Surface acoustic wave device, manufacturing method thereof, radio frequency front-end module and electronic equipment

Abstract

The invention discloses a surface acoustic wave device, a manufacturing method thereof, a radio frequency front-end module and electronic equipment. The manufacturing method comprises the following steps: providing a piezoelectric substrate; forming an interdigital transducer on the piezoelectric substrate, wherein the interdigital transducer is provided with an electrode finger; forming a frequency modulation layer on the interdigital transducer, wherein the frequency modulation layer comprises a first region and a plurality of second regions; and the frequency modulation layer in the first area is thinned, so that the frequency modulation layer in each second area forms a protruding part relative to the thinned frequency modulation layer in the first area in the thickness direction, each protruding part forms a mass load strip, and the mass load strips are located above the end parts of the electrode fingers. According to the invention, the mass load strip is formed by the protruding part remained after local thinning of the frequency modulation layer, so that the problem of performance degradation caused by existence of a transverse mode can be solved, and compared with a process of forming PST through deposition, the process is simplified, the problem of self-alignment deviation which is easy to occur is eliminated, and thus the process complexity and the production cost are reduced.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more specifically to a surface acoustic wave device and its manufacturing method, a radio frequency front-end module, and an electronic device. Background Technology

[0002] Surface acoustic wave (SAW) devices process acoustic signals propagating on the surface of piezoelectric materials using acoustic-to-electric transducers. They offer advantages such as low cost, small size, and multiple functions, and are widely used in radar, communication, navigation, and identification fields. These devices include interdigital transducers (IDTs) that enable the conversion between electrical and acoustic signals.

[0003] However, the parasitic transverse modes of the piezoelectric substrate have a significant impact on the passband flatness. The acoustic waves they induce propagate not only in the direction perpendicular to the electrode fingers but also in the direction parallel to the electrode fingers, resulting in transverse mode spurious propagation, passband disturbances, increased energy loss, and decreased Q value in the frequency characteristics. This causes the performance of existing surface acoustic wave devices to degrade due to the presence of transverse modes. Summary of the Invention

[0004] The summary section introduces a series of simplified concepts, which will be further explained in detail in the detailed description section. This summary section is not intended to limit the key and essential technical features of the claimed technical solution, nor is it intended to determine the scope of protection of the claimed technical solution.

[0005] To address the existing problems, this invention provides a method for manufacturing a surface acoustic wave (SAW) device, the method comprising:

[0006] Provide piezoelectric substrates;

[0007] An interdigital transducer is formed on a piezoelectric substrate, the interdigital transducer having at least one electrode finger;

[0008] A frequency modulation layer is formed on the interdigital transducer, the frequency modulation layer including a first region and multiple second regions;

[0009] The frequency modulation layer of the first region is thinned so that the frequency modulation layer of each second region forms a protrusion in the thickness direction relative to the thinned frequency modulation layer of the first region. Each protrusion constitutes a mass load bar, which is located above the tip of the electrode finger.

[0010] In some embodiments of this application, the frequency modulation layer of the first region is thinned, including:

[0011] A first photoresist layer is formed on the frequency modulation layer;

[0012] The first photoresist layer is patterned, and the patterned first photoresist layer covers the frequency modulation layer of the second region and exposes the frequency modulation layer of the first region.

[0013] Using the patterned first photoresist layer as a mask, the frequency modulation layer in the exposed first region is thinned.

[0014] Remove the first photoresist layer after patterning.

[0015] In some embodiments of this application, the mass load bar is located at at least two ends of each electrode finger.

[0016] In some embodiments of this application, the mass load bar is made of a dielectric material.

[0017] In some embodiments of this application, an interdigital transducer is formed on a piezoelectric substrate, including:

[0018] A second photoresist layer is formed on the piezoelectric substrate;

[0019] The second photoresist layer is patterned, and the patterned second photoresist layer defines the pattern in which the interdigital transducer is to be formed, and the pattern exposes part of the surface of the piezoelectric substrate.

[0020] Metal material is deposited on the surface of the patterned second photoresist layer and the exposed piezoelectric substrate.

[0021] After removing the patterned second photoresist layer and the metal material on its surface, the remaining metal material on the exposed piezoelectric substrate surface forms an interdigital transducer.

