Surface acoustic wave device and method of manufacturing the same

Abstract

This invention relates to the field of microelectronic device technology and discloses a surface acoustic wave (SAW) device and its fabrication method. The device includes a substrate layer, an electrode layer, a bridging layer, and a protective structure. The electrode layer is disposed on the substrate layer and includes multiple transducer units with transducer structures and connection terminals. The bridging layer is disposed on the electrode layer and located on one side of the connection terminal. The bridging layer is electrically connected to at least a portion of the connection terminal and electrically isolated from at least a portion of the connection terminal. The protective structure is disposed between the electrically isolated connection terminal and the bridging layer and includes an insulating layer and a blocking layer disposed on at least one side surface of the insulating layer. In this invention, the protective structure includes a blocking layer with a diffusion coefficient lower than that of the insulating layer, forming a dense physical barrier on the surface of the insulating layer. This physically alters the interaction between particles and the surface of the contact film layer, simultaneously suppressing particle adhesion and blocking electrode metal diffusion, thus ensuring the performance and reliability of the SAW device.

Description

Technical Field

[0001] This invention relates to the field of microelectronic device technology, specifically to surface acoustic wave devices and their fabrication methods. Background Technology

[0002] Surface acoustic wave (SAW) devices play a crucial role in modern electronic systems, with a wide range of applications covering multiple fields such as radio frequency front-ends, sensors, and communication equipment. One of the core structures of SAW devices is the insulating isolation layer (ISO layer), which is typically composed of aluminum oxide, silicon nitride, or a composite film of the two. The ISO layer is not only responsible for achieving insulation between electrodes but also for regulating sound propagation, playing a decisive role in the overall performance of the device.

[0003] However, during the manufacturing process of SAW devices, the ISO layer is highly susceptible to particulate contamination. These particles come from a wide range of sources, including photoresist residue, silicon shavings generated during dicing, and metal debris. When these particles adhere to the surface of the ISO layer or are embedded in the interface, they can cause a series of serious problems. For example, particulate contamination may lead to insulation failure of the ISO layer, rendering the device unable to function properly; at the same time, particle adhesion can also cause stress delamination, reducing the mechanical stability of the device; in addition, the presence of particles can increase the loss during sound propagation, affecting the signal transmission quality, thereby seriously affecting the reliability and performance of the device. Summary of the Invention

[0004] This invention provides a surface acoustic wave (SAW) device and its fabrication method to solve the problem that impurity particles easily adhere to the insulating layer in existing SAW devices, thereby affecting the performance and reliability of the SAW devices.

[0005] In a first aspect, the present invention provides a surface acoustic wave (SAW) device, comprising: a substrate layer, an electrode layer, a bridging layer, and a protective structure. The electrode layer is disposed on one side surface of the substrate layer and includes a plurality of transducer units arranged along a first direction. Each transducer unit includes a transducer structure and a connection terminal connected to at least one side of the transducer structure in a second direction, wherein the first direction intersects the second direction. The bridging layer is disposed on the side of the electrode layer away from the substrate layer and located on the side where the connection terminal is located. The bridging layer is electrically connected to at least a portion of the connection terminal and electrically isolated from at least a portion of the connection terminal. The protective structure is disposed between the electrically isolated connection terminal and the bridging layer. The protective structure includes an insulating layer and a barrier layer disposed on at least one side surface of the insulating layer, wherein the diffusion coefficient of at least one metal element in the barrier layer is less than its diffusion coefficient in the insulating layer.

[0006] Beneficial Effects: This invention provides a protective structure between a portion of the electrode layer and the bridging layer. Specifically, it can achieve electrical isolation by providing a protective structure between a portion of the connection end and the bridging layer. The protective structure can include an insulating layer and two blocking layers disposed on both sides of the insulating layer, such as a first blocking layer and a second blocking layer. The insulating layer, disposed between the electrode layer and the bridging layer, can effectively block the current path and prevent leakage. Simultaneously, when electrical signals are coupled to the electrode layer through parasitic capacitance or inductance, it can reduce parasitic coupling effects and signal interference. Furthermore, it can act as a buffer layer to absorb some stress, enhancing mechanical reliability. Crucially, the use of a blocking layer with a diffusion coefficient lower than that of the insulating layer creates a dense physical barrier on the surface of the insulating layer. This physically alters the interaction between particles and the contact film surface, simultaneously suppressing particle adhesion and blocking electrode metal diffusion. This effectively prevents metal particles in the bridging layer from entering the insulating layer and external impurity particles from eroding into the insulating layer, ensuring that the isolation performance of the insulating layer is not affected and guaranteeing the performance and reliability of the surface acoustic wave device.

[0007] In one alternative embodiment, the surface roughness of the barrier layer is less than or equal to 5 nm, and the surface energy is less than or equal to 30 mN / m.

[0008] Beneficial effects: By combining surface property optimization with particle adhesion suppression, a barrier layer with smooth and low surface energy characteristics is obtained by precisely controlling surface roughness and surface energy. This changes the interaction between particles and the barrier layer surface from a physical level, making it difficult for even nanoscale particles to adhere to the smooth and low surface energy interface. This significantly reduces particle adhesion on the surface of the insulation layer and provides a new approach to solving the problem of particle contamination.

