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 the electromechanical coupling coefficient. The resonator may comprise a substrate, a first electrode, a piezoelectric transducer layer and a plurality of second electrodes; the first electrode, the piezoelectric transducer layer and the plurality of second electrodes are arranged on the substrate; the piezoelectric transducer layer has a first side and a second side, the plurality of second electrodes being located on the first side and being arranged side by side in a first direction, the first electrode being located on the second side, the first side facing away from the substrate, and the second side facing the substrate; the piezoelectric transducer layer comprises a first piezoelectric layer and a second piezoelectric layer which are stacked; the first piezoelectric layer has a first piezoelectric tensor component e33, and the second piezoelectric layer has a second piezoelectric tensor component e33, the first piezoelectric tensor component e33 and the second piezoelectric tensor component e33 being opposite to each other. The adjacent piezoelectric layers having the opposite piezoelectric tensor components e33 enable the resonator to have relatively large vibration, thereby improving the 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 16, 2023, with application number 202311537342.2 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 having a resonator, and an electronic device including a filter or a resonator. 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 the resonator, and an electronic device including the filter. 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 piezoelectric transducer layer, and a plurality of second electrodes; the first electrode, the piezoelectric transducer layer, and the plurality of second electrodes are arranged on the substrate, the piezoelectric transducer 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; wherein the piezoelectric transducer layer comprises a first piezoelectric layer and a second piezoelectric layer stacked; the first piezoelectric layer has a first piezoelectric tensor component e 33 , the second piezoelectric layer has a second piezoelectric tensor component e 33 , the first piezoelectric tensor component e 33 and the second piezoelectric tensor component e 33 On the contrary, the first piezoelectric tensor component e 33 and the second piezoelectric tensor component e 33 They are opposite numbers.

[0011] In the resonator provided in the present application, the piezoelectric transducer 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 33 and the second piezoelectric tensor component e of the second piezoelectric layer 33 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, along the stacking direction of the first piezoelectric layer and the second piezoelectric layer, when the first piezoelectric layer is stretched and the second piezoelectric layer is compressed, the vibration direction of the part of the first piezoelectric layer that is in contact with the second piezoelectric layer is toward the second piezoelectric layer, and the vibration direction of the part of the second piezoelectric layer that is in contact with the first piezoelectric layer is also toward the second 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 transducer layer, thereby improving the electromechanical coupling coefficient of the entire resonator.

[0012] In one achievable manner, the first electrode includes a first surface and a second surface facing 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.

[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; the piezoelectric transducer layer has a groove at a position opposite to the gap, and the groove is connected to the gap.

[0015] Since the grooves are formed in the piezoelectric transducer 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 piezoelectric transducer layer and the depth dimension h of the groove satisfy 30% H≤h≤H.

[0017] When the depth of the groove is small, the vibration of the portion of the piezoelectric transducer layer located at the first electrode and the second electrode will be 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 transducer 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 piezoelectric transducer 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 piezoelectric transducer 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 examples of this application, the thickness of the piezoelectric transducer layer can be increased to reduce the thickness ratio of the electrode to the piezoelectric transducer layer. This approach neither poses challenges to the etching process nor reduces 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 every 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 piezoelectric transducer layer satisfy: P / H≥1; the width dimension of each first interdigitated electrode is t1, the spacing between every 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 piezoelectric transducer layer to generate a first resonant mode, where a vibration direction of the first resonant mode is perpendicular to the surface of the substrate.

[0029] The first resonance mode is the main resonance mode of the resonator.

[0030] In one possible implementation, the first piezoelectric layer includes a first piezoelectric material, and the second piezoelectric layer includes a second piezoelectric material; the Euler angle of the crystal of the first piezoelectric material is (0°, 0°, 0°), and the Euler angle of the crystal of the second piezoelectric material is (0°, 180°, 0°), wherein the c-axis of the piezoelectric material of the first piezoelectric layer is opposite to the c-axis of the piezoelectric material of the second piezoelectric layer, one of which is facing upward along the thickness of the piezoelectric layer, and the other is facing downward along the thickness of the piezoelectric layer.

[0031] In one possible implementation, the electromechanical coupling coefficient Kt of the resonator is 2 ≥23%.

[0032] In one achievable manner, the material of the piezoelectric transducer layer includes a combination of nitrogen, scandium, and aluminum; the mass fraction of the scandium is greater than or equal to 10%, or may be less than or equal to 40%.

[0033] For example, the mass fraction of scandium may be 25%, 30%, or 40%.

[0034] In one possible implementation, the material of the piezoelectric transducer layer includes a combination of zinc and oxygen, such as zinc oxide. The material of the piezoelectric transducer layer may also include quartz or lead zirconate titanate (PZT).

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] In another aspect, the present application further provides a method for preparing a resonator, the method comprising:

[0044] forming a first electrode on a substrate;

[0045] A first piezoelectric layer is formed on the first electrode, and a second piezoelectric layer is formed on the first piezoelectric layer, wherein the first piezoelectric layer has a first piezoelectric tensor component e 33 , the second piezoelectric layer has a second piezoelectric tensor component e 33 , the first piezoelectric tensor component e 33 and the second piezoelectric tensor component e 33 on the contrary;

[0046] A plurality of second electrodes are manufactured on the second piezoelectric layer, and the plurality of second electrodes are arranged side by side in a first direction.

[0047] In the resonator manufactured by the above method, the piezoelectric transducer layer includes multiple stacked piezoelectric layers, and the two adjacent piezoelectric layers have opposite piezoelectric tensor component polarities. In this way, when the resonator is working, resonant coupling will be generated at the interface between the two adjacent piezoelectric layers, thereby improving the electromechanical coupling coefficient of the resonator.

[0048] In one achievable manner, the first piezoelectric layer and the second piezoelectric layer are prepared by using an epitaxial growth technique.

[0049] In one achievable method, when a plurality of second electrodes are produced on the second piezoelectric layer, the method includes: arranging a plurality of second electrodes arranged side by side on the second piezoelectric layer, with a gap between two adjacent second electrodes; and opening a groove at a position opposite to the gap including the first piezoelectric layer and the second piezoelectric layer.

[0050] In one achievable manner, the groove passes through the first piezoelectric layer and the second piezoelectric layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] FIG1 is a schematic diagram of a partial structure of an electronic device;

[0052] FIG2 is a schematic diagram of a portion of the structure of an electronic device;

[0053] FIG3 is a schematic diagram of a partial structure of a filter in an electronic device;

[0054] FIG4 is a schematic diagram of a partial structure of a resonator;

[0055] FIG5 is a schematic diagram showing a partial structure of a resonator provided in an embodiment of the present application;

[0056] FIG6 is a schematic structural diagram illustrating a resonator vibration according to an embodiment of the present application;

[0057] FIG7 shows a schematic structural diagram of a resonator vibration provided by the related art;

[0058] FIG8 is a schematic diagram showing a structure of a resonator vibration provided by the related art;

[0059] FIG9 is a schematic diagram showing a partial structure of a resonator provided in an embodiment of the present application;

[0060] FIG10 is a schematic diagram showing a partial structure of a resonator provided in an embodiment of the present application;

[0061] FIG11 is a schematic diagram showing a partial structure of a resonator provided in an embodiment of the present application;

[0062] FIG12 is a schematic diagram showing a partial structure of a resonator provided in an embodiment of the present application;

[0063] FIG13 is a schematic diagram showing a structure of a resonator vibration provided by the related art;

[0064] FIG14 is a schematic structural diagram illustrating a resonator vibration according to an embodiment of the present application;

[0065] FIG15 is a schematic diagram showing a partial structure of a resonator provided in an embodiment of the present application;

[0066] FIG16 is a schematic diagram showing a partial structure of a resonator provided in an embodiment of the present application;

[0067] FIG17A is a schematic structural diagram illustrating a resonator vibration according to an embodiment of the present application;

[0068] FIG17B is a schematic diagram showing a structure of a resonator vibration provided by the related art;

[0069] FIG18A shows an admittance curve of the structure shown in FIG17A ;

[0070] FIG18B shows an admittance curve diagram of the structure shown in FIG17B ;

[0071] FIG19 is a process flow chart of a method for preparing a resonator provided in an embodiment of the present application;

[0072] FIG20 is a schematic diagram of the structure of a filter provided in an embodiment of the present application;

[0073] FIG21 is the admittance curve and filter bandpass diagram of each resonator in FIG20.

[0074] Reference numerals: 100 - electronic device; 200 - filter; 300 - resonator; 400, 410, 420, 430, 440 - resonators; 500 - antenna; 600 - receiver; 700 - transmitter; 800 - baseband chip; 900 - switch; 60a, 60c, 70a - filters; 60b - low-noise amplifier; 60d - mixer; 60e - buffer; 60f, 70d - voltage-controlled oscillator; 70b - amplifier; 70c - driver; 10 - substrate; 101 - cavity; 20 - first electrode; 30 - piezoelectric transducer layer; 301 - first piezoelectric layer; 302 - second piezoelectric layer; 40 - second electrode; 401 - first interdigitated electrode; 402 - second interdigitated electrode; 50 - dielectric layer; 601 - first bus bar; 602 - second bus bar; 70 - groove. DETAILED DESCRIPTION

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] Piezoelectric tensor components: 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 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:

[0080] 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.

[0081] 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.

[0082] For the piezoelectric material crystal orientation with Euler angle (0,0,0), taking LN as an example,

[0083] 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 ,cE 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 *10 11 N / m 2 ;

[0084] 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.

[0085] 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 Spq ', can be calculated by the following formula:

[0086] c E pqrs '=c E ijkl A ip A jq A kr A ls ;

[0087] e pqr '=e ijk A ip A jq A kr ;

[0088] ε S pq '=ε S ij A ip A jq ;

[0089] 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).

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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 .

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 3 , the filter 200 may include multiple series-connected resonators 300, or multiple parallel-connected resonators 300, or a combination of series-connected and parallel-connected resonators 300. At least one of the multiple resonators included in the filter 200 may be the resonator shown in FIG4 .

[0100] 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 transducer layer 30, and multiple second electrodes 40. The first electrode 20, the piezoelectric transducer layer 30, and the multiple second electrodes 40 are disposed on the substrate 10. The multiple second electrodes 40 are arranged side by side in a first direction. The piezoelectric transducer layer 30 has a first side and a second side. The multiple 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 transducer layer 30 is stacked between the first electrode 20 and the multiple second electrodes 40.

[0101] 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 transducer layer 30 and the first and second electrodes 20 and 40.

[0102] 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.

[0103] 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 transducer layer 30. The piezoelectric transducer layer 30 utilizes this electric field to produce a piezoelectric effect. The example in Figure 4 illustrates the use of a vertical electric field E to excite the piezoelectric transducer layer 30 to produce resonance, thereby converting electrical energy into mechanical energy.

[0104] The resonator shown in FIG4 resonates along the thickness direction of the piezoelectric transducer layer 30. In one embodiment, it can be referred to as a vertically-excited bulk acoustic resonator (YBAR). The thickness direction of the piezoelectric transducer layer 30 here can be understood as the direction parallel to the stacking direction of the multiple membrane layers (substrate, first electrode, piezoelectric layer) on the piezoelectric transducer layer 30.

[0105] As shown in FIG4 , since the portion of the piezoelectric transducer 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 transducer layer 30 is limited, resulting in an electromechanical coupling coefficient Kt of the resonator. 2 It 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.

[0106] In order to improve the electromechanical coupling coefficient Kt of the resonator 2 This application exemplifies some novel resonator process structures, as detailed below.

[0107] Figure 5 is a process structure diagram of a resonator according to 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 transducer 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 transducer 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.

[0108] The differences between the example shown in FIG5 and FIG4 are as follows: In FIG5, the piezoelectric transducer layer 30 includes multiple layers stacked together. For example, FIG5 exemplarily shows that the piezoelectric transducer layer 30 includes a first piezoelectric layer 301 and a second piezoelectric layer 302 stacked together. In other examples, more piezoelectric layers may be included, for example, three, four, or more layers.

[0109] In a multilayer piezoelectric layer, some piezoelectric tensor components of two adjacent piezoelectric layers are opposite. For example, as shown in Figure 5, the first piezoelectric layer 301 has a first piezoelectric tensor component, and the second piezoelectric layer 302 has a second piezoelectric tensor component. The first piezoelectric tensor component and the second piezoelectric tensor component are opposite. This means that in this example, adjacent piezoelectric layers have opposite piezoelectric tensor component polarities.

[0110] 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.

[0111] 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.

[0112] The second electrode 40 may be made of any possible conductive metal, including but not limited to Al, Cu, W, Mo, Ru, Pt, etc.

[0113] The first electrode 20 and the second electrode 40 may be made of the same conductive metal or different conductive metals.

[0114] In this example, the first piezoelectric layer 301 has a first piezoelectric tensor component e 33 , the second piezoelectric layer 302 has a second piezoelectric tensor component e 33 , where the first piezoelectric tensor component e 33 and the second piezoelectric tensor component e 33 The two piezoelectric layers are opposite (i.e., opposite in number to each other), so that the two piezoelectric layers have opposite polarities of piezoelectric tensor components.

[0115] In some examples, the first piezoelectric layer 301 and the second piezoelectric layer 302 may both include a wurtzite structure, for example, a combination of nitrogen and aluminum, or a combination of nitrogen, scandium, and aluminum. For example, they may include AlScN material. In AlScN, the mass fraction of Sc may be greater than or equal to 0 and less than or equal to 40%. In some examples, the mass fraction of Sc may be greater than or equal to 10%, for example, the mass fraction of Sc may be 20%, 30%, 35%, or 40%.

[0116] In some other examples, the first piezoelectric layer 301 and the second piezoelectric layer 302 may both include a combination of oxygen and zinc, such as zinc oxide. The first piezoelectric layer 301 and the second piezoelectric layer 302 may also include quartz or lead zirconate titanate (PZT) material.

[0117] Piezoelectric materials such as the above examples including a combination of nitrogen, scandium and aluminum, or zinc oxide each contain a piezoelectric tensor component e 33 , the present application can make the piezoelectric tensor component e in two adjacent piezoelectric layers 33 They are opposite numbers.

[0118] In this application example, the piezoelectric tensor component e of the piezoelectric layer 33 Under the action of the force, the resonator vibrates along the stacking direction of the first piezoelectric layer 301 and the second piezoelectric layer 302 .

[0119] In some examples, the first piezoelectric layer 301 and the second piezoelectric layer 302 both include AlScN. When the Euler angle of the piezoelectric material of the first piezoelectric layer 301 is (0°, 90°, 0°), the piezoelectric tensor component e of the first piezoelectric layer 301 is 33 = +2.42, when the Euler angle of the crystal of the piezoelectric material of the second piezoelectric layer 302 is (0°, 270°, 0°), the piezoelectric tensor component e of the second piezoelectric layer 302 is 33 =-2.42.

[0120] The c-axis of the piezoelectric material of the first piezoelectric layer is opposite to the c-axis of the piezoelectric material of the second piezoelectric layer, one of which points upward along the thickness of the piezoelectric layer, and the other points downward along the thickness of the piezoelectric layer.

[0121] FIG6 exemplarily shows the structure shown in FIG5 of the present application, which improves the electromechanical coupling coefficient Kt 2 principle.

[0122] In FIG6 , the first piezoelectric layer 301 and the second piezoelectric layer 302 may both include AlScN, and the piezoelectric tensor component e of the first piezoelectric layer 301 is 33 and the piezoelectric tensor component e of the second piezoelectric layer 302 33 In contrast, the vibration directions of the first piezoelectric layer 301 and the second piezoelectric layer 302 are both along direction 3. 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 in the second electrode. The fill pattern in FIG6 illustrates the approximate area where the resonator vibrates.

[0123] 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 component polarizations, the first piezoelectric layer 301 may be compressed along direction 3 and the second piezoelectric layer 302 may be stretched along direction 3 .

[0124] When the second piezoelectric layer 302 is stretched along direction 3, the portion of the second piezoelectric layer 302 close to the second electrode 401 (such as portion A1 in Figure 6) vibrates upward, and the portion of the second piezoelectric layer 302 close to the first piezoelectric layer 301 (such as portion B1 in Figure 6) vibrates downward; when the first piezoelectric layer 301 is compressed along direction 3, the portion of the first piezoelectric layer 301 close to the second piezoelectric layer 302 (such as portion C1 in Figure 6) vibrates downward, and the portion of the first piezoelectric layer 301 close to the first electrode 20 (such as portion D1 in Figure 6) vibrates upward.

[0125] 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 downward vibrations are coupled, so that mechanical vibrations are generated inside the entire piezoelectric layer.

[0126] For another example, when a negative voltage is applied to the second electrode 401 , since the first piezoelectric layer 301 and the second piezoelectric layer 302 have opposite piezoelectric tensor component polarizations, the first piezoelectric layer 301 may be stretched along direction 3 and the second piezoelectric layer 302 may be compressed along direction 3 .

[0127] When the second piezoelectric layer 302 is compressed along direction 3, the portion of the second piezoelectric layer 302 close to the second electrode 401 (such as portion A2 in Figure 6) vibrates downward, and the portion of the second piezoelectric layer 302 close to the first piezoelectric layer 301 (such as portion B2 in Figure 6) vibrates upward; when the first piezoelectric layer 301 is stretched along direction 3, the portion of the first piezoelectric layer 301 close to the second piezoelectric layer 302 (such as portion C2 in Figure 6) vibrates upward, and the portion of the first piezoelectric layer 301 close to the first electrode 20 (such as portion D2 in Figure 6) vibrates downward.

[0128] 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 upward vibrations are coupled, so that mechanical vibrations are generated inside the entire piezoelectric layer.

[0129] Therefore, in the resonator structure of FIG6 of the present application example, when the polarities of the piezoelectric tensor components of adjacent piezoelectric layers are opposite, the multilayer piezoelectric layers will produce coupled resonance at the interface, thereby increasing the electromechanical coupling coefficient Kt 2 .

[0130] 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 3 to increase the vibration amount of the entire resonator.

[0131] Similarly, due to the gap between the second electrode 401 and the second electrode 402, compared to the resonator in which the second electrode 401 and the second electrode 402 are connected as one body (such as a film cavity acoustic resonator FBAR), the second electrode 402 in FIG6 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 FIG6, the second electrode 402 can also vibrate along direction 3 to increase the vibration of the entire resonator. In this way, the electromechanical coupling coefficient Kt of the resonator can be further improved. 2 .

[0132] Figure 7 illustrates the vibration diagram when a single piezoelectric layer is used. The portion of the piezoelectric transducer layer 30 that contacts the second electrode 401 (such as portion A1 in Figure 7 ) vibrates upward, while the portion of the piezoelectric transducer layer 30 that contacts the first electrode 20 (such as portion B1 in Figure 7 ) vibrates downward.

[0133] Compared with FIG6 above, in FIG7, the interior of the piezoelectric transducer layer 30 basically does not vibrate, while in FIG6 of the example of the present application, not only the upper and lower surface portions of the piezoelectric layer vibrate, but also the interface between the adjacent piezoelectric layers vibrates. In some scenarios, even if the vibration of the portion where the piezoelectric layer and the first electrode 20 are in contact is limited, the resonator of the example of the present application can still improve the electromechanical coupling coefficient Kt 2 .

[0134] Comparing Figures 6 and 7, the sum of the thicknesses 2h of the first piezoelectric layer 301 and the second piezoelectric layer 302 in Figure 6 is substantially equal to or nearly equal to the thickness of the piezoelectric transducer layer 30 in Figure 7. The resonant frequency in Figure 6 is substantially equal to or nearly equal to the resonant frequency in Figure 7.

[0135] 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 .

[0136] Direction 3 in the embodiments of the present application can be understood as a direction perpendicular to the surface of substrate 10, or parallel to the stacking direction of first piezoelectric layer 301 and second piezoelectric layer 302. Direction 1 can be understood as a direction parallel to the surface of substrate 10 and perpendicular to the extension direction of second electrode 40. Direction 2 can be understood as a direction parallel to the extension direction of second electrode 40.

[0137] In some examples, to increase the resonant frequency, the resonator shown in FIG8 may also be used. Compared to FIG7 , FIG8 shows that the thickness of the piezoelectric transducer layer 30 in FIG8 is h, while the thickness of the piezoelectric transducer layer 30 in FIG7 is 2h. For example, the resonant frequency in FIG7 may be f, while the resonant frequency in FIG8 may be 2f. This means that the resonant frequency of the resonator can be increased by reducing the thickness of the piezoelectric transducer layer 30. However, increasing the resonant frequency by thinning the piezoelectric transducer layer 30 may pose significant challenges to photolithography technology during the manufacturing process. Therefore, the increase in resonant frequency is subject to certain limitations, and the high-frequency applications of the resonators shown in FIG7 and FIG8 are limited.

[0138] However, when the resonator shown in FIG6 is used, the limitations imposed by the photolithography technology are alleviated by stacking multiple piezoelectric layers. Thus, while improving the stability and robustness of the resonator, the resonator can also be used in a high-frequency range.

[0139] Figure 9 is a process structure diagram of another resonator exemplified in the present application. In this resonator, a cavity 101 is provided in a substrate 10. Such a resonator can be called a cavity-type suspended piezoelectric thin film resonator.

[0140] In FIG9 , the second electrode 20 has a first surface and a second surface that are back-to-back, the first surface being closer to the piezoelectric transducer layer 30 than the second surface, the substrate 10 being provided with a cavity 101, at least a portion of the second surface of the first electrode 20 being used to enclose the cavity 101, and at least a portion of the first electrode 20 being disposed between the cavity 101 and the piezoelectric transducer layer 30.

[0141] In this example, the piezoelectric transducer layer 30 may also include multiple stacked layers, for example, a first piezoelectric layer 301 and a second piezoelectric layer 302. In the multi-layer piezoelectric layer, adjacent piezoelectric layers have opposite polarities of piezoelectric tensor components. For example, the piezoelectric tensor component e of the first piezoelectric layer 301 is 33 and the piezoelectric tensor component e of the second piezoelectric layer 302 33 on the contrary.

[0142] Figures 10, 11, and 12 are process structure diagrams of three other resonators provided in embodiments of the present application. In this example, a dielectric layer 50 is also 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).

[0143] 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 .

[0144] As shown in Figures 13 and 14, in Figure 13, the piezoelectric transducer layer 30 includes a piezoelectric layer. In Figure 14, the piezoelectric transducer layer 30 includes a stacked first piezoelectric layer 301 and a second piezoelectric layer 302, and further includes a dielectric layer 50 stacked between the substrate 10 and the first electrode 20.

[0145] In FIG13 , since the first electrode 20 of the metal layer is directly stacked on the substrate 10, the vibration amplitude of the piezoelectric transducer layer 30 and the first electrode 20 is limited. As shown in FIG13 , the vibration area and vibration amplitude are very small. However, as shown in FIG14 , since a dielectric layer with lower hardness is stacked between the substrate 10 and the first electrode 20, mechanical vibrations are also generated in the first electrode 20 and the dielectric layer 50 compared to FIG13 , thereby increasing the vibration of the entire resonator and improving the electromechanical coupling coefficient Kt. 2 .

[0146] Returning to FIG. 10 to FIG. 12 , a groove 70 is further provided in the resonator. There is a gap between two adjacent second electrodes 40 . The groove 70 is provided in the piezoelectric transducer layer 30 , and the groove 70 is opposite to the gap. That is, it can be understood that the groove 70 is connected to the gap.

[0147] In some examples, such as Figures 10 and 11 , the first piezoelectric layer 301 is closer to the substrate 10 than the second piezoelectric layer 302, and the groove 70 may penetrate the second piezoelectric layer 302 and a portion of the first piezoelectric layer 301. In other examples, such as Figure 12 , the groove 70 may penetrate the second piezoelectric layer 302 and the first piezoelectric layer 301, reaching the surface of the first electrode 20.

[0148] That is, it can be understood that, in the example of the present application, the groove 70 may penetrate a portion of the piezoelectric transduction layer 30 , or may penetrate the entire piezoelectric transduction layer 30 , reaching the surface of the first electrode 20 .

[0149] 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.

[0150] 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 transducer layer 30. For example, h = 50% H, h = 60% H, h = 70% H, h = 80% H, h = 90% H, or h = H.

[0151] Furthermore, in some achievable examples, the radial dimension of the groove 70 gradually decreases from the top surface to the bottom surface. For example, as shown in FIG11 , the inclination angle α of the groove 70 can be: 45°≤α≤90°. For example, in FIG11 , the inclination angle α is approximately 60°, and in FIG10 and FIG12 , the inclination angle α is approximately 90°.

[0152] 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 .

[0153] FIG15 shows a process structure diagram of a resonator according to an embodiment of the present application, and FIG16 shows a distribution diagram of the second electrode in FIG15 .

