A high power surface acoustic wave filter and a method of manufacturing the same

Abstract

The application discloses a high-power surface acoustic wave filter and a preparation method thereof, which comprises a piezoelectric substrate and a plurality of interdigital electrodes arranged on the piezoelectric substrate. The interdigital electrode comprises a compensation layer and a metal layer, the metal layer is in contact with the compensation layer, the compensation layer is arranged on the piezoelectric substrate, and the material of the compensation layer is silicon dioxide; the metal layer comprises a first metal layer arranged on the compensation layer and a second metal layer in contact with the first metal layer, the Young's modulus of the material of the second metal layer is greater than the Young's modulus of the material of the first metal layer; and the sidewall of the interdigital electrode is plated with a protective film, and the Young's modulus of the material of the protective film is greater than the Young's modulus of the material of the metal layer. Thus, the technical problem that the high-frequency alternating stress and temperature rise caused by high input power in the prior art can cause the reliability of the interdigital electrode to decrease and the working frequency of the surface acoustic wave filter to drift, thereby causing the surface acoustic wave filter to fail is solved.

Description

Technical Field

[0001] This application relates to the field of surface acoustic wave (SAW) device technology, and in particular to a high-power SAW filter and its fabrication method. Background Technology

[0002] Surface acoustic wave (SAW) filters are widely used in radio frequency (RF) front-ends in mobile communications due to their advantages such as small size, low cost, and excellent performance. Their core structure is an interdigital transducer (IDT), which uses the piezoelectric effect to convert electrical signals into surface acoustic waves. With the rapid development of 5G technology, higher requirements, such as higher power, are being placed on SAW filters.

[0003] However, when surface acoustic wave (SAW) filters are subjected to high input power, alternating stress and Joule heating can occur. Furthermore, to ensure the low resistivity of the interdigital electrodes, they are typically made of metals with low Young's modulus and a softer texture.

[0004] Therefore, the high-frequency alternating stress and temperature rise caused by high input power lead to deformation of the interdigital electrodes. In particular, the bottom edge region of the discontinuous interdigital electrodes becomes a stress concentration area, making them more prone to deformation. This reduces the reliability of the interdigital electrodes and ultimately leads to the failure of the surface acoustic wave filter.

[0005] Furthermore, the piezoelectric material used in the substrate of the surface acoustic wave (SAW) filter has a large temperature drift coefficient. Therefore, the temperature rise caused by high input power can lead to a drift in the operating frequency of the SAW filter, potentially exceeding its effective bandwidth. This can result in the failure of the SAW filter.

[0006] The publication number is CN220586258U, and the name is a surface acoustic wave filter, which includes a substrate and an electrode connected to the substrate. The electrode includes a first functional layer and a second functional layer. A first adhesive layer for preventing the migration and diffusion of metal atoms in the first functional layer is provided between the first functional layer and the substrate. A second adhesive layer for preventing the migration and diffusion of metal atoms in the first functional layer and the second functional layer is provided between the first functional layer and the second functional layer.

[0007] The publication number is CN104467735A, and the title is "An Impedance Element Type Surface Acoustic Wave Filter with Strong Anti-static Capability". It includes a first interdigital transducer array, a first reflective array, and a second reflective array. The first reflective array and the second reflective array are located on both sides of the first interdigital transducer array. The finger electrodes of the first reflective array and the second reflective array are connected end to end to form an equivalent resistance. The two equivalent resistances formed by the first reflective array and the second reflective array are electrically connected to the first interdigital transducer array in parallel.

[0008] There is currently no effective solution to the technical problem in the existing technology where high input power leads to high-frequency alternating stress and temperature rise, which causes reduced reliability of interdigital electrodes and drift of the operating frequency of the surface acoustic wave filter, thus leading to filter failure. Summary of the Invention

[0009] This disclosure provides a high-power surface acoustic wave (SAW) filter and its fabrication method, which at least solves the technical problem in the prior art where high input power leads to high-frequency alternating stress and temperature rise, which causes a decrease in the reliability of the interdigital electrodes and a drift in the operating frequency of the SAW filter, thus resulting in the failure of the SAW filter.

