Surface acoustic wave filter and forming method of surface acoustic wave filter

Abstract

The invention discloses a surface acoustic wave filter and a forming method of the surface acoustic wave filter, and the surface acoustic wave filter comprises a substrate which comprises a base and a piezoelectric layer located on the base, the substrate comprises an interdigital region, connection regions located at the two sides of the interdigital region, and spacer regions located between the connection regions and the interdigital region, the interdigital region, the connecting region and the spacer region are arranged along a first direction, the interdigital region comprises a first region and second regions located at two sides of the first region, the first region and the second regions are arranged along the first direction, and the first direction is parallel to the surface of the substrate; the electrode layer is located on the partial surface of the side, away from the substrate, of the piezoelectric layer, the electrode layer comprises a plurality of interdigital electrodes located on the surface of the interdigital area, the interdigital electrodes are arranged in parallel in the second direction, and the second direction is parallel to the surface of the substrate and perpendicular to the first direction; and the mass block is positioned between the piezoelectric layer and the electrode layer in the second region. Through the arrangement of the mass block in the technical scheme, the capability of suppressing a transverse mode and clutters 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 (SAW) filter is a filtering device that utilizes surface acoustic waves propagating on the surface of a piezoelectric material. Its operating principle is to create interdigital transducers on a piezoelectric substrate, converting electrical input signals into SAWs and then converting the SAWs back into electrical output signals, thereby filtering the signal. This filter offers advantages such as small size, stable performance, and low insertion loss, and is widely used in communications systems.

[0003] However, due to the physical structure and propagation characteristics of the surface acoustic wave filter, during its operation, it will not only excite the main mode of sound waves, but also other transverse mode sound waves. At the same time, during the propagation of the surface acoustic wave, it may be affected by factors such as material inhomogeneity, electrode structure defects or surface reflection, which may cause interference, thereby reducing the signal quality. 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: A substrate comprising a substrate and a piezoelectric layer located on the substrate, the substrate comprising 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, the interdigital region, the connecting region, and the spacer region being arranged along a first direction, the interdigital region comprising a first region and second regions located on both sides of the first region, the first region and the second region being arranged along the first direction, and the first direction being parallel to the substrate surface; 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 parallel to the substrate surface and perpendicular to the first direction; The mass block is located between the piezoelectric layer in the second region and the electrode layer.

[0007] Optionally, the mass block includes a first side wall adjacent to the first region, the first side wall is parallel to the second direction, and the first side wall is inclined relative to the surface of the piezoelectric layer.

[0008] Optionally, the mass block further includes a first surface in contact with the piezoelectric layer, and a first angle is formed between the first side wall and the first surface; a sine value of the first angle ranges from 0.7 to 0.9.

[0009] Optionally, the mass block further includes a second side wall opposite to the first side wall, the second side wall is parallel to a second direction, and the second side wall is inclined relative to the surface of the piezoelectric layer.

[0010] Optionally, the mass block further includes a first surface in contact with the piezoelectric layer, a second angle is formed between the second sidewall and the first surface, and a sine value of the second angle ranges from 0.7 to 0.9; The second angle is the same as or different from the first angle.

[0011] Optionally, the electrode layer also includes a first connection layer and a second connection layer, and the first connection layer and the second connection layer are respectively located on the surface of the connection area on both sides of the interdigitated area; the interdigitated electrode includes a first electrode and a second electrode parallel to the first direction, and the first electrode and the second electrode are staggered along the second direction, one end of the first electrode is connected to the first connection layer, and one end of the second electrode is connected to the second connection layer.

[0012] Optionally, the mass block is also located on a portion of the surface of the spacer area.

[0013] Optionally, the mass block is further located on the surface of the spacer region and the surface of the connection region, and the mass block is located between the first connection layer and the piezoelectric layer, and between the second connection layer and the piezoelectric layer.

[0014] Optionally, the first bus bar and the second bus bar respectively located on the spacing area on both sides of the interdigital area are both located on the electrode layer and extend along the second direction.

