Surface acoustic wave filter and method for forming a surface acoustic wave filter

Abstract

The present invention discloses a surface acoustic wave filter and a method for forming a surface acoustic wave filter. The surface acoustic wave filter comprises: a substrate comprising a base and a piezoelectric layer located on the base, the substrate comprising an interdigital region, a connection region, and a spacer region located between the connection region and the interdigital region, wherein the interdigital region, the connection region, and the spacer region are arranged along a first direction; an electrode layer located on a portion of the surface of the piezoelectric layer facing away from the base, the electrode layer comprising a plurality of interdigital electrodes located on the surface of the interdigital region, wherein the plurality of interdigital electrodes are arranged in parallel along a second direction; each interdigital electrode comprises an interdigital portion and a buffer portion located at both ends of the interdigital portion, the buffer portion comprising a first portion and a second portion located between the first portion and the interdigital portion, the first portion having a larger dimension in the second direction than the interdigital portion, and the second portion having a dimension in the second direction gradually decreasing from the first portion to the interdigital portion. By providing a mass block in the above technical solution, the ability to suppress transverse modes and clutter can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of filters, and in particular to a surface acoustic wave filter and a method for forming the surface acoustic wave filter. Background Art

[0002] A surface acoustic wave filter is a filtering device that utilizes surface acoustic waves propagating on the surface of a piezoelectric material. Its operating principle is to achieve an electrical-to-acoustic-to-electrical energy conversion process through an interdigitated electrode structure. During operation, the interdigitated transducer at the input end converts the electromagnetic signal into an elastic wave that propagates along the surface of the piezoelectric substrate. During transmission, this surface wave performs spectrum selection through the acoustic resonance effect and is ultimately reconstructed into an electrical signal by the output transducer. Due to its miniaturized structure, excellent temperature stability, and low energy loss, this type of filter has become a key component in modern wireless communication systems.

[0003] However, due to limitations in its physical structure and acoustic wave propagation characteristics, this device is prone to multimodal waveguide phenomena during operation: in addition to the main resonant mode, undesirable transverse mode waves are also generated. Furthermore, process and structural factors such as uneven substrate material distribution, electrode processing deviations, and boundary reflections can all lead to parasitic acoustic interference in the transmission path. When these abnormal wave modes are superimposed on the main signal, they can cause signal distortion issues such as increased passband ripple and degraded stopband rejection, directly impacting the transmission quality of the communication system. Summary of the Invention

[0004] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is how to improve the ability to suppress transverse modes and clutter.

[0005] In order to solve at least one of the above-mentioned technical problems, the present invention discloses a surface acoustic wave filter and a method for forming the surface acoustic wave filter.

[0006] According to one aspect of the present application, there is provided a surface acoustic wave filter, comprising:

[0007] A substrate comprising a base and a piezoelectric layer located on the base, the substrate comprising an interdigital region, a connecting region located on both sides of the interdigital region, and a spacer region located between the connecting region and the interdigital region, wherein the interdigital region, the connecting region, and the spacer region are arranged along a first direction parallel to a surface of the substrate;

[0008] an electrode layer located on a portion of a surface of the piezoelectric layer facing away from the substrate, the electrode layer comprising a plurality of interdigital electrodes located on a surface of the interdigital region, the plurality of interdigital electrodes being arranged in parallel along a second direction, the second direction being parallel to the surface of the substrate and perpendicular to the first direction;

[0009] In which, each of the interdigitated electrodes includes an interdigitated portion and a buffer portion located at both ends of the interdigitated portion, the buffer portion includes a first portion and a second portion located between the first portion and the interdigitated portion, the size of the first portion in the second direction is larger than the size of the interdigitated portion in the second direction, and the size of the second portion in the second direction gradually decreases from the first portion to the interdigitated portion.

[0010] Optionally, side walls of several of the buffer portions protrude toward the same side along the second direction relative to the side walls of the interdigital portions.

[0011] Optionally, the second portion has a first side wall connected to the forked portion, and the first side wall is inclined relative to the side wall of the forked portion to which it is connected; the second portion also has a second side wall connected to the forked portion, the second side wall and the first side wall are distributed along the second direction, and the second side wall is flush with the side wall of the forked portion to which it is connected.

[0012] Optionally, a first angle is formed between the first side wall and the connected side wall of the interdigital portion, and the angle range of the first angle is 20° to 85°.

[0013] Optionally, the first portion has a third sidewall perpendicular to the surface of the substrate and parallel to the second direction.

[0014] Optionally, side walls of several of the buffer portions protrude toward both sides along the second direction relative to side walls of the interdigital portion.

[0015] Optionally, the second portion further has a fourth side wall and a fifth side wall connected to the interdigital portion, and the fourth side wall and the fifth side wall are symmetrically distributed relative to the central axis of the interdigital portion along the first direction.

[0016] The fourth side wall and the fifth side wall are parallel to the second direction and inclined relative to the side wall of the interdigital portion.

[0017] Optionally, a second angle is formed between the fourth side wall and the side wall of the interdigital portion to which it is connected, and a third angle is formed between the fifth side wall and the side wall of the interdigital portion to which it is connected.

[0018] The second angle has an angle range of 10° to 85°, the third angle has an angle range of 10° to 85°, and the second angle is the same as or different from the third angle.

[0019] Optionally, the first portion has a sixth sidewall perpendicular to the surface of the substrate and parallel to the second direction.

[0020] Optionally, the electrode layer further includes a plurality of connection portions located on the spacer region, each connection portion is connected to the buffer portion of any one of the interdigital electrodes, and two connection portions connected to two adjacent interdigital electrodes are respectively located on both sides of the interdigital region.

[0021] Optionally, the buffer portion further includes a third portion located between the first portion and the connecting portion, and a size of the third portion in the second direction gradually decreases from the first portion to the connecting portion;

[0022] The side walls of the plurality of buffer portions protrude toward both sides along the second direction relative to the side walls of the interdigital portion.

[0023] Optionally, the third portion has a seventh side wall and an eighth side wall connected to the connecting portion, and the seventh side wall and the eighth side wall are symmetrically distributed relative to the central axis of the connecting portion along the first direction.

[0024] The seventh side wall and the eighth side wall are parallel to the second direction and inclined relative to the side wall of the connecting portion.

