A silicon-based millimeter wave filter chip and a packaging structure thereof

Abstract

The application provides a silicon-based millimeter wave filter chip and a packaging structure thereof, and belongs to the technical field of filters.The silicon-based millimeter wave filter chip comprises at least one silicon cavity resonant unit, the silicon cavity resonant unit comprises a bottom metal layer, a high-Q high-resistance silicon dielectric layer and a top metal layer which are sequentially stacked from bottom to top; the silicon-based millimeter wave filter chip is provided with a recessed part on the side where the top metal layer is located; the area corresponding to the recessed part in the top metal layer is provided with at least one slot-line cross resonator, the slot-line cross resonator comprises a first slot line, a second slot line and a third slot line; one end of the second slot line and the third slot line is communicated with the midpoint of the first slot line; the two ends of the first slot line, the other end of the second slot line and the other end of the third slot line form a closed loop structure by being collected into a ring. The filter chip can improve the out-of-band suppression degree on both sides of the passband, reduce electromagnetic energy leakage and additional spurious resonance, and balance miniaturization, low loss and high out-of-band suppression performance.

Description

Technical Field

[0001] This invention belongs to the field of filter technology, and in particular relates to a silicon-based millimeter-wave filter chip and its packaging structure. Background Technology

[0002] Filters are widely used in radio frequency (RF) and millimeter-wave communication systems to select signals in specific frequency bands and suppress signals in other frequency bands. As millimeter-wave systems evolve towards miniaturization and high integration, filters need to simultaneously meet requirements for low loss, high out-of-band rejection, and small size. SIW-type cavity silicon-based filters are increasingly being used in millimeter-wave filtering applications due to their low loss and ease of chip integration. SIW stands for Substrate Integrated Waveguide.

[0003] To achieve a steeper out-of-band rejection ratio (OBRR), conventional multi-cavity silicon-based filters typically require an increased number of cavity resonator stages, often reaching six or more. This leads to a larger filter size, hindering multi-chip interconnection and high-density integration. Existing technologies can improve OBRR and reduce the number of cavity resonators by etching slotted resonators onto a metal surface to introduce transmission zeros on both sides of the passband.

[0004] However, when slotted structures are introduced into the metal surface, some electromagnetic energy can easily leak from the ends of the slots or the slotted area, leading to increased losses in the passband and potentially generating additional parasitic resonances in the out-of-band response. This affects the frequency selectivity and operational stability of the silicon-based millimeter-wave filter. Therefore, further improvements are needed to reduce electromagnetic energy leakage and parasitic resonances caused by the slotted structure while maintaining filter miniaturization and high out-of-band rejection. Summary of the Invention

[0005] The purpose of this invention is to provide a silicon-based millimeter-wave filter chip and its packaging structure, which can improve the out-of-band rejection on both sides of the passband without increasing the filter size, and reduce electromagnetic energy leakage and additional parasitic resonance caused by the slot end and slotted area, thereby taking into account the miniaturization, low loss and high out-of-band rejection performance of silicon-based millimeter-wave filters.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a silicon-based millimeter-wave filter chip, comprising: At least one silicon cavity resonant unit, the silicon cavity resonant unit comprising a bottom metal layer, a high-Q high-resistivity silicon dielectric layer and a top metal layer stacked from bottom to top; The silicon-based millimeter-wave filter chip has a recess on the side where the top metal layer is located; At least one slotted cross resonator is provided in the region corresponding to the recess in the top metal layer, and the slotted cross resonator includes a first slot, a second slot, and a third slot. One end of both the second and third grooves is connected to the midpoint of the first groove. The two ends of the first groove, the other end of the second groove, and the other end of the third groove are respectively looped to form a closed loop structure.

[0007] Furthermore, each silicon cavity resonant unit has multiple TSV metal vias spaced at its edges. The TSV metal vias penetrate the bottom metal layer, the high-Q high-resistivity silicon dielectric layer, and the top metal layer, and the inner surface of the TSV metal vias is provided with a metal sputtering layer. The silicon-based millimeter-wave filter chip also includes an input feed slot, an output feed slot, a first defect coupling slot, and a second defect coupling slot formed on the top metal layer. The input feed slot is connected to the first defect coupling slot, and the output feed slot is connected to the second defect coupling slot.

