Acoustic piezoelectric thin film device structure

Abstract

The application provides an acoustic piezoelectric film device structure, comprising: a support body; a piezoelectric film layer structure covering an area surrounded by the support body and fixedly connected to the support body at the periphery, the piezoelectric film layer structure comprising a piezoelectric layer and an electrode layer covering the upper and lower surfaces of the piezoelectric layer, the piezoelectric film layer structure comprising an inner area and an outer area surrounding the inner area, and the inner area and the outer area having an electrode separation zone therebetween, the electrode separation zone separating the electrode layer into a central electrode layer and a peripheral electrode layer. The acoustic piezoelectric film layer structure designed by the application can reduce the warping degree of the piezoelectric film layer structure and control the increase of the width of the acoustic transmission channel of the slit area caused by warping, the electrode layer of the application fully covers the surface of the piezoelectric film layer, and the novel separation and series or parallel electrical connection mode between the longitudinal multiple piezoelectric layers and the transverse multiple electrode layers can realize the electromechanical conversion of the whole area of the piezoelectric film layer and improve the electromechanical conversion efficiency of the piezoelectric film device.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of acoustic sensing, and particularly relates to an acoustic piezoelectric thin film device structure. BACKGROUND

[0002] In recent years, MEMS (Micro Electro Mechanical System) acoustic devices produced and manufactured by using MEMS technology are used more and more widely in devices such as smart phones. At the same time, not only smart phones, but also wearable products, action cameras or digital cameras and other electronic devices with the function of identifying the surrounding situation by sound or the function of making sound put forward higher requirements for further miniaturization and signal-to-noise ratio characteristics of MEMS acoustic devices. MEMS acoustic devices are highly sensitive, low in power consumption, flat in frequency response and have many other advantages, and have become the mainstream of today's micro acoustic device market.

[0003] The MEMS piezoelectric transducer on the market is different in working frequency band and working mode according to application requirements, such as human ear audible frequency band (20Hz-20KHz) and ultrasonic frequency band (>20KHz), and the transducer is divided into transmitter (Tx) and receiver (Rx). According to application requirements, the transducer can also work in a resonant state or a non-resonant state. However, the main structure and basic working principle of the piezoelectric unit are similar. Generally, MEMS piezoelectric transducers include a substrate, a support and a piezoelectric diaphragm structure. Among them, the diaphragm structure is mostly composed of relatively independent fan-shaped, triangular or other symmetrical diaphragm structures, and one end of the diaphragm is fixed on the support, and the other end or the center area has a relative freedom, which can be a cantilever beam or a diaphragm structure.

[0004] On the one hand, when the traditional cantilever beam structure design has residual stress after process manufacturing, the initial warping of the free end of the structure is large. Taking a low frequency (20Hz-20KHz) receiver (Rx) application as an example, the initial warping greatly changes the size of the sound transmission slit structure of the transducer. Further, in the working state, the structure vibrates with the incident sound wave, and the size of the sound transmission slit structure also changes with the vibration amplitude, thereby affecting the frequency response of the receiver in the low frequency band (such as in the case of working frequency <5KHz). At the same time, the reliability of the cantilever beam structure also has certain problems when dealing with large sound pressure level impact or large voltage sound emission.

[0005] On the other hand, whether as a transmitter (Tx) or a receiver (Rx) (such as a piezoelectric ultrasonic transducer-pMUT), the effective piezoelectric area does not completely cover the entire mechanical structure area (generally only accounts for about 50% of the effective area). This results in that a large amount of mechanical energy cannot be effectively converted into electrical energy in the receiving state, and vice versa in the transmitting mode. SUMMARY

[0006] In view of the above-mentioned shortcomings of the prior art, the present application aims to provide an acoustic piezoelectric thin film device structure for solving the problems of low reliability and low effective piezoelectric area of the conventional cantilever beam structure in the prior art.

[0007] To achieve the above-mentioned objects and other related objects, the present application provides an acoustic piezoelectric thin film device structure, which comprises a support body and a piezoelectric film layer structure covering an area surrounded by the support body, the peripheral edge of the piezoelectric film layer structure being fixedly connected to the support body, the piezoelectric film layer structure comprising a piezoelectric layer and an electrode layer covering all surfaces of the piezoelectric layer, the piezoelectric film layer structure comprising an inner region and an outer region surrounding the inner region, and having an electrode separation zone between the inner region and the outer region, the electrode separation zone separating the electrode layer into a central electrode layer and a peripheral electrode layer.

[0008] Optionally, the piezoelectric film layer structure has a plurality of slit zones penetrating the piezoelectric film layer structure in the longitudinal direction to divide the piezoelectric film layer structure into a plurality of piezoelectric unit zones, the slit zones extending in the transverse direction from the peripheral edge of the piezoelectric film layer structure towards the center point of the piezoelectric film layer structure and having a spacing from the center point to reserve a central connecting portion in the center of the piezoelectric film layer structure for mechanically connecting the piezoelectric unit zones, the physical separation area of the piezoelectric layer caused by the slit zones being consistent with or not consistent with the physical area of the piezoelectric effective electrical unit caused by the electrode separation, depending on specific requirements.

[0009] Optionally, the area of the central connecting portion accounts for 5% to 95% of the total area of the piezoelectric film layer structure.

[0010] Optionally, the piezoelectric film layer structure comprises a first piezoelectric layer and a second piezoelectric layer in the longitudinal direction, the upper surface of the first piezoelectric layer being entirely covered with a first electrode, the lower surface of the second piezoelectric layer being entirely covered with a second electrode, and the first piezoelectric layer and the second piezoelectric layer being entirely covered with a third electrode in between, the piezoelectric film layer structure comprising an inner region and an outer region surrounding the inner region in the transverse direction, the inner region and the outer region having an electrode separation zone therebetween, the electrode separation zone separating the first electrode into a first central electrode and a first peripheral electrode, separating the second electrode into a second central electrode and a second peripheral electrode, and separating the third electrode into a third central electrode and a third peripheral electrode.

