High-frequency acoustic resonator and communication equipment

Abstract

The invention relates to the technical field of resonators, in particular to a high-frequency acoustic resonator and communication equipment. The high-frequency acoustic resonator comprises a supporting substrate, a reflecting structure, a piezoelectric layer and an interdigital electrode which are sequentially arranged from bottom to top, the reflection structure comprises a first reflection layer and a second reflection layer which are stacked; the acoustic impedance of the first reflecting layer is different from that of the second reflecting layer; the target mode of the high-frequency acoustic wave resonator is a high sound velocity mode, the product of the distance between the electrode fingers of the interdigital electrode and the anti-resonant frequency is larger than the slow shear wave sound velocity of the supporting substrate, and the product of the distance between the electrode fingers of the interdigital electrode and the resonator frequency is smaller than the longitudinal wave sound velocity of the supporting substrate; the distance between the electrode fingers of the interdigital electrodes is the distance between the centers of the adjacent electrode fingers on the same bus bar of the interdigital electrodes, the upper sound velocity limit of the target mode is improved from the slow shear wave sound velocity of the supporting substrate to the longitudinal wave sound velocity, and the method can be applied to high-frequency scenes.

Description

Technical Field

[0001] The present invention relates to the technical field of resonators, and in particular to a high-frequency acoustic wave resonator and communication equipment. Background Art

[0002] Acoustic wave filters mainly include bulk acoustic wave (BAW) filters and surface acoustic wave (SAW) filters. In addition, plate wave filters have also attracted widespread attention in recent years due to their higher acoustic velocity.

[0003] In order to increase the operating frequency of the filter, BAW devices are usually implemented by reducing the thickness of the piezoelectric film. However, for BAW devices with suspended films, overly thin piezoelectric films have mechanical stability issues. For solid-mounted resonators (SMR), BAW devices are based on the Bragg reflector layer set inside them. However, as we all know, the Bragg reflector layer usually includes a layer structure of at least 6 layers, which greatly increases the difficulty of device processing. In particular, it is difficult to prepare a qualified Bragg reflector layer for devices using single-crystal piezoelectric films. For SAW devices, the operating frequency is increased by reducing the period of the electrode. However, when the target mode is the common zero-order horizontal shear mode and Rayleigh mode, the sound speed is only 4000m / s, making it difficult to achieve applications above 3.5GHz under existing lithography conditions. Therefore, how to provide a resonator with a simple structure, easy to prepare and applicable to high-frequency bands has become an urgent problem that needs to be solved. Summary of the Invention

[0004] To solve the above technical problems, the present application discloses, on one hand, a high-frequency acoustic wave resonator, comprising a supporting substrate, a reflective structure, a piezoelectric layer, and interdigital electrodes arranged in sequence from bottom to top;

[0005] The reflective structure includes a first reflective layer and a second reflective layer stacked together; the first reflective layer and the second reflective layer have different acoustic impedances;

[0006] The target mode of the high-frequency acoustic wave resonator is a high sound velocity mode, the product of the spacing between the electrode fingers of the forked electrode and the antiresonance frequency is greater than the slow shear wave sound velocity of the supporting substrate, and the product of the spacing between the electrode fingers of the forked electrode and the resonator frequency is less than the longitudinal wave sound velocity of the supporting substrate; the spacing between the electrode fingers of the forked electrode is the distance between the centers of adjacent electrode fingers on the same bus bar of the forked electrode.

[0007] In a feasible embodiment, the first reflective layer is close to the piezoelectric layer; and the acoustic impedance of the second reflective layer is greater than twice the acoustic impedance of the first reflective layer.

[0008] In a feasible embodiment, the reflective structure includes a plurality of first reflective layers and second reflective layers stacked alternately;

[0009] The total number of the first reflective layers and the second reflective layers included in the reflective structure is less than or equal to 5.

[0010] In a feasible embodiment, the piezoelectric layer includes at least two stacked sub-piezoelectric layers;

[0011] Adjacent piezoelectric sub-layers in the at least two piezoelectric sub-layers are of different material types or cut types.

[0012] In a feasible embodiment, a functional layer is further provided between the reflective structure and the piezoelectric layer;

[0013] The functional layer includes one or more of a temperature compensation layer, a heat dissipation layer, and a trap-rich layer.

[0014] In a feasible embodiment, the support substrate includes a stacked support layer and a high acoustic velocity layer;

[0015] The high acoustic velocity layer is made of a material that is easy to shape and process; the material of the high acoustic velocity layer is any one of silicon carbide, diamond, diamond-like carbon, aluminum oxide, aluminum nitride, boron nitride, boron carbide and silicon nitride of different crystal forms and different cuts;

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

[0017] In a feasible embodiment, a bonding layer is further included between the reflective layer and the supporting substrate.

[0018] In a feasible embodiment, a bottom electrode is provided between the reflective structure and the piezoelectric layer;

[0019] The target mode is a high-speed sound mode excited by a longitudinal electric field.

[0020] In a feasible embodiment, the bottom electrode is one or more combinations of copper, aluminum, gold, silver, tungsten, platinum, nickel, chromium, molybdenum, titanium, graphene, copper-aluminum alloy, aluminum-silicon alloy, doped silicon, silicon carbide, and gallium nitride;

[0021] The width of the bottom electrode does not exceed the width of the aperture region, and the aperture region is the region where the electrode fingers of the interdigitated electrodes overlap.

