JP2006093312A - Piezoelectric element, liquid injection head, and their manufacturing methods - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric element capable of improving the characteristics of a piezoelectric layer constituting the piezoelectric element with the characteristics of the piezoelectric layer being stabilized, also to provide a liquid injection head using the piezoelectric element and its manufacturing method, and further to provide a liquid injection apparatus using the piezoelectric element. <P>SOLUTION: There are provided a lower electrode formed via a diaphragm, a piezoelectric layer formed on the lower electrode, and an upper electrode formed on the piezoelectric layer. The surface roughness Ra of the lower electrode ranges from 0.05 to 2 nm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a piezoelectric element, a liquid ejecting head, a liquid ejecting apparatus, and a method for manufacturing a piezoelectric element.

  An actuator device including a piezoelectric element that is displaced by applying a voltage is mounted on, for example, a liquid ejecting head that ejects droplets. As such a liquid ejecting head, for example, a part of a pressure generation chamber communicating with a nozzle opening is configured by a vibration plate, and the vibration plate is deformed by a piezoelectric element so as to pressurize ink in the pressure generation chamber to form a nozzle opening. Inkjet recording heads that discharge ink droplets are known. Two types of ink jet recording heads have been put into practical use: those equipped with a piezoelectric actuator device in a longitudinal vibration mode that extends and contracts in the axial direction of the piezoelectric element, and those equipped with a piezoelectric actuator device in a flexural vibration mode. Yes. As an actuator using a flexural vibration mode actuator, for example, a uniform piezoelectric film is formed over the entire surface of the diaphragm by a film forming technique, and this piezoelectric layer is formed into a pressure generating chamber by a lithography method. There is one in which a piezoelectric element is formed so as to be independent for each pressure generating chamber by cutting into corresponding shapes.

  As the piezoelectric layer (piezoelectric thin film), for example, a ferroelectric such as lead zirconate titanate (PZT) is used. Such a piezoelectric thin film is formed, for example, by forming a titanium crystal on the lower electrode by sputtering or the like, and forming a piezoelectric precursor film on the titanium crystal by a sol-gel method. The film is formed by firing (see, for example, Patent Document 1).

  When the piezoelectric layer is formed by such a method, the crystal of the piezoelectric layer grows with the titanium crystal as a nucleus, and a relatively dense columnar crystal can be obtained. However, it is difficult to control the crystallinity of the piezoelectric layer, and the electrical or mechanical characteristics of the piezoelectric layer cannot be made uniform, resulting in variations in the displacement characteristics of the piezoelectric elements. . Such a problem exists not only when manufacturing an actuator device mounted on a liquid ejecting head such as an ink jet recording head but also when manufacturing an actuator device mounted on another device.

JP 2001-274472 A (page 5)

  In view of the circumstances described above, the present invention provides a piezoelectric element that can improve the characteristics of the piezoelectric layer constituting the piezoelectric element and stabilize the characteristics of the piezoelectric layer, a liquid ejecting head using the piezoelectric element, a manufacturing method thereof, and the It is an object to provide a liquid ejecting head and a liquid ejecting apparatus using a piezoelectric element.

According to a first aspect of the present invention for solving the above problems, a lower electrode formed via a diaphragm, a piezoelectric layer formed on the lower electrode, and an upper electrode formed on the piezoelectric layer And the surface roughness Ra of the lower electrode is in the range of 0.05 to 2 nm.
In the first aspect, since the surface roughness Ra of the lower electrode is controlled in the range of 0.05 to 2 nm, the characteristics of the piezoelectric layer are improved.

According to a second aspect of the present invention, in the first aspect, the lower electrode has an adhesion layer that is a lowermost layer located on the diaphragm side, and a surface roughness of the adhesion layer is a surface of the lower electrode. The piezoelectric element is characterized by being smaller in roughness.
In the second aspect, the surface roughness Ra of the adhesion layer is controlled to be smaller than the surface roughness of the lower electrode, that is, smaller than 2 nm, and the surface roughness Ra of the lower electrode having a layer laminated thereon is It is controlled relatively easily in the range of 0.05 to 2 nm.

According to a third aspect of the present invention, in the piezoelectric element according to the second aspect, the adhesion layer is made of titanium (Ti).
In the third aspect, the surface roughness of the lower electrode is relatively easily controlled by controlling the surface roughness of the adhesion layer made of titanium.

