JP5636654B2 - Carbon nanotube sheet structure, manufacturing method thereof, and semiconductor device - Google Patents

Description

  The present invention generally relates to semiconductor devices, and more particularly to a carbon nanotube sheet structure, a method for manufacturing the same, and a semiconductor device.

  2. Description of the Related Art Conventionally, in electronic devices such as servers and personal computers, heat spreaders are used for heat dissipation of semiconductor devices that generate heat such as CPUs. As such a heat spreader, copper having a high thermal conductivity is used as a material. For example, a semiconductor chip is typically mounted directly under such a heat spreader via an indium layer.

  However, since indium is used for transparent electrodes such as ITO, there has been a significant increase in demand in recent years, and the price has greatly increased. For this reason, the advent of alternative materials cheaper than indium is awaited. In addition, indium is not high in thermal conductivity of about 50 W / m · K, and a heat dissipation material having higher thermal conductivity (Thermal Interface Material: TIM) in order to more efficiently dissipate heat from the semiconductor element. ) Is desired.

Japanese Unexamined Patent Publication No. 2007-121982 JP 2005-150362 A JP 2006-147801 A JP 2008-251963 A

  Recently, Patent Document 1 proposes a heat dissipation sheet using graphite as an indium substitute material. Such a heat-dissipating sheet is a resin sheet obtained by adding a resin to graphite powder, and a resin having a thermal conductivity of about 1 to 10 W / m · K is interposed between the graphite powders. Sex cannot be used effectively. Graphite has a structure in which graphene sheets composed of six-membered rings of carbon atoms are stacked. Even though it exhibits excellent heat conduction in the in-plane direction of the graphene sheet, heat conduction in the direction perpendicular to the surface is not The heat from the semiconductor chip cannot be effectively transmitted to the heat radiating member.

  Carbon nanotubes have a very high thermal conductivity of about 1500 W / m · K, are excellent in flexibility and heat resistance, and have a high ability as a heat dissipation material. Therefore, for example, if a carbon nanotube sheet structure is constituted by oriented carbon nanotube bundles, and such a carbon nanotube sheet structure can be used as a heat transfer portion between a heat dissipation material on a semiconductor chip, such carbon The nanotube sheet structure exhibits high heat conduction in the direction perpendicular to the substrate, that is, in the direction to dissipate heat, so that an ideal indium substitute material is expected to be obtained.

  However, the ordinary carbon nanotube sheet structure only holds the bundle shape due to the weak van der Waals force between the carbon nanotubes, so when used as an indium substitute material, it is easy to install and handle. The bundle is likely to unwind and the carbon nanotubes are dispersed, and is not suitable for introduction into a semiconductor element as it is.

  Therefore, it is conceivable to produce a carbon nanotube sheet structure with a stable shape by embedding a resin or the like between the carbon nanotubes in the carbon nanotube bundle. For example, Patent Document 2 proposes a structure in which nanotubes are simply dispersed in a resin. However, in the structure of Patent Document 2, a thermal resistance is generated at the contact point between the dispersed nanotubes, and furthermore, since the dispersed nanotubes do not have orientation, a desired heat dissipation characteristic cannot be obtained. It is difficult to use as a heat dissipation material.

  Patent Document 3 discloses a technique of directly embedding a resin or the like in a carbon nanotube bundle that is oriented and grown on the entire surface of a substrate. In the case of this prior art, the orientation is improved as compared with the case where the carbon nanotubes are dispersed in the resin. However, since the resin is interposed between the carbon nanotubes which are thermal conductors and the heat radiator or the heat spreader, The high thermal conductivity of the carbon nanotubes is impaired by the thermal resistance of the resin intervening portion. As described above, the thermal conductivity of the resin itself is about 1 to 10 W / m · K, which is three orders of magnitude different from the thermal conductivity of the carbon nanotube, so the influence is very large.

  For example, when an integrated circuit is mounted on a printed board, the heat dissipation sheet may require an electrical connection function in addition to the heat dissipation function. In such a case, when a conventional combination of carbon nanotubes and resin is used, non-conductive resin exists at the interface between the carbon nanotubes and the circuit side to be mounted, the interface resistance increases, and the function as electrical wiring It is difficult to fulfill. In addition, even if the resin is removed sufficiently, the carbon nanotube alone has a diameter of only a few nanometers to several tens of nanometers, and it will be connected to the upper electrode in a point contact, which is the original excellent nanotube. Electric conductivity cannot be used.

  Although it is not a heat dissipation sheet, a known example (Patent Document 4) relating to an electrode structure using carbon nanotubes proposes a structure that enlarges the contact area with the upper electrode by plating the carbon nanotube bundle with metal. However, although this technique has improved in terms of securing the contact area with the metal electrode, the carbon nanotube itself is hollow, and thus the contact resistance between the carbon nanotube and the metal electrode has the same problem as described above. doing.

  Thus, a heat-dissipating sheet structure using carbon nanotubes that can withstand practical use has not been known.

According to one aspect, the carbon nanotube sheet structure includes a medium defined by opposing first and second main surfaces, and each of the medium from the first main surface to the second main surface. A plurality of carbon nanotubes extending to a first end portion exposed on the first main surface and a second end exposed on the second main surface. The first end of the plurality of carbon nanotubes is open at the first main surface, and the second end is open at the second main surface. Each of the plurality of carbon nanotubes is filled with metal from the first end portion to the second end portion, and the metal includes Au, Ag, Cu, Ni, Al From the group consisting of Mo, Ta, Pt and Co Ri Na from the metal or alloy containing at least one barrel in the said medium, said has a first major surface is a metal film is formed, said first end of said plurality of carbon nanotubes from the metallic film Exposed .

