JP2002319714A - Piezoelectric element and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric element, having a stable and high piezoelectric characteristics by obtaining a prescribed orientation degree of a piezoelectric film stably and with high reproducibility and provide a method for manufacturing the same. SOLUTION: The method comprises a step (S1) of forming a diaphragm film 30 (31 or 32) on a substrate 20, a step of forming a lower electrode 33 on the film 30, a first step (S2) of forming a Ti layer on the electrode 33, a step of patterning the electrode 33 into a prescribed shape, a second step (S3) of forming a Ti layer on the electrode 33 which remains after patterning and on the film 30 from which the lower electrode is removed, a step (S4) of forming a PZT layer 43 (Pb, Zr, Ti-lead zirconate titanate) on the lower electrode layer on which the Ti layer is formed by the step (S3), and a step (S5) of forming an upper electrode 44 on the layer 43.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric element having an electromechanical conversion function, and more particularly, to a piezoelectric element capable of obtaining excellent piezoelectric characteristics when used in an ink jet recording head, and a method of manufacturing the same. The present invention relates to an ink jet recording head and a printer using the piezoelectric element.

[0002]

2. Description of the Related Art An ink jet recording head uses a piezoelectric element as a driving source for ink ejection of a printer. This piezoelectric element generally includes a piezoelectric thin film and an upper electrode and a lower electrode which are arranged to sandwich the piezoelectric thin film.

Conventionally, the crystal structure of a thin film made of lead zirconate titanate (PZT) has been defined, and Ti
Piezoelectric elements with improved characteristics by forming nuclei have been developed. For example, Japanese Patent Application Laid-Open No. H10-8101
No. 6 discloses a PZT thin film having a rhombohedral crystal structure and a predetermined degree of orientation. Japanese Patent Application Laid-Open No. 8-335676 discloses a piezoelectric element in which a titanium nucleus is formed on a lower electrode of Ir.

[0004]

However, the conventional piezoelectric element has a problem that it is difficult to stably obtain a predetermined degree of orientation of the piezoelectric film with good reproducibility. With such a piezoelectric element, it is difficult to obtain stable and high piezoelectric characteristics, and this is a factor that makes it impossible to obtain sufficient printing performance of an ink jet recording head or a printer.

In particular, when a piezoelectric film is formed on the lower electrode after the lower electrode formed on the diaphragm film is patterned into a predetermined shape, the predetermined degree of orientation of the piezoelectric film is stabilized. It was difficult to obtain with good reproducibility.

Accordingly, an object of the present invention is to provide a piezoelectric element having stable and high piezoelectric characteristics by stably obtaining a predetermined degree of orientation of a piezoelectric film with good reproducibility, and a method of manufacturing the same. I do.

It is still another object of the present invention to provide an ink jet recording head using the piezoelectric element as an ink discharge driving source, a method of manufacturing the same, and an ink jet printer.

[0008]

In order to solve the above-mentioned problems, a method of manufacturing a piezoelectric element according to the present invention comprises the steps of forming a diaphragm film on a substrate and forming a lower electrode on the diaphragm film. Forming a Ti layer on the lower electrode, forming a Ti layer on the lower electrode, patterning the lower electrode into a predetermined shape, removing the lower electrode and the lower electrode left by the patterning. Forming a Ti layer on the formed diaphragm film, forming a Ti layer on the lower electrode, and forming a PZT layer on the lower electrode on which the Ti layer is formed by the Ti layer forming second step. Forming an upper electrode on the PZT layer.

[0009] By forming the Ti layer twice, it has become possible to form PZT having a stable 100-plane orientation degree without being affected by humidity or the like.

In the above manufacturing method, it is desirable that the thickness of the Ti layer formed in the first step of forming the Ti layer is larger than the thickness of the Ti layer formed in the second step of forming the Ti layer. In this case, the reproducibility of the degree of 100-plane orientation was higher.

In the above manufacturing method, the total thickness of the Ti layer formed in the Ti layer forming first step and the Ti layer formed in the Ti layer forming second step is 3n.
It is desirable that the thickness be not less than m and not more than 20 nm.

