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

Abstract

The present invention relates to the field of microelectronic devices, and in particular to a surface acoustic wave resonator and a preparation method thereof, and a filter. The surface acoustic wave resonator comprises a supporting substrate, a functional layer and an interdigital transducer arranged in sequence from bottom to top; the functional layer comprises a first dielectric region, a piezoelectric region and a second dielectric region arranged in sequence along a first direction; by arranging the piezoelectric layer and the bottom electrode in the aperture region of the interdigital transducer, the width of the aperture region can be less than or equal to the width of the aperture region, the aperture region is the region where two oppositely arranged interdigital electrodes 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, thereby being able to avoid parasitic body acoustic waves generated by the longitudinal electric field excitation, and also being conducive to the suppression of transverse high-order modes.

Description

Technical Field

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

[0002] The modern communication industry has increasingly higher requirements for signal quality and the competition for communication spectrum resources is becoming more and more intense. Low loss, wide bandwidth, tunability and temperature stability have become the common goals pursued by the communication industry. Among them, surface acoustic wave (SAW) resonators based on piezoelectric heterogeneous substrates have great advantages in Q value, volume, temperature stability and power capacity.

[0003] However, the commonly used surface acoustic wave modes 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 meet the requirements of the N77 band in the 5G frequency band. The surface acoustic wave mode excited by the longitudinal electric field shows great potential in both sound speed and electromechanical coupling coefficient. However, the resonator in the prior art is usually Figure 1 The structure shown in the figure uses a plate wave mode or a quasi-bulk acoustic wave mode with a very high sound velocity, so the leakage of acoustic wave energy can only be avoided by leaving the film suspended in the air. The piezoelectric film is suspended by back etching, and finally a 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 scheme 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. Summary of the invention

[0004] 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;

[0005] 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;

[0006] 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 a supporting substrate;

[0007] Among them, the width of the piezoelectric zone is less than or equal to the width of the projection zone of the aperture zone of the interdigital transducer; the projection zone 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 staggered; 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.

[0008] 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.

[0009] 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.

[0010] Optionally, the width of the piezoelectric region is greater than 5 times the distance between centers of adjacent first interdigital electrodes.

[0011] Optionally, the width of the piezoelectric layer is equal to the width of the bottom electrode.

[0012] 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.

[0013] Optionally, the support substrate includes a stacked support layer and a high acoustic velocity layer;

[0014] The support layer is made of a material that is easy to shape and process;

[0015] The material of the support layer includes any one of quartz, silicon, sapphire, spinel, and yttrium aluminum garnet;

[0016] 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.

[0017] 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.

[0018] 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 of different crystal forms and different cut shapes.

[0019] Optionally, the material of the piezoelectric layer is a combination of one or more of lithium tantalate, lithium niobate, potassium niobate, lead zirconate titanate or lead magnesium niobate-lead titanate;

[0020] 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;

[0021] 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;

[0022] 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 types of silicon oxide, silicon nitride, aluminum nitride, aluminum oxide, zinc oxide, and silicon.

[0023] In another aspect, the present application discloses a method for preparing a surface acoustic wave resonator, comprising:

[0024] providing a supporting substrate;

[0025] A functional layer is formed on a 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;

[0026] An interdigital transducer is formed on the functional layer; 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 first direction is the length direction of the first interdigital electrode or the second interdigital electrode;

[0027] Among them, the width of the piezoelectric zone is less than or equal to the width of the projection zone of the aperture zone of the interdigital transducer; the projection zone 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 staggered; 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.

[0028] Optionally, forming a functional layer on a supporting substrate includes:

[0029] forming a piezoelectric region on a supporting substrate to obtain a first structure;

[0030] 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.

[0031] Optionally, a piezoelectric region is formed on a supporting substrate to obtain a first structure, comprising:

[0032] A conductive material layer and a piezoelectric material layer are obtained on a supporting substrate by deposition or bonding and stripping in sequence;

[0033] 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.