[0008] Furthermore, the number of silicon cavity resonant units is multiple, and the multiple silicon cavity resonant units are arranged sequentially or in a matrix; two adjacent silicon cavity resonant units in the same row share one slotted cross resonator.

[0009] Furthermore, the recess is disposed between the first defect coupling groove and the second defect coupling groove.

[0010] Furthermore, the first slot line is used to control the transmission zero point outside the low-frequency band, the second slot line is used to control the transmission zero point outside the high-frequency band, and the third slot line is used to control another transmission zero point outside the high-frequency band.

[0011] Furthermore, the closed-loop structure can be square, circular, arc-shaped, ring-shaped, or folded-back closed structure.

[0012] Furthermore, the first groove line, the second groove line, and the third groove line are respectively straight groove lines, arc groove lines, wavy groove lines, or bent groove lines.

[0013] Furthermore, the thickness of the bottom metal layer is D1, the thickness of the top metal layer is D2, and the thickness of the high-Q high-resistivity silicon dielectric layer is D3, wherein D1≤10μm, D2≤10μm, 200μm≤D3≤500μm; the resistivity of the high-Q high-resistivity silicon dielectric layer is R1, wherein R1≥3000Ω·cm.

[0014] In a second aspect, the present invention provides a packaging structure for a silicon-based millimeter-wave filter chip, comprising a silicon-based adapter board and the silicon-based millimeter-wave filter chip, wherein the top metal layer of the silicon-based millimeter-wave filter chip is bonded to the silicon-based adapter board, and the recessed portion and the surface of the silicon-based adapter board enclose a closed cavity.

[0015] Furthermore, the silicon-based millimeter-wave filter chip is bonded to the silicon-based adapter board via copper pillar microbumps located between the top metal layer and the silicon-based adapter board. The silicon-based adapter board is provided with a metal wiring layer and pads, and the copper pillar microbumps are connected to the pads.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention provides a recessed portion on the side of the top metal layer of a silicon-based millimeter-wave filter chip, and a slotted cross resonator is provided in the area corresponding to the recessed portion in the top metal layer. One end of the second and third slotted lines is connected to the midpoint of the first slotted line. At the same time, the two ends of the first slotted line, the other end of the second slotted line, and the other end of the third slotted line are respectively looped to form a closed-loop structure. This can form multiple transmission zeros on both sides of the passband and guide the electromagnetic waves emitted from the ends of the slotted lines back into the slotted lines. Thus, without increasing the filter size, the out-of-band suppression on both sides of the passband is improved, and the additional parasitic resonance caused by the ends of the slotted lines is reduced.

[0017] 2. This invention forms a metallized shielding boundary around the silicon cavity resonator unit by setting a TSV metal via penetrating the bottom metal layer, the high-Q high-resistivity silicon dielectric layer, and the top metal layer at the edge of the silicon cavity resonator unit, and setting a metal sputtering layer on the inner surface of the TSV metal via. This reduces electromagnetic wave leakage from the silicon cavity resonator unit to the outside. At the same time, signal input, coupling, and output are achieved through the input feed slot, the output feed slot, the first defect coupling slot, and the second defect coupling slot, which helps to ensure the signal transmission and filtering coupling stability of the silicon-based millimeter-wave filter chip.

[0018] 3. This invention improves the integration and compactness of the multi-cavity filter structure by setting up multiple silicon cavity resonant units arranged sequentially or in a matrix, and by having two adjacent silicon cavity resonant units in the same row share a slotted cross resonator. At the same time, by having the first slotted line, the second slotted line, and the third slotted line correspond to different out-of-band transmission zeros, and by using different slotted line shapes and closed-loop structure shapes for adjustment, it is beneficial to realize the corresponding control of multiple out-of-band transmission zeros, while taking into account miniaturization, high out-of-band rejection, and low loss performance. Attached Figure Description

[0019] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the structure of a silicon-based millimeter-wave filter chip provided in an embodiment of the present invention; Figure 2 for Figure 1 A sectional view along the A-A' direction. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0021] The following detailed description is exemplary and intended to provide further detailed explanation of the invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention.