[0022] In a feasible embodiment, the material of the piezoelectric layer is one or a combination of lithium tantalate, lithium niobate, potassium niobate, aluminum nitride, scandium-doped aluminum nitride, lead zirconate titanate, or lead magnesium niobate-lead titanate;

[0023] The support substrate is a combination of one or more of silicon carbide, diamond, diamond-like carbon, silicon, sapphire, aluminum nitride, boron nitride, boron carbide and silicon nitride with different crystal forms and different cut shapes.

[0024] In a feasible embodiment, the material of the first reflective layer is any one of silicon oxide, aluminum, germanium, titanium, silicon, magnesium alloy, and ion-implanted or doped silicon oxide;

[0025] The material of the second reflective layer is any one of tungsten, platinum, tungsten nitride, hafnium oxide, hafnium nitride, tungsten oxide, aluminum oxide, aluminum nitride, silicon carbide, titanium oxide, gold, nickel, molybdenum, tantalum, chromium, and copper.

[0026] In a feasible embodiment, the product of the spacing between the electrode fingers of the interdigitated electrode and the anti-resonance frequency exceeds 7000 m / s;

[0027] The longitudinal wave sound velocity of the supporting substrate exceeds 7000 m / s.

[0028] In a feasible embodiment, the target mode of the high-frequency acoustic wave resonator is one of a longitudinal leakage surface acoustic wave mode, a high-order horizontal shear mode, a high-order Lamb wave mode, and a high-order Rayleigh mode.

[0029] In another aspect, the present application discloses a communication device, comprising the high-frequency acoustic wave resonator described above;

[0030] The communication device includes at least one of a filter, a duplexer, and a multiplexer.

[0031] By adopting the above technical solution, the high-frequency acoustic wave resonator provided by this application has the following beneficial effects:

[0032] The high-frequency acoustic wave resonator includes a supporting substrate, a reflective structure, a piezoelectric layer and an interdigitated electrode arranged in sequence from bottom to top; the reflective structure includes a stacked first reflective layer and a second reflective layer; the acoustic impedances of the first reflective layer and the second reflective layer are different; the target mode of the high-frequency acoustic wave resonator is a high sound velocity mode, the product of the spacing between the electrode fingers of the interdigitated electrode and the antiresonance frequency is greater than the slow shear wave sound velocity of the supporting substrate, and the product of the spacing between the electrode fingers of the interdigitated electrode and the resonator frequency is less than the longitudinal wave sound velocity of the supporting substrate; the spacing between the electrode fingers of the interdigitated electrode is the distance between the centers of adjacent electrode fingers on the same bus bar of the interdigitated electrode. The overall structure is not only simple and easy to form and process, but also by arranging a pair of reflective layers with different acoustic impedances between the piezoelectric layer and the supporting substrate, the target mode can still be constrained on the surface of the supporting substrate when it is at a higher frequency, so that the resonator can be applied to high-frequency scenarios and the upper limit of the sound velocity of the high-order acoustic wave mode can be further increased, thereby increasing the sound velocity difference between the target mode and the zero-order mode, ensuring that the parasitic mode appears outside the passband. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] 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.

[0034] Figure 1 This is a schematic structural diagram of the first high-frequency acoustic wave resonator provided by this application;

[0035] Figure 2 yes Figure 1 A simulated admittance and conductance curve corresponding to the structure;

[0036] Figure 3 yes Figure 1 Another simulated admittance and conductance curve corresponding to the structure;

[0037] Figure 4 This is a schematic structural diagram of the second high-frequency acoustic wave resonator provided by this application;

[0038] Figure 5 yes Figure 4 A partial top view of the structure shown;

[0039] Figure 6 This is a schematic structural diagram of Comparative Example 1 provided in this application;

[0040] Figure 7 It is a simulated admittance curve of Comparative Example 1 and Example 1 provided in this application;

[0041] Figure 8 This is a simulated conductivity curve of Comparative Example 1 and Example 1 provided in this application;

[0042] Figure 9 This is a simulated Bode-Q curve of Comparative Example 1 and Example 1 provided in this application

[0043] Figure 10 This is a comparative example 1 provided in this application at the anti-resonance frequency f p The vibration mode diagram at ;

[0044] Figure 11 This application provides an example 1 at the anti-resonance frequency f p The vibration mode diagram at ;

[0045] Figure 12 This is a simulated admittance curve and a simulated conductance curve of Comparative Example 2 provided in this application;

[0046] Figure 13 This is a simulated admittance curve and a simulated conductance curve of Example 2 provided in this application;

[0047] Figure 14 This is an S21 curve corresponding to a filter constructed based on the resonator of Comparative Example 2 provided in this application;

[0048] Figure 15 is an S21 curve corresponding to a filter constructed based on the resonator of Example 2 provided in this application;

[0049] Figure 16 This is a schematic structural diagram of the third high-frequency acoustic wave resonator provided by this application;

[0050] Figure 17 is a simulated admittance ratio corresponding to Comparative Example 3 provided in this application;

[0051] Figure 18 This is a simulated admittance curve corresponding to Comparative Example 3 provided in this application;

[0052] Figure 19 is a simulated admittance ratio corresponding to Comparative Example 3 and Example 3 provided in this application;

[0053] Figure 20 is a simulated admittance curve corresponding to Example 3 provided in this application;

[0054] Figure 21 This is a vibration mode diagram corresponding to Example 3 provided in this application;

[0055] Figure 22 1 is an admittance curve of Comparative Example 3 and Example 3 provided in this application when the number of reflective layers N is equal to 2;

[0056] Figure 23 This is a simulated admittance curve and a simulated conductance curve of Example 4 provided in this application;

[0057] Figure 24 This is a schematic structural diagram of the fourth high-frequency acoustic wave resonator provided by the present application;

[0058] Figure 25 is a schematic structural diagram of the fifth high-frequency acoustic wave resonator provided by this application;

[0059] Figure 26 This is a schematic structural diagram of the sixth high-frequency acoustic wave resonator provided in this application.

