Film surface acoustic wave filter packaging structure, preparation method thereof and radio frequency equipment

Abstract

The invention provides a thin film surface acoustic wave filter packaging structure, a preparation method thereof and radio frequency equipment, and relates to the technical field of semiconductors. The groove area arranged on the packaging cover plate is used for forming a cavity area. The annular enclosing wall structure is arranged between the substrate and the packaging cover plate to achieve the purpose of isolating water vapor, so that the air tightness of the film surface acoustic wave filter packaging structure is better. Based on the characteristics of the packaging cover plate and the dry film, the strength of the packaging cover plate is higher than that of the dry film, in the layout process, the packaging cover plate only needs to form a circle around the chip based on the cavity area, and compared with an existing double-layer dry film packaging technology, the area of the chip can be smaller, and the supporting problem does not need to be considered. In other words, compared with a double-layer dry film packaging technology, the technical scheme of the invention is greatly improved in the aspects of stability, supporting performance, air tightness and the like.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a thin film surface acoustic wave filter packaging structure and a preparation method thereof, and a radio frequency device. Background Art

[0002] SAW (Surface Acoustic Wave) filter is the abbreviation of surface acoustic wave filter. It is a special filtering device made by using its piezoelectric effect and the physical characteristics of surface acoustic wave propagation. It is widely used in various fields, such as radio frequency. Among them, surface acoustic wave is an elastic wave with energy concentrated near the surface.

[0003] For TF-SAW (Thin-Film Surface Acoustic Wave) filters, the current packaging structure of thin-film surface acoustic wave filters is to form a cavity area by covering with dry film. Since the material of the dry film is usually organic material, it cannot completely isolate water vapor. And because the dry film is not rigid enough, it is necessary to add dry film between the interdigitated electrodes as support, resulting in a larger chip area. This traditional packaging technology is also called double-layer dry film packaging technology in the field.

[0004] Therefore, how to optimize the packaging structure of the thin film surface acoustic wave filter is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0005] In view of the above problems, the present application provides a thin film surface acoustic wave filter packaging structure and a preparation method thereof, and a radio frequency device, so as to achieve the purpose of improving the stability of the thin film surface acoustic wave filter packaging structure and reducing the chip area. The specific scheme is as follows:

[0006] A first aspect of the present application provides a thin film surface acoustic wave filter packaging structure, the thin film surface acoustic wave filter packaging structure comprising:

[0007] A substrate and a packaging cover plate arranged opposite to each other, wherein the packaging cover plate comprises a groove area arranged toward one side of the substrate;

[0008] A piezoelectric film layer and an annular wall structure located between the substrate and the packaging cover and on the substrate, and an interdigitated electrode located on a side of the piezoelectric film layer away from the substrate;

[0009] In which, the interdigitated electrode is located inside the annular wall structure; in the first direction, the orthographic projection of the groove area at least covers the orthographic projection of the interdigitated electrode, and there is a gap between the interdigitated electrode and the bottom of the groove area in the first direction; the first direction is perpendicular to the plane where the substrate is located.

[0010] Preferably, in the above-mentioned thin film surface acoustic wave filter packaging structure, the material of the annular wall structure is a metal material or an inorganic material.

[0011] Preferably, in the above-mentioned thin film surface acoustic wave filter packaging structure, the width of the annular wall structure ranges from 2 μm to 5 μm;

[0012] The thickness of the annular wall structure is in the range of 1 μm to 2 μm.

[0013] Preferably, in the above-mentioned thin film surface acoustic wave filter packaging structure, the depth of the groove area ranges from 5 μm to 15 μm.

[0014] Preferably, in the above-mentioned thin film surface acoustic wave filter packaging structure, the packaging cover plate is a Si cover plate.

[0015] Preferably, in the above-mentioned thin film surface acoustic wave filter packaging structure, the thin film surface acoustic wave filter packaging structure further includes:

[0016] At least one dielectric layer is located between the piezoelectric film layer and the substrate.

[0017] Preferably, in the above-mentioned thin film surface acoustic wave filter packaging structure, the thin film surface acoustic wave filter packaging structure further includes:

[0018] A pad structure located between the substrate and the package cover plate and on the substrate;

[0019] The pad structure is located inside the annular wall structure.

[0020] Preferably, in the above-mentioned thin film surface acoustic wave filter packaging structure, the thin film surface acoustic wave filter packaging structure further comprises: a protective layer;

[0021] The protective layer covers the interdigitated electrodes, the pad structure and the annular wall structure;

[0022] The protection layer has a first through hole, and the first through hole exposes a portion of the surface of the pad structure.

[0023] Preferably, in the above-mentioned thin film surface acoustic wave filter packaging structure, the thin film surface acoustic wave filter packaging structure further includes:

[0024] A second through hole passes through the package cover plate, wherein the second through hole exposes a portion of the surface of the pad structure.

