JP6504426B2 - Method of forming an electromechanical conversion member - Google Patents

Description

The present invention relates to a method of forming the electro-mechanical conversion layer Yusuke that electrical-mechanical conversion member such as a piezoelectric layer is deformed by the drive voltage signal is applied.

  As this type of electromechanical conversion member, for example, one that pressurizes a pressurized liquid chamber in order to eject the liquid in the pressurized liquid chamber from a nozzle hole of a droplet ejection device of an ink jet recording apparatus is known.

Patent Document 1 discloses a method of manufacturing an electromechanical transducer having a ferroelectric crystal film (piezoelectric layer) made of lead zirconate titanate (hereinafter referred to as "PZT"). In this manufacturing method, a lower electrode (first electrode) is formed on a substrate, an SrRuO ₃ film is formed as an orientation control layer, and a PZT film is formed thereon.

Piezoelectric layers such as PZT tend to be films oriented in the same crystal direction as the underlying layer. The piezoelectric constant of the piezoelectric layer changes depending on which direction the crystal direction is aligned with. Therefore, for example, in the case where it is desired to form a piezoelectric layer in which the crystal direction is aligned with (100), if it is intended to directly form the piezoelectric layer on the lower electrode whose crystal direction is (111), It is difficult to obtain a uniform piezoelectric layer. Therefore, in the manufacturing method described in Patent Document 1, in order to align the crystal direction of the piezoelectric layer in a desired direction, an orientation control layer which is a SrRuO ₃ film having the desired crystal direction is used as a base layer on the lower electrode. It is formed. Thereby, a piezoelectric layer in which crystal directions are aligned in a desired direction can be obtained.

  However, even in the case of forming the orientation control layer, there is still a problem that it is difficult to stably obtain a piezoelectric layer in which the crystal orientation is sufficiently aligned in the desired direction. This problem is not limited to the case of forming the orientation control layer, but is the same as in the case of directly forming the piezoelectric layer on the lower electrode (first electrode) having the same crystal direction as the target crystal direction of the piezoelectric layer.

To solve the problems described above, the present invention is the diaphragm layer, the electrode contact layer, a platinum electrode layer, and, by sequentially forming a titanium oxide emissions or Ranaru orientation control layer, on the orientation control layer In the method of forming an electromechanical conversion member, in which the piezoelectric layer and the upper electrode layer are sequentially formed, the orientation control layer made of titanium oxide is formed by using a vacuum degree of 8.6 × 10 ⁻⁵ [Pa] or more and 1.0 × 10 5 and wherein the formation child by sputtering in an environment at ^{-4 [Pa]} or less.

  According to the present invention, an excellent effect of stably obtaining a piezoelectric layer in which crystal directions are aligned in a desired direction is exhibited.

It is sectional drawing which shows the basic layer structure of the piezoelectric element of embodiment. (A) shows the result of SEM observation, FIG. 2 (b) shows the analysis result of crystallinity by EBSB, FIG. 2 (c) is a positive electrode dot diagram, and the left column shows the result of Comparative Example 1 And the results in Example 1 are shown in the right column. (A) is explanatory drawing of the result of SEM observation corresponding to the left row of Fig.2 (a). (B) is explanatory drawing of the analysis result of crystallinity by EBSB corresponding to the left row of FIG.2 (b). (A) is a graph which shows particle size distribution of the white turbidity part in comparative example 1, and (b) is a graph which shows particle size distribution of the white turbidity part in Example 1. FIG. FIG. 2 is a cross-sectional view of a droplet discharge head employing the piezoelectric element of the embodiment. It is a disassembled perspective view of the same droplet discharge head. FIG. 2 is a perspective view illustrating an ink jet recording apparatus provided with the same droplet discharge head. It is a side view which illustrates the same ink jet recording device.

  Hereinafter, an embodiment in which a piezoelectric element as an electromechanical conversion member according to the present invention is applied to a droplet discharge head as a droplet discharge device in an ink jet recording device as an image forming device will be described.

FIG. 1 is a cross-sectional view showing the basic layer configuration of the piezoelectric element of the present embodiment.
The piezoelectric element includes a diaphragm layer 11, a lower electrode layer 20, a piezoelectric layer (piezoelectric film) 30 which is an electromechanical conversion layer, an upper electrode layer 40, a protective layer 50, an interlayer insulating layer (not shown) on a substrate 10. ), And an electrode wiring layer (not shown) or the like.

  As the substrate 10, a silicon single crystal substrate is preferably used, and one having a thickness of 100 μm to 600 μm is preferable. There are three kinds of plane orientations such as (100), (110) and (111), but (100) and (111) are widely used generally in the semiconductor industry, and in the present embodiment, they are mainly used. A silicon single crystal substrate having a (100) plane orientation is used.

  When processing a silicon single crystal substrate using an etching technique, it is general to use anisotropic etching as the etching method. Anisotropic etching is an etching method utilizing the property that etching rates differ with respect to the plane orientation of a crystal structure. For example, in anisotropic etching immersed in an alkaline solution such as KOH, an etching rate of about 1/400 is obtained in the case of having the (111) crystal direction as compared with the case of having the (100) crystal direction. . Therefore, in the case of having the (100) crystal orientation, a structure having an inclination of about 54.74 [°] can be produced, whereas in the case of having the (110) crystal orientation, it is necessary to dent the deep groove. It has been found that the arrangement density can be increased while maintaining the rigidity. Taking this into consideration, in the present embodiment, it is also possible to use a silicon single crystal substrate having a (110) crystal orientation.

