Acoustic resonator, preparation method thereof and filter

Abstract

The invention provides a sound wave resonator, a preparation method thereof and a filter, and aims at sound waves with strong dispersion characteristics in a target mode, the influence of the thickness of a piezoelectric film on sound velocity far exceeds the duty ratio 2W / lambda of an interdigital transducer electrode. The thickness of a piezoelectric film corresponding to the lower part from a certain area at the tail end of an electrode finger overlapping area of the interdigital transducer to the tail end part of a bus bar is increased, so that the thickness of the piezoelectric film is thicker than that of a piezoelectric film corresponding to the middle part of the electrode finger overlapping area; therefore, the sound velocity of the target mode in the piezoelectric film in the thicker area is lower than the sound velocity of the target mode in the piezoelectric film in the thinner area, so that the transverse high-order mode is effectively inhibited, and the performance of the device is improved. Besides, the structure can suppress the transverse high-order mode only by increasing the thickness of the partial area of the piezoelectric film, the structure is simple, the preparation is easy, the requirement on the process precision is low, and the process complexity and the manufacturing cost can be effectively reduced on the premise of effectively ensuring the performance of the resonator.

Description

Technical Field

[0001] The invention belongs to the field of microelectronic devices, and in particular relates to an acoustic wave resonator and a preparation method and a filter thereof. Background Art

[0002] With the development of wireless communication systems, the requirements for signal quality are getting higher and higher, and the competition for communication spectrum resources is becoming more and more fierce. Filters with low loss, large bandwidth, high frequency and flat passband have become the common pursuit of the communication industry.

[0003] Acoustic filter technology is the most widely used filter technology at present, mainly including Bulk Acoustic Wave (BAW) and Surface Acoustic Wave (SAW) filter technology. In addition, plate wave filter technology based on single crystal piezoelectric film has also received widespread attention in recent years. However, no matter which acoustic filter technology is used, it will cause lateral high-order modes due to the limited length of the lateral waveguide. The lateral high-order mode generally appears near the anti-resonance frequency of the resonator and between the resonant frequency and the anti-resonance frequency, which will correspondingly cause ripples in the passband of the filter. Therefore, suppressing the lateral high-order mode becomes the key to achieving a high-performance filter with a flat passband.

[0004] It should be noted that the above introduction to the technical background is only for the convenience of providing a clear and complete description of the technical solutions of the present application and for the convenience of understanding by those skilled in the art. It cannot be considered that the above technical solutions are well known to those skilled in the art simply because they are described in the background technology section of the present application. Summary of the invention

[0005] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide an acoustic wave resonator and a preparation method and a filter, which are used to solve the problem that the acoustic wave resonator in the prior art will generate lateral high-order modes due to the limited length of the lateral waveguide, resulting in reduced device performance.

[0006] To achieve the above-mentioned object and other related objects, the present invention provides an acoustic wave resonator, the acoustic wave resonator comprising: a piezoelectric film and an interdigital transducer disposed on the piezoelectric film;

[0007] The interdigital transducer comprises: two interdigital electrodes; each of the interdigital electrodes comprises a bus bar and a plurality of electrode fingers, and all the electrode fingers are connected to the bus bar; the electrode fingers of the two interdigital electrodes extend in opposite directions and are arranged crosswise; the electrode fingers of the two interdigital electrodes comprise an interdigital overlap region and an interdigital gap region;

[0008] The piezoelectric film includes a first piezoelectric film area and a second piezoelectric film area, and the thickness of the first piezoelectric film area is less than the thickness of the second piezoelectric film area; the second piezoelectric film area is located at least part of the plane from the preset length at the end of the interdigital overlap area to the corresponding area of ​​the corresponding end of the bus bar, and the second piezoelectric film area needs to extend at least from the end of the interdigital overlap area to the corresponding area of ​​the corresponding end of the bus bar, wherein the preset length is not greater than 1 / 5 of the length of the interdigital overlap area;

[0009] The center distance between the adjacent electrode fingers connected to the same bus bar is denoted as λ, and the resonant frequency of the acoustic wave resonator is f s The product of λ is the acoustic velocity v of the target mode of the acoustic resonator. s ;

[0010] The target mode of the acoustic wave resonator has a strong dispersion characteristic.

[0011] Optionally, the interdigital transducer is arranged on the upper surface of the piezoelectric film; the target mode of the acoustic wave resonator is a zero-order acoustic wave mode; the acoustic wave resonator also includes a first high acoustic velocity support substrate located below the piezoelectric film, and the slow shear wave sound velocity of the first high acoustic velocity support substrate is greater than the sound velocity of the target mode.

[0012] Further, the piezoelectric film is in direct contact with the first high acoustic velocity support substrate; or the piezoelectric film is formed on the upper surface of the first high acoustic velocity support substrate through a first dielectric layer, wherein the acoustic velocity of the first dielectric layer is smaller than the acoustic velocity of the target mode, and the thickness of the dielectric layer is smaller than the thickness of the first piezoelectric film region and is smaller than 0.1λ.

[0013] Furthermore, the material of the first high acoustic velocity support substrate is one of silicon carbide, diamond, diamond-like carbon, sapphire, aluminum oxide, aluminum nitride, boron nitride, boron carbide and silicon nitride of different crystal forms and different cuts; the material of the first dielectric layer is one of silicon oxide, polycrystalline silicon, amorphous silicon, aluminum oxide, silicon nitride and aluminum nitride.

[0014] Furthermore, the first high acoustic velocity support substrate is composed of a support substrate away from the side of the piezoelectric film and a high acoustic velocity material layer close to the side of the piezoelectric film; the material of the support substrate is one of quartz, silicon, sapphire, spinel, and yttrium aluminum garnet; the material of the high acoustic velocity material layer is one of silicon carbide, diamond, diamond-like carbon, aluminum oxide, aluminum nitride, boron nitride, boron carbide and silicon nitride.

[0015] Optionally, the target mode of the acoustic wave resonator is a high-order acoustic wave mode.

[0016] Furthermore, the acoustic wave resonator also includes a suspended bottom electrode disposed on the lower surface of the piezoelectric film, and the suspended bottom electrode is directly below the interdigital overlapping region, and the high-order acoustic wave mode is formed by the interdigital transducer and the suspended bottom electrode.

[0017] Furthermore, the interdigital transducer is arranged on the upper surface of the piezoelectric film; the acoustic wave resonator also includes a second dielectric layer and a second high acoustic velocity support substrate sequentially located below the piezoelectric film, and the slow shear wave sound velocity of the second high acoustic velocity support substrate is greater than the sound velocity of the target mode to reduce the leakage of the target mode into the second high acoustic velocity support substrate; the second dielectric layer is an insulating dielectric layer; the suspended bottom electrode is embedded in the second dielectric layer.

[0018] Furthermore, the second high acoustic velocity support substrate is composed of a support substrate away from the side of the piezoelectric film and a high acoustic velocity material layer close to the side of the piezoelectric film; the material of the support substrate is one of quartz, silicon, sapphire, spinel, and yttrium aluminum garnet; the material of the high acoustic velocity material layer is one of silicon carbide, diamond, diamond-like carbon, aluminum oxide, aluminum nitride, boron nitride, boron carbide and silicon nitride.

[0019] Furthermore, the acoustic wave resonator also includes a third dielectric layer, a fourth dielectric layer and a third high acoustic velocity support substrate which are sequentially located below the interdigital transducer, and the slow shear wave velocity of the third high acoustic velocity support substrate is greater than the velocity of the target mode to reduce the leakage of the target mode into the third high acoustic velocity support substrate; the piezoelectric film is embedded in the third dielectric layer and in contact with the interdigital transducer; and the suspended bottom electrode is embedded in the fourth dielectric layer.

