Substrate structure, filter and duplexer

Abstract

A substrate structure and its manufacturing method, a filter, and a duplexer, which relate to the field of filter technology. The substrate structure includes a support substrate and a piezoelectric layer located on the support substrate, where the material of the support substrate is a polycrystalline material, and the porosity of the support substrate is less than 0.0045% or more than 0.6%. The substrate structure can effectively improve the generation of interference noise and improve the operating performance of the device.

Description

[Technical Field]

[0001] The present disclosure relates to the technical field of electronic devices, and more particularly to a substrate structure and its manufacturing method, a filter, and a duplexer. [Background technology]

[0002] Surface acoustic wave filters are widely used in various communication devices. In order to adapt to various more severe external environments in future communication applications, there is a strong demand for improving the operational stability of surface acoustic wave filters. Conventional surface acoustic wave filters have low Q values ​​(<1000), low operating frequencies, and frequency drift with changes in operating temperature. These characteristics make it difficult to meet the filter requirements of high-frequency terminals in the 5G era, where frequency bands will become increasingly crowded. Therefore, conventional surface acoustic wave filters must evolve into temperature-compensated filters with high frequencies and stable temperature characteristics.

[0003] warm The degree compensation filter is Generally Piezoelectric layer A temperature compensation layer is coated or bonded on the piezoelectric layer. For example, the bonding structure usually has a temperature compensation function on the piezoelectric layer. Add support layer structure and used as a temperature compensation layer Adding a support layer structure effectively reduces the thickness of the piezoelectric layer, increasing the Q value of the device, and also improves the temperature-induced frequency drift of the device because the support layer structure has a better thermal expansion coefficient. However, the support layer structure of conventional temperature-compensated filter devices is generally made of high-density, high-acoustic-speed materials, which cannot improve the device's temperature drift characteristics while avoiding the generation of a large amount of interference noise. Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a substrate structure, a manufacturing method thereof, a filter, and a duplexer that can effectively reduce interference noise and improve the operating performance of a device. [Means for solving the problem]

[0005] One aspect of the present disclosure provides a substrate structure, the substrate structure including 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 more than 0.6%, and the number of grain boundary layers of the support substrate is three or more.

[0006] In this substrate structure, the pores and grain boundaries in the polycrystalline material can both absorb and attenuate the scattering of acoustic waves, and further allow the surface acoustic waves to be consumed in the process of being transmitted to the inside or bottom surface of the supporting substrate, thereby significantly reducing the acoustic waves reflected on the top surface, effectively reducing the generation of interference noise, and improving the operating performance of the device.

[0007] Another aspect of the present disclosure provides a method for manufacturing a substrate structure, the method including: providing a 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 more than 0.6%; and bonding a piezoelectric substrate onto the support substrate to obtain the substrate structure.

[0008] Another aspect of the present invention provides a compensated substrate including 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 number of crystal grains per unit area of ​​the support substrate is 6 or more, the unit area is 100 μm×100 μm, and the number of crystal grain boundary layers is 3 or more.

[0009] The compensated substrate provided by the present disclosure effectively reduces the thickness of the piezoelectric substrate by placing a support substrate under the piezoelectric substrate, increasing the filter's Q value and achieving a technological improvement over conventional surface acoustic wave filters, resulting in a temperature-compensated SAW filter with high frequencies and stable temperature characteristics. The grain boundaries of polycrystalline materials absorb and attenuate scattering of acoustic waves. The surface acoustic waves are transmitted to the interior or underside of the support substrate, where the acoustic waves are consumed by the grain boundaries and pores. The acoustic waves reflected from the surface are significantly reduced, thereby reducing noise. Therefore, using a polycrystalline material for the support substrate can effectively reduce noise. Limiting the number of grains per unit area allows for control of the grain size in polycrystalline materials. Setting the number of grains per unit area avoids, on the one hand, the problem of too large a grain size resulting in fewer grain boundaries and thus more noise in the manufactured filter device, and, on the other hand, the problem of too small a grain size resulting in an increase in pores and a decrease in the device's Q value.

[0010] In another aspect of the present disclosure, the present disclosure provides a method for manufacturing a compensated substrate, comprising the steps of: providing a support substrate, the support substrate being made of a polycrystalline material, the number of crystal grains per unit area of ​​the support substrate being 6 or more, and the unit area being 100 μm × 100 μm; and bonding a piezoelectric substrate onto the support substrate to obtain a compensated substrate. The method for manufacturing a compensated substrate provided by the present disclosure, by bonding a piezoelectric substrate onto the support substrate to obtain a compensated substrate, can be applied to a temperature-compensated filter, and can effectively improve the frequency drift due to temperature of the support substrate and increase the Q value of the device.

