A method for preparing a piezoelectric copolymer film for MEMS hydrophone

Abstract

The present invention relates to a method for preparing a piezoelectric copolymer film for a MEMS hydrophone, comprising the following steps: step 1, oxidation treatment of the substrate surface, selecting a single crystal silicon wafer as the substrate, ultrasonically cleaning the substrate with acetone, anhydrous ethanol, and ultrapure water for more than 10 minutes each, then drying the substrate, and preparing a 250-250nm insulating silicon dioxide layer on the single crystal silicon substrate by a wet oxygen oxidation treatment method, which functions to ensure the insulation between the piezoelectric MEMS device and the single crystal silicon substrate, and to improve the bonding force between the lower electrode layer, the piezoelectric copolymer film layer and the substrate. The present invention can achieve the preparation of a 5-10μm film.

Description

Technical Field

[0001] The invention belongs to the technical field of thin films and relates to a method for preparing a piezoelectric copolymer film for a MEMS hydrophone. Background Art

[0002] MEMS hydrophones are a type of sensor developed using micro-electro-mechanical system technology that has the ability to pick up underwater acoustic signals. Due to the high compatibility between the MEMS manufacturing process and the integrated circuit process, MEMS acoustic sensors have outstanding advantages such as small size, high performance consistency, convenient mass production, and integrated design and preparation with signal conditioning modules. They have been widely used in consumer electronics, medical monitoring, aerospace and other fields. As a type of MEMS acoustic sensor, MEMS hydrophones are also developing rapidly, from single devices to arrays, with technical advantages such as high sensitivity and noise resistance.

[0003] The working principles of MEMS hydrophones are mainly piezoresistive or piezoelectric. Typical piezoelectric MEMS hydrophones are based on active materials with mature thin film preparation processes such as AlN, ZnO, and PZT. Such hydrophones often face problems such as low sensitivity and introduction of additional noise. How to improve the output signal-to-noise ratio of MEMS hydrophones and reduce hydrophone noise is still a major difficulty of this technology.

[0004] MEMS hydrophones based on piezoelectric copolymer films can adopt 31 working mode or 33 working mode. The 31 working mode requires the construction of a cavity structure between the piezoelectric film and its substrate to meet the requirement of bending deformation of the piezoelectric film under the condition of sound pressure excitation. Its disadvantage is that it has poor hydrostatic pressure resistance and is difficult to perform well when working at different water depths. The 33 mode is a thickness vibration mode. There is no need to construct a cavity in the device structure. The piezoelectric film is tightly combined with the substrate, which is more conducive to use in a high hydrostatic pressure environment and meets the needs of working at different water depths. Since the acoustic reception sensitivity of the hydrophone using the 33 mode is proportional to the thickness of the piezoelectric film, in order to obtain a MEMS hydrophone with higher reception performance, a piezoelectric copolymer film with high voltage electrical activity with a certain thickness should be prepared as much as possible. The thickness should be no less than 5μm and as thick as possible.

[0005] The existing piezoelectric copolymer spin coating film forming technology mostly adopts a single spin coating and annealing method. The thickness of the prepared film is no more than 2μm, which is controlled by the concentration of the spin coating solution and the spin coating conditions. It is difficult to obtain a film with a thickness of 5μm or more. Some works use a multiple spin coating process method, and the same concentration of spin coating solution is used for multiple spin coating operations. The thickness of the prepared film can only reach 5-6μm. The technology to further increase the thickness has not been recorded in the public literature. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing a piezoelectric copolymer film for a MEMS hydrophone, wherein the method can realize the preparation of a film with a thickness of 5-10 μm.