[0025] Preferably, in the above-mentioned thin film surface acoustic wave filter packaging structure, the thin film surface acoustic wave filter packaging structure further includes:

[0026] A first metal layer fills the second through hole, wherein the first metal layer is electrically connected to the pad structure.

[0027] Preferably, in the above-mentioned thin film surface acoustic wave filter packaging structure, the thin film surface acoustic wave filter packaging structure further includes:

[0028] a solder ball located on a side of the package cover plate facing away from the substrate, the solder ball being electrically connected to the first metal layer;

[0029] At least one second metal layer is located between the solder ball and the first metal layer.

[0030] Preferably, in the above-mentioned thin film surface acoustic wave filter packaging structure, the interdigitated electrodes include a first bus bar and a second bus bar arranged opposite to each other in the second direction, and a first electrode finger located on the first bus bar and a second electrode finger located on the second bus bar;

[0031] The first bus bar and the second bus bar have the same length extension direction, both extending along a third direction. The second direction and the third direction are parallel to the plane where the substrate is located, and the second direction and the third direction intersect.

[0032] A second aspect of the present application provides a method for preparing a thin film surface acoustic wave filter packaging structure, the method for preparing a thin film surface acoustic wave filter packaging structure comprising:

[0033] Providing a substrate, forming a piezoelectric film layer, interdigital electrodes and an annular wall structure on the substrate, wherein the interdigital electrodes are located on a side of the piezoelectric film layer away from the substrate;

[0034] Providing a packaging cover plate, and processing the packaging cover plate to form a groove area;

[0035] The packaging cover plate is bonded to the substrate; after the bonding is completed, the groove area faces one side of the substrate, and the piezoelectric film layer, the interdigitated electrodes and the annular wall structure are located between the substrate and the packaging cover plate; wherein the interdigitated electrodes are located inside the annular wall structure; in a first direction, the orthographic projection of the groove area at least covers the orthographic projection of the interdigitated electrodes, and in the first direction, there is a gap between the interdigitated electrodes and the bottom of the groove area; the first direction is perpendicular to the plane where the substrate is located.

[0036] Preferably, in the above-mentioned method for preparing the thin film surface acoustic wave filter packaging structure, bonding the packaging cover plate to the substrate comprises:

[0037] The packaging cover plate is bonded to the substrate by applying glue.

[0038] Preferably, in the above-mentioned method for preparing the thin film surface acoustic wave filter packaging structure, the step of bonding the packaging cover plate to the substrate by applying glue comprises:

[0039] Under the conditions of a temperature range of 130° C.-170° C. and a pressure range of 4000N-6000N, the packaging cover plate is bonded to the substrate by applying glue.

[0040] Preferably, in the method for preparing the above-mentioned thin film surface acoustic wave filter packaging structure, the thin film surface acoustic wave filter packaging structure further comprises: a pad structure located between the substrate and the packaging cover plate and located on the substrate; the pad structure is located inside the annular wall structure;

[0041] The method for preparing the thin film surface acoustic wave filter packaging structure further comprises:

[0042] The package cover plate is processed to form a second through hole penetrating the package cover plate, wherein the second through hole exposes a portion of the surface of the pad structure.

[0043] Preferably, in the above-mentioned method for preparing a thin film surface acoustic wave filter packaging structure, the method for preparing a thin film surface acoustic wave filter packaging structure further comprises:

[0044] A first metal layer filling the second through hole is formed in the second through hole, and the first metal layer is electrically connected to the pad structure.

[0045] Preferably, in the above-mentioned method for preparing a thin film surface acoustic wave filter packaging structure, the method for preparing a thin film surface acoustic wave filter packaging structure further comprises:

[0046] forming a solder ball on a side of the package cover plate facing away from the substrate, wherein the solder ball is electrically connected to the first metal layer;

[0047] Wherein, at least one second metal layer is arranged between the solder ball and the first metal layer.

[0048] A third aspect of the present application provides a radio frequency device, which includes the thin film surface acoustic wave filter packaging structure described in any one of the above items.

[0049] With the help of the above technical scheme, the present application provides a thin film surface acoustic wave filter packaging structure and its preparation method, and a radio frequency device. The packaging cover is provided with a groove area, and the orthographic projection of the groove area in the first direction at least covers the orthographic projection of the interdigitated electrode, and there is a gap between the interdigitated electrode and the bottom of the groove area in the first direction, thereby forming the cavity area required for the thin film surface acoustic wave filter packaging structure.

[0050] An annular wall structure is arranged between the substrate and the packaging cover plate to isolate water vapor and improve the air tightness of the thin film surface acoustic wave filter packaging structure.

