JP2014166676A - Method of growing carbon structure, method of producing sheet-like structure and method of producing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a sheet-like structure which has excellent thermal conductivity and electrical conductivity, not only in the direction vertical to a sheet surface but in the direction in parallel with the sheet surface.SOLUTION: A method of growing a carbon structure includes forming a first catalyst metal film in a first area of a substrate 30, forming a second catalyst metal film different from the first catalyst metal film in a second area adjacent to the first area of the substrate, forming a first carbon structure having a plurality of linear structures 12 composed of carbon elements selectively in the first area, with the first catalyst metal film as catalyst, and forming a second carbon structure 14 having a graphite layer selectively in the second area, with the second catalyst metal film as catalyst.

Description

  The present invention relates to a sheet-like structure having a linear structure made of a carbon element, a semiconductor device, and a carbon structure growth method.

  Electronic components used in central processing units (CPUs) of servers and personal computers are heat conductive sheets such as indium sheets provided directly above them to efficiently dissipate heat generated from semiconductor elements. The heat spreader made of a material having a high thermal conductivity such as copper is disposed through the structure.

  However, the price of indium has soared due to a significant increase in demand for rare metals in recent years, and an alternative material that is cheaper than indium is expected. In addition, in terms of physical properties, the thermal conductivity (50 W / m · K) of indium is not high, and a material having higher thermal conductivity in order to dissipate the heat generated from the semiconductor element more efficiently. Is desired.

  From such a background, as a material having a higher thermal conductivity than indium, a linear structure made of a carbon element typified by a carbon nanotube has attracted attention. Carbon nanotubes not only have a very high thermal conductivity (1500 W / m · K), but also are excellent in flexibility and heat resistance, and have a high potential as a heat dissipation material.

  As a heat conductive sheet using carbon nanotubes, for example, Patent Document 1 discloses a heat conductive sheet in which carbon nanotubes are dispersed in a resin. For example, Patent Document 2 discloses a heat conductive sheet in which a bundle of carbon nanotubes oriented and grown on a substrate is embedded with a resin or the like.

  Carbon nanotubes are also attracting attention as wiring materials used in semiconductor devices and the like. Many problems such as reliability degradation due to electromigration have become apparent in copper wiring that is currently used mainly in integrated circuit devices as devices become finer. Therefore, carbon nanotubes having excellent electrical conductivity and excellent characteristics such as allowable current density and ballistic electron transport characteristics that are about 1000 times higher than copper are expected as next-generation wiring materials.

As wiring using carbon nanotubes, proposals have been made regarding vertical nanotube wiring using vias (for example, see Non-Patent Document 1).
JP 2005-150362 A JP 2006-147801 A JP 2006-303240 A JP 09-031757 A JP 2004-262666 A JP 2005-285821 A JP 2006-297549 A JP 2006-339552 A JP 2003-238123 A M. Nihei et al., "Electrical properties of carbon nanotube bundles for future via interconnects", Japanese Journal of Applied Physics, Vol. 44, No. 4A, 2005, pp.1626-1628

  The heat conductive sheet described in Patent Document 1 is obtained by simply dispersing carbon nanotubes in a resin, and thermal resistance is generated at the contact points between the dispersed carbon nanotubes. In addition, carbon nanotubes have the characteristic that the thermal conductivity in the direction along the orientation direction is the smallest. However, in the heat conduction sheet described in Patent Document 1, the orientation directions of the carbon nanotubes are not uniform, and the high thermal conductivity of the carbon nanotubes. I could not make full use of the degree. In this respect, the thermal conductive sheet described in Patent Document 2 uses a bundle of carbon nanotubes that are oriented and grown on the substrate, and therefore achieves higher thermal conductivity than the thermal conductive sheet described in Patent Document 1. Can do.

  However, the inventors of the present invention have studied the heat conductive sheet described in Patent Document 2, and as a result, when the resin is filled between the carbon nanotubes, the carbon nanotube bundles are aggregated or biased. It has been found that the uniformity of the nanotubes is compromised and the expected thermal conductivity cannot be achieved. Also, with this structure, heat dissipation in the vertical direction (perpendicular to the sheet surface) can be secured to some extent, but heat dissipation in the lateral direction (direction parallel to the sheet surface) is ensured. It was difficult to do. That is, since the thermal conductivity of the resin itself is about 1 (W / m · K), it is about three orders of magnitude lower than the high thermal conductivity in the vertical direction due to the carbon nanotubes, and the heat dissipation effect in the horizontal direction is low. It was very low.

  Moreover, as a wiring material, it is desired that not only a wiring structure connected in the vertical direction as described in Non-Patent Document 1, but also a wiring structure connected in the horizontal direction can be formed. However, the lateral wiring using carbon nanotubes has many difficulties in controlling the lateral growth of the nanotubes, and also creates an electrode block that connects the via wiring and the lateral wiring that are the starting point of the lateral wiring. This is difficult in terms of process and has not been realized yet.

  An object of the present invention is to provide a sheet-like structure excellent in thermal conductivity and conductivity not only in a direction perpendicular to the sheet surface but also in a direction parallel to the sheet surface, and a method for producing the same. Another object of the present invention is to provide a semiconductor device having a low-resistance via wiring, a low-resistance lateral wiring layer connected to the via wiring, and a manufacturing method thereof.

  According to an aspect of the present invention, a linear structure including a plurality of carbon elements arranged with a first gap between each other, and a plurality of arranged with a second gap larger than the first gap. A linear structure bundle, a graphite layer formed in a region between the plurality of linear structure bundles and connected to the plurality of linear structure bundles, and the first gap and the second gap; There is provided a sheet-like structure that is filled and has the plurality of linear structure bundles and a filling layer that holds the graphite layer.

  According to another aspect of the present invention, the first wiring layer formed on the semiconductor substrate and a linear structure bundle including a plurality of linear structures made of a carbon element, the first structure A via wiring connected to the wiring layer; an insulating film formed on the semiconductor substrate excluding the via wiring formation region so as to cover the first wiring layer; the via wiring and the insulating film; And a second wiring layer having a graphite layer formed on the semiconductor device.