[0009] In one alternative embodiment, the barrier layer includes a first barrier layer and a second barrier layer located on opposite sides of the insulating layer in the thickness direction, wherein the first barrier layer is disposed relatively close to the substrate layer, and the thickness of the second barrier layer is greater than or equal to the thickness of the first barrier layer.

[0010] In one alternative embodiment, the material of the barrier layer includes one or more of titanium-tungsten alloy, tantalum nitride, nickel-tungsten alloy, and nickel-chromium alloy; In titanium-tungsten alloys, the mass ratio of titanium to tungsten ranges from 1:9 to 2:8. In tantalum nitride, the mass ratio of nitrogen to tantalum ranges from 1:9 to 2:8. The thickness of the barrier layer ranges from 50 to 200 nm.

[0011] Beneficial effects: The innovative selection of materials such as titanium-tungsten alloy and tantalum nitride, which combine diffusion blocking, low surface energy, and high density, as the barrier layer not only effectively blocks metal diffusion but also possesses the characteristics of low surface energy and high density. This fundamentally solves the defect of conventional barrier structures that do not prevent particles, and achieves the organic integration of three major functions: particle adhesion suppression, metal diffusion blocking, and enhanced interface adhesion. No additional external protective layer is required, simplifying the process flow, reducing production costs, and improving the overall performance and stability of the device.

[0012] In one alternative implementation, the area of ​​the barrier layer projected onto the substrate covers more than 95% of the area of ​​the connection end projected onto the substrate.

[0013] Beneficial effects: The barrier layer can be set to provide basic full coverage. The area of ​​the barrier layer is basically the same as that of the insulation layer. The area of ​​the overlap between the barrier layer and the signal end accounts for more than 95% of the total area of ​​the connection end, thus providing all-round protection for the insulation layer and the connection end.

[0014] In one alternative embodiment, in the second direction, the outer edge of the barrier layer protrudes relative to the outer edge of the bridging layer, and the width of the protruding portion in the second direction ranges from 2.5 μm to 5 μm.

[0015] Beneficial effects: The barrier layer can be set as a partial cover, that is, the size of the barrier layer is not determined by the insulating layer or the connection end, but by the size of the bridging layer. This ensures that the areas connected in the electrode layer and the bridging layer have reliable insulation and isolation effects, which can significantly reduce the amount of precious metals used and effectively reduce the additional losses introduced by full coverage.

[0016] The barrier layer can be laid out in a way that provides full coverage or partial coverage of key areas. This flexible layout design can be tailored to different application needs and cost considerations, ensuring the protective effect while reasonably controlling the process cost, thus improving the practicality and economy of the technical solution.

[0017] In one optional embodiment, the device further includes a sealing structure, which is at least disposed on the outside of the electrode layer; the material and surface properties of the sealing structure are the same as those of the barrier layer, and the width of the sealing structure is in the range of 10 μm to 30 μm.

[0018] Beneficial effects: The sealing structure can be a sealing ring with the same material and surface properties as the barrier layer, including surface roughness and surface energy. Specifically, the sealing structure can be a ring-shaped barrier structure placed around the entire periphery of the device in the overall package after the various structures of the device have been formed, ensuring that the internal structural layers are protected from the intrusion of external impurities.

[0019] In an optional embodiment, the protective structure further includes: a transition layer disposed between the insulating layer and the barrier layer, wherein the transition layer is matched with at least one component of the insulating layer and the barrier layer, and / or the coefficient of thermal expansion of the transition layer is between the coefficient of thermal expansion of the insulating layer and the coefficient of thermal expansion of the barrier layer.

[0020] Beneficial effects: Setting a transition layer between the insulating layer and the barrier layer improves the interfacial bonding ability and forms a thermal expansion gradient from the insulating layer to the transition layer and then to the barrier layer. This buffers stress concentration and avoids stress-induced interfacial cracking or delamination. It can effectively prevent delamination of surface acoustic wave devices under thermal cycling (such as annealing, encapsulation and curing) or mechanical stress (such as dicing, chip handling) during the manufacturing process.

[0021] Secondly, the present invention also provides a method for fabricating a surface acoustic wave device, comprising: Provide a base layer; An electrode layer is formed on one side surface of the substrate layer. The electrode layer includes a plurality of transducer units arranged along a first direction. Each transducer unit includes a transducer structure and a connection end connected to at least one side of the transducer structure in a second direction. The first direction intersects the second direction. A protective structure is formed on the side of a portion of the connection segment in the electrode layer that is away from the base layer. The protective structure includes an insulating layer and a barrier layer disposed on at least one surface of the insulating layer. The diffusion coefficient of the metal element in the barrier layer is less than its diffusion coefficient in the insulating layer. A bridging layer is formed on the side of the protective structure away from the base layer, and the bridging layer is located on the side where the connection end is located in the second direction; the bridging layer is electrically connected to at least a portion of the connection end, and is electrically isolated from at least a portion of the connection end by the protective structure.