[0022] Example 1 like Figure 1 and Figure 2 As shown, this embodiment provides a silicon-based millimeter-wave filter chip. Figure 1 This is a schematic diagram of the silicon-based millimeter-wave filter chip in this embodiment. Figure 2 yes Figure 1 A cross-sectional view along the A-A' direction. This silicon-based millimeter-wave filter chip can be used for frequency-selective filtering in millimeter-wave systems to improve out-of-band rejection on both sides of the passband while miniaturizing the chip, and to reduce additional parasitic electromagnetic resonances caused by the slotted structure.

[0023] The silicon-based millimeter-wave filter chip provided by the present invention includes: at least one silicon cavity resonant unit, wherein the silicon cavity resonant unit includes a bottom metal layer, a high-Q high-resistivity silicon dielectric layer and a top metal layer stacked from bottom to top.

[0024] Specifically, such as Figure 1 and Figure 2 As shown, the silicon cavity resonant unit 11 includes a bottom metal layer 21, a high-Q, high-resistivity silicon dielectric layer 22, and a top metal layer 23, which are stacked sequentially from bottom to top. Figure 1 In the embodiment shown, there are three silicon cavity resonant units 11, which are arranged side by side as a first silicon cavity resonant unit 111, a second silicon cavity resonant unit 112, and a third silicon cavity resonant unit 113.

[0025] The bottom metal layer 21 and the top metal layer 23 can be copper or gold layers to reduce metal loss. A high-Q, high-resistivity silicon dielectric layer 22 is used to form a low-loss silicon-based dielectric resonant region. The thickness of the bottom metal layer is D1, the thickness of the top metal layer is D2, and the thickness of the high-Q, high-resistivity silicon dielectric layer is D3. In this embodiment, D1 ≤ 10 μm, D2 ≤ 10 μm, and 200 μm ≤ D3 ≤ 500 μm. The resistivity of the high-Q, high-resistivity silicon dielectric layer is R1, where R1 ≥ 3000 Ω·cm. As a preferred embodiment, the thickness of the bottom metal layer 21 and the top metal layer 23 can be 10 μm, and the thickness of the high-Q, high-resistivity silicon dielectric layer 22 can be 400 μm.

[0026] The silicon cavity resonator 11 can be rectangular, square, circular, or other polygonal. By adjusting the shape and size of the silicon cavity resonator 11, the filtering frequency of the silicon cavity resonator 11 can be determined, thereby obtaining a silicon-based millimeter-wave filter chip that meets the requirements of the target operating frequency band.

[0027] Each silicon cavity resonator unit has multiple TSV metal vias spaced at its edge. The TSV metal vias penetrate the bottom metal layer, the high-Q high-resistivity silicon dielectric layer, and the top metal layer, and the inner surface of the TSV metal vias is provided with a metal sputtering layer.

[0028] Specifically, each silicon cavity resonator unit 11 has multiple TSV metal vias 12 spaced at its edge. These TSV metal vias 12 are formed using ICP deep silicon etching technology. The TSV metal vias 12 penetrate the bottom metal layer 21, the high-Q, high-resistivity silicon dielectric layer 22, and the top metal layer 23, and a metal sputtering layer is disposed on the inner surface of the TSV metal via 12. The TSV metal via 12 can be a full via 122 or an open semi-via 121. Adjacent silicon cavity resonator units 11 can share some TSV metal vias 12; for example, the open semi-vias 121 of adjacent silicon cavity resonator units 11 can be connected to form a full via 122. After the metal sputtering layer is disposed on the inner surface of the TSV metal via 12, it can cooperate with the bottom metal layer 21 and the top metal layer 23 to form a metallized shielding boundary, thereby confining electromagnetic waves inside the silicon cavity resonator unit 11, reducing energy loss caused by electromagnetic wave leakage, and reducing the impact of the external electromagnetic environment on the internal circuitry of the filter.