  According to still another aspect of the present invention, a step of forming a first catalytic metal film on a first region of a substrate, and a second region adjacent to the first region of the substrate. A step of forming a second catalytic metal film different from the first catalytic metal film, and a plurality of lines made of carbon elements on the first region using the first catalytic metal film as a catalyst. A step of selectively forming a first carbon structure having a shaped structure, and a second carbon structure having a graphite layer on the second region using the second catalytic metal film as a catalyst. And a method of selectively forming the carbon structure.

  According to the present invention, since a linear structure bundle made of a plurality of carbon elements spaced apart from each other is formed on a substrate, a filling layer is formed by filling the filler and holding the linear structure bundle. In this case, the shape change of the linear structure bundle can be prevented. Thereby, the sheet-like structure in which the linear structure bundle is oriented in the film thickness direction of the sheet can be easily formed. Moreover, the both ends of the linear structure bundle can be easily exposed from the filling layer, and the thermal conductivity and electrical conductivity with respect to the adherend can be improved. Thereby, the reliability of the electronic device using this sheet-like structure can be improved. In addition, since the graphite layer is formed in the gap between the linear structure bundles by connecting to the linear structure bundle, the thermal conductivity and the electric conductivity in the direction parallel to the surface of the sheet can be improved. . Further, since the linear structure bundle and the graphite layer can be formed at the same time, the carbon nanotube sheet can be formed without significantly changing the manufacturing process. Thereby, the increase in manufacturing cost can be prevented.

  In addition, since a semiconductor device having a via wiring made of a linear structure made of a carbon element and a wiring layer made of a graphite layer connected to the via wiring is configured, the electrical resistance of the via wiring and the wiring layer is greatly increased. Can be reduced. Thereby, the characteristics of the semiconductor device can be improved. Moreover, since the via wiring and the wiring layer can be formed at the same time, the wiring structure can be formed without significantly changing the manufacturing process. Thereby, the increase in manufacturing cost can be prevented.

FIG. 1 is a plan view and a schematic sectional view showing the structure of a carbon nanotube sheet according to a first embodiment of the present invention. FIG. 2 is a plan view showing the shape of a carbon nanotube bundle in the carbon nanotube sheet according to the first embodiment of the present invention. FIG. 3 is a schematic cross-sectional view showing the structure of the carbon nanotube sheet according to the first embodiment of the present invention. FIG. 4 is a process cross-sectional view (part 1) illustrating the method of manufacturing the carbon nanotube sheet according to the first embodiment of the present invention. FIG. 5 is a process cross-sectional view (part 2) illustrating the method of manufacturing the carbon nanotube sheet according to the first embodiment of the present invention. FIG. 6 is a plan view and a schematic sectional view showing the structure of the carbon nanotube sheet according to the second embodiment of the present invention. FIG. 7 is a process cross-sectional view (part 1) illustrating the method of manufacturing the carbon nanotube sheet according to the second embodiment of the present invention. FIG. 8 is a process cross-sectional view (part 2) illustrating the method of manufacturing the carbon nanotube sheet according to the second embodiment of the present invention. FIG. 9 is a schematic cross-sectional view showing the structure of a carbon nanotube sheet according to a modification of the second embodiment of the present invention. FIG. 10 is a schematic cross-sectional view showing the structure of the semiconductor device according to the third embodiment of the present invention. FIG. 11 is a process cross-sectional view (No. 1) illustrating the method for manufacturing the semiconductor device according to the third embodiment of the invention. FIG. 12 is a process cross-sectional view (part 1) illustrating the method for manufacturing the semiconductor device according to the third embodiment of the invention. FIG. 13 is a process cross-sectional view (No. 1) illustrating the method for manufacturing the semiconductor device according to the third embodiment of the invention. FIG. 14 is a schematic cross-sectional view showing the structure of the semiconductor device according to the fourth embodiment of the present invention. FIG. 15 is a process cross-sectional view (No. 1) illustrating the method for manufacturing the semiconductor device according to the fourth embodiment of the invention. FIG. 16 is a process cross-sectional view (part 2) illustrating the method for manufacturing the semiconductor device according to the fourth embodiment of the invention. FIG. 17 is a process cross-sectional view (No. 3) illustrating the method for manufacturing the semiconductor device according to the fourth embodiment of the invention. FIG. 18 is a schematic cross-sectional view showing the structure of an electronic device according to the fifth embodiment of the present invention. FIG. 19 is a perspective view showing the structure of an electronic device according to the sixth embodiment of the present invention.

DESCRIPTION OF SYMBOLS 10 ... Carbon nanotube sheet 12 ... Carbon nanotube bundle 14, 20 ... Graphite layer 16 ... Packing layer 18 ... Carbon nanotube layer 30, 40 ... Substrate 32, 32a, 32b, 38 ... Catalytic metal film 34, 48, 54, 78 ... Photo Resist film 36 ... openings 42, 66, 74, 84 ... wiring layers 44, 68, 76 ... interlayer insulating film 46 ... contact holes 50, 60, 70 ... TiN films 52, 58, 62 ... Co film 56 ... TiO ₂ film 64, 72 ... via wiring 66a, 66b ... graphite layer 80 ... Ti film 82 ... TiC film 100 ... circuit substrate 102 ... solder bump 104 ... underfill 106 ... semiconductor elements 108, 112, 126 ... carbon nanotube sheet 110 ... heat spreader 114, 124 ... heat sink 120 ... high power amplifier 122 ... packet Page

[First Embodiment]
A carbon nanotube sheet and a manufacturing method thereof according to a first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a plan view and a schematic sectional view showing the structure of a carbon nanotube sheet according to the present embodiment, FIG. 2 is a plan view showing the shape of a carbon nanotube bundle in the carbon nanotube sheet according to the present embodiment, and FIG. FIG. 4 and FIG. 5 are process cross-sectional views illustrating the method of manufacturing a carbon nanotube sheet according to the present embodiment.

  First, the structure of the carbon nanotube sheet according to the present embodiment will be described with reference to FIG. FIG. 1A and FIG. 1B are a plan view and a cross-sectional view showing the structure of the carbon nanotube sheet according to the present embodiment, respectively.