[0011] Optionally, the piezoelectric film layer structure has a plurality of slit regions extending through the first electrode, the first piezoelectric layer, the third electrode, the second piezoelectric layer and the second electrode in the longitudinal direction, which physically divides the piezoelectric film layer structure into a plurality of piezoelectric unit regions, the electrical division of the piezoelectric layer is determined by the electrode structure, and the electrode division can be the same as or different from the division of the slit regions, the slit regions extend from the periphery of the piezoelectric film layer structure to the center point of the piezoelectric film layer structure in the transverse direction and have a spacing from the center point, so as to reserve a center connecting part mechanically connecting the centers of the piezoelectric unit regions in the center of the piezoelectric film layer structure, and the area of the center connecting part accounts for 5% to 95% of the total area of the piezoelectric film layer structure.

[0012] Optionally, the plurality of piezoelectric units operate at the same vibration phase and vibration frequency.

[0013] Optionally, the surface of the center connecting part has an electrode or an insulator.

[0014] Optionally, the plurality of piezoelectric units divided by the slit regions are symmetrical in shape and have the same area.

[0015] Optionally, the width of the slit region is less than or equal to 10 microns.

[0016] Optionally, the first center electrode, the first piezoelectric layer and the third center electrode in the same piezoelectric unit region form a first center capacitor, the third center electrode, the second piezoelectric layer and the second center electrode form a second center capacitor, the first peripheral electrode, the first piezoelectric layer and the third peripheral electrode form a first peripheral capacitor, the third peripheral electrode, the second piezoelectric layer and the second peripheral electrode form a second peripheral capacitor, and the first center capacitor, the second center capacitor, the first peripheral capacitor and the second peripheral capacitor are mutually insulated, connected in parallel, connected in series or connected in series-parallel.

[0017] Optionally, the first center capacitor, the second center capacitor, the first peripheral capacitor and the second peripheral capacitor of the plurality of piezoelectric unit regions are mutually insulated, connected in parallel, connected in series or connected in series-parallel.

[0018] Optionally, by interconnection between the piezoelectric layer and the electrode, only two-port power supply (such as high-voltage source-V dd and ground-GND, or positive and negative power supply (V+ and V-), etc.) is needed, and when the transducer structure emits a signal, the mechanical amplitude of the piezoelectric film layer structure is increased by applying reverse electrical signals (such as V dd and GND, or positive and negative power supply (V+ and V-)) to the external and internal regions, and when the transducer structure receives a signal, the received signal is maximized by superimposing the electrical signals of the external and internal regions in two ways.

[0019] Optionally, the support body is a polygonal ring, and the piezoelectric film layer structure is in the form of a polygonal surface covering the area surrounded by the support body, the polygonal ring including one of an equilateral triangle ring, an equilateral quadrilateral ring, an equilateral pentagon ring, an equilateral hexagon ring and an equilateral octagon ring, and the support body shape and the piezoelectric film layer structure shape can be related or unrelated.

[0020] Optionally, the slit region extends from the corner end of the polygonal ring to the midpoint of the polygonal ring.

[0021] Optionally, the support body is a circular ring or an elliptical ring, and the piezoelectric film layer structure is in the form of a circular surface covering the area surrounded by the support body, and the support body shape and the piezoelectric film layer structure shape can be related or unrelated.

[0022] Optionally, the slit region extends from the circumferential edge of the circular ring to the center of the circular ring.

[0023] Optionally, the piezoelectric layer material includes one of AlN, AlN material based on different proportions of doping, PZT, PMN-PT, ZnO, PVDF and LiNbO3.

[0024] Optionally, the acoustic piezoelectric thin film device structure is a transmitter or a receiver, and the acoustic piezoelectric thin film device structure works in a resonance mode or a non-resonance frequency.

[0025] As described above, the acoustic piezoelectric thin film device structure of the present application has the following beneficial effects:

[0026] The present application proposes an acoustic piezoelectric diaphragm structure, the outer ring of which is fixed to a support body, and a slit region (i.e. a sound transmission channel) and its size are added or adjusted on the diaphragm structure through a semiconductor process, which has an advantage in controlling the initial warping caused by pre-stress; under the same pre-stress, the initial warping of the acoustic piezoelectric diaphragm structure is about one tenth of that of a cantilever beam structure, which ensures the mechanical stability of the transducer.

[0027] When the acoustic piezoelectric film layer structure proposed by the present application is used as a transducer, due to the consistency of the width of the middle slit region and the fact that it does not change with warping, the low frequency response of the transducer will not be reduced due to the decrease of the acoustic resistance of the slit region, and the low frequency dynamic sensitivity of the acoustic receiver is improved. At the same time, under the premise of releasing the same area of the structure, the high frequency flat band of the transducer (such as a receiver) can work in a wider bandwidth.

[0028] The acoustic piezoelectric film layer structure provided by the application has opposite potential distribution directions in the outer ring and inner ring regions, and the absolute values are close. By using the double-layer piezoelectric film layer structure and only two electrical ports (for example, V+ and V-), the following can be achieved: 1) the receiver can output signals from the electrodes in the outer ring and inner ring regions respectively, and enhance the sensitivity of the receiving end through the series-parallel combination; 2) the transmitter can also load signals through the double-layer structure, and enhance the sound signal intensity of the transmitting end. Compared with the general cantilever beam or single piezoelectric layer transducer, the utilization rate of mechanical energy and electrical signals of the application is doubled, and the performance of the transducer is improved.

