Surface acoustic wave resonator, filter, radio frequency front-end module and electronic device

Abstract

Embodiments of the present application relate to the technical field of radio frequency, and provide a surface acoustic wave (SAW) resonator, a filter, a radio frequency front-end module and an electronic device, for use in improving the suppression effect on spurious modes in SAW filters. The SAW resonator comprises a substrate, and a low acoustic velocity layer, a first high acoustic velocity layer, a piezoelectric layer and interdigital electrodes which are arranged on the same side of the substrate. The material of the piezoelectric layer comprises LiNbO3 single crystal. The first high acoustic velocity layer is arranged on the side of the low acoustic velocity layer away from the substrate, the piezoelectric layer is arranged on the side of the first high acoustic velocity layer away from the substrate, and the interdigital electrodes are arranged on the side of the piezoelectric layer away from the substrate. By arranging the first high acoustic velocity layer between the low acoustic velocity layer and the piezoelectric layer, the strength of a Rayleigh mode on the low-frequency side of a main mode in the SAW resonator can be effectively suppressed.

Description

Surface acoustic wave resonators, filters, RF front-end modules, electronic devices

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on February 1, 2024, with application number 202410146507.1 and invention name “Surface acoustic wave resonator, filter, RF front-end module, electronic device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of radio frequency technology, and in particular to a surface acoustic wave resonator, a filter, a radio frequency front-end module, and an electronic device. Background Art

[0003] With the explosive growth of mobile data, the communications industry is moving towards fifth-generation mobile communication technology (5G). This requires RF front-end filters to have higher frequencies, wider bandwidths, and stronger power tolerance. Currently, RF front-end filters primarily fall into two categories: surface acoustic wave (SAW) filters and bulk acoustic wave (BAW) filters. SAW filters are effective in suppressing high-order harmonics, image information, transmission leakage signals, and various parasitic interference in electronic devices.

[0004] As the fourth generation mobile communication technology (4G) and the fifth generation mobile communication technology (5G) use higher frequency carrier frequencies to achieve large bandwidth and low latency communications, the industry urgently needs surface acoustic wave filters with higher frequencies, higher quality factors, and low or no spurious modes.

[0005] Summary of the Invention

[0006] The embodiments of the present application provide a surface acoustic wave resonator, a filter, a radio frequency front-end module, and an electronic device for improving the suppression effect of heterodyne modes in a SAW filter.

[0007] To achieve the above objectives, this application adopts the following technical solutions:

[0008] According to a first aspect of an embodiment of the present application, a surface acoustic wave resonator is provided, comprising: a substrate, and a low acoustic velocity layer, a first high acoustic velocity layer, a piezoelectric layer, and interdigital electrodes (IDE) disposed on the same side of the substrate. The piezoelectric layer is made of a lithium niobate (LiNbO3, LN) single crystal. The low acoustic velocity layer is disposed on one side of the substrate, the first high acoustic velocity layer is disposed on the side of the low acoustic velocity layer away from the substrate, the piezoelectric layer is disposed on the side of the first high acoustic velocity layer away from the substrate, and the interdigital electrodes are disposed on the side of the piezoelectric layer away from the substrate. The horizontal shear surface wave velocity of the piezoelectric layer material is greater than the horizontal shear bulk acoustic wave velocity of the low acoustic velocity layer material, and the horizontal shear surface wave velocity of the piezoelectric layer material is less than the horizontal shear bulk acoustic wave velocity of the first high acoustic velocity layer material. The horizontal shear bulk acoustic wave velocity refers to the propagation velocity of a surface wave with a vibration direction in the shear direction in the direction of arrangement of the interdigital electrodes. The horizontal shear bulk acoustic wave velocity refers to the propagation velocity of a bulk acoustic wave with a vibration direction in the shear direction in the direction of arrangement of the interdigital electrodes. The shear direction is perpendicular to the thickness direction of the surface acoustic wave resonator and the arrangement direction of the interdigital electrodes.

[0009] When the piezoelectric layer in a surface acoustic wave resonator is made of LiNbO3 single crystal, hybrid modes such as the Rayleigh mode typically exist on the low-frequency side of the main mode. By providing a first high-acoustic-velocity layer between the low-acoustic-velocity layer and the piezoelectric layer, the first high-acoustic-velocity layer enhances the acoustic velocity of the Rayleigh mode more effectively than the main mode, as the Rayleigh mode is distributed deeper through the thickness of the surface acoustic wave resonator than the main mode. This reduces the frequency spacing between the Rayleigh and main modes, leading to acoustic coupling between the Rayleigh and main modes and effectively suppressing the intensity of the Rayleigh mode on the low-frequency side of the main mode in the surface acoustic wave resonator.

[0010] In one possible implementation, the thickness h1 of the first high-acoustic-velocity layer is 0.1λ to λ, where λ is the wavelength of a surface acoustic wave. By limiting the thickness of the first high-acoustic-velocity layer to 0.1λ to λ, the spurious modes (Rayleigh modes) on the low-frequency side of the main mode can be effectively suppressed. If the thickness of the first high-acoustic-velocity layer is too thin, even after the low-acoustic-velocity layer and the first high-acoustic-velocity layer are stacked, the suppression effect on the Rayleigh mode may not be ideal.