According to a fourth aspect of the present invention, in the second or third aspect, the lower electrode is located on the piezoelectric layer side and includes a first layer containing Ir, and a lower layer located on the lower side of the first layer. And a second layer including the piezoelectric element.
In the fourth aspect, the lower electrode has a first layer containing Ir on the piezoelectric layer side and a second layer containing Pt on the lower side of the first layer, and the surface roughness of the adhesion layer is By the control, the surface roughness Ra of the first layer becomes 2 nm or less relatively easily.

A fifth aspect of the present invention is the piezoelectric element according to the fourth aspect, wherein the lower electrode has a third layer containing Ir between the adhesion layer and the second layer.
The fifth aspect includes a third layer containing Ir provided on the adhesion layer, a second layer provided on the third layer, and a first layer provided on the second layer. The surface roughness Ra of the first layer is controlled to 2 nm or less.

A sixth aspect of the present invention is the piezoelectric element according to any one of the first to fifth aspects, wherein the piezoelectric layer is preferentially oriented in a rhombohedral (100) plane. .
In the sixth aspect, since the crystal orientation of the piezoelectric layer is controlled, the mechanical characteristics are excellent.

According to a seventh aspect of the present invention, in any one of the first to sixth aspects, the piezoelectric layer is formed on a seed Ti layer provided at a desired thickness on the lower electrode. The piezoelectric element is characterized by the above.
In the seventh aspect, since the piezoelectric layer is formed on the seed Ti layer provided on the lower electrode whose surface roughness is controlled, the crystallinity is improved.

According to an eighth aspect of the present invention, there is provided a liquid ejecting head including the piezoelectric element according to any one of the first to seventh aspects as a piezoelectric actuator.
According to the eighth aspect, a liquid jet head including a piezoelectric actuator with improved displacement characteristics can be realized.

According to a ninth aspect of the invention, there is provided a liquid ejecting apparatus including the liquid ejecting head according to the eighth aspect.
In the ninth aspect, since the liquid ejecting head including the piezoelectric actuator with improved displacement characteristics is mounted, a liquid ejecting apparatus with improved liquid ejecting characteristics can be realized.

According to a tenth aspect of the present invention, there is provided a step of forming a lower electrode on a diaphragm provided on one surface of a substrate so that the surface roughness Ra is in the range of 0.05 to 2 nm, and the lower electrode A step of applying titanium (Ti) by sputtering to form a seed titanium layer, and applying a piezoelectric material on the seed titanium layer to form a piezoelectric precursor film, and forming the piezoelectric precursor film The piezoelectric element manufacturing method includes a step of forming the piezoelectric layer by firing and crystallizing, and a step of forming an upper electrode on the piezoelectric layer.
In the tenth aspect, since the seed titanium layer is provided on the lower electrode whose surface roughness is controlled to a predetermined value to form the piezoelectric layer, the seed titanium layer effectively acts to improve the crystallinity. A piezoelectric element having the piezoelectric layer can be manufactured relatively easily.

According to an eleventh aspect of the present invention, in the tenth aspect, in the step of forming the lower electrode, the adhesion layer is formed on the diaphragm so that the surface roughness Ra is in the range of 0.05 to 2 nm. Forming, forming a first Ir layer on the adhesion layer, forming a Pt layer on the first Ir layer, and forming a second Ir layer on the Pt layer. And a step of manufacturing the piezoelectric element.
In the eleventh aspect, the surface roughness of the first Ir layer, the Pt layer, and the second Ir layer laminated thereon is controlled by controlling the surface roughness of the adhesion layer to be in a desired range. The lower electrode having a surface roughness Ra in the range of 0.05 to 2 nm can be manufactured relatively easily.

A twelfth aspect of the present invention is the method for manufacturing a piezoelectric element according to the eleventh aspect, wherein the adhesion layer is made of titanium (Ti).
In the twelfth aspect, by controlling the surface roughness of the adhesion layer made of titanium, the surface roughness of each layer laminated thereon can be controlled relatively easily.

A thirteenth aspect of the present invention is the manufacture of a piezoelectric element according to the eleventh or twelfth aspect, wherein the adhesion layer is formed by a sputtering method under a pressure of 0.01 to 0.2 Pa. Is in the way.
In the thirteenth aspect, the surface roughness Ra is relatively easily in the range of 0.05 to 2 nm by forming the adhesion layer by sputtering under a pressure of 0.01 to 0.2 Pa. It can be a layer.

A fourteenth aspect of the present invention is that, in the thirteenth aspect, the adhesion layer is formed by sputtering under conditions where the temperature is in the range of room temperature to 200 ° C. and the power density is 3 to 10 kW / m ^2. It is in the manufacturing method of the piezoelectric element characterized.
In the fourteenth aspect, an adhesion layer having a surface roughness Ra in the range of 0.05 to 2 nm can be formed relatively easily.

