Surface acoustic wave device, preparation method and filtering device

Abstract

The invention relates to the technical field of acoustic wave devices, in particular to an acoustic surface wave device, a preparation method and a filtering device. The surface acoustic wave device includes: a piezoelectric layer; an electrode layer formed on the piezoelectric layer; the electrode layer comprises an electrode area and an exposed area, electrode stripes are formed in the electrode area, and the exposed area is exposed out of the surface of the piezoelectric layer; the electrode stripes have top surfaces and side surfaces; the passivation layer comprises a first region, a second region and a third region; the first region is formed on the surface of the piezoelectric layer exposed by the exposed region, the second region is formed on the top surface of the electrode stripe, and the third region is formed on the side surface of the electrode stripe; the thickness difference among the passivation layer of the first region, the passivation layer of the second region and the passivation layer of the third region is smaller than or equal to a thickness difference threshold value. According to the scheme, the failure of the heterostructure can be avoided, the center frequency deviation problem of the high-frequency surface acoustic wave is optimized, the overall reliability of the device is enhanced, and meanwhile, the process yield of the high-frequency surface acoustic wave device is improved.

Description

Technical Field

[0001] The present application relates to the technical field of acoustic wave devices, and in particular to a surface acoustic wave device, a preparation method and a filtering device. Background Art

[0002] As people pursue higher data transmission speed, performance, and power consumption of telecommunication equipment, new chip integration solutions are needed to achieve high-performance, high-integration, and low-power chip technology. The rise of piezoelectric thin film heterostructures has enabled related optical and acoustic devices to greatly reduce device size, improve work efficiency, and achieve high data throughput rates.

[0003] Currently, in the application of high-frequency surface acoustic wave devices, the use of new piezoelectric film substrates can achieve high performance comparable to that of bulk acoustic wave devices. However, in the application process, the passivation layer, which protects the metal layer from adverse factors such as temperature, humidity, oxidation, etc., has a large difference in thickness in different areas, which greatly deteriorates the reliability and yield of surface acoustic wave devices. Summary of the invention

[0004] In order to solve the above technical problems, the present application provides a surface acoustic wave device, a preparation method and a filtering device.

[0005] In a first aspect, an embodiment of the present application discloses a surface acoustic wave device, comprising:

[0006] Piezoelectric layer;

[0007] An electrode layer is formed on the piezoelectric layer; the electrode layer includes an electrode area and a bare area, an electrode stripe is formed in the electrode area, and the bare area exposes the surface of the piezoelectric layer; the electrode stripe has a top surface and a side surface;

[0008] The passivation layer includes a first region, a second region and a third region; the first region is formed on the surface of the piezoelectric layer exposed in the bare area, the second region is formed on the top surface of the electrode stripes, and the third region is formed on the side surfaces of the electrode stripes; the thickness difference between the passivation layer of the first region, the passivation layer of the second region and the passivation layer of the third region is less than or equal to a thickness difference threshold.

[0009] In some optional embodiments, the thickness difference threshold is 10%.

[0010] In some optional embodiments, the material of the passivation layer is any one of silicon oxide, silicon nitride, aluminum nitride, and aluminum oxide.

[0011] In some optional embodiments, the thickness of the passivation layer is less than or equal to 100 nm.

[0012] In some optional embodiments, the material of the electrode layer is at least one of aluminum, platinum, silver, gold, titanium, chromium, tungsten, molybdenum, and nickel.

[0013] In some optional embodiments, the thickness of the electrode layer is 1 nm to 1000 nm.

[0014] In some optional embodiments, the material of the piezoelectric layer is lithium niobate, lithium tantalate, aluminum nitride, zinc oxide, quartz, or lead zirconate titanate.

[0015] In some optional embodiments, the surface acoustic wave device further includes a supporting substrate and a temperature compensation layer;

[0016] The temperature compensation layer is formed on the supporting substrate;

[0017] The piezoelectric layer is formed on the temperature compensation layer.

[0018] In some optional embodiments, the support substrate is at least one of a silicon substrate, a silicon oxide substrate, a sapphire substrate, a diamond substrate, an aluminum nitride substrate, a gallium nitride substrate, a silicon carbide substrate, and a silicon-on-insulator substrate.

