Piezoelectric film sensor based on metal substrate and processing technology

Abstract

The invention belongs to the technical field of film sensors, and particularly relates to a piezoelectric film sensor based on a metal substrate, the end face of the metal substrate is provided with a plurality of layer structures, the plurality of layer structures comprise a piezoelectric layer and a plurality of electrode layers, and the plurality of electrode layers are stacked on the piezoelectric layer layer by layer. On the premise that the material and the structure of the piezoelectric layer are not changed, the intensity of ultrasonic echo signals is remarkably improved by increasing the thickness of the electrode layers layer by layer, and the situation that the electrode layers are cracked and fall off due to overlarge internal stress caused by direct growth of the thick electrode layers is avoided by depositing the electrode layers layer by layer.

Description

Technical Field

[0001] The present invention belongs to the technical field of thin film sensors, and in particular relates to a piezoelectric thin film sensor based on a metal substrate and a processing technology thereof. Background Art

[0002] The safety of structural connections in extreme environments such as aerospace, oil exploration, and nuclear power is a key factor in the reliable operation of important equipment and facilities, and it is also a pain point and difficulty in the industry. Measuring bolt preload based on the acoustic elastic method has the advantages of real-time, fast, and accurate measurement. Its principle is to rely on a piezoelectric film sensor to transmit an ultrasonic signal from the top of the bolt, propagate to the bottom of the bolt, and then reflect back to the piezoelectric sensor from the bottom. By recording the propagation time of the ultrasonic wave in the bolt and calibrating the preload, the real-time preload of the bolt can be measured. Especially in harsh environments, such as high temperature and high pressure, the internal structure of the bolt changes, and the ultrasonic signal is easily scattered and absorbed during the propagation process. Whether the echo signal reflected from the bottom surface can be stably received is the key to accurate detection of preload. Therefore, it is necessary to improve the signal strength of the ultrasonic echo of the piezoelectric film sensor during the preload detection process.

[0003] Generally speaking, the piezoelectric constant d 33 The larger the piezoelectric material, the stronger the ultrasonic signal it generates. However, existing piezoelectric materials such as PZT with high piezoelectric coefficients will depolarize after high-temperature cycles and are not suitable for long-term use. AlN has good high-temperature stability, good chemical stability, and good thermal conductivity, and can be used in various harsh environments. Some scholars have reported that increasing the thickness of the piezoelectric layer and electrode layer of the sensor can enhance the ultrasonic echo signal to a certain extent. However, using physical vapor deposition to grow a very thick film layer at one time will lead to greater internal stress, and the film layer is prone to cracking and falling off, which is not conducive to production and manufacturing.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a piezoelectric film sensor and processing technology based on a metal substrate, which is used to solve the technical problem that the high enhancement effect of the ultrasonic echo signal of the piezoelectric film sensor and the structural stability of the piezoelectric film sensor cannot be achieved at the same time.

[0006] In order to solve the above technical problems, the first aspect of the present invention proposes a piezoelectric film sensor based on a metal substrate, wherein the end face of the metal substrate is provided with a plurality of layer structures, wherein the plurality of layer structures include a piezoelectric layer and a plurality of electrode layers, and the plurality of electrode layers are stacked layer by layer on the piezoelectric layer.

[0007] Based on the piezoelectric film sensor of the first aspect of the present invention, further optionally, in two adjacent electrode layers, the upper end surface of the electrode layer located at the lower layer has a microstructure groove, and the lower end surface of the electrode layer located at the upper layer has a microstructure protrusion, and the microstructure protrusion extends into the microstructure groove to fill the microstructure groove.

[0008] Based on the piezoelectric film sensor of the first aspect of the present invention, further optionally, in an ultrasonic signal measurement state, the greater the thickness of the electrode layer, the stronger the echo signal of the piezoelectric film sensor.