[0022] In some embodiments of this application, before forming the frequency modulation layer on the interdigital transducer, the method further includes:

[0023] A first protective layer is formed on the interdigital transducer, and a frequency modulation layer is formed on the first protective layer.

[0024] In some embodiments of this application, it further includes: forming a second protective layer that covers the mass load bar and the frequency modulation layer of the thinned first region.

[0025] In another aspect, the present invention provides a surface acoustic wave device, which is obtained by any of the manufacturing methods described above.

[0026] In another aspect, the present invention provides a radio frequency front-end module, which includes a surface acoustic wave device.

[0027] In another aspect, the present invention provides an electronic device, which includes a radio frequency front-end module.

[0028] The surface acoustic wave (SAW) device, its manufacturing method, RF front-end module, and electronic device disclosed in this application solve the performance degradation problem caused by the presence of lateral modes in SAW devices by thinning the frequency modulation layer in the first region and forming a mass load bar by the protruding portion of the frequency modulation layer in the second region relative to the thinned frequency modulation layer in the thickness direction. At the same time, forming the mass load bar by locally thinning the frequency modulation layer simplifies the process compared to the deposition-forming PST process and eliminates the self-alignment deviation problem that is prone to occur in the deposition-forming PST process, thereby reducing process complexity and production costs. Attached Figure Description

[0029] The following drawings, which are incorporated herein by reference as part of this invention, are provided for understanding the invention. The drawings illustrate embodiments of the invention and their descriptions, serving to explain the principles of the invention.

[0030] In the attached image:

[0031] Figure 1A-1F A cross-sectional schematic diagram of a semiconductor device obtained by sequentially implementing the process flow of depositing PST in related technologies is shown.

[0032] Figure 2 A flowchart illustrating a method for manufacturing a surface acoustic wave device according to a specific embodiment of this application is shown.

[0033] Figures 3A-3E This illustration shows a cross-sectional schematic diagram of a semiconductor device obtained by sequentially implementing a method for manufacturing a surface acoustic wave device according to a specific embodiment of this application.

[0034] Figure 4 A top view of a surface acoustic wave device according to an embodiment of this application is shown.

[0035] Figure 5 It shows Figure 4 A schematic diagram of the cross section along the middle AA.

[0036] Figure 6 The impedance curves of a surface acoustic wave device according to an embodiment of this application are shown in a comparison diagram. Detailed Implementation

[0037] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid obscuring the invention.

[0038] It should be understood that the invention can be embodied in various forms and should not be construed as being limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, for clarity, the dimensions and relative dimensions of layers and regions may be exaggerated. The same reference numerals denote the same elements throughout.

[0039] It should be understood that when an element or layer is referred to as "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it may be directly on, adjacent to, connected to, or coupled to other elements or layers, or there may be intervening elements or layers. Conversely, when an element is referred to as "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc., may be used to describe various elements, components, areas, layers, and / or portions, these elements, components, areas, layers, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, area, layer, or portion from another element, component, area, layer, or portion. Therefore, without departing from the teachings of this invention, the first element, component, area, layer, or portion discussed below may be referred to as the second element, component, area, layer, or portion.

[0040] Spatial relation terms such as “below,” “under,” “below,” “under,” “above,” “above,” etc., are used herein for convenience of description to describe the relationship between one element or feature shown in the figure and other elements or features. It should be understood that, in addition to the orientation shown in the figure, spatial relation terms are intended to also include different orientations of the device in use and operation. For example, if the device in the figure is flipped, then the element or feature described as “below” or “under” the other element or feature will be oriented “above” the other element or feature. Therefore, the exemplary terms “below” and “under” can include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or otherwise) and the spatial descriptive terms used herein will be interpreted accordingly.

[0041] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. When used herein, the singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising” and / or “including,” when used in this specification, identify the presence of features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups. When used herein, the term “and / or” includes any and all combinations of the associated listed items.

[0042] To fully understand this application, detailed steps and structures will be presented in the following description to illustrate the technical solutions proposed in this application. Preferred embodiments of this application are described in detail below; however, in addition to these detailed descriptions, this application may have other implementation methods.

[0043] The parasitic lateral modes of piezoelectric substrates have a significant impact on passband flatness, leading to performance degradation of existing surface acoustic wave devices due to the presence of lateral modes.

