Patent Publication Number: US-2010123761-A1

Title: Liquid ejecting head, liquid ejecting apparatus, actuator device, and method for manufacturing the liquid ejecting head

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to a liquid ejecting head ejecting liquid, a liquid ejecting apparatus, an actuator device and a method for manufacturing the liquid ejecting head. 
     2. Related Art 
     In an ink jet recording head, part of pressure generating chambers communicating with nozzle apertures are formed of a vibration plate, and the vibration plate is deformed by a piezoelectric elements to compress the ink in the pressure generating chambers, thereby ejecting ink droplets through the nozzle apertures. In practice, for example, an ink jet recording head uses deflection of a type of piezoelectric element including a lower electrode, a piezoelectric layer and an upper electrode. 
     The vibration plate may include a silicon oxide layer defining part of pressure generating chambers, and a zirconium oxide layer disposed on the silicon oxide layer. 
     For forming the zirconium oxide layer, JP-A-2005-166719 discloses the method of thermally oxidizing zirconium deposited on the silicon oxide layer by sputtering. 
     JP-A-09-254386 discloses the method of directly forming a zirconium oxide layer by sputtering using a zirconium oxide target. 
     The zirconium oxide layer formed by thermal oxidation as in the method disclosed in the above cited JP-A-2005-166719 exhibits high adhesion to the silicon oxide. However, if foreign matter is present on the silicon oxide layer, the zirconium oxide layer is often cracked undesirably from the point where the foreign matter is present. 
     The zirconium oxide layer directly formed by sputtering as in the method disclosed in JP-A-09-254386 can prevent the crack caused by the presence of foreign matter, but exhibits low adhesion to oxides, particularly to the silicon oxide layer. Accordingly, the zirconium oxide layer may separate undesirably to break. 
     These problems can arise not only in liquid ejecting heads represented by the ink jet recording head, but also in actuator devices installed in other apparatuses. 
     SUMMARY 
     Accordingly, an advantage of some aspects of the invention is that it provides a liquid ejecting head and an actuator device that can reduce cracks, separation and other breakage of the zirconium oxide layer therein, a liquid ejecting apparatus including the liquid ejecting head, and a method for manufacturing the liquid ejecting head. 
     According to an aspect of the invention, a liquid ejection head is provided which includes a first layer essentially composed of silicon oxide disposed over a substrate, a second layer essentially composed of zirconium oxide formed by depositing zirconium on the first layer and thermally oxidizing the zirconium, a third layer essentially composed of zirconium oxide deposited on the second layer by sputtering, and a pressure generating element disposed over the third layer. 
     In this embodiment, the second layer formed by thermal oxidation ensures the adhesion to the first layer to prevent the zirconium oxide layer from separating. Even if the second layer cracks, the third layer formed by sputtering, covering the second layer  56  can suppress the spread of the crack. The words “over something such as a substrate or a layer” mentioned herein mean that it may be directly disposed on something or disposed with another member therebetween. 
     Preferably, the third layer has a thickness equal to or larger than the thickness of the second layer. Thus, the third layer can reliably cover cracks produced in the second layer. 
     According to another aspect of the invention, a liquid ejecting apparatus including the above-described liquid ejecting head is provided. The liquid ejecting apparatus can exhibit enhanced durability and reliability. 
     According to still another aspect of the invention, an actuator device is provided which includes a first layer essentially composed of silicon oxide disposed over a substrate, a second layer essentially composed of zirconium oxide formed by depositing zirconium on the first layer and thermally oxidizing the zirconium, a third layer essentially composed of zirconium oxide deposited on the second layer by sputtering; and a pressure generating element disposed over the third layer. 
     In this embodiment, the second layer formed by thermal oxidation ensures the adhesion to the first layer to prevent the zirconium oxide layer from separating. Even if the second layer cracks, the third layer formed by sputtering, covering the second layer can suppress the spread of the crack. 
     According to further aspect of the invention, a method for manufacturing a liquid ejecting head is provided. The method includes forming a zirconium layer essentially composed of zirconium on a silicon oxide-based first layer disposed over a substrate; thermally oxidizing the zirconium layer to form a second layer essentially composed of zirconium oxide; and depositing zirconium oxide on the second layer by sputtering, thereby forming a third layer essentially composed of zirconium oxide. 
