Preparation method of surface acoustic wave resonator, surface acoustic wave resonator and related equipment

Abstract

This application discloses a method for fabricating a surface acoustic wave (SAW) resonator, the SAW resonator, and related equipment, relating to the field of radio frequency (RF) technology. The method employs a subtractive process: first, a sufficiently thick interdigitated electrode and its leads are deposited; then, using a barrier layer as an etching barrier, the central portion of the interdigitated electrode and its leads are etched to the target thickness, integrally forming the interdigitated electrode and a protrusion structure at the end of the interdigitated electrode. There is no separating interface between the two. The protrusion structure is self-aligned with the ends of the first and second interdigitated electrodes in both directions perpendicular to and parallel to the plane of the piezoelectric substrate, and its position is fixed. This ensures consistency among multiple resonators / filters, helping to improve production efficiency and product yield. Finally, the barrier layer on the protrusion structure is retained to further block diffusion.

Description

Technical Field

[0001] This application relates to the field of radio frequency technology, and in particular to a method for fabricating a surface acoustic wave resonator, a surface acoustic wave resonator, and related equipment. Background Technology

[0002] Surface acoustic wave (SAW) resonators are widely used in the radio frequency field. They combine low insertion loss and good suppression performance with a small size. They mainly utilize the piezoelectric effect to convert electrical energy and mechanical energy into each other, which is used to combine signal transmission to achieve gating characteristics.

[0003] There are various types of surface acoustic wave (SAW) resonators, such as SAW resonators with interdigital transducers containing dummy fingers, SAW resonators with reflective grids on both sides of the interdigital transducer, temperature-compensated SAW (TC-SAW) resonators, and thin-film SAW (TC-SAW) resonators. For any type of SAW resonator, the transversely propagating sound waves will cause the resonator to exhibit transverse resonant modes, i.e., clutter appearing in and near the passband. This clutter will increase device losses, cause large fluctuations in the Q value, and reduce the performance of the resonator and filter.

[0004] Currently, the industry commonly uses the Piston structure to suppress cross-mode. The Piston structure is a raised metal block structure, which is usually attached to the end of the interdigital electrode after the interdigital electrode is fabricated through a lift-off process. That is, it and the interdigital electrode are not a single material, but two independent material layers. The lift-off process involves performing a photolithography process (coating photoresist, exposure, and development) on the wafer to obtain an opening that exposes the end of the interdigital electrode. Then, metal is evaporated, and the photoresist and the metal attached to the photoresist are stripped, leaving the metal deposited at the end of the interdigital electrode, thus obtaining the raised metal block structure at the end of the interdigital electrode.

[0005] However, the photolithography process has deviations in alignment with the interdigitated electrode layer, and the window linewidth of the photolithography process itself also has certain differences. This will cause the raised metal block to not be completely vertically aligned with the edge of the interdigitated electrode end. This will result in differences in the effect of noise suppression, affecting the filter performance and the individual consistency of the filter. Obviously, this is not conducive to improving production efficiency and will lead to a decrease in product yield. Summary of the Invention

[0006] To address the aforementioned technical problems, this application provides a method for fabricating a surface acoustic wave (SAW) resonator, a SAW resonator, and related equipment. By etching the interdigitated electrodes, a protrusion structure that suppresses transverse modes is formed at the end of the interdigitated electrodes. This ensures that the protrusion structure is fixed to the position of the interdigitated electrodes in both the horizontal and vertical directions, guaranteeing consistency among multiple resonators / filters and helping to improve production efficiency and product yield.

[0007] To achieve the above objectives, the embodiments of this application provide the following technical solutions:

[0008] A method for fabricating a surface acoustic wave resonator includes:

[0009] Provide piezoelectric substrates;

[0010] A first interdigital electrode lead-out portion, a plurality of first interdigital electrodes connected to the first interdigital electrode lead-out portion, a second interdigital electrode lead-out portion, and a plurality of second interdigital electrodes connected to the second interdigital electrode lead-out portion are formed on the piezoelectric substrate. The first interdigital electrodes and the second interdigital electrodes are arranged in parallel and intersecting directions. Each of the first interdigital electrodes and the second interdigital electrodes includes a central portion of the interdigital electrode connected to its respective lead-out portion and a terminal portion of the interdigital electrode away from its respective lead-out portion.

[0011] A barrier layer is formed, which covers the piezoelectric substrate, the first interdigital electrode lead-out portion, the first interdigital electrode, the second interdigital electrode lead-out portion, and the second interdigital electrode;

[0012] The barrier layer is etched to retain the interdigitated electrode ends of the first interdigitated electrode and the second interdigitated electrode, as well as the barrier layer on the piezoelectric substrate, while removing the barrier layer in other areas.

[0013] The exposed central portions of the first and second interdigital electrodes, the lead-out portions of the first and second interdigital electrodes, and the lead-out portions of the second interdigital electrodes are etched to the remaining target thickness, such that the terminal portions of the first and second interdigital electrodes protrude relative to the central portions of the first and second interdigital electrodes and the lead-out portions of the first and second interdigital electrodes to form a protruding structure. The protruding structure is self-aligned with the terminal portions of the first and second interdigital electrodes in both the direction perpendicular to the plane of the piezoelectric substrate and the direction parallel to the plane of the piezoelectric substrate.

[0014] Remove the barrier layer on the piezoelectric substrate, and retain the barrier layer on the protrusion structure.

[0015] Optionally, the method for fabricating the surface acoustic wave resonator further includes:

[0016] A temperature compensation layer is formed, which covers the piezoelectric substrate, the first interdigital electrode lead-out portion, the first interdigital electrode, the second interdigital electrode lead-out portion, and the second interdigital electrode. The temperature compensation layer is etched to form a first through-hole and a second through-hole. The first through-hole exposes the first interdigital electrode lead-out portion, and the second through-hole exposes the second interdigital electrode lead-out portion.

[0017] A first PAD metal layer and a second PAD metal layer are formed. The first PAD metal layer is in contact with the first interdigital electrode lead-out portion through the first through hole, and the second PAD metal layer is in contact with the second interdigital electrode lead-out portion through the second through hole.

[0018] A passivation layer is formed, which covers the temperature compensation layer, the first PAD metal layer, and the second PAD metal layer. The passivation layer is then etched to form a first contact window exposing the first PAD metal layer and a second contact window exposing the second PAD metal layer.

[0019] Optionally, the material of the barrier layer includes one or more of silicon nitride, aluminum oxide, tantalum oxide, thallium nitride, and chromium oxide.

[0020] Optionally, the process of etching the barrier layer includes:

[0021] A first photoresist layer is coated on the barrier layer;

[0022] After the first photoresist layer is exposed and developed, a first photoresist pattern is formed. The first photoresist pattern covers the end portions of the first interdigitated electrode and the second interdigitated electrode, as well as the barrier layer on the piezoelectric substrate, while exposing the barrier layer in other areas.