[0011] Another aspect of the present disclosure provides a filter, the filter including a substrate structure and an electrode disposed on the substrate structure.

[0012] Another aspect of the present disclosure provides a duplexer, the duplexer including a transmit filter and a receive filter, wherein the transmit filter and / or the receive filter employs the above filter. [Effects of the Invention]

[0013] Compared with the prior art, the filter provided by the present disclosure effectively improves the performance of the filter and greatly reduces the noise interference. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a structural schematic diagram of a substrate structure provided in accordance with some embodiments of the present disclosure. [Figure 2] 1 is a structural schematic diagram of a support substrate provided according to some embodiments of the present disclosure. [Figure 3] 2 is a structural schematic diagram 2 of a support substrate provided according to some embodiments of the present disclosure. [Figure 4] 3 is a structural schematic diagram of a support substrate provided according to some embodiments of the present disclosure. [Figure 5] 4 is a structural schematic diagram of a support substrate provided according to some embodiments of the present disclosure. [Figure 6] 5 is a structural schematic diagram of a support substrate provided according to some embodiments of the present disclosure. [Figure 7] 6 is a structural schematic diagram of a support substrate provided according to some embodiments of the present disclosure. [Figure 8] FIG. 1 is a schematic diagram of a noise measurement scheme provided by some embodiments of the present disclosure. [Figure 9] 1 is a flowchart 1 of a method for manufacturing a substrate structure provided according to some embodiments of the present disclosure. [Figure 10] 2 is a flowchart 2 of a method for manufacturing a substrate structure provided according to some embodiments of the present disclosure. [Figure 11] 1 is a structural schematic diagram of a filter provided in accordance with some embodiments of the present disclosure. [Figure 12] 1 is a structural schematic diagram of a substrate structure provided in accordance with some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0015] Conventional temperature-compensated filter devices generally add a support structure to the piezoelectric layer structure, but the conventional support structure generally selects materials with high density and high acoustic velocity, which may cause a large amount of noise during use of the device. To solve the above problem, the present application provides a new substrate structure, which has a special polycrystalline structure, and the filter using this substrate structure can fulfill the basic function of the filter and improve noise.

[0016] Hereinafter, the present application will discuss and explain in detail the specific structure of the new substrate structure. Example 1

[0017] 1, the substrate structure provided in this embodiment includes a support substrate 10 and a piezoelectric substrate 20 located on the support substrate 10, where the support substrate 10 is made of a polycrystalline material and has a porosity of less than 0.0045% or greater than 0.6%. This substrate structure can effectively reduce interference noise and improve the operating performance of the device.

[0018] Here, the material of the support substrate 10 is a polycrystalline material, and for example, the polycrystalline material may be any one of polycrystalline spinel, polycrystalline sapphire, polycrystalline silicon, polycrystalline quartz, and polycrystalline aluminum nitride.

[0019] The piezoelectric substrate 20 can be selected from LT (lithium tantalate) or LN (lithium niobate).

[0020] Furthermore, the main cause of sound wave attenuation is the absorption of sound waves by the medium. Therefore, the present application selects a polycrystalline material with a certain porosity as the material for the support substrate 10. As a result, factors such as the grain boundaries of the polycrystalline material and the unevenness of the microdomains (i.e., pores), as shown in Figure 1, can effectively reduce the energy of longitudinal wave transmission and further suppress and attenuate noise.

[0021] In this embodiment, the porosity of the support substrate 10 is less than 0.0045% or greater than 0.6%. For example, if the porosity of the support substrate 10 is less than 0.0045%, the specific porosity of the support substrate 10 may be 0.0044%, 0.0043%, 0.0040%, 0.0035%, 0.0030%, 0.0020%, 0.0010%, etc., and this application does not recite each one individually.

[0022] When the porosity of the support substrate 10 is greater than 0.6%, the specific porosity of the support substrate 10 may be 0.65%, 0.7%, 0.8%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, etc. Of course, the specific values ​​of the porosity of the support substrate 10 are merely examples and are not limitations on the specific porosity of the support substrate 10. Those skilled in the art can select an appropriate porosity as needed, as long as the porosity is less than 0.0045% or greater than 0.6%.

