Filter, forming method thereof and electronic equipment

Abstract

The invention discloses a filter, a forming method thereof and electronic equipment. The forming method comprises the following steps: forming a convex initial piston structure on a first interdigital electrode material layer in an edge region; forming a second interdigital electrode material layer covering the first interdigital electrode material layer and the initial piston structure in a shape-preserving manner; a preset pattern corresponding to the interdigital electrode is transferred to the initial piston structure, the first interdigital electrode material layer and the second interdigital electrode material layer, and bus bars located in a bus region and electrode fingers located in a central region and an edge region are formed through the first interdigital electrode material layer and the second interdigital electrode material layer; a piston structure located on the electrode fingers in the edge area is formed; the initial piston structure is located on the first interdigital electrode material layer, the first interdigital electrode material layer is directly formed on the substrate, the piston structure is closer to the substrate, sound wave interaction between the piston structure and the surface of the substrate is facilitated, transverse propagation sound waves in the filter are further inhibited, and then the electromechanical coupling coefficient of the filter is improved.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the field of semiconductor manufacturing, and in particular to a filter and a forming method thereof, and an electronic device. BACKGROUND

[0002] A radio frequency (RF) front-end chip of a wireless communication device includes a power amplifier, an antenna switch, a radio frequency filter, a multiplexer, and a low noise amplifier, etc. Among them, the radio frequency filter includes a surface acoustic wave (SAW) filter, a bulk acoustic wave (BAW) filter, a micro-electro-mechanical system (MEMS) filter, an integrated passive device (IPD) filter, etc.

[0003] The SAW filter has a high quality factor value (Q value), and a radio frequency filter with low insertion loss and high out-of-band rejection is made from the SAW filter. As a widely used filter in current wireless communication devices, a SAW filter with high reliability can prolong the service life of electronic devices and expand the use range.

[0004] At present, there are still many problems in the performance of the SAW filter. SUMMARY

[0005] The problem solved by embodiments of the present application is to provide a filter and a forming method thereof, and an electronic device, which is conducive to improving the electromechanical coupling coefficient of the filter.

[0006] To solve the above problems, the embodiment of the present application provides a filter forming method, comprising: providing a substrate, the substrate comprising a center area, a convergence area and an edge area between the center area and the convergence area, the center area, the edge area and the convergence area being arranged along a first direction; forming a first interdigital electrode material layer on the substrate in the center area, the edge area and the convergence area; forming a protruding initial piston structure on the first interdigital electrode material layer in the edge area; forming a second interdigital electrode material layer conformally covering the first interdigital electrode material layer and the initial piston structure; transferring a predetermined pattern corresponding to the interdigital electrode to the initial piston structure, the first interdigital electrode material layer and the second interdigital electrode material layer, forming a bus bar in the convergence area through the first interdigital electrode material layer and the second interdigital electrode material layer, and forming an electrode finger in the center area and the edge area and a piston structure on the electrode finger in the edge area, the bus bar, the piston structure and the electrode finger constituting an interdigital electrode, the electrode finger extending along the first direction and being arranged in intervals along a second direction, the bus bar extending along the second direction and connecting each of the electrode fingers, and the first direction intersecting the second direction.

[0007] Correspondingly, the embodiment of the present application provides a filter, comprising: a substrate, the substrate comprising a center area, a convergence area and an edge area between the center area and the convergence area, the center area, the convergence area and the edge area being arranged along a first direction; an interdigital electrode, located on the substrate in the center area, the convergence area and the edge area, the interdigital electrode comprising a bus bar in the convergence area, a plurality of electrode fingers in the edge area and the center area, and a piston structure on the electrode finger in the edge area, the bus bar extending along a second direction and connecting each of the electrode fingers, the electrode finger extending along the first direction and being arranged in intervals along the second direction, and the first direction intersecting the second direction; wherein the interdigital electrode further comprises a first interdigital electrode layer and a second interdigital electrode layer located on the first interdigital electrode layer; and the piston structure is located on the first interdigital electrode layer and in contact with the top surface of the first interdigital electrode layer.

[0008] Correspondingly, the present application further provides an electronic device comprising the filter according to any one of the embodiments of the present application.

[0009] Compared with the prior art, the technical scheme of the embodiment of the present application has the following advantages: This invention provides a method for forming a filter. A first interdigitated electrode material layer is formed on a substrate comprising a central region, an edge region, and a busbar region. A protruding initial piston structure is formed on the first interdigitated electrode material layer in the edge region. A second interdigitated electrode material layer is formed, conformally covering the first interdigitated electrode material layer and the initial piston structure. A predetermined pattern corresponding to the interdigitated electrode is transferred to the initial piston structure, the first interdigitated electrode material layer, and the second interdigitated electrode material layer. A busbar located in the busbar region and electrode fingers located in the central region and the edge region are formed through the first interdigitated electrode material layer and the second interdigitated electrode material layer. A piston structure is formed on the electrode fingers in the edge region. The busbar, piston structure, and electrode fingers constitute interdigitated electrodes. In this embodiment, since the initial piston structure is located on the first interdigitated electrode material layer, and the first interdigitated electrode material layer is directly formed on the substrate, i.e., the piston structure is closer to the substrate, which is beneficial for the interaction of the piston structure with the acoustic waves on the substrate surface. This helps the piston structure further suppress the transversely propagating acoustic waves in the filter, thereby improving the electromechanical coupling coefficient of the filter.

[0010] This invention also provides a filter with interdigitated electrodes located on a substrate in the central region, the bus region, and the edge region. The interdigitated electrodes include a busbar located in the bus region, multiple electrode fingers located in the edge region and the central region, and a piston structure on the electrode fingers in the edge region. The busbar extends along a second direction and connects each of the electrode fingers. The electrode fingers extend along a first direction and are spaced apart along the second direction, the first direction intersecting the second direction. The interdigitated electrodes also include a first interdigitated electrode layer and a second interdigitated electrode layer located on the first interdigitated electrode layer. The piston structure is located on the first interdigitated electrode layer and contacts the top surface of the first interdigitated electrode layer. In this embodiment, because the piston structure is located on the first interdigitated electrode layer and contacts the top surface of the first interdigitated electrode layer, and the first interdigitated electrode layer is directly formed on the substrate, i.e., the piston structure is closer to the substrate, which is beneficial for the interaction of acoustic waves between the piston structure and the substrate surface. This helps the piston structure further suppress transversely propagating acoustic waves in the filter, thereby improving the electromechanical coupling coefficient of the filter. Attached Figure Description

[0011] Figures 1 to 15 This is a schematic diagram of the structure corresponding to each step in one embodiment of the filter formation method of the present invention; Figures 16 to 18 This is a schematic diagram of the structure of an embodiment of the filter of the present invention. Detailed Implementation

[0012] As can be seen from the background technology, the performance of SAW filters still needs to be improved.

[0013] There are generally two methods to suppress transversely propagating sound waves in a SAW filter. One method is to thicken the ends of the interdigital electrodes of the SAW filter to form a piston structure; the other method is to thicken the ends of the interdigital electrodes to form a hammerhead structure. Both methods increase the mass of the ends of the interdigital electrodes, thereby reducing the propagation speed of transversely propagating sound waves in that region, thus suppressing transversely propagating sound waves in the SAW filter and improving the filter's performance accordingly.

[0014] Research has shown that the piston structure is generally located at the very top of the interdigitated electrode, meaning that the piston structure is far from the piezoelectric substrate. This makes it easier to affect the interaction between the piston structure and the substrate surface, thereby affecting the piston structure's ability to suppress transversely propagating sound waves in the filter, and consequently affecting the electromechanical coupling coefficient of the filter.

