A wiring structure for an interposer

Abstract

The application provides a wiring structure for an interposer. The wiring structure for the interposer provided by the application includes a stack composed of multiple metal layers, and the wiring structure includes: at least one signal metal layer for transmitting signals; a ground potential layer above and below the signal metal layer for providing longitudinal shielding enclosure; a lateral shielding array composed of multiple metal vias as a lateral reference ground for signal lines in the signal metal layer, the lateral shielding array is in electrical communication with the ground potential layer and jointly encloses at least one longitudinally extending shielding cavity; wherein at least part of the signal lines in the signal metal layer are contained in the shielding cavity, so that the transmission path of the signal lines is constrained in the vertical and horizontal lateral directions by the equipotential shielding body composed of the ground potential layer and the lateral shielding array in electrical communication.

Description

Technical Field

[0001] This application relates to the field of integrated circuit technology, and more particularly to a wiring structure for an interposer layer. Background Technology

[0002] With the rapid development of applications such as artificial intelligence, big data, and cloud computing, the bandwidth and data rate of high-bandwidth memory (HBM) have continued to climb, evolving from HBM1 to HBM3, HBM3E, and even the future HBM4. This development has placed stringent requirements on the signal integrity of silicon interposers, requiring lower insertion loss and lower crosstalk at higher frequencies. However, the increase in the number of I / Os and the improvement in micro-bump pin density have made transmission loss and lateral crosstalk problems increasingly prominent, and traditional interposer wiring structures are no longer able to meet the performance specifications of HBM3E / HBM4.

[0003] Current interposer routing solutions mainly include single-layer routing based on microstrip lines, striplines, or coplanar waveguide structures, as well as routing methods with orthogonal interleaving between different metal layers. The performance of these two solutions can only meet the current requirements for lower speeds. In recent years, to reduce impedance without increasing lateral area, the industry has generally adopted thicker metal layers to increase conductivity; simultaneously, to achieve high-density interconnects, line width and spacing have continued to shrink. The combination of these two trends has resulted in the height of the metal layer gradually exceeding its width, forming a high aspect ratio (high AR) structure. While this reduces conductor loss, it leads to a significant increase in lateral electric field coupling, thus worsening lateral crosstalk. To address this contradiction, simultaneously achieving low insertion loss and low crosstalk typically requires increasing the signal line spacing to meet the 3W rule, or introducing additional grounding structures between signal lines for isolation. However, both of these approaches significantly increase the lateral routing area, contradicting the requirements of high-density integration. Another approach attempts to replace the silicon interposer with an organic substrate, utilizing its lower dielectric loss to improve channel performance. However, the coefficient of thermal expansion (CTE) of the organic substrate differs greatly from that of the silicon chip, which can easily lead to solder joint stress failure during temperature cycling, bringing new reliability risks.

[0004] Therefore, there is an urgent need for a cabling structure that can reduce transmission loss and suppress crosstalk between all signal lines without increasing the lateral cabling area. Summary of the Invention

[0005] In view of this, this application provides a wiring structure for an interposer layer to reduce transmission loss and suppress crosstalk between all signal lines without increasing the lateral wiring area.

[0006] Specifically, this application is implemented through the following technical solution:

[0007] A first aspect of this application provides a wiring structure for an interposer layer, the interposer layer comprising a stack of multiple metal layers, the wiring structure comprising:

[0008] At least one signal metal layer is used for signal transmission;

[0009] The ground potential layers located above and below the signal metal layer are used to provide longitudinal shielding enclosure;

[0010] A lateral shielding array consisting of multiple metal vias serves as a lateral reference ground for the signal lines in the signal metal layer. The lateral shielding array is electrically connected to the ground potential layer and together they enclose at least one shielding cavity extending longitudinally.

[0011] In this embodiment, at least a portion of the signal lines in the signal metal layer are housed within the shielding cavity, such that the transmission path of the signal lines is constrained by the equipotential shield in both the vertical and lateral directions. The equipotential shield is formed by the ground potential layer and the lateral shielding array being electrically connected.

[0012] Optionally, the thickness of the signal metal layer is greater than that of other metal layers outside the shielding cavity, excluding the redistribution layer.

[0013] Optionally, the thickness of the signal metal layer is 2 μm or more, and the metal height of the signal metal layer is greater than the minimum linewidth.

[0014] Optionally, the lateral physical distance between the signal line housed in the shielded cavity and the signal line in the adjacent shielded cavity can be less than 3 times the signal line width.

[0015] Optionally, the wiring structure further includes a redistribution layer located above the ground potential layer, wherein at least a portion of the signal lines in the redistribution layer are staggered with the traces of the signal metal layer below, forming a three-dimensional wiring topology that is mixed in both vertical and horizontal directions.

[0016] Optionally, in the lateral direction perpendicular to the signal transmission direction, the signal metal layer includes a ground structure, which works in conjunction with the lateral shielding array to suppress lateral electric field coupling between adjacent shielding cavities.

[0017] Optionally, any of the ground potential layers consists of one or more metal layers that are neither the top nor the bottom layer of the stack.

[0018] Optionally, the interlayer includes at least two metal layers, the thickness of which is set differently according to the impedance requirements of the signal lines they carry, so that longitudinally staggered stripline units are formed between different metal layers during signal transmission.

[0019] Optionally, the lateral shielding array consists of two rows of closely spaced metal through holes, which are arranged along the signal extension direction on both sides of the shielding cavity that accommodates the signal line and connected to the ground potential layer to form a quasi-coaxial electromagnetic shielding channel.