According to a fifteenth aspect of the present invention, in any one of the first to fourteenth aspects, the first Ir layer, the Pt layer, and the second Ir layer have a power density of 8 to 30 kW / m ² , 0. The piezoelectric element manufacturing method is characterized by being formed by sputtering under the conditions of a pressure of 0.01 to 0.3 Pa and a temperature of room temperature to 200 ° C.
In the fifteenth aspect, a lower electrode having a surface roughness Ra in the range of 0.05 to 2 nm can be manufactured relatively easily.

  Hereinafter, the present invention will be described in detail based on embodiments.

(Embodiment 1)
FIG. 1 is an exploded perspective view showing an ink jet recording head as an example of a liquid jet head according to Embodiment 1 of the present invention, and FIG. 2 is a plan view and a cross-sectional view of 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. The flow path forming substrate 10 is formed by anisotropic etching from the other side, and a plurality of pressure generating chambers 12 partitioned by the partition walls 11 are arranged in parallel in the width direction. In addition, a communication portion 13 is formed in a region outside the longitudinal direction of the pressure generation chamber 12 of the flow path forming substrate 10, and the communication portion 13 and each pressure generation chamber 12 are provided for each pressure generation chamber 12. Communication is made via a supply path 14. 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, 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 on the opening surface side of the flow path forming substrate 10 will be described later. It is fixed by an adhesive, a heat welding film or the like through a mask film. The nozzle plate 20 has a thickness of, for example, 0.01 to 1 mm, a linear expansion coefficient of 300 ° C. or less, for example, 2.5 to 4.5 [× 10 ⁻⁶ / ° C.], glass ceramics, silicon It consists of a single crystal substrate or non-rust steel.

On the other hand, as described above, the elastic film 50 made of silicon dioxide (SiO ₂ ) 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. On the elastic film 50, an insulator film 55 made of zirconium oxide (ZrO ₂ ) having a thickness of, for example, about 0.4 μm is formed. Further, on the insulator film 55, a lower electrode film 60 having a thickness of, for example, about 0.1 to 0.2 μm, a piezoelectric layer 70 having a thickness of, for example, about 1.0 μm, and a thickness of For example, the upper electrode film 80 of about 0.05 μm is laminated and formed by a process described later to constitute the piezoelectric element 300.

  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 addition, here, a portion that is configured by any one of the patterned electrodes and the piezoelectric layer 70 and in which piezoelectric distortion is generated by applying a voltage to both electrodes is referred to as a piezoelectric active portion. In the present embodiment, the lower electrode film 60 is used as a common electrode of the piezoelectric element 300 and the upper electrode film 80 is used as an individual electrode of the piezoelectric element 300. However, there is no problem even if this is reversed for convenience of a drive circuit and wiring. In either case, a piezoelectric active part is formed for each pressure generating chamber.

  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. In the example described above, the elastic film 50, the insulator film 55, and the lower electrode film 60 serve as a diaphragm.

  Further, a lead electrode 90 is connected to the upper electrode film 80 of each piezoelectric element 300, and a voltage is selectively applied to each piezoelectric element 300 via the lead electrode 90. .

  Here, the surface roughness Ra (arithmetic mean roughness) of the lower electrode film 60 which is the base of the piezoelectric layer 70 constituting the piezoelectric element 300 is in the range of 0.05 to 2 nm, preferably 1.5 nm or less. More preferably, it is 1.0 nm or less. As will be described in detail later, the characteristics of the piezoelectric layer 70 are improved by controlling the surface roughness Ra of the lower electrode film 60 within a desired range. Note that it is considered that the smaller the surface roughness of the lower electrode film 60 is, the more the characteristics of the piezoelectric layer 70 are improved. If the surface roughness is larger than the above range, the effect of remarkably improving the characteristics of the piezoelectric layer 70 cannot be obtained. On the other hand, it is practically difficult to obtain a surface roughness smaller than the above range.

  Further, the protective substrate 30 having the piezoelectric element holding portion 31 is bonded to the surface of the flow path forming substrate 10 on the piezoelectric element 300 side in a region facing the piezoelectric element 300 via an adhesive. Since the piezoelectric element 300 is formed in the piezoelectric element holding part 31, it is protected in a state hardly affected by the external environment. Further, the protective substrate 30 is provided with a reservoir portion 32 in a region corresponding to the communication portion 13 of the flow path forming substrate 10. In this embodiment, the reservoir portion 32 is provided along the direction in which the pressure generating chambers 12 are arranged so as to penetrate the protective substrate 30 in the thickness direction, and as described above, the communication portion of the flow path forming substrate 10. The reservoir 100 is connected to the pressure generation chamber 12 and serves as a common ink chamber for the pressure generation chambers 12.

