Elastic wave device, preparation method therefor, and elastic wave apparatus

Abstract

The present invention relates to the technical field of elastic wave devices, and in particular relates to a preparation method for an elastic wave device, said method comprising the following steps: forming a photoresist structure on a partial region on a substrate; forming an IDT metal layer (12) by means of deposition on the substrate and the photoresist structure, the IDT metal layer (12) having a footing (122); providing a self-alignment layer (14) on a surface of the IDT metal layer (12), the self-alignment layer (14) not completely covering the footing (122); removing the footing (122) not covered by the self-alignment layer (14) and removing the photoresist structure; and forming a frequency modulation dielectric layer (16) on the IDT metal layer (12) and on the substrate. By virtue of this arrangement, most of the footing (122) of the IDT metal layer (12) can be effectively removed, so that the prepared elastic wave device has excellent product properties.

Description

Elastic wave device and preparation method thereof, and elastic wave device Technical Field

[0001] The present invention relates to the technical field of elastic wave devices, and in particular to an elastic wave device and a preparation method thereof, and an elastic wave apparatus comprising the elastic wave device. Background Art

[0002] Elastic wave devices are high-frequency filters with a passband frequency range from tens of MHz to several GHz. These devices consist of a piezoelectric substrate and an interdigital transducer (IDT) electrode with comb-shaped electrode fingers arranged on the top surface of the piezoelectric substrate, also known as an IDT metal layer. Elastic waves are excited by applying a high-frequency electric field from a power supply-side lead terminal through a wiring pattern to the IDT metal layer. The piezoelectric effect converts the elastic waves into a high-frequency electric field, thereby achieving filter characteristics.

[0003] The morphology of the IDT metal layer is crucial for achieving a filter with stable, excellent characteristics. Currently, the IDT metal layer's patterning is primarily achieved through a lift-off process. Because the IDT metal layer is formed by vapor deposition, footing (often referred to as "footing," which refers to the phenomenon in the photolithography process where the bottom of the photoresist pattern is wide due to factors such as insufficient development) is unavoidable. This footing prevents the filter from achieving excellent K and Q values. The K value refers to the relationship between the conductivity and temperature of a semiconductor material and is commonly used to describe its electrical properties. The Q value is a key parameter for measuring inductors and is the ratio of the inductive reactance to its equivalent loss resistance when the inductor operates under an AC voltage of a certain frequency.

[0004] Therefore, how to prevent the IDT metal layer from tailing has become one of the technical problems that those skilled in the art need to solve urgently.

[0005] It should be noted that the information disclosed in this background technology section is only intended to increase understanding of the overall background of the present invention, and should not be regarded as an admission or any form of implication that the information constitutes prior art already known to those skilled in the art. Summary of the Invention

[0006] The present invention provides a method for preparing an elastic wave device, which comprises the following steps: forming a photoresist structure in a partial area on a substrate; depositing an IDT metal layer on the substrate and the photoresist structure, wherein the IDT metal layer has an extension leg; providing a self-alignment layer on the surface of the IDT metal layer, wherein the self-alignment layer does not completely cover the extension leg; removing the extension leg and the photoresist structure not covered by the self-alignment layer; and forming a frequency modulation dielectric layer on the IDT metal layer and the substrate.

[0007] The present invention also provides an elastic wave device, which comprises a substrate, an IDT metal layer, a self-alignment layer and a frequency modulation dielectric layer.

[0008] The substrate has an upper surface and a lower surface facing each other. The IDT metal layer is located on the upper surface of the substrate. The self-aligned layer covers the upper surface and a portion of the side surface of the IDT metal layer. The frequency modulation dielectric layer covers the substrate, the IDT metal layer, and the self-aligned layer.

[0009] The present invention also provides an elastic wave device, which includes an elastic wave component and a circuit substrate. The elastic wave component is arranged on the circuit substrate, and the elastic wave component can be the elastic wave component described above.

