Surface acoustic wave filter and manufacturing method thereof

Abstract

The present application relates to a surface acoustic wave filter and a method for manufacturing the same, wherein the surface acoustic wave filter comprises a stacked piezoelectric substrate, an interdigital transduction layer, and a shear wave suppression layer. The interdigital transduction layer comprises a plurality of finger electrodes spaced apart along a first direction, wherein the region where each finger electrode overlaps with an adjacent finger electrode in the first direction comprises an interdigital region and a suppression region located on both sides of the interdigital region in a second direction. The shear wave suppression layer comprises a first portion and a second portion, wherein the first portion covers the interdigital region and the second portion covers the suppression region, and the thickness of the first portion is greater than that of the second portion. Through the above-mentioned technical solution, the shear wave suppression layer laid in the present application can make the sound velocity of the sound wave in the interdigital region higher than the sound velocity of the suppression region, effectively control the energy within the interdigital region, reduce the propagation energy in the lateral direction (second direction), and thus reduce the impact of the lateral stray mode.

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 manufacturing method thereof. Background Art

[0002] Surface acoustic wave (SAW) filters are electronic components that utilize the piezoelectric effect and the propagation characteristics of acoustic waves to filter signals. Compared to traditional passive filters (such as those composed of capacitors and inductors), SAW filters offer advantages such as miniaturization, low insertion loss, and a high quality factor (Q factor). They are widely used in mobile phone base stations, RF communication modules, satellite communications, and other fields.

[0003] Ideally, the acoustic wave propagation of a surface acoustic wave filter should strictly follow the direction pointed by the IDT at the input. However, because surface acoustic waves are affected by factors such as boundary effects, substrate material properties, and structural inhomogeneities when propagating on the surface of piezoelectric materials, in addition to propagating along the main propagation direction, surface acoustic waves also propagate transversely, that is, acoustic wave modes propagating in directions perpendicular to the main propagation direction. These transversely propagating surface acoustic waves cannot be effectively guided to the IDT at the output end. Instead, they reflect and interfere within the filter, forming so-called transverse clutter modes. The presence of transverse clutter modes disperses some of the acoustic wave energy from the main propagation path, resulting in a reduction in the energy of the main mode, thereby increasing insertion loss and reducing the filter's energy conversion efficiency. At the same time, additional resonance peaks are formed within and near the passband. These peaks correspond to clutter signals, making it impossible for the filter to effectively distinguish between target signals and interference signals, thereby reducing the filter's frequency selectivity and affecting the filter's stability and consistency. Summary of the Invention

[0004] The embodiments of the present application provide a surface acoustic wave filter and a manufacturing method thereof, which are intended to suppress the influence of lateral clutter modes, thereby reducing the insertion loss of the surface acoustic wave filter and improving its stability and consistency.

[0005] To achieve the above-mentioned object, according to a first aspect of the present application, there is provided a surface acoustic wave filter, comprising: a piezoelectric substrate comprising a base layer and a piezoelectric layer located on the base layer;

[0006] an interdigital transduction layer, located on a surface of the piezoelectric layer facing away from the substrate layer, comprising a plurality of finger electrodes spaced apart along a first direction, wherein an area where each finger electrode overlaps with an adjacent finger electrode in the first direction comprises an interdigital region and an inhibition region, wherein the inhibition region is located on both sides of the interdigital region in a second direction, and the first direction and the second direction intersect and are both parallel to the surface of the piezoelectric layer;

[0007] A shear wave suppression layer is located on a side of the interdigital transduction layer away from the piezoelectric substrate and covers the interdigital transduction layer and the piezoelectric layer exposed on the interdigital transduction layer; the shear wave suppression layer includes a first portion and a second portion, the first portion covers the interdigital area, the second portion covers the suppression area, and the thickness of the first portion is greater than the thickness of the second portion.

[0008] Optionally, in the second direction, the first portion has two opposite connecting sidewalls, the connecting sidewalls are connected to the second portion on the same side, and the connecting sidewalls are inclined relative to a surface of the second portion facing away from the interdigital transduction layer.

[0009] Optionally, a plane where a surface of the second portion facing away from the interdigital transduction layer is located is a first plane, a first inclination angle α is formed between the connecting sidewall and the first plane, and the first inclination angle α is in a range of [30°, 85°].

[0010] Optionally, a surface of the first portion facing away from the IDT layer has a height difference with respect to a surface of the second portion facing away from the IDT layer, and a value range of the height difference is [20 nm, 80 nm].

[0011] Optionally, the interdigital transduction layer further includes a first bus bar and a second bus bar respectively located on both sides of the finger electrodes in the second direction, the first bus bar and the second bus bar extend along the first direction, and the finger electrodes extend along the second direction. In the first direction, one of two adjacent finger electrodes is connected to the first bus bar, and the other is connected to the second bus bar.