[0015] To address the aforementioned technical problems, embodiments of the present invention provide a method for forming a filter, comprising: providing a substrate, the substrate including a central region, a bus region, and an edge region located between the central region and the bus region, the central region, the edge region, and the bus region being arranged along a first direction; forming a first interdigitated electrode material layer on the substrate of the central region, the edge region, and the bus region; forming a protruding initial piston structure on the first interdigitated electrode material layer in the edge region; forming a second interdigitated electrode material layer conformally covering the first interdigitated electrode material layer and the initial piston structure; transferring a predetermined pattern corresponding to the interdigitated electrode to the initial piston structure, the first interdigitated electrode material layer, and the second interdigitated electrode material layer; forming a bus bar located in the bus region and electrode fingers located in the central region and the edge region through the first interdigitated electrode material layer and the second interdigitated electrode material layer; and forming a piston structure on the electrode fingers located in the edge region, the bus bar, the piston structure, and the electrode fingers constituting interdigitated electrodes; the electrode fingers extending along the first direction and spaced apart along a second direction; the bus bar extending along the second direction and connecting each of the electrode fingers; the first direction intersecting the second direction.

[0016] In the scheme disclosed in the embodiments of the present invention, since the initial piston structure is located on the first interdigital electrode material layer and the first interdigital electrode material layer is directly formed on the substrate, that is, the piston structure is closer to the substrate, which is beneficial to the interaction of the piston structure with the acoustic waves on the substrate surface. This is beneficial to the piston structure further suppressing the transversely propagating acoustic waves in the filter, thereby improving the electromechanical coupling coefficient of the filter.

[0017] To make the above-mentioned objects, features and advantages of the embodiments of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0018] Figures 1 to 15 This is a schematic diagram of the structure corresponding to each step in one embodiment of the filter formation method of the present invention; specifically, Figure 1 It provides a top view of the base. Figure 2 This is a top view of the formation of the initial first interdigitated electrode material layer. Figure 3 yes Figure 2 A cross-sectional view along the AA1 direction. Figure 4 This is a top view of the patterned second mask layer formed on the initial first interdigitated electrode material layer. Figure 5 yes Figure 4 A cross-sectional view along the AA1 direction. Figure 6 This is a top view showing the initial piston structure forming a convex shape. Figure 7 yes Figure 6 Top view along the AA1 direction, Figure 8 This is a top view of the second interdigital electrode material layer that conformally covers the first interdigital electrode material layer and the initial piston structure. Figure 9 yes Figure 8 A cross-sectional view along the AA1 direction. Figure 10 This is a top view of a first mask layer with a predetermined pattern formed on the second interdigitated electrode material layer. Figure 11 yes Figure 10 A cross-sectional view along the AA1 direction. Figure 12 This is a top view of the busbar, electrode fingers, and piston structure. Figure 13 yes Figure 12 A cross-sectional view along the AA1 direction. Figure 14 yes Figure 12 A cross-sectional view along the BB1 ​​direction. Figure 15 It is a top view showing the initial piston structure arranged at intervals along the second direction in the edge region, and corresponding one-to-one with the formation position of the electrode fingers in the second direction.

[0019] refer to Figure 1 A substrate 100 is provided, the substrate including a central region I, a confluence region II and an edge region III located between the central region I and the confluence region II, the central region I, the edge region III and the confluence region II being arranged along a first direction X.

[0020] Substrate 100 provides a fabrication platform for subsequent fabrication of surface acoustic wave (SAW) filters. SAW filters are specialized filtering devices made using the piezoelectric effect and the physical characteristics of surface acoustic wave propagation. In a SAW filter, the signal undergoes two electro-acoustic-electro-electric conversions, thus achieving frequency selectivity. SAW filters offer advantages such as high operating frequency, simple manufacturing process, low manufacturing cost, and high frequency response consistency, and are therefore widely used in various electronic devices.

[0021] In this embodiment, the substrate 100 is a piezoelectric substrate, so that the subsequent surface acoustic wave filter structure can utilize the piezoelectric effect for filtering.

[0022] The substrate 100 may be made of lithium niobate (LiNbO3), lithium tantalate (LiTaO3), quartz, or piezoelectric ceramic. As an example, the substrate 100 may be made of lithium niobate. In other embodiments, the substrate may also be a piezoelectric on insulator (POI).

[0023] The busbar region II provides space for the subsequent formation of the busbar strip, the edge region III provides space for the subsequent formation of the piston structure and electrode fingers, and the center region I provides space for the subsequent formation of the electrode fingers.

[0024] refer to Figures 2 to 7 A first interdigitated electrode material layer 101 is formed on the substrate 100 of the central region I, edge region III, and busbar region II (e.g., Figures 6 to 7 (As shown).

[0025] The first interdigital electrode material layer 101 is used to form the busbar and electrode fingers in the interdigital electrode.

[0026] In the step of forming the first interdigitated electrode material layer 101 on the substrate 100 of the central region I, edge region III and busbar region II, the first interdigitated electrode material layer 101 is a stacked structure or a single-layer structure.

[0027] In this embodiment, the first interdigital electrode material layer 101 is a stacked structure.

[0028] refer to Figure 7 As an example, when the first interdigital electrode material layer 101 is a stacked structure, the topmost first interdigital electrode material layer 101 serves as the first sub-interdigital electrode material layer 102, and the first interdigital electrode material layer 101 located between the first sub-interdigital electrode material layer 102 and the substrate 100 serves as the second sub-interdigital electrode material layer 103. The mass of the first sub-interdigital electrode material layer 102 is greater than that of the second sub-interdigital electrode material layer 103, and the adhesion of the second sub-interdigital electrode material layer 103 to the substrate 100 is greater than that of the first sub-interdigital electrode material layer 102 to the substrate 100.

[0029] Specifically, the second sub-interdigital electrode material layer 103 is used to improve the adhesion between the first sub-interdigital electrode material layer 102 and the substrate 100, and the first sub-interdigital electrode material layer 101 is used to increase the quality of the filter.

[0030] In other embodiments, the first sub-interdigital electrode material layer may be a single-layer structure, or the number of layers of the first sub-interdigital electrode material layer may be greater than three.

[0031] The material of the second interdigital electrode material layer 103 includes titanium, chromium, titanium nitride, aluminum nitride, or titanium tungsten.

[0032] It should be noted that titanium, chromium, titanium nitride, aluminum nitride, or titanium tungsten have good adhesion; therefore, titanium, chromium, titanium nitride, aluminum nitride, or titanium tungsten can improve the adhesion between the substrate 100 and the first sub-interdigital electrode material layer 102. As an example, the material of the second sub-interdigital electrode material layer 103 is titanium.

[0033] The first interdigitated electrode material layer 102 includes tungsten or molybdenum.

[0034] It should be noted that tungsten or molybdenum have a large mass; therefore, tungsten or molybdenum can reduce the propagation speed of transversely propagating sound waves in the filter, thereby reducing the characteristic dimension (CD) value of the interdigital electrodes. As an example, the material of the first sub-interdigital electrode material layer 102 is tungsten.

[0035] In other embodiments, when the first interdigital electrode material layer is a single-layer structure, the material of the first interdigital electrode material layer is tungsten or molybdenum.

[0036] Continue to refer to Figures 2 to 7 An initial piston structure 104 is formed on the first interdigital electrode material layer 101 in the edge region III (e.g., Figures 6 to 7 (As shown).

[0037] The initial piston structure 104 is used to form the piston structure.

[0038] In this embodiment, in the step of forming the initial piston structure 104, the initial piston structure 104 extends along the second direction Y in the edge region III, and the size of the initial piston structure 104 along the second direction Y is larger than the preset size of the electrode finger along the second direction Y, thereby increasing the process window for aligning the sidewall of the piston structure with the sidewall of the electrode finger.

[0039] In other embodiments, such as Figure 15 In the step of forming the initial piston structure 104, the initial piston structure 104 is arranged at intervals along the second direction Y in the edge region III, and corresponds one-to-one with the formation position of the electrode finger in the second direction Y.

