Filter and method for forming the same, electronic device

Abstract

The application discloses a filter and a forming method thereof and an electronic device, and the forming method of the filter comprises the following steps: after a pad is formed, an acoustic transducer located on a substrate of a transducing area is formed, and a connecting part located on a side of the acoustic transducer and connected with the acoustic transducer is formed, so that the process step of forming the pad has no influence on the acoustic transducer and the connecting part, the probability of damage of the acoustic transducer and the connecting part is correspondingly reduced, the integrity, the pattern quality and the film layer quality of the acoustic transducer and the connecting part are beneficially ensured, the effect of the acoustic transducer for sound-electricity conversion and the connecting effect of the connecting part and the acoustic transducer are correspondingly guaranteed, and in addition, the connecting part not only contacts the top of the pad, but also contacts the side of the pad, so that the contact area between the connecting part and the pad is increased, the contact resistance between the connecting part and the pad is reduced, and the electrical connection performance of the connecting part and the pad is improved; as a result, the performance of the filter is improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a filter and its forming method, and an electronic device. Background Technology

[0002] Radio frequency (RF) front-end chips in wireless communication devices include power amplifiers, antenna switches, RF filters, multiplexers, and low-noise amplifiers. Among these, RF filters include surface acoustic wave (SAW) filters, bulk acoustic wave (BAW) filters, micro-electro-mechanical system (MEMS) filters, and integrated passive device (IPD) filters.

[0003] Surface acoustic waves (SAWs) are elastic waves generated and propagating on the surface of a piezoelectric element. Their amplitude rapidly decreases with increasing depth into the piezoelectric element, and their energy is highly concentrated on the material surface. SAW filters offer advantages such as small size, suitability for micro-packaging, good consistency, low cost, and low insertion loss (IL), making them widely used in mobile communications.

[0004] However, the performance of the filters still needs to be improved. Summary of the Invention

[0005] The problem solved by the embodiments of the present invention is to provide a filter and its formation method and electronic device, thereby improving the performance of the filter.

[0006] To address the aforementioned problems, embodiments of the present invention provide a method for forming a filter, comprising: providing a substrate, the substrate including a transducer region for performing acoustic-to-electric conversion and a connection region for connecting the filter to an external circuit; forming a pad on the substrate of the connection region; forming an acoustic transducer located on the substrate of the transducer region, and a connection portion located on the side of the acoustic transducer and connected to the acoustic transducer, the connection portion contacting the side and a portion of the top of the pad, and exposing a portion of the top of the pad.

[0007] Accordingly, embodiments of the present invention also provide a filter, comprising: a substrate, the substrate including a transducer region for performing acoustic-to-electric conversion and a connection region for connecting the filter to an external circuit; a pad located on the substrate of the connection region; an acoustic transducer located on the substrate of the transducer region; and a connection portion located on the side of the acoustic transducer and connected to the acoustic transducer, the connection portion further extending on the side and part of the top of the pad, and exposing part of the top of the pad.

[0008] Accordingly, embodiments of the present invention also provide an electronic device, including the filter provided in embodiments of the present invention.

[0009] Compared with the prior art, the technical solution of the embodiments of the present invention has the following advantages: The filter formation method provided in this embodiment of the invention involves forming a pad on the substrate of the connection region, followed by forming an acoustic transducer on the substrate of the transducer region and a connecting portion located on the side of the acoustic transducer and connected to it. The connecting portion contacts the side and part of the top of the pad, and exposes part of the top of the pad. Compared with the scheme of forming the pad after forming the acoustic transducer and the connecting portion, this embodiment of the invention avoids the impact of the pad formation process on the acoustic transducer and the connecting portion, thereby reducing the probability of damage to the acoustic transducer and the connecting portion. This helps to ensure the integrity, pattern quality, and film quality of the acoustic transducer and the connecting portion, and correspondingly ensures the effect of the acoustic transducer for acoustic-to-electric conversion and the connection effect between the connecting portion and the acoustic transducer. Moreover, the connecting portion contacts not only part of the top of the pad but also the side of the pad, thereby increasing the contact area between the connecting portion and the pad, reducing the contact resistance between the connecting portion and the pad, and improving the electrical connection performance between the connecting portion and the pad. In summary, this embodiment of the invention improves the performance of the filter.

[0010] In the filter provided by this embodiment of the invention, an acoustic transducer is located on the substrate of the transducer region; a connecting portion is located on the side of the acoustic transducer and connected to the acoustic transducer. The connecting portion also extends to the side and part of the top of the pad, exposing part of the top of the pad. This is because, in the filter formation step, the connecting portion and the acoustic transducer are formed after the pad, avoiding the influence of the pad formation process on the acoustic transducer and the connecting portion, thereby reducing the probability of damage to the acoustic transducer and the connecting portion. This helps to ensure the integrity, pattern quality, and film quality of the acoustic transducer and the connecting portion, and correspondingly ensures the effect of the acoustic transducer for acoustic-to-electric conversion and the connection effect between the connecting portion and the acoustic transducer. Moreover, the connecting portion not only contacts part of the top of the pad but also contacts the side of the pad, thereby increasing the contact area between the connecting portion and the pad, reducing the contact resistance between the connecting portion and the pad, and improving the electrical connection performance between the connecting portion and the pad. In summary, this embodiment of the invention improves the performance of the filter. Attached Figure Description

[0011] Figures 1 to 3 This is a schematic diagram of the structure corresponding to each step of a filter formation method; Figures 4 to 11 This is a schematic diagram of the structure corresponding to each step in one embodiment of the filter formation method of the present invention; Figure 12 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 current filters needs to be improved.

