A surface acoustic wave resonator

Abstract

The embodiment of the present invention discloses a surface acoustic wave resonator, comprising: a piezoelectric substrate; an interdigital transducer structure, located on one side of the piezoelectric substrate; the interdigital transducer structure comprises two bus bars arranged opposite to each other, and a plurality of electrode fingers arranged side by side between the two bus bars; each electrode finger is electrically connected to one of the bus bars alternately; a plurality of dummy fingers, each dummy finger being correspondingly located between an end of an electrode finger and a bus bar on the opposite side; along a direction parallel to the bus bar, the width of the dummy finger is equal to the width of the electrode bar; a sound velocity mutation structure is arranged on a side of the dummy finger, the electrode finger and the grid conductor of the reflection grid close to the piezoelectric substrate, a side away from the piezoelectric substrate, or on a layer where the dummy finger, the electrode finger and the reflection grid are located; this structure can effectively suppress the lateral mode while ensuring the Q value of the resonator by arranging the sound velocity mutation structure at a position close to the dummy finger, the electrode finger and the reflection grid.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of surface acoustic wave devices, and in particular to a surface acoustic wave resonator. Background Art

[0002] In modern communication systems, filters are often used to filter out unnecessary signals outside the target communication frequency band. Surface acoustic wave (SAW) resonators have been widely used in high-frequency filter design due to their advantages such as high Q value, small size, high reliability, and easy mass production. SAW is generally composed of a piezoelectric substrate, an interdigital transducer (IDT), and a reflective grating, and is produced using semiconductor technology.

[0003] Usually, while SAW resonators excite the main wave mode, they will also generate unwanted transverse modes. In the frequency response of the SAW filter, the transverse mode will introduce spurious responses, reduce the Q value of the IDT, increase the insertion loss of the filter, and have a significant impact on the performance of the device. This is mainly caused by energy leakage, especially in heterogeneous semiconductor films. Existing transverse mode suppression methods, such as adding dummy fingers (false fingers) to the bus bar on the opposite side of the plug finger (electrode finger), the width and thickness of the dummy are generally consistent with the plug finger (electrode finger), but the transverse mode suppression effect is not good. For example, the method of dummy finger weighting, although it has a better effect in suppressing the transverse mode, it may affect the resonator Q value and increase the filter loss. Therefore, how to effectively suppress the transverse mode excited by the SAW resonator has always been a major challenge in engineering design. Summary of the invention

[0004] The embodiment of the present invention provides a surface acoustic wave resonator, which can effectively suppress the transverse mode while ensuring the Q value of the resonator.

[0005] An embodiment of the present invention provides a surface acoustic wave resonator, comprising:

[0006] Piezoelectric substrate;

[0007] An interdigital transducing structure is located on one side of the piezoelectric substrate; the interdigital transducing structure comprises two bus bars arranged opposite to each other, and a plurality of electrode fingers arranged side by side between the two bus bars; each electrode finger is alternately electrically connected to one of the bus bars;

[0008] A plurality of dummy fingers, each dummy finger being located between an end of the electrode finger and a bus bar on the opposite side; along a direction parallel to the bus bar, a width of the dummy finger is equal to a width of the electrode bar;

[0009] A first sound velocity mutation structure, wherein the first sound velocity mutation structure is located at least one of a side of the dummy finger away from the piezoelectric substrate, a side of the dummy finger close to the piezoelectric substrate, and a layer where the dummy finger is located; along a direction parallel to the bus bar, a width of the first sound velocity mutation structure is greater than a width of the dummy finger.

[0010] Optionally, the first sound velocity mutation structure includes a plurality of load blocks, each load block is located at the end of a corresponding dummy finger; the load blocks located at the ends of the same row of dummy fingers are equidistant from the ends of the opposite electrode fingers.

[0011] Optionally, the first sound velocity mutation structure includes multiple load blocks; the vertical projection of each load block on the piezoelectric substrate partially overlaps with the vertical projection of a dummy finger on the piezoelectric substrate; the distance from the load block at the end of the same row of dummy fingers to the end of the opposite electrode finger increases or decreases.