[0029] The acoustic piezoelectric film layer structure designed by the application can reduce the warping degree of the piezoelectric film layer structure and control the increase of the width of the sound transmission channel in the slit area caused by warping. The electrode layer of the application fully covers the surface of the piezoelectric film layer, and the novel splitting and series-parallel electrical connection mode between the longitudinal multiple piezoelectric layers and the transverse multiple electrode layers can realize the electromechanical conversion of the whole area of the piezoelectric film layer, and improve the electromechanical conversion efficiency of the piezoelectric thin film device. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 A three-dimensional structure schematic diagram of the acoustic piezoelectric thin film device structure of the embodiment is shown, Figure 2 A cross-sectional structure schematic diagram of the acoustic piezoelectric thin film device structure of the embodiment is shown, Figure 3 A back structure schematic diagram of the acoustic piezoelectric thin film device structure of the embodiment is shown.

[0031] Figures 4 to 10 Several structure schematic diagrams of the acoustic piezoelectric thin film device structure of the application are shown.

[0032] Figure 11 And Figure 12 A flexure schematic diagram of the acoustic piezoelectric thin film device structure of the application and a flexure schematic diagram of the multiple cantilever beam structures are shown respectively.

[0033] Figure 13 A deformation diagram of the cantilever beam structure after warping, Figure 14 A deformation diagram of the acoustic piezoelectric thin film device structure of the application after warping.

[0034] Figure 15 An acoustic theory equivalent model diagram of the middle slit area is shown.

[0035] Figure 16 An equivalent circuit model of a receiving sensor is shown.

[0036] Figure 17 A normalized displacement frequency response curve diagram of the acoustic piezoelectric thin film device structure of the application and a normalized displacement frequency response curve diagram of the multiple cantilever beam structures are shown.

[0037] Figure 18 AndFigure 19 Potential distribution diagrams showing a plurality of cantilever beam structures and the acoustic piezoelectric thin film device structure of the present application, respectively.

[0038] Figure 20 and Figure 21 Potential distribution diagrams showing a double piezoelectric film layer structure of the acoustic piezoelectric thin film device structure of the present application.

[0039] Figure 22 Electrode division diagram showing a double piezoelectric film layer structure of the acoustic piezoelectric thin film device structure of the present application.

[0040] Figure 23 and Figure 24 Equivalent circuit diagram showing an electrode connection of a double piezoelectric film layer structure of the acoustic piezoelectric thin film device structure of the present application.

[0041] Explanation of element reference numerals

[0042] 10 support body

[0043] 20 piezoelectric film layer structure

[0044] 201 outer region

[0045] 202 inner region

[0046] 203 center connection portion

[0047] 204 first piezoelectric layer

[0048] 205 second piezoelectric layer

[0049] 206 first electrode

[0050] 207 second electrode

[0051] 208 third electrode

[0052] 209 first center electrode

[0053] 210 first peripheral electrode

[0054] 211 second center electrode

[0055] 212 second peripheral electrode

[0056] 213 third center electrode

[0057] 214 third peripheral electrode

[0058] 215 electrode division region

[0059] 30 slit region

[0060] 40 back cavity structure DETAILED DESCRIPTION

[0061] Other advantages and novel features of the present application will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

[0062] When embodying the present application, for the convenience of description, the sectional view of the device structure may be partially enlarged without the general proportion, and the schematic view is only an example, which should not limit the scope of protection of the present application. In addition, the three-dimensional spatial dimensions of length, width and depth should be included in actual production.

[0063] For the convenience of description, spatial relationship words such as "under", "below", "lower", "under", "above", "upper" and the like may be used to describe the relationship of one element or feature with other elements or features shown in the drawings. It will be understood that these spatial relationship words are intended to include other directions of the device in use or operation in addition to the directions depicted in the drawings. In addition, when a layer is referred to as "between" two layers, it can be the only layer between the two layers, or one or more intervening layers can also be present.

[0064] In the context of the present application, the structure described as the first feature "above" the second feature can include the embodiment in which the first and second features are formed in direct contact, and can also include the embodiment in which another feature is formed between the first and second features, so that the first and second features can not be in direct contact.

[0065] It should be noted that the diagrams provided in the embodiments only schematically illustrate the basic concept of the present application, and only the components related to the present application are shown in the diagrams, not the number, shape and size of the components when actually implemented. The actual implementation of each component can be a random change, and the component layout pattern can be more complex.

[0066] As shown in FIG. 1, the acoustic piezoelectric thin film device structure of the present embodiment is shown as a perspective structural schematic diagram, Figures 1 to 3 As shown in FIG. 2, the acoustic piezoelectric thin film device structure of the present embodiment is shown as a sectional structural schematic diagram, Figure 1 As shown in FIG. 3, the acoustic piezoelectric thin film device structure of the present embodiment is shown as a perspective structural schematic diagram, Figure 2 As shown in FIG. 4, the acoustic piezoelectric thin film device structure of the present embodiment is shown as a sectional structural schematic diagram, Figure 3Figure 8 shows a schematic diagram of the back structure of the acoustic piezoelectric thin film device structure according to the present embodiment. The present embodiment provides an acoustic piezoelectric thin film device structure, which comprises a support body 10 and a piezoelectric film layer structure 20 covering the area surrounded by the support body 10, the peripheral edge of the piezoelectric film layer structure 20 is fixedly connected to the support body 10, unlike the cantilever beam structure, the piezoelectric film layer structure 20 does not have a free end, the piezoelectric film layer structure 20 comprises a piezoelectric layer and an electrode layer covering all the surfaces of the piezoelectric layer, the piezoelectric film layer structure 20 comprises an inner region and an outer region surrounding the inner region, and the inner region and the outer region have an electrode separation zone 215 therebetween, the electrode separation zone 215 separates the electrode layer into a central electrode layer and a peripheral electrode layer, in an embodiment, the area ratio of the central electrode layer to the peripheral electrode layer can be between 4:1 and 1:4, for example, between 2:1 and 1:2, preferably 1:1. The piezoelectric film layer structure 20 covers the area surrounded by the support body 10 to form a back cavity structure 40 at the back of the piezoelectric film layer structure 20. In an embodiment, the support body 10 is a closed loop support body.

