Surface acoustic wave resonator and manufacturing method therefor, and filter

Abstract

The present invention relates to the field microelectronic devices, and in particular to a surface acoustic wave resonator and a manufacturing method therefor, and a filter. The surface acoustic wave resonator comprises a support substrate, a functional layer, and an interdigital transducer which are sequentially arranged from bottom to top; the functional layer comprises a first dielectric region, a piezoelectric region, and a second dielectric region which are sequentially arranged in the first direction; a piezoelectric layer and a bottom electrode are arranged in an aperture region of the interdigital transducer, the width of the piezoelectric layer and the bottom electrode can be less than or equal to the width of the aperture region, the aperture region is a region where two types of oppositely arranged interdigital electrodes in the interdigital transducer are interlaced, and a target mode of the surface acoustic wave resonator is a high-order surface acoustic wave mode excited by a longitudinal electric field; and the product of the distance between adjacent first interdigital electrodes and the frequency of the target mode is less than the speed of sound of the support substrate, thereby avoiding parasitic bulk acoustic waves generated by excitation of the longitudinal electric field, and facilitating suppression of a transverse high-order mode.

Description

A surface acoustic wave resonator and its preparation method, and filter Technical Field

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

[0002] The modern communications industry is facing increasingly stringent requirements for signal quality and fierce competition for spectrum resources. Low loss, wide bandwidth, tunability, and temperature stability have become universal goals in the communications industry. Surface acoustic wave (SAW) resonators based on piezoelectric heterostructure substrates offer significant advantages in terms of Q, size, temperature stability, and power handling.

[0003] However, the commonly used surface acoustic wave modes at present are mainly horizontal shear mode and Rayleigh mode, which have limited sound speed and are difficult to apply to higher frequencies. The electromechanical coupling coefficient of the longitudinal leakage surface acoustic wave mode with higher sound speed cannot yet meet the requirements of the N77 frequency band in the 5G frequency band. The surface acoustic wave mode excited by the longitudinal electric field shows great potential in terms of both sound speed and electromechanical coupling coefficient. However, the resonator in the prior art is usually a structure as shown in Figure 1, which utilizes a plate wave mode or quasi-bulk acoustic wave mode with a very high sound speed. Therefore, the leakage of acoustic wave energy can only be avoided by making the film suspended in the air. The suspension of the piezoelectric film is achieved by back etching, and finally the metal bottom electrode is deposited through the cavity on the back. At this time, the shape of the suspended bottom electrode is determined by the shape of the etched cavity. This solution uses a cavity structure, which is unstable and has poor heat dissipation. Depositing metal from the etched cavity easily causes metal to be deposited on the side walls of the cavity, resulting in new parasitic effects.

[0004] Summary of the Invention

[0005] To solve the above technical problems, in one aspect, the present application discloses a surface acoustic wave resonator, which includes a supporting substrate, a functional layer and an interdigital transducer arranged in sequence from bottom to top;

[0006] The interdigital transducer includes a first bus bar, a first interdigital electrode connected to the first bus bar, a second bus bar, and a second interdigital electrode connected to the second bus bar; the first interdigital electrode and the second interdigital electrode are arranged alternately;

[0007] The functional layer includes a first dielectric region, a piezoelectric region, and a second dielectric region sequentially arranged along a first direction; the first direction is the length direction of the first interdigital electrode or the second interdigital electrode; the piezoelectric region includes a stacked bottom electrode and a piezoelectric layer; the bottom electrode is located on a supporting substrate;

[0008] Among them, the width of the piezoelectric zone is less than or equal to the width of the projection area of ​​the aperture zone of the interdigital transducer; the projection area of ​​the aperture zone is the area where the aperture zone is projected on the functional layer; the aperture zone is the area where the first interdigital electrode and the second interdigital electrode in the interdigital transducer are intertwined; the target mode of the surface acoustic wave resonator is a high-order surface acoustic wave mode excited by the longitudinal electric field; the product of the distance between adjacent first interdigital electrodes and the frequency of the target mode is less than the sound velocity of the supporting substrate.

[0009] Optionally, a first dielectric layer is provided between the functional layer and the supporting substrate, and / or a second dielectric layer is provided between the functional layer and the interdigital transducer.

[0010] Optionally, a third dielectric layer is provided between the piezoelectric region and the first dielectric region, and / or a fourth dielectric layer is provided between the piezoelectric region and the second dielectric region.

[0011] Optionally, the width of the piezoelectric region is greater than 5 times the distance between centers of adjacent first interdigital electrodes.

[0012] Optionally, the width of the piezoelectric layer is equal to the width of the bottom electrode.

[0013] Optionally, the top surface of the piezoelectric layer is higher than the top surface of the first dielectric zone, and the distance between the top surface of the piezoelectric layer and the top surface of the first dielectric zone is less than or equal to the thickness of the interdigital transducer; or, the top surface of the piezoelectric layer is lower than the top surface of the first dielectric zone, and the distance between the top surface of the piezoelectric layer and the top surface of the first dielectric zone is less than or equal to the thickness of the interdigital transducer.

[0014] Optionally, the supporting substrate includes a stacked supporting layer and a high acoustic velocity layer;

[0015] The supporting layer is made of a material that is easy to shape and process;

[0016] The material of the support layer includes any one of quartz, silicon, sapphire, spinel, and yttrium aluminum garnet;

[0017] 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 with different crystal forms and different cuts.

[0018] Optionally, the thickness of the high acoustic velocity layer is greater than or equal to 0.5 times the distance between centers of adjacent first interdigital electrodes.

[0019] Optionally, the support substrate is a combination of one or more of silicon carbide, diamond, diamond-like carbon, sapphire, aluminum nitride, boron nitride, boron carbide and silicon nitride with different crystal forms and different cut shapes.

