A surface acoustic wave resonator

Abstract

This invention discloses a surface acoustic wave (SAW) resonator, comprising a piezoelectric layer; an electrode layer on the piezoelectric layer; and a transducer comprising a first busbar, a first long finger, a first dummy finger, a second busbar, a second long finger, and a second dummy finger. The first and second busbars extend along a first direction and are positioned opposite each other. The first long finger, second dummy finger, second long finger, and first dummy finger extend along a second direction and are all located between the first and second busbars. The first long finger and second dummy finger are positioned opposite each other. The piezoelectric layer includes at least one heterostructure, the depth of which is greater than the transducer thickness. The propagation speed of SAW in the heterostructure differs from its propagation speed in the piezoelectric layer. The heterostructure extends along the first direction, and its vertical projection onto the piezoelectric layer overlaps with the vertical projection onto the piezoelectric layer but does not overlap with the vertical projections onto the first and second gaps. This invention suppresses lateral mode transmission and improves filter performance.

Description

Technical Field

[0001] This invention relates to the field of semiconductor packaging technology, and more particularly to a surface acoustic wave resonator. Background Technology

[0002] With the development of communication technology, product terminals have placed stringent requirements on the performance of various devices, and filters are key components in communication systems. As technology advances, the types of filters are also increasing, from LCR filters to cavity filters, from LTCC ceramic filters to surface acoustic wave (SAW) filters; filter technology continues to evolve. Since the advent of the LTE era, SAW filters have played an increasingly important role in communication systems. Simultaneously, with the development of communication technology, the requirements for filters are becoming increasingly stringent; especially with the arrival of 5G (5th Generation) mobile communication technology, the filter industry faces both significant challenges and opportunities.

[0003] Surface acoustic wave (SAW) filters are widely used in radio frequency (RF) front-ends and have advantages such as low insertion loss, wide bandwidth, and small size. However, SAW resonators have various clutter modes that seriously affect the performance of the filter. Transverse modes are one of the main clutter modes, so suppressing transverse modes is of great significance for improving the performance of SAW filters. Summary of the Invention

[0004] This invention provides a surface acoustic wave resonator that can suppress the transmission of transverse modes, thereby improving the performance of the filter.

[0005] This invention provides a surface acoustic wave (SAW) resonator, which includes:

[0006] piezoelectric layer;

[0007] Electrode layer located on the piezoelectric layer;

[0008] The electrode layer includes a transducer, which comprises: a first busbar, a first long finger, a first dummy finger, a second busbar, a second long finger, and a second dummy finger; the first busbar and the second busbar both extend along a first direction and are arranged opposite to each other; the first long finger, the second dummy finger, the second long finger, and the first dummy finger all extend along a second direction and are all located between the first busbar and the second busbar; the first long finger and the first dummy finger are alternately arranged along the first direction and are both connected to the first busbar; the second long finger and the second dummy finger are alternately arranged along the first direction and are both connected to the second busbar; the first long finger and the second dummy finger are arranged opposite to each other, with a first gap between them, and the second long finger and the first dummy finger are arranged opposite to each other, with a second gap between them; wherein the second direction intersects the first direction.

[0009] The piezoelectric layer includes at least one heterostructure, the depth of which is greater than the thickness of the transducer, the propagation speed of surface acoustic waves in the heterostructure is different from that in the piezoelectric layer, the heterostructure extends along the first direction, the heterostructure overlaps with the vertical projection of the transducer in the piezoelectric layer, and does not overlap with the vertical projections of the first gap and the second gap in the piezoelectric layer.

[0010] Optionally, the heterostructure includes a first heterostructure strip and a second heterostructure strip.

[0011] The first heterogeneous strip is located below the first long finger, and the side of the first heterogeneous strip adjacent to the first gap is flush with the top of the first long finger away from the first busbar;

[0012] The second heterogeneous strip is located below the second long finger, and the side of the second heterogeneous strip adjacent to the second gap is flush with the top of the second long finger away from the second busbar.

[0013] Optionally, the heterostructure includes a third heterostructure strip and a fourth heterostructure strip.

