Elastic wave device, elastic wave filter, and multiplexer

Abstract

The invention relates to an elastic wave device with high linearity, an elastic wave filter and a multiplexer, and belongs to the technical field of elastic waves. The elastic wave device comprises a supporting substrate, a Bragg reflector and a piezoelectric substrate; the Euler angle of the piezoelectric substrate is (90 degrees, 90 degrees, psi), and psi is more than or equal to 0 degree and less than or equal to 180 degrees; along a third direction, a Bragg reflector is formed above the supporting substrate, the Bragg reflector supports the piezoelectric substrate, and an electrode pattern is formed above the piezoelectric substrate; the electrode pattern includes an interdigital transducer and a plurality of reflectors, the Bragg reflector includes a plurality of low acoustic impedance portions and a plurality of high acoustic impedance layer portions, and the low acoustic impedance portions and the high acoustic impedance portions are alternately stacked along the third direction. A filter or multiplexer has a series arm resonator and a parallel arm resonator, and the series arm resonator and the parallel arm resonator include an elastic wave device. According to the invention, the high-frequency Lamb wave type elastic wave device can be obtained.

Description

Technical Field

[0001] The present invention relates to the field of radio frequency technology, in particular to elastic wave devices, elastic wave filters, and multiplexers. Background Art

[0002] The most commonly used elastic wave devices in mobile phone and base station communications include elastic wave resonators, elastic wave filters composed of multiple elastic wave resonators, elastic wave duplexers composed of multiple elastic wave filters, and elastic wave multiplexers composed of multiple elastic wave filters. In any type of elastic wave device, an electrode pattern is typically arranged on the device's piezoelectric multilayer substrate to define several interdigital transducer electrodes and reflective gate electrodes. These interdigital transducers convert electrical signals into elastic waves, leveraging the frequency characteristics of these waves to achieve bandpass filtering.

[0003] Mobile communication systems are evolving from 3G and 4G to 5G, with their frequency bands trending toward higher frequencies and wider bandwidths. Global mobile 5G network deployments already include the sub-6GHz band of 3 to 7 GHz. Piezoelectric crystal materials such as lithium niobate and lithium tantalate, currently widely used in elastic wave device fabrication, have acoustic velocities of approximately 3000 to 4000 m / s. Using existing photolithography techniques, it is difficult to fabricate devices above 3 GHz without significantly increasing costs. Furthermore, to achieve higher frequencies in elastic wave devices, the elastic wave wavelength, defined by the spacing between the interdigital transducer electrodes, can be reduced. However, at higher frequencies, the interdigital electrodes become narrower and thinner, increasing ohmic losses and reducing the device's Q. Furthermore, the electrode material is susceptible to damage, severely impacting the performance and reliability of the elastic wave device. Therefore, achieving higher acoustic velocities is crucial for achieving higher frequencies in elastic wave devices.

[0004] Lamb waves are elastic waves formed by the coupling of longitudinal waves and shear waves (transverse waves). Their speed can usually reach over 6000 m / s, making it possible to increase the frequency of elastic wave devices. However, designing a Lamb wave-type elastic wave device with high frequency, large bandwidth, low loss and simple preparation process has become an urgent problem to be solved. Summary of the Invention

[0005] This invention provides an elastic wave device, an elastic wave filter, and a multiplexer, aiming to partially or completely address the existing technical problem of designing a Lamb wave elastic wave device with high frequency, wide bandwidth, low loss, and simple fabrication process. To achieve these objectives, this invention employs the following technical solutions:

[0006] In a first aspect, an elastic wave device includes:

[0007] Support substrate, Bragg reflector and piezoelectric substrate;

[0008] The Euler angles of the piezoelectric substrate are (90°, 90°, ψ), 0°≤ψ≤180°;

[0009] Along the third direction, a Bragg reflector is formed above the supporting substrate, the Bragg reflector supports the piezoelectric substrate, and an electrode pattern is formed above the piezoelectric substrate;