[0013] Specifically, the filter contains an acoustic transducer for sound-to-electric conversion and pads for electrical connection between the filter and external circuitry.

[0014] Traditional acoustic transducer fabrication methods typically involve creating voids using photoresist, then forming a metal layer on the photoresist and within the voids. A metal lift-off process is then used to remove the photoresist and excess metal layer, thus creating the acoustic transducer pattern. However, this fabrication method is prone to anomalies such as photoresist peeling and deformation, which can reduce the fabrication quality and pattern accuracy of the acoustic transducer.

[0015] Figures 1 to 3 This is a schematic diagram of the structure corresponding to each step in a filter fabrication method. (Reference) Figures 1 to 3 A method for forming a filter includes: refer to Figure 1A substrate 10 is provided, the substrate 10 including a transduction region 10a for forming an acoustic transducer and a connection region 10b for connecting a filter to an external circuit.

[0016] Continue to refer to Figure 1 An acoustic transducer 11 is formed on the substrate 10 of the transducer region 10a, and the acoustic transducer 11 also extends to be formed on the substrate 10 of the connection region 10b.

[0017] Reference Figure 1 and Figure 2 A protective layer 12 is formed on the substrate 10, the protective layer 12 covering the acoustic transducer 11 and exposing the acoustic transducer 11 of the connection region 10b.

[0018] refer to Figure 3 A pad 13 is formed on the acoustic transducer 11 of the connection area 10b exposed in the protective layer 12, and the pad 13 is electrically connected to the acoustic transducer 11.

[0019] In the method of forming the filter, in the step of forming pads 13 on the acoustic transducer 11 of the connection area 10b exposed by the protective layer 12, the acoustic transducer 11 is likely to be damaged, and the process of forming pads 13 is also more difficult.

[0020] Specifically, the step of forming pads 13 on the acoustic transducer 11 of the connection area 10b exposed by the protective layer 12 typically includes: forming a pad material layer (not shown) on the substrate 10 exposed by the protective layer 12, the pad material layer also extending to cover the protective layer 12; removing the pad material layer located in the transducer area 10a, and using the remaining portion of the pad material layer located in the connection area 10b as the pads 13.

[0021] The step of removing the pad material layer located in the transducer region 10a typically includes an etching process. This etching process is prone to causing accidental etching of the acoustic transducer 11, and removing the pad material layer in the transducer region 10a is a challenging process. Specifically, wet etching or dry etching is typically used to remove the pad material layer in the transducer region 10a. When using wet etching, it is necessary to consider whether the protective layer 12 provides sufficient protection for the acoustic transducer 11. If the protective layer 12 is thin or has defects, it may not provide adequate protection for the acoustic transducer 11, potentially damaging it and reducing its effectiveness in sound-to-electric conversion, resulting in poor filter performance. When using dry etching, the selective ratio of etching the pad material layer to etching the protective layer 12, as well as the morphology of the etched protective layer 12, must be considered, making the process quite challenging.

[0022] To address the aforementioned technical problem, embodiments of the present invention provide a method for forming a filter, comprising: providing a substrate, the substrate including a transducer region for performing acoustic-to-electric conversion and a connection region for connecting the filter to an external circuit; forming a pad on the substrate of the connection region; forming an acoustic transducer located on the substrate of the transducer region, and a connection portion located on the side of the acoustic transducer and connected to the acoustic transducer, the connection portion contacting the side and a portion of the top of the pad, and exposing a portion of the top of the pad.

[0023] The filter formation method provided in this embodiment of the invention involves forming a pad on the substrate of the connection region, followed by forming an acoustic transducer on the substrate of the transducer region and a connecting portion located on the side of the acoustic transducer and connected to it. The connecting portion contacts the side and part of the top of the pad, and exposes part of the top of the pad. Compared with the scheme of forming the pad after forming the acoustic transducer and the connecting portion, this embodiment of the invention avoids the impact of the pad formation process on the acoustic transducer and the connecting portion, thereby reducing the probability of damage to the acoustic transducer and the connecting portion. This helps to ensure the integrity, pattern quality, and film quality of the acoustic transducer and the connecting portion, and correspondingly ensures the effect of the acoustic transducer for acoustic-to-electric conversion and the connection effect between the connecting portion and the acoustic transducer. Moreover, the connecting portion contacts not only part of the top of the pad but also the side of the pad, thereby increasing the contact area between the connecting portion and the pad, reducing the contact resistance between the connecting portion and the pad, and improving the electrical connection performance between the connecting portion and the pad. In summary, this embodiment of the invention improves the performance of the filter.

[0024] 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. Figures 4 to 11 This is a schematic diagram of the structure corresponding to each step in one embodiment of the filter formation method of the present invention.

[0025] refer to Figures 4 to 5 , Figure 4 This is a top view. Figure 5 for Figure 4 A cross-sectional view along the A-A1 direction shows a substrate 100, which includes a transducer region 100a for performing acoustic-to-electric conversion and a connection region 100b for connecting a filter to an external circuit.

[0026] The substrate 100 is used to provide a process platform for the subsequent formation of filters.

[0027] Specifically, in this embodiment, the substrate 100 provides a process platform for the subsequent fabrication of a surface acoustic wave (SAW) filter. A SAW filter is a specialized filtering device 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, thereby achieving frequency selectivity. SAW filters have advantages such as high operating frequency, simple manufacturing process, low manufacturing cost, and high frequency response consistency; therefore, they are widely used in various electronic devices.

[0028] The transducer region 100a is used to subsequently form an acoustic transducer so as to realize the conversion between acoustic energy and electrical energy through the acoustic transducer.

