A double-sided integrated surface acoustic wave filter

Abstract

This invention provides a double-sided integrated surface acoustic wave (SAW) filter, relating to the field of radio frequency microelectronic device technology. The invention includes a double-sided symmetrical piezoelectric insulator substrate having a first surface and a second surface, a first filter unit disposed on the first surface, and a second filter unit disposed on the second surface. The first and second filter units are independently formed on opposite sides of the double-sided symmetrical piezoelectric insulator substrate. The excitation and propagation of SAW waves are achieved through the symmetrical piezoelectric layer of the double-sided symmetrical piezoelectric insulator substrate. This invention overcomes the shortcomings of existing multi-filter integration technologies, which require multiple chips, have complex packaging, and are bulky, by integrating multiple filter functions on a single chip, significantly improving integration density and reducing cost and size.

Description

Technical Field

[0001] This invention relates to the field of radio frequency microelectronic device technology, and in particular to a double-sided integrated surface acoustic wave filter. Background Technology

[0002] Surface acoustic wave (SAW) filters are radio frequency (RF) devices that utilize the acoustic-electric conversion properties of piezoelectric materials to filter signals. They offer advantages such as small size, stable performance, and good process compatibility, and are widely used in mobile communication terminals, base stations, navigation equipment, and other fields. With the large-scale commercialization of 5G mobile communication technology, the demand for filters in the RF front end has increased significantly, while the size of devices must be continuously reduced, posing a greater challenge to the integration of filters.

[0003] Currently, multi-band, multi-mode RF front-end solutions typically require multiple filter chips placed side-by-side or using a stacked packaging method. For example, existing technology discloses a bifacial filter that reduces its lateral size by stacking two independent surface acoustic wave (SAW) filter chips face-to-face with a shared cavity formed by an adhesive support structure. However, this approach requires two separate chips and a complex packaging process, resulting in high cost and a large overall thickness after stacking.

[0004] Another technical approach uses a thickness-integrated structure, where multiple chips are stacked sequentially along the thickness direction on a packaging substrate and electrically connected through conductive channels. However, this approach also requires multiple independent chips and has high requirements for the bonding process.

[0005] In the existing technology, there is no known method for simultaneously fabricating multiple filter units on both sides of a single substrate. Traditional piezoelectric insulator substrates only have a piezoelectric functional layer on one side, limiting further improvements in their integration density. How to integrate multiple filter functions on the same chip while maintaining a small chip area and a simple fabrication process is a technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the aforementioned shortcomings of existing technologies, this invention provides a dual-sided integrated surface acoustic wave filter that overcomes the drawbacks of existing technologies where multi-filter integration requires multiple chips, involves complex packaging, and has a large size. This invention achieves the integration of multiple filter functions on a single chip, significantly improving integration and reducing cost and size.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a double-sided integrated surface acoustic wave filter, comprising a double-sided symmetrical piezoelectric insulator substrate having a first surface and a second surface, a first filter unit disposed on the first surface, and a second filter unit disposed on the second surface. The first filter unit and the second filter unit are independently formed on the front and back sides of the double-sided symmetrical piezoelectric insulator substrate, and the excitation and propagation of surface acoustic waves are realized through the symmetrical piezoelectric layer of the double-sided symmetrical piezoelectric insulator substrate.

[0008] The beneficial effects of this invention are as follows: By employing a double-sided symmetrical piezoelectric insulator substrate and independently integrating the first and second filter units on its front and back sides, this invention achieves double-sided utilization and functional multiplexing of the filter structure, significantly improving the device integration and functional density per unit area. The independent formation of filter units on both sides helps reduce electromagnetic coupling and signal crosstalk caused by same-sided wiring, improving the filter's isolation and out-of-band suppression performance. Simultaneously, utilizing the symmetrical piezoelectric layer of the double-sided symmetrical piezoelectric insulator substrate to excite and propagate surface acoustic waves helps achieve symmetrical distribution and efficient transmission of acoustic wave energy, reducing propagation loss and improving the quality factor (Q value). Furthermore, the filters on both sides can be designed for different frequency bands or different functions (such as transmission and reception), facilitating the construction of miniaturized, high-performance RF front-end modules to meet the application requirements of multi-band, multi-mode communication systems.