[0012] Optionally, the first sound velocity mutation structure includes multiple load blocks; the vertical projection of each load block on the piezoelectric substrate partially overlaps with the vertical projection of a dummy finger on the piezoelectric substrate; the distances from the load blocks at the ends of the same row of dummy fingers to the ends of the opposite electrode fingers are alternately equal.

[0013] Optionally, along a direction parallel to the bus bar, the width of each load block is less than or equal to the width between two adjacent electrode fingers located on two sides thereof.

[0014] Optionally, the first sound velocity mutation structure includes two load bars, which are arranged opposite to each other and are both parallel to the bus bar; along the direction parallel to the bus bar, the width of the load bar is greater than or equal to the width of the bus bar.

[0015] Optionally, the surface acoustic wave resonator also includes a passivation layer, which covers the side of the electrode fingers and the dummy fingers away from the piezoelectric substrate, and the piezoelectric substrate not covered by the electrode fingers and the dummy fingers; the first sound velocity mutation structure is located on the side of the passivation layer away from the piezoelectric substrate; the material of the first sound velocity mutation structure includes a polymer coating material.

[0016] Optionally, the first sound velocity mutation structure includes two load layers, and the vertical projection of each load layer on the piezoelectric substrate covers a corresponding dummy finger area; along the direction parallel to the bus bar, the width of the dummy finger area is greater than or equal to the width of the bus bar, and along the direction perpendicular to the bus bar, the length of the dummy finger area is equal to the length of the dummy finger.

[0017] Optionally, the surface acoustic wave resonator further comprises:

[0018] a second sound velocity mutation structure, the second sound velocity mutation structure being located at at least one of a side of the electrode finger away from the piezoelectric substrate, a side of the electrode finger close to the piezoelectric substrate, and a layer where the electrode finger is located; along a direction parallel to the bus bar, a width of the second sound velocity mutation structure is greater than a width of the electrode finger;

[0019] a pair of reflection gratings, wherein the reflection gratings are located on the same side of the piezoelectric substrate and the interdigital transducing structure, and are respectively located on two opposite sides of the interdigital transducing structure;

[0020] A third sound velocity mutation structure is located at least one of a side of the reflection grating away from the piezoelectric substrate, a side of the reflection grating close to the piezoelectric substrate, and a layer where the reflection grating is located; along a direction parallel to the bus bar, a width of the third sound velocity mutation structure is greater than a width of half a period of the reflection grating.

[0021] Optionally, the piezoelectric substrate includes a silicon layer and a polysilicon layer, a silicon oxide layer and a lithium niobate crystal layer sequentially formed on the silicon layer.

[0022] An embodiment of the present invention provides a surface acoustic wave resonator, comprising: a piezoelectric substrate; an interdigital transducer structure, located on one side of the piezoelectric substrate; the interdigital transducer structure comprises two bus bars arranged opposite to each other, and a plurality of electrode fingers arranged side by side between the two bus bars; each electrode finger is electrically connected alternately to one of the bus bars; a plurality of dummy fingers, each dummy finger being correspondingly located between an end of an electrode finger and the bus bar on the opposite side; along a direction parallel to the bus bar, the width of the dummy finger is equal to the width of the electrode bar; a first sound velocity mutation structure, the first sound velocity mutation structure being located on a side of the dummy finger away from the piezoelectric substrate, a side of the dummy finger close to the piezoelectric substrate, and at least one of the layers where the dummy finger is located; along a direction parallel to the bus bar, the width of the first sound velocity mutation structure is greater than the width of the dummy finger. The technical solution provided by the embodiment of the present invention is to set a first sound velocity mutation structure on the side of the dummy finger away from the piezoelectric substrate, the side of the dummy finger close to the piezoelectric substrate, and at least one place in the layer where the dummy finger is located, so that the lateral mode can be suppressed by adjusting the lateral acoustic velocity distribution. Compared with the method of only using dummy fingers in the prior art, the lateral mode can be further effectively suppressed, and the use of the dummy finger weighting method to affect the resonator Q value can be avoided. Therefore, while effectively suppressing the lateral mode, the Q value of the resonator is guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a structural schematic diagram of a surface acoustic wave resonator provided by an embodiment of the present invention and a corresponding partial velocity spectrum;