[0020] Furthermore, the third high acoustic velocity support substrate is composed of a support substrate away from the side of the piezoelectric film and a high acoustic velocity material layer close to the side of the piezoelectric film; the material of the support substrate is one of quartz, silicon, sapphire, spinel, and yttrium aluminum garnet; the material of the high acoustic velocity material layer is one of silicon carbide, diamond, diamond-like carbon, aluminum oxide, aluminum nitride, boron nitride, boron carbide and silicon nitride.

[0021] Furthermore, the interdigital transducer is arranged on the upper surface of the piezoelectric film, and the acoustic wave resonator also includes a first supporting layer and a first supporting substrate located sequentially below the piezoelectric film; wherein a cavity is formed in the first supporting layer, and the cavity exposes the corresponding piezoelectric film below the interdigital transducer, or the first supporting layer includes a fifth dielectric layer and a Bragg reflection layer, and the suspended bottom electrode is embedded in the fifth dielectric layer.

[0022] Furthermore, the interdigital transducer is arranged on the upper surface of the piezoelectric film; the acoustic wave resonator also includes a second supporting substrate located below the piezoelectric film, wherein a through cavity is formed in the second supporting substrate, and the cavity exposes the corresponding piezoelectric film below the interdigital transducer.

[0023] Optionally, the interdigital transducer is arranged on the upper surface of the piezoelectric film, and the high-order acoustic wave mode is formed by the interdigital transducer, and the acoustic wave resonator also includes a second supporting layer and a third supporting substrate sequentially located below the piezoelectric film; wherein a cavity is formed in the second supporting layer, and the cavity exposes the corresponding piezoelectric film below the interdigital transducer, or the second supporting layer is a Bragg reflection layer.

[0024] Optionally, the interdigital transducer is arranged on the upper surface of the piezoelectric film, and the high-order acoustic wave mode is formed by the interdigital transducer, and the acoustic wave resonator also includes a fourth supporting substrate located below the piezoelectric film, wherein a through cavity is formed in the fourth supporting substrate, and the cavity exposes the corresponding piezoelectric film below the interdigital transducer.

[0025] Optionally, the second piezoelectric film area is located in the entire plane corresponding to the area of ​​the preset length at the end of the interdigital overlapping area; or the second piezoelectric film area is located in the entire plane extending from the end of the interdigital overlapping area to the area corresponding to the preset length of the interdigital gap area; or the second piezoelectric film area is located in the plane corresponding to the entire interdigital gap area not covered by the electrode fingers; or the second piezoelectric film area is located in the entire plane extending from the end of the interdigital overlapping area to the area corresponding to the preset length of the corresponding bus bar.

[0026] The present invention further provides a filter, comprising a plurality of acoustic wave resonators, wherein the acoustic wave resonators are the acoustic wave resonators as described in any one of the above items.

[0027] The present invention also provides a method for preparing an acoustic wave resonator, the method comprising the steps of preparing the piezoelectric film of the acoustic wave resonator as described in any one of the above, the steps comprising:

[0028] forming a piezoelectric thin film material layer on the lower substrate;

[0029] forming a patterned mask layer in a preset area of ​​the piezoelectric thin film material layer;

[0030] Etching the piezoelectric thin film material layer based on the patterned mask layer to thin the piezoelectric thin film material layer outside the area covered by the patterned mask layer;

[0031] The patterned mask layer is removed.

[0032] As described above, the acoustic wave resonator and its preparation method and filter of the present invention, for acoustic waves with strong dispersion characteristics in the target mode, such as high-order acoustic wave modes or zero-order acoustic wave modes in contact with a high sound velocity material layer, the thickness of the piezoelectric film has an effect on the sound velocity far exceeding the duty cycle 2W / λ of the interdigital transducer electrode, by thickening the thickness of the piezoelectric film corresponding to the lower part of the area from a certain area at the end of the interdigital transducer electrode finger overlapping area to the end of the bus bar, so that it is thicker than the piezoelectric film corresponding to the middle part of the electrode finger overlapping area, so that the sound velocity of the target mode in the piezoelectric film in the thicker area is lower than the sound velocity of the target mode in the piezoelectric film in the thinner area, thereby achieving effective suppression of lateral high-order modes and improving device performance; in addition, the structure can suppress lateral high-order modes by only increasing the thickness of a partial area of ​​the piezoelectric film, has a simple structure, is easy to prepare, and has low requirements on process precision, and can effectively reduce process complexity and manufacturing cost while effectively ensuring the performance of the resonator. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Shown is a schematic top view of the structure of an example of the acoustic wave resonator of the present invention.

[0034] Figure 2 Display as Figure 1 Schematic diagram of the longitudinal cross-section structure at position aa in the middle.

[0035] Figure 3 Shown is a schematic top view of the structure of an example of an interdigital transducer in the acoustic wave resonator of the present invention.

[0036] Figure 4 Display as Figure 3 Schematic diagram of the top view structure of the interdigital electrodes in the interdigital transducer.

[0037] Figures 5 to 7 Shown are schematic top views of three examples of the acoustic wave resonator of the present invention.

[0038] Figures 8 to 19 The longitudinal cross-sectional structure schematic diagrams of multiple examples of the acoustic wave resonator of the present invention are shown, and they are all along the Figure 1 Schematic diagram of the longitudinal cross-section structure at position aa in the middle.

[0039] Figure 20 to Figure 23 It is a schematic diagram of the longitudinal cross-sectional structure of the preparation process of the piezoelectric film of the acoustic wave resonator of the present invention.

[0040] Fig.24 The longitudinal cross-sectional structure diagram of the acoustic wave resonator of the comparative example 1 of the present invention and the target mode sound velocity distribution diagram of different regions are shown, and the longitudinal cross-sectional structure diagram of the acoustic wave resonator of the comparative example 1 of the present invention and the target mode sound velocity distribution diagram of different regions are shown. Figure 1 Schematic diagram of the longitudinal cross-section structure at position aa in the middle.

[0041] Fig.25 The longitudinal cross-sectional structure diagram of the acoustic wave resonator of the first embodiment of the present invention and the target mode sound velocity distribution diagram of different regions are shown, and the longitudinal cross-sectional structure diagram of the acoustic wave resonator of the first embodiment of the present invention and the target mode sound velocity distribution diagram of different regions are shown. Figure 1 Schematic diagram of the longitudinal cross-section structure at position aa in the middle.

[0042] Fig.26 The target mode sound velocity v of the acoustic wave resonator of the comparative example 1 of the present invention is shown as s (f s ×λ) versus duty cycle (2W / λ).

[0043] Fig. 27 The target mode sound velocity v of the acoustic wave resonator of the first embodiment of the present invention is shown as s (f s ×λ), where the abscissa is the ratio of the thickness h of the piezoelectric film to the electrode finger spacing λ, h / λ.

[0044] Fig.28 Shown is a simulated admittance / conductance curve of the acoustic wave resonator of comparative example 1 of the present invention.

[0045] Fig.29 Shown is a simulated admittance / conductance curve of the acoustic wave resonator according to the first embodiment of the present invention.

[0046] Fig.30 It is a schematic diagram of the longitudinal cross-sectional structure of the acoustic wave resonator of the second comparative example of the present invention, and is Figure 1 Schematic diagram of the longitudinal cross-section structure at position aa in the middle.

[0047] Fig.31 The longitudinal cross-sectional structure diagram of the acoustic wave resonator of the second embodiment of the present invention is shown. Figure 1 Schematic diagram of the longitudinal cross-section structure at position aa in the middle.

[0048] Fig.32 The target mode sound velocity v of the acoustic wave resonator of the second comparative example of the present invention is shown as s (f s ×λ) versus duty cycle (2W / λ).

