A surface acoustic wave device

Abstract

The application discloses a surface acoustic wave device. The surface acoustic wave device comprises an interdigital transducer; the interdigital transducer comprises a first bus bar, a second bus bar, a plurality of first long electrode fingers connected with the first bus bar and a plurality of second long electrode fingers connected with the second bus bar; an active region of the interdigital transducer is an area in which the first long electrode fingers and the second long electrode fingers overlap along a first direction; the first long electrode fingers and the second long electrode fingers in the active region are arranged alternately along the first direction and extend along a second direction, wherein the second direction intersects with the first direction; along the second direction, the width of the first long electrode fingers in the active region gradually decreases and then gradually increases; along the second direction, the width of the second long electrode fingers in the active region gradually decreases and then gradually increases. The long electrode fingers in the active region are configured in a concave profile, so that the stray mode can be suppressed while the electromechanical coupling coefficient of the main mode of the surface acoustic wave device, the quality factor and the electromechanical coupling coefficient are maintained.

Description

Technical Field

[0001] This invention relates to the field of communication technology, and in particular to a surface acoustic wave device. Background Technology

[0002] The deployment of 5G new radio (NR) bands has created an urgent need for high-performance surface acoustic wave (SAW) resonators that can operate in the multi-megahertz band while also having a large electromechanical coupling coefficient (k²).

[0003] Currently, three types of devices have emerged as the main candidates: longitudinal leaky surface acoustic wave (LLSAW) resonators, thin-film surface acoustic wave (TF-SAW) resonators, and solid-state assembled surface acoustic wave (SMR-SAW) resonators. All of these device families include interdigital transducers, which are typically made of aluminum, but any compatible conductive metal material can also be used.

[0004] Although the above three devices possess high-frequency operation capability and a high electromechanical coupling coefficient (k²), they are all limited by the following spurious modes and the trade-off between the electromechanical coupling coefficient (k²) and spurious suppression, resulting in a decrease in in-band and out-of-band performance:

[0005] 1. Lateral stray mode

[0006] The sound velocity within the effective aperture is lower than that in the surrounding busbar region, forming an acoustic waveguide structure. While this waveguide can confine the dominant mode, it also excites higher-order transverse modes, manifesting as passband ripples.

[0007] 2. Horizontal Shear (SH) Mode and Rayleigh Mode

[0008] Depending on the thickness of the piezoelectric film and the metal layer of the interdigital transducer, horizontal shear surface acoustic waves and Rayleigh modes will appear on the upper and lower sides of the target resonant / anti-resonant frequency. These modes will generate out-of-band notches, thereby reducing the stopband attenuation and exacerbating coexistence interference with the 4G-LTE band.

[0009] 3. The trade-off between electromechanical coupling coefficient (k²) and spurious suppression

[0010] Taking a specific longitudinal leaky surface acoustic wave (LLSAW) as an example, rotating the in-plane orientation of the X-cut lithium niobate (e.g., from X-37°-Y to X-55°-Y) can suppress horizontal shear surface acoustic waves and Rayleigh modes, but simultaneously reduces the electromechanical coupling coefficient (k²) by a certain percentage. Currently, in the LLSAW, TF-SAW, and SMR-SAW series architectures, no existing geometry can simultaneously achieve a high electromechanical coupling coefficient, a high quality factor (Q value), and broad stray mode suppression capabilities. Summary of the Invention

[0011] This invention provides a surface acoustic wave (SAW) device to solve the problem that existing SAW devices cannot simultaneously achieve a high electromechanical coupling coefficient, a high quality factor (Q value), and a wide range of stray mode suppression capabilities.

[0012] This invention provides a surface acoustic wave device, including an interdigital transducer;

[0013] The interdigital transducer includes a first busbar, a second busbar, a plurality of first long electrode fingers connected to the first busbar, and a plurality of second long electrode fingers connected to the second busbar;

[0014] The active region of the interdigital transducer is the area where the first long electrode finger and the second long electrode finger overlap along the first direction;

[0015] The first long electrode finger and the second long electrode finger located in the active region are alternately arranged along the first direction and extend along the second direction, wherein the second direction intersects with the first direction;

[0016] Along the second direction, the width of the first long electrode finger located in the active region first gradually decreases and then gradually increases;

[0017] Along the second direction, the width of the second long electrode finger located in the active region first gradually decreases and then gradually increases.

[0018] Optionally, in the active region, the width of the first long electrode finger located on the first axis is minimized, wherein the first axis extends along the first direction and passes through the center of the active region;

[0019] In the active region, the width of the first long electrode finger located on the second axis and the width of the first long electrode finger located on the third axis are the same and the maximum, wherein the second axis extends along the first direction and passes through the active region near the side of the first busbar, and the third axis extends along the first direction and passes through the active region near the side of the second busbar.