[0010] The electrode pattern includes an interdigital transducer and multiple reflectors. The interdigital transducer includes multiple first electrode fingers and multiple second electrode fingers arranged alternately along a first direction. The reflector includes multiple reflector electrode fingers, a third bus bar and a fourth bus bar. Along the second direction, the first bus bar and the second bus bar are opposite to each other, and the third bus bar and the fourth bus bar are opposite to each other. Multiple first electrode fingers are all connected to the first bus bar, multiple second electrode fingers are all connected to the second bus bar, and multiple reflector electrode fingers are all connected to the third bus bar and the fourth bus bar. The Bragg reflector includes multiple low acoustic impedance portions and multiple high acoustic impedance layer portions. Along the third direction, the low acoustic impedance portions and the high acoustic impedance portions are alternately stacked.

[0011] Optionally, the wavelength of the elastic wave is λ, and along the third direction, when the material of the electrode pattern is aluminum, the thickness of the electrode pattern is 4%λ to 6%λ; or, when the material of the electrode pattern is copper, the thickness of the electrode pattern is 1%λ to 3%λ.

[0012] Optionally, the material of the piezoelectric substrate is lithium niobate; and / or, the Euler angle of the piezoelectric substrate is (90°, 90°, 37°); and / or, the low acoustic impedance portion includes one or more of silicon dioxide and silicon oxycarbide; and the high acoustic impedance portion includes one or more of tungsten, tantalum oxide, and hafnium oxide.

[0013] Optionally, the piezoelectric substrate is a lithium niobate film with a thickness of 284 nm along the third direction and an Euler angle of (90°, 90°, 37°); when the material of the electrode pattern is aluminum, the thickness of the electrode pattern along the third direction is 6%λ; the supporting substrate is a lithium niobate film with a thickness of 500 μm along the third direction and an Euler angle of (90°, 90°, 37°); the Bragg reflector includes three low acoustic impedance parts and two high acoustic impedance parts, and along the third direction, the three low acoustic impedance parts are, from top to bottom, respectively: silicon dioxide with a thickness of 344 nm, silicon dioxide with a thickness of 360 nm, and silicon dioxide with a thickness of 360 nm; along the third direction, the two high acoustic impedance parts are, from top to bottom, respectively: tantalum oxide with a thickness of 280 nm and tantalum oxide with a thickness of 280 nm.

[0014] In a second aspect, an elastic wave filter includes:

[0015] substrate layer, piezoelectric layer, Bragg reflector layer, multiple pad electrodes and conductive film pattern;

[0016] The Euler angles of the piezoelectric layer are (90°, 90°, ψ), 0°≤ψ≤180°;

[0017] Along the third direction, the Bragg reflector layer is arranged between the substrate layer and the piezoelectric layer, and the conductive film pattern and a plurality of pad electrodes are formed above the piezoelectric layer;

[0018] The conductive film pattern includes at least one series resonator and at least one parallel resonator, and the at least one series resonator is electrically connected to the at least one parallel resonator;

[0019] The conductive film pattern is connected to a plurality of pad electrodes, and the plurality of pad electrodes correspondingly form an input terminal, an output terminal and at least two ground terminals;

[0020] The Bragg reflector layer includes multiple low acoustic impedance layers and multiple high acoustic impedance layers. Along the third direction, the low acoustic impedance layers and the high acoustic impedance layers are alternately stacked, satisfying: λ2>λ1, λ1 is the wavelength of the series resonator, and λ2 is the wavelength of the parallel resonator.

[0021] Optionally, along the third direction, the low acoustic impedance layer has a thickness of h1 and the high acoustic impedance layer has a thickness of h2, satisfying: h1+h2<1 / 2×(λ1+λ2).

[0022] Optionally, the material of the piezoelectric layer is lithium niobate; and / or, the Euler angle of the piezoelectric layer is (90°, 90°, 37°); and / or, the low acoustic impedance layer includes one or more of silicon dioxide and silicon oxycarbide; and the high acoustic impedance layer includes one or more of tungsten, tantalum oxide, and hafnium oxide.

