An acoustic resonator, an acoustic wave filter, and a communication device

Abstract

The present invention relates to the field of microelectronics technology, and particularly to an acoustic resonator, an acoustic filter and a communication device. The acoustic resonator includes a piezoelectric thin film, a top electrode and two reflection gratings located on the piezoelectric thin film; one of the reflection gratings is provided on each side of the top electrode; the top electrode is an interdigital electrode; the interdigital electrode includes a plurality of electrode fingers, and the extending directions of the plurality of electrode fingers are perpendicular to the acoustic wave propagation direction of the acoustic resonator; wherein, a conductive region is provided on the piezoelectric thin film, and the conductive region is located in the region between adjacent reflection bars of the reflection grating. Thereby, the boundary condition on the surface of the corresponding piezoelectric thin film can be changed from an open circuit to a short circuit, the sound velocity is reduced, and part of the longitudinal high-order mode can leak to the outside of the resonator without affecting the main mode, greatly weakening the intensity of the longitudinal high-order mode.

Description

Technical Field

[0001] The present invention relates to the field of microelectronic technology, and particularly relates to an acoustic resonator, an acoustic filter and a communication device. Background Art

[0002] At present, acoustic filters are widely used in modern wireless communication systems. Their technical types are specifically divided into bulk acoustic wave (BAW) and surface acoustic wave (SAW) filter technologies, as well as plate wave filter technologies based on single-crystal piezoelectric thin films. Among them, the electrodes of surface acoustic wave resonators and plate wave resonators are interdigital electrodes, and the operating frequency can be regulated by the period of the interdigital electrodes. However, this resonator will generate longitudinal higher-order modes due to the finite-length longitudinal waveguide, resulting in ripples in the passband of the corresponding filter, or fluctuations in the transition band and stop band.

[0003] In related technologies, a scheme to weaken longitudinal higher-order modes can weaken the intensity of longitudinal higher-order modes by reducing the number of reflection gratings, but this method will lead to a decrease in the Q value of the resonator. Another scheme to weaken longitudinal higher-order modes can weaken the intensity of longitudinal higher-order modes by increasing the number of interdigital electrodes, but it will lead to an increase in the device area. Therefore, how to provide an acoustic resonator that can weaken longitudinal higher-order modes without increasing the device area or reducing the Q value of the resonator has become an urgent technical problem to be solved. Summary of the Invention

[0004] To solve the above technical problems, the present application discloses an acoustic resonator on the one hand, which at least includes:

[0005] A piezoelectric thin film;

[0006] And a top electrode and two reflection gratings located on the piezoelectric thin film; one of the reflection gratings is provided on each side of the top electrode; the top electrode is an interdigital electrode; the interdigital electrode includes a plurality of electrode fingers, and the extending direction of the plurality of electrode fingers is perpendicular to the acoustic wave propagation direction of the acoustic resonator;

[0007] Wherein, a conductive region is provided on the piezoelectric thin film, and the conductive region is located in the region between adjacent reflection bars of the reflection grating.

[0008] Further, the reflection grating includes a plurality of reflection bars; the area of the conductive region is greater than or equal to 1% of the sum of the areas of all regions between adjacent reflection bars among the plurality of reflection bars.

[0009] Further, the thickness of the conductive region does not exceed 0.1 times the thickness of the reflection bar.

[0010] Furthermore, the conductive region is also located in the region of the positive projection of the reflective bars of the reflective grating on the piezoelectric thin film.

[0011] Furthermore, the top electrode further includes dummy finger electrodes;

[0012] The interdigital electrode further includes a first bus bar and a second bus bar;

[0013] The electrode fingers include first electrode fingers and second electrode fingers;

[0014] The first bus bar is connected to a plurality of the first electrode fingers; the second bus bar is connected to a plurality of the second electrode fingers; the plurality of the first electrode fingers and the plurality of the second electrode fingers are arranged alternately along a first direction; the first direction is the width direction of the first electrode finger or the second electrode finger;

[0015] The dummy finger electrodes are located in the air gap region of the interdigital electrode; the air gap region is the region between the free ends of the first electrode fingers and the second bus bar and the region between the second electrode fingers and the first bus bar.

[0016] Furthermore, the free ends of adjacent first electrode fingers and the free ends of second electrode fingers in the interdigital electrode are sequentially connected to form end connections; the angles between the end connections and the acoustic wave propagation direction of the acoustic wave resonator are all non-zero; or,

[0017] The angle between the in-plane symmetry axis of the piezoelectric thin film and the acoustic wave propagation direction of the acoustic wave resonator is non-zero.

[0018] Furthermore, the conductive region is also located in the region on the piezoelectric thin film except for the region between adjacent reflective bars of the reflective grating, and there is no overlapping region between the conductive region and the aperture region of the interdigital electrode; the aperture region of the interdigital electrode is the region where a plurality of the electrode fingers overlap.

[0019] Furthermore, the conductive region is located in the region of the positive projection of the bus bar of the reflective grating on the piezoelectric thin film, and / or the conductive region is located in the region of the positive projection of the air gap region of the interdigital electrode on the piezoelectric thin film; the air gap region of the interdigital electrode is the region between the free ends of the electrode fingers and the bus bar on the opposite side of the electrode fingers.

[0020] Furthermore, a bottom electrode is further included;

[0021] The piezoelectric thin film is provided on the bottom electrode;

[0022] The bottom electrode is a planar electrode or an interdigital electrode;

[0023] When the bottom electrode is an interdigital electrode, the misalignment distance between the electrode fingers of the interdigital electrode of the bottom electrode corresponding to the electrode fingers of the interdigital electrode of the top electrode does not exceed 25% of the width of the electrode fingers of the top electrode.

[0024] Further, it further includes a dielectric layer;

[0025] The piezoelectric thin film is provided on the dielectric layer;

[0026] The dielectric layer is a single-layer material or a multi-layer material, including one or more of silicon oxide, silicon nitride, polysilicon, amorphous silicon, aluminum oxide, aluminum nitride, or a combination of one or more of a temperature compensation layer, a heat dissipation layer, a rich trap layer, a bonding layer, and a low sound velocity layer.