[0020] The wiring structure for the intermediate layer provided in this application constructs a shielded cavity enclosed by a ground potential layer and a lateral shielding array. This cavity houses the signal line, ensuring it is fully enclosed and constrained by the equipotential shield in all four directions (up, down, left, and right). This forces the electromagnetic field of the signal line from a "free-diffusion mode" to a "three-dimensional constrained mode." In traditional solutions, the electric field of the signal line can freely diffuse to adjacent signal lines in the lateral dimension. Crosstalk can only be suppressed by increasing the line spacing or inserting ground wires, both of which consume lateral area. This application, based on the upper and lower ground potential layers, introduces a lateral shielding array composed of closely spaced metal vias on both sides of the signal line. This lateral shielding array serves as the lateral reference ground for the signal line in the signal metal layer and is electrically connected to the upper and lower grounds as an equipotential body. This is equivalent to building a grounded metal wall on each side of the signal line, forming a quasi-coaxial enclosure structure together with the upper and lower ground planes. After the signal lines are embedded, most of their electric field lines are forcibly terminated at the inner walls of the lateral via walls and the upper and lower reference grounds. The electromagnetic field shifts from the lateral direction to the longitudinal direction, and leakage to adjacent cavities is physically blocked. The lateral line spacing can be compressed to a value far less than the traditional 3W rule, while crosstalk decreases instead of increasing, breaking the established rule that "isolation must sacrifice density." Simultaneously, the equipotential shield provides four adjacent low-impedance return paths for the signal lines (top, bottom, left, and right). The return current selects the shortest path to return to the source, significantly reducing the return loop area, lowering return inductance and ground bounce noise, and reducing transmission loss while suppressing crosstalk. Furthermore, each signal line is independently encapsulated in its own shielded cavity, resulting in a highly consistent and decoupled electromagnetic environment, significantly improving the integrity and consistency of multi-channel signals. In other words, this application simultaneously achieves multiple effects: suppressing crosstalk, shortening return current, reducing loss, and improving multi-channel consistency, systematically resolving the inherent contradiction of density, loss, and crosstalk without increasing the lateral area. Attached Figure Description

[0021] Figure 1 This is a cross-sectional schematic diagram of the wiring structure for the intermediary layer provided in Embodiment 1 of this application;

[0022] Figure 2 This is a top view of a typical layout unit in the wiring structure used in the intermediary layer of this application;

[0023] Figure 3 A comparison diagram of insertion loss between the signal metal layer provided in this application and a conventional unthickened metal layer;

[0024] Figure 4 A comparison diagram showing the isolation effect between the signal metal layer provided in this application and a traditional unthickened metal layer;

[0025] Figure 5 The eye diagram comparison results are shown between the wiring structure of this application and the traditional wiring structure under the condition of a wiring length of 5.3mm.

[0026] Figure 6 A schematic diagram showing the different orientations of the strip lines provided in this application;

[0027] Figure 7 This is a cross-sectional schematic diagram of the wiring structure for the intermediary layer provided in Embodiment 2 of this application. Detailed Implementation

[0028] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application.

[0029] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used herein are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0030] It should be understood that although the terms first, second, third, etc., may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0031] The following specific embodiments are given to illustrate the technical solution of this application in detail.

[0032] Figure 1 This is a cross-sectional schematic diagram of the wiring structure for the interposer layer provided in Embodiment 1 of this application. Please refer to... Figure 1 The wiring structure for the interposer layer provided in this embodiment includes a stack of multiple metal layers, and the wiring structure includes:

[0033] At least one signal metal layer is used for signal transmission;

[0034] The ground potential layers located above and below the signal metal layer are used to provide longitudinal shielding enclosure;

[0035] A lateral shielding array consisting of multiple metal vias serves as a lateral reference ground for the signal lines in the signal metal layer. The lateral shielding array is electrically connected to the ground potential layer and together with it forms at least one longitudinally extending shielding cavity.

[0036] In this embodiment, at least a portion of the signal lines in the signal metal layer are housed within the shielding cavity, such that the transmission path of the signal lines is constrained by the equipotential shield in both the vertical and lateral directions. The equipotential shield is formed by the ground potential layer and the lateral shielding array being electrically connected.

[0037] Figure 2 This is a top view of a typical layout unit in the wiring structure used in the interposer layer of this application. For example... Figure 2 As shown, the layout unit includes a signal line located in the signal metal layer and lateral shielding arrays disposed on both sides of the signal line. The lateral shielding arrays consist of multiple metal vias, which are spaced apart along the signal transmission direction. The lateral shielding arrays are electrically connected to the ground potential layer in the longitudinal direction, thereby forming a shielding cavity surrounding the signal line together with the ground potential layers located above and below the signal metal layer.

[0038] Specifically, the interposer is a stack composed of multiple alternating metal layers and dielectric layers. Electrical isolation between the metal layers is achieved through dielectric layers, and interlayer interconnection is achieved through metal vias. Figure 1 In the example shown, the stack, from bottom to top, includes: a bottom metal layer (Metal1), sequentially stacked metal layers (Metal2 to Metal5), and a top ground metal layer (Ground). It should be noted that... Figure 1 The number and arrangement of metal layers shown are for illustrative purposes only and can be adjusted according to actual wiring requirements.

[0039] Furthermore, based on the aforementioned interposer stack, this embodiment provides a wiring structure with three-dimensional electromagnetic shielding. This wiring structure selects at least one layer from the multiple metal layers of the interposer stack as a signal metal layer to carry the high-speed signal transmission lines requiring protection. For example, in... Figure 1 In this design, the signal metal layers are specifically Metal2 and Metal5, each containing at least one signal line. The signal line extends in a direction perpendicular to the plane of the paper. Above and below the signal metal layers are ground potential layers, both electrically connected to the ground potential. These layers are used to constrain the electromagnetic field generated by the signal line in the longitudinal direction and, together with the lateral shielding array, form a complete shielding enclosure.