[0009] Furthermore, a first piezoelectric functional layer is disposed on the first surface, and a second piezoelectric functional layer is disposed on the second surface; The first filter unit includes at least one set of first interdigital transducers, which are disposed on the first piezoelectric functional layer; The second filter unit includes at least one set of second interdigital transducers, which are disposed on the second piezoelectric functional layer.

[0010] The beneficial effects of the above-mentioned further solutions are as follows: By setting independent first and second piezoelectric functional layers on the first and second surfaces of the double-sided symmetrical piezoelectric insulator substrate, and forming first and second interdigital transducers on them respectively, the excitation and propagation of surface acoustic waves on both sides are physically decoupled, avoiding mutual leakage and cross-interference of acoustic wave energy in the same layer of piezoelectric material, and significantly improving the isolation between the two filter units. At the same time, the interdigital transducers on each side can independently optimize their electrode materials, film thickness, period and aperture, etc., to match different frequency bands or different filtering performance indicators (such as bandwidth, insertion loss, temperature stability, etc.), realizing flexible dual-frequency or multi-mode design. In addition, the piezoelectric functional layer and the piezoelectric insulator substrate can form a composite piezoelectric structure, which helps to enhance acoustic wave energy confinement and reduce the radiation loss of acoustic waves into the substrate, thereby improving the quality factor (Q value) and out-of-band rejection capability of the filter, meeting the stringent requirements of high-performance RF front-ends for miniaturization, high isolation and multi-frequency parallel operation.

[0011] Furthermore, the first filter unit includes one or more filters disposed on the first piezoelectric functional layer.

[0012] The beneficial effects of the above-mentioned further solutions are as follows: By setting one or more filters on the first piezoelectric functional layer of the double-sided integrated surface acoustic wave filter, the present invention further improves the functional integration and design flexibility at the chip level. Specifically: On the one hand, multiple filters can achieve combinations of different frequency bands, different bandwidths, or different filtering characteristics on the first surface (such as multiple filtering channels in a duplexer or multiplexer), which is beneficial for building complex RF front-end modules within a limited chip area; on the other hand, since the filters on the first surface and the filters on the second surface are physically isolated by a double-sided symmetrical piezoelectric insulator substrate, only a small lateral spacing is needed between multiple filters inside the first surface to avoid crosstalk, without significantly increasing the overall package size. In addition, multiple filters on the same piezoelectric functional layer can share the same fabrication process and mask design, reducing manufacturing costs and process complexity, while facilitating collaborative optimization with the filter units on the second surface (such as undertaking different sub-band filtering tasks for the transmit and receive channels respectively), providing a miniaturized solution with high integration and high isolation for multi-band, multi-mode wireless communication systems.

[0013] Furthermore, the second filter unit is independent of the first filter unit, and the connection between the first filter unit and the second filter unit is achieved through an electrical connection structure that runs through the double-sided symmetrical piezoelectric insulator substrate.

[0014] The beneficial effects of the above-mentioned further solutions are: by making the second filter unit and the first filter unit independent of each other, and by using an electrical connection structure that penetrates the double-sided symmetrical piezoelectric insulator substrate to achieve the connection between the two, the present invention increases the flexibility of internal electrical interconnection and functional integration capability of the device while maintaining the advantages of independent design and independent process manufacturing of the two-sided filters. Specifically: On the one hand, through-substrate electrical interconnect structures (such as vertical interconnects in the form of through-silicon vias or glass vias) can significantly shorten the signal transmission path between the front and back filters, avoiding the parasitic inductance and capacitance caused by the use of peripheral leads or edge traces, thereby reducing insertion loss and signal distortion at high frequencies and improving the amplitude-frequency characteristic consistency of the filters; on the other hand, this electrical interconnect structure allows the first filter unit and the second filter unit to form a cascaded filter network (such as a duplexer, multiplexer, or higher-order filter topology) in a three-dimensional stacking manner, realizing more complex circuit functions without increasing the chip projection area; at the same time, vertical interconnects can also combine filters of different frequency bands set on the front and back sides into integrated modules with shared input / output ports, simplifying module-level packaging and system board-level design, and improving the miniaturization and electromagnetic compatibility performance of the overall RF front end.

