Patent Description:
High-speed signal-ended buses are widely used for both on-package and off-package lines of communication to address high bandwidth demands of integrated circuit (IC) packages. However, crosstalk, especially that of the vertical interconnects, may limit the data rate that these high-speed signal-ended buses are able to achieve and, therefore, may pose a challenge in meeting signaling performance targets. Additional pins may be utilized for ground connections so that more vertical interconnects are available to be assigned as grounds in an effort to isolate signals from each other and hence lower crosstalk between signals. However, these additional pins may increase the package form factor and may increase the cost of manufacturing.

<CIT> relates to a multilayer wiring board, a semiconductor package and a method of manufacturing the same. In the multilayer wiring board having a wiring layer, a pad, an insulating layer provided between the wiring layer and the pad, and a plurality of connecting vias provided on the insulating layer and connecting the wiring layer to the pad, the connecting vias are provided on a peripheral edge of the pad.

The background description provided herein is for generally presenting the context of the disclosure. Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art or suggestions of the prior art by inclusion in this section.

Embodiments of the present disclosure describe techniques and configurations associated with ground via clustering for crosstalk mitigation in integrated circuit (IC) assemblies. For example, techniques described herein may be used to fabricate a package substrate having vertical interconnects with clusters of ground vias. In the following description, various aspects of the illustrative implementations will be described using terms commonly employed by those skilled in the art to convey the substance of their work to others skilled in the art. However, it will be apparent to those skilled in the art that embodiments of the present disclosure may be practiced with only some of the described aspects. For purposes of explanation, specific numbers, materials, and configurations are set forth in order to provide a thorough understanding of the illustrative implementations. However, it will be apparent to one skilled in the art that embodiments of the present disclosure may be practiced without the specific details. In other instances, well-known features are omitted or simplified in order not to obscure the illustrative implementations.

In the following detailed description, reference is made to the accompanying drawings that form a part hereof, wherein like numerals designate like parts throughout, and in which is shown by way of illustration embodiments in which the subject matter of the present disclosure may be practiced. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. Therefore, the following detailed description is not to be taken in a limiting sense, and the scope of embodiments is defined by the appended claims and their equivalents.

For the purposes of the present disclosure, the phrase "A, B, and/or C" means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C).

The description may use perspective-based descriptions such as top/bottom, in/out, over/under, and the like. Such descriptions are merely used to facilitate the discussion and are not intended to restrict the application of embodiments described herein to any particular orientation.

The description may use the phrases "in an embodiment," "in embodiments," or "in some embodiments," which may each refer to one or more of the same or different embodiments.

The term "coupled with," along with its derivatives, may be used herein. "Coupled" may mean one or more of the following. "Coupled" may mean that two or more elements are in direct physical or electrical contact. However, "coupled" may also mean that two or more elements indirectly contact each other, but yet still cooperate or interact with each other, and may mean that one or more other elements are coupled or connected between the elements that are said to be coupled with each other. The term "directly coupled" may mean that two or more elements are in direct contact.

In various embodiments, the phrase "a first feature formed, deposited, or otherwise disposed on a second feature" may mean that the first feature is formed, deposited, or disposed over the second feature, and at least a part of the first feature may be in direct contact (e.g., direct physical and/or electrical contact) or indirect contact (e.g., having one or more other features between the first feature and the second feature) with at least a part of the second feature.

As used herein, the term "module" may refer to, be part of, or include an Application Specific Integrated Circuit (ASIC), an electronic circuit, a system-on-chip (SoC), a processor (shared, dedicated, or group), and/or memory (shared, dedicated, or group) that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. The term "processor" may refer to any device or portion of a device that processes electronic data from registers and/or memory to transform that electronic data into other electronic data that may be stored in registers and/or memory.

<FIG> schematically illustrates a cross-section side view of an example IC assembly <NUM> including package substrates <NUM> and <NUM> having vertical interconnects with clusters of ground vias, in accordance with some embodiments.

