JPWO2007111107A1 - Device structure of carbon fiber and manufacturing method thereof - Google Patents

Abstract

A technology for increasing the density of carbon nanotubes is provided. An aggregate structure of carbon-based fibers is an aggregate structure of the carbon-based fibers composed of a plurality of carbon-based fibers, and the density of the carbon-based fibers at one end and the carbon-based at the other end It consists of the aggregate | assembly of the said carbonaceous fiber in which the said carbonaceous fiber from which the density of a fiber differs was arranged in the length direction.

Description

  The present invention relates to a carbon fiber device structure and a method for producing the same.

Carbon nanotubes (Carbon Nano Tubes (CNT)) are excellent in electrical conductivity, thermal conductivity, and mechanical properties, and thus have been tried to be applied in various fields. Therefore, applications as electronic devices, heat dissipation devices, LSI (Large Scale Integration) wiring, transistor channels, heat dissipation bumps, and electron emission sources are expected. In particular, oriented and grown carbon nanotubes are expected to be used for wiring and heat dissipation. As a method for aligning and growing carbon nanotubes, the chemical vapor deposition (CVD) method is currently mainstream, and CNTs are generally grown directly on a desired substrate. Examples of methods for aligning and growing carbon nanotubes include a thermal CVD method, a plasma CVD method, and a hot filament CVD method. Further, as a method of obtaining carbon nanotubes close to the closest packing, there is a thermal decomposition method of SiC.
JP 2004-185985 A Special Table 2002-530805 gazette Japanese Patent No. 3183845 JP 2002-329723 A A. Bezyadin, Outside, Nature, Vol. 386, 1997, p. 474 T. Iwai, et al., IEEE IEDM Tech. Digest, 2005, p. 265 AG Rinzler, Outside, Science, Vol. 269, 1995, p. 1550

  Many of the applications of carbon nanotubes use carbon nanotubes that are oriented and grown on a substrate. Examples of application of carbon nanotubes include LSI wiring and heat dissipation bumps. When carbon nanotubes are applied, it is desirable to grow carbon nanotubes with the highest possible density on the substrate from the viewpoints of reducing wiring resistance and improving heat dissipation efficiency. However, carbon nanotubes oriented and grown by conventional methods have a low density. Also, some of the adjacent carbon nanotubes are in contact, but not all of them are in contact. That is, there is a problem that an interval between adjacent carbon nanotubes is increased. Growth of high-density carbon nanotubes is generally not easy, and the volume occupation ratio of carbon nanotubes oriented and grown by a conventional method is about 10%. Moreover, the thermal decomposition temperature of SiC is 1200-2200 degreeC in heat processing temperature. For this reason, it becomes difficult to select a substrate and process matching with other devices. An object of the present invention is to provide a technique for increasing the density of carbon nanotubes.

  The present invention employs the following means in order to solve the above problems. That is, the aggregate structure of the carbon-based fibers of the present invention is an aggregate structure of the carbon-based fibers composed of a plurality of carbon-based fibers, and the density of the carbon-based fibers at one end and the other end It consists of the aggregate | assembly of the said carbonaceous fiber in which the said carbonaceous fiber in which the density of the said carbonaceous fiber in a part differs was arranged in the length direction. According to the present invention, the density of both ends of the aggregate of carbon-based fibers is different at one end and the other end, and the carbon-based at the other end is higher than the density of the carbon-based fiber at one end. Fiber density is high.

  Moreover, the aggregate structure of the carbon-based fibers of the present invention may include a substance different from the carbon-based fibers between the aggregates of the adjacent carbon-based fibers. According to the present invention, the density of both ends of the carbon-based fiber aggregate is different between one end and the other end. Therefore, it becomes possible to have a substance different from the carbon fiber between the aggregates of adjacent carbon fibers. As a result, the aggregate structure of carbon-based fibers according to the present invention can combine an aggregate of carbon-based fibers and a substance different from the carbon-based fibers.

  Moreover, the aggregate structure of the carbon-based fibers of the present invention may have a space between the aggregates of the adjacent carbon-based fibers. According to the present invention, the density of both ends of the carbon-based fiber aggregate is different between one end and the other end. Therefore, there is a space between adjacent carbon-based fiber aggregates. As a result, the aggregate structure of carbon-based fibers of the present invention can effectively utilize the space between the aggregates of adjacent carbon-based fibers.

  In the carbon-based fiber aggregate structure of the present invention, adjacent carbon-based fiber aggregates may be arranged in different directions. According to the present invention, the density of both ends of the carbon-based fiber aggregate is different between one end and the other end. Therefore, the carbon-based fiber aggregates can be arranged in different directions between adjacent carbon-based fiber aggregates. As a result, the aggregate structure of carbon-based fibers of the present invention can combine an aggregate of carbon-based fibers and an aggregate of carbon-based fibers arranged in different directions.

  In the carbon-based fiber aggregate structure of the present invention, the carbon-based fibers at the other end, which is higher than the density of the carbon-based fibers at one end, are in close contact with each other. It may be formed. According to the present invention, the density of both ends of the aggregate of carbon-based fibers differs between one end and the other end, and the carbon-based fibers are formed in close contact with each other. As a result, by forming the carbon-based fibers in close contact with each other, the density of the carbon-based fibers at the other end can be made higher than the density of the carbon-based fibers at one end.

  In the carbon-based fiber aggregate structure of the present invention, one end is bonded to the package substrate, and the other end that is higher in density than the carbon-based fiber at one end is a semiconductor. It may be joined to the element.

  In the aggregate structure of carbon-based fibers of the present invention, the carbon-based fibers may be hollow. Furthermore, in the aggregate structure of carbon-based fibers of the present invention, the carbon-based fibers may be carbon nanotubes. In the aggregate structure of carbon-based fibers of the present invention, the carbon-based fibers may be carbon nanofibers. Furthermore, in the aggregate structure of carbon-based fibers of the present invention, the substance different from the carbon-based fibers may be any one of a dielectric, an organic substance, a metal, and an insulator.

  The method for producing an aggregate structure of carbon-based fibers according to the present invention includes a step of growing an aggregate of carbon-based fibers in which carbon-based fibers are arranged in a length direction in a substantially vertical direction from a substrate surface; And a dense process for densely gathering one end in the length direction of the aggregate. According to the present invention, one end in the length direction of the aggregate of carbon-based fibers can be densely packed. Therefore, it becomes possible to manufacture an aggregate structure of carbon-based fibers having different densities at one end and the other end.

  The method for producing an aggregate structure of carbon-based fibers according to the present invention includes a step of growing the aggregate of carbon-based fibers in which carbon-based fibers are arranged in a length direction in a substantially vertical direction from the substrate surface of the first substrate; A dense step of densely gathering one end in the length direction of the aggregate of carbon-based fibers, and the other end in the length direction of the aggregate of carbon-based fibers are brought into close contact with the substrate surface of the second substrate. A step of peeling the aggregate of carbon fibers grown on the substrate surface of the first substrate from the substrate surface of the first substrate, and the other end in the length direction of the aggregate of carbon-based fibers. A compacting process for compacting the parts. According to the present invention, both ends in the length direction of the carbon-based fiber aggregate can be densely packed.

  Further, in the method for producing a carbon fiber aggregate structure according to the present invention, the dense step includes impregnating the carbon fiber aggregate with a solvent containing an adhesion substance different from the carbon fiber, and the solvent. And a step of evaporating. In the method for producing an aggregate structure of carbon-based fibers according to the present invention, the dense step includes the step of impregnating the aggregate of carbon-based fibers with the solvent, and the aggregate of carbon-based fibers and the solvent are dried. It may have a process to make.

  In the method for producing an aggregate structure of carbon-based fibers according to the present invention, the solvent may be selected from the group consisting of N, N-dimethylformamide, dichloroethane, isopropyl alcohol, methanol, and ethanol. In the method for producing an aggregate structure of carbon-based fibers of the present invention, the solvent may contain a surfactant or a functional polymer.

  The wiring formation method for a semiconductor substrate according to the present invention includes a step of forming an aggregate structure of the carbon-based fibers composed of a plurality of carbon-based fibers on an electrode included in the semiconductor substrate, and the electrode and the carbon-based structure. Adhering a fiber aggregate structure; forming a conductor on the carbon-based fiber aggregate structure; forming the carbon-based fiber aggregate structure on the conductor; Bonding a conductor and an aggregate structure of the carbon-based fibers, and the carbon-based fiber aggregate is configured such that the carbon-based fibers are arranged in a length direction, and the carbon-based one end is the carbon-based fiber The density of the fiber is different from the density of the carbon-based fiber at the other end, and the carbon-based fiber at the other end, which is higher than the density of the carbon-based fiber at one end, The fibers are formed in close contact with each other. According to the present invention, the electrode provided in the semiconductor substrate and the conductor are electrically connected by the aggregate structure of the carbon-based fibers. As a result, even when the current density increases, the possibility of disconnection between the electrode and the conductor can be reduced.

  Further, in the method for forming a wiring of a semiconductor substrate according to the present invention, the step of bonding the electrode and the aggregate structure of the carbon-based fibers is performed by depositing a catalyst film on the electrode and using a process gas. And bonding the electrode and the carbon-based fiber aggregate structure to each other, and the step of adhering the conductor and the carbon-based fiber aggregate structure to form a catalyst film on the conductor. A step of depositing and melting the catalyst film using a process gas to bond the conductor and the aggregate structure of the carbon-based fibers may be used.

  In the semiconductor substrate wiring formation method of the present invention, the catalyst film may be made of a metal selected from the group consisting of cobalt, iron, and nickel, or an alloy containing the metal. In the semiconductor substrate wiring formation method of the present invention, the process gas may include at least one of a hydrocarbon-based gas and alcohol.

  According to the present invention, the density of carbon nanotubes can be increased.