[0009] Based on the piezoelectric film sensor of the first aspect of the present invention, further optionally, the thickness of each electrode layer is in the range of 5.8 μm to 6.4 μm.

[0010] Based on the piezoelectric film sensor of the first aspect of the present invention, further optionally, the total number of the plurality of electrode layers is greater than or equal to 2 and less than or equal to 8.

[0011] On the basis of the piezoelectric film sensor of the first aspect of the present invention, further optionally, the material of the piezoelectric layer is at least one of AlN, PZT, ZnO, LiNbO3 and alloys thereof;

[0012] And / or, the material of the electrode layer is any one of Mo, Sn, Al, Ag, Ti and alloys thereof.

[0013] The second aspect of the present invention provides a processing technology for a piezoelectric film sensor based on a metal substrate, the processing technology comprising:

[0014] growing a piezoelectric layer on an end surface of a metal substrate;

[0015] A plurality of electrode layers are grown layer by layer on the surface of the piezoelectric layer.

[0016] On the basis of the processing technology of the second aspect of the present invention, further optionally, before growing the first electrode layer on the piezoelectric layer, the surface of the piezoelectric layer is first cleaned by an ion source;

[0017] Before growing the upper electrode layer on the lower electrode layer, the surface of the lower electrode layer is first cleaned by an ion source.

[0018] On the basis of the processing technology of the second aspect of the present invention, further optionally, when the plurality of electrode layers are grown layer by layer, the growth parameters of each electrode layer are the same;

[0019] And / or, the growth parameters of the electrode layer include:

[0020] The sputtering power is 1400W to 2000W, the working gas pressure is 0.5Pa to 1.5Pa, the target substrate distance is 6cm to 12cm, and the deposition time is 100min to 200min.

[0021] On the basis of the processing technology of the second aspect of the present invention, further optionally, before growing the upper electrode layer on the lower electrode layer, the metal substrate on which the lower electrode layer is grown is placed in an atmospheric environment for 2 hours to 12 hours.

[0022] After adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0023] (1) The present invention significantly improves the intensity of the ultrasonic echo signal by gradually increasing the thickness of the electrode layer without changing the material and structure of the piezoelectric layer.

[0024] (2) The present invention deposits multiple electrode layers layer by layer to avoid the direct growth of thicker electrode layers, which may cause the electrode layers to fall off due to excessive internal stress.

[0025] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings are part of the present invention and are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but do not constitute an improper limitation of the present invention. Obviously, the drawings described below are only some embodiments. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the accompanying drawings:

[0027] Figure 1 Explosion diagram and electron microscope diagram of each structure of the piezoelectric film sensor based on the metal substrate according to the embodiment of the present invention.

[0028] Figure 2 It is a schematic diagram of the structure of a relatively thick electrode layer grown at one time in the prior art.

[0029] Figure 3 It is a structural diagram of a plurality of electrode layers stacked in an embodiment of the present invention.

[0030] Figure 4 The figure is a process flow chart of a piezoelectric film sensor based on a metal substrate according to an embodiment of the present invention.

[0031] Figure 5 The figure is a processing flow chart of a piezoelectric film sensor based on a metal substrate according to a specific example of the present invention.

[0032] Figure 6This is a graph showing the variation trend of the ultrasonic echo signal intensity of the piezoelectric film sensor based on a metal substrate with the thickness of the electrode layer according to an embodiment of the present invention.

[0033] Figure 7 This is a comparison diagram of the first echo of the ultrasonic signal of the piezoelectric film sensor with different electrode layer thicknesses on the same metal substrate according to the embodiment of the present invention.

[0034] Among them: 1. metal substrate; 2. piezoelectric layer; 3. electrode layer; 31. inner electrode; 32. outer electrode; 301. internal pores; 302. microstructure grooves; 303. microstructure protrusions.