[0015] Optionally, the substrate further comprises: The temperature compensation layer is located between the substrate and the piezoelectric layer.

[0016] Optionally, the surface acoustic wave filter further includes: 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.

[0017] According to a second aspect of the present application, a method for forming a surface acoustic wave filter is provided, comprising: A substrate is provided, comprising a substrate and a piezoelectric layer located on the substrate, 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, wherein the interdigital region comprises a first region and a second region located on both sides of the first region, wherein the first region and the second region are arranged along the first direction, and the first direction is parallel to the surface of the substrate; forming a mass block, wherein the mass block is located on a side of the piezoelectric layer facing away from the substrate; An electrode layer is formed on a portion of the surface of the piezoelectric layer facing away from the substrate and a portion of the surface of the mass block facing away from the substrate, the electrode layer includes a plurality of interdigitated electrodes located on the surface of the interdigitated area, and the plurality of interdigitated electrodes are arranged in parallel along a second direction, which is parallel to the substrate surface and perpendicular to the first direction.

[0018] Optionally, 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.

[0019] Optionally, the substrate further includes a temperature compensation layer located between the base and the piezoelectric layer.

[0020] In the surface acoustic wave filter of the embodiment of the present application, a mass block is set between the electrode layer and the piezoelectric layer located in the interdigital area, so that the sound speed of the sound wave changes during the propagation process, that is, the sound speed decreases when the sound wave passes through the mass block, and the sound speed increases again after passing through the mass block. Through the effect of the acoustic potential barrier, the energy is controlled in the effective vibration area, so that 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. At the same time, the mass blocks are set on both sides of the interdigital area, which can guide the sound wave to propagate along a predetermined path. 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.

[0021] Other features and advantages of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS 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.

[0022] 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.

[0023] Figure 1 A first structural side view of a surface acoustic wave filter provided for an exemplary embodiment of the present disclosure; Figure 2 A first structural top view of a surface acoustic wave filter provided by an exemplary embodiment of the present disclosure; Figure 3 A second structural side view of a surface acoustic wave filter provided for an exemplary embodiment of the present disclosure; Figure 4 A second structural top view of a surface acoustic wave filter provided by an exemplary embodiment of the present disclosure; Figure 5 A third structural side view of a surface acoustic wave filter provided as an exemplary embodiment of the present disclosure; Figure 6 A third structural top view of a surface acoustic wave filter provided by an exemplary embodiment of the present disclosure; Figure 7 A fourth structural side view of a surface acoustic wave filter provided as an exemplary embodiment of the present disclosure; Figure 8 A fourth structural top view of a surface acoustic wave filter provided by an exemplary embodiment of the present disclosure; Figure 9 A fifth structural side view of a surface acoustic wave filter provided as an exemplary embodiment of the present disclosure; Figure 10 A fifth structural top view of a surface acoustic wave filter provided as an exemplary embodiment of the present disclosure; Figure 11 A sixth structural side view of a surface acoustic wave filter provided as an exemplary embodiment of the present disclosure; Figure 12 A sixth structural top view of a surface acoustic wave filter provided as an exemplary embodiment of the present disclosure; Figure 13 A first sound velocity variation diagram of a surface acoustic wave filter provided by an exemplary embodiment of the present disclosure; Figure 14 A second sound velocity variation diagram of a surface acoustic wave filter provided by an exemplary embodiment of the present disclosure; Figure 15 A third sound velocity variation diagram of a surface acoustic wave filter provided by an exemplary embodiment of the present disclosure; Figure 16 A fourth sound velocity variation diagram of a surface acoustic wave filter provided by an exemplary embodiment of the present disclosure; Figure 17 A fifth sound velocity variation diagram of a surface acoustic wave filter provided by an exemplary embodiment of the present disclosure; Figure 18 A sixth sound velocity variation diagram of the surface acoustic wave filter provided by the exemplary embodiment of the present disclosure.