Next, a method of manufacturing the piezoelectric element in the present embodiment will be described.
First, the diaphragm layer 11 is formed on a substrate 10 made of a silicon single crystal substrate having a crystal orientation of (100) surface orientation. The diaphragm layer 11 is displaceable by receiving a force generated by the deformation of the piezoelectric layer 30. The method for forming the diaphragm layer 11 includes sputtering, a combination of sputtering and thermal oxidation, heat treatment film forming, metal organic chemical vapor deposition (MOCVD), low pressure chemical vapor deposition (LPCVD), etc. Be

  In the present embodiment, for the diaphragm layer 11, for example, a silicon oxide film having a thickness of 200 nm is formed by the LPCVD method. The surface roughness of the silicon oxide film is preferably 5 nm or less in arithmetic average roughness. Thereafter, for example, a polysilicon film (eg, 500 nm thick) having a thickness of 500 nm is formed. The thickness of the polysilicon film is preferably 0.1 to 3 [μm], and the surface roughness is preferably 5 [nm] or less in arithmetic average roughness. Next, for example, a silicon nitride film having a thickness of 150 nm is formed by the LPCVD method. These films are alternately laminated as many times as necessary, and finally, stop when the stress balance as the diaphragm layer 11 reaches equilibrium. However, the outermost surface of the diaphragm layer 11 is a silicon oxide film. The diaphragm layer 11 of the present embodiment has a multi-layer structure in which a plurality of films are stacked, but may be a single-layer structure of a single material.

  The surface roughness of the diaphragm layer 11 thus formed is preferably 4 nm or less in arithmetic average roughness. If the thickness is larger than 4 [nm], the withstand voltage of the piezoelectric layer 30 or the like to be formed subsequently is apt to deteriorate, and leakage tends to occur. Moreover, if it is a film formed into a film by LPCVD method, since it is generally applied conventionally to a semiconductor, a MEMS device, etc. and processing is easy, it will not introduce a new process subject, and SOI (Silicon on) The stable diaphragm layer 11 can be obtained without using an expensive substrate such as Insulator.

Next, although Pt electrode 22 which is a common electrode as a 1st electrode is formed on diaphragm layer 11, Pt electrode 22 has bad adhesion with diaphragm layer 11 mentioned above. Therefore, in the present embodiment, the electrode adhesion layer 21 made of Ti, TiO ₂ , Ta, Ta ₂ O ₅ , Ta ₃ N ₅ or the like is formed on the diaphragm layer 11 and then the Pt electrode 22 is formed. The Pt electrode 22 of the present embodiment has high orientation in the (111) crystal direction, and when the crystallinity of Pt is evaluated by X-ray diffraction, a Pt film having a high peak intensity is obtained. ing. Therefore, in order to form the piezoelectric layer 30 made of PZT having a crystal direction of (100) or (001), the orientation control layer 23 is formed as a base layer of the piezoelectric layer 30 in this embodiment.

  The orientation control layer 23 can be formed of, for example, titanium oxide. In this case, the Ti-rich PZT film is generated by reacting with the PZT of the sol-gel solution stacked thereon, and the Ti-rich film acts as a crystal source of PZT having a (100) crystal direction, and is further stacked. The (100) or (001) crystal orientation of the PZT film can be aligned. The orientation control layer 23 is not limited to titanium oxide, but may be formed of other materials such as lead titanate. Lead titanate is preferable because it directly acts as a crystal source of PZT having a (100) crystal orientation.

The electrode adhesion layer 21, the Pt electrode 22, and the orientation control layer 23 constituting the lower electrode layer 20 are formed in an environment with a high degree of vacuum, such as a sputtering method or a vacuum evaporation method. In particular, in the present embodiment, the lower electrode layer 20 is formed by sputtering under an environment in which the degree of vacuum is 1.0 × 10 ⁻⁴ [Pa] or less. The total layer thickness of the lower electrode layer 20 is preferably 0.02 μm or more and 0.5 μm or less, and more preferably 0.02 μm or more and 0.05 μm or less. More preferable.

The piezoelectric layer 30 is preferably formed of a perovskite-type oxide dielectric containing lead, titanium and zirconium, and is formed of PZT in this embodiment. PZT is a solid solution of lead zirconate (PbZrO ₃ ) and lead titanate (PbTiO ₃ ), and has different characteristics depending on the ratio. In general, the composition showing excellent piezoelectric characteristics is a composition in which the ratio of PbZrO ₃ to PbTiO _{3 is} a ratio of 53:47, and it is expressed as Pb (Zr _0.53 Ti _0.47 ) O ₃ in chemical formula. And may be denoted as PZT (53/47).

  As the piezoelectric layer 30, barium titanate may be used other than PZT. The piezoelectric layer 30 can be formed, for example, by preparing a barium titanate precursor solution by dissolving it in a common solvent using a barium alkoxide or a titanium alkoxide compound as a starting material.

The material of the perovskite type oxide dielectric can be described by the general formula ABO3 type structure, for example, A = Pb, Ba, Sr, B = Ti, Zr, Sn, Ni, Zn, Mg, Nb as main components The corresponding composite oxide is applicable. As a specific description, (Pb ₁ -X, Ba) (Zr, Ti) O ₃ , (Pb _1-X , Sr) (Zr, Ti) O ₃ or the like. This indicates that a part of Pb at the A site is substituted with Ba or Sr. Such substitution is possible if it is a divalent element, and its effect is to reduce the characteristic deterioration due to the evaporation of lead during heat treatment.

