Surface acoustic wave filter structure and electronic equipment

Abstract

A surface acoustic wave filter structure 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 of the embodiment of the utility model, the performance of the surface acoustic wave filter structure can be improved.

Description

Technical Field

[0001] The embodiments of the utility model relate to the field of semiconductors, and in particular to a surface acoustic wave filter structure and electronic equipment. Background Art

[0002] With the rapid development of wireless communication technology, 5G communication protocols are becoming more mature, and the market has also put forward more stringent standards for the performance of RF filters in all aspects. With the development of wireless communication technology, traditional single-band single-standard equipment can no longer meet the diversified requirements of communication systems. At present, communication systems are increasingly tending to multi-band, which requires communication terminals to be able to accept various frequency bands to meet the requirements of different communication service providers and different regions.

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

[0004] However, the performance of current filter structures still needs to be improved. Utility Model Content

[0005] The problem solved by the embodiments of the utility model is to provide a surface acoustic wave filter structure and electronic equipment, which are beneficial to improving the performance of the surface acoustic wave filter structure.

[0006] In order to solve the above problems, the present invention provides a surface acoustic wave filter structure, comprising:

[0007] A substrate, the substrate comprising a piezoelectric oscillation effective area and a peripheral area surrounding the piezoelectric oscillation effective area;

[0008] an acoustic transducer, located on the substrate of the piezoelectric oscillation effective area;

[0009] A connection layer, located on the substrate in the peripheral area, the connection layer comprising a first interconnection layer and a sealing layer surrounding the first interconnection layer, the first interconnection layer being electrically connected to the acoustic transducer;

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

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

[0012] Correspondingly, an embodiment of the utility model further provides an electronic device, comprising the surface acoustic wave filter structure as described in any one of the above items.

[0013] Compared with the prior art, the technical solution of the embodiment of the utility model has the following advantages:

[0014] An embodiment of the utility model provides a 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; an acoustic transducer, located on the substrate of the piezoelectric oscillation effective area; a connecting layer, located on the substrate of the peripheral area, the connecting layer comprising a first interconnection layer and a sealing layer surrounding 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 walls of the first interconnection layer and the substrate form a cavity, the cavity is used to accommodate the acoustic transducer.

[0015] The surface acoustic wave filter structure in the embodiment of the utility model includes a first protective layer covering the acoustic transducer. The first protective layer can protect the acoustic transducer in the subsequent process of forming a packaging layer, thereby avoiding corrosion of the acoustic transducer caused by acidic or alkaline developers in the process of forming the packaging layer, which correspondingly helps to improve the performance of the surface acoustic wave filter structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of an existing surface acoustic wave filter structure;

[0017] Figure 2 and Figure 3 It is a schematic diagram of the cross-sectional structure of an embodiment of a surface acoustic wave filter structure provided by the technical solution of the utility model along the first direction and the second direction respectively;

[0018] Figures 4 to 11 It is a schematic diagram of the intermediate structure formed by each step of the manufacturing method of the surface acoustic wave filter structure provided by the technical solution of the utility model;

[0019] 12 is a schematic diagram comparing the performance parameters of the surface acoustic wave filter structure in the embodiment of the utility model and the existing surface acoustic wave filter structure;

[0020] FIG. 13 is a schematic diagram of test results of a highly accelerated temperature, humidity and bias test of a surface acoustic wave filter structure provided by the technical solution of the present utility model. DETAILED DESCRIPTION

[0021] As can be seen from the background technology, the performance of the surface acoustic wave filter structure still needs to be improved. Figure 1A schematic structural diagram of a surface acoustic wave filter structure is shown, and the reasons for the poor performance of the surface acoustic wave filter structure are analyzed.

[0022] See also Figure 1 A surface acoustic wave filter structure includes: a substrate 10; the substrate 10 includes a piezoelectric oscillation effective area 10A and a peripheral area 10B surrounding the piezoelectric oscillation effective area 10A; an acoustic transducer 11, located on the substrate 10 in the piezoelectric oscillation effective area 10A; an interconnection layer 12, located on the top of the substrate 10 in the peripheral area 10B; a sealing layer 13, located on the top of the substrate 10 outside the interconnection layer 12; a packaging layer 14, located on the top of the interconnection layer 12 and the sealing layer 13, the packaging layer 14 and the side wall of the interconnection layer 12 and the substrate 10 form a cavity 15, 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.

[0023] In the above-mentioned surface acoustic wave filter structure, during the subsequent process of forming the packaging layer 14, the acoustic transducer 11 is exposed to the cavity 15. The acid- 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, thereby reducing the performance of the formed surface acoustic wave filter structure.

[0024] To solve the above technical problems, an embodiment of the utility model provides a 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; an acoustic transducer, located on the substrate of the piezoelectric oscillation effective area; a connecting layer, located on the substrate of the peripheral area, the connecting layer comprising a first interconnection layer and a sealing layer surrounding 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 walls of the first interconnection layer and the substrate forming a cavity, the cavity being used to accommodate the acoustic transducer.

[0025] The surface acoustic wave filter structure in the embodiment of the utility model includes a first protective layer covering the acoustic transducer. The first protective layer can protect the acoustic transducer in the subsequent process of forming a packaging layer, thereby avoiding corrosion of the acoustic transducer caused by acidic or alkaline developers in the process of forming the packaging layer, which correspondingly helps to improve the performance of the surface acoustic wave filter structure.

[0026] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0027] Figure 2 and Figure 3 It is a schematic diagram of the cross-sectional structure of an embodiment of a surface acoustic wave filter structure provided by the technical solution of the utility model along the first direction and the second direction respectively.

