JP2009238947A - Manufacturing method of piezoelectric element, piezoelectric element, and manufacturing method of device for discharging droplet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a piezoelectric element capable of improving a piezoelectric characteristic of the piezoelectric element, the piezoelectric element whose piezoelectric characteristic is improved, and a manufacturing method of a device for discharging droplet using the piezoelectric element whose piezoelectric characteristic is improved. <P>SOLUTION: The manufacturing method of the piezoelectric element comprises the steps of: forming a lower electrode film 14 on an Si substrate 12 (step 100); forming an amorphous layer of a PZT (step 102); forming a PbO film 18 on the amorphous layer by carrying out a film formation by a sputtering method (step 104); thereafter carrying out a crystallization of the amorphous layer by an annealing treatment in an atmosphere to form a piezoelectric substance layer 16 (step 106); and forming an upper electrode film 20 on the piezoelectric substance layer 16 (step 108). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a piezoelectric element, a method for manufacturing a piezoelectric element, and a droplet discharge device, and more particularly, to a method for manufacturing a piezoelectric element, a piezoelectric element, and a droplet discharge device including a step of crystallizing a piezoelectric body. It relates to a manufacturing method.

  2. Description of the Related Art In general, there is an image forming apparatus that includes a droplet discharge device that forms an image on a recording medium by discharging droplets from nozzles based on image data. As a droplet discharge device, a piezo method is known in which a piezoelectric element including a piezoelectric body is used to change the pressure in a pressure chamber to discharge an ink droplet from a nozzle.

  As a method of manufacturing a piezoelectric element including a piezoelectric body, an electrode is formed on a substrate, and while the piezoelectric material (amorphous layer) is sputtered on the electrode, the substrate is heated to the crystallization temperature of the piezoelectric material, A manufacturing method including a step of performing sputtering in the heated state is generally performed.

Also known is a technique including a step of forming an electrode on an MgO single crystal substrate, forming an alignment layer thereon by heating, forming an amorphous layer thereon without heating, and crystallizing by annealing. (For example, refer to Patent Document 1).
JP 2004-214270 A

  However, in the conventional technique, a pyrochlore layer (A2B2O7), which is an impurity layer, is formed during the crystallization process, and as a result, the piezoelectric characteristics of the piezoelectric element may deteriorate.

  For example, when the substrate is heated to the crystallization temperature during sputtering of the piezoelectric material, oxygen may not be sufficiently taken in during film formation, and oxygen defects may be caused to form a pyrochlore layer. Further, in this case, the internal stress in the piezoelectric film becomes a problem.

  Further, in the above conventional technique, when the amorphous layer is annealed, Pb loss occurs and a pyrochlore layer is formed.

  The present invention relates to a method for manufacturing a piezoelectric element capable of improving the piezoelectric characteristics of the piezoelectric element, a piezoelectric element having improved piezoelectric characteristics, and a method for manufacturing a droplet discharge device using the piezoelectric element having improved piezoelectric characteristics, The purpose is to provide.

  In order to achieve the above object, the piezoelectric element manufacturing method according to claim 1 includes a lower electrode film forming step of forming a lower electrode film preferentially oriented on a (111) lattice plane on a substrate, and the lower electrode film An amorphous layer forming step for forming an amorphous layer containing a Pb element thereon, a PbO film forming step for forming a PbO film on the amorphous layer, and a heat treatment for heating the amorphous layer on which the PbO film is formed And an upper electrode film forming step of forming an upper electrode film on the PbO film subjected to the heat treatment.

  The method for manufacturing a piezoelectric element according to claim 2 is the method for manufacturing a piezoelectric element according to claim 1, wherein the amorphous layer further contains elements of Ti and Zr.

The amorphous layer formed by the amorphous layer forming step may further contain elements of Ti and Zr in addition to Pb. An example of such an amorphous layer is an amorphous layer of PZT (a solid solution of PbZrO ₃ and PbTiO ₃ ).

  The method for manufacturing a piezoelectric element according to claim 3 is the method for manufacturing a piezoelectric element according to claim 1 or 2, wherein the PbO film forming step is such that the thickness of the PbO film is less than 700 nm. The PbO film is formed.

  When the thickness of the PbO film exceeds 700 nm, the piezoelectric characteristics of the manufactured piezoelectric element deteriorate due to the residual PbO. Therefore, in the PbO film formation step, it is preferable to form the PbO film so that the thickness of the PbO film is less than 700 nm.

  The method for manufacturing a piezoelectric element according to claim 4 is the method for manufacturing a piezoelectric element according to any one of claims 1 to 3, wherein the heating process is performed at a heating temperature of 500 ° C or higher. The temperature is in the range of 700 ° C. or lower.