     By forming the second layer by thermal oxidation, the adhesion between the zirconium oxide layer and the first layer can be enhanced to prevent the zirconium oxide layer from separating. By forming the third layer by sputtering, the third layer covers cracks that may occur in the second layer to suppress the spread of the cracks. 
     According to still further aspect of the invention, a method for manufacturing a liquid ejecting head is provided. The method includes forming a zirconium layer essentially composed of zirconium on a silicon oxide-based first layer disposed over a substrate; depositing zirconium oxide on the zirconium layer by sputtering, there by forming a third layer essentially composed of zirconium oxide; and subsequently thermally oxidizing the zirconium layer to form a second layer essentially composed of zirconium oxide. 
     By forming the second layer by thermal oxidation, the adhesion between the zirconium oxide layer and the first layer can be enhanced to prevent the zirconium oxide layer from separating. In addition, by forming the second layer by thermally oxidizing a zirconium layer after forming the third layer on the zirconium layer, the second layer can be prevented from cracking at the point where foreign matter is present during the formation of the second layer. Even if the second layer cracks, the third layer covering the second layer can suppress the spread of the crack. 
     Preferably, the method further includes forming a piezoelectric element by forming a first electrode, a piezoelectric layer and a second electrode over the third layer after forming the second layer and the third layer. Thus, the third layer can prevent the occurrence of cracks even if a stress is placed on the second layer for forming the piezoelectric element. If a crack occurs, the third layer can suppress the spread of the crack. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is an exploded perspective view of a recording head according to an embodiment of the invention. 
         FIG. 2A  is a plan view of the recording head according to the embodiment, and 
         FIG. 2B  is a sectional view of the recording head. 
         FIGS. 3A to 3E  are sectional views showing a method for manufacturing the recording head according to the embodiment. 
         FIGS. 4A to 4C  are sectional views showing steps subsequent to the step shown in  FIG. 3E . 
         FIGS. 5A to 5C  are sectional views showing steps subsequent to the step shown in  FIG. 4C . 
         FIG. 6  is a sectional view showing a step subsequent to the step shown in  FIG. 5C . 
         FIGS. 7A to 7D  are sectional views showing a method for manufacturing a recording head according to another embodiment of the invention. 
         FIG. 8  is a schematic perspective view of a recording apparatus according to an embodiment of the invention. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The invention will be further described with reference to exemplary embodiments. 
     First Embodiment 
       FIG. 1  is an exploded perspective view of an ink jet recording head I, which is a type of liquid ejecting head, according to a first embodiment, and  FIGS. 2A and 2B  are plan view of the ink jet recording head shown in  FIG. 1  and a sectional view take along line IIB-IIB shown in  FIG. 2A , respectively. 
     The ink jet recording head I includes a monocrystalline silicon flow channel substrate  10 , and an elastic film  50  essentially composed of silicon oxide, which corresponds a first layer, is disposed over a surface of the flow channel substrate. 
     The flow channel substrate  10  has a plurality of pressure generating chambers  12  arranged in parallel. The flow channel substrate  10  also has a communicating section  13  therein in a region to the outside of the lengths of the pressure generating chambers  12 , and communicates with the pressure generating chambers  12  through their respective ink supply channels  14  and communication paths  15 . The communicating section  13  communicates with a reservoir section  31  formed in a protective substrate (described later) to define part of a reservoir acting as a common ink chamber of the pressure generating chambers  12 . The ink supply channels  14  each have a smaller width than the pressure generating chambers  12 , so that the flow resistances to the ink delivered to the pressure generating chambers  12  from the communicating section  13  is kept constant. Although the ink supply channels  14  are formed by narrowing the flow paths from one side in the present embodiment, the flow paths may be narrowed from both sides. Alternatively, the ink supply channels  414  may be formed by reducing the depth of the flow paths, instead of narrowing the flow paths. 
     In the present embodiment, the flow channel substrate  10  has liquid flow channels including the pressure generating chambers  12 , the communicating section  13 , the ink supply channels  14  and the communication paths  15 . 
