JP2014179468A - Electromechanical conversion element, electromechanical conversion element manufacturing method, droplet discharge head, and droplet discharge device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromechanical conversion element whose polarization treatment is capable of being performed reliably.SOLUTION: An electromechanical conversion element includes a plurality of electromechanical conversion parts, each of which includes a lower electrode 21, an electromechanical conversion film 22 arranged on the lower electrode, and an upper electrode 23 arranged on the electromechanical conversion film, wherein one of the lower electrode 21 and the upper electrode 23 is constructed as a common electrode that is common among the plurality of electromechanical conversion parts, and the other of the lower electrode 21 and the upper electrode 23 is constructed as an individual electrode corresponding to each electromechanical conversion part on a one-to-one basis, with an amount of leakage current between the common electrode and the individual electrode being equal to or smaller than a predetermined value.

Description

  The present invention relates to an electro-mechanical transducer, a method for manufacturing an electro-mechanical transducer, a droplet ejection head, and a droplet ejection apparatus.

  The electro-mechanical conversion element has a characteristic that its shape changes in accordance with an applied voltage. Conventionally, the electro-mechanical conversion element has been used in a droplet discharge head of an image forming apparatus and various applications by taking advantage of such a characteristic. Yes.

  As shown in FIG. 1A, the piezoelectric crystal included in the electro-mechanical conversion film constituting the electro-mechanical conversion element has a random polarization direction immediately before voltage application. On the other hand, by repeating the voltage application, the piezoelectric crystal becomes an aggregate of domains in which the polarization directions are aligned as shown in FIG.

  Thus, the displacement amount with respect to the drive voltage is not stable until the polarization directions of the piezoelectric crystals are aligned. For this reason, attempts have been made to align the direction of polarization in advance, and contrivances have been made to stabilize the amount of displacement with respect to a predetermined drive voltage called an aging process or a poling (polarization process) process.

  For example, in Patent Document 1, first, a corona wire is disposed via a gap on a second surface of a piezoelectric body having an electrode formed on the first surface and facing the first surface. An inorganic piezoelectric material poling method is disclosed in which a voltage is applied between an electrode and a corona wire to supply electric charges to a second surface of the piezoelectric material to generate an electric field in the piezoelectric material.

  However, even if the polarization process is performed by the polarization process method disclosed in Patent Document 1, the polarization process may not proceed depending on the electromechanical conversion element.

  In view of the above-described problems of the prior art, an object of the present invention is to provide an electromechanical conversion element that can be reliably subjected to polarization treatment.

  In order to achieve the above-described object, the present invention provides an electric device comprising a lower electrode, an electro-mechanical conversion film disposed on the lower electrode, and an upper electrode disposed on the electro-mechanical conversion film. -An electro-mechanical conversion element having a plurality of mechanical conversion units, wherein one of the lower electrode and the upper electrode is configured as one common electrode common to the plurality of electro-mechanical conversion units The other electrode of the lower electrode or the upper electrode is configured as an individual electrode corresponding to each electro-mechanical converter, and the amount of leakage current between the common electrode and the individual electrode An electromechanical conversion element having a value equal to or less than a predetermined value is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the electromechanical conversion element which can perform a polarization process reliably can be provided.

Explanatory drawing of the change of the direction of polarization in a piezoelectric crystal. Sectional drawing of the electromechanical conversion part in the 1st Embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS Configuration explanatory drawing of the electromechanical conversion element in the 1st Embodiment of this invention. Explanatory drawing of the structural example of the polarization apparatus used when performing a polarization process. Explanatory drawing of a polarization process. Explanatory drawing of Pr and Pind. Explanatory drawing of the generation mechanism of leak current. X-ray diffraction pattern when SrRuO ₃ film is formed on platinum film FIG. 6 is a configuration explanatory diagram of a droplet discharge head according to a second embodiment of the present invention. FIG. 6 is a configuration explanatory diagram of a droplet discharge head according to a second embodiment of the present invention. FIG. 9 is a perspective explanatory view of a droplet discharge device according to a third embodiment of the present invention. Side surface explanatory drawing of the mechanism part of the droplet discharge apparatus in the 3rd Embodiment of this invention. Typical PE hysteresis curve in an Example.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments, and the following embodiments are not departed from the scope of the present invention. Various modifications and substitutions can be made.
[First Embodiment]
In the present embodiment, first, a configuration example of the electro-mechanical conversion element of the present invention will be described.

  The electro-mechanical conversion element of this embodiment includes an electric electrode including a lower electrode, an electro-mechanical conversion film disposed on the lower electrode, and an upper electrode disposed on the electro-mechanical conversion film. A plurality of mechanical conversion units are provided. One of the lower electrode and the upper electrode is configured as one common electrode common to the plurality of electro-mechanical converters, and the other electrode of the lower electrode or the upper electrode is It is comprised as an individual electrode corresponding to each electromechanical conversion part. The leakage current amount between the common electrode and the individual electrode is not more than a predetermined value.

  The configuration of the electro-mechanical converter of this embodiment is shown in FIG. FIG. 2 shows a cross-sectional configuration diagram of the electro-mechanical converter. As shown in FIG. 2, the electro-mechanical conversion unit 20 of the present embodiment has a configuration in which a lower electrode 21, an electro-mechanical conversion film 22, and an upper electrode 23 are laminated.

  And the electromechanical conversion element of this embodiment has the structure provided with two or more said electromechanical conversion parts. A specific configuration example will be described with reference to FIG.

  FIG. 3A shows a cross-sectional configuration diagram of the electro-mechanical conversion element, and FIG. 3B shows a top view of the electro-mechanical conversion element. In FIG. 3B, the description of the first and second protective films (interlayer insulating films) is omitted for easy understanding of the configuration.

  First, as shown in FIG. 3A, the electro-mechanical conversion element of this embodiment has an electro-mechanical conversion unit 20 including a lower electrode 21, an electro-mechanical conversion film 22, and an upper electrode 23. As shown in FIG. 3B, a plurality of such electro-mechanical converters 20 are provided. Such an electromechanical conversion unit 20 can be disposed on the substrate 31 as shown in FIG. 3, for example, and when used as a droplet discharge head described later, a diaphragm (not shown) may be provided. it can. Further, in order to improve the adhesion between the lower electrode 21 and the substrate 31, an adhesion layer (not shown) or the like can be provided.

  One of the lower electrode 21 and the upper electrode 23 can be configured as one common electrode that is common among the plurality of electro-mechanical conversion units 20. In this case, the other of the lower electrode 21 and the upper electrode 23 is configured as an individual electrode corresponding to each electro-mechanical converter. FIG. 3 shows an example in which the lower electrode 21 is configured as one common electrode between the electromechanical conversion units 20 and the upper electrode 23 is configured as a separate individual electrode independent for each electromechanical conversion unit 20. However, it is not limited to the form which concerns as mentioned above.

  The first insulating protective film 32 can be provided on the upper electrode 23 and the lower electrode 21. The first insulating protective film 32 is preferably made of an inorganic compound as will be described later, and the upper electrode 23 and the lower electrode 21 can be electrically connected to other members on the first insulating protective film 32. Thus, the contact hole 33 is preferably provided.

  In addition, the individual electrodes, that is, the upper electrode 23 in FIG. 3 can be configured to be connected to the individual electrode pads 35, respectively, and the connection between the individual electrodes and the individual electrode pads is between the individual electrodes and the individual electrode pads. The members 34 can be electrically connected.

