JP2009113419A - Manufacturing method of liquid jet head and manufacturing method of piezoelectric element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a liquid jet head capable of surely preventing breakage of a lower electrode and a piezoelectric element, and a manufacturing method of a piezoelectric element. <P>SOLUTION: The method includes the step of: stacking an adhesion layer of titanium, a platinum layer of platinum, titanium layer of titanium and a diffusion-preventing layer of iridium, which overlie, in this order, one surface of a conduit-forming substrate on which a pressure-generating chamber communicating with a nozzle opening for jetting a liquid, to form the lower electrode 60; forming a piezoelectric precursor film on the lower electrode 60 and sintering the same to form a piezoelectric layer 70; and forming an upper electrode on the piezoelectric layer 70 to form the piezoelectric element comprising the lower electrode 60, the piezoelectric layer 70 and the upper electrode 80. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a liquid ejecting head that ejects liquid from a nozzle opening and a method for manufacturing a piezoelectric element.

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

  In addition, a piezoelectric element used in an ink jet recording head is formed by forming a piezoelectric element including a lower electrode, a piezoelectric layer, and an upper electrode on a flow path forming substrate provided with a pressure generating chamber communicating with a nozzle opening. Is formed.

  And what provided the adhesion layer which consists of titanium, the platinum layer which consists of platinum provided on the adhesion layer, and the iridium layer which consists of iridium provided on the platinum layer as a lower electrode which constitutes a piezoelectric element It has been proposed (see, for example, Patent Document 1). The platinum layer constituting the lower electrode is selected as a material that does not lose conductivity even when the piezoelectric layer is subjected to high-temperature heat treatment, and the iridium layer is formed by the high-temperature heat treatment when forming the piezoelectric layer. It functions as a diffusion preventing layer for preventing components constituting the layer from diffusing into the lower electrode.

JP 2001-274472 A

  However, the lower electrode is heated at the same time as the piezoelectric layer is fired, and titanium, which is an adhesion layer, is formed as titanium oxide at the interface between the iridium layer and the platinum layer. Titanium oxide is unevenly distributed between the iridium layer and the platinum layer. Due to variations in titanium oxide on platinum, local stress concentration occurs in the lower electrode, and cracks occur in the lower electrode. There is a problem that the destruction of. The stress concentration occurs due to thermal expansion or contraction when the lower electrode film is heated, or deformation of the piezoelectric element.

  Such a problem exists not only in an ink jet recording head that ejects ink, but also in a liquid ejecting head that ejects liquid other than ink. Further, not only piezoelectric elements as pressure generating means for causing a pressure change in the pressure generating chamber of the liquid ejecting head but also piezoelectric elements used for other devices.

  SUMMARY An advantage of some aspects of the invention is that it provides a method for manufacturing a liquid ejecting head and a method for manufacturing a piezoelectric element that can reliably prevent the lower electrode and the piezoelectric element from being destroyed.

An aspect of the present invention that solves the above problem is that an adhesive layer made of titanium is formed on one surface side of a flow path forming substrate provided with a pressure generating chamber communicating with a nozzle opening for ejecting liquid, and platinum is formed on the adhesive layer. A lower electrode is formed by laminating a platinum layer made of titanium, a titanium layer made of titanium on the platinum layer, and a diffusion preventing layer made of iridium on the titanium layer, and a piezoelectric precursor on the lower electrode Forming a piezoelectric layer by firing the piezoelectric precursor film and forming an upper electrode on the piezoelectric layer, thereby forming the lower electrode, the piezoelectric layer, and the piezoelectric layer. According to another aspect of the invention, there is provided a method of manufacturing a liquid ejecting head, wherein a piezoelectric element including an upper electrode is formed.
In this embodiment, when the piezoelectric precursor film is baked to form the piezoelectric layer, the lower electrode is also heat-treated at the same time, so that the lower electrode is configured by the adhesion layer, the platinum layer, the titanium oxide layer, and the iridium oxide layer. Thus, a titanium oxide layer can be formed with a substantially uniform thickness between the platinum layer and the iridium oxide layer. Thereby, it is possible to prevent stress concentration due to non-uniform presence of titanium oxide on the platinum layer and to prevent the lower electrode from being broken such as cracks.

