JP2017037933A - Piezoelectric element, piezoelectric element application device, and manufacturing method of piezoelectric element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric element having a piezoelectric body layer capable of controlling orientation of crystal, a piezoelectric element application device, and a manufacturing method of piezoelectric element.SOLUTION: The piezoelectric element comprises: a first electrode 60; a piezoelectric body layer 70 formed on the first electrode 60, which is constituted of a crystal of composite oxide having a perovskite-type structure containing bismuth and iron; a second electrode 80 formed on the piezoelectric body layer 70; and buffer layer 65 formed between the first electrode 60 and the piezoelectric body layer 70, which is constituted of an oxide containing bismuth and vanadium.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a piezoelectric element, a piezoelectric element application device, and a method for manufacturing a piezoelectric element.

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

Among the piezoelectric materials used for such piezoelectric elements, as a piezoelectric material not containing lead, for example, a composite having a perovskite structure of bismuth ferrate (BiFeO ₃ ) containing bismuth (Bi) and iron (Fe) There are compounds (see, for example, Patent Document 1). Hereinafter, the composite oxide having a perovskite structure may be simply referred to as “composite oxide” or “oxide”.

  In such a piezoelectric material, it is desirable that the oxide crystal constituting the piezoelectric layer is oriented in a specific direction in order to sufficiently exhibit the piezoelectric characteristics. As a technique for orienting bismuth ferrate crystals in the (100) plane, a technique using a buffer layer made of bismuth manganate or a mixed crystal of bismuth manganate and bismuth ferrate is known (Patent Document 2). reference).

JP 2007-287745 A JP2013-226818A

However, there is a demand for controlling a piezoelectric layer made of a BiFeO ₃ based piezoelectric material to have an orientation other than the (100) plane.

  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 elements used in other than liquid ejecting heads. Exist as well.

  In view of such circumstances, an object of the present invention is to provide a piezoelectric element having a piezoelectric layer whose crystal orientation is controlled, a piezoelectric element applied device, and a method for manufacturing the piezoelectric element.

An aspect of the present invention that solves the above problems includes a first electrode, a piezoelectric layer that is provided on the first electrode and includes a crystal of a complex oxide having a perovskite structure including bismuth and iron, and the piezoelectric layer. A piezoelectric element comprising: a second electrode provided; and a buffer layer provided between the first electrode and the piezoelectric layer and made of an oxide containing bismuth and vanadium.
In such an embodiment, by using a buffer layer made of an oxide containing bismuth and vanadium, it is possible to control the crystal orientation of the composite oxide having a perovskite structure containing bismuth and iron. Therefore, a piezoelectric element having a piezoelectric layer with controlled crystal orientation can be obtained. The “buffer layer” includes not only a form in which the oxide is present between the first electrode and the piezoelectric layer as a whole with a constant thickness but also a form in which the oxide exists in an island shape.

  Here, the piezoelectric material layer preferably includes bismuth, iron, barium, and titanium. Thereby, it can be set as the piezoelectric element which the piezoelectric characteristic of the piezoelectric material layer improved.

  The piezoelectric material layer preferably further contains manganese. As a result, the leakage characteristics of the piezoelectric layer can be improved.

  Further, the molar ratio Bi / V of bismuth to vanadium in the buffer layer is preferably 3.03 or more and 4.55 or less, and the piezoelectric layer is preferably preferentially oriented in the (100) plane. Thereby, a piezoelectric element having a piezoelectric layer in which crystals are preferentially oriented in the (100) plane can be obtained.

  Further, it is preferable that the molar ratio Bi / V of bismuth to vanadium in the buffer layer is 6.82 or more, and the piezoelectric layer is preferentially oriented in the (110) plane. Thereby, a piezoelectric element having a piezoelectric layer in which crystals are preferentially oriented in the (110) plane can be obtained.

  In addition, the molar ratio Bi / V of bismuth to vanadium in the buffer layer is preferably 1.95 or less, and the piezoelectric layer is preferably in a random orientation. Thereby, a piezoelectric element having a piezoelectric layer with random crystal orientation can be obtained.

  Another aspect of the present invention is a piezoelectric element application device comprising the piezoelectric element according to the above aspect. According to this aspect, since the piezoelectric element having a predetermined orientation and improved characteristics is provided, a piezoelectric element application device having excellent characteristics can be realized.

According to another aspect of the present invention, there is provided a method of manufacturing a piezoelectric element including a piezoelectric layer, and a first electrode and a second electrode provided on the piezoelectric layer. Forming a buffer layer made of an oxide containing vanadium, and forming a piezoelectric layer made of a complex oxide crystal of a perovskite structure containing bismuth and iron on the buffer layer. There is a method for manufacturing a piezoelectric element.
In such an embodiment, by using a buffer layer made of an oxide containing bismuth and vanadium, it is possible to control the crystal orientation of the composite oxide having a perovskite structure containing bismuth and iron. Therefore, a piezoelectric element having a piezoelectric layer in which the crystal orientation is controlled can be manufactured.

  In the step of forming the buffer layer, it is preferable that a molar ratio of the bismuth to the vanadium is set to 3.03 or more and 4.55 or less, and the crystals of the composite oxide are preferentially arranged on the (100) plane. Alternatively, in the step of forming the buffer layer, it is preferable that the molar ratio of the bismuth to the vanadium is set to 6.82 or more and the crystals of the composite oxide are preferentially oriented in the (110) plane. Alternatively, in the step of forming the buffer layer, it is preferable that the molar ratio of the bismuth to the vanadium is set to 1.95 or less to make the crystal orientation of the composite oxide random. Thus, when forming the buffer layer, the orientation of the crystals of the complex oxide constituting the piezoelectric layer can be controlled by changing the molar ratio of bismuth and vanadium.