[0051] Based on the characteristics of the packaging cover and the dry film, it can be seen that the strength of the packaging cover is stronger than that of the dry film. During the layout process, the packaging cover based on the cavity area only needs to form a circle around the chip. Compared with the existing double-layer dry film packaging technology, the chip area can be made smaller and there is no need to consider support issues.

[0052] In general, the technical solution of the present application has a huge improvement in stability, support, and airtightness compared to the double-layer dry film packaging technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The above and other features, advantages and aspects of the embodiments of the present disclosure will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings. Throughout the accompanying drawings, the same or similar reference numerals represent the same or similar elements. It should be understood that the drawings are schematic and the originals and elements are not necessarily drawn to scale.

[0054] Figure 1 A schematic structural diagram of a thin film surface acoustic wave filter packaging structure provided by an embodiment of the present invention;

[0055] Figure 2 A schematic structural diagram of another thin film surface acoustic wave filter packaging structure provided by an embodiment of the present invention;

[0056] Figure 3 A schematic diagram of the structure of an interdigital electrode provided by an embodiment of the present invention;

[0057] Figure 4 A schematic flow chart of a method for preparing a thin film surface acoustic wave filter packaging structure provided by an embodiment of the present invention;

[0058] Figure 5-Figure 9 for Figure 4 Schematic diagram of the partial structure corresponding to the preparation method shown. DETAILED DESCRIPTION

[0059] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application. The terms used in the implementation mode of the present application are only used to explain the specific embodiments of the present application, and are not intended to limit the present application. It is known to those skilled in the art that with the development of technology and the emergence of new scenarios, the technical solutions provided in the embodiments of the present application are also applicable to similar technical problems.

[0060] It should be noted that the directional words appearing in the present invention are based on the relative position relationship shown in the drawings and cannot be used as an absolute limitation to the present application.

[0061] Combined with the content recorded in the background technology, surface acoustic wave resonators and filters are acoustic devices widely used in the field of radio frequency. They combine low insertion loss and good suppression performance, and are relatively small in size. They are used to filter out the interference of heterodyne signals, attenuate some frequency components, and only allow specified frequency components. They are the technical basis for the application of wireless spectrum as a non-renewable scarce resource. Among them, the design of the filter often uses the resonator as the basic unit, which can form the corresponding topology and amplify the specified frequency component signal.

[0062] Its specific principle can be simply understood as based on the piezoelectric properties of piezoelectric materials, using input and output transducer devices such as interdigital transducers to convert electrical signals into mechanical energy, which are then converted back into electrical signals after processing, in order to amplify the required signals, filter out noise signals and improve signal quality. It is widely used in various wireless communication equipment.

[0063] At present, filters are mainly divided into SAW filters and BAW (Bulk Acoustic Wave) filters. Surface acoustic waves are an elastic wave that is generated and propagated on the surface of a piezoelectric substrate with piezoelectric properties, and whose amplitude decreases rapidly as the depth of the piezoelectric substrate increases. For SAW filters, their manufacturing cost is lower than that of BAW filters. They are mainly used in low-frequency bands, have low insertion loss and good suppression, and are highly temperature sensitive.

[0064] At the same time, it should be noted that SAW filters also have corresponding limitations. One of them is that they are easily affected by temperature changes. When the temperature rises, the stiffness of the substrate material tends to decrease and the sound speed will also decrease. It can also be said that SAW filters have the defect of temperature drift, that is, the frequency will drift with the operating temperature. Therefore, based on the traditional SAW filter, the TC-SAW filter, that is, the temperature compensated SAW filter, is produced accordingly. It mainly utilizes the temperature elastic properties of the temperature compensation layer (such as SiO2 layer) and the piezoelectric layer opposite to realize the compensation of the temperature drift characteristics.

[0065] It should be further explained that SAW filters also have product designs such as TF-SAW filters. TF-SAW is a technology that uses the characteristics of thin film materials and sound wave propagation to achieve signal conversion and processing. Its working principle is based on the propagation and reflection characteristics of sound waves on the surface of the film. The sound waves are excited by electrical signals, and the sound waves are captured and converted into electrical signals after propagating on the surface of the film, thereby realizing signal conversion and processing. TF-SAW technology has the advantages of high precision and high sensitivity, and is suitable for precise measurement and transmission within a small size range. In addition, TF-SAW filters also have the characteristics of high-speed signal processing and low power consumption, and are suitable for a variety of applications.

[0066] For TF-SAW filters, the current packaging structure of thin-film surface acoustic wave filters is to form a cavity area by covering with a dry film. Since the material of the dry film is usually an organic material, it cannot completely isolate water vapor. In addition, due to the insufficient rigidity of the dry film, a dry film needs to be added between the interdigitated electrodes as a support, resulting in a larger chip area.