  The piezoelectric layer 30 can be formed by using a sputtering method, a sol-gel method, or the like. Since the formation of the piezoelectric layer 30 requires a patterning process, the piezoelectric layer 30 is formed into a desired shape by photolithography and the like. When PZT is formed by a sol-gel method, lead acetate, a zirconium alkoxide, and a titanium alkoxide compound are used as starting materials, and dissolved in methoxyethanol as a common solvent to form a uniform solution, thereby preparing a PZT precursor solution. The metal alkoxide compound is easily hydrolyzed by moisture in the air, so an appropriate amount of a stabilizer such as acetylacetone, acetic acid, diethanolamine or the like may be added as a stabilizer to the PZT precursor solution.

  When a PZT film is formed on the entire surface of the substrate 10, a PZT precursor solution is coated by a solution coating method such as spin coating, and the piezoelectric layer is subjected to heat treatment such as solvent drying, thermal decomposition, and crystallization. Form 30. Since transformation from a coating film to a crystallized film is accompanied by volume contraction, the concentration of the PZT precursor solution is adjusted so that the film thickness formed in one step is 100 nm or less so as not to cause a crack. It is preferable to adjust.

  On the other hand, when the PZT film is formed by the inkjet method, the piezoelectric layer 30 patterned from the beginning can be obtained. The surface modifier may vary depending on the material of the underlayer, but a silane compound is mainly used in the case of using an oxide as the underlayer, and alkanethiol can be mainly used in the case of using a metal as the underlayer.

  The thickness of the piezoelectric layer 30 is preferably 0.5 μm or more and 5 μm or less, and more preferably 1 μm or more and 2 μm or less. If it is less than 0.5 [μm], it becomes difficult to generate sufficient deformation due to the drive voltage signal, and if it exceeds 5 [μm], the number of layers increases, so the number of steps increases and the process time becomes long Become.

In the present embodiment, the orientation (the degree to which the crystal orientation is aligned with the desired direction) of the piezoelectric layer 30 can be determined by coating the PZT by spin coating using a PZT precursor solution prepared by sol-gel method. [mu] m] is deposited and evaluated using an X-ray diffractometer. Specifically, assuming that the sum of peak intensities in respective crystal directions is 1 using an X-ray diffractometer, the ratio (orientation degree ρ) of the respective crystal directions is calculated from the following equation (1). Evaluate by height. In the present embodiment, a PZT film having high orientation in the (100) crystal direction has an orientation degree ρ of 0.85 or more in the (100) crystal direction, and with respect to the (110) crystal direction. Is less than 0.05. If it is out of this range, sufficient characteristics can not be obtained with respect to displacement deterioration after continuously driving the piezoelectric element.
ρ = I (h k l) / I I (h k l)
Right side denominator: Sum of peak intensities in each crystal direction Right side numerator: Peak intensity in target crystal direction

An upper electrode layer 40 is formed on such a piezoelectric layer 30. The material of the upper electrode layer 40 is not particularly limited, and can be formed of a material used in a general semiconductor process, such as Al or Cu, and a combination thereof. In this embodiment, the Pt electrode 42 is formed after the SRO (SrRuO ₃ ) having the same structure of the perovskite system is formed as the underlying layer 41 in order to improve the adhesion to the piezoelectric layer 30 composed of PZT. It formed.

Example 1
Next, an example of the piezoelectric element in the present embodiment (hereinafter, this example will be referred to as “example 1”) will be described.
In Example 1, after forming a thermal oxide film on the surface of a silicon single crystal substrate, the laminated diaphragm layer 11 is formed by the CVD method. Specifically, a thermal oxide film with a film thickness of 600 nm is formed on a silicon wafer to be the substrate 10, and a polysilicon film with a thickness of 200 nm and a silicon oxide with a thickness of 100 nm are formed thereon. Film, 150 nm thick silicon nitride film, 150 nm thick silicon oxide film, 150 nm thick silicon nitride film, 100 nm thick silicon oxide film, 200 thick Finally, a silicon oxide film with a thickness of 600 nm is formed as a diaphragm layer 11. In FIG. 1, the diaphragm layer 11 is shown as a single layer.

Subsequently, the electrode adhesion layer 21 constituting the lower electrode layer 20 is formed on the diaphragm layer 11 thus formed. The electrode adhesion layer 21 is formed by forming a metal film of Ti by sputtering, and then performing oxidation treatment in an oxygen atmosphere by an RTA (Rapid Thermal Anneal) apparatus to form a TiO ₂ film, which is used as an electrode adhesion layer. It was 21. As a Ti metal film deposition apparatus, a sputtering apparatus SME-200E manufactured by ULVAC, Inc. was used. The conditions for forming the electrode adhesion layer 21 were a substrate temperature of 150 ° C., a DC input power of 300 W, an Ar gas pressure of 0.14 Pa, and a film thickness of 50 nm. Then, the Ti metal film was thermally oxidized and fired for 3 minutes in an atmosphere of 730 [° C.] (heating rate 30 [° C./sec]), oxygen flow rate 1 [sccm] and oxygen 100 [%]. The film thickness after firing was 83 to 86 [nm].

Next, a Pt electrode 22 constituting the lower electrode layer 20 was formed to a thickness of 160 nm. Before depositing the Pt electrode 22, the degree of vacuum of the process chamber and the transfer chamber was set to 1.0 × 10 ⁻⁴ [Pa]. The process conditions were such that the substrate temperature was 500 ° C., the RF input power was 500 W, and the Ar gas pressure was 0.16 Pa. As a result, the (111) plane of the Pt electrode 22 was oriented in the film thickness direction.