[0027] Further, it further includes a support substrate;

[0028] The piezoelectric thin film is provided on the support substrate;

[0029] The support substrate is any one of sapphire, silicon, spinel, silicon carbide, diamond, diamond-like, silicon nitride, boron nitride, boron carbide, quartz, germanium, aluminum nitride, silicon nitride, yttrium aluminum garnet, lithium tantalate, and lithium niobate with different crystal forms.

[0030] Further, the support substrate includes a stacked support layer and a high sound velocity layer;

[0031] The high sound velocity layer is a material that is easy to form and process; the material of the high sound velocity layer is any one of silicon carbide, diamond, diamond-like, aluminum oxide, aluminum nitride, boron nitride, boron carbide, and silicon nitride with different crystal forms and different cutting types;

[0032] The material of the support layer includes any one of quartz, silicon, sapphire, spinel, and yttrium aluminum garnet.

[0033] Further, a Bragg reflection layer is further provided between the piezoelectric thin film and the support substrate.

[0034] Further, the material of the piezoelectric thin film is lithium tantalate or lithium niobate;

[0035] The material of the support substrate is silicon, sapphire, quartz, or silicon carbide.

[0036] Further, the material of the piezoelectric thin film is lithium tantalate or lithium niobate;

[0037] A dielectric layer is further provided between the piezoelectric thin film and the support substrate; the material of the dielectric layer is silicon oxide;

[0038] The material of the support substrate is sapphire, quartz, or silicon carbide.

[0039] Further, the material of the piezoelectric thin film is lithium tantalate or lithium niobate;

[0040] A dielectric layer is further provided between the piezoelectric thin film and the support substrate; the material of the dielectric layer is silicon oxide and polysilicon;

[0041] The material of the support substrate is silicon.

[0042] Further, the material of the top electrode is one or a combination of copper, aluminum, gold, silver, tungsten, platinum, nickel, chromium, molybdenum, titanium, graphene, copper-aluminum alloy, aluminum-silicon alloy, doped silicon, silicon carbide, gallium nitride.

[0043] Further, the conductive region is a conductive film formed by a deposition process, and the material of the conductive film is one or a combination of copper, aluminum, gold, silver, tungsten, platinum, nickel, chromium, molybdenum, titanium, graphene, copper-aluminum alloy, aluminum-silicon alloy, doped silicon, silicon carbide, gallium nitride.

[0044] Further, the conductive region is also located on the surface of the reflective bars of the reflective grating.

[0045] Further, the conductive region is formed by doping the surface of the piezoelectric thin film.

[0046] On the other hand, the present application also discloses an acoustic wave filter, including the above-mentioned acoustic wave resonator.

[0047] On the other hand, the present application also discloses a communication device, including the above-mentioned acoustic wave resonator;

[0048] The communication device includes at least one of a filter, a duplexer, and a multiplexer.

[0049] The embodiment of the present application provides an acoustic wave resonator, which includes a piezoelectric thin film, and a top electrode and two reflective gratings located on the piezoelectric thin film; one of the reflective gratings is provided on each side of the top electrode; the top electrode is an interdigital electrode; the interdigital electrode includes a plurality of electrode fingers, and the extending direction of the plurality of electrode fingers is perpendicular to the acoustic wave propagation direction of the acoustic wave resonator; wherein, a conductive region is provided on the piezoelectric thin film, and the conductive region is located in the region between adjacent reflective bars of the reflective grating. Thus, the boundary condition on the surface of the corresponding piezoelectric thin film can be changed from open circuit to short circuit, and the sound velocity can be reduced, so that part of the longitudinal high-order mode can leak to the outside of the resonator without affecting the main mode, and the intensity of the longitudinal high-order mode can be greatly weakened. Description of the Drawings

[0050] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0051] Figure 1 is a cross-sectional view of the first exemplary acoustic resonator of the present application;

[0052] Figure 2 is Figure 1 a top view of the acoustic resonator shown;

[0053] Figure 3 is a cross-sectional view of the second exemplary acoustic resonator of the present application;

[0054] Figure 4 is a cross-sectional view of the third exemplary acoustic resonator of the present application;

[0055] Figure 5 is a cross-sectional view of the fourth exemplary acoustic resonator of the present application;

[0056] Figure 6 is a cross-sectional view of the fifth exemplary acoustic resonator of the present application;

[0057] Figure 7 is a cross-sectional view of the sixth exemplary acoustic resonator of the present application;

[0058] Figure 8 is a cross-sectional view of the seventh exemplary acoustic resonator of the present application;

[0059] Figure 9 is a cross-sectional view of the eighth exemplary acoustic resonator of the present application;

[0060] Figure 10 is a cross-sectional view of the ninth exemplary acoustic resonator of the present application;

[0061] Figure 11 is a distribution diagram of the first exemplary conductive region of the present application;

[0062] Figure 12 is a distribution diagram of the second exemplary conductive region of the present application;

[0063] Figure 13 is a distribution diagram of the third exemplary conductive region of the present application;

[0064] Figure 14 is a distribution diagram of the fourth exemplary conductive region of the present application;

[0065] Figure 15It is the distribution diagram of the fifth exemplary conductive region of this application;

[0066] Figure 16 It is the distribution diagram of the sixth exemplary conductive region of this application;

[0067] Figure 17 It is the distribution diagram of the seventh exemplary conductive region of this application;

[0068] Figure 18 It is the distribution diagram of the eighth exemplary conductive region of this application;

[0069] Figure 19 It is the structural schematic diagram of an existing acoustic resonator;

[0070] Figure 20 It is a simulated admittance curve corresponding to Comparative Example 1;

[0071] Figure 21 It is an impedance phase diagram corresponding to Comparative Example 1;

[0072] Figure 22 It is another simulated admittance curve corresponding to Comparative Example 1;

[0073] Figure 23 It is another impedance phase diagram corresponding to Comparative Example 1;

[0074] Figure 24 It is Figure 22 The corresponding Bode-Q curve;

