Acoustic resonator device, forming method thereof and radio frequency filter

Abstract

The invention relates to an acoustic resonator device and a forming method thereof, and a radio frequency filter. The acoustic resonator device comprises a substrate layer; the sacrificial layer is located on the substrate layer and comprises a cavity; the piezoelectric film layer is located on the sacrificial layer and comprises at least one strip-shaped piezoelectric film and etching grooves located in the two sides of each strip-shaped piezoelectric film, and the etching grooves are communicated with the cavity; the bottom conductor layer is located below the piezoelectric film layer and comprises a bottom bus bar and at least one bottom finger bar electrode suspended in the cavity; the top conductor layer is located on the piezoelectric film layer and comprises a top bus bar, a top terminal, a bottom terminal and at least one top finger bar electrode; the top finger strip electrodes, the bottom finger strip electrodes and the strip-shaped piezoelectric films are in one-to-one correspondence. In the embodiment of the invention, the suspended top finger strip electrode, the strip-shaped piezoelectric film and the bottom finger strip electrode are arranged in the device to support a mode of double shear bulk acoustic waves excited by a vertical electric field, so that the device meets the requirements of higher frequency and larger bandwidth.

Description

Technical Field

[0001] The present invention belongs to the technical field of resonators, and specifically relates to an acoustic wave resonator device, a forming method thereof, and a radio frequency filter. Background Art

[0002] As an important component in the front-end module, a radio frequency filter is a two-port element used to allow and control the passage of radio frequency signals within a specific frequency range, and block or attenuate radio frequency signals within the remaining frequency ranges. Radio frequency filters are crucial in systems using wireless communication networks, including base stations, mobile terminals, Internet of Things devices, automobiles, new industrial management systems, and so on. The performance of radio frequency filters is mainly evaluated by parameters such as the center frequency of the passband, bandwidth, insertion loss, rejection, isolation, and power handling capacity. Using radio frequency filters with better performance in mobile communication, satellite communication, broadcasting, and other communication systems can achieve better signal quality, larger network capacity, higher energy efficiency, etc. at all levels of the system, helping to separate different signal frequency bands, improve signal quality, and reduce interference.

[0003] With the rapid development of communication standards, the widely promoted 5G communication and future 6G communication standards have put forward higher requirements for radio frequency filters, mainly including higher frequencies, larger bandwidths, and smaller sizes. The bandwidth and insertion loss of radio frequency filters, as important parameters, have a huge impact on the performance of the entire radio frequency system. In the spectrum specification of 5G communication, the n77 band and n79 band in the first frequency band (Frequency Range 1, FR1) have bandwidths of 900 MHz and 600 MHz at a center frequency of about 4 GHz, which pose huge challenges for the thin film bulk acoustic resonators (FBARs) and surface acoustic wave (SAW) resonators used in traditional radio frequency filters. For the future 5G first frequency band spectrum and 6G communication spectrum (greater than 6 GHz), existing technologies are difficult to simultaneously meet the requirements of radio frequency filters for high frequencies and high performance. Therefore, there is an urgent need for a new type of acoustic wave resonator that can solve the technical problem that traditional acoustic wave resonators cannot meet the requirements of higher frequencies and larger bandwidths. Summary of the Invention

[0004] To solve the above technical problems, the present application provides an acoustic wave resonator device, a forming method thereof, and a radio frequency filter.

[0005] In a first aspect, an embodiment of the present application discloses an acoustic wave resonator device, including:

[0006] A substrate layer;

[0007] A sacrificial layer located on a substrate layer; the sacrificial layer includes at least one cavity;

[0008] A piezoelectric thin film layer located on the sacrificial layer; the piezoelectric thin film layer includes at least one strip-shaped piezoelectric thin film arranged in parallel and etching grooves located on both sides of each strip-shaped piezoelectric thin film; the etching grooves communicate with the cavity;

[0009] A bottom conductor layer located under the piezoelectric thin film layer; the bottom conductor layer is in contact with the strip-shaped piezoelectric thin film; the bottom conductor layer includes a bottom bus bar and at least one bottom finger electrode, and at least one bottom finger electrode is connected to the bottom bus bar; the bottom finger electrode is suspended in the cavity; the bottom finger electrode and the strip-shaped piezoelectric thin film correspond one by one;

[0010] A top conductor layer located on the piezoelectric thin film layer; the top conductor layer is in contact with the strip-shaped piezoelectric thin film; the top conductor layer includes a top bus bar, a top terminal, a bottom terminal and at least one top finger electrode; one end of the top bus bar is connected to the top terminal, and the other end is connected to at least one top finger electrode; the bottom terminal is partially located in the piezoelectric thin film layer and is in contact with the bottom bus bar; the top finger electrode and the strip-shaped piezoelectric thin film correspond one by one.

[0011] In some possible embodiments,

[0012] The piezoelectric thin film layer includes a through hole; the bottom terminal is partially located in the through hole and is in contact with the bottom bus bar.

[0013] In some possible embodiments,

[0014] At least one bottom finger electrode and its corresponding top finger electrode are configured to apply corresponding radio frequency signals to excite dual shear bulk acoustic waves in the corresponding strip-shaped piezoelectric thin film.

[0015] In some possible embodiments,

[0016] The resonant frequency of the acoustic wave resonator device is jointly determined by the width and thickness of the stack formed by the top finger electrode, the strip-shaped piezoelectric thin film and the bottom finger electrode.

[0017] In some possible embodiments,

[0018] The width of the strip-shaped piezoelectric thin film is less than or equal to the width of the bottom finger electrode, and the length of the strip-shaped piezoelectric thin film is greater than or equal to the length of the bottom finger electrode;

[0019] The width of the strip-shaped piezoelectric thin film is greater than or equal to the width of the top finger electrode, and the length of the strip-shaped piezoelectric thin film is greater than or equal to the length of the top finger electrode.

[0020] In some possible embodiments,

[0021] The ratio range of the sum of the thicknesses of the top finger electrode, the strip-shaped piezoelectric thin film and the bottom finger electrode to the width of the strip-shaped piezoelectric thin film is 0.5 - 1.5.

[0022] In some possible embodiments,

[0023] the material of the piezoelectric thin film layer is at least one of lithium niobate, lithium tantalate, and aluminum nitride; the thickness of the piezoelectric thin film is 50-1000 nanometers;

[0024] the material of the top conductor layer is at least one of aluminum, molybdenum, chromium, gold, platinum, and titanium;

[0025] the material of the bottom conductor layer is at least one of aluminum, molybdenum, chromium, gold, platinum, and titanium.

[0026] In some possible embodiments,

[0027] the substrate layer is a single-layer structure composed of silicon or silicon dioxide;

[0028] or; the substrate layer is a laminated structure composed of at least two materials of silicon, silicon carbide, sapphire, or silicon dioxide.

[0029] In some possible embodiments,

[0030] the material of the sacrificial layer is silicon or silicon dioxide.

[0031] In a second aspect, an embodiment of the present application discloses a radio frequency filter, including the acoustic wave resonator device described in any one of the above;

[0032] A plurality of acoustic wave resonator devices are conductively interconnected to form a plurality of series resonators and a plurality of parallel resonators required for the topological structure of the radio frequency filter; when the thicknesses of the top finger bar electrodes, the strip-shaped piezoelectric thin films, and the bottom finger bar electrodes in each acoustic wave resonator device are the same, a radio frequency filter with a preset frequency band is obtained by adjusting the widths of the top finger bar electrodes, the strip-shaped piezoelectric thin films, and the bottom finger bar electrodes, and the values of the widths in the parallel resonators are greater than the values of the widths in the series resonators.

[0033] In a third aspect, an embodiment of the present application discloses a method for forming an acoustic wave resonator device, including:

[0034] Providing a combination; the combination includes a substrate layer, a sacrificial layer located on the substrate layer, an initial bottom conductor layer located in the sacrificial layer, and a piezoelectric thin film layer located on the sacrificial layer and the initial bottom conductor layer; the initial bottom conductor layer includes a bottom bus bar and a bottom finger bar electrode part;

[0035] Etching the piezoelectric thin film layer to form a through hole to expose a part of the bottom bus bar;

[0036] Form an initial top conductor layer on the remaining piezoelectric thin film layer; the initial top conductor layer includes a top terminal, a bottom terminal, a top bus bar, and a top finger electrode portion, the bottom terminal fills the via hole and contacts the bottom bus bar, and the top terminal contacts the top bus bar;

[0037] Etch the stack formed by the bottom finger electrode portion, the piezoelectric thin film layer, and the top finger electrode portion to obtain at least one resonator structure arranged in parallel and etching grooves on both sides of each resonator structure; each resonator structure includes a top finger electrode, a strip-shaped piezoelectric thin film, and a bottom finger electrode, the top finger electrode is connected to the top electrode bus bar, and the bottom finger electrode is connected to the bottom bus bar;

[0038] Remove a part of the sacrificial layer under the bottom finger electrode to form a cavity, obtaining an acoustic wave resonator device; the resonator structure is suspended in the cavity.

