CN101246948B - Piezoelectric element and head for jetting liquid - Google Patents

Abstract

Provided are a piezoelectric element in which favorable crystallinity can be obtained with improved uniformity, breakage of a piezoelectric film can be prevented, and thereby stable displacement properties can be obtained, a liquid-jet head using the piezoelectric element. The piezoelectric element includes a lower electrode, a piezoelectric film formed on the lower electrode, and an upper electrode formed on the piezoelectric film, wherein the piezoelectric film includes a lower layer portion having column crystals, and an upper layer portion having column crystals which are continuous from those in the lower layer portion and have sizes larger than those in the lower layer portion.

Description

Piezoelectric element and liquid nozzle

This application is a divisional application of the application with the application number 03814872.2, the application date is June 24, 2003, and the title is "Piezoelectric element and liquid ejection head and its manufacturing method".

technical field

The present invention relates to a piezoelectric element and a liquid ejection head using the piezoelectric element, in particular to a method for manufacturing a piezoelectric element capable of uniform crystal orientation on a wafer plane and uniform piezoelectric characteristics.

Background technique

A piezoelectric element is an element in which a piezoelectric film exhibiting an electromechanical conversion function is sandwiched between two electrodes, and the piezoelectric film is composed of crystallized piezoelectric ceramics.

Conventionally, a so-called sol-gel method has been known as a method for manufacturing a piezoelectric element. That is, the sol of the organometallic compound is coated on the substrate on which the lower electrode is formed, dried and degreased to form a precursor of the piezoelectric body. After performing this coating, drying, and degreasing process a predetermined number of times, heat treatment is performed at a high temperature to crystallize it. In order to further increase the film thickness, the sol coating, drying and degreasing steps, and the crystallization step are further repeated on the crystallized piezoelectric layer.

As a method for degreasing the above-mentioned sol of the organometallic compound, a method using a box-type dryer and a method using an electric furnace are known.

In addition, the piezoelectric element is suitable for use in a liquid discharge head such as an ink-jet type recording head in which a vibrating membrane is used to constitute a part of a pressure generating chamber communicating with a nozzle opening for ejecting ink droplets, and the piezoelectric element This vibrating membrane is deformed to pressurize the ink in the pressure generating chamber, thereby ejecting ink droplets from the nozzle openings. The inkjet recording head is divided into two types according to the actual application: the inkjet recording head using the piezoelectric actuator in the longitudinal vibration mode that expands and contracts in the axial direction of the piezoelectric element and the piezoelectric recording head using the flexural vibration mode. Electric actuators for inkjet recording heads. As an ink jet recording head using a piezoelectric actuator in a flexural vibration mode, for example, an ink jet recording head in which a piezoelectric element is formed by forming a uniform film over the entire surface of the vibrating film is known. The piezoelectric layer is cut into shapes corresponding to the pressure generating chambers using lithography to make each pressure generating chamber independent.

And, as disclosed in Japanese Patent Laid-Open No. 2000-326503, for example, in an inkjet recording head having a piezoelectric element in such a flexural vibration mode, by Patterning the lower electrode constituting the piezoelectric element can suppress the initial deflection of the vibrating membrane and increase the amount of displacement of the vibrating membrane caused by driving the piezoelectric element.

In the conventional degreasing step in the manufacture of piezoelectric elements, it is difficult to form piezoelectric crystal nuclei in the piezoelectric precursor. Therefore, it is difficult to obtain desired crystals at the time of crystallization. In addition, variations in the rate of temperature rise occur depending on the in-plane position of the wafer, resulting in various degreasing conditions. Therefore, variations in crystal orientation and piezoelectric properties also occur.

In addition, if the piezoelectric film is formed on the lower electrode patterned as described above, the quality of the piezoelectric film formed on the end portion of the lower electrode and its outer side is poor, and there is a problem that the driving reliability of the piezoelectric element is reduced. . That is, the piezoelectric film on the lower electrode and the piezoelectric film outside the lower electrode have different properties such as crystallinity, so that the piezoelectric layer is substantially discontinuous near the end of the lower electrode. Therefore, when a voltage is applied to the piezoelectric film, damage such as cracks may occur. Especially the piezoelectric film in the region corresponding to the end of the lower electrode in the length direction is easily broken.

Contents of the invention

In view of the above problems, the problem to be solved by the present invention is to provide a piezoelectric element, a liquid ejection head using the piezoelectric element and their manufacturing method, the piezoelectric element can obtain desired good crystallinity, and can improve its uniformity. In addition, the destruction of the piezoelectric film can be prevented and stable displacement characteristics can be obtained.

In order to solve the above problems, the present invention provides a piezoelectric element having a lower electrode, a piezoelectric film formed on the lower electrode, and an upper electrode formed on the piezoelectric film, characterized in that the The piezoelectric film has columnar crystals, the crystal grain size of the columnar crystals is larger on the side of the upper electrode than on the side of the lower electrode, and an orientation degree of a predetermined plane orientation of the piezoelectric film is higher than that of other plane orientations. high degree.

In the present invention described above, the film quality such as the crystallinity of the piezoelectric film is improved, and the film quality can be made uniform.