[0010] An elastic wave device, an elastic wave component, and a method for fabricating the same are provided in one embodiment of the present invention. By adding a self-aligned layer, most of the extended footing of the IDT metal layer can be effectively removed, thereby avoiding the tailing phenomenon and ensuring that the fabricated elastic wave component has excellent product characteristics.

[0011] Other features and beneficial effects of the present invention will be described in the following description, and some of the technical features and beneficial effects can be obviously derived from the description or understood by practicing the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, some of the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0013] FIG1 is a schematic structural diagram of an elastic wave device provided by a first embodiment of the present invention;

[0014] FIG2 is a partial enlarged schematic diagram of area A in FIG1 ;

[0015] 3 to 8 are schematic structural diagrams of the elastic wave device shown in FIG1 at various stages in the preparation process;

[0016] 9 is a schematic structural diagram of an elastic wave device provided in a second embodiment of the present invention;

[0017] 10 to 15 are schematic structural diagrams of the elastic wave device shown in FIG. 9 at various stages in the preparation process;

[0018] FIG16 is a schematic structural diagram of an elastic wave device provided in one embodiment of the present invention;

[0019] FIG17 is a schematic top view showing an electrode structure on a piezoelectric substrate;

[0020] FIG18 is a schematic diagram showing an elastic wave device provided by an embodiment of the present invention having a bulk acoustic wave structure. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments; the technical features designed in different implementation modes of the present invention described below can be combined with each other as long as they do not conflict with each other; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0022] In the description of the present invention, it should be understood that the terms "center", "lateral", "up", "down", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more. In addition, the term "including" and any variations thereof all mean "at least including".

[0023] Please refer to Figures 1 to 8. Figure 1 is a schematic diagram of the structure of an elastic wave device provided by the first embodiment of the present invention. Figure 2 is a partially enlarged schematic diagram of area A in Figure 1. Figures 3 to 8 are schematic diagrams of the structure of the elastic wave device shown in Figure 1 at various stages of its fabrication. To achieve at least one of the aforementioned advantages, or other advantages, an embodiment of the present invention provides an elastic wave device. As shown in the figures, the elastic wave device may include at least a substrate 11, an IDT metal layer 12, a self-aligned layer 14, and a frequency-modulated dielectric layer 16.

[0024] Substrate 11 has opposing upper and lower surfaces. The material of substrate 11 can be lithium tantalate (LT) or lithium niobate (LN), but this invention is not limited thereto. Substrate 11 can also be made of other materials with relatively stable crystal structures, such as quartz. In some embodiments, substrate 11 can also comprise a multilayer structure composed of sapphire, silicon, aluminum oxide, spinel, crystal, or glass stacked with a piezoelectric layer.

[0025] The IDT metal layer 12 is located on the upper surface of the substrate 11. IDT (Inter Digital Transducer) is an interdigital transducer. By applying a high-frequency electrical signal to the IDT metal layer 12 from the lead terminal on the power supply side through the wiring pattern, the surface of the substrate 11 will generate mechanical vibrations and simultaneously excite surface acoustic waves with the same frequency as the external electrical signal. Such surface acoustic waves will propagate along the surface of the substrate 11. The number of IDT metal layers 12 can be multiple, and the multiple IDT metal layers 12 are arranged at intervals on the substrate 11. The number, position and spacing of the IDT metal layers 12 can be adjusted according to actual needs. The material of the IDT metal layer 12 may include metals such as Ti, Al, Cu, and Au.