[0011] In a possible implementation, the thickness h1 of the first high acoustic velocity layer satisfies:

[0012] V is the horizontal shear bulk acoustic wave velocity of the material of the first high-acoustic-velocity layer, h2 is the thickness of the interdigital electrodes, h3 is the thickness of the piezoelectric layer, and h4 is the thickness of the low-acoustic-velocity layer. This almost completely suppresses the spurious modes (Rayleigh modes) on the low-frequency side of the main mode, resulting in superior surface acoustic wave filter performance.

[0013] In one possible implementation, the surface acoustic wave resonator further includes a second, high-acoustic-velocity layer disposed on the substrate-side of the low-acoustic-velocity layer. The horizontal shear bulk acoustic wave velocity of the material of the second, high-acoustic-velocity layer is greater than the horizontal shear bulk acoustic wave velocity of the material of the low-acoustic-velocity layer. By disposing the second, high-acoustic-velocity layer on the substrate-side of the low-acoustic-velocity layer, acoustic waves are prevented from leaking to the substrate-side of the second, high-acoustic-velocity layer. The waves are instead confined within the space between the stacked piezoelectric layer and the low-acoustic-velocity layer, allowing for repeated use and reducing Q loss.

[0014] In one possible implementation, the material of the first high acoustic velocity layer includes at least one of silicon nitride, polysilicon, silicon carbide, and silicon oxynitride, which is a technically mature material selection.

[0015] In one possible implementation, the thickness h4 of the low-acoustic-velocity layer is 0.1λ to λ, where λ is the wavelength of the surface acoustic wave. By limiting the thickness of the low-acoustic-velocity layer to 0.1λ to λ, the spurious modes (Rayleigh modes) on the low-frequency side of the main mode can be effectively suppressed. If the low-acoustic-velocity layer is too thin, even after stacking the low-acoustic-velocity layer with the first high-acoustic-velocity layer, the suppression effect on the Rayleigh mode may not be ideal.

[0016] In one possible implementation, the thickness h3 of the piezoelectric layer is 0.1λ to 0.5λ, where λ is the wavelength of the surface acoustic wave. By limiting the thickness of the piezoelectric layer to 0.1λ to 0.5λ, the spurious mode (Rayleigh mode) on the low-frequency side of the main mode can be effectively suppressed.

[0017] In one possible implementation, the thickness h2 of the interdigital electrodes is 0.05λ to 0.1λ, where λ is the wavelength of the surface acoustic wave. By limiting the thickness of the interdigital electrodes to 0.05λ to 0.1λ, the spurious modes (Rayleigh modes) on the low-frequency side of the main mode can be effectively suppressed.

[0018] In one possible implementation, the thickness h5 of the second high-acoustic-velocity layer is 0.1λ to λ, where λ is the wavelength of the surface acoustic wave. By limiting the thickness of the second high-acoustic-velocity layer to 0.1λ to λ, the spurious mode (Rayleigh mode) on the low-frequency side of the main mode can be effectively suppressed.

[0019] According to a second aspect of the embodiments of the present application, a filter is provided, comprising a plurality of cascaded surface acoustic wave resonators; wherein the surface acoustic wave resonator comprises the surface acoustic wave resonator of any one of the first aspects.

[0020] The filter provided in the second aspect of the embodiment of the present application includes the surface acoustic wave resonator in the first aspect, and its beneficial effects are the same as those of the surface acoustic wave resonator, which will not be repeated here.

[0021] According to a third aspect of an embodiment of the present application, a radio frequency front-end module is provided. The radio frequency front-end module includes a filter and an amplifier, wherein the filter is coupled to the amplifier; the filter includes the filter of the second aspect.

[0022] The RF front-end module provided in the third aspect of the embodiment of the present application includes the filter in the second aspect, and its beneficial effects are the same as those of the filter, which will not be repeated here.

[0023] According to a fourth aspect of the embodiments of the present application, an electronic device is provided. The electronic device includes a filter and a circuit board, where the filter is arranged on the circuit board; the filter includes the filter according to the second aspect.

[0024] The electronic device provided in the fourth aspect of the embodiment of the present application includes the filter in the second aspect, and its beneficial effects are the same as those of the filter, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG1 is a schematic structural diagram of an electronic device provided in an embodiment of the present application;

[0026] FIG2 is a schematic structural diagram of an RF front-end module provided in an embodiment of the present application;

[0027] FIG3 is a topological diagram of a filter provided in an embodiment of the present application;

[0028] FIG4 is a schematic structural diagram of a surface acoustic wave resonator provided in an embodiment of the present application;

[0029] FIG5 is an admittance curve diagram of a surface acoustic wave resonator provided in an embodiment of the present application;

[0030] FIG6 is a schematic structural diagram of a surface acoustic wave resonator provided in an embodiment of the present application;

[0031] FIG7 is an admittance curve diagram of a surface acoustic wave resonator provided in an embodiment of the present application;

[0032] FIG8 is an admittance curve diagram of a surface acoustic wave resonator provided in an embodiment of the present application;

[0033] FIG9 is a schematic structural diagram of a surface acoustic wave resonator provided in an embodiment of the present application;

[0034] FIG10 is a top view of an interdigitated electrode provided in an embodiment of the present application. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0036] Hereinafter, the terms "second," "first," etc., are used for descriptive convenience only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature qualified as "second," "first," etc., may explicitly or implicitly include one or more of such features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0037] In addition, in the embodiments of the present application, directional terms such as "up", "down", "left", and "right" may be defined including but not limited to the orientation relative to the schematic placement of the components in the drawings. It should be understood that these directional terms may be relative concepts, which are used for relative descriptions and clarifications, and may change accordingly according to changes in the orientation of the components in the drawings.

