Substrate structure, surface acoustic wave resonator, filter, radio frequency front-end module, and mobile terminal

Abstract

The embodiments of the present application relate to the technical field of radio frequency. Provided are a substrate structure, a surface acoustic wave resonator, a filter, a radio frequency front-end module, and a mobile terminal, which are used for improving the effect of suppressing spurious modes in the filter. The substrate structure comprises a substrate, and a first high-acoustic-velocity layer, a low-acoustic-velocity layer and a piezoelectric layer, which are disposed on one side of the substrate, wherein the first high-acoustic-velocity layer is disposed on one side of the substrate, the low-acoustic-velocity layer is disposed on the side of the first high-acoustic-velocity layer that is away from the substrate, and the piezoelectric layer is disposed on the side of the low-acoustic-velocity layer that is away from the substrate; and among the first high-acoustic-velocity layer, the low-acoustic-velocity layer, the substrate and the piezoelectric layer, both the shear wave acoustic velocity and longitudinal wave acoustic velocity of the material of the first high-acoustic-velocity layer are the maximum, such that the first high-acoustic-velocity layer can achieve the effect of suppressing the vibration amplitude of a high-order spurious mode of each mode by means of changing the acoustic impedance distribution during the propagation of the high-order spurious mode.

Description

Substrate structure, surface acoustic wave resonator, filter, RF front-end module, mobile terminal

[0001] This application claims priority to Chinese patent application filed on June 20, 2024, with application number 202410805838.1 and entitled "Substrate Structure, Surface Acoustic Wave Resonator, Filter, RF Front-End Module, Mobile Terminal", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of radio frequency technology, and in particular to a substrate structure, a surface acoustic wave resonator, a filter, a radio frequency front-end module, and a mobile terminal. Background Technology

[0003] With the explosive growth of mobile data, the communications industry has moved towards 5G, which requires radio frequency (RF) front-end filters to have higher frequencies, larger bandwidths, and stronger power tolerance. Currently, RF front-end filters are mainly divided into two categories: surface acoustic wave (SAW) filters and bulk acoustic wave (BAW) filters. SAW filters play a significant role in suppressing high-order harmonics, image information, transmitted leakage signals, and various parasitic clutter interferences in mobile terminals.

[0004] With the use of higher frequency carrier frequencies in fourth-generation mobile communication technology (4G) and fifth-generation mobile communication technology (5G) to achieve high bandwidth and low latency communication, the industry urgently needs surface acoustic wave filters with higher quality factors and low or no clutter modes. Summary of the Invention

[0005] This application provides a substrate structure, a surface acoustic wave resonator, a filter, an RF front-end module, and a mobile terminal to improve the suppression effect of stray modes in the filter.

[0006] To achieve the above objectives, this application adopts the following technical solution:

[0007] A first aspect of this application provides a substrate structure for use in a surface acoustic wave (SAW) device. The substrate structure includes a substrate and a first high-velocity layer, a low-velocity layer, and a piezoelectric layer disposed on one side of the substrate. The first high-velocity layer is disposed on one side of the substrate, the low-velocity layer is disposed on the side of the first high-velocity layer away from the substrate, and the piezoelectric layer is disposed on the side of the low-velocity layer away from the substrate. Among the first high-velocity layer, the low-velocity layer, the substrate, and the piezoelectric layer, the material of the first high-velocity layer has the highest shear wave velocity and the highest longitudinal wave velocity.

[0008] The substrate structure provided in this application, by setting a first high-velocity layer below the low-velocity layer with relatively high shear wave velocity and longitudinal wave velocity, can change the acoustic impedance distribution during the propagation of higher-order heterogeneous modes, thereby suppressing the vibration amplitude of each mode of higher-order heterogeneous modes. Specifically, it has a suppressive effect on higher-order heterogeneous modes with the longitudinal component as the main vibration mode, and also on higher-order heterogeneous modes with the shear component as the main vibration mode. This weakens the resonant response intensity excited on the interdigitated electrodes of the surface acoustic wave device by the strain generated by the vibration of higher-order heterogeneous modes, improving the higher-order heterogeneous mode suppression capability of the surface acoustic wave device.

[0009] In one possible implementation, the substrate structure further includes a second hypersonic layer; the second hypersonic layer is disposed between the first hypersonic layer and the low-velocity layer; the shear wave velocity of the material in the second hypersonic layer is lower than that of the material in the first hypersonic layer; and the longitudinal wave velocity of the material in the second hypersonic layer is lower than that of the material in the first hypersonic layer; the shear wave velocity of the material in the second hypersonic layer is higher than that of the material in the low-velocity layer; or, the longitudinal wave velocity of the material in the second hypersonic layer is higher than that of the material in the low-velocity layer. By disposing the second hypersonic layer between the first hypersonic layer and the low-velocity layer, and with the velocity of the second hypersonic layer located between the first hypersonic layer and the low-velocity layer, the velocity gradient between the low-velocity layer and the first hypersonic layer can be adjusted, thereby further improving the suppression effect of higher-order heterogeneous modes.

[0010] In one possible implementation, the bulk wave velocity of the substrate material is higher than the velocity of the dominant surface wave mode in the surface acoustic wave device (SAW), but lower than the velocity of the lowest-velocity higher-order miscellaneous mode in the SAW device. This allows the energy of the higher-order miscellaneous mode to propagate and leak more easily into the substrate, further reducing the intensity of the higher-order miscellaneous mode.

[0011] In one possible implementation, the substrate material is monocrystalline silicon, and the substrate tangentially has the following orientations: (α, β, θ), where α = -45° ± 15° or α = 135° ± 15°, β = 90° ± 20° or β = -90° ± 20°, and θ = 0° ± 50°. This allows higher-order miscellaneous mode energy to propagate and leak more easily into the substrate, further reducing the intensity of the higher-order miscellaneous modes.

[0012] In one possible implementation, the substrate material is monocrystalline silicon, and the substrate tangential is (α, β, θ), where α = -45° ± 15° or α = 135° ± 15°, β = 54.74° ± 15° or β = -54.74° ± 15°, and θ = 0° ± 90°. This allows higher-order miscellaneous mode energy to propagate and leak more easily into the substrate, further reducing the intensity of the higher-order miscellaneous modes.

[0013] In one possible implementation, the substrate structure further includes a connection auxiliary layer disposed between the first hypersonic layer and the substrate. The shear wave velocity of the material in the connection auxiliary layer is lower than that of the material in the first hypersonic layer, and the longitudinal wave velocity of the material in the connection auxiliary layer is lower than that of the material in the first hypersonic layer. By providing a connection auxiliary layer between the first hypersonic layer and the substrate, the connection process between the first hypersonic layer and the substrate can be simplified, and the support strength of the substrate can be improved.

[0014] In one possible implementation, the shear wave velocity of the material in the low-velocity layer is lower than that of the material in the piezoelectric layer. This confines the acoustic energy to the substrate surface region dominated by the piezoelectric and low-velocity layers, improving the quality factor of the surface acoustic wave device and providing a certain degree of temperature compensation.

[0015] In one possible implementation, the shear wave velocity of the first hypersonic layer is in the range of 5500 m / s to 13000 m / s, and the longitudinal wave velocity of the first hypersonic layer is in the range of 8000 m / s to 20000 m / s. This allows the acoustic impedance of the first hypersonic layer to reach a certain value, thereby achieving a better suppression effect on higher-order miscellaneous modes.

[0016] In one possible implementation, the thickness of the first hypersonic layer is in the range of 0.025λ to 0.8λ, where λ is the wavelength of the surface acoustic wave propagating in the surface acoustic wave device. If the thickness of the first hypersonic layer is too thick, it will affect the leakage of higher-order heterogeneous modes into the substrate, thus impacting the suppression effect. If the thickness of the first hypersonic layer is too thin, it will not significantly alter the acoustic impedance distribution to suppress higher-order heterogeneous modes. Setting the thickness of the first hypersonic layer in the range of 0.025λ to 0.8λ provides a better suppression effect on higher-order heterogeneous modes.

[0017] In one possible implementation, the material of the first hypersonic layer includes at least one of diamond, silicon carbide, sapphire, spinel, or silicon nitride. These are some technologically mature and low-cost material choices.