[0023] In this embodiment, when the porosity of the support substrate 10 is greater than 0.6%, the porosity of the support substrate 10 can be selectively selected to be greater than 0.65%, thereby more effectively suppressing and attenuating noise generation.

[0024] In order to further suppress and attenuate interference noise and improve the operation performance of the device, the porosity of the support substrate 10 is optionally 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%, 1.4%, etc.

[0025] In this embodiment, the number of grain boundary layers in the support substrate 10 is optionally three or more.

[0026] First, the material of the support substrate 10 is a polycrystalline material, and therefore, as shown in Figures 2 and 3, the support substrate 10 has a plurality of crystal grains. Here, the crystal grain boundary is the boundary between two adjacent crystal grain layers, and includes three crystal grain boundary layers in Figure 3 corresponding to Figure 3 (the three crystal grain boundary layers are respectively indicated by black lines in Figure 3).

[0027] Next, grain boundaries in the medium and uneven microdomains (e.g., pores) can cause sound waves to scatter at the interfaces of these regions, resulting in energy attenuation (scattering attenuation). Since there are more grain boundary layers in the support substrate 10 than pores in the support substrate 10, the grain boundary layers can provide good suppression and attenuation for sound waves propagating downward from the surface of the electrode 30.

[0028] The multiple grain boundaries of the support substrate 10 absorb and attenuate the scattering of acoustic waves, and acoustic waves transmitted to the interior or underside of the support substrate 10 of the surface acoustic wave are consumed by the grain boundaries and pores, resulting in a significant reduction in the acoustic waves reflected from the surface, as shown in FIG. 1, thereby reducing noise.

[0029] 4 to 7, which are drawings showing cases where the number of grain boundary layers in the support substrate 10 is at least 0, 1, 2, and 3, respectively. The positions indicated by the white arrows indicate the positions with the fewest grain boundary layers in the side cross sections of the four types of samples. The locations where the number of grain boundary layers is reduced correspond to larger grain sizes and fewer grains per unit area. The areas near the white arrows are generally the locations with the fewest number of grains per unit area, which are 3, 4, 5, and 7 grains, respectively. The characteristics of filters manufactured using these four types of support substrate 10 are shown in the table below.

[0030] [Table 1] The noise measurement method in the above table is shown in FIG. 8. 21 positions are selected at fixed coordinate points of each sample to manufacture a filter and test its characteristics. If no noise occurs at any of the 21 test points, the noise yield is expressed as 100% (sample 4 in the above table). If noise occurs at one position, the noise yield can be calculated as 95% based on the ratio.

[0031] As can be seen from the above table, the four different samples have similar characteristics except for the clearly distinguishable noise. This shows that the number of grain boundary layers definitely affects noise, and as can be seen from analyzing the table data, noise generation can be better suppressed when the number of grain boundary layers is ≥ 3.

[0032] On polycrystalline substrates , number of grain boundaries is related to the size of the crystal grains, especially the size of the largest crystal grain. Preferably, the number of crystal grain boundaries is controlled by controlling the size of the crystal grains in the polycrystalline substrate. If the size is too large, there will be few grain boundaries, and the manufactured filter device will be prone to noise. On the other hand, in the case of polycrystalline substrates, If the grain size is too small, porosity will occur. teeth Increased Q factor of the device of Decline Fear of causing Therefore, in this embodiment, the number of grain boundary layers is selectively set to 40 or less. Specifically, the specific number of grain boundary layers may be selected by those skilled in the art according to the actual situation, and is not particularly limited by the present application.

[0033] Optionally, the support substrate 10 provided by the present application includes a plurality of crystal grains, and the average grain size of the crystal grains is between 2 μm and 60 μm. Illustratively, the average grain size of the crystal grains may be 2 μm, 10 μm, 20 μm, 30 μm, 50 μm, or 60 μm.

[0034] In this embodiment, the grain size of the crystal grains can be between 1 μm and 80 μm. For example, the grain size of the crystal grains may be 1 μm, 5 μm, 20 μm, 40 μm, 50 μm, or 80 μm.

[0035] In addition, the crystal grain Maximum particle size is related to the thickness T of the support substrate, and the number of grain boundary layers of the support substrate 10 of the present invention must be three or more. maximum The grain size should be less than one-third of the thickness T of the supporting substrate.