As used herein, first level interconnect (FLI) may refer to an interconnect between a die (e.g., die <NUM> or <NUM>) and a package substrate (e.g., package substrate <NUM> or <NUM>), while second level interconnect (SLI) may refer to the interconnect between the package substrate (e.g., package substrate <NUM> or <NUM>) and another package substrate (e.g., interposer <NUM>) or circuit board. In embodiments, IC assembly <NUM> may include one or more dies (e.g., dies <NUM> and <NUM>). Dies <NUM> and <NUM> may be electrically and/or physically coupled with package substrates <NUM> and <NUM>, respectively, via one or more FLI structures. Package substrates <NUM> and <NUM> may further be electrically coupled with interposer <NUM> via one or more SLI structures.

Either or both of dies <NUM> and <NUM> may represent a discrete unit made from a semiconductor material using semiconductor fabrication techniques such as thin film deposition, lithography, etching, and the like. In some embodiments, either or both of dies <NUM> and <NUM> may include or be a part of a processor, memory, switch, ASIC, or SoC. Dies <NUM> and <NUM> may be electrically and/or physically coupled with package substrates <NUM> and <NUM>, respectively, according to a variety of suitable configurations, including a flip-chip configuration, as depicted, or other configurations such as, for example, being embedded in the package substrate.

In the flip-chip configuration, die <NUM> may be coupled with surface <NUM> of package substrate <NUM> using FLI structures such as the interconnect structures depicted. These interconnect structures may be configured to electrically and/or physically couple die <NUM> with the package substrate <NUM>. In various embodiments, these interconnect structures may be electrically coupled with electrical routing features of interposer <NUM> configured to route electrical signals between die <NUM> and die <NUM>, or between die <NUM> and any other electrical components. Similarly, die <NUM> may be coupled with a surface <NUM> of package substrate <NUM> using FLI structures such as the interconnect structures depicted. These interconnect structures may be configured to electrically and/or physically couple die <NUM> with the package substrate <NUM>. In embodiments, these interconnect structures may be electrically coupled with electrical routing features of interposer <NUM> configured to route electrical signals between die <NUM> and die <NUM>, or between die <NUM> and any other electrical components. In some embodiments, the electrical signals may include input/output (I/O) signals and/or power/ground associated with operation of the dies <NUM> and/or <NUM>.

In some embodiments, various components in <FIG> may form a package-level high-speed single-ended channel. In such embodiments, package substrate <NUM> may be a stacked via laminate core (SVLC) package substrate, and package substrate <NUM> may be a standard core package substrate. In some embodiments, die <NUM> may be a processor, and die <NUM> may be another processor, a memory device, or a field-programmable gate array (FPGA) device such as a network switch. As depicted, die <NUM> may be coupled with the SVLC package substrate while die <NUM> may be coupled with the standard core package substrate. Both the SVLC package substrate and the standard core package substrate may then be coupled with another package substrate (e.g., interposer <NUM>), via, for example, ball grid array (BGA) interconnect structures (e.g., solder balls <NUM> or <NUM>) to complete the high-speed single-ended channel.

It will be appreciated that the BGA interconnect structures depicted by solder balls <NUM> or <NUM> are merely meant to be example interconnect structures for the sake of discussion. In other embodiments, land-grid array (LGA) structures may electrically couple one or more lands on package substrate <NUM> with one or more pads on interposer <NUM>, which may route electrical signals between package substrate <NUM> and interposer <NUM>. It will be appreciated that the above discussed examples are meant to be illustrative and that any of a variety of suitable interconnect structures and/or layers may be utilized to electrically couple dies <NUM> and <NUM> or other dies (not shown) with the interposer <NUM>. It will be appreciated that various embodiments may additionally include other interconnect structures, such as, for example, trenches, vias, traces, or conductive layers, and the like that may be utilized to implement a high-speed single-ended channel to route electrical signals between die <NUM> and die <NUM>.

The vertical interconnects in package substrate <NUM> may be schematically illustrated by the 3D model <NUM>. In one embodiment, the vertical interconnect <NUM> may correspond to three vertical interconnect sub-components <NUM>, <NUM>, and <NUM>. In various embodiments, the three vertical interconnect sub-components <NUM>, <NUM>, and <NUM> may be used to route a ground between package substrate <NUM> and interposer <NUM>, e.g., through surface <NUM>. Further, in some embodiments, the three vertical interconnect sub-components <NUM>, <NUM>, and <NUM> may be surrounded by several vertical interconnects (e.g., interconnect <NUM>) that may route input/output (I/O) signals between package substrate <NUM> and interposer <NUM>. In some embodiments, the vertical interconnects depicted in 3D model <NUM> may form a <NUM>:<NUM> signal-to-ground ratio.