[0022] Beneficial Effects: The fabrication method of the surface acoustic wave (SAW) device of this invention employs mature magnetron sputtering and chemical vapor deposition processes to prepare the relevant structural layers, resulting in a protective structure including an insulating layer and barrier layers disposed on both sides of the insulating layer. The insulating layer, positioned between the electrode layer and the bridging layer, effectively blocks the current path, preventing leakage. Simultaneously, when electrical signals are coupled to the electrode layer through parasitic capacitance or inductance, it reduces parasitic coupling effects and signal interference. Furthermore, it acts as a buffer layer to absorb some stress, enhancing mechanical reliability. The barrier layers, with a diffusion coefficient significantly lower than that of the insulating layer, form a dense physical barrier on the surface of the insulating layer. This physically alters the interaction between particles and the contact film surface, simultaneously suppressing particle adhesion and blocking electrode metal diffusion. This effectively prevents metal particles in the bridging layer from entering the insulating layer and external impurity particles from eroding into the insulating layer, ensuring that the isolation performance of the insulating layer remains unaffected and guaranteeing the performance and reliability of the SAW device. This fabrication process can be directly integrated into existing SAW device manufacturing production lines without requiring additional equipment, facilitating large-scale application and demonstrating promising industrial application prospects.

[0023] In one alternative implementation, a barrier layer is formed using a magnetron sputtering process, and the surface roughness of the barrier layer is less than or equal to 5 nm and the surface energy is less than or equal to 30 mN / m by controlling the sputtering parameters. Attached Figure Description

[0024] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of a surface acoustic wave device according to an embodiment of the present invention; Figure 2 This is a top view schematic diagram of a surface acoustic wave device according to an embodiment of the present invention; Figure 3 This is a schematic diagram of another structure of the surface acoustic wave device according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the complete insertion loss curve of the surface acoustic wave device according to an embodiment of the present invention; Figure 5 This is an enlarged view of the insertion loss curve of the passband of the surface acoustic wave device according to an embodiment of the present invention; Figure 6 This is a schematic flowchart illustrating the fabrication method of a surface acoustic wave device according to an embodiment of the present invention.

[0026] Explanation of reference numerals in the attached figures: 1. Basal layer; 2. Electrode layer; 21. Transducer unit; 211. Transducer structure; 212. Signal terminal; 213. Grounding terminal; 22. Reflector grating; 3. Connecting layer; 31. First connecting component; 32. Second connecting component; 4. Protective structure; 41. Insulating layer; 42. Barrier layer; 421. First barrier layer; 422. Second barrier layer; 43. Transition layer; 431. First transition layer; 432. Second transition layer; 5. Sealed structure. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] To address the issue of particulate contamination, relevant technologies primarily rely on two methods: process cleaning and parameter optimization. Process cleaning methods, such as plasma ashing and megasonic cleaning, can remove some particles to a certain extent. However, due to the strong adhesion between nanoscale particles and the ISO layer surface, and the fact that particles embedded in micro-defects are firmly fixed, conventional cleaning methods struggle to reach nanoscale particles and those embedded in micro-defects within the ISO layer, resulting in less than ideal cleaning effects. On the other hand, parameter optimization methods, such as adjusting the dicing speed, can reduce particle generation but cannot fundamentally suppress particle adhesion. During subsequent packaging and thermal cycling processes, changes in environmental conditions can lead to particle migration and re-adhesion, causing the particulate contamination problem to reappear. In other words, current technical solutions cannot effectively address the challenges posed by particulate contamination and are insufficient to further improve the performance and reliability of SAW devices.

[0029] Based on this, such as Figures 1 to 5As shown, this embodiment provides a surface acoustic wave device, including: a substrate layer 1, an electrode layer 2, a bridging layer 3, and a protective structure 4. The electrode layer 2 is disposed on one side surface of the substrate layer 1 and includes a plurality of transducer units 21 arranged along a first direction. Each transducer unit 21 includes a transducer structure 211 and a connection end connected to at least one side of the transducer structure 211 in a second direction. The first direction intersects the second direction. The bridging layer 3 is disposed on the side of the electrode layer 2 away from the substrate layer 1 and located on the side where the connection end is located. The bridging layer 3 is electrically connected to at least a portion of the connection end and electrically isolated from at least a portion of the connection end. The protective structure 4 is disposed between the electrically isolated connection end and the bridging layer 3. The protective structure 4 includes an insulating layer 41 and a barrier layer 42 disposed on at least one side surface of the insulating layer 41. The diffusion coefficient of at least one metal element in the barrier layer 42 is less than its diffusion coefficient in the insulating layer 41. For example, the substrate 1 can be a piezoelectric substrate or a silicon substrate. The piezoelectric substrate can be made of lithium niobate (LiNbO3) or lithium tantalate (LiTaO3), which have excellent piezoelectric properties and help to achieve efficient electroacoustic conversion.