[0075] Figure 25 It is Figure 24 The corresponding Qp curve;

[0076] Figure 26 It is the cross-sectional view of the tenth exemplary acoustic resonator of this application;

[0077] Figure 27 It is a simulated admittance curve corresponding to Example 1;

[0078] Figure 28 It is an impedance phase diagram corresponding to Example 1;

[0079] Figure 29 It is Figure 27 The corresponding Bode-Q curve;

[0080] Figure 30 It is Figure 29 The corresponding Qp curve;

[0081] Figure 31 It is the simulated admittance curves respectively corresponding to Comparative Example 2 and Example 2;

[0082] Figure 32are the impedance phase diagrams corresponding to Comparative Example 2 and Example 2 respectively;

[0083] Figure 33 are the Bode-Q curves corresponding to Comparative Example 2 and Example 2 respectively;

[0084] Figure 34 is a schematic structural diagram of an exemplary top electrode of the present application;

[0085] Figure 35 is a schematic structural diagram of another exemplary top electrode of the present application;

[0086] Figure 36 is a distribution diagram of the ninth exemplary conductive region of the present application;

[0087] Figure 37 is a distribution diagram of the tenth exemplary conductive region of the present application;

[0088] Figure 38 is a distribution diagram of the eleventh exemplary conductive region of the present application.

[0089] The following is a supplementary description of the drawings:

[0090] 1 - Piezoelectric thin film; 2 - Reflective grating; 201 - Reflective strip; 202 - First region; 203 - Second region; 204 - Third bus bar; 205 - Fourth bus bar; 3 - Top electrode; 301 - First bus bar; 302 - Second bus bar; 303 - Electrode finger; 3031 - First electrode finger; 3032 - Second electrode finger; 304 - False finger electrode; 304 - Aperture region; 305 - Air gap region; 4 - Conductive region; 5 - Support substrate; 6 - Dielectric layer; 7 - Bragg reflection layer; 8 - Bottom electrode. Detailed implementation manners

[0091] Next, the technical solutions in the embodiments of the present application will be clearly and completely described with reference to 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 of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0092] As used herein, "one embodiment" or "an embodiment" refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present application. In the description of the present application, it should be understood that the orientation or positional relationship indicated by terms such as "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 of the present application. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity 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, terms such as "first" and "second" are used to distinguish similar objects and do not necessarily have 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 herein can be implemented in an order other than those illustrated or described herein.

[0093] When a numerical range is disclosed herein, the above range is considered continuous and includes the minimum and maximum values of the range, as well as each value therebetween. Further, when the range refers to integers, each integer between the minimum and maximum values of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein. For example, the specified range from "1 to 10" should be considered to include any and all sub-ranges between the minimum value 1 and the maximum value 10. Exemplary sub-ranges of the range 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, etc.

[0094] Please refer to Figure 1 and Figure 2 , Figure 1 is a cross-sectional view of a first exemplary acoustic resonator of the present application; Figure 2 is Figure 1 the corresponding top view. The acoustic resonator provided by the present application at least includes a piezoelectric thin film 1, and a top electrode 3 and two reflection gratings 2 located on the piezoelectric thin film 1; one of the reflection gratings 2 is provided on each side of the top electrode 3; the top electrode 3 is an interdigital electrode; the interdigital electrode includes a plurality of electrode fingers 303, and the extending directions of the plurality of electrode fingers 303 are perpendicular to the acoustic wave propagation direction of the acoustic resonator; wherein, a conductive region 4 is provided on the piezoelectric thin film 1, and the conductive region 4 is located in the region between the reflection bars 201 of the reflection grating 2.

[0095] In an exemplary embodiment, please refer toFigure 2 , the interdigital electrode further includes a first bus bar 301 and a second bus bar 302; the electrode fingers 303 include a first electrode finger 3031 and a second electrode finger 3032; the first bus bar 301 is connected to a plurality of the first electrode fingers 3031; the second bus bar is connected to a plurality of the second electrode fingers 3032; a plurality of the first electrode fingers 3031 and a plurality of the second electrode fingers 3032 are arranged alternately along a first direction; the first direction is the width direction of the first electrode finger 3031 or the second electrode finger 3032, specifically, it can be Figure 2 the x direction in. Optionally, the distance between adjacent first electrode fingers 3031 is equal to the distance between adjacent second electrode fingers 3032. Therefore, the electrode pitch of this acoustic resonator can refer to the pitch between adjacent electrode fingers 303 in the same bus bar, which can be denoted as λ. Specifically, the distance between the centers of adjacent first electrode fingers 3031 and second electrode fingers 3032 is λ, the distance between the centers of adjacent first electrode fingers 3031 is λ, and the distance between the centers of adjacent second electrode fingers 3032 is λ. The aperture region 304 is the region where a plurality of the first electrode fingers 3031 and a plurality of the second electrode fingers 3032 overlap; the interdigital electrode further includes an air gap region 305, and the air gap region 305 is the region between the free end of the second electrode finger 3032 and the first bus bar 301, and the region between the free end of the first electrode finger 3031 and the second bus bar 302. That is to say, the aperture region 304 is the region where a plurality of the electrode fingers 303 overlap alternately; the air gap region 305 is the region between the free end of the electrode finger 303 and the bus bar on the opposite side of the electrode finger 303. Optionally, the electrode finger pair is adjacent electrode fingers 303 located on different bus bars.

[0096] In an exemplary embodiment, the material of the piezoelectric thin film 1 is lithium tantalate or lithium niobate.

[0097] In an exemplary embodiment, the material of the top electrode 3 is one or a combination of copper, aluminum, gold, silver, tungsten, platinum, nickel, chromium, molybdenum, titanium, graphene, copper-aluminum alloy, aluminum-silicon alloy, doped silicon, silicon carbide, gallium nitride, that is, as long as it can achieve conductivity.