[0023] Optionally, the series resonator and the parallel resonator each include an interdigital transducer and a plurality of reflectors, the interdigital transducer including a plurality of first electrode fingers and a plurality of second electrode fingers alternately arranged along a first direction, and the reflector including a plurality of reflector electrode fingers, a third bus bar, and a fourth bus bar; along the second direction, the first bus bar and the second bus bar are opposite to each other, and the third bus bar and the fourth bus bar are opposite to each other; the plurality of first electrode fingers are all connected to the first bus bar, the plurality of second electrode fingers are all connected to the second bus bar, and the plurality of reflector electrode fingers are all connected to the third bus bar and the fourth bus bar;

[0024] Optionally, the wavelength λ of the elastic wave is 1.6μm, the piezoelectric layer is a lithium niobate film with a thickness of 284nm along the third direction, and the Euler angle is (90°, 90°, 37°); when the material of the electrode pattern is aluminum, the thickness of the electrode pattern is 6%λ along the third direction; the supporting substrate is a lithium niobate film with a thickness of 500μm along the third direction, and the Euler angle is (90°, 90°, 37°); the Bragg reflector includes three low acoustic impedance parts and two high acoustic impedance parts, and along the third direction, the three low acoustic impedance parts are, from top to bottom: silicon dioxide with a thickness of 344nm, silicon dioxide with a thickness of 360nm, and silicon dioxide with a thickness of 360nm; along the third direction, the two high acoustic impedance parts are, from top to bottom: tantalum oxide with a thickness of 280nm and tantalum oxide with a thickness of 280nm.

[0025] In a third aspect, a multiplexer is provided, comprising at least one filter device, wherein at least one filter device is the elastic wave filter described in any one of the second aspects.

[0026] In summary, the present invention has the following beneficial technical effects:

[0027] (1) In the present invention application, the wavelength (1.6 μm) of the elastic wave device is suitable, and the operating frequency band can reach above 3 GHz without increasing the difficulty of preparation, meeting the needs of 5G communication; the electromechanical coupling coefficient is increased to above 15%, greatly enhancing the energy conversion efficiency and signal bandwidth; the clutter response is relatively small, and the amplitude is generally less than 10 dB or far away from the main resonant mode.

[0028] (2) In the present invention application, the elastic wave filter can meet the design requirements of the 5G communication frequency band for high-frequency and large-bandwidth devices; the loss of the filter is within a controllable range, effectively reducing the attenuation of the device to the signal; and the preparation process of the filter is relatively simple.

[0029] Description of the accompanying drawings

[0030] Figure 1 is a schematic structural diagram of an elastic wave device 200 according to an embodiment of the present invention;

[0031] Figure 2 This is a comparison diagram of admittance-frequency curves of elastic wave devices 200 with different electrode pattern thicknesses according to an embodiment of the present invention;

[0032] Figure 3 is a comparison diagram of admittance-frequency curves of another elastic wave device 200 with different electrode pattern thicknesses according to an embodiment of the present invention;

[0033] Figure 4This is a comparison diagram of admittance / conductance-frequency curves of an elastic wave device 200 made of different electrode pattern materials according to an embodiment of the present invention;

[0034] Figure 5 is a graph showing the variation of the electromechanical coupling coefficient of the elastic wave device 200 according to an embodiment of the present invention with the propagation angle ψ;

[0035] Figure 6 is a graph showing the admittance / conductance versus frequency of an elastic wave device 200 according to an embodiment of the present invention;

[0036] Figure 7 1 is a schematic structural diagram of an elastic wave filter 300 according to an embodiment of the present invention;

[0037] Figure 8 This is a schematic diagram of the electrical connection principle of an elastic wave filter 300 according to an embodiment of the present invention;

[0038] Figure 9 This is an insertion loss-frequency curve of an elastic wave filter 300 according to an embodiment of the present invention;

[0039] Figure 10 FIG. 4 is an insertion loss-frequency curve of another elastic wave filter 300 according to the present invention. DETAILED DESCRIPTION

[0040] The following will be combined with the 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 the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0041] Among them, the same parts are represented by the same figure marks. It should be noted that the words "front", "rear", "left", "right", "up" and "down" used in the following description refer to the directions in the drawings of the present application specification, and the words "bottom" and "top", "inside" and "outside" refer to directions toward or away from specific parts, respectively. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present application specification, the meaning of "multiple" is two or more. The present application is further explained below in conjunction with the drawings and embodiments.