[0067] The piezoelectric film layer structure 20 can be a single-layer piezoelectric layer, a double-layer piezoelectric layer or a multi-layer piezoelectric layer. As shown in Figure 4 、 6 , 8 and Figure 10 , the piezoelectric film layer structure 20 covers the area surrounded by the support body 10, the peripheral edge of the piezoelectric film layer structure 20 is fixedly connected to the support body 10, the piezoelectric film layer structure 20 comprises a first piezoelectric layer 204 and a second piezoelectric layer 205 in the longitudinal direction, the upper surface of the first piezoelectric layer 204 is entirely covered with a first electrode 206, the lower surface of the second piezoelectric layer 205 is entirely covered with a second electrode 207, and the first piezoelectric layer 204 and the second piezoelectric layer 205 are entirely covered with a third electrode 208, the piezoelectric film layer structure 20 comprises an inner region 202 and an outer region 201 surrounding the inner region 202 in the transverse direction, the inner region 202 and the outer region 201 have an electrode separation zone 215 therebetween, the electrode separation zone 215 separates the first electrode 206 into a first central electrode and a first peripheral electrode, separates the second electrode 207 into a second central electrode and a second peripheral electrode, and separates the third electrode 208 into a third central electrode and a third peripheral electrode. In an embodiment, the materials of the first piezoelectric layer 204 and the second piezoelectric layer 205 comprise one of AlN, AlN materials based on different proportions of doping, PZT, PMN-PT, ZnO, PVDF and LiNbO3.

[0068] In an embodiment, as shown in Figure 5 ,7 , 9 and Figure 10 are shown in FIG. 6, wherein, Figure 10 are shown in FIG. 6, wherein, Figure 5 A cross-sectional structure schematic diagram at A-A' in FIG. 6 shows that the piezoelectric film layer structure 20 has a plurality of slit regions 30, which pass through the first electrode 206, the first piezoelectric layer 204, the third electrode 208, the second piezoelectric layer 205 and the second electrode 207 in the longitudinal direction, to physically divide the piezoelectric film layer structure 20 into a plurality of piezoelectric unit regions, the slit regions 30 extend from the periphery of the piezoelectric film layer structure 20 to the center point of the piezoelectric film layer structure 20 in the transverse direction and have a spacing from the center point, to reserve a center connection part 203 in the center of the piezoelectric film layer structure 20, which mechanically connects the centers of the piezoelectric unit regions, the starting point of the slit region 30 can not be at the periphery of the piezoelectric film layer structure 20, but can be inside the outer region 201, and even the starting point can be inside the inner region 202, the ending point of the slit region 30 can be inside the outer region 201 or inside the inner region 202, preferably, the starting point of the slit region 30 is the periphery of the piezoelectric film layer structure 20, and the ending point is inside the inner region 202. Wherein, the physical division region of the piezoelectric layer caused by the slit region can be consistent with or inconsistent with the physical region of the piezoelectric effective electrical unit caused by the electrode division, depending on specific requirements. The proportion of the area of the center connection part 203 to the total area of the piezoelectric film layer structure 20 is between 5% and 95%, for example, in an embodiment, the proportion of the area of the center connection part 203 to the total area of the piezoelectric film layer structure 20 is 10%, of course, the radial size of the center connection part 203 can actually be greater than the radial size of the inner region 202, at this time, the slit region 30 is only provided in the outer region 201, the center connection part 203 contains the inner region 202 and crosses the electrode division region 215 to reach the outer region 201, but the center connection part 203 does not change the original settings in the outer region 201, the inner region 202 and the electrode division region 215. This embodiment can use a semiconductor processing technology to form the slit region 30 in the first piezoelectric layer 204 and the second piezoelectric layer 205, effectively adjust the working frequency of the transducer structure by adjusting the size of the slit region 30 (and the sound transmission channel), the size of the back cavity structure 40 and the thickness of the first piezoelectric layer 204 and the second piezoelectric layer 205, etc. Through the semiconductor process, the width of the slit region 30 can be set to be less than or equal to 10 microns, preferably, the width of the slit region 30 can be set to be 1-3 microns, to avoid the increase of acoustic resistance, so that the piezoelectric film layer structure 20 of the present application is suitable for various application scenarios and working modes of acoustic transducers, such as transmitters or receivers, at the same time, the transmitter or receiver can work in resonance mode or non-resonance frequency.

[0069] In one embodiment, the plurality of piezoelectric units work at the same vibration phase and vibration frequency, so that the signals of the plurality of piezoelectric units are enhanced when working, and the sensitivity of the acoustic piezoelectric film device structure is improved.

[0070] In one embodiment, the center connecting part 203 physically connects the plurality of piezoelectric unit regions together, and the surface of the center connecting part 203 has an electrode or is insulated. When the surface of the center connecting part 203 has an electrode, the internal regions 202 of the plurality of piezoelectric unit regions can be electrically connected together. When the surface of the center connecting part 203 is insulated, the internal regions 202 of the plurality of piezoelectric unit regions can be electrically isolated.

[0071] In one embodiment, the plurality of piezoelectric units divided by the slit region 30 are symmetrical in shape and have the same area, so as to facilitate the regulation of each piezoelectric unit.