Here, the piezoelectric film preferably has a (100) plane orientation higher than other plane orientations. Accordingly, film quality such as crystallinity of the piezoelectric film can be more reliably improved, and the film quality can be made more uniform.

Further, it is preferable that the lower electrode is patterned into a predetermined shape, and only the first piezoelectric layer which is the lowermost layer among the multilayer piezoelectric layers constituting the piezoelectric film is formed on the lower electrode, The other piezoelectric layer covers the end surface of the lower electrode and the end surface of the first piezoelectric layer, and the first piezoelectric layer and the second piezoelectric layer formed immediately above the first piezoelectric layer constitute the Describe the lower part. As a result, film quality such as crystallinity of the piezoelectric film is more reliably improved. In particular, the film quality of the end face of the lower electrode and the outer piezoelectric film is improved, so that good piezoelectric characteristics can be obtained.

In addition, it is preferable that the respective thicknesses of the first and second piezoelectric layers are thinner than the respective thicknesses of the other piezoelectric layers. As a result, the film quality of the piezoelectric film is more reliably improved.

Furthermore, it is preferable that an end surface of the lower electrode and an end surface of the first piezoelectric layer are inclined surfaces. As a result, the film quality of the lower electrode and the second piezoelectric layer formed immediately above the first piezoelectric layer is improved, thereby preventing the piezoelectric film from being cracked or the like due to voltage application.

In addition, it is preferable that a metal layer not electrically connected to the lower electrode is provided near an end portion of the piezoelectric film in the longitudinal direction. Thus, since crystallization proceeds under substantially uniform heating conditions to form a piezoelectric layer, a piezoelectric film with good film quality can be obtained.

The present invention also provides a liquid ejection head characterized by having the piezoelectric element as described above as a liquid ejection driving source.

In the present invention described above, since the ejection characteristics are improved and made uniform, a liquid ejection head with improved reliability can be realized.

Description of drawings

Fig. 1 is a schematic structural view of the printer in the first embodiment;

2 is a schematic exploded perspective view showing the recording head in the first embodiment;

3 is a plan view and a sectional view of the recording head in the first embodiment;

4 is a schematic cross-sectional view showing the layered structure of the piezoelectric element in the first embodiment;

5 is a cross-sectional view of the manufacturing process of the recording head in the first embodiment;

6 is a cross-sectional view of the manufacturing process of the recording head in the first embodiment;

Fig. 7 is a partial cross-sectional view showing a detailed layer structure of a piezoelectric element;

8 is a schematic exploded perspective view showing a recording head in a second embodiment;

9 is a plan view and a sectional view of a recording head in a second embodiment;

10 is a sectional view of a recording head in a second embodiment;

11 is a cross-sectional view of the manufacturing process of the recording head in the second embodiment;

12 is a cross-sectional view of the manufacturing process of the recording head in the second embodiment;

13 is a cross-sectional view of the manufacturing process of the recording head in the second embodiment;

14 is a cross-sectional view of the manufacturing process of the recording head in the second embodiment;

15 is a cross-sectional view of the manufacturing process of the recording head in the second embodiment;

16 is a plan view and a cross-sectional view of a recording head in a third embodiment.

Detailed ways

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(first embodiment)

1 is a schematic structural view of a printer (an example of a liquid ejection device) using an ink jet recording head (an example of a liquid ejection head) having a piezoelectric element. In this printer, a tray 3 , a discharge port 4 , and operation buttons 9 are provided on a main body 2 . In addition, the main body 2 has an inkjet recording head 1 , a paper feeding mechanism 6 , and a control circuit 8 .

The ink jet recording head 1 has a piezoelectric element manufactured by the manufacturing method of the present invention. The inkjet recording head 1 can eject ink from the nozzles in response to an ejection signal supplied from the control circuit 8 .

The main body 2 is a frame of the printer, and a paper feeding mechanism 6 is arranged at a position where paper 5 can be supplied from a tray 3 , and an inkjet recording head 1 is arranged so as to print on paper 5 . The tray 3 is configured to supply the unprinted paper 5 to the paper feeding mechanism 6 , and the discharge port 4 is an outlet for discharging the printed paper 5 .

The paper feeding mechanism 6 has a motor 600, rollers 601, 602 and other mechanical structures not shown in the figure. The motor 600 can rotate in response to a driving signal provided by the control circuit 8 . The mechanical structure can transmit the torque of the motor 600 to the rollers 601 , 602 . After the torque of the motor 600 is transmitted, the rollers 601 and 602 are rotated, and the paper 5 placed on the tray 3 is drawn in through the rotation, so that it can be supplied to the head 1 for printing.

The control circuit 8 has a CPU, ROM, RAM, interface circuit, etc. not shown in the figure, so that it can provide a driving signal to the paper feeding mechanism 6 or an ejection signal to the inkjet recording head 1 corresponding to the printing information, wherein the printing Information is provided by the computer through connectors not shown. In addition, the control circuit 8 can perform operation mode setting, reset processing, and the like in response to an operation signal from the operation button 9 .