[0020] In the active region, the width of the second long electrode finger located on the first axis is the smallest;

[0021] In the active region, the width of the second long electrode finger located on the second axis is the same as and the maximum width of the second long electrode finger located on the third axis.

[0022] Optionally, the surface acoustic wave device further includes an interdigitated filling structure located in the active region;

[0023] The interdigitated filling structure includes a first interdigitated filling unit arranged along the first direction and located on both sides of the first long electrode finger, and a second interdigitated filling unit arranged along the first direction and located on both sides of the second long electrode finger.

[0024] Optionally, the curvature of the surface of the first interdigital filling unit near the first long electrode finger is the same as the curvature of the surface of the first long electrode finger near the first interdigital filling unit.

[0025] The curvature of the surface of the second interdigital filling unit near the second long electrode finger is the same as the curvature of the surface of the second long electrode finger near the second interdigital filling unit.

[0026] Optionally, the material of the filling structure includes silicon dioxide, silicon nitride, hafnium dioxide, the same material as the interdigital transducer, or a material whose acoustic impedance difference with the interdigital transducer material meets a preset range.

[0027] Optionally, the surface acoustic wave device further includes a first reflective grating and a second reflective grating;

[0028] Along the first direction, the first reflective grating and the second reflective grating are respectively located on opposite sides of the interdigital transducer;

[0029] Along the first direction, the first effective reflection area of ​​the first reflective grating and the second effective reflection area of ​​the second reflection are respectively located on opposite sides of the active region;

[0030] The first reflective grating includes a plurality of first reflective electrodes arranged along the first direction;

[0031] The second reflective grating includes a plurality of second reflective electrodes arranged along the first direction;

[0032] Along the second direction, the width of the first reflective electrode located in the first effective reflective area first gradually decreases and then gradually increases;

[0033] Along the second direction, the width of the second reflective electrode located in the second effective reflective area first gradually decreases and then gradually increases.

[0034] Optionally, the surface acoustic wave device further includes a first reflective filling structure located in the first effective reflection region and a second reflective filling structure located in the second effective reflection region;

[0035] The first reflective filling structure includes first reflective filling units arranged along the first direction and located on both sides of the first reflective electrode;

[0036] The second reflective filling structure includes second reflective filling units arranged along the first direction and located on both sides of the second reflective electrode.

[0037] Optionally, the curvature of the surface of the first reflective filling unit near the first reflective electrode is the same as the curvature of the surface of the first reflective electrode near the first reflective filling unit.

[0038] The curvature of the surface of the second reflective filling unit near the second reflective electrode is the same as the curvature of the surface of the second reflective electrode near the second reflective filling unit.

[0039] Optionally, the interdigital transducer further includes a plurality of first short electrode fingers connected to the first busbar and a plurality of second short electrode fingers connected to the second busbar;

[0040] The first short electrode finger and the second short electrode finger are arranged alternately along the first direction, and the first short electrode finger and the second short electrode finger extend along the second direction;

[0041] Along the second direction, there is a gap between the corresponding first long electrode finger and the corresponding second short electrode finger;

[0042] Alternatively, along the second direction, there is a gap between the corresponding first long electrode finger and the corresponding second long electrode finger, a gap between the corresponding first long electrode finger and the corresponding first short electrode finger, and a gap between the corresponding second long electrode finger and the corresponding second short electrode finger.

[0043] Optionally, along the second direction, the width of the first short electrode finger first gradually decreases and then gradually increases;

[0044] Along the second direction, the width of the second short electrode finger first gradually decreases and then gradually increases.

[0045] The technical solution of this invention, by setting the first and second long electrode fingers of the active region to adopt a concave profile configuration, can change the sound velocity distribution of the surface acoustic wave device, so that only one propagation mode with a flat shape exists in the active region. In this way, transverse spurious modes, horizontal shear and Rayleigh spurious modes are suppressed while keeping the phase velocity, quality factor and electromechanical coupling coefficient of the resonator main mode unchanged.