[0029] The connection area 100b is used to form pads in the future, so as to realize the electrical connection between the filter and the external circuit through the pads.

[0030] In this embodiment, the substrate 100 is a piezoelectric substrate, enabling the subsequent surface acoustic wave filter structure to utilize the piezoelectric effect for filtering. In this embodiment, the material of the substrate 100 includes lithium niobate (LiNbO3), lithium tantalate (LiTaO3), quartz, or piezoelectric ceramics. As an example, the material of the substrate 100 is lithium tantalate.

[0031] In other embodiments, the substrate 100 may also be a piezoelectric on-insulator (POI), which can effectively confine acoustic wave energy, improve the electromechanical coupling coefficient, and enhance temperature stability. The substrate 100 comprises, from top to bottom, a piezoelectric material layer, a low-velocity layer, a high-velocity layer, and a high-resistivity silicon substrate. The piezoelectric material layer is made of lithium tantalate or lithium niobate; the low-velocity layer is made of silicon oxide, glass, silicon oxynitride, or tantalum oxide; and the high-velocity layer is made of polycrystalline silicon, silicon nitride, aluminum oxide, aluminum nitride, or silicon carbide. As an example, the piezoelectric material layer is made of lithium tantalate, the low-velocity layer is made of silicon oxide, and the high-velocity layer is made of polycrystalline silicon.

[0032] Reference Figures 4 to 7 , Figure 4 and Figure 6 This is a top view. Figure 5 and Figure 7 They are respectively Figure 4 , Figure 6 A cross-sectional view along the A-A1 direction shows that a pad 120 is formed on the substrate 100 of the connection area 100b.

[0033] The pad 120 is used to realize the electrical connection between the filter and the external circuit.

[0034] In this embodiment, an acoustic transducer is subsequently formed on the substrate 100 of the transducer region 100a, and a connecting portion is formed on the side of the acoustic transducer and connected to the acoustic transducer. The connecting portion contacts the side and part of the top of the pad 120 and exposes part of the top of the pad 120. Correspondingly, the pad 120 is electrically connected to the connecting portion, thereby realizing the electrical connection between the pad 120 and the acoustic transducer through the connecting portion to achieve acoustic-to-electric conversion.

[0035] The pad 120 is made of a conductive material. In this embodiment, the pad 120 is made of a metallic material, including one or more of Al, Cu, Ti, Ru, Mo, and Pt.

[0036] As an example, the pad 120 has a stacked structure, including an adhesion layer 21, a conductive layer 22 on the adhesion layer 21, and a capping layer 23 on the conductive layer 22.

[0037] The adhesion layer 21 is used to improve the adhesion between the pad 120 and the substrate 100, and also acts as a diffusion barrier between the conductive layer 22 and the substrate 100, reducing the probability of metal atoms in the conductive layer 22 diffusing into the substrate 100. As an example, the material of the adhesion layer 21 is Ti.

[0038] The conductive layer 22 serves as the primary current-conducting layer, providing a low-resistance current transmission path. As an example, the material of the conductive layer 22 is AlCu. Compared to pure Al, the addition of a small amount of Cu significantly improves the electromigration resistance of the conductive layer 22, thereby enhancing the long-term reliability of the device.

[0039] The capping layer 23 serves to protect the conductive layer 22, reducing the probability of oxidation on the surface of the conductive layer 22 and the probability of damage to the conductive layer 22 in subsequent processes, thereby improving the bonding quality of subsequent bonding on the surface of the pad 120. As an example, the material of the capping layer 23 is Ti.

[0040] Compared to the approach of forming pads after forming acoustic transducers and connectors, this embodiment forms pads 120 before forming acoustic transducers and connectors. This avoids the impact of the pad formation process on acoustic transducers and connectors, thereby reducing the probability of subsequent damage to acoustic transducers and connectors. Furthermore, since there is no need to consider the impact on acoustic transducers and connectors during the pad formation process, it also improves the process freedom and flexibility of forming pads 120, and reduces the process difficulty.

[0041] In the subsequent steps of forming an acoustic transducer located on the substrate 100 of the transducer region 100a and a connecting portion located on the side of the acoustic transducer and connected to the acoustic transducer, the connecting portion contacts the side and part of the top of the pad 120. Therefore, in the step of forming the pad 120, the included angle α between the side and bottom surface of the pad 120 should not be too large; otherwise, it is easy to reduce the coverage of the subsequent connecting portion on the side and top of the pad 120, thereby easily reducing the film quality of the connecting portion, easily increasing the probability of breakage and gaps in the connecting portion, and correspondingly easily reducing the electrical connection performance between the connecting portion and the pad 120. Therefore, in this embodiment, in the step of forming the pad 120, the included angle α between the side and bottom surface of the pad 120 is less than 90°.

[0042] In this embodiment, the step of forming the pad 120 includes: like Figure 4 and Figure 5 As shown, a pad material layer 110 is formed on the substrate 100.

[0043] The pad material layer 110 is used for subsequent pad formation.

[0044] In this embodiment, the pad material layer 110 is a stacked structure, which includes an adhesive material layer 111, a conductive material layer 112 located on the adhesive material layer 111, and a capping material layer 113 located on the conductive material layer 112.

[0045] As an example, the pad material layer 110 is formed using a sputtering process.

[0046] Combination Figure 4 and Figure 5 ,like Figure 6 and Figure 7 As shown, the pad material layer 110 located in the transducer region 100a is removed, and the remaining pad material layer 110 located in the connection region 100b is used as the pad 120.

