Carbon nanotube-based conductive connections for integrated circuit devices

Electrical connection in an integrated circuit arrangement is facilitated with carbon nanotubes. According to various example embodiments, a carbon nanotube material (120, 135) is associated with another material (130, 125) such as a metal. The carbon nanotube material facilitates the electrical connection between different circuit components.

The present invention is directed to integrated circuit devices and approaches and, more particularly, to integrated circuit connectors employing nanotube material.

Technological advances in the semiconductor industry have permitted dramatic increases in circuit density, complexity and functionality. To meet the needs of such high-density and high functionality, increased numbers of external electrical connections are implemented within circuit chips, on the exterior of the chips and on the exterior of the semiconductor packages which receive the chips and for connecting packaged devices to external systems, such as a printed circuit board. With these and other varied applications, many different types of electrical connectors are used.

Some connectors are implemented internally (e.g., within a chip or package substrate) for connecting different circuit components and/or connecting circuit components to external connections, such as pads. For example, interconnects or traces are used to connect circuit components on a particular level in a semiconductor device. Vias are used to connect different levels in the device, and to make connection with external connectors (e.g., solder ball pads).

Externally-implemented connectors electrically connect different circuit components such as bonded chips, flip-chips, package substrates, ball grid array (BGA) substrates and pin grid array (PGA) substrates. These electrical connections facilitate the transfer of signals between the circuit components for a variety of purposes.

Each of these applications benefit from various circuit connector characteristics such as strength, electrical conductivity (and resistivity), size, stiffness and thermal conductivity. Other factors such as cost, manufacturability and reliability are also important for these applications. Achieving desirable circuit connector characteristics has been challenging, however, while meeting such other factors. In addition, connector materials and approaches that meet certain desirable characteristics often sacrifice other characteristics. Furthermore, the above-discussed advances in the semiconductor industry often demand higher performance than previous approaches have provided.

These and other difficulties present challenges to the implementation of circuit substrates for a variety of applications.

Various aspects of the present invention involve circuit connectors and approaches with integrated circuits and other devices. The present invention is exemplified in a number of implementations and applications, some of which are summarized below.

According to an example embodiment, an integrated circuit arrangement includes a carbon nanotube-based composite conductor that electrically connects electrical components in an integrated circuit and/or between integrated circuit devices.

In another example embodiment, an integrated circuit arrangement includes an integrated circuit die coupled to a package. A carbon nanotube-based composite conductor electrically connects electrical components of the integrated circuit die-package arrangement. The composite conductor includes carbon nanotube material with another material in one or more of a variety of arrangements such as a coated carbon nanotube or coated nanotubes, nanotubes coating another material or a mixture of carbon nanotube material in a base type material.

In another example embodiment of the present invention, an integrated circuit arrangement includes an integrated circuit substrate with a carbon nanotube-based composite interconnect therein. The interconnect electrically connects electrical components of the integrated circuit arrangement via carbon nanotube material associated with a non-carbon nanotube material. The carbon nanotube material may include, for example, carbon nanotubes and/or carbon nanotube pieces or dust mixed with a compound that holds the carbon nanotubes.

Another example embodiment is directed to an integrated circuit bondwire connector arrangement for connecting integrated circuit components. The bondwire connector arrangement includes a bondwire including a composite of metal and carbon nanotube-based material extending along a length of the bondwire. The carbon nanotube-based material is arranged for conducting electricity between integrated circuit components, such as between an integrated circuit die and a substrate or other external component.

A bondwire arrangement is manufactured in accordance with another example embodiment of the present invention. A metal core material having a length is provided (e.g., manufactured and/or otherwise presented for processing). Carbon nanotubes are coupled onto the metal core material along the length of the metal core material. Electric conduction is thus facilitated along the bondwire and, e.g., in the carbon nanotubes at an outer portion of the bondwire.

In another example embodiment, a bondwire arrangement is manufactured by first providing (e.g., manufacturing, growing or otherwise presenting for processing) a carbon nanotube core material having a length. Metal is coupled onto the carbon nanotube core along the length of the carbon nanotube core material. Electric conduction is thus facilitated along the bondwire and, e.g., in the carbon nanotube core, with the outer metal enhancing the strength of the bondwire.

