Acoustic resonator with thickness direction excitation shear mode

Abstract

The present application relates to a thickness direction excitation shear mode acoustic resonator, comprising: an acoustic mirror, comprising at least one first acoustic reflection layer and at least one second acoustic reflection layer, the acoustic impedance of each first acoustic reflection layer is less than the acoustic impedance of each second acoustic reflection layer; a bottom electrode layer is located on the acoustic mirror; a piezoelectric layer is arranged on the bottom electrode layer, the piezoelectric layer comprises lithium niobate of single crystal material and / or lithium tantalate of single crystal material; an electrode unit is arranged on the piezoelectric layer; a transverse reflector is arranged on the piezoelectric layer, comprising a first reflector located on the first side of the electrode unit and a second reflector located on the second side of the electrode unit, the transverse reflector is used for transverse reflection of acoustic waves; wherein the bottom electrode layer and the electrode unit are used to form an electric field. The present application can have high electromechanical coupling coefficient and high Q value at a frequency of 3GHz or more.

Description

Technical Field

[0001] This application relates to the field of resonator technology, and in particular to an acoustic resonator with a thickness-direction shear mode. Background Technology

[0002] Radio frequency acoustic resonators are small, micro-synthesized structures used for synthesized filtering functions or as frequency sources. Due to their smaller size and higher quality factor (Q), acoustic resonators have replaced other types of resonators used in mobile phones, small base stations, and IoT devices. They offer advantages such as low loss (low power consumption), high rejection and high signal-to-noise ratio, as well as thinner packaging.

[0003] With the release of new communication standards (i.e., fifth-generation mobile networks), it is necessary to expand the operating range of resonators to higher frequencies while maintaining high electromechanical coupling coefficients and high Q values. Summary of the Invention

[0004] Therefore, it is necessary to provide an acoustic resonator with a thickness-direction shear mode that can have a high electromechanical coupling coefficient and a high Q value at frequencies above 3 GHz.

[0005] An acoustic resonator with a thickness-direction excited shear mode includes: an acoustic mirror comprising at least one first acoustic reflection layer and at least one second acoustic reflection layer, wherein the acoustic impedance of each first acoustic reflection layer is less than the acoustic impedance of each second acoustic reflection layer; a bottom electrode layer located on the acoustic mirror; a piezoelectric layer disposed on the bottom electrode layer, the piezoelectric layer comprising lithium niobate and / or lithium tantalate of single crystal material; an electrode unit disposed on the piezoelectric layer; and a lateral reflector disposed on the piezoelectric layer, comprising a first reflector located on a first side of the electrode unit and a second reflector located on a second side of the electrode unit, the first side and the second side being opposite sides, the lateral reflector being used for lateral reflection of sound waves; wherein the bottom electrode layer and the electrode unit are used to form an electric field.

[0006] In one embodiment, the electric field formed by the bottom electrode layer and the electrode unit is mainly in the thickness direction of the piezoelectric layer, and the bottom electrode layer and the electrode unit are also used to generate mechanical waves in shear mode over the entire thickness of the piezoelectric layer.

[0007] In one embodiment, the first acoustic reflective layer is thicker the farther it is from the bottom electrode layer; the second acoustic reflective layer is thicker the farther it is from the bottom electrode layer.

[0008] In one embodiment, the acoustic mirror includes three first acoustic reflection layers and two second acoustic reflection layers, with the first and second acoustic reflection layers alternately arranged in the acoustic mirror.

[0009] In one embodiment, the material of the first acoustic reflective layer includes at least one of silicon dioxide, aluminum, benzocyclobutene, polyimide, and spin glass, and the material of the second acoustic reflective layer includes at least one of molybdenum, tungsten, titanium, platinum, aluminum nitride, tungsten oxide, and silicon nitride.

[0010] In one embodiment, the electrode unit includes a first common electrode, a second common electrode, a plurality of first interdigital electrodes, and a plurality of second interdigital electrodes. Each first interdigital electrode is electrically connected to the first common electrode, and each second interdigital electrode is electrically connected to the second common electrode. The first interdigital electrodes and the second interdigital electrodes are insulated from each other. The first common electrode is used to receive an input voltage, and the second common electrode is used to ground.

