CN116113308A - Piezoelectric film, piezoelectric device, preparation method of piezoelectric device and electronic equipment - Google Patents

Abstract

The invention discloses a piezoelectric film, a piezoelectric device, a preparation method thereof, and an electronic device. When manufacturing the piezoelectric film, nanocrystals can be added to a body (the main raw material of the process) to form a mixed material. The body can be a liquid phase or aerosol phase, nanocrystals can be used as the seed layer for piezoelectric film formation, and then the mixed material can be made into piezoelectric film by sol-gel method or aerosol method, and the traditional seed layer film can be replaced by the seed layer in the form of particles layer, forming a piezoelectric film in which nanocrystals are uniformly dispersed in the body, and due to the existence of nanocrystal particles, the free energy of grain growth can be reduced, so that a relatively low annealing temperature (such as 450 ° C ~ 550 ° C) can be used for After the piezoelectric film is annealed, the piezoelectric film can obtain excellent piezoelectric properties, which can expand the application field of the piezoelectric film. Therefore, the piezoelectric thin film provided by the embodiment of the present invention can achieve high piezoelectric performance under low temperature annealing.

Description

A piezoelectric film, a piezoelectric device and its preparation method, and electronic equipment

technical field

The invention relates to the technical field of piezoelectric materials, in particular to a piezoelectric film, a piezoelectric device, a preparation method thereof, and electronic equipment.

Background technique

Piezoelectric films usually have the advantages of light weight, wide frequency response, high output voltage, high dielectric strength, and low acoustic impedance, and can be used to manufacture resonators, filters, ultrasonic motors, sensors, sonar, hydrophones, etc. Devices are widely used in electronic and electrical, medical equipment, automobile transportation, aerospace, industrial equipment and other fields.

Contents of the invention

Embodiments of the present invention provide a piezoelectric film, a piezoelectric device and a preparation method thereof, and an electronic device, which are used for annealing the piezoelectric film at a relatively low temperature and obtaining better piezoelectric performance.

An embodiment of the present invention provides a piezoelectric thin film, comprising: a body, and nanocrystals dispersed in the body; the particle size of the nanocrystals is 10nm-100nm.

In a possible implementation manner, in the above piezoelectric device provided by the embodiment of the present invention, the material of the body includes PZT.

In a possible implementation manner, in the above piezoelectric device provided by the embodiment of the present invention, the nanocrystalline material includes at least one of PZT, PbZrO ₄ , PbTiO ₄ , Pt, and HfO ₂ .

In a possible implementation manner, in the above piezoelectric device provided by the embodiment of the present invention, the shape of the nanocrystal includes a spherical shape or an ellipsoidal shape.

In a possible implementation manner, in the above piezoelectric device provided by the embodiment of the present invention, the mass fraction of nanocrystals in the piezoelectric film is 0.1%-10%.

In a possible implementation manner, in the above piezoelectric device provided by the embodiment of the present invention, the nanocrystals are uniformly dispersed in the body.

In a possible implementation manner, the above-mentioned piezoelectric device provided in the embodiment of the present invention includes a first electrode, a piezoelectric film and a second electrode arranged in layers, and the piezoelectric film is the piezoelectric film provided in the embodiment of the present invention. The aforementioned piezoelectric film.

In a possible implementation manner, in the above piezoelectric device provided by the embodiment of the present invention, the material of the first electrode and the material of the second electrode are both transparent conductive materials.

Correspondingly, an embodiment of the present invention also provides a method for manufacturing a piezoelectric device, including:

forming a first electrode on the substrate;

Forming the above-mentioned piezoelectric film as provided in the embodiment of the present invention on the side of the first electrode away from the substrate by using a sol-gel or aerosol method;

performing an annealing process on the piezoelectric film; the temperature of the annealing process is 450°C to 550°C;

A second electrode is formed on a side of the piezoelectric film facing away from the substrate.

Correspondingly, an embodiment of the present invention also provides an electronic device, including the above-mentioned piezoelectric device provided by the embodiment of the present invention.

