Surface acoustic wave filter and manufacturing method thereof

Abstract

The invention relates to a surface acoustic wave filter and a manufacturing method thereof. The surface acoustic wave filter comprises a piezoelectric substrate, an interdigital transduction layer and a transverse wave suppression layer which are stacked. The interdigital transduction layer comprises a plurality of finger electrodes which are arranged at intervals in the first direction, and the overlapped area of each finger electrode and the adjacent finger electrode in the first direction comprises an interdigital area and suppression areas located on the two sides of the interdigital area in the second direction. The transverse wave suppression layer comprises a first part and a second part, the first part covers the interdigital area, the second part covers the suppression area, and the thickness of the first part is larger than that of the second part. According to the technical scheme, the transverse wave suppression layer laid in the invention can make the sound velocity of sound waves in the interdigital area higher than the sound velocity of the suppression area, energy is effectively controlled in the interdigital area, transverse (second direction) propagation energy is reduced, and thus the influence of a transverse stray mode is reduced.

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; 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; The shear wave suppression layer is located on the side of the interdigital transducer layer facing away from the piezoelectric substrate, and covers the interdigital transducer layer and the piezoelectric layer exposed on the interdigital transducer layer; the shear wave suppression layer includes a first part and a second part, the first part covers the interdigital region, the second part covers the suppression region, and the thickness of the first part is greater than the thickness of the second part.

[0006] Optionally, in the second direction, the first part has two connecting side walls arranged opposite to each other, the connecting side walls are connected to the second part on the same side, and the connecting side walls are inclined with respect to the surface of the second part facing away from the interdigital transducer layer.

[0007] Optionally, the plane where the surface of the second part facing away from the interdigital transducer layer is the first plane, and there is a first inclination angle α between the connecting side wall and the first plane, and the range of the first inclination angle α is [30°, 85°].

[0008] Optionally, the surface of the first part facing away from the interdigital transducer layer has a height difference with respect to the surface of the second part facing away from the interdigital transducer layer, and the value range of the height difference is [20nm, 80nm].

[0009] Optionally, the interdigital transducer layer further includes a first bus bar and a second bus bar respectively located on both sides of the finger electrode in the second direction, the first bus bar and the second bus bar extend along the first direction, the finger electrode extends along the second direction, and 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; There is a second gap between the end of the finger electrode connected to the first bus bar facing away from the first bus bar and the second bus bar, and there is a first gap between the end of the finger electrode connected to the second bus bar facing away from the second bus bar and the first bus bar.

[0010] Optionally, the finger electrode further includes a connection region located between the suppression region and the bus bar adjacent to the suppression region; the shear wave suppression layer further includes a third part covering the connection region 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.

[0011] Optionally, the finger electrode further includes a connection region located between the suppression region and the bus bar adjacent to the suppression region; the shear wave suppression layer further includes a fourth part and a fifth part, the fourth part covers the connection region, the fifth part covers the bus bar connected to the finger electrode, and the thickness of the fourth part is the same as the thickness of the second part; The fifth part includes a first sub - part and a second sub - part connected to each other. In the second direction, the first sub - part is close to the finger electrode. The first sub - part has the same thickness as the second part, and the thickness of the second sub - part is greater than that of the second part.

[0012] Optionally, the transverse - wave suppression layer further includes a first spacer part filled in the first interval and the second interval. The distance from the side surface of the first spacer part facing away from the piezoelectric layer to the piezoelectric layer is less than the distance from the side surface of the second part facing away from the piezoelectric layer to the piezoelectric layer.

[0013] Optionally, the transverse - wave suppression layer further includes a second spacer part filled in the interval between two adjacent finger electrodes. The distance from the side surface of the second spacer part facing away from the piezoelectric layer to the piezoelectric layer is less than the distance from the side surface of the second part facing away from the piezoelectric layer to the piezoelectric layer.

[0014] Optionally, it further includes two third bus bars arranged opposite to each other in the second direction. The third bus bars extend in the first direction and are located on the side of the interdigital transducer 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 side surface of the piezoelectric layer facing away from the base layer.