[0025] Optionally, a fourth angle is formed between the seventh side wall and the side wall of the connecting portion to which it is connected, and a fifth angle is formed between the eighth side wall and the side wall of the connecting portion to which it is connected.

[0026] The fourth angle has an angle range of 10° to 85°, the fifth angle has an angle range of 10° to 85°, and the fourth angle is the same as or different from the fifth angle.

[0027] Optionally, the buffer portion has a first curved side wall and a second curved side wall connected to the interdigital portion, and the first curved side wall and the second curved side wall are symmetrically distributed relative to a central axis of the interdigital portion along the first direction.

[0028] Optionally, the electrode layer further includes:

[0029] The first bus bar and the second bus bar are respectively located on the spacing area on both sides of the interdigital area, and both the first bus bar and the second bus bar extend along the second direction.

[0030] Optionally, the substrate further comprises:

[0031] The temperature compensation layer is located between the substrate and the piezoelectric layer.

[0032] Optionally, the surface acoustic wave filter further includes:

[0033] The protective layer is located on a side of the electrode layer facing away from the substrate, and covers the electrode layer and the piezoelectric layer exposed between two adjacent interdigital electrodes.

[0034] According to a second aspect of the present application, a method for forming a surface acoustic wave filter is provided, comprising:

[0035] Providing a substrate, comprising a base and a piezoelectric layer located on the base, wherein the substrate comprises an interdigital region, connecting regions located on both sides of the interdigital region, and a spacer region located between the connecting region and the interdigital region, wherein the interdigital region, the connecting region, and the spacer region are arranged along a first direction, and the first direction is parallel to the surface of the substrate;

[0036] forming an electrode layer on a portion of a surface of the piezoelectric layer facing away from the substrate, the electrode layer comprising a plurality of interdigital electrodes located on a surface of the interdigital region, the plurality of interdigital electrodes being arranged in parallel along a second direction, the second direction being parallel to the substrate surface and perpendicular to the first direction;

[0037] In which, each of the interdigitated electrodes includes an interdigitated portion and a buffer portion located at both ends of the interdigitated portion, the buffer portion includes a first portion and a second portion located between the first portion and the interdigitated portion, the size of the first portion in the second direction is larger than the size of the interdigitated portion in the second direction, and the size of the second portion in the second direction gradually decreases from the first portion to the interdigitated portion.

[0038] Optionally, after forming the electrode layer, the method further includes:

[0039] A protective layer is formed, where the protective layer is located on a side of the electrode layer facing away from the substrate, and covers the electrode layer and the piezoelectric layer exposed between two adjacent interdigital electrodes.

[0040] Optionally, the substrate further includes a temperature compensation layer located between the base and the piezoelectric layer.

[0041] Optionally, the electrode layer further includes:

[0042] The first bus bar and the second bus bar are respectively located on the spacing area on both sides of the interdigital area, and both the first bus bar and the second bus bar extend along the second direction.

[0043] In the surface acoustic wave filter of the embodiment of the present application, the three areas of the interdigital area, the connection area and the spacer area are arranged along the first direction, which can set the propagation path of the surface acoustic wave. By arranging buffer parts at both ends of the interdigital electrode, the second part with a gradual size connects the interdigital part and the first part with an expanded diameter, a sound wave reflection barrier can be formed, thereby limiting the stray reflection wave to the buffer zone and preventing it from interfering with the main sound wave propagation path. In addition, since the size of the second part decreases from the first part to the interdigital part, it can play a buffering role in the propagation process of the sound wave, thereby achieving a smooth transition of the sound wave energy. The sound speed decreases when the sound wave passes through the first part, and the sound speed gradually increases after passing through the first part. The energy of the main mode is focused and continues to propagate, while the energy of the high-order transverse mode is dispersed or leaked, thereby reducing the energy scattering and mode coupling caused by speed mismatch during the propagation of the surface acoustic wave. Through the above technical solution, the excitation probability of the transverse mode can be effectively reduced, and the generation of clutter can be reduced, thereby improving the suppression performance of the surface acoustic wave filter for the transverse mode and clutter.

[0044] Other features and advantages of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0046] In order to more completely understand the present application and its beneficial effects, the following description will be given in conjunction with the accompanying drawings, wherein the same drawing numbers represent the same parts in the following description.

[0047] Figure 1 A first top view of a surface acoustic wave filter provided in a specific embodiment of the present disclosure;

[0048] Figure 2 A second top view of a surface acoustic wave filter provided in a specific embodiment of the present disclosure;

[0049] Figure 3 A third top view of a surface acoustic wave filter provided in a specific embodiment of the present disclosure;

[0050] Figure 4 A first side view of a surface acoustic wave filter provided in accordance with an embodiment of the present disclosure;

[0051] Figure 5 A first structural schematic diagram of a buffer portion provided in a specific embodiment of the present disclosure;

[0052] Figure 6 A second structural schematic diagram of a buffer portion provided in a specific embodiment of the present disclosure;

[0053] Figure 7 A fourth top view of a surface acoustic wave filter provided in a specific embodiment of the present disclosure;

[0054] Figure 8 A fifth top view of a surface acoustic wave filter provided in a specific embodiment of the present disclosure;

[0055] Figure 9 A sixth top view of a surface acoustic wave filter provided in a specific embodiment of the present disclosure;

[0056] Figure 10 A second side view of a surface acoustic wave filter provided in accordance with an embodiment of the present disclosure;

[0057] Figure 11 A first sound velocity diagram of a surface acoustic wave filter provided in a specific embodiment of the present disclosure;

[0058] Figure 12 A second sound velocity diagram of a surface acoustic wave filter provided in a specific embodiment of the present disclosure;

[0059] Figure 13 A third sound velocity diagram of a surface acoustic wave filter provided in a specific embodiment of the present disclosure;

[0060] Figure 14 A fourth sound velocity diagram of a surface acoustic wave filter provided in a specific embodiment of the present disclosure;

[0061] Figure 15 A fifth sound velocity diagram of a surface acoustic wave filter provided in a specific embodiment of the present disclosure;

[0062] Figure 16 A sixth sound velocity diagram of a surface acoustic wave filter provided in a specific embodiment of the present disclosure;

[0063] Figure 17 A first side view of another surface acoustic wave filter provided in accordance with an embodiment of the present disclosure;

[0064] Figure 18 A second side view of another surface acoustic wave filter provided according to a specific embodiment of the present disclosure.