[0012] There is a second gap between one end of the finger electrode connected to the first bus bar and the second bus bar, and there is a first gap between one end of the finger electrode connected to the second bus bar and the first bus bar.

[0013] Optionally, the finger electrode further includes a connection area, which is located between the suppression area and a bus bar adjacent to the suppression area; the shear wave suppression layer further includes a third part, which covers the connection area and the bus bar connected to the finger electrode, and the thickness of the third part is the same as the thickness of the second part.

[0014] Optionally, the finger electrodes further include a connection region, the connection region being located between the suppression region and a bus bar adjacent to the suppression region; the shear wave suppression layer further includes a fourth portion and a fifth portion, the fourth portion covering the connection region, the fifth portion covering the bus bar connected to the finger electrodes, and the thickness of the fourth portion being the same as that of the second portion;

[0015] The fifth portion includes a first sub-portion and a second sub-portion connected to each other. In the second direction, the first sub-portion is close to the finger electrode. The first sub-portion and the second sub-portion have the same thickness, and the second sub-portion is thicker than the second sub-portion.

[0016] Optionally, the shear wave suppression layer further includes a first spacer portion filled in the first spacer and the second spacer, and a distance from a surface of the first spacer portion facing away from the piezoelectric layer to the piezoelectric layer is smaller than a distance from a surface of the second spacer portion facing away from the piezoelectric layer to the piezoelectric layer.

[0017] Optionally, the shear wave suppression layer also includes a second spacer portion filled in the gap between two adjacent finger electrodes, and the distance from the side surface of the second spacer portion facing away from the piezoelectric layer to the piezoelectric layer is smaller than the distance from the side surface of the second portion facing away from the piezoelectric layer to the piezoelectric layer.

[0018] Optionally, two third bus bars are arranged opposite to each other along the second direction, and the third bus bars extend along the first direction. The third bus bars are located on the side of the interdigitated transduction layer facing away from the piezoelectric substrate. In the third direction, the projection of one of the two third bus bars overlaps with the projection of the first interval, and the projection of the other overlaps with the projection of the second interval. The third direction is perpendicular to the surface of the piezoelectric layer facing away from the base layer.

[0019] According to a second aspect of the present application, there is provided a method for manufacturing a surface acoustic wave filter, comprising:

[0020] forming a piezoelectric substrate, the piezoelectric substrate comprising a base layer and a piezoelectric layer stacked together;

[0021] An interdigital transduction layer is formed on a surface of the piezoelectric layer facing away from the substrate layer, the interdigital transduction layer comprising a plurality of finger electrodes spaced apart along a first direction, wherein an area where two adjacent finger electrodes overlap in the first direction comprises an interdigital region and an inhibition region, the inhibition region being located on both sides of the interdigital region in a second direction, the first direction and the second direction intersecting and both being parallel to the surface of the piezoelectric layer facing away from the substrate layer;

[0022] A shear wave suppression layer is formed on a side of the interdigital transduction layer facing away from the piezoelectric substrate, and the shear wave suppression layer covers the interdigital transduction layer and the piezoelectric layer exposed on the interdigital transduction layer; the shear wave suppression layer includes a first portion and a second portion, the first portion covers the interdigital area, the second portion covers the suppression area, and a surface of the first portion facing away from the interdigital transduction layer protrudes from a surface of the second portion facing away from the interdigital transduction layer.

[0023] In the surface acoustic wave filter of the embodiment of the present application, through the above-mentioned technical solution, when the acoustic wave excited by the interdigital transduction layer propagates along the first direction (the main propagation direction), part of the energy propagates along the second direction (the transverse direction), forming a transverse spurious mode. This transverse spurious mode disperses the acoustic wave energy, increases insertion loss, and forms additional resonance peaks, affecting the frequency selectivity of the surface acoustic wave filter. In the embodiment disclosed herein, the region where each finger electrode overlaps with the adjacent finger electrode in the first direction is the area where the acoustic wave is primarily excited and converted. Specifically, this region includes an interdigital region and a suppression region located on either side of the interdigital region in the second direction. A thicker shear wave suppression layer (first portion) covers the interdigital region, while a thinner shear wave suppression layer (second portion) covers the suppression region located on either side of the interdigital region. Compared to the interdigital transduction layer, the acoustic wave propagates faster in the shear wave suppression layer. This arrangement of the shear wave suppression layer ensures that the acoustic wave velocity in the interdigital region is higher than that in the suppression region. As the transverse acoustic wave propagates from the interdigital region to the suppression region, the acoustic wave propagation velocity gradually decreases. Furthermore, one of the two suppression zones has a first gap on the side facing away from the interdigital zone, and the other has a second gap on the side facing away from the interdigital zone. When the sound wave is transmitted to the first gap and the second gap on both sides, the gap area has a low coverage metallization rate, and the sound wave propagation speed increases, forming an acoustic potential barrier, which effectively controls the energy within the interdigital zone, reduces the lateral (second direction) propagation energy, and thus reduces the impact of the lateral stray mode.

