Elastic wave resonator, filter and communication device

Abstract

Disclosed in the present application are an elastic wave resonator, a filter and a communication device. The elastic wave resonator comprises: a support layer, a piezoelectric layer and an interdigital transducer which are sequentially stacked, wherein the interdigital transducer comprises a plurality of first electrode fingers and a plurality of second electrode fingers, the first electrode fingers and the second electrode fingers extend in a first direction and are alternately arranged in a second direction, overlapping portions of the first electrode fingers and the second electrode fingers form an aperture region, and gap regions are formed between the aperture region and bus bars. The elastic wave resonator further comprises a thin film layer, wherein the thin film layer is arranged between the piezoelectric layer and the interdigital transducer and / or on the side of the interdigital transducer away from the piezoelectric layer, the orthographic projection of the thin film layer on the interdigital transducer is located in the gap regions, and the propagation velocity Vgap of an acoustic wave within the gap regions satisfies: 0.9V0<Vgap<V0, or V0<Vgap<1.1V0, with V0 being the propagation velocity of the acoustic wave within the aperture region.

Description

Elastic Wave Resonator, Filter and Communication Device Technical Field

[0001] This application belongs to the technical field of surface acoustic wave, and particularly relates to an elastic wave resonator, a filter and a communication device. Background Art

[0002] In an elastic wave device excited by an interdigital transducer, the acoustic wave propagating transversely reflects at the boundary of the electrode fingers, resulting in the emergence of a transverse mode in the resonator. The existence of the transverse mode causes ripples in the piezoelectric filter within the band and near the passband, which increase the device loss and reduce the performance of the resonator and the filter. Summary of the Invention

[0003] This application aims to solve at least one of the technical problems existing in the related art. For this purpose, this application provides an elastic wave resonator, a filter and a communication device to destroy the conditions for generating the transverse mode, thereby suppressing the generation of the transverse mode and further improving the performance of the resonator.

[0004] In a first aspect, an embodiment of this application provides an elastic wave resonator, which includes: a support layer, a piezoelectric layer and an interdigital transducer stacked in sequence. The interdigital transducer includes a plurality of first electrode fingers, a plurality of second electrode fingers, a first bus bar and a second bus bar. The first bus bar and the second bus bar are arranged opposite to each other in a first direction. The first electrode fingers are connected to the first bus bar, and the second electrode fingers are connected to the second bus bar. The first electrode fingers and the second electrode fingers extend in the first direction and are alternately arranged in a second direction. In the second direction, the intersecting parts of the first electrode fingers and the second electrode fingers form an aperture region, and there is a gap region between the aperture region and any one of the bus bars. The first direction intersects with the second direction. The elastic wave resonator further includes a thin film layer, which is disposed between the piezoelectric layer and the interdigital transducer, and / or the thin film layer is disposed on the side of the interdigital transducer away from the piezoelectric layer, and the orthographic projection of the thin film layer on the interdigital transducer is located within the gap region. The propagation speed Vgap of the acoustic wave in the gap region satisfies: 0.9V0 < Vgap < V0, or, V0 < Vgap < 1.1V0, where V0 is the propagation speed of the acoustic wave in the aperture region.

[0005] According to an embodiment of this application, the first bus bar includes third electrode fingers arranged in the second direction, and the second bus bar includes fourth electrode fingers arranged in the second direction. Along the first direction, the third electrode fingers are arranged opposite to the second electrode fingers, and the fourth electrode fingers are arranged opposite to the first electrode fingers. The third electrode fingers and the fourth electrode fingers form a dummy finger region, and the gap region is located between the dummy finger region and the aperture region.

[0006] According to an embodiment of this application, the orthographic projection of the thin film layer on the interdigital transducer is further located within the dummy finger region.

[0007] According to one embodiment of this application, the thin film layer includes a plurality of discrete thin film units, which are arranged at intervals along a second direction in the same gap region. The orthographic projection of each discrete thin film unit on the interdigital transducer at least partially overlaps with the orthographic projection of an electrode finger.

[0008] According to one embodiment of this application, the thin film layer includes at least one continuous thin film unit, the orthographic projection of the continuous thin film unit on the interdigital transducer at least partially overlapping the orthographic projection of the plurality of electrode fingers.

[0009] According to one embodiment of this application, along the second direction, the width of the portion of at least one electrode finger located in the gap region is greater than or equal to the width of the portion of the electrode finger located in the aperture region.

[0010] According to one embodiment of this application, the length of the gap region along the first direction is 0.1λ to 2.5λ, where λ is the wavelength of the elastic wave.

[0011] According to one embodiment of this application, the thin film layer includes a dielectric layer and / or a metal layer.

[0012] According to one embodiment of this application, the dielectric layer is made of aluminum oxide, silicon dioxide, or silicon nitride; the metal layer is made of gold, silver, aluminum, or platinum.

[0013] According to one embodiment of this application, a thin film layer is disposed on the side of the interdigital transducer away from the piezoelectric layer, and in a first direction, the length of the thin film layer is less than or equal to the length of the gap region.

[0014] According to one embodiment of this application, in a first direction, the length of the thin film layer is less than the length of the gap region, the thin film layer is disposed on the side of the gap region away from the busbar, and a preset distance is provided between the side of the thin film layer close to the busbar and the busbar.

[0015] According to one embodiment of this application, in a first direction, the length of the thin film layer is less than or equal to half the length of the gap region.

[0016] According to one embodiment of this application, a thin film layer is disposed on the side of the interdigital transducer away from the piezoelectric layer and covers the entire area of ​​the interdigital transducer located within the gap region.

[0017] Secondly, embodiments of this application provide a filter including at least one of the aforementioned elastic wave resonators.

[0018] Thirdly, embodiments of this application provide a communication device, which includes at least one of the aforementioned elastic wave resonators.

[0019] According to several embodiments of the elastic wave resonator and filter of this application, a thin film layer is provided on the electrode fingers corresponding to the gap region, which can reduce the propagation speed of the sound wave in the gap region, so that the phase of the sound wave reflected at the boundary of the electrode fingers changes, destroying the conditions for the generation of transverse modes, thereby suppressing the generation of transverse modes and improving the performance of the resonator.