1 is a diagram illustrating a schematic configuration of a recording apparatus. FIG. 2 is an exploded perspective view illustrating a schematic configuration of a recording head. The top view of a recording head. FIG. 4 is a cross-sectional view and a main part enlarged cross-sectional view of a recording head. Sectional drawing which shows the manufacturing process of a recording head. Sectional drawing which shows the manufacturing process of a recording head. Sectional drawing which shows the manufacturing process of a recording head. Sectional drawing which shows the manufacturing process of a recording head. The figure which shows the peak of the X-ray diffraction of the piezoelectric material layer of an Example. It is a figure which shows an IV curve.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the following description shows one embodiment of the present invention, and can be arbitrarily changed within the scope of the present invention. In the drawings, the same reference numerals denote the same members, and descriptions thereof are omitted as appropriate. 2 to 6, X, Y, and Z represent three spatial axes that are orthogonal to each other. In this specification, directions along these axes will be described as an X direction, a Y direction, and a Z direction, respectively. The Z direction represents the thickness direction or the stacking direction of the plates, layers, and films. The X direction and the Y direction represent in-plane directions of the plate, layer, and film.

  FIG. 1 shows an ink jet recording apparatus which is an example of a liquid ejecting apparatus according to an embodiment of the present invention. As shown in the figure, in the ink jet recording apparatus I, cartridges 2A and 2B constituting ink supply means can be attached to and detached from an ink jet recording head unit (head unit) II (see FIG. 2) having a plurality of ink jet recording heads. Is provided. The carriage 3 on which the head unit II is mounted is provided on a carriage shaft 5 attached to the apparatus main body 4 so as to be movable in the axial direction, and for example, ejects 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 through a plurality of gears and a timing belt 7 (not shown), so that the carriage 3 on which the head unit II is mounted is moved along the carriage shaft 5. On the other hand, the apparatus main body 4 is provided with a conveyance roller 8 as a conveyance means, and a recording sheet S which is a recording medium such as paper is conveyed by the conveyance roller 8. The conveying means for conveying the recording sheet S is not limited to the conveying roller, and may be a belt, a drum, or the like.

  The ink jet recording apparatus I is a type of recording apparatus in which the head unit II is mounted on the carriage 3 and moves in the main scanning direction, but the configuration is not particularly limited. The ink jet recording apparatus I may be, for example, a so-called line recording apparatus that performs printing by fixing the head unit II and moving a recording sheet S such as paper in the sub-scanning direction.

  An example of the head unit II mounted on the ink jet recording apparatus I described above will be described with reference to FIGS. 2 is an exploded perspective view showing a schematic configuration of an ink jet recording head which is an example of a liquid ejecting head manufactured by the manufacturing method according to the first embodiment of the present invention. FIG. 3 is a plan view of FIG. FIG. 4 is a cross-sectional view taken along line AA ′ of FIG.

  The flow path forming substrate 10 (hereinafter referred to as “substrate 10”) is made of, for example, a silicon single crystal substrate, and has a pressure generating chamber 12 formed therein. The pressure generating chambers 12 partitioned by the plurality of partition walls 11 are provided with a plurality of nozzle openings 21 that discharge the same color ink along the X direction. The material of the substrate 10 is not limited to silicon, but may be SOI or glass.

  An ink supply path 13 and a communication path 14 are formed on one end side in the Y direction of the pressure generation chamber 12 in the substrate 10. The ink supply path 13 is configured so that one side of the pressure generation chamber 12 is narrowed from the X direction so that the opening area thereof is reduced. The communication passage 14 has substantially the same width as the pressure generation chamber 12 in the X direction. A communication portion 15 is formed on the outside (+ Y direction side) of the communication path 14. The communication part 15 constitutes a part of the manifold 100. The manifold 100 serves as an ink chamber common to the pressure generation chambers 12. As described above, the substrate 10 is formed with a liquid flow path including the pressure generation chamber 12, the ink supply path 13, the communication path 14, and the communication portion 15.

  On one surface (surface on the −Z direction side) of the substrate 10, for example, a SUS nozzle plate 20 is bonded. Nozzle openings 21 are arranged in the nozzle plate 20 along the X direction. The nozzle opening 21 communicates with each pressure generation chamber 12. The nozzle plate 20 can be bonded to the substrate 10 with an adhesive, a heat welding film, or the like.

A diaphragm 50 is formed on the other surface (the surface on the + Z direction side) of the substrate 10. The diaphragm 50 is constituted by, for example, an elastic film 51 formed on the substrate 10 and an insulator film 52 formed on the elastic film 51. The elastic film 51 is made of, for example, silicon dioxide (SiO ₂ ), and the insulator film 52 is made of, for example, zirconium oxide (ZrO ₂ ). The elastic film 51 may not be a separate member from the substrate 10. A part of the substrate 10 may be processed to be thin and used as an elastic film.

On the insulator film 52, a piezoelectric element 300 including a buffer layer 65, a first electrode 60, a piezoelectric layer 70, and a second electrode 80 is formed via an adhesion layer 56. The adhesion layer 56 is for improving the adhesion between the buffer layer 65 and the first electrode 60 and the base. As the adhesion layer 56, for example, titanium oxide (TiO _X ), titanium (Ti), silicon nitride (SiN), or the like can be used. Note that the adhesion layer 56 can be omitted.

  In the present embodiment, the diaphragm 50 and the first electrode 60 are displaced by the displacement of the piezoelectric layer 70 having electromechanical conversion characteristics. That is, in the present embodiment, the diaphragm 50 and the first electrode 60 substantially have a function as a diaphragm. The elastic film 51 and the insulator film 52 may be omitted, and only the first electrode 60 may function as a diaphragm. When the first electrode 60 is directly provided on the substrate 10, it is preferable to protect the first electrode 60 with an insulating protective film or the like so that ink does not contact the first electrode 60.