[0060] The following is a supplementary description of the accompanying drawings:

[0061] 1-support substrate; 101-support layer; 102-high acoustic velocity layer; 2-reflection structure; 201-first reflective layer; 202-second reflective layer; 3-piezoelectric layer; 301-sub-piezoelectric layer; 4-interdigitated electrodes; 401-first bus bar; 402-second bus bar; 403-electrode fingers; 404-aperture region; 5-bottom electrode; 6-bonding layer. DETAILED DESCRIPTION

[0062] 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.

[0063] 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.

[0064] 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.

[0065] The following is an explanation of the English abbreviations and symbols involved in the embodiments of this application:

[0066] LL-SAW stands for longitudinal leaky surface acoustic wave.

[0067] SH0 stands for zero-order horizontal shear mode, the full name of which is Fundamental shear horizontal mode.

[0068] SH1 represents the first-order horizontal shear mode, the full name of which is First-order shear horizontal mode

[0069] S1 represents the first-order symmetric Lamb wave mode.

[0070] f s Represents the resonator frequency of the resonator, which is the frequency corresponding to the maximum point of the admittance curve

[0071] f p Represents the antiresonant frequency of the resonator, which is the frequency corresponding to the minimum point of the admittance curve

[0072] λ represents the spacing between the electrode fingers of the interdigitated electrode of the resonator. The spacing between the electrode fingers of the interdigitated electrode is the distance between the centers of adjacent electrode fingers on the same busbar of the interdigitated electrode.

[0073] ν p The product of the interdigital electrode pitch of the resonator and the antiresonance frequency

[0074] ν s The product of the interdigital electrode spacing of the resonator and the resonator frequency

[0075] ν l . represents the longitudinal wave speed of the resonator's supporting substrate

[0076] ν ss represents the slow shear wave velocity of the resonator's supporting substrate

[0077] ν fs represents the fast shear wave speed of the resonator's supporting substrate

[0078] In the prior art, there are four common types of acoustic wave resonators. The first type targets a zero-order horizontal shear mode, and its structure includes a supporting substrate, a dielectric layer, a piezoelectric film, and a top electrode stacked from bottom to top. p Only about 4000m / s, which is less than the slow shear wave speed ν of the supporting substrate ss , so the target mode can be confined to the surface of the supporting substrate, achieving a higher Q value. However, the sound velocity is low, making it difficult to achieve applications in the frequency band above 3.5GHz. The second type is that the target mode is the S0 plate wave mode in lithium niobate. The structure includes a supporting substrate, a Bragg reflection layer, a piezoelectric film and a top electrode stacked from bottom to top. p Generally, it is 6000m / s to 7000m / s, and a Bragg reflection layer is used to constrain the target mode. The third type is the SH1 mode in X-cut lithium niobate, with the same structure as the second type, ν p The target mode is about 10000m / s, and a Bragg reflection layer is used to constrain the target mode. The fourth type is a high-order acoustic wave mode, and the structure includes a supporting substrate, a bottom electrode, a piezoelectric film and a top electrode stacked in sequence from bottom to top.p Less than the slow shear wave velocity ν of the supporting substrate ss , a high acoustic velocity support substrate is used to increase the upper limit of the acoustic velocity of the target mode.

[0079] However, the above four structural solutions have the following disadvantages:

[0080] In the first structure, due to its ν p About 4000m / s, which is less than the slow shear wave speed ν of most common supporting substrate materials ss For example, the ν of silicon ss The operating frequency is approximately 5800 m / s, compared to approximately 5000 m / s for quartz and approximately 6000 m / s for sapphire. This allows the SH0 mode to be well confined to the substrate surface, achieving a high Q value. However, the operating frequency is inversely proportional to λ. To increase the frequency, the electrode line width and spacing must be reduced, placing higher demands on photolithography technology. Under current photolithography conditions, advancements above 3.5 GHz are difficult.

[0081] In the second structure, although effective confinement of the target mode is achieved, the multi-layer Bragg reflection layer structure makes the device processing very complicated.

[0082] In the third structure, while effective confinement of the target mode is achieved, the multi-layer Bragg reflector structure complicates device fabrication. Furthermore, the frequency of the target mode is highly sensitive to the thickness of each film layer, requiring precise control of the thickness of each reflector layer, which is very difficult to fabricate in practice.

[0083] In the fourth structure, although the target mode can already meet the requirements of the Sub-6 GHz band under relatively relaxed lithography conditions, the operating frequency cannot be further increased. Furthermore, due to the upper limit of the speed of sound, the frequency difference between the parasitic mode and the target mode cannot be further controlled. The parasitic mode usually appears near the left edge of the target passband, resulting in a decrease in out-of-band suppression.

[0084] In order to address the shortcomings of the above existing solutions, this solution proposes to use a high acoustic velocity support substrate and insert two reflective layers between the support substrate and the piezoelectric film. The acoustic impedances of the reflective layers are different. Unlike the structure that only contains one reflective layer or no reflective layer, when the target mode ν p Exceeds the ν of the supporting substrate ss When the target mode is ν, it can still be well confined to the substrate surface. Different from the structure with multiple Bragg reflection layers, this structure makes full use of the reflection effect of the high acoustic velocity support substrate itself to confine the target mode to the ν s ν is limited to the supporting substrate l By adding only two reflective layers, the high-speed target mode can be confined to the substrate surface. The structure is greatly simplified, and the common support substrate, νl . Usually close to ν ss twice as much, such as ν for sapphire l . Up to 11113m / s, silicon carbide ν l This greatly increases the upper limit of the target mode's sound velocity, with the highest frequency reaching over 10 GHz, and maximizes the acoustic potential of the high-sound-velocity support substrate.