[0011] In one embodiment, a passivation layer is further provided on the piezoelectric layer, the passivation layer covering each of the first interdigital electrodes and each of the second interdigital electrodes.

[0012] In one embodiment, the line connecting the transverse reflectors on both sides of the electrode unit is the direction of sound wave propagation; the width of the bottom electrode layer is smaller than the spacing between the first common electrode and the second common electrode, such that the orthographic projection of the bottom electrode layer onto the plane of the electrode unit is located between the first common electrode and the second common electrode; the orthographic projection of each of the first acoustic reflection layers and the second acoustic reflection layer onto the plane extends beyond the first reflector and the second reflector in the direction of the line connecting them.

[0013] In one embodiment, the orthographic projection of each of the second acoustic reflective layers onto the plane where the bottom electrode layer is located extends beyond both sides of the bottom electrode layer in a first direction, or the orthographic projection of each of the first and second acoustic reflective layers onto the plane where the bottom electrode layer is located is covered by the bottom electrode layer; the first direction is parallel to the propagation direction of the sound wave.

[0014] In one embodiment, both the first reflector and the second reflector include at least one electrode strip, wherein the center of the electrode strip closest to the electrode unit in the first reflector is 1 / 8 to 2 wavelengths of the sound wave from the center of the interdigitated electrode on the first side edge of the electrode unit, and the center of the electrode strip closest to the electrode unit in the second reflector is 1 / 8 to 2 wavelengths of the sound wave from the center of the interdigitated electrode on the second side edge of the electrode unit.

[0015] In one embodiment, a first metal element disposed on the first common electrode and a second metal element disposed on the second common electrode are further provided. The thickness of the first metal element and the second metal element is greater than the thickness of the electrode unit. The first metal element and the second metal element are used for acoustic reflection in a second direction, which is perpendicular to the propagation direction of the sound wave.

[0016] In one embodiment, the electrode unit is made of the same material as the lateral reflector and is a metal and / or alloy.

[0017] In one embodiment, a first acoustic reflective layer is located closer to the bottom electrode layer than all of the second acoustic reflective layers.

[0018] The aforementioned acoustic resonator with thickness-direction excitation shear mode generates an electric field through the electrode unit and bottom electrode layer, and reflects the sound wave laterally through a transverse reflector, thus exciting the acoustic resonator into a thickness-direction shear vibration mode. Furthermore, because the piezoelectric layer uses single-crystal materials such as lithium niobate or lithium tantalate, it can exhibit high electromechanical coupling coefficients and high Q values ​​at frequencies above 3 GHz. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a top view of a portion of the structure of an acoustic resonator with a thickness-direction excitation shear mode in one embodiment.

[0021] Figure 2 It is along Figure 1 A sectional view of line A-A' in the middle;

[0022] Figure 3 This is a schematic diagram showing the propagation direction of the electric field and mechanical waves in a piezoelectric layer.

[0023] Figure 4 This is a schematic diagram showing the thickness of each reflective layer of a mirror in one embodiment;

[0024] Figure 5 This is a schematic diagram of the structure of the first reflector in one embodiment;

[0025] Figure 6 It is along Figure 1 A sectional view of line B-B' in the middle;

[0026] Figure 7 In one embodiment, Wg The illustration;

[0027] Figure 8 The simulation results show the characteristic admittance of an acoustic resonator with thickness-direction excitation shear mode according to one embodiment. Detailed Implementation

[0028] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0030] It should be understood that when an element or layer is referred to as "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it may be directly on, adjacent to, connected to, or coupled to other elements or layers, or there may be intervening elements or layers. Conversely, when an element is referred to as "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc., may be used to describe various elements, parts, regions, layers, doping types, and / or portions, these elements, parts, regions, layers, doping types, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, part, region, layer, doping type, or portion from another element, part, region, layer, doping type, or portion. Therefore, without departing from the teachings of this invention, the first element, component, region, layer, doping type, or portion discussed below may be represented as a second element, component, region, layer, or portion; for example, the first doping type may be referred to as the second doping type, and similarly, the second doping type may be referred to as the first doping type; the first doping type and the second doping type are different doping types, for example, the first doping type may be P-type and the second doping type may be N-type, or the first doping type may be N-type and the second doping type may be P-type.

