JP2007152912A - Manufacturing method for piezoelectric element, piezoelectric element and liquid jet head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To relatively easily control a crystallinity, and to obtain a stable and good characteristic. <P>SOLUTION: A process of forming a piezoelectric layer 70 includes a first process and a second process. In the first process, a ferroelectric material is applied on a lower electrode film 60, dried and degreased, whereby a ferroelectric precursor film is formed in a predetermined thickness. At the same time, the ferroelectric precursor film is baked to form a first ferroelectric film 71a which becomes the lowest layer of a plurality of layers of ferroelectric films. In the second process, a plurality of layers of ferroelectric films 71b, 71c and 71d are formed by repeating a process by a plurality of the number of times of forming a ferroelectric precursor film in a predetermined film thickness so that a film thickness of the ferroelectric films formed on the first ferroelectric film becomes 330[nm] or smaller, and of baking the ferroelectric precursor film by a temperature rise rate of not smaller than 100[°C/sec], thereby forming the ferroelectric films. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a piezoelectric element having a piezoelectric layer made of a ferroelectric material including a piezoelectric material, a piezoelectric element, and a liquid ejecting head.

  A piezoelectric element used for a liquid jet head or the like is an element in which a piezoelectric film made of a piezoelectric material exhibiting an electromechanical conversion function is sandwiched between two electrodes, and the piezoelectric film is made of, for example, crystallized piezoelectric ceramics Has been.

  As a liquid ejecting head using such a piezoelectric element, for example, a part of a pressure generating chamber communicating with a nozzle opening for ejecting ink droplets is constituted by a vibration plate, and the vibration plate is deformed by the piezoelectric element and pressure is applied. There is an ink jet recording head that pressurizes ink in a generation chamber and ejects ink droplets from nozzle openings. Two types of ink jet recording heads have been put into practical use: those using a longitudinal vibration mode piezoelectric actuator that extends and contracts in the axial direction of the piezoelectric element, and those using a flexural vibration mode piezoelectric actuator. As an actuator using a flexural vibration mode actuator, for example, a uniform piezoelectric film is formed by a film forming technique over the entire surface of the diaphragm, and this piezoelectric layer is applied to the pressure generation chamber by a lithography method. A device in which a piezoelectric element is formed so as to be independent for each pressure generating chamber by dividing into shapes is known.

  Here, as a method for forming a piezoelectric layer constituting such a piezoelectric element, a so-called sol-gel method or the like is known. Specifically, the step of applying a sol of an organometallic compound on the substrate on which the lower electrode is formed and drying and gelling (degreasing) to form a piezoelectric precursor film is performed at least once, and thereafter And crystallize by heat treatment at high temperature. A piezoelectric layer (piezoelectric thin film) having a predetermined thickness is formed by repeating these steps a plurality of times (see, for example, Patent Document 1). As a method for forming the piezoelectric layer, a so-called MOD (Metal-Organic Decomposition) method, that is, generally, an organic metal compound such as a metal alkoxide is dissolved in alcohol, and a hydrolysis inhibitor or the like is added thereto. There is also a method in which the obtained colloid solution is applied onto an object and then dried and fired.

  According to such a method, for example, a piezoelectric layer having a thickness of 1 μm or more can be formed relatively well, and the displacement characteristics of the piezoelectric element can be improved. However, it is difficult to control crystallinity such as crystal grain size and orientation of the piezoelectric layer, and there is a problem that a piezoelectric element having desired displacement characteristics cannot be formed. Such a problem is not limited to a piezoelectric element mounted on a liquid ejecting head or the like, and similarly exists in a piezoelectric element mounted on another device.

JP-A-9-223830 (pages 4-6)

  In view of such circumstances, it is an object of the present invention to provide a piezoelectric element manufacturing method, a piezoelectric element, and a liquid ejecting head that can control crystallinity relatively easily and obtain stable and stable characteristics. .