[0024] Description of reference numerals: 100 - substrate, 110 - base, 111 - interdigital region, 112 - first region, 113 - second region, 114 - connection region, 115 - spacer region, 120 - piezoelectric layer, 130 - temperature compensation layer; 200 - electrode layer, 210 - interdigitated electrode, 211 - first electrode, 212 - second electrode, 220 - first connecting layer, 230 - second connecting layer; 300 - mass block, 310 - first side wall, 320 - second side wall, 330 - first surface, 340 - second surface; 400-first bus bar, 410-second bus bar; 500-protective layer; α is the first angle, β is the second angle. DETAILED DESCRIPTION

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] Figure 1 A first structural side view of a surface acoustic wave filter provided by an exemplary embodiment of the present disclosure, Figure 2 A first structural top 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 2 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: Substrate 100 includes a substrate 110 and a piezoelectric layer 120 located on substrate 110. Substrate 100 includes an interdigital region 111, connecting regions 114 located on both sides of the interdigital region 111, and a spacer region 115 located between the connecting region 114 and the interdigital region 111. The interdigital region 111, the connecting region 114, and the spacer region 115 are arranged along a first direction. The interdigital region 111 includes a first region 112 and second regions 113 located on both sides of the first region 112. The first region 112 and the second region 113 are arranged along the first direction, which is parallel to the surface of substrate 100. The substrate 100 further includes a temperature compensation layer 130 located between the base 110 and the piezoelectric layer 120 .

[0032] 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; The electrode layer 200 further includes a first connection layer 220 and a second connection layer 230, which are respectively located on the surfaces of the connection region 114 on both sides of the interdigital region 111. The interdigital electrodes 210 include first electrodes 211 and second electrodes 212 parallel to the first direction, and the first electrodes 211 and the second electrodes 212 are alternately arranged along the second direction. One end of each first electrode 211 is connected to the first connection layer 220, and one end of each second electrode 212 is connected to the second connection layer 230. The mass block 300 is located between the piezoelectric layer 120 and the electrode layer 200 in the second region 113 .

[0033] The protective layer 500 is located on a side of the electrode layer 200 facing away from the substrate 110 . The protective layer 500 covers the electrode layer 200 and the piezoelectric layer 120 exposed between two adjacent interdigital electrodes 210 .

[0034] In a specific embodiment, a surface acoustic wave filter includes a substrate 100, an electrode layer 200, and a mass block 300. Substrate 100 may include a base 110, a temperature compensation layer 130, and a piezoelectric layer 120, which are stacked in sequence. Base 110 is a high-acoustic-velocity material, typically silicon, such as single-crystal silicon, polycrystalline silicon, or sapphire. Piezoelectric layer 120 may be made of materials such as lithium niobate or lithium tantalate. Temperature compensation layer 130 is used to compensate for the effects of temperature changes on the performance of the surface acoustic wave filter and is typically made of a temperature compensation material such as tantalum oxide or silicon dioxide.

[0035] The substrate 100 can be divided into an interdigital region 111, a connection region 114, and a spacer region 115 based on the structure and functional areas of its upper electrode layer 200. The connection region 114, spacer region 115, and interdigital region 111 are arranged along a first direction. The interdigital region 111 can be further divided into a first region 112 and a second region 113. The first region 112 is the IDT region (interdigital transducer region), which is used to convert electrical signals into surface acoustic waves. The second region 113 is symmetrically arranged on either side of the first region 112. Combined with the position of the mass block 300, it can be seen that the second region 113 is the area where the mass block 300 and the interdigital region 111 are stacked.