[0024] Figure 2 It is a structural schematic diagram of a surface acoustic wave resonator provided in the prior art and a corresponding partial velocity spectrum;

[0025] Figure 3 is a schematic structural diagram of another surface acoustic wave resonator provided by an embodiment of the present invention and a corresponding partial velocity spectrum;

[0026] Figure 4 is a schematic structural diagram of another surface acoustic wave resonator provided by an embodiment of the present invention and a corresponding partial velocity spectrum;

[0027] Figure 5 It is a comparison diagram of the amplitude values ​​of the admittance curves of a surface acoustic wave resonator with and without a load block provided by an embodiment of the present invention;

[0028] Figure 6 It is a comparison diagram of the real part of the admittance in the admittance curve of a surface acoustic wave resonator with and without a load block provided by an embodiment of the present invention;

[0029] Figure 7 is a schematic structural diagram of another surface acoustic wave resonator provided by an embodiment of the present invention;

[0030] Figure 8 is a schematic structural diagram of another surface acoustic wave resonator provided by an embodiment of the present invention;

[0031] Fig. 9 is a schematic structural diagram of another surface acoustic wave resonator provided by an embodiment of the present invention;

[0032] Fig.10 is a schematic structural diagram of another surface acoustic wave resonator provided by an embodiment of the present invention;

[0033] Fig.11 is a schematic structural diagram of another surface acoustic wave resonator provided by an embodiment of the present invention and a corresponding partial velocity spectrum;

[0034] Fig.12 yes Fig.11 Cross-section along AA1. DETAILED DESCRIPTION

[0035] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0036] An embodiment of the present invention provides a surface acoustic wave resonator. Figure 1 is a schematic diagram of the structure of a surface acoustic wave resonator provided by an embodiment of the present invention and a corresponding partial velocity spectrum, reference Figure 1 , the surface acoustic wave resonator includes:

[0037] Piezoelectric substrate (not shown);

[0038] The interdigital transducer structure 20 is located on one side of the piezoelectric substrate; the interdigital transducer structure 20 includes two bus bars 21 disposed opposite to each other, and a plurality of electrode fingers 22 disposed side by side between the two bus bars 21; each electrode finger 22 is alternately electrically connected to one of the bus bars 21;

[0039] A plurality of dummy fingers 30, each dummy finger 30 is located between an end of an electrode finger 22 and the opposite bus bar 21; along a direction parallel to the bus bar 21, the width of the dummy finger 30 is equal to the width of the electrode bar;

[0040] A first sound velocity mutation structure 40 is located at a side of the dummy finger 30 away from the piezoelectric substrate, a side of the dummy finger 30 close to the piezoelectric substrate, and at least one of the layers where the dummy finger 30 is located; along a direction parallel to the bus bar 21, the width of the first sound velocity mutation structure 40 is greater than the width of the dummy finger 30.

[0041] Specifically, the finger transducer structure 20 is a finger transducer, which can be understood as a metal pattern shaped like the crossed fingers of two hands formed on the surface of the piezoelectric substrate, and its function is to realize acoustic-electric transduction. The finger transducer structure 20 includes a first bus bar, a second bus bar and a plurality of electrode fingers 22; the first bus bar and the second bus bar are arranged opposite to each other; along the direction parallel to the bus bar 21, a plurality of electrode fingers 22 are arranged side by side between the first bus bar 21 and the second bus bar 21, and are alternately electrically connected to the first bus bar 21 and the second bus bar 21 in turn, and the electrode fingers 22 that bite each other are used to excite the sound wave. In the direction of sound wave propagation, the sound trajectory is usually limited by a reflector to reduce the energy loss caused by the emission of the sound wave in the horizontal direction. The reflector may include a pair of reflection gratings 50, which are located on the same side of the piezoelectric substrate and the finger transducer structure 20, and on opposite sides of the finger transducer structure 20. The dummy finger 30 is disposed between the end of each electrode finger 22 and the bus bar 21 to suppress lateral leakage of energy and confine more energy within the resonator, thereby improving the Q value of the resonator.