According to a first aspect of the present invention for solving the above-described problem, a lower electrode film is formed on the surface of a flow path forming substrate on which a pressure generating chamber communicating with a nozzle opening from which droplets are ejected is formed. Forming a piezoelectric layer composed of a plurality of ferroelectric films, forming an upper electrode film on the piezoelectric layer, and at least the piezoelectric layer in a region corresponding to each pressure generating chamber And patterning the upper electrode film, and forming the piezoelectric layer comprises applying a ferroelectric material on the lower electrode film, drying and degreasing the ferroelectric precursor film to a predetermined A first step of forming a first ferroelectric film as a lowermost layer of the plurality of ferroelectric films by forming the thickness and firing the ferroelectric precursor film; and Ferroelectric precursor film so that the thickness of the ferroelectric film formed on the ferroelectric film is 330 nm or less. A process of forming the ferroelectric film by repeating the process of forming the ferroelectric film by a plurality of times by forming the ferroelectric precursor film at a temperature rising rate of 100 [° C./sec] or more while forming with a predetermined film thickness. And a second step of forming a ferroelectric film.
In the first aspect, the crystallinity of the piezoelectric layer is improved. That is, the piezoelectric layer 70 (ferroelectric film) is formed with a relatively small grain size and uniform crystals, and the formation of large crystals is substantially prevented. Thereby, since the displacement characteristic of the piezoelectric element 300 is improved, an ink jet recording head having excellent ink ejection characteristics can be realized.

In the second aspect of the present invention, in the second step, the step of applying, drying, and degreasing a ferroelectric material on the first ferroelectric film is repeated at least twice or more. In the method of manufacturing a piezoelectric element according to the first aspect, the precursor film is formed to a predetermined thickness.
In the second aspect, it is possible to improve the production efficiency and form a piezoelectric layer having excellent crystallinity in a relatively short time.

According to a third aspect of the present invention, the piezoelectric precursor film according to the first or second aspect is characterized in that, when the ferroelectric precursor film is fired, the dielectric precursor film is heated by an RTA method. It exists in the manufacturing method of an element.
In the third aspect, the ferroelectric precursor film can be heated more reliably at a temperature increase rate of 100 ° C./sec or more.

According to a fourth aspect of the present invention, in the piezoelectric element manufacturing method according to any one of the first to third aspects, the ferroelectric material is lead zirconate titanate (PZT).
In the fourth aspect, by using a predetermined ferroelectric material, a piezoelectric layer having excellent crystallinity can be obtained more reliably.

According to a fifth aspect of the present invention, there is provided a piezoelectric element manufactured by the manufacturing method according to any one of the first to fourth aspects.
In the fifth aspect, the displacement characteristics of the piezoelectric element are improved as a result of the improved crystallinity of the piezoelectric layer.

According to a sixth aspect of the present invention, there is provided a liquid ejecting head using the piezoelectric element manufactured by the manufacturing method according to the fifth aspect.
In the sixth aspect, it is possible to realize a liquid jet head with improved droplet discharge characteristics.

Hereinafter, the present invention will be described in detail based on an embodiment.
FIG. 1 is an exploded perspective view showing an outline of an ink jet recording head according to an embodiment of the present invention, FIG. 2 is a plan view of FIG. 1 and a cross-sectional view along AA ′, and FIG. 3 is a schematic diagram showing a layer structure of an element 300. FIG. As shown in the drawing, the flow path forming substrate 10 is made of a silicon single crystal substrate having a plane orientation (110) in this embodiment, and one surface thereof is made of silicon dioxide previously formed by thermal oxidation. An elastic film 50 of 5 to 2 μm is formed. A plurality of pressure generating chambers 12 are arranged in parallel in the width direction of the flow path forming substrate 10. In addition, a communication portion 13 is formed in a region on the outer side in the longitudinal direction of the pressure generation chamber 12 of the flow path forming substrate 10, and the communication portion 13 and each pressure generation chamber 12 communicate with each other via the ink supply path 14. The communication part 13 constitutes a part of a reservoir that communicates with a reservoir part of a protective substrate, which will be described later, and serves as a common ink chamber for the pressure generating chambers 12. The ink supply path 14 is formed with a narrower width than the pressure generation chamber 12, and maintains a constant flow path resistance of ink flowing into the pressure generation chamber 12 from the communication portion 13.