[0067] Based on this, the embodiment of the present invention provides a thin film surface acoustic wave filter packaging structure and a preparation method thereof, and a radio frequency device, so as to achieve the purpose of improving the stability of the thin film surface acoustic wave filter packaging structure and reducing the chip area. In order to make the above-mentioned purpose, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0068] refer to Figure 1 , Figure 1 A schematic diagram of a thin film surface acoustic wave filter packaging structure provided by an embodiment of the present invention, referring to Figure 2 , Figure 2 A schematic diagram of another thin film surface acoustic wave filter packaging structure provided by an embodiment of the present invention. The thin film surface acoustic wave filter packaging structure provided by an embodiment of the present invention includes:

[0069] A substrate 11 and a package cover plate 12 are arranged opposite to each other, and the package cover plate 12 includes a groove area 13 arranged toward one side of the substrate 11 .

[0070] A piezoelectric film layer 14 and an annular wall structure 15 are located between the substrate 11 and the packaging cover plate 12 and on the substrate 11 , and an interdigital electrode 16 is located on a side of the piezoelectric film layer 14 away from the substrate 11 .

[0071] Among them, the interdigitated electrode 16 is located inside the annular wall structure 15; in the first direction X, the orthographic projection of the groove area 13 at least covers the orthographic projection of the interdigitated electrode 16, and there is a gap between the interdigitated electrode 16 and the bottom of the groove area 13 in the first direction X; the first direction X is perpendicular to the plane where the substrate 11 is located.

[0072] Specifically, in the embodiment of the present invention, the packaging structure of the thin film surface acoustic wave filter is mainly divided into two parts from a structural point of view, namely, Device Wafer and Cap Wafer. The Device Wafer is the part where the thin film surface acoustic wave filter is located, which is the main working area of ​​the filter, mainly including the substrate 11, the piezoelectric film layer 14, the interdigital electrode 16 and the annular wall structure 15; the Cap Wafer is a structural component that is inverted on the Device Wafer and used as a wafer-level package, that is, the packaging cover plate 12 described in the embodiment of the present application. In other words, the packaging structure of the thin film surface acoustic wave filter provided by the technical solution of the present application belongs to a wafer-level packaging structure.

[0073] In the embodiment of the present invention, the package cover plate 12 includes but is not limited to a Si cover plate, that is, the package cover plate 12 can be processed from a Si wafer.

[0074] Among them, the packaging cover plate 12 is provided with a groove area 13, the orthographic projection of the groove area 13 in the first direction X at least covers the orthographic projection of the interdigitated electrode 16, and there is a gap between the interdigitated electrode 16 and the bottom of the groove area 13 in the first direction X, thereby forming a cavity area required for the packaging structure of the thin film surface acoustic wave filter.

[0075] An annular wall structure 15 is provided between the substrate 11 and the package cover plate 12 to isolate water vapor and improve the air tightness of the thin film surface acoustic wave filter package structure. In an optional embodiment of the present invention, the material of the annular wall structure 15 is a metal material or an inorganic material, which has a better effect of isolating water vapor than a dry film of an organic material, and can meet the high reliability requirements of subsequent industrial and automotive electronic products.

[0076] Based on the characteristics of the packaging cover plate 12 and the dry film, it can be known that the strength of the packaging cover plate 12 is stronger than that of the dry film, and the rigidity of the portion corresponding to the formed groove area 13 is better. In the process of layout, based on the cavity area, the packaging cover plate 12 only needs to form a circle around the chip. Compared with the existing double-layer dry film packaging technology, the chip area can be made smaller, and there is no need to consider support issues. In other words, based on the double-layer dry film packaging technology, in order to increase the strength of the dry film support, the width of the dry film used for support is usually increased. Obviously, this operation is not conducive to the miniaturization design of the chip. Since there is no problem of support strength in the embodiment of the present application, it can also indirectly illustrate that the technical solution of the present application has also greatly improved in the aspect of chip miniaturization design compared with the double-layer dry film packaging technology.

[0077] In general, the technical solution of the present application has a huge improvement in stability, support, and airtightness compared to the double-layer dry film packaging technology.

[0078] Optionally, the width of the annular wall structure 15 ranges from 2 μm to 5 μm; exemplary widths of the annular wall structure 15 are 2 μm, 3.5 μm or 5 μm, etc. The selection of specific parameters may be determined according to actual conditions and is not limited in the embodiments of the present invention.

[0079] Optionally, the thickness of the annular wall structure 15 ranges from 1 μm to 2 μm; exemplary thickness of the annular wall structure 15 is 1 μm, 1.5 μm or 2 μm, etc. The selection of specific parameters can be determined according to actual conditions and is not limited in the embodiments of the present invention.

