Longitudinal leakage surface acoustic wave resonator and application thereof

Abstract

The invention provides a longitudinal leakage surface acoustic wave resonator and application thereof, and the longitudinal leakage surface acoustic wave resonator comprises a substrate of which one side is provided with a silicon nitride dielectric layer, and at least two interdigital transducers, a photonic crystal reflector and a photonic crystal reflector which are located on the surface of one side of the silicon nitride dielectric layer on the substrate, the interdigital transducers are arranged in a first direction and extend in a second direction, the first direction and the second direction intersect and are parallel to the plane where the substrate is located, and the photonic crystal reflectors are arranged on the two sides of the interdigital transducers in the first direction. According to the longitudinal leakage surface acoustic wave resonator disclosed by the invention, while the electromechanical coupling coefficient of a main mode is maintained, a stray mode caused by sound wave scattering at a reflector grid and an interdigital transducer can be remarkably inhibited, and a quality factor is maintained, so that a filter adopting the resonator can realize good in-band filtering performance.

Description

Technical Field

[0001] This invention belongs to the field of filter technology and relates to a longitudinal leakage surface acoustic wave resonator and its application. Background Technology

[0002] Longitudinal leakage surface acoustic wave (LLLSAW) resonators are a type of surface acoustic wave (SAW) device that has attracted considerable attention due to its potential in high-frequency applications, such as new 5G radio frequency bands. The development of LLSAW resonators aims to address the limitations of traditional SAW devices, such as relatively low phase velocity and electromechanical coupling coefficients. With the emergence of new 5G frequency bands, the market demands high-performance SAW devices capable of operating at higher frequencies and with lower propagation losses. This has driven extensive research into different wave modes, substrate cuts, layered structures, and piezoelectric materials to improve the performance of SAW devices.

[0003] Similar to conventional SAW devices, LLSAW resonators employ interdigital transducer (IDT) electrodes with metal gate reflectors positioned on either side of the IDT. Due to the high phase velocity of the substrate, these devices can effectively excite longitudinally leaking surface acoustic wave (LLSAW) modes, thus facilitating the realization of high-frequency resonators.

[0004] Traditional reflective gratings are used in longitudinal leakage mode SAW devices. When the reflective grating and IDT have similar center-to-center distances, as with conventional SAW devices, they will be strongly scattered at the connection between the IDT and the reflective grating electrode, generating parasitic modes. This affects the flatness of the filter passband, reduces the filter performance, and leads to deterioration of the in-band filter performance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a longitudinal leakage surface acoustic wave resonator and its application. The longitudinal leakage surface acoustic wave resonator of the present invention can significantly suppress stray modes caused by acoustic wave scattering at the reflector grid and interdigital transducers while maintaining the electromechanical coupling coefficient of the master mode, and maintain the quality factor. This enables filters using this resonator to achieve good in-band filtering performance.

[0006] To achieve this objective, the present invention employs the following technical solution:

[0007] In a first aspect, the present invention provides a longitudinal leakage surface acoustic wave resonator, the longitudinal leakage surface acoustic wave resonator comprising a substrate having a silicon nitride dielectric layer disposed on one side, at least two interdigital transducers and a phononic crystal reflector located on one side surface of the silicon nitride dielectric layer on the substrate, the interdigital transducers being arranged along a first direction and all extending along a second direction, the first direction intersecting the second direction and all being parallel to the plane of the substrate;

[0008] The phononic crystal reflector is disposed on both sides of the interdigital transducer along the first direction. Along the first direction, there is a gap between two adjacent phononic crystal reflectors, and the diameters of the phononic crystal reflectors located on both sides of the same interdigital transducer are equal. A gap is provided between the phononic crystal reflector and the interdigital transducer.

[0009] The phononic crystal reflector includes a nanopillar phononic crystal reflector and / or a nanotrap phononic crystal reflector.

[0010] The nanopillar phononic crystal reflector of the present invention is based on the nanotrap phononic crystal reflector, in which a metallic nanopillar is filled in the nanotrap.

[0011] The longitudinal leakage surface acoustic wave resonator of the present invention modifies the reflector grid by using a phononic crystal (PnC)-based reflector located on a Si3N4 dielectric layer, suppresses stray modes caused by acoustic wave scattering at the reflector grid and interdigital transducers, and maintains the quality factor, thereby enabling the filter using the resonator to achieve good in-band filtering performance.