Next, the structure of the ink jet type recording head mounted on the above-mentioned printer will be described. 2 is a schematic exploded perspective view showing the ink jet recording head in the first embodiment of the present invention, and FIG. 3 is a plan view and A-A' sectional view of FIG. 2 . Fig. 4 is a schematic cross-sectional view showing a layered structure of a piezoelectric element.

As shown in the figure, in this embodiment, the channel-forming substrate 10 is composed of a (110) oriented silicon single crystal substrate, and an elastic film 50 with a thickness of 1 to 2 μm is formed on one surface thereof. Consists of silica formed by preheated oxidation. A plurality of pressure generating chambers 12 are arranged side by side in the width direction on the flow path forming substrate 10 . Further, on the longitudinally outer region of the pressure generating chambers 12 of the flow path forming substrate 10 is formed a communicating portion 13 which communicates with the pressure generating chambers 12 via an ink supply passage 14 provided on each pressure generating chamber 12 . Furthermore, the communication portion 13 communicates with a reservoir portion 31 of a reservoir forming substrate 30 described later, and constitutes a part of the reservoir 100 as a common ink chamber for each pressure generating chamber 12 . The ink supply passage 14 is formed to be narrower than the pressure generating chamber 12 to keep the flow path resistance of the ink flowing from the communicating portion 13 into the pressure generating chamber 12 constant.

In addition, the thickness of the flow path forming substrate 10 on which the pressure generating chambers 12 and the like are formed is preferably selected in accordance with the density of the pressure generating chambers 12 to be installed. For example, when the pressure generating chambers 12 are arranged at about 180 per inch (180 dpi), the appropriate thickness of the channel forming substrate 10 is about 180 to 280 μm, preferably about 220 μm. Furthermore, for example, when the pressure generating chambers 12 are arranged at a relatively high density of about 360 dpi, the thickness of the flow path forming substrate 10 is preferably 100 μm or less. This is because such an arrangement can increase the arrangement density while maintaining the rigidity of the diaphragm 11 between adjacent pressure generating chambers 12 .

In addition, a nozzle plate 20 is fixed on the opening surface side of the flow path forming substrate 10 with an adhesive or a heat-welded film, etc., and a nozzle opening 21 is provided through the nozzle plate 20, and it is connected to each pressure generating chamber. 12 communicates with the vicinity of the end portion on the side opposite to the ink supply path 14 . In addition, the nozzle plate 20 is made of glass ceramics, silicon single crystal substrate, or stainless steel with a thickness of, for example, 0.1 to 1 mm and a linear expansion coefficient of, for example, 2.5 to 4.5 [×10 ^-6 /°C] below 300°C.

On the other hand, as shown in FIG. 4, on the side opposite to the opening surface of the flow path forming substrate 10, as described above, an elastic film 50 having a thickness of, for example, about 1.0 μm is formed. An insulating film 55 having a thickness of, for example, about 0.4 μm is formed thereon. Furthermore, a lower electrode film 60 having a thickness of, for example, about 0.2 μm, a piezoelectric layer 70 having a thickness of, for example, about 1.0 μm, and an upper electrode film 80 having a thickness of, for example, about 0.05 μm are stacked on the insulating film 55 by a process described later. , thereby constituting 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, any 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, a portion that is constituted by any one of the patterned electrodes and the piezoelectric layer 70 and that generates piezoelectric strain due to voltage application to both electrodes is referred to as a piezoelectric actuator portion. In the present embodiment, the lower electrode film 60 is used as the common electrode of the piezoelectric element 300 and the upper electrode film 80 is used as the dedicated electrode of the piezoelectric element 300 , but the arrangement may be reversed as long as the driving circuit and wiring allow. In either case, a piezoelectric actuator is formed on each pressure generating chamber. In addition, here, the piezoelectric element 300 and the vibrating membrane that is displaced by driving the piezoelectric element 300 are collectively referred to as a piezoelectric actuator.

Here, in this embodiment, the lower electrode film 60 is formed in the same region as the insulating film 55, and the lower electrode film 60 also serves as a vibrating film, so that the lower electrode film 60 serves as a substrate for forming the flow path. 10 functions as a common electrode of the plurality of piezoelectric elements 300 . In addition, the material of the lower electrode film 60 is preferably a conductive material, such as platinum, iridium, and the like. This is because the piezoelectric film 70 formed by the reactive sputtering method or the sol-gel method described below must be sintered and crystallized at a temperature of about 600 to 1000° C. in an air atmosphere or an oxygen atmosphere after film formation.

In addition, piezoelectric ceramics such as lead zirconate titanate (Pb(Zr _0.56 , Ti _0.44 )O ₃ :PZT)) are used for the composition of the piezoelectric film 70 . Others may also be lead lanthanum titanate ((Pb, La)TiO ₃ ), lead lanthanum zirconate ((Pb, La) ZrO ₃ ), or lead magnesium niobate-lead zirconate titanate (Pb(Mg, Nb) ( Zr, Ti)O ₃ : PMN-PZT), barium zirconate titanate (Ba(Zr, Ti)O ₃ : BZT), etc. In addition, the material of the upper electrode film 80 is not particularly limited as long as it is a conductive material, for example, iridium (Ir) is used in the present embodiment.