[0046] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a schematic diagram of the structure of a surface acoustic wave device provided in an embodiment of the present invention;

[0049] Figure 2 for Figure 1 A schematic diagram of a cross-section line A-A';

[0050] Figure 3 for Figure 1 A magnified view of a portion of S1 in the middle;

[0051] Figure 4 This is a schematic diagram of another surface acoustic wave device provided in an embodiment of the present invention;

[0052] Figure 5 for Figure 4 A schematic diagram of a cross-section line B-B';

[0053] Figure 6 for Figure 4 A magnified view of a portion of point S2 in the middle;

[0054] Figure 7 This is a schematic diagram of the structure of another surface acoustic wave device provided in an embodiment of the present invention;

[0055] Figure 8 This is a schematic diagram of the structure of another surface acoustic wave device provided in an embodiment of the present invention;

[0056] Figure 9 Admittance amplitude response curves of surface acoustic wave devices provided for the prior art;

[0057] Figure 10 A comparison of the admittance amplitude response curves of surface acoustic wave devices provided by the prior art and the surface acoustic wave devices provided by the embodiments of the present invention;

[0058] Figure 11 A comparison of admittance amplitude response curves of surface acoustic wave devices provided by the prior art and surface acoustic wave devices with different concavities of long electrodes provided by the embodiments of the present invention;

[0059] Figure 12 A comparison of admittance amplitude response curves of surface acoustic wave devices provided by the prior art and surface acoustic wave devices with interdigitated filling structures provided by the embodiments of the present invention using different materials;

[0060] Figure 13 This is a schematic diagram of the structure of another surface acoustic wave device provided in an embodiment of the present invention;

[0061] Figure 14 This is a schematic diagram of the structure of another surface acoustic wave device provided in an embodiment of the present invention;

[0062] Figure 15 This is a schematic diagram of the structure of another surface acoustic wave device provided in an embodiment of the present invention;

[0063] Explanation of reference numerals in the attached figures: 10, interdigital transducer; 11, first busbar; 12, second busbar; 13, first long electrode finger; 14, second long electrode finger; 15, first short electrode finger; 16, second short electrode finger; 101, active region; X, first direction; Y, second direction; Z, third direction; 20, substrate; 30, piezoelectric layer; 40, interdigital filling structure; 41, first interdigital filling unit; 42, second interdigital filling unit; 131. First inclined section; 141. Second inclined section; 50. First reflective grid; 60. Second reflective grid; 501. First effective reflective area; 601. Second effective reflective area; 51. First reflective electrode; 52. Third busbar; 53. Fourth busbar; 61. Second reflective electrode; 62. Fifth busbar; 63. Sixth busbar; 70. First reflective filling structure; 71. First reflective filling unit; 80. Second reflective filling structure; 81. Second reflective filling unit. Detailed Implementation

[0064] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0065] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices. The terms "upper," "lower," "left," "right," etc., indicate orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings and are only used to describe the relative positional relationships between components or constituent parts, and do not specifically limit the specific installation orientation of each component or constituent part.

[0066] Figure 1 This is a schematic diagram of the structure of a surface acoustic wave device provided in an embodiment of the present invention, with reference to... Figure 1 The surface acoustic wave device in this embodiment of the invention includes an interdigital transducer 10; the interdigital transducer 10 includes a first busbar 11, a second busbar 12, a plurality of first long electrode fingers 13 connected to the first busbar 11, and a plurality of second long electrode fingers 14 connected to the second busbar 12; the active region 101 of the interdigital transducer 10 is the region where the first long electrode fingers 13 and the second long electrode fingers 14 overlap along a first direction X; the first long electrode fingers 13 and the second long electrode fingers 14 located in the active region 101 are alternately arranged along the first direction X and extend along a second direction Y, wherein the second direction Y intersects with the first direction X; along the second direction Y, the width of the first long electrode fingers 13 located in the active region 101 first gradually decreases and then gradually increases; along the second direction Y, the width of the second long electrode fingers 14 located in the active region 101 first gradually decreases and then gradually increases.

[0067] It should be noted that the surface acoustic wave (SAW) device in this embodiment of the invention is a SAW resonator architecture that can be implemented on any heterostructure substrate and is adaptable to different SAW configurations based on heterostructure substrates. This SAW device employs a layered structure comprising two or more layers and is compatible with, but not limited to, longitudinal leakage SAW (LLSAW), thin-film SAW (TF-SAW), and solid-state assembled SAW resonator (SMR-SAW) devices.