[0012] The silicon nitride dielectric layer described in this invention plays a crucial role in longitudinally leaking surface acoustic wave (SAW) resonators, with the following specific functions and advantages: Sound wave guiding and confinement: The phononic crystal structure effectively guides and confines sound wave propagation, ensuring efficient transmission within the device while significantly reducing transmission loss and scattering. In the case of nanowell phononic crystals, the Si3N4 layer can be completely or partially etched to adjust the device's bandgap. This allows for precise control of the frequencies of sound wave transmission and reflection, thereby suppressing higher-order overtones and parasitic modes. Structural stability assurance: Si3N4 possesses a stable crystal structure and excellent mechanical strength, ensuring the reflector region maintains structural integrity under the mechanical stress generated by sound wave propagation. Process compatibility advantage: Si3N4 material is fully compatible with standard manufacturing processes, facilitating large-scale production of SAW resonators and ensuring high yield and repeatability in device manufacturing. Acoustic performance optimization: The material properties of Si3N4 (such as density and elastic constant) affect the scattering and absorption of sound waves in the device. This invention optimizes the sound wave scattering and absorption characteristics by controlling the material parameters of Si3N4, thereby significantly improving device performance. Nanopillar structure support (for nanopillar structures): The Si3N4 layer provides a stable growth substrate for the nanopillars, ensuring their uniform arrangement and precise positioning, which is crucial for achieving the desired acoustic properties.

[0013] The phononic crystal described in this invention can be either a nanopillar type or a nanowell type. In the case of a nanopillar type, the metal of the pillar can be similar to the metal used in IDTs. In the case of a nanowell type, the well can be designed with different geometries.

[0014] In some embodiments, the longitudinally leaking surface acoustic wave resonator is further provided with busbars, the busbars including a first busbar and a second busbar arranged along the second direction; the interdigital transducer includes a first interdigital transducer and a second interdigital transducer; the first interdigital transducer is electrically connected to the first busbar, and the second interdigital transducer is electrically connected to the second busbar; a gap is provided between the end of the first interdigital transducer and the second busbar, and a gap is provided between the end of the second interdigital transducer and the first busbar.

[0015] In some embodiments, the substrate includes a substrate layer, a piezoelectric layer, and a silicon nitride dielectric layer stacked sequentially.

[0016] In some embodiments, the thickness of the substrate layer is 500μm to 600μm, for example: 500μm, 520μm, 550μm, 580μm or 600μm, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0017] In some embodiments, the substrate layer is made of silicon carbide and / or sapphire.

[0018] In some embodiments, the thickness of the piezoelectric layer is 250nm to 550nm, for example: 250nm, 300nm, 350nm, 400nm, 450nm or 550nm, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0019] In some embodiments, the material of the piezoelectric layer includes lithium XY-cut niobate.

[0020] The Si3N4 dielectric layer described in this invention exists only in the reflector region of the device, while the interdigital transducer is directly deposited on the piezoelectric layer.

[0021] In some embodiments, the thickness of the silicon nitride dielectric layer is 50nm to 100nm, for example: 50nm, 60nm, 70nm, 80nm, 90nm or 100nm, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0022] For nanotrap phononic crystal structures, the silicon nitride dielectric layer can be fully or partially etched depending on the bandgap requirements of the specific device. In nanopillar phononic crystal structures, the nanopillars can be made of the same metal material as interdigital transducers (IDTs), but lightweight metals such as aluminum (Al) are generally preferred.

[0023] In some embodiments, an intermediate layer is further disposed between the substrate layer and the piezoelectric layer.

[0024] In some embodiments, the thickness of the intermediate layer is 0nm to 1000nm, for example: 0nm, 10nm, 50nm, 100nm, 200nm or 1000nm, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] In some embodiments, the material of the intermediate layer includes silicon dioxide.

[0026] In some embodiments, the interdigital transducer is made of any one or a combination of at least two of aluminum, copper, gold, tungsten, molybdenum, or silver. Typical but non-limiting combinations include combinations of aluminum and gold, gold and silver, or aluminum and molybdenum.