Similarly, the vertical interconnects in package substrate <NUM> may be schematically illustrated by the 3D model <NUM>. In one embodiment, the vertical interconnect <NUM> may correspond to three vertical interconnect sub-components <NUM>, <NUM>, and <NUM>. In various embodiments, the three vertical interconnect sub-components <NUM>, <NUM>, and <NUM> may be used to route a ground between package substrate <NUM> and interposer <NUM>, e.g., through surface <NUM>. Further, in some embodiments, the three vertical interconnect sub-components <NUM>, <NUM>, and <NUM> may be surrounded by several vertical interconnects (e.g., interconnect <NUM>) that may route input/output (I/O) signals between package substrate <NUM> and interposer <NUM>. In some embodiments, the vertical interconnects depicted in 3D model <NUM> may also form a <NUM>:<NUM> signal-to-ground ratio.

In various embodiments, the three vertical interconnect sub-components <NUM>, <NUM>, and <NUM> may form at least one ground via cluster. Similarly, the three vertical interconnect sub-components <NUM>, <NUM>, and <NUM> may also form at least one ground via cluster. 3D model <NUM> and 3D model <NUM> reflects the effect of ground via clustering. In some embodiments, the extra ground interconnect sub-components (e.g., <NUM> and <NUM>) may be only applied to the outermost column of ground interconnects, or the column of ground interconnects that are closest to a signal source (e.g., vertical interconnects <NUM> and <NUM>). Such an embodiment, may be beneficial because the first two columns of interconnects may demonstrate more crosstalk between the signals carried by these interconnects than those of inner columns. In other embodiments, the extra ground interconnect sub-components (e.g., <NUM> and <NUM>) may also be applied to other inner ground columns.

Crosstalk of the single-ended signaling may be highly sensitive to the ground reference design in the vertical interconnects. For example, when the coupling between a first signal and an associated ground gets stronger, the mutual coupling between the first signal and a second signal may become weaker. As a result, the crosstalk may be mitigated between these two signals by increasing the strength of the coupling between these two signals and the respective grounds associated with these two signals. As such, adding more interconnect structures (e.g., BGA connections) and assigning them to ground may produce better signal-to-signal isolation. For example, changing to a conservative <NUM>:<NUM> signal-to-ground ratio from a <NUM>:<NUM> signal-to-ground ratio may help mitigate the signaling risk, but such a configuration would require additional <NUM> ground balls for a 2x40 interface, which would consequentially increase the cost and the size of the package form factor.

In various embodiments, the ground via clustering design, as shown in 3D model <NUM> and 3D model <NUM>, would eliminate or reduce the increase in size of the package form factor discussed above. As such, clustering ground vias adjacent to each other, as shown in 3D model <NUM> and 3D model <NUM>, may increase the size of ground and, as a result, may boost the coupling between a signal and an associated ground without increasing the corresponding footprint. Thus, the ground via clustering may be implemented with existing substrate design rules and without impacting the rest of the package design.

In various embodiments, ground via clustering may reduce both far-end and the near-end crosstalk. Thus, ground via clustering may be implemented in both terminated and un-terminated high-speed single-ended channels. In some instances, ground via clustering may reduce crosstalk by <NUM>% or more. Moreover, the ground via clustering design may also improve signal-to-noise ratio (SNR) of the signal. Thus, channel signaling risk may be reduced without a corresponding increase in a size of the package form factor.

<FIG> schematically illustrates a top view <NUM> and a cross-section side view <NUM> of example two-via clustering patterns, in accordance with some embodiments. Three-via clustering patterns or ground via clustering patterns with more than three ground vias may also be used in other embodiments. In various embodiments, a cluster of ground vias instead of a single ground via may be used to mitigate or reduce the crosstalk without the need for any additional interconnect structures between two package substrates.

In some embodiments, such as that depicted, the cluster of ground vias may be surrounded by signal vias, of a same layer (e.g., layer <NUM>), in a hexagonal pattern. For example, one cluster of ground vias (e.g., ground vias <NUM> and <NUM>) may be surrounded by six signal vias (e.g., signal via <NUM>) having respective ball pad <NUM> in a hexagonal arrangement. In other embodiments, other patterns, e.g., four signal vias disposed in a square arrangement around a cluster of ground vias, may also be used without departing from the scope of this disclosure.

In some embodiments, the two ground vias may be formed substantially apart from each other, but may still contact the same underlying contact structure (e.g., ball pad). For example, as depicted, ground vias <NUM> and <NUM> are formed apart from each other, but still contact the same ball pad <NUM>.

Cross-section side view <NUM> schematically illustrates an example two-via clustering pattern. Package substrate <NUM> has one side (e.g., side <NUM>) to receive a die and another side (e.g., side <NUM>) to be coupled with another package substrate or circuit board. In various embodiments, vertical interconnect structures (e.g., vertical interconnect structures <NUM>, <NUM>, and <NUM>) may be disposed in package substrate <NUM>. Vertical interconnect structures may electrically couple structures such as, for example, traces, trenches, vias, lands, pads or other structures that may establish corresponding electrical pathways for electrical signals through package substrate <NUM>.

In some embodiments, e.g., for implementation in server products, vertical interconnect structures may be longer than <NUM> millimeter (mm), including stacks of micro-vias and core vias, and a solder ball. A core via may be an opening through the core substrate filled with conducting material that may be used to connect routing features, e.g., a metal pad, placed on one face of the substrate core with routing features, e.g., another metal pad, placed on the opposite face of the substrate core. In various embodiments, a core via may be much bigger than a micro-via as the core layer may be much thicker than build-up layers in an organic package. In such embodiments, vertical interconnect structure <NUM> includes stacks of vias disposed on ball pad <NUM>, which in turn has solder ball <NUM> disposed thereon. Vertical interconnect structure <NUM> is used to route signals through package substrate <NUM>.

As depicted, in some embodiments, vertical interconnect structure <NUM> includes stacks of vias (e.g., via <NUM>, via <NUM>, and via <NUM>) disposed on ball pad <NUM>, which in turn has solder ball <NUM> disposed thereon. Vertical interconnect structure <NUM> is used to route a ground through package substrate <NUM>. Similarly, vertical interconnect structure <NUM> includes stacks of vias (e.g., via <NUM>, via <NUM>, and via <NUM>) disposed on a same ball pad <NUM>, which in turn has solder ball <NUM> disposed thereon. Vertical interconnect structure <NUM> is also used to route a ground through package substrate <NUM>.

In some embodiments, package substrate <NUM> may be an epoxy-based laminate substrate having build-up layers such as, for example, an Ajinomoto Build-up Film (ABF) substrate. In various embodiments, package substrate <NUM> may include other suitable types of substrates including, for example, substrates formed from glass, ceramic, or semiconductor materials. In various embodiments, via <NUM> and via <NUM> are formed in the same substrate layer <NUM>, while via <NUM> and via <NUM> are formed in the same substrate layer <NUM>. Similarly, via <NUM> and via <NUM> may be formed in the same substrate layer <NUM>. In some embodiments, via <NUM> and via <NUM> may be core vias in a core layer. Thus, Via <NUM> and via <NUM> form a ground via cluster in layer <NUM>, while via <NUM> and via <NUM> form another ground via cluster in layer <NUM>. Similarly, via <NUM> and via <NUM> may form yet another ground via cluster in layer <NUM>.

In various embodiments, via <NUM> and via <NUM> are formed in layer <NUM> in any conventional manner known in the art. For example, an opening may be formed over pad <NUM> by drilling in a region of dielectric material disposed over pad <NUM>, using a technique, such as employing CO2 or a UV laser. In embodiments, any conventional plating operations may be used to deposit electrically conductive material into the openings to form vias. In some embodiments, electrolytic plating operations may be used to deposit the electrically conductive material into the drilled openings, and chemical, mechanical polishing (CMP) or copper (Cu) etching operations may be used after depositing the electrically conductive material to remove any excess electrically conductive material. In various embodiments, via <NUM> and via <NUM> may be formed in layer <NUM> with similar or different manners known in the art.