[0040] It should be noted that since the initial piston structure 104 is located on the first interdigital electrode material layer 101, and the first interdigital electrode material layer 101 is directly formed on the substrate 100, the piston structure is closer to the substrate 100, which is beneficial to the interaction of the piston structure with the acoustic waves on the substrate surface. This is beneficial to the piston structure to further suppress the transversely propagating acoustic waves in the filter, thereby improving the electromechanical coupling coefficient of the filter.

[0041] In this embodiment, during the step of forming the initial piston structure 104, the initial piston structure 104 covers the edge region III along the second direction Y.

[0042] It should be noted that the initial piston structure 104 covers the edge region III along the second direction Y, which helps to increase the process window for forming the piston structure and reduce the difficulty of subsequent piston structure formation.

[0043] In other embodiments, in the second direction, there are multiple initial piston structures, which are spaced apart along the second direction, and the dimension of the initial piston structure along the second direction is larger than the dimension of the electrode finger along the second direction. For example, in the second direction, one initial piston structure may correspond to multiple electrode fingers.

[0044] In this embodiment, when the first interdigital electrode material layer 101 is a stacked structure, the initial piston structure 104 and the topmost first interdigital electrode material layer 101 are an integral structure. On the one hand, this helps to simplify the process steps and improve production efficiency. On the other hand, it can enhance the stability between the initial piston structure 104 and the topmost first interdigital electrode material layer 101. In subsequent processes, this helps to reduce the probability of separation between the initial piston structure 104 and the topmost first interdigital electrode material layer 101.

[0045] In other embodiments, when the first interdigital electrode material layer is a single-layer structure, the initial piston structure and the first interdigital electrode material layer are an integral structure.

[0046] In this embodiment, the steps of forming the first interdigitated electrode material layer 101 and the initial piston structure 104 include: referencing Figures 2 to 3 An initial first interdigitated electrode material layer 105 is formed on the substrate 100 of the central region I, the busbar region II, and the edge region III; Reference Figures 4 to 7 The initial first interdigital electrode material layer 105 of a certain thickness is patterned to form a protruding initial piston structure 104. The initial piston structure 104 is located on the remaining thickness of the initial first interdigital electrode material layer 105 in the edge region III, and the remaining thickness of the initial first interdigital electrode material layer 105 serves as the first interdigital electrode material layer 101.

[0047] The initial first interdigital electrode material layer 105 is used to form the initial piston structure 104 and the first interdigital electrode material layer 101.

[0048] It should be noted that an initial first interdigital electrode material layer 105 is formed on the substrate 100 of the central region I, the busbar region II and the edge region III. Then, the initial first interdigital electrode material layer 105 of a certain thickness is patterned. That is, the initial piston structure 104 and the first interdigital electrode material layer 101 can be formed in the same step, which helps to reduce the complexity of the process.

[0049] It should also be noted that, in this embodiment, since the first interdigital electrode material layer 101 is a stacked structure, the initial first interdigital electrode material layer 105 is also a stacked structure. (See reference...) Figure 3 As an example, the initial first interdigital electrode material layer 105 includes an initial second subinterdigital electrode material layer 103a located on the substrate 100 and an initial first subinterdigital electrode material layer 102a located on the initial second subinterdigital electrode material layer 103a.

[0050] The process of forming an initial first interdigitated electrode material layer 105 on a substrate 100 in the central region I, the condenser region II, and the edge region III includes sputtering, atomic layer deposition, or vapor deposition.

[0051] It should be noted that using sputtering, atomic layer deposition, or vapor deposition processes can improve the film quality of the initial first interdigital electrode material layer 105, and correspondingly improve the film quality of the first interdigital electrode material layer 101 and the initial piston structure 104.

[0052] As an example, the process of forming the initial first interdigitated electrode material layer 105 on the substrate 100 of the central region I, the busbar region II and the edge region III is a sputtering process.

[0053] Specifically, the step of patterning the initial first interdigital electrode material layer 105 of a certain thickness includes: referencing Figures 4 to 5 A patterned second mask layer 106 is formed on the initial first interdigitated electrode material layer 105, the second mask layer 106 being located in the edge region III; Reference Figures 6 to 7 Using the second mask layer 106 as a mask, the initial first interdigitated electrode material layer 105 of the exposed thickness of the second mask layer 106 is removed.

[0054] The second mask layer 106 is used as a mask for forming the initial piston structure 104.

[0055] like Figure 4As shown, in this embodiment, the second mask layer 106 extends along the second direction Y and covers the edge region III.

[0056] In other embodiments, the second mask layers are spaced apart in the edge region along the second direction and correspond one-to-one with the formation positions of the electrode fingers in the second direction.

[0057] In this embodiment, the material of the second mask layer 106 includes photoresist. Photoresist has high resolution, allowing for precise control of the area to be removed; simultaneously, photoresist is easy to remove, thereby reducing process complexity and improving production efficiency. In other embodiments, the second mask layer may also be made of other materials that can serve as etching masks and are easy to remove.

[0058] In this embodiment, the process of removing the exposed portion of the initial first interdigital electrode material layer 105 from the second mask layer 106 includes an ion beam trimming process.

[0059] It should be noted that the ion beam trimming process uses a high-energy ion beam to remove the portion of the initial first interdigital electrode material layer 105 exposed by the second mask layer 106. This helps to reduce the surface roughness of the remaining initial first interdigital electrode material layer 105, thereby improving the morphological quality of the initial piston structure 104 and the first interdigital electrode material layer 101.

[0060] In this embodiment, the process parameters of the ion beam trimming process include: the etching gas includes a mixture of argon and fluorine-based gas, and the ion source power is 60 watts to 80 watts.

[0061] Continue to refer to Figures 6 to 7 After forming the initial piston structure 104 and before forming the second interdigitated electrode material layer, the method further includes: removing the second mask layer 106.

[0062] It should be noted that removing the second mask layer 106 is to prepare for the subsequent formation of the second interdigitated electrode material layer.

[0063] Specifically, the second mask layer 106 is removed by wet desmearing or ashing process.

[0064] In other embodiments, the initial first interdigital electrode material layer of a certain thickness exposed by the second mask layer can be removed by first using an etching process; after removing the initial first interdigital electrode material layer of a certain thickness, the second mask layer can be removed; after removing the second mask layer, the thickness of the first interdigital electrode material layer can be adjusted by an ion beam trimming process.

[0065] refer to Figures 8 to 9A second interdigital electrode material layer 107 is formed to conformally cover the first interdigital electrode material layer 101 and the initial piston structure 104.

[0066] Specifically, the first interdigital electrode material layer 101 and the second interdigital electrode material layer 107 are both used to form a busbar and an electrode finger, the busbar extending along the second direction Y, and the electrode finger extending along the first direction X.

[0067] It should be noted that the surface roughness of the first interdigital electrode material layer 101 and the initial piston structure 104 can be reduced by using an ion beam trimming process, thereby providing a smooth surface for the subsequent formation of the second interdigital electrode material layer 107, which in turn helps to improve the electrical performance of the second interdigital electrode material layer 107.

[0068] It should also be noted that, since the second interdigital electrode material layer 107 conformally covers the first interdigital electrode material layer 101 and the initial piston structure 104, and the initial piston structure 104 protrudes from the first interdigital electrode material layer 101, the second interdigital electrode material layer 107 located on top of the initial piston structure 104 is higher than the second interdigital electrode material layer 107 located on the first interdigital electrode material layer 101, which is beneficial for forming the piston structure, electrode fingers and busbar in the same step, thus simplifying the process flow.

[0069] In this embodiment, in the step of forming the second interdigital electrode material layer 107, the mass of the first interdigital electrode material layer 101 is greater than the mass of the second interdigital electrode material layer 107.