  When the heating temperature in the heating process is less than 500 ° C., a heterophase pyrochlore layer as an impurity layer is formed, and when the heating temperature exceeds 800 ° C., the formed film is peeled off from the substrate. Therefore, the heating temperature is preferably 500 ° C. or higher at which the pyrochlore layer is not formed and 700 ° C. or lower in which the adhesion between the formed film and the substrate is good.

  The piezoelectric element according to claim 5 is formed by crystallizing a lower electrode film preferentially oriented on a (111) lattice plane formed on a substrate and an amorphous layer containing a Pb element on the lower electrode film. A piezoelectric layer; a PbO film formed on the piezoelectric layer; and an upper electrode film formed on the PbO film.

  A method for manufacturing a droplet discharge device according to a sixth aspect includes a step of manufacturing the piezoelectric element according to any one of claims 1 to 4 on a droplet discharge element forming substrate, and the liquid Forming a pressure chamber on the droplet discharge element forming substrate; and forming a droplet discharge port on the droplet discharge element forming substrate on which the pressure chamber is formed.

  As described above, according to the first to fifth aspects of the present invention, the piezoelectric characteristic of the piezoelectric element can be improved.

  According to the sixth aspect of the present invention, there is an effect that a droplet discharge device using a piezoelectric element with improved piezoelectric characteristics can be obtained.

[First Embodiment]
Hereinafter, a piezoelectric element and a manufacturing method thereof according to an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an example of a schematic configuration of a piezoelectric element according to an embodiment of the present invention. As shown in FIG. 1, a piezoelectric element 10 according to an embodiment of the present invention includes a substrate 12, a lower electrode film 14, a piezoelectric layer 16, a PbO (lead oxide) film 18, and an upper electrode film 20. Yes.

  Examples of the substrate 12 include a Si (silicon) substrate and a MgO single crystal substrate.

  Examples of the lower electrode film 14 include a thin film of Pt (platinum) or Ir (iridium) preferentially oriented on the (111) plane of the crystal lattice.

The piezoelectric layer 16 is a layer (film) formed of a piezoelectric material containing at least Pb, and is preferably a layer obtained by crystallizing a piezoelectric material further containing Zr and Ti as main components. In this embodiment, PZT (a solid solution of PbZrO ₃ and PbTiO ₃ ) is used, but the present invention is not limited to this.

  The PbO film 18 is a film having a thickness of 700 nm or less (details will be described later).

  The upper electrode film 20 may be a thin film of Pt or Ir as in the case of the lower electrode film, but is not limited thereto.

  FIG. 2 is an example of a flowchart showing an outline of the procedure of the method for manufacturing a piezoelectric element according to the embodiment of the present invention.

  First, in step 100, the lower electrode film 14 is formed on the substrate 12. The lower electrode film 14 is formed by, for example, sputtering, but is not limited thereto.

  In the next step 102, an amorphous layer of PZT is formed on the lower electrode film 14 without heating. In this embodiment, a PZT amorphous layer is formed on the lower electrode film 14 by sputtering at room temperature. In this embodiment, an amorphous layer having a thickness of 4 μm is formed as a specific example. In addition, the formation method of the amorphous layer of PZT is not limited to this, and other PVD (physical vapor deposition method) such as vacuum deposition, CVD (chemical vapor deposition method), hydrothermal synthesis method, sol-gel method, liquid A phase growth method or the like may be used.

  In the next step 104, the PbO film 18 is vacuum-deposited on the amorphous layer. The thickness of the PbO film is 700 nm or less, preferably 500 nm or less. In this embodiment, as a specific example, a PbO film having a thickness of 500 nm or less is formed by a sputtering method under a sputtering condition with a power of 500 W and a sputtering gas pressure of 1.0 Pa by a sputtering method. The method for forming the PbO film is not limited to this, and it may be vacuum film formation, and may be other PVD (physical vapor deposition method) such as vacuum vapor deposition, CVD (chemical vapor deposition method), or the like.

  In the next step 106, the piezoelectric layer 16 is formed by annealing in the atmosphere and crystallizing the amorphous layer. In the present embodiment, as a specific example, annealing is performed in the air under an annealing condition of a temperature rising temperature of 10 ° C./min, an annealing temperature of 500 to 700 ° C., and an annealing time of 30 min. The annealing conditions are not limited to this, but if the annealing temperature is less than 500 ° C., a pyrochlore layer as an impurity layer (different layer) is formed, and if the annealing temperature exceeds 800 ° C., the sputtered film is peeled off from the substrate. Therefore, the annealing temperature is preferably in the range of 500 to 700 ° C. Within this temperature range, a high-performance piezoelectric body that is in close contact with the substrate can be formed without forming a pyrochlore layer.