[0027] In some embodiments, the pitch between adjacent interdigital transducers is 0.3λ to 0.7λ, for example: 0.3λ, 0.4λ, 0.5λ, 0.6λ or 0.7λ, etc., not limited to the listed values, other unlisted values ​​within this range are also applicable, where λ is the resonant wavelength.

[0028] In some embodiments, the nanopillars in the nanopillar phononic crystal reflector are made of the same material as the interdigital transducer.

[0029] In some embodiments, in the nanowell-type phononic crystal reflector, the depth of the nanowell is less than or equal to the thickness of the dielectric layer.

[0030] In a second aspect, the present invention provides a filter comprising a longitudinally leaking surface acoustic wave resonator as described in the first aspect.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The silicon nitride dielectric layer in the longitudinal leakage surface acoustic wave resonator of this invention ensures that the electromechanical coupling coefficient of the master mode is not affected, thus maintaining the efficiency of the surface acoustic wave resonator. The phononic crystal reflector, through its tunable bandgap characteristics, can effectively suppress high-order harmonics and spurious modes, thereby achieving ripple-free filtering performance. This is crucial for applications requiring high selectivity and low signal distortion. The synergistic effect of each component can significantly suppress spurious modes caused by acoustic wave scattering at the reflector grid and interdigital transducers, and maintain the quality factor, enabling filters using this resonator to achieve good in-band filtering performance. Attached Figure Description

[0033] Figure 1 This is a top view schematic diagram of a longitudinally leaking surface acoustic wave resonator based on a nanowell phononic crystal reflector structure provided in an embodiment of the present invention.

[0034] Figure 2This is a schematic cross-sectional view of a longitudinally leaking surface acoustic wave resonator based on a nanowell phononic crystal reflector structure provided in an embodiment of the present invention.

[0035] Figure 3 This is a schematic diagram of a single cell of a nanowell-type phononic crystal in a longitudinally leaking surface acoustic wave resonator provided in an embodiment of the present invention.

[0036] Figure 4 This is a schematic cross-sectional view of a longitudinally leaking surface acoustic wave resonator based on a nanopillar phononic crystal reflector structure provided in an embodiment of the present invention.

[0037] Figure 5 This is a schematic diagram of a single cell of a nanopillar phononic crystal in a longitudinally leaking surface acoustic wave resonator provided in an embodiment of the present invention.

[0038] Figure 6 This is a dispersion characteristic diagram of a nanopillar phonon crystal based on a Si3N4 / X37°-Y-cut LiNbO3 / SiC heterostructure provided in an embodiment of the present invention.

[0039] Figure 7 This is a schematic diagram of a transmission line model provided in an embodiment of the present invention for verifying the transmission characteristics of a nanowell-type phonon crystal.

[0040] Figure 8 This is a diagram showing the total energy storage distribution of the transmission line A-A' cross section in different frequency bands (passband and bandgap) provided in an embodiment of the present invention.

[0041] Figure 9 This is a diagram showing the total stress distribution of the transmission line A-A' cross section in different frequency bands (passband and bandgap) provided in an embodiment of the present invention.

[0042] Figure 10 The embodiments of the present invention are based on Figure 7 Transmission response diagram of nano-trap PnC of the model.

[0043] Figure 11 The diagram shows the admittance (Y) and conductance (G) response characteristics of an LLSAW resonator using a conventional grid reflector.

[0044] Figure 12 The diagram shows the admittance (Y) and conductance (G) response characteristics of the LLSAW resonator using the nanowell phononic crystal reflector provided in the embodiments of the present invention.

[0045] Figure 13 This is a comparison of the total stress distribution at the resonant frequency of LLSAW resonators based on traditional grid reflectors and nanowell reflectors.