[0019] In a second aspect, an embodiment of the present application discloses a method for preparing a surface acoustic wave device, the method comprising:

[0020] Providing a base structure;

[0021] forming a piezoelectric layer on the base structure;

[0022] An electrode layer is formed on the piezoelectric layer; the electrode layer comprises an electrode region and an exposed region, an electrode stripe is formed in the electrode region, and the exposed region exposes the surface of the piezoelectric layer; the electrode stripe has a top surface and a side surface;

[0023] A passivation layer is formed on the electrode layer; the passivation layer includes a first region, a second region and a third region; the first region is formed on the surface of the piezoelectric layer exposed in the bare area, the second region is formed on the top surface of the electrode stripes, and the third region is formed on the side surfaces of the electrode stripes; the thickness difference between the passivation layer of the first region, the passivation layer of the second region and the passivation layer of the third region is less than or equal to a thickness difference threshold.

[0024] In some optional embodiments, forming a passivation layer on the electrode layer includes:

[0025] A passivation layer is deposited on the electrode layer based on a chemical vapor deposition method; wherein the bias voltage of a radio frequency source used in the process of depositing the passivation layer is greater than 150V.

[0026] In some optional embodiments, forming a passivation layer on the electrode layer includes:

[0027] A passivation layer is deposited on the electrode layer based on a physical vapor deposition method; wherein the bias voltage of the radio frequency source used in the process of depositing the passivation layer is greater than 200V.

[0028] In some optional embodiments, forming a passivation layer on the electrode layer includes:

[0029] forming an initial passivation layer on the electrode layer;

[0030] The initial passivation layer is selectively modified so that the thickness difference between the passivation layer in the first region, the passivation layer in the second region and the passivation layer in the third region is less than or equal to a thickness difference threshold.

[0031] In a third aspect, an embodiment of the present application discloses a filtering device, which includes the surface acoustic wave device as described above.

[0032] The technical solution provided by the embodiment of the present application has the following technical effects:

[0033] The surface acoustic wave device described in the embodiment of the present application includes a piezoelectric layer, an electrode layer and a passivation layer, the electrode layer is formed on the piezoelectric layer, the electrode layer includes an electrode area and an exposed area, electrode stripes are formed in the electrode area, the exposed area exposes the surface of the piezoelectric layer, the electrode stripes have a top surface and a side surface, the passivation layer includes a first area, a second area and a third area, the first area is formed on the surface of the piezoelectric layer exposed in the exposed area, the second area is formed on the top surface of the electrode stripes, and the third area is formed on the side surface of the electrode stripes. By setting the thickness difference between the passivation layer of the first area, the passivation layer of the second area and the passivation layer of the third area to be less than or equal to a thickness difference threshold, failure of the heterogeneous structure can be avoided, the problem of high-frequency surface acoustic wave center frequency offset can be optimized, the overall reliability of the device can be enhanced, and the process yield of the high-frequency surface acoustic wave device can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0035] Figure 1 This is a schematic diagram of the structure of a surface acoustic wave device provided in an embodiment of the present application. Figure 1 ;

[0036] Figure 2 This is a schematic diagram of the structure of a surface acoustic wave device provided in an embodiment of the present application. Figure 2 ;

[0037] FIG3 is a diagram showing the relationship between stress and temperature in different electrode structures and passivation layer structures provided in an embodiment of the present application;

[0038] Figure 4 is a wavelength-frequency dispersion diagram of a surface acoustic wave device provided in an embodiment of the present application;

[0039] Figure 5 It is a schematic flow chart of a method for preparing a surface acoustic wave device provided in an embodiment of the present application.

[0040] The following is a supplementary description of the attached drawings:

[0041] 10 - piezoelectric layer; 20 - electrode layer; 30 - passivation layer; 31 - first region; 32 - second region; 33 - third region; 40 - supporting substrate; 50 - temperature compensation layer. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0043] It should be noted that the "one embodiment" or "embodiment" referred to in the specification of the embodiment of the present application refers to a specific feature, structure or characteristic that can be included in at least one implementation of the present application. It should be understood that in the specification and claims of the embodiment of the present application and the above-mentioned drawings, the orientation or position relationship indicated by the terms "upper", "lower", "top", "bottom", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. The terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" can explicitly or implicitly include one or more of the features. Moreover, the terms "first", "second", etc. are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described here can be implemented in an order other than those illustrated or described here. In addition, in the description of the present embodiment, unless otherwise specified, "plurality" means two or more. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system or product including a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0044] 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 can be directly on, adjacent to, connected to or coupled to other elements or layers, or there can be intervening elements or layers. On the contrary, when an element is referred to as "directly on ...", "directly adjacent to ...", "directly connected to" or "directly coupled to" other elements or layers, there is no intervening element or layer. It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present application, the first element, component, region, layer or part discussed below can be represented as the second element, component, region, layer or part. And when the second element, component, region, layer or part is discussed, it does not indicate that the present application necessarily has the first element, component, region, layer or part.

