Resonator, filter and radio frequency front-end module

Abstract

The utility model is applicable to the technical field of radio frequency filtering, and discloses a resonator, a filter and a radio frequency front-end module, the resonator comprises a piezoelectric substrate, an interdigital transducer and a dielectric layer, the interdigital transducer is arranged on the piezoelectric substrate, and the dielectric layer is arranged on the piezoelectric substrate and covers the interdigital transducer. The interdigital transducer comprises two bus bars arranged along a first direction, the two bus bars are respectively connected with at least one electrode finger, the electrode fingers are arranged at intervals along a second direction, and the second direction intersects with the first direction; in the thickness direction of the dielectric layer, the width of one side of each electrode finger close to the piezoelectric substrate is smaller than that of one side of each electrode finger away from the piezoelectric substrate. Therefore, the performance of the resonator is improved.

Description

Technical Field

[0001] This application relates to the field of radio frequency filtering technology, and in particular to a resonator, filter and radio frequency front-end module. Background Technology

[0002] Resonators mainly include surface acoustic wave (SAW) resonators and bulk acoustic wave (BAW) resonators. SAW resonators consist of a piezoelectric substrate and interdigital transducers. The interdigital transducers are formed on the piezoelectric substrate and are used to convert electrical signals into acoustic signals or vice versa. BAW resonators, such as laterally excited thin-film bulk acoustic wave resonators (XBAR), include a substrate, a piezoelectric layer, and interdigital transducers. The substrate has a cavity, the piezoelectric layer is disposed on the upper surface of the substrate, and the interdigital transducers are disposed on the upper surface of the piezoelectric layer, opposite to the cavity.

[0003] It is understood that surface acoustic waves are accompanied by bulk acoustic waves during propagation. If the bulk acoustic waves are too close to the resonant point or have too strong an amplitude, they can easily affect the dominant mode, thereby affecting the performance of the filter's passband or transition band, and consequently affecting the performance of the SAW filter. Utility Model Content

[0004] In view of the shortcomings of the prior art, the purpose of this application is to provide a resonator, filter and RF front-end module, which aims to improve the performance of the resonator.

[0005] To address the aforementioned technical problems, embodiments of this application provide a resonator, comprising:

[0006] piezoelectric substrate;

[0007] An interdigital transducer is disposed on the piezoelectric substrate;

[0008] A dielectric layer is disposed on the piezoelectric substrate and covers the interdigital transducer;

[0009] The interdigital transducer includes two busbars arranged along a first direction, each of the two busbars being connected to at least one electrode finger, the electrode fingers being arranged at intervals along a second direction;

[0010] Along the thickness direction of the dielectric layer, the width of the electrode finger on the side closer to the piezoelectric substrate is smaller than the width of the electrode finger on the side farther from the piezoelectric substrate, and the second direction intersects the first direction.

[0011] This application also provides a resonator, which includes:

[0012] Substrate, the substrate having a cavity;

[0013] A piezoelectric layer disposed on the upper surface of the substrate;

[0014] An interdigital transducer is disposed on the piezoelectric layer and faces the cavity across the piezoelectric layer.

[0015] The interdigital transducer includes two busbars arranged opposite each other along a first direction, and each of the two busbars is connected to at least one electrode finger, which is spaced apart along a second direction.

[0016] Along the thickness direction of the piezoelectric layer, the width of the electrode finger on the side closer to the piezoelectric layer is smaller than the width of the electrode finger on the side farther away from the piezoelectric layer, and the second direction intersects the first direction.

[0017] This application also provides a filter that includes any of the resonators described above.

[0018] This application also provides an RF front-end module, which includes any of the resonators described above.

[0019] The resonator provided in this application has the following beneficial effects:

[0020] The resonator in this embodiment, by placing the interdigital transducers on the piezoelectric substrate, reduces manufacturing complexity and is easier to implement compared to embedding the interdigital transducers within the piezoelectric substrate. Furthermore, the interdigital transducers are positioned along the thickness direction of the electrode fingers, with the width of the electrode fingers increasing with distance from the piezoelectric substrate. This causes the sides of the electrode fingers to be inclined relative to the piezoelectric substrate, allowing sound waves propagating obliquely upwards from the piezoelectric substrate to the area above it to be reflected. Thus, when this electrode finger structure is applied to a surface acoustic wave resonator, it can reflect some of the plate waves formed in the dielectric layer, thereby reducing the intensity of the plate waves, increasing their frequency, and increasing the distance between the plate wave frequency and the resonant point. This reduces the influence of the plate waves on the dominant mode, improves the resonator's performance, and consequently enhances the performance of filters incorporating this resonator. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the first structure of the resonator in the first set of embodiments provided in this application;

[0023] Figure 2 yes Figure 1 A magnified view of a portion of point i;

[0024] Figure 3 This is a schematic diagram of the second structure of the resonator in the first set of embodiments provided in this application;

[0025] Figure 4 This is a schematic diagram of the third structure of the resonator in the first set of embodiments provided in this application;

[0026] Figure 5 yes Figure 4 A magnified view of a portion of point ii;

[0027] Figure 6 This is a schematic diagram of the structure of the interdigital transducer disposed on the piezoelectric substrate in the first set of embodiments provided in this application;

[0028] Figure 7 This is a schematic diagram of the structure in the first set of embodiments provided in this application, showing that the electrode fingers are disposed on the piezoelectric substrate;

[0029] Figure 8 This is a schematic diagram of the structure of an interdigital transducer in the first set of embodiments provided in this application;

[0030] Figure 9 This is a schematic diagram of a resonator structure in the second set of embodiments provided in this application;

[0031] Figure 10 This is a schematic diagram of the resonator structure in the comparative example provided in the embodiments of this application;

[0032] Figure 11 This is a comparison chart of the admittance curves of Embodiment 1 and the comparative example of the filter provided in this application.

