Piezoelectric film based on MEMS electric field sensor and manufacturing method

Abstract

The invention discloses a piezoelectric film based on an MEMS electric field sensor and a manufacturing method of the piezoelectric film. The piezoelectric film comprises a substrate layer, an electrode layer and a PZT layer. The manufacturing method comprises the following steps: preparing PZT sol, forming an amorphous form, and then forming the crystalline PZT piezoelectric film. PZT is adopted as a piezoelectric material, large driving force can be obtained, the degree of converting electric energy into mechanical energy is high, reliability is good, and compatibility with the technology is good. The PZT piezoelectric film is prepared through a sol-gel method, good controllability is achieved, operation is easy and convenient, it is ensured that the structure of the piezoelectric film is more stable through multiple times of coating and high-temperature annealing treatment, the crystalline PZT piezoelectric film can be formed easily, and therefore the piezoelectric performance and stability of the piezoelectric film are remarkably improved, and the piezoelectric film can be applied to the field of piezoelectric devices. The method is suitable for large-scale production and application of various high-performance piezoelectric devices.

Description

Technical Field

[0001] The present invention relates to the technical field of piezoelectric film preparation, in particular to a piezoelectric film based on a MEMS electric field sensor and a preparation method thereof. Background Art

[0002] Traditional piezoelectric film preparation methods usually face problems such as low process precision, high integration difficulty and low electric field sensing efficiency. The main reason is that the preparation process of piezoelectric materials is difficult to be compatible with the micro-electromechanical system (MEMS) process, which limits the application of piezoelectric films in miniaturization and integration. In addition, piezoelectric films prepared by traditional methods usually have disadvantages such as large size, high power consumption and poor sensing stability, which limits their application and development in some precision sensors and smart devices.

[0003] Therefore, the present invention proposes a piezoelectric film based on MEMS electric field sensor and a manufacturing method, which improves process accuracy and manufacturing efficiency, while achieving the goals of miniaturization and low power consumption. Compared with the traditional method, the piezoelectric film prepared by the present invention not only has higher sensitivity, but also can maintain stable performance in a small size, which makes it have a wider application prospect in the fields of high-precision sensors, smart devices, etc. Summary of the invention

[0004] In view of the above problems existing in the prior art, the present invention is proposed.

[0005] Therefore, the problem to be solved by the present invention is how to prepare a piezoelectric film with miniaturization, low power consumption and high sensitivity and good process compatibility.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: a piezoelectric film based on a MEMS electric field sensor, which includes a substrate layer, an electrode layer and a PZT layer.

[0007] As a preferred solution of the piezoelectric film based on the MEMS electric field sensor described in the present invention, a substrate layer is provided at the bottom of the electrode layer, and a PZT layer prepared by a sol-gel method is provided on the top of the electrode layer.

[0008] To solve the above technical problems, the present invention also provides the following technical solutions: a method for manufacturing a piezoelectric film based on a MEMS electric field sensor, comprising preparing a PZT sol, forming an amorphous PZT piezoelectric film and forming a crystalline PZT piezoelectric film.

[0009] As a preferred solution of the method for manufacturing a piezoelectric film based on a MEMS electric field sensor according to the present invention, wherein: preparing a PZT sol comprises dissolving a metal salt containing zirconium, titanium and lead in a solvent, and forming a uniform and stable PZT sol through hydrolysis and polycondensation of the metal salt;

[0010] Forming an amorphous PZT piezoelectric film, including uniformly coating the PZT sol on the electrode layer and heating to form the amorphous PZT piezoelectric film;

[0011] The method forms a crystalline PZT piezoelectric film, including repeatedly applying glue and heating, and then annealing the piezoelectric film at high temperature to form a crystalline PZT piezoelectric film.

[0012] As a preferred solution of the method for manufacturing the piezoelectric film based on the MEMS electric field sensor of the present invention, the preparation of the PZT sol includes selecting a solvent, a precursor, a stabilizer and a catalyst, and allowing the precursor to be fully mixed in the solvent.