[0098] In an exemplary embodiment, please refer to Figure 3 , the acoustic resonator further includes a bottom electrode 8; the piezoelectric thin film 1 is provided on the bottom electrode 8; the bottom electrode 8 is a planar electrode. In another exemplary embodiment, please refer to Figure 4, the bottom electrode 8 can also be an interdigital electrode. Optionally, when the bottom electrode 8 is an interdigital electrode, the misalignment distance between the electrode fingers 303 of the bottom electrode 8 corresponding to the electrode fingers 303 of the top electrode 3 does not exceed 25% of the width of the electrode fingers 303 of the top electrode 3. Specifically, the interdigital electrode structure of the top electrode 3 and the interdigital electrode structure of the bottom electrode 8 can be the same, such as the width and the number of the electrode fingers 303 of the top electrode 3 being the same as those of the electrode fingers 303 of the bottom electrode 8. Optionally, the central axes of the electrode fingers 303 in the top electrode 3 corresponding to the electrode fingers 303 in the bottom electrode 8 can be coincident (such as Figure 4 shown), and there can also be a certain distance misalignment between their central axes. Optionally, the misalignment distance does not exceed 25% of the width of the electrode fingers 303 of the top electrode 3. Optionally, a reflection grating 2 can be distributed on both sides of the bottom electrode 8, and a conductive region 4 is further provided between the reflection grating 2 and the piezoelectric thin film 1. Specifically, the conductive region 4 can be only located above one reflection grating 2, or conductive regions 4 can be provided above both of these reflection gratings 2. Optionally, the material of the top electrode 3 is one or a combination of more of copper, aluminum, gold, silver, tungsten, platinum, nickel, chromium, molybdenum, titanium, graphene, copper-aluminum alloy, aluminum-silicon alloy, doped silicon, silicon carbide, and gallium nitride, that is, as long as it can conduct electricity.

[0099] In an exemplary embodiment, please refer to Figure 5 . The acoustic resonator further includes a dielectric layer 6; the piezoelectric thin film 1 is provided on the dielectric layer 6. Optionally, the dielectric layer 6 is a single-layer material or a multi-layer material, including one or more of silicon oxide, silicon nitride, polysilicon, amorphous silicon, aluminum oxide, and aluminum nitride. Optionally, the dielectric layer 6 is a combination of one or more of a temperature compensation layer, a heat dissipation layer, a rich trap layer, a bonding layer, and a low sound velocity layer.

[0100] In an exemplary embodiment, please refer to Figure 6 . The acoustic resonator further includes a support substrate 5; the piezoelectric thin film 1 is provided on the support substrate 5. Optionally, the support substrate 5 is any one of sapphire, silicon, spinel, silicon carbide, diamond, diamond-like, silicon nitride, boron nitride, boron carbide, quartz, germanium, aluminum nitride, silicon nitride, yttrium aluminum garnet, lithium tantalate, and lithium niobate with different crystal forms.

[0101] In an exemplary embodiment, the support substrate 5 includes a stacked support layer and a high sound velocity layer; the high sound velocity layer is close to the piezoelectric thin film 1. The high sound velocity layer is a material that is easy to form and process; the material of the high sound velocity layer is any one of silicon carbide, diamond, diamond-like, aluminum oxide, aluminum nitride, boron nitride, boron carbide, and silicon nitride with different crystal forms and different cutting types; the material of the support layer includes any one of quartz, silicon, sapphire, spinel, and yttrium aluminum garnet.

[0102] In an exemplary embodiment, please refer to Figure 7 , a Bragg reflection layer 7 is further provided between the piezoelectric thin film 1 and the support substrate 5.

[0103] The above mainly exemplifies the feasible solutions of the layer structures that can be distributed along the height direction of the acoustic wave resonator (such as the z direction shown in Figure 1 ). In fact, it can also be a combination of the above layer solutions. For example, when the acoustic wave resonator is provided with a bottom electrode 8, a dielectric layer 6 and a support substrate 5 can also be provided below it, that is, it can form a top electrode 3 + conductive region 4 + piezoelectric thin film 1 + bottom electrode 8 + dielectric layer 6, or, top electrode 3 + conductive region 4 + piezoelectric thin film 1 + bottom electrode 8 + dielectric layer 6 + support substrate 5, or, top electrode 3 + conductive region 4 + piezoelectric thin film 1 + bottom electrode 8 + support substrate 5 (such as the structure shown in Figure 8 ), all of which are feasible solutions. Similarly, if the acoustic wave resonator does not include a bottom electrode 8 and a dielectric layer 6 and a support substrate 5 are provided below it, that is, it can form a structure of top electrode 3 + conductive region 4 + piezoelectric thin film 1 + dielectric layer 6 + support substrate 5, and an acoustic wave resonator as shown in Figure 9 can be obtained. And since the dielectric layer 6 can be a multi-layer material structure, an acoustic wave resonator as shown in Figure 10 can also be formed.

[0104] In addition to the solutions that can include different layer structures, the embodiments of the present application can also be classified according to the setting position of the conductive region 4, and specifically can include the following several feasible solutions. First, the structure of the reflection grating 2 will be described first. Please continue to refer to Figure 2 , a reflection grating 2 is respectively provided on both sides of the top electrode 3. The reflection grating 2 specifically includes a third bus bar 204, a fourth bus bar 205 and a plurality of reflection bars 201; the third bus bar 204 and the fourth bus bar are arranged at intervals along the length direction of the electrode finger 303 (specifically, it can be the y direction shown in Figure 2 ), the plurality of reflection bars 201 are arranged at intervals along the first direction, and one end of each reflection bar 201 is connected to the third bus bar 204, and the other end of the reflection bar 201 is connected to the fourth bus bar 205. Optionally, the two reflection gratings 2 can be in a centrosymmetric structure. Optionally, the shapes of the reflection bars 201 in each reflection grating 2 can be the same or different, which is not limited here. The positional relationship between each reflection grating 2 and the conductive region 4 will be described below.

