JP7567231B2 - Sensor device and method for manufacturing the same - Google Patents

Description

The present invention relates to a sensor device and a method for manufacturing a sensor device.

Piezoelectric materials are materials that exhibit the phenomenon of generating a voltage proportional to the pressure applied, and deforming when a voltage is applied (piezoelectric effect), and are used in actuators, sensors, and oscillator circuits and filter circuits in analog circuits. Known piezoelectric materials include ceramic materials such as lead zirconate titanate (PZT) and organic piezoelectric materials such as polyfluorovinylidene (PVDF).

In particular, organic piezoelectric materials have low dielectric constants and high piezoelectric constants. They can also be made into inks and formed by coating or printing. They also have chemical stability and flexibility. As a result, their applications to flexible pressure and vibration sensors, energy harvesting elements, actuators, and other applications are being considered.

Known sensors formed on films include sensors that use organic piezoelectric layers, which are highly flexible and are expected to be used in flexible large-area pressure sensors.
As an example of such a method, the one disclosed in Japanese Patent Application Laid-Open No. 2003-233666 has been proposed.
The pressure sensor disclosed in Patent Document 1 has a structure in which a transistor and an organic piezoelectric layer are laminated together. The transistor and the organic piezoelectric layer are in close contact with each other, thereby functioning as a pressure sensor.

Patent Publication No. 2017-219336

However, the pressure sensor shown in Patent Document 1, which has a structure in which a transistor and an organic piezoelectric layer are stacked, does not take into consideration the structure to increase the degree of adhesion between the organic piezoelectric layer and the organic semiconductor layer. Therefore, when such a pressure sensor is used in a manner that, for example, it is attached to a curved surface, there is a risk of peeling at the interface between the organic piezoelectric layer and the organic semiconductor layer due to bending.

In addition, when making a transistor array, the upper electrode connected to the organic piezoelectric layer needs to be patterned to correspond to each pixel. However, if the adhesion area of the upper electrode alone is insufficient, an adhesive layer can be formed in the same layer as the upper electrode to improve adhesion to the organic piezoelectric layer.

In this case, the upper electrode and the adhesive layer need to be formed in the same layer, but the film thickness of the upper electrode and the adhesive electrode formed as the adhesive layer will be the same. When pressure is applied after the pressure sensor is made, the pressure will be dispersed between the upper electrode and the adhesive electrode as shown in Figure 7, resulting in a problem that the data relative to the magnitude of pressure will be unstable.
7 is a cross-sectional view of a pressure sensor in which the height of the upper electrode 8 is equal to the height of the adhesive electrode 9. When pressure is applied from above the common electrode 11 in the direction of the arrow, the force is also distributed to the adhesive electrode 9.

Therefore, an object of the present invention is to provide a highly reliable sensor device and a manufacturing method thereof, which has a structure that suppresses peeling at the interface between an organic piezoelectric film and a thin-film transistor, and is capable of highly accurate measurements, in a sensor device that is expected to be used in a manner that involves bending.

One aspect of the present invention for solving the above problem is to
The sensor device has a thin film transistor formed on a substrate, and an upper electrode, an organic piezoelectric film, and a common electrode laminated thereon, the sensor device having an adhesive electrode in the same layer as the upper electrode, the upper electrode having an average film thickness greater than the average film thickness of the adhesive electrode, and the difference in average film thickness being 5 μm to 30 μm.

The sensor device is also characterized in that the average thickness of the upper electrode is 10 μm to 50 μm.

The sensor device is also characterized in that the upper electrode and the adhesive electrode contain at least conductive particles and a resin component.

The sensor device is also characterized in that the conductive particles are silver particles.

The method for manufacturing a sensor device is also characterized in that the upper electrode is formed by a screen printing method.

The method for manufacturing a sensor device is also characterized in that after attaching the upper electrode and the adhesive electrode to the organic piezoelectric film, they are bonded by heat treatment.

The present invention provides a sensor device and a method for manufacturing the sensor device that has high adhesion, resistance to bending, and high reliability in pressure detection.