[0015] According to the second aspect of the present application, a manufacturing method of a surface acoustic wave filter is provided, including: Forming a piezoelectric substrate, the piezoelectric substrate includes a base layer and a piezoelectric layer stacked; Forming an interdigital transducer layer on the side surface of the piezoelectric layer facing away from the base layer. The interdigital transducer layer includes a plurality of finger electrodes arranged at intervals in the first direction. The overlapping area of two adjacent finger electrodes in the first direction includes an interdigital area and a suppression area. The suppression area is located on both sides of the interdigital area in the second direction. The first direction and the second direction intersect and are both parallel to the side surface of the piezoelectric layer facing away from the base layer; Forming a transverse - wave suppression layer on the side of the interdigital transducer layer facing away from the piezoelectric substrate. The transverse - wave suppression layer covers the interdigital transducer layer and the piezoelectric layer exposed on the interdigital transducer layer; the transverse - wave suppression layer includes a first part and a second part. The first part covers the interdigital area, and the second part covers the suppression area. The side surface of the first part facing away from the interdigital transducer layer protrudes from the side surface of the second part facing away from the interdigital transducer layer.

[0016] In the surface acoustic wave filter according to the embodiments of the present application, through the above technical solution, in the surface acoustic wave filter, when the acoustic wave excited by the interdigital transducer layer propagates along the first direction (main propagation direction), part of the energy will propagate along the second direction (lateral direction), forming a lateral clutter mode. The lateral clutter mode will disperse the acoustic wave energy, increase the insertion loss, and will form additional resonance peaks, affecting the frequency selectivity of the surface acoustic wave filter. In the embodiments disclosed in the present application, the region where each finger electrode overlaps with the adjacent finger electrode in the first direction is the region where the acoustic wave is mainly excited and converted. Specifically, this region includes the interdigital region and the suppression regions located on both sides of the interdigital region in the second direction. A relatively thick shear wave suppression layer (the first part) is covered on the interdigital region, and a relatively thin shear wave suppression layer (the second part) is covered on the suppression regions located on both sides of the interdigital region. Compared with the interdigital transducer layer, the propagation speed of the acoustic wave in the shear wave suppression layer is faster. Laying the shear wave suppression layer in this way can make the sound velocity of the acoustic wave in the interdigital region higher than that in the suppression region. When the lateral acoustic wave is transmitted from the interdigital region to the suppression region, the propagation speed of the acoustic wave gradually decreases. Further, one of the two suppression regions has a first gap on the side facing away from the interdigital region, and the other has a second gap on the side facing away from the interdigital region. When the acoustic wave is transmitted to the first gap and the second gap on both sides, due to the lower metallization rate in the gap region, the propagation speed of the acoustic wave increases, forming an acoustic barrier, effectively controlling the energy within the interdigital region, reducing the propagation energy in the lateral direction (the second direction), and thus reducing the influence of the lateral clutter mode.

[0017] Other features and advantages of the present application will be described in detail in the subsequent specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those skilled in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] In order to more completely understand the present application and its beneficial effects, the following will be described in conjunction with the drawings, where the same reference numerals represent the same parts in the following description.

[0019] Figure 1 is a schematic top view of the surface acoustic wave filter provided by the embodiment of the present application Figure 1 ; Figure 2 is a cross-sectional view taken along A-A of a surface acoustic wave filter provided by the embodiment of the present application Figure 1 in Figure 3 is Figure 2 the sound velocity change diagram of the surface acoustic wave filter shown Figure 4 Another cross-sectional view of the surface acoustic wave filter provided by an embodiment of the present application at A-A in Figure 1 ; Figure 5 is Figure 2 an enlarged view of the D part of the surface acoustic wave filter shown in Figure 6 is Figure 4 the sound velocity variation diagram of the surface acoustic wave filter shown in Figure 7 A cross-sectional view of a surface acoustic wave filter provided by an embodiment of the present application at B-B in Figure 1 ; Figure 8 is a schematic Figure 2 of the top view of the surface acoustic wave filter provided by an embodiment of the present application; Figure 9 A cross-sectional view of a surface acoustic wave filter provided by an embodiment of the present application at C-C in Figure 8 ; Figure 10 is Figure 9 the sound velocity variation diagram of the surface acoustic wave filter shown in Figure 11 Another cross-sectional view of the surface acoustic wave filter provided by an embodiment of the present application at C-C in Figure 8 ; Figure 12 is Figure 11 the sound velocity variation diagram of the surface acoustic wave filter shown in Figure 13 is the characteristic diagram of the real part of the admittance of the surface acoustic wave filter varying with frequency under different first structural parts.