[0026] The self-aligning layer 14 covers the upper surface and part of the side surface of the IDT metal layer 12. By setting the self-aligning layer 14, most of the extended pins 122 of the conventionally prepared lower IDT metal layer 12 can be removed, so that the elastic wave device can obtain a better K value and Q value, thereby obtaining relatively excellent product characteristics. The material of the self-aligning layer 14 is different from that of the IDT metal layer 12, so that during the preparation process, the extended pins 122 not covered by the self-aligning layer 14 can be removed by means of process means. In some embodiments, the self-aligning layer 14 can be an oxide layer. The material of the self-aligning layer 14 can include at least one selected from the group consisting of silicon oxide, silicon nitride, polyethylene and polysilicon. For example: SiO2, Si x N y 、Poly、Si x O y However, the present invention is not limited thereto. The self-aligning layer 14 may also be a metal layer, wherein the atomic weight of the metal in the self-aligning layer 14 is greater than the atomic weight of the metal in the IDT metal layer 12. The material of the self-aligning layer 14 may include at least one selected from the group consisting of Au, Cu, Cr, and Ni. In some embodiments, the thickness S1 of the self-aligning layer 14 may range from 5 to 100 nm.

[0027] Frequency-modulated dielectric layer 16 covers substrate 11, IDT metal layer 12, and self-aligned layer 14. Adjusting the thickness of frequency-modulated dielectric layer 16 can, on the one hand, adjust the frequency of the elastic wave device to achieve the desired target frequency and adapt to product requirements; on the other hand, it can cover and protect the IDT metal layer not covered by self-aligned layer 14. In some embodiments, the material of frequency-modulated dielectric layer 16 may include SiO2.

[0028] The IDT metal layer 12 has an upper width and a lower width. The lower width of the IDT metal corresponds to the line width of the IDT metal. A significant difference between this line width and the upper width will affect the performance of the elastic wave device. For example, when the longitudinal cross-section of the IDT metal layer 12 is rectangular, the elastic wave device performs better. However, due to current process limitations, the longitudinal cross-section of the IDT metal layer 12 typically exhibits a trapezoidal shape, as shown in the figure. In this case, the lower width of the IDT metal layer 12 needs to be as close as possible to the upper width to effectively improve the performance of the elastic wave device. Conventional fabrication methods, however, result in the formation of long extension legs 122, as shown in Figure 6. This results in an excessively large lower width of the IDT metal layer 12, reducing the K and Q values ​​of the elastic wave device. To address this issue, this embodiment adds a self-alignment layer 14 to remove the portions of the extension legs 122 not covered by the self-alignment layer 14, thereby reducing the lower width of the IDT metal layer 12 and improving the performance of the elastic wave device. In some embodiments, the ratio of the upper width to the lower width of the IDT metal layer 12 can be in the range of 0.75:1 to 1:1, for example, 0.9:1.

[0029] In some embodiments, the sidewalls of the IDT metal layer 12, along the direction from the bottom surface to the top surface of the substrate 11 (i.e., from bottom to top in the figure), include a first sidewall 21, a second sidewall 22, and a third sidewall 23. The first sidewall 21 protrudes beyond the third sidewall 23, i.e., the first sidewall 21 is more outwardly disposed than the third sidewall 23. The self-alignment layer 14 covers at least the third sidewall 23. Optionally, the self-alignment layer 14 may cover the second sidewall 22. To further effectively remove excessively long extension legs 122 of the IDT metal layer 12, the height H1 of the first sidewall 21 can be set within a range of 5 to 100 nm. That is, the height of the sidewall of the IDT metal layer 12 not covered by the self-alignment layer 14 is within a range of 5 to 100 nm. The height refers to the vertical distance from the upper end point of the sidewall to the upper surface of the substrate 11. It should be noted that the right and left figures in Figure 2 depict the same structure; the right figure is intended to illustrate the markings of various dimensions and angles.

[0030] In some embodiments, the angle B between the first side wall 21 and the horizontal plane and the angle between the third side wall 23 and the horizontal plane are both greater than the angle between the second side wall 22 and the horizontal plane. For clarity, only the angle B between the first side wall 21 and the horizontal plane is labeled; the remaining angles can be understood by reference to this label. In the figure, the angle B between the first side wall 21 and the horizontal plane, the angle between the second side wall 22 and the horizontal plane, and the angle between the third side wall 23 and the horizontal plane are approximately 80°, 30°, and 78°, respectively.