[0015] Furthermore, the electrical connection structure includes a conductive pillar penetrating a double-sided symmetrical piezoelectric insulator substrate to achieve vertical interconnection and signal routing between the second filter unit and the first filter unit.

[0016] The beneficial effects of the above-mentioned further solutions are: by using conductive pillars that penetrate through a double-sided symmetrical piezoelectric insulator substrate as electrical connection structures, the present invention achieves vertical interconnection and signal routing of the shortest path between the first filter unit and the second filter unit. Specifically: On the one hand, the conductive pillars directly penetrate the substrate to connect both sides, avoiding the long traces caused by traditional side leads or bonding wires, significantly reducing interconnect parasitic inductance and capacitance, and significantly reducing insertion loss and phase shift during high-frequency signal transmission, which is beneficial for maintaining the high-frequency performance and group delay characteristics of the filter; on the other hand, the vertical interconnect structure allows for flexible cascading of filters on both sides (such as series, parallel, or forming a bridge topology), providing a compact three-dimensional integration solution for achieving high-order filtering response, full-duplex or multiplex functions. At the same time, the conductive pillars can be used for ground shielding or differential signal pair design to enhance anti-interference capabilities; in addition, the conductive pillar structure is compatible with substrate processing and wafer-level packaging in terms of process technology, which helps to achieve batch interconnection and hermetic packaging between filter units, improve device reliability and module integration density, and meet the stringent requirements of 5G / 6G communication for miniaturization, low loss and high isolation of RF front-end.

[0017] Furthermore, the fabrication method of the dual-sided integrated surface acoustic wave filter includes the following steps: S1. A double-sided symmetrical piezoelectric insulator substrate is provided, wherein the double-sided symmetrical piezoelectric insulator substrate has a first surface and a second surface opposite to each other, and a first piezoelectric functional layer is disposed on the first surface and a second piezoelectric functional layer is disposed on the second surface. S2. Fabricate a first filter unit on the first surface and use a process to form an interdigital transducer; S3. Protect the completed structure of the first surface; S4. Prepare a second filter unit on the second surface and form a second interdigital transducer by photolithography. S5. Remove the protective layer to obtain a double-sided integrated surface acoustic wave filter.

[0018] The beneficial effects of the above-mentioned further scheme are as follows: The above fabrication method achieves efficient and reliable manufacturing of a double-sided integrated surface acoustic wave (SAW) filter. Specifically: First, S1 provides a substrate with a double-sided symmetrical piezoelectric functional layer, laying the material foundation for independent excitation and propagation of SAW waves on both sides; S2 fabricates a first filter unit on the first surface and forms an interdigital transducer; S3, after completing the first-side process, a protective layer is used to protect the processed structure, effectively preventing physical damage or chemical contamination to the completed first-side device by subsequent second-side processes (such as photolithography, development, etching, metal deposition, etc.), significantly improving process yield and device consistency; S4 forms a second interdigital transducer on the second surface through photolithography, realizing independent control and optimization of the patterned processing on both sides; finally, S5 removes the protective layer to obtain the final device. The entire process is compatible with existing semiconductor planar processes and SAW device manufacturing technologies, requiring no additional complex equipment, and possesses good process scalability and mass production capabilities. Furthermore, this method allows for the use of different materials, thicknesses, and finger cycles for the interdigital transducers on both sides, providing a practical and feasible technical path for the low-cost, high-yield manufacturing of dual-band, multi-functional integrated filters.

[0019] Furthermore, step S3 includes the following steps: A temporary bonding method is used to temporarily bond the carrier wafer to the first surface. After the second surface process is completed, the bonding is debonded and the carrier wafer is removed, thus protecting the structure of the first surface.

