Surface acoustic wave filter structure, manufacturing method thereof and electronic equipment

Abstract

A surface acoustic wave filter structure and a manufacturing method thereof, and an electronic device, the surface acoustic wave filter structure comprising: a substrate, the substrate comprising a piezoelectric oscillation effective area and a peripheral area surrounding the piezoelectric oscillation effective area; the acoustic transducer is positioned on the substrate of the piezoelectric oscillation effective area; a first protective layer covering the acoustic transducer; the connecting layer is located on the substrate in the peripheral area, the connecting layer comprises a first interconnection layer and a sealing layer surrounding the periphery of the first interconnection layer, and the first interconnection layer is electrically connected with an acoustic transducer; the packaging layer is located at the top of the first interconnection layer, a cavity is defined by the packaging layer, the side wall of the first interconnection layer and the substrate, and the cavity is used for containing the acoustic transducer. According to the technical scheme in the embodiment of the invention, the performance of the surface acoustic wave filter structure can be improved.

Description

Technical Field

[0001] Embodiments of the present invention relate to the field of semiconductors, and in particular, to a surface acoustic wave filter structure, a manufacturing method thereof, and an electronic device. Background Art

[0002] With the rapid development of wireless communication technology, the 5G communication protocol is becoming increasingly mature, and the market has put forward more stringent standards for the performance of radio frequency filters in all aspects. With the development of wireless communication technology, traditional single-band and single-mode devices can no longer meet the diverse requirements of communication systems. Currently, communication systems are becoming more and more multi-band, which requires communication terminals to be able to receive each frequency band to meet the requirements of different communication service providers and different regions.

[0003] A radio frequency filter, also known as a radio frequency interference filter, is a filter circuit composed of capacitors, inductors, and resistors, and is mainly responsible for filtering the signal frequency in a communication channel. Specifically, the filter allows signals that meet specific frequencies to pass through, while suppressing other unwanted frequency signals, and can solve the signal interference problems generated between different frequency bands and communication systems, and is widely used in the radio frequency signal processing systems of base stations and terminal devices.

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

[0005] The problem solved by the embodiments of the present invention is to provide a surface acoustic wave filter structure, a manufacturing method thereof, and an electronic device, which are beneficial to improving the performance of the surface acoustic wave filter structure.

[0006] To solve the above problems, embodiments of the present invention provide a surface acoustic wave filter structure, including:

[0007] A substrate, the substrate includes a piezoelectric oscillation effective area and an outer area surrounding the piezoelectric oscillation effective area;

[0008] An acoustic transducer, located on the substrate in the piezoelectric oscillation effective area;

[0009] A connection layer, located on the substrate in the outer area, the connection layer includes a first interconnection layer and a sealing layer surrounding the periphery of the first interconnection layer, and the first interconnection layer is electrically connected to the acoustic transducer;

[0010] A first protective layer, located on the acoustic transducer;

[0011] A packaging layer, located on the top of the first interconnection layer, and the packaging layer, the side wall of the first interconnection layer, and the substrate enclose a cavity, and the cavity is used to accommodate the acoustic transducer and the first protective layer.

[0012] Accordingly, an embodiment of the present invention further provides a manufacturing method of a surface acoustic wave filter structure, including:

[0013] Providing a substrate, the substrate including a piezoelectric oscillation effective region and a peripheral region surrounding the piezoelectric oscillation effective region;

[0014] Forming an acoustic transducer on the substrate of the piezoelectric oscillation effective region;

[0015] Forming a connection layer on the substrate of the peripheral region, the connection layer including a first interconnection layer and a sealing layer surrounding the periphery of the first interconnection layer, the first interconnection layer being electrically connected to the acoustic transducer;

[0016] Forming a first protective layer covering the acoustic transducer;

[0017] Forming a packaging layer on the connection layer, the packaging layer, the sealing layer and the substrate enclosing a cavity for accommodating the acoustic transducer.

[0018] Accordingly, an embodiment of the present invention further provides an electronic device, including the surface acoustic wave filter structure as described in any one of the above.

[0019] Compared with the prior art, the technical solution of the embodiment of the present invention has the following advantages:

[0020] An embodiment of the present invention provides a surface acoustic wave filter structure, including: a substrate, the substrate including a piezoelectric oscillation effective region and a peripheral region surrounding the piezoelectric oscillation effective region; an acoustic transducer located on the substrate of the piezoelectric oscillation effective region; a connection layer located on the substrate of the peripheral region, the connection layer including a first interconnection layer and a sealing layer surrounding the periphery of the first interconnection layer, the first interconnection layer being electrically connected to the acoustic transducer; a first protective layer covering the acoustic transducer; a packaging layer located on the top of the first interconnection layer, the packaging layer and the side wall of the first interconnection layer and the substrate enclosing a cavity for accommodating the acoustic transducer.

[0021] The surface acoustic wave filter structure in the embodiment of the present invention includes a first protective layer covering the acoustic transducer, and the first protective layer can protect the acoustic transducer during the subsequent formation of the packaging layer, avoiding the corrosion of the acoustic transducer caused by the acid or alkali developer during the formation of the packaging layer, and correspondingly helping to improve the performance of the surface acoustic wave filter structure. Description of the Drawings

[0022] Figure 1 is a structural schematic diagram of an existing surface acoustic wave filter structure;

[0023] Figure 2 and Figure 3FIG. 0 is a schematic cross-sectional structure diagram of an embodiment of a surface acoustic wave filter structure provided by the technical solution of the present invention along the first direction and the second direction respectively;

[0024] Figures 4 to 11 FIG. 4 is a schematic diagram of an intermediate structure formed by each step of a manufacturing method of a surface acoustic wave filter structure provided by the technical solution of the present invention;

[0025] FIG. 12 is a schematic diagram for comparing performance parameters of a surface acoustic wave filter structure in an embodiment of the present invention with those of an existing surface acoustic wave filter structure;

[0026] FIG. 13 is a schematic diagram of test results of high-accelerated temperature, humidity and bias tests on a surface acoustic wave filter structure provided by the technical solution of the present invention. Detailed Embodiments

[0027] As can be seen from the background art, the performance of the current surface acoustic wave filter structure still needs to be improved. Now, in combination with Figure 1 FIG. 21 showing a schematic structural diagram of a surface acoustic wave filter structure, the reasons for the poor performance of the surface acoustic wave filter structure are analyzed.

[0028] Referring to Figure 1 , a surface acoustic wave filter structure includes: a substrate 10; the substrate 10 includes a piezoelectric oscillation effective region 10A and an outer region 10B surrounding the piezoelectric oscillation effective region 10A; an acoustic transducer 11 located on the substrate 10 in the piezoelectric oscillation effective region 10A; an interconnection layer 12 located on top of the substrate 10 in the outer region 10B; a sealing layer 13 located on top of the substrate 10 outside the interconnection layer 12; a packaging layer 14 located on top of the interconnection layer 12 and the sealing layer 13, and a cavity 15 is formed by the packaging layer 14, the side wall of the interconnection layer 12 and the substrate 10, and the cavity 15 is used to accommodate the acoustic transducer 11; an interconnection structure 16 located in the packaging layer 14 and electrically connected to the interconnection layer 12.

[0029] In the above surface acoustic wave filter structure, during the subsequent formation of the packaging layer 14, the acoustic transducer 11 is exposed in the cavity 15, and the acid-containing or alkali-containing developer used in the formation process of the packaging layer 14 will corrode the acoustic transducer 11, causing damage to the acoustic transducer 11 and reducing the performance of the formed surface acoustic wave filter structure.