[0040] Optionally, any of the ground potential layers consists of one or more metal layers that are neither the top nor the bottom layer of the stack.

[0041] For example, in Figure 1 In one configuration shown, the ground potential layer above the signal metal layer Metal5 is served by the immediately above redistribution layer, and the ground potential layer below the signal metal layer Metal5 is served by the immediately below metal layer Metal4. The ground potential layer above the signal metal layer Metal2 is served by the immediately above metal layer Metal3, and the ground potential layer below the signal metal layer Metal2 is served by the immediately below metal layer Metal1. It is understood that in different channels or different metal layer groups, the ground potential layer can also be selected from other metal layers that are not the top or bottom layers of the stack, and is not limited to these configurations. Figure 1 The specific layer shown.

[0042] The wiring structure provided in this embodiment breaks the rigid constraint of "the ground potential layer must be taken from the top and bottom physical layers" in traditional interposer layer designs by flexibly setting the ground potential layer, thus releasing a huge degree of freedom in the vertical direction of wiring. In traditional solutions, all signal lines can only be arranged between the two fixed ground planes of the top and bottom physical layers. The entire stack forms only one large shielding space, and all signal lines are squeezed together, relying only on lateral spacing for isolation. As the number of signal channels increases, the lateral area inevitably expands. However, this application allows the selection of the ground potential layer from any layer in the middle of the stack, which means that multiple independent shielding cavities can be divided vertically within the same physical stack. For example, the redistribution layer and Metal4 can be used as the ground potential layer for one group of signal lines, while Metal3 and Metal1 can be used as the ground potential layer for another group of signal lines. The two groups of signal lines each have complete equipotential shielding in the vertical direction and do not interfere with each other. Through vertical partitioning, the increase in wiring density no longer depends on the expansion of the lateral area, but instead shifts to vertical stacking, directly breaking the bottleneck of "density and isolation cannot be achieved simultaneously" in traditional solutions. The ground potential layers of different shielding cavities can be allocated independently. Designers can make differentiated configurations based on the rate and crosstalk tolerance of each channel, providing adjacent and independent ground potential layers for critical high-speed channels, while non-critical channels can share or relax reference requirements, realizing on-demand deployment of shielding resources and achieving the optimal balance between overall performance and cabling resource utilization.

[0043] In the horizontal direction, this cabling structure includes a lateral shielding array. This lateral shielding array consists of multiple metal vias arranged at preset intervals along the signal extension direction, with both ends physically and electrically connected to the ground potential layer. Figure 1Within the cross-sectional plane, the lateral shielding array appears as vertical metal through-hole walls located on both sides of the signal line. Thus, the ground potential layer above the signal metal layer (upper wall), the ground potential layer below the signal metal layer (lower wall), and the lateral shielding arrays (left and right side walls) together enclose a shielding cavity extending longitudinally along the signal extension direction. This shielding cavity forms an approximately rectangular closed or semi-closed enclosed space in cross-section.

[0044] At least a portion of the signal lines in the signal metal layer are completely contained within the internal space of the shielding cavity. The aforementioned ground potential layer and the lateral shielding array are electrically interconnected as an equipotential body, forming an equipotential shield surrounding the signal lines. In this way, the signal lines are constrained by the equipotential shield in all four directions—above, below, left, and right—along their entire transmission path. The electromagnetic field is confined within the shielding cavity, making it difficult for it to radiate outwards and also difficult to be interfered with by external electromagnetic fields. This achieves highly efficient three-dimensional electromagnetic isolation within a limited lateral wiring space.

[0045] It should be noted that in this cabling structure, the lateral shielding array not only serves as the sidewall of the shielding cavity, but also constitutes the lateral reference ground for the signal line due to its spatial relationship with the signal line. Specifically, the lateral shielding array is arranged adjacent to both sides of the signal line in the form of closely spaced metal vias. The lateral spacing between the lateral shielding array and the sidewall of the signal line is smaller than the longitudinal spacing between the signal line and the upper or lower ground potential layer. Since electromagnetic fields always preferentially choose the shortest path with the lowest impedance to terminate around the transmission line, and the lateral shielding array provides a shorter return path and a stronger electric field termination effect than the upper and lower ground potential layers, the electromagnetic field generated by the signal line mainly originates from the sidewall and terminates on the inner wall of the lateral shielding array. The return current also mainly flows through the lateral shielding array. In this sense, the lateral shielding array assumes the role of the main reference ground for the signal line, while the upper and lower ground potential layers provide auxiliary longitudinal shielding enclosure. Together, the three constitute a complete equipotential shield, ensuring that the signal line is adequately electromagnetically isolated in all four directions (up, down, left, and right).