[0023] Using the first photoresist pattern as a mask, the barrier layer is etched, retaining the interdigitated electrode ends of the first interdigitated electrode and the second interdigitated electrode, as well as the barrier layer on the piezoelectric substrate, while removing the barrier layer in other areas.

[0024] The first photoresist pattern can be removed, or the first photoresist pattern can be removed after etching the exposed central portion of the first interdigital electrode and the second interdigital electrode, the lead-out portion of the first interdigital electrode and the lead-out portion of the second interdigital electrode to the remaining target thickness, and forming the protrusion structure at the end portion of the first interdigital electrode and the second interdigital electrode.

[0025] Optionally, the process of removing the barrier layer on the piezoelectric substrate includes:

[0026] A second photoresist layer is applied, which covers the barrier layer, the first interdigital electrode lead-out portion, the first interdigital electrode, the second interdigital electrode lead-out portion, and the second interdigital electrode.

[0027] After the second photoresist layer is exposed and developed, a second photoresist pattern is formed, and the second photoresist pattern exposes the barrier layer on the piezoelectric substrate;

[0028] Using the second photoresist pattern as a mask, the barrier layer is etched to remove the barrier layer on the piezoelectric substrate, while retaining the barrier layer on the protrusion structure.

[0029] Remove the second photoresist layer.

[0030] Optionally, the temperature compensation layer includes a single SiO2 layer, or includes a SiN layer, an AlN layer, an amorphous silicon layer, a GaN layer, and a SiO2 layer stacked in a direction away from the piezoelectric substrate.

[0031] A surface acoustic wave (SAW) resonator, wherein the SAW resonator is prepared by the method described in any one of the preceding claims; the SAW resonator comprises:

[0032] piezoelectric substrate;

[0033] The piezoelectric substrate includes a first interdigital electrode lead-out portion, a plurality of first interdigital electrodes connected to the first interdigital electrode lead-out portion, a second interdigital electrode lead-out portion, and a plurality of second interdigital electrodes connected to the second interdigital electrode lead-out portion. The first interdigital electrodes and the second interdigital electrodes are arranged in parallel and intersecting directions. Each of the first interdigital electrodes and the second interdigital electrodes includes a central portion of the interdigital electrode connected to its respective lead-out portion and a terminal portion of the interdigital electrode away from its respective lead-out portion.

[0034] The center portion of the first interdigital electrode and the center portion of the second interdigital electrode, the lead-out portion of the first interdigital electrode, and the lead-out portion of the second interdigital electrode have a target thickness. The end portion of the first interdigital electrode and the second interdigital electrode protrudes relative to the center portion of the first interdigital electrode and the lead-out portion of the first interdigital electrode and the lead-out portion of the second interdigital electrode, forming a protruding structure. The protruding structure is self-aligned with the end portion of the first interdigital electrode and the second interdigital electrode in both the direction perpendicular to the plane of the piezoelectric substrate and the direction parallel to the plane of the piezoelectric substrate.

[0035] The protruding structure has a barrier layer.

[0036] Optionally, the surface acoustic wave resonator further includes:

[0037] A temperature compensation layer covers the piezoelectric substrate, the first interdigital electrode lead-out portion, the first interdigital electrode, the second interdigital electrode lead-out portion, and the second interdigital electrode. The temperature compensation layer has a first through-hole and a second through-hole, the first through-hole exposing the first interdigital electrode lead-out portion and the second through-hole exposing the second interdigital electrode lead-out portion.

[0038] A first PAD metal layer and a second PAD metal layer, wherein the first PAD metal layer is in contact with the first interdigital electrode lead-out portion through the first through hole, and the second PAD metal layer is in contact with the second interdigital electrode lead-out portion through the second through hole;

[0039] A passivation layer covering the temperature compensation layer, the first PAD metal layer, and the second PAD metal layer, the passivation layer having a first contact window exposing the first PAD metal layer and a second contact window exposing the second PAD metal layer.

[0040] Optionally, the angle θp between the sidewall of the protrusion structure and the direction perpendicular to the plane of the piezoelectric substrate satisfies: 5°≤θp≤10°.

[0041] A filter comprising the surface acoustic wave resonator described in any of the preceding claims.

[0042] An electronic device comprising the surface acoustic wave resonator described in any one of the preceding claims, or the filter described above.

[0043] Compared with existing technologies, the above technical solution has the following advantages:

[0044] The surface acoustic wave resonator fabrication method provided in this application embodiment first provides a piezoelectric substrate, and forms a first interdigital electrode lead-out portion, a plurality of first interdigital electrodes connected to the first interdigital electrode lead-out portion, a second interdigital electrode lead-out portion, and a plurality of second interdigital electrodes connected to the second interdigital electrode lead-out portion on the piezoelectric substrate. The first interdigital electrodes and the second interdigital electrodes are arranged in a cross-parallel manner. Each first interdigital electrode and the second interdigital electrode includes a central portion of the interdigital electrode connected to its respective lead-out portion and a terminal portion of the interdigital electrode away from its respective lead-out portion. Then, a barrier layer is formed over the entire surface, and the barrier layer is etched to protect the terminal portions of the first interdigital electrodes and the second interdigital electrodes as well as the surface of the piezoelectric substrate. The first interdigital electrodes and the second interdigital electrodes exposed by the barrier layer are thinned by etching. The thickness of the central portion of the interdigital electrode, the lead-out portion of the first interdigital electrode, and the lead-out portion of the second interdigital electrode reaches the target thickness. A protruding structure is formed at the end portion of the first and second interdigital electrodes, making the protruding structure and the interdigital electrodes an integrally formed structure with no separating interface between them. Thus, the protruding structure is self-aligned with the end portion of the first and second interdigital electrodes in both the direction perpendicular to the plane of the piezoelectric substrate and the direction parallel to the plane of the piezoelectric substrate, and its position is fixed. This can ensure the consistency between multiple resonators / filters, which helps to improve production efficiency and product yield. Finally, the blocking layer of the protruding structure is retained, and the blocking layer on the surface of the piezoelectric substrate is removed to obtain the surface acoustic wave resonator structure.

[0045] It is important to emphasize that this application employs a "subtractive" process, which involves first depositing a metal layer of sufficient thickness, and then etching away the unwanted portions of the metal layer to integrally form the interdigital electrodes and the protrusion structure located at the ends of the interdigital electrodes. This requires precise control over the etching process; otherwise, the metal layer thickness may be insufficient, affecting the performance of the interdigital electrodes. When thinning the exposed thickness of the first and second interdigital electrodes by etching the barrier layer, specifically the central portions of the first and second interdigital electrodes, the lead-out portions of the first and second interdigital electrodes, and the surface of the piezoelectric substrate, the barrier layer effectively prevents the etching of the interdigital electrodes at their ends and the piezoelectric substrate surface. This precise control over the etching process ensures the performance of the interdigital electrodes.

