WO2024046095A1 - 兰姆波谐振器及制备方法、滤波器、射频模组、电子设备 - Google Patents

兰姆波谐振器及制备方法、滤波器、射频模组、电子设备 Download PDF

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Publication number
WO2024046095A1
WO2024046095A1 PCT/CN2023/112621 CN2023112621W WO2024046095A1 WO 2024046095 A1 WO2024046095 A1 WO 2024046095A1 CN 2023112621 W CN2023112621 W CN 2023112621W WO 2024046095 A1 WO2024046095 A1 WO 2024046095A1
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Prior art keywords
layer
wave resonator
lamb wave
lamb
reflection layer
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PCT/CN2023/112621
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English (en)
French (fr)
Inventor
陶翔
蒋欣
唐戴平
古健
柯汉
栾仲智
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华为技术有限公司
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Publication of WO2024046095A1 publication Critical patent/WO2024046095A1/zh

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
    • H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
    • H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
    • H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material

Definitions

  • the present application relates to the field of radio frequency technology, and in particular to a Lamb wave resonator and preparation method, filter, radio frequency module, and electronic equipment.
  • the current RF front-end resonators mainly include surface acoustic wave (SAW) resonators and bulk acoustic wave (BAW) resonators.
  • SAW surface acoustic wave
  • BAW bulk acoustic wave
  • the frequency of the SAW resonator is lower than 3.5GHz, and the electromechanical coupling coefficient is only about 10%.
  • the electromechanical coupling coefficient of BAW resonators is also smaller.
  • Lamb wave resonators have become a research hotspot in recent years due to their advantages such as high sound speed (for example, 12000m/s ⁇ 15000m/s) and large electromechanical coupling coefficient (for example, up to 25%).
  • Embodiments of the present application provide a Lamb wave resonator and a preparation method, a filter, a radio frequency module, and an electronic device, which are used to solve the current problems of complicated processes and low yield rate in preparing lamb wave resonators.
  • a first aspect of the embodiment of the present application provides a Lamb wave resonator.
  • the lamb wave resonator serves as a filter element and can be applied to radio frequency devices.
  • the lamb wave resonator includes: a substrate, an acoustic wave reflection layer disposed on the substrate, a piezoelectric layer disposed on the acoustic wave reflection layer, and an interdigital transducer disposed on the piezoelectric layer.
  • the acoustic impedance of the sound wave reflection layer is smaller than the acoustic impedance of the piezoelectric layer.
  • the sound wave reflection coefficient of the surface of the sound wave reflection layer facing the piezoelectric layer can be limited to 0.5-0.86 (0.5 ⁇ sound wave reflection coefficient R ⁇ 0.86). In this way, sound waves in A1, S0, SH0 and other modes will be reflected at the interface between the sound wave reflection layer and the piezoelectric layer, locking the sound waves in the piezoelectric layer.
  • the lamb wave resonator provided in the embodiment of the present application is provided with an acoustic wave reflection layer on the side of the piezoelectric layer close to the substrate, and the acoustic impedance of the acoustic wave reflection layer is smaller than the acoustic impedance of the piezoelectric layer. In this way, the sound waves excited by the lamb wave resonator will be reflected on the surface of the sound wave reflection layer facing the piezoelectric layer and reflected back to the piezoelectric layer.
  • the acoustic wave can be locked in the piezoelectric layer, thus avoiding the serious degradation of device performance caused by a large amount of acoustic waves excited by the lamb wave resonator leaking to the substrate.
  • the acoustic wave reflection layer replaces the traditional air cavity and Bragg reflection structure, without the need to dig out a cavity or form a complex Bragg reflection structure, simplifying the preparation process of lamb wave resonators and reducing the difficulty of preparing lamb wave resonators.
  • the lamb wave resonator provided by the present application, there is no need to form an air cavity on the substrate. When no air cavity is provided on the substrate, the mechanical strength of the lamb wave resonator can be enhanced and the yield of the lamb wave resonator can be improved.
  • the acoustic wave reflection coefficient R of the surface of the acoustic wave reflection layer facing the piezoelectric layer is limited to 0.5-0.86, which can better limit the acoustic wave mode in the piezoelectric layer. And it can not only improve the problem that the sound wave reflection coefficient R is too small (less than 0.5), the sound wave will not be well restricted in the piezoelectric layer, or the sound wave reflection layer used to limit the sound wave needs to be very thick, which is difficult to implement in engineering. . It can also be improved because the sound wave reflection coefficient R is too large (greater than 0.86), resulting in relatively small parameters such as density and Young's modulus of the sound wave reflection layer material, and the material is relatively soft.
  • the acoustic reflective layer is prone to deformation, causing wrinkles or fragmentation of the piezoelectric layer above it, which affects product yield.
  • the material selection range of the sound wave reflection layer is wide, the sound wave reflection coefficient R of the sound wave reflection layer of each material is different, and the thickness of the sound wave reflection layer of each material is also different.
  • the thickness of the sound wave reflection layer is 3.5 ⁇ m-30 ⁇ m. This is a thickness range that is convenient for mass production.
  • the material of the sound wave reflection layer is a polymer material.
  • the sound wave reflection layer in the embodiment of the present application has a wide range of material selection and is easy to implement.
  • the material of the sound wave reflection layer includes polyimide, polydimethylsiloxane, polymethyl methacrylate, polyvinylidene fluoride, or polyethylene terephthalate.
  • polyimide polydimethylsiloxane
  • polymethyl methacrylate polymethyl methacrylate
  • polyvinylidene fluoride polyvinylidene fluoride
  • polyethylene terephthalate polyethylene terephthalate
  • the sound wave reflection layer has a single film layer structure.
  • the sound wave reflection layer with a single film layer structure has a simple structure and a simple process.
  • the tangential direction of the material of the piezoelectric layer is Z-tangential.
  • the piezoelectric layer of this material enables lamb-wave resonators with wider bandwidths.
  • the Euler angle of the material of the piezoelectric layer is (0, 20, 0) to (0, 40, 0). Euler angles in this range enable lamb wave resonators with wider bandwidths.
  • the lamb wave resonator further includes a frequency shifting layer, which is used to adjust the frequency of the lamb wave resonator; the frequency shifting layer is provided between the piezoelectric layer and the acoustic wave reflection layer.
  • the lamb wave resonator includes a frequency shifting layer, there is no need to change the structure of other film layers in the lamb wave resonator. By adjusting the thickness of the frequency shifting layer, the frequency of the lamb wave resonator can be adjusted to the required value.
  • the lamb wave resonator further includes a frequency shifting layer, which is used to adjust the frequency of the lamb wave resonator; the frequency shifting layer is arranged on the side of the interdigital transducer away from the piezoelectric layer.
  • the lamb wave resonator includes a frequency shifting layer, there is no need to change the structure of other film layers in the lamb wave resonator. By adjusting the thickness of the frequency shifting layer, the frequency of the lamb wave resonator can be adjusted to the required value.
  • the lamb wave resonator further includes a temperature compensation layer, which is used to compensate the frequency temperature coefficient of the lamb wave resonator; the temperature compensation layer is disposed between the piezoelectric layer and the acoustic wave reflection layer.
  • the temperature compensation layer can be used to perform temperature compensation on the lamb wave resonator, so that the absolute value of the temperature coefficient of frequency (TCF) of the lamb wave resonator decreases.
  • the lamb wave resonator also includes a temperature compensation layer.
  • the temperature compensation layer is used to compensate the frequency temperature coefficient of the lamb wave resonator; the temperature compensation layer is arranged on the side of the interdigital transducer away from the piezoelectric layer.
  • the temperature compensation layer can be used to perform temperature compensation on the lamb wave resonator, so that the absolute value of the temperature coefficient of frequency (TCF) of the lamb wave resonator is reduced.
  • the thickness of the piezoelectric layer is 0.2 ⁇ m-1 ⁇ m.
  • the interdigital transducer includes a plurality of first electrode fingers and a plurality of second electrode fingers, and the plurality of first electrode fingers and the plurality of second electrode fingers are arranged alternately in sequence; the first electrode The width of the fingers and the second electrode fingers is 200nm-1000nm. In this way, the lamb wave resonator can be made to work in the 5G frequency band and have a wider bandwidth.
  • the interdigital transducer includes a plurality of first electrode fingers and a plurality of second electrode fingers, and the plurality of first electrode fingers and the plurality of second electrode fingers are alternately arranged in sequence; adjacent The distance between one electrode finger and the second electrode finger is 2 ⁇ m-10 ⁇ m. In this way, the lamb wave resonator can be made to work in the 5G frequency band and have a wider bandwidth.
  • a phononic crystal layer is further provided between the substrate and the acoustic wave reflection layer.
  • the phononic crystal layer can further restrict the sound waves and perform sound wave reflection function on the sound wave reflection layer. can increase the bandwidth of the lamb wave resonator.
  • the surface of the substrate facing the acoustic wave reflection layer is a plane. There is no need to hollow out the substrate, the preparation process is simple, and the reliability is high.
  • no openings are provided on the substrate. There is no need to hollow out the substrate, the preparation process is simple, and the reliability is high.
  • a second aspect of the embodiments of the present application provides a filter including a plurality of cascaded lamb wave resonators; wherein the lamb wave resonators are any of the lamb wave resonators of the first aspect.
  • the filter provided in the second aspect of the embodiment of the present application includes the lamb wave resonator of the first aspect, and its beneficial effects are the same as those of the lamb wave resonator, which will not be described again here.
  • a third aspect of the embodiment of the present application provides a radio frequency module, including a filter and a power amplifier.
  • the filter is coupled to the power amplifier; the filter is the filter of the second aspect.
  • the radio frequency module provided in the third aspect of the embodiment of the present application includes the lamb wave resonator of the first aspect, and its beneficial effects are the same as those of the lamb wave resonator, which will not be described again here.
  • a fourth aspect of the embodiments of the present application provides an electronic device, including a filter and a circuit board.
  • the filter is disposed on the circuit board; the filter is the filter of the second aspect.
  • the electronic device provided in the fourth aspect of the embodiment of the present application includes the lamb wave resonator of the first aspect, and its beneficial effects are the same as those of the lamb wave resonator, which will not be described again here.
  • a fifth aspect of the embodiments of the present application provides a method for preparing a lamb wave resonator, which is used to prepare the lamb wave resonator according to any one of the first aspects.
  • Figure 1 is a schematic framework diagram of an electronic device provided by an embodiment of the present application.
  • Figure 2 is a schematic diagram of the topological structure of the filter provided by the embodiment of the present application.