The method of manufacturing the carbon nanotube sheet structure according to another aspect, a plurality of carbon nanotubes on a substrate, from a first end of the base plate, grown to a second end opposite the first end A step of opening the plurality of carbon nanotubes at the second end, and filling a metal into the plurality of carbon nanotubes;
Embedding a medium between the plurality of carbon nanotubes on the substrate;
See containing and a step of removing the substrate, wherein the metal, Au, Ag, Cu, made of metal or an alloy containing Ni, Al, Mo, Ta, at least one selected from the group consisting of Pt and Co, the The step of embedding the medium is performed after the step of filling the metal .

According to another aspect, a semiconductor device includes a medium defined by opposing first and second main surfaces, and each extending from the first main surface to the second main surface of the medium. A plurality of carbon nanotubes, each of the plurality of carbon nanotubes including a first end portion exposed on the first main surface and a second end portion exposed on the second main surface. The first end portions of the plurality of carbon nanotubes are open at the first main surface, and the second end portions are open at the second main surface, Each of the plurality of carbon nanotubes is filled with a metal from the first end portion to the second end portion, and the metal includes Au, Ag, Cu, Ni, Al, Mo, Ta , Pt and Co, at least one selected from the group consisting of The carbon nanotube sheet structure consisting of metal-free or alloy, a semiconductor chip formed in close contact with the first major surface of the medium, and the heat spreader formed in close contact with the second main surface of the medium, including.

According to another aspect, a semiconductor device includes a mounting substrate, a semiconductor chip flip-chip mounted on the mounting substrate, and a connection electrode portion that connects the semiconductor chip to the mounting substrate. Comprises a medium defined by opposing first and second principal surfaces, and a plurality of carbon nanotubes each extending from the first principal surface to the second principal surface of the medium. Each of the plurality of carbon nanotubes has a first end portion exposed on the first main surface and a second end portion exposed on the second main surface, and the plurality of carbon nanotubes The first terminal portion of the nanotube is open at the first main surface, and the second terminal portion is open at the second main surface, and each of the plurality of carbon nanotubes The interior extends from the first end to the first Until the distal end, is filled by the metal, the metal, Au, Ag, Cu, Ni , Al, Mo, Ta, carbon nanotubes made from metal or an alloy containing at least one selected from the group consisting of Pt and Co It consists of a sheet structure.

  According to the present invention, in the carbon nanotube sheet structure, the carbon nanotubes are opened at the first end portion and the second end portion thereof, so that the carbon nanotube has a thermal conductivity and electrical conductivity such as metal. A large material can be filled, and the carbon nanotube sheet structure can be used as an excellent heat dissipation sheet and electrode material.

It is a figure (the 1) explaining the manufacturing process of the carbon nanotube sheet structure by 1st Embodiment. It is FIG. (2) explaining the manufacturing process of the carbon nanotube sheet structure by 1st Embodiment. It is FIG. (3) explaining the manufacturing process of the carbon nanotube sheet structure by 1st Embodiment. FIG. 6 is a view (No. 4) for explaining a production process of the carbon nanotube sheet structure according to the first embodiment. It is FIG. (5) explaining the manufacturing process of the carbon nanotube sheet structure by 1st Embodiment. It is FIG. (6) explaining the manufacturing process of the carbon nanotube sheet structure by 1st Embodiment. It is a figure which shows the example of the carbon nanotube by 1st Embodiment. It is a figure which shows the subject of the conventional carbon nanotube. It is a figure which shows the modification of the carbon nanotube sheet structure by 1st Embodiment. It is a figure which shows another modification of the carbon nanotube sheet structure by 1st Embodiment. It is a figure which shows the further modification of the carbon nanotube sheet structure by 1st Embodiment. It is a figure explaining the effect | action of the carbon nanotube sheet structure by 1st Embodiment. It is a figure explaining the effect | action of the carbon nanotube sheet structure by one modification. It is a figure explaining the effect | action of the carbon nanotube sheet structure by another modification. It is a figure explaining the subject of the conventional carbon nanotube sheet. It is a figure which shows the structure of the semiconductor device by 2nd Embodiment. FIG. 7 is a diagram (part 1) for explaining a manufacturing process of the semiconductor device of FIG. 6; FIG. 7 is a diagram (part 2) for explaining a manufacturing process of the semiconductor device of FIG. 6; FIG. 7 is a diagram (No. 3) for describing a manufacturing step of the semiconductor device of FIG. 6; FIG. 7 is a diagram (No. 4) for explaining a manufacturing step of the semiconductor device of FIG. 6; FIG. 7 is a diagram (No. 5) for explaining a manufacturing process of the semiconductor device of FIG. 6; FIG. 7 is a view (No. 6) for explaining a manufacturing step of the semiconductor device of FIG. 6; It is a figure which shows the structure of the semiconductor device by 3rd Embodiment. It is an enlarged view which expands and shows a part of FIG. It is an enlarged view which expands and shows a part of Drawing 9A further. FIG. 9 is a diagram (No. 1) for explaining a manufacturing step of the semiconductor device of FIG. 8; FIG. 9 is a diagram (No. 2) for describing a manufacturing step of the semiconductor device of FIG. 8; FIG. 9 is a diagram (No. 3) for explaining a manufacturing step of the semiconductor device of FIG. 8; FIG. 10 is a diagram (No. 4) for explaining a manufacturing step of the semiconductor device of FIG. 8; FIG. 10 is a view (No. 5) for explaining a manufacturing step of the semiconductor device of FIG. 8; FIG. 10 is a diagram (No. 6) for explaining a manufacturing step of the semiconductor device of FIG. 8; FIG. 9 is a view (No. 7) for explaining a manufacturing step of the semiconductor device of FIG. 8; FIG. 9 is a diagram illustrating a modification of the semiconductor device in FIG. 8.