  Further, on the opening surface side of the flow path forming substrate 10, a nozzle plate 20 having a nozzle opening 21 communicating with the vicinity of the end portion of each pressure generating chamber 12 on the side opposite to the ink supply path 14 is provided with an adhesive or It is fixed by a heat welding film or the like.

  On the other hand, as described above, the elastic film 50 having a thickness of, for example, about 1.0 μm is formed on the side opposite to the opening surface of the flow path forming substrate 10. For example, an insulator film 55 having a thickness of about 0.4 μm is formed. Further, on the insulator film 55, a lower electrode film 60 having a thickness of, for example, about 0.2 μm, a piezoelectric layer 70 having a thickness of, for example, about 1.0 μm, and a thickness of, for example, about 0 A piezoelectric element 300 composed of an upper electrode film 80 of .05 μm is formed. Here, the piezoelectric element 300 refers to a portion including the lower electrode film 60, the piezoelectric layer 70, and the upper electrode film 80. In general, one electrode of the piezoelectric element 300 is used as a common electrode, and the other electrode and the piezoelectric layer 70 are patterned for each pressure generating chamber 12. In this embodiment, the lower electrode film 60 is used as a common electrode for the piezoelectric element 300, and the upper electrode film 80 is used as an individual electrode for the piezoelectric element 300. Absent. Further, here, the piezoelectric element 300 and the vibration plate that is displaced by driving the piezoelectric element 300 are collectively referred to as a piezoelectric actuator.

  Here, the lower electrode film 60 constituting the piezoelectric element 300 is patterned in the vicinity of both end portions of the pressure generating chamber 12 and continuously provided along the direction in which the pressure generating chambers 12 are arranged side by side. The end surface of the lower electrode film 60 in the region corresponding to the pressure generation chamber 12 is an inclined surface that is inclined at a predetermined angle with respect to the insulator film 55.

  The piezoelectric layer 70 is provided independently for each pressure generating chamber 12 and is composed of a plurality of layers of ferroelectric films 71 (71a to 71d) as shown in FIG. The first ferroelectric film 71a, which is the lowermost layer of the plurality of ferroelectric films 71, is provided only on the lower electrode film 60, and its end surface is an inclined surface continuous with the end surface of the lower electrode film 60. It has become. The second to fourth ferroelectric films 71b to 71d formed on the first ferroelectric film 71a are extended to the top of the insulator film 55 so as to cover the end surfaces which are inclined surfaces. . Further, the upper electrode film 80 is provided independently for each pressure generating chamber 12, similarly to the piezoelectric layer 70. Each upper electrode film 80 is connected to a lead electrode 90 made of, for example, gold (Au) or the like and extending to the insulator film 55.

  A protective substrate 30 having a piezoelectric element holding portion 31 for protecting the piezoelectric element 300 is joined to a region facing the piezoelectric element 300 on the flow path forming substrate 10 on which the piezoelectric element 300 is formed. Yes. The piezoelectric element holding part 31 may be sealed, but may not be sealed. Further, the protective substrate 30 is provided with a reservoir portion 32 that constitutes at least a part of the reservoir 100 serving as an ink chamber common to the pressure generation chambers 12. Furthermore, on the protective substrate 30, there is a compliance substrate 40 including a sealing film 41 made of a material having low rigidity and flexibility and a fixing plate 42 made of a hard and rigid material such as metal. It is joined. A region of the fixing plate 42 facing the reservoir 100 is an opening 43 that is completely removed in the thickness direction, and one surface of the reservoir 100 is sealed only by the sealing film 41.

  Such an ink jet recording head of this embodiment takes in ink from an external ink supply means (not shown), fills the interior from the reservoir 100 to the nozzle opening 21, and then follows a recording signal from a drive circuit (not shown). A voltage is applied between the lower electrode film 60 and the upper electrode film 80 corresponding to the pressure generation chamber 12 via the external wiring, and the elastic film 50, the insulator film 55, the lower electrode film 60, and the piezoelectric layer. By bending and deforming 70, the pressure in each pressure generating chamber 12 is increased, and ink droplets are ejected from the nozzle openings 21.