[0049] Fig.33 The target mode sound velocity v of the acoustic wave resonator of the second embodiment of the present invention is shown as s (f s ×λ), where the abscissa is the ratio of the thickness h of the piezoelectric film to the electrode spacing λ, h / λ.

[0050] Fig.34 Shown is a simulated admittance / conductance curve of the acoustic wave resonator of comparative example 2 of the present invention.

[0051] Fig.35Shown is a simulated admittance / conductance curve of the acoustic wave resonator according to the second embodiment of the present invention.

[0052] Fig.36 It is a schematic diagram of the longitudinal cross-sectional structure of the acoustic wave resonator of comparative example 3 of the present invention, and is Figure 1 Schematic diagram of the longitudinal cross-section structure at position aa in the middle.

[0053] Fig.37 The longitudinal cross-sectional structure diagram of the acoustic wave resonator of the third embodiment of the present invention is shown. Figure 1 Schematic diagram of the longitudinal cross-section structure at position aa in the middle.

[0054] Fig.38 Shown is a simulated admittance / conductance curve of the acoustic wave resonator of comparative example 3 of the present invention.

[0055] Fig.39 Shown is a simulated admittance / conductance curve of the acoustic wave resonator according to the third embodiment of the present invention.

[0056] Component number description

[0057] 10 Piezoelectric film

[0058] 100 First piezoelectric film area

[0059] 101 Second piezoelectric film area

[0060] 11 Interdigital transducer

[0061] 110 Interdigital Electrodes

[0062] 111 Busbar

[0063] 112 electrode fingers

[0064] 113 Interdigitated overlap area

[0065] 114 Interdigital gap area

[0066] 12 The first high acoustic velocity support substrate

[0067] 13. First dielectric layer

[0068] 14 Floating bottom electrode

[0069] 15 Second dielectric layer

[0070] 150 Insulation material layer

[0071] 16. Second Highest Acoustic Velocity Support Substrate

[0072] 17 Third dielectric layer

[0073] 18 Fourth dielectric layer

[0074] 19 The third highest acoustic velocity support substrate

[0075] 20 First support layer

[0076] 200 Fifth dielectric layer

[0077] 201 Bragg reflector

[0078] 202 Cavity

[0079] 21. first supporting substrate

[0080] 22. Second supporting substrate

[0081] 220 Cavity

[0082] 23 Second support layer

[0083] 230 Cavity

[0084] 24. Third supporting substrate

[0085] 25 fourth supporting substrate

[0086] 250 Cavity

[0087] 26 Lower base

[0088] 27 Piezoelectric thin film material layer

[0089] 28 Patterned mask layer DETAILED DESCRIPTION

[0090] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0091] For example, when describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional view showing the device structure will not be partially enlarged according to the general scale, and the schematic view is only an example, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional space dimensions of length, width and depth should be included.

[0092] For ease of description, spatial relational terms such as “under”, “below”, “below”, “below”, “over”, etc. may be used herein to describe the relationship of one element or feature shown in the drawings to other elements or features. It will be understood that these spatial relational terms are intended to include other orientations of the device in use or operation in addition to the orientation depicted in the drawings, and may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features are formed between the first and second features, so that the first and second features may not be in direct contact. In addition, when a layer is referred to as being “between” two layers, it may be the only layer between the two layers, or one or more intervening layers may also be present.

[0093] See also Figures 1 to 39 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0094] like Figures 1 to 4 As shown, this embodiment provides an acoustic wave resonator, and the acoustic wave resonator includes: a piezoelectric film 10 and an interdigital transducer 11 disposed on the piezoelectric film 10; it should be noted that the interdigital transducer 11 is disposed on the piezoelectric film 10, which means that the interdigital transducer 11 is entirely disposed on the upper surface of the piezoelectric film 10, and may also be partially disposed on the upper surface of the piezoelectric film 10;

[0095] like Figure 3 and Figure 4 As shown, the interdigital transducer 11 comprises: two interdigital electrodes 110; each of the interdigital electrodes 110 comprises a bus bar 111 and a plurality of electrode fingers 112, and all of the electrode fingers 112 are connected to the bus bar 111; the electrode fingers 112 of the two interdigital electrodes 110 extend in opposite directions and are arranged crosswise; Figure 1 As shown, the electrode fingers 112 of the two interdigitated electrodes 110 include an interdigitated overlap region 113 and an interdigitated gap region 114. It should be noted that the interdigitated overlap region 113 and the interdigitated gap region 114 refer to the entire plane of the corresponding region. For example, the interdigitated overlap region 113 refers to Figure 1 The overlapped region of the two groups of electrode fingers 112 is a continuous plane region along the X direction and the Y direction in the rectangular coordinate system, generally located in the middle region of the electrode fingers 112. The interdigital gap region 114 refers to Figure 1The non-overlapping regions of the two groups of electrode fingers 112 are continuous plane regions along the X direction and the Y direction in the rectangular coordinate system, and are located at the regions on both sides of the electrode fingers 112;

[0096] like Figure 2 As shown, the piezoelectric film 10 includes a first piezoelectric film area 100 and a second piezoelectric film area 101, and the thickness of the first piezoelectric film area 100 is less than the thickness of the second piezoelectric film area 101; the second piezoelectric film area 101 is located at least part of the plane from the preset length at the end of the interdigital overlap area 113 to the corresponding area at the end of the corresponding bus bar 111, and the second piezoelectric film area 101 needs to at least extend from the end of the interdigital overlap area 113 to the corresponding area at the end of the corresponding bus bar 111, wherein the preset length is not greater than 1 / 5 of the length of the interdigital overlap area 113;

[0097] like Figure 4 As shown, the center distance between the adjacent electrode fingers 112 connected to the same bus bar 111 is denoted as λ, and the resonant frequency f of the acoustic wave resonator is s The product of λ is the acoustic velocity v of the target mode of the acoustic resonator. s ;

[0098] The target mode of the acoustic wave resonator has a strong dispersion characteristic.

[0099] The acoustic wave resonator of this embodiment targets acoustic waves with strong dispersion characteristics in the target mode, such as high-order acoustic wave modes or zero-order acoustic wave modes in contact with a high sound velocity material layer. The thickness of the piezoelectric film has an influence on the sound velocity far exceeding the duty cycle 2W / λ of the electrode of the interdigital transducer. The thickness of the piezoelectric film corresponding to the lower part of the area from a certain area at the end of the overlapping area of ​​the electrode fingers of the interdigital transducer to the end of the bus bar is thickened to make it thicker than the piezoelectric film corresponding to the middle part of the overlapping area of ​​the electrode fingers, so that the sound velocity of the target mode in the piezoelectric film in the thicker area is lower than the sound velocity of the target mode in the piezoelectric film in the thinner area, thereby achieving effective suppression of lateral high-order modes and improving device performance. In addition, the structure can suppress lateral high-order modes by only increasing the thickness of a partial area of ​​the piezoelectric film. The structure is simple in structure, easy to prepare, and has low requirements on process precision. It can effectively reduce process complexity and manufacturing cost while effectively ensuring the performance of the resonator.