[First Embodiment]
1A to 1F are views for explaining a manufacturing process of a carbon nanotube sheet structure according to the first embodiment.

  Referring to FIG. 1A, for example, an average film thickness of, for example, 2. RF is formed on the entire surface of a substrate 11 made of, for example, an iron catalyst using alumina or quartz, or a silicon substrate carrying a thermal oxide film. The catalyst metal layer 12 is formed by depositing to 5 nm. The catalytic metal layer 12 thus formed aggregates on the substrate 11 to form an island structure. In the case where the carbon nanotube sheet structure is used for an electrode or the like and it is necessary to form the carbon nanotube sheet structure in an electrode shape, as described in a later embodiment, in the stage of FIG. The catalytic metal layer 12 is patterned into a desired shape by lithography. Here, the deposition of the catalyst metal layer 12 is not limited to the RF plasma sputtering method, and there is no particular limitation as long as it is a method that can obtain a catalyst thin film having a desired thickness. For example, a DC plasma sputtering method, an impactor method, an ALD (atomic layer deposition) method, an electron beam evaporation (EB) method, or a molecular beam epitaxy (MBE) method can be used. As described below, carbon nanotubes grow from the catalytic metal layer 12, but according to recent knowledge, the catalytic metal layer 12 needs to have an island-like structure as shown in FIG. 1A. In addition, it has been confirmed that desired carbon nanotube growth occurs even in a continuous film.

  Next, in the process of FIG. 1B, a mixed gas of acetylene and argon at a substrate temperature of 620 ° C. to 650 ° C., for example, 650 ° C. under a pressure of 1 kPa, for example, by a hot filament chemical vapor deposition (CVD) method. As a raw material gas, a large number of carbon nanotubes 13 grow from the catalytic metal layer 12. In FIG. 1B, the catalytic metal layer 12 is not shown.

For example, a mixture of acetylene gas and argon gas in a volume ratio of 1: 9 is used as the mixed gas, and this is supplied to a processing vessel of a CVD apparatus at a flow rate of 200 sccm together with a carrier gas having a flow rate of 100 sccm. A bundle composed of a large number of carbon nanotubes 13 having a diameter of 5 nm to 20 nm can be obtained with a surface density of about 10 ¹⁰ to 10 ¹² pieces / cm ² .

  In the step of FIG. 1B, the length of the carbon nanotube 13 can be arbitrarily adjusted according to the growth conditions and growth time in the CVD apparatus. For example, when the thickness of the metal catalyst layer 12 is 2.5 nm, a multi-wall carbon nanotube having a length of about 150 μm can be grown as the carbon nanotube 13 by setting the growth time to 60 minutes. .

  As a method for growing the carbon nanotubes 13, it is also possible to use a remote plasma CVD method, a plasma CVD method, or a thermal CVD method. The raw material gas of the carbon nanotube 13 is not limited to acetylene, and other hydrocarbons such as methane and ethylene and alcohols such as ethanol and methanol can be used. The catalyst constituting the metal catalyst layer 12 is not limited to iron, and may be cobalt, nickel, iron, gold, silver, platinum, or an alloy thereof.

  In addition to the catalytic metal layer 12, molybdenum, titanium, hafnium, zirconium, niobium, vanadium, tantalum nitride, titanium nitride, hafnium nitride, zirconium nitride, niobium nitride, vanadium nitride, titanium silicide, tantalum silicide , Tungsten nitride, aluminum, aluminum nitride, aluminum oxide, molybdenum oxide, titanium oxide, tantalum oxide, hafnium oxide, zirconium oxide, niobium oxide, vanadium oxide, tungsten oxide, tantalum, tungsten, copper, gold, platinum, etc. It is also possible to use at least one kind of metal or alloy as the base metal, the upper metal, or the upper and lower metals.

  FIG. 2A is a perspective view showing an example of a single carbon nanotube 13 formed in this way.

  Referring to FIG. 2A, the carbon nanotube 13 has a multi-walled carbon nanotube structure, and graphene sheets 13a to 13c constituted by six-membered rings of carbon atoms are wound coaxially or spirally to form a hollow shape. A main body 13A is formed. Further, a cap structure 13C having a five-membered ring of carbon atoms is formed at the tip of the main body 13A. In the schematic view of FIG. 1B, the tip of the carbon nanotube 13 is shown in a flat shape, but actually a substantially hemispherical cap structure 13C is formed as shown in FIG. 2B. If such a hemispherical cap structure 13C is present at the tip, the carbon nanotubes are in point contact with the semiconductor chip and the heat spreader, causing thermal resistance.

  In the present embodiment, in the step of FIG. 1C, after the growth of the carbon nanotubes 13 of FIG. 1B, a heat treatment is performed at a temperature of 450 ° C. to 650 ° C. in an oxygen atmosphere or in the air, Then, the cap structure 13C is removed. In the carbon nanotube 13, it is known that the cap structure 13C at the tip thereof is selectively burned by the heat treatment in the oxygen-containing atmosphere, whereby the main body 13A can be easily opened. This is because the cap structure 13C mainly includes a five-membered ring having a chemically active double bond, and the carbon atoms constituting such a double bond are preferentially combined with oxygen atoms. This is because it reacts (oxidizes) and is removed as carbon monoxide or carbon dioxide. In addition, when the carbon atoms are removed in this way, the remaining defect portion becomes more active and continuously undergoes an oxidation reaction. As a result, all of the cap structure 13C is removed, and the tip portion of the carbon nanotube 13 is removed. It will be opened. In this case, the carbon nanotube 13 is composed only of the main body portion 13A. The graphene sheet constituting the surface of the carbon nanotube body portion 13A is stable, and even when such an oxygen heat treatment is performed, carbon atoms are not desorbed except at the tip portion. Due to the open ends of the carbon nanotubes 13 having a hollow structure, the internal space communicates with the space outside the carbon nanotubes.