[0035] It should be noted that these drawings and textual descriptions are not intended to limit the conceptual scope of the present invention in any way, but are intended to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0036] In the description of the present invention, it should be noted that the terms "inside", "outside", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0037] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "contacted", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] Embodiment 1

[0039] like Figure 1 As shown, this embodiment proposes a piezoelectric film sensor based on a metal substrate 1. The metal substrate 1 is, for example, a bolt. The material of the metal substrate 1 can be any one of stainless steel, titanium alloy, high-temperature alloy, and aluminum alloy. The end surface of the metal substrate 1 is provided with a plurality of layer structures, and the plurality of layer structures include a piezoelectric layer 2 and a plurality of electrode layers 3. The piezoelectric layer 2 is directly grown on the end surface of the metal substrate 1, and the plurality of electrode layers 3 are stacked layer by layer on the piezoelectric layer 2. Each electrode layer 3 includes an inner electrode 31 and an outer electrode 32 arranged around the outer periphery of the inner electrode 31.

[0040] The piezoelectric layer 2 and the electrode layer 3 are deposited layer by layer on the end face of the metal substrate 1 by physical vapor deposition (PVD), chemical vapor deposition (CVD), magnetron sputtering, evaporation or electroplating. The material of the piezoelectric layer 2 is at least one of AlN (aluminum nitride), PZT (lead zirconate titanate), ZnO (zinc oxide), LiNbO3 (lithium niobate) and their alloys. Since AlN has the advantages of high sound velocity, large quality factor, strong chemical stability and high temperature resistance, it can withstand extremely harsh environments. Therefore, the piezoelectric layer 2 is preferably aluminum nitride to ensure that the ultrasonic echo signal can be accurately measured in harsh environments. The material of the electrode layer 3 is any one of Mo (molybdenum), Sn (tin), Al (aluminum), Ag (silver), Ti (titanium) and their alloys. Exemplarily, a layer of AlN piezoelectric layer 2 is first grown on the end face of the metal substrate 1 by magnetron sputtering, and then a plurality of Mo electrode layers 3 are grown layer by layer on the AlN piezoelectric layer 2.

[0041] Since the intensity of the echo signal of the piezoelectric film sensor is directly related to the thickness of the electrode layer 3, if a thicker electrode layer 3 is grown on the piezoelectric layer 2 at one time, the internal stress of the electrode layer 3 will be relatively large, and the electrode layer 3 is prone to cracking or even falling off. This embodiment can effectively reduce the internal stress of the electrode layer 3 by stacking multiple electrode layers 3 layer by layer. In the ultrasonic signal measurement state, the thicker the electrode layer 3 of the piezoelectric film sensor, the stronger the echo signal of the piezoelectric film sensor, and the piezoelectric film sensor will not fall off even when the total thickness of the multiple electrode layers 3 is relatively large, thereby ensuring the reliability of the combination between the piezoelectric film sensor and the metal substrate 1 and improving the accuracy of the preload detection structure.

[0042] Further optionally, if Figure 3 As shown, in two adjacent electrode layers 3, the upper end surface of the electrode layer located at the lower layer has a microstructure groove, and the lower end surface of the electrode layer located at the upper layer has a microstructure protrusion, and the microstructure protrusion extends into the microstructure groove to fill the microstructure groove, so as to make the multi-layer electrode structure denser.

[0043] refer to Figure 2The schematic diagram of the structure of the electrode layer 3 with a large thickness grown at one time, after the electrode layer 3 is grown and formed, microstructure grooves 302 are easily generated on the surface of the electrode layer 3, and internal pores 301 are formed inside the electrode layer 3. The microstructure grooves 302 will absorb moisture and gas when the temperature changes, which may cause the electrode layer 3 to crack, and the thicker the electrode layer 3 is, the deeper the microstructure grooves 302 and internal pores 301 of the electrode layer 3 extend along the thickness direction of the electrode layer 3, and the easier it is to cause the electrode layer 3 to crack or even fall off. Therefore, in the multiple electrode layers 3 of this embodiment, the protrusions 303 on the lower end surface of the electrode layer 3 located in the upper layer cooperate with the microstructure grooves 302 on the upper end surface of the electrode layer 3 located in the lower layer, so that the microstructure grooves 302 on the upper end surface of the electrode layer 3 located in the lower layer can be filled, eliminating the microstructure grooves 302 between adjacent electrode layers 3, effectively improving the cracking phenomenon of the electrode layer 3 caused by the microstructure grooves 302, and this filling method also makes the combination between adjacent electrode layers 3 tighter, and it is not easy for the electrode layer 3 to fall off.