[0065] Description of reference numerals:

[0066] 100 - substrate, 110 - base, 111 - interdigital region, 112 - connection region, 113 - spacer region, 120 - piezoelectric layer, 130 - temperature compensation layer;

[0067] 200 - electrode layer, 210 - interdigital electrode, 220 - interdigital portion, 221 - interdigital portion sidewall, 230 - buffer portion, 240 - connecting portion, 250 - connector;

[0068] 300-first part, 310-third side wall, 320-sixth side wall;

[0069] 400 - second part, 410 - first side wall, 420 - second side wall, 430 - fourth side wall, 440 - fifth side wall;

[0070] 500-third part, 510-seventh side wall, 520-eighth side wall;

[0071] 600 - first curved side wall, 610 - second curved side wall, 620 - first bus bar, 630 - second bus bar, 640 - third curved side wall, 650 - fourth curved side wall;

[0072] 700-protective layer;

[0073] α-first angle, β-second angle, γ-third angle, λ-fourth angle, φ-fifth angle, θ-sixth angle, ω-seventh angle;

[0074] H1 - first size, H2 - second size, H3 - third size, H4 - fourth size, H5 - fifth size. DETAILED DESCRIPTION

[0075] The following will be combined with the drawings in the embodiments of this specification to clearly and completely describe the technical solutions in the embodiments of this specification. Obviously, the embodiments described are only part of the embodiments of this specification, not all of the embodiments. Based on the embodiments in this specification, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this invention.

[0076] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way are interchangeable where appropriate so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or server that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0077] Various exemplary embodiments, features, and aspects of the present disclosure will be described in detail below with reference to the accompanying drawings. The same reference numerals in the accompanying drawings represent elements with the same or similar functions. Although various aspects of the embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless otherwise indicated.

[0078] The word “exemplary” is used exclusively herein to mean “serving as an example, example, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[0079] The term "and / or" as used herein describes an association relationship between associated objects, indicating that three relationships can exist. For example, "A and / or B" can represent the existence of A alone, the simultaneous existence of A and B, and the existence of B alone. Furthermore, the term "at least one" as used herein refers to any combination of at least two of any one or more of a plurality of items. For example, "at least one of A, B, and C" can represent any one or more elements selected from the set consisting of A, B, and C.

[0080] In addition, numerous specific details are provided in the following detailed description to better illustrate the present disclosure. Those skilled in the art will appreciate that the present disclosure can be practiced without certain specific details. In some instances, methods, means, components, and circuits well known to those skilled in the art are not described in detail in order to highlight the main points of the present disclosure.

[0081] Figure 1 A first structural top view of a surface acoustic wave filter provided by an exemplary embodiment of the present disclosure, Figure 4 A first structural side view of a surface acoustic wave filter provided by an exemplary embodiment of the present disclosure, as shown in FIG. Figure 1 as well as Figure 4 As shown, the first direction is the x direction, the second direction is the y direction, and the third direction is the z direction. A surface acoustic wave filter includes:

[0082] The substrate 100 includes a base 110 and a piezoelectric layer 120 located on the base 110. The substrate 100 includes an interdigital region 111, a connecting region 112 located on both sides of the interdigital region 111, and a spacer region 113 located between the connecting region 112 and the interdigital region 111. The interdigital region 111, the connecting region 112, and the spacer region 113 are arranged along a first direction, which is parallel to the surface of the substrate 100.

[0083] The substrate 100 further includes a temperature compensation layer 130 located between the base 110 and the piezoelectric layer 120 .

[0084] an electrode layer 200 located on a portion of the surface of the piezoelectric layer 120 facing away from the substrate 110 , the electrode layer 200 including a plurality of interdigital electrodes 210 located on the surface of the interdigital region 111 , the plurality of interdigital electrodes 210 being arranged in parallel along a second direction parallel to the surface of the substrate 100 and perpendicular to the first direction;

[0085] Among them, each interdigitated electrode 210 includes an interdigitated portion 220 and a buffer portion 230 located at both ends of the interdigitated portion 220, the buffer portion 230 includes a first portion 300 and a second portion 400 located between the first portion 300 and the interdigitated portion 220, the size of the first portion 300 in the second direction is larger than the size of the interdigitated portion 220 in the second direction, and the size of the second portion 400 in the second direction gradually decreases from the first portion 300 to the interdigitated portion 220.

[0086] The electrode layer 200 further includes a plurality of connecting portions 240 located on the spacer region 113 . Each connecting portion 240 is connected to the buffer portion 230 of any interdigital electrode 210 . The two connecting portions 240 connected to two adjacent interdigital electrodes 210 are located on both sides of the interdigital region 111 .

[0087] The protective layer 700 is located on a side of the electrode layer 200 facing away from the substrate 110 . The protective layer 700 covers the electrode layer 200 and the piezoelectric layer 120 exposed between two adjacent interdigital electrodes 210 .

[0088] In a specific embodiment, a surface acoustic wave filter includes a substrate 100 and an electrode layer 200. The substrate 100 may include a base 110, a temperature compensation layer 130, and a piezoelectric layer 120, which are stacked in sequence. The base 110 is made of a high-acoustic-velocity material, typically silicon, such as single-crystal silicon, polycrystalline silicon, or sapphire. The piezoelectric layer 120 may be made of a material such as lithium niobate or lithium tantalate. The temperature compensation layer 130 is used to compensate for the effects of temperature changes on the performance of the surface acoustic wave filter and may typically be made of a temperature compensation material such as tantalum oxide or silicon dioxide.

[0089] The substrate 100 can be divided into an interdigital region 111, a connection region 112, and a spacer region 113 based on the structure and functional areas of the upper electrode layer 200. The connection region 112, the spacer region 113, and the interdigital region 111 are arranged along a first direction. The interdigital region 111 includes an IDT region (Interdigital Transducer Region), which is used to convert electrical signals into surface acoustic waves.

[0090] The electrode layer 200 is located on the side of the piezoelectric layer 120 away from the substrate 110 and includes a plurality of interdigital electrodes 210 located on the surface of the interdigital region 111 . The plurality of interdigital electrodes 210 are parallel to the first direction and arranged in parallel and staggered manner along the second direction.