[0036] In this embodiment, the thickness of the piezoelectric substrate is optionally between 0.1 μm and 10 μm, and preferably between 0.5 μm and 5 μm.

[0037] Furthermore, the material of the support substrate 10 is a polycrystalline material, and the number of crystal grains per unit area of ​​the support substrate 10 is 6 or more, and the number of crystal grains per unit area of ​​the support substrate 10 is 200 or less, and the unit area is 100 μm × 100 μm.

[0038] For example, the number of crystal grains per unit area of ​​the support substrate 10 may be between 10 and 100. If the number of crystal grains is too large, the hardness of the support substrate 10 increases, which is disadvantageous for thinning and polishing the support substrate 10 and increases material loss and processing time. On the other hand, if the number of crystal grains is too small, the support substrate 10 can be made easier to process, but the material strength of the support substrate 10 decreases. For this reason, the number of crystal grains per unit area of ​​the support substrate 10 is preferably between 10 and 30.

[0039] In short, the substrate structure provided by the present application includes a support substrate 10 and a piezoelectric substrate 20 located on the support substrate 10, wherein 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%. By selecting a polycrystalline material as the material of the support substrate 10 and setting the porosity of the support substrate 10 to less than 0.0045% or greater than 0.6%, the pores and grain boundaries in the polycrystalline material can both absorb and attenuate the scattering of acoustic waves, and can be consumed in the process of transmitting surface acoustic waves to the interior or bottom surface of the support substrate 10, thereby significantly reducing the acoustic waves reflected on the top surface, thereby reducing noise and improving the operating performance of the device. Example 2

[0040] A polycrystalline spinel support substrate 10 is selected, characterized in that the porosity of the support substrate 10 is between 1% and 1.5%, the number of grain boundary layers is 40 layers or more, and the average grain size is about 6 μm.

[0041] The support substrate 10 and piezoelectric substrate 20 were bonded together, and then thinned and polished to obtain a finished substrate structure with a piezoelectric substrate 20 thickness of 5 μm and a support substrate thickness T of 250 μm. Electrodes 30 were then formed on the substrate structure to obtain a filter, and the characteristics of the filter were verified. The characteristics of a filter manufactured using a support substrate 10 with a porosity between 0.0045% and 0.6% were used as the reference standard, and the obtained parameters are shown in the table below.

[0042] [Table 2]

[0043] As can be seen from analyzing the above table, when the porosity is between 0.0045% and 6%, there is still significant noise interference, but when the porosity of the support substrate 10 is selected between 1% and 1.5%, the noise can be significantly improved.

[0044] Furthermore, if the porosity of the support substrate 10 is between 1% and 1.5%, a decrease in material strength is unavoidable due to the high porosity. 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 crystal grain size of ≦4 μm may be selected, with the grain size D of most of the crystal grains being between 1 μm and 2 μm. The smaller the grain size D of the selected crystal grains, the better the mechanical performance of the material. Macroscopically, this results in increased yield and tensile strength, increased surface hardness, and increased fatigue life. The specific principle is that the finer the crystal grains, the greater the number of crystal grains per unit volume, and the greater the number of crystal grains involved in deformation, resulting in more uniform deformation and greater plastic deformation before fracture. Strength and plasticity increase simultaneously, and the material's power consumption before fracture increases, resulting in higher toughness. Example 3

[0045] A polycrystalline spinel support substrate 10 is selected, characterized in that the porosity of the support substrate 10 is between 0.65% and 1%, the number of grain boundary layers is 40 layers or more, and the average grain size is about 45 μm.

[0046] The support substrate 10 and piezoelectric substrate 20 were bonded together, and then thinned and polished to obtain a finished substrate structure with a piezoelectric substrate 20 thickness of 5 μm and a support substrate thickness T of 250 μm. Electrodes 30 were then formed on the substrate structure to obtain a filter, and the characteristics of the filter were verified. The characteristics of a filter manufactured using a support substrate 10 with a porosity between 0.0045% and 0.6% were used as the reference standard, and the obtained parameters are shown in the table below.

[0047] [Table 3]

[0048] As can be seen from analyzing the above table, there is still a large noise interference when the porosity is between 0.0045% and 0.6%, and after the porosity of the support substrate 10 is set to 0.6% or more, it can significantly improve the noise. Example 4

[0049] A polycrystalline spinel support substrate 10 is selected, characterized in that the porosity of the support substrate 10 is 0.0045% or less, the number of grain boundary layers is 40 layers or more, and the average grain size is about 10 μm.