  The common electrode, that is, the lower electrode 21 in FIG. 3 can also be configured to be connected to the common electrode pad 37, and the common electrode and the common electrode pad are connected by a common electrode-common electrode pad connecting member 36. Can be electrically connected.

  Further, the second insulating protective film 38 may be provided on the common electrode pad 37 and the individual electrode pad 35. The second insulating protective film is preferably composed of an inorganic compound as will be described later. The second insulating protective film 38 is preferably provided with an opening for exposing the common electrode pad and the individual electrode pads.

  A method for applying polarization treatment to the electromechanical conversion element having the above configuration will be described.

  The polarization process can be performed by a polarization device 40 as shown in FIG.

  The polarization device 40 includes a corona electrode 41 and a grid electrode 42. The corona electrode 41 and the grid electrode 42 are connected to a corona electrode power source 411 and a grid electrode power source 421, respectively. The grid electrode 42 is preferably configured so that mesh processing is performed and ions, charges, and the like generated by corona discharge are efficiently poured onto the lower sample stage when a high voltage is applied to the corona electrode. And it is preferable that the ground wire 44 is connected to the stage 43 on which the sample is placed so that the electric charge can easily flow to the sample. The stage 43 may be provided with a temperature control function so that, for example, the electro-mechanical conversion element can be heated. The heating temperature at this time is not particularly limited, but is preferably configured to be heated up to 350 ° C.

  The magnitude of the voltage applied to the corona electrode and the grid electrode and the distance between the sample and each electrode are not particularly limited, and these are adjusted according to the sample so that sufficient polarization treatment can be performed. The intensity of discharge can be applied.

  When corona discharge is performed using a corona electrode (corona wire) as described above, the polarization treatment generates cations by ionizing molecules in the atmosphere as shown in FIG. The generated cations flow into the electro-mechanical conversion element via, for example, the common electrode pad or the individual electrode pad of the electro-mechanical conversion element, and charge is accumulated in the piezoelectric element. Then, it is considered that an internal potential difference is generated by the charge difference between the upper electrode and the lower electrode, and the polarization process is performed.

At this time, the charge amount Q required for the polarization treatment is not particularly limited, but it is preferable that a charge amount of 1.0 × 10 ⁻⁸ C or more is accumulated in the electromechanical conversion element. More preferably, a charge amount of 0 × 10 ⁻⁸ C or more is accumulated. By accumulating the charge amount in such a range in the electro-mechanical conversion element, it is possible to perform the polarization process so that the polarizability described later can be obtained more reliably.

  Here, the state of the polarization treatment can be determined from the PE hysteresis loop of the electromechanical conversion element. A method of determining the polarization process will be described with reference to FIG.

  Examples of the PE hysteresis loop are shown in FIGS. FIG. 6A shows a sample before the polarization process, and FIG. 6B shows a PE hysteresis loop after the polarization process.

  As shown in FIGS. 6A and 6B, when the hysteresis loop is measured with an electric field strength of ± 150 kV / cm, the polarization at 0 kV / cm before applying the voltage is Pind, and +150 kV / cm Let Pr be the polarization at 0 kV / cm when the voltage is returned to 0 kV / cm after voltage application.

At this time, the value of Pr-Pind is defined as the polarizability, and it is possible to determine whether or not the polarization state is appropriate based on this polarizability. Specifically, as shown in FIG. 6B, for the sample after the polarization treatment, the value of the polarizability Pr-Pind is preferably equal to or less than a predetermined value. For example, it is preferable that has a 10 [mu] C / cm ² or less, further preferably has a 5 [mu] C / cm ² or less. When the value of Pr-Pind is not sufficiently small, polarization is not sufficiently performed, and the displacement amount of the electromechanical conversion element with respect to the predetermined drive voltage is not stable.

  Even if the polarization treatment as described above is performed, in the conventional electro-mechanical conversion element as described above, an element that is not subjected to the polarization treatment may occur. In this case, a predetermined drive voltage of the electro-mechanical conversion element is generated. This is a problem because the amount of displacement is not stable.

  When the inventors of the present invention have repeatedly investigated the cause of this, in an electro-mechanical conversion element that has not been subjected to polarization treatment, mainly between the upper electrode and the lower electrode, that is, between the common electrode and the individual electrode. It was found that leak current was generated. For this reason, the electric charge supplied in the polarization process flows without staying in the electro-mechanical converter, and the polarization process cannot be performed appropriately.

  Based on such knowledge, in order to obtain an electro-mechanical conversion element that can perform polarization processing stably and reliably, in the electro-mechanical conversion element of the present embodiment, the leakage current between the common electrode and the individual electrode The amount is a predetermined value or less.

At this time, the allowable range of the amount of leakage current between the common electrode and the individual electrode is not particularly limited, and can be selected according to the conditions for performing the polarization process. However, in order to perform the polarization process more reliably, it is preferable that the amount of leakage current when a voltage of 50 V is applied between the common electrode and the individual electrode is 1.0 × 10 ⁻⁸ A or less. Moreover, it is more preferable that the amount of leakage current when a voltage of 50 V is applied between the common electrode and the individual electrode is 8.0 × 10 ⁻¹⁰ A or less.

  As shown in FIG. 7, the leakage current generated between the upper electrode 23 and the lower electrode 21 (between the common electrode and the individual electrode) is firstly an electro-mechanical conversion film indicated by A in the figure. A case in which a leak current flows in 22 is considered. Furthermore, it is conceivable that the electric current flows along the side wall portion of the electromechanical conversion film 22, that is, along the interface between the electromechanical conversion film 22 and the first insulating protective film 32, as indicated by B in the drawing.

First, in order to suppress the leakage current of A, it is preferable that the insulation resistance of the electromechanical conversion film 22 is higher than a predetermined value. In particular, the insulation resistance of the electromechanical conversion film 22 is preferably 5.0 × 10 ¹⁰ Ω or more, and more preferably 1.0 × 10 ¹⁰ Ω or more.

  In general, an electro-mechanical conversion element is manufactured so as to form a plurality of electro-mechanical conversion units by laminating a lower electrode, an electro-mechanical conversion film, and an upper electrode and then patterning them. The insulation resistance may be a measured value in any state, but particularly after the patterning, that is, after the step of individualizing the electromechanical conversion film, which is close to the actual product state, the predetermined insulation resistance. It is preferable that

  As described above, when forming the electro-mechanical conversion part, usually, after laminating each layer to be the lower electrode, the electro-mechanical conversion film, and the upper electrode, by patterning, the electro-mechanical conversion film and the upper electrode, depending on circumstances Further, a method is used in which the lower electrode is patterned and individualized.

  In FIG. 7, the cause of the leakage current indicated by B is that the residue generated during the patterning adheres to the side surface (side wall) of the electromechanical conversion film.

In particular, when PZT is used as the electromechanical conversion film, the manner in which the residue emerges varies depending on the Pb content of PZT. When Al ₂ O ₃ is used as the first insulating protective film, the reaction product of the residue and Al ₂ O ₃ becomes a leak path depending on the Al ₂ O ₃ film forming conditions, and the amount of leak current increases. May end up.