[0046] Furthermore, after completing the interdigitated electrode and the protrusion structure located at the end of the interdigitated electrode, this application does not remove the barrier layer on the protrusion structure, but retains the barrier layer on the protrusion structure, thereby continuing to use the barrier layer to protect the protrusion structure and prevent the metal (such as aluminum, copper, etc.) of the protrusion structure from diffusing to other film layers, which would cause deformation of the protrusion structure or changes in its physicochemical properties and thus affect the performance of the interdigitated electrode. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a top view schematic diagram of an existing surface acoustic wave resonator;

[0049] Figure 2 This is a schematic cross-sectional view of a surface acoustic wave resonator.

[0050] Figure 3 This is a top view schematic diagram of another existing surface acoustic wave resonator;

[0051] Figure 4 This is a top view schematic diagram of another existing surface acoustic wave resonator;

[0052] Figure 5 This is a schematic cross-sectional view of another existing surface acoustic wave resonator.

[0053] Figure 6 This is a schematic cross-sectional view of another existing surface acoustic wave resonator.

[0054] Figure 7 A top view schematic diagram of another existing surface acoustic wave resonator;

[0055] Figure 8 This is a schematic diagram of an existing surface acoustic wave resonator in which the protruding metal block and the edges of the interdigitated electrodes are not vertically aligned.

[0056] Figure 9 This is another schematic diagram of an existing surface acoustic wave resonator where the protruding metal block and the edges of the interdigitated electrodes are not vertically aligned.

[0057] Figures 10a-10l A schematic diagram of each process step in a method for fabricating a surface acoustic wave resonator provided in an embodiment of this application;

[0058] Figure 11 This is a schematic cross-sectional view of a surface acoustic wave resonator provided in an embodiment of this application.

[0059] Figure 12 for Figure 11 A top view schematic diagram of the surface acoustic wave resonator shown;

[0060] Figure 13An enlarged cross-sectional view of the protrusion structure at the end of the interdigitated electrode of the first or second interdigitated electrode located on the piezoelectric substrate in the surface acoustic wave resonator provided in the embodiments of this application.

[0061] Figures 14a-14d A schematic diagram of the process steps of another method for fabricating a surface acoustic wave resonator provided in this application embodiment;

[0062] Figure 15 This is a schematic cross-sectional view of another surface acoustic wave resonator provided in an embodiment of this application.

[0063] Figure label:

[0064] 10-Piezoelectric substrate; 20-First interdigital electrode lead-out portion; 30-First interdigital electrode; 40-Second interdigital electrode lead-out portion; 50-Second interdigital electrode; 60-Barrier layer; 61-First photoresist layer; 62-First photoresist pattern; 63-Second photoresist layer; 64-Second photoresist pattern; 70-Temperature compensation layer; 80-Passivation layer; T1-Protrusion structure; A1-Center portion of interdigital electrode; A2-End portion of interdigital electrode; K1-First through-hole; K2-Second through-hole; M1-First PAD metal layer; M2-Second PAD metal layer; Y1-First contact window; Y2-Second contact window. Detailed Implementation

[0065] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0066] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0067] Secondly, this application provides a detailed description in conjunction with schematic diagrams. When detailing the embodiments of this application, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not adhering to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of this application. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.

[0068] Figure 1 This diagram shows a top view of a common surface acoustic wave resonator. Figure 2 It shows Figure 1 A schematic cross-sectional view of a surface acoustic wave resonator along section AA', combined with... Figure 1 and Figure 2 As shown, the existing surface acoustic wave resonator includes a substrate 01 and an interdigital transducer 02 located on the substrate 01. The interdigital transducer 02 includes two busbars 021 and 022 parallel to the main acoustic mode propagation direction X0, and two electrode fingers 023 and 024 alternately arranged between the two busbars 021 and 022 along the main acoustic mode propagation direction X0. The electrode finger 023 is connected to the busbar 021, and the electrode finger 024 is connected to the busbar 022.

[0069] Figure 3 A top view schematic diagram of another existing surface acoustic wave resonator is shown, and... Figure 1 Compared to the surface acoustic wave resonator shown, Figure 3 In the surface acoustic wave resonator shown, the interdigital transducer 02 also includes a pseudo-finger 025 positioned opposite to the electrode finger 023 and a pseudo-finger 026 positioned opposite to the electrode finger 024. The pseudo-finger 025 is connected to the bus bar 022, and the pseudo-finger 026 is connected to the bus bar 021. That is, pseudo-fingers 025 and 026 are added to the interdigital transducer 02. With this arrangement, the transverse mode can be reflected through the boundary of the abrupt change in sound velocity in the pseudo-finger region, avoiding the formation of resonance conditions and achieving better resonator performance. However, it also requires more space.

[0070] Figure 4 This shows a top view schematic diagram of another existing surface acoustic wave resonator, and... Figure 1 Compared to the surface acoustic wave resonator shown, Figure 4 In the surface acoustic wave resonator shown, reflective gratings 03 and 04 are added on both sides of the interdigital transducer 02 along the main acoustic mode propagation direction X0 to reflect sound waves, help to form better resonance in the main resonant region, and improve the transmission performance of the resonator.

[0071] Figure 5 A schematic cross-sectional view of another existing surface acoustic wave resonator is shown, and... Figure 2 Compared to the surface acoustic wave resonator shown, Figure 5 The surface acoustic wave resonator shown is a temperature-compensated surface acoustic wave resonator TC-SAW. A temperature compensation layer 05 is provided above the electrode fingers. The temperature compensation layer 05 can be a SiO2 layer. The temperature drift coefficient of the temperature compensation layer 05 is opposite to that of the piezoelectric material, which is used to overcome the temperature drift problem and improve the temperature stability of the resonator.

[0072] Figure 6 This shows a schematic cross-sectional view of another existing surface acoustic wave resonator, and... Figure 2 Compared to the surface acoustic wave resonator shown, Figure 6The surface acoustic wave resonator shown is a thin film surface acoustic wave resonator TC-SAW, wherein a piezoelectric thin film 011 is disposed on the substrate 01, and the interdigital transducer 02 is located on the side of the piezoelectric thin film 011 away from the substrate 01.

[0073] As described in the background section, for any type of surface acoustic wave resonator, transversely propagating acoustic waves will cause transverse resonant modes to appear in the resonator, i.e., clutter that appears in and near the passband. This clutter will increase device losses, cause large fluctuations in Q value, and reduce the performance of resonators and filters.

[0074] Currently, the industry generally uses the Piston structure to suppress transverse dies, specifically as follows: Figure 7 The middle electrode refers to the hammer-shaped portion 027 at the end of 021 / 022. The Piston structure is a raised metal block structure 027, which is usually attached to the end of the interdigital electrode after the interdigital electrode is fabricated using a lift-off process. That is, it and the interdigital electrode are not made of the same material, but are two independent material layers. The lift-off process involves performing a photolithography process (coating photoresist, exposure, and development) on the wafer to create an opening that exposes the end of the interdigital electrode. Then, metal is evaporated, and the photoresist and the metal attached to the photoresist are stripped, leaving the metal deposited at the end of the interdigital electrode, thus obtaining the raised metal block structure 027 at the end of the interdigital electrode.