[0044] In related technologies, after forming an interdigital transducer on a piezoelectric substrate, a mass load strip (Piston, abbreviated as PST, also known as a piston structure) is formed by depositing a metal or dielectric layer on the electrode fingers of the interdigital transducer to improve the performance problems of surface acoustic wave devices caused by the presence of transverse modes.

[0045] For example, such as Figures 1A to 1F The diagram illustrates the process flow for depositing PST in related technologies, which mainly includes the following steps:

[0046] S11, such as Figure 1A As shown, a piezoelectric substrate 110 is provided;

[0047] S12, as Figure 1B As shown, an interdigital transducer 120 is formed on a piezoelectric substrate 110 by photolithography and deposition processes;

[0048] S13, as Figure 1C As shown, a mass load strip 130 is formed by photolithography and deposition processes. The mass load strip 130 is located at positions corresponding to the two ends of the electrode fingers of the interdigital transducer 120.

[0049] S14, as Figure 1D As shown, a first protective layer 140 is formed, which covers the interdigital transducer 120 and the mass load bar 130;

[0050] S15, such as Figure 1E As shown, a frequency modulation layer 150 is formed, and the frequency modulation layer 150 covers the first protective layer 140;

[0051] S16, as Figure 1F As shown, the frequency modulation layer 150 is thinned.

[0052] However, the above-mentioned process for depositing PST has two problems. First, the process is not optimized enough. Second, when forming mass load strips on both ends of the electrode fingers of the interdigital transducer through photolithography and deposition, PST self-alignment deviation is prone to occur, which leads to increased process complexity and high production costs.

[0053] Therefore, in view of the aforementioned technical problems, the present invention proposes a method for manufacturing a surface acoustic wave device, such as... Figure 2 As shown, it mainly includes the following steps:

[0054] Step S21, provide a piezoelectric substrate;

[0055] Step S22: An interdigital transducer is formed on a piezoelectric substrate, the interdigital transducer having at least one electrode finger;

[0056] Step S23: A frequency modulation layer is formed on the interdigital transducer, the frequency modulation layer including a first region and a plurality of second regions;

[0057] Step S24: The frequency modulation layer of the first region is thinned so that the frequency modulation layer of each second region forms a protrusion in the thickness direction relative to the thinned frequency modulation layer of the first region. Each protrusion constitutes a mass load bar, which is located above the end of the electrode finger.

[0058] In this embodiment, by thinning the frequency modulation layer in the first region, a mass load bar is formed by the protruding portion of the frequency modulation layer in the second region relative to the thinned frequency modulation layer in the thickness direction. This solves the performance degradation problem caused by the presence of transverse modes in surface acoustic wave devices. At the same time, forming the mass load bar by locally thinning the frequency modulation layer simplifies the process compared to the deposition PST process and eliminates the self-alignment deviation problem that is prone to occur in the deposition PST process, thereby reducing process complexity and production costs.

[0059] Example 1

[0060] Below, for reference Figures 3A to 3E , Figure 4 and Figure 5 The manufacturing method of the surface acoustic wave device of the present invention is described in detail, wherein, Figures 3A-3E This illustration shows a cross-sectional schematic diagram of a semiconductor device obtained by sequentially implementing a method for manufacturing a surface acoustic wave device according to a specific embodiment of this application. Figure 4 A top view of a surface acoustic wave device according to an embodiment of this application is shown; Figure 5 It shows Figure 4 A schematic diagram of the cross section along the middle AA.

[0061] For example, the method for manufacturing the surface acoustic wave device of this application includes the following steps:

[0062] First, execute step S21, as follows: Figure 3A As shown, a piezoelectric substrate 310 is provided.

[0063] In some embodiments, the piezoelectric substrate 310 may be made of a material with piezoelectric properties, such as at least one selected from quartz, aluminum nitride, sapphire, lithium niobate (LiNbO3, abbreviated as LN), lithium tantalate (LiTaO3, abbreviated as LT), etc., and this embodiment does not specifically limit the choice. For example, the piezoelectric substrate 310 may be made of lithium tantalate.

[0064] Next, proceed to step S22, as follows: Figure 3B As shown, an interdigital transducer 320 is formed on a piezoelectric substrate 310, and the interdigital transducer 320 has at least one electrode finger 321.