[0020] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0021] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings.

[0022] Figure 1 is a schematic diagram of the structure of an elastic wave resonator in related technologies.

[0023] Figure 2 is a cross-sectional schematic diagram of the elastic wave resonator provided in an embodiment of this application.

[0024] Figure 3 is a schematic diagram of an elastic wave resonator provided in an embodiment of this application.

[0025] Figure 4 is a schematic diagram of the cross section of the interdigital transducer of the elastic wave resonator shown in Figure 3 along AA'.

[0026] Figure 5 is a schematic diagram of another structure of the elastic wave resonator provided in the embodiment of this application.

[0027] Figure 6 is a schematic diagram of the sound velocity distribution in various regions provided in the embodiments of this application.

[0028] Figure 7 is one of the simulation curves comparing the admittance of an elastic wave resonator in the embodiments of this application with frequency in related technologies.

[0029] Figure 8 is one of the simulation curves comparing the real part of the admittance of an elastic wave resonator in the embodiments of this application and in related technologies with frequency.

[0030] Figure 9 is a schematic diagram of another structure of the elastic wave resonator provided in the embodiment of this application.

[0031] Figure 10 is a schematic diagram of the cross section of the interdigital transducer of the elastic wave resonator shown in Figure 9 along AA'.

[0032] Figure 11 is a schematic diagram of another structure of the elastic wave resonator provided in the embodiment of this application.

[0033] Figure 12 is a schematic diagram of the cross section of the interdigital transducer of the elastic wave resonator shown in Figure 11 along AA'.

[0034] Figure 13 is a schematic diagram of another structure of the elastic wave resonator provided in the embodiment of this application.

[0035] Figure 14 is a schematic diagram of another structure of the elastic wave resonator provided in the embodiment of this application.

[0036] Figure 15 is a schematic diagram of another structure of the elastic wave resonator provided in the embodiment of this application.

[0037] Figure 16 is one of the simulation curves of admittance versus frequency under different sound velocities in the gap region according to the embodiments of this application.

[0038] Figure 17 is one of the simulation curves comparing the real part of the admittance with frequency under different sound velocities in the gap region according to the embodiments of this application.

[0039] Figure 18 is the second comparison of simulation curves of admittance versus frequency under different sound velocities in the gap region according to the embodiments of this application.

[0040] Figure 19 is the second comparison of simulation curves of the real part of admittance changing with frequency under different sound velocities in the gap region according to the embodiments of this application.

[0041] Figure 20 is a comparison of simulation curves of admittance versus frequency under different gap region lengths in the embodiments of this application.

[0042] Figure 21 is a comparison of simulation curves showing the change of the real part of the admittance with frequency under different gap region lengths in the embodiments of this application.

[0043] Reference numerals: 10, support layer; 20, piezoelectric layer; 30, interdigitated transducer; 31, first electrode finger; 32, first busbar; 33, second electrode finger; 34, third electrode finger; 35, second busbar; 36, fourth electrode finger; 40, thin film layer; 40a, discrete thin film unit; 40b, continuous thin film unit; 50, gap region; 60, aperture region; 71, first reflective grating; 72, second reflective grating; 80, pseudo-finger region; 30', interdigitated transducer. Detailed Implementation

[0044] The embodiments of this application are described in detail below, with examples of these embodiments shown in the accompanying drawings. Throughout, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0045] In the following description, a "circuit" refers to a conductive loop consisting of at least one element or sub-circuit connected by an electrical or electromagnetic link. When an element or circuit is said to be "coupled to" or "connected to" another element, or when an element / circuit is said to be "coupled at" or "connected at" two nodes, it can be directly coupled to or connected to the other element, or there may be intermediate elements. The connection between elements can be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there are no intermediate elements between them.

[0046] In the description, the terms "first," "second," etc., are used to distinguish similar objects, not to describe a specific order or sequence. It should be understood that such numerical descriptors can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class, not limited in number; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0047] Furthermore, the use of terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicates that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0048] With the continuous development and application of communication technology, the requirements for radio frequency components are becoming increasingly stringent. As an important component of filters, elastic wave resonators are also facing severe challenges.

[0049] Referring to Figure 1, which illustrates the structure of an elastic wave resonator in the related art, the elastic wave resonator comprises a support layer, a piezoelectric layer, and an interdigital transducer 30' stacked sequentially. A gap region is formed between the electrode fingers of the interdigital transducer 30' and the opposite busbar. In an elastic wave device excited by the interdigital transducer 30', the reflection of transversely propagating acoustic waves in the gap region causes the resonator to exhibit a transverse mode. The presence of the transverse mode leads to ripple in the piezoelectric filter's band and near the passband, which increases device losses and thus degrades the performance of the resonator and filter.

[0050] Referring to FIGS. 2, 3 and 4, FIG. 2 shows a cross-sectional structure of an elastic wave resonator of the present application, FIG. 3 shows a structure of the elastic wave resonator of an embodiment of the present application, and FIG. 4 shows a cross-section of the interdigital transducer 30 of the elastic wave resonator shown in FIG. 3. An embodiment of the present application provides an elastic wave resonator including: a support layer 10, a piezoelectric layer 20 and an interdigital transducer 30 stacked in sequence. The interdigital transducer 30 includes a plurality of first electrode fingers 31, a plurality of second electrode fingers 33, a first bus bar 32 and a second bus bar 35. The first bus bar 32 and the second bus bar 35 are arranged opposite to each other in a first direction. The first electrode fingers 31 are connected to the first bus bar 32, and the second electrode fingers 33 are connected to the second bus bar 35. The first electrode fingers 31 and the second electrode fingers 33 extend in the first direction and are alternately arranged in a second direction. In the second direction, the intersecting portions of the first electrode fingers 31 and the second electrode fingers 33 form an aperture region 60. There is a gap region 50 between the aperture region 60 and any one of the bus bars. The first direction intersects the second direction. The elastic wave resonator further includes a thin film layer 40. The thin film layer 40 is disposed between the piezoelectric layer 20 and the interdigital transducer 30, and / or the thin film layer 40 is disposed on a side of the interdigital transducer 30 away from the piezoelectric layer 20, and a positive projection of the thin film layer 40 on the interdigital transducer 30 is located within the gap region 50. The propagation speed Vgap of the sound wave in the gap region 50 satisfies: 0.9V0 < Vgap < V0, or V0 < Vgap < 1.1V0. Here, V0 is the propagation speed of the sound wave in the aperture region 60.