[0013] As a preferred solution of the method for manufacturing the piezoelectric film based on the MEMS electric field sensor described in the present invention, the selection of solvent, precursor, stabilizer and catalyst includes: the solvent is ethylene glycol methyl ether and formamide, the catalyst is acetic acid, the precursor is zirconium nitrate, lead acetate and tetrabutyl titanate, and the stabilizer is acetylacetone.

[0014] As a preferred solution of the method for manufacturing the piezoelectric film based on the MEMS electric field sensor described in the present invention, wherein: the step of fully mixing the precursors in the solvent includes adding acetic acid to ethylene glycol methyl ether and stirring to fully mix them; adding zirconium nitrate and lead acetate to the mixed solvent, heating in a water bath and stirring to fully mix them; adding acetylacetone to the mixed solvent and stirring to fully mix them; adding tetrabutyl titanate to the mixed solvent and stirring to fully mix them; adding formamide to the mixed solvent and stirring to fully mix them, thereby completing the configuration of the PZT sol.

[0015] As a preferred solution of the method for manufacturing the piezoelectric film based on the MEMS electric field sensor of the present invention, the forming of the amorphous PZT piezoelectric film includes using a spin coater to evenly spin coat the PZT sol on the unpatterned electrode layer.

[0016] As a preferred solution of the method for manufacturing a piezoelectric film based on a MEMS electric field sensor according to the present invention, the electrode layer spin-coated with PZT sol is treated at 180 degrees for 10 minutes using a hot plate to complete the manufacturing of a layer of amorphous PZT piezoelectric film.

[0017] As a preferred solution of the method for manufacturing the piezoelectric film based on the MEMS electric field sensor of the present invention, the amorphous PZT piezoelectric film is manufactured repeatedly once or multiple times.

[0018] As a preferred solution of the method for manufacturing the piezoelectric film based on the MEMS electric field sensor of the present invention, the forming of the crystalline PZT piezoelectric film includes high-temperature thermal annealing of the amorphous PZT piezoelectric film.

[0019] As a preferred solution of the method for manufacturing the piezoelectric film based on the MEMS electric field sensor described in the present invention, the high-temperature thermal annealing includes placing the amorphous PZT piezoelectric film in a muffle furnace, using a step-by-step heating method, first keeping it at 400 degrees for 20 minutes, then heating it to 650 degrees, annealing for 60 minutes and then cooling it naturally.

[0020] The invention has the following beneficial effects: the invention adopts PZT as the piezoelectric material, can obtain a larger driving force and a higher degree of conversion of electrical energy into mechanical energy, has good reliability and good process compatibility. The PZT piezoelectric film is prepared by the sol-gel method, has good controllability and is easy to operate, and after multiple coatings and high-temperature annealing treatments, the structure of the piezoelectric film is ensured to be more stable, which is helpful to form a crystalline PZT piezoelectric film, thereby significantly improving the piezoelectric performance and stability of the piezoelectric film, and is suitable for large-scale production and the application of various high-performance piezoelectric devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0022] Figure 1 This is the overall structure diagram of the piezoelectric film based MEMS electric field sensor.

[0023] Figure 2 This is a flow chart for the production of piezoelectric film based on MEMS electric field sensor.

[0024] Figure 3 This is the annealing temperature rise curve of the piezoelectric film based on MEMS electric field sensor.

[0025] Figure 4 This is the surface SEM image of the piezoelectric film based on the MEMS electric field sensor.

[0026] Figure 5 This is a side SEM image of the piezoelectric film based on the MEMS electric field sensor.

[0027] Figure 6 This is an AFM image of the 2D morphology of the piezoelectric film based on the MEMS electric field sensor.

[0028] Figure 7 This is an AFM image of the 3D morphology of the piezoelectric film based on the MEMS electric field sensor.

[0029] Figure 8 This is the XRD pattern of the piezoelectric film based on MEMS electric field sensor.