[0029] The silicon-based millimeter-wave filter chip has a recess on the side where the top metal layer is located.

[0030] Specifically, such as Figure 2As shown, the recess can be formed by etching and lifting the top silicon dielectric. The recess is located on the side of the top metal layer 23 of the silicon-based millimeter-wave filter chip, and it manifests as a recessed structure on the side of the top metal layer 23 in the chip body. The recess itself is not limited to a closed cavity; when the silicon-based millimeter-wave filter chip is bonded to a silicon-based adapter plate on the side of the top metal layer 23, the recess can form a closed cavity with the surface of the silicon-based adapter plate. Figure 2 The diagram also illustrates the layered structure of the copper pillar microbumps 24 and the silicon-based adapter. Specifically, the silicon-based adapter may include a top metal layer 25, an intermediate dielectric layer 26, and a bottom metal layer 27. The top metal layer 25 may include pads or metal wiring layers for bonding with the copper pillar microbumps 24. The intermediate dielectric layer 26 can serve as the dielectric layer of the silicon-based adapter, and the bottom metal layer 27 can serve as the bottom metal wiring layer of the silicon-based adapter. The copper pillar microbumps 24 can be disposed between the top metal layer 23 and the silicon-based adapter to achieve low-temperature bonding between the silicon-based millimeter-wave filter chip and the silicon-based adapter in subsequent packaging structures.

[0031] At least one slotted cross resonator is provided in the region corresponding to the recess in the top metal layer. The slotted cross resonator includes a first slot, a second slot, and a third slot. When there are multiple silicon cavity resonator units, the multiple silicon cavity resonator units are arranged sequentially or in a matrix; two adjacent silicon cavity resonator units in the same row share one slotted cross resonator.

[0032] Specifically, at least one slotted cross resonator 13 is provided in the region corresponding to the recess in the top metal layer 23. The slotted cross resonator 13 includes a first slot 131, a second slot 132, and a third slot 133. Figure 1 The diagram shows two slotted-line cross resonators 13, located between a first silicon cavity resonator unit 111 and a second silicon cavity resonator unit 112, and between the second silicon cavity resonator unit 112 and a third silicon cavity resonator unit 113, respectively. The slotted-line cross resonators 13 are formed on the top metal layer 23.

[0033] exist Figure 1 In the illustrated embodiment, there are multiple silicon cavity resonator units 11, with a first silicon cavity resonator unit 111, a second silicon cavity resonator unit 112, and a third silicon cavity resonator unit 113 arranged sequentially. The first silicon cavity resonator unit 111 and the second silicon cavity resonator unit 112 share a slotted-line cross resonator 13, and the second silicon cavity resonator unit 112 and the third silicon cavity resonator unit 113 share another slotted-line cross resonator 13. In other embodiments, the multiple silicon cavity resonator units 11 can also be arranged in a matrix, with two adjacent silicon cavity resonator units 11 in the same row sharing a slotted-line cross resonator 13.

[0034] The recess is located between the first defect coupling groove and the second defect coupling groove.

[0035] Specifically, in Figure 1 and Figure 2 In the illustrated embodiment, the recess is disposed between the first defect coupling groove 15 and the second defect coupling groove 17. Therefore, during subsequent bonding to form the package structure, the recess can form a closed space with the surface of the silicon-based adapter board, thereby reducing electromagnetic wave energy leakage caused by the slotted area.

[0036] One end of the second and third grooves is connected to the midpoint of the first groove.

[0037] Specifically, such as Figure 1 As shown, one end of the second slot line 132 and one end of the third slot line 133 are both connected to the midpoint of the first slot line 131. Through this connection, the first slot line 131, the second slot line 132, and the third slot line 133 form a slot-line cross resonator 13. The first slot line 131, the second slot line 132, and the third slot line 133 are not independent slotted structures, but are connected through the midpoint of the first slot line 131 to introduce multiple tunable out-of-band transmission zeros within a limited chip area.