[0065] In some embodiments, forming an interdigital transducer 320 on a piezoelectric substrate 310 may include the following steps S221 to S224.

[0066] Step S221: A second photoresist layer is formed on the piezoelectric substrate 310.

[0067] This step involves forming a continuous and uniform second photoresist layer on the surface of the piezoelectric substrate 310 through processes such as coating. Its function is to serve as a medium carrier for subsequent patterning processing, providing a physical basis for the pattern definition of the interdigital transducer 320, and ensuring that the pattern can be accurately transferred to the surface of the piezoelectric substrate 310.

[0068] Step S222: The second photoresist layer is patterned. The patterned second photoresist layer defines the pattern of the interdigital transducer 320 to be formed. The pattern exposes part of the surface of the piezoelectric substrate 310.

[0069] Patterning typically involves exposure and development processes: based on a pre-defined mask pattern for the interdigital transducer 320, the second photoresist layer is selectively exposed, causing a chemical change in the exposed area of ​​the photoresist; subsequently, the unexposed (or exposed) photoresist portions are removed using a developer, ultimately forming a pattern on the second photoresist layer that matches the shape of the interdigital transducer 320. The retained photoresist areas correspond to portions where no metal material needs to be deposited subsequently, while the exposed piezoelectric substrate 310 surface is the formation area of ​​the interdigital transducer 320.

[0070] Step S223: Deposit metal material on the surface of the patterned second photoresist layer and the exposed piezoelectric substrate 310.

[0071] Exemplarily, various deposition methods commonly used in the art can be employed to deposit metal materials on the surface of the second photoresist layer and the exposed piezoelectric substrate 310, such as chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD). Exemplarily, the deposited metal material can be a single metal material or a composite or alloy of different metals. Optionally, the metal material can be one of aluminum, molybdenum, copper, gold, platinum, silver, nickel, chromium, tungsten, or a composite or alloy thereof, without limitation. The metal material deposited on the exposed piezoelectric substrate 310 will serve as the body of the interdigital transducer 320, while the metal material deposited on the surface of the second photoresist layer will be removed in a subsequent lift-off process.

[0072] Step S224: Remove the patterned second photoresist layer and the metal material on its surface, and the remaining metal material on the exposed piezoelectric substrate 310 forms the interdigital transducer 320.

[0073] The second photoresist layer is removed using a lift-off process. During the removal of the second photoresist layer, the metal material attached to its surface is also removed, leaving only the metal material deposited on the exposed surface of the piezoelectric substrate 310. This metal material is the required interdigital transducer 320, ensuring that the shape, size, and positional accuracy of the interdigital transducer 320 meet the design requirements.

[0074] Next, proceed to step S23, as follows: Figure 3D As shown, a frequency modulation layer 340 is formed on the interdigital transducer 320, and the frequency modulation layer 340 includes a first region 341 and a plurality of second regions 342.

[0075] The core function of the frequency modulation layer 340 is to regulate the propagation characteristics of surface acoustic waves in the device. By changing the propagation speed of surface acoustic waves through its material properties and thickness parameters, the operating frequency of the device can be precisely adjusted to meet the frequency response requirements in the design.

[0076] For example, the frequency modulation layer 340 can be formed on the interdigital transducer 320 by various deposition methods commonly used in the art, such as chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD).

[0077] The frequency modulation layer 340 can be made of dielectric materials, such as oxides or nitrides, specifically silicon dioxide, carbon-doped silicon oxide, silicon carbonitride, etc., without limitation. On the one hand, dielectric materials have stable chemical properties and are not prone to reacting with the metal materials of the interdigital transducer 320, which can effectively avoid interface degradation; on the other hand, dielectric materials have good insulation properties and structural stability, which can maintain consistency in morphology and performance during subsequent processes and device operation.

[0078] In the frequency modulation layer 340 formed, the first region 341 is the region to be thinned and the second region 342 is the region not to be thinned. This not only provides a structural basis for the subsequent local thinning of the frequency modulation layer 340 to construct the mass load bar 343, but also enables effective control of the surface acoustic wave frequency through its intrinsic characteristics, ensuring the core performance of the device.

[0079] In some embodiments, such as Figure 3C As shown, before the frequency modulation layer 340 is formed on the interdigital transducer 320, the method further includes: forming a first protective layer 330 on the interdigital transducer 320, and the frequency modulation layer 340 is formed on the first protective layer 330.