In various embodiments, layer <NUM>, layer <NUM>, or layer <NUM> are a dielectric layer composed of any of a wide variety of suitable dielectric materials including, for example, epoxy-based laminate material, silicon oxide (SiO2), silicon carbide (SiC), silicon carbonitride (SiCN), or a silicon nitride (e.g., SiN, Si3N4, etc.). In embodiments, layer <NUM> or layer <NUM> may include a polymer (e.g., epoxy-based resin) and may further include a filler (e.g., silica) to provide suitable mechanical properties to meet reliability standards of the resulting package. In embodiments, layer <NUM>, layer <NUM>, or layer <NUM> may be formed as a film of polymer, such as by ABF lamination. In embodiments, layer <NUM>, layer <NUM>, or layer <NUM> may be formed by depositing a dielectric material using any suitable technique including, for example, atomic layer deposition (ALD), physical vapor deposition (PVD) or chemical vapor deposition (CVD) techniques.

In embodiments, substrate <NUM> includes multiple routing features, such as pad <NUM> or pad <NUM>, configured to advance the electrical pathways within or through the substrate. In various embodiments, pad <NUM> or pad <NUM> may be composed of any suitable electrically conductive material such as metal including, for example, nickel (Ni), palladium (Pd), gold (Au), silver (Ag), copper (Cu), or any combinations thereof. In some embodiments, pad <NUM> or pad <NUM> may be formed using a patterned metal layer configured to: electrically couple pad <NUM> with vertical interconnect structure <NUM> to route electrical signals through the package substrate <NUM>; or electrically couple pad <NUM> with vertical interconnect structures <NUM> and <NUM> to route a ground through the package substrate <NUM>. The patterned metal layer may be formed in any conventional manner known in the art. For example, the patterned metal layer may be an inner or outermost conductive layer of a build-up layer formed with a semi-additive process (SAP).

<FIG> schematically illustrates a top view of example three-via clustering patterns, in accordance with some embodiments. In some embodiments, examples of using three-via clustering may be used in a hexagonal arrangement. For example, a cluster of ground vias may be surrounded by signal vias, of the same layer of vias, disposed in a hexagonal pattern, i.e., one cluster of ground vias surrounded by six signal vias. As illustrated in <FIG>, the cluster of ground vias <NUM>, <NUM>, and <NUM> are surrounded by signal vias including signal via <NUM> in a hexagonal arrangement. Similarly, the cluster of ground vias <NUM>, <NUM>, and <NUM> may also be surrounded by signal vias in a similar hexagonal arrangement. In other embodiments, other patterns, e.g., four signal vias disposed in a square arrangement around a cluster of ground vias, may also be used to arrange signals vias surrounding the cluster of ground vias without departing from the scope of the present disclosure.

As discussed in reference to <FIG>, above, ground via clustering may be used for the SVLC package substrates and standard core package substrates. The SVLC package substrates and the standard core package substrates may have to comport with various different design rules and different ball pitches. However, as depicted, two ground vias may be successfully added to form the three-via cluster without violating these existing design rules. For example, vertical interconnect structure stacks of micro-vias and core-vias may be formed adjacent to original ground vias in an existing design, and, as a result, may maintain the form factor of the design.

In some embodiments, the cluster of ground vias may be in a triangular arrangement. As an example, ground vias <NUM>, <NUM>, and <NUM> are depicted in a triangular arrangement. Similarly, ground vias <NUM>, <NUM>, and <NUM> are depicted in another triangular arrangement. In some embodiments, one ground via may be disposed over the center of the underlying contact (e.g., a ball pad), and the other two ground vias may be added to a side of the underlying contact. For example, among the cluster of ground vias <NUM>, <NUM>, and <NUM>, via <NUM> is placed at the center of ball pad <NUM>, in a similar manner to ground via <NUM> and its associated ball pad. However, ground vias <NUM> and <NUM> may be added to ground via <NUM> to form the ground via cluster in a triangular arrangement. In some embodiments, the center of the triangular arrangement of ground vias may be disposed over the center of the underlying contact. For example, ground vias <NUM>, <NUM>, and <NUM> form a triangular arrangement, and the center of the cluster overlaps with the center of ball pad <NUM>.

In various embodiments, two or more ground vias may be arranged in various cluster designs. For example, the number of ground vias to be clustered may be more than three depending on the design space or other design constraints. In some embodiments, the ground via cluster may be placed closer to certain signals as an emphasis. As an example, the arrangement of ground vias <NUM>, <NUM>, and <NUM> has more emphasis on signals near edge <NUM> because those signals generally demonstrate greater inclination for crosstalk. In some embodiments, the ground via cluster may be centered, as shown in the arrangement of ground vias <NUM>, <NUM>, and <NUM>, which may provide an equal improvement on all the surrounding signals. In various embodiments, ground via clustering, as shown in <FIG>, may reduce far-end crosstalk (FEXT) and near-end crosstalk (NEXT). Consequently, the signal-to-noise ratio (SNR) may be improved for the channel.

<FIG> schematically illustrates a flow diagram of an example process <NUM> of forming a ground via cluster for crosstalk mitigation in IC assemblies (e.g., IC assembly <NUM> of <FIG>), in accordance with some embodiments. The process <NUM> may comport with embodiments described in connection with previous figures according to various embodiments.

At block <NUM>, the process <NUM> may include forming a plurality of electrical contacts on one side of a first package substrate configured to route input/output (I/O) signals and ground between a die and a second package substrate. In various embodiments, the contacts on the side of the first package substrate may include ball pads. In some embodiments, ball pads may be solder mask defined (SMD). In other embodiments, ball pads may be non-solder mask defined (NSMD). In some embodiments, forming contacts on one side of the package substrate may be realized by embedding the contacts (e.g., pads) in build-up layers (e.g., the outermost build-up layer) as part of the formation of the build-up layers. In some embodiments, forming contacts on one side of the package substrate may be realized by forming openings in the build-up layers and disposing the contacts (e.g., pads) into the cavities subsequent to formation of the build-up layers, according to any suitable technique.

At block <NUM>, the process <NUM> may include forming a cluster of ground vias with at least two ground vias, of a same layer of vias, to electrically couple with an individual contact of the plurality of contacts. Block <NUM> may be performed during the fabrication process of a package substrate according to various embodiments, e.g., during the fabrication of various layers of package substrate <NUM>, such as layer <NUM> or layer <NUM>. In various embodiments, forming the cluster of ground vias may include forming the cluster of ground vias in a column of ground vias closest to an edge of the package substrate, such as the first column of ground vias. The first two columns of signals may demonstrate a higher susceptibility to crosstalk than the inner columns; thus, forming the cluster of ground vias in a column of ground vias closest to an edge of the package substrate may mitigate such crosstalk. In some embodiments, block <NUM> may be performed only to the column of ground vias closest to the edge, which may yield a cost-effective solution in reducing such crosstalk.

In various embodiments, forming the cluster of ground vias may include forming a vertical interconnect structures including the cluster of ground vias between two sides of the first package substrate, e.g., the vertical interconnect structures <NUM> and <NUM> in <FIG> formed between side <NUM> and side <NUM> of package substrate <NUM>. In some embodiments, forming the cluster of ground vias may include forming the cluster of ground vias in an outermost layer of vias adjacent to the side, e.g., via <NUM> and via <NUM> in <FIG> as a part of the outermost layer of vias in layer <NUM>. In some embodiments, forming the cluster of ground vias may include forming the cluster of ground vias in a second layer of vias directly adjacent to the outermost layer of vias, e.g., as via <NUM> and via <NUM> in layer <NUM> in <FIG>. In some embodiments, forming the cluster of ground vias may include forming the cluster of core vias in a same layer of vias, e.g., as via <NUM> and via <NUM> in layer <NUM> in <FIG>.

In some embodiments, forming the cluster of ground vias may include forming two ground vias apart from each other. As illustrated in <FIG>, the cluster of ground vias <NUM> and <NUM> may be formed apart from each other, but still in contact with the same ball pad <NUM>. In some embodiments, forming the cluster of ground vias may include forming three ground vias in a triangular arrangement. In such embodiments, the center of the triangular arrangement of ground vias may be disposed over a center of the ball pad. As illustrated in <FIG>, ground vias <NUM>, <NUM>, and <NUM> may form a triangular arrangement, and the center of the cluster may overlap with the center of ball pad <NUM>. In various embodiments, forming the cluster of ground vias may include forming the cluster of ground vias surrounded by signal vias of the same layer of vias. As illustrated in <FIG>, the cluster of ground vias <NUM>, <NUM>, and <NUM> may be surrounded by signal vias including signal via <NUM> in a hexagonal arrangement.

At block <NUM>, the process <NUM> may include forming an individual solder joint on an individual contact to electrically couple the first package substrate to the second package substrate or circuit board. In various embodiments, the individual contact on the first package substrate may be a ball pad, which may correspond to a counterpart contact on the second package substrate, such as a solder pad. A solder ball may then be used to couple the ball pad with the solder pad, e.g., in a BGA configuration, to form a corresponding solder joint that may be configured to further route the electrical signals between the first and second package substrates. In other embodiments, individual solder joint may be formed as other types of package interconnects, such as land-grid array (LGA) structures or other suitable structures.

Various operations are described as multiple discrete operations in turn, in a manner that is most helpful in understanding the claimed subject matter. However, the order of description should not be construed as to imply that these operations are necessarily order dependent. Operations of the process <NUM> may be performed in another suitable order than depicted.

Embodiments of the present disclosure may be implemented into a system using any suitable hardware and/or software to configure as desired. <FIG> schematically illustrates a computing device that includes ground via clustering for crosstalk mitigation in integrated circuit assemblies, as described herein, in accordance with some embodiments. The computing device <NUM> may house a board such as motherboard <NUM>. Motherboard <NUM> may include a number of components, including but not limited to processor <NUM> and at least one communication chip <NUM>. Processor <NUM> may be physically and electrically coupled to motherboard <NUM>. In some implementations, the at least one communication chip <NUM> may also be physically and electrically coupled to motherboard <NUM>. In further implementations, communication chip <NUM> may be part of processor <NUM>.

Depending on its applications, computing device <NUM> may include other components that may or may not be physically and electrically coupled to motherboard <NUM>. These other components may include, but are not limited to, volatile memory (e.g., DRAM), non-volatile memory (e.g., ROM), flash memory, a graphics processor, a digital signal processor, a crypto processor, a chipset, an antenna, a display, a touchscreen display, a touchscreen controller, a battery, an audio codec, a video codec, a power amplifier, a global positioning system (GPS) device, a compass, a Geiger counter, an accelerometer, a gyroscope, a speaker, a camera, and a mass storage device (such as hard disk drive, compact disk (CD), digital versatile disk (DVD), and so forth).

Communication chip <NUM> may enable wireless communications for the transfer of data to and from computing device <NUM>. Communication chip <NUM> may implement any of a number of wireless standards or protocols, including but not limited to Institute for Electrical and Electronic Engineers (IEEE) standards including Wi-Fi (IEEE <NUM> family), IEEE <NUM> standards (e.g., IEEE <NUM>-<NUM> Amendment), Long-Term Evolution (LTE) project along with any amendments, updates, and/or revisions (e.g., advanced LTE project, ultra-mobile broadband (UMB) project (also referred to as "3GPP2"), etc.). IEEE <NUM> compatible BWA networks are generally referred to as WiMAX networks, an acronym that stands for Worldwide Interoperability for Microwave Access, which is a certification mark for products that pass conformity and interoperability tests for the IEEE <NUM> standards. Communication chip <NUM> may operate in accordance with a Global System for Mobile Communication (GSM), General Packet Radio Service (GPRS), Universal Mobile Telecommunications System (UMTS), High Speed Packet Access (HSPA), Evolved HSPA (E-HSPA), or LTE network. Communication chip <NUM> may operate in accordance with Enhanced Data for GSM Evolution (EDGE), GSM EDGE Radio Access Network (GERAN), Universal Terrestrial Radio Access Network (UTRAN), or Evolved UTRAN (E-UTRAN). Communication chip <NUM> may operate in accordance with Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Digital Enhanced Cordless Telecommunications (DECT), Evolution-Data Optimized (EV-DO), derivatives thereof, as well as any other wireless protocols that are designated as <NUM>, <NUM>, <NUM>, and beyond. Communication chip <NUM> may operate in accordance with other wireless protocols in other embodiments.