[0070] It should be noted that, since the mass of the first interdigital electrode material layer 101 is greater than the mass of the second interdigital electrode material layer 107, and the second interdigital electrode material layer 107 is located on top of the first interdigital electrode material layer 101, the correspondingly larger mass of the first interdigital electrode material layer 101 enhances the electric field concentration effect, which is beneficial to improving the electromechanical coupling coefficient of the filter. On the other hand, the smaller mass of the second interdigital electrode material layer 107 reduces the acoustic impedance gradient and reduces interface reflection loss, thereby accelerating the sound speed propagation of the filter and thus improving the response speed of the filter.

[0071] In the step of forming the second interdigital electrode material layer 107, the second interdigital electrode material layer 107 is a stacked structure or a single-layer structure.

[0072] In this embodiment, the second interdigital electrode material layer 107 is a stacked structure.

[0073] refer to Figure 9As an example, when the second interdigital electrode material layer 107 is a stacked structure, the topmost second interdigital electrode material layer 107 serves as the third sub-interdigital electrode material layer 108, and the second interdigital electrode material layer 107 located between the third sub-interdigital electrode material layer 108 and the first interdigital electrode material layer 101 serves as the fourth sub-interdigital electrode material layer 109. The resistivity of the fourth sub-interdigital electrode material layer 109 is lower than that of the first interdigital electrode material layer 101, and the resistivity of the fourth sub-interdigital electrode material layer 109 is lower than that of the third sub-interdigital electrode material layer 108.

[0074] Specifically, since the resistivity of the fourth sub-interdigital electrode material layer 109 is lower than that of the first interdigital electrode material layer 101, and the resistivity of the fourth sub-interdigital electrode material layer 109 is lower than that of the third sub-interdigital electrode material layer 108, the fourth sub-interdigital electrode material layer 109 can be used to reduce the resistivity of the filter.

[0075] In this embodiment, the material of the fourth interdigital electrode material layer 109 includes an aluminum-copper alloy or aluminum.

[0076] Aluminum-copper alloys or aluminum have low resistivity; therefore, aluminum-copper alloys or aluminum can reduce the resistivity of the filter. As an example, the material of the fourth sub-interdigital electrode layer 109 is aluminum.

[0077] The third sub-interdigital electrode material layer 108 is used to protect the fourth sub-interdigital electrode material layer 109 and prevent the third sub-interdigital electrode material layer 108 from being affected by the external environment (e.g., oxidation, corrosion).

[0078] In this embodiment, the material of the third interdigital electrode material layer 108 includes titanium, chromium, titanium nitride, aluminum nitride, or titanium tungsten.

[0079] Titanium, chromium, titanium nitride, aluminum nitride, or titanium tungsten have relatively stable chemical and physical properties. Therefore, the third sub-interdigital electrode material layer 108 can reduce the influence of the external environment (e.g., oxidation, corrosion, wear, etc.) on the fourth sub-interdigital electrode material layer 109.

[0080] In other embodiments, when the second interdigital electrode material layer is a single-layer structure, the material of the second interdigital electrode material layer is an aluminum-copper alloy or aluminum.

[0081] refer to Figures 10 to 14The predetermined pattern 111 corresponding to the interdigital electrode 110 is transferred to the initial piston structure 104, the first interdigital electrode material layer 101, and the second interdigital electrode material layer 107. The first interdigital electrode material layer 101 and the second interdigital electrode material layer 107 form a busbar 112 located in the busbar region II and electrode fingers 113 located in the central region I and the edge region III. A piston structure 114 is formed on the electrode fingers 113 located in the edge region III. The busbar 112, the piston structure 114, and the electrode fingers 113 constitute the interdigital electrode 110. The electrode fingers 110 extend along the first direction X and are spaced apart along the second direction Y. The busbar 112 extends along the second direction Y and connects each of the electrode fingers 113. The first direction X intersects the second direction Y.

[0082] As an example, the first direction X is perpendicular to the second direction Y. It is understood that in other embodiments, the angle between the first and second directions may be other angles, depending on actual needs.

[0083] In this embodiment, in the step of transferring the predetermined pattern 111 corresponding to the interdigital electrode 110 onto the initial piston structure 104, the first interdigital electrode material layer 101, and the second interdigital electrode material layer 107, the projection of the predetermined pattern 111 onto the second interdigital electrode material layer 107 intersects with the initial piston structure 104, so as to form the piston structure 114 at the intersection of the projection of the predetermined pattern 111 and the initial piston structure 104.

[0084] It should be noted that the projection of the predetermined pattern 111 onto the second interdigitated electrode material layer 107 intersects with the initial piston structure 104, so that the piston structure 114 is formed at the intersection of the projection of the predetermined pattern 111 and the initial piston structure 104. This makes the sidewall of the piston structure 114 aligned with the sidewall of the electrode finger 113, which helps to improve the morphological quality of the interdigitated electrode 110 and the alignment accuracy of the electrode finger 113 and the piston structure 114, thereby enhancing the filter's ability to suppress clutter and improving the filter's performance.

[0085] In this embodiment, the predetermined pattern 111 corresponding to the interdigital electrode 110 is transferred to the initial piston structure 114, the first interdigital electrode material layer 101, and the second interdigital electrode material layer 107 using the first mask layer 115 with a predetermined pattern 111.

[0086] The steps of transferring the predetermined pattern 111 corresponding to the interdigital electrode 110 onto the initial piston structure 114, the first interdigital electrode material layer 101, and the second interdigital electrode material layer 107 will be described below with reference to the accompanying drawings.

[0087] refer toFigures 10 to 11 A first mask layer 115 with a predetermined pattern 111 is formed on the second interdigital electrode material layer 107. The first mask layer 115 includes a first mask portion 116 and a second mask portion 117. The first mask portion 116 is located on the second interdigital electrode material layer 107 of the busbar region II. The first mask portion 116 extends along the second direction Y and connects each of the second mask portions 117. The second mask portions 117 extend along the first direction X and are spaced apart along the second direction Y. The second mask portions 117 are located on the second interdigital electrode material layer 107 of the central region I and the edge region III and intersect with the initial piston structure 104.

[0088] The first mask layer 115 serves as a mask layer for forming the interdigitated electrode 110. Specifically, the first mask portion 116 provides a first predetermined pattern 118 corresponding to the busbar 112, the first mask portion 111 serves as a mask layer for forming the busbar 112, the second mask portion 117 provides a second predetermined pattern 119 corresponding to the electrode finger 113, and the second mask portion 117 serves as a mask layer for forming the electrode finger 113 and the piston structure 114.

[0089] It should be noted that the morphology of the first mask layer 115 is arranged as a first mask portion 116 and a plurality of second mask portions 117, and the second mask portions 117 intersect with the initial piston structure 104, which is beneficial for defining the position and shape of the subsequently formed busbar, electrode fingers and piston structure.

[0090] In this embodiment, the material of the first mask layer 115 includes photoresist. Photoresist has high resolution, allowing for precise control of the area to be removed; simultaneously, photoresist is easy to remove, thereby reducing process complexity and improving production efficiency. In other embodiments, the first mask layer may also be made of other materials that can serve as etching masks and are easy to remove.

[0091] refer to Figures 12 to 14 Using the first mask layer 115 as a mask, the first interdigital electrode material layer 101, the second interdigital electrode material layer 107, and the initial piston structure 104 are patterned. The first interdigital electrode material layer 101 and the second interdigital electrode material layer 107 in the busbar region II are patterned as busbars 112 corresponding to the first mask portion 116. The first interdigital electrode material layer 101 and the second interdigital electrode material layer 107 in the central region II and the edge region III are patterned as electrode fingers 113 corresponding to the second mask portion 116. In the edge region III, the remaining initial piston structure 104 and the second interdigital electrode material layer 107 covering the remaining initial piston structure 104 are used as piston structure 114.

[0092] The interdigitated electrode 110 is used to realize the mutual conversion between electrical signals and acoustic signals, so that the surface acoustic wave filter can filter the signal.

[0093] Busbar 112 is used to transmit telecommunications from the input of the filter to the output.

[0094] Electrode 113 is used to realize the mutual conversion between electrical signals and acoustic signals.

[0095] The piston structure 114 is used to suppress transversely propagating sound waves in the filter. Specifically, the piston structure 114 increases the mass of the interdigitated electrode 110 located in edge region III, thereby reducing the propagation speed of transversely propagating sound waves in this region and thus suppressing transversely propagating sound waves in the filter.

[0096] It should be noted that the interdigital electrodes 110 are arranged as busbars 112 and multiple electrode fingers 113, with piston structures 114 formed on the electrode fingers 113, which helps to reduce the area of ​​the interdigital electrodes 110 while enhancing the acoustic-to-electric conversion efficiency of the filter.

[0097] In this embodiment, the busbar 112 includes a first busbar 120 and a second busbar 121 disposed opposite to each other along the first direction X, and both the first busbar 120 and the second busbar 121 extend along the second direction Y; the electrode finger 113 includes a first electrode finger 122 connected to the first busbar 120 and a second electrode finger 123 connected to the second busbar 121, and the first electrode finger 122 and the second electrode finger 123 are arranged in a cross pattern.

[0098] It should be noted that the first busbar 120 and the second busbar 121 are arranged opposite each other along the first direction X, and the first electrode finger 122 and the second electrode finger 123 are arranged in a cross pattern. This allows the busbar 112 and the electrode finger 113 to make full use of the space formed, resulting in a higher pattern density and saving space area without interfering with each other.

[0099] Specifically, when the first busbar 120 and the first electrode finger 122 serve as input terminals, the second busbar 121 and the second electrode finger 123 serve as output terminals. The input terminals are used to convert electrical signals into acoustic signals, and the output terminals are used to convert acoustic signals into electrical signals, thereby achieving filtering. In other embodiments, the first busbar and the first electrode finger can also serve as output terminals, and the second busbar and the second electrode finger can serve as input terminals.

[0100] In this embodiment, reference Figure 13In the step of transferring the predetermined pattern 111 corresponding to the interdigital electrode 110 onto the initial piston structure 104, the first interdigital electrode material layer 101, and the second interdigital electrode material layer 107, along the stacking direction of the first interdigital electrode material layer 101 and the second interdigital electrode material layer 107, the remaining initial piston structure 104 serves as the first piston structure 124; the second interdigital electrode material layer 107 also conformally covers the top and sidewalls of the first piston structure 124, and the second interdigital electrode material layer 107 located on the top and sidewalls of the first piston structure 124 serves as the second piston structure 125, and the first piston structure 124 and the second piston structure 125 constitute the piston structure 114.

[0101] It should be noted that the piston structure 114 is composed of the first piston structure 124 and the second piston structure 125. Therefore, the mass of the piston structure 114 is further increased, which in turn further increases the mass of the interdigitated electrode 110 located in the edge region III, thereby further reducing the propagation speed of the transversely propagating sound wave in this region and thus suppressing the transversely propagating sound wave in the filter.

[0102] It should also be noted that the second interdigital electrode material layer 107 also conformally covers the top and sidewalls of the first piston structure 124, which facilitates the alignment of the sidewalls of the second piston structure 125 with the sidewalls of the first piston structure 124, and the alignment of the sidewalls of the first piston structure 124 with the sidewalls of the electrode fingers 113. Consequently, the alignment of the sidewalls of the second piston structure 125 with the sidewalls of the electrode fingers 113 is also achieved, which helps to improve the morphological quality of the interdigital electrode 110 and the alignment accuracy of the electrode fingers 113, the first piston structure 124, and the second piston structure 125.

[0103] Continue to refer to Figures 12 to 14 After forming the busbar 112, electrode fingers 113, and piston structure 114, the first mask layer 115 is removed. Specifically, the first mask layer 115 is removed by wet desmearing or ashing processes.

[0104] Accordingly, the present invention also provides a filter. Figure 16 This is a schematic diagram of the structure of an embodiment of the filter of the present invention. Figure 16 This is a top view of the busbar, electrode fingers, and piston structure. Figure 17 yes Figure 16 A cross-sectional view along the aa1 direction. Figure 18 yes Figure 16 A sectional view along the bb1 direction.

[0105] refer to Figures 16 to 18The filter includes: a substrate 500, the substrate 500 including a central region i, a bus region ii, and an edge region iii located between the central region i and the bus region ii, the central region i, the bus region ii, and the edge region iii being arranged along a first direction x; and interdigital electrodes 501 located on the substrate 500 of the central region i, the bus region ii, and the edge region iii, the interdigital electrodes 501 including a bus bar 502 located in the bus region ii, a plurality of electrode fingers 503 located in the edge region iii and the central region ii, and an electrode finger 503 located in the edge region iii. The piston structure 504 on the electrode finger 503, the busbar 502 extends along the second direction y and connects each of the electrode fingers 503, the electrode fingers 503 extend along the first direction x and are spaced apart along the second direction y, the first direction x and the second direction y intersect; wherein, the interdigitated electrode 501 further includes a first interdigitated electrode layer 505 and a second interdigitated electrode layer 506 located on the first interdigitated electrode layer 505; the piston structure 504 is located on the first interdigitated electrode layer 505 and is in contact with the top surface of the first interdigitated electrode layer 505.

[0106] It should be noted that, since the piston structure 504 is located on the first interdigital electrode layer 505 and in contact with the top surface of the first interdigital electrode layer 505, and the first interdigital electrode layer 505 is directly formed on the substrate 500, the piston structure 504 is closer to the substrate 500. This is beneficial for the interaction of sound waves between the piston structure 504 and the surface of the substrate 500, thereby helping the piston structure 504 to further suppress the transversely propagating sound waves in the filter, and thus improve the electromechanical coupling coefficient of the filter.

[0107] The substrate 500 provides a process platform for subsequent fabrication of surface acoustic wave (SAW) filters. SAW filters are specialized filtering devices made using the piezoelectric effect and the physical characteristics of surface acoustic wave propagation. In a SAW filter, the signal undergoes two conversions: electro-acoustic and electro-acoustic, thus achieving frequency selectivity. SAW filters offer advantages such as high operating frequency, simple manufacturing process, low manufacturing cost, and high frequency response consistency, and are therefore widely used in various electronic devices.

[0108] In this embodiment, the substrate 500 is a piezoelectric substrate, so that the subsequent surface acoustic wave filter structure can utilize the piezoelectric effect for filtering.

[0109] The substrate 500 may be made of lithium niobate, lithium tantalate, quartz, or piezoelectric ceramic. As an example, the substrate 500 may be made of lithium niobate. In other embodiments, the substrate may also be a piezoelectric substrate on an insulator.

[0110] The busbar region ii provides a spatial position for the formed busbar 502, the edge region iii provides a spatial position for the formed piston structure 504 and electrode fingers 503, the center region i provides a spatial position for the subsequently formed electrode fingers 503, and the interdigitated electrode 501 is used to realize the mutual conversion between electrical signals and acoustic signals, so that the surface acoustic wave filter can filter the signals.

[0111] Busbar 502 is used to transmit telecommunications from the input of the filter to the output.

[0112] Electrode 503 is used to realize the mutual conversion between electrical signals and acoustic signals.

[0113] The piston structure 504 is used to suppress transversely propagating sound waves in the filter. Specifically, the piston structure 504 increases the mass of the interdigitated electrode 501 located in the edge region iii, thereby reducing the propagation speed of transversely propagating sound waves in this region and thus suppressing transversely propagating sound waves in the filter.