[0047] Remove the pad material layer 110 located in the transducer region 100a to complete the patterning of the pad material layer 110 and form the pattern of the pad 120.

[0048] Specifically, in this embodiment, the step of removing the pad material layer 110 located in the transducer region 100a includes: forming a cover layer 115 on the pad material layer 110 located in the connection region 100b, the cover layer 115 exposing the pad material layer 110 located in the transducer region 100a; and removing the pad material layer 110 exposed by the cover layer 115 using the cover layer 115 as a mask.

[0049] The cover layer 115 is used as a mask for patterning the pad material layer 110.

[0050] In this embodiment, the material of the cover layer 115 includes photoresist. Accordingly, the process for forming the cover layer 115 includes a photolithography process.

[0051] In this embodiment, the process of removing the exposed pad material layer 110 of the cover layer 115 includes a wet etching process. In this embodiment, during the formation of the pad 120, there is no need to consider the influence of the process of forming the pad 120 on the metal layer and the connection. Therefore, the process of removing the exposed pad material layer 110 of the cover layer 115 has a high degree of selectivity and flexibility. By selecting the wet etching process, the etching selection is better and the etching rate is faster. It is also beneficial to make the cross-section of the formed pad 120 a trapezoidal structure, so that the included angle α between the side surface and the bottom surface of the pad 120 is less than 90°.

[0052] In other embodiments, based on the actual material and process requirements of the pad material layer 110, other etching processes can be used to remove the exposed pad material layer 110 of the cover layer 115. For example, a dry etching process, or a process combining dry and wet etching processes, can be used to remove the exposed pad material layer 110 of the cover layer 115.

[0053] In this embodiment, after removing the exposed pad material layer 110 of the cover layer 115, the method further includes removing the cover layer 115. As an example, a combination of dry etching and wet etching is used to remove the cover layer 115.

[0054] refer to Figures 8 to 11 , Figure 8 and Figure 10 This is a top view. Figure 9 and Figure 11 They are respectively Figure 8 , Figure 10A cross-sectional view along the A-A1 direction shows an acoustic transducer 150 located on a substrate 100 of the transducer region 100a, and a connecting portion 150a located on the side of the acoustic transducer 150 and connected to the acoustic transducer 150. The connecting portion 150a contacts the side and part of the top of the pad 120 and exposes part of the top of the pad 120.

[0055] The acoustic transducer 150 is used to realize the mutual conversion between electrical signals and acoustic signals, so that the surface acoustic wave filter can filter the signal.

[0056] After forming pads 120 on the substrate 100 of the connection region 100b, an acoustic transducer 150 is formed on the substrate 100 of the transducer region 100a, and a connection portion 150a is formed on the side of the acoustic transducer 150 and connected to the acoustic transducer 150. Compared with the scheme of forming pads after forming the acoustic transducer 150 and the connection portion, this embodiment avoids the process step of forming pads 120 from affecting the acoustic transducer 150 and the connection portion 150a, thereby reducing the probability of damage to the acoustic transducer 150 and the connection portion 150a, which is beneficial to ensuring the acoustic transducer 150. The integrity, pattern quality, and film quality of the acoustic transducer 150 and the connecting portion 150a respectively ensure the effectiveness of the acoustic transducer 150 in acoustic-to-electric conversion and the connection effect between the connecting portion 150a and the acoustic transducer 150. Moreover, the connecting portion 150a not only contacts part of the top of the pad 120, but also contacts the side of the pad 120, thereby increasing the contact area between the connecting portion 150a and the pad 120, reducing the contact resistance between the connecting portion 150a and the pad 120, and improving the electrical connection performance between the connecting portion 150a and the pad 120. In summary, this embodiment improves the performance of the filter.

[0057] As an example, the filter is a SAW filter, and the acoustic transducer 150 is an interdigital transducer (IDT). The interdigital transducer is used to convert between electrical and acoustic signals, thereby enabling the surface acoustic wave filter to filter the signal. In this embodiment, the interdigital transducer has an interdigital electrode structure. Specifically, in this embodiment, the interdigital transducer is a metal interdigital transducer.

[0058] Specifically, the basic structure of a SAW filter consists of a piezoelectric substrate and two acoustic transducers 150 fabricated on it, serving as the transmitting transducer and the receiving transducer, respectively. During operation, the transmitting transducer converts the radio frequency (RF) signal into surface acoustic waves (SAWs). The sound waves propagate along the substrate surface, and after a certain delay, the receiving transducer converts the acoustic signal into an electrical signal for output. The filtering function is achieved through the piezoelectric conversion processes of electro-acoustic and acoustic-electric conversion. The interdigital transducer is the core component of the SAW filter. By adjusting the electrode spacing of the interdigital transducer, the resonant frequency of the SAWs can be adjusted; by changing the shape of the interdigital transducer, the sound field distribution can be adjusted, thereby achieving precise control of the filter's frequency characteristics.

[0059] Therefore, the filter formation method of this embodiment reduces the probability of damage to the interdigital transducer and the connecting part 150a, and ensures the integrity, pattern quality and film quality of the interdigital transducer and the connecting part 150a. Accordingly, it ensures the effect of the interdigital transducer for acoustic-electric conversion and the connection effect between the connecting part 150a and the interdigital transducer, and significantly improves the performance of the filter.

[0060] In this embodiment, the material of the acoustic transducer 150 includes one or more of the following: Mo, Al, Pt, W, Au, Ti, Cr, Cu, Ni, and Ag.

[0061] As an example, the acoustic transducer 150 is a stacked structure, comprising a bottom layer (not shown), a functional layer (not shown), and a top layer (not shown) stacked sequentially along a direction perpendicular to the substrate 100.