[0018] In one possible implementation, the shear wave velocity of the second hypersonic layer is in the range of 4000 m / s to 7000 m / s, and the longitudinal wave velocity of the second hypersonic layer is in the range of 5500 m / s to 12000 m / s. This can improve both the suppression of higher-order heterodynes and the quality factor.

[0019] In one possible implementation, the thickness of the second high-velocity layer is in the range of 0.03λ to 1λ, where λ is the wavelength of the surface acoustic wave propagating in the surface acoustic wave device. By setting the thickness of the second high-velocity layer in the range of 0.03λ to 1λ, the suppression effect of higher-order heterogeneous modes can be improved. On the other hand, it can prevent sound waves from leaking to the side of the second high-velocity layer near the substrate, further confining the sound wave energy to the substrate surface region dominated by the piezoelectric layer and the low-velocity layer, thereby improving the quality factor of the surface acoustic wave device.

[0020] In one possible implementation, the material of the second hypersonic layer includes at least one of silicon nitride, polycrystalline silicon, alumina, or aluminum nitride. These are some technologically mature and low-cost material choices.

[0021] In one possible implementation, the shear wave velocity of the low-velocity layer is in the range of 2000 m / s to 4500 m / s, and the longitudinal wave velocity of the low-velocity layer is in the range of 3500 m / s to 7000 m / s. This can improve the quality factor.

[0022] In one possible implementation, the shear wave velocity of the piezoelectric layer is in the range of 2500 m / s to 5000 m / s, and the longitudinal wave velocity of the piezoelectric layer is in the range of 4000 m / s to 7500 m / s. This can improve the quality factor.

[0023] A second aspect of the embodiments of this application provides a surface acoustic wave resonator, the surface acoustic wave resonator including a substrate structure and interdigitated electrodes; the substrate structure includes the substrate structure of any one of the first aspects; the interdigitated electrodes are disposed on the side of the piezoelectric layer away from the substrate.

[0024] A third aspect of the embodiments of this application provides a filter including a plurality of cascaded surface acoustic wave (SAW) resonators; wherein the SAW resonators include the SAW resonators of any one of the second aspects.

[0025] A fourth aspect of the embodiments of this application provides a radio frequency front-end module, including a filter and an amplifier, wherein the filter is coupled to the amplifier; the filter includes the filter of the third aspect.

[0026] A fifth aspect of the embodiments of this application provides a mobile terminal, including a filter and a circuit board, wherein the filter is disposed on the circuit board; the filter includes the filter of the third aspect.

[0027] A sixth aspect of the embodiments of this application provides a mobile terminal, including a radio frequency front-end module and a circuit board, wherein the radio frequency front-end module is disposed on the circuit board; the radio frequency front-end module includes the radio frequency front-end module of the fourth aspect. Attached Figure Description

[0028] Figure 1 is a schematic diagram of the structure of a mobile terminal provided in an embodiment of this application;

[0029] Figure 2 is a structural schematic diagram of an RF front-end module provided in an embodiment of this application;

[0030] Figure 3 is a schematic diagram of the topology of a filter provided in an embodiment of this application;

[0031] Figure 4A is a schematic diagram of the structure of a surface acoustic wave resonator provided in an embodiment of this application;

[0032] Figure 4B is a schematic diagram of the sound velocity of each membrane layer in Figure 4A;

[0033] Figure 4C is a schematic diagram of the admittance curve of a surface acoustic wave resonator provided in an embodiment of this application;

[0034] Figure 5 is a schematic diagram of a surface acoustic wave resonator provided in an embodiment of this application;

[0035] Figure 6 is a schematic diagram of a surface acoustic wave resonator provided in an embodiment of this application;

[0036] Figure 7 is a schematic diagram of a surface acoustic wave resonator provided in an embodiment of this application;

[0037] Figure 8 is a sound velocity diagram of each film layer in the substrate structure shown in Figure 7 provided in the embodiment of this application;

[0038] Figure 9 is a schematic diagram of a substrate structure provided in an embodiment of this application;

[0039] Figure 10 is a sound velocity diagram of each film layer in the substrate structure shown in Figure 9 provided in the embodiment of this application;

[0040] Figure 11 is a schematic diagram of a substrate structure provided in an embodiment of this application;

[0041] Figure 12 is a top view of an interdigitated electrode provided in an embodiment of this application;

[0042] Figure 13A is a schematic diagram of a surface acoustic wave resonator provided in an embodiment of this application;

[0043] Figure 13B is a schematic diagram comparing the admittance curves of three types of surface acoustic wave resonators;

[0044] Figure 14A is a schematic diagram of the admittance curve of the surface acoustic wave resonator shown in Comparative Example 2;

[0045] Figure 14B is a modal diagram of the miscellaneous mode at the first position in Figure 14A;

[0046] Figure 14C is the modal diagram of the miscellaneous mode at the second position in Figure 14A;

[0047] Figure 15A is a schematic diagram of the admittance curve of the surface acoustic wave resonator shown in Example 1;

[0048] Figure 15B is the modal diagram of the miscellaneous mode at the first position in Figure 15A;

[0049] Figure 15C is the modal diagram of the miscellaneous mode at the second position in Figure 15A;

[0050] Figure 16 is a schematic diagram of the admittance curves of the surface acoustic wave resonators shown in Comparative Example 1 and Example 2.

[0051] Figure 17 is a schematic diagram of the admittance curves of the surface acoustic wave resonators shown in Comparative Example 1, Example 2 and Example 3.

[0052] Figure 18 is a schematic diagram of the admittance curves of the surface acoustic wave resonators shown in Comparative Example 1, Example 2 and Example 4. Detailed Implementation

[0053] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0054] 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 indicated technical features. Therefore, a feature defined with "second," "first," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0055] Furthermore, in the embodiments of this application, directional terms such as "upper," "lower," "left," and "right" may be defined relative to the orientation in which the components are schematically placed in the accompanying drawings. It should be understood that these directional terms can be relative concepts, used for relative description and clarification, and can change accordingly based on the orientation of the components in the accompanying drawings.

[0056] In the embodiments of this application, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral part; it can be a direct connection or an indirect connection through an intermediate medium. Furthermore, the term "coupled connection" can be a direct electrical connection or an indirect electrical connection through an intermediate medium. The term "contact" can be direct contact or indirect contact through an intermediate medium.

[0057] In this embodiment of the application, "and / or" describes the relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following associated objects have an "or" relationship.

[0058] The technical solution of this application can be applied to various mobile terminals that include surface acoustic wave (SAW) filters. These mobile terminals can be deployed on land, including indoors or outdoors, handheld or vehicle-mounted. They can also be deployed on water (such as ships) or in the air (e.g., on airplanes, 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, tablets, laptops, PDAs, mobile internet devices (MIDs), wearable devices (such as smartwatches, smart bracelets, pedometers, etc.), in-vehicle devices (such as cars, bicycles, electric vehicles, airplanes, ships, trains, high-speed trains, etc.), virtual reality (VR) devices, augmented reality (AR) devices, wireless terminals in industrial control, smart home devices (such as refrigerators, televisions, air conditioners, electricity meters, etc.), smart 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, flying equipment (such as smart robots, hot air balloons, drones, airplanes), radio frequency front-end modules, etc.

[0059] Figure 1 is a schematic diagram of the structure of a mobile terminal provided in an embodiment of this application. The mobile terminal 1 is illustrated using a mobile phone as an example. The mobile terminal 1 includes: a radio frequency (RF) front-end module 101, a memory 102, a processor 103, a sensor assembly 104, a multimedia assembly 105, a power supply assembly 106, and an input / output interface 107.

[0060] The following is a detailed introduction to the various components of this mobile phone, with reference to Figure 1:

[0061] The RF front-end module 101 can be used to receive and send signals during information transmission or calls. In particular, it receives downlink information from the mobile terminal and processes it with the processor 103, and sends uplink data to the mobile terminal.

[0062] The memory 102 can be used to store data, software programs, and modules. The mobile phone may include high-speed random access memory and may also include non-volatile memory, such as at least one disk storage device, flash memory device, or other volatile solid-state storage device.

[0063] The processor 103 is the control center of the mobile phone. It connects to various parts of the device through various interfaces and lines. By running or executing software programs and / or modules stored in the memory 102, and by calling data stored in the memory 102, it performs various functions and processes data of the mobile phone, thereby controlling the mobile phone as a whole. The processor may include, for example, an application processor or a baseband processor.