[0085] In addition, when the target mode is a high-order mode, if its bandwidth is large. Usually the zero-order mode will appear near the low-frequency cutoff frequency edge of the target passband, resulting in a decrease in the in-band ripple or out-of-band suppression level of the filter. The high-order mode has a strong dispersion effect, and its acoustic velocity can be changed by adjusting the thickness and load of the piezoelectric layer, thereby changing its frequency difference with the parasitic mode. However, it is limited by the slow shear wave acoustic velocity ν of the supporting substrate. ss , the speed control range of high-order modes is limited. When two reflective layers are added, the upper limit of the speed of high-order modes is greatly increased. Therefore, the relative frequency of the parasitic mode and the target mode can be flexibly controlled to improve the out-of-band suppression level in a specific frequency band.

[0086] In general, the structure is relatively simple, avoids the use of multiple layers of Bragg reflection layers, and fully utilizes the advantages of the high acoustic velocity support substrate, which is conducive to the mass production of high-performance high-frequency resonators and filters and improves the yield.

[0087] For details, please refer to Figure 1 , which is a structural schematic diagram of the first high-frequency acoustic wave resonator provided by the present application, the high-frequency acoustic wave resonator includes a supporting substrate 1, a reflective structure 2, a piezoelectric layer 3 and an interdigitated electrode 4 arranged in sequence from bottom to top; the reflective structure 2 includes a stacked first reflective layer 201 and a second reflective layer 202; the first reflective layer 201 and the second reflective layer 202 have different acoustic impedances; the target mode of the high-frequency acoustic wave resonator is a high sound velocity mode, the product of the spacing between the electrode fingers 403 of the interdigitated electrode 4 and the antiresonance frequency is greater than the slow shear wave sound velocity of the supporting substrate 1, and the product of the spacing between the electrode fingers 403 of the interdigitated electrode 4 and the resonator frequency is less than the longitudinal wave sound velocity of the supporting substrate 1; the spacing between the electrode fingers 403 of the interdigitated electrode 4 is the distance between the centers of adjacent electrode fingers 403 on the same bus bar of the interdigitated electrode 4.

[0088] In a feasible embodiment, the first reflective layer 201 is close to the piezoelectric layer 3 ; and the acoustic impedance of the second reflective layer 202 is greater than twice the acoustic impedance of the first reflective layer 201 .

[0089] In a feasible embodiment, the material of the piezoelectric layer 3 is one or a combination of lithium tantalate, lithium niobate, potassium niobate, aluminum nitride, scandium-doped aluminum nitride, lead zirconate titanate, or lead magnesium niobate-lead titanate.

[0090] In a feasible embodiment, the support substrate 1 is a combination of one or more of silicon carbide, diamond, diamond-like carbon, silicon, sapphire, aluminum nitride, boron nitride, boron carbide and silicon nitride with different crystal forms and different cut shapes.

[0091] In a feasible embodiment, the material of the first reflective layer 201 is any one of silicon oxide, aluminum, germanium, titanium, silicon, magnesium alloy, and ion-implanted or doped silicon oxide.

[0092] In a feasible embodiment, the material of the second reflective layer 202 is any one of tungsten, platinum, tungsten nitride, hafnium oxide, hafnium nitride, tungsten oxide, aluminum oxide, aluminum nitride, silicon carbide, titanium oxide, gold, nickel, molybdenum, tantalum, chromium, and copper.

[0093] In a feasible embodiment, the product of the spacing between the electrode fingers 403 of the interdigitated electrode 4 and the anti-resonance frequency exceeds 7000 m / s; and the longitudinal wave speed of the supporting substrate 1 exceeds 7000 m / s.

[0094] In a feasible embodiment, the target mode of the high-frequency acoustic wave resonator is one of a longitudinal leakage surface acoustic wave mode, a high-order horizontal shear mode, a high-order Lamb wave mode, and a high-order Rayleigh mode.

[0095] In an exemplary embodiment, Figure 1 In the structure shown, the support substrate 1 is made of silicon, the second reflective layer 202 is made of tungsten nitride with a thickness of 165 nm, the first reflective layer 201 is made of silicon oxide with a thickness of 270 nm, the piezoelectric layer 3 is made of 30% scandium-doped aluminum nitride on the a-plane with a thickness of 400 nm, and the interdigital electrodes 4 are made of aluminum with a thickness of 50 nm and a λ of 1 μm. The target mode is the LL-SAW mode, with ν s is 7181m / s, ν p The ν of silicon is 7351m / s. ss and ν fs Both are 5846m / s, the longitudinal wave speed ν l . About 8442m / s. Subsequent relevant calculations can be obtained as follows Figure 2 The simulated admittance curve and simulated conductance curve shown in the figure show that the sound velocity of the LL-SAW mode is less than the longitudinal wave sound velocity ν of the supporting substrate 1. l . , and thus can be constrained on the surface of the supporting substrate 1.