[0039] In some possible embodiments,

[0040] Provide a combination body including:

[0041] Provide a transfer substrate layer and a piezoelectric thin film layer;

[0042] Bond the transfer substrate layer and the piezoelectric thin film layer;

[0043] Form an initial bottom conductor layer on the piezoelectric thin film layer;

[0044] Form a sacrificial layer on the initial bottom conductor layer and the piezoelectric thin film layer not covered by the initial bottom conductor layer;

[0045] Bond the upper interface of the sacrificial layer to the substrate layer;

[0046] Remove the transfer substrate layer to obtain the combination body.

[0047] The technical solution provided by the embodiments of the present application has the following technical effects:

[0048] The acoustic resonator device of the embodiment of the present application includes a substrate layer; a sacrificial layer located on the substrate layer; the sacrificial layer includes at least one cavity; a piezoelectric thin film layer located on the sacrificial layer; the piezoelectric thin film layer includes at least one strip-shaped piezoelectric thin film arranged in parallel and etching grooves located on both sides of each strip-shaped piezoelectric thin film; the etching grooves communicate with the cavities; a bottom conductor layer located under the piezoelectric thin film layer; the bottom conductor layer is in contact with the strip-shaped piezoelectric thin film; the bottom conductor layer includes a bottom bus bar and at least one bottom finger electrode, and at least one bottom finger electrode is connected to the bottom bus bar; the bottom finger electrode is suspended in the cavity; the bottom finger electrode and the strip-shaped piezoelectric thin film correspond one by one; a top conductor layer located on the piezoelectric thin film layer; the top conductor layer is in contact with the strip-shaped piezoelectric thin film; the top conductor layer includes a top bus bar, a top terminal, a bottom terminal and at least one top finger electrode; one end of the top bus bar is connected to the top terminal, and the other end is connected to at least one top finger electrode; the bottom terminal is partially located in the piezoelectric thin film layer and is in contact with the bottom bus bar; the top finger electrode and the strip-shaped piezoelectric thin film correspond one by one. In the embodiment of the present application, by providing suspended top finger electrodes, strip-shaped piezoelectric thin films and bottom finger electrodes in the device to support the mode of dual-shear bulk acoustic wave excited by a vertical electric field, the device can meet the requirements of higher frequency and larger bandwidth. Description of the Drawings

[0049] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0050] Figure 1 A schematic structural diagram of an acoustic resonator device provided by an embodiment of the present application from a top view angle;

[0051] Figure 2 is a schematic structural diagram of a transverse cross-section of an acoustic resonator device provided by an embodiment of the present application;

[0052] Figure 3 is a schematic structural diagram of a longitudinal cross-section of an acoustic resonator device provided by an embodiment of the present application;

[0053] Figure 4 is a schematic diagram of a resonator structure provided by an embodiment of the present application;

[0054] Figure 5 A schematic structural diagram of an acoustic resonator device provided by an embodiment of the present application including multiple resonator structures from a top view angle;

[0055] Figure 6It is a schematic cross-sectional structure diagram of an acoustic wave resonator device including multiple resonator structures provided by an embodiment of the present application;

[0056] Figure 7 It is a schematic flowchart of a method for forming an acoustic wave resonator device provided by an embodiment of the present application;

[0057] Figure 8 and Figures 10 - 18 It is a schematic structure diagram during the formation process of an acoustic wave resonator device provided by an embodiment of the present application;

[0058] Figure 9 It is a schematic flowchart of a method for forming a combination body provided by an embodiment of the present application;

[0059] Figure 19 It is a schematic diagram of the displacement of the main resonance mode of an acoustic wave resonator device provided by an embodiment of the present application;

[0060] Figure 20 It is a schematic diagram of the finite element simulation admittance curve of an acoustic wave resonator device provided by an embodiment of the present application;

[0061] Figure 21 It is a schematic diagram of the finite element simulation admittance curve of an acoustic wave resonator device using strip-shaped piezoelectric thin films with different widths provided by an embodiment of the present application;

[0062] Figure 22 It is a schematic diagram of the resonance frequencies of acoustic wave resonator devices using strip-shaped piezoelectric thin films with different widths corresponding to top finger electrodes and bottom finger electrodes made of different materials provided by an embodiment of the present application;

[0063] Figure 23 It is a schematic diagram of a radio frequency filter including multiple acoustic wave resonator devices provided by an embodiment of the present application;

[0064] Figure 24 It is a schematic diagram of the admittance curve of an acoustic wave resonator device in a radio frequency filter including multiple acoustic wave resonator devices provided by an embodiment of the present application;

[0065] Figure 25 It is a schematic diagram of the insertion loss curve of an acoustic wave resonator device in a radio frequency filter including multiple acoustic wave resonator devices provided by an embodiment of the present application.

[0066] In the figure:

[0067] 100 - Substrate layer, 200 - Sacrificial layer, 201 - Cavity, 300 - Piezoelectric thin film layer, 301 - Strip-shaped piezoelectric thin film, 302 - Etching groove, 303 - Through hole, 410 - Initial bottom conductor layer, 411 - Bottom finger electrode, 412 - Bottom bus bar, 413 - Bottom terminal, 414 - Bottom finger electrode part, 420 - Initial top conductor layer, 421 - Top finger electrode, 422 - Top bus bar, 423 - Top terminal, 424 - Top finger electrode part, 500 - Transfer substrate layer. Detailed implementation manners

[0068] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0069] It should be noted that the term "one embodiment" or "embodiment" in the description of the embodiments of the present application refers to a specific feature, structure, or characteristic that may be included in at least one implementation manner of the present application. It should be understood that in the description and claims of the embodiments of the present application and the above drawings, the orientation or positional relationship indicated by the terms "upper", "lower", "top", "bottom", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application. The terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. Moreover, the terms "first", "second", etc. are used to distinguish similar objects and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present application described here can be implemented in an order other than those illustrated or described here. In addition, in the description of this embodiment, unless otherwise specified, the meaning of "a plurality" is two or more. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, or product that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0070] It should be understood that when an element or layer is referred to as being "on", "adjacent to", "connected to", or "coupled to" another element or layer, it can be directly on, adjacent to, connected, or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as being "directly on", "directly adjacent to", "directly connected to", or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although terms such as first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Thus, without departing from the teachings of the present application, the first element, component, region, layer, or part discussed below may be referred to as the second element, component, region, layer, or part. And when discussing the second element, component, region, layer, or part, it does not imply that there must be a first element, component, region, layer, or part in the present application.

[0071] For the purpose of making the objectives, technical solutions, and advantages of the embodiments of the present application more clearly understood, the following further describes the embodiments of the present application in detail in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present application and are not used to limit the embodiments of the present application.

[0072] The present application provides a novel acoustic resonator device to solve the problem that traditional acoustic resonators cannot meet the requirements of higher frequencies and larger bandwidths. The acoustic resonator device utilizes a brand-new mode to achieve higher frequency selectivity, smaller size, and higher stability. The RF filter prepared by using the acoustic resonator device can meet the requirements of higher frequencies and larger bandwidths for RF filters proposed by 5G communication and future 6G communication standards.

[0073] Figure 1 A schematic structural view of an acoustic resonator device provided by an embodiment of the present application from a top view angle, Figure 2 is a schematic structural view of a transverse cross-section of an acoustic resonator device provided by an embodiment of the present application, Figure 3 is a schematic structural view of a longitudinal cross-section of an acoustic resonator device provided by an embodiment of the present application. Among them, Figure 2 is Figure 1 a schematic view of cross-section A-A of the structure shown, Figure 3 is Figure 1 a schematic view of cross-section B-B of the structure shown.

[0074] In the embodiments of the present application, as Figures 1 - 3As shown, the acoustic resonator device includes a substrate layer, a sacrificial layer located on the substrate layer, a piezoelectric thin film layer located on the sacrificial layer, a bottom conductor layer located under the piezoelectric thin film layer, and a top conductor layer located on the piezoelectric thin film layer. The sacrificial layer includes at least one cavity. The piezoelectric thin film layer includes at least one strip-shaped piezoelectric thin film arranged side by side and etching grooves located on both sides of each strip-shaped piezoelectric thin film, and the etching grooves communicate with the cavity. The bottom conductor layer is in contact with the strip-shaped piezoelectric thin film. The bottom conductor layer includes a bottom bus bar and at least one bottom finger electrode, and at least one bottom finger electrode is connected to the bottom bus bar. The bottom finger electrode is suspended in the cavity, and the bottom finger electrode and the strip-shaped piezoelectric thin film correspond one by one. The top conductor layer is in contact with the strip-shaped piezoelectric thin film. The top conductor layer includes a top bus bar, a top terminal, a bottom terminal, and at least one top finger electrode; one end of the top bus bar is connected to the top terminal, and the other end is connected to at least one top finger electrode; the bottom terminal is partially located in the piezoelectric thin film layer and is in contact with the bottom bus bar. The top finger electrode and the strip-shaped piezoelectric thin film correspond one by one.