[0007] The technical solution of the present invention is to provide a method for preparing a piezoelectric copolymer film for a MEMS hydrophone, comprising the following steps:

[0008] Step 1, oxidation treatment of the substrate surface, a single crystal silicon wafer is selected as the substrate, and the substrate is ultrasonically cleaned with acetone, anhydrous ethanol, and ultrapure water for more than 10 minutes each, and then the substrate is dried, and a 250-250nm insulating silicon dioxide layer is prepared on the single crystal silicon substrate by a wet oxygen oxidation treatment method, which is used to ensure the insulation between the piezoelectric MEMS device and the single crystal silicon substrate, and to improve the bonding force between the lower electrode layer, the piezoelectric copolymer film layer and the substrate; dry air can be used to dry it;

[0009] Step 2, patterning preparation of the lower electrode layer, preparing the lower electrode layer on the surface of the silicon dioxide layer of the substrate by physical vapor deposition (PVD), the thickness of the lower electrode layer is 100-500nm, the lower electrode layer adopts a patterned design, and the patterning is achieved by using a mask with a pattern of a specific size during the electrode preparation process, and the patterned structure includes an electrode area, a pin area, a lead area, and a polarization contact area;

[0010] Step 3, preparing a piezoelectric copolymer thin film layer, preparing a piezoelectric copolymer thin film layer on the lower electrode layer by multiple spin coating-heating drying cycles and annealing crystallization methods, the thickness of which is 5-10 μm;

[0011] Step 4, patterned etching of the piezoelectric copolymer thin film layer. To ensure the subsequent preparation of the upper electrode layer and the lead wires and the implementation of the polarization operation, a specific mask is used and an ultraviolet laser etching method is used to complete the patterned etching of the piezoelectric copolymer thin film layer, so as to obtain a piezoelectric copolymer thin film layer with a specified size centered at the center point of the electrode area of ​​the lower electrode layer. The piezoelectric copolymer thin film in the remaining area is completely etched away, so that the area of ​​the piezoelectric copolymer thin film layer is slightly larger than the area of ​​the electrode area of ​​the lower electrode layer.

[0012] Step 5, plasma treatment of the surface of the piezoelectric copolymer film layer and patterning of the upper electrode layer. The piezoelectric copolymer film layer is surface treated by a plasma sputtering method, and an upper electrode layer is prepared on the surface of the piezoelectric copolymer film layer by a physical vapor deposition method. The thickness of the upper electrode layer is 100-500nm. The upper electrode layer adopts a patterned design, and patterning is achieved by using a mask with a pattern of a specific size during the electrode preparation process. The patterned structure includes an electrode area, a pin area, a lead area, and a polarization contact area;

[0013] Step 6, polarization of the piezoelectric copolymer thin film layer. Since the polarization contact areas led out from the upper and lower electrodes are located on the same side of the substrate, a specially designed piezoelectric copolymer thin film layer polarization contact device with two copper pillars arranged on the same side is required. The two copper pillars are connected to the positive and negative electrodes respectively, and the MEMS hydrophone and the piezoelectric copolymer thin film layer polarization contact device are placed in high-viscosity insulating silicone oil for DC polarization; that is, using the piezoelectric copolymer thin film layer polarization contact device, the MEMS hydrophone is placed together with it in high-viscosity insulating silicone oil for DC polarization, and the polarization electric field strength is not less than 140V / μm.

[0014] Through the above steps, a piezoelectric copolymer film for MEMS hydrophone can be successfully prepared. The thickness of such a piezoelectric copolymer film can reach up to 10 μm, and it has a high piezoelectric coefficient and can be used for MEMS hydrophone production.

[0015] Preferably, in step 2, the physical vapor deposition method is any one of thermal evaporation, magnetron sputtering, and electron beam evaporation, and the material of the lower electrode layer is any one of single metal Au, Ag, Al, Ni, Ti, Cu or double layer metal Ti-Ni, Ti-Au.

[0016] Preferably, the physical vapor deposition method adopts a magnetron sputtering method, the material of the lower electrode layer is an Al single metal layer, and the thickness of the lower electrode layer is 200 nm.

[0017] Preferably, in step 3, the thickness of the piezoelectric copolymer film layer is 10 μm.