[0046] The wiring structure provided in this embodiment, consisting of a shielded cavity enclosed by a ground potential layer and a lateral shielding array, provides three-dimensional electromagnetic isolation for the signal line in all four directions (up, down, left, and right). In traditional microstrip or stripline structures, although the upper and lower ground planes can provide longitudinal shielding, the lateral electric field of the signal line can still freely couple to adjacent signal lines on the left and right sides. This necessitates increasing the lateral spacing or inserting ground wires to suppress crosstalk, which is extremely costly in high-density interconnect scenarios. However, this application introduces an array of metal vias electrically connected to the upper and lower ground potential layers on both sides of the signal line, effectively constructing two lateral metal walls. The signal line is embedded within a quasi-coaxial metal cavity, resembling a coaxial cable. Because the lateral shielding array is arranged close to the signal line, the lateral spacing between it and the signal line sidewalls is typically smaller than the longitudinal spacing between the signal line and the upper and lower ground potential layers. The electromagnetic field preferentially terminates along the shortest path with the lowest impedance. Therefore, most of the electric field lines of the signal line originate from the sidewalls and terminate on the inner wall of the lateral via walls, greatly suppressing the energy coupling to adjacent cavities on the left and right sides. This means that adjacent signal lines can still achieve excellent near-end and far-end crosstalk suppression performance even with a lateral spacing much smaller than the traditional 3W rule, directly breaking the traditional design convention that "crosstalk suppression inevitably sacrifices wiring density." Furthermore, the signal line position within the shielded cavity in this structure is not necessarily centered; it can be flexibly offset according to actual wiring requirements. When the signal line is offset towards one side of the via wall, the lateral distance on that side decreases, coupling increases, while the lateral distance from the signal line to the other side of the via wall increases, and the longitudinal distance to the upper and lower ground potential layers also changes accordingly. By comprehensively adjusting the sum of the lateral and longitudinal distances of the signal line to the surrounding ground boundaries, crosstalk and impedance can be finely optimized without increasing the overall wiring area, forming an off-center wiring strategy that further expands design freedom. Simultaneously, the fully enclosed equipotential shield provides four adjacent return paths for the signal. The return current can choose the path with the lowest impedance to return to the source, significantly reducing the return loop area and equivalent inductance, thus reducing return loss during signal transmission and effectively suppressing ground bounce and synchronous switching noise. Furthermore, since the shielded cavity physically encapsulates each signal line independently, the electromagnetic environment of each signal line is highly consistent and does not interfere with each other, significantly improving the signal integrity consistency between channels. This is especially important for HBM interfaces that need to transmit a large number of high-speed signals in parallel at the same time.

[0047] The following sections will introduce each layer in turn.

[0048] Specifically, the signal metal layer is the core functional layer in this cabling structure that carries high-speed signal transmission, and it is selected from one or more metal layers in the interposer stack. In terms of structural arrangement, the signal metal layer is sandwiched between the upper and lower ground potential layers, and at least part of the signal lines laid within it are completely contained in the shielded cavity formed by the upper and lower ground potential layers and the lateral shielding arrays on both sides, so that the signal lines are fully surrounded and constrained by the equipotential shielding in both the vertical and horizontal directions.

[0049] Optionally, the thickness of the signal metal layer is greater than that of other metal layers outside the shielding cavity, excluding the redistribution layer, but not greater than 3 μm. Alternatively, the thickness of the signal metal layer may be 2 μm or more, and the metal height of the signal metal layer may be greater than the minimum linewidth.

[0050] In terms of geometry, to reduce transmission loss without increasing the lateral wiring area, the thickness of the signal metal layer is set to be greater than the thickness of other non-signal metal layers outside the shielding cavity, excluding the redistribution layer, but not exceeding 3 μm. Preferably, the thickness of the signal metal layer is greater than 2 μm, and its metal height is greater than the minimum linewidth, thus forming a high aspect ratio (high AR) conductor cross-section. This thickened design directly reduces the resistance loss per unit length by increasing the conductor cross-sectional area, thereby improving the insertion loss index. At the same time, since the signal line is embedded in the quasi-coaxial shielding cavity, the side effect of enhanced lateral electric field coupling caused by the increased area of ​​the thickened metal sidewalls is forcibly diverted to the upper and lower reference ground layers by the lateral shielding array, so that the loss reduction benefits can be realized without incurring crosstalk costs. In terms of characteristic impedance control, while ensuring the target impedance (such as 50Ω single-ended or 100Ω differential), the impedance requirements of different layers and channels can be adapted by optimizing the ratio of linewidth to thickness, and the minimum line spacing can be reduced to 2 μm or lower to meet the wiring requirements of high-density interconnects. Figure 3 This is a comparison diagram showing the insertion loss between the signal metal layer provided in this application and a conventional unthickened metal layer. Figure 4 This figure shows a comparison of the isolation effect between the signal metal layer provided in this application and a conventional unthickened metal layer. The solid line in the figure represents the signal metal layer of this application, and the dashed line represents the conventional unthickened metal layer, which is 1µm thick. Please also refer to... Figure 3 and Figure 4 The thickness of the conventional, unthickened Metal layer is increased from 1µm to 2µm, significantly reducing signal transmission loss while maintaining the characteristic impedance of the transmission line. Simultaneously, the interposer layer, originally around 110µm thick, is increased by 5µm without affecting mounting. Furthermore, the new ground shielding space constructed using the Metal layer and the lateral shielding array provides superior isolation compared to traditional solutions.

[0051] Furthermore, to further verify the improvement effect of the wiring structure of this application on high-speed signal transmission performance, eye diagram simulation analysis was performed on the wiring structure of this application and the traditional wiring structure. The eye diagram is an important indicator for evaluating the quality of high-speed digital signal transmission, and its aperture height and aperture width can reflect signal integrity, inter-symbol interference, and noise interference. Figure 5 The image shows a comparison of eye diagrams between the wiring structure of this application and a conventional wiring structure, with a wiring length of 5.3 mm. The left image shows the eye diagram of the wiring structure of this application, and the right image shows the eye diagram of the conventional wiring structure. Figure 5 As can be seen, compared with the traditional wiring structure, the eye diagram formed by the wiring structure of this application is larger, and the eye height and eye width are improved, indicating that the attenuation, jitter and inter-symbol interference generated during signal transmission are effectively suppressed, and the signal integrity is significantly improved.

[0052] Optionally, the lateral physical distance between the signal line housed in the shielded cavity and the signal line in the adjacent shielded cavity can be less than 3 times the signal line width.