[0012] A method of manufacturing an ink jet recording head according to the present invention includes a step of providing a piezoelectric element obtained by the above method and etching the substrate to form a pressure chamber.
Forming a nozzle plate that covers the pressure chamber.

The piezoelectric element of the present invention is a piezoelectric element in which a diaphragm film, a lower electrode, a PZT layer, and an upper electrode are sequentially laminated on a substrate, and the lower electrode is patterned into a predetermined shape. The PZT layer is formed on the lower electrode left by patterning and on the diaphragm film from which the lower electrode has been removed, and a portion of the PZT layer formed on the diaphragm film has a predetermined orientation. It has characteristics.

In the above-described piezoelectric element, a portion of the PZT layer formed on the diaphragm film from which the lower electrode has been removed may have a 111 plane preferential orientation.

In the above-mentioned piezoelectric element, it is preferable that a portion of the PZT layer formed on the lower electrode left by the patterning has a degree of 100 plane orientation of 70% or more.

[0016] The ink jet recording head of the present invention comprises:
It is characterized by comprising the above-mentioned piezoelectric element, a pressure chamber whose internal volume changes due to mechanical displacement of the piezoelectric element, and a discharge port for discharging ink droplets in communication with the pressure chamber.

A printer according to the present invention includes the above-described ink jet recording head in a printing mechanism.

The term "degree of 100-plane orientation" used in the present application means that the diffraction intensity of the peak (2θ) corresponding to the XYZ plane when CuKα radiation is used in the X-ray diffraction wide-angle method is I (X
YZ), I (100) of I (100)
, I (110) and I (111).

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

<Overall Configuration of Inkjet Printer> FIG. 1 is a perspective view illustrating the structure of a printer using the piezoelectric element of the present embodiment. In this printer, a tray 3, a discharge port 4 and an operation button 9 are provided on a main body 2. Further, an ink jet recording head 1, a supply mechanism 6, and a control circuit 8 are provided inside the main body 2.

The ink jet recording head 1 includes a plurality of piezoelectric elements formed on a substrate, and is configured to be able to discharge ink from nozzles in accordance with a discharge signal supplied from a control circuit 8.

The main body 2 is a housing of the printer, in which a supply mechanism 6 is disposed at a position where the paper 5 can be supplied from the tray 3, and the ink jet recording head 1 is disposed so as to print on the paper 5. I have. The tray 3 is configured to be able to supply the paper 5 before printing to the supply mechanism 6, and the outlet 4 is an outlet for discharging the paper 5 on which printing has been completed.

The supply mechanism 6 includes a motor 600, a roller 60
1, 602 and other mechanical structures (not shown). The motor 600 is rotatable in accordance with a drive signal supplied from the control circuit 8. The mechanical structure is configured to transmit the rotational force of the motor 600 to the rollers 601 and 602. The rollers 601 and 602 rotate when the rotational force of the motor 600 is transmitted. The rollers 601 and 602 draw the paper 5 placed on the tray 3 by rotation, and supply the paper 5 so that the head 1 can print. I have.

The control circuit 8 includes a CPU (not shown) and an RO (not shown).
M, a RAM, an interface circuit, and the like. The drive signal is supplied to the supply mechanism 6 and the ejection signal is supplied to the ink jet recording head 1 in accordance with print information supplied from a computer via a connector (not shown). Or you can do it. The control circuit 8 can set an operation mode, perform a reset process, and the like in accordance with an operation signal from the operation panel 9.

The printer of the present embodiment has an ink jet recording head having stable high piezoelectric characteristics and good printing performance, which will be described later, so that the printer has high performance.

<Structure of Inkjet Recording Head> FIG. 2 is an explanatory diagram of the structure of the inkjet recording head having the piezoelectric element according to the present embodiment. As shown in the drawing, the inkjet recording head 1 includes a nozzle plate 10,
The pressure chamber substrate 20 and the vibration plate 30 are provided.