[0038] In the embodiments of this application, unless otherwise specified or limited, the term "connection" should be understood in a broad sense. For example, "connection" can mean fixed connection, detachable connection, or integration; it can mean direct connection or indirect connection through an intermediate medium. In addition, the term "coupling" can mean direct electrical connection or indirect electrical connection through an intermediate medium. The term "contact" can mean direct contact or indirect contact through an intermediate medium.

[0039] In the embodiments of the present application, "and / or" describes the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0040] The technical solution of the present application can be applied to various electronic devices containing power amplifiers. The electronic device can be deployed on land, including indoors or outdoors, handheld or vehicle-mounted. It can also be deployed on water (such as on ships, etc.). It can also be deployed in the air (for example, on aircraft, balloons, and satellites). For example, the channel device can be a terminal or a base station. For example, the terminal includes but is not limited to: mobile phones, tablet computers, laptops, PDAs, mobile internet devices (MIDs), wearable devices (such as smart watches, smart bracelets, pedometers, etc.), vehicle-mounted equipment (such as cars, bicycles, electric vehicles, airplanes, ships, trains, high-speed railways, etc.), virtual reality (VR) equipment, augmented reality (AR) equipment, wireless terminals in industrial control, smart home devices (such as refrigerators, televisions, air conditioners, electricity meters, etc.), intelligent robots, workshop equipment, wireless terminals in self-driving, wireless terminals in remote medical surgery, wireless terminals in smart grids, wireless terminals in transportation safety, wireless terminals in smart cities, or wireless terminals in smart homes, flight equipment (such as intelligent robots, hot air balloons, drones, airplanes), RF front-end modules, etc.

[0041] Figure 1 is a schematic diagram of the structure of an electronic device provided in an embodiment of the present application, using a mobile phone as an example. The electronic device includes a radio frequency (RF) front-end module 101, a memory 102, a processor 103, a sensor component 104, a multimedia component 105, a power supply component 106, and an input / output interface 107.

[0042] The following is a detailed introduction to the various components of the mobile phone in conjunction with Figure 1:

[0043] The RF front-end module 101 may be used to receive and send signals during information transmission or calls. In particular, it receives downlink information from the electronic device and sends it to the processor 103 for processing, and sends uplink data to the electronic device.

[0044] The memory 102 may be used to store data, software programs, and modules. The mobile phone may include high-speed random access memory and non-volatile memory, such as at least one disk storage device, flash memory device, or other volatile solid-state storage device.

[0045] The processor 103 is the control center of the mobile phone. It uses various interfaces and lines to connect various parts of the entire device. By running or executing software programs and / or modules stored in the memory 102 and calling data stored in the memory 102, it performs various functions of the mobile phone and processes data, thereby performing overall control of the mobile phone.

[0046] Sensor assembly 104 includes one or more sensors for assessing various aspects of the phone's status. Sensor assembly 104 may include an accelerometer, a gyroscope, a magnetic sensor, a pressure sensor, or a temperature sensor. Sensor assembly 104 can detect the phone's acceleration / deceleration, orientation, open / closed state, relative positioning of components, or temperature changes. Sensor assembly 104 may also include an optical sensor, such as a CMOS or CCD image sensor, for use in imaging applications.

[0047] The multimedia component 105 provides a screen as an output interface between the mobile phone and the user. The screen may be a touch panel, and when the screen is a touch panel, the screen may be implemented as a touch screen to receive input signals from the user. In addition, the multimedia component 105 also includes at least one camera, for example, the multimedia component 105 includes a front camera and / or a rear camera.

[0048] The power supply component 106 is used to provide power to various components of the mobile phone. The power supply component 106 may include a power management system, one or more power supplies, and other components associated with generating, managing, and distributing power to the mobile phone.

[0049] The input / output interface 107 provides an interface between the processor 103 and a peripheral interface module, for example, the peripheral interface module may be a keyboard, a mouse, etc.

[0050] Although not shown, the mobile phone may further include an audio component and a communication module, for example, the audio component includes a microphone and a speaker, and the communication module may include one or more of a wireless fidelity (WiFi) module, a Bluetooth module, a near field communication (NFC) module, a global navigation satellite system (GNSS) module, or a frequency modulation (FM) module, which will not be described in detail in the embodiments of the present application. Those skilled in the art will understand that the mobile phone structure shown in FIG1 does not constitute a limitation on the mobile phone, and may include more or fewer components than shown, or combine certain components, or arrange the components differently.

[0051] FIG2 is a schematic structural diagram of an RF front-end module provided in an embodiment of the present application.