[0018] Preferably, in step 3, the piezoelectric copolymer thin film layer preparation process is as follows: 1) prepare a P (VDF-TrFE) solution, wherein the piezoelectric copolymer P (VDF-TrFE) is selected to have a VDF molar percentage of 70%-80%, and the solvent is selected to be any one of 2-butanone, N,N-dimethylformamide (DMF), and acetone, The mass concentration of the P(VDF-TrFE) solution is selected to be 4-14wt%, and solutions of different concentrations are prepared; 2) The basic process for preparing the piezoelectric copolymer thin film layer is the spin coating-heat drying method. Specifically, the substrate silicon wafer on which the lower electrode layer has been patterned is fixed on a coating machine by vacuum adsorption, and the P(VDF-TrFE) solution is dripped on the lower electrode area of ​​the lower electrode layer. The rotation speed and rotation time are set, and the solution is centrifugally flattened and volatilized to form a film by rotating the substrate silicon wafer. After the rotation is completed, the substrate is transferred to a hot stage with a set temperature for heating and drying to completely remove the solvent, wherein the rotation speed is 500-3000rpm, the rotation time is 15-60s, the hot stage treatment temperature is 60-90℃, and the hot stage treatment time is 30- 60min; 3), repeat step 2), continue to add P(VDF-TrFE) solution to the surface of the prepared film, and complete spin coating and temperature drying until the thickness of the piezoelectric copolymer film has reached 5μm (the final film layer thickness is directly related to the number of repetitions); 4), before each spin coating-temperature drying operation after the number of repetitions reaches more than 5 times, based on the fact that the thickness of the piezoelectric copolymer film has reached more than 5μm, it is necessary to increase high-temperature annealing treatment, and anneal in an oven environment for 1-10h. The annealing temperature is slightly higher than the Curie transition temperature of the piezoelectric copolymer and lower than the melting temperature. After that, it is cooled to room temperature and the next spin coating-temperature drying cycle is performed; 5), after repeating 5-9 times, a piezoelectric copolymer film layer with a thickness of 5-10μm and uniformity is prepared.

[0019] Preferably, in step 5, the physical vapor deposition method is any one of thermal evaporation, magnetron sputtering, and electron beam evaporation, and the upper electrode layer material is selected from single metal Au, Ag, Al, Ni, Ti, Cu or double layer metal Ti-Ni, Ti-Au.

[0020] Preferably, in order to avoid unnecessary electrical short circuit or electrical breakdown during the polarization process, the electrode areas of the upper electrode layer and the lower electrode layer completely correspond to each other in the vertical direction, and the pin area, the lead area, and the polarization contact area are staggered in the vertical direction. It should be noted that the electrode area and the pin area of ​​the upper electrode layer are completely located on the piezoelectric copolymer film layer, the lead area spans the piezoelectric copolymer film layer and the base silicon dioxide layer, and the polarization contact area is completely located on the base silicon dioxide layer.

[0021] Preferably, in step 2, the electrode area is a square with a size of 5 mm×5 mm, the pin area is a square connected to one corner of the electrode area with a size of 1 mm×1 mm, the lead area is a rectangle connected to the pin area and the polarization contact area respectively, with a size of 100 μm×4 mm, and the polarization contact area is a square connected to the lead area with a size of 5 mm×5 mm;

[0022] In step 5, the electrode area is a square with a size of 5mm×5mm, the pin area is a square connected to one corner of the electrode area with a size of 1mm×1mm, the lead area is a rectangle connected to the pin area and the polarization contact area respectively, with a size of 100μm×4mm, and the polarization contact area is a square connected to the lead area with a size of 5mm×5mm.

[0023] Furthermore, in step 3, the solvent is 2-butanone.

[0024] Furthermore, the piezoelectric copolymer film layer polarization contact device is a double copper column clamping structure arranged on the same side, and a conductive rubber block is sleeved on the end of the copper column to ensure that the electrode layer will not be damaged when touching the polarization contact area of ​​the MEMS device, thereby ensuring normal polarization.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] The present invention can successfully prepare a piezoelectric copolymer film for a MEMS hydrophone. The piezoelectric copolymer film has a maximum thickness of 10 μm and a high piezoelectric coefficient, and can be used for manufacturing a MEMS hydrophone. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a flow chart of an embodiment of the present invention.