[0024] Other features and advantages of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] To more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present application. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0026] 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.

[0027] Figure 1 This is a schematic diagram of a top view of a surface acoustic wave filter provided in an embodiment of the present application. Figure 1 ;

[0028] Figure 2 This is a surface acoustic wave filter provided by the embodiment of the present application. Figure 1 Cross-sectional view at AA in the middle;

[0029] Figure 3 yes Figure 2The sound velocity variation diagram of the surface acoustic wave filter shown;

[0030] Figure 4 Another surface acoustic wave filter provided by the embodiment of the present application is Figure 1 Cross-sectional view at AA in the middle;

[0031] Figure 5 yes Figure 2 An enlarged view of a surface acoustic wave filter at position D is shown;

[0032] Figure 6 yes Figure 4 The sound velocity variation diagram of the surface acoustic wave filter shown;

[0033] Figure 7 This is a surface acoustic wave filter provided by the embodiment of the present application. Figure 1 Cross-sectional view at the middle BB;

[0034] Figure 8 This is a schematic diagram of a top view of a surface acoustic wave filter provided in an embodiment of the present application. Figure 2 ;

[0035] Figure 9 This is a surface acoustic wave filter provided by the embodiment of the present application. Figure 8 Cross-sectional view at CC;

[0036] Figure 10 yes Figure 9 The sound velocity variation diagram of the surface acoustic wave filter shown;

[0037] Figure 11 Another surface acoustic wave filter provided by the embodiment of the present application is Figure 8 Cross-sectional view at CC;

[0038] Figure 12 yes Figure 11 The sound velocity variation diagram of the surface acoustic wave filter shown;

[0039] Figure 13 This is a characteristic diagram of the change of the real part of the admittance of the surface acoustic wave filter with frequency under different first-part structures.

[0040] Description of reference numerals:

[0041] 100, piezoelectric substrate; 101, base layer; 1011, substrate; 1012, temperature compensation structure; 102, piezoelectric layer;

[0042] 200, interdigital transduction layer; 201, finger electrode; 202, first bus bar; 203, second bus bar; 204, third bus bar;

[0043] 300, shear wave suppression layer; 301, first portion; 3011, connecting side wall; 302, second portion; 303, third portion; 304, fourth portion; 305, fifth portion; 3051, first sub-portion; 3052, second sub-portion; 306, first spacer; 307, second spacer;

[0044] 10. Interdigital region; 11. Inhibitory region; 12. Connecting region; 13. First spacer; 14. Second spacer;

[0045] 20. First plane. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0047] According to a first aspect of the present application, a surface acoustic wave filter is provided. The embodiment of the surface acoustic wave filter disclosed in the present application is as follows: Figure 2 As shown ( Figure 2 This is a surface acoustic wave filter provided by the embodiment of the present application. Figure 1 (a cross-sectional view taken at AA in FIG. 1 ), the surface acoustic wave filter comprises: a piezoelectric substrate 100, an interdigital transduction layer 200, and a shear wave suppression layer 300. Specifically, the piezoelectric substrate 100 comprises a base layer 101 and a piezoelectric layer 102 located on the base layer 101. The interdigital transduction layer 200 is located on a side of the piezoelectric layer 102 facing away from the base layer 101. The shear wave suppression layer 300 is located on a side of the interdigital transduction layer 200 facing away from the piezoelectric substrate 100, and covers the interdigital transduction layer 200 and the piezoelectric layer 102 exposed on the interdigital transduction layer 200. Figure 1 , Figure 1 This is a schematic diagram of a top view of a surface acoustic wave filter provided in an embodiment of the present application. Figure 1 (It should be noted that, to facilitate observation of the structure, the top view shows the interdigital transduction layer 200. In the actual product, the interdigital transduction layer is covered by the shear wave suppression layer 300 and is not shown in the top view.) The interdigital transduction layer 200 includes a plurality of finger electrodes 201 spaced apart along a first direction. The area where each finger electrode 201 overlaps with the adjacent finger electrode 201 in the first direction includes an interdigital region 10 and a suppression region 11. The suppression region 11 is located on both sides of the interdigital region 10 in the second direction. The first direction and the second direction intersect and are both parallel to the surface of the piezoelectric layer 102. Figure 1 and Figure 2The shear wave suppression layer 300 includes a first portion 301 and a second portion 302 . The first portion 301 covers the interdigital region 10 , and the second portion 302 covers the suppression region 11 . The thickness of the first portion 301 is greater than that of the second portion 302 .