[0020] Explanation of reference numerals: 100, piezoelectric substrate; 101, base layer; 1011, substrate; 1012, temperature compensation structure; 102, piezoelectric layer; 200, interdigital transducer layer; 201, finger electrode; 202, first bus bar; 203, second bus bar; 204, third bus bar; 300, transverse wave suppression layer; 301, first part; 3011, connecting side wall; 302, second part; 303, third part; 304, fourth part; 305, fifth part; 3051, first sub-part; 3052, second sub-part; 306, first spacer; 307, second spacer; 10, interdigital region; 11, suppression region; 12, connection region; 13, first spacer; 14, second spacer; 20, first plane. Detailed implementation manners

[0021] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0022] According to the first aspect of the present application, a surface acoustic wave filter is provided. An embodiment of the surface acoustic wave filter disclosed in the present application is as shown in Figure 2 ( Figure 2 is a cross-sectional view taken along the line A-A in Figure 1 of the surface acoustic wave filter provided by an embodiment of the present application). The surface acoustic wave filter includes: a piezoelectric substrate 100, an interdigital transducer layer 200, and a transverse wave suppression layer 300. Specifically, the piezoelectric substrate 100 includes a base layer 101 and a piezoelectric layer 102 located on the base layer 101. The interdigital transducer layer 200 is located on a surface of the piezoelectric layer 102 facing away from the base layer 101, and the transverse wave suppression layer 300 is located on a side of the interdigital transducer layer 200 facing away from the piezoelectric substrate 100 and covers the interdigital transducer layer 200 and the piezoelectric layer 102 exposed on the interdigital transducer layer 200. Referring to Figure 1 , Figure 1 is a schematic top view of the surface acoustic wave filter provided by an embodiment of the present application Figure 1 (it should be noted that for the convenience of observing the structure, the top view shows the interdigital transducer layer 200, and in the actual product, the interdigital transducer layer is covered by the transverse wave suppression layer 300 and will not be shown in the top view). The interdigital transducer layer 200 includes a plurality of finger electrodes 201 arranged at intervals along a first direction. An overlapping region of each finger electrode 201 and an 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 a second direction. The first direction and the second direction intersect and are both parallel to the surface of the piezoelectric layer 102. Referring to Figure 1 and Figure 2 , the transverse 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 the thickness of the second portion 302.

[0023] In a surface acoustic wave filter, when the acoustic wave excited by the interdigital transducer layer 200 propagates along the first direction (main propagation direction), part of the energy will propagate in the second direction (transverse direction), forming a transverse clutter mode. The transverse clutter mode will disperse the acoustic wave energy, increase the insertion loss, and form additional resonance peaks, affecting the frequency selectivity of the surface acoustic wave filter. In the embodiments disclosed in the present application, the region where each finger electrode 201 overlaps with the adjacent finger electrode 201 in the first direction is the region where the acoustic wave is mainly excited and converted. Specifically, this region includes the interdigital region 10 and the suppression regions 11 on both sides of the interdigital region 10 in the second direction. A relatively thick transverse wave suppression layer 300 (the first part 301) is covered on the interdigital region 10, and a relatively thin transverse wave suppression layer 300 (the second part 302) is covered on the suppression regions 11 on both sides of the interdigital region 10. Compared with the interdigital transducer layer 200, the propagation speed of the acoustic wave in the transverse wave suppression layer 300 is fast. Laying the transverse wave suppression layer 300 like this can make the acoustic velocity in the interdigital region 10 higher than that in the suppression region 11. When the transverse acoustic wave is transmitted from the interdigital region 10 to the suppression region 11, the propagation speed of the acoustic wave gradually decreases. Further, 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 acoustic wave is transmitted to the first gap 13 and the second gap 14 on both sides, the propagation speed of the acoustic wave increases due to the relatively low metallization rate in the gap region, forming an acoustic barrier, effectively controlling the energy within the interdigital region 10, reducing the propagation energy in the transverse direction (the second direction), and thus reducing the influence of the transverse clutter mode.