[0075] However, the photolithography process has misalignment issues with the interdigitated electrode layer, and the window linewidths in the photolithography process itself also vary. This means that the raised metal block 027 cannot be perfectly vertically aligned with the edge of the interdigitated electrode end. For example, as shown... Figure 8 As shown, the protruding metal block 027 is closer to the inner side of the electrode fingers than the end edges of the electrode fingers 023 / 024, forming a step-like structure; for example... Figure 9 As shown, the protruding metal block 027 is closer to the outer edge of the electrode fingers 023 / 024 than the end edge of the electrode fingers, forming a structure similar to an eave or bridge. This will result in differences in the effect of suppressing clutter, affecting the filter performance and the individual consistency of the filter. Obviously, this is not conducive to improving production efficiency and will lead to a decrease in product yield.

[0076] In view of this, embodiments of this application provide a method for fabricating a surface acoustic wave (SAW) resonator, the method comprising:

[0077] S100: As Figure 10a As shown, a piezoelectric substrate 10 is provided.

[0078] Optionally, the piezoelectric substrate 10 can be made of lithium niobate or lithium tantalate.

[0079] S200: such as Figure 10b and Figure 10c As shown, a first interdigital electrode lead-out portion 20, a plurality of first interdigital electrodes 30 connected to the first interdigital electrode lead-out portion 20, a second interdigital electrode lead-out portion 40, and a plurality of second interdigital electrodes 50 connected to the second interdigital electrode lead-out portion 40 are formed on the piezoelectric substrate 10. The first interdigital electrodes 30 and the second interdigital electrodes 50 are arranged in parallel and intersecting directions. Each of the first interdigital electrodes 30 and the second interdigital electrodes 50 includes an interdigital electrode center portion A1 connected to its respective lead-out portion and an interdigital electrode end portion A2 away from its respective lead-out portion.

[0080] in, Figure 10b for Figure 10c A schematic diagram along section I-I'.

[0081] It is understandable that the first interdigital electrode lead-out portion 20 is the external electrical connection portion of the first interdigital electrode 30, and the second interdigital electrode lead-out portion 40 is the external electrical connection portion of the second interdigital electrode 50.

[0082] Optionally, a lift-off process can be used to form a first interdigital electrode lead-out portion 20, a plurality of first interdigital electrodes 30 connected to the first interdigital electrode lead-out portion 20, a second interdigital electrode lead-out portion 40, and a plurality of second interdigital electrodes 50 connected to the second interdigital electrode lead-out portion 40 on the piezoelectric substrate 10. Specifically, a photolithography process (coating photoresist, exposure, and development) is performed on the piezoelectric substrate 10 to obtain windows exposing the interdigital electrodes and interdigital electrode lead-out portions. Then, metal is evaporated, and the photoresist and the metal attached to the photoresist are stripped off, leaving the first interdigital electrode lead-out portion 20, the plurality of first interdigital electrodes 30, the second interdigital electrode lead-out portion 40, and the plurality of second interdigital electrodes 50 deposited on the piezoelectric substrate 10.

[0083] Optionally, the materials of the interdigitated electrodes and interdigitated electrode leads can be one of Ti, Cr, Ag, Cu, Mo, Pt, W, Al and AlCu, or a combination of two or more.

[0084] like Figure 10b and Figure 10c As shown, one end of the first interdigital electrode 30 is connected to the first interdigital electrode lead-out portion 20, and the edge region of the other end of the first interdigital electrode 30 is the interdigital electrode end portion A2. Similarly, one end of the second interdigital electrode 50 is connected to the second interdigital electrode lead-out portion 40, and the edge region of the other end of the second interdigital electrode 50 is the interdigital electrode end portion A2. The region between the interdigital electrode end portion A2 of the first interdigital electrode 30 and the interdigital electrode end portion A2 of the second interdigital electrode 50 corresponds to the interdigital electrode center portion A1 of the first interdigital electrode 30 and the second interdigital electrode 50.

[0085] S300: such as Figure 10d As shown, a barrier layer 60 is formed, which covers the piezoelectric substrate 10, the first interdigital electrode lead-out portion 20, the first interdigital electrode 30, the second interdigital electrode lead-out portion 40, and the second interdigital electrode 50.

[0086] Optionally, a barrier layer 60 can be formed by sputtering the entire surface, with a thickness of 10 nm.

[0087] S400: Etch the barrier layer 60, retain the interdigital electrode end portion A2 of the first interdigital electrode 30 and the second interdigital electrode 50 and the barrier layer 60 on the piezoelectric substrate 10, and remove the barrier layer 60 in other areas.

[0088] Optionally, the etching process of the barrier layer 60 in step S400 includes:

[0089] S410: As Figure 10e As shown, a first photoresist layer 61 is coated on the barrier layer 60.

[0090] S420: such as Figure 10f As shown, after the first photoresist layer 61 is exposed and developed, a first photoresist pattern 62 is formed. The first photoresist pattern 62 covers the interdigital electrode end portion A2 of the first interdigital electrode 30 and the second interdigital electrode 50 and the barrier layer 60 on the piezoelectric substrate 10, while exposing the barrier layer 60 in other areas.

[0091] Specifically, the first photoresist layer 61 is exposed using a pre-made photomask, and then developed to form the first photoresist pattern 62.

[0092] It is understood that the first photoresist layer 61 can be either a positive or negative photoresist layer, and this application does not limit this. If the first photoresist layer 61 is a positive photoresist layer, after exposure, the photoresist in the photosensitive portion of the first photoresist layer 61 will become soluble in the developer, and thus be removed during the development process, leaving the unexposed photoresist portion, forming a first photoresist pattern 62 with the same pattern as the photomask. If the first photoresist layer 61 is a negative photoresist layer, the situation is exactly the opposite of the case where the first photoresist layer 61 is a positive photoresist layer. After exposure, the unexposed photoresist in the first photoresist layer 61 will become soluble in the developer, and thus be removed during the development process, leaving the photosensitive photoresist portion, forming a first photoresist pattern 62 with the same pattern as the photomask.

[0093] S430: such as Figure 10g As shown, the first photoresist pattern 62 is used as a mask to etch the barrier layer 60, retaining the interdigital electrode end portion A2 of the first interdigital electrode 30 and the second interdigital electrode 50 as well as the barrier layer 60 on the piezoelectric substrate 10, while removing the barrier layer 60 in other areas.