[0028] Combined with reference Figure 2 and Figure 3 A surface acoustic wave filter structure includes: a substrate 100, wherein the substrate 100 includes a piezoelectric oscillation effective area I and a peripheral area II surrounding the piezoelectric oscillation effective area I; an acoustic transducer 200, located on the substrate 100 in the piezoelectric oscillation effective area I; a connecting layer 110, located on the substrate 100 in the peripheral area II, wherein the connecting layer 110 includes a first interconnection layer 111 and a sealing layer 112 surrounding the first interconnection layer 111, wherein 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 top of the first interconnection layer 111, wherein the packaging layer 140, the sidewall of the first interconnection layer 111 and the substrate 100 form a cavity 105, wherein the cavity 105 is used to accommodate the acoustic transducer 200.

[0029] The substrate 100 is used to provide a process platform for forming a surface acoustic wave filter structure.

[0030] In this embodiment, the substrate 100 is a wafer-level substrate. By manufacturing the surface acoustic wave filter structure on a wafer-level substrate, the process cost can be reduced and batch production can be achieved, which is conducive to improving the reliability of the surface acoustic wave filter structure and improving the manufacturing efficiency.

[0031] The substrate 100 includes a piezoelectric oscillation effective area I, which is a working area of ​​the surface acoustic wave filter structure for realizing a filtering function. In this embodiment, the substrate 100 is a wafer-level substrate, and therefore, the substrate 100 includes a plurality of isolated piezoelectric oscillation effective areas I.

[0032] In this embodiment, the formed surface acoustic wave filter structure is a surface acoustic wave (SAW) filter structure as an example for description.

[0033] The SAW filter structure is a special filtering device made by using the piezoelectric effect and the physical characteristics of surface acoustic wave propagation. In the SAW filter structure, the signal undergoes two conversions from electric to acoustic to electric, thereby realizing the frequency selection characteristics. The SAW filter structure has the advantages of high operating frequency, simple manufacturing process, low manufacturing cost, and high consistency of frequency characteristics. Therefore, it is widely used in various electronic devices.

[0034] Accordingly, the substrate 100 is a piezoelectric substrate, so that the subsequent surface acoustic wave filter structure can use the piezoelectric effect for filtering. 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, apatite, 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 Love waves on a non-piezoelectric substrate.

[0035] The acoustic transducer 200 is used to realize the mutual conversion between the electric signal and the acoustic signal, so that the surface acoustic wave filter structure performs filtering processing on the signal. Specifically, the acoustic transducer 200 is an acoustic transducer with a piezoelectric structure.

[0036] In this embodiment, the filter structure formed is a SAW filter structure, and accordingly, the acoustic transducer 200 is a metal interdigital transducer (IDT). The IDT includes two groups of interdigital electrodes with energy conversion functions, namely an input interdigital transducer and an output interdigital transducer. When the input interdigital transducer receives an electrical signal, the surface of the piezoelectric substrate vibrates and excites an acoustic wave with the same frequency as the external signal. The acoustic wave propagates along the surface of the piezoelectric substrate, and a part of the acoustic wave is transmitted to the output interdigital transducer, which converts the mechanical vibration into an electrical signal, which is output by the output interdigital transducer.

[0037] The material of the interdigital electrode includes one or more of molybdenum (Mo), aluminum (Al), platinum (Pt), tungsten (W), gold (Au), nickel (Ni) and silver (Ag). Specifically, the acoustic transducer 200 is formed by evaporating a metal film on the substrate 100 and patterning the metal film through photolithography and etching processes. In this embodiment, the interdigital electrode is an interdigital aluminum electrode.

[0038] The first interconnection layer 111 is used as the input / output (I / O) terminal of the acoustic transducer 200, and is used 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, and prevent water vapor from entering the piezoelectric oscillation effective area I, which is beneficial to reduce the probability of oxidation and corrosion of the acoustic transducer 200 in the piezoelectric oscillation effective area I. Accordingly, the existence of the sealing layer 112 also reduces the probability of oxidation and corrosion of the first interconnection layer 111.

[0039] In this embodiment, the first interconnection layer 111 and the sealing layer 112 are made of the same material.

[0040] Specifically, the materials of the first interconnection 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 area I to be electrically connected to the external circuit structure through the first interconnection layer 111. As an example, the material of the first interconnection layer 111 is aluminum.

[0041] 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 of patterning the first interconnection layer 111 will increase, and the formation efficiency of the first interconnection layer 111 will be reduced; if the thickness of the first interconnection layer 111 is too small, it will easily lead to the effective height of the cavity 105 subsequently formed on the piezoelectric oscillation effective area I being too small. Accordingly, after the packaging layer 140 is deformed by external force, the probability of the packaging layer 140 contacting the acoustic transducer 200 is increased, thereby reducing the reliability of the surface acoustic wave filter structure. For this reason, in this embodiment, the thickness of the first interconnection layer 111 is 2 microns to 30 microns.

[0042] In this embodiment, the material of the sealing layer 112 is the same as the material of the first interconnection layer 111. Accordingly, the material of the sealing layer 112 includes one or more of titanium, copper, aluminum and nickel.

[0043] The material of the sealing layer 112 is metal. Since the metal atoms are closely arranged, the sealing layer 112 has good compactness, thereby being able to play a good sealing role. The sealing layer 112 and the first interconnection layer 111 are made of the same material, so that the sealing layer 112 and the first interconnection layer 111 can be etched in the same step, which is conducive to simplifying the filter formation process and improving efficiency.

[0044] In this embodiment, the thickness of the sealing layer 112 is substantially the same as the thickness of the first interconnection 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 interconnection layer 111 is less than 3 micrometers.