  The carbon nanotube sheet (sheet-like structure) 10 according to the present embodiment has a plurality of carbon nanotube bundles (linear structure bundles) 12 arranged at intervals (see FIG. 1A). . A graphite layer 14 formed on one surface side of the sheet and a filling layer 16 made of a resin material or the like are embedded in the gap between the carbon nanotube bundles 12 (see FIGS. 1A and 1B). . The filling layer 16 is also embedded in the gaps in the carbon nanotube bundle 12 and the graphite layer 14. The graphite layer 14 is thermally and electrically connected to the carbon nanotube bundle 12.

  Each carbon nanotube bundle 12 is formed so as to extend in a direction perpendicular to the surface of the sheet, and a plurality of carbon nanotubes (linear structures made of carbon elements) oriented in a direction perpendicular to the surface of the sheet. have.

The carbon nanotube may be either a single-walled carbon nanotube or a multi-walled carbon nanotube. The density of the carbon nanotubes contained in the carbon nanotube bundle 12 is desirably 1 × 10 ¹⁰ pieces / cm ² or more from the viewpoint of heat dissipation and electrical conductivity. The length (sheet thickness) of the carbon nanotube bundle 12 is determined by the use of the carbon nanotube sheet 10 and is not particularly limited, but can be preferably set to a value of about 5 μm to 500 μm.

  In the carbon nanotube sheet 10 according to the present embodiment, a gap is provided between the carbon nanotube bundles 12, and a filling layer 16 is formed in this gap. This enhances the permeability of the filler when forming the filling layer 16 between the carbon nanotubes, suppresses the shape change such as the carbon nanotubes falling sideways, and maintains the orientation originally held by the carbon nanotubes. (See the manufacturing method described later).

  Although there is no restriction | limiting in particular about the width of the formation area of the carbon nanotube bundle 12, When a formation area is circular, for example, a diameter can be set to the range of 10 micrometers-1000 mm.

  The necessary gap between the carbon nanotube bundles 12 varies depending on the viscosity or the like of the filler used as the filling layer 16, but cannot be determined unconditionally. However, the gap between the carbon nanotubes constituting each of the carbon nanotube bundles 12 can be determined. It can be set to a sufficiently wide width, preferably about 0.1 μm to 200 μm. However, as the distance between the carbon nanotube bundles 12 increases, the surface density of the carbon nanotubes in the sheet surface decreases, that is, the thermal conductivity as a sheet decreases. Further, the surface density of the carbon nanotubes in the sheet surface also varies depending on the size of the carbon nanotube bundle 12. Therefore, the interval between the carbon nanotube bundles 12 needs to be appropriately set in consideration of the size of the carbon nanotube bundles 12 according to the thermal conductivity required for the sheet.

  The planar shape of each carbon nanotube bundle 12 is not limited to the circular shape shown in FIG. As the planar shape of the carbon nanotube bundle 12, in addition to a circle, for example, a polygon such as a triangle, a quadrangle, or a hexagon may be used.

  Further, the arrangement of the plurality of carbon nanotube bundles 12 is not limited to a circular close-packed arrangement as shown in FIG. For example, as shown in FIGS. 2 (a) and 2 (b), the carbon nanotube bundles 12 may be arranged so as to be positioned at each lattice point of a square lattice. In addition, as shown in FIG. 2C, the carbon nanotube bundles 12 having a triangular planar shape may be arranged for each line by changing the vertical direction. Further, as shown in FIG. 2D, the carbon nanotube bundle 12 may be formed in a stripe pattern. Further, as shown in FIG. 2 (e), the carbon nanotube bundle 12 may have a comb-teeth pattern.

  The graphite layer 14 is made of graphite having a layered structure parallel to the surface of the sheet, and is formed so as to be connected to the side surface of the carbon nanotube bundle 12. The thickness of the graphite layer 14 is, for example, about several nm to several hundred nm.

  The constituent material of the filling layer 16 is not particularly limited as long as it shows a liquid property at the time of embedding the carbon nanotube and can be cured thereafter. For example, an acrylic resin, an epoxy resin, a silicone resin, a polyimide resin, or the like can be applied as the organic filler. As the inorganic filler, a coating-type insulating film forming composition such as SOG (Spin On Glass) can be applied. A metal material such as indium, solder, or a metal paste (eg, silver paste) can also be used. In addition, conductive polymers such as polyaniline and polythiophene can also be applied.

  Moreover, you may disperse and mix an additive with the filled layer 16 as needed. As the additive, for example, a substance having high thermal conductivity or a substance having high conductivity can be considered. By dispersing and mixing an additive having high thermal conductivity in the filled layer 16 portion, the thermal conductivity of the filled layer 16 portion can be improved, and the thermal conductivity of the entire carbon nanotube sheet can be improved. In the case where the carbon nanotube sheet is used as a conductive sheet, the conductivity of the filling layer 16 portion can be improved by dispersing and mixing an additive having high conductivity in the filling layer 16 portion. The conductivity of the nanotube sheet as a whole can be improved. This is particularly effective when an insulating material having low thermal conductivity such as an organic filler is used as the filling layer 16. As the material having high thermal conductivity, carbon nanotube, metal material, aluminum nitride, silica, alumina, graphite, fullerene, or the like can be used. As the highly conductive material, carbon nanotubes, metal materials, and the like can be applied.

  As described above, the carbon nanotube sheet 10 according to the present embodiment includes the carbon nanotube bundle 12 oriented in a direction perpendicular to the surface of the sheet, and the graphite layer 14 made of graphite having a layered structure parallel to the surface of the sheet. Yes. Carbon nanotubes have a very high thermal conductivity of about 1500 (W / m · K) along the alignment direction. Graphite does not have the thermal conductivity of carbon nanotubes, but the thermal conductivity in the direction parallel to the layer surface (a-axis) is about 500 (W / m · K), which is also very high heat. It has conductivity.

  Therefore, the carbon nanotube sheet 10 is configured by combining the carbon nanotube bundle 12 and the graphite layer 14 as in this embodiment, so that the thermal conductivity in the direction perpendicular to the surface of the sheet is mainly the carbon nanotube (carbon nanotube bundle). 12), and thermal conductivity in a direction parallel to the surface of the sheet can be ensured mainly by graphite (graphite layer 14).