[0036] The electrode layer 200 is located on the side of the piezoelectric layer 120 facing away from the substrate 110 and includes a plurality of interdigital electrodes 210 located on the surface of the interdigital region 111, and a first connection layer 220 and a second connection layer 230 disposed on the surfaces of the connection region 114 on both sides of the interdigital region 111 and connected to the plurality of interdigital electrodes 210. The plurality of interdigital electrodes 210 are arranged in parallel along the second direction and can be divided into a plurality of first electrodes 211 and a plurality of second electrodes 212. That is, the plurality of first electrodes 211 and the plurality of second electrodes 212 are parallel to the first direction and arranged in parallel and staggered along the second direction.

[0037] A protective layer 500 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 500 may be made of nitride, such as silicon nitride, etc. The protective layer 500 covers the electrode layer 200 and the piezoelectric layer 120 exposed between two adjacent interdigital electrodes 210 .

[0038] In addition, in order to clearly show the arrangement of the electrode layer 200 and the mass block 300 on the substrate 100, the top view of any structure corresponding to the surface acoustic wave filter disclosed in the present invention does not show the protective layer 500, the piezoelectric layer 120 and the temperature compensation layer 130.

[0039] In this embodiment, for the structure of the mass block 300, as shown in FIG. Figure 1 as well as Figure 2 As shown, the mass block 300 is located between the piezoelectric layer 120 and the electrode layer 200 in the second region 113. The mass block 300 includes a first sidewall 310 adjacent to the first region 112, parallel to the second direction, and inclined relative to the surface of the piezoelectric layer 120.

[0040] The mass block 300 further includes a first surface 330 in contact with the piezoelectric layer 120 . A first angle α is formed between the first sidewall 310 and the first surface 330 . The sine value of the first angle α ranges from 0.7 to 0.9.

[0041] Specifically, such as Figure 1 as well as Figure 2 As shown, the mass block 300 is located between the piezoelectric layer 120 and the electrode layer 200 in the second region 113. The surface of the mass block 300 adjacent to the first region 112 is a first sidewall 310, and the surface in contact with the piezoelectric layer 120 is a first surface 330. The first sidewall 310 is parallel to the second direction, and a first angle α is formed between the first sidewall 310 and the first surface 330. The sine value of the first angle α may range from 0.01 to 1. In some embodiments, the sine value of the first angle α may range from 0.7 to 0.9.

[0042] In addition to the first surface 330 and the first sidewall 310, the mass block 300 also includes a second surface 340 parallel to and opposite to the first surface 330, and a second sidewall 320 opposite to the first sidewall 310. In the embodiment of the present invention, the first surface 330 and the second surface 340 of the mass block 300 are parallel, and the first sidewall 310 is inclined relative to the surface of the piezoelectric layer 120. The mass block 300 is an integral structure, and its length along the second direction is the same as the width of the substrate 100 along the second direction. At the same time, as Figure 1 As shown, the second sidewall 320 is perpendicular to the surface of the piezoelectric layer 120 .

[0043] The mass blocks 300 are disposed on both sides of the first region 112. When the sound wave propagates in the first direction, the sound wave encounters the mass blocks 300 on both sides of the first region 112 and is reflected and refracted. Figure 13 As shown, after the mass block 300 is added to the surface acoustic wave filter, the propagation speed of the acoustic wave changes significantly. When the acoustic wave enters the surface acoustic wave filter and encounters the mass block 300, the sound speed is significantly reduced compared to the corresponding sound speed of the sound wave in the first connection layer 220 and the spacer region 115. In other words, the sound wave decreases when entering the first region 112. When the sound wave leaves the mass block 300 and enters the first region 112, the sound wave propagation speed increases. This shows that the addition of the mass block 300 can focus the energy of the main mode and continue to propagate, while the energy of the higher-order transverse modes is dispersed or leaked, thereby reducing energy scattering and mode coupling caused by velocity mismatch during the propagation of the surface acoustic wave.

[0044] 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 mass block 300 is located between the piezoelectric layer 120 and the electrode layer 200 in the second region 113 , and the mass block 300 is also located on a portion of the surface of the spacing region 115 .

[0045] In addition to the first sidewall 310 , the mass block 300 also includes a second sidewall 320 opposite to the first sidewall 310 . The second sidewall 320 is parallel to the second direction and inclined relative to the surface of the piezoelectric layer 120 .