[0052] Typically, the RF front-end module 101 includes, but is not limited to, a radio frequency switch, a duplexer, a filter, a power amplifier (PA), a low noise amplifier (LNA), etc. For example, as shown in FIG2 , the RF front-end module 101 may include: a radio frequency switch, a duplexer, a filter, a PA, and an LNA.

[0053] The RF front-end module 101 may include a transmitting channel and a receiving channel. The transmitting channel includes a PA and a transmitting channel filter. The RF output end of the PA is coupled to the input end of the transmitting channel filter. The receiving channel includes an LNA and a receiving channel filter. The output end of the receiving channel filter is coupled to the RF input end of the LNA.

[0054] The duplexer is responsible for duplex switching of the frequency division duplex system and filtering of RF signals in the receiving channel / transmitting channel, while the RF switch is responsible for switching between the receiving channel and the transmitting channel.

[0055] The baseband signal is transmitted by the transceiver to the transmit channel, which amplifies the received RF signal and outputs it to the antenna for transmission. The PA amplifies the RF signal in the transmit channel, while the transmit channel filter filters it.

[0056] It should be explained that when an electronic device includes multiple antennas, one antenna may correspond to one PA, one antenna may correspond to multiple PAs, or multiple antennas may share one PA. The application scenarios in the relevant technologies are all applicable to the embodiments of this application.

[0057] The receive channel receives the RF signal from the antenna, amplifies it, and transmits it to the baseband through the transceiver. The LNA amplifies the RF signal, while the receive channel filter filters it.

[0058] As 4th and 5th generation mobile communication technologies (4G and 5G) utilize higher-frequency carrier frequencies to achieve wide-bandwidth, low-latency communications, the industry urgently needs surface acoustic wave filters with higher frequencies, higher quality factors, and low or no spurious modes. Carrier aggregation technology requires simultaneous operation of signal paths in different frequency bands, a characteristic that demands filters with excellent stopband rejection performance.

[0059] The embodiments of the present application provide a filter that can be applied to the electronic device 1 described above, for example, in the RF front-end module 101 of the electronic device 1, where the filter is coupled to an amplifier for signal processing and transmission. Alternatively, the filter can be directly disposed on the circuit board of the electronic device 1. The embodiments of the present application do not limit the form of the filter in the electronic device 1.

[0060] The filter provided in the embodiment of the present application may be, for example, a low-pass filter, a high-pass filter, a band-pass filter, a band-stop filter, or an active filter. The filter provided in the embodiment of the present application is not limited to application in the electronic device 1 described above. The filter may also be applied to fields such as sensing and detection. Filters in electronic devices in related technologies may be replaced by the filter provided in the embodiment of the present application.

[0061] Of course, the filter provided in 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 components such as a power amplifier into a module (such as a radio frequency device, a radio frequency front-end module, a filter module, etc.).

[0062] FIG3 is a topological diagram of a filter provided in an embodiment of the present application.

[0063] In some embodiments, as shown in FIG3 , a filter 100 includes a plurality of cascaded surface acoustic wave (SAW) resonators 10. These plurality of SAW resonators 10 may have different resonant frequencies and may be cascaded together in series and parallel configurations. FIG3 also illustrates a signal input terminal Vi, a signal output terminal Vo, and a ground terminal GND of the filter 100.

[0064] The performance of the surface acoustic wave resonator 10 directly affects the performance of the filter 100 . The structure of the surface acoustic wave resonator 10 provided in the embodiment of the present application is schematically described below.

[0065] FIG4 is a schematic structural diagram of a surface acoustic wave resonator provided in an embodiment of the present application.

[0066] In some embodiments, as shown in FIG. 4 , a surface acoustic wave resonator 10 includes a substrate 11 and a high acoustic velocity layer 12 , a low acoustic velocity layer 13 , a piezoelectric layer 14 , and interdigital electrodes (IDE) sequentially disposed on the substrate 11 .

[0067] The surface acoustic wave resonator 10 shown in FIG4 utilizes a sequentially arranged layered structure to obtain a high-quality factor (Q) and high-performance surface acoustic wave resonator 10 . This structure is named an incredible high performance (IHP) structure in the art.

[0068] FIG5 is an admittance curve diagram of a surface acoustic wave resonator provided in an embodiment of the present application.

[0069] When the piezoelectric layer 14 in the surface acoustic wave resonator 10 shown in FIG4 is made of lithium niobate (LiNbO3, LN) single crystal, the surface acoustic wave resonator 10 can provide a wide bandwidth. In FIG5 , the horizontal axis represents frequency, the vertical axis represents admittance, and the two curves represent the modulus and real part of the admittance curve, respectively. The admittance curve in FIG5 , obtained through simulation, reveals the presence of a spurious mode (Rayleigh mode) on the low-frequency side of the main surface acoustic wave mode. When such a surface acoustic wave resonator 10 is used to form a filter 100, the Rayleigh mode can degrade the insertion loss or out-of-band suppression of the filter 100.

[0070] The embodiment of the present application further provides a surface acoustic wave resonator 10 for reducing the intensity of the Rayleigh mode on the low-frequency side of the main mode.