[0034] Optionally, a piezoelectric region is formed on a supporting substrate to obtain a first structure, comprising:

[0035] Providing a piezoelectric substrate having a conductive material layer on its surface;

[0036] Performing local ion implantation into a predetermined depth of the piezoelectric substrate;

[0037] Bonding the conductive material layer to the supporting substrate to obtain a bonding structure;

[0038] The bonding structure is subjected to annealing and peeling treatment to obtain a first structure.

[0039] 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.

[0040] In another aspect, the present application discloses a filter, which includes the above-mentioned surface acoustic wave resonator.

[0041] By adopting the above technical solution, the surface acoustic wave resonator provided by the present application has the following beneficial effects:

[0042] 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 area, a piezoelectric area and a second dielectric area arranged in sequence along a first direction, and by setting the width of the piezoelectric layer and the bottom electrode to be smaller than the width of the interdigital transducer, the width of the interdigital transducer specifically arranged in the aperture area of ​​the interdigital transducer can be smaller than or equal to the width of the aperture area, the aperture area is the area where two oppositely arranged interdigital electrodes in the interdigital transducer are staggered, and 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

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. 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 paying any creative work.

[0044] Figure 1 is a cross-sectional view of an existing acoustic wave resonator provided in an embodiment of the present application;

[0045] Figure 2 is a cross-sectional view of a first surface acoustic wave resonator provided in an embodiment of the present application;

[0046] Figure 3 is a top view of a first surface acoustic wave resonator provided in an embodiment of the present application;

[0047] Figure 4 is a cross-sectional view of a second surface acoustic wave resonator provided in an embodiment of the present application;

[0048] Figure 5 is a cross-sectional view of a surface acoustic wave resonator corresponding to Comparative Example 1 provided in an embodiment of the present application;

[0049] Figure 6 is a top view of a surface acoustic wave resonator corresponding to comparative example 1 provided in an embodiment of the present application;

[0050] Figure 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;

[0051] Figure 8 is a top view of a surface acoustic wave resonator corresponding to comparative example 2 provided in an embodiment of the present application;

[0052] Fig. 9 It is a simulation result diagram including comparative example 1 and comparative example 2 provided in an embodiment of the present application;

[0053] Fig.10 The embodiment of this application provides Fig. 9 The vibration mode diagram near the anti-resonance frequency of comparative example 1;

[0054] Fig.11 The embodiment of this application provides Fig. 9 The vibration mode diagram near the anti-resonance frequency of comparative example 2;

[0055] Fig.12 is a cross-sectional view of a surface acoustic wave resonator corresponding to Comparative Example 3 provided in an embodiment of the present application;

[0056] Fig.13 It is a schematic diagram of simulation results including comparative example 2 and comparative example 3 provided in an embodiment of the present application;

[0057] Fig.14 The embodiment of this application provides Fig.13 The vibration mode diagram near the anti-resonance frequency of comparative example 3;

[0058] Fig.15This is a comparative example 2 and Figure 4 Schematic diagram of simulation results of the structure shown;

[0059] Fig.16 This is a comparative example 2 and Figure 4 Comparison of the conductivity curves corresponding to the structures shown;

[0060] Fig.17 is a cross-sectional view of a third surface acoustic wave resonator provided in an embodiment of the present application;

[0061] Fig.18 The embodiment of this application provides Fig.17 a top view of the corresponding surface acoustic wave resonator;

[0062] Fig.19 is a cross-sectional view of a fourth surface acoustic wave resonator provided in an embodiment of the present application;

[0063] Fig. 20 It is a comparison diagram of simulation results corresponding to different alignment deviations between the center of a piezoelectric region and the center of an aperture region provided in an embodiment of the present application;

[0064] Fig.21 is a cross-sectional view of a fifth surface acoustic wave resonator provided in an embodiment of the present application;