  • Figure 3 is a particle displacement diagram of the lamb wave resonator provided by the embodiment of the present application.
  • Figure 4A is a schematic structural diagram of a back-etched lamb wave resonator illustrating an embodiment of the present application
  • Figure 4B is a schematic structural diagram of an air-gap lamb wave resonator illustrating an embodiment of the present application
  • Figure 4C is a schematic structural diagram of a solid-state assembled lamb wave resonator illustrating an embodiment of the present application
  • Figure 5 is a schematic structural diagram of a lamb wave resonator provided by an embodiment of the present application.
  • Figure 6A is a modeling diagram of a lamb wave resonator provided by an embodiment of the present application.
  • Figure 6B- Figure 6D are schematic diagrams of the particle displacement distribution of the lamb wave resonator in the vertical direction when the thickness of the acoustic wave reflection layer is different;
  • Figure 6E is an admittance curve diagram of a lamb wave resonator 100 provided by an embodiment of the present application.
  • Figure 7 is a schematic structural diagram of an interdigital transducer provided by an embodiment of the present application.
  • Figure 8 is a schematic structural diagram of another lamb wave resonator provided by an embodiment of the present application.
  • Figure 9 is a schematic structural diagram of another lamb wave resonator provided by an embodiment of the present application.
  • FIG. 10 is a schematic structural diagram of another lamb wave resonator provided by an embodiment of the present application.
  • azimuth terms such as “upper”, “lower”, “left” and “right” may include but are not limited to relative figures. It should be understood that these directional terms may be relative concepts and are used for relative description and clarification, which may change according to the orientation of the components in the drawings. And change accordingly.
  • connection should be understood in a broad sense.
  • connection can be a fixed connection, a detachable connection, or an integral body; it can be a direct connection. , can also be connected indirectly through intermediaries.
  • phase coupling may refer to a direct electrical connection or an indirect electrical connection through an intermediate medium.
  • contact can mean direct contact or indirect contact through an intermediary.
  • the electronic equipment is, for example, consumer electronic products, household electronic products, vehicle-mounted electronic products, financial terminal products, and communication electronic products.
  • consumer electronic products include mobile phones, tablets, laptops, e-readers, personal computers (PC), personal digital assistants (PDA), desktop monitors, Smart wearable products (such as smart watches, smart bracelets), virtual reality (VR) terminal devices, augmented reality (AR) terminal devices, drones, etc.
  • Home electronic products include smart door locks, TVs, remote controls, refrigerators, rechargeable small household appliances (such as soymilk machines, sweeping robots), etc.
  • Vehicle-mounted electronic products such as car navigation systems, vehicle-mounted high-density digital video discs (digital video discs, DVDs), etc.
  • Financial terminal products include automated teller machines (ATMs), self-service terminals, etc.
  • Communication electronic products include servers, memories, radars, base stations and other communication equipment.
  • the electronic device is a mobile phone as an example below.
  • the electronic device 1 mainly includes a cover 11 , a display 12 , a middle frame 13 and a rear case 14 .
  • the back shell 14 and the display screen 12 are respectively located on both sides of the middle frame 13 , and the middle frame 13 and the display screen 12 are arranged in the back shell 14 .
  • the cover plate 11 is disposed on the side of the display screen 12 away from the middle frame 13 .
  • the display screen 12 The display surface faces the cover 11.
  • the above-mentioned display screen 12 may be a liquid crystal display (LCD).
  • the liquid crystal display screen includes a liquid crystal display panel and a backlight module.
  • the liquid crystal display panel is disposed between the cover 11 and the backlight module.
  • the backlight The module is used to provide light source for the LCD panel.
  • the above-mentioned display screen 12 may also be an organic light emitting diode (organic light emitting diode, OLED) display screen. Since the OLED display is a self-luminous display, there is no need to set up a backlight module.
  • OLED organic light emitting diode
  • the above-mentioned middle frame 13 includes a bearing plate 131 and a frame 132 surrounding the bearing plate 131 .
  • the above-mentioned electronic device 1 may also include printed circuit boards (PCB), batteries, cameras and other electronic components.
  • PCB printed circuit boards
  • the printed circuit boards, batteries, cameras and other electronic components may be provided on the carrier board 131 .
  • the above-mentioned electronic device 1 may also include a system on chip (SOC), a radio frequency chip, etc. provided on the PCB.
  • SOC system on chip
  • the PCB is used to carry the system on chip, a radio frequency chip, etc., and is electrically connected to the system on chip, a radio frequency chip, etc. .
  • the radio frequency chip can include filters, processors and other parts.
  • the processor is used to process various signals, and the filter is an important part of RF signal processing. It is used to pass signals of specific frequencies and block signals of other frequencies.
  • the embodiment of the present application provides a filter, which can be applied to the above-mentioned electronic device 1, for example, applied to a radio frequency chip in the electronic device 1.
  • the filter provided by the embodiment of the present application can be, for example, a low-pass wave. Filter, high-pass filter, band-pass filter, band-reject filter or active filter, etc.
  • the filter provided by the embodiment of the present application is not limited to being integrated in the electronic device 1 .
  • the filter can also be used as a separate component, or the filter can be integrated with a power amplifier and other components into a module (such as a radio frequency device, radio frequency module, filter module, etc.), and the filter is coupled to the power amplifier. Perform signal processing and transmission.
  • the filter 10 provided by the embodiment of the present application includes a plurality of cascaded Lamb wave (lamb wave) resonators 100.
  • the plurality of Lamb wave (lamb wave) resonators 100 may have different resonant frequencies. , and can be cascaded together in series and parallel.
  • FIG. 2 also illustrates the signal input terminal Vi, the signal output terminal Vo and the ground terminal GND of the filter 10 .
  • the lamb wave resonator 100 has the advantages of high sound speed (for example, 12000m/s to 15000m/s) and large electromechanical coupling coefficient (for example, up to 25%), and is often used in various radio frequency terminal equipment.
  • the filter 10 composed of a cascade of series-parallel lamb wave resonators 100 with different resonant frequencies has the advantages of small passband insertion loss, high out-of-band steepness, and strong power tolerance.
  • the particle displacement diagram of the lamb wave resonator 100 is shown in Figure 3 (only the piezoelectric layer and a single pair of electrode fingers are drawn in Figure 3).
  • the direction of the electric field is mainly horizontal ( (X direction in Figure 3), or parallel to the piezoelectric layer, will excite shear waves that propagate along the thickness direction of the piezoelectric layer, and the thickness direction is the Z direction in Figure 3.
  • the solid arrows indicate the vibration direction of the particles
  • the dotted arrows indicate the direction of the electric field.
  • the lamb wave resonator 100 In order for the lamb wave resonator 100 to have a high sound speed and a large electromechanical coupling coefficient, it is generally necessary to confine the sound wave energy in the piezoelectric layer.
  • the lamb wave resonator 100 has a back-etching structure.
  • the back etching process is used to remove the substrate under the middle area of the piezoelectric layer, so that the piezoelectric layer in the middle area is suspended and the lower surface is in contact with the air.
  • the acoustic impedance of air is relatively low, which can reflect sound waves back to the piezoelectric layer, thereby confining the sound wave energy in the piezoelectric layer.
  • the process of the lamb wave resonator 100 with a back-etching structure is relatively simple, but because the silicon under the piezoelectric layer is removed, the mechanical strength of the lamb wave resonator 100 is poor and the yield is low.
  • the lamb wave resonator 100 is an air gap structure.
  • the acoustic impedance of air is relatively low, which can reflect sound waves back to the piezoelectric layer, thereby confining the sound waves in the piezoelectric layer.
  • the lamb wave resonator 100 with an air gap type structure has a higher mechanical strength than the lamb wave resonator 100 with a back etching type structure.
  • the manufacturing process requires cavity removal and the process is relatively complicated.
  • the lamb wave resonator 100 is a solid-state assembly structure.
  • a Bragg reflector structure consisting of alternating high-acoustic impedance layers and low-acoustic impedance layers is prepared below the piezoelectric layer to confine sound waves in the piezoelectric layer.
  • the material of the low acoustic impedance layer may be, for example, zinc oxide, silicon dioxide, etc.
  • the material of the high acoustic impedance layer may be, for example, heavy metal. Heavy metals refer to metals with a density greater than 4.5g/ cm3 , including gold, silver, copper, iron, mercury, lead, cadmium, etc.
  • the low-acoustic impedance layer is a film layer with slightly lower acoustic impedance than the high-acoustic impedance layer.
  • the acoustic impedance of both the low-acoustic impedance layer and the high acoustic impedance layer may be greater than the piezoelectric layer.
  • the lamb wave resonator 100 with a solid-state assembly structure needs to accurately control the thickness of each layer in the Bragg reflection layer.
  • the process is relatively complex, the yield is difficult to improve, and the cost is high, which affects the mass production of the device.
  • the lamb wave resonator 100 includes: a substrate 110, an acoustic wave reflection layer 120, a piezoelectric layer 130, and an interdigital transducer 140.
  • the material of the substrate 110 may be, for example, lithium niobate (LiNbO 3 , LN), lithium tantalate (LiTaO 3 , LT), quartz (quartz), silicon (Si), ceramics (ceramics), or glass (glass).
  • the main components of ceramics include, for example, silicates and aluminosilicates, refractory metal oxides, metal nitrides, borides, etc.
  • the main components of glass include, for example, hexasilica, calcium oxide, and sodium oxide (Na 2 O ⁇ CaO ⁇ 6SiO 2 ).
  • the structure of the substrate 110 is any substrate structure in the related art.
  • the structure of the substrate 110 is any of the structures shown in FIGS. 4A-4C.
  • the surface of the substrate 110 facing the acoustic wave reflective layer 120 is flat.
  • part of the surface of the substrate 110 facing the acoustic wave reflective layer 120 has not been removed, no opening is provided on the substrate 110 , and there is no gap between the substrate 110 and the film layer (such as the acoustic wave reflective layer 120 ) provided on the surface of the substrate 110 air cavity.
  • the sound wave reflection layer 120 is disposed on one side of the substrate 110 .
  • the sound wave reflection layer 120 may be disposed on the surface of the substrate 110 .
  • the piezoelectric layer 130 is disposed on the side of the sound wave reflection layer 120 away from the substrate 110 .
  • the piezoelectric layer 130 can be disposed on the surface of the sound wave reflection layer 120 .
  • the acoustic impedance of the piezoelectric layer 130 must be greater than the acoustic impedance of the sound wave reflection layer 120 , so that the sound waves can travel on the surface of the sound wave reflection layer 120 toward the piezoelectric layer 130 Reflection occurs and is reflected back to the piezoelectric layer 130 .
  • the acoustic impedance of the acoustic wave reflection layer 120 only needs to be smaller than the acoustic impedance of the piezoelectric layer 130 , and the relationship between the acoustic impedance between the acoustic wave reflection layer 120 and the substrate 110 is not limited.