[0048] In a surface acoustic wave filter, when the acoustic waves excited by the interdigital transduction layer 200 propagate along a first direction (the main propagation direction), some of the energy propagates in a second direction (the transverse direction), forming transverse noise modes. Transverse noise modes disperse the acoustic wave energy, increase insertion loss, and form additional resonance peaks, affecting the frequency selectivity of the surface acoustic wave filter. In the embodiment disclosed in this application, the region where each finger electrode 201 overlaps with an adjacent finger electrode 201 in the first direction is the area where the acoustic waves are primarily excited and converted. Specifically, this region includes an interdigital region 10 and suppression regions 11 located on either side of the interdigital region 10 in the second direction. The interdigital region 10 is covered by a thicker shear wave suppression layer 300 (first portion 301), while the suppression regions 11 located on either side of the interdigital region 10 are covered by a thinner shear wave suppression layer 300 (second portion 302). Compared to the interdigital transducer layer 200, sound waves propagate faster in the shear-wave suppression layer 300. Laying the shear-wave suppression layer 300 in this manner ensures that the sound wave velocity in the interdigital region 10 is higher than that in the suppression region 11. As the transverse sound wave propagates from the interdigital region 10 to the suppression region 11, the propagation velocity of the sound wave gradually decreases. Furthermore, one of the two suppression regions 11 has a first gap 13 on the side facing away from the interdigital region 10, and the other has a second gap 14 on the side facing away from the interdigital region 10. When the sound wave propagates to the first gap 13 and the second gap 14, the gap regions have a lower metallization rate, increasing the sound wave propagation velocity and forming an acoustic barrier. This effectively confines the energy within the interdigital region 10, reducing the propagation energy in the lateral direction (the second direction), thereby alleviating the impact of transverse spurious modes.

[0049] It should be noted that in the embodiment disclosed in this application, the material of the interdigital transducer layer 200 is a material such as chromium or gold that has high conductivity and can form effective acoustic-to-electrical conversion with the piezoelectric layer 102. The material of the shear wave suppression layer 300 is a nitride material, such as silicon nitride.

[0050] In order to further reduce the interference of the lateral clutter mode on the sound waves in the main propagation direction (first direction), refer to Figure 2 and Figure 5In the embodiment disclosed in the present application, the first part 301 has two connecting side walls 3011 arranged opposite to each other on both sides of the second direction, and the connecting side walls 3011 are connected to the second part 302 located on the same side, and the connecting side walls 3011 are inclined relative to the surface of the second part 302 that is away from the interdigital transduction layer 200. Specifically, when the sound wave propagates in the second direction, the sound wave is transmitted to the first interval 13 and the second interval 14 on both sides, and reflection and refraction will occur, which helps to reduce the propagation of the sound wave in unnecessary directions and allows the sound wave to be more concentrated in the main propagation direction. Furthermore, the plane where the surface of the second part 302 that is away from the interdigital transduction layer 200 is located is the first plane 20, and there is a first inclination angle α between the connecting side wall 3011 and the first plane 20. The angle of the first inclination angle α will affect the suppression effect of the surface acoustic wave filter on the lateral noise mode. Specifically, referring to Figure 13 , Figure 13 This is a characteristic diagram of the real part of the admittance of the surface acoustic wave filter changing with frequency under different first-part structures. Figure 13 The frequency range of the medium shear wave (the sound wave propagating in the second direction) is [0.91GHZ, 0.94GHZ], and the observation Figure 13 It can be seen that, in the surface acoustic wave filter whose first portion 301 has no inclined sidewalls, the real part of admittance fluctuates greatly with frequency near the shear wave frequency; in the surface acoustic wave filter whose first portion 301 has inclined sidewalls, the real part of admittance fluctuates less with frequency near the shear wave frequency, and the curve of the real part of admittance changing with frequency is smoother. Figure 13 This indicates that a surface acoustic wave filter with an inclined sidewall in the first portion 301 can effectively suppress signals within the shear wave frequency range. Based on the above considerations, in the embodiments disclosed herein, the preferred range of the first tilt angle α is [30°, 85°]. Furthermore, the thickness of the first portion 301 is greater than the thickness of the second portion 302. In other words, the surface of the first portion 301 facing away from the IDT layer 200 has a height difference relative to the surface of the second portion 302 facing away from the IDT layer 200. In the embodiments disclosed herein, the preferred range of this height difference is [20 nm, 80 nm].