  The first electrode 60 is cut for each pressure generation chamber 12. That is, the first electrode 60 is configured as an individual electrode independent for each pressure generating chamber 12. The first electrode 60 is formed with a width narrower than the width of the pressure generating chamber 12 in the X direction. The first electrode 60 is formed with a width wider than the pressure generation chamber 12 in the Y direction.

  The piezoelectric layer 70 and the second electrode 80 are continuously provided on the first electrode 60 and the diaphragm 50 in the X direction. The size of the piezoelectric layer 70 and the second electrode 80 in the Y direction is larger than the size of the pressure generating chamber 12 in the Y direction.

  In addition, the piezoelectric layer 70 has a recess 71 corresponding to each partition wall 11. The size of the recess 71 in the X direction is substantially the same as or larger than the size of each partition wall 11 in the X direction.

  The second electrode 80 is configured as a common electrode common to the plurality of piezoelectric layers 70. Instead of the second electrode 80, the first electrode 60 may be a common electrode. In the present embodiment, the second electrode 80 includes a first layer 81 provided on the piezoelectric layer 70 side and a second layer 82 provided on the opposite side of the first layer 81 from the piezoelectric layer 70. It has. The second layer 82 may be omitted.

  The end of the first electrode 60 on the ink supply path 13 side (the end on the + Y direction side) is covered with the piezoelectric layer 70 and the second electrode 80. On the other hand, the end portion on the nozzle opening 21 side (end portion on the −Y direction side) of the first electrode 60 is exposed from the end portion on the −Y direction side of the piezoelectric layer 70. The end of the first electrode 60 on the −Y direction side is connected to the lead electrode 90a via a material layer (first layers 81 and 82 described later) formed in the same process as the process of forming the second electrode 80. Connected.

  Further, the lead electrode 90 b is connected to the second electrode 80. The lead electrodes 90a and 90b are formed on the substrate 10 on which the diaphragm 50 to the second electrode 80 are formed over the entire surface of the material constituting the lead electrodes 90a and 90b. By patterning into shapes, they can be formed simultaneously.

  In this embodiment, the 1st electrode 60 comprises the separate electrode provided independently corresponding to the pressure generation chamber 12, and the 2nd electrode 80 is continuously provided over the parallel arrangement direction of the pressure generation chamber 12. FIG. The liquid ejecting head constituting the common electrode is illustrated, but the first electrode 60 constitutes the common electrode continuously provided across the juxtaposed direction of the pressure generating chambers 12, and the second electrode 80 may constitute an individual electrode provided independently corresponding to the pressure generating chamber 12.

  A protective substrate 30 is bonded to the substrate 10 on which the piezoelectric element 300 is formed by an adhesive 35. The protective substrate 30 has a manifold portion 32. The manifold part 32 constitutes at least a part of the manifold 100. The manifold portion 32 according to the present embodiment penetrates the protective substrate 30 in the thickness direction (Z direction), and is further formed across the width direction (X direction) of the pressure generating chamber 12. The manifold portion 32 communicates with the communication portion 15 of the substrate 10 as described above. With these configurations, the manifold 100 serving as an ink chamber common to the pressure generation chambers 12 is configured.

  A compliance substrate 40 including a sealing film 41 and a fixing plate 42 is bonded onto the protective substrate 30. A region of the fixing plate 42 facing the manifold 100 is an opening 43 that is completely removed in the thickness direction (Z direction). One surface (the surface on the + Z direction side) of the manifold 100 is sealed only with a flexible sealing film 41.

  In such an ink jet recording head, ink is taken in from an ink introduction port connected to an external ink supply means (not shown), filled with ink from the manifold 100 to the nozzle opening 21, and then recorded from a drive circuit (not shown). In accordance with the signal, a voltage is applied between each of the first electrode 60 and the second electrode 80 corresponding to the pressure generation chamber 12, and the diaphragm 50, the adhesion layer 56, the first electrode 60, the buffer layer 65, and the piezoelectric layer. By bending and deforming 70, the pressure in each pressure generating chamber 12 is increased, and ink droplets are ejected from the nozzle openings 21.

  Next, the piezoelectric element 300 will be described in more detail. The piezoelectric element 300 includes a first electrode 60, a second electrode 80, and a piezoelectric layer 70 provided between the first electrode 60 and the second electrode 80. The thickness of the first electrode 60 is about 50 nm. The piezoelectric layer 70 is a so-called thin film piezoelectric body having a thickness of 50 nm to 2000 nm. The thickness of the second electrode 80 is about 50 nm. The thickness of each element listed here is an example, and can be changed within a range not changing the gist of the present invention.

  The material of the first electrode 60 needs to be a material that does not oxidize when the buffer layer 65 and the piezoelectric layer 70 are formed and can maintain conductivity. For example, a noble metal such as platinum (Pt) or iridium (Ir), or a conductive oxide represented by lanthanum nickel oxide (LNO) or the like can be given. Among these, it is preferable to use platinum from the viewpoint of easy orientation of the piezoelectric layer 70. In the present embodiment, platinum that is preferentially oriented in the (111) plane and has a half-value width of a diffraction peak by an X-ray diffraction method derived from the (111) plane of 10 degrees or less is used as the first electrode 60. Here, “preferentially oriented” means that all or almost all crystals (for example, 50% or more, preferably 80% or more) are oriented in a specific orientation, for example, (111) plane or (100) plane. Say that.

  The buffer layer 65 is an oxide containing bismuth and vanadium. The molar ratio Bi / V of bismuth to vanadium is 0.51 to 40.91, preferably 1.14 to 18.18, and more preferably 1.95 to 10.61.

