Carbon nanotube dispersions for co-electrodeposition of metal matrices

Abstract

Disclosed are compositions and methods for co-electrodepositing carbon nanotubes into metal matrices. A composition suitable for use in an electrodeposition bath dispersion comprises a plurality of carbon nanotubes maintained in a stable, predominantly discrete state, wherein agglomerates exceeding a defined size constitute less than a specified fraction of the carbon nanotube population and the dispersion remains stable for a defined period without sedimentation or growth of agglomerates. The dispersion further comprises a medium containing metal ions capable of electrochemical reduction. During electrodeposition, the carbon nanotubes are incorporated into a growing metal matrix concurrently with metal deposition, resulting in metal matrix composites having a process-defined, substantially consistent carbon nanotube concentration across a thickness of the deposited metal. The compositions and methods are applicable to a variety of metals and metal alloys and may be used to form electrodeposited structures for electronic and industrial applications.

Description

PCT APPLICATIONDocket No.33733.15PCT APPLICATION ofBrandon Sweeney Aaron Morelos GomezThomas AcheeBrent Williams andSteve Lowder forCarbon Nanotube Dispersions for Co-Electrodeposition of Metal MatricesKIRTON I McCONKIE TELEPHONE: (801) 328-3600A PROFESSIONAL CORPORATION FACSIMILE: (801) 321-4893 ATTORNEYS AT LAW36 SOUTH STATE STREET, #1900SALT LAKE CITY, UTAH 84111PRIORITY CLAIM

[0001] This application claims priority to United States Provisional Patent Application No. 63 / 737,442 filed December 20, 2024, and United States Non-Provisional Patent Application No. 19 / 429,326 filed December 22, 2025.TITLE

[0002] Carbon nanotube dispersions for co-electrodeposition of metal matrices.BACKGROUND

[0003] Semiconductor packaging interconnects provide electrical, thermal, and mechanical connections between semiconductor devices and external circuitry. Common interconnect structures include solder balls, microbumps, copper pillars, vias, and redistribution layers. As interconnect dimensions shrink and current densities increase, these structures face growing challenges related to electrical performance, reliability, and thermal management.

[0004] Conventional copper and solder-based interconnects are limited by factors such as ampacity, electromigration resistance, and mechanical durability. Assembly processes such as thermal compression bonding typically rely on global heating of an assembly, which can increase cycle times and subject temperature- sensitive components to thermal stress. Alternative approaches intended to reduce bonding temperatures or improve performance, including sintered nanoparticle pastes and transient liquid phase bonding, have introduced additional limitations related to processing speed, scalability, or material integrity.

[0005] Carbon nanotubes have been investigated for use in metal systems due to their favorable electrical and mechanical properties. However, incorporating carbon nanotubes into metals in a controlled and reproducible manner remains challenging, particularly in electrochemicaldeposition processes. Electrodeposition environments often involve high ionic strength, reactive chemical conditions, and a range of additives used to control deposition behavior. Under such conditions, carbon nanotubes tend to agglomerate or settle, which can lead to non-uniform incorporation and heterogeneous material properties when electrodeposition is attempted.

[0006] As a result, existing approaches to forming electrodeposited metal structures containing carbon nanotubes have struggled to achieve consistent dispersion and reproducible incorporation. Challenges remain in maintaining dispersion quality of carbon nanotubes in electrodeposition baths and in forming electrodeposited metal matrices with reliable and material characteristics suitable for advanced packaging and related applications.SUMMARY

[0007] The disclosure relates to compositions and methods for incorporating carbon nanotubes into electrodeposited metal matrices. In one aspect, the disclosure provides a composition of matter suitable for use in an electrodeposition bath. The composition comprises a dispersion of a plurality of carbon nanotubes in a medium configured to facilitate electrodeposition of a metal matrix. The dispersion is characterized by a limited population of carbon nanotube agglomerates exceeding a defined size threshold and remains stable for a defined period without visible sedimentation or an increase in agglomerate population when present in an electrodeposition bath. By maintaining the carbon nanotubes in a stable, predominantly discrete state under electrodeposition conditions, the dispersion enables controlled incorporation of carbon nanotubes during metal deposition.

[0008] In another aspect, the disclosure provides a method of co-depositing carbon nanotubes and a metal matrix. The method includes providing the dispersion in an electrodeposition bath, interfacing a conductive substrate as a cathode, and applying an electrical potential toelectrochemically reduce metal ions onto the substrate while simultaneously incorporating the carbon nanotubes into a growing metal matrix. In certain embodiments, incorporation of the carbon nanotubes occurs during electrochemical reduction and not through post-deposition infiltration or non-electrochemical processing routes, resulting in metal matrix composites having a process-defined, substantially consistent carbon nanotube concentration across a thickness of the deposited metal.DETAILED DESCRIPTION

[0009] Definitions

[0010] As used herein, the following terms are provided to clarify the scope and meaning of the disclosed embodiments. These definitions are intended to facilitate understanding of the disclosure and are not intended to limit the scope of the appended claims.

[0011] The term “dispersion” refers to a physical distribution of carbon nanotubes within a liquid medium in which the carbon nanotubes retain their individual structural identity and are present as physically separate entities rather than as irreversibly fused, sintered, or permanently bonded aggregates. A dispersion may include transient physical contacts between carbon nanotubes, such as contacts arising from van der Waals interactions or incidental entanglement, provided that such contacts do not result in stable agglomerates that persist under the conditions of use described herein.

[0012] The term “stable,” when used in reference to a dispersion, refers to the ability of the dispersion to maintain substantially the same population characteristics of carbon nanotubes over a defined period of time, without macroscopic settling, phase separation, or growth of agglomerated carbon nanotube populations beyond a defined reference state. Stability does not require thecomplete absence of motion, Brownian interaction, or transient contact among carbon nanotubes and does not require the dispersion to remain unchanged indefinitely.

[0013] The term “increase,” when used in reference to agglomerates or clusters of carbon nanotubes, refers to a measurable change relative to an initial state of the dispersion. In certain embodiments, the initial state corresponds to the condition of the dispersion at the beginning of a defined observation interval, such as immediately prior to placement in an electrodeposition bath or immediately following cessation of active mixing or sonication. An increase may be evaluated based on changes in agglomerate size distribution, agglomerate population fraction, or mass fraction of agglomerated carbon nanotubes.

[0014] The term “discrete carbon nanotubes” refers to carbon nanotubes that are not permanently bonded, fused, sintered, or chemically crosslinked to other carbon nanotubes. Discrete carbon nanotubes may be functionalized, coated, doped, or otherwise modified at their surfaces, provided that such modification does not result in irreversible bonding between adjacent nanotubes. Discrete carbon nanotubes may exhibit transient physical contact during dispersion or transport but remain physically separable within an electrodeposition medium.

[0015] In the context of a dispersion, discrete carbon nanotubes may coexist with a limited population of carbon nanotube agglomerates or clusters. Unless otherwise specified, references herein to dispersions of carbon nanotubes encompass dispersions in which discrete carbon nanotubes constitute a majority of the carbon nanotube population, while a minority of the population may be present as agglomerates or clusters that satisfy defined size and population thresholds.