  Here, in the step of forming the piezoelectric layer, a coating step of applying the piezoelectric precursor film on the lower electrode, a drying step of drying the piezoelectric precursor film, and the dried piezoelectric precursor film It is preferable to include a degreasing step for degreasing and a firing step for firing the degreased piezoelectric precursor film to form the piezoelectric layer. According to this, a piezoelectric layer having excellent piezoelectric characteristics can be formed by forming a piezoelectric layer by coating, drying, degreasing and firing processes, and the lower electrode is heated by heat treatment in each process. Even if expansion and thermal contraction are repeated, stress concentration due to uneven formation of titanium oxide can be reliably prevented.

  Further, in the step of forming the piezoelectric layer, it is preferable to repeat the coating step, the drying step, the degreasing step, and the firing step to form a plurality of piezoelectric layers. According to this, a piezoelectric layer having a desired thickness can be obtained, and even if the lower electrode repeats thermal expansion / contraction by multiple heat treatments, titanium oxide is formed unevenly. It is possible to reliably prevent stress concentration due to.

Furthermore, another aspect of the present invention provides a piezoelectric element comprising a lower electrode provided on a substrate, a piezoelectric layer provided on the lower electrode, and an upper electrode provided on the piezoelectric layer. The method comprises: an adhesion layer made of titanium on one side of the substrate, a platinum layer made of platinum on the adhesion layer, a titanium layer made of titanium on the platinum layer, and iridium on the titanium layer. A step of forming a lower electrode by laminating a diffusion prevention layer comprising: a step of forming a piezoelectric precursor film on the lower electrode, and firing the piezoelectric precursor film to form a piezoelectric layer; And a step of forming an upper electrode on the piezoelectric layer.
In this embodiment, when the piezoelectric precursor film is baked to form the piezoelectric layer, the lower electrode is also heat-treated at the same time, so that the lower electrode is configured by the adhesion layer, the platinum layer, the titanium oxide layer, and the iridium oxide layer. Thus, a titanium oxide layer can be formed with a substantially uniform thickness between the platinum layer and the iridium oxide layer. Thereby, it is possible to prevent stress concentration due to non-uniform presence of titanium oxide on the platinum layer and to prevent the lower electrode from being broken such as cracks.

Hereinafter, the present invention will be described in detail based on embodiments.
(Embodiment 1)
FIG. 1 is an exploded perspective view showing a schematic configuration of an ink jet recording head which is an example of a liquid ejecting head according to Embodiment 1 of the present invention. FIG. 2 is a plan view of FIG. 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 the present embodiment, and an elastic film 50 having a thickness of 0.5 to 2 μm made of silicon dioxide on one surface thereof. 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 and a communication path 15. The communication part 13 communicates with a reservoir part 31 of a protective substrate, which will be described later, and constitutes a part of a reservoir that becomes a common ink chamber of the pressure generation 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. In this embodiment, the ink supply path 14 is formed by narrowing the width of the flow path from one side. However, the ink supply path may be formed by narrowing the width of the flow path from both sides. Further, the ink supply path may be formed by narrowing from the thickness direction instead of narrowing the width of the flow path. Further, each communication passage 15 is formed by extending the partition walls 11 on both sides in the width direction of the pressure generating chamber 12 to the communication portion 13 side to partition the space between the ink supply path 14 and the communication portion 13. Yes. That is, the flow path forming substrate 10 has an ink supply path 14 having a cross-sectional area smaller than the cross-sectional area of the pressure generating chamber 12 in the width direction, and communicates with the ink supply path 14 and disconnects the ink supply path 14 in the width direction. A communication passage 15 having a cross-sectional area larger than the area is provided by being partitioned by a plurality of partition walls 11.