  As will be described in detail later, the buffer layer 65 can be formed by a solution method. In this case, the crystals constituting the buffer layer 65 may not be in the form of a film having a constant thickness as a whole between the first electrode and the piezoelectric layer, but may be in the form of islands. That is, the buffer layer 65 includes not only a form (film form) in which the oxide is present between the first electrode and the piezoelectric layer as a whole with a constant thickness but also an island form. In addition, when the plurality of piezoelectric material layers 74 are baked, the buffer layer 65 may cause diffusion of component elements between the piezoelectric material layers 74 and may not be detected as a completely separated layer. There is. However, even in such a case, it can be confirmed that a region having a high vanadium (V) concentration, for example, is present on the first electrode side of the piezoelectric layer 70, thereby The existence can be confirmed.

  The buffer layer 65 can control the crystal orientation of the complex oxide constituting the piezoelectric layer 70 formed on the buffer layer 65. Specifically, as will be described later, by changing the molar ratio of bismuth to vanadium in the buffer layer 65, the orientation of the crystals constituting the piezoelectric layer 70 is made random, or the crystals are (100) planes. Can be preferentially oriented to the (110) plane.

  Piezoelectric materials have different physical properties such as displacement, dielectric constant, Young's modulus, etc., depending on crystal orientation. Therefore, it is easier to obtain an excellent piezoelectric element when the complex oxide crystals constituting the piezoelectric layer are preferentially oriented in a specific direction.

  The piezoelectric layer 70 is made of a composite oxide having a perovskite structure including bismuth (Bi) and iron (Fe), or bismuth (Bi), iron (Fe), barium (Ba), and titanium (Ti).

In the perovskite structure, that is, the A site of the ABO ₃ type structure, oxygen is 12-coordinated, and oxygen is 6-coordinated to the B site to form an octahedron. In a composite oxide having a perovskite structure containing bismuth and iron, or bismuth, iron, barium and titanium, bismuth (Bi) and barium (Ba) are located at the A site, and iron (Fe) and titanium (Ti) are located at the B site. To do.

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

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 Although it is also known that it has been replaced with bismuth ferrate or barium titanate in this embodiment, it is deviated from the stoichiometric composition due to deficiency or excess unless the basic characteristics are changed. And those in which some of the elements are replaced with other elements are also included in the ranges of bismuth ferrate and barium titanate. In the composite oxide having a perovskite structure containing bismuth, iron, barium and titanium, the ratio of bismuth ferrate manganate to barium titanate can be variously changed.

The composition of the complex oxide having a perovskite structure containing Bi and Fe is represented by BiFeO ₃ . The composition of the composite oxide having a perovskite structure containing Bi, Fe, Ba, and Ti is represented by ((Bi, Ba) (Fe, Ti) O ₃ ). These are typically 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 ≦ 0.50)
(Bi _1-x Ba _x ) (Fe _1-x Ti _x ) O ₃ (1 ′)
(0 ≦ x ≦ 0.50)

  The complex oxide having the perovskite structure may further contain an element (additive element) other than Bi, Fe, Ba, and Ti. Examples of the additive element include Mn, Co, Cr, and the like. When Mn, Co and Cr are included, these elements are located at the B site. For example, when Mn is included, the composite oxide has a structure in which part of Fe is substituted with Mn in a solid solution in which bismuth ferrate or bismuth ferrate and barium titanate are uniformly dissolved. In the latter case, it is also expressed as a complex oxide having a perovskite structure of mixed crystal of bismuth ferrate manganate and barium titanate. The basic characteristics of the composite oxide having the perovskite structure to which Mn is added are the same as those of the composite oxide having the perovskite structure to which Mn is not added, but it is known 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 manganate ferrate, bismuth ferrate cobaltate, and bismuth ferrate 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. The composite oxide constituting the piezoelectric layer 70 may further contain other known additive elements in order to improve the characteristics.

  A perovskite complex oxide containing such an additive element is typically represented by the following general formula (2). Further, the formula (2) can also be expressed by the following general formula (2 ′). In the general formula (2) and the general formula (2 ′), M1, M2, M3, and M4 are all additive elements, and one or more metals that can be substituted for part of Bi, Fe, Ba, and Ti, respectively. It is an element. 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 compositional deviation is acceptable. 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} 1-a M1 a) (Fe 1-b M2 b) O 3] -x [(Ba 1-c M3 c) (Ti 1-d M4 d) O 3] (2)
(0 ≦ x ≦ 0.50, 0.01 <a <0.10, 0.01 <b <0.10, 0.01 <c <0.10, 0.01 <d <0.10)
[(Bi _1-a M1 _a ) _1-x (Ba _1-c M3 _c ) _x ] [(Fe _1-b M2 _b ) _1-x (Ti _1-d M4 _d ) _x ] O ₃ (2 ′)
(0 ≦ x ≦ 0.50, 0.01 <a <0.10, 0.01 <b <0.10, 0.01 <c <0.10, 0.01 <d <0.10)

  Next, an example of a method for manufacturing the piezoelectric element 300 of the present embodiment will be described with reference to FIGS. 5 to 8 together with a method for manufacturing an ink jet recording head. 5 to 8 are cross-sectional views in the longitudinal direction (second direction) of the pressure generating chamber. In the present embodiment, the case where a composite oxide containing Bi, Fe, Ba, and Ti is formed as the piezoelectric material layer 74 is illustrated.