[0064] Sensor assembly 104 includes one or more sensors for providing various aspects of the mobile phone's status assessment. Sensor assembly 104 may include one or more of the following: accelerometer, gyroscope, magnetometer, pressure sensor, temperature sensor, and light sensor. Sensor assembly 104 can detect the mobile phone's acceleration / deceleration, orientation, on / off state, relative positioning of components, or temperature changes, etc. Furthermore, sensor assembly 104 may also include a light sensor, such as a CMOS or CCD image sensor, for use in imaging applications.

[0065] The multimedia component 105 provides a screen that serves as an output interface between the mobile phone and the user. This screen can be a touch panel, and when it is a touch panel, it can be implemented as a touchscreen to receive input signals from the user. Furthermore, the multimedia component 105 also includes at least one camera; for example, it includes a front-facing camera and / or a rear-facing camera.

[0066] The power supply component 106 is used to provide power to the 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 the generation, management and distribution of power by the mobile phone.

[0067] Input / output interface 107 provides an interface between processor 103 and peripheral interface modules, such as keyboards and mice.

[0068] In some embodiments, the mobile terminal 1 further includes a circuit board, and the RF front-end module 101 can be disposed on the circuit board.

[0069] Figure 2 is a structural schematic diagram of an RF front-end module provided in an embodiment of this application.

[0070] The RF front-end module 101 is a key module for wireless communication in a mobile terminal. It processes radio frequency analog signals through components such as RF switches, filters / multiplexers, power amplifiers (PA), and low noise amplifiers (LNA). That is, the RF front-end module 101 typically includes, but is not limited to, RF switches, duplexers, filters, PAs, and LNAs.

[0071] For example, as shown in FIG2, the RF front-end module 101 may include: an RF switch, a duplexer, a filter, a power amplifier (PA), and an LNA.

[0072] The RF front-end module 101 may include a transmit channel and a receive channel. The transmit channel includes a power amplifier (PA) and a transmit channel filter. The RF output of the PA is coupled to the input of the transmit channel filter. The receive channel includes an low-frequency receiver (LNA) and a receive channel filter. The output of the receive channel filter is coupled to the RF input of the LNA.

[0073] The duplexer is responsible for duplex switching in the frequency division duplex system and filtering of RF signals in the receive / transmit channel, while the RF switch is responsible for switching between the receive and transmit channels.

[0074] The baseband signal is transmitted to the transmit channel via the transceiver. The transmit channel amplifies the received RF signal and outputs it to the antenna, which then transmits it. The PA is responsible for amplifying the RF signal from the transmit channel, and the transmit channel filter is responsible for filtering the RF signal from the transmit channel.

[0075] The receiving channel receives radio frequency (RF) signals from the antenna. These RF signals are amplified by the receiving channel and then output, before being transmitted to the baseband via a transceiver. The LNA amplifies the RF signals from the receiving channel, while the receiving channel filter filters them.

[0076] With the use of higher frequency carrier frequencies in fourth-generation mobile communication technology (4G) and fifth-generation mobile communication technology (5G) to achieve high bandwidth and low latency communication, the industry urgently needs surface acoustic wave (SAW) filters with higher frequency, higher quality factor, and low or no clutter modes.

[0077] This application provides a filter that can be applied to the mobile terminal 1 described above, for example, in the radio frequency front-end module 101 of the mobile terminal 1. 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 mobile terminal 1. This application does not limit the form of the filter in the mobile terminal 1.

[0078] The filters provided in this application embodiment can be, for example, low-pass filters, high-pass filters, band-pass filters, band-stop filters, or active filters. The filters provided in this application embodiment are not limited to application in the aforementioned mobile terminal 1; they can also be applied to sensing, detection, and other fields. Filters within mobile terminals in related technologies can all be replaced by the filters provided in this application embodiment.

[0079] Of course, the filter provided in this application embodiment is not limited to being integrated into the mobile terminal 1. When the filter is integrated into the mobile terminal 1, the filter can be directly mounted on the circuit board, or the filter can be packaged with other components and mounted on the circuit board. The filter can also be a standalone component, or the filter can be integrated with components such as power amplifiers into a module (e.g., RF devices, RF front-end modules, filter modules, etc.).

[0080] Figure 3 is a schematic diagram of the topology of a filter provided in an embodiment of this application.

[0081] In some embodiments, as shown in FIG3, the 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 a series-parallel manner. FIG3 also illustrates the signal input terminal Vi, the signal output terminal Vo, and the ground terminal GND of the filter 100.

[0082] 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 embodiments of this application is illustrated below.

[0083] Figure 4A is a schematic diagram of the structure of a surface acoustic wave resonator provided in an embodiment of this application, Figure 4B is a schematic diagram of the sound velocity of each film layer in Figure 4A, and Figure 4C is a schematic diagram of the admittance curve of a surface acoustic wave resonator provided in an embodiment of this application.

[0084] In some embodiments, as shown in FIG4A, the surface acoustic wave resonator 10 includes a substrate 11 and a high-velocity layer 12, a low-velocity layer 13, a piezoelectric layer 14, and an interdigital transducer (IDT) sequentially disposed on the substrate 11.

[0085] As shown in Figure 4B, in the surface acoustic wave resonator 10 shown in Figure 4A, the shear wave velocity of the high-velocity layer 12 is the largest, and the longitudinal wave velocity of the substrate 11 is the largest.

[0086] The surface acoustic wave resonator 10 shown in Figure 4A utilizes a sequentially arranged layered structure to obtain a high quality factor (Q) value and high performance.

[0087] However, this type of surface acoustic wave (SAW) resonator 10 excites strong higher-order clutter modes. Since these higher-order clutter modes can be combinations of various vibration modes (e.g., transverse shear mode, vertical shear mode, longitudinal mode, etc.), multiple higher-order clutter modes often coexist. These clutter modes typically exist as plate waves in the quasi-surface layer of the SAW resonator 10. When the strain caused by the plate wave vibration is transmitted to the piezoelectric layer 14 and interdigitated electrodes (IDT) of the surface layer, high-frequency resonance peaks are generated in the frequency response through the piezoelectric effect. Therefore, these higher-order clutter modes significantly degrade the high-frequency suppression capability of the filter 100. As shown in Figure 4C, especially with the increasing prevalence of 5G, these higher-order clutter modes significantly degrade communication link performance in carrier aggregation (CA) bands and E-UTRA / NR dual connectivity (or 4G-5G air interface technology dual connectivity mode) (E-UTRAN new radio dual connectivity, ENDC) bands, thereby affecting the communication experience of mobile terminals. Meanwhile, as the transmit power of the RF front-end module 101 continues to increase, the nonlinear effect is amplified. If higher-order miscellaneous modes fall at the harmonics, causing the corresponding frequency band suppression to deteriorate, the link nonlinearity specifications may not meet the relevant regulatory requirements.

[0088] Figure 5 is a schematic diagram of the structure of a surface acoustic wave resonator provided in an embodiment of this application.

[0089] In some embodiments, as shown in FIG5, the surface acoustic wave resonator 10 includes a substrate 11 and a low-velocity acoustic layer 13, a piezoelectric layer 14, and interdigitated electrodes (IDTs) sequentially disposed on the substrate 11. The substrate 11 is a high-velocity acoustic support layer. The substrate 11 is processed (e.g., ion irradiation) to create a surface region with poor crystallinity (characterized by the number of diffraction spots), dividing the substrate 11 into a surface region and a support region. After the substrate 11 is divided into the surface region and the support region, the acoustic impedance of the high-velocity substrate 11 changes gradually, rather than abruptly. Here, the acoustic impedance is equal to the product of the sound velocity and the density of the medium.

[0090] This can reduce the strength of higher-order miscellaneous modes, but it increases the complexity of the process and the cost of the substrate wafer, and makes it difficult to control the consistency of the substrate surface area.

[0091] Figure 6 is a schematic diagram of the structure of a surface acoustic wave resonator provided in an embodiment of this application.

[0092] In some embodiments, as shown in FIG6, the surface acoustic wave resonator 10 includes a substrate 11, a piezoelectric layer 14, a functional layer, and interdigitated electrodes (IDTs) disposed on the substrate 11. The functional layer includes, for example, a low-velocity layer 13 and a high-velocity layer 12.