  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 of each pressure generating chamber 12 on the side opposite to the ink supply path 14 is provided with an adhesive. Or a heat-welded film or the like. The nozzle plate 20 is made of, for example, glass ceramics, a silicon 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 1.1 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 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 addition, here, the piezoelectric element 300 and the diaphragm that is displaced by driving the piezoelectric element 300 are collectively referred to as an actuator device. 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 present invention is not limited to this, and for example, the elastic film 50 and the insulator film 55 are provided. Instead, only the lower electrode film 60 may act as a diaphragm. Further, the piezoelectric element 300 itself may substantially serve as a diaphragm.

Then, the heat-treated lower electrode film 60 includes an adhesion layer 61 made of titanium (Ti) and a platinum layer made of platinum (Pt) provided on the adhesion layer 61 as shown in FIG. 62, a titanium oxide layer 63 made of titanium oxide (TiO _x ) provided on the platinum layer 62, and an iridium oxide layer 64 made of iridium oxide (IrO _x ) provided on the titanium oxide layer 63. It has become. The platinum layer 62 is selected as a material that does not lose its conductivity even in a high-temperature heat treatment when the piezoelectric layer 70 is formed by firing the piezoelectric precursor film. In addition, the iridium oxide layer 64 functions as a diffusion preventing layer that prevents components constituting the piezoelectric layer 70 from diffusing into the lower electrode film 60 due to high-temperature heat treatment when the piezoelectric layer 70 is formed.

  The platinum layer 62 is made of columnar crystals, and has a grain boundary layer 63a made of titanium oxide that is continuously present from the titanium oxide layer 63 at the grain boundary of each columnar crystal grain 62a.

  Each of these layers 61 to 64 is formed by thermal diffusion simultaneously with heat treatment when the piezoelectric precursor film is formed by firing the piezoelectric precursor film after film formation by a manufacturing process as described later. It is. These layer structures illustrate the results observed by microscopic observation. The layer structure may not be clearly identified, and the interface of the layer may not be clear. The layer structure of the form is formed by a manufacturing process described later.

  That is, the lower electrode film 60 of this embodiment is formed of titanium (not shown) on the insulator film 55 before the piezoelectric layer 70 is formed, as shown in FIG. An adhesion layer 65 made of Ti), a platinum layer 66 made of platinum (Pt) on the adhesion layer 65, a titanium layer 67 made of titanium (Ti) on the platinum layer 66, and a diffusion made of iridium on the titanium layer 67. When the piezoelectric layer 70 is crystallized by firing after sequentially laminating the prevention layer 68, the lower electrode film 60 is also formed by heat treatment at the same time.

  In such a lower electrode film 60, as shown in FIG. 3, the titanium constituting the adhesion layer 65 diffuses during the firing and segregates and segregates at the grain boundaries of the columnar crystal grains 62a of the platinum layer 62. 63a is formed and a part of the titanium oxide layer 63 on the upper surface of the platinum layer 62 is formed. Further, the titanium layer 67 provided on the upper surface of the platinum layer 66 is thermally oxidized to form the titanium oxide layer 63.

  Thus, by forming the titanium layer 67 on the platinum layer 66 in advance, the titanium oxide layer 63 is formed to have a substantially uniform film thickness between the platinum layer 62 and the iridium oxide layer 64 when the heat treatment is performed. Can be formed. Therefore, titanium oxide is prevented from being unevenly present between the platinum layer 62 and the iridium oxide layer 64, and local stress concentration is prevented from occurring in the lower electrode film 60, thereby preventing the lower electrode film 60. It is possible to prevent breakage such as cracks from occurring. Since the titanium oxide layer 63 has a higher proportion of titanium constituting the titanium layer 67 than titanium constituting the adhesion layer 65, the diffusion of titanium constituting the adhesion layer 65 is within the plane of the upper surface of the platinum layer 62. Even if it is uneven, the effect is low.