[0014] The third heterogeneous strip is located below the second busbar, and the side of the third heterogeneous strip adjacent to the second prosthetic finger is flush with the end of the second prosthetic finger adjacent to the second busbar;

[0015] The fourth heterogeneous strip is located below the first busbar, and the side of the fourth heterogeneous strip adjacent to the first prosthetic finger is flush with the end of the first prosthetic finger adjacent to the first busbar.

[0016] Optionally, the surface of the piezoelectric layer adjacent to the electrode layer is provided with a cavity structure, and the heterostructure includes the cavity structure.

[0017] Optionally, a groove is provided on the surface of the piezoelectric layer adjacent to the electrode layer, and the groove is filled with a heterogeneous material layer, wherein the heterogeneous structure includes the heterogeneous material layer.

[0018] Optionally, the heterogeneous material layer may be made of silicon dioxide or silicon nitride.

[0019] Optionally, a doped region is provided on the surface of the piezoelectric layer adjacent to the electrode layer, and the heterostructure includes the piezoelectric layer of the doped region after doping with specified particles.

[0020] Optionally, the set particle includes vanadium, or the set particle includes hydrogen and helium.

[0021] Optionally, the width W of the heterostructure along the second direction and the sound velocity difference ΔV between the sound velocity of the surface acoustic wave resonator and the sound velocity of the heterostructure satisfy the following relationship: W=K*ΔV*λ / V, where λ is the wavelength of the surface acoustic wave, V is the sound velocity of the piezoelectric layer material, K is an adjustment coefficient, and the value of K ranges from 0.8 to 1.2.

[0022] The depth of the heterostructure along the thickness direction of the surface acoustic wave resonator includes 0.3λ-3λ, where λ is the wavelength of the surface acoustic wave, and the length of the heterostructure along the first direction is greater than the length of the surface acoustic wave resonator.

[0023] Optionally, the surface acoustic wave resonator further includes a temperature compensation layer and a substrate, wherein the temperature compensation layer is located on the side of the electrode layer away from the piezoelectric layer, and the substrate is located on the side of the piezoelectric layer away from the electrode layer.

[0024] This embodiment incorporates a heterostructure within the piezoelectric layer. The heterostructure exhibits a different sound velocity than the piezoelectric layer, creating a sudden change in sound velocity in the transverse direction of the resonator. This confines the surface acoustic wave (SAW) within the resonator. Furthermore, the depth of this heterostructure is greater than the transducer thickness, further suppressing transverse modes and thus improving the Q-value of the resonator while preventing transverse crosstalk between adjacent resonators. This solution addresses the problem of strong transverse modes in traditional SAW resonators and filters, which degrades overall device performance. The technical solution in this embodiment effectively suppresses transverse modes, thereby improving filter performance. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of a surface acoustic wave resonator provided in an embodiment of the present invention;

[0026] Figure 2 This is a partial planar schematic diagram of a surface acoustic wave resonator provided in an embodiment of the present invention;

[0027] Figure 3 This is a schematic diagram of the surface wave velocity distribution of a conventional resonator provided in an embodiment of the present invention;

[0028] Figure 4 This is a schematic diagram of the surface wave velocity distribution of a high-velocity heterostructure resonator provided in an embodiment of the present invention;

[0029] Figure 5 This is a schematic diagram of the surface wave velocity distribution of a low-velocity heterostructure resonator provided in an embodiment of the present invention;

[0030] Figure 6 This is provided by the embodiments of the present invention. Figure 2 The corresponding cross-sectional view of the surface acoustic wave resonator along section line AA;

[0031] Figure 7 This is a partial planar schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present invention;

[0032] Figure 8 This is provided by the embodiments of the present invention. Figure 7 The corresponding cross-sectional view of the surface acoustic wave resonator along the profile line BB;

[0033] Figure 9 This is a partial planar schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present invention;

[0034] Figure 10 This is a schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present invention;

[0035] Figure 11 This is provided by the embodiments of the present invention. Figure 2 The corresponding cross-sectional view of the surface acoustic wave resonator with temperature compensation layer along section line AA;

[0036] Figure 12 This is provided by the embodiments of the present invention. Figure 7 The corresponding cross-sectional view of the surface acoustic wave resonator with temperature compensation layer along section line BB;

[0037] Figure 13 This is provided by the embodiments of the present invention. Figure 2 A cross-sectional view of a surface acoustic wave resonator with a substrate along section line AA.