[0031] Spatial relation terms such as “below,” “under,” “below,” “under,” “above,” “above,” etc., are used herein to describe the relationship between one element or feature shown in the figure and other elements or features. It should be understood that, in addition to the orientation shown in the figure, spatial relation terms also include different orientations of the device in use and operation. For example, if the device in the figure is flipped, the element or feature described as “below,” “under,” or “below” will be oriented “above” the other element or feature. Therefore, the exemplary terms “below” and “under” can include both above and below orientations. Furthermore, the device may also include other orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptive terms used herein will be interpreted accordingly.

[0032] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, in this specification, the term “and / or” includes any and all combinations of the associated listed items.

[0033] Embodiments of the invention are described herein with reference to cross-sectional views illustrating ideal embodiments (and intermediate structures) of the invention, thus allowing for variations in the illustrated shape due to, for example, manufacturing techniques and / or tolerances. Therefore, embodiments of the invention should not be limited to the specific shapes of the regions shown herein, but rather include shape deviations due to, for example, manufacturing techniques. For instance, implantation regions shown as rectangular typically have rounded or curved features at their edges and / or implantation concentration gradients, rather than a binary change from implantation regions to non-implantation regions. Similarly, the buried regions formed by implantation can result in some implantation in the region between the buried region and the surface traversed during implantation. Therefore, the regions shown in the figures are substantially schematic, and their shapes do not represent the actual shapes of regions of the device and do not limit the scope of the invention.

[0034] Bulk acoustic wave (BAW) and surface acoustic wave (SAW) resonators are the most commonly used devices for synthesizing filters and resonators between 0.6 GHz and 3 GHz. These acoustic devices are commercially successful and widely used in mobile phone front-end modules or as discrete components in radio front-ends. Existing BAW and SAW devices can exhibit Q values ​​exceeding 1000 and electromechanical coupling coefficients of approximately 7%–10% at frequencies below 3 GHz. However, extending their operating frequency range above 3 GHz encounters several technical uncertainties and physical limitations. The new 5G standard requires electromechanical coupling coefficients exceeding 10%, a requirement that BAW and SAW devices cannot achieve without changes to the constituent materials or operating modes. Similarly, material losses fundamentally limit the maximum achievable Q values ​​of conventional BAW and SAW devices above 3 GHz.

[0035] In summary, the market needs new devices that can achieve high electromechanical coupling and high quality factor at frequencies above 3 GHz.

[0036] This application aims to develop a novel wafer-level mechanical / acoustic resonator capable of exhibiting high Q-value and high electromechanical coupling coefficient at frequencies above 3 GHz. This resonator will support the synthesis of high-performance passband filters, thereby meeting the new requirements of 5G communication standards and future upgrades.

[0037] Figure 1 This is a top view of a portion of the structure of an acoustic resonator with a thickness-direction excitation shear mode in one embodiment. Figure 2 It is along Figure 1 A sectional view along line A-A'. See also Figure 1 and Figure 2 The thickness-direction excited shear mode acoustic resonator includes an acoustic mirror 120, a bottom electrode layer 170, a piezoelectric layer 130, electrode units, and a lateral reflector. Figure 1 The main purpose is to illustrate the shape of the electrode unit and the lateral reflector in the corresponding embodiment, so other structures on the piezoelectric layer 130 are omitted.