[0046] The mass block 300 further includes a first surface 330 in contact with the piezoelectric layer 120 , and a second angle β is formed between the second sidewall 320 and the first surface 330 , wherein the sine value of the second angle β ranges from 0.7 to 0.9; The second angle β is the same as or different from the first angle α.

[0047] In this embodiment, the surface acoustic wave filter may include a substrate 100, a temperature compensating layer 130, an electrode layer 200, a protective layer 500, and a mass block 300. The stacking relationship and structural arrangement of the substrate 100, temperature compensating layer 130, and electrode layer 200 are the same as those in the previous embodiment; only the structure of the mass block 300 is different. Therefore, other structures are not described in detail in this embodiment. The mass block 300 will be described in detail below.

[0048] Specifically, such as Figure 3 as well as Figure 4 As shown, in this embodiment, the mass block 300 further has a second side wall 320 inclined relative to the surface of the piezoelectric layer 120 on the basis of the previous embodiment, and a second angle β is formed between the second side wall 320 and the first surface 330, and the sine value of the second angle β can range from 0.01 to 1. In some embodiments, the sine value of the second angle β can range from 0.7 to 0.9.

[0049] For a mass block 300, when its second sidewall 320 changes from being perpendicular to the surface of the piezoelectric layer 120 in the previous embodiment to being inclined to the surface of the piezoelectric layer 120 in this embodiment, and the size of the second surface 340 remains unchanged, the size of its first surface 330 increases. Therefore, in this embodiment, the mass block 300, while being located between the piezoelectric layer 120 and the electrode layer 200 in the second region 113, is also located on the surface of a portion of the spacer region 115. Furthermore, the first angle α and the second angle β can be the same or different, but their sine values are preferably in the range of 0.7 to 0.9.

[0050] In the embodiment of the present invention, it can be combined with Figure 14 As shown, compared to the previous embodiment, when the second sidewall 320 of the mass block 300 also forms a second angle β with the first surface 330, preferably with a sine value in the range of 0.7 to 0.9, the acoustic wave propagation speed first decreases upon encountering the second sidewall 320, and then further decreases as it propagates within the mass block 300. This shows that, in addition to the technical effects achieved by incorporating a surface acoustic wave filter into the mass block 300, the inclined second sidewall 320 can provide a buffering effect during the acoustic velocity reduction process.

[0051] Another surface acoustic wave filter according to the embodiment of the present application is as follows Figure 5 as well as Figure 6 As shown, the mass block 300 is also located on the surface of the spacer region 115 and the surface of the connection region 114 . The mass block 300 is located between the first connection layer 220 and the piezoelectric layer 120 , and between the second connection layer 230 and the piezoelectric layer 120 .

[0052] In this embodiment, the surface acoustic wave filter may include a substrate 100, a temperature compensating layer 130, an electrode layer 200, a protective layer 500, and a mass block 300. The stacking relationship and structural arrangement of the substrate 100, temperature compensating layer 130, and electrode layer 200 are the same as those in the previous embodiment; only the structure of the mass block 300 is different. Therefore, other structures are not described in detail in this embodiment. The mass block 300 will be described in detail below.

[0053] Specifically, such as Figure 5 as well as Figure 6 As shown, in this embodiment, mass block 300, based on the previous embodiment, has its width modified along the first direction. Specifically, the dimensions of first surface 330 and second surface 340 have changed. First sidewall 310 remains adjacent to first region 112 and forms first angle α, while second sidewall 320 is perpendicular to the surface of piezoelectric layer 120. The sine value of first angle α remains in the range of 0.01 to 1, with a preferred range of 0.7 to 0.9.