[0051] In the present application, the first direction refers to the Y direction shown in the figure, and the second direction refers to the X direction shown in the figure. The first direction and the second direction may be orthogonal or oblique.

[0052] The support layer 10 is mainly used to support the main structure of the entire elastic wave resonator, ensure that the elastic wave resonator is not easily damaged when subjected to external stress, and provide necessary strength and protection for the elastic wave resonator. The support layer 10 is usually formed of a material with a relatively high hardness. The specific material and thickness of the support layer 10 can be selected according to the actual application scenario and are not limited herein. For example, the support layer 10 can be made of silicon or made of silicon and silicon dioxide. The thickness of the support layer 10 can be any value between 0.01λ and 0.5λ, where λ is the wavelength of the elastic wave.

[0053] The piezoelectric layer 20 is the core component of the resonator, enabling it to function. When the frequency of the applied electrical signal matches the resonator's natural frequency, the material in the piezoelectric layer 20 deforms, generating mechanical vibration. This mechanical vibration further interacts with the electrical signal, achieving resonant amplification of the elastic wave. The material of the piezoelectric layer 20 typically possesses high mechanical strength and stiffness to withstand external forces and maintain structural stability, while maintaining stable piezoelectric properties within a certain temperature range. The specific material and thickness of the piezoelectric layer 20 can be selected based on the actual application scenario and are not limited here. For example, the piezoelectric layer 20 can contain silicon dioxide, aluminum nitride, zinc oxide, lead zirconate titanate piezoelectric ceramics, polyvinylidene fluoride, or lithium tantalate, etc. The thickness of the piezoelectric layer 20 can range from 0.01λ to 0.5λ, where λ is the wavelength of the elastic wave.

[0054] The interdigital transducer 30 can be composed of one or more of titanium, nickel, molybdenum, copper, tungsten, gold, silver, aluminum, and platinum, and is mainly used to realize the mutual conversion between acoustic signals and electrical signals. The thickness of the interdigital transducer 30 can be selected according to the actual application scenario and is not limited here. For example, the thickness of the interdigital transducer 30 can be from 0.01λ to 0.15λ, where λ is the wavelength of the elastic wave.

[0055] In the second direction, the portion where the first electrode finger 31 and the second electrode finger 33 intersect (i.e., the overlapping portion) forms the aperture region 60. The gap region 50 refers to the region between the aperture region 60 and the first busbar 32 and the region between the aperture region 60 and the second busbar 35.

[0056] Taking a set of electrode fingers including a first electrode finger 31 and a second electrode finger 33 as an example, in the aperture region 60, one cycle includes two electrode fingers, while in the gap region 50, one cycle includes one electrode finger. Therefore, the sound wave propagation speed in the gap region 50 is greater than that in the aperture region 60.

[0057] Thin film layer 40 can be disposed between piezoelectric layer 20 and interdigital transducer 30, or it can be disposed on the side of interdigital transducer 30 away from piezoelectric layer 20, indicating that thin film layer 40 and interdigital transducer 30 are stacked. Thin film layer 40 can also be disposed above and below interdigital transducer 30 simultaneously. The orthographic projection of thin film layer 40 on interdigital transducer 30 is located within gap region 50, that is, within gap region 50. Thin film layer 40 is disposed on the side of at least one first electrode finger 31 and at least one second electrode finger 33 near piezoelectric layer 20 and / or away from piezoelectric layer 20. The placement of thin film layer 40 can reduce the propagation speed of sound waves within gap region 50, causing the reflection phase of transverse sound waves propagating from aperture region 60 to gap region 50 to change at the boundary between aperture region 60 and gap region 50, thus disrupting the conditions for the generation of transverse modes and suppressing the generation of transverse modes.

[0058] It should be noted that the thin film layer 40 and the first electrode fingers 31 and the second electrode fingers 33 are partially stacked in the gap region 50. The thin film layer 40 may cover all the first electrode fingers 31 and the second electrode fingers 33 in the gap region 50, or may cover some of the first electrode fingers 31 and the second electrode fingers 33. For one electrode finger, the thin film layer 40 may cover all the corresponding portions of the electrode finger in the gap region 50, or may cover some regions of the electrode finger in the gap region 50. The thin film layer 40 may be provided on the side of the first electrode fingers 31 and the second electrode fingers 33 close to the piezoelectric layer 20, or may be provided on the side of the first electrode fingers 31 and the second electrode fingers 33 away from the piezoelectric layer 20, or may be provided on both the side of the first electrode fingers 31 and the second electrode fingers 33 close to the piezoelectric layer 20 and the side away from the piezoelectric layer 20. The specific coverage range of the thin film layer 40 can be selected according to the actual application scenario and is not limited herein.

[0059] Referring to FIG. 5, FIG. 5 shows another structure of the elastic wave resonator according to an embodiment of the present application. As an example, the thin film layer 40 is arranged at intervals on the side of a plurality of first electrode fingers 31 and second electrode fingers 33 corresponding to the gap region 50 and away from the piezoelectric layer 20, and for the electrode fingers it covers, the thin film layer 40 may cover the entire range of the electrode fingers in the gap region 50.

[0060] In some embodiments, the interdigital transducer 30 is made of aluminum, the thickness of the interdigital transducer 30 is 160 nm, the piezoelectric layer 20 is made of lithium tantalate, the thickness of the piezoelectric layer 20 is 530 nm, the length of the aperture region 60 is 20λ, and a metal layer is provided on the electrode fingers of the interdigital transducer 30 corresponding to the gap region 50, and the thickness of the metal layer is 120 nm.