[0038] Electrode units are disposed on the piezoelectric layer 130. The electrode units may include interdigitated electrodes. Figure 1 and Figure 2 In the illustrated embodiment, the electrode unit includes a set of first interdigital electrodes 141 and a set of second interdigital electrodes 143, the first interdigital electrodes 141 and the second interdigital electrodes 143 pointing towards... Figure 1The electrodes extend in the Y direction and are therefore parallel to each other. Each first interdigital electrode 141 and each second interdigital electrode 143 are insulated from each other. The first interdigital electrode 141 is used to connect to the input voltage, and the second interdigital electrode 143 is used for grounding. The electrode unit also includes a first common electrode 142 and a second common electrode 144. One end of each first interdigital electrode 141 is connected to the first common electrode 142, and one end of each second interdigital electrode 143 is connected to the second common electrode 144. The common electrode is also called a busbar.

[0039] The transverse reflector is also disposed on the piezoelectric layer 130 and can be disposed on the same layer as the electrode unit, including the one located on the first side of the electrode unit. Figure 1 The first reflector 152 (left side) and the second reflector located on the electrode unit (left side) Figure 1 The second reflector 154 (on the right side of the middle section). The transverse reflector is insulated from the electrode unit and is used to reflect sound waves laterally.

[0040] A piezoelectric layer 130 is disposed on the bottom electrode layer 170. The piezoelectric layer 130 comprises lithium niobate and / or lithium tantalate, both of which are single-crystal materials.

[0041] The bottom electrode layer 170 is disposed on the acoustic mirror 120. The bottom electrode layer 170 and the electrode units are used to form an electric field.

[0042] The acoustic mirror 120 includes at least one first acoustic reflective layer and at least one second acoustic reflective layer, wherein the acoustic impedance of each first acoustic reflective layer is less than the acoustic impedance of each second acoustic reflective layer. In one embodiment of this application, the layer of the acoustic mirror 120 closest to the bottom electrode layer 170 should be the first acoustic reflective layer, that is, there exists a first acoustic reflective layer that is closer to the bottom electrode layer 170 than all the second acoustic reflective layers. Figure 2 In the embodiment shown, the acoustic mirror 120 includes three first acoustic reflection layers (i.e., first acoustic reflection layer 121, first acoustic reflection layer 123, and first acoustic reflection layer 125) and two second acoustic reflection layers (i.e., second acoustic reflection layer 122 and second acoustic reflection layer 124), with each first acoustic reflection layer and second acoustic reflection layer alternately arranged.

[0043] The aforementioned acoustic resonator with thickness-direction excitation shear mode generates an electric field through the electrode unit and bottom electrode layer, and reflects the sound wave laterally through a transverse reflector, thus exciting the acoustic resonator into a thickness-direction shear vibration mode. Furthermore, because the piezoelectric layer uses single-crystal materials such as lithium niobate or lithium tantalate, it can exhibit high electromechanical coupling coefficients and high Q values ​​at frequencies above 3 GHz.

[0044] See Figure 3In the figure, the large arrows indicate the direction of the electric field, and the small arrows indicate the direction of mechanical wave propagation in the shear vibration mode. The electric field direction is mainly along the thickness direction of the piezoelectric layer 130. The bottom electrode layer 170 and the electrode units are also used to generate mechanical waves in the shear mode across the entire thickness of the piezoelectric layer 130. The single-crystal lithium niobate / lithium tantalate material, combined with the electrode unit structure and lateral reflector structure of this application, can obtain an optimized shear vibration mode with a higher sound wave velocity. While keeping the critical dimensions of the device (such as the interdigital step size) unchanged, it can achieve a higher frequency than conventional commercial filters.

[0045] In one embodiment of this application, the electrode unit is made of the same material as the lateral reflector and is a metal and / or alloy. In another embodiment of this application, the electrode unit may be made of aluminum (Al), copper (Cu), aluminum copper (AlCu), aluminum silicon copper (AlSiCu), molybdenum (Mo), tungsten (W), silver (Ag), or any other conductive metal.

[0046] In one embodiment of this application, the material of the bottom electrode layer 170 may include one or more of molybdenum, tungsten, ruthenium, platinum, titanium, aluminum, aluminum copper, aluminum silicon copper, and chromium.

[0047] exist Figure 2 In the illustrated embodiment, the acoustic resonator for the thickness-direction excitation shear mode further includes a carrier wafer 110. An acoustic mirror 120 is disposed on the carrier wafer 110.

