Substrate structure and method of manufacturing the same, filter, duplexer

Abstract

The application discloses a substrate structure, a preparation method thereof, a filter and a duplexer, and relates to the technical field of filters.The substrate structure comprises a support substrate and a piezoelectric substrate located on the support substrate; wherein the material of the support substrate is a polycrystalline material, and the porosity of the support substrate is less than 0.0045% or greater than 0.6%. The substrate structure can effectively improve the generation of interference noise and improve the working performance of a device.

Description

Technical Field

[0001] This disclosure relates to the field of filter technology, and more specifically, to a substrate structure and its fabrication method, a filter, and a duplexer. Background Technology

[0002] Surface acoustic wave (SAW) filters are widely used in various communication devices. In future communication applications, in order to adapt to various harsher external environments, it is urgent to improve the working stability of SAW filters. However, traditional SAW filters have the characteristics of low Q value (<1000), low operating frequency, and frequency drift with changes in operating temperature. They are no longer able to meet the requirements of RF terminals in the 5G era, where frequency bands are becoming increasingly crowded. Therefore, traditional SAW filters must be developed into temperature-compensated filters with high frequency and stable temperature characteristics.

[0003] The key to transforming traditional surface acoustic wave (SAW) filters into temperature-compensated filters lies in adding a support layer to the simple piezoelectric layer structure. Adding a support layer effectively reduces the thickness of the piezoelectric layer, improving the device's Q-factor. Furthermore, the support layer's superior coefficient of thermal expansion effectively mitigates temperature-induced frequency drift. However, existing temperature-compensated filter devices typically use high-density, high-velocity acoustic materials for their support layers, inevitably generating significant interference noise while improving temperature drift characteristics. Summary of the Invention

[0004] The purpose of this invention is to provide a substrate structure and its fabrication method, a filter, and a duplexer. This substrate structure and its fabrication method, the filter, and the duplexer can effectively reduce the generation of interference noise and improve the operating performance of the device.

[0005] The embodiments of this disclosure are implemented as follows:

[0006] In one aspect, this disclosure provides a substrate structure including a support substrate and a piezoelectric substrate located on the support substrate; wherein the support substrate is made of a polycrystalline material, and the porosity of the support substrate is less than 0.0045% or greater than 0.6%. This substrate structure can effectively reduce the generation of interference noise and improve the operating performance of the device.

[0007] Optionally, the porosity of the support substrate is greater than 0.65%.

[0008] Optionally, the porosity of the support substrate is greater than 0.65% and less than 1.5%.

[0009] Optionally, the number of grain boundary layers supporting the substrate is greater than or equal to 3.

[0010] Optionally, the number of grain boundary layers is less than or equal to 40.

[0011] Optionally, the support substrate includes a plurality of grains, and the average grain size is between 2 μm and 60 μm.

[0012] Optionally, the material of the support substrate is any one of polycrystalline spinel, polycrystalline sapphire, polycrystalline silicon, polycrystalline quartz, and polycrystalline aluminum nitride.

[0013] Optionally, the support substrate includes a plurality of grains, the average grain size of which is less than or equal to one-third of the thickness of the support substrate.

[0014] Optionally, the thickness of the piezoelectric substrate is between 0.1 μm and 10 μm.

[0015] In another aspect of this disclosure, a method for preparing a substrate structure is provided, the method comprising: providing a support substrate, the support substrate being made of a polycrystalline material and having a porosity of less than 0.0045% or greater than 0.6%; and bonding a piezoelectric substrate onto the support substrate to obtain the substrate structure.

[0016] Optionally, a piezoelectric substrate is bonded to a support substrate to obtain a substrate structure, including: bonding the piezoelectric substrate to the support substrate; thinning and polishing the side of the piezoelectric substrate away from the support substrate so that the thickness of the piezoelectric substrate is less than 10 μm; and thinning and polishing the side of the support substrate away from the piezoelectric substrate so that the thickness of the support substrate is less than 400 μm to obtain a substrate structure.

[0017] In another aspect of this disclosure, a filter is provided, the filter including a substrate structure and electrodes disposed on the substrate structure.

[0018] In another aspect of this disclosure, a duplexer is provided, comprising a transmit filter and a receive filter, wherein the transmit filter and / or the receive filter employs the filters described above.