[0020] Optionally, the material of the piezoelectric layer is one or more of lithium tantalate, lithium niobate, potassium niobate, lead zirconate titanate, or a combination of lead magnesium niobate-lead titanate;

[0021] The material of the interdigital transducer includes one or more combinations of copper, aluminum, gold, silver, tungsten, platinum, nickel, chromium, molybdenum, titanium, graphene, copper-aluminum alloy, and aluminum-silicon alloy;

[0022] The material of the bottom electrode includes 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;

[0023] The materials of the first dielectric region and the second dielectric region are single-layer materials or multi-layer materials, including one or a combination of silicon oxide, silicon nitride, aluminum nitride, aluminum oxide, zinc oxide, and silicon.

[0024] In another aspect, the present application discloses a method for preparing a surface acoustic wave resonator, comprising:

[0025] providing a supporting substrate;

[0026] A functional layer is formed on a supporting substrate; the functional layer includes a first dielectric region, a piezoelectric region, and a second dielectric region sequentially arranged along a first direction; the piezoelectric region includes a stacked bottom electrode and a piezoelectric layer; the bottom electrode is located on the supporting substrate;

[0027] An interdigital transducer is formed on the functional layer; the interdigital transducer includes a first bus bar, a first interdigital electrode connected to the first bus bar, a second bus bar, and a second interdigital electrode connected to the second bus bar; the first interdigital electrode and the second interdigital electrode are arranged alternately; the first direction is the length direction of the first interdigital electrode or the second interdigital electrode;

[0028] Among them, the width of the piezoelectric zone is less than or equal to the width of the projection area of ​​the aperture zone of the interdigital transducer; the projection area of ​​the aperture zone is the area where the aperture zone is projected on the functional layer; the aperture zone is the area where the first interdigital electrode and the second interdigital electrode in the interdigital transducer are intertwined; the target mode of the surface acoustic wave resonator is a high-order surface acoustic wave mode excited by the longitudinal electric field; the product of the distance between adjacent first interdigital electrodes and the frequency of the target mode is less than the sound velocity of the supporting substrate.

[0029] Optionally, forming a functional layer on a supporting substrate includes:

[0030] forming a piezoelectric region on a supporting substrate to obtain a first structure;

[0031] A dielectric material is deposited on the first structure, and excess dielectric material is removed to form a first dielectric region and a second dielectric region on the substrate, thereby obtaining a second structure.

[0032] Optionally, forming a piezoelectric region on a supporting substrate to obtain a first structure includes:

[0033] A conductive material layer and a piezoelectric material layer are obtained on a supporting substrate by sequentially depositing or bonding and stripping;

[0034] The piezoelectric material layer and the conductive material layer are patterned to form a piezoelectric region on the supporting substrate to obtain a first structure.

[0035] Optionally, forming a piezoelectric region on a supporting substrate to obtain a first structure includes:

[0036] Providing a piezoelectric substrate having a conductive material layer on its surface;

[0037] performing local ion implantation into a predetermined depth of the piezoelectric substrate;

[0038] bonding the conductive material layer to the supporting substrate to obtain a bonding structure;

[0039] The bonding structure is subjected to annealing and peeling treatment to obtain a first structure.

[0040] Optionally, the etching depth during the patterning process of the piezoelectric material layer and the conductive material layer is greater than or equal to the sum of the thicknesses of the piezoelectric material layer and the conductive material layer.

[0041] In another aspect, the present application discloses a filter comprising the above-mentioned surface acoustic wave resonator.

[0042] By adopting the above technical solution, the surface acoustic wave resonator provided by this application has the following beneficial effects:

[0043] The surface acoustic wave resonator includes a supporting substrate, a functional layer and an interdigital transducer arranged in sequence from bottom to top; the functional layer includes a first dielectric region, a piezoelectric region and a second dielectric region arranged in sequence along a first direction. By setting the width of the piezoelectric layer and the bottom electrode to be smaller than the width of the interdigital transducer, it is specifically set in the aperture region of the interdigital transducer, which can be smaller than or equal to the width of the aperture region. The aperture region is the area where two oppositely arranged interdigital electrodes in the interdigital transducer are staggered. The target mode of the surface acoustic wave resonator is a high-order surface acoustic wave mode excited by a longitudinal electric field; the product of the distance between adjacent first interdigital electrodes and the frequency of the target mode is smaller than the sound velocity of the supporting substrate, thereby avoiding parasitic body acoustic waves generated by the longitudinal electric field excitation, and is also beneficial to the suppression of transverse high-order modes. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0045] FIG1 is a cross-sectional view of a conventional acoustic wave resonator provided in an embodiment of the present application;

[0046] FIG2 is a cross-sectional view of a first surface acoustic wave resonator provided in an embodiment of the present application;

[0047] FIG3 is a top view of a first surface acoustic wave resonator provided in an embodiment of the present application;

[0048] FIG4 is a cross-sectional view of a second surface acoustic wave resonator provided in an embodiment of the present application;

[0049] FIG5 is a cross-sectional view of a surface acoustic wave resonator corresponding to Comparative Example 1 provided in an embodiment of the present application;

[0050] FIG6 is a top view of a surface acoustic wave resonator corresponding to Comparative Example 1 provided in an embodiment of the present application;

[0051] 7 is a cross-sectional view of a surface acoustic wave resonator corresponding to Comparative Example 2 provided in an embodiment of the present application;

[0052] FIG8 is a top view of a surface acoustic wave resonator corresponding to Comparative Example 2 provided in an embodiment of the present application;

[0053] FIG9 is a diagram of simulation results including Comparative Example 1 and Comparative Example 2 provided in an embodiment of the present application;

[0054] FIG10 is a vibration mode diagram near the anti-resonance frequency of Comparative Example 1 in FIG9 provided in an embodiment of the present application;

[0055] FIG11 is a vibration mode diagram near the anti-resonance frequency of Comparative Example 2 in FIG9 provided in an embodiment of the present application;

[0056] FIG12 is a cross-sectional view of a surface acoustic wave resonator corresponding to Comparative Example 3 provided in an embodiment of the present application;