  In addition, a through hole 33 that penetrates the protective substrate 30 in the thickness direction is provided in a region between the piezoelectric element holding portion 31 and the reservoir portion 32 of the protective substrate 30, and the lower electrode film 60 is provided in the through hole 33. And the other end of the connection wiring having one end connected to the drive IC (not shown) are connected to the lower electrode film 60 and the lead electrode 90.

  In addition, examples of the material of the protective substrate 30 include glass, ceramic material, metal, resin, and the like, but it is more preferable that the material is substantially the same as the coefficient of thermal expansion of the flow path forming substrate 10. In this embodiment, the silicon single crystal substrate made of the same material as the flow path forming substrate 10 is used.

  A compliance substrate 40 including a sealing film 41 and a fixing plate 42 is bonded onto the protective substrate 30. The sealing film 41 is made of a material having low rigidity and flexibility (for example, a polyphenylene sulfide (PPS) film having a thickness of 6 μm). Yes. The fixing plate 42 is made of a hard material such as metal (for example, stainless steel (SUS) having a thickness of 30 μm). Since the region of the fixing plate 42 facing the reservoir 100 is an opening 43 that is completely removed in the thickness direction, one surface of the reservoir 100 is sealed only with a flexible sealing film 41. Has been.

  In such an ink jet recording head of this embodiment, ink is taken in from an external ink supply means (not shown), filled with ink from the reservoir 100 to the nozzle opening 21, and then in accordance with a recording signal from a drive IC (not shown). Then, a voltage is applied between each of the lower electrode film 60 and the upper electrode film 80 corresponding to the pressure generation chamber 12 to bend and deform the elastic film 50, the insulator film 55, the lower electrode film 60, and the piezoelectric layer 70. As a result, the pressure in each pressure generating chamber 12 increases and ink is ejected from the nozzle openings 21.

  Here, a method of manufacturing such an ink jet recording head will be described with reference to FIGS. 3 to 6 are cross-sectional views of the pressure generating chamber 12 in the longitudinal direction. First, as shown in FIG. 3A, a channel forming substrate wafer 110 which is a silicon wafer is thermally oxidized in a diffusion furnace at about 1100 ° C., and a silicon dioxide film 51 constituting an elastic film 50 is formed on the surface thereof. To do. In this embodiment, a silicon wafer having a relatively thick film thickness of about 625 μm and a high rigidity is used as the flow path forming substrate wafer 110.

  Next, as shown in FIG. 3B, an insulator film 55 made of zirconium oxide is formed on the elastic film 50 (silicon dioxide film 51). Specifically, a zirconium (Zr) layer is formed on the elastic film 50 (silicon dioxide film 51) by DC sputtering or RF sputtering. At this time, the surface roughness (arithmetic average roughness Ra) of the zirconium layer is controlled to be 1 to 3 nm, preferably 1.5 nm or more, and more preferably greater than 2.0 nm.

  Furthermore, it is preferable that the (002) plane orientation degree of the surface of the zirconium layer is 80% or more. Here, “degree of orientation” refers to the ratio of the diffraction intensity generated when the zirconium layer is measured by the X-ray diffraction wide angle method. Specifically, when the zirconium layer is measured by the X-ray diffraction wide angle method, peaks of diffraction intensity corresponding to the (100) plane, the (002) plane, and the (101) plane are generated. The “(002) plane orientation degree” means the ratio of the peak intensity corresponding to the (002) plane to the sum of the peak intensity corresponding to each plane.

  And in order to make surface roughness Ra of a zirconium layer into the range of 1-3 nm in this way, it is preferable that the sputtering output at the time of forming a zirconium layer shall be 500 W or less. The sputtering temperature is preferably room temperature (about 23 to 25 ° C.). Furthermore, the sputtering pressure is preferably 0.5 Pa or more. Further, the target interval (distance between the target and the substrate) is preferably set to 100 mm or less. Thus, by appropriately selecting the film forming conditions and forming the zirconium layer, the surface roughness Ra of the zirconium layer can be controlled within the range of 1 to 3 nm, and at the same time the (002) plane orientation degree is 80. % Or more.