[0042] First, as Figure 1 As shown, the present invention provides an elastic wave device 200, comprising:

[0043] A supporting substrate 7, a Bragg reflector 8, and a piezoelectric substrate 1, wherein the Bragg reflector 8 is formed on the supporting substrate 7 along the third direction, and the Bragg reflector 8 supports the piezoelectric substrate 1, and an electrode pattern is formed on the piezoelectric substrate 1;

[0044] The electrode pattern includes an interdigital transducer and multiple reflectors. The interdigital transducer includes multiple first electrode fingers 2a1 and multiple second electrode fingers 2a2 arranged alternately along a first direction, and the reflector includes multiple reflector electrode fingers 2b, a third bus bar 4b1 and a fourth bus bar 4b2; along the second direction, the first bus bar 4a1 and the second bus bar 4a2 are opposite to each other, and the third bus bar 4b1 and the fourth bus bar 4b2 are opposite to each other; multiple first electrode fingers 2a1 are all connected to the first bus bar 4a1, multiple second electrode fingers 2a2 are all connected to the second bus bar 4a2, and multiple reflector electrode fingers 2b are all connected to the third bus bar 4b1 and the fourth bus bar 4b2; the Bragg reflector 8 includes multiple low acoustic impedance portions 5 and multiple high acoustic impedance layer portions 6, and along the third direction, the low acoustic impedance portions 5 and the high acoustic impedance portions 6 are alternately stacked.

[0045] In some embodiments, the first direction can be the arrangement direction of the first electrode finger 2a1 or the second electrode finger 2a2, the first direction can also be the x-axis direction, the x-axis direction is also the propagation direction of the elastic wave, the second direction can be the extension direction of the first electrode finger 2a1 or the second electrode finger 2a2, the second direction can also be the y-axis direction, the third direction can be the height direction of the elastic wave device, the third direction can also be the z-axis direction, the first direction, the second direction, and the third direction intersect with each other, preferably, the first direction, the second direction, and the third direction are perpendicular to each other.

[0046] In some embodiments, the material of the electrode pattern may be copper or aluminum, the low acoustic impedance portion 5 includes one or more of silicon dioxide and silicon oxycarbide, and the high acoustic impedance portion 6 includes one or more of tungsten, tantalum oxide, and hafnium oxide.

[0047] In some embodiments, the material of piezoelectric substrate 1 is lithium niobate, lithium tantalate, gallium nitride, aluminum nitride, zinc oxide, or the like. Piezoelectric substrate 1 generally includes a front surface and a back surface corresponding to the front surface. Cutting is typically performed to align the front and back crystal axes of piezoelectric substrate 1. The Euler angles of piezoelectric substrate 1 not only determine the crystal orientation but also affect the propagation speed and mode of elastic waves. The definition and setting of the Euler angles of piezoelectric substrate 1 are common knowledge in the field of elastic wave device technology and are not specifically limited in the present application. In the present application, the Euler angles of piezoelectric substrate 1 can be set to (90°, 90°, ψ), with 0°≤ψ≤180°.

[0048] Optionally, the wavelength λ of the elastic wave is 1.6 μm, and along the third direction, when the material of the electrode pattern is aluminum, the thickness of the electrode pattern is 4%λ to 6%λ; or, when the material of the electrode pattern is copper, the thickness of the electrode pattern is 1%λ to 3%λ.