  Incidentally, when the titanium layer 67 is not provided as the lower electrode film 60 before the heat treatment, titanium in the adhesion layer 65 diffuses into the grain boundary of the platinum layer 62 and is oxidized, and titanium oxide is formed on the platinum layer 62. Although the layer 63 is formed, it is difficult to control the amount and direction in which the titanium in the adhesion layer 65 is diffused, and the titanium oxide layer 63 is formed on the platinum layer 62 in a non-uniform state. When stress is applied to the lower electrode film 60, stress concentration is locally generated in the region where the titanium oxide is formed, compared to the region where the titanium oxide is not formed on the platinum layer 62. The electrode film 60 may be broken such as cracks. The stress is applied to the lower electrode film 60 by, for example, thermal expansion / contraction when the lower electrode film 60 is heat-treated, or deformation of the piezoelectric element 300.

  Further, since the platinum layer 62 and the columnar crystal grains 62a forming the platinum layer 62 are surrounded by titanium oxide, the rigidity and toughness of the lower electrode film 60 are improved. Further, the adhesion between the lower electrode film 60 and the insulator film 55 made of zirconium oxide is improved, and the platinum layer 62 and the iridium oxide layer 64 are firmly adhered via the titanium oxide layer 63. Become.

The piezoelectric layer 70 is a crystal film having a perovskite structure formed on the lower electrode film 60. As the piezoelectric layer 70, for example, a ferroelectric 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 ferroelectric material is suitable. The metal oxide is not limited to niobium oxide, nickel oxide, or magnesium oxide. 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. Alternatively, the communication portion 13 of the flow path forming substrate 10 may be divided into a plurality of pressure generation chambers 12 and only the reservoir portion 31 may be used as the reservoir. Further, for example, only the pressure generation chamber 12 is provided in the flow path forming substrate 10, and a reservoir and a member interposed between the flow path forming substrate 10 and the protective substrate 30 (for example, the elastic film 50, the insulator film 55, etc.) An ink supply path 14 that communicates with each pressure generating chamber 12 may be provided.

  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 120 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 120. The drive circuit 120 and the lead electrode 90 are electrically connected via a connection wiring 121 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), and one surface of the reservoir portion 31 is sealed by the sealing film 41. The fixing plate 42 is made of a hard material such as metal (for example, stainless steel (SUS)). 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 the present embodiment, ink is taken in from an ink introduction port connected to an external ink supply means (not shown), and the interior from the reservoir 100 to the nozzle opening 21 is filled with ink, and then the drive circuit 120. In accordance with the recording signal from, 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 insulator film 55, the lower electrode film 60, and the piezoelectric layer. By bending and deforming 70, the pressure in each pressure generating chamber 12 is increased, and ink droplets are ejected from the nozzle openings 21.

Hereinafter, a method for manufacturing such an ink jet recording head will be described with reference to FIGS. 4 to 7 are cross-sectional views in the longitudinal direction of the pressure generating chamber showing the method of manufacturing the ink jet recording head which is an example of the liquid jet head according to the first embodiment of the present invention. First, as shown in FIG. 4A, a silicon dioxide film 51 made of silicon dioxide (SiO ₂ ) constituting the elastic film 50 is formed on the surface of a flow path forming substrate wafer 110 that is a silicon wafer.

Next, as shown in FIG. 4B, an insulator film 55 made of zirconium oxide is formed on the elastic film 50 (silicon dioxide film 51). Specifically, after forming a zirconium (Zr) layer on the elastic film 50 (silicon dioxide film 51) by, for example, sputtering, the zirconium layer is thermally oxidized in a diffusion furnace, for example, to form zirconium oxide ( An insulator film 55 made of ZrO ₂ ) is formed.

