JP2007173605A - Method of manufacturing piezoelectric element and method of manufacturing liquid jetting head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a piezoelectric element capable of improving the characteristics of a piezoelectric layer and equalizing the characteristics of the piezoelectric layer, and a method of manufacturing a liquid jetting head. <P>SOLUTION: The method of manufacturing the piezoelectric element is provided with a process of forming a lower electrode 60 on a substrate 110; a process of forming a seed titanium layer 64 having a thickness of 3.5-5.5 nm on the lower electrode 60; a process of forming a piezoelectric precursor film 71 made of a piezoelectric material on the seed titanium layer 64, forming a piezoelectric layer 70 made of a piezoelectric film 72 formed by baking the piezoelectric precursor film 71 at a temperature increase rate of 50°C/sec or more and crystallizing it; and a process of forming an upper electrode on the piezoelectric layer 70. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a piezoelectric element including a lower electrode, a piezoelectric layer, and an upper electrode, and more particularly to a method for manufacturing a liquid ejecting head that discharges droplets from nozzle openings.

  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.

  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. It is formed by baking (for example, refer 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. .

JP 2001-274472 A (page 5)

  In view of such circumstances, it is an object of the present invention to provide a method for manufacturing a piezoelectric element and a method for manufacturing a liquid jet head that can improve the characteristics of the piezoelectric layer and make the characteristics of the piezoelectric layer uniform.

The first aspect of the present invention for solving the above problems includes a step of forming a lower electrode on a substrate, a step of forming a seed titanium layer having a thickness of 3.5 to 5.5 nm on the lower electrode, A piezoelectric body formed of a piezoelectric film formed by forming a piezoelectric precursor film made of a piezoelectric material on the seed titanium layer and crystallizing the piezoelectric precursor film by firing at a temperature rising rate of 50 ° C./sec or more. A method of manufacturing a piezoelectric element comprising: a step of forming a layer; and a step of forming an upper electrode on the piezoelectric layer.
In the first aspect, by defining the thickness of the seed titanium layer and the rate of temperature increase when the piezoelectric layer is formed by firing, the crystals of the piezoelectric layer are formed relatively densely, and the crystallinity is greatly increased. In addition, the foreign matter generated in the piezoelectric layer can be reduced, variation in the characteristics of the piezoelectric layer in the same substrate can be suppressed, and the displacement characteristics of the piezoelectric elements can be made uniform. Furthermore, by making the temperature rising rate relatively high at 50 ° C./sec or more, energy can be saved as compared with the case of firing at a low temperature rising rate, and the manufacturing cost can be reduced.

According to a second aspect of the present invention, in the method of manufacturing a piezoelectric element according to the first aspect, in the step of forming the lower electrode, a diffusion prevention layer is formed on at least the uppermost layer on the seed titanium layer side. is there.
In the second aspect, it is possible to prevent the components of the piezoelectric layer from diffusing into the lower electrode, and it is possible to obtain a piezoelectric layer having excellent piezoelectric characteristics.

According to a third aspect of the present invention, the diffusion preventing layer is formed of a material mainly composed of at least one selected from the group consisting of iridium, palladium, rhodium, ruthenium and osmium. The method of manufacturing a piezoelectric element according to the above aspect.
In the third aspect, by using the predetermined diffusion preventing layer, it is possible to prevent the components of the piezoelectric layer from diffusing into the lower electrode, and a piezoelectric layer having excellent piezoelectric characteristics can be obtained.

According to a fourth aspect of the present invention, in the method of manufacturing a piezoelectric element according to any one of the first to third aspects, in the step of forming the lower electrode, an adhesion layer is formed on the substrate side.
In the fourth aspect, the adhesion between the base substrate and the lower electrode can be improved, and the components of the adhesion layer can be prevented from diffusing to the piezoelectric layer side. A body layer can be obtained.

According to a fifth aspect of the present invention, in the fourth aspect, the adhesion layer is formed of a material whose main component is at least one selected from the group consisting of titanium, chromium, tantalum, zirconium, and tungsten. It exists in the manufacturing method of the piezoelectric element of an aspect.
In the fifth aspect, the adhesion between the base substrate and the lower electrode can be improved by using a predetermined adhesion layer.