[0068] Figure 2 for Figure 1 A schematic diagram of a cross-section along section line A-A', see reference. Figure 2The surface acoustic wave device in this embodiment of the invention further includes a substrate 20 and a piezoelectric layer 30 stacked along a third direction Z-axis. Specifically, the piezoelectric layer 30 is located on one side of the substrate 20, and the interdigital transducer 10 is located on the side of the piezoelectric layer 30 away from the substrate 20. The material of the piezoelectric layer 30 is preferably X-cut lithium niobate (…). However, lithium tantalate of any cut shape can also be used. ) or lithium niobate. The substrate 20 is preferably made of 4H-silicon carbide (4H-SiC), but sapphire ( Diamond or other hypersonic substrate 20 materials are also suitable. It should be noted that the heterostructure stacked below the interdigital transducer 10 is not limited to the two layers mentioned above; examples of multilayer heterostructures include: / Polycrystalline silicon (Si) / / Si、 / / W / / … / Si, etc., other multilayer structures based on lithium niobate are also feasible. Furthermore, the piezoelectric layer 30 can also be a multilayer piezoelectric heterostructure, such as X( )-Y LN / X( In the case of X37°-Y LN / SiC, the top piezoelectric material has different tangential orientations. In a specific example, if the top layer is X37°-Y LN, the bottom layer can be set to X(180°-37°)-Y LN. This is only an exemplary combination, and different tangential combinations can be used according to specific needs.

[0069] Figure 3 for Figure 1 A magnified view of a portion of point S1. Figure 3 The detailed structure of the interdigital transducer 10 is shown. The first busbar 11 is connected to one end of the first long electrode finger 13, while the other end of the first long electrode finger 13 has a gap and does not contact the second busbar 12. The second busbar 12 is connected to one end of the second long electrode finger 14, while the other end of the second long electrode finger 14 has a gap and does not contact the first busbar 11. Within the effective aperture region (i.e., the active region 101), the side surface of the second long electrode finger 14 is concave, and the curvature of this concave surface is determined by… Figure 3 X1 and Y1 are defined together. It should be noted that X1 represents the distance between the maximum and minimum width of the second long electrode finger 14 within the active region 101 in the first direction X, and Y1 represents the depth of the indentation of the side of the second long electrode finger 14 at the minimum width within the active region 101 in the second direction Y. The case of the first long electrode finger 13 is similar to that of the second long electrode finger 14, and will not be described in detail here.

[0070] refer to Figure 1 and Figure 2In this embodiment of the invention, the first direction X, the second direction Y, and the third direction Z can be perpendicular to each other. The interdigital transducer 10, which includes two busbars and multiple electrode fingers, in the surface acoustic wave device can be used to convert electrical signals into sound waves. Specifically, by applying an electrical signal to the first busbar 11 and the second busbar 12, the piezoelectric layer 30 can vibrate to generate sound waves. Ideally, the sound waves should only propagate on the piezoelectric layer 30 in the active region 101. However, in reality, a portion of the sound waves leaks out, forming transverse mode waves. These transverse mode waves interfere with the sound waves propagating on the piezoelectric layer 30 in the active region 101, thereby affecting the filtering performance of the surface acoustic wave resonator. In this embodiment of the invention, by setting the first long electrode finger 13 and the second long electrode finger 14 of the active region 101 to adopt a concave profile configuration, the sound velocity distribution of the surface acoustic wave device can be changed, so that only one propagation mode with a flat shape exists in the active region 101. In this way, while keeping the phase velocity, quality factor and electromechanical coupling coefficient of the resonator main mode unchanged, transverse spurious modes, horizontal shear and Rayleigh spurious modes are suppressed.

[0071] Specifically, in the active region 101, the width of the first long electrode finger 13 located on the first axis is the smallest, wherein the first axis extends along the first direction X and passes through the center of the active region 101; in the active region 101, the width of the first long electrode finger 13 located on the second axis and the width of the first long electrode finger 13 located on the third axis are the same and the largest, wherein the second axis extends along the first direction X and passes through the active region 101 near the first busbar 11, and the third axis extends along the first direction X and passes through the active region 101 near the second busbar 12; in the active region 101, the width of the second long electrode finger 14 located on the first axis is the smallest; in the active region 101, the width of the second long electrode finger 14 located on the second axis and the width of the second long electrode finger 14 located on the third axis are the same and the largest.

[0072] For example, the length (i.e. width) of the first long electrode finger 13 located in the active region 101 in the first direction X can be monotonically increased from the center of the longitudinal direction (i.e. the second direction Y) of the active region 101 towards both ends of the first long electrode finger 13, and reaches the maximum width at the end.

[0073] Figure 4 This is a schematic diagram of another surface acoustic wave device provided in an embodiment of the present invention, with reference to... Figure 4The surface acoustic wave device in this embodiment of the invention also includes a plurality of interdigitated filling structures 40 located in the active region 101; the interdigitated filling structure 40 includes a first interdigitated filling unit 41 arranged along the first direction X and located on both sides of the first long electrode finger 13 and a second interdigitated filling unit 42 arranged along the first direction X and located on both sides of the second long electrode finger 14.

[0074] In this embodiment of the invention, the active region 101 is configured as follows: Figure 4 The interdigitated fill structure 40 shown can break the acoustic impedance continuity of the active region 101, enabling the filter using this surface acoustic wave device to achieve better (ripple-free) in-band and out-of-band filtering performance.

