Resonator, filter and electronic device

Abstract

The present application relates to the technical field of resonators. Provided are a resonator, a filter and an electronic device. The resonator can improve an electromechanical coupling coefficient. The resonator may comprise a substrate, a first electrode, a plurality of piezoelectric layers and a plurality of second electrodes, wherein the first electrode, the plurality of piezoelectric layers and the plurality of second electrodes are arranged on the substrate, the plurality of piezoelectric layers have a first side and a second side, the plurality of second electrodes are located on the first side and arranged side by side in a first direction, the first electrode is located on the second side, the first side faces away from the substrate, and the second side faces the substrate. The plurality of piezoelectric layers comprise a first piezoelectric layer and a second piezoelectric layer, which are stacked, wherein a piezoelectric material of the first piezoelectric layer has a first piezoelectric tensor component e34, a piezoelectric material of the second piezoelectric layer has a second piezoelectric tensor component e34, and the first piezoelectric tensor component e34 is opposite to the second piezoelectric tensor component e34. Piezoelectric layers having piezoelectric tensor components e34 that are opposite to each other are used, such that the resonator has relatively large vibration, thereby improving an electromechanical coupling coefficient.

Description

Resonators, filters, electronic devices

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on November 30, 2023, with application number 202311635958.3 and invention name “Resonator, filter, electronic device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of resonators, and in particular to a resonator, a filter, an electronic device including a filter or a resonator, and a method for preparing the resonator or the filter. Background Art

[0003] With the development of communication technology, the demand for resonators in electronic devices will increase significantly. For example, BAW resonators such as horizontally-excited bulk acoustic resonators (XBARs), vertically-excited bulk acoustic resonators (YBARs), and film bulk acoustic resonators (FBARs) have attracted widespread attention.

[0004] Among them, YBAR has greater coupling and more effective resonance modes and can be used in a larger passband bandwidth.

[0005] However, in YBAR devices, since the piezoelectric layer is attached to the substrate, the acoustic resonant vibration of the part of the piezoelectric layer close to the substrate is restricted, which suppresses the improvement of the electromechanical coupling coefficient of the resonator.

[0006] Summary of the Invention

[0007] The present application provides a resonator, a filter having a resonator, an electronic device including a filter or a resonator, and a method for preparing a resonator. The purpose is to provide a resonator that can improve the electromechanical coupling coefficient.

[0008] To achieve the above objectives, the embodiments of the present application adopt the following technical solutions:

[0009] In one aspect, the present application provides a resonator. In one embodiment, the resonator may be an acoustic wave resonator, such as a YBAR.

[0010] The resonator comprises: a substrate, a first electrode, a multilayer piezoelectric layer and a plurality of second electrodes; the first electrode, the multilayer piezoelectric layer and the plurality of second electrodes are arranged on the substrate, the multilayer piezoelectric layer has a first side and a second side, the plurality of second electrodes are located on the first side and arranged side by side in a first direction, the first electrode is located on the second side, the first side faces away from the substrate and the second side faces the substrate; the multilayer piezoelectric layer comprises a first piezoelectric layer and a second piezoelectric layer stacked; the piezoelectric material of the first piezoelectric layer has a first piezoelectric tensor component e 34 , the piezoelectric material of the second piezoelectric layer has a second piezoelectric tensor component e 34 , the first piezoelectric tensor component e 34 and the second piezoelectric tensor component e 34 On the contrary, the first piezoelectric tensor component e 34 and the second piezoelectric tensor component e 34 They are opposite numbers.

[0011] In the resonator provided in the present application, the piezoelectric layer includes multiple layers, for example, a stacked first piezoelectric layer and a second piezoelectric layer, and the first piezoelectric tensor component e of the first piezoelectric layer is 34 and the second piezoelectric tensor component e of the second piezoelectric layer 34 On the contrary, under the action of the electric field, the deformation direction of the first piezoelectric layer is opposite to the deformation direction of the second piezoelectric layer. For example, when the vibration direction of the part of the first piezoelectric layer that is in contact with the second piezoelectric layer vibrates along the extension direction of the second electrode toward away from the piezoelectric layer, the vibration direction of the part of the second piezoelectric layer that is in contact with the first piezoelectric layer also vibrates along the extension direction of the second electrode toward away from the piezoelectric layer. These two vibrations couple and resonate at the position where the first piezoelectric layer and the second piezoelectric layer are in contact, so that mechanical vibrations are also generated inside the entire piezoelectric layer, thereby improving the electromechanical coupling coefficient of the entire resonator.

[0012] In one achievable manner, the first electrode has a first surface and a second surface opposite to each other, the first surface is closer to the piezoelectric layer than the second surface, and the second surface of the first electrode is completely disposed on the substrate.

[0013] The resonator given in this example can be called a solid-state substrate resonator. A resonator with this structure can improve the heat dissipation capability and robustness of the device.

[0014] In one possible implementation, there is a gap between two adjacent second electrodes; a groove is provided at a position of the multilayer piezoelectric layer opposite to the gap, and the groove is connected to the gap.

[0015] Since the grooves are formed in the piezoelectric layer, the grooves help to further increase the electromechanical coupling coefficient of the resonator and can also suppress or frequency-shift parasitic modes.

[0016] In one implementation, the thickness dimension H of the multi-layer piezoelectric layer and the depth dimension h of the groove satisfy 30% H≤h≤H.

[0017] When the groove depth is small, the vibration of the portion of the piezoelectric layer located at the first electrode and the second electrode is restricted.

[0018] In one achievable manner, the first piezoelectric layer is arranged closer to the substrate than the second piezoelectric layer; the second piezoelectric layer has a top surface away from the first piezoelectric layer, the first piezoelectric layer has a bottom surface away from the second piezoelectric layer, and the groove runs through the top surface and the bottom surface.

[0019] Since the grooves penetrate from the top surface to the bottom surface of the piezoelectric layer, the electromechanical coupling coefficient can be further increased.

[0020] In one implementation, the radial dimension of the groove gradually increases from the top surface to the bottom surface.

[0021] For example, the inclination angle α of the side surface of the groove satisfies: 45°<α<90°; or, 60°<α<90°.

[0022] In one achievable manner, the thickness dimension S1 of the second electrode and the thickness dimension H of the multi-layer piezoelectric layer are such that S1 / H≤0.35.

[0023] In one achievable manner, the thickness dimension S2 of the first electrode and the thickness dimension H of the multi-layer piezoelectric layer are such that S2 / H≤0.35.

[0024] In some examples, to reduce acoustic loss at the electrodes, the thickness of the first or second electrode can be reduced. However, when the electrode thickness is reduced, the power handling capability of the electrode is reduced. In the example of this application, the thickness of the piezoelectric layer can be increased to reduce the thickness ratio of the electrode to the piezoelectric layer. This does not pose a challenge to the etching process and does not reduce the power handling capability of the electrode.

[0025] In one possible implementation, the resonator further includes: a first bus bar and a second bus bar; one of each two adjacent second electrodes in the plurality of second electrodes is a first interdigitated electrode, and the other is a second interdigitated electrode; the first interdigitated electrode and the second interdigitated electrode are spaced in a first direction; a plurality of first interdigitated electrodes in the plurality of second electrodes are connected by a first bus bar, and a plurality of second interdigitated electrodes in the plurality of second electrodes are connected by a second bus bar; the finger spacing P and the thickness dimension H of the multilayer piezoelectric layer satisfy: P / H≥1; the width dimension of each first interdigitated electrode is t1, the spacing between each two adjacent first interdigitated electrodes and the second interdigitated electrode is t2, the finger spacing P=t1+t2, and the width dimension is a dimension parallel to the surface of the substrate and perpendicular to the extension direction of the first interdigitated electrode.

[0026] In order to increase the resonant frequency of the resonator, the finger spacing P can be reduced. However, a smaller finger spacing P will not only pose a challenge to the etching process, but will also introduce parasitic heterogeneous modes. In the embodiment of the present application, since a multi-layer stacked piezoelectric layer is used, by limiting the ratio of the finger spacing to the piezoelectric layer thickness, not only will it not pose a challenge to the etching process, but it can also suppress parasitic heterogeneous modes.

[0027] In one achievable manner, the thickness dimension S1 of the first piezoelectric layer and the thickness dimension S2 of the second piezoelectric layer are equal or nearly equal.

[0028] In one achievable manner, based on applying voltage to the plurality of second electrodes, the resonator is used to excite the multilayer piezoelectric layer to generate a first resonant mode, where a vibration direction of the first resonant mode is parallel to an extension direction of the second electrodes.

[0029] In one possible implementation, the electromechanical coupling coefficient Kt of the resonator is 2 ≥24%.

[0030] In one implementation, the piezoelectric material of the first piezoelectric layer and the second piezoelectric layer includes at least one of a combination of niobium and lithium and a combination of tantalum and lithium.

[0031] In one achievable manner, a dielectric layer is stacked between the substrate and the first electrode, and the thickness g of the dielectric layer satisfies: g=λ / 4, where λ is the wavelength of the acoustic wave of the resonator at the resonant frequency in the material of the dielectric layer.

[0032] By providing a dielectric layer between the substrate and the first electrode, coupling between the piezoelectric layer and the substrate is prevented, thereby increasing the electromechanical coupling coefficient of the device. Moreover, when the thickness g of the dielectric layer satisfies: g=λ / 4, the electromechanical coupling coefficient can be further improved.

[0033] In one possible implementation, the first piezoelectric layer and the second piezoelectric layer are adjacent layers.