[0080] The purpose of this step is to provide physical isolation and protection for the interdigital transducer 320, to prevent the subsequent process of forming the frequency modulation layer 340 from damaging the metal electrodes of the interdigital transducer 320, and to reduce the impact of the external environment on the performance of the interdigital transducer 320, thus ensuring the stability of its electrical and acoustic characteristics.

[0081] For example, the first protective layer 330 can be formed on the interdigital transducer 320 by various deposition methods commonly used in the art, such as chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD).

[0082] In one specific embodiment, a first protective layer 330 covers the upper surface and side surfaces of the interdigital transducer 320, and a frequency modulation layer 340 covers the upper surface and side surfaces of the first protective layer 330. Specifically, as... Figure 5 As shown, it is Figure 4 A cross-sectional schematic diagram along the AA direction shows that: the first protective layer 330 at this cross-sectional position covers the upper surface and side surface of the electrode fingers 321 of the interdigital transducer 320; the frequency modulation layer 340 at this cross-sectional position belongs to the second region 342; the frequency modulation layer 340 in the second region 342 will not be thinned subsequently, and it covers the upper surface and side surface of the first protective layer 330.

[0083] Next, proceed to step S24, as follows: Figure 3E and Figure 4As shown, the frequency modulation layer 340 of the first region 341 is thinned so that the frequency modulation layer 340 of each second region 342 forms a protrusion in the thickness direction relative to the thinned frequency modulation layer 340 of the first region 341. Each protrusion constitutes a mass load strip 343, which is located above the end of the electrode finger 321. In other words, the frequency modulation layer 340 is locally thinned, and the protrusion remaining after the local thinning of the frequency modulation layer 340 constitutes the mass load strip 343.

[0084] In some embodiments, locally thinning the frequency modulation layer 340 may include the following steps S241 to S244.

[0085] Step S241: A first photoresist layer is formed on the frequency modulation layer 340.

[0086] The purpose of forming the first photoresist layer is to provide a medium for subsequent patterning processing. Through processes such as coating, the photoresist is uniformly covered on the surface of the frequency modulation layer 340 to ensure that it can completely carry the subsequent pattern information and lay the foundation for defining the thinning area.

[0087] Step S242: The first photoresist layer is patterned, and the patterned first photoresist layer covers the frequency modulation layer 340 of the second region 342 and exposes the frequency modulation layer 340 of the first region 341.

[0088] Patterning typically includes exposure and development processes. Based on a preset mask pattern, the portion of the frequency modulation layer 340 in the first photoresist layer corresponding to the second region 342 is retained, while the photoresist in other regions (the portion of the frequency modulation layer 340 in the first region 341 of the first photoresist layer) is removed. This patterning of the first photoresist layer enables precise definition of the thinning area of ​​the frequency modulation layer 340, ensuring that subsequent thinning operations only apply to the frequency modulation layer 340 in the first region 341.

[0089] Step S243: Using the patterned first photoresist layer as a mask, the frequency modulation layer 340 of the exposed first region 341 is thinned.

[0090] The patterned first photoresist layer acts as a protective structure, and the frequency modulation layer 340 in the second region 342 covered by it is not affected by the thinning process. However, the frequency modulation layer 340 in the exposed first region 341 has part of its thickness removed through etching and other processes to achieve a thinning effect. The core of this operation is to utilize the selective protection effect of the mask to create thickness differences in different regions of the frequency modulation layer 340, thus creating conditions for the formation of subsequent protrusions.

[0091] Step S244: Remove the patterned first photoresist layer.

[0092] The first photoresist layer can be removed by processes such as peeling or ashing to completely remove the photoresist covering the surface of the frequency modulation layer 340. At this time, the first region 341 of the frequency modulation layer 340, which is thinned because it is not covered by photoresist, is thinner, while the second region 342, which is covered by photoresist and is not affected by thinning, maintains its original thickness. The frequency modulation layer 340 of each second region 342 forms a protrusion in the thickness direction relative to the frequency modulation layer 340 of the thinned first region 341. This protrusion is the required mass load bar 343, which can effectively play the role of suppressing lateral modes.