  After the zirconium layer is thus formed, the zirconium layer is thermally oxidized to form an insulator film 55 made of zirconium oxide. The heating temperature at this time is 900 ° C. or less, preferably 700 to 900 ° C. Thus, by adjusting the heating temperature during thermal oxidation, the insulator film 55 is formed so that the surface roughness Ra is within a range of 1 to 3 nm. For example, in this embodiment, the flow path forming substrate wafer 110 is inserted into a diffusion furnace in an oxygen atmosphere heated to about 700 to 900 ° C. at a speed of 300 mm / min or more, preferably 500 mm / min or more. The zirconium layer was thermally oxidized for about 15-60 minutes.

  Thereby, the insulator film 55 having a good crystal state is obtained, and the surface roughness Ra of the insulator film 55 falls within the range of 1 to 3 nm. That is, the crystal of zirconium oxide constituting the insulator film 55 grows substantially uniformly and becomes a continuous columnar crystal from the lower surface to the upper surface, so that the surface roughness Ra becomes relatively rough within a range of 1 to 3 nm. . In this embodiment, the insulator film 55 is provided. However, the insulator film 55 is not necessarily provided, and the surface roughness may be outside the above range.

  Next, as shown in FIG. 3C, for example, a lower electrode film 60 made of at least platinum and iridium is formed on the entire surface of the insulator film 55 by sputtering or the like. In the present embodiment, the adhesion layer 61 is formed on the lowermost layer, the Ir layer 62 is formed on the third layer, the Pt layer 63 is formed on the second layer, and the Ir layer 64 is formed on the first layer to form the lower electrode film 60. Here, if the surface roughness of the lower electrode film 60, that is, the surface roughness Ra of the first Ir layer 64 is in the range of 0.05 to 2 nm, the characteristics of the piezoelectric layer 70 as described above. In the present embodiment, the surface roughness of the adhesion layer 61, the Ir layer 62, and the Pt layer 63, particularly the adhesion layer 61 is adjusted by adjusting the film formation conditions of the Ir layer 64 (lower electrode). By controlling the film 60) to be smaller than the desired surface roughness, the surface roughness Ra of the Ir layer 64 is controlled to a desired range relatively easily.

  Here, the thickness of the adhesion layer 61 is preferably 10 nm or more so as to ensure adhesion. The adhesion layer 61 is for improving the adhesion between the lower electrode film 60 and the underlying layer, and may be a metal layer such as titanium (Ti) or chromium (Cr), preferably a Ti layer. In this embodiment, the Ti layer is used.

In this embodiment, the adhesion layer 61, the Ir layer 62, the Pt layer 63, and the Ir layer 64 are sequentially stacked by a sputtering method such as a DC sputtering method or an RF sputtering method. Here, the Ti layer as the adhesion layer 61 is preferably formed under a pressure of 0.2 Pa or less. This is because if the pressure is higher than this, the surface roughness becomes large and the smoothness becomes poor, and as a result, the condition that the surface roughness Ra of the lower electrode film 60 is 2 nm or less cannot be satisfied. The power density is 3 kW · m ² or more, preferably at most about 10 kW · m ² , and the temperature is preferably in the range of room temperature (about 23 to 25 ° C.) to 200 ° C.

The Ir layer 62, the Pt layer 63, and the Ir layer 64 formed on the adhesion layer 61 that has become a relatively smooth layer as described above can be formed relatively smoothly due to the smoothness of the adhesion layer 61. Each layer can be formed preferably under conditions of, for example, a pressure of 0.3 Pa or less, a power density of 30 kW · m ² or less, and a temperature of 200 ° C. or less.

  When manufactured under such conditions, the lower electrode film 60 having good crystallinity, a smooth surface and almost no defects can be obtained. In particular, when the adhesion layer 61 is provided under the above-described conditions, variations in the surface roughness of the base, for example, the insulator layer 55 within the same wafer are reduced. For example, the surface roughness Ra of the insulator film 55 is reduced. The variation of the surface roughness Ra of the lower electrode film 60 can be suppressed to a very small value with respect to the variation of about 1.7 nm in the central portion and about 1.4 nm in the outer peripheral portion. With such a layer structure, a piezoelectric precursor film is formed by firing a piezoelectric film as will be described later, so that a first layer containing Ir and Pt are included in this order from the piezoelectric layer side. The lower electrode film 60 is composed of the second layer, the third layer containing Ir, and the lowermost layer containing Ti.

Next, as shown in FIG. 3D, after patterning the lower electrode film 60 into a predetermined shape, titanium (Ti) is sputtered onto the lower electrode film 60 and the insulator film 55, for example, DC sputtering. The seed titanium layer 65 having a predetermined thickness is formed by coating twice or more in this embodiment. The sputtering conditions at this time are not particularly limited, but the sputtering pressure is preferably in the range of 0.4 to 4.0 Pa. The sputtering output is preferably 50 to 100 W, and the sputtering temperature is preferably in the range of room temperature (about 23 to 25 ° C.) to 200 ° C. Furthermore, the power density is preferably about 1 to 4 kW / m ² . Further, as described above, here, by applying titanium twice, a large number of seed titanium serving as the crystal nucleus of the piezoelectric layer 70 to be formed in the next step can be formed.