[0042] The speed of the acoustic wave at the surface of the piezoelectric substrate depends on the mass distribution of the piezoelectric substrate, i.e. the mass of the layers arranged on the piezoelectric substrate. Here, the higher the mass distribution, the slower the acoustic wave, and the higher the elastic constant of the material of the mass distribution, the faster the acoustic wave. In the direction perpendicular to the busbar 21, the converter is constructed so that the acoustic wave has different lateral propagation speeds in a plurality of regions extending parallel to the acoustic track. The lateral direction is a direction parallel to the busbar 21. Therefore, the widening of the pseudo fingers 30 limited to the inner edge region is a simple but effective means to reduce the lateral speed in the inner edge region.

[0043] On this basis, a first sound velocity mutation structure 40 is set on a side of the dummy finger 30 away from the piezoelectric substrate, a side of the dummy finger 30 close to the piezoelectric substrate, and at least one place in the layer where the dummy finger 30 is located, and the width of the first sound velocity mutation structure 40 is set to be greater than the width of the dummy finger 30 along a direction parallel to the bus bar 21. Figure 1 In the figure, it is shown that the first sound velocity mutation structure 40 is set on the side of the dummy finger 30 away from the piezoelectric substrate. The first sound velocity mutation structure 40 is set to be wider than the width of the dummy finger 30, and the mass distribution of this area is larger than the dummy finger 30 on the upper side and the gap area on the lower side, so the lateral velocity at the position of the first sound velocity mutation structure 40 is the smallest. The gap area on the lower side of the first sound velocity mutation structure 40 has the smallest mass, so the lateral velocity of the gap area is the largest. Figure 2 This is a schematic diagram of the structure of a surface acoustic wave resonator provided in the prior art and the corresponding partial velocity spectrum. Figure 1 and Figure 2 The setting of the first sound velocity mutation structure 40 can increase the amplitude of the sound velocity mutation, so that the transverse mode can be suppressed by adjusting the transverse acoustic velocity distribution.

[0044] The first sound velocity mutation structure 40 can be a load block 41, a load bar or a load layer. The material of the first sound velocity mutation structure 40 can be a metal material, an oxide material, a polymer coating material, etc., preferably a metal material. The first sound velocity mutation structure 40 is generally in a different layer from the dummy finger 30, or can be in the same layer. Compared with the method of only using the dummy finger 30 in the prior art, the lateral mode can be further effectively suppressed, and the weighting method of the dummy finger 30 can be avoided to affect the Q value of the resonator. Therefore, while effectively suppressing the lateral mode, the Q value of the resonator is guaranteed.

[0045] A surface acoustic wave resonator provided by an embodiment of the present invention provides a first sound velocity mutation structure 40 on the side of the dummy finger 30 away from the piezoelectric substrate, the side of the dummy finger 30 close to the piezoelectric substrate, and at least one place in the layer where the dummy finger 30 is located, and the finger is thickened and widened according to the material parameters, providing the possibility of changing the mass distribution. By adjusting the thickness and width of the finger, the sound velocity can be easily adjusted to obtain an improved piston mode. The characteristic of the piston mode is that there is no or at most a minimum sound wave propagating in the lateral direction. Therefore, realizing the piston mode is an effective means to reduce the energy loss caused by the lateral emission of the sound wave from the sound track, and at the same time achieve improved performance by suppressing the lateral mode. Compared with the method of only using the dummy finger 30 in the prior art, the lateral mode can be further effectively suppressed, and the weighting method of the dummy finger 30 can be avoided to affect the resonator Q value.

[0046] In one embodiment of the present invention, reference Figure 3 , Figure 4 and Figure 7 to Figure 11, a surface acoustic wave resonator, further comprising:

[0047] A second sound velocity mutation structure 60 is located at a side of the electrode finger 22 away from the piezoelectric substrate, a side of the electrode finger 22 close to the piezoelectric substrate, and at least one of the layers where the electrode finger 22 is located; along a direction parallel to the bus bar 21, the width of the second sound velocity mutation structure 60 is greater than the width of the electrode finger 22.

[0048] The second sound velocity mutation structure 60 can be a load block, which is arranged at the end of the electrode finger 22 and the corresponding lateral position of the electrode finger 22 with opposite polarity, so as to improve the acoustics of the resonator by establishing a piston mode. The use of a piston mode electroacoustic transducer structure can form an acoustic waveguide in the horizontal direction, reduce the sound waves propagating in the vertical direction, and achieve the effect of suppressing the lateral mode.

[0049] contrast Figure 4 and Figure 3 , Figure 4 The structure shown is a piston mode electroacoustic transducer structure in which the dummy finger 30 and the first sound velocity mutation structure 40 are not provided, and only the second sound velocity mutation structure 60 is provided at the end of the electrode finger 22 and the corresponding lateral position of the electrode finger 22 with opposite polarity. It is known that the piston mode electroacoustic transducer structure can form an acoustic waveguide in the horizontal direction, reduce the sound waves propagating in the vertical direction, and achieve the effect of suppressing the transverse mode. However, due to the diffraction of the wave, part of the sound wave can also excite the transverse mode through the piston gap. Figure 3 The structure shown is a piston mode electroacoustic transducer structure in which a second sound velocity mutation structure 60 of a pseudo finger 30 is added, so as to form a second acoustic waveguide structure and enhance the lateral mode suppression effect. Figure 3 It is shown in the figure as an example that the width of the first sound velocity jump structure 40 on the dummy finger 30 is greater than the width of the second sound velocity jump structure 60 on the electrode finger 22 .

[0050] In addition, the surface acoustic wave resonator may further include a third sound velocity mutation structure 70, which is located at a side of the reflection grid 50 away from the piezoelectric substrate, a side of the reflection grid 50 close to the piezoelectric substrate, and at least one of the layers where the reflection grid 50 is located; along the direction parallel to the bus bar 21, the width of the third sound velocity mutation structure 70 is greater than the width of half a period of the reflection grid 50. By constructing the sound velocity mutation structure on the dummy finger 30 and the electrode finger 22 of the surface acoustic wave resonator and on the grid conductor of the reflection grid 50, the generation of the lateral mode can be further effectively suppressed.

[0051] Figure 5 It is a comparison diagram of the amplitude values ​​of the admittance curves of a surface acoustic wave resonator with and without a load block provided by an embodiment of the present invention; Figure 6: is a comparison diagram of the real part of the admittance in the admittance curve of a surface acoustic wave resonator with and without a load block provided by an embodiment of the present invention. Among them, the solid line a corresponds to Figure 2 The structure shown, the dotted line b corresponds to Figure 3 Compared with the resonator without the sound velocity mutation structure, the structure of the present invention has better amplitude-frequency characteristics. It can be seen that by optimizing the size and position of the sound velocity mutation structure, the Q value can be significantly improved (the sharper the Q value, the higher the Q value), and the amplitude of the real part of the admittance above 2200MHz will also be lower, indicating that the structure of the present invention can better prevent the leakage of transverse mode energy.

[0052] In one embodiment of the present invention, reference Figure 1 and Figure 3 The first sound velocity mutation structure 40 includes a plurality of load blocks 41 , each load block 41 is located at the end of a corresponding dummy finger 30 ; the distances between the load blocks 41 located at the ends of the dummy fingers 30 on the same side and the ends of the electrode fingers 22 on the opposite side are equal.