[0045] In order to make the purpose, technical solution and advantages disclosed in the embodiments of the present application more clearly understood, the embodiments of the present application are further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present application and are not used to limit the embodiments of the present application.

[0046] Surface acoustic wave (SAW) devices have been widely used in mobile communications in our daily lives due to their simple process, low cost, outstanding performance and high integration. However, the lift-off process used usually produces a trapezoidal metal electrode. In order to protect the metal layer, a denser passivation layer preparation method, namely, vapor deposition, is currently used. This results in better directionality during the production of the passivation layer, that is, the thickness of the passivation layer varies greatly on the surface of the metal layer in different areas, causing abnormalities in the overall yield of the device. At the same time, due to the large difference in thermal expansion coefficients between heterogeneous materials, it is easy to have a large reliability degradation phenomenon at the discontinuity.

[0047] In view of this, an embodiment of the present application proposes a surface acoustic wave device, a preparation method and a filtering device, wherein the surface acoustic wave device includes a piezoelectric layer, an electrode layer and a passivation layer, the electrode layer is formed on the piezoelectric layer, the electrode layer includes an electrode area and an exposed area, an electrode stripe is formed in the electrode area, the exposed area exposes the surface of the piezoelectric layer, the electrode stripe has a top surface and a side surface, the passivation layer includes a first region, a second region and a third region, the first region is formed on the surface of the piezoelectric layer exposed in the exposed area, the second region is formed on the top surface of the electrode stripe, and the third region is formed on the side surface of the electrode stripe. By setting the thickness difference between the passivation layer of the first region, the passivation layer of the second region and the passivation layer of the third region to be less than or equal to a thickness difference threshold, failure of the heterogeneous structure can be avoided, the problem of high-frequency surface acoustic wave center frequency offset can be optimized, the overall reliability of the device can be enhanced, and the process yield of the high-frequency surface acoustic wave device can be improved.

[0048] See also Figure 1 , Figure 1 This is a schematic diagram of the structure of a surface acoustic wave device provided in an embodiment of the present application. Figure 1 ,like Figure 1 As shown, the surface acoustic wave device includes a piezoelectric layer 10 , an electrode layer 20 and a passivation layer 30 .

[0049] In the embodiment of the present application, the material of the piezoelectric layer 10 is a material having a piezoelectric effect. The piezoelectric layer 10 is used to convert an electrical signal into a mechanical vibration or convert a mechanical vibration into an electrical signal. Under the action of a driving electrode of a specific structure, the piezoelectric layer 10 can enhance or suppress sound waves of a specific frequency, thereby achieving frequency selection, thereby separating the required frequency components, and removing noise and interference. Optionally, the piezoelectric layer 10 can be a piezoelectric film or a piezoelectric substrate. The material of the piezoelectric layer 10 includes but is not limited to lithium niobate, lithium tantalate, aluminum nitride, zinc oxide, quartz, lead zirconate titanate, etc.

[0050] like Figure 1 As shown, the electrode layer 20 is formed on the piezoelectric layer 10. Optionally, the thickness of the electrode layer 20 is 1nm to 1000nm. The electrode layer 20 includes an electrode area and an exposed area, in which electrode stripes are formed, and the exposed area exposes the surface of the piezoelectric layer 10. Specifically, a driving electrode, such as an interdigital transducer (IDT), is formed in the electrode layer 20. The driving electrode can convert an electrical signal into a surface acoustic wave, and convert the received surface acoustic wave back into an electrical signal. The driving electrode may include a plurality of electrode stripes formed on the piezoelectric layer 10, such as finger electrodes. There is an exposed area between adjacent electrode stripes, which exposes the surface of the piezoelectric layer 10. Optionally, the material of the driving electrode includes but is not limited to metals such as aluminum, platinum, silver, gold, titanium, chromium, tungsten, molybdenum, nickel, and their alloys. Optionally, the thickness of the electrode layer is 1nm to 1000nm.