According to a sixth aspect of the present invention, in the piezoelectric element according to any one of the first to fifth aspects, the piezoelectric precursor film is fired by the RTA method when the piezoelectric layer is formed. Is in the way.
In the sixth aspect, the piezoelectric layer can be fired at a relatively fast desired temperature increase rate.

According to a seventh aspect of the present invention, in the method of manufacturing a piezoelectric element according to any one of the first to sixth aspects, in the step of forming the piezoelectric layer, a plurality of the piezoelectric films are formed. .
In the seventh aspect, the piezoelectric layer having a predetermined thickness can be formed with high quality and high accuracy.

According to an eighth aspect of the present invention, there is provided a liquid ejecting head manufacturing method using the piezoelectric element manufactured by the manufacturing method according to any one of the first to seventh aspects.
In the eighth aspect, a liquid ejecting head in which the displacement characteristics of the piezoelectric element are made uniform can be realized.

Hereinafter, the present invention will be described in detail based on embodiments.
(Embodiment 1)
FIG. 1 is an exploded perspective view showing an outline of a liquid jet head according to a first embodiment of the present invention, and FIG. 2 is a plan view of FIG.

As shown in the drawing, the flow path forming substrate 10 is made of a silicon single crystal substrate having a crystal plane orientation of (110) in this embodiment, and one surface thereof is made of silicon oxide (SiO ₂ ) previously formed by thermal oxidation. An elastic film 50 having a thickness of 0.5 to 2.0 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 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, 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 used to generate pressure. The chamber 12 is fixed by an adhesive, a heat welding film or the like through a mask film 51 used as a mask when forming the chamber 12. 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 stainless steel.

  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 The upper electrode film 80 having a thickness of 0.05 μm is laminated 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 this case, 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 320. In this embodiment, the lower electrode film 60 is a common electrode of the piezoelectric element 300, and the upper electrode film 80 is an individual electrode of the piezoelectric element 300. However, there is no problem even if this is reversed for the convenience of the drive circuit and wiring. In either case, the piezoelectric active part 320 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 above-described example, the elastic film 50, the insulator film 55, and the lower electrode film 60 function as a diaphragm. However, the elastic film 50 and the insulator film 55 are not provided, and only the lower electrode film 60 is left. The electrode film 60 may be a diaphragm.

  In the lower electrode film 60 of the present embodiment, an adhesion layer, a platinum layer made of platinum (Pt) on the adhesion layer, and a diffusion prevention layer are sequentially laminated before the piezoelectric layer 70 is formed. The lower electrode film 60 is also heated at the same time when the piezoelectric layer 70 is baked and crystallized by a manufacturing method described in detail later.

The piezoelectric layer 70 is a perovskite structure crystal film made of a ferroelectric ceramic material having an electromechanical conversion effect and formed on the lower electrode film 60. As a material of the piezoelectric layer 70, for example, a ferroelectric piezoelectric material such as lead zirconate titanate (PZT) or a material obtained by adding a metal oxide such as niobium oxide, nickel oxide or magnesium oxide to the piezoelectric material is suitable. It is. Specifically, lead titanate (PbTiO ₃ ), lead zirconate titanate (Pb (Zr, Ti) O ₃ ), lead zirconate (PbZrO ₃ ), lead lanthanum titanate ((Pb, La), TiO ₃ ) ) Lead lanthanum zirconate titanate ((Pb, La) (Zr, Ti) O ₃ ) or lead magnesium titanate zirconate titanate (Pb (Zr, Ti) (Mg, Nb) O ₃ ) or the like is used. it can. The piezoelectric layer 70 is formed thick enough to suppress the thickness so as not to generate cracks in the manufacturing process and to exhibit sufficient displacement characteristics. For example, in this embodiment, the piezoelectric layer 70 is formed with a thickness of about 1 to 2 μm.

  Further, each upper electrode film 80 that is an individual electrode of the piezoelectric element 300 is drawn from the vicinity of the end on the ink supply path 14 side and extended to the insulator film 55, for example, gold (Au) or the like. The lead electrode 90 which consists of is connected.

  On the flow path forming substrate 10 on which such a piezoelectric element 300 is formed, that is, on the lower electrode film 60, the elastic film 50, and the lead electrode 90, a protection having a reservoir portion 31 constituting at least a part of the reservoir 100. The substrate 30 is bonded via an adhesive 35. In the present embodiment, the reservoir portion 31 is formed through the protective substrate 30 in the thickness direction and across the width direction of the pressure generation chamber 12. As described above, the communication portion 13 of the flow path forming substrate 10. The reservoir 100 is configured as a common ink chamber for the pressure generation chambers 12.