[0046] Icons: 101 busbar, 102 interdigitated transducer, 103 interdigitated transducer width, 104 interdigitated transducer pitch, 105 aperture length, 106 gap between the busbar and the end of the interdigitated transducer, 107 gap between the interdigitated transducer and the nanowell phononic crystal reflector, 108 length of the nanowell phononic crystal reflector, 109 length of the nanopillar phononic crystal reflector, 110 diameter of the nanowell phononic crystal, 111 gap between nanowell phononic crystals, 112 lattice constant of the nanowell phononic crystal reflector. 201 is the silicon nitride dielectric layer, 202 is the piezoelectric layer, 203 is the intermediate layer, 204 is the substrate layer, 301 is the lattice constant of the nanowell phononic crystal, 302 is the diameter of the nanowell phononic crystal, 401 is the lattice constant of the nanopillar phononic crystal, 402 is the diameter of the nanopillar in the nanopillar phononic crystal, 501 is the length of the nanopillar in the nanopillar phononic crystal, 601 is the bandgap between 3.68 and 3.74 GHz for the continuous Rayleigh and LLSAW modes, 602 is the main bandgap of the LLSAW wave, 603 is the acoustic ray, 604 is the total displacement field distribution of the continuous Rayleigh and LLSAW modes at the reduced wave vector value k=1, 701 is the spacing between the interdigital transducer and the phononic crystal reflector, and 702 is the right-hand region of the model. 703 is an X37°-Y cut lithium niobate layer, 704 is a matching layer, 801(a) is the bandgap, 802(a) is the passband, 901(b) is the 4.4 GHz bandgap, 902(b) is the 3.4 GHz passband, 1001 is bandgap 1, 1002 is bandgap 2, 1101 is the resonator admittance and conductance curve of a resonator with a conventional grid reflector, 1201 is the resonator admittance and conductance curve of a resonator with a nanowell-type PnC as a reflector, 1301 is the end energy field distribution mode of a conventional gate, 1302 is the end energy field distribution mode of a conventional gate, 1303 is the end energy field distribution mode of the phononic crystal reflector of the LLSAW embodiment of the present invention, and 1304 is the end energy field distribution mode of the phononic crystal reflector of the LLSAW embodiment of the present invention. Detailed Implementation

[0047] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0048] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0049] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0050] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0051] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0052] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0053] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0054] In this invention, the terms "first," "second," "third," "fourth," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0055] This invention modifies the reflector grating by using a phononic crystal (PnC)-based reflector located on a Si3N4 dielectric layer. This suppresses spurious modes caused by acoustic wave scattering at the reflector grating and interdigital transducers, while maintaining the quality factor. Consequently, the filter employing this resonator achieves good in-band filtering performance. The technical details of this invention will now be described in detail with reference to the accompanying drawings.

[0056] Figure 1This is a top view schematic diagram of a longitudinally leaking surface acoustic wave resonator provided in an embodiment of the present invention. The longitudinally leaking surface acoustic wave resonator includes a busbar 101 as the main conductive path, which is connected to an interdigital transducer (IDT) 102 for realizing the mutual conversion between electrical signals and surface acoustic waves. The width 103 of the interdigital transducer is a key parameter for controlling impedance matching and conversion efficiency, while the pitch 104 of the interdigital transducer is set to half the wavelength (0.5λ). The aperture length 105 represents the effective area for sound wave generation and propagation. Gaps 106 are provided between the ends of the busbar 101 and the interdigital transducer 102 to prevent short circuits and ensure normal signal transmission. In addition, a gap 107 is provided between the IDT and the nanowell phononic crystal reflector to optimize the interaction between the sound wave and the reflector. The length 108 of the nanowell phononic crystal reflector is crucial for achieving a high reflectivity. The diameter 110 of the nanowell phononic crystal and the gap 111 between the nanowell phononic crystals are key parameters for controlling the bandgap characteristics and reflectivity. The lattice constant of the nanowell phononic crystal, measured from the center of the PnC hole to the center, is denoted as 112, which is crucial for determining the periodicity and bandgap properties of the nanowell phononic crystal.

[0057] Figure 2 This is a cross-sectional schematic diagram of a longitudinally leaking surface acoustic wave resonator based on a nanowell phononic crystal reflector structure provided in an embodiment of the present invention. The longitudinally leaking surface acoustic wave resonator adopts a multi-layer structure design, with each functional layer synergistically optimizing device performance. The top silicon nitride dielectric layer 201 is dedicated to the reflector region; its thickness variation can control the frequency and width of the bandgap. Increasing the thickness shifts the bandgap to lower frequencies and reduces the bandwidth. The depth of the nanowell phononic crystal can be adjusted by extending it throughout the dielectric layer or confining it to a specific cross-section, thereby achieving fine-tuning of the resonant frequency and bandgap characteristics. The thickness of the piezoelectric layer 202 can vary between 250 nm and 550 nm, and this parameter directly affects the operating frequency of the resonator. The preferred piezoelectric material is X-cut lithium niobate. The thickness combination of the silicon nitride dielectric layer 201 and the piezoelectric layer 202 needs to be optimized through acoustic coupling simulation to ensure optimal electromechanical conversion efficiency and bandgap control capability. An optional intermediate layer 203 is made of silicon dioxide. Its thickness can be adjusted from 0 nm to 1000 nm, which provides design flexibility and the potential to further optimize the resonator's performance. The substrate 204 is made of silicon carbide.