  • the acoustic impedance of the acoustic wave reflective layer 120 may be smaller than the acoustic impedance of the substrate 110 .
  • the acoustic impedance of the acoustic wave reflective layer 120 may also be larger than the acoustic impedance of the substrate 110 .
  • the acoustic impedance of the acoustic wave reflective layer 120 The impedance may also be equal to the acoustic impedance of the substrate 110 .
  • Acoustic impedance is a mechanical term that refers to the complex ratio of the pressure of the medium on a certain area of the wave front to the volume velocity passing through this area.
  • the unit of acoustic impedance is Pascal ⁇ per square meter ⁇ second (Pa ⁇ m - 2 s -1 ).
  • v 120 and v 130 are the shear wave speeds in the Z direction in the acoustic wave reflection layer 120 and the piezoelectric layer 130
  • ⁇ 120 and ⁇ 130 are the densities of the acoustic wave reflection layer 120 and the piezoelectric layer 130
  • C 44 is the piezoelectric layer 130
  • E is the Young's modulus of the sound wave reflection layer 120
  • the units of Young's modulus are Pa, Mpa, and Gpa
  • ⁇ is the Poisson's ratio of the sound wave reflection layer 120 .
  • the greater the sound wave reflection coefficient R of the surface of the sound wave reflection layer 120 facing the piezoelectric layer 130 the better the sound wave confinement effect.
  • the sound wave reflection coefficient R can be calculated by the following formula:
  • the sound wave reflection coefficient R is related to the limiting effect of sound waves.
  • the value range of the acoustic wave reflection coefficient R is 0.5 ⁇ R ⁇ 0.86.
  • the values of the sound wave reflection coefficient R are 0.6, 0.65, 0.7, 0.75, 0.8, and 0.85.
  • the sound wave reflection coefficient R By limiting the sound wave reflection coefficient R to be greater than or equal to 0.5, the sound wave can be more effectively limited in the piezoelectric layer 130, making the performance of the lamb wave resonator 100 provided by the embodiment of the present application comparable to that of the air gap type lamb wave resonator. Performance is similar.
  • the sound wave reflection coefficient R is too small (less than 0.5), the sound wave will not be well confined in the piezoelectric layer 130, or the sound wave reflection layer 120 used to limit the sound wave needs to be very thick, which is difficult to engineer. Implementation issues. It can also be improved because the sound wave reflection coefficient R is too large (greater than 0.86), resulting in relatively small parameters such as density and Young's modulus of the sound wave reflection layer 120 material, and the material is relatively soft.
  • the processing of the lamb wave resonator 100 such as annealing after bonding the piezoelectric layer
  • the acoustic wave reflective layer 120 is easily deformed, causing the piezoelectric layer 130 above it to wrinkle or crack, affecting product yield.
  • the material of the sound wave reflection layer 120 can be any material that satisfies the sound wave reflection coefficient R.
  • the material of the sound wave reflection layer 120 is a macromolecular material.
  • Polymer materials also known as polymer materials, are materials composed of polymer compounds as a matrix and other additives (auxiliaries).
  • Examples of materials for the sound wave reflection layer 120 include polyimide (PI), polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA), and polyvinylidene fluoride. (polyvinylidene fluoride, PVDF) or polyethylene glycol terephthalate (polyethylene glycol terephthalate, PET), etc.
  • PI polyimide
  • PDMS polydimethylsiloxane
  • PMMA polymethyl methacrylate
  • PVDF polyvinylidene fluoride
  • PET polyethylene glycol terephthalate
  • spin coating magnetron sputtering, physical vapor deposition, chemical vapor deposition, epitaxial growth and other processes can be used to form the acoustic wave reflection layer 120 .
  • the process is simple, the cost is low and the yield is high.
  • the acoustic wave reflective layer 120 is a single film layer.
  • the sound wave reflection layer 120 is a single film layer and is not a structure formed by laminating multiple film layers.
  • the sound wave is reflected from the surface of the sound wave reflection layer 120 toward the piezoelectric layer 130 based on the acoustic impedance difference between the sound wave reflection layer 120 and the piezoelectric layer 130 . Therefore, the sound wave reflection layer 120 is a single film layer, with a simple structure and a simple manufacturing process.
  • the sound wave reflection layer 120 may also include multiple film layers, and is a structure composed of multiple film layers laminated.
  • the embodiment of the present application does not limit the specific structure of the sound wave reflection layer 120, nor does it limit the relationship between the acoustic impedances between the multi-layer film layers. Sound waves can be reflected on the surface of the sound wave reflection layer 120 toward the piezoelectric layer 130. That is, Can.
  • the material of the piezoelectric layer 130 includes one or more piezoelectric materials such as LiNbO 3 , LiTaO 3 , aluminum nitride (AlN), zinc oxide (ZnO), or quartz.
  • the material of piezoelectric layer 130 may be tangential.
  • the material of the piezoelectric layer 130 is LiNbO 3 , and its tangential direction is the Z tangential direction.
  • the Z-tangential LiNbO 3 piezoelectric material can increase the bandwidth of the lamb wave resonator 100.
  • the material of the piezoelectric layer 130 is LiNbO 3 , and its Euler angle ranges from (0, 20, 0) to (0, 40, 0).
  • the material of the piezoelectric layer 130 is LiNbO 3 , and its Euler angles are (0, 25, 0), (0, 30, 0), and (0, 35, 0).
  • the three numbers ( ⁇ , ⁇ , ⁇ ) in the Euler angle respectively represent that the single crystal pulled out first rotates ⁇ around the z-axis, then rotates ⁇ around the x-axis, and finally rotates ⁇ around the z-axis. This determines the tangential direction of the crystal. Therefore, once the Euler angle is determined, the tangential direction of the crystal is determined.
  • the resonance characteristics of the lamb wave resonator 100 can be improved.
  • the piezoelectric layer 130 may be formed using processes such as magnetron sputtering, physical vapor deposition, chemical vapor deposition, epitaxial growth, or bonding between crystals.
  • the acoustic impedance of polymer materials is relatively close to the acoustic impedance of air. Through the materials of the above-mentioned acoustic wave reflection layer 120 and piezoelectric layer 130 , most of the acoustic wave energy can be well confined in the piezoelectric layer 130 .
  • a finite element simulation is performed on the lamb wave resonator 100 provided in the embodiment of the present application.
  • the finite element simulation model of the lamb wave resonator 100 is shown in Figure 6A.
  • the thickness of the acoustic wave reflection layer 120 material is PI
  • the performance of the lamb wave resonator 100 under different thicknesses of the acoustic wave reflection layer 120 is obtained.
  • select the position in the middle of the model shown as a dotted line
  • draw a particle displacement diagram at that position to represent the propagation depth of sound wave energy in the vertical direction In the case where there is no acoustic wave reflection layer 120 (the thickness of the acoustic wave reflection layer 120 is 0 ⁇ m), the particle displacement distribution in the vertical direction is as shown in FIG. 6B .
  • the particle displacement distribution in the vertical direction is as shown in FIG. 6C .
  • the particle displacement distribution in the vertical direction is as shown in FIG. 6D .
  • the abscissas in Figures 6B to 6D are the thickness positions of the model in Figure 6A from top to bottom.
  • the ordinate of Figure 6B to Figure 6D is the size of particle displacement.
  • the thickness of the acoustic wave reflection layer 120 When the thickness of the acoustic wave reflection layer 120 is 0 ⁇ m, the particle displacement at the substrate 110 is very strong, indicating that the acoustic wave energy leaks into the substrate 110 . As the thickness of the acoustic wave reflective layer 120 increases, the particle displacements in the substrate 110 and the acoustic wave reflective layer 120 weaken, and most of the acoustic wave energy is well confined in the piezoelectric layer 130 . When the thickness of the acoustic wave reflection layer 120 is different, the performance of the lamb wave resonator 100 will also change. When the materials of the sound wave reflection layer 120 are different, the thickness requirements of the sound wave reflection layer 120 are also different.
  • the sound wave reflection coefficient R of the sound wave reflection layer 120 is different, and the minimum thickness of the sound wave reflection layer 120 is also different.
  • the thickness of the acoustic reflective layer 120 ranges from 3.5 ⁇ m to 30 ⁇ m.
  • the thickness of the sound wave reflection layer 120 is 10 ⁇ m, 15 ⁇ m, 20 ⁇ m or 25 ⁇ m.
  • Table 2 shows the minimum thickness y of the sound wave reflection layer 120 under different sound wave reflection coefficients R. The smaller the acoustic reflection coefficient R of the material selected for the acoustic reflection layer 120 is, the greater the thickness of the acoustic reflection layer 120 is.
  • the thickness of the acoustic wave reflection layer 120 is related to the performance of the lamb wave resonator 100 .
  • the thickness of the acoustic wave reflection layer 120 is still related to the performance of the lamb wave resonator 100.
  • the resonant frequency fr of the air-gap lamb wave resonator is 4778MHz
  • the anti-resonant frequency fa is 5379
  • the resonance peak-inverse The relative distance of the resonance peak (fa-fr)/fa is 0.111730805
  • the electromechanical coupling coefficient K2 is 0.247427933.
  • the thickness of the acoustic wave reflection layer 120 is greater than 6 ⁇ m, the performance of the lamb wave resonator 100 provided in the embodiment of the present application is close to that of the air gap type lamb wave resonator, and the relative bandwidth and electromechanical coupling coefficient reach almost the same level. .
  • FIG. 6E illustrates a comparison diagram of the admittance curve of the lamb wave resonator 100 and the admittance curve of the air gap type lamb wave resonator when the thickness of the acoustic wave reflection layer 120 is 8 ⁇ m.
  • the abscissa is frequency and the ordinate is Admittance.
  • the thickness of piezoelectric layer 130 is 0.2 ⁇ m-1 ⁇ m.
  • the thickness of the piezoelectric layer 130 is 0.3 ⁇ m, 0.4 ⁇ m, 0.5 ⁇ m, 0.6 ⁇ m, 0.7 ⁇ m, 0.8 ⁇ m, and 0.9 ⁇ m.
  • the thickness of the piezoelectric layer 130 is directly related to the frequency of the lamb wave resonator 100. The thinner the piezoelectric layer 130, the lower the frequency of the lamb wave resonator. The frequency of 100 is higher. This application limits the thickness of the piezoelectric layer 130 to 0.2 ⁇ m-1 ⁇ m, which allows the lamb wave resonator 100 to be applied to high frequencies, which may be, for example, 3.3 GHz or above.
  • the interdigital transducer 140 is disposed on a side of the piezoelectric layer 130 away from the substrate 110 .
  • the interdigital transducer 140 is disposed on a surface of the piezoelectric layer 130 away from the substrate 110 .
  • the interdigital transducer 140 can be understood as forming a metal pattern shaped like intersecting fingers of two hands on the surface of the piezoelectric layer 130, and its function is to realize acoustic and electrical transduction.
  • the above-mentioned interdigital transducer 140 includes a first busbar (busbar) 141a and a second busbar 142a arranged oppositely, and a plurality of first electrode fingers (interdigitated transducer, IDT). ) 141b, and a plurality of second electrode fingers 142b.
  • the extension direction of the first bus bar 141a and the second bus bar 142a is parallel to the first direction X
  • the extension direction of the first electrode finger 141b is parallel to the second direction Y
  • the first electrode finger 141b extends from the first bus bar 141a to the second direction
  • the bus bar 142a protrudes, and the plurality of first electrode fingers 141b are sequentially arranged along the extending direction of the first bus bar 141a (first direction X).
  • the plurality of first electrode fingers 141b are coupled to the first bus bar 141a.
  • the extending direction of the second electrode fingers 142b is parallel to the second direction Y.