  Graphite has a thermal conductivity of 500 times or more compared to a resin material (thermal conductivity: about 1 (W / m · K)). Therefore, by providing the graphite layer 14, the heat dissipation in the direction parallel to the surface of the sheet can be greatly improved by 500 times or more compared with the case where the graphite layer 14 is not formed.

  In the carbon nanotube sheet 10 according to the present embodiment, the upper end and the lower end of the carbon nanotube bundle 12 are not covered with the filling layer 16. Thereby, when the carbon nanotube sheet 10 is brought into contact with the heat radiating body or the heat generating body, the carbon nanotube bundle 12 is in direct contact with the heat radiating body or the heat generating body, so that the heat conduction efficiency can be greatly increased.

  Since the carbon nanotube and the graphite have both high conductivity, the carbon nanotube bundle 12 can be used as a wiring body penetrating the sheet by exposing the upper end and the lower end of the carbon nanotube bundle 12. Moreover, the graphite layer 14 can also be used as a wiring body in a direction parallel to the surface of the sheet. That is, the carbon nanotube sheet 10 according to the present embodiment can be used not only as a heat conductive sheet but also as a wiring sheet.

  The relationship between the height of the carbon nanotube bundle 12 and the thickness of the filling layer 16 (the length in the thickness direction of the sheet) may be the same as shown in FIG. As shown in FIG. 3B, one end portion of the carbon nanotube bundle 12 may be recessed from the surface of the filling layer 16, and one end portion of the carbon nanotube bundle 12 is the surface of the filling layer 16 as shown in FIG. It may be more protruding. These shapes can be created separately by changing the material and manufacturing conditions of the filling layer 16 (see the manufacturing method described later).

  The shape of FIG. 3B can be expected to relieve the stress applied to the carbon nanotube bundle 12 by the filling layer 16 when the carbon nanotube sheet 10 is disposed between the heat radiating body and the heat generating body and bonded. On the other hand, in the shape of FIG.3 (c), it can anticipate that the adhesiveness of the carbon nanotube bundle 12 with respect to a heat radiator and a heat generating body will improve, and a thermal conductivity will improve. It is desirable that the relationship between the height of the carbon nanotube bundle 12 and the thickness of the filling layer 16 is appropriately set according to the purpose of use of the carbon nanotube sheet 10 and the stress applied to the sheet.

  Next, the method for manufacturing the carbon nanotube sheet according to the present embodiment will be explained with reference to FIGS.

  First, a substrate 30 used as a base for forming the carbon nanotube sheet 10 is prepared. As the substrate 30, a semiconductor substrate such as a silicon substrate, or an insulating substrate such as an alumina (sapphire) substrate, an MgO substrate, or a glass substrate can be used. In addition, a thin film may be formed on these substrates. For example, a silicon substrate having a silicon oxide film with a thickness of about 300 nm can be used.

  The substrate 30 is peeled off after the carbon nanotube sheet 10 is formed. For this purpose, as the substrate 30, at least the surface in contact with the carbon nanotube sheet 10 is made of a material that can be easily peeled off from the carbon nanotube sheet 10, or is selectively etched with respect to the carbon nanotube sheet 10. It is desirable to be made of a material that can be used.

  For example, when an acrylic resin is used as the material of the filling layer 16, a carbon nanotube sheet 10 is formed on the surface of the substrate 30 by forming a material having a low adhesion to the acrylic resin, such as a silicon oxide film or a silicon nitride film. Can be easily peeled off. Alternatively, the surface of the substrate 30 is made of a material that can be selectively etched with respect to the carbon nanotube sheet 10 such as a silicon oxide film or a silicon nitride film, and the carbon nanotube sheet is removed by etching. 10 can be released from the substrate 30.

  Next, an Fe (iron) film having a film thickness of about 0.3 to 10 nm, for example, 2.5 nm is formed on the substrate 30 by, eg, sputtering, and a catalytic metal film 32a made of Fe is formed (FIG. 4 ( a)). The catalytic metal film 32a may be formed by an electron beam evaporation method, an MBE method, or the like.

  As the catalyst metal, in addition to Fe, Co (cobalt), Ni (nickel), Au (gold), Ag (silver), Pt (platinum), or an alloy containing at least one of these materials may be used. In addition to the metal film, metal fine particles prepared by controlling the size in advance using a differential mobility analyzer (DMA) or the like may be used as the catalyst. In this case, the metal species may be the same as in the case of the thin film.

In addition, as a base film of these catalyst metals, Mo (molybdenum), Ti (titanium), Hf (hafnium), Zr (zirconium), Nb (niobium), V (vanadium), TaN (tantalum nitride), TiSi _x (titanium) Silicide), Al (aluminum), Al ₂ O ₃ (aluminum oxide), TiO _x (titanium oxide), Ta (tantalum), W (tungsten), Cu (copper), Au (gold), Pt (platinum), Pd A film made of (palladium), TiN (titanium nitride), or the like, or a film made of an alloy containing at least one of these materials may be formed. For example, a stacked structure of Fe (2.5 nm) / Al (10 nm), a stacked structure of Co (2.6 nm) / TiN (5 nm), and the like can be applied. When metal fine particles are used, for example, a laminated structure such as Co (average diameter: 3.8 nm) / TiN (5 nm) can be applied.

  Next, a photoresist film 34 is formed on the catalytic metal film 32a by spin coating.

  Next, an opening 36 is formed in the photoresist film 34 by photolithography so as to cover the region where the carbon nanotube bundle 12 is to be formed and expose the region where the graphite layer 14 is to be formed. As the pattern of the openings 36, for example, the pattern shown in FIG. 1A is used. The diameter of the openings 36 (the diameter of the formation region of the carbon nanotube bundles 12) is 100 μm, and the openings 36 (between the carbon nanotube bundles 12). Is set to 20 μm. As the pattern of the opening 36 formed in the photoresist film 34, for example, various patterns as shown in FIGS. 3A to 3E can be applied in addition to the pattern shown in FIG. it can.