[0044] Further optionally, the thickness of each electrode layer 3 is in the range of 5.8 μm to 6.4 μm. The thickness of the single-layer electrode layer 3 is within this range, so that the number of internal pores 301 formed inside each electrode layer 3 is small, and the internal pores 301 extend to a small depth along the thickness direction of the electrode layer 3, which effectively reduces the internal stress of each electrode layer 3 and improves the reliability of the piezoelectric film sensor.

[0045] Further optionally, the number of the plurality of electrode layers 3 is greater than or equal to 2 and less than or equal to 8. When the number of the electrode layers 3 is within this range, the ultrasonic echo signal will gradually increase, and the electrode layers 3 will not crack or fall off.

[0046] Embodiment 2

[0047] This embodiment also proposes a processing technology for a piezoelectric film sensor based on a metal substrate 1, such as Figure 4 As shown in the flowchart, the processing technology includes the following steps:

[0048] Step 1: growing a piezoelectric layer 2 on the end surface of a metal substrate 1.

[0049] Specifically, a piezoelectric layer 2 is grown on the end surface of the substrate by using methods such as physical vapor deposition (PVD), chemical vapor deposition (CVD), magnetron sputtering, evaporation or electroplating.

[0050] Step 2: growing a plurality of electrode layers 3 layer by layer on the surface of the piezoelectric layer 2.

[0051] Specifically, a mask is placed on the piezoelectric layer 2, and the first electrode layer 3 is deposited first. The portion of the electrode layer 3 located inside the mask is the inner electrode 31, and the portion of the electrode layer 3 located outside the mask is the outer electrode 32. After the first electrode layer 3 is prepared, the second electrode layer 3 is grown on the first electrode layer 3 in the same manner, and so on, until the number of electrode layers 3 reaches the maximum number of layers. The maximum number of layers of the electrode layer 3 is not clearly defined, and its size is related to the material of the electrode layer 3. Exemplarily, the electrode layer 3 is a Mo electrode layer 3, and the maximum number of layers of the electrode layer 3 is 5 layers. Among them, when multiple electrode layers 3 are grown layer by layer, the growth parameters of each electrode layer 3 are the same, and the growth parameters of the electrode layer 3 include: sputtering power of 1400W to 2000W, working gas pressure of 0.5Pa to 1.5Pa, target substrate distance of 6cm to 12cm, and deposition time of 100min to 200min.

[0052] Further optionally, before growing the first electrode layer 3 on the piezoelectric layer 2 , the surface of the piezoelectric layer 2 is first cleaned by an ion source; before growing the upper electrode layer 3 on the lower electrode layer 3 , the surface of the lower electrode layer 3 is first cleaned by an ion source.

[0053] Specifically, before growing the first electrode layer 3 on the piezoelectric layer 2, the surface of the piezoelectric layer 2 is first cleaned by an ion source to remove impurities on the surface of the piezoelectric layer 2 and increase the surface energy, thereby enhancing the bonding force between the piezoelectric layer 2 and the electrode layer 3. Before growing the second electrode layer 3 on the first electrode layer 3, the surface of the first electrode layer 3 is also first cleaned by an ion source to enhance the bonding ability between the first electrode layer 3 and the second electrode layer 3. Similarly, before growing the upper electrode layer 3 on the lower electrode layer 3, the surface of the lower electrode layer 3 needs to be cleaned by an ion source. The ion source uses an electron beam to directly impact gas molecules to ionize them, forming high-speed ions to bombard the piezoelectric layer 2 or the electrode layer 3, thereby removing surface pollutants and achieving a cleaning effect.