  In this embodiment, after annealing for a predetermined time (30 minutes in the above specific example), the heater (heating means heated to the annealing temperature) is stopped at the annealing temperature and cooled by natural heat dissipation.

  In the next step 108, an upper electrode film is formed on the PbO film 18. The upper electrode film 18 is formed by, for example, sputtering, but is not limited thereto. Moreover, the same method as the lower electrode film 14 may be used, or a different method may be used.

  Thereby, the piezoelectric element 10 is completed.

  FIG. 3 shows the results of XRD (X-ray diffraction) measurement when a PbO film is formed on an amorphous layer and then annealed (this embodiment) and when the PbO film is annealed without being formed. .

  Here, as a manufacturing method of the present embodiment, after a PbT film having a thickness of 150 nm is formed on a PZT amorphous layer by a sputtering method, an annealing process is performed under conditions of an annealing temperature of 700 ° C. and an annealing time of 30 min. We use what we did.

  As shown in FIG. 3, in the conventional case in which no PbO film is formed, a pyrochlore layer that is an impurity layer is present, but in the present embodiment, annealing is performed after the PbO film is formed. In this case, there is no pyrochlore layer as an impurity layer. In this way, by forming the PbO film on the amorphous layer and then performing the annealing (crystallization) process, the PbO film supplements the Pb that escapes from the amorphous layer during the annealing, thereby suppressing the formation of the pyrochlore layer. be able to.

  FIG. 4 shows the relationship between the thickness of the formed PbO film and the piezoelectric constant (d constant). The piezoelectric constant is a constant representing how much the piezoelectric element changes when a voltage is applied between the upper voltage and the lower voltage of the piezoelectric element, and represents the piezoelectric characteristics of the piezoelectric element. In general, when the d31 constant of the piezoelectric element is less than 50 pm / V, it is not possible to eject ink at a pressure chamber size (300 μm as a specific example) that can be employed in a high-density nozzle wiring of about 1200 dpi, for example. Therefore, the d31 constant is preferably 50 pm / V or more.

  As shown in FIG. 4, when the thickness of the PbO film is up to 150 nm, the d31 constant increases as the thickness increases. However, when the thickness exceeds 150 nm, the d31 constant decreases. This is considered to be caused by PbO remaining. And if it exceeds 700 nm, d31 constant will be 50 pm / V or less. Therefore, the thickness of PbO is preferably 700 nm or less, preferably 500 nm, and a more preferable optimum range is 100 to 200 nm.

  As described above, in the method for manufacturing the piezoelectric element 10 of the present embodiment, after forming the PZT amorphous layer, the PbO film 18 is formed by sputtering, and then annealed in the atmosphere. Since the amorphous layer is crystallized to form the piezoelectric layer 16, the piezoelectric layer 16 can be formed without forming the pyrochlore layer as an impurity layer in the amorphous layer, and the pyrochlore layer is formed. Piezoelectric element 10 can be produced. Therefore, the piezoelectric characteristics of the piezoelectric element 10 can be improved.

[Second Embodiment]
Hereinafter, a manufacturing method of an ink jet head (droplet discharge device) using the piezoelectric element 10 of the first embodiment, which is an embodiment of the present invention, will be described in detail with reference to the drawings. Here, a manufacturing method (configuration) corresponding to one nozzle that discharges ink has been described. However, in the case of a droplet discharge device including a plurality of nozzles, one nozzle can be manufactured at a time. Alternatively, a plurality of nozzles may be manufactured at the same time.

  FIG. 5 is an example of a flowchart showing an outline of the procedure of the method of manufacturing the inkjet head 30 according to the embodiment of the present invention. FIG. 6 is an explanatory diagram for explaining each step of the method of manufacturing the inkjet head 30 shown in FIG.

  The substrate 32 (see FIG. 6A) for forming the ink jet head 30 may be a Si substrate or the like, but may be a multilayer substrate in which other functional films are formed.

  First, in step 200, the piezoelectric element 10 of the first embodiment is manufactured on the substrate 32 (see FIG. 6B). Note that the piezoelectric element 10 is in a state of being patterned in accordance with desired characteristics and specifications of the inkjet head 30. As an example of the patterning method of the piezoelectric element 10, for example, the Si substrate 12 and the lower electrode film 14 are formed on the substrate 21, a patterned resist layer is formed on the lower electrode film 14, and the resist layer is formed. The lower electrode film 14 is dry-etched and patterned as a mask, and further, the piezoelectric layer 16, the PbO film 18, and the upper electrode film 20 are formed, and a patterned resist layer is formed thereon, and the resist layer is masked. A method of etching may be used, but the method is not limited to this.