[0045] In this embodiment, the distance between the sealing layer 112 and the first interconnection layer 111 is greater than 2 microns, such as 5 microns and 8 microns. In some embodiments, the distance is 3-10 microns. If the distance is too small, it is easy to cause a short circuit. If the distance is too large, the surface acoustic wave filter structure formed 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 conducive it is to achieve miniaturization of the package.

[0046] In this embodiment, the width of the sealing layer 112 is greater than 10 microns, such as 15 microns, 25 microns, etc. In some embodiments, the width of the sealing layer 112 is 20-40 microns, such as 30 microns, 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 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.

[0047] It should be noted that, in this embodiment, there are multiple first interconnection layers 111 , and the multiple first interconnection layers 111 are spaced apart from each other, so that the multiple first interconnection layers 111 are not in contact with each other, that is, the multiple first interconnection layers 111 are in an open circuit state.

[0048] As an example, two first interconnection layers 111 are shown in the figure, wherein one first interconnection layer 111 is used to be connected to the input end of the acoustic transducer 200 , and the other first interconnection layer 111 is used to be electrically connected to the output end of the acoustic transducer 200 .

[0049] As an example, Figure 2 and Figure 3 As shown, two first interconnection layers 111 are located on both sides of the piezoelectric oscillation effective area I.

[0050] The sealing layer 112 is spaced from the first interconnection layer 111, or the sealing layer 112 is connected to only one first interconnection layer 111, so that the sealing layer 112 and the first interconnection layer 111 are in an open circuit state, so that the sealing layer 112 cannot function as an electrical connection.

[0051] It should be noted that when the sealing layer 112 is connected to one first interconnect layer 111 and disconnected from another 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 to avoid affecting the working performance of the acoustic transducer 200.

[0052] In this embodiment, the sealing layer 112 is annular, that is, the sealing layer 112 surrounds the first interconnection layer 111 , which is beneficial to improving the airtightness of the cavity 105 formed with the packaging layer 140 .

[0053] The first protective layer 120 is used to protect the acoustic transducer 200. Specifically, the first protective layer 120 can block the acidic or alkaline developer used in the subsequent process of forming the encapsulation layer 140, thereby preventing the acidic or alkaline developer used in the subsequent process of forming the encapsulation layer 140 from corroding the IDT and causing damage to the IDT.

[0054] Therefore, the first protective layer 120 is made of a material that can effectively resist corrosive liquids such as acidic or alkaline developer used in the process of forming the encapsulation layer 140, and the presence of the first protective layer 120 has little effect on the substrate 100 and the acoustic transducer 200 in the piezoelectric oscillation effective area I. In addition, the material of the first protective layer 120 can ensure that the first protective layer 120 has good coverage, so that the acoustic transducer 200 and the substrate 100 in the piezoelectric oscillation effective area I can be completely covered. For example, the material of the first protective layer 120 may include at least one of silicon nitride, silicon carbonitride, silicon carbonitride oxide, silicon oxynitride, boron nitride and boron carbonitride.

[0055] 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 acid or alkali developer used in the process of forming the encapsulation layer 140 from corroding the IDT, which helps to reduce the insertion loss of the IDT. At the same time, silicon nitride also has the characteristics of high strength, high hardness, high thermal conductivity and high temperature resistance, which is conducive to improving the reliability of the formed surface acoustic wave filter structure.

[0056] The thickness of the first protective layer 120 should not be too large or too small. If the thickness of the first protective layer 120 is too small, it cannot provide good protection for the acoustic transducer 200 during 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 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. For this reason, 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.

[0057] In this embodiment, the first protective layer 120 covers the substrate 100 and the acoustic transducer 200 in the piezoelectric oscillation effective area 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.

[0058] Compared with the method in which the first protective layer 120 only covers the acoustic transducer 200, the first protective layer 120 covers the substrate 100 and the acoustic transducer 200 of the piezoelectric oscillation effective area I, which can omit the corresponding photolithography and etching processes, which is beneficial to reducing process steps and reducing process costs.

[0059] 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 area I, and the frequency modulation layer 131 covers the acoustic transducer 200. Accordingly, the first protective layer 120 is located on the frequency modulation layer 131.

[0060] The frequency modulation layer 131 is used to adjust the working frequency of the acoustic transducer 200 .

[0061] The material of the frequency modulation layer 131 includes metal or insulating dielectric. The metal used to form the frequency modulation layer 131 includes molybdenum, ruthenium, tungsten, platinum, iridium, magnesium, aluminum, beryllium, copper, gold, chromium, cobalt and titanium; the insulating dielectric used to form the frequency modulation layer 131 includes silicon nitride, silicon oxide, aluminum oxide, silicon carbide, silicon oxycarbide, aluminum nitride, gallium arsenide or gallium nitride.

[0062] 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 relatively high, the silicon dioxide layer is selected as the material of the frequency modulation layer 131, which can reduce the operating frequency of the acoustic transducer 200; when the operating frequency of the acoustic transducer 200 is relatively low, the operating frequency of the acoustic transducer 200 can be increased by selecting at least one of silicon nitride, aluminum nitride, and silicon carbide as the material of the frequency modulation layer 131.

[0063] The thickness of the frequency modulation layer 131 should not be too large or too small. If the thickness of the frequency modulation layer 131 is too small, it cannot play a good role in regulating the working frequency of the acoustic transducer 200; if 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 is not conducive to the integration of the formed surface acoustic wave filter structure. For this reason, in this embodiment, the thickness of the frequency modulation layer 131 is 5nm to 500nm.

[0064] In this embodiment, the surface acoustic wave filter structure further includes: a second protective layer 132 located on the substrate 100 in the piezoelectric oscillation effective area I, and the second protective layer 132 covers the acoustic transducer 200. Accordingly, the frequency modulation layer 131 is located on the second protective layer 132.