[0093] The substrate 11 is defined and selected (e.g., the tangential direction of the substrate 11 is adjusted) to change the volume wave velocity in the substrate 11, thereby reducing the cutoff frequency of higher-order miscellaneous modes in the substrate 11. That is, the tangential direction of the substrate 11 is changed so that the volume wave velocity of the substrate 11 is lower than the velocity of higher-order miscellaneous modes.

[0094] This makes it easier for higher-order miscellaneous mode energy to propagate and leak to the substrate 11, thereby reducing the intensity of higher-order miscellaneous modes. The surface acoustic wave resonator 10 in Figure 6 can effectively suppress higher-order miscellaneous modes with shear components as the main vibration mode within a certain frequency range. However, the suppression effect on higher-order miscellaneous modes with longitudinal components as the main vibration mode at higher frequencies is limited. At the same time, the suppression capability of higher-order miscellaneous modes with shear components as the main vibration mode also weakens after the resonant frequency of the main mode exceeds a certain range.

[0095] This application also provides a surface acoustic wave resonator 10 to improve the suppression effect on higher-order miscellaneous modes.

[0096] Figure 7 is a schematic diagram of the structure of a surface acoustic wave resonator provided in an embodiment of this application.

[0097] This application provides a surface acoustic wave (SAW) resonator 10, as shown in FIG7. The SAW resonator 10 includes a substrate structure 20 and interdigitated electrodes (IDTs) disposed on the surface of the substrate structure 20. The film structure of the substrate structure 20 determines the suppression effect of the SAW resonator 10 on higher-order heterodynes.

[0098] Based on this, this application embodiment also provides a substrate structure 20, which is applied in the surface acoustic wave device (surface acoustic wave resonator 10 or filter 100) provided in this application embodiment.

[0099] As shown in Figure 7, the substrate structure 20 includes a substrate 11, a first high-velocity layer 121, a low-velocity layer 13 and a piezoelectric layer 14 disposed on the substrate 11.

[0100] The first high-velocity layer 121 is disposed on one side of the substrate 11, the low-velocity layer 13 is disposed on the side of the first high-velocity layer 121 away from the substrate 11, and the piezoelectric layer 14 is disposed on the side of the low-velocity layer 13 away from the substrate 11.

[0101] Figure 8 is a sound velocity diagram of each film layer in the substrate structure shown in Figure 7 provided in the embodiment of this application.

[0102] As shown in Figure 8, among the first high-velocity layer 121, the low-velocity layer 13, the substrate 11, and the piezoelectric layer 14, the material of the first high-velocity layer 121 has the maximum shear wave velocity and longitudinal wave velocity.

[0103] That is, the shear wave velocity of the material of the first high-velocity layer 121 is higher than that of the material of the low-velocity layer 13, higher than that of the material of the substrate 11, and higher than that of the material of the piezoelectric layer 14.

[0104] The longitudinal wave velocity of the material of the first high-velocity layer 121 is higher than that of the material of the low-velocity layer 13, higher than that of the material of the substrate 11, and higher than that of the material of the piezoelectric layer 14.

[0105] In elastic waves propagating in solids, those where particles vibrate along the direction of propagation are called longitudinal waves, and those where particles vibrate perpendicular to the direction of propagation are called shear waves. For elastic waves propagating in anisotropic materials, shear waves can be further subdivided into slow shear waves and fast shear waves due to their different polarization directions. The propagation speed of longitudinal waves in solid materials is called the longitudinal wave velocity, and the propagation speed of shear waves in solid materials is called the shear wave velocity.

[0106] The substrate structure 20 provided in this embodiment includes a first high-velocity layer 121 below the low-velocity layer 13, which has relatively high shear wave velocity and longitudinal wave velocity. This layer can alter the acoustic impedance distribution during the propagation of higher-order heterogeneous modes, thereby suppressing the vibration amplitude of each mode. Specifically, it suppresses higher-order heterogeneous modes with longitudinal components as the dominant vibration mode, and it also suppresses higher-order heterogeneous modes with shear components as the dominant vibration mode. This weakens the resonant response intensity excited on the interdigitated electrode (IDT) by the strain generated by the vibration of higher-order heterogeneous modes, thus improving the higher-order heterogeneous mode suppression capability of the surface acoustic wave device.

[0107] In some embodiments, the shear wave velocity of the first hypersonic layer 121 is in the range of 5500 m / s to 13000 m / s, and the longitudinal wave velocity of the first hypersonic layer 121 is in the range of 8000 m / s to 20000 m / s.

[0108] For example, the shear wave velocity of the first hypersonic layer 121 is 5500m / s, 6000m / s, 6500m / s, 7000m / s, 7500m / s, 8000m / s, 8500m / s, 9000m / s, 9500m / s, 10000m / s, 10500m / s, 11000m / s, 11500m / s, 12000m / s, 12500m / s, or 13000m / s. The longitudinal wave speeds of the first hypersonic layer 121 are 8000 m / s, 9000 m / s, 10000 m / s, 11000 m / s, 12000 m / s, 13000 m / s, 14000 m / s, 15000 m / s, 16000 m / s, 17000 m / s, 18000 m / s, 19000 m / s, or 20000 m / s.

[0109] Within the aforementioned sound velocity range, the first high-velocity layer 121 has a good suppression effect on high-order miscellaneous molds.

[0110] In some embodiments, the thickness of the first high-velocity acoustic layer 121 is in the range of 0.025λ to 0.8λ, where λ is the wavelength of the surface acoustic wave propagating in the surface acoustic wave resonator 10.

[0111] For example, the thickness of the first hypersonic layer 121 is 0.025λ, 0.05λ, 0.1λ, 0.15λ, 0.2λ, 0.25λ, 0.3λ, 0.35λ, 0.4λ, 0.45λ, 0.5λ, 0.55λ, 0.6λ, 0.65λ, 0.7λ, 0.75λ, or 0.8λ.

[0112] If the thickness of the first hypersonic layer 121 is too thick, it will affect the leakage of higher-order heterogeneous modes into the substrate 11, thus affecting the suppression effect of higher-order heterogeneous modes. If the thickness of the first hypersonic layer 121 is too thin, it will not be able to significantly change the acoustic impedance distribution and thus suppress higher-order heterogeneous modes. Setting the thickness of the first hypersonic layer 121 in the range of 0.05λ to 1λ results in a better suppression effect of higher-order heterogeneous modes.

[0113] For example, the shear wave velocity of the first hypersonic layer 121 is in the range of 5500 m / s to 7500 m / s, the longitudinal wave velocity of the first hypersonic layer 121 is in the range of 8000 m / s to 12000 m / s, and the thickness of the first hypersonic layer 121 is in the range of 0.1λ to 0.8λ.

[0114] Alternatively, for example, the shear wave velocity of the first hypersonic layer 121 is in the range of 7500 m / s to 10000 m / s, the longitudinal wave velocity of the first hypersonic layer 121 is in the range of 12000 m / s to 16500 m / s, and the thickness of the first hypersonic layer 121 is in the range of 0.05λ to 0.6λ.

[0115] Alternatively, for example, the shear wave velocity of the first hypersonic layer 121 is in the range of 10000m / s to 13000m / s, the longitudinal wave velocity of the first hypersonic layer 121 is in the range of 16500m / s to 20000m / s, and the thickness of the first hypersonic layer 121 is in the range of 0.025λ to 0.4λ.

[0116] In some embodiments, the material of the first hypersonic layer 121 includes at least one of diamond, silicon carbide (SiC), sapphire, spinel, or silicon nitride (Si3N4). These are some technologically mature and low-cost material choices.

[0117] In some embodiments, the bulk wave velocity of the material of substrate 11 is higher than the surface wave dominant mode velocity of the surface acoustic wave device including substrate structure 20. Furthermore, the bulk wave velocity of the material of substrate 11 is lower than the velocity of the lowest-velocity high-order spurious mode among all high-order spurious modes included in the surface acoustic wave device including substrate structure 20.

[0118] Body waves include shear waves and longitudinal waves. The sound velocity of body waves includes the propagation speed of longitudinal waves in solid materials (longitudinal wave velocity) and the propagation speed of shear waves in solid materials (shear wave velocity).