[0062] The bottom layer is used to enhance the adhesion between the functional layer and the substrate 100 to prevent the functional layer from detaching during the manufacturing process. As an example, the material of the bottom layer is Ti.

[0063] The functional layer serves as the core functional layer of the acoustic transducer 150. In this embodiment, the material of the functional layer is W. W has a high density, and a high-density electrode can better confine sound wave energy to the surface of the substrate 100, increasing the electromechanical coupling coefficient (K²), which is beneficial for improving the bandwidth and frequency characteristics of the filter. In addition, W has high hardness and strong etching resistance, resulting in high pattern fidelity in dry etching, making it suitable for fabricating fine lines and patterns in the acoustic transducer 150.

[0064] The top layer serves as a protective layer to prevent oxidation of the functional layer surface and reduces the likelihood of damage to the functional layer during the process. Furthermore, the top layer helps provide a uniform surface morphology, which is beneficial for alignment accuracy during photolithography. In this embodiment, the material of the top layer is Ti.

[0065] The connecting portion 150a is used to realize the electrical connection between the acoustic transducer 150 and the pad 120, thereby realizing the electrical connection between the acoustic transducer 150 and the external circuit structure. Alternatively, the connecting portion 150a can also be used to realize the electrical connection between acoustic transducers 150 in different regions.

[0066] In this embodiment, the connecting portion 150a contacts the side and part of the top of the pad 120, thereby enabling an electrical connection with the pad 120. The connecting portion 150a exposes part of the top of the pad 120 so that subsequent bonding can be performed on the top of the pad 120 to achieve an electrical connection between the pad 120 and the external circuit.

[0067] In this embodiment, an acoustic transducer 150 located on the substrate 100 of the transducer region 100a and a connecting portion 150a located on the side of the acoustic transducer 150 and connected to the acoustic transducer 150 are formed in the same step. The connecting portion 150a and the acoustic transducer 150 are formed in the same step, which helps to reduce process steps and lower process costs. Therefore, in this embodiment, the connecting portion 150a is made of the same material as the acoustic transducer 150, and the connecting portion 150a has the same membrane structure as the acoustic transducer 150.

[0068] Accordingly, in this embodiment, the connecting part 150a and the acoustic transducer 150 are an integral structure, which improves the connection performance between the connecting part 150a and the acoustic transducer 150.

[0069] In this embodiment, the steps of forming the acoustic transducer 150 and the connecting portion 150a include: like Figures 8 to 9 As shown, a metal layer 130 is formed on the substrate 100, the metal layer 130 covering the top and sides of the pad 120.

[0070] The metal layer 130 is used to subsequently form the acoustic transducer 150.

[0071] In this embodiment, the metal layer 130 is also used to subsequently form the connecting portion 150a.

[0072] In this embodiment, the metal layer 130 covers the top and sides of the pad 120, as well as the exposed substrate 100 of the pad 120. The angle α between the side and bottom surfaces of the pad 120 is less than 90°, which facilitates the formation of the metal layer 130 on the sides and top of the pad 120, reduces the difficulty of covering the sides and top of the pad 120, and thus improves the film consistency, uniformity, and quality of the metal layer 130.

[0073] In this embodiment, the metal layer 130 has a stacked structure, including a bottom film, a functional film, and a top film stacked sequentially.

[0074] In this embodiment, the process of forming the metal layer 130 on the substrate 100 includes a sputtering process. The film formed by the sputtering process has high density, strong adhesion, controllable alloy composition, good composition uniformity, and good step coverage, which is beneficial to improving the adhesion of the metal layer 130 on the top and sides of the pad 120 and on the substrate 100, thereby improving the film consistency and formation quality of the metal layer 130.

[0075] like Figures 8 to 9 As shown, a patterned layer 140 is formed on the metal layer 130, and a patterned opening 40 is formed in the patterned layer 140. The patterned opening 40 exposes a portion of the top of the metal layer 130 located in the transducer region 100a and a portion of the top of the metal layer 130 located on the pad 120.

[0076] The pattern layer 140 is used as a mask for subsequent patterning of the metal layer 130 to define the patterns of the acoustic transducer 150 and the connector 150a.

[0077] In this embodiment, the metal layer 130 exposed by the patterned opening 40 is the part that needs to be removed in subsequent processes.

[0078] In this embodiment, the material of the pattern layer 140 is photoresist. Accordingly, the pattern layer 140 and the pattern opening 40 are formed using a photolithography process.

[0079] like Figures 10 to 11 As shown, using the pattern layer 140 as a mask, the metal layer 130 at the bottom of the pattern opening 40 is removed, and the remaining metal layer 130 located in the transducer region 100a is used as the acoustic transducer 150. The remaining metal layer 130 located on the side of the transducer is used as the connecting part 150a.

[0080] In this embodiment, the connection portion 150a is formed using the process steps for forming the acoustic transducer 150, which helps to further reduce process steps and lower process costs.

[0081] In this embodiment, the process of removing the metal layer 130 at the bottom of the patterned opening 40 includes a dry etching process. The dry etching process offers high etching precision and good control over the etching profile, which is beneficial for improving the pattern precision and quality of the acoustic transducer 150 and the connecting portion 150a.

[0082] In this embodiment, after removing the metal layer 130 at the bottom of the patterned opening 40 using the patterned layer 140 as a mask, the process further includes removing the patterned layer 140. As an example, a combination of dry etching and wet etching is used to remove the patterned layer 140.