[0071] FIG6 is a schematic structural diagram of a surface acoustic wave resonator provided in an embodiment of the present application.

[0072] An embodiment of the present application provides a surface acoustic wave resonator 10. As shown in FIG6 , the surface acoustic wave resonator 10 includes a substrate 11 and a low acoustic velocity layer 13, a first high acoustic velocity layer 15, a piezoelectric layer 14, and interdigital electrodes IDE arranged on one side of the substrate 11.

[0073] The first high acoustic velocity layer 15 is disposed on a side of the low acoustic velocity layer 13 away from the substrate 11. For example, the first high acoustic velocity layer 15 is disposed on a surface of the low acoustic velocity layer 13 away from the substrate 11. The piezoelectric layer 14 is disposed on a side of the first high acoustic velocity layer 15 away from the substrate 11. For example, the piezoelectric layer 14 is disposed on a surface of the first high acoustic velocity layer 15 away from the substrate 11. The interdigital electrode IDE is disposed on a side of the piezoelectric layer 14 away from the substrate 11. For example, the interdigital electrode IDE is disposed on a surface of the piezoelectric layer 14 away from the substrate 11. In the surface acoustic wave resonator 10 provided in the embodiment of the present application, the first high acoustic velocity layer 15 is disposed between the low acoustic velocity layer 13 and the piezoelectric layer 14.

[0074] The material of the substrate 11 may include, for example, glass, silicon (Si), aluminum oxide (Al2O3), silicon carbide (SiC), etc. The thickness of the substrate 11 may be, for example, 100 μm to 1000 μm. For example, the thickness of the substrate 11 may be 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, or 1000 μm.

[0075] In the embodiment of the present application, the first high acoustic velocity layer 15 refers to a membrane layer in which the acoustic velocity of the bulk waves in the first high acoustic velocity layer 15 is higher than that of the surface waves propagating in the piezoelectric layer 14. The low acoustic velocity layer 13 refers to a membrane layer in which the acoustic velocity of the bulk waves in the low acoustic velocity layer 13 is lower than that of the surface waves propagating in the piezoelectric layer 14.

[0076] For example, the material of the piezoelectric layer 14 includes LiNbO3 single crystal. The low acoustic velocity layer 13 and the first high acoustic velocity layer 15 are made of appropriate dielectric materials that can achieve the high acoustic velocity and low acoustic velocity determined above.

[0077] In some embodiments, when selecting the material of the low acoustic velocity layer 13 , the horizontal shear surface wave velocity of the material of the piezoelectric layer 14 is greater than the horizontal shear bulk acoustic wave velocity of the material of the low acoustic velocity layer 13 .

[0078] The horizontal shear bulk acoustic wave velocity refers to the propagation velocity of a surface wave with a vibration direction in the shear direction (the second direction Y in FIG6 ) in the arrangement direction of the interdigital electrodes IDE (the first direction X in FIG6 ). The horizontal shear bulk acoustic wave velocity refers to the propagation velocity of a bulk acoustic wave with a vibration direction in the shear direction in the arrangement direction of the interdigital electrodes IDE. The shear direction is perpendicular to the thickness direction of the surface acoustic wave resonator 10 (the third direction Z in FIG6 ) and the arrangement direction of the interdigital electrodes IDE.

[0079] For example, the material of the low acoustic velocity layer 13 includes silicon dioxide (SiO2), a compound of SiO2 with fluorine (F), carbon (C), or boron (B), silicon oxynitride (SiO x N y), at least one of tantalum oxide (Ta2O5).

[0080] In some embodiments, when selecting the material of the first high acoustic velocity layer 15 , the horizontal shear surface wave velocity of the material of the piezoelectric layer 14 is smaller than the horizontal shear bulk acoustic wave velocity of the material of the first high acoustic velocity layer 15 .

[0081] For example, the material of the first high acoustic velocity layer 15 is at least one of silicon nitride (Si 3 N 4 ), polysilicon, SiC, and silicon oxynitride.

[0082] When the piezoelectric layer in a surface acoustic wave resonator is made of lithium niobate single crystal, a Rayleigh mode or other heterogeneous modes typically exist on the low-frequency side of the main mode. In the embodiment of the present application, by providing a first high-acoustic-velocity layer 15 between the low-acoustic-velocity layer 13 and the piezoelectric layer 14, the first high-acoustic-velocity layer 15 has a better acoustic-velocity-enhancing effect on the Rayleigh mode than on the main mode, because the Rayleigh mode is distributed deeper in the thickness direction of the surface acoustic wave resonator 10 than the main mode. This reduces the frequency spacing between the Rayleigh mode and the main mode, thereby coupling the Rayleigh mode and the main mode, effectively suppressing the intensity of the Rayleigh mode on the low-frequency side of the main mode in the surface acoustic wave resonator 10.

[0083] In some embodiments, the thickness h1 of the first high acoustic velocity layer 15 is 0.1λ~λ. For example, the thickness h1 of the first high acoustic velocity layer 15 is 0.1λ, 0.2λ, 0.3λ, 0.4λ, 0.5λ, 0.6λ, 0.7λ, 0.8λ, 0.9λ or λ.