[0010] According to one aspect of this application, a high-power surface acoustic wave (SAW) filter is provided, comprising: a piezoelectric substrate and a plurality of interdigitated electrodes spaced apart on the piezoelectric substrate. Each interdigitated electrode includes a compensation layer and a metal layer, wherein the metal layer is in contact with the compensation layer, the compensation layer is disposed on the piezoelectric substrate, and the compensation layer is made of silicon dioxide; the metal layer includes a first metal layer disposed on the compensation layer and a second metal layer in contact with the first metal layer, wherein the Young's modulus of the material of the second metal layer is greater than the Young's modulus of the material of the first metal layer; and the sidewalls of the interdigitated electrodes are coated with a protective film, wherein the Young's modulus of the material of the protective film is greater than the Young's modulus of the material of the metal layer.

[0011] According to another aspect of this application, a method for fabricating a high-power surface acoustic wave (SAW) filter is provided, comprising: providing a piezoelectric substrate; depositing and etching a compensation layer on the piezoelectric substrate; depositing and etching a first metal layer on the piezoelectric substrate and the compensation layer; depositing and etching a second metal layer on the piezoelectric substrate and the first metal layer to obtain interdigitated electrodes and busbars; and depositing and etching a protective film on the piezoelectric substrate and the interdigitated electrodes, and etching to form a protective film encapsulating the sidewalls of the interdigitated electrodes to obtain a high-power SAW filter.

[0012] To address the aforementioned technical problems, this application provides a high-power surface acoustic wave (SAW) filter. In the interdigitated electrodes of this high-power SAW filter, the metal layer comprises a first metal layer and a second metal layer. Since the Young's modulus of the material in the second metal layer is greater than that of the material in the first metal layer, the higher Young's modulus of the second metal layer improves the deformation resistance of the interdigitated electrodes under high-frequency alternating stress and high temperatures caused by high input power. This enhances the reliability of the interdigitated electrodes under high input power.

[0013] Furthermore, the interdigital electrodes are coated with a protective film with a higher Young's modulus on their sidewalls. Therefore, by utilizing this protective film to directly bear most of the stress, the stress intensity on the interdigital electrodes can be reduced, and the relatively soft internal interdigital electrodes can be prevented from undergoing drastic volume expansion, contraction, or creep. This further improves the reliability of the interdigital electrodes under high input power.

[0014] Furthermore, a temperature compensation layer, made of silicon dioxide, is disposed between the piezoelectric substrate and the metal layer. Therefore, the positive resonant frequency temperature coefficient of silicon dioxide can offset the negative resonant frequency temperature coefficient of the piezoelectric substrate material. Thus, the compensation layer reduces the temperature drift coefficient of the high-power surface acoustic wave (SAW) filter, preventing its failure due to operating frequency drift.

[0015] Therefore, under high-frequency alternating stress and high temperature caused by high input power, the above structure can improve the reliability of the interdigital electrodes and reduce the occurrence of operating frequency drift in high-power surface acoustic wave (SAW) filters. This solves the technical problem in the prior art where high input power leads to high-frequency alternating stress and temperature rise, causing reduced reliability of the interdigital electrodes and operating frequency drift in the SAW filter, ultimately resulting in SAW filter failure.

[0016] The above and other objects, advantages and features of this application will become more apparent to those skilled in the art from the following detailed description of specific embodiments of this application in conjunction with the accompanying drawings. Attached Figure Description