  In the first embodiment, the reason why the Pt electrode 22 is set to 160 nm is that the Pt electrode 22 has a film thickness exceeding 250 nm when the film forming temperature condition of the Pt electrode 22 is 550 ° C. or higher. Since white turbidity was observed in the film itself, it is in the range which does not show white turbidity. The reason why the white turbidity was observed is considered to be that the surface roughness increased. In the present embodiment, the target surface roughness Sa is 15 [nm] or more and 20 [nm] or less. The film thickness is 160 [nm] as a value at which no void is formed in the Pt electrode 22.

Next, as the orientation control layer 23 constituting the lower electrode layer 20, a Ti film was formed with a film thickness of 5 nm. The formation conditions were such that the substrate temperature was 150 [° C.], the DC input power was 300 [W], and Ar gas was a sputtering gas, and the gas pressure was 0.14 [Pa]. At this time, the degree of vacuum of the process chamber and the transfer chamber before sputtering was set to 1.0 × 10 ⁻⁴ [Pa]. After Ti film formation, heat treatment was performed in an oxidizing atmosphere with an RTA apparatus to obtain titanium oxide. The Ti metal film was thermally oxidized and fired for 1 minute in an atmosphere of 730 [° C.] (heating rate 30 [° C./sec]), oxygen flow rate 1 [sccm] and oxygen 100 [%]. The film thickness after firing was 8.1 to 8.5 [nm]. This film thickness is measured by small angle scattering of an X-ray diffractometer and obtained by fitting.

  Next, the piezoelectric layer 30 was formed. As a piezoelectric material, the most common raw material of PZT (composition to be Zr / Ti = 52/48 after firing, Pb excess amount is 15 [atomic%]) was selected. The alkoxide which has the metal element Pb, Zr, and Ti which comprise PZT as a component was formed as a starting material. After spin-coating the first layer, it was baked for 5 minutes in an oxygen atmosphere at a temperature of 490 [° C.] using an RTA apparatus. Subsequently, the second and third layers were similarly solidified and fired, and then fired for 3 minutes in an atmosphere of dry air at 750 ° C. as firing for crystallization. The film thickness at the time of laminating these three layers (M = 3) was 250 [nm]. The lamination of these three layers was repeated in the same procedure to form a piezoelectric layer 30 having a film thickness of 2 μm as a whole.

After the piezoelectric layer 30 was formed in this manner, the piezoelectric layer 30 was evaluated.
First, when SEM observation was performed, the average particle diameter of the crystals was 0.18 μm, and the distribution range of the particle diameter was 0.05 to 0.5 μm. At this time, when the presence or absence of the white turbidity of the piezoelectric layer 30 was observed under the light of strong illuminance, the white turbidity was not observed. Moreover, when the orientation was examined by EBSD (Electron Backscatter Diffraction), it showed high orientation in the (100) crystal direction, and showed good crystallinity in the positive electrode dot diagram. The result of X-ray diffraction at this time is that the peak intensity in the crystal direction of (100) is 150 [kcps] or more (150 to 200 [kcps]), and the degree of orientation in the crystal direction of (100) is 92 to It was 95 [%]. In addition, D8 DISCOVER made by Bruker was used for the X-ray-diffraction apparatus.

After the piezoelectric layer 30 is formed in this manner, the upper electrode layer 40 is formed. Specifically, first, SrRuO ₃ , which is a conductive oxide layer, was formed to a thickness of 40 [nm] as the underlying layer 41 on the piezoelectric layer 30. The forming conditions are as follows: substrate temperature is 550 [° C.], RF input power is 400 [W], Ar gas containing 30% of O ₂ gas is sputtering gas, and the gas pressure is 1.6 [Pa] And Furthermore, a Pt electrode 42, which is a second electrode, was formed to a thickness of 125 nm. Process conditions set the substrate temperature to 300 [° C.], the RF input power to 500 [W], and the Ar gas pressure to 0.16 [Pa].

  Then, after forming a resist pattern using the technique of photolithography, etching and resist ashing of laminated structure were performed so that it might become a shape shown in FIG. The size of the Pt electrode 42 was a strip of 45 μm × 1 mm.

  Thereafter, a passivation film, which is a protective layer 50 for protecting the piezoelectric element, is formed, and formation of an interlayer insulating layer not shown, connection between the Pt electrode 42 and the wiring pattern, formation of a passivation film for protecting the wiring pattern, etc. Then, a piezoelectric element was manufactured.

After producing the piezoelectric element in this manner, polarization processing was performed, and then the leakage current between the upper and lower electrodes was measured. At this time, the side of the upper electrode layer 40 was set to a positive potential, and the side of the lower electrode layer 20 was set to a negative potential (earth potential). As polarization processing conditions, increase the voltage slowly from 0 [V] in 3 minutes to set the applied voltage to 40 [V], hold the applied voltage for 1 minute, and then slowly reduce the voltage to 0 [V] in 3 minutes I made it. In addition, as the amount of leakage current of the piezoelectric element, the amount of leakage current when 30 [V] is applied is 1.8 to 2.7 × 10 ⁻⁷ [A / cm ⁻² ] in the evaluation after polarization processing. did. The amount of leakage current is a value small enough to perform the function of the piezoelectric element. In addition, the result of these electrical characteristics is sufficient as a droplet discharge head.

  The piezoelectric element produced in this manner was used in the ink jet recording apparatus of the present embodiment, and the ink discharge evaluation was performed after the ink was filled. The ink was adjusted to a viscosity of 5 [cp], and when the driving voltage signal of -10 [V] to -30 [V] with a simple Push waveform was applied, all nozzle holes were confirmed. It was confirmed from the results that an appropriate discharge operation was performed.