[0019] The beneficial effects of this disclosure include:

[0020] The substrate structure provided in this application includes a support substrate and a piezoelectric substrate located on the support substrate; wherein, the support substrate is made of a polycrystalline material, and the porosity of the support substrate is less than 0.0045% or greater than 0.6%. By selecting a polycrystalline material for the support substrate and making the porosity of the support substrate less than 0.0045% or greater than 0.6%, the pores and grain boundaries in the polycrystalline material can absorb and attenuate the scattering of sound waves, thereby allowing the surface acoustic waves to be consumed during their transmission to the interior or lower surface of the support substrate. This significantly reduces the sound waves reflected back to the upper surface, thereby reducing noise and improving the operating performance of the device. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this disclosure and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the substrate structure provided in some embodiments of the present disclosure;

[0023] Figure 2 This is one of the structural schematic diagrams of the support substrate provided in some embodiments of this disclosure;

[0024] Figure 3 This is a second schematic diagram of the structure of the support substrate provided in some embodiments of this disclosure;

[0025] Figure 4 This is the third schematic diagram of the structure of the support substrate provided in some embodiments of this disclosure;

[0026] Figure 5 Fourth schematic diagram of the structure of the support substrate provided in some embodiments of this disclosure;

[0027] Figure 6 Fifth of some embodiments of the present disclosure, showing the structure of the support substrate;

[0028] Figure 7 This is the sixth schematic diagram of the structure of the support substrate provided in some embodiments of this disclosure;

[0029] Figure 8 A schematic diagram illustrating noise measurement methods provided in some embodiments of this disclosure;

[0030] Figure 9 This is one of the schematic flowcharts of a method for fabricating a substrate structure provided in some embodiments of this disclosure;

[0031] Figure 10 This is a second schematic flowchart illustrating a method for fabricating a substrate structure according to some embodiments of this disclosure.

[0032] Figure 11 This is a schematic diagram of the structure of a filter provided in some embodiments of this disclosure.

[0033] Icons: 10 - Support substrate; 20 - Piezoelectric substrate; 30 - Electrode; T - Thickness of support substrate; D - Grain size. Detailed Implementation

[0034] The embodiments described below represent the information necessary for those skilled in the art to practice the embodiments and illustrate the best mode for practicing the embodiments. After reading the following description with reference to the accompanying drawings, those skilled in the art will understand the concepts of this disclosure and will recognize the application of these concepts not specifically set forth herein. It should be understood that these concepts and applications fall within the scope of this disclosure and the appended claims.

[0035] It should be understood that while the terms first, second, etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, without departing from the scope of this disclosure, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0036] It should be understood that when an element (such as a layer, region, or substrate) is referred to as "on another element" or "extending to another element," it may be directly on or directly extended to the other element, or there may be an intermediate element. Conversely, when an element is referred to as "directly on another element" or "directly extending to another element," there is no intermediate element. Similarly, it should be understood that when an element (such as a layer, region, or substrate) is referred to as "above another element" or "extending above another element," it may be directly on or directly extended to the other element, or there may be an intermediate element. Conversely, when an element is referred to as "directly on another element" or "extending directly to another element," there is no intermediate element. It should also be understood that when an element is referred to as "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or there may be an intermediate element. Conversely, when an element is referred to as "directly connected" or "directly coupled" to another element, there is no intermediate element.

[0037] Related terms such as “below”, “above”, “upper”, “lower”, “horizontal”, or “vertical” are used herein to describe the relationship of one element, layer, or region to another, as illustrated in the figures. It should be understood that these terms, and those discussed above, are intended to cover different orientations of the device other than those depicted in the figures.

[0038] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that, when used herein, the term “comprising” indicates the presence of the stated feature, integer, step, operation, element, and / or component, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups of the foregoing.

[0039] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It should also be understood that the terms used herein should be interpreted as having the same meaning as they would in the context of this specification and the relevant field, and not in an idealized or overly formal sense, unless expressly defined herein.

[0040] Existing temperature-compensated filter devices typically add a support structure to the piezoelectric layer. However, existing support structures usually use high-density, high-velocity materials, which can lead to a significant amount of noise during device operation. To address this issue, this application provides a novel substrate structure with a special polycrystalline structure. Filters using this substrate structure can not only fulfill the basic functions of a filter but also improve noise reduction.