[0030] For example, the electrode layer 2 can be made of aluminum-based alloy or copper-based alloy, and the thickness of the electrode layer 2 ranges from 200 nm to 500 nm. The electrode layer 2 may include a plurality of transducer units 21 and reflective gratings 22 disposed on both sides of the plurality of transducer units 21 in a first direction, such as... Figure 2 As shown, any transducer unit 21 includes a transducer structure 211 and connection terminals located on both sides of the transducer structure 211 in a second direction. The transducer structure 211 can be an interdigitated transducer, and the connection terminals can be divided into a signal terminal 212 and a ground terminal 213. The signal terminal 212 and the ground terminal 213 can be arranged alternately along the first direction, and the first direction and the second direction are perpendicular. Figure 2Taking the three transducer units 21 shown as an example, the upper electrode of the middle transducer structure 211 serves as the ground terminal 213, and the lower electrode serves as the signal terminal 212. The upper electrodes of the transducer structures 211 on both sides serve as the signal terminals 212, and the lower electrodes serve as the ground terminals 213. The signal terminal 212 can be either a signal input terminal or a signal output terminal. For example, the signal terminal 212 at the upper end of the transducer structure 211 can be the signal input terminal, and the signal terminal 212 at the lower end of the transducer structure 211 can be the signal output terminal. In this case, the first and second bridging components of the bridging layer can be respectively set on both sides of the transducer structure in the second direction. The first and second bridging components are used for grounding output. In other examples, the grounding terminal of each transducer unit can be set on the same side of the transducer structure 211 in the second direction, and the signal terminal is set on the other side of the transducer structure 211. The signal input terminal and the signal output terminal of the signal terminal are alternately set along the second direction. In this case, the bridging layer can only set one bridging member on the side where the signal terminal is located. The bridging member is used to connect the external signal output or the external signal input.

[0031] For example, the bridging layer 3 can be an aluminum-copper alloy with a thickness of approximately 2.5 μm. Specifically, it can be configured as a first bridging member 31 and a second bridging member 32 located on both sides of the transducer structure 211 in the second direction. In a specific example, both the first bridging member 31 and the second bridging member 32 are used to connect the ground terminal 213 of the transducer unit 21 to the ground of the entire device, flexibly realizing the grounding connection of different transducer units 21 on different sides. For example, it can connect the ground terminal of a dual-mode surface acoustic wave filter (DMS) structure to the ground of the entire device. The electrode layer 2 and the bridging layer 3 are tightly fitted to complete the signal processing function of the surface acoustic wave device. It should be noted that... Figure 2 For illustrative purposes only, in actual applications, the number of bridging elements included in the bridging layer 3, and the connection or insulation relationship between the bridging elements and different connection terminals in the transducer unit 21, are not limited to this. Figure 2 As shown.

[0032] For example, the insulating layer 41 (ISO layer) in the protective structure 4 can be made of silicon oxide (SiO2), silicon nitride (Si3N4) or a composite layer of silicon oxide and silicon nitride, and the thickness of the insulating layer 41 ranges from 500nm to 2000nm; the barrier layer 42 can be made of a metal or alloy with extremely low diffusion coefficient and strong chemical inertness.

[0033] In some embodiments, such as Figure 1As shown, the protective structure 4 may include an insulating layer 41 and two blocking layers 42 disposed on both sides of the insulating layer 41, such as a first blocking layer 421 and a second blocking layer 422. The first blocking layer 421 is disposed relatively close to the base layer 1, and the insulating layer 41 is disposed between the electrode layer 2 and the bridging layer 3. It can effectively block the current path and prevent leakage. At the same time, when the electrical signal is coupled to the electrode layer 2 through parasitic capacitance or inductance, it can reduce the parasitic coupling effect and reduce signal interference. In addition, it can also act as a buffer layer to absorb part of the stress and enhance mechanical reliability. Crucially, barrier layers 42 are provided on both sides of the insulating layer 41. The diffusion coefficient of impurities such as metal elements and silicon wafer debris in the barrier layer 42 is lower than that in the insulating layer 41. This creates a dense physical barrier on both sides of the insulating layer 41, which changes the interaction between particles and the surface of the contact film layer at the physical level. This simultaneously suppresses particle adhesion and blocks electrode metal diffusion, effectively preventing metal particles in the bridging layer 3 from entering the insulating layer 41 and preventing external impurity particles from eroding into the insulating layer 41. This ensures that the isolation performance of the insulating layer 41 is not affected, guaranteeing the performance and reliability of the surface acoustic wave device.

[0034] The aforementioned particles mainly include photoresist residue particles, silicon chips generated during the dicing process, and metal debris particles, with a particle size range of 0.05μm to 5μm.

[0035] Of course, in other embodiments, depending on the specific device structure, the barrier layer 42 may be provided only on one side of the insulating layer 41, such as providing only the first barrier layer 421 or only the second barrier layer 422.

[0036] In some embodiments, the thickness of the second barrier layer 422 is greater than or equal to the thickness of the first barrier layer 421, further preventing the bridging layer 3 and external metal elements from entering the insulating layer 41, thereby ensuring the performance of the insulating layer 41 and the device as a whole.

[0037] In some embodiments, the surface roughness of the barrier layer 42 is less than or equal to 5 nm, and the surface energy is less than or equal to 30 mN / m.

[0038] This approach combines surface characteristic optimization with particle adhesion suppression. By precisely controlling surface roughness and surface energy, a barrier layer 42 with smooth, low surface energy characteristics is obtained. This physically alters the interaction between particles and the surface of the barrier layer 42, making it difficult for even nanoscale particles to adhere to the smooth, low surface energy interface. This significantly reduces particle adhesion on the surface of the insulating layer 41, providing a novel approach to solving the particle contamination problem. Testing shows that compared to traditional protective structures without the barrier layer 42, the particle adhesion density on the surface of the insulating layer 41 in this embodiment is reduced by more than 60%, especially for nanoscale particles, where the adhesion rate is reduced by 80%. This effectively avoids insulation failure and stress delamination caused by particles, significantly improving the reliability of the device.