[0053] In another embodiment of the present invention, reference Figure 7 The first sound velocity mutation structure 40 includes a plurality of load blocks 41; the vertical projection of each load block 41 on the piezoelectric substrate corresponds to a vertical projection of a dummy finger 30 on the piezoelectric substrate and partially overlaps; the distance from the load block 41 at the end of the same row of dummy fingers 30 to the end of the opposite electrode finger 22 increases or decreases.

[0054] In another embodiment of the present invention, reference Figure 8 The first sound velocity mutation structure 40 includes a plurality of load blocks 41; the vertical projection of each load block 41 on the piezoelectric substrate corresponds to a vertical projection of a dummy finger 30 on the piezoelectric substrate and partially overlaps; the distances from the load block 41 at the end of the dummy finger 30 on the same side to the end of the electrode finger 22 on the opposite side are alternately equal.

[0055] Along the direction parallel to the bus bar 21, the width of each load block 41 is less than or equal to the width between two adjacent electrode fingers 22 located on both sides thereof. Figure 3 , Figure 7 as well as Figure 8 , exemplarily showing that the width of each load block 41 is smaller than the width between two adjacent electrode fingers 22 located on both sides thereof. Fig. 9 , it is exemplarily shown that the width of each load block 41 extends horizontally to be equal to the distance between two adjacent electrode fingers 22 located on both sides thereof, which can further reduce the diffraction of acoustic waves.

[0056] In one embodiment of the present invention, reference Fig.10The first sound velocity mutation structure 40 includes two load bars 42, which are arranged opposite to each other and are parallel to the bus bar 21; along the direction parallel to the bus bar 21, the width of the load bar 42 is greater than or equal to the width of the bus bar 21. It can be understood that in order to further reduce the diffraction of the sound wave, the load block can be extended in the horizontal direction to form a load bar 42 parallel to the bus bar 21.

[0057] In one embodiment of the present invention, reference Fig.11 and Fig.12 The surface acoustic wave resonator further includes a passivation layer 90, which covers the side of the electrode finger 22 and the dummy finger 30 away from the piezoelectric substrate, and the piezoelectric substrate not covered by the electrode finger 22 and the dummy finger 30; the first sound velocity mutation structure 40 is located on the side of the passivation layer 90 away from the piezoelectric substrate; the material of the first sound velocity mutation structure 40 includes a polymer coating material. The material of the passivation layer 90 can be silicon dioxide or silicon nitride, and the polymer coating material can be polyimide, etc.

[0058] The first sound velocity mutation structure 40 includes two load layers 43, and the vertical projection of each load layer 43 on the piezoelectric substrate covers a corresponding dummy finger 30 area; along the direction parallel to the bus bar 21, the width of the dummy finger 30 area is greater than or equal to the width of the bus bar 21, and along the direction perpendicular to the bus bar 21, the length of the dummy finger 30 area is equal to the length of the dummy finger 30. The load is settled in the entire dummy finger 30 area to increase the difference in sound velocity mutation, which can further suppress the lateral mode while ensuring the Q value of the resonator.

[0059] refer to Fig.12 The resonator can be a TF-SAW filter (Thin Film Surface Acoustic Wave Filter). The piezoelectric substrate 10 includes a silicon layer 11 and a polysilicon layer 12, a silicon oxide layer 13 and a lithium niobate crystal layer 14 formed on the silicon layer in sequence. The TF-SAW filter can provide a relatively large bandwidth, while providing good temperature compensation performance and an effective path for multi-band integration.