The pressure chamber substrate 20 has a cavity (pressure chamber).
21, side wall (partition wall) 22, reservoir 23 and supply port 2
4 is provided. The cavity 21 is a space for storing ink or the like formed by etching a substrate such as silicon for discharging. The side wall 22 is formed so as to partition between the cavities 21. The reservoir 23 is a flow path for filling the respective cavities 21 with ink in common. The supply port 24 is formed so that ink can be introduced from the reservoir 23 into each cavity 21.

The nozzle plate 10 is bonded to one surface of the pressure chamber substrate 20 such that the nozzle holes 11 are arranged at positions corresponding to the cavities 21 provided in the pressure chamber substrate 20. The pressure chamber substrate 20 to which the nozzle plate 10 is attached is further housed in a housing 25 to constitute the ink jet recording head 1.

The vibration plate 30 is bonded to the other surface of the pressure chamber substrate 20. The vibration plate 30 is provided with a piezoelectric element (not shown). The diaphragm 30 is provided with an ink tank opening (not shown) so that ink stored in an ink tank (not shown) can be supplied into the pressure chamber substrate 20.

<Structure of Piezoelectric Element> FIGS. 3A and 3B are an enlarged plan view of the piezoelectric element portion of the ink jet recording head and a sectional view taken along line ii of FIG. FIG.
FIG. 4 is a sectional view taken along line ii-ii of FIG.

As shown in these figures, the piezoelectric element
A ZrO ₂ film 32, a lower electrode 33, a piezoelectric film 43, and an upper electrode 44 are sequentially laminated on an insulating film 31.

The insulating film 31 is formed on the pressure chamber substrate 20 made of, for example, single-crystal silicon having a thickness of 220 μm. Preferably, a film made of silicon oxide (SiO ₂ ) has a thickness of 1.0 μm.
m.

The ZrO ₂ film 32 is a layer having elasticity, and constitutes the diaphragm 30 integrally with the insulating film 31. Since the ZrO ₂ film 32 has a function of giving elasticity, it preferably has a thickness of 200 nm or more and 800 nm or less.

Between the ZrO ₂ film 32 and the lower electrode 33,
An adhesion layer (not shown) made of a metal, preferably titanium or chromium, that adheres both layers may be provided. When the adhesion layer is provided, the thickness is preferably 10 nm or more.

The lower electrode 33 is formed of a layer containing at least Ir, for example, a layer containing Ir / a layer containing Pt / I
It has a layer structure of a layer containing r. The overall thickness of the lower electrode 33 is, for example, 100 nm. The layer structure of the lower electrode 33 is not limited to this.
It may have a layer structure or a two-layer structure of a layer containing Pt / a layer containing Ir. Further, it may be constituted only by a layer containing Ir.

Here, the piezoelectric film 43 uses lead zirconate titanate (PZT). PZT may be added with a metal oxide such as niobium oxide, nickel oxide or magnesium oxide as needed.

The portion of the piezoelectric film 43 formed on the lower electrode 33 must have a 100-plane orientation degree of 70% or more measured by the X-ray diffraction wide angle method in order to exhibit good piezoelectric characteristics. Is desirable. And the 110 plane orientation degree is 10
% Or less, and the degree of orientation in the 111 plane is desirably the remainder.
The thickness of the piezoelectric film 43 is, for example, 1000 nm or more and 150
0 nm or less. However, the sum of the 100-, 110-, and 111-plane orientations is 100%.

The upper electrode 44 is an electrode paired with the lower electrode 33, and is preferably made of Pt or Ir. The thickness of the upper electrode 44 is preferably about 50 nm.

The lower electrode 33 is an electrode common to each piezoelectric element. On the other hand, the lower electrode for wiring 33a is located in a layer having the same height as the lower electrode 33, but is separated from the lower electrode 33 and other lower electrodes for wiring 33a, and the upper electrode 44 via the narrow band electrode 45. Can be conducted.

<Operation of Inkjet Recording Head> In the configuration of the inkjet recording head 1, a printing operation will be described. When a drive signal is output from the control circuit 8, the supply mechanism 6 operates and the paper 5 is transported by the head 1 to a printable position. When the ejection signal is not supplied from the control circuit 8 and no voltage is applied between the lower electrode 33 and the upper electrode 44 of the piezoelectric element, the piezoelectric film 43 does not deform. No pressure change occurs in the cavity 21 provided with the piezoelectric element to which the ejection signal is not supplied, and no ink droplet is ejected from the nozzle hole 11.