[0065] Fig. 22 is a cross-sectional view of a sixth surface acoustic wave resonator provided in an embodiment of the present application;

[0066] Fig.23 is a cross-sectional view of a seventh surface acoustic wave resonator provided in an embodiment of the present application;

[0067] Fig.24 is a cross-sectional view of an eighth surface acoustic wave resonator provided in an embodiment of the present application;

[0068] Fig.25 is a cross-sectional view of a ninth surface acoustic wave resonator provided in an embodiment of the present application;

[0069] Fig.26 is a cross-sectional view of a tenth surface acoustic wave resonator provided in an embodiment of the present application;

[0070] Fig. 27 is a top view of an eleventh surface acoustic wave resonator provided in an embodiment of the present application;

[0071] Fig.28 is a top view of a twelfth surface acoustic wave resonator provided in an embodiment of the present application;

[0072] Fig.29 is a top view of a thirteenth surface acoustic wave resonator provided in an embodiment of the present application;

[0073] Fig.30 is a top view of a fourteenth surface acoustic wave resonator provided in an embodiment of the present application;

[0074] Fig.31 is a top view of a fifteenth surface acoustic wave resonator provided in an embodiment of the present application;

[0075] Fig.32 is a top view of a sixteenth surface acoustic wave resonator provided in an embodiment of the present application;

[0076] Fig.33 is a top view of a seventeenth surface acoustic wave resonator provided in an embodiment of the present application;

[0077] Fig.34 is a top view of an eighteenth surface acoustic wave resonator provided by an embodiment of the present application;

[0078] Fig.35 is a top view of a nineteenth surface acoustic wave resonator provided in an embodiment of the present application;

[0079] Fig.36 It is a schematic diagram of a preparation process of a surface acoustic wave resonator provided in an embodiment of the present application;

[0080] Fig.37 is a structural schematic diagram of a first structure provided in an embodiment of the present application;

[0081] Figures 38 to 41 is a structural schematic diagram of a process of forming a functional layer in a surface acoustic wave resonator provided in an embodiment of the present application;

[0082] Fig.42 is a schematic structural diagram of a piezoelectric substrate provided in an embodiment of the present application;

[0083] Fig.43 This is a method provided by the embodiment of the present application. Fig.42 Schematic diagram of the structure after local ion implantation.

[0084] The following is a supplementary description of the attached drawings:

[0085] 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-pseudo-finger 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 technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0087] The term "one embodiment" or "embodiment" as used herein 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 the terms "upper", "lower", "top", "bottom", etc. is based on the orientation or positional relationship shown in the accompanying drawings, which 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 cannot be understood as a limitation of the present application. In addition, the terms "first" and "second" are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may include one or more of the features explicitly or implicitly. Moreover, the terms "first", "second", etc. are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described here can be implemented in an order other than those illustrated or described here.

[0088] When a numerical range is disclosed herein, the above range is deemed to be continuous and includes the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, 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 merged. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all sub-ranges included therein. For example, a specified range from "1 to 10" should be deemed to include any and all sub-ranges between a minimum of 1 and a maximum of 10. Exemplary sub-ranges of ranges 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, etc.

[0089] See also 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 bulk 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 produce 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 bulk acoustic wave parasitics and transverse electric field excited parasitic modes and suppress transverse high-order modes with a simple process without affecting the main mode is the key to realizing a high-performance high-frequency and large-bandwidth filter.

[0090] See also Figure 2The present application discloses a surface acoustic wave resonator, which includes a supporting substrate 1, a functional layer 2 and an interdigital transducer 3 arranged in sequence from bottom to top; 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 alternately; 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; wherein the width of the piezoelectric region 202 is less than or equal to the width of the projection region of the aperture region 305 of the interdigital transducer 3; the projection region of the aperture region 305 is the region where the aperture region 305 is projected on the functional layer 2; the aperture region 305 is the region where the first interdigital electrode 303 and the second interdigital electrode 304 in the interdigital transducer 3 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 303 and the frequency of the target mode is less than the sound velocity of the supporting substrate 1. In this way, not only can the parasitic body acoustic wave problem and the photolithography alignment problem existing in the acoustic resonator excited by the longitudinal electric field be solved, but the lateral high-order mode is also greatly weakened.