[0119] That is, the shear wave velocity and longitudinal wave velocity of the material of substrate 11 are both higher than the surface wave dominant mode velocity of surface acoustic wave resonator 10. The shear wave velocity and longitudinal wave velocity of the material of substrate 11 are both lower than the velocity of the lowest-speed higher-order miscellaneous mode among all the higher-order miscellaneous modes contained in the surface acoustic wave device.

[0120] The dominant mode refers to the mode primarily used in the surface wave propagation of the surface acoustic wave resonator 10. For example, the dominant mode may be the Rayleigh mode, the horizontal shear wave (SH) mode, or the longitudinal wave mode. The dominant mode velocity refers to the propagation speed of the dominant mode in a solid material.

[0121] Higher-order hybrid modes refer to the modes in the surface waves of the surface acoustic wave resonator 10 whose frequencies are higher than the dominant mode. The sound velocity of higher-order hybrid modes refers to the propagation speed of higher-order hybrid modes in solid materials.

[0122] For example, the material of substrate 11 is single-crystal silicon, and the tangential orientation of substrate 11 is (α, β, θ), where α = -45° ± 15 or α = 135° ± 15, β = 90° ± 20° or β = -90° ± 20°, and θ = 0° ± 50°. For example, the crystal orientation of substrate 11 is (110), or it is a (110) orientation deflected by a certain angle.

[0123] For example, α=-45°±13, α=-45°±10, α=-45°±7, α=-45°±5, α=-45°±3, α=-45°, α=135°±13, α=135°±10, α=135°±7, α=135°±5, α=135°±3 or α=135°.

[0124] β=90°±20°, β=90°±17°, β=90°±15°, β=90°±13°, β=90°±10°, β=90°±7°, β=90°±5°, β=90°±3°, β=90°, β=-90 °±20°, β=-90°±17°, β=-90°±15°, β=-90°±13°, β=-90°±10°, β=-90°±7°, β=-90°±5°, β=-90°±3° or β=-90°.

[0125] θ=0°±50°, θ=0°±45°, θ=0°±40°, θ=0°±35°, θ=0°±30°, θ=0°±25°, θ=0°±20°, θ=0°±15°, θ=0°±10°, θ=0°±5° or θ=0°.

[0126] Alternatively, for example, the material of substrate 11 is single-crystal silicon, and the tangential orientation of substrate 11 is (α, β, θ), where α = -45° ± 15 or α = 135° ± 15, β = 54.74° ± 15° or β = -54.74° ± 15°, and θ = 0° ± 90°. For example, the crystal orientation of substrate 11 is (111), or it is a (111) orientation deflected by a certain angle.

[0127] For example, α=-45°±13, α=-45°±10, α=-45°±7, α=-45°±5, α=-45°±3, α=-45°, α=135°±13, α=135°±10, α=135°±7, α=135°±5, α=135°±3 or α=135°.

[0128] β=54.74°±15°, β=54.74°±13°, β=54.74°±10°, β=54.74°±7°, β=54.74°±5°, β=54.74°±3°, β=54.74°, β=-5 4.74°±15°, β=-54.74°±13°, β=-54.74°±10°, β=-54.74°±7°, β=-54.74°±5°, β=-54.74°±3° or β=-54.74°.

[0129] θ=0°±90°, θ=0°±85°, θ=0°±80°, θ=0°±75°, θ=0°±70°, θ=0°±65°, θ=0°±60°, θ=0°±55°, θ=0°±50°, θ= 0°±45°, θ=0°±40°, θ=0°±35°, θ=0°±30°, θ=0°±25°, θ=0°±20°, θ=0°±15°, θ=0°±10°, θ=0°±5° or θ=0°.

[0130] In this way, the energy of higher-order miscellaneous modes can more easily propagate and leak to the substrate 11, further reducing the strength of higher-order miscellaneous modes.

[0131] In some embodiments, the material of the substrate 11 may include, for example, glass, silicon (Si), alumina (Al2O3), silicon carbide (SiC), etc.

[0132] In some embodiments, the thickness of the substrate 11 is, for example, in the range of 100um to 1000um. For example, the thickness of the substrate 11 is 100um, 200um, 300um, 400um, 500um, 600um, 700um, 800um, 900um or 1000um.

[0133] In some embodiments, the shear wave velocity of the material of the low-velocity layer 13 is lower than that of the material of the piezoelectric layer 14.

[0134] The longitudinal wave velocity of the material in the low-velocity layer 13 is lower than that of the material in the piezoelectric layer 14. Alternatively, the longitudinal wave velocity of the material in the low-velocity layer 13 is equal to that of the material in the piezoelectric layer 14. Alternatively, the longitudinal wave velocity of the material in the low-velocity layer 13 is higher than that of the material in the piezoelectric layer 14.

[0135] This confines the acoustic energy to the substrate surface region dominated by the piezoelectric layer 14 and the low-velocity layer 13, improving the quality factor of the surface acoustic wave device and providing a certain degree of temperature compensation.

[0136] In some embodiments, the shear wave velocity of the low-velocity layer 13 is in the range of 2000 m / s to 4500 m / s, and the longitudinal wave velocity of the low-velocity layer 13 is in the range of 3500 m / s to 7000 m / s. For example, the shear wave velocity of the low-velocity layer 13 is 2000 m / s, 2500 m / s, 3000 m / s, 3500 m / s, 4000 m / s, or 4500 m / s. The longitudinal wave velocity of the low-velocity layer 13 is 3500 m / s, 4000 m / s, 4500 m / s, 5000 m / s, 5500 m / s, 6000 m / s, 6500 m / s, or 7000 m / s. This optimizes the Q value of the substrate structure 20.

[0137] In some embodiments, the thickness of the low-velocity layer 13 is in the range of 0.05λ to 1λ. For example, the thickness of the low-velocity layer 13 is 0.05λ, 0.1λ, 0.15λ, 0.2λ, 0.25λ, 0.3λ, 0.35λ, 0.4λ, 0.45λ, 0.5λ, 0.55λ, 0.6λ, 0.65λ, 0.7λ, 0.75λ, 0.8λ, 0.85λ, 0.9λ, 0.95λ, or 1λ. This optimizes the Q value of the substrate structure 20.

[0138] In some embodiments, the material of the low-velocity layer 13 includes at least one of silicon dioxide (SiO2), a compound of SiO2 with added fluorine (F), carbon (C), or boron (B), silicon oxynitride (SiOxNy), and tantalum oxide (Ta2O5). These are some technologically mature and low-cost material choices.

[0139] In some embodiments, the shear wave velocity of the piezoelectric layer 14 is in the range of 2500 m / s to 5000 m / s, and the longitudinal wave velocity of the piezoelectric layer 14 is in the range of 4000 m / s to 7500 m / s. For example, the shear wave velocity of the piezoelectric layer 14 is 2500 m / s, 3000 m / s, 3500 m / s, 4000 m / s, 4500 m / s, or 5000 m / s. The longitudinal wave velocity of the piezoelectric layer 14 is 4000 m / s, 4500 m / s, 5000 m / s, 5500 m / s, 6000 m / s, 6500 m / s, 7000 m / s, or 7500 m / s. This optimizes the Q value of the substrate structure 20.

[0140] In some embodiments, the thickness of the piezoelectric layer 14 is in the range of 0.05λ to 1λ. For example, the thickness of the piezoelectric layer 14 is 0.05λ, 0.1λ, 0.15λ, 0.2λ, 0.25λ, 0.3λ, 0.35λ, 0.4λ, 0.45λ, 0.5λ, 0.55λ, 0.6λ, 0.65λ, 0.7λ, 0.75λ, 0.8λ, 0.85λ, 0.9λ, 0.95λ, or 1λ. This optimizes the Q value of the substrate structure 20.

[0141] In some embodiments, the material of the piezoelectric layer 14 includes lithium niobate, lithium tantalate, etc. These are some technologically mature and low-cost material choices.

[0142] Figure 9 is a schematic diagram of a substrate structure provided in an embodiment of this application. Figure 10 is a sound velocity diagram of each film layer in the substrate structure shown in Figure 9 provided in an embodiment of this application.

[0143] In some embodiments, as shown in FIG9, the substrate structure 20 further includes a second high-velocity layer 122, which is disposed between the first high-velocity layer 121 and the low-velocity layer 13.