[0017] The following sections will describe some specific embodiments of this application in detail by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or components. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 This is a schematic diagram of the structure of a high-power surface acoustic wave filter according to an embodiment of this application; Figure 2 This is a schematic diagram of another high-power surface acoustic wave filter according to an embodiment of this application; Figure 3 This is a schematic diagram of the structure of a high-power surface acoustic wave filter with an equal width of compensation layer and metal layer according to an embodiment of this application; Figure 4 This is a schematic diagram of a high-power surface acoustic wave filter with a first metal layer wider than the second metal layer, according to an embodiment of this application. Figure 5 This is a schematic diagram of a high-power surface acoustic wave filter whose two sides of the second part are aligned with the two sides of the first metal layer according to an embodiment of this application. Figure 6 This is a schematic diagram of a high-power surface acoustic wave filter whose width of the second part is smaller than the width of the first metal layer at the corresponding position, according to an embodiment of this application. Figure 7 This is a schematic diagram of the silicon dioxide layer according to the embodiments of this application; Figure 8 This is a schematic diagram of photoresist coating on a silicon dioxide layer according to an embodiment of this application; Figure 9 This is a schematic diagram of the photoresist pattern on the silicon dioxide layer according to the embodiments of this application; Figure 10 This is a schematic diagram of the etching of the silicon dioxide layer according to the embodiments of this application; Figure 11 This is a schematic diagram of the compensation layer according to an embodiment of this application; Figure 12 This is a schematic diagram of the first metal film according to an embodiment of this application; Figure 13 This is a schematic diagram of the photoresist pattern on the first metal film according to the embodiments of this application; Figure 14 This is a schematic diagram of etching the first metal film according to an embodiment of this application; Figure 15 This is a schematic diagram of the compensation layer and the first metal layer according to the embodiments of this application; Figure 16 This is a schematic diagram of the second metal film according to an embodiment of this application; Figure 17 This is a schematic diagram of the photoresist pattern on the second metal film according to the embodiments of this application; and Figure 18 This is a schematic diagram of etching the second metal film according to an embodiment of this application. Detailed Implementation

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in this disclosure can be combined with each other. This disclosure will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] To enable those skilled in the art to better understand the present disclosure, the technical solutions of the present disclosure will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present disclosure, and not all embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present disclosure.

[0020] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate for the embodiments of this disclosure described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0021] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0022] Figure 1 This is a schematic diagram of the structure of a high-power surface acoustic wave filter according to an embodiment of this application. Figure 2 This is a schematic diagram of another high-power surface acoustic wave (SAW) filter according to an embodiment of this application. According to one aspect of this embodiment, a high-power SAW filter 10 is provided, comprising: a piezoelectric substrate 100 and a plurality of interdigitated electrodes 200 spaced apart on the piezoelectric substrate 100. Each interdigitated electrode 200 includes: a compensation layer 210 and a metal layer 220, wherein the metal layer 220 is in contact with the compensation layer 210, the compensation layer 210 is disposed on the piezoelectric substrate 100, and the material of the compensation layer 210 is silicon dioxide; the metal layer 220 includes: a first metal layer 221 disposed on the compensation layer 210 and a second metal layer 222 in contact with the first metal layer 221, wherein the Young's modulus of the material of the second metal layer 222 is greater than the Young's modulus of the material of the first metal layer 221; and the sidewalls of the interdigitated electrodes 200 are coated with a protective film 300, wherein the Young's modulus of the material of the protective film 300 is greater than the Young's modulus of the material of the metal layer 220.

[0023] Specifically, refer to Figure 1 and Figure 2 As shown, in the high-power surface acoustic wave filter 10, a plurality of interdigitated electrodes 200 are spaced apart on the piezoelectric substrate 100. Each interdigitated electrode 200 includes a compensation layer 210 disposed on the piezoelectric substrate 100 and a metal layer 220 in contact with the compensation layer 210. Furthermore, the compensation layer 210 is made of silicon dioxide.

[0024] Furthermore, the metal layer 220 includes a first metal layer 221 disposed on the compensation layer 210 and a second metal layer 222 in contact with the first metal layer 221. The Young's modulus of the material of the second metal layer 222 is greater than that of the material of the first metal layer 221.

[0025] Furthermore, a protective film 300 is deposited on the sidewall of the interdigitated electrode 200. The Young's modulus of the material of the protective film 300 is greater than that of the material of the metal layer 220. That is, the Young's modulus of the material of the protective film 300 is greater than that of the material of the second metal layer 222, and the Young's modulus of the material of the protective film 300 is greater than that of the material of the first metal layer 221.

[0026] Therefore, under high-frequency alternating stress and high temperature caused by high input power, the second metal layer 222 with a large Young's modulus can improve the deformation resistance of the interdigital electrode 200. Furthermore, the protective film 300 with an even larger Young's modulus directly bears most of the stress, reducing the stress intensity on the interdigital electrode 200 and preventing severe volume expansion, contraction, or creep of the softer internal interdigital electrode 200. This improves the reliability of the interdigital electrode 200 under high input power, and consequently enhances the power tolerance performance of the high-power surface acoustic wave filter 10.