[0024] It should be noted that in the embodiments disclosed in the present application, the material of the interdigital transducer layer 200 is a material with high conductivity such as chromium or gold and can form an effective acoustic-electric conversion with the piezoelectric layer 102. The material of the transverse wave suppression layer 300 is a nitride material, such as silicon nitride.

[0025] In order to further reduce the interference of the transverse clutter mode on the acoustic wave in the main propagation direction (the 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 (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].

[0026] Continue to refer to Figure 1 and Figure 2, the interdigital transducer layer 200 further includes 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 extend along the first direction, and 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. There is a second gap 14 between the end of the finger electrode 201 connected to the first bus bar 202, which is away from the first bus bar 202, and the second bus bar 203. There is a first gap 13 between the end of the finger electrode 201 connected to the second bus bar 203, which is away from the second bus bar 203, and the first bus bar 202. The portion of the finger electrode 201 for connecting to the bus bar is a connection area 12. Specifically, the connection area 12 is located between the suppression area 11 and the bus bar adjacent to the suppression area 11.

[0027] Referring to Figure 2 and Figure 7 , in some embodiments, the shear wave suppression layer 300 further includes a third portion 303, a first spacer portion 306, and a second spacer portion 307. 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. The first spacer portion 306 is filled in the first gap 13 and the second gap 14. The distance from the surface of the first spacer portion 306, which is away from the piezoelectric layer 102, to the piezoelectric layer 102 is less than the distance from the surface of the second portion 302, which is away from the piezoelectric layer 102, to the piezoelectric layer 102. The second spacer portion 307 is filled in the gap between two adjacent finger electrodes 201. The distance from the surface of the second spacer portion 307, which is away from the piezoelectric layer 102, to the piezoelectric layer 102 is less than the distance from the surface of the second portion 302, which is away from the piezoelectric layer 102, to the piezoelectric layer 102. With such a setting, the sound velocity of the acoustic wave at the first gap 13 and the second gap 14 is greater than the sound velocity on both sides of the first gap 13 in the second direction, and greater than the sound velocity on both sides of the second gap 14 in the second direction, so that a sound velocity difference interface is formed between the first bus bar 202 and the first gap 13, and a sound velocity difference interface is formed between the first gap 13 and the second portion 302. The energy is effectively controlled within the interdigital area 10, reducing the outward propagation of energy in the transverse direction (the second direction), and thus suppressing the formation of transverse clutter modes. Specifically referring to Figure 3 , Figure 3 is Figure 2 the sound velocity change diagram of the surface acoustic wave filter shown, it can be clearly known that the sound velocity of the acoustic wave at the first gap 13 and the second gap 14 is significantly higher than the sound velocity on both sides in the second direction, and the second portion 302 located on both sides of the first portion 301 can effectively reduce the sound velocity of the acoustic wave. (It should be noted that Figure 3 , Figure 6 and Figure 10They are all graphs of the change in sound velocity. In this application, the abscissa of the graph of the change in sound velocity represents different positions in the surface acoustic wave filter by different regions of the interdigital transducer layer 200).