[0033] Explanation of icon numbers:

[0034] C. Crossover region; C1. Middle region; C2. Edge region; G. Gap region; 1. Resonator; 10. Piezoelectric substrate; 11. Piezoelectric layer; 12. Substrate; 20. Interdigital transducer; 21. Busbar; 22. Electrode finger; 22A. First electrode finger; 22B. Second electrode finger; 221. First side surface; 222. Second side surface; 23. Mass load structure; 30. Dielectric layer; 31. First dielectric layer; 32. Second dielectric layer; 40. Cavity. Detailed Implementation

[0035] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0036] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship and movement of each component in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0037] It should also be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on the other component or may be connected to an intermediary component. When a component is referred to as being "connected to" another component, it can be directly connected to the other component or indirectly connected to the other component through an intermediary component.

[0038] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0039] In related technologies, temperature-compensated surface acoustic wave (TCSAW) filters use lithium niobate as a piezoelectric substrate. In this case, the bulk acoustic wave formed by the oblique propagation from the piezoelectric substrate to the dielectric layer is likely to appear to the right of the resonant point of the resonator in the range of tens to hundreds of MHz. If the bulk acoustic wave is too close to the resonant point or the amplitude is too strong, it can easily affect the main mode, thereby affecting the performance of the filter's passband or transition band.

[0040] In view of this, such as Figure 4 As shown in the embodiment of this application, by changing the structure of the electrode finger 22, when the TCSAW device is working, the surface acoustic wave formed in the piezoelectric layer 11 will propagate obliquely to the dielectric layer 30 to form a plate wave, that is, a bulk acoustic wave. Some of the plate waves will be reflected back by the inclined sidewalls in the electrode finger 22 to a certain extent, thereby reducing the plate wave intensity and increasing the plate wave frequency.

[0041] Specifically, such as Figure 1 As shown, Figure 1 An exemplary schematic diagram of the resonator 1 in this embodiment is shown. Figure 1In this embodiment, the Y direction represents the thickness direction, which can be either the thickness direction of the electrode finger 22 or the thickness direction of the dielectric layer 30. In the resonator 1 provided in this application, the width of the electrode finger 22 increases with distance from the piezoelectric substrate 10 along its thickness direction, allowing the side of the electrode finger 22 to reflect acoustic waves propagating obliquely to the dielectric layer 30. Thus, when the aforementioned electrode finger 22 structure is applied to a surface acoustic wave resonator, it can reflect a portion of the plate wave formed on the dielectric layer 30, thereby reducing the intensity of the plate wave, increasing its frequency, increasing the distance between the plate wave frequency and the main mode resonant point, reducing the influence of the plate wave on the main mode, improving the performance of the resonator 1, and consequently improving the performance of the filter with this resonator 1.

[0042] The following is in conjunction with the appendix Figures 1 to 8 This application provides a detailed description of some embodiments. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0043] It should be noted that in the attached diagram, Figures 1 to 8 This is merely an example, where, Figure 1 , Figure 3 and Figure 4 Each of the above examples illustrates a structural schematic diagram of the resonator 1 in this embodiment. Figure 2 yes Figure 1 A magnified view of a portion at point i. Figure 5 yes Figure 4 A magnified view of a section at point ii. Figure 6 An exemplary schematic diagram of the structure of the interdigital transducer 20 disposed on the piezoelectric substrate 10 in the resonator 1 of this embodiment is shown. Figure 7 An exemplary schematic diagram of the electrode finger 22 in the resonator 1 of this embodiment is shown. Figure 8 The accompanying drawings illustrate an exemplary structural schematic of the interdigital transducer 20 in the resonator 1 of this embodiment. These drawings do not limit the construction of the resonator 1, filter (not shown), and RF front-end module (not shown) of this embodiment. The drawings can be combined with each other without conflict.

[0044] First set of embodiments:

[0045] The resonator 1 provided in this embodiment can be found in [reference]. Figures 1 to 8 .

[0046] like Figure 1 and Figure 6As shown, the resonator 1 in the embodiment of the application includes a piezoelectric substrate 10, an interdigital transducer 20, and a dielectric layer 30. The interdigital transducer 20 is disposed on the piezoelectric substrate 10, and the dielectric layer 30 is disposed on the piezoelectric substrate 10 and covers the interdigital transducer 20. The interdigital transducer 20 includes two busbars 21 arranged along a first direction, and each of the two busbars 21 is connected to at least one electrode finger 22. The electrode fingers 22 are spaced apart along a second direction, which intersects the first direction. The first direction can be understood as the arrangement direction of the two busbars 21. In the following embodiments, the first direction and the second direction are perpendicular to each other as an example. Other intersecting angles are also within the protection scope of this application. Along the thickness direction of the dielectric layer 30, the width of the electrode finger 22 on the side closer to the piezoelectric substrate 10 is smaller than the width of the electrode finger 22 on the side farther from the piezoelectric substrate 10. Optionally, see details. Figure 1 In the middle, the cross-sectional shape of electrode finger 22 is set as an inverted trapezoidal structure.

[0047] In this embodiment, the resonator 1 can be a surface acoustic wave (SAW) resonator. By placing the interdigital transducer 20 on the piezoelectric substrate 10, compared to embedding the interdigital transducer 20 within the piezoelectric substrate 10, the manufacturing process is simplified and easier to implement. Furthermore, by positioning the electrode finger 22 along the thickness direction of the dielectric layer 30 (i.e., from a bottom view, from the piezoelectric substrate 10 towards the dielectric layer 30), the width of the electrode finger 22 on the side closer to the piezoelectric substrate 10 is smaller than the width on the side farther from the piezoelectric substrate 10. In other words, the width of the electrode finger 22 increases as it moves away from the piezoelectric substrate 10. In this embodiment, the increase in the width of the electrode finger 22 can be a linear, gradual increase, or other non-linear increases. This causes the side of the electrode finger 22 to be inclined relative to the piezoelectric substrate 10. When the acoustic wave generated by the piezoelectric substrate 10 propagates obliquely to the dielectric layer 30 to form a plate wave, the side of the electrode finger 22 can reflect a portion of the acoustic wave back to the piezoelectric substrate 10, reducing the intensity of the plate wave. The width of electrode finger 22 is the width of electrode finger 22 in the second direction. The second direction can be understood as the arrangement direction of electrode finger 22, or as the length extension direction of bus bar 21.