  The heat treatment conditions in FIG. 1C can be executed, for example, by setting the substrate temperature to 550 ° C. and the oxygen pressure to 1 kPa. Alternatively, the same effect can be obtained by treatment at room temperature, such as oxygen plasma treatment. For example, it is possible to remove the cap structure 13C at the tip by performing such oxygen plasma treatment for 10 minutes at a power of 200 W. As another process, after the resin is first embedded, the tip portion can be removed together with the resin by a chemical mechanical polishing (CMP) method. After polishing, the tip of the carbon nanotube 13 is open.

  Next, in the step of FIG. 1D, the structure of FIG. 1C is introduced into a metal film forming apparatus, and a metal film, for example, a Ni film is deposited on the structure of FIG. 1C by, for example, MBE. In this case, metal atoms are preferentially deposited in the internal space of the carbon nanotubes 13 over the outer wall portion, and therefore, the fine metal wires 14 are formed by the metal atoms in the open carbon nanotubes 13.

  In order to enclose such fine metal wires 14 in the carbon nanotubes 13, it is better to use an electron beam vapor deposition method or an MBE (molecular beam epitaxy) method having a lower energy than a sputtering method, and the size is smaller than that of a cluster. The MBE method capable of vapor deposition is most preferable. An ALD (atomic layer growth) method can also be used. Moreover, it is also possible to form the said metal fine wire 14 using a supercritical fluid. When a supercritical fluid is used, it becomes possible to cover the inside and outside of the open carbon nanotube 13 with a desired metal thin film almost simultaneously due to the nature of the supercritical fluid. The metal thin film may be made of a metal or alloy containing at least one kind of Ag, Cu, Ni, Al, Mo, Ta, Pt, and Co other than Au, but is not particularly limited.

For example, when the fine metal wire 14 is formed by gold electron beam evaporation, the evaporation is preferably 1 × 10 ⁻⁴ Torr (1.33 × 10 ⁻² Pa) or less, for example, 1 × 10 ⁻⁶ Torr. It can be performed at room temperature under a high vacuum environment (1.33 × 10 ⁻⁴ Pa) at a deposition rate of about 0.2 nm / second.

For example, when the metal thin wire 14 is formed by the MBE method of nickel, the deposition is preferably 1 × 10 ⁻⁶ Torr (1.33 × 10 ⁻⁴ Pa) or less, for example, 1 × 10 ⁻⁷ Torr ( In a high vacuum environment of 1.33 × 10 ⁻⁵ Pa), the crucible temperature can be set to, for example, 1500 ° C. at room temperature, and the deposition rate can be about 0.2 nm / second.

Further, when the metal thin wire 14 is formed by the ALD method of aluminum, the deposition is preferably 1 × 10 ⁻⁴ Torr (1.33 × 10 ⁻² Pa) or less, for example, 1 × 10 ⁻⁶ Torr (1 .33 × 10 ⁻⁴ Pa) at a substrate temperature of about 200 ° C. and a deposition rate of about 0.2 nm / second.

  1D, by continuing the deposition of the metal film, as shown in FIGS. 3A and 3B, the metal films 14A and 14B are attached to the surface of the substrate 11 and the outside of the carbon nanotubes 13. It can also be deposited on the wall surface. Since deposition of a metal film is unlikely to occur on the surface of the carbon nanotubes 13, when the metal film is continuously deposited in this way, a metal film 14A is first formed on the substrate 11, and further the deposition of the metal film is continued. As a result, the metal film 14 </ b> B can be formed on the outer wall surface of the carbon nanotube 13.

  Next, in the step of FIG. 1E, the medium 15 is embedded with a thermosetting resin (hot melt resin) or the like from above in the structure of FIG. 1D.

  For example, in the process of FIG. 1E, an uncured sheet of thermosetting resin having a thickness of 50 to 100 μm is used as the medium, and the medium 15 is used above the structure of FIG. 1D, that is, in the extending direction of the carbon nanotubes 13. Then, the carbon nanotube 13 is pushed in the direction toward the substrate 11 until the upper end portion of the carbon nanotube 13 is exposed on the upper main surface of the medium 15. In the step of FIG. 1E, an ashing process using oxygen plasma may be performed on the upper main surface of the medium 15 in order to reliably expose the upper end portion of the carbon nanotube 13 on the upper main surface of the resin sheet 15. As an example, the ashing process can be performed at a plasma power of 200 W for about 10 minutes.

  Further, by curing the resin sheet serving as the medium 15 and further removing the substrate 11, a carbon nanotube sheet structure having a structure in which the hollow open carbon nanotubes 13 are filled with the thin metal wires 14 as shown in FIG. 1F is obtained. can get.