[0020] The beneficial effects of the above-mentioned further solution are as follows: By using a temporary bonding carrier wafer in S3 to protect the completed structure of the first surface, a highly reliable and compatible process solution is provided for the manufacturing of double-sided integrated surface acoustic wave filters. Specifically: On the one hand, the temporary bonding between the carrier wafer and the first surface can provide physical isolation and chemical barriers for the interdigital transducers and piezoelectric functional layers on the first surface during high-temperature or chemical etching processes such as photolithography, development, metal deposition, and etching on the second surface, effectively avoiding problems such as particle contamination, scratches, chemical erosion, and photoresist residue, and significantly improving the processing window and device yield of the second surface process; on the other hand, the carrier wafer can increase the mechanical strength of the entire substrate after bonding, reducing the risk of fragmentation of the thin double-sided substrate in subsequent processes, which is especially suitable for large-size wafer-level manufacturing; after the second surface process is completed, the carrier wafer can be removed by means of thermal sliding, laser debonding, or chemical release without damaging the fine electrode structure already formed on the first surface, achieving non-destructive processing. This method is fully compatible with existing semiconductor temporary bonding / debonding equipment and processes, and is easy to integrate with wafer-level packaging technology, providing an engineering-feasible technical path for the large-scale, low-cost manufacturing of two-sided surface acoustic wave filters.

[0021] Furthermore, before and after fabricating the first filter unit and the second filter unit, through-holes penetrating the substrate are etched and filled with conductive material to form a silicon through-hole structure.

[0022] The beneficial effect of the above-mentioned further scheme is that by etching through-holes through the substrate and filling them with conductive material before or after the fabrication of the first filter unit and the second filter unit to form a silicon through-hole structure, a compact and low-loss three-dimensional electrical interconnection scheme is provided for the double-sided integrated surface acoustic wave filter. Specifically: On the one hand, the through-silicon via (TSV) structure achieves vertical interconnection of the shortest path between the first and second filter units, avoiding the parasitic effects caused by traditional edge leads or bonding wires, significantly reducing insertion loss and signal reflection during high-frequency signal transmission, and helping to maintain the amplitude-frequency characteristics and group delay consistency of the filter; on the other hand, the processing sequence of TSV is flexible (it can be performed before or after filter unit fabrication), and the scheme of via before device or device before via can be selected according to process compatibility, which is convenient for integration with existing semiconductor manufacturing processes; in addition, the TSV structure can be designed as a ground shielding via or a coaxial structure, effectively suppressing electromagnetic coupling and crosstalk between signals on the front and back sides, further improving the isolation of double-sided integrated filters; at the same time, TSV technology enables filter chips to achieve wafer-level three-dimensional stacking and packaging, greatly reducing the module's board area, and providing key technical support for the miniaturization and high reliability of high-density RF front-end modules (such as multi-band multiplexers and filter arrays).

[0023] In summary, the present invention has at least the following beneficial effects: First, it achieves dual functionality on a single chip. By fabricating filter units on both sides of a double-sided symmetrical POI substrate, two independent filter functions are integrated on a single chip, overcoming the integration limitations of traditional single-sided substrates. Compared to existing dual-chip stacking solutions, this invention eliminates the need for two separate chips and complex stacking packaging, significantly simplifying the manufacturing process.

[0024] Second, the chip area is halved. With the same number of filters, the planar projected area of ​​the chip of this invention is only half that of the traditional side-by-side placement scheme, which greatly improves the chip area utilization rate and is conducive to the miniaturization of the RF front-end module.

[0025] Third, it has good process compatibility. The fabrication method of this invention is highly compatible with existing surface acoustic wave filter fabrication lines, requiring only the addition of a back-side process step and temporary bonding protection. No special equipment needs to be developed, making it easy to implement in industrial applications.

[0026] Fourth, it offers high design flexibility. Filters with different frequency bands and bandwidths can be designed independently on both sides to meet the needs of multi-frequency and multi-mode communication; the filters on both sides can be vertically interconnected through through-silicon vias (TSVs), allowing for the construction of more complex RF front-end functional modules.

[0027] Fifth, small package size. The chip of this invention can be directly packaged using standard surface mount technology. The package thickness is only slightly larger than that of traditional single-sided chips, but the planar area is significantly reduced, resulting in a clear advantage in overall size. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the dual-sided integrated surface acoustic wave filter chip provided in Embodiment 2 of the present invention.

