Compensation type substrate, method for manufacturing the same, and filter

Abstract

The present disclosure provides a compensation type substrate, a preparation method thereof and a filter, and relates to the technical field of filters.The compensation type substrate comprises a support substrate and a piezoelectric substrate on the support substrate; the material of the support substrate is a polycrystalline material, and the number of crystal grains in a unit area of the support substrate is greater than or equal to 6, and the unit area is 100 mu m*100 mu m. The preparation method comprises the following steps: providing a support substrate, the material of the support substrate is a polycrystalline material, bonding a piezoelectric substrate on the support substrate to obtain a compensation type substrate. The purpose of the present application is to provide a compensation type substrate and a temperature compensation type filter, which can effectively improve the generation of interference noise and improve the working performance of the device.

Description

Technical Field

[0001] This disclosure relates to the field of filter technology, and more specifically, to a compensation substrate and its fabrication method, and a filter. 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 compensation substrate and a temperature compensation filter. The compensation substrate, its preparation method, and the filter 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 a first aspect, this disclosure provides a compensation substrate, 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 number of grains in the support substrate per unit area is greater than or equal to 6, and the unit area is 100μm×100μm.

[0007] Optionally, the number of grains per unit area of ​​the support substrate is less than or equal to 200.

[0008] Optionally, the porosity of the support substrate is less than 0.0045% and greater than or equal to 0.001%.

[0009] Optionally, the porosity of the support substrate is greater than 0.65%.

[0010] Optionally, the porosity of the support substrate is less than 1.5%.

[0011] Optionally, the number of grain boundary layers is greater than or equal to 3; and / or, the number of grain boundary layers is less than or equal to 40.

[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 thickness of the piezoelectric substrate is 0.1–10 μm. More preferably, the thickness of the piezoelectric substrate is 0.5–5 μm.

[0014] In a second aspect, this disclosure provides a method for preparing a compensation substrate, comprising: providing a support substrate, wherein the material of the support substrate is a polycrystalline material, and the number of grains in the support substrate per unit area is greater than or equal to 6, and the unit area is 100μm×100μm; and bonding a piezoelectric substrate on the support substrate to obtain a compensation substrate.

[0015] Optionally, a piezoelectric substrate is bonded to a support substrate to obtain a compensation substrate, comprising: bonding a piezoelectric substrate to a support substrate; sequentially thinning and polishing the side of the piezoelectric substrate away from the support substrate to make the thickness of the piezoelectric substrate less than 10 μm; and sequentially thinning and polishing the side of the support substrate away from the piezoelectric substrate to make the thickness of the support substrate less than 250 μm to obtain a compensation substrate.

[0016] Thirdly, this disclosure provides a filter, including the aforementioned compensation substrate and an electrode disposed on and connected to the compensation substrate.

[0017] The beneficial effects of this disclosure include: The compensation substrate provided by this disclosure, by setting a support substrate under the piezoelectric substrate, can effectively reduce the thickness of the piezoelectric substrate, improve the Q value of the filter, and realize the technical improvement from a traditional surface acoustic wave (SAW) filter to a temperature-compensated SAW filter with stable high-frequency-temperature characteristics. Since the grain boundaries of polycrystalline materials absorb and attenuate the scattering of sound waves, when SAW waves are transmitted to the interior or lower surface of the support substrate, the sound waves are consumed by the grain boundaries and pores, significantly reducing the sound waves reflected back to the surface, thereby reducing noise. Therefore, setting the material of the support substrate to a polycrystalline material can effectively reduce noise. By limiting the number of grains per unit area, the grain size in the polycrystalline material can be controlled. Setting the number of grains per unit area avoids both excessively large grain sizes, resulting in fewer grain boundaries and making the fabricated filter device prone to noise, and excessively small grain sizes, leading to increased pores and a decrease in the Q value of the device.

[0018] Furthermore, the method for fabricating the compensation substrate provided in this disclosure obtains the compensation substrate by bonding a piezoelectric substrate onto a support substrate. This compensation substrate can be applied to temperature-compensated filters, effectively improving the frequency drift of the support substrate caused by temperature and increasing the Q value of the device.

[0019] Compared to traditional technologies, the filter provided in this disclosure effectively improves the filter's performance and significantly reduces noise interference. Attached Figure Description

[0020] 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.