[0050] The support substrate 10 and piezoelectric substrate 20 were bonded together, and then thinned and polished to obtain a finished substrate structure with a piezoelectric substrate 20 thickness of 5 μm and a support substrate thickness T of 250 μm. Electrodes 30 were then formed on the substrate structure to obtain a filter, and the characteristics of the filter were verified. The characteristics of a filter manufactured using a support substrate 10 with a porosity between 0.0045% and 0.6% were used as the reference standard, and the obtained parameters are shown in the table below.

[0051] [Table 4]

[0052] As can be seen from analyzing the above table, when the porosity is between 0.0045% and 0.6%, there is still significant noise interference, but when the porosity of the support substrate 10 is selected to be 0.0045% or less, the noise can be significantly improved.

[0053] According to the above three embodiments, when the support substrate 10 is made of a polycrystalline material and the porosity of the polycrystalline material is selected to be less than 0.0045% or greater than 0.6%, noise can be significantly improved, thereby improving the operating performance of the device.

[0054] Referring to FIG. 9 , another aspect of the present disclosure provides a method for manufacturing a substrate structure, the method comprising: Step S100 of providing a support substrate 10, the material of which is a polycrystalline material, and the porosity of which is less than 0.0045% or more than 0.6%; and step S200 of bonding the piezoelectric substrate 20 onto the support substrate 10 to obtain a substrate structure.

[0055] It should be noted that the material of the support substrate 10 is a polycrystalline material, and for the specific type of the polycrystalline material and the specific selection of the porosity of the polycrystalline material, those skilled in the art may refer to the above description, and the present application will not repeat the description.

[0056] Similarly, reference may be made to the above description regarding the specific material of the piezoelectric substrate 20. The bonding process is well known to those skilled in the art, and therefore will not be repeated here.

[0057] Also, referring to FIG. 10, optionally, the above step S200 of bonding the piezoelectric substrate 20 onto the support substrate 10 to obtain a substrate structure includes steps S210 to S230.

[0058] In S210, the piezoelectric substrate 20 is bonded onto the support substrate 10.

[0059] Before bonding, the bonding surface of the piezoelectric substrate 20 may be polished to a roughness of 0.3 nm or less, and similarly, the bonding surface of the support substrate 10 may be polished before bonding to a roughness of 0.8 nm or less.

[0060] The bonding may be performed in a room temperature, high vacuum environment by an ion activation method.

[0061] In S220, the surface of the piezoelectric substrate 20 that faces away from the support substrate 10 is thinned and polished to a thickness of less than 10 μm.

[0062] In S230, the surface of the support substrate 10 that faces away from the piezoelectric substrate 20 is thinned and polished to a thickness T of the support substrate 10 of less than 250 μm, thereby obtaining a substrate structure.

[0063] Referring to FIG. 11, another aspect of the present disclosure provides a filter, which includes a substrate structure and an electrode 30 disposed on the substrate structure.

[0064] The electrodes 30 are electrode fingers 30, and the specific structure and beneficial effects of the substrate structure have been described in detail above, so further description is omitted here.

[0065] Another aspect of the present disclosure provides a duplexer, which includes a transmit filter and a receive filter, and the transmit filter and / or the receive filter employs the above-described filter. The specific structure and effects of the filter have been described in detail above, and therefore will not be described here.

[0066] 12 , the present application further provides a compensated substrate for use in a filter device, the compensated substrate including 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 number of crystal grains per unit area of ​​the support substrate 10 is six or more, with a unit area of ​​100 μm × 100 μm. In this embodiment, the number of crystal grains per unit area of ​​the support substrate 10 is six or more, but the specific number of crystal grains is not limited and can be determined as needed by those skilled in the art. The compensated substrate described in this embodiment effectively reduces the thickness of the piezoelectric substrate 20 by placing the support substrate 10 below the piezoelectric substrate 20, thereby increasing the Q value of the filter and technically improving the conventional surface acoustic wave filter into a temperature-compensated SAW filter with high frequency and stable temperature characteristics. The grain boundaries of polycrystalline materials play a role in absorbing and attenuating the scattering of acoustic waves, and as the surface acoustic waves are transmitted to the interior or underside of the support substrate, the acoustic waves are consumed by the grain boundaries and pores, and the acoustic waves reflected from the surface are significantly reduced, thereby reducing noise. Therefore, by using a polycrystalline material for the support substrate 10, noise can be effectively reduced. In filters using this compensated substrate, the number of pores in the polycrystalline substrate can be controlled by limiting the number of crystal grains per unit area, thereby avoiding a decrease in the device's Q value due to an excess of pores.