[0084] By limiting the thickness h1 of the first high-acoustic-velocity layer 15 to 0.1λ~λ, the heterodyne mode (Rayleigh mode) on the low-frequency side of the main mode can be better suppressed. If the thickness h1 of the first high-acoustic-velocity layer 15 is too thin, even if the low-acoustic-velocity layer 13 and the first high-acoustic-velocity layer 15 are stacked, the suppression effect on the Rayleigh mode may not be ideal.

[0085] In some embodiments, the thickness h4 of the low acoustic velocity layer 13 is 0.1λ to λ. For example, the thickness h4 of the low acoustic velocity layer 13 is 0.1λ, 0.2λ, 0.3λ, 0.4λ, 0.5λ, 0.6λ, 0.7λ, 0.8λ, 0.9λ or λ.

[0086] By limiting the thickness h4 of the low-acoustic-velocity layer 13 to 0.1λ~λ, the heterodyne mode (Rayleigh mode) on the low-frequency side of the main mode can be better suppressed. If the thickness of the low-acoustic-velocity layer is too thin, even if the low-acoustic-velocity layer is stacked with the first high-acoustic-velocity layer, the suppression effect on the Rayleigh mode may not be ideal.

[0087] In some embodiments, the thickness h3 of the piezoelectric layer 14 is 0.1λ to 0.5λ. For example, the thickness h3 of the piezoelectric layer 14 is 0.1λ, 0.2λ, 0.3λ, 0.4λ, or 0.5λ.

[0088] By limiting the thickness h3 of the piezoelectric layer 14 to 0.1λ to 0.5λ, the spurious modes (Rayleigh modes) on the low-frequency side of the main mode can be effectively suppressed. Furthermore, the thickness of the piezoelectric layer 14 is directly related to the frequency of the surface acoustic wave resonator 10: the thinner the piezoelectric layer 14, the higher the frequency of the surface acoustic wave resonator 10. By limiting the thickness of the piezoelectric layer 14 to 0.1λ to 0.5λ, the surface acoustic wave resonator 10 can be used in high-frequency applications, such as above 3.3 GHz.

[0089] In some embodiments, the thickness h2 of the interdigital electrode IDE is 0.05λ to 0.1λ. For example, the thickness h2 of the interdigital electrode IDE is 0.05λ, 0.06λ, 0.07λ, 0.08λ, 0.09λ or 0.1λ.

[0090] By limiting the thickness h2 of the interdigital electrode IDE to 0.05λ to 0.1λ, the spurious mode (Rayleigh mode) on the low-frequency side of the main mode can be effectively suppressed.

[0091] FIG7 is an admittance curve diagram of a surface acoustic wave resonator provided in an embodiment of the present application.

[0092] For example, the wavelength λ of the surface acoustic wave is set to 1200 μm, the thickness h2 of the interdigital electrode IDE is set to 15.8% λ, and the material of the interdigital electrode IDE is aluminum (Al). The thickness h3 of the piezoelectric layer 14 is set to 25% λ, and the material of the piezoelectric layer 14 is LiNbO3 single crystal. The thickness h4 of the low acoustic velocity layer 13 is set to 60% λ, and the material of the low acoustic velocity layer 13 is silicon dioxide. The thickness h1 of the first high acoustic velocity layer 15 is set to 8.3% λ, and the material of the first high acoustic velocity layer 15 is silicon nitride. The horizontal shear bulk acoustic wave velocity V of the first high acoustic velocity layer 15 is 5725 m / s. The thickness h5 of the second high acoustic velocity layer 16 is set to 83% λ, and the material of the second high acoustic velocity layer 16 is polycrystalline silicon. The thickness of the substrate 11 is set to 100 μm, and the material of the substrate 11 is single crystal silicon. The simulated admittance curve of the surface acoustic wave resonator 10 is shown in FIG7 . Comparing FIG7 with FIG5 , it can be seen from the simulation results that the spurious mode (Rayleigh mode) on the low-frequency side of the main mode has been successfully suppressed.

[0093] FIG8 is an admittance curve diagram of a surface acoustic wave resonator provided in an embodiment of the present application.

[0094] When the thickness h1 of the first high acoustic velocity layer 15 is changed to 12.5%λ and other parameters remain unchanged, the simulated admittance curve of the surface acoustic wave resonator 10 is shown in FIG8 . In the real part, a strong spurious mode (Rayleigh mode) is generated on the high-frequency side of the main mode.

[0095] In some embodiments, the thickness h1 of the first high acoustic velocity layer 15 satisfies:

[0096] Wherein, V is the horizontal shear bulk acoustic wave velocity of the material of the first high acoustic velocity layer 15 , h2 is the thickness of the interdigital electrode IDE, h3 is the thickness of the piezoelectric layer 14 , and h4 is the thickness of the low acoustic velocity layer 13 .

[0097] In the embodiment of the present application, the thickness can be understood as the dimension in the direction perpendicular to the substrate 11 , or the dimension in the stacking direction of the low acoustic velocity layer 13 and the first high acoustic velocity layer 15 .