[0041] The following application will describe and explain in detail the specific structure of the new substrate.

[0042] Please refer to Figure 1 The substrate structure provided in this embodiment includes a support substrate 10 and a piezoelectric substrate 20 located on the support substrate 10; wherein, the support substrate 10 is made of a polycrystalline material, and the porosity of the support substrate 10 is less than 0.0045% or greater than 0.6%. This substrate structure can effectively improve the generation of interference noise and enhance the operating performance of the device.

[0043] The material of the support substrate 10 is a polycrystalline material. For example, the polycrystalline material can be any one of polycrystalline spinel, polycrystalline sapphire, polycrystalline silicon, polycrystalline quartz and polycrystalline aluminum nitride.

[0044] The piezoelectric substrate 20 mentioned above can be an LT (lithium tantalate) or LN (lithium niobate) piezoelectric substrate 20.

[0045] It should be noted that the main reason for sound wave attenuation is the absorption of sound waves by the medium. Therefore, this application selects a polycrystalline material with a certain porosity as the material for the support substrate 10. Figure 1As shown, factors such as grain boundaries and micro-region inhomogeneities (i.e., pores) in polycrystalline materials can effectively reduce the energy of longitudinal wave transmission, thereby suppressing and attenuating noise.

[0046] In this embodiment, the porosity of the support substrate 10 is less than 0.0045% or greater than 0.6%. For example, when the porosity of the support substrate 10 is less than 0.0045%, the specific porosity of the support substrate 10 can be 0.0044%, 0.0043%, 0.0040%, 0.0035%, 0.0030%, 0.0020%, or 0.0010%, etc., and will not be listed individually in this application.

[0047] When the porosity of the support substrate 10 is greater than 0.6%, the specific porosity of the support substrate 10 can be 0.65%, 0.7%, 0.8%, 1.0%, 1.1%, 1.2%, 1.3%, or 1.4%, etc. Of course, the specific values ​​of the porosity of the support substrate 10 mentioned above are merely examples and are not intended to limit the specific porosity of the support substrate 10. Those skilled in the art can select a suitable porosity as needed, as long as the porosity is less than 0.0045% or greater than 0.6%.

[0048] In this embodiment, when the porosity of the support substrate 10 is greater than 0.6%, optionally, the porosity of the support substrate 10 can be greater than 0.65%. This can more effectively suppress and attenuate the generation of noise.

[0049] To further suppress and attenuate interference noise and improve device performance, the porosity of the support substrate 10 may optionally be greater than 0.65% and less than 1.5%. For example, the porosity of the support substrate 10 may be 0.7%, 0.9%, 1.0%, 1.3%, or 1.4%, etc.

[0050] In addition, in this embodiment, optionally, the number of grain boundary layers of the supporting substrate 10 is greater than or equal to 3 layers.

[0051] It should be noted that, firstly, the material of the support substrate 10 is a polycrystalline material; therefore, the support substrate 10 contains multiple grains, such as... Figure 2 and Figure 3 As shown. Grain boundaries are the boundaries between two adjacent grain layers, corresponding to... Figure 3 middle, Figure 3 The middle layer includes three grain boundary layers (these three grain boundary layers are in Figure 3 (These are marked with black lines).

[0052] Second, since the grain boundaries and micro-regions in the medium are inhomogeneous (such as pores), sound waves can be scattered at the interface of these regions and cause energy attenuation (scattering attenuation). Compared with the pores in the support substrate 10, the number of grain boundary layers in the support substrate 10 is more ubiquitous. Therefore, the grain boundary layer can play a good role in suppressing and attenuating sound waves propagating downward from the surface of the electrode 30.

[0053] Multiple grain boundaries of the supporting substrate 10 absorb and attenuate the scattering of sound waves. Sound waves propagating from the surface acoustic wave (SAW) substrate 10 to its interior or lower surface are consumed by the grain boundaries and pores, significantly reducing the number of sound waves reflected back to the surface. Figure 1 This helps reduce noise.