For this reason, when the electro-mechanical conversion film is formed of PZT, by adjusting the composition of the electro-mechanical conversion film, the generation of residue can be suppressed and the generation of the leakage current indicated by B can be suppressed. it can. Specifically, in the electromechanical conversion film formed of PZT, it is preferable that the substance amount of Pb is 105% or more and 120% or less with respect to the sum of the substance amounts of Zr and Ti. That is, it is preferable that Pb / (Zr + Ti) is 1.05 or more and 1.20 or less in terms of the amount of substance. If the ratio of the amount of Pb is less than the lower limit value, the electro-mechanical conversion element may not be sufficiently displaced, which is not preferable. Further, if the ratio of the amount of Pb exceeds the upper limit, residues are likely to be generated, and the amount of leakage current increases, which is not preferable.
In particular, the amount of Pb relative to the total amount of Zr and Ti is more preferably 110% to 120%.

In addition, as described above, in the electro-mechanical conversion element, when the individual electrode is connected to the individual electrode pad, if a leakage current is generated between the individual electrode pads, the charge is generated when the polarization process is performed in the same manner. May flow not only in the electro-mechanical converter, but the polarization process may not be performed properly. For this reason, it is preferable that the leakage current be set to a predetermined value or less between the individual electrode pads. Specifically, the amount of leakage current when a voltage of 50 V is applied between the individual electrode pads is preferably 1.0 × 10 ⁻⁸ A or less. Moreover, it is more preferable that the amount of leakage current when a voltage of 50 V is applied between the individual electrodes is 8.0 × 10 ⁻¹⁰ A or less.

  Thus, in order to suppress the leakage current between the individual electrode pads, it is preferable to set the distance between the individual electrode pads to a predetermined value or more. Specifically, for example, the distance between the individual electrode pads is preferably 50 μm or more, and more preferably 100 μm or more.

Hereinafter, each member of the electro-mechanical conversion element of the present embodiment will be described. As described above, the electro-mechanical conversion element of the present embodiment can be formed on the substrate 31.

  The material of the substrate 31 is not particularly limited, but it is preferable to use a silicon single crystal substrate in view of ease of processing, availability, and the like.

  The silicon single crystal substrate has three types of plane orientations (100), (110), and (111), but is not particularly limited, and an appropriate substrate can be selected according to the content of processing. it can.

  For example, when etching processing is required for a substrate, a substrate having a predetermined plane orientation can be selected in accordance with the content of the etching processing. In the case of forming a droplet discharge head, which will be described later, as an example, a pressure chamber is usually formed on a substrate by etching, and anisotropic etching is generally used as an etching method at this time. Here, the anisotropic etching utilizes the property that the etching rate is different with respect to the plane orientation of the crystal structure. For example, in anisotropic etching immersed in an alkaline solution such as KOH, the (100) plane is used. In contrast, the (111) plane has an etching rate of about 1/400. Accordingly, while a structure having an inclination of about 54 ° can be produced in the plane orientation (100), deep grooves can be dug in the plane orientation (110), and the arrangement density is increased while maintaining rigidity. I know I can. For this reason, for example, in the case of a substrate constituting a droplet discharge head, a silicon single crystal substrate having a (110) plane orientation can be preferably used.

  Although the thickness of the board | substrate 31 can be selected by a use etc. and is not specifically limited, For example, what has a thickness of 100-600 micrometers can be used preferably.

  The lower electrode 21 is not particularly limited and can be arbitrarily selected. For example, it can be composed of a metal electrode film or an oxide electrode film, and is particularly preferably a laminate of a metal electrode film and an oxide electrode film.

  Examples of the metal electrode film include platinum group elements such as platinum, iridium, and rhodium, and films made of these alloys such as platinum-rhodium.

In the case where platinum is used as the metal electrode film, the adhesion between the substrate and the metal electrode film is poor because the adhesion to the substrate (especially when SiO ₂ is formed on the substrate surface) is poor. It is preferable to form an adhesion layer to be described later.

  The method for producing the metal electrode film is not particularly limited, and various film forming methods can be employed. For example, vacuum film formation such as sputtering or vacuum deposition is common. The film thickness is not particularly limited, but is preferably 80 nm to 200 nm, and preferably 100 nm to 150 nm. This is because sufficient current may not be supplied when the metal electrode film is too thin. If the film thickness is too thick, the metal electrode film is composed of an expensive white metal material, which increases the cost. If the film thickness is increased, the surface roughness increases. This is because the surface roughness and crystal orientation of the layer laminated thereon may be affected.

The material of the oxide electrode film is not particularly limited, but for example, SrRuO ₃ can be preferably used. In addition to SrRuO ₃ , Sr _x A _(1-x) Ru _y O _(1-y) (A: Ba, Ca B: Co, Ni x, y = 0 to 0.5) Can also be preferably used.

  A method for forming the oxide electrode film is not particularly limited, but the oxide electrode film can be formed by a sputtering method.

As the electro-mechanical conversion film described later, PZT is preferably used, and PZT is preferably (111) oriented. Therefore, when SrRuO ₃ is used as the oxide electrode film, SrRuO ₃ is also (111) oriented. Preferably it is. However, SrRuO ₃ is known to film quality varies depending on sputtering conditions, for example as the metal electrode film (111) using a Pt orientation, in the case of forming an SrRuO ₃ film on the Pt film, SrRuO ₃ When forming the film, it is preferable to heat the substrate to 500 ° C. or higher to form the film.

Note that the crystallinity of the SrRuO ₃ film fabricated on Pt (111) is close to the lattice constant between Pt and SrRuO ₃ film, and therefore, in normal θ-2θ measurement, the SrRuO ₃ film (111) and Pt (111) These 2θ positions overlap and are difficult to discriminate. With respect to Pt, diffraction lines cancel each other at a position where 2θ tilted by Psi = 35 ° is about 32 ° due to the disappearance rule, and no diffraction intensity is observed. Therefore, it is possible to confirm whether the SrRuO ₃ film is preferentially oriented to (1119) by tilting the Psi direction by about 35 ° and judging from the peak intensity where 2θ is about 32 °.

FIG. 8 shows data when 2θ = 32 ° is fixed and Psi is shaken. When Psi = 0 °, almost no diffraction intensity is observed in the SrRuO ₃ film (110), and the diffraction intensity is observed in the vicinity of Psi = 35 °. From this, it can be confirmed that the SrRuO ₃ film is (111) oriented in the sample shown in FIG. In addition, regarding the SrRuO ₃ film produced by the room temperature film formation + RTA process described above, the diffraction intensity of SRO (110) is observed when Psi = 0 °.

The surface roughness of the SrRuO ₃ film is not particularly limited, but is preferably 4 nm or more and 15 nm, and more preferably 6 nm or more and 10 nm or less. This is because if the surface roughness is larger than the above range, the withstand voltage of the electro-mechanical conversion film formed thereafter may deteriorate and a leakage current may be generated.

Further, although it is preferable that the surface roughness is small, the surface roughness is affected by the film formation temperature, and when the film is formed from room temperature to 300 ° C., the surface roughness can be extremely reduced, for example, 2 nm or less. It can also be. However, this is not preferable because the crystallinity of the SrRuO ₃ film is lowered. For this reason, it is preferable that surface roughness Ra is the said range. In addition, the surface roughness here means surface roughness Ra (center line average roughness) measured by AFM. In order to obtain the SrRuO ₃ film having the above surface roughness and high crystallinity, the film forming temperature is preferably 500 ° C. to 700 ° C., more preferably 520 ° C. to 600 ° C. .

When SrRuO ₃ is used as the oxide electrode film, the Sr / Ru (ratio of substance amount) is 0.82 or more and 1.22 or less with respect to the composition ratio of Sr and Ru after the formation of the SrRuO ₃ film. It is preferable. This is because if it is out of this range, the specific resistance increases, and sufficient conductivity as an electrode may not be obtained.