  A piezoelectric element holding portion 32 having a space that does not hinder the movement of the piezoelectric element 300 is provided in a region of the protective substrate 30 that faces the piezoelectric element 300. The piezoelectric element holding part 32 only needs to have a space that does not hinder the movement of the piezoelectric element 300, and the space may be sealed or unsealed.

  As such a protective substrate 30, it is preferable to use substantially the same material as the coefficient of thermal expansion of the flow path forming substrate 10, for example, glass, ceramic material, etc. In this embodiment, the same material as the flow path forming substrate 10 is used. The silicon single crystal substrate was used.

  The protective substrate 30 is provided with a through hole 33 that penetrates the protective substrate 30 in the thickness direction. The vicinity of the end portion of the lead electrode 90 drawn from each piezoelectric element 300 is provided so as to be exposed in the through hole 33.

  A drive circuit 200 for driving the piezoelectric elements 300 arranged in parallel is fixed on the protective substrate 30. For example, a circuit board or a semiconductor integrated circuit (IC) can be used as the drive circuit 200. The drive circuit 200 and the lead electrode 90 are electrically connected via a connection wiring 210 made of a conductive wire such as a bonding wire.

  In addition, a compliance substrate 40 including a sealing film 41 and a fixing plate 42 is bonded onto the protective substrate 30. Here, 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), and the sealing film 41 seals one surface of the reservoir portion 31. It has been stopped. 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.

  An ink introduction port 44 for supplying ink to the reservoir 100 is formed on the compliance substrate 40 on the outer side of the central portion of the reservoir 100 in the longitudinal direction. Further, the protective substrate 30 is provided with an ink introduction path 34 that allows the ink introduction port 44 and the side wall of the reservoir 100 to communicate with each other.

  In such an ink jet recording head of this embodiment, ink is taken in from an ink introduction port 44 connected to an external ink supply means (not shown), and the interior is filled with ink from the reservoir 100 to the nozzle opening 21. In accordance with the recording signal from 200, a voltage is applied between each of the lower electrode film 60 and the upper electrode film 80 corresponding to the pressure generating chamber 12, and the elastic film 50, the lower electrode film 60, and the piezoelectric layer 70 are bent and deformed. By doing so, the pressure in each pressure generating chamber 12 increases, and ink droplets are ejected from the nozzle openings 21.

  Hereinafter, a method for 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 52 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 52). Specifically, after forming a zirconium (Zr) layer on the elastic film 50 (silicon dioxide film 52) by, for example, sputtering, the zirconium layer is thermally oxidized in a diffusion furnace at 500 to 1200 ° C., for example. Thus, the insulator film 55 made of zirconium oxide (ZrO ₂ ) is formed.

  Next, as illustrated in FIG. 3C, a lower electrode film 60 including an adhesion layer 61, a platinum layer 62, and a diffusion prevention layer 63 is formed. Specifically, first, the adhesion layer 61 is formed on the insulator film 55. As the adhesion layer 61, for example, at least one element selected from the group consisting of titanium (Ti), chromium (Cr), tantalum (Ta), zirconium (Zr), and tungsten (W) having a thickness of 10 to 50 nm. Is the main component. In this embodiment, 20 nm-thick titanium (Ti) is provided as the adhesion layer 61. Thus, by providing the adhesion layer 61 in the lowermost layer of the lower electrode film 60, the adhesion force between the insulator film 55 and the lower electrode film 60 can be enhanced. Next, a platinum layer 62 made of platinum (Pt) and having a thickness of 50 to 500 nm is formed on the adhesion layer 61. In the present embodiment, the platinum layer 62 is formed with a thickness of 130 nm. Then, a diffusion preventing layer 63 is formed on the platinum layer 62. Thereby, the lower electrode film 60 including the adhesion layer 61, the platinum layer 62, and the diffusion preventing layer 63 is formed. The diffusion preventing layer 63 prevents the components of the adhesion layer 61 from diffusing into the piezoelectric layer 70 when the piezoelectric layer 70 is formed by firing and crystallizing in a later step. This is to prevent the component 70 from diffusing into the lower electrode film 60. Such a diffusion preventing layer 63 is at least one selected from the group consisting of iridium (Ir), palladium (Pb), rhodium (Rh), ruthenium (Ru) and osmium (Os) having a thickness of 5 to 20 nm. The main component is one element. In the present embodiment, iridium (Ir) having a thickness of 10 nm is used as the diffusion preventing layer 63.