  • the second electrode fingers 142b protrude from the second bus bar 142a toward the first bus bar 141a.
  • the plurality of second electrode fingers 142b are along the extending direction of the second bus bar 142a.
  • (first direction X) are arranged in sequence, and the plurality of second electrode fingers 142b are coupled to the second bus bar 142a.
  • the first direction X intersects the second direction Y.
  • parallel in the embodiment of the present application includes approximately parallel, and deviations within the range of process errors (for example, ⁇ 5°) belong to parallel in the embodiment of the present application.
  • a plurality of first electrode fingers 141b and a plurality of second electrode fingers 142b are alternately arranged along the first direction X between the first bus bar 141a and the second bus bar 142a. There is no contact between the electrode fingers 142b.
  • the plurality of first electrode fingers 141b and the plurality of second electrode fingers 142b are alternately arranged in sequence between the first bus bar 141a and the second bus bar 142a along the first direction Between the bar 141a and the second bus bar 142a, a second electrode finger 142b is disposed between every two first electrode fingers 141b, and a first electrode finger 141b is disposed between every two second electrode fingers 142b.
  • the number of first electrode fingers 141b and the number of second electrode fingers 142b in the interdigital transducer 140 are not limited and can be set as needed.
  • the plurality of first electrode fingers 141b may be arranged at equal intervals or may be arranged at non-equal intervals.
  • the plurality of second electrode fingers 142b may be arranged at equal intervals or at non-equal intervals.
  • the non-equally spaced arrangement of the plurality of first electrode fingers 141b refers to the distance between at least one pair of adjacent first electrode fingers 141b and the distance between another pair of adjacent first electrode fingers. The spacing between 141b is not the same.
  • the plurality of first electrode fingers 141b and the plurality of second electrode fingers 142b are arranged alternately in sequence.
  • the spacing between adjacent first electrode fingers 141b and the second electrode fingers 142b may be the same; or there may be multiple pairs of opposite electrode fingers 141b and second electrode fingers 142b.
  • the spacing between adjacent first electrode fingers 141b and second electrode fingers 142b is not exactly the same, that is, the spacing between at least one pair of adjacent first electrode fingers 141b and second electrode fingers 142b is different from another pair of adjacent first electrode fingers 141b and second electrode fingers 142b.
  • the spacing between the first electrode finger 141b and the second electrode finger 142b is different.
  • the spacing between adjacent first electrode fingers 141b and second electrode fingers 142b is 2 ⁇ m-10 ⁇ m.
  • first electrode fingers 141b and second electrode fingers 142b are 3 ⁇ m-4 ⁇ m, 4 ⁇ m-5 ⁇ m, 5 ⁇ m-6 ⁇ m, 6 ⁇ m-7 ⁇ m, 7 ⁇ m-8 ⁇ m, 8 ⁇ m-9 ⁇ m, or 9 ⁇ m-10 ⁇ m.
  • the spacing between the first electrode finger 141b and the second electrode finger 142b directly affects the frequency of the lamb wave resonator 100, it also affects the bandwidth of the lamb wave resonator 100. Generally speaking, the greater the spacing, the greater the bandwidth. Therefore, by limiting the spacing between adjacent first electrode fingers 141b and second electrode fingers 142b to 2 ⁇ m-10 ⁇ m, the lamb wave resonator 100 can be made to work in the fifth generation mobile communication technology (5G). ) frequency band, with a wider bandwidth.
  • 5G fifth generation mobile communication technology
  • the width of the first electrode finger 141b is 200 nm-1000 nm
  • the width of the second electrode finger 142b is 200 nm-1000 nm.
  • the width of the first electrode finger 141b and the second electrode finger 142b is between 200nm-300nm, between 300nm-400nm, between 400nm-500nm, between 500nm-600nm, between 600nm-700nm, and 700nm-800nm. between, between 800nm-900nm or between 900nm-1000nm.
  • the duty cycle mainly affects the bandwidth of the lamb wave resonator 100, it also affects the frequency of the lamb wave resonator 100.
  • the duty cycle the width of the electrode fingers/(the width of the electrode fingers + the spacing between the electrode fingers), when the spacing between the electrode fingers is determined, adjusting the width of the electrode fingers can adjust the lamb wave resonator 100 bandwidth and frequency. Therefore, by placing the adjacent first electrical
  • the width of the pole finger 141b and the second electrode finger 142b is limited to 200nm-1000nm, which allows the lamb wave resonator 100 to operate in the 5G frequency band and have a wide bandwidth.
  • the pitch between the first electrode finger 141b and the second electrode finger 142b and the width of the first electrode finger 141b and the second electrode finger 142b are mainly affected by the photolithography and development processes.
  • the resonant frequency and bandwidth of the lamb wave resonator 100 can be changed, so that a specific Electronic signals with frequencies can pass through the lamb wave resonator 100 , while electronic signals with other frequencies will be filtered out by the lamb wave resonator 100 .
  • first bus bar 141a, the first electrode finger 141b, the second bus bar 142a and the second electrode finger 142b can be manufactured at the same time. You may also make the first bus bar 141a and the first electrode finger 141b first, and then make the second bus bar 142a and the second electrode finger 142b. Alternatively, the second bus bar 142a and the second electrode finger 142b are formed first, and then the first bus bar 141a and the first electrode finger 141b are formed.
  • the materials of the first electrode finger 141b and the second electrode finger 142b may include aluminum (Al), copper (Cu), platinum (Pt), gold (Au), nickel (Ni), titanium (Ti), and Ag (silver). , chromium (Cr), molybdenum (Mo), tungsten (W), tantalum (Ta), etc. One or more.
  • the substrate 110 in the lamb wave resonator 100 provided by this application is a silicon substrate.
  • the material of the sound wave reflection layer 120 is PI, and the thickness of the sound wave reflection layer 120 is 8 ⁇ m.
  • the material of the piezoelectric layer 130 is Z-cut LiNbO 3 , and the thickness of the piezoelectric layer 130 is 400 nm.
  • the material of the first electrode finger 141b and the second electrode finger 142b is Al, the thickness of the first electrode finger 141b and the second electrode finger 142b is 100nm, the width of the first electrode finger 141b and the second electrode finger 142b is 500nm, and the adjacent first electrode finger 141b and the second electrode finger 142b are 500nm in width.
  • the distance between the electrode finger 141b and the second electrode finger 142b is 3 ⁇ m.
  • the lamb wave resonator 100 provided by the embodiment of the present application disposes the acoustic wave reflection layer 120 on the side of the piezoelectric layer 130 close to the substrate 110, and the acoustic impedance of the acoustic wave reflection layer 120 is smaller than the acoustic impedance of the piezoelectric layer 130. In this way, the sound wave will be reflected on the surface of the sound wave reflection layer 120 facing the piezoelectric layer 130 and reflected back to the piezoelectric layer 130 to achieve the purpose of confining the sound wave energy in the piezoelectric layer 130 .
  • the acoustic wave reflection layer 120 can be realized through a simple process, which simplifies the preparation process of the lamb wave resonator 100 and reduces the difficulty of preparing the lamb wave resonator 100 .
  • the lamb wave resonator 100 provided by the present application, there is no need to form an air cavity on the substrate 110 .
  • the mechanical strength of the lamb wave resonator 100 can be enhanced and the yield of the lamb wave resonator 100 can be improved.
  • the lamb wave resonator 100 provided by the embodiment of the present application is applicable to the first-order antisymmetric (A1) mode, the lowest-order symmetric (S0) mode, and the lowest-order (SH0) mode, and has a wide application range. And it can meet the equipment's demand for high-frequency and large-bandwidth resonators.
  • the operating frequency is from 450MHz to 6000MHz.
  • the lamb wave resonator 100 provided in the embodiment of the present application can be used.
  • the lamb wave resonator 100 further includes a frequency shifting layer, and the frequency shifting layer is used to adjust the frequency of the lamb wave resonator 100 .
  • the frequency shifting layer 150 is disposed between the piezoelectric layer 130 and the acoustic wave reflection layer 120 .
  • the frequency shifting layer 150 is disposed on the side of the interdigital transducer 140 away from the piezoelectric layer 130 .
  • the frequency shifting layer 150 may also be provided both below the piezoelectric layer 130 and above the interdigital transducer 140 .
  • the material of the frequency shifting layer 150 may be, for example, silicon nitride (SiN), aluminum oxide (Al 2 O 3 ) or silicon oxide (SiO 2 ).
  • the lamb wave resonator 100 when the lamb wave resonator 100 includes the frequency shifting layer 150, there is no need to change the structure of other film layers in the lamb wave resonator 100.
  • the thickness of the frequency shifting layer 150 By adjusting the thickness of the frequency shifting layer 150, the frequency of the lamb wave resonator 100 can be adjusted. to the required value.
  • the lamb wave resonator 100 further includes a temperature compensation layer, which is used to compensate the frequency temperature coefficient of the lamb wave resonator 100 .
  • the temperature compensation layer is disposed at the same position as the frequency shifting layer 150 .
  • the temperature compensation layer is disposed between the piezoelectric layer 130 and the acoustic wave reflection layer 120 .
  • the temperature compensation layer is disposed on the side of the interdigital transducer 140 away from the piezoelectric layer 130 .
  • a temperature compensation layer is provided below the piezoelectric layer 130 and above the interdigital transducer 140 .
  • the material of the temperature compensation layer may be SiO 2 , for example.
  • the lamb wave resonator 100 can also include a frequency shifting layer 150 and a temperature compensation layer at the same time.
  • the frequency shifting layer 150 and the temperature compensation layer are stacked, or the frequency shifting layer 150 and the temperature compensation layer are arranged on two opposite sides of the piezoelectric layer 130 . side.
  • the temperature compensation layer can be used to perform temperature compensation on the lamb wave resonator 100, so that the absolute value of the temperature coefficient of frequency (TCF) of the lamb wave resonator 100 is reduced.
  • TCF temperature coefficient of frequency
  • the lamb wave resonator 100 further includes a phononic crystal layer 160 disposed between the substrate 110 and the acoustic wave reflection layer 120 .
  • the phononic crystal layer 160 includes phononic crystals, which are, for example, columnar structures.
  • the phononic crystal layer 160 can further restrict the sound waves, supplement the sound wave reflection function of the sound wave reflection layer 120 , and increase the bandwidth of the lamb wave resonator 100 .
  • the lamb wave resonator 100 may include the frequency shifting layer 150 and the phononic crystal layer 160 at the same time, or the lamb wave resonator 100 may include the temperature compensation layer and the phononic crystal layer 160 at the same time, or the lamb wave resonator 100 may include It also includes a frequency shifting layer 150, a temperature compensation layer and a phononic crystal layer 160.
  • the structure in Figure 10 is only an illustration without any limitation.
  • An embodiment of the present application also provides a method for preparing a lamb wave resonator 100, which is used to prepare any of the above lamb wave resonators 100.
  • the acoustic wave reflection layer 120 is directly formed on the substrate 110 without hollowing out the substrate 110. Then, the piezoelectric layer 130 and the interdigital transducer 140 are formed.
  • the surface of the substrate 110 is flat, and there is no recessed section after being dug out. It can be understood that the plane here is relative, and the surface height difference within the process error range belongs to the plane of the embodiment of the present application.
  • the formed substrate 110 may be as shown in FIGS. 4A and 4B.