[0057] FIG13 is a schematic diagram of simulation results including Comparative Example 2 and Comparative Example 3 provided in an embodiment of the present application;

[0058] FIG14 is a vibration mode diagram near the anti-resonance frequency of Comparative Example 3 in FIG13 provided in an embodiment of the present application;

[0059] FIG15 is a schematic diagram of simulation results of a comparative example 2 and the structure shown in FIG4 provided in an embodiment of the present application;

[0060] FIG16 is a comparison diagram of conductive curves corresponding to a comparative example 2 provided in an embodiment of the present application and the structure shown in FIG4 ;

[0061] FIG17 is a cross-sectional view of a third surface acoustic wave resonator provided in an embodiment of the present application;

[0062] FIG18 is a top view of the surface acoustic wave resonator corresponding to FIG17 provided in an embodiment of the present application;

[0063] FIG19 is a cross-sectional view of a fourth surface acoustic wave resonator provided in an embodiment of the present application;

[0064] FIG20 is a comparison diagram of simulation results corresponding to different alignment deviations between the center of the piezoelectric region and the center of the aperture region provided by an embodiment of the present application;

[0065] FIG21 is a cross-sectional view of a fifth surface acoustic wave resonator provided in an embodiment of the present application;

[0066] FIG22 is a cross-sectional view of a sixth surface acoustic wave resonator provided in an embodiment of the present application;

[0067] FIG23 is a cross-sectional view of a seventh surface acoustic wave resonator provided in an embodiment of the present application;

[0068] FIG24 is a cross-sectional view of an eighth surface acoustic wave resonator provided in an embodiment of the present application;

[0069] FIG25 is a cross-sectional view of a ninth surface acoustic wave resonator provided in an embodiment of the present application;

[0070] FIG26 is a cross-sectional view of a tenth surface acoustic wave resonator provided in an embodiment of the present application;

[0071] FIG27 is a top view of an eleventh surface acoustic wave resonator provided in an embodiment of the present application;

[0072] FIG28 is a top view of a twelfth surface acoustic wave resonator provided in an embodiment of the present application;

[0073] FIG29 is a top view of a thirteenth surface acoustic wave resonator provided in an embodiment of the present application;

[0074] FIG30 is a top view of a fourteenth surface acoustic wave resonator provided in an embodiment of the present application;

[0075] FIG31 is a top view of a fifteenth surface acoustic wave resonator provided in an embodiment of the present application;

[0076] FIG32 is a top view of a sixteenth surface acoustic wave resonator provided in an embodiment of the present application;

[0077] FIG33 is a top view of a seventeenth surface acoustic wave resonator provided in an embodiment of the present application;

[0078] FIG34 is a top view of an eighteenth surface acoustic wave resonator provided in an embodiment of the present application;

[0079] FIG35 is a top view of a nineteenth surface acoustic wave resonator provided in an embodiment of the present application;

[0080] FIG36 is a schematic diagram of a preparation process of a surface acoustic wave resonator provided in an embodiment of the present application;

[0081] FIG37 is a schematic structural diagram of a first structure provided in an embodiment of the present application;

[0082] 38 to 41 are schematic structural diagrams showing the process of forming a functional layer in a surface acoustic wave resonator provided by an embodiment of the present application;

[0083] FIG42 is a schematic structural diagram of a piezoelectric substrate provided in an embodiment of the present application;

[0084] Figure 43 is a structural schematic diagram of a structure after local ion implantation of the structure shown in Figure 42 provided in an embodiment of the present application.

[0085] The following is a supplementary explanation of the accompanying drawings: 1-support substrate; 101-support layer; 102-high acoustic velocity layer; 2-functional layer; 201-first dielectric region; 202-piezoelectric region; 2021-bottom electrode; 2022-piezoelectric layer; 203-second dielectric region; 3-interdigital transducer; 301-first bus bar; 302-second bus bar; 303-first interdigital electrode; 304-second interdigital electrode; 305-aperture region; 306-air gap region; 307-dummy electrode; 4-first dielectric layer; 5-second dielectric layer; 6-third dielectric layer; 7-fourth dielectric layer; 8-conductive material layer; 9-piezoelectric material layer; 10-first dislocation region; 11-second dislocation region; 12-piezoelectric substrate; 1201-damage layer. DETAILED DESCRIPTION

[0086] The following will be combined with the accompanying drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making any creative work are within the scope of protection of this application.

[0087] References to "one embodiment" or "embodiment" herein refer to specific features, structures, or characteristics that may be included in at least one implementation of the present application. Throughout the description of this application, it should be understood that the terms "upper," "lower," "top," and "bottom," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely for ease of description and simplification. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation, and are therefore not to be construed as limiting the present application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly specifying the number of the technical features indicated. Thus, a feature designated "first" or "second" may explicitly or implicitly include one or more of such features. Furthermore, the terms "first," "second," etc. are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential sequence. It should be understood that such terms are interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein.

[0088] When a numerical range is disclosed herein, the above range is considered to be continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be merged. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all subranges included therein. For example, a specified range from "1 to 10" should be considered to include any and all subranges between a minimum of 1 and a maximum of 10. Exemplary subranges 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.

[0089] Please refer to Figure 1, which shows a cross-sectional view of an existing acoustic wave resonator provided by an embodiment of the present application. It is a suspended piezoelectric film structure. However, there is an overlapping part between the bottom electrode and the piezoelectric film and the air gap of the interdigital transducer of the top electrode, which will form a parasitic mode of the body acoustic wave. Moreover, since the width of the piezoelectric film is greater than the width of the bottom electrode, there is a piezoelectric film in the area where the interdigital transducer exceeds the bottom electrode, which will generate a parasitic mode excited by the transverse electric field. In addition, the transverse high-order mode of the main mode will also affect the in-band flatness of the filter. Therefore, how to avoid the problems of body acoustic wave parasitics and transverse electric field excited parasitic modes with a simple process without affecting the main mode, and how to suppress the transverse high-order mode, is the key to achieving high-performance high-frequency and large-bandwidth filters.

[0090] Referring to FIG. 2 , the present application discloses a surface acoustic wave resonator, which includes, from bottom to top, a supporting substrate 1, a functional layer 2, and an interdigital transducer 3. The interdigital transducer 3 includes a first bus bar 301, a first interdigital electrode 303 connected to the first bus bar 301, a second bus bar 302, and a second interdigital electrode 304 connected to the second bus bar 302. The first interdigital electrodes 303 and the second interdigital electrodes 304 are arranged in an alternating manner. The functional layer 2 includes a first dielectric region 201, a piezoelectric region 202, and a second dielectric region 203 arranged in sequence along a first direction. The first direction is the length direction of the first interdigital electrode 303 or the second interdigital electrode 304. The piezoelectric region 202 includes a stacked bottom electrode 2021 and a piezoelectric layer 2022; the bottom electrode 2021 is located on the supporting substrate 1; the width of the piezoelectric region 202 is less than or equal to the width of the projection area of ​​the aperture region 305 of the IDT 3; the projection area of ​​the aperture region 305 is the area where the aperture region 305 is projected onto the functional layer 2; the aperture region 305 is the region where the first interdigital electrodes 303 and the second interdigital electrodes 304 of the IDT 3 intersect; the target mode of the surface acoustic wave resonator is a high-order surface acoustic wave mode excited by a longitudinal electric field; the product of the distance between adjacent first interdigital electrodes 303 and the frequency of the target mode is less than the acoustic velocity of the supporting substrate 1. This not only solves the parasitic bulk acoustic wave and photolithography alignment problems that exist in acoustic resonators excited by longitudinal electric fields, but also significantly reduces transverse high-order modes.

[0091] In this embodiment, the width of the piezoelectric region 202 can be in the direction of the length extension of the first interdigital electrode 303 and the second interdigital electrode 304. The aperture region 305 is the region indicated by the dotted line box in FIG3 . When there is no dummy electrode 307 , the air gap region 306 can be the region between the first bus bar 301 and the second bus bar 302 excluding the aperture region 305, that is, the region where the first interdigital electrode 303 and the second interdigital electrode 304 do not intersect. The number of the first interdigital electrode 303 and the second interdigital electrode 304 can be designed according to actual needs and can be 1, 2, 3, or the like. The width of the first interdigital electrode 303 and the length and width of the second interdigital electrode 304 can be designed according to actual needs and are not limited here.

[0092] In some possible examples, the target mode is one of a high-order Lamb wave, a high-order horizontal shear wave, and a high-order Rayleigh mode.

[0093] In some possible examples, the width of the piezoelectric region 202 is greater than five times the distance between the centers of adjacent first interdigital electrodes 303 .

[0094] In some possible examples, the width of the piezoelectric layer 2022 is equal to the width of the bottom electrode 2021 (see Figure 2). Of course, depending on the actual process conditions, the widths of the two may not be completely equal, and a smaller width error may also be acceptable, for example, the misalignment difference between the two in the width direction is ±0.5 microns.

[0095] In some possible examples, please refer to Figure 4, a first dielectric layer 4 is provided between the functional layer 2 and the supporting substrate 1; in other possible examples, a second dielectric layer 5 is provided between the functional layer 2 and the interdigital transducer 3; optionally, a first dielectric layer 4 may be provided between the functional layer 2 and the supporting substrate 1, and at the same time, a second dielectric layer 5 is provided between the functional layer 2 and the interdigital transducer 3.

[0096] In some possible examples, a third dielectric layer 6 is provided between the piezoelectric region 202 and the first dielectric region 201. In other possible examples, a fourth dielectric layer 7 is provided between the piezoelectric region 202 and the second dielectric region 203. Alternatively, the third dielectric layer 6 may be provided between the piezoelectric region 202 and the first dielectric region 201, and the fourth dielectric layer 7 may be provided between the piezoelectric region 202 and the second dielectric region 203.

[0097] In some possible examples, please continue to refer to Figure 2. The first dielectric area 201 can fill the entire area between the interdigital transducer 3 and the supporting substrate 1 on one side of the piezoelectric area 202, and the second dielectric area 203 can fill the entire area between the interdigital transducer 3 and the supporting substrate 1 on the other side of the piezoelectric area 202. As needed, the first dielectric area 201 can be filled in a local area between the interdigital transducer 3 and the supporting substrate 1 on one side of the piezoelectric area 202, and the second dielectric area 203 can be filled in a local area between the interdigital transducer 3 and the supporting substrate 1 on the other side of the piezoelectric area 202. At this time, the width of the first dielectric area 201 is smaller than the distance between one side of the piezoelectric area 202 and the adjacent side of the supporting substrate 1, and the width of the second dielectric area 203 is smaller than the distance between the other side of the piezoelectric side and the adjacent side of the supporting substrate 1. Optionally, the first dielectric area 201 and the second dielectric area 203 include at least an area of ​​±0.5 μm from the boundary of the aperture area 305 to ensure that there is no short circuit between the upper and lower electrodes.

[0098] In some possible examples, the support substrate 1 is a combination of one or more of silicon carbide, diamond, diamond-like carbon, sapphire, aluminum nitride, boron nitride, boron carbide and silicon nitride with different crystal forms and different cut shapes.

[0099] In some possible examples, the material of the piezoelectric layer 2022 is one or more of lithium tantalate, lithium niobate, potassium niobate, lead zirconate titanate, or a combination of lead magnesium niobate-lead titanate.

[0100] In some possible examples, the material of the IDT 3 includes one or more combinations of copper, aluminum, gold, silver, tungsten, platinum, nickel, chromium, molybdenum, titanium, graphene, copper-aluminum alloy, and aluminum-silicon alloy.