[0154] In the resonators illustrated in Figures 15 and 16 , 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.

[0155] 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 FIG16 , the first bus bar 601 and the second bus bar 602 extend in a first direction.

[0156] The finger pitch (Pitch) P can be understood as shown in Figure 16, 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.

[0157] 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.

[0158] 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 15).

[0159] The duty cycle is the ratio of the width t1 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.

[0160] When the resonator is operating, acoustic loss is generated at the electrodes, reducing device performance. For example, as shown in FIG15 , acoustic loss may be generated at the first electrode 20 or the second electrode 40. To reduce electrode acoustic loss, in some examples, the thickness of the electrodes can be reduced. However, when the thickness of the electrodes is reduced, the power handling capability of the electrodes is weakened, shortening the device lifespan.

[0161] 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.

[0162] In some examples, as shown in FIG15 , 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.

[0163] 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.

[0164] To increase the resonant frequency of the resonator, in some examples, the finger pitch shown in FIG16 can be reduced. However, when the finger pitch is reduced, it will pose challenges to the photolithography technology. In this example, the finger pitch P can satisfy the thickness of the piezoelectric transducer layer 30: P / d ≥ 1.

[0165] 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.

[0166] The following compares the electromechanical coupling coefficients of the resonator given in the embodiment of the present application and the resonator in the related art with reference to the accompanying drawings and table data.

[0167] FIG17A is a process structure diagram of a resonator provided in an embodiment of the present application. FIG17A is used to illustrate vibration along direction 3.

[0168] FIG17B is a process structure diagram of a resonator having a piezoelectric layer, and FIG17B is used to illustrate the vibration along direction 3.

[0169] In both FIG. 17A and FIG. 17B , grooves are opened in the piezoelectric transducer layer, and the grooves penetrate through the piezoelectric transducer layer.

[0170] As shown in FIG17A , the second piezoelectric layer 302 vibrates along Direction 3 at the position where it contacts the second electrode 401 and the second electrode 402, and the interface between the second piezoelectric layer 302 and the first piezoelectric layer 301 vibrates along Direction 3. Furthermore, the interface between the first electrode 20 and the dielectric layer 50 vibrates slightly along Direction 3.

[0171] As shown in Figure 17B , the piezoelectric transducer layer 30 vibrates along Direction 3 at the locations where it contacts the second electrode 401 and the second electrode 402, and there is slight vibration along Direction 3 at the interface between the dielectric layer 50 and the first electrode 20. Compared to Figures 17A and 17B , Figure 17A of the present application demonstrates coupled resonance within the entire piezoelectric layer.

[0172] Figure 18A is an admittance simulation curve obtained by using the structure of Figure 17A and the physical parameters shown in Table 1. Figure 18B is an admittance simulation curve obtained by using the structure of Figure 17B and the physical parameters shown in Table 2.

[0173] Table 1

[0174] Table 2

[0175] The Sc mass fractions in Table 1 and Table 2 are examples of the present application. The materials of the first piezoelectric layer 301 and the second piezoelectric layer 302 may include AlScN, and the Sc mass fraction may be 40%.

[0176] 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.

[0177] The admittance simulation curves of FIG18A and FIG18B respectively show the modulus (abs) and real part (Re) of the admittance curves.

[0178] Comparing the admittance simulation curve of FIG18A with the admittance simulation curve of FIG18B, it can be seen that when the resonator of FIG17A of the example of the present application is used, the electromechanical coupling coefficient Kt 2 When a piezoelectric layer as shown in FIG17B 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 .

[0179] In some embodiments, the electromechanical coupling coefficient Kt of the resonator of the present application example is 2 It can be greater than or equal to 23%, for example, 25%, 30%, or even greater.

[0180] Continuing to refer to FIG18A and FIG18B, there is essentially no parasitic mode. Therefore, the resonator of this example comprising at least two piezoelectric layers can not only improve the electromechanical coupling coefficient and increase the resonant frequency, but also suppress parasitic modes, further optimizing the resonator performance.

[0181] The present application also provides a method for preparing a resonator including a multi-layer piezoelectric layer, as shown in FIG19 . FIG19 exemplarily shows a flowchart of a method for preparing a resonator. The method includes:

[0182] Step S1: forming a first electrode on a substrate.