  In the next step 202, a pressure chamber (ink storage chamber) 34 is formed (see FIG. 6C). In the present embodiment, part of the substrate 32 is removed by etching or the like to form the pressure chamber 34.

  In the next step 204, the nozzles 38 for ejecting ink are formed (see FIG. 6D). In the present embodiment, the base body 36 on which the nozzles 38 are formed is separately prepared and bonded to the base body 32 on which the pressure chambers 34 are formed. Although the material of the base | substrate 32 is not limited, As a specific example, nonmetallic materials, such as metal materials, such as SUS and Ni, and a polyimide, are mentioned.

  Thereby, the inkjet head 30 is completed.

  Although omitted in the description of the manufacturing method of the present embodiment, in addition to the pressure chamber 34 (or together with the pressure chamber 34), a supply port for filling the pressure chamber 34 with ink and the like are formed.

  The details of the method of manufacturing the inkjet head 30 are not limited to this, and the piezoelectric element 10 of the first embodiment is manufactured on the substrate 32, and then the piezoelectric element 10 of the substrate 32 is formed. The pressure chamber 34, the nozzle 38, and the like may be formed on the opposite surface.

  In the inkjet head 30, when a driving voltage is applied between the lower electrode film 14 and the upper electrode film 20, the piezoelectric layer 16 is deformed to change the volume of the pressure chamber 34, and the pressure change accompanying this changes. The ink stored in the pressure chamber 34 is ejected from the nozzle 38. After the ink is ejected, when the deformation of the piezoelectric layer 16 is restored, new pressure ink is refilled into the pressure chamber 34 through a supply port (not shown).

  As described above, in the method of manufacturing the inkjet head 30 according to the present embodiment, the piezoelectric element 10 according to the first embodiment is manufactured on the substrate 32, and then the piezoelectric element 10 of the substrate 32 is formed. Since the pressure chamber 34 and the nozzle 38 are formed on the opposite side of the surface, the inkjet head 30 using the piezoelectric element 10 with improved piezoelectric characteristics can be manufactured. Therefore, a high quality image can be formed.

It is sectional drawing which showed one of the schematic structures of the piezoelectric element which concerns on the 1st Embodiment of this invention. It is an example of the flowchart which shows the outline of the procedure of the manufacturing method of the piezoelectric element which concerns on the 1st Embodiment of this invention. FIG. 4 is an XRD diffractogram showing results of XRD (X-ray diffraction) measurement when a PbO film is formed on an amorphous layer and then annealed (this embodiment) and when annealed without forming a PbO film. is there. It is explanatory drawing for demonstrating the relationship between the thickness of a PbO film | membrane, and a piezoelectric constant. It is an example of the flowchart which shows the outline of the procedure of the manufacturing method of the inkjet head which concerns on the 2nd Embodiment of this invention. It is explanatory drawing for demonstrating each process of an example of the manufacturing method of the inkjet head which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Piezoelectric element 12 Si substrate 14 Lower electrode 16 Piezoelectric 18 PbO film 20 Upper electrode 30 Inkjet head 32 Substrate 34 Pressure chamber 36 Base 38 Nozzle

Claims (6)

Forming a lower electrode film preferentially oriented in a (111) lattice plane on a substrate;
An amorphous layer forming step of forming an amorphous layer containing an element of Pb on the lower electrode film;
A PbO film forming step of forming a PbO film on the amorphous layer;
A heat treatment step of heat-treating the amorphous layer on which the PbO film is formed;
An upper electrode film forming step of forming an upper electrode film on the heat-treated PbO film;
A method for manufacturing a piezoelectric element comprising: The amorphous layer further includes elements of Ti and Zr.
The method for manufacturing a piezoelectric element according to claim 1. In the PbO film forming step, the PbO film is formed so that the thickness of the PbO film is less than 700 nm.
The method for manufacturing a piezoelectric element according to claim 1 or 2. In the heating process, the heating temperature is 500 ° C. or higher and 700 ° C. or lower.
The method for manufacturing a piezoelectric element according to any one of claims 1 to 3. A lower electrode film formed on a substrate and preferentially oriented in a (111) lattice plane;
A piezoelectric layer obtained by crystallizing an amorphous layer containing an element of Pb on the lower electrode film;
A PbO film formed on the piezoelectric layer;
An upper electrode film formed on the PbO film;
A piezoelectric element comprising A step of manufacturing the piezoelectric element according to any one of claims 1 to 4 on a droplet discharge element forming substrate;
Forming a pressure chamber in the droplet discharge element forming substrate;
Forming a droplet discharge port in the droplet discharge element forming substrate in which the pressure chamber is formed;
A method for manufacturing a droplet discharge device comprising: