A surface acoustic wave resonator and filter

Abstract

The application discloses a surface acoustic wave resonator and filter, which comprises a substrate, an interdigital transducer located on one side of the substrate, and a reflection grating arranged in the same layer as the interdigital transducer and located on both sides of the interdigital transducer along a first direction; a plurality of reflection gratings are arranged along the first direction and extend along a second direction; along the first direction, any two adjacent reflection gratings comprise a reflection grating gap; the first direction and the second direction are perpendicular to each other and parallel to the plane of the substrate; an acoustic impedance structure, the orthographic projection of the acoustic impedance structure on the plane of the substrate at least overlaps with the orthographic projection of the reflection grating gap on the plane of the substrate; the acoustic impedance of the acoustic impedance structure is different from the acoustic impedance of the reflection grating. By adopting the above technical means, the acoustic impedance structure is arranged, and the acoustic impedance of the acoustic impedance structure is different from the acoustic impedance of the reflection grating, so that the spurious mode in the resonator can be suppressed, and the performance of the surface acoustic wave resonator is improved.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the technical field of filter, and particularly relate to a surface acoustic wave resonator and a filter. BACKGROUND

[0002] With the development of communication technology and the re-allocation of spectrum resources, there is a new demand for high-performance surface acoustic wave devices capable of operating at higher frequencies and having a large electromechanical coupling coefficient.

[0003] In this context, longitudinal leaky surface acoustic wave resonators have attracted extensive attention. Similar to traditional surface acoustic wave devices, such devices also use an interdigital transducer electrode configured with a metal reflector, and the metal reflector is located on the left and right of the interdigital electrode. Due to the high phase velocity characteristics of the substrate, these devices can effectively excite longitudinal leaky surface acoustic wave modes, which helps to realize resonators with high frequency and large electromechanical coupling coefficient.

[0004] However, when the reflector and the interdigital transducer have similar center spacings, similar to traditional surface acoustic wave devices, the connection between the interdigital electrode and the reflector, i.e., the transition region, will produce strong scattering, resulting in spurious modes. When the longitudinal leaky surface acoustic wave resonator forms a filter, these spurious modes will seriously affect the insertion loss and flatness of the filter passband. SUMMARY

[0005] Therefore, embodiments of the present application provide a surface acoustic wave resonator and a filter to suppress spurious modes in the resonator, thereby improving the performance of the surface acoustic wave resonator.

[0006] In a first aspect, embodiments of the present application provide a surface acoustic wave resonator, comprising:

[0007] a substrate;

[0008] an interdigital transducer located on one side of the substrate;

[0009] a reflector disposed in the same layer as the interdigital transducer and located on both sides of the interdigital transducer along a first direction; a plurality of the reflectors are arranged along the first direction and each extends along a second direction; along the first direction, any two adjacent reflectors include a reflector gap; the first direction and the second direction are perpendicular to each other and parallel to the plane on which the substrate lies;

[0010] an acoustic impedance structure, a normal projection of the acoustic impedance structure on the plane on which the substrate lies at least overlaps with a normal projection of the reflector gap on the plane on which the substrate lies; the acoustic impedance of the acoustic impedance structure is different from the acoustic impedance of the reflector.

[0011] Optionally, a projection of the acoustic impedance structure on a plane where the substrate is located covers a projection of the reflector gap on the plane where the substrate is located and covers a projection of the reflector on the plane where the substrate is located.

[0012] Optionally, the acoustic impedance structure comprises a first surface away from a side of the substrate; the reflector comprises a second surface away from the side of the substrate.

[0013] The first surface is flush with the second surface; or the first surface is located at a side of the second surface close to the substrate.

[0014] Optionally, the substrate comprises a groove; the groove is located in the reflector gap.

[0015] In a thickness direction of the surface acoustic wave resonator, the groove penetrates through part of the substrate.

[0016] The acoustic impedance structure is located in the groove.

[0017] Optionally, in the thickness direction of the surface acoustic wave resonator, a depth of the groove is less than or equal to a thickness of the reflector.

[0018] Optionally, in the first direction, a width of the groove is less than or equal to a width of the reflector gap.

[0019] Optionally, the substrate comprises a support substrate and a piezoelectric layer arranged in a stack.

[0020] A thickness of the support substrate is greater than a thickness of the piezoelectric layer.

[0021] Optionally, a material of the acoustic impedance structure comprises silicon dioxide, silicon nitride, hafnium oxide or aluminum nitride.

[0022] Optionally, the interdigital transducer comprises interdigital electrodes and a first bus bar and a second bus bar located at two sides of the interdigital electrodes respectively in the second direction.

[0023] The plurality of interdigital electrodes comprises a plurality of first interdigital electrodes and a plurality of second interdigital electrodes; the first interdigital electrodes and the second interdigital electrodes are arranged alternately in a first direction and extend in a second direction.

[0024] The plurality of first interdigital electrodes are electrically connected to the first bus bar, and the plurality of second interdigital electrodes are electrically connected to the second bus bar.

[0025] In a second aspect, an embodiment of the present application further provides a filter comprising the surface acoustic wave resonator of any one of the first aspect.

[0026] The technical scheme provided by the embodiment of the present application can reduce the leakage of the surface acoustic wave, limit the surface acoustic wave in the central region of the interdigital transducer, and reduce the sound energy loss by arranging the reflection grating on both sides of the interdigital transducer along the first direction. In addition, the sound impedance structure is arranged, and the orthographic projection of the sound impedance structure on the plane where the substrate is located at least overlaps the orthographic projection of the reflection grating gap on the plane where the substrate is located. Since the sound impedance of the sound impedance structure is different from the sound impedance of the reflection grating, a sound velocity difference is generated at the positions of the reflection grating and the sound impedance structure when the surface acoustic wave is transmitted along the first direction, so that the leakage of the surface acoustic wave can be reduced, the spurious mode in the resonator can be inhibited, and the performance of the surface acoustic wave resonator can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 A top view schematic diagram of a first surface acoustic wave resonator provided by the embodiment of the present application is shown in FIG. 1.

[0028] Figure 2 A top view schematic diagram of a second surface acoustic wave resonator provided by the embodiment of the present application is shown in FIG. 2. Figure 1 A first cross-sectional structure schematic diagram along the cross-sectional line A-A' in FIG. 1 is shown in FIG. 3.

[0029] Figure 3 A top view schematic diagram of a second surface acoustic wave resonator provided by the embodiment of the present application is shown in FIG. 2.

[0030] Figure 4 A top view schematic diagram of a second surface acoustic wave resonator provided by the embodiment of the present application is shown in FIG. 2. Figure 3 A cross-sectional structure schematic diagram along the cross-sectional line B-B' in FIG. 2 is shown in FIG. 4.

[0031] Figure 5 A top view schematic diagram of a second surface acoustic wave resonator provided by the embodiment of the present application is shown in FIG. 2. Figure 1 A second cross-sectional structure schematic diagram along the cross-sectional line A-A' in FIG. 1 is shown in FIG. 5.

[0032] Figure 6 A top view schematic diagram of a second surface acoustic wave resonator provided by the embodiment of the present application is shown in FIG. 2. Figure 1 A third cross-sectional structure schematic diagram along the cross-sectional line A-A' in FIG. 1 is shown in FIG. 6.

[0033] Figure 7 A top view schematic diagram of a third surface acoustic wave resonator provided by the embodiment of the present application is shown in FIG. 7.

[0034] Figure 8 A top view schematic diagram of a second surface acoustic wave resonator provided by the embodiment of the present application is shown in FIG. 2. Figure 7 A first cross-sectional structure schematic diagram along the cross-sectional line C-C' in FIG. 7 is shown in FIG. 8.

[0035] Figure 9 A top view schematic diagram of a second surface acoustic wave resonator provided by the embodiment of the present application is shown in FIG. 2. Figure 7 A second cross-sectional structure schematic diagram along the cross-sectional line C-C' in FIG. 7 is shown in FIG. 9.

[0036] Figure 10 A top view schematic diagram of a second surface acoustic wave resonator provided by the embodiment of the present application is shown in FIG. 2.

[0037] Figure 11A schematic diagram of a filter structure provided in an embodiment of the present invention;

[0038] Figure 12 for Figure 11 Schematic diagram of the admittance response curves of parallel and series surface acoustic wave resonators in the corresponding filter;

[0039] Figure 13 for Figure 11 The corresponding schematic diagram of the transmission response curves of parallel and series surface acoustic wave resonators in the filter. Detailed Implementation

[0040] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0041] Figure 1 This is a top view schematic diagram of the first type of surface acoustic wave resonator provided in an embodiment of the present invention. Figure 2 for Figure 1 A schematic diagram of the first type of cross-sectional structure along section line A-A', as shown below. Figure 1 and Figure 2 As shown, the surface acoustic wave resonator 100 includes: a substrate 10; an interdigital transducer 20 located on one side of the substrate 10; and a reflective grating 30 disposed on the same layer as the interdigital transducer 20 and along a first direction (e.g., ...). Figure 1 The reflective gratings 30 (shown in the X direction) are located on both sides of the interdigital transducer 20; multiple reflective gratings 30 are arranged along the first direction X and all along the second direction (as shown in the X direction). Figure 1 The first direction X extends along the Y direction; any two adjacent reflective gratings 30 are separated by a reflective grating gap 40; the first direction X intersects the second direction Y and is parallel to the plane of the substrate 10; the acoustic impedance structure 50, the orthographic projection of the acoustic impedance structure 50 on the plane of the substrate 10 overlaps at least with the orthographic projection of the reflective grating gap 40 on the plane of the substrate 10; the acoustic impedance of the acoustic impedance structure 50 is different from the acoustic impedance of the reflective grating 30.

[0042] Specifically, substrate 10 can be a piezoelectric substrate. For example, the material of substrate 10 can be a substrate material with a high acoustic phase velocity, such as lithium niobate or lithium tantalate.

[0043] Specifically, the interdigital transducer 20 is located at the center of the surface acoustic wave resonator 100 and is responsible for converting electrical signals and acoustic wave signals. The interdigital transducer 20 includes interdigital electrodes 201 and a bus bar 202. When an alternating current signal of a certain frequency is applied to the bus bar 202, a surface acoustic wave can be generated in the surface acoustic wave resonator 100. The surface acoustic wave is mainly concentrated in the effective aperture area aa and mainly propagates along the first direction X, but part of the transverse wave will propagate and leak to the side of the bus bar 202 along the second direction Y.

[0044] It should be noted that the effective aperture area aa can be an area where the plurality of interdigital electrodes 201 overlap along the first direction X.

[0045] Specifically, the reflective grating 30 is disposed in the same layer as the interdigital transducer 20, that is, the reflective grating 30 and the interdigital transducer 20 can be made of the same material and are prepared in the same process step. The reflective grating 30 is located on both sides of the interdigital transducer 20 along the first direction X, that is, the reflective grating 30 can be located on the left and right sides of the interdigital transducer 20. In this way, by arranging the reflective grating 30, the leakage of the surface acoustic wave can be further reduced, that is, the reflective grating 30 can reflect the surface acoustic wave propagating in the horizontal direction back to the effective aperture area aa.

[0046] Specifically, along the first direction X, there is a reflective grating gap 40 between the two adjacent reflective gratings 30. The surface acoustic wave impedance structure 50 is at least overlapped with the projection of the reflective grating gap 40 on the plane of the substrate 10, that is, the surface acoustic wave impedance structure 50 can be arranged between the two adjacent reflective gratings 30. The acoustic impedance is a physical quantity describing the hindering effect of the medium on the surface acoustic wave when the surface acoustic wave propagates in the medium. The embodiment of the present application arranges the acoustic impedance of the acoustic impedance structure 50 to be different from the acoustic impedance of the reflective grating 30, that is, the acoustic impedance of the acoustic impedance structure 50 can be greater than the acoustic impedance of the reflective grating 30, and the acoustic impedance of the acoustic impedance structure 50 can also be less than the acoustic impedance of the reflective grating 30. In this way, the transmission speed of the surface acoustic wave in the acoustic impedance structure 50 is different from the transmission speed of the surface acoustic wave in the reflective grating 30, and then a speed difference occurs at the positions of the reflective grating 30 and the acoustic impedance structure 50 when the surface acoustic wave propagates along the first direction X, that is, a speed mutation occurs, and then the spurious mode can be suppressed and the surface acoustic wave can be limited in the effective aperture area aa.

[0047] The surface acoustic wave resonator provided by the embodiment of the present application arranges the acoustic impedance structure, and the projection of the acoustic impedance structure on the plane of the substrate is at least overlapped with the projection of the reflective grating gap on the plane of the substrate. Since the acoustic impedance of the acoustic impedance structure is different from the acoustic impedance of the reflective grating, a speed difference occurs at the positions of the reflective grating and the acoustic impedance structure when the surface acoustic wave propagates along the first direction, so the leakage of the surface acoustic wave can be reduced, the spurious mode in the resonator can be suppressed, and the performance of the surface acoustic wave resonator can be improved.

[0048] Optionally, Figure 3 A second top view schematic diagram of a surface acoustic wave resonator according to an embodiment of the present application is provided, Figure 4 A second cross-sectional structure schematic diagram along a cross-sectional line A-A' of the surface acoustic wave resonator is provided, Figure 3 As shown in Figure 3 , Figure 4 and , the acoustic impedance structure 50 covers the reflection gap 40 and the reflection grating 30 in the plane of the substrate 10.

[0049] Specifically, the acoustic impedance structure 50 covers the reflection gap 40 and the reflection grating 30 in the plane of the substrate 10, that is, the acoustic impedance structure 50 covers the upper surface of the reflection gap 40 and the reflection grating 30, and the thickness of the acoustic impedance structure 50 is greater than the thickness of the reflection grating 30, which is conducive to ensuring that the acoustic impedance of the reflection grating 30 is significantly different from the acoustic impedance of the acoustic impedance structure 50, thereby suppressing the leakage caused by high-order modes and reducing unnecessary acoustic energy loss. By covering the reflection gap 40 and the reflection grating 30 in the plane of the substrate 10, on the one hand, the acoustic impedance structure 50 can suppress the spurious modes in the resonator, and on the other hand, the preparation process of the acoustic impedance structure 50 is simple.

[0050] Specifically, in the preparation process of the surface acoustic wave resonator 100, after the interdigital transducer 20 and the reflection grating 30 are prepared, the acoustic impedance structure 50 can be directly prepared on the side of the reflection grating 30 away from the substrate 10, and the acoustic impedance structure 50 covers the reflection grating 30 and the reflection gap 40, so that the preparation process of the acoustic impedance structure 50 is simple.

[0051] Optionally, Figure 5 A second cross-sectional structure schematic diagram along a cross-sectional line A-A' of the surface acoustic wave resonator is provided, Figure 1 A second cross-sectional structure schematic diagram along a cross-sectional line A-A' of the surface acoustic wave resonator is provided, Figure 1 , Figure 2 and Figure 5 , the acoustic impedance structure 50 includes a first surface a1 away from the substrate 10; the reflection grating 30 includes a second surface a2 away from the substrate 10; the first surface a1 is flush with the second surface a2; or, the first surface a1 is located on the side of the second surface a2 close to the substrate 10.

[0052] As a feasible implementation manner, reference is made to Figure 1 and Figure 2, the first surface a1 can be understood as the upper surface of the acoustic impedance structure 50. The reflective grating 30 comprises a second surface a2 away from the substrate 10, that is, the second surface a2 can be understood as the upper surface of the reflective grating 30. The first surface a1 is flush with the second surface a2, that is, the first surface a1 is coplanar with the second surface a2. In other words, along the thickness direction (such as the Z direction shown in Figure 2 , the thickness of the acoustic impedance structure 50 is equal to the thickness of the reflective grating 30, so on the one hand, the acoustic impedance structure 50 can suppress the spurious mode in the resonator, and on the other hand, the flexibility of the thickness of the acoustic impedance structure 50 can be realized, thereby realizing the diversified setting of the surface acoustic wave resonator 100.

[0053] As another possible implementation, with reference to Figure 5 , the first surface a1 is located on the side of the second surface a2 close to the substrate 10, that is, compared with the second surface a2, the first surface a1 is closer to the substrate 10. In other words, along the thickness direction Z of the surface acoustic wave resonator, the thickness of the acoustic impedance structure 50 is less than the thickness of the reflective grating 30, so on the one hand, the acoustic impedance structure 50 can suppress the spurious mode in the resonator, and on the other hand, the flexibility of the thickness of the acoustic impedance structure 50 can be realized, thereby realizing the diversified setting of the surface acoustic wave resonator 100.

[0054] In the preparation process of the surface acoustic wave resonator 100, after the interdigital transducer 20 and the reflective grating 30 are prepared, the acoustic impedance layer is prepared on the side of the reflective grating 30 away from the substrate 10, the acoustic impedance layer covers the reflective grating 30 and the reflective grating gap 40, and the acoustic impedance structure 50 is formed by patterning the acoustic impedance layer, so that the first surface a1 is flush with the second surface a2 or the first surface a1 is located on the side of the second surface a2 close to the substrate 10.

[0055] It should be noted that if the acoustic impedance of the acoustic impedance structure 50 is greatly different from the acoustic impedance of the reflective grating 30, the thickness of the acoustic impedance structure 50 can be set to be smaller. The specific thickness of the acoustic impedance structure 50 can be set by those skilled in the art according to specific acoustic impedance requirements.

[0056] Optionally, Figure 6 , as shown in Figure 1 , the third cross-sectional structure along the cross-sectional line A-A' is shown in Figure 1 and Figure 6 , the substrate 10 comprises a groove 60; the groove 60 is located in the reflective grating gap 40; along the thickness direction Z of the surface acoustic wave resonator, the groove 60 penetrates part of the substrate 10; and the acoustic impedance structure 50 is located in the groove 60.

[0057] Specifically, the recess 60 is formed on the upper surface of the substrate 10, and the acoustic impedance structure 50 is arranged in the recess 60, so that the acoustic impedance structure 50 can suppress the spurious mode in the resonator, and the acoustic impedance structure 50 can be arranged flexibly, and the acoustic surface wave resonator 100 can be arranged diversely.

[0058] Specifically, in the preparation process of the acoustic surface wave resonator 100, after the interdigital transducer 20 and the reflector 30 are prepared, the recess 60 is prepared on the upper surface of the substrate 10, the recess 60 penetrates part of the substrate 10 along the thickness direction Z of the acoustic surface wave resonator, and then the acoustic impedance layer is prepared on the side of the reflector 30 away from the substrate 10, and the acoustic impedance structure 50 is formed by patterning the acoustic impedance layer.

[0059] Optionally, continuing to refer to Figure 6 The depth of the recess 60 is less than or equal to the thickness of the reflector 30 along the thickness direction Z of the acoustic surface wave resonator.

[0060] Specifically, when the depth of the recess 60 is greater than the thickness of the reflector 30, that is, the depth of the recess 60 is large, on the one hand, the substrate 10 is easy to be etched through in the etching process of the substrate 10, and then the piezoelectric performance of the substrate is affected, and the performance of the acoustic surface wave resonator 100 is affected, on the other hand, the depth of the recess 60 is large, and then more acoustic impedance material is needed to fill the recess 60, so that the preparation cost is increased.

[0061] As a feasible implementation, the depth of the recess 60 is less than the thickness of the reflector 30, so that the depth of the recess 60 is moderate, the preparation process of the recess 60 is simple, and the suppression effect of the acoustic impedance structure 50 on the spurious mode is ensured.

[0062] As another feasible implementation, the depth of the recess 60 is equal to the thickness of the reflector 30, so that the thickness of the acoustic impedance structure 50 can be arranged flexibly, and the acoustic surface wave resonator can be arranged diversely.

[0063] Specifically, the thickness of the acoustic impedance structure 50 can be 100 nm, and the thickness of the substrate 10 can be 250 nm.

[0064] Optionally, Figure 7 a third top view schematic diagram of the acoustic surface wave resonator is provided for the embodiment of the present application, Figure 8 a first cross-sectional structure schematic diagram along the cross-sectional line C-C’ in the Figure 7 a second cross-sectional structure schematic diagram along the cross-sectional line C-C’ in the Figure 9 a second cross-sectional structure schematic diagram along the cross-sectional line C-C’ in the Figure 7 refer to Figure 1 andFigures 6-9 As shown, along the first direction X, the width of the groove 60 is less than or equal to the width of the reflector gap 40.

[0065] As a feasible implementation, with continued reference to Figure 1 and Figure 6 , along the first direction X, the width of the groove 60 is equal to the width of the reflector gap 40, that is, the orthogonal projection of the groove 60 on the plane where the substrate 10 is located coincides with the orthogonal projection of the reflector gap 40 on the plane where the substrate 10 is located, so as to on the one hand inhibit the spurious mode in the resonator, and on the other hand realize the diversified setting of the surface acoustic wave resonator.

[0066] As another feasible implementation, with continued reference to Figure 7 and Figure 8 , along the first direction X, the width of the groove 60 is less than the width of the reflector gap 40, that is, the orthogonal projection of the reflector gap 40 on the plane where the substrate 10 is located covers the orthogonal projection of the groove 60 on the plane where the substrate 10 is located, so as to on the one hand reduce the alignment difficulty between the groove 60 and the reflector gap 40 in the process of preparing the groove 60, and further simplify the preparation process of the groove 60, and on the other hand realize the flexibility of the setting of the acoustic impedance structure 50 and the flexibility of the size setting of the groove 60, which is conducive to realizing the diversified setting of the surface acoustic wave resonator 100.

[0067] Exemplarily, Figure 8 it is shown that the width of the acoustic impedance structure 50 located in the groove 60 along the first direction X is equal to the width of the acoustic impedance structure 50 located outside the groove 60 along the first direction X, that is, the cross-sectional view of the acoustic impedance structure 50 is similar to a rectangle. With continued reference to Figure 8 , along the first direction X, there is a gap between the reflector 30 and the acoustic impedance structure 50, so that when the surface acoustic wave transmits along the first direction X, the acoustic velocity of the surface acoustic wave at the positions of “reflector 30 - gap between the reflector 30 and the acoustic impedance structure 50 - acoustic impedance structure 50” are all different, thereby being able to produce an acoustic velocity mutation, and further confine the surface acoustic wave in the effective aperture region. Exemplarily, Figure 9 it is shown that the width of the acoustic impedance structure 50 located outside the groove 60 along the first direction X is greater than the width of the acoustic impedance structure 50 located in the groove 60 along the first direction X, that is, the cross-sectional view of the acoustic impedance structure 50 is similar to a “T” shape, so as to on the one hand simplify the preparation mode of the acoustic impedance structure 50, and on the other hand be conducive to realizing the diversified setting of the surface acoustic wave resonator 100.

[0068] Optionally, with continued reference to Figure 2 , the substrate 10 comprises a support substrate 101 and a piezoelectric layer 102 which are arranged in a stack; the thickness of the support substrate 101 is greater than the thickness of the piezoelectric layer 102.

[0069] Specifically, the substrate 10 includes two layers of film layers arranged in a stack, so as to ensure the support effect of the upper film layer by the support substrate 101, and the bandwidth and Q value of the surface acoustic wave resonator 100 can be improved by arranging the piezoelectric layer 102.

[0070] Specifically, the thickness of the support substrate 101 is greater than the thickness of the piezoelectric layer 102, which is conducive to reducing the warping, cracking or thermal stress in the preparation process of the surface acoustic wave resonator 100, and thus the stability and reliability of the surface acoustic wave resonator can be improved.

[0071] Specifically, the thickness of the support substrate 101 is greater than the thickness of the piezoelectric layer 102, which is conducive to reducing the warping, cracking or thermal stress in the preparation process of the surface acoustic wave resonator 100, and thus the stability and reliability of the surface acoustic wave resonator can be improved.

[0072] Specifically, the thickness of the support substrate 101 is greater than the thickness of the piezoelectric layer 102, which is conducive to reducing the warping, cracking or thermal stress in the preparation process of the surface acoustic wave resonator 100, and thus the stability and reliability of the surface acoustic wave resonator can be improved.

[0073] Optionally, continuing to refer to Figure 1 The material of the acoustic impedance structure 50 includes silicon dioxide, silicon nitride, hafnium oxide or aluminum nitride.

[0074] Figure 10 A schematic diagram of the admittance response curve of the surface acoustic wave resonator provided by the embodiment of the present application is shown in FIG. 2. Figure 10As shown, curve b1 represents the admittance amplitude curve of the prior art without the acoustic impedance structure, curve b2 represents the admittance amplitude curve of the embodiment of the present application with the acoustic impedance structure and the material of the acoustic impedance structure being silicon nitride, curve b3 represents the admittance amplitude curve of the embodiment of the present application with the acoustic impedance structure and the material of the acoustic impedance structure being silicon dioxide, and curve b4 represents the admittance amplitude curve of the embodiment of the present application with the acoustic impedance structure and the material of the acoustic impedance structure being hafnium oxide. By comparing curve b1, curve b2, curve b3 and curve b4, it can be found that the general shapes of curve b1, curve b2, curve b3 and curve b4 are the same, which indicates that the embodiment of the present application can ensure that the main mode phase velocity and the electromechanical coupling coefficient of the surface acoustic wave resonator are unchanged by setting the acoustic impedance structure. In addition, curve b1 has a significant spurious mode between the resonance frequency and the anti-resonance frequency, that is, curve b1 has burrs when the frequency is between 4800 MHz and 5200 MHz, and the smoothness of curve b1 is low. However, curve b2, curve b3 and curve b4 are smoother than curve b1 in this frequency range, which indicates that the embodiment of the present application can suppress the spurious mode caused by the leakage of the high-order mode by setting the acoustic impedance structure and using silicon dioxide, silicon nitride, hafnium oxide or aluminum nitride as the material of the acoustic impedance structure, so as to obtain a response curve with almost no spurious mode, that is, the spurious mode caused by the scattering of acoustic waves at the reflective grating and the interdigital transducer due to the high-order harmonic mode can be significantly suppressed, which enables the formed filter to achieve better in-band filtering performance, that is, smaller insertion loss and smaller in-band ripple, thereby facilitating the improvement of the performance of the surface acoustic wave resonator.

[0075] It should be noted that when the material of the acoustic impedance structure includes silicon dioxide, it can not only suppress the spurious mode, but also improve the frequency temperature coefficient of the surface acoustic wave resonator, thereby further improving the performance of the surface acoustic wave resonator.

[0076] Optionally, continuing to refer to Figure 1 The interdigital transducer 20 includes the interdigital electrodes 201, the first bus bar 21 and the second bus bar 22 located on both sides of the interdigital electrodes 201 along the second direction Y; the plurality of interdigital electrodes 201 include a plurality of first interdigital electrodes 2011 and a plurality of second interdigital electrodes 2012; the first interdigital electrodes 2011 and the second interdigital electrodes 2012 are alternately arranged along the first direction X and extend along the second direction Y; the plurality of first interdigital electrodes 2011 are electrically connected to the first bus bar 21, and the plurality of second interdigital electrodes 2012 are electrically connected to the second bus bar 22.

[0077] Specifically, both the first interdigital electrode 2011 and the second interdigital electrode 2012 can be long finger electrodes, i.e., true finger electrodes. The first interdigital electrode 2011 and the second interdigital electrode 2012 are alternately arranged along the first direction X and both extend along the second direction Y; multiple first interdigital electrodes 2011 are electrically connected to the first bus bar 21, and multiple second interdigital electrodes 2012 are electrically connected to the second bus bar 22. Thus, the shape formed by multiple first interdigital electrodes 2011 and the first bus bar 21 is similar to a comb, and the shape formed by multiple second interdigital electrodes 2012 and the second bus bar 22 is similar to a comb, in order to ensure signal transmission efficiency.

[0078] For example, the interdigital transducer 20 can be made of at least one of copper, aluminum, titanium, tungsten, and silver. The interdigital transducer 20 can be made of a single metal material or an alloy composed of multiple metal materials.

[0079] It should be noted that the interdigital transducer 20 may also include a third interdigital electrode ( Figure 1 (not shown in the image) and the fourth interdigital electrode ( Figure 1 (Not shown in the diagram). The first interdigital electrode 2011 and the third interdigital electrode are arranged alternately along the first direction X and both extend along the second direction Y. The second interdigital electrode 2012 and the fourth interdigital electrode are arranged alternately along the first direction X and both extend along the second direction Y. The first interdigital electrode 2011 and the third interdigital electrode are both electrically connected to the first busbar 21, and the second interdigital electrode 2012 and the fourth interdigital electrode are both electrically connected to the second busbar 22. The extension length of the third interdigital electrode and the fourth interdigital electrode along the second direction Y is less than the extension length of the first interdigital electrode 2011 and the second interdigital electrode 2012 along the second direction Y, that is, the third interdigital electrode and the fourth interdigital electrode are short interdigital electrodes, i.e., pseudo-interdigital electrodes. By setting the third interdigital electrode and the fourth interdigital electrode, the surface acoustic wave leaking along the second direction Y can be reflected back to the effective aperture region aa, thereby further reducing the leakage of surface acoustic wave and improving the performance of the surface acoustic wave resonator.

[0080] Based on the same inventive concept, this invention also provides a filter. Figure 11 A schematic diagram of a filter structure provided in an embodiment of the present invention is shown below. Figure 11 As shown, the filter 1000 includes the surface acoustic wave (SAW) resonator 100 described in the above embodiments. The filter 1000 includes at least one parallel SAW resonator 1001 and at least one series SAW resonator 1002. The series SAW resonator 1002 is connected in series in the loop between the input terminal 200 and the output terminal 300. One end of the parallel SAW resonator 1001 is connected in the loop between the input terminal 200 and the output terminal 300, and the other end is grounded.

[0081] Specifically, Figure 12 For Figure 11 The schematic diagram of the admittance response curve of the parallel SAW resonator and the series SAW resonator in the corresponding filter is shown in Fig. 3. Figure 12 As shown in Fig. 3, the curve c1 represents the admittance amplitude curve of the parallel SAW resonator in the prior art, the curve c2 represents the admittance amplitude curve of the series SAW resonator in the prior art, the curve c3 represents the admittance amplitude curve of the parallel SAW resonator in the embodiment of the present application, and the curve c4 represents the admittance amplitude curve of the series SAW resonator in the embodiment of the present application. When the frequency is at 4800-5000 MHz, the admittance amplitude curve corresponding to the curve c2 has a burr, while the admittance amplitude curve corresponding to the curve c4 is relatively smooth without burr. This shows that the series SAW resonator in the embodiment of the present application can suppress the spurious mode in the resonator by setting the acoustic impedance structure, thereby improving the performance of the series SAW resonator.

[0082] When the frequency is at 4400 MHz, the admittance amplitude curve corresponding to the curve c1 has a burr, while the admittance amplitude curve corresponding to the curve c3 is relatively smooth without burr. This shows that the parallel SAW resonator in the embodiment of the present application can suppress the spurious mode in the resonator by setting the acoustic impedance structure, thereby improving the performance of the parallel SAW resonator and the performance of the filter.

[0083] Figure 13 For Figure 11 The schematic diagram of the transmission response curve of the parallel SAW resonator and the series SAW resonator in the corresponding filter is shown in Fig. 4. Figure 13 As shown in Fig. 4, the black solid line represents the transmission response curve of the filter in the prior art, and the red dashed line represents the transmission response curve of the filter provided in the embodiment of the present application. As can be seen from the comparison of the d1 position and the d2 position, the black curve has burrs at the two positions, i.e., there are significant in-band waves at the d1 position and the d2 position. However, the red curve corresponding to the embodiment of the present application is relatively smooth at the two positions, i.e., the performance of the filter can present a smooth in-band response by setting the acoustic impedance structure.

[0084] Note that the above is only the preferred embodiment of the present application and the applied technical principle. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and those skilled in the art can make various obvious changes, re-adjustments, mutual combinations and substitutions without departing from the protection scope of the present application. Therefore, although the present application has been described in more detail through the above embodiments, the present application is not limited to the above embodiments, and can include more other equivalent embodiments without departing from the concept of the present application, and the scope of the present application is determined by the appended claims.

Claims

1. A surface acoustic wave resonator, characterized by, The application relates to a surface acoustic wave resonator. The application relates to a surface acoustic wave resonator. The application relates to a surface acoustic wave resonator. The application relates to a surface acoustic wave resonator. The application relates to a surface acoustic wave resonator. The application relates to a surface acoustic wave resonator. The application relates to a surface acoustic wave resonator. The application relates to a surface acoustic wave resonator. The application relates to a surface acoustic wave resonator.

2. The SAW resonator according to claim 1, wherein, The application relates to a surface acoustic wave resonator.

3. The SAW resonator of claim 1, wherein, The application relates to a surface acoustic wave resonator. The application relates to a surface acoustic wave resonator.

4. The SAW resonator of claim 1, wherein, The application relates to a surface acoustic wave resonator.

5. The SAW resonator of claim 1, wherein, The application relates to a surface acoustic wave resonator. The application relates to a surface acoustic wave resonator.

6. The SAW resonator of claim 1, wherein, The application relates to a surface acoustic wave resonator.

7. The SAW resonator of claim 1, wherein, The application relates to a surface acoustic wave resonator. The application relates to a surface acoustic wave resonator. The application relates to a surface acoustic wave resonator.

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