[0065] The second protective layer 132 is used to protect the acoustic transducer 200 in the subsequent process after the acoustic transducer 200 is formed. Specifically, the second protective layer 132 is used to protect the acoustic transducer 200 in the process of forming the frequency modulation layer 131 subsequently.

[0066] According to actual needs, the thickness of the second protective layer 132 may be 20 angstroms to 1000 angstroms. In some embodiments, the thickness of the second protective layer 132 is 50 angstroms to 150 angstroms, such as 50 angstroms, 80 angstroms, or 100 angstroms.

[0067] The material of the second protective layer 132 is as described above with reference to the corresponding contents regarding the first protective layer 120 , and will not be described in detail here.

[0068] It should be noted that, in this embodiment, the second protective layer 132 is located on the substrate 100 in the piezoelectric oscillation active area 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.

[0069] The packaging layer 140 is used to realize the packaging of the surface acoustic wave filter structure, and plays a role of sealing and moisture-proofing, which correspondingly reduces the impact 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.

[0070] In this embodiment, the encapsulation layer 140 is located on the top of the connection layer 110 .

[0071] The material of the encapsulation layer 140 includes a photosensitive material or a non-photosensitive material. As an example, the material of the encapsulation layer 140 is a photosensitive material, which is conducive to the subsequent patterning of the encapsulation layer 140, thereby reducing the complexity of the patterning process and improving the process accuracy. Specifically, the photosensitive material is a dry film. The dry film is a permanent bonding film with a high bonding strength, so that the bonding strength between the encapsulation layer 140 and the connecting layer 110 is guaranteed, and at the same time, it is conducive to improving the sealing of the cavity 105.

[0072] In this embodiment, the photosensitive material is a film-like dry film, which makes the process of forming the encapsulation layer 140 simple. The film-like dry film is manufactured by coating a solvent-free photoresist on a polyester base, and then covering it with a polyethylene film; when in use, the polyethylene film is peeled off and the solvent-free photoresist is pressed on the base.

[0073] In some other embodiments, the material of the encapsulation layer can also be a liquid dry film, wherein the liquid dry film refers to a film-like dry film in which the components exist in a liquid form.

[0074] In other embodiments, the material of the encapsulation layer may also be a dielectric material or an organic material, wherein the dielectric material may be silicon oxide, phosphosilicate glass (PSG) or borophosphorus glass (BPSG), etc., and the organic material may be polyimide, etc.

[0075] 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, the difficulty of removing the encapsulation layer 140 will be increased in the subsequent process of forming the interconnection holes. At the same time, the size of the interconnection holes formed in the encapsulation layer 140 will become larger, which will increase the overall area of ​​the surface acoustic wave filter structure and waste too much material of the encapsulation layer 140, increasing the process cost. If the thickness of the encapsulation layer 140 is too small, it will easily lead to a decrease in the external extrusion ability that the encapsulation layer 140 can withstand, and the air tightness and waterproof performance of the encapsulation layer 140 will be reduced, thereby putting forward higher requirements for the subsequent process and application environment of the surface acoustic wave filter structure. For this reason, in this embodiment, the thickness of the encapsulation layer 140 is 5 microns to 60 microns.

[0076] The interconnect structure 150 is used to realize electrical connection between the first interconnect layer 111 and an external circuit structure.

[0077] In this embodiment, the interconnect structure 150 includes a conductive pillar 151 and a solder ball 152 located on a top surface of the conductive pillar 151 .

[0078] 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.

[0079] The material of the solder ball 152 can be tin solder, silver solder or tin-silver alloy solder. In this embodiment, the material of the solder ball 152 is tin-silver alloy solder.

[0080] refer to Fig.10 In some other embodiments, the interconnect structure 150 may also include only the conductive pillar 151 .

[0081] refer to Fig.11 In other embodiments, the interconnect structure 150 may also be a second interconnect layer, which is located at the bottom and sidewalls of the interconnect hole and also extends to cover a portion of the top of the packaging layer 140 .

[0082] Figures 4 to 11It is a structural schematic diagram corresponding to each step in an embodiment of a method for forming a surface acoustic wave filter structure of the utility model.

[0083] refer to Figure 4 , providing a substrate 100, wherein the substrate 100 includes a piezoelectric oscillation effective area I and a peripheral area II surrounding the piezoelectric oscillation effective area I, and an acoustic transducer 200 is formed on the substrate 100 in the piezoelectric oscillation effective area I.

[0084] The substrate 100 is used to provide a process platform for the subsequent formation of a surface acoustic wave filter structure. In this embodiment, the substrate 100 is a wafer-level substrate. By manufacturing the surface acoustic wave filter structure on a wafer-level substrate, the process cost can be reduced and batch production can be achieved, which is conducive to improving the reliability of the surface acoustic wave filter structure and improving manufacturing efficiency.

[0085] The substrate 100 includes a piezoelectric oscillation effective area I, which is a working area of ​​the surface acoustic wave filter structure for realizing a filtering function. In this embodiment, the substrate 100 is a wafer-level substrate, and therefore, the substrate 100 includes a plurality of isolated piezoelectric oscillation effective areas I.

[0086] In this embodiment, the formed filter structure is a SAW filter structure as an example for description.

[0087] The SAW filter structure is a special filtering device made by using the piezoelectric effect and the physical characteristics of surface acoustic wave propagation. In the SAW filter structure, the signal undergoes two conversions from electric to acoustic to electric, thereby realizing the frequency selection characteristics. The SAW filter structure has the advantages of high operating frequency, simple manufacturing process, low manufacturing cost, and high consistency of frequency characteristics. Therefore, it is widely used in various electronic devices.

[0088] Accordingly, the substrate 100 is a piezoelectric substrate, so that the subsequent surface acoustic wave filter structure can use the piezoelectric effect for filtering. 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, apatite, 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 Love waves on a non-piezoelectric substrate.