[0144] As shown in Figure 10, the shear wave velocity of the material in the second hypersonic layer 122 is lower than that of the material in the first hypersonic layer 121. The longitudinal wave velocity of the material in the second hypersonic layer 122 is also lower than that of the material in the first hypersonic layer 121.

[0145] The shear wave velocity of the material in the second hypersonic layer 122 is higher than that of the material in the low-sonic layer 13. Alternatively, the longitudinal wave velocity of the material in the second hypersonic layer 122 is higher than that of the material in the low-sonic layer 13. Or neither of the above conditions is met.

[0146] By setting a second high-speed sound layer 122 between the first high-speed sound layer 121 and the low-speed sound layer 13, and the sound speed of the second high-speed sound layer 122 is located between the first high-speed sound layer 121 and the low-speed sound layer 13, the sound speed gradient between the low-speed sound layer 13 and the first high-speed sound layer 121 can be adjusted, thereby further improving the suppression effect of higher-order heterogeneous modes.

[0147] In some embodiments, the shear wave velocity of the second hypersonic layer 122 is in the range of 4000 m / s to 7000 m / s, and the longitudinal wave velocity of the second hypersonic layer 122 is in the range of 5500 m / s to 12000 m / s. For example, the shear wave velocity of the second hypersonic layer 122 is 4000 m / s, 4500 m / s, 5000 m / s, 5500 m / s, 6000 m / s, 6500 m / s, or 7000 m / s. The longitudinal wave velocity of the second hypersonic layer 122 is 5500 m / s, 6000 m / s, 7000 m / s, 8000 m / s, 9000 m / s, 10000 m / s, 11000 m / s, or 12000 m / s.

[0148] This allows for better adjustment of the sound velocity gradient between the low-velocity layer 13 and the first high-velocity layer 121, thereby further improving the suppression effect of higher-order miscellaneous modes.

[0149] In some embodiments, the thickness of the second hypersonic layer 122 is in the range of 0.03λ to 1λ. For example, the thickness of the second hypersonic layer 122 is 0.03λ, 0.05λ, 0.1λ, 0.15λ, 0.2λ, 0.25λ, 0.3λ, 0.35λ, 0.4λ, 0.45λ, 0.5λ, 0.55λ, 0.6λ, 0.65λ, 0.7λ, 0.75λ, 0.8λ, 0.85λ, 0.9λ, 0.95λ, or 1λ.

[0150] By setting the thickness of the second high-velocity acoustic layer 122 in the range of 0.03λ to 1λ, the suppression effect of higher-order miscellaneous modes can be improved on the one hand, and the sound waves can be prevented from leaking to the side of the second high-velocity acoustic layer 122 near the substrate 11 on the other hand, and the sound wave energy can be further confined to the substrate surface region dominated by the piezoelectric layer 14 and the low-velocity acoustic layer 13, thereby improving the quality factor of the surface acoustic wave device.

[0151] In some embodiments, the material of the second hypersonic layer 122 includes at least one of silicon nitride, polycrystalline silicon, alumina, or aluminum nitride. These are some technologically mature and low-cost material choices.

[0152] Figure 11 is a schematic diagram of a substrate structure provided in an embodiment of this application.

[0153] In some embodiments, as shown in FIG11, the substrate structure 20 further includes a connection auxiliary layer 15, which is disposed between the first hypersonic layer 121 and the substrate 11.

[0154] The shear wave velocity of the material connecting the auxiliary layer 15 is lower than that of the material of the first high-velocity layer 121. The longitudinal wave velocity of the material connecting the auxiliary layer 15 is lower than that of the material of the first high-velocity layer 121.

[0155] For example, the materials used to connect the auxiliary layer 15 include silicon oxide, silicon nitride, polycrystalline silicon, etc.

[0156] By providing a connecting auxiliary layer 15 between the first hypersonic layer 121 and the substrate 11, the connection difficulty between the first hypersonic layer 121 and the substrate 11 can be reduced, the manufacturing difficulty can be reduced, and the support strength of the substrate 11 can be improved.

[0157] Figure 12 is a top view of an interdigitated electrode provided in an embodiment of this application.

[0158] When the substrate structure 20 provided in the embodiments of this application is applied to the surface acoustic wave resonator 10 provided in the embodiments of this application, the surface acoustic wave resonator 10 further includes an interdigital electrode (IDT), which is disposed on the side of the piezoelectric layer 14 away from the substrate 11.

[0159] In one embodiment, as shown in FIG12, the interdigitated electrode IDT includes a first busbar 171a and a second busbar 172a disposed opposite to each other, a plurality of first electrode fingers 171b, and a plurality of second electrode fingers 172b. The extension directions of the first busbar 171a and the second busbar 172a are parallel to a first direction X, and the extension directions of the first electrode fingers 171b are parallel to a second direction Y. The first electrode fingers 171b protrude from the first busbar 171a toward the second busbar 172a, and the plurality of first electrode fingers 171b are arranged sequentially along the extension direction of the first busbar 171a (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 finger 172b is parallel to the second direction Y. The second electrode finger 172b protrudes from the second busbar 172a toward the first busbar 171a. Multiple second electrode fingers 172b are arranged sequentially along the extension direction of the second busbar 172a (first direction X), and are coupled to the second busbar 172a. The first direction X intersects the second direction Y. In this embodiment, parallelism includes approximate parallelism; deviations within the range of process error (e.g., ±5°) are considered parallelism in this embodiment.

[0160] Among them, a plurality of first electrode fingers 171b and a plurality of second electrode fingers 172b are arranged alternately along the first direction X between the first bus bar 171a and the second bus bar 172a, and the first electrode fingers 171b and the second electrode fingers 172b do not contact each other.

[0161] The aforementioned "multiple first electrode fingers 171b and multiple second electrode fingers 172b are arranged alternately along the first direction X between the first bus bar 171a and the second bus bar 172a" means that between the first bus bar 171a and the second bus bar 172a, there is one second electrode finger 172b between every two first electrode fingers 171b and one first electrode finger 171b between every two second electrode fingers 172b.

[0162] The number of first electrode fingers 171b and second electrode fingers 172b in the interdigitated electrode IDT is not limited and can be set as needed. Multiple first electrode fingers 171b can be arranged with equal spacing or with non-equal spacing. Similarly, multiple second electrode fingers 172b can be arranged with equal spacing or with non-equal spacing. Taking the first electrode fingers 171b as an example, a non-equal spacing arrangement of 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.

[0163] Furthermore, the multiple first electrode fingers 171b and multiple second electrode fingers 172b are arranged alternately in sequence. The spacing between adjacent first electrode fingers 171b and second electrode fingers 172b can be the same. Alternatively, the spacing between multiple pairs of adjacent first electrode fingers 171b and second electrode fingers 172b can be not entirely 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.

[0164] It is understandable that the pitch between the first electrode finger 171b and the second electrode finger 172b, and the finger strip width of the first electrode finger 171b and the second electrode finger 172b are mainly affected by the photolithography and development process. By adjusting the pitch between the first electrode finger 171b and the second electrode finger 172b, and the finger strip 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. Therefore, 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.

[0165] The distance between the first electrode finger 171b and the second electrode finger 172b can be the distance from the center of the first electrode finger 171b to the center of the second electrode finger 172b.

[0166] 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.

[0167] 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 171b and the second electrode finger 172b, thereby determining the thickness of each film layer in the substrate structure 20.

[0168] The surface acoustic wave resonator 10 provided in the embodiments of this application will be illustrated below with several detailed examples.

[0169] Example 1

[0170] As shown in Figure 13A, the surface acoustic wave resonator 10 includes a substrate 11 and a first high-velocity layer 121, a second high-velocity layer 122, a low-velocity layer 13, a piezoelectric layer 14, and an interdigital electrode (IDT) sequentially disposed on the substrate 11.

[0171] To facilitate the explanation of sound velocity relationships, Vs will be used to represent the shear wave velocity and Vl to represent the longitudinal wave velocity. For isotropic materials, there is no distinction between fast and slow shear waves; Vs will be used uniformly to represent the shear wave velocity. For anisotropic materials, if it is piezoelectric layer 14, Vs specifically refers to the fast shear wave velocity. If it is another layer, Vs specifically refers to the slow shear wave velocity.

[0172] The piezoelectric layer 14 is made of lithium tantalate with a 42° Y-tangent propagation in the X direction. The thickness of the piezoelectric layer 14 is between 0.1λ and 0.5λ. The shear wave velocity Vs is about 4227 m / s and the longitudinal wave velocity Vl is about 5589 m / s.