[0075] In an embodiment of the present application, the substrate layer 100 and the sacrificial layer 200 at the bottom end of the acoustic resonator device provide mechanical support for the piezoelectric thin film layer 300 located thereon.

[0076] In an embodiment of the present application, the substrate layer 100 may be a single-layer structure composed of silicon or silicon dioxide, or a laminated structure composed of at least two materials among silicon, silicon carbide, sapphire, or silicon dioxide.

[0077] In an embodiment of the present application, the material of the sacrificial layer 200 is silicon or silicon dioxide.

[0078] In an embodiment of the present application, as Figure 2 and Figure 3 shown, the cavity 201 in the sacrificial layer 200 is obtained by etching the sacrificial layer 200 with an etchant. Generally, a certain thickness of the sacrificial layer 200 remains below the cavity 201.

[0079] In some possible embodiments, the cavity 201 penetrates the sacrificial layer 200 in the vertical direction and communicates with the substrate layer 100. In some cases, the cavity 201 may also extend into the substrate layer 100 in the vertical direction, or even penetrate the substrate layer 100 in the vertical direction.

[0080] In some possible embodiments, the cavity 201 may have different shapes, such as a rectangle, a rounded rectangle, or an irregular polygon.

[0081] In an embodiment of the present application, as Figures 1 - 3As shown, the bottom conductor layer is located below the piezoelectric thin film layer 300 and contacts the bottom end of the strip-shaped piezoelectric thin film 301. The bottom conductor layer includes a bottom bus bar 412 and at least one bottom finger electrode 411. All the bottom finger electrodes 411 are arranged in parallel, and one end of each bottom finger electrode 411 is connected to the bottom bus bar 412. All the bottom finger electrodes 411 are suspended in the cavity 201, and each bottom finger electrode 411 corresponds to the strip-shaped piezoelectric thin film 301 one by one.

[0082] In the embodiment of the present application, as Figures 1 - 3 shown, the top conductor layer is located above the piezoelectric thin film layer 300 and contacts the top end of the strip-shaped piezoelectric thin film 301. The top conductor layer includes a top bus bar 422, a top terminal 423, a bottom terminal 413, and at least one top finger electrode 421. All the top finger electrodes 421 are arranged in parallel, and each top finger electrode 421 corresponds to the strip-shaped piezoelectric thin film 301 one by one. One end of the top bus bar 422 is connected to the top terminal 423, and the other end is connected to all the top finger electrodes 421. Part of the bottom terminal 413 is located on the piezoelectric thin film layer 300, and part of it is located in the piezoelectric thin film layer 300. The part of the bottom terminal 413 located in the piezoelectric thin film layer 300 contacts the bottom bus bar 412. Among them, the occupied space of the part of the bottom terminal 413 located in the piezoelectric thin film layer 300 does not need to be too large, and the contact between the bottom terminal 413 and the bottom bus bar 412 can be achieved.

[0083] In the implementation of the present application, the top bus bar 422 and the top finger electrode 421 have the same material composition, and the bottom bus bar 422 and the bottom finger electrode 411 have the same material composition. The materials of the top finger electrode 421, the top bus bar 422, the bottom finger electrode 411, the bottom bus bar 412, the top terminal 423, and the bottom terminal 413 are all at least one of aluminum, molybdenum, chromium, gold, platinum, and titanium.

[0084] In some possible embodiments, the bottom finger electrode 411 and the top finger electrode 421 have the same material composition, and the top bus bar 422 and the bottom bus bar 422 have the same material composition.

[0085] In some possible embodiments, the bottom finger electrode 411 and the top finger electrode 421 have different material compositions, and the top bus bar 422 and the bottom bus bar 422 have different material compositions.

[0086] In the embodiment of the present application, during the preparation process of the acoustic wave resonator device, in order to connect the bottom bus bar 412 located below the piezoelectric thin film layer 300 and the bottom terminal 413 located above the piezoelectric thin film layer 300, it is selected to form a through hole in the piezoelectric thin film layer 300, and during the process of preparing the top conductor layer, a part of the bottom terminal 413 is filled into the through hole and made to contact the bottom bus bar 412, so as to realize the connection between the bottom terminal 413 and the bottom bus bar 412.

[0087] In some possible embodiments, during the process of fabricating the top conductor layer, the through holes in the piezoelectric thin film layer 300 are completely filled with the bottom terminals 413, resulting in no through holes remaining in the piezoelectric thin film layer 300 in the finally formed acoustic wave resonator device.

[0088] In some possible embodiments, during the process of fabricating the top conductor layer, the through holes in the piezoelectric thin film layer 300 are not completely filled with the bottom terminals 413, resulting in through holes still existing in the piezoelectric thin film layer 300 in the finally formed acoustic wave resonator device, and the bottom terminals 413 are partially located in the through holes and in contact with the bottom bus bar 412.

[0089] In the embodiments of the present application, the portion of the piezoelectric thin film layer 300 other than the strip-shaped piezoelectric thin film 301, the etching groove 302, and the bottom terminals 413 located in the piezoelectric thin film layer 300 is attached to the upper surface of the sacrificial layer 200.

[0090] In some possible embodiments, the thickness of the piezoelectric thin film layer 300 is 50 - 1000 nanometers.

[0091] Optionally, the thickness of the piezoelectric thin film layer 300 is 50 nanometers; optionally, the thickness of the piezoelectric thin film layer 300 is 525 nanometers; optionally, the thickness of the piezoelectric thin film layer 300 is 1000 nanometers.

[0092] In some possible embodiments, the thickness of the strip-shaped piezoelectric thin film 301 is 50 - 1000 nanometers.

[0093] Optionally, the thickness of the strip-shaped piezoelectric thin film 301 is 50 nanometers; optionally, the thickness of the strip-shaped piezoelectric thin film 301 is 525 nanometers; optionally, the thickness of the strip-shaped piezoelectric thin film 301 is 1000 nanometers.

[0094] In the embodiments of the present application, the material of the piezoelectric thin film layer 300 can be a piezoelectric material such as lithium niobate, lithium tantalate, or aluminum nitride. Moreover, a piezoelectric material with an X-cut direction (especially an X-cut lithium niobate material) is preferably selected to form the piezoelectric thin film layer 300 so that the acoustic wave resonator device can obtain a larger electromechanical coupling coefficient. As Figure 1 shown, the arrow direction in the figure indicates the long side direction of the acoustic wave resonator device, and its direction is between the +Y axis and the +Z axis.

[0095] In the embodiments of the present application, each strip-shaped piezoelectric thin film 301 has its corresponding top finger electrode 421 and bottom finger electrode 411, and each strip-shaped piezoelectric thin film 301, the top finger electrode 421 located thereon and the bottom finger electrode 411 located thereunder form a resonator structure. The resonator structure is located in the cavity 201. The bottom finger electrode 411 at the bottom end of the resonator structure is suspended in the cavity 201, the top finger electrode 421 at the top end of the resonator structure is exposed to the external environment, and etching grooves 302 communicating with the cavity 201 are arranged on both sides of the strip-shaped piezoelectric thin film 301 in the resonator structure. In the entire acoustic wave resonator device, the upper and lower bottom surfaces and the left and right side surfaces of each resonator structure are all mechanically free interfaces that are not in contact with other objects.

[0096] In some possible embodiments, the material of the strip-shaped piezoelectric thin film 301 is a piezoelectric material with an X-cut, and α in its Euler angles (α, 90, -90) is between 90 degrees and 180 degrees. Here, the definition of the Euler angles uses the order of (Z, X, Z). The selection of the Euler angles is crucial for determining the piezoelectric properties of the material, the electromechanical coupling coefficient, and the overall performance of the acoustic wave resonator. By optimizing the selection of the Euler angles, an acoustic wave resonator device with better performance that meets the requirements can be designed. At this time, the directions of the top finger electrode 421 and the bottom finger electrode 411 in each resonator structure are between the +Y axis and the +Z axis or between the -Y axis and the -Z axis of the strip-shaped piezoelectric thin film 301.

[0097] In the embodiments of the present application, since the density and Young's modulus of the materials selected for the top finger electrode 421 and the bottom finger electrode 411 will significantly affect the resonance frequency of the acoustic wave resonator device, it is necessary to select appropriate materials to prepare the top finger electrode 421 and the bottom finger electrode 411 according to the requirements.