  Next, as shown in FIG. 4C, a lower electrode film 60 including an adhesion layer 65, a platinum layer 66, a titanium layer 67, and a diffusion prevention layer 68 is formed. Specifically, first, an adhesion layer 65 made of titanium (Ti) having a thickness of 10 to 50 nm is formed on the insulator film 55. In this embodiment, 20 nm-thick titanium (Ti) is provided as the adhesion layer 65. Thus, by providing the adhesion layer 65 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 66 made of platinum (Pt) and having a thickness of 50 to 500 nm is formed on the adhesion layer 65. Next, a titanium layer 67 made of titanium (Ti) is formed on the platinum layer 66. Then, a diffusion preventing layer 68 made of iridium (Ir) is formed on the titanium layer 67. Thereby, the lower electrode film 60 including the adhesion layer 65, the platinum layer 66, the titanium layer 67, and the diffusion prevention layer 68 is formed.

  As shown in FIG. 3, when the piezoelectric layer 70 is fired and crystallized in a later step, the titanium layer 67 is formed of a platinum layer 62 and an iridium oxide layer 64 (a layer in which the diffusion preventing layer 68 is oxidized). ) Is formed to prevent uneven diffusion of the components of the adhesion layer 65. Such a titanium layer 67 is preferably formed with a thickness of 2 to 10 nm. If the titanium layer 67 is thinner than 2 nm, when the titanium oxide layer 63 is formed, the proportion of titanium diffused and oxidized in the adhesion layer 65 increases, and the influence on the thickness of the titanium oxide layer 63 in the plane is affected. This is because there is a possibility that the stress becomes concentrated and stress concentration occurs. Further, when the titanium layer 67 is thicker than 10 nm, the (100) orientation strength of the piezoelectric layer 70 is lowered, and there is a concern about deterioration of piezoelectric performance.

  The diffusion preventing layer 68 prevents the components (titanium) of the adhesion layer 65 and the titanium layer 67 from diffusing into the piezoelectric layer 70 when the piezoelectric layer 70 is fired and crystallized in a later step. In addition, the components of the piezoelectric layer 70 are prevented from diffusing into the lower electrode film 60. The thickness of the diffusion preventing layer 68 is preferably 5 to 20 nm.

  The lower electrode film 60 including the adhesion layer 65, the platinum layer 66, the titanium layer 67, and the diffusion prevention layer 68 can be sequentially formed by, for example, a sputtering method, a CVD method (chemical vapor deposition method), or the like.

  Here, the platinum layer 66 needs to be columnar crystals with crystals extending in the thickness direction, but in order to satisfactorily form the grain boundary layer 63a at the crystal grain boundaries, the platinum layer 66 is made as clean as possible. Crystals are preferred. Such a clean columnar crystal platinum layer 66 preferably has a relatively low sputtering pressure, for example. Thus, by making the platinum layer 66 a clean columnar crystal, it effectively works to set the preferential orientation direction of the piezoelectric layer 70 to be described later to (100), for example.

Further, such a lower electrode film 60 is heated at the same time when the piezoelectric layer 70 described later is crystallized by firing. At this time, in this embodiment, since the platinum layer 66, the titanium layer 67, and the diffusion prevention layer 68 are provided on the adhesion layer 65, the metal constituting the adhesion layer 65, that is, titanium (Ti) in this embodiment is 3, while being diffused and oxidized, as shown in FIG. 3, it proceeds to the upper surface side of the platinum layer 62 through the grain boundary of the columnar crystal grains 62 a forming the platinum layer 62. At this time, the grain boundary layer 63 a in which oxidized titanium oxide (TiO _x ) is unevenly distributed is formed, and the titanium oxide layer 63 is formed together with the titanium layer 67 formed in advance on the upper surface side of the platinum layer 62.