[0031] As shown in FIG. 3 to FIG. 8 , a method for manufacturing the elastic wave device shown in FIG. 1 is disclosed below.

[0032] First, as shown in FIG3 , a photoresist structure 18 is formed on a portion of the substrate 11. The photoresist structure 18 in the figure is a double-layer structure. Specifically, a conventional bi-layer method can be used to complete the yellowing process to form the photoresist structure 18. The upper layer of the photoresist is wider, and the lower layer of the photoresist is partially undercut.

[0033] Next, as shown in Figure 4 , an IDT metal layer 12 is deposited on the substrate 11 and the photoresist structure 18. The resulting IDT metal layer 12 has extended legs 122. Specifically, an evaporation process can be used to deposit the IDT metal over the entire surface, covering the substrate 11 and the photoresist structure 18. As shown in the enlarged portion of the figure, the evaporation process inevitably creates longer extended legs 122 on the IDT metal layer 12.

[0034] Then, as shown in FIG5 , a self-aligned layer 14 is provided on the surface of the IDT metal layer 12. The self-aligned layer 14 does not completely cover the extended leg 122. The self-aligned layer 14 can be a thin oxide layer formed by low-temperature sputtering, or a thin non-IDT metal layer formed by evaporation. The thickness S1 of the self-aligned layer 14 can be 5 to 100 nm. The non-IDT metal refers to a metal that is different from the material of the IDT metal layer 12 and has an atomic weight greater than that of the metal of the IDT metal layer 12. Since the non-IDT metal self-aligned layer 14 is thin, the diffusion time is very short, and an extended leg 122 as long as the IDT metal layer 12 will not be formed on the surface of the IDT metal layer 12.

[0035] 6 , the photoresist structure 18 and the IDT metal layer 12 on the photoresist structure 18 may be removed first. Specifically, this may be achieved by using a conventional lift-off process to perform metal stripping.

[0036] Then, as shown in Figure 7, the extension pins 122 not covered by the self-alignment layer 14 are removed to improve the performance of the elastic wave device. Specifically, different methods can be used to remove the extension pins 122 depending on the material of the self-alignment layer 14. For example, when the self-alignment layer 14 is a metal layer other than the IDT metal, such as Cu, and the IDT metal layer 12 is Al, since Cu has a relatively large atomic weight, a dry etching process with a high Al:Cu selectivity can be used to perform a descum process on the Al film. This will completely remove the extension pins 122 not covered by the Cu film, thereby achieving self-aligned etching. When the self-alignment layer 14 is an oxide layer, the gas introduced can be controlled to react only with the metal extension pins 122, rather than the oxide layer, to remove the extension pins 122 not covered by the oxide layer, thereby achieving the purpose of removing the extension pins 122.

[0037] Finally, as shown in Figure 8, a frequency-modulated dielectric layer 16 is formed on the IDT metal layer 12 and the substrate 11. Conventional processes can be used to directly form a SiO2 film as a frequency-modulated layer, after testing the frequency, as needed to form the frequency-modulated dielectric layer 16. In some embodiments, a SiO2 film of a certain thickness can be formed first, and then the thickness of the SiO2 film can be adjusted based on the frequency to achieve frequency modulation.

[0038] Please refer to Figures 9 to 15. Figure 9 is a schematic diagram of the structure of the elastic wave device provided by the second embodiment of the present invention. Figures 10 to 15 are schematic diagrams of the structure of the elastic wave device shown in Figure 9 at various stages of the preparation process. Compared to the elastic wave device shown in Figure 1, the elastic wave device of this embodiment differs primarily in that it also includes an anti-reflection layer 20, which is located between the IDT metal layer 12 and the substrate 11. The function of the anti-reflection layer 20 is to reduce the standing wave effect and the uniformity of light reflection by utilizing the light absorption effect. The material of the anti-reflection layer 20 may include a metal material. The material of the anti-reflection layer 20 may include materials such as Ti, TlN, Cr, and Ni.