  Next, a piezoelectric layer 70 made of, for example, lead zirconate titanate (PZT) is formed on the seed titanium layer 65 thus formed. In the present embodiment, a so-called sol-gel method is used in which a so-called sol in which a metal organic substance is dissolved and dispersed in a catalyst is applied and dried to be gelled, and further fired at a high temperature to obtain a piezoelectric layer 70 made of metal oxide. Thus, the piezoelectric layer 70 made of PZT was formed.

  As a procedure for forming the piezoelectric layer 70, first, as shown in FIG. 4A, a piezoelectric precursor film 71 which is a PZT precursor film is formed on the seed titanium layer 65. That is, a sol (solution) containing a metal organic compound is applied onto the flow path forming substrate wafer 110. Next, the piezoelectric precursor film 71 is heated to a predetermined temperature and dried for a predetermined time, and the sol solvent is evaporated to dry the piezoelectric precursor film 71. Further, the piezoelectric precursor film 71 is degreased at a constant temperature for a predetermined time in an air atmosphere. In addition, degreasing here is removing the organic component of a sol film.

  Then, by repeating such coating, drying, and degreasing processes a predetermined number of times, for example, twice in the present embodiment, the piezoelectric precursor film 71 has a predetermined thickness as shown in FIG. Then, the piezoelectric precursor film 71 is crystallized by heat treatment in a diffusion furnace to form the piezoelectric film 72. That is, by firing the piezoelectric precursor film 71, crystals grow with the seed titanium layer 65 as a nucleus to form the piezoelectric film 72. For example, in this embodiment, the piezoelectric precursor film 71 is baked by heating at about 700 ° C. for 30 minutes to form the piezoelectric film 72. The crystal of the piezoelectric film 72 thus formed is preferentially oriented in the (100) plane.

  Further, by repeating the above-described coating, drying, degreasing, and firing steps a plurality of times, as shown in FIG. 4C, a predetermined thickness composed of a plurality of layers, in this embodiment, five layers of piezoelectric films 72. The piezoelectric layer 70 is formed. For example, when the film thickness per sol application is about 0.1 μm, the entire film thickness of the piezoelectric layer 70 is about 1 μm.

  By forming the piezoelectric layer 70 through the steps as described above, the characteristics of the piezoelectric layer 70 can be improved and the characteristics can be stabilized. That is, the crystallinity of the piezoelectric layer 70, for example, the degree of orientation, the strength, the particle size, and the like are easily affected by the base, but in the present invention, the surface roughness Ra of the lower electrode film 60 serving as the base is set to 0. The seed titanium of the seed titanium layer 65 provided on the seed titanium layer 65 can be effectively acted by controlling the crystallinity within a range of 0.05 nm to 2 nm and controlling the crystallinity thereof satisfactorily. The crystallinity of 70 is improved. That is, the surface roughness Ra of the lower electrode film 60 is 2 nm or less, whereas the seed titanium particle size of the seed titanium layer 65 is larger than 2 nm, so that it is effective without entering the recesses on the surface of the lower electrode film 60. It is considered that it can contribute to the improvement of the characteristics of the piezoelectric layer 70 by acting on the above. Thereby, the piezoelectric layer 70 having excellent electrical and mechanical characteristics can be formed. In addition, since variations in the surface roughness and crystallinity of the lower electrode film 60 within the same wafer are suppressed, variations in the characteristics of the piezoelectric layer 70 can be suppressed to an extremely low level.

  Furthermore, the crystallinity of the piezoelectric layer 70 can be easily controlled, the piezoelectric layer 70 having desired characteristics can be manufactured relatively easily, and mass productivity is greatly improved. That is, in the present invention, by controlling the surface roughness Ra of the lower electrode film 60 to be in the range of 0.05 to 2 nm, the sputtering conditions for forming the seed titanium layer 65 thereon are strictly limited. Even if it is not controlled, the crystal of the piezoelectric layer 70 formed on the lower electrode film 60 is more easily given priority over the (100) plane than when the surface roughness Ra of the lower electrode film 60 is outside the predetermined range. It can be oriented and its characteristics can be improved relatively easily, and the characteristics of the piezoelectric layer can be stabilized relatively easily. Thereby, a yield can be improved.