  The thickness of the oxide electrode film is not particularly limited, but is preferably 40 nm or more and 150 nm or less, and more preferably 50 nm or more and 80 nm or less. If the thickness is less than this range, sufficient characteristics cannot be obtained for initial displacement and displacement deterioration after continuous driving, or as a stop etching layer for suppressing over-etching when etching an electro-mechanical conversion film. It becomes difficult to obtain functions. On the other hand, if the thickness is larger than the above range, the dielectric strength of the electro-mechanical conversion film formed thereafter is deteriorated, which may cause a leakage current, which is not preferable.

The specific resistance of the oxide electrode film is preferably 5 × 10 ⁻³ Ω · cm or less and more preferably 1 × 10 ⁻³ Ω · cm or less in order to have sufficient conductivity as an electrode. More preferably.

Further, as described above, an adhesion layer can be provided between the substrate and the lower electrode. A TiO ₂ film can be preferably used as the adhesion layer. In addition, oxides such as Ta, Ir, and Ru can be preferably used.

The method for forming the TiO ₂ film is not particularly limited. For example, the film can be formed by reactive sputtering, but a titanium film thermally oxidized at a high temperature can be preferably used. Specifically, it is preferable to use a material obtained by thermal oxidation in an oxygen atmosphere at 650 to 800 ° C. for 1 to 30 minutes using an RTA (rapid thermal annealing) apparatus after sputtering sputtering of Ti. .

  This is because the production by reactive sputtering requires heating the silicon substrate at a high temperature and requires a special sputtering chamber configuration. Furthermore, according to oxidation in a normal heating furnace, an easily oxidizable titanium film forms several crystal structures at low temperatures, so it is necessary to break it once. This is because good crystals can be formed. An oxide film can be formed in the same manner for other metals.

  The thickness of the adhesion layer is preferably 10 nm to 50 nm, and more preferably 15 nm to 30 nm. If it is thinner than this, it may not have the effect of sufficiently improving the adhesion, and if it is thicker than this range, it may affect the quality of the crystal such as the electrode film laminated on it. .

  The electro-mechanical conversion film can be used as long as it exhibits a piezoelectric characteristic, and is not particularly limited, but is preferably formed from an oxide containing Pb.

In particular, as an electro-mechanical conversion film, PZT can be preferably used because of its high piezoelectric characteristics. PZT is a solid solution of lead zirconate (PbTiO ₃ ) and titanic acid (PbTiO ₃ ), and the characteristics differ depending on the ratio. In general, the composition exhibiting excellent piezoelectric characteristics has a ratio of PbZrO ₃ and PbTiO ₃ of 53:47. In terms of chemical formula, Pb (Zr _0.53 , Ti _0.47 ) O ₃ , generally PZT Also shown as (53/47). When PZT is used as the electro-mechanical conversion film, the amount of Pb with respect to the total amount of Zr and Ti is 105% or more and 120% or less in order to reduce the leakage current as described above. It is preferably 110% or more and 120% or less. That is, it is preferable to add Pb in excess of the stoichiometric ratio of the above formula.

  Examples of composite oxides other than PZT include barium titanate. In this case, it is also possible to prepare a barium titanate precursor solution by dissolving barium alkoxide and a titanium alkoxide compound in a common solvent. is there.

These materials are described by the general formula ABO ₃ where A is one or more elements selected from Pb, Ba, Sr, and B is selected from Ti, Zr, Sn, Ni, Zn, Mg, Nb. One or more of the selected elements. Then, a composite oxide composed mainly of ABO ₃ according electrically - can be preferably used as the transducer layer. The A, element B is at its specifically described as _{(Pb 1-x, Ba x} ) (Zr, Ti) O 3, (Pb 1-x, Sr x) (Zr, Ti) O 3, etc. be able to. This is the case where Pb at the A site is partially replaced with Ba or Sr. Such substitution is possible with a divalent element, and the effect thereof has an effect of reducing characteristic deterioration due to evaporation of lead during heat treatment.

  The relative dielectric constant of the electromechanical conversion film is preferably 600 or more and 2000 or less, and more preferably 1200 or more and 1600 or less. By setting the relative dielectric constant within the above range, sufficient displacement characteristics can be obtained. Further, the polarization process can be sufficiently performed, and sufficient characteristics can be obtained with respect to the displacement deterioration after continuous driving.

  The method for producing the electro-mechanical conversion film is not particularly limited, but for example, it can be produced by a spin coater using a sputtering method or a Sol-gel method. In any case, since patterning is required, a desired pattern is obtained by photolithography etching or the like.

  The production procedure will be described taking as an example the case of producing PZT by the Sol-gel method. First, lead acetate, zirconium alkoxide, and titanium alkoxide compounds are used as starting materials, and these starting materials are dissolved in methoxyethanol as a common solvent to obtain a uniform solution, whereby a PZT precursor solution can be prepared. Since the metal alkoxide compound is easily hydrolyzed by moisture in the atmosphere, an appropriate amount of a stabilizer such as acetylacetone, acetic acid or diethanolamine may be added to the precursor solution as a stabilizer.

  When a PZT film is obtained on the entire surface of the base substrate on which the lower electrode and the like are formed, it is obtained by forming a coating film by a solution coating method such as spin coating, and performing heat treatments such as solvent drying, thermal decomposition, and crystallization. Since the transformation from the coating film to the crystallized film involves volume shrinkage, it is preferable to adjust the concentration of the precursor solution so that a film thickness of 100 nm or less can be obtained in one step in order to obtain a crack-free film. .

  The thickness of the electro-mechanical conversion film is not particularly limited, and can be arbitrarily selected depending on the required displacement amount. For example, the film thickness is preferably 0.5 to 5 μm, and more preferably 1 μm to 2 μm. Sufficient displacement can be generated by setting the film thickness within such a range. In addition, if the film thickness is in such a range, the number of steps to be stacked and formed does not increase more than necessary, so that it can be manufactured with high productivity.

  The upper electrode 23 is not particularly limited and can be arbitrarily selected. For example, it can be composed of a metal electrode film or an oxide electrode film, and is particularly preferably a laminate of a metal electrode film and an oxide electrode film.

  The metal electrode film is not particularly limited, and for example, the same material as that for the lower electrode can be preferably used.

  The film thickness is preferably 30 nm to 200 nm, more preferably 50 nm to 120 nm. If the film thickness is made thinner than the above range, there may be a case where a sufficient current cannot be supplied as an electrode. If the film thickness is larger than the above range, the cost increases when an expensive material of a platinum group element is used as the electrode material. In particular, when platinum is used as the material, the surface roughness increases as the film thickness is increased, and film peeling may occur when another material is laminated on the metal electrode film.

  The material of the oxide electrode film is not particularly limited, but for example, the same material as that of the lower electrode can be preferably used.

  The thickness of the oxide electrode film is not particularly limited, but is preferably 20 nm to 80 nm, and more preferably 40 nm to 60 nm. If it is thinner than this film thickness range, sufficient initial displacement and displacement deterioration characteristics may not be obtained. On the other hand, if it exceeds this range, the dielectric strength voltage of the PZT formed thereafter is very bad, and it may become easy to leak, which is not preferable.