[0048] It is known that in the sound waves propagating obliquely from the piezoelectric substrate 10 to the dielectric layer 30, the smaller the angle with the upper surface of the piezoelectric substrate 10, the longer the wavelength; conversely, the larger the angle with the upper surface of the piezoelectric substrate 10, the shorter the wavelength. In this embodiment, the electrode fingers 22 with inclined sides can reflect longer wavelength sound waves to a certain extent, thereby reducing the proportion of longer wavelength sound waves propagating to the dielectric layer 30. This, to a certain extent, ensures that the sound waves propagating to the dielectric layer 30 are short wavelength sound waves with a large angle with the upper surface of the piezoelectric substrate 10. Thus, according to λ... B *f B =v, where v is the speed of sound, λ B Let f be the wavelength of the plate wave.B Let λ be the frequency of the plate wave. When the speed of sound v remains constant, that is, under the condition that the dielectric layer 30 is made of the same material, the wavelength λ of the plate wave formed by the oblique propagation to the dielectric layer 30 is... B Smaller size can increase the frequency f of the plate wave formed in dielectric layer 30. B By widening the gap between the plate wave frequency and the dominant mode frequency, the distance between the plate wave frequency and the resonant point is increased, thus extending the plate wave resonance distance beyond the passband. This reduces the influence of the plate wave on the dominant mode and improves the performance of resonator 1. In practical applications, by changing the cross-sectional shape of electrode finger 22, the influence of the plate wave on the dominant mode of the filter with the aforementioned resonator 1 is reduced, decreasing its impact on the filter's passband or transition band, thereby improving the filter's performance.

[0049] like Figure 6 As shown, in some embodiments, the interdigital transducer 20 is disposed on the upper surface of the piezoelectric substrate 10, which can further reduce the manufacturing difficulty when fabricating the resonator 1 and is easier to implement. In some embodiments, the electrode fingers 22 can be perpendicular to the busbar 21 or inclined relative to the busbar 21, which is not specifically limited in this embodiment.

[0050] like Figure 1 As shown, in some embodiments, the side surface of the electrode finger 22 in the second direction can be a flat slope, for example, the cross-sectional shape of the electrode finger 22 in the first direction is an inverted trapezoid, so that the width of the electrode finger 22 gradually increases from the piezoelectric substrate 10 to the dielectric layer 30; the side surface of the electrode finger 22 in the second direction can also be an uneven slope, for example, a slope with multiple protrusions (not shown) arranged to form an inverted stepped slope, which can achieve the width of the electrode finger 22 increasing as it moves away from the piezoelectric substrate 10.

[0051] like Figure 1 and Figure 2 As shown, in some embodiments, in the second direction, the electrode finger 22 includes a first side surface 221 and a second side surface 222 opposite to the first side surface 221, the angle between the first side surface 221 and the bottom surface of the electrode finger 22 is an obtuse angle, and the angle between the second side surface 222 and the bottom surface of the electrode finger 22 is an obtuse angle.

[0052] In this embodiment, both the first side surface 221 and the second side surface 222 are inclined relative to the piezoelectric substrate 10. When the sound wave formed by the piezoelectric substrate 10 propagates obliquely to the dielectric layer 30, both the first side surface 221 and the second side surface 222 can reflect a portion of the longer wavelength sound wave back to the piezoelectric substrate 10, further reducing the intensity of the plate wave formed on the dielectric layer 30. At the same time, it can further reduce the proportion of longer wavelength sound waves propagating on the dielectric layer 30. This helps to increase the frequency of the plate wave formed on the dielectric layer 30 while keeping the sound velocity of the dielectric layer 30 constant, making the plate wave resonance distance farther from the passband, thereby reducing the influence of the plate wave on the main mode and improving the performance of the resonator 1.

[0053] It is known that, in the same electrode finger 22, the obtuse angle formed between the first side surface 221 and the bottom surface of the electrode finger 22 cannot be too large, and the obtuse angle formed between the second side surface 222 and the bottom surface of the electrode finger 22 cannot be too large either. Therefore, in some embodiments, in the same electrode finger 22, the included angle between the first side surface 221 and the bottom surface of the electrode finger 22 is α1, and the included angle between the second side surface 222 and the bottom surface of the electrode finger 22 is α2; wherein, α1 satisfies: 90°<α1<130°, and α2 satisfies: 90°<α2<130°. For example, in the embodiments of this application, α1 is set to 95°, 100°, 110°, 115°, 120° or 125°, and α2 is set to 94°, 98°, 102°, 106°, 120°, 124° or 128°, so that the first side surface 221 and the second side surface 222 respectively reflect a portion of the sound waves that propagate obliquely upward from the piezoelectric substrate 10. Preferably, α1 satisfies: 100° < α1 < 110°, as in the embodiments of this application, α1 is set to 101°, 103°, 105°, 107° or 109°; and / or, α2 satisfies: 100° < α2 < 110°, as in the embodiments of this application, α2 is set to 102°, 104°, 106° or 108°. In this way, the first side surface 221 and the second side surface 222 can respectively reflect a portion of the acoustic waves propagating obliquely upward from the piezoelectric substrate 10, so as to achieve the purpose of increasing the plate wave frequency, reducing the plate wave intensity, and improving the device performance.

[0054] like Figure 1 and Figure 2As shown, in some embodiments, in the same electrode finger 22, the angle between the first side surface 221 and the bottom surface of the electrode finger 22 is α1, and the angle between the second side surface 222 and the bottom surface of the electrode finger 22 is α2, wherein |α1-α2| < 10°. As in the embodiments of this application, |α1-α2| is set to 1°, 3°, 5°, 7° or 9°. In this way, the first side surface 221 and the second side surface 222 can respectively reflect a portion of the sound waves propagating obliquely upward from the piezoelectric substrate 10, so as to achieve the purpose of increasing the plate wave frequency, reducing the plate wave intensity, and improving the device performance. In this embodiment, while keeping |α1-α2| < 10°, α1 and α2 can be the same or different. For example, in one embodiment of this application, α1 and α2 are both 102°, while in another embodiment of this application, α1 is 104° and α2 is 107°. That is, relative to the upper surface of the piezoelectric substrate 10, the tilt angle of the first side surface 221 and the tilt angle of the second side surface 222 can be the same or different.