[0038] Specifically, the first slot line 131, the second slot line 132, and the third slot line 133 each form a different slot line resonant path. The length, width, bending shape, and connection relationship with the midpoint of the first slot line 131 of each slot line jointly determine the corresponding resonant frequency position. Therefore, the low-frequency out-of-band transmission zero can be adjusted by selecting or adjusting the length, width, and shape of the first slot line 131; the high-frequency out-of-band transmission zero can be adjusted by selecting or adjusting the length, width, and shape of the second slot line 132; and the high-frequency out-of-band transmission zero can be adjusted by selecting or adjusting the length, width, and shape of the third slot line 133. That is, a transmission zero can be introduced on the low-frequency side of the filter's passband through the first slot line 131, and two transmission zeros can be introduced on the high-frequency side of the filter's passband through the second slot line 132 and the third slot line 133. Thus, the slot line cross resonator 13 can form multiple adjustable transmission zeros on both sides of the filter's passband without increasing the number of silicon cavity resonant units 11, thereby improving the out-of-band rejection on both sides of the passband.

[0039] The two ends of the first groove, the other end of the second groove, and the other end of the third groove are respectively looped to form a closed loop structure.

[0040] Specifically, the two ends of the first slot line 131, the other end of the second slot line 132, and the other end of the third slot line 133 are respectively looped to form a closed-loop structure. By looping the two ends of the first slot line 131 and the ends of the second slot line 132 and the third slot line 133 away from the first slot line 131, the electromagnetic waves emitted from the slot line ends can be guided back into the slot lines, reducing the additional parasitic resonances caused by electromagnetic waves leaking out from the slot line ends, thereby improving the out-of-band response of the filter and creating a suppression effect on parasitic resonances.

[0041] Specifically, the closed-loop structure can be configured as a square closed loop, circular closed loop, arc closed loop, ring closed loop or folded closed structure according to the specific shape of the end of the groove line. As long as the end of the groove line can form a closed recovery path to guide the electromagnetic waves emitted from the end of the groove line back into the groove line.

[0042] The first, second, and third grooves are respectively straight grooves, curved grooves, wavy grooves, or bent grooves.

[0043] Specifically, in one embodiment, the first groove line 131, the second groove line 132, and the third groove line 133 can be straight groove lines, arc groove lines, wavy groove lines, or bent groove lines, respectively. Figure 1 The slotted cross resonator 13 shown is an example of a specific bending configuration, but should not be construed as the sole limitation on the specific line shapes of the first slot 131, the second slot 132, and the third slot 133. As long as one end of the second slot 132 and the third slot 133 are connected to the midpoint of the first slot 131, and both ends of the first slot 131, the other end of the second slot 132, and the other end of the third slot 133 are respectively looped to form a closed-loop structure, a slotted cross resonator 13 for achieving the aforementioned transmission zero-point modulation and parasitic resonance suppression can be formed.

[0044] The silicon-based millimeter-wave filter chip also includes an input feed slot, an output feed slot, a first defect coupling slot, and a second defect coupling slot formed on the top metal layer. The input feed slot is connected to the first defect coupling slot, and the output feed slot is connected to the second defect coupling slot.

[0045] Specifically, such as Figure 1As shown, the input feed slot 14, output feed slot 16, first defect coupling slot 15, and second defect coupling slot 17 are all formed on the top metal layer 23. The input feed slot 14 is connected to the first defect coupling slot 15, and the output feed slot 16 is connected to the second defect coupling slot 17. The input feed slot 14 and the first defect coupling slot 15 are formed on the top metal layer 23 of the first silicon cavity resonant unit 11, that is, on the top metal layer 23 of the first silicon cavity resonant unit 111. The output feed slot 16 and the second defect coupling slot 17 are formed on the top metal layer 23 of the last silicon cavity resonant unit 11, that is, on the top metal layer 23 of the third silicon cavity resonant unit 113.

[0046] The input feed slot 14 is used to input the signal to be filtered, the first defect coupling slot 15 is used to couple the signal to be filtered to the first silicon cavity resonator unit 111; the second defect coupling slot 17 is used to couple the filtered signal from the third silicon cavity resonator unit 113 to the output feed slot 16, and the output feed slot 16 is used to output the filtered signal formed after the signal to be filtered is filtered.