[0030] To solve the above technical problems, an embodiment of the present invention provides a surface acoustic wave filter structure, including: a substrate, the substrate includes a piezoelectric oscillation effective region and a peripheral region surrounding the piezoelectric oscillation effective region; an acoustic transducer, located on the substrate of the piezoelectric oscillation effective region; a connection layer, located on the substrate of the peripheral region, the connection layer includes a first interconnection layer and a sealing layer surrounding the periphery of the first interconnection layer, the first interconnection layer is electrically connected to the acoustic transducer; a first protective layer, covering the acoustic transducer; a packaging layer, located on the top of the first interconnection layer, the packaging layer and the side wall of the first interconnection layer and the substrate enclose a cavity, and the cavity is used to accommodate the acoustic transducer.

[0031] In the surface acoustic wave filter structure of the embodiment of the present invention, there is a first protective layer covering the acoustic transducer. The first protective layer can protect the acoustic transducer during the subsequent formation of the packaging layer, and avoid the corrosion of the acoustic transducer caused by the acid or alkali developer during the formation of the packaging layer, which correspondingly helps to improve the performance of the surface acoustic wave filter structure.

[0032] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following will describe the specific embodiments of the present invention in detail with reference to the accompanying drawings.

[0033] Figure 2 and Figure 3 are schematic cross-sectional structure diagrams of an embodiment of the surface acoustic wave filter structure provided by the technical solution of the present invention along the first direction and the second direction respectively.

[0034] With reference to Figure 2 and Figure 3 , a surface acoustic wave filter structure includes: a substrate 100, the substrate 100 includes a piezoelectric oscillation effective region I and a peripheral region II surrounding the piezoelectric oscillation effective region I; an acoustic transducer 200, located on the substrate 100 of the piezoelectric oscillation effective region I; a connection layer 110, located on the substrate 100 of the peripheral region II, the connection layer 110 includes a first interconnection layer 111 and a sealing layer 112 surrounding the periphery of the first interconnection layer 111, the first interconnection layer 111 is electrically connected to the acoustic transducer 200; a first protective layer 120, covering the acoustic transducer 200; a packaging layer 140, located on the top of the first interconnection layer 111, the packaging layer 140 and the side wall of the first interconnection layer 111 and the substrate 100 enclose a cavity 105, and the cavity 105 is used to accommodate the acoustic transducer 200.

[0035] The substrate 100 is used to provide a process platform for forming the surface acoustic wave filter structure.

[0036] In this embodiment, the substrate 100 is a wafer-level substrate. By fabricating the surface acoustic wave filter structure on the wafer-level substrate, the process cost can be reduced and mass production can be achieved, which is beneficial to improving the reliability of the surface acoustic wave filter structure and the manufacturing efficiency.

[0037] The substrate 100 includes a piezoelectric oscillation active region I, and the piezoelectric oscillation active region I is the working region where the surface acoustic wave filter structure realizes the filtering function. In this embodiment, since the substrate 100 is a wafer-level substrate, the substrate 100 includes a plurality of isolated piezoelectric oscillation active regions I.

[0038] In this embodiment, the formed surface acoustic wave filter structure is taken as an example of a surface acoustic wave (SAW) filter structure for illustration.

[0039] The SAW filter structure is a dedicated filtering device made by utilizing the piezoelectric effect and the physical characteristics of surface acoustic wave propagation. In the SAW filter structure, the signal undergoes two conversions of electric-acoustic-electric, thereby realizing the frequency selection characteristic. The SAW filter structure has the advantages of high operating frequency, simple manufacturing process, low manufacturing cost, high frequency characteristic consistency, etc., and thus is widely used in various electronic devices.

[0040] Correspondingly, the substrate 100 is a piezoelectric substrate, so that the subsequent surface acoustic wave filter structure can utilize the piezoelectric effect for filtering processing. In this embodiment, the material of the substrate 100 includes at least one of quartz, lithium tantalate, lanthanum gallium silicate, lanthanum gallium tantalate, lanthanum gallium niobate, lead zirconate titanate, cadmium sulfide, berlinite, lithium iodate, lithium tetraborate, and bismuth germanium oxide. In some embodiments, the piezoelectric substrate includes a piezoelectric crystal layer, and the piezoelectric crystal layer may include a thickness greater than the penetration depth of the Love wave on the non-piezoelectric substrate.

[0041] The acoustic transducer 200 is used to realize the mutual conversion between the electrical signal and the acoustic signal, so that the surface acoustic wave filter structure can filter the signal. Specifically, the acoustic transducer 200 is an acoustic transducer with a piezoelectric structure.

[0042] In this embodiment, the formed filter structure is a SAW filter structure. Correspondingly, the acoustic transducer 200 is an Inter-digital Transducer (IDT). The IDT includes two sets of interdigital electrodes with energy conversion functions, namely an input interdigital transducer and an output interdigital transducer. Among them, when the input interdigital transducer receives an electrical signal, the surface of the piezoelectric substrate will vibrate and excite an acoustic wave with the same frequency as the applied signal. The acoustic wave propagates along the surface direction of the piezoelectric substrate, and a part of the acoustic wave is transmitted to the output interdigital transducer. The output interdigital transducer converts mechanical vibration into an electrical signal and outputs it through the output interdigital transducer.

[0043] The material of the interdigital electrodes includes one or more of molybdenum (Mo), aluminum (Al), platinum (Pt), tungsten (W), gold (Au), nickel (Ni), and silver (Ag). Specifically, a metal film is deposited on the substrate 100, and the metal film is patterned through photolithography and etching processes to form the acoustic transducer 200. In this embodiment, the interdigital electrode is an interdigital aluminum electrode.

[0044] The first interconnect layer 111 is used as the input / output (I / O) terminal of the acoustic transducer 200 to realize the electrical connection between the acoustic transducer 200 and the external circuit structure; the sealing layer 112 is used to protect the first interconnect layer 111 and the acoustic transducer 200 located therein from the side, preventing water vapor from entering the piezoelectric oscillation effective region I, which is beneficial to reducing the probability of oxidation and corrosion of the acoustic transducer 200 in the piezoelectric oscillation effective region I. Correspondingly, the presence of the sealing layer 112 also reduces the probability of oxidation and corrosion of the first interconnect layer 111.

[0045] In this embodiment, the first interconnect layer 111 and the sealing layer 112 are made of the same material.

[0046] Specifically, the materials of the first interconnect layer 111 and the sealing layer 112 include one or more of titanium (Ti), copper (Cu), aluminum (Al), and nickel (Ni). Specifically, titanium, copper, aluminum, and nickel are all conductive materials, which can enable the acoustic transducer 200 in the piezoelectric oscillation effective region I to be electrically connected to the external circuit structure through the first interconnect layer 111. As an example, the material of the first interconnect layer 111 is aluminum.

[0047] It should be noted that the thickness of the first interconnection layer 111 should not be too large or too small. If the thickness of the first interconnection layer 111 is too large, the process difficulty and process time for patterning the first interconnection layer 111 are increased, and the formation efficiency of the first interconnection layer 111 is reduced. If the thickness of the first interconnection layer 111 is too small, it is likely that the effective height of the cavity 105 formed on the piezoelectric oscillation effective region I subsequently is too small. Correspondingly, after the encapsulation layer 140 deforms under external force extrusion, the probability of contact between the encapsulation layer 140 and the acoustic transducer 200 is increased, resulting in a reduction in the reliability of the surface acoustic wave filter structure. Therefore, in this embodiment, the thickness of the first interconnection layer 111 is 2 μm to 30 μm.

[0048] In this embodiment, the material of the sealing layer 112 is the same as that of the first interconnection layer 111. Correspondingly, the material of the sealing layer 112 includes one or more of titanium, copper, aluminum, and nickel.

[0049] The material of the sealing layer 112 is a metal. Due to the close arrangement of metal atoms, the sealing layer 112 has good denseness, thus being able to play a good sealing role. The sealing layer 112 and the first interconnection layer 111 are made of the same material, enabling the sealing layer 112 and the first interconnection layer 111 to be etched in the same step, which is beneficial to simplifying the formation process of the filter and improving the efficiency.