[0101] In some possible examples, the material of the bottom electrode 2021 includes 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.

[0102] In some possible examples, the materials of the first dielectric region 201 and the second dielectric region 203 are single-layer materials or multi-layer materials, including one or a combination of silicon oxide, silicon nitride, aluminum nitride, aluminum oxide, zinc oxide, and silicon.

[0103] Please refer to Figures 5 and 6, which are respectively a cross-sectional view and a top view of Comparative Example 1. Compared with Figure 4 of the present application, Comparative Example 1 differs in that the piezoelectric layer 2022 and the bottom electrode 2021 of Comparative Example 1 are both complete structures. Please refer to Figures 7 and 8, which are respectively a cross-sectional view and a top view of Comparative Example 2. Compared with Figure 4 of the present application, the piezoelectric layer 2022 of Comparative Example 1 is a complete structure, so that the bottom electrode 2021 of Comparative Example 2 is also only present in the area below the aperture region 305. Specifically, the material of the supporting substrate 1 is 4H-SiC, and the first dielectric region 201 and the second dielectric region 203 are The material of the bottom electrode 2021 is silicon oxide, and its thickness is the same as that of the bottom electrode 2021. The material of the bottom electrode 2021 is platinum, and its thickness is 50nm. The material of the piezoelectric layer 2022 is X-cut lithium niobate, and its thickness is 325nm. The material of the interdigital transducer 3 is aluminum / tungsten, and its thickness is 65 / 35nm. The period of the interdigital transducer 3 is 1.65μm (i.e., the distance between the centers of adjacent first interdigital electrodes 303 or the centers of adjacent second interdigital electrodes 304). The aperture length is 20 times the distance between the centers of adjacent first interdigital electrodes 303. The material of the first dielectric layer 4 is silicon oxide, and its thickness is 200nm. The bottom electrode 2021 of Comparative Example 2 completely overlaps with the aperture region 305, and the main mode is the SH1 mode (i.e., the first-order horizontal shear mode). By performing simulation tests on the structures of Comparative Examples 1 and 2, the simulation results shown in FIG9 are obtained. It can be seen that patterning the bottom electrode 2021 (i.e., designing it to exist only below the aperture region 305) suppresses the bulk acoustic wave mode excited by the busbar and air gap region 306, thereby significantly improving the admittance ratio of the resonator. FIG10 further shows that the busbar and the electrode in the air gap region 306, the piezoelectric layer 2022, and the bottom electrode 2021 form a "sandwich" structure, thereby exciting a bulk acoustic wave mode, specifically the thickness shear mode in this case. This mode cannot be constrained by the high acoustic velocity support substrate 1 and thus leaks into the substrate, becoming a source of energy leakage and causing a significant decrease in the device Q value. FIG11 shows that since the bottom electrode 2021 is not present below the busbar and air gap region 306, no longitudinal electric field can be formed, and thus no bulk acoustic wave mode can be excited. This results in only the main mode vibration existing in the aperture region 305, and no energy leaks into the substrate. Comparative Examples 1 and 2 above illustrate that patterning the bottom electrode 2021 can effectively suppress the bulk acoustic wave mode excited by the bus bar and the air gap region 306, so that only the main mode vibration exists in the aperture region 305, and no energy leaks to the substrate.

[0104] Please refer to Figure 12, which shows the cross-sectional views corresponding to Comparative Example 3. Compared with Comparative Example 2, the difference between Comparative Example 3 and Comparative Example 2 is that the bottom electrode 2021 of Comparative Example 3 is misaligned with the aperture region 305, specifically including the first misalignment region 10 and the second misalignment region 11. The width of the first misalignment region 10 and the second misalignment region 11 is W1, and W1 is 2μm. Please refer to Figure 13, which shows a schematic diagram of the simulation results of Comparative Example 2 and Comparative Example 3 provided in the embodiment of the present application. It can be seen that when the bottom electrode 2021 does not completely overlap with the aperture region 305, even if the alignment error is only 2μm, the admittance ratio of the resonator will drop significantly. This is because the second misalignment region 11 excites the bulk acoustic wave mode, while the first misalignment region 10 will excite other parasitic modes due to the lateral electric field. It can be further seen from Figure 14 that the second misalignment region 11 excites the bulk acoustic wave mode and causes energy to leak to the substrate. This shows that, in the case of patterning only the bottom electrode 2021 , if there is a misalignment between the bottom electrode 2021 and the aperture region 305 , even if the misalignment range is very small, a parasitic mode will be generated, causing energy leakage to the substrate.

[0105] Furthermore, by conducting a simulation test on the structure shown in FIG4 provided in the embodiment of the present application, a simulation result as shown in FIG15 can be obtained. By comparing the simulation results of the structure shown in FIG4 (i.e., both the piezoelectric layer 2022 and the bottom electrode 2021 are patterned) and the comparative example 2 (i.e., only the bottom electrode 2021 is patterned), it can be seen that the frequency response gap between the two is very small. However, referring to FIG16, which shows a comparison of the conductive curves corresponding to the structures shown in comparative example 2 and FIG4, when only the bottom electrode 2021 is patterned, there is a strong transverse high-order mode between the resonant frequency and the anti-resonant frequency of the resonator. After the piezoelectric layer 2022 is patterned, the transverse high-order mode is significantly weakened. It can be seen that the use of a patterned piezoelectric layer 2022 helps to suppress the transverse high-order mode.

[0106] In some possible examples, please refer to Figures 17 and 18. The width of the piezoelectric region 202 is smaller than the width of the aperture region 305, that is, there is a width misalignment between the piezoelectric region 202 and the aperture region 305, but the center of the piezoelectric region 202 and the center of the aperture region 305 are aligned. Please refer to Figure 19. There is an alignment deviation between the center of the piezoelectric region 202 and the center of the aperture region 305. Specifically, the deviation may be 2μm and 5μm. By performing simulation tests on the structures shown in Figures 18 and 19, a simulation result as shown in Figure 20 can be obtained. It can be seen from Figure 20 that the difference in the response frequencies of the three is very small. From this, it can be seen that the resonator structure provided in the embodiment of the present application has very low alignment accuracy requirements when the interdigital transducer 3 is formed by photolithography.