[0028] Embodiment 2 disclosed in this application, as Figure 4 shown, different from Embodiment 1, the transverse wave suppression layer 300 does not include the third part 303, and includes the fourth part 304 and the 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 connected first sub-part 3051 and a second sub-part 3052. In the second direction, the first sub-part 3051 is close to the finger electrode 201, the thickness of the first sub-part 3051 is the same as that of the second part 302, and the thickness of the second sub-part 3052 is greater than that of the second part 302. With such a setting, referring to Figure 6 , in Embodiment 2, the sound velocity of the sound wave in the first sub-part 3051 is greater than that in the second sub-part 3052. While suppressing the transverse clutter mode, the sound velocity of the sound wave in the bus bar and the corresponding interval in Embodiment 2 can smoothly transition, reducing energy loss.

[0029] It should be noted that in Embodiment 2, within the distribution area of the finger electrode 201, the thickness of the first part 301 is greater than that of the second part 302, and the sound velocity of the sound wave can be increased; while within the distribution area of the bus bar, the thickness of the second sub-part 3052 is greater than that of the first sub-part 3051, and the sound velocity of the sound wave decreases because the propagation of the sound wave is restricted by the overall structure. Considering the whole, within the distribution area of the bus bar, both the first bus bar 202 and the second bus bar 203 extend along the first direction and are continuous structures. Within the distribution area of the finger electrode 201, multiple finger electrodes 201 are arranged at intervals in the first direction, and the second interval part 307 is filled in the intervals. Therefore, although the cross-sectional structure seems the same, the influence of the overall structure of the distribution area on the propagation speed of the sound wave will also be different.

[0030] In some embodiments, such as Figure 2, the base layer 101 includes a substrate 1011 and a temperature compensation structure 1012 which are stacked in sequence. The piezoelectric layer 102 is located on the side of the temperature compensation structure 1012 away from the substrate 1011. The substrate 1011 is usually made of a high sound velocity material, specifically polysilicon or single crystal silicon. The material of the piezoelectric layer 102 can be lithium niobate (LiNbO3) or lithium tantalate (LiTaO3). Further, the performance of the surface acoustic wave filter (such as resonance frequency, bandwidth, etc.) usually drifts with temperature change. The piezoelectric layer 102 usually has a positive temperature coefficient, and by covering the substrate 1011 with a temperature compensation structure 1012 having a negative temperature coefficient, the influence of temperature change 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 a negative temperature coefficient and stable material properties, which can balance the temperature coefficient of the surface acoustic wave filter, thereby stabilizing the performance of the surface acoustic wave filter and enabling it to maintain consistent operating characteristics at different temperatures.

[0031] Example three disclosed in this application is as Figure 8 and Figure 9 shown. Compared with Example one and Example two, the surface acoustic wave filter disclosed in Example three further includes two third bus bars 204 which are arranged opposite to each other in the second direction. The third bus bar 204 extends in the first direction. The third bus bar 204 is located on the side of the interdigital 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 piezoelectric layer 102 away from the base layer 101. Specifically, the surface acoustic wave filter disclosed in Example three has two structural forms. Refer to Figure 9 , the first structural form is to set the third bus bar 204 on the basis of Example one; refer to Figure 11 , the second structural form is to set the third bus bar 204 on the basis of Example two. Whether it is the first structural form or the second structural form, the third bus bar 204 is connected to the first interval portion 306 when it is located above the first interval 13, and is connected to the side of the finger electrode 201 away from the piezoelectric layer 102 when it is located above the connection area 12. Refer to Figure 10 and Figure 12, by introducing the third bus bar 204, in both the first structural form and the second structural form, the sound velocity of the acoustic wave in the first interval 13 and the second interval 14 will change in the pattern of increase - decrease - increase, forming a sound barrier. When the acoustic wave enters and leaves the first interval 13 and the second interval 14, the sound barrier effectively controls the energy within the finger electrode 201 region, reducing the outward propagation of energy in the lateral direction (the second direction). The sound velocity decreases within the first interval 13 and the second interval 14, which can disperse the high - order lateral modes and suppress the propagation of lateral clutter modes.

