Elastic wave resonator, filter, and communication device

Abstract

The utility model discloses an elastic wave resonator, a filter and communication equipment, and belongs to the technical field of surface acoustic waves. The elastic wave resonator comprises a supporting layer, a piezoelectric layer and an interdigital transducer which are stacked in sequence, 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 the first direction and are alternately arranged in the second direction, the crossed parts of the first electrode fingers and the second electrode fingers form an aperture area, and the aperture area is located between the first electrode fingers and the second electrode fingers. A gap area is formed between the aperture area and the bus bar; the elastic wave resonator comprises a thin film layer, the thin film layer is arranged between the piezoelectric layer and the interdigital transducer and / or the side, away from the piezoelectric layer, of the interdigital transducer, the orthographic projection of the thin film layer on the interdigital transducer is located in the gap area, and the propagation velocity Vgap of sound waves in the gap area meets the following conditions: 0.9 V0lt; vgapt, Vgapt; v0, V0lt; vgapt, Vgapt; 1.1 V0, V0 is the propagation velocity of sound waves in the aperture region, and generation of a transverse mode can be inhibited.

Description

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, which causes a transverse mode in the resonator. The existence of the transverse mode leads to ripples in the piezoelectric filter within the band and near the passband. These ripples increase the device loss and reduce the performance of the resonator and the filter. Summary of the Utility Model

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

[0004] In a first aspect, this application provides an elastic wave resonator, including: 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, and a first bus bar and a second bus bar arranged oppositely along a first direction. The first electrode fingers are connected to the first bus bar, the second electrode fingers are connected to the second bus bar, the first electrode fingers and the second electrode fingers extend along the first direction and are alternately arranged along a second direction. In the second direction, the crossing part of the first electrode fingers and the second electrode fingers forms an aperture region, and a gap region is formed between the aperture region and the bus bar. The first direction intersects with the second direction.

[0005] The elastic wave resonator further includes a thin film layer, and the thin film layer is disposed between the piezoelectric layer and the interdigital transducer and / or the thin film layer is disposed on a 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.

[0006] The propagation speed Vgap of the acoustic wave in the gap region satisfies: 0.9V0 < Vgap < V0, V0 < Vgap < 1.1V0, where V0 is the propagation speed of the acoustic wave in the aperture region.

[0007] According to an embodiment of this application, the first bus bar includes third electrode fingers arranged along the second direction, the second bus bar includes fourth electrode fingers arranged along the second direction, the third electrode fingers are arranged oppositely to the second electrode fingers, the fourth electrode fingers are arranged oppositely to the first electrode fingers, the third electrode fingers and the fourth electrode fingers form a dummy finger region, the gap region is located between the dummy finger region and the aperture region, and the orthographic projection of the thin film layer on the interdigital transducer is located within the dummy finger region.

[0008] 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.

[0009] According to one embodiment of this application, the thin film layer includes a dielectric layer and / or a metal layer.

[0010] 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.

[0011] 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 end of the thin film layer near the busbar and the busbar.

[0012] 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.

[0013] Secondly, this application provides a filter including at least one of the aforementioned elastic wave resonators.

[0014] Thirdly, this application provides a communication device, which includes at least one of the aforementioned elastic wave resonators.

[0015] 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.

[0016] 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

[0017] 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, in which:

[0018] Figure 1 This is a schematic cross-sectional view of the elastic wave resonator provided in the embodiments of this application;

[0019] Figure 2 This is a schematic diagram of the structure of an elastic wave resonator in related technologies;

[0020] Figure 3 This is one of the structural schematic diagrams of the elastic wave resonator provided in the embodiments of this application;

[0021] Figure 4 yes Figure 3 A schematic diagram of the cross-section of the interdigital transducer of the elastic wave resonator along AA';

[0022] Figure 5 This is a second schematic diagram of the structure of the elastic wave resonator provided in the embodiments of this application;

[0023] Figure 6 This is a schematic diagram of the sound velocity distribution in various regions provided in the embodiments of this application;

[0024] Figure 7 This is one of the simulation comparison graphs showing the admittance curves of elastic wave resonators in embodiments of this application and related technologies as a function of frequency.

[0025] Figure 8 This is one of the simulation comparison graphs of the real part of the admittance of an elastic wave resonator as a function of frequency in embodiments of this application and related technologies;

[0026] Figure 9 This is the third schematic diagram of the elastic wave resonator provided in the embodiments of this application;

[0027] Figure 10 yes Figure 9 A schematic diagram of the cross-section of the interdigital transducer of the elastic wave resonator along AA';

[0028] Figure 11 This is the fourth schematic diagram of the structure of the elastic wave resonator provided in the embodiments of this application;

[0029] Figure 12 yes Figure 11 A schematic diagram of the cross-section of the interdigital transducer of the elastic wave resonator along AA';

[0030] Figure 13 This is one of the curves showing the change of admittance with frequency under different sound velocities in the gap region according to the embodiments of this application;

[0031] Figure 14 This is one of the curves showing the change of the real part of the admittance with frequency under different sound velocities in the gap region according to the embodiments of this application;

[0032] Figure 15 This is the second curve of admittance versus frequency in the embodiment of this application under different sound velocities in the gap region;

[0033] Figure 16 This is the second curve of the real part of admittance changing with frequency under different sound velocities in the gap region according to the embodiments of this application;

[0034] Figure 17 This is a curve showing the admittance as a function of frequency for different gap region lengths in embodiments of this application;

[0035] Figure 18 This is a curve showing the change of the real part of the admittance with frequency under different lengths of the gap region in the embodiments of this application.

[0036] Figure label:

[0037] Support layer 10, piezoelectric layer 20, interdigital transducer 30, first electrode finger 31, first busbar 32, second electrode finger 33, third electrode finger 34, second busbar 35, fourth electrode finger 36, thin film layer 40, gap region 50, aperture region 60, first reflective grating 71, second reflective grating 72, pseudofinger region 80. Detailed Implementation

[0038] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] Reference Figure 1 and Figure 2 , Figure 1 A cross-sectional structure of an elastic wave resonator is shown. Figure 2 The structure of an elastic wave resonator in the related art is shown. The elastic wave resonator includes a support layer, a piezoelectric layer, and an interdigital transducer stacked sequentially. A gap region is formed between the electrode fingers in the interdigital transducer and the busbar opposite them. In an elastic wave device excited by an interdigital transducer, the reflection of transversely propagating sound waves in the gap region causes the resonator to exhibit transverse modes. The presence of transverse modes leads to ripple in the piezoelectric filter's band and near the passband. These ripples increase device losses and degrade the performance of the resonator and filter.

[0044] Reference Figure 3 and Figure 4 , Figure 3 The structure of the elastic wave resonator according to an embodiment of this application is shown. Figure 4 It shows Figure 3Cross-section of the interdigital transducer 30 of the elastic wave resonator shown. An embodiment of the present application provides an elastic wave resonator, comprising: 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, and a first bus bar 32 and a second bus bar 35 arranged opposite to each other in the first direction. The first electrode fingers 31 are connected to the first bus bar 32, 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 the second direction. In the second direction, the crossing portions of the first electrode fingers 31 and the second electrode fingers 33 form an aperture region 60, and a gap region 50 is formed between the aperture region 60 and 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 the side of the interdigital transducer 30 away from the piezoelectric layer 20, and the orthographic 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 satisfies: 0.9V0 < Vgap < V0, V0 < Vgap < 1.1V0, where V0 is the propagation speed of the sound wave in the aperture region.

[0045] 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.

[0046] The support layer 10 is mainly used to support the main structure of the entire elastic wave resonator, ensuring that the elastic wave resonator is not easily damaged when subjected to external stress, and providing the 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 can be made of silicon and silicon dioxide. The thickness of the support layer 10 can be 0.01λ~0.5λ, where λ is the wavelength of the elastic wave.

[0047] The piezoelectric layer 20 is the core part for the resonator to achieve its function. When the externally applied electrical signal frequency is the same as the natural frequency of the resonator, the material in the piezoelectric layer 20 will deform, thereby generating mechanical vibration. This mechanical vibration will further interact with the electrical signal to achieve resonance amplification of the elastic wave. The material of the piezoelectric layer 20 usually has relatively high mechanical strength and stiffness to withstand external forces and maintain the structural stability, and maintains stable piezoelectric properties within a certain temperature range. The specific material and thickness of the piezoelectric layer 20 can be selected according to the actual application scenario and are not limited herein. For example, the piezoelectric layer 20 can include 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 be 0.01λ~0.5λ, where λ is the wavelength of the elastic wave.

[0048] 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 0.01λ~0.15λ, where λ is the wavelength of the elastic wave.

[0049] In the second direction, the intersection of the first electrode finger 31 and the second electrode finger 33 forms an 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.

[0050] 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.

[0051] The thin film layer 40 can be disposed between the piezoelectric layer 20 and the interdigital transducer 30, or it can be disposed on the side of the interdigital transducer 30 away from the piezoelectric layer 20, indicating that the thin film layer 40 and the interdigital transducer 30 are stacked. The thin film layer 40 can also be disposed both above and below the interdigital transducer 30. The orthogonal projection of the thin film layer 40 onto the interdigital transducer 30 is located within the gap region 50, that is, within the gap region 50. The thin film layer 40 is disposed on the side closer to the piezoelectric layer 20 and / or the side away from the piezoelectric layer 20 of at least one first electrode finger 31 and at least one second electrode finger 33. This can reduce the propagation speed of sound waves within the gap region 50, causing the reflection phase of the transverse sound waves propagating from the aperture region 60 to the gap region 50 to change at the boundary between the aperture region 60 and the gap region 50, thereby disrupting the conditions for transverse mode generation and suppressing the generation of transverse modes.

[0052] 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.

[0053] It should be noted that the thin film layer 40 and the portions of the first electrode fingers 31 and the second electrode fingers 33 located in the gap region 50 are arranged in a partially overlapping manner. The thin film layer 40 may cover all of the first electrode fingers 31 and the second electrode fingers 33 within 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 of the corresponding portions of the electrode finger located in the gap region 50, or may cover a partial region of the electrode finger located within the gap region 50. The thin film layer 40 may be disposed on the side of the first electrode fingers 31 and the second electrode fingers 33 close to the piezoelectric layer 20, may also be disposed on the side of the first electrode fingers 31 and the second electrode fingers 33 away from the piezoelectric layer 20, or may be disposed 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 simultaneously. The specific coverage range of the thin film layer 40 may be selected according to the actual application scenario and is not limited herein.

[0054] Referring to Figure 5 , Figure 5 FIG. shows the 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 covers the entire range of the electrode fingers located in the gap region 50.

[0055] 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.

[0056] Referring to Figure 6 , Figure 6 FIG. shows the sound velocity distribution of each region of the elastic wave resonator in the above embodiment. As can be seen from Figure 6 , 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, the sound velocity in the gap region 50 can be reduced, so that the phase change of the reflection of the transverse acoustic wave propagating from the aperture region 60 to the gap region at the boundary between the aperture and the gap region 50 is changed, and the conditions for generating the transverse mode are destroyed.

[0057] Referring to Figure 7 and Figure 8 , Figure 7 FIG. shows a simulation comparison diagram of the admittance curves of the elastic wave resonator in the embodiment of the present application and in the related art varying with frequency, Figure 8The figure shows a simulation comparison of the real part of the admittance of an elastic wave resonator in the embodiments of this application and in related technologies as a function of frequency. Figure 7 Curve (1) represents the admittance of an elastic wave resonator as a function of frequency in the related art, and curve (2) represents the admittance of an elastic wave resonator as a function of frequency in the embodiment of this application. Figure 8 Curve (3) represents the curve of the real part of the admittance of an elastic wave resonator as a function of frequency in related technologies, and curve (4) represents the curve of the real part of the admittance of an elastic wave resonator as a function of frequency in the embodiment of this application. Figure 7 and Figure 8 It is understood that the embodiments of this application can effectively reduce the intensity of the transverse modes of the elastic wave resonator.

[0058] In some embodiments, the elastic wave resonator further includes a first reflective grating 71 and a second reflective grating 72. The first reflective grating 71 is disposed at a first end of the interdigital transducer 30 in a first direction, and the second reflective grating 72 is disposed at a second end opposite to the first end in the first direction. The first reflective grating 71 and the second reflective grating 72 include a plurality of electrode fingers connected between busbars, and a thin film layer 40 may also be disposed on the electrode fingers of the first reflective grating 71 and the second reflective grating 72.

[0059] Understandably, acoustic reflections in the gap region 50 are primarily caused by 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, altering the reflection coefficient characteristics. 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, thus improving the mode suppression effect.

[0060] 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 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.

[0061] Reference Figure 9 and Figure 10 , Figure 9 The structure of the elastic wave resonator according to an embodiment of this application is shown. Figure 10 It shows Figure 9 The cross-section of the interdigital transducer 30 of the elastic wave resonator is shown. For clarity, Figure 9The structural diagram of the subsequent elastic wave resonator is not shown. The structure of the reflector grating can be found in the following diagram: Figure 3 or Figure 5 In some embodiments, the first busbar 32 includes a third electrode finger 34 arranged along a second direction, and the second busbar 35 includes a fourth electrode finger 36 arranged along a second direction. The third electrode finger 34 is arranged opposite to the second electrode finger 33, and the fourth electrode finger 36 is arranged opposite to the first electrode finger 31. The third electrode finger 34 and the fourth electrode finger 36 form a pseudo-finger region 80, and the gap region 50 is located between the pseudo-finger region 80 and the aperture region 60.

[0062] 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.

[0063] 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 phase of the sound wave reflected at the boundary of the electrode finger to change, thereby disrupting the conditions for the generation of the transverse mode.

[0064] The structure and location of the thin film layer 40 can be referred to in the aforementioned embodiments, and will not be repeated here.

[0065] In some embodiments, the orthographic projection of the thin film layer 40 onto the interdigital transducer 30 lies within the pseudofinger region 80.

[0066] 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.

[0067] 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.

[0068] Reference Figure 11 and Figure 12 , Figure 11 The structure of the elastic wave resonator according to an embodiment of this application is shown. Figure 12 It shows Figure 11 The cross-section of the interdigital transducer 30 of the elastic wave resonator is shown. 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.

[0069] As another example, thin film layers 40 are provided on the sides of the first electrode fingers 31 and the second electrode fingers 33 corresponding to the gap region 50, which are away from the piezoelectric layer 20. Along the second direction, thin film layers 40 are provided at intervals on the sides of the first electrode fingers 31 and the second electrode fingers 33 corresponding to the dummy finger region 80, which are away from the piezoelectric layer 20.

[0070] Meanwhile, by providing the thin film layers 40 on the first electrode fingers 31 and the second electrode fingers 33 within both the gap region 50 and the dummy finger region 80, the acoustic wave propagation speed in the gap region 50 and the dummy finger region 80 can be changed to some extent, so that the phase of the acoustic wave reflected at the boundary of the electrode fingers is changed, and the conditions for generating the transverse mode are destroyed.

[0071] Refer to Figure 13 and Figure 14 , Figure 13 shows the curve of the admittance varying with frequency of the elastic wave resonator according to the embodiment of the present application when V0 < Vgap < 1.1V0. Figure 14 shows the curve of the real part of the admittance varying with frequency of the elastic wave resonator according to the embodiment of the present application when V0 < Vgap < 1.1V0. In some embodiments, the acoustic wave propagation speed Vgap in the gap region 50 satisfies: 0.9V0 < Vgap < V0, V0 < Vgap < 1.1V0, where V0 is the acoustic wave propagation speed in the aperture region 60.

[0072] In the embodiments of the present application, by providing the thin film layer 40 on the side of the electrode finger close to the piezoelectric layer 20 and / or on the side away from the piezoelectric layer 20, the acoustic wave propagation speed in the gap region 50 is reduced to satisfy 0.9V0 < Vgap < V0, V0 < Vgap < 1.1V0.

[0073] From Figure 13 it can be seen that 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. From Figure 14It can be seen that 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 wave velocity in the gap region 50, the better the effect of reducing the transverse mode of the elastic wave resonator. When the wave velocity Vgap in the gap region 50 increases to 1.1V0, the suppression effect on the transverse mode of the elastic wave resonator decreases. Therefore, for the elastic wave resonator of the present application, V0 < Vgap < 1.1V0.

[0074] Referring to Figure 15 and Figure 16 , Figure 15 FIG. shows the curve of the admittance of the elastic wave resonator according to the embodiment of the present application varying with frequency when 0.9V0 < Vgap < V0. Figure 16 FIG. shows the 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 0.9V0 < Vgap < V0. As can be seen from Figure 15 it, when Vgap = 0.95V0, 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 = 0.9V0, 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 Figure 16 it, when Vgap = 0.95V0, 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 = 0.9V0, 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 smaller the wave velocity in the gap region 50, the better the effect of reducing the transverse mode of the elastic wave resonator. When the wave velocity Vgap in the gap region 50 decreases to 0.9V0, the suppression effect on the transverse mode of the elastic wave resonator decreases. Therefore, for the elastic wave resonator of the present application, 0.9V0 < Vgap < V0.

[0075] The propagation speed of sound waves affects the phase change during reflection at the interface of different media. When the wave speed in the gap region 50 is adjusted, the reflection phase of the transverse sound waves at the aperture region 60 and the gap region boundary will also change accordingly. The change in the reflection phase can cause an interference effect of the waves at the boundary, thereby affecting the excitation conditions of the transverse mode. When 0.9V0 < Vgap < V0 or V0 < Vgap < 1.1V0, the embodiments of the elastic wave resonator in this application can effectively reduce the intensity of the transverse mode of the elastic wave resonator.

[0076] Referring to Figure 17 and Figure 18 , Figure 17 shows the curves of the admittance varying with frequency when the length of the gap region 50 of the elastic wave resonator in the embodiments of this application is different. Figure 18 shows the curves of the real part of the admittance varying with frequency when the length of the gap region 50 of the elastic wave resonator in the embodiments of this application is different. In some embodiments, the length of the gap region 50 in the first direction is 0.1λ - 2.5λ, where λ is the wavelength of the elastic wave.

[0077] The length of the gap region 50 can affect the propagation path and propagation time of sound waves therein. A longer gap will increase the phase delay of the sound waves, possibly causing the phase difference with the reflected waves in the aperture region 60 to reach the condition, thereby resulting in 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.

[0078] Figure 17 In (5), the curve is the 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. From Figure 17 it can be seen that when the length of the gap region 50 of the elastic wave resonator of this application is within the range of 0.1λ - 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. Figure 18 In (6), the curve is the 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. From Figure 18 it can be seen that when the length of the gap region 50 of the real part of the admittance of the elastic wave resonator of this application is within the range of 0.1λ - 2.5λ, the right side of the resonance peak of the real part of the admittance curve of the elastic wave resonator of this 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 in the first direction is 0.1λ - 2.5λ, the intensity of the transverse mode of the elastic wave resonator can be effectively reduced.

[0079] It is understandable that the propagation speed of sound waves affects the phase change when they are reflected at the interface of different media. When the wave speed 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 lead to an interference effect of the waves at the boundary, thereby affecting the excitation conditions of the transverse mode.

[0080] 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 waves 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, so that the propagation speed Vgap of the sound wave in the gap region 50 satisfies: 0.9V0 < Vgap < V0, V0 < Vgap < 1.1V0, and at the same time, the length of the gap region 50 in the first direction is 0.1λ to 2.5λ. By adjusting the wave speed and length simultaneously, it can ensure that the phase change reaches the expected effect, so that the transverse mode cannot be excited within a specific frequency range.

[0081] In some embodiments, the thin film layer 40 includes a dielectric layer and / or a metal layer.

[0082] 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.

[0083] 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 form of the metal layer and the dielectric layer can be selected according to the actual application scenario and is not limited here.

[0084] 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.

[0085] 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.

[0086] In some embodiments, the thin film layer 40 is disposed on the side of the interdigital transducer 30 far from the piezoelectric layer 20, and in the first direction, the length of the thin film layer 40 is greater than or equal to half of the length of the gap region 50.

[0087] 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 root of the first electrode finger 31 and the second electrode finger 33 corresponding to the gap region 50, or it can be disposed away from the root of the first electrode finger 31 and the second electrode finger 33 corresponding to the gap region 50, or it can be disposed in the middle range of the first electrode finger 31 and the second electrode finger 33 corresponding to the gap region 50.

[0088] As an example, the gap region 50 has a length of 2λ, and the thin film layer 40 can be disposed within the λ length range of the first electrode finger 31 near the first busbar 32, or it can be disposed within the λ length range of the first electrode finger 31 near the second busbar 35.

[0089] Having a length of thin film layer 40 greater than or equal to half the length of gap region 50 facilitates reducing the propagation speed of sound waves within gap region 50, ensuring it meets the 0.9V0 standard. <Vgap<V0,V0<Vgap<1.1V0。

[0090] 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 busbar, and a preset distance is provided between the end of the thin film layer 40 near the busbar and the busbar.

[0091] 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.

[0092] As an example, the preset distance is half of the gap region 50, that is, the length of the gap region 50 is 2λ, and the thin film layer 40 is set within the gap region at a length of λ away from the busbar, and the thin film layer 40 does not contact the busbar.

[0093] 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.

[0094] As another example, the gap region 50 has a length of 2λ, and the thin film layer 40 is disposed within the gap region near the busbar within a length of λ, and the thin film layer 40 is in contact with the busbar.

[0095] 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.

[0096] 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.

[0097] Continue to refer to Figure 3 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.

[0098] The thin film layer 40 covers the entire area of ​​each first electrode finger 31 and 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 speed of sound wave propagation 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.

[0099] One embodiment of this application provides a filter that includes at least one of the aforementioned elastic wave resonators.

[0100] The specific structure and function of the elastic wave resonator can be referred to the aforementioned embodiments, and will not be repeated here.

[0101] 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 50 of the elastic wave resonator, which can reduce the propagation speed of the sound wave in the gap region 50, 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.

[0102] One embodiment of this application provides a communication device that includes the aforementioned filter.

[0103] The filter includes at least one elastic wave resonator, which precisely selects a specific frequency band of the signal by choosing the resonant frequency, filters out unnecessary frequencies, and ensures that only signals of specific frequencies can pass through, thereby improving the signal quality of the communication system.

[0104] The specific structure and function of the elastic wave resonator can be referred to the aforementioned embodiments, and will not be repeated here.

[0105] According to the communication device of this application, a thin film layer is provided on the first electrode finger and the second electrode finger corresponding to the gap region 50 of the elastic wave resonator, which can reduce the propagation speed of the sound wave in the gap region 50, so that the phase of the sound wave reflected at the boundary of the electrode finger changes, destroying the conditions for the generation of transverse mode, thereby suppressing the generation of transverse mode and improving the performance of the resonator.

[0106] 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 by, The elastic wave resonator comprises a support layer, a piezoelectric layer and an interdigital transducer which are sequentially stacked, the interdigital transducer comprises a plurality of first electrode fingers, a plurality of second electrode fingers, and a first bus bar and a second bus bar which are oppositely arranged along a first direction, the first electrode fingers are connected to the first bus bar, the second electrode fingers are connected to the second bus bar, the first electrode fingers and the second electrode fingers extend along the first direction and are alternately arranged along a second direction, in the second direction, intersection portions of the first electrode fingers and the second electrode fingers form an aperture region, and a gap region is formed between the aperture region and the bus bars, and the first direction intersects the second direction. The elastic wave resonator further comprises a thin film layer which is arranged between the piezoelectric layer and the interdigital transducer and / or which is arranged on a side of the interdigital transducer away from the piezoelectric layer, and a normal projection of the thin film layer on the interdigital transducer is located in the gap region. A propagation speed Vgap of a sound wave in the gap region satisfies 0.9V0<Vgap<V0, V0<Vgap<1.1V0, wherein V0 is a propagation speed of a sound wave in the aperture region.

2. The elastic wave resonator according to claim 1, characterized by, The first bus bar comprises third electrode fingers arranged along the second direction, the second bus bar comprises fourth electrode fingers arranged along the second direction, the third electrode fingers are oppositely arranged to the second electrode fingers, the fourth electrode fingers are oppositely arranged to the first electrode fingers, the third electrode fingers and the fourth electrode fingers form a dummy finger region, the gap region is located between the dummy finger region and the aperture region, and a normal projection of the thin film layer on the interdigital transducer is located in the dummy finger region.

3. The elastic wave resonator according to claim 1 or 2, characterized by, A length of the gap region along the first direction is 0.1λ-2.5λ, and λ is a wavelength of the elastic wave.

4. The elastic wave resonator according to claim 1 or 2, characterized by, The thin film layer comprises a dielectric layer and / or a metal layer.

5. The elastic wave resonator according to claim 1 or 2, characterized by, The thin film layer is arranged on a side of the interdigital transducer away from the piezoelectric layer, and a length of the thin film layer along the first direction is less than or equal to a length of the gap region.

6. The elastic wave resonator according to claim 5, 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 arranged on a side of the gap region away from the bus bar, and a preset distance is arranged between an end of the thin film layer close to the bus bar and the bus bar.

7. The elastic wave resonator according to claim 1 or 2, characterized by, The thin film layer is arranged on a side of the interdigital transducer away from the piezoelectric layer, and covers all regions of the interdigital transducer located in the gap region.

8. A filter, characterized by The filter comprises at least one elastic wave resonator according to any one of claims 1-7.

9. A communication device, characterized by The filter comprises the filter according to claim 8.

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