[0173] The material of the low-velocity layer 13 is silicon oxide, and the thickness of the low-velocity layer 13 is between 0.1λ and 0.5λ. The shear wave velocity Vs is about 3687 m / s, and the longitudinal wave velocity Vl is about 5640 m / s.

[0174] The second hypersonic layer 122 is made of silicon nitride, and its thickness is between 0.03λ and 1λ. The shear wave velocity Vs is approximately 5725 m / s, and the longitudinal wave velocity Vl is approximately 8980 m / s.

[0175] The first hypersonic layer 121 is made of silicon carbide, and its thickness is between 0.025λ and 0.8λ. The shear wave velocity Vs is approximately 8955 m / s, and the longitudinal wave velocity Vl is approximately 15250 m / s.

[0176] The substrate 11 is made of single-crystal Si (111) with a tangential orientation of (-45°, 54.74°, 0°). The shear wave velocity Vs is approximately 4676 m / s, and the longitudinal wave velocity Vl is approximately 9135 m / s.

[0177] The metal layer material where the interdigital electrode IDT is located is aluminum, and the thickness of the interdigital electrode IDT is between 0.01λ and 0.1λ.

[0178] In the aforementioned surface acoustic wave resonator 10, the lowest sound velocity among all higher-order miscellaneous modes is approximately 5223 m / s.

[0179] The surface acoustic wave resonator 10 shown in Figure 4A is used as a comparative example. The arrangement of the piezoelectric layer 14, the low-velocity layer 13, and the interdigitated electrode (IDT) in the comparative example is the same as that in the surface acoustic wave resonator 10 shown in Figure 13A. In another comparative example, the high-velocity layer 12 is made of polycrystalline silicon, with a thickness ranging from 0.1λ to 0.5λ. The shear wave velocity Vs is approximately 5323 m / s, and the longitudinal wave velocity Vl is approximately 8304 m / s. The substrate 11 is a single-crystal Si(100) with a tangential orientation of (90°, 90°, 0°). The shear wave velocity Vs is approximately 5842 m / s, and the longitudinal wave velocity Vl is approximately 8437 m / s.

[0180] Using the surface acoustic wave resonator 10 shown in Figure 6 as Comparative Example 2, in order to maintain a single variable, a low-velocity layer 13 and a high-velocity layer 12 are also provided between the piezoelectric layer 14 and the substrate 11, based on the structure shown in Figure 6. In Comparative Example 2, the interdigitated electrode IDT, piezoelectric layer 14, low-velocity layer 13, and high-velocity layer 12 are the same as in Comparative Example 1, and the substrate 11 is single-crystal Si(111).

[0181] Figure 13B is a schematic diagram comparing the admittance curves of three types of surface acoustic wave resonators.

[0182] Figure 13B shows the admittance curves for Example 1, Comparative Example 1, and Comparative Example 2. Besides the dominant mode on the far left, the intensity of the higher-order miscellaneous modes on the right can be observed. A comparison between Example 1 and Comparative Example 1 demonstrates that the surface acoustic wave resonator 10 shown in Figure 13A can effectively suppress higher-order miscellaneous modes. A comparison between Example 1 and Comparative Example 2 shows that the surface acoustic wave resonator 10 shown in Figure 13A has a better suppression effect than the surface acoustic wave resonator 10 shown in Figure 6.

[0183] Figure 14A is a schematic diagram of the admittance curve of the surface acoustic wave resonator shown in Comparative Example 2. Figure 14B is a mode diagram of the miscellaneous mode at the first position in Figure 14A. Figure 14C is a mode diagram of the miscellaneous mode at the second position in Figure 14A.

[0184] Figure 14A shows the admittance curve of the surface acoustic wave resonator 10 shown in Comparative Example 2. Modal analysis is performed on the higher-order clutter mode at the first position A1 (near 2.5 GHz) in the admittance curve. Figure 14B shows the displacement of the higher-order clutter mode at the first position A1 in the three vertical components of the first direction X, the second direction Y, and the third direction Z. Modal analysis is performed on the higher-order clutter mode at the second position B1 (near 3.5 GHz) in the admittance curve. Figure 14C shows the displacement of the higher-order clutter mode at the second position B1 in the three vertical components of the first direction X, the second direction Y, and the third direction Z.

[0185] As shown in Figure 14B, the higher-order hybrid mode located at the first position A1 in Comparative Example 2 is dominated by shear modes (second direction Y and third direction Z). As shown in Figure 14C, the higher-order hybrid mode located at the second position B1 is dominated by longitudinal (first direction X) modes. The amplitudes of both higher-order hybrid modes are mainly concentrated in the low-velocity layer 13 and the high-velocity layer 12.

[0186] Figure 15A is a schematic diagram of the admittance curve of the surface acoustic wave resonator shown in Example 1, Figure 15B is a mode diagram of the miscellaneous mode at the first position in Figure 15A, and Figure 15C is a mode diagram of the miscellaneous mode at the second position in Figure 15A.

[0187] Figure 15A shows the admittance curve of the surface acoustic wave resonator 10 shown in Example 1. Modal analysis is performed on the higher-order clutter mode at the first position A2 (near 2.5 GHz) in the admittance curve. Figure 15B shows the displacement of the higher-order clutter mode at the first position A2 in the three vertical components of the first direction X, the second direction Y, and the third direction Z. Modal analysis is performed on the higher-order clutter mode at the second position B2 (near 3.5 GHz) in the admittance curve. Figure 15C shows the displacement of the higher-order clutter mode at the second position B2 in the three vertical components of the first direction X, the second direction Y, and the third direction Z.

[0188] Comparing the higher-order hybrid mode at position A2 in Example 1 shown in Figure 15B with the higher-order hybrid mode at position A1 in Comparative Example 2 shown in Figure 14B, and comparing the higher-order hybrid mode at position B2 in Example 1 shown in Figure 15C with the higher-order hybrid mode at position B1 in Comparative Example 2 shown in Figure 14C, the presence of the first hypersonic layer 122 effectively limits the amplitude of the shear and longitudinal components in the higher-order hybrid mode, disrupting the conditions for large-scale vibration of the higher-order hybrid mode. This weakens the overall strength of the higher-order hybrid mode, reduces the amplitude transmitted to the interdigital electrode (IDT) region, and ultimately makes the admittance curve smoother.

[0189] Based on this, the surface acoustic wave resonator 10 provided in this application embodiment can significantly reduce the intensity of each higher-order miscellaneous mode while maintaining the quality factor of the main mode by introducing a first high-velocity layer 121 and a second high-velocity layer 122.

[0190] Example 2

[0191] The main difference between Example 2 and Example 1 is that the materials of the first hypersonic layer 121 and the second hypersonic layer 122 are different.

[0192] As shown in Figure 13A, the surface acoustic wave resonator 10 includes a substrate 11 and a first high-velocity layer 121, a second high-velocity layer 122, a low-velocity layer 13, a piezoelectric layer 14, and an interdigital electrode (IDT) sequentially disposed on the substrate 11.

[0193] The material of the second hypersonic layer 122 is polycrystalline silicon, and the thickness of the second hypersonic layer 122 is between 0.03λ and 1λ. The shear wave velocity Vs is about 5323 m / s, and the longitudinal wave velocity Vl is about 8304 m / s.

[0194] The first hypersonic layer 121 is made of high-hardness silicon nitride, and its thickness is between 0.025λ and 0.8λ. The shear wave velocity Vs is approximately 7243 m / s, and the longitudinal wave velocity Vl is approximately 11359 m / s.

[0195] The substrate 11 is made of single-crystal Si (110) with a tangential orientation of (-45°, 90°, 0°). The shear wave velocity Vs is approximately 4676 m / s, and the longitudinal wave velocity Vl is approximately 9135 m / s.

[0196] The rest of the structure is the same as in Example 1. In the above surface acoustic wave resonator 10, the lowest sound velocity in all higher-order miscellaneous modes is about 5401 m / s.

[0197] Figure 16 is a schematic diagram of the admittance curves of the surface acoustic wave resonators shown in Comparative Example 1 and Example 2.