[0050] In this embodiment, the thickness of the sealing layer 112 is basically the same as that of the first interconnection layer 111. Specifically, the thickness of the sealing layer 112 is 2 μm to 30 μm. The height difference between the sealing layer 112 and the first interconnection layer 111 is less than 3 μm.

[0051] In this embodiment, the distance between the sealing layer 112 and the first interconnection layer 111 is greater than 2 μm, such as 5 μm, 8 μm. In some embodiments, this distance is 3 - 10 μm. If the distance is too small, it is easy to cause a short circuit. If the distance is too large, the formed surface acoustic wave filter structure occupies a large space, which is not conducive to the miniaturization of the surface acoustic wave filter structure. It can be understood that within the range allowed by the process, the smaller the distance between the sealing layer 112 and the first interconnection layer 111, the more beneficial it is to achieve the miniaturization of the package.

[0052] In this embodiment, the width of the sealing layer 112 is greater than 10 μm, such as 15 μm, 25 μm, etc. In some embodiments, the width of the sealing layer 112 is 20 - 40 μm, such as 30 μm, etc. The width of the sealing layer 112 determines the bonding strength between the sealing layer 112 and the encapsulation layer 140. The wider the width, the greater the bonding strength, and at the same time, the stronger the ability to prevent water vapor from entering the cavity 105. According to the size of the encapsulation layer 140, a suitable width is selected by comprehensively considering the bonding strength and the area occupied by the sealing layer 112.

[0053] It should be noted that in this embodiment, the number of the first interconnect layers 111 is multiple, and the multiple first interconnect layers 111 are spaced apart from each other, so that the multiple first interconnect layers 111 do not contact each other, that is, the multiple first interconnect layers 111 are in an open circuit state.

[0054] As an example, two first interconnect layers 111 are shown in the figure. Among them, one first interconnect layer 111 is used to connect to the input end of the acoustic transducer 200, and the other first interconnect layer 111 is used to electrically connect to the output end of the acoustic transducer 200.

[0055] As an example, as Figure 2 and Figure 3 shown, the two first interconnect layers 111 are located on both sides of the piezoelectric oscillation effective region I.

[0056] The sealing layer 112 is spaced apart from the first interconnect layer 111, or the sealing layer 112 is only connected to one first interconnect layer 111, so that the sealing layer 112 and the first interconnect layer 111 are in an open circuit state, so that the sealing layer 112 cannot play the role of electrical connection.

[0057] It should be noted that when the sealing layer 112 is connected to one first interconnect layer 111 and disconnected from the other first interconnect layer 111, an insulating layer (not shown in the figure) is formed at the bottom of the first interconnect layer 111 connected to the sealing layer 112. The insulating layer is used to achieve electrical isolation between the first interconnect layer 111 connected to the sealing layer 112 and the substrate 100, so as to avoid affecting the working performance of the acoustic transducer 200.

[0058] In this embodiment, the sealing layer 112 is annular, that is, the sealing layer 112 surrounds the first interconnect layer 111 on all sides, which is beneficial to improving the tightness of the cavity 105 formed with the encapsulation layer 140.

[0059] The first protective layer 120 is used to protect the acoustic transducer 200. Specifically, the first protective layer 120 can block the acid-containing or alkali-containing developer used in the subsequent process of forming the encapsulation layer 140, etc., and avoid the damage of the IDT caused by the acid-containing or alkali-containing developer used in the subsequent process of forming the encapsulation layer 140 from corroding the IDT.

[0060] Therefore, the first protective layer 120 is selected from materials that can effectively resist corrosive liquids such as acid or alkali developing solutions used in the process of forming the encapsulation layer 140, and the presence of the first protective layer 120 has little impact on the substrate 100 and the acoustic transducer 200 in the piezoelectric oscillation effective region I. In addition, the material of the first protective layer 120 can ensure that the first protective layer 120 has good coverage, so as to completely cover the acoustic transducer 200 and the substrate 100 in the piezoelectric oscillation effective region I. For example, the material of the first protective layer 120 may include at least one of silicon nitride, silicon carbonitride, silicon carbon oxynitride, silicon oxynitride, boron nitride, and carbon boron nitride.

[0061] In this embodiment, the material of the first protective layer 120 is silicon nitride. Silicon nitride has strong acid and alkali resistance, can effectively avoid corroding the IDT by the acid or alkali developing solution used in the process of forming the encapsulation layer 140, and helps to reduce the insertion loss of the IDT. At the same time, silicon nitride also has characteristics such as high strength, high hardness, high thermal conductivity, and high heat resistance, which is beneficial to improving the reliability of the formed surface acoustic wave filter structure.

[0062] The thickness of the first protective layer 120 should neither be too large nor too small. If the thickness of the first protective layer 120 is too small, it cannot play a good protective role for the acoustic transducer 200 in the process of forming the encapsulation layer 140; if the thickness of the first protective layer 120 is too large, it will affect the performance of the acoustic transducer 200, and will also increase the size of the formed surface acoustic wave filter structure in the longitudinal direction, which is not conducive to the integration of the surface acoustic wave filter structure. Therefore, in this embodiment, the thickness of the first protective layer 120 is 20 angstroms to 200 angstroms, such as 50 angstroms, 70 angstroms, or 90 angstroms, etc.

[0063] In this embodiment, the first protective layer 120 covers the substrate 100 and the acoustic transducer 200 in the piezoelectric oscillation effective region I. In other embodiments, the first protective layer can also only cover the acoustic transducer, that is, the first protective layer is located on the top and side walls of the acoustic transducer.

[0064] Compared with the way that the first protective layer 120 only covers the acoustic transducer 200, the first protective layer 120 covering the substrate 100 and the acoustic transducer 200 in the piezoelectric oscillation effective region I can eliminate the corresponding photolithography and etching processes, which is beneficial to reducing the process steps and the process cost.

[0065] In this embodiment, the surface acoustic wave filter structure further includes: a frequency modulation layer 131, located on the substrate 100 in the piezoelectric oscillation effective region I, and the frequency modulation layer 131 covers the acoustic transducer 200. Correspondingly, the first protective layer 120 is located on the frequency modulation layer 131.

[0066] The frequency modulation layer 131 is used to adjust the operating frequency of the acoustic transducer 200.

[0067] The material of the frequency modulation layer 131 includes metals or insulating dielectrics. Among them, the metals used to form the frequency modulation layer 131 include molybdenum, ruthenium, tungsten, platinum, iridium, magnesium, aluminum, beryllium, copper, gold, chromium, cobalt, and titanium; the insulating dielectrics used to form the frequency modulation layer 131 include silicon nitride, silicon oxide, aluminum oxide, silicon carbide, silicon oxycarbide, aluminum nitride, gallium arsenide, or gallium nitride.

[0068] As an example, the material of the frequency modulation layer 131 can be selected from at least one of silicon dioxide, silicon nitride, aluminum nitride, and silicon carbide according to the adjustment requirements of the operating frequency of the acoustic transducer 200. Specifically, when the operating frequency of the acoustic transducer 200 is too high, selecting a silicon dioxide layer as the material of the frequency modulation layer 131 can reduce the operating frequency of the acoustic transducer 200; when the operating frequency of the acoustic transducer 200 is too low, selecting at least one of silicon nitride, aluminum nitride, and silicon carbide as the material of the frequency modulation layer 131 can increase the operating frequency of the acoustic transducer 200.

[0069] The thickness of the frequency modulation layer 131 should not be too large or too small. When the thickness of the frequency modulation layer 131 is too small, it cannot play a good role in adjusting the operating frequency of the acoustic transducer 200; when the thickness of the frequency modulation layer 131 is too large, the presence of the frequency modulation layer 131 will affect the filtering performance of the acoustic transducer 200 and is also not conducive to the integration of the formed surface acoustic wave filter structure. Therefore, in this embodiment, the thickness of the frequency modulation layer 131 is 5 nm to 500 nm.