[0053] Regarding the lateral spacing between adjacent signal lines, the physical lateral spacing between a signal line housed within a shielded cavity and a signal line within an adjacent shielded cavity can be less than three times the signal line width, meaning the traditional 3W isolation principle is not mandatory. This is because the lateral shielding array already provides effective lateral electromagnetic isolation, and crosstalk suppression between signal lines no longer relies on large lateral spacing. This allows for low crosstalk characteristics to be maintained even with a compact spacing, freeing up valuable lateral space for high-density cabling.

[0054] Optionally, the interlayer includes at least two metal layers, the thickness of which is set differently according to the impedance requirements of the signal lines they carry, so that longitudinally staggered stripline units are formed between different metal layers during signal transmission.

[0055] In terms of multi-layer extension, the interposer layer can include at least two metal layers, each of which can be used for signal transmission or as a ground potential layer. When multiple metal layers are used as signal metal layers, each signal metal layer can be enclosed by independent upper and lower ground potential layers and lateral shielding arrays, forming multiple isolated shielding cavities in the vertical direction. When different metal layers are present, the thickness of each metal layer can be differentiated according to the impedance requirements of the signal lines carried by each layer, allowing thicker layers to handle high-speed critical signal transmission and thinner layers to handle lower-speed signals, thereby achieving fine-grained resource allocation of signal metal layers in the vertical space. During signal transmission, different metal layers can form longitudinally staggered stripline units to further reduce interlayer crosstalk.

[0056] It should be noted that, in terms of routing topology, this application is not limited to a pure longitudinal stripline structure in which signal lines have the same direction within the same signal metal layer. Figure 6 This is a schematic diagram illustrating the different orientations of the strip lines provided in this application. Please refer to... Figure 6 Between different signal metal layers, the routing direction of signal lines can be flexibly configured. A hybrid vertical and horizontal routing structure with orthogonal interleaving of signal lines from different layers can be used, or a segmented hybrid routing method can be adopted, with vertical routing in some areas and horizontal routing in others within the same shielded cavity. This is to address the varying requirements for impedance, loss, and isolation in complex scenarios. Through hybrid vertical and horizontal routing, the accumulated crosstalk caused by long-distance parallel traces within the same layer can be effectively reduced without increasing the horizontal routing area, while providing greater routing freedom for chip pin fan-out and multi-directional interconnects.

[0057] Optionally, in the lateral direction perpendicular to the signal transmission direction, the signal metal layer includes a ground structure, which works in conjunction with the lateral shielding array to suppress lateral electric field coupling between adjacent shielding cavities.

[0058] In terms of shielding enhancement, a ground wire structure can also be installed within the signal metal layer in the lateral direction perpendicular to the signal transmission direction. This ground wire structure works in conjunction with the lateral shielding array to provide dual suppression of residual lateral electric field coupling between adjacent shielding cavities, further improving the isolation between channels and meeting the requirements of high-speed channels with extremely stringent crosstalk requirements.

[0059] Regarding the stripline construction, this application establishes various three-dimensional stripline topologies based on the aforementioned shielded cavity architecture. Signal lines in the signal metal layer are positioned between the upper and lower ground potential layers, with a metal height greater than the minimum linewidth, employing a high aspect ratio conductor cross-section to reduce transmission loss. Lateral shielding arrays composed of metal via arrays on both sides of the signal lines provide a lateral reference plane, significantly reducing the requirement for lateral wiring spacing. The routing direction of signal lines between different signal metal layers can be flexibly configured. This can include a pure longitudinal stripline structure with consistent signal line routing within the same layer, a mixed longitudinal and lateral wiring structure with orthogonally intersecting signal line routing in different layers, or a multi-layered interlaced stripline structure with varying metal layer thicknesses and intersecting routing directions, to meet the differentiated impedance, loss, and isolation requirements of different channels.

[0060] The upper and lower ground potential layers form the upper and lower boundaries of the shielding cavity, located above and below the signal metal layer, respectively. Both are electrically connected to the ground potential and together provide longitudinal shielding enclosure, confining the electromagnetic field generated by the signal line within the vertical space between the upper and lower ground potential layers.

[0061] In terms of physical configuration, any upper or lower ground potential layer can be served by one or more metal layers that are neither the top nor the bottom layer of the intermediate layer stack. This means that the ground potential layer does not necessarily have to be taken from the topmost ground metal layer or the bottommost Metal1 of the intermediate layer, but can be selected from any metal layer in the middle of the stack. For example, when the signal line is laid on Metal5, the redistribution layer immediately above it can be selected as the ground potential layer, and the Metal4 immediately below it can be selected as the ground potential layer, while the top and bottom physical layers do not participate in the construction of the shielding cavity at all. This design of selecting the ground potential layer nearby greatly reduces the inductance and impedance of the return path, which is beneficial for suppressing synchronous switching noise and ground bounce effect, while releasing the top and bottom physical layers for use by shielding cavities of other signal channels. This flexible configuration allows multiple shielding cavities with independent ground potential layers to be divided vertically within the same intermediate layer stack, with each cavity being highly isolated in the longitudinal direction. Designers can allocate different upper and lower ground potential layers to different shielding cavities according to the rate and crosstalk tolerance requirements of each channel. Critical channels can be provided with adjacent and independent ground potential layers, while non-critical channels can have their reference ground distances relaxed or share a reference plane, enabling on-demand deployment of shielding resources. In multi-layered metal structures, the same metal layer can serve as a signal metal layer in one channel area and as a ground potential layer for adjacent channels in another channel area. This functional reuse further improves the space utilization of the stack.

[0062] Optionally, at least some of the signal lines in the signal metal layer do not have the ground potential layer in the vertical direction, but only the lateral shielding array located on both sides of the signal line serves as the lateral reference ground, forming a laterally open shielding channel.