[0038] Figure 14 This is provided by the embodiments of the present invention. Figure 2 A cross-sectional view of another type of surface acoustic wave resonator with a substrate along section line AA.

[0039] Figure 15 This is provided by the embodiments of the present invention. Figure 7 A cross-sectional view of a corresponding surface acoustic wave resonator with a substrate along section line BB;

[0040] Figure 16 This is provided by the embodiments of the present invention. Figure 7 A cross-sectional view of another type of surface acoustic wave resonator with a substrate along section line BB. Detailed Implementation

[0041] 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.

[0042] Figure 1 This is a schematic diagram of the structure of a surface acoustic wave resonator provided in an embodiment of the present invention. Figure 2 This is a partial planar schematic diagram of a surface acoustic wave resonator provided in an embodiment of the present invention, with reference to... Figure 1 and Figure 2 This invention provides a surface acoustic wave (SAW) resonator for suppressing transverse modes. The SAW resonator includes: a piezoelectric layer 120; an electrode layer 130 located on the piezoelectric layer 120; the electrode layer 130 includes a transducer 131, which includes: a first busbar 10, a first long finger 11, a first dummy finger 12, a second busbar 20, a second long finger 21, and a second dummy finger 22; the first busbar 10 and the second busbar 20 both extend along a first direction 1 and are disposed opposite to each other; the first long finger 11, the second dummy finger 22, the second long finger 21, and the first dummy finger 12 all extend along a second direction 2 and are all located between the first busbar 10 and the second busbar 20; the first long finger 11 and the first dummy finger 12 are alternately arranged along the first direction 1 and are both connected to the first busbar 10; the second long finger 21 and the second dummy finger 22 extend along the first direction 1... Alternating arrangement and all connected to the second busbar 20; the first long finger 11 and the second pseudo finger 22 are arranged opposite to each other, with a first gap 1122 between the first long finger 11 and the second pseudo finger 22; the second long finger 21 and the first pseudo finger 12 are arranged opposite to each other, with a second gap 2112 between the second long finger 21 and the first pseudo finger 12; wherein, the second direction 2 intersects with the first direction 1; the piezoelectric layer 120 includes at least one heterostructure 121, the depth of the heterostructure is greater than the thickness of the transducer, the propagation speed of surface acoustic waves in the heterostructure 121 is different from the propagation speed in the piezoelectric layer 120, the heterostructure 121 extends along the first direction 1, the heterostructure 121 overlaps with the vertical projection of the transducer 131 in the piezoelectric layer 120, and does not overlap with the vertical projection of the first gap 1122 and the second gap 2112 in the piezoelectric layer 120.

[0043] Specifically, the piezoelectric layer 120 can be made of lithium niobate or lithium cobalt oxide. An electrode layer 130 is formed on the surface of the piezoelectric layer 120 by depositing a metal film using methods such as electron beam evaporation, plasma deposition, or magnetron sputtering. The material for depositing the metal film can be titanium, chromium, copper, silver, aluminum, or a combination thereof. The number of the first long finger 11, the second pseudo finger 22, the second long finger 21, and the first pseudo finger 12 are all equal. The first busbar 10 and the second busbar 20 are always parallel to the first direction 1. The angle between the second direction 2 and the first direction 1 can be set as needed; an embodiment of the present invention exemplarily shows a case where the angle is 90°.

[0044] There can be multiple transducers 131 in the electrode layer 130, and the number of heterostructures 121 in the piezoelectric layer 120 can be one or more, and the specific number can be set according to actual needs. Each transducer 131 corresponds to at least one heterostructure 121. The heterostructure 121 cannot be located below the first gap 1122 and the second gap 2112. The heterostructure 121 can be located at any position below the first busbar 10, the first long finger 11, the first dummy finger 12, the second busbar 20, the second long finger 21, and the second dummy finger 22.

[0045] Heterogeneous structures can be either high-velocity heterostructures or low-velocity heterostructures. High-velocity heterostructures refer to heterostructures with sound speeds higher than those of the piezoelectric layer, while low-velocity heterostructures refer to heterostructures with sound speeds lower than those of the piezoelectric layer. Figure 3 This is a schematic diagram of the surface wave velocity distribution of a conventional resonator provided in an embodiment of the present invention. Figure 4 This is a schematic diagram of the surface wave velocity distribution of a high-velocity heterostructure resonator provided in an embodiment of the present invention. Figure 5 This is a schematic diagram of the surface wave velocity distribution of a low-velocity heterostructure resonator provided in an embodiment of the present invention. (Refer to...) Figure 3-5 ,from Figure 4 It can be seen that the wave velocity in the intermediate region separating the two hypersonic heterostructures differs significantly from that in the heterostructure region; from Figure 5 It can be seen that the wave velocity in the intermediate region separated by the two low-sound-velocity heterostructures differs significantly from that in the heterostructure region. In summary, heterostructures can restrict the transmission of transverse modes, confining surface acoustic waves within the resonator and thus improving its performance.

[0046] This embodiment incorporates a heterostructure within the piezoelectric layer. The heterostructure exhibits a different sound velocity than the piezoelectric layer, creating a sudden change in sound velocity in the transverse direction of the resonator. This confines the surface acoustic wave (SAW) within the resonator. Furthermore, the depth of this heterostructure exceeds the thickness of the transducer, further suppressing transverse modes and thus improving the Q-value of the resonator while preventing transverse crosstalk between adjacent resonators. This solution addresses the problem of strong transverse modes in traditional SAW resonators and filters, which degrades overall device performance. The technical solution in this embodiment effectively suppresses transverse modes, thereby improving filter performance.

[0047] Continue to refer to Figure 2 Optionally, the heterostructure 121 includes a first heterostructure strip 1211 and a second heterostructure strip 1212. The first heterostructure strip 1211 is located below the first long finger 11, and the side of the first heterostructure strip 1211 adjacent to the first gap 1122 is flush with the top of the first long finger 11 away from the first busbar 10.

[0048] The second heterogeneous strip 1212 is located below the second long finger 21, and the side of the second heterogeneous strip 1212 adjacent to the second gap 2112 is flush with the top of the second long finger 21 away from the second busbar 20.

[0049] Figure 6 This is provided by the embodiments of the present invention. Figure 2 The corresponding cross-sectional view of the surface acoustic wave resonator along section line AA is shown in the reference diagram. Figure 6 The figure clearly shows the position information of the first heterogeneous strip 1211 and the second heterogeneous strip 1212, as well as the depth and width of the first heterogeneous strip 1211 and the second heterogeneous strip 1212.

[0050] Figure 7 This is a partial planar schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present invention, for reference. Figure 7 Optionally, the heterostructure 121 includes a third heterostructure strip 1213 and a fourth heterostructure strip 1214.

[0051] The third heterogeneous strip 1213 is located below the second busbar 20, and the side of the third heterogeneous strip 1213 adjacent to the second prosthetic finger 22 is flush with the end of the second prosthetic finger 22 adjacent to the second busbar 20.

[0052] The fourth heterogeneous strip 1214 is located below the first busbar 10, and the side of the fourth heterogeneous strip 1214 adjacent to the first prosthetic finger 12 is flush with the end of the first prosthetic finger 12 adjacent to the first busbar 10.

[0053] Figure 8 This is provided by the embodiments of the present invention. Figure 7 The corresponding cross-sectional view of the surface acoustic wave resonator along section line BB is shown in the reference diagram. Figure 8 The figure clearly shows the position information of the third heterogeneous strip 1213 and the fourth heterogeneous strip 1214, as well as their depth and width.

[0054] The first heterogeneous strip 1211, the second heterogeneous strip 1212, the third heterogeneous strip 1213, and the fourth heterogeneous strip 1214 in the heterostructure 121 have different sound velocities than the piezoelectric layer. They have a sudden change in sound velocity in the transverse direction of the resonator, which can confine the surface acoustic wave in the resonator and effectively suppress the transverse mode, thereby improving the performance of the filter.

[0055] Positioning the first heterogeneous strip 1211 below the first long finger 11 and the second heterogeneous strip 1212 below the second long finger 21 intensifies the abrupt change in sound velocity in the lateral direction, thus better confining the surface acoustic waves within the resonator. Positioning the third heterogeneous strip 1213 below the second busbar 20 and the fourth heterogeneous strip 1214 below the first busbar 10 reduces manufacturing complexity and prevents lateral crosstalk between adjacent resonators.

[0056] Figure 9 This is a partial planar schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present invention, for reference. Figure 9 , Figure 9 The diagram shows a case where the heterostructure 121 includes a first heterostructure strip 1211, a second heterostructure strip 1212, a third heterostructure strip 1213, and a fourth heterostructure strip 1214.

[0057] The electrode layer 130 also includes a first reflective grid structure 132 and a second reflective grid structure 133, which are respectively disposed on both sides of the transducer 131. The first reflective grid structure 132 and the second reflective grid structure 133 each include a third bus bar 30, a fourth bus bar 40 and multiple reflective grids 50. The third bus bar 30 and the fourth bus bar 40 extend along the first direction 1. The first end of the reflective grid 50 is connected to the third bus bar 30 and the second end of the reflective grid 50 is connected to the fourth bus bar 40.

[0058] The first reflective grating structure 132 and the second reflective grating structure 133 can each have five reflective gratings. The first reflective grating structure 132 and the second reflective grating structure 133 can reflect the energy of surface acoustic waves and concentrate the energy in the transducer 131. In this embodiment of the invention, multiple reflective gratings 50 are arranged parallel to the first long finger 11, the second pseudo finger 22, the second long finger 21, and the first pseudo finger 12, further ensuring that the multiple reflective gratings 50 in the first reflective grating structure 132 and the second reflective grating structure 133 concentrate the reflected surface acoustic wave energy into the transducer, thereby improving the Q value of the surface acoustic wave resonator.

[0059] Optionally, a cavity structure is provided on the surface of the piezoelectric layer adjacent to the electrode layer, and the heterostructure includes the cavity structure.

[0060] Specifically, the cavity structure can be filled with air. The specific manufacturing process of the cavity structure can be as follows: using an etching process to etch corresponding grooves on the piezoelectric layer at the positions corresponding to the heterostructure, then filling the grooves with sacrificial material, and finally etching away the sacrificial material after the transducer is completed.

[0061] Optionally, a groove is provided on the surface of the piezoelectric layer adjacent to the electrode layer, and the groove is filled with a heterogeneous material layer, wherein the heterogeneous structure includes the heterogeneous material layer.

[0062] Specifically, corresponding grooves are etched at the positions of the heterostructures on the piezoelectric layer. Since the heteromaterial layer and the piezoelectric layer are made of different materials, their sound velocities are different. There is a sudden change in the sound velocity between the heteromaterial layer and the piezoelectric layer in the transverse direction of the resonator, thereby confining the surface acoustic waves within the resonator.

[0063] Alternatively, the heterogeneous material layer may be made of silicon dioxide or silicon nitride.

[0064] Specifically, after etching, silicon dioxide or silicon nitride is formed in the groove through processes such as plasma vapor deposition. Then, the flatness is repaired by etching or chemical mechanical polishing. Then, the transducer is deposited and etched. The subsequent processes are the same as those of conventional surface acoustic wave resonators.

[0065] Optionally, a doped region is provided on the surface of the piezoelectric layer adjacent to the electrode layer, and the heterostructure includes a piezoelectric layer with a doped region after doping with specified particles.

[0066] Specifically, based on the location and structure of the resonator, the corresponding position of the piezoelectric layer needs to be doped with ions, and the ion implantation process is used to inject the set ions into the doped region of the piezoelectric layer adjacent to the electrode layer surface at high speed.

[0067] Optionally, the particles may include vanadium or hydrogen and helium.

[0068] Specifically, vanadium doping can form a high-velocity layer, while hydrogen and helium doping can form a low-velocity layer. When vanadium or similar particles are used as dopants, the sound velocity in the heterostructure is significantly higher than that in the piezoelectric layer, resulting in a sudden change in sound velocity in the transverse direction, thus confining the surface acoustic waves within the resonator. Furthermore, because the depth of this heterostructure is greater than the transducer thickness, it can also suppress transverse volume waves, thereby improving the Q value of the resonator and preventing transverse crosstalk between adjacent resonators.

[0069] Using hydrogen and helium as dopants can create a low-velocity sound layer, i.e., a defect layer. The sound velocity in the heterostructure is lower than that in the piezoelectric layer, and there are also abrupt changes in sound velocity in the lateral direction, thus confining the surface acoustic waves within the resonator. Furthermore, because the depth of this heterostructure is greater than the thickness of the transducer, it can also suppress lateral volume waves, thereby improving the Q value of the resonator and preventing lateral crosstalk between adjacent resonators.

[0070] Optionally, the width W of the heterostructure along the second direction and the sound velocity difference ΔV between the sound velocity of the surface acoustic wave resonator and the sound velocity of the heterostructure satisfy the following relationship: W=K*ΔV*λ / V, where λ is the wavelength of the surface acoustic wave, V is the sound velocity of the piezoelectric layer material, K is an adjustment coefficient, and the value of K ranges from 0.8 to 1.2.

[0071] The depth of the heterostructure along the thickness direction of the surface acoustic wave resonator includes 0.3λ-3λ, where λ is the wavelength of the surface acoustic wave, and the length of the heterostructure along the first direction is greater than the length of the surface acoustic wave resonator.

[0072] Specifically, the width of the heterostructure along the second direction and the depth along the thickness direction of the surface acoustic wave resonator are closely related to the material of the piezoelectric layer, the resonator structure, and the sound velocity of the heterostructure. The width W of the heterostructure along the second direction is proportional to the sound velocity difference ΔV between the sound velocity V1 of the surface acoustic wave resonator and the sound velocity V2 of the heterostructure. Specifically, the calculation formula is as follows: W=K*ΔV*λ / V, ΔV=(V1-V2), where the value of K ranges from 0.8 to 1.2.

[0073] The depth of the heterostructure along the thickness direction of the surface acoustic wave resonator needs to take into account the performance requirements of the resonator. For example, its depth can vary from 0.3λ to 3λ. On the one hand, this can reduce the difficulty of the process, and on the other hand, the depth can be flexibly adjusted, which can confine the surface acoustic wave in the resonator and effectively suppress the transverse mode.

[0074] Figure 10 This is a schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present invention, for reference. Figure 10 Optionally, the surface acoustic wave resonator further includes a temperature compensation layer 140 and a substrate 110, wherein the temperature compensation layer 140 is located on the side of the electrode layer 130 away from the piezoelectric layer 120, and the substrate 110 is located on the side of the piezoelectric layer 120 away from the electrode layer 130.

[0075] Specifically, the substrate 110 can be made of high-resistivity silicon, or it can be a composite multilayer substrate, which enables the surface acoustic wave resonator to achieve low insertion loss, smooth passband, high Q value, and excellent low-frequency temperature characteristics. The temperature compensation layer 140 can be made of silicon dioxide or silicon nitride.

[0076] Figure 11 This is provided by the embodiments of the present invention. Figure 2 The corresponding cross-sectional view of the surface acoustic wave resonator with temperature compensation layer along section line AA. Figure 12 This is provided by the embodiments of the present invention. Figure 7 The corresponding cross-sectional view of the surface acoustic wave resonator with temperature compensation layer along section line BB is shown in the reference diagram. Figure 11 and Figure 12 The temperature compensation layer 140 can prevent temperature changes from affecting the resonant frequency of the surface acoustic wave resonator.

[0077] Figure 13 This is provided by the embodiments of the present invention. Figure 2 A cross-sectional view of a surface acoustic wave resonator with a substrate along section line AA. Figure 14 This is provided by the embodiments of the present invention. Figure 2 A cross-sectional view of another type of surface acoustic wave resonator with a substrate along section line AA is shown in the reference diagram. Figure 13 and Figure 14 , Figure 13 and Figure 14 The cases of heterostructures at different depths are shown respectively.

[0078] Figure 15 This is provided by the embodiments of the present invention. Figure 7 A cross-sectional view of a surface acoustic wave resonator with a substrate along section line BB. Figure 16 This is provided by the embodiments of the present invention. Figure 7 A cross-sectional view of a surface acoustic wave resonator with a substrate along section line BB is shown in the reference diagram. Figure 15 and Figure 16 , Figure 15 and Figure 16 The cases of heterostructures at different depths are shown respectively.