[0094] Specifically, methods such as precision ion beam etching (IBE) can be used to precisely etch away the central portion A1 of the interdigital electrodes of the first interdigital electrode 30 and the second interdigital electrode 50, the first interdigital electrode lead-out portion 20, and the barrier layer on the second interdigital electrode lead-out portion 40, while retaining the end portion A2 of the interdigital electrodes of the first interdigital electrode 30 and the second interdigital electrode 50, as well as the barrier layer 60 on the piezoelectric substrate 10.

[0095] Thus, the etching of the barrier layer 60 has been completed, and the barrier layer 60 exposes the central portion of the interdigital electrodes of the first interdigital electrode 30 and the second interdigital electrode 50, the first interdigital electrode lead-out portion 20 and the second interdigital electrode lead-out portion 40, which facilitates the next step of etching the central portion of the interdigital electrodes of the first interdigital electrode 30 and the second interdigital electrode 50, the first interdigital electrode lead-out portion 20 and the second interdigital electrode lead-out portion 40 exposed in the barrier layer 60.

[0096] It should be noted that the first photoresist pattern 62 can be removed after etching the barrier layer 60. However, since the next step involves etching the central portion of the interdigitated electrodes of the first interdigitated electrode 30 and the second interdigitated electrode 50 exposed by the barrier layer 60, the first interdigitated electrode lead-out portion 20, and the second interdigitated electrode lead-out portion 40, it is better not to remove the first photoresist pattern 62 first. Instead, the remaining barrier layer 60 and the first photoresist pattern 62 should be used together to protect the interdigitated electrode end portions A2 of the first interdigitated electrode 30 and the second interdigitated electrode 50, as well as the surface of the piezoelectric substrate 10, from etching. The first photoresist pattern 62 can be removed after the etching of the central portion of the interdigitated electrodes of the first interdigitated electrode 30 and the second interdigitated electrode 50 exposed by the barrier layer 60, the first interdigitated electrode lead-out portion 20, and the second interdigitated electrode lead-out portion 40, and after the protrusion structure is formed on the interdigitated electrode end portions A2 of the first interdigitated electrode 30 and the second interdigitated electrode 50.

[0097] S500: such as Figure 10h As shown, the exposed interdigital electrode 30 and the interdigital electrode 50, the interdigital electrode center portion A1, the first interdigital electrode lead-out portion 20, and the second interdigital electrode lead-out portion 40 are etched to the remaining target thickness, such that the interdigital electrode end portion A2 of the first interdigital electrode 30 and the second interdigital electrode 50 protrudes relative to the interdigital electrode center portion A1, the first interdigital electrode lead-out portion 20, and the second interdigital electrode lead-out portion 40 to form a protrusion structure. The protrusion structure T1 is self-aligned with the interdigital electrode end portion A2 of the first interdigital electrode 30 and the second interdigital electrode 50 in both the direction perpendicular to the plane of the piezoelectric substrate 10 and the direction parallel to the plane of the piezoelectric substrate 10.

[0098] Specifically, methods such as precision ion beam etching (IBE) can be used to precisely etch away part of the thickness of the exposed interdigital electrode center portion A1, the first interdigital electrode lead-out portion 20, and the second interdigital electrode lead-out portion 40 of the first interdigital electrode 30 and the second interdigital electrode 50, so that the remaining thickness of the interdigital electrode center portion A1, the first interdigital electrode lead-out portion 20, and the second interdigital electrode lead-out portion 40 of the first interdigital electrode 30 and the second interdigital electrode 50 is uniform and meets the target thickness requirements. A protrusion structure T1 is formed at the interdigital electrode end portion A2 of the first interdigital electrode 30 and the second interdigital electrode 50 to suppress transverse mode.

[0099] It is understandable that by etching to thin the thickness of the interdigital electrode center portion A1, the first interdigital electrode lead-out portion 20, and the second interdigital electrode lead-out portion 40 of the first interdigital electrode 30 and the second interdigital electrode 50, the interdigital electrode end portion A2 of the first interdigital electrode 30 and the second interdigital electrode 50 protrudes relative to the interdigital electrode center portion A1, the first interdigital electrode lead-out portion 20, and the second interdigital electrode lead-out portion 40, forming a protruding structure T1. Thus, the protruding structure T1 and the interdigital electrode... The electrodes (first interdigital electrode 30 or second interdigital electrode 50) are integrally formed structures with no separating interface between them. Therefore, the protrusion T1 is self-aligned with the interdigital electrode ends A2 of the first interdigital electrode 30 and the second interdigital electrode 50 in both the direction perpendicular to the plane of the piezoelectric substrate 10 (i.e., vertical direction) and the direction parallel to the plane of the piezoelectric substrate 10 (i.e., horizontal direction), and its position is fixed. This ensures consistency among multiple resonators / filters, helping to improve production efficiency and product yield.

[0100] Furthermore, during the etching process of the interdigital electrode center portion A1, the first interdigital electrode lead-out portion 20, and the second interdigital electrode lead-out portion 40 of the first interdigital electrode 30 and the second interdigital electrode 50, the interdigital electrode end portions of the first interdigital electrode 30 and the second interdigital electrode 50, as well as the surface of the piezoelectric substrate 10, are always protected by the barrier layer 60 and the first photoresist pattern, and are not damaged during etching.

[0101] like Figure 10i As shown, after the protrusion structure T1 is formed at the end portion A2 of the first interdigital electrode 30 and the second interdigital electrode 50, the first photoresist pattern 62 is removed.

[0102] It is important to emphasize that this application employs a "subtractive" process, which involves first depositing a metal layer of sufficient thickness, and then etching away the unwanted portions of the metal layer to integrally form the interdigital electrode and the protrusion structure located at the end of the interdigital electrode. This requires precise control over the etching process; otherwise, the metal layer thickness may be insufficient, affecting the performance of the interdigital electrode. When the thickness of the central portion A1 of the first interdigital electrode 30 and the second interdigital electrode 50, the first interdigital electrode lead-out portion 20, and the second interdigital electrode lead-out portion 40 exposed by the barrier layer 60 is reduced by etching, the barrier layer 60 precisely blocks the etching of the interdigital electrode end portion A2 of the first interdigital electrode 30 and the second interdigital electrode 50, as well as the surface of the piezoelectric substrate 10, thereby precisely controlling the etching process and ensuring the performance of the interdigital electrode.

[0103] S600: Remove the barrier layer 60 on the piezoelectric substrate 10, and retain the barrier layer 60 on the protrusion structure T1.

[0104] Optionally, the process of removing the barrier layer 60 on the piezoelectric substrate 10 in step S600 includes:

[0105] S610: As Figure 10j As shown, a second photoresist layer 63 is coated, which covers the barrier layer 60, the first interdigital electrode lead-out portion 20, the first interdigital electrode 30, the second interdigital electrode lead-out portion 40, and the second interdigital electrode 50.

[0106] S620: such as Figure 10k As shown, after the second photoresist layer 63 is exposed and developed, a second photoresist pattern 64 is formed, and the second photoresist pattern 64 exposes the barrier layer 60 on the piezoelectric substrate 10.