[0098] In some possible embodiments, the materials of the top finger electrode 421 and the bottom finger electrode 411 are both at least one of aluminum, molybdenum, chromium, gold, platinum, and titanium. The top finger electrode 421 and the bottom finger electrode 411 can both be composed of one or more layers of conductive materials, and each layer of conductive material is a material such as aluminum, molybdenum, chromium, gold, platinum, and titanium or a combination of these materials. Moreover, when the materials at the uppermost end and / or the lowermost end of the top finger electrode 421 and the bottom finger electrode 411 are metal materials such as titanium or chromium, the adhesion between the top finger electrode 421 and the bottom finger electrode 411 and other structures can be improved, the power capacity can be increased, and the top finger electrode 421 and the bottom finger electrode 411 can be protected.

[0099] In the embodiments of the present application, the top finger electrode 421 and the bottom finger electrode 411 have exactly the same composition. Moreover, the top finger electrode 421 and the bottom finger electrode 411 have the same thickness. By providing the top finger electrode 421 and the bottom finger electrode 411 with the same composition and the same thickness, spurious modes can be reduced to ensure the flatness of the passband of the filter composed of such a SAW resonator device.

[0100] Figure 4 is a schematic diagram of a resonator structure provided by an embodiment of the present application, as Figure 4 shown, the width of the top finger electrode 421 is Wt, the thickness is Ht, and the length is Lt; the width of the strip-shaped piezoelectric thin film 301 is Wp, the thickness is Hp, and the length is Lp; the width of the bottom finger electrode 411 is Wb, the thickness is Hb, and the length is Lb. Wt is less than or equal to Wp, and Wp is less than or equal to Wb, that is, the width of the top finger electrode 421 is less than or equal to the width of the strip-shaped piezoelectric thin film 301, and the width of the strip-shaped piezoelectric thin film 301 is less than or equal to the width of the bottom finger electrode 411. Both Lt and Lb are less than or equal to Lp, that is, the length of the strip-shaped piezoelectric thin film 301 is greater than or equal to the length of the bottom finger electrode 411, and the length of the strip-shaped piezoelectric thin film 301 is greater than or equal to the length of the top finger electrode 421. As Figure 3 shown, the bottom finger electrode 411, the top finger electrode 421 and the strip-shaped piezoelectric thin film 301 have an overlapping length, and this length is defined as the aperture Ap of the resonator structure.

[0101] In the embodiments of the present application, the widths of the top finger electrode 421, the strip-shaped piezoelectric thin film 301, and the bottom finger electrode 411 are equal. At this time, the cross-section of the resonator structure composed of the top finger electrode 421, the strip-shaped piezoelectric thin film 301, and the bottom finger electrode 411 is in the shape of a rectangle as Figure 4 shown.

[0102] In some possible embodiments, limited by the manufacturing process, the width of the entire resonator structure increases from the top end of the top finger electrode 421 to the bottom end of the bottom finger electrode 411, resulting in the shape of the cross-section of the entire resonator structure no longer being a rectangle as Figure 4 shown, but a trapezoid with a narrow top and a wide bottom. Although the width of the entire resonator structure increases from top to bottom, since the numerical change in the width is extremely small, the performance of the resonator structure is not adversely affected thereby.

[0103] In the embodiments of the present application, the ratio range of the sum of the thicknesses of the top finger electrode 421, the strip-shaped piezoelectric thin film 301, and the bottom finger electrode 411 (that is, the sum of Ht, Hp, and Hb) to the width Wp of the strip-shaped piezoelectric thin film 301 is 0.5 - 1.5.

[0104] In the embodiments of the present application, the resonant frequency of the acoustic resonator device is jointly determined by the width and thickness of the stack formed by the top finger electrode 421, the strip-shaped piezoelectric thin film 301, and the bottom finger electrode 411.

[0105] In the embodiments of the present application, the cavity 201 is rectangular. The length of the rectangle is greater than the aperture Ap, and the width of the rectangle is greater than the width Wp of the strip-shaped piezoelectric thin film 301.

[0106] In some possible embodiments, the sacrificial layer 200 includes at least one cavity 201, and at least one resonator structure is disposed in each cavity 201. According to different requirements, the cavities 201 with the required number and size can be provided in the sacrificial layer 200, and the same number or different numbers of resonator structures can be provided in different cavities 201. Among them, Figures 1 - 3 The sacrificial layer 200 in the shown acoustic resonator device includes one cavity 201, and one resonator structure is disposed in the cavity 201.

[0107] In some possible embodiments, when multiple resonator structures are provided in the acoustic resonator device, the multiple resonator structures are arranged in parallel, and the distance between any two adjacent resonator structures can be adjusted according to actual requirements. All the resonator structures can be arranged in a parallel form or a non-parallel form.

[0108] In some possible embodiments, when multiple resonator structures are provided in the acoustic resonator device, the sizes of all the resonator structures are the same, that is, the sizes of the strip-shaped piezoelectric thin film 301, the bottom finger electrode 411, and the top finger electrode 421 in all the resonator structures are the same.

[0109] In the embodiments of the present application, the top terminal 423 in contact connection with the top bus bar 422 and the bottom terminal 413 in contact connection with the bottom electrode bus bar 311 are the radio frequency terminals of the resonator structure, and the radio frequency signal required for the target mode of the acoustic resonator device can be applied thereto.

[0110] In the embodiments of the present application, the target mode of the acoustic resonator device is a dual-shear bulk acoustic wave excited by a vertical electric field. The dual-shear bulk acoustic wave is generated by coupling a horizontal shear wave and a vertical shear wave, and only half a wavelength exists in both the thickness and width of the structural cross-section for this mode. At least one bottom finger electrode 411 and its corresponding top finger electrode 421 in the acoustic resonator device are configured to apply corresponding radio frequency signals to excite the dual-shear bulk acoustic wave in the corresponding strip-shaped piezoelectric thin film 301. In this regard, the resonator structure composed of the finger electrode 421, the strip-shaped piezoelectric thin film 301, and the bottom finger electrode 411 provides the necessary condition for the dual-shear bulk acoustic wave, which has four mechanical free interfaces in the structural cross-section. When the horizontal shear wave and the vertical shear wave have the same resonance frequency for a resonator structure with specific dimensions, the electromechanical coupling coefficient of the dual-shear bulk acoustic wave reaches the maximum value.

[0111] Figure 5 Schematic structural diagram of an acoustic resonator device including a plurality of resonator structures from a top-down perspective provided by an embodiment of the present application, Figure 6 is a schematic structural diagram of a transverse cross-section of an acoustic resonator device including a plurality of resonator structures provided by an embodiment of the present application. Among them, Figure 6 is Figure 5 a schematic diagram of cross-section C-C of the structure shown.

[0112] In the embodiments of the present application, as Figure 5 and Figure 6 shown, a plurality of resonator structures arranged in parallel are provided in the acoustic resonator device. Each resonator structure is composed of a top finger electrode 421 ( Figure 6 There are 6 top finger electrodes 421, and the serial number indicates one of them), a strip-shaped piezoelectric thin film 301 ( Figure 6 There are 6 strip-shaped piezoelectric thin films 301, and the serial number indicates one of them), and a bottom finger electrode 411 ( Figure 6 There are 6 bottom finger electrodes 411, and the serial number indicates one of them). By providing a plurality of resonator structures in the acoustic resonator device, the capacitance requirements of a radio frequency filter formed by the acoustic resonator device can be met, thereby meeting the impedance requirements of the radio frequency filter.

[0113] The present application provides a method for forming an acoustic resonator device. Figure 7 is a schematic flowchart of a method for forming an acoustic resonator device provided by an embodiment of the present application. As Figure 7 shown, the flowchart includes at least the following steps S701-S705:

[0114] In step S701, a combination body is provided; the combination body includes a substrate layer, a sacrificial layer located on the substrate layer, an initial bottom conductor layer located in the sacrificial layer, and a piezoelectric thin film layer located on the sacrificial layer and the initial bottom conductor layer; the initial bottom conductor layer includes a bottom bus bar and a bottom finger electrode portion.

[0115] Figure 8 It is a schematic structure diagram during the formation process of an acoustic wave resonator device provided by an embodiment of the present application Figure One , such as Figure 8 shown, the combination body includes a substrate layer 100, a sacrificial layer 200 located on the substrate layer 100, an initial bottom conductor layer 410 located in the sacrificial layer 200, and a piezoelectric thin film layer 300 located on the sacrificial layer 200. Among them, the initial bottom conductor layer 410 includes a bottom bus bar and a bottom finger electrode portion.

[0116] Figure 9 It is a schematic flow chart of a method for forming a combination body provided by an embodiment of the present application. As Figure 9 shown, the flow chart at least includes the following steps S901 - S906:

[0117] In step S901, a transfer substrate layer and a piezoelectric thin film layer are provided.