[0067] Optionally, the number of crystal grains per unit area of ​​the support substrate 10 is 200 or less. In this embodiment, the number of crystal grains in the support substrate 10 per unit area of ​​100 μm×100 μm must be 200 or less and 6 or more. More preferably, the number of crystal grains in the support substrate 10 per unit area of ​​100 μm×100 μm is 10 to 100. Illustratively, the number of crystal grains in the support substrate 10 per unit area of ​​100 μm×100 μm may be 10, 30, or 100.

[0068] In a filter using this compensation type substrate, theBy controlling the number of crystal grains within the range of 10 to 100 grains, noise can be improved while maintaining the strength of the material within an appropriate range, without increasing the difficulty of processing the material. If the number of crystal grains is too large, the hardness of the material of the support substrate 10 increases, which is disadvantageous when thinning and polishing the support substrate 10, resulting in increased material loss and processing time. Therefore, controlling the number of crystal grains not only improves noise, but also effectively reduces the difficulty of production processing. The specific number of crystal grains is not limited herein and can be determined by those skilled in the art according to actual needs.

[0069] Optionally, the number of grain boundary layers is 3 or more, and / or the number of grain boundary layers is 40 or less. By limiting the number of grain boundary layers, the arrangement of grains in the cross section of the support substrate can be controlled. If the number of grain boundary layers is less than 3, the number of grain boundaries will be too small, and sound waves cannot be effectively absorbed and consumed, which is disadvantageous for noise reduction. If the number of grain boundary layers is too large, , too many pores , the Q factor of the device decreases. fear There is.

[0070] Optionally, the material of the support substrate 10 is one of polycrystalline spinel, polycrystalline sapphire, polycrystalline silicon, polycrystalline quartz, and polycrystalline aluminum nitride.

[0071] Optionally, the piezoelectric substrate 20 is made of a piezoelectric material and has a piezoelectric effect. In this embodiment, the piezoelectric material is lithium tantalate, but in other embodiments of the present invention, the piezoelectric material may be lithium niobate. In this embodiment, the thickness of the piezoelectric substrate is 0.1 to 10 μm, and more preferably 0.5 to 5 μm.

[0072] The manufacturing method of the compensated substrate provided by this embodiment includes the steps of providing a support substrate 10, where the material of the support substrate 10 is a polycrystalline material, the number of crystal grains per unit area of ​​the support substrate 10 is 6 or more, and the unit area is 100 μm × 100 μm; and bonding a piezoelectric substrate 20 onto the support substrate 10 to obtain a compensated substrate.

[0073] Here, the step of bonding the piezoelectric substrate 20 onto the support substrate 10 to obtain a compensated substrate includes the steps of bonding the piezoelectric substrate 20 onto the support substrate 10, sequentially thinning and polishing the surface of the piezoelectric substrate 20 facing away from the support substrate to a thickness of less than 10 μm, and sequentially thinning and polishing the surface of the support substrate 10 facing away from the piezoelectric substrate 20 to a thickness of less than 400 μm to obtain a compensated substrate. A compensated substrate obtained by setting the thickness of the support substrate 10 between 150 and 250 μm exhibits excellent performance, and may be set to, for example, 180 to 220 μm. Bonding the piezoelectric substrate 20 onto the support substrate 10 to obtain a compensated substrate can be used in a temperature-compensated filter, effectively reducing the frequency drift due to temperature of the support substrate 10 and increasing the Q value of the device.

[0074] Specifically, LT (lithium tantalate) is selected for the piezoelectric substrate 20, one side of which is polished to a surface roughness of 0.3 nm or less, and this processed surface serves as the bonding surface for the piezoelectric substrate 20. Polycrystalline spinel is selected for the support substrate 10, one side of which is polished to a surface roughness of 0.8 nm or less, and this processed surface serves as the bonding surface for the support substrate 10. The bonding surfaces of the piezoelectric substrate 20 and the support substrate 10 are bonded using an ion activation method in a room-temperature, high-vacuum environment. Finally, a compensated substrate is obtained with a LT thickness of 5 μm and a spinel thickness of 240 μm.

[0075] To further illustrate the superior performance of the filters provided by the embodiments of the present application, tests are conducted using the filters provided by the present application.