[0070] In this embodiment, the surface acoustic wave filter structure further includes: a second protective layer 132, located on the substrate 100 of the piezoelectric oscillation effective region I, and the second protective layer 132 covers the acoustic transducer 200. Correspondingly, the frequency modulation layer 131 is located on the second protective layer 132.

[0071] The second protective layer 132 is used to protect the acoustic transducer 200 during the subsequent process after the formation of the acoustic transducer 200. Specifically, the second protective layer 132 is used to protect the acoustic transducer 200 during the subsequent formation of the frequency modulation layer 131.

[0072] According to actual needs, the thickness of the second protective layer 132 can be 20 angstroms - 1000 angstroms. In some embodiments, the thickness of the second protective layer 132 is 50 angstroms - 150 angstroms, such as 50 angstroms, 80 angstroms, or 100 angstroms, etc.

[0073] For the material of the second protective layer 132, refer to the corresponding content regarding the first protective layer 120 described above, which will not be elaborated here.

[0074] It should be noted that in this embodiment, the second protective layer 132 is located on the substrate 100 of the piezoelectric oscillation effective region I, and the second protective layer 132 covers the acoustic transducer 200. In other embodiments, the second protective layer can also only cover the acoustic transducer.

[0075] The encapsulation layer 140 is used to encapsulate the surface acoustic wave filter structure, and functions to seal and prevent moisture, correspondingly reducing the influence of subsequent processes on the acoustic transducer 200, thereby improving the reliability of the formed surface acoustic wave filter structure. At the same time, by sealing the cavity 105, it is also beneficial to isolate the cavity 105 from the external environment, thereby maintaining the stability of the acoustic performance of the acoustic transducer 200.

[0076] In this embodiment, the encapsulation layer 140 is located on the top of the connection layer 110.

[0077] The material of the encapsulation layer 140 includes photosensitive material or non - photosensitive material. As an example, the material of the encapsulation layer 140 is photosensitive material, which is beneficial to subsequent patterning of the encapsulation layer 140, thereby reducing the complexity of the patterning process and being beneficial to improving the process precision. Specifically, the photosensitive material is a dry film. The dry film is a permanent bonding film, and the bonding strength of the dry film is relatively high, so that the bonding strength between the encapsulation layer 140 and the connection layer 110 is guaranteed. At the same time, it is beneficial to improve the sealing performance of the cavity 105.

[0078] In this embodiment, the photosensitive material is a film - like dry film, which makes the process of forming the encapsulation layer 140 simple. The manufacturing of the film - like dry film is to coat a solvent - free photoresist on a polyester film base and then cover it with a polyethylene film; when in use, the polyethylene film is removed and the solvent - free photoresist is pressed onto the substrate.

[0079] In some other embodiments, the material of the encapsulation layer can also be a liquid dry film. Among them, the liquid dry film means that the components in the film - like dry film exist in a liquid form.

[0080] In other embodiments, the material of the encapsulation layer can also be a dielectric material or an organic material. Among them, the dielectric material can be silicon oxide, phosphosilicate glass (PSG) or borophosphosilicate glass (BPSG), etc., and the organic material can be polyimide, etc.

[0081] It should be noted that the thickness of the encapsulation layer 140 should not be too large or too small. If the thickness of the encapsulation layer 140 is too large, during the subsequent formation of the interconnecting holes, the process difficulty of removing the encapsulation layer 140 increases. At the same time, the size of the interconnecting holes formed in the encapsulation layer 140 also becomes larger. Correspondingly, the overall area of the surface acoustic wave filter structure increases, and the material waste of the formed encapsulation layer 140 is excessive, increasing the process cost. If the thickness of the encapsulation layer 140 is too small, it is likely to cause a reduction in the ability of the encapsulation layer 140 to withstand external extrusion, resulting in a decline in the airtightness and waterproof performance of the encapsulation layer 140, thereby posing higher requirements for the subsequent manufacturing process and application environment of the surface acoustic wave filter structure. Therefore, in this embodiment, the thickness of the encapsulation layer 140 is 5 micrometers to 60 micrometers.

[0082] The interconnecting structure 150 is used to realize the electrical connection between the first interconnecting layer 111 and an external circuit structure.

[0083] In this embodiment, the interconnecting structure 150 includes conductive posts 151 and solder balls 152 located on the top surfaces of the conductive posts 151.

[0084] In this embodiment, the material of the conductive posts 151 may include copper, nickel, and tin-silver alloy. In other embodiments, the material of the conductive posts may also include copper and tin-silver alloy.

[0085] The material of the solder balls 152 may be tin solder, silver solder, or tin-silver alloy solder. In this embodiment, the material of the solder balls 152 is tin-silver alloy solder.

[0086] Reference Figure 10 , in some other embodiments, the interconnecting structure 150 may also only include conductive posts 151.

[0087] Reference Figure 11 , in other embodiments, the interconnecting structure 150 may also be a second interconnecting layer, which is located at the bottom and side walls of the interconnecting holes and also extends to cover a part of the top of the encapsulation layer 140.

[0088] Figures 4 to 11 is a schematic structural diagram corresponding to each step in an embodiment of the method for forming the surface acoustic wave filter structure of the present invention.

[0089] Reference Figure 4 , provide a substrate 100, the substrate 100 includes a piezoelectric oscillation effective region I and a peripheral region II surrounding the piezoelectric oscillation effective region I, and an acoustic transducer 200 is formed on the substrate 100 of the piezoelectric oscillation effective region I.

[0090] The substrate 100 is used to provide a process platform for the subsequent formation of the surface acoustic wave filter structure. In this embodiment, the substrate 100 is a wafer-level substrate. By fabricating the surface acoustic wave filter structure on the wafer-level substrate, the process cost can be reduced and mass production can be achieved, which is beneficial to improving the reliability of the surface acoustic wave filter structure and the manufacturing efficiency.

[0091] The substrate 100 includes a piezoelectric oscillation active region I, which is the working region for the surface acoustic wave filter structure to achieve the filtering function. In this embodiment, since the substrate 100 is a wafer-level substrate, the substrate 100 includes a plurality of mutually isolated piezoelectric oscillation active regions I.

[0092] In this embodiment, the formed filter structure is taken as an example of a SAW filter structure for illustration.

[0093] The SAW filter structure is a dedicated filtering device made by utilizing the piezoelectric effect and the physical characteristics of surface acoustic wave propagation. In the SAW filter structure, the signal undergoes two conversions of electric-acoustic-electric, thereby achieving the frequency selection characteristic. The SAW filter structure has the advantages of high operating frequency, simple manufacturing process, low manufacturing cost, high consistency of frequency characteristics, etc. Therefore, it is widely used in various electronic devices.

[0094] Correspondingly, the substrate 100 is a piezoelectric substrate, so that the subsequent surface acoustic wave filter structure can perform filtering processing by utilizing the piezoelectric effect. In this embodiment, the material of the substrate 100 includes at least one of quartz, lithium tantalate, lanthanum gallium silicate, lanthanum gallium tantalate, lanthanum gallium niobate, lead zirconate titanate, cadmium sulfide, berlinite, lithium iodate, lithium tetraborate, and bismuth germanium oxide. In some embodiments, the piezoelectric substrate includes a piezoelectric crystal layer, and the piezoelectric crystal layer may include a thickness greater than the penetration depth of the Love wave on the non-piezoelectric substrate.

[0095] Reference Figure 5 , a connection layer 110 is formed on the substrate 100 in the peripheral region II. The connection layer 110 includes a first interconnection layer 111 and a sealing layer 112 surrounding the periphery of the first interconnection layer 111. The first interconnection layer 111 is electrically connected to the acoustic transducer 200.