[0051] Continue to refer to Figure 1 and Figure 2The interdigitated transduction layer 200 further includes a first bus bar 202 and a second bus bar 203, respectively, located on either side of the finger electrode 201 in the second direction. The first bus bar 202 and the second bus bar 203 extend along the first direction, while the finger electrode 201 extends along the second direction. In the first direction, one of two adjacent finger electrodes 201 is connected to the first bus bar 202, and the other is connected to the second bus bar 203. A second gap 14 is defined between the end of the finger electrode 201 connected to the first bus bar 202 that faces away from the first bus bar 202 and the second bus bar 203. A first gap 13 is defined between the end of the finger electrode 201 connected to the second bus bar 203 that faces away from the second bus bar 203 and the first bus bar 202. The portion of the finger electrode 201 used for connecting to the bus bar is a connection region 12. Specifically, the connection region 12 is located between the suppression region 11 and the bus bar adjacent to the suppression region 11.

[0052] Reference Figure 2 and Figure 7 In some embodiments, the shear wave suppression layer 300 further includes a third portion 303, a first spacer 306, and a second spacer 307. The third portion 303 covers the connection area 12 and the busbar connected to the finger electrode 201. The thickness of the third portion 303 is the same as that of the second portion 302. The first spacer 306 fills the first gap 13 and the second gap 14. The distance between the surface of the first spacer 306 facing away from the piezoelectric layer 102 and the piezoelectric layer 102 is less than the distance between the surface of the second portion 302 facing away from the piezoelectric layer 102 and the piezoelectric layer 102. The second spacer 307 fills the gap between two adjacent finger electrodes 201. The distance between the surface of the second spacer 307 facing away from the piezoelectric layer 102 and the piezoelectric layer 102 is less than the distance between the surface of the second portion 302 facing away from the piezoelectric layer 102 and the piezoelectric layer 102. With this arrangement, the acoustic velocity of the sound wave at the first interval 13 and the second interval 14 is greater than the acoustic velocity on both sides of the first interval 13 in the second direction, and greater than the acoustic velocity on both sides of the second interval 14 in the second direction, so that a sound velocity difference interface is formed between the first bus bar 202 and the first interval 13, and a sound velocity difference interface is formed between the first interval 13 and the second portion 302. Energy is effectively controlled within the interdigital area 10, reducing the outward propagation of energy in the lateral direction (second direction), thereby suppressing the formation of lateral clutter modes. For details, see Figure 3 , Figure 3 for Figure 2 The sound velocity variation diagram of the surface acoustic wave filter shown in the figure clearly shows that the sound velocity of the sound wave at the first interval 13 and the second interval 14 is significantly higher than the sound velocity on both sides of the second direction, and the second part 302 located on both sides of the first part 301 can effectively reduce the sound velocity of the sound wave. (It should be noted that Figure 3 、 Figure 6 and Figure 10They are all sound velocity change diagrams. In this application, the horizontal axis of the sound velocity change diagram represents different positions in the surface acoustic wave filter with different areas of the interdigital transducing layer 200).

[0053] The second embodiment disclosed in this application is as follows: Figure 4 As shown, different from the first embodiment, the shear wave suppression layer 300 does not include the third part 303, but includes a fourth part 304 and a fifth part 305. The fourth part 304 covers the connection area 12, and the fifth part 305 covers the bus bar connected to the finger electrode 201. The thickness of the fourth part 304 is the same as that of the second part 302. The fifth part 305 includes a first sub-part 3051 and a second sub-part 3052 connected to each other. In the second direction, the first sub-part 3051 is close to the finger electrode 201, and the thickness of the first sub-part 3051 is the same as that of the second part 302. The thickness of the second sub-part 3052 is greater than that of the second part 302. With this arrangement, referring to Figure 6 In the second embodiment, the sound velocity of the sound wave in the first section 3051 is greater than the sound velocity in the second section 3052. While suppressing the lateral clutter mode, the sound velocity of the sound wave in the second embodiment can smoothly transition between the bus bar and the corresponding interval, thereby reducing energy loss.

[0054] It should be noted that in Example 2, within the finger electrode 201 distribution area, the thickness of the first portion 301 is greater than the thickness of the second portion 302, and the sound velocity of the sound wave can be increased; while in the bus bar distribution area, the thickness of the second section 3052 is greater than the thickness of the first section 3051, but the sound velocity of the sound wave is reduced. This is because the propagation of the sound wave is constrained by the overall structure. From an overall perspective, within the bus bar distribution area, the first bus bar 202 and the second bus bar 203 both extend along the first direction and are a continuous structure. Within the finger electrode 201 distribution area, multiple finger electrodes 201 are arranged at intervals in the first direction, and the intervals are also filled with second spacing portions 307. Therefore, although the cross-sectional structures appear to be the same, the different overall structures of the distribution areas will have different effects on the propagation velocity of the sound wave.