[0054] Further optionally, in step 2, before growing the upper electrode layer 3 on the lower electrode layer 3, the lower electrode layer 3 is placed in an atmospheric environment for 2 hours to 12 hours to release the internal stress of the electrode layer 3, thereby further preventing the electrode layer 3 from cracking or even falling off.

[0055] Because the electrode layer 3 may crack or peel off when the number of electrode layers 3 is greater than the maximum number of layers, before preparing the piezoelectric film sensor of the technical basis of this embodiment, it is necessary to determine the maximum number of electrode layers 3 that the piezoelectric film sensor can withstand through a limited number of experiments. In actual production, the number of electrode layers 3 is controlled to be less than or equal to the maximum number of layers to ensure that the echo signal is significantly improved and the electrode layer 3 will not crack or peel off.

[0056] The following is a detailed introduction to the method of determining the maximum number of electrode layers through a specific experiment. Figure 5 The specific steps are as follows:

[0057] S51: growing an AlN piezoelectric layer 2 on the end face of the bolt using a magnetron sputtering device.

[0058] S52: First, place a mask plate on the AlN piezoelectric layer 2. Before depositing the first Mo electrode layer 3, the surface of the AlN piezoelectric layer 2 needs to be cleaned with an ion source to remove impurities on the surface of the AlN piezoelectric layer 2 and increase the surface energy, thereby enhancing the bonding force between the film layers. The sputtering power of the first Mo electrode is 1500W, the working pressure is 0.8Pa, the target-substrate distance is 10cm, and the deposition time is 150min. The thickness of the first Mo electrode is 6.206μm, and the total thickness of the electrode layer 3 is 6.206μm. Then, after the bolts on which the first electrode layer 3 has been grown are vacuum cooled for 3h to 12h, the bolts are taken out and the mask plate is torn off, and ultrasonic signal measurement is performed to record the echo signals with a gain of 5dB to 50dB. Then, in the atmospheric state, place it at room temperature for 2h to 12h to release the internal stress, and observe whether cracks or film peeling occur on the surface of the thin film sensor. If cracks or film peeling occur, stop the experiment. If cracks or film peeling do not occur, enter S53.

[0059] S53, first place a mask plate at the same position as in S52. Before depositing the second Mo electrode layer 3, the surface of the first Mo electrode layer needs to be cleaned with an ion source to remove surface impurities and increase surface energy to enhance the bonding force between film layers. The sputtering parameters of the second Mo electrode layer are the same as those of S52. The actual thickness of the second Mo electrode layer is 6.098μm, and the total thickness of the electrode layer 3 is 12.304μm. Then, after the bolts with the second electrode layer 3 grown are vacuum cooled for 3h to 12h, the bolts are taken out and the mask plate is torn off, and ultrasonic signal measurement is performed to record the echo signals with a gain of 5dB to 50dB. Then, in the atmospheric state, place it at room temperature for 2h to 12h to release the internal stress, and observe whether cracks or delamination occur on the surface of the thin film sensor. If cracks or delamination occur, stop the experiment. If cracks or delamination do not occur, enter S54.

[0060] S54, first place a mask at the same position as in steps S52 and S53. Before depositing the third Mo electrode layer 3, the surface of the second Mo electrode needs to be cleaned with an ion source to remove surface impurities and increase surface energy, thereby enhancing the bonding force between film layers. The sputtering parameters of the third Mo electrode are the same as those of S52 and S53. The thickness of the third Mo electrode is 5.990μm, and the total thickness of the electrode layer 3 is 18.294μm. Then, after the bolts on which the third electrode layer 3 has been grown are vacuum cooled for 3h to 12h, the bolts are taken out, the mask is torn off, and ultrasonic signal measurement is performed, and echo signals with a gain of 5dB to 50dB are recorded respectively. Then, in the atmospheric state, place at room temperature for 2h to 12h to release internal stress, and observe whether cracks or delamination occur on the surface of the thin film sensor. If cracks or delamination occur, stop the experiment. If cracks or delamination do not occur, proceed to S54.