[0027] Furthermore, the interdigitated electrode 200 of this application is provided with a compensation layer 210, and the material of the compensation layer 210 is silicon dioxide. Therefore, by utilizing the positive resonant frequency temperature coefficient of silicon dioxide, the negative resonant frequency temperature coefficient of the piezoelectric substrate 100 material can be offset. Thus, through the compensation layer 210, the temperature drift coefficient of the high-power surface acoustic wave filter 10 can be reduced. Consequently, at high temperatures caused by high input power, failure of the high-power surface acoustic wave filter 10 due to operating frequency drift can be avoided.

[0028] As described in the background section, surface acoustic wave (SAW) filters are widely used in radio frequency (RF) front-ends such as mobile communications due to their advantages of small size, low cost, and excellent performance. Their core structure is an interdigital transducer (IDT), which uses the piezoelectric effect to convert electrical signals into surface acoustic waves. With the rapid development of fifth-generation (5G) mobile communication technology, higher requirements, such as higher power, are being placed on SAW filters.

[0029] However, when surface acoustic wave (SAW) filters are subjected to high input power, alternating stress and Joule heating can occur. Furthermore, to ensure the low resistivity of the interdigital electrodes, they are typically made of metals with low Young's modulus and a softer texture.

[0030] Therefore, the high-frequency alternating stress and temperature rise caused by high input power lead to deformation of the interdigital electrodes. In particular, the bottom edge region of the discontinuous interdigital electrodes becomes a stress concentration area, making them more prone to deformation. This reduces the reliability of the interdigital electrodes and ultimately leads to the failure of the surface acoustic wave filter.

[0031] Furthermore, the piezoelectric material used in the substrate of the surface acoustic wave (SAW) filter has a large temperature drift coefficient. Therefore, the temperature rise caused by high input power can lead to a drift in the operating frequency of the SAW filter, potentially exceeding its effective bandwidth. This can result in the failure of the SAW filter.

[0032] In view of this, this application provides a high-power surface acoustic wave (SAW) filter. In the interdigitated electrodes of this high-power SAW filter, the metal layer includes a first metal layer and a second metal layer. Since the Young's modulus of the material in the second metal layer is greater than that of the material in the first metal layer, the higher Young's modulus of the second metal layer improves the deformation resistance of the interdigitated electrodes under high-frequency alternating stress and high temperature caused by high input power. This enhances the reliability of the interdigitated electrodes under high input power.

[0033] Furthermore, the interdigital electrodes are coated with a protective film with a higher Young's modulus on their sidewalls. Therefore, by utilizing this protective film to directly bear most of the stress, the stress intensity on the interdigital electrodes can be reduced, and the relatively soft internal interdigital electrodes can be prevented from undergoing drastic volume expansion, contraction, or creep. This further improves the reliability of the interdigital electrodes under high input power.

[0034] Furthermore, a temperature compensation layer, made of silicon dioxide, is disposed between the piezoelectric substrate and the metal layer. Therefore, the positive resonant frequency temperature coefficient of silicon dioxide can offset the negative resonant frequency temperature coefficient of the piezoelectric substrate material. Thus, the compensation layer reduces the temperature drift coefficient of the high-power surface acoustic wave (SAW) filter, preventing its failure due to operating frequency drift.

[0035] Therefore, under high-frequency alternating stress and high temperature caused by high input power, the above structure can improve the reliability of the interdigital electrodes and reduce the occurrence of operating frequency drift in high-power surface acoustic wave (SAW) filters. This solves the technical problem in the prior art where high input power leads to high-frequency alternating stress and temperature rise, causing reduced reliability of the interdigital electrodes and operating frequency drift in the SAW filter, ultimately resulting in SAW filter failure.

[0036] Preferably, the material of the piezoelectric substrate 100 may be, for example, lithium tantalate or lithium niobate.

[0037] Preferably, the material of the second metal layer 222 may be, for example, one of molybdenum (Mo), chromium (Cr), or nickel (Ni).

[0038] Optionally, the upper surface of the interdigital electrode 200 is coated with a protective film 300.

[0039] Specifically, such as Figure 1 and Figure 2 The sidewalls of the interdigital electrode 200 shown are coated with a protective film 300, and a protective film 300 can also be coated on the upper surface of the interdigital electrode 200.