[0089] refer to Figure 5 A connection layer 110 is formed on the substrate 100 in the peripheral area II. The connection layer 110 includes a first interconnection layer 111 and a sealing layer 112 surrounding the first interconnection layer 111. The first interconnection layer 111 is electrically connected to the acoustic transducer 200.

[0090] The first interconnection layer 111 is used as the I / O terminal of the acoustic transducer 200, and is used 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, and prevent water vapor from entering the piezoelectric oscillation effective area I, which is beneficial to reduce the probability of oxidation and corrosion of the acoustic transducer 200 in the piezoelectric oscillation effective area I. Correspondingly, the existence of the sealing layer 112 also reduces the probability of oxidation and corrosion of the first interconnection layer 111.

[0091] In this embodiment, the first interconnection layer 111 and the sealing layer 112 are made of the same material. Accordingly, the first interconnection layer 111 and the sealing layer 112 are formed in the same step.

[0092] Compared with forming the first interconnection layer 111 and the sealing layer 112 in separate steps, forming the first interconnection layer 111 and the sealing layer 112 in the same step is beneficial to improving the manufacturing efficiency of the surface acoustic wave filter structure and reducing the process cost.

[0093] In this embodiment, the material of the first interconnection layer 111 and the sealing layer 112 includes 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 area I to be electrically connected to the external circuit structure through the first interconnection layer 111. As an example, the material of the first interconnection layer 111 is aluminum.

[0094] The steps of forming the first interconnection 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 area II; patterning the connection material layer to form the first interconnection layer 111 and the sealing layer 112, and the first interconnection layer 111 and the sealing layer 112 constitute the connection layer 110.

[0095] In this embodiment, the connection material layer is formed by chemical electroplating process. 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.

[0096] In this embodiment, a dry etching process is used to pattern the connection material layer to form the first interconnection layer 111 and the sealing layer 112 .

[0097] 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 of patterning the connection material layer will be increased; if the thickness of the first interconnection layer 111 is too small, it will easily lead to the effective height of the cavity formed in the piezoelectric oscillation effective area I being too small. Accordingly, after the packaging layer 140 is deformed by external force, the probability of the packaging layer 140 contacting the acoustic transducer 200 is increased, thereby reducing the reliability of the surface acoustic wave filter structure. For this reason, in this embodiment, the thickness of the first interconnection layer 111 is 2 microns to 30 microns.

[0098] In this embodiment, the material of the sealing layer 112 is the same as the material of the first interconnection layer 111 . Accordingly, the material of the sealing layer 112 includes one or more of titanium, copper, aluminum and nickel.

[0099] The material of the sealing layer 112 is metal. Since the metal atoms are closely arranged, the sealing layer 112 has good compactness, thereby being able to play a good sealing role. The sealing layer 112 and the first interconnection layer 111 are made of the same material, so that the sealing layer 112 and the first interconnection layer 111 can be formed by etching the connection material layer in the same step, which is conducive to simplifying the filter formation process and improving efficiency.

[0100] In this embodiment, the sealing layer 112 and the first interconnection layer 111 are formed in the same step, so the thickness of the sealing layer 112 is substantially the same as the thickness of the first interconnection layer 111. Specifically, the thickness of the sealing layer 112 is 2 microns to 30 microns. The height difference between the sealing layer 112 and the first interconnection layer 111 is less than 3 microns. In other embodiments, the sealing layer and the first interconnection layer may also be formed separately in different steps.

[0101] In this embodiment, the distance between the sealing layer 112 and the first interconnection layer 111 is greater than 2 microns, such as 5 microns and 8 microns. In some embodiments, the distance is 3-10 microns. If the distance is too small, it is easy to cause a short circuit. If the distance is too large, the surface acoustic wave filter structure formed 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 conducive it is to achieve miniaturization of the package.

[0102] In this embodiment, the width of the sealing layer 112 is greater than 10 microns, such as 15 microns, 25 microns, etc. In some embodiments, the width of the sealing layer 112 is 20 to 40 microns, such as 30 microns, 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 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.

[0103] It should be noted that, in the step of forming the connecting layer 110 on the substrate 100 in the peripheral area II, the number of the first interconnection layers 111 is multiple, and the multiple first interconnection layers 111 are spaced apart from each other, so that the multiple first interconnection layers 111 are not in contact with each other, that is, the multiple first interconnection layers 111 are in an open circuit state.

[0104] As an example, two first interconnection layers 111 are shown in the figure, wherein one first interconnection layer 111 is used to connect to the input end of the IDT, and the other first interconnection layer 111 is used to electrically connect to the output end of the IDT.

[0105] As an example, Figure 2 and Figure 3 As shown, two first interconnection layers 111 are located on both sides of the piezoelectric oscillation effective area I.

[0106] The sealing layer 112 is spaced apart from the first interconnection layer 111 , or the sealing layer 112 is connected to only one first interconnection layer 111 , so that the sealing layer 112 and the first interconnection layer 111 are in an open circuit state, so that the sealing layer 112 cannot function as an electrical connection.

[0107] It should be noted that when the sealing layer 112 is connected to one first interconnect layer 111 and disconnected from another 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 to avoid affecting the working performance of the acoustic transducer 200.

[0108] In this embodiment, the sealing layer 112 is annular, that is, the sealing layer 112 surrounds the first interconnection layer 111 , which is beneficial to improving the airtightness of the cavity formed subsequently with the packaging layer.

[0109] refer to Figure 6 , a first protective layer 120 is formed on the substrate 100 in the piezoelectric oscillation effective area I, and the first protective layer 120 covers the acoustic transducer 200.