[0198] As shown in Figure 16, compared with the above comparative example 1, the surface wave resonator 10 provided in this application embodiment can still achieve a good high-order miscellaneous mode suppression effect by changing the material of the internal film layer.

[0199] Example 3

[0200] The main difference between Example 3 and Example 2 is that the surface acoustic wave resonator 10 also includes a connecting auxiliary layer 15.

[0201] As shown in Figure 11, the surface acoustic wave resonator 10 includes a substrate 11 and a connection auxiliary layer 15, a first high-velocity layer 121, a second high-velocity layer 122, a low-velocity layer 13, a piezoelectric layer 14, and an interdigitated electrode (IDT) (not shown in the figure) sequentially disposed on the substrate 11.

[0202] The material of the connecting auxiliary layer 15 is silicon nitride, with a shear wave velocity Vs of approximately 5725 m / s and a longitudinal wave velocity Vl of approximately 8980 m / s.

[0203] The rest of the structure is the same as in Example 2. In the above-mentioned surface acoustic wave resonator 10, the lowest sound velocity in all higher-order miscellaneous modes is about 5401 m / s.

[0204] Figure 17 is a schematic diagram of the admittance curves of the surface acoustic wave resonators shown in Comparative Example 1, Example 2 and Example 3.

[0205] As shown in Figure 17, compared to Comparative Example 1 above, the surface wave resonator 10 provided in this embodiment of the application can still achieve a good high-order miscellaneous mode suppression effect by changing the material of the internal film layer. Compared to Example 2, adding a connecting auxiliary layer 15 to the surface wave resonator 10 can reduce the manufacturing difficulty and improve the mechanical strength of the substrate 11, while not affecting the high-order miscellaneous mode suppression effect.

[0206] Example 4

[0207] The main difference between Example 4 and Example 3 is that the material used to connect the auxiliary layer 15 is different.

[0208] As shown in Figure 11, the surface acoustic wave resonator 10 includes a substrate 11 and a connection auxiliary layer 15, a first high-velocity layer 121, a second high-velocity layer 122, a low-velocity layer 13, a piezoelectric layer 14, and an interdigitated electrode (IDT) (not shown in the figure) sequentially disposed on the substrate 11.

[0209] The material of the connecting auxiliary layer 15 is silicon oxide, with a shear wave velocity Vs of approximately 3687 m / s and a longitudinal wave velocity Vl of approximately 5640 m / s.

[0210] The rest of the structure is the same as in Example 3. In the above-mentioned surface acoustic wave resonator 10, the lowest sound velocity in all higher-order miscellaneous modes is about 5401 m / s.

[0211] Figure 18 is a schematic diagram of the admittance curves of the surface acoustic wave resonators shown in Comparative Example 1, Example 2 and Example 4.

[0212] As shown in Figure 18, compared to Comparative Example 1 above, the surface wave resonator 10 provided in this application, by changing the material of the internal film layer, can still achieve a good high-order miscellaneous mode suppression effect. Compared to Example 2, the surface wave resonator 10 adds a connecting auxiliary layer 15 with lower shear wave velocity Vs and longitudinal wave velocity Vl, which still does not affect the high-order miscellaneous mode suppression effect.

[0213] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A substrate structure, characterized in that, For use in surface acoustic wave devices, the substrate structure includes: Base; A first hypersonic layer is disposed on one side of the substrate; A low-velocity layer is disposed on the side of the first high-velocity layer away from the substrate; A piezoelectric layer is disposed on the side of the low-velocity layer away from the substrate; Among the first high-velocity layer, the low-velocity layer, the substrate, and the piezoelectric layer, the material of the first high-velocity layer has the highest shear wave velocity and longitudinal wave velocity.

2. The substrate structure according to claim 1, characterized in that, The substrate structure further includes a second high-velocity acoustic layer; the second high-velocity acoustic layer is disposed between the first high-velocity acoustic layer and the low-velocity acoustic layer; The shear wave velocity of the material of the second hypersonic layer is lower than that of the material of the first hypersonic layer; and the longitudinal wave velocity of the material of the second hypersonic layer is lower than that of the material of the first hypersonic layer. The shear wave velocity of the material in the second high-velocity layer is higher than that of the material in the low-velocity layer; or, the longitudinal wave velocity of the material in the second high-velocity layer is higher than that of the material in the low-velocity layer.

3. The substrate structure according to claim 1 or 2, characterized in that, The volume wave velocity of the substrate material is higher than the surface wave principal mode velocity of the surface acoustic wave device, but lower than the velocity of the lowest-speed higher-order miscellaneous mode in the surface acoustic wave device.

4. The substrate structure according to claim 3, characterized in that, The substrate is made of single-crystal silicon, and the tangential orientation of the substrate is (α, β, θ), where α = -45° ± 15° or α = 135° ± 15°, β = 90° ± 20° or β = -90° ± 20°, and θ = 0° ± 50°. or, The substrate is made of monocrystalline silicon, and the tangential orientation of the substrate is (α, β, θ), where α = -45° ± 15° or α = 135° ± 15°, β = 54.74° ± 15° or β = -54.74° ± 15°, and θ = 0° ± 90°.

5. The substrate structure according to any one of claims 1-4, characterized in that, The substrate structure further includes a connection auxiliary layer disposed between the first hypersonic layer and the substrate; the shear wave velocity of the material of the connection auxiliary layer is lower than the shear wave velocity of the material of the first hypersonic layer; and the longitudinal wave velocity of the material of the connection auxiliary layer is lower than the longitudinal wave velocity of the material of the first hypersonic layer.

6. The substrate structure according to any one of claims 1-5, characterized in that, The shear wave velocity of the material in the low-velocity layer is lower than that of the material in the piezoelectric layer.

7. The substrate structure according to any one of claims 1-6, characterized in that, The shear wave velocity of the first hypersonic layer is in the range of 5500 m / s to 13000 m / s, and the longitudinal wave velocity is in the range of 8000 m / s to 20000 m / s.

8. The substrate structure according to any one of claims 1-7, characterized in that, The thickness of the first high-velocity acoustic layer is in the range of 0.025λ to 0.8λ, where λ is the wavelength of the surface acoustic wave propagating in the surface acoustic wave device.

9. The substrate structure according to any one of claims 1-8, characterized in that, The material of the first hypersonic layer includes at least one of diamond, silicon carbide, sapphire, spinel, or silicon nitride.

10. The substrate structure according to any one of claims 1-9, characterized in that, The shear wave velocity of the second hypersonic layer is in the range of 4000 m / s to 7000 m / s, and the longitudinal wave velocity is in the range of 5500 m / s to 12000 m / s.

11. The substrate structure according to any one of claims 2-10, characterized in that, The thickness of the second high-velocity acoustic layer is in the range of 0.03λ to 1λ, where λ is the wavelength of the surface acoustic wave propagating in the surface acoustic wave device.

12. The substrate structure according to any one of claims 2-11, characterized in that, The material of the second hypersonic layer includes at least one of silicon nitride, polycrystalline silicon, aluminum oxide, or aluminum nitride.

13. The substrate structure according to any one of claims 1-12, characterized in that, The shear wave velocity of the low-velocity layer is in the range of 2000 m / s to 4500 m / s, and the longitudinal wave velocity is in the range of 3500 m / s to 7000 m / s.

14. The substrate structure according to any one of claims 1-13, characterized in that, The shear wave velocity of the piezoelectric layer is in the range of 2500m / s to 5000m / s, and the longitudinal wave velocity is in the range of 4000m / s to 7500m / s.

15. A surface acoustic wave resonator, characterized in that, The surface acoustic wave resonator includes a substrate structure and interdigitated electrodes; the substrate structure includes the substrate structure according to any one of claims 1-14; the interdigitated electrodes are disposed on the side of the piezoelectric layer away from the substrate.

16. A filter, characterized in that, It includes multiple cascaded surface acoustic wave resonators; wherein the surface acoustic wave resonators include the surface acoustic wave resonator of claim 15.

17. A radio frequency front-end module, characterized in that, It includes a filter and an amplifier, the filter being coupled to the amplifier; the filter includes the filter of claim 16.

18. A mobile terminal, characterized in that, The mobile terminal includes: Circuit board; A filter is disposed on the circuit board; the filter includes the filter of claim 16. or, A radio frequency front-end module is disposed on the circuit board, and the radio frequency front-end module includes the radio frequency front-end module according to claim 17.

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