[0040] Therefore, under high-frequency alternating stress and high temperature caused by high input power, the protective film 300 can withstand most of the stress, reducing the stress intensity on the interdigital electrode 200 and preventing deformation of the upper surface and sidewalls of the interdigital electrode 200. This, in turn, improves the reliability of the interdigital electrode 200 and avoids failure of the high-power surface acoustic wave filter 10.

[0041] Optionally, the second metal layer 222 wraps around the outer periphery of the compensation layer 210 and the first metal layer 221, and the second metal layer 222 is in contact with the piezoelectric substrate 100.

[0042] Specifically, refer to Figure 1 and Figure 2 As shown, the compensation layer 210 and the first metal layer 221 are surrounded by a second metal layer 222, and the second metal layer 222 is in contact with the piezoelectric substrate 100.

[0043] Therefore, by using a second metal layer 222 with a larger Young's modulus as the outermost layer of the interdigital electrode 200, the deformation resistance of the interdigital electrode 200 can be improved. Furthermore, this improves the reliability of the interdigital electrode 200 and prevents the high-power surface acoustic wave filter 10 from failing.

[0044] Optionally, the second metal layer 222 is formed on the first metal layer 221, and the width of the compensation layer 210 is equal to the width of the metal layer 220.

[0045] Specifically, Figure 3 This is a schematic diagram of a high-power surface acoustic wave filter with a compensation layer and a metal layer of equal width, according to an embodiment of this application. (Reference) Figure 3 As shown, the second metal layer 222 is formed on the first metal layer 221. Furthermore, the width of the compensation layer 210 is equal to the width of the metal layer 220. That is, the width of the compensation layer 210 is equal to the width of the first metal layer 221, and the width of the compensation layer 210 is equal to the width of the second metal layer 222.

[0046] Therefore, by having the second metal layer 222 and the protective film 300 bear most of the stress, the stress borne by the first metal layer 221, which has a lower Young's modulus, can be reduced, thereby improving the deformation resistance of the interdigital electrode 200. This, in turn, improves the reliability of the interdigital electrode 200 and prevents the high-power surface acoustic wave filter 10 from failing.

[0047] Optionally, the second metal layer 222 is formed on the first metal layer 221, and the width of the first metal layer 221 is greater than the width of the second metal layer 222, and the width of the compensation layer 210 is equal to the width of the first metal layer 221.

[0048] Specifically, Figure 4 This is a schematic diagram of a high-power surface acoustic wave filter according to an embodiment of this application, where the width of the first metal layer is greater than the width of the second metal layer. (Reference) Figure 4 As shown, the second metal layer 222 is formed on the first metal layer 221. Furthermore, the width of the first metal layer 221 is greater than the width of the second metal layer 222, and the width of the compensation layer 210 is equal to the width of the first metal layer 221.

[0049] Therefore, by having the second metal layer 222 and the protective film 300 bear most of the stress, the stress borne by the first metal layer 221, which has a lower Young's modulus, can be reduced, thereby improving the deformation resistance of the interdigital electrode 200. This, in turn, improves the reliability of the interdigital electrode 200 and prevents the high-power surface acoustic wave filter 10 from failing.

[0050] Optionally, the second metal layer 222 includes a first portion 2221 and a second portion 2222 formed on the first portion 2221, wherein the width of the second portion 2222 is greater than the width of the first portion 2221; the first portion 2221 passes through the compensation layer 210 and the first metal layer 221 and contacts the piezoelectric substrate 100; and the second portion 2222 is disposed on the compensation layer 210.

[0051] Specifically, Figure 5 This is a schematic diagram of the structure of a high-power surface acoustic wave filter with both sides of the second part aligned with both sides of the first metal layer, according to an embodiment of this application. Figure 6 This is a schematic diagram of a high-power surface acoustic wave filter, according to an embodiment of this application, where the width of the second portion is smaller than the width of the first metal layer at the corresponding location. (Reference) Figure 5 and Figure 6 As shown, the second portion 2222 of the second metal layer 222 is formed on the first portion 2221, and the width of the second portion 2222 is greater than the width of the first portion 2221.