Furthermore, on the flow path forming substrate 10 on which the piezoelectric element 300 is formed, a liquid reservoir forming substrate 30 having a reservoir constituting a common ink chamber for each pressure generating chamber 12 is bonded. The reservoir portion 31 of at least a part of the liquid reservoir 100 . Furthermore, a flexible substrate 40 including a sealing film 41 made of a low-rigidity but flexible material and a fixing film made of a hard material such as metal is bonded to the reservoir forming substrate 30 . plate 42. In addition, an area of the fixing plate 42 opposite to the liquid reservoir 100 is formed with an opening portion 43 completely cut out in the width direction, and only one surface of the liquid reservoir 100 is sealed by the sealing film 41 .

As described above, the inkjet recording head of this embodiment obtains ink from an external ink supply device not shown in the figure, and after the inside from the liquid reservoir 100 to the nozzle opening 21 is filled with ink, according to the The recording signal of the drive circuit not shown in the figure applies a voltage between the lower electrode film 60 and the upper electrode film 80 corresponding to the pressure generating chamber 12 respectively through external wiring, so that the elastic film 50, the insulating film 55, the lower electrode film The electrode film 60 and the piezoelectric layer 70 are deflected and deformed, thereby increasing the pressure in each pressure generating chamber 12 to eject ink droplets from the nozzle openings 21 .

Hereinafter, a method of manufacturing the ink jet recording head in the present embodiment, particularly a method of manufacturing the piezoelectric element, will be described with reference to FIGS. 5 to 7 . First, as shown in FIG. 5( a ), the silicon wafer 110 forming the flow path forming substrate 10 is thermally oxidized in a diffusion furnace at about 1100° C., thereby forming silicon dioxide constituting the elastic film 50 and the mask 51 on the entire surface. Film 52. Next, as shown in FIG. 5( b ), after forming a zirconium (Zr) layer on the elastic film 50 (silicon dioxide film 52 ), thermal oxidation is performed in a diffusion furnace at, for example, 500 to 1200° C. to form a zirconium dioxide (Zr) layer. ZrO ₂ ) insulating film 55 . Next, as shown in FIG. 5( c ), a lower electrode film 60 made of, for example, platinum and iridium is formed on the insulating film 55 . In addition, not shown in the following figures, a crystalline seed layer made of titanium or titanium dioxide and preferably having a thickness in the range of about 2 nm to 200 nm, preferably 5 nm, is formed on the lower electrode film 60 . When forming this titanium seed layer, for example, a known DC sputtering method or the like is used. The seed layer is formed with the same thickness, but may be formed into an island shape depending on the situation.

In addition, a titanium film or a titanium dioxide film (adhesive layer: not shown in the drawing) may be further formed between the lower electrode film 60 and the insulating film 55 with a thickness of about 20 nm. By providing the adhesive layer, the adhesiveness between the insulating film 55 and the lower electrode film 60 can be improved.

Next, as shown in Fig. 5(d), a piezoelectric precursor film 711' is formed on the lower electrode film 60. The piezoelectric precursor film 711' is constituted as an amorphous film until it is crystallized in a process described later to form the first piezoelectric layer 711. In this embodiment, the PZT precursor film is formed using a sol-gel method.

The so-called sol-gel method is a method of hydrolyzing metal organic compounds such as metal alkoxides in a solution and polycondensing them. Specifically, first, a solution (sol) 711" containing a metal organic compound is coated on a substrate and dried. The metal organic compound used may, for example, be methoxide or ethoxide of a metal constituting an inorganic oxide. , isopropanol, butanol and other alkoxide or acetate compounds, etc. It can also be inorganic salts such as nitrate, oxalic acid and perchlorate.

In this embodiment, a mixture of Pb(CH ₃ COO) ₂ ·3H ₂ O, Zr(t-OCH ₄ H ₉ ) ₄ , and Ti(i-OC ₃ H ₇ ) ₄ was prepared as the starting material of the PZT film. solution (sol). This mixed solution was spin-coated at 1500 rpm to a thickness of 0.1 μm. At the stage after coating, metal atoms constituting PZT are dispersed as an organometallic complex.

After coating, it is dried at a certain temperature for a certain time, thereby evaporating the solvent of the sol. For example, the drying temperature is set to, for example, 150°C or more and 200°C or less. Best to dry at 180°C. The drying time is, for example, not less than 5 minutes and not more than 15 minutes. It is best to dry for about 10 minutes.

After drying, degreasing is further carried out for a certain period of time in the air atmosphere and at a certain degreasing temperature. In addition, the degreasing mentioned here is to remove the organic components of the sol film, such as NO ₂ , CO ₂ , H ₂ O and the like. The degreasing temperature is preferably in the range of 300°C to 500°C. This is because crystallization starts at a temperature higher than this range, and sufficient degreasing cannot be performed at a temperature lower than this range. It is best to set it at about 360°C to 400°C. The degreasing time is, for example, not less than 5 minutes and not more than 90 minutes. This is because if the time is longer than this range, crystallization will start only on the surface of the film without crystallization inside the film, and if the time is shorter than this range, sufficient degreasing cannot be performed. Degreasing for about 10 minutes is best. By degreasing, the organic matter coordinated into the metal is separated from the metal and undergoes a combustion oxidation reaction, thereby scattering into the atmosphere.