Hereinafter, a method for manufacturing the ink jet recording head according to this embodiment, particularly a method for manufacturing a piezoelectric element, will be described with reference to FIGS. First, as shown in FIG. 4A, the flow path forming substrate wafer 110 to be the flow path forming substrate 10 is thermally oxidized in a diffusion furnace at about 1100 ° C. to form a silicon dioxide film 51 constituting the elastic film 50 over the entire surface. To form. Next, as shown in FIG. 4B, a zirconium (Zr) layer is formed on the elastic film 50 (silicon dioxide film 51), and then thermally oxidized in, for example, a diffusion furnace at 500 to 1200 ° C. to form zirconium oxide ( An insulator film 55 made of ZrO ₂ ) is formed. Next, as shown in FIG. 4C, for example, a lower electrode film 60 made of platinum and iridium is formed on the insulator film 55. As a material of the lower electrode film 60, platinum, iridium or the like is suitable. This is because a piezoelectric layer 70 described later formed by sputtering or sol-gel method needs to be crystallized by baking at a temperature of about 600 to 1000 ° C. in an air atmosphere or an oxygen atmosphere after the film formation. Because. That is, the material of the lower electrode film 60 must be able to maintain conductivity under such a high temperature and oxidizing atmosphere, and lead zirconate titanate (PZT) is used as the piezoelectric layer 70 as in this embodiment. When used, it is desirable that there is little change in conductivity due to diffusion of lead oxide. For these reasons, platinum, iridium and the like are preferable.

  Next, the piezoelectric layer 70 is formed on the lower electrode film 60. The piezoelectric layer 70 is formed by stacking a plurality of ferroelectric films 71a to 71d as described above, and in the present embodiment, these ferroelectric films 71 are formed using a so-called sol-gel method. is doing. That is, after dissolving / dispersing a metal organic substance in a catalyst, applying a sol, drying and gelling to form a ferroelectric precursor film 72, and degreasing the ferroelectric precursor film 72 to release organic components. Each ferroelectric film 71 is obtained by crystallization by firing.

  Specifically, first, as shown in FIG. 5A, a crystal seed (layer) 65 made of titanium or titanium oxide is formed on the lower electrode film 60 by sputtering. Next, for example, a ferroelectric material is applied by using a spin coat method, and as shown in FIG. 5B, an uncrystallized ferroelectric precursor film 72a is formed with a predetermined thickness. Note that the thickness of the ferroelectric precursor film 72a is determined based on the thickness of the ferroelectric film 71a after the ferroelectric precursor film 72a is baked. For example, in the present embodiment, the ferroelectric precursor film 72a is formed with a predetermined thickness so that the ferroelectric film 71a has a thickness of 110 nm. The ferroelectric precursor film 72a is dried at a predetermined temperature for a predetermined time to evaporate the solvent. The temperature at which the ferroelectric precursor film 72a is dried is preferably, for example, 150 ° C. or more and 200 ° C. or less, and preferably about 180 ° C. The drying time is preferably, for example, from 5 minutes to 15 minutes, and preferably about 10 minutes.

Then, the dried ferroelectric precursor film 72a is degreased at a predetermined temperature. The degreasing referred to here is to release the organic component of the ferroelectric precursor film 72a as, for example, NO ₂ , CO ₂ , H ₂ O or the like. The heating temperature of the flow path forming substrate wafer 110 during degreasing is preferably about 300 ° C. to 500 ° C. This is because crystallization of the ferroelectric precursor film 72a starts if the temperature is too high, and sufficient degreasing cannot be performed if the temperature is too low. For example, in this embodiment, the flow path forming substrate wafer 110 is heated to about 400 ° C. by a hot plate, and the ferroelectric precursor film 72a is degreased.

  After degreasing the ferroelectric precursor film 72a in this way, the flow path forming substrate wafer 110 is inserted into, for example, an RTA (Rapid Thermal Annealing) apparatus, and the ferroelectric precursor film 72a is By baking and crystallizing at a high temperature of about 700 ° C., the first ferroelectric film 71 a is formed on the lower electrode film 60. The film thickness of the first ferroelectric film 71a is about 110 nm.