[0016] The term “uniform” or “substantially uniform,” when used in reference to a distribution of carbon nanotubes within a dispersion or within an electrodeposited metal matrix, refers to the absence of macroscopic clustering, banding, or localized accumulation of carbon nanotubes atscales relevant to the intended application. A uniform or substantially uniform distribution permits local statistical variation consistent with stochastic transport and deposition processes and does not require a mathematically even, periodic, or perfectly homogeneous spatial arrangement.

[0017] The term “plurality” means two or more.

[0018] The term “electrodeposition bath” or “bath” refers to a liquid medium containing metal ions capable of electrochemical reduction, together with any additives, solvents, electrolytes, stabilizers, surfactants, brighteners, suppressors, levelers, or other components commonly used in electrodeposition processes. The term “electrodeposition bath” refers to the chemical and electrochemical environment provided by the liquid medium, and does not refer to the physical container, vessel, tank, or apparatus as the subject matter of the invention, although such containers or apparatuses may be used to hold the liquid medium during operation. The electrodeposition bath may be aqueous or non-aqueous and may exhibit ionic strength, pH, redox activity, or chemical reactivity sufficient to challenge the stability of dispersed nanomaterials. References to an electrodeposition bath include static, flowing, recirculating, or localized liquid media used for electrodeposition and do not imply any particular physical configuration of the associated equipment.

[0019] The term “concentration,” when used in reference to carbon nanotubes within a dispersion or within an electrodeposited metal matrix, refers to the relative amount of carbon nanotubes present within a defined volume, mass, or number basis. Concentration may be expressed on a number basis, a weight basis, a volume fraction basis, or another suitable quantitative basis, unless otherwise specified.

[0020] The term “process-defined,” when used in reference to a distribution or concentration of carbon nanotubes within an electrodeposited metal matrix, refers to a distribution that arises from the conditions and parameters of the electrodeposition process itself, including dispersion quality in the electrodeposition bath, electrical conditions, and transport phenomena, rather than from postdeposition modification or redistribution.

[0021] Dispersion Quality in Electrodeposition Environments

[0022] Embodiments described herein relate to dispersions of carbon nanotubes that are suitable for use in electrodeposition environments and that enable reliable incorporation of carbon nanotubes into electrodeposited metal matrices. Electrodeposition environments may present conditions that are materially different from those encountered in conventional colloidal dispersions, including high ionic strength, the presence of aggressive acids or bases, redox-active species, and a complex mixture of organic and inorganic additives. These conditions can promote agglomeration, settling, or loss of dispersion quality for nanomaterials that are otherwise dispersible in less demanding environments.

[0023] In prior approaches, attempts to incorporate carbon nanotubes into electrodeposited metals have frequently resulted in non-uniform incorporation, banding, localized clustering, or settling of carbon nanotubes within the plating bath, leading to electrodeposited structures with heterogeneous properties. Such outcomes limit reproducibility, reduce performance gains, and complicate scaling to manufacturing environments.

[0024] In contrast, embodiments disclosed herein emphasize the quality and stability of the carbon nanotube dispersion within the electrodeposition bath itself as a controlling factor for downstream incorporation into the electrodeposited metal matrix. A dispersion in which discrete carbon nanotubes constitute a majority of the carbon nanotube population and in which a limitedpopulation of agglomerates is maintained within defined thresholds within the electrodeposition bath enables the availability of carbon nanotubes throughout the bath medium during electrochemical reduction of metal ions, thereby supporting consistent incorporation of carbon nanotubes into the growing metal deposit.

[0025] In certain embodiments, the dispersion is characterized by a limited population of carbon nanotube agglomerates or clusters above a defined size threshold. In one exemplary embodiment, agglomerates or clusters having a characteristic dimension greater than about 10 micrometers constitute less than about 1% by weight of the total carbon nanotubes present in the dispersion. In other exemplary embodiments, alternative size thresholds, mass fractions, or combinations thereof may be employed, including characteristic dimensions greater than about 1 micrometer, 5 micrometers, or 20 micrometers, and agglomerate mass fractions less than about 5%, 0.5%, or 0.1% by weight. These values are provided as illustrative examples and are not intended to define absolute limits.

[0026] In certain embodiments, dispersion stability is evaluated over a defined time interval following preparation of the dispersion or following introduction of the dispersion into an electrodeposition bath. In one exemplary embodiment, the dispersion remains stable for at least about one hour without visible sedimentation or without an increase in the population of agglomerates exceeding a defined size threshold. In other exemplary embodiments, stability intervals of at least about 30 minutes, 2 hours, or 24 hours may be used. Stability may be assessed after cessation of active mixing, agitation, or sonication, and does not require continuous energy input to maintain dispersion during the evaluation interval.

[0027] In some embodiments, dispersion quality is assessed relative to an initial reference state. In some embodiments, an initial distribution of carbon nanotube sizes and populations may be establishedat the beginning of an observation interval, and subsequent evaluation may determine whether agglomerate populations increase relative to that initial state. This approach enables characterization of dispersion stability without requiring the complete absence of transient interactions or Brownian motion among carbon nanotubes.

[0028] In certain embodiments, the dispersion is configured such that the carbon nanotubes remain available for transport toward an electrode surface during electrochemical reduction of metal ions. In some embodiments maintaining a stable dispersion reduces localized depletion or enrichment of carbon nanotubes within the electrodeposition bath and supports incorporation mechanisms that operate concurrently with metal deposition.

[0029] In some embodiments, the quality of the dispersion in the electrodeposition bath correlates with the resulting distribution of carbon nanotubes within the electrodeposited metal matrix. In these embodiments, dispersions that remain stable and substantially non-settling during electrodeposition tend to produce metal matrices in which carbon nanotubes are incorporated with a substantially consistent concentration across a thickness of the deposited metal. In other embodiments, variations in dispersion quality may intentionally be used to produce graded or spatially varying carbon nanotube distributions.

[0030] In certain embodiments, the dispersion quality may be evaluated using observational or analytical techniques such as optical inspection, microscopic analysis, or mass-based measurements. Such techniques are provided as illustrative examples and are not required in all embodiments. The disclosed dispersions are defined by their physical and functional characteristics within the electrodeposition environment rather than by any particular method of verification.

[0031] The dispersion quality concepts described herein are applicable across a range of electrodeposition media, including aqueous electrolytes, ionic liquids, and deep eutectic solvents, and across a range of metals and metal alloys capable of electrodeposition. The ability to maintain discrete carbon nanotubes in a stable dispersion under these diverse conditions enables the formation of metal matrix composites that are not readily achievable using post-deposition infiltration, powder metallurgy, mechanical mixing, sintering, evaporation, or sputtering techniques.

[0032] In some embodiments, a composition suitable for use in an electrodeposition bath comprises a dispersion of carbon nanotubes in a liquid electrodeposition bath medium. The dispersion may include a population of predominantly discrete carbon nanotubes together with a limited population of carbon nanotube agglomerates or clusters. Discrete carbon nanotubes may constitute a majority of the carbon nanotube population, while agglomerates or clusters may be present below defined size and population thresholds.

[0033] In certain embodiments, carbon nanotube agglomerates or clusters having a characteristic dimension greater than about 10 micrometers constitute less than about 1% by weight of the total carbon nanotubes present in the dispersion. In other embodiments, alternative size thresholds or population fractions may be used, including agglomerates having characteristic dimensions greater than about 1 micrometer, 5 micrometers, or 20 micrometers, and agglomerate populations below about 5%. 0.5%, or 0.1% by weight.