[0100] Specifically, the second piezoelectric film area 101 is located at least partially in the plane from the preset length at the end of the interdigital overlap area 113 to the corresponding area at the end of the corresponding bus bar 111, and the second piezoelectric film area 101 needs to at least extend from the end of the interdigital overlap area 113 to the corresponding area at the end of the corresponding bus bar 111, wherein the preset length is not greater than 1 / 5 of the length of the interdigital overlap area 113. In other words, the second piezoelectric film area 101 needs to at least extend outward from the end of the interdigital overlap area 113. Figures 5 to 7 In the embodiment, the second piezoelectric film region 101 extends outward from the end of the interdigitated overlapping region 113, and the extension may be a continuous plane extension or a discontinuous plane extension, such as Figure 5 and Figure 6 The middle is the extension of the entire continuous plane. Figure 5 The interdigital gap region 114 extends to a predetermined length. Figure 6 The bus bar 111 is extended to a preset length. Figure 7 It is a discontinuous extension of the entire plane, and the second piezoelectric film area 101 is located in the plane corresponding to the area of ​​the entire interdigital gap area 114 that is not covered by the electrode fingers 112; Figure 2 As shown, the second piezoelectric film area 101 extends from the preset length at the end of the interdigital overlap area 113 to the entire plane of the area corresponding to the end of the interdigital overlap area 113, but is not limited thereto, and may also extend to the plane of the area corresponding to the interdigital gap area 114 or to the plane of the area corresponding to the corresponding bus bar 111. The specific selection is made according to the actual structural requirements.

[0101] The sound wave with strong dispersion characteristics may be a high-order sound wave mode or a zero-order sound wave mode in contact with a high-speed material layer. The high-order sound wave mode may be, for example, a high-order Lamb wave, a high-order horizontal shear wave, a high-order Rayleigh mode or other high-order modes; the zero-order sound wave mode may be a zero-order horizontal shear mode, a zero-order longitudinal leakage surface acoustic wave mode, a zero-order Rayleigh mode or other zero-order modes.

[0102] When the target mode of the acoustic wave resonator is the zero-order acoustic wave mode, as Figure 8 As shown, the interdigital transducer 11 is arranged on the entire upper surface of the piezoelectric film 10, and the acoustic wave resonator also includes a first high acoustic velocity support substrate 12 located below the piezoelectric film 10, and the slow shear wave sound velocity of the first high acoustic velocity support substrate 12 is greater than the sound velocity of the target mode. The sound wave whose target mode is the zero-order acoustic wave mode formed by the interdigital transducer 11 in the piezoelectric film 10 will have a lower sound velocity in the second piezoelectric film area 101, thereby achieving suppression of lateral high-order modes. Furthermore, the piezoelectric film 10 can be in direct contact with the first high acoustic velocity support substrate 12, such as Figure 8 As shown; in addition, the piezoelectric film 10 can also be formed on the upper surface of the first high acoustic velocity support substrate 12 through the first dielectric layer 13, where the first dielectric layer 13 needs to satisfy that the acoustic velocity of the first dielectric layer 13 is less than the acoustic velocity of the target mode, and the thickness of the dielectric layer 13 is less than the thickness of the first piezoelectric film region 100 and less than 0.1λ. Preferably, the material of the first high acoustic velocity support substrate 12 is one of silicon carbide, diamond, diamond-like carbon, sapphire, aluminum oxide, aluminum nitride, boron nitride, boron carbide and silicon nitride of different crystal forms and different cuts; the material of the first dielectric layer 13 is one of silicon oxide, polycrystalline silicon, amorphous silicon, aluminum oxide, silicon nitride and aluminum nitride. In addition, the first high acoustic velocity support substrate 12 can be a single-layer structure, for example Figure 8 As shown, at this time, the slow shear wave sound velocity of the first high acoustic velocity supporting substrate 12 of the single-layer structure is greater than the sound velocity of the target mode; the first high acoustic velocity supporting substrate 12 can also be a stacked structure, consisting of a supporting substrate away from the side of the piezoelectric film 10 and a high acoustic velocity material layer close to the side of the piezoelectric film 10. At this time, as long as the slow shear wave sound velocity of the high acoustic velocity material layer is greater than the sound velocity of the target mode, the material of the supporting substrate can be selected from one of quartz, silicon, sapphire, spinel, and yttrium aluminum garnet, and the material of the high acoustic velocity material layer can be selected from one of silicon carbide, diamond, diamond-like carbon, aluminum oxide, aluminum nitride, boron nitride, boron carbide and silicon nitride.

[0103] The sound wave with strong dispersion characteristics can be a high-order sound wave mode or a zero-order sound wave mode in contact with a high-speed sound material layer. When the target mode of the sound wave resonator is a high-order sound wave mode, the high-order sound wave mode can be excited by the interdigital transducer 11, or by the interdigital transducer 11 and the suspended bottom electrode 14 formed on the lower surface of the piezoelectric film 10. Figures 10 to 16 As shown, the target mode of the acoustic wave resonator is a high-order acoustic wave mode excited by the interdigital transducer 11 and the suspended bottom electrode 14 formed on the lower surface of the piezoelectric film 10; Figures 17 to 19 As shown, the target mode of the acoustic wave resonator is a high-order acoustic wave mode excited by the interdigital transducer 11 .

[0104] like Figures 10 to 16 As shown, when the target mode of the acoustic wave resonator is a high-order acoustic wave mode excited by the interdigital transducer 11 and the suspended bottom electrode 14 formed on the lower surface of the piezoelectric film 10 , the suspended bottom electrode 14 is directly below the interdigital overlapping region 113 .

[0105] like Figures 10 to 12As shown, as an example, when the target mode of the acoustic wave resonator is a high-order acoustic wave mode, the interdigital transducer 11 is arranged on the upper surface of the piezoelectric film 10; the acoustic wave resonator also includes a second dielectric layer 15 and a second high acoustic velocity support substrate 16 sequentially located below the piezoelectric film 10, and the slow shear wave speed of the second high acoustic velocity support substrate 16 is greater than the sound speed of the target mode to reduce the leakage of the target mode into the second high acoustic velocity support substrate 16; the second dielectric layer 15 is an insulating dielectric layer; the suspended bottom electrode 14 is embedded in the second dielectric layer 15. The second dielectric layer 15 has the function of embedding the floating bottom electrode 14 and bonding the second high acoustic velocity support substrate 16 to the piezoelectric film 10. In addition, when it is necessary to improve the RF performance of the entire acoustic wave resonator, a temperature compensation layer and / or a trap capture layer may be provided in the second dielectric layer 15. The temperature compensation layer is used to reduce the frequency drift of the target mode in the piezoelectric film 10 caused by temperature changes. The trap capture layer is used to capture the free carriers on the top of the second high acoustic velocity support substrate 16 to reduce RF losses. Therefore, based on the function of the second dielectric layer 15, it may be a single-layer insulating material layer 150 (such as Fig.10 As shown), it can also be a laminated insulating material layer 150, and the material of each insulating material layer 150 in the laminated insulating material layer 150 can be the same (as shown Fig.12 ) can also be different (such as Fig.11 As shown). Generally, the material of the second dielectric layer 15 can be selected from silicon oxide, polycrystalline silicon, silicon nitride, silicon carbide, aluminum nitride, polycrystalline aluminum oxide or other suitable insulating materials. Preferably, the material of the second high acoustic velocity support substrate 16 is one of silicon carbide, diamond, diamond-like carbon, sapphire, aluminum oxide, aluminum nitride, boron nitride, boron carbide and silicon nitride of different crystal forms and different cuts. In addition, the second high acoustic velocity support substrate 16 can be a single-layer structure, for example Figures 10 to 12 As shown, at this time, the slow shear wave sound velocity of the second high acoustic velocity supporting substrate 16 of the single-layer structure is greater than the sound velocity of the target mode; the second high acoustic velocity supporting substrate 16 can also be a stacked structure, consisting of a supporting substrate away from the side of the piezoelectric film 10 and a high acoustic velocity material layer close to the side of the piezoelectric film 10. At this time, as long as the slow shear wave sound velocity of the high acoustic velocity material layer is greater than the sound velocity of the target mode, the material of the supporting substrate can be selected from one of quartz, silicon, sapphire, spinel, and yttrium aluminum garnet, and the material of the high acoustic velocity material layer can be selected from one of silicon carbide, diamond, diamond-like carbon, aluminum oxide, aluminum nitride, boron nitride, boron carbide and silicon nitride.