[0039] As shown in FIG. 10 to FIG. 15 , a method for manufacturing the elastic wave device shown in FIG. 9 is disclosed below.

[0040] First, as shown in FIG10 , an anti-reflection layer 20 is provided on the entire surface of the substrate 11. Then, a photoresist structure 18 is formed in a portion of the anti-reflection layer 20. The photoresist structure 18 may be a double-layer structure, a single-layer structure, or the like. Specifically, the photoresist structure 18 may be formed by a conventional bi-layer method to complete a yellowing process.

[0041] Next, as shown in Figure 11, an IDT metal layer 12 is deposited on the substrate 11 and the photoresist structure 18. The resulting IDT metal layer 12 has extended legs 122. Specifically, an evaporation process can be used to deposit the IDT metal over the entire surface, covering the substrate 11 and the photoresist structure 18 to form the IDT metal layer 12. During the evaporation process, the IDT metal layer 12 inevitably forms longer extended legs 122.

[0042] Then, as shown in FIG12 , a self-aligned layer 14 is formed on the surface of the IDT metal layer 12. The self-aligned layer 14 does not completely cover the extended leg 122. The self-aligned layer 14 can be a thin oxide layer formed by low-temperature sputtering, or a thin non-IDT metal layer formed by evaporation. The non-IDT metal is a metal different from the IDT metal layer 12 and having a greater atomic weight than the metal of the IDT metal layer 12. Since the non-IDT metal self-aligned layer 14 is thin, the diffusion time is very short, and the extended leg 122 as long as the IDT metal layer 12 will not be formed on the surface of the IDT metal layer 12.

[0043] Next, as shown in FIG13 , the photoresist structure 18 and the IDT metal layer 12 on the photoresist structure 18 may be removed first. Specifically, this may be accomplished by using a conventional lift-off process to perform metal stripping. During this removal process, the anti-reflective layer 20 beneath the photoresist structure 18 is also removed.

[0044] Then, as shown in Figure 14, the extension pins 122 not covered by the self-alignment layer 14 are removed to improve the performance of the elastic wave device. During this process, the anti-reflection layer 20 located beneath the extension pins 122 not covered by the self-alignment layer 14 is also removed. Specifically, different methods can be used to remove the extension pins 122 depending on the material of the self-alignment layer 14. For example, when the self-alignment layer 14 is a non-IDT metal layer, such as Cu, and the IDT metal layer 12 is Al, due to the relatively large atomic weight of Cu, a dry etching process with a high Al:Cu selectivity can be used to perform a descum process on the Al film. This will completely remove the extension pins 122 not covered by the Cu film, thereby achieving self-aligned etching. When the self-alignment layer 14 is an oxide layer, the gas introduced can be controlled to react only with the metal extension pins 122 and not with the oxide layer, thereby removing the extension pins 122 not covered by the oxide layer, thereby achieving the purpose of removing the extension pins 122.

[0045] 15 , a frequency modulation dielectric layer 16 is formed on the IDT metal layer 12 and the substrate 11. Specifically, conventional processes can be used to directly plate a SiO2 film of the frequency modulation layer according to actual needs after testing the frequency to form the frequency modulation dielectric layer 16.

[0046] Please refer to Figures 16 and 17. Figure 16 is a schematic diagram of the structure of an elastic wave device according to one embodiment of the present invention, and Figure 17 is a schematic top view illustrating the electrode structure on piezoelectric substrate 1. Figure 17 schematically illustrates the top view without sidewall 7, cover 8, and external connector 9 in Figure 16. As shown in Figure 16, the elastic wave device includes piezoelectric substrate 1, elastic wave assembly 2, sidewall 7, cover 8, and external connector 9.