[0034] In one possible implementation, the first piezoelectric layer and the second piezoelectric layer have opposite polarities.

[0035] In this way, greater mechanical vibrations can be generated inside the piezoelectric layer, further improving the electromechanical coupling coefficient.

[0036] In one possible implementation, the piezoelectric tensor component e of the piezoelectric material of the first piezoelectric layer is 31 、e 32 、e 33 、e 14 、e 24 、e 15 、e 25 、e 36, the piezoelectric tensor component e corresponding to the piezoelectric material of the second piezoelectric layer 31 、e 32 、e 33 、e 14 、e 24 、e 15 、e 25 、e 36 The same; the piezoelectric tensor component e of the piezoelectric material of the first piezoelectric layer 11 、e 12 、e 13 、e 16 、e 21 、e 22 、e 23 、e 26 、e 35 , the piezoelectric tensor component e corresponding to the piezoelectric material of the second piezoelectric layer 11 、e 12 、e 13 、e 16 、e 21 、e 22 、e 23 、e 26 、e 35 on the contrary.

[0037] When the first piezoelectric layer is rotated 180° around an axis perpendicular to the plane of the first piezoelectric layer and the two piezoelectric layers meet the above-mentioned requirements for the piezoelectric tensor components, the polarities of the two piezoelectric layers may be opposite.

[0038] In one possible implementation, the piezoelectric tensor component e of the piezoelectric material of the first piezoelectric layer is 11 、e 12 、e 13 、e 14 、e 25 、e 35 、e 26 、e 36 , the piezoelectric tensor component e corresponding to the piezoelectric material of the second piezoelectric layer 11 、e 12 、e 13 、e 14 、e 25 、e 35 、e 26 、e 36 The same; the piezoelectric tensor component e of the piezoelectric material of the first piezoelectric layer 15 、e 16 、e 21 、e 22 、e 23 、e 24 、e 31 、e 32 、e33 , the piezoelectric tensor component e corresponding to the piezoelectric material of the second piezoelectric layer 15 、e 16 、e 21 、e 22 、e 23 、e 24 、e 31 、e 32 、e 33 on the contrary.

[0039] When the first piezoelectric layer is rotated 180° around an axis parallel to the plane of the first piezoelectric layer and perpendicular to the extension direction of the second electrode, and the two piezoelectric layers meet the above-mentioned piezoelectric tensor component requirements, the polarities of the two piezoelectric layers can be opposite.

[0040] In one possible implementation, the Euler angles of the piezoelectric material of the first piezoelectric layer are (0°, 90°, 0°), and the Euler angles of the piezoelectric material of the second piezoelectric layer are (0°, 90°, 180°), or,

[0041] The Euler angles of the crystal of the piezoelectric material of the first piezoelectric layer are (0°, 270°, 0°), and the Euler angles of the crystal of the piezoelectric material of the second piezoelectric layer are (0°, 270°, 180°), or,

[0042] The crystal Euler angles of the piezoelectric material of the first piezoelectric layer are (90°, 90°, 210°), and the crystal Euler angles of the piezoelectric material of the second piezoelectric layer are (90°, 90°, 30°).

[0043] On the other hand, the present application also provides a filter, which may include a plurality of electrically connected resonators, and at least one of the plurality of resonators may be the resonator mentioned above.

[0044] Because the filter provided in this application includes the resonator of the aforementioned implementation structure, and because the resonator includes at least two piezoelectric layers with opposite polarization directions, the resonator has a large electromechanical coupling coefficient. This resonator, when used in a filter, can improve the filter's out-of-band rejection performance.

[0045] On the other hand, the present application further provides a duplexer, which includes a transmitting channel filter and a receiving channel filter. At least one of the transmitting channel filter and the receiving channel filter can be filtered using the above-mentioned filter.

[0046] On the other hand, the present application also provides a multiplexer, which includes multiple transmit channel filters and multiple receive channel filters, wherein at least one of the multiple transmit channel filters, or at least one of the multiple receive channel filters can adopt the filter involved in the embodiment of the present application.

[0047] On the other hand, the present application also provides an electronic device, which includes an amplifier, and the filter, duplexer or multiplexer in the above-mentioned implementation method, and the filter, duplexer or multiplexer can be electrically connected to the amplifier.

[0048] The electronic device provided in the embodiment of the present application includes the above-mentioned filter, duplexer or multiplexer. Therefore, the electronic device provided in the embodiment of the present application and the filter, duplexer or multiplexer of the above-mentioned technical solution can solve the same technical problem and achieve the same expected effect.

[0049] In another aspect, the present application further provides a method for preparing a resonator, the method comprising:

[0050] forming a first electrode on a substrate;

[0051] A first piezoelectric layer and a second piezoelectric layer are stacked on the first electrode, and a plurality of second electrodes are formed on the second piezoelectric layer, wherein the plurality of second electrodes are arranged side by side along a first direction;

[0052] The piezoelectric material of the first piezoelectric layer has a first piezoelectric tensor component e 34 , the piezoelectric material of the second piezoelectric layer has a second piezoelectric tensor component e 34 , the first piezoelectric tensor component e 34 and the second piezoelectric tensor component e 34 on the contrary.

[0053] In the resonator prepared by the preparation method of the present application, the first piezoelectric tensor component e of the piezoelectric material of the first piezoelectric layer is 34 and the second piezoelectric tensor component e of the piezoelectric material of the second piezoelectric layer 34 On the contrary, coupled resonance will be generated at the position where the first piezoelectric layer and the second piezoelectric layer are attached, so that mechanical vibration will also be generated inside the entire piezoelectric layer, thereby improving the electromechanical coupling coefficient of the entire resonator.

[0054] In one achievable manner, a first electrode is formed on a substrate, a stacked first piezoelectric layer and a second piezoelectric layer are formed on the first electrode, and a plurality of second electrodes are formed on the second piezoelectric layer, including:

[0055] A first electrode is formed on one side of a first piezoelectric wafer, a substrate is bonded to the first piezoelectric wafer, and the first piezoelectric wafer is thinned to form a first piezoelectric layer, wherein the first electrode is located between the first piezoelectric layer and the substrate;

[0056] bonding the second piezoelectric wafer to the first piezoelectric wafer, and thinning the second piezoelectric wafer to produce a stacked first piezoelectric layer and a second piezoelectric layer;

[0057] A plurality of second electrodes are formed on the second piezoelectric layer.

[0058] In this example, a resonator having multiple piezoelectric layers can be manufactured by piezoelectric wafer bonding.

[0059] In one achievable manner, the preparation method further includes: forming grooves on the first piezoelectric layer and the second piezoelectric layer at positions opposite to the gaps between two adjacent second electrodes, such that the grooves are connected to the gaps.

[0060] The groove can be used to further improve the electromechanical coupling coefficient or suppress parasitic heterogeneous modes.

[0061] On the other hand, the present application also provides a method for preparing a filter, which may include the method for preparing the resonator described above.

[0062] The filter made by this method has a first piezoelectric tensor component e of the piezoelectric material of the first piezoelectric layer. 34 and the second piezoelectric tensor component e of the piezoelectric material of the second piezoelectric layer 34 On the contrary, coupled resonance will be generated at the position where the first piezoelectric layer and the second piezoelectric layer are bonded, so that mechanical vibration will also be generated inside the entire piezoelectric layer, thereby improving the electromechanical coupling coefficient of the entire resonator and optimizing the performance of the filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] FIG1 is a schematic diagram of a partial structure of an electronic device;

[0064] FIG2 is a schematic diagram of a portion of the structure of an electronic device;

[0065] FIG3 is a schematic diagram of a partial structure of a filter in an electronic device;

[0066] FIG4 is a schematic diagram of a partial structure of a resonator;

[0067] FIG5 is a schematic diagram showing a partial structure of a resonator provided in an embodiment of the present application;

[0068] FIG6 is a schematic structural diagram illustrating a resonator vibration according to an embodiment of the present application;

[0069] FIG7 shows a schematic structural diagram of a resonator vibration provided by the related art;

[0070] FIG8 is a schematic diagram showing a structure of a resonator vibration provided by the related art;

[0071] FIG9 is a schematic diagram showing a partial structure of a resonator provided in an embodiment of the present application;

[0072] FIG10 is a schematic diagram showing a partial structure of a resonator provided in an embodiment of the present application;

[0073] FIG11 is a schematic diagram showing a structure of a resonator vibration provided by the related art;

[0074] FIG12 is a schematic structural diagram illustrating a resonator vibration according to an embodiment of the present application;

[0075] FIG13 is a schematic diagram showing a partial structure of a resonator provided in an embodiment of the present application;

[0076] FIG14 is a schematic diagram showing a partial structure of a resonator provided in an embodiment of the present application;

[0077] FIG15A is a schematic structural diagram illustrating a resonator vibration provided by the related art;

[0078] FIG15B is a schematic structural diagram illustrating a resonator vibration according to an embodiment of the present application;

[0079] FIG16A is a schematic structural diagram illustrating a resonator vibration provided by the related art;

[0080] FIG16B is a schematic structural diagram illustrating a resonator vibration according to an embodiment of the present application;

[0081] FIG17A shows an admittance curve diagram of the structure shown in FIG15A ;

[0082] FIG17B shows an admittance curve diagram of the structure shown in FIG15B ;

[0083] FIG18 is a schematic diagram showing a partial structure of a resonator provided in an embodiment of the present application;

[0084] FIG19 is a schematic diagram showing a partial structure of a resonator provided in an embodiment of the present application;

[0085] FIG20 is a schematic diagram showing a partial structure of a resonator provided in an embodiment of the present application;

[0086] FIG21 is a schematic diagram showing a structure of a resonator vibration provided by the related art;

[0087] FIG22 shows an admittance curve diagram of the structure shown in FIG20 ;

[0088] FIG23 shows an admittance curve diagram of the structure shown in FIG21 ;

[0089] FIG24 shows an admittance curve diagram of the structure shown in FIG20 ;

[0090] FIG25 shows an admittance curve diagram of the structure shown in FIG21;

[0091] FIG26 is a process flow chart of a method for preparing a resonator provided in an embodiment of the present application;

[0092] 27A to 27F are process structure diagrams after each step of a resonator manufacturing method provided in an embodiment of the present application is completed;

[0093] FIG28 is a schematic diagram of the structure of a filter provided in an embodiment of the present application;

[0094] FIG29 is the admittance curve and filter bandpass diagram of each resonator in FIG28.