[0039] In some embodiments, the material of the barrier layer 42 includes one or more of titanium-tungsten alloy, tantalum nitride, nickel-tungsten alloy, and nickel-chromium alloy, wherein the mass ratio of titanium to tungsten in the titanium-tungsten alloy ranges from 1:9 to 2:8; the mass ratio of nitrogen to tantalum in the tantalum nitride ranges from 1:9 to 2:8; and the thickness of the barrier layer 42 ranges from 50 nm to 200 nm.

[0040] Specifically, the innovative selection of materials such as titanium-tungsten alloy and tantalum nitride, which combine diffusion blocking, low surface energy, and high density, as the barrier layer 42 not only effectively blocks metal diffusion but also possesses the characteristics of low surface energy and high density. This fundamentally solves the defect of conventional barrier structures that do not prevent particles, achieving the organic integration of three major functions: particle adhesion suppression, metal diffusion blocking, and enhanced interface adhesion. No additional external protective layer is required, simplifying the process, reducing production costs, and improving the overall performance and stability of the device.

[0041] In an alternative implementation, the aforementioned barrier layer 42 can be configured to provide substantially full coverage, such as... Figure 2 The barrier layer 42 on the left and middle transducer units 21 of the three transducer units 21 is shown. The area of ​​the barrier layer 42 is basically the same as that of the insulating layer 41. The projected area of ​​the barrier layer 42 on the substrate 1 covers more than 95% of the projected area of ​​the signal terminal 212 on the substrate 1, thus achieving all-round protection of the insulating layer 41.

[0042] In another alternative implementation, the barrier layer 42 can be configured as a partial cover, such as... Figure 2 As shown in the right transducer unit 21 of the three transducer units 21, the area of ​​the blocking layer 42 is not determined by the size of the signal terminal 212, but by the size of the bridging layer 3. This ensures reliable insulation and isolation between the electrode layer 2 and the bridging layer 3, significantly reducing the amount of precious metals used and effectively reducing the additional losses introduced by full coverage. Specifically, the first bridging member 31 and the second bridging member 32 are typically strip-shaped metal conductive structures. Figure 2 In the second direction shown, the width of the first bridging member 31 and the second bridging member 32 is usually smaller than the width of the insulating layer 41, and the width of the barrier layer 42 is greater than or equal to the width of the first bridging member 31 or the second bridging member 32 connected to it. That is, in the second direction, the outer edge of the barrier layer 42 protrudes relative to the outer edge of the bridging layer 3, and the width of the protruding part in the second direction is in the range of 2.5μm to 5μm.

[0043] In summary, the barrier layer 42 can be laid out in a manner that provides full coverage or partial coverage of key areas. This flexible layout design can effectively control process costs while ensuring protective effects, thus improving the practicality and economy of the technical solution, based on different application requirements and cost considerations.

[0044] In some embodiments, such as Figure 2 As shown, the above-mentioned surface acoustic wave device further includes: a sealing structure 5, which is at least disposed on the outside of the electrode layer 2. The material and surface properties of the sealing structure 5 are the same as those of the barrier layer 42. The width of the sealing structure 5 is in the range of 10μm to 30μm.

[0045] For example, the sealing structure 5 can be a sealing ring with the same material and surface properties as the barrier layer 42, where the surface properties include the aforementioned surface roughness and surface energy. Specifically, the sealing structure 5 can be an annular barrier structure disposed around the entire periphery of the device in the overall package after the various structures of the device have been formed, to ensure that the internal structural layers are protected from the intrusion of external impurities.

[0046] In some embodiments, such as Figure 3 As shown, the protective structure 4 in the above-mentioned surface acoustic wave device further includes a transition layer 43 disposed between the insulating layer 41 and the blocking layer 42. The transition layer 43 is matched with at least one component of the insulating layer 41 and the blocking layer 42, and the thermal expansion coefficient of the transition layer 43 is between the thermal expansion coefficient of the insulating layer 41 and the thermal expansion coefficient of the blocking layer 42. Here, "component matching" can mean that the transition layer includes at least one element from the insulating layer and the blocking layer to which it is connected.

[0047] For example, the transition layer 43 can be made of chromium, and may specifically include a first transition layer 431 and a second transition layer 432. The first transition layer 431 is disposed between the insulating layer 41 and the first barrier layer 421, and the second transition layer 432 is disposed between the insulating layer 41 and the second barrier layer 422. The transition layer 43, disposed between the insulating layer 41 and the barrier layer 42, improves interfacial bonding and forms a thermal expansion gradient from the insulating layer 41 to the transition layer 43 and then to the barrier layer 42. This buffers stress concentration and prevents stress-induced interfacial cracking or delamination, effectively preventing delamination of the surface acoustic wave device under thermal cycling (such as annealing, encapsulation curing) or mechanical stress (such as dicing, chip handling) during the manufacturing process.