[0028] Figure 2 It is a schematic structural diagram of a piezoelectric copolymer thin film layer polarization contact device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The present invention will be further described below with reference to the accompanying drawings:

[0030] The present invention provides a method for preparing a piezoelectric copolymer film for a MEMS hydrophone, such as Figure 1 As shown, the method comprises the following steps: (1) oxidation treatment of the substrate surface; (2) patterning preparation of the lower electrode layer; (3) preparation of the piezoelectric copolymer thin film layer; (4) patterning etching of the piezoelectric copolymer thin film layer; (5) plasma treatment of the surface of the piezoelectric copolymer thin film layer and patterning preparation of the upper electrode layer; (6) polarization of the piezoelectric copolymer thin film layer. The specific steps of the preparation method and the materials and process selection involved are described in detail below.

[0031] (1) Substrate surface oxidation treatment: To cooperate with the MEMS process, the substrate is selected as a single crystal silicon wafer. The single crystal silicon wafer substrate can be selected from 4-inch, 6-inch or 8-inch wafers. This embodiment uses a 6-inch wafer. The working surface is subjected to surface oxidation treatment. The basic process is: ultrasonically clean the substrate with acetone, anhydrous ethanol, and ultrapure water for 15 minutes each, blow dry the substrate with dry air, and use a wet oxygen oxidation method to prepare an insulating silicon dioxide layer on the single crystal silicon substrate with a thickness of 300nm. Its function is to ensure the insulation between the piezoelectric MEMS hydrophone and the single crystal silicon substrate, and to improve the bonding force between the lower electrode layer, the piezoelectric copolymer film layer and the substrate.

[0032] (2) Patterned preparation of the lower electrode layer: The lower electrode layer is prepared on the surface of the silicon dioxide layer of the substrate by physical vapor deposition (PVD). The selectable PVD methods include thermal evaporation, magnetron sputtering, and electron beam evaporation. The material of the lower electrode layer is selected from single metal Au, Ag, Al, Ni, Ti, Cu or double metal Ti-Ni, Ti-Au. The thickness of the lower electrode layer is 100-500nm. In this embodiment, the PVD method adopts a magnetron sputtering method, the material of the lower electrode layer is selected from a single metal layer of Al, and the thickness of the lower electrode layer is 200nm. The lower electrode layer adopts a patterned design, and patterning is achieved by using a mask with a pattern of a specific size during the electrode preparation process. The patterned structure includes an electrode area, a pin area, a lead area, and a polarized contact area. The electrode area is a square (size is 5mm×5mm), the pin area is a square connected to one corner of the electrode area (size is 1mm×1mm), the lead area is a rectangle connected to the pin area and the polarized contact area respectively (size is 100μm×4mm), and the polarized contact area is a square connected to the lead area (size is 5mm×5mm).