[0095] Reference numerals:

[0096] 100-Electronic equipment;

[0097] 200-filter;

[0098] 300-Resonator;

[0099] 400, 410, 420, 430, 440 - resonators;

[0100] 500-antenna;

[0101] 600-Receiver;

[0102] 700-transmitter;

[0103] 800-baseband chip;

[0104] 900-switch;

[0105] 60a, 60c, 70a - filter; 60b - low noise amplifier; 60d - mixer; 60e - buffer; 60f, 70d - voltage controlled oscillator; 70b - amplifier; 70c - driver;

[0106] 10-substrate; 101-cavity;

[0107] 20-first electrode;

[0108] 30-piezoelectric layer; 301-first piezoelectric layer; 302-second piezoelectric layer;

[0109] 40 - second electrode; 401 - first interdigital electrode; 402 - second interdigital electrode;

[0110] 50-dielectric layer;

[0111] 601-first bus bar; 602-second bus bar;

[0112] 70-groove. DETAILED DESCRIPTION

[0113] Before introducing the structure that can be implemented in the embodiments of the present application, the technical terms involved in the embodiments of the present application are first introduced.

[0114] Piezoelectric effect: This includes the direct piezoelectric effect and the inverse piezoelectric effect. The direct piezoelectric effect refers to the change in the electrical polarization of a piezoelectric material when subjected to a mechanical force, while the inverse piezoelectric effect refers to the deformation of the material when an external electric field is applied. The piezoelectric effect is primarily due to the anisotropy of the piezoelectric material's crystal structure and polarization.

[0115] Main resonant mode, parasitic spurious modes: The parasitic resonant frequency generated by a resonator may be close to the main resonant frequency. These spurious resonances may affect the main resonant mode, thereby affecting the filter's in-band insertion loss and out-of-band rejection performance. The parasitic resonances of a resonator are often referred to as spurious modes. When spurious modes fall near the main resonant mode, for example, near the resonance point or antiresonance point of the main resonant mode, they can affect the filter's in-band insertion loss and out-of-band rejection performance.

[0116] Piezoelectric coupling factor Kt 2 : It is a key parameter of the resonator, the electromechanical coupling coefficient Kt 2 It can reflect the conversion efficiency between mechanical energy and electrical energy, the electromechanical coupling coefficient Kt of the resonator 2 Determines the relative frequency width between the resonant frequency and the anti-resonant frequency of the resonator. For example, when the resonator is used in filter design, this relative frequency width directly determines the bandwidth of the filter. It can be considered that the electromechanical coupling coefficient Kt 2 The larger it is, the larger the bandwidth of the filter built through the ladder structure can be, and the better the performance.

[0117] For single crystal piezoelectric materials, it has a fourth-order elastic tensor c, a third-order piezoelectric tensor e, and a second-order dielectric tensor ε. According to the right-hand rectangular coordinate system, it has the elastic tensor components c ijkl , piezoelectric tensor component e ijk , dielectric tensor component ε ij , where i,j,k,l={1,2,3}. Due to the symmetry of the single crystal structure, for example, c 1323 =c 3132 , we can simplify the component order and define {23,32}→4, {13,31}→5, {12,21}→6, for example, c 1323 =c 3132 →c 54 , then there is an elastic tensor component c xy (6*6), piezoelectric tensor component e ix(3*6), dielectric tensor component ε ij (3*3), where i, j = {1, 2, 3}, x, y = {1, 2, 3, 4, 5, 6}. Electromechanical coupling coefficient components kxy 2 It is calculated from the elastic tensor component, piezoelectric tensor component, and dielectric tensor component of the material, and the formula is:

[0118] Among them, x={1,2,3}, y={1,2,3,4,5,6}, ε xx S is the dielectric tensor component under fixed strain, c yy E is the elastic tensor component under fixed electric field strength.

[0119] The following explains the calculation methods and formulas of the elastic tensor components, piezoelectric tensor components, and dielectric tensor components at different crystal Euler angles.

[0120] For the piezoelectric material crystal orientation with Euler angle (0,0,0), taking LN as an example,

[0121] c E 11 =2.03,c E 12 =0.53,c E 13 =0.75,c E 14 =0.09,c E 44 =0.60,c E 33 =2.43,c E 22 =c E 11 ,c E 23 =c E 13 ,c E 24 =-c E 14 ,c E 55 =c E 44 ,c E 56 =c E 14 ,c E 66 =(c E 11 -c E 12 ) / 2, unit is *1011 N / m 2 ;

[0122] e 15 =3.70,e 16 =-2.53,e 31 =0.19,e 33 =1.31,e 21 =e 16 ,e 22 =-e 16 ,e 24 =e 15 ,e 32 =e 31 , unit is C / m 2 ; ε S 11 =43.6*ε0,ε S 33 =29.2*ε0,ε S 22 =ε S 11 , where ε0 is the dielectric constant of vacuum, 8.85*10 -12 F / m. The remaining components can be obtained by tensor symmetry, and the components without values ​​are zero. The components are simplified expressions. For the fourth-order elastic tensor component c E ijkl , the third-order piezoelectric tensor component e ijk , which can be expanded accordingly.

[0123] Now for the crystal orientation of piezoelectric materials with Euler angles (α, β, γ), the corresponding elastic tensor component c is E pqrs ', piezoelectric tensor component e pqr ', dielectric tensor component ε S pq ', can be calculated by the following formula:

[0124] c E pqrs '=c E ijkl A ip A jq A kr A ls ;

[0125] e pqr '=e ijk A ip A jq A kr ;

[0126] ε Spq '=ε S ij A ip A jq ;

[0127] The formula adopts the Einstein summation convention, where the 3*3 matrix A=(cosαcosγ-sinαcosβsinγ,-cosαsinγ-sinαcosβcosγ,sinαsinβ; sinαcosγ+cosαcosβsinγ,-sinαsinγ+cosαcosβcosγ,-cosαsinβ; sinβsinγ,sinβcosγ,cosβ).

[0128] Euler angle of piezoelectric material: The Euler angle characterizes the relative rotation angle relationship between the original piezoelectric crystal structure in the X direction or Y direction, perpendicular to or parallel to the extension direction of the resonator fingers, respectively, in the wafer plane.

[0129] Admittance: In power electronics, admittance is defined as the reciprocal of impedance, symbolized by Y and measured in siemens (S). Like impedance, admittance is a complex number consisting of a real part (conductance G) and an imaginary part (susceptance B): Y = G + jB.

[0130] Admittance curve abs and admittance curve Re: Admittance curve abs(Y) = |Y|, which is the modulus (also known as amplitude) of Y and represents the overall response of the resonator. Re(Y) is the real part of Y, that is, the conductance G, which represents the loss of the resonator.

[0131] The present application provides an electronic device, including but not limited to products such as a radio frequency front end and a filter amplifier module, and may also include terminal devices such as mobile phones, tablet computers (pads), smart wearable products (e.g., smart watches, smart bracelets), virtual reality (VR) devices, augmented reality (AR) devices, drones, or other devices, or may also be base stations, televisions, routers, automobiles, and other devices. The present application does not impose any particular restrictions on the specific form of the electronic device.

[0132] In an electronic device such as the one described above, as shown in FIG1 , the electronic device 100 may include a filter 200 , which may effectively filter out a specific frequency point in the signal or frequencies other than the frequency point to obtain a signal of a specific frequency, or eliminate a signal after a specific frequency, so as to improve the working performance of the electronic device 100 .

[0133] FIG2 shows a partial circuit diagram of some electronic devices 100. As shown in FIG2 , the electronic device 100 includes a receiver 600, a transmitter 700, an antenna 500, and a baseband chip 800. The antenna 500 is electrically connected to the receiver 600 and the transmitter 700 via a switch 900, respectively. Furthermore, the receiver 600 and the transmitter 700 are electrically connected to the baseband chip 800.

[0134] Receiver 600 shown in FIG2 includes filter 60a and filter 60c. A low-noise amplifier 60b is electrically connected between filter 60a and filter 60c. Filter 60c is electrically connected to buffer 60e via mixer 60d. Buffer 60e is electrically connected to voltage-controlled oscillator 60f. FIG2 is merely an exemplary receiver; electronic components may be added or reduced based on this circuit structure.

[0135] Transmitter 700 shown in FIG2 includes a power amplifier (PA) 70b, which is electrically connected to a filter 70a and a driver 70c, respectively. Driver 70c is electrically connected to a voltage-controlled oscillator 70d. Similarly, FIG2 is merely an exemplary transmitter, and electronic components may be added or reduced based on this circuit structure.