The beneficial effects of the embodiments of the present invention are as follows:

The embodiment of the present invention provides a piezoelectric film, a piezoelectric device and its preparation method, and electronic equipment. When making the piezoelectric film, nanocrystals can be added to the body (the main raw material of the process) to form a mixed material, and the body can be It is a liquid phase or an aerosol phase. Nanocrystals can be used as a seed layer for the formation of a piezoelectric film, and then the mixed material can be made into a piezoelectric film by using the sol-gel method or aerosol method, and the traditional seed can be replaced by the seed layer in the form of particles. Layer by layer, forming a piezoelectric film in which nanocrystals are uniformly dispersed in the body, and due to the existence of nanocrystal particles, the free energy of grain growth can be reduced, so that relatively low annealing temperatures (such as 450°C to 550°C can be used) ) annealing the piezoelectric film, the piezoelectric film can obtain excellent piezoelectric properties, so compared with the traditional piezoelectric film that requires an annealing process greater than 700 ° C, the present invention can expand the application field of the piezoelectric film. Therefore, the piezoelectric thin film provided by the embodiment of the present invention can achieve high piezoelectric performance under low temperature annealing.

Description of drawings

FIG. 1 is a schematic plan view of a piezoelectric film provided by an embodiment of the present invention;

Fig. 2A is a schematic diagram of mixing bulk and nanocrystals;

Figure 2B is a schematic diagram of the PZT film growth corresponding to Figure 2A;

FIG. 3A is a TEM photo corresponding to FIG. 2A;

Figure 3B is a TEM photo corresponding to Figure 2B;

Fig. 3 C is the TEM photograph corresponding to Fig. 1;

Figure 4A is a schematic diagram of yet another bulk and nanocrystal mix;

Fig. 4B is a schematic diagram of crushing or deformation of the bulk particles corresponding to Fig. 4A;

Figure 4C is a schematic diagram of the PZT film growth corresponding to Figure 4B;

FIG. 5 is a schematic structural diagram of a piezoelectric device provided by an embodiment of the present invention;

FIG. 6 is a schematic flowchart of a method for manufacturing a piezoelectric device provided by an embodiment of the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the following will clearly and completely describe the technical solutions of the embodiments of the present invention in conjunction with the drawings of the embodiments of the present invention. Apparently, the described embodiments are some, not all, embodiments of the present invention. And in the case of no conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. Based on the described embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the usual meanings understood by those skilled in the art to which the present invention belongs. The words "comprising" or "comprising" and similar words used in the present invention mean that the elements or objects appearing before the words include the elements or objects listed after the words and their equivalents, without excluding other elements or objects. Words such as "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Inner", "outer", "upper", "lower" and so on are only used to indicate relative positional relationship. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

It should be noted that the size and shape of each figure in the drawings do not reflect the actual scale, but are only intended to schematically illustrate the content of the present invention. And the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout.

At present, PZT (lead zirconate titanate) thin films have become the main direction of research due to their excellent piezoelectric properties. The deposition of PZT thin films has high piezoelectric coefficients and electromechanical coupling coefficients. It is crucial for the production of future smart sensors and actuators in applications such as heads, haptic feedback, micro-speakers and more.

At present, there are many methods for making PZT thin films, but in order to achieve good piezoelectric constant characteristics, PZT thin films need to undergo a high-temperature annealing process. However, traditional PZT thin films need to grow PZT grains in an air environment greater than 700°C to form a good piezoelectric constant. solid solution phase. But not all substrates and devices can withstand such high temperatures, for example:

(1) For CMOS devices, because the manufacturing process requires ion implantation and diffusion, if the annealing temperature is too high, the diffusion will fail and the device will lose its switching function.

(2) If glass is used as the substrate, the softening temperature of high-temperature glass is generally less than 650°C, and the thermal expansion coefficient of glass is generally 2-4ppm/K. If high-temperature annealing is performed, the glass will soften and deform, and the annealing temperature of PZT film is higher than At 550°C, its thermal expansion coefficient changes drastically, ranging from 2ppm/K to 8ppm/K.