[0114] In this embodiment, the interdigitated electrode 501 includes a busbar 502 located in the busbar region ii, a plurality of electrode fingers 503 located in the edge region iii and the center region ii, and a piston structure 504 located on the electrode fingers 503 in the edge region iii. The busbar 502 extends along the second direction y and connects each of the electrode fingers 503. The electrode fingers 503 extend along the first direction x and are spaced apart along the second direction y. The first direction x intersects the second direction y.

[0115] As an example, the first direction x is perpendicular to the second direction y. It is understood that in other embodiments, the angle between the first and second directions may be other angles, depending on actual needs.

[0116] It should be noted that the interdigital electrode 501 is arranged as a bus bar 502 and multiple electrode fingers 503. A piston structure 504 is formed on the electrode fingers 503, which helps to reduce the area of ​​the interdigital electrode 501 while enhancing the acoustic-to-electric conversion efficiency of the filter.

[0117] In this embodiment, the busbar 502 includes a first busbar 507 and a second busbar 508 disposed opposite to each other along the first direction x, and both the first busbar 507 and the second busbar 508 extend along the second direction y; the electrode finger 503 includes a first electrode finger 509 connected to the first busbar 507 and a second electrode finger 510 connected to the second busbar 508, and the first electrode finger 509 and the second electrode finger 510 are arranged in a cross pattern.

[0118] It should be noted that the first busbar 507 and the second busbar 508 are arranged opposite each other along the first direction x, and the first electrode finger 509 and the second electrode finger 510 are arranged in a cross pattern. This allows the busbar 502 and the electrode finger 503 to make full use of the space formed, resulting in a higher pattern density and saving space area without interfering with each other.

[0119] Specifically, when the first busbar 507 and the first electrode finger 509 serve as input terminals, the second busbar 508 and the second electrode finger 510 serve as output terminals. The input terminals are used to convert electrical signals into acoustic signals, and the output terminals are used to convert acoustic signals into electrical signals, thereby achieving filtering. In other embodiments, the first busbar and the first electrode finger can also serve as output terminals, and the second busbar and the second electrode finger can serve as input terminals.

[0120] In this embodiment, in the second direction y, the sidewall of the piston structure 504 is aligned with the sidewall of the electrode finger 503.

[0121] It should be noted that since the sidewall of the piston structure 504 is aligned with the sidewall of the electrode finger 503, it is beneficial to improve the morphological quality of the interdigital electrode 501 and the alignment accuracy of the electrode finger 503 and the piston structure 504, thereby improving the filter's ability to suppress clutter and thus improving the filter's performance.

[0122] The first interdigital electrode 505 is a stacked structure or a single-layer structure.

[0123] In this embodiment, the first interdigital electrode 505 has a stacked structure.

[0124] As an example, see reference Figures 17 to 18 When the first interdigital electrode layer 505 is a stacked structure, the topmost first interdigital electrode layer 505 serves as the first sub-interdigital electrode layer 511, and the first interdigital electrode layer 505 located between the first sub-interdigital electrode layer 511 and the substrate 500 serves as the second sub-interdigital electrode layer 512. The mass of the first sub-interdigital electrode layer 511 is greater than that of the second sub-interdigital electrode layer 512, and the adhesion of the second sub-interdigital electrode layer 512 to the substrate 500 is greater than that of the first sub-interdigital electrode layer 511 to the substrate 500.

[0125] Specifically, the second sub-interdigital electrode layer 512 is used to improve the adhesion between the first sub-interdigital electrode layer 511 and the substrate 500, and the first sub-interdigital electrode layer 511 is used to increase the quality of the filter.

[0126] In other embodiments, the first interdigital electrode layer may be a single-layer structure, or the number of layers of the first interdigital electrode layer may be greater than three.

[0127] The material of the second sub-interdigital electrode layer 512 includes titanium, chromium, titanium nitride, aluminum nitride, or titanium tungsten.

[0128] It should be noted that titanium, chromium, titanium nitride, aluminum nitride, or titanium tungsten have good adhesion; therefore, titanium, chromium, titanium nitride, aluminum nitride, or titanium tungsten can improve the adhesion between the substrate 500 and the first sub-interdigital electrode layer 511. As an example, the material of the second sub-interdigital electrode layer 512 is titanium.

[0129] The material of the first interdigitated electrode layer 511 includes tungsten or molybdenum.

[0130] It should be noted that tungsten or molybdenum has a large mass; therefore, tungsten or molybdenum can reduce the propagation speed of transversely propagating sound waves in the filter, thereby reducing the characteristic size (CD) value of the interdigital electrodes. As an example, the material of the first sub-interdigital electrode layer 511 is tungsten.

[0131] In other embodiments, when the first interdigital electrode layer is a single-layer structure, the material of the first interdigital electrode layer is tungsten or molybdenum.

[0132] As an example, when the first interdigital electrode layer 505 is a stacked structure, the portion of the piston structure 504 that contacts the top surface of the first interdigital electrode layer 505 is integral with the topmost first interdigital electrode layer 505. On the one hand, this simplifies the process steps and improves production efficiency; on the other hand, it enhances the stability between the portion of the piston structure 504 that contacts the top surface of the first interdigital electrode layer 505 and the topmost first interdigital electrode layer 505. In subsequent processes, this helps reduce the probability of separation between the portion of the piston structure 504 that contacts the top surface of the first interdigital electrode layer 505 and the topmost first interdigital electrode layer 505.

[0133] In other embodiments, when the first interdigital electrode layer is a single-layer structure, the portion of the piston structure that contacts the top surface of the first interdigital electrode layer is an integral structure with the first interdigital electrode layer.

[0134] The second interdigitated electrode layer 506 is a stacked structure or a single-layer structure.

[0135] In this embodiment, the second interdigital electrode layer 506 is a stacked structure.

[0136] As an example, see reference Figures 17 to 18When the second interdigital electrode layer 506 is a stacked structure, the topmost second interdigital electrode layer 506 serves as the third sub-interdigital electrode layer 514, and the second interdigital electrode layer 506 located between the third sub-interdigital electrode layer 514 and the first interdigital electrode layer 513 serves as the fourth sub-interdigital electrode layer 515. The resistivity of the fourth sub-interdigital electrode layer 515 is lower than that of the first interdigital electrode layer 505, and the resistivity of the fourth sub-interdigital electrode layer 515 is lower than that of the third sub-interdigital electrode layer 514.

[0137] Specifically, since the resistivity of the fourth sub-interdigital electrode layer 515 is lower than that of the first interdigital electrode layer 505, and the resistivity of the fourth sub-interdigital electrode layer 515 is lower than that of the third sub-interdigital electrode layer 514, the fourth sub-interdigital electrode layer 515 can be used to reduce the resistivity of the filter.

[0138] In this embodiment, the material of the fourth sub-interdigital electrode layer 515 includes an aluminum-copper alloy or aluminum.

[0139] Copper alloys or aluminum have low resistivity; therefore, aluminum-copper alloys or aluminum can reduce the resistivity of the filter. As an example, the fourth sub-interdigital electrode layer 515 is made of aluminum.

[0140] The third sub-interdigital electrode layer 514 is used to protect the fourth sub-interdigital electrode layer 515 and prevent the third sub-interdigital electrode layer 514 from being affected by the external environment (e.g., oxidation, corrosion).

[0141] The material of the third sub-interdigital electrode layer 514 includes titanium, chromium, titanium nitride, aluminum nitride, or titanium tungsten.

[0142] Titanium, chromium, titanium nitride, aluminum nitride, or titanium tungsten have relatively stable chemical and physical properties, thus reducing the impact of the external environment (e.g., oxidation, corrosion, wear, etc.) on the fourth sub-interdigital electrode layer 515.

[0143] In other embodiments, when the second interdigital electrode layer is a single-layer structure, the material of the second interdigital electrode layer is an aluminum-copper alloy or aluminum.

[0144] In this embodiment, the mass of the first interdigital electrode layer 505 is greater than the mass of the second interdigital electrode layer 506.