  As described above, the first insulating protective film 32 can be provided in the electromechanical conversion element of this embodiment. As the first insulating protective film, it is preferable to use a material that prevents damage to the electromechanical conversion element due to the film formation / etching process and is difficult to transmit moisture in the atmosphere. For this reason, it is preferable to use a dense inorganic material (inorganic compound).

In order to obtain high protection performance with a thin film, it is preferable to use an oxide, nitride, or carbonized film. In particular, the material is in contact with the first insulating protective film, that is, the material of the upper electrode 23 and the lower electrode 21, the material of the electromechanical conversion film 22, and the material of the upper surface of the substrate 31. It is preferable. _{Therefore, Al 2 O 3, ZrO 2} , Y 2 O 3, Ta 2 O 3, an oxide film used in the ceramic material, such as TiO ₂ can be cited as examples.

  The method for forming the first insulating protective film is not particularly limited, but it is preferable to select a film forming method that does not damage the electromechanical conversion element. For this reason, the vapor deposition method and the ALD method can be preferably used, and it is preferable to form the film by the ALD method having many choices of applicable materials. In particular, according to the ALD method, a thin film having a very high film density can be produced, and damage to the electromechanical conversion element during the process can be suppressed.

  The film thickness of the first insulating protective film is not particularly limited, but is sufficient to ensure the protection performance of the electromechanical conversion element and does not hinder the displacement of the electromechanical conversion element. Is preferably as thin as possible. For example, the thickness of the first insulating protective film is preferably in the range of 20 nm to 100 nm. If it is thicker than 100 nm, displacement of the electromechanical conversion element may be hindered. On the other hand, when the thickness is smaller than 20 nm, the function as a protective layer of the electro-mechanical conversion element is not sufficient, and the performance of the electro-mechanical conversion element may be deteriorated.

In addition, the first insulating protective film can be composed of a plurality of layers. For example, in the case of two layers, an opening is formed in the second insulating protective film in the vicinity of the upper electrode so as not to significantly disturb the vibration displacement of the electromechanical conversion element in order to increase the thickness of the second insulating protective film. The structure to do is also mentioned. In this case, as the second insulating protective film, any oxide, nitride, carbide, or a composite compound thereof can be used. For example, it is preferable to use SiO ₂ generally used in semiconductor devices. Arbitrary techniques can be used for film formation, and film formation can be performed by a CVD method, a sputtering method, or the like. In particular, it is preferable to use a CVD method capable of forming an isotropic film in consideration of the step coverage of the pattern forming portion such as the electrode forming portion.

  The film thickness of the second insulating protective film is not particularly limited, and it is preferable to select a film thickness that does not cause dielectric breakdown in consideration of the voltage applied to each electrode. That is, it is preferable to set the electric field strength applied to the insulating protective film within a range not causing dielectric breakdown. Furthermore, considering the surface properties of the base of the insulating protective film, pinholes, etc., the film thickness is preferably 200 nm or more, and more preferably 500 nm or more.

  As described above, the individual electrode and the common electrode can be configured to be connected to the individual electrode pad and the common electrode pad, respectively.

  In this case, the materials of the individual electrode-individual electrode pad connecting member 34 and the common electrode-common electrode pad connecting member 36 that connect each electrode and the pad are not particularly limited, and various conductive materials are used. be able to. In particular, any metal electrode material selected from Cu, Al, Au, Pt, Ir, Ag alloy, and Al alloy is preferable.

  The manufacturing method of the individual electrode-individual electrode pad connecting member 34 and the common electrode-common electrode pad connecting member 36 is not particularly limited, and can be formed by any method. For example, a desired pattern can be obtained by using a sputtering method or a spin coating method and then photolithography etching or the like.

  The thickness of the connecting member is not particularly limited, but is preferably 0.1 μm or more and 20 μm or less, and more preferably 0.2 μm or more and 10 μm or less. If the film thickness is smaller than the range, the resistance increases, and a sufficient current may not flow through the electrode. Further, if the film thickness is thicker than the range, it takes time for the manufacturing process, which is not preferable because productivity is lowered.

  Further, when the first insulating protective film is provided, each of these connection members can be provided with a contact hole portion in the first insulating protective film, and can be connected to the common electrode and the individual electrode in the contact hole portion. The size of the contact hole portion is not particularly limited, but can be, for example, 10 μm × 10 μm. The contact resistance in the contact hole portion is preferably configured to be 10Ω or less for the common electrode and 1Ω or less for the individual electrode. This range is preferable because a sufficient current can be stably supplied to each electrode. In particular, the common electrode is preferably set to 5Ω or less and the individual electrode is set to 0.5Ω or less.

  Further, the second insulating protective film 38 can be provided in the electromechanical conversion film of the present embodiment. The second insulating protective film 38 is a passivation layer having a function of protecting the individual electrode-individual electrode pad connecting member 34 and the common electrode-common electrode pad connecting member 36.

  As shown in FIG. 5, the second insulating protective film is formed on the individual electrode-individual electrode pad connecting member 34 and the common electrode-common electrode pad connecting member 36 except for the individual electrode pad 35 and the common electrode pad 37. Cover. Thereby, even when inexpensive Al or an alloy material mainly composed of Al is used for these connecting members, the reliability of the electromechanical conversion element can be enhanced. Moreover, since an inexpensive material can be used for these connection members and the like, the cost of the electromechanical conversion element can be reduced.

The material of the second insulating protective film is not particularly limited, and any inorganic material or organic material can be used, but a material with particularly low moisture permeability is preferable. As the inorganic material, for example, oxide, nitride, carbide, or the like can be used. Moreover, as an organic material, a polyimide, an acrylic resin, a urethane resin etc. can be used, for example. However, in the case of an organic material, in order to function as an insulating protective film, the film thickness becomes thick and it may be difficult to perform patterning. For this reason, the inorganic material which can exhibit a wiring protection function with a thin film can be used more preferably. In particular, when Al wiring is used as the individual electrode-individual electrode pad connecting member 34 and the common electrode-common electrode pad connecting member 36, Si ₃ N ₄ is used as the second insulating protective film. This is preferable because it is a proven technology for semiconductor devices.

  The thickness of the second insulating protective film is preferably 200 nm or more, and more preferably 500 nm or more. This is because when the film thickness is thin, a sufficient passivation function cannot be exhibited, and thus the reliability may be lowered due to disconnection due to corrosion of the connecting member.

  In addition, the second insulating protective film preferably has a structure having an opening on the electromechanical conversion element. In the case of a liquid droplet ejection head described later, the diaphragm also has a structure having an opening. Is preferred. Thereby, it can be set as a highly efficient and reliable electromechanical conversion element, and is preferable.

  The second insulating protective film can form an opening for exposing the common electrode pad and the individual electrode pad. Photolithography and dry etching can be used to form the opening.

Further, the areas of the common electrode pad part and the individual electrode pad part are not particularly limited, but when the polarization process is performed after the pad part and the second insulating protective film are formed, charges are supplied from the pad part. Therefore, it is preferable to select the area so that the polarization treatment can be sufficiently performed. For example, the size of each pad is preferably 50 × 50 μm ² or more, and more preferably 100 × 300 μm ² or more.

  As mentioned above, although the electromechanical conversion element of this embodiment was demonstrated, according to the electromechanical conversion element which concerns, a polarization process can be performed reliably.

  As described above, the electromechanical conversion element of this embodiment can be manufactured by stacking the members shown in FIG. 3, for example, and patterning the members into a desired shape at a predetermined timing.