     The flow channel substrate  10  is joined with a nozzle plate  20  at the open side thereof with an adhesive, thermal fusion film or the like. The nozzle plate  20  has nozzle apertures  21  communicating with end portions of the respective pressure generating chambers  12  opposite to the ink supply channels. The nozzle plate  20  can be made of, for example, glass, ceramic, monocrystalline silicon or stainless steel. 
     On the other hand, an elastic film  50  is formed over the other side, opposite to the open side, of the flow channel substrate  10 , and an insulating film  55  is formed on the elastic film  50 . In addition, a first electrode  60 , a piezoelectric layer  70  and a second electrode  80  are formed over the insulating film  55  to form piezoelectric elements  300  corresponding to pressure generating elements. Each piezoelectric element  300  mentioned herein refers to the portion including the first electrode  60 , the piezoelectric layer  70  and the second electrode  80 . In general, either electrode of the piezoelectric element  300  acts as a common electrode, and the other electrode and the piezoelectric layer  70  are formed for each pressure generating chamber  12  by patterning. Although in the present embodiment, the first electrode  60  acts as the common electrode of the piezoelectric elements  300  and the second electrode  80  is defined by discrete electrodes of the piezoelectric elements  300 , the functions of the first and second electrodes may be reversed for the sake of convenience of the driving circuit and wiring. An actuator device used herein is defined by the piezoelectric element  300  and a vibration plate that is deformed by the operation of the piezoelectric element  300 . Although in the structure shown in  FIG. 1 , the elastic film  50 , the insulating film  55  and the first electrode  60  constitute the vibration plate, the vibration plate is not limited to this structure. For example, only the first electrode  60  may act as the vibration plate without using the elastic film  50  or the insulating film  55 . The piezoelectric element  300  may double as a vibration plate. 
     The insulating film  55  includes a second layer  56  essentially composed of zirconium oxide formed by thermally oxidizing zirconium and a third layer  57  essentially composed of zirconium oxide formed on the second layer  56  by sputtering. 
     For forming the second layer  56 , more specifically, a zirconium layer essentially composed of zirconium is formed on the elastic film  50 , and the zirconium layer is heated to perform thermal oxidation. By forming the second layer  56  by thermal oxidation on the elastic film  50 , the resulting insulating film  55  can exhibit high adhesion to the elastic film  50 . Hence, the second layer  56  acts as an adhesion layer of the insulating film  55 . 
     The third layer  57  is formed by depositing zirconium oxide directly on the second layer  56  by sputtering. The third layer  57  formed directly on the second layer  56  by sputtering can prevent the occurrence of cracks in the second layer  56 . Even if the second layer  56  is cracked, the third layer  57  covers the crack to prevent the crack from spreading. 
     If the insulating film  55  is composed of only the third layer  57 , the insulating film  55  of an oxide (zirconium oxide) is formed directly on the elastic film  50  of an oxide (silicon oxide) by sputtering. An oxide layer formed directly on an oxide by sputtering has a lower adhesion therebetween than a thermally oxidized oxide layer. In the present embodiment, the second layer  56  is formed on the elastic film  50  of an oxide (silicon oxide) by thermal oxidation so that the adhesion between the elastic film  50  and the insulating film  55  can be enhanced. Consequently, the separation between these layers during operation of the piezoelectric element  300  can be prevented, and the durability and reliability can be enhanced. 
     The insulating film  55  may be composed of only the second layer  56 . If foreign matter is present on the elastic film  50 , however, thermal oxidation causes the second layer to crack at a point where foreign matter is present. Even if the second layer is not cracked during its formation, a crack may be formed in the second layer  56  by a stress for forming the piezoelectric elements  300  or displacement of the piezoelectric elements  300  during operation. In the present embodiment, even if the second layer  56  cracks, the third layer  57  formed over the second layer  56  by sputtering covers the crack in the second layer  56  to prevent the crack from spreading. When the second layer  56  is not cracked during its formation, the second layer  56  can further be prevented from being cracked later by the stress for forming the piezoelectric elements  300  or by operating the piezoelectric elements  300  because the second layer  56  is protected by being covered with the third layer  57 . 