[0047] In this embodiment, the input feed slot 14 and the first defect coupling slot 15 can correspond one-to-one and be vertically connected, and the output feed slot 16 and the second defect coupling slot 17 can be vertically connected. The impedance of the input feed slot 14 and the output feed slot 16 can be 50Ω. The slot width of the input feed slot 14 and the output feed slot 16 can be 88μm, the gap between the two input feed slots 14 can be 70μm, and the length of the first defect coupling slot 15 and the second defect coupling slot 17 can both be 1.1mm, and the width can both be 0.22mm. The depth of the input feed slot 14, the output feed slot 16, the first defect coupling slot 15, and the second defect coupling slot 17 can be equal to the thickness of the top metal layer 23.

[0048] The size of the first defect coupling slot 15 determines the coupling strength between the input feed slot 14 and the first silicon cavity resonant unit 111, and the size of the second defect coupling slot 17 determines the coupling strength between the output feed slot 16 and the third silicon cavity resonant unit 113. Specifically, the larger the size of the first defect coupling slot 15 and the second defect coupling slot 17, the greater the corresponding coupling strength.

[0049] The first silicon cavity resonant unit 111 and the second silicon cavity resonant unit 112 can be coupled through the spacing between the TSV metal vias 12 on the upper and lower sides of the corresponding slotted cross resonator 13; the second silicon cavity resonant unit 112 and the third silicon cavity resonant unit 113 can also be coupled through the spacing between the TSV metal vias 12 on the upper and lower sides of the corresponding slotted cross resonator 13. The larger the spacing, the smaller the coupling between two adjacent silicon cavity resonant units 11; the smaller the spacing, the larger the coupling between two adjacent silicon cavity resonant units 11.

[0050] The silicon-based millimeter-wave filter chip in this embodiment can be fabricated using microelectromechanical processing (MEMS) technology. Its silicon cavity resonant unit 11, TSV metal via 12, slot-line cross resonator 13 on the top metal layer 23, and input / output coupling structure are all compatible with semiconductor integrated circuit technology, which is beneficial for miniaturization and chip-based fabrication of the filter.

[0051] like Figure 2 As shown, when a silicon-based millimeter-wave filter chip is used for packaging, the side containing the top metal layer 23 of the silicon-based millimeter-wave filter chip can be cryogenically bonded to the microbumps on the surface of the silicon-based adapter board via copper pillar microbumps 24. At this time, the recessed portion of the silicon-based millimeter-wave filter chip and the surface of the silicon-based adapter board enclose a closed cavity. This closed cavity can reduce electromagnetic wave energy leakage caused by slotting, further reducing the problem of increased losses due to electromagnetic wave energy leakage caused by slotting. Figure 2 In this process, the silicon-based adapter board may include a first adapter board layer 25, a second adapter board layer 26, and a third adapter board layer 27.

[0052] With the above structure, the silicon-based millimeter-wave filter chip provided in this embodiment has a slotted cross resonator 13 in the region corresponding to the recess in the top metal layer 23. Multiple out-of-band transmission zeros are formed through the cross-connection of the first slot 131, the second slot 132, and the third slot 133, which can improve the out-of-band suppression on both sides of the passband without increasing the filter size. Simultaneously, by forming a closed-loop structure by looping the two ends of the first slot 131, the other end of the second slot 132, and the other end of the third slot 133, additional parasitic resonances caused by electromagnetic wave leakage at the slot ends can be reduced. Furthermore, during packaging, the recess and the surface of the silicon-based adapter plate form a closed cavity, further reducing electromagnetic wave energy leakage in the slotted region. Therefore, this embodiment achieves parasitic suppression on both sides of the passband without the need for additional loading structures or sensitive control parameters to suppress parasitic resonances, giving the silicon-based millimeter-wave filter chip the characteristics of small size, low loss, high out-of-band suppression, and few parasitic resonances.