[0107] Specifically, the second photoresist layer 63 is exposed using a pre-made photomask, and then developed to form the second photoresist pattern 64.

[0108] It is understood that the second photoresist layer 63 can be either a positive or negative photoresist layer, and this application does not limit this. Whether the second photoresist layer 63 is a positive or negative photoresist layer is similar to that of the first photoresist layer 61, and will not be described in detail here.

[0109] It should be noted that the second photoresist pattern 64 completely covers the first interdigital electrode lead-out portion 20, the first interdigital electrode 30, the second interdigital electrode lead-out portion 40, and the second interdigital electrode 50, and covers the barrier layer 60 on the protrusion structure T1, exposing only the barrier layer 60 on the piezoelectric substrate 10.

[0110] S630: such as Figure 10lAs shown, the second photoresist pattern 64 is used as a mask to etch the barrier layer 60, removing the barrier layer 60 on the piezoelectric substrate 10 and retaining the barrier layer on the protrusion structure T1.

[0111] Specifically, the barrier layer 60 on the piezoelectric substrate 10 can be precisely etched away using methods such as precise ion beam etching (IBE), while retaining the barrier layer on the protrusion structure T1.

[0112] S640: such as Figure 11 As shown, the second photoresist pattern 64 is removed.

[0113] Thus, we have obtained Figure 11 The surface acoustic wave resonator structure shown is as follows. Figure 12 It shows Figure 11 The diagram shows a top view of a surface acoustic wave resonator.

[0114] As can be seen, after completing the interdigitated electrode and the protrusion structure located at the end of the interdigitated electrode, this application does not remove the barrier layer 60 on the protrusion structure T1, but retains the barrier layer 60 on the protrusion structure T1, so as to continue to use the barrier layer 60 to protect the protrusion structure T1 and prevent the metal (such as aluminum, copper, etc.) of the protrusion structure T1 from diffusing to other film layers, which would cause the protrusion structure T1 to deform or change its physicochemical properties and thus affect the performance of the interdigitated electrode.

[0115] As described above, the barrier layer 60 serves not only as an etching barrier layer but also as a diffusion barrier layer. Optionally, the material of the barrier layer 60 may include one or more of silicon nitride, aluminum oxide, tantalum oxide, thallium nitride, and chromium oxide. Any material that can serve as both an etching barrier and a diffusion barrier can constitute the barrier layer 60.

[0116] It should be noted that, as Figure 12 As shown, the portion of the first interdigital electrode 30 corresponding to the interdigital electrode end A2 of the second interdigital electrode 50 also has a protruding structure T1, and the portion of the second interdigital electrode 50 corresponding to the interdigital electrode end A2 of the first interdigital electrode 30 also has a protruding structure T1. This is for matching structure to achieve better resonator performance. Of course, the portion of the first interdigital electrode 30 corresponding to the interdigital electrode end A2 of the second interdigital electrode 50 may not have the protruding structure T1, and the portion of the second interdigital electrode 50 corresponding to the interdigital electrode end A2 of the first interdigital electrode 30 may not have the protruding structure T1.

[0117] Figure 13 Further shown Figure 11The enlarged cross-sectional view of the protruding structure A2 at the end of the first interdigital electrode 30 or the second interdigital electrode 50 on the piezoelectric substrate 10 in the surface acoustic wave resonator shown illustrates that the angle between the sidewall of the protruding structure T1 and the direction perpendicular to the plane of the piezoelectric substrate 10 is the notch side angle θp. Due to the actual IBE etching process, the notch side angle θp cannot be 0°, meaning the sidewall of the protruding structure T1 cannot be parallel to the direction perpendicular to the plane of the piezoelectric substrate 10, and therefore cannot be ideally perpendicular to the plane of the piezoelectric substrate 10. However, the notch side angle θp satisfies: 5°≤θp≤10°, which is a small angle, and can be approximated as the sidewall of the protruding structure T1 being perpendicular to the plane of the piezoelectric substrate 10.

[0118] from Figure 13 It can also be seen that the angle between the sidewall of the interdigital electrode end portion A2 of the first interdigital electrode 30 or the second interdigital electrode 50 and the direction perpendicular to the plane of the piezoelectric substrate 10 is θt. Due to the actual process of forming interdigital electrodes by evaporation and deposition, θt is not 90°, but usually around 75°.

[0119] Optionally, the surface acoustic wave resonator prepared by the method provided in this application embodiment can be a temperature-compensated surface acoustic wave resonator (TC-SAW). Therefore, the preparation method of the surface acoustic wave resonator provided in this application embodiment may further include:

[0120] S700: such as Figure 14a As shown, a temperature compensation layer 70 is formed, which covers the piezoelectric substrate 10, the first interdigital electrode lead-out portion 20, the first interdigital electrode 30, the second interdigital electrode lead-out portion 40, and the second interdigital electrode 50. Furthermore... Figure 14b As shown, the temperature compensation layer 70 is etched to form a first through hole K1 and a second through hole K2. The first through hole K1 exposes the first interdigital electrode lead-out portion 20, and the second through hole K2 exposes the second interdigital electrode lead-out portion 40.

[0121] Specifically, a temperature compensation layer 70 is deposited and planarized using CMP, such that the temperature compensation layer 70 covers the piezoelectric substrate 10, the first interdigital electrode lead-out portion 20, the first interdigital electrode 30, the second interdigital electrode lead-out portion 40, and the second interdigital electrode 50.

[0122] Optionally, the temperature compensation layer 70 may include a single layer of SiO2, or the temperature compensation layer 70 may include a SiN layer, an AlN layer, an amorphous silicon layer, a GaN layer, and a SiO2 layer stacked along the direction away from the piezoelectric substrate 10. The thin films of materials such as the SiN layer, AlN layer, amorphous silicon layer, and GaN layer can serve as protective layers for the exposed interdigital electrodes and their leads, preventing oxidation of the interdigital electrodes and their leads during the deposition of the SiO2 layer.

[0123] S800: such as Figure 14c As shown, a first PAD metal layer M1 and a second PAD metal layer M2 are formed. The first PAD metal layer M1 is connected to the first interdigital electrode lead-out portion 20 through the first through hole K1, and the second PAD metal layer M2 is connected to the second interdigital electrode lead-out portion 40 through the second through hole K2.

[0124] Optionally, a lift-off process can be used to form the first PAD metal layer M1 and the second PAD metal layer M2.

[0125] Optionally, the materials of the first PAD metal layer M1 and the second PAD metal layer M2 can be Ti, Cr, Al, Cu, Ni, Ag and Au, or a combination of two or more of these materials.

[0126] S900: such as Figure 14d As shown, a passivation layer 80 is formed, which covers the temperature compensation layer 70, the first PAD metal layer M1, and the second PAD metal layer M2. (Further details omitted) Figure 15 As shown, the passivation layer 80 is etched to form a first contact window Y1 that exposes the first PAD metal layer M1 and a second contact window Y2 that exposes the second PAD metal layer M2.