[0083] Accordingly, the present invention also provides a filter. Figure 12 This is a schematic diagram of the structure of an embodiment of the filter of the present invention. Specifically, in conjunction with... Figure 10 A top view of an embodiment of the filter of the present invention is also shown. Figure 12 for Figure 10 A cross-sectional view along the A-A1 direction. The filter of this embodiment will be described in detail below with reference to the accompanying drawings.

[0084] Reference Figure 10 and Figure 12 The filter includes: a substrate 100, the substrate 100 including a transducer region 100a for performing acoustic-to-electric conversion and a connection region 100b for connecting the filter to an external circuit; a pad 120 located on the substrate 100 of the connection region 100b; an acoustic transducer 150 located on the substrate 100 of the transducer region 100a; and a connection portion 150a located on the side of the acoustic transducer 150 and connected to the acoustic transducer 150, the connection portion 150a also extending on the side and part of the top of the pad 120, and exposing part of the top of the pad 120.

[0085] In the filter provided in this embodiment, the acoustic transducer 150 is located on the substrate 100 of the transduction region 100a; the connecting portion 150a is located on the side of the acoustic transducer 150 and connected to the acoustic transducer 150. The connecting portion 150a also extends to the side and part of the top of the pad 120, and exposes part of the top of the pad 120. This is because, in the filter formation step, the connecting portion 150a and the acoustic transducer 150 are formed after the pad 120, avoiding the influence of the pad 120 formation process on the acoustic transducer 150 and the connecting portion 150a, and correspondingly reducing the impact on the acoustic transducer 150 and the connecting portion 150a. The reduced probability of damage helps ensure the integrity, pattern quality, and diaphragm quality of the acoustic transducer 150 and the connector 150a, thereby guaranteeing the acoustic transducer 150's effectiveness in acoustic-to-electric conversion and the connection between the connector 150a and the acoustic transducer 150. Furthermore, the connector 150a contacts not only part of the top of the pad 120 but also the side of the pad 120, increasing the contact area between the connector 150a and the pad 120, reducing the contact resistance between them, and improving the electrical connection performance between the connector 150a and the pad 120. In summary, this embodiment of the invention improves the filter's performance.

[0086] The substrate 100 is used to provide a process platform for the formation of the filter.

[0087] Specifically, in this embodiment, the substrate 100 provides a process platform for forming a surface acoustic wave (SAW) filter. A SAW filter is a specialized filtering device made using the piezoelectric effect and the physical characteristics of surface acoustic wave propagation. In a SAW filter, the signal undergoes two conversions—electroacoustic and electrical—to achieve frequency selectivity. SAW filters have advantages such as high operating frequency, simple manufacturing process, low manufacturing cost, and high frequency response consistency; therefore, they are widely used in various electronic devices.

[0088] The transducer region 100a is used to form an acoustic transducer 150 so as to realize the conversion between acoustic energy and electrical energy through the acoustic transducer 150.

[0089] The connection area 100b is used to form a pad 120 to realize the electrical connection between the filter and the external circuit through the pad 120.

[0090] In this embodiment, the substrate 100 is a piezoelectric substrate, enabling the surface acoustic wave filter structure to utilize the piezoelectric effect for filtering. In this embodiment, the material of the substrate 100 includes lithium niobate (LiNbO3), lithium tantalate (LiTaO3), quartz, or piezoelectric ceramics. As an example, the material of the substrate 100 is lithium tantalate.

[0091] In other embodiments, the substrate 100 may also be a piezoelectric on-insulator (POI), which can effectively confine acoustic wave energy, improve the electromechanical coupling coefficient, and enhance temperature stability. The substrate 100 comprises, from top to bottom, a piezoelectric material layer, a low-velocity layer, a high-velocity layer, and a high-resistivity silicon substrate. The piezoelectric material layer is made of lithium tantalate or lithium niobate; the low-velocity layer is made of silicon oxide, glass, silicon oxynitride, or tantalum oxide; and the high-velocity layer is made of polycrystalline silicon, silicon nitride, aluminum oxide, aluminum nitride, or silicon carbide. As an example, the piezoelectric material layer is made of lithium tantalate, the low-velocity layer is made of silicon oxide, and the high-velocity layer is made of polycrystalline silicon.

[0092] The pad 120 is used to realize the electrical connection between the filter and the external circuit.

[0093] In this embodiment, the acoustic transducer 150 is located on the substrate 100 of the transducer region 100a, and the connecting part 150a is located on the side of the acoustic transducer 150 and connected to the acoustic transducer 150. The connecting part 150a contacts the side and part of the top of the pad 120 and exposes part of the top of the pad 120. Correspondingly, the pad 120 and the connecting part 150a are electrically connected, thereby realizing the electrical connection between the pad 120 and the acoustic transducer 150 through the connecting part 150a, so as to realize the sound-to-electric conversion.

[0094] The pad 120 is made of a conductive material. In this embodiment, the pad 120 is made of a metallic material, including one or more of Al, Cu, Ti, Ru, Mo, and Pt.

[0095] As an example, the pad 120 has a stacked structure, including an adhesion layer 21, a conductive layer 22 on the adhesion layer 21, and a capping layer 23 on the conductive layer 22.

[0096] The adhesion layer 21 is used to improve the adhesion between the pad 120 and the substrate 100, and also acts as a diffusion barrier between the conductive layer 22 and the substrate 100, reducing the probability of metal atoms in the conductive layer 22 diffusing into the substrate 100. As an example, the material of the adhesion layer 21 is Ti.