[0061] Referring to FIG. 6, FIG. 6 shows the sound velocity distribution of each region of the elastic wave resonator in the above embodiment. It can be seen from FIG. 6 that the sound velocity Vgap in the gap region 50 is approximately 1.02V0, satisfying V0 < Vgap < 1.1V0, where V0 is the propagation velocity of the acoustic wave in the aperture region 60. By providing the thin film layer 40 on the electrode fingers in the gap region 50, the sound velocity in the gap region 50 can be reduced, so that the reflection phase of the transverse acoustic wave propagating from the aperture region 60 to the gap region 50 at the boundary between the aperture region 60 and the gap region 50 is changed, destroying the conditions for generating the transverse mode.

[0062] Referring to Figures 7 and 8, Figure 7 shows a comparison of simulation curves showing the admittance of the elastic wave resonator in the embodiments of this application and related technologies as a function of frequency, and Figure 8 shows a comparison of simulation curves showing the real part of the admittance of the elastic wave resonator in the embodiments of this application and related technologies as a function of frequency. In Figure 7, curve (1) represents the simulation curve of the admittance of the elastic wave resonator in related technologies as a function of frequency, and curve (2) represents the simulation curve of the admittance of the elastic wave resonator in the embodiments of this application as a function of frequency. In Figure 8, curve (3) represents the simulation curve of the real part of the admittance of the elastic wave resonator in related technologies as a function of frequency, and curve (4) represents the simulation curve of the real part of the admittance of the elastic wave resonator in the embodiments of this application as a function of frequency. As can be seen from Figures 7 and 8, the elastic wave resonator provided by the embodiments of this application can effectively reduce the intensity of the transverse mode of the elastic wave resonator.

[0063] In some embodiments, as shown in Figures 3 and 5, the elastic wave resonator further includes a first reflective grating 71 and a second reflective grating 72. The first reflective grating 71 is disposed on a first side of the interdigital transducer 30 in a first direction, and the second side is disposed opposite to the first side in the first direction. The first reflective grating 71 and the second reflective grating 72 include a plurality of reflective electrode fingers connected between reflective busbars. A thin film layer 40 may also be disposed on the reflective electrode fingers of the first reflective grating 71 and the second reflective grating 72.

[0064] Understandably, the acoustic reflections in the gap region 50 are primarily due to acoustic impedance mismatch. In a typical interdigital transducer 30, the reflection coefficient phase in the gap region 50 is close to the fixed boundary (180 degrees), while the phase at the free boundary is 0 degrees. However, according to the scalar potential principle, the free boundary can more effectively suppress transverse modes. Different mode suppression structures require adjusting the reflection coefficient phase in the gap region to optimize the mode suppression effect. The deposited thin film layer 40 can be considered a phase shifter, which can alter the reflection coefficient characteristics. Therefore, by rationally designing the dimensions of the deposited thin film layer 40, the reflection phase can be made closer to the boundary conditions of free vibration, improving the transverse mode suppression effect.

[0065] According to the elastic wave resonator of this application, a thin film layer 40 is provided on the electrode fingers corresponding to the gap region 50, which can reduce the propagation speed of the sound wave in the gap region 50, so that the reflection phase of the sound wave at the boundary of the electrode fingers changes, destroying the conditions for the generation of transverse modes, thereby suppressing the generation of transverse modes and improving the performance of the resonator.

[0066] Referring to Figures 9 to 12, Figure 9 shows another structure of the elastic wave resonator according to an embodiment of this application, and Figure 10 shows a cross-section of the interdigital transducer 30 of the elastic wave resonator shown in Figure 9. Figure 11 shows a fourth structure of the elastic wave resonator according to an embodiment of this application, and Figure 12 shows a cross-section of the interdigital transducer 30 of the elastic wave resonator shown in Figure 11. For clarity, the structure of the reflective grating is not shown in Figure 9 and subsequent structural schematic diagrams of the elastic wave resonator; the structure of the reflective grating can be referred to Figure 3 or Figure 5. In some embodiments, the first busbar 32 includes third electrode fingers 34 arranged along a second direction, and the second busbar 35 includes fourth electrode fingers 36 arranged along a second direction. Along the first direction, the third electrode fingers 34 and the second electrode fingers 33 are arranged opposite to each other, and the fourth electrode fingers 36 are arranged opposite to the first electrode fingers 31. The third electrode fingers 34 and the fourth electrode fingers 36 form a pseudo-finger region 80, and a gap region 50 is located between the pseudo-finger region 80 and the aperture region 60. A thin film layer 40 is located in the gap region 50.

[0067] The third electrode finger 34 and the fourth electrode finger 36 are dummy fingers. The busbar is designed to include the dummy fingers, which can reduce the propagation speed of sound waves in the gap region 50 to a certain extent.

[0068] For an elastic wave resonator with a pseudo-finger, a thin film layer 40 is provided on the side of the electrode finger corresponding to the gap region 50 that is close to the piezoelectric layer 20 and / or away from the piezoelectric layer 20. This can further reduce the propagation speed of the sound wave in the gap region 50, causing the reflection phase of the sound wave at the boundary of the electrode finger to change, thereby disrupting the conditions for the generation of the transverse mode.

[0069] The structure and location of the thin film layer 40 can be referred to in the aforementioned embodiments, and will not be repeated here.

[0070] In some embodiments, as shown in Figures 11 and 12, the orthographic projection of the thin film layer 40 onto the interdigital transducer 30 is also located within the pseudofinger region 80.

[0071] Within the pseudofinger region 80, a thin film layer 40 is disposed on the side of at least one first electrode finger 31 and at least one second electrode finger 33 near the piezoelectric layer 20 and / or away from the piezoelectric layer 20.

[0072] The arrangement positions of the thin film layer 40 on the first electrode finger 31 and the second electrode finger 33 corresponding to the gap region 50 and the pseudo-finger region 80 can be selected according to the actual application scenario, and are not limited here.