[0127] It is understandable that the passivation layer 80 serves two purposes: first, to protect the first PAD metal layer M1 and the second PAD metal layer M2; and second, to act as a frequency adjustment layer for the resonator / filter.

[0128] Optionally, the passivation layer 80 can be made of insulating materials such as SiN, AlN, amorphous silicon, and GaN, or a combination of two or more of these materials.

[0129] It is also understandable that the first contact window Y1 and the second contact window Y2 are external electrical connection contact windows.

[0130] Thus, the temperature-compensated surface acoustic wave resonator TC-SAW was formed.

[0131] Accordingly, this application also provides a surface acoustic wave resonator, which is prepared by the method provided in any of the above embodiments, such as... Figure 11 and Figure 12 As shown, the surface acoustic wave resonator includes:

[0132] Piezoelectric substrate 10;

[0133] The piezoelectric substrate 10 includes a first interdigital electrode lead-out portion 20, a plurality of first interdigital electrodes 30 connected to the first interdigital electrode lead-out portion 20, a second interdigital electrode lead-out portion 40, and a plurality of second interdigital electrodes 50 connected to the second interdigital electrode lead-out portion. The first interdigital electrodes 30 and the second interdigital electrodes 50 are arranged in parallel and intersecting directions. Each of the first interdigital electrodes 30 and the second interdigital electrodes 50 includes a central portion A1 of the interdigital electrode connected to its respective lead-out portion and a terminal portion A2 of the interdigital electrode away from its respective lead-out portion.

[0134] The interdigitated center portion A1, the first interdigitated electrode lead-out portion 20, and the second interdigitated electrode lead-out portion 40 of the first interdigitated electrode 30 and the second interdigitated electrode 50 are of target thickness. The interdigitated end portion A2 of the first interdigitated electrode 30 and the second interdigitated electrode 50 protrudes relative to the interdigitated center portion A1, the first interdigitated electrode lead-out portion 20, and the second interdigitated electrode lead-out portion 40, forming a protrusion structure T1. The protrusion structure T1 is self-aligned with the interdigitated end portion A2 of the first interdigitated electrode 30 and the second interdigitated electrode 50 in both the direction perpendicular to the plane of the piezoelectric substrate 10 and the direction parallel to the plane of the piezoelectric substrate 10.

[0135] The raised structure T1 has a barrier layer 60.

[0136] In fabricating the surface acoustic wave resonator provided in this embodiment, the thickness of the interdigital electrode center portion A1, the first interdigital electrode lead-out portion 20, and the second interdigital electrode lead-out portion 40 of the first interdigital electrode 30 and the second interdigital electrode 50 is reduced by etching, so that the interdigital electrode end portion A2 of the first interdigital electrode 30 and the second interdigital electrode 50 protrudes relative to the interdigital electrode center portion A1, the first interdigital electrode lead-out portion 20, and the second interdigital electrode lead-out portion 40, forming a protrusion structure T1. Thus, the protrusion... Structure T1 and the interdigitated electrodes (first interdigitated electrode 30 or second interdigitated electrode 50) are integrally formed without a separating interface. Therefore, the protruding structure T1 is self-aligned with the interdigitated electrode ends A2 of the first interdigitated electrode 30 and the second interdigitated electrode 50 in both the direction perpendicular to the plane of the piezoelectric substrate 10 (i.e., vertical direction) and the direction parallel to the plane of the piezoelectric substrate 10 (i.e., horizontal direction), and its position is fixed. This ensures consistency among multiple resonators / filters, helping to improve production efficiency and product yield.

[0137] Furthermore, during the etching process of the interdigital electrode center portion A1, the first interdigital electrode lead-out portion 20, and the second interdigital electrode lead-out portion 40 of the first interdigital electrode 30 and the second interdigital electrode 50, the interdigital electrode end portions of the first interdigital electrode 30 and the second interdigital electrode 50, as well as the surface of the piezoelectric substrate 10, are always protected by the barrier layer 60 and the first photoresist pattern, and are not damaged during etching.

[0138] Further optionally, the surface acoustic wave resonator provided in the embodiments of this application can be a temperature-compensated surface acoustic wave resonator (TC-SAW). Therefore, as... Figure 15 As shown, the surface acoustic wave resonator provided in this application embodiment may further include:

[0139] A temperature compensation layer 70 covers a piezoelectric substrate 10, a first interdigital electrode lead-out portion 20, a first interdigital electrode 30, a second interdigital electrode lead-out portion 40, and a second interdigital electrode 50. The temperature compensation layer 70 has a first through-hole K1 and a second through-hole K2. The first through-hole K1 exposes the first interdigital electrode lead-out portion 20, and the second through-hole K2 exposes the second interdigital electrode lead-out portion 40.

[0140] The first PAD metal layer M1 and the second PAD metal layer M2 are connected to the first interdigital electrode lead-out portion 20 through the first through hole K1, and the second PAD metal layer M2 is connected to the second interdigital electrode lead-out portion 40 through the second through hole K2.

[0141] Passivation layer 80 covers temperature compensation layer 70, first PAD metal layer M1 and second PAD metal layer M2, and passivation layer 80 has a first contact window Y1 exposing the first PAD metal layer M1 and a second contact window Y2 exposing the second PAD metal layer M2.

[0142] This application also provides a filter, including the above-described surface acoustic wave resonator.

[0143] This application also provides an electronic device, including the above-described surface acoustic wave resonator and / or the above-described filter.

[0144] Since the surface acoustic wave resonator prepared by the method provided in this application has been described in detail in the foregoing embodiments, it will not be repeated here.

[0145] The various parts of this manual are described in a combination of parallel and progressive methods. Each part focuses on the differences between the other parts, and the same or similar parts can be referred to each other.

[0146] The features described above regarding the disclosed embodiments can be substituted or combined with each other to enable those skilled in the art to implement or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for fabricating a surface acoustic wave resonator, characterized in that, include: Provide piezoelectric substrates; A first interdigital electrode lead-out portion, a plurality of first interdigital electrodes connected to the first interdigital electrode lead-out portion, a second interdigital electrode lead-out portion, and a plurality of second interdigital electrodes connected to the second interdigital electrode lead-out portion are formed on the piezoelectric substrate. The first interdigital electrodes and the second interdigital electrodes are arranged in parallel and intersecting directions. Each of the first interdigital electrodes and the second interdigital electrodes includes a central portion of the interdigital electrode connected to its respective lead-out portion and a terminal portion of the interdigital electrode away from its respective lead-out portion. A barrier layer is formed, which covers the piezoelectric substrate, the first interdigital electrode lead-out portion, the first interdigital electrode, the second interdigital electrode lead-out portion, and the second interdigital electrode; The barrier layer is etched to retain the interdigitated electrode ends of the first interdigitated electrode and the second interdigitated electrode, as well as the barrier layer on the piezoelectric substrate, while removing the barrier layer in other areas. The exposed central portions of the first and second interdigital electrodes, the lead-out portions of the first and second interdigital electrodes, and the lead-out portions of the second interdigital electrodes are etched to the remaining target thickness, such that the terminal portions of the first and second interdigital electrodes protrude relative to the central portions of the first and second interdigital electrodes and the lead-out portions of the first and second interdigital electrodes to form a protruding structure. The protruding structure is self-aligned with the terminal portions of the first and second interdigital electrodes in both the direction perpendicular to the plane of the piezoelectric substrate and the direction parallel to the plane of the piezoelectric substrate. Remove the barrier layer on the piezoelectric substrate, and retain the barrier layer on the protrusion structure.