     In the present embodiment, for example, the second layer  56  is formed to a thickness of 0.2 μm and the third layer  57  is formed to a thickness of 0.2 μm. Hence, the insulating film  55  has a thickness of about 0.4 μm. Preferably, the thickness of the third layer  57  is equal to or more than that of the second layer  56 . In other words, it is preferably that the thickness of the second layer  56  be less than or equal to half of the total thickness of the second layer  56  and the third layer  57  (thickness of the insulating film  55 ). By forming the third layer  57  to a thickness equal to or more than the thickness of the second layer  56 , the third layer  57  can reliably cover cracks produced in the second layer  56  and can prevent the second layer  56  from cracking. 
     Zirconium oxide mentioned herein includes known compounds formed by combining zirconium and oxygen, such as ZrO 2 , and mixtures of zirconium oxide, zirconium and oxygen, and the second layer  56  and the third layer  57  may contain other elements as long as they are essentially composed of zirconium oxide. 
     Although the second layer  56  and the third layer  57  are made of the same material, their elemental ratios and crystal structures differ from each other because the second layer  56  and the third layer  57  are formed by different methods. Such differences can easily be known by analyzing the elemental ratios and crystal structures. 
     The piezoelectric layer  70  is formed of a piezoelectric material having an electromechanical conversion effect, particularly a metal oxide having a perovskite structure expressed by the general formula ABO 3 , on the first electrode  60 . Preferably, the piezoelectric layer  70  is formed of a ferroelectric material, such as lead zirconate titanate (PZT), or a ferroelectric material to which a metal oxide, such as niobium oxide, nickel oxide or magnesium oxide, is added. More specifically, materials of the piezoelectric layer  70  include 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 ) and lead zirconium titanate magnesium niobate (Pb(Zr,Ti)(Mg,Nb)O 3 ). The present embodiment does not involve a particular limitation of piezoelectric material, and the effect of the embodiment can be produced without limiting the material of the piezoelectric layer  70 . 
     The piezoelectric layer  70  has such a small thickness as the piezoelectric layer  70  does not crack in the manufacturing process, and the thickness is large to the extent that the piezoelectric layer  70  can produce displacement. For example, the piezoelectric layer  70  is formed to a thickness of about 1 to 5 μm. 
     Lead electrodes  90  made of, for example, gold (Au) are connected to the respective discrete second electrodes  80  of the piezoelectric elements  300  so as to extend from one ends at the ink supply channel  14  side of the second electrodes  80  to the surface of the insulating film  55 . 
     A protective substrate  30  having a reservoir section  31  defining at least part of a reservoir  100  is joined to the flow channel substrate  10  having the piezoelectric elements  300  with an adhesive  35  so as to cover the first electrodes  60 , the insulating film  55  and the lead electrodes  90 . The reservoir section  31  passes through the thickness of the protective substrate  30  and extends along the widths of the pressure generating chambers  12 . Thus, the reservoir section  31  communicates with the communicating section  13  of the flow channel substrate  10  to form the reservoir  100  acting as the common ink chamber of the pressure generating chambers  12 . The communicating section  13  of the flow channel substrate  10  may be divided for each pressure generating chamber  12 , and only the reservoir section  31  may serve as the reservoir. Alternatively, the flow channel substrate  10  may have only the pressure generating chambers  12 , and the reservoir and ink supply channels  14  communicating with the respective pressure generating chambers  12  are formed in a member, such as the elastic film  50  or the insulating film  55 , between the flow channel substrate  10  and the protective substrate  30 . 
     Piezoelectric element-protecting section  32  is formed in the region corresponding to the piezoelectric elements  300  in the protective substrate  30 . The Piezoelectric element-protecting section has a space so that the piezoelectric elements  300  can operate without interference. The space of the piezoelectric element-protecting section  32  is intended to ensure the operation of the piezoelectric elements  300 , and may or may not be sealed. 
     Preferably, the protective substrate  30  is made of a material having substantially the same thermal expansion coefficient as the flow channel substrate  10 , such as glass or ceramic. In the present embodiment, the protective substrate  30  is made of the same monocrystalline silicon as the flow channel substrate  10 . 
     The protective substrate  30  has a through hole  33  passing through the thickness of the protective substrate  30 . The respective lead electrodes  90  extending from the piezoelectric elements  300  are exposed in the through hole  33 . 