[0047] The piezoelectric substrate 1 is made of a piezoelectric single crystal, such as lithium tantalate, lithium niobate, or quartz, or can also be made of piezoelectric ceramics. In some embodiments, the piezoelectric substrate 1 can also be bonded to a circuit substrate 10, such as a sapphire substrate, an alumina substrate, a spinel substrate, or a silicon substrate. In a specific embodiment, the piezoelectric substrate 1 includes a first surface on which the elastic wave component 2 is provided and a second surface opposite the first surface, which can be bonded to the circuit substrate 10.

[0048] The elastic wave assembly 2 is disposed on the first surface of the piezoelectric substrate 1. A self-aligning layer 14 covers the surface of the elastic wave assembly 2, removing most of the extended legs of the elastic wave assembly 2 and preventing tailing. This ensures that the fabricated elastic wave device has excellent product characteristics. A frequency-modulated dielectric layer 16 is disposed on the piezoelectric substrate 1, also covering the elastic wave assembly 2 and the self-aligning layer 14.

[0049] In practice, the elastic wave component 2 comprises multiple resonators 2a, thereby forming an elastic wave filter. More specifically, the resonators 2a include interdigital electrodes (or interdigital transducers, or IDTs) 2a for exciting surface acoustic waves and reflectors 2b formed on the piezoelectric substrate 1. The interdigital electrodes 2a include a pair of comb-shaped electrodes 2c arranged opposite each other. Each comb-shaped electrode 2c has multiple electrode fingers 2d and bus bars 2e connected to the electrode fingers 2d. The reflectors 2b are arranged on both sides of the interdigital electrodes 2a.

[0050] The elastic wave assembly 2 is electrically connected to the wiring constituting the input terminal In, the output terminal Out, and the ground terminal GND by first wiring 3 and second wiring 4 disposed on the piezoelectric substrate 1. The first wiring 3 and second wiring 4 can be made of a suitable metal or alloy, such as silver, aluminum, copper, titanium, or palladium.

[0051] The side wall portion 7 surrounds the elastic wave component 2. The side wall portion 7 is made of a synthetic resin. Preferably, the side wall portion 7 is made of a photosensitive resin. Photosensitive resin can be easily patterned using photolithography. This makes it easy to obtain an opening for forming a space that does not hinder the vibration of the elastic wave component 2, or a through hole for wiring of the external connection portion 9. The photosensitive resin can use photosensitive polyimide, photosensitive epoxy resin, photosensitive silicone, etc. Preferably, in order to achieve precise patterning, photosensitive polyimide can be used, but it is not limited to this.

[0052] Cover 8 cooperates with sidewall 7 to form and seal elastic wave module 2 without obstructing its vibration, thereby creating a sealed cavity that allows for proper operation of elastic wave module 2. Cover 8 can be made of a synthetic resin, such as, but not limited to, epoxy resin or polyimide. Preferably, epoxy resin can be used, and cover 8 can be formed through a low-temperature curing process.

[0053] The elastic wave assembly 2, along with first wiring 3 and second wiring 4, is formed on the piezoelectric substrate 1. To achieve desired bandpass filter characteristics, the elastic wave assembly 2 can employ a DMS structure or a ladder design. Part of the first wiring 3 and part of the second wiring 4 form the wiring for the input terminal In, the output terminal Out, and the ground terminal GND. The elastic wave assembly 2 is electrically connected to these terminals In, Out, and the ground terminal GND via the first wiring 3.

[0054] Please refer to Figure 18, which is a schematic diagram of an elastic wave device provided by one embodiment of the present invention having a bulk acoustic wave structure. As shown in the figure, the elastic wave device can be a bulk acoustic wave structure. The thickness of the piezoelectric layer 50 is not particularly limited, but in order to effectively excite the thickness shear first-order mode, it is preferably greater than 50 nm and less than 1000 nm. The piezoelectric layer 50 has an upper surface and a lower surface that are perpendicular to each other. Electrode fingers 53 and electrode fingers 54 are provided on the upper surface. The surfaces of the electrode fingers 53 and electrode fingers 54 are covered with a self-aligning layer 14 to remove most of the extended legs of the electrode fingers 53 and electrode fingers 54, thereby preventing tailing and ensuring that the prepared elastic wave device has excellent product characteristics. A frequency-modulated dielectric layer 16 is provided on the piezoelectric layer 50, and the frequency-modulated dielectric layer 16 also covers the electrode fingers 53, electrode fingers 54, and the self-aligning layer 14.