Example 2
Next, another example of the piezoelectric element in the present embodiment (hereinafter, this example will be referred to as “example 2”) will be described.
The second embodiment is the same as the first embodiment except that the degree of vacuum of the process chamber at the time of forming the Pt electrode 22 and the orientation control layer 23 in the first embodiment is 9.8 × 10 ⁻⁵ [Pa]. The piezoelectric layer 30 was formed under the same conditions. Also in Example 2, when the presence or absence of the white turbidity of the piezoelectric layer 30 was observed under the light of strong illuminance, the white turbidity was not observed.

[Example 3]
Next, still another example of the piezoelectric element in the present embodiment (hereinafter, this example will be referred to as “example 3”) will be described.
The third embodiment is the same as the first embodiment except that the vacuum degree of the process chamber at the time of forming the Pt electrode 22 and the orientation control layer 23 in the first embodiment is 8.6 × 10 ⁻⁵ [Pa]. The piezoelectric layer 30 was formed under the same conditions. Also in Example 3, when the presence or absence of the white turbidity of the piezoelectric layer 30 was observed under the light of strong illuminance, the white turbidity was not observed.

Example 4
Next, still another example of the piezoelectric element in the present embodiment (hereinafter, this example will be referred to as “example 4”) will be described.
In the fourth embodiment, the vacuum degree of the process chamber at the time of formation of the Pt electrode 22 in the first embodiment is 1.1 × 10 ⁻⁵ [Pa], and the vacuum degree of the process chamber at the time of formation of the orientation control layer 23 is The piezoelectric layer 30 was formed under exactly the same conditions as in Example 1 except that the pressure was set to 8.6 × 10 ⁻⁵ [Pa]. Also in Example 4, when the presence or absence of the white turbidity of the piezoelectric layer 30 was observed under the light of the strong illuminance, the white turbidity was not observed.

[Example 5]
Next, still another example of the piezoelectric element in the present embodiment (hereinafter, this example will be referred to as “example 5”) will be described.
The piezoelectric layer 30 was formed under exactly the same conditions as in Example 1 except that the orientation control layer 23 was formed of lead titanate (PbTiO ₃ ). In addition, after forming the first layer by the sol-gel method, the orientation control layer 23 in the present example 5 does not perform thermal oxidation, but only performs solvent drying at 140 [° C.] for 3 minutes. The layers and the third layer were formed, and the three layers were collectively subjected to crystallization thermal oxidation. Also in Example 5, when the presence or absence of the white turbidity of the piezoelectric layer 30 was observed under the light of strong illuminance, the white turbidity was not observed.

Comparative Example 1
Next, a comparative example of the piezoelectric element (hereinafter, this comparative example will be referred to as “comparative example 1”) to be compared with the above-described Examples 1 to 5 will be described.
Comparative Example 1 is the same as Example 1 except that the degree of vacuum of the process chamber at the time of formation of the Pt electrode 22 and the orientation control layer 23 in Example 1 is 1.4 × 10 ⁻⁴ [Pa]. The piezoelectric layer 30 is formed under the same conditions.

  In Comparative Example 1, when the presence or absence of white turbidity of the piezoelectric layer 30 was observed under the light of strong illuminance, clear white turbidity was observed. The state of the white portion was observed by SEM, and the crystallinity was further evaluated by EBSB. Fig.2 (a) shows the result of SEM observation, FIG.2 (b) shows the analysis result of crystallinity by EBSB, FIG.2 (c) is a positive electrode dot figure. The left row of FIG. 2 shows the result of the white turbidity portion in the present comparative example 1, and the right row of FIG. 2 shows the result of the first example (non-white turbidity portion).

  As shown in the left row of FIG. 2 (a), in the white turbidity part of Comparative Example 1, a large number of portions where the boundaries of crystal grains are unclear (portions surrounded by broken lines in FIG. 3 (a)) are confirmed. On the other hand, in the non-white turbidity part of Example 1, the part in which the boundary of the crystal grain is unclear is not confirmed.

  In addition, as shown in the left column of FIG. 2 (b), in the portion where the boundaries of the crystal grains are unclear (the portion surrounded by the broken line in FIG. 3 (b)), the crystal orientation is changed compared to the other portions. The Specifically, while the target crystal orientation is (001), the crystal orientation of the portion where the crystal grain boundaries are unclear is mainly (111). In addition, it is also apparent from the positive electrode point diagram shown in the left row of FIG. 2C that the crystal directions are not aligned. When the crystal orientations are aligned, as shown in the right column of FIG. 2C, the positive electrode dot diagram becomes annular.

  Moreover, when X-ray diffraction was performed in Comparative Example 1, the peak intensity in the crystal direction of (100) is 120 kcps or less (20 to 120 kcps), and the degree of orientation in the crystal direction of (100) Was 40-82%.

FIG. 4 (a) is a graph showing the particle size distribution of the white turbidity portion in Comparative Example 1, and FIG. 4 (b) is a graph showing the particle size distribution of the white turbidity portion in Example 1. FIG.
In Comparative Example 1, as shown in FIG. 4A, the figure average crystal grain size is 0.25 μm, and the distribution range of the grain size is 0.05 to 0.85 μm, What contains a crystal grain larger than Example 1 shown in FIG.4 (b) is contained.