[0096] The first interconnection layer 111 is used as the I / O terminal of the acoustic transducer 200 to realize the electrical connection between the acoustic transducer 200 and the external circuit structure; the sealing layer 112 is used to protect the first interconnection layer 111 and the acoustic transducer 200 located therein from the side, preventing water vapor from entering the piezoelectric oscillation active region I, which is beneficial to reducing the probability of oxidation and corrosion of the acoustic transducer 200 in the piezoelectric oscillation active region I. Correspondingly, the presence of the sealing layer 112 also reduces the probability of oxidation and corrosion of the first interconnection layer 111.

[0097] In this embodiment, the first interconnect layer 111 and the sealing layer 112 are made of the same material. Correspondingly, the first interconnect layer 111 and the sealing layer 112 are formed in the same step.

[0098] Compared with the method of forming the first interconnect layer 111 and the sealing layer 112 in sequence in separate steps, forming the first interconnect layer 111 and the sealing layer 112 in the same step is conducive to improving the manufacturing efficiency of the surface acoustic wave filter structure and also reduces the process cost.

[0099] In this embodiment, the materials of the first interconnect layer 111 and the sealing layer 112 include one or more of titanium, copper, aluminum, and nickel. Specifically, titanium, copper, aluminum, and nickel are all conductive materials, which can enable the acoustic transducer 200 in the piezoelectric oscillation effective region I to be electrically connected to the external circuit structure through the first interconnect layer 111. As an example, the material of the first interconnect layer 111 is aluminum.

[0100] The steps of forming the first interconnect layer 111 and the sealing layer 112 include: forming a connection material layer (not shown in the figure) on the substrate 100 in the peripheral region II; patterning the connection material layer to form the first interconnect layer 111 and the sealing layer 112, and the first interconnect layer 111 and the sealing layer 112 constitute the connection layer 110.

[0101] In this embodiment, an electroless plating process is used to form the connection material layer. In other embodiments, the process of forming the connection material layer may also include at least one of physical vapor deposition process (PVD), vacuum evaporation process, or chemical vapor deposition process.

[0102] In this embodiment, a dry etching process is used to pattern the connection material layer to form the first interconnect layer 111 and the sealing layer 112.

[0103] It should be noted that the thickness of the first interconnect layer 111 should not be too large or too small. If the thickness of the first interconnect layer 111 is too large, the process difficulty and process time of patterning the connection material layer will increase; if the thickness of the first interconnect layer 111 is too small, it is easy to cause the effective height of the cavity formed in the piezoelectric oscillation effective region I to be too small. Correspondingly, after the encapsulation layer 140 is deformed under external force extrusion, the probability of contact between the encapsulation layer 140 and the acoustic transducer 200 increases, resulting in a reduction in the reliability of the surface acoustic wave filter structure. Therefore, in this embodiment, the thickness of the first interconnect layer 111 is 2 micrometers to 30 micrometers.

[0104] In this embodiment, the material of the sealing layer 112 is the same as that of the first interconnecting layer 111. Correspondingly, the material of the sealing layer 112 includes one or more of titanium, copper, aluminum, and nickel.

[0105] The material of the sealing layer 112 is a metal. Due to the close arrangement of metal atoms, the sealing layer 112 has good compactness, thus being able to play a good sealing role. The sealing layer 112 and the first interconnecting layer 111 are made of the same material, enabling the sealing layer 112 and the first interconnecting layer 111 to be etched and connected to the material layer in the same step, which is conducive to simplifying the formation process of the filter and improving efficiency.

[0106] In this embodiment, the sealing layer 112 and the first interconnecting layer 111 are formed in the same step. Therefore, the thickness of the sealing layer 112 is basically the same as that of the first interconnecting layer 111. Specifically, the thickness of the sealing layer 112 is 2 micrometers to 30 micrometers. The height difference between the sealing layer 112 and the first interconnecting layer 111 is less than 3 micrometers. In other embodiments, the sealing layer and the first interconnecting layer can also be formed in different steps.

[0107] In this embodiment, the distance between the sealing layer 112 and the first interconnecting layer 111 is greater than 2 micrometers, such as 5 micrometers or 8 micrometers. In some embodiments, this distance is 3 - 10 micrometers. If the distance is too small, short circuits are likely to occur. If the distance is too large, the formed surface acoustic wave filter structure occupies a large space, which is not conducive to the miniaturization of the surface acoustic wave filter structure. It can be understood that within the range allowed by the process, the smaller the distance between the sealing layer 112 and the first interconnecting layer 111, the more conducive it is to the miniaturization of the package.

[0108] In this embodiment, the width of the sealing layer 112 is greater than 10 micrometers, such as 15 micrometers, 25 micrometers, etc. In some embodiments, the width of the sealing layer 112 is 20 - 40 micrometers, such as 30 micrometers, etc. The width of the sealing layer 112 determines the bonding strength between the sealing layer 112 and the encapsulation layer 140. The wider the width, the greater the bonding strength, and at the same time, the stronger the ability to prevent water vapor from entering the cavity 105. According to the size of the encapsulation layer 140, a suitable width is selected by comprehensively considering the bonding strength and the area occupied by the sealing layer 112.

[0109] It should be noted that in the step of forming the connection layer 110 on the substrate 100 in the peripheral region II, the number of the first interconnecting layers 111 is multiple, and the multiple first interconnecting layers 111 are spaced apart from each other, so that the multiple first interconnecting layers 111 do not contact each other, that is, the multiple first interconnecting layers 111 are in an open - circuit state.

[0110] As an example, two first interconnect layers 111 are shown in the figure. One of the first interconnect layers 111 is used to connect to the input end of the IDT, and the other first interconnect layer 111 is used to electrically connect to the output end of the IDT.

[0111] As an example, as Figure 2 and Figure 3 shown, the two first interconnect layers 111 are located on both sides of the piezoelectric oscillation effective region I.

[0112] The sealing layer 112 is spaced apart from the first interconnect layer 111, or the sealing layer 112 is only connected to one first interconnect layer 111, so that the sealing layer 112 and the first interconnect layer 111 are in an open circuit state, so that the sealing layer 112 cannot play the role of electrical connection.

[0113] It should be noted that when the sealing layer 112 is connected to one first interconnect layer 111 and disconnected from the other first interconnect layer 111, an insulating layer (not shown in the figure) is formed at the bottom of the first interconnect layer 111 connected to the sealing layer 112. The insulating layer is used to achieve electrical isolation between the first interconnect layer 111 connected to the sealing layer 112 and the substrate 100, so as to avoid affecting the working performance of the acoustic transducer 200.

[0114] In this embodiment, the sealing layer 112 is annular, that is, the sealing layer 112 surrounds the first interconnect layer 111, which is beneficial to improving the tightness of the cavity formed with the encapsulation layer subsequently.

[0115] Referring to Figure 6 , a first protective layer 120 is formed on the substrate 100 in the piezoelectric oscillation effective region I, and the first protective layer 120 covers the acoustic transducer 200.

[0116] The first protective layer 120 is used to protect the acoustic transducer 200. Specifically, the first protective layer 120 can block the acid-containing or alkali-containing developer used in the process of forming the encapsulation layer 140 subsequently, and avoid the damage of the IDT caused by the acid-containing or alkali-containing developer used in the process of forming the encapsulation layer 140 subsequently corroding the IDT.

[0117] Therefore, the first protective layer 120 is selected from materials that can effectively resist corrosive liquids such as acid or alkali developing solutions used in the process of forming the encapsulation layer 140, and the presence of the first protective layer 120 has little impact on the substrate 100 and the acoustic transducer 200 in the piezoelectric oscillation effective region I. In addition, the material of the first protective layer 120 can ensure that the first protective layer 120 has good coverage, so as to completely cover the acoustic transducer 200 and the substrate 100 in the piezoelectric oscillation effective region I. For example, the material of the first protective layer 120 may include at least one of silicon nitride, silicon carbonitride, silicon carbon oxynitride, silicon oxynitride, boron nitride, and carbon boron nitride.