2. The method for fabricating a surface acoustic wave resonator according to claim 1, characterized in that, The method for fabricating the surface acoustic wave resonator further includes: A temperature compensation layer is formed, which covers the piezoelectric substrate, the first interdigital electrode lead-out portion, the first interdigital electrode, the second interdigital electrode lead-out portion, and the second interdigital electrode. The temperature compensation layer is etched to form a first through-hole and a second through-hole. The first through-hole exposes the first interdigital electrode lead-out portion, and the second through-hole exposes the second interdigital electrode lead-out portion. A first PAD metal layer and a second PAD metal layer are formed. The first PAD metal layer is in contact with the first interdigital electrode lead-out portion through the first through hole, and the second PAD metal layer is in contact with the second interdigital electrode lead-out portion through the second through hole. A passivation layer is formed, which covers the temperature compensation layer, the first PAD metal layer, and the second PAD metal layer. The passivation layer is then etched to form a first contact window exposing the first PAD metal layer and a second contact window exposing the second PAD metal layer.

3. The method for fabricating a surface acoustic wave resonator according to claim 1 or 2, characterized in that, The barrier layer is made of one or more of silicon nitride, aluminum oxide, tantalum oxide, thallium nitride, and chromium oxide.

4. The method for fabricating a surface acoustic wave resonator according to claim 1 or 2, characterized in that, The process of etching the barrier layer includes: A first photoresist layer is coated on the barrier layer; After the first photoresist layer is exposed and developed, a first photoresist pattern is formed. The first photoresist pattern covers the end portions of the first interdigitated electrode and the second interdigitated electrode, as well as the barrier layer on the piezoelectric substrate, while exposing the barrier layer in other areas. Using the first photoresist pattern as a mask, the barrier layer is etched, retaining the interdigitated electrode ends of the first interdigitated electrode and the second interdigitated electrode, as well as the barrier layer on the piezoelectric substrate, while removing the barrier layer in other areas. The first photoresist pattern can be removed, or the first photoresist pattern can be removed after etching the exposed central portion of the first interdigital electrode and the second interdigital electrode, the lead-out portion of the first interdigital electrode and the lead-out portion of the second interdigital electrode to the remaining target thickness, and forming the protrusion structure at the end portion of the first interdigital electrode and the second interdigital electrode.

5. The method for fabricating a surface acoustic wave resonator according to claim 1 or 2, characterized in that, The process of removing the barrier layer on the piezoelectric substrate includes: A second photoresist layer is applied, which covers the barrier layer, the first interdigital electrode lead-out portion, the first interdigital electrode, the second interdigital electrode lead-out portion, and the second interdigital electrode. After the second photoresist layer is exposed and developed, a second photoresist pattern is formed, and the second photoresist pattern exposes the barrier layer on the piezoelectric substrate; Using the second photoresist pattern as a mask, the barrier layer is etched to remove the barrier layer on the piezoelectric substrate, while retaining the barrier layer on the protrusion structure. Remove the second photoresist layer.

6. The method for fabricating a surface acoustic wave resonator according to claim 2, characterized in that, The temperature compensation layer includes a single SiO2 layer, or includes a SiN layer, an AlN layer, an amorphous silicon layer, a GaN layer, and a SiO2 layer stacked in a direction away from the piezoelectric substrate.

7. A surface acoustic wave resonator, characterized in that, The surface acoustic wave resonator is prepared by the method according to any one of claims 1-6; the surface acoustic wave resonator comprises: piezoelectric substrate; The piezoelectric substrate includes a first interdigital electrode lead-out portion, a plurality of first interdigital electrodes connected to the first interdigital electrode lead-out portion, a second interdigital electrode lead-out portion, and a plurality of second interdigital electrodes connected to the second interdigital electrode lead-out portion. The first interdigital electrodes and the second interdigital electrodes are arranged in parallel and intersecting directions. Each of the first interdigital electrodes and the second interdigital electrodes includes a central portion of the interdigital electrode connected to its respective lead-out portion and a terminal portion of the interdigital electrode away from its respective lead-out portion. The center portion of the first interdigital electrode and the center portion of the second interdigital electrode, the lead-out portion of the first interdigital electrode, and the lead-out portion of the second interdigital electrode have a target thickness. The end portion of the first interdigital electrode and the second interdigital electrode protrudes relative to the center portion of the first interdigital electrode and the lead-out portion of the first interdigital electrode and the lead-out portion of the second interdigital electrode, forming a protruding structure. The protruding structure is self-aligned with the end portion of the first interdigital electrode and the second interdigital electrode in both the direction perpendicular to the plane of the piezoelectric substrate and the direction parallel to the plane of the piezoelectric substrate. The protruding structure has a barrier layer.

8. The surface acoustic wave resonator according to claim 7, characterized in that, The surface acoustic wave resonator also includes: A temperature compensation layer covers the piezoelectric substrate, the first interdigital electrode lead-out portion, the first interdigital electrode, the second interdigital electrode lead-out portion, and the second interdigital electrode. The temperature compensation layer has a first through-hole and a second through-hole, the first through-hole exposing the first interdigital electrode lead-out portion and the second through-hole exposing the second interdigital electrode lead-out portion. A first PAD metal layer and a second PAD metal layer, wherein the first PAD metal layer is in contact with the first interdigital electrode lead-out portion through the first through hole, and the second PAD metal layer is in contact with the second interdigital electrode lead-out portion through the second through hole; A passivation layer covering the temperature compensation layer, the first PAD metal layer, and the second PAD metal layer, the passivation layer having a first contact window exposing the first PAD metal layer and a second contact window exposing the second PAD metal layer.

9. The surface acoustic wave resonator according to claim 7 or 8, characterized in that, The angle θp between the sidewall of the protrusion structure and the direction perpendicular to the plane of the piezoelectric substrate satisfies: 5°≤θp≤10°.

10. A filter, characterized in that, Includes the surface acoustic wave resonator according to any one of claims 7-9.

11. An electronic device, characterized in that, Includes the surface acoustic wave resonator according to any one of claims 7-9, or the filter according to claim 10.

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