[0055] A support substrate 58 is stacked on the lower surface of the piezoelectric layer 50 via a dielectric film 57. The dielectric film 57 and the support substrate 58 have frame-like shapes and have openings 57a and 58a, respectively, thereby forming a cavity 59 (air gap).

[0056] The cavity 59 is provided so as not to interfere with the vibration of the excitation region of the piezoelectric layer 50. Therefore, the support substrate 58 is laminated on the lower surface via the dielectric film 57 at a position that does not overlap with the portion where the at least one pair of electrode fingers 53 and electrode fingers 54 are provided. Alternatively, the dielectric film 57 may not be provided. Therefore, the support substrate 58 can be laminated directly or indirectly on the lower surface of the piezoelectric layer 50.

[0057] The dielectric film 57 is formed of silicon oxide. However, the dielectric film 57 can be formed of an appropriate insulating material other than silicon oxide, such as silicon nitride or alumina.

[0058] The support substrate 58 is formed of Si. Preferably, Si with a high resistivity of 4 kΩ or higher is suitable. However, the support substrate 58 can also be formed of an appropriate insulating material or semiconductor material. Examples of materials that can be used for the support substrate 58 include piezoelectric materials such as aluminum oxide, lithium tantalate, lithium niobate, and quartz; various ceramics such as alumina, magnesium oxide, sapphire, silicon nitride, aluminum nitride, silicon carbide, zirconium oxide, cordierite, mullite, steatite, and forsterite; dielectric materials such as diamond and glass; and semiconductors such as gallium nitride.

[0059] The plurality of electrode fingers 53 and 54 may include an appropriate metal or alloy such as Al or AlCu alloy. The electrode fingers 53 and 54 have a structure in which an Al film is stacked on a Ti film. Alternatively, an adhesive layer other than a Ti film may be used.

[0060] During driving, an AC voltage is applied between the electrode fingers 53 and the electrode fingers 54. More specifically, an AC voltage is applied between the two bus bar electrodes. This achieves resonance characteristics utilizing the bulk wave of the thickness shear first-order mode excited in the piezoelectric layer 50.

[0061] An embodiment of the present invention further provides an elastic wave device, comprising an elastic wave component and a circuit substrate. The elastic wave component is disposed on the circuit substrate and can be the elastic wave component described above.

[0062] In summary, an elastic wave device, an elastic wave component, and a method for preparing the same, provided by one embodiment of the present invention, can effectively remove most of the extended feet 122 (footing) of the IDT metal layer 12 by adding the self-alignment layer 14, thereby avoiding the occurrence of tailing, and ensuring that the prepared elastic wave component has excellent product characteristics.

[0063] In addition, those skilled in the art should understand that, although there are many problems in the prior art, each embodiment or technical solution of the present invention may be improved in only one or several aspects, without having to simultaneously solve all the technical problems listed in the prior art or background art. Those skilled in the art should understand that any content not mentioned in a claim should not be construed as limiting the claim.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for manufacturing an elastic wave device, characterized in that: The method for manufacturing the elastic wave device includes the following steps: Form a photoresist structure in a partial area on the substrate; Deposit and form an IDT metal layer on the substrate and the photoresist structure, and the IDT metal layer has extension feet; Set a self-alignment layer on the surface of the IDT metal layer, and the self-alignment layer does not completely cover the extension feet; Remove the extension feet and the photoresist structure that are not covered by the self-alignment layer; Form a frequency modulation dielectric layer on the IDT metal layer and the substrate.