[0075] Figure 5 for Figure 4 A schematic diagram of a cross-section along section line B-B', see reference. Figure 5 In this embodiment of the invention, the interdigitated filling structure 40 is located on the side of the piezoelectric layer 30 away from the substrate 20.

[0076] Optionally, the curvature of the surface of the first interdigital filling unit 41 near the first long electrode finger 13 is the same as the curvature of the surface of the first long electrode finger 13 near the first interdigital filling unit 41; the curvature of the surface of the second interdigital filling unit 42 near the second long electrode finger 14 is the same as the curvature of the surface of the second long electrode finger 14 near the second interdigital filling unit 42.

[0077] Figure 6 for Figure 4 A magnified view of a portion of point S2. Figure 6 The detailed structure of the interdigital transducer 10, the first interdigital filling unit 41, and the second interdigital filling unit 42 is shown. Within the effective aperture region (i.e., the active region 101), the side of the second interdigital filling unit 42 facing the second long electrode finger 14 is convex, while the side away from the second long electrode finger 14 is planar. The curvature of the aforementioned convex surface is determined by… Figure 3 X2 and Y2 are defined together. It should be noted that X2 represents the distance between the maximum and minimum width of the second interdigital filling unit 42 within the active region 101 in the second direction Y. Y1 represents the height of the side of the second interdigital filling unit 42 at its maximum width within the active region 101 protruding in the second direction Y. It should be noted that the curvature of the surface of the second interdigital filling unit 42 near the second long electrode finger 14 being the same as the curvature of the surface of the second long electrode finger 14 near the second interdigital filling unit 42 means that X1 and X2 are equal, and Y1 and Y2 are equal. The relationship between the first interdigital filling unit 41 and the first long electrode finger 13 is the same as the relationship between the second interdigital filling unit 42 and the second long electrode finger 14, and will not be elaborated here.

[0078] refer to Figure 4 and Figure 6 The planes of the first interdigital filling unit 41 and the second interdigital filling unit 42, which are adjacent in the second direction Y and do not have long electrode fingers (first long electrode finger 13 and second long electrode finger 14) between them, can contact each other to form an elliptical configuration.

[0079] In this embodiment of the invention, by setting the curvature of the surface of the first interdigital filling unit 41 near the first long electrode finger 13 to be the same as the curvature of the surface of the first long electrode finger 13 near the first interdigital filling unit 41, and setting the curvature of the surface of the second interdigital filling unit 42 near the second long electrode finger 14 to be the same as the curvature of the surface of the second long electrode finger 14 near the second interdigital filling unit 42, a unique acoustic impedance (Z) partition can be formed in the inter-IDT region, thereby effectively suppressing stray modes and improving overall performance.

[0080] Figure 7 This is a schematic diagram of the structure of another surface acoustic wave device provided in an embodiment of the present invention. Figure 7 The surface acoustic wave device shown is Figure 1 The difference in the surface acoustic wave device shown is that, Figure 7 The first long electrode finger 13 and the second long electrode finger 14 in the interdigital transducer 10 of the surface acoustic wave device shown are in an inclined configuration rather than as shown. Figure 1 The linear configuration shown. Figure 7 The first long electrode finger 13 includes a first inclined portion 131, and the second long electrode finger 14 includes a second inclined portion 141. By setting the long electrode fingers (first long electrode finger 13 and second long electrode finger 14) to adopt an inclined configuration instead of a straight configuration, stray gap modes that may be excited between the bus bar and the long electrode finger located at the end of the active region 101 can be suppressed, while reducing the leakage of acoustic energy to the bus bar.

[0081] Figure 8 This is a schematic diagram of another surface acoustic wave device provided in an embodiment of the present invention. Figure 7 Same, Figure 8 In the surface acoustic wave device, the first long electrode finger 13 and the second long electrode finger 14 of the interdigital transducer 10 adopt an inclined configuration. Figure 8 The active region 101 of the interdigital transducer 10 is also provided with, for example Figure 4 The interdigitated filling structure 40 shown helps to break the acoustic impedance continuity of the active region 101, enabling the filter using this surface acoustic wave device to achieve better (ripple-free) in-band and out-of-band filtering performance.

[0082] Figure 9 The admittance amplitude response curves of surface acoustic wave devices provided for the prior art should be noted as follows: Figure 9Curve S11 in the figure represents the admittance amplitude |Y| (dB) curve of a conventional resonator using rectangular electrodes. Dense ripples (a1) appear between its resonant and anti-resonant frequencies, originating from the transverse resonant mode; at the same time, out-of-band spurious responses (a2) are observed, mainly dominated by SH-SAW and Rayleigh modes.