[0048] In one embodiment of this application, a bonding aid layer is further provided between the carrier wafer 110 and the acoustic mirror 120 to assist in the bonding between the carrier wafer 110 and the acoustic mirror 120. In one embodiment of this application, the bonding aid layer is a thin layer of silicon dioxide.

[0049] In one embodiment of this application, each first acoustic reflector layer uses a low acoustic impedance material, and each second acoustic reflector layer uses a high acoustic impedance material. The low acoustic impedance material can be at least one selected from silicon dioxide, aluminum, benzocyclobutene (BCB), polyimide, and spin-on glass, while the high acoustic impedance material can be at least one selected from molybdenum, tungsten, titanium, platinum, aluminum nitride, aluminum oxide, tungsten oxide, and silicon nitride. It is understood that in other embodiments, the low acoustic impedance material and the high acoustic impedance material can also be combinations of other materials with a large impedance ratio.

[0050] The first and second acoustic reflective layers of the acoustic mirror 120 can have equal or unequal thicknesses. In one embodiment of this application, the first acoustic reflective layer is thicker the farther it is from the bottom electrode layer 170; the second acoustic reflective layer is thicker the farther it is from the bottom electrode layer 170. This design can achieve a larger Q value. See also Figure 4 ,exist Figure 4 In the illustrated embodiment, the thickness Tl1 of the first acoustic reflective layer 121 < the thickness Tl2 of the first acoustic reflective layer 123 < the thickness Tl3 of the first acoustic reflective layer 125, and the thickness Th1 of the second reflective layer 122 < the thickness Th2 of the second reflective layer 124. It is understood that in other embodiments, the thickness relationship between the first and second acoustic reflective layers can also be set according to other rules, for example, Tl1 = Tl2 = Tl3, Th1 = Th2; or Tl1 > Tl2 > Tl3, Th1 > Th2; or Tl1 <Tl2,Tl3<Tl2,Th1<Th2。

[0051] Figure 1 The position of the acoustic mirror 120 from a top-down perspective is also shown. Figure 1 The X-direction in the diagram represents the direction of sound wave propagation. The bottom electrode layer 170 is formed through patterning, and its width in the Y-direction can be the same as or different (greater or less) than the width of the acoustic mirror 120 in the Y-direction. The width of the bottom electrode layer 170 (i.e., Figure 1 The dimension in the Y direction is smaller than the spacing between the first common electrode 142 and the second common electrode 144, so that the orthographic projection of the bottom electrode layer 170 onto the plane containing the electrode unit is located between the first common electrode 142 and the second common electrode 144 in the Y direction. Figure 1 In the embodiment shown, the side of the bottom electrode layer 170 near the first common electrode 142 on the orthographic projection extends beyond the end of each second interdigital electrode 143 near the first common electrode 142, and the side near the second common electrode 144 extends beyond the end of each first interdigital electrode 141 near the second common electrode 144. That is, the bottom electrode layer 170 is wide enough so that both sides of its orthographic projection fall outside the second interdigital electrode 143 / outside the first interdigital electrode 141, respectively.

[0052] exist Figure 1 In the embodiment shown, the length and width of the bottom electrode layer 170 are both greater than those of the acoustic mirror 120, thereby covering the acoustic mirror 120 in both the X and Y directions.

[0053] The X-axis dimensions of the first and second acoustic reflectors can be the same or different. Figure 1 In the embodiment shown, the orthographic projection of each first acoustic reflector layer and the second acoustic reflector layer onto the plane where the electrode unit is located extends beyond the first reflector 152 and the second reflector 154 in the X direction. That is, the left edge of the orthographic projection falls to the left of the left edge of the first reflector 152, and the right edge falls to the right of the right edge of the second reflector 154.

[0054] exist Figure 1In the illustrated embodiment, the orthographic projections of each first acoustic reflector layer and second acoustic reflector layer onto the plane of the bottom electrode layer 170 are covered by the bottom electrode layer 170 in the X direction (i.e., the lengths of the first and second acoustic reflector layers in the X direction are less than the length of the bottom electrode layer 170 in the X direction). In another embodiment of this application, the orthographic projections of each second acoustic reflector layer onto the plane of the bottom electrode layer 170 extend beyond both sides of the bottom electrode layer 170 in the X direction, i.e., the length of the second acoustic reflector layer in the X direction is greater than the length of the bottom electrode layer 170 in the X direction.