[0107] In some other possible examples, the width of the piezoelectric region 202 is smaller than the width of the aperture region 305 , and no first dielectric layer 4 is provided between the functional layer 2 and the supporting substrate 1 , that is, the structure shown in FIG. 21 .

[0108] In other possible examples, referring to FIG. 22 , support substrate 1 includes a stacked support layer 101 and a high-acoustic-velocity layer 102. Support layer 101 is made of a material that is easily formed and processed. The material of support layer 101 includes any one of quartz, silicon, sapphire, spinel, and yttrium aluminum garnet. The material of high-acoustic-velocity layer 102 includes any one of silicon carbide, diamond, diamond-like carbon, aluminum oxide, aluminum nitride, boron nitride, boron carbide, and silicon nitride, with different crystal forms and cuts. In some possible examples, the thickness of high-acoustic-velocity layer 102 is greater than or equal to 0.5 times the distance between the centers of adjacent first interdigital electrodes 303.

[0109] In other possible examples, the top surface of the piezoelectric layer 2022 is higher than the top surface of the first dielectric zone 201, and the distance between the top surface of the piezoelectric layer 2022 and the top surface of the first dielectric zone 201 is less than or equal to the thickness of the interdigital transducer 3, that is, the structure shown in Figure 23. Optionally, the width of the piezoelectric zone 202 is less than or equal to the width of the aperture zone 305.

[0110] In other possible examples, referring to FIG24 , the top surface of the piezoelectric layer 2022 is lower than the top surface of the first dielectric region 201, and the distance between the top surface of the piezoelectric layer 2022 and the top surface of the first dielectric region 201 is less than or equal to the thickness of the interdigital transducer 3. Optionally, the width of the piezoelectric region 202 is less than or equal to the width of the aperture region 305.

[0111] In other possible examples, please refer to Figure 25, a third dielectric layer 6 is provided between the piezoelectric region 202 and the first dielectric region 201, and a fourth dielectric layer 7 is provided between the piezoelectric region 202 and the second dielectric region 203. Optionally, the width of the piezoelectric region 202 is less than or equal to the width of the aperture region 305.

[0112] In other possible examples, please refer to Figure 26, a first dielectric layer 4 is provided between the functional layer 2 and the supporting substrate 1, and a second dielectric layer 5 is provided between the functional layer 2 and the interdigital transducer 3. Optionally, the width of the piezoelectric region 202 is less than or equal to the width of the aperture region 305.

[0113] In other possible examples, referring to FIG27 , the interdigital transducer 3 further includes dummy electrodes 307. Corresponding dummy electrodes 307 may be provided on opposite sides of the first interdigital electrode 303 and the second interdigital electrode 304, thereby including at least two dummy electrodes 307. Alternatively, the number and position of the dummy electrodes 307 may be set according to actual needs, without limitation. There is no piezoelectric layer 2022 below the area where the dummy electrodes 307 are located. Alternatively, referring to FIG28 , compared to the structure shown in FIG27 , the aperture region 305 may be designed to be larger than the width of the piezoelectric region 202. Alternatively, referring to FIG29 , the boundary of the piezoelectric layer 2022 and the aperture region 305 are both polygonal. Alternatively, referring to FIG30 , the boundary of the piezoelectric layer 2022 and the aperture region 305 are both polygonal, and the width of the aperture region 305 is greater than the width of the piezoelectric layer 2022. Optionally, referring to FIG31 , the boundary of the piezoelectric layer 2022 and the aperture region 305 are both polygonal, the width of the aperture region 305 is greater than the width of the piezoelectric layer 2022, and the aperture region 305 is rectangular. Optionally, referring to FIG32 , the difference from the structure shown in FIG30 is that the boundary of the piezoelectric layer 2022 is rectangular. Optionally, referring to FIG33 , the difference from the structure shown in FIG4 is that the width of the aperture region 305 is greater than the width of the piezoelectric layer 2022, and the edge of the piezoelectric layer 2022 is serrated. Optionally, referring to FIG34 , the difference from the structure shown in FIG31 is that the boundary of the piezoelectric layer 2022 is a parallelogram. Optionally, referring to FIG35 , the difference from the structure shown in FIG34 is that the aperture region 305 is also a parallelogram.

[0114] It is understandable that the surface acoustic wave resonator provided in this application does not limit the shape and position of the piezoelectric layer 2022 and the aperture region 305, as long as the width of the piezoelectric region 202 is less than or equal to the width of the aperture region 305, and does not limit the position and number of dielectric layers.

[0115] Referring to FIG. 36 , an embodiment of the present application provides a method for preparing a surface acoustic wave resonator, which includes:

[0116] S3601: Provide a supporting substrate 1.

[0117] In this embodiment, the supporting substrate 1 may be a single-layer structure or a multi-layer structure, as described above for details.

[0118] S3603: forming a functional layer 2 on the supporting substrate 1; the functional layer 2 includes a first dielectric region 201, a piezoelectric region 202, and a second dielectric region 203 arranged in sequence along a first direction; the piezoelectric region 202 includes a stacked bottom electrode 2021 and a piezoelectric layer 2022; the bottom electrode 2021 is located on the supporting substrate 1.

[0119] In some possible examples, the specific implementation of S3603 may include: forming a piezoelectric region 202 on a supporting substrate 1 to obtain a first structure (i.e., a structure as shown in FIG37 ); depositing a dielectric material on the first structure to obtain a structure as shown in FIG38 , and subsequently removing the raised dielectric material by etching or other methods (such as grinding), which are not limited here, to obtain a structure as shown in FIG39 , and subsequently grinding or polishing the surface of the structure in FIG39 to remove excess dielectric material to form a first dielectric region 201 and a second dielectric region 203 on the substrate to obtain a second structure (i.e., a structure as shown in FIG40 ).