[0054] That is, the mass block 300 of this embodiment is located between the piezoelectric layer 120 and the electrode layer 200 in the second region 113, and is also located on the surface of the spacer region 115 and the surface of the connection region 114. The mass blocks 300 disposed on both sides of the first region 112 are located between the first connection layer 220 and the piezoelectric layer 120, and between the second connection layer 230 and the piezoelectric layer 120, respectively.

[0055] In the embodiment of the present invention, it can be combined with Figure 15 As shown, when an acoustic wave enters the surface acoustic wave filter, the arrangement of the mass block 300 can cause the acoustic wave to decrease upon entering the first region 112; and when the acoustic wave leaves the mass block 300 and enters the first region 112, the acoustic wave propagation velocity increases. This embodiment can also achieve the same technical effects as the previous embodiment.

[0056] Another surface acoustic wave filter according to the embodiment of the present application is as follows Figures 7 to 12 As shown in any of the figures, the surface acoustic wave filter further includes a first bus bar 400 and a second bus bar 410 respectively located on the spacer area 115 on both sides of the interdigital area 111, and the first bus bar 400 and the second bus bar 410 are both located on the electrode layer 200 and extend along the second direction.

[0057] In this embodiment, compared with any of the previous embodiments, two bus bars are added to the structure of the surface acoustic wave filter. Therefore, the structure of the surface acoustic wave filter described in the above embodiments will not be repeated. The bus bars will be described below.

[0058] Specifically, for a surface acoustic wave filter, it can also include a first bus bar 400 and a second bus bar 410 respectively located on the spacer area 115 on both sides of the interdigital area 111. The first bus bar 400 and the second bus bar 410 both extend along the second direction, and the two have the same length and the same size as the substrate 100 along the second direction.

[0059] The first bus bar 400 and the second bus bar 410 are located in the same layer and can be located in the same layer as the electrode layer 200 and on the side of the electrode layer 200 facing away from the substrate 100. For example, when the structure of the mass block 300 is the first of the multiple preceding embodiments, please refer to Figure 7 and Figure 8 , the first bus bar 400 and the second bus bar 410 are both located in the same layer as the portion of the electrode layer 200 covering the second surface 340 of the mass block 300; when the structure of the mass block 300 is the second of the multiple preceding embodiments, please refer to Figure 9 and Figure 10 , the first bus bar 400 and the second bus bar 410 are both located in the same layer as the portion of the electrode layer 200 covering the second surface 340 of the mass block 300; when the structure of the mass block 300 is the third of the multiple preceding embodiments, please refer to Figure 11 and Figure 12 The first bus bar 400 and the second bus bar 410 are both located on the upper layer of the electrode layer 200 , and a protective layer 500 is formed between the electrode layer 200 and the first bus bar 400 and the second bus bar 410 .

[0060] Also, see Figures 7 to 12 As shown in any of the figures, the first bus bar 400 and the second bus bar 410 can be arranged close to the mass block 300, but there needs to be a gap between the first bus bar 400, the second bus bar 410 and the mass block 300 to avoid short circuit when the first bus bar 400, the second bus bar 410 and the electrode layer 200 are located in the same layer.

[0061] In the embodiment of the present invention, it can be combined with Figures 16 to 18As shown in the figure, after the busbars and mass block 300 are added to the surface acoustic wave filter, the propagation speed of the acoustic wave changes significantly. When the acoustic wave enters the surface acoustic wave filter, it first encounters the first busbar 400, where the sound speed decreases significantly. Then, as the acoustic wave enters the gap between the first busbar 400 and the mass block 300, the sound speed increases. When the acoustic wave encounters the mass block 300, the sound speed is significantly lower than the corresponding sound speed in the first connection layer 220, the gap 115, and the area where the first busbar 400 is located. In other words, the sound wave decreases when entering the first area 112. When the sound wave leaves the mass block 300 and enters the first area 112, the sound wave propagation speed increases. This shows that the addition of the mass block 300 can focus the energy of the main mode and continue to propagate, while the energy of the higher-order transverse modes is dispersed or leaked, thereby reducing energy scattering and mode coupling caused by velocity mismatch during surface acoustic wave propagation.