  Next, as shown in FIG. 3D, a seed titanium layer 64 made of titanium (Ti) is formed on the lower electrode film 60. The seed titanium layer 64 is formed with a thickness of 3.5 to 5.5 nm. The thickness of the seed titanium layer 64 is preferably 4.0 nm. In the present embodiment, the seed titanium layer 64 is formed with a thickness of 4 nm.

The seed titanium layer 64 thus formed preferably has a film density (Ti density) as high as possible, and is preferably at least 4.5 g / cm ³ or more. This is because as the film density of the seed titanium layer 64 is higher, the thickness of the oxide layer formed on the surface is reduced with time, and the crystal of the piezoelectric layer 70 grows better. The film density of the seed titanium layer 64 is determined by the film formation conditions regardless of the thickness. Furthermore, the seed titanium layer 64 is preferably amorphous. Specifically, it is preferable that the X-ray diffraction intensity of the seed titanium layer 64, in particular, the (002) plane X-ray diffraction intensity (XRD intensity) is substantially zero. When the seed titanium layer 64 is amorphous in this way, the film density of the seed titanium layer 64 is increased, and the thickness of the oxide layer formed on the surface layer can be reduced, and as a result, the crystal of the piezoelectric layer 70 can be further improved. It is because it can be made to grow.

  By providing the seed titanium layer 64 on the lower electrode film 60 in this manner, the piezoelectric layer 70 is formed when the piezoelectric layer 70 is formed on the lower electrode film 60 via the seed titanium layer 64 in a later step. Can be controlled to (100) or (111), and a piezoelectric layer 70 suitable as an electromechanical transducer can be obtained. The seed titanium layer 64 functions as a seed that promotes crystallization when the piezoelectric layer 70 is crystallized, and diffuses into the piezoelectric layer 70 after the piezoelectric layer 70 is fired.

  Note that each of the layers 61 to 63 and the seed titanium layer 64 of the lower electrode film 60 can be formed by, for example, a DC magnetron sputtering method as described above. Further, it is preferable that at least the platinum layer 62, the diffusion preventing layer 63, and the seed titanium layer 64 of the lower electrode film 60 are continuously formed without being released from the vacuum state in the sputtering apparatus. Thus, by continuously forming the platinum layer 62, the diffusion preventing layer 63, and the seed titanium layer 64 of the lower electrode film 60, the adhesion force of the platinum layer 62, the diffusion preventing layer 63, and the seed titanium layer 64 of the lower electrode film 60. Can be increased to prevent delamination in the lower electrode film 60.

  Next, a piezoelectric layer 70 made of lead zirconate titanate (PZT) is formed. Here, in the present embodiment, a so-called sol-gel is obtained in which a so-called sol in which a metal organic material is dissolved and dispersed in a catalyst is applied, dried, gelled, and further fired at a high temperature to obtain a piezoelectric layer 70 made of a metal oxide. The piezoelectric layer 70 is formed using the method. The material of the piezoelectric layer 70 is not limited to lead zirconate titanate, and other piezoelectric materials such as relaxor ferroelectrics (for example, PMN-PT, PZN-PT, PNN-PT, etc.) are used. May be. 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.

  As a specific procedure for forming the piezoelectric layer 70, first, as shown in FIG. 4A, a piezoelectric precursor film 71 that is a PZT precursor film is formed on the lower electrode film 60. That is, a sol (solution) containing a metal organic compound is applied onto the flow path forming substrate 10 on which the lower electrode film 60 is formed (application process). Next, the piezoelectric precursor film 71 is heated to a predetermined temperature and dried for a predetermined time (drying step). For example, in the present embodiment, the piezoelectric precursor film 71 can be dried by holding at 170 to 180 ° C. for 8 to 30 minutes. Moreover, 0.5-1.5 degreeC / sec is suitable for the temperature increase rate in a drying process. The “temperature increase rate” referred to here is the time from the temperature at which the temperature difference between the temperature at the start of heating (room temperature) and the attained temperature increases by 20% to the temperature at which the temperature difference reaches 80%. It is defined as the rate of change. For example, when the temperature is raised from room temperature 25 ° C. to 100 ° C. in 50 seconds, the rate of temperature rise is (100−25) × (0.8−0.2) /50=0.9 [° C./sec]. Become.