It is a figure at the time of carrying out orientation growth of the carbon nanotube 1 by the conventional method. It is a front view of the carbon nanotube 1 at the time of aligning and growing the carbon nanotube 1 by the conventional method. It is a top view of the carbon nanotube 1 when the carbon nanotube 1 is oriented and grown by a conventional method. It is a figure which shows the growth method of the carbon nanotube 1 of 1st Embodiment. It is a figure which shows the example which the carbon nanotube group 5 grew. It is a figure which immerses carbon nanotube group 5 in container 6 filled with resin containing an organic solvent. It is a figure which immerses carbon nanotube group 5 in container 6 filled with resin containing an organic solvent. It is a figure which immerses carbon nanotube group 5 in container 6 filled with resin containing an organic solvent. It is a figure which immerses carbon nanotube group 5 in container 6 filled with resin containing an organic solvent. FIG. 3 is a front view of a carbon nanotube group 5 formed with one end of each carbon nanotube 1 snuggled up. 3 is a top view of a group of carbon nanotubes 5 formed with one of the end portions of each carbon nanotube 1 approaching each other. FIG. FIG. 3 is a front view of a carbon nanotube group 5 formed with one end of each carbon nanotube 1 snuggled up. 3 is a top view of a group of carbon nanotubes 5 formed with one of the end portions of each carbon nanotube 1 approaching each other. FIG. It is a figure which shows the space where the carbon nanotube 1 does not exist. It is the figure which has arrange | positioned multiple carbon nanotube groups 5 from which density differs. It is a front view at the time of arrange | positioning multiple carbon nanotube groups 5 from which a density differs so that the direction of a high-density edge part may become alternate. It is a figure which shows the iron film 8 after patterning. It is a figure which shows the carbon nanotube group 5 which carried out orientation growth on the silicon substrate 7 with an oxide film. It is a figure which shows the process of attaching a solvent to the carbon nanotube group 5. FIG. It is a figure which shows the process of attaching a solvent to the carbon nanotube group 5. FIG. It is a figure which shows the process of attaching a solvent to the carbon nanotube group 5. FIG. It is a figure which shows the process of attaching a solvent to the carbon nanotube group 5. FIG. It is a figure which shows the process of attaching a solvent to the carbon nanotube group 5. FIG. It is a figure which shows the process of attaching a solvent to the carbon nanotube group 5. FIG. FIG. 3 is a front view of a carbon nanotube group 5 formed with one end of each carbon nanotube 1 snuggled up. It is a figure which shows the carbon nanotube group 5 and the board | substrate 20 which were densified. FIG. 3 is a diagram showing the structure of a substrate 20 and a substrate 23. It is a figure which shows the structure where the board | substrate 23 with a low melting-point metal film and the board | substrate 20 were piled up. It is a figure which shows the structure where the carbon nanotube group 5 was peeled off from the board | substrate 20, and the carbon nanotube group 5 contact | adhered to the board | substrate 23 with a low melting-point metal film. FIG. 6 is a process diagram in the case of performing the densification process shown in the third embodiment on the carbon nanotube group 5. FIG. 6 is a process diagram in the case of performing the densification process shown in the third embodiment on the carbon nanotube group 5. FIG. 6 is a process diagram in the case of performing the densification process shown in the third embodiment on the carbon nanotube group 5. FIG. 6 is a process diagram in the case of performing the densification process shown in the third embodiment on the carbon nanotube group 5. It is a structural diagram showing conventional transistor mounting. It is a structural diagram showing flip chip mounting. It is a structural diagram showing flip chip mounting. It is a figure which shows the structure of the aluminum nitride board | substrate 50 in which the electrode 51 was formed. It is a figure which shows the structure of the aluminum nitride board | substrate 50 in which the carbon nanotube group 5 was formed. It is a figure which shows the structure of the aluminum nitride board | substrate 50 in which the carbon nanotube group 5 densified was formed. It is a figure which shows the structure of the aluminum nitride board | substrate 50 in which the carbon nanotube group 5 in which the length of each carbon nanotube 1 was nonuniform was formed. 3 is a view showing a structure of an aluminum nitride substrate 50 on which an interlayer insulating film 60 is deposited so as to cover a carbon nanotube group 5. FIG. It is a figure which shows the structure of the aluminum nitride board | substrate 50 after the carbon nanotube group 5 and the interlayer insulation film 60 were grind | polished. 2 is a view showing a structure of an aluminum nitride substrate 50 provided with a high-power transistor chip 40. FIG. 1 is a diagram illustrating a structure of an LSI (Large Scale Integration) 70. FIG. It is a figure which shows the structure of the board | substrate 74 and the LSI board | substrate 75 with which the carbon nanotube group 5 was grown. It is a figure which shows the structure where the board | substrate 74 and the LSI board | substrate 75 were piled up. 3 is a view showing a structure in which a gap between a substrate 74 and an LSI substrate 75 is filled with an interlayer insulating film 80. FIG. It is a figure which shows the structure of the board | substrate 74 in which the interlayer insulation film 80 was deposited so that the carbon nanotube group 5 might be covered. It is a figure which shows the structure which made the front-end | tip of the carbon nanotube group 5 protrude. 3 is a view showing a structure of an LSI substrate 75 in which a carbon nanotube group 5 and an interlayer insulating film 80 are polished. FIG. It is a figure which shows the structure of the LSI board | substrate 75 in which the copper wiring 71 was formed. It is a figure which shows the structure of the LSI board | substrate 75 and the board | substrate 74 in which the copper wiring 71 was formed. It is a figure which shows the structure where the board | substrate 74 and the LSI board | substrate 75 with which the copper wiring 71 was formed were piled up. 3 is a view showing a structure in which a carbon nanotube group 5 is in close contact with a copper wiring 71 formed on an LSI substrate 75. FIG. 3 is a view showing a structure of an LSI substrate 75 in which a carbon nanotube group 5 and an interlayer insulating film 80 are polished. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Carbon nanotube 2 Silicon substrate 3 Titanium layer 4 Cobalt layer 5 Carbon nanotube group 6 Container 7 Silicon substrate with oxide film 8 Iron film 9 Solvent 10 Container 20 Substrate 21 Substrate 22 Low melting point metal film 23 Substrate with low melting point metal film 30 Low Substrate 31 with melting point metal film Substrate 32 Low melting point metal film 50 Aluminum nitride substrate 51 Electrode 60 Interlayer insulating film 70 LSI (Large Scale Integration)
71 Copper wiring 72 Insulating film 73 Via 74 Substrate 75 LSI substrate 76 Electrode 77 Cobalt film 78 Tantalum film 79 Titanium film 80 Interlayer insulating film

  The best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described below with reference to the drawings. The configuration of the following embodiment is an exemplification, and the present invention is not limited to the configuration of the embodiment.

  FIG. 1 is a view when carbon nanotubes 1 are oriented and grown by a conventional method. As shown in FIG. 1, a large amount of carbon nanotubes 1 are growing. However, the adjacent carbon nanotubes 1 may not be in contact with each other. FIG. 2 is a front view of the carbon nanotube 1 when the carbon nanotube 1 is oriented and grown by a conventional method. FIG. 3 is a top view of the carbon nanotube 1 when the carbon nanotube 1 is oriented and grown by a conventional method. As shown in FIGS. 2 and 3, there is a space between adjacent carbon nanotubes 1. That is, a gap is generated between adjacent carbon nanotubes 1. However, everything is not isolated without contact. In some cases, contacted portions are also required for orientation growth. In particular, when the carbon nanotube is thinned, it becomes difficult to grow the alignment without a part of the carbon nanotube. Even in this case, a gap is generated between the adjacent carbon nanotubes 1.

<First Embodiment>
A method for growing the carbon nanotube 1 of this embodiment will be described with reference to FIGS. As shown in FIG. 4, a titanium (Ti) layer is formed on the silicon substrate 2. Then, a cobalt (Co) layer 4 is formed on the titanium layer 3. In this case, the cobalt layer 4 is patterned with a diameter of about 1 μm. In this embodiment, the cobalt layer 4 is patterned with a diameter of about 1 μm, but the present invention is not limited to this, and the cobalt layer 4 may be patterned to an arbitrary size. By patterning the cobalt layer 4, the position where the carbon nanotube 1 grows can be controlled.

Next, the silicon substrate 2 on which the titanium layer 3 and the cobalt layer 4 are formed is introduced into a thermal CVD chamber. Then, a mixed gas (9: 1) of argon (Ar) and acetylene (C ₂ H ₂ ) is introduced into the thermal CVD chamber at 1 kPa.

  Furthermore, after the pressure in the thermal CVD chamber is stabilized, the silicon substrate 2 is heated to 510 ° C. over 30 minutes. Next, the silicon substrate 2 is held at 510 ° C. for 10 minutes. Through the above process, the carbon nanotubes 1 grow on the cobalt layer 4. FIG. 5 is a diagram in which the carbon nanotube group 5 is grown on the cobalt layer 4. The carbon nanotube group 5 refers to a group of carbon nanotubes 1 grown on the cobalt layer 4.

  As shown in FIG. 5, the carbon nanotubes 1 on the cobalt layer 4 are grown in the vertical direction. FIG. 5 is an example in which the carbon nanotube group 5 is grown, and the number of the carbon nanotubes 1 is not limited to this. Moreover, in this embodiment, when growing the carbon nanotube 1, cobalt is used as a catalyst metal. However, the catalyst metal is not limited to cobalt, and a transition metal such as iron (Fe) or nickel (Ni) may be used. Further, as a method for growing the carbon nanotube 1, a chemical vapor deposition method (CVD method), a hot filament CVD method, and a plasma CVD method may be used.

  Next, the carbon nanotube group 5 is immersed in a resin containing an organic solvent (a solvent containing an adhesion substance different from the carbon nanotube). Specifically, the carbon nanotube group 5 shown in FIG. 5 is immersed in a container 6 filled with a resin containing an organic solvent. When the carbon nanotube group 5 is immersed in a resin containing an organic solvent, the carbon nanotube group 5 is immersed together with the silicon substrate 2. FIG. 6 is a diagram in which the carbon nanotube group 5 is immersed in a resin containing an organic solvent.

  For example, as shown in FIG. 6, the carbon nanotube group 5 is immersed up to a portion A in a container 6 filled with a resin containing an organic solvent. Further, for example, as shown in FIG. 7, the carbon nanotube group 5 is immersed up to a portion B in a container 6 filled with a resin containing an organic solvent. FIGS. 6 and 7 are views showing a state immediately after immersing the carbon nanotube group 5 in a container 6 filled with a resin containing an organic solvent.

  In FIG. 6, the immersed portion of the carbon nanotube 1 is about half the length of the carbon nanotube 1. The immersion part refers to a part where the carbon nanotubes 1 are immersed in a container 6 filled with a resin containing an organic solvent. In FIG. 7, the immersion portion is about 20 percent of the length of the carbon nanotube 1. The immersion part can be appropriately changed according to the type of organic solvent, the type of resin, and the like.

  6 and 7, the base side (the end side in contact with the silicon substrate 2) of the carbon nanotube group 5 is an immersion part. Moreover, when the carbon nanotube group 5 is immersed in the container 6 filled with resin containing an organic solvent, the front end side (end part side which is not in contact with the silicon substrate 2) of the carbon nanotube group 5 can also be immersed.

  For example, as shown in FIG. 8, the tip side of each carbon nanotube 1 is an immersion part. In this case, as shown in FIG. 8, the carbon nanotube group 5 is immersed to a portion C in a container 6 filled with a resin containing an organic solvent. For example, as shown in FIG. 9, the carbon nanotube group 5 is immersed to a portion D in a container 6 filled with a resin containing an organic solvent. FIG. 8 and FIG. 9 are views showing a state immediately after the carbon nanotube group 5 is immersed in the container 6 filled with a resin containing an organic solvent. In FIG. 8, the immersed portion of the carbon nanotube 1 is about half the length of the carbon nanotube 1. In FIG. 9, the immersion portion is about 20 percent of the length of the carbon nanotube 1.

  The time for immersing the carbon nanotube group 5 in the resin containing the organic solvent is about 1 minute. In this embodiment, the time for immersing the carbon nanotube group 5 in a resin containing an organic solvent is set to about 1 minute. However, the present invention is not limited to this. Therefore, the structure may be changed as appropriate depending on the structure and number of the carbon nanotubes 1.