[0072] In one embodiment, the first center electrode, the first piezoelectric layer, and the third center electrode in the same piezoelectric unit region form a first center capacitor, the third center electrode, the second piezoelectric layer, and the second center electrode form a second center capacitor, the first peripheral electrode, the first piezoelectric layer, and the third peripheral electrode form a first peripheral capacitor, the third peripheral electrode, the second piezoelectric layer, and the second peripheral electrode form a second peripheral capacitor, and the first center capacitor, the second center capacitor, the first peripheral capacitor, and the second peripheral capacitor are insulated from each other, connected in parallel, connected in series, or connected in series-parallel. In one embodiment, the first center capacitor, the second center capacitor, the first peripheral capacitor, and the second peripheral capacitor of the plurality of piezoelectric unit regions are insulated from each other, connected in parallel, connected in series, or connected in series-parallel. The electrode layer of the application fully covers the surface of the piezoelectric layer, and the electrode layer has a novel division and connection mode, which can realize full-area piezoelectric conversion and improve the utilization rate of piezoelectric materials.

[0073] In one embodiment, by interconnecting between the piezoelectric layer and the electrode, only two ports are powered (such as a high-voltage source-V dd and ground-GND, or a combination of positive and negative power supplies (V+&V-), etc.), and when the transducer structure emits a signal, by applying a reverse electrical signal (such as V dd and GND, or a combination of positive and negative power supplies V+ and V-) to the external region 201 and the internal region 202, the mechanical amplitude of the piezoelectric film layer structure is increased, and when the transducer structure receives a signal, by superimposing the electrical signals of the external region 201 and the internal region 202 in two ways, the received signal is maximized.

[0074] For example, Figure 6 and 8As shown, the support body 10 is a polygonal ring, and the piezoelectric film layer structure 20 is polygonally covered on the area surrounded by the support body 10. For example, the polygonal ring includes one of a regular triangle ring, a regular quadrilateral ring, a regular pentagon ring, a regular hexagon ring, and a regular octagon ring. The support body 10 shape and the piezoelectric film layer structure 20 shape can be related or unrelated.

[0075] In one embodiment, as shown in Figure 6 As shown, the polygonal ring includes a regular hexagon ring, and the piezoelectric film layer structure 20 is polygonally covered on the area surrounded by the support body 10.

[0076] In one embodiment, as shown in Figure 8 As shown, the polygonal ring includes a regular quadrilateral ring, and the piezoelectric film layer structure 20 is polygonally covered on the area surrounded by the support body 10.

[0077] As shown in Figure 7 and Figure 9 As shown, the support body 10 is a polygonal ring, and the piezoelectric film layer structure 20 is polygonally covered on the area surrounded by the support body 10. For example, the polygonal ring includes one of a regular triangle ring, a regular quadrilateral ring, a regular pentagon ring, a regular hexagon ring, and a regular octagon ring. The piezoelectric film layer structure 20 has a plurality of slit regions 30, which longitudinally pass through the first electrode 206, the first piezoelectric layer 204, the third electrode 208, the second piezoelectric layer 205, and the second electrode 207, so as to divide the piezoelectric film layer structure 20 into a plurality of piezoelectric unit regions. The slit regions 30 extend from the corner end of the polygonal ring to the midpoint of the polygonal ring.

[0078] In one embodiment, as shown in Figure 4 As shown, the support body 10 is a circular ring or an elliptical ring, and the piezoelectric film layer structure 20 is circularly covered on the area surrounded by the support body 10. The support body 10 shape and the piezoelectric film layer structure 20 shape can be related or unrelated.

[0079] In one embodiment, as shown in Figure 5 As shown, the support body 10 is a circular ring or an elliptical ring, and the piezoelectric film layer structure 20 is circularly covered on the area surrounded by the support body 10. The piezoelectric film layer structure 20 has a plurality of slit regions 30, which longitudinally pass through the first electrode 206, the first piezoelectric layer 204, the third electrode 208, the second piezoelectric layer 205, and the second electrode 207, so as to divide the piezoelectric film layer structure 20 into a plurality of piezoelectric unit regions. The slit regions 30 extend from the circumferential edge of the circular ring to the center of the circular ring.

[0080] As shown in Figure 11 andFigure 12 As shown, compared to the multiple cantilever beam structures of typical piezoelectric devices ( Figure 11 The acoustic piezoelectric thin film device structure of the present invention ( Figure 12 Due to the connection in the central region, the deflection (pre-strain) of the acoustic piezoelectric thin film device structure of this invention is smaller. Preliminary simulation calculations show that under a pre-stress of 100 MPa, the deflection of the acoustic piezoelectric thin film device structure of this invention is approximately one-tenth that of a typical cantilever beam structure. Since residual stress is generated during the manufacturing process of MEMS piezoelectric devices, this residual stress can cause device deflection. Under different deflections, the performance of the piezoelectric transducer (mostly a receiver) will change. To ensure consistent product performance, it is necessary to control the consistency of device deflection. Generally, low-frequency (≤20 kHz) piezoelectric receivers have multiple cantilever beam structures, and due to manufacturing processes, the deflections of these multiple cantilever beams are inconsistent. The diaphragm structure used in the acoustic piezoelectric thin film device structure of this invention has better consistency in deflection across different regions due to the connection in the central region. Furthermore, because the acoustic piezoelectric thin film device structure of this invention is a diaphragm structure, even under the same initial structural deflection, the acoustically permeable gaps in the diaphragm structure will not change in size due to changes in stress or incident sound waves, thereby optimizing the frequency response in the low-frequency range (generally ≤5 kHz). Furthermore, the warpage of piezoelectric devices also affects the reliability of MEMS piezoelectric devices. The acoustic piezoelectric thin film device structure of the present invention can better control warpage, and therefore has better reliability.