[0048] For example, the performance of the surface acoustic wave device of this embodiment and the surface acoustic wave device of the comparative example that is not affected by particles are compared through performance testing, and the results are as follows: Figure 4 and Figure 5 The comparison diagram shown has red lines representing this embodiment and blue lines representing the comparative example. Figure 5 for Figure 4 A magnified schematic diagram of the passband portion. The surface acoustic wave device in this embodiment includes: a lithium niobate piezoelectric substrate; an insulating layer 41 made of silicon oxide or silicon nitride with a thickness of 800 nm, prepared by CVD deposition at a temperature controlled at 350°C and a pressure of 3 Torr; a barrier layer 42 made of titanium-tungsten alloy with a titanium to tungsten mass ratio of 15:85 and a thickness of 100 nm, prepared by magnetron sputtering using argon gas as the sputtering gas, with the self-bias voltage of the substrate layer 1 set to -20V, a deposition temperature of 250°C, and subsequent annealing at 420°C for 40 minutes to densify the film grains, ultimately obtaining a barrier layer 42 with a surface roughness of 3.2 nm and a surface energy of 28 mN / m; and an electrode layer 2 made of Ti / Cu / Al based electrodes with a thickness of 400 nm.

[0049] Tests showed that, compared to the traditional structure without a barrier layer 42, the adhesion density of particles with a diameter greater than or equal to 0.1 μm was reduced from 0.12 particles / cm². 2 Reduced to 0.04 cells / cm 2 The adhesion rate decreased by 66.7%, effectively verifying the inhibitory effect of barrier layer 42 on particle adhesion. After 1000 hours of testing in a high-temperature and high-humidity environment (85℃ / 85% RH), the insulation resistance decreased by only one order of magnitude, while the traditional structure decreased by three orders of magnitude, indicating that this protective structure 4 can significantly improve the insulation performance and environmental adaptability of the device. Figure 4 and Figure 5As shown, the surface acoustic wave device with insulating layer 41 and blocking layer 42 in this embodiment has no significant performance difference from the conventional surface acoustic wave device with clean insulating layer 41. In this embodiment, the increase in acoustic propagation loss is less than or equal to 0.2dB, that is, the protective structure 4 can effectively eliminate the influence of particles adhering to insulating layer 41 on the overall performance of the device, meet the strict requirements of high-frequency surface acoustic wave devices for acoustic propagation loss, and ensure the signal transmission quality of the device.

[0050] like Figures 1 to 6 As shown, this embodiment also provides a method for fabricating a surface acoustic wave (SAW) device, which can be used to fabricate the aforementioned SAW device. Figure 6 The diagram below illustrates the preparation method, which specifically includes the following steps: Step S601, provide base layer 1.

[0051] For example, the substrate 1 can be a piezoelectric substrate or a silicon substrate, and the material of the piezoelectric substrate can be lithium niobate (LiNbO3) or lithium tantalate (LiTaO3).

[0052] The aforementioned substrate 1 is a pretreated substrate 1. The pretreatment includes ultrasonic cleaning, deionized water rinsing and drying in sequence. The ultrasonic cleaning agent is a mixture of sulfuric acid and hydrogen peroxide with a volume ratio of 1:1. The cleaning temperature is 60℃~80℃ and the cleaning time is 10min~20min. The deionized water rinsing time is 5min~10min. The drying temperature is 100℃~120℃ and the drying time is 30min~60min.

[0053] Step S602: An electrode layer 2 is formed on one side surface of the substrate layer 1. The electrode layer includes a plurality of transducer units 21 arranged along a first direction. Each transducer unit 21 includes a transducer structure 211 and a connection end connected to at least one side of the transducer structure 211 in a second direction. The first direction intersects the second direction.

[0054] For example, an electrode layer 2 can be deposited on the substrate layer 1 using electron beam evaporation or magnetron sputtering processes at a deposition temperature of less than or equal to 250°C. After deposition, an annealing treatment is performed at 200-250°C for 10-30 minutes to reduce the internal stress of the electrode layer 2.

[0055] In step S603, a protective structure 4 is formed on the side of the electrode layer 2 where a portion of the connection ends are away from the base layer 1. The protective structure 4 includes an insulating layer 41 and a barrier layer 42 disposed on at least one side surface of the insulating layer 41. The diffusion coefficient of the metal element in the barrier layer 42 is less than its diffusion coefficient in the insulating layer 41.

[0056] For example, the barrier layer 42 can be deposited using a magnetron sputtering process, and the sputtering parameters can be controlled so that the surface roughness of the barrier layer 42 is less than or equal to 5 nm and the surface energy is less than or equal to 30 mN / m.

[0057] For example, the insulating layer 41 is deposited by chemical vapor deposition at a deposition temperature of 300°C to 400°C, a deposition pressure of 1 Torr to 5 Torr, and a deposition rate of 50 nm / h to 100 nm / h. The first barrier layer 421 and the second barrier layer 422 can be prepared using the same process.

[0058] In step S604, a bridging layer 3 is formed on the side of the protective structure 4 away from the base layer 1. The bridging layer 3 is located on the side where the connection end is located in the second direction. The bridging layer 3 is electrically connected to at least a portion of the connection end and electrically isolated from at least a portion of the connection end through the protective structure 4.

[0059] For example, the bridging layer 3 can be prepared using the same process as the electrode layer 2, which will not be described in detail here.