[0055] like Figure 5 As shown, the electrode strips of the transverse reflector can be disconnected from each other, or they can be arranged as shown in the diagram. Figure 1 The electrodes shown are interconnected via a transverse structure. The electrode strips of the transverse reflector can be arranged parallel to the interdigitated fingers of the electrode unit.

[0056] Figure 6 It is along Figure 1 A cross-sectional view along line B-B'. In this embodiment, the areas of the acoustic mirror 120 and the bottom electrode layer 170 are smaller than the areas of the piezoelectric layer 130 and the carrier wafer 110; therefore, a filling layer is also provided around the acoustic mirror 120 (and the bottom electrode layer 170). In one embodiment of this application, the material of the filling layer may include one or more of silicon dioxide, molybdenum, tungsten, tungsten oxide, or silicon nitride. In one embodiment of this application, the material of the filling layer is the same as the material of each of the first acoustic reflection layers, thereby improving the quality factor of the acoustic resonator.

[0057] exist Figure 6 In the illustrated embodiment, the acoustic resonator for thickness-direction excitation shear mode further includes a first metal element 145 disposed on the first common electrode 141 and a second metal element 147 disposed on the second common electrode 143. The thickness of the first metal element 145 and the second metal element 147 is greater than the thickness of the electrode unit. The first metal element 145 and the second metal element 147 are used for... Figure 1 Acoustic reflection occurs in the Y direction.

[0058] In one embodiment of this application, the distance W between the center of the electrode strip closest to the electrode unit in the first reflector 152 and the center of the interdigitated electrode on the first side edge of the electrode unit is... g (For reference) Figure 7 The distance between the center of the electrode strip closest to the electrode unit in the second reflector 154 and the center of the interdigitated electrode on the second side edge of the electrode unit is 1 / 8 to 2 wavelengths of the sound wave.

[0059] The vibration frequency of the mechanical wave of the shear vibration mode formed in the piezoelectric layer 130 is related to the thickness of each film layer and the spacing between adjacent interdigital electrodes in the electrode unit. The stress is mainly limited to the area without metal coverage between the first interdigital electrode 141 and the second interdigital electrode 143.

[0060] exist Figure 6 In the illustrated embodiment, the acoustic resonator with thickness-direction excitation shear mode further includes a passivation layer 160. The passivation layer 160 is disposed on the piezoelectric layer 130 and covers the first interdigital electrode 141 and the second interdigital electrode 143. The passivation layer 160 can reduce the frequency temperature coefficient of the resonator and passivate the metal electrodes.

[0061] Figure 8 The simulation results show the characteristic admittance of an acoustic resonator with a thickness-direction excitation shear mode according to one embodiment. Where (b) is a local curve of (a), k t The electromechanical coupling coefficient is used. Characteristic frequency simulations were used to obtain the optimized stacked reflector thickness for the 4.07 GHz resonant frequency. The same characteristic frequency analysis was used to determine the optimal in-plane reflector layer location and the relative position of the reflector layer stack with respect to the interdigitated electrodes.