[0118] In this embodiment, the material of the first protective layer 120 is silicon nitride. Silicon nitride has strong acid and alkali resistance, which can effectively prevent the IDT from being corroded by acid or alkali developing solutions used in the process of forming the encapsulation layer 140, and helps to reduce the insertion loss of the IDT. At the same time, silicon nitride also has characteristics such as high strength, high hardness, high thermal conductivity, and high heat resistance, which is beneficial to improving the reliability of the formed surface acoustic wave filter structure.

[0119] In this embodiment, the first protective layer 120 is formed by chemical vapor deposition (CVD) process. The chemical vapor deposition process has good deposition effect and high gap filling ability, so that the morphology quality of the formed first protective layer 120 is better, and it can better cover the acoustic transducer 200 and the substrate 100 in the piezoelectric oscillation effective region I.

[0120] In other embodiments, other suitable processes can also be used to form the first protective layer, which can be selected by those skilled in the art according to actual needs and will not be limited here.

[0121] The thickness of the first protective layer 120 should neither be too large nor too small. If the thickness of the first protective layer 120 is too small, it cannot play a good protective role for the acoustic transducer 200 in the process of forming the encapsulation layer 140; if the thickness of the first protective layer 120 is too large, it will affect the performance of the acoustic transducer 200. For this reason, in this embodiment, the thickness of the first protective layer 120 is 20 Å to 200 Å, such as 50 Å, 70 Å, 90 Å, etc.

[0122] It should be noted that in this embodiment, the first protective layer 120 covers the substrate 100 and the acoustic transducer 200 in the piezoelectric oscillation effective region I. In other embodiments, the first protective layer can also only cover the acoustic transducer, that is, the first protective layer is only located on the top and side walls of the acoustic transducer.

[0123] Compared with the way that the first protective layer 120 only covers the acoustic transducer 200, covering the substrate 100 and the acoustic transducer 200 of the piezoelectric oscillation active region I by the first protective layer 120 can eliminate the corresponding photolithography and etching processes, which is beneficial to reducing process steps and process costs.

[0124] Please continue to refer to Figure 6 , before forming the first protective layer 120, the manufacturing method of the surface acoustic wave filter structure may further include: forming a frequency modulation layer 131 on the substrate 100 of the piezoelectric oscillation active region I, and the frequency modulation layer 131 covers the acoustic transducer 200. Correspondingly, after forming the first protective layer 120, the first protective layer 120 is located on the frequency modulation layer 131.

[0125] The frequency modulation layer 131 is used to adjust the operating frequency of the acoustic transducer 200.

[0126] The material of the frequency modulation layer 131 includes metal or insulating dielectric. Among them, the metals used to form the frequency modulation layer 131 include molybdenum, ruthenium, tungsten, platinum, iridium, magnesium, aluminum, beryllium, copper, gold, chromium, cobalt and titanium; the insulating dielectrics used to form the frequency modulation layer 131 include silicon nitride, silicon oxide, aluminum oxide, silicon carbide, silicon carbon oxide, aluminum nitride, gallium arsenide or gallium nitride.

[0127] As an example, the material of the frequency modulation layer 131 can be selected from at least one of silicon dioxide, silicon nitride, aluminum nitride and silicon carbide according to the adjustment requirement of the operating frequency of the acoustic transducer 200. Specifically, when the operating frequency of the acoustic transducer 200 is too high, selecting a silicon dioxide layer as the material of the frequency modulation layer 131 can reduce the operating frequency of the acoustic transducer 200; when the operating frequency of the acoustic transducer 200 is too low, selecting at least one of silicon nitride, aluminum nitride and silicon carbide as the material of the frequency modulation layer 131 can increase the operating frequency of the acoustic transducer 200.

[0128] The thickness of the frequency modulation layer 131 should not be too large or too small. When the thickness of the frequency modulation layer 131 is too small, it cannot play a good role in adjusting the operating frequency of the acoustic transducer 200; when the thickness of the frequency modulation layer 131 is too large, the existence of the frequency modulation layer 131 will affect the filtering performance of the acoustic transducer 200, and it is also not conducive to the integration degree of the formed surface acoustic wave filter structure. Therefore, in this embodiment, the thickness of the frequency modulation layer 131 is 5nm to 500nm.

[0129] Please continue to refer to Figure 6, before forming the frequency modulation layer 131, the manufacturing method of the surface acoustic wave filter structure may further include: forming a second protective layer 132 on the substrate 100 of the piezoelectric oscillation active region I, and the second protective layer 132 covers the acoustic transducer 200. Correspondingly, after forming the frequency modulation layer 131, the frequency modulation layer 131 is located on the second protective layer 132.

[0130] The second protective layer 132 is used to protect the acoustic transducer 200 during subsequent process steps after the formation of the acoustic transducer 200. Specifically, the second protective layer 132 is used to protect the acoustic transducer 200 during the subsequent formation of the frequency modulation layer 131.

[0131] According to actual needs, the thickness of the second protective layer 132 can be 20 Å to 1000 Å. In some embodiments, the thickness of the second protective layer 132 is 50 Å to 150 Å, such as 50 Å, 80 Å or 100 Å, etc.

[0132] Regarding the material and formation process of the second protective layer 132, please refer to the corresponding content of the foregoing first protective layer 120, and details are not described herein again.

[0133] It should be noted that in this embodiment, the second protective layer 132 is located on the substrate 100 of the piezoelectric oscillation active region I, and the second protective layer 132 covers the acoustic transducer 200. In other embodiments, the second protective layer can also only cover the acoustic transducer.

[0134] Reference Figure 7 , forming an encapsulation layer 140 on the connection layer 110, and the encapsulation layer 140, the sealing layer 112 and the substrate 100 enclose a cavity 105, and the cavity 105 is used to accommodate the acoustic transducer 200.

[0135] The encapsulation layer 140 is used to realize the encapsulation of the surface acoustic wave filter structure, and plays a role in sealing and moisture-proofing, correspondingly reducing the influence of subsequent processes on the acoustic transducer 200, thereby improving the reliability of the formed surface acoustic wave filter structure. At the same time, by sealing the cavity 105, it is also beneficial to isolate the cavity 105 from the external environment, thereby maintaining the stability of the acoustic performance of the acoustic transducer 200.

[0136] In this embodiment, the encapsulation layer 140 is located on the top of the connection layer 110.

[0137] The material of the encapsulation layer 140 includes photosensitive material or non - photosensitive material. As an example, the material of the encapsulation layer 140 is photosensitive material, which is beneficial to subsequent patterning of the encapsulation layer 140, thereby reducing the process complexity of the patterning process and being conducive to improving the process accuracy. Specifically, the photosensitive material is dry film. Dry film is a permanent bonding film with relatively high bonding strength, which ensures the bonding strength between the encapsulation layer 140 and the connection layer 110. At the same time, it is beneficial to improve the sealing performance of the cavity 105.

[0138] In this embodiment, the photosensitive material is film - like dry film, which makes the process of forming the encapsulation layer 140 simple. The manufacturing of film - like dry film is to coat a solvent - free photoresist on a polyester film base and then cover it with a polyethylene film; when in use, the polyethylene film is peeled off and the solvent - free photoresist is pressed onto the substrate. Therefore, in this embodiment, the encapsulation layer 140 is formed by a film - sticking process. Among them, the film - sticking process is carried out in a vacuum environment, has good step coverage ability, and can significantly improve the adhesion degree and adhesion strength between the encapsulation layer 140 and the connection layer 110.

[0139] In some other embodiments, the encapsulation layer can also be formed by using liquid dry film. Among them, liquid dry film means that the components in the film - like dry film exist in a liquid form. Correspondingly, the steps of forming the encapsulation layer include: coating the liquid dry film by a spin - coating process; curing the liquid dry film to form the encapsulation layer. Among them, the cured liquid dry film is also a photosensitive material.