[0081] like Figure 13 and Figure 14 As shown, where, Figure 13 The image shows the deformation of the cantilever beam structure after warping. It can be seen that the closer to the free end of the cantilever beam, the wider the area of ​​the hollow risk (and sound-transmitting slits) between the cantilever beam structures becomes. Figure 14 This is a deformation diagram of the acoustic piezoelectric thin film device structure after warping. Due to the connection in the middle region, the size of the slit area remains basically unchanged. However, due to the warping of the cantilever beam structure, the gap between the cantilever beams increases. Preliminary calculations show that under a prestress of 100 MPa, the gap at the tip of the cantilever beam increases by three times compared to the design value, resulting in a significant decrease in low-frequency response sensitivity. The specific theoretical model is as follows:

[0082] like Figure 15 As shown, in acoustic theory, when the thickness of the slit region satisfies the following condition, the acoustic impedance can be equivalent to:

[0083]

[0084]

[0085] As shown in the formula above, t is the slit width, l is the length of the piezoelectric layer, d is the width of the piezoelectric layer, f is the operating frequency, η is the air viscosity coefficient, ρ is the air density, and R... slita For acoustic impedance, M slita For example, the acoustic impedance R of the 30-slit region in the middle slit area. slita The acoustic impedance R is inversely proportional to the cube of the slit width t. As the slit width t in the middle slit region increases, the acoustic impedance R... slita Rapidly decreases; acoustic impedance R slita The reduced size leads to low-frequency signal leakage, affecting the low-frequency performance of piezo-acoustic devices.

[0086] like Figure 16 As shown, the low-frequency sensitivity of the receiving sensor is not only related to the characteristics of the piezoelectric film layer structure 20, but also affected by the size of the sound-transmitting hole and the rear cavity. Figure 16 The equivalent circuit model of a simple receiving sensor shows the equivalent acoustic impedance R in the 30-domain region of the central slit. Leak Equivalent acoustic volume C of the back cavity BackVolume This forms an RC high-pass filter circuit with a cutoff frequency of... Below the cutoff frequency, sensitivity decreases by 20 dB for every 10-fold decrease in frequency.

[0087] To ensure low-frequency sensitivity, the low-frequency cutoff frequency should be as low as possible, which requires a large acoustic impedance in the middle slit region 30, meaning the width of the middle slit region should be as small as possible. Compared to general cantilever beam receiver sensors, the acoustic piezoelectric thin film device structure of this invention has a basically consistent deflection between regions due to the connection of the middle region, and will not produce sound leakage caused by vertical misalignment.

[0088] Based on the above analysis, the acoustic piezoelectric thin film device structure of the present invention has advantages in controlling the width of the intermediate slit region, and can reduce the cutoff frequency of the RC circuit and improve low-frequency sensitivity.

[0089] like Figure 17 As shown, Figure 17 The normalized displacement frequency response of the cantilever beam structure and the acoustic piezoelectric thin film device structure of the present invention are compared, and the vibrating diaphragm areas of the two piezoelectric device structures are similar. From the normalized displacement responses corresponding to slit widths of 1µm and 3µm for the cantilever beam structure MEMS receiving sensor, it can be seen that as the slit width increases, the low-frequency cutoff frequency increases, and the low-frequency displacement response decreases. Furthermore, from the normalized displacement response curve of the acoustic piezoelectric thin film device structure of the present invention with a slit width of 1µm, it can be seen that the low-frequency response of the acoustic piezoelectric thin film device structure of the present invention does not decrease due to initial warping.

[0090] like Figure 17As shown, the application frequency band of the cantilever beam structure is located between the black vertical short dashed lines on the left and right two inner sides, and the audio frequency band of the acoustic piezoelectric thin film device structure of the application is located between the vertical long dashed lines on the left and right two outer sides. The audio flat frequency operating bandwidth of the application is increased by about 2k compared with the cantilever beam structure.

[0091] The pre-stress of the general cantilever beam type piezoelectric device causes the cantilever beam end to be warped, and after warping, the width of the middle slit area increases, or due to the inconsistency of the deflection between the cantilever beams, the upper and lower misalignment is formed between the cantilever beams, which also increases the sound transmission area. These factors will cause the acoustic resistance of the slit area 30 domain to decrease; whether for a receiving sensor or an executing sensor, the decrease of the acoustic resistance of the middle slit area will affect the low frequency response; the decrease of the acoustic resistance of the middle slit area leads to low frequency signal leakage (sound leakage), and the low frequency response of the piezoelectric device is reduced; compared with the general cantilever beam type piezoelectric transducer, the structure of the application has the following advantages due to the use of the diaphragm structure instead of the cantilever beam and the full freedom structure in the direction of one-end incident sound wave: 1) the center area is not sound-transparent, and the increase of the deflection has no effect on the center area, which enhances the mechanical stability and yield, 2) the deflection is basically consistent between the areas, and there is no sound leakage caused by the upper and lower misalignment, which improves the low frequency band (≤5KHz) dynamic response sensitivity; 3) under the premise of the same structure release area, the resonance frequency of the diaphragm structure of the application is higher than that of the cantilever beam structure, so the low frequency flat band bandwidth is expanded, and the dynamic frequency response range of the low frequency receiver is further optimized.

[0092] As shown in Figure 18 and Figure 19 , wherein, Figure 18 The potential distribution diagram of the cantilever beam structure is shown, and it can be seen from the diagram that the potential direction is basically unchanged from the edge to the center area, Figure 19 The potential distribution diagram of the acoustic piezoelectric thin film device structure of the application is shown, and from the edge to the center area, the potential direction changes, the absolute value is the same but the direction is opposite. In actual design, the electrode layer at the center and the edge of the piezoelectric device can be physically separated through the electrode separation area 215, and then connected through electrical series or parallel connection, thereby increasing the utilization efficiency of the piezoelectric material and fully utilizing the whole area of the release structure.