[0091] A protective layer 700 may be provided on the side of the electrode layer 200 facing away from the substrate 110 to protect other layers and prevent oxidation. The protective layer 700 may be made of nitride, such as silicon nitride, etc. The protective layer 700 covers the electrode layer 200 and the exposed piezoelectric layer 120 between two adjacent interdigital electrodes 210 .

[0092] In addition, in order to clearly show the arrangement of the electrode layer 200 on the piezoelectric layer 120, the top view of any structure corresponding to the surface acoustic wave filter disclosed in the present invention does not reflect the protective layer 700, the substrate 100 and the temperature compensation layer 130. At the same time, since the side views corresponding to different buffering parts 230 structures are the same, the present invention uses multiple side views to correspond to the top views of multiple different surface acoustic wave filters. The correspondence between the top view and the side view can be determined in combination with the description of different embodiments. For example, in one embodiment, Figure 1 and Figure 4 Corresponding to the reference, when a surface acoustic wave filter has Figure 1 The top view is shown, and the side view is Figure 4 .

[0093] In this embodiment, the electrode layer 200 may further include a connector 250 located in the connection region 112. Each interdigital electrode 210 may be divided into an interdigital portion 220, a buffer portion 230, and a connecting portion 240. The interdigital portion 220 may constitute an IDT region. The buffer portions 230 are located at both ends of the interdigital portion 220. The connecting portion 240 is located in the spacer region 113 and connected to the connector 250. Each connecting portion 240 is connected to the buffer portion 230 of any interdigital electrode 210, and the two connecting portions 240 connected to two adjacent interdigital electrodes 210 are located on either side of the interdigital region 111. Furthermore, the buffer portion 230 may be divided into a first portion 300 and a second portion 400. The connecting portion 240 is connected to the first portion 300, and the second portion 400 is located between the interdigital portion 220 and the first portion 300. The dimensions and tilt angles of the first portion 300 and the second portion 400 may be defined in conjunction with the second direction and the interdigital portion 220.

[0094] Specifically, such as Figure 1 and Figure 4 As shown, the side walls of the plurality of buffer portions 230 protrude toward the same side along the second direction relative to the side walls 221 of the interdigital portions.

[0095] The second part 400 has a first side wall 410 connected to the fork finger part 220, and the first side wall 410 is inclined relative to the fork finger part side wall 221 to which it is connected; the second part 400 also has a second side wall 420 connected to the fork finger part 220, and the second side wall 420 and the first side wall 410 are distributed along the second direction, and the second side wall 420 is flush with the fork finger part side wall 221 to which it is connected.

[0096] A first angle α is formed between the first side wall 410 and the interdigital side wall 221 to which it is connected. The first angle α ranges from 20° to 85°.

[0097] The first portion 300 has a third sidewall 310 perpendicular to the surface of the substrate 100 and parallel to the second direction.

[0098] In this embodiment, the interdigital portion 220 has two interdigital sidewalls 221 that are parallel to each other and opposite in the second direction. The buffer portion 230 of each interdigital electrode 210 is located on the same side of the interdigital sidewall 221. The first portion 300 of the buffer portion 230 has a fixed size in the second direction and is larger than the size of the interdigital portion 220 in the second direction. The second portion 400 of the buffer portion 230 has a size that gradually decreases in the second direction from the first portion 300 to the interdigital portion 220, thereby forming a first sidewall 410 connected to the interdigital portion 220. A first angle α is formed between the first sidewall 410 and the interdigital sidewall 221. The first angle α can range from 20° to 85°. The dimension of the second portion 400 from the first portion 300 in the second direction is a first dimension H1, and the range of the first dimension H1 can be 0.5μm~1.5μm; the first portion 300 has a third side wall 310 perpendicular to the surface of the substrate 100 and parallel to the second direction. The dimension of the first portion 300 in the second direction, that is, the dimension of the third side wall 310 in the second direction, is the sum of the dimension of the interdigital portion 220 in the second direction and the first dimension H1.

[0099] In addition, the second part 400 also has a second side wall 420, which is parallel to the first direction. The forked finger side wall 221 connected to the first side wall 410 is the side of the buffer part 230 protruding along the second direction, and the forked finger side wall 221 connected to and flush with the second side wall 420 is the side of the buffer part 230 that does not protrude along the second direction.

[0100] Buffers 230 are provided at the ends of the interdigital electrodes 210 along the first direction near the spacer 113. When sound waves propagate in the first direction, they are reflected and refracted upon encountering the buffers 230. The provision of the buffers 230 alters the propagation path of the sound waves, causing them to be reflected back toward the primary propagation direction (the second direction). This helps reduce the propagation of sound waves in undesirable directions and allows them to be more concentrated in the primary propagation direction.

[0101] In this embodiment, it can be combined with Figure 11As shown, after buffers 230 are provided at both ends of the interdigital electrodes 210 along the first direction in a surface acoustic wave filter, the propagation velocity of the acoustic wave changes significantly. During device operation, the acoustic wave propagates from the interdigital electrodes 210 toward the buffers 230. Upon encountering the second portion 400, the propagation velocity corresponding to the acoustic wave gradually decreases due to the gradual decrease in the second direction dimension of the second portion 400 from the first portion 300 to the interdigital portions 220. When the acoustic wave reaches the first portion 300, the acoustic velocity drops to its lowest point. Due to the low metallization ratio and low mass load in the spacer 113, the acoustic wave propagation velocity is highest, forming an acoustic potential barrier that effectively confines the energy to the vibration region of the interdigital electrodes 210. Thus, the provision of the buffers 230 allows the energy of the main mode to be focused and continue to propagate, while the energy of higher-order transverse modes is dispersed or leaked, thereby reducing energy scattering and mode coupling caused by velocity mismatch during surface acoustic wave propagation. Furthermore, the provision of the second portion 400 acts as a buffer, allowing the acoustic velocity to gradually change.

[0102] Another surface acoustic wave filter according to the embodiment of the present application is as follows Figure 2 as well as Figure 4 As shown, the side walls of the plurality of buffer portions 230 protrude toward both sides along the second direction relative to the side walls 221 of the interdigital portion.

[0103] The second part 400 also has a fourth side wall 430 and a fifth side wall 440 connected to the fork finger part 220. The fourth side wall 430 and the fifth side wall 440 are symmetrically distributed relative to the central axis of the fork finger part 220 along the first direction. The fourth side wall 430 and the fifth side wall 440 are parallel to the second direction and inclined relative to the fork finger part side wall 221.