     A driving circuit  120  is fixed on the protective substrate  30  to drive the piezoelectric elements  300  arranged in parallel. The driving circuit  120  may be a circuit board or a semiconductor integrated circuit (IC). The driving circuit  120  is electrically connected to each lead electrode  90  with an electroconductive connection wire  121 , such as bonding wire. 
     Furthermore, a compliance substrate  40  including a sealing film  41  and a fixing plate  42  is joined on the protective substrate  30 . The sealing film  41  is made of a flexible material having a low rigidity, and seals one side of the reservoir section  32 . The fixing plate  42  is made of a relatively hard material. The portion of the fixing plate  42  opposing the reservoir  100  is completely removed in the thickness direction to form an opening  43 ; hence only the flexible sealing film  41  seals the one side of the reservoir  100 . 
     The ink jet recording head of the present embodiment draws an ink through an ink inlet connected to an external ink supply means (not shown). The ink is delivered to fill the spaces from the reservoir  100  to the nozzle apertures  21 . Then, the ink jet recording head applies a voltage between the first electrode  60  and each second electrode  80  corresponding to the pressure generating chambers  12 , according to the recording signal from the driving circuit  120 . Thus, the elastic film  50 , the insulating film  55 , the first electrode  60  and the piezoelectric layers  70  are deflected to increase the internal pressure in the pressure generating chambers  12 , thereby ejecting the ink from the nozzle apertures  21 . 
     A method for manufacturing the ink jet recording head will now be described with reference to  FIGS. 3A to 3E ,  4 A to  4 C,  5 A to  5 C, and  6 . These figures are sectional views showing a method for manufacturing the ink jet recording head being a type of liquid ejecting head according to an embodiment of the invention, taken in the longitudinal direction of the pressure generating chamber. 
     As shown in  FIG. 3A , first, an oxide film  51  for the elastic film  50  is formed over the surface of a flow channel substrate silicon wafer  110  in which a plurality of flow channel substrates  10  are to be formed integrally. In the present embodiment, the oxide film  51  is formed by thermally oxidizing the flow channel substrate silicon wafer  110 , and the oxide film  51  is thus of silicon dioxide. 
     Then, a second layer  56  of zirconium oxide is formed on the elastic film  50  (oxide film  51 ). More specifically, a zirconium layer  156  essentially composed of zirconium is formed on the elastic film  50  by, for example, sputtering, as shown in  FIG. 3B , and then, the zirconium layer  156  is thermally oxidized to form the second layer  56  essentially composed of zirconium oxide in, for example, a diffusion furnace of 500 to 1200° C., as shown in  FIG. 3C . 
     Turning now to  FIG. 3D , a third layer  57  essentially composed of zirconium oxide is formed on the second layer  56 . More specifically, the third layer  57  is formed by depositing zirconium oxide directly on the second layer  56  by sputtering. Thus, an insulating film  55  is formed including the second layer  56  and the third layer  57 . 
     Then, a first electrode  60  is formed over the entire surface of the insulating film  55  and is patterned into a predetermined shape, as shown in  FIG. 3E . If the piezoelectric layer  70  is made of lead zirconate titanate (PZT), preferably, the first electrode  60  is made of, but not limited to, a material whose electric conductivity is not varied much by the diffusion of lead oxide. Accordingly, for example, platinum and iridium are suitable as the material of the first electrode  60 . The first electrode  60  is formed by, for example, sputtering or PVD (physical vapor deposition). 
     Turning now to  FIG. 4A , a piezoelectric layer  70  of, for example, lead zirconate titanate (PZT) and a second electrode  80  of, for example, iridium are formed over the entire surface of the flow channel substrate wafer  110 . In the present embodiment, the piezoelectric layer  70  is formed by a so-called sol-gel method. In the sol-gel method, a sol containing an organic metal dissolved or dispersed therein is applied onto a surface and dried into a gel coating, and the gel coating is fired at a high temperature to form a metal oxide piezoelectric layer  70 . The piezoelectric layer  70  can be formed by any method without particular limitation, and may be formed by, for example, MOD (Metal-Organic Decomposition), or PVD (Physical Vapor Deposition) such as sputtering or laser ablation. 