[0062] In the description of this specification, references to terms such as "some embodiments," "other embodiments," and "ideal embodiments" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0063] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features of the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0064] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. An acoustic resonator with a thickness-direction excitation shear mode, characterized in that, include: An acoustic mirror includes at least one first acoustic reflective layer and at least one second acoustic reflective layer, wherein the acoustic impedance of each first acoustic reflective layer is less than the acoustic impedance of each second acoustic reflective layer. The bottom electrode layer is located on the acoustic mirror; A piezoelectric layer is disposed on the bottom electrode layer, wherein the piezoelectric layer comprises lithium niobate and / or lithium tantalate of single crystal material; Electrode units are disposed on the piezoelectric layer; A lateral reflector, disposed on the piezoelectric layer, includes a first reflector located on a first side of the electrode unit and a second reflector located on a second side of the electrode unit, wherein the first side and the second side are opposite sides, and the lateral reflector is used to reflect sound waves laterally; The bottom electrode layer and electrode units are used to form an electric field; The electrode unit includes a first common electrode, a second common electrode, multiple first interdigital electrodes, and multiple second interdigital electrodes. Each first interdigital electrode is electrically connected to the first common electrode, and each second interdigital electrode is electrically connected to the second common electrode. Furthermore, each first interdigital electrode and each second interdigital electrode are insulated from each other. The first common electrode is used to receive the input voltage, and the second common electrode is used to ground. The width of the bottom electrode layer is smaller than the spacing between the first common electrode and the second common electrode, so that the orthographic projection of the bottom electrode layer on the plane where the electrode unit is located is between the first common electrode and the second common electrode; on the orthographic projection, the side of the bottom electrode layer near the first common electrode extends beyond the end of each second interdigital electrode near the first common electrode, and the side of the bottom electrode layer near the second common electrode extends beyond the end of each first interdigital electrode near the second common electrode. The acoustic resonator further includes a first metal component disposed on the first common electrode and a second metal component disposed on the second common electrode. The thickness of the first metal component and the second metal component is greater than the thickness of the electrode unit. The first metal component and the second metal component are used for acoustic reflection in a second direction. The second direction is perpendicular to the line connecting the transverse reflectors on both sides of the electrode unit and perpendicular to the thickness direction.

2. The acoustic resonator with thickness-direction excitation shear mode according to claim 1, characterized in that, The electric field formed by the bottom electrode layer and the electrode unit is mainly in the thickness direction of the piezoelectric layer. The bottom electrode layer and the electrode unit are also used to generate mechanical waves in shear mode over the entire thickness of the piezoelectric layer.

3. The acoustic resonator with thickness-direction excitation shear mode according to claim 1, characterized in that, The first acoustic reflection layer is thicker the farther it is from the bottom electrode layer; the second acoustic reflection layer is thicker the farther it is from the bottom electrode layer.

4. The acoustic resonator with thickness-direction excitation shear mode according to claim 1, characterized in that, The acoustic mirror comprises three first acoustic reflection layers and two second acoustic reflection layers, with the first and second acoustic reflection layers alternately arranged in the acoustic mirror.

5. The acoustic resonator with thickness-direction excitation shear mode according to claim 1, characterized in that, The material of the first acoustic reflective layer includes at least one of silicon dioxide, aluminum, benzocyclobutene, polyimide and spin glass, and the material of the second acoustic reflective layer includes at least one of molybdenum, tungsten, titanium, platinum, aluminum nitride, tungsten oxide and silicon nitride.

6. The acoustic resonator with thickness-direction excitation shear mode according to claim 1, characterized in that, The direction of the line connecting the transverse reflectors on both sides of the electrode unit is the direction of sound wave propagation; the orthographic projection of each of the first and second acoustic reflection layers on the plane extends beyond the first and second reflectors in the direction of the line connecting them.

7. The acoustic resonator with thickness-direction excitation shear mode according to claim 1 or 6, characterized in that, The orthographic projection of each of the second acoustic reflection layers onto the plane where the bottom electrode layer is located extends beyond both sides of the bottom electrode layer in a first direction, or the orthographic projection of each of the first and second acoustic reflection layers onto the plane where the bottom electrode layer is located is covered by the bottom electrode layer. The first direction is parallel to the direction of sound wave propagation.

8. The acoustic resonator with thickness-direction excitation shear mode according to claim 1, characterized in that, The first reflector and the second reflector each include at least one electrode strip. The center of the electrode strip closest to the electrode unit in the first reflector is 1 / 8 to 2 wavelengths of the sound wave from the center of the interdigitated electrode on the first side edge of the electrode unit. The center of the electrode strip closest to the electrode unit in the second reflector is 1 / 8 to 2 wavelengths of the sound wave from the center of the interdigitated electrode on the second side edge of the electrode unit.

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