Comparative Examples 2 to 4
Next, other comparative examples 2 to 4 of the piezoelectric element will be described.
Comparative Example 2 is the same as Example 1 except that the degree of vacuum of the process chamber at the time of formation of the Pt electrode 22 and the orientation control layer 23 in Example 1 is 1.3 × 10 ⁻⁴ [Pa]. The piezoelectric layer 30 is formed under the same conditions.
Comparative Example 3 is the same as Example 1 except that the degree of vacuum of the process chamber at the time of formation of the Pt electrode 22 and the orientation control layer 23 in Example 1 is 1.2 × 10 ⁻⁴ [Pa]. The piezoelectric layer 30 is formed under the same conditions.
Comparative Example 4 is the same as Example 1 except that the degree of vacuum of the process chamber at the time of formation of the Pt electrode 22 and the orientation control layer 23 in Example 1 is 1.1 × 10 ⁻⁴ [Pa]. The piezoelectric layer 30 is formed under the same conditions.

  Also in the comparative examples 2 to 4, when the presence or absence of the white turbidity of the piezoelectric layer 30 was observed under the light of strong illuminance, the white turbidity was observed as in the comparative example 1. However, the degree of cloudiness was gradually reduced as the degree of vacuum was lower (closer to the vacuum state). In particular, in Comparative Example 4, there was an example in which white turbidity did not occur, but white turbidity occurred with about half of the frequency. When Example 1 and Comparative Example 4 are compared, a slight difference in pressure causes a difference in occurrence of white turbidity. This difference is considered to be due to a slight change in the interface state of the crystal, but it is not clear whether it is the difference in interface energy because the state in vacuum can not be investigated.

[Comparative Examples 5 to 7]
Next, further comparative examples 5 to 7 of the piezoelectric element will be described.
Comparative Example 5 is the same as Example 4 except that the vacuum degree of the process chamber at the time of forming the orientation control layer 23 in Example 4 is 1.5 × 10 ⁻⁴ [Pa]. The piezoelectric layer 30 is formed.
Comparative Example 6 was performed under exactly the same conditions as in Example 4 except that the degree of vacuum in the process chamber at the time of forming the orientation control layer 23 in Example 4 was set to 2.0 × 10 ⁻⁴ [Pa]. The piezoelectric layer 30 is formed.
Comparative Example 7 was performed under exactly the same conditions as in Example 4 except that the degree of vacuum in the process chamber at the time of forming the orientation control layer 23 in Example 4 was set to 2.5 × 10 ⁻⁴ [Pa]. The piezoelectric layer 30 is formed.

Table 1 below summarizes the results of Examples 1 to 5 and Comparative Examples 1 to 7 described above.

Next, a droplet discharge head using the piezoelectric element in the present embodiment will be described.
FIG. 5 is a cross-sectional view of a droplet discharge head employing the piezoelectric element of the present embodiment.
The droplet discharge head according to the present embodiment is a liquid that digs from the back surface (the lower surface in FIG. 1) of the substrate 10 to the portion of the diaphragm layer 11 by ICP (Inductively Coupled Plasma) etching using photolithography technology. The chamber portion 70 is formed. Thus, the actuator substrate 71 as the flow path forming substrate is completed. A nozzle plate 80 having a nozzle hole 79 is joined to the actuator substrate 71, and a drive circuit and an ink liquid supply mechanism are assembled to form a droplet discharge head. In FIG. 5, the description of the liquid supply means, the flow path, and the fluid resistance is omitted.

FIG. 6 is an exploded perspective view of the droplet discharge head.
In FIG. 6, the nozzle plate 80, the actuator substrate (channel forming substrate) 71, and the common channel forming substrate 72 are shown from the upper side. The actuator substrate 71 includes a flexible printed circuit (FPC) 73 on which a drive circuit for driving the piezoelectric element is mounted. Further, in FIG. 6, the common flow path forming substrate 72 has a piezoelectric element protection space 74.

Next, an example of an ink jet recording apparatus equipped with the droplet discharge head according to the present embodiment will be described with reference to FIGS. 7 and 8. FIG.
FIG. 7 is a perspective view illustrating the ink jet recording apparatus, and FIG. 8 is a side view illustrating the ink jet recording apparatus.

  The inkjet recording apparatus 100 mainly uses a carriage 101 movable in the main scanning direction inside the recording apparatus main body, a recording head 104 including a droplet discharge head 1 mounted on the carriage 101, and the recording head 104 The printing mechanism unit 103 is configured to include an ink cartridge 102 to be supplied.

  In the lower part of the apparatus main body, a sheet feeding cassette 130 capable of loading a large number of sheets P can be removably inserted from the front side, and a manual feed tray 105 for manually feeding the sheets P is provided. The sheet P fed from the sheet feeding cassette 130 or the manual feed tray 105 can be opened, and after a required image is recorded by the printing mechanism unit 103, the sheet P is discharged to the sheet discharge tray 106 mounted on the rear side. To paper.

  The printing mechanism section 103 slidably holds the carriage 101 in the main scanning direction by the main guide rods 107 and the secondary guide rods 108 which are guide members laterally extended on left and right side plates (not shown). A plurality of recording heads 104 each including an inkjet head, which is an example of the droplet discharge head 1 according to the embodiment, which discharges ink droplets of each color of (Y), cyan (C), magenta (M), and black (Bk). The ink discharge ports (nozzles) are arranged in a direction intersecting the main scanning direction, and the ink droplet discharge direction is mounted downward.

  Further, the ink cartridges 102 for supplying the ink of each color to the recording head 104 are exchangeably mounted on the carriage 101. The ink cartridge 102 has an atmosphere port communicating with the atmosphere at the upper side, a supply port for supplying the ink to the recording head 104 at the lower side, and a porous body filled with the ink inside, and the capillary of the porous body The force is used to maintain the ink supplied to the recording head 104 at a slight negative pressure.