[0054] Please refer to Figures 4 to 7 , Figures 4 to 7 The images show the minimum number of grain boundary layers on the supporting substrate 10: 0, 1, 2, and 3 layers. The white arrows indicate the locations with the fewest grain boundary layers in the four sample cross-sections. Furthermore, areas with fewer grain boundary layers correspond to larger grain sizes and fewer grains per unit area; the white arrows indicate the areas with the fewest grains per unit area, with 3, 4, 5, and 7 grains respectively. The characteristics of the filters fabricated using these four supporting substrates 10 are shown in the table below:

[0055]

[0056]

[0057] Please refer to the table above for the method of measuring noise. Figure 8 Filters were fabricated at 21 locations at fixed coordinates for each sample, and their characteristics were tested. If no noise was generated at any of the 21 test points, the noise yield was 100% (as shown in sample 4 in the table above). If noise appeared at one location, the noise yield was 95% based on the proportion.

[0058] Analysis of the table above shows that, apart from significant differences in noise, the four different samples exhibit largely similar characteristics. This demonstrates that the number of grain boundary layers does indeed affect noise, and the data in the table shows that a grain boundary layer count of ≥3 effectively suppresses noise generation.

[0059] Furthermore, controlling the number of grain boundaries depends on controlling the grain size of the polycrystalline substrate. If the grain size is too large, there will be fewer grain boundaries, making the fabricated filter device prone to noise. Conversely, if the grain size is too small, although more grain boundaries are added, more porosity will also increase, potentially reducing the Q value of the device while improving noise reduction. Therefore, the number of grain boundary layers cannot be increased indefinitely. For this reason, in this embodiment, optionally, the number of grain boundary layers is less than or equal to 40 layers. The specific number of grain boundary layers can be chosen by those skilled in the art based on actual conditions, and this application does not impose specific limitations.

[0060] Optionally, the support substrate 10 provided in this application includes a plurality of grains, and the average grain size is between 2 μm and 60 μm. For example, the average grain size can be 2 μm, 10 μm, 20 μm, 30 μm, 50 μm, or 60 μm, etc.

[0061] Additionally, it should be noted that in this embodiment, the grain size can be between 1 μm and 80 μm. For example, the grain size can be 1 μm, 5 μm, 20 μm, 40 μm, 50 μm, or 80 μm, etc.

[0062] It should be noted that since the average grain size is related to the thickness T of the support substrate, and the number of grain boundary layers of the support substrate 10 in this application needs to be greater than or equal to 3 layers, the average grain size should be less than or equal to one-third of the thickness T of the support substrate.

[0063] In this embodiment, optionally, the thickness of the piezoelectric substrate is between 0.1 μm and 10 μm. Preferably, the thickness of the piezoelectric substrate is between 0.5 μm and 5 μm.

[0064] Furthermore, the material of the aforementioned support substrate 10 is a polycrystalline material, and the number of grains in the support substrate 10 per unit area is greater than or equal to 6, and the number of grains in the support substrate 10 per unit area is less than or equal to 200, and the unit area is 100μm×100μm.

[0065] For example, the number of grains per unit area of ​​the support substrate 10 can be between 10 and 100. Too many grains will increase the hardness of the support substrate 10, which is detrimental to the thinning and polishing of the support substrate 10, and will also increase material loss and processing time; while too few grains, although reducing the processing difficulty of the support substrate 10, will lead to a decrease in the material strength of the support substrate 10. Therefore, preferably, the number of grains per unit area of ​​the support substrate 10 is between 10 and 30.

[0066] In summary, the substrate structure provided in this application includes a support substrate 10 and a piezoelectric substrate 20 located on the support substrate 10. The support substrate 10 is made of a polycrystalline material, and its porosity is less than 0.0045% or greater than 0.6%. By selecting a polycrystalline material for the support substrate 10 and ensuring its porosity is less than 0.0045% or greater than 0.6%, the pores and grain boundaries within the polycrystalline material can absorb and attenuate the scattering of sound waves. This allows surface acoustic waves to be consumed during their propagation into the interior or lower surface of the support substrate 10, significantly reducing the sound waves reflected back to the upper surface. This, in turn, reduces noise and improves the device's performance.

[0067] First Embodiment

[0068] Please select a polycrystalline spinel support substrate 10 with the following characteristics: the porosity of the support substrate 10 is between 1% and 1.5%, the number of grain boundary layers is greater than 10 and the average grain size is about 6 μm.