[0029] Figure 2 This is a schematic diagram of the structure of a double-sided integrated surface acoustic wave filter chip with through-hole interconnects provided in Embodiment 3 of the present invention.

[0030] Figure 3 This is a schematic diagram of the preparation method of the present invention.

[0031] Among them, 1-double-sided symmetrical piezoelectric insulator substrate, 2-front chip PAD, 3-front chip functional area, 4-back chip functional area, 5-through-hole interconnect metal area. Detailed Implementation

[0032] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0033] Example 1 This invention provides a dual-sided integrated surface acoustic wave filter, comprising a dual-sided symmetrical piezoelectric insulator substrate having a first surface and a second surface, a first filter unit disposed on the first surface, and a second filter unit disposed on the second surface. The first filter unit and the second filter unit are independently formed on opposite sides of the dual-sided symmetrical piezoelectric insulator substrate, and the excitation and propagation of surface acoustic waves are realized through the symmetrical piezoelectric layer of the dual-sided symmetrical piezoelectric insulator substrate.

[0034] In this embodiment, a first piezoelectric functional layer is disposed on the first surface, and a second piezoelectric functional layer is disposed on the second surface; the first filter unit may include one or more filters, for example, forming a duplexer or multiplexer, and the filters are disposed on the first piezoelectric functional layer.

[0035] In this embodiment, the first filter unit includes at least a set of first interdigital transducers disposed on the first piezoelectric functional layer; the second filter unit includes at least a set of second interdigital transducers disposed on the second piezoelectric functional layer. The second filter unit is independent of the first filter unit and can have different frequency response characteristics, such as operating in different communication frequency bands.

[0036] In this embodiment, the first filter unit and the second filter unit operate in different frequency bands, for example, one operates in the B3 band and the other operates in the B7 band, in order to meet the requirements of multi-frequency multi-mode RF front-end.

[0037] In this embodiment, the invention may further include an electrical connection structure that penetrates the double-sided symmetrical piezoelectric insulator substrate to achieve electrical connection between the first filter unit and the second filter unit. The electrical connection structure may be a through-silicon via (TSV) structure, including conductive pillars penetrating the substrate, thereby achieving vertical interconnection and signal routing between the two filters.

[0038] In this embodiment, the fabrication method of the dual-sided integrated surface acoustic wave filter includes the following steps: S1. A double-sided symmetrical piezoelectric insulator substrate is provided, wherein the double-sided symmetrical piezoelectric insulator substrate has a first surface and a second surface opposite to each other, and a first piezoelectric functional layer is disposed on the first surface and a second piezoelectric functional layer is disposed on the second surface. S2. Fabricate a first filter unit on the first surface and use a process to form an interdigital transducer; In this embodiment, the first interdigital transducer is formed by processes such as photolithography, metal deposition, stripping, or etching.

[0039] S3. Protect the completed structure of the first surface to prevent damage to the front structure from subsequent back-side processes; S4. Prepare a second filter unit on the second surface and form a second interdigital transducer by photolithography. In this embodiment, photolithographic alignment can be achieved using infrared alignment or a double-sided photolithography machine.

[0040] S5. Remove the protective layer to obtain a double-sided integrated surface acoustic wave filter.

[0041] In this embodiment, S3 includes the following steps: A temporary bonding method is used to temporarily bond the carrier wafer to the first surface. After the second surface process is completed, the bonding is debonded and the carrier wafer is removed, thus protecting the structure of the first surface.

[0042] In this embodiment, the carrier wafer can be glass or silicon, and is bonded to the front of the chip using temporary bonding adhesive.

[0043] In this embodiment, before and / or after fabricating the first filter unit and the second filter unit, a through-hole is etched to form a through-hole through the substrate, and a conductive material is filled into the through-hole to form a silicon through-hole structure.

[0044] In this embodiment, if the double-sided integrated surface acoustic wave filter chip needs to form an electrical connection structure that penetrates the substrate, a through-hole can be etched before or after the fabrication of the first filter unit and the second filter unit, and a conductive material, such as copper or tungsten, can be filled into the through-hole to form a silicon through-hole structure.