  Next, an Fe (iron) film having a thickness of about 10 to 200 nm, for example, 97.5 nm, is formed by sputtering, for example, and a catalytic metal film 32b made of Fe is formed. The catalyst metal film 32b is formed on the photoresist film 34 and on the catalyst metal film 32a in the opening 36 (FIG. 4B). As the constituent material of the catalyst metal film 32b, the same catalyst metal material as that of the catalyst metal film 32a is used. The catalytic metal film 32b may be formed by an electron beam evaporation method, an MBE method, or the like.

  Next, the catalyst metal film 32b on the photoresist film 34 is lifted off together with the photoresist film 34, and the catalyst metal film 32b is selectively left on the catalyst metal film 32b in the region where the graphite layer 14 is to be formed. As a result, a catalytic metal film 32a made of an Fe film having a film thickness of 2.5 nm is formed in a region where the carbon nanotube bundle 12 is to be formed, and an area where the graphite layer 14 is to be formed is made of an Fe film having a thickness of 100 nm. Catalyst metal films 32a and 32b are formed (FIG. 4C).

  Next, on the substrate 30, for example, by hot filament CVD, using the catalytic metal films 32 a and 32 b as catalysts, carbon nanotubes are formed on the region where the carbon nanotube bundle 12 is to be formed, graphite is formed on the region where the graphite layer 14 is to be formed, Each grows.

  At this time, the carbon nanotubes and the graphite can be grown at the same time by appropriately setting the film thickness and growth conditions of the catalytic metal films 32a and 32b.

  In an area where the catalytic metal film is thin (area where carbon nanotube bundles are to be formed), the catalytic metal aggregates into fine particles due to the temperature during growth. Thereby, the growth proceeds with the catalytic metal fine particles as nuclei, and carbon nanotubes are formed. On the other hand, in the region where the catalyst metal film is thick (the region where the graphite layer 14 is to be formed), the catalyst metal does not aggregate at the growth temperature and remains in a film shape. As a result, the growth proceeds flatly with the catalytic metal film as a nucleus, and graphite is formed.

  Therefore, a catalyst metal film having a film thickness is formed in the carbon nanotube bundle formation region where the catalyst metal aggregates and becomes fine particles depending on the growth temperature, and the graphite layer formation region is formed in the growth region. A catalyst metal film having a film thickness at which the catalyst metal does not aggregate at the temperature is formed.

A catalytic metal film 32a made of an Fe film with a thickness of 2.5 nm is formed in a region where the carbon nanotube bundle 12 is to be formed, and catalytic metal films 32a and 32b made of an Fe film with a thickness of 100 nm are formed in the region where the graphite layer 14 is to be formed. In the formed example, for example, a mixed gas of acetylene and argon (partial pressure ratio 1: 9) is used as the source gas, the total gas pressure in the film forming chamber is 1 kPa, the temperature is 620 ° C., and the growth time is 30 minutes. As a result, on the region where the carbon nanotube bundle 12 is to be formed, the number of layers is 3 to 6 (average 4 layers), the diameter is 4 to 8 nm (average 6 nm), the length is 100 μm, and the density is 1 × 10 ^11. Multi-walled carbon nanotubes of about 1 / cm ² were grown, and graphite having a film thickness of 13 nm could be grown on the region where the graphite layer 14 was to be formed.

  In the case of using the above growth conditions, the relationship between the thickness of the Fe film as the catalyst metal film and the growth was examined, and the following results were obtained. When the thickness of the catalytic metal film was less than 10 nm, carbon nanotubes grew. When the thickness of the catalytic metal film was 10 nm or more and less than 20 nm, both carbon nanotubes and graphite grew. When the thickness of the catalytic metal film was 20 nm to 200 nm, graphite grew.

  Note that the catalyst metal atomization tends to occur as the growth temperature increases. Moreover, the conditions for forming fine particles vary depending on the type of catalyst metal. Therefore, it is desirable that the film thickness of the catalyst metal film is appropriately adjusted according to the type of catalyst metal, the growth temperature, and the like.

  Carbon nanotubes and graphite may be formed by other film forming methods such as a thermal CVD method and a remote plasma CVD method. The growing carbon nanotube may be a single-walled carbon nanotube. Moreover, as a carbon raw material, you may use hydrocarbons, such as methane and ethylene other than acetylene, alcohols, such as ethanol and methanol.

  Thus, the carbon nanotube bundle 12 having a plurality of carbon nanotubes oriented in the normal direction of the substrate 30 (vertical orientation) and the graphite layer 14 made of graphite having a layered structure parallel to the surface of the sheet are formed on the substrate 30. (FIG. 5A).

  Next, a filler to be the filling layer 16 is applied by, eg, spin coating. At this time, the viscosity of the coating solution and the rotation speed of the spin coater are appropriately set so that the filler does not cover the carbon nanotube bundle 12.

  For example, in the case where an acrylic resin is used as a filler, when the height of the carbon nanotube bundle 12 and the thickness of the filler layer 16 are substantially equal, for example, an acrylic resin having a viscosity of 440 mPa · s is used under the condition of 2000 rpm for 20 seconds. This can be realized by coating.

  Moreover, when making the filling layer 16 thinner than the height of the carbon nanotube bundle 12, for example, it can be realized by applying an acrylic resin having a viscosity of 440 mPa · s under the condition of 4000 rpm for 20 seconds. Or it can implement | achieve by apply | coating the acrylic resin diluted to 80 w% with MEK (methyl ethyl ketone) solution on 2000 rpm and the conditions for 20 seconds.

  After forming the filler so as to cover the carbon nanotube bundle 12, the upper surface of the carbon nanotube bundle 12 may be exposed by ashing or the like.

  Further, a metal thin film may be deposited on the carbon nanotube bundle 12 and the graphite layer 14 before applying the filler. As the metal thin film, for example, gold (Au) with a film thickness of 300 nm is deposited. By depositing the metal thin film on the carbon nanotube bundle, it is possible to reduce the thermal resistance and electrical resistance between the carbon nanotubes and further improve the heat dissipation of the carbon nanotube sheet.