[0097] The conductive layer 22 serves as the primary current-conducting layer, providing a low-resistance current transmission path. As an example, the material of the conductive layer 22 is AlCu. Compared to pure Al, the addition of a small amount of Cu significantly improves electromigration resistance and enhances the long-term reliability of the device.

[0098] The capping layer 23 serves to protect the conductive layer 22, reducing the probability of oxidation on the surface of the conductive layer 22 and the probability of damage to the conductive layer 22 in subsequent processes, thereby improving the bonding quality of bonding on the surface of the pad 120. As an example, the material of the capping layer 23 is Ti.

[0099] In this embodiment, during the filter formation step, the pad 120 is formed before the acoustic transducer and the connector 150a are formed. This avoids the impact of the pad 120 formation process on the acoustic transducer 150 and the connector 150a, thereby reducing the probability of damage to the acoustic transducer 150 and the connector 150a. Furthermore, since there is no need to consider the impact on the acoustic transducer 150 and the connector 150a during the pad 120 formation step, it also helps to improve the freedom and flexibility of the pad 120 formation process, reducing the process difficulty and improving the formation quality of the pad 120.

[0100] In this embodiment, the connecting portion 150a contacts the side and part of the top of the pad 120. The angle α between the side and bottom of the pad 120 should not be too large; otherwise, the coverage of the connecting portion 150a on the side and top of the pad 120 will be reduced, which will in turn reduce the film quality of the connecting portion 150a and increase the probability of breakage or gaps in the connecting portion 150a, thereby reducing the electrical connection performance between the connecting portion 150a and the pad 120. Therefore, in this embodiment, the angle α between the side and bottom of the pad 120 is less than 90°.

[0101] The acoustic transducer 150 is used to realize the mutual conversion between electrical signals and acoustic signals, so that the surface acoustic wave filter can filter the signal.

[0102] In this embodiment, the acoustic transducer 150 is located on the substrate 100 of the transduction region 100a; the connecting portion 150a is located on the side of the acoustic transducer 150 and connected to the acoustic transducer 150. The connecting portion 150a also extends to the side and part of the top of the pad 120, and exposes part of the top of the pad 120. This is because in the filter formation step, the connecting portion 150a and the acoustic transducer 150 are formed after the pad 120, avoiding the influence of the pad 120 formation process on the acoustic transducer 150 and the connecting portion 150a, thereby reducing the probability of damage to the acoustic transducer 150 and the connecting portion 150a. This helps to ensure the integrity, pattern quality and film quality of the acoustic transducer 150 and the connecting portion 150a, and correspondingly ensures the effect of the acoustic transducer 150 in acoustic-electric conversion and the connection effect between the connecting portion 150a and the acoustic transducer 150.

[0103] As an example, the filter is a SAW filter, and the acoustic transducer 150 is an interdigital transducer. The interdigital transducer is used to achieve the mutual conversion between electrical signals and acoustic signals, thereby enabling the surface acoustic wave filter to filter the signals. In this embodiment, the interdigital transducer correspondingly has an interdigital electrode structure. Specifically, in this embodiment, the interdigital transducer is a metal interdigital transducer.

[0104] Specifically, the basic structure of a SAW filter consists of a piezoelectric substrate and two acoustic transducers 150 fabricated on it, serving as the transmitting transducer and the receiving transducer, respectively. During operation, the transmitting transducer converts the radio frequency signal into surface acoustic waves (SAWs). The sound waves propagate along the substrate surface, and after a certain delay, the receiving transducer converts the acoustic signal into an electrical signal for output. The filtering function is achieved through the piezoelectric conversion processes of electro-acoustic and acoustic-electric conversion. The interdigital transducer is the core component of the SAW filter. By adjusting the electrode spacing of the interdigital transducer, the resonant frequency of the SAWs can be adjusted; by changing the shape of the interdigital transducer, the sound field distribution can be adjusted, thereby achieving precise control of the filter's frequency characteristics.

[0105] Therefore, this embodiment reduces the probability of damage to the interdigital transducer and the connecting part 150a, ensuring the integrity, pattern quality, and film quality of the interdigital transducer and the connecting part 150a. Consequently, it ensures the effectiveness of the interdigital transducer in acoustic-electric conversion and the connection effect between the connecting part 150a and the interdigital transducer, significantly improving the performance of the filter.

[0106] In this embodiment, the material of the acoustic transducer 150 includes one or more of the following: Mo, Al, Pt, W, Au, Ti, Cr, Cu, Ni, and Ag.

[0107] As an example, the acoustic transducer 150 is a stacked structure, comprising a bottom layer (not shown), a functional layer (not shown), and a top layer (not shown) stacked sequentially along a direction perpendicular to the substrate 100.

[0108] The bottom layer is used to enhance the adhesion between the functional layer and the substrate 100 to prevent the functional layer from detaching during the manufacturing process. As an example, the material of the bottom layer is Ti.

[0109] The functional layer serves as the core functional layer of the acoustic transducer 150. In this embodiment, the material of the functional layer is W. W has a high density, and a high-density electrode can better confine sound wave energy to the surface of the substrate 100, increasing the electromechanical coupling coefficient (K²), which is beneficial for improving the bandwidth and frequency characteristics of the filter. In addition, W has high hardness and strong etching resistance, resulting in high pattern fidelity in dry etching, making it suitable for fabricating fine lines and patterns in the acoustic transducer 150.

[0110] The top layer serves as a protective layer to prevent oxidation of the functional layer surface and reduces the likelihood of damage to the functional layer during the process. Furthermore, the top layer helps provide a uniform surface morphology, which is beneficial for alignment accuracy during photolithography. In this embodiment, the material of the top layer is Ti.