[0080] Optionally, the depth of the groove region 13 ranges from 5 μm to 15 μm; exemplary depths of the groove region 13 are 5 μm, 10 μm, 12.5 μm or 15 μm, etc. The selection of specific parameters may be determined according to actual conditions and is not limited in the embodiments of the present invention.

[0081] In an optional embodiment of the present invention, Figure 1 As shown, the thin film surface acoustic wave filter packaging structure provided by the embodiment of the present invention also includes:

[0082] At least one dielectric layer is located between the piezoelectric film layer 14 and the substrate 11 .

[0083] Specifically, in the embodiment of the present invention, the dielectric layer between the piezoelectric film layer 14 and the substrate 11 can be any number of dielectric layers such as an insertion layer, a protective layer, an adjustment layer, a temperature compensation layer, a speed change layer, etc., to form a stacked layer structure, thereby achieving a variety of different technical effects. In the embodiment of the present invention, the number and function of the dielectric layer are not limited, and only the example of having three dielectric layers (i.e., the first dielectric layer 17, the second dielectric layer 18, and the third dielectric layer 19) between the piezoelectric film layer 14 and the substrate 11 is used for explanation.

[0084] In an optional embodiment of the present invention, Figure 1 As shown, the thin film surface acoustic wave filter packaging structure further includes: a pad structure 20 located between the substrate 11 and the packaging cover plate 12 and located on the substrate 11 .

[0085] The pad structure 20 is located inside the annular wall structure 15 .

[0086] The thin film surface acoustic wave filter packaging structure further includes: a protective layer 21 , wherein the protective layer 21 covers the interdigitated electrodes 16 , the pad structure 20 and the annular wall structure 15 .

[0087] The protection layer 21 has a first through hole, and the first through hole exposes a portion of the surface of the pad structure 20 .

[0088] The thin film surface acoustic wave filter packaging structure also includes: a second through hole penetrating the packaging cover plate 12, the second through hole exposing a portion of the surface of the pad structure 20. The second through hole is also called a TSV (through silicon via) hole in the field. Based on the thin film surface acoustic wave filter packaging structure provided in the embodiment of the present application, the second through hole penetrates the packaging cover plate 12 instead of penetrating the thin film surface acoustic wave filter, that is, this hole opening method is equivalent to the design of opening a TSV hole on the front.

[0089] The thin film surface acoustic wave filter packaging structure further includes: a first metal layer 22 filling the second through hole, and the first metal layer 22 is electrically connected to the pad structure 20 .

[0090] The thin film surface acoustic wave filter packaging structure further includes: a solder ball 23 located on a side of the packaging cover plate 12 away from the substrate 11 , and the solder ball 23 is electrically connected to the first metal layer 22 .

[0091] At least one second metal layer is located between the solder ball 23 and the first metal layer 22 .

[0092] Specifically, in the embodiment of the present invention, the protection layer 21 is provided to protect the components such as the interdigital electrodes 16, the pad structure 20 and the annular wall structure 15, and a part of the surface of the pad structure 20 is exposed through the first through hole to achieve electrical connection between the pad structure 20 and the first metal layer 22. The pad structure 20 is provided in combination with the first metal layer 22 and the solder ball 23 to achieve electrical connection between the thin film surface acoustic wave filter and other components. Figure 2 As shown, four pad structures 20 are used as an example for explanation. The material of the first metal layer 22 includes but is not limited to copper material, and the material of the second metal layer includes but is not limited to copper material and nickel material. The material of the solder ball 23 includes but is not limited to tin material, and the solder ball 23 is also called tin ball in the field. The electrical connection stability between the solder ball 23 and the first metal layer 22 can be improved by providing the second metal layer.

[0093] Optionally, in the embodiment of the present invention, the second metal layer includes two metal layers (ie, metal layer 24 and metal layer 25) stacked in sequence, wherein the metal layer 24 is a metal layer made of copper material, and the metal layer 25 is a metal layer made of nickel material.

[0094] Among them, TSV technology can greatly improve the integration of electronic components, reduce the geometric size and weight of the package, and meet the requirements of microelectronic products for multi-function and miniaturization; because TSV technology can greatly shorten the length of electrical interconnection, it can solve the signal delay problem and improve the electrical performance of the device.

[0095] It should be noted that Figure 1 The reference numeral 26 indicates glue, which indicates that in an optional embodiment of the present application, the packaging cover plate 12 and the substrate 11 are bonded together by applying the glue 26 .

[0096] In an optional embodiment of the present invention, reference Figure 3 , Figure 3 A schematic diagram of the structure of an interdigitated electrode provided in an embodiment of the present invention. The interdigitated electrode 16 includes a first bus bar 161 and a second bus bar 162 arranged opposite to each other in a second direction Y, and a first electrode finger 163 located on the first bus bar 161 and a second electrode finger 164 located on the second bus bar 162.