[0091] In this embodiment, the width of the piezoelectric region 202 may be the length extension direction of the first interdigital electrode 303 and the second interdigital electrode 304. Figure 3 In the area shown in the dotted box, when there is no fake finger electrode 307, the air gap area 306 can be the area between the first bus bar 301 and the second bus bar 302 except the aperture area 305, that is, the area where the first interdigitated electrode 303 and the second interdigitated electrode 304 are not interlaced. The number of the first interdigitated electrode 303 and the second interdigitated electrode 304 can be designed according to actual needs, and can be 1, 2, 3, etc., and the width of the first interdigitated electrode 303 and the length and width of the second interdigitated electrode 304 can be designed according to needs, and there is no limitation 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 5 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, according to the actual process conditions, the widths of the two may not be completely equal, and a small width error may also be acceptable, for example, the misalignment difference between the two in the width direction is ±0.5 microns.

[0095] For some possible examples, see Figure 4 , a first dielectric layer 4 is provided between the functional layer 2 and the supporting substrate 1; in some 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 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; optionally, 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.

[0097] For some possible examples, see Figure 2 The first dielectric region 201 can fill the entire area between the interdigital transducer 3 and the supporting substrate 1 on one side of the piezoelectric region 202, and the second dielectric region 203 can fill the entire area between the interdigital transducer 3 and the supporting substrate 1 on the other side of the piezoelectric region 202; as needed, the first dielectric region 201 can fill the local area between the interdigital transducer 3 and the supporting substrate 1 on one side of the piezoelectric region 202, and the second dielectric region 203 can fill the local area between the interdigital transducer 3 and the supporting substrate 1 on the other side of the piezoelectric region 202. At this time, the width of the first dielectric region 201 is smaller than the distance between one side of the piezoelectric region 202 and the adjacent side of the supporting substrate 1, and the width of the second dielectric region 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 region 201 and the second dielectric region 203 at least include an area of ​​±0.5 μm of the boundary of the aperture region 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 of different crystal forms and different cuts.

[0099] In some possible examples, the material of the piezoelectric layer 2022 is a combination of one or more of lithium tantalate, lithium niobate, potassium niobate, lead zirconate titanate, or 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] See also Figure 5 and 6 , which respectively show the cross-sectional view and top view of comparative example 1, which is different from the present application Figure 4 The difference is that the piezoelectric layer 2022 and the bottom electrode 2021 of the comparative example 1 are both complete structures, see Figure 7 and 8 , which respectively show the cross-sectional view and top view of comparative example 2, which are different from the Figure 4 In comparison, the difference is that the piezoelectric layer 2022 of comparative example 1 is a complete structure, so that the bottom electrode 2021 of comparative example 2 also only exists in the area below the aperture area 305. Specifically, the material of the supporting substrate 1 is 4H-SiC, the material of the first dielectric area 201 and the second dielectric area 203 is silicon oxide, and the thickness is the same as that of the bottom electrode 2021. The material of the bottom electrode 2021 is platinum, and the thickness is 50nm. The material of the piezoelectric layer 2022 is X-cut lithium niobate, and the thickness is 325nm. The material of the interdigital transducer 3 is aluminum / tungsten, and the thickness is 65 / 35nm. The period of the interdigital transducer 3 is 1.65μm (that is, 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, and the material of the first dielectric layer 4 is silicon oxide, and the 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, it can be obtained as follows: Fig. 9 From the simulation results shown, it can be seen that after patterning the bottom electrode 2021 (i.e., designing it to exist only below the aperture region 305), the bulk acoustic wave mode excited by the bus bar and the air gap region 306 is suppressed, thereby greatly improving the admittance ratio of the resonator. Fig.10It can be seen that the busbars and the electrodes in the air gap region 306, the piezoelectric layer 2022 and the bottom electrode 2021 form a "sandwich" structure, which excites the 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 an energy leakage source, resulting in a significant decrease in the device Q value. Fig.11 It can be seen that, since there is no bottom electrode 2021 under the bus bar and the air gap region 306, a longitudinal electric field cannot be formed, and thus the bulk acoustic wave mode will not be excited, which makes the main mode vibration exist only in the aperture region 305, and the energy does not leak to the substrate. It can be seen from the above comparative examples 1 and 2 that the bulk acoustic wave mode excited by the bus bar and the air gap region 306 can be effectively suppressed by patterning the bottom electrode 2021, so that the main mode vibration exists only in the aperture region 305, and the energy does not leak to the substrate.