[0034] In some embodiments, the dispersion remains stable for a defined period when present in an electrodeposition bath medium. For example, in certain embodiments the dispersion remains stable for at least about one hour without visible sedimentation or without an increase in the population of agglomerates exceeding a defined size threshold. In other embodiments, stabilityintervals of at least about 30 minutes, 2 hours, or 24 hours may be used. Stability may be assessed relative to an initial reference state and does not require continuous agitation, mixing, or sonication during the stability interval.

[0035] Electrodeposition Media and Bath Chemistries

[0036] Embodiments described herein employ dispersions of carbon nanotubes that are compatible with electrodeposition media used for forming metal or metal alloy structures. The electrodeposition medium provides a liquid environment containing metal species capable of electrochemical reduction, together with additional components that influence deposition kinetics, morphology, and interfacial behavior. The ability of a dispersion of carbon nanotubes to remain stable and predominantly discrete within such media is a key factor enabling co-deposition of carbon nanotubes with electrodeposited metals.

[0037] Electrodeposition media suitable for use with the disclosed dispersions may be aqueous or nonaqueous. In aqueous embodiments, the electrodeposition medium may comprise water together with dissolved metal salts, acids, bases, buffers, or combinations thereof. Examples include sulfate-based, methanesulfonate-based, chloride-containing, or mixed-acid systems commonly used for electrodeposition of copper, tin, silver, nickel, cobalt, or metal alloys. Such aqueous media may exhibit high ionic strength, low pH, or both, and may further contain organic or inorganic additives that modify deposition behavior.

[0038] In certain embodiments, the electrodeposition medium includes one or more additives selected from brighteners, levelers, suppressors, accelerators, complexing agents, or combinations thereof. These additives are commonly employed in advanced electrodeposition processes to control grain size, surface roughness, deposition rate, or feature filling behavior. The dispersionsdisclosed herein are configured to maintain discrete carbon nanotubes in the presence of such additives, which may otherwise promote aggregation or destabilization of nanomaterials.

[0039] In additional embodiments, the electrodeposition medium is a non-aqueous medium. Nonaqueous media may include ionic liquids, deep eutectic solvents, molten salts, or other solvent systems capable of supporting electrochemical reduction of metal species. In some embodiments ionic liquids may include imidazolium-based. pyrrolidinium-based, ammonium-based, or phosphonium-based salts, optionally combined with metal-containing anions. Deep eutectic solvents may comprise eutectic mixtures formed from Lewis acids and Lewis bases, Brpnsted acids and Brpnsted bases, or combinations thereof. Such non-aqueous systems may enable electrodeposition of metals or metal alloys that are difficult or impractical to deposit from aqueous solutions, including aluminum, titanium, tantalum, or certain noble metals.

[0040] In some embodiments, the electrodeposition medium is selected to deposit a metal matrix comprising copper, tin, silver, nickel, cobalt, gold, palladium, indium, bismuth, zinc, iron, tungsten, molybdenum, or alloys thereof. In other embodiments, the electrodeposition medium is configured to deposit solder-forming metals or alloys, including tin-based alloys or tin-silver- copper alloys. The disclosed dispersions are not limited to any particular metal system and may be adapted to electrodeposition media selected based on application-specific requirements.

[0041] The chemical environment of an electrodeposition medium may include redox-active species, high concentrations of dissolved ions, and surface-active additives. These conditions can differ substantially from those encountered in conventional colloidal dispersions or polymer-based suspensions. Accordingly, dispersions of carbon nanotubes suitable for electrodeposition media are configured to resist agglomeration, settling, or loss of dispersion quality under these conditions for a period sufficient to support electrodeposition.

[0042] In certain embodiments, the dispersion of carbon nanotubes is introduced into an electrodeposition medium as a concentrate or masterbatch that is subsequently diluted to a working concentration. In other embodiments, the dispersion is prepared directly within the electrodeposition medium. In either case, the dispersion may be subjected to mixing, agitation, shear, or other handling steps commonly used in electrodeposition processes. The stability characteristics described herein enable the dispersion to remain suitable for electrodeposition following such handling.

[0043] In some embodiments, the electrodeposition medium is maintained under agitation, circulation, or flow during electrodeposition to promote uniform distribution of metal ions and additives. In other embodiments, the dispersion of carbon nanotubes remains sufficiently stable that localized settling or depletion of carbon nanotubes does not occur over the time scales relevant to electrodeposition, even in the absence of continuous agitation. These embodiments illustrate that dispersion stability may be achieved through surface chemistry and interaction with the medium, rather than through reliance on mechanical mixing alone.

[0044] The electrodeposition media described herein may be employed in a variety of electrodeposition configurations, including tank plating, wafer-level plating, patterned feature plating, or localized electrodeposition processes. The dispersions disclosed herein are compatible with electrodeposition media used in semiconductor packaging, printed circuit board fabrication, and other electronic or industrial metal deposition applications.

[0045] The selection of electrodeposition medium, metal species, additives, and operating conditions may be varied independently of the dispersion quality criteria described herein. The disclosed dispersions are defined by their ability to maintain discrete carbon nanotubes in a stable,predominantly discrete state within the selected electrodeposition medium, rather than by any specific bath formulation.

[0046] Carbon Nanotube Functionalization Strategies Enabling Dispersion and Incorporation

[0047] Embodiments described herein may employ surface modification or functionalization of carbon nanotubes to promote dispersion stability within electrodeposition media and to facilitate incorporation of carbon nanotubes into electrodeposited metal matrices. Functionalization strategies described in this section are provided as enabling approaches that may be used individually or in combination and are not required in all embodiments.

[0048] Carbon nanotubes, in their native state, may exhibit limited compatibility with electrodeposition media due to hydrophobic surfaces, strong inter-tube van der Waals interactions, or insufficient interaction with metal ions or bath additives. Surface modification of carbon nanotubes can alter interfacial energetics, surface charge, wettability, or chemical affinity in ways that support stable dispersion and controlled incorporation during electrodeposition.

[0049] In certain embodiments, carbon nanotubes are functionalized using covalent surface modification. Covalent functionalization may include attachment of chemical groups to carbon nanotube sidewalls, defect sites, or end caps. Suitable functional groups may include oxygencontaining groups, nitrogen-containing groups, or combinations thereof. Examples include hydroxyl, carbonyl, carboxylate, amine, amide, nitrile, azine, pyridinic nitrogen, pyrrolic nitrogen, or graphitic (quaternary) nitrogen functionalities. Such groups may increase interaction with polar solvents, metal ions, or bath additives and may reduce inter-tube attraction that leads to agglomeration.

[0050] In other embodiments, carbon nanotubes are functionalized using non-covalent surface modification. Non-covalent functionalization may include adsorption of surfactants, dispersants,polymers, aromatic molecules, or other surface-active species onto the carbon nanotube surface. These species may stabilize discrete carbon nanotubes through steric hindrance, electrostatic repulsion, or 71-71 interactions, while preserving the intrinsic structure of the carbon nanotubes. Non-covalent functionalization may be advantageous in embodiments where preservation of carbon nanotube electrical or mechanical properties is desired.

[0051] In some embodiments, a surfactant is associated with the carbon nanotubes to promote dispersion stability within an electrodeposition bath medium. Surfactants may be anionic, cationic, nonionic, zwitterionic, or combinations thereof.