In the first degreasing, that is, the degreasing for forming the first piezoelectric layer 711 , at least the temperature increase rate during the first degreasing should be 500° C./min or less. By heating slowly at a low heating rate, the degreasing conditions can be made uniform, and many small seed crystals can be produced in the coated sol 711". In order to control the heating rate below 500°C/min, the coated sol can be The substrate at normal temperature is placed on the aluminum substrate at normal temperature, for example, and then placed on a heating plate heated to 400 ° C. Thus, the temperature rise rate is about 430 ° C / min. Make the surface coated with sol in contact with the heating plate The side opposite to the bearing surface can be degreased evenly and efficiently because it is heated from the substrate side.

The above steps of coating, drying, and degreasing are repeated a predetermined number of times, for example, twice to form a first piezoelectric precursor film 711' composed of two gel layers (Fig. 5(e)). At this time, it is also preferable to heat the second degreasing process at a heating rate of 500° C./min or less as in the first degreasing process. In addition, the number of times of repeating these coating, drying, and degreasing is not limited to two times, and may be one time or three times.

Next, the first piezoelectric layer 711 is formed by heat-treating the first piezoelectric precursor film 711' obtained in the above steps (FIG. 5(f)). The sintering conditions vary depending on the material, but in the present embodiment, heating is performed at 700° C. for 30 minutes in an oxygen atmosphere. The heating device may be an RTA (rapid annealing furnace) in addition to a diffusion furnace. The first piezoelectric layer 711 is formed by this crystallization. According to this embodiment, since the degree of (100) plane orientation of crystallized PZT is 80%, a piezoelectric film having excellent piezoelectric characteristics can be formed. In addition, good characteristics can be obtained with little variation within the surface of the substrate and throughout the entire substrate.

Next, the piezoelectric film 70 having a predetermined thickness is formed by repeating five times the same process as the above-described process of repeating the above-mentioned sol application, drying, degreasing, and then crystallizing the sol twice. For example, when the film thickness of the sol per coating is about 0.1 μm, the film thickness of the piezoelectric film 70 as a whole is about 1 μm. Fig. 7 is a cross-sectional view showing a part of the detailed layer structure of the piezoelectric element. A plurality of piezoelectric layers 712 to 715 are stacked on the first piezoelectric layer 711 formed in the first crystallization step.

In the degreasing step performed after the primary crystallization, the temperature increase rate is set to 1000° C./min or more. In order to control the temperature rise rate above 1000°C/min, the normal temperature substrate coated with the sol can be directly placed on a heating plate heated to eg 400°C. Thus, the heating rate is about 25000C/min.

By heating rapidly by increasing the rate of temperature increase compared to the first time, it is difficult to generate seed crystals in the sol film. Since it is difficult to generate seed crystals, the piezoelectric crystals crystallized previously are used as nuclei for crystal growth in the subsequent crystallization process. Therefore, it is possible to prevent the piezoelectric crystals from being discontinuous in the upper and lower layers. As described above, by heating at a lower rate of temperature increase during the first degreasing than during other degreasing, columnar crystals with small particle sizes are formed on the first piezoelectric layer 711, while the second and subsequent layers On the piezoelectric layers 712 to 715 , columnar crystals that are continuous with the columnar crystals of the first piezoelectric layer 711 and have a larger particle diameter than the columnar crystals are formed. In addition, according to the present embodiment, since the crystallized PZT is influenced by the lower layer, the degree of (100) plane orientation can reach 80% or more, and the in-plane variation of the substrate is small.

Next, as shown in FIG. 6(a), an upper electrode film 80 is formed on the piezoelectric film 70 formed as described above. Specifically, platinum (Pt) as the upper electrode film 80 is formed into a film having a film thickness of about 0.05 μm by a DC sputtering method.

Next, after spin-coating a resist on the upper electrode film 80 , exposure and development are performed corresponding to the positions where the ink chambers are to be formed, thereby performing patterning. Using the remaining resist as a mask, the upper electrode film 80 and the piezoelectric film 70 are etched by ion milling or the like ( FIG. 6( b )).

Next, as shown in FIG. 6( c ), the pressure generating chamber 12 is formed on the flow path forming substrate 10 . Specifically, the mask 51 provided on the channel-forming substrate 10 is patterned into a predetermined shape, and the mask 51 is used as an etching mask, and is etched by a dry method such as parallel plate reactive ion etching using an active gas. Etching is performed to a predetermined depth, and in this embodiment, etching is performed until the substrate 10 for penetrating the flow path is etched to form the pressure generating chamber 12 . In addition, the portion left without being etched becomes the diaphragm 11 .