On the other hand, when a discharge signal is supplied from the control circuit 8 and a constant voltage is applied between the lower electrode 33 and the upper electrode 44 of the piezoelectric element, the piezoelectric film 43 is deformed.
In the cavity 21 in which the piezoelectric element to which the ejection signal is supplied is provided, the vibration plate 30 is largely bent. Therefore, the pressure in the cavity 21 increases instantaneously, and ink droplets are ejected from the nozzle holes 11. Arbitrary characters and figures can be printed by individually supplying an ejection signal to the piezoelectric element at a position where printing is desired in the head.

<Manufacturing Method> Next, a method for manufacturing the piezoelectric element of the present invention will be described. 5 and 6 are schematic cross-sectional views illustrating a method for manufacturing the piezoelectric element and the ink jet recording head according to the present embodiment.

Vibration Plate Forming Step (S1) An insulating film 31 is formed on the silicon substrate 20. The thickness of the silicon substrate 20 is, for example, about 200 μm. To manufacture the insulating film, high-temperature treatment is performed in an oxidizing atmosphere containing oxygen or water vapor to form a silicon dioxide (SiO ₂ ) film having a thickness of about 1 μm, for example. In this step, a CVD method can be used in addition to a thermal oxidation method that is usually used.

Further, on the insulating film 31, a thickness of 400 nm
Further, a ZrO ₂ film 32 of a degree is further formed. The ZrO ₂ film 32 is obtained by high-temperature processes that form a layer of Zr by sputtering or a vacuum evaporation method or the like in an oxygen atmosphere.

Step of Forming Lower Electrode (S 2) Next, a lower electrode 33 is formed on the ZrO ₂ film 32. The lower electrode 33 includes, for example, a step of forming a layer containing Ir,
The method includes a step of forming a layer containing Pt thereon, and a step of forming a layer containing Ir thereon.

[0046] The layers constituting the lower electrode 33, the Ir or Pt on ZrO ₂ film 32, respectively, forming a film deposited at a sputtering method or the like. Prior to the formation of the lower electrode 33, an adhesion layer made of titanium or chromium (not shown)
May be formed by a sputtering method or a vacuum evaporation method.

Immediately after the formation of the lower electrode 33, the lower electrode 3
A first step of forming a Ti layer (nucleus) on the third layer is performed. For example, a Ti layer is formed to a thickness of 2 nm to 18 nm by a sputtering method or the like. Ti layer is lower electrode 3
The film is uniformly formed on the substrate 3, but may be island-shaped depending on the case.

Patterning step (S) after lower electrode formation
3) Next, the lower electrode 33 is masked into a desired shape to separate it from the lower electrode for wiring 33a, and patterning is performed by etching the periphery. Specifically, first, a resist material having a uniform thickness is applied on the lower electrode by a spinner method, a spray method or the like (not shown), and then a mask is formed in the shape of a piezoelectric element, and then exposed and developed. Then, a resist pattern is formed on the lower electrode (not shown). This lower electrode 33 is etched away usually by ion milling or dry etching method is used to expose the ZrO ₂ film 32.

Next, in order to remove contaminants and oxidized portions attached to the lower electrode surface in the patterning step, cleaning by reverse sputtering is performed (not shown). In the present embodiment, since the Ti layer formed in the first step of forming the Ti layer is formed on the lower electrode 33, it is considered that the lower electrode 33 is hardly affected by the reverse sputtering.

Subsequently, a second step of forming a Ti layer (nucleus) on the lower electrode 33 and the ZrO ₂ film 32 is performed by a sputtering method or the like. Ti deposited here
The layer has a thickness of 1 nm to 2 nm. From the thickness of the Ti layer formed in the first step, the T
It is desirable to reduce the thickness of the i-layer. The total thickness of the Ti layers provided in the two steps is 3 nm or more and 20 nm or less.