[0052] Furthermore, the second portion 2222 is disposed on the compensation layer 210; the first portion 2221 passes through the compensation layer 210 and the first metal layer 221, so that the first portion 2221 is in contact with the piezoelectric substrate 100.

[0053] Thus, the interdigital electrode 200 is anchored to the piezoelectric substrate 100 by the vertical first portion 2221, and the deformation of the first metal layer 221 when subjected to bending stress in the vertical direction is reduced by the second portion 2222 parallel to the first metal layer 221. Therefore, the deformation resistance of the interdigital electrode 200 can be improved by the second metal layer 222. Furthermore, the reliability of the interdigital electrode 200 can be improved, avoiding failure of the high-power surface acoustic wave filter 10.

[0054] Optionally, the two sides of the second portion 2222 are aligned with the two sides of the first metal layer 221, and the two sides of the first metal layer 221 are aligned with the two sides of the compensation layer 210.

[0055] Specifically, refer to Figure 5 As shown, the two sides of the second portion 2222 of the second metal layer 222 are aligned with the two sides of the first metal layer 221. Furthermore, the two sides of the first metal layer 221 are aligned with the two sides of the compensation layer 210.

[0056] Therefore, by using the second portion 2222 parallel to the first metal layer 221, the deformation of the first metal layer 221 when subjected to bending stress in the vertical direction can be reduced, thereby improving the deformation resistance of the interdigital electrode 200. Furthermore, this improves the reliability of the interdigital electrode 200 and prevents the high-power surface acoustic wave filter 10 from failing.

[0057] Optionally, the two sides of the first metal layer 221 are aligned with the two sides of the compensation layer 210; and the width of the second portion 2222 is smaller than the width of the first metal layer 221 at the corresponding position.

[0058] Specifically, refer to Figure 6 As shown, the width of the second portion 2222 of the second metal layer 222 is smaller than the width of the first metal layer 221 at the corresponding position. That is, the first metal layer 221 wraps around the outer wall of the second portion 2222. Furthermore, the width of the second portion 2222 is smaller than the width of the first metal layer 221 at the corresponding position.

[0059] Therefore, by using the second portion 2222 parallel to the first metal layer 221, the deformation of the first metal layer 221 when subjected to bending stress in the vertical direction can be reduced, thereby improving the deformation resistance of the interdigital electrode 200. Furthermore, this improves the reliability of the interdigital electrode 200 and prevents the high-power surface acoustic wave filter 10 from failing.

[0060] It is important to note that, in cases such as Figures 3-6In the high-power surface acoustic wave filter 10 shown, the protective film 300 can either wrap only the sidewalls of the interdigital electrode 200, or wrap both the sidewalls and the top surface of the interdigital electrode 200.

[0061] Optionally, it also includes: a busbar 400 disposed on both sides of the plurality of interdigitated electrodes 200, wherein the busbar 400 includes a compensation layer 210 and a metal layer 220, and the width of the compensation layer 210 is equal to the width of the metal layer 220.

[0062] Specifically, refer to Figures 1-6 As shown, a busbar 400 is also disposed on the piezoelectric substrate 100, and the busbar 400 is disposed opposite to each other on both sides of the plurality of interdigitated electrodes 200. The busbar 400 includes a compensation layer 210 and a metal layer 220, and the width of the compensation layer 210 is equal to the width of the metal layer 220.

[0063] Because a second metal layer 222 with a larger Young's modulus is provided in the metal layer 220, the deformation resistance of the busbar 400 can be improved. Furthermore, by compensating for the positive resonant frequency temperature coefficient of the layer 210, the negative resonant frequency temperature coefficient of the piezoelectric substrate 100 can be offset, thereby reducing the temperature drift coefficient of the high-power surface acoustic wave filter 10.

[0064] This improves the reliability of the busbar 400 and reduces the occurrence of frequency drift in the high-power surface acoustic wave filter 10. Consequently, it prevents the high-power surface acoustic wave filter 10 from failing.