[0069] The support substrate 10 and piezoelectric substrate 20 were bonded together, and then thinned and polished to obtain a substrate structure with a piezoelectric substrate 20 thickness of 5 μm and a support substrate thickness T of 250 μm. Electrodes 30 were formed on this substrate structure to obtain a filter, and the characteristics of the filter were verified. Using the filter characteristics prepared on the support substrate 10 with a porosity between 0.0045% and 0.6% as a reference, the parameters are shown in the table below.

[0070]

[0071] Analysis of the table above shows that a porosity between 0.0045% and 0.6% still results in significant noise interference, while setting the porosity of the support substrate 10 between 1% and 1.5% can significantly improve the noise level.

[0072] Furthermore, when the porosity of the support substrate 10 is between 1% and 1.5%, the high porosity inevitably leads to a decrease in material strength. To address this, the average grain size of the support substrate 10 can be appropriately reduced. For example, a support substrate 10 with an average grain size ≤ 4 μm can be selected, so that the grain size D of most grains is between 1 μm and 2 μm. Thus, the smaller the grain size D selected, the better the mechanical properties of the material. Macroscopically, this manifests as increased yield and tensile strength, increased surface hardness, and increased fatigue life. The specific principle is that the finer the grains, the more grains per unit volume, and the more grains participate in deformation, resulting in more uniform deformation and greater plastic deformation before fracture. With both strength and plasticity increasing simultaneously, the material consumes more work before fracture, thus exhibiting better toughness.

[0073] Second Embodiment

[0074] Please select a polycrystalline spinel support substrate 10 with the following characteristics: the porosity of the support substrate 10 is between 0.65% and 1%, the number of grain boundary layers is greater than 3 (≥40 layers), and the average grain size is about 45 μm.

[0075] The support substrate 10 and piezoelectric substrate 20 were bonded together, and then thinned and polished to obtain a substrate structure with a piezoelectric substrate 20 thickness of 5 μm and a support substrate thickness T of 250 μm. Electrodes 30 were formed on this substrate structure to obtain a filter, and the characteristics of the filter were verified. Using the filter characteristics prepared on the support substrate 10 with a porosity between 0.0045% and 0.6% as a reference, the parameters are shown in the table below.

[0076]

[0077] Analysis of the table above shows that a porosity between 0.0045% and 0.6% still results in significant noise interference, while setting the porosity of the support substrate 10 to above 0.6% can significantly improve the noise level.

[0078] Third Embodiment

[0079] Please select a polycrystalline spinel support substrate 10 with the following characteristics: the porosity of the support substrate 10 is less than 0.0045%, the number of grain boundary layers is ≥10 and the average grain size is about 10μm.

[0080] The support substrate 10 and piezoelectric substrate 20 were bonded together, and then thinned and polished to obtain a substrate structure with a piezoelectric substrate 20 thickness of 5 μm and a support substrate thickness T of 250 μm. Electrodes 30 were formed on this substrate structure to obtain a filter, and the characteristics of the filter were verified. Using the filter characteristics prepared on the support substrate 10 with a porosity between 0.0045% and 0.6% as a reference, the parameters are shown in the table below.

[0081]

[0082] Analysis of the table above shows that a porosity between 0.0045% and 0.6% still results in significant noise interference, while setting the porosity of the support substrate 10 below 0.0045% can significantly improve the noise level.

[0083] The above three embodiments demonstrate that when the support substrate 10 is made of polycrystalline material, and the porosity of the polycrystalline material is selected to be less than 0.0045% or greater than 0.6%, it can significantly improve noise and thus improve the device's operating performance.

[0084] Please refer to Figure 9 In another aspect, this disclosure provides a method for fabricating a substrate structure, the method comprising:

[0085] S100. A support substrate 10 is provided, the material of the support substrate 10 is a polycrystalline material, and the porosity of the support substrate 10 is less than 0.0045% or greater than 0.6%.

[0086] S200: Bond the piezoelectric substrate 20 onto the support substrate 10 to obtain the substrate structure.

[0087] It should be noted that the material of the aforementioned support substrate 10 is a polycrystalline material. The specific type of the polycrystalline material and the specific selection of its porosity can be referred to the preceding description by those skilled in the art, and will not be repeated in this application.

[0088] Similarly, the specific material of the piezoelectric substrate 20 can be found in the preceding description. As the bonding process is well known to those skilled in the art, it will not be described further in this application.