[0062] 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 Figures 1 to 6 shown.

[0063] Please refer to Figures 1 to 6 As shown in any one of the figures, a substrate 100 is provided, including a base 110 and a piezoelectric layer 120 located on the base 110, the substrate 100 includes a finger region 111, a connection region 114 located on both sides of the finger region 111, and a spacer region 115 located between the connection region 114 and the finger region 111, the finger region 111, the connection region 114 and the spacer region 115 are arranged along a first direction, the finger region 111 includes a first region 112 and a second region 113 located on both sides of the first region 112, the first region 112 and the second region 113 are arranged along the first direction, and the first direction is parallel to the surface of the substrate 100.

[0064] 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 114, and a spacer region 115 based on the structure and functional regions of the electrode layer 200 and the position of the mass block 300. The materials, stacking relationship, and functions of the base 110, the temperature compensation layer 130, and the piezoelectric layer 120 have been described in the previous embodiments and will not be repeated here.

[0065] Please refer to Figure 1 、 Figure 3 or Figure 5 As shown in either case, a proof mass 300 is formed and is located on a side of the piezoelectric layer 120 facing away from the substrate 110 .

[0066] In a specific embodiment, corresponding to different embodiments in the preceding order, the mass block 300 may be located on the surface of the piezoelectric layer 120 in the second zone 113 facing away from the substrate 110, or may be located on the surface of the piezoelectric layer 120 in the second zone 113 and part of the spacing zone 115 facing away from the substrate 110, or may be located on the surface of the piezoelectric layer 120 in the second zone 113, the spacing zone 115 and the connecting zone 114 facing away from the substrate 110.

[0067] Please continue to refer to Figures 1 to 6 As shown in any one of the figures, an electrode layer 200 is formed on a portion of the surface of the piezoelectric layer 120 facing away from the substrate 110 and a portion of the surface of the mass block 300 facing away from the substrate 110. The electrode layer 200 includes a plurality of interdigitated electrodes 210 located on the surface of the interdigitated region 111. The plurality of interdigitated 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.

[0068] In a specific embodiment, after determining the position of the mass block 300, the mass block 300 is formed on the side of the piezoelectric layer 120 facing away from the substrate 110. The corresponding electrode layer 200 is formed based on the positions of the first region 112, the second region 113, the spacer region 115, and the connection region 114. The electrode layer 200 includes a first connection layer 220, a second connection layer 230, and a plurality of interdigital electrodes 210 (i.e., a plurality of first electrodes 211 and a plurality of second electrodes 212 arranged parallel and interlaced along the second direction). The structure of the resulting surface acoustic wave filter corresponds to the structure of any of the preceding embodiments.

[0069] In some steps, after forming the electrode layer 200, it is also necessary to form a protective layer 500, that is, Please refer to Figure 1 、 Figure 3 or Figure 5 As shown in any one of the figures, a protective layer 500 is formed. The protective layer 500 is located on the side of the electrode layer 200 facing away from the substrate 110 . The protective layer 500 covers the electrode layer 200 and the piezoelectric layer 120 exposed between two adjacent interdigital electrodes 210 .

[0070] Specifically, the protective layer 500 covers the electrode layer 200 and the piezoelectric layer 120 exposed between two adjacent first electrodes 211 and second electrodes 212, but the protective layer 500 does not cover the spacer area 115, that is, the piezoelectric layer 120 located in the spacer area 115 and the mass block 300 located in the spacer area 115 are exposed from the protective layer 500.

[0071] In other embodiments, when the surface acoustic wave filter further includes a first bus bar 400 and a second bus bar 410, Please refer to Figures 7 to 12As shown in any one of the following examples, after forming the protective layer 500, grooves for forming the first bus bar 400 and the second bus bar 410 are etched on the protective layer 500. After forming the first bus bar 400 and the second bus bar 410, the protective layer 500 is formed on the first bus bar 400 and the second bus bar 410. At the same time, the piezoelectric layer 120 and / or the mass block 300 exposed from the spacer 115 are also covered by the protective layer 500. The etching position on the protective layer 500 can be determined according to the last of the multiple preceding embodiments and in conjunction with the accompanying drawings. Figures 7 to 12 The positions of the first bus bar 400 and the second bus bar 410 are determined.