Therefore, the high annealing temperature of the existing PZT thin film limits the application of the PZT thin film.

In addition, the PZT film piezoelectric material has high dielectric constant and transparency, which is very suitable for the vibrator structure integrated with the screen, and the vibrator structure can be used to realize the tactile feedback function of electronic equipment. However, at present, when making PZT thin films, Pt material is generally used to make the seed layer. The seed layer cannot transmit light, so it cannot meet the transparency requirements of glass substrates.

In view of this, in order to solve the above problems, an embodiment of the present invention provides a piezoelectric film, as shown in Figure 1, comprising: a body 1, and nanocrystals 2 dispersed in the body 1; the particle size of the nanocrystals 2 is 10nm ~ 100nm.

The above-mentioned piezoelectric film provided by the embodiment of the present invention, when making the piezoelectric film, can first add nanocrystals to form a mixed material in the body (the main raw material of the process), the body can be in a liquid phase or an aerosol phase, and the nanocrystals can be used as The seed layer formed by the piezoelectric film can then use the sol-gel method or aerosol method to make the mixed material into a piezoelectric film, and replace the traditional seed layer with the seed layer in the form of particles to form nanocrystals uniformly dispersed in the body The piezoelectric film, and due to the existence of nanocrystalline particles, can reduce the free energy of grain growth, so that the piezoelectric film can be annealed at a relatively low annealing temperature (for example, 450 ° C ~ 550 ° C), and the piezoelectric film will be Excellent piezoelectric performance can be obtained, so compared with the traditional piezoelectric film that needs an annealing process greater than 700°C, the invention can expand the application field of the piezoelectric film. Therefore, the piezoelectric thin film provided by the embodiment of the present invention can achieve high piezoelectric performance under low temperature annealing.

Optionally, the source of the nanocrystals can be synthesized by a sol-gel method or obtained by pulverizing and ball-milling PZT single crystals.

In specific implementation, in the above-mentioned piezoelectric film provided by the embodiment of the present invention, as shown in Figure 1, the material of the body 1 may include but not limited to PZT. The electrical coefficient ensures the piezoelectric properties of the corresponding piezoelectric film, and the corresponding piezoelectric film can be applied to tactile feedback devices, and PZT has high light transmittance. When it is integrated into a display device, it does not Affect the display quality of the display device.

In specific implementation, the material of the body can also be aluminum nitride (AlN), ZnO (zinc oxide), barium titanate (BaTiO ₃ ), lead titanate (PbTiO ₃ ), potassium niobate (KNbO ₃ ), niobate At least one of lithium (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ), and lanthanum gallium silicate (La ₃ Ga ₅ SiO ₁₄ ), in this way, while taking into account the transparency of the piezoelectric film, it ensures that the piezoelectric film The vibration characteristics of the piezoelectric film can be specifically selected according to the actual use needs of those skilled in the art, and the body material required for making the piezoelectric film is not limited here.

In specific implementation, in the piezoelectric thin film provided by the embodiment of the present invention, as shown in FIG. 1 , the material of the nanocrystal 2 includes but not limited to at least one of PZT, PbZrO ₄ , PbTiO ₄ , Pt, and HfO ₂ .

In specific implementation, in the above-mentioned piezoelectric film provided by the embodiment of the present invention, as shown in Figure 1, the shape of the nanocrystal 2 can be spherical, but it is certainly not limited thereto, for example, the shape of the nanocrystal 2 can also be an ellipsoid, etc. other shapes.

In specific implementation, in the above-mentioned piezoelectric film provided by the embodiment of the present invention, as shown in Figure 1, the mass fraction of nanocrystals 2 in the piezoelectric film can be 0.1% to 10%, so that the nanocrystals in this mass fraction range The addition of 2, not only can be used as a seed layer to reduce the free energy of grain growth to lower the annealing temperature of the piezoelectric film, but also will not affect the piezoelectric properties of the piezoelectric film.