[0021] Figure 1 This is one of the structural schematic diagrams of the compensation substrate according to some embodiments of this disclosure;

[0022] Figure 2 This refers to the grain boundary layer formed between the grains of the polycrystalline material in the embodiments of this disclosure;

[0023] Figure 3 This is a second schematic diagram of the structure of the compensation substrate according to some embodiments of this disclosure;

[0024] Figure 4 This is one of the structural schematic diagrams of the support substrate provided in some embodiments of this disclosure;

[0025] Figure 5 This is a second schematic diagram of the structure of the support substrate provided in some embodiments of this disclosure;

[0026] Figure 6 This is the third schematic diagram of the structure of the support substrate provided in some embodiments of this disclosure;

[0027] Figure 7 Fourth schematic diagram of the structure of the support substrate provided in some embodiments of this disclosure;

[0028] Figure 8 This is a schematic diagram illustrating a noise measurement method provided in some embodiments of this disclosure.

[0029] Icons: 10 - Support substrate; 20 - Piezoelectric substrate; 30 - Electrode. Detailed Implementation

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] Traditional surface acoustic wave (SAW) filter technology suffers from low Q values ​​(<1000) and frequency drift with temperature variations, and its relatively low operating frequency makes it difficult to meet the filter requirements of increasingly congested 5G RF terminals. Therefore, traditional SAW filters must evolve into temperature-compensated SAW filters (TC-SAW, TF-SAW) with high frequency-temperature stability. The key to this transformation lies in adding a support layer to the piezoelectric layer structure. Adding a support layer effectively reduces the piezoelectric layer thickness, improving the device's Q value; furthermore, the support layer's superior thermal expansion coefficient effectively mitigates temperature-induced frequency drift. However, existing temperature-compensated filter devices typically use high-density, high-velocity materials for their support layers, inevitably generating significant interference noise while improving temperature drift characteristics.

[0037] Therefore, how to effectively reduce the generation of interference noise and improve the performance of filtering devices has become an urgent technical problem to be solved.

[0038] Reference Figure 1As shown, this embodiment provides a compensation substrate, including 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 the number of grains per unit area is greater than or equal to 6, with a unit area of ​​100μm × 100μm. In this embodiment, the number of grains per unit area of ​​the support substrate 10 is greater than or equal to 6, but the specific number of grains is not limited and can be set as needed by those skilled in the art. This embodiment, by setting the support substrate 10 under the piezoelectric substrate 20, can effectively reduce the thickness of the piezoelectric substrate 20, improve the Q value of the filter, and achieve a technical improvement from a traditional surface acoustic wave (SAW) filter to a temperature-compensated SAW filter with stable high-frequency-temperature characteristics. Since the grain boundaries of the polycrystalline material absorb and attenuate the scattering of sound waves, when SAW waves are transmitted to the interior or lower surface of the support substrate, the sound waves are consumed by the grain boundaries and pores, significantly reducing the sound waves reflected back to the surface, thereby reducing noise. Therefore, setting the material of the support substrate 10 to a polycrystalline material can effectively reduce noise. By limiting the number of grains per unit area, the grain size in polycrystalline materials can be controlled. Setting the number of grains per unit area avoids two problems: firstly, excessively large grains lead to fewer grain boundaries, making the fabricated filter devices prone to noise; secondly, excessively small grains result in increased porosity, causing a decrease in the device's Q value.

[0039] Optionally, the number of grains in the support substrate 10 per unit area is less than or equal to 200. In this embodiment, the number of grains in the support substrate 10 per unit area of ​​100μm × 100μm needs to be less than or equal to 200, and greater than or equal to 6. More preferably, the number of grains in the support substrate 10 per unit area of ​​100μm × 100μm is 10 to 100. For example, the number of grains in the support substrate 10 per unit area of ​​100μm × 100μm can be 10, 30, or 100. By controlling the number of grains within the range of 10 to 100, noise can be improved on the one hand, and the strength of the material can be ensured to be within a suitable range on the other hand, thus not increasing the processing difficulty of the material. If the number of grains is too large, the hardness of the support substrate 10 material will increase, which is not conducive to the thinning and polishing of the support substrate 10, and will increase material loss and processing time. Therefore, controlling the number of chips can not only improve noise reduction but also effectively reduce the difficulty of manufacturing. The specific number of chips is not limited here; those skilled in the art can set it according to actual needs.