[0136] For example, in the transmitter 700 shown in FIG2 , the filter can effectively filter out a specific frequency point or frequencies other than the specific frequency point after the power amplifier amplifies the signal, or the filter can filter out noise signals of the low noise amplifier.

[0137] As shown in FIG3 , the filter 200 may include a plurality of resonators 300 connected in series, or a plurality of resonators 300 connected in parallel, or a combination of resonators 300 connected in series and in parallel.

[0138] At least one of the plurality of resonators included in the filter 200 may be the resonator shown in FIG. 4 .

[0139] As shown in Figure 4, a portion of a process structure diagram of a resonator is shown. The resonator includes a substrate 10, a first electrode 20, a piezoelectric layer 30, and a plurality of second electrodes 40. The first electrode 20, the piezoelectric layer 30, and the plurality of second electrodes 40 are disposed on the substrate 10. The plurality of second electrodes 40 are arranged side by side in a first direction. The piezoelectric layer 30 has a first side and a second side. The plurality of second electrodes 40 are located on the first side, and the first electrode 20 is located on the second side. The first side faces away from the substrate 10, and the second side faces the substrate 10. For example, as shown in Figure 4, the piezoelectric layer 30 is stacked between the first electrode 20 and the plurality of second electrodes 40.

[0140] In the resonator illustrated in FIG4 , the plurality of second electrodes 40 are arranged along a first direction, where the first direction can be understood as a direction perpendicular to or nearly perpendicular to the extending direction of the second electrodes 40. In one embodiment, the first direction is perpendicular to the stacking direction of the piezoelectric layer 30 and the first and second electrodes 20 and 40.

[0141] The example structure in Figure 4 can be used in a bulk acoustic wave resonator (BAW). The main working principle of a BAW resonator is to utilize the piezoelectric effect of piezoelectric materials. Using input and output transducers, the input radio wave signal is converted into mechanical energy. After processing, the mechanical energy is converted back into an electrical signal to filter out unnecessary signals and noise, thereby improving reception quality.

[0142] During operation, the resonator shown in Figure 4 can operate without an electrical signal connection to the first electrode 20. Instead, an alternating voltage of a certain frequency is applied to the second electrode 40, generating an electric field E between the first electrode 20 and the second electrode 40 along the thickness of the piezoelectric layer 30. The piezoelectric layer 30 utilizes this electric field to produce a piezoelectric effect. The example in Figure 4 utilizes a vertical electric field E to excite the piezoelectric layer 30 to resonate, thereby converting electrical energy into mechanical energy.

[0143] The resonator shown in FIG4 is excited to resonate along the thickness direction of the piezoelectric layer 30. In one embodiment, it can be referred to as a vertically-excited bulk acoustic resonator (YBAR). The thickness direction of the piezoelectric layer 30 here can be understood as the direction of the piezoelectric layer 30 parallel to the stacking direction of the multiple membrane layers (substrate, first electrode, piezoelectric layer).

[0144] As shown in FIG4 , since the portion of the piezoelectric layer 30 close to the first electrode 20 (the Q region indicated by the dotted line in FIG4 ) is attached to the first electrode 20, the acoustic resonance vibration of the region (the Q region indicated by the dotted line in FIG4 ) is limited, and the vibration amount of the piezoelectric layer 30 is limited, resulting in the electromechanical coupling coefficient Kt of the resonator being 2It is too small to be used in a larger passband bandwidth, for example, it cannot meet the passband bandwidth of the Sub-6GHz to Sub-15GHz frequency band.

[0145] In order to improve the electromechanical coupling coefficient Kt of the resonator 2 This application exemplifies some novel resonator process structures, as detailed below.

[0146] As shown in Figure 5, Figure 5 is a process structure diagram of a resonator provided in an embodiment of the present application. Similar to Figure 4 above, the resonator includes a substrate 10, a first electrode 20 stacked on the substrate 10, a piezoelectric layer 30, and a plurality of second electrodes 40. Furthermore, the second electrode 20 has a first surface and a second surface facing back to back, the first surface being closer to the piezoelectric layer 30 than the second surface, and the second surface of the first electrode 20 being completely disposed on the substrate 10. Such a resonator can be referred to as a solid-state substrate resonator.

[0147] The difference between the example shown in FIG5 and FIG4 is that in FIG5, the piezoelectric layer 30 includes multiple layers stacked together. For example, FIG5 exemplarily shows a stacked first piezoelectric layer 301 and a second piezoelectric layer 302. In other examples, more piezoelectric layers may be included, for example, three, four, or more layers.

[0148] In a multilayer piezoelectric layer, some piezoelectric tensor components of the piezoelectric materials of two adjacent piezoelectric layers are opposite. For example, as shown in Figure 5, the piezoelectric material of the first piezoelectric layer 301 has a first piezoelectric tensor component, and the piezoelectric material of the second piezoelectric layer 302 has a second piezoelectric tensor component, and the first piezoelectric tensor component and the second piezoelectric tensor component are opposite.

[0149] In some examples, the substrate 10 may be a high acoustic velocity substrate, for example, any one of silicon carbide (SiC), diamond, and boron nitride (BN), or a combination of multiple materials.

[0150] The first electrode 20 can be made of any possible conductive metal, including but not limited to Al, Cu, W, Mo, Ru, Pt, etc., and can also be made of a conductive metal with high acoustic impedance, including but not limited to W, Ru, Mo, Pt, etc. These metals with high acoustic impedance help to increase the electromechanical coupling coefficient and improve the quality factor Q, thereby further improving the performance of the resonator.

[0151] The second electrode 40 may be made of any possible conductive metal, including but not limited to Al, Cu, W, Mo, Ru, Pt, etc.

[0152] The first electrode 20 and the second electrode 40 may be made of the same conductive metal or different conductive metals.

[0153] In this example, the piezoelectric material of the first piezoelectric layer 301 has a first piezoelectric tensor component e 34 , the piezoelectric material of the second piezoelectric layer 302 has a second piezoelectric tensor component e 34 , where the first piezoelectric tensor component e 34 and the second piezoelectric tensor component e 34 on the contrary.

[0154] The first piezoelectric tensor component e of the example of this application 34 and the second piezoelectric tensor component e 34 On the contrary, it can be understood that the first piezoelectric tensor component e 34 and the second piezoelectric tensor component e 34 They are opposite numbers.

[0155] The first piezoelectric tensor component e 34 and the second piezoelectric tensor component e 34 In some examples, the first piezoelectric tensor component e 34 The absolute value of the second piezoelectric tensor component e 34 The absolute value of the first piezoelectric tensor component e can be completely equal, or 34 The absolute value of X1, the second piezoelectric tensor component e 34 The absolute value of is X2,

[0156] In the BAW resonator YBAR given in this application, the main resonant mode of the BAW resonator YBAR can be represented by the piezoelectric tensor component e 34 Determine the piezoelectric tensor component e 34 The absolute value of may be the maximum value among the absolute values ​​of all piezoelectric tensor components, or may be less than the maximum value among the absolute values ​​of the piezoelectric tensor components, for example, may be greater than or equal to 70% of the maximum value among the absolute values ​​of the piezoelectric tensor components.

[0157] In some possible structures, the first piezoelectric layer 301 and the second piezoelectric layer 302 may be two adjacent layers. In some other examples, other piezoelectric layers may be stacked between the first piezoelectric layer 301 and the second piezoelectric layer 302 .

[0158] In some examples, the piezoelectric material of the first piezoelectric layer 301 and the piezoelectric material of the second piezoelectric layer 302 may include at least one of a combination of niobium and lithium, or a combination of tantalum and lithium. For example, the material of the first piezoelectric layer 301 and the second piezoelectric layer 302 may include any one of lithium tantalate (LiTaO3), lithium niobate (LiNbO3), aluminum nitride (AlN), zinc oxide (ZnO), or a combination thereof.

[0159] In this application example, the piezoelectric layer has a piezoelectric tensor component e34 Under the action of the first piezoelectric layer 301 and the second piezoelectric layer 302 vibrate along the extension direction of the second electrode 40 .

[0160] In some examples, the first piezoelectric layer 301 and the second piezoelectric layer 302 both contain lithium niobate (LiNbO3), and when the crystal Euler angle of the piezoelectric material of the first piezoelectric layer 301 is (0°, 90°, 0°), the piezoelectric tensor component e of the piezoelectric material of the first piezoelectric layer 301 is 34 = +3.696, when the Euler angle of the crystal of the piezoelectric material of the second piezoelectric layer 302 is (0°, 90°, 180°), the piezoelectric tensor component e of the piezoelectric material of the second piezoelectric layer 302 is 34 =-3.696.

[0161] In some other examples, the first piezoelectric layer 301 and the second piezoelectric layer 302 both contain lithium niobate (LiNbO3), and when the crystal Euler angle of the piezoelectric material of the first piezoelectric layer 301 is (0°, 270°, 0°), the piezoelectric tensor component e of the piezoelectric material of the first piezoelectric layer 301 is 34 =-3.696, when the Euler angles of the crystal of the piezoelectric material of the second piezoelectric layer 302 are (0°, 270°, 180°), the piezoelectric tensor component e of the piezoelectric material of the second piezoelectric layer 302 34 =+3.696.

[0162] In the example of this application, the Euler angles (0°, 90°, 0°), Euler angles (0°, 90°, 180°), Euler angles (0°, 270°, 0°), and Euler angles (0°, 270°, 180°) may allow for a certain error range.