[0052] In exemplary embodiments, the surfactant is present at a loading from about 0.01:1 to about 20:1, expressed as a mass ratio of surfactant to carbon nanotubes. In other embodiments, the surfactant is present at a loading from about 0.1:1 to about 10:1 by mass relative to the carbon nanotubes. In further embodiments, the surfactant is present at a loading from about 0.25:1 to about 5:1 by mass relative to the carbon nanotubes. These ranges may be selected to inhibit agglomeration while maintaining compatibility with electrodeposition processes.

[0053] In some embodiments, carbon nanotubes are functionalized with metals or metal-containing species to promote interaction with electrodeposited metals. Such functionalization may include attachment of one or more elements selected from Group 9 or Group 10 of the periodic table, including cobalt, nickel, rhodium, palladium, platinum, or combinations thereof. These elements may be present as coatings, partial coatings, discontinuous surface domains, nanoparticles, coordination complexes, organometallic residues, or interfacial layers on exterior surfaces of the carbon nanotubes. Metal functionalization may enhance wettability, promote electron transfer, or facilitate interfacial bonding between the carbon nanotubes and the growing metal matrix during electrodeposition.

[0054] In certain embodiments, carbon nanotubes are nitrogen-doped, either alone or in combination with other functionalization strategies. Nitrogen incorporation into the carbon lattice may modify electronic properties, alter surface charge characteristics, or increase affinity for metal ions. Nitrogen-doped carbon nanotubes may exhibit improved dispersion behavior in electrodeposition media and enhanced incorporation into electrodeposited metals.

[0055] In some embodiments, functionalization strategies are selected to impart a net surface charge to the carbon nanotubes within the electrodeposition bath medium. Charged carbon nanotubes may experience electrophoretic or electrostatic transport toward an electrode during application of an electrical potential, occurring concurrently with electrochemical reduction of metal ions. Such transport mechanisms may contribute to incorporation of carbon nanotubes into the growing metal deposit and may be influenced by the nature and density of surface functionalization.

[0056] In some embodiments, multiple functionalization strategies are combined. Carbon nanotubes may be both nitrogen-doped and metal-functionalized, or may include covalent surface groups together with non-covalent dispersants. The selection and combination of functionalization strategies may be tailored based on the electrodeposition medium, target metal or metal alloy, desired dispersion stability, and intended application of the resulting composite.

[0057] Functionalization strategies described herein may be applied prior to introduction of carbon nanotubes into an electrodeposition medium, or may be applied in situ during preparation of a dispersion. In certain embodiments, functionalized carbon nanotubes are supplied as a concentrate, masterbatch, or pre-dispersed composition for subsequent use in an electrodeposition bath.

[0058] The functionalization strategies described in this section are not mutually exclusive and do not limit the invention to any particular surface chemistry. Rather, they provide illustrativeapproaches for enabling stable dispersion of discrete carbon nanotubes in electrodeposition environments and for facilitating incorporation of carbon nanotubes into electrodeposited metal matrices under a wide range of conditions.

[0059] In certain embodiments, carbon nanotubes are functionalized with oxygen-containing or nitro gen-containing species to promote dispersion stability, interaction with metal ions, or electrochemical incorporation during electrodeposition. Such functionalization may include incorporation of heteroatoms into the carbon nanotube lattice, attachment at defect sites, or association with exterior surfaces. Oxygen- or nitrogen-containing species may include hydroxyl, carbonyl, carboxylate, amine, amide, nitrile, azine, pyridinic nitrogen, pyrrolic nitrogen, or graphitic (quaternary) nitrogen functionalities.

[0060] In exemplary embodiments, oxygen or nitrogen is present in an amount from about 0.1% to about 10% by atomic fraction, relative to the total atoms of the carbon nanotubes. In other embodiments, oxygen or nitrogen is present in an amount from about 0.5% to about 5% by atomic fraction. In further embodiments, oxygen or nitrogen is present in an amount from about 1% to about 3% by atomic fraction. These ranges may be selected to enhance wettability, surface charge, or affinity for metal ions while preserving the intrinsic structure and electrical properties of the carbon nanotubes and maintaining dispersion stability.

[0061] Co-Electrodeposition Mechanisms and Transport Phenomena

[0062] Embodiments described herein involve the simultaneous incorporation of carbon nanotubes and metal species during electrodeposition, resulting in formation of metal matrix composites containing embedded carbon nanotubes. This co-electrodeposition process differs from approaches in which carbon nanotubes are introduced into a metal structure after deposition or by non-electrochemical routes.

[0063] During electrodeposition, metal ions present in the electrodeposition bath medium are electrochemically reduced at a conductive substrate serving as a cathode. Concurrently, carbon nanotubes dispersed within the electrodeposition bath medium are transported toward the cathode and incorporated into the growing metal deposit. The incorporation of carbon nanotubes occurs during electrochemical reduction of the metal ions and is influenced by dispersion quality, surface functionalization, and transport phenomena within the electrodeposition environment.

[0064] In certain embodiments, incorporation of carbon nanotubes occurs through a combination of electrochemical and physical mechanisms. While the reduction of metal ions proceeds via redox reactions at the cathode surface, carbon nanotubes may be incorporated through electrophoretic transport, electrostatic attraction, field-assisted migration, convective transport, adsorption, or combinations thereof. These mechanisms may operate simultaneously or sequentially during deposition and may be influenced by applied electrical potential, current density, waveform, and bath composition.

[0065] In some embodiments, functionalized carbon nanotubes carry a net surface charge within the electrodeposition bath medium. Upon application of an electrical potential, such charged carbon nanotubes may migrate toward the cathode under the influence of the electric field in a manner analogous to electrophoretic deposition. This transport occurs concurrently with electrochemical reduction of metal ions and contributes to embedding of carbon nanotubes within the metal matrix as metal grains nucleate and grow.

[0066] In other embodiments, carbon nanotube incorporation occurs through electrostatic or surface- mediated interactions without requiring a persistent net charge. In some embodiments, functionalized carbon nanotubes may adsorb at or near the cathode surface due to affinity for metal ions, bath additives, or nascent metal surfaces, and may become physically entrapped asthe metal deposit grows around them. Such incorporation mechanisms may operate even when electrophoretic forces are minimal.

[0067] In certain embodiments, transport and incorporation of carbon nanotubes are influenced by convective forces arising from bath agitation, circulation, or flow. Agitation may be employed to maintain uniform distribution of metal ions and additives within the bath and may also contribute to maintaining availability of carbon nanotubes throughout the electrodeposition bath medium. However, the disclosed embodiments do not rely solely on mechanical agitation to achieve incorporation, and dispersion stability may be sufficient to support co-electrodeposition in the absence of continuous agitation over relevant time scales.

[0068] In some embodiments, electrical parameters are selected to influence the relative rates of metal deposition and carbon nanotube incorporation. Parameters such as current density, voltage, waveform shape, pulse duration, reverse-pulse intervals, or modulation frequency may be adjusted to control nucleation behavior, grain growth, and the probability that carbon nanotubes become incorporated into the growing metal matrix. Pulse plating or reverse-pulse plating techniques may be employed to tune incorporation behavior without altering the composition of the electrodeposition bath.

[0069] The resulting metal matrix composites formed by co-electrodeposition exhibit characteristics distinct from structures produced by alternative routes. In particular, carbon nanotubes are incorporated during metal growth rather than being introduced into pre-formed metal structures. This distinction enables intimate interfacial contact between carbon nanotubes and metal grains and supports formation of composites with substantially consistent carbon nanotube concentration across a thickness of the deposited metal.