[0033] (3) Preparation of piezoelectric copolymer thin film layer: A piezoelectric copolymer thin film layer is prepared on the lower electrode layer by multiple spin coating-heating drying cycles and annealing crystallization methods, and its thickness is 5-10 μm. In this embodiment, the thickness of the piezoelectric copolymer thin film layer is 10 μm. The specific preparation process of the piezoelectric copolymer thin film layer is as follows: 1) Prepare a P (VDF-TrFE) solution, the piezoelectric copolymer P (VDF-TrFE) is selected to have a VDF molar percentage of 70-80%, and the solvent is selected from 2-butanone, N,N-dimethylformamide (DMF), and acetone. In this embodiment, the solvent is selected from 2-butanone. The mass concentration of the P(VDF-TrFE) solution is selected to be 4-14wt%. In this embodiment, the mass concentrations of the P(VDF-TrFE) solution are respectively prepared at 8wt%, 12wt% and 14wt%; 2) The basic process for preparing the piezoelectric copolymer thin film layer is the spin coating-heat drying method. Specifically, the substrate silicon wafer on which the patterned lower electrode layer has been prepared is fixed on a coating machine by vacuum adsorption, and 8wt% of the P(VDF-TrFE) solution is dripped on the lower electrode area of ​​the lower electrode layer. The rotation speed and rotation time are set, and the solution is centrifugally flattened and volatilized to form a film by rotating the substrate silicon wafer. After the rotation is completed, the substrate is transferred to a hot stage with a set temperature for heating and drying to completely remove the solvent. In this embodiment, the rotation speed is 1500rpm, the rotation time is 30s, the hot stage treatment temperature is 80℃, and the hot stage treatment time is 40min; 3), repeat step 2), continue to drip 8wt% P(VDF-TrFE) solution on the surface of the prepared film, and complete spin coating and temperature drying. It should be noted that the final film layer thickness is directly related to the number of repetitions. In this embodiment, 8wt% P(VDF-TrFE) solution is used for the first three times, and 12wt% P(VDF-TrFE) solution is used for the fourth and fifth times. After repeating 5 times, the thickness of the piezoelectric copolymer film has reached 5μm; 4), when repeated for the sixth time, since the thickness of the piezoelectric copolymer film has reached more than 5μm at this time, high-temperature annealing treatment needs to be added before the subsequent coating-temperature drying operation. When repeated for the sixth time, annealing is carried out in an oven environment for 2h. The annealing temperature is slightly higher than the Curie transition temperature of the piezoelectric copolymer and lower than the melting temperature. In this embodiment, the annealing temperature is 138℃ and the annealing time is 2h. After cooling to room temperature, the seventh spin coating-heat drying cycle is performed, wherein 14wt% P(VDF-TrFE) solution is used in the sixth and seventh cycles; 5) after repeating 7 times in total, a uniform piezoelectric copolymer film layer with a thickness of not less than 8μm can be prepared.

[0034] (4) Patterned etching of the piezoelectric copolymer thin film layer: To ensure the subsequent preparation of the upper electrode layer and leads and the implementation of the polarization operation, a specific mask is used and an ultraviolet laser etching method is adopted to complete the patterned etching of the piezoelectric copolymer thin film layer, thereby obtaining a piezoelectric copolymer thin film layer with a size of 6 mm × 6 mm centered on the center point of the electrode area of ​​the lower electrode layer. The piezoelectric copolymer thin film in the remaining area is completely etched away, so that the area of ​​the piezoelectric copolymer thin film layer is slightly larger than the area of ​​the electrode area of ​​the lower electrode layer.

[0035] (5) Surface plasma treatment of piezoelectric copolymer film layer and patterned preparation of upper electrode layer: The piezoelectric copolymer film layer is surface treated by plasma sputtering, and the upper electrode layer is prepared on the surface of the piezoelectric copolymer film layer by physical vapor deposition (PVD). The optional PVD methods include thermal evaporation, magnetron sputtering, and electron beam evaporation. The material of the upper electrode layer is selected from single metal Au, Ag, Al, Ni, Ti, Cu or double metal Ti-Ni, Ti-Au, and the thickness of the upper electrode layer is 100-500nm. In this embodiment, the PVD method adopts a magnetron sputtering method, and the material of the upper electrode layer is selected from a single metal layer of aluminum, and the thickness of the upper electrode layer is 200nm. The upper electrode layer adopts a patterned design, and patterning is achieved by using a mask with a pattern of a specific size during the electrode preparation process. The patterned structure includes an electrode area, a pin area, a lead area, and a polarization contact area. The electrode area is a square (size is 5mm×5mm), the pin area is a square connected to one corner of the electrode area (size is 1mm×1mm), the lead area is a rectangle connected to the pin area and the polarization contact area respectively (size is 100μm×4mm), and the polarization contact area is a square connected to the lead area (size is 5mm×5mm). In order to avoid unnecessary electrical short circuits or electrical breakdown during the polarization process, the electrode areas of the upper electrode layer and the lower electrode layer are completely corresponding in the vertical direction, but the pin area, lead area, and polarization contact area are staggered in the vertical direction. It should be noted that the electrode area and the pin area of ​​the upper electrode layer are completely located on the piezoelectric copolymer film layer, the lead area spans the piezoelectric copolymer film layer and the base silicon dioxide layer, and the polarization contact area is completely located on the base silicon dioxide layer.