[0163] For example, it can be Euler angle (0°±5°, 90°±5°, 0°±5°), Euler angle (0°±5°, 90°±5°, 180°±5°), Euler angle (0°±5°, 270°±5°, 0°±5°), Euler angle (0°±5°, 270°±5°, 180°±5°).

[0164] FIG6 exemplarily shows how to improve the electromechanical coupling coefficient Kt of the structure shown in FIG5 of the present application 2 principle.

[0165] In FIG6 , both the first piezoelectric layer 301 and the second piezoelectric layer 302 can be made of lithium niobate (LiNbO 3 ). The vibration direction of the first piezoelectric layer 301 and the second piezoelectric layer 302 is along Direction 2. The first piezoelectric layer 301 is arranged closer to the first electrode 20 than the second piezoelectric layer 302. FIG6 exemplarily shows the second electrode 401 and the second electrode 402 of the second electrode. The fill pattern in FIG6 illustrates the approximate area where the resonator vibrates.

[0166] For example, when a positive voltage is applied to the second electrode 401, since the first piezoelectric layer 301 and the second piezoelectric layer 302 have opposite piezoelectric tensor components e 34 The portion of the second piezoelectric layer 302 close to the second electrode 401 (such as portion A1 in FIG6 ) vibrates along the negative direction of Direction 2, and the portion of the second piezoelectric layer 302 close to the first piezoelectric layer 301 (such as portion B1 in FIG6 ) vibrates along the positive direction of Direction 2; the portion of the first piezoelectric layer 301 close to the second piezoelectric layer 302 (such as portion C1 in FIG6 ) vibrates along the positive direction of Direction 2, and the portion of the first piezoelectric layer 301 close to the first electrode 20 (such as portion D1 in FIG6 ) vibrates along the negative direction of Direction 2.

[0167] As shown in FIG6 , between the second electrode 401 and the first electrode 20 , at the bonding position of the first piezoelectric layer 301 and the second piezoelectric layer 302 , two positive vibrations along direction 2 are coupled, so that mechanical vibrations are generated inside the entire piezoelectric layer.

[0168] For another example, when a negative voltage is applied to the second electrode 401, the portion of the second piezoelectric layer 302 close to the second electrode 401 (such as portion A2 in Figure 6) vibrates along the positive direction 2, and the portion of the second piezoelectric layer 302 close to the first piezoelectric layer 301 (such as portion B2 in Figure 6) vibrates along the negative direction 2; the portion of the first piezoelectric layer 301 close to the second piezoelectric layer 302 (such as portion C2 in Figure 6) vibrates along the negative direction 2, and the portion of the first piezoelectric layer 301 close to the first electrode 20 (such as portion D2 in Figure 6) vibrates along the positive direction 2.

[0169] As shown in FIG6 , between the second electrode 402 and the first electrode 20 , at the bonding position of the first piezoelectric layer 301 and the second piezoelectric layer 302 , two negative vibrations along direction 2 are coupled, so that mechanical vibrations are generated inside the entire piezoelectric layer.

[0170] Therefore, in the resonator structure of FIG6 of the present application example, the piezoelectric tensor component e of the adjacent piezoelectric layers is 34 When the values ​​are opposite to each other, the multilayer piezoelectric layers will produce coupled resonance at the interface, which will generate mechanical vibration inside the entire piezoelectric layer, thereby increasing the electromechanical coupling coefficient Kt. 2 .

[0171] In the example of the present application, since there is a gap between the second electrode 401 and the second electrode 402, compared with the resonator in which the second electrode 401 and the second electrode 402 are connected as an integral whole (such as a thin film cavity acoustic resonator FBAR), the second electrode 401 in Figure 6 of the present application will not be constrained by the second electrode 402 and has greater freedom. Furthermore, as shown in Figure 6, the second electrode 402 can also vibrate along direction 2 to increase the vibration amount of the entire resonator.

[0172] Similarly, since there is a gap between the second electrode 401 and the second electrode 402, compared with the resonator in which the second electrode 401 and the second electrode 402 are connected as an integral whole (such as a film cavity acoustic resonator FBAR), the second electrode 402 in Figure 6 of the present application will not be constrained by the second electrode 401 or other second electrodes, so that the second electrode 402 has a greater degree of freedom. Furthermore, as shown in Figure 6, the second electrode 402 can also vibrate along direction 2 to increase the vibration amount of the entire resonator.

[0173] In this way, the electromechanical coupling coefficient Kt of the resonator can be further improved. 2 .

[0174] The polarities of the first piezoelectric layer 301 and the second piezoelectric layer 302 may be opposite, which can make the vibration amplitude in the piezoelectric layer larger and further improve the electromechanical coupling coefficient.

[0175] In some implementations, as shown in FIG6 , the first piezoelectric layer 301 can be rotated 180° around an axis perpendicular to the plane of the first piezoelectric layer 301 (such as direction 3 in FIG7 ) to obtain a second piezoelectric layer 302 with a polarity opposite to that of the first piezoelectric layer 301. Then the piezoelectric tensor component e of the first piezoelectric layer 301 and the second piezoelectric layer is 31 、e 32 、e 33 、e 14 、e 24 、e 15 、e 25 、e 36 The other piezoelectric tensor components are opposite to each other, for example, e 11 、e 12 、e 13 、e 16 、e 21 、e 22 、e 23 、e 26 、e 34 、e 35 They are opposite numbers.

[0176] In some other possible implementations, as shown in FIG6 , the first piezoelectric layer 301 can be rotated 180° around an axis parallel to the plane of the first piezoelectric layer 301 and perpendicular to the extension direction of the second electrode (such as direction 1 in FIG7 ), to obtain a second piezoelectric layer 302 with a polarity opposite to that of the first piezoelectric layer 301. Then the piezoelectric tensor component e of the first piezoelectric layer 301 and the second piezoelectric layer is 11 、e 12 、e 13 、e 14 、e 25 、e 35 、e26 、e 36 The other piezoelectric tensor components are opposite to each other, for example, e 15 、e 16 、e 21 、e 22 、e 23 、e 24 、e 31 、e 32 、e 33 、e 34 They are opposite numbers.

[0177] FIG7 illustrates a vibration diagram when a single piezoelectric layer is used. The portion of the piezoelectric layer 30 that is in contact with the second electrode 401 (such as portion A1 in FIG7 ) vibrates in the negative direction of direction 2, and the portion of the piezoelectric layer 30 that is in contact with the first electrode 20 (such as portion B1 in FIG7 ) vibrates in the positive direction of direction 2. Compared with FIG6 above, in FIG7 , the interior of the entire piezoelectric layer 30 basically does not vibrate, while in FIG6 of the example of the present application, not only the upper and lower surfaces of the piezoelectric layer will vibrate, but also the interfaces between adjacent piezoelectric layers will vibrate. In some scenarios, even if the vibration of the portion of the piezoelectric layer that is in contact with the first electrode 20 is limited, the resonator of the example of the present application can still improve the electromechanical coupling coefficient Kt 2 .

[0178] Comparing Figures 6 and 7, the sum of the thicknesses 2h of the first and second piezoelectric layers 301 and 302 in Figure 6 is substantially equal or nearly equal to the thickness of the piezoelectric layer 30 in Figure 7. The resonant frequencies in Figures 6 and 7 are substantially equal or nearly equal.

[0179] The resonator in FIG6 of the example of this application can improve the electromechanical coupling coefficient Kt on the basis of ensuring that the resonant frequency meets the requirements 2 .

[0180] Direction 2 in the embodiments of the present application can be understood as being parallel to the extension direction of the second electrode 40. Direction 3 can be understood as being perpendicular to the surface of the substrate 10, or parallel to the stacking direction of the first piezoelectric layer 301 and the second piezoelectric layer 302. Direction 1 can be understood as being parallel to the surface of the substrate 10 and perpendicular to the extension direction of the second electrode 40.

[0181] In some examples, to increase the resonant frequency, the resonator shown in FIG8 may also be used. Compared with FIG7 , FIG8 has a thickness of h for the piezoelectric layer 30 of the single-layer structure, while FIG7 has a thickness of 2h for the piezoelectric layer 30 of the single-layer structure. For example, in FIG7 , the resonant frequency may be f, while in FIG8 , the resonant frequency may be 2f, that is, the resonant frequency of the resonator may be increased by reducing the thickness of the piezoelectric layer 30. However, in the process, increasing the resonant frequency by thinning the thickness of the piezoelectric layer 30 may pose a significant challenge to photolithography technology. Therefore, the increase in the resonant frequency is subject to certain limitations, and the high-frequency applications of the resonators shown in FIG7 and FIG8 are limited.

[0182] However, when using the resonator shown in FIG6 , the limitations imposed by photolithography technology are alleviated by stacking multiple piezoelectric layers, thereby improving the stability and robustness of the resonator and making the resonator applicable in a high-frequency range.

[0183] Figure 9 is a process structure diagram of another resonator exemplified in the present application. In this resonator, a cavity 101 is opened in the substrate 10. Such a resonator can be called a cavity-type suspended piezoelectric thin film resonator.

[0184] In Figure 9, the second electrode 20 has a first surface and a second surface back to back, the first surface is closer to the piezoelectric layer 30 than the second surface, the substrate 10 is provided with a cavity 101, at least a portion of the second surface of the first electrode 20 is used to enclose the cavity 101, and at least a portion of the first electrode 20 is arranged between the cavity 101 and the piezoelectric layer 30.