[0145] It should be noted that, since the mass of the first interdigital electrode layer 505 is greater than that of the second interdigital electrode layer 506, and the second interdigital electrode layer 506 is located on top of the first interdigital electrode layer 505, the correspondingly larger mass of the first interdigital electrode layer 505 enhances the electric field concentration effect, which is beneficial to improving the electromechanical coupling coefficient of the filter. Meanwhile, the smaller mass of the second interdigital electrode layer 506 reduces the acoustic impedance gradient and reduces interface reflection loss, thereby accelerating the sound propagation speed of the filter and thus improving the response speed of the filter.

[0146] In this embodiment, reference Figure 17 Along the stacking direction of the first interdigital electrode layer 505 and the second interdigital electrode layer 506, the piston structure 504 includes a first piston structure 516 located on the first interdigital electrode layer 505 and in contact with the top surface of the first interdigital electrode layer 505; the second interdigital electrode layer 506 also conformally covers the top and sidewalls of the first piston structure 516, and the second interdigital electrode layer 506 located on the top and sidewalls of the first piston structure 516 serves as a second piston structure 517, and the first piston structure 516 and the second piston structure 517 constitute a piston structure.

[0147] In this embodiment, the portion that contacts the top surface of the first interdigital electrode layer 505 is the first piston structure 516.

[0148] It should be noted that the piston structure 504 is composed of the first piston structure 516 and the second piston structure 517. Therefore, the mass of the piston structure 504 is further increased, which in turn further increases the mass of the interdigitated electrode 501 located in the edge region iii, thereby further reducing the propagation speed of the transversely propagating sound wave in this region and thus suppressing the transversely propagating sound wave in the filter.

[0149] It should also be noted that the second interdigital electrode layer 506 also conformally covers the top and sidewalls of the first piston structure 516, which facilitates the alignment of the sidewalls of the second piston structure 517 with the sidewalls of the first piston structure 516, and the alignment of the sidewalls of the first piston structure 516 with the sidewalls of the electrode fingers 503. Consequently, the alignment of the sidewalls of the second piston structure 517 with the sidewalls of the electrode fingers 503 is achieved, which helps to improve the morphological quality of the interdigital electrode 501 and the alignment accuracy of the electrode fingers 503, the first piston structure 516, and the second piston structure 517.

[0150] The filter structure of this embodiment can be formed using the filter structure formation method of the aforementioned embodiment, or it can be formed using other filter structure formation methods, which will not be described again in this embodiment.

[0151] Accordingly, embodiments of the present invention also provide an electronic device, which includes a filter according to any embodiment of the present invention.

[0152] Filters can be integrated into various electronic devices. As the foregoing analysis shows, filters offer high performance, which in turn enables the creation of high-performance electronic devices. These electronic devices can include personal computers, smartphones and other mobile terminals, media players, navigation devices, video game consoles, game controllers, tablet computers, wearable devices, security access control systems, POS terminals, medical devices, flight simulators, and more.

[0153] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for forming a filter, characterized in that, include: A substrate is provided, the substrate including a central region, a confluence region and an edge region located between the central region and the confluence region, the central region, the edge region and the confluence region being arranged along a first direction; A first interdigitated electrode material layer is formed on the substrate of the central region, edge region, and bus region; An initial piston structure is formed on the first interdigitated electrode material layer in the edge region; A second interdigital electrode material layer is formed to conformally cover the first interdigital electrode material layer and the initial piston structure; The predetermined pattern corresponding to the interdigitated electrode is transferred to the initial piston structure, the first interdigitated electrode material layer, and the second interdigitated electrode material layer. A busbar located in the busbar region and electrode fingers located in the central region and the edge region are formed through the first interdigitated electrode material layer and the second interdigitated electrode material layer. A piston structure is formed on the electrode fingers located in the edge region. The busbar, the piston structure, and the electrode fingers constitute the interdigitated electrode. The electrode fingers extend along the first direction and are spaced apart along the second direction. The busbar extends along the second direction and connects each of the electrode fingers. The first direction intersects the second direction.

2. The method for forming a filter as described in claim 1, characterized in that, The first interdigital electrode material layer and the second interdigital electrode material layer are both used to form busbars and electrode fingers, the busbars extending along a second direction and the electrode fingers extending along a first direction; In the step of forming the initial piston structure, the initial piston structure is arranged at intervals along the second direction in the edge region, and corresponds one-to-one with the formation position of the electrode finger in the second direction.

3. The method for forming a filter as described in claim 1, characterized in that, The first interdigital electrode material layer and the second interdigital electrode material layer are both used to form busbars and electrode fingers, the busbars extending along a second direction and the electrode fingers extending along a first direction; In the step of forming the initial piston structure, the initial piston structure extends along the second direction in the edge region, and the dimension of the initial piston structure along the second direction is larger than the preset dimension of the electrode finger along the second direction; In the step of transferring the predetermined pattern corresponding to the interdigitated electrode to the initial piston structure, the first interdigitated electrode material layer, and the second interdigitated electrode material layer, the projection of the predetermined pattern on the second interdigitated electrode material layer intersects with the initial piston structure to form the piston structure at the intersection of the projection of the predetermined pattern and the initial piston structure.

4. The method for forming a filter as described in claim 3, characterized in that, The step of transferring the predetermined pattern corresponding to the interdigitated electrode to the initial piston structure, the first interdigitated electrode material layer, and the second interdigitated electrode material layer includes: forming a first mask layer with a predetermined pattern on the second interdigitated electrode material layer, the first mask layer including a first mask portion and a second mask portion, the first mask portion being located on the second interdigitated electrode material layer in the busbar region, the first mask portion extending along the second direction and connecting each of the second mask portions, the second mask portions extending along the first direction and spaced apart along the second direction, the second mask portions being located on the second interdigitated electrode material layers in the central region and the edge region and intersecting with the initial piston structure; Using the first mask layer as a mask, the first interdigital electrode material layer, the second interdigital electrode material layer, and the initial piston structure are patterned. The first interdigital electrode material layer and the second interdigital electrode material layer in the busbar region are patterned as busbars corresponding to the first mask portion. The first interdigital electrode material layer and the second interdigital electrode material layer in the central region and the edge region are patterned as electrode fingers corresponding to the second mask portion. In the edge region, the remaining initial piston structure and the second interdigital electrode material layer covering the remaining initial piston structure are used as piston structures. After forming the busbar, electrode fingers, and piston structure, the first mask layer is removed.

5. The method for forming a filter as described in claim 3, characterized in that, In the step of forming the initial piston structure, the initial piston structure covers the edge region along the second direction.

6. The method for forming a filter as described in claim 1, characterized in that, In the step of forming a first interdigitated electrode material layer on the substrate of the central region, edge region and bus region, the first interdigitated electrode material layer is a stacked structure or a single-layer structure. Wherein, when the first interdigital electrode material layer is a single-layer structure, the initial piston structure and the first interdigital electrode material layer are an integral structure; when the first interdigital electrode material layer is a stacked structure, the initial piston structure and the topmost first interdigital electrode material layer are an integral structure. In the step of forming the second interdigital electrode material layer, the mass of the first interdigital electrode material layer is greater than the mass of the second interdigital electrode material layer.

7. The method for forming a filter according to any one of claims 1 to 6, characterized in that, The steps of forming the first interdigitated electrode material layer and the initial piston structure include: forming the initial first interdigitated electrode material layer on the substrate of the central region, the bus region and the edge region; A portion of the initial first interdigital electrode material layer of a certain thickness is patterned to form a protruding initial piston structure. The initial piston structure is located on the remaining thickness of the initial first interdigital electrode material layer in the edge region, and the remaining thickness of the initial first interdigital electrode material layer serves as the first interdigital electrode material layer.