[0093] As shown in 20- Figure 21As shown, the present application is a Bimorph double-layer piezoelectric film layer structure 20, under the action of an external force in a uniform direction, it can be seen that the potential direction of the upper layer and the lower layer is just opposite, the potential of the outer circle and the inner circle of the same layer is reversed, and the absolute value is basically equal; compared with the cantilever beam structure which generally only uses the electrodes of the outer circle area, the present application respectively uses the electrical signals of the outer circle and the inner circle area of the same layer of piezoelectric material through electrical leads or loading, the utilization area of the piezoelectric material increases nearly one time (the area is close to the whole diaphragm release area), and the mechanical energy and electrical energy conversion efficiency also increases one time, thereby improving the receiving and transmitting ability of the transducer.

[0094] As shown in Figure 22 and Figure 24 , the figure is a Bimorph double-layer piezoelectric film layer structure 20, the figure shows the cross-sectional view from the edge to the center of the piezoelectric film layer structure 20, which is only half of the overall cross-sectional view, so it only contains one fixed support structure; the electrodes are divided by the electrode division area 215, and the signals are respectively led out or loaded, which can improve the utilization efficiency of the piezoelectric material. As shown in Figures 22 to 24 , the double-layer piezoelectric film layer structure 20 of the present application can be equivalent to four capacitors C1, C2, C3 and C4 due to the division of the electrodes; the electrodes can be marked as outer circle electrodes T1, M1 and B1, and the inner circle electrodes can be marked as T2, M2 and B2.

[0095] As shown in Figure 23 and Figure 24 , the acoustic piezoelectric thin film device structure of the present application can equivalent the piezoelectric layer between the two electrode layers to a capacitor, and since the same layer of piezoelectric material is divided into two parts through different electrodes, the same layer of piezoelectric material can be equivalent to two capacitors, i.e. C1 and C3 of the same layer, or C2 and C4 of the same layer; in one embodiment, the Bimorph double-layer piezoelectric material of the present application can be equivalent to four capacitors C1, C2, C3 and C4 due to the double-layer structure, and the connection mode of the present application can include the following:

[0096] 1) connecting through parallel connection of the upper and lower capacitors (i.e. parallel connection of C1 and C2, and parallel connection of C3 and C4), and then series connection of the outer circle electrodes and the inner circle electrodes (i.e. series connection after parallel connection of C1 and C2, and parallel connection of C3 and C4), as shown in Figure 23 .

[0097] 2) connecting through parallel connection of the upper and lower capacitors (i.e. parallel connection of C1 and C2; parallel connection of C3 and C4), and then parallel connection of the outer circle electrodes and the inner circle electrodes (i.e. parallel connection after parallel connection of C1 and C2, and parallel connection of C3 and C4), as shown in Figure 24 .

[0098] The above electrical connection is only some examples, and other different capacitors can be connected in series or parallel to establish the same type of electrical connection. In addition, this connection method is suitable for any double-electrical-port (such as V+ and V-) double-piezoelectric layer structure electrical signal connection combination, and is not limited to the examples listed here.

[0099] As described above, the acoustic piezoelectric film device structure of the present application has the following beneficial effects:

[0100] The acoustic piezoelectric film structure is fixed to the support body by the outer ring, and the slotted area (i.e. the sound transmission channel) and its size are added or adjusted on the film structure by a semiconductor process, which has an advantage in controlling the initial warping caused by the pre-stress. Under the same pre-stress, the initial warping of the acoustic piezoelectric film structure is about one-tenth of that of the cantilever beam structure, which ensures the mechanical stability of the transducer.

[0101] When the acoustic piezoelectric film layer structure is used as a transducer, due to the consistency of the width of the middle slotted area and the fact that it does not change with warping, the low frequency response of the transducer will not be reduced due to the decrease in the acoustic resistance of the slotted area, and the low frequency dynamic sensitivity of the acoustic receiver is improved. At the same time, under the premise of releasing the same area of the structure, the high frequency flat band of the transducer (such as the receiver) can be expanded.

[0102] The potential distribution direction of the outer and inner ring regions of the acoustic piezoelectric film layer structure is opposite, and the absolute value is close. Using a double-layer piezoelectric film layer structure and only double electrical ports (such as V+ and V-), the following can be achieved: 1) the receiver can output signals from the electrodes of the outer and inner ring regions respectively, and enhance the sensitivity of the receiving end through series and parallel combination; 2) the transmitter can also load signals through the double-layer structure to enhance the sound signal strength of the transmitting end. Compared with the general cantilever beam or single piezoelectric layer transducer, the mechanical energy and electrical signal utilization rate of the present application is doubled, and the performance of the transducer is improved.

[0103] The acoustic piezoelectric film layer structure designed by the present application can reduce the warping degree of the piezoelectric film layer structure and control the increase in the width of the slotted area caused by warping. In addition, the electrode layer of the present application fully covers the surface of the piezoelectric film layer, and can realize the electromechanical conversion of the whole area of the piezoelectric film layer through the novel division and series or parallel electrical connection method between the longitudinal multi-piezoelectric layer and the transverse multi-electrode layer, thereby improving the electromechanical conversion efficiency of the piezoelectric film device.

[0104] Therefore, the present application effectively overcomes the shortcomings of the prior art and has high industrial utilization value.

[0105] The above embodiments are only illustrative of the principles of the present application and its efficacy, and are not intended to limit the present application. Any modification or change made by any person skilled in the art without departing from the spirit and scope of the present application shall be covered by the claims of the present application.