  That is, if the titanium layer 67 is not formed on the platinum layer 66 as the lower electrode film 60, titanium that is a component of the adhesion layer 65 is diffused and oxidized to exist on the upper surface (grain boundary) of the platinum layer 62 by segregation. That is, it is unevenly distributed, and titanium oxide is unevenly formed on the upper surface (grain boundary) of the platinum layer 62. On the other hand, by forming a titanium layer 67 in advance on the platinum layer 66 as the lower electrode film 60 before the heat treatment, the titanium oxide has a surface on the platinum layer 62 when the heat treatment is performed. Thus, the titanium oxide layer 63 can be formed on the platinum layer 62 with a substantially uniform film thickness. This prevents the titanium oxide from being unevenly present between the platinum layer 62 and the iridium oxide layer 64, thereby preventing local stress concentration from occurring in the lower electrode film 60. It is possible to prevent breakage such as cracks in 60. Since the titanium oxide layer 63 has a higher proportion of titanium constituting the titanium layer 67 than titanium constituting the adhesion layer 65, the diffusion of titanium constituting the adhesion layer 65 is within the plane of the upper surface of the platinum layer 62. Even if it is uneven, the effect is low.

  Incidentally, it is conceivable that a titanium oxide layer made of titanium oxide is formed on the platinum layer 66 as the lower electrode film 60 before the heat treatment. However, titanium oxide has a weak adhesion, and Since there exists a possibility that delamination with the diffusion prevention layer 68 may generate | occur | produce, it is not preferable.

Next, as shown in FIG. 4D, a crystal seed layer 69 made of titanium (Ti) is formed on the lower electrode film 60. The crystal seed layer 69 is formed with a thickness of 3.5 to 5.5 nm. The crystal seed layer 69 preferably has a thickness of 4.0 nm. In the present embodiment, the crystal seed layer 69 is formed with a thickness of 4.0 nm. In this embodiment, titanium (Ti) is used as the crystal seed layer 69, but the crystal seed layer 69 is a crystal of the piezoelectric layer 70 when the piezoelectric layer 70 is formed in a later step. For example, titanium oxide (TiO _x ) may be used as the crystal seed layer 69.

The crystal seed layer 69 formed in this way 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 crystal seed layer 69 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 crystal seed layer 69 is determined by the film formation conditions regardless of the thickness. Furthermore, the crystal seed layer 69 is preferably amorphous. Specifically, it is preferable that the X-ray diffraction intensity of the crystal seed layer 69, in particular, the (002) plane X-ray diffraction intensity (XRD intensity) is substantially zero. When the crystal seed layer 69 is amorphous as described above, the film density of the crystal seed layer 69 is increased, and the thickness of the oxide layer formed on the surface layer can be suppressed thin. As a result, the crystal of the piezoelectric layer 70 is further improved. It is because it can be made to grow.

  By providing the crystal seed layer 69 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 crystal seed layer 69 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 crystal seed layer 69 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.

  Such a crystal seed layer 69 can be formed by, for example, a sputtering method, a CVD method (chemical vapor deposition method), or the like.

  Next, a piezoelectric layer 70 made of lead zirconate titanate (PZT) is formed. Here, in this embodiment, a so-called sol in which an organometallic compound is dissolved and dispersed in a solvent 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 a gel method. 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 a sputtering method may be used.

  As a specific procedure for forming the piezoelectric layer 70, first, as shown in FIG. 5A, 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 an organometallic 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). 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). Next, as shown in FIG. 5B, 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 addition, as a heating apparatus used in such a drying process, a degreasing process, and a baking process, for example, a hot plate, an RTP (Rapid Thermal Processing) apparatus that heats by irradiation with an infrared lamp, or the like can be used.

  Next, as shown in FIG. 5C, when the first piezoelectric film 72 is formed on the lower electrode film 60, the lower electrode film 60 and the first piezoelectric film 72 are formed on their side surfaces. Are simultaneously patterned so as to be inclined. The patterning of the lower electrode film 60 and the first piezoelectric film 72 can be performed by dry etching such as ion milling, for example.