     Turning now to  FIG. 4B , the second electrode  80  and the piezoelectric layer  70  are simultaneously etched to form piezoelectric elements  300  in the region corresponding to the pressure generating chambers  12 . The etching of the second electrode  80  and the piezoelectric layer  70  can be performed by dry etching, such as reactive ion etching or ion milling. 
     Then, a gold (Au) layer for the lead electrodes  90  is formed over the entire surface of the flow channel substrate wafer  110 , and is patterned into a plurality of lead electrodes  90  for the respective piezoelectric elements  300 , as shown in  FIG. 4C . 
     Turning now to  FIG. 5A , a protective substrate wafer  130  is bonded to the flow channel substrate wafer  110  with an adhesive  35 . The protective substrate wafer  130  includes a plurality of protective substrates  30  therein, including the reservoir sections  31  and the piezoelectric element-protecting sections  32 . By joining the protective substrate wafer  130 , the rigidity of the flow channel substrate wafer  110  is considerably enhanced. 
     Subsequently, the thickness of the flow channel substrate wafer  110  is reduced to a predetermined level, as shown in  FIG. 5B . 
     Then, a layer for a mask  52  is formed on a surface of the flow channel substrate wafer  110  opposite to the protective substrate wafer  130  and is patterned into a predetermined shape, as shown in  FIG. 5C . Turning to  FIG. 6 , the flow channel substrate wafer  110  is subjected to anisotropic etching (wet etching) using an alkaline solution, such as KOH, through the mask  52 , and thus, the pressure generating chambers  12  corresponding to the piezoelectric elements  300 , the communicating section  13 , the ink supply channels  14  and the communication paths  15  are formed. 
     Then, the mask  52  is removed from the flow channel substrate wafer  110 , and unnecessary outer portions of the flow channel substrate wafer  110  and the protective substrate wafer  130  are cut off by, for example, dicing. Subsequently, a nozzle plate  20  having nozzle apertures  21  therein is joined to the surface of the flow channel substrate wafer  110  opposite to the protective substrate wafer  130 , and a compliance substrate  40  is joined to the protective substrate wafer  130 . The flow channel substrate wafer  110  joined with other substrates together is cut into chips, each including a flow channel substrate  10  and other members, and thus an ink jet recording head according to the present embodiment is produced. 
     In the manufacturing method of the ink jet recording head I according to the present embodiment, a zirconium-based zirconium layer  156  is formed on an elastic film  50 , and the zirconium layer  156  is thermally oxidized by heating, as described above. Consequently, the adhesion between the elastic film  50  and the insulating film  55  can be enhanced to prevent the separation between those layers during operation of the piezoelectric element  300 , and thus the durability and reliability can be enhanced. 
     Furthermore, the third layer  57  formed directly on the second layer  56  by sputtering can reduce the occurrence of cracks in the second layer  56 . Even if the second layer  56  is cracked, the third layer  57  covers the crack to prevent the crack from spreading. 
     Second Embodiment 
       FIGS. 7A to 7D  are sectional views showing a method for manufacturing an ink jet recording head being a type of liquid ejecting head according to another embodiment of the invention, taken in the longitudinal direction of the pressure generating chamber. The same parts as in the first embodiment are designated by the same reference numerals and the same description will not be repeated. 
     As in the step shown in  FIG. 3A , an elastic film  50  is formed over the surface of the flow channel substrate wafer  110 . 
     Subsequently, a zirconium layer  156  essentially composed of zirconium is formed on the elastic film  50 , as shown in  FIG. 7A . The zirconium layer  156  can be formed by, for example, sputtering or CVD. 
     Turning to  FIG. 7B , a third layer  57  essentially composed of zirconium oxide is formed on the zirconium layer  156 . The third layer  57  is formed by directly depositing zirconium oxide on the zirconium layer  156  by sputtering, as in the first embodiment. 
     Then, as shown in  FIG. 7C , a second layer  56  essentially composed of zirconium oxide is formed by thermally oxidizing the zirconium layer  156 , as shown in  FIG. 7C . Although the surface of the zirconium layer  156  is covered with the third layer  57 , the heated third layer  57  allows the permeation of oxygen and, thus, the zirconium layer can be thermally oxidized. 