[0096] In another exemplary embodiment, Figure 1 In the structure shown, the support substrate 1 is made of silicon, the second reflective layer 202 is made of tungsten nitride with a thickness of 200nm; the first reflective layer 201 is made of silicon oxide with a thickness of 370nm; the piezoelectric layer 3 is made of 30% scandium-doped aluminum nitride on the a-plane with a thickness of 263nm; the interdigital electrodes 4 are made of aluminum with a thickness of 50nm and a value of λ of 1μm. The target mode is the S1 mode, and ν s is 7825m / s, ν p is 7972m / s. Subsequent calculations can be performed to obtain the following Figure 3 From the simulated admittance curve and the simulated conductance curve shown, it can be seen that the sound speeds of the LL-SAW mode and the S1 mode are both lower than the longitudinal wave sound speed of the supporting substrate 1 , and therefore are both well constrained.

[0097] In another possible embodiment, see Figure 4 A bottom electrode 5 is provided between the reflective structure 2 and the piezoelectric layer 3; and the target mode is a high-acoustic-velocity mode excited by a longitudinal electric field.

[0098] In a feasible embodiment, the bottom electrode 5 is a combination of one or more of copper, aluminum, gold, silver, tungsten, platinum, nickel, chromium, molybdenum, titanium, graphene, copper-aluminum alloy, aluminum-silicon alloy, doped silicon, silicon carbide, and gallium nitride; the width of the bottom electrode 5 does not exceed the width of the aperture region 404, see Figure 5 The aperture region 404 is an area where the electrode fingers of the interdigitated electrode 4 overlap. Specifically, the interdigitated electrode 4 includes a first bus bar 401, a second bus bar 402, and a plurality of electrode fingers 403. The first bus bar 401 is provided with a plurality of electrode fingers 403 spaced apart, and the second bus bar 402 is also provided with a plurality of electrode fingers spaced apart. The electrode fingers 403 on different bus bars are arranged in an interlaced manner. The distance between the centers of adjacent electrode fingers 403 on the same bus bar is the spacing λ of the electrode fingers 403 of the interdigitated electrode 4.

[0099] For example, the present application provides a comparative example 1 and an example 1, wherein the comparative example 1 can be specifically as follows Figure 6 The structure shown in FIG. 1 includes a supporting substrate 1, a first reflective layer 201, a bottom electrode 5, a piezoelectric layer 3 and interdigital electrodes 4 arranged in sequence from bottom to top. The structure of Example 1 can be as follows Figure 4 The structure shown in FIG1 is different from that of Example 1 in that Example 1 further includes a second reflective layer 202 having an acoustic impedance different from that of the first reflective layer 201. The other parameters are the same, that is, the material of the supporting substrate 1 is 4H-SiC, the slow shear wave velocity ν ss About 7126m / s, fast shear wave speed ν fs About 7794m / s, longitudinal wave speed ν l. It is about 12493m / s, the material of the first reflective layer 201 is silicon oxide, and the material of the second reflective layer 202 is tungsten; the bottom electrode 5 is platinum with a thickness of 20nm; the material of the piezoelectric layer 3 is Y171-cut lithium niobate with a thickness of 150nm; the interdigitated electrode 4 is 50nm / 12nm aluminum / tungsten, λ is 1μm, and the number of interdigitated electrode pairs (adjacent electrode fingers located on different bus bars are usually called interdigitated electrode pairs) is 20 pairs. Among them, the thickness of the first reflective layer 201 in Comparative Example 1 is 100nm, the thickness of the first reflective layer 201 in Example 1 is 180nm, and the thickness of the second reflective layer 202 is 100nm. The target modes of Comparative Example 1 and Example 1 are both SH1 modes. After simulation calculations of the two, it can be obtained as follows Figure 7 and 8 The simulated admittance results and the simulated conductance results shown in the figure show that the anti-resonance frequency f p Roughly equivalent, and both exceed the slow shear wave velocity ν of the supporting substrate 1 ss The ratio of the admittance ratio of comparative example 1 is significantly lower than that of example 1, especially when the value exceeds ν ss / λ frequency band, there is a big gap between the two. Figure 8 The conductivity curve shown reflects the acoustic loss due to body wave radiation. Figure 8 It can be seen that the amplitude of the conductance curve of Example 1 is significantly lower than that of Comparative Example 1, especially at frequencies close to and greater than ν ss / λ, the difference between the two becomes larger. The conductivity curve of Example 1 is larger than ν ss / λ, the body wave radiation remains at a low level, which shows that even if ν p The slow shear wave velocity of the supporting substrate 1 is exceeded, and Example 1 can still maintain a high Q value, and the upper limit of the velocity of the target mode is further improved. Figure 9 It can be seen that the Q value of comparative example 1 is close to or exceeds ν ss / λ, while the Q value of Example 1 drops significantly when it exceeds ν ss The frequency of / λ still maintains a high level. This shows that the upper limit of the sound velocity of comparative example 1 is the slow shear wave sound velocity ν of the supporting substrate 1 ss , while Example 1 breaks through this limitation, at least when the fast shear wave speed ν of the supporting substrate 1 fs There is still no obvious sound wave energy leakage near the frequency of / λ. For further information, please refer to Figure 10 and 11 , which are respectively the anti-resonance frequency f of comparative example 1 and example 1 pFrom the vibration mode diagram at , it can be seen that a large amount of acoustic wave energy of comparative example 1 leaks into the supporting substrate 1, while the acoustic wave energy of example 1 is well confined to the substrate surface. This shows that the structure of the acoustic wave resonator provided by the present application, which includes two reflective layers with different acoustic impedances, can still be confined to the surface of the supporting substrate 1 when the target mode is at a higher frequency, so that the resonator can be applied to high-frequency scenarios and the upper limit of the sound velocity of the high-order acoustic wave mode can be further increased, thereby increasing the sound velocity difference between the target mode and the zero-order mode, ensuring that the parasitic mode appears outside the passband.