[0104] See also Fig.12 , which respectively show 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 a first misaligned region 10 and a second misaligned region 11. The widths of the first misaligned region 10 and the second misaligned region 11 are both W1, and W1 is 2 μm. Please refer to Fig.13 , which is a schematic diagram of the simulation results of Comparative Examples 2 and 3 provided in the embodiments 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 misaligned region 11 excites the bulk acoustic wave mode, while the first misaligned region 10 excites other parasitic modes due to the lateral electric field. Further through Fig.14 It can be seen that the second misaligned region 11 excites the bulk acoustic wave mode and causes energy to leak to the substrate. This shows that in the case of only patterning 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, and there will be a problem of energy leakage to the substrate.

[0105] Further, by providing the embodiments of the present application Figure 4 The structure shown in the figure is simulated and tested, and the following results can be obtained: Fig.15 The simulation results shown are compared Figure 4 The simulation results of the structure shown (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) show that the difference in frequency response between the two is very small. Fig.16 , which shows Comparative Example 2 and Figure 4The conductive curve comparison diagram corresponding to the structure shown in the figure shows that when only the bottom electrode 2021 is patterned, there is a strong lateral high-order mode between the resonant frequency and the anti-resonant frequency of the resonator. After the piezoelectric layer 2022 is patterned, the lateral high-order mode is significantly weakened. It can be seen that the use of patterned piezoelectric layer 2022 helps to suppress lateral high-order modes.

[0106] For some possible examples, see Fig.17 and 18 , the width of the piezoelectric region 202 is smaller than the width of the aperture region 305, that is, the piezoelectric region 202 and the aperture region 305 are misaligned in the width direction, but the center of the piezoelectric region 202 and the center of the aperture region 305 are aligned, see Fig.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 2 μm and 5 μm. Fig.18 and 19 The structure shown in the figure is simulated and tested, and the following results can be obtained: Fig. 20 The simulation results shown are from Fig. 20 It can be seen that the difference between the response frequencies of the three is very small, from which it can be seen that the resonator structure provided in the embodiment of the present application has a very low requirement for alignment accuracy 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 the first dielectric layer 4 is not provided between the functional layer 2 and the supporting substrate 1. Fig.21 The structure shown.

[0108] For other possible examples, see Fig. 22 The support substrate 1 includes a stacked support layer 101 and a high acoustic velocity layer 102; the support layer 101 is a material that is easy to shape and process; the material of the support layer 101 includes any one of quartz, silicon, sapphire, spinel, and yttrium aluminum garnet; the material of the high acoustic velocity layer 102 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. In some possible examples, the thickness of the 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 some other possible examples, the top surface of the piezoelectric layer 2022 is higher 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, that is, Fig.23 In the structure shown, optionally, the width of the piezoelectric region 202 is less than or equal to the width of the aperture region 305 .