[0049] In the present application, Figure 2 As shown in the figure, a comparison of the admittance-frequency curves of the elastic wave device 200 with different electrode pattern thicknesses is shown. The wavelength λ of the elastic wave is 1.6μm, the material of the electrode pattern is aluminum, and the thicknesses are 12%λ, 10%λ, 8%λ, 6%λ, and 4%λ, respectively. It can be seen that when the electrode pattern is aluminum and the thickness is 4%λ~6%λ, the impedance characteristics of the elastic wave device are better, which is specifically manifested in a larger electromechanical coupling coefficient and a smaller clutter response.

[0050] In the present application, Figure 3 As shown in the figure, a comparison of the admittance-frequency curves of the elastic wave device 200 with different electrode pattern thicknesses is shown. The wavelength λ of the elastic wave is 1.6μm, the material of the electrode pattern is copper, and the thicknesses are 1%λ, 2%λ, and 3%, respectively. It can be seen that when the electrode pattern is copper and the thickness is 1%λ~3%λ, the impedance characteristics of the elastic wave device are better, specifically manifested in a larger electromechanical coupling coefficient and a smaller clutter response.

[0051] In the present application, Figure 4 As shown in the figure, a comparison of the admittance / conductance-frequency curves of elastic wave devices 200 made with different electrode pattern materials shows that, for an elastic wave wavelength λ of 1.6 μm, the electrode pattern thickness is 6%λ when made of aluminum, and 3%λ when made of copper. It can be seen that the impedance characteristics of elastic wave devices 200 are relatively good regardless of whether the electrode pattern is made of aluminum or copper. This allows for flexible selection of different electrode pattern materials to address diverse design requirements in subsequent designs.

[0052] Optionally, the material of the piezoelectric substrate 1 is lithium niobate, and the Euler angles are (90°, 90°, 37°).

[0053] In the present application, Figure 5 As shown in the curve graph of the electromechanical coupling coefficient of the elastic wave device 200 changing with the propagation angle ψ, it can be seen that the electromechanical coupling coefficient of the elastic wave device 200 shows a trend of first increasing and then decreasing with the propagation angle ψ. When the propagation angle ψ is 37°, the electromechanical coupling coefficient of the elastic wave device 200 reaches its maximum.

[0054] Optionally, the piezoelectric substrate 1 is a lithium niobate film with a thickness of 284 nm along the third direction and an Euler angle of (90°, 90°, 37°); when the material of the electrode pattern is aluminum, the thickness of the electrode pattern along the third direction is 6%λ; the supporting substrate 7 is a lithium niobate film with a thickness of 500 μm along the third direction and an Euler angle of (90°, 90°, 37°); the Bragg reflector 8 includes three low acoustic impedance parts 5 and two high acoustic impedance parts 6, and along the third direction, the three low acoustic impedance parts 5 are, from top to bottom, respectively: silicon dioxide with a thickness of 344 nm, silicon dioxide with a thickness of 360 nm, and silicon dioxide with a thickness of 360 nm; along the third direction, the two high acoustic impedance parts 6 are, from top to bottom, respectively: tantalum oxide with a thickness of 280 nm and tantalum oxide with a thickness of 280 nm.

[0055] In the present application, along the third direction, three low acoustic impedance parts 5 and two high acoustic impedance parts 6 are alternately stacked, as shown in FIG. Figure 6 As shown in the admittance / conductance-frequency curve of elastic wave device 200, it can be seen that the main mode of elastic wave device 200 has a resonant frequency of 3630 MHz and an antiresonant frequency of 4015 MHz, the main mode is S0, and the electromechanical coupling coefficient is 23.7%. In addition, elastic wave device 200 has a weak spurious response and excellent impedance characteristics.

[0056] The elastic wave device applied for in the present invention has achieved significant technical effects: the wavelength of the elastic wave device (1.6μm) is suitable, and the operating frequency band can reach above 3GHz without increasing the difficulty of preparation, meeting the needs of 5G communication; the electromechanical coupling coefficient is increased to more than 15%, greatly enhancing the energy conversion efficiency and signal bandwidth; the clutter response is relatively small, and the amplitude is generally less than 10dB or far away from the main resonant mode.