[0072] By using the above-mentioned method for forming a surface acoustic wave filter, a surface acoustic wave filter as described 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.

[0073] 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.

[0074] 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.

[0075] The embodiments, implementation methods and related technical features of the present application can be combined and replaced with each other without conflict.

[0076] 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 substrate and a piezoelectric layer located on the substrate, the substrate comprising 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, the interdigital region, the connecting region, and the spacer region being arranged along a first direction, the interdigital region comprising a first region and second regions located on both sides of the first region, the first region and the second region being arranged along the first direction, and the first direction being parallel to the substrate surface; 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 substrate surface and perpendicular to the first direction; The mass block is located between the piezoelectric layer in the second region and the electrode layer.

2. The surface acoustic wave filter according to claim 1, wherein The proof mass includes a first sidewall adjacent to the first region, the first sidewall is parallel to the second direction, and the first sidewall is inclined relative to a surface of the piezoelectric layer.

3. The surface acoustic wave filter according to claim 2, wherein The mass block further includes a first surface in contact with the piezoelectric layer, and a first angle is formed between the first side wall and the first surface; a sine value of the first angle ranges from 0.7 to 0.

9.

4. The surface acoustic wave filter according to claim 2, wherein The mass block further includes a second side wall opposite to the first side wall, the second side wall is parallel to a second direction, and the second side wall is inclined relative to a surface of the piezoelectric layer.

5. The surface acoustic wave filter according to claim 4, wherein The mass block further includes a first surface in contact with the piezoelectric layer, a second angle is formed between the second sidewall and the first surface, and a sine value of the second angle ranges from 0.7 to 0.9; The second angle is the same as or different from the first angle.

6. The surface acoustic wave filter according to claim 1, wherein The electrode layer further includes a first connection layer and a second connection layer, wherein the first connection layer and the second connection layer are respectively located on surfaces of the connection area on both sides of the interdigital area; The interdigitated electrodes include a first electrode and a second electrode parallel to the first direction. The first electrode and the second electrode are alternately arranged along the second direction. One end of each of the first electrodes is connected to the first connection layer, and one end of each of the second electrodes is connected to the second connection layer.

7. The surface acoustic wave filter according to claim 6, wherein The mass block is also located on a portion of the surface of the spacer area.

8. The surface acoustic wave filter according to claim 6, wherein The proof mass is further located on the surface of the spacer region and the surface of the connection region. The proof mass is located between the first connection layer and the piezoelectric layer, and between the second connection layer and the piezoelectric layer.

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

10. 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.

11. 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.

12. A method for forming a surface acoustic wave filter, characterized in that: The method comprises: A substrate is provided, comprising a substrate and a piezoelectric layer located on the substrate, 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, wherein the interdigital region comprises a first region and a second region located on both sides of the first region, wherein the first region and the second region are arranged along the first direction, and the first direction is parallel to the surface of the substrate; forming a mass block, wherein the mass block is located on a side of the piezoelectric layer facing away from the substrate; An electrode layer is formed on a portion of the surface of the piezoelectric layer facing away from the substrate and a portion of the surface of the mass block facing away from the substrate, the electrode layer includes a plurality of interdigitated electrodes located on the surface of the interdigitated area, and the plurality of interdigitated electrodes are arranged in parallel along a second direction, which is parallel to the substrate surface and perpendicular to the first direction.

13. The method for forming a surface acoustic wave filter according to claim 12, 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.

14. The method for forming a surface acoustic wave filter according to claim 12, wherein: The substrate further includes a temperature compensation layer located between the base and the piezoelectric layer.

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