  Here, the carriage 101 is slidably fitted on the main guide rod 107 on the rear side (downstream side in the sheet conveying direction) and slidably mounted on the secondary guide rod 108 on the front side (upstream side in the sheet conveying direction). doing. Then, in order to move and scan the carriage 101 in the main scanning direction, a timing belt 112 is stretched between a drive pulley 110 and a driven pulley 111 driven to rotate by the main scanning motor 109, and the timing belt 112 is mounted on the carriage 101. The carriage 101 is reciprocally driven by the forward and reverse rotation of the main scanning motor 109.

  On the other hand, in order to transport the sheet P set in the sheet feeding cassette 130 to the lower side of the recording head 104, the sheet P is guided by the sheet feeding roller 113 and friction pad 114 for separating and feeding the sheet P from the sheet feeding cassette 130. The guide member 115, the conveyance roller 168 for conveying the fed sheet P by inverting the sheet P, the feed roller 117 pressed against the circumferential surface of the feed roller 116, and the delivery angle of the sheet P from the feed roller 116 are defined. A tip roller 110 is provided. The conveyance roller 116 is rotationally driven by the sub scanning motor 128 via a gear train. A print receiving member 119, which is a sheet guide member for guiding the sheet P fed from the conveyance roller 116 below the recording head 104, is provided corresponding to the movement range of the carriage 101 in the main scanning direction. On the downstream side of the print receiving member 119 in the sheet conveyance direction, a conveyance roller 120 rotationally driven to feed the sheet P in the sheet ejection direction and a spur 123 are provided, and the sheet P is ejected to the sheet ejection tray 108 A roller 121 and a spur 124, and guide members 125 and 126 forming a sheet discharge path are provided.

  At the time of recording, the recording head 104 is driven according to the image signal while moving the carriage 101 to eject ink onto the stopped sheet P to record one line, and after the sheet P is conveyed by a predetermined amount, the next Record the line of By receiving a recording end signal or a signal that the trailing edge of the sheet P has reached the recording area, the recording operation is ended and the sheet P is discharged.

  Further, at a position outside the recording area on the right side in the moving direction of the carriage 101, a recovery device 127 for recovering the ejection failure of the recording head 104 is disposed. The recovery device 127 has cap means, suction means and cleaning means. The carriage 101 is moved to the recovery device 127 side while waiting for printing and the recording head 104 is capped by the capping means, and the discharge port is kept wet to prevent discharge failure due to ink drying. Further, by discharging the ink not related to the recording in the middle of the recording or the like, the ink viscosity of all the discharge ports is made constant, and the stable discharge performance is maintained.

  If a discharge failure occurs, etc., the discharge port (nozzle) of the recording head 104 is sealed by the capping unit, and bubbles and the like are sucked out together with the ink from the discharge port by the suction unit through the tube. And the like are removed by the cleaning means, and the discharge failure is recovered. Also, 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 the ink absorber inside the waste ink reservoir.

  As described above, in the ink jet recording apparatus 100, since the recording head 104 which is the droplet discharge head (ink jet head) 1 employing the piezoelectric actuator of the embodiment is mounted, stable ink droplet discharge characteristics can be obtained. , Improve the image quality.

Although the ink jet recording apparatus in the present embodiment is an example of ejecting ink, the liquid to be ejected is not limited to ink, and is not particularly limited as long as it becomes liquid when ejected. For example, DNA samples, resists, pattern materials and the like are also included.
Moreover, in this embodiment, although the example which used the piezoelectric element which is an electromechanical conversion member as an actuator of an inkjet head was demonstrated, it is not restricted to this. For example, the present invention can also be applied to drive means of a deflection mirror that deflects the direction of the deflection mirror for scanning light according to the displacement of the diaphragm layer of the actuator substrate. In addition, for example, it can be applied as a piezoelectric element of a ferroelectric memory. A ferroelectric memory is called FeRAM (Ferroelectric Random Access Memory), and as a non-volatile semiconductor memory, the polarization inversion time of a ferroelectric film is fast (1 [ns] or less), so high-speed operation similar to DRAM can be expected.

What has been described above is an example, and the present invention has unique effects in each of the following modes.
(Aspect A)
A first electrode such as a Pt electrode 22 provided on a substrate 10, and the first electrode as an underlayer or an orientation control layer 23 provided on the first electrode as an underlayer In the electromechanical conversion member such as a piezoelectric element having an electromechanical conversion layer such as a piezoelectric layer 30 and a second electrode such as a Pt electrode 42 provided on the electromechanical conversion layer, the base layer has a degree of vacuum It is characterized in that it is formed under an environment of 1.0 × 10 ⁻⁴ [Pa] or less.
As a result of intensive studies, the present inventor has found that a piezoelectric layer in which impurities such as H ₂ O, O ₂ , H ₂ and CO ₂ which may be mixed when forming an underlayer of a piezoelectric layer are aligned in a desired direction. It has been found that it has a great influence on the inability to obtain stable. That is, it is considered that gas components at the time of forming the underlayer by sputtering or the like become impurities that inhibit crystal growth. In particular, H ₂ O and O ₂ may react with the metal of the film component to form a compound, which is considered to have a great effect on stably obtaining a piezoelectric layer aligned in a desired direction. . In this embodiment, the underlayer is formed in a high vacuum state of 1.0 × 10 ⁻⁴ [Pa] or less, and the inclusion of impurities in the underlayer is suppressed. As a result, since an underlayer with few impurities can be formed, it becomes possible to stably obtain a piezoelectric layer aligned in a desired direction.

(Aspect B)
In the embodiment A, the substrate is characterized in that a laminated diaphragm layer such as a diaphragm layer 11 made of silicon nitride, silicon oxide or polysilicon is formed on a silicon substrate.
According to this, it is possible to realize a diaphragm layer which can be appropriately displaced even by a drive voltage signal having a high frequency.