[0097] The first bus bar 161 and the second bus bar 162 have the same length extension direction, both extending along the third direction Z. The second direction Y and the third direction Z are parallel to the plane where the substrate 11 is located, and the second direction Y and the third direction Z intersect.

[0098] Specifically, in the embodiment of the present invention, the second direction Y is perpendicular to the third direction Z. The first electrode fingers 163 and the second electrode fingers 164 have the same length extension direction, which are parallel to the second direction Y respectively. The multiple first electrode fingers 163 on the first bus bar 161 are arranged at intervals in the third direction Z, and the multiple second electrode fingers 164 on the second bus bar 162 are arranged at intervals in the third direction Z. The multiple first electrode fingers 163 on the first bus bar 161 and the multiple second electrode fingers 164 on the second bus bar 162 are arranged in sequence in the third direction Z in a cross-arranged manner, and there is a gap between the multiple first electrode fingers 163 on the first bus bar 161 and the second bus bar 162, and there is a gap between the multiple second electrode fingers 164 on the second bus bar 162 and the first bus bar 161. At this time, the bus bars and the electrode fingers are distributed in a manner similar to crossing fingers, forming a so-called interdigitated electrode 16. When the first bus bar 161 and the first electrode finger 163 thereon are used as the transmitting end, the second bus bar 162 and the second electrode finger 164 thereon are used as the receiving end. Conversely, when the first bus bar 161 and the first electrode finger 163 thereon are used as the receiving end, the second bus bar 162 and the second electrode finger 164 thereon are used as the transmitting end. The transmitting end part is used to convert the electrical signal into an acoustic wave, and the acoustic wave mainly propagates on the surface of the substrate, and the receiving end part is used to convert the received acoustic wave into an electrical signal output, thereby realizing filtering.

[0099] Based on the above embodiments of the present invention, another embodiment of the present invention further provides a method for preparing a thin film surface acoustic wave filter packaging structure, referring to Figure 4 , Figure 4 A schematic flow chart of a method for preparing a thin film surface acoustic wave filter packaging structure provided by an embodiment of the present invention. The method for preparing a thin film surface acoustic wave filter packaging structure provided by an embodiment of the present invention comprises:

[0100] S101: Figure 5 As shown, a substrate 11 is provided, on which a piezoelectric film layer 14 , interdigital electrodes 16 and an annular wall structure 15 are formed. The interdigital electrodes 16 are located on a side of the piezoelectric film layer 14 away from the substrate 11 .

[0101] Specifically, in the embodiment of the present invention, a pad structure 20 may be formed on the substrate 11, and the pad structure 20 is located inside the annular wall structure 15. A protective layer 21 is formed, and the protective layer 21 covers the interdigitated electrodes 16, the pad structure 20, and the annular wall structure 15. The protective layer 21 has a first through hole 27, and the first through hole 27 exposes a portion of the surface of the pad structure 20.

[0102] like Figure 5As shown, at least one dielectric layer may be formed on the substrate 11, and the at least one dielectric layer is located between the piezoelectric film layer 14 and the substrate 11. In the embodiment of the present invention, the number and function of the dielectric layer are not limited, and only an example of three dielectric layers (i.e., the first dielectric layer 17, the second dielectric layer 18, and the third dielectric layer 19) between the piezoelectric film layer 14 and the substrate 11 is used for description.

[0103] S102: Figure 6 As shown, a packaging cover plate 12 is provided, and the packaging cover plate 12 is processed to form a groove area 13.

[0104] Specifically, in the embodiment of the present invention, including but not limited to coating photoresist, exposing the area where the groove area 13 is to be formed through exposure, development, etc., then including but not limited to forming the groove area 13 through dry etching, and finally removing the photoresist.

[0105] S103: Figure 7 As shown, the packaging cover plate 12 is bonded to the substrate 11; after the bonding is completed, the groove area 13 faces one side of the substrate 11, and the piezoelectric film layer 14, the interdigitated electrodes 16 and the annular wall structure 15 are located between the substrate 11 and the packaging cover plate 12; wherein the interdigitated electrodes 16 are located inside the annular wall structure 15; in a first direction X, the orthographic projection of the groove area 13 at least covers the orthographic projection of the interdigitated electrodes 16, and there is a gap between the interdigitated electrodes 16 and the bottom of the groove area 13 in the first direction X; the first direction X is perpendicular to the plane where the substrate 11 is located.

[0106] Specifically, in the embodiment of the present invention, one possible way to bond the package cover plate 12 to the substrate 11 is:

[0107] The packaging cover plate 12 is bonded to the substrate 11 by applying glue 26 .