[0089] Please refer to the reference again. Figure 10 Optionally, step S200, bonding the piezoelectric substrate 20 onto the support substrate 10 to obtain the substrate structure, includes the following steps:

[0090] S210, Bond the piezoelectric substrate 20 onto the support substrate 10.

[0091] It should be noted that, before bonding, the bonding surface of the piezoelectric substrate 20 can be polished to make its roughness below 0.3nm; similarly, the bonding surface of the support substrate 10 can also be polished before bonding to make its roughness below 0.8nm.

[0092] During bonding, bonding can be performed in a high vacuum environment at room temperature by ion activation.

[0093] S220. Thinning and polishing the side of the piezoelectric substrate 20 away from the support substrate 10 so that the thickness of the piezoelectric substrate 20 is less than 10μm.

[0094] S230. The side of the support substrate 10 facing away from the piezoelectric substrate 20 is thinned and polished so that the thickness T of the support substrate is less than 250 μm, so as to obtain the substrate structure.

[0095] Please refer to Figure 11 In another aspect, this disclosure provides a filter including a substrate structure and electrodes 30 disposed on the substrate structure.

[0096] Among them, the aforementioned electrode 30 is an interdigitated electrode 30. Since the specific structure of the substrate and its beneficial effects have been described in detail above, this application will not repeat them here.

[0097] In another aspect, this disclosure provides a duplexer comprising a transmit filter and a receive filter, wherein the transmit filter and / or the receive filter employs the filters described above. Since the specific structure and effectiveness of the filters have been described in detail above, they will not be repeated here.

[0098] The above description is merely an optional embodiment of this disclosure and is not intended to limit this disclosure. Various modifications and variations can be made to this disclosure by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.

[0099] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

Claims

1. A substrate structure, characterized in that, It includes a support substrate and a piezoelectric substrate located on the support substrate; wherein the support substrate is made of a polycrystalline material, and the porosity of the support substrate is less than 0.0045% or greater than 0.6%, and the number of grain boundary layers of the support substrate is greater than 10 layers and less than or equal to 40 layers.

2. The substrate structure according to claim 1, characterized in that, The porosity of the supporting substrate is greater than 0.65%.

3. The substrate structure according to claim 2, characterized in that, The porosity of the supporting substrate is greater than 0.65% and less than 1.5%.

4. The substrate structure according to claim 1, characterized in that, The supporting substrate includes a plurality of grains, and the average grain size of the grains is between 2 μm and 60 μm.

5. The substrate structure according to claim 1, characterized in that, The material of the supporting substrate is any one of polycrystalline spinel, polycrystalline sapphire, polycrystalline silicon, polycrystalline quartz, and polycrystalline aluminum nitride.

6. The substrate structure according to claim 1, characterized in that, The support substrate includes a plurality of grains, the average grain size of which is less than or equal to one-third of the thickness of the support substrate.

7. The substrate structure according to claim 1, characterized in that, The thickness of the piezoelectric substrate is between 0.1 μm and 10 μm.

8. A method for preparing a substrate structure, characterized in that, include: A support substrate is provided, wherein the support substrate is made of a polycrystalline material, and the porosity of the support substrate is less than 0.0045% or greater than 0.6%, and the number of grain boundary layers of the support substrate is greater than 10 layers and less than or equal to 40 layers. A piezoelectric substrate is bonded onto the support substrate to obtain a substrate structure.

9. The method for preparing the substrate structure according to claim 8, characterized in that, The bonding of the piezoelectric substrate onto the supporting substrate to obtain the substrate structure includes: A piezoelectric substrate is bonded onto the support substrate; The side of the piezoelectric substrate facing away from the supporting substrate is thinned and polished so that the thickness of the piezoelectric substrate is less than 10 μm; The side of the support substrate facing away from the piezoelectric substrate is thinned and polished to make the thickness of the support substrate less than 400 μm, so as to obtain the substrate structure.

10. A filter, characterized in that, It includes the substrate structure as described in any one of claims 1 to 7 and the electrodes disposed on the substrate structure.

11. A duplexer, characterized in that, It includes a transmit filter and a receive filter, wherein the transmit filter and / or the receive filter employs the filter described in claim 10.

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