[0093] On the one hand, by thinning the frequency modulation layer 340 of the first region 341, the protruding portion of the frequency modulation layer 340 of the second region 342 relative to the thinned frequency modulation layer 340 of the first region 341 in the thickness direction forms a mass load strip 343, which can effectively suppress the parasitic transverse mode of the piezoelectric substrate 310 and block the propagation of sound waves along the direction parallel to the electrode, thereby improving the frequency characteristics of the surface acoustic wave device—specifically, reducing transverse mode spurious emissions, reducing in-passband disturbances, reducing energy loss, and increasing Q value, so as to improve the performance of the surface acoustic wave device.

[0094] On the other hand, by combining the formation of the mass load strip 343 with the local thinning of the frequency modulation layer 340, the process flow of PST deposition in related technologies is simplified—eliminating the additional steps of photolithography and deposition in the PST deposition process; at the same time, by using the local thinning of the frequency modulation layer 340 to form the mass load strip 343, the self-alignment deviation problem that is prone to occur in the PST deposition process is eliminated, thereby reducing process complexity and production costs.

[0095] In some embodiments, the mass load bar 343 is located above at least both ends of each electrode finger 321. For example, as shown... Figure 4 As shown, each electrode finger 321 has a mass load bar 343 at each of its two ends. Alternatively, the mass load bar 343 can be placed at any other suitable position on the electrode finger 321, without limitation.

[0096] In some embodiments, the material of the mass load bar 343 is the same as that of the frequency modulation layer 340, including a dielectric material, such as an oxide or nitride, specifically silicon dioxide, carbon-doped silicon oxide, silicon carbonitride, etc., without limitation. In this embodiment, the mass load bar 343 is made of a dielectric material such as an oxide. On the one hand, the dielectric material has excellent chemical stability and insulation, and as a dielectric material, it will not undergo electrochemical reactions or generate electrical coupling interference with the metal electrodes of the interdigital transducer 320. On the other hand, the physical parameters of the dielectric material (such as density, elastic modulus, acoustic impedance, etc.) are better matched with the piezoelectric substrate 310 and the interdigital transducer 320, which can reduce the energy loss of surface acoustic waves during propagation and help maintain the high Q value and passband flatness of the device.

[0097] It is also worth noting that in the related technologies, the metal mass load strip 130 needs to be formed by additional photolithography and metal deposition, which not only increases the process steps and costs, but may also lead to the risk of falling off due to the poor adhesion of the metal material; while the dielectric material mass load strip 343 in this embodiment is formed by local thinning of the frequency modulation layer 340, without the need to introduce additional heterogeneous materials, which simplifies the process flow and eliminates the risk of falling off due to the poor adhesion of the metal material.

[0098] In some embodiments, the manufacturing method further includes forming a second protective layer that covers the mass load bar 343 and the frequency modulation layer 340 of the thinned first region 341.

[0099] The purpose of forming the second protective layer is to provide protection for the structure of the device: on the one hand, the mass load bar 343, as a functional structure for suppressing transverse modes, directly affects the frequency characteristics of the device in terms of its shape and dimensional accuracy, while the thinned area of ​​the frequency modulation layer 340 is an important path for the propagation of surface acoustic waves. Both of them need to be protected from physical damage or chemical corrosion during subsequent processes or long-term operation of the device; on the other hand, the second protective layer can isolate the external environment from the above structure, maintain the stability of its physicochemical properties, and thus ensure the long-term reliability of the device performance.

[0100] For example, the second protective layer can be formed by various deposition methods commonly used in the art, such as chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD).

[0101] The second protective layer formed through the above steps can provide stable and reliable protection for the thinned areas of the mass load bar 343 and the frequency modulation layer 340 without affecting the core function of the device, thereby further improving the process tolerance and service life of the device.

[0102] This concludes the description of the key steps in the manufacturing method of the surface acoustic wave device of the present invention. The complete manufacturing method of the surface acoustic wave device may also include other steps, which will not be elaborated here. It is worth mentioning that the order of the above steps can be adjusted without conflict.