[0083] Figure 10 The diagram compares the admittance amplitude response curves of surface acoustic wave (SAW) devices provided in the prior art and those provided in the embodiments of the present invention. It should be noted that curves S21, S22, and S23 correspond to the admittance amplitude |Y| (dB) of three resonator variants, respectively. Curve S21 corresponds to a conventional resonator using rectangular electrode fingers, curve S22 corresponds to a resonator with concave long electrode fingers provided in the embodiments of the present invention, and curve S23 corresponds to a resonator with concave long electrode fingers and a filling structure provided in the embodiments of the present invention. The conventional design exhibits significant transverse spurious response (b1) as well as SH-SAW and Rayleigh modes (b5). The two improved concave long electrode finger designs provided in the embodiments of the present invention almost completely eliminate transverse modes (b2, b3). However, the resonator without the filling structure exhibits a split resonance peak (b4) and retains SH-SAW spurious response below the resonant frequency. These anomalies disappear in the resonator with the filling structure, producing a clean, spurious-free, wide-range response.

[0084] Figure 11 A comparison of admittance amplitude response curves of surface acoustic wave (SAW) devices provided by existing technologies and SAW devices with long electrode fingers having different concavities provided by embodiments of the present invention. Figure 11 The admittance amplitude |Y| (dB) curve (S31) of a conventional resonator with rectangular electrode fingers is compared with that of a resonator with concave long electrode fingers and a filling structure, wherein the filling structure and the concave long electrode fingers are made of the same material. Four concavity depths (Y1) were tested: 60 nm (S32), 75 nm (S33), 90 nm (S34), and 105 nm (S35). The 60–90 nm device completely suppressed the transverse spurious modes (c2–c4), while the 105 nm device showed obvious transverse modes and a split main peak. All four variants suppressed SH-SAW and Rayleigh spurious modes (c6).

[0085] Optionally, the filling structure may be made of silicon dioxide, silicon nitride, hafnium dioxide, the same material as the interdigital transducer 10, or a material whose acoustic impedance difference with that of the interdigital transducer 10 meets a preset range.

[0086] For example, the material of the filling structure can be the same metal (e.g., aluminum) as the interdigital transducer 10, or a different metal / non-metal material, preferably a dielectric material such as... , or .

[0087] Figure 12 The graph compares the admittance amplitude response curves of surface acoustic wave (SAW) devices using different materials in the prior art and the interdigitated filling structure provided in the embodiments of the present invention. It should be noted that... Figure 12 This paper compares the admittance amplitude |Y| (dB) curves of a traditional resonator and an improved resonator. The latter uses concave long electrode fingers and a filling structure made of six different materials. Curve S41 corresponds to the traditional resonator, curve S42 corresponds to the improved resonator with an Al filling structure, curve S43 corresponds to the improved resonator with a Cu filling structure, and curve S44 corresponds to the improved resonator with a Cu filling structure. The improved resonator, curve S45 corresponds to the improved resonator with Ti material for the filling structure, and curve S46 corresponds to the improved resonator with Ti material for the filling structure. An improved resonator, curve S47 corresponds to an improved resonator using W as the filling material. Filled with Al, Cu, Ti or The gaps effectively suppress transverse modes (d2–d6). However, the gaps in the filler W, due to excessive mass load, failed to suppress these modes (d7). All gap materials still suppress SH-SAW and Rayleigh stray modes (d8). Velocity mismatch between the filler material and the substrate causes a slight frequency shift. Using the same metal or dielectric material as the interdigital transducer 10, such as… , or These frequency offsets can be minimized and overall performance improved.

[0088] Figure 13 This is a schematic diagram of another surface acoustic wave device provided in an embodiment of the present invention; see reference. Figure 13 The surface acoustic wave device in this embodiment of the invention further includes a first reflective grating 50 and a second reflective grating 60; along the first direction X, the first reflective grating 50 and the second reflective grating 60 are respectively located on opposite sides of the interdigital transducer 10; along the first direction X, the first effective reflection area 501 and the second effective reflection area 601 of the first reflective grating 50 are respectively located on opposite sides of the active region 101; the first reflective grating 50 includes a plurality of first reflective electrodes 51 arranged along the first direction X; the second reflective grating 60 includes a plurality of second reflective electrodes 61 arranged along the first direction X; along the second direction Y, the width of the first reflective electrode 51 located in the first effective reflection area 501 gradually decreases and then gradually increases; along the second direction Y, the width of the second reflective electrode 61 located in the second effective reflection area 601 gradually decreases and then gradually increases.