[0040] Reference Figure 2As shown, optionally, the number of grain boundary layers is greater than or equal to 3; and / or, the number of grain boundary layers is less than or equal to 40. Limiting the number of grain boundary layers allows control over the grain arrangement in the cross-section of the supporting substrate. Fewer than 3 grain boundary layers result in too few grain boundaries, hindering effective absorption and dissipation of acoustic waves and negatively impacting noise reduction. Too many grain boundary layers lead to excessively small grain sizes and increased porosity, potentially reducing the Q value of the device while improving noise reduction.

[0041] Optionally, the material of the support substrate 10 is any one of polycrystalline spinel, polycrystalline sapphire, polycrystalline silicon, polycrystalline quartz, and polycrystalline aluminum nitride.

[0042] Optionally, the piezoelectric substrate 20 is made of a piezoelectric material and has a piezoelectric effect. In this first embodiment, the piezoelectric material is lithium tantalate, but in other embodiments of the invention, the piezoelectric material can also be lithium niobate. In this embodiment, the thickness of the piezoelectric substrate is 0.1–10 μm, more preferably 0.5–5 μm.

[0043] This embodiment provides a method for preparing a compensation substrate, comprising: providing a support substrate 10, wherein the material of the 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 unit area is 100μm×100μm; and bonding a piezoelectric substrate 20 onto the support substrate 10 to obtain a compensation substrate.

[0044] The process of bonding a piezoelectric substrate 20 onto a support substrate 10 to obtain a compensation substrate includes: bonding the piezoelectric substrate 20 onto the support substrate 10; sequentially thinning and polishing the side of the piezoelectric substrate 20 away from the support substrate 10 to make the thickness of the piezoelectric substrate 20 less than 10 μm; and sequentially thinning and polishing the side of the support substrate 10 away from the piezoelectric substrate 20 to make the thickness of the support substrate 10 less than or equal to 400 μm to obtain a compensation substrate. A compensation substrate with a thickness of 150-250 μm for the support substrate 10 exhibits better performance; for example, a thickness of 180-220 μm is preferable. By bonding the piezoelectric substrate 20 onto the support substrate 10 to obtain a compensation substrate, it can be applied to temperature-compensated filters, effectively improving the frequency drift of the support substrate 10 caused by temperature and increasing the Q value of the device.

[0045] Specifically, lithium tantalate (LT) is selected as the piezoelectric substrate 20. One side of the piezoelectric substrate 20 is polished to a surface roughness of less than 0.3 nm; this polished surface serves as the bonding surface of the piezoelectric substrate 20. Polycrystalline spinel is selected as the support substrate 10. One side of the support substrate 10 is polished to a surface roughness of less than 0.8 nm; this polished surface serves as the bonding surface of the support substrate 10. The bonding surfaces of the piezoelectric substrate 20 and the support substrate 10 are bonded together using ion activation in a high-vacuum environment at room temperature. The final product is a compensation substrate with a thickness of 5 μm for the LT and a thickness of 240 μm for the spinel.

[0046] Reference Figure 3 As shown, this embodiment provides a filter, including the aforementioned compensation substrate and an electrode 30 disposed on and connected to the compensation substrate. The electrode 30 is an IDT electrode, and is disposed on one surface of a piezoelectric substrate 20, on which a reflector is also disposed. The surface where the electrode 30 is disposed corresponds to the bonding surface of the piezoelectric substrate 20. The thickness of the electrode 30 is 10–5000 nm. The electrode 30 includes multiple finger-shaped electrode strips. In practical applications, the shape and number of electrode strips can be changed as needed, and the method of setting the electrode strips is common knowledge to those skilled in the art and will not be described in detail here. This embodiment effectively improves the performance of the filter and significantly reduces noise interference. 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. 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:

[0047] Sample 1 Sample 2 Sample 3 Sample 4 number of grain boundary layers ≥0 ≥1 ≥2 ≥3 Number of grains per unit area ≥3 ≥4 ≥5 ≥7 Porosity ＜0.0045％ ＜0.0045％ ＜0.0045％ ＜0.0045％ Noise 43％ 71％ 85％ 100％ Mechanical coupling coefficient 8.75 8.5 8.5 8.6 Maximum quality factor 1415 1669 1664 1507

[0048] 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.

[0049] 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.

[0050] 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 no specific limitation is made here.

[0051] To further illustrate the superior performance of the filter provided in the embodiments of this application, experiments were conducted using the filter provided in this application.