[0055] In some embodiments, as Figure 2The base layer 101 includes a substrate 1011 and a temperature-compensating structure 1012 stacked in sequence. The piezoelectric layer 102 is located on the side of the temperature-compensating structure 1012 facing away from the substrate 1011. The substrate 1011 is typically made of a high-acoustic-velocity material, specifically polycrystalline silicon or single-crystal silicon. The piezoelectric layer 102 can be made of lithium niobate (LiNbO3) or lithium tantalate (LiTaO3). Furthermore, the performance of a surface acoustic wave filter (such as resonant frequency and bandwidth) typically drifts with temperature. The piezoelectric layer 102 typically has a positive temperature coefficient. By covering the substrate 1011 with a temperature-compensating structure 1012 having a negative temperature coefficient, the effect of temperature changes on the performance of the surface acoustic wave filter can be effectively offset. Specifically, the temperature compensation structure 1012 is usually made of silicon dioxide (SiO2) or tantalum pentoxide (Ta2O5). Both silicon dioxide (SiO2) and tantalum pentoxide (Ta2O5) have negative temperature coefficients and stable material properties. They can balance the temperature coefficient of the surface acoustic wave filter, thereby stabilizing the performance of the surface acoustic wave filter and maintaining consistent operating characteristics at different temperatures.

[0056] The third embodiment disclosed in this application is as follows Figure 8 and Figure 9 As shown, compared with the first and second embodiments, the surface acoustic wave filter disclosed in the third embodiment further includes two third bus bars 204 arranged opposite to each other along the second direction. The third bus bar 204 extends along the first direction. The third bus bar 204 is located on the side of the interdigitated transducer layer 200 away from the piezoelectric substrate 100. In the third direction, the projection of one of the two third bus bars 204 overlaps with the projection of the first interval 13, and the projection of the other overlaps with the projection of the second interval 14. The third direction is perpendicular to the surface of the side of the piezoelectric layer 102 away from the base layer 101. Specifically, the surface acoustic wave filter disclosed in the third embodiment has two structural forms, with reference to FIG. Figure 9 The first structural form is to set a third bus bar 204 on the basis of the first embodiment; Figure 11 The second structural form is based on the second embodiment and provides a third bus bar 204. In both the first and second structural forms, the third bus bar 204 is connected to the first spacer 306 when located above the first spacer 13 and the second spacer 14, and is connected to the side of the finger electrode 201 away from the piezoelectric layer 102 when located above the connection area 12. Figure 10 and Figure 12By introducing the third bus bar 204, regardless of the first or second structural form, the sound velocity of the sound wave in the first interval 13 and the second interval 14 will undergo an increase-decrease-increase change, forming an acoustic potential barrier. When the sound wave enters the first interval 13 and the second interval 14, and leaves the first interval 13 and the second interval 14, the acoustic potential barrier effectively controls the energy within the finger electrode 201 area, reducing the outward propagation of energy in the lateral direction (second direction). The sound velocity is reduced in the first interval 13 and the second interval 14, which can disperse high-order lateral modes and suppress the propagation of lateral noise modes.

[0057] According to a second aspect of the present application, a method for manufacturing a surface acoustic wave filter is provided. The method for manufacturing a surface acoustic wave filter can be used to manufacture the surface acoustic wave filter disclosed above, and the method comprises:

[0058] S100. Forming a piezoelectric substrate, the piezoelectric substrate comprising a base layer and a piezoelectric layer stacked;

[0059] S200. Forming an interdigital transduction layer on a surface of the piezoelectric layer facing away from the substrate layer, the interdigital transduction layer comprising a plurality of finger electrodes spaced apart along a first direction, wherein an area where each finger electrode overlaps with an adjacent finger electrode in the first direction comprises an interdigital region and an inhibition region, wherein the inhibition region is located on either side of the interdigital region in a second direction, the first direction and the second direction intersecting and both being parallel to the surface of the piezoelectric layer facing away from the substrate layer;

[0060] S300. A shear wave suppression layer is formed on a side of the interdigital transduction layer facing away from the piezoelectric substrate, wherein the shear wave suppression layer covers the interdigital transduction layer and the piezoelectric layer exposed on the interdigital transduction layer; the shear wave suppression layer includes a first portion and a second portion, wherein the first portion covers the interdigital region and the second portion covers the suppression region, and the thickness of the first portion is greater than the thickness of the second portion.