In another example embodiment of the present invention, an integrated circuit leadframe arrangement includes a carbon nanotube composite material. The arrangement includes a leadframe having a combination of metal and carbon nanotube material and arranged for electrically coupling an external circuit component or circuit components to an integrated circuit die.

A carbon nanotube-based interconnect is manufactured in accordance with another example embodiment of the present invention. A trench is etched in a substrate and a portion of the trench is filled with a metal material. Carbon nanotubes are coupled to a surface of the metal material. In some applications, the carbon nanotubes are coupled to (or grown from) an upper surface of the metal material after the metal is grown. In other applications, additional metal material is formed in the trench over and/or on the grown carbon nanotube material. In still other applications, carbon nanotube material is first deposited into the trench and the metal material is filled in the trench and over and/or on the carbon nanotube material. Additional carbon nanotubes are optionally formed in the trench over and/or on the metal filled over and/or on the carbon nanotube material.

The above summary of the present invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The figures and detailed description that follow more particularly exemplify these embodiments.

The present invention is believed to be applicable to a variety of circuits and approaches, and in particular, to integrated circuit type approaches involving electrical conductors implemented for making connection between different components in a circuit package. While the present invention is not necessarily limited to such applications, an appreciation of various aspects of the invention is best gained through a discussion of examples in such an environment.

According to an example embodiment of the present invention, an integrated circuit connector includes a carbon nanotube-metal combination. The connector includes carbon nanotubes with a metal in a conductive arrangement, and facilitates the electrical coupling of different circuits (e.g., an integrated circuit and a package to which it is connected or circuit components on a circuit board). The carbon nanotubes facilitate electrical connection between the different circuit components, such as between a die and a package substrate. Furthermore, the carbon nanotubes enhance connector characteristics such as strength, conductivity, heat transfer and others desirably possessed by the connector.

In another example embodiment of the present invention, a nanotube-metal composite bondwire is used to electrically couple a chip to a package substrate. The nanotube-metal composite bondwire is implemented with a multitude of carbon nanotubes and a conductive metal in different arrangements, depending upon the implementation. In one instance, the carbon nanotubes are formed as a core of the bondwire, with a metal coating generally surrounding the carbon nanotube core. In another instance, carbon nanotubes are coated around a metal core. In still another instance, carbon nanotubes are mixed with a metal to form the composite bondwire.

A leadframe structure includes an outer carbon nanotube-based region surrounding a metal core, according to another example embodiment of the present invention. An integrated circuit die is coupled to a package substrate, and the leadframe facilitates the electrical coupling of the integrated circuit die to other circuit components. The die, package substrate and at least a portion of the leadframe are encapsulated with a mold type material.

In another example embodiment of the present invention, a nanotube connector-type material is arranged for an on-chip connector to which external circuits can be connected. The on-chip connector may be implemented, for example, with an interconnect, or trace, type of connector as may be applicable, e.g., to a region near a surface of the chip. The connector-type material is implemented in a variety of arrangements including, e.g., a carbon nanotube core surrounded by a metal, a metal core surrounded by a carbon nanotube material or a mixture of carbon nanotube material and other material such as metal or semiconducting material.

FIG. 1Ashows a cross-sectional view of a carbon-nanotube enhanced electrical connector100, according to an example embodiment of the present invention. The connector100includes a carbon nanotube core120surrounded by a conductive metal region130, and extending a length (represented by “L” and shown truncated) selected to meet the particular application. The carbon nanotube core120includes one or more carbon nanotubes arranged for conducting along a length of the connector100. The nanotube or nanotubes in the core120are formed in various arrangements to meet the needs of the particular application. For example, bundled chains of carbon nanotubes, nanotube matrices or other arrangements that facilitate electrical conductivity can be implemented with the core120.

The surrounding metal region130is implemented with different types of metals, such as gold, aluminum, copper or alloys thereof, depending upon the application and available material. In one application, metal is plated and/or sputtered onto an existing single carbon nanotube, nanotube rope or bundle of nanotubes. In general, the metal region130extends the length of the connector100and, correspondingly, surrounding the carbon nanotube core120along its entire length.