[0058] Figure 3This is a schematic diagram of a single cell of a nanowell-type phononic crystal in a longitudinally leaking surface acoustic wave resonator provided in this embodiment of the invention. The dimensions of this cell structure are crucial for determining the acoustic properties of the crystal. In this design, the lattice constant is set to 301, which determines the periodicity of the phononic crystal and helps determine the frequency at which the bandgap occurs. For example, in C-band applications, the lattice constant can vary from 500 nm to 1000 nm. Notably, an increase in the lattice constant leads to a decrease in frequency; this inverse relationship allows the characteristics of the phononic crystal to be adjusted according to specific acoustic manipulation requirements. The diameter 302 of the phononic crystal plays a significant role in determining the fill ratio of the resonator. The fill ratio is calculated as the ratio of the area occupied by the nanowell to the total area covered by the PnC. By adjusting the diameter, the fill ratio can be controlled, thereby affecting the overall performance of the phononic crystal. A higher fill ratio generally results in a stronger acoustic confinement effect within the nanowell, thereby improving the crystal's reflectivity and selectivity.

[0059] Figure 4 This is a cross-sectional schematic diagram of a longitudinally leaking surface acoustic wave resonator based on a nanopillar-type phononic crystal reflector structure provided in an embodiment of the present invention. The lattice constant 401 of the nanopillars (PnC) in the longitudinally leaking surface acoustic wave resonator determines the periodicity, and thus affects the position and width of the band gap. The diameter 402 of the nanopillars affects the fill rate of the PnC, i.e., the ratio of the area covered by the nanopillars to the total area covered by PnC. Adjusting the diameter can control the fill rate, thereby affecting the overall performance of the phononic crystal. The nanopillars are made of the same lightweight aluminum material as the interdigital transducer. By precisely controlling the dimensions of the nanopillars, including the lattice constant and diameter, device performance can be optimized for specific applications.

[0060] Figure 5 This is a schematic diagram of a single cell of a nanopillar phononic crystal in a longitudinally leaking surface acoustic wave resonator provided in this embodiment of the invention. The single cell is characterized by specific parameters that are crucial to its acoustic properties. One of these parameters is the lattice constant 401 of the nanopillar phononic crystal, which is the regular spacing between the centers of adjacent nanopillars in the crystal lattice structure. This constant is essential for establishing the phonon bandgap characteristics of the crystal. The diameter of the nanopillar is 402. This measurement defines the width of each individual nanopillar in the PnC and plays a significant role in determining the fill fraction of the single cell. The fill fraction is calculated as the ratio of the cross-sectional area of ​​the nanopillar to the total cross-sectional area of ​​the single cell. This ratio is a key factor affecting the phonon bandgap strength and the overall effectiveness of the phononic crystal in reflecting certain frequencies of sound waves. By carefully controlling these dimensions, the behavior of the phononic crystal can be customized to meet specific acoustic management requirements, making it a versatile component in the design of advanced acoustic devices.