[0106] like Fig.13As shown, as an example, when the target mode of the acoustic wave resonator is a high-order acoustic wave mode, the interdigital transducer 11 is partially arranged on the upper surface of the piezoelectric film 10; the acoustic wave resonator also includes a third dielectric layer 17, a fourth dielectric layer 18 and a third high acoustic velocity support substrate 19 which are sequentially located below the interdigital transducer 11, and the slow shear wave velocity of the third high acoustic velocity support substrate 19 is greater than the velocity of the target mode to reduce the leakage of the target mode into the third high acoustic velocity support substrate 19; the piezoelectric film 10 is embedded in the third dielectric layer 17 and in contact with the interdigital transducer 11; the suspended bottom electrode 14 is embedded in the fourth dielectric layer 18. The main function of the third dielectric layer 17 is to fill and isolate the top electrode and the bottom electrode. The function of the fourth dielectric layer 18 is to embed the suspended bottom electrode 14 and bond the third high acoustic velocity support substrate 19 to the third dielectric layer 17. In addition, when it is necessary to improve the RF performance of the entire acoustic wave resonator, a temperature compensation layer and / or a trap capture layer can be set in the fourth dielectric layer 18. The temperature compensation layer is used to reduce the frequency drift of the target mode in the piezoelectric film 10 caused by temperature changes. The trap capture layer is used to capture the free carriers on the top of the third high acoustic velocity support substrate 19 to reduce RF losses. Therefore, based on the role of the fourth dielectric layer 18, it can be a single-layer insulating material layer or a stacked insulating material layer, and the material of each insulating material layer 150 in the stacked insulating material layer 150 can be the same (such as Fig.13 The dielectric layer 17 may be made of silicon oxide, polycrystalline silicon, silicon nitride, silicon carbide, aluminum nitride, polycrystalline aluminum oxide or other suitable insulating materials, and the dielectric layer 18 may be made of silicon oxide, polycrystalline silicon, silicon nitride, silicon carbide, aluminum nitride, polycrystalline aluminum oxide or other suitable insulating materials. Preferably, the material of the third high acoustic velocity support substrate 19 is one of silicon carbide, diamond, diamond-like carbon, sapphire, aluminum oxide, aluminum nitride, boron nitride, boron carbide and silicon nitride of different crystal forms and different cuts. In addition, the third high acoustic velocity support substrate 19 may be a single-layer structure, for example Fig.13 As shown, at this time, the slow shear wave sound velocity of the third high acoustic velocity support substrate 19 of the single-layer structure is greater than the sound velocity of the target mode; the third high acoustic velocity support substrate 19 can also be a stacked structure, consisting of a support substrate away from the side of the piezoelectric film 10 and a high acoustic velocity material layer close to the side of the piezoelectric film 10. At this time, as long as the slow shear wave sound velocity of the high acoustic velocity material layer is greater than the sound velocity of the target mode, the material of the support substrate can be selected from one of quartz, silicon, sapphire, spinel, and yttrium aluminum garnet, and the material of the high acoustic velocity material layer can be selected from one of silicon carbide, diamond, diamond-like carbon, aluminum oxide, aluminum nitride, boron nitride, boron carbide and silicon nitride.

[0107] like Fig.14 As shown, as an example, when the target mode of the acoustic wave resonator is a high-order acoustic wave mode, the interdigital transducer 11 is arranged on the upper surface of the piezoelectric film 10, and the acoustic wave resonator further includes a first support layer 20 and a first support substrate 21 sequentially located below the piezoelectric film 10; wherein a cavity 202 is formed in the first support layer 20, and the cavity 202 exposes the corresponding piezoelectric film 10 below the interdigital transducer 11. The cavity 202 can effectively reduce the leakage of the target mode into the first support substrate 21.

[0108] like Fig.15 As shown, as another example, when the target mode of the acoustic wave resonator is a high-order acoustic wave mode, the interdigital transducer 11 is arranged on the upper surface of the piezoelectric film 10, and the acoustic wave resonator further includes a first support layer 20 and a first support substrate 21 sequentially located below the piezoelectric film 10; wherein the first support layer 20 includes a fifth dielectric layer 200 and a Bragg reflection layer 201, and the floating bottom electrode 14 is embedded in the fifth dielectric layer 200. The Bragg reflection layer 201 can effectively reduce the leakage of the target mode into the first support substrate 21.

[0109] like Fig.16 As shown, as another example, when the target mode of the acoustic wave resonator is a high-order acoustic wave mode, the interdigital transducer 11 is disposed on the upper surface of the piezoelectric film 10, and the acoustic wave resonator further includes a second supporting substrate 22 located below the piezoelectric film 10, wherein a through cavity 220 is formed in the second supporting substrate 22, and the cavity 220 exposes the corresponding piezoelectric film 10 below the interdigital transducer 11. The cavity 220 can effectively reduce the leakage of the target mode into the second supporting substrate 22.

[0110] like Fig.17 As shown, as an example, when the target mode of the acoustic wave resonator is a high-order acoustic wave mode excited by the interdigital transducer 11, the interdigital transducer 11 is arranged on the upper surface of the piezoelectric film 10, and the acoustic wave resonator also includes a second supporting layer 23 and a third supporting substrate 24 sequentially located below the piezoelectric film 10; wherein a cavity 230 is formed in the second supporting layer 23, and the cavity 230 exposes the corresponding piezoelectric film 10 below the interdigital transducer 11, and the cavity 230 can effectively reduce the leakage of the target mode into the third supporting substrate 24.

[0111] like Fig.18As shown, as an example, when the target mode of the acoustic wave resonator is a high-order acoustic wave mode excited by the interdigital transducer 11, the interdigital transducer 11 is arranged on the upper surface of the piezoelectric film 10, and the acoustic wave resonator also includes a second supporting layer 23 and a third supporting substrate 24 sequentially located below the piezoelectric film 10; wherein the second supporting layer is a Bragg reflection layer 201, and the Bragg reflection layer 201 can effectively reduce the leakage of the target mode into the third supporting substrate 24.

[0112] like Fig.19 As shown, as an example, when the target mode of the acoustic wave resonator is a high-order acoustic wave mode excited by the interdigital transducer 11, the interdigital transducer 11 is arranged on the upper surface of the piezoelectric film 10, and the acoustic wave resonator also includes a fourth supporting substrate 25 located below the piezoelectric film 10, wherein a through cavity 250 is formed in the fourth supporting substrate 25, and the cavity 250 exposes the corresponding piezoelectric film 10 below the interdigital transducer 11, and the cavity 250 can effectively reduce the leakage of the target mode into the fourth supporting substrate 25.

[0113] As an example, the IDT 11 may also include reflection grating bus bars arranged on both sides of the IDT 11 and reflection grating electrodes connected to the reflection grating bus bars, so as to reflect the acoustic wave energy through the reflection grating bus bars and the reflection grating electrodes, thereby reducing the leakage of the acoustic wave in the horizontal propagation direction.