[0110] The first protective layer 120 is used to protect the acoustic transducer 200. Specifically, the first protective layer 120 can block the acidic or alkaline developer used in the subsequent process of forming the encapsulation layer 140, thereby preventing the acidic or alkaline developer used in the subsequent process of forming the encapsulation layer 140 from corroding the IDT and causing damage to the IDT.

[0111] Therefore, the first protective layer 120 is made of a material that can effectively resist corrosive liquids such as acidic or alkaline developer used in the process of forming the encapsulation layer 140, and the presence of the first protective layer 120 has little effect on the substrate 100 and the acoustic transducer 200 in the piezoelectric oscillation effective area I. In addition, the material of the first protective layer 120 can ensure that the first protective layer 120 has good coverage, so that the acoustic transducer 200 and the substrate 100 in the piezoelectric oscillation effective area I can be completely covered. For example, the material of the first protective layer 120 may include at least one of silicon nitride, silicon carbonitride, silicon carbonitride oxide, silicon oxynitride, boron nitride and boron carbonitride.

[0112] 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 acid or alkali developer used in the process of forming the encapsulation layer 140 from corroding the IDT, which helps to reduce the insertion loss of the IDT. At the same time, silicon nitride also has the characteristics of high strength, high hardness, high thermal conductivity and high temperature resistance, which is conducive to improving the reliability of the formed surface acoustic wave filter structure.

[0113] In this embodiment, a chemical vapor deposition (CVD) process is used to form the first protective layer 120. The chemical vapor deposition process has a good deposition effect and a high gap filling ability, so that the first protective layer 120 formed has a good morphology quality and can better cover the acoustic transducer 200 and the substrate 100 of the piezoelectric oscillation effective area I.

[0114] In other embodiments, other suitable processes may be used to form the first protective layer, and those skilled in the art may select other suitable processes according to actual needs, and no limitation is made here.

[0115] The thickness of the first protective layer 120 should not be too large or too small. If the thickness of the first protective layer 120 is too small, it cannot provide good protection for the acoustic transducer 200 during 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. To this end, in this embodiment, the thickness of the first protective layer 120 is 20 angstroms to 200 angstroms, such as 50 angstroms, 70 angstroms, 90 angstroms, etc.

[0116] 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 area 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.

[0117] Compared with the method in which the first protective layer 120 only covers the acoustic transducer 200, the first protective layer 120 covers the substrate 100 and the acoustic transducer 200 of the piezoelectric oscillation effective area I, which can omit the corresponding photolithography and etching processes, which is beneficial to reducing process steps and reducing process costs.

[0118] Please continue to refer to Figure 6 Before forming the first protective layer 120, the method for manufacturing the surface acoustic wave filter structure may further include: forming a frequency modulation layer 131 on the substrate 100 of the piezoelectric oscillation effective area I, wherein the frequency modulation layer 131 covers the acoustic transducer 200. Accordingly, after forming the first protective layer 120, the first protective layer 120 is located on the frequency modulation layer 131.

[0119] The frequency modulation layer 131 is used to adjust the working frequency of the acoustic transducer 200 .

[0120] The material of the frequency modulation layer 131 includes metal or insulating dielectric. The metal used to form the frequency modulation layer 131 includes molybdenum, ruthenium, tungsten, platinum, iridium, magnesium, aluminum, beryllium, copper, gold, chromium, cobalt and titanium; the insulating dielectric used to form the frequency modulation layer 131 includes silicon nitride, silicon oxide, aluminum oxide, silicon carbide, silicon oxycarbide, aluminum nitride, gallium arsenide or gallium nitride.

[0121] 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 relatively high, the silicon dioxide layer is selected as the material of the frequency modulation layer 131, which can reduce the operating frequency of the acoustic transducer 200; when the operating frequency of the acoustic transducer 200 is relatively low, the operating frequency of the acoustic transducer 200 can be increased by selecting at least one of silicon nitride, aluminum nitride, and silicon carbide as the material of the frequency modulation layer 131.

[0122] The thickness of the frequency modulation layer 131 should not be too large or too small. If the thickness of the frequency modulation layer 131 is too small, it cannot play a good role in regulating the working frequency of the acoustic transducer 200; if 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 is not conducive to the integration of the formed surface acoustic wave filter structure. For this reason, in this embodiment, the thickness of the frequency modulation layer 131 is 5nm to 500nm.

[0123] Please continue to refer to Figure 6 Before forming the frequency modulation layer 131, the method for manufacturing the surface acoustic wave filter structure may further include: forming a second protective layer 132 on the substrate 100 of the piezoelectric oscillation effective area I, wherein the second protective layer 132 covers the acoustic transducer 200. Accordingly, after forming the frequency modulation layer 131, the frequency modulation layer 131 is located on the second protective layer 132.

[0124] The second protective layer 132 is used to protect the acoustic transducer 200 in the subsequent process after the acoustic transducer 200 is formed. Specifically, the second protective layer 132 is used to protect the acoustic transducer 200 in the process of forming the frequency modulation layer 131 subsequently.

[0125] According to actual needs, the thickness of the second protective layer 132 may be 20 angstroms to 1000 angstroms. In some embodiments, the thickness of the second protective layer 132 is 50 angstroms to 150 angstroms, such as 50 angstroms, 80 angstroms, or 100 angstroms.

[0126] Regarding the material and formation process of the second protection layer 132 , please refer to the corresponding contents regarding the first protection layer 120 , which will not be repeated here.

[0127] It should be noted that, in this embodiment, the second protective layer 132 is located on the substrate 100 in the piezoelectric oscillation active area 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.

[0128] refer to Figure 7 A packaging layer 140 is formed on the connecting layer 110 . The packaging layer 140 , the sealing layer 112 and the substrate 100 form a cavity 105 . The cavity 105 is used to accommodate the acoustic transducer 200 .