[0140] In other embodiments, the material of the encapsulation layer can also be dielectric material or organic material. Correspondingly, the encapsulation layer can be formed by a deposition process or a coating process respectively. Among them, the dielectric material can be silicon oxide, phosphosilicate glass or borophosphosilicate glass, and the organic material can be polyimide.

[0141] It should be noted that the thickness of the encapsulation layer 140 should not be too large or too small. If the thickness of the encapsulation layer 140 is too large, during the subsequent process of forming the interconnecting holes, the process difficulty of removing the encapsulation layer 140 increases. At the same time, the size of the interconnecting holes formed in the encapsulation layer 140 also becomes larger. Correspondingly, it leads to an increase in the overall area of the surface acoustic wave filter structure and also results in excessive waste of the material of the formed encapsulation layer 140, increasing the process cost; if the thickness of the encapsulation layer 140 is too small, it is easy to cause the reduction of the external extrusion resistance that the encapsulation layer 140 can withstand, resulting in the decline of the airtightness and waterproof performance of the encapsulation layer 140, thus posing higher requirements for the subsequent manufacturing process and application environment of the surface acoustic wave filter structure. Therefore, in this embodiment, the thickness of the encapsulation layer 140 is 5 microns to 60 microns.

[0142] ReferenceFigure 8 , an interconnect via 145 exposing the top of the first interconnect layer 111 is formed in the encapsulation layer 140.

[0143] The interconnect via 145 is used to provide a spatial position for the subsequent formed interconnect structure.

[0144] In this embodiment, the interconnect via 145 penetrates through the encapsulation layer 140.

[0145] Specifically, the interconnect via 145 penetrates through the encapsulation layer 140, exposing the top surface of the first interconnect layer 111, which is conducive to the subsequent formed interconnect structure contacting the exposed top surface of the first interconnect layer 111, thereby realizing the electrical connection between the interconnect structure and the first interconnect layer 111.

[0146] Refer to Figure 9 , an interconnect structure 150 is formed in the interconnect via 145, and the bottom of the interconnect structure 150 is electrically connected to the top of the first interconnect layer 111.

[0147] The interconnect structure 150 is used to realize the electrical connection between the first interconnect layer 111 and the external circuit structure.

[0148] In this embodiment, the bump process is adopted to form the interconnect structure 150 in the interconnect via 145. By adopting the bump process, it is convenient for subsequent packaging processes.

[0149] The bump process is a metal pillar process. Specifically, the steps of the bump process include: filling and forming a conductive pillar 151 in the interconnect via 145; forming a solder ball 152 on the top surface of the conductive pillar 151, and the solder ball 152 and the conductive pillar 151 are used to constitute the interconnect structure 150.

[0150] Specifically, the steps of forming the conductive pillar 151 include: forming a first seed layer (not shown in the figure) on the top of the encapsulation layer 140, as well as the bottom and side walls of the interconnect via 145; forming a first mask layer (not shown in the figure) on the top of the first seed layer located outside the interconnect via 145; after forming the first mask layer, forming the conductive pillar 151 in the remaining space of the interconnect via 145.

[0151] In this embodiment, the material of the conductive pillar 151 may include copper, nickel, and tin-silver alloy. In other embodiments, the material of the conductive pillar may also include copper and tin-silver alloy.

[0152] In this embodiment, the conductive pillar 151 can be formed by electroplating process. In other embodiments, the conductive pillar can also be formed by any one of physical vapor deposition (PVD) process, chemical vapor deposition process, vacuum evaporation, or electroless plating.

[0153] It should be noted that after forming the conductive pillar 151, the method further includes removing the first mask layer and the first seed layer exposed by the conductive pillar 151.

[0154] In this embodiment, the process of removing the first mask layer and the first seed layer exposed by the interconnect structure 150 includes a dry etching process or a wet etching process.

[0155] In this embodiment, after removing the first mask layer and the first seed layer exposed by the interconnect structure 150, a solder ball 152 is formed on the top surface of the conductive pillar 151, and the solder ball 152 and the conductive pillar 151 are used to form the interconnect structure 150.

[0156] The material of the solder ball 152 may be a tin solder, a silver solder or a tin-silver alloy solder, and the solder ball 152 may be formed by any one of a physical vapor deposition process, a chemical vapor deposition process, a vacuum evaporation, an electroplating or an electroless plating process. In this embodiment, the material of the solder ball 152 is a tin-silver alloy solder.

[0157] Reference Figure 10 , in some other embodiments, a conductive pillar may also be formed in the interconnect hole, and the conductive pillar is used as the interconnect structure.

[0158] Specifically, a conductive pillar is formed in the interconnect hole by using an electroless plating process.

[0159] It should be noted that the steps of forming a conductive pillar in the interconnect hole by using an electroless plating process include: removing a small amount of organic residues on the surface of the first interconnect layer; etching the first interconnect layer to expose a new metal surface of the first interconnect layer; depositing a potion containing active target ions on the surface of the first interconnect layer; preliminarily cleaning the potion on the surface of the first interconnect layer; cleaning the surface of the first interconnect layer again to wash away the target atoms on the surface of the first interconnect layer; depositing a nickel-phosphorus alloy with palladium atoms as the center, and a new nickel layer will continue to be deposited on the surface of nickel, and the above reactions continue until the interconnect hole part of the encapsulation layer 140 is completely filled with nickel (nickel-phosphorus alloy), that is, a conductive pillar is formed in the interconnect hole.

[0160] Reference Figure 11 , in other embodiments, a second interconnect layer may also be formed on the bottom and side walls of the interconnect hole 145, and the second interconnect layer extends to cover a part of the top of the encapsulation layer 140, and the second interconnect layer is used as the interconnect structure 150.

[0161] Specifically, the steps of forming the interconnect structure include: forming a second seed layer on the top of the encapsulation layer 140, as well as on the bottom and sidewalls of the interconnect hole 145; forming a second mask layer on the top of the second seed layer located outside the interconnect hole 145; after forming the second mask layer, forming a conductive layer on the top of the second seed layer by an electroplating process, and the conductive layer and the second seed layer constitute the interconnect structure.

[0162] It should be noted that after forming the interconnect structure 150, it further includes: removing the second mask layer and the second seed layer exposed by the interconnect structure 150.

[0163] FIG. 12 shows a schematic diagram of the comparison of the performance parameters between the surface acoustic wave filter structure in the embodiment of the present invention and the existing surface acoustic wave filter structure, and Table 1 shows the change amount of the main performance indicators of the surface acoustic wave filter structure and the main performance indicators of the surface acoustic wave filter structure in the embodiment of the present invention.

[0164] Table 1

[0165]

[0166] Combined with reference to Table 1 and FIG. 12, experimental verification shows that the insertion loss, waveform, quality factor, and impedance, including impedance magnitude (ZMagnitude) parameter, magnetic spurious (Mag_spur ) parameter, and electromechanical coupling coefficient (keff2) and other main performance indicators of the surface acoustic wave filter structure in the embodiment of the present invention are all within the process allowable range and are superior to the existing surface acoustic wave filter structure.

[0167] FIG. 13 and Table 2 show the comparison of the test results of the high-accelerated temperature, humidity and bias test (ubias Highly Accelerated Stress Test, uHAST) between the surface acoustic wave filter structure in the embodiment of the present invention and the existing surface acoustic wave filter structure.

[0168] Table 2

[0169]

[0170]

[0171] Combined with reference table 2 and FIG13, the uHAST test results show that the frequency deviation, insertion loss, and waveform of the surface acoustic wave filter structure in the embodiment of the present invention before and after uHAST are better than those of the existing surface acoustic wave filter structure, and the acoustic transducer in the image of the surface acoustic wave filter structure in the embodiment of the present invention observed by an optical microscope (as shown in FIG13 (e)) has almost no damage, while the acoustic transducer in the image of the existing surface acoustic wave filter structure (as shown in FIG13 (f)) has more damage. Therefore, the reliability of the surface acoustic wave filter structure in the embodiment of the present invention under uHAST is better than that of the existing surface acoustic wave filter structure.