[0073] Referring to Figures 11 and 12, Figure 11 shows a fourth structure of the elastic wave resonator according to an embodiment of this application, and Figure 12 shows a cross-section of the interdigital transducer 30 of the elastic wave resonator shown in Figure 11. As an example, a thin film layer 40 is provided on the side of the first electrode finger 31 and the second electrode finger 33 corresponding to the gap region 50 and the pseudo-finger region 80 away from the piezoelectric layer 20.

[0074] As another example, thin film layers 40 are provided on the side of the first electrode finger 31 and the second electrode finger 33 corresponding to the gap region 50 away from the piezoelectric layer 20, and thin film layers 40 are provided at intervals along the second direction on the side of the first electrode finger 31 and the second electrode finger 33 corresponding to the pseudo-finger region 80 away from the piezoelectric layer 20.

[0075] Meanwhile, a thin film layer 40 is provided on the first electrode finger 31 and the second electrode finger 33 in the gap region 50 and the pseudo-finger region 80, which can change the propagation speed of the sound wave in the gap region 50 and the pseudo-finger region 80 to a certain extent, so that the reflection phase of the sound wave at the boundary of the electrode finger changes, thus destroying the conditions for the generation of the transverse mode.

[0076] In some embodiments, as shown in Figures 3 to 5 and Figures 9 to 12, the thin film layer 40 includes a plurality of discrete thin film units 40a. The discrete thin film units 40a located in the same gap region 50 are spaced apart along a second direction. The orthographic projection of each discrete thin film unit 40a on the interdigital transducer 30 at least partially overlaps with the orthographic projection of an electrode finger. For example, the plurality of discrete thin film units 40a close to the first busbar 32 can be correspondingly arranged with the plurality of first electrode fingers 31. That is, the plurality of discrete thin film units 40a close to the first busbar 32 are correspondingly arranged on the side of the plurality of first electrode fingers 31 located in the gap region 50 away from the piezoelectric layer 20 or between that part and the piezoelectric layer 20. The plurality of discrete thin film units 40a close to the second busbar 35 can be correspondingly arranged with the plurality of second electrode fingers 33.

[0077] In some embodiments, the width of the portion of at least one electrode finger located in the gap region 50 is greater than or equal to the width of the portion of the electrode finger located in the aperture region 60. For example, the width of the portion of at least one first electrode finger 31 located in the gap region 50 is greater than or equal to the width of the portion of the first electrode finger 31 located in the aperture region 60, and / or, the width of the portion of at least one second electrode finger 33 located in the gap region 50 is greater than or equal to the width of the portion of the second electrode finger 33 located in the aperture region 60. Thus, the combined effect of adjusting the width of the portion of the electrode finger in the gap region 50 and the arrangement of the thin film layer 40 on sound velocity adjustment can effectively reduce the propagation speed of sound in the gap region 50, thereby effectively suppressing the generation of transverse modes.

[0078] As an example, when the interdigital transducer 30 also includes a pseudofinger region 80, the width of the portion of at least one electrode finger located in the pseudofinger region 80 is greater than or equal to the width of the portion of the electrode finger located in the aperture region 60. For example, the width of the portion of at least one first electrode finger 31 located in the pseudofinger region 80 is greater than or equal to the width of the portion of the first electrode finger 31 located in the aperture region 60, and / or, the width of the portion of at least one second electrode finger 33 located in the pseudofinger region 80 is greater than or equal to the width of the portion of the second electrode finger 33 located in the aperture region 60.

[0079] In some embodiments, referring to FIGS. 13 to 15, the thin film layer 40 includes at least one continuous thin film unit 40b, the orthographic projection of which on the interdigital transducer 30 at least partially coincides with the orthographic projection of the plurality of electrode fingers. That is, compared to discrete thin film units 40a corresponding to one electrode finger, the continuous thin film unit 40b can correspond to the plurality of electrode fingers. Furthermore, one continuous thin film unit 40b can correspond to all first electrode fingers 31, or one continuous thin film unit 40b can correspond to all second electrode fingers 33. In addition, the projection of the continuous thin film unit 40b on the piezoelectric layer 20 also falls on the area of ​​the piezoelectric layer 20 located in the gap region 50 that is not covered by the electrode fingers. When the thin film layer 40 is located on the side of the interdigital transducer 30 away from the piezoelectric layer 20, the continuous thin film unit 40b covers not only the portion of the plurality of electrode fingers located in the gap region 50, but also the portion of the piezoelectric layer 20 corresponding to the gap region 50. Compared to thin film layer 40 which only includes multiple discrete thin film units 40a, thin film layer 40 includes continuous thin film units 40b. In addition to saving process time and improving process yield, it can also more effectively adjust the propagation speed Vgap in the gap region 50.

[0080] In some embodiments, the thin film layer 40 includes one continuous thin film unit 40b, which is disposed corresponding to a gap region 50; or, the thin film layer 40 includes two continuous thin film units 40b, which are located on opposite sides of the aperture region 60 in a first direction, that is, each gap region 50 is disposed corresponding to one continuous thin film unit 40b; or, the thin film layer 40 includes two or more continuous thin film units 40b, and at least one gap region 50 is disposed corresponding to two or more continuous thin film units 40b, and the continuous thin film units 40b disposed corresponding to the same gap region 50 are spaced apart in the first direction.

[0081] Referring to FIGS. 16 and 17, FIG. 16 shows the simulation curve of the admittance of the elastic wave resonator according to the embodiment of the present application varying with frequency when V0 < Vgap < 1.1V0, and FIG. 17 shows the simulation curve of the real part of the admittance of the elastic wave resonator according to the embodiment of the present application varying with frequency when V0 < Vgap < 1.1V0. In some embodiments, the propagation speed Vgap of the acoustic wave in the gap region 50 satisfies: 0.9V0 < Vgap < V0, or V0 < Vgap < 1.1V0, where V0 is the propagation speed of the acoustic wave in the aperture region 60.

[0082] In the embodiments of the present application, a thin film layer 40 is provided on one side of the electrode finger close to the piezoelectric layer 20 and / or on one side away from the piezoelectric layer 20 to reduce the propagation speed of the acoustic wave in the gap region 50 so that it satisfies 0.9V0 < Vgap < V0, or V0 < Vgap < 1.1V0.