(Aspect C)
In the aspect A or B, the first electrode is formed by depositing platinum or iridium by a sputtering method.
According to this, it is possible to obtain the first electrode which does not change with respect to the process of high temperature treatment by the sol-gel method or the like.

(Aspect D)
In any of the embodiments A to C, the electromechanical conversion layer is a perovskite type oxide dielectric such as PZT containing at least lead, titanium and zirconium, and the crystal direction is (100) or (001). The crystal grain size is in the range of 0.05 μm or more and 0.3 μm or less and the average grain diameter is 0.2 μm or less. It is characterized by being.
According to this, the excellent effect that the crystal grains of the electromechanical conversion layer are aligned and the variation of the deformation characteristics of the electromechanical conversion layer can be reduced is exhibited.

(Aspect E)
The aspect D is characterized in that the orientation control layer is formed of titanium oxide or lead titanate.
When titanium oxide is used as the orientation control layer, a seed crystal which newly contributes to the orientation is generated by the reaction between the titanium oxide and the PZT precursor liquid by the sol-gel method or the like to be treated thereon. By using titanium oxide having a small orientation as the orientation control layer, an electromechanical conversion layer mainly oriented to (100) or (001) can be obtained. In addition, when lead titanate is used as the orientation control layer, a seed crystal is formed as it is, and an electromechanical conversion layer having a main orientation of (100) or (001) is obtained.

(Aspect F)
A liquid chamber 70 communicated with a nozzle such as a nozzle hole 79 for discharging a droplet such as ink, and a wall portion of the liquid chamber so that the liquid in the liquid chamber can be pressurized according to an input drive signal. In a droplet discharge apparatus such as a droplet discharge head having an electromechanical conversion member for partially displacing, the electromechanical conversion member according to any one of the aspects A to E is used as the electromechanical conversion member. It is characterized by
According to this, a droplet discharge device having stable discharge performance can be obtained.

(Aspect G)
In an image forming apparatus such as an inkjet recording apparatus that forms droplets by discharging droplets from a droplet discharge device, the droplet discharge device according to aspect F is used as the droplet discharge device.
According to this, it is possible to form an image using a droplet discharge device having stable discharge performance.

(Aspect G)
After forming a first electrode such as a Pt electrode 22 on the substrate 10, an electromechanical conversion layer such as a piezoelectric layer 30 on a base layer which is the first electrode or the orientation control layer 23 provided on the first electrode In the method of manufacturing an electromechanical conversion member such as a piezoelectric element which further forms a second electrode such as a Pt electrode 42 on the electromechanical conversion layer, the base layer has a degree of vacuum of 1.0 × 10 ⁻ It is characterized in that it is formed under an environment of ⁴ [Pa] or less.
According to this, it is possible to stably obtain a piezoelectric layer aligned in a desired direction.

DESCRIPTION OF SYMBOLS 1 droplet discharge head 10 substrate 11 diaphragm layer 20 lower electrode layer 21 electrode adhesion layer 22 Pt electrode (first electrode)
23 Orientation control layer 30 Piezoelectric layer 40 Upper electrode layer 41 Underlay layer 42 Pt electrode (second electrode)
50 Protective Layer 70 Liquid Chamber 71 Actuator Substrate 72 Common Channel Forming Substrate 74 Piezoelectric Element Protective Space 79 Nozzle Hole 80 Nozzle Plate 100 Inkjet Recording Device 101 Carriage 102 Ink Cartridge 104 Recording Head

JP, 2013-251490, A

Claims (6)

The diaphragm layer, the electrode contact layer, a platinum electrode layer, and, by sequentially forming a titanium oxide emissions or Ranaru orientation control layer are sequentially formed piezoelectric layer and an upper electrode layer on the orientation control layer electrically In a method of forming a machine conversion member,
The alignment control layer composed of the titanium oxide, and wherein the formation child by sputtering in an environment at a vacuum degree of 8.6 × ¹⁰ -5 [Pa] or 1.0 × ¹⁰ -4 [Pa] or less Method of forming an electro-mechanical conversion member.   In the method of forming an electromechanical transducer according to claim 1,
  The platinum electrode layer has a degree of vacuum of 1.0 × 10 ^-4 A method of forming an electro-mechanical conversion member, characterized by forming by sputtering under an environment of [Pa] or less. In the method of forming an electromechanical transducer according to claim 2 ,
A vacuum degree at the time of forming the platinum electrode layer is 1.1 × 10 ⁻⁵ [Pa] or more. In the method of forming an electromechanical transducer according to any one of claims 1 to 3,
The piezoelectric layer is a perovskite-type oxide dielectric containing at least lead, titanium and zirconium and is formed of a polycrystal whose crystal orientation is preferentially oriented to (100) or (001), A method of forming an electromechanical transducer, wherein the crystal grain size is in the range of 0.05 μm or more and 0.3 μm or less and the average grain size is 0.2 μm or less. In the method of forming an electromechanical transducer according to any one of claims 1 to 4,
The method of forming an electromechanical transducer according to claim 1, wherein the diaphragm layer is a laminated diaphragm layer made of silicon nitride, silicon oxide, or polysilicon on a silicon substrate. In the method of forming an electromechanical transducer according to any one of claims 1 to 5,
The electro-mechanical conversion member displaces a part of a wall portion of the liquid chamber so as to be able to pressurize the liquid in the liquid chamber communicating with the nozzle that discharges the droplet according to the input drive signal. What is claimed is: 1. A method of forming an electro-mechanical transducer member, comprising: using the electro-mechanical transducer member of an ejection device.