First, as shown in FIG. 5A, a silicon substrate 110 is prepared. Next, the silicon substrate 110 is thermally oxidized to form an elastic film 51 made of silicon dioxide (SiO ₂ ) or the like on the surface thereof. Further, a zirconium film is formed on the elastic film 51 by a sputtering method, and this is thermally oxidized to obtain an insulator film 52 made of a zirconium oxide film. In this way, the diaphragm 50 composed of the elastic film 51 and the insulator film 52 is formed. Further, a titanium film is formed on the insulator film 52 by a sputtering link method, and thermally oxidized to form a titanium oxide film constituting the adhesion layer 56.

  Next, as shown in FIG. 5B, a platinum layer constituting the first electrode 60 is formed by a sputtering method, a vapor deposition method, or the like. Thereafter, as shown in FIG. 5C, the titanium oxide film constituting the adhesion layer 56 and the platinum layer constituting the first electrode 60 are simultaneously patterned to have a desired shape. For the patterning of the adhesion layer 56 and the first electrode 60, for example, a mask having a predetermined shape (not shown) is formed on the first electrode 60, and the adhesion layer 56 and the first electrode 60 are etched through the mask. Photolithographic methods can be used.

  Next, as shown in FIG. 5D, a buffer layer 65 containing bismuth and vanadium is formed on the first electrode 60 (and the insulator film 52). The buffer layer 65 can be formed by, for example, a solution method such as a MOD (Metal-Organic Decomposition) method or a sol-gel method. The buffer layer 65 can also be formed by a solid phase method such as a laser ablation method, a sputtering method, a pulse laser deposition method (PLD method), a CVD method, or an aerosol deposition method.

  A specific procedure for forming the buffer layer 65 by a solution method is as follows. First, a MOD solution containing a metal complex and a precursor solution for the buffer layer 65 made of a sol are prepared. Next, as shown in FIG. 5C, this precursor solution is applied onto the first electrode 60 by a spin coating method or the like to form a precursor film (application step).

  The precursor solution for the buffer layer 65 is obtained by mixing a metal complex capable of forming an oxide containing bismuth (Bi) and vanadium (V) by firing, and dissolving or dispersing the mixture in an organic solvent. . As a metal complex containing Bi or V, for example, an alkoxide, an organic acid salt, a β-diketone complex, or the like can be used. Examples of the metal complex containing Bi include bismuth 2-ethylhexanoate and bismuth acetate. Examples of the metal complex containing V include vanadium 2-ethylhexanoate and vanadium acetate. Two or more metal complexes containing each element may be used. For example, two or more metal complexes containing Bi 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.

In the precursor solution for the buffer layer 65, the mixing ratio of the metal complex is determined so that each metal has a desired molar ratio. The crystal orientation of the composite oxide constituting the piezoelectric layer 70 formed on the buffer layer 65 is controlled as follows.
(1) When the molar ratio Bi / V of bismuth to vanadium is relatively small, random (2) When Bi / V is medium, (100) Preferred orientation to the plane (3) When Bi / V is relatively large Controls the orientation of the crystals of the composite oxide constituting the piezoelectric layer by changing the molar ratio of bismuth and vanadium when forming the buffer layer 65, that is, the preferred orientation to the (110) plane. Can do. In the solution method, when the precursor solution for the buffer layer 65 is prepared, the molar ratio of bismuth and vanadium may be set.

Next, the precursor film is heated to a predetermined temperature (for example, 150 to 200 ° C.) and dried for a predetermined time (drying step). Next, the dried precursor film is heated to a predetermined temperature (for example, 350 to 450 ° C.), and degreased by holding at this temperature for a predetermined time (degreasing step). Degreasing as used herein refers to desorbing organic components contained in the precursor film, for example, as 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.

  Finally, the degreased precursor film is heated to a higher temperature, for example, about 600 to 850 ° C., and is crystallized by holding at this temperature for a certain time, for example, 1 to 10 minutes (firing step). The buffer layer 65 is completed.

  Also in the firing step, the atmosphere is not limited, and it may be in the air, in an oxygen atmosphere, or in an inert gas. Examples of the heating device used in the buffer layer drying step, the buffer layer degreasing step, and the buffer layer baking step include an RTA (Rapid Thermal Annealing) device that heats by irradiation with an infrared lamp, a hot plate, and the like.

  In the present embodiment, a single buffer layer 65 is formed with one coating step, but the above-described buffer layer coating step, buffer layer drying step, buffer layer degreasing step, buffer layer coating step, buffer layer drying step The buffer layer degreasing step and the buffer layer baking step may be repeated a plurality of times depending on the desired film thickness and the like to form a buffer layer 65 composed of a plurality of layers.

  When the buffer layer 65 is formed by a solution method, the concentration of the solution to be applied is thin and the film to be applied is also thin. Therefore, the film shrinks during firing, and the produced crystal becomes the first electrode and the piezoelectric film. In some cases, it does not have a film shape with a constant thickness between the body layer and an island shape. In FIG. 5D and the like, the buffer layer 65 is shown in a form (film shape) in which the oxide is present between the first electrode and the piezoelectric layer with a constant thickness as a whole. Including islands.

  Next, a piezoelectric layer 70 composed of a plurality of piezoelectric films 72 is formed on the buffer layer 65. The piezoelectric layer 70 can be manufactured by the same method as the buffer layer 65. FIG. 6A shows an example in which the piezoelectric layer 70 is formed by a liquid phase method. As shown in FIG. 6A, the piezoelectric layer 70 formed by the liquid phase method has a plurality of piezoelectric films 72 formed by a series of steps from the coating step to the firing step. That is, the piezoelectric layer 70 is formed by repeating a series of steps from the coating step to the firing step a plurality of times. A series of steps from the coating step to the firing step includes a step of forming the buffer layer 65 by a liquid phase method except that a precursor solution for the piezoelectric film 72 is used instead of the precursor solution for the buffer layer 65. It is the same.