[0110] For other possible examples, see Fig.24 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] For other possible examples, see Fig.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] For other possible examples, see Fig.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] For other possible examples, see Fig. 27 The interdigital transducer 3 further includes a pseudo-finger electrode 307, which may be provided on the opposite sides of the first interdigital electrode 303 and the second interdigital electrode 304. Then, at least two pseudo-finger electrodes 307 are provided. The number and position of the pseudo-finger electrodes 307 may also be set according to actual needs. There is no limitation here. There is no piezoelectric layer 2022 under the area where the pseudo-finger electrode 307 is located. Optional, please refer to Fig.28 ,and Fig. 27 Compared with the structure shown in FIG. 1 , the aperture region 305 can also be designed to be larger than the width of the piezoelectric region 202. Fig.29 , the boundary of the piezoelectric layer 2022 and the aperture region 305 are both polygonal. Fig.30 , 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. Fig.31 , 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. Fig.32 , compared to Fig.30 The difference between the structures shown is that the boundary of the piezoelectric layer 2022 is a rectangle. Fig.33 , compared to Figure 4 The difference between the structures shown 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. Fig.34 , compared to Fig.31The difference between the structures shown is that the boundary of the piezoelectric layer 2022 is a parallelogram. Fig.35 , compared to Fig.34 The structure shown differs in that the aperture region 305 is also a parallelogram.

[0114] It is understandable that the surface acoustic wave resonator provided in the present 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] See also Fig.36 , the present application embodiment 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 comprises 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 comprises 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, a specific implementation of S3603 may include: forming a piezoelectric region 202 on the support substrate 1 to obtain a first structure (ie, Fig.37 The dielectric material is deposited on the first structure, so that the structure shown in FIG. Fig.38 The structure shown in FIG. 1 can be subsequently removed by etching or by other methods (such as grinding), which are not limited here, so as to obtain the following: Fig.39 The structure shown can be ground or polished later. Fig.39 The surface of the structure is removed, and the excess dielectric material is removed to form a first dielectric region 201 and a second dielectric region 203 on the substrate to obtain a second structure (ie, Fig.40 structure shown).

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

[0121] In some other possible examples, a piezoelectric region 202 is formed on a supporting substrate 1 to obtain a first structure, including: providing a piezoelectric substrate 12 having a conductive material layer 8 on its surface (see Fig.42 ); performing local ion implantation into a preset depth of the piezoelectric substrate 12 to form a damaged layer 1201 at a preset depth of the piezoelectric substrate 12, and obtaining Fig.43 The structure shown; bonding the conductive material layer 8 to the supporting substrate 1 to obtain a bonding structure; annealing and stripping the bonding structure to obtain a first structure. Optionally, the implantation surface of the ion implantation can 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 may be formed by deposition or bonding stripping, as well as graphical methods, or by ion implantation and annealing stripping methods.

[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, so that the following can be obtained: 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, so that the support substrate 1 has 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 area 305 of the interdigital transducer 3 is equal to that of the projection area of ​​the aperture area 305; the projection area of ​​the aperture area 305 is the area where the aperture area 305 is projected on the functional layer 2; the aperture area 305 is the area where the first interdigital electrode 303 and the second interdigital electrode 304 in the interdigital transducer 3 are interlaced; 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 303 and the frequency of the target mode is less than the sound velocity of the supporting substrate 1.

[0125] Through the above preparation method, the following can be obtained: Figure 2 The structure shown, 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 method for preparing the surface acoustic wave resonator provided in the embodiment of the present application utilizes the high-order surface acoustic wave mode excited by the longitudinal electric field as the target mode, and uses a high-acoustic-velocity supporting substrate 1 to constrain the target mode on 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 of the body 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 the piezoelectric film is patterned step by step and the bottom electrode 2021 is suspended, and also avoids the problem of lithography 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. It can be seen from the above description that the surface acoustic wave resonator has a patterned piezoelectric layer and a bottom electrode, so that 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 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 only an optional embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope 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; A 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; An interdigital transducer is formed on the functional layer; 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 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 13, 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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