1 is a cross-sectional view of a sensor device according to a first embodiment of the present invention. 1 is a plan view of a sensor device according to a first embodiment of the present invention. FIG. 1 is a diagram showing a sensor array according to a first embodiment of the present invention. FIG. 13 is a diagram showing the propagation of pressure with respect to an applied pressure. FIG. 4 is a cross-sectional view showing a sensor device according to a comparative example of the present invention. FIG. 4 is a cross-sectional view showing a sensor device according to a comparative example of the present invention. FIG. 13 is a diagram showing pressure distribution with respect to applied pressure. FIG. 4 is a cross-sectional view showing an example of a means for forming an upper electrode and an adhesive electrode.

The following describes in detail the embodiments of the present invention with reference to the drawings, but the present invention is not limited to these.

Figure 1 shows a cross-sectional view of a thin film transistor according to a first embodiment of the present invention. The thin film transistor 100 includes a substrate 1, a gate electrode 2, a gate insulating film 3, a source electrode 4, a drain electrode 5, a semiconductor layer 6 laminated between the source electrode 4 and the drain electrode 5, a protective layer 7 laminated on the semiconductor layer 6, an interlayer insulating film 7 formed on the source electrode 4, the drain electrode 5 and the semiconductor protective layer 6, an upper electrode 8 formed on the interlayer insulating film 7, an organic piezoelectric film 10 on which a voltage is generated in response to pressure and displacement, and a common electrode 11.

In the embodiment of the present invention, the material used for the substrate 1 is not particularly limited, but may be polyethylene terephthalate (PET), polyimide, polyethersulfone (PES),
Examples of such materials include flexible plastic materials such as polyethylene naphthalate (PEN) and polycarbonate.
The substrate 1 according to this embodiment is preferably made of a material that is flexible and easily bendable, taking into consideration cases where the substrate 1 is used as a sensor and installed on a curved surface.

The material used for the gate electrode 2 is not particularly limited, but metals such as Al, Cr, Au, Ag, Ni, Cu, Mo, etc., and transparent conductive films such as ITO can be used. As a forming method, the gate electrode 2 may be formed by photolithography after deposition or sputtering, but printing methods (screen printing, flexographic printing, gravure printing, offset printing, reverse offset printing, etc.) can also be used. When printing is used, Ag ink, Ni ink, Cu ink, etc. can be used. In particular, flexographic printing and reverse offset printing are suitable for the gate electrode 2, as they allow thin film printing and have excellent flatness.

The material of the gate insulating film 3 may be, but is not limited to, oxide insulating materials such as silicon oxide (SiOx), aluminum oxide (AlOx), tantalum oxide (TaOx), yttrium oxide (YOx), zirconium oxide (ZrOx), hafnium oxide (HfOx), silicon nitride (SiNx), silicon oxynitride (SiON), polyacrylates such as polymethyl methacrylate (PMMA), resin materials such as polyvinyl alcohol (PVA), polyvinyl phenol (PVP), and organic/inorganic hybrid resins such as polysilsesquioxane (PSQ). These may be a single layer or two or more layers stacked, and the composition may be graded in the growth direction.

The gate insulating film 3 may be formed by a known thin film formation technique, such as vacuum deposition techniques including vacuum evaporation, ion plating, sputtering, laser ablation, plasma CVD, photo CVD, and hot wire CVD, or wet deposition techniques including spin coating, die coating, and screen printing, depending on the material.

Next, a source electrode 4 and a drain electrode 5 are formed on the gate insulating film 3. The source electrode 4 and the drain electrode 5 can be made of metal materials such as aluminum (Al), molybdenum (Mo) and other molybdenum alloys such as MoNb, or conductive metal oxide materials such as indium oxide (InO), tin oxide (SnO), zinc oxide (ZnO), indium tin oxide (ITO) and indium zinc oxide (IZO). Noble metals such as silver, gold, platinum and palladium have a large work function and are preferred because they reduce the hole injection barrier into the organic semiconductor.

The source electrode 4 and the drain electrode 5 are preferably formed by a wet film formation method using a precursor or nanoparticles of a conductive material. For example, an inkjet method, letterpress printing, lithographic printing, intaglio printing, screen printing, or other method can be used. Patterning can be performed, for example, by using a photolithography method to protect the pattern formation area with a resist, and removing unnecessary areas by etching, or by directly patterning using a printing method, but is not limited to these methods.