Finally, as shown in FIG. 6( d ), the nozzle plate 20 is bonded to the flow path forming substrate 10 using resin or the like. When bonding the nozzle plate 20 to the flow path forming substrate 10 , positioning is performed so that the nozzle openings 21 are arranged corresponding to the respective spaces of the pressure generating chamber 12 . Through the above steps, an ink jet type recording head is formed.

(second embodiment)

8 is a schematic exploded perspective view showing a recording head in the second embodiment, FIG. 9 is a plan view and a B-B' sectional view of FIG. 8 , and FIG. 10 is a schematic view showing a layered structure of a piezoelectric element. In addition, the same code|symbol is attached|subjected to the same member as the member demonstrated in 1st Embodiment, and overlapping description is abbreviate|omitted.

This embodiment is another example of the layer structure of the piezoelectric element. Specifically, as shown in FIGS. patterned and arranged continuously along the direction in which the pressure generating chambers 12 are juxtaposed. In addition, in the present embodiment, the end surface of the lower electrode film 60A in the region facing each pressure generating chamber 12 is an inclined surface inclined at a predetermined angle with respect to the surface of the flow path forming substrate 10 .

The piezoelectric film 70A is provided independently for each of the piezoelectric generating chambers 12, and as shown in FIG. The first piezoelectric layer 721 is provided only on the lower electrode film 60A. Also, the end surface of the first piezoelectric layer 721 is an inclined surface continuous with the end surface of the lower electrode film 60A. In addition, the second to sixth piezoelectric layers 722 to 726 formed on the first piezoelectric layer 721 are provided to extend from the first piezoelectric layer 721 to the insulating film 55 to cover the first piezoelectric layer 721 and The inclined end surface of the lower electrode 60A.

Here, the first piezoelectric layer 721 and the second piezoelectric layer 722 formed on the first piezoelectric layer 721 are formed in crystals whose crystal density is lower than that of the remaining third to sixth piezoelectric layers 723 to 726. high density. That is, the third to sixth piezoelectric layers 723 to 726 as the upper layer of the piezoelectric layer 70A have columnar crystals larger in diameter than the columnar crystals of the first and second piezoelectric layers 721 and 722 as the lower layer. crystallization. As a result, the crystal orientation and density of the piezoelectric layers 721 to 726 can be improved, and the film quality of the piezoelectric film 70A can be significantly improved.

In addition, the second piezoelectric layer 722 formed on the first piezoelectric layer 721 is preferably formed thinner than the other third to sixth piezoelectric layers 723 to 726 . For example, in this embodiment, the first and second piezoelectric layers 721 and 722 are formed with a thickness of approximately 0.1 μm, and the other third to sixth piezoelectric layers 723 to 726 are formed with a thickness of approximately 0.2 μm.

In addition, in the present embodiment, lead electrodes 90 formed of, for example, gold (Au) etc. are respectively connected to the upper electrode film 80 provided on the above-mentioned piezoelectric film 70A, and the lead electrodes 90 are extended to the insulating film 55 . superior.

In addition, in the present embodiment, a liquid reservoir bonded to the flow path forming substrate 10 is formed in a state where a space is secured in the region facing the piezoelectric element 300 so that the movement of the piezoelectric element 300 is not hindered. A piezoelectric element holding portion 32 capable of sealing the space is provided on the substrate 30A. In addition, each piezoelectric element 300 is sealed in the piezoelectric element holding portion 32 so as to be isolated from the external environment. In addition, a through-hole 33 penetrating through the reservoir forming substrate 30A in the thickness direction is provided in a region between the reservoir portion 31 and the piezoelectric element holding portion 32 of the reservoir forming substrate 30A, and from each piezoelectric element 300 The vicinity of the end of the drawn-out lead electrode 90 is exposed in the through hole 33 .

A method of manufacturing the ink jet recording head in the present embodiment, particularly a method of manufacturing the piezoelectric element will be described below. 11 to 15 are cross-sectional views of the manufacturing process of the ink jet recording head in this embodiment.

First, as shown in FIG. 11(a) to FIG. 11(c), a silicon dioxide film 52, an insulating film 55, and The lower electrode film 60A. Next, as shown in FIG. 12( a ), a crystal seed (layer) 65 made of titanium or titanium dioxide is formed on the lower electrode film 60A. In addition, in this embodiment, the crystal seed is formed in an island shape. Next, as shown in FIG. 12(b), an uncrystallized piezoelectric precursor film 721' having a predetermined thickness, 0.1 µm in this embodiment, is formed. In addition, the piezoelectric precursor film 721' is formed by the sol-gel method as in the first embodiment, that is, a solution (sol) containing a metal-organic compound is applied to a predetermined thickness, then dried and degreased. form.

Here, in the present embodiment, the rate of temperature rise during degreasing is lower than when the third to sixth piezoelectric layers 723 to 726 are formed in the subsequent process. Specifically, the rate of temperature increase during degreasing is preferably a temperature rate of about 1.5 to 2°C/sec, for example, at the stage of rising from 250°C to 300°C. Thus, since many crystal nuclei are generated on the piezoelectric precursor film 721', the density and orientation of the first piezoelectric layer 721 obtained through the sintering process described later are improved.