[0060] The fabrication method of the surface acoustic wave (SAW) device in this embodiment employs mature magnetron sputtering and chemical vapor deposition processes to prepare the relevant structural layers, resulting in a protective structure 4 comprising an insulating layer 41 and barrier layers 42 disposed on both sides of the insulating layer 41. The insulating layer 41 is disposed between the electrode layer 2 and the bridging layer 3, effectively blocking the current path and preventing leakage. Simultaneously, when electrical signals are coupled to the electrode layer 2 through parasitic capacitance or inductance, it reduces parasitic coupling effects and signal interference. Furthermore, it acts as a buffer layer to absorb some stress, enhancing mechanical reliability. The barrier layers 42, with a diffusion coefficient much lower than that of the insulating layer 41, form a dense physical barrier on the surface of the insulating layer 41. This physically alters the interaction between particles and the contact film surface, simultaneously suppressing particle adhesion and blocking electrode metal diffusion. This effectively prevents metal particles in the bridging layer 3 from entering the insulating layer 41 and external impurity particles from eroding into the insulating layer 41, ensuring that the isolation performance of the insulating layer 41 is unaffected and guaranteeing the performance and reliability of the SAW device. This fabrication process can be directly integrated into existing surface acoustic wave (SAW) device manufacturing production lines without the need for additional equipment, making it easy to promote and apply on a large scale and showing promising prospects for industrial applications.

[0061] Specifically, in some embodiments, a barrier layer 42 is formed using a magnetron sputtering process. By controlling the sputtering parameters, the surface roughness of the barrier layer 42 is made less than or equal to 5 nm, and the surface energy is made less than or equal to 30 mN / m. Further, the sputtering parameters include multiple parameters such as sputtering pressure, sputtering power, self-bias voltage of the substrate layer 1, deposition temperature, and deposition rate. The specific sputtering parameters need to be adjusted based on the material of the barrier layer 42.

[0062] In an optional embodiment, when the barrier layer 42 is a titanium-tungsten alloy, the step of forming the barrier layer 42 includes: A barrier layer 42 is formed using magnetron sputtering. The sputtering target is a titanium-tungsten alloy with a purity greater than or equal to 99.99%, a diameter ranging from 100 mm to 150 mm, and a thickness ranging from 5 mm to 10 mm. The sputtering gas is argon with a purity greater than or equal to 99.999%, a sputtering pressure ranging from 0.5 Pa to 2 Pa, and a sputtering power ranging from 100 W to 300 W. The self-bias voltage of the substrate layer 1 ranges from -10 V to -30 V, the deposition temperature ranges from 200 °C to 300 °C, and the deposition rate ranges from 10 nm / min to 30 nm / min. Furthermore, the barrier layer 42 undergoes annealing treatment at a temperature range of 400℃ to 450℃ in a nitrogen atmosphere with a purity greater than or equal to 99.999%. The holding time ranges from 30 min to 60 min, the heating rate ranges from 5℃ / min to 10℃ / min, and the cooling rate is less than or equal to 5℃ / min. Annealing treatment repairs lattice defects within the barrier layer 42 to increase structural density, thereby enhancing its barrier function. Simultaneously, it releases residual stress within the barrier layer 42, strengthens the interfacial bonding between it and the insulating layer 41, and ensures the reliability of the protective structure.

[0063] Using the above-mentioned process steps and parameters, a smooth, low-surface-energy titanium-tungsten alloy barrier layer 42 is precisely obtained, which improves the surface properties of the barrier layer 42 and ensures the inhibition effect on particle adhesion.

[0064] In another alternative embodiment, when the barrier layer 42 is tantalum nitride, the step of forming the barrier layer 42 includes: A barrier layer 42 is formed using magnetron sputtering. The sputtering target is a tantalum metal target with a purity greater than or equal to 99.99%. The sputtering gas is a mixture of argon and ammonia with a volume ratio of 9:1 to 7:3 and a total purity of 99.999%. The sputtering pressure ranges from 1 Pa to 3 Pa, the sputtering power ranges from 200 W to 400 W, the self-bias voltage of the substrate layer 1 ranges from -20 V to -40 V, the deposition temperature ranges from 250 °C to 350 °C, and the deposition rate ranges from 5 nm / min to 20 nm / min. Furthermore, the barrier layer 42 is subjected to nitrogen plasma treatment. The plasma power ranges from 100W to 200W, the treatment time ranges from 5min to 15min, and the treatment pressure ranges from 0.1Pa to 0.5Pa. Nitrogen plasma treatment can, on the one hand, densify the surface of the tantalum nitride barrier layer 42 through ion bombardment, compensate for surface defects caused by slight gas flow fluctuations during deposition, and improve its ability to block the diffusion of metal elements. On the other hand, it can avoid the formation of a large number of grain boundaries due to the formation of a polycrystalline structure inside during high-temperature annealing, which would degrade its barrier performance.

[0065] Similarly, by using the above-mentioned process steps and parameters, a smooth, low-surface-energy tantalum nitride barrier layer 42 can be accurately obtained, thereby improving the surface properties of the barrier layer 42 and ensuring the suppression effect on particle adhesion.