[0051] The passivation layer 30 is formed on the electrode layer 20. The passivation layer 30 can prevent the influence of moisture, oxygen, pollutants, etc. in the external environment on the device, avoid electrode oxidation and corrosion, and extend the service life of the surface acoustic wave device. In addition, the passivation layer 30 can reduce the influence of temperature changes on the performance of the surface acoustic wave device and improve the stability of the device under different temperature conditions. In addition, the passivation layer 30 can also provide a certain mechanical strength to prevent the device from being mechanically damaged during use, thereby improving the stability and reliability of the device.

[0052] like Figure 1As shown, the electrode stripes have a top surface and a side surface. The passivation layer 30 includes a first region 31, a second region 32 and a third region 33. The first region 31 is formed on the surface of the piezoelectric layer 10 exposed in the bare area, the second region 32 is formed on the top surface of the electrode stripes, and the third region 33 is formed on the side surface of the electrode stripes, so that the driving electrode can be isolated from the external environment and short circuit between the electrodes can be prevented, thereby ensuring the normal operation of the surface acoustic wave device. Optionally, the material of the passivation layer 30 is any one of silicon oxide, silicon nitride, aluminum nitride, and aluminum oxide. Optionally, the passivation layer 30 can be formed by vapor deposition so that the obtained passivation layer 30 has a dense internal structure, thereby ensuring the protective effect of the passivation layer 30 on the electrode stripes. Optionally, the thickness of the passivation layer 30 is less than or equal to 100nm.

[0053] like Figure 1 As shown, the cross section of the electrode stripe is a trapezoid, such as the electrode stripe structure prepared by the stripping process. Since the photoresist has a certain thickness when the surface pattern is defined by the photolithography technology in the process of preparing the electrode structure, the pattern structure usually has a certain inclination angle (usually an inverted trapezoid) on the side wall, so after the electrode deposition and lift-off stripping process are performed again, the electrode structure formed is usually a trapezoidal structure. For the electrode stripe of the trapezoidal structure, when the passivation layer 30 is formed thereon by the vapor deposition method, the thickness of the passivation layer 30 formed in different regions of the electrode layer 20 is uneven and there are large differences due to the good directionality of the vapor deposition method. The passivation layer 30 with different thicknesses in different regions will cause the sound velocity of the local area on the driving electrode of the surface acoustic wave device to change, causing the frequency response of the device to deviate, thereby causing the performance of the surface acoustic wave device to decrease, and the device yield to decrease. At the same time, due to the large difference in the thermal expansion coefficient of the material between the passivation layer 30 and the driving electrode, there will be a large stress between the two. The reliability test of the device involves drastic temperature and humidity changes and structural reliability tests such as dropping. The stress within the structure has an adverse effect on the reliability of the device, and it is easy to cause significant reliability degradation at the discontinuity of the click stripes.

[0054] In order to avoid the above problems, in the embodiment of the present application, the thickness difference between the passivation layer 30 of the first area 31, the passivation layer 30 of the second area 32 and the passivation layer 30 of the third area 33 is less than or equal to the thickness difference threshold. Specifically, the thickness difference between the passivation layer 30 of the first area 31 and the passivation layer 30 of the second area 32 is less than or equal to the thickness difference threshold. The thickness difference between the passivation layer 30 of the second area 32 and the passivation layer 30 of the third area 33 is less than or equal to the thickness difference threshold. The thickness difference between the passivation layer 30 of the first area 31 and the passivation layer 30 of the third area 33 is less than or equal to the thickness difference threshold. Optionally, the thickness difference threshold is 10%. Generally speaking, the smaller the thickness uniformity of the passivation layer 30 in different areas, the better the reliability of the surface acoustic wave device and the higher the yield.