  In this embodiment, in the step of FIG. 1F, by appropriately controlling the solidification temperature and the solidification time of the resin sheet to be the medium 15, the medium 15 contacts the substrate 11 immediately after solidification as shown in FIG. 1F. It is preferable to adjust so that it does not. In this case, since the medium 15 does not stick to the substrate 11, the substrate 11 can be easily removed mechanically, and the carbon nanotube sheet structure shown in FIG. 1F can be easily obtained. is there. In this case, it is preferable to set the thickness of the medium 15 to be smaller than the length of the carbon nanotube 13, for example, about 20 to 30 μm.

  As the resin sheet 15, an acrylic resin, an epoxy resin, a silicon resin, a polyethylene resin, a nylon resin, or the like can be used in addition to the hot melt resin. Further, the material is not limited as long as it is possible to embed a cavity between the carbon nanotubes 13 or inside the carbon nanotubes 13.

  Furthermore, by dispersing a conductive substance such as metal, graphite, or carbon nanotube in the resin in the resin sheet 15, a sheet with improved heat dissipation and conductivity can be produced. Further, the substrate 11 is peeled by dissolving the substrate 11 by performing a dissolving process such as hydrofluoric acid on the structure shown in FIG. 1E in addition to the physical peeling step performed after the resin sheet 15 is solidified. Can also be executed. This is effective when a glass substrate or a silicon substrate carrying an oxide film is used as the substrate 11. In this case, the carbon nanotubes 13 do not need to protrude from the lower main surface of the medium as in FIG. 1F, and the carbon nanotube sheet structure has a lower end portion of the carbon nanotubes 13 as shown in FIG. May have a structure coincident with the lower main surface of the medium 15.

  In addition to the resin sheet, the medium 15 may be made of metal, solder, metal paste, or the like.

  FIG. 5A is an enlarged view showing a part of the carbon nanotube sheet structure thus formed.

  Referring to FIG. 5A, in such a carbon nanotube sheet structure, heat is transported along the path (1) in the carbon nanotube and the path (2) in the buried metal thin wire 14, as shown in FIG. 5D. It can be seen that the thermal conductivity can be greatly improved as compared with the conventional hollow carbon nanotube sheet structure. In particular, in the present embodiment, the carbon nanotube 13 has a flat open end as a result of the removal of the tip portion 13C (see FIG. 2B). As described in the next embodiment, the carbon nanotube 13 is connected to a heat spreader or a semiconductor chip. The contact area is larger than that of the conventional carbon nanotube having the hemispherical tip portion 13C, and a favorable effect of reducing thermal resistance can be obtained. The heat transport by the path (2) is due to the heat conduction in the metal and is not as efficient as the heat transport along the path (1) through the carbon nanotube, but the heat conductivity of the metal is still in the heat conductivity of the resin. Compared to this, since it is two orders of magnitude larger, such a structure can effectively compensate for an increase in electrical resistance and thermal resistance resulting from the use of the resin when the resin is used as the medium 15.

  5B corresponds to the modification of FIG. 3A. Compared with the structure of FIG. 5A, the heat transport path (3) in the in-plane direction of the carbon nanotube sheet structure is newly formed by the metal layer 14A. You can see it happening. This is a heat transport path that cannot be obtained with a structure composed only of carbon nanotubes, and efficiently transports heat in a direction perpendicular to the surface while performing thermal diffusion in the in-plane direction of the carbon nanotube sheet structure. Can be done.

  5C corresponds to the modification of FIG. 3B. Compared with the structure of FIG. 5B, the heat transport path (4) in the direction perpendicular to the surface of the carbon nanotube sheet structure is formed outside the carbon nanotube 13. Can be seen newly. This further promotes heat transport in the direction perpendicular to the surface of the carbon nanotube sheet structure.

[Second Embodiment]
Next, a semiconductor device using the carbon nanotube sheet structure according to the first embodiment will be described.

  FIG. 6 is a cross-sectional view showing the configuration of the semiconductor device 20 according to the second embodiment.

  Referring to FIG. 6, the semiconductor chip 21 is made of a heat conductive metal such as copper, and the carbon nanotube sheet structure 22 described in the first embodiment is often disposed on a heat spreader 23 plated with nickel. It is joined via.

  A large number of solder bumps 21A form a ball grid array on the lower main surface of the semiconductor chip 21, and the semiconductor chip 21 is flip-chip mounted on a mounting substrate 24, which is typically a build-up substrate. A semiconductor device 20 is formed. At that time, the outer peripheral portion 23A of the heat spreader 23 is joined to the upper main surface of the mounting substrate 24 by an adhesive layer 23B such as a sealant.

  The mounting substrate 24 has solder bumps 24A on the lower main surface thereof, and is mounted in a state in which the solder bumps 24A are bonded to a wiring pattern on the printed circuit board 25 of the electronic device.

  In the semiconductor device having such a configuration, the heat generated in the semiconductor chip 21 is very efficiently transported to the heat spreader 23 through the carbon nanotube sheet structure 22, and the temperature rise of the semiconductor chip 21 is suppressed. .

  Next, the assembly process of the semiconductor device of FIG. 6 will be described with reference to FIGS. Hereinafter, a case where a hot melt resin is used as the medium 15 in the carbon nanotube structure 22 will be described.

  Referring to FIG. 7A, the carbon nanotube sheet structure 22 is bonded to the upper surface of the heat spreader 23 (the lower surface in the state of FIG. 6).