And, by inserting the silicon wafer 110 formed with the piezoelectric precursor film 721' as described above into a predetermined diffusion furnace, and sintering the piezoelectric precursor film 721' at a high temperature of about 700° C. to crystallize it, thereby The first piezoelectric layer 721 closest to the lower electrode film 60A is formed.

Next, the lower electrode film 60A and the first piezoelectric layer 721 are patterned simultaneously. Specifically, first, as shown in FIG. 12( c ), a resist film 200 of a predetermined pattern is formed by applying a resist on the first piezoelectric layer 721 and performing exposure and development using a mask. Here, the resist is formed by, for example, applying a negative resist using a spin coating method, and the resist film 200 is formed by exposing, developing, and baking using a predetermined mask. Of course, a positive resist can also be used instead of a negative resist. In addition, in the present embodiment, the end surface 201 of the resist film 200 is formed with an inclination of a predetermined angle. The inclination angle of the end surface of the resist film 200 decreases as the baking time increases. In addition, the tilt angle can also be adjusted by exposing too much.

Then, as shown in FIG. 13( a ), the lower electrode film 60A and the first piezoelectric layer 721 are patterned by ion milling through the resist film. At this time, these lower electrode films 60A and the first piezoelectric layer 721 are patterned along the inclined end faces 201 of the resist film 200 so that these end faces become inclined faces inclined at a predetermined angle with respect to the vibrating film. By making the end faces of the lower electrode film 60A and the first piezoelectric layer 721 inclined, other piezoelectric layers can be formed on the first piezoelectric layer 721 with good film quality.

Next, as shown in FIG. 13(b), after forming the crystal seed (layer) 65A again on the entire surface of the silicon wafer 110 including the first piezoelectric layer 721, a predetermined thickness is formed by spin coating or the like. An embodiment piezoelectric precursor film 722' is approximately 0.1 μm thick. Then, the piezoelectric precursor film 722' is dried, degreased, and sintered to form the second piezoelectric layer 722. In addition, degreasing of the piezoelectric precursor film 722' serving as the second piezoelectric layer 722 is also the same as that of the first piezoelectric layer 721, and it is preferable to lower the temperature rise rate of the piezoelectric precursor film 722'. Thereby, many good crystallization nuclei can be generated on the piezoelectric precursor film 722'. That is, the second piezoelectric layer 722 in which many crystal nuclei are formed substantially uniformly can be obtained from the region facing the lower electrode film 60A to the region facing the insulating film 55 .

Next, as shown in FIG. 13(c), a piezoelectric precursor film 723' having a predetermined thickness, 0.2 µm in this embodiment, is formed on the second piezoelectric layer 722. Since the thickness of the piezoelectric precursor film coated once is about 0.1 μm, in this embodiment, the piezoelectric precursor film 723' of desired thickness is obtained by coating, drying, and degreasing twice. Then, the piezoelectric precursor film 723' is sintered and crystallized as the third piezoelectric layer 723. Then, by repeating the process of forming the piezoelectric precursor film twice as described above, drying, and degreasing and the process of sintering the piezoelectric precursor film four times in this embodiment, to form The third to sixth piezoelectric layers 723 to 726 . Thus, a piezoelectric film 70A composed of the multilayer piezoelectric layers 721 to 726 and having a thickness of about 1 μm is formed.

In addition, when degreasing the piezoelectric precursor films 723' to 726' on which the third to sixth piezoelectric layers 723 to 726 can be formed, as described above, it is preferable to make the rate of temperature rise high. In the embodiment, the temperature increase rate is made higher than the temperature increase rate when degreasing the piezoelectric precursor films 721 ′, 722 ′ serving as the first and second piezoelectric layers 721 , 722 .

Then, after forming the piezoelectric film 70A, as shown in FIG. The film 80 is patterned, thereby forming a piezoelectric element 300 (FIG. 14(b)).

As described above, in this embodiment, when forming the first and second piezoelectric layers 721, 722 constituting the piezoelectric film 70A, the piezoelectric precursor films 721', 722' should be heated at a relatively low temperature rise rate. Degreasing is performed, and when forming the remaining third to sixth piezoelectric layers 723 to 726 , the piezoelectric precursor films 723 ′ to 726 ′ should be degreased at a relatively high heating rate. Thus, the first and second piezoelectric layers 721 and 722 generate many crystal nuclei, thereby greatly improving the density and orientation of crystals. In addition, the crystals of the second piezoelectric layer 722 are used as nuclei, and the crystals of the remaining third to sixth piezoelectric layers 723 to 726 are continuously and favorably formed. Therefore, the film quality of the piezoelectric film 70A is improved, and the film quality is substantially uniform in all parts. Therefore, when a voltage is applied to the piezoelectric element 300 , good displacement characteristics can be obtained, and the piezoelectric element 300 can be obtained with excellent reliability without breaking the piezoelectric film 70A even when a high voltage is applied.