Next, the dried piezoelectric precursor film 71 is degreased by heating it to a predetermined temperature and holding it for a predetermined time (degreasing step). For example, in this embodiment, the piezoelectric precursor film 71 is degreased by heating to a temperature of about 300 to 400 ° C. and holding for about 10 to 30 minutes. Here, degreasing refers, the organic components contained in the piezoelectric precursor film 71, for _example, is to be detached as _{NO 2, CO 2, H 2} O or the like. In the degreasing step, it is preferable that the temperature rising rate is 0.5 to 1.5 ° C./sec.

  Next, as shown in FIG. 4B, the piezoelectric precursor film 71 is crystallized by being heated to a predetermined temperature and held for a predetermined time to form a piezoelectric film 72 (firing step). In the firing step, it is preferable to heat the piezoelectric precursor film 71 to 680 to 900 ° C. In this embodiment, the piezoelectric precursor film 71 is fired by heating at 680 ° C. for 5 to 30 minutes. A film 72 was formed. Here, the heating method in the firing step is not particularly limited, but it is preferable to use a RTA (Rapid Thermal Annealing) method or the like, for example, to relatively increase the temperature rising rate. For example, in the present embodiment, the piezoelectric film is heated at a relatively high rate of temperature rise using an RTP (Rapid Thermal Processing) apparatus that is heated by irradiation with an infrared lamp. Note that the rate of temperature rise when firing the piezoelectric film is 50 ° C./sec or more.

  Moreover, as a heating apparatus used at a drying process and a degreasing process, a hot plate, an RTP apparatus, etc. can be used, for example.

  4C, when the first layer of the piezoelectric film 72 is formed on the lower electrode film 60, the side surfaces of the lower electrode film 60 and the first piezoelectric film 72 are the same. Patterning is performed simultaneously to incline.

  Here, for example, when forming the first piezoelectric film 72 after forming the seed titanium layer 64 on the lower electrode film 60 and then patterning, the lower electrode film 60 is subjected to a photo process, ion milling, and ashing. The seed titanium layer 64 is altered in order to pattern the film, and even if the first piezoelectric film 72 is formed on the altered seed titanium layer 64, the crystallinity of the piezoelectric film 72 is not good. Since the other piezoelectric film 72 formed on the first piezoelectric film 72 also grows by affecting the crystal state of the first piezoelectric film 72, the piezoelectric film having good crystallinity. The body film 72 is not formed.

  In contrast, if the first piezoelectric film 72 is formed and then patterned simultaneously with the lower electrode film 60, the first piezoelectric film 72 is the second and subsequent piezoelectric films 72 compared to the seed titanium layer 64. As a seed for seed crystal growth, the property is strong. Even if an extremely thin altered layer is formed on the surface layer by patterning, the crystal growth of the second and subsequent piezoelectric films 72 is not greatly affected.

  After the patterning, the piezoelectric film forming process including the coating process, the drying process, the degreasing process, and the baking process described above is repeated a plurality of times, thereby forming a plurality of piezoelectric films 72 as shown in FIG. A piezoelectric layer 70 having a predetermined thickness is formed. For example, when the film thickness per sol is about 0.1 μm, the entire film thickness of the piezoelectric layer 70 composed of ten piezoelectric films 72 is about 1.1 μm, for example.

  As described above, when the first layer of the piezoelectric film 72 is formed on the lower electrode film 60, these are simultaneously patterned to incline the side surfaces of the lower electrode film 60 and the first piezoelectric film 72. As a result, when the second piezoelectric film 72 is formed, due to the difference in the base in the vicinity of the boundary between the portion where the lower electrode film 60 and the first piezoelectric film 72 are formed and the other portions. The adverse effect on the crystallinity of the second-layer piezoelectric film 72 can be reduced, that is, reduced. Thereby, in the vicinity of the boundary between the lower electrode film 60 and other portions, the crystal growth of the second piezoelectric film 72 proceeds well, and the piezoelectric layer 70 having excellent crystallinity can be formed. Further, by tilting the side surfaces of the lower electrode film 60 and the first-layer piezoelectric film 72, it is possible to improve the contact of the second-layer and subsequent piezoelectric precursor films 71. Thereby, the piezoelectric layer 70 having excellent adhesion and reliability can be formed.