During specific implementation, in the above-mentioned piezoelectric thin film provided by the embodiment of the present invention, as shown in FIG. 1 , the nanocrystals 2 are uniformly dispersed in the body 1 . In this way, when the nanocrystal 2 is added into the body 1, it can be fully mixed uniformly, so that the piezoelectric performance of the manufactured piezoelectric film is uniform.

In the specific implementation, in the above-mentioned piezoelectric film provided by the embodiment of the present invention, as shown in Figure 1, the manufacturing method of the piezoelectric film can be the sol-gel method or the aerosol method, and the following two methods are used as examples The fabrication of the piezoelectric film provided in the embodiment of the present invention will be described.

Embodiment 1: The piezoelectric film shown in Figure 1 of the embodiment of the present invention is produced by the sol-gel method, and the specific process is as follows:

(1) Dissolve lead acetate (Pb(CH ₃ COO) ₂ ) in acetic acid (CH ₃ COOH) for distillation to remove water, while zirconium nitrate (Zr(NO ₃ ) ₄ ·5H ₂ O) is dissolved in a certain stoichiometric ratio Ethylene glycol monomethyl ether CH ₃ OCH ₂ CH ₂ O until clear and transparent, then mix the two and add a certain amount of tetrabutyl titanate (Ti(C ₄ H ₉ O) ₄ ) and the nanocrystals (as shown in Figure 2A, body 1 and nanocrystals 2 are mixed), the nanocrystals are used as seeds (seed crystals) to achieve PZT thin film growth (as shown in Figure 2B, the film grows along the seed crystals), and at 80 ° C Reflux to clarification, form a transparent light yellow sol, and produce Tyndall effect, in order to make the raw materials mix fully, the whole reaction process is all completed on the magnetic stirrer.

(2) Put the upper driving chamber of the substrate on the glue leveler, evenly coat the light yellow sol formed in step (1) on the upper surface of the driving chamber, and then rotate at 3800r/s for 40s. After drying at 350°C for 20s, the PZT piezoelectric film was formed. In order to reduce the internal stress of the PZT piezoelectric film and prevent the film from cracking, the substrate containing the PZT piezoelectric film was placed in a sintering furnace and annealed at 550°C for 3 hours. The annealing process can remove organic matter and promote the crystallization of PZT piezoelectric thin film. After repeating the steps of leveling and drying for many times, until the PZT piezoelectric film with the required thickness is obtained, as shown in FIG. 1 .

As an example to verify that the above-mentioned nanocrystals added in the process of making piezoelectric thin films by the sol-gel method played a role as a seed layer, the inventors of this case carried out transmission electron microscopy on the structures of Figure 2A, Figure 2B and Figure 1 TEM) test, as shown in Figure 3A-Figure 3C, Figure 3A is the corresponding TEM photograph of Figure 2A, Figure 3B is the corresponding TEM photograph of Figure 2B, Figure 3C is the corresponding TEM photograph of Figure 1, from Figure 3A to Figure 3C can It can be seen that the crystals inside the crystal grains all start to grow from the surface of the seed layer (nanocrystal 2), and grow to the grain boundary to form a PZT piezoelectric film. It has been verified that it can be obtained by annealing at a temperature of 450°C to 550°C. High piezoelectric performance.

Embodiment 2: The piezoelectric film shown in Figure 1 of the embodiment of the present invention is produced by aerosol method, and the specific process is as follows:

Taking brittle PZT ceramic material (body 1) as the main component, adding nanocrystal 2 (with a particle size of 10nm to 100nm) into the brittle PZT ceramic material to form mixed particles, and then adding carrier gas to the mixed particles to form an aerosol, such as Shown in Figure 4A; The surface that this aerosol sprays to substrate makes mixing particle and substrate collide afterwards, by this collision particle is pulverized or deformed (as shown in Figure 4B, aerosol deposits amorphous state; As shown in Figure 4C, grow along the seed crystal) to form a piezoelectric film on the substrate (as shown in Figure 1). Specifically, the brittle PZT ceramic material (particle size greater than 200nm) and the nanocrystal 2 are mixed in a certain mass ratio to form an aerosol, and the aerosol is sprayed to the substrate, preferably by spraying the aerosol from a nozzle, more preferably while using The nozzle moves relative to the substrate and ejects the aerosol. At this time, the forming speed of the piezoelectric thin film is preferably 1.0 μm·cm/min or more, and the jetting speed of the aerosol is preferably in the range of 50 to 450 m/s. Within such a range, a new surface is easily formed when the fine particles collide with the substrate, the film-forming property is excellent, and the film formation rate also becomes high. After the film is formed, it can be annealed at 450°C, or it can be used directly as a sample at room temperature. It has been verified that high piezoelectric properties can be obtained by annealing at a temperature of 450°C.

The inventors of this case also conducted TEM tests on the piezoelectric film formed by the aerosol method, and found that the TEM photos are basically the same as those shown in Figure 3C.

In summary, the piezoelectric film provided by the embodiment of the present invention can be annealed at a temperature of 450° C. to 550° C. to obtain high piezoelectric performance.

Based on the same inventive concept, the embodiment of the present invention also provides a piezoelectric device, as shown in FIG. The embodiment provides the above piezoelectric film shown in FIG. 1 .

The above-mentioned piezoelectric device provided by the embodiment of the present invention adopts the piezoelectric film shown in Figure 1 of the present invention, and can obtain high piezoelectric performance by annealing at a temperature of 450°C to 550°C, and the annealing temperature will not soften the piezoelectric film. Therefore, compared with the traditional piezoelectric thin film, which requires an annealing process greater than 700° C., the present invention can expand the application field of piezoelectric devices.

In specific implementation, in the above-mentioned piezoelectric device provided by the embodiment of the present invention, as shown in FIG. ), can also be indium zinc oxide (IZO), etc. Those skilled in the art can set the materials of the first electrode and the second electrode according to actual application needs, and there is no limitation here.

Optionally, the above-mentioned piezoelectric device can be integrated with the display screen to realize tactile feedback, for example, the first electrode can be grounded, the second electrode can be connected to the driving signal terminal, and the inverse piezoelectric effect can be used to apply a high-frequency AC voltage signal to the second electrode (V _AC ), realize the application of high-frequency AC voltage signal to the piezoelectric film, thereby generating high-frequency vibration, and laser can be used to measure the vibration displacement, so as to ensure the performance of the piezoelectric film.

Of course, the piezoelectric device provided by the embodiment of the present invention is not limited to the field of tactile feedback technology, but can also be used in fields such as medical treatment, automotive electronics, and motion tracking systems. It is especially suitable for the field of wearable devices, monitoring and treatment outside the body or implanted in the human body, or electronic skin applied to artificial intelligence and other fields. Specifically, piezoelectric devices can be applied to brake pads, keyboards, mobile terminals, game handles, vehicles, and other devices that can generate vibration and mechanical properties.

Based on the same inventive concept, an embodiment of the present invention also provides a method for manufacturing a piezoelectric device, which is used to manufacture the piezoelectric device shown in FIG. 5. As shown in FIG. 6, the preparation method may include:

S601, forming a first electrode on a substrate;

Alternatively, the substrate may be a glass substrate or the like.

S602, using a sol-gel or aerosol method to form the piezoelectric film shown in Figure 1 provided by the embodiment of the present invention on the side of the first electrode away from the substrate;

Specifically, refer to the manufacturing method of the piezoelectric film in the above-mentioned piezoelectric film.

S603. Perform an annealing process on the piezoelectric thin film; the temperature of the annealing process is 450° C. to 550° C.;

Specifically, the annealing temperature of 450° C. to 550° C. will not affect the properties of the substrate, for example, it will not soften the substrate to deform it.

S604, forming a second electrode on a side of the piezoelectric film away from the substrate.