[0066] In some embodiments, the process further includes forming a transition layer 43 between the insulating layer 41 and the barrier layer 42, specifically including the following steps: A transition layer 43 is formed using a magnetron sputtering process. The sputtering target of the transition layer 43 is a chromium metal target with a purity greater than or equal to 99.99%. The sputtering gas is argon gas with a purity greater than or equal to 99.999%. The sputtering power ranges from 50W to 100W, the deposition temperature ranges from 150℃ to 200℃, the deposition rate ranges from 5nm / min to 15nm / min, and the deposition thickness ranges from 20nm to 50nm. The transition layer 43 is annealed at a temperature range of 180℃ to 220℃ for a time range of 20 min to 40 min, under an argon atmosphere.

[0067] In summary, the surface acoustic wave (SAW) device and its fabrication method described in this embodiment are applicable to SAW devices with low to medium frequency, high frequency (3GHz~10GHz) and high reliability requirements. They are particularly suitable for application scenarios with extremely high requirements for device performance and reliability, such as 5G / 6G communication and automotive electronics, and can meet the diverse needs of different fields for SAW devices.

[0068] This embodiment also provides an electronic device that includes the surface acoustic wave device described above.

[0069] Further functional descriptions of the above structures are the same as those of the corresponding embodiments described above, and will not be repeated here.

[0070] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A surface acoustic wave device, characterized in that, include: basal layer; An electrode layer is disposed on one side surface of the substrate layer. The electrode layer includes a plurality of transducer units arranged along a first direction. Each transducer unit includes a transducer structure and a connection end connected to at least one side of the transducer structure in a second direction. The first direction intersects the second direction. A bridging layer is disposed on the side of the electrode layer opposite to the substrate layer and on the side where the connection terminal is located. The bridging layer is electrically connected to at least a portion of the connection terminal and electrically isolated from at least a portion of the connection terminal. A protective structure is disposed between the electrically isolated connection end and the bridging layer; the protective structure includes an insulating layer and a barrier layer disposed on at least one surface of the insulating layer, wherein the diffusion coefficient of at least one metal element in the barrier layer is less than its diffusion coefficient in the insulating layer.

2. The surface acoustic wave device according to claim 1, characterized in that, The surface roughness of the barrier layer is less than or equal to 5 nm, and the surface energy is less than or equal to 30 mN / m.

3. The surface acoustic wave device according to claim 1, characterized in that, The barrier layer includes a first barrier layer and a second barrier layer located on both sides of the insulating layer in the thickness direction, wherein the first barrier layer is disposed relatively close to the substrate layer, and the thickness of the second barrier layer is greater than or equal to the thickness of the first barrier layer.

4. The surface acoustic wave device according to claim 1, characterized in that, The material of the barrier layer includes one or more of titanium-tungsten alloy, tantalum nitride, nickel-tungsten alloy, and nickel-chromium alloy; The mass ratio of titanium to tungsten in the titanium-tungsten alloy is in the range of 1:9 to 2:

8. The mass ratio of nitrogen to tantalum in the tantalum nitride is in the range of 1:9 to 2:

8. The thickness of the barrier layer ranges from 50 nm to 200 nm.

5. The surface acoustic wave device according to any one of claims 1 to 4, characterized in that, The projected area of ​​the barrier layer on the base layer covers more than 95% of the projected area of ​​the connection end on the base layer.

6. The surface acoustic wave device according to any one of claims 1 to 4, characterized in that, In the second direction, the outer edge of the barrier layer protrudes relative to the outer edge of the bridging layer, and the width of the protruding portion in the second direction ranges from 2.5 μm to 5 μm.

7. The surface acoustic wave device according to claim 1, characterized in that, Also includes: A sealing structure is provided at least on the outside of the electrode layer; the material and surface properties of the sealing structure are the same as those of the barrier layer, and the width of the sealing structure ranges from 10 μm to 30 μm.

8. The surface acoustic wave device according to claim 1, characterized in that, The protective structure also includes: A transition layer is disposed between the insulating layer and the barrier layer, wherein the transition layer is matched with at least one component of the insulating layer and the barrier layer, and / or the coefficient of thermal expansion of the transition layer is between the coefficient of thermal expansion of the insulating layer and the coefficient of thermal expansion of the barrier layer.

9. A method for fabricating a surface acoustic wave device, characterized in that, include: Provide a base layer; An electrode layer is formed on one side surface of the substrate layer. The electrode layer includes a plurality of transducer units arranged along a first direction. Each transducer unit includes a transducer structure and a connection end connected to at least one side of the transducer structure in a second direction. The first direction intersects the second direction. A protective structure is formed on the side of the electrode layer away from the base layer, wherein the protective structure includes an insulating layer and a barrier layer disposed on at least one surface of the insulating layer, wherein the diffusion coefficient of the metal element in the barrier layer is less than its diffusion coefficient in the insulating layer. A bridging layer is formed on the side of the protective structure away from the base layer, the bridging layer being located on the side where the connection end is located in the second direction; the bridging layer is electrically connected to at least a portion of the connection end, and is electrically isolated from at least a portion of the connection end through the protective structure.

10. The method for fabricating a surface acoustic wave device according to claim 9, characterized in that, The barrier layer is formed by magnetron sputtering. By controlling the sputtering parameters, the surface roughness of the barrier layer is less than or equal to 5 nm, and the surface energy is less than or equal to 30 mN / m.

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