  After the first ferroelectric film 71a is thus formed, the lower electrode film 60 and the first ferroelectric film 71a are patterned at the same time. At this time, patterning is performed so that the end surfaces of the lower electrode film 60 and the first ferroelectric film 71a are inclined surfaces inclined at a predetermined angle. Specifically, as shown in FIG. 5C, a resist film 200 having a predetermined pattern is formed by applying a resist on the first ferroelectric film 71a, exposing and developing using a mask having a predetermined shape. To do. Then, as shown in FIG. 6A, when the first ferroelectric film 71a and the lower electrode film 60 are patterned by ion milling using the resist film 200 as a mask, the first ferroelectric film 71a and the lower electrode are patterned. Since the resist film 200 is gradually etched together with the film 60, the end surfaces of the lower electrode film 60 and the first ferroelectric film 71a become inclined surfaces.

  Next, as shown in FIG. 6B, a ferroelectric precursor film 72b is formed on the first ferroelectric film 71a to a predetermined thickness, specifically, the ferroelectric precursor film 72b is baked. Then, the ferroelectric film 71b is formed to have a thickness of 330 nm or less. In the present embodiment, the ferroelectric precursor film 72b having a desired thickness is obtained by repeating the coating, drying, and degreasing processes described above three times. Thereafter, the ferroelectric precursor film 72b is heated and baked at a temperature rising rate of 100 [° C./sec] or more, preferably 110 [° C./sec] or more, so that the film thickness is 330 nm or less. A second ferroelectric film 71b is formed. In the present embodiment, the second ferroelectric 71b is formed so that the film thickness is about 330 nm.

  The heating device used for firing such a ferroelectric precursor film is not particularly limited, but by using an RTA (Rapid Thermal Annealing) device, the ferroelectric precursor film can be increased by 100 [° C./sec] or more. Heating can be ensured at a temperature rate. Note that, before forming the ferroelectric film 71b, a crystal seed (crystal layer) made of titanium or titanium oxide may be formed again on the first ferroelectric film 71a.

  Thereafter, as shown in FIG. 6C, a process of applying a ferroelectric material on the second ferroelectric film 71b, and drying and degreasing the same as the second ferroelectric film 71b described above. Is repeated to form a third ferroelectric precursor film 72c, and the third ferroelectric precursor film 72c is heated and baked at a temperature rising rate of 100 [° C./sec] or more. A third ferroelectric film 71c having a thickness of 330 nm or less is formed. Further, a fourth ferroelectric film 71d is similarly formed on the third ferroelectric film 71c. As a result, a piezoelectric layer 70 composed of a plurality of ferroelectric films 71a to 71d and having a thickness of about 1 μm is formed.

  When the piezoelectric layer 70 is formed in this way, the ferroelectric precursor films 72b to 72d are formed, and then heated and baked at a temperature rising rate of 100 [° C./sec] or higher to be the ferroelectric film 71b. The crystallinity of the piezoelectric layer 70 is improved by setting each film thickness of ˜71d to 330 nm or less. That is, the piezoelectric layer 70 (ferroelectric film 71) is formed with a relatively small grain size and uniform crystals, and the formation of large grain crystals is substantially prevented. This is because the crystals of the second to fourth ferroelectric films 71b to 71d constituting the piezoelectric layer 70 are formed taking over the crystallinity of the first ferroelectric film 71a. This is probably because the first ferroelectric film 71a to the fourth ferroelectric film 71d are continuously formed. In addition, since the crystallinity of the piezoelectric layer 70 is improved in this manner, the displacement characteristics of the piezoelectric element 300 are improved. As a result, an ink jet recording head having excellent ink ejection characteristics can be realized. Further, a thin ferroelectric film (for example, the first ferroelectric film 71a) and a thick ferroelectric film (for example, the second ferroelectric film 71b) formed thereon are provided. If the difference is at least 100 nm or more, it is formed with a uniform crystal having a smaller particle size, and the formation of a larger crystal is substantially prevented.