[0100] This application provides another comparative example 2 and example 2. Comparative example 1 can be specifically as follows Figure 6 The structure shown in Example 2 can be as follows Figure 4 In the structure shown, the support substrate 1 is made of 4H-SiC, the first reflective layer 201 is made of silicon oxide, and the second reflective layer 202 is made of tungsten. The bottom electrode 5 is made of tungsten with a thickness of 100 nm. The piezoelectric layer 3 is made of X-cut lithium niobate with a thickness of 200 nm. The interdigital electrodes 4 are made of 25 nm / 75 nm tungsten / aluminum. In Comparative Example 1, the thickness of the first reflective layer 201 is 200 nm, and λ is 1.573 μm, slightly smaller than ν ss / f p In Example 1, the thickness of the first reflective layer 201 is 200 nm, the thickness of the second reflective layer 202 is 255 nm, and λ is 1.72 μm, which is slightly smaller than ν fs / f p The target modes of comparative example 1 and example 1 are both SH1 mode. The simulation results of comparative example 2 and example 2 are as follows: Figure 12 and Figure 13 As shown, it can be seen that in comparative example 2, the LL-SAW appears as a parasitic mode on the left side of the resonant frequency of the target mode, which is limited by the ν of the supporting substrate 1. ss , the frequency difference Δf between the two modes has reached the limit, which is about 554MHz. In Example 2, LL-SAW also appears as a parasitic mode on the left side of the resonant frequency of the target mode. Since the target mode has a strong dispersion effect, the frequency is mainly determined by the thickness of the piezoelectric film and the load. When the upper limit of the speed of sound of the target mode is increased, λ increases, and the speed of sound difference between the LL-SAW and SH1 modes increases. At this time, Δf is about 740MHz. It can be seen that Δf in Comparative Example 2 is smaller than Δf in Example 2, that is, the clutter in the structure of the present application is farther away from the target mode, so that the position of the clutter can be flexibly adjusted later.

[0101] When a filter is constructed based on the resonator of Comparative Example 2, the λ of each resonator in the filter satisfies λ<ν ss / f p The S21 curve corresponding to the filter is as follows Figure 14 As shown in Figure 3, the LL-SAW appears as a parasitic mode on the left side of the target passband, resulting in a decrease in the out-of-band suppression level.

[0102] When constructing a filter based on the resonator of Example 2, the λ of each resonator in the filter satisfies λ>ν ss / f p The S21 curve corresponding to the filter is as follows Figure 15 As shown in Figure 1, the LL-SAW is shifted to a lower frequency. In this case, the spurious mode is moved closer to the filter zero, improving the out-of-band suppression level to the left of the passband by approximately 20 dB. Due to the increased upper limit of the speed of sound, the spurious mode can also be flexibly adjusted to a frequency band with lower suppression requirements as needed.

[0103] In another possible embodiment, see Figure 16 The reflective structure 2 includes a plurality of first reflective layers 201 and second reflective layers 202 that are alternately stacked; the total number of the first reflective layers 201 and second reflective layers 202 included in the reflective structure 2 is less than or equal to 5. For example, the reflective structure 2 may be a structure including only the first reflective layer 201 and the second reflective layer 202, that is, Figure 1 The structure shown may also be a structure including two first reflective layers 201 and one second reflective layer 202. Specifically, the reflective structure 2 is a first reflective layer 201, a second reflective layer 202, and a first reflective layer 201 arranged in sequence from bottom to top. It may also be a structure including two first reflective layers 201 and two second reflective layers 202, or a structure including three first reflective layers 201 and two second reflective layers 202.

[0104] For example, when the total number of reflective layers included in the reflective structure 2 is set to N, the present application provides a pair of ratios 3, the structure of which is as follows: Figure 16 In the structure shown, the support substrate 1 is made of sapphire; the second reflective layer 202 is made of tungsten with a thickness of 120 nm; the first reflective layer 201 is made of silicon oxide with a thickness of 145 nm; the bottom electrode 5 is made of platinum with a thickness of 50 nm; the piezoelectric layer 3 is made of Y36-cut lithium niobate with a thickness of 200 nm; the interdigital electrodes 4 are made of aluminum with a thickness of 50 nm, and λ is 1.25 μm. The target mode is the S1 mode, and the target mode's ν s and ν p All exceed 11300m / s. The slow shear wave velocity of sapphire is ν ss About 6045m / s, fast shear wave speed ν fs About 6383m / s, longitudinal wave speed ν l About 11113m / s, when the number of reflective layers in the reflective structure 2 is changed and the resonator containing different reflective layers is simulated and calculated, the following can be obtained: Figure 17 The simulated admittance ratio is shown in FIG. 2 , and it can be seen that due to the ν s and ν p All of them exceed the longitudinal wave sound velocity of the supporting substrate 1. Here, more than 6 reflective layers are required to obtain a larger admittance ratio. When the number of reflective layers N exceeds 8 layers, the admittance ratio no longer increases. For further information, please refer to Figure 18 , compared with the simulated admittance curves of the above comparative example 3 with the number of reflection layers being 1, 2 and 16, it can be seen that due to the ν s and ν p Both exceed the longitudinal wave sound velocity of the supporting substrate 1. When N=1, the admittance ratio of the target mode is extremely low and basically leaks completely. Although the admittance ratio is improved when N=2, it is far from meeting the needs of actual filtering elements. When N=16, the target mode is completely confined to the substrate surface.