[0104] There is a second angle β between the fourth side wall 430 and the connected fork finger side wall 221, and there is a third angle γ between the fifth side wall 440 and the connected fork finger side wall 221. The angle range of the second angle β is 10°~85°, and the angle range of the third angle γ is 10°~85°. The angle of the second angle β is the same as or different from the angle of the third angle γ.

[0105] The first portion 300 has a sixth sidewall 320 perpendicular to the surface of the substrate 100 and parallel to the second direction.

[0106] In this embodiment, the surface acoustic wave filter may include a substrate 100, a temperature compensating layer 130, an electrode layer 200, a piezoelectric layer 120, and a protective layer 700. The stacking relationship and material selection of the substrate 100, temperature compensating layer 130, electrode layer 200, protective layer 700, and piezoelectric layer 120 are the same as those in the previous embodiment. The structural arrangement of the substrate 100, temperature compensating layer 130, protective layer 700, and piezoelectric layer 120, as well as the structural division of the electrode layer 200, are also the same as those in the previous embodiment. The structure of the buffer portion 230 included in the electrode layer 200 has changed. Therefore, other structures are not described in detail in this embodiment. The structure of the buffer portion 230 will be described in detail below.

[0107] like Figure 2 as well as Figure 4 As shown, in this embodiment, the buffer portion 230 of each interdigital electrode 210 is located on either side of the interdigital sidewall 221. The first portion 300 of the buffer portion 230 has a fixed size in the second direction and is larger than the size of the interdigital portion 220 in the second direction. The second portion 400 has a size in the second direction that gradually decreases from the first portion 300 to the interdigital portion 220, thereby forming a fourth sidewall 430 and a fifth sidewall 440 connected to the interdigital portion 220 on either side of the interdigital sidewall 221. A second angle β is formed between the fourth sidewall 430 and the interdigital sidewall 221, and the second angle β can range from 10° to 85°. A third angle γ is formed between the fifth sidewall 440 and the interdigital sidewall 221, and the third angle γ can range from 10° to 85°.

[0108] Meanwhile, in this embodiment, for the fourth sidewall 430, the dimension of the second portion 400 from the first portion 300 in the second direction is a second dimension H2, which may range from 0.1 μm to 1 μm. For the fifth sidewall 440, the dimension of the second portion 400 from the first portion 300 in the second direction is a third dimension H3, which may range from 0.1 μm to 1 μm. Furthermore, in this embodiment, the first portion 300 has a sixth sidewall 320 perpendicular to the surface of the substrate 100 and parallel to the second direction. The dimension of the first portion 300 in the second direction, i.e., the dimension of the sixth sidewall 320 in the second direction, is the sum of the dimension of the interdigital portion 220 in the second direction, the first dimension H1, and the third dimension H3.

[0109] Specifically, the second angle β and the third angle γ may be the same or different. When the second angle β and the third angle γ are the same, the fourth sidewall 430 and the fifth sidewall 440 are symmetrically distributed with respect to the central axis of the interdigital portion 220 along the first direction, and the second dimension H2 is equal to the third dimension H3.

[0110] In this embodiment, it can be combined with Figure 12As shown, after the buffer portions 230 are provided at both ends of the interdigital electrodes 210 along the first direction in the surface acoustic wave filter, the propagation speed of the acoustic wave changes significantly. That is, this embodiment can achieve the same technical effects as the previous embodiment.

[0111] Another surface acoustic wave filter according to the embodiment of the present application is as follows Figure 3 as well as Figure 4 As shown, the buffer portion 230 also includes a third portion 500 located between the first portion 300 and the connecting portion 240, and the size of the third portion 500 in the second direction gradually decreases from the first portion 300 to the connecting portion 240; the side walls of several buffer portions 230 protrude toward both sides along the second direction relative to the side walls 221 of the fork finger portion.

[0112] The third portion 500 has a seventh side wall 510 and an eighth side wall 520 connected to the connecting portion 240. The seventh side wall 510 and the eighth side wall 520 are symmetrically distributed relative to the central axis of the connecting portion 240 along the first direction. The seventh side wall 510 and the eighth side wall 520 are parallel to the second direction and inclined relative to the side wall of the connecting portion 240.

[0113] There is a fourth angle λ between the seventh side wall 510 and the side wall of the connecting portion 240 to which it is connected, and there is a fifth angle φ between the eighth side wall 520 and the side wall of the connecting portion 240 to which it is connected. The angle range of the fourth angle λ is 10°~85°, and the angle range of the fifth angle φ is 10°~85°. The angle of the fourth angle λ is the same as or different from the angle of the fifth angle φ.

[0114] In this embodiment, the surface acoustic wave filter may include a substrate 100, a temperature compensating layer 130, an electrode layer 200, a piezoelectric layer 120, and a protective layer 700. The stacking relationship and material selection of the substrate 100, temperature compensating layer 130, electrode layer 200, protective layer 700, and piezoelectric layer 120 are the same as those in the previous embodiment. The structural arrangement of the substrate 100, temperature compensating layer 130, protective layer 700, and piezoelectric layer 120, as well as the structural division of the electrode layer 200, are also the same as those in the previous embodiment. The structure of the buffer portion 230 included in the electrode layer 200 has changed. Therefore, other structures are not described in detail in this embodiment. The structure of the buffer portion 230 will be described in detail below.

[0115] like Figure 3 and Figure 4As shown, the buffer portion 230 of each interdigital electrode 210 is located on either side of the interdigital sidewall 221, and the buffer portions 230 at both ends of the interdigital electrode 210 have different structures. Specifically, the buffer portion 230 also includes a third portion 500 located between the first portion 300 and the connecting portion 240. The buffer portion 230 at one end of the interdigital electrode 210 includes the first portion 300 and second portion 400 described in the previous embodiment, while the buffer portion 230 at the other end includes the first portion 300, second portion 400, and third portion 500 described in the previous embodiment. In this embodiment, the structure and related dimensions of the first portion 300 and second portion 400 can be referred to in the previous embodiment and will not be repeated here.