[0070] In certain embodiments, the co-electrodeposition process yields metal matrix composites in which carbon nanotubes are incorporated exclusively during electrochemical reduction of metal ions. Embodiments described herein exclude incorporation mechanisms based on post-deposition infiltration, mechanical mixing of powders, sintering, evaporation, sputtering, or other nonelectrochemical deposition techniques. Such exclusion distinguishes the disclosed processes from approaches that do not provide the same level of control over dispersion-derived incorporation.

[0071] In some embodiments, the spatial distribution of carbon nanotubes within the deposited metal matrix reflects the dispersion quality and transport conditions present during deposition. Dispersions that maintain discrete carbon nanotubes in a stable, predominantly discrete state during electrodeposition tend to produce metal deposits with substantially uniform or substantially consistent carbon nanotube concentration. In other embodiments, controlled variations in dispersion conditions or electrical parameters may be used to intentionally produce graded or spatially varying distributions.

[0072] The co-electrodeposition mechanisms described herein are applicable across a range of electrodeposition media, metal systems, and substrate configurations. By enabling concurrent metal deposition and carbon nanotube incorporation, the disclosed approaches provide a route to forming metal matrix composites with properties that are difficult to achieve using sequential or post-processing methods.

[0073] In certain embodiments, carbon nanotubes are further functionalized with magnetic material. Magnetic functionalization may include attachment or incorporation of iron, cobalt, nickel, ferrites, alloys thereof, or combinations thereof. Magnetic material may be present asnanoparticles, coatings, partial coatings, discontinuous surface domains, or inclusions associated with the carbon nanotubes.

[0074] In exemplary embodiments, the magnetic material is present in an amount from about 1% to about 80% by weight relative to the carbon nanotubes. In other embodiments, the magnetic material is present in an amount from about 5% to about 40% by weight relative to the carbon nanotubes. In further embodiments, the magnetic material is present in an amount from about 10% to about 25% by weight relative to the carbon nanotubes. In some embodiments, only a subset of the carbon nanotubes present in a dispersion are magnetically functionalized, while remaining carbon nanotubes are non-magnetic.

[0075] In some embodiments, carbon nanotubes dispersed within an electrodeposition bath medium are co-electrodeposited with a metal matrix during electrochemical reduction of metal ions. Incorporation may occur through electrophoretic transport, electrostatic attraction, adsorption, convective transport, field-assisted migration, or combinations thereof. In certain embodiments, incorporation of carbon nanotubes occurs during electrochemical reduction and not through postdeposition infiltration, mechanical mixing, sintering, evaporation, or sputtering.

[0076] Alternative Carbon Nanotube Incorporation Pathways

[0077] In certain embodiments, incorporation of carbon nanotubes into the electrodeposited metal matrix occurs predominantly through electrophoretic transport. In such embodiments, surface functionalization imparts a net charge to at least a portion of the carbon nanotubes within the electrodeposition bath medium, and the carbon nanotubes migrate toward the cathode under the applied electric field during electrodeposition. Electrophoretic transport may occur concurrently with electrochemical reduction of metal ions and may contribute to controlled incorporation of carbon nanotubes into the growing metal deposit.

[0078] In other embodiments, incorporation of carbon nanotubes occurs predominantly through surface- mediated adsorption mechanisms. In such embodiments, carbon nanotubes dispersed within the electrodeposition bath medium exhibit affinity for metal ions, bath additives, or nascent metal surfaces at the cathode. The carbon nanotubes may adsorb at or near the cathode surface and become physically entrapped as metal grains nucleate and grow, without requiring sustained electrophoretic migration.

[0079] In further embodiments, incorporation of carbon nanotubes occurs through a combination of electrophoretic transport, surface adsorption, convective transport, and field-assisted migration. The relative contribution of these mechanisms may vary depending on dispersion composition, carbon nanotube functionalization, bath chemistry, and electrical operating conditions.

[0080] In some embodiments, electrical waveforms applied during electrodeposition are selected to influence carbon nanotube incorporation behavior. Pulse plating, reverse-pulse plating, or modulated current density may be employed to adjust nucleation frequency, grain growth dynamics, and the probability of carbon nanotube entrapment within the growing metal matrix. Such waveform control may be used independently of, or in combination with, dispersion composition and functionalization strategies.

[0081] Resulting Metal Matrix Composites and Structural Characteristics

[0082] Embodiments described herein yield metal matrix composites formed by co-electrodeposition of metals or metal alloys with carbon nanotubes dispersed within an electrodeposition bath. The resulting composites comprise a continuous metal matrix having carbon nanotubes embedded therein, with structural characteristics influenced by dispersion quality, functionalization strategies, and electrodeposition conditions.

[0083] In certain embodiments, the resulting metal matrix composite comprises carbon nanotubes incorporated within the metal matrix with a substantially consistent carbon nanotube concentration across a thickness of the deposited metal. Such consistency may be evaluated on a number basis, a weight basis, a volume fraction basis, or another suitable quantitative basis, as defined herein. A substantially consistent concentration does not require exact uniformity at all length scales and permits local statistical variation consistent with stochastic deposition processes.

[0084] In some embodiments, the distribution of carbon nanotubes within the metal matrix lacks macroscopic clustering, banding, or stratification across the deposited thickness. In these embodiments, carbon nanotubes are present throughout the metal matrix rather than being concentrated near a surface, interface, or discrete region. Such distributions may arise when dispersion stability and transport phenomena during electrodeposition are maintained within ranges suitable for concurrent metal growth and nanotube incorporation.

[0085] In other embodiments, the metal matrix composite exhibits intentionally non-uniform or graded distributions of carbon nanotubes. For example, electrodeposition conditions, bath composition, electrical parameters, or dispersion characteristics may be varied over time to produce metal matrices having regions of differing carbon nanotube concentration. Such graded structures may be useful for tailoring electrical, thermal, mechanical, or electromagnetic properties within a single deposited feature.

[0086] In certain embodiments, carbon nanotubes embedded within the metal matrix maintain their discrete character and are not present as irreversibly fused or sintered bundles. Discrete carbon nanotubes may exhibit intimate contact with surrounding metal grains, interfaces, or boundaries.In some embodiments, such contact contributes to improved load transfer, enhanced electrical conduction pathways, or modified thermal transport behavior within the composite.

[0087] In some embodiments, the metal matrix composite exhibits enhanced electrical, thermal, or mechanical properties relative to a corresponding metal deposited in the absence of carbon nanotubes. For example, incorporation of carbon nanotubes may increase current-carrying capacity, reduce electromigration susceptibility, modify thermal conductivity, alter coefficient of thermal expansion, or improve resistance to fatigue or creep. These property enhancements are provided as illustrative outcomes and are not required in all embodiments.

[0088] In certain embodiments, the structural characteristics of the metal matrix composite are influenced by the scale and distribution of carbon nanotubes relative to metal grain size. Carbon nanotubes may be embedded within metal grains, located at grain boundaries, or span multiple grains, depending on deposition conditions and nanotube dimensions. Such configurations may influence grain growth, boundary mobility, or diffusion behavior during and after deposition.