Computing device <NUM> may include a plurality of communication chips <NUM>. For instance, a first communication chip <NUM> may be dedicated to shorter range wireless communications such as Wi-Fi and Bluetooth, and a second communication chip <NUM> may be dedicated to longer range wireless communications such as GPS, EDGE, GPRS, CDMA, WiMAX, LTE, EV-DO, and others.

Processor <NUM> of computing device <NUM> may be packaged in an IC assembly (e.g., IC assembly <NUM> of <FIG>) that includes a substrate (e.g., package substrate <NUM> of <FIG>) with vertical interconnect structures having ground via clusters formed according to techniques as described herein. For example, processor <NUM> may be die <NUM> coupled to package substrate <NUM> using interconnect structures. The term "processor" may refer to any device or portion of a device that processes electronic data from registers and/or memory to transform that electronic data into other electronic data that may be stored in registers and/or memory.

Communication chip <NUM> may also include one or more dies that may be packaged in an IC assembly (e.g., IC assembly <NUM> of <FIG>) that includes a substrate (e.g., package substrate <NUM> of <FIG>) with vertical interconnect structures having ground via clusters formed according to techniques as described herein.

In further implementations, another component (e.g., memory device or other integrated circuit device) housed within computing device <NUM> may include one or more dies that may be packaged in an IC assembly (e.g., IC assembly <NUM> of <FIG>) that includes a substrate (e.g., package substrate <NUM> of <FIG>) with vertical interconnect structures having ground via clusters formed according to techniques as described herein.

According to some embodiments, multiple processor chips and/or memory chips may be disposed in an IC assembly including a package substrate with ground via clusters in vertical interconnect structures, which may be a part of the channel to electrically route signals between any two of the processor or memory chips.

Claim 1:
A semiconductor package (<NUM>), comprising:
a package substrate (<NUM>) having a first side (<NUM>) and a second side (<NUM>) opposite the first side (<NUM>), the package substrate (<NUM>) comprising:
a first layer (<NUM>) of dielectric material adjacent the first side (<NUM>) of the package substrate (<NUM>);
a second layer (<NUM>) of dielectric material on the first layer (<NUM>) of dielectric material, the first layer (<NUM>) of dielectric material being between the second layer (<NUM>) of dielectric material and the first side (<NUM>) of the package substrate (<NUM>);
a ground solder ball pad (<NUM>) adjacent the first side (<NUM>) of the package substrate (<NUM>);
a first via (<NUM>) above and electrically coupled to the ground solder ball pad (<NUM>), the first (<NUM>) via being in the first layer (<NUM>) of dielectric material of the package substrate (<NUM>);
a second via (<NUM>) above and electrically coupled to the ground solder ball pad (<NUM>), the second via (<NUM>) being in the first layer (<NUM>) of dielectric material of the package substrate (<NUM>), the second via (<NUM>) laterally spaced apart from the first via (<NUM>);
a third via (<NUM>) above and electrically coupled to the first via (<NUM>) and being in the second layer (<NUM>) of dielectric material of the package substrate (<NUM>);
a fourth via (<NUM>) above and electrically coupled to the second via (<NUM>) and being in the second layer (<NUM>) of dielectric material of the package substrate (<NUM>), the fourth via (<NUM>) laterally spaced apart from the third via (<NUM>);
wherein a first line perpendicular to the first side (<NUM>) of the package substrate (<NUM>) intersects the ground solder ball pad (<NUM>), the first via (<NUM>), and the third via (<NUM>); and
wherein a second line perpendicular to the first side (<NUM>) of the package substrate (<NUM>) intersects the ground solder ball pad (<NUM>), the second via (<NUM>), and the fourth via (<NUM>);
a die (<NUM>) coupled to the second side (<NUM>) of the package substrate (<NUM>); and
a solder ball (<NUM>) disposed on the ground solder ball pad (<NUM>).