[0105] When the conductive region 4 is only located between the reflection grating 2 and the piezoelectric thin film 1, in an exemplary embodiment, please refer to Figure 11, the conductive region 4 can be only located in the region between adjacent reflective strips 201 of the reflective grating 2. Thereby, a short circuit can be formed between the reflective strips 201, making the surface of the piezoelectric film 1 between the reflective strips 201 conductive. In this way, the boundary condition on the surface of the corresponding piezoelectric film 1 can be changed from an open circuit to a short circuit, the corresponding sound velocity decreases, and the reflection efficiency near the frequency where the longitudinal higher-order mode is located decreases, while the reflection efficiency near the anti-resonant frequency of the main mode remains unchanged. Therefore, the longitudinal higher-order mode can be significantly weakened without changing the area of the resonator and without sacrificing the Q value of the resonator. In another exemplary embodiment, the conductive region 4 can be not only located in the region between adjacent reflective strips 201 of the reflective grating 2, but also located below the reflective strips 201, that is, the region where the reflective strips 201 are orthogonally projected on the piezoelectric film 1 is also provided with the conductive region 4, that is, as shown in Figure 10 shown in the structure. In other embodiments, the conductive region 4 can also be only provided below the reflective strips 201 and not provided below the bus bars of the reflective grating 2, that is, as shown in Figure 12 shown in the structure. Of course, it can also be provided below the bus bars of the reflective grating 2, that is, as shown in Figure 2 shown in the case. The conductive region 4 can also be provided below a part of the reflective strips 201 of the reflective grating 2. For example, a conductive region 4 can be provided below a part of the reflective strips 201 far from the top electrode 3 (that is, as shown in Figure 13 shown in the structure), or it can be provided below a preset number of reflective strips 201 in the middle of the reflective grating 2 (that is, as shown in Figure 14 shown in the structure). It is also possible to divide the reflective grating 2 into an upper region, a middle region, and a lower region along the length direction of the reflective strips 201. The conductive region 4 can be provided in the upper region and the lower region, that is, as shown in Figure 15 shown in the structure, or it can be only provided in the middle region, which is not limited here. Moreover, the shape of the conductive region 4 below the reflective grating 2 can also be irregular, that is, as shown in Figure 16 and 17 shown in the structure, and is not limited to a combination shape of a rectangle, a triangle, an ellipse, a trapezoid, etc. The above are only exemplary implementation schemes, and structures with the same concept as the above exemplary scheme all belong to the protection scope of this application, as long as the area of the conductive region 4 can meet the requirement of being greater than or equal to the sum of the areas of all regions between adjacent reflective strips 201 in the reflective grating 2 by 1%.

[0106] In another exemplary embodiment, please refer to Figure 18 , in addition to being able to be located between the reflective strips 201, the conductive region 4 can be located on the surface of the reflective strips 201 (specifically including the top and side walls of the reflective strips 201), and can be specifically formed based on a deposition process.

[0107] In an exemplary embodiment, the thickness of the conductive region 4 does not exceed 0.1 times the thickness of the reflective strip 201.

[0108] In an exemplary embodiment, the conductive region 4 is a conductive film formed by a deposition process, and the material of the conductive film is one or a combination of copper, aluminum, gold, silver, tungsten, platinum, nickel, chromium, molybdenum, titanium, graphene, copper-aluminum alloy, aluminum-silicon alloy, doped silicon, silicon carbide, gallium nitride. In another exemplary embodiment, the conductive region 4 is formed by doping the surface of the piezoelectric thin film 1. Optionally, the specific doping method may be ion implantation or thermal diffusion to a preset depth of the piezoelectric thin film, and the doping elements may include hydrogen, helium, oxygen, carbon, fluorine, sulfur, argon, silicon, nitrogen, phosphorus, boron, arsenic, selenium, gold, platinum, aluminum, iron, cobalt, copper, chromium, manganese, magnesium, zinc, gallium, titanium, tungsten, antimony or silver, etc., and the doping concentration range is 10 13 ~10 21 / cm3. According to different types of doped elements, the corresponding doping concentration ranges are also different, as long as the surface of the piezoelectric thin film 1 between the reflective strips 201 can be made conductive.

[0109] The following will illustrate the advantages of the present application compared with the existing structure with a specific embodiment.

[0110] Provide an existing structure, specifically, it can be the structure as Figure 19 shown, denoted as the structure of Comparative Example 1, which includes a support substrate 5, a dielectric layer 6, a piezoelectric thin film 1 arranged in sequence from bottom to top, and a top electrode 3 and a reflective grating 2 located on the piezoelectric thin film 1. The top electrode 3 is an interdigital electrode. It can be seen that the boundary condition of the surface of the piezoelectric thin film 1 under the reflective strip 201 of the reflective grating 2 is short-circuited, and the boundary condition of the surface of the piezoelectric thin film 1 between the reflective strips 201 is open-circuited. Specifically, the period of the interdigital electrode can be denoted as λ, which can refer to the distance between the central axes of adjacent electrode fingers 303 on the same bus bar.

[0111] Specifically, in this Comparative Example 1, the material of the support substrate 5 is silicon, the dielectric layer 6 is a two-layer structure, one layer structure is polysilicon with a thickness of 1000 nm, and the other layer structure is silicon oxide with a thickness of 500 nm; the material of the piezoelectric thin film 1 is Y42-cut lithium tantalate with a thickness of 600 nm; the material of the top electrode 3 is aluminum with a thickness of 170 nm; λ is 2.0 μm; and the interdigital electrode includes 60 pairs of electrode fingers 303, and the reflective grating 2 includes 50 reflective strips 201. The target mode of this acoustic wave resonator is the SH0 mode. Subsequent relevant calculations are carried out on it, and the simulation admittance curve as Figure 20 shown can be obtained. It can be seen that there is a strong longitudinal high-order mode on the high-frequency side of the anti-resonant frequency of the main mode. This makes that for a parallel resonator, the longitudinal high-order mode may cause fluctuations in the passband or transition band; for a series resonator, the longitudinal high-order mode may cause fluctuations in the transition band or stop band. And further, thus Figure 21As can be seen from the impedance phase diagram of Comparative Example 1 shown, there is a strong blocking phase peak. Generally, the more the impedance phase peak of the longitudinal high-order mode deviates from -90 dB, the stronger it is.