[0116] The dimension of the third portion 500 in the second direction gradually decreases from the first portion 300 to the interdigital portion 220, thereby forming a seventh sidewall 510 and an eighth sidewall 520 connected to the interdigital portion 220 on either side of the interdigital portion sidewall 221. A fourth angle λ is formed between the seventh sidewall 510 and the interdigital portion sidewall 221, and the fourth angle λ can range from 10° to 85°. A fifth angle φ is formed between the eighth sidewall 520 and the interdigital portion sidewall 221, and the fifth angle φ can range from 10° to 85°.

[0117] At the same time, in this embodiment, for the seventh sidewall 510, the dimension of the third portion 500 from the first portion 300 in the second direction is a fourth dimension H4, and the range of the fourth dimension H4 can be 0.1μm~1μm; for the eighth sidewall 520, the dimension of the third portion 500 from the first portion 300 in the second direction is a fifth dimension H5, and the range of the fifth dimension H5 can be 0.1μm~1μm.

[0118] Specifically, the fourth angle λ and the fifth angle φ may be the same or different. When the fourth angle λ and the fifth angle φ are the same, the seventh sidewall 510 and the eighth sidewall 520 are symmetrically distributed with respect to the central axis of the interdigital portion 220 along the first direction, and the fourth dimension H4 is equal to the fifth dimension H5.

[0119] In this embodiment, it can be combined with Figure 13 As shown, after the buffer portions 230 are provided at both ends of the interdigital electrodes 210 along the first direction in the surface acoustic wave filter, the propagation speed of the acoustic wave changes significantly. That is, this embodiment can achieve the same technical effects as the previous embodiment.

[0120] In other embodiments, Figure 5 as well as Figure 6 As shown, the buffer portion 230 has a first curved sidewall 600 and a second curved sidewall 610 connected to the interdigital portion 220 . The first curved sidewall 600 and the second curved sidewall 610 are symmetrically distributed relative to the central axis of the interdigital portion 220 along the first direction.

[0121] Specifically, such as Figure 5 As shown, the structure of the buffer portion 230 may further include a first curved sidewall 600 and a second curved sidewall 610 connected to the interdigital portion 220. The first curved sidewall 600 and the second curved sidewall 610 are symmetrically distributed relative to the central axis of the interdigital portion 220 along the first direction, and the radius corresponding to the first curved sidewall 600 is equal to the radius corresponding to the second curved sidewall 610, and the radius ranges from 0.1 μm to 3 μm. A sixth angle θ is formed from the ends of the first curved sidewall 600 to the center of the first curved sidewall 600, or from the ends of the second curved sidewall 610 to the center of the second curved sidewall 610. The sixth angle θ ranges from 70° to 140°.

[0122] or, as Figure 6 As shown, the structure of the buffer portion 230 may further include a third curved sidewall 640 and a fourth curved sidewall 650 connected to the interdigital portion 220. The third curved sidewall 640 and the fourth curved sidewall 650 are symmetrically distributed relative to the central axis of the interdigital portion 220 along the first direction, and the radius corresponding to the third curved sidewall 640 is equal to the radius corresponding to the fourth curved sidewall 650, and the radius ranges from 0.1 μm to 3 μm. A seventh angle ω is formed from the end of the third curved sidewall 640 away from the interdigital portion 220 to the center of the third curved sidewall 640, or from the ends of the fourth curved sidewall 650 to the center of the fourth curved sidewall 650. The seventh angle ω ranges from 35° to 70°.

[0123] In other embodiments, for an interdigitated electrode 210, the buffer portions 230 provided at both ends along the first direction may have a combination of any structures in any of the preceding embodiments, that is, the structures of the buffer portions 230 at both ends of the interdigitated electrode 210 may be the same or different.

[0124] Another surface acoustic wave filter according to the embodiment of the present application is as follows Figures 7 to 10 As shown in any of the figures, the electrode layer 200 further includes a first bus bar 620 and a second bus bar 630 respectively located on the spacer regions 113 on both sides of the interdigital region 111 , and both the first bus bar 620 and the second bus bar 630 extend along the second direction.

[0125] Compared with any of the foregoing embodiments, a bus bar is added to the structure of the surface acoustic wave filter in this embodiment. Therefore, the structure of the surface acoustic wave filter described in the foregoing embodiments will not be described in detail. The bus bar will be described below.

[0126] Specifically, the surface acoustic wave filter may further include a first bus bar 620 and a second bus bar 630, each located on the spacer region 113 on both sides of the interdigital region 111. The first bus bar 620 and the second bus bar 630 both extend along the second direction and have the same length, and are the same size as the substrate 100 along the second direction. The first bus bar 620 and the second bus bar 630 are located on the same layer, and may be located on the same layer as the electrode layer 200.

[0127] In the embodiment of the present invention, it can be combined with Figures 14 to 16 As shown in any of the above, after the busbar is added to the surface acoustic wave filter, the propagation speed of the sound wave changes significantly. When the sound wave enters the surface acoustic wave filter and encounters the first busbar 620, the sound speed drops significantly, and then the sound wave enters the gap between the first busbar 620 and the buffer portion 230, and the sound speed increases. When encountering the first part 300 in the buffer portion 230, the sound speed is significantly lower than the sound speed corresponding to the first connection layer, the spacer 113 and the area where the first busbar 620 is located; when encountering the second part 400, due to the setting of the side wall of the second part 400, the sound wave propagation speed gradually increases. It can be seen that this embodiment can achieve the same technical effect as any of the previous embodiments.

[0128] Another surface acoustic wave filter according to an embodiment of the present application has a side view as shown in FIG. Figure 17 as well as Figure 18 As shown in any example, the surface acoustic wave filter may include a temperature compensation layer 130, an electrode layer 200, a piezoelectric layer 120, and a protective layer 700. The electrode layer 200 is located on one surface of the piezoelectric layer 120, the temperature compensation layer 130 is located on the side of the electrode layer 200 facing away from the piezoelectric layer 120, and the protective layer 700 is located on the side of the temperature compensation layer 130 facing away from the piezoelectric layer 120.