[0114] This embodiment also provides a method for preparing an acoustic wave resonator, the method comprising the steps of preparing the piezoelectric film 10 of the acoustic wave resonator as described in the above embodiment, such as Figure 20 to Figure 23 As shown, the step includes:

[0115] S1, such as Fig. 20 As shown, a piezoelectric film material layer 27 is formed on the lower substrate 26; it should be noted here that the lower substrate 26 is all the structures located below the piezoelectric film 10 in the acoustic wave resonator structure of the above embodiment, which can be specifically understood in combination with the content of the above embodiment;

[0116] S2, such as Fig.21 As shown, a patterned mask layer 28 is formed in a preset area of ​​the piezoelectric film material layer 27; the patterned mask layer 28 is made of any material suitable as a mask layer, and no excessive restrictions are made here;

[0117] S3, such as Fig. 22As shown, the piezoelectric film material layer 27 is etched based on the patterned mask layer 28 to thin the piezoelectric film material layer 27 outside the area covered by the patterned mask layer 28, so that the thickness of the piezoelectric film material layer 27 under the area covered by the patterned mask layer 28 is greater than the thickness of the piezoelectric film material layer 27 outside the area covered by the patterned mask layer 28;

[0118] S4, such as Fig.23 As shown, the patterned mask layer 28 is removed, thereby forming the piezoelectric film 10 .

[0119] The other structures of the acoustic wave resonator can be implemented using existing conventional technologies. The preparation steps of the piezoelectric film 10 of this embodiment can be achieved by etching the piezoelectric film material layer 27 through a patterned mask layer. The process method is simple, and the requirements for lithography accuracy and alignment accuracy are low. There is no additional load material, which can effectively reduce the process difficulty and manufacturing cost.

[0120] This embodiment further provides a filter, which includes a plurality of acoustic wave resonators, and the acoustic wave resonators are the acoustic wave resonators described in the above embodiment.

[0121] The beneficial effects that can be achieved by the acoustic wave resonator of the present invention are further illustrated below in combination with embodiments and comparative examples.

[0122] Comparative Example 1

[0123] like Fig.24 As shown, the structure of the acoustic wave resonator of the comparative example is: from bottom to top, it includes a first high sound velocity support substrate 12, a piezoelectric film 10 and an interdigital transducer 11, wherein the target mode of the acoustic wave resonator is a zero-order acoustic wave mode, and its sound velocity v s =f s ×λ, the interdigital transducer 11 is arranged on the upper surface of the piezoelectric film 10, the thickness of the piezoelectric film 10 is constant, and the structure of the interdigital transducer 11 can be seen in Figure 3 and Figure 4 ; The material of the first high acoustic velocity support substrate 12 is 4H-SiC; the material of the piezoelectric film 10 is X-cut lithium niobate with a thickness of 300nm, and the in-plane orientation (perpendicular to the electrode extension direction) is at an angle of 30° with the crystal Y axis; the material of the interdigital transducer 11 is aluminum with a thickness of 80nm, and the center spacing λ of adjacent electrode fingers 112 connected to the same bus bar 111 is 1.2μm, and the width W of the electrode finger 112 is a variable.

[0124] Fig.26 and Fig.28 are the target mode sound velocity v of the acoustic wave resonator of this comparative example respectively. s (f s×λ) and duty cycle (2W / λ) and the simulated admittance / conductance curve of the acoustic wave resonator. Fig.26 It can be seen that when the duty cycle changes from 0.3 to 0.7, the maximum change in sound speed reaches 259m / s, but the corresponding minimum line width is only 180nm, which requires very high lithography accuracy. With the current lithography accuracy, the lithography line width can be ensured to be above 250nm. In this case, the maximum change range of the duty cycle is 0.417 to 0.583, and the corresponding maximum change range of the sound speed is only 108m / s, which is not enough to suppress the lateral high-order modes. Fig.28 In the simulated admittance / conductance curve of the acoustic wave resonator, the duty cycle (2W / λ) is taken as 0.5. It can be seen that a large number of transverse high-order modes appear between the resonant frequency and the anti-resonant frequency at this time.

[0125] Embodiment 1

[0126] like Fig.25 As shown, the structure of the acoustic wave resonator of this embodiment is basically the same as that of the acoustic wave resonator of comparative example 1, except that: the piezoelectric film 10 is divided into a first piezoelectric film area 100 and a second piezoelectric film area 101, the thickness of the first piezoelectric film area 100 is h1, the thickness of the second piezoelectric film area 101 is h2, and the second piezoelectric film area 101 is located in the entire plane corresponding to the area of ​​the preset length L at the end of the interdigital overlapping area 113; the material of the first high acoustic velocity support substrate 12 is 4H-SiC; the material of the piezoelectric film 10 is X-cut lithium niobate, and the in-plane orientation (perpendicular to the electrode extension direction) is at an angle of 30° with the crystal Y axis; the material of the interdigital transducer 11 is aluminum, the thickness is 80nm, the duty cycle (2W / λ) is 0.5, and the thickness h of the piezoelectric film 10 is a variable.

[0127] Fig. 27 and Fig.29 are the target mode sound velocity v of the acoustic wave resonator of this embodiment respectively. s (f s ×λ) dispersion curve (where the abscissa is the ratio of the thickness h of the piezoelectric film 10 to the electrode finger spacing λ h / λ) and the simulated admittance / conductance curve of the acoustic wave resonator. Fig. 27 It can be seen that h / λ only changes from 0.23 to 0.32, v s The change amplitude reaches 408m / s, and the corresponding thickness change of the piezoelectric film 10 is 100nm, so Fig.25 The acoustic wave resonator structure shown can significantly reduce the sound velocity in the end region of the interdigital electrode without changing the electrode line width W. Fig.29In the figure, the parameters are h1=300nm, h2=350nm, and L=0.8λ. It can be seen that the lateral high-order modes between the resonant frequency and the anti-resonant frequency are basically suppressed at this time. Therefore, the acoustic wave resonator using this structure can suppress the lateral high-order modes without increasing the difficulty of lithography and adding additional loads.

[0128] Comparative Example 2

[0129] like Fig.30 As shown, the structure of the acoustic wave resonator of the comparative example is: from bottom to top, it includes a second high sound velocity support substrate 16, a second dielectric layer 15, a suspended bottom electrode 14, a piezoelectric film 10 and an interdigital transducer 11, the suspended bottom electrode 14 is embedded in the second dielectric layer 15, and the suspended bottom electrode 14 is directly below the interdigital overlap region 113, wherein the target mode of the acoustic wave resonator is the SH1 high-order acoustic wave mode (first-order horizontal shear mode), and is excited by the interdigital transducer 11 and the suspended bottom electrode 14 formed on the lower surface of the piezoelectric film 10, and its sound velocity v s =f s ×λ, the interdigital transducer 11 is arranged on the upper surface of the piezoelectric film 10, the thickness of the piezoelectric film 10 is constant, and the structure of the interdigital transducer 11 can be seen in Figure 3 and Figure 4 The material of the second high acoustic velocity support substrate 16 is 4H-SiC; the material of the piezoelectric film 10 is X-cut lithium niobate with a thickness of 200nm, and the in-plane orientation (perpendicular to the electrode extension direction) is at an angle of 30° with the crystal Y axis; the material of the suspended bottom electrode 14 is tungsten with a thickness of 100nm; the material of the second dielectric layer 15 is silicon oxide, and the thickness of the second dielectric layer 15 under the suspended bottom electrode 14 is 200nm; the material of the interdigital transducer 11 is a stack of 80nm thick aluminum and 20nm thick platinum, and the center spacing λ of adjacent electrode fingers 112 connected to the same bus bar 111 is 1.6μm, and the width W of the electrode fingers 112 is a variable.

[0130] Fig.32 and Fig.34 are the target mode sound velocity v of the acoustic wave resonator of this comparative example respectively. s (f s ×λ) and duty cycle (2W / λ) and the simulated admittance / conductance curve of the acoustic wave resonator. Fig.32 It can be seen that when the duty cycle changes from 0.3 to 0.7, the maximum change in sound speed reaches 383m / s. Fig.34 In the simulated admittance / conductance curve of the acoustic wave resonator, the duty cycle (2W / λ) is taken as 0.5. It can be seen that a large number of transverse high-order modes appear between the resonant frequency and the anti-resonant frequency at this time.