Examples of the material of the piezoelectric layer 70 constituting the piezoelectric element 300 include a ferroelectric piezoelectric material such as lead zirconate titanate (PZT), niobium, nickel, magnesium, bismuth, A relaxor ferroelectric material to which a metal such as yttrium is added is used. The composition may be appropriately selected in consideration of the characteristics, application, etc. of the piezoelectric element 300. For example, PbTiO ₃ (PT), PbZrO ₃ (PZ), Pb (Zr _x Ti _1-x ) O ₃ (PZT) ), Pb (Mg _1/3 Nb _2/3 ) O ₃ —PbTiO ₃ (PMN-PT), Pb (Zn _1/3 Nb _2/3 ) O ₃ —PbTiO ₃ (PZN—PT), Pb (Ni ₁ ) _{/ 3 Nb 2/3) O 3 -PbTiO} 3 (PNN-PT), Pb (In 1/2 Nb 1/2) O 3 -PbTiO 3 (PIN-PT), Pb (Sc 1/2 Ta 1/2 _{) O 3 -PbTiO 3 (PST-} PT), Pb (Sc 1/2 Nb 1/2) O 3 -PbTiO 3 (PSN-PT), BiScO 3 -PbTiO 3 (BS-PT), BiYbO 3 -PbTiO 3 (BY PT), and the like. In the present embodiment, each ferroelectric film 71 constituting the piezoelectric layer 70 is formed by a sol-gel method. However, the present invention is not limited to this. For example, an organometallic compound such as a metal alkoxide is dissolved in alcohol. Then, a colloidal solution obtained by adding a hydrolysis inhibitor or the like to this is coated on the object, and then dried and baked to form a film, so-called MOD (Metal-Organic Decomposition) method May be.

  Then, after forming the piezoelectric layer 70 made of such a plurality of ferroelectric films 71a to 71d, as shown in FIG. 6D, for example, an upper electrode film 80 made of iridium (Ir) is formed. A piezoelectric element 300 is formed by laminating and patterning the piezoelectric layer 70 and the upper electrode film 80 in a region facing each pressure generating chamber 12 (FIG. 6E).

  After the piezoelectric element 300 is formed in this way, a metal layer made of gold (Au) is formed over the entire surface of the flow path forming substrate 10 as shown in FIG. A lead electrode 90 is formed by patterning this metal layer for each piezoelectric element 300 through a mask pattern (not shown).

  Next, as shown in FIG. 7B, a protective substrate wafer 130 in which a plurality of protective substrates 30 are integrally formed is bonded onto the flow path forming substrate wafer 110 with an adhesive 35. The protective substrate wafer 130 is previously formed with a piezoelectric element holding portion 31, a reservoir portion 32, and the like. Further, the protective substrate wafer 130 is, for example, a flow path forming substrate wafer having a thickness of about 400 μm, and the rigidity of the flow path forming substrate wafer 110 is remarkably improved by bonding the protective substrate wafer 130. It will be.

  Next, as shown in FIG. 7C, after the flow path forming substrate wafer 110 is polished to a certain thickness, the flow path forming substrate wafer 110 is further etched to a predetermined thickness by wet etching with hydrofluoric acid. To. For example, in this embodiment, the flow path forming substrate wafer 110 is processed to have a thickness of about 70 μm by polishing and wet etching. Next, as shown in FIG. 8A, a mask film 52 made of, for example, silicon nitride (SiN) is newly formed on the flow path forming substrate wafer 110 and patterned into a predetermined shape. Then, as shown in FIG. 8B, the flow path forming substrate wafer 110 is anisotropically etched (wet etching) through the mask film 52, so that the pressure generating chamber is formed in the flow path forming substrate wafer 110. 12, a communication portion 13, an ink supply path 14, and the like are formed.

  Thereafter, unnecessary portions of the outer peripheral edge portions of the flow path forming substrate wafer 110 and the protective substrate wafer 130 are removed by cutting, for example, by dicing. The nozzle plate 20 having the nozzle openings 21 formed on the surface of the flow path forming substrate wafer 110 opposite to the protective substrate wafer 130 is bonded, and the compliance substrate 40 is bonded to the protective substrate wafer 130. The ink jet type recording head having the above-described structure is manufactured by dividing the flow path forming substrate wafer 110 and the like into a single chip size flow path forming substrate 10 as shown in FIG.