As a material of the piezoelectric layer 70, for example, a relaxor ferroelectric material obtained by adding a metal such as niobium, nickel, magnesium, bismuth or yttrium to a ferroelectric piezoelectric material such as lead zirconate titanate (PZT). Etc. may be used. The composition may be appropriately selected in consideration of the characteristics and application of the piezoelectric element. 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 _1/3 Ta _1/2 ) O ₃ -PbTiO ₃ (PST-PT), Pb (Sc _1/3 Nb _1/2 ) O ₃ -PbTiO ₃ (PSN-PT), BiScO ₃ -PbTiO ₃ (BS-PT), BiYbO ₃ -PbTiO ₃ ( BY-PT Etc. The. The method for manufacturing the piezoelectric layer 70 is not limited to the sol-gel method, and for example, a MOD (Metal-Organic Decomposition) method or the like may be used.

  After the piezoelectric layer 70 is formed in this way, as shown in FIG. 5A, for example, an upper electrode film 80 made of iridium is formed on the entire surface of the flow path forming substrate wafer 110. Next, as shown in FIG. 5B, the piezoelectric layer 300 and the upper electrode film 80 are patterned in a region facing each pressure generating chamber 12 to form the piezoelectric element 300. Next, the lead electrode 90 is formed. Specifically, as shown in FIG. 5C, a metal layer 91 made of, for example, gold (Au) or the like is formed over the entire surface of the flow path forming substrate wafer 110. Thereafter, for example, the lead electrode 90 is formed by patterning the metal layer 91 for each piezoelectric element 300 through a mask pattern (not shown) made of a resist or the like.

  Next, as shown in FIG. 5D, a protective substrate wafer 130 that is a silicon wafer and serves as a plurality of protective substrates 30 is bonded to the piezoelectric element 300 side of the flow path forming substrate wafer 110. Since the protective substrate wafer 130 has a thickness of, for example, about 400 μm, the rigidity of the flow path forming substrate wafer 110 is remarkably improved by bonding the protective substrate wafer 130.

  Next, as shown in FIG. 6A, after the flow path forming substrate wafer 110 is polished to a certain thickness, it is further wet-etched with fluorinated nitric acid, so that the flow path forming substrate wafer 110 is Make it thick. For example, in this embodiment, the flow path forming substrate wafer 110 is etched so as to have a thickness of about 70 μm. Next, as shown in FIG. 6B, 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, the flow path forming substrate wafer 110 is anisotropically etched through the mask film 52, whereby, as shown in FIG. 13 and the ink supply path 14 are formed.

  After that, 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. By dividing the flow path forming substrate wafer 110 and the like into the flow path forming substrate 10 and the like of one chip size as shown in FIG. 1, the ink jet recording head of this embodiment is obtained.

Here, the sputtering pressure when forming the adhesion layer 61 is about 0.2 Pa, the sputtering output is 9 kW / m ² , the temperature is room temperature (about 25 ° C.), and the sputtering pressures of the Ir layer 62, the Pt layer 63, and the Ir layer 64 are set. The ink jet recording head of Example 1 was manufactured by the above-described manufacturing method except that the lower electrode film 60 was formed at about 0.3 Pa, the sputtering output was 8 kW / m ² , the temperature was 100 ° C. The surface roughness Ra of the lower electrode of Example 1 was about 1.5 nm.

  On the other hand, a head manufactured in the same manner as in Example 1 was used as Comparative Example 1 except that the sputtering pressure when forming the adhesion layer 61 was about 0.3 Pa. The surface roughness Ra of the lower electrode film of this head was about 2.1 nm.

  FIG. 7A shows a SEM (scanning electron microscope) photograph of the surface of the lower electrode film of Example 1. FIG. FIG. 8A shows a SEM (scanning electron microscope) photograph of the surface of the adhesion layer of Example 1. FIG.

  FIG. 7B shows an SEM photograph of the surface of the lower electrode film in Comparative Example 1. FIG. 8B shows a SEM (scanning electron microscope) photograph of the surface of the adhesion layer of Comparative Example 1.

  As shown in FIGS. 7A and 7B and FIGS. 8A and 8B, the lower electrode film of Example 1 is a smoother layer than the lower electrode film of Comparative Example 1. It can be confirmed. When the characteristics of the piezoelectric element (piezoelectric layer) were compared for the heads of Example 1 and Comparative Example 1, the head of Example 1 had higher characteristics of the piezoelectric layer than the head of Comparative Example 1. I found out.