[0108] Exemplarily, under the conditions of a temperature range of 130° C.-170° C. and a pressure range of 4000N-6000N, the package cover plate 12 is bonded to the substrate 11 by applying glue 26. Specifically, glue 26 is applied on the surface of the package cover plate 12, and a wafer-level bonding device is used for bonding.

[0109] like Figure 8 As shown, the method for preparing the thin film surface acoustic wave filter packaging structure also includes:

[0110] The package cover plate 12 is processed to form a second through hole 28 penetrating the package cover plate 12 , wherein the second through hole 28 exposes a portion of the surface of the pad structure 20 .

[0111] Exemplarily, the package cover plate 12 is first thinned to a target thickness, for example, the package cover plate 12 is thinned to a thickness range of 90 μm-110 μm; then, including but not limited to coating a photoresist, exposing the area where the second through hole 28 is to be formed through exposure, development, etc.; then, including but not limited to forming the second through hole 28 through dry etching, and finally removing the photoresist.

[0112] like Fig. 9 As shown, the method for preparing the thin film surface acoustic wave filter packaging structure also includes:

[0113] A first metal layer 22 filling the second through hole 28 is formed in the second through hole 28 , and the first metal layer 22 is electrically connected to the pad structure 20 .

[0114] Exemplarily, titanium and copper metals are first deposited on the surface of the package cover plate 12 facing away from the substrate 11, and then copper is electroplated in the second through hole 28 using an electroplating device. The titanium and copper metals on the surface are then removed, leaving only the copper in the second through hole 28 to form a first metal layer 22.

[0115] like Figure 1 As shown, the method for preparing the thin film surface acoustic wave filter packaging structure also includes:

[0116] A solder ball 23 is formed on the side of the package cover plate 12 facing away from the substrate 11, and the solder ball 23 is electrically connected to the first metal layer 22; wherein at least one second metal layer is disposed between the solder ball 23 and the first metal layer 22. Optionally, in the embodiment of the present invention, the second metal layer includes two metal layers (i.e., a metal layer 24 and a metal layer 25) stacked in sequence, wherein the metal layer 24 is a metal layer of copper material, and the metal layer 25 is a metal layer of nickel material.

[0117] Exemplarily, titanium and copper metals are first deposited on the surface of the package cover 12 facing away from the substrate 11; then, the area where the solder ball 23 needs to be formed is exposed by methods including but not limited to coating photoresist, exposing, developing, etc.; then, a metal layer 24, a metal layer 25 and a solder ball 23 are formed in sequence; finally, the photoresist and the titanium and copper metals on the surface are removed, and processes such as reflow and cleaning are performed.

[0118] Based on the above embodiment of the present invention, a radio frequency device is provided in another embodiment of the present invention. The radio frequency device includes the thin film surface acoustic wave filter packaging structure described in the above embodiment.

[0119] The above is a detailed introduction to a thin film surface acoustic wave filter packaging structure and a preparation method and a radio frequency device provided by the present invention. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for general technicians in this field, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

[0120] It should be noted that each embodiment in this specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description.

[0121] It should also be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device that includes a series of elements is inherent to the elements, or also includes elements inherent to these processes, methods, articles or devices. In the absence of further restrictions, the elements defined by the sentence "including a..." do not exclude the presence of other identical elements in the process, method, article or device that includes the elements.

[0122] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A thin film surface acoustic wave filter packaging structure, characterized in that: The thin film surface acoustic wave filter packaging structure comprises: A substrate and a packaging cover plate arranged opposite to each other, wherein the packaging cover plate comprises a groove area arranged toward one side of the substrate; A piezoelectric film layer and an annular wall structure located between the substrate and the packaging cover and on the substrate, and an interdigitated electrode located on a side of the piezoelectric film layer away from the substrate; Wherein, the interdigitated electrode is located inside the annular wall structure; in the first direction, the orthographic projection of the groove area at least covers the orthographic projection of the interdigitated electrode, and there is a gap between the interdigitated electrode and the bottom of the groove area in the first direction; the first direction is perpendicular to the plane where the substrate is located.

2. The thin film surface acoustic wave filter packaging structure according to claim 1, characterized in that: The material of the annular wall structure is metal material or inorganic material.

3. The thin film surface acoustic wave filter packaging structure according to claim 1, characterized in that: The width of the annular wall structure ranges from 2 μm to 5 μm; The thickness of the annular wall structure is in the range of 1 μm to 2 μm.

4. The thin film surface acoustic wave filter packaging structure according to claim 1, characterized in that: The depth of the groove region ranges from 5 μm to 15 μm.

5. The thin film surface acoustic wave filter packaging structure according to claim 1, characterized in that: The packaging cover plate is a Si cover plate.