  FIG. 7B is an enlarged view of a part of FIG. 7A. The carbon nanotube sheet structure in the state of FIG. 1F causes the protruding end of the carbon nanotube 13 to abut on the heat spreader 23. In this state, it is pressed lightly, for example, with a pressure of about 0.5 MPa, and heated to a temperature of about 350 ° C. to each of the carbon nanotubes 13 and the fine metal wires 24 inside the carbon nanotubes 13. To join. In addition to heating, by passing a current of about several milliamperes to each of the carbon nanotubes 13 and the metal thin wires 24 inside the carbon nanotubes 13, the metal thin wires 24 can be electro-crimped and bonded to the heat spreader 23. is there. By using electro-compression bonding, a larger contact area, that is, thermal conductivity and greater adhesion can be realized between the carbon nanotubes 14 and the fine metal wires 14 and the heat spreader 23 than when simply pressed. Can do.

  In the present embodiment, as described above, the tip end portion 13C of the carbon nanotube 13 is removed to form a flat open end structure, which increases the contact area with the heat spreader 23 and reduces the thermal resistance. doing. The same applies to the bonding to the semiconductor chip 21 described later.

  At the time of electro-compression bonding, it is preferable that a film of the same metal as the thin metal wire 24 is formed on the surface of the heat spreader 23. For example, when the thin metal wire 24 is made of nickel and the heat spreader 23 is made of copper, a nickel coating is preferably formed on the surface of the heat spreader 23 by plating or the like. Similarly, when the metal thin wire 24 is made of gold and the heat spreader 23 is made of copper, a gold coating is preferably formed on the surface of the heat spreader 23 by plating or the like. However, the present invention is not limited to such specific metal combinations. In addition, the electrical crimping is not essential, and the carbon nanotube sheet structure 22 is also pressed by heating the carbon nanotube sheet structure 22 to the heat spreader 23 at a temperature of 50 to 300 ° C., for example, about 150 ° C. 23 can be joined.

  Next, in the step of FIG. 7C, the structure of FIG. 7B is heated to a temperature of about 50 ° C. to 300 ° C., for example, about 150 ° C., depending on the type of the resin 11. And is in close contact with the heat spreader 23. As a result of the lowering of the medium 15, the upper end portion of the carbon nanotube 13 is exposed and protrudes on the upper surface of the medium 15 in the state of FIG. 7C.

  Further, in the step of FIG. 7D, the semiconductor chip 21 is bonded onto the structure of FIG. 7C with the surface on which the solder bumps 21A are formed preferably facing the upper side, preferably by performing electro-compression bonding as in the previous case. . When electro-compression bonding is performed, it is preferable to form a coating on the same metal as the thin metal wires 14 on the bonding surface of the semiconductor chip as in the case of the heat spreader 23. However, the carbon nanotube 13 and the semiconductor chip 21 can also be joined by pressing while applying a pressure of about 0.5 Pa at a temperature of about 50 ° C. to 300 ° C., for example, about 150 ° C.

  Further, in the process of FIG. 7E, the structure of FIG. 7D is turned upside down and flip-chip mounted on the mounting substrate 24.

  At that time, the heat spreader 23 needs to be in close contact with the mounting substrate 24 via the sealant 23B at the outer peripheral portion 23A. For this reason, the heat spreader 23 is pressed against the mounting substrate 24. The protruding end portion of the carbon nanotube 13 is deformed or bent, and a semiconductor device having a structure shown in FIG. 7F is finally obtained. Although the deformation of the carbon nanotube 13 is not shown in FIG. 7F, even if such a deformation occurs, for example, even if the carbon nanotubes 13 come into contact with each other as a result of the deformation, the carbon nanotube sheet structure 22 There is no substantial adverse effect on the heat conduction characteristics.

  In the above description, the medium 15 is a hot melt resin. However, in the present invention, the medium 15 is not necessarily a hot melt resin, and an acrylic resin, an epoxy resin, a silicon resin, or the like can be used. In addition to the resin, metal, solder, metal paste, etc. can be used. Furthermore, the carbon nanotube sheet structure 22 is not limited to the structure shown in FIG. 1F, and for example, the structure described with reference to FIGS. 3A and 3B or FIG. 4 may be used.

  When the semiconductor device of FIG. 6 is manufactured using the carbon nanotube sheet of FIG. 4, the end of the carbon nanotube 13 exposed on the same surface as the medium 15 is bonded to the heat spreader 23 or the semiconductor chip 21. In order to ensure, especially when the medium 15 is made of a resin, it is possible to perform an ashing process using oxygen plasma so that the tip part slightly protrudes from the medium 15. . As an example, such an ashing process can be performed at a power of 200 W for about 10 minutes.

  In this embodiment, it is also possible to use a fast atom bombardment (FAB) technique instead of the electrocrimping described above. In the high-speed atom bombardment technique, a rare gas ion such as argon or xenon accelerated to several kilovolts, for example, 5 kilovolts, is implanted into one side of the carbon nanotube sheet structure 22 in a vacuum and subjected to surface treatment. In addition, the technology removes the oxidized portion of the encapsulated metal thin wire 14 and presses the heat spreader 23 and the semiconductor chip 21 to join the metal thin wire 14, the heat spreader 23, and the semiconductor chip 21 before the exposed end surface is contaminated with the bonding species. It is. By using the high-speed atom bombardment technique, even when the thin metal wire 14 and the heat spreader 23 or the semiconductor chip 21 are not formed of the same metal, the bonding can be performed.

[Third Embodiment]
FIG. 8 is a cross-sectional view showing a configuration of a semiconductor device 40 according to the third embodiment of the present invention. However, in the figure, the same reference numerals are assigned to portions corresponding to the portions described above, and description thereof is omitted.

  Referring to FIG. 8, in this embodiment, the carbon nanotube sheet structure described in the first embodiment is used as the connection electrode portion 41A instead of the solder bump 21A.

  9A is an enlarged view of the carbon nanotube sheet structure constituting the connection electrode portion 41A, and FIG. 9B is a further enlarged view of the enlarged view of FIG. 9A.