[0063] Figure 7This is a cross-sectional schematic diagram of the wiring structure for the interposer layer provided in Embodiment 2 of this application. It should be noted that, based on the aforementioned shielding cavity, this application also provides a flexible configuration scheme for optional upper and lower ground potential layers. When the lateral shielding array is arranged adjacent to both sides of the signal line, since the lateral spacing between the lateral shielding array and the sidewall of the signal line is less than or equal to the longitudinal spacing of the upper and lower ground potential layers in the conventional scheme, the electromagnetic field preferentially terminates on the path with the shortest distance and lowest impedance, and the return current also mainly flows through the lateral shielding array. In this case, the lateral shielding array can independently serve as the main reference ground for the signal line, and ground potential layers can be omitted above and below the signal metal layer, with only the lateral shielding arrays located on both sides of the signal line serving as the reference ground, forming a laterally open shielding channel. Compared to a closed shielding cavity surrounded on all four sides, this configuration releases more wiring space in the vertical direction, allowing adjacent areas above and below to be used for the arrangement of other signal channels or reducing the number of metal layers used, thereby further reducing process complexity and manufacturing costs while meeting crosstalk suppression requirements. Meanwhile, by omitting the upper and lower ground potential layers, the parasitic capacitance of the signal lines in the vertical direction is reduced, which, under certain conditions, helps to reduce the insertion loss of the transmission line. Designers can flexibly choose whether to set upper and lower ground potential layers according to the rate level and crosstalk budget of different channels—using fully enclosed shielded cavities for critical high-speed channels to obtain the strongest isolation, and using side-open shielded channels for channels with relatively low rate requirements to exchange for cabling resources and process simplification, thus achieving a demand-driven balance between shielding strength and resource consumption.

[0064] The lateral shielding array is the key structure for achieving the three-dimensional electromagnetic isolation of this application. It consists of multiple metal through-holes arranged at preset intervals along the signal extension direction, with its two ends physically connected and electrically connected to the upper and lower ground potential layers, respectively. In terms of spatial arrangement, the lateral shielding array is set on both sides of the shielding cavity that houses the signal lines, forming two vertical metal through-hole walls in the lateral direction perpendicular to the signal transmission direction.

[0065] Optionally, the lateral shielding array consists of two rows of closely spaced metal through holes, which are arranged along the signal extension direction on both sides of the shielding cavity that accommodates the signal line and connected to the ground potential layer to form a quasi-coaxial electromagnetic shielding channel.

[0066] As a preferred implementation, the lateral shielding array consists of two rows of closely spaced metal vias, continuously or quasi-continuously arranged on both sides of the shielding cavity along the signal extension direction, forming a quasi-coaxial electromagnetic shielding channel together with the upper and lower ground potential layers. Here, "quasi-coaxial" means that the signal line resembles the central conductor of a coaxial cable, while the upper and lower ground potential layers and the lateral shielding array together constitute an enclosing structure similar to the annular outer conductor of a coaxial cable. Although this enclosing structure presents a rectangular enclosure rather than an ideal circular enclosure in cross-section, its electrical effect is highly similar; the electromagnetic field generated by the signal line is forcibly confined within this channel, making it difficult to radiate and diffuse outwards.

[0067] The introduction of lateral shielding arrays fundamentally changes the coupling mechanism between signal lines in traditional interposer cabling structures. In traditional microstrip or stripline structures, crosstalk between signal lines can only be suppressed by lateral spacing, and the lateral electric fields of adjacent signal lines can freely couple through the dielectric layer. However, in this application, the lateral shielding array constructs low-impedance grounding walls on both sides of the signal lines. After the electric field lines originate from the sidewalls of the signal lines, most are forcibly terminated within the inner wall of these grounding walls, greatly suppressing energy leakage into adjacent cavities. This allows signal lines within adjacent shielded cavities to achieve excellent near-end and far-end crosstalk suppression performance even with a lateral physical spacing much smaller than the traditional 3W rule, thus achieving high isolation without sacrificing cabling density.

[0068] It should be noted that the aforementioned shielding cavity structure can be configured differently in different regions according to actual performance requirements. This application provides a flexible shielding strategy ranging from fully enclosed to partially open. For critical channels with extremely stringent crosstalk tolerance, such as clock signals and ultra-high-speed data signals, a fully enclosed enhanced shielding structure can be used in this channel region. That is, the upper and lower ground potential layers and the two lateral shielding arrays form a complete equipotential enclosure in the four directions of the signal line, forming a quasi-coaxial closed cavity similar to a Faraday cage. Within this cavity, the electromagnetic field of the signal line is completely constrained, and electromagnetic interference between adjacent channels is completely blocked.

[0069] For non-critical channels with relatively low rate requirements or more lenient crosstalk budgets, a partially incomplete shielding structure can be adopted while ensuring basic signal integrity. For example, the ground potential layer covering the channel can be omitted, allowing it to operate in a manner similar to a microstrip line; or the via density of the lateral shielding array can be reduced on one side, or some sidewall vias can be omitted. This partially open design can free up wiring resources occupied by the metal layer, reduce the difficulty of via etching and metal filling processes, and reduce unnecessary parasitic capacitance, thereby achieving a flexible balance between overall performance and wiring resource utilization. In addition, multiple shielding cavities can be independently set up in different local areas of the same interposer layer, with each cavity enclosing signal line groups with different performance requirements. This allows designers to divide hundreds of signal channels on an interposer layer as needed and provide differentiated isolation levels for each area, achieving optimal allocation of shielding resources.

[0070] Optionally, the wiring structure further includes a redistribution layer located above the ground potential layer, wherein at least a portion of the signal lines in the redistribution layer are staggered with the traces of the signal metal layer below, forming a three-dimensional wiring topology that is mixed in both vertical and horizontal directions.