[0083] As can be seen from FIG. 16, when Vgap = 1.05V0, the right side of the resonance peak of the admittance curve of the elastic wave resonator according to the embodiment of the present application is smoother than the right side of the resonance peak of the admittance curve of the elastic wave resonator in the related art. When Vgap = 1.1V0, the right side of the resonance peak of the admittance curve of the elastic wave resonator according to the embodiment of the present application is more tortuous than the right side of the resonance peak of the admittance curve of the elastic wave resonator in the related art. As can be seen from FIG. 17, when Vgap = 1.05V0, the right side of the resonance peak of the real part of the admittance curve of the elastic wave resonator according to the embodiment of the present application is smoother than the right side of the resonance peak of the real part of the admittance curve of the elastic wave resonator in the related art. When Vgap = 1.1V0, the right side of the resonance peak of the real part of the admittance curve of the elastic wave resonator according to the embodiment of the present application is more tortuous than the right side of the resonance peak of the real part of the admittance curve of the elastic wave resonator in the related art. That is, within a certain range where Vgap > V0, the greater the propagation speed Vgap of the acoustic wave in the gap region 50, the better the effect of reducing the transverse mode of the elastic wave resonator. When the propagation speed Vgap of the acoustic wave in the gap region 50 increases to 1.1V0, the suppression effect on the transverse mode of the elastic wave resonator decreases. Therefore, when the elastic wave resonator of the present application satisfies V0 < Vgap < 1.1V0, a good transverse mode suppression effect can be achieved.

[0084] Referring to FIGS. 18 and 19, FIG. 18 shows a comparison diagram of simulation curves of the admittance of the elastic wave resonator according to an embodiment of the present application varying with frequency when 0.9V0 < Vgap < V0, and FIG. 19 shows a comparison diagram of simulation curves of the real part of the admittance of the elastic wave resonator according to an embodiment of the present application varying with frequency when 0.9V0 < Vgap < V0. As can be seen from FIG. 18, when Vgap = 0.95V0, the right side of the admittance curve resonance peak of the elastic wave resonator according to the embodiment of the present application is smoother than the right side of the admittance curve resonance peak of the elastic wave resonator in the related art. When Vgap = 0.9V0, the right side of the admittance curve resonance peak of the elastic wave resonator according to the embodiment of the present application is more tortuous than the right side of the admittance curve resonance peak of the elastic wave resonator in the related art. As can be seen from FIG. 19, when Vgap = 0.95V0, the right side of the real part of the admittance curve resonance peak of the elastic wave resonator according to the embodiment of the present application is smoother than the right side of the real part of the admittance curve resonance peak of the elastic wave resonator in the related art. When Vgap = 0.9V0, the right side of the real part of the admittance curve resonance peak of the elastic wave resonator according to the embodiment of the present application is more tortuous than the right side of the real part of the admittance curve resonance peak of the elastic wave resonator in the related art. That is, within a certain range where Vgap < V0, the smaller the propagation speed Vgap of the sound wave in the gap region 50, the better the effect of reducing the transverse mode of the elastic wave resonator. When the propagation speed Vgap of the sound wave in the gap region 50 decreases to 0.9V0, the suppression effect on the transverse mode of the elastic wave resonator decreases. Therefore, when the elastic wave resonator of the present application satisfies 0.9V0 < Vgap < V0, a good transverse mode suppression effect can be achieved.

[0085] The propagation speed of the sound wave affects the phase change when it is reflected at different medium interfaces. When the propagation speed of the sound wave in the gap region 50 is adjusted, the reflection phase of the transverse sound wave at the boundary between the aperture region 60 and the gap region 50 will also change accordingly. The change in the reflection phase can cause an interference effect of the sound wave at the boundary, thereby affecting the excitation condition of the transverse mode. When 0.9V0 < Vgap < V0 or V0 < Vgap < 1.1V0, the elastic wave resonator according to the embodiment of the present application can effectively reduce the intensity of the transverse mode of the elastic wave resonator.

[0086] Referring to FIGS. 20 and 21, FIG. 20 shows a comparison diagram of simulation curves of the admittance of the elastic wave resonator according to an embodiment of the present application varying with frequency under different lengths of the gap region 50, and FIG. 21 shows a comparison diagram of simulation curves of the real part of the admittance of the elastic wave resonator according to an embodiment of the present application varying with frequency under different lengths of the gap region 50.

[0087] In FIG. 20, curve (5) is a simulation curve of the admittance varying with frequency when the length of the gap region of the elastic wave resonator in the related art is λ. As can be seen from FIG. 20, when the length of the gap region 50 of the elastic wave resonator of the present application is within the range of 0.1λ to 2.5λ, the right side of the resonance peak of the admittance curve is smoother than the right side of the resonance peak of the admittance curve of the elastic wave resonator in the related art. In FIG. 21, curve (6) is a simulation curve of the real part of the admittance varying with frequency when the length of the gap region of the elastic wave resonator in the related art is λ. As can be seen from FIG. 21, when the length of the gap region 50 of the elastic wave resonator of the present application is within the range of 0.1λ to 2.5λ, the right side of the resonance peak of the real part of the admittance curve of the elastic wave resonator of the present application is smoother than the right side of the resonance peak of the admittance curve of the elastic wave resonator in the related art. In summary, when the length of the gap region 50 along the first direction is within 0.1λ to 2.5λ, the intensity of the transverse mode of the elastic wave resonator can be effectively reduced.

[0088] It can be understood that the propagation speed of the sound wave affects the phase change when it is reflected at the interface of different media. When the propagation speed of the sound wave in the gap region 50 is adjusted, the reflection phase of the transverse sound wave at the boundary between the aperture region 60 and the gap region 50 will also change accordingly. The change in the reflection phase can cause the interference effect of the wave at the boundary, thereby affecting the excitation condition of the transverse mode.

[0089] The length of the gap region 50 can affect the propagation path and propagation time of the sound wave therein. A longer gap will increase the phase delay of the sound wave, which may cause the phase difference with the reflected wave in the aperture region to reach the condition, thereby causing the generation of the transverse mode. Therefore, adjusting the length can effectively control the reflection phase difference and reduce the interference of the transverse mode.