2. The method for manufacturing an elastic wave device according to claim 1, characterized in that: The material of the self-alignment layer is different from the material of the IDT metal layer.

3. The method for manufacturing an elastic wave device according to claim 1, characterized in that: The self-alignment layer is an oxide layer.

4. The method for manufacturing an elastic wave device according to claim 1 or 3, characterized in that: The material of the self-alignment layer includes at least one selected from the group consisting of silicon oxide, silicon nitride, and polyethylene.

5. The method for manufacturing an elastic wave device according to claim 1, characterized in that: The self-alignment layer is a metal layer, and the atomic weight of the metal of the self-alignment layer is greater than the atomic weight of the metal of the IDT metal layer.

6. The method for manufacturing an elastic wave device according to claim 1 or 5, characterized in that: The material of the self-alignment layer includes at least one selected from the group consisting of Au, Cu, Cr, and Ni.

7. The method for manufacturing an elastic wave device according to claim 1, characterized in that: The material of the frequency modulation dielectric layer includes SiO 2 .

8. The method for manufacturing an elastic wave device according to claim 1, characterized in that: Before the step of forming the photoresist structure, the following steps are further included: Set an anti-reflection layer on the substrate, and the material of the anti-reflection layer includes a metal material.

9. The method for manufacturing an elastic wave device according to claim 1, characterized in that: The process of removing the extension feet is a dry etching process.

10. An elastic wave device, characterized in that: The elastic wave device includes: A substrate having opposite upper and lower surfaces; An IDT metal layer located on the upper surface of the substrate; A self-alignment layer covering the upper surface and part of the side surface of the IDT metal layer; A frequency modulation dielectric layer covering the substrate, the IDT metal layer, and the self-alignment layer.

11. The elastic wave device according to claim 10, characterized in that: The IDT metal layer has an upper width and a lower width, and the ratio range of the upper width to the lower width is 0.75:1 to 1:

1.

12. The elastic wave device according to claim 10, characterized in that: The side wall of the IDT metal layer sequentially includes a first side wall, a second side wall, and a third side wall in the direction from the lower surface to the upper surface of the substrate. The first side wall protrudes from the third side wall, and the self-alignment layer covers at least the third side wall.

13. The elastic wave device according to claim 12, characterized in that: The ratio range of the sum of the lengths of the first side wall and the second side wall to the length of the third side wall is 1:1 to 1.3:

1.

14. The elastic wave device according to claim 12, wherein: the self-alignment layer covers the second sidewall.

15. The elastic wave device according to claim 12, wherein: the angle between the first sidewall and the horizontal plane and the angle between the third sidewall and the horizontal plane are greater than the angle between the second sidewall and the horizontal plane.

16. The elastic wave device according to claim 10, wherein: the material of the self-alignment layer is different from the material of the IDT metal layer.

17. The elastic wave device according to claim 10, wherein: the self-alignment layer is an oxide layer.

18. The elastic wave device according to claim 10 or 17, wherein: the material of the self-alignment layer includes at least one selected from the group consisting of silicon oxide, silicon nitride, and polyethylene.

19. The elastic wave device according to claim 10, wherein: the self-alignment layer is a metal layer, and the atomic weight of the metal of the self-alignment layer is greater than the atomic weight of the metal of the IDT metal layer.

20. The elastic wave device according to claim 10 or 18, wherein: the material of the self-alignment layer includes at least one selected from the group consisting of Au, Cu, Cr, and Ni.

21. The elastic wave device according to claim 10, wherein: the thickness range of the self-alignment layer is 5 to 100 nm.

22. The elastic wave device according to claim 10, wherein: the elastic wave device further includes an antireflection layer, and the antireflection layer is located between the IDT metal layer and the substrate.

23. An elastic wave device, wherein, the elastic wave device includes an elastic wave device and a circuit board, the elastic wave device is disposed on the circuit board, and the elastic wave device employs the elastic wave device according to any one of claims 10 to 22.

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