[0089] In some embodiments, the resulting metal matrix composite exhibits structural features that are observable using analytical techniques such as optical microscopy, scanning electron microscopy, focused ion beam cross-sectioning, or related methods. Such observability may enable characterization of carbon nanotube distribution, agglomeration state, or concentration gradients within the deposited metal. These techniques are described as illustrative tools for characterization and are not required for practicing the disclosed embodiments.

[0090] In certain embodiments, the metal matrix composite forms discrete structures including pillars, bumps, vias, redistribution layers, coatings, conductive traces, or other electrodeposited features. The geometry, pitch, and dimensions of such structures may be defined lithographically or by other patterning techniques prior to electrodeposition. The structural characteristics describedherein may be present within individual features or across arrays of features formed simultaneously.

[0091] The resulting metal matrix composites described in this section are distinguishable from materials produced by post-deposition infiltration, mechanical mixing of powders, sintering, evaporation, sputtering, or other non-electrochemical routes. In the disclosed embodiments, carbon nanotubes are incorporated during electrochemical deposition of the metal matrix, resulting in composites whose structural characteristics reflect dispersion-derived incorporation rather than post-processing addition.

[0092] Carbon Nanotube Characteristics

[0093] The carbon nanotubes may comprise single-wall carbon nanotubes, double-wall carbon nanotubes, few-wall carbon nanotubes, multi-wall carbon nanotubes, or combinations thereof, and the aspect ratio distribution may be unimodal or multimodal. Selection of aspect ratio may be based on desired dispersion stability, electrophoretic mobility, mechanical reinforcement, or interaction with metal grain growth during electrodeposition. The aspect ratio values disclosed herein are illustrative and are not intended to limit the scope of the disclosed embodiments.

[0094] In some embodiments, the carbon nanotubes comprise single-wall carbon nanotubes, double-wall carbon nanotubes, few-wall carbon nanotubes, multi-wall carbon nanotubes, or combinations thereof. In certain embodiments, the carbon nanotubes exhibit a high aspect ratio. For example, the carbon nanotubes may have an aspect ratio of at least about 10:1. In other embodiments, the aspect ratio may be at least about 20:1, 50:1, 100:1, or 500:1. In further embodiments, the aspect ratio may be from about 20:1 to about 5,000:1, from about 50:1 to about 10,000:1, or from about 100:1 to about 20,000:1. Aspect ratio selection may influence dispersion stability, transport behavior, and incorporation during electrodeposition.

[0095] Optional Magnetic Functionalization and Induction Response

[0096] In certain embodiments, carbon nanotubes employed in the disclosed dispersions are further functionalized with magnetic materials. Magnetic functionalization is optional and may be employed in embodiments where response to magnetic or induction fields, localized heating, or electromagnetic functionality is desired.

[0097] Magnetic functionalization may include attachment, incorporation, or association of one or more magnetic materials with carbon nanotubes. Suitable magnetic materials may include iron, cobalt, nickel, ferrites, alloys thereof, or combinations thereof. Such materials may be present as nanoparticles, partial coatings, discontinuous coatings, surface decorations, inclusions, or interfacial layers associated with exterior surfaces of the carbon nanotubes. Magnetic materials may also be present as endohedral inclusions or otherwise coupled to the carbon nanotube structure.

[0098] In some embodiments, magnetic functionalization enables carbon nanotubes embedded within a metal matrix to respond to alternating magnetic fields or induction fields. When exposed to such fields, magnetically functionalized carbon nanotubes may generate localized heating due to magnetic hysteresis, eddy current effects, or related electromagnetic phenomena. The resulting localized heating may be confined within or near the metal matrix composite without requiring bulk heating of surrounding materials.

[0099] In certain embodiments, localized heating generated by magnetically functionalized carbon nanotubes supports thermal processing operations, such as bonding joining, or reflow, within structures formed from the disclosed metal matrix composites. Such heating may be used, for example, to promote diffusion, metallurgical bonding, or softening of adjacent materials.Magnetic induction response may enable rapid heating and cooling cycles with reduced thermal exposure of surrounding components.

[0100] In some embodiments, magnetic functionalization is selected to provide temperaturedependent or self-limiting heating behavior. For example, ferrite materials exhibiting Curie-point behavior may be used to limit heating above a defined temperature. Such embodiments may provide inherent temperature regulation during exposure to induction fields.

[0101] In additional embodiments, magnetically functionalized carbon nanotubes impart electromagnetic functionality to the resulting metal matrix composite beyond heating effects. For example, embedded magnetic materials may contribute inductive behavior, influence electromagnetic interference characteristics, or modify current distribution within conductive structures. Such effects may be advantageous in power delivery networks, interconnect structures, or other electronic applications.

[0102] Magnetic functionalization may be combined with other functionalization strategies described herein, including covalent surface modification, non-covalent dispersants, metal functionalization, or nitrogen doping. The selection and combination of functionalization strategies may be tailored based on desired dispersion stability, electrodeposition behavior, and post-deposition functionality.

[0103] In certain embodiments, magnetically functionalized carbon nanotubes are incorporated into the metal matrix composite during co-electrodeposition in the same manner as non-magnetic carbon nanotubes. The presence of magnetic materials does not require modification of the electrodeposition process and does not preclude formation of composites exhibiting substantially consistent carbon nanotube concentration across a thickness of the deposited metal.

[0104] The embodiments described in this section illustrate optional enhancements that may be incorporated into the disclosed dispersions and resulting metal matrix composites. Magnetic functionalization and induction response are not required in all embodiments and do not limit the invention to applications involving induction heating or magnetic fields.

[0105] In some embodiments, interfacial bonding between carbon nanotubes and an electrodeposited metal matrix is enhanced by association of metallic material with exterior surfaces of the carbon nanotubes. Metallic material may be present as a coating, partial coating, discontinuous coating, nanoparticle decoration, substitutional incorporation of heteroatoms into a carbon lattice, or an interfacial layer. Metallic materials suitable for interfacial bonding enhancement may include cobalt, nickel, palladium, platinum, rhodium, or combinations or alloys thereof.

[0106] In exemplary embodiments, the metallic material is present in an amount from about 0.01% to about 25% by weight relative to the carbon nanotubes. In other embodiments, the metallic material is present in an amount from about 0.1% to about 10% by weight relative to the carbon nanotubes. In further embodiments, the metallic material is present in an amount from about 0.5% to about 2% by weight relative to the carbon nanotubes. These loadings may be selected to promote metal nucleation on the carbon nanotubes, enhance interfacial adhesion, or facilitate electron transfer during electrochemical reduction, while maintaining dispersion stability.

[0107] Representative Electrodeposited Structures and Use Contexts

[0108] Embodiments described herein may be used to form a variety of electrodeposited structures comprising metal matrix composites with embedded carbon nanotubes. The specificgeometry, dimensions, and application context of such structures may vary depending on the intended use, electrodeposition configuration, and substrate design.

[0109] In certain embodiments, the disclosed dispersions are employed to form electrodeposited interconnect structures used in semiconductor packaging. Such structures may include microbumps, pillars, vias, redistribution layers, conductive traces, pads, caps or combinations thereof. These structures may serve as electrical, thermal, or mechanical connections between semiconductor dies, interposers, substrates, or printed circuit boards.