[0055] It can be understood that, with the thickness of electrode finger 22 remaining constant, i.e., with the distance between the upper and lower surfaces of electrode finger 22 remaining constant, when α1 = α2, the cross-sectional shape of electrode finger 22 in the first direction is an inverted trapezoid, and it is an isosceles trapezoid. In this case, the length of the first side surface 221 is equal to the length of the second side surface 222, which can ensure the consistency between the first side surface 221 and the second side surface 222. When α1 > α2, the length of the first side surface 221 is greater than the length of the second side surface 222, and the first side surface 221 can reflect a greater proportion of sound waves than the second side surface 222. When α1 < α2, the length of the first side surface 221 is less than the length of the second side surface 222, and the second side surface 222 can reflect a greater proportion of sound waves than the first side surface 221.

[0056] like Figure 6 As shown, in some embodiments, along the second direction, among two adjacent electrode fingers 22 connected on the same busbar 21, the distance between the centerline of one electrode finger 22 and the centerline of the other electrode finger 22 is λ, and the width of the upper surface of the electrode finger 22 along the second direction is d, where 0.175≤d / λ≤0.275. As in the embodiments of this application, d / λ is set to 0.185, 0.195, 0.205, 0.215, 0.225, 0.235, 0.245, 0.255, 0.265 or 0.27.

[0057] It can be known that in the interdigital transducer 20, the metallization rate η = d / p, where p is the pitch and p = 0.5λ. According to the above formula 0.175 ≤ d / λ ≤ 0.275. In this embodiment, the metallization rate η can be within the range of 0.35 to 0.55. For example, η is 0.38, 0.4, 0.45 or 0.5. This can not only reduce the manufacturing difficulty but also ensure that there is an appropriate spacing between two adjacent electrode fingers 22 respectively connected to two bus bars 21. On this basis, by setting the cross-sectional shape of the electrode finger 22 to be an inverted trapezoid, the plate wave frequency can be increased, the plate wave intensity can be reduced, and the device performance can be improved. In some embodiments, the upper surface of the electrode finger 22 is a flat plane, thereby reducing its forming difficulty.

[0058] As Figure 2 and Figure 6 shown, in some embodiments, along the second direction, among two adjacent electrode fingers 22 connected to the same bus bar 21, the distance between the midline of one electrode finger 22 and the midline of the other electrode finger 22 is λ, and the thickness of the electrode finger 22 is T, where 0.06 < T / λ < 0.12. In the embodiments of the present application, T / λ is 0.07, 0.08, 0.09, 0.10, 0.11, 0.115 or 0.119. When setting the electrode finger 22 in this embodiment, the width of the electrode finger 22 closer to the piezoelectric substrate 10 is smaller than the width of the electrode finger 22 farther from the piezoelectric substrate 10. On the basis of ensuring the above structural characteristics of the electrode finger, the above film thickness ratio is also controlled. By combining the electrode finger structure with the film thickness ratio, the frequency of the plate wave formed on the dielectric layer 30 can be further increased, and the intensity of the plate wave can be reduced.

[0059] As Figure 6 and Figure 7As shown, in some embodiments, along the second direction, the electrode finger 22 includes a first electrode finger 22A and a second electrode finger 22B adjacent to the first electrode finger 22A. The first electrode finger 22A and the second electrode finger 22B are respectively connected to two busbars 21. The first electrode finger 22A and the second electrode finger 22B are symmetrically arranged. Specifically, the first electrode finger 22A and the second electrode finger 22B are mirror-symmetrically arranged. Specifically, in one embodiment of this application, at least the part where the first electrode finger 22A and the second electrode finger 22B intersect is mirror-symmetrically arranged. Specifically, in another embodiment of this application, the mirror symmetry of the first electrode finger 22A and the second electrode finger 22B can be understood as follows: after translating the first electrode finger 22A and the second electrode finger 22B along the first direction and aligning the two ends of the first electrode finger 22A and the two ends of the second electrode finger 22B along the second direction, the first electrode finger 22A and the second electrode finger 22B are mirror-symmetrical to each other. In this embodiment, the first electrode finger 22A and the second electrode finger 22B, which are symmetrically arranged, can be used as a set of electrode fingers 22, one of which is a positive electrode and the other is a negative electrode, so as to realize the sound-to-electric energy conversion.

[0060] like Figure 5 and Figure 7 As shown, in some embodiments, the angle between the side of the first electrode finger 22A near the second electrode finger 22B and the bottom surface of the first electrode finger 22A, and the angle between the side of the second electrode finger 22B near the first electrode finger 22A and the bottom surface of the second electrode finger 22B are both the first included angle β1; the angle between the side of the first electrode finger 22A away from the second electrode finger 22B and the bottom surface of the first electrode finger 22A, and the angle between the side of the second electrode finger 22B away from the first electrode finger 22A and the bottom surface of the second electrode finger 22B are both the second included angle β2, wherein the first included angle β1 is less than or equal to the second included angle β2.

[0061] In this embodiment, the length of the side of the first electrode finger 22A near the second electrode finger 22B and the length of the side of the second electrode finger 22B near the first electrode finger 22A are both L1, and the length of the side of the first electrode finger 22A away from the second electrode finger 22B and the length of the side of the second electrode finger 22B away from the first electrode finger 22A are both L2. When β1 is less than β2, L1 is less than L2. In this case, compared to the side of the first electrode finger 22A near the second electrode finger 22B, the side of the first electrode finger 22A away from the second electrode finger 22B can reflect more sound waves. At the same time, compared to the side of the second electrode finger 22B near the first electrode finger 22A, the side of the second electrode finger 22B away from the first electrode finger 22A can reflect more sound waves. This achieves that both sides of the first electrode finger 22 along the second direction can reflect a portion of the sound waves, thereby reducing the volume wave intensity formed in the dielectric layer 30 and increasing the volume wave frequency. Figure 5 When β1 equals β2, L1 equals L2. In this case, the cross-sectional shape of the electrode finger 22 in the first direction is an inverted trapezoid, such as an isosceles trapezoid. This can ensure the consistency of the two sides of the electrode finger 22 in the first direction, and also enable the electrode finger 22 to reflect a portion of the sound waves on both sides along the second direction, thereby reducing the volume wave intensity formed in the dielectric layer 30 and increasing the volume wave frequency.