[0045] Example 2 This embodiment uses a dual-band, dual-sided integrated filter chip as an example for illustration.

[0046] This embodiment provides a dual-sided integrated surface acoustic wave filter chip that integrates filters for both the B3 and B7 frequency bands. The specific structure is as follows: Figure 1 As shown, Figure 1 In the diagram, 1 represents a double-sided symmetrical piezoelectric insulator substrate, 2 represents the front-side chip PAD disposed on the double-sided symmetrical piezoelectric insulator substrate, 3 represents the front-side chip functional area, 4 represents the back-side chip functional area, and 5 represents the via interconnect metal area. The fabrication steps are as follows: (1) Provide a double-sided symmetrical POI substrate: LT / SiO2 / Si / SiO2 / LT substrate, wherein LT is 42°YX tangential lithium tantalate with a thickness of 0.6μm; SiO2 layer thickness is 0.6μm; Si support layer thickness is 500μm. The substrate has a first surface (front side) and a second surface (back side), both of which have piezoelectric functional layers.

[0047] (2) Fabrication of the front-side filter: The IDT pattern of the B3 band filter was defined on the front side of the double-sided symmetrical POI substrate using photolithography. An AlCu alloy electrode with a thickness of 150 nm was deposited by electron beam evaporation, and an interdigital transducer was formed by lift-off. The electrode linewidth was designed according to the n41 band and was approximately 0.3 μm.

[0048] (3) Front structure protection: The wafer with the completed front process is bonded to the temporary carrier wafer (glass sheet) with temporary bonding adhesive to protect the front structure.

[0049] (4) Backside filter fabrication: The bonded wafer is flipped over, and photolithography is performed on the backside. An infrared alignment system is used to align the backside pattern with the frontside pattern. The IDT pattern of the B7 band filter is defined, and an AlCu alloy electrode with a thickness of 120 nm is deposited to form an interdigital transducer. The linewidth of the B7 band electrode is approximately 0.25 μm.

[0050] (5) Debonding: After the back side process is completed, the temporary carrier wafer is removed by thermal sliding or laser debonding, and the residual temporary bonding adhesive is cleaned away.

[0051] (6) Dicing: The wafer is cut into individual chips to obtain a double-sided integrated surface acoustic wave filter chip.

[0052] Example 3 The following explanation uses a double-sided integrated filter chip with vertical interconnects as an example.

[0053] This embodiment provides a double-sided integrated surface acoustic wave filter chip with through-silicon via interconnects, the structure of which is as follows: Figure 2 As shown, vertical signal transmission from both filters can be achieved. Figure 1 In the diagram, 1 represents a double-sided symmetrical piezoelectric insulator substrate, 2 represents the front-side chip PAD disposed on the double-sided symmetrical piezoelectric insulator substrate, 3 represents the front-side chip functional area, 4 represents the back-side chip functional area, and 5 represents the via interconnect metal area. The fabrication steps are as follows: (1) Provide a double-sided symmetrical POI substrate: Same as in Example 2.

[0054] (2) Forming through-silicon vias: First, the via locations are defined by photolithography on the front side of the substrate. Then, deep reactive ion etching is used to form through-holes that penetrate the substrate. The via diameter is 50 μm. The via locations are in the non-functional area at the edge of the chip.

[0055] (3) Through-hole insulation and filling: A SiO2 insulating layer is deposited by PECVD to cover the sidewalls of the through-hole. Then, a Ti / Cu seed layer is deposited, and copper is filled by electroplating to form a conductive pillar.

[0056] (4) Fabrication of front-side filter: The first filter unit is fabricated on the front side of the substrate, and the process is the same as in Example 2.

[0057] (5) Exposed through holes on the back side: Grind or etch the back side to expose the filled through holes on the back side.

[0058] (6) Backside filter fabrication: A second filter unit is fabricated on the backside of the substrate, and a backside wiring layer is formed at the same time. The second filter unit is electrically connected to the via.

[0059] (7) Complete the chip: The subsequent process is the same as in Example 2.