[0090] In summary, to achieve effective transverse mode suppression, it is necessary to ensure that the sound wave propagation in the gap region 50 matches the reflection phase of the sound wave in the aperture region 60 or the phase difference is large enough. The elastic wave resonator of the present application deposits a thin film layer 40 in the gap region 50, so that the propagation speed Vgap of the sound wave in the gap region 50 satisfies: 0.9V0 < Vgap < V0, or, V0 < Vgap < 1.1V0, and at the same time, the length of the gap region 50 along the first direction is 0.1λ to 2.5λ. By adjusting the propagation speed of the sound wave in the gap region 50 and the length of the gap region 50 in the first direction at the same time, it can be ensured that the change in the reflection phase reaches the expected effect, so that the transverse mode cannot be excited within a specific frequency range.

[0091] In some embodiments, the thin film layer 40 includes a dielectric layer and / or a metal layer.

[0092] The specific materials of the dielectric layer and the metal layer can be selected according to the actual application scenario and are not limited here. For example, the dielectric layer can be alumina, silica, silicon nitride, etc. The metal layer can be gold, silver, aluminum, platinum, etc.

[0093] The metal layer can be disposed on the side of the electrode finger close to the piezoelectric layer 20 or on the side of the electrode finger far from the piezoelectric layer 20. Similarly, the dielectric layer can be disposed on the side of the electrode finger close to the piezoelectric layer 20 or on the side of the electrode finger far from the piezoelectric layer 20. The specific setting forms of the metal layer and the dielectric layer can be selected according to the actual application scenario and are not limited here. The specific material of the thin film layer 40 can be selected according to the actual application scenario and is not limited here. For example, the thin film layer 40 can be alumina or platinum, etc.

[0094] As an example, in the gap region 50, a dielectric layer is disposed on the side of the first electrode finger 31 and the second electrode finger 33 close to the piezoelectric layer 20, and a metal layer is disposed on the side of the electrode finger far from the piezoelectric layer 20.

[0095] As another example, in the gap region 50, a metal layer and a dielectric layer are stacked in sequence on the side of the first electrode finger 31 and the second electrode finger 33 far from the piezoelectric layer 20.

[0096] In some embodiments, the thin film layer 40 is disposed on the side of the interdigital transducer 30 far from the piezoelectric layer 20. In the first direction, the length of the thin film layer 40 is less than or equal to the length of the gap region 50.

[0097] When the length of the thin film layer 40 is less than the length of the gap region 50, the thin film layer 40 can be disposed close to the roots of the first electrode finger 31 and the second electrode finger 33 corresponding to the gap region 50, or far from the roots of the first electrode finger 31 and the second electrode finger 33 corresponding to the gap region 50, or can be disposed within the middle range of the first electrode finger 31 and the second electrode finger 33 corresponding to the gap region 50.

[0098] As an example, when the length of the gap region 50 is 2λ, the thin film layer 40 can be disposed within the λ length range of the first electrode finger 31 close to the first bus bar 32, or can be disposed within the λ length range of the first electrode finger 31 close to the second bus bar 35.

[0099] When the length of the thin film layer 40 is greater than or equal to half of the length of the gap region 50, it is convenient to reduce the propagation speed of the acoustic wave in the gap region 50 so that it satisfies 0.9V0 < Vgap < V0, or V0 < Vgap < 1.1V0.

[0100] In some embodiments, the length of the thin film layer 40 is less than the length of the gap region 50, the thin film layer 40 is disposed on the side of the gap region 50 away from the adjacent busbar, and a preset distance is provided between the end of the thin film layer 40 near the busbar and the busbar.

[0101] When the length of the thin film layer 40 is less than the length of the gap region 50, the thin film layer 40 may or may not contact the busbar. The specific length of the preset distance between the thin film layer 40 and the busbar can be selected according to the actual application scenario, and is not limited here.

[0102] As an example, the preset distance is half the length of the gap region 50, that is, the length of the gap region 50 is 2λ. The thin film layer 40 is disposed in the gap region 50 at a distance of λ from the busbar, and the thin film layer 40 does not contact the busbar.

[0103] In other embodiments, the length of the thin film layer 40 is less than the length of the gap region 50, and the thin film layer 40 is disposed on the side of the gap region 50 near the busbar.

[0104] As another example, the gap region 50 has a length of 2λ, and the thin film layer 40 is disposed in the gap region 50 within the λ length range close to the busbar, and the thin film layer 40 is in contact with the busbar.

[0105] In some embodiments, in the first direction, the length of the thin film layer 40 is equal to the length of the gap region 50.

[0106] The thin film layer 40 covers the entire gap region 50 in the first direction, which can not only reduce the speed of sound wave propagation in the gap region 50 to a large extent, but also facilitate the manufacturing process.

[0107] Referring again to FIG3, in some embodiments, the thin film layer 40 is disposed on the side of the interdigital transducer 30 away from the piezoelectric layer 20 and covers the entire area of ​​the interdigital transducer 30 located within the gap region 50.

[0108] The thin film layer 40 covers the entire area of ​​each first electrode finger 31 and each second electrode finger 33 within the gap region 50. That is, the length of the thin film layer 40 is greater than or equal to the length of the gap region 50, and the width of the thin film layer 40 is greater than or equal to the width of the gap region 50. This can reduce the propagation speed of the sound wave in the gap region 50 to a greater extent, effectively reduce the intensity of the transverse mode of the elastic wave resonator, and facilitate the manufacturing process.

[0109] It should be noted that Figures 4, 10 and 12 of this application are illustrated with the thin film layer 40 located on the side of the interdigital transducer 30 away from the piezoelectric layer 20. However, it is easy to understand that the thin film layer 40 of this application can also be located between the interdigital transducer 30 and the piezoelectric layer 20 to reduce the acoustic wave propagation speed in the gap region 50, thereby achieving the suppression effect of the transverse mode.

