum load: 0.5mN
・ Load / Unload Increments: 20 (Linear)
・ Unloading to: 70% of max
• Enable unload on increments: Unload In
crements 1
・ Dwell: 1 sec
・ Indent Delay: 30 sec

(Test Example 2)
In Examples 1-2 and Comparative Examples 1-2, the KOH solution was used through the mask film until the silicon oxide film was exposed from the surface of the single crystal silicon substrate opposite to the side where the piezoelectric actuator 300 was provided. The pressure generating chamber 12 corresponding to the piezoelectric actuator 300 was formed by performing anisotropic etching (wet etching). The width of the pressure generating chamber 12 was set to 57.5 μm. By forming the pressure generating chamber 12 in this way, the silicon oxide film, the titanium oxide film, the first electrode 60 and the piezoelectric layer 70 are bent so that the pressure generating chamber 12 side is convex. ) Was measured with an optical interference shape measuring instrument (manufactured by Nippon Beco Co., Ltd., Wyko NT9300DMEMS). The amount of deflection is the maximum value of the difference between the position of the silicon oxide film in the state where the pressure generation chamber 12 is not formed and the position of the silicon oxide film after the pressure generation chamber 12 is formed. The results are shown in Table 1.

  In addition, by performing the same operation as described above, for each of the piezoelectric actuators 300 of Examples 1 to 2 and Comparative Examples 1 to 2, 45 pressure generating chambers 12 were formed in the corresponding regions. The piezoelectric actuator 300 was broken when the pressure generating chamber 12 was formed. Table 1 shows the number of piezoelectric actuators that are not broken / 45. The breakage of the piezoelectric actuator 300 is a breakage caused by bending toward the pressure generating chamber 12 side.

  As a result, as shown in Table 1, in Examples 1 and 2 and Comparative Example 2, the number of ruptured piezoelectric actuators was small, the yield was good, and the initial deflection was small.

(Test Example 3)
By performing the same operation as in Test Example 1, ten piezoelectric actuators 300 each having the pressure generation chamber 12 were prepared for each Example 1 and Comparative Example 1, and the first electrode 60 was set to a reference potential (in FIG. 9). 9), a durability test was performed in which the driving waveform 200 shown in FIG. 9 was continuously applied 6 billion times to the second electrode 80. The resonance frequency (Fa) of the piezoelectric actuator when this driving waveform 200 was applied was 2.5 MHz. In the drive waveform 200 shown in FIG. 9, the voltage above the reference potential (Gnd) is a positive voltage, and the voltage below the reference potential (Gnd) is a negative voltage. V ₁ is a voltage (intermediate voltage) applied in the standby state. In Test Example 3, V ₁ = 17.5 V, V ₂ = −5 V, and V ₃ = 45 V were set.

  As a result, even after applying a drive voltage having a high voltage of ΔV = 50 V 6 billion times, none of the piezoelectric actuators were broken in Example 1. On the other hand, in Comparative Example 1, two piezoelectric actuators were broken when 3 billion times were applied, and all 10 piezoelectric actuators were broken when 6 billion times were applied. The breakage of the piezoelectric actuator 300 is a breakage caused by bending toward the pressure generating chamber 12 side.

(Test Example 4)
The same operation as in Test Example 1 was performed to form a pressure generating chamber 12 corresponding to each of the piezoelectric actuators 300 of Examples 1-2 and Comparative Examples 1-2. Then, the displacement amount when the drive waveform 200 shown in FIG. 9 was applied to the second electrode 80 with the first electrode 60 as a reference potential was determined for each piezoelectric actuator 300. The resonance frequency (Fa) of the piezoelectric actuator when this driving waveform 200 was applied was 2.5 MHz. The amount of displacement was measured at room temperature (25 ° C.) using a laser Doppler displacement meter manufactured by Graphtec. In Test Example 4, V ₁ is fixed at 15V and ΔV = 35, and V ₂ is changed from 0V to −7V every 1V to change V ₃ from 35V to 28V. Asked. The results are shown in Table 2.

As a result, as shown in Table 2, the displacement amount of the piezoelectric actuators of Examples 1 and 2 was significantly larger than those of Comparative Examples 1 and _{2 at} any voltage V2.

  From the results of Test Examples 1 to 4, the second electrode 80 is made of iridium, the film thickness is 30 nm to 50 nm, and the piezoelectric actuator 300 according to the present invention has a compressive stress of 0.4 GPa to 1.0 GPa. It was confirmed that the breakage of the piezoelectric actuator caused by the deflection can be suppressed and the displacement amount can be remarkably improved.