And in particular, in the electro-mechanical conversion element of the present embodiment, since the polarization treatment can be stably and reliably performed as described above, the manufacturing method of the electro-mechanical conversion element of the present embodiment is: It preferably has a polarization treatment step. Specifically, a positively charged charge is generated by corona discharge or glow discharge so that the charge amount is 1.0 × 10 ⁻⁸ C or more, and the electro-mechanical conversion is performed via a common electrode and individual electrodes. It is preferable to have a polarization step for performing polarization treatment of the film.

At this time, the amount of positively charged charges generated by corona discharge or glow discharge is more preferably 4.0 × 10 ⁻⁸ C or more.

Such a polarization step can be performed using, for example, the polarization processing apparatus shown in FIG. 4 as described above. According to the method for manufacturing an electro-mechanical conversion element, since the electro-mechanical conversion element according to the present embodiment is used, it is possible to reliably perform polarization processing on all the electro-mechanical conversion elements, and to improve the yield. Can be made.
[Second Embodiment]
In this embodiment, a droplet discharge head including the electro-mechanical conversion element described in the first embodiment will be described.

  The droplet discharge head according to the present embodiment includes a nozzle that discharges a droplet, a pressurizing chamber that communicates with the nozzle, and a discharge driving unit that pressurizes the liquid in the pressurizing chamber.

  And the said discharge drive means has a diaphragm which comprises a part of wall of the said pressurization chamber, and the electromechanical conversion element demonstrated in 1st Embodiment arrange | positioned at this diaphragm.

  A specific configuration will be described with reference to FIGS.

  FIG. 9 shows the configuration of a one-nozzle droplet discharge head. FIG. 10 shows the arrangement of a plurality of these.

  As shown in FIG. 9, the droplet discharge head of this embodiment has a pressurizing chamber 82 formed in the substrate 31 portion, and a nozzle 83 that discharges droplets is provided in the lower end portion of the pressurizing chamber 82. A nozzle plate 84 is arranged. When a voltage is applied to the electro-mechanical conversion element and the electro-mechanical conversion film 22 is displaced, the vibration plate 81 is deformed and displaced, and the liquid in the pressurizing chamber 82 is discharged from the nozzle 83. And as shown in FIG. 10, it can also be set as the structure which arranged the several droplet discharge head. In the figure, descriptions of liquid supply means, flow paths, and fluid resistance are omitted.

Here, the diaphragm 81 receives the force generated by the electro-mechanical conversion film as described above, deforms and displaces, and discharges the liquid (for example, ink) in the pressurizing chamber. Therefore, it is preferable that the diaphragm 81 has a predetermined strength. Examples of the material include Si, SiO ₂ , and Si ₃ N ₄ produced by the CVD method. In particular, it is preferable to select a material close to the linear expansion coefficient of the lower electrode and the electromechanical conversion film. When PZT is used as the electro-mechanical conversion film, it has a linear expansion coefficient of 5 × 10 ⁻⁶ to 10 × 10 ⁻⁶ (1 / K), which is close to its linear expansion coefficient of 8 × 10 ⁻⁶ (1 / K). The material having a linear expansion coefficient of 7 × 10 ^{−6 to} 9 × 10 ⁻⁶ (1 / K) is more preferable.

  Specifically, for example, aluminum oxide, zirconium oxide, iridium oxide, ruthenium oxide, tantalum oxide, hafnium oxide, osmium oxide, rhenium oxide, rhodium oxide, palladium oxide, and compounds thereof can be preferably used.

  A method for forming the diaphragm is not particularly limited, but the diaphragm can be formed by a spin coater using a sputtering method or a Sol-gel method.

  The film thickness of the diaphragm is not particularly limited, but is preferably 0.1 μm or more and 10 μm or less, and more preferably 0.5 μm or more and 3 μm or less. If it is smaller than this range, it becomes difficult to process the pressurizing chamber as shown in FIG.

Since the droplet discharge head as described above includes the electromechanical conversion element 20 described in the first embodiment, the polarization process can be reliably performed in advance. For this reason, the electro-mechanical conversion element is stably deformed with respect to a predetermined potential, and as a result, the droplet discharge head can also stably discharge the droplet.
[Third Embodiment]
In this embodiment, a droplet discharge apparatus including the droplet discharge head described in the second embodiment will be described.

  A configuration example of the droplet discharge device of this embodiment will be described with reference to FIGS. 11 and 12. 11 is a perspective explanatory view of the droplet discharge device, and FIG. 12 is a side view of a mechanism portion of the droplet discharge device.

The liquid droplet ejection apparatus includes a carriage that can move in the main scanning direction inside the recording apparatus main body 91, a recording head that includes the liquid droplet ejection head that implements the present invention mounted on the carriage, and an ink cartridge that supplies ink to the recording head. The printing mechanism part 92 etc. comprised by these are accommodated.
A sheet feeding cassette (or a sheet feeding tray) 94 on which a large number of sheets 93 can be stacked from the front side can be removably mounted on the lower part of the apparatus main body 91, and the sheets 93 can be manually inserted. The manual feed tray 95 for feeding paper can be turned over. Then, the paper 93 fed from the paper feed cassette 94 or the manual feed tray 95 is taken in, and after a required image is recorded by the printing mechanism unit 92, the paper is discharged onto a paper discharge tray 96 mounted on the rear side.

  The printing mechanism 92 holds the carriage 103 slidably in the main scanning direction with a main guide rod 101 and a sub guide rod 102 which are guide members horizontally mounted on left and right side plates (not shown). The carriage 103 has a plurality of ink discharge ports (nozzles) as a head 104 including a droplet discharge head for discharging ink droplets of yellow (Y), cyan (C), magenta (M), and black (Bk). They are arranged in a direction crossing the scanning direction. The ink droplet is ejected in the downward direction. Each ink cartridge 105 for supplying ink of each color to the head 104 is replaceably mounted on the carriage 103.

  The ink cartridge 105 has an atmosphere port communicating with the atmosphere above, a supply port for supplying ink to the inkjet head below, and a porous body filled with ink inside. The ink supplied to the inkjet head is maintained at a slight negative pressure by the capillary force of the porous body. Further, although the heads 104 of the respective colors are used here as the recording heads, a single head having nozzles that eject ink droplets of the respective colors may be used.

  Here, the carriage 103 is slidably fitted to the main guide rod 101 on the rear side (downstream side in the paper conveyance direction), and is slidably mounted on the secondary guide rod 102 on the front side (upstream side in the paper conveyance direction). doing. In order to move and scan the carriage 103 in the main scanning direction, a timing belt 110 is stretched between a driving pulley 108 and a driven pulley 109 that are rotationally driven by a main scanning motor 107. The timing belt 110 is fixed to the carriage 103, and the carriage 103 is reciprocated by forward and reverse rotation of the main scanning motor 107.

  Next, a mechanism for conveying the sheet 93 set in the sheet feeding cassette 94 to the lower side of the head 104 will be described. First, a sheet feeding roller 111 and a friction pad 112 for separating and feeding the sheet 93 from the sheet feeding cassette 94, a guide member 113 for guiding the sheet 93, and a conveying roller 114 for inverting and feeding the fed sheet 93 are provided. Have. A conveyance roller 115 pressed against the peripheral surface of the conveyance roller 114 and a leading end roller 116 for defining a feeding angle of the sheet 93 from the conveyance roller 114 are provided. The conveyance roller 114 is driven to rotate by a sub-scanning motor 117 through a gear train.