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Abstract

本申请实施例提供一种兰姆(lamb)波谐振器及制备方法、滤波器、射频模组、电子设备。lamb波谐振器包括：衬底、设置在衬底上的声波反射层、设置在声波反射层上的压电层以及设置在压电层上的叉指换能器。声波反射层的声阻抗小于压电层的声阻抗，声波反射层朝向压电层的表面的声波反射系数为R，0.5≤R≤0.86。

Description

兰姆波谐振器及制备方法、滤波器、射频模组、电子设备
本申请要求于2022年08月27日提交国家知识产权局、申请号为202211036176.3、申请名称为“兰姆波谐振器及制备方法、滤波器、射频模组、电子设备”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及射频技术领域，尤其涉及一种兰姆波谐振器及制备方法、滤波器、射频模组、电子设备。
背景技术
随着移动数据的爆炸式增长，通讯行业已经向第五代移动通信技术(5th generation mobile communication technology，5G)迈进，这要求射频前端的谐振器要具有更高的频率、更大的带宽和更强的功率耐受。目前的射频前端谐振器主要有声表面波(surface acoustic wave，SAW)谐振器和体声波(bulk acoustic wave，BAW)谐振器两大类。SAW谐振器的频率低于3.5GHz，且机电耦合系数只有10％左右。BAW谐振器的机电耦合系数也较小。而，兰姆波(lamb wave)谐振器因其具有声速高(例如，12000m/s～15000m/s)、机电耦合系数大(例如，可达25％)等优点，成为近年来的研究热点。
但是，目前制备lamb波谐振器的工艺较为复杂、良品率低。因此，如何采用简单工艺制备良品率高的lamb波谐振器成为当下急需解决的技术问题。
发明内容
本申请实施例提供一种兰姆波谐振器及制备方法、滤波器、射频模组、电子设备，用于解决当下制备lamb波谐振器的工艺复杂、良品率低的问题。
为达到上述目的，本申请采用如下技术方案：
本申请实施例的第一方面，提供一种兰姆lamb波谐振器，lamb波谐振器作为滤波器的元件，可以应用于射频器件中。lamb波谐振器包括：衬底、设置在衬底上的声波反射层、设置在声波反射层上的压电层以及设置在压电层上的叉指换能器。声波反射层的声阻抗小于压电层的声阻抗，压电层的材料选定后，通过调整声波反射层的材料和厚度，可将声波反射层朝向压电层的表面的声波反射系数限定在0.5-0.86(0.5≤声波反射系数R≤0.86)。这样一来，A1、S0、SH0等模式的声波在声波反射层朝向压电层的界面处会发生反射，将声波锁定在压电层中。
本申请实施例提供的lamb波谐振器，通过在压电层靠近衬底一侧设置声波反射层，且声波反射层的声阻抗小于压电层的声阻抗。这样一来，lamb波谐振器激发出的声波会在声波反射层朝向压电层的表面发生反射，反射回压电层。采用形成在衬底上的单层声波反射层，即可实现将声波锁定在压电层中，避免了lamb波谐振器所激发的声波大量向衬底泄露而导致的器件性能严重退化的问题。声波反射层替代了传统的空气腔和布拉格反射结构，无需掏腔或者形成复杂的布拉格反射结构，简化了lamb波谐振器的制备流程，降低了lamb波谐振器的制备难度。此外，由于本申请提供的lamb波谐振器中，可以无需在衬底上形成空气腔。当衬底上不设置空气腔时，可增强lamb波谐振器的机械强度，提高lamb波谐振器的良率。
在此基础上，将声波反射层朝向压电层的表面的声波反射系数R限定在0.5-0.86内，可以较好的将声波模态限制在压电层当中。并且既可以改善因声波反射系数R太小(小于0.5)，导致声波将不能被很好的限制在压电层当中，或者用于限制声波的声波反射层需要很厚，工程上难以实现的问题。又可以改善因声波反射系数R太大(大于0.86)，导致声波反射层材料的密度和杨氏模量等参量比较小，材料比较柔软。在lamb波谐振器加工过程中(例如键合压电层后退火)，声波反射层容易发生形变，造成其上方的压电层出现褶皱或者碎裂，影响产品良率的问题。
在一种可能的实现方式中，0.55≤R≤0.8。通过将声波反射系数R限定在0.55-0.8，在满足器件性能的基础上，可以同时兼顾声波反射层的选材、厚度设定以及制备工艺等问题，降低制备成本。
在一种可能的实现方式中，声波反射层的最小厚度为y，y＝77.75379*R2-173.22328*R+97.70404。本申请实施例中，声波反射层的选材范围广，每种材料的声波反射层的声波反射系数R不同，每种材料的声波反射层的厚度也不同。本申请通过限定声波反射层的最小厚度，既可以使lamb波谐振器的特性满足需求，又可以便于声波反射层的制备，以兼顾lamb波谐振器的性能、成本、工艺、可靠性等多种特性。
在一种可能的实现方式中，声波反射层的厚度为3.5μm-30μm。这是一种便于量产的厚度范围。
在一种可能的实现方式中，声波反射层的材料为高分子材料。本申请实施例中声波反射层的选材范围广，易于实现。
在一种可能的实现方式中，声波反射层的材料包括聚酰亚胺、聚二甲基硅氧烷、聚甲基丙烯酸甲酯、聚偏氟乙烯或者聚对苯二甲酸乙二醇酯。这是一些成本较低、易于实现的选材。
在一种可能的实现方式中，声波反射层为单膜层结构。单膜层结构的声波反射层结构简单、工艺简单。
在一种可能的实现方式中，压电层的材料的切向为Z切。这种材料的压电层可使lamb波谐振器具有较宽的带宽。
在一种可能的实现方式中，压电层的材料的欧拉角为(0，20，0)到(0，40，0)。该范围内的欧拉角可使lamb波谐振器具有较宽的带宽。
在一种可能的实现方式中，lamb波谐振器还包括移频层，移频层用于调整lamb波谐振器的频率；移频层设置在压电层与声波反射层之间。lamb波谐振器包括移频层的情况下，无需改变lamb波谐振器中其他膜层的结构，通过调整移频层的厚度，可将lamb波谐振器的频率调整至需要值。
在一种可能的实现方式中，lamb波谐振器还包括移频层，移频层用于调整lamb波谐振器的频率；移频层设置在叉指换能器远离压电层一侧。lamb波谐振器包括移频层的情况下，无需改变lamb波谐振器中其他膜层的结构，通过调整移频层的厚度，可将lamb波谐振器的频率调整至需要值。
在一种可能的实现方式中，lamb波谐振器还包括温度补偿层，温度补偿层用于补偿lamb波谐振器的频率温度系数；温度补偿层设置在压电层与声波反射层之间。lamb波谐振器包括温度补偿层的情况下，可通过温度补偿层对lamb波谐振器进行温度补偿，使得lamb波谐振器的频率温度系数(TCF)的绝对值下降。
在一种可能的实现方式中，lamb波谐振器还包括温度补偿层，温度补偿层用于补偿lamb波谐振器的频率温度系数；温度补偿层设置在叉指换能器远离压电层一侧。lamb波谐振器包括温度补偿层的情况下，可通过温度补偿层对lamb波谐振器进行温度补偿，使得lamb波谐振器的频率温度系数(TCF)的绝对值下降。
在一种可能的实现方式中，压电层的厚度为0.2μm-1μm。通过将压电层130的厚度限定在1μm以下，可以满足对lamb波谐振器100带宽、频率的要求，又可以使lamb波谐振器100小型化。在一种可能的实现方式中，叉指换能器包括多个第一电极指和多个第二电极指，多个第一电极指和多个第二电极指依次交替排布；第一电极指和第二电极指的宽度为200nm-1000nm。这样一来，可以使lamb波谐振器工作在5G频段，且具有较宽的带宽。
在一种可能的实现方式中，叉指换能器包括多个第一电极指和多个第二电极指，多个第一电极指和多个第二电极指依次交替排布；相邻第一电极指和第二电极指之间的间距为2μm-10μm。这样一来，可以使lamb波谐振器工作在5G频段，且具有较宽的带宽。
在一种可能的实现方式中，衬底与声波反射层之间还设置有声子晶体层。通过在lamb波谐振器中设置声子晶体层，声子晶体层可对声波进行进一步的限制，对声波反射层进行声波反射功 能的补充，提高lamb波谐振器的带宽。
在一种可能的实现方式中，衬底朝向声波反射层的表面为平面。无需对衬底进行掏空处理，制备工艺简单，可靠性高。
在一种可能的实现方式中，衬底上未设置开口。无需对衬底进行掏空处理，制备工艺简单，可靠性高。
本申请实施例的第二方面，提供一种滤波器，包括多个级联的lamb波谐振器；其中，lamb波谐振器为第一方面任一项的lamb波谐振器。
本申请实施例第二方面提供的滤波器包括第一方面的lamb波谐振器，其有益效果与lamb波谐振器的有益效果相同，此处不再赘述。
本申请实施例的第三方面，提供一种射频模组，包括滤波器和功率放大器，滤波器与功率放大器耦接；滤波器为第二方面的滤波器。
本申请实施例第三方面提供的射频模组包括第一方面的lamb波谐振器，其有益效果与lamb波谐振器的有益效果相同，此处不再赘述。
本申请实施例的第四方面，提供一种电子设备，包括滤波器和电路板，滤波器设置在电路板上；滤波器为第二方面的滤波器。
本申请实施例第四方面提供的电子设备包括第一方面的lamb波谐振器，其有益效果与lamb波谐振器的有益效果相同，此处不再赘述。
本申请实施例的第五方面，提供一种lamb波谐振器的制备方法，用于制备第一方面任一项的lamb波谐振器。
附图说明
图1为本申请实施例提供的电子设备的框架示意图；
图2为本申请实施例提供的滤波器的拓扑结构示意图；
图3为本申请实施例提供的lamb波谐振器的粒子位移图；
图4A为本申请实施例示意的一种背刻蚀型lamb波谐振器的结构示意图；
图4B为本申请实施例示意的一种空气隙型lamb波谐振器的结构示意图；
图4C为本申请实施例示意的一种固态装配型lamb波谐振器的结构示意图；
图5为本申请实施例提供的一种lamb波谐振器的结构示意图；
图6A为本申请实施例提供的一种lamb波谐振器的建模图；
图6B-图6D为声波反射层厚度不同时，lamb波谐振器在垂直方向的粒子位移分布示意图；
图6E为本申请实施例提供的一种lamb波谐振器100的导纳曲线图；
图7为本申请实施例提供的一种叉指换能器的结构示意图；
图8为本申请实施例提供的另一种lamb波谐振器的结构示意图；
图9为本申请实施例提供的又一种lamb波谐振器的结构示意图；
图10为本申请实施例提供的又一种lamb波谐振器的结构示意图。
附图标记：
1-电子设备；11-盖板；12-显示屏；13-中框；131-承载板；132-边框；14-后壳；10-滤波
器；100-谐振器；110-衬底；120-声波反射层；130-压电层；140-叉指换能器；141a-第一汇流条；142a-第二汇流条；141b第一电极指；142b-第二电极指；150-移频层；160-声子晶体层。
具体实施方式
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行描述，显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。
以下，术语“第二”、“第一”等仅用于描述方便，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量。由此，限定有“第二”、“第一”等的特征可以明示或者隐含地包括一个或者更多个该特征。在本申请的描述中，除非另有说明，“多个”的含义是两个或两个以上。
此外，本申请实施例中，“上”、“下”、“左”、“右”等方位术语可以包括但不限于相对附图中 的部件示意置放的方位来定义的，应当理解到，这些方向性术语可以是相对的概念，它们用于相对于的描述和澄清，其可以根据附图中部件附图所放置的方位的变化而相应地发生变化。
在本申请实施例中，除非另有明确的规定和限定，术语“连接”应做广义理解，例如，“连接”可以是固定连接，也可以是可拆卸连接，或成一体；可以是直接相连，也可以通过中间媒介间接相连。此外，术语“相耦接”可以是直接的电性连接，也可以通过中间媒介间接的电性连接。术语“接触”可以是直接接触，也可以是通过中间媒介间接的接触。
本申请实施例中，“和/或”，描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B的情况，其中A，B可以是单数或者复数。字符“/”一般表示前后关联对象是一种“或”的关系。
本申请实施例提供一种的电子设备。该电子设备例如为消费性电子产品、家居式电子产品、车载式电子产品、金融终端产品、通信电子产品。其中，消费性电子产品如为手机(mobile phone)、平板电脑(pad)、笔记本电脑、电子阅读器、个人计算机(personal computer，PC)、个人数字助理(personal digital assistant，PDA)、桌面显示器、智能穿戴产品(例如，智能手表、智能手环)、虚拟现实(virtual reality，VR)终端设备、增强现实(augmented reality，AR)终端设备、无人机等。家居式电子产品如为智能门锁、电视、遥控器、冰箱、充电家用小型电器(例如豆浆机、扫地机器人)等。车载式电子产品如为车载导航仪、车载高密度数字视频光盘(digital video disc，DVD)等。金融终端产品如为自动取款机(automated teller machine，ATM)机、自助办理业务的终端等。通信电子产品如为服务器、存储器、雷达、基站等通信设备。
以下为了方便说明，以电子设备为手机为例进行举例说明。如图1所示，电子设备1主要包括盖板11、显示屏12、中框13以及后壳14。后壳14和显示屏12分别位于中框13的两侧，且中框13和显示屏12设置于后壳14内，盖板11设置在显示屏12远离中框13的一侧，显示屏12的显示面朝向盖板11。
上述显示屏12可以是液晶显示屏(liquid crystal display，LCD)，在此情况下，液晶显示屏包括液晶显示面板和背光模组，液晶显示面板设置在盖板11和背光模组之间，背光模组用于为液晶显示面板提供光源。上述显示屏12也可以为有机发光二极管(organic light emitting diode，OLED)显示屏。由于OLED显示屏为自发光显示屏，因而无需设置背光模组。
上述中框13包括承载板131以及绕承载板131一周的边框132。上述电子设备1还可以包括印刷电路板(printed circuit boards，PCB)、电池、摄像头等电子元器件，印刷电路板、电池、摄像头等电子元器件可以设置在承载板131上。
上述电子设备1还可以包括设置于PCB上的系统级芯片(system on chip，SOC)、射频芯片等，PCB用于承载系统级芯片、射频芯片等，且与系统级芯片、射频芯片等电连接。其中，射频芯片可以包括滤波器、处理器等部分。处理器用于对各种信号进行处理，滤波器是射频信号处理的重要部分，用于通过特定频率的信号，让其他频率的信号受阻。
本申请的实施例提供一种滤波器，该滤波器可以应用于上述的电子设备1中，例如应用于电子设备1中的射频芯片中，本申请实施例提供的滤波器例如可以为低通波滤波器、高通滤波器、带通滤波器、带阻滤波器或有源滤波器等。
当然，本申请实施例提供的滤波器并不限定为集成在电子设备1中。滤波器也可以单独作为一个部件，或者，滤波器也可以和功率放大器等部件集成为一种模组(例如射频器件、射频模组、滤波器模组等)，滤波器与功率放大器耦接，进行信号处理和传输。
如图2所示，本申请实施例提供的滤波器10包括多个级联的兰姆波(lamb wave)谐振器100，这多个兰姆(lamb)波谐振器100可以具有不同的谐振频率，且可以通过串并联的方式级联在一起。图2还示意出了滤波器10的信号输入端Vi、信号输出端Vo以及接地端GND。
此处，lamb波谐振器100具有声速高(例如，12000m/s～15000m/s)、机电耦合系数大(例如，可达25％)等优点，多用于各种射频终端设备。而由具有不同谐振频率的串并联lamb波谐振器100级联构成的滤波器10具有通带插损小、带外陡峭度高及功率耐受性强等优点。
lamb波谐振器100的粒子位移图如图3所示(图3中只绘出了压电层和单对电极指)，当在电极指上施加交变电场时，电场方向主要是水平的(图3中的X方向)，或与压电层平行，会激励起沿压电层厚度方向传播的剪切波，厚度方向为图3中的Z方向。图3中实线箭头表示粒子的振动方向，虚线箭头表示电场方向。
为了使lamb波谐振器100具有较高的声速和较大的机电耦合系数，通常需要将声波能量限制在压电层中。
为了达到上述目的，在一些技术中，如图4A所示，lamb波谐振器100为背刻蚀型结构。使用背刻蚀工艺，去除压电层中间区域下方的衬底，使中间区域的压电层悬浮、下表面与空气接触。空气的声阻抗比较低，可将声波反射回压电层，从而实现将声波能量限制在压电层中。
背刻蚀型结构的lamb波谐振器100，工艺相对简单，但由于压电层下方的硅被去除，导致lamb波谐振器100的机械强度差，成品率低。
在另一些技术中，如图4B所示，lamb波谐振器100为空气隙型结构。使用刻蚀工艺，在压电层中刻蚀出释放窗，再通过释放工艺，释放掉压电层中间区域下方的衬底或牺牲层，使中间区域的压电层悬浮、下表面与空气接触。空气的声阻抗比较低，可将声波反射回压电层，从而实现将声波限制在压电层中。
空气隙型结构的lamb波谐振器100，机械强度高于背刻蚀型结构的lamb波谐振器100，制作时需要掏腔，工艺比较复杂。
在又一些技术中，如图4C所示，lamb波谐振器100为固态装配型结构。在压电层下方制备由高声阻抗层和低声阻抗层交替组成的布拉格反射(Bragg reflector)结构，将声波限制在压电层中。其中，低声阻抗层的材料例如可以为氧化锌、二氧化硅等，高声阻抗层的材料例如可以为重金属等。重金属是指密度大于4.5g/cm3的金属，包括金、银、铜、铁、汞、铅、镉等。声波在低声阻抗层和高声阻抗层的交界处发生反射，反射回压电层中。其中，低声阻抗层是相对高声阻抗层而言声阻抗略低的膜层，低声阻抗层和高声阻抗层的声阻抗均可能大于压电层。
固态装配型结构的lamb波谐振器100，需要准确控制布拉格反射层中各层的厚度，工艺较为复杂，良率难以提高，成本高，影响器件量产。
本申请实施例提供一种lamb波谐振器，如图5所示，lamb波谐振器100包括：衬底110、声波反射层120、压电层130以及叉指换能器140。
衬底110的材料例如可以为铌酸锂(LiNbO3，LN)、钽酸锂(LiTaO3，LT)、石英(quartz)、硅(Si)、陶瓷(ceramics)或者玻璃(glass)等。陶瓷的主要成分例如包括硅酸盐和铝硅酸盐、耐熔金属氧化物和金属氮化物、硼化物等，玻璃的主要成分例如包括六二氧化硅合氧化钙合氧化钠(Na2O·CaO·6SiO2)。
在一些实施例中，衬底110的结构为相关技术中的任一种衬底结构。示例的，衬底110的结构为图4A-图4C所示的任一种结构。
在另一些实施例中，衬底110朝向声波反射层120的表面为平面。例如，衬底110朝向声波反射层120的表面未被去除一部分，衬底110上未设置开口，衬底110与设置在衬底110表面上的膜层(例如声波反射层120)之间不存在空气腔。
声波反射层120设置在衬底110一侧，例如，声波反射层120可以设置在衬底110的表面上。
压电层130设置在声波反射层120远离衬底110一侧，例如，压电层130可以设置在声波反射层120的表面上。
其中，在对声波反射层120和压电层130进行选材时，满足压电层130的声阻抗大于声波反射层120的声阻抗，以实现声波在声波反射层120朝向压电层130的表面处发生反射，反射回压电层130。
需要强调的是，本申请中，声波反射层120的声阻抗小于压电层130的声阻抗即可，对声波反射层120与衬底110之间声阻抗的大小关系不做限定。声波反射层120的声阻抗可以小于衬底110的声阻抗，声波反射层120的声阻抗也可以大于衬底110的声阻抗，声波反射层120的声阻 抗还可以等于衬底110的声阻抗。
声阻抗(acoustic impedance)是力学术语，指媒质在波阵面某个面积上的压强与通过这个面积的体积速度的复数比值，声阻抗的单位是帕斯卡·每平方米·秒(Pa·m-2s-1)。
声波反射层的声阻抗Z120和压电层的声阻抗Z130可以分别通过下面公式计算得到：
Z120＝v120*ρ120；
Z130＝v130*ρ130；
以lamb波为一阶反对称(A1)模态，声波反射层120为各向同性材料为例：