(Test Example 5)
For the piezoelectric actuators of Examples 1 and 2 and Comparative Examples 1 and 2, “D8 Discover” manufactured by Bruker AXS was used, CuKα rays were used as the X-ray source, and the piezoelectric layer 70 was formed at room temperature (25 ° C.). An X-ray diffraction pattern was determined. As a result, in all of Examples 1-2 and Comparative Examples 1-2, a peak due to the perovskite structure and a peak derived from the substrate were observed, and no heterogeneous phase was confirmed.

(Other embodiments)
As mentioned above, although one Embodiment of this invention was described, the basic composition of this invention is not limited to what was mentioned above. For example, in the above-described embodiment, the silicon single crystal substrate is exemplified as the flow path forming substrate 10, but the present invention is not particularly limited thereto, and for example, a material such as an SOI substrate or glass may be used.

  In addition, the ink jet recording head of these embodiments constitutes a part of a recording head unit including an ink flow path communicating with an ink cartridge or the like, and is mounted on the ink jet recording apparatus. FIG. 10 is a schematic view showing an example of the ink jet recording apparatus.

  In the ink jet recording apparatus II shown in FIG. 10, the recording head units 1A and 1B having the ink jet recording head I are detachably provided with cartridges 2A and 2B constituting the ink supply means, and the recording head units 1A and 1B. Is mounted on a carriage shaft 5 attached to the apparatus main body 4 so as to be movable in the axial direction. The recording head units 1A and 1B, for example, are configured to eject a black ink composition and a color ink composition, respectively.

  Then, the driving force of the driving motor 6 is transmitted to the carriage 3 via a plurality of gears and a timing belt 7 (not shown), so that the carriage 3 on which the recording head units 1A and 1B are mounted is moved along the carriage shaft 5. The On the other hand, the apparatus body 4 is provided with a platen 8 along the carriage shaft 5, and a recording sheet S that is a recording medium such as paper fed by a paper feed roller (not shown) is wound around the platen 8. It is designed to be transported.

  In the above-described embodiment, the ink jet recording head has been described as an example of the liquid ejecting head. However, the present invention is widely applied to all liquid ejecting heads, and the liquid ejecting ejects a liquid other than ink. Of course, it can also be applied to the head. Other liquid ejecting heads include, for example, various recording heads used in image recording apparatuses such as printers, color material ejecting heads used in the manufacture of color filters such as liquid crystal displays, organic EL displays, and FEDs (field emission displays). Examples thereof include an electrode material ejection head used for electrode formation, a bioorganic matter ejection head used for biochip production, and the like.

  The present invention is not limited to a piezoelectric actuator mounted on a liquid ejecting head typified by an ink jet recording head, and can be applied to a piezoelectric actuator mounted on another device such as an ultrasonic motor or a piezoelectric sensor. it can.

  I ink jet recording head (liquid ejecting head), II ink jet recording apparatus (liquid ejecting apparatus), 10 flow path forming substrate, 12 pressure generating chamber, 13 communicating portion, 14 ink supply path, 20 nozzle plate, 21 nozzle opening, 30 protective substrate, 31 manifold portion, 32 piezoelectric actuator holding portion, 40 compliance substrate, 50 elastic film, 60 first electrode, 70 piezoelectric layer, 80 second electrode, 90 lead electrode, 100 manifold, 120 drive circuit, 300 piezoelectric Actuator

Claims (5)

A first electrode, a piezoelectric layer provided on the first electrode, and a second electrode provided on the piezoelectric layer;
The piezoelectric layer is made of a complex oxide having a perovskite structure containing Bi, Fe, Ba and Ti,
The piezoelectric actuator is characterized in that the second electrode is made of an iridium film having a thickness of 30 nm to 50 nm and a compressive stress of 0.4 GPa to 1.0 GPa.   A liquid ejecting head comprising: a pressure generating chamber communicating with a nozzle opening for ejecting liquid; and the piezoelectric actuator according to claim 1 for causing a pressure change in the pressure generating chamber.   A liquid ejecting apparatus comprising the liquid ejecting head according to claim 2. A method of manufacturing a piezoelectric actuator comprising a first electrode, a piezoelectric layer provided on the first electrode, and a second electrode provided on the piezoelectric layer,
Forming a piezoelectric layer made of a complex oxide having a perovskite structure containing Bi, Fe, Ba, and Ti on the first electrode;
A piezoelectric actuator comprising a step of forming a second electrode made of an iridium film having a compressive stress of not less than 30 nm and not more than 50 nm and not less than 0.4 GPa and not more than 1.0 GPa on the piezoelectric layer. Manufacturing method.   5. A method of manufacturing a liquid ejecting head comprising a pressure generation chamber communicating with a nozzle opening and a piezoelectric actuator that causes a pressure change in the pressure generation chamber, wherein the piezoelectric actuator is manufactured by the piezoelectric actuator manufacturing method according to claim 4. A method of manufacturing a liquid ejecting head, comprising a step of manufacturing an actuator.

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