  As the organic solvent, for example, alcohol such as methanol and ethanol is used. Further, as the resin, for example, a thermosetting resin, a photocurable resin, or the like is used. More specifically, for example, an epoxy resin is used as the resin.

  As shown in FIGS. 6 and 7, when the carbon nanotube group 5 is immersed in a container 6 filled with a resin containing an organic solvent, a gap between adjacent carbon nanotubes 1 is filled with a resin containing an organic solvent. The carbon nanotube group 5 on the silicon substrate 2 is formed such that one of the end portions of each carbon nanotube 1 is close to the carbon nanotube group 1.

  When the carbon nanotube group 5 is immersed in the container 6 filled with the resin containing the organic solvent, the resin containing the organic solvent moves to a portion where the carbon nanotube 1 is not immersed due to a capillary phenomenon. Then, the resin containing the organic solvent moves to the end of the carbon nanotube 1. When the resin containing the organic solvent moves to the end of the carbon nanotube 1, the carbon nanotube 1 is covered with the resin containing the organic solvent.

  When the resin containing the organic solvent moves to the end of the carbon nanotube 1, the adjacent carbon nanotubes 1 snuggle up due to the surface tension. Further, when the organic solvent is volatilized, the carbon nanotubes 1 are covered with a resin. Then, the carbon nanotubes 1 covered with the resin come close to each other due to volume shrinkage when the organic solvent volatilizes. That is, when the organic solvent is volatilized from the resin containing the organic solvent, only the resin covers each carbon nanotube 1. Therefore, the carbon nanotubes 1 covered with the resin further approach each other.

  Therefore, the carbon nanotubes 1 covered with the resin come close to each other to form the carbon nanotube group 5. Further, when each carbon nanotube 1 comes into contact with the adjacent carbon nanotube 1, each carbon nanotube 1 maintains a state of being close to each other. That is, the carbon nanotubes 1 are held close to each other by the resin covering the carbon nanotubes 1. In other words, the resin covering each carbon nanotube 1 maintains the state in which the adjacent carbon nanotubes 1 are fixed to each other.

  FIG. 10 is a front view of the carbon nanotube group 5 formed with one of the end portions of each carbon nanotube 1 snuggled up. FIG. 10 is a view after the carbon nanotube group 5 is immersed in the container 6 filled with the resin containing the organic solvent and the carbon nanotube group 5 is pulled up from the container 6.

  FIG. 11 is a top view of the carbon nanotube group 5 formed with one end portion of each carbon nanotube 1 snuggled up. FIG. 11 is a view after the carbon nanotube group 5 is immersed in the container 6 filled with the resin containing the organic solvent and the carbon nanotube group 5 is pulled up from the container 6.

  As shown in FIGS. 10 and 11, when the carbon nanotube group 5 is immersed in a container 6 filled with a resin containing an organic solvent, one end of each carbon nanotube 1 is formed close to each other.

  Instead of immersing the carbon nanotube group 5 in a resin containing an organic solvent, a resin containing an organic solvent may be dropped into the carbon nanotube group 5. Further, a resin containing an organic solvent may be dropped onto the carbon nanotube group 5 by using a spin coating method.

  When a resin containing an organic solvent is dropped on the carbon nanotube group 5, each carbon nanotube 1 is dropped so as to be covered with a resin containing an organic solvent. Specifically, a resin containing an organic solvent is dropped onto a part of each carbon nanotube 1. When a resin containing an organic solvent is dropped onto a part of each carbon nanotube 1, the resin containing the organic solvent moves to a portion where the resin containing the organic solvent is not dropped due to a capillary phenomenon. When the resin containing the organic solvent moves to a portion where the resin containing the organic solvent is not dropped, the carbon nanotubes 1 are covered with the resin containing the organic solvent.

  When the resin containing the organic solvent moves to a portion where the resin containing the organic solvent is not dripped, the adjacent carbon nanotubes 1 approach each other due to the surface tension. Further, when the organic solvent is volatilized, the carbon nanotubes 1 are covered with a resin. Then, the carbon nanotubes 1 covered with the resin come close to each other due to volume shrinkage when the organic solvent volatilizes. That is, when the organic solvent is volatilized from the resin containing the organic solvent, only the resin covers each carbon nanotube 1. Therefore, the carbon nanotubes 1 covered with the resin further approach each other.

  Therefore, the carbon nanotubes 1 covered with the resin come close to each other to form the carbon nanotube group 5. Further, when each carbon nanotube 1 comes into contact with the adjacent carbon nanotube 1, each carbon nanotube 1 maintains a state of being close to each other. That is, the carbon nanotubes 1 are held close to each other by the resin covering the carbon nanotubes 1. In other words, the resin covering each carbon nanotube 1 maintains the state in which the adjacent carbon nanotubes 1 are fixed to each other.

  As described above, each of the carbon nanotubes 1 covered with the resin is formed such that one of the end portions is close to each other. As a result, the density of the carbon nanotubes 1 in the carbon nanotube group 5 is different between the tip side and the root side of the carbon nanotube group 5. That is, the carbon nanotube group 5 in which the density of the carbon nanotubes 1 is different at one end and the other end is formed. The density of the carbon nanotubes 1 on the front end side of the carbon nanotube group 5 is higher than the density of the carbon nanotubes 1 on the root side of the carbon nanotube group 5.

  For example, when ethanol is used as the organic solvent and an epoxy resin is used as the resin, the resin containing the organic solvent is an epoxy resin diluted with ethanol. Moreover, the ratio of ethanol and an epoxy resin is arbitrary. However, the gap between the adjacent carbon nanotubes 1 is not filled with the epoxy resin. When all the gaps between the adjacent carbon nanotubes 1 are filled with the epoxy resin, the adjacent carbon nanotubes 1 cannot approach each other. As a result, each of the carbon nanotubes 1 covered with the resin cannot be formed with one of the end portions close to each other. Therefore, for example, the volume of the resin containing the organic solvent is made smaller than the volume of the carbon nanotube group 5. Thereby, all the gaps between the adjacent carbon nanotubes 1 are not filled with the epoxy resin.

  In this embodiment, a combination of an organic solvent and a resin is shown, but a microcrystalline material such as nanoporous silica (dielectric material) may be used instead of the resin. In this way, carbon nanotubes can be formed that are not only resin but also dielectric materials.

Second Embodiment
A second embodiment of the present invention will be described with reference to the drawings of FIGS. In the said 1st Embodiment, the method of forming the carbon nanotube group 5 from which the density of the carbon nanotube 1 differs in one edge part and the other edge part by covering each carbon nanotube 1 using resin containing an organic solvent Explained. In the present embodiment, a method of forming the carbon nanotube group 5 in which the density of the carbon nanotubes 1 is different between one end and the other end by covering each carbon nanotube 1 with a metal will be described. Other configurations and operations are the same as those in the first embodiment. Therefore, the same components are denoted by the same reference numerals as those in the first embodiment, and description thereof is omitted. Further, the drawings in FIGS. 5 to 11 are referred to as necessary.

  First, the carbon nanotube group 5 is grown on the silicon substrate 2 on which the titanium layer 3 and the cobalt layer 4 shown in FIG. 5 are formed. The growth method of the carbon nanotube group 5 is the same as that of the first embodiment, and the description thereof is omitted here. Next, a metal is deposited on each carbon nanotube 1. For example, gold (Au) is used as a metal to be deposited on each carbon nanotube 1. Moreover, as a metal vapor-deposited on each carbon nanotube 1, you may use copper (Cu), aluminum (Al), lead (Pb), solder etc., for example.

  When gold is vapor-deposited on each carbon nanotube 1, gold is vapor-deposited on the surface of each carbon nanotube 1 with a thickness of about 1 nanometer (nm) by sputtering. By using the sputtering method, gold can be accurately deposited on each carbon nanotube 1. For example, when a sputtering apparatus is used, by setting the film thickness of gold to be deposited to 1 nanometer (nm), each carbon nanotube 1 is deposited with gold having a film thickness of 1 nanometer (nm). In this case, the portion for depositing gold on the carbon nanotube 1 is arbitrary. The volume of gold to be deposited is determined by the volume of the carbon nanotube group 5 to be deposited. Further, instead of depositing a metal on each carbon nanotube 1, each carbon nanotube 1 may be immersed in a molten metal.

  Next, the carbon nanotube group 5 is heat-treated at about 300 degrees. The melting point of gold usually exceeds 1000 degrees. However, when gold is reduced to nano size, the melting point of gold decreases. Therefore, when the carbon nanotube group 5 is heat-treated at about 300 degrees, the gold deposited on each carbon nanotube 1 is melted. Each carbon nanotube 1 is covered with molten gold. The temperature of the heat treatment when copper (Cu), aluminum (Al), lead (Pb), solder, or the like is used as the metal deposited on each carbon nanotube 1 may be obtained by experiment or simulation.

  When the gold deposited on each carbon nanotube 1 melts, the carbon nanotubes 1 covered with the adjacent gold nestle due to surface tension. The carbon nanotubes 1 covered with gold are formed close to each other. Accordingly, the carbon nanotubes 1 covered with gold are close to each other to form a carbon nanotube group 5. Further, when each carbon nanotube 1 comes into contact with the adjacent carbon nanotube 1, each carbon nanotube 1 maintains a state of being close to each other. That is, the carbon nanotubes 1 are held close to each other by the gold covering the carbon nanotubes 1. In other words, the gold covering each carbon nanotube 1 maintains the state in which the adjacent carbon nanotubes 1 are fixed to each other.

  As described above, each of the carbon nanotubes 1 covered with gold is formed such that one of the end portions is close to each other. As a result, the density of the carbon nanotubes 1 in the carbon nanotube group 5 is different between the tip side and the root side of the carbon nanotube group 5. That is, the carbon nanotube group 5 in which the density of the carbon nanotubes 1 is different at one end and the other end is formed. The density of the carbon nanotubes 1 on the front end side of the carbon nanotube group 5 is higher than the density of the carbon nanotubes 1 on the root side of the carbon nanotube group 5.

  FIG. 12 is a front view of the carbon nanotube group 5 formed with one of the end portions of each carbon nanotube 1 snuggled up. FIG. 13 is a top view of the carbon nanotube group 5 formed with one end portion of each carbon nanotube 1 snuggled up. As shown in FIGS. 12 and 13, by covering each carbon nanotube 1 with gold, a carbon nanotube group 5 in which the density of the carbon nanotubes 1 is different at one end and the other end is formed. Thus, the process of increasing the density of the carbon nanotubes 1 of the carbon nanotube group 5 is referred to as a densification process.

  Further, the method according to the present embodiment may be performed together with the method of the first embodiment. That is, the carbon nanotubes 1 are covered with a metal, and the carbon nanotubes 1 are covered with a resin containing an organic solvent. When a large amount of metal is deposited on the tip side of each carbon nanotube 1, the carbon nanotube group 5 is immersed in a resin containing an organic solvent. Accordingly, it is possible to promote that one of the end portions of each carbon nanotube 1 is formed close to each other. The carbon nanotube group 5 in which the density of the carbon nanotubes 1 is different at one end and the other end can be used for, for example, an electron source for field emission.