Claims

1. An acoustic piezoelectric thin film device structure, characterized by, The acoustic piezoelectric film device structure comprises: a support body; a piezoelectric film layer structure covering the area surrounded by the support body, the peripheral edge of the piezoelectric film layer structure being fixedly connected to the support body, the piezoelectric film layer structure comprising a piezoelectric layer and an electrode layer covering the upper and lower surfaces of the piezoelectric layer, the piezoelectric film layer structure comprising an inner region and an outer region surrounding the inner region, the inner region and the outer region being separated by an electrode separation zone, the electrode separation zone separating the electrode layer into a central electrode layer and a peripheral electrode layer; the piezoelectric film layer structure comprises a first piezoelectric layer and a second piezoelectric layer in the longitudinal direction, the upper surface of the first piezoelectric layer being entirely covered by a first electrode, the lower surface of the second piezoelectric layer being entirely covered by a second electrode, and the first piezoelectric layer and the second piezoelectric layer being entirely covered by a third electrode, the piezoelectric film layer structure comprising an inner region and an outer region surrounding the inner region in the transverse direction, the inner region and the outer region being separated by an electrode separation zone, the electrode separation zone separating the first electrode into a first central electrode and a first peripheral electrode, separating the second electrode into a second central electrode and a second peripheral electrode, and separating the third electrode into a third central electrode and a third peripheral electrode; the potential distribution directions of the outer ring region and the inner ring region of the piezoelectric film layer structure are opposite.

2. An acoustic piezoelectric thin film device structure according to claim 1, wherein: the piezoelectric film layer structure has a plurality of slit regions, the slit regions penetrating the piezoelectric film layer structure in the longitudinal direction to divide the piezoelectric film layer structure into a plurality of piezoelectric unit regions, the slit regions extending from the peripheral edge of the piezoelectric film layer structure towards the center point of the piezoelectric film layer structure in the transverse direction and having a spacing from the center point to reserve a central connection part in the center of the piezoelectric film layer structure for mechanically connecting each piezoelectric unit region.

3. An acoustic piezoelectric thin film device structure according to claim 2, wherein: the proportion of the area of the central connection part to the total area of the piezoelectric film layer structure is between 5% and 95%.

4. The acoustical piezoelectric thin film device structure of claim 1, wherein: the piezoelectric film layer structure has a plurality of slit regions, the slit regions penetrating the first electrode, the first piezoelectric layer, the third electrode, the second piezoelectric layer and the second electrode in the longitudinal direction, the slit regions physically dividing the piezoelectric film layer structure into a plurality of piezoelectric unit regions, the slit regions extending from the peripheral edge of the piezoelectric film layer structure towards the center point of the piezoelectric film layer structure in the transverse direction and having a spacing from the center point to reserve a central connection part in the center of the piezoelectric film layer structure for mechanically connecting each piezoelectric unit region, the proportion of the area of the central connection part to the total area of the piezoelectric film layer structure being between 5% and 95%.

5. An acoustic piezoelectric thin film device structure according to claim 2 or 4, characterised in that: a plurality of the piezoelectric units operate at the same vibration phase and vibration frequency.

6. An acoustic piezoelectric thin film device structure according to claim 2 or 4, wherein: the surface of the central connection part has an electrode or is insulated.

7. An acoustic piezoelectric thin film device structure according to claim 2 or 4, wherein: the shapes of the plurality of piezoelectric unit regions divided by the slit regions are symmetrical and have the same area.

8. An acoustic piezoelectric thin film device structure according to claim 2 or 4, wherein: the width of the slit region is less than or equal to 10 microns.

9. An acoustic piezoelectric thin film device structure according to claim 2 or 4, wherein: The first center electrode, the first piezoelectric layer and the third center electrode in the same piezoelectric unit area form a first center capacitor, the third center electrode, the second piezoelectric layer and the second center electrode form a second center capacitor, the first peripheral electrode, the first piezoelectric layer and the third peripheral electrode form a first peripheral capacitor, the third peripheral electrode, the second piezoelectric layer and the second peripheral electrode form a second peripheral capacitor, and the first center capacitor, the second center capacitor, the first peripheral capacitor and the second peripheral capacitor are mutually insulated, connected in parallel, connected in series or connected in series-parallel.

10. An acoustic piezoelectric thin film device structure according to claim 9, wherein: The first center capacitor, the second center capacitor, the first peripheral capacitor and the second peripheral capacitor of a plurality of the piezoelectric unit areas are mutually insulated, connected in parallel, connected in series or connected in series-parallel.

11. An acoustic piezoelectric thin film device structure according to claim 10, wherein: Through the interconnection between the piezoelectric layer and the electrode, only through the double-port power supply, the mechanical amplitude of the piezoelectric film layer structure is increased by applying a reverse electric signal in the external area and the internal area when the transducer structure emits a signal, and the received end signal is maximized by double-path superposition of the electric signals of the external area and the internal area when the transducer structure receives a signal.

12. An acoustic piezoelectric thin film device structure according to claim 2 or 4, wherein: The support body is a polygonal ring, and the piezoelectric film layer structure is in the form of a polygonal surface covering the area surrounded by the support body, and the polygonal ring includes one of a regular triangle ring, a regular quadrilateral ring, a regular pentagon ring, a regular hexagon ring and a regular octagon ring.

13. An acoustic piezoelectric thin film device structure according to claim 12, wherein: The slit area extends from the corner end of the polygonal ring to the midpoint of the polygonal ring.

14. An acoustic piezoelectric thin film device structure according to claim 2 or 4, wherein: The support body is a circular ring or an elliptical ring, and the piezoelectric film layer structure is in the form of a circular surface covering the area surrounded by the support body.

15. An acoustic piezoelectric thin film device structure according to claim 14, wherein: The slit area extends from the circumferential edge of the circular ring to the center of the circular ring.

16. The acoustical piezoelectric thin film device structure of claim 1, wherein: The piezoelectric film layer material includes one of AlN, AlN material based on different proportion of doping, PZT, PMN-PT, ZnO, PVDF and LiNbO3.

17. The acoustical piezoelectric thin film device structure of claim 1, wherein: The acoustic piezoelectric thin film device structure is a transmitter or a receiver, and the acoustic piezoelectric thin film device structure works in a resonance mode or a non-resonance frequency.

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