[0118] In an embodiment of the present application, the transfer substrate layer 500 includes a silicon material layer and a thin silicon dioxide layer located on the silicon material layer. The material of the piezoelectric thin film layer 300 is a piezoelectric material such as lithium niobate, lithium tantalate, or aluminum nitride.

[0119] In some possible embodiments, the material of the transfer substrate layer 500 can also be other material combinations that can be bonded to the piezoelectric thin film layer 300 and peeled off through etching or other processes.

[0120] In some possible embodiments, the material of the piezoelectric thin film layer 300 can also be other single - crystal piezoelectric materials with excellent performance in terms of electromechanical coupling coefficient and quality factor.

[0121] In step S902, the transfer substrate layer and the piezoelectric thin film layer are bonded.

[0122] Figure 10 It is a schematic structure diagram during the formation process of an acoustic wave resonator device provided by an embodiment of the present application Figure Two .

[0123] In an embodiment of the present application, first, the surfaces to be bonded in the transfer substrate layer 500 and the piezoelectric thin film layer 300 are polished respectively, and then the transfer substrate layer 500 and the piezoelectric thin film layer 300 are bonded through a wafer bonding process to obtain the structure as Figure 10 shown. This structure includes a transfer substrate layer 500 and a piezoelectric thin film layer 300 located on the transfer substrate layer 500.

[0124] In step S903, an initial bottom conductor layer is formed on the piezoelectric thin film layer.

[0125] Figure 11 It is a schematic structure in the formation process of an acoustic wave resonator device provided by an embodiment of the present application Figure Three .

[0126] In the embodiment of the present application, on the basis of the structure as Figure 10 shown, an initial bottom conductor layer 410 in the structure as Figure 11 shown is formed on the upper surface of the piezoelectric thin film layer 300 through a deposition / lift-off process. Among them, the structure in the dashed box is the initial bottom conductor layer 410 from a top view angle. The initial bottom conductor layer 410 includes a bottom bus bar 412 and a bottom finger electrode portion 414 that are in contact connection. The bottom finger electrode portion 414 is patterned in subsequent operations to form at least one bottom finger electrode 411.

[0127] In some possible embodiments, the initial bottom conductor layer 410 is at least one of aluminum, molybdenum, chromium, gold, platinum, and titanium. The initial bottom conductor layer 410 can be composed of one or more layers of conductive materials, and each layer of conductive material is a material such as aluminum, molybdenum, chromium, gold, platinum, and titanium or a combination of these materials.

[0128] In step S904, a sacrificial layer is formed on the initial bottom conductor layer and the piezoelectric thin film layer not covered by the initial bottom conductor layer.

[0129] Figure 12 It is a schematic structure in the formation process of an acoustic wave resonator device provided by an embodiment of the present application Figure Four .

[0130] In the embodiment of the present application, on the basis of the structure as Figure 11 shown, a sacrificial material is deposited on the initial bottom conductor layer 410 and the piezoelectric thin film layer 300 not covered by the initial bottom conductor layer 410 through a deposition process. The sacrificial material is polished to make its surface flat, and the sacrificial layer 200 in the structure as Figure 12 shown is obtained.

[0131] In the embodiment of the present application, the material of the sacrificial layer 200 is silicon or silicon dioxide.

[0132] In step S905, the upper interface of the sacrificial layer is bonded to the substrate layer.

[0133] Figure 13 It is a schematic structure in the formation process of an acoustic wave resonator device provided by an embodiment of the present application Figure Five .

[0134] In the embodiment of the present application, as Figure 12The structure shown is inverted, and the sacrificial layer 200 in the structure shown as Figure 12 is bonded to the substrate layer 100 through a wafer bonding process to obtain the structure shown as Figure 13 shown.

[0135] In the embodiment of the present application, the substrate layer 100 can be a single-layer structure composed of silicon or silicon dioxide, or a laminated structure composed of at least two materials of silicon, silicon carbide, sapphire, or silicon dioxide.

[0136] In step S906, the transfer substrate layer is removed to obtain a bonded body.

[0137] In the embodiment of the present application, on the basis of the structure shown as Figure 13 shown, the silicon material in the transfer substrate layer 500 is removed through a grinding process, and the silicon dioxide material in the transfer substrate layer 500 is removed by using a chemical reagent that reacts with silicon dioxide, so that the transfer substrate layer 500 can be removed to obtain the bonded body shown as Figure 8 shown.

[0138] Through the above steps S901 - S906, the bonded body provided by the present application as shown in Figure 8 shown can be obtained.

[0139] In step S702, the piezoelectric thin film layer is etched to form a through hole to expose part of the bottom bus bar.

[0140] Figure 14 is a schematic diagram of the structure during the formation process of an acoustic wave resonator device provided by the embodiment of the present application Figure Six . As Figure 14 shown, the schematic diagram of the structure is a longitudinal cross-sectional schematic diagram of the structure.

[0141] In the embodiment of the present application, on the basis of the structure shown as Figure 8 shown, the piezoelectric thin film layer 300 on the bottom bus bar 412 in the initial bottom conductor layer 410 is etched. By removing part of the piezoelectric thin film layer 300 on the bottom bus bar 412, a through hole 303 in the structure shown as Figure 14 shown can be formed in the piezoelectric thin film layer 300, so as to expose the bottom bus bar 412 located below the piezoelectric thin film layer 300, so that the bottom bus bar 412 located below the piezoelectric thin film layer 300 can be in contact connection with the bottom terminal 413 located above the piezoelectric thin film layer 300 in the subsequent process.

[0142] In the embodiment of the present application, the through hole 303 does not need to be too large, and it is sufficient to expose the bottom bus bar 412.

[0143] In some possible embodiments, a dry etching process is used to remove a part of the piezoelectric thin film layer 300 to form a through hole 303. Alternatively, an isotropic etchant is used for selective wet etching to remove a part of the piezoelectric thin film layer 300 to form a through hole 303.

[0144] In step S703, an initial top conductor layer is formed on the remaining piezoelectric thin film layer; the initial top conductor layer includes a top terminal, a bottom terminal, a top bus bar, and a top finger electrode portion. The bottom terminal fills the through hole and contacts the bottom bus bar, and the top terminal contacts the top bus bar.

[0145] Figures 15 - 17 is a schematic structural diagram during the formation process of an acoustic resonator device provided by an embodiment of the present application Figures Seven - Nine . Among them, Figures 15 - 17 are schematic structural diagrams of different perspectives of the same structure, Figure 15 is a schematic structural diagram of the top view angle of the structure, Figure 16 is a schematic structural diagram of the transverse cross-section of the structure (which is also Figure 15 a schematic diagram of cross-section A-A of the structure shown), Figure 17 is a schematic structural diagram of the longitudinal cross-section of the structure (which is also Figure 15 a schematic diagram of cross-section B-B of the structure shown).

[0146] In the embodiment of the present application, on the basis of the structure shown in Figure 14 , an initial top conductor layer 420 in the structure shown in Figures 15 - 17 is formed on the upper surface of the piezoelectric thin film layer 300 through a deposition / stripping process. The initial top conductor layer 420 includes a top terminal 423, a bottom terminal 413, a top bus bar 422, and a top finger electrode portion 424. Both ends of the top bus bar 422 are respectively in contact connection with the top terminal 423 and the top finger electrode portion 424. The top finger electrode portion 424 is patterned in subsequent operations to form at least one top finger electrode 421. Since the formation position of the bottom terminal 413 is above the through hole 303 formed by etching the piezoelectric thin film layer 300 in step S702, a part of the bottom terminal 413 will fill into the through hole 303 and contact the bottom bus bar 412, thereby realizing the connection between the bottom terminal 413 and the bottom bus bar 412.

[0147] In some possible embodiments, the through hole 303 is completely filled with the bottom terminal 413, resulting in no through hole 303 in the piezoelectric thin film layer 300.

[0148] In some possible embodiments, the through hole 303 is not completely filled with the bottom terminal 413, resulting in the presence of the through hole 303 in the piezoelectric thin film layer 300, and a part of the bottom terminal 413 located in the through hole 303 is in contact connection with the bottom bus bar 412.

[0149] In the embodiments of the present application, the compositions of the bottom conductor material and the top conductor material are exactly the same, that is, the compositions of the top terminal 423, the bottom terminal 413, the top bus bar 422, and the top finger electrode portion 424 formed by the top conductor material are exactly the same as the compositions of the bottom bus bar 412 and the bottom finger electrode portion 414 formed by the bottom conductor material. Moreover, the thicknesses of the top finger electrode portion 424 and the bottom finger electrode portion 414 are the same.

[0150] In some possible embodiments, the material of the initial top conductor layer 420 is at least one of aluminum, molybdenum, chromium, gold, platinum, and titanium. The initial top conductor layer 420 may be composed of one or more layers of conductive materials, and each layer of conductive material is a material such as aluminum, molybdenum, chromium, gold, platinum, and titanium or a combination of these materials.