(Other embodiments)
Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment. In the above-described embodiment, the ink jet recording head is exemplified as an example of the head used in the liquid ejecting apparatus. However, the present invention is widely intended for the entire liquid ejecting head, and liquid other than ink is used. Of course, the present invention can also be applied to a jet. Other liquid ejecting heads include, for example, various recording heads used in image recording apparatuses such as printers, color material ejecting heads used in the manufacture of color filters such as liquid crystal displays, organic EL displays, and FEDs (surface emitting displays). Examples thereof include an electrode material ejection head used for electrode formation, a bioorganic matter ejection head used for biochip production, and the like. The present invention can be applied not only to an actuator device mounted as liquid ejecting means on such a liquid jet head (inkjet recording head) but also to an actuator device mounted on any device. For example, the actuator device can be applied to a sensor or the like in addition to the head described above.

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. 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. 3 is a SEM photograph of the surface of the lower electrode film of Example 1 and Comparative Example 1. 2 is a SEM photograph of the surface of the adhesion layer of Example 1 and Comparative Example 1.

Explanation of symbols

  10 flow path forming substrate, 12 pressure generating chamber, 20 nozzle plate, 21 nozzle opening, 30 protective substrate, 40 compliance substrate, 50 elastic film, 55 insulator film, 60 lower electrode film, 61 adhesion layer, 62 Ir layer, 63 Pt layer, 64 Ir layer, 65 seed titanium layer, 70 piezoelectric film, 80 upper electrode film, 300 piezoelectric element

Claims (15)

A lower electrode formed through the diaphragm; a piezoelectric layer formed on the lower electrode; and an upper electrode formed on the piezoelectric layer, wherein the surface roughness Ra of the lower electrode is A piezoelectric element having a range of 0.05 to 2 nm. 2. The piezoelectric element according to claim 1, wherein the lower electrode has an adhesion layer which is a lowermost layer located on the diaphragm side, and a surface roughness of the adhesion layer is smaller than a surface roughness of the lower electrode. . 3. The piezoelectric element according to claim 2, wherein the adhesion layer is made of titanium (Ti). 4. The lower electrode according to claim 2, wherein the lower electrode includes a first layer located on the piezoelectric layer side and containing Ir, and a second layer located below the first layer and containing Pt. A piezoelectric element. 5. The piezoelectric element according to claim 4, wherein the lower electrode has a third layer containing Ir between the adhesion layer and the second layer. 6. The piezoelectric element according to claim 1, wherein the piezoelectric layer is preferentially oriented in a rhombohedral (100) plane. 7. The piezoelectric element according to claim 1, wherein the piezoelectric layer is formed on a seed Ti layer provided at a desired thickness on the lower electrode. A liquid ejecting head comprising the piezoelectric element according to claim 1 as a piezoelectric actuator. A liquid ejecting apparatus comprising the liquid ejecting head according to claim 8. A step of forming a lower electrode on a diaphragm provided on one surface of the substrate so that the surface roughness Ra is in the range of 0.05 to 2 nm, and titanium (Ti) on the lower electrode by sputtering. Forming a seed titanium layer by applying a piezoelectric material, forming a piezoelectric precursor film by applying a piezoelectric material on the seed titanium layer, and firing and crystallizing the piezoelectric precursor film. A method for manufacturing a piezoelectric element, comprising: a step of forming a piezoelectric layer; and a step of forming an upper electrode on the piezoelectric layer. 11. The step of forming the lower electrode according to claim 10, the step of forming an adhesion layer on the diaphragm so that the surface roughness Ra is in the range of 0.05 to 2 nm, and the step of forming an adhesion layer on the adhesion layer. A piezoelectric device comprising: a step of forming a first Ir layer; a step of forming a Pt layer on the first Ir layer; and a step of forming a second Ir layer on the Pt layer. Device manufacturing method. 12. The method for manufacturing a piezoelectric element according to claim 11, wherein the adhesion layer is made of titanium (Ti). 13. The method for manufacturing a piezoelectric element according to claim 11, wherein the adhesion layer is formed by a sputtering method under a pressure of 0.01 to 0.2 Pa. 14. The method for manufacturing a piezoelectric element according to claim 13, wherein the adhesion layer is formed by a sputtering method under conditions where a temperature is in a range from room temperature to 200 ° C. and a power density is 3 to 10 kW / m ² . 15. The method according to claim 11, wherein the first Ir layer, the Pt layer, and the second Ir layer have a power density of 8 to 30 kW / m ² , a pressure of 0.01 to 0.3 Pa, and a normal temperature. A method for manufacturing a piezoelectric element, characterized in that the piezoelectric element is formed by sputtering under a temperature of 200 ° C. to 200 ° C.

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