[0061] Figure 6This is a dispersion characteristic diagram of a nanopillar phonon crystal based on a Si3N4 / X37°-Y-cut LiNbO3 / SiC heterostructure provided in an embodiment of the present invention. The sample nanowell PnC adopts a square lattice pattern design and is located on a silicon nitride dielectric layer, which in turn is located on an X-cut 37°Y lithium niobate piezoelectric layer bonded to a silicon carbide substrate layer. The geometric parameters of this PnC are defined as follows: lattice constant 301 is 0.7µm, the thickness of the SiC substrate 204 is 550µm, the thickness of the LiNbO3 piezoelectric layer 202 is 0.3µm, the thickness of the silicon nitride dielectric layer 201 is 0.07µm, the nanowell depth is 0.07µm (equal to the thickness of the silicon nitride dielectric layer), and the diameter of the nanowell 302 is 0.5µm. The dispersion characteristics of the surface acoustic wave are determined by calculating the eigenmodes of the wave vector varying in the y-direction. Specifically, 604 in the figure represents the total displacement field distribution of the continuous Rayleigh and LLSAW modes at the reduced wave vector value k=1. Dispersion characteristics indicate a small band gap, denoted as 601, exists between 3.68 and 3.74 GHz. This band gap is due to the weak coupling between the LLSAW and Rayleigh modes. Furthermore, the dominant band gap for LLSAW waves is 602, occurring between 4.05 GHz and 4.50 GHz. Additionally, 603 in the figure represents a ray, which in turn represents a radiation region. The radiation region is determined by the ray, which corresponds to the slowest volume sound wave. It is noteworthy that pure SAW modes do not exist above the ray. Conversely, modes located below the ray are classified as pure SAW.

[0062] Figure 7 This is a schematic diagram of a transmission line model provided in an embodiment of the present invention for verifying the transmission characteristics of a nanowell-type phononic crystal. The model includes an interdigital transducer 102 for exciting longitudinal leakage surface acoustic waves and a nanowell PnC. The interdigital transducer 102 is located on the left side of the model, spaced 701 from the nanowell PnC. This gap needs to be properly designed to better attenuate the acoustic waves. In this specific case, the interdigital transducer 102 is set to a quarter wavelength. Generally, odd multiples of a quarter wavelength can provide good attenuation. Under excitation, the longitudinal leakage surface acoustic wave propagates to the right into the phononic crystal structure consisting of a silicon nitride dielectric layer 201 and air holes. The structure includes a 300nm x 37° Y-cut lithium niobate layer 703, a 500nm silicon dioxide interlayer 203, a 550μm silicon carbide substrate layer 204, and a matching layer 704. After traversing the entire structure, the sound wave is finally output from the right end of the model. In addition, the transmittance of surface acoustic waves through the nano-well PnC is determined by calculating the ratio of the total acoustic energy in the right-end region 702 (marked as the output) of the model, including the cases with and without nano-well PnC.

[0063] Figure 8This is a diagram showing the total energy storage distribution of the transmission line A-A' cross-section in different frequency bands (passband and bandgap) according to an embodiment of the present invention. Figure 9 This is a total stress distribution diagram of the transmission line A-A' cross-section provided in this embodiment of the invention at different frequency bands (passband and bandgap), showing the total displacement field on the surface and cross-section of the transmission model at two different frequencies (4.4 GHz (bandgap) 901(b) and 3.4 GHz (passband) 902(b)). At the 3.4 GHz passband frequency, the LLSAW wave experiences minimal loss when crossing the PnC. In contrast, at the 4.4 GHz bandgap frequency, the LLSAW wave attenuates rapidly after entering the PnC, clearly demonstrating a significant attenuation characteristic. This attenuation situation... Figure 8 The storage energy density is further illustrated in 801(a) and 802(a), which represent the total energy distribution of the transmission line at the bandgap frequency and the passband frequency, respectively.

[0064] Figure 10 The embodiments of the present invention are based on Figure 7 The transmission response plot of the nanowell-type PnC of the model shows the calculated transmission spectrum, which exhibits two distinct troughs, corresponding to the frequency ranges of band gap 1 (1001) and band gap 2 (1002), respectively. These results are consistent with... Figure 6 The dispersion analysis results presented in the paper are highly consistent.

[0065] Figure 11 This is a graph showing the admittance (Y) and conductance (G) response characteristics of an LLSAW resonator using a conventional grid reflector. Figure 12 The figures show the admittance (Y) and conductance (G) response characteristics of the LLSAW resonator using the nanowell phononic crystal reflector provided in this embodiment of the invention. The figures compare the amplitude-frequency response characteristics of the resonator admittance using a conventional grid reflector (20 grid electrodes) and a nanowell phononic crystal reflector (20 nanowell units). The results show that the resonator (1101) with the conventional grid reflector exhibits in-band spurious modes, while the resonator (1201) with a nanowell PnC as the reflector has no spurious response.