  The filler is not particularly limited as long as it shows liquid properties and can be cured thereafter. For example, an acrylic resin, an epoxy resin, a silicone resin, a polyimide resin, or the like can be applied as the organic filler. Further, as the inorganic filler, a coating type insulating film forming composition such as SOG can be applied. A metal material such as indium, solder, or a metal paste (eg, silver paste) can also be used. In addition, conductive polymers such as polyaniline and polythiophene can also be applied.

  When the filling layer 16 is formed, since the plurality of carbon nanotube bundles 12 are formed on the substrate 30 at intervals, the applied filling material first spreads over the entire surface of the substrate 30 along this gap. After that, the filler penetrates into the carbon nanotube bundle 12 and the graphite layer 14.

  When carbon nanotubes are formed on the entire surface of the substrate, when the filler penetrates into the carbon nanotube bundle, the individual carbon nanotubes aggregate together, and the orientation that the carbon nanotube bundle originally held For example, trying to cause a shape change such as falling sideways.

  However, by providing a gap between the carbon nanotube bundles 12 as in the present embodiment, the filler spreads over the entire surface of the substrate 30 and then penetrates into the carbon nanotube bundles 12. For this reason, the filler previously filled between the carbon nanotube bundles 12 serves as a supporter for maintaining the shape of the carbon nanotubes when the filler penetrates into the carbon nanotube bundles. The shape change can be suppressed. Thereby, the filled layer 16 can be formed while maintaining the orientation direction of the carbon nanotube bundle 12.

  The necessary gap between the carbon nanotube bundles 12 varies depending on the type and viscosity of the filler, and thus cannot be determined in general. However, according to the study by the present inventors, an interval of 0.1 μm or more should be provided. Thus, it has been confirmed that the shape change of the carbon nanotube bundle can be prevented.

  The resin layer 16 may be formed by immersing the substrate 30 in a filler solution (so-called dipping method). Also in this case, a change in the shape of the carbon nanotube bundle can be prevented by the gap provided between the carbon nanotube bundles 12.

  Next, the filler is cured to form the filler layer 16 made of the filler (FIG. 5B). For example, when a photocurable material such as an acrylic resin is used as the filler, the filler can be cured by light irradiation. In addition, when a thermosetting material such as an epoxy resin or a silicone resin is used as the filler, the filler can be cured by heat treatment. In the case of an epoxy resin, it can be cured by heat treatment at 150 ° C. for 1 hour, for example. In the case of a silicone resin, it can be cured by heat treatment at 200 ° C. for 1 hour, for example.

  If the upper end portion of the carbon nanotube bundle 12 is not sufficiently exposed or covered by the filling layer 16 after the filling layer 16 is cured, chemical mechanical polishing (CMP), oxygen The filling layer 16 on the carbon nanotube bundle 12 may be removed by plasma ashing, argon ion milling, or the like.

  Next, the carbon nanotube bundle 12, the graphite layer 14, and the resin layer 16 are peeled from the substrate 30 to obtain the carbon nanotube sheet 10 (FIG. 5C).

  At this time, when the surface of the substrate 30 is made of a material that can easily peel the carbon nanotube sheet 10, for example, a silicon oxide film or a silicon nitride film is formed on the surface of the substrate 30, and the filling layer 16 is made of acrylic. In the case of being formed of resin, the substrate 30 can be easily peeled from the carbon nanotube sheet 10.

  Alternatively, when the carbon nanotube sheet 10 cannot be easily peeled off on the surface of the substrate 30 but a layer that can be selectively etched with respect to the carbon nanotube sheet 10 is formed, for example, silicon oxide is formed on the surface of the substrate 30. When a film or a silicon nitride film is formed and the filling layer 16 is formed of an epoxy resin, the silicon oxide film or the silicon nitride film is wet etched using a hydrofluoric acid aqueous solution or hot phosphoric acid. The carbon nanotube sheet 10 can be released from the substrate 30 by removing by the above.

  When the surface of the substrate 30 is formed of a material that cannot easily separate the carbon nanotube sheet 10 and cannot be selectively removed, for example, the substrate 30 is a sapphire substrate and the filling layer 16 is silicone. In the case of being formed of a system resin, the carbon nanotube sheet 10 can be peeled from the substrate 30 by inserting a sharp blade between the substrate 30 and the carbon nanotube sheet 10.

  Since the carbon nanotube bundle 12 and the graphite layer 14 are in direct contact with the substrate 30 before peeling, the carbon nanotube bundle 12 and the graphite layer 14 are exposed on the surface of the peeled carbon nanotube sheet 10 on the substrate 30 side. . Therefore, in the carbon nanotube sheet 10 formed by the manufacturing method described above, the carbon nanotube bundle 12 can be exposed on both surfaces of the sheet, and the graphite layer 14 can be exposed on one surface. It is also possible to connect to the exposed portions of the carbon nanotube bundle 12 or the graphite layer 14 via a metal such as In, solder, plating such as AuSn, or a metal paste.

  The thermal resistance of an indium sheet conventionally used is 0.21 (° C./W), whereas the thermal resistance of a carbon nanotube sheet composed only of carbon nanotubes manufactured by the same process as described above is 0.13. (° C / W). Since the difference in thermal conductivity is reflected in the difference in thermal resistance, the thermal resistance is further reduced in the carbon nanotube of this embodiment in which a graphite layer capable of radiating heat in the plane parallel direction is added in addition to the carbon nanotube. It is clear.

  Thus, according to the present embodiment, after forming a plurality of carbon nanotube bundles spaced apart from each other on the substrate, a filling layer is formed by filling the filler and holding the carbon nanotube bundle. The shape change of the carbon nanotube bundle can be prevented. Thereby, it is possible to easily form a carbon nanotube sheet in which the carbon nanotube bundles are oriented in the film thickness direction of the sheet. Moreover, since both ends of the carbon nanotube bundle can be exposed from the filling layer, the thermal conductivity and electrical conductivity with respect to the adherend can be improved.

  In addition, since the graphite layer is formed in the gap between the carbon nanotube bundles so as to be connected to the carbon nanotube bundle, the thermal conductivity and the electric conductivity in the direction parallel to the surface of the sheet can be improved.