  Referring to FIG. 9, the carbon nanotube sheet structure constituting the connection electrode portion 41 </ b> A corresponds to the insulating medium 15 such as resin and the solder bump 21 </ b> A in FIG. 6 in the insulating medium 15. A plurality of formed carbon nanotube bundle regions 41a are formed, and each of the carbon nanotube bundle regions 41a is formed with a large number of carbon nanotubes 13 including the open end thin metal wires 14 described with reference to FIG. 1F or FIG. Has been.

  The carbon nanotubes 13 have not only high thermal conductivity in the extending direction but also high electrical conductivity, and together with the fine metal wires 14 encapsulated in the carbon nanotubes 13, the carbon nanotubes 13 with respect to the surface of the carbon nanotube sheet structure 14 In addition to acting as a low-resistance electrode in the vertical direction, the tip end portion 13C is open and has a flat shape, so that the contact resistance can also be reduced.

  The semiconductor device 40 of FIG. 8 is mounted on the printed circuit board 25 and constitutes an electronic device in the same manner as the semiconductor device 20 described above.

  10A to 10G are diagrams showing manufacturing steps of the semiconductor device 40 of FIG.

  FIG. 10A corresponds to FIG. 1A, but shows the substrate 11 over a wider range.

  Referring to FIG. 10A, a catalytic metal layer 12 is formed on the substrate 11. The catalyst metal layer 12 is shown as a continuous layer in FIG. 10A, but actually has an island structure as shown in FIG. 1A. However, as described above, according to recent knowledge, it is known that the catalytic metal layer 12 may be a continuous film.

  Next, in this embodiment, as shown in FIG. 10B, the catalytic metal layer 12 is patterned to form a catalytic metal pattern 12A corresponding to the plurality of carbon nanotube bundle regions 41a.

  Further, in the step of FIG. 10C, the steps described in FIGS. 1B to 1D are performed to grow a carbon nanotube bundle made of the carbon nanotubes 13 from the catalytic metal pattern 12A in each of the plurality of carbon nanotube bundle regions 41a. Furthermore, after opening this at the front-end | tip part, the metal fine wire 14 is embedded. In addition, illustration of the catalyst metal layer 12 is abbreviate | omitted in FIG. 10B transfer.

  Further, in the process of FIG. 10D, the resin sheet 15 such as hot melt resin, acrylic resin, epoxy resin, or silicon resin described above is pushed into the structure having the carbon nanotubes 13 and the fine metal wires 14 thus obtained. The connection electrode portion 41A is obtained by removing the substrate 11 in the step of FIG. 10E.

  Next, in the step of FIG. 10F, the connection electrode portion 41A is disposed on the circuit surface of the semiconductor chip, that is, the main surface on the side where the semiconductor element is formed, and by using an electric pressure bonding or a fast atom bombardment technique, or simply By pressing while heating, the metal regeneration 14 is joined to a corresponding electrode pad (not shown) on the circuit surface.

  Further, in the step of FIG. 10G, the semiconductor chip 21 thus formed with the connection electrode portion 41A is flip-chip mounted on the mounting substrate 24, and the semiconductor device 40 is obtained.

  Further, the semiconductor device 40 thus formed on the mounting substrate 24 is mounted on the printed circuit board of the electronic device, and a desired electronic device is assembled.

  In addition, as shown in the semiconductor device 60 according to one modification of FIG. 11, a similar connection electrode portion is also used for the connection electrode portion 64A that connects the mounting substrate 24 and the printed board 25, instead of the solder bump 24A. Similar to the carbon nanotube bundle region 41a of the connection electrode portion 41A, the carbon nanotube bundle region 64a having the carbon nanotubes 13 and the fine metal wires 14 can be used.

As mentioned above, although this invention was described about preferable embodiment, this invention is not limited to this specific embodiment, A various deformation | transformation and change are possible within the summary described in the claim.
(Appendix 1)
A medium defined by opposing first and second major surfaces;
A plurality of carbon nanotubes each extending from the first major surface of the medium to the second major surface,
Each of the plurality of carbon nanotubes has a first end portion exposed on the first main surface and a second end portion exposed on the second main surface;
The first end portions of the plurality of carbon nanotubes are open at the first main surface, and the second end portions are open at the second main surface,
Each of the plurality of carbon nanotubes is filled with metal from the first end portion to the second end portion.
(Appendix 2)
The carbon nanotube sheet structure according to claim 1, wherein the first end portion is flush with the first main surface, and the second end portion protrudes from the second main surface. .
(Appendix 3)
The medium according to claim 1, wherein a metal film is formed on the first main surface, and the first end portions of the plurality of carbon nanotubes are exposed from the metal surface. 2. The carbon nanotube sheet structure according to 2.
(Appendix 4)
Each of the plurality of carbon nanotubes is covered with a metal sleeve extending from the metal film, and the metal sleeve is exposed on the second main surface of the medium. The carbon nanotube sheet structure described.
(Appendix 5)
Growing a plurality of carbon nanotubes on a substrate from a first end on the substrate side to a second end opposite to the first end;
Opening the plurality of carbon nanotubes at the second end;
Filling the plurality of carbon nanotubes with metal;
Embedding a medium between the plurality of carbon nanotubes on the substrate;
Removing the substrate;
The manufacturing method of the carbon nanotube sheet structure characterized by including this.
(Appendix 6)
The carbon nanotube according to claim 5, wherein the step of opening the plurality of carbon nanotubes at the second end is performed by heat-treating the plurality of carbon nanotubes in an atmosphere containing oxygen. A manufacturing method of a sheet structure.
(Appendix 7)
The carbon nanotube sheet structure according to appendix 5 or 6, wherein the step of embedding the medium is performed so that the resin film is not in contact with the substrate in a state of being embedded between the plurality of carbon nanotubes. Body manufacturing method.
(Appendix 8)
The carbon nanotube sheet structure according to any one of appendices 1 to 4, and
A semiconductor chip formed in close contact with the first main surface of the medium;
And a heat spreader formed in close contact with the second main surface of the medium.
(Appendix 9)
The carbon nanotube sheet structure according to any one of appendices 1 to 4 is disposed on a heat spreader member with the second main surface of the medium facing downward, and the second end portion Contacting the heat spreader member;
Fixing the second end to the heat spreader member;
The carbon nanotube sheet sheet structure is heated to soften the medium, the medium is moved relative to the plurality of carbon nanotubes so as to contact the heat spreader member, and the first end portion is moved to the medium Projecting from the first main surface of
Disposing a semiconductor chip on the first main surface of the medium and contacting the first end;
Fixing the first end to the semiconductor chip;
A method for manufacturing a semiconductor device, comprising:
(Appendix 10)
A mounting board;
A semiconductor chip flip-chip mounted on the mounting substrate;
A connection electrode portion for connecting the semiconductor chip to the mounting substrate,
The said connection electrode part consists of a carbon nanotube sheet structure as described in any one of Claims 1-4, The semiconductor device characterized by the above-mentioned.
(Appendix 11)
The mounting substrate is connected to a printed circuit board of an electronic device by a second connection electrode portion, and the second connection electrode portion is based on the carbon nanotube sheet structure according to any one of appendices 1 to 4. The semiconductor device according to claim 10.