[0111] The connecting portion 150a is used to realize the electrical connection between the acoustic transducer 150 and the pad 120, thereby realizing the electrical connection between the acoustic transducer 150 and the external circuit structure. Alternatively, the connecting portion 150a can also be used to realize the electrical connection between acoustic transducers 150 in different regions.

[0112] In this embodiment, the connecting portion 150a not only contacts the top part of the pad 120, but also contacts the side of the pad 120, thereby increasing the contact area between the connecting portion 150a and the pad 120, reducing the contact resistance between the connecting portion 150a and the pad 120, and improving the electrical connection performance between the connecting portion 150a and the pad 120.

[0113] In this embodiment, the connecting portion 150a contacts the side and part of the top of the pad 120, thereby enabling an electrical connection with the pad 120. The connecting portion 150a exposes part of the top of the pad 120 for bonding on the top of the pad 120, thereby enabling an electrical connection between the pad 120 and an external circuit.

[0114] In this embodiment, the connecting portion 150a and the acoustic transducer 150 are formed in the same step during the filter formation process, which helps to reduce process steps and lower process costs. Therefore, in this embodiment, the connecting portion 150a and the acoustic transducer 150 are made of the same material, and the connecting portion 150a and the acoustic transducer 150 have the same membrane structure.

[0115] Accordingly, in this embodiment, the connecting part 150a and the acoustic transducer 150 are an integral structure, which improves the connection performance between the connecting part 150a and the acoustic transducer 150.

[0116] The filter provided in this embodiment of the invention can be formed by the filter forming method of this embodiment of the invention, or by other filter forming methods.

[0117] Accordingly, embodiments of the present invention also provide an electronic device, which includes the filter provided in the embodiments of the present invention.

[0118] The filter can be integrated into various electronic devices. As the foregoing analysis shows, the filter has high performance, which in turn enables high-performance electronic devices.

[0119] Electronic devices may include personal computers, smartphones and other mobile terminals, media players, navigation devices, video game devices, game controllers, tablet computers, wearable devices, security access control systems, POS terminals, medical devices, flight simulators, etc.

[0120] 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 transducer region for performing acoustic-to-electric conversion and a connection region for connecting a filter to an external circuit; A pad is formed on the substrate of the connection area; An acoustic transducer is formed on the substrate of the transducer region, and a connecting portion is formed on the side of the acoustic transducer and connected to the acoustic transducer. The connecting portion contacts the side and part of the top of the pad and exposes part of the top of the pad.

2. The method for forming a filter as described in claim 1, characterized in that, In the step of forming the pad, the angle between the side surface and the bottom surface of the pad is less than 90°.

3. The method for forming a filter as described in claim 1, characterized in that, In the same step, an acoustic transducer is formed on the substrate of the transducer region, and a connecting portion is formed on the side of the acoustic transducer and connected to the acoustic transducer.

4. The method for forming a filter as described in claim 3, characterized in that, The steps of forming the acoustic transducer and the connector include: forming a metal layer on the substrate, the metal layer covering the top and sides of the pad; A patterned layer is formed on the metal layer, and a patterned opening is formed in the patterned layer, the patterned opening exposing a portion of the top of the metal layer located in the transducer region and a portion of the metal layer located on top of the pad portion; Using the patterned layer as a mask, the metal layer at the bottom of the patterned opening is removed, and the remaining metal layer in the transducer area is used as the acoustic transducer. The remaining metal layer on the side of the transducer is used as the connecting part.

5. The method for forming a filter as described in claim 4, characterized in that, The process of forming a metal layer on the substrate includes a sputtering process.

6. The method for forming a filter as described in claim 4, characterized in that, The process for removing the metal layer at the bottom of the patterned opening includes a dry etching process.

7. The method for forming a filter as described in claim 1, characterized in that, The step of forming the pads includes: forming a pad material layer on the substrate; Remove the pad material layer located in the transducer region, and use the remaining pad material layer located in the connection region as the pad.

8. The method for forming a filter as described in claim 7, characterized in that, The step of removing the pad material layer located in the transducer region includes: forming a cover layer on the pad material layer located in the connection region, the cover layer exposing the pad material layer located in the transducer region; and removing the exposed pad material layer using the cover layer as a mask.

9. The method for forming a filter as described in claim 7 or 8, characterized in that, The process for removing the pad material layer located in the transducer region includes a wet etching process.

10. A filter, characterized in that, include: The substrate includes a transducer region for performing acoustic-to-electric conversion and a connection region for connecting the filter to an external circuit. The pads are located on the substrate of the connection area; An acoustic transducer is located on the substrate of the transducer region; A connecting portion is located on the side of the acoustic transducer and connected to the acoustic transducer. The connecting portion also extends on the side and part of the top of the pad, and exposes part of the top of the pad.

11. The filter as claimed in claim 10, characterized in that, The angle between the side and bottom of the pad is less than 90°.

12. The filter as described in claim 10, characterized in that, The connecting part is made of the same material as the acoustic transducer, and the connecting part has the same membrane structure as the acoustic transducer.

13. The filter as described in claim 10 or 12, characterized in that, The acoustic transducer is made of one or more of the following materials: Mo, Al, Pt, W, Au, Ti, Cr, Cu, Ni, and Ag.

14. The filter as described in claim 10, characterized in that, The pad material includes one or more of Al, Cu, Ti, Ru, Mo, and Pt.

15. The filter as claimed in claim 10, characterized in that, The substrate includes a piezoelectric substrate or a piezoelectric substrate on an insulator.

16. An electronic device, characterized in that, include: The filter as described in any one of claims 10 to 15.

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