6. The thin film surface acoustic wave filter packaging structure according to claim 1, characterized in that: The thin film surface acoustic wave filter packaging structure also includes: At least one dielectric layer is located between the piezoelectric film layer and the substrate.

7. The thin film surface acoustic wave filter packaging structure according to claim 1, characterized in that: The thin film surface acoustic wave filter packaging structure also includes: A pad structure located between the substrate and the package cover plate and on the substrate; The pad structure is located inside the annular wall structure.

8. The thin film surface acoustic wave filter packaging structure according to claim 7, characterized in that: The thin film surface acoustic wave filter packaging structure further includes: a protective layer, the protective layer covers the interdigitated electrodes, the pad structure and the annular wall structure; The protection layer has a first through hole, and the first through hole exposes a portion of the surface of the pad structure.

9. The thin film surface acoustic wave filter packaging structure according to any one of claims 1 to 8, characterized in that: The thin film surface acoustic wave filter packaging structure also includes: A second through hole passes through the package cover plate, wherein the second through hole exposes a portion of the surface of the pad structure.

10. The thin film surface acoustic wave filter packaging structure according to claim 9, characterized in that: The thin film surface acoustic wave filter packaging structure also includes: A first metal layer fills the second through hole, wherein the first metal layer is electrically connected to the pad structure.

11. The thin film surface acoustic wave filter packaging structure according to claim 10, characterized in that: The thin film surface acoustic wave filter packaging structure also includes: a solder ball located on a side of the package cover plate facing away from the substrate, the solder ball being electrically connected to the first metal layer; At least one second metal layer is located between the solder ball and the first metal layer.

12. The thin film surface acoustic wave filter packaging structure according to claim 1, characterized in that: The interdigitated electrodes include a first bus bar and a second bus bar disposed opposite to each other in a second direction, and a first electrode finger located on the first bus bar and a second electrode finger located on the second bus bar; The first bus bar and the second bus bar have the same length extension direction, both extending along a third direction. The second direction and the third direction are parallel to the plane where the substrate is located, and the second direction and the third direction intersect.

13. A method for preparing a thin film surface acoustic wave filter packaging structure, characterized in that: The method for preparing the thin film surface acoustic wave filter packaging structure comprises: Providing a substrate, forming a piezoelectric film layer, interdigital electrodes and an annular wall structure on the substrate, wherein the interdigital electrodes are located on a side of the piezoelectric film layer away from the substrate; Providing a packaging cover plate, and processing the packaging cover plate to form a groove area; The packaging cover plate is bonded to the substrate; after the bonding is completed, the groove area faces one side of the substrate, and the piezoelectric film layer, the interdigitated electrodes and the annular wall structure are located between the substrate and the packaging cover plate; wherein the interdigitated electrodes are located inside the annular wall structure; in a first direction, the orthographic projection of the groove area at least covers the orthographic projection of the interdigitated electrodes, and in the first direction, there is a gap between the interdigitated electrodes and the bottom of the groove area; the first direction is perpendicular to the plane where the substrate is located.

14. The method for preparing a thin film surface acoustic wave filter packaging structure according to claim 13, characterized in that: The step of bonding the package cover plate to the substrate comprises: The packaging cover plate is bonded to the substrate by applying glue.

15. The method for preparing a thin film surface acoustic wave filter packaging structure according to claim 14, characterized in that: The method of bonding the package cover plate to the substrate by applying glue comprises: Under the conditions of a temperature range of 130° C.-170° C. and a pressure range of 4000N-6000N, the packaging cover plate is bonded to the substrate by applying glue.

16. The method for preparing a thin film surface acoustic wave filter packaging structure according to claim 13, characterized in that: The thin film surface acoustic wave filter packaging structure further includes: a pad structure located between the substrate and the packaging cover plate and located on the substrate; the pad structure is located inside the annular wall structure; The method for preparing the thin film surface acoustic wave filter packaging structure further comprises: The package cover plate is processed to form a second through hole penetrating the package cover plate, wherein the second through hole exposes a portion of the surface of the pad structure.

17. The method for preparing a thin film surface acoustic wave filter packaging structure according to claim 16, characterized in that: The method for preparing the thin film surface acoustic wave filter packaging structure further comprises: A first metal layer filling the second through hole is formed in the second through hole, and the first metal layer is electrically connected to the pad structure.

18. The method for preparing a thin film surface acoustic wave filter packaging structure according to claim 17, characterized in that: The method for preparing the thin film surface acoustic wave filter packaging structure further comprises: A solder ball is formed on a side of the package cover plate facing away from the substrate, and the solder ball is electrically connected to the first metal layer; wherein at least one second metal layer is disposed between the solder ball and the first metal layer.

19. A radio frequency device, characterized in that: The radio frequency device comprises the thin film surface acoustic wave filter packaging structure according to any one of claims 1-12.

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