[0103] In summary, the manufacturing method of this application embodiment, by thinning the frequency modulation layer 340 of the first region 341, forms a mass load strip 343 by the protruding portion of the frequency modulation layer 340 of the second region 342 relative to the thinned frequency modulation layer 340 of the first region 341 in the thickness direction. This solves the performance degradation problem caused by the presence of lateral modes in surface acoustic wave devices. At the same time, by forming the mass load strip 343 by locally thinning the frequency modulation layer 340, the process is simplified compared to the deposition formation PST process, and the self-alignment deviation problem that is prone to occur in the deposition formation PST process is eliminated, thereby reducing process complexity and production costs.

[0104] Example 2

[0105] This application also provides a surface acoustic wave device, as described below, with reference to... Figure 3E , Figures 4-6 This application provides a detailed description and explanation of the surface acoustic wave device.

[0106] Specifically, such as Figure 3E , Figure 4 and Figure 5 As shown, the surface acoustic wave device includes: a piezoelectric substrate 310; an interdigital transducer 320 disposed on the piezoelectric substrate 310, the interdigital transducer 320 having at least one electrode finger 321; and a frequency modulation layer 340 disposed on the interdigital transducer 320. The frequency modulation layer 340 includes a first region 341 and a plurality of second regions 342. The frequency modulation layer 340 of the first region 341 is thinned. The frequency modulation layer 340 of each second region 342 has a protrusion in the thickness direction relative to the frequency modulation layer 340 of the thinned first region 341. Each protrusion constitutes a mass load bar 343, and the mass load bar 343 is located above the end of the electrode finger 321.

[0107] On the one hand, by thinning the frequency modulation layer 340 of the first region 341, the protruding part of the frequency modulation layer 340 of the second region 342 relative to the thinned frequency modulation layer 340 of the first region 341 in the thickness direction forms a mass load bar 343, which can effectively suppress the parasitic transverse mode of the piezoelectric substrate 310 and block the propagation of sound waves along the direction parallel to the electrode, thereby improving the frequency characteristics of the surface acoustic wave device—specifically, reducing transverse mode spurious emissions, reducing passband disturbances, reducing energy loss, and increasing Q value, so as to improve the performance of the surface acoustic wave device.

[0108] On the other hand, by combining the formation of the mass load strip 343 with the local thinning of the frequency modulation layer 340, the process flow of PST deposition in related technologies is simplified—eliminating the additional steps of photolithography and deposition in the PST deposition process; at the same time, by using the local thinning of the frequency modulation layer 340 to form the mass load strip 343, the self-alignment deviation problem that is prone to occur in the PST deposition process is eliminated, thereby reducing process complexity and production costs.

[0109] In some embodiments, the surface acoustic wave (SAW) device may include a SAW resonator. The SAW resonator may be a normal SAW resonator (Normal-SAW), a temperature-compensated SAW resonator (TC-SAW), a SAW resonator with a multilayer piezoelectric substrate structure, or a laterally excited thin-film bulk acoustic wave resonator, etc., and is not limited thereto.

[0110] In some embodiments, such as Figure 4 As shown, each electrode finger 321 has a mass load bar 343 at each of its two ends. Alternatively, the mass load bar 343 can be placed at any other suitable position on the electrode finger 321, without limitation.

[0111] In some embodiments, the material of the frequency modulation layer 340 includes a dielectric material.

[0112] In some embodiments, such as Figure 3E and Figure 5 As shown, the surface acoustic wave device also includes a first protective layer 330, which is disposed between the interdigital transducer 320 and the frequency modulation layer 340.

[0113] In some embodiments, the surface acoustic wave device further includes a second protective layer covering the mass load bar 343 and the frequency modulation layer 340 of the thinned first region 341.

[0114] Figure 6 This is a comparison diagram of impedance curves of a surface acoustic wave device according to an embodiment of this application. Each line is a schematic diagram of the impedance curve of a surface acoustic wave device. Different surface acoustic wave devices have the same initial thickness, but different degrees of thinning. Figure 6 The horizontal axis represents frequency in MHz; the vertical axis represents impedance in Ω. Figure 6 It can be seen that the degree of thinning of the frequency modulation layer 340 will only affect the frequency of the frequency modulation layer 340, and will not affect the noise mode of the surface acoustic wave device. That is, the degree of thinning of the frequency modulation layer 340 will not affect the effect of the mass load bar 343.

[0115] It is understood that the surface acoustic wave device in this embodiment can be obtained by the manufacturing method in the aforementioned embodiment one. In order to avoid repetition, only a brief description is given for the same components and structures as in the aforementioned embodiment one. For specific explanations and descriptions, please refer to the description in embodiment one.