  Thus, the thickness of the seed titanium layer 64 before forming the piezoelectric layer 70 is set to 3.5 to 5.5 nm, and the rate of temperature increase when the piezoelectric layer 70 is formed by firing is 50 ° C./sec. By setting it as the above, the piezoelectric material layer 70 can be formed with the favorable preferential orientation direction of (100) plane. In particular, since the crystal of the piezoelectric layer 70 grows from a large number of seed titanium, the crystallinity is greatly improved by forming the crystal of the piezoelectric layer 70 relatively densely. In addition, by setting the temperature rising rate during firing of the piezoelectric layer 70 to 50 ° C./sec or more, foreign matter generated in the piezoelectric layer 70 is reduced, and the characteristics of the piezoelectric layer 70 in the same substrate 110 are reduced. Variations can be suppressed, and the displacement characteristics of each piezoelectric element can be made uniform.

  Furthermore, by setting the temperature rise rate during firing of the piezoelectric layer 70 to 50 ° C./sec or more, it is possible to perform energy saving and in a short time compared to the case where the temperature rise rate is low for a long time.

(Example)
An elastic film made of silicon dioxide (SiO ₂ ) is formed by thermally oxidizing a flow path forming substrate wafer made of a silicon wafer by a manufacturing method similar to that of the first embodiment described above, and zirconium oxide (SiO ₂ ) is formed on the elastic film. An insulator film made of ZrO ₂ ) is formed. Next, an adhesion layer made of titanium (Ti) with a thickness of 20 nm, a platinum layer made of platinum (Pt) with a thickness of 130 nm, and iridium with a thickness of 10 nm as a lower electrode film on the insulator film. A diffusion prevention layer made of (Ir) is sequentially laminated. A plurality of seed titanium layers made of titanium (Ti) having a thickness of 3.5 to 5 nm on the diffusion prevention layer were prepared. Note that each layer of the lower electrode film and the seed titanium layer were continuously formed by the DC magnetron sputtering method without releasing from the vacuum state in the sputtering apparatus.

(Comparative example)
The seed titanium layer was formed by the same configuration and manufacturing method as in the above-described example except that a plurality of seed titanium layers formed with thicknesses of 2 nm, 3 nm, and 6 nm were prepared.

(Test Example 1)
A piezoelectric layer was formed on the seed titanium layers of these examples and comparative examples by the same manufacturing method as in the first embodiment. That is, on each lower electrode film, lead zirconate titanate (PZT) was applied, a drying process was performed at 180 ° C. for 10 minutes, a degreasing process was performed at 400 ° C. for 10 minutes, and then the temperature was increased by an RTA method. A piezoelectric film forming step of forming a piezoelectric film was performed by heating at a rate of 110 ° C./sec and performing a baking process at 700 ° C. for 30 minutes to form a 0.1 μm piezoelectric layer. After forming the piezoelectric layer in this way, the diffraction intensity (cps) of the (100) plane of the piezoelectric layer was measured at 9 points on the wafer for flow path forming substrate by the wide angle X-ray diffraction method. From this result, the diffraction intensity deviation (%) of the (100) plane of the piezoelectric layer obtained by dividing the standard deviation of diffraction intensity by the average value was calculated. Here, the (100) plane orientation degree was defined by (100 plane diffraction intensity) / ((100 plane diffraction intensity) + (110 plane diffraction intensity)). These results are shown in FIG. 7 is a graph showing the test results of Test Example 1, FIG. 7 (a) is a graph showing the diffraction intensity and the intensity deviation, and FIG. 7 (b) is a graph showing the degree of orientation.

  As shown in FIG. 7A, when the seed titanium layer is formed with a thickness of 3.5 to about 5.5 nm, a piezoelectric layer having a high (100) plane diffraction intensity and excellent orientation is obtained. I was able to. Further, it was found that when the seed titanium layer was formed with a thickness of 3.5 to about 5.5 nm, the diffraction intensity deviation of the (100) plane was low and the variation was small. That is, when the seed titanium layer is formed with a thickness of 3.5 to about 5.5 nm, it is possible to obtain a piezoelectric layer that has excellent orientation and suppresses variations in piezoelectric characteristics and uniform displacement characteristics. it can. In particular, it has been found that such an effect appears remarkably when the thickness of the seed titanium layer is 4 nm.