[0076] Test Example 1: In a specific test, the average grain size of the support substrate 10 was set to about 6 μm, the number of grain boundary layers was set to more than 10, and the number of grains within a 100 μm × 100 μm area of ​​the support substrate 10 was set to about 100. This was then bonded to the LT piezoelectric substrate 20, thinned, polished, and so on, until a final compensated substrate was obtained with an LT piezoelectric substrate thickness of 5 μm and a spinel thickness of 250 μm. A filter was manufactured using this compensated substrate, and the final filter was obtained. When its characteristics were verified, no noise was generated, i.e., the noise yield was 100%.

[0077] Test Example 2: The average grain size of the support substrate 10 was set to about 45 μm, the number of grain boundary layers was set to more than three, and the number of grains within a 100 μm × 100 μm area of ​​the support substrate 10 was set to about 50. This was then bonded to the LT piezoelectric substrate 20, thinned, polished, and other processes were performed sequentially to obtain a final compensated substrate with an LT piezoelectric substrate thickness of 5 μm and a spinel thickness of 250 μm. A filter was manufactured using this compensated substrate, and the final filter was obtained and its characteristics were verified. Similarly, no noise was generated, meaning the noise yield was 100%.

[0078] Test Example 3: Unlike Test Example 1, the number of crystal grains within a 100 μm x 100 μm area of ​​the support substrate 10 was set to approximately 3, and the number of crystal grain boundary layers was set to a minimum of 0. The final filter was obtained and its characteristics were verified, resulting in a noise yield of 43%.

[0079] Test Example 4: Unlike Test Example 3, the number of crystal grains within a 100 μm x 100 μm area of ​​the support substrate 10 was set to approximately 5, and the number of crystal grain boundary layers was set to a minimum of 2. The final filter was obtained and its characteristics were verified, resulting in a noise yield of 85%.

[0080] Test Example 5: Unlike Test Example 3, the number of crystal grains within a 100 μm x 100 μm area of ​​the support substrate 10 was set to approximately 7 grains, and the number of crystal grain boundary layers was set to a minimum of 3 layers.The final filter was obtained and its characteristics were verified, and the noise yield was 100%.

[0081] The above are only preferred embodiments of the present disclosure and are not used to limit the present disclosure, and those skilled in the art can make various modifications and changes to the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present disclosure should all fall within the protection scope of the present disclosure.

[0082] It should be noted that the specific technical features described in the above specific embodiments can be combined in any suitable manner if not contradictory, and in order to avoid unnecessary duplication, the present disclosure will not re-describe various possible combination manners. [Explanation of symbols]

[0083] 10...Support substrate, 20...piezoelectric substrate, 30...electrode, T: thickness of the support substrate, D...grain size.

Claims

1. a support substrate and a piezoelectric layer disposed on the support substrate; wherein the material of the support substrate is a polycrystalline material, and the porosity of the support substrate is greater than 0.6% and less than 1.5%; A substrate structure, characterized in that the support substrate includes a plurality of crystal grains, the average grain size of the crystal grains is 4 μm or less, and the number of crystal grain boundary layers of the support substrate is three or more.

2. 2. The substrate structure of claim 1, wherein the porosity of the support substrate is greater than 0.65% and less than 1.5%.

3. 2. The substrate structure according to claim 1, wherein the number of said grain boundary layers is 10 or more and 40 or less.

4. 2. The substrate structure according to claim 1, wherein the support substrate includes a plurality of crystal grains, and the maximum grain size of the crystal grains is one-third or less of the thickness of the support substrate.

5. 2. The substrate structure according to claim 1, wherein the number of crystal grains per unit area of ​​the support substrate is 6 or more and 200 or less, and the unit area is 100 μm×100 μm.

6. 2. The substrate structure according to claim 1, wherein the surface of the support substrate that contacts the piezoelectric layer has a roughness of 0.8 nm or less.

7. A support substrate; a piezoelectric substrate positioned on the support substrate; an electrode provided on the piezoelectric substrate; a support substrate made of a polycrystalline material, the support substrate having a porosity greater than 0.6% and less than 1.5%, the support substrate including a plurality of crystal grains, the average grain size of the crystal grains being 4 μm or less, and the number of crystal grain boundary layers of the support substrate being three or more.

8. a transmit filter and a receive filter; Here, the duplexer is characterized in that the transmit filter and / or the receive filter employs the filter according to claim 7.

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