[0062] like Figure 4 and Figure 8 As shown, in some embodiments, along the second direction, electrode fingers 22 connected to one of the busbars 21 and electrode fingers 22 connected to the other busbar 21 are alternately arranged to form a cross region C. Along the first direction, the cross region C includes a middle region C1 and two edge regions C2, with the two edge regions C2 located on both sides of the middle region C1. At least one electrode finger 22 is provided with a mass load structure 23 located in the edge region C2. Along the thickness direction of the dielectric layer 30, the width of the mass load structure 23 on the side closer to the piezoelectric substrate 10 is smaller than the width of the mass load structure 23 on the side farther from the piezoelectric substrate 10.

[0063] It is known that, along the first direction, there are two gap regions G located at both ends of the cross region C between the two busbars 21. In addition to generating the main mode required during operation, the surface acoustic wave resonator 1 also generates transverse modes. Therefore, in this embodiment, a mass load structure 23 is set in the edge region C2, which can reduce the sound velocity in the edge region C2. As a result, the sound velocity in the middle region C1 is greater than the sound velocity in the edge region C2, and the sound velocity in the gap region G is greater than the sound velocity in the edge region C2. In this way, a piston mode is formed in the gap region G, the edge region C2 and the cross region C on one side, which effectively suppresses the transverse mode.

[0064] Furthermore, in this embodiment, as the width of the electrode finger 22 increases with distance from the piezoelectric substrate 10, the width of the mass load structure 23 also increases with distance from the piezoelectric substrate 10. As a result, the side of the mass load structure 23 can reflect some sound waves back to the piezoelectric substrate 10, reducing the intensity of the plate wave. At the same time, the side of the mass load structure 23 can also reflect longer wavelength sound waves to a certain extent, thereby further reducing the proportion of longer wavelength sound waves propagating onto the dielectric layer 30. Consequently, with the same dielectric layer 30 material, the wavelength of the sound waves propagating obliquely to the dielectric layer 30 becomes smaller, which can increase the frequency of the plate wave formed on the dielectric layer 30, widening the gap between the plate wave frequency and the main mode frequency. This results in a longer plate wave resonance distance passband, thereby reducing the influence of the plate wave on the main mode and improving the performance of the resonator 1.

[0065] like Figure 8As shown, in some embodiments, the width of the electrode finger 22 in the second direction is less than or equal to the width of the mass load structure 23 in the second direction. In this embodiment, the electrode finger 22 is widened or thickened to form the mass load structure 23 in the portion of the electrode finger 22 located in the edge region C2, thereby reducing the sound velocity in the edge region C2.

[0066] like Figure 3 and Figure 6 As shown, in some embodiments, the dielectric layer 30 includes a first dielectric layer 31 and a second dielectric layer 32. The first dielectric layer 31 is disposed on the piezoelectric substrate 10 and covers the interdigital transducer 20. The second dielectric layer 32 is disposed on the side of the first dielectric layer 31 away from the piezoelectric substrate 10. The sound velocity of the first dielectric layer 31 is less than that of the second dielectric layer 32. In this embodiment, the first dielectric layer 31 can protect the interdigital transducer 20. The fact that the sound velocity of the first dielectric layer 31 is less than that of the second dielectric layer 32 allows the upwardly propagating sound waves to be reflected at the interface between the first dielectric layer 31 and the second dielectric layer 32. The first dielectric layer 31 may completely cover the interdigital transducer 20 or may not completely cover it, for example, only covering the area where the electrode fingers 22 of the interdigital transducer 20 are located, while the busbar 21 is not covered by the first dielectric layer 31.

[0067] It can be known that if the electrode fingers 22 of the interdigital transducer 20 are of a conventional electrode finger structure, combined with Figure 10 That is, the width of the electrode finger 22 remains unchanged in the thickness direction of the dielectric layer 30. Because the sound speed in the first dielectric layer 31 is less than that in the second dielectric layer 32, the sound wave propagating obliquely upward from the piezoelectric substrate 10 to the first dielectric layer 31 will be reflected at the interface between the first dielectric layer 31 and the second dielectric layer 32. At the same time, if the interface meets certain conditions, the sound wave will resonate in the first dielectric layer 31, forming a plate wave.

[0068] Define the angle between the direction of plate wave propagation and the third direction as θ, the third direction as perpendicular to the thickness direction of the first dielectric layer 31, the thickness of the first dielectric layer 31 as t, and the wavelength of the plate wave as λ. B Considering the half-wave loss during reflection, the resonance condition is:

[0069]

[0070] Where n is a positive integer, n = 1, 2, 3, ..., according to the above formula, the smaller θ is, the greater λ BThe longer it is, so, in this embodiment, the side surface of the electrode finger 22 used is inclined with respect to the piezoelectric substrate 10, and the width of the electrode finger 22 increases as the distance from the piezoelectric substrate 10 becomes farther, so that the inclined side surface of the electrode finger 22 can reflect sound waves with longer wavelengths to a certain extent, thereby reducing the proportion of sound waves with longer wavelengths propagating onto the first dielectric layer 31. Furthermore, to a certain extent, it ensures that the sound waves propagating onto the first dielectric layer 31 are sound waves with short wavelengths and a large angle with the upper surface of the piezoelectric substrate 10. Thus, according to λ B *f B =v, where v is the sound velocity, and f B is the frequency of the plate wave. When the sound velocity v remains unchanged, that is, in the case of the first dielectric layer 31 of the same material, the wavelength of the plate wave formed by obliquely propagating to the first dielectric layer 31 becomes smaller, which can increase the frequency of the plate wave formed on the first dielectric layer 31, widen the distance between the plate wave frequency and the main mode frequency, and make the distance between the plate wave frequency and the resonance point larger. Thus, the plate wave resonance distance passband is farther, and further reduce the influence of the plate wave on the main mode, improving the performance of the resonator 1.