[0098] The thickness of each film layer in the surface acoustic wave resonator 10 that obtains the admittance curve shown in Figure 7 satisfies the above formula. As can be seen from Figure 7, the spurious mode (Rayleigh mode) on the low-frequency side of the main mode is almost completely suppressed, and the performance of the surface acoustic wave resonator 10 is relatively good.

[0099] In the embodiment of the present application, the interdigitated electrode IDE can be understood as a metal pattern formed on the surface of the piezoelectric layer 14 in a shape like the crossed fingers of two hands, and its function is to realize acoustic-electrical transduction.

[0100] FIG9 is a schematic structural diagram of a surface acoustic wave resonator provided in an embodiment of the present application.

[0101] 9 , the SAW resonator 10 further includes a second high acoustic velocity layer 16 . The second high acoustic velocity layer 16 is disposed on the side of the low acoustic velocity layer 13 close to the substrate 11 . For example, the second high acoustic velocity layer 16 is disposed on the surface of the low acoustic velocity layer 13 close to the substrate 11 .

[0102] In some embodiments, the material of the second high acoustic velocity layer 16 is selected so that the horizontal shear bulk acoustic wave velocity of the material of the second high acoustic velocity layer 16 is greater than the horizontal shear bulk acoustic wave velocity of the material of the low acoustic velocity layer 13. For example, the material of the second high acoustic velocity layer 16 is at least one of silicon nitride (Si3N4), polysilicon, SiC, and silicon oxynitride.

[0103] The material of the first high-acoustic-velocity layer 15 and the material of the second high-acoustic-velocity layer 16 may be the same or different.

[0104] By setting a second high acoustic velocity layer 16 on the side of the low acoustic velocity layer 13 close to the substrate 11, the sound waves can be prevented from leaking to the side of the second high acoustic velocity layer 16 close to the substrate 11, and the surface acoustic waves can be sealed in the space where the piezoelectric layer 14 and the low acoustic velocity layer 13 are stacked, and reused, thereby reducing the loss of Q value.

[0105] In some embodiments, the thickness h5 of the second high acoustic velocity layer 16 is 0.1λ to λ. For example, the thickness h5 of the second high acoustic velocity layer 16 is 0.1λ, 0.2λ, 0.3λ, 0.4λ, 0.5λ, 0.6λ, 0.7λ, 0.8λ, 0.9λ or λ.

[0106] The thickness h1 of the first high-acoustic-velocity layer 15 may be the same as or different from the thickness h5 of the second high-acoustic-velocity layer 16. By adjusting the thickness h5 of the second high-acoustic-velocity layer 16, the Q value may be adjusted to meet different requirements.

[0107] FIG10 is a top view of an interdigitated electrode provided in an embodiment of the present application.

[0108] In one embodiment, as shown in FIG10 , the interdigitated electrode IDE includes a first busbar 171a and a second busbar 172a disposed opposite each other, a plurality of first electrode fingers 171b, and a plurality of second electrode fingers 172b. The first busbar 171a and the second busbar 172a extend in a direction parallel to a first direction X, and the first electrode fingers 171b extend in a direction parallel to a second direction Y. The first electrode fingers 171b protrude from the first busbar 171a toward the second busbar 172a. The plurality of first electrode fingers 171b are arranged sequentially along the extension direction of the first busbar 171a (the first direction X), and the plurality of first electrode fingers 171b are coupled to the first busbar 171a. The extension direction of the second electrode fingers 172b is parallel to the second direction Y. The second electrode fingers 172b protrude from the second bus bar 172a toward the first bus bar 171a. Multiple second electrode fingers 172b are arranged sequentially along the extension direction of the second bus bar 172a (first direction X). The multiple second electrode fingers 172b are coupled to the second bus bar 172a. The first direction X intersects the second direction Y. In this embodiment of the present application, "parallel" includes "approximately parallel." Deviations within the range of process error (e.g., ±5°) are considered parallel in this embodiment of the present application.

[0109] The plurality of first electrode fingers 171 b and the plurality of second electrode fingers 172 b are alternately arranged along the first direction X between the first bus bar 171 a and the second bus bar 172 a , and the first electrode fingers 171 b and the second electrode fingers 172 b do not contact each other.

[0110] The above-mentioned “a plurality of first electrode fingers 171 b and a plurality of second electrode fingers 172 b are alternately arranged in sequence along the first direction X between the first bus bar 171 a and the second bus bar 172 a” means that between the first bus bar 171 a and the second bus bar 172 a , a second electrode finger 172 b is provided between every two first electrode fingers 171 b , and a first electrode finger 171 b is provided between every two second electrode fingers 172 b .

[0111] There is no limit on the number of first electrode fingers 171b and the number of second electrode fingers 172b in the interdigitated electrode 1D and they can be set as needed. The multiple first electrode fingers 171b can be arranged at equal intervals or at non-equal intervals. Similarly, the multiple second electrode fingers 172b can be arranged at equal intervals or at non-equal intervals. Taking the first electrode fingers 171b as an example, the non-equal spacing of the multiple first electrode fingers 171b means that the spacing between at least one pair of adjacent first electrode fingers 171b is different from the spacing between another pair of adjacent first electrode fingers 171b.