  A printing receiving member 119 is provided as a paper guide member for guiding the paper sheet 93 fed from the transport roller 114 below the recording head 104 in accordance with the movement range of the carriage 103 in the main scanning direction. On the downstream side of the printing receiving member 119 in the paper conveyance direction, a conveyance roller 121 and a spur 122 that are rotationally driven to send the paper 93 in the paper discharge direction are provided. Further, a discharge roller 123 and a spur 124 for feeding the sheet 93 to the discharge tray 96, and guide members 125 and 126 for forming a discharge path are provided.

  At the time of recording, the recording head 104 is driven according to the image signal while moving the carriage 103, thereby ejecting ink onto the stopped sheet 93 to record one line. Record the line. Upon receiving a recording end signal or a signal that the trailing edge of the sheet 93 has reached the recording area, the recording operation is terminated and the sheet 93 is discharged.

  Further, a recovery device 127 for recovering the ejection failure of the head 104 is disposed at a position outside the recording area on the right end side in the movement direction of the carriage 103. The recovery device 127 includes a cap unit, a suction unit, and a cleaning unit. While waiting for printing, the carriage 103 is moved to the recovery device 127 side and the head 104 is capped by the capping unit, and the ejection port portion is kept in a wet state to prevent ejection failure due to ink drying. Further, by ejecting ink that is not related to recording during recording or the like, the ink viscosity of all the ejection ports is made constant and stable ejection performance is maintained.

  When an ejection failure occurs, the ejection port (nozzle) of the head 104 is sealed by the capping unit, and bubbles and the like are sucked out from the ejection port by the suction unit through the tube. As a result, the ink, dust, etc. adhering to the ejection port surface are removed by the cleaning means, and the ejection failure is recovered. Further, the sucked ink is discharged to a waste ink reservoir (not shown) installed at the lower part of the main body and absorbed and held by an ink absorber inside the waste ink reservoir.

  Since the droplet discharge apparatus according to the present embodiment includes the droplet discharge head described in the second embodiment, the electro-mechanical conversion element included in the droplet discharge head is surely subjected to polarization processing in advance. be able to. Therefore, the electro-mechanical conversion element is stably deformed with respect to a predetermined potential, and as a result, the droplet discharge device can stably discharge the droplet.

  Specific examples will be described below, but the present invention is not limited to these examples.

First, sample evaluation methods in the following examples and comparative examples will be described.
(Leakage current between individual electrode and common electrode)
Between the individual electrode pad and the common electrode pad of the produced electromechanical conversion element, the leakage current between the individual electrode and the common electrode when 50 V voltage was applied was measured by IV measurement.
(Leakage current between individual electrode pads)
Between the individual electrode pads of the produced electro-mechanical transducer, the leakage current between the individual electrode pads when a 50 V voltage was applied was measured by IV measurement.
(Insulation resistance of electro-mechanical conversion film)
The insulation resistance of the electro-mechanical conversion film is determined by the leak current when 50V voltage is applied between the upper and lower electrodes by IV measurement after the electro-mechanical conversion part is separated by forming the upper electrode and patterning. And the insulation resistance (R) was estimated from R = V / I.
(Pr-Pind)
With respect to the obtained electro-mechanical conversion film, a hysteresis loop was measured with an electric field strength of ± 150 kV / cm as shown in FIG. In this case, the polarization at 0 kV / cm before applying the voltage is Pind, the polarization at 0 kV / cm when the voltage is returned to 0 kV / cm after applying the voltage of +150 kV / cm is Pr, and the value of Pr−Pind is the polarization Calculated as a rate.

In Table 1, the measured values after the polarization treatment are shown.
(Piezoelectric constant)
D31 which is an electro-mechanical conversion ability (piezoelectric constant) was calculated by measuring the amount of deformation by applying an electric field (150 kV / cm) with a laser Doppler vibrometer and fitting by simulation. A typical PE hysteresis curve measured at this time is shown in FIG. After evaluating the initial characteristics, durability (characteristics immediately after applying the applied voltage 10 to ¹⁰ times) was evaluated.

  In addition, all the samples which evaluated the initial characteristic shown as the initial stage in Table 1 have shown the measured value about the sample after performing the polarization process.

Next, sample preparation procedures of each example and comparative example will be described.
[Example 1]
A thermal oxide film (film thickness 1 μm) was formed on a 6 inch silicon wafer and used as a substrate.

  Next, a lower electrode was formed on the substrate. The lower electrode has a structure in which an adhesion layer, a metal electrode film, and an oxide electrode film are laminated.

First, the adhesion layer was formed by thermally oxidizing at 750 ° C. using RTA after forming a titanium film (film thickness 30 nm) with a sputtering apparatus. Subsequently, a platinum film (film thickness: 100 nm) was formed as a metal electrode film, and a SrRuO ₃ film (film thickness: 60 nm) was formed by sputtering as an oxide electrode film. The substrate was heated at 550 ° C. during the sputtering film formation.

  Next, a solution having a substance amount ratio adjusted to Pb: Zr: Ti = 114: 53: 47 was prepared as an electro-mechanical conversion film, and a film was formed by spin coating.

  For the synthesis of a specific precursor coating solution, lead acetate trihydrate, isopropoxide titanium and isopropoxide zirconium were used as starting materials. Crystal water of lead acetate was dissolved in methoxyethanol and then dehydrated. The lead amount is excessive with respect to the stoichiometric composition. This is to prevent crystallinity deterioration due to so-called lead loss during heat treatment. Isopropoxide titanium and isopropoxide zirconium were dissolved in methoxyethanol, the alcohol exchange reaction and the esterification reaction were advanced, and the PZT precursor solution was synthesized by mixing with the methoxyethanol solution in which the lead acetate was dissolved. At this time, the PZT concentration in the PZT precursor solution was 0.5 mol / L.

  Using this PZT precursor solution, a film was formed by spin coating, followed by drying at 120 ° C. and thermal decomposition at 500 ° C. And the process of film-forming, drying, and thermal decomposition was repeated, and the laminated film was formed. After thermal decomposition treatment of the third layer, crystallization heat treatment (temperature: 750 ° C.) was performed by RTA (rapid heat treatment). At this time, the film thickness of PZT was 240 nm. This process was repeated a total of 8 times, that is, a total of 24 layers were laminated to obtain an electromechanical conversion film having a thickness of about 2 μm.

Next, an upper electrode was formed. First, an SrRuO ₃ film (film thickness 40 nm) was formed as an oxide electrode film, and a platinum film (film thickness 125 nm) was further formed by sputtering as a metal electrode film. Thereafter, a photoresist made by Tokyo Ohka Co., Ltd. (TSMR8800) is formed by spin coating, a resist pattern is formed by normal photolithography, and then a pattern as shown in FIG. 3 is formed using an ICP etching apparatus (manufactured by Samco). Produced.

Next, an Al ₂ O ₃ film was formed as a first insulating protective film so as to have a film thickness of 50 nm by using the ALD method. At this time, the film formation was advanced by alternately supplying and laminating TMA (trimethylaluminum) for Al and O ₃ generated by an ozone generator for O.

  Thereafter, as shown in FIG. 3, a contact hole 33 was formed by etching.

  Then, Al was sputtered as an individual electrode-individual electrode pad connecting member 34, a common electrode-common electrode pad connecting member 36, an individual electrode pad, and a common electrode pad, and patterned by etching.