[0071] Such as Figure 3 and Figure 6 shown, in some embodiments, along the second direction, among two adjacent electrode fingers 22 connected to the same bus bar 21, the distance between the center line of one electrode finger 22 and the center line of the other electrode finger 22 is λ, the thickness of the first dielectric layer 31 is t, and the thickness of the electrode finger 22 is T. Among them, 0.15 < t / λ < 0.4, 0.06 < T / λ < 0.12. In the embodiments of this application, t / λ is set to 0.2, 0.25, 0.3 or 0.35, and T / λ is set to 0.075, 0.085, 0.09, 0.095, 0.105 or 0.11. In this embodiment, the film thickness ratio of the first dielectric layer 31 is greater than the film thickness ratio of the electrode finger 22, which can ensure that the first dielectric layer 31 covers the electrode finger 22 and can also play a role in protecting the electrode finger 22.

[0072] Combined with Figure 3 , in some embodiments, the material of the first dielectric layer 31 includes at least one of silicon oxide, silicon oxynitride, and silicon nitride. In this embodiment, the material of the first dielectric layer 31 can be a material with a positive temperature compensation coefficient, playing a role in temperature compensation, being able to appropriately improve the frequency temperature characteristics and reduce the influence of temperature on the resonator 1.

[0073] Combined with Figure 3 , in some embodiments, the material of the second dielectric layer 32 includes at least one of silicon dioxide, silicon nitride, aluminum nitride, and aluminum oxide. In this embodiment, the second dielectric layer 32 can protect the circuit including the interdigital transducer 20 below. The second dielectric layer 32 can be a frequency modulation layer, which can both protect the circuit below and correct the frequency.

[0074] Combination Figure 3 In some embodiments, the side of the first dielectric layer 31 facing away from the piezoelectric substrate 10 is a flat plane, so that the interface between the first dielectric layer 31 and the second dielectric layer 32 is a plane. Moreover, it is convenient to form the second dielectric layer 32 on the first dielectric layer 31 by electroplating, and it can also effectively ensure that the upper surface of the second dielectric layer 32 is flat.

[0075] Combination Figure 3 In some embodiments, the piezoelectric substrate 10 includes a lithium niobate substrate with a YX cut and a cut angle in the range of 30° to 50°. For example, in the embodiments of this application, the cut angle is set to 34°, 36°, 40°, 44°, or 48°. By controlling the cut and cut angle of the lithium niobate substrate, the device performance can be further improved. Furthermore, the width of the electrode fingers 22 near the piezoelectric substrate 10 is smaller than the width of the electrode fingers 22 away from the piezoelectric substrate 10. This can increase the frequency of the plate wave formed on the dielectric layer 30 and reduce the intensity of the plate wave.

[0076] Combination Figure 3 In some embodiments, the piezoelectric substrate 10 further includes a lithium tantalate substrate with a YX cut and a cut angle in the range of 20° to 50° or 110° to 170°. For example, in the embodiments of this application, the cut angle is set to 25°, 30°, 35°, 40°, 45°, 48°, 115°, 125°, 135°, 145°, 155°, or 165°. This allows for further improvement of device performance by controlling the cut and cut angle of the lithium niobate substrate. Furthermore, the width of the electrode fingers 22 near the piezoelectric substrate 10 is smaller than the width of the electrode fingers 22 away from the piezoelectric substrate 10. This can increase the frequency of the plate wave formed on the dielectric layer 30 and reduce the intensity of the plate wave.

[0077] Combination Figure 6 In some embodiments, the interdigital transducer 20 is made of at least one of aluminum, molybdenum, copper, gold, platinum, silver, nickel, chromium, and tungsten, giving the interdigital transducer 20 good conductivity. In this embodiment, the interdigital transducer 20 can be made of a single metal material or a composite or alloy of different metals. Optionally, the material can be one of aluminum, molybdenum, copper, gold, platinum, silver, nickel, chromium, tungsten, or a composite or alloy of the above metals. This embodiment does not impose specific limitations on this.

[0078] Combination Figure 3 In some embodiments, the piezoelectric substrate 10 is made of at least one of quartz, aluminum nitride, sapphire, lithium niobate, and lithium tantalate, which reduces the difficulty of preparing the piezoelectric substrate 10.

[0079] like Figure 4 and Figure 6 As shown, in some embodiments, the piezoelectric substrate 10 includes a piezoelectric layer 11 and a substrate 12. The piezoelectric layer 11 is disposed on the substrate 12, the interdigital transducer 20 is formed on the side of the piezoelectric layer 11 away from the substrate 12, and the dielectric layer 30 is disposed on the piezoelectric layer 11. In this embodiment, the piezoelectric layer 11 can support the interdigital transducer 20 and the dielectric layer 30.

[0080] In an embodiment where the piezoelectric substrate 10 includes a piezoelectric layer 11 and a substrate 12, the dielectric layer 30 includes a first dielectric layer 31 and a second dielectric layer 32 stacked together. The first dielectric layer 31 covers the interdigital transducer 20. In this case, part of the acoustic wave that propagates obliquely upward from the piezoelectric layer 11 to the first dielectric layer 31 will be reflected by the side of the electrode finger 22, which can reduce the intensity of the plate wave formed in the first dielectric layer 31.

[0081] Combination Figure 4 In some embodiments, the temperature coefficient of the substrate 12 is smaller than that of the piezoelectric layer 11, which can improve the performance and stability of the resonator 1.

[0082] Combination Figure 4 In some embodiments, the piezoelectric substrate 10 further includes an intermediate layer (not shown), disposed between the piezoelectric layer 11 and the substrate 12. The intermediate layer includes at least one low-velocity sound layer or low-acoustic impedance layer, and the sound velocity in the intermediate layer is less than the sound velocity in the piezoelectric layer 11. In this embodiment, an intermediate layer is disposed between the piezoelectric layer 11 and the substrate 12. The intermediate layer includes at least one low-velocity sound layer or low-acoustic impedance layer, and the sound velocity or acoustic impedance of the intermediate layer is less than the sound velocity or acoustic impedance of the piezoelectric layer 11. The sound velocity or acoustic impedance of the substrate 12 is greater than the sound velocity or acoustic impedance of the piezoelectric layer 11. The arrangement of the substrate 12 and the intermediate layer not only provides temperature compensation for the piezoelectric layer 11 but also forms an acoustic reflection structure below the piezoelectric layer 11, reducing the longitudinal leakage of sound wave energy. Here, longitudinal refers to the thickness direction of the piezoelectric layer 11.