<Third Embodiment>
A third embodiment of the present invention will be described with reference to the drawing of FIG. In the said 1st Embodiment and the said 2nd Embodiment, the method of forming the carbon nanotube group 5 from which the density of the carbon nanotube 1 differs in one edge part and the other edge part was demonstrated. The carbon nanotube groups 5 having different densities of the carbon nanotubes 1 are formed such that one of the end portions is close to each other. The carbon nanotube group 5 in which the density of the carbon nanotubes 1 is different refers to the carbon nanotube group 5 in which the density of the carbon nanotubes 1 is different at one end and the other end.

  The carbon nanotube group 5 in which the density of the carbon nanotubes 1 is different includes a space where the carbon nanotubes 1 do not exist. That is, as shown in FIG. 14, there is a space where the carbon nanotubes 1 do not exist in the portion E.

  In the present embodiment, a method of using a space where the carbon nanotube 1 does not exist will be described. In the present embodiment, a dielectric film is formed in a space where the carbon nanotube 1 does not exist. That is, a dielectric film is formed at a portion E in FIG. As described above, by forming the dielectric film in the space where the carbon nanotubes 1 do not exist, the carbon nanotube groups 5 having different densities of the carbon nanotubes 1 can be used as the strength reinforcing goods of the dielectric film. For example, nanoporous silica that functions as a dielectric film has low mechanical strength. Therefore, it is possible to reinforce the mechanical strength of the dielectric film by using the carbon nanotube group 5 having different densities of the carbon nanotubes 1 as a strength reinforcing material for the dielectric film.

Moreover, you may form the metal by plating in the space where the carbon nanotube 1 does not exist. That is, a metal layer may be formed in a space where the carbon nanotube 1 does not exist. Further, a resin may be filled in a space where the carbon nanotubes 1 do not exist. Examples of the resin that fills the space where the carbon nanotubes 1 do not exist include organic substances. Further, an insulating film such as SiO ₂ may be formed in a space where the carbon nanotube 1 does not exist.

  Thus, by forming a dielectric film, a metal layer, a resin, an insulating film, and the like in a space where the carbon nanotube 1 does not exist, it is possible to improve device characteristics, heat dissipation characteristics, and device strength.

<Fourth embodiment>
A fourth embodiment of the present invention will be described with reference to FIGS. 15 and 16. In the present embodiment, a method of combining the carbon nanotube groups 5 having different densities formed according to the first embodiment or the second embodiment will be described.

  First, a plurality of carbon nanotube groups 5 having different densities of the carbon nanotubes 1 are arranged on the same straight line. In this case, it arrange | positions so that the other edge part which is denser than one edge part may become the same direction. As shown in FIG. 15, a plurality of carbon nanotube groups 5 having different carbon nanotube 1 densities are arranged on the same straight line. Further, the carbon nanotubes 1 are arranged so that the other end portion in which the density of the carbon nanotubes 1 is higher than the one end portion is in the same direction. Here, among the end portions of the carbon nanotube group 5, the other end portion in which the density of the carbon nanotubes 1 is higher than that of one end portion is referred to as a high-density end portion.

  Next, the carbon nanotube groups 5 having different densities of the carbon nanotubes 1 are further arranged between the carbon nanotube groups 5 having different densities of the plurality of carbon nanotubes 1 arranged on the same straight line. In this case, the density of the carbon nanotubes 1 is different so that the high-density ends are opposite to the high-density ends of the carbon nanotube groups 5 having different densities of the plurality of carbon nanotubes 1 already arranged. The nanotube group 5 is further arranged. That is, a plurality of carbon nanotube groups 5 having different density of the carbon nanotubes 1 are arranged on the same straight line so that the directions of the high density end portions are alternated. FIG. 16 is a front view when a plurality of carbon nanotube groups 5 having different densities of the carbon nanotubes 1 are arranged on the same straight line so that the directions of the high density end portions are staggered.

  The density of the carbon nanotube group 5 can be increased by further disposing the carbon nanotube group 5 having a different density of the carbon nanotube 1 in a space where the carbon nanotube 1 does not exist. That is, the high-density carbon nanotube group 5 can be formed.

<Fifth Embodiment>
A fifth embodiment of the present invention will be described with reference to the drawings of FIGS. The growth method of the carbon nanotube 1 of this embodiment is demonstrated using drawing of FIG.17 and FIG.18. First, a catalyst is deposited on the silicon substrate 7 with an oxide film. In this case, a finely divided catalyst may be used, or a film-like catalyst deposited by a sputtering method may be used.

  In the present embodiment, description will be made using iron as a catalyst to be deposited on the silicon substrate 7 with an oxide film. In the present embodiment, a sputtering method will be described as a method for depositing an iron catalyst on the silicon substrate 7 with an oxide film. An iron film 8 having a thickness of 1 nm is deposited on a silicon substrate 7 with an oxide film by sputtering, and patterning is performed by using photolithography so that the iron film 8 has a diameter of about 5 μm. FIG. 17 shows the iron film 8 after patterning. As shown in FIG. 17, a substantially circular iron film 8 is formed by patterning on a silicon substrate 7 with an oxide film. The diameter of the iron film 8 is an example, and the present invention is not limited to this, and the iron film 8 may be patterned with an arbitrary size.

The oxide-coated silicon substrate 7 on which the patterned iron film 8 is formed is placed on an overheating stage in a normal thermal CVD furnace, and evacuated. Then, the silicon substrate 7 with an oxide film is heated until the temperature of the silicon substrate 7 with an oxide film reaches 590 ° C. Thereafter, a mixed gas of argon (Ar) and acetylene (C ₂ H ₂ ) is introduced into the thermal CVD furnace for 30 periods. In this case, the pressure of the mixed gas of argon (Ar) and acetylene (C ₂ H ₂ ) is 1 kPa. In this manner, the carbon nanotubes 1 are oriented and grown on the silicon substrate 7 with an oxide film.

FIG. 18 shows a group of carbon nanotubes 5 oriented and grown on the oxide-coated silicon substrate 7. Each carbon nanotube 1 has a diameter of about 10 nm and a length of about 20 μm. The density of the carbon nanotubes 1 in the carbon nanotube group 5 is about 10 ¹¹ pieces / cm ² . Since the density of the carbon nanotubes having a diameter of 5 nm in the close-packed state is about 10 ¹² pieces / cm ² , the occupation ratio of the carbon nanotubes is only about 10%.

  Next, a process for increasing the density of the carbon nanotubes 1 of the carbon nanotube group 5 will be described with reference to FIGS. 19 to 25. First, the carbon nanotube group 5 is immersed in the solvent 9. As the solvent 9 in which the carbon nanotube group 5 is immersed, an organic solvent such as DMF (N, N-dimethylformamide), dichloroethane, isopropyl alcohol, ethanol, methanol, or an inorganic solvent such as water is used.

  Specifically, a solvent 9 at room temperature is placed in a container 10 having a size capable of containing a silicon substrate 7 with an oxide film. And the carbon nanotube group 5 is immersed in the solvent 9 by putting the silicon substrate 7 with an oxide film vertically or horizontally into the container 10 containing the solvent 9.

  FIGS. 19 to 21 are views showing a process of attaching the solvent 9 to the carbon nanotube group 5. In this step, the silicon substrate 7 with an oxide film is placed in a container 10 containing the solvent 9 and the carbon nanotube group 5 is immersed in the solvent 9, and then the silicon film with an oxide film is added from the container 10 containing the solvent 9. The substrate 7 is pulled up. Specifically, as shown in FIG. 19, the silicon substrate 7 with an oxide film is disposed horizontally. And as shown in FIG. 20, the silicon substrate 7 with an oxide film is immersed in the container 10 containing the solvent 9. In this case, the entire carbon nanotube group 5 is immersed in the solvent 9. That is, the solvent 9 is attached to the entire carbon nanotube group 5.

  Next, after immersing the carbon nanotube group 5 in the solvent 9 for about 1 minute, the carbon nanotube group 5 is pulled up from the solvent 9 as shown in FIG. The time for immersing the carbon nanotube group 5 in the solvent 9 is not limited to 1 minute, and the immersion time is appropriately adjusted depending on the state of the solvent 9 attached to the carbon nanotube group 5.

  FIG. 22 to FIG. 24 are diagrams showing a process of attaching the solvent 9 to the carbon nanotube group 5. In this step, a silicon substrate 7 with an oxide film is placed vertically in a container 10 containing a solvent 9, the carbon nanotube group 5 is immersed in the solvent 9, and then the silicon 10 with an oxide film is added from the container 10 containing the solvent 9. The substrate 7 is pulled up. Specifically, as shown in FIG. 22, the silicon substrate 7 with an oxide film is arranged vertically. And as shown in FIG. 23, the silicon substrate 7 with an oxide film is immersed in the container 10 containing the solvent 9. In this case, the entire carbon nanotube group 5 is immersed in the solvent 9. That is, the solvent 9 is attached to the entire carbon nanotube group 5.

  Next, after the carbon nanotube group 5 is immersed in the solvent 9 for about 1 minute, the carbon nanotube group 5 is pulled up from the solvent 9 as shown in FIG. The time for immersing the carbon nanotube group 5 in the solvent 9 is not limited to 1 minute, and the immersion time is appropriately adjusted depending on the state of the solvent 9 attached to the carbon nanotube group 5.

  Further, when the adhesion state of the solvent 9 to the carbon nanotube group 5 is poor, a surfactant such as SDS (sodium dodecyl sulfate) or a functional molecule such as pyrene, perylene, anthracene, porphyrin, phthalocyanine, DNA is added to the solvent 9. As a result, the adhesion state of the solvent 9 to the carbon nanotube group 5 is improved.

  In the present embodiment, a silicon substrate 7 with an oxide film is placed in a container 10 containing a solvent 9, the carbon nanotube group 5 is immersed in the solvent 9, and then the silicon substrate 7 with an oxide film is contained in the container 10 containing the solvent 9. Explained how to raise. However, the present invention is not limited to this, and the solvent 9 may be attached to the carbon nanotube group 5 by dropping the solvent 9 onto the carbon nanotube group 5 using a spin coating method.

  After the solvent 9 is attached to the carbon nanotube group 5, the carbon nanotube group 5 is dried. The method of drying the carbon nanotube group 5 may be a method of naturally drying the carbon nanotube group 5, or a method of heating the temperature of the silicon substrate with an oxide film to about 200 ° C. and rapidly drying it.

  In the process of drying the carbon nanotube group 5, the carbon nanotubes 1 at the tip part of the carbon nanotube group 5 (the end part of the carbon nanotube group 5 that is not in contact with the silicon substrate 7 with an oxide film) The nanotubes 1 are attracted to each other. The carbon nanotubes 1 attracted to each other are brought into close contact with each other by intermolecular force. Therefore, as shown in FIG. 25, the carbon nanotube group 5 is formed in a state where the carbon nanotubes 1 are close to each other at the tip portion. That is, the density of the carbon nanotubes 1 at the tip of the carbon nanotube group 5 and the carbon nanotubes at the root of the carbon nanotube group 5 (the end of the carbon nanotube group 5 that is in contact with the silicon substrate with an oxide film). A group of carbon nanotubes 5 having a density different from that of 1 is formed.