[0061] In some embodiments, the interdigital transduction layer formed in step S200 further includes a first bus bar and a second bus bar. The first bus bar and the second bus bar are located on either side of the finger electrode in the second direction, respectively. The first bus bar and the second bus bar extend along the first direction, and the finger electrode extends along the second direction. In the first direction, one of two adjacent finger electrodes is connected to the first bus bar, and the other is connected to the second bus bar. A second gap exists between the end of the finger electrode connected to the first bus bar that faces away from the first bus bar and the second bus bar. A first gap exists between the end of the finger electrode connected to the second bus bar that faces away from the second bus bar and the first bus bar. The portion of the finger electrode used to connect to the bus bar is the connection region. Specifically, the connection region is located between the suppression region and the bus bar adjacent to the suppression region. Based on this, in one embodiment of step S300, the shear wave suppression layer formed in step S300 further includes a third portion, a first spacer portion, and a second spacer portion. The third portion covers the connection region and the bus bar connected to the finger electrode, and the thickness of the third portion is the same as that of the second portion. The first spacer is filled in the first and second spaces, and the distance between the surface of the first spacer facing away from the piezoelectric layer and the piezoelectric layer is smaller than the distance between the surface of the second spacer facing away from the piezoelectric layer and the piezoelectric layer. The second spacer is filled in the space between two adjacent finger electrodes, and the distance between the surface of the second spacer facing away from the piezoelectric layer and the piezoelectric layer is smaller than the distance between the surface of the second spacer facing away from the piezoelectric layer and the piezoelectric layer.

[0062] In some embodiments, in another embodiment of step S300, the shear wave suppression layer does not include the third portion, but includes a fourth portion and a fifth portion. The fourth portion covers the connection area, and the fifth portion covers the busbar connected to the finger electrodes. The thickness of the fourth portion is the same as that of the second portion. The fifth portion includes a first sub-portion and a second sub-portion connected thereto. In the second direction, the first sub-portion is adjacent to the finger electrodes, the first sub-portion and the second sub-portion have the same thickness, and the second sub-portion is thicker than the second portion.

[0063] Furthermore, in some embodiments, before step S300, the method for manufacturing a surface acoustic wave filter further includes forming two third bus bars disposed opposite each other along a second direction on a side of the interdigital transduction layer facing away from the piezoelectric substrate, the third bus bars extending along the first direction. In the third direction, the projection of one of the two third bus bars overlaps with the projection of the first interval, and the projection of the other overlaps with the projection of the second interval, and the third direction is perpendicular to the surface of the piezoelectric layer facing away from the base layer. After this step is completed, step S300 is then initiated, i.e., forming a shear wave suppression layer on the side of the interdigital transduction layer facing away from the piezoelectric substrate, wherein the formed shear wave suppression layer wraps around the third bus bars.

[0064] 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.

[0065] 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.

[0066] The embodiments, implementation methods and related technical features of the present application can be combined and replaced with each other without conflict.

[0067] The above are merely preferred embodiments of the present application and do not constitute any form of limitation to the present application. 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 are still within the scope of the technical solution of the present application.

Claims

1. A surface acoustic wave filter, characterized in that: include: A piezoelectric substrate (100) comprising a base layer (101) and a piezoelectric layer (102) located on the base layer (101); An interdigital transduction layer (200) is located on a surface of the piezoelectric layer (102) facing away from the substrate layer (101), comprising a plurality of finger electrodes (201) spaced apart along a first direction, wherein an area where each finger electrode (201) overlaps with an adjacent finger electrode (201) in the first direction comprises an interdigital region (10) and an inhibition region (11), wherein the inhibition region (11) is located on both sides of the interdigital region (10) in a second direction, wherein the first direction and the second direction intersect and are both parallel to the surface of the piezoelectric layer (102); A shear wave suppression layer (300) is located on a side of the interdigital transduction layer (200) facing away from the piezoelectric substrate (100), and covers the interdigital transduction layer (200) and the piezoelectric layer (102) exposed on the interdigital transduction layer (200); the shear wave suppression layer (300) comprises a first portion (301) and a second portion (302), wherein the first portion (301) covers the interdigital region (10), and the second portion (302) covers the suppression region (11), and the thickness of the first portion (301) is greater than the thickness of the second portion (302).

2. The surface acoustic wave filter according to claim 1, wherein In the second direction, the first portion (301) has two connecting side walls (3011) arranged opposite to each other, the connecting side walls (3011) are connected to the second portion (302) located on the same side, and the connecting side walls (3011) are inclined relative to a surface of the second portion (302) facing away from the interdigital transduction layer (200).

3. The surface acoustic wave filter according to claim 2, wherein The plane where the surface of the second portion (302) facing away from the interdigital transduction layer (200) lies is a first plane (20), and a first tilt angle α is formed between the connecting side wall (3011) and the first plane (20), and the range of the first tilt angle α is [30°, 85°].