[0151] In step S704, an etching process is performed on the stack formed by the bottom finger electrode portion, the piezoelectric thin film layer, and the top finger electrode portion to obtain at least one resonator structure arranged in parallel and etching grooves located on both sides of each resonator structure; each resonator structure includes a top finger electrode, a strip-shaped piezoelectric thin film, and a bottom finger electrode, and the top finger electrode is connected to the top electrode bus bar, and the bottom finger electrode is connected to the bottom bus bar.

[0152] Figure 18 It is a schematic structure during the formation process of an acoustic wave resonator device provided by an embodiment of the present application Figure Ten 。

[0153] In the embodiments of the present application, on the basis of the structure shown in Figures 15 - 17 , an etching process is performed on the stack formed by the bottom finger electrode portion 410, the piezoelectric thin film layer 300, and the top finger electrode portion 420 through a dry etching process or an etching process with high perpendicularity to form at least one resonator structure arranged in parallel in the structure shown in Figure 18 ( Figure 18 there is 1 resonator structure) and etching grooves 302 located on both sides of each resonator structure. Each resonator structure includes a top finger electrode 421, a strip-shaped piezoelectric thin film 301, and a bottom finger electrode 411, and the top finger electrode 421 is connected to the top bus bar 422, and the bottom finger electrode 411 is connected to the bottom bus bar 421. The presence of the etching grooves 302 enables the top finger electrode 421, the strip-shaped piezoelectric thin film 301, and the bottom finger electrode 411 in the resonator structure to have mechanically free interfaces on both the left and right sides, which helps the acoustic wave resonator device to be excited by a vertical electric field and generate double-shear bulk acoustic waves. Moreover, through the etching grooves 302, it is more convenient to etch the sacrificial layer 200 in subsequent steps to form a cavity 201 in the sacrificial layer 200.

[0154] In step S705, a part of the sacrificial layer located under the bottom finger electrode is removed to form a cavity, and an acoustic wave resonator device is obtained; the resonator structure is suspended in the cavity.

[0155] In the embodiments of the present application, an isotropic etchant is used to etch the sacrificial layer 200 from the position where the etching groove 302 is located, removing the part of the sacrificial layer 200 located below the etching groove 302 and the bottom finger electrodes 411 in each resonator structure, and forming a cavity 201 in the structure as shown in Figure 2 and Figure 3 . By forming the cavity 201 in the sacrificial layer 200, the bottom finger electrodes 411 are suspended in the cavity 201, and an acoustic wave resonator device as shown in Figures 1 - 3 is obtained.

[0156] In the embodiments of the present application, a certain thickness of the sacrificial layer 200 is still reserved below the cavity 201.

[0157] In some possible embodiments, the cavity 201 penetrates the sacrificial layer 200 in the vertical direction and communicates with the substrate layer 100. In some cases, the cavity 201 can also extend into the substrate layer 100 in the vertical direction, or even penetrate the substrate layer 100 in the vertical direction.

[0158] In some possible embodiments, the cavity 201 can have different shapes, such as a rectangle, a rounded rectangle, or an irregular polygon.

[0159] In the embodiments of the present application, through the above steps S701-S705, the acoustic wave resonator device provided by the present application can be obtained.

[0160] The embodiments of the present application also provide a radio frequency filter. The radio frequency filter includes a plurality of acoustic wave resonator devices provided by the present application. The structure of each acoustic wave resonator device is as shown in Figures 1 - 3 .

[0161] In the embodiments of the present application, the plurality of acoustic wave resonator devices in the radio frequency filter are conductively interconnected to form a plurality of series resonators and a plurality of parallel resonators required for the topological structure of the radio frequency filter. According to different frequency requirements or other requirements of the radio frequency filter, the number of acoustic wave resonator devices and their connection manners can be adjusted.

[0162] In some possible embodiments, in a radio frequency filter composed of a plurality of acoustic resonator devices, when the thicknesses of the top finger electrodes 421, the strip-shaped piezoelectric thin films 301, and the bottom finger electrodes 411 in all the acoustic resonator devices are the same, a radio frequency filter with a preset frequency band can be obtained by adjusting the widths of the top finger electrodes 421, the strip-shaped piezoelectric thin films 301, and the bottom finger electrodes 411 in each acoustic resonator device. Among them, the width of the top finger electrode 421 in the parallel resonator is greater than the width of the top finger electrode 421 in the series resonator, the width of the strip-shaped piezoelectric thin film 301 in the parallel resonator is greater than the width of the strip-shaped piezoelectric thin film 301 in the series resonator, and the width of the bottom finger electrode 411 in the parallel resonator is greater than the width of the bottom finger electrode 411 in the series resonator.

[0163] In some possible embodiments, the plurality of acoustic resonator devices in the radio frequency filter may have the same or different material compositions and dimensions. Each acoustic resonator device may include one or more resonator structures. According to different frequency requirements or other requirements of the radio frequency filter, the composition materials and dimensions of the acoustic resonator devices can be adjusted.

[0164] Figure 19 It is a schematic diagram of the displacement of the main resonance mode of an acoustic resonator device provided by an embodiment of the present application, where the contour lines are used to assist in expressing the displacement distribution, and the arrows represent the direction and magnitude of the total displacement.

[0165] In the embodiment of the present application, as Figure 19 shown, when a radio frequency signal is applied to the bottom finger electrode 411 and the top finger electrode 421 through the bottom terminal 413 and the top terminal 423 respectively, an alternating electric field is formed in the vertical direction of the strip-shaped piezoelectric thin film 301. As Figure 19 shown by the contour lines in, relying on the strip-shaped piezoelectric thin film 301, the electric field simultaneously generates a horizontal shear wave (i.e., a horizontal shear wave) and a vertical shear wave (i.e., a vertical shear wave) in the strip-shaped structure composed of the bottom finger electrode 411, the strip-shaped piezoelectric thin film 301, and the top finger electrode 421. Shear deformation is defined as that the structure is divided into two parts along a certain plane, and the two parts undergo relative translational displacement along this plane. Since two mutually perpendicular shear deformations are simultaneously generated in the resonator structure, the coupling of the two shear deformations causes the displacement to mainly occur at the four corners. The shear stress at the center of the structure causes the four corners to deform towards or away from the center.

[0166] In the embodiments of the present application, in order to simultaneously excite horizontal shear waves and vertical shear waves, the thickness and width of the resonator structure need to simultaneously meet the excitation conditions of horizontal shear waves and vertical shear waves at the same frequency. This makes the acoustic wave resonator device that generates double-shear bulk acoustic waves by vertical electric field excitation different from the surface acoustic wave resonator or the laterally excited bulk acoustic wave resonator in the prior art, that is, the wave vector of the target mode in the acoustic wave resonator device provided in the present application has components in both the horizontal and vertical directions. The target mode in the acoustic wave resonator device provided in the present application does not use a multi-periodic structure in the horizontal direction, and there is only half a wavelength in both the horizontal and vertical directions to avoid the coupling interference of high-order modes in these two directions on the low-order main mode. In order to generate double-shear bulk acoustic waves by vertical electric field excitation in this acoustic wave resonator device, it is required that both the upper and lower bottom surfaces and the left and right side surfaces of the resonator structure are mechanically free interfaces.

[0167] In the embodiments of the present application, the bottom finger electrodes 411 and the top finger electrodes 421 in the acoustic wave resonator device also strongly participate in this resonance mode (that is, generating double-shear bulk acoustic waves by vertical electric field excitation). Due to the characteristics of this resonance mode, both the width and thickness of the resonator structure will affect the resonance frequency, which enables different acoustic wave resonator devices with a wide frequency range to be obtained by only changing the width of the resonator structure without changing the thickness of the resonator structure for a certain frequency band. This feature is beneficial to simplifying the process, that is, there is no need to add a dielectric layer for frequency adjustment like a laterally excited Lamb wave resonator, and the frequency adjustment can be achieved only by adjusting the width of the resonator structure through a single lithography process.

[0168] In the embodiments of the present application, compared with the thin film bulk acoustic wave resonator and the solidly mounted bulk acoustic wave resonator in the current technology, the coupling coefficient of the acoustic wave resonator device provided in the present application is larger (>30%), and different-width strip-shaped piezoelectric thin films 301 can be obtained through a single lithography process for obtaining different-width etching grooves 302, so as to obtain acoustic wave resonator devices with different resonance frequencies.