其中，v120、v130为声波反射层120和压电层130中的Z方向剪切波速，ρ120、ρ130为声波反射层120和压电层130的密度，C44为压电层130的弹性劲度系数，E为声波反射层120的杨氏模量(Young's modulus)，杨氏模量的单位为Pa、Mpa、Gpa，σ为声波反射层120的泊松比(Poisson's ratio)。
在一些实施例中，声波反射层120朝向压电层130的表面的声波反射系数为R越大，对声波的限制效果越好。
关于声波反射系数R可以通过下面的公式计算得到：
其中，声波反射系数R与声波的限制效果相关。
在一些实施例中，声波反射系数R的取值范围为0.5≤R<0.86。例如，声波反射系数R的取值为0.6、0.65、0.7、0.75、0.8、0.85。
通过将声波反射系数R限定在大于等于0.5，可以较为有效的将声波限制在压电层130中，可使本申请实施例提供的lamb波谐振器100的性能与空气隙型lamb波谐振器的性能相近。
并且，既可以改善因声波反射系数R太小(小于0.5)，导致声波将不能被很好的限制在压电层130当中，或者用于限制声波的声波反射层120需要很厚，工程上难以实现的问题。又可以改善因声波反射系数R太大(大于0.86)，导致声波反射层120材料的密度和杨氏模量等参量比较小，材料比较柔软。在lamb波谐振器100加工过程中(例如键合压电层后退火)，声波反射层120容易发生形变，造成其上方的压电层130出现褶皱或者碎裂，影响产品良率的问题。
其中，声波反射层120的材料可以为满足声波反射系数R的任意材料。
在一些实施例中，声波反射层120的材料为高分子材料(macromolecular material)。
高分子材料，也称为聚合物材料，是以高分子化合物为基体，再配有其他添加剂(助剂)所构成的材料。
示例的，声波反射层120的材料包括聚酰亚胺(polyimide，PI)，聚二甲基硅氧烷(polydimethylsiloxane，PDMS)、聚甲基丙烯酸甲酯(polymethyl methacrylate，PMMA)、聚偏氟乙烯(polyvinylidene fluoride，PVDF)或者聚对苯二甲酸乙二醇酯(polyethylene glycol terephthalate，PET)等。
例如，可以采用旋涂、磁控溅射、物理气相沉积、化学气相沉积、外延生长等工艺，形成声波反射层120。工艺简单，成本低，成品率高。
通过上述公式，如表1所示，可得到本申请实施例中几种可选的材料的声波反射系数R。
表1 不同材料的声速、声阻抗与声波反射系数