[0129] In this embodiment, the material selection and structural arrangement of the temperature compensating layer 130, the electrode layer 200, the protective layer 700, and the piezoelectric layer 120 are the same as those in the previous embodiment. The structural division of the electrode layer 200 and the structure of the buffer portion 230 included in the electrode layer 200 are also the same as those in the previous embodiment. Only the stacking relationship between the temperature compensating layer 130, the electrode layer 200, the piezoelectric layer 120, and the protective layer 700 is changed. Therefore, Figure 17 The corresponding top view of the SAW filter structure can be Figure 1 、 Figure 2 as well as Figure 3 , the sound velocity graph can be Figure 11 、 Figure 12 as well as Figure 13 ; Figure 18 The corresponding top view of the SAW filter structure can be Figure 7 、 Figure 8 as well as Figure 9; The speed of sound graph can be Figure 14 、 Figure 15 as well as Figure 16 In addition, the surface acoustic wave filter in this embodiment may also include Figures 17 and 18 The substrate 100 is not shown in FIG.

[0130] The stacking structure of the surface acoustic wave filter has changed compared to the previous embodiment, but the change in the stacking structure does not affect the change in sound velocity brought about by the addition of the buffer portion 230 and the bus bar, that is, the setting of the buffer portion 230 and the bus bar can adapt to surface acoustic wave filters with different stacking structures to improve the surface acoustic wave filter's ability to suppress transverse modes and clutter.

[0131] Accordingly, the technical solution of the present application also discloses an embodiment of a method for forming a surface acoustic wave filter, which is used to form a surface acoustic wave filter as in any of the above embodiments, such as Figure 1 、 Figure 7 or Figure 17 shown.

[0132] Please refer to Figure 1 or Figure 7 As shown, a substrate 100 is provided, including a base 110 and a piezoelectric layer 120 located on the substrate 110, the substrate 100 includes a finger region 111, a connection region 112 located on both sides of the finger region 111, and a spacer region 113 located between the connection region 112 and the finger region 111, the finger region 111, the connection region 112 and the spacer region 113 are arranged along a first direction, and the first direction is parallel to the surface of the substrate 100.

[0133] In a specific embodiment, the substrate 100 may include a base 110 and a piezoelectric layer 120 located on the base 110. In some steps, the substrate 100 may further include a temperature compensation layer 130 located between the base 110 and the piezoelectric layer 120. The substrate 100 may be divided into an interdigitated region 111, a connection region 112, and a spacer region 113 based on the structure and functional regions of the electrode layer 200. The materials, stacking relationships, functions, etc. of the base 110, the electrode layer 200, the temperature compensation layer 130, and the piezoelectric layer 120 have been described in the previous embodiments and will not be repeated here.

[0134] Please refer to Figure 1 or Figure 7 An electrode layer 200 is formed on a portion of the surface of the piezoelectric layer 120 facing away from the substrate 110. The electrode layer 200 includes a plurality of interdigital electrodes 210 located on the surface of the interdigital region 111. The plurality of interdigital electrodes 210 are arranged in parallel along a second direction, which is parallel to the surface of the substrate 100 and perpendicular to the first direction.

[0135] Among them, each interdigitated electrode 210 includes an interdigitated portion 220 and a buffer portion 230 located at both ends of the interdigitated portion 220, the buffer portion 230 includes a first portion 300 and a second portion 400 located between the first portion 300 and the interdigitated portion 220, the size of the first portion 300 in the second direction is larger than the size of the interdigitated portion 220 in the second direction, and the size of the second portion 400 in the second direction gradually decreases from the first portion 300 to the interdigitated portion 220.

[0136] See also Figure 7 In other embodiments, the electrode layer 200 further includes a first bus bar 620 and a second bus bar 630 respectively located on the spacer region 113 on both sides of the interdigital region 111, and the first bus bar 620 and the second bus bar 630 both extend along the second direction.

[0137] The structural arrangement of the electrode layer 200 and the structural arrangement of the buffer portion 230 have been described in a number of previous embodiments and will not be repeated here.

[0138] Please refer to Figure 1 or Figure 7 After forming the electrode layer 200, a protective layer 700 is formed. The protective layer 700 is located on the side of the electrode layer 200 facing away from the substrate 110. The protective layer 700 covers the electrode layer 200 and the piezoelectric layer 120 exposed between two adjacent interdigital electrodes 210. Specifically, the protective layer 700 covers the electrode layer 200, the spacer 113, and the piezoelectric layer 120 exposed between two adjacent interdigital electrodes 210.

[0139] In other embodiments, see Figure 17 When the stacked structure of the surface acoustic wave filter is changed, its formation method is to first form the piezoelectric layer 120, then form the electrode layer 200 on one side of the piezoelectric layer 120, form the temperature compensation layer 130 on the side of the electrode layer 200 facing away from the piezoelectric layer 120, and finally form the protective layer 700 on the side of the temperature compensation layer 130 facing away from the piezoelectric layer 120. The structure, material selection, and function of each layer are the same as those in the previous embodiment and will not be repeated here.

[0140] By using the above-mentioned method for forming a surface acoustic wave filter, a surface acoustic wave filter as in any of the above embodiments can be formed. The formed surface acoustic wave filter can effectively reduce the probability of excitation of the transverse mode and reduce the generation of clutter, thereby improving the suppression performance of the surface acoustic wave filter for the transverse mode and clutter.

[0141] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0142] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0143] The embodiments, implementation methods and related technical features of the present application can be combined and replaced with each other without conflict.

[0144] The above are only preferred embodiments of the present application and are not intended to limit the present application in any form. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present application without departing from the content of the technical solution of the present application shall still fall within the scope of the technical solution of the present application. The selection of terms used in this article is intended to best explain the principles, practical applications, or technical improvements of each embodiment in the market, or to enable other ordinary technicians in this technical field to understand the embodiments disclosed herein.

Claims

1. A surface acoustic wave filter, characterized in that: include: A substrate comprising a base and a piezoelectric layer located on the base, the substrate comprising an interdigital region, a connecting region located on both sides of the interdigital region, and a spacer region located between the connecting region and the interdigital region, wherein the interdigital region, the connecting region, and the spacer region are arranged along a first direction parallel to a surface of the substrate; an electrode layer located on a portion of a surface of the piezoelectric layer facing away from the substrate, the electrode layer comprising a plurality of interdigital electrodes located on a surface of the interdigital region, the plurality of interdigital electrodes being arranged in parallel along a second direction, the second direction being parallel to the surface of the substrate and perpendicular to the first direction; Each of the interdigital electrodes includes an interdigital portion and buffer portions located at both ends of the interdigital portion, the buffer portion includes a first portion and a second portion located between the first portion and the interdigital portion, the first portion having a size in the second direction larger than the size of the interdigital portion in the second direction, and the second portion having a size in the second direction gradually decreasing from the first portion to the interdigital portion; The interdigital region includes an IDT area, and the interdigital portion constitutes the IDT area.