[0061] S55. First, place a mask at the same position as in steps S52 to S54. Before depositing the fourth Mo electrode layer 3, the surface of the third Mo electrode needs to be cleaned with an ion source to remove surface impurities and increase surface energy to enhance the bonding force between film layers. The sputtering parameters of the fourth Mo electrode are the same as those of steps S52 to S54. The fourth Mo thickness is 6.260 μm, and the total thickness of the electrode layer 3 is 24.554 μm. Then, after the bolts on which the fourth electrode layer 3 has been grown are vacuum cooled for 3 h to 12 h, the bolts are taken out, the mask is torn off, and ultrasonic signal measurement is performed to record echo signals with a gain of 5 dB to 50 dB. Then, place the sample at room temperature for 2 h to 12 h in the atmosphere to release internal stress and observe whether cracking or delamination occurs in the thin film sensor. If cracking or delamination occurs, stop the experiment. If cracking or delamination does not occur, proceed to S56.

[0062] S56. First, place a mask at the same position as in steps S52 to S55. Before depositing the fifth Mo electrode layer 3, use an ion source to clean the surface of the fourth Mo electrode to remove surface impurities and increase surface energy, thereby enhancing the bonding force between film layers. The sputtering parameters of the fifth Mo electrode are the same as those of S52 to S54. The thickness of the fifth Mo electrode is 6.206 μm, and the total thickness of the electrode layer 3 is 30.76 μm. Then, after the bolts with the fifth electrode layer 3 grown are vacuum cooled for 3 h to 12 h, the bolts are taken out, the mask is torn off, and ultrasonic signal measurement is performed to record echo signals with a gain of 5 dB to 50 dB. Then, place the bolts at room temperature for 2 h to 12 h in the atmosphere to release internal stress, and observe whether cracks or film peeling occur on the bolt surface. If cracks or film peeling occur, stop the experiment. If cracks or film peeling do not occur, continue coating.

[0063] The multilayer structure of the electrode layer 3 finally grown is as follows Figure 3In the case of conventional one-time growth of a thick film, microstructure grooves 302 are formed on the surface of the film, and internal pores 301 are formed inside (such as Figure 2 ), when the temperature changes, it will absorb moisture and gas to cause the film to crack. The thicker the film is, the deeper the pores on the surface and inside of the film extend along the thickness direction of the electrode layer 3, which is more likely to cause the film to crack or even fall off. In this embodiment, by depositing multiple electrode layers 3 layer by layer, the microstructure grooves 302 of the electrode layer 3 can be filled, and the connection between the multiple electrode layers 3 is more dense. The film peeling phenomenon will only occur when the internal stress is greater than the interface stress.

[0064] In this experiment, a layer of AlN piezoelectric layer 2 was first grown on the end face of the same bolt by magnetron sputtering, and then each layer of Mo electrode layer 3 was grown in sequence. After each layer of Mo electrode was grown, the bolt was taken out and ultrasonic signal measurement was performed before the next layer of Mo electrode was grown. The growth parameters of each electrode layer 3 were consistent: sputtering power was 1500W, working pressure was 0.8Pa, target substrate distance was 10cm, deposition time was 150min, and the thickness of each electrode layer 3 was about 6μm.