  Further, since the carbon nanotube bundle and the graphite layer can be formed at the same time, the carbon nanotube sheet can be formed without significantly changing the manufacturing process. Thereby, the increase in manufacturing cost can be prevented.

[Second Embodiment]
A carbon nanotube sheet and a method for manufacturing the same according to a second embodiment of the present invention will be described with reference to FIGS. Components similar to those of the carbon nanotube sheet and the manufacturing method thereof according to the first embodiment shown in FIGS. 1 to 5 are denoted by the same reference numerals, and description thereof is omitted or simplified.

  FIG. 6 is a plan view and a schematic cross-sectional view showing the structure of the carbon nanotube sheet according to the present embodiment, FIG. 7 is a schematic cross-sectional view showing the structure of the carbon nanotube sheet according to a modification of the present embodiment, and FIGS. It is process sectional drawing which shows the manufacturing method of the carbon nanotube sheet by a form.

  First, the structure of the carbon nanotube sheet according to the present embodiment will be explained with reference to FIG. FIGS. 6A and 6B are a plan view and a cross-sectional view showing the structure of the carbon nanotube sheet according to the present embodiment, respectively.

  The carbon nanotube sheet 10 according to the present embodiment has a plurality of carbon nanotube bundles 12 that are spaced apart from each other (see FIG. 6A). In the gap between the carbon nanotube bundles 12, a carbon nanotube layer (linear structure layer made of carbon element) 18 having one end exposed on the surface of the sheet, a graphite layer 20 formed on the carbon nanotube layer 18, and a resin material A filling layer 16 made of the same is embedded (see FIGS. 6A and 6B). The graphite layer 20 is thermally and electrically connected to the carbon nanotube bundle 12 and the carbon nanotube layer 20.

  In the present specification, a structure composed of a carbon nanotube bundle, a carbon nanotube layer, a graphite layer, or a combination thereof may be referred to as a carbon structure.

  The carbon nanotube bundle 12 is formed so as to extend in a direction perpendicular to the surface of the sheet, and has a plurality of carbon nanotubes oriented in a direction perpendicular to the surface of the sheet.

The carbon nanotubes constituting the carbon nanotube bundle 12 may be either single-walled carbon nanotubes or multi-walled carbon nanotubes. The density of the carbon nanotubes contained in the carbon nanotube bundle 12 is desirably 1 × 10 ¹⁰ pieces / cm ² or more from the viewpoint of heat dissipation and electrical conductivity. The length (sheet thickness) of the carbon nanotube bundle 12 is determined by the use of the carbon nanotube sheet 10 and is not particularly limited, but can be preferably set to a value of about 5 μm to 500 μm.

  In the carbon nanotube sheet 10 according to the present embodiment, a gap is provided between the carbon nanotube bundles 12 on the graphite layer 20, and the filling layer 16 is formed in this gap. This enhances the permeability of the filler when forming the filling layer 16 between the carbon nanotubes, suppresses the shape change such as the carbon nanotubes falling sideways, and maintains the orientation originally held by the carbon nanotubes. This is for the purpose (see the first embodiment).

  The shape, arrangement, and the like of the carbon nanotube bundle 12 are the same as in the first embodiment.

  The carbon nanotube layer 18 is formed so as to extend in a direction perpendicular to the surface of the sheet, and has a plurality of carbon nanotubes oriented in a direction perpendicular to the surface of the sheet.

The carbon nanotubes constituting the carbon nanotube layer 18 may be single-walled carbon nanotubes or multi-walled carbon nanotubes. The density of the carbon nanotubes contained in the carbon nanotube layer 18 is desirably 1 × 10 ¹⁰ pieces / cm ² or more from the viewpoint of heat dissipation and electrical conductivity. The length of the carbon nanotube layer 18 is determined by the use of the carbon nanotube sheet 10 and is not particularly limited, but can be preferably set to a value of about 5 μm to 500 μm.

  The graphite layer 20 is made of graphite having a layered structure parallel to the surface of the sheet, and is formed so as to be connected to the side surface of the carbon nanotube bundle 12 and the upper surface of the carbon nanotube layer 18. The thickness of the graphite layer 20 is, for example, about several nm to several tens of nm.

  About the constituent material of the filling layer 16, it is the same as that of the case of 1st Embodiment.

  As described above, the carbon nanotube sheet 10 according to the present embodiment includes the carbon nanotube bundle 12 and the carbon nanotube layer 18 oriented in a direction perpendicular to the surface of the sheet, and the graphite layer 20 made of graphite having a layered structure parallel to the surface of the sheet. And have. Carbon nanotubes have a very high thermal conductivity of about 1500 (W / m · K) along the alignment direction. Graphite does not have the thermal conductivity of carbon nanotubes, but the thermal conductivity in the direction parallel to the layer surface (a-axis) is about 500 (W / m · K), which is also very high heat. It has conductivity.

  Therefore, by forming the carbon nanotube sheet 10 by combining the carbon nanotube bundle 12, the carbon nanotube layer 18, and the graphite layer 20 as in the present embodiment, the carbon nanotubes mainly have thermal conductivity in the direction perpendicular to the surface of the sheet. It can be ensured by (the carbon nanotube bundle 12 and the carbon nanotube layer 18), and the thermal conductivity in the direction parallel to the surface of the sheet can be ensured mainly by graphite (graphite layer 20).

  Graphite has a thermal conductivity of 500 times or more compared to a resin material (thermal conductivity: about 1 (W / m · K)). Therefore, by providing the graphite layer 20, the heat dissipation in the direction parallel to the surface of the sheet can be greatly improved by 500 times or more compared with the case where the graphite layer 20 is not formed.

  The carbon nanotube sheet according to the present embodiment is superior to the carbon nanotube sheet according to the first embodiment in that the graphite layer 20 is indirectly connected to the heat sink and the carbon nanotube layer 18 disposed below the carbon nanotube sheet. Is connected to. That is, the carbon nanotube sheet of the present embodiment that once radiates heat to the graphite layer 20 through the carbon nanotube layer 18 is compared with the carbon nanotube sheet according to the first embodiment in which the heat radiating body and the graphite layer 20 are directly connected. And especially when the contact surface of a heat radiator and a sheet | seat is comparable as the magnitude | size of a sheet | seat, the heat dissipation in a parallel direction is excellent.