2. The surface acoustic wave filter according to claim 1, wherein The side walls of the plurality of buffer portions protrude toward the same side along the second direction relative to the side walls of the interdigital portions.

3. The surface acoustic wave filter according to claim 2, wherein The second portion has a first side wall connected to the interdigital portion, and the first side wall is inclined relative to the side wall of the interdigital portion to which it is connected; the second portion also has a second side wall connected to the interdigital portion, the second side wall and the first side wall are distributed along the second direction, and the second side wall is flush with the side wall of the interdigital portion to which it is connected.

4. The surface acoustic wave filter according to claim 3, wherein A first angle is formed between the first side wall and the connected side wall of the interdigital portion, and the angle range of the first angle is 20° to 85°.

5. The surface acoustic wave filter according to claim 2, wherein The first portion has a third sidewall perpendicular to the surface of the substrate and parallel to the second direction.

6. The surface acoustic wave filter according to claim 1, wherein The side walls of the plurality of buffer portions protrude toward both sides along the second direction relative to the side walls of the interdigital portion.

7. The surface acoustic wave filter according to claim 6, wherein The second portion further comprises a fourth side wall and a fifth side wall connected to the interdigital portion, wherein the fourth side wall and the fifth side wall are symmetrically distributed relative to the central axis of the interdigital portion along the first direction. The fourth side wall and the fifth side wall are parallel to the second direction and inclined relative to the side wall of the interdigital portion.

8. The surface acoustic wave filter according to claim 7, wherein The fourth side wall has a second included angle with the connected side wall of the interdigital portion, and the fifth side wall has a third included angle with the connected side wall of the interdigital portion. The second angle has an angle range of 10° to 85°, the third angle has an angle range of 10° to 85°, and the second angle is the same as or different from the third angle.

9. The surface acoustic wave filter according to claim 6, wherein The first portion has a sixth sidewall perpendicular to the surface of the substrate and parallel to the second direction.

10. The surface acoustic wave filter according to claim 1, wherein The electrode layer further includes a plurality of connection portions located on the spacer region, each connection portion being connected to the buffer portion of any one of the interdigital electrodes, and two connection portions connected to two adjacent interdigital electrodes being located on both sides of the interdigital region.

11. The surface acoustic wave filter according to claim 10, wherein The buffer portion further includes a third portion located between the first portion and the connecting portion, wherein a size of the third portion in the second direction gradually decreases from the first portion to the connecting portion; The side walls of the plurality of buffer portions protrude toward both sides along the second direction relative to the side walls of the interdigital portion.

12. The surface acoustic wave filter according to claim 11, wherein The third portion has a seventh side wall and an eighth side wall connected to the connecting portion, and the seventh side wall and the eighth side wall are symmetrically distributed relative to the central axis of the connecting portion along the first direction. The seventh side wall and the eighth side wall are parallel to the second direction and inclined relative to the side wall of the connecting portion.

13. The surface acoustic wave filter according to claim 12, wherein A fourth angle is formed between the seventh side wall and the side wall of the connecting portion to which it is connected, and a fifth angle is formed between the eighth side wall and the side wall of the connecting portion to which it is connected. The fourth angle has an angle range of 10° to 85°, the fifth angle has an angle range of 10° to 85°, and the fourth angle is the same as or different from the fifth angle.

14. The surface acoustic wave filter according to claim 6, wherein The buffer portion has a first arcuate sidewall and a second arcuate sidewall connected to the interdigital portion, and the first arcuate sidewall and the second arcuate sidewall are symmetrically distributed relative to the central axis of the interdigital portion along the first direction.

15. The surface acoustic wave filter according to claim 1, wherein Also includes: The electrode layer further comprises: The first bus bar and the second bus bar are respectively located on the spacing area on both sides of the interdigital area, and both the first bus bar and the second bus bar extend along the second direction.

16. The surface acoustic wave filter according to claim 1, wherein The substrate further comprises: The temperature compensation layer is located between the substrate and the piezoelectric layer.

17. The surface acoustic wave filter according to claim 1, wherein The surface acoustic wave filter further comprises: The protective layer is located on a side of the electrode layer facing away from the substrate, and covers the electrode layer and the piezoelectric layer exposed between two adjacent interdigital electrodes.

18. A method for forming a surface acoustic wave filter, characterized in that: The method comprises: Providing a substrate, comprising a base and a piezoelectric layer located on the base, wherein the substrate comprises an interdigital region, connecting regions located on both sides of the interdigital region, and a spacer region located between the connecting region and the interdigital region, wherein the interdigital region, the connecting region, and the spacer region are arranged along a first direction, and the first direction is parallel to the surface of the substrate; forming an electrode layer on a portion of a surface of the piezoelectric layer facing away from the substrate, the electrode layer comprising a plurality of interdigital electrodes located on a surface of the interdigital region, the plurality of interdigital electrodes being arranged in parallel along a second direction, the second direction being parallel to the substrate surface and perpendicular to the first direction; Each of the interdigital electrodes includes an interdigital portion and buffer portions located at both ends of the interdigital portion, the buffer portion includes a first portion and a second portion located between the first portion and the interdigital portion, the first portion having a size in the second direction larger than the size of the interdigital portion in the second direction, and the second portion having a size in the second direction gradually decreasing from the first portion to the interdigital portion; The interdigital region includes an IDT area, and the interdigital portion constitutes the IDT area.

19. The method for forming a surface acoustic wave filter according to claim 18, wherein: After forming the electrode layer, the method further includes: A protective layer is formed, where the protective layer is located on a side of the electrode layer facing away from the substrate, and covers the electrode layer and the piezoelectric layer exposed between two adjacent interdigital electrodes.

20. The method for forming a surface acoustic wave filter according to claim 18, wherein: The substrate further includes a temperature compensation layer located between the base and the piezoelectric layer.

21. The method for forming a surface acoustic wave filter according to claim 18, wherein: The electrode layer further comprises: The first bus bar and the second bus bar are respectively located on the spacing area on both sides of the interdigital area, and both the first bus bar and the second bus bar extend along the second direction.

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