  The density of the carbon nanotubes 1 of the carbon nanotube group 5 formed in this way differs between the tip portion and the root portion of the carbon nanotube group 5. That is, a carbon nanotube group in which the density of the carbon nanotubes 1 is different at one end and the other end of the carbon nanotube group 5 is formed. The density of the carbon nanotubes 1 at the tip portion of the carbon nanotube group 5 is higher than the density of the carbon nanotubes 1 at the root portion of the carbon nanotube group 5. Therefore, in the carbon nanotube group 5 shown in FIG. 25, the carbon nanotubes 1 at the tip of the carbon nanotube group 5 have a high density that is about the closest packing.

<Sixth Embodiment>
A sixth embodiment of the present invention will be described with reference to the drawings in FIGS. The carbon nanotube group 5 formed by the method described in the first embodiment, the second embodiment, or the fifth embodiment has a high density of the carbon nanotubes 1 at one end of the end portions of the carbon nanotube group 5. It becomes density. In the present embodiment, a method for increasing the density of the carbon nanotubes 1 at both ends of the carbon nanotube group 5 will be described. That is, a method of forming a state in which the carbon nanotubes 1 at both ends of the carbon nanotube group 5 are formed close to each other and the carbon nanotubes 1 of the carbon nanotube group 5 are formed as a whole will be described.

  First, the substrate 20 on which the carbon nanotube group 5 is grown is prepared. In this embodiment, the silicon substrate 2 shown in the first embodiment and the second embodiment or the silicon substrate 7 with an oxide film shown in the fifth embodiment is used as the substrate 20. Here, the process of increasing the density of the carbon nanotubes 1 of the carbon nanotube group 5 described in the first embodiment, the second embodiment, or the fifth embodiment is referred to as a densification process. The carbon nanotube group 5 in which the density of the carbon nanotubes 1 in the carbon nanotube group 5 is high is referred to as a densified carbon nanotube group 5. The carbon nanotube group 5 grown on the substrate 20 is subjected to the densification process described in the first embodiment, the second embodiment, or the fifth embodiment to increase the density of the carbon nanotubes 1 in the carbon nanotube group 5. Densify. FIG. 26 shows the densified carbon nanotube group 5 and the substrate 20.

  Next, as shown in FIG. 27, a substrate 21 having the same size as the substrate 20 on which the carbon nanotube group 5 is grown is prepared. Then, a low melting point metal film 22 such as solder or indium is deposited on the surface of the substrate 21. The thickness of the low melting point metal film 22 deposited on the surface of the substrate 21 is several μm. Thus, when the low melting point metal film 22 is deposited on the surface of the substrate 21, the substrate 23 with the low melting point metal film is manufactured.

  And as shown in FIG. 28, the board | substrate 23 with a low melting-point metal film and the board | substrate 20 are piled up so that the carbon nanotube group 5 may be pinched | interposed. Specifically, the low melting point metal film 22 deposited on the surface of the substrate 21 and the end of the carbon nanotube group 5 (the end of the carbon nanotube group 5 that does not contact the substrate 20) are in contact with each other. The substrate 23 with the melting point metal film and the substrate 20 are overlapped.

  Then, after heating the substrate 23 with the low melting point metal film so that the temperature of the substrate 23 with the low melting point metal film becomes equal to or higher than the melting point of the low melting point metal film 22, the substrate 23 with the low melting point metal film is cooled. . After the substrate 23 with the low melting point metal film is cooled, the substrate 23 with the low melting point metal film and the substrate 20 are separated. When the substrate 23 with the low melting point metal film and the substrate 20 are separated from each other, the carbon nanotube group 5 and the substrate 23 with the low melting point metal film are in close contact with each other. That is, the carbon nanotube group 5 is peeled off from the substrate 20, and the carbon nanotube group 5 is in close contact with the substrate 23 with the low melting point metal film. As shown in FIG. 29, the carbon nanotube group 5 is peeled off from the substrate 20, and the carbon nanotube group 5 is in close contact with the substrate 23 with the low melting point metal film.

  When the adhesion between the substrate 20 and the carbon nanotube group 5 is strong, the carbon nanotube group 5 is not peeled off from the substrate 20, and the carbon nanotube group 5 does not adhere to the substrate 23 with the low melting point metal film. In the first embodiment, the second embodiment, and the fifth embodiment, after depositing an extremely thin catalyst film (catalyst film of several nm or less) on the silicon substrate 2 or the silicon substrate 7 with an oxide film, the carbon nanotube group 5 is growing. In this embodiment, the silicon substrate 2 or the silicon substrate 7 with an oxide film is used as the substrate 20. Therefore, when an extremely thin catalyst film is deposited on the substrate 20, the adhesion between the substrate 20 and the carbon nanotube group 5 is weak. Therefore, the problem that the carbon nanotube group 5 is not peeled off from the substrate 20 does not occur.

  As shown in FIG. 29, of the ends of the carbon nanotube group 5 in close contact with the substrate 23 with a low melting point metal film, the end in contact with the substrate 23 with a low melting point metal film is the other end (carbon nanotubes). The density of the carbon nanotubes 1 is higher than the end of the group 5 that is not in contact with the substrate 23 with the low melting point metal film. The width of the carbon nanotube group 5 increases as the distance from the substrate 23 with the low melting point metal film increases. That is, the density of the carbon nanotubes 1 in the carbon nanotube group 5 decreases as the distance between the carbon nanotube group 5 and the substrate 23 with the low melting point metal film increases.

  In the first embodiment, the second embodiment, or the fifth embodiment, the substrate 23 with the low melting point metal film in which the ends of the carbon nanotubes 1 having the high density of the carbon nanotube groups 5 are in close contact with each other. The described densification process is performed. That is, the densification process described in the first embodiment, the second embodiment, or the fifth embodiment is performed on the end portions of the carbon nanotube group 5 where the density of the carbon nanotubes 1 is low.

  Carbon nanotubes in which the carbon nanotubes 1 at both ends of the carbon nanotube group 5 have a high density when the densification treatment is performed on the ends of the carbon nanotube group 5 at which the density of the carbon nanotubes 1 is low. Group 5 is formed.

  FIG. 30 shows a step of immersing the carbon nanotube group 5 in close contact with the substrate 23 with the low melting point metal film in the container 10 containing the solvent 9. FIG. 31 shows a step of pulling up the carbon nanotube group 5 closely attached to the substrate 23 with the low melting point metal film from the container containing the solvent 9. In the carbon nanotube group 5 shown in FIG. 31, the carbon nanotubes 1 at both ends have a high density close to the closest packing.

  Further, when low melting point metals (alloys) having different melting points are used, the densified carbon nanotube group 5 can be further densified. A method for further densifying the carbon nanotube group 5 in which the carbon nanotubes 1 at both ends of the carbon nanotube group 5 are densified will be described with reference to FIGS. 32 and 33.

  As shown in FIG. 32, a substrate 23 with a low melting point metal film in which the carbon nanotube groups 5 in which the carbon nanotubes 1 at both ends of the carbon nanotube group 5 are densified are in close contact, and a substrate 30 with a low melting point metal film, Prepare. The substrate 23 with the low melting point metal film and the substrate 30 with the low melting point metal film have the same size. The substrate 30 with the low melting point metal film is obtained by depositing a low melting point metal film 32 such as solder or indium on the surface of the substrate 31. In this case, a low melting point metal film 32 having a melting point higher than that of the low melting point metal film 22 deposited on the substrate 23 with the low melting point metal film is deposited on the surface of the substrate 31. Further, the thickness of the low melting point metal film 32 deposited on the surface of the substrate 31 is set to several μm.

  Next, as shown in FIG. 33, the substrate 23 with the low melting point metal film and the substrate 30 with the low melting point metal film are overlaid. Specifically, the end of the carbon nanotube group 5 (the end of the end of the carbon nanotube group 5 that is not in contact with the substrate 23 with the low melting point metal film) and the low melting point metal film deposited on the surface of the substrate 31 The substrate 23 with the low-melting point metal film and the substrate 30 with the low-melting point metal film are overlapped so that 32 is in contact.

  Then, the substrate 23 with the low melting point metal film and the low melting point metal so that the temperature of the substrate 23 with the low melting point metal film and the temperature of the substrate 30 with the low melting point metal film are equal to or higher than the melting point of the low melting point metal film 32. The substrate with film 30 is heated. Thereafter, the substrate 23 with the low melting point metal film and the substrate 30 with the low melting point metal film are cooled. In this case, the temperature of the substrate 23 with the low melting point metal film and the temperature of the substrate 30 with the low melting point metal film are not less than the melting point of the low melting point metal film 22 and not more than the melting point of the low melting point metal film 32. Cooling.

  Then, the substrate 23 with the low melting point metal film and the substrate 30 with the low melting point metal film are separated. When the substrate 23 with the low melting point metal film and the substrate 30 with the low melting point metal film are separated from each other, the carbon nanotube group 5 and the substrate 30 with the low melting point metal film are in close contact with each other. That is, the carbon nanotube group 5 is peeled off from the substrate 23 with the low-melting point metal film and is in close contact with the substrate 30 with the low-melting point metal film.

  When the temperature is equal to or higher than the melting point of the low melting point metal film 22 and lower than the melting point of the low melting point metal film 32, the low melting point metal film 22 deposited on the substrate 23 with the low melting point metal film is in a molten state. Therefore, the adhesion between the carbon nanotube group 5 and the substrate 30 with the low melting point metal film is stronger than the adhesion between the carbon nanotube group 5 and the substrate 23 with the low melting point metal film. Accordingly, the carbon nanotube group 5 is peeled off from the substrate 23 with the low melting point metal film and is in close contact with the substrate 30 with the low melting point metal film.

  Then, the carbon nanotube group 5 bonded to the substrate 30 with the low melting point metal film is subjected to the densification process described in the first embodiment, the second embodiment, or the fifth embodiment, thereby obtaining the carbon nanotube group. Thus, the density of the carbon nanotubes 1 can be further increased. Such a process can be repeated a plurality of times, and the density of the carbon nanotubes 1 of the carbon nanotube group 5 can be further increased.

According to this embodiment, the density of the carbon nanotubes 1 of the carbon nanotube group 5 can be made high as a whole.
<Seventh embodiment>
A seventh embodiment of the present invention will be described with reference to the drawings in FIGS. In the present embodiment, a method of applying the carbon nanotube group 5 densified by the densification process described in the first embodiment, the second embodiment, or the fifth embodiment to a heat radiation bump will be described.

  Conventionally, a face-up structure in which the high-power transistor chip 40 is directly bonded to the package 41 has been used. FIG. 34 shows a conventional transistor implementation. The high output transistor chip 40 and the package 41 are connected by wire bonding. That is, the electrode 42 formed on the surface of the high-power transistor chip 40 and the electrode (not shown) formed on the package 41 are connected by a wire such as a gold wire. The transistor mounting shown in FIG. 34 uses a face-up structure and ensures heat dissipation by releasing heat through the high-power transistor chip 40.