4. The surface acoustic wave filter according to claim 1, wherein A surface of the first portion (301) facing away from the interdigital transduction layer (200) has a height difference relative to a surface of the second portion (302) facing away from the interdigital transduction layer (200), and the value range of the height difference is [20 nm, 80 nm].

5. The surface acoustic wave filter according to claim 1, wherein The interdigital transduction layer (200) further comprises a first bus bar (202) and a second bus bar (203) respectively located on both sides of the finger electrode (201) in the second direction, the first bus bar (202) and the second bus bar (203) extending along the first direction, the finger electrode (201) extending along the second direction, and in the first direction, one of two adjacent finger electrodes (201) is connected to the first bus bar (202), and the other is connected to the second bus bar (203); A second gap (14) is provided between an end of the finger electrode (201) connected to the first bus bar (202) facing away from the first bus bar (202) and the second bus bar (203), and a first gap (13) is provided between an end of the finger electrode (201) connected to the second bus bar (203) facing away from the second bus bar (203) and the first bus bar (202).

6. The surface acoustic wave filter according to claim 5, wherein The finger electrode (201) further includes a connection area (12), wherein the connection area (12) is located between the suppression area (11) and a bus bar adjacent to the suppression area (11); the transverse wave suppression layer (300) further includes a third portion (303), wherein the third portion (303) covers the connection area (12) and the bus bar connected to the finger electrode (201), and the thickness of the third portion (303) is the same as the thickness of the second portion (302).

7. The surface acoustic wave filter according to claim 5, wherein The finger electrode (201) further comprises a connection area (12), wherein the connection area (12) is located between the suppression area (11) and a bus bar adjacent to the suppression area (11); the transverse wave suppression layer (300) further comprises a fourth portion (304) and a fifth portion (305), wherein the fourth portion (304) covers the connection area (12), and the fifth portion (305) covers the bus bar connected to the finger electrode (201); the thickness of the fourth portion (304) is the same as the thickness of the second portion (302); The fifth portion (305) includes a first sub-portion (3051) and a second sub-portion (3052) connected to each other. In the second direction, the first sub-portion (3051) is close to the finger electrode (201). The first sub-portion (3051) and the second portion (302) have the same thickness, and the second sub-portion (3052) is thicker than the second portion (302).

8. The surface acoustic wave filter according to claim 6 or 7, wherein: The shear wave suppression layer (300) further includes a first spacer portion (306) filled in the first spacer (13) and the second spacer (14), wherein a distance from a side surface of the first spacer portion (306) facing away from the piezoelectric layer (102) to the piezoelectric layer (102) is smaller than a distance from a side surface of the second portion (302) facing away from the piezoelectric layer (102) to the piezoelectric layer (102).

9. The surface acoustic wave filter according to claim 6 or 7, wherein: The shear wave suppression layer (300) further includes a second spacer (307) filled in the gap between two adjacent finger electrodes (201), wherein the distance from the surface of the second spacer (307) facing away from the piezoelectric layer (102) to the piezoelectric layer (102) is smaller than the distance from the surface of the second portion (302) facing away from the piezoelectric layer (102) to the piezoelectric layer (102).

10. The surface acoustic wave filter according to claim 8, wherein The invention also includes two third bus bars (204) arranged opposite to each other along a second direction, wherein the third bus bars (204) extend along the first direction, and are located on a side of the interdigitated transducer layer (200) facing away from the piezoelectric substrate (100). In the third direction, the projection of one of the two third bus bars (204) overlaps with the projection of the first interval (13), and the projection of the other overlaps with the projection of the second interval (14). The third direction is perpendicular to the surface of the side of the piezoelectric layer (102) facing away from the base layer (101).

11. A method for manufacturing a surface acoustic wave filter, characterized in that: include: forming a piezoelectric substrate, the piezoelectric substrate comprising a base layer and a piezoelectric layer stacked together; An interdigital transduction layer is formed on a surface of the piezoelectric layer facing away from the substrate layer, the interdigital transduction layer comprising a plurality of finger electrodes spaced apart along a first direction, wherein an area where each finger electrode overlaps with an adjacent finger electrode in the first direction comprises an interdigital region and an inhibition region, the inhibition region being located on both sides of the interdigital region in a second direction, the first direction and the second direction intersecting and both being parallel to the surface of the piezoelectric layer facing away from the substrate layer; A shear wave suppression layer is formed on a side of the interdigital transduction layer facing away from the piezoelectric substrate, and the shear wave suppression layer covers the interdigital transduction layer and the piezoelectric layer exposed on the interdigital transduction layer; the shear wave suppression layer includes a first portion and a second portion, the first portion covers the interdigital area, the second portion covers the suppression area, and the thickness of the first portion is greater than the thickness of the second portion.

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