[0110] In some embodiments, electrodeposited pillars or vias are formed within patterned openings defined by photoresist or other masking layers over a conductive seed layer. The lateral dimensions, height, and pitch of the structures may be selected based on application requirements. The carbon nanotubes incorporated within the metal matrix may be distributed throughout the thickness of the electrodeposited structure, as described herein, providing composite features with substantially consistent carbon nanotube concentration across their height.

[0111] In certain embodiments, the metal matrix comprises copper or a copper-based alloy, and the electrodeposited structures function as power delivery or signal routing elements. Such copper-based composite structures may exhibit enhanced current-carrying capacity, reduced electromigration susceptibility, or modified thermal behavior relative to comparable structures formed without carbon nanotubes. These embodiments may be particularly suitable for high- density interconnect architectures, advanced node semiconductor devices, or power delivery networks.

[0112] In other embodiments, the metal matrix comprises tin, tin-based alloys, or solder-forming alloys such as tin-silver-copper alloys. In such embodiments, electrodeposited compositestructures may form solder bumps, microbumps, caps, or bonding features used in hybrid bonding, thermal compression bonding, or related assembly processes. Carbon nanotubes embedded within solder-forming matrices may influence mechanical integrity, wetting behavior, thermal response, or current handling characteristics of the resulting structures.

[0113] In some embodiments, electrodeposited composite structures are formed as arrays of repeated features across a substrate. Each feature in the array may exhibit similar structural characteristics due to the use of a common dispersion and electrodeposition process. Such arrays may be used in fine-pitch interconnect applications, three-dimensional integrated circuits, chiplet-based architectures, or heterogeneous integration schemes.

[0114] In certain embodiments, electrodeposited composite structures are formed as continuous layers or traces rather than discrete features. For example, redistribution layers, power planes, conductive coatings, or patterned traces may be formed by electrodeposition of metal matrix composites containing carbon nanotubes. Such structures may be used in semiconductor packaging, printed circuit board fabrication, or other electronic assemblies.

[0115] The representative structures described herein are not limited to semiconductor applications. In additional embodiments, electrodeposited metal matrix composites containing carbon nanotubes are used in non-semiconductor contexts, including printed circuit boards, connectors, bus bars, wires, coatings, or other metal components where enhanced electrical, thermal, or mechanical properties are desired. The dispersions and electrodeposition approaches described herein are applicable across these contexts without requiring fundamental changes to the underlying dispersion quality criteria.

[0116] In some embodiments, the electrodeposited composite structures are subsequently subjected to additional processing steps, such as planarization, polishing, bonding, orencapsulation. Such post-deposition processing does not alter the fact that carbon nanotubes are incorporated into the metal matrix during electrodeposition, and the structural characteristics described herein reflect incorporation during metal growth rather than post-deposition addition.

[0117] The use contexts and representative structures described in this section illustrate how the disclosed dispersions and co-electrodeposition processes may be employed in practical applications. These examples are provided to demonstrate applicability and are not intended to limit the scope of the disclosed embodiments to any particular structure, geometry, or industry.

[0118] Caps and Composite Pillar Structures (Additional Representative Embodiments)

[0119] In certain embodiments, electrodeposited metal matrix composite structures further include caps formed on or over underlying electrodeposited features. Such caps may be used, for example, in composite pillar structures comprising an electrodeposited metal pillar and a cap configured to facilitate bonding, joining, or electrical contact with an opposing structure.

[0120] In some embodiments, an electrodeposited pillar comprises a copper or copper-based metal matrix composite containing embedded carbon nanotubes, and a cap is formed on a distal end of the pillar. The cap may comprise a different metal or metal alloy than the pillar, including solder-forming metals or alloys such as tin, tin-based alloys, or tin-silver-copper alloys. In other embodiments, the cap comprises copper, a copper alloy, or another electrodepositable metal selected based on application requirements.

[0121] Caps may be formed by electrodeposition, plating, immersion processes, or other metal deposition techniques compatible with the underlying pillar structure. In certain embodiments, carbon nanotubes are incorporated within the cap material, either by co-electrodeposition with the cap metal or by deposition of a cap onto an underlying structure that already containsembedded carbon nanotubes. In other embodiments, the cap is substantially free of carbon nanotubes.

[0122] In some embodiments, the cap functions as a bonding interface, diffusion layer, wetting layer, or compliant layer during subsequent assembly operations. For example, solder-based caps may facilitate bonding between opposing pillars, pads, or substrates, while copper-based caps may serve as contact or interface regions for hybrid bonding or metallurgical joining processes. The presence or absence of carbon nanotubes in the cap may be selected independently of the composition of the underlying pillar.

[0123] Composite structures comprising electrodeposited pillars and caps may be formed as individual features or as arrays of repeated features across a substrate. Such composite pillar- and-cap structures may be used in semiconductor packaging, including microbump arrays, pillarbased interconnects, hybrid bonding structures, or other fine-pitch interconnection schemes. The use of caps in these embodiments is illustrative and not required in all implementations of the disclosed dispersions and electrodeposition processes.

[0124] Method Embodiments and Process Variations

[0125] Embodiments described herein further include methods of co-depositing carbon nanotubes and a metal matrix using electrodeposition processes. The method embodiments described in this section illustrate representative process flows and variations that may be used with the disclosed dispersions and structures and are not intended to limit the scope of the invention.

[0126] In certain embodiments, a method comprises providing a dispersion of carbon nanotubes in an electrodeposition bath, as described herein. The electrodeposition bath contains metal ionscapable of electrochemical reduction and may further include additives, solvents, or other components suitable for electrodeposition of a selected metal or metal alloy.

[0127] A conductive substrate or portion thereof is positioned in the electrodeposition bath and serves as a cathode. Upon application of an electrical potential between the cathode and an anode, metal ions are electrochemically reduced at the cathode surface, forming a growing metal deposit. Concurrently, carbon nanotubes dispersed within the electrodeposition bath are transported toward the cathode and incorporated into the growing metal matrix during deposition.

[0128] In some embodiments, the dispersion is allowed to remain quiescent or substantially quiescent for a defined period prior to electrodeposition, such that dispersion stability may be assessed before application of the electrical potential. In certain embodiments, stability of the dispersion for at least about one hour prior to electrodeposition contributes to incorporation of carbon nanotubes with a substantially consistent concentration across a thickness of the deposited metal matrix.

[0129] In certain embodiments, incorporation of carbon nanotubes occurs through electrophoretic transport, electrostatic attraction, field-assisted migration, convective transport, adsorption, or combinations thereof, occurring concurrently with electrochemical reduction of metal ions. The relative contribution of these mechanisms may vary depending on dispersion composition, functionalization strategy, bath chemistry, and electrical parameters.

[0130] In some embodiments, electrical parameters such as current density, applied voltage, waveform shape, pulse duration, reverse-pulse intervals, or modulation frequency are selected to influence metal deposition kinetics and carbon nanotube incorporation behavior. Pulse plating,reverse-pulse plating, or other modulated current techniques may be employed to control grain growth, surface morphology, or incorporation rates.

[0131] In certain embodiments, the method includes forming composite structures such as pillars, vias, redistribution layers, or other features by electrodeposition within patterned openings defined on the substrate. In additional embodiments, the method includes forming caps on electrodeposited features, including solder-based or metal-based caps, as described above. Cap formation may occur in the same electrodeposition bath, in a subsequent electrodeposition bath, or using a different deposition technique.