[0185] In this example, the piezoelectric layer 30 may also include multiple layers stacked, for example, a first piezoelectric layer 301 and a second piezoelectric layer 302. In the multilayer piezoelectric layer, adjacent piezoelectric layers have opposite piezoelectric tensor components. For example, the piezoelectric tensor component e of the first piezoelectric layer 301 is 34 and the piezoelectric tensor component e of the second piezoelectric layer 302 34 on the contrary.

[0186] 10 is a process structure diagram of another resonator according to an embodiment of the present application. In this example, a dielectric layer 50 is further included, and the dielectric layer 50 is stacked between the substrate 10 and the first electrode 20. For example, the dielectric layer 50 can be silicon oxide (SiO2).

[0187] In some examples, the thickness g of the dielectric layer 50 satisfies: g=λ / 4, where λ is the wavelength of the acoustic wave at the resonant frequency of the resonator in the material of the dielectric layer 50 .

[0188] As shown in FIG11 and FIG12 , in FIG11 , the piezoelectric layer 30 includes a piezoelectric layer. In FIG12 , the piezoelectric layer 30 includes a first piezoelectric layer 301 and a second piezoelectric layer 302 stacked together, and further includes a dielectric layer 50 stacked between the substrate 10 and the first electrode 20.

[0189] In Figure 11, since the first electrode 20 of the metal layer is directly stacked on the substrate 10, the vibration amplitude of the piezoelectric layer 30 and the first electrode 20 is limited. As shown in Figure 11, the vibration area and vibration amplitude are very small. However, as shown in Figure 12, because a dielectric layer with lower hardness is stacked between the substrate 10 and the first electrode 20, compared with Figure 11, mechanical vibrations are also generated in the first electrode 20 and the dielectric layer 50, thereby increasing the vibration of the entire resonator and improving the electromechanical coupling coefficient Kt. 2 .

[0190] FIG13 is a process structure diagram of a resonator provided in an embodiment of the present application, and FIG14 shows a distribution diagram of the second electrode in FIG13 .

[0191] In the resonators illustrated in Figures 13 and 14 , the plurality of second electrodes include a plurality of first interdigital electrodes 401 and a plurality of second interdigital electrodes 402. For example, the plurality of first interdigital electrodes 401 and the plurality of second interdigital electrodes 402 may be arranged side by side along a direction perpendicular to the direction in which the first interdigital electrodes 401 extend. Alternatively, the plurality of first interdigital electrodes 401 and the plurality of second interdigital electrodes 402 may be arranged in an alternating pattern, that is, a second interdigital electrode 402 may be disposed between two adjacent first interdigital electrodes 401. Alternatively, the first interdigital electrodes 401 and the second interdigital electrodes 402 may be spaced apart in the first direction, and the extending direction of the first interdigital electrodes 401 and / or the second interdigital electrodes 402 is perpendicular to the first direction.

[0192] The plurality of first interdigital electrodes 401 are connected via a first bus bar 601, and the plurality of second interdigital electrodes 402 are connected via a second bus bar 602. For example, the first bus bar 601 and the second bus bar 602 are arranged in parallel, and both the first bus bar 601 and the second bus bar 602 extend in a direction perpendicular to the direction in which the first interdigital electrodes 401 or the second interdigital electrodes 402 extend. As shown in FIG. 14 , the first bus bar 601 and the second bus bar 602 extend in a first direction.

[0193] The finger pitch (Pitch) P can be understood as shown in Figure 12, where the width of each first interdigital electrode 401 is t1, and the spacing between each two adjacent first interdigital electrodes 401 and second interdigital electrodes 402 is t2. The finger pitch (Pitch) P is the sum of the width t1 and the spacing t2.

[0194] In some examples, the width dimension t1 of the plurality of first interdigital electrodes 401 has a process tolerance, and the interval t2 between two adjacent first interdigital electrodes 401 and second interdigital electrodes 402 also has a process tolerance.

[0195] The thickness of the piezoelectric layer, the thickness of the first electrode, and the thickness of the second electrode are the height dimensions of the piezoelectric layer, the height dimensions of the first electrode, and the height dimensions of the second electrode along the stacking direction of the multiple membrane layer structures (such as the L direction in Figure 13).

[0196] The duty cycle is the ratio of the width s1 of the first interdigital electrode 401 to the interdigital pitch P, or the ratio of the width of the second interdigital electrode 402 to the interdigital pitch P. In some examples, the width of the first interdigital electrode 401 is equal to the width of the second interdigital electrode 402.

[0197] When the resonator is operating, acoustic loss may occur at the electrodes, reducing device performance. For example, acoustic loss may occur at the first electrode 20 or the second electrode 40. To reduce electrode acoustic loss, in some examples, the thickness of the electrodes may be reduced. However, reducing the thickness of the electrodes can weaken the power handling capability of the electrodes, shortening the device's service life.

[0198] In the resonator of the example of this application, by adopting a multi-layer stacked piezoelectric layer, the thickness of the entire piezoelectric layer is increased, thereby reducing the ratio of the thickness of the electrode layer to the thickness of the entire piezoelectric layer. By using a thicker piezoelectric layer, the acoustic loss in the electrode is reduced, thereby also ensuring the power tolerance of the electrode.

[0199] In some examples, as shown in FIG13 , the thickness of the second electrode layer 40 is S1, and the sum of the thicknesses of the first piezoelectric layer and the second piezoelectric layer is S2, where S1 / S2 ≤ 0.35. For example, S1 / S2 ≤ 0.3, or S1 / S2 ≤ 0.2, or S1 / S2 ≤ 0.1.

[0200] In some examples, the thickness of the first electrode is S3, and the sum of the thicknesses of the first piezoelectric layer and the second piezoelectric layer is S2, where S3 / S2 ≤ 0.35, for example, S3 / S2 ≤ 0.3, for example, S3 / S2 ≤ 0.2, and for example, S3 / S2 ≤ 0.1.

[0201] In order to increase the resonant frequency of the resonator, in some examples, the finger pitch shown in FIG14 can be reduced. However, when the finger pitch is reduced, it will bring challenges to the photolithography technology. In the example of this application, the finger pitch P can satisfy the thickness of the piezoelectric layer 30: P / d ≥ 1;

[0202] In some examples, the resonant frequency of the resonator can be greater than or equal to 3.64 GHz, for example, can reach 4.34 GHz.

[0203] The following, in conjunction with the accompanying drawings and table data, compares the resonator given in the embodiment of the present application with the resonator in the related art, the electromechanical coupling coefficient, and how to suppress parasitic heterogeneous modes.

[0204] Figure 15A is a process structure diagram of a resonator given in an embodiment of the present application. Figure 15A is used to illustrate the vibration along direction 2.

[0205] FIG15B is a process structure diagram of a resonator having a piezoelectric layer, and FIG15B is used to illustrate the vibration along direction 2.

[0206] As shown in FIG15A , the second piezoelectric layer 302 vibrates along direction 2 at the position where it contacts the second electrode 401 and the second electrode 402. The interface between the second piezoelectric layer 302 and the first piezoelectric layer 301 also vibrates along direction 2. Furthermore, the interface between the dielectric layer 50 and the first electrode 20 also vibrates slightly along direction 2. The main resonant mode SH1 of the resonator is generated in direction 2, that is, the vibration direction of the main resonant mode SH1 of the resonator is parallel to direction 2, which is the extension direction of the second electrode 40.

[0207] As shown in FIG15B , the piezoelectric layer 30 vibrates along direction 2 at the location where it contacts the second electrode 401 and the second electrode 402, and slightly vibrates along direction 2 at the interface between the dielectric layer 50 and the first electrode 20. In this resonator, the main resonant mode SH1 of the resonator is generated in direction 2, that is, the vibration direction of the main resonant mode SH1 of the resonator is parallel to direction 2, which is the extension direction of the second electrode 40.

[0208] Compared with FIG. 15A and FIG. 15B , in FIG. 15A of the example of the present application, coupled resonance is generated inside the entire piezoelectric layer.

[0209] Fig. 16A is a schematic diagram of the vibration of the resonator shown in Fig. 15A along direction 1. Fig. 16B is a schematic diagram of the vibration of the resonator shown in Fig. 15B along direction 1.

[0210] In the example diagram of vibration along direction 1 in FIG16A , the second piezoelectric layer 302 vibrates along direction 1 at the position where it contacts the second electrode 401 and the second electrode 402, and there is slight vibration along direction 1 at the interface between the dielectric layer 50 and the first electrode 20. A parasitic mode S0 of the resonator is generated in direction 1.

[0211] In the diagram of vibration along direction 1 shown in FIG16B , the entire piezoelectric layer 30 vibrates along direction 1, and at the interface between the piezoelectric layer 30 and the first electrode 20, the first electrode 20 also vibrates along direction 1. A parasitic mode S0 of the resonator is generated in direction 1.

[0212] Comparing FIG. 16A and FIG. 16B , in FIG. 16B , the vibration area generating the parasitic spurious mode S0 is larger, while in FIG. 16A , the vibration area generating the parasitic spurious mode S0 is smaller.

[0213] Figure 17A is an admittance simulation curve obtained by using the structure of Figure 15A and the physical parameters shown in Table 1. Figure 17B is an admittance simulation curve obtained by using the structure of Figure 15B and the physical parameters shown in Table 2.

[0214] Table 1

[0215] Table 2

[0216] Comparing Tables 1 and 2, the physical parameters of the two resonator structures show equal fin pitch P, equal duty cycle, equal second electrode thickness, equal first electrode thickness, and equal dielectric layer thickness. Because the Euler angles of the two piezoelectric layer materials in Table 1 are rotated 180°, the piezoelectric polarization directions of the first and second piezoelectric layers are opposite.