  On the other hand, when the seed titanium layer is formed with a thickness of 2, 3, 6 nm, that is, when the seed titanium layer is formed with a thickness other than 3.5 to 5.5 nm, the diffraction intensity of the (100) plane Is low, and the piezoelectric layer has large variations.

(Test Example 2)
A piezoelectric layer was formed on the seed titanium layers of Examples and Comparative Examples by the same manufacturing method as in Embodiment 1 described above. That is, on each lower electrode film, lead zirconate titanate (PZT) was applied, dried at 180 ° C. for 10 minutes, degreased at 400 ° C. for 10 minutes, and then heated in a diffusion furnace. A piezoelectric film forming step of forming a piezoelectric film was performed by heating at a rate of 5 ° C./sec and performing a baking process at 700 ° C. for 30 minutes to form a 0.1 μm piezoelectric layer. After forming the piezoelectric layer in this way, the diffraction intensity (cps) of the (100) plane of the piezoelectric layer was measured at nine points on the wafer for flow path forming substrate. Further, from this result, the diffraction intensity deviation (%) of the (100) plane of the piezoelectric layer obtained by dividing the standard deviation by the average value was calculated. These results are shown in FIG. 8 is a graph showing the test results of Test Example 2, FIG. 8 (a) is a graph showing the diffraction intensity and the intensity deviation, and FIG. 8 (b) is a graph showing the degree of orientation.

  As shown in FIG. 8, it was found that the diffraction intensity, variation, and (100) plane orientation of the (100) plane of the piezoelectric layer did not change greatly regardless of the thickness of the seed titanium layer.

  As described above, from the results of Test Example 1 and Test Example 2, the thickness of the seed titanium layer is set to 3.5 to 5.5 nm, preferably 4 nm, and the temperature increase rate when the piezoelectric layer is formed by firing is 50. By setting it to ° C./sec or more, it is possible to obtain a piezoelectric layer that has excellent orientation and suppresses variations in piezoelectric characteristics and uniform displacement characteristics. In the above-described embodiments, the crystallinity of the piezoelectric layer composed of one piezoelectric film has been described. However, in the case of a piezoelectric layer composed of a plurality of piezoelectric films, the second and subsequent piezoelectric bodies are also provided. Since the film is crystal-grown using the first piezoelectric film as a seed, the crystallinity of the first piezoelectric film becomes important.

  After the piezoelectric layer 70 is formed by the steps shown in FIGS. 4A to 4D, the upper electrode film 80 made of, for example, iridium (Ir) is formed as shown in FIG. The piezoelectric element 300 is formed by patterning the piezoelectric layer 70 and the upper electrode film 80 on regions facing the pressure generating chambers 12, which are formed on the entire surface of the flow path forming substrate wafer 110. Next, the lead electrode 90 is formed. Specifically, as shown in FIG. 5B, the lead electrode 90 made of, for example, gold (Au) or the like is formed over the entire surface of the flow path forming substrate wafer 110, and then made of, for example, a resist or the like. It is formed by patterning each piezoelectric element 300 via a mask pattern (not shown).

  Next, as shown in FIG. 5 (c), a protective substrate wafer 130 that is a silicon wafer and serves as a plurality of protective substrates 30 is placed on the flow path forming substrate wafer 110 via the adhesive 35 on the piezoelectric element 300 side. Join. 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. After the flow path forming substrate wafer 110 is polished to a certain thickness, the flow path forming substrate wafer 110 is made to have a predetermined thickness by wet etching with hydrofluoric acid. 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. 6A, a mask film 51 made of, for example, silicon nitride (SiN) is newly formed on the flow path forming substrate wafer 110 and patterned into a predetermined shape. 6B, the flow path forming substrate wafer 110 is anisotropically etched (wet etching) using an alkaline solution such as KOH through the mask film 51, whereby the piezoelectric element 300 is formed. Corresponding pressure generation chambers 12, communication portions 13, ink supply paths 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. 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.