(Test example)
In forming the ferroelectric film, the thickness of the ferroelectric precursor film and the temperature increase rate when firing the ferroelectric precursor film were changed to change the following Examples 1 and 2 and Comparative Example 1 , 2 samples were prepared, and the surface area of large crystals generated in the ferroelectric films of the examples and comparative examples were examined. The results are shown in Table 1 below. Moreover, the SEM image of the surface of the ferroelectric film which concerns on the sample of each Example and each comparative example is shown in FIG.9 and FIG.10. Here, the surface area of the large crystal is the ratio of the surface area of the large crystal to the surface area of the ferroelectric film.

Example 1
A first ferroelectric precursor film having a predetermined thickness is formed on the lower electrode film formed on the substrate, and the first ferroelectric film is formed at a temperature rising rate of about 100 [° C./sec]. A first ferroelectric film having a thickness of about 110 nm was formed by heating and baking. Then, a second ferroelectric precursor film is formed by repeating a process of applying a ferroelectric material on the first ferroelectric film, drying and degreasing three times, and then, forming the second ferroelectric film. The ferroelectric precursor film was heated at a temperature elevation rate of about 100 [° C./sec] and baked to form a second ferroelectric film having a thickness of about 330 nm as the sample of Example 1. did.

(Example 2)
Similar to the first embodiment, a first ferroelectric film having a thickness of about 110 nm is formed on the lower electrode film, and the same conditions as the first ferroelectric film are formed on the first ferroelectric film. A second ferroelectric film having a thickness of about 330 nm was formed. Then, a ferroelectric material is applied onto the second ferroelectric film, and a third ferroelectric precursor film is formed by repeating the drying and degreasing processes twice. Thereafter, the third ferroelectric film is formed. A sample of Example 2 in which a ferroelectric precursor film was heated at a rate of about 100 [° C./sec] and baked to form a third ferroelectric film having a thickness of about 220 nm. It was.

(Comparative Example 1)
A sample of Comparative Example 1 was obtained in the same manner as in Example 1 except that the rate of temperature increase when firing the second ferroelectric precursor film was about 30 [° C./sec].

(Comparative Example 2)
A sample of Comparative Example 2 was obtained in the same manner as in Example 1 except that the temperature rising rate when firing the second ferroelectric precursor film was about 60 [° C./sec].

  As shown in FIGS. 9 and 10 and Table 1 above, in the samples of Comparative Examples 1 and 2, there were relatively many large crystals in the ferroelectric film, and the surface area of the large crystals was 30% or more. On the other hand, in the samples of Examples 1 and 2, there were almost no large crystals in the ferroelectric film, and the surface area of the large crystals was less than 5%. The (100) diffraction intensity in the four layers of the ferroelectric film was 450 to 600 [cps], and the (100) half width was 0.22 to 0.25 °. Therefore, according to the manufacturing method of the present invention, high crystallinity of the piezoelectric layer and high displacement characteristics of the piezoelectric element can be expected. If the large grain surface area is about 10% or less, sufficient displacement characteristics can be obtained for a piezoelectric element used in an ink jet recording head.

(Other embodiments)
As mentioned above, although embodiment of this invention was described, the structure of this invention is not limited to what was mentioned above. For example, in the above-described embodiment, the second to fourth ferroelectric films 71b to 71d formed on the first ferroelectric film 71a are formed by repeating the coating, drying and degreasing processes three times. The ferroelectric precursor films 72b to 72d are formed by firing after the body precursor films 72b to 72d are formed. Of course, the invention is not limited to this. Each of the ferroelectric precursor films 72b to 72d only needs to have a film thickness of 330 nm or less after firing, and the number of repetitions of the coating, drying, and degreasing processes may be twice. Of course, it may be four times or more. However, it is preferable that the second to fourth ferroelectric films 72b to 72d repeat the coating, drying and degreasing processes twice or more. That is, it is preferable that the second to fourth ferroelectric films 72b to 72d are formed relatively thick in the range of 330 nm or less. This is because the piezoelectric layer 70 having excellent crystallinity can be formed in a relatively short time by reducing the number of firings.