     The subsequent steps including forming the piezoelectric element  300 , binding the protective substrate wafer  130 , and forming the pressure generating chambers  12  are performed in the same manner as in the first embodiment, and the same descriptions will be omitted. 
     In the second embodiment, the third layer  57  is formed on the zirconium layer  156  before thermally oxidizing the zirconium layer  156  to form the second layer  56 . Therefore, the third layer  57  reinforces the zirconium layer  156  to prevent the second layer  56  from cracking at the point of foreign matter on the elastic film  50  when the zirconium layer  156  is thermally oxidized. Even if the second layer  56  cracks, the third layer  57  covering the second layer  56  can suppress the spread of the crack. 
     Although the method of the second embodiment is different from that of the first embodiment, the resulting ink jet recording head  1  has the same structure and accordingly produces the same effects; hence, the second layer  56  enhances the adhesion to the elastic film  50  and the third layer  57  reduces the occurrence of cracks and suppresses the spread of the cracks. 
     Other Embodiments 
     Although exemplary embodiments of the invention have been described, the invention is not limited to those embodiments. For example, thin-film piezoelectric elements  300  of an actuator device is used as pressure generating elements to vary the pressures of the pressure generating chambers  12  in the first and the second embodiment. However, any type of pressure generating element can be used without particular limitation, including, for example, the element of a thick-film actuator device produced by bonding a green sheet and the element of a vertical vibration actuator device produced by alternately forming piezoelectric layers and electrode layers so as to expand and contract in the axis direction. An electrostatic actuator may be used as the pressure generating element. The electrostatic actuator generates static electricity between a vibration plate and an electrode to deform the vibration plate, thereby ejecting droplets through nozzle apertures. 
     In the first and the second embodiment, the piezoelectric elements  300  acting as pressure generating elements are disposed on the third layer  57 . The pressure generating elements may be provided directly on the third layer  57  or with another member their between, as long as they are present over the third layer  57 . 
     In the first and the second embodiment, a monocrystalline silicon substrate is used as the flow channel substrate  10 . The monocrystalline silicon substrate may have a crystal plane orientation of ( 100 ) or ( 110 ). Also, a SOI substrate or a glass substrate may be used without limiting to a monocrystalline silicon substrate. 
     The ink jet recording head according to any one of those embodiments of the invention is installed in an ink jet recording apparatus to serve as a part of a recording head unit including a flow channel communicating with an ink cartridge or the like.  FIG. 8  is a schematic perspective view of an ink jet recording apparatus including the ink jet recording head. 
     The ink jet recording apparatus II shown in  FIG. 8  includes recording head units  1 A and  1 B each including the ink jet recording head I, and cartridges  2 A and  2 B for supplying ink are mounted in the respective recoding head units  1 A and  1 B. The recording head units  1 A and  1 B are loaded on a carriage  3  secured for movement along a carriage shaft  5  of an apparatus body  4 . The recording head units  1 A and  1 B eject, for example, a black ink composition and a color ink composition, respectively. 
     The carriage  3  on which the recording head units  1 A and  1 B are mounted is moved along the carriage shaft  5  by transmitting the driving force from a driving motor  6  to the carriage  3  through a plurality of gears (not shown) and a timing belt  7 . In the apparatus body  4 , a platen  8  is disposed along the carriage shaft  5  so that a recording sheet S being a print medium, such as paper, fed from a paper feed roller or the like (not shown) is transported over the platen  8 . 
     Although the first embodiment and the second embodiment have described an ink jet recording head as the liquid ejecting head, the invention is intended for all types of liquid ejecting head, and may be applied to other liquid ejecting heads ejecting liquid other than ink. Other liquid ejecting heads include various types of recording heads used in image recording apparatuses such as printers, color material ejecting heads used for manufacturing color filters of liquid crystal displays or the like, electrode material ejecting heads used for forming electrodes of organic EL displays or FEDs (field emission displays), and bioorganic material ejecting heads used for manufacturing bio-chips. 
     Also, other types of actuator device may be used without particular limitation to the type used in the above embodiments.