[0105] This application provides an example 3, the structure of which is as follows Figure 16 The structure shown in FIG. 1 is made of Y45-cut 4H-SiC support substrate 1. The remaining structural parameters are the same as those in Comparative Example 3. The target mode is S1 mode. s and ν p The slow shear wave velocity ν of Y-cut 4H-SiC is between 11300m / s and 11900m / s. ss About 7467m / s, fast shear wave speed ν fs About 8602m / s, longitudinal wave speed ν l . About 12493m / s. Please refer to Figure 19 By comparing the admittance ratios of Comparative Example 3 and Example 3 under different numbers of reflection layers, it can be seen that since the supporting substrate 1 of Comparative Example 3 is sapphire, the ν s and ν p are slightly larger than the ν of the supporting substrate 1 l The supporting substrate 1 of Example 3 is Y45-cut 4H-SiC, and the target mode ν s and ν p are all smaller than the ν of the supporting substrate 1 l When N≥8, the admittance ratios corresponding to different support substrates 1 are basically the same. At this time, the sound velocity of the support substrate 1 has almost no effect on the target mode. When N is less than 8, a higher longitudinal wave sound velocity of the support substrate 1 means a higher Q value. When the longitudinal wave sound velocity of the support substrate 1 is ν l . is greater than the target mode's ν s and ν pWhen N = 2, a larger admittance ratio can be obtained, and when N = 6, the loss of the sound wave is minimized. Therefore, the total number of the first reflective layer 201 and the second reflective layer 202 included in the reflective structure 2 of the present application can be set to be less than or equal to 5, which can achieve the advantages of both easy molding and high-frequency application.

[0106] For further information, see Figure 20 , which shows a simulated admittance curve of Example 3 provided in an embodiment of the present application. It can be seen that the ν of the target mode of Example 3 s and ν p are all less than the longitudinal wave speed of the supporting substrate 1. When N = 1, the admittance ratio of the target mode is extremely low, and when N = 2, the admittance ratio is only slightly less than when N = 16. This shows that as long as the ν s and ν p Smaller than the ν of the supporting substrate 1 l . With only two reflective layers, the target pattern is essentially confined to the substrate surface. Figure 21 Figure (a) in the figure shows the mode shape diagram when the number of reflection layers N=1 in Example 3. In this case, a large amount of sound waves leak into the substrate. Figure 21 Figure (b) in the figure shows the vibration mode diagram when the number of reflection layers N=2 in Example 3. In this case, the acoustic wave is basically confined to the substrate surface.

[0107] Moreover, by comparing the admittance curves of Comparative Example 3 and Example 3 when the number of reflective layers N=2 (e.g. Figure 22 As shown), it can be seen that the resonant frequency is less than ν l . / λ is the key to using fewer reflective layers to constrain the target mode. Among them, ν1 and ν2 are the longitudinal wave sound speeds of sapphire and silicon carbide respectively. It further illustrates that the reflective layer protected by this application has two different acoustic impedances, and the product of the spacing between the electrode fingers 403 of the interdigitated electrode 4 and the antiresonance frequency ν p Greater than the slow shear wave velocity ν of the supporting substrate 1 ss , and the product of the spacing between the electrode fingers 403 of the interdigitated electrode 4 and the resonator frequency ν s Less than the longitudinal wave sound velocity ν of the supporting substrate 1 l The resonator under this condition can be applied in high frequency fields. In order to further illustrate the above effect, the present application provides another example 4, the structure of which can be as follows: Figure 4 As shown, the material of the supporting substrate 1 is Y45-cut 4H-SiC, the thickness of the first reflective layer 201 is 160nm, the thickness of the second reflective layer 202 is 135nm, the thickness of the piezoelectric layer 3 is 195nm, λ is 1.33μm, and the other structural parameters are the same as those of the comparative example 3. s Reaching 12090m / s, close to the longitudinal wave sound velocity ν of the supporting substrate 1l . , ν p The value is 12654 m / s, which exceeds the longitudinal wave sound velocity ν of the supporting substrate 1. l ..from Figure 23 It can be seen that the body wave radiation near the antiresonance frequency is significantly enhanced, but the Q value is still high near the resonant frequency. s Less than ν l . , the resonator can still constitute an effective filtering element, which is sufficient for a series resonator in a filter.

[0108] In another possible embodiment, see Figure 24 The piezoelectric layer 3 includes at least two stacked sub-piezoelectric layers 301 ; the adjacent sub-piezoelectric layers 301 in the at least two sub-piezoelectric layers 301 have different material types or cut types.

[0109] In another feasible embodiment, a functional layer is further provided between the reflective structure 2 and the piezoelectric layer 3 ; the functional layer includes one or more of a temperature compensation layer, a heat dissipation layer, and a trap-rich layer.

[0110] In another possible embodiment, see Figure 25 A bonding layer 6 is further included between the reflective layer and the supporting substrate 1 .

[0111] In another possible embodiment, see Figure 26 The supporting substrate 1 includes a stacked supporting layer 101 and a high acoustic velocity layer 102; the high acoustic velocity layer 102 is a material that is easy to form and process; 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 with different crystal forms and different cuts; the material of the supporting layer 101 includes any one of quartz, silicon, sapphire, spinel and yttrium aluminum garnet.