Next, Si ₃ N ₄ is formed as a second insulating protective film so as to have a film thickness of 500 nm by plasma CVD, and then an opening is formed in the individual electrode pad and the common electrode pad part, and electro-mechanical conversion is performed. An element was produced.

Thereafter, polarization treatment was performed by corona charging treatment using the polarization treatment apparatus shown in FIG. As a corona electrode used for the corona charging treatment, a tungsten wire of φ50 μm is used. Table 1 shows the detailed conditions of the polarization treatment and the evaluation results of the electromechanical conversion element.
[Example 2]
An electro-mechanical conversion element was formed in the same manner as in Example 1 except that the Pb content in forming the electro-mechanical conversion film was changed and the insulation resistance of the electro-mechanical conversion film was changed thereby. Similarly, polarization treatment was performed. The results are shown in Table 1.
[Example 3]
An electro-mechanical conversion element was formed in the same manner as in Example 1 except that the Pb content in forming the electro-mechanical conversion film was changed and the insulation resistance of the electro-mechanical conversion film was changed thereby. Similarly, polarization treatment was performed. The results are shown in Table 1.
[Example 4]
An electromechanical transducer was prepared in the same manner as in Example 1 except that the distance between the individual electrode pads was 50 μm.

Also, polarization treatment was performed immediately after the SrRuO ₃ film (film thickness of 40 nm) as the upper electrode and the platinum film (film thickness of 125 nm) were formed by sputtering, and then the electromechanical conversion element was formed in the same manner as in Example 1. Produced. The results are shown in Table 1.
[Example 5]
The distance between the individual electrode pads was set to 50 μm, the Pb content when the electro-mechanical conversion film was formed was changed, and the insulation resistance of the electro-mechanical conversion film was changed thereby. An electromechanical conversion element was produced.

Moreover, after sputter-depositing a SrRuO ₃ film (film thickness of 40 nm) as an upper electrode and a platinum film (film thickness of 125 nm), a pattern as shown in FIG. 3 was produced using an ICP etching apparatus (manufactured by Samco). Immediately after that, polarization treatment was performed. Thereafter, an electromechanical conversion element was produced in the same manner as in Example 1. The results are shown in Table 1.
[Example 6]
An electro-mechanical conversion element was formed in the same manner as in Example 1 except that the Pb content in forming the electro-mechanical conversion film was changed and the insulation resistance of the electro-mechanical conversion film was changed thereby. Similarly, polarization treatment was performed. The results are shown in Table 1.
[Comparative Example 1]
An electro-mechanical conversion element was formed in the same manner as in Example 1 except that the Pb content in forming the electro-mechanical conversion film was changed and the insulation resistance of the electro-mechanical conversion film was changed thereby. Similarly, polarization treatment was performed. The results are shown in Table 1.

  Examples 1 to 5 have the same initial characteristics and results after the durability test as those of a general ceramic sintered body (piezoelectric constant is -120 to -160 pm / V), especially the initial characteristics. It can be seen that after the durability test, no significant change in performance was observed and the test was stable.

  In Example 6, although the initial characteristics are slightly inferior, it can be confirmed that there is no significant change in the characteristics even after the durability test.

  On the other hand, in Comparative Example 1, the result after the durability test is greatly reduced as compared with the initial characteristics, and it can be seen that the change width is increased as compared with Examples 1-6. .

  This is probably because, in Comparative Example 1, leakage current was generated in the electromechanical conversion element, and the polarization treatment could not be performed sufficiently, so that the performance was greatly deteriorated when the durability test was performed.

Using the electro-mechanical conversion elements produced in Examples 1 to 6, the liquid ejection head of FIG. 9 was produced and the liquid ejection was evaluated. Using an ink whose viscosity was adjusted to 5 cp, and confirming the discharge situation when an applied voltage of -10 to -30 V was applied with a simple Push waveform, it was confirmed that all the nozzle holes could be discharged.

20 Electro-mechanical converter 21 Lower electrode 22 Electro-mechanical conversion film 23 Upper electrode 32 First insulating protective film 33 Contact hole 35 Individual electrode pad 37 Common electrode pad 38 Second insulating protective film 81 Diaphragm 82 Pressure chamber 83 nozzles

JP 2006-203190 A

Claims (13)

A lower electrode;
An electro-mechanical conversion film disposed on the lower electrode;
An electro-mechanical conversion element including a plurality of electro-mechanical conversion units including an upper electrode disposed on the electro-mechanical conversion film,
One electrode of the lower electrode and the upper electrode is configured as one common electrode common to the plurality of electro-mechanical conversion units,
The other electrode of the lower electrode or the upper electrode is configured as an individual electrode corresponding to each electro-mechanical converter,
An electro-mechanical conversion element in which an amount of leakage current between the common electrode and the individual electrode is a predetermined value or less. 2. The electromechanical transducer according to claim 1, wherein a leakage current amount when a voltage of 50 V is applied between the common electrode and the individual electrode is 1.0 × 10 ⁻⁸ A or less. The electro-mechanical conversion element according to claim 1, wherein an insulation resistance of the electro-mechanical conversion film is 5.0 × 10 ¹⁰ Ω or more.   The electro-mechanical conversion element according to any one of claims 1 to 3, wherein the electro-mechanical conversion film is formed of an oxide containing Pb. The electro-mechanical conversion film is made of PZT,
5. The electro-mechanical conversion element according to claim 1, wherein in the electro-mechanical conversion film, the amount of Pb with respect to the total amount of Zr and Ti is 105% or more and 120% or less. . When a hysteresis loop is measured on the electro-mechanical conversion film with an electric field strength of ± 150 kV / cm,
The polarization at 0 kV / cm before applying voltage is Pind,
When the polarization at 0 kV / cm when returning to 0 kV / cm after applying a voltage of +150 kV / cm is Pr,
6. The electromechanical transducer according to claim 1, wherein the polarizability Pr-Pind is 10 [mu] C / cm < ² > or less. A first insulating protective film is provided on the upper electrode and the lower electrode,
The first insulating protective film is made of an inorganic compound;
The electromechanical conversion element according to claim 1, wherein the first insulating protective film is provided with a contact hole. Each of the individual electrodes is connected to an individual electrode pad,
The electro-mechanical conversion element according to any one of claims 1 to 7, wherein a leakage current amount when a voltage of 50 V is applied between the individual electrode pads is 1.0 × 10 ^-8 A or less.   The electromechanical transducer according to claim 8, wherein a distance between the individual electrode pads is 50 μm or more. The common electrode is connected to a common electrode pad;
A second insulating protective film is provided on the common electrode pad and the individual electrode pad,
10. The electromechanical conversion element according to claim 8, wherein the second insulating protective film is provided with an opening that exposes the common electrode pad and the individual electrode pad. 11. The electro-mechanical conversion element according to any one of claims 1 to 10, wherein a positively charged charge is generated by corona discharge or glow discharge so that a charge amount is 1.0 × 10 ^-8 C or more. A method for producing an electromechanical conversion element, comprising a polarization step of performing polarization treatment of the electromechanical conversion film through the common electrode and the individual electrode. A nozzle for discharging droplets;
A pressurizing chamber to which the nozzle communicates;
A droplet discharge head comprising discharge driving means for increasing the pressure of the liquid in the pressurizing chamber,
The discharge driving means is
A diaphragm constituting a part of the wall of the pressurizing chamber;
A liquid droplet ejection head comprising: the electromechanical conversion element according to any one of claims 1 to 10 disposed on the diaphragm.   A droplet discharge device comprising the droplet discharge head according to claim 12.

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