In the manufacturing method of the above-mentioned piezoelectric device provided by the embodiment of the present invention, since the piezoelectric film shown in Figure 1 of the present invention is used, high piezoelectric performance can be obtained by annealing at a temperature of 450°C to 550°C, and the annealing temperature is not It will soften the manufacturing substrate of the piezoelectric device, so compared with the traditional piezoelectric film, an annealing process of more than 700° C. is required, and the piezoelectric film provided by the embodiment of the present invention can expand the application field of the piezoelectric device.

Based on the same inventive concept, an embodiment of the present invention further provides an electronic device, including the above-mentioned piezoelectric device provided by the embodiment of the present invention. Since the problem-solving principle of the electronic device is similar to that of the aforementioned piezoelectric device, the implementation of the electronic device can refer to the implementation of the aforementioned piezoelectric device, and the repetition will not be repeated.

A piezoelectric film, a piezoelectric device and its preparation method, and an electronic device provided in the embodiments of the present invention, when making the piezoelectric film, nanocrystals can be added to the main body (the main raw material of the process) to form a mixed material, and the main body can be It is a liquid phase or an aerosol phase. Nanocrystals can be used as a seed layer for the formation of a piezoelectric film, and then the mixed material can be made into a piezoelectric film by using the sol-gel method or aerosol method, and the traditional seed can be replaced by the seed layer in the form of particles. Layer by layer, forming a piezoelectric film in which nanocrystals are uniformly dispersed in the body, and due to the existence of nanocrystal particles, the free energy of grain growth can be reduced, so that relatively low annealing temperatures (such as 450°C to 550°C can be used) ) annealing the piezoelectric film, the piezoelectric film can obtain excellent piezoelectric properties, and can expand the application field of the piezoelectric film. Therefore, the piezoelectric thin film provided by the embodiment of the present invention can achieve high piezoelectric performance under low temperature annealing.

While preferred embodiments of the invention have been described, additional changes and modifications to these embodiments can be made by those skilled in the art once the basic inventive concept is appreciated. Therefore, it is intended that the appended claims be construed to cover the preferred embodiment as well as all changes and modifications which fall within the scope of the invention.

Apparently, those skilled in the art can make various changes and modifications to the embodiments of the present invention without departing from the spirit and scope of the embodiments of the present invention. In this way, if the modifications and variations of the embodiments of the present invention fall within the scope of the claims of the present invention and equivalent technologies, the present invention also intends to include these modifications and variations.

Claims (10)

1. A piezoelectric thin film, characterized by comprising: a body, and nanocrystals dispersed in the body; the particle size of the nanocrystals is 10nm-100nm. 2. The piezoelectric film of claim 1, wherein the material of the body comprises PZT. 3 . The piezoelectric thin film according to claim 1 , wherein the nanocrystalline material comprises at least one of PZT, PbZrO ₄ , PbTiO ₄ , Pt, and HfO ₂ . 4 . The piezoelectric thin film according to claim 1 , wherein the shape of the nanocrystals includes spherical or ellipsoidal. 5. The piezoelectric film according to claim 1, characterized in that the mass fraction of nanocrystals in the piezoelectric film is 0.1%-10%. 6. The piezoelectric thin film according to any one of claims 1-5, wherein the nanocrystals are uniformly dispersed in the body. 7. A piezoelectric device, characterized in that it comprises a first electrode, a piezoelectric film and a second electrode arranged in layers, and the piezoelectric film is the piezoelectric film according to any one of claims 1-6. 8. The piezoelectric device according to claim 7, wherein the material of the first electrode and the material of the second electrode are transparent conductive materials. 9. A method for preparing a piezoelectric device, comprising: forming a first electrode on the substrate; forming the piezoelectric film according to any one of claims 1-6 on the side of the first electrode away from the substrate by using a sol-gel or aerosol method; performing an annealing process on the piezoelectric film; the temperature of the annealing process is 450°C to 550°C; A second electrode is formed on a side of the piezoelectric film facing away from the substrate. 10. An electronic device, comprising the piezoelectric device according to claim 7 or 8.

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