8. The method for forming a filter as described in claim 7, characterized in that, The step of patterning a portion of the initial first interdigital electrode material layer includes: forming a patterned second mask layer on the initial first interdigital electrode material layer, the second mask layer being located in the edge region; Using the second mask layer as a mask, the initial first interdigitated electrode material layer of a certain thickness exposed by the second mask layer is removed; After forming the initial piston structure and before forming the second interdigitated electrode material layer, the method further includes: removing the second mask layer.

9. The method for forming a filter as described in claim 8, characterized in that, The process of removing the portion of the initial first interdigitated electrode material layer exposed by the second mask layer includes an ion beam trimming process.

10. The method for forming a filter as described in claim 1, characterized in that, In the step of forming the first interdigitated electrode material layer on the substrate of the central region, edge region and confluence region, the first interdigitated electrode material layer is a stacked structure or a single-layer structure. Wherein, when the first interdigital electrode material layer is a stacked structure, the topmost first interdigital electrode material layer is used as the first sub-interdigital electrode material layer, and the first interdigital electrode material layer located between the first sub-interdigital electrode material layer and the substrate is used as the second sub-interdigital electrode material layer. The mass of the first sub-interdigital electrode material layer is greater than that of the second sub-interdigital electrode material layer, and the adhesion of the second sub-interdigital electrode material layer to the substrate is greater than that of the first sub-interdigital electrode material layer to the substrate.

11. The method for forming a filter as described in claim 10, characterized in that, When the first interdigital electrode material layer is a stacked structure, the material of the second sub-interdigital electrode material layer includes titanium, chromium, titanium nitride, aluminum nitride, or titanium tungsten; the first sub-interdigital electrode material layer includes tungsten or molybdenum. Alternatively, when the first interdigital electrode material layer is a single-layer structure, the material of the first interdigital electrode material layer includes tungsten or molybdenum.

12. The method for forming a filter as described in claim 1, characterized in that, In the step of forming the second interdigitated electrode material layer, the second interdigitated electrode material layer is a stacked structure or a single-layer structure; Wherein, when the second interdigital electrode material layer is a stacked structure, the topmost second interdigital electrode material layer serves as the third sub-interdigital electrode material layer, and the second interdigital electrode material layer located between the third sub-interdigital electrode material layer and the first interdigital electrode material layer serves as the fourth sub-interdigital electrode material layer. The resistivity of the fourth sub-interdigital electrode material layer is lower than that of the first interdigital electrode material layer, and the resistivity of the fourth sub-interdigital electrode material layer is lower than that of the third sub-interdigital electrode material layer.

13. The method for forming a filter as described in claim 12, characterized in that, When the second interdigital electrode material layer is a stacked structure, the material of the fourth sub-interdigital electrode material layer includes an aluminum-copper alloy or aluminum; the material of the third sub-interdigital electrode material layer includes titanium, chromium, titanium nitride, aluminum nitride or titanium tungsten. Alternatively, when the second interdigital electrode material layer is a single-layer structure, the material of the second interdigital electrode material layer includes an aluminum-copper alloy or aluminum.

14. The method for forming a filter as described in claim 1, characterized in that, In the step of transferring the predetermined pattern corresponding to the interdigitated electrode to the initial piston structure, the first interdigitated electrode material layer and the second interdigitated electrode material layer, along the stacking direction of the first interdigitated electrode material layer and the second interdigitated electrode material layer, the remaining initial piston structure serves as the first piston structure. The second interdigitated electrode material layer also conformally covers the top and sidewalls of the first piston structure. The second interdigitated electrode material layer located on the top and sidewalls of the first piston structure serves as the second piston structure. The first piston structure and the second piston structure constitute the piston structure.

15. A filter, characterized in that, include: The substrate includes a central region, a confluence region, and an edge region located between the central region and the confluence region, wherein the central region, the confluence region, and the edge region are arranged along a first direction; An interdigitated electrode is located on a substrate in the central region, the busbar region, and the edge region. The interdigitated electrode includes a busbar in the busbar region, a plurality of electrode fingers in the edge region and the central region, and a piston structure on the electrode fingers in the edge region. The busbar extends along a second direction and connects each of the electrode fingers. The electrode fingers extend along a first direction and are spaced apart along the second direction. The first direction intersects the second direction. The interdigitated electrode further includes a first interdigitated electrode layer and a second interdigitated electrode layer located on the first interdigitated electrode layer; the piston structure is located on the first interdigitated electrode layer and is in contact with the top surface of the first interdigitated electrode layer.

16. The filter as claimed in claim 15, characterized in that, In the second direction, the sidewall of the piston structure is aligned with the sidewall of the electrode finger.

17. The filter as claimed in claim 15, characterized in that, The first interdigitated electrode layer is a stacked structure or a single-layer structure; Wherein, when the first interdigital electrode layer is a single-layer structure, the portion of the piston structure that contacts the top surface of the first interdigital electrode layer is an integral structure with the first interdigital electrode layer; when the first interdigital electrode layer is a stacked structure, the portion of the piston structure that contacts the top surface of the first interdigital electrode layer is an integral structure with the topmost first interdigital electrode layer. The mass of the first interdigital electrode layer is greater than the mass of the second interdigital electrode layer.

18. The filter as claimed in claim 15, characterized in that, The first interdigitated electrode layer is a stacked structure or a single-layer structure; Wherein, when the first interdigital electrode layer is a stacked structure, the topmost first interdigital electrode layer is used as the first sub-interdigital electrode layer, and the first interdigital electrode layer located between the first sub-interdigital electrode layer and the substrate is used as the second sub-interdigital electrode layer. The mass of the first sub-interdigital electrode layer is greater than that of the second sub-interdigital electrode layer, and the adhesion of the second sub-interdigital electrode layer to the substrate is greater than that of the first sub-interdigital electrode layer to the substrate.

19. The filter as claimed in claim 18, characterized in that, When the first interdigital electrode layer is a stacked structure, the material of the second sub-interdigital electrode layer includes titanium, chromium, titanium nitride, aluminum nitride, or titanium tungsten; the material of the first sub-interdigital electrode layer includes tungsten or molybdenum. Alternatively, when the first interdigital electrode layer is a single-layer structure, the material of the first interdigital electrode layer is tungsten or molybdenum.

20. The filter as claimed in claim 15, characterized in that, The second interdigitated electrode layer is a stacked structure or a single-layer structure; Wherein, when the second interdigital electrode layer is a stacked structure, the topmost second interdigital electrode layer serves as the third sub-interdigital electrode layer, and the second interdigital electrode layer located between the third sub-interdigital electrode layer and the first interdigital electrode layer serves as the fourth sub-interdigital electrode layer. The resistivity of the fourth sub-interdigital electrode layer is lower than that of the first interdigital electrode layer, and the resistivity of the fourth sub-interdigital electrode layer is lower than that of the third sub-interdigital electrode layer.

21. The filter as claimed in claim 20, characterized in that, When the second interdigital electrode layer is a stacked structure, the material of the fourth sub-interdigital electrode layer includes an aluminum-copper alloy or aluminum; the material of the third sub-interdigital electrode layer includes titanium, chromium, titanium nitride, aluminum nitride or titanium tungsten. Alternatively, when the second interdigital electrode layer is a single-layer structure, the material of the second interdigital electrode layer is an aluminum-copper alloy or aluminum.

22. The filter as described in claim 20, characterized in that, Along the stacking direction of the first interdigital electrode layer and the second interdigital electrode layer, the piston structure includes a first piston structure located on the first interdigital electrode layer and in contact with the top surface of the first interdigital electrode layer; The second interdigitated electrode layer also conformally covers the top and sidewalls of the first piston structure. The second interdigitated electrode layer located on the top and sidewalls of the first piston structure serves as the second piston structure. The first piston structure and the second piston structure constitute the piston structure.

23. An electronic device, characterized in that, Includes the filter as described in any one of claims 16 to 22.

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