  Here, for example, when the first piezoelectric film 72 is formed after the crystal seed layer 69 is formed on the lower electrode film 60 and then patterned, the lower electrode film 60 is subjected to a photo process, ion milling, and ashing. As a result, the crystal seed layer 69 is altered to form a pattern, and even if the piezoelectric film 72 is formed on the altered crystal seed layer 69, the crystallinity of the piezoelectric film 72 is not good, and the second layer Since the subsequent piezoelectric film 72 also grows by affecting the crystal state of the first piezoelectric film 72, the piezoelectric layer 70 having good crystallinity cannot be 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 crystal seed layer 69. 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.

  Then, after 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 stacking a plurality of piezoelectric films 72 as shown in FIG. Form. 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 films 72. Thereby, the piezoelectric layer 70 having excellent adhesion and reliability can be formed.

  As described above, the lower electrode film 60 before the piezoelectric layer 70 is crystallized by firing is composed of the adhesion layer 65 made of titanium, the platinum layer 66, the titanium layer 67 made of titanium, and the diffusion prevention layer 68. When the piezoelectric layer 70 is fired, the lower electrode film 60 as shown in FIG. 3 described above is used, so that titanium oxide is unevenly present between the platinum layer 62 and the iridium oxide layer 64. It is possible to prevent the local stress concentration from occurring in the lower electrode film 60 and to prevent the lower electrode film 60 from being broken such as cracks.

  Further, since the platinum layer 62 and the columnar crystal grains 62a forming the platinum layer 62 are surrounded by the grain boundary layer 63a made of titanium oxide, the rigidity and toughness of the lower electrode film 60 are improved. Further, the adhesion between the lower electrode film 60 and the insulator film 55 made of zirconium oxide is improved, and the platinum layer 62 and the iridium oxide layer 64 are firmly adhered via the titanium oxide layer 63. Become.

  Next, as shown in FIG. 6A, an upper electrode film 80 made of, for example, iridium (Ir) is formed over the piezoelectric layer 70, and the piezoelectric layer 70 and the upper electrode film 80 are The piezoelectric element 300 is formed by patterning in a region facing each pressure generating chamber 12. Examples of the patterning of the piezoelectric layer 70 and the upper electrode film 80 include dry etching such as reactive ion etching and ion milling.

  Next, the lead electrode 90 is formed. Specifically, as shown in FIG. 6B, after the lead electrode 90 is formed over the entire surface of the flow path forming substrate wafer 110, for example, each through a mask pattern (not shown) made of a resist or the like. Each piezoelectric element 300 is formed by patterning.

  Next, as shown in FIG. 6 (c), a protective substrate wafer 130 that is a silicon wafer and serves as a plurality of protective substrates 30 is placed on the piezoelectric element 300 side of the flow path forming substrate wafer 110 via an adhesive 35. Join.

  Next, as shown in FIG. 7A, the flow path forming substrate wafer 110 is thinned to a predetermined thickness. Next, as shown in FIG. 7B, a mask film 52 is newly formed on the flow path forming substrate wafer 110 and patterned into a predetermined shape. Then, as shown in FIG. 7C, the flow path forming substrate wafer 110 is anisotropically etched (wet etching) using an alkaline solution such as KOH through the mask film 52, thereby forming the piezoelectric element 300. Corresponding pressure generating chambers 12, communication portions 13, ink supply passages 14, communication passages 15 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)
As mentioned above, although one Embodiment of this invention was described, the basic composition of this invention is not limited to what was mentioned above. For example, in the first embodiment described above, the configuration in which the adhesion layer 65 is formed in the lowermost layer of the lower electrode film 60 before the heat treatment and the adhesion layer 61 is formed in the lowermost layer of the lower electrode film 60 after the heat treatment is illustrated. However, the present invention is not particularly limited thereto, and titanium as a component of the adhesion layer 65 formed before the heat treatment may be all diffused by heating. That is, after the heat treatment, the lowermost layer of the lower electrode film 60 may be the platinum layer 62. Whether or not such an adhesion layer 61 is formed depends on the thickness of the adhesion layer 65, the temperature condition of the heat treatment, and the like.