(Other embodiments)
The first embodiment of the present invention has been described above, but the basic configuration of the ink jet recording head is not limited to that described above. For example, in Embodiment 1 described above, the piezoelectric precursor film 71 is applied, dried, and degreased, and then baked to form the piezoelectric film 72. However, the present invention is not particularly limited thereto. The step of applying, drying and degreasing the precursor film 71 may be repeated a plurality of times, for example, twice, and then baked to form the piezoelectric film 72.

  In the first embodiment described above, the piezoelectric layer 70 is formed using the sol-gel method. However, the present invention is not particularly limited thereto. For example, the piezoelectric layer 70 is formed by the MOD method, the sputtering method, or the like. You may make it do.

  Furthermore, in Embodiment 1 described above, the adhesion layer 61, the platinum layer 62, and the diffusion prevention layer 63 are used as the lower electrode film 60. However, the present invention is not particularly limited to this, for example, the adhesion layer 61 and the platinum layer 62. A diffusion preventing layer may be formed to prevent the adhesion layer from diffusing into the platinum layer and maintain adhesion.

  In the first embodiment described above, an ink jet recording head has been described as an example of a liquid ejecting head. However, the present invention is widely intended for all liquid ejecting heads, and is a liquid ejecting a liquid other than ink. Of course, the present invention can also be applied to a method of manufacturing an ejection head. 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.

  Further, the present invention is not limited to a method for manufacturing a piezoelectric element mounted on a liquid ejecting head typified by an ink jet recording head, and can also be applied to a method for manufacturing a piezoelectric element mounted on another apparatus.

FIG. 2 is an exploded perspective view illustrating a schematic configuration 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. 4 is a cross-sectional view illustrating the recording head manufacturing method according to the first embodiment. FIG. 4 is a cross-sectional view illustrating the recording head manufacturing method according to the first embodiment. FIG. 4 is a cross-sectional view illustrating the recording head manufacturing method according to the first embodiment. FIG. 4 is a cross-sectional view illustrating the recording head manufacturing method according to the first embodiment. 6 is a graph showing test results according to Test Example 1. 10 is a graph showing test results according to Test Example 2.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Flow path formation board | substrate, 12 Pressure generation chamber, 13 Communication part, 14 Ink supply path, 20 Nozzle plate, 21 Nozzle opening, 30 Protection board, 31 Reservoir part, 32 Piezoelectric element holding part, 40 Compliance board, 60 Lower electrode film , 61 adhesion layer, 62 platinum layer, 63 diffusion preventing layer, 64 titanium layer, 70 piezoelectric layer, 80 upper electrode film, 90 lead electrode, 100 reservoir, 200 drive circuit, 210 connection wiring, 300 piezoelectric element

Claims (8)

A step of forming a lower electrode on the substrate, a step of forming a seed titanium layer having a thickness of 3.5 to 5.5 nm on the lower electrode, and a piezoelectric precursor made of a piezoelectric material on the seed titanium layer Forming a piezoelectric layer composed of a piezoelectric film formed by firing and crystallizing the piezoelectric precursor film at a heating rate of 50 ° C./sec or more, and forming an upper layer on the piezoelectric layer. And a process for forming an electrode. 2. The method of manufacturing a piezoelectric element according to claim 1, wherein in the step of forming the lower electrode, a diffusion prevention layer is formed at least on the uppermost layer side of the seed titanium layer. 3. The method for manufacturing a piezoelectric element according to claim 2, wherein the diffusion preventing layer is formed of a material mainly containing at least one selected from the group consisting of iridium, palladium, rhodium, ruthenium and osmium. The method for manufacturing a piezoelectric element according to claim 1, wherein in the step of forming the lower electrode, an adhesion layer is formed on the substrate side. 5. The method for manufacturing a piezoelectric element according to claim 4, wherein the adhesion layer is formed of a material mainly containing at least one selected from the group consisting of titanium, chromium, tantalum, zirconium, and tungsten. The method for manufacturing a piezoelectric element according to claim 1, wherein the piezoelectric precursor film is fired by the RTA method when forming the piezoelectric layer. The method for manufacturing a piezoelectric element according to claim 1, wherein in the step of forming the piezoelectric layer, a plurality of layers of the piezoelectric film are formed. A method for manufacturing a liquid jet head, comprising using the piezoelectric element manufactured by the manufacturing method according to claim 1.

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