In one implementation, the connector100is used in wirebonding (bondwire) applications. Wirebonding provides, e.g., electrical connection between an integrated circuit die, or chip, with connectors (e.g., leads) of a package substrate. One end of the connector100is coupled (bonded) to the integrated circuit, and another end of the connector is bonded to the connectors of the package substrate. This arrangement of a carbon nanotube core120surrounded by a metal material130facilitates relatively high current bondwire applications. Further, the carbon nanotube core120facilitates the implementation of a relatively small diameter (across the cross-section of the connector100as shown inFIG. 1A) while maintaining desirable characteristics such as strength and conductivity, typically associated with larger (non-carbon nanotube) wires.

FIG. 1Bshows a cross-sectional view of a carbon-nanotube enhanced electrical connector105, according to another example embodiment of the present invention. The connector105has a conductive metal core125coated with carbon nanotube material135. As with the connector100shown inFIG. 1A, the connector105extends a length (represented by “L” and shown truncated) selected to meet the particular application.

The metal core125includes one or more types of metals such as gold, aluminum, copper or alloys thereof, depending upon the application and available material. In some applications, the metal core125is conventional bondwire. In other implementations, is a variation on conventional bondwire that is amenable to association with the coated carbon nanotube material135. In still other applications, the metal core125includes carbon nanotube material mixed with metal.

The surrounding carbon nanotube material135generally extends the length “L” of the connector105, and is arranged for conducting along the length. Carbon nanotubes in the surrounding carbon nanotube material135are formed in various arrangements to meet the needs of the particular application. For example, bundled chains of carbon nanotubes, nanotube matrices or other arrangements that facilitate electrical conductivity can be implemented with the surrounding carbon nanotube material135.

The carbon nanotube material135is associated with the metal core125in one or more of a variety of manners, depending upon the application. In one implementation, carbon nanotubes are painted on the outside of the metal core125using conventional and/or electrostatic paint processes. Another implementation involves a squeegee approach, wherein carbon nanotubes are transferred to an interconnect (in a pattern) by, e.g., forcing a material through open areas of a screen using a wiping action of a soft squeegee. In another implementation, the metal core125is softened by heating and the carbon nanotube material135is coupled thereto by contact with the softened metal core. As the metal core cools, the carbon nanotube material135is coupled thereto.

FIG. 2shows an integrated circuit arrangement200with a carbon nanotube-based leadframe, according to another example embodiment of the present invention. The arrangement200includes an integrated circuit die210coupled to a package substrate220. A leadframe is shown in cross-section, with portions240and250respectively coupled to the integrated circuit die210.

An encapsulating material230(i.e., mold material) seals the integrated circuit die210, the package substrate220and portions of the leadframe coupled to the integrated circuit die. The shown arrangement and geometry of the encapsulating material230is exemplary; various shapes, arrangements, thicknesses and other characteristics of the encapsulating material230can be implemented for a variety of purposes.

The leadframe includes a carbon nanotube coating around a metal-type core. Referring to leadframe portion240, metal-type core242is surrounded by a carbon nanotube coating244, with the metal-type core coupled to the integrated circuit die210via a conductive connector212. Similarly, leadframe portion240includes a metal-type core252surrounded by carbon nanotube material254, with the metal-type core coupled to the integrated circuit die210via a conductive connector214.

The carbon nanotube material244and254is associated with the metal-type material242and252in a variety of manners. For instance, conventional and/or electrostatic painting approaches are used in some applications for coating the carbon nanotube material244and254onto the metal-type material242and252. In addition, a soft-metal bonding approach, similar to that discussed above in connection withFIG. 1B, is used in other applications.

In some embodiments, carbon nanotube material is associated with metal-type material using a mixing approach. In one application, carbon nanotubes are embedded in the metal-type core242and252. In other applications, the carbon nanotube material244and254includes a carbon nanotube-metal combination with, e.g., carbon nanotubes embedded in metal. In still other applications, the leadframe portions240and250are each a continuous piece, with an outer portion thereof, respectively portions244and254, having carbon nanotubes embedded therein.

In other embodiments, carbon nanotubes are grown from the metal-type core242and252. In many applications, the growth generally involves the introduction of a carbon-containing gas to the metal-type core242and252, with carbon from the gas forming the nanotubes on the core. In some instances, the carbon nanotube growth involves the use of a catalyst type material on the metal-type core242and252.