DESCRIPTION OF SYMBOLS 11 Board | substrate 12 Catalytic metal layer 13 Carbon nanotube 13A Carbon nanotube main-body part 13C Carbon nanotube front-end | tip part 13a-13c Graphene sheet 14 Metal fine wire 15 Medium 14A, 14B Metal layer 20, 40, 60 Semiconductor device 21 Semiconductor chip 21A Solder bump 22 Carbon nanotube Sheet structure 23 Heat spreader 23A Heat spreader peripheral portion 23B Adhesive layer 24 Mounting substrate 24A Solder bump 25 Printed circuit board 41A, 64A Connection electrode portion 41a, 64a Carbon nanotube bundle region

Claims (5)

A medium defined by opposing first and second major surfaces;
A plurality of carbon nanotubes each extending from the first major surface of the medium to the second major surface,
Each of the plurality of carbon nanotubes has a first end portion exposed on the first main surface and a second end portion exposed on the second main surface;
The first end portions of the plurality of carbon nanotubes are open at the first main surface, and the second end portions are open at the second main surface,
The inside of each of the plurality of carbon nanotubes is filled with metal from the first end portion to the second end portion,
Said metals, Ri Na from the metal or alloy containing at least one selected Au, Ag, Cu, Ni, Al, Mo, Ta, from the group consisting of Pt and Co,
The carbon nanotube sheet , wherein the medium has a metal film formed on the first main surface, and the first end portions of the plurality of carbon nanotubes are exposed from the metal film. Structure. 2. The plurality of carbon nanotubes are each covered with a metal sleeve extending from the metal film, and the metal sleeve is exposed on a second main surface of the medium. 2. The carbon nanotube sheet structure according to 1 . Growing a plurality of carbon nanotubes on a substrate from a first end of the substrate to a second end opposite the first end;
Opening the plurality of carbon nanotubes at the second end;
Filling the plurality of carbon nanotubes with metal;
Embedding a medium between the plurality of carbon nanotubes on the substrate;
Removing the substrate;
Including
The metal is made of a metal or alloy containing at least one selected from the group consisting of Au, Ag, Cu, Ni, Al, Mo, Ta, Pt and Co,
The method of manufacturing a carbon nanotube sheet structure, wherein the step of embedding the medium is performed after the step of filling the metal. A medium defined by opposing first and second main surfaces, and a plurality of carbon nanotubes each extending from the first main surface to the second main surface of the medium, Each of the plurality of carbon nanotubes has a first end portion exposed on the first main surface and a second end portion exposed on the second main surface. The first end portion is open at the first main surface, the second end portion is open at the second main surface, and the interior of each of the plurality of carbon nanotubes is The first end portion to the second end portion are filled with a metal, and the metal is selected from the group consisting of Au, Ag, Cu, Ni, Al, Mo, Ta, Pt, and Co. car made of a metal or an alloy containing at least one And nanotube sheet structure,
A semiconductor chip formed in close contact with the first main surface of the medium;
And a heat spreader formed in close contact with the second main surface of the medium. A mounting board;
A semiconductor chip flip-chip mounted on the mounting substrate;
A connection electrode portion for connecting the semiconductor chip to the mounting substrate,
The connection electrode part is
A medium defined by opposing first and second main surfaces, and a plurality of carbon nanotubes each extending from the first main surface to the second main surface of the medium, Each of the plurality of carbon nanotubes has a first end portion exposed on the first main surface and a second end portion exposed on the second main surface. The first end portion is open at the first main surface, the second end portion is open at the second main surface, and the interior of each of the plurality of carbon nanotubes is The first end portion to the second end portion are filled with a metal, and the metal is selected from the group consisting of Au, Ag, Cu, Ni, Al, Mo, Ta, Pt, and Co. car made of a metal or an alloy containing at least one Wherein a formed of nanotubes sheet structure.

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