Next, a semiconductor layer 6 is formed on the gate insulating film 3, the source electrode 4, and the drain electrode 5 so as to connect the source electrode 4 and the drain electrode 5. The semiconductor layer 6 may be made of an organic semiconductor material, such as a low molecular weight semiconductor such as pentacene and its derivatives, or a polymer organic semiconductor material such as polythiophene, polyallylamine, fluorene bithiophene copolymer and its derivatives, or an oxide semiconductor material mainly composed of a metal oxide, such as zinc oxide (ZnO), indium oxide (InO), indium zinc oxide (In-Zn-O), tin oxide (SnO), tungsten oxide (WO), and indium zinc gallium oxide (In-Ga-Zn-O), which are oxides containing one or more elements selected from zinc (Zn), indium (In), tin (Sn), tungsten (W), zirconium (Zr), and gallium (Ga). The structure of these materials may be single crystal, polycrystal, microcrystal, mixed crystal of crystal and amorphous, amorphous with scattered nanocrystals, or amorphous.

When an organic semiconductor material is used as the semiconductor layer 6, the semiconductor layer 6 can be formed by a wet film formation method such as letterpress printing, screen printing, an inkjet method, or nozzle printing, which uses a solution in which the organic semiconductor material is dissolved or dispersed as ink, or by a method in which powder or crystals of the organic semiconductor material are vapor-deposited in a vacuum state.
In addition, when an oxide semiconductor material is used as the semiconductor material, a vacuum film formation method such as a CVD method, a sputtering method, a pulsed laser deposition method, or a vacuum evaporation method, a sol-gel method or a chemical bath deposition method using an organometallic compound as a precursor, or a wet film formation method such as a method of applying a solution in which microcrystals and nanocrystals of a metal oxide are dispersed, can be used; however, the method of forming the semiconductor layer is not limited to these, and a publicly known general method can also be used.

An interlayer insulating film 7 is formed on the source electrode 4 , the drain electrode 5 and the semiconductor layer 6 .
The material used for the interlayer insulating film 7 is not particularly limited, but commonly used insulating materials include organic materials such as polyvinylphenol, polymethyl methacrylate, polyimide, polyvinyl alcohol, and epoxy resin.
When forming the interlayer insulating film 7, known methods such as letterpress printing, reverse offset printing, inkjet printing, screen printing, spray coating, and spin coating can be suitably used. However, in consideration of flexibility and low cost, it is preferable to form it by a printing method.

An upper electrode 8, an adhesive electrode 9, and an organic piezoelectric film 10 are formed on the interlayer insulating film 7. The upper electrode 8 and the adhesive electrode 9 are in the same layer, i.e., on the interlayer insulating film 7, and are arranged so as not to overlap.
The material used for the upper electrode 8 and the adhesive electrode 9 on the interlayer insulating film 7 is not particularly limited, but is preferably a solution in which metals such as platinum, nickel, indium tin oxide, or metal colloid particles such as gold, silver, nickel, etc. are dispersed, or a paste in which metal particles are used as conductive particles and mixed with a resin component. Furthermore, the resin component contained in this paste is not particularly limited, but includes thermoplastic resins such as acrylic resins and polyester resins, and thermosetting resins such as epoxy resins, and a plurality of these may be used simultaneously.

Furthermore, when a ferroelectric material such as polyvinylidene fluoride-trifluoroethylene copolymer (P(VDF-TrFE)) is used as the material of the organic piezoelectric film 10 in contact with the upper electrode 8 and the adhesive electrode 9, such a ferroelectric material may lose its polarization property, which is an important property of a dielectric, when subjected to heat treatment at or above its Curie temperature. For this reason, the upper electrode 8 and the adhesive electrode 9 are preferably made of a material that can be formed at or below the Curie temperature of the ferroelectric material.
As such a material, a paste containing a resin component using silver particles as a conductive material, so-called silver paste, which can be fired at a low temperature and is easily conductive at a low temperature, is particularly preferable.

A printing method that can be realized at low cost is suitable as a method for forming the upper electrode 8 using a paste containing metal particles as a conductive material and a resin component. Such printing methods include screen printing, flexographic printing, inkjet printing, etc. Among these, screen printing is particularly preferable because the usable viscosity range of the paste is wide and the resin component can be selected widely.
In this disclosure (specification), "screen printing" refers to a type of stencil printing method in which ink is passed through a fine mesh called a frame, which is woven from synthetic fibers such as polyester, or stainless steel or various metal fibers, to print on an object.