In another embodiment, a coating layer is formed at (e.g., on and/or near) an outer surface of the carbon nanotube material244and254. In one implementation, a solder-type metal layer or layers are formed on the surface of the carbon nanotube material244and254. Soldering metal layers, such as nickel and tin, can be formed directly on the carbon nanotube material244and254.

As with the above discussion, the integrated circuit arrangement200is applicable to many different circuit applications. In one embodiment, the integrated circuit arrangement200is adapted for use in high frequency applications, such as RF microwave applications. The carbon nanotube material244and254is arranged on the periphery of the leadframe as shown inFIG. 2, such that current travels through the periphery (relative, e.g., to the metal-type core242and252). In another embodiment, the circuit arrangement200is implemented in applications benefiting from high-strength leadframe components, using a small leadframe (relative to metal leadframes), reinforced by carbon nanotube material.

FIG. 3Ashows a cross-sectional view of a composite carbon nanotube-based connector310with carbon nanotube outer portions thereof, according to another example embodiment of the present invention. The connector310, as well as those discussed below in connection withFIGS. 3B and 3C, is applicable for use with one or more of BGA, PCB, or other substrate interconnect applications. The nanotube-based connector300includes a core metal layer312with carbon nanotube material310and314on outer portions of the connector. In one application, the carbon nanotube material is layered on one side, or surface, of the core metal layer312. In other applications (as shown inFIG. 3Aby way of example), the carbon nanotube material is generally arranged on all sides of the metal core312.

FIG. 3Bshows a cross-sectional view of a composite carbon nanotube-based connector320, similar to the connector300shown inFIG. 3Aand having a carbon nanotube core, according to another example embodiment of the present invention. In this embodiment, a core carbon nanotube layer332has a metal layer on one or more outer portions thereof. The particular arrangement of the metal layer inFIG. 3Bshows portions330and334above and below a substantial portion of the carbon nanotube layer332. With bothFIG. 3AandFIG. 3B, three layers are shown, including a middle layer (312,332) with top (310,330) and bottom (314,334) layers; however, in various implementations, one of the shown top and bottom layers is omitted.

FIG. 3Cshows a cross-sectional view of a composite carbon nanotube-based connector340, similar to the connectors shown inFIGS. 3A and 3Band having a mixture of carbon nanotubes, according to another example embodiment of the present invention. The connector340includes a mixture of carbon nanotubes, with a representative nanotube352shown, in another material350such as a metal, epoxy, resin or semiconducting material. Carbon nanotubes, carbon nanotube dust and/or combinations of carbon nanotubes are used with the connector340, depending upon the application. The mixture of carbon nanotubes with other materials conducts electricity along the connector340and with conductive connectors coupled thereto (e.g., for electrical coupling with external circuits).

In each of the above embodiments discussed in connection withFIGS. 3A-3C, the carbon nanotubes can be mixed and/or otherwise associated with a variety of materials. In applications involving conductive metals, the carbon nanotubes can be associated with copper, aluminum or gold as core layers, outer layers and/or mixtures with the carbon nanotubes. In other applications, the carbon nanotubes are mixed with materials, or implemented with substrate materials, such as ceramic or organic substrate materials (e.g., resin or epoxy, such as BT (Bismaleimide Triazine) and/or FR4).

The connectors300,320and340are manufactured using one or more of a variety of approaches. In one implementation, metal (e.g., copper) interconnects are coupled with carbon nanotubes, with a metal layer formed first and nanotubes subsequently coupled thereto using an approach such as painting, a squeegee approach or others discussed above. In some applications, the carbon nanotubes are mixed with a metal and painted onto a metal layer of a connector. In another implementation, a carbon nanotube layer is first formed and metal is subsequently coupled thereto using a process such as sputtering.

Where more than one outer layer is desirable (as shown inFIGS. 3A and 3B), a third layer is subsequently implemented. Where the carbon nanotubes are at the core of the interconnect as withFIG. 3B, a first portion of the metal layer is formed at about half thickness, the carbon nanotubes are coupled thereto and another metal layer is coupled on a side of the carbon nanotubes that is opposite the first half layer. Where the metal layer is at the core of the interconnect as withFIG. 3A, the metal layer is formed at a full desired thickness, with nanotubes being coupled thereto on opposite sides of the metal layer. Alternately, a nanotube layer is first formed, with a metal layer formed thereon and a further carbon nanotube layer (if desired) formed on top of the metal layer. These layers may, for example, be formed on or in a surface layer of an integrated circuit die.