[0112] Subsequently, based on the above Comparative Example 1, by adjusting the number of reflective bars 201 of the reflective grating 2 and performing relevant calculations on Comparative Example 1 with different numbers of reflective bars 201, the following can be obtained Figure 22 The simulated admittance curve shown. It can be seen that as the number of reflective bars 201 continuously decreases, the admittance response of the longitudinal high-order mode corresponding to the resonator gradually weakens. Please refer to Figure 23 , which shows another impedance phase diagram corresponding to Comparative Example 1, specifically Figure 22 The impedance phase diagram of the corresponding longitudinal high-order mode. It can be seen that as the number of reflective bars 201 of the reflective grating 2 increases, the impedance phase corresponding to this resonator deviates more from -90 dB, that is, the blocking phase is stronger. When the number of reflective bars 201 of the reflective grating 2 is 10, the impedance phase is -73.37 dB. This shows that reducing the number of reflective bars 201 of the reflective grating 2 can effectively weaken the longitudinal high-order mode. Further, please refer to Figure 24 , which shows Figure 22 The corresponding Bode-Q curve. It can be seen that when the number of reflective bars 201 of the reflective grating 2 is reduced to less than 30, the Bode-Q curve drops significantly. By extracting Figure 24 The quality factor values (i.e., Qp values) of each curve at the anti-resonator frequency point fp in, the following curve diagram can be obtained Figure 25 It can be seen that when the number of reflective bars 201 of the reflective grating 2 is reduced to less than 30, Qp drops significantly. This shows that reducing the number of reflective bars 201 of the reflective grating 2 can reduce the intensity of the longitudinal high-order mode of the resonator, but will reduce the Q value of the resonator.

[0113] Another Embodiment 1 is provided, which is the structure shown Figure 10 It can be seen that the boundary conditions on the surface of the piezoelectric thin film 1 below the reflective grating 2 and the boundary conditions on the surface of the piezoelectric thin film 1 between the reflective bars 201 of the reflective grating 2 are both short circuits. Specifically, the material of the support substrate 5 is silicon, the dielectric layer 6 is a two-layer structure, one layer structure is polysilicon with a thickness of 1000 nm, and the other layer structure is silicon oxide with a thickness of 500 nm; the material of the piezoelectric thin film 1 is Y42-cut lithium tantalate with a thickness of 600 nm; the material of the top electrode 3 is aluminum with a thickness of 170 nm; λ is 2.0 μm; and the interdigital electrode includes 60 pairs of electrode fingers 303, and the reflective grating 2 includes 50 reflective bars 201. The target mode of this acoustic resonator is the SH0 mode. The difference between it and Comparative Example 1 is only that there is a conductive region 4 between the reflective bars 201 of the reflective grating 2 in Embodiment 1. Further, please refer to Figure 26 andFigure 13 , by dividing the reflection grating 2 into a first region 202 and a second region 203, where the first region 202 is the region of the reflection grating 2 close to the top electrode 3, and there is no conductive region 4 between the reflection bars 201 it contains, and the second region 203 is the region of the reflection grating 2 far from the top electrode 3, and there is a conductive region 4 between the reflection bars 201 it contains. On the basis of the above Embodiment 1, by adjusting the number of reflection bars 201 in the first region 202 and performing relevant calculations on the embodiments 1 with different numbers of reflection bars 201 in the first region 202, the simulation admittance curve as shown in Figure 27 can be obtained. It can be seen that no matter whether the number of reflection bars 201 in the first region 202 is 0, 5, 10, or 15, the response of the longitudinal higher-order mode of the corresponding acoustic wave resonator is significantly weaker than that in Figure 20 . This verifies that when the boundary condition on the surface of the piezoelectric film 1 between all or part of the reflection bars 201 in the reflection grating 2 is changed from open circuit to short circuit, the longitudinal higher-order mode can be effectively weakened. Please refer to Figure 28 , which shows an impedance phase diagram corresponding to Embodiment 1, specifically Figure 27 the impedance phase diagram of the corresponding longitudinal higher-order mode. It can be seen that when the number of reflection bars 201 in the first region 202 is 5, the impedance phase of the corresponding resonator is the smallest, -75.54 dB, which is lower than the result in Figure 23 when the reflection grating 2 has only 10 reflection bars. Further, please refer to Figure 29 , which shows Figure 27 the corresponding Bode-Q curve. It can be seen that the number of reflection bars 201 in the first region 202 has little effect on the Bode-Q curve. By extracting the quality factor values (i.e., Qp values) of each curve at the anti-resonator frequency point fp in Figure 29 , the curve graph as shown in Figure 30 can be obtained. It can be seen that the number of reflection bars 201 in the first region 202 has almost no effect on Qp. And when the number of reflection bars 201 of the reflection grating 2 in Comparative Example 1 and Embodiment 1 is both 50, their respective performances are compared, such as comparing Figure 20 and Figure 27 , comparing Figure 21 and Figure 28 , comparing Figure 25 and Figure 30 It can be seen that the parasitic response corresponding to the longitudinal higher-order mode in Embodiment 1 of this solution is greatly weakened, the impedance phase of the longitudinal higher-order mode drops significantly, and at the same time, the Qp value can be ensured to remain basically unchanged.