[0032] According to the second aspect of the present application, there is provided a method for manufacturing a surface acoustic wave filter. This method for manufacturing a surface acoustic wave filter can be used to manufacture the surface acoustic wave filter disclosed above, and it includes: S100. Form a piezoelectric substrate, which includes a base layer and a piezoelectric layer stacked. S200. Form an interdigital transducer layer on the side surface of the piezoelectric layer facing away from the base layer. The interdigital transducer layer includes a plurality of finger electrodes arranged at intervals along the first direction. The overlapping region of each finger electrode with the adjacent finger electrode in the first direction includes an interdigital region and a suppression region. The suppression region is located on both sides of the interdigital region in the second direction. The first direction and the second direction intersect and are both parallel to the side surface of the piezoelectric layer facing away from the base layer. S300. Form a transverse wave suppression layer on the side of the interdigital transducer layer facing away from the piezoelectric substrate. The transverse wave suppression layer covers the interdigital transducer layer and the piezoelectric layer exposed on the interdigital transducer layer. The transverse wave suppression layer includes a first part and a second part. The first part covers the interdigital region, and the second part covers the suppression region. The thickness of the first part is greater than the thickness of the second part.

[0033] In some embodiments, the interdigital transducer 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 respectively located on two 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. There is a second gap between the end of the finger electrode connected to the first bus bar, which faces away from the first bus bar, and the second bus bar. There is a first gap between the end of the finger electrode connected to the second bus bar, which faces away from the second bus bar, and the first bus bar. The part of the finger electrode for connecting to the bus bar is the connection area. Specifically, the connection area is located between the suppression area and the bus bar adjacent to the suppression area. On this basis, in one embodiment of step S300, the shear wave suppression layer formed in step S300 further includes a third part, a first gap part and a second gap part. The third part covers the connection area and the bus bar connected to the finger electrode, and the thickness of the third part is the same as that of the second part. The first gap part is filled in the first gap and the second gap, and the distance from the surface of the first gap part facing away from the piezoelectric layer to the piezoelectric layer is less than the distance from the surface of the second part facing away from the piezoelectric layer to the piezoelectric layer. The second gap part is filled in the gap between two adjacent finger electrodes, and the distance from the surface of the second gap part facing away from the piezoelectric layer to the piezoelectric layer is less than the distance from the surface of the second part facing away from the piezoelectric layer to the piezoelectric layer.

[0034] In some embodiments, in another embodiment of step S300, the shear wave suppression layer does not include the third part, but includes a fourth part and a fifth part. The fourth part covers the connection area, and the fifth part covers the bus bar connected to the finger electrode. The thickness of the fourth part is the same as that of the second part. The fifth part includes a first sub-part and a second sub-part connected to each other. In the second direction, the first sub-part is close to the finger electrode, and the thickness of the first sub-part is the same as that of the second part, and the thickness of the second sub-part is greater than that of the second part.

[0035] Furthermore, in some embodiments, before step S300, the manufacturing method of the surface acoustic wave filter further includes forming two third bus bars arranged opposite to each other in the second direction on the side of the interdigital transducer layer facing away from the piezoelectric substrate. The third bus bars extend 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 gap, and the projection of the other overlaps with the projection of the second gap. The third direction is perpendicular to the side surface of the piezoelectric layer facing away from the base layer. After this step is completed, step S300 is then implemented, that is, a shear wave suppression layer is formed on the side of the interdigital transducer layer facing away from the piezoelectric substrate, and the formed shear wave suppression layer wraps the third bus bars.

[0036] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more features. In the description of this application, "a plurality of" means two or more, unless otherwise specifically defined.

[0037] In the above embodiments, the descriptions of each embodiment have their own emphases. For parts not detailed in a certain embodiment, reference may be made to the relevant descriptions of other embodiments.

[0038] The embodiments, implementation manners and related technical features of this application can be combined and replaced with each other without conflict.

[0039] The above are only the preferred embodiments of this application and do not impose any formal restrictions on this application. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of this application without departing from the content of the technical solution of this application still fall within the scope of the technical solution of this 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 side 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 side 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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