  Further, there is flip chip mounting in which the high output transistor chip 40 is turned over, and the electrodes 42 formed on the surface of the high output transistor chip 40 and the electrodes of the package 41 are connected by carbon nanotube bumps 43. As shown in FIG. 35, in flip chip mounting, the high output transistor chip 40 is turned upside down, so that an electrode 42 formed on the surface of the high output transistor chip 40 and an electrode (not shown) formed on the package 41 are provided. Connect. That is, the electrode 42 formed on the surface of the high-power transistor chip 40 and the electrode formed on the package 41 are connected with the surface of the high-power transistor chip 40 facing the package 41. Here, the bump is a terminal formed in a protruding shape. The carbon nanotube bump 43 is a terminal in which the carbon nanotube group 5 is formed on the protrusion.

  As shown in FIG. 36, the carbon nanotube bump 43 connects the electrode 42 formed on the surface of the high-power transistor chip 40 and the electrode formed on the package 41. In FIG. 36, the high-power transistor chip 40 is turned upside down, and the electrodes 42 formed on the surface of the high-power transistor chip 40 face the direction of the package 41. The carbon nanotube bump 43 serves as a heat dissipation path for dissipating heat generated by the high-power transistor chip 40. In order to sufficiently dissipate heat generated by the high-power transistor chip 40, it is necessary to increase the density of the carbon nanotubes 1 of the carbon nanotube bumps 43. However, the occupation ratio of the carbon nanotubes 1 in the conventional carbon nanotube bumps 43 is about 10%, and it has been desired to increase the density of the carbon nanotubes 1 in the conventional carbon nanotube bumps 43.

  In this embodiment, the carbon nanotube group 5 densified by the densification process described in the first embodiment, the second embodiment, or the fifth embodiment is used for the carbon nanotube bump 43. That is, by using the densified carbon nanotube group 5 as the carbon nanotube bump 43, the electrode 42 formed on the surface of the high-power transistor chip 40 and the electrode formed on the package 41 are connected. In the present embodiment, an aluminum nitride substrate 50 is used as a substrate for growing the carbon nanotubes 1. The aluminum nitride substrate 50 is used as a material for manufacturing the package 41. However, the aluminum nitride substrate 50 used as a substrate for growing the carbon nanotubes 1 is an example, and the present invention is not limited to this.

  As shown in FIG. 37, an electrode 51 is formed of a metal such as gold on an aluminum nitride substrate 50. Aluminum having a thickness of 5 nm is deposited on the electrode 51. Then, iron having a thickness of 1 nm is deposited on the aluminum deposited on the electrode 51. In this case, aluminum and iron are used as a catalyst for growing the carbon nanotubes 1.

  Patterning is performed on the aluminum deposited on the electrode 51 and the iron deposited on the aluminum. In this case, the shape of aluminum and iron formed by patterning is made to be the same shape as the shape of the electrode 42 formed on the surface of the high-power transistor chip 40. Further, the center position of aluminum and iron formed by patterning is set to the same position as the center position of the electrode 42 formed on the surface of the high-power transistor chip 40. The size of aluminum and iron formed by patterning may be the same as the size of the electrode 42 formed on the surface of the high-power transistor chip 40, or may be several times larger.

  Next, the carbon nanotube group 5 having a length of 20 μm or more is grown on the aluminum nitride substrate 50 by using the method described in the first embodiment or the fifth embodiment. FIG. 38 shows the carbon nanotube group 5 grown on the aluminum nitride substrate 50. The occupation ratio of the carbon nanotubes 1 in the carbon nanotube group 5 shown in FIG. 38 is about 10%.

  Then, using the densification process described in the first embodiment, the second embodiment, or the fifth embodiment, the density of the carbon nanotubes 1 at the ends of the carbon nanotube groups 5 not in contact with the aluminum nitride substrate 50 is increased. Densify. In this case, the diameter of the end of the carbon nanotube group 5 where the density of the carbon nanotubes 1 is high is the same as the size of the electrode 42 of the high-power transistor chip 40 or the high-power transistor chip 40. The carbon nanotube group 5 is grown so as to be smaller than the size of the electrode 42.

  By changing the size of the catalyst deposited on the aluminum nitride substrate 50, the size of the diameter of the end of the carbon nanotube group 5 where the density of the carbon nanotubes 1 is high can be changed. Therefore, when patterning the catalyst deposited on the aluminum nitride substrate 50 on which the carbon nanotube group 5 is grown, the size of the catalyst is changed in consideration of the size of the electrode 42 of the high-power transistor chip 40. The relationship between the size of the catalyst deposited on the aluminum nitride substrate 50 and the size of the diameter of the end of the carbon nanotube group 5 where the density of the carbon nanotubes 1 is high can be obtained by experiment or simulation. Good.

  FIG. 39 shows the densified carbon nanotube group 5 and the aluminum nitride substrate 50. The carbon nanotube groups 5 formed by the method described in the first embodiment, the second embodiment, or the fifth embodiment are different in the length of the carbon nanotubes 1. That is, the carbon nanotube group 5 is highly likely to grow with the lengths of the carbon nanotubes 1 being uneven. When the degree of unevenness of the lengths of the carbon nanotubes 1 in the carbon nanotube group 5 is large, a process for making the lengths of the carbon nanotubes 1 in the carbon nanotube group 5 uniform is performed.

  With reference to FIGS. 40 to 43, a process for making the lengths of the carbon nanotubes 1 of the carbon nanotube group 5 uniform will be described. As shown in FIG. 40, in the carbon nanotube group 5 grown on the aluminum nitride substrate 50, the length of each carbon nanotube 1 is not uniform. The carbon nanotube group 5 shown in FIG. 40 is subjected to the densification process described in the first embodiment, the second embodiment, or the fifth embodiment.

  First, an interlayer insulating film 60 is deposited on the aluminum nitride substrate 50 so as to cover the carbon nanotube group 5. As the interlayer insulating film 60, a porous silica film, an SOG (spin on glass) film, or the like is used. After the interlayer insulating film 60 is deposited on the aluminum nitride substrate 50, heat treatment is performed to solidify the interlayer insulating film 60. FIG. 41 is a view showing the structure of the aluminum nitride substrate 50 on which the interlayer insulating film 60 is deposited so as to cover the carbon nanotube group 5.

  When the interlayer insulating film 60 is deposited on the aluminum nitride substrate 50 and heat treatment is performed, the carbon nanotube group 5 is solidified together with the interlayer insulating film 60. After the carbon nanotube group 5 is solidified together with the interlayer insulating film 60, the carbon nanotube group 5 and the interlayer insulating film 60 are polished by a chemical mechanical polishing (CMP) process. In this case, the carbon nanotube group 5 and the interlayer insulating film 60 are polished until the length of each carbon nanotube 1 of the carbon nanotube group 5 becomes uniform. FIG. 42 shows the aluminum nitride substrate 50 after the carbon nanotube group 5 and the interlayer insulating film 60 have been polished.

  Thereafter, the interlayer insulating film 60 deposited on the aluminum nitride substrate 50 is removed. However, if there is no need to remove the interlayer insulating film 60 deposited on the aluminum nitride substrate 50, the interlayer insulating film 60 deposited on the aluminum nitride substrate 50 may not be removed.

  Thus, by making the lengths of the carbon nanotubes 1 of the carbon nanotube group 5 uniform, the carbon nanotube group 5 can be stably bonded to the high-power transistor chip 40.

  Next, a method of connecting the electrode 42 formed on the surface of the high-power transistor chip 40 and the electrode formed on the package 41 by using the carbon nanotube group 5 as the carbon nanotube bump 43 will be described.

  First, an aluminum nitride substrate 50 used for manufacturing the package 41 is prepared. The carbon nanotube group 5 is grown on the aluminum nitride substrate 50 by the growth method of the carbon nanotube group 5 described in the first embodiment or the second embodiment. The carbon nanotube group 5 formed on the aluminum nitride substrate 50 is subjected to the densification process described in the first embodiment, the second embodiment, or the fifth embodiment. Further, the carbon nanotube group 5 formed on the aluminum nitride substrate 50 may have been subjected to a process for making the lengths of the carbon nanotubes 1 uniform.

  Next, gold having a thickness of 1 μm is deposited on the carbon nanotube group 5 formed on the aluminum nitride substrate 50. However, the thickness of gold deposited on the carbon nanotube group 5 is an example, and the present invention is not limited to this. Further, gold may be deposited on a portion of the carbon nanotube group 5 formed on the aluminum nitride substrate 50 to be bonded to the electrode 42 formed on the surface of the high-power transistor chip 40.

Then, using a normal flip chip bonder, the carbon nanotube group 5 on which gold is deposited and the electrode 42 formed on the surface of the high output transistor chip 40 are bonded. The pressure used for bonding the carbon nanotube group 5 and the electrode 42 formed on the surface of the high-power transistor chip 40 is 6 kg / cm ² and the temperature is 345 ° C. However, the pressure and temperature are examples, and the present invention is not limited to these.

  FIG. 43 is a diagram showing the structure of the aluminum nitride substrate 50 provided with the high-power transistor chip 40. As shown in FIG. In FIG. 43, the carbon nanotube group 5 is used as the carbon nanotube bump 43. The electrode 42 formed on the surface of the high-power transistor chip 40 and the electrode 51 on the aluminum nitride substrate 50 are connected via the carbon nanotube group 5. Among the ends of the carbon nanotube group 5, the density of the carbon nanotube 1 at the end bonded to the high output transistor chip 40 is 10 times the density of the carbon nanotube 1 at the end not bonded to the high output transistor chip 40. It is about twice. Therefore, it has higher heat dissipation than the conventional carbon nanotube bump 43. The end of the carbon nanotube group 5 having the high density of the carbon nanotubes 1 is bonded to the electrode 42 formed on the high output transistor chip 40, so that the heat of the high output transistor chip 40 is increased. Heat is dissipated through the carbon nanotube group 5.

  Further, the carbon nanotube group 5 in which the density of the carbon nanotubes 1 is generally high is used to connect the electrode 42 formed on the surface of the high-power transistor chip 40 and the electrode 51 on the aluminum nitride substrate 50. You can also. The carbon nanotube group 5 in which the density of the carbon nanotubes 1 is high as a whole can be produced by the method described in the sixth embodiment. By using the carbon nanotube group 5 in which the density of the carbon nanotubes 1 is high as a whole, it is possible to increase the degree of freedom in designing the wiring board.

<Eighth Embodiment>
An eighth embodiment of the present invention will be described with reference to the drawings in FIGS. Currently, LSI wiring is a multilayer wiring of 10 layers or more, and copper is usually used as a wiring material. However, there is a concern about disconnection due to electromigration due to an increase in current density accompanying a reduction in LSI wiring width. Therefore, an attempt has been made to replace the vertical wiring (via wiring) of the LSI with the carbon nanotube 1 that can withstand a higher current density. FIG. 44 shows the structure of the LSI 70. As shown in FIG. 44, the LSI 70 includes an insulating film 72 that sandwiches the copper wiring 71, and a via 73 that electrically connects the copper wiring 71 and the other copper wiring 71.