[0169] In the embodiments of the present application, compared with the laterally excited Lamb wave resonator capable of frequency adjustment, the acoustic wave resonator device provided by the present application also has the advantage of frequency adjustment. At the same time, due to the use of the laminated structure of the top finger electrode 421, the strip-shaped piezoelectric thin film 301, and the bottom finger electrode 411, the acoustic wave resonator device in the present application has a huge capacitance per unit area compared with the laterally excited Lamb wave resonator, which will have a significant advantage in the impedance matching of the RF filter and help to significantly reduce the area of the RF filter. Compared with the traditional surface acoustic wave resonator, the acoustic wave resonator device in the present application is suspended in the cavity 201 of the sacrificial layer 200 due to the use of the resonator structure, breaking away from the sound velocity limitation in the substrate layer 100. This acoustic wave resonator device is more suitable for high-frequency applications and has the advantage of a small area.

[0170] Figure 20 It is a schematic diagram of the admittance curve of the finite element simulation of an acoustic wave resonator device provided by the embodiments of the present application. In this simulation, the structure of the acoustic wave resonator device is as Figures 1 - 3 shown. The material of the strip-shaped piezoelectric thin film 301 is single-crystal lithium niobate in the X-cut direction, the materials of the bottom finger electrode 411 and the top finger electrode 421 are both copper, and the material of the substrate layer 100 is silicon. The thickness Hp of the strip-shaped piezoelectric thin film 301 is 200 nanometers, the width Wp of the strip-shaped piezoelectric thin film 301 is 400 nanometers, the thickness Ht of the top finger electrode 421 is 100 nanometers, and the thickness Hb of the bottom finger electrode 411 is 100 nanometers. As Figure 20 shown, the resonance frequency of this acoustic wave resonator device is 4180 MHz, the anti-resonance frequency is 4860 MHz, the difference between the two resonance frequencies is 680 MHz, and its electromechanical coupling coefficient is 43%. Among them, the resonance frequency is the frequency corresponding to the maximum value point of the admittance curve, the anti-resonance frequency is the frequency corresponding to the minimum value point of the admittance curve, and the electromechanical coupling coefficient is the relative spacing between the anti-resonance frequency and the resonance frequency. The larger the electromechanical coupling coefficient of the acoustic wave resonator device, the larger the upper limit of the bandwidth of the RF filter prepared from the acoustic wave resonator device. This acoustic wave resonator device exhibits a clean admittance characteristic and a large coupling coefficient in the frequency range of 2.5 GHz to 6 GHz, which enables it to meet the large bandwidth requirements in the definition of the communication frequency band.

[0171] Figure 21 It is a schematic diagram of the admittance curve of the finite element simulation of an acoustic wave resonator device using strip-shaped piezoelectric thin films with different widths provided by the embodiments of the present application. The constituent materials of each structure in the acoustic wave resonator device used in this simulation are the same as Figure 20The constituent materials of the respective structures in the acoustic resonator device used in the corresponding simulation are the same. In this simulation, the thickness Hp of the strip-shaped piezoelectric thin film 301 is 300 nanometers, the thickness Ht of the top finger electrode 421 is 100 nanometers, and the thickness Hb of the bottom finger electrode 411 is 100 nanometers. In this simulation, acoustic resonator devices with strip-shaped piezoelectric thin films 301 having widths Wp of 300 nanometers, 400 nanometers, and 500 nanometers respectively are used for simulation. For the acoustic resonator devices with strip-shaped piezoelectric thin films 301 having widths of 300 nanometers, 400 nanometers, and 500 nanometers, their resonance frequencies are 5440 MHz, 4720 MHz, and 3980 MHz respectively, the anti-resonance frequencies are 5960 MHz, 5600 MHz, and 4760 MHz respectively, and the electromechanical coupling coefficients are 25%, 50%, and 53% respectively. It can be seen from this that by increasing the width of the strip-shaped piezoelectric thin film 301 in the acoustic resonator device, the resonance frequency of the acoustic resonator device gradually decreases, the anti-resonance frequency gradually increases, and the electromechanical coupling coefficient gradually increases. By adjusting the width of the strip-shaped piezoelectric thin film 301 between 300 nanometers and 500 nanometers, the width adjustment range of the strip-shaped piezoelectric thin film 301 is 200 nanometers, and the corresponding resonance frequencies cover a frequency range of 1460 MHz.

[0172] Figure 22 It is a schematic diagram of the resonance frequencies of an acoustic resonator device using strip-shaped piezoelectric thin films with different widths corresponding to top finger electrodes and bottom finger electrodes of different materials provided in an embodiment of the present application. In this simulation, the structure of the acoustic resonator device is as Figures 1 - 3 shown. The material of the strip-shaped piezoelectric thin film 301 is X-cut single crystal lithium niobate, the materials of the top finger electrode 421 and the bottom finger electrode 411 are copper or aluminum, and the material of the second substrate layer 103 in the substrate layer 100 is silicon. The thickness Hp of the strip-shaped piezoelectric thin film 301 is 300 nanometers, the thickness Ht of the top finger electrode 421 is 100 nanometers, the thickness Hb of the bottom finger electrode 411 is 100 nanometers, and the width Wp of the strip-shaped piezoelectric thin film 301 is increased by 100 nanometers in sequence from 200 nanometers until it reaches 1000 nanometers.

[0173] In an embodiment of the present application, as Figure 22 shown by the solid line in, when the materials of both the top finger electrode 421 and the bottom finger electrode 411 are copper, and when the width Wp of the strip-shaped piezoelectric thin film 301 is increased by 100 nanometers in sequence from 200 nanometers until it reaches 1000 nanometers, the corresponding resonance frequencies of the acoustic resonator device are 5440 MHz, 4720 MHz MHz, 3980 MHz, 3500 MHz, 3200 MHz, 2930 MHz, 2760 MHz, 2600 MHz, and 2435 MHz respectively. As Figure 22As shown by the dashed line in the figure, when the materials of the top finger electrode 421 and the bottom finger electrode 411 are both aluminum, and when the width Wp of the strip-shaped piezoelectric thin film 301 is increased by 100 nanometers in sequence from 200 nanometers until it reaches 1000 nanometers, the resonance frequencies are 7080 MHz, 6320 MHz, 5340 MHz, 4760 MHz, 4320 MHz, 4020 MHz, 3760 MHz, 3480 MHz, and 3200 MHz respectively. Regardless of whether the materials of the top finger electrode 421 and the bottom finger electrode 411 are copper or aluminum, the resonance frequency of the acoustic wave resonator device decreases as the width Wp of the strip-shaped piezoelectric thin film 301 increases. Since the material density of copper is greater than that of aluminum, the acoustic wave resonator device with the top finger electrode 421 and the bottom finger electrode 411 made of copper has a greater mass load, resulting in a lower resonance frequency than the acoustic wave resonator device with the top finger electrode 421 and the bottom finger electrode 411 made of aluminum.

[0174] Figure 23 is a schematic diagram of a radio frequency filter including multiple acoustic wave resonator devices provided by an embodiment of the present application. As Figure 23 shown, the radio frequency filter has a traditional ladder filter structure. The radio frequency filter includes 3 series-connected acoustic wave resonator devices and 2 parallel-connected acoustic wave resonator devices. The 3 series-connected acoustic wave resonator devices are Rs1, Rs2, and Rs1 respectively, which are connected between two ports, and the two ports are marked as "IN" and "OUT" respectively. The two parallel-connected acoustic wave resonator devices Rp are respectively connected between the two series-connected acoustic wave resonator devices (Rs1, Rs2) and the ground port GND.

[0175] Figure 24 is a schematic diagram of the admittance curve of the acoustic wave resonator device in a radio frequency filter including multiple acoustic wave resonator devices provided by an embodiment of the present application. Figure 24 The corresponding radio frequency filter is Figure 23 the radio frequency filter shown. The structures of the acoustic wave resonator devices (Rs1, Rs2, and Rp) in the radio frequency filter are as Figures 1 - 3 shown. The material of the strip-shaped piezoelectric thin film 301 is X-cut single crystal lithium niobate, the materials of the top finger electrode 421 and the bottom finger electrode 411 are both copper, and the material of the substrate layer 100 is silicon. The thickness Hp of the strip-shaped piezoelectric thin film 301 is 300 nanometers, the thickness Ht of the top finger electrode 421 is 100 nanometers, and the thickness Hb of the bottom finger electrode 411 is 100 nanometers. Among them, the width Wp of the strip-shaped piezoelectric thin film 301 in the acoustic wave resonator device Rs1 is 340 nanometers, the width Wp of the strip-shaped piezoelectric thin film 301 in the acoustic wave resonator device Rs2 is 320 nanometers, and the width Wp of the acoustic wave resonator device Rp is 440 nanometers. As Figure 24As shown, the resonant frequencies of the acoustic wave resonator devices Rs1, Rs2, and Rp are 4400 MHz, 4560 MHz, and 3775 MHz respectively, the anti-resonant frequencies are 5251 MHz, 5436 MHz, and 4500 MHz respectively, and the electromechanical coupling coefficients are 52.3%, 52.0%, and 52.0% respectively. It can be seen that when the thicknesses of the top finger electrodes 421, the strip-shaped piezoelectric thin film 301, and the bottom finger electrodes 411 in multiple acoustic wave resonator devices in the RF filter are equal, the requirements of the filter topology can be met only by adjusting the width of the strip-shaped piezoelectric thin film 301, without affecting the electromechanical coupling coefficient performance.