[0053] Example 2 like Figure 2 As shown, based on the same inventive concept as the above embodiments, this embodiment provides a packaging structure for a silicon-based millimeter-wave filter chip. This packaging structure includes a silicon-based adapter board and the silicon-based millimeter-wave filter chip as described in Embodiment 1. The top metal layer 23 of the silicon-based millimeter-wave filter chip is bonded to the silicon-based adapter board, and the recessed portion and the surface of the silicon-based adapter board enclose a closed cavity.

[0054] Specifically, the silicon-based millimeter-wave filter chip includes at least one silicon cavity resonant unit 11. The silicon cavity resonant unit 11 includes a bottom metal layer 21, a high-Q, high-resistivity silicon dielectric layer 22, and a top metal layer 23. The silicon-based millimeter-wave filter chip has a recess on the side where the top metal layer 23 is located. A slotted cross resonator 13 is disposed in the region of the top metal layer 23 corresponding to the recess. The slotted cross resonator 13 includes a first slot 131, a second slot 132, and a third slot 133. One end of the second slot 132 and the third slot 133 are connected to the midpoint of the first slot 131. The two ends of the first slot 131, the other end of the second slot 132, and the other end of the third slot 133 are respectively looped to form a closed-loop structure.

[0055] During packaging, the side of the top metal layer 23 of the silicon-based millimeter-wave filter chip faces the silicon-based adapter and is bonded to the silicon-based adapter. Since the recess is located on the side of the top metal layer 23 of the silicon-based millimeter-wave filter chip, and the slotted cross resonator 13 is formed in the region of the top metal layer 23 corresponding to the recess, after the silicon-based millimeter-wave filter chip and the silicon-based adapter are bonded, the recess and the surface of the silicon-based adapter together form a closed cavity. This closed cavity corresponds to the slotted area where the slotted cross resonator 13 is located, which can reduce electromagnetic wave energy leakage caused by the slotted area from the packaging structure perspective.

[0056] The silicon-based millimeter-wave filter chip is bonded to the silicon-based adapter board via copper pillar microbumps located between the top metal layer and the silicon-based adapter board. The silicon-based adapter board has a metal wiring layer and pads, and the copper pillar microbumps are connected to the pads.

[0057] Specifically, such as Figure 2 As shown, copper pillar microbumps 24 are disposed between the top metal layer 23 of the silicon-based millimeter-wave filter chip and the silicon-based adapter board. One side of the copper pillar microbumps 24 is connected to the silicon-based millimeter-wave filter chip, and the other side is connected to the pads on the silicon-based adapter board, thereby realizing the bonding connection between the silicon-based millimeter-wave filter chip and the silicon-based adapter board. Low-temperature bonding can be used to reduce the impact of the packaging process on the silicon cavity resonant unit 11 and the slotted cross resonator 13 inside the silicon-based millimeter-wave filter chip.

[0058] like Figure 2As shown, the silicon-based adapter board may include a top metal layer 25, an intermediate dielectric layer 26, and a bottom metal layer 27. The top metal layer 25 may include pads or metal wiring layers for bonding with the copper pillar microbumps 24. The intermediate dielectric layer 26 can serve as the dielectric layer of the silicon-based adapter board, and the bottom metal layer 27 can serve as the bottom metal wiring layer. Through this layered structure, the silicon-based adapter board can support silicon-based millimeter-wave filter chips and achieve signal switching and packaging connections through pads, metal wiring layers, and copper pillar microbumps 24.

[0059] In this embodiment, the enclosed cavity is formed jointly by the recessed portion of the silicon-based millimeter-wave filter chip and the surface of the silicon-based adapter plate. Compared to the recessed portion that exists independently in the chip body, the enclosed cavity is an enclosed space formed after the silicon-based millimeter-wave filter chip and the silicon-based adapter plate are bonded together. This enclosed space can cover or correspond to the slotted area where the slotted cross resonator 13 is located, so that the electromagnetic field around the first slot 131, the second slot 132, and the third slot 133 is further confined within the enclosed cavity, thereby reducing the problem of increased loss caused by electromagnetic wave energy leakage from the slot.