  In the present embodiment, a method of applying the carbon nanotube group 5 densified by the densification process described in the first embodiment, the second embodiment, or the fifth embodiment to LSI wiring will be described. In the present embodiment, the via 73 constituting the LSI 70 shown in FIG. 44 is replaced with the densified carbon nanotube group 5. Hereinafter, a method of replacing the via 73 constituting the LSI 70 with the densified carbon nanotube group 5 will be described with reference to FIGS. 45 to 51.

  First, as shown in FIG. 45, a substrate 74 on which the carbon nanotube group 5 is grown is prepared. In this case, as the substrate 74, the silicon substrate 2 or the silicon substrate 7 with an oxide film may be used, or another substrate may be used. The carbon nanotube group 5 is grown on the substrate 74 using the method for growing the carbon nanotubes 1 shown in the first embodiment or the fifth embodiment. Further, the carbon nanotube group 5 is densified using the densification process shown in the first embodiment, the second embodiment, or the fifth embodiment. In the present embodiment, cobalt, iron or other metals are used as a catalyst for growing the carbon nanotube group 5 on the substrate 74.

  It is necessary to grow the carbon nanotube group 5 on the substrate 74 so that the carbon nanotube group 5 can be disposed at the position of the via 73 constituting the LSI 70. Therefore, in the present embodiment, the carbon nanotube group 5 is grown on the substrate 74 by patterning the catalyst so that the carbon nanotube group 5 can be arranged at the position of the via 70 constituting the LSI 70.

  Next, a cobalt film 77 is deposited to a thickness of 5 nm on the electrode 76 of the LSI substrate 75, a tantalum film 78 is deposited to a thickness of 5 nm on the cobalt film 77, and a titanium film is deposited on the tantalum film 78. 79 is deposited with a thickness of 5 nm. In place of the cobalt film 77, a film of iron, nickel, or the like may be used. Further, instead of the cobalt film 77, a film of cobalt alloy, iron alloy, nickel alloy or the like may be used.

  The LSI substrate 75 on which the cobalt film 77, the tantalum film 78, and the titanium film 79 are deposited and the substrate 74 are overlaid. Specifically, as shown in FIG. 46, the end of the carbon nanotube group 5 (the end of the end of the carbon nanotube group 5 that is not in contact with the substrate 74) is in contact with the electrode 76 of the LSI substrate 75. As described above, the substrate 74 and the LSI substrate 75 are overlapped. In this case, the substrate 74 and the LSI substrate 75 are overlapped so that the longitudinal direction of the substrate 74 is substantially parallel to the longitudinal direction of the LSI substrate 75. Further, by optical alignment, the substrate 74 and the LSI substrate 75 are overlapped so that the end of the carbon nanotube group 5 and the electrode 76 of the LSI substrate 75 are in contact with each other.

In a state where the substrate 74 and the LSI substrate 75 are superposed, they are transferred into the CVD furnace. After evacuation in the CVD furnace, the stage on which the substrate 74 and the LSI substrate 75 are placed is heated. Then, after the temperature in the CVD furnace is stabilized, a process gas (mixed gas) is introduced into the CVD furnace at 1 kPa. In this embodiment, argon and acetylene (C ₂ H ₂ ) are used as the process gas. Further, a hydrocarbon gas such as methane (CH ₄ ) or ethylene (C ₂ H ₄ ) or alcohol may be added to the process gas of argon and acetylene (C ₂ H ₂ ). Further, instead of acetylene (C ₂ H ₂ ) in the process gas, a hydrocarbon gas such as methane (CH ₄ ) or ethylene (C ₂ H ₄ ) or alcohol may be used. Further, the process gas may be composed of a plurality of types of hydrocarbon-based gas, or may be composed of a plurality of types of hydrocarbon-based gas and alcohol.

  By introducing the process gas into the CVD furnace, the cobalt film 77 deposited on the electrode 76 of the LSI substrate 75 is in a molten state. Therefore, the carbon nanotube group 5 and the electrode 76 of the LSI substrate 75 are firmly bonded.

  The temperature of the stage in the CVD furnace is desirably set to a temperature at which the carbon nanotubes 1 of the carbon nanotube group 5 do not grow (for example, a temperature of about 350 ° C.) although the cobalt film 77 reacts with the process gas. Note that the temperature of the stage in the CVD furnace may vary depending on the type of process gas and the thickness of the film deposited on the LSI substrate 75.

  After combining the carbon nanotube group 5 and the electrode 76 of the LSI substrate 75, the substrate 74 and the LSI substrate 75 are taken out from the CVD furnace. Then, the substrate 74 and the LSI substrate 75 are separated. When the substrate 74 and the LSI substrate 75 are separated, the carbon nanotube group 5 and the electrode 76 of the LSI substrate 75 are in close contact with each other. That is, the carbon nanotube group 5 is peeled off from the substrate 74 and is in close contact with the electrode 76 of the LSI substrate 75.

  In the present embodiment, the carbon nanotube group 5 is grown on the substrate 74 using the growth method of the carbon nanotubes 1 described in the first embodiment or the fifth embodiment. That is, after a very thin catalyst film (a catalyst film of several nm or less) is deposited on the substrate 74, the carbon nanotube group 5 is grown. Since an extremely thin catalyst film is deposited on the substrate 74, the adhesion between the substrate 74 and the carbon nanotube group 5 is weak. Therefore, the problem that the carbon nanotube group 5 is not peeled off from the substrate 74 does not occur.

  47, after the gap between the substrate 74 and the LSI substrate 75 is filled with an interlayer insulating film 80 such as an SOG film or a porous silica film, the substrate 74 and the LSI substrate 75 are separated from each other. Good. In this case, the interlayer insulating film 80 is dissolved in a suitable solvent to make the interlayer insulating film 80 liquid.

  Then, the gap between the substrate 74 and the LSI substrate 75 is filled with the interlayer insulating film 80 by immersing the substrate 74 and the LSI substrate 75 in the liquid interlayer insulating film 80. Alternatively, a liquid interlayer insulating film 80 is injected into the gap between the substrate 74 and the LSI substrate 75, thereby filling the gap between the substrate 74 and the LSI substrate 75 with the interlayer insulating film 80. May be.

  Then, by performing heat treatment on the substrate 74 and the LSI substrate 75, the interlayer insulating film 80 is solidified, and the interlayer insulating film 80 is formed between the substrate 74 and the LSI substrate 75.

  If the substrate 74 and the LSI substrate 75 are separated before the interlayer insulating film 80 is formed in the gap between the substrate 74 and the LSI substrate 75, the interlayer insulating film is attached to the LSI substrate 75 to which the carbon nanotube group 5 is in close contact. 80 is formed. Specifically, the interlayer insulating film 80 is formed on the LSI substrate 75 by applying the liquid interlayer insulating film 80 to the LSI substrate 75 in close contact with the carbon nanotube group 5 by using spin coating or the like.

  Further, after the interlayer insulating film 80 is formed on the substrate 74, the substrate 74 and the LSI substrate 75 may be overlapped. That is, using the substrate 74 on which the interlayer insulating film 80 has already been formed, the substrate 74 and the LSI substrate 75 are overlaid. In this case, the interlayer insulating film 80 is formed on the substrate 74 by the following method.

  First, an interlayer insulating film 80 is deposited on the substrate 74 so as to cover the carbon nanotube group 5. After the interlayer insulating film 80 is deposited on the substrate 74, heat treatment is performed to solidify the interlayer insulating film 80. FIG. 48 is a view showing the structure of the substrate 74 on which the interlayer insulating film 80 is deposited so as to cover the carbon nanotube group 5. When the interlayer insulating film 80 is deposited on the substrate 74 and heat treatment is performed, the carbon nanotube group 5 is solidified together with the interlayer insulating film 80. Thus, the interlayer insulating film 80 is formed on the substrate 74.

  In addition, after the carbon nanotube group 5 is solidified together with the interlayer insulating film 80, the interlayer insulating film 80 is polished by a chemical mechanical polishing (CMP) process. In this case, the interlayer insulating film 80 is polished so that the tips of the carbon nanotube groups 5 are exposed. Furthermore, when the length of each carbon nanotube 1 of the carbon nanotube group 5 is not uniform, the carbon nanotube group 5 and the interlayer insulating film 80 are polished until the length of each carbon nanotube 1 of the carbon nanotube group 5 is uniform. Also good.

  Further, when the substrate 74 on which the interlayer insulating film 80 is already formed is used and the substrate 74 and the LSI substrate 75 are overlapped, the tip of the carbon nanotube group 5 may be protruded. That is, as shown in FIG. 49, the length of the carbon nanotube group 5 is made longer than the length of the interlayer insulating film 80 formed on the substrate 74 in the thickness direction. Specifically, wet etching or dry etching is performed on the interlayer insulating film 80 to scrape only the interlayer insulating film 80. By cutting only the interlayer insulating film 80, the tip of the carbon nanotube group 5 can be protruded.

  The wet etching in this embodiment uses liquid or gaseous dilute hydrogen fluoride. When a porous silica film is used as the interlayer insulating film 80, only the interlayer insulating film 80 is etched when wet etching is performed. Therefore, the tip of the carbon nanotube group 5 can be protruded. When the interlayer insulating film 80 is cut by dry etching, argon ions are struck against the interlayer insulating film 80 by a sputtering method. When dry etching is performed, only the interlayer insulating film 80 is etched. Therefore, the tip of the carbon nanotube group 5 can be protruded.

  After the interlayer insulating film 80 is formed on the substrate 74 in this way, the substrate 74 and the LSI substrate 75 are overlapped, and the substrate 74 and the LSI substrate 75 are separated, whereby the interlayer insulating film 80 is formed on the LSI substrate 75. The carbon nanotube group 5 is formed and in close contact.

  Next, chemical mechanical polishing (CMP) is performed on the LSI substrate 75 on which the interlayer insulating film 80 is formed, so that the length of the carbon nanotube group 5 and the thickness of the interlayer insulating film 80 are in desired ranges. Until this, the carbon nanotube group 5 and the interlayer insulating film 80 are polished. The LSI substrate 75 on which the interlayer insulating film 80 is formed may be an LSI substrate 75 on which the interlayer insulating film 80 is formed after the substrate 74 and the LSI substrate 75 are separated from each other, or the substrate 74 and the LSI substrate 75 are separated from each other. It may be an LSI substrate 75 on which an interlayer insulating film 80 has been previously formed. FIG. 50 shows the LSI substrate 75 after the carbon nanotube group 5 and the interlayer insulating film 80 have been polished.

  Next, copper wiring 71 is formed on the LSI substrate 75. Specifically, copper is deposited on the carbon nanotube group 5 in close contact with the LSI substrate 75, and copper is deposited on the interlayer insulating film 80 formed on the LSI substrate 75. Then, the deposited copper is patterned to form a copper wiring 71 on the LSI substrate 75. An interlayer insulating film 80 is formed between the copper wiring 71 and another copper wiring 71. However, the formation of the interlayer insulating film 80 may not be performed at this stage. FIG. 51 shows the LSI substrate 75 after the copper wiring 71 is formed.