[0129] The packaging layer 140 is used to realize the packaging of the surface acoustic wave filter structure, and plays a role of sealing and moisture-proofing, which correspondingly reduces the impact 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.

[0130] In this embodiment, the encapsulation layer 140 is located on the top of the connection layer 110 .

[0131] The material of the encapsulation layer 140 includes a photosensitive material or a non-photosensitive material. As an example, the material of the encapsulation layer 140 is a photosensitive material, which is conducive to the subsequent patterning of the encapsulation layer 140, thereby reducing the process complexity of the patterning process and improving the process accuracy. Specifically, the photosensitive material is a dry film. The dry film is a permanent bonding film with a high bonding strength, so that the bonding strength between the encapsulation layer 140 and the connecting layer 110 is guaranteed, and at the same time, it is conducive to improving the sealing of the cavity 105.

[0132] In this embodiment, the photosensitive material is a film-like dry film, which makes the process of forming the encapsulation layer 140 simple. The manufacture of the film-like dry film is to apply a solvent-free photoresist on a polyester 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 on the base. For this reason, in this embodiment, a film laminating process is used to form the encapsulation layer 140. Among them, the film laminating process is carried out in a vacuum environment, has good step coverage ability, and can significantly improve the fit and adhesion strength of the encapsulation layer 140 and the connection layer 110.

[0133] In some other embodiments, the encapsulation layer may also be formed by a liquid dry film. The liquid dry film refers to a film-like dry film in which the components exist in a liquid form. Accordingly, the step of forming the encapsulation layer includes: applying the liquid dry film by a spin coating process; and curing the liquid dry film to form an encapsulation layer. The cured liquid dry film is also a photosensitive material.

[0134] In other embodiments, the material of the encapsulation layer may also be a dielectric material or an organic material. Accordingly, the encapsulation layer may be formed by a deposition process or a coating process, respectively. The dielectric material may be silicon oxide, phosphosilicate glass or borophosphorus glass, and the organic material may be polyimide.

[0135] 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, the difficulty of removing the encapsulation layer 140 will be increased in the subsequent process of forming the interconnection holes. At the same time, the size of the interconnection holes formed in the encapsulation layer 140 will be larger, which will increase the overall area of ​​the surface acoustic wave filter structure and waste too much material of the encapsulation layer 140, increasing the process cost. If the thickness of the encapsulation layer 140 is too small, it will easily lead to a decrease in the external extrusion ability that the encapsulation layer 140 can withstand, and the air tightness and waterproof performance of the encapsulation layer 140 will be reduced, thereby putting forward higher requirements for the subsequent process and application environment of the surface acoustic wave filter structure. For this reason, in this embodiment, the thickness of the encapsulation layer 140 is 5 microns to 60 microns.

[0136] refer to Figure 8 , an interconnection hole 145 exposing the top of the first interconnection layer 111 is formed in the packaging layer 140 .

[0137] The interconnection holes 145 are used to provide a spatial location for an interconnection structure to be formed subsequently.

[0138] In this embodiment, the interconnection hole 145 passes through the packaging layer 140 .

[0139] Specifically, the interconnection hole 145 penetrates the packaging layer 140 to expose the top surface of the first interconnection layer 111 , which facilitates the interconnection structure subsequently formed therein to contact the exposed top surface of the first interconnection layer 111 , thereby achieving electrical connection between the interconnection structure and the first interconnection layer 111 .

[0140] refer to Fig. 9 , an interconnection structure 150 is formed in the interconnection hole 145 , and a bottom of the interconnection structure 150 is electrically connected to a top of the first interconnection layer 111 .

[0141] The interconnect structure 150 is used to realize electrical connection between the first interconnect layer 111 and an external circuit structure.

[0142] In this embodiment, a bump process is used to form the interconnection structure 150 in the interconnection hole 145. The bump process is used to facilitate the subsequent packaging process.

[0143] The bumping process is a metal pillar process. Specifically, the steps of the bumping process include: filling the interconnection hole 145 to form a conductive pillar 151 ; 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 interconnection structure 150 .

[0144] Specifically, the step of forming the conductive pillar 151 includes: forming a first seed layer (not shown) on the top of the encapsulation layer 140 and the bottom and sidewall of the interconnection hole 145; forming a first mask layer (not shown) on the top of the first seed layer located outside the interconnection hole 145; after forming the first mask layer, forming the conductive pillar 151 in the remaining space of the interconnection hole 145.

[0145] 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.

[0146] In this embodiment, the conductive pillar 151 may be formed by an electroplating process. In other embodiments, the conductive pillar may be formed by any one of a physical vapor deposition (PVD) process, a chemical vapor deposition process, vacuum evaporation or chemical plating process.

[0147] 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 .

[0148] 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.

[0149] 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 . The solder ball 152 and the conductive pillar 151 are used to constitute the interconnect structure 150 .

[0150] The material of the solder ball 152 can be tin solder, silver solder or tin-silver alloy solder, and can be formed by any one of physical vapor deposition process, chemical vapor deposition process, vacuum evaporation, electroplating or chemical plating. In this embodiment, the material of the solder ball 152 is tin-silver alloy solder.

[0151] refer to Fig.10 In some other embodiments, a conductive column may be formed in the interconnection hole, and the conductive column is used as the interconnection structure.

[0152] Specifically, a conductive column is formed in the interconnection hole by adopting a chemical plating process.

[0153] It should be noted that the steps of forming a conductive column in the interconnect hole by using a chemical plating process include: removing a small amount of organic residue 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 solution containing active target ions on the surface of the first interconnect layer; preliminarily cleaning the solution on the surface of the first interconnect layer; cleaning the surface of the first interconnect layer again to clean 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 the nickel. The above reactions continue, and eventually the interconnect hole of the packaging layer 140 is completely filled with nickel (nickel-phosphorus alloy), that is, a conductive column is formed in the interconnect hole.