在一些实施例中，如图5所示，声波反射层120为单层膜层。
也可以理解为，声波反射层120是一层膜层，不是多层膜层层叠后构成的结构。
本申请实施例中，是基于声波反射层120与压电层130之间的声阻抗差，使得声波在声波反射层120朝向压电层130的表面反射。因此，声波反射层120为单层膜层，结构简单制备工艺简单。
当然，声波反射层120也可以包括多层膜层，是由多层膜层层叠后构成的结构。
本申请实施例对声波反射层120的具体结构不做限定，多层膜层之间的声阻抗的关系也不做限定，能够使声波在声波反射层120朝向压电层130的表面发生反射即可。
在一些实施例中，压电层130的材料包括LiNbO3、LiTaO3、氮化铝(AlN)、氧化锌(ZnO)或者石英等压电材料中的一种或多种。压电层130的材料可以是各切向的。
在一些实施例中，压电层130的材料为LiNbO3，其切向为Z切向。
Z切向的LiNbO3压电材料，可提高lamb波谐振器100的带宽。
在一些实施例中，压电层130的材料为LiNbO3，其欧拉角为(0，20，0)到(0，40，0)。
示例的，压电层130的材料为LiNbO3，其欧拉角为(0，25，0)、(0，30，0)、(0，35，0)。
其中，欧拉角中的三个数字(α，β，γ)分别代表直拉出来的单晶先绕z轴旋转α，再绕x轴旋转β，最后再绕z轴旋转γ，这样就确定了晶体的切向。因此，欧拉角确定了，晶体的切向就确定了。
压电层130材料的欧拉角在上述范围，可以提高lamb波谐振器100的谐振特性。
例如，采用采磁控溅射、物理气相沉积、化学气相沉积、外延生长或者晶体间的键合(bonding)等工艺形成压电层130。
高分子材料的声阻抗与空气的声阻抗较为接近，通过上述声波反射层120和压电层130的材料，可使大部分声波能量被很好地限制在压电层130中。
以衬底110的材料为Si，声波反射层120的材料为PI，压电层130的材料为Z切LiNbO3为例，对本申请实施例提供的lamb波谐振器100进行有限元仿真。
lamb波谐振器100的有限元仿真模型如图6A所示，改变模型中声波反射层120(材料为PI)的厚度，获得不同声波反射层120厚度下的lamb波谐振器100性能。同时选取模型中间的位置(点画线所示)，作出该位置的粒子位移图，用来表征声波能量在垂直方向的传播深度。在没有声波反射层120(声波反射层120的厚度为0μm)的情况下，垂直方向的粒子位移分布如图6B所示。在声波反射层120的厚度为4μm的情况下，垂直方向的粒子位移分布如图6C所示。在声波反射层120的厚度为8μm的情况下，垂直方向的粒子位移分布如图6D所示。其中，图6B-图6D的横坐标为图6A中模型从上到下的厚度位置。图6B-图6D的纵坐标为粒子位移的大小。
在声波反射层120的厚度为0μm的情况下，衬底110处的粒子位移十分强烈，说明声波能量泄露到了衬底110中。随着声波反射层120厚度的增加，衬底110和声波反射层120中的粒子位移减弱，大部分声波能量被很好地限制在压电层130当中。在声波反射层120厚度不同的情况下，lamb波谐振器100的性能也会发生变化。而声波反射层120的材料不同的情况下，声波反射层120厚度要求也不相同。
在一些实施例中，声波反射层120的最小厚度为y，最小厚度y可以通过下面的公式计算得到：
y＝77.75379*R2-173.22328*R+97.70404；
本申请实施例中，声波反射层120的材料不同的情况下，声波反射层120的声波反射系数R不同，声波反射层120的最小厚度也不同。
在一些实施例中，声波反射层120的厚度范围为3.5μm-30μm。
示例的，声波反射层120的厚度为10μm、15μm、20μm或者25μm。
表2示意不同声波反射系数R下，声波反射层120的最小厚度y。声波反射层120所选材料的声波反射系数R越小，声波反射层120的厚度越大。
通过表2可知，声波反射层120的材料不同的情况下，声波反射层120的厚度与lamb波谐振器100的性能相关。而在声波反射层120的材料固定的情况下，如表3所示，声波反射层120的厚度依旧与lamb波谐振器100的性能相关。
表2 声波反射层的最小厚度与声波反射层的反射系数的关系
表3 不同声波反射层厚度下，lamb波谐振器的性能参数
以衬底的材料为Si，压电层的材料为Z切LiNbO3为例进行有限元仿真，空气隙型lamb波谐振器的谐振频率fr为4778MHz，反谐振频率fa为5379，谐振峰-反谐振峰的相对距离(fa-fr)/fa为0.111730805，机电耦合系数K2为0.247427933。通过对比发现，当声波反射层120的厚度大于6μm时，本申请实施例提供的lamb波谐振器100的性能与空气隙型lamb波谐振器的性能接近，相对带宽与机电耦合系数几乎达到同一水平。
图6E示意出声波反射层120的厚度为8μm时，lamb波谐振器100的导纳曲线与空气隙型lamb波谐振器的导纳曲线的比较图，图6E中横坐标为频率，纵坐标为导纳。从图中可以看出，本申请实施例提供的lamb波谐振器100的性能与空气隙型lamb波谐振器的性能差别不大，但本申请实施例提供的lamb波谐振器100的制备工艺明显简单，良品率高。
在一些实施例中，压电层130的厚度为0.2μm-1μm。
示例的，压电层130的厚度为0.3μm、0.4μm、0.5μm、0.6μm、0.7μm、0.8μm、0.9μm。
压电层130的厚度与lamb波谐振器100的频率直接相关，压电层130越薄，lamb波谐振器 100的频率越高。本申请将压电层130的厚度限定在0.2μm-1μm，可使lamb波谐振器100应用于高频中，高频例如可以是3.3GHz以上。
叉指换能器140设置在压电层130远离衬底110一侧，例如，叉指换能器140设置在压电层130远离衬底110的表面上。
叉指换能器140可以理解为是在压电层130表面上形成形状像两只手的手指交叉状的金属图案，它的作用是实现声电换能。在一种实施例中，如图7所示，上述叉指换能器140包括相对设置的第一汇流条(busbar)141a和第二汇流条142a、多个第一电极指(interdigitated transducer，IDT)141b、以及多个第二电极指142b。第一汇流条141a和第二汇流条142a的延伸方向与第一方向X平行，第一电极指141b的延伸方向与第二方向Y平行，第一电极指141b从第一汇流条141a向第二汇流条142a凸出，多个第一电极指141b沿第一汇流条141a延伸方向(第一方向X)依次排布，多个第一电极指141b与第一汇流条141a耦接。第二电极指142b的延伸方向与第二方向Y平行，第二电极指142b从第二汇流条142a向第一汇流条141a凸出，多个第二电极指142b沿第二汇流条142a延伸方向(第一方向X)依次排布，多个第二电极指142b与第二汇流条142a耦接。第一方向X与第二方向Y相交。其中，本申请实施例中的平行包括近似平行，工艺误差(例如±5°)范围内的偏差均属于本申请实施例中的平行。
其中，多个第一电极指141b和多个第二电极指142b，在第一汇流条141a和第二汇流条142a之间沿第一方向X依次交替排布，第一电极指141b和第二电极指142b之间不接触。
上述“多个第一电极指141b和多个第二电极指142b，在第一汇流条141a和第二汇流条142a之间沿第一方向X依次交替排布”指的是：在第一汇流条141a和第二汇流条142a之间，每两个第一电极指141b之间设有一个第二电极指142b、每两个第二电极指142b之间设有一个第一电极指141b。
对于叉指换能器140中第一电极指141b的数量和第二电极指142b的数量不进行限定，可以根据需要进行设置。多个第一电极指141b可以是等间距排布，也可以是非等间距排布。同样的，多个第二电极指142b可以是等间距排布，也可以是非等间距排布。以第一电极指141b为例，多个第一电极指141b非等间距排布指的是至少一对相邻的第一电极指141b之间的间距与另一对相邻的第一电极指141b之间的间距不相同。
此外，多个第一电极指141b和多个第二电极指142b依次交替排布，可以是相邻第一电极指141b和第二电极指142b之间的间距均相同；也可以是多对相邻的第一电极指141b和第二电极指142b之间的间距不完全相同，即至少一对相邻的第一电极指141b和第二电极指142b之间的间距与另一对相邻的第一电极指141b和第二电极指142b之间的间距不相同。
在一些实施例中，相邻第一电极指141b和第二电极指142b之间的间距为2μm-10μm。
示例的，相邻第一电极指141b和第二电极指142b之间的间距为3μm-4μm、4μm-5μm、5μm-6μm、6μm-7μm、7μm-8μm、8μm-9μm或者9μm-10μm。
由于第一电极指141b和第二电极指142b之间的间距直接影响lamb波谐振器100的频率，同时对lamb波谐振器100的带宽也有影响。一般来说间距越大，带宽越大。因此，通过将相邻第一电极指141b和第二电极指142b之间的间距限定在2μm-10μm，可以使lamb波谐振器100工作在第五代移动通信技术(5th generation mobile communication technology，5G)频段，具有较宽的带宽。
在一些实施例中，第一电极指141b的宽度为200nm-1000nm，第二电极指142b的宽度为200nm-1000nm。
示例的，第一电极指141b和第二电极指142b的宽度为200nm-300nm之间、300nm-400nm之间、400nm-500nm之间、500nm-600nm之间、600nm-700nm之间、700nm-800nm之间、800nm-900nm之间或者900nm-1000nm之间。
由于占空比主要影响lamb波谐振器100的带宽，对lamb波谐振器100的频率也有影响。而占空比＝电极指的宽度/(电极指的宽度+电极指之间的间距)，在电极指之间的间距确定的情况下，调整电极指的宽度，可以调整lamb波谐振器100的带宽和频率。因此，通过将相邻第一电 极指141b和第二电极指142b的宽度限定在200nm-1000nm，可以使lamb波谐振器100工作在5G频段，且具有较宽的带宽。
可以理解的是，第一电极指141b和第二电极指142b之间的间距(pitch)、第一电极指141b和第二电极指142b的指条宽度主要受光刻和显影工艺的影响，通过调整第一电极指141b和第二电极指142b之间的间距、第一电极指141b和第二电极指142b的指条宽度，可以改变lamb波谐振器100的谐振频率和带宽，因此可以使得特定频率的电子信号得以通过lamb波谐振器100，而其他频率的电子信号则会被lamb波谐振器100滤除。
需要说明的是，第一汇流条141a、第一电极指141b、第二汇流条142a和第二电极指142b可以同时制作。也可以先制作第一汇流条141a和第一电极指141b，再制作第二汇流条142a和第二电极指142b。或者，先制作第二汇流条142a和第二电极指142b，再制作第一汇流条141a和第一电极指141b。
其中，第一电极指141b和第二电极指142b材料可以包括铝(Al)、铜(Cu)、铂(Pt)、金(Au)、镍(Ni)、钛(Ti)、Ag(银)、铬(Cr)、钼(Mo)、钨(W)、钽(Ta)等的一种或多种。
在一些实施例中，本申请提供的lamb波谐振器100中衬底110为硅衬底。声波反射层120的材料为PI，声波反射层120的厚度为8μm。压电层130的材料为Z切LiNbO3，压电层130的厚度为400nm。第一电极指141b和第二电极指142b材料为Al，第一电极指141b和第二电极指142b的厚度为100nm，第一电极指141b和第二电极指142b的宽度500nm，相邻第一电极指141b和第二电极指142b之间的间距为3μm。
本申请实施例提供的lamb波谐振器100，通过在压电层130靠近衬底110一侧设置声波反射层120，且声波反射层120的声阻抗小于压电层130的声阻抗。这样一来，声波在声波反射层120朝向压电层130的表面会发生反射，反射回压电层130，以达到将声波能量限制在压电层130中的目的。声波反射层120可以通过简易的工艺过程实现，简化了lamb波谐振器100的制备流程，降低了lamb波谐振器100的制备难度。此外，由于本申请提供的lamb波谐振器100中，可以无需在衬底110上形成空气腔。当衬底110上不设置空气腔时，可增强lamb波谐振器100的机械强度，提高lamb波谐振器100的良率。
再者，本申请实施例提供的lamb波谐振器100对一阶反对称(A1)模态、最低阶对称(S0)模态、最低阶(SH0)模态均适用，适用范围广。且能够满足设备对高频率、大带宽谐振器的需求。例如，当需要n77频带(例如，3.3GHz-4.2GHz)、n78频带(例如，3.3GHz-3.8GHz)、n79频带(例如，4.4GHz-5.0GHz)等5G频段中工作频率在450MHz到6000MHz的6G以下频段(sub-6G频段)的滤波器时，可以采用本申请实施例提供的lamb波谐振器100。
在一些实施例中，lamb波谐振器100还包括移频层，移频层用于调整lamb波谐振器100的频率。
在一种实施例中，如图8所示，移频层150设置在压电层130与声波反射层120之间。
在另一种实施例中，如图9所示，移频层150设置在叉指换能器140远离压电层130一侧。
当然，也可以是压电层130下方和叉指换能器140上方均设置有移频层150。
其中，移频层150的材料，例如可以是氮化硅(SiN)、氧化铝(Al2O3)或者氧化硅(SiO2)。
本申请中lamb波谐振器100包括移频层150的情况下，无需改变lamb波谐振器100中其他膜层的结构，通过调整移频层150的厚度，可将lamb波谐振器100的频率调整至需要值。
在一些实施例中，lamb波谐振器100还包括温度补偿层，温度补偿层用于补偿lamb波谐振器100的频率温度系数。
温度补偿层的设置位置与上述移频层150的设置位置相同，示例的，温度补偿层设置在压电层130与声波反射层120之间。或者，温度补偿层设置在叉指换能器140远离压电层130一侧。或者，示例的，压电层130下方和叉指换能器140上方均设置有温度补偿层。
其中，温度补偿层的材料，例如可以是SiO2。
当然，lamb波谐振器100中也可以同时包括移频层150和温度补偿层，移频层150和温度补偿层层叠设置，或者移频层150和温度补偿层设置在压电层130相对的两侧。
本申请中lamb波谐振器100包括温度补偿层的情况下，可通过温度补偿层对lamb波谐振器100进行温度补偿，使得lamb波谐振器100的频率温度系数(TCF)的绝对值下降。
在一些实施例中，如图10所示，lamb波谐振器100还包括声子晶体层160，声子晶体层160设置在衬底110与声波反射层120之间。
声子晶体层160包括声子晶体(phononic crystals)，声子晶体例如为柱状结构。
通过在lamb波谐振器100中设置声子晶体层160，声子晶体层160可对声波进行进一步的限制，对声波反射层120进行声波反射功能的补充，提高lamb波谐振器100的带宽。
当然，lamb波谐振器100中可以同时包括移频层150和声子晶体层160，或者lamb波谐振器100中可以同时包括温度补偿层和声子晶体层160，或者lamb波谐振器100中可以同时包括移频层150、温度补偿层和声子晶体层160。图10中的结构仅为一种示意，不做任何限定。
本申请实施例还提供一种lamb波谐振器100的制备方法，用于制备上述任一种lamb波谐振器100。
示例的，制备lamb波谐振器100时，先在衬底110上直接形成声波反射层120，无需对衬底110进行掏空处理。然后，再形成压电层130和叉指换能器140。
其中，衬底110的表面为平面，不存在被掏后的凹陷断面。可以理解的是，此处的平面是相对而言的，工艺误差范围内的表面高度差属于本申请实施例的平面。
或者，示例的，制备lamb波谐振器100时，还包括对衬底110进行掏空处理的步骤。在这种情况下，形成的衬底110可以如图4A和图4B所示。
以上所述，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何在本申请揭露的技术范围内的变化或替换，都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以所述权利要求的保护范围为准。