  The process of forming the carbon nanotube group 5 and the interlayer insulating film 80 on the LSI substrate 75 and forming the copper wiring 71 on the carbon nanotube group 5 and the interlayer insulating film 80 is referred to as a first wiring process. After performing the first wiring process, the carbon nanotube group 5 is further formed on the LSI substrate 75. That is, the carbon nanotube group 5 is formed on the copper wiring 71, and the LSI substrate 75 is multilayered. A process of forming the carbon nanotube group 5 on the copper wiring 71 will be described below.

  As shown in FIG. 52, a substrate 74 on which the carbon nanotube group 5 is grown is prepared. The density of the carbon nanotube group 5 grown on the substrate 74 is the same as in the first wiring process. In addition, the patterning is performed on the catalyst so that the carbon nanotube group 5 is grown on the substrate 74 so that the carbon nanotube group 5 can be arranged at the position of the via 70 constituting the LSI 70, as in the first wiring process. is there. Further, the patterning is performed on the catalyst so that the carbon nanotube group 5 can be disposed at the position of the via 70 constituting the LSI 70, and the carbon nanotube group 5 is grown on the substrate 74, as in the first wiring process. is there.

  Next, a cobalt film 77 is deposited to a thickness of 5 nm on the copper wiring 71, a tantalum film 78 is deposited to a thickness of 5 nm on the cobalt film 77, and a titanium film 79 is deposited to 5 nm on the tantalum film 78. Deposit at a thickness of. Instead of the cobalt film 77, a film of iron, nickel, or the like may be used.

  Then, the LSI substrate 75 on which the copper wiring 71 is formed and the substrate 74 are overlaid. Specifically, as shown in FIG. 53, the substrate 74 and the LSI substrate 75 are overlapped so that the end portions of the carbon nanotube groups 5 not in contact with the substrate 74 are in contact with the copper wiring 71. In this case, the substrate 74 and the LSI substrate 75 are overlapped so that the longitudinal direction of the substrate 74 is substantially parallel to the longitudinal direction of the LSI substrate 75. Further, by optical alignment, the substrate 74 and the LSI substrate 75 are overlapped so that the end of the carbon nanotube group 5 and the electrode 76 of the LSI substrate 75 are in contact with each other.

  Here, the method of bonding the end of the carbon nanotube group 5 (the end of the carbon nanotube group 5 that is not in contact with the substrate 74) to the copper wiring 71 is the same as that of the carbon nanotube group 5 in the first wiring process. This is the same as the method of coupling to the electrode 76.

  After the gap between the substrate 74 and the copper wiring 71 is filled with the interlayer insulating film 80, the substrate 74 and the LSI substrate 75 are separated. When the substrate 74 and the LSI substrate 75 are separated, the carbon nanotube group 5 and the copper wiring 71 are in close contact with each other. That is, the carbon nanotube group 5 is peeled off from the substrate 74 and is in close contact with the copper wiring 71. FIG. 54 shows a state in which the carbon nanotube group 5 is peeled off from the substrate 74 and the carbon nanotube group 5 is in close contact with the copper wiring 71 formed on the LSI substrate 75.

  Next, chemical mechanical polishing (CMP) is performed on the LSI substrate 75 on which the interlayer insulating film 80 is formed, so that the length of the carbon nanotube group 5 and the thickness of the interlayer insulating film 80 are in desired ranges. Until this, the carbon nanotube group 5 and the interlayer insulating film 80 are polished. FIG. 55 shows the LSI substrate 75 after the carbon nanotube group 5 and the interlayer insulating film 80 have been polished.

  Then, copper wiring 71 is formed on the LSI substrate 75. The method for forming the copper wiring 71 on the LSI substrate is the same as in the first wiring process. The process of forming the carbon nanotube group 5 and the interlayer insulating film 80 on the copper wiring 71 and further forming the copper wiring 71 is referred to as a second wiring process. The material and method used in the first wiring process can be used in the second wiring process.

  In the present embodiment, the first wiring process is performed in which the carbon nanotube group 5 and the interlayer insulating film 80 are formed on the LSI substrate 75 and the copper wiring 71 is formed on the carbon nanotube group 5 and the interlayer insulating film 80. In this embodiment, the carbon nanotube group 5 and the interlayer insulating film 80 are formed on the copper wiring 71, and a second wiring process for forming the copper wiring 71 is performed. By repeating the second wiring step, a multi-layered LSI using the carbon nanotube group 5 is formed.

  Further, the method of bonding the carbon nanotube group 5 to the electrode 76 or the copper wiring 71 using the cobalt film 77, the tantalum film 78, and the titanium film 79 of the present embodiment can also be used in the seventh embodiment. . That is, the carbon nanotube group 5 in the seventh embodiment may be bonded to the electrode formed on the surface of the high-power transistor chip 40 by using the method for bonding the carbon nanotube group 5 and the electrode 76 in the present embodiment. .

  According to the present embodiment, by replacing the via 73 constituting the LSI 70 with the densified carbon nanotube group 5, the possibility of disconnection due to electromigration can be reduced. That is, the possibility of disconnection between the electrode 76 and the copper wiring 71 constituting the LSI 70 can be reduced.

<Modification>
In the first to eighth embodiments of the present invention, carbon nanofibers may be used instead of the carbon nanotubes 1. The growth method of the carbon nanofiber is the same as the growth method of the carbon nanotube 1, and the description thereof is omitted here. In addition, the structures and methods of the first to eighth embodiments of the present invention can be applied to fine wire-like substances such as carbon nanotubes 1 and carbon fibers. Furthermore, the structure and method of the first to eighth embodiments of the present invention can be applied to carbon-based fibers. In addition, the structures and methods of the first to eighth embodiments of the present invention can be applied to hollow carbon fibers and non-hollow carbon fibers.

Claims (20)

An aggregate structure of the carbon-based fibers composed of a plurality of carbon-based fibers,
A carbon-based fiber comprising an assembly of the carbon-based fibers in which the carbon-based fibers having different densities of the carbon-based fibers at one end and the carbon-based fibers at the other end are arranged in the length direction. Aggregate structure.   The aggregate structure of carbon-based fibers according to claim 1, wherein a substance different from the carbon-based fibers is present between adjacent aggregates of the carbon-based fibers.   The aggregate structure of carbon-based fibers according to claim 1, wherein a space is provided between the aggregates of the adjacent carbon-based fibers.   The aggregate structure of carbon-based fibers according to claim 1, wherein the aggregates of the adjacent carbon-based fibers are arranged in different directions.   2. The carbon-based fiber according to claim 1, wherein the carbon-based fiber at the other end, which is higher in density than the carbon-based fiber at one end, is formed such that the carbon-based fibers are in close contact with each other. Aggregate structure.   6. The carbon-based fiber according to claim 5, wherein one end is bonded to the package substrate, and the other end that is higher in density than the carbon-based fiber at one end is bonded to the semiconductor element. Aggregate structure.   The aggregate structure of carbon-based fibers according to any one of claims 1 to 6, wherein the carbon-based fibers are either carbon nanotubes or carbon nanofibers.   The aggregate structure of carbon-based fibers according to claim 2, wherein the substance different from the carbon-based fibers is any one of a dielectric, an organic substance, a metal, and an insulator. Growing an aggregate of carbon-based fibers in which carbon-based fibers are arranged in a length direction in a substantially vertical direction from a substrate surface;
A method for producing an aggregate structure of carbon-based fibers, the method comprising a compacting step of compacting one end portion in the length direction of the aggregate of carbon-based fibers. The dense step includes impregnating the carbon-based fiber aggregate with a solvent containing an adhesion substance different from the carbon-based fiber; and
The method for producing an aggregate structure of carbon-based fibers according to claim 9, further comprising a step of evaporating the solvent. The dense step includes impregnating a solvent with the aggregate of carbon-based fibers;
The method for producing a carbon-based fiber aggregate structure according to claim 9, further comprising a step of drying the carbon-based fiber aggregate and the solvent. Growing the aggregate of carbon-based fibers in which carbon-based fibers are arranged in a length direction in a substantially vertical direction from the substrate surface of the first substrate;
A compaction step of compacting one end in the length direction of the aggregate of carbon-based fibers;
Adhering the other end in the length direction of the aggregate of carbon-based fibers to the substrate surface of the second substrate;
Peeling the aggregate of carbon fibers grown on the substrate surface of the first substrate from the substrate surface of the first substrate;
A method for producing an aggregate structure of carbon-based fibers, the method comprising a dense step of densely gathering the other end portion in the length direction of the aggregate of carbon-based fibers. The dense step includes impregnating a solvent with the aggregate of carbon-based fibers;
The method for producing a carbon-based fiber aggregate structure according to claim 12, further comprising a step of drying the carbon-based fiber aggregate and the solvent. The dense step includes impregnating the carbon-based fiber aggregate with a solvent containing an adhesion substance different from the carbon-based fiber; and
The method for producing an aggregate structure of carbon-based fibers according to claim 12, further comprising a step of evaporating the solvent.   14. The method for producing an aggregate structure of carbon fibers according to 13, wherein the solvent is selected from the group consisting of N, N-dimethylformamide, dichloroethane, isopropyl alcohol, methanol, and ethanol.   The method for producing an aggregate structure of carbon-based fibers according to claim 13, wherein the solvent contains a surfactant or a functional polymer. A method for forming a wiring on a semiconductor substrate, comprising:
Forming an aggregate structure of the carbon-based fibers composed of a plurality of carbon-based fibers on an electrode included in the semiconductor substrate;
Bonding the electrode and the aggregate structure of the carbon-based fibers;
Forming a conductor on the carbon fiber aggregate structure;
Forming an aggregate structure of the carbon-based fibers on the conductor;
Adhering the conductor and the aggregate structure of the carbon-based fibers,
In the aggregate of carbon-based fibers, the carbon-based fibers are arranged in a length direction, and the density of the carbon-based fibers at one end is different from the density of the carbon-based fibers at the other end. The method of forming a wiring on a semiconductor substrate, wherein the carbon fibers at the other end, which is higher in density than the carbon fibers at the end, are formed in close contact with each other. The step of adhering the electrode and the carbon-based fiber aggregate structure includes depositing a catalyst film on the electrode and melting the catalyst film using a process gas to collect the electrode and the carbon-based fiber. It is a process of bonding the body structure,
The step of adhering the conductor and the aggregate structure of the carbon-based fibers includes depositing a catalyst film on the conductor and melting the catalyst film using a process gas to form the conductor and the carbon-based material. 18. The method for forming a wiring of a semiconductor substrate according to claim 17, which is a step of adhering the fiber aggregate structure.   19. The method for forming a wiring of a semiconductor substrate according to claim 18, wherein the catalyst film is made of a metal selected from the group consisting of cobalt, iron, and nickel, or an alloy containing the metal.   The method for forming a wiring of a semiconductor substrate according to claim 18, wherein the process gas includes at least one of a hydrocarbon-based gas and alcohol.

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