[0110] Secondly, embodiments of this application provide a filter that includes at least one of the aforementioned elastic wave resonators.

[0111] The specific structure and function of the elastic wave resonator can be referred to the embodiment in the first aspect, and will not be repeated here.

[0112] According to the filter of this application, a thin film layer is provided on the first and second electrode fingers corresponding to the gap region of the elastic wave resonator, which can reduce the propagation speed of the sound wave in the gap region, so that the reflection phase of the sound wave at the boundary of the electrode fingers changes, destroying the conditions for the generation of transverse modes, thereby suppressing the generation of transverse modes and improving the performance of the resonator.

[0113] Thirdly, embodiments of this application provide a communication device that includes the aforementioned filter. The filter includes at least one elastic wave resonator, which, by selecting its resonant frequency, precisely selects a specific frequency band of the signal, filters out unnecessary frequencies, and ensures that only signals of a specific frequency can pass through, thereby improving the signal quality of the communication system.

[0114] The specific structure and function of the elastic wave resonator can be referred to the embodiment in the first aspect, and will not be repeated here.

[0115] According to the communication device of this application, a thin film layer is provided on the first and second electrode fingers corresponding to the gap region of the elastic wave resonator, which can reduce the propagation speed of the sound wave in the gap region, so that the reflected phase of the sound wave at the boundary of the electrode fingers changes, destroying the conditions for the generation of transverse modes, thereby suppressing the generation of transverse modes and improving the performance of the resonator.

[0116] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. An elastic wave resonator, characterized in that, It includes a support layer, a piezoelectric layer, and an interdigital transducer stacked in sequence. The interdigital transducer includes a plurality of first electrode fingers, a plurality of second electrode fingers, a first bus bar, and a second bus bar. The first bus bar and the second bus bar are arranged opposite to each other in a first direction. The first electrode fingers are connected to the first bus bar, and the second electrode fingers are connected to the second bus bar. The first electrode fingers and the second electrode fingers extend in the first direction and are alternately arranged in a second direction. In the second direction, the intersecting portions of the first electrode fingers and the second electrode fingers form a pore region, and there is a gap region between the pore region and any one of the bus bars. The first direction intersects with the second direction; The elastic wave resonator further includes a thin film layer disposed between the piezoelectric layer and the interdigital transducer; and the positive projection of the thin film layer on the interdigital transducer is located within the gap region, where The propagation speed Vgap of the sound wave in the gap region satisfies: 0.9V0 < Vgap < V0, or V0 < Vgap < 1.1V0, where V0 is the propagation speed of the sound wave in the pore region.

2. The elastic wave resonator according to claim 1, characterized in that, The thin film layer is disposed on the side of the interdigital transducer away from the piezoelectric layer.

3. The elastic wave resonator according to claim 1 or 2, characterized in that, The first bus bar includes third electrode fingers arranged in the second direction, and the second bus bar includes fourth electrode fingers arranged in the second direction. Along the first direction, the third electrode fingers are arranged opposite to the second electrode fingers, and the fourth electrode fingers are arranged opposite to the first electrode fingers. The third electrode fingers and the fourth electrode fingers form a dummy finger region, and the gap region is located between the dummy finger region and the pore region.

4. The elastic wave resonator according to any one of claims 1 to 3, characterized in that, The positive projection of the thin film layer on the interdigital transducer is located within the dummy finger region.

5. The elastic wave resonator according to any one of claims 1 to 4, characterized in that, The thin film layer includes a plurality of discrete thin film units, and the plurality of discrete thin film units located in the same gap region are arranged at intervals in the second direction. The positive projection of each discrete thin film unit on the interdigital transducer at least partially coincides with the positive projection of one of the first electrode fingers or the second electrode fingers.

6. The elastic wave resonator according to any one of claims 1 to 4, characterized in that, The thin film layer includes at least one continuous thin film unit, and the positive projection of the continuous thin film unit on the interdigital transducer at least partially coincides with the positive projections of the plurality of first electrode fingers and the second electrode fingers.

7. The elastic wave resonator according to any one of claims 1 to 6, characterized in that, Along the second direction, the width of at least a part of the first electrode finger located in the gap region is greater than or equal to the width of the part of the first electrode finger located in the pore region; and / or The width of at least a part of the second electrode finger located in the gap region is greater than or equal to the width of the part of the second electrode finger located in the pore region.

8. The elastic wave resonator according to any one of claims 1 to 7, characterized in that, The length of the gap region in the first direction is 0.1λ to 2.5λ, where λ is the wavelength of the elastic wave.

9. The elastic wave resonator according to any one of claims 1 to 8, characterized in that, The thin film layer includes a dielectric layer and / or a metal layer.

10. The elastic wave resonator according to claim 9, characterized in that, The material of the dielectric layer includes alumina, silica, or silicon nitride.

11. The elastic wave resonator according to any one of claims 1 to 10, characterized in that, The thin film layer includes a metal layer.

12. The elastic wave resonator according to claim 11, characterized in that, The material of the metal layer includes gold, silver, aluminum, or platinum.

13. The elastic wave resonator according to any one of claims 1 to 12, characterized in that, The thin film layer is disposed only on the side of the interdigital transducer away from the piezoelectric layer, and in the first direction, the length of the thin film layer is less than or equal to the length of the gap region.

14. The elastic wave resonator according to claim 13, characterized in that, In the first direction, the length of the thin film layer is less than the length of the gap region, the thin film layer is disposed on the side of the gap region away from the busbar, and the side of the thin film layer close to the busbar is provided with a preset distance from the busbar.

15. The elastic wave resonator according to claim 13 or 14, characterized in that, In the first direction, the length of the thin film layer is less than or equal to half the length of the gap region.

16. The elastic wave resonator according to any one of claims 1 to 15, characterized in that, The thin film layer is disposed only on the side of the interdigital transducer away from the piezoelectric layer, and covers the entire area of ​​the interdigital transducer located within the gap region.

17. A filter, characterized in that, It includes at least one elastic wave resonator according to any one of claims 1 to 16.

18. A communication device, characterized in that, Includes the filter according to claim 17.

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