  In the above-described embodiment, the ink jet recording head has been described as an example. However, the present invention is widely intended for all liquid ejecting heads. Examples of the liquid ejecting head include a recording head used in an image recording apparatus such as a printer, a color material ejecting head used for manufacturing a color filter such as a liquid crystal display, an organic EL display, and an electrode formation such as an FED (surface emitting display). Electrode material ejecting heads used in manufacturing, bioorganic matter ejecting heads used in biochip production, and the like. Furthermore, it goes without saying that the present invention can be applied not only to the piezoelectric element used in the liquid ejecting head but also to any other device, for example, a piezoelectric element mounted on a microphone, a sounding body, various vibrators, an oscillator, and the like. Yes.

FIG. 3 is an exploded perspective view of the recording head according to the first embodiment. 2A and 2B are a plan view and a cross-sectional view of the recording head according to the first embodiment. FIG. 2 is a schematic diagram illustrating a layer structure of a piezoelectric element 300 according to Embodiment 1. 5 is a cross-sectional view illustrating a manufacturing process of the recording head according to Embodiment 1. FIG. 5 is a cross-sectional view illustrating a manufacturing process of the recording head according to Embodiment 1. FIG. 5 is a cross-sectional view illustrating a manufacturing process of the recording head according to Embodiment 1. FIG. 5 is a cross-sectional view illustrating a manufacturing process of the recording head according to Embodiment 1. FIG. 5 is a cross-sectional view illustrating a manufacturing process of the recording head according to Embodiment 1. FIG. It is a SEM image of the surface of the ferroelectric film which concerns on the sample of an Example. It is a SEM image of the surface of the ferroelectric film which concerns on the sample of a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Flow path formation board | substrate, 12 Pressure generation chamber, 20 Nozzle plate, 21 Nozzle opening, 30 Protection board, 31 Piezoelectric element holding | maintenance part, 32 Reservoir part, 40 Compliance board | substrate, 50 Elastic film, 55 Insulator film, 60 Lower electrode film , 70 piezoelectric film, 80 upper electrode film, 100 reservoir, 300 piezoelectric element

Claims (6)

A piezoelectric body composed of a plurality of ferroelectric films on a lower electrode film after forming a lower electrode film on the surface of a flow path forming substrate in which a pressure generating chamber communicating with a nozzle opening for ejecting droplets is formed Forming a layer, forming an upper electrode film on the piezoelectric layer, and patterning at least the piezoelectric layer and the upper electrode film in a region corresponding to each pressure generating chamber,
The step of forming the piezoelectric layer comprises applying a ferroelectric material on the lower electrode film, drying and degreasing to form a ferroelectric precursor film with a predetermined thickness, and forming the ferroelectric precursor film. A first step of firing to form a first ferroelectric film which is a lowermost layer of the plurality of ferroelectric films; and a film of a ferroelectric film formed on the first ferroelectric film The ferroelectric precursor film is formed with a predetermined thickness so that the thickness is 330 [nm] or less, and the ferroelectric precursor film is baked at a temperature rising rate of 100 [° C./sec] or more. And a second step of forming the multi-layered ferroelectric film by repeating the step of forming the ferroelectric film a plurality of times. In the second step, the step of applying, drying and degreasing a ferroelectric material on the first ferroelectric film is repeated at least twice, so that the ferroelectric precursor film has a predetermined thickness. The method for manufacturing a piezoelectric element according to claim 1, wherein the piezoelectric element is formed. 3. The method of manufacturing a piezoelectric element according to claim 1, wherein the dielectric precursor film is heated by an RTA method when the ferroelectric precursor film is baked. The method for manufacturing a piezoelectric element according to claim 1, wherein the ferroelectric material is lead zirconate titanate (PZT). A piezoelectric element manufactured by the manufacturing method according to claim 1. A liquid ejecting head using the piezoelectric element manufactured by the manufacturing method according to claim 5.

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