[0176] Figure 25 It is a schematic diagram of the insertion loss curve of the acoustic wave resonator device in a radio frequency filter including multiple acoustic wave resonator devices provided by an embodiment of the present application. Figure 25 The corresponding RF filter is Figure 23 the RF filter shown. The insertion loss curve of the RF filter is the S21 curve, which is an important parameter describing the performance of the RF filter. The S21 curve represents the decibel value (dB) of the ratio of the signal power at the output port to the signal power at the input port after the signal passes through the RF filter. As Figure 25 shown, the 3 dB bandwidth of this RF filter is 855 MHz, the center frequency is 4558 MHz, and the fractional bandwidth is 19%. Among them, the 3 dB bandwidth is the frequency range corresponding to the power in the S21 curve dropping to half of the maximum power (or the gain dropping by 3 dB), the center frequency is the center frequency point of the 3 dB bandwidth, and the fractional bandwidth is the ratio of the 3 dB bandwidth to the center frequency. Since this RF filter has a relatively large fractional bandwidth value, the RF filter can allow a wider frequency range to pass through.

[0177] In the embodiment of the present application, a stacked structure of a suspended top finger electrode 421, a strip-shaped piezoelectric thin film 301, and a bottom finger electrode 411 is set in the device to support the mode of double shear bulk acoustic wave excited by a vertical electric field. The acoustic wave resonator device based on this mode has a high coupling coefficient and a high frequency, and is suitable for the higher frequency and larger bandwidth requirements of the RF filter proposed by the widely promoted 5G communication and future 6G communication standards.

[0178] It should be noted that the above order of the embodiments of the present application is only for description and does not represent the superiority or inferiority of the embodiments. And the above specific embodiments of this specification have been described. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims may be performed in a different order than in the embodiments and still achieve the desired result. Additionally, the processes depicted in the drawings do not necessarily require the particular order or sequential order shown to achieve the desired result. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0179] Each embodiment in this specification is described in a progressive manner. For the same or similar parts among the embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the device embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can refer to the partial description of the method embodiments.

[0180] Those of ordinary skill in the art can understand that all or part of the steps to implement the above embodiments can be completed by hardware or by a program instructing relevant hardware. The program can be stored in a computer-readable storage medium. The storage medium mentioned above can be a read-only memory, a magnetic disk, an optical disc, etc.

[0181] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An acoustic resonator device, characterized in that, Comprising: A substrate layer; A sacrificial layer located on the substrate layer; the sacrificial layer includes at least one cavity; A piezoelectric thin film layer located on the sacrificial layer; the piezoelectric thin film layer includes at least one strip-shaped piezoelectric thin film arranged in parallel and etching grooves located on both sides of each strip-shaped piezoelectric thin film; the etching grooves communicate with the cavities; A bottom conductor layer located under the piezoelectric thin film layer; The bottom conductor layer is in contact with the strip-shaped piezoelectric thin film; the bottom conductor layer includes a bottom bus bar and at least one bottom finger electrode, and the at least one bottom finger electrode is connected to the bottom bus bar; the bottom finger electrode is suspended in the cavity; the bottom finger electrode and the strip-shaped piezoelectric thin film correspond one by one; A top conductor layer located on the piezoelectric thin film layer; the top conductor layer is in contact with the strip-shaped piezoelectric thin film; the top conductor layer includes a top bus bar, a top terminal, a bottom terminal and at least one top finger electrode; one end of the top bus bar is connected to the top terminal, and the other end is connected to the at least one top finger electrode; the bottom terminal is partially located in the piezoelectric thin film layer and is in contact with the bottom bus bar; the top finger electrode and the strip-shaped piezoelectric thin film correspond one by one.

2. The acoustic resonator device according to claim 1, characterized in that, The piezoelectric thin film layer includes through holes; the bottom terminal is partially located in the through holes and is in contact with the bottom bus bar.

3. The acoustic resonator device according to claim 1, characterized in that, The at least one bottom finger electrode and its corresponding top finger electrode are configured to apply corresponding radio frequency signals to excite dual shear bulk acoustic waves in the corresponding strip-shaped piezoelectric thin film.

4. The acoustic resonator device according to claim 1, wherein, The resonant frequency of the acoustic wave resonator device is jointly determined by the width and thickness of the stack formed by the top finger electrode, the strip-shaped piezoelectric thin film and the bottom finger electrode.

5. The acoustic resonator device according to claim 1, characterized in that, The width of the strip-shaped piezoelectric thin film is less than or equal to the width of the bottom finger electrode, and the length of the strip-shaped piezoelectric thin film is greater than or equal to the length of the bottom finger electrode; The width of the strip-shaped piezoelectric thin film is greater than or equal to the width of the top finger electrode, and the length of the strip-shaped piezoelectric thin film is greater than or equal to the length of the top finger electrode.

6. The acoustic resonator device according to claim 3, wherein The ratio of the sum of the thicknesses of the top finger electrode, the strip-shaped piezoelectric thin film and the bottom finger electrode to the width of the strip-shaped piezoelectric thin film ranges from 0.5 to 1.

5.

7. The acoustic resonator device according to claim 1, wherein The material of the piezoelectric thin film layer is at least one of lithium niobate, lithium tantalate and aluminum nitride; the thickness of the piezoelectric thin film is 50 - 1000 nanometers; The material of the top conductor layer is at least one of aluminum, molybdenum, chromium, gold, platinum and titanium; The material of the bottom conductor layer is at least one of aluminum, molybdenum, chromium, gold, platinum and titanium.

8. The acoustic resonator device according to claim 1, characterized in that, The substrate layer is a single-layer structure composed of silicon or silicon dioxide; Or; the substrate layer is a laminated structure composed of at least two materials of silicon, silicon carbide, sapphire or silicon dioxide.

9. The acoustic resonator device according to claim 1, wherein The material of the sacrificial layer is silicon or silicon dioxide.

10. A radio frequency filter, characterized in that, Including a plurality of acoustic wave resonator devices as described in any one of claims 1 to 9; A plurality of series resonators and a plurality of parallel resonators required for the conductor interconnection of the plurality of acoustic resonator devices to form the topology of the RF filter; when the thicknesses of the top finger bar electrodes, the strip-shaped piezoelectric thin film, and the bottom finger bar electrodes in each of the acoustic resonator devices are the same, the RF filter in a preset frequency band is obtained by adjusting the widths of the top finger bar electrodes, the strip-shaped piezoelectric thin film, and the bottom finger bar electrodes, and the values of the widths in the parallel resonators are greater than the values of the widths in the series resonators.

11. A method for forming an acoustic resonator device, characterized in that, Comprising: Providing a combination body; The combination body includes a substrate layer, a sacrificial layer located on the substrate layer, an initial bottom conductor layer located in the sacrificial layer, and a piezoelectric thin film layer located on the sacrificial layer and the initial bottom conductor layer; The initial bottom conductor layer includes a bottom bus bar and a bottom finger bar electrode portion; Etching the piezoelectric thin film layer to form a through hole to expose a part of the bottom bus bar; Forming an initial top conductor layer on the remaining piezoelectric thin film layer; the initial top conductor layer includes a top terminal, a bottom terminal, a top bus bar, and a top finger bar electrode portion, the bottom terminal fills the through hole and contacts the bottom bus bar, and the top terminal contacts the top bus bar; Etching the stack formed by the bottom finger bar electrode portion, the piezoelectric thin film layer, and the top finger bar electrode portion to obtain at least one resonator structure arranged in parallel and etching grooves on both sides of each resonator structure; each resonator structure includes a top finger bar electrode, a strip-shaped piezoelectric thin film, and a bottom finger bar electrode, the top finger bar electrode is connected to the top electrode bus bar, and the bottom finger bar electrode is connected to the bottom bus bar; Removing a part of the sacrificial layer under the bottom finger bar electrode to form a cavity, obtaining an acoustic resonator device; the resonator structure is suspended in the cavity.

12. The method for forming the acoustic resonator device according to claim 11, wherein The providing the combination body includes: Providing a transfer substrate layer and the piezoelectric thin film layer; Bonding the transfer substrate layer and the piezoelectric thin film layer; Forming the initial bottom conductor layer on the piezoelectric thin film layer; Forming the sacrificial layer on the initial bottom conductor layer and the piezoelectric thin film layer not covered by the initial bottom conductor layer; Bonding the upper interface of the sacrificial layer to the substrate layer; Removing the transfer substrate layer to obtain the combination body.

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