[0183] The substrate of the example of the present application 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.

[0184] Step S2: a first piezoelectric layer is formed on the first electrode, and a second piezoelectric layer is formed on the first piezoelectric layer, wherein the first piezoelectric layer has a first piezoelectric tensor component e 33 , the second piezoelectric layer has a second piezoelectric tensor component e 33 , the first piezoelectric tensor component e 33 and the second piezoelectric tensor component e 33 on the contrary.

[0185] Among some selectable materials, the material of the first piezoelectric layer and the second piezoelectric layer may include AlScN.

[0186] When preparing the first piezoelectric layer and the second piezoelectric layer, an epitaxial growth technique may be used. In addition, the epitaxial growth technique also makes it easier to control the polarization direction of the piezoelectric layer.

[0187] Step S3: a plurality of second electrodes are formed on the second piezoelectric layer, wherein the plurality of second electrodes are arranged side by side in a first direction, which may be perpendicular to the stacking direction of the multi-layer piezoelectric layer.

[0188] 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.

[0189] 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.

[0190] 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.

[0191] Furthermore, the aforementioned cavity-type suspended piezoelectric thin film resonators or solid-substrate piezoelectric thin film resonators can be electrically connected in a ladder structure, as shown in FIG20 , 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.

[0192] In the example of FIG20 , 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.

[0193] In some examples, such as FIG21 , FIG21 shows the relationship between the admittance curve of each resonator and the filter transmission loss curve of the ladder filter in FIG20 . Referring to FIG21 , 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.

[0194] 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.

[0195] 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: include: substrate; A first electrode, a piezoelectric transducer layer and a plurality of second electrodes, wherein the first electrode, the piezoelectric transducer layer and the plurality of second electrodes are arranged on the substrate, the piezoelectric transducer 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 piezoelectric transducer layer comprises a first piezoelectric layer and a second piezoelectric layer which are stacked; The first piezoelectric layer has a first piezoelectric tensor component e 33 , the second piezoelectric layer has a second piezoelectric tensor component e 33 , the first piezoelectric tensor component e 33 and the second piezoelectric tensor component e 33 on the contrary.

2. The resonator according to claim 1, characterized in that There is a gap between two adjacent second electrodes; The piezoelectric transducer layer has a groove at a position opposite to the gap, and the groove penetrates the gap.

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

4. The resonator according to claim 2 or 3, characterized in that 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 passes through the top surface and the bottom surface.

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

35.

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

35.

7. The resonator according to any one of claims 1 to 6, characterized in that: The resonator further includes: a first bus bar and a second bus bar; One of every 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 apart in the first direction; A plurality of the first interdigitated electrodes among the plurality of second electrodes are connected via the first bus bar, and a plurality of the second interdigitated electrodes among the plurality of second electrodes are connected via the second bus bar; The finger spacing P and the thickness dimension H of the piezoelectric transducer layer satisfy: P / H≥1; The width dimension of each first interdigitated electrode is t1, the spacing between each adjacent two first interdigitated electrodes and the second interdigitated electrodes 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 electrodes.

8. The resonator according to any one of claims 1 to 7, characterized in that: Based on applying voltage to the plurality of second electrodes, the resonator is used to excite the piezoelectric transducer layer to generate a first resonance mode, wherein a vibration direction of the first resonance mode is perpendicular to the surface of the substrate.

9. The resonator according to any one of claims 1 to 8, characterized in that: The electromechanical coupling coefficient Kt of the resonator 2 ≥23%.

10. The resonator according to any one of claims 1 to 9, characterized in that: The material of the piezoelectric transducer layer includes a combination of nitrogen, scandium and aluminum, and the mass fraction of the scandium is greater than or equal to 10%; or, The material of the piezoelectric conversion layer includes a combination of zinc and oxygen.

11. The resonator according to any one of claims 1 to 10, characterized in that The first electrode has a first surface and a second surface facing each other, 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. A filter, characterized in that: include: A plurality of electrically connected resonators, at least one of the plurality of resonators being the resonator according to any one of claims 1 to 11.

13. An electronic device, characterized in that: include: Amplifier; The resonator according to any one of claims 1 to 11, or the filter according to claim 12, wherein the resonator or the filter is electrically connected to the amplifier.

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