[0030] Fig. 9 This is the PZT sol production process based on piezoelectric film for MEMS electric field sensors. DETAILED DESCRIPTION

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0032] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0033] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it a separate or selective embodiment that is mutually exclusive with other embodiments.

[0034] Example 1, reference Figure 1 , which is the first embodiment of the present invention, and this embodiment provides a piezoelectric film based on a MEMS electric field sensor, including a substrate layer 100, an electrode layer 200 and a PZT layer 300. The substrate layer 100 is arranged at the bottom of the electrode layer 200, and the PZT layer 300 is arranged on the top of the electrode layer 200. The substrate layer 100 is made of a smooth and stable material, such as silicon or silicon dioxide, and has good mechanical strength and thermal stability; the electrode layer 200 is used to apply an electric field and detect the mechanical response of the piezoelectric film, and is made of metal materials, such as platinum, gold or aluminum, which have good conductivity and can be well deposited on the film, which is helpful to transfer the charge caused by the piezoelectric effect; the PZT layer 300 has a piezoelectric effect, can be deformed under the action of an external electric field, and can also generate an electric field when subjected to mechanical stress. The PZT layer 300 of the present invention is prepared by a sol-gel method.

[0035] When in use, the substrate layer 100 provides mechanical support and attachment surface for the electrode layer 200. The electrode layer 200 transmits the current generated by the PZT layer 300. The PZT layer 300 is responsible for realizing the piezoelectric effect. Through an external electric field or stress, the PZT layer 300 can be deformed and converted into mechanical energy or electrical energy.

[0036] Example 2, reference Figure 2 and Fig. 9, which is the second embodiment of the present invention, provides a method for manufacturing a piezoelectric film based on a MEMS electric field sensor, including preparing a PZT sol, forming an amorphous PZT piezoelectric film, and forming a crystalline PZT piezoelectric film.

[0037] Specifically, the PZT sol is prepared using a sol-gel method, wherein precursors containing lead, zirconium and titanium elements such as zirconium nitrate, lead acetate and tetrabutyl titanate are dissolved in a suitable solvent such as ethylene glycol methyl ether and formamide, and hydrolysis and polycondensation reactions occur in the solution to form a uniform sol.

[0038] Next, the PZT sol is evenly coated on the surface of the substrate layer 100 provided with the electrode layer 200, and then heated to form an amorphous PZT piezoelectric film. After repeated multiple times, high-temperature thermal annealing is used to make the amorphous PZT piezoelectric film into a crystalline PZT piezoelectric film.

[0039] In this way, a piezoelectric film is made. This method is easy to operate and is suitable for the preparation of large-area, uniform films. After multiple coatings and high-temperature annealing treatments, the structure of the piezoelectric film is ensured to be more stable, which helps to form a crystalline PZT piezoelectric film, thereby significantly improving the piezoelectric performance and stability of the piezoelectric film. It can also effectively promote the crystallization process of the film and improve the mechanical and electrical properties of the film. It is suitable for large-scale production and application of various high-performance piezoelectric devices.

[0040] Example 3, reference Figures 1 to 9 , which is the third embodiment of the present invention, and this embodiment is based on the previous embodiment.

[0041] Specifically, the preparation of PZT sol includes dissolving metal salts containing zirconium, titanium and lead in a solvent, and forming a uniform and stable PZT sol through hydrolysis and condensation reaction of the metal salts. In this stage, suitable metal salts and solvents are selected, and the conditions of hydrolysis and condensation reactions are controlled to prepare a uniform and stable PZT sol, which is the basis for the subsequent formation of piezoelectric film.

[0042] The amorphous PZT piezoelectric film is formed by uniformly coating the PZT sol on the electrode layer 200 and heating the layer to form the amorphous PZT piezoelectric film; heating removes the solvent and retains the PZT piezoelectric film.

[0043] The formation of a crystalline PZT piezoelectric film includes repeatedly applying glue and heating, and then annealing the piezoelectric film at high temperature to form a crystalline PZT piezoelectric film. Repeating the process will thicken the PZT piezoelectric film, and high-temperature annealing will promote the crystallization of the film, so that it has good piezoelectric properties and a stable structure.