[0055] Figure 2 This is a schematic diagram of the structure of a surface acoustic wave device provided in an embodiment of the present application. Figure 2 ,like Figure 2 As shown, the surface acoustic wave device also includes a supporting substrate 40 and a temperature compensation layer 50. The temperature compensation layer 50 is formed on the supporting substrate 40, and the piezoelectric layer 10 is formed on the temperature compensation layer 50. The supporting substrate 40 can be a silicon substrate, a silicon oxide substrate, a sapphire substrate, a diamond substrate, an aluminum nitride substrate, a gallium nitride substrate, a silicon carbide substrate, and a silicon-on-insulator substrate, etc., but is not limited thereto. The temperature compensation layer 50 is used to improve the stability of the device under different temperature conditions and reduce the temperature drift phenomenon. As the temperature changes, the elastic constant and dielectric constant of the piezoelectric material will change, causing the operating frequency of the surface acoustic wave device to drift. The temperature compensation layer 50 can compensate for the frequency drift caused by temperature changes by changing the stress state of the piezoelectric material and adjusting its elastic constant, and can also further reduce the influence of temperature changes on the frequency response by changing the dielectric constant of the piezoelectric material. Optionally, the material of the temperature compensation layer 50 includes but is not limited to quartz, silicon nitride, aluminum oxide, etc.

[0056] In the embodiment of the present application, the thickness of the passivation layer 30 in the first region 31 is h1, the thickness of the passivation layer 30 in the second region 32 is h2, and the thickness of the passivation layer 30 in the third region 33 is h3. FIG3 is a graph showing the relationship between stress and temperature in a different electrode structure and a passivation layer 30 structure provided in the embodiment of the present application, wherein: Figure 3a The corresponding thickness of the passivation layer 30 is h1 30 nm, h2 30 nm, and h3 10 nm. Figure 3b The corresponding thickness of the passivation layer 30 is h1 30nm, h2 30nm, and h3 30nm. As shown in FIG3 , after the temperature rises from room temperature to the same temperature, Figure 3b The corresponding stress exhibited by the passivation layer 30 structure is only Figure 3aThe corresponding passivation layer 30 structure exhibits half of the stress. Therefore, by controlling the thickness difference between the passivation layer 30 in the first area 31, the passivation layer 30 in the second area 32 and the passivation layer 30 in the third area 33 to be less than or equal to the thickness difference threshold, the reliability of the device will be improved.

[0057] Figure 4 is a wavelength-frequency dispersion diagram of a surface acoustic wave device provided in an embodiment of the present application, such as Figure 4 As shown, the horizontal axis is the wavelength of the surface acoustic wave device (i.e., the photolithographic feature size, i.e., the line width of the electrode stripes in the structure), and the vertical axis is the frequency response of the prepared RF device. The product of the wavelength and the device-affecting frequency is the sound velocity of the structure. In a fixed structure (electrode & substrate), the thickness of the passivation layer 30 on the top will become an important factor affecting the structure. In small wavelengths, i.e., narrow electrode stripe widths, i.e., high-frequency devices, the deviation of the device center frequency caused by the uneven thickness of the passivation layer 30 will be more obvious. At high frequencies (i.e., short wavelengths, small photolithographic line widths), the frequency of the surface acoustic wave device is greatly affected by line width fluctuations, and the device center frequency deviation caused by the uneven passivation layer 30 will be very obvious, affecting the device yield. Therefore, a uniform thickness of the passivation layer 30 will also improve the yield of device manufacturing.

[0058] The surface acoustic wave device described in the embodiment of the present application can avoid heterogeneous structure failure and optimize the high-frequency surface acoustic wave center frequency offset problem by controlling the thickness of the passivation layer 30 in the metallized area and the non-metallized area in the high-frequency surface acoustic wave device, thereby enhancing the overall reliability of the device and improving the process yield of the high-frequency surface acoustic wave device.

[0059] The present application also provides a method for preparing a surface acoustic wave device. Figure 5 is a schematic flow chart of a method for preparing a surface acoustic wave device provided in an embodiment of the present application, such as Figure 5 As shown, the preparation method comprises:

[0060] S01: Provide a base structure.

[0061] In the embodiment of the present application, the base structure can be prepared by a semiconductor processing technology. Specifically, the base structure is obtained by forming a temperature compensation layer 50 on a supporting substrate 40 .

[0062] S03: forming a piezoelectric layer 10 on the base structure.

[0063] In the embodiment of the present application, the base structure includes a supporting substrate 40 and a temperature compensation layer 50 , and the piezoelectric layer 10 is formed on the temperature compensation layer 50 .