After the upper electrode 8 and the adhesive electrode 9 are formed, it is preferable to use a heat treatment to bond the organic piezoelectric film 10 onto the upper electrode 8 and the adhesive electrode 9. This bonding by heat treatment is performed so that the upper electrode 8, the adhesive electrode 9, and the organic piezoelectric film 10 can function sufficiently as a pressure sensor, and the organic piezoelectric film 10, which is in close contact with the upper electrode 8 and the adhesive electrode 9, does not peel off even in a curved state.
At this time, the material constituting the organic piezoelectric film has polarization, but the polarization disappears when heat of the Curie temperature or higher is applied. Therefore, it is desirable to carry out the heating at a temperature range of about 70°C to 100°C, but the temperature conditions are not limited to this temperature range and can be appropriately determined depending on the conditions such as the selection of materials.

The average film thickness of the upper electrode 8 is preferably 10 μm to 50 μm. To make it less than 10 μm, the emulsion thickness of the screen must be reduced, but if it is made too thin, mesh marks of the screen will appear in the pattern, resulting in poor flatness. Also, if it is made thicker, the amount of ink ejected will increase, which is disadvantageous, especially when increasing the resolution.

As shown in Fig. 4, the upper electrode 8 is thicker than the adhesive electrode 9, and the average thickness difference between them is preferably 5 µm to 30 µm. When the pressure indicated by the arrow in Fig. 4 is applied, the pressure is applied only to the upper electrode 8, and a stable pressure measurement value can be obtained.
If the difference is less than 5 μm, when pressure is applied, the pressure is dispersed to the upper electrode 8 and the adhesive electrode 9 as shown in FIG. 7, causing an error in pressure detection.
Furthermore, if the average film thickness difference exceeds 30 μm, the step between the electrodes becomes large, and distortion is likely to occur when the organic piezoelectric film is attached.

The adhesive electrode 9 may have any average thickness difference with the upper electrode 8 as described above, and there are no particular limitations on the average thickness.

The average thickness of the formed electrode is calculated from the arithmetic mean value of the data obtained by scanning from one end of the electrode pattern to the other end with a stylus-type thickness gauge.

In addition, when the organic piezoelectric film 10 is bent, peeling is likely to occur at the edge regions of the organic piezoelectric film 10, so by forming the adhesive electrode 9 so that it overlaps with the organic piezoelectric film edge portion 20 (see Figures 2 and 3), peeling can be prevented.

For example, if the organic piezoelectric film 10 has a square shape, it is preferable that the adhesive electrode 9 is formed on all four sides. For example, if it is formed on only one side, peeling is likely to occur when bending from the unformed part. The shape of the organic piezoelectric film is not limited to this.

The material used for the organic piezoelectric film 10 is not particularly limited, but examples include polyvinylidene fluoride (PVDF) and polyvinylidene trifluoroethylene copolymer (P(VDF-TrFE)). These materials are preferred because they have the advantages of a large piezoelectric constant, light weight, flexibility, and wide bandwidth. It is also preferred to use a film that has been subjected to a polarization treatment in advance.
Here, the polarization treatment refers to a treatment in which a high voltage is applied to align the electric charges in the material in a uniform direction.

A common electrode 11 is formed on the organic piezoelectric film 10. The common electrode 11 can be made of the same material and formed by the same method as the gate electrode and source/drain electrodes described above. It is also possible to form the common electrode 11 on the organic piezoelectric film 10 in advance and then attach it to the upper electrode 8.

<Sensor device>
A sensor device using a thin film transistor array can be formed by arranging a plurality of thin film transistors in a matrix, which enables planar detection.

FIG. 2 shows a plan view of the sensor device according to the first embodiment of the present invention.
In this sensor device, a thin film transistor is formed by arranging the above-mentioned gate electrode 2, source electrode 4, drain electrode 5, semiconductor layer 6, upper electrode 8, adhesive electrode 9, organic piezoelectric film 10, common electrode 11, etc. Furthermore, each wiring is patterned so that a gate wiring 31 is connected to the gate electrode 2, a source wiring 32 is connected to the source electrode 4, and a drain wiring 33 is connected to the drain electrode 5.

Fig. 3 is a plan view showing a thin film transistor array in which the thin film transistors shown in Fig. 2 are arranged in a 2 x 2 matrix. Each individual thin film transistor is connected by a gate wiring 31, a source wiring 32, and a drain wiring 33.
The following will explain the present invention based on examples.