[0112] It is understandable that the above-mentioned resonators (such as Figures 25-26 The structure shown in FIG2 may also include a case where a bottom electrode 5 is provided below the piezoelectric layer 3. That is, the resonator protected by this application may be all feasible combinations of the several resonators described in the examples above, and is not limited to the illustrated scheme. For example, Figure 24 + Figure 26 + bottom electrode solution, that is, the resonator includes a support layer 101, a high acoustic velocity layer 102, a second reflection layer 202, a first reflection layer 201, a bottom electrode 5, two sub-piezoelectric layers 301 and an interdigital electrode 4 arranged in sequence from bottom to top.

[0113] On the other hand, the present application discloses a communication device, including the above-mentioned high-frequency acoustic wave resonator; the communication device includes at least one of a filter, a duplexer, and a multiplexer.

[0114] 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 high-frequency acoustic wave resonator, characterized in that: It includes a supporting substrate, a reflective structure, a piezoelectric layer and interdigital electrodes arranged in sequence from bottom to top; The reflective structure comprises a first reflective layer and a second reflective layer stacked together; the first reflective layer and the second reflective layer have different acoustic impedances; The target mode of the high-frequency acoustic wave resonator is a high sound velocity mode, the product of the spacing between the electrode fingers of the forked electrode and the antiresonance frequency is greater than the slow shear wave sound velocity of the supporting substrate, and the product of the spacing between the electrode fingers of the forked electrode and the resonator frequency is less than the longitudinal wave sound velocity of the supporting substrate; the spacing between the electrode fingers of the forked electrode is the distance between the centers of adjacent electrode fingers on the same bus bar of the forked electrode.

2. The high-frequency acoustic wave resonator according to claim 1, characterized in that: The first reflection layer is close to the piezoelectric layer; and the acoustic impedance of the second reflection layer is greater than twice the acoustic impedance of the first reflection layer.

3. The high-frequency acoustic wave resonator according to claim 2, characterized in that: The reflective structure includes a plurality of first reflective layers and second reflective layers which are alternately stacked; The total number of the first reflective layers and the second reflective layers included in the reflective structure is less than or equal to 5.

4. The high-frequency acoustic wave resonator according to claim 1, characterized in that: The piezoelectric layer includes at least two stacked sub-piezoelectric layers; Adjacent piezoelectric sub-layers in the at least two piezoelectric sub-layers have different material types or different cutting patterns.

5. The high-frequency acoustic wave resonator according to claim 1, characterized in that: A functional layer is also provided between the reflective structure and the piezoelectric layer; The functional layer includes one or more of a temperature compensation layer, a heat dissipation layer, and a trap-rich layer.

6. The high-frequency 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 high acoustic velocity layer is made of a material that is easy to shape and process; the material of the high acoustic velocity layer is any one of silicon carbide, diamond, diamond-like carbon, aluminum oxide, aluminum nitride, boron nitride, boron carbide and silicon nitride of different crystal forms and different cuts; The material of the support layer includes any one of quartz, silicon, sapphire, spinel, and yttrium aluminum garnet.

7. The high-frequency acoustic wave resonator according to claim 1, characterized in that: A bonding layer is also included between the reflective layer and the supporting substrate.

8. The high-frequency acoustic wave resonator according to claim 1, characterized in that: A bottom electrode is provided between the reflective structure and the piezoelectric layer; The target mode is a high-speed sound mode excited by a longitudinal electric field.

9. The high-frequency acoustic wave resonator according to claim 8, characterized in that: The bottom electrode is a combination of one or more of copper, aluminum, gold, silver, tungsten, platinum, nickel, chromium, molybdenum, titanium, graphene, copper-aluminum alloy, aluminum-silicon alloy, doped silicon, silicon carbide, and gallium nitride; The width of the bottom electrode does not exceed the width of the aperture region, and the aperture region is the region where the electrode fingers of the interdigitated electrodes overlap.

10. The high-frequency acoustic wave resonator according to claim 1, characterized in that: The material of the piezoelectric layer is one or a combination of lithium tantalate, lithium niobate, potassium niobate, aluminum nitride, scandium-doped aluminum nitride, lead zirconate titanate or lead magnesium niobate-lead titanate; The support substrate is a combination of one or more of silicon carbide, diamond, diamond-like carbon, silicon, sapphire, aluminum nitride, boron nitride, boron carbide and silicon nitride in different crystal forms and different cut shapes.

11. The high-frequency acoustic wave resonator according to claim 1, characterized in that: The material of the first reflective layer is any one of silicon oxide, aluminum, germanium, titanium, silicon, magnesium alloy, and ion-implanted or doped silicon oxide; The material of the second reflective layer is any one of tungsten, platinum, tungsten nitride, hafnium oxide, hafnium nitride, tungsten oxide, aluminum oxide, aluminum nitride, silicon carbide, titanium oxide, gold, nickel, molybdenum, tantalum, chromium, and copper.

12. The high-frequency acoustic wave resonator according to claim 1, characterized in that: The product of the spacing between the electrode fingers of the interdigitated electrode and the anti-resonance frequency exceeds 7000 m / s; The longitudinal wave sound velocity of the supporting substrate exceeds 7000 m / s.

13. The high-frequency acoustic wave resonator according to claim 1, characterized in that: The target mode of the high-frequency acoustic wave resonator is one of a longitudinal leakage surface acoustic wave mode, a high-order horizontal shear mode, a high-order Lamb wave mode and a high-order Rayleigh mode.

14. A communication device, characterized in that: A high-frequency acoustic wave resonator comprising any one of claims 1 to 13; The communication device includes at least one of a filter, a duplexer and a multiplexer.

Images