[0071] Specifically, the redistribution layer, located above the ground plane, is an optional signal routing resource layer within the interposer stack. In traditional designs, the redistribution layer is typically used only for chip pin fan-out or physical connections to microbumps. In this application, the redistribution layer is incorporated into a three-dimensional routing architecture, working in conjunction with the underlying core signal metal layer to further expand the spatial dimension of the three-dimensional routing. Specifically, at least a portion of the signal lines in the redistribution layer are staggered with the traces in the underlying signal metal layer, forming a vertically and horizontally interlaced three-dimensional routing topology. This arrangement allows the signal lines in the redistribution layer to utilize the ground plane as their underlying reference ground, transmitting in an approximate microstrip line mode. Lateral isolation can be achieved by creating vias in the ground plane that connect to the lateral shielding array. By diverting a portion of the signal lines to the redistribution layer and interlacing them with the lower layer signal lines, the total capacity of available routing channels can be further increased without increasing the lateral area of ​​the interposer, while reducing the risk of routing congestion and residual crosstalk caused by excessive signal line density within the same layer. The introduction of the redistribution layer also allows designers to retain the most critical signals in the core signal metal layer with a complete quasi-coaxial shielded cavity, based on the rate and isolation requirements of each channel, while distributing signals with slightly lower rate or isolation requirements to the redistribution layer, thus achieving hierarchical management of signal channels.

[0072] In summary, the core working principle of the wiring structure proposed in this application lies in extending the traditional two-dimensional planar constraint of transmission lines to a three-dimensional spatial constraint, specifically manifested in the following four collaborative mechanisms. First, the electromagnetic field is shifted from lateral expansion to longitudinal constraint. In traditional structures, the electromagnetic field generated by signal lines is significantly distributed in both the lateral and longitudinal dimensions, with the lateral component requiring control based on wiring spacing. This application, by arranging signal lines within a three-dimensional equipotential shield composed of upper and lower ground potential layers and a lateral shielding array, forces the electromagnetic field into a lateral boundary condition constraint by the lateral shielding array. Most electric field lines terminate on the inner wall of the lateral via wall, while magnetic field lines are confined to a narrow annular region between the signal line and the lateral via wall. Thus, the main distribution of the electromagnetic field is shifted from the lateral to the longitudinal direction, fundamentally weakening the physical source of crosstalk.

[0073] Second, the construction of a stable, low-impedance return path. In traditional structures, the signal return path is often circuitous, especially when the ground potential plane is discontinuous or far apart. The return current needs to detour, increasing the loop area and equivalent inductance, leading to increased transmission loss and exacerbated ground bounce. In this application, the upper and lower ground potential layers and the lateral shielding array are electrically connected as equipotential bodies, providing four adjacent return paths for the signal line. The return current can choose the path with the lowest impedance nearby, significantly reducing the return loop area, lowering return conduction loss and ground bounce noise, thereby improving the overall signal transmission quality.

[0074] Third, the lateral shielding array blocks the coupling path. In traditional equal-spacing cabling, crosstalk between adjacent signal lines is mainly generated through two paths: lateral electric field coupling and mutual inductance coupling. This application, by setting a densely packed array of metal vias on both sides of the signal lines, physically constitutes a grounded metal wall, strongly reflecting and absorbing laterally propagating electromagnetic waves, thus cutting off the direct coupling path between adjacent signal lines. Simultaneously, the connection between the via array and the upper and lower ground potential layers forms a low-impedance shunt channel to ground. Even if a small amount of electromagnetic energy penetrates the via gaps, it is preferentially discharged to ground through this low-impedance path rather than coupled to adjacent signal lines.

[0075] Fourth, low crosstalk is achieved without increasing the horizontal wiring spacing. Traditional solutions to reduce crosstalk either increase the signal line spacing to 3W or more, or insert additional grounding wires between signal lines, both of which occupy horizontal wiring area. This application transfers the crosstalk suppression function from large horizontal spacing to a lateral shielding array. The physical horizontal spacing between signal lines can be compressed to less than three times the signal line width, while the crosstalk suppression effect is better than the traditional 3W spacing solution. This allows more signal channels to be arranged within the same horizontal wiring area, or to achieve better signal integrity with the same number of channels, fundamentally solving the contradiction between density and isolation in traditional interposer layer designs.

[0076] The wiring structure for the intermediate layer provided in this embodiment, in a first aspect, constructs a shielded cavity formed by upper and lower ground potential layers and a lateral shielding array, accommodating the signal line within it. This ensures that the signal line is fully surrounded and constrained by the equipotential shield in all four directions (up, down, left, and right), forcibly converting the electromagnetic field of the signal line from a "free divergence" mode to a "three-dimensional constraint" mode. In traditional microstrip or stripline structures, the lateral electric field of the signal line can freely diffuse to adjacent signal lines, and crosstalk can only be suppressed by increasing the line spacing or inserting ground wires, both of which consume lateral area. However, this application, based on the upper and lower ground potential layers, introduces a lateral shielding array composed of closely packed metal vias on both sides of the signal line and electrically connects them to form an equipotential body. This is equivalent to building a grounded metal wall on each side of the signal line, which, together with the upper and lower ground potential layers, forms a quasi-coaxial enclosure structure. After the signal lines are embedded, most of their electric field lines are forcibly terminated at the inner walls of the lateral via walls and the upper and lower ground potential layers. The electromagnetic field shifts from the lateral direction to the longitudinal direction, and leakage to adjacent cavities is physically blocked. This allows adjacent signal lines to achieve excellent crosstalk suppression performance even with a lateral spacing much smaller than the traditional 3W rule, directly breaking the design convention that "isolation must sacrifice density." At the same time, the fully enclosed equipotential shield provides four adjacent low-impedance return paths for the signal lines in the top, bottom, left, and right directions. The return current selects the shortest path to return to the source, significantly reducing the return loop area, reducing return inductance and ground bounce noise, and reducing return transmission loss while suppressing crosstalk.