[0057] Second, as Figure 7 As shown, the present invention provides an elastic wave filter 300, comprising: a substrate layer 37, a piezoelectric layer 31, a Bragg reflector layer 38, a plurality of pad electrodes and a conductive film pattern; along a third direction, the Bragg reflector layer 38 is arranged between the substrate layer 37 and the piezoelectric layer 31, and the conductive film pattern and a plurality of pad electrodes are formed above the piezoelectric layer 31; the conductive film pattern includes at least one series resonator and at least one parallel resonator, and the at least one series resonator is electrically connected to the at least one parallel resonator, and the conductive film pattern is connected to the plurality of pad electrodes; the plurality of pad electrodes correspondingly form an input terminal, an output terminal and at least two ground terminals; the Bragg reflector layer 38 includes a plurality of low acoustic impedance layers 35 and a plurality of high acoustic impedance layers 36, and along the third direction, the low acoustic impedance layers 35 and the high acoustic impedance layers 36 are alternately stacked to satisfy: λ2>λ1, where λ1 is the wavelength of the series resonator and λ2 is the wavelength of the parallel resonator.

[0058] In some embodiments, the substrate layer 37 can be the same as the technical issues, technical contents, and technical effects of the supporting substrate 7 recorded in the first aspect, the piezoelectric layer 31 can be the same as the technical issues, technical contents, and technical effects of the piezoelectric substrate 1 recorded in the first aspect, the Bragg reflector layer 38 can be the same as the technical issues, technical contents, and technical effects of the Bragg reflector 8 recorded in the first aspect, the low acoustic impedance layer 35 and the high acoustic impedance layer 36 can be the same as the technical issues, technical contents, and technical effects of the low acoustic impedance part 5 and the high acoustic impedance part 6 recorded in the first aspect, respectively, and the present invention application will not repeat them again.

[0059] In some embodiments, the series resonator can be the same as the technical issues, technical content, and technical effects of the electrode pattern recorded in the first aspect, and the parallel resonator can be the same as the technical issues, technical content, and technical effects of the electrode pattern recorded in the first aspect, that is, the series resonator and the parallel resonator both include the same interdigital transducer and multiple reflectors as recorded in the first aspect, and the present invention application will not repeat them again.

[0060] In some embodiments, as Figure 7 、 Figure 8 As shown, the conductive film pattern includes three series resonators and three parallel resonators. The three series resonators are the first series resonator S1, the second series resonator S2 and the third series resonator S3, respectively. The three parallel resonators are the first parallel resonator P1, the second parallel resonator P2 and the third parallel resonator P3, respectively. The four pad electrodes are the first welding electrode 315, the second pad electrode 316, the third pad electrode 317 and the fourth pad electrode 318, respectively. The first pad electrode 315 corresponds to the ground terminal GND (also known as the first ground terminal), the second pad electrode 316 corresponds to the output terminal OUT, the third pad electrode 317 corresponds to the input terminal IN, and the fourth pad electrode 318 corresponds to the ground terminal GND (also known as the second ground terminal).

[0061] In some embodiments, as Figure 7 、 Figure 8 As shown, the three series resonators are electrically connected to the three parallel resonators, and the conductive film pattern is connected to the four pad electrodes, correspondingly: the first parallel resonator P1 is connected to the first series resonator S1, and the first parallel resonator P1 is connected to the first pad electrode 315 and the third pad electrode 317; the second parallel resonator P2 is connected to the first series resonator S1 and the second series resonator S2; the third parallel resonator P3 is connected to the second series resonator S2 and the third series resonator S3, and the third parallel resonator P3 is connected to the fourth pad electrode 318; the first series resonator S1 is connected to the first pad electrode 315, and the third series resonator S3 is connected to the second pad electrode 316.

[0062] In some embodiments, as Figure 7 、 Figure 8 As shown, the three series resonators are electrically connected to the three parallel resonators to form a conductive track 319. The number and distribution of the conductive tracks 319 are set according to the number and distribution of the pad electrodes and the resonators.