[0131] Embodiment 2

[0132] like Fig.31 As shown, the structure of the acoustic wave resonator of this embodiment is basically the same as that of the acoustic wave resonator of the comparative example 2, except that: the piezoelectric film 10 is divided into a first piezoelectric film region 100 and a second piezoelectric film region 101, the thickness of the first piezoelectric film region 100 is h1, the thickness of the second piezoelectric film region 101 is h2, and the second piezoelectric film region 101 is located in the entire plane of the area corresponding to the preset length L at the end of the interdigital overlap region 113; the material of the second high acoustic velocity support substrate 16 is 4H-SiC; The material of the piezoelectric film 10 is X-cut lithium niobate, and the in-plane orientation (perpendicular to the electrode extension direction) is at an angle of 30° with the Y-axis of the crystal; the material of the suspended bottom electrode 14 is tungsten, and the thickness is 100nm; the material of the second dielectric layer 15 is silicon oxide, and the thickness of the second dielectric layer 15 under the suspended bottom electrode 14 is 200nm; the material of the interdigital transducer 11 is a stack of 80nm thick aluminum and 20nm thick platinum, the duty cycle (2W / λ) is 0.5, and the thickness h of the piezoelectric film 10 is a variable.

[0133] Fig.33 and Fig.35 are the target mode sound velocity v of the acoustic wave resonator of this embodiment respectively. s (f s ×λ) dispersion curve (where the abscissa is the ratio of the thickness h of the piezoelectric film 10 to the electrode finger spacing λ h / λ) and the simulated admittance / conductance curve of the acoustic wave resonator. Fig.33 It can be seen that h / λ only changes from 0.11 to 0.175, v s The change amplitude reaches 913m / s, which is far beyond the limit of sound speed control that can be achieved by only changing the duty cycle. The corresponding thickness change of the piezoelectric film 10 is 100nm. Fig.31 The acoustic wave resonator structure shown can significantly reduce the sound velocity in the end region of the interdigital electrode without changing the electrode line width W. Fig.35 In the figure, the parameters are h1=200nm, h2=230nm, and L=0.3λ. It can be seen that the lateral high-order modes between the resonant frequency and the anti-resonant frequency are basically suppressed at this time. Therefore, the acoustic wave resonator using this structure can suppress the lateral high-order modes without increasing the difficulty of lithography and adding additional loads.

[0134] Comparative Example 3

[0135] like Fig.36As shown, the structure of the acoustic wave resonator of the comparative example is: from bottom to top, it includes a third supporting substrate 24, a second supporting layer 23, a piezoelectric film 10 and an IDT 11, a cavity 230 is formed in the second supporting layer 23, and the cavity 230 exposes the corresponding piezoelectric film 10 below the IDT 11, wherein the target mode of the acoustic wave resonator is an A1 high-order acoustic wave mode (a first-order antisymmetric Lamb wave mode), and is formed by the horizontal electric field excitation of the IDT 11, and its sound velocity v s =f s ×λ, the interdigital transducer 11 is arranged on the upper surface of the piezoelectric film 10, the thickness of the piezoelectric film 10 is constant, and the structure of the interdigital transducer 11 can be seen in Figure 3 and Figure 4 The material of the piezoelectric film 10 is Y124-cut lithium niobate with a thickness of 300 nm, and the in-plane orientation (perpendicular to the electrode extension direction) is parallel to the crystal X-axis; the material of the interdigital transducer 11 is 80 nm thick aluminum, and the center spacing λ of adjacent electrode fingers 112 connected to the same bus bar 111 is 2 μm, and the duty cycle (2W / λ) is 0.5. Fig.38 This is the simulated admittance / conductance curve of the acoustic wave resonator. It can be seen that a large number of transverse high-order modes appear between the resonant frequency and the anti-resonant frequency.

[0136] Embodiment 3

[0137] like Fig.37 As shown, the structure of the acoustic wave resonator of this embodiment is basically the same as that of the acoustic wave resonator of comparative example 3, except that: the piezoelectric film 10 is divided into a first piezoelectric film area 100 and a second piezoelectric film area 101, the thickness of the first piezoelectric film area 100 is h1, the thickness of the second piezoelectric film area 101 is h2, the second piezoelectric film area 101 is located in the entire plane of the area corresponding to the preset length L at the end of the interdigital overlap area 113, h1 = 300nm, h2 = 310nm, L = 0.3λ; the target mode of the acoustic wave resonator is the A1 high-order acoustic wave mode (first-order antisymmetric Lamb wave mode), and is formed by the horizontal electric field excitation of the interdigital transducer 11, and its sound velocity ν s =f s ×λ, the IDT 11 is arranged on the upper surface of the piezoelectric film 10. The structure of the IDT 11 can be seen in Figure 3 and Figure 4 The material of the piezoelectric film 10 is Y124-cut lithium niobate, and the in-plane orientation (perpendicular to the electrode extension direction) is parallel to the crystal X-axis; the material of the interdigital transducer 11 is 80nm thick aluminum, and the duty cycle (2W / λ) is 0.5. Fig.39This is a simulated admittance / conductance curve of the acoustic wave resonator. It can be seen that the lateral high-order modes between the resonant frequency and the anti-resonant frequency are basically suppressed at this time. Therefore, the acoustic wave resonator using this structure can suppress the lateral high-order modes without increasing the difficulty of lithography and adding additional loads.

[0138] In summary, the present invention provides an acoustic wave resonator and a preparation method and filter thereof. For acoustic waves with strong dispersion characteristics in the target mode, such as high-order acoustic wave modes or zero-order acoustic wave modes in contact with a high-sound-velocity material layer, the thickness of the piezoelectric film has a far greater influence on the sound velocity than the duty cycle 2W / λ of the interdigital transducer electrode. By thickening the thickness of the piezoelectric film corresponding to the lower part of the region from a certain area at the end of the interdigital transducer electrode finger overlap region to the end of the busbar, making it thicker than the piezoelectric film corresponding to the middle part of the electrode finger overlap region, the sound velocity of the target mode in the piezoelectric film in the thicker region is lower than the sound velocity of the target mode in the piezoelectric film in the thinner region, thereby achieving effective suppression of the lateral high-order mode and improving the device performance; in addition, the structure can achieve suppression of the lateral high-order mode by only increasing the thickness of a part of the piezoelectric film region, the structure is simple, easy to prepare, and has low requirements for process accuracy, and can effectively reduce the process complexity and manufacturing cost while effectively ensuring the performance of the resonator. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and has a high industrial utilization value.

[0139] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. An acoustic wave resonator, characterized in that: The acoustic wave resonator comprises: a piezoelectric film and an interdigital transducer arranged on the piezoelectric film; The interdigital transducer comprises: two interdigital electrodes; each of the interdigital electrodes comprises a bus bar and a plurality of electrode fingers, and all the electrode fingers are connected to the bus bar; the electrode fingers of the two interdigital electrodes extend in opposite directions and are arranged crosswise; the electrode fingers of the two interdigital electrodes comprise an interdigital overlap region and an interdigital gap region; The piezoelectric film includes a first piezoelectric film area and a second piezoelectric film area, and the thickness of the first piezoelectric film area is less than the thickness of the second piezoelectric film area; the second piezoelectric film area is located at least part of the plane from the preset length at the end of the interdigital overlap area to the corresponding area of ​​the corresponding end of the bus bar, and the second piezoelectric film area needs to extend at least from the end of the interdigital overlap area to the corresponding area of ​​the corresponding end of the bus bar, wherein the preset length is not greater than 1 / 5 of the length of the interdigital overlap area; The center distance between the adjacent electrode fingers connected to the same bus bar is denoted as λ, and the resonant frequency of the acoustic wave resonator is f s The product of λ is the acoustic velocity v of the target mode of the acoustic resonator. s ; The target mode of the acoustic wave resonator has a strong dispersion characteristic.