The thin-film transistor array shown in FIG. 3 was manufactured by arranging the thin-film transistors shown in FIG. 1 according to the first embodiment of the present invention in an array, and the results of its evaluation are shown below.

[Example 1]
A 125 μm-thick polyethylene naphthalate substrate 1 was used, and a 80 nm-thick Mo (molybdenum) film was formed at room temperature by sputtering thereon. After the film formation, a resist pattern was formed by photolithography, followed by dry etching and resist peeling, thereby simultaneously forming a gate electrode 2 and a gate wiring 31.

Next, a 300 nm thick SiOx film was formed at room temperature using a sputtering method. After film formation, a resist pattern was formed using a photolithography method, followed by dry etching and resist removal to form the gate insulating film 3.

Next, a 80 nm thick Mo film was formed at room temperature using a sputtering method, and a resist pattern was formed using a photolithography method. Dry etching and resist removal were then performed to simultaneously form the source electrode 4, drain electrode 5, source wiring 32, and drain wiring 33.

Next, a 40 nm thick InGaZnO film was formed at room temperature by sputtering. The input power during film formation was 100 W, the gas flow rates were Ar = 100 SCCM, O ₂ = 1 SCCM, and the film formation pressure was 1.0 Pa. Next, a resist pattern was formed by photolithography, followed by wet etching and resist removal to form a semiconductor layer 6.

A negative photosensitive acrylic resin material was used as the material for the interlayer insulating film 7, and this was applied by spin coating. After drying, exposure was performed using a photomask of a desired shape, and unnecessary resin material was removed by development to form a desired pattern shape. Then, baking was performed at 150° C. to form the interlayer insulating film 7.

Next, as shown in FIG. 8A, an upper electrode 8a was printed on the interlayer insulating film 7 by a first screen printing using silver paste.
Next, as shown in FIG. 8( b ), an upper electrode 8 b of the same shape was superimposed on the upper electrode 8 a by a second screen printing using silver paste, and an adhesive electrode 9 was printed so as not to overlap the upper electrode, thereby making the thickness of the upper electrode 8 thicker than that of the adhesive electrode 9.
Further, preliminary drying was carried out at 80°C.

After that, a polyvinylidene trifluoroethylene copolymer film, on which Mo had been previously deposited to a thickness of 100 nm by sputtering as the common electrode 11, was attached to the upper layer, and then baked at 100°C to obtain a sensor device using a thin-film transistor 100 in which a polyvinylidene trifluoroethylene copolymer film was bonded to the upper electrode 8 as the organic piezoelectric film 10. The average thickness of the upper electrode 8 was 33 μm, and the average thickness of the adhesive electrode 9 was 20 μm.

<Evaluation of Example 1>
When the sensor device prepared in Example 1 was used for evaluation, data on pressure could be obtained. In addition, when the same pressure was applied multiple times and data was obtained, there was no difference in the data. Furthermore, data could be obtained even when the sensor device was bent to a curvature radius R of 5 mm.

Next, the manufacturing method was the same as in Example 1, but the specifications of the screen plate were changed, and the average film thickness of the upper electrode and the adhesive electrode were changed in several ways. After obtaining a sensor device using the thin-film transistor 100 of Examples 2, 3, and 4 described below, an evaluation was performed.

[Example 2]
As Example 2, a sensor device using a thin film transistor 100 having the same configuration as Example 1 except that the average thickness of the upper electrode was 40 μm and the average thickness of the adhesive electrode was 17 μm was obtained, and then evaluation was performed.

[Example 3]
As Example 3, a sensor device using a thin film transistor 100 having the same configuration as Example 1 except that the average thickness of the upper electrode was 26 μm and the average thickness of the adhesive electrode was 19 μm was obtained, and then evaluation was performed.

[Example 4]
As Example 4, a sensor device using a thin film transistor 100 having the same configuration as Example 1 except that the average thickness of the upper electrode was 48 μm and the average thickness of the adhesive electrode was 19 μm was obtained, and then evaluation was performed.

<Evaluation of Examples 2, 3, and 4>
As in Example 1, data on pressure could be obtained in Examples 2, 3, and 4. The same pressure was applied multiple times to obtain data, and no difference was observed in the data, making it possible to obtain stable data. Data could also be obtained in a state where the sample was bent to a radius of curvature R of 5 mm.