Step of Forming Piezoelectric Film (S4) Next, a piezoelectric film 43 is formed on the lower electrode 33. First, a piezoelectric precursor film is formed by a sol-gel method.
Specifically, a sol composed of an organic metal alkoxide solution is applied on the Ti nucleus by an application method such as spin coating. Next, drying is performed at a constant temperature for a predetermined time, and the solvent is evaporated. After drying, degreasing is further performed at a predetermined high temperature in an air atmosphere for a certain period of time, and the organic ligand coordinated to the metal is thermally decomposed into a metal oxide. These steps of coating, drying, and degreasing are repeated a predetermined number of times, for example, twice, so that two piezoelectric precursor films are laminated. By these drying and degreasing,
The metal alkoxide and acetate in the solution form a network of metal, oxygen and metal through thermal decomposition of the ligand.

Next, the piezoelectric precursor film is fired to crystallize the piezoelectric film. By this baking, the piezoelectric precursor film becomes
It changes from an amorphous state to a rhombohedral crystal structure to a film exhibiting an electromechanical conversion action.

By repeating the above-described formation and firing of the piezoelectric film a plurality of times, the desired thickness of the piezoelectric thin film can be obtained. For example, the thickness of the precursor film applied per firing is set to 200 nm, and this is repeated five times.

The portion of the piezoelectric film 43 thus formed on the lower electrode 33 is affected by the composition of the lower electrode and the Ti layer formed in the first and second steps of forming the Ti layer.
The degree of orientation of 100 planes measured by X-ray diffraction wide angle method is about 80%
Of the piezoelectric film. The portion ZrO ₂ film 32 lower electrode 33 is removed by patterning is formed on the portion exposed was formed by the Ti layer forming second step Ti
Under the influence of the layer, it is preferentially oriented on the 100 plane or the 111 plane. Since the PZT on the ZrO ₂ film 32 is oriented, the crystallinity of the PZT is good and the crystal grains are fine, so that there is little possibility of cracking.

Upper Electrode Forming Step (S5) An upper electrode 44 is formed on the piezoelectric film 43 by an electron beam evaporation method or a sputtering method. The upper electrode 44 is formed of platinum (Pt), iridium (Ir), or another metal and is formed to a thickness of 50 nm.

Step of Removing Piezoelectric Film and Upper Electrode (S6) The piezoelectric film 43 and the upper electrode 44 are patterned into a predetermined shape of the piezoelectric element. Specifically, after a resist is spin-coated on the upper electrode 44, patterning is performed by exposing and developing in accordance with a position where a pressure chamber is to be formed. The upper electrode 44 and the piezoelectric film 43 are formed by using the remaining resist as a mask.
Is etched by ion milling or the like. Through the above steps, a piezoelectric element is formed.

Narrow Band Electrode Forming Step (S7) Next, a narrow band electrode 45 for conducting between the upper electrode 44 and the lower electrode for wiring 33a is formed. The material of the narrow band electrode 45 is preferably gold having low rigidity and low electric resistance. Besides, aluminum, copper and the like are also suitable. The band electrode 45 is about 0.2 μm
Then, patterning is performed so that a conductive portion between each upper electrode and the lower electrode for wiring remains.

Pressure Chamber Forming Step (S8) Next, an active gas such as anisotropic etching or parallel plate reactive ion etching is used on the other surface of the pressure chamber substrate 20 on which the piezoelectric element 40 is formed. The pressure chamber 21 is formed by performing anisotropic etching. The portion left without being etched becomes the side wall 22.

Nozzle Plate Bonding Step (S9) Finally, the nozzle plate 10 is placed on the pressure chamber substrate 20 after etching.
Are bonded with an adhesive. At the time of bonding, the nozzles 11 are aligned so as to be arranged in the respective spaces of the pressure chambers 21. Pressure chamber substrate 2 to which nozzle plate 10 is attached
0 is attached to a housing (not shown) to complete the ink jet recording head 1.