  As an example, when forming the piezoelectric film 72 made of a complex oxide having a perovskite structure containing Bi, Ba, Fe and Ti, a complex oxide containing Bi, Ba, Fe and Ti can be formed by firing. A solution obtained by dissolving or dispersing a metal complex in an organic solvent is used as a precursor solution. When a small amount of metal such as Mn, Co, or Cr is added to the base material system, a metal complex containing such an added metal is further added to the precursor solution.

  As the metal complex, as in the case of the buffer layer 65, for example, an alkoxide, an organic acid salt, a β-diketone complex, or the like can be used. About the metal complex containing Bi, Fe, and Ti, the same metal complex as that used when forming the precursor film for the buffer layer 65 can be used. Examples of the metal complex containing Ba include barium acetate, barium isopropoxide, barium 2-ethylhexanoate, barium 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. A metal complex containing two or more of Bi, Ba, Fe, Ti and the like may be used. Moreover, you may use 2 or more types of metal complexes containing each element. For example, two or more metal complexes containing Bi 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.

  FIG. 6A shows an example in which a series of steps from the coating step to the firing step described above is repeated nine times to form a piezoelectric layer 70 composed of nine layers of piezoelectric films 72. When the film thickness of the precursor film formed by the coating process is about 0.1 μm, the entire film thickness of the piezoelectric layer 70 composed of the nine piezoelectric films 72 is about 0.9 μm.

  As described above, the orientation of the crystals of the composite oxide constituting the piezoelectric layer 70 formed on the buffer layer 65 is controlled by changing the molar ratio of bismuth to vanadium in the buffer layer 65, and is randomly selected. Either the preferred orientation to the (100) plane or the preferred orientation to the (110) plane.

  Next, as shown in FIG. 6B, the first layer 81 is formed as a part of the second electrode 80 on the piezoelectric layer 70. The first layer 81 is formed by sputtering platinum.

  Next, as shown in FIG. 7A, the first layer 81 and the piezoelectric layer 70 are patterned corresponding to each pressure generating chamber 12. For patterning the first layer 81 and the piezoelectric layer 70, for example, a mask (not shown) having a predetermined shape is formed on the first layer 81, and the first layer 81 and the piezoelectric layer 70 are etched through the mask. It is possible to use a so-called photolithography method.

  Next, as shown in FIG. 7B, the second layer 82 is formed on one side of the substrate 110 (the side on which the piezoelectric layer 70 is formed). Similar to the first layer 81, the second layer 82 can be formed by sputtering platinum.

  Through the above steps, the piezoelectric element 300 including the first electrode 60, the piezoelectric layer 70, and the second electrode 80 is completed. In the present embodiment, the portion where the first electrode 60, the piezoelectric layer 70, and the second electrode 80 overlap substantially functions as the piezoelectric element 300.

  Next, as shown in FIG. 7C, lead electrodes 90 a and 90 b made of, for example, gold (Au) are formed on the substrate 110. The lead electrodes 90a and 90b can be simultaneously formed by forming a layer of the material constituting the lead electrodes 90a and 90b over the entire surface on the substrate 110 and then patterning the layer into a predetermined shape. . The photolithography method described above can also be used for patterning at this time.

  Next, as illustrated in FIG. 8A, a protective substrate wafer 130 is bonded to the surface of the substrate 110 on the piezoelectric element 300 side via an adhesive 35. Further, the manifold portion 32 and the through hole 33 are formed in the protective substrate wafer 130.

  Next, the surface of the substrate 110 is cut and thinned. Then, as shown in FIG. 8B, a mask film 54 is newly formed on the substrate 110 and patterned into a predetermined shape. Then, as shown in FIG. 8C, anisotropic etching (wet etching) using an alkaline solution such as KOH is performed on the substrate 110 through the mask film 54. Thereby, the pressure generating chamber 12, the ink supply path 13, the communication path 14, and the communication part 15 are formed.

  Next, unnecessary portions of the outer peripheral edge portions of the silicon substrate 110 and the protective substrate wafer 130 are cut and removed by dicing or the like. Further, the nozzle plate 20 is bonded to the surface of the silicon substrate 110 opposite to the piezoelectric element 300 (see FIG. 4A). Further, the compliance substrate 40 is bonded to the protective substrate wafer 130 (see FIG. 4A). The assembly of the chips of the head unit II is completed through the steps so far. The head unit II is obtained by dividing the aggregate into individual chips.

Hereinafter, the present invention will be described more specifically with reference to production examples. In addition, this invention is not limited to a following example.
Example 1
<Preparation of substrate>
First, an elastic film 51 made of a silicon dioxide film having a thickness of 170 nm was formed on the surface by oxidizing a single crystal silicon substrate. Next, a zirconium film having a thickness of 285 nm was formed on the silicon dioxide film by sputtering, and this was thermally oxidized to form an insulator film 52 made of a zirconium oxide film. Thereafter, a titanium film having a thickness of 20 nm was formed on the zirconium oxide film by sputtering, and this was thermally oxidized to form an adhesion layer 56 made of a titanium oxide film. Next, a first electrode 60 having a thickness of 130 nm was formed on the titanium oxide film by a sputtering method to obtain a substrate with an electrode.

<Preparation of precursor solution for buffer layer>
Next, a buffer layer 65 containing Bi and vanadium was formed on the first electrode 60. The method is as follows. First, an n-octane solution (solution 1) of bismuth 2-ethylhexanoate and an n-octane solution (solution 2) of vanadium 2-ethylhexanoate have a Bi concentration of 0.5 mol / L and a V concentration of 0. It was prepared to be 11 mol / L. Next, the solution 1 and the solution 2 are mixed so that the volume ratio is 3: 7, and further diluted with an n-octane solution so that the concentration of Bi becomes 0.015 mol / L. A precursor solution for 65 was prepared. The molar ratio Bi / V of bismuth to vanadium is 1.95.