[0114] The embodiments of the present application also provide another Comparative Example 2 and Embodiment 2, specifically Figure 9For the structures shown, the main difference between Comparative Example 2 and Example 2 is that there is a conductive region 4 between some of the reflective bars 201 in the reflective grating 2 of Example 2, while there is no conductive region 4 under the reflective grating 2 in Comparative Example 2. Specifically, in Comparative Example 2 and Example 2, the material of the support substrate 5 is silicon carbide, the material of the dielectric layer 6 is silicon oxide, and the thickness is 150 nm; the material of the piezoelectric thin film 1 is X-cut lithium niobate, and the thickness is 250 nm; the material of the top electrode 3 is copper, and the thickness is 50 nm; λ is 1.5 μm. The top electrode 3 has 60 pairs of electrode fingers, and the reflective grating 2 includes 50 reflective bars 201. Among them, the number of reflective bars 201 in the first region 202 in Example 2 is 1. The target modes corresponding to Comparative Example 2 and Example 2 are the LL-SAW mode. By performing relevant calculations on them respectively, the simulation admittance curve as shown in Figure 31 can be obtained. It can be seen that compared with Comparative Example 2, the parasitic response corresponding to the longitudinal high-order mode in Example 2 is greatly weakened. Please refer to Figure 32 , which shows Figure 31 the impedance phase diagram of the corresponding longitudinal high-order mode. It can be seen that compared with Comparative Example 2, the impedance phase of the longitudinal high-order mode in Example 2 drops significantly. Further, please refer to Figure 33 , which shows Figure 31 the Bode-Q curve corresponding to. It can be seen that the Bode-Q value of Example 2 near the anti-resonant frequency fp is the same as that of Comparative Example 2. This shows that, under the condition that the number of reflective bars 201 in the reflective grating 2 of Example 2 and Comparative Example 2 is the same, this solution can greatly weaken the longitudinal high-order mode while ensuring that the Qp value remains basically unchanged.

[0115] In addition, through Figure 27 and Figure 28 it can be seen that when the number of reflective bars 201 in the first region 202 is 5, the impedance phase of the longitudinal high-order mode is the lowest, indicating that when there are a small number of reflective bars 201 in the first region 202, it can help to further weaken the longitudinal mode. Specifically, the number of reflective bars 201 in the first region 202 can be determined according to parameters such as the specific layer structure of the resonator and the target mode.

[0116] In addition to the above solutions, this application can also be classified according to the structure of the top electrode 3, and specifically includes the following feasible solutions.

[0117] In an exemplary embodiment, please refer to Figure 34 . The top electrode 3 further includes dummy finger electrodes 304; the dummy finger electrodes 304 are located in the air gap region 305 of the interdigital electrodes. Optionally, the lengths of the electrode fingers 303 in the top electrode 3 can be the same, that is, as shown in Figure 34The structure shown. The lengths of the electrode fingers 303 in the top electrode 3 can be different, that is, as Figure 35 shown in the structure, in this way, the free ends of adjacent first electrode fingers 3031 and second electrode fingers 3032 in the interdigital electrode are sequentially connected to form an end connection; the angles between the end connection and the acoustic wave propagation direction of the acoustic wave resonator are all non-zero.

[0118] Please refer to Figure 36 , the top electrode 3 of the resonator provided in the embodiment of the present application can be inclined, so that the in-plane symmetry axis of the piezoelectric thin film 1 (such as Figure 36 the dotted line in) and the acoustic wave propagation direction of the acoustic wave resonator (such as Figure 36 the x direction in) have a non-zero angle.

[0119] In an exemplary embodiment, please refer to Figure 37 and Figure 38 , the conductive region 4 is also located in the region of the piezoelectric thin film 1 other than the region between the reflective bars 201 of the reflective grating 2, and there is no overlapping region between the conductive region 4 and the aperture region 304 of the interdigital electrode; the aperture region 304 of the interdigital electrode is the region where multiple electrode fingers 303 overlap. Optionally, the conductive region 4 is located in the region of the piezoelectric thin film 1 where the positive projection of the bus bar of the reflective grating 2 is located. Optionally, the conductive region 4 can be located in the region of the piezoelectric thin film 1 where the positive projection of the air gap region 305 of the interdigital electrode is located; the air gap region 305 of the interdigital electrode is the region between the free end of the electrode finger 303 and the bus bar on the opposite side of the electrode finger 303. Optionally, the conductive region 4 is located in the region of the piezoelectric thin film 1 where the positive projection of the bus bar of the reflective grating 2 is located, and is located in the region of the piezoelectric thin film 1 where the positive projection of the air gap region 305 of the interdigital electrode is located. There is no limitation here.

[0120] In an exemplary embodiment, the material of the piezoelectric thin film 1 is lithium tantalate or lithium niobate; the material of the support substrate 5 is silicon, sapphire, quartz or silicon carbide.

[0121] In another exemplary embodiment, the material of the piezoelectric thin film 1 is lithium tantalate or lithium niobate; a dielectric layer 6 is further provided between the piezoelectric thin film 1 and the support substrate 5; the material of the dielectric layer 6 is silicon oxide; the material of the support substrate 5 is sapphire, quartz or silicon carbide.

[0122] In another exemplary embodiment, the material of the piezoelectric thin film 1 is lithium tantalate or lithium niobate; a dielectric layer 6 is further provided between the piezoelectric thin film 1 and the support substrate 5; the material of the dielectric layer 6 is silicon oxide and polysilicon; the material of the support substrate 5 is silicon.

[0123] An embodiment of the present application further provides a filter, including the acoustic wave resonator of any one of the above.

[0124] An embodiment of the present application further provides a communication device, including the acoustic wave resonator of any one of the above; the communication device includes at least one of a filter, a duplexer, and a multiplexer.

[0125] The above are only optional 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 within the protection scope of the present application.

Claims

1. An acoustic wave resonator, characterized in that: At least: Piezoelectric film; and a top electrode and two reflection grids located on the piezoelectric film; the reflection grids are respectively provided on both sides of the top electrode; the reflection grids include a plurality of reflection strips; the top electrode is an interdigitated electrode; the interdigitated electrode includes a plurality of electrode fingers, and the extension direction of the plurality of electrode fingers is perpendicular to the acoustic wave propagation direction of the acoustic wave resonator; Wherein, a conductive area is provided on the piezoelectric film, and the conductive area is formed by doping or depositing the surface of the piezoelectric film; the conductive area is located in the area between adjacent reflective strips of the reflective grid, and the conductive area is also located in the orthographic projection area of ​​the reflective strips of the reflective grid on the piezoelectric film, and / or located in the partial orthographic projection area of ​​the reflective strips of the reflective grid on the piezoelectric film, and / or located in the orthographic projection area of ​​the bus bars of the reflective grid on the piezoelectric film; The area of ​​the conductive region is greater than or equal to 1% of the sum of the areas of regions between all adjacent reflective strips in the plurality of reflective strips; and the thickness of the conductive region is no more than 0.1 times the thickness of the reflective strip.