FIG. 4Ashows a cross-sectional view of a circuit substrate device400employing carbon nanotube-including interconnects, according to another example embodiment of the present invention. The circuit substrate device400includes a plurality of connectors, including interconnects420,430,440and450, in a substrate-type material410. Interconnects420and430are coupled to one another by via425, and interconnects440and450are coupled to one another by via445. The substrate-type material410includes one or more of a variety of materials, such as epoxy, resin, ceramic, semiconducting materials and others.

The interconnects420,430,440and450are formed using approaches as discussed in connection withFIGS. 3A-3C, with each interconnect formed as the substrate-type material410is built up.FIGS. 4B-4Eshow one example approach for manufacturing the circuit substrate device400. In this regard, reference numbers used in connection withFIG. 4Aare used in connection withFIGS. 4B-4Efor brevity and by way of example.

Beginning withFIG. 4B, a trench451is formed in a substrate410and having a length (L), depth (D) and width (i.e., into the page, relative to the cross-section) selected to fit the particular application to which the device400is applied. InFIG. 4C, the trench451has been filled with a lower layer452. Where carbon nanotubes are to be on the outer portion of the interconnect being formed in the trench451, the first layer452is a carbon nanotube layer. Where carbon nanotubes are to be the core of the interconnect formed in the trench451, the first layer452is a metal.

After the first layer452is formed, a second layer453is formed as shown inFIG. 4Dand having a composition relative to the first layer approach discussed above. Specifically, when the interconnect being formed in the trench451is to have carbon nanotubes on the outer portion thereof, the first layer452is a carbon nanotube layer and the second layer453is a metal layer. Conversely, when the first layer452is a metal layer, with the interconnect being formed having a carbon nanotube core, the second layer453is a carbon nanotube layer for the core.

After the first (452) and second (453) layers are formed, a third layer454is formed on the second layer as shown inFIG. 4E. The first (452), second (453) and third (454) layers together implement an interconnect, such as interconnect450shown inFIG. 4A. After the third layer is formed, additional substrate material411can be formed over the interconnect as shown by dashed lines, and further interconnects can be formed using trenches in the additional substrate material in a similar manner.

In most implementations, the composition of the third layer454matches that of the first layer452. For instance, where the interconnect being formed in the trench451is to have a metal core, the first (452) and third (454) layers are carbon nanotube layers, with the second layer453being the metal core. Where the interconnect being formed in the trench452is to have a carbon nanotube core, the first (452) and third (454) layers are metal layers, with the second layer453being the carbon nanotube core.

In some implementations, the third layer454is a material having a composition that does not necessarily match the composition of the first layer452. For example, the third layer454may include a carbon nanotube mixture, where the second core layer453can be either metal or carbon nanotube-based. The carbon nanotube mixture may include, for example, a carbon nanotube-metal mixture or a mixture of carbon nanotubes and a semiconducting or non-conducting material. As another example, the third layer454can be an insulating layer. Such an insulating layer approach may be applicable, for example, wherein electrical insulation from additional circuits to be formed over the interconnect is desirable.

The various embodiments described above and shown in the figures are provided by way of illustration only and should not be construed to limit the invention. Based on the above discussion and illustrations, those skilled in the art will readily recognize that various modifications and changes may be made to the present invention without strictly following the exemplary embodiments and applications illustrated and described herein. For example, the carbon nanotubes may be implemented with material different from, or in addition, to, carbon, such as Boron. The carbon nanotubes include one or more of a variety of nanotubes in various implementations, such as single-walled carbon nanotubes (SWNTs), multi-walled carbon nanotubes (MWNTs), carbon nanotube matrices, carbon nanotube ropes and carbon nanotube dust (i.e., finely ground carbon nanotubes). In addition, the conductive-type materials discussed by way of example may be implemented with a multitude of different types of materials, used alone and/or in conjunction with one another or with the above-described materials. Such modifications and changes do not depart from the true spirit and scope of the present invention.