[0083] Second set of embodiments:

[0084] The resonator 1 provided in this embodiment can be found in [reference]. Figure 9 The similarity between this embodiment and the first embodiment is that they use interdigital transducers 20 with the same structure, and the main difference is that the substrate 12 is constructed differently.

[0085] like Figure 9 As shown, combined with Figure 6This embodiment also provides a resonator 1, including a piezoelectric layer 11, a substrate 12, and an interdigital transducer 20. The substrate 12 has a cavity 40, and the piezoelectric layer 11 is disposed on the upper surface of the substrate 12. The interdigital transducer 20 is disposed on the piezoelectric layer 11 and is opposite to the cavity 40 through the piezoelectric layer 11. The interdigital transducer 20 includes two busbars 21 disposed opposite to each other along a first direction. Each of the two busbars 21 is connected to at least one electrode finger 22. The electrode fingers 22 are spaced apart along a second direction. Along the thickness direction of the piezoelectric layer 11, the width of the electrode finger 22 on the side closer to the piezoelectric layer 11 is smaller than the width of the electrode finger 22 on the side farther from the piezoelectric layer 11. The second direction intersects the first direction.

[0086] In this embodiment, the resonator 1 can be a laterally excited thin-film bulk acoustic resonator (XBAR), which is disposed on the piezoelectric layer 11 by setting interdigital transducers 20. Compared with embedding the interdigital transducers 20 into the piezoelectric layer 11, this reduces the manufacturing difficulty and is easier to implement. It is known that for a bulk acoustic resonator, the dominant mode is a plate wave, and the heterogeneous mode is a surface acoustic wave. Therefore, in this embodiment, the width of the electrode fingers 22 on the side closer to the piezoelectric layer 11 is smaller than the width on the side farther from the piezoelectric layer 11, i.e., viewed from below, is disposed in the thickness direction of the piezoelectric layer 11. In other words, the width of the electrode fingers 22 increases as they move away from the piezoelectric layer 11. In this embodiment, the increase in the width of the electrode fingers 22 can be a linear gradual increase or other nonlinear increases, thereby reducing the contact area between the electrode fingers 22 and the piezoelectric layer 11, reducing the excitation intensity of the surface acoustic wave, and avoiding interference of the dominant mode by the surface acoustic wave.

[0087] like Figure 9 As shown, combined with Figure 6 In some embodiments, the interdigital transducer 20 is formed on the upper surface of the piezoelectric layer 11, and the wiring width of its electrode fingers 22 on the side closer to the piezoelectric layer 11 is smaller than the wiring width on the side farther from the piezoelectric layer 11. This reduces the contact area between the electrode fingers 22 and the piezoelectric layer 11 while ensuring device performance, thereby reducing the excitation intensity of surface acoustic waves and avoiding interference of surface acoustic waves with the master mode.

[0088] Combination Figure 9 In some embodiments, the substrate 12 may be made of materials such as monocrystalline silicon or polycrystalline silicon.

[0089] Combination Figure 1 or Figure 9 This embodiment also provides a filter (not shown), including the resonator 1 in any of the above embodiments. By using the resonator 1 in any of the above embodiments, the filter performance of this embodiment can be improved.

[0090] Combination Figure 1 or Figure 9This embodiment also provides a radio frequency front-end module (not shown), including the resonator 1 in any of the above embodiments. By using the resonator 1 in any of the above embodiments, the operating performance of the radio frequency front-end module can be improved.

[0091] Based on the resonator 1 and the filter having the resonator 1 provided in the first set of embodiments above, the first embodiment and the comparative example in multiple embodiments are selected for comparison to make the effect of the embodiments of this application more intuitive.

[0092] Among them, combined Figure 1 In Embodiment 1, the filter includes a resonator 1, which has a piezoelectric substrate 10, a dielectric layer 30, and electrode fingers 22 disposed on the piezoelectric substrate 10. The cross-sectional shape of the electrode fingers 22 in a first direction is an inverted trapezoid, and the angle between the side surface of the electrode fingers 22 and the bottom surface is 105°. (Combined with...) Figure 10 , Figure 10 This is a schematic diagram of the structure of resonator 1 in the comparative example filter. In the comparative example, the filter includes resonator 1, which has a piezoelectric substrate 10, a dielectric layer 30, and two busbars 21 and several electrode fingers 22 in the basic structure of the current interdigital transducer 20. However, the electrode fingers 22 are conventional electrode finger 22 structures, that is, the width of the electrode fingers 22 remains unchanged in the thickness direction of the dielectric layer 30.

[0093] Combination Figure 11 This diagram shows a comparison of admittance curves for Embodiment 1 and a comparative example provided in this application. The solid curves represent the admittance curves of the comparative example, and the dashed curves represent the admittance curves of Embodiment 1. The horizontal axis represents frequency in Hz, and the vertical axis represents admittance in dB. Figure 10 As can be seen, compared with the comparative example, the plate wave clutter mode in Example 1 at 9.3-9.4 GHz shifted to the right by nearly 10 MHz. That is, in this embodiment, by setting the cross-sectional shape of the electrode finger structure to an inverted trapezoid and controlling its metallization rate and film thickness ratio, the distance between the plate wave clutter mode and the resonant point (fr) in the device was effectively increased by about 10 MHz. This made the plate wave clutter mode in Example 1 farther from the passband than that in the comparative example. At the same time, the position and intensity of the main mode in Example 1 were not affected.