[0060] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A surface acoustic wave resonator, characterized in that: include: Piezoelectric substrate; An interdigital transducer structure, located on one side of the piezoelectric substrate; The interdigital transducing structure comprises two bus bars arranged opposite to each other, and a plurality of electrode fingers arranged side by side between the two bus bars; each electrode finger is electrically connected to one of the bus bars alternately; A plurality of dummy fingers, each dummy finger being located between an end of the electrode finger and a bus bar on the opposite side; along a direction parallel to the bus bar, a width of the dummy finger is equal to a width of the electrode finger; a first sound velocity mutation structure, the first sound velocity mutation structure being located at least one of a side of the dummy finger away from the piezoelectric substrate, a side of the dummy finger close to the piezoelectric substrate, and a layer where the dummy finger is located; along a direction parallel to the bus bar, a width of the first sound velocity mutation structure is greater than a width of the dummy finger; a second sound velocity mutation structure, the second sound velocity mutation structure being located at at least one of a side of the electrode finger away from the piezoelectric substrate, a side of the electrode finger close to the piezoelectric substrate, and a layer where the electrode finger is located; along a direction parallel to the bus bar, a width of the second sound velocity mutation structure is greater than a width of the electrode finger; A pair of reflection gratings and a third sound velocity mutation structure, wherein the reflection grating is located on the same side of the piezoelectric substrate and the interdigital transducer structure, and respectively located on two opposite sides of the interdigital transducer structure; the third sound velocity mutation structure is located at least one of a side of the reflection grating away from the piezoelectric substrate, a side of the reflection grating close to the piezoelectric substrate, and a layer where the reflection grating is located; along a direction parallel to the bus bar, a width of the third sound velocity mutation structure is greater than a width of half a period of the reflection grating; The width of the first sound velocity mutation structure is greater than the width of the second sound velocity mutation structure.

2. The surface acoustic wave resonator according to claim 1, characterized in that: The first sound velocity mutation structure includes a plurality of load blocks, each of which is located at the end of a corresponding dummy finger; the distances between the load blocks located at the ends of the dummy fingers in the same row and the ends of the opposite electrode fingers are equal.

3. The surface acoustic wave resonator according to claim 1, characterized in that: The first sound velocity mutation structure includes multiple load blocks; the vertical projection of each load block on the piezoelectric substrate partially overlaps with the vertical projection of a dummy finger on the piezoelectric substrate; the distance from the load block at the end of the same row of dummy fingers to the end of the opposite electrode finger increases or decreases.

4. The surface acoustic wave resonator according to claim 1, characterized in that: The first sound velocity mutation structure includes multiple load blocks; the vertical projection of each load block on the piezoelectric substrate partially overlaps with the vertical projection of a dummy finger on the piezoelectric substrate; the distances from the load blocks at the ends of the same row of dummy fingers to the ends of the opposite electrode fingers are alternately equal.

5. The surface acoustic wave resonator according to any one of claims 2 to 4, characterized in that: Along a direction parallel to the busbar, the width of each load block is less than or equal to the width between two adjacent electrode fingers located on two sides thereof.

6. The surface acoustic wave resonator according to claim 1, characterized in that: The first sound velocity mutation structure includes two load bars, which are arranged opposite to each other and are both parallel to the bus bar; along the direction parallel to the bus bar, the width of the load bar is greater than or equal to the width of the bus bar.

7. The surface acoustic wave resonator according to claim 1, characterized in that: It also includes a passivation layer, which covers the side of the electrode fingers and the dummy fingers away from the piezoelectric substrate, and the piezoelectric substrate not covered by the electrode fingers and the dummy fingers; the first sound velocity mutation structure is located on the side of the passivation layer away from the piezoelectric substrate; the material of the first sound velocity mutation structure includes a polymer coating material.

8. The surface acoustic wave resonator according to claim 7, characterized in that: The first sound velocity mutation structure includes two load layers, and the vertical projection of each load layer on the piezoelectric substrate covers a corresponding dummy finger area; along the direction parallel to the bus bar, the width of the dummy finger area is greater than or equal to the width of the bus bar, and along the direction perpendicular to the bus bar, the length of the dummy finger area is equal to the length of the dummy finger.

9. The surface acoustic wave resonator according to claim 1, characterized in that: The piezoelectric substrate includes a silicon layer, and a polysilicon layer, a silicon oxide layer, and a lithium niobate crystal layer sequentially formed on the silicon layer.

Images