[0064] S05: forming an electrode layer 20 on the piezoelectric layer 10; the electrode layer 20 comprises an electrode region and an exposed region, wherein electrode stripes are formed in the electrode region, and the exposed region exposes the surface of the piezoelectric layer 10; the electrode stripes have a top surface and a side surface.

[0065] In the embodiment of the present application, after the piezoelectric layer 10 is obtained, an electrode layer 20 is formed on the piezoelectric layer 10 by a lift-off peeling process. A driving electrode is formed in the electrode layer 20, and the driving electrode includes a plurality of electrode stripes. The cross-sectional shape of the electrode stripes is a trapezoid. The area between adjacent electrode stripes is an exposed area.

[0066] S07: A passivation layer 30 is formed on the electrode layer 20; the passivation layer 30 includes a first region 31, a second region 32 and a third region 33; the first region 31 is formed on the surface of the piezoelectric layer 10 exposed in the bare area, the second region 32 is formed on the top surface of the electrode stripes, and the third region 33 is formed on the side surfaces of the electrode stripes; the thickness difference between the passivation layer 30 of the first region 31, the passivation layer 30 of the second region 32 and the passivation layer 30 of the third region 33 is less than or equal to a thickness difference threshold.

[0067] In an embodiment of the present application, the passivation layer 30 can be formed on the electrode layer 20 by a vapor deposition method. The passivation layer 30 is formed by a vapor deposition method so that the obtained passivation layer 30 has a dense internal structure, thereby ensuring the protective effect of the passivation layer 30 on the electrode stripes. Optionally, in order to improve the uniformity of the thickness of the passivation layer 30, the RF voltage during the meteorological deposition process can be controlled. Specifically, the RF voltage is used to excite the reaction gas, and the magnitude of the RF voltage directly affects the density, energy and distribution of the plasma, thereby affecting the deposition rate and the quality of the deposited structure. When the RF voltage is high, the plasma density is large, the amount of active substances increases, and the deposition rate is accelerated.

[0068] As an optional embodiment, when the passivation layer 30 is formed on the electrode layer 20, the passivation layer 30 can be deposited on the electrode layer 20 based on chemical vapor deposition. In order to ensure that the thickness difference between the passivation layer 30 in the first region 31, the passivation layer 30 in the second region 32 and the passivation layer 30 in the third region 33 is less than or equal to the thickness difference threshold, when the passivation layer 30 is formed by chemical vapor deposition, the RF source bias voltage used in the process of depositing the passivation layer 30 is greater than 150V. By controlling the RF voltage during the chemical vapor deposition process, the thickness uniformity of the passivation layer 30 in different regions can be improved.

[0069] As another optional embodiment, when the passivation layer 30 is formed on the electrode layer 20, the passivation layer 30 can be deposited on the electrode layer 20 based on physical vapor deposition. In order to ensure that the thickness difference between the passivation layer 30 in the first region 31, the passivation layer 30 in the second region 32 and the passivation layer 30 in the third region 33 is less than or equal to the thickness difference threshold, when the passivation layer 30 is formed by physical vapor deposition, the RF source bias voltage used in the process of depositing the passivation layer 30 is greater than 200 V. By controlling the RF voltage during the chemical vapor deposition process, the thickness uniformity of the passivation layer 30 in different regions can be improved.

[0070] In the embodiment of the present application, in order to further improve the thickness uniformity of the passivation layer 30 in different regions, when forming the passivation layer 30 on the electrode layer 20, an initial passivation layer 30 may be first formed on the electrode layer 20, and then the initial passivation layer 30 may be selectively modified so that the thickness difference between the passivation layer 30 in the first region 31, the passivation layer 30 in the second region 32, and the passivation layer 30 in the third region 33 is less than or equal to the thickness difference threshold. For example, the initial passivation layer 30 may be modified using techniques such as chemical mechanical planarization, dry etching, wet etching, laser trimming, and ion beam etching to make the thickness of the passivation layer 30 in different regions consistent.

[0071] An embodiment of the present application also provides a filtering device, which includes the surface acoustic wave device as described above.

[0072] It should be noted that the above-mentioned sequence of the embodiments of the present application is for description only and does not represent the advantages and disadvantages of the embodiments. The above-mentioned specific embodiments of this specification are described. Other embodiments are within the scope of the attached claims. In some cases, the actions or steps recorded in the claims can be performed in an order different from that in the embodiments and still achieve the desired results. In addition, the processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0073] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0074] A person skilled in the art will understand that all or part of the steps to implement the above embodiments may be accomplished by hardware or by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, and the above-mentioned storage medium may be a read-only memory, a disk or an optical disk, etc.