  In the first embodiment, the piezoelectric precursor film 71 is applied, dried, and degreased, and then fired 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, a silicon single crystal substrate having a (110) crystal plane orientation is exemplified as the flow path forming substrate 10, but the present invention is not particularly limited thereto. For example, the crystal plane orientation is (100). A plane silicon single crystal substrate may be used, or a material such as an SOI substrate or glass may be used.

  In the first embodiment described above, the ink jet recording head has been described as an example of the liquid ejecting head. However, the present invention is widely applied to all liquid ejecting heads, and is a liquid ejecting liquid other than ink. Of course, the present invention can also be applied to 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 (field emission 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 of the invention. 2A and 2B are a plan view and a cross-sectional view of the recording head according to Embodiment 1 of the invention. FIG. 2 is a schematic cross-sectional view of a main part of the recording head according to Embodiment 1 of the invention. 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.

Explanation of symbols

I ink jet recording head (liquid ejecting head), 10 flow path forming substrate, 12 pressure generating chamber, 13 communication section, 14 ink supply path, 20 nozzle plate, 21 nozzle opening, 30 protective substrate, 31 reservoir section, 32 piezoelectric element Holding part, 40 compliance substrate, 60 lower electrode film, 61, 65 adhesion layer, 62, 66 platinum layer, 63 titanium oxide layer, 64 iridium oxide layer, 67 titanium layer, 68 diffusion prevention layer, 69 crystal seed layer, 70 piezoelectric Body layer, 71 piezoelectric precursor film, 72 piezoelectric film, 80 upper electrode film, 90 lead electrode, 100 reservoir, 120 drive circuit, 121 connection wiring, 300 piezoelectric element

Claims (4)

  An adhesion layer made of titanium on one side of a flow path forming substrate provided with a pressure generating chamber communicating with a nozzle opening for injecting a liquid, a platinum layer made of platinum on the adhesion layer, and titanium on the platinum layer A step of forming a lower electrode by laminating a titanium layer comprising: a diffusion preventing layer comprising iridium on the titanium layer; and forming a piezoelectric precursor film on the lower electrode; Forming a piezoelectric layer by firing the film, and forming an upper electrode on the piezoelectric layer to form a piezoelectric element comprising the lower electrode, the piezoelectric layer, and the upper electrode. A method of manufacturing a liquid ejecting head.   In the step of forming the piezoelectric layer, a coating step of applying the piezoelectric precursor film on the lower electrode, a drying step of drying the piezoelectric precursor film, and degreasing the dried piezoelectric precursor film The method of manufacturing a liquid jet head according to claim 1, further comprising a degreasing step and a firing step of firing the degreased piezoelectric precursor film to form the piezoelectric layer.   3. The liquid jet head manufacturing method according to claim 2, wherein in the step of forming the piezoelectric layer, the coating step, the drying step, the degreasing step, and the firing step are repeatedly performed to form a plurality of piezoelectric layers. Method. A method for manufacturing a piezoelectric element comprising: a lower electrode provided on a substrate; a piezoelectric layer provided on the lower electrode; and an upper electrode provided on the piezoelectric layer,
An adhesion layer made of titanium on one side of the substrate, a platinum layer made of platinum on the adhesion layer, a titanium layer made of titanium on the platinum layer, and a diffusion prevention layer made of iridium on the titanium layer A step of laminating and forming a lower electrode; a step of forming a piezoelectric precursor film on the lower electrode; and firing the piezoelectric precursor film to form a piezoelectric layer; and And a step of forming an upper electrode.

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