[0036] (6) Piezoelectric copolymer thin film layer polarization: Since the polarization contact area led by the upper and lower electrodes is located on the same side of the substrate, a specially designed piezoelectric copolymer thin film layer polarization contact device with two copper pillars arranged on the same side is used. The two copper pillars are connected to the positive and negative electrodes respectively. The MEMS hydrophone and the piezoelectric copolymer thin film layer polarization contact device are placed in high-viscosity insulating silicone oil for DC polarization. The polarization electric field strength is 150V / μm. The piezoelectric copolymer thin film layer polarization contact device is a double copper pillar clamping structure arranged on the same side, such as Figure 2As shown, the device includes a base 4, a piezoelectric copolymer thin film element 6 is placed on the base, a positive copper column 1 and a negative copper column 2 are arranged above the base, the upper ends of the positive copper column 1 and the negative copper column 2 are respectively connected to wires 5, and the lower ends of the positive copper column 1 and the negative copper column 2 are respectively covered with conductive rubber blocks 3 to ensure that the electrode layer will not be damaged when touching the polarization contact area of ​​the MEMS hydrophone, thereby ensuring normal polarization.

[0037] Through the above steps, a piezoelectric copolymer film for MEMS hydrophone can be successfully prepared. The thickness of such a piezoelectric copolymer film can reach up to 10 μm, and it has a high piezoelectric coefficient and can be used for MEMS hydrophone production.

[0038] The above is only an explanation of the preferred embodiments of the present invention, which should not be construed as a limitation on the claims. Any equivalent process changes made using the present invention specification are included in the patent protection scope of the present invention.

Claims

1. A method for preparing a piezoelectric copolymer film for a MEMS hydrophone, characterized in that: The following steps are included: Step 1, oxidation treatment of the substrate surface, selecting a single crystal silicon wafer as the substrate, ultrasonically cleaning the substrate with acetone, anhydrous ethanol, and ultrapure water for more than 10 minutes each, then drying the substrate, and preparing a 250-250nm insulating silicon dioxide layer on the single crystal silicon substrate by wet oxygen oxidation treatment; Step 2, patterning preparation of the lower electrode layer, preparing the lower electrode layer on the surface of the silicon dioxide layer of the substrate by physical vapor deposition method, the thickness of the lower electrode layer is 100-500nm, the lower electrode layer adopts a patterned design, and the patterning is achieved by using a mask with a pattern of a specific size during the electrode preparation process, and the patterned structure includes an electrode area, a pin area, a lead area, and a polarization contact area; Step 3, preparation of a piezoelectric copolymer thin film layer, the preparation process is a spin coating - heating and drying method, the spin coating - heating and drying method is to transfer the substrate to a hot stage for heating and drying after completing the spin coating; wherein, 8wt% P (VDF-TrFE) solution is used for the first three times of the spin coating - heating and drying method, and 12wt% P (VDF-TrFE) solution is used for the fourth and fifth times of the spin coating - heating and drying method, so that the thickness of the piezoelectric copolymer film reaches 5μm; high temperature annealing treatment is also performed before repeating the sixth and seventh times of the spin coating - heating and drying method, the temperature of the high temperature annealing treatment is slightly higher than the Curie transition temperature of the piezoelectric copolymer and lower than the melting temperature, and 14wt% P (VDF-TrFE) solution is used for the sixth and seventh times of the spin coating - heating and drying method; Step 4, patterned etching of the piezoelectric copolymer thin film layer, using a specific mask and an ultraviolet laser etching method to complete patterned etching of the piezoelectric copolymer thin film layer, to obtain a piezoelectric copolymer thin film layer of a specified size centered at the center point of the electrode area of ​​the lower electrode layer, and to etch away all the piezoelectric copolymer thin films in the remaining areas, so that the area of ​​the piezoelectric copolymer thin film layer is slightly larger than the area of ​​the electrode area of ​​the lower electrode layer; Step 5, plasma treatment of the surface of the piezoelectric copolymer film layer and patterning preparation of the upper electrode layer, using a plasma sputtering method to treat the surface of the piezoelectric copolymer film layer, and preparing an upper electrode layer on the surface of the piezoelectric copolymer film layer by a physical vapor deposition method, the thickness of the upper electrode layer is 100-500nm, and the upper electrode layer adopts a patterned design, and the patterning is achieved by using a mask with a pattern of a specific size during the electrode preparation process. The patterned structure includes an electrode area, a pin area, a lead area, and a polarization contact area; Step 6, polarizing the piezoelectric copolymer thin film layer, using a piezoelectric copolymer thin film layer polarization contact device, placing the MEMS hydrophone together with the piezoelectric copolymer thin film layer polarization contact device in high-viscosity insulating silicone oil for DC polarization, with a polarization electric field strength of not less than 140V / μm.