2. The acoustic wave resonator according to claim 1, characterized in that The top electrode also includes a dummy finger electrode; The interdigitated electrode further includes a first bus bar and a second bus bar; The electrode fingers include first electrode fingers and second electrode fingers; The first bus bar is connected to the plurality of the first electrode fingers; the second bus bar is connected to the plurality of the second electrode fingers; the plurality of the first electrode fingers and the plurality of the second electrode fingers are staggered along a first direction; the first direction is a width direction of the first electrode fingers or the second electrode fingers; The dummy electrode is located in the air gap region of the interdigitated electrode; the air gap region is the region between the free end of the first electrode finger and the second bus bar and the region between the second electrode finger and the first bus bar.

3. The acoustic wave resonator according to claim 2, characterized in that The free ends of the adjacent first electrode fingers and the free ends of the second electrode fingers in the interdigitated electrodes are connected in sequence to form terminal lines; the angles between the terminal lines and the sound wave propagation direction of the acoustic wave resonator are not zero; or, the angle between the in-plane symmetry axis of the piezoelectric film and the sound wave propagation direction of the acoustic wave resonator is not zero.

4. The acoustic wave resonator according to claim 1, characterized in that The conductive area is also located on the piezoelectric film except for the area between adjacent reflective strips of the reflective grating, and there is no overlapping area between the conductive area and the aperture area of ​​the interdigitated electrode; the aperture area of ​​the interdigitated electrode is the area where multiple electrode fingers overlap.

5. The acoustic wave resonator according to claim 4, characterized in that The conductive area is located in the area where the air gap area of ​​the interdigitated electrodes of the top electrode is projected onto the piezoelectric film; the air gap area of ​​the interdigitated electrodes of the top electrode is the area between the free end of the electrode finger and the bus bar on the opposite side of the electrode finger.

6. The acoustic wave resonator according to claim 1, characterized in that Also included is a bottom electrode; The piezoelectric film is disposed on the bottom electrode; The bottom electrode is a surface electrode or an interdigitated electrode; When the bottom electrode is an interdigitated electrode, the misalignment distance between electrode fingers in the interdigitated electrodes of the bottom electrode corresponding to electrode fingers of the interdigitated electrodes of the top electrode does not exceed 25% of the width of the electrode fingers of the top electrode.

7. The acoustic wave resonator according to any one of claims 1 to 5, characterized in that: Also includes a dielectric layer; The piezoelectric film is provided on the dielectric layer; The dielectric layer is a single-layer material or a multi-layer material, including one or more of silicon oxide, silicon nitride, polycrystalline silicon, amorphous silicon, aluminum oxide, and aluminum nitride; or, the dielectric layer is a combination of one or more of a temperature compensation layer, a heat dissipation layer, a trap-rich layer, a bonding layer, and a low acoustic velocity layer.

8. The acoustic wave resonator according to any one of claims 1 to 5, characterized in that: Also included is a supporting substrate; The piezoelectric film is provided on the supporting substrate; The support substrate is any one of sapphire, silicon, spinel, silicon carbide, diamond, diamond-like carbon, silicon nitride, boron nitride, boron carbide, quartz, germanium, aluminum nitride, silicon nitride, yttrium aluminum garnet, lithium tantalate, and lithium niobate in different crystal forms.

9. The acoustic wave resonator according to claim 8, characterized in that The support substrate comprises a stacked support layer and a high acoustic velocity layer; The high acoustic velocity layer is made of a material that is easy to shape and process; the material of the high acoustic velocity layer is any one of silicon carbide, diamond, diamond-like carbon, aluminum oxide, aluminum nitride, boron nitride, boron carbide and silicon nitride of different crystal forms and different cuts; The material of the support layer includes any one of quartz, silicon, sapphire, spinel, and yttrium aluminum garnet.

10. The acoustic wave resonator according to claim 8, characterized in that A Bragg reflection layer is also provided between the piezoelectric film and the supporting substrate.

11. The acoustic wave resonator according to claim 8, characterized in that The material of the piezoelectric film is lithium tantalate or lithium niobate; The material of the support substrate is silicon, sapphire, quartz or silicon carbide.

12. The acoustic wave resonator according to claim 8, characterized in that The material of the piezoelectric film is lithium tantalate or lithium niobate; A dielectric layer is also provided between the piezoelectric film and the supporting substrate; the material of the dielectric layer is silicon oxide; The material of the support substrate is sapphire, quartz or silicon carbide.

13. The acoustic wave resonator according to claim 8, characterized in that The material of the piezoelectric film is lithium tantalate or lithium niobate; A dielectric layer is also provided between the piezoelectric film and the supporting substrate; the material of the dielectric layer is silicon oxide and polysilicon; The material of the supporting substrate is silicon.

14. The acoustic wave resonator according to claim 1, characterized in that The material of the top electrode is one or more combinations of copper, aluminum, gold, silver, tungsten, platinum, nickel, chromium, molybdenum, titanium, graphene, copper-aluminum alloy, aluminum-silicon alloy, doped silicon, silicon carbide, and gallium nitride.

15. The acoustic wave resonator according to claim 1, characterized in that The conductive area is a conductive film formed by a deposition process, and the material of the conductive film is a combination of one or more of copper, aluminum, gold, silver, tungsten, platinum, nickel, chromium, molybdenum, titanium, graphene, copper-aluminum alloy, aluminum-silicon alloy, doped silicon, silicon carbide, and gallium nitride.

16. The acoustic wave resonator according to claim 15, characterized in that The conductive area is also located on the surface of the reflective strips of the reflective grid.

17. An acoustic wave filter, characterized in that: The acoustic wave resonator comprises the acoustic wave resonator according to any one of claims 1 to 16.

18. A communication device, characterized in that: An acoustic wave resonator comprising any one of claims 1 to 16; The communication device includes at least one of a filter, a duplexer and a multiplexer.

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