Claims (20)

  1. 一种兰姆lamb波谐振器，其特征在于，包括：
    衬底；
    声波反射层，设置在所述衬底的一侧；
    压电层，设置在所述声波反射层远离所述衬底一侧；所述声波反射层朝向所述压电层的表面的声波反射系数为R，0.5≤R≤0.86；
    叉指换能器，设置在所述压电层远离所述衬底一侧。
  2. 根据权利要求1所述的lamb波谐振器，其特征在于，0.55≤R≤0.8。
  3. 根据权利要求1或2所述的lamb波谐振器，其特征在于，所述声波反射层的最小厚度为y，y＝77.75379*R2-173.22328*R+97.70404。
  4. 根据权利要求1或2所述的lamb波谐振器，其特征在于，所述声波反射层的厚度为3.5μm-30μm。
  5. 根据权利要求1-4任一项所述的lamb波谐振器，其特征在于，所述声波反射层的材料为高分子材料。
  6. 根据权利要求5所述的lamb波谐振器，其特征在于，所述声波反射层的材料包括聚酰亚胺、聚二甲基硅氧烷、聚甲基丙烯酸甲酯、聚偏氟乙烯或者聚对苯二甲酸乙二醇酯。
  7. 根据权利要求1-6任一项所述的lamb波谐振器，其特征在于，所述声波反射层为单膜层结构。
  8. 根据权利要求1-7任一项所述的lamb波谐振器，其特征在于，所述压电层的材料的切向为Z切。
  9. 根据权利要求1-8任一项所述的lamb波谐振器，其特征在于，所述压电层的材料的欧拉角为(0，20，0)到(0，40，0)。
  10. 根据权利要求1-9任一项所述的lamb波谐振器，其特征在于，所述lamb波谐振器还包括移频层，所述移频层用于调整所述lamb波谐振器的频率；
    所述移频层设置在所述压电层与所述声波反射层之间；
    和/或，
    所述移频层设置在所述叉指换能器远离所述压电层一侧。
  11. 根据权利要求1-10任一项所述的lamb波谐振器，其特征在于，所述lamb波谐振器还包括温度补偿层，所述温度补偿层用于补偿所述lamb波谐振器的频率温度系数；
    所述温度补偿层设置在所述压电层与所述声波反射层之间；
    和/或，
    所述温度补偿层设置在所述叉指换能器远离所述压电层一侧。
  12. 根据权利要求1-11任一项所述的lamb波谐振器，其特征在于，所述压电层的厚度为0.2μm-1μm。
  13. 根据权利要求1-12任一项所述的lamb波谐振器，其特征在于，所述叉指换能器包括多个第一电极指和多个第二电极指，所述多个第一电极指和所述多个第二电极指依次交替排布；
    所述第一电极指和所述第二电极指的宽度为200nm-1000nm，和/或，相邻所述第一电极指和所述第二电极指之间的间距为2μm-10μm。
  14. 根据权利要求1-13任一项所述的lamb波谐振器，其特征在于，所述衬底与所述声波反射层之间还设置有声子晶体层。
  15. 根据权利要求1-14任一项所述的lamb波谐振器，其特征在于，所述衬底朝向所述声波反射层的表面为平面。
  16. 根据权利要求1-15任一项所述的lamb波谐振器，其特征在于，所述衬底上未设置开口。
  17. 一种滤波器，其特征在于，包括多个级联的lamb波谐振器；其中，所述lamb波谐振器为如权利要求1-16任一项所述的lamb波谐振器。
  18. 一种射频模组，其特征在于，包括滤波器和功率放大器，所述滤波器与所述功率放大器 耦接；所述滤波器为权利要求17所述的滤波器。
  19. 一种电子设备，其特征在于，包括滤波器和电路板，所述滤波器设置在所述电路板上；所述滤波器为权利要求17所述的滤波器。
  20. 一种lamb波谐振器的制备方法，其特征在于，用于制备权利要求1-16任一项所述的lamb波谐振器。
PCT/CN2023/112621 2022-08-27 2023-08-11 兰姆波谐振器及制备方法、滤波器、射频模组、电子设备 WO2024046095A1 (zh)

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CN103269209A (zh) * 2013-04-19 2013-08-28 山东科技大学 一种具有锯齿状内侧边缘电极的薄膜体声波谐振器
US20190181830A1 (en) * 2017-12-12 2019-06-13 Ii-Vi Incorporated Acoustic Resonator
CN110572135A (zh) * 2019-09-17 2019-12-13 中国科学院上海微系统与信息技术研究所 高频声波谐振器及其制备方法
CN113328723A (zh) * 2021-06-16 2021-08-31 中国科学院上海微系统与信息技术研究所 一种弹性波谐振器及其制备方法

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CN103269209A (zh) * 2013-04-19 2013-08-28 山东科技大学 一种具有锯齿状内侧边缘电极的薄膜体声波谐振器
US20190181830A1 (en) * 2017-12-12 2019-06-13 Ii-Vi Incorporated Acoustic Resonator
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