[0120] In some possible examples, a piezoelectric region 202 is formed on a supporting substrate 1 to obtain a first structure, including: obtaining a conductive material layer 8 and a piezoelectric material layer 9 on the supporting substrate 1 in sequence by deposition or bonding and peeling, and a structure as shown in Figure 41 can be obtained; and the piezoelectric material layer 9 and the conductive material layer 8 are patterned to form a piezoelectric region 202 on the supporting substrate 1 to obtain the first structure.

[0121] In other possible examples, forming the piezoelectric region 202 on the support substrate 1 to obtain the first structure includes: providing a piezoelectric substrate 12 having a conductive material layer 8 on its surface (see FIG42 ); performing localized ion implantation into a predetermined depth of the piezoelectric substrate 12 to form a damaged layer 1201 at the predetermined depth of the piezoelectric substrate 12 , thereby obtaining the structure shown in FIG43 ; bonding the conductive material layer 8 to the support substrate 1 to obtain a bonded structure; and performing an annealing and stripping process on the bonded structure to obtain the first structure. Optionally, the ion implantation surface may be the surface of the conductive material layer 8.

[0122] In the embodiment of the present application, the patterned piezoelectric layer 2022 and the bottom electrode 2021 can be formed by deposition or bonding stripping, as well as graphical methods, or by ion implantation and annealing stripping.

[0123] In some possible examples, the etching depth during the patterning process of the piezoelectric material layer 9 and the conductive material layer 8 is equal to the sum of the thicknesses of the piezoelectric material layer 9 and the conductive material layer 8, thereby obtaining the structure shown in Figure 2. In some possible examples, the etching depth during the patterning process of the piezoelectric material layer 9 and the conductive material layer 8 is greater than the sum of the thicknesses of the piezoelectric material layer 9 and the conductive material layer 8, thereby making the support substrate 1 a convex structure.

[0124] S3605: forming an IDT 3 on the functional layer 2; the IDT 3 comprises a first bus bar 301, a first interdigital electrode 303 connected to the first bus bar 301, a second bus bar 302 and a second interdigital electrode 304 connected to the second bus bar 302; the first interdigital electrodes 303 and the second interdigital electrodes 304 are arranged alternately; the first direction is the length direction of the first interdigital electrode 303 or the second interdigital electrode 304; wherein the width of the piezoelectric region 202 is less than or equal to the width of the projection area of ​​the aperture region 305 of the IDT 3; the projection area of ​​the aperture region 305 is the area where the aperture region 305 is projected on the functional layer 2; the aperture region 305 is the area where the first interdigital electrode 303 and the second interdigital electrode 304 in the IDT 3 are projected. There are staggered regions; the target mode of the surface acoustic wave resonator is a high-order surface acoustic wave mode excited by the longitudinal electric field; the product of the distance between adjacent first interdigitated electrodes 303 and the frequency of the target mode is less than the sound velocity of the supporting substrate 1.

[0125] The structure shown in FIG2 can be obtained by the above preparation method. The preparation process of other optional surface acoustic wave resonator structures includes the process described above. Of course, due to the differences in the surface acoustic wave resonator structures, the preparation process will also be adaptively adjusted.

[0126] The preparation method of the surface acoustic wave resonator provided in the embodiment of the present application utilizes a high-order surface acoustic wave mode excited by a longitudinal electric field as a target mode, and uses a high-acoustic-velocity supporting substrate 1 to constrain the target mode to the substrate surface. The structure is simple, stable, and has good heat dissipation. The unnecessary piezoelectric region 202 is etched away to avoid the parasitic presence of the bulk acoustic wave mode. The patterning of the piezoelectric layer 2022 and the bottom electrode 2021 is completed at the same time, ensuring that the bottom electrode 2021 exists only in the area where the target mode vibrates. This method avoids the alignment deviation problem that is prone to occur when patterning the piezoelectric film and the suspended bottom electrode 2021 in steps, and also avoids the problem of photolithography alignment error. The patterned piezoelectric film and the filling of the dielectric material also provide new degrees of freedom for the design of the resonator, which is conducive to the suppression of lateral high-order modes.

[0127] The embodiment of the present application provides a filter, which includes the above-mentioned surface acoustic wave resonator. From the above description, it can be seen that since the surface acoustic wave resonator has a patterned piezoelectric layer and a bottom electrode, the piezoelectric area does not exceed the aperture area of ​​the interdigital transducer, avoiding the formation of a "sandwich" structure of the upper electrode, the piezoelectric film and the lower electrode in the area outside the aperture area, thereby avoiding the excitation of the bulk acoustic wave mode and the problems of stray response and bulk acoustic wave energy leakage caused by it, and greatly reducing the requirements for alignment accuracy when forming the top interdigital transducer. The shape of the piezoelectric layer can be selected as needed, and the appropriate dielectric material can be used to fill the etched area, which is also beneficial to the suppression of lateral high-order modes.

[0128] The above description is merely an optional embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A surface acoustic wave resonator, characterized in that: It includes a supporting substrate, a functional layer and an interdigital transducer arranged in sequence from bottom to top; The interdigital transducer comprises a first bus bar, a first interdigital electrode connected to the first bus bar, a second bus bar, and a second interdigital electrode connected to the second bus bar; the first interdigital electrode and the second interdigital electrode are arranged alternately; The functional layer includes a first dielectric region, a piezoelectric region, and a second dielectric region arranged in sequence along a first direction; the first direction is the length direction of the first interdigital electrode or the second interdigital electrode; the piezoelectric region includes a stacked bottom electrode and a piezoelectric layer; the bottom electrode is located on the supporting substrate; Among them, the width of the piezoelectric zone is less than or equal to the width of the projection area of ​​the aperture zone of the interdigital transducer; the projection area of ​​the aperture zone is the area where the aperture zone is projected on the functional layer; the aperture zone is the area where the first interdigital electrodes and the second interdigital electrodes in the interdigital transducer are intertwined; the target mode of the surface acoustic wave resonator is a high-order surface acoustic wave mode excited by the longitudinal electric field; the product of the distance between adjacent first interdigital electrodes and the frequency of the target mode is less than the sound velocity of the supporting substrate.