[0154] refer to Fig.11 In other embodiments, a second interconnection layer may be formed at the bottom and sidewalls of the interconnection hole 145 , and the second interconnection layer extends to cover a portion of the top of the packaging layer 140 , and the second interconnection layer is used as the interconnection structure 150 .

[0155] Specifically, the steps of forming the interconnect structure include: forming a second seed layer on the top of the packaging layer 140, and on the bottom and sidewalls of the interconnect hole 145; forming a second mask layer on the top of the second seed layer outside the interconnect hole 145; after forming the second mask layer, forming a conductive layer on the top of the second seed layer using an electroplating process, and the conductive layer and the second seed layer constitute the interconnect structure.

[0156] It should be noted that after forming the interconnect structure 150 , the process further includes: removing the second mask layer and the second seed layer exposed by the interconnect structure 150 .

[0157] Figure 12 shows a schematic diagram comparing the performance parameters of the surface acoustic wave filter structure in the embodiment of the utility model and the existing surface acoustic wave filter structure, and Table 1 shows the changes in 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 utility model.

[0158] Table 1

[0159]

[0160]

[0161] Combined with reference to Table 1 and FIG. 12, experimental verification shows that the insertion loss, waveform, quality factor (Quality Factor) of the surface acoustic wave filter structure in the embodiment of the utility model, as well as the impedance amplitude (ZMagnitude) parameter, stray wave (Magnetic spurious, Mag_spur ) The main performance indicators such as impedance including parameters and electromechanical coupling coefficient (keff2) are all within the process allowable range and are better than the existing surface acoustic wave filter structure.

[0162] FIG. 13 and Table 2 show the comparison of the test results of the high accelerated temperature and humidity and bias voltage test (ubias Highly Accelerated Stress Test, uHAST) of the surface acoustic wave filter structure in the embodiment of the utility model and the existing surface acoustic wave filter structure.

[0163] Table 2

[0164]

[0165] Combined with reference table 2 and Figure 13, 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 utility model before and after uHAST are better than those of the existing surface acoustic wave filter structure, and the image of the surface acoustic wave filter structure in the embodiment of the utility model observed by an optical microscope (as shown in Figure 13 (e)) shows that there is almost no damage to the acoustic transducer, while the image of the existing surface acoustic wave filter structure (as shown in Figure 13 (f)) shows that there is more damage to the acoustic transducer. Therefore, the reliability of the surface acoustic wave filter structure in the embodiment of the utility model under uHAST is better than that of the existing surface acoustic wave filter structure.

[0166] 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.

[0167] Although the utility model is disclosed as above, the utility model 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 utility model. Therefore, the protection scope of the utility model shall be subject to the scope defined by the claims.

Claims

1. A surface acoustic wave filter structure, characterized in that: include: A substrate, the substrate comprising a piezoelectric oscillation effective area and a peripheral area surrounding the piezoelectric oscillation effective area; an acoustic transducer, located on the substrate of the piezoelectric oscillation effective area; A connection layer, located on the substrate in the peripheral area, the connection layer comprising a first interconnection layer and a sealing layer surrounding the first interconnection layer, the first interconnection layer being electrically connected to the acoustic transducer; a first protective layer, covering the acoustic transducer; The packaging layer is located on the top of the first interconnection layer. The packaging layer, the side wall of the first interconnection layer and the substrate form a cavity, and the cavity is used to accommodate the acoustic transducer.

2. The surface acoustic wave filter structure according to claim 1, characterized in that: The first protection layer is also located on the base of the piezoelectric oscillation effective area 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 includes any one of silicon nitride, silicon carbonitride, silicon carbonitride oxide, silicon nitride oxide, 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 angstroms to 200 angstroms.

5. The surface acoustic wave filter structure according to claim 1, characterized in that: Also includes: A frequency modulation layer covers the substrate of the piezoelectric oscillation effective area and the acoustic transducer, and the first protective layer is located on the frequency modulation layer.

6. The surface acoustic wave filter structure according to claim 5, characterized in that: The material of the frequency modulation layer includes any one of silicon oxide, silicon nitride, aluminum oxide, silicon carbide, silicon oxycarbide, aluminum nitride, gallium arsenide and gallium nitride.

7. The surface acoustic wave filter structure according to claim 5, characterized in that: Also includes: a second protective layer covering the acoustic transducer, or covering the substrate of the piezoelectric oscillation effective area and the acoustic transducer; The frequency modulation layer is located on the second protection layer.

8. The surface acoustic wave filter structure according to claim 7, characterized in that: The material of the second protective layer includes any one of silicon nitride, silicon carbonitride, silicon carbonitride oxide, silicon nitride oxide, boron nitride and boron carbonitride.

9. The surface acoustic wave filter structure according to claim 1, characterized in that: Also includes: The interconnection structure is located in the packaging layer on the first interconnection layer and is electrically connected to the first interconnection layer.

10. The surface acoustic wave filter structure according to claim 9, characterized in that: Also includes: an interconnection hole, penetrating the packaging layer in the peripheral region and exposing a top of the first interconnection layer; The interconnect structure includes a conductive column and a solder ball located on the top surface of the conductive column, and the conductive column is located in the interconnect hole; Alternatively, the interconnection structure is a second interconnection layer, and the second interconnection layer is located at the bottom and sidewalls of the interconnection hole and extends to cover a portion of the top of the packaging layer.

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

12. An electronic device, characterized in that: The method comprises a surface acoustic wave filter structure as claimed in any one of claims 1 to 11.

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