[0112] In addition, multiple first electrode fingers 171b and multiple second electrode fingers 172b are arranged alternately in sequence, and the spacing between adjacent first electrode fingers 171b and second electrode fingers 172b can be the same; or the spacing between multiple pairs of adjacent first electrode fingers 171b and second electrode fingers 172b is not exactly the same, that is, the spacing between at least one pair of adjacent first electrode fingers 171b and second electrode fingers 172b is different from the spacing between another pair of adjacent first electrode fingers 171b and second electrode fingers 172b.

[0113] It can be understood that the pitch between the first electrode finger 171b and the second electrode finger 172b and the finger width of the first electrode finger 171b and the second electrode finger 172b are mainly affected by the photolithography and development processes. By adjusting the pitch between the first electrode finger 171b and the second electrode finger 172b and the finger width of the first electrode finger 171b and the second electrode finger 172b, the resonant frequency and bandwidth of the surface acoustic wave resonator 10 can be changed, so that electronic signals of a specific frequency can pass through the surface acoustic wave resonator 10, while electronic signals of other frequencies will be filtered out by the surface acoustic wave resonator 10.

[0114] The distance between the first electrode finger 171 b and the second electrode finger 172 b may be the distance from the center of the first electrode finger 171 b to the center of the second electrode finger 172 b .

[0115] In some embodiments, the materials of the first electrode finger 171b and the second electrode finger 172b may include one or more of aluminum (Al), copper (Cu), platinum (Pt), gold (Au), nickel (Ni), titanium (Ti), Ag (silver), chromium (Cr), molybdenum (Mo), tungsten (W), tantalum (Ta), etc.

[0116] In some embodiments, λ=2*pitch. The wavelength λ of the surface acoustic wave can be determined by the pitch between the first electrode finger 171 b and the second electrode finger 172 b, thereby determining the thickness of each film layer in the surface acoustic wave resonator 10.

[0117] The above are only specific embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any changes or replacements within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A surface acoustic wave resonator, characterized in that: include: substrate; A low acoustic velocity layer is provided on one side of the substrate; a first high sound velocity layer, arranged on a side of the low sound velocity layer away from the substrate; A piezoelectric layer is provided on a side of the first high acoustic velocity layer away from the substrate; the material of the piezoelectric layer comprises lithium niobate single crystal; an interdigitated electrode, disposed on a side of the piezoelectric layer away from the substrate; The horizontal shear surface wave velocity of the material of the piezoelectric layer is greater than the horizontal shear bulk acoustic wave velocity of the material of the low acoustic velocity layer, and less than the horizontal shear bulk acoustic wave velocity of the material of the first high acoustic velocity layer.

2. The surface acoustic wave resonator according to claim 1, wherein The thickness h1 of the first high acoustic velocity layer is in the range of 0.1λ to λ, where λ is the wavelength of the surface acoustic wave.

3. The surface acoustic wave resonator according to claim 2, wherein The thickness h1 of the first high acoustic velocity layer satisfies: V is the horizontal shear bulk acoustic wave velocity of the material of the first high acoustic velocity layer, h2 is the thickness of the interdigital electrode; h3 is the thickness of the piezoelectric layer, and h4 is the thickness of the low acoustic velocity layer.

4. The surface acoustic wave resonator according to any one of claims 1 to 3, characterized in that: The surface acoustic wave resonator also includes a second high acoustic velocity layer; the second high acoustic velocity layer is arranged on the side of the low acoustic velocity layer close to the substrate; the horizontal shear bulk acoustic wave velocity of the material of the second high acoustic velocity layer is greater than the horizontal shear bulk acoustic wave velocity of the material of the low acoustic velocity layer.

5. The surface acoustic wave resonator according to any one of claims 1 to 4, characterized in that: The material of the first high acoustic velocity layer includes at least one of silicon nitride, polysilicon, silicon carbide, and silicon oxynitride.

6. The surface acoustic wave resonator according to any one of claims 1 to 5, characterized in that: The thickness h4 of the low acoustic velocity layer is in the range of 0.1λ to λ, where λ is the wavelength of the surface acoustic wave.

7. The surface acoustic wave resonator according to any one of claims 1 to 6, characterized in that: The thickness h3 of the piezoelectric layer is 0.1λ to 0.5λ, where λ is the wavelength of the surface acoustic wave.

8. The surface acoustic wave resonator according to any one of claims 1 to 7, characterized in that: The thickness h2 of the interdigital electrode is 0.05λ to 0.1λ, where λ is the wavelength of the surface acoustic wave.

9. The surface acoustic wave resonator according to claim 4, characterized in that The thickness h5 of the second high acoustic velocity layer is in the range of 0.1λ to λ, where λ is the wavelength of the surface acoustic wave.

10. A filter, characterized in that: The invention comprises a plurality of cascaded surface acoustic wave resonators; wherein the surface acoustic wave resonator comprises the surface acoustic wave resonator according to any one of claims 1 to 9.

11. A radio frequency front-end module, characterized in that: The invention comprises a filter and an amplifier, wherein the filter is coupled to the amplifier; the filter comprises the filter according to claim 10.

12. An electronic device, characterized in that: The invention comprises a filter and a circuit board, wherein the filter is arranged on the circuit board; the filter comprises the filter according to claim 10.

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