[0089] Further reference Figure 13 The first reflective grid 50 further includes a third bus bar 52 and a fourth bus bar 53, and the first reflective electrode 51 extends along the second direction Y and is located between the third bus bar 52 and the fourth bus bar 53; the second reflective grid 60 further includes a fifth bus bar 62 and a sixth bus bar 63, and the second reflective electrode 61 extends along the second direction Y and is located between the fifth bus bar 62 and the sixth bus bar 63.

[0090] For example, the first reflective grating 50 and the second reflective grating 60 are located on both sides of the interdigital transducer 10 and can be used to reflect sound waves back to the aperture region, thereby improving device performance.

[0091] This invention provides a reflective grating on both sides of the interdigital transducer 10, and the reflective electrodes in the reflective grating have concave surfaces, just like the long electrodes in the interdigital transducer 10. This helps to maintain the continuity of the sound field and further suppress stray modes.

[0092] Figure 14 This is a schematic diagram of another surface acoustic wave device provided in an embodiment of the present invention, with reference to... Figure 14 The surface acoustic wave device further includes a first reflective filling structure 70 located in the first effective reflection region 501 and a second reflective filling structure 80 located in the second effective reflection region 601; the first reflective filling structure 70 includes first reflective filling units 71 arranged along the first direction X and located on both sides of the first reflective electrode 51; the second reflective filling structure 80 includes second reflective filling units 81 arranged along the first direction X and located on both sides of the second reflective electrode 61.

[0093] The embodiments of the present invention can further suppress stray modes by providing a first reflective filling structure 70 on both sides of the first reflective electrode 51 and a second reflective filling structure 80 on both sides of the second reflective electrode 61.

[0094] As one possible implementation, the curvature of the surface of the first reflective filling unit 71 near the first reflective electrode 51 is the same as the curvature of the surface of the first reflective electrode 51 near the first reflective filling unit 71; the curvature of the surface of the second reflective filling unit 81 near the second reflective electrode 61 is the same as the curvature of the surface of the second reflective electrode 61 near the second reflective filling unit 81.

[0095] It should be noted that the above-mentioned same curvature can be referred to the previous description of the curvature of the surface of the second interdigital filling unit 42 near the second long electrode finger 14 being the same as the curvature of the surface of the second long electrode finger 14 near the second interdigital filling unit 42, which will not be repeated here.

[0096] Figure 15 This is a schematic diagram of another surface acoustic wave device provided in an embodiment of the present invention, with reference to... Figure 1, Figure 3 , Figure 4 , Figure 6 , Figure 7 , Figure 8 , Figure 13 and Figure 13 The interdigital transducer 10 also includes a plurality of first short electrode fingers 15 connected to the first busbar 11 and a plurality of second short electrode fingers 16 connected to the second busbar 12; the first short electrode fingers 15 and the second short electrode fingers 16 are arranged alternately along the first direction X, and the first short electrode fingers 15 and the second short electrode fingers 16 extend along the second direction Y; along the second direction Y, there is a gap between the corresponding first long electrode fingers 13 and the second short electrode fingers 16, and there is a gap between the corresponding second long electrode fingers 14 and the first short electrode fingers 15; or, along the second direction Y, there is a gap between the corresponding first long electrode fingers 13 and the second long electrode fingers 14, there is a gap between the corresponding first long electrode fingers 13 and the first short electrode fingers 15, and there is a gap between the corresponding second long electrode fingers 14 and the second short electrode fingers 16.

[0097] The embodiments of the present invention can purify the spectrum, improve out-of-band rejection, and reduce insertion loss by setting the first short electrode finger 15 and the second short electrode finger 16.

[0098] Figure 15 This is a schematic diagram of another surface acoustic wave device provided in an embodiment of the present invention, with reference to... Figure 15 Along the second direction Y, the width of the first short electrode finger 15 first gradually decreases and then gradually increases; along the second direction Y, the width of the second short electrode finger 16 first gradually decreases and then gradually increases.

[0099] It should be noted that although aluminum (Al) is often used to make busbars, interdigital transducers 10 and reflective grids due to its high conductivity, any other suitable metal or conductive material can also be used.