[0075] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A surface acoustic wave device, characterized in that: include: Piezoelectric layer; An electrode layer is formed on the piezoelectric layer; the electrode layer comprises an electrode region and a bare region, the electrode region is formed with electrode stripes, and the bare region exposes the surface of the piezoelectric layer; The electrode stripes have a top surface and a side surface; A passivation layer, the passivation layer comprising a first region, a second region and a third region; the first region is formed on the surface of the piezoelectric layer exposed in the bare region, the second region is formed on the top surface of the electrode stripes, and the third region is formed on the side surfaces of the electrode stripes; A thickness difference among the passivation layer in the first region, the passivation layer in the second region, and the passivation layer in the third region is less than or equal to a thickness difference threshold.

2. The surface acoustic wave device according to claim 1, characterized in that: The thickness difference threshold is 10%.

3. The surface acoustic wave device according to claim 1 or 2, characterized in that: The material of the passivation layer is any one of silicon oxide, silicon nitride, aluminum nitride and aluminum oxide.

4. The surface acoustic wave device according to claim 3, characterized in that: The thickness of the passivation layer is less than or equal to 100 nm.

5. The surface acoustic wave device according to claim 1, characterized in that: The material of the electrode layer is at least one of aluminum, platinum, silver, gold, titanium, chromium, tungsten, molybdenum, and nickel.

6. The surface acoustic wave device according to claim 5, characterized in that: The thickness of the electrode layer is 1 nm to 1000 nm.

7. The surface acoustic wave device according to claim 1 or 6, characterized in that: The material of the piezoelectric layer is lithium niobate, lithium tantalate, aluminum nitride, zinc oxide, quartz, or lead zirconate titanate.

8. The surface acoustic wave device according to claim 1, characterized in that: The surface acoustic wave device also includes a supporting substrate and a temperature compensation layer; The temperature compensation layer is formed on the supporting substrate; The piezoelectric layer is formed on the temperature compensation layer.

9. The surface acoustic wave device according to claim 8, characterized in that: The support substrate is at least one of a silicon substrate, a silicon oxide substrate, a sapphire substrate, a diamond substrate, an aluminum nitride substrate, a gallium nitride substrate, a silicon carbide substrate and a silicon-on-insulator substrate.

10. A method for preparing a surface acoustic wave device, characterized in that: include: Providing a base structure; forming a piezoelectric layer on the base structure; An electrode layer is formed on the piezoelectric layer; the electrode layer comprises an electrode region and an exposed region, wherein electrode stripes are formed in the electrode region, and the exposed region exposes the surface of the piezoelectric layer; The electrode stripes have a top surface and a side surface; forming a passivation layer on the electrode layer; The passivation layer comprises a first region, a second region and a third region; the first region is formed on the surface of the piezoelectric layer exposed in the bare region, the second region is formed on the top surface of the electrode stripe, and the third region is formed on the side surface of the electrode stripe; A thickness difference among the passivation layer in the first region, the passivation layer in the second region, and the passivation layer in the third region is less than or equal to a thickness difference threshold.

11. The preparation method according to claim 10, characterized in that: The step of forming a passivation layer on the electrode layer comprises: The passivation layer is deposited on the electrode layer based on chemical vapor deposition; wherein the bias voltage of the radio frequency source used in the process of depositing the passivation layer is greater than 150V.

12. The preparation method according to claim 10, characterized in that: The step of forming a passivation layer on the electrode layer comprises: The passivation layer is deposited on the electrode layer based on physical vapor deposition; wherein the bias voltage of the radio frequency source used in the process of depositing the passivation layer is greater than 200V.

13. The preparation method according to claim 11 or 12, characterized in that: The step of forming a passivation layer on the electrode layer comprises: forming an initial passivation layer on the electrode layer; The initial passivation layer is selectively modified so that a thickness difference between the passivation layer in the first region, the passivation layer in the second region, and the passivation layer in the third region is less than or equal to a thickness difference threshold.

14. A filtering device, characterized in that: The filtering device comprises the surface acoustic wave device according to any one of claims 1 to 9.

Images