[0065] According to another aspect of this embodiment, a method for fabricating a high-power surface acoustic wave filter 10 is provided, comprising: providing a piezoelectric substrate 100; depositing and etching a compensation layer 210 on the piezoelectric substrate 100; depositing and etching a first metal layer 221 on the piezoelectric substrate 100 and the compensation layer 210; depositing and etching a second metal layer 222 on the piezoelectric substrate 100 and the first metal layer 221 to obtain an interdigitated electrode 200 and a busbar 400; and depositing a film on the piezoelectric substrate 100 and the interdigitated electrode 200, and etching to form a protective film 300 encapsulating the sidewall of the interdigitated electrode 200 to obtain a high-power surface acoustic wave filter 10.

[0066] Specifically, Figure 7 This is a schematic diagram of the silicon dioxide layer according to an embodiment of this application. Figure 8 This is a schematic diagram of photoresist coating on a silicon dioxide layer according to an embodiment of this application. Figure 9 This is a schematic diagram of the photoresist pattern on the silicon dioxide layer according to the embodiments of this application. Figure 10 This is a schematic diagram of the etching of the silicon dioxide layer according to the embodiments of this application. Figure 11 This is a schematic diagram of the compensation layer according to an embodiment of this application. Figure 12 This is a schematic diagram of the first metal film according to an embodiment of this application. Figure 13 This is a schematic diagram of the photoresist pattern on the first metal film according to the embodiments of this application. Figure 14 This is a schematic diagram of etching the first metal film according to an embodiment of this application. Figure 15 This is a schematic diagram of the compensation layer and the first metal layer according to the embodiments of this application. Figure 16 This is a schematic diagram of the second metal film according to an embodiment of this application. Figure 17 This is a schematic diagram of the photoresist pattern on the second metal film according to the embodiments of this application. Figure 18 This is a schematic diagram of etching the second metal film according to an embodiment of this application.

[0067] refer to Figure 1 and Figures 7-18 As shown, firstly, a piezoelectric substrate 100 is provided, and silicon dioxide is sputtered on the piezoelectric substrate 100. The substrate is then planarized using a chemical mechanical polishing (CMP) process, and finely adjusted using a trimming process to obtain a silicon dioxide layer.

[0068] Next, photoresist is uniformly coated onto the silicon dioxide layer. Using a photolithography machine, ultraviolet light is passed through a patterned mask and irradiated onto the photoresist-coated silicon dioxide layer. Then, a developer is used to develop the silicon dioxide layer, revealing the pattern to be used in subsequent etching steps. Furthermore, the silicon dioxide layer is etched according to the pattern to form a compensation layer 210, and the photoresist is then stripped off.

[0069] Furthermore, a first metal film is obtained by evaporation on the piezoelectric substrate 100 and the compensation layer 210, planarization by chemical mechanical polishing (CMP), and fine adjustment by trimming.

[0070] Furthermore, photoresist is uniformly coated onto the first metal film. Using a photolithography machine, ultraviolet light is passed through a patterned mask and irradiated onto the photoresist-coated first metal film. Then, a developing solution is used for development, resulting in a pattern on the first metal film for subsequent etching steps. Following this, the first metal film is etched according to the pattern to form a first metal layer 221, and the photoresist is then stripped off.

[0071] Subsequently, a second metal film is obtained by evaporation on the piezoelectric substrate 100 and the first metal layer 221, planarization by chemical mechanical polishing (CMP), and fine adjustment by trimming.

[0072] Furthermore, photoresist is uniformly coated onto the second metal film. Using a photolithography machine, ultraviolet light is passed through a patterned mask and irradiated onto the photoresist-coated second metal film. Then, a developing solution is used for development, resulting in a pattern on the second metal film for subsequent etching steps. Following this pattern, the second metal film is etched to form a second metal layer 222, and the photoresist is then stripped off.

[0073] Thus, through the above steps, a plurality of interdigitated electrodes 200 and busbars 400 disposed on opposite sides of the plurality of interdigitated electrodes 200 can be obtained on the piezoelectric substrate 100.

[0074] Finally, a film is deposited on the piezoelectric substrate 100 and the interdigital electrode 200 using a sputtering process. Then, a protective film 300 is formed by argon ion etching, ultimately encapsulating the sidewalls of the interdigital electrode 200. Thus, a high-power surface acoustic wave filter 10 is obtained.

[0075] Therefore, the high-power surface acoustic wave filter 10 prepared through the above steps can improve the temperature drift coefficient and enhance the reliability of the interdigital electrode 200 and the busbar 400. Furthermore, it can prevent the high-power surface acoustic wave filter 10 from failing due to operating frequency drift and deformation of the interdigital electrode 200.