2. The method for preparing a piezoelectric copolymer film for a MEMS hydrophone according to claim 1, characterized in that: In step 2, the physical vapor deposition method is any one of thermal evaporation, magnetron sputtering, and electron beam evaporation, and the lower electrode layer material is selected from single metal Au, Ag, Al, Ni, Ti, Cu or double layer metal Ti-Ni, Ti-Au.

3. The method for preparing a piezoelectric copolymer film for a MEMS hydrophone according to claim 2, characterized in that: The physical vapor deposition method adopts a magnetron sputtering method, the material of the lower electrode layer selects an Al single metal layer, and the thickness of the lower electrode layer is 200 nm.

4. The method for preparing a piezoelectric copolymer film for a MEMS hydrophone according to claim 1, characterized in that: In step 3, the thickness of the piezoelectric copolymer film layer is 10 μm.

5. The method for preparing a piezoelectric copolymer film for a MEMS hydrophone according to claim 1, characterized in that: In step 5, the physical vapor deposition method is any one of thermal evaporation, magnetron sputtering, and electron beam evaporation, and the upper electrode layer material is selected from single metal Au, Ag, Al, Ni, Ti, Cu or double-layer metal Ti-Ni, Ti-Au.

6. The method for preparing a piezoelectric copolymer film for a MEMS hydrophone according to claim 1, characterized in that: The electrode areas of the upper electrode layer and the lower electrode layer completely correspond to each other in the vertical direction, and the pin area, the lead area, and the polarization contact area are staggered in the vertical direction. The electrode area and the pin area of ​​the upper electrode layer are completely located on the piezoelectric copolymer film layer, the lead area spans the piezoelectric copolymer film layer and the base silicon dioxide layer, and the polarization contact area is completely located on the base silicon dioxide layer.

7. The method for preparing a piezoelectric copolymer film for a MEMS hydrophone according to claim 1, characterized in that: In step 2, the electrode area is a square with a size of 5 mm × 5 mm, the pin area is a square connected to one corner of the electrode area with a size of 1 mm × 1 mm, the lead area is a rectangle connected to the pin area and the polarization contact area respectively, with a size of 100 μm × 4 mm, and the polarization contact area is a square connected to the lead area with a size of 5 mm × 5 mm; In step 5, the electrode area is a square with a size of 5mm×5mm, the pin area is a square connected to one corner of the electrode area with a size of 1mm×1mm, the lead area is a rectangle connected to the pin area and the polarization contact area respectively, with a size of 100μm×4mm, and the polarization contact area is a square connected to the lead area with a size of 5mm×5mm.

8. The method for preparing a piezoelectric copolymer film for a MEMS hydrophone according to claim 1, characterized in that: The piezoelectric copolymer film layer polarization contact device is a double copper column clamping structure arranged on the same side, and a conductive rubber block is sleeved on the end of the copper column.

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