In addition, after that, as shown in FIG. 15( a), after forming a metal layer made of gold (Au) over the entire surface of the silicon wafer 110, for example, through a mask pattern formed of a resist or the like (FIG. (not shown in ), the metal layer is patterned for each of the piezoelectric elements 300 to form the guide electrode 90 . Then, after forming the film as described above, as shown in FIG. 15( b ), the pressure generating chamber 12 and the like are formed by bonding the reservoir forming substrate 30A to the silicon wafer 110 . In this embodiment, the pressure generating chamber 12 and the like are formed by performing anisotropic etching on the silicon wafer 110 . Thereafter, the above-mentioned nozzle plate 20 and flexible substrate 40 are bonded on the silicon wafer 110 so as to be integrated, and the silicon wafer 110 is formed by corresponding to each flow path forming substrate 10 having a chip size as shown in FIG. 8 . segmented to form an inkjet recording head.

In addition, in this embodiment, the lower electrode film 60A is provided continuously in the region corresponding to the piezoelectric generating chambers 12 arranged in parallel, but the present invention is not limited thereto. The lower electrode film in the area facing each pressure generating chamber is substantially independent.

(third embodiment)

16 is a plan view and a cross-sectional view of an ink jet recording head in a third embodiment.

This embodiment is an example in which a metal layer is provided on the vibrating film near the end of the piezoelectric film 70A, and is the same as the second embodiment except that the metal layer is provided. Specifically, as shown in FIG. 16 , near the end portion in the longitudinal direction of the piezoelectric film 70A, a metal layer 61 is provided, which is formed of the same layer as the lower electrode film 60A but is different from the lower electrode film 60A. Not conductive. In addition, the piezoelectric films 70A extend to a part of these metal layers 61 .

In addition, in the present embodiment, the metal film 61A provided near the end portion of the piezoelectric film 70A on the guide electrode 90 side is separately provided for each piezoelectric element, and the guide electrode is extended on the metal layer 61A. 90. On the other hand, the metal layer 61B provided near the end portion on the side opposite to the guide electrode 90 is continuously provided in a region corresponding to the plurality of piezoelectric elements 300 .

In this configuration, when the piezoelectric precursor film is sintered, the piezoelectric precursor film can be heated substantially uniformly, so that the piezoelectric film 70A having uniform piezoelectric characteristics can be formed. That is, since the insulating film 55 made of zirconia has a lower near-infrared absorption rate than the lower electrode film 60A, the temperature rise during sintering is slow in the region where the lower electrode film 60A is not formed. Therefore, the piezoelectric characteristics may not be uniform between the region corresponding to the lower electrode film 60A of the piezoelectric film 70A and other regions. However, in this embodiment, since the metal layers 61A, 61B are provided in regions corresponding to both ends of the piezoelectric film 70A, the piezoelectric precursor film can be uniformly heated during sintering, thereby The piezoelectric film 70A having uniform piezoelectric characteristics as a whole can be formed.

(Other implementations)

As mentioned above, although embodiment of this invention was described, the structure of this invention is not limited to the said content.

For example, in the above-mentioned embodiment, the inkjet type recording head was described as an example, but the present invention is also applicable to heads for ejecting various liquids, such as pigments used in the manufacture of color filters for liquid crystal displays and the like. Nozzles, electrode material nozzles used to form electrodes such as organic EL displays or FEDs (Front Emitting Displays), bioorganic material nozzles used to manufacture biochips, etc. In addition, of course, the piezoelectric element of the present invention is not limited to a liquid ejection head, and is applicable to any device as long as it uses an actuator in a flexural vibration mode.

Industrial Applicability

According to the present invention, it is possible to provide a method for manufacturing a piezoelectric element that can obtain ideally good crystallinity and improve the in-plane uniformity of piezoelectric characteristics, and provide a piezoelectric element that improves the uniformity . In addition, it is possible to obtain a piezoelectric element with excellent reliability that does not destroy the piezoelectric film even if a high voltage is applied.

Claims (6)

1. A piezoelectric element having a lower electrode, a piezoelectric film formed on the lower electrode, and an upper electrode formed on the piezoelectric film, characterized in that, The piezoelectric film has columnar crystals having a larger grain size on the side of the upper electrode than on the side of the lower electrode, The degree of orientation of the (100) plane of the piezoelectric film is higher than that of other plane orientations. 2. The piezoelectric element according to claim 1, wherein the lower electrode is patterned into a predetermined shape, and only one of the piezoelectric layers constituting the piezoelectric film is formed on the lower electrode. , as the bottommost first piezoelectric layer, other piezoelectric layers are formed to cover the end faces of the lower electrode and the end faces of the first piezoelectric layer, The first piezoelectric layer and the second piezoelectric layer formed immediately above the first piezoelectric layer constitute the piezoelectric film. 3. The piezoelectric element according to claim 2, wherein each thickness of the first and second piezoelectric layers is thinner than that of the other piezoelectric layers. 4. The piezoelectric element according to claim 2, wherein an end surface of the lower electrode and an end surface of the first piezoelectric layer are inclined surfaces. 5. The piezoelectric element according to claim 2, wherein a metal layer not electrically connected to the lower electrode is provided near an end portion of the piezoelectric film in the longitudinal direction. 6. A liquid ejection head comprising the piezoelectric element according to any one of claims 1 to 5 as a liquid ejection drive source.

Images