[0132] In some embodiments, the method results in incorporation of carbon nanotubes into the metal matrix exclusively during electrochemical reduction of metal ions. Embodiments described herein exclude methods in which carbon nanotubes are incorporated into metal structures by post-deposition infiltration, mechanical mixing, sintering, evaporation, sputtering, or other nonelectrochemical processes.

[0133] Electrodeposition Media and Metals

[0134] In some embodiments, the electrodeposition bath medium is aqueous, non-aqueous, or mixed. Non-aqueous media may include ionic liquids or deep eutectic solvents formed from Lewis acids and Lewis bases, BrOns ted acids and Bronsted bases, or combinations thereof. The electrodeposition bath medium may include additives such as suppressors, levelers, accelerators, or wetting agents.

[0135] In certain embodiments, electrodeposition is used to deposit a metal matrix comprising copper, tin, silver, nickel, cobalt, gold, palladium, indium, bismuth, zinc, iron, tungsten, molybdenum, or alloys thereof, including solder-forming alloys such as tin-based or tin-silver- copper alloys.

[0136] Co-Electrodeposition and Resulting Structures

[0137] In some embodiments, co-electrodeposition results in metal matrix composites in which carbon nanotubes are incorporated with a process-defined, substantially consistent carbon nanotube concentration across a thickness of the deposited metal. In other embodiments, graded or spatially varying distributions may be produced by adjusting dispersion characteristics or electrodeposition conditions.

[0138] In certain embodiments, the electrodeposited metal matrix composite forms structures such as microbumps, pillars, vias, redistribution layers, conductive traces, coatings, or caps, including composite pillar-and-cap structures used in semiconductor packaging or related applications.

[0139] An embodiment of composition for the plating bath may comprise:

[0140] The method embodiments described herein may be applied to a variety of electrodeposition configurations, including wafer-level processing, panel-level processing, or batch plating systems, and may be adapted for semiconductor packaging, printed circuit board fabrication, or other metal deposition applications.

Claims

CLAIMSWhat is claimed and desired to be secured by Letters Patent is:

1. A composition of matter suitable for use in an electrodeposition bath, comprising: a plurality of carbon nanotubes in a dispersion; wherein carbon nanotube agglomerates or clusters having a characteristic dimension greater than 10 micrometers constitute less than 1% by weight of the total carbon nanotubes present in the dispersion; wherein the dispersion remains stable for at least one hour without visible sedimentation or an increase in carbon nanotube agglomerates or clusters having a characteristic dimension greater than 10 micrometers when present in an electrodeposition bath; and wherein the dispersion further comprises a medium configured to facilitate an electrodeposition of a metal matrix comprising a metal or metal alloy.

2. The dispersion of claim 1, wherein the metal matrix comprises copper, tin, silver, nickel, cobalt, gold, palladium, indium, bismuth, zinc, iron, tungsten, molybdenum, or alloys thereof used in semiconductor packaging or electronic interconnect fabrication.

3. The dispersion of claim 1, wherein a portion of the plurality of carbon nanotubes comprise single-wall carbon nanotubes, double-wall carbon nanotubes, few-wall carbon nanotubes, multiwall carbon nanotubes, or combinations thereof, having an aspect ratio of 20:1 to 5000:1, andwherein the carbon nanotubes constitute a majority of all carbon nanotubes present on a number basis.

4. The dispersion of claim 1, wherein an outer surface of at least a portion of the carbon nanotubes is modified to promote dispersion in the electrodeposition medium and to promote electrochemical incorporation and interfacial bonding with an electrodeposited metal matrix using covalent functionalization, non-covalent functionalization, or combinations thereof.

5. The dispersion of claim 4, wherein the outer surface of at least a portion of the carbon nanotubes is modified with functional groups comprising oxygen or nitrogen selected from hydroxyl, carbonyl, carboxylate, graphitic (quaternary) nitrogen, pyridinic nitrogen, pyrrolic nitrogen, amine, amide, azine, nitrile, or combinations thereof that associate with metal ions.

6. The dispersion of claim 4, wherein interfacial bonding with the electrodeposited metal matrix is enhanced by attachment of an element or combination of elements on an exterior surface of at least a portion of the carbon nanotubes, the elements being selected from cobalt, nickel, palladium, platinum, rhodium, or combination alloys thereof.

7. The dispersion of claim 6, wherein the element is present as a coating, partial coating, discontinuous coating, nanoparticle decoration, substitutional incorporation of heteroatoms into a carbon lattice, or interfacial layer on sidewalls of at least a portion of the carbon nanotubes.

8. The dispersion of claim 1, wherein the medium of the electrodeposition bath is selected from a class of liquids comprising an aqueous medium, an ionic liquid, or a deep eutectic solvent,wherein the deep eutectic solvent comprises a eutectic mixture formed from a Lewis acid and a Lewis base, a Brpnsted acid and a BrOns ted base, or combinations thereof.

9. The dispersion of claim 1, further comprising a surfactant selected from a class comprising anionic, cationic, non-ionic, zwitterionic surfactants, or combinations thereof.

10. The dispersion of claim 1, wherein upon electrodeposition of a metal matrix from the dispersion, a plurality of carbon nanotubes are incorporated within the metal matrix with a process-defined, substantially consistent carbon nanotube concentration across a thickness of the electrodeposited metal matrix.

11. The dispersion of claim 10, wherein the metal matrix comprises tin, a tin-based alloy, or a tin-silver-copper alloy.

12. The dispersion of claim 10, wherein the metal matrix comprises copper, or a copper-based alloy.

13. The dispersion of claim 1, wherein at least a portion of the carbon nanotubes are further functionalized with a magnetic material comprising iron, cobalt, nickel, a ferrite, or combinations thereof.

14. A method of co-depositing carbon nanotubes and a metal matrix, comprising: providing the dispersion of claim 1 in an electrodeposition bath; interfacing at least a portion of a conductive substrate as a cathode within the electrodeposition bath; andapplying an electrical potential to electrochemically reduce metal ions onto the substrate while simultaneously incorporating the discrete carbon nanotubes into a growing metal matrix.

15. The method of claim 14, wherein stability of the dispersion for at least one hour prior to electrodeposition results in incorporation of the discrete carbon nanotubes into the metal matrix with a process-defined substantially uniform concentration through a thickness of the deposited metal matrix.

16. The method of claim 14, wherein the discrete carbon nanotubes are surface-functionalized to exhibit electrochemical affinity for metal ions such that metal nucleation occurs on surfaces of the carbon nanotubes during electrochemical reduction.

17. The method of claim 14, wherein incorporation of the discrete carbon nanotubes occurs through electrophoretic transport, electrostatic attraction, field-assisted migration, or combinations thereof during electrochemical reduction, and wherein the discrete carbon nanotubes are incorporated into the metal matrix exclusively during electrochemical reduction and not by post-deposition infiltration, mechanical mixing, sintering, evaporation, or sputtering.

18. The method of claim 14, wherein applying the electrical potential comprises pulse plating, reverse-pulse plating, or modulated current density selected to control a rate of carbon nanotube incorporation relative to metal deposition.

19. The method of claim 14, wherein the dispersion comprises the magnetic-functionalized discrete carbon nanotubes of claim 13, and wherein the resulting metal matrix composite is configured to generate localized heating when exposed to an alternating magnetic or induction field.

20. The method of claim 14, wherein the metal matrix is deposited as an interconnect structure selected from a microbump, pillar, via, redistribution layer, or conductive trace.

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