[0060] In the fabricated chip, the filters on both sides can be electrically connected through through-silicon vias (TSVs). For example, the input or output terminals of the two filters can be connected inside the chip to form a more complex filtering function.

[0061] In this embodiment, two independent single-sided filter chips are fabricated using a conventional method, operating in the B3 and B7 frequency bands respectively. Each chip has a size of 1.0 mm × 0.8 mm. The two chips are then placed side-by-side on a packaging substrate for encapsulation.

[0062] Performance comparison: Example 1 and the comparative example were compared and evaluated, and the results are shown in Table 1 below. Table 1 is the performance evaluation table.

[0063] Table 1

[0064] The results show that this invention significantly reduces chip area while maintaining overall cost advantages, achieving a good balance between high integration and low cost. The double-sided integrated surface acoustic wave filter chip provided by this invention can be widely used in various RF front-end modules, including mobile phones, base stations, IoT devices, and satellite navigation terminals. Integrating this chip with power amplifiers, low-noise amplifiers, switches, and other devices in the same module can further reduce the overall size of the RF front-end, meeting the miniaturization requirements of terminal devices.

[0065] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A two-sided integrated surface acoustic wave filter, characterized in that, It includes a biplane symmetrical piezoelectric insulator substrate having a first surface and a second surface, a first filter unit disposed on the first surface, and a second filter unit disposed on the second surface. The first filter unit and the second filter unit are formed independently on the front and back sides of the biplane symmetrical piezoelectric insulator substrate, and the excitation and propagation of surface acoustic waves are realized through the symmetrical piezoelectric layer of the biplane symmetrical piezoelectric insulator substrate.

2. The dual-sided integrated surface acoustic wave filter according to claim 1, characterized in that, A first piezoelectric functional layer is disposed on the first surface, and a second piezoelectric functional layer is disposed on the second surface; The first filter unit includes at least one set of first interdigital transducers, which are disposed on the first piezoelectric functional layer; The second filter unit includes at least one set of second interdigital transducers, which are disposed on the second piezoelectric functional layer.

3. The dual-sided integrated surface acoustic wave filter according to claim 2, characterized in that, The first filter unit includes one or more filters, which are disposed on the first piezoelectric functional layer.

4. The dual-sided integrated surface acoustic wave filter according to claim 2, characterized in that, The second filter unit is independent of the first filter unit, and the connection between the first filter unit and the second filter unit is achieved through an electrical connection structure that runs through a double-sided symmetrical piezoelectric insulator substrate.

5. The dual-sided integrated surface acoustic wave filter according to claim 4, characterized in that, The electrical connection structure includes a conductive pillar penetrating a double-sided symmetrical piezoelectric insulator substrate, enabling vertical interconnection and signal routing between the second filter unit and the first filter unit.

6. The dual-sided integrated surface acoustic wave filter according to any one of claims 1 to 4, characterized in that, The fabrication method of the dual-sided integrated surface acoustic wave filter includes the following steps: S1. A double-sided symmetrical piezoelectric insulator substrate is provided, wherein the double-sided symmetrical piezoelectric insulator substrate has a first surface and a second surface opposite to each other, and a first piezoelectric functional layer is disposed on the first surface and a second piezoelectric functional layer is disposed on the second surface. S2. Fabricate a first filter unit on the first surface and use a process to form an interdigital transducer; S3. Protect the completed structure of the first surface; S4. Prepare a second filter unit on the second surface and form a second interdigital transducer by photolithography. S5. Remove the protective layer to obtain a double-sided integrated surface acoustic wave filter.

7. The dual-sided integrated surface acoustic wave filter according to claim 6, characterized in that, S3 includes the following steps: A temporary bonding method is used to temporarily bond the carrier wafer to the first surface. After the second surface process is completed, the bonding is debonded and the carrier wafer is removed, thus protecting the structure of the first surface.

8. The dual-sided integrated surface acoustic wave filter according to claim 6, characterized in that, Before or after fabricating the first filter unit and the second filter unit, through-holes are etched to form through the substrate, and conductive material is filled into the through-holes to form a silicon through-hole structure.

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