[Comparative Example 1]
As Comparative Example 1, a thin film transistor array 101 shown in Fig. 5 was produced. The sensor device using the thin film transistor according to Comparative Example 1 is similar to Example 1, except that the average film thickness of the upper electrode and the adhesive electrode are both equal at 25 µm, as shown in Fig. 5.

In Comparative Example 1, the upper electrode and the polyvinylidene trifluoroethylene copolymer film were bonded together, but when the same pressure was applied multiple times to evaluate the sensor device, differences arose in the data obtained, and stable data could not be obtained.

[Comparative Example 2]
As Comparative Example 2, a thin-film transistor array 102 shown in Fig. 6 was produced. The average film thickness of the upper electrode 8 was 17 µm, and the average film thickness of the adhesive electrode 9 was 20 µm. The configuration was the same as that of Example 1, except that the average film thickness of the adhesive electrode 9 was thicker than that of the upper electrode 8 as shown in Fig. 6.

Comparative Example 2 was bonded in the same way as Comparative Example 1, but when the same pressure was applied multiple times to evaluate the sensor device, accurate data could not be obtained because the average film thickness of the adhesive electrode was thicker than that of the upper electrode, and stable data could not be obtained.

Next, the manufacturing method was the same as in Example 1, except that the specifications of the screen plate were changed, and the average film thickness of the upper electrode and the adhesive electrode were changed in several ways. After obtaining sensor devices using the thin-film transistors 100 of Comparative Examples 3 and 4, evaluations were performed.

[Comparative Example 3]
As Comparative Example 3, a sensor device using a thin film transistor 100 having the same configuration as in Example 1 except that the average thickness of the upper electrode was 25 μm and the average thickness of the adhesive electrode was 24 μm was obtained, and then evaluation was performed.

Comparative Example 3 was bonded in the same way as Comparative Example 1, but when the same pressure was applied multiple times to evaluate the sensor device, differences arose in the data obtained, and stable data could not be obtained.

[Comparative Example 4]
As Comparative Example 4, a sensor device using a thin film transistor 100 having the same configuration as in Example 1 except that the average thickness of the upper electrode was 55 μm and the average thickness of the adhesive electrode was 19 μm was obtained, and then evaluation was performed.

Comparative Example 4 was bonded in the same way as Comparative Example 1, but when the same pressure was applied multiple times to evaluate the sensor device, differences arose in the data obtained, and stable data could not be obtained.

The results of the stability of the data obtained for the average film thickness of the upper electrode and adhesive layer electrode in Examples 1 to 4 and Comparative Examples 1 to 4 are summarized in Table 1.

The sensor device according to the present invention can be used to detect pressure, displacement, vibration, etc.

REFERENCE SIGNS LIST 1 Substrate 2 Gate electrode 3 Gate insulating film 4 Source electrode 5 Drain electrode 6 Semiconductor layer 7 Interlayer insulating film 8 Upper electrode 8a Upper electrode by first screen printing 8b Upper electrode by second screen printing 9 Adhesive electrode 10 Organic piezoelectric film 11 Common electrode 20 Organic piezoelectric film edge portion 31 Gate wiring 32 Source wiring 33 Drain wiring 100, 101, 102 Thin film transistor

Claims (6)

A sensor device having a thin film transistor formed on a substrate, and an upper electrode, an organic piezoelectric film, and a common electrode laminated thereon,
A sensor device having an adhesive electrode in the same layer as the upper electrode, the upper electrode having a thicker average film thickness than the adhesive electrode, the difference in average film thickness being 5 μm to 30 μm. The sensor device according to claim 1, characterized in that the average thickness of the upper electrode is 10 μm to 50 μm. The sensor device according to claim 1 or 2, characterized in that the upper electrode and the adhesive electrode contain at least conductive particles and a resin component. 4. The sensor device according to claim 3 , wherein the conductive particles are silver particles. A method for manufacturing a sensor device according to any one of claims 1 to 4, comprising the steps of:
A method for manufacturing a sensor device, comprising forming the upper electrode by a screen printing method. A method for manufacturing a sensor device according to claim 5,
a bonding step of bonding the upper electrode and the adhesive electrode to the organic piezoelectric film by a heat treatment after the upper electrode and the adhesive electrode are attached to the organic piezoelectric film;