<Preparation of precursor solution for piezoelectric layer>
In order to form a piezoelectric film 72 made of a composite oxide having a perovskite structure containing Bi, Ba, Fe, Ti and Mn, bismuth 2-ethylhexanoate, barium 2-ethylhexanoate, 2-ethylhexanoic acid Each n-octane solution of iron, titanium 2-ethylhexanoate and manganese 2-ethylhexanoate was mixed, and the molar ratio of Bi: Ba: Fe: Ti: Mn was Bi: Ba: Fe: Ti: Mn = 75. : 25: 71.25: 25: 3.75, and mixed with a precursor solution of a piezoelectric layer containing Bi, Ba, Fe, Ti and Mn (hereinafter referred to as “BFM-BT precursor solution”) ) Was prepared.

<Formation of buffer layer>
The precursor solution for the buffer layer was dropped on the substrate with electrodes, and the substrate with electrodes was rotated at 3000 rpm and spin-coated to form a buffer layer precursor film (coating step). Next, after heating for 4 minutes on a 180 degreeC hotplate, it heated for 4 minutes at 350 degreeC (a drying process and a degreasing process). Next, it baked for 5 minutes at 700 degreeC using the RTA apparatus (baking process). Through the above steps, an island-like buffer layer 65 made of bismuth vanadate and having a thickness of about 10 nm was formed.

<Formation of piezoelectric layer>
Next, the BFM-BT precursor solution was dropped onto the electrode-attached substrate, and the precursor solution was spin-coated by rotating the electrode-attached substrate at 3000 rpm, thereby forming a piezoelectric layer precursor film ( Application process). Next, it was dried at 180 ° C. for 2 minutes on a hot plate (drying process). Next, degreasing was performed at 350 ° C. for 2 minutes (degreasing step). After repeating the steps from the coating step to the degreasing step twice, firing was performed at 750 ° C. for 2 minutes in an oxygen atmosphere using an RTA apparatus (firing step). By repeating the above process four times, a composite oxide having a perovskite structure (hereinafter also referred to as “BFM-BT”) containing Bi, Ba, Fe, Ti, and Mn is formed. A body layer 70 was formed.

(Example 2)
When preparing the precursor solution for the buffer layer 65, the solution 1 and the solution 2 are mixed so that the volume ratio is 4: 6, and the Bi concentration is 0.020 mol / L. The same operation as in Example 1 was performed, except that dilution with n-octane was performed. In Example 2, the molar ratio Bi / V of bismuth to vanadium in the buffer layer 65 is 3.03.

(Example 3)
When preparing the precursor solution for the buffer layer 65, the solution 1 and the solution 2 are mixed so that the volume ratio is Bi: V = 5: 5, and the concentration of Bi is further set to 0.025 mol / L. The same operation as in Example 1 was performed except that the solution was diluted with n-octane so that In Example 3, the molar ratio Bi / V of bismuth to vanadium is 4.55.

Example 4
When preparing the precursor solution for the buffer layer 65, the solution 1 and the solution 2 are mixed so that the volume ratio is Bi: V = 6: 4, and the Bi concentration is 0.030 mol / L. The same operation as in Example 1 was performed except that the solution was diluted with n-octane so that In Example 4, the molar ratio Bi / V of bismuth to vanadium is 6.82.

(Example 5)
When preparing the precursor solution for the buffer layer 65, the solution 1 and the solution 2 are mixed so that the volume ratio is Bi: V = 7: 3, and the Bi concentration is 0.035 mol / L. The same operation as in Example 1 was performed except that the solution was diluted with n-octane so that In Example 5, the molar ratio Bi / V of bismuth to vanadium is 10.61.

(Reference example)
As a precursor solution for the buffer layer 65, an n-octane solution of bismuth 2-ethylhexanoate and manganese 2-ethylhexanoate was mixed so that the molar concentration ratio was Bi: Mn = 1: 1. The same operation as in Example 1 was performed, except that the one adjusted with n-octane so that the molar concentration was 0.03125 mol / L was used.

(Test Example 1)
For the piezoelectric layer of Example 1-5, X-ray diffraction was measured using “D8 Discover” manufactured by Bruker AXS, and CuKα rays were used as the X-ray source. An X-ray diffraction chart was obtained. The result is shown in FIG.

  In these figures, the peak in the vicinity of 2θ = 22.5 ° is a peak indicating orientation to the (100) plane. Further, the peak near 2θ = 32 ° is a peak indicating the orientation to the (110) plane. These peaks are mainly peaks derived from the perovskite constituting the piezoelectric layer 70. The peak around 2θ = 36 ° is a peak derived from zirconium oxide constituting the insulator film 52. The peak near 2θ = 40 ° is a peak derived from platinum constituting the electrode.

  As shown in FIG. 9, in Example 1, a peak indicating the (100) plane and a peak indicating the (110) plane were recognized. Separately, a more detailed analysis was performed using a two-dimensional image obtained by X-ray analysis. As a result, in Example 1, it was found that the orientation of crystals of the complex oxide having a perovskite structure constituting the piezoelectric layer 70 was random. For X-ray analysis, Bruker AXS D8 Discover was used, and CuKα rays were used as the X-ray source. A two-dimensional detector (Hi-STAR) was used as the detector. The measurement conditions were such that the collimator on the X-ray source side used 50 umφ, the voltage of the X-ray source was 50 kV, the current was 100 mA, and the distance from the sample to the two-dimensional detector was 15 cm.

  In Example 2 and Example 3, a peak indicating the (100) plane was observed, and the crystals of the complex oxide having a perovskite structure constituting the piezoelectric layer 70 were preferentially oriented in the (100) plane. all right. Further, in Example 4 and Example 5, a peak indicating the (110) plane is observed, and the crystals of the complex oxide having a perovskite structure constituting the piezoelectric layer 70 are preferentially oriented in the (110) plane. all right.