<Other Applications> The present invention can be applied in various modifications without depending on the above embodiment.
For example, the piezoelectric element manufactured by the present invention is not limited to the piezoelectric element of the above-described ink jet recording head, but also includes a nonvolatile semiconductor memory device, a thin film capacitor, a pyroelectric detector, a sensor, a surface acoustic wave optical waveguide, and an optical memory. The present invention can be applied to the manufacture of ferroelectric devices, such as devices, spatial light modulators, frequency doublers for diode lasers, etc., dielectric devices, pyroelectric devices, piezoelectric devices, and electro-optical devices.

[0061]

According to the present invention, the degree of 100-plane orientation of the piezoelectric film can be obtained stably with good reproducibility. As a result, it is possible to provide a piezoelectric element having stable and high piezoelectric characteristics at both high and low frequencies, and an ink jet recording head, a printer and a method of manufacturing the piezoelectric element using the same.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a structure of a printer using a piezoelectric element according to an embodiment.

FIG. 2 is an explanatory diagram of a structure of an ink jet recording head including a piezoelectric element according to the present embodiment.

FIGS. 3A and 3B are an enlarged plan view of a piezoelectric element portion of the ink jet recording head and a cross-sectional view taken along line ii of FIG.

FIG. 4 is a sectional view taken along line ii-ii of FIG.

FIG. 5 is a schematic cross-sectional view illustrating a method of manufacturing the piezoelectric element and the ink jet recording head according to the embodiment.

FIG. 6 is a schematic sectional view illustrating a method for manufacturing the piezoelectric element and the ink jet recording head according to the embodiment.

[Explanation of symbols]

20: pressure chamber substrate, 30: diaphragm, 31: insulating film, 32
... ZrO ₂ film, 40 ... piezoelectric element, 33 ... lower electrode, 4
3: Piezoelectric film, 44: Upper electrode

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H01L 41/187 H01L 41/08 C 41/22

Claims (9)

[Claims] A step of forming a diaphragm film on the substrate; a step of forming a lower electrode on the diaphragm film; and forming a Ti layer on the lower electrode. A step of patterning the lower electrode into a predetermined shape; and forming a Ti layer on the lower electrode left by the patterning and on the diaphragm film from which the lower electrode has been removed.
a second step of forming an i-layer, a step of forming a PZT layer on the lower electrode on which the Ti layer is formed by the second step of forming a Ti layer, and a step of forming an upper electrode on the PZT layer. A method for manufacturing a piezoelectric element comprising: 2. The piezoelectric body according to claim 1, wherein the thickness of the Ti layer formed in the first step of forming the Ti layer is larger than the thickness of the Ti layer formed in the second step of forming the Ti layer. Device manufacturing method. 3. The film thickness of the Ti layer formed in the Ti layer forming first step and the Ti layer formed in the Ti layer forming second step according to claim 1 or 2. The total is a method for manufacturing a piezoelectric element having a thickness of 3 nm or more and 20 nm or less. 4. A method of manufacturing an ink jet recording head including a piezoelectric element obtained by the method according to claim 1, wherein the pressure chamber is formed by etching the substrate. A method for manufacturing an ink jet recording head, comprising: a step of forming; and a step of forming a nozzle plate that covers the pressure chamber. 5. A diaphragm film, a lower electrode, a PZT on a substrate
A piezoelectric element formed by sequentially laminating a layer and an upper electrode, wherein the lower electrode is patterned into a predetermined shape, and the PZT layer is formed by removing the lower electrode and the lower electrode left by patterning. A piezoelectric element formed on a diaphragm film, wherein a portion of the PZT layer formed on the diaphragm film has a predetermined orientation. 6. The PZT layer according to claim 5, wherein a portion of the PZT layer formed on the diaphragm film from which the lower electrode has been removed has a 100 plane preferential orientation or 11
A piezoelectric element having one-plane preferred orientation. 7. The PZT layer according to claim 5, wherein a portion of the PZT layer formed on the lower electrode left by the patterning has a 100-plane orientation degree of 70%.
The piezoelectric element described above. 8. The piezoelectric element according to claim 5, a pressure chamber whose internal volume changes due to mechanical displacement of the piezoelectric element, and a pressure chamber communicating with the pressure chamber. An ink jet recording head, comprising: a discharge port for discharging ink droplets. 9. An ink jet printer comprising the ink jet recording head according to claim 8 in a printing mechanism.