[0063] In the present application, Figure 9 As shown in the insertion loss-frequency curve of the elastic wave filter 300, the applicable frequency band of the elastic wave filter 300 is the N78 band (3300MHz~3800MHz), and the bandwidth is 500MHz, thereby obtaining a Lamb wave elastic wave device with high frequency, large bandwidth, low loss and simple preparation process.

[0064] Optionally, along the third direction, the low acoustic impedance layer 35 has a thickness of h1 and the high acoustic impedance layer 36 has a thickness of h2, satisfying h1+h2<1 / 2×(λ1+λ2).

[0065] In the present application, when the thickness of the low acoustic impedance layer 35 is h1 and the thickness of the high acoustic impedance layer 36 is h2 along the third direction, and h1+h2>1 / 2×(λ1+λ2), as Figure 10 As shown in the insertion loss-frequency curve of the elastic wave filter 300 , the in-band insertion loss of the elastic wave filter 300 is significantly increased, and the in-band jitter is relatively large.

[0066] The elastic wave filter applied for in the present invention has achieved significant technical effects: the elastic wave filter can meet the design requirements of the 5G communication frequency band for high-frequency and large-bandwidth devices; the loss of the filter is within a controllable range, effectively reducing the attenuation of the device to the signal; and the preparation process of the filter is relatively simple.

[0067] According to a third aspect, a multiplexer includes a series arm resonator and a parallel arm resonator, wherein the series arm resonator and the parallel arm resonator include the elastic wave device according to any one of the first aspects.

[0068] In some embodiments, a filter or a multiplexer comprises a series arm resonator and a parallel arm resonator, wherein the series arm resonator and the parallel arm resonator comprise any elastic wave device described in the first aspect.

[0069] The above description is merely a preferred embodiment of the present invention, and the present invention is not limited to the above embodiments. It is understood that other improvements and variations directly derived or imagined by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included in the scope of protection of the present invention.

[0070] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes may be made to the form and details without departing from the spirit and scope of the present invention as defined in the appended claims.

Claims

1. An elastic wave device, characterized in that: include: Support substrate, Bragg reflector and piezoelectric substrate; The Euler angles of the piezoelectric substrate are (90°, 90°, ψ), 0°≤ψ≤180°; Along the third direction, a Bragg reflector is formed above the supporting substrate, the Bragg reflector supports the piezoelectric substrate, and an electrode pattern is formed above the piezoelectric substrate; The electrode pattern includes an interdigital transducer and multiple reflectors. The interdigital transducer includes multiple first electrode fingers and multiple second electrode fingers arranged alternately along a first direction. The reflector includes multiple reflector electrode fingers, a third bus bar and a fourth bus bar. Along the second direction, the first bus bar and the second bus bar are opposite to each other, and the third bus bar and the fourth bus bar are opposite to each other. Multiple first electrode fingers are all connected to the first bus bar, multiple second electrode fingers are all connected to the second bus bar, and multiple reflector electrode fingers are all connected to the third bus bar and the fourth bus bar. The Bragg reflector includes multiple low acoustic impedance portions and multiple high acoustic impedance layer portions. Along the third direction, the low acoustic impedance portions and the high acoustic impedance portions are alternately stacked.

2. The elastic wave device according to claim 1, wherein: The wavelength of the elastic wave is λ. Along the third direction, when the material of the electrode pattern is aluminum, the thickness of the electrode pattern is 4%λ to 6%λ; or, when the material of the electrode pattern is copper, the thickness of the electrode pattern is 1%λ to 3%λ.

3. The elastic wave device according to claim 1, wherein: The material of the piezoelectric substrate is lithium niobate; and / or the Euler angle of the piezoelectric substrate is (90°, 90°, 37°); and / or the low acoustic impedance portion includes one or more of silicon dioxide and silicon oxycarbide; and the high acoustic impedance portion includes one or more of tungsten, tantalum oxide, and hafnium oxide.