[0076] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of this disclosure. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0077] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0078] In the description of this disclosure, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings and is only for the convenience of describing this disclosure and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this disclosure; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0079] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A high-power surface acoustic wave filter (10), characterized in that, include: A piezoelectric substrate (100) and a plurality of interdigitated electrodes (200) spaced apart on the piezoelectric substrate (100), wherein The interdigitated electrode (200) includes a compensation layer (210) and a metal layer (220), wherein the metal layer (220) is in contact with the compensation layer (210), the compensation layer (210) is disposed on the piezoelectric substrate (100), and the material of the compensation layer (210) is silicon dioxide; The metal layer (220) includes: a first metal layer (221) disposed on the compensation layer (210) and a second metal layer (222) partially formed outside the first metal layer (221), wherein the Young's modulus of the material of the second metal layer (222) is greater than the Young's modulus of the material of the first metal layer (221); and The sidewalls of the interdigitated electrode (200) are coated with a protective film (300), and the material of the protective film (300) has a Young's modulus greater than that of the material of the metal layer (220).

2. The high-power surface acoustic wave filter (10) according to claim 1, characterized in that, The upper surface of the interdigitated electrode (200) is coated with the protective film (300).

3. The high-power surface acoustic wave filter (10) according to claim 1 or 2, characterized in that, The second metal layer (222) wraps around the outer periphery of the compensation layer (210) and the first metal layer (221), and the second metal layer (222) is in contact with the piezoelectric substrate (100).

4. The high-power surface acoustic wave filter (10) according to claim 1 or 2, characterized in that, The second metal layer (222) is formed on the first metal layer (221), and the width of the compensation layer (210) is equal to the width of the metal layer (220).

5. The high-power surface acoustic wave filter (10) according to claim 1 or 2, characterized in that, The second metal layer (222) is formed on the first metal layer (221), and the width of the first metal layer (221) is greater than the width of the second metal layer (222), and the width of the compensation layer (210) is equal to the width of the first metal layer (221).

6. The high-power surface acoustic wave filter (10) according to claim 1 or 2, characterized in that, The second metal layer (222) includes a first portion (2221) and a second portion (2222) formed on the first portion (2221), wherein the width of the second portion (2222) is greater than the width of the first portion (2221); The first portion (2221) passes through the compensation layer (210) and the first metal layer (221) and is in contact with the piezoelectric substrate (100); and The second part (2222) is disposed on the compensation layer (210).

7. The high-power surface acoustic wave filter (10) according to claim 6, characterized in that, The two sides of the second part (2222) are aligned with the two sides of the first metal layer (221), and the two sides of the first metal layer (221) are aligned with the two sides of the compensation layer (210).

8. The high-power surface acoustic wave filter (10) according to claim 6, characterized in that, The two sides of the first metal layer (221) are aligned with the two sides of the compensation layer (210); and The width of the second part (2222) is smaller than the width of the first metal layer (221) at the corresponding position.

9. The high-power surface acoustic wave filter (10) according to claim 1, characterized in that, It also includes: a busbar (400) disposed on both sides of the plurality of interdigitated electrodes (200), wherein the busbar (400) includes the compensation layer (210) and the metal layer (220), and the width of the compensation layer (210) is equal to the width of the metal layer (220).

10. A method for fabricating a high-power surface acoustic wave filter (10), characterized in that, The high-power surface acoustic wave filter (10) as described in any one of claims 1 to 9 is prepared by the following steps: Provide a piezoelectric substrate (100); A compensation layer (210) is deposited and etched on the piezoelectric substrate (100). A first metal layer (221) is deposited and etched on the piezoelectric substrate (100) and the compensation layer (210). A second metal layer (222) is deposited and etched on the piezoelectric substrate (100) and the first metal layer (221) to obtain interdigitated electrodes (200) and busbars (400). as well as A protective film (300) is deposited on the piezoelectric substrate (100) and the interdigitated electrode (200) and etched to form a protective film (300) that wraps around the sidewall of the interdigitated electrode (200) to obtain a high-power surface acoustic wave filter (10).

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