[0100] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A surface acoustic wave device, characterized in that, Including interdigital transducers; The interdigital transducer includes a first busbar, a second busbar, a plurality of first long electrode fingers connected to the first busbar, and a plurality of second long electrode fingers connected to the second busbar; The active region of the interdigital transducer is the area where the first long electrode finger and the second long electrode finger overlap along the first direction; The first long electrode finger and the second long electrode finger located in the active region are alternately arranged along the first direction and extend along the second direction, wherein the second direction intersects with the first direction; Along the second direction, the width of the first long electrode finger located in the active region first gradually decreases and then gradually increases; Along the second direction, the width of the second long electrode finger located in the active region first gradually decreases and then gradually increases; The surface acoustic wave device further includes an interdigitated filling structure located in the active region; the interdigitated filling structure is used to break the acoustic impedance continuity of the active region; the interdigitated filling structure is used to reduce the stray response in the frequency region below the resonant frequency in the surface acoustic wave device; The interdigitated filling structure includes a first interdigitated filling unit arranged along the first direction and located on both sides of the first long electrode finger, and a second interdigitated filling unit arranged along the first direction and located on both sides of the second long electrode finger. The side of the first interdigital filling unit facing the first long electrode finger is convex, and the side away from the first long electrode finger is flat; the side of the second interdigital filling unit facing the second long electrode finger is convex, and the side away from the second long electrode finger is flat.

2. The surface acoustic wave device according to claim 1, characterized in that, In the active region, the width of the first long electrode finger located on the first axis is the smallest, wherein the first axis extends along the first direction and passes through the center of the active region; In the active region, the width of the first long electrode finger located on the second axis and the width of the first long electrode finger located on the third axis are the same and the maximum, wherein the second axis extends along the first direction and passes through the active region near the side of the first busbar, and the third axis extends along the first direction and passes through the active region near the side of the second busbar. In the active region, the width of the second long electrode finger located on the first axis is the smallest; In the active region, the width of the second long electrode finger located on the second axis is the same as and the maximum width of the second long electrode finger located on the third axis.

3. The surface acoustic wave device according to claim 1, characterized in that, The curvature of the surface of the first interdigital filling unit near the first long electrode finger is the same as the curvature of the surface of the first long electrode finger near the first interdigital filling unit. The curvature of the surface of the second interdigital filling unit near the second long electrode finger is the same as the curvature of the surface of the second long electrode finger near the second interdigital filling unit.

4. The surface acoustic wave device according to claim 1, characterized in that, The filling structure is made of materials including silicon dioxide, silicon nitride, hafnium dioxide, the same material as the interdigital transducer, or a material whose acoustic impedance difference with the interdigital transducer meets a preset range.

5. The surface acoustic wave device according to claim 1, characterized in that, The surface acoustic wave device further includes a first reflective grating and a second reflective grating; Along the first direction, the first reflective grating and the second reflective grating are respectively located on opposite sides of the interdigital transducer; Along the first direction, the first effective reflection area of ​​the first reflective grating and the second effective reflection area of ​​the second reflection are respectively located on opposite sides of the active region; The first reflective grating includes a plurality of first reflective electrodes arranged along the first direction; The second reflective grating includes a plurality of second reflective electrodes arranged along the first direction; Along the second direction, the width of the first reflective electrode located in the first effective reflective area first gradually decreases and then gradually increases; Along the second direction, the width of the second reflective electrode located in the second effective reflective area first gradually decreases and then gradually increases.

6. The surface acoustic wave device according to claim 5, characterized in that, The surface acoustic wave device further includes a first reflective filling structure located in the first effective reflection region and a second reflective filling structure located in the second effective reflection region; The first reflective filling structure includes first reflective filling units arranged along the first direction and located on both sides of the first reflective electrode; The second reflective filling structure includes second reflective filling units arranged along the first direction and located on both sides of the second reflective electrode.

7. The surface acoustic wave device according to claim 6, characterized in that, The curvature of the surface of the first reflective filling unit near the first reflective electrode is the same as the curvature of the surface of the first reflective electrode near the first reflective filling unit. The curvature of the surface of the second reflective filling unit near the second reflective electrode is the same as the curvature of the surface of the second reflective electrode near the second reflective filling unit.

8. The surface acoustic wave device according to claim 1, characterized in that, The interdigital transducer further includes a plurality of first short electrode fingers connected to the first busbar and a plurality of second short electrode fingers connected to the second busbar; The first short electrode finger and the second short electrode finger are arranged alternately along the first direction, and the first short electrode finger and the second short electrode finger extend along the second direction; Along the second direction, there is a gap between the corresponding first long electrode finger and the corresponding second short electrode finger; Alternatively, along the second direction, there is a gap between the corresponding first long electrode finger and the corresponding second long electrode finger, a gap between the corresponding first long electrode finger and the corresponding first short electrode finger, and a gap between the corresponding second long electrode finger and the corresponding second short electrode finger.

9. The surface acoustic wave device according to claim 8, characterized in that, Along the second direction, the width of the first short electrode finger first gradually decreases and then gradually increases; Along the second direction, the width of the second short electrode finger first gradually decreases and then gradually increases.

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