[0217] As shown in FIG17A , in the resonator provided by the present application, the excited S0 longitudinal wave spurious mode is relatively small near the resonance point of the SH1 main resonant mode. In contrast, in the admittance curve shown in FIG17B , a relatively large S0 longitudinal wave spurious mode is excited near the resonance point of the SH1 main resonant mode.

[0218] In addition, as shown in FIG17A , in the resonator of the present application example, the electromechanical coupling coefficient Kt 2 In the resonator with a piezoelectric layer, as shown in Figure 17B, the electromechanical coupling coefficient Kt 2 Obviously, the resonator with multi-layer piezoelectric layer provided in the embodiment of the present application can improve the electromechanical coupling coefficient Kt 2 For example, the electromechanical coupling coefficient Kt can be made 2 Greater than or equal to 20%.

[0219] The resonant frequency of the resonator in FIG15A of the example of the present application is increased from 4.7 GHz to 5.1 GHz compared to the resonant frequency of the resonator in FIG15B .

[0220] Therefore, the resonator comprising at least two piezoelectric layers in the example of the present application can not only improve the electromechanical coupling coefficient and increase the resonant frequency, but also suppress parasitic modes and further optimize the resonator performance.

[0221] Figures 18, 19, and 20 are process structure diagrams of three other resonators provided in the embodiments of this application. In this example, the resonator further includes a groove 70, with a gap between two adjacent second electrodes 40. The groove 70 is provided in the piezoelectric layer 30, and the groove 70 is opposite to the gap, which can be understood as the groove 70 being connected to the gap.

[0222] In some examples, such as Figures 18 and 19 , the first piezoelectric layer 301 is closer to the substrate 10 than the second piezoelectric layer 302, and the groove 70 may pass through the second piezoelectric layer 302 and a portion of the first piezoelectric layer 301. In other examples, such as Figure 20 , the groove 70 may pass through the second piezoelectric layer 302 and the first piezoelectric layer 301, reaching the surface of the first electrode 20.

[0223] That is, it can be understood that, in the example of the present application, the groove 70 may penetrate part of the piezoelectric layer 30 , or may penetrate the entire piezoelectric layer 30 , reaching the surface of the first electrode 20 .

[0224] By opening grooves in the multilayer piezoelectric layer, the limitation of the piezoelectric layer can be reduced, and the electromechanical coupling coefficient Kt of the resonator can be further increased. 2 , and, the groove 70 also helps to suppress or frequency shift spurious modes.

[0225] In some implementations, the deeper the trench 70 is, the greater the electromechanical coupling coefficient Kt of the resonator is. 2 In the embodiment of the present application, as shown in FIG11 , the depth h of the groove 70 can satisfy the following: 30% H ≤ h ≤ H, where H is the thickness of the piezoelectric layer 30. For example, h = 50% H, h = 60% H, h = 70% H, h = 80% H, h = 90% H, or h = H.

[0226] Furthermore, in some practicable examples, the radial dimension of the groove 70 gradually decreases from the top surface to the bottom surface. For example, as shown in FIG19 , the inclination angle α of the groove 70 can be: 45° ≤ α ≤ 90°. For example, in FIG19 , the inclination angle α is approximately 60°, and in FIG18 and FIG20 , the inclination angle α is approximately 90°.

[0227] The inclination angle α of the groove 70 may be understood as the angle between the side surface of the groove 70 and a reference plane, where the reference plane is a plane parallel to the surface of the substrate 10 .

[0228] Figure 21 is a process diagram of a resonator having a piezoelectric layer 30. Similar to Figures 18 and 20 of the examples of this application, this resonator also has a groove 70, with a gap between two adjacent second electrodes 40. The groove 70 is formed in the piezoelectric layer 30 and extends through the gap.

[0229] FIG22 is an admittance simulation curve obtained by using the structure of FIG20 and the physical parameters shown in Table 3, and FIG23 is an admittance simulation curve obtained by using the structure of FIG21 and the physical parameters shown in Table 4.

[0230] Table 3

[0231] Table 4

[0232] When the parameters in the above table are used, the frequency band range of the resonator shown in FIG20 and the resonator shown in FIG21 can be set to N77.

[0233] Comparing the admittance simulation curve of FIG22 and the admittance simulation curve of FIG23, it can be seen that when the resonator of FIG20 of the example of this application is used, the electromechanical coupling coefficient Kt 2 When a piezoelectric layer as shown in FIG21 is used, the electromechanical coupling coefficient Kt 2 Obviously, when grooves are opened in the piezoelectric layer and multiple piezoelectric layers with opposite polarities are included, the electromechanical coupling coefficient Kt can be improved. 2 .

[0234] The resonant frequency of the resonator in FIG20 of the example of the present application is increased from 3.35 GHz to 3.81 GHz compared to the resonant frequency of the resonator in FIG21 .

[0235] Continuing with Figure 22, in this admittance simulation curve, near the resonance point of the SH1 main resonant mode and near the antiresonance point of the SH1 main resonant mode, the excitation of the S0 longitudinal wave spurious mode is effectively suppressed. In the resonator admittance simulation curve shown in Figure 23, a large S0 longitudinal wave spurious mode is excited near the resonance point of the SH1 main resonant mode and near the antiresonance point of the SH1 main resonant mode.

[0236] FIG24 is an admittance simulation curve obtained by using the structure of FIG20 and the physical parameters shown in Table 5, and FIG25 is an admittance simulation curve obtained by using the structure of FIG21 and the physical parameters shown in Table 6.

[0237] Table 5

[0238] Table 6

[0239] When the parameters in the above table are used, the frequency band range of the resonator shown in FIG20 and the resonator shown in FIG21 can be set to N79.

[0240] Comparing the admittance simulation curve of FIG24 with the admittance simulation curve of FIG25, it can be seen that when the resonator of FIG20 of the example of the present application is used, the electromechanical coupling coefficient Kt 2 When a piezoelectric layer as shown in FIG21 is used, the electromechanical coupling coefficient Kt 2 Obviously, when grooves are opened in the piezoelectric layer and multiple piezoelectric layers with opposite polarities are included, the electromechanical coupling coefficient Kt can be improved. 2 .

[0241] The resonant frequency of the resonator in FIG20 of the example of the present application is increased from 4.02 GHz to 4.32 GHz compared to the resonant frequency of the resonator in FIG21 .

[0242] The embodiment of the present application also provides a method for preparing a resonator including multiple piezoelectric layers, as shown in FIG26 , which exemplarily shows a flow chart of the method for preparing a resonator.

[0243] The preparation method comprises:

[0244] Step S1: forming a first electrode on a substrate;

[0245] Step S2: a first piezoelectric layer and a second piezoelectric layer are stacked on the first electrode, and a plurality of second electrodes are formed on the second piezoelectric layer, wherein the plurality of second electrodes are arranged side by side along the first direction; wherein the piezoelectric material of the first piezoelectric layer has a first piezoelectric tensor component e 34 , the piezoelectric material of the second piezoelectric layer has a second piezoelectric tensor component e 34 , the first piezoelectric tensor component e 34 and the second piezoelectric tensor component e 34 on the contrary.

[0246] 27A to 27F show the process structure diagrams corresponding to each step in preparing a solid substrate piezoelectric thin film resonator.

[0247] 27A , a first electrode 20 is formed on one side of a first piezoelectric wafer, and a dielectric layer 50 is formed on the first electrode 20 .

[0248] 27B , the first piezoelectric wafer including the first electrode 20 and the dielectric layer 50 is bonded to the substrate 10 .

[0249] As shown in FIG27C , the first piezoelectric wafer may be thinned to a target thickness by ion implantation cutting or chemical-mechanical polishing (CMP) to form a first piezoelectric layer.

[0250] See FIG. 27D , where a second piezoelectric wafer is bonded to the first piezoelectric layer in FIG. 27C .

[0251] As shown in FIG27E , the second piezoelectric wafer may be thinned to a target thickness by ion implantation cutting or chemical-mechanical polishing (CMP) to form a second piezoelectric layer.

[0252] 27F , a plurality of second electrodes arranged in parallel are formed on the second piezoelectric layer, thereby forming a solid substrate piezoelectric thin film resonator.

[0253] The first electrode can be made of any possible conductive metal (including but not limited to Al, Cu, W, Mo, Ru, Pt, etc.), or a conductive metal with high acoustic impedance (including but not limited to W, Ru, Mo, Pt, etc.) can be selected. These metals with high acoustic impedance help to increase the electromechanical coupling coefficient and improve the quality factor Q, further improving the performance of the resonator.

[0254] The second electrode can be made of any possible conductive metal (including but not limited to Al, Cu, W, Mo, Ru, Pt, etc.). The first electrode 20 and the second electrode 40 can be made of the same conductive metal or different conductive metals.

[0255] The materials of the first piezoelectric layer and the second piezoelectric layer include at least one of a combination of niobium and lithium and a combination of tantalum and lithium.

[0256] In some examples, more piezoelectric layers can also be produced.

[0257] In other examples, a groove can be provided at a position corresponding to the gap between the piezoelectric layer and two adjacent second electrodes. The groove can penetrate the entire piezoelectric layer or a portion of the piezoelectric layer to improve the electromechanical coupling coefficient or suppress parasitic modes.

[0258] Solid-state substrate piezoelectric thin film resonators or cavity-type suspended piezoelectric thin film resonators, such as those mentioned above, can be used as sensors, such as temperature, humidity, and pressure sensors. Alternatively, they can be used as delay line devices for various high-frequency signal processing applications, such as those in the 100 MHz to 30 GHz range.