[0077] Secondly, the signal metal layer adopts a thickened design, with a thickness greater than that of other non-signal metal layers outside the shielding cavity (excluding the redistribution layer) but not exceeding 3μm, preferably 2μm or more. The metal height is greater than the minimum linewidth, forming a high aspect ratio conductor cross-section. By increasing the cross-sectional area, the resistance loss per unit length is directly reduced, thereby improving the insertion loss index. The increased lateral electric field coupling caused by the thickened metal sidewall area is precisely forcibly diverted to the upper and lower ground potential layers by the lateral shielding array, allowing the loss reduction benefits to be safely realized without incurring additional crosstalk costs, achieving simultaneous optimization of both loss and crosstalk indicators. The lateral physical spacing between the signal lines contained within the shielding cavity and the signal lines in adjacent shielding cavities can be less than 3 times the signal linewidth, without being strictly bound by the traditional 3W isolation principle, because the lateral shielding array already provides effective lateral electromagnetic isolation. Crosstalk suppression no longer relies on a large lateral spacing, thus freeing up valuable lateral space for high-density cabling within a compact spacing.

[0078] Thirdly, in the vertical direction, by flexibly setting upper and lower ground potential layers, the rigid constraint that the reference ground must be taken from the top and bottom physical layers in the traditional scheme is broken. It allows the selection of upper and lower ground potential layers from any layer in the middle of the stack, so that multiple independent shielding cavities can be divided longitudinally within the same stack. The increase in wiring density no longer depends on lateral expansion, but shifts to vertical partitioning and stacking. Furthermore, a redistribution layer located above the upper ground potential layer is introduced, incorporating the redistribution layer into the three-dimensional wiring system. At least a portion of the signal lines are staggered with the wiring of the signal metal layer below, forming a three-dimensional wiring topology that mixes vertical and horizontal directions. This further increases the total capacity of available wiring channels without increasing the lateral area, and supports keeping the most critical signals in the core signal metal layer with a complete quasi-coaxial shielding cavity, while allocating signals with slightly lower rate requirements to the redistribution layer, realizing hierarchical management of signal channels. In addition, it provides flexible shielding strategies from fully enclosed to partially open. Fully enclosed enhanced shielding is used for critical channels, while partially enclosed structures can be used for non-critical channels in exchange for wiring resources and process simplification. Furthermore, dual crosstalk suppression can be provided by setting ground wire structures in the lateral direction of the signal metal layer in conjunction with the lateral shielding array. By setting different thicknesses of different metal layers to form longitudinally staggered stripline units, interlayer crosstalk can be further reduced.

[0079] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A wiring structure for an interposer layer, said interposer layer comprising a stack of multiple metal layers, characterized in that, The wiring structure includes: At least one signal metal layer is used for signal transmission; The ground potential layers located above and below the signal metal layer are used to provide longitudinal shielding enclosure; A lateral shielding array consisting of multiple metal vias serves as a lateral reference ground for the signal lines in the signal metal layer. The lateral shielding array is electrically connected to the ground potential layer and together they enclose at least one shielding cavity extending longitudinally. In this embodiment, at least a portion of the signal lines in the signal metal layer are housed within the shielding cavity, such that the transmission path of the signal lines is constrained by the equipotential shield in both the vertical and lateral directions. The equipotential shield is formed by the ground potential layer and the lateral shielding array being electrically connected.

2. The wiring structure according to claim 1, characterized in that, The thickness of the signal metal layer is greater than that of other metal layers outside the shielding cavity, excluding the redistribution layer.

3. The wiring structure according to claim 1, characterized in that, The thickness of the signal metal layer is greater than 2 μm, and the metal height of the signal metal layer is greater than the minimum linewidth.

4. The wiring structure according to claim 1, characterized in that, The lateral physical distance between the signal line contained in the shielded cavity and the signal line in the adjacent shielded cavity can be less than 3 times the signal line width.

5. The wiring structure according to claim 1, characterized in that, The wiring structure also includes a redistribution layer located above the ground potential layer, wherein at least a portion of the signal lines in the redistribution layer are staggered with the traces of the signal metal layer below, forming a three-dimensional wiring topology that is mixed in both vertical and horizontal directions.

6. The wiring structure according to claim 1, characterized in that, In the lateral direction perpendicular to the signal transmission direction, the signal metal layer includes a ground structure that works in conjunction with the lateral shielding array to suppress lateral electric field coupling between adjacent shielding cavities.

7. The wiring structure according to claim 1, characterized in that, Each of the aforementioned ground potential layers is composed of one or more metal layers that are neither the top nor the bottom layer of the stack.

8. The wiring structure according to claim 1, characterized in that, The interlayer includes at least two metal layers, and the thickness of the different metal layers is set differently according to the impedance requirements of the signal lines they carry, so that longitudinally staggered stripline units are formed between the different metal layers during signal transmission.

9. The wiring structure according to claim 1, characterized in that, The lateral shielding array consists of two rows of closely spaced metal through holes, which are arranged on both sides of the shielding cavity that accommodates the signal line along the signal extension direction and connected to the ground potential layer to form a quasi-coaxial electromagnetic shielding channel.

10. The wiring structure according to claim 1, characterized in that, At least a portion of the signal lines in the signal metal layer do not have the ground potential layer in their vertical direction, but are instead supported by the lateral shielding arrays located on both sides of the signal lines as lateral reference grounds, forming a laterally open shielding channel.

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