[0044] Specifically, the selection of solvent, precursor, stabilizer and catalyst includes: ethylene glycol methyl ether and formamide as solvent, acetic acid as catalyst, zirconium nitrate, lead acetate and tetrabutyl titanate as precursor, and acetylacetone as stabilizer. Ethylene glycol methyl ether and formamide as solvent can effectively dissolve the precursor; acetic acid as catalyst promotes the reaction; acetylacetone as stabilizer helps control the composition and stability of the sol.

[0045] Specifically, the precursors are fully mixed in the solvent, including adding acetic acid to ethylene glycol methyl ether and stirring to fully mix; adding zirconium nitrate and lead acetate to the mixed solvent, heating it to 80 degrees in a water bath and stirring to fully mix it; adding acetylacetone to the mixed solvent and stirring to fully mix it; adding tetrabutyl titanate to the mixed solvent and stirring to fully mix it; adding formamide to the mixed solvent and stirring to fully mix it, and completing the configuration of PZT sol. The gradual mixing of the precursor and the solvent ensures that each component is completely dissolved and reacted in the solution to form a uniform and stable sol.

[0046] Specifically, the formation of an amorphous PZT piezoelectric film includes using a spin coater to evenly spin coat the PZT sol on the unpatterned electrode layer 200. Spin coating allows the PZT sol to be evenly distributed, ensuring the quality and performance of the film. The electrode layer 200 spin-coated with the PZT sol is treated at 180 degrees for 10 minutes using a hot plate to complete the production of a layer of amorphous PZT piezoelectric film. During the heat treatment process, the solvent in the sol is removed to form an amorphous, solidified PZT piezoelectric film. Repeat the production of the amorphous PZT piezoelectric film once or multiple times. Gradually increase the thickness of the film while ensuring the uniformity of each layer.

[0047] Specifically, forming a crystalline PZT piezoelectric film includes high-temperature thermal annealing of the amorphous PZT piezoelectric film. High-temperature annealing is a key step in forming crystals. Through thermal annealing, the amorphous structure in the PZT piezoelectric film is converted into a crystalline structure, thereby stimulating its piezoelectric effect and improving performance. High-temperature thermal annealing includes placing the amorphous PZT piezoelectric film in a muffle furnace, using a step-by-step heating method, first keeping the temperature at 400 degrees for 20 minutes, then heating to 650 degrees, annealing for 60 minutes and then cooling naturally. The annealing temperature and heating curve are as follows: Figure 3 As shown. By precisely controlling the annealing temperature and time, the PZT piezoelectric film is ensured to be completely crystallized, the cracking phenomenon that is easy to occur in the PZT film during high-temperature annealing is avoided, and the negative impact of excessive heating or excessive annealing time on the film structure and performance is avoided. After complete crystallization, a protective layer can be set on the top of the film, using materials such as aluminum oxide or silicon dioxide to prevent physical damage, improve the electrical properties of the film, and reduce the impact of environmental factors such as humidity and temperature on the film performance.

[0048] After preparation, the surface and side of the PZT film were observed using a scanning electron microscope. Figure 4 and Figure 5 ; Use atomic force microscopy to observe the surface morphology of PZT films, such as Figure 6 and Figure 7 As shown. The arithmetic average roughness Ra of the PZT film was measured by AFM to be 0.296nm, and the root mean square roughness Rq was 0.367nm. The crystallinity and preferred orientation of the PZT film were analyzed using X-ray diffraction equipment. The XRD spectrum is shown in Figure 8 .