[0079] This invention also provides a filter comprising at least two surface acoustic wave resonators according to any one of the above embodiments.

[0080] The filter can be formed by connecting two or more surface acoustic wave resonators in series and / or in parallel as described in the above embodiments.

[0081] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A surface acoustic wave resonator, characterized in that, include: piezoelectric layer; Electrode layer located on the piezoelectric layer; The electrode layer includes a transducer, which comprises: a first busbar, a first long finger, a first dummy finger, a second busbar, a second long finger, and a second dummy finger; the first busbar and the second busbar both extend along a first direction and are arranged opposite to each other; the first long finger, the second dummy finger, the second long finger, and the first dummy finger all extend along a second direction and are all located between the first busbar and the second busbar; the first long finger and the first dummy finger are alternately arranged along the first direction and are both connected to the first busbar; the second long finger and the second dummy finger are alternately arranged along the first direction and are both connected to the second busbar; the first long finger and the second dummy finger are arranged opposite to each other, with a first gap between them, and the second long finger and the first dummy finger are arranged opposite to each other, with a second gap between them; wherein the second direction intersects the first direction. The piezoelectric layer includes at least one heterostructure, the depth of which is greater than the thickness of the transducer, the propagation speed of surface acoustic waves in the heterostructure is different from that in the piezoelectric layer, the heterostructure extends along the first direction, the heterostructure overlaps with the vertical projection of the transducer in the piezoelectric layer, and does not overlap with the vertical projections of the first gap and the second gap in the piezoelectric layer. Wherein, the width W of the heterostructure along the second direction is the difference between the sound velocity of the surface acoustic wave resonator and the sound velocity of the heterostructure. V satisfies the following relationship: W=K* V*λ / V, where λ is the wavelength of the surface acoustic wave, V is the sound velocity of the piezoelectric layer material, and K is an adjustment coefficient, with a value ranging from 0.8 to 1.

2. The depth of the heterostructure along the thickness direction of the surface acoustic wave resonator includes 0.3λ-3λ, where λ is the wavelength of the surface acoustic wave, and the length of the heterostructure along the first direction is greater than the length of the surface acoustic wave resonator. The surface of the piezoelectric layer adjacent to the electrode layer is provided with a groove, and the groove is filled with a heterogeneous material layer, the heterogeneous structure including the heterogeneous material layer; The heterogeneous material layer is made of materials including silicon dioxide or silicon nitride.

2. The surface acoustic wave resonator according to claim 1, characterized in that, The heterostructure includes a first heterostructure strip and a second heterostructure strip. The first heterogeneous strip is located below the first long finger, and the side of the first heterogeneous strip adjacent to the first gap is flush with the top of the first long finger away from the first busbar; The second heterogeneous strip is located below the second long finger, and the side of the second heterogeneous strip adjacent to the second gap is flush with the top of the second long finger away from the second busbar.

3. The surface acoustic wave resonator according to claim 1 or 2, characterized in that, The heterostructure includes a third heterostructure strip and a fourth heterostructure strip. The third heterogeneous strip is located below the second busbar, and the side of the third heterogeneous strip adjacent to the second prosthetic finger is flush with the end of the second prosthetic finger adjacent to the second busbar; The fourth heterogeneous strip is located below the first busbar, and the side of the fourth heterogeneous strip adjacent to the first prosthetic finger is flush with the end of the first prosthetic finger adjacent to the first busbar.

4. The surface acoustic wave resonator according to claim 1, characterized in that, The piezoelectric layer has a cavity structure on its surface adjacent to the electrode layer, and the heterostructure includes the cavity structure.

5. The surface acoustic wave resonator according to claim 1, characterized in that, The surface of the piezoelectric layer adjacent to the electrode layer is provided with a doped region, and the heterostructure includes the piezoelectric layer of the doped region after doping with a set of particles.

6. The surface acoustic wave resonator according to claim 5, characterized in that, The specified particles may include vanadium or hydrogen and helium.

7. The surface acoustic wave resonator according to claim 1, characterized in that, It also includes a temperature compensation layer and a substrate, wherein the temperature compensation layer is located on the side of the electrode layer away from the piezoelectric layer, and the substrate is located on the side of the piezoelectric layer away from the electrode layer.

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