2. The surface acoustic wave resonator according to claim 1, characterized in that: A first dielectric layer is provided between the functional layer and the supporting substrate, and / or a second dielectric layer is provided between the functional layer and the interdigital transducer.

3. The surface acoustic wave resonator according to claim 1, characterized in that: A third dielectric layer is provided between the piezoelectric region and the first dielectric region, and / or a fourth dielectric layer is provided between the piezoelectric region and the second dielectric region.

4. The surface acoustic wave resonator according to claim 1, characterized in that: The width of the piezoelectric region is greater than 5 times the distance between centers of adjacent first interdigital electrodes.

5. The surface acoustic wave resonator according to claim 1, characterized in that: The width of the piezoelectric layer is equal to the width of the bottom electrode.

6. The surface acoustic wave resonator according to claim 1, characterized in that: The top surface of the piezoelectric layer is higher than the top surface of the first dielectric zone, and the distance between the top surface of the piezoelectric layer and the top surface of the first dielectric zone is less than or equal to the thickness of the interdigital transducer; or, the top surface of the piezoelectric layer is lower than the top surface of the first dielectric zone, and the distance between the top surface of the piezoelectric layer and the top surface of the first dielectric zone is less than or equal to the thickness of the interdigital transducer.

7. The surface acoustic wave resonator according to claim 1, characterized in that: The support substrate comprises a stacked support layer and a high acoustic velocity layer; The support layer is made of a material that is easy to shape and process; The material of the support layer includes any one of quartz, silicon, sapphire, spinel, and yttrium aluminum garnet; 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 in different crystal forms and different cuts.

8. The surface acoustic wave resonator according to claim 7, characterized in that: The thickness of the high acoustic velocity layer is greater than or equal to 0.5 times the distance between centers of adjacent first interdigital electrodes.

9. The surface acoustic wave resonator according to claim 1, characterized in that: The support substrate is a combination of one or more of silicon carbide, diamond, diamond-like carbon, sapphire, aluminum nitride, boron nitride, boron carbide and silicon nitride of different crystal forms and different cut shapes.

10. The surface acoustic wave resonator according to claim 1, characterized in that: The material of the piezoelectric layer is one or more of lithium tantalate, lithium niobate, potassium niobate, lead zirconate titanate or lead magnesium niobate-lead titanate; The material of the interdigital transducer includes one or more combinations of copper, aluminum, gold, silver, tungsten, platinum, nickel, chromium, molybdenum, titanium, graphene, copper-aluminum alloy, and aluminum-silicon alloy; The material of the bottom electrode includes 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; The materials of the first dielectric region and the second dielectric region are single-layer materials or multi-layer materials, including one or a combination of multiple materials selected from silicon oxide, silicon nitride, aluminum nitride, aluminum oxide, zinc oxide, and silicon.

11. A method for preparing a surface acoustic wave resonator, characterized in that: include: providing a supporting substrate; The functional layer is formed on the supporting substrate; the functional layer comprises a first dielectric region, a piezoelectric region and a second dielectric region arranged in sequence along a first direction; the piezoelectric region comprises a stacked bottom electrode and a piezoelectric layer; the bottom electrode is located on the supporting substrate; The IDT is formed on the functional layer; the IDT comprises a first bus bar, a first interdigital electrode connected to the first bus bar, a second bus bar, and a second interdigital electrode connected to the second bus bar; the first interdigital electrodes and the second interdigital electrodes are arranged alternately; the first direction is the length direction of the first interdigital electrode or the second interdigital electrode; Wherein, the width of the piezoelectric region is less than or equal to the width of the projection area of ​​the aperture region of the interdigital transducer; the projection area of ​​the aperture region is the area where the aperture region is projected on the functional layer; The aperture region is the area where the first interdigital electrode and the second interdigital electrode in the interdigital transducer are interlaced; the target mode of the surface acoustic wave resonator is a high-order surface acoustic wave mode excited by a longitudinal electric field; the product of the distance between adjacent first interdigital electrodes and the frequency of the target mode is less than the sound velocity of the supporting substrate.

12. The preparation method according to claim 11, characterized in that: The forming of the functional layer on the supporting substrate comprises: forming the piezoelectric region on the supporting substrate to obtain a first structure; A dielectric material is deposited on the first structure, and excess dielectric material is removed to form the first dielectric region and the second dielectric region on the substrate to obtain a second structure.

13. The preparation method according to claim 12, characterized in that: The step of forming the piezoelectric region on the supporting substrate to obtain a first structure comprises: On the supporting substrate, a conductive material layer and a piezoelectric material layer are obtained in sequence by deposition or bonding and stripping; The piezoelectric material layer and the conductive material layer are patterned to form the piezoelectric region on the supporting substrate to obtain the first structure.

14. The preparation method according to claim 12, characterized in that: The step of forming the piezoelectric region on the supporting substrate to obtain a first structure comprises: Providing a piezoelectric substrate having a conductive material layer on its surface; Performing local ion implantation into a preset depth of the piezoelectric substrate; Bonding the conductive material layer to the support substrate to obtain a bonding structure; The bonding structure is subjected to annealing and peeling treatment to obtain the first structure.

15. The preparation method according to claim 11, characterized in that: The etching depth during the patterning process of the piezoelectric material layer and the conductive material layer is greater than or equal to the sum of the thicknesses of the piezoelectric material layer and the conductive material layer.

16. A filter, characterized in that: The invention comprises a surface acoustic wave resonator as claimed in any one of claims 1 to 10.

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