[0060] Through the aforementioned packaging structure, on the one hand, the slotted cross resonator 13 in the silicon-based millimeter-wave filter chip can form multiple out-of-band transmission zeros through the first slot 131, the second slot 132, and the third slot 133, thereby improving the out-of-band rejection on both sides of the passband; on the other hand, the closed cavity formed by the recess and the surface of the silicon-based adapter board can further constrain electromagnetic energy leakage in the region where the slotted cross resonator 13 is located. Thus, this packaging structure can reduce additional parasitic resonances and lower losses caused by slotted electromagnetic wave energy leakage without increasing the size of the filter chip, in conjunction with the closed-loop structure at the end of the slot.

[0061] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A silicon-based millimeter-wave filter chip, characterized in that, include: At least one silicon cavity resonant unit, the silicon cavity resonant unit comprising a bottom metal layer, a high-Q high-resistivity silicon dielectric layer and a top metal layer stacked from bottom to top; The silicon-based millimeter-wave filter chip has a recess on the side where the top metal layer is located; At least one slotted cross resonator is provided in the region corresponding to the recess in the top metal layer, and the slotted cross resonator includes a first slot, a second slot, and a third slot. One end of both the second and third grooves is connected to the midpoint of the first groove. The two ends of the first groove, the other end of the second groove, and the other end of the third groove are respectively looped to form a closed loop structure.

2. The silicon-based millimeter-wave filter chip according to claim 1, characterized in that, Each silicon cavity resonant unit has multiple TSV metal vias spaced at its edges. The TSV metal vias penetrate the bottom metal layer, the high-Q high-resistivity silicon dielectric layer, and the top metal layer. The inner surface of each TSV metal via is provided with a metal sputtering layer. The silicon-based millimeter-wave filter chip also includes an input feed slot, an output feed slot, a first defect coupling slot, and a second defect coupling slot formed on the top metal layer. The input feed slot is connected to the first defect coupling slot, and the output feed slot is connected to the second defect coupling slot.

3. The silicon-based millimeter-wave filter chip according to claim 1, characterized in that, The number of silicon cavity resonant units is multiple, and the multiple silicon cavity resonant units are arranged sequentially or in a matrix; two adjacent silicon cavity resonant units in the same row share one slotted cross resonator.

4. The silicon-based millimeter-wave filter chip according to claim 3, characterized in that, The recess is located between the first defect coupling groove and the second defect coupling groove.

5. The silicon-based millimeter-wave filter chip according to claim 1, characterized in that, The first slot line is used to control the transmission zero point outside the low frequency band, the second slot line is used to control the transmission zero point outside the high frequency band, and the third slot line is used to control another transmission zero point outside the high frequency band.

6. The silicon-based millimeter-wave filter chip according to claim 1, characterized in that, The closed-loop structure can be square, circular, arc-shaped, ring-shaped, or folded-back closed structure.

7. The silicon-based millimeter-wave filter chip according to claim 1, characterized in that, The first groove, the second groove, and the third groove are respectively straight grooves, arc grooves, wavy grooves, or bent grooves.

8. The silicon-based millimeter-wave filter chip according to claim 1, characterized in that, The thickness of the bottom metal layer is D1, the thickness of the top metal layer is D2, and the thickness of the high-Q high-resistivity silicon dielectric layer is D3, wherein D1≤10μm, D2≤10μm, 200μm≤D3≤500μm; the resistivity of the high-Q high-resistivity silicon dielectric layer is R1, wherein R1≥3000Ω·cm.

9. A packaging structure for a silicon-based millimeter-wave filter chip, characterized in that, The invention includes a silicon-based adapter board and a silicon-based millimeter-wave filter chip as described in any one of claims 1 to 8, wherein the top metal layer of the silicon-based millimeter-wave filter chip is bonded to the silicon-based adapter board, and the recessed portion and the surface of the silicon-based adapter board enclose a closed cavity.

10. The packaging structure of the silicon-based millimeter-wave filter chip according to claim 9, characterized in that, The silicon-based millimeter-wave filter chip is bonded to the silicon-based adapter board via copper pillar microbumps located between the top metal layer and the silicon-based adapter board. The silicon-based adapter board has a metal wiring layer and pads, and the copper pillar microbumps are connected to the pads.

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