[0049] When in use, a precursor containing lead, zirconium and titanium elements is dissolved in a solvent using a sol-gel method to form a PZT colloid, the PZT colloid is repeatedly spin-coated on a substrate layer 100 attached with an electrode layer 200 and heated to form an amorphous PZT piezoelectric film, and finally a high-temperature thermal annealing is used to convert the amorphous PZT piezoelectric film into a crystalline PZT piezoelectric film, thereby completing the production of the piezoelectric film. The method is simple to operate, suitable for large-area, uniform film preparation, and after multiple coatings and high-temperature annealing treatments, the structure of the piezoelectric film is ensured to be more stable, which helps to form a crystalline PZT piezoelectric film, thereby significantly improving the piezoelectric performance and stability of the piezoelectric film, and can also effectively promote the crystallization process of the film, improve the mechanical and electrical properties of the film, and is suitable for large-scale production and the application of various high-performance piezoelectric devices.

[0050] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A piezoelectric film based on a MEMS electric field sensor, characterized in that: include, The electrode layer (200) has a substrate layer (100) at the bottom and a PZT layer (300) prepared by a sol-gel method at the top.

2. A method for manufacturing a piezoelectric film based on a MEMS electric field sensor, characterized in that: The preparation of PZT sol includes dissolving a metal salt containing zirconium, titanium and lead in a solvent, and forming a uniform and stable PZT sol through hydrolysis and polycondensation of the metal salt; Forming an amorphous PZT piezoelectric film, comprising uniformly coating a PZT sol on an electrode layer (200) and heating the layer to form the amorphous PZT piezoelectric film; The method forms a crystalline PZT piezoelectric film, including repeatedly applying glue and heating, and then annealing the piezoelectric film at high temperature to form a crystalline PZT piezoelectric film.

3. The method for manufacturing a piezoelectric film based on a MEMS electric field sensor according to claim 2, characterized in that: The preparation of the PZT sol comprises selecting a solvent, a precursor, a stabilizer and a catalyst, and allowing the precursor to be fully mixed in the solvent.

4. The method for manufacturing a piezoelectric film based on a MEMS electric field sensor according to claim 3, characterized in that: The selection of solvent, precursor, stabilizer and catalyst includes: ethylene glycol methyl ether and formamide as solvent, acetic acid as catalyst, zirconium nitrate, lead acetate and tetrabutyl titanate as precursor, and acetylacetone as stabilizer.

5. The method for manufacturing a piezoelectric film based on a MEMS electric field sensor according to claim 4, characterized in that: The step of fully mixing the precursors in the solvent includes adding acetic acid to ethylene glycol methyl ether and stirring to fully mix them; adding zirconium nitrate and lead acetate to the mixed solvent, heating in a water bath and stirring to fully mix them; adding acetylacetone to the mixed solvent and stirring to fully mix them; adding tetrabutyl titanate to the mixed solvent and stirring to fully mix them; adding formamide to the mixed solvent and stirring to fully mix them, thereby completing the configuration of the PZT sol.

6. The method for manufacturing a piezoelectric film based on a MEMS electric field sensor according to claim 5, characterized in that: The forming of the amorphous PZT piezoelectric film comprises using a spin coater to evenly spin coat the PZT sol on the unpatterned electrode layer (200).

7. The method for manufacturing a piezoelectric film based on a MEMS electric field sensor according to claim 6, characterized in that: The electrode layer (200) on which the PZT sol is spin-coated is treated at 180 degrees for 10 minutes using a hot plate to complete the preparation of a layer of amorphous PZT piezoelectric film.

8. The method for manufacturing a piezoelectric film based on a MEMS electric field sensor according to claim 7, characterized in that: The amorphous PZT piezoelectric thin film is repeatedly produced one or more times.

9. The method for manufacturing a piezoelectric film based on a MEMS electric field sensor according to claim 8, characterized in that: The forming of the crystalline PZT piezoelectric film includes subjecting the amorphous PZT piezoelectric film to high temperature thermal annealing.

10. The method for manufacturing a piezoelectric film based on a MEMS electric field sensor according to claim 9, characterized in that: The high temperature thermal annealing includes placing the amorphous PZT piezoelectric film in a muffle furnace, using a step-by-step heating method, first keeping the temperature at 400 degrees for 20 minutes, then heating to 650 degrees, annealing for 60 minutes and then cooling naturally.

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