[0259] Furthermore, the aforementioned cavity-type suspended piezoelectric thin film resonators or solid-substrate piezoelectric thin film resonators can be electrically connected in a ladder configuration, as shown in FIG28 , to implement a filter for radio frequency communications. In the filter, resonators can be connected in series or in parallel, and the resonant frequency of the parallel resonators can be lower than the resonant frequency of the series resonators.

[0260] In the example of FIG28 , resonators 400, 410, 420, 430, and 440 are included. Resonators 400, 410, and 420 are series resonators, while resonators 430 and 440 are parallel resonators. At least one of resonators 400 to 440 may be the resonator described in the above embodiments.

[0261] In some examples, such as FIG29 , FIG29 shows the relationship between the admittance curves of each resonator and the transmission loss curve of the filter in FIG28 . Referring to FIG29 , the resonance points of the series resonators (such as resonators 400 , 410 , and 420 ) and the anti-resonance points of the parallel resonators (such as resonators 430 and 440 ) are located within the passband frequency band, forming the passband of the filter. The anti-resonance points of the series resonators (such as resonators 400 , 410 , and 420 ) are located on the high-frequency side outside the passband, and the resonance points of the parallel resonators (such as resonators 430 and 440 ) are located on the low-frequency side outside the passband. As a result, the filter has the characteristics of high roll-off and high out-of-band suppression.

[0262] In the description of this specification, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0263] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A resonator, characterized in that, comprising: a substrate; a first electrode, a multi-layer piezoelectric layer, and a plurality of second electrodes, the first electrode, the multi-layer piezoelectric layer, and the plurality of second electrodes are disposed on the substrate, the multi-layer piezoelectric layer has a first side and a second side, the plurality of second electrodes are located on the first side and are arranged side by side in a first direction, the first electrode is located on the second side, the first side faces away from the substrate, and the second side faces the substrate; the multi-layer piezoelectric layer includes a first piezoelectric layer and a second piezoelectric layer stacked; The piezoelectric material of the first piezoelectric layer has a first piezoelectric tensor component e 34 , and the piezoelectric material of the second piezoelectric layer has a second piezoelectric tensor component e 34 . The first piezoelectric tensor component e 34 is opposite to the second piezoelectric tensor component e 34 .

2. The resonator according to claim 1, characterized in that, there is a gap between two adjacent second electrodes; a groove is provided at a position of the multi-layer piezoelectric layer opposite to the gap, and the groove communicates with the gap.

3. The resonator according to claim 2, characterized in that, the thickness dimension H of the multi-layer piezoelectric layer, the depth dimension h of the groove, 30%H ≤ h ≤ H.

4. The resonator according to claim 2 or 3, characterized in that, the first piezoelectric layer is disposed closer to the substrate than the second piezoelectric layer; the second piezoelectric layer has a top surface away from the first piezoelectric layer, the first piezoelectric layer has a bottom surface away from the second piezoelectric layer, and the groove penetrates the top surface and the bottom surface.

5. The resonator according to any one of claims 1-4, characterized in that, the thickness dimension S1 of the second electrode, the thickness dimension H of the multi-layer piezoelectric layer, S1 / H ≤ 0.

35.

6. The resonator according to any one of claims 1-5, characterized in that, the thickness dimension S2 of the first electrode, the thickness dimension H of the multi-layer piezoelectric layer, S2 / H ≤ 0.

35.

7. The resonator according to any one of claims 1-6, characterized in that, the resonator further includes: a first bus bar and a second bus bar; one of every two adjacent second electrodes among the plurality of second electrodes is a first interdigital electrode, and the other is a second interdigital electrode; the first interdigital electrode and the second interdigital electrode are spaced apart in the first direction; the plurality of first interdigital electrodes among the plurality of second electrodes are connected by the first bus bar, and the plurality of second interdigital electrodes among the plurality of second electrodes are connected by the second bus bar; the finger pitch P and the thickness dimension H of the multi-layer piezoelectric layer satisfy: P / H ≥ 1; the width dimension of each first interdigital electrode is t1, the spacing between every two adjacent first interdigital electrodes and second interdigital electrodes is t2, the finger pitch P = t1 + t2, and the width dimension is the dimension parallel to the surface of the substrate and perpendicular to the extending direction of the first interdigital electrode.

8. The resonator according to any one of claims 1-7, characterized in that, based on applying a voltage to the plurality of second electrodes, the resonator is used to excite the multi-layer piezoelectric layer to generate a first resonance mode, and the vibration direction of the first resonance mode is parallel to the extending direction of the second electrode.

9. The resonator according to any one of claims 1-8, characterized in that, The electromechanical coupling coefficient Kt of the resonator 2 ≥ 24%.

10. The resonator according to any one of claims 1-9, characterized in that, the piezoelectric materials of the first piezoelectric layer and the second piezoelectric layer include at least one combination of a combination of niobium and lithium and a combination of tantalum and lithium.

11. The resonator according to any one of claims 1-10, characterized in that, for the first electrode, the first surface and the second surface are back-to-back, the second surface is closer to the substrate than the first surface, and the second surface of the first electrode is completely disposed on the substrate.

12. The resonator according to any one of claims 1-11, characterized in that, The piezoelectric tensor components e 31 、e 32 、e 33 、e 14 、e 24 、e 15 、e 25 、e 36 of the piezoelectric material of the first piezoelectric layer are the same as the piezoelectric tensor components e 31 、e 32 、e 33 、e 14 、e 24 、e 15 、e 25 、e 36 corresponding to the piezoelectric material of the second piezoelectric layer; The piezoelectric tensor components e 11 、e 12 、e 13 、e 16 、e 21 、e 22 、e 23 、e 26 、e 35 of the piezoelectric material of the first piezoelectric layer are opposite to the piezoelectric tensor components e 11 、e 12 、e 13 、e 16 、e 21 、e 22 、e 23 、e 26 、e 35 of the piezoelectric material corresponding to the second piezoelectric layer.

13. The resonator according to any one of claims 1-11, characterized in that, The piezoelectric tensor components e 11 、e 12 、e 13 、e 14 、e 25 、e 35 、e 26 、e 36 of the piezoelectric material of the first piezoelectric layer are the same as those of the second piezoelectric The piezoelectric tensor components e corresponding to the piezoelectric material of the electric layer 11 and e 12 and e 13 and e 14 and e 25 and e 35 and e 26 and e 36 are the same; The piezoelectric tensor components e 15 、e 16 、e 21 、e 22 、e 23 、e 24 、e 31 、e 32 、e 33 of the piezoelectric material of the first piezoelectric layer are opposite to the piezoelectric tensor components e 15 、e 16 、e 21 、e 22 、e 23 、e 24 、e 31 、e 32 、e 33 of the piezoelectric material corresponding to the second piezoelectric layer.

14. The resonator according to any one of claims 1-13, characterized in that, the first piezoelectric layer and the second piezoelectric layer are adjacent layers.

15. The resonator according to any one of claims 1-14, characterized in that, the first piezoelectric layer and the second piezoelectric layer have opposite polarities.

16. The resonator according to any one of claims 1-15, characterized in that, the Euler angles of the crystal of the piezoelectric material of the first piezoelectric layer are (0°, 90°, 0°), and the Euler angles of the crystal of the piezoelectric material of the second piezoelectric layer are (0°, 90°, 180°), or, the Euler angles of the crystal of the piezoelectric material of the first piezoelectric layer are (0°, 270°, 0°), and the Euler angles of the crystal of the piezoelectric material of the second piezoelectric layer are (0°, 270°, 180°), or, the Euler angles of the crystal of the piezoelectric material of the first piezoelectric layer are (90°, 90°, 210°), and the Euler angles of the crystal of the piezoelectric material of the second piezoelectric layer are (90°, 90°, 30°).

17. A filter, characterized in that, comprising: a plurality of electrically connected resonators, at least one of the plurality of resonators being the resonator according to any one of claims 1-16.

18. An electronic device, characterized in that, comprising: an amplifier; the resonator according to any one of claims 1-16, or the filter according to claim 17, the resonator or the filter being electrically connected to the amplifier.

19. A method for manufacturing a resonator, characterized in that, comprising: fabricating a first electrode on a substrate; fabricating a stacked first piezoelectric layer and second piezoelectric layer on the first electrode, and fabricating a plurality of second electrodes on the second piezoelectric layer, the plurality of second electrodes being arranged side by side in a first direction; Among them, the piezoelectric material of the first piezoelectric layer has a first piezoelectric tensor component e 34 , the piezoelectric material of the second piezoelectric layer has a second piezoelectric tensor component e 34 , the first piezoelectric tensor component e 34 and the second piezoelectric tensor component e 34 are opposite.

20. The method for manufacturing a resonator according to claim 19, characterized in that, fabricating the first electrode on the substrate, fabricating the stacked first piezoelectric layer and the second piezoelectric layer on the first electrode, and fabricating the plurality of second electrodes on the second piezoelectric layer, comprising: fabricating a first electrode on one side of a first piezoelectric wafer, bonding the substrate to the first piezoelectric wafer, thinning the first piezoelectric wafer, and fabricating the first piezoelectric layer, the first electrode being located between the first piezoelectric layer and the substrate; Bond the second piezoelectric wafer to the first piezoelectric wafer, and thin the second piezoelectric wafer to obtain a stacked first piezoelectric layer and second piezoelectric layer; Form a plurality of second electrodes on the second piezoelectric layer.

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