[0172] It should be pointed out that the specific values ​​of the parameters shown in Table 1, Table 2, Figure 12 and Figure 13 change with the process node and device constant configuration, and the specific values ​​of the parameters shown in Table 1, Table 2, Figure 12 and Figure 13 are only for example.

[0173] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A surface acoustic wave filter structure, characterized in that, Comprising: A substrate, the substrate comprising a piezoelectric oscillation active region and a peripheral region surrounding the piezoelectric oscillation active region; An acoustic transducer located on the substrate of the piezoelectric oscillation active region; A connection layer located on the substrate of the peripheral region, the connection layer comprising a first interconnect layer and a sealing layer surrounding the periphery of the first interconnect layer, the first interconnect layer being electrically connected to the acoustic transducer; A first protective layer covering the acoustic transducer; An encapsulation layer located on top of the first interconnect layer, the encapsulation layer, the sidewall of the first interconnect layer and the substrate enclosing a cavity for accommodating the acoustic transducer.

2. The surface acoustic wave filter structure according to claim 1, wherein The first protective layer is also located on the substrate of the piezoelectric oscillation active region exposed by the acoustic transducer.

3. The surface acoustic wave filter structure according to claim 1, characterized in that, The material of the first protective layer comprises at least one of silicon nitride, silicon carbonitride, silicon carbon oxynitride, silicon oxynitride, boron nitride and boron carbonitride.

4. The surface acoustic wave filter structure according to claim 1, wherein The thickness of the first protective layer is 50 Å to 200 Å.

5. The surface acoustic wave filter structure according to claim 1, wherein Further comprising: A frequency modulation layer covering the substrate of the piezoelectric oscillation active region and the acoustic transducer, the first protective layer being located on the frequency modulation layer.

6. The surface acoustic wave filter structure according to claim 5, wherein The material of the frequency modulation layer comprises at least one of silicon oxide, silicon nitride, aluminum oxide, silicon carbide, silicon carbon oxide, aluminum nitride, gallium arsenide and gallium nitride.

7. The surface acoustic wave filter structure according to claim 5, wherein Further comprising: A second protective layer covering the acoustic transducer, or covering the substrate of the piezoelectric oscillation active region and the acoustic transducer; The frequency modulation layer is located on the second protective layer.

8. The surface acoustic wave filter structure according to claim 7, wherein The material of the second protective layer comprises at least one of silicon nitride, silicon carbonitride, silicon carbon oxynitride, silicon oxynitride, boron nitride and boron carbonitride.

9. The surface acoustic wave filter structure according to claim 1, wherein Further comprising: An interconnect structure located in the encapsulation layer on the first interconnect layer and electrically connected to the first interconnect layer.

10. The surface acoustic wave filter structure according to claim 9, characterized in that, Further comprising: An interconnect hole penetrating the encapsulation layer of the peripheral region and exposing the top of the first interconnect layer; The interconnect structure comprises a conductive pillar and a solder ball located on the top surface of the conductive pillar, the conductive pillar being located in the interconnect hole; Alternatively, the interconnect structure is a second interconnect layer, the second interconnect layer being located at the bottom and sidewall of the interconnect hole and extending to cover part of the top of the encapsulation layer.

11. The surface acoustic wave filter structure according to claim 1, characterized in that, The number of the first interconnect layers is multiple, and the multiple first interconnect layers are spaced apart from each other; The sealing layer is spaced apart from the first interconnect layer, or the sealing layer is only connected to one of the first interconnect layers.

12. A manufacturing method of a surface acoustic wave filter structure, characterized in that, Comprising: Providing a substrate, the substrate comprising a piezoelectric oscillation active region and a peripheral region surrounding the piezoelectric oscillation active region; Forming an acoustic transducer on the substrate of the piezoelectric oscillation active region; Forming a connection layer on the substrate of the peripheral region, the connection layer comprising a first interconnect layer and a sealing layer surrounding the periphery of the first interconnect layer, the first interconnect layer being electrically connected to the acoustic transducer; Forming a first protective layer covering the acoustic transducer; Forming an encapsulation layer on the connection layer, the encapsulation layer, the sealing layer and the substrate enclosing a cavity for accommodating the acoustic transducer.

13. The manufacturing method of the surface acoustic wave filter structure according to claim 12, characterized in that, In the step of forming the first protective layer covering the acoustic transducer, the first protective layer also covers the substrate of the piezoelectric oscillation active region exposed by the acoustic transducer.

14. The manufacturing method of the surface acoustic wave filter structure according to claim 12, characterized in that, The material of the first protective layer includes at least one of silicon nitride, silicon carbonitride, silicon carbon oxynitride, silicon oxynitride, boron nitride, and boron carbonitride.

15. The manufacturing method of the surface acoustic wave filter structure according to claim 12, characterized in that, The thickness of the first protective layer is 50 angstroms to 200 angstroms.

16. The manufacturing method of the surface acoustic wave filter structure according to claim 12, characterized in that, The process of forming the first protective layer includes a chemical vapor deposition process.

17. The manufacturing method of the surface acoustic wave filter structure according to claim 12, characterized in that, After forming an acoustic transducer on the substrate of the piezoelectric oscillation effective region and before forming the first protective layer on the acoustic transducer, it further includes: forming a frequency modulation layer on the substrate of the piezoelectric oscillation effective region, and the frequency modulation layer covers the acoustic transducer; After forming the first protective layer, the first protective layer covers the frequency modulation layer.

18. The manufacturing method of the surface acoustic wave filter structure according to claim 17, characterized in that, Before forming the frequency modulation layer on the acoustic transducer, it further includes: forming a second protective layer covering the acoustic transducer, or forming a second protective layer covering the substrate of the piezoelectric oscillation effective region and the acoustic transducer; After forming the frequency modulation layer, the frequency modulation layer covers the second protective layer.

19. The manufacturing method of the surface acoustic wave filter structure according to claim 12, characterized in that, It further includes: Forming an interconnect structure in the encapsulation layer on the first interconnect layer, and the interconnect structure is electrically connected to the first interconnect layer.

20. The manufacturing method of the surface acoustic wave filter structure according to claim 19, characterized in that, In the step of forming the encapsulation layer on the connection layer, the encapsulation layer includes an interconnect hole exposing the first interconnect layer; The interconnect structure is a conductive pillar and a solder ball located on the top surface of the conductive pillar. The steps of forming the interconnect structure include: forming a first seed layer on the top of the encapsulation layer, and the bottom and side walls of the interconnect hole; forming a first mask layer on the top of the first seed layer located outside the interconnect hole; after forming the first mask layer, filling a conductive material in the remaining space of the interconnect hole to form a conductive pillar; forming a solder ball on the conductive pillar; Alternatively, the interconnect structure is a second interconnect layer, and the second interconnect layer is located at the bottom and side walls of the interconnect hole and extends to cover a part of the top of the encapsulation layer. The steps of forming the interconnect structure include: forming a second seed layer on the top of the encapsulation layer, and the bottom and side walls of the interconnect hole; forming a second mask layer on the top of the second seed layer located outside the interconnect hole; after forming the second mask layer, forming a conductive layer on the top of the second seed layer, and the conductive layer and the second seed layer constitute the second interconnect layer.

21. The manufacturing method of the surface acoustic wave filter structure according to claim 13, characterized in that, In the step of forming the connection layer on the substrate of the peripheral region, the number of the first interconnect layers is multiple, and the multiple first interconnect layers are spaced apart; The sealing layer is spaced apart from the first interconnect layer, or the sealing layer is only connected to one first interconnect layer.

22. An electronic device, characterized in that, It includes the surface acoustic wave filter structure according to any one of claims 1 to 11.

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