2. The acoustic wave resonator according to claim 1, characterized in that: The interdigital transducer is arranged on the upper surface of the piezoelectric film; the target mode of the acoustic wave resonator is the zero-order acoustic wave mode; the acoustic wave resonator also includes a first high acoustic velocity support substrate located below the piezoelectric film, and the slow shear wave sound velocity of the first high acoustic velocity support substrate is greater than the sound velocity of the target mode.

3. The acoustic wave resonator according to claim 2, characterized in that: The piezoelectric film is in direct contact with the first high acoustic velocity support substrate; or the piezoelectric film is formed on the upper surface of the first high acoustic velocity support substrate through a first dielectric layer, wherein the acoustic velocity of the first dielectric layer is smaller than the acoustic velocity of the target mode, and the thickness of the dielectric layer is smaller than the thickness of the first piezoelectric film region and is smaller than 0.1λ.

4. The acoustic wave resonator according to claim 3, characterized in that: The material of the first high acoustic velocity support substrate is one of silicon carbide, diamond, diamond-like carbon, sapphire, aluminum oxide, aluminum nitride, boron nitride, boron carbide and silicon nitride of different crystal forms and different cuts; the material of the first dielectric layer is one of silicon oxide, polycrystalline silicon, amorphous silicon, aluminum oxide, silicon nitride and aluminum nitride.

5. The acoustic wave resonator according to claim 2, characterized in that: The first high acoustic velocity support substrate is composed of a support substrate away from the side of the piezoelectric film and a high acoustic velocity material layer close to the side of the piezoelectric film; the material of the support substrate is one of quartz, silicon, sapphire, spinel, and yttrium aluminum garnet; the material of the high acoustic velocity material layer is one of silicon carbide, diamond, diamond-like carbon, aluminum oxide, aluminum nitride, boron nitride, boron carbide and silicon nitride.

6. The acoustic wave resonator according to claim 1, characterized in that: The target mode of the acoustic wave resonator is a high-order acoustic wave mode.

7. The acoustic wave resonator according to claim 6, characterized in that: The acoustic wave resonator further comprises a suspended bottom electrode arranged on the lower surface of the piezoelectric film, and the suspended bottom electrode is directly opposite to the bottom of the interdigital overlapping area, and the high-order acoustic wave mode is formed by the interdigital transducer and the suspended bottom electrode.

8. The acoustic wave resonator according to claim 7, characterized in that: The interdigital transducer is arranged on the upper surface of the piezoelectric film; the acoustic wave resonator also includes a second dielectric layer and a second high-acoustic-velocity support substrate sequentially located below the piezoelectric film, and the slow shear wave speed of the second high-acoustic-velocity support substrate is greater than the speed of the target mode, so as to reduce the leakage of the target mode into the second high-acoustic-velocity support substrate; The second dielectric layer is an insulating dielectric layer; the floating bottom electrode is embedded in the second dielectric layer.

9. The acoustic wave resonator according to claim 8, characterized in that: The second high acoustic velocity support substrate is composed of a support substrate away from the side of the piezoelectric film and a high acoustic velocity material layer close to the side of the piezoelectric film; the material of the support substrate is one of quartz, silicon, sapphire, spinel, and yttrium aluminum garnet; the material of the high acoustic velocity material layer is one of silicon carbide, diamond, diamond-like carbon, aluminum oxide, aluminum nitride, boron nitride, boron carbide and silicon nitride.

10. The acoustic wave resonator according to claim 7, characterized in that: The acoustic wave resonator further includes a third dielectric layer, a fourth dielectric layer and a third high acoustic velocity support substrate sequentially located below the interdigital transducer, and the slow shear wave acoustic velocity of the third high acoustic velocity support substrate is greater than the acoustic velocity of the target mode, so as to reduce the leakage of the target mode into the third high acoustic velocity support substrate; The piezoelectric film is embedded in the third dielectric layer and contacts the interdigital transducer; and the suspended bottom electrode is embedded in the fourth dielectric layer.

11. The acoustic wave resonator according to claim 10, characterized in that: The third high acoustic velocity support substrate is composed of a support substrate away from the side of the piezoelectric film and a high acoustic velocity material layer close to the side of the piezoelectric film; the material of the support substrate is one of quartz, silicon, sapphire, spinel, and yttrium aluminum garnet; the material of the high acoustic velocity material layer is one of silicon carbide, diamond, diamond-like carbon, aluminum oxide, aluminum nitride, boron nitride, boron carbide and silicon nitride.

12. The acoustic wave resonator according to claim 7, characterized in that: The interdigital transducer is arranged on the upper surface of the piezoelectric film, and the acoustic wave resonator also includes a first supporting layer and a first supporting substrate sequentially located below the piezoelectric film; wherein a cavity is formed in the first supporting layer, and the cavity exposes the corresponding piezoelectric film below the interdigital transducer, or the first supporting layer includes a fifth dielectric layer and a Bragg reflection layer, and the suspended bottom electrode is embedded in the fifth dielectric layer.

13. The acoustic wave resonator according to claim 7, characterized in that: The interdigital transducer is arranged on the upper surface of the piezoelectric film; the acoustic wave resonator also includes a second supporting substrate located below the piezoelectric film, wherein a through cavity is formed in the second supporting substrate, and the cavity exposes the corresponding piezoelectric film below the interdigital transducer.

14. The acoustic wave resonator according to claim 6, characterized in that: The interdigital transducer is arranged on the upper surface of the piezoelectric film, and the high-order acoustic wave mode is formed by the interdigital transducer. The acoustic wave resonator also includes a second supporting layer and a third supporting substrate which are sequentially located below the piezoelectric film; wherein a cavity is formed in the second supporting layer, and the cavity exposes the corresponding piezoelectric film below the interdigital transducer, or the second supporting layer is a Bragg reflection layer.

15. The acoustic wave resonator according to claim 6, characterized in that: The interdigital transducer is arranged on the upper surface of the piezoelectric film, and the high-order acoustic wave mode is formed by the interdigital transducer. The acoustic wave resonator also includes a fourth supporting substrate located below the piezoelectric film, wherein a through cavity is formed in the fourth supporting substrate, and the cavity exposes the corresponding piezoelectric film below the interdigital transducer.

16. The acoustic wave resonator according to claim 1, characterized in that: The second piezoelectric film area is located in the entire plane corresponding to the area of ​​the preset length at the end of the interdigital overlapping area; or the second piezoelectric film area is located in the entire plane extending from the end of the interdigital overlapping area to the area corresponding to the preset length of the interdigital gap area; or the second piezoelectric film area is located in the plane corresponding to the entire interdigital gap area not covered by the electrode fingers; or the second piezoelectric film area is located in the entire plane extending from the end of the interdigital overlapping area to the area corresponding to the preset length of the corresponding bus bar.

17. A filter, characterized in that: It comprises a plurality of acoustic wave resonators, wherein the acoustic wave resonator is the acoustic wave resonator according to any one of claims 1 to 16.

18. A method for preparing an acoustic wave resonator, characterized in that: The preparation method comprises the step of preparing the piezoelectric film of the acoustic wave resonator according to any one of claims 1 to 16, the step comprising: forming a piezoelectric thin film material layer on the lower substrate; forming a patterned mask layer in a preset area of ​​the piezoelectric thin film material layer; Etching the piezoelectric thin film material layer based on the patterned mask layer to thin the piezoelectric thin film material layer outside the area covered by the patterned mask layer; The patterned mask layer is removed.

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