[0094] The above description is merely a preferred embodiment of this application and does not limit the patent scope of this application. Any equivalent structural transformations made based on the content of this application's specification and drawings under the concept of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A resonator, characterized in that, include: piezoelectric substrate; An interdigital transducer is disposed on the piezoelectric substrate; A dielectric layer is disposed on the piezoelectric substrate and covers the interdigital transducer; The interdigital transducer includes two busbars arranged along a first direction, each of the two busbars being connected to at least one electrode finger, the electrode fingers being arranged at intervals along a second direction; Along the thickness direction of the dielectric layer, the width of the electrode finger on the side closer to the piezoelectric substrate is smaller than the width of the electrode finger on the side farther from the piezoelectric substrate, and the second direction intersects the first direction.

2. The resonator as described in claim 1, characterized in that, In the second direction, the electrode finger includes a first side surface and a second side surface opposite to the first side surface, the angle between the first side surface and the bottom surface of the electrode finger is an obtuse angle, and the angle between the second side surface and the bottom surface of the electrode finger is an obtuse angle.

3. The resonator as described in claim 2, characterized in that, In the same electrode finger, the angle between the first side surface and the bottom surface of the electrode finger is α1, and the angle between the second side surface and the bottom surface of the electrode finger is α2. Wherein, α1 satisfies: 90°<α1<130°, and α2 satisfies: 90°<α2<130°.

4. The resonator as described in claim 3, characterized in that, The α1 satisfies: 100° < α1 < 110°; and / or the α2 satisfies: 100° < α2 < 110°.

5. The resonator as described in claim 2, characterized in that, In the same electrode finger, the angle between the first side surface and the bottom surface of the electrode finger is α1, and the angle between the second side surface and the bottom surface of the electrode finger is α2, wherein |α1-α2|<10°.

6. The resonator as claimed in claim 1, characterized in that, Along the second direction, among two adjacent electrode fingers connected on the same busbar, the distance between the centerline of one electrode finger and the centerline of the other electrode finger is λ, and the width of the upper surface of the electrode finger along the second direction is d, where 0.175≤d / λ≤0.

275.

7. The resonator as claimed in claim 1, characterized in that, Along the second direction, in two adjacent electrode fingers connected on the same busbar, the distance between the centerline of one electrode finger and the centerline of the other electrode finger is λ, and the thickness of the electrode finger is T, where 0.06 <T / λ<0.12。 8. The resonator as claimed in claim 1, characterized in that, The dielectric layer includes a first dielectric layer and a second dielectric layer. The first dielectric layer is disposed on the piezoelectric substrate and covers the interdigital transducer. The second dielectric layer is disposed on the side of the first dielectric layer away from the piezoelectric substrate. The sound velocity of the first dielectric layer is less than the sound velocity of the second dielectric layer.

9. The resonator as claimed in claim 8, characterized in that, Along the second direction, in two adjacent electrode fingers connected on the same busbar, the distance between the centerline of one electrode finger and the centerline of the other electrode finger is λ, and the thickness of the first dielectric layer is t, where 0.15 <t / λ<0.4。 10. The resonator as claimed in claim 8, characterized in that, The material of the first dielectric layer includes at least one of silicon oxide, silicon oxynitride, and silicon nitride; and / or, The material of the second dielectric layer includes at least one of silicon dioxide, silicon nitride, aluminum nitride, and aluminum oxide.

11. The resonator as claimed in claim 1, characterized in that, The piezoelectric substrate includes a lithium niobate substrate, which is YX cut with a cutting angle in the range of 30° to 50°.

12. The resonator as claimed in claim 1, characterized in that, The piezoelectric substrate includes a lithium tantalate substrate, which is YX cut with a cutting angle in the range of 20° to 50° or in the range of 110° to 170°.

13. The resonator as claimed in claim 1, characterized in that, The interdigital transducer is made of at least one of aluminum, molybdenum, copper, gold, platinum, silver, nickel, chromium, and tungsten; and / or, The piezoelectric substrate is made of at least one of the following materials: quartz, aluminum nitride, sapphire, lithium niobate, and lithium tantalate.

14. The resonator as claimed in claim 1, characterized in that, Along the second direction, the electrode finger includes a first electrode finger and a second electrode finger adjacent to the first electrode finger. The first electrode finger and the second electrode finger are respectively connected to two busbars, and the first electrode finger and the second electrode finger are symmetrically arranged.

15. The resonator as claimed in claim 14, characterized in that, The angle between the side of the first electrode finger near the second electrode finger and the bottom surface of the first electrode finger, and the angle between the side of the second electrode finger near the first electrode finger and the bottom surface of the second electrode finger are both the first angle; The angle between the side of the first electrode finger away from the second electrode finger and the bottom surface of the first electrode finger, and the angle between the side of the second electrode finger away from the first electrode finger and the bottom surface of the second electrode finger are both the second included angle, wherein the first included angle is less than or equal to the second included angle.

16. The resonator as claimed in claim 1, characterized in that, Along the second direction, the electrode fingers connected to one of the busbars and the electrode fingers connected to the other busbar are alternately arranged to form an intersection area. Along the first direction, the intersection area includes a middle area and two edge areas, with the two edge areas located on both sides of the middle area. At least one of the electrodes has a mass load structure located in the edge region, and along the thickness direction of the dielectric layer, the width of the mass load structure on the side closer to the piezoelectric substrate is smaller than the width of the mass load structure on the side farther from the piezoelectric substrate.

17. The resonator as claimed in claim 16, characterized in that, The width of the electrode fingers is less than or equal to the width of the mass load structure.

18. A resonator, characterized in that, include: Substrate, the substrate having a cavity; A piezoelectric layer disposed on the upper surface of the substrate; An interdigital transducer is disposed on the piezoelectric layer and faces the cavity across the piezoelectric layer. The interdigital transducer includes two busbars arranged opposite each other along a first direction, and each of the two busbars is connected to at least one electrode finger, which is spaced apart along a second direction. Along the thickness direction of the piezoelectric layer, the width of the electrode finger on the side closer to the piezoelectric layer is smaller than the width of the electrode finger on the side farther away from the piezoelectric layer, and the second direction intersects the first direction.

19. A filter, characterized in that, Including the resonator as described in any one of claims 1-18.

20. A radio frequency front-end module, characterized in that, Including the resonator as described in any one of claims 1-18.

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