  The above results are summarized in Table 1.

From Table 1, it can be seen that the orientation of crystals constituting the piezoelectric layer 70 can be controlled by changing the molar ratio of bismuth to vanadium. The orientation tendency is
(1) When the molar ratio Bi / V of bismuth to vanadium is relatively small, random (2) When Bi / V is medium, (100) Preferred orientation to the plane (3) When Bi / V is relatively large It can be seen that is a preferred orientation to the (110) plane.

  Further, in view of this tendency, in the region where the molar ratio Bi / V of bismuth to vanadium is smaller than 1.95, the orientation of crystals of the complex oxide of the perovskite structure constituting the piezoelectric layer 70 is the same as in Example 1. Will be random. Further, in the region where the molar ratio Bi / V of bismuth to vanadium is larger than 10.61, the complex oxide crystal of the perovskite structure constituting the piezoelectric layer 70 is the (110) plane as in Examples 4 and 5. The preferential orientation is considered.

(Test Example 2)
In the piezoelectric element of Example 3 and the reference example, the second electrode 80 having a thickness of 50 nm was manufactured by further sputtering platinum on the piezoelectric layer 70. And the voltage (± 50V) was applied between the 1st electrode 60 and the 2nd electrode 80, and the relationship (IV characteristic) of electric current (I) and voltage (V) was evaluated. The measurement was performed in the atmosphere using “4140B” manufactured by Hewlett-Packard Co., with the holding time at the time of measurement being 2 seconds. The result is shown in FIG.

  As shown in FIG. 10, it was found that the piezoelectric elements of the examples tend to have a smaller current density (leakage current) than the reference examples. That is, when a buffer layer containing bismuth and vanadium is used, there is less Mn on the first electrode side, which is better than the reference example using the buffer layer containing bismuth and manganese, and the breakdown voltage characteristics on the minus side It was found that the reduction of

(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.
In the above-described embodiment, an ink jet recording head has been described as an example of a liquid ejecting head. However, the present invention is widely intended for all liquid ejecting heads, and is a liquid ejecting head that ejects liquid other than ink. Of course, it can also be applied. 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.

  Further, the piezoelectric element according to the present invention is not limited to the piezoelectric element used in the liquid ejecting head, and can be used in other devices. Examples of such piezoelectric element applied devices include ultrasonic devices such as ultrasonic transmitters, ultrasonic motors, temperature-electrical converters, pressure-electrical converters, ferroelectric transistors, piezoelectric transformers, and infrared rays. Examples of the filter include a light blocking filter, an optical filter using a photonic crystal effect by quantum dot formation, and an optical filter using optical interference of a thin film. The present invention can also be applied to a piezoelectric element used as a sensor and a piezoelectric element used as a ferroelectric memory. Examples of the sensor using the piezoelectric element include an infrared sensor, an ultrasonic sensor, a thermal sensor, a pressure sensor, a pyroelectric sensor, and a gyro sensor (angular velocity sensor).

  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 ink supply path, 15 communicating portion, 20 nozzle plate, 21 nozzle opening, 30 protective substrate, 32 manifold section, 40 compliance substrate, 50 elastic film, 60 first electrode, 65 buffer layer, 70 piezoelectric layer, 74 piezoelectric material layer, 80 second electrode, 90 lead electrode, 100 manifold, 300 piezoelectric element

Claims (11)

  A first electrode; a piezoelectric layer provided on the first electrode and made of a complex oxide crystal having a perovskite structure including bismuth and iron; a second electrode provided on the piezoelectric layer; A piezoelectric element comprising a buffer layer provided between an electrode and the piezoelectric layer and made of an oxide containing bismuth and vanadium.   The piezoelectric element according to claim 1, wherein the piezoelectric material layer includes bismuth, iron, barium, and titanium.   The piezoelectric element according to claim 1, wherein the piezoelectric material layer further contains manganese.   The molar ratio Bi / V of bismuth to vanadium in the buffer layer is 3.03 or more and 4.55 or less, and the crystals of the composite oxide are preferentially oriented in the (100) plane. The piezoelectric element as described in any one of -3.   The molar ratio Bi / V of vanadium to vanadium in the buffer layer is 6.82 or more, and the crystals of the composite oxide are preferentially oriented in the (110) plane. The piezoelectric element according to claim 1.   The molar ratio Bi / V of bismuth to vanadium in the buffer layer is 1.95 or less, and the crystal orientation of the composite oxide is random. Piezoelectric element.   A piezoelectric element application device comprising the piezoelectric element according to claim 1. In a method for manufacturing a piezoelectric element comprising a piezoelectric layer, and a first electrode and a second electrode provided on the piezoelectric layer,
Forming a buffer layer made of an oxide containing bismuth and vanadium on the first electrode;
Forming a piezoelectric layer made of a complex oxide crystal having a perovskite structure containing bismuth and iron on the buffer layer.   In the step of forming the buffer layer, the molar ratio of the bismuth to the vanadium is set to 3.03 or more and 4.55 or less, and crystals of the composite oxide are preferentially arranged on the (100) plane, A method for manufacturing a piezoelectric element according to claim 8.   9. The step of forming the buffer layer, wherein a molar ratio of the bismuth to the vanadium is set to 6.82 or more to preferentially orient the crystals of the complex oxide in a (110) plane. The manufacturing method of the piezoelectric element as described in any one of.   9. The step of forming the buffer layer, wherein the molar ratio of the bismuth to the vanadium is set to 1.95 or less, and the crystal orientation of the composite oxide is randomized. A method for manufacturing a piezoelectric element.