[0065] This experiment uses ultrasonic measuring equipment to perform echo tests on piezoelectric film sensors based on metal substrates 1, measuring the longitudinal wave echo signals of sensors with different electrode layer 3 thicknesses on the same bolt. The measurement results are shown in Figure 7 In order to better observe the echo signal of the thin film sensor under different electrode layer 3 thicknesses, the data when the gain is 20dB is selected. The experimental results show that with the increase of the electrode layer 3 thickness, the echo signal gradually increases. The peak value Vpp of the highest peak and the lowest peak of the ultrasonic signal is used to measure the strength of the echo signal. The peak value Vpp under different Mo electrode thicknesses is recorded, such as Figure 6 , when the Mo electrode thickness increased from 6.206 μm to 30.76 μm, the ultrasonic signal intensity increased by 14.7 times.

[0066] In the above experiment, after the Mo electrode thickness grew to 5 layers (30.76 μm), there was still no electrode cracking or delamination, indicating that the method of growing the electrode layer 3 layer by layer on the surface of the piezoelectric layer 2 in this embodiment can effectively eliminate internal stress and effectively enhance the echo signal strength.

[0067] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment, it is not used to limit the present invention. Any technician familiar with this patent can make some changes or modify the technical contents suggested above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the solution of the present invention.

Claims

1. A piezoelectric film sensor based on a metal substrate, characterized in that: The end surface of the metal substrate is provided with a plurality of layer structures, wherein the plurality of layer structures comprises a piezoelectric layer and a plurality of electrode layers, and the plurality of electrode layers are stacked layer by layer on the piezoelectric layer.

2. The piezoelectric film sensor based on a metal substrate according to claim 1, characterized in that: In two adjacent electrode layers, the upper end surface of the lower electrode layer has a microstructure groove, and the lower end surface of the upper electrode layer has a microstructure protrusion, which extends into the microstructure groove to fill the microstructure groove.

3. The piezoelectric film sensor based on a metal substrate according to claim 1, characterized in that: In the ultrasonic signal measurement state, the greater the thickness of the electrode layer, the stronger the echo signal of the piezoelectric film sensor.

4. The piezoelectric film sensor based on a metal substrate according to claim 1, characterized in that: The thickness of each electrode layer ranges from 5.8 μm to 6.4 μm.

5. The piezoelectric film sensor based on a metal substrate according to claim 1, characterized in that: The total number of the plurality of electrode layers is greater than or equal to 2 and less than or equal to 8.

6. The piezoelectric film sensor based on a metal substrate according to claim 1, characterized in that: The material of the piezoelectric layer is at least one of AlN, PZT, ZnO, LiNbO3 and alloys thereof; And / or, the material of the electrode layer is any one of Mo, Sn, Al, Ag, Ti and alloys thereof.

7. A processing technology for a piezoelectric film sensor based on a metal substrate, characterized in that: The processing technology includes: growing a piezoelectric layer on an end surface of a metal substrate; A plurality of electrode layers are grown layer by layer on the surface of the piezoelectric layer.

8. The processing technology of the piezoelectric film sensor based on the metal substrate according to claim 7 is characterized in that: Before growing the first electrode layer on the piezoelectric layer, the surface of the piezoelectric layer is first cleaned by an ion source; Before growing the upper electrode layer on the lower electrode layer, the surface of the lower electrode layer is first cleaned by an ion source.

9. The processing technology of the piezoelectric film sensor based on the metal substrate according to claim 7 is characterized in that: When the plurality of electrode layers are grown layer by layer, the growth parameters of each electrode layer are the same; And / or, the growth parameters of the electrode layer include: sputtering power of 1400W to 2000W, working gas pressure of 0.5Pa to 1.5Pa, target-substrate distance of 6cm to 12cm, and deposition time of 100min to 200min.

10. The processing technology of the piezoelectric film sensor based on the metal substrate according to claim 7, characterized in that: Before growing the upper electrode layer on the lower electrode layer, the metal substrate on which the lower electrode layer is grown is placed in an atmospheric environment for 2 hours to 12 hours.

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