[0052] Example 1: In a specific experiment, the average grain size of the grains in the support substrate 10 was approximately 6 μm, and the number of grain boundary layers was greater than 10. The support substrate 10 contained approximately 100 grains within a 100 μm × 100 μm range, which were bonded to the LT piezoelectric substrate 20. Thinning and polishing processes were then performed sequentially, resulting in a finished LT piezoelectric substrate with a thickness of 5 μm and a spinel thickness of 250 μm—a compensation substrate. A filter was fabricated using this compensation substrate, and the final filter's characteristics were verified. No noise was observed, indicating a noise yield of 100%.

[0053] Example 2: The average grain size of the grains in the support substrate 10 is approximately 45 μm, and the number of grain boundary layers is greater than 3. The support substrate 10 contains approximately 50 grains within a 100 μm × 100 μm area, which are bonded to the LT piezoelectric substrate 20. Thinning and polishing processes are then performed sequentially to obtain a compensation substrate with a final LT piezoelectric substrate thickness of 5 μm and a spinel thickness of 250 μm. A filter was fabricated using this compensation substrate, and the final filter's characteristics were verified. No noise was observed, indicating a noise yield of 100%.

[0054] Example 3: Unlike Example 1, the number of grains in the support substrate 10 within the range of 100μm×100μm is about 3, and the minimum number of grain boundary layers is 0. The final filter was obtained and its characteristics were verified, with a noise yield of 43%.

[0055] Example 4: Unlike Example 3, the number of grains in the support substrate 10 within the range of 100μm×100μm is about 5, and the minimum number of grain boundary layers is 2. The final filter was obtained and its characteristics were verified, with a noise yield of 85%.

[0056] Example 5: Unlike Example 3, the number of grains in the support substrate 10 within the range of 100μm×100μm is about 7, and the minimum number of grain boundary layers is 3. The final filter was obtained and its characteristics were verified, with a noise yield of 100%.

[0057] In summary, it can be confirmed that the number of grain boundaries must be greater than or equal to 3 layers and the number of grains per unit area must be more than 6 to ensure the noise suppression of the filtering device. The above description is merely an optional embodiment of this disclosure and is not intended to limit this disclosure. For those skilled in the art, this disclosure can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

[0058] 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 compensating substrate, characterized by, The support substrate comprises a polycrystalline material, and the number of crystal grains in a unit area of the support substrate is greater than or equal to 6, the unit area being 100 μm x 100 μm; and the number of crystal grains in a unit area of the support substrate is less than or equal to 200.

2. The compensation substrate according to claim 1, wherein The porosity of the support substrate is less than 0.0045% and greater than or equal to 0.001%.

3. The compensation substrate according to claim 1, wherein The porosity of the support substrate is greater than 0.65%.

4. The compensation substrate according to claim 3, wherein The porosity of the support substrate is less than 1.5%.

5. The compensation substrate according to claim 1, wherein The polycrystalline material has a grain boundary layer, and the number of grain boundary layers is greater than or equal to 3; and / or, the number of grain boundary layers is less than or equal to 40.

6. The compensation substrate according to claim 1, wherein The material of the support substrate is any one of polycrystalline spinel, polycrystalline sapphire, polycrystalline silicon, polycrystalline quartz and polycrystalline aluminum nitride.

7. The compensation substrate according to claim 1, wherein: The thickness of the piezoelectric substrate is 0.1-10 μm.

8. A method for manufacturing a compensating substrate, characterized by, The support substrate comprises a polycrystalline material, and the number of crystal grains in a unit area of the support substrate is greater than or equal to 6, the unit area being 100 μm x 100 μm; The support substrate comprises a polycrystalline material, and the number of crystal grains in a unit area of the support substrate is greater than or equal to 6, the unit area being 100 μm x 100 μm; and the number of crystal grains in a unit area of the support substrate is less than or equal to 200. The support substrate comprises a polycrystalline material, and the number of crystal grains in a unit area of the support substrate is greater than or equal to 6, the unit area being 100 μm x 100 μm; 9. The method of claim 8, wherein The support substrate comprises a polycrystalline material, and the number of crystal grains in a unit area of the support substrate is greater than or equal to 6, the unit area being 100 μm x 100 μm; and the number of crystal grains in a unit area of the support substrate is less than or equal to 200.

10. A filter, characterized by, ​

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