4. An elastic wave device according to claim 1, wherein the piezoelectric substrate is a lithium niobate thin film with a thickness of 284 nm along the third direction and Euler angles of (90°, 90°, 37°); when the electrode pattern is made of aluminum, the thickness of the electrode pattern along the third direction is 6%λ; the supporting substrate is a lithium niobate thin film with a thickness of 500 μm along the third direction and Euler angles of (90°, 90°, 37°); the Bragg reflector includes three low acoustic impedance portions and two high acoustic impedance portions, wherein along the third direction, the three low acoustic impedance portions are, from top to bottom, 344 nm thick silicon dioxide, 360 nm thick silicon dioxide, and 360 nm thick silicon dioxide; and the two high acoustic impedance portions are, from top to bottom, 280 nm thick tantalum oxide and 280 nm thick tantalum oxide.

5. An elastic wave filter, characterized in that: include: substrate layer, piezoelectric layer, Bragg reflector layer, multiple pad electrodes and conductive film pattern; The Euler angles of the piezoelectric layer are (90°, 90°, ψ), 0°≤ψ≤180°; Along the third direction, the Bragg reflector layer is arranged between the substrate layer and the piezoelectric layer, and the conductive film pattern and a plurality of pad electrodes are formed above the piezoelectric layer; The conductive film pattern includes at least one series resonator and at least one parallel resonator, and the at least one series resonator is electrically connected to the at least one parallel resonator; The conductive film pattern is connected to a plurality of pad electrodes, and the plurality of pad electrodes correspondingly form an input terminal, an output terminal and at least two ground terminals; The Bragg reflector layer includes a plurality of low acoustic impedance layers and a plurality of high acoustic impedance layers. The low acoustic impedance layers and the high acoustic impedance layers are alternately stacked along the third direction to meet the following requirements: λ2>λ1, λ1 is the wavelength of the series resonator, and λ2 is the wavelength of the parallel resonator.

6. The elastic wave filter according to claim 5, characterized in that: Along the third direction, the thickness of the low acoustic impedance layer is h1, and the thickness of the high acoustic impedance layer is h2, satisfying: h1+h2<1 / 2×(λ1+λ2).

7. The elastic wave filter according to claim 6, characterized in that: The material of the piezoelectric layer is lithium niobate; and / or the Euler angle of the piezoelectric layer is (90°, 90°, 37°); and / or the low acoustic impedance layer includes one or more of silicon dioxide and silicon oxycarbide; and the high acoustic impedance layer includes one or more of tungsten, tantalum oxide, and hafnium oxide.

8. The elastic wave filter according to claim 6, characterized in that: Both the series resonator and the parallel resonator include an interdigital transducer and multiple reflectors. The interdigital transducer includes multiple first electrode fingers and multiple second electrode fingers arranged alternately along a first direction. The reflector includes multiple reflector electrode fingers, a third bus bar and a fourth bus bar. Along the second direction, the first bus bar and the second bus bar are opposite to each other, and the third bus bar and the fourth bus bar are opposite to each other. Multiple first electrode fingers are connected to the first bus bar, multiple second electrode fingers are connected to the second bus bar, and multiple reflector electrode fingers are connected to the third bus bar and the fourth bus bar.

9. The elastic wave filter according to claim 6, characterized in that: The wavelength λ of the elastic wave is 1.6 μm. The piezoelectric layer is a lithium niobate film with a thickness of 284 nm along the third direction and an Euler angle of (90°, 90°, 37°). When the material of the electrode pattern is aluminum, the thickness of the electrode pattern along the third direction is 6% λ. The supporting substrate is a lithium niobate film with a thickness of 500 μm along the third direction and an Euler angle of (90°, 90°, 37°). The Bragg reflector includes three low acoustic impedance parts and two high acoustic impedance parts. Along the third direction, the three low acoustic impedance parts are, from top to bottom, 344 nm thick silicon dioxide, 360 nm thick silicon dioxide, and 360 nm thick silicon dioxide. Along the third direction, the two high acoustic impedance parts are, from top to bottom, 280 nm thick tantalum oxide and 280 nm thick tantalum oxide. 10 . A multiplexer, comprising at least one filter device, wherein the at least one filter device is the elastic wave filter according to claim 6 .

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