[0116] Example 3

[0117] This application also provides a radio frequency front-end module, which includes a surface acoustic wave device.

[0118] Among them, the surface acoustic wave device can be implemented as the surface acoustic wave device mentioned above, which can be referred to in the above introduction, and will not be repeated here.

[0119] In some implementations, the radio frequency front-end module can be applied to electronic devices, which may include, but are not limited to, mobile phones, tablets, laptops, netbooks, game consoles, televisions, VCDs, DVDs, navigators, cameras, camcorders, voice recorders, MP3 players, MP4 players, PSPs, and other electronic devices or components with PCBs. This application does not impose any limitations on this.

[0120] Example 4

[0121] This application also provides an electronic device that includes a radio frequency front-end module.

[0122] The radio frequency front-end module can be implemented as described above, and will not be repeated here.

[0123] In some implementations, the electronic device can be any electronic product or device such as a mobile phone, tablet computer, laptop computer, netbook, game console, television, VCD, DVD, navigator, camera, camcorder, voice recorder, MP3, MP4, PSP, etc., or it can be an intermediate product with the above-mentioned radio frequency front-end module, such as a mobile phone motherboard with the radio frequency front-end module.

[0124] The present invention has been described through the above embodiments. However, it should be understood that the above embodiments are for illustrative purposes only and are not intended to limit the invention to the scope of the described embodiments. Furthermore, those skilled in the art will understand that the present invention is not limited to the above embodiments, and many more variations and modifications can be made based on the teachings of the present invention, all of which fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for manufacturing a surface acoustic wave device, characterized in that, include: Provide piezoelectric substrates; An interdigital transducer is formed on the piezoelectric substrate, the interdigital transducer having at least one electrode finger; A frequency modulation layer is formed on the interdigital transducer, the frequency modulation layer including a first region and a plurality of second regions; The frequency modulation layer of the first region is thinned so that the frequency modulation layer of each second region forms a protrusion in the thickness direction relative to the thinned frequency modulation layer of the first region. Each of the protrusions constitutes a mass load bar, which is located above the end of the electrode finger.

2. The manufacturing method as described in claim 1, characterized in that, The thinning of the frequency modulation layer in the first region includes: A first photoresist layer is formed on the frequency modulation layer; The first photoresist layer is patterned, and the patterned first photoresist layer covers the frequency modulation layer of the second region and exposes the frequency modulation layer of the first region. Using the patterned first photoresist layer as a mask, the frequency modulation layer in the exposed first region is thinned. Remove the first photoresist layer after patterning.

3. The manufacturing method as described in claim 1, characterized in that, The mass load bar is located above at least two ends of each of the electrode fingers.

4. The manufacturing method as described in claim 1, characterized in that, The material of the mass load bar includes a medium material.

5. The manufacturing method as described in claim 1, characterized in that, The process of forming an interdigital transducer on the piezoelectric substrate includes: A second photoresist layer is formed on the piezoelectric substrate; The second photoresist layer is patterned, and the patterned second photoresist layer defines a pattern in which the interdigital transducer is to be formed, and the pattern exposes a portion of the surface of the piezoelectric substrate. Metal material is deposited on the surface of the patterned second photoresist layer and the exposed piezoelectric substrate. The patterned second photoresist layer and its surface metal material are removed, and the remaining metal material on the exposed piezoelectric substrate surface forms the interdigital transducer.

6. The manufacturing method as described in claim 1, characterized in that, Before forming the frequency modulation layer on the interdigital transducer, the method further includes: A first protective layer is formed on the interdigital transducer, and the frequency modulation layer is formed on the first protective layer.

7. The manufacturing method as described in claim 1, characterized in that, Also includes: A second protective layer is formed, which covers the mass load bar and the frequency modulation layer of the thinned first region.

8. A surface acoustic wave device, characterized in that, The surface acoustic wave device is obtained by the manufacturing method as described in any one of claims 1-7.

9. A radio frequency front-end module, characterized in that, The radio frequency front-end module includes the surface acoustic wave device as described in claim 8.

10. An electronic device, characterized in that, The electronic device includes the radio frequency front-end module as described in claim 9.

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