[0066] Figure 13This is a comparison of the total stress distribution at the resonant frequency of LLSAW resonators based on conventional grid reflectors and nanowell-type reflectors, using the longitudinally leaking surface acoustic wave (LLSAW) energy field distribution characteristics of two different reflectors (conventional 20-gate reflector and 20-nanowell phononic crystal reflector). For the conventional gate, the energy field distribution shows significant lateral (end) leakage, as shown in regions 1301 and 1302. This leakage is due to the weak reflectivity of the gate reflector for LLSAW. Therefore, the number of 20 gate electrodes proves insufficient to effectively confine the LLSAW within the resonant cavity. In contrast, the nanowell-based PnC reflector of the same size shows superior ability to confine the LLSAW within the resonant cavity. This is demonstrated in the energy field distribution patterns in regions 1303 and 1304. The PnC-based reflector effectively reduces end leakage and confines the LLSAW, thus making the energy distribution within the resonator more restricted and controllable.

[0067] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A longitudinally leaking surface acoustic wave resonator, characterized in that, The longitudinal leakage surface acoustic wave resonator includes a substrate with a silicon nitride dielectric layer on one side, at least two interdigital transducers located on one side surface of the silicon nitride dielectric layer on the substrate, and a phononic crystal reflector. The interdigital transducers are arranged along a first direction and all extend along a second direction. The first direction intersects the second direction and are all parallel to the plane of the substrate. The phononic crystal reflector is disposed on both sides of the interdigital transducer along the first direction. Along the first direction, there is a gap between two adjacent phononic crystal reflectors, and the diameters of the phononic crystal reflectors located on both sides of the same interdigital transducer are equal. A gap is provided between the phononic crystal reflector and the interdigital transducer. The phononic crystal reflector includes a nanopillar phononic crystal reflector and / or a nanotrap phononic crystal reflector.

2. The longitudinal leakage surface acoustic wave resonator as described in claim 1, characterized in that, The longitudinal leakage surface acoustic wave resonator is further provided with a busbar, the busbar including a first busbar and a second busbar arranged along the second direction; The interdigital transducer includes a first interdigital transducer and a second interdigital transducer. The first interdigital transducer is electrically connected to the first busbar, and the second interdigital transducer is electrically connected to the second busbar; A gap is provided between the end of the first interdigital transducer and the second busbar, and a gap is provided between the end of the second interdigital transducer and the first busbar.

3. The longitudinal leakage surface acoustic wave resonator as described in claim 1, characterized in that, The substrate comprises a substrate layer, a piezoelectric layer, and a silicon nitride dielectric layer stacked sequentially.

4. The longitudinal leakage surface acoustic wave resonator as described in claim 3, characterized in that, The thickness of the substrate layer is 500μm~600μm; And / or, the material of the substrate layer includes silicon carbide and / or sapphire; And / or, the thickness of the piezoelectric layer is 250nm~550nm; And / or, the material of the piezoelectric layer includes lithium XY-cut niobate; And / or, the thickness of the silicon nitride dielectric layer is 50nm~100nm.

5. The longitudinal leakage surface acoustic wave resonator as described in claim 3, characterized in that, An intermediate layer is also provided between the substrate layer and the piezoelectric layer; And / or, the thickness of the intermediate layer is 0 nm to 1000 nm; And / or, the material of the intermediate layer includes silicon dioxide.

6. The longitudinally leaking surface acoustic wave resonator as described in claim 1, characterized in that, The interdigital transducer is made of any one or a combination of at least two of the following materials: aluminum, copper, gold, tungsten, molybdenum, or silver.

7. The longitudinally leaking surface acoustic wave resonator as described in claim 1, characterized in that, The pitch between adjacent interdigital transducers is 0.3λ~0.7λ, where λ is the resonant wavelength.

8. The longitudinal leakage surface acoustic wave resonator as described in claim 1, characterized in that, The nanopillars in the nanopillar phononic crystal reflector are made of the same material as the interdigital transducer.

9. The longitudinal leakage surface acoustic wave resonator as described in claim 1, characterized in that, In the nanowell-type phononic crystal reflector, the depth of the nanowell is less than or equal to the thickness of the dielectric layer.

10. A filter, characterized in that, The filter contains a longitudinally leaking surface acoustic wave resonator as described in any one of claims 1-9.

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