  In the carbon nanotube sheet 10 according to the present embodiment, the upper end and the lower end of the carbon nanotube bundle 12 are not covered with the filling layer 16. Thereby, when the carbon nanotube sheet 10 is brought into contact with the heat radiating body or the heat generating body, the carbon nanotube bundle 12 is in direct contact with the heat radiating body or the heat generating body, so that the heat conduction efficiency can be greatly increased.

  Since the carbon nanotube and the graphite have both high conductivity, the carbon nanotube bundle 12 can be used as a wiring body penetrating the sheet by exposing the upper end and the lower end of the carbon nanotube bundle 12. Moreover, the graphite layer 20 can also be used as a wiring body in a direction parallel to the surface of the sheet. That is, the carbon nanotube sheet 10 according to the present embodiment can be used not only as a heat conductive sheet but also as a wiring sheet.

  The relationship between the height of the carbon nanotube bundle 12 and the thickness of the filling layer 16 (the length in the thickness direction of the sheet) is the same as in the first embodiment.

  The carbon nanotube layer 18 and the graphite layer 20 formed between the carbon nanotube bundles 12 may be laminated repeatedly as shown in FIG. 7, for example. In the example of FIG. 7, the stacked structure of the carbon nanotube layer 18 and the graphite layer 20 is a stacked structure, but three or more layers may be stacked.

  By providing a plurality of graphite layers 20, the substantial film thickness of the graphite layer 20 increases, and the thermal conductivity and electrical conductivity in the lateral direction can be improved.

  Next, the manufacturing method of the carbon nanotube sheet according to the present embodiment will be explained with reference to FIGS.

  First, a substrate 30 used as a base for forming the carbon nanotube sheet 10 is prepared. As the substrate 30, various substrates described in the first embodiment can be used.

  Next, a photoresist film (not shown) that exposes a region where the carbon nanotube bundle 12 is to be formed is formed on the substrate 30. The shape and arrangement of the region where the carbon nanotube bundle 12 is to be formed are the same as in the first embodiment. The region where the carbon nanotube bundle 12 is to be formed is, for example, a circular shape having a diameter of 100 μm, and the interval between adjacent regions is, for example, 100 μm.

  Next, an Fe film having a thickness of, for example, 2.5 nm is deposited by, eg, sputtering, and a catalytic metal film 32 made of the Fe film is formed. As the catalyst metal, the same catalyst metal material as in the first embodiment can be used.

  Next, the catalyst metal film 32 on the photoresist film is lifted off together with the photoresist film, and the catalyst metal film 32 is selectively left in the region where the carbon nanotube bundle 12 is to be formed. In this way, the catalytic metal film 32 made of, for example, an Fe film having a film thickness of 2.5 nm is formed in a region where the carbon nanotube bundle 12 is to be formed (FIG. 8A).

  Next, carbon nanotubes are grown on the substrate 30 by, for example, hot filament CVD using the catalytic metal film 32 as a catalyst. The carbon nanotube growth conditions are, for example, using a mixed gas of acetylene and argon (partial pressure ratio 1: 9) as a source gas, a total gas pressure in the film formation chamber of 1 kPa, a temperature of 620 ° C., and a growth time of 30 minutes. . As a result, it is possible to grow multi-walled carbon nanotubes having 3 to 6 layers (average of about 4 layers), a diameter of 4 to 8 nm (average of 6 nm), and a length of 100 μm. The carbon nanotubes may be formed by other film forming methods such as a thermal CVD method and a remote plasma CVD method. The growing carbon nanotube may be a single-walled carbon nanotube. Moreover, as a carbon raw material, you may use hydrocarbons, such as methane and ethylene other than acetylene, alcohols, such as ethanol and methanol.

Thus, the carbon nanotube bundle 12 having a plurality of carbon nanotubes oriented in the normal direction (vertical orientation) of the substrate 30 is selectively formed on the region of the substrate 30 where the catalytic metal film 32 is formed (FIG. 8 ( b)). In the carbon nanotube bundle 12 formed under the above growth conditions, the carbon nanotube density in the carbon nanotube bundle 12 was about 1 × 10 ¹¹ pieces / cm ² .

Next, a TiN film having a thickness of, for example, 5 nm and a Co film having a thickness of, for example, 2.6 nm are sequentially deposited on the substrate 30 on which the carbon nanotube bundles 12 are formed by, for example, sputtering. A catalytic metal film 38 is formed (FIG. 8C). At this time, since the upper end of the carbon nanotube bundle 12 does not constitute a continuous plane, the catalytic metal film 38 is not formed as a film on the carbon nanotube bundle 12. In addition to TiN, other materials containing Ti, such as Ti (titanium) and TiO ₂ (titanium oxide), can be used as the base film of the catalytic metal film 38.

  Next, the carbon nanotube layer 18 whose upper surface is covered with the graphite layer 20 is formed on the substrate 30 by, for example, a thermal CVD method using the catalytic metal film 38 as a catalyst (FIG. 9A).

  The carbon nanotube layer 18 whose upper surface is covered with the graphite layer 20 is formed by growing at a relatively low temperature of about 450 ° C. to 510 ° C. using a raw material gas of hydrocarbons such as acetylene, methane, and ethylene. Can do. For example, a mixed gas of acetylene and argon (partial pressure ratio 1: 9) is used as the source gas, the total gas pressure in the deposition chamber is 1 kPa, the temperature is 450 ° C. to 510 ° C., and the growth time is 30 minutes. Thereby, the carbon nanotube layer 18 having multi-walled carbon nanotubes having 3 to 6 layers (average of about 4 layers), a diameter of 4 to 8 nm (average of 6 nm), and a length of 20 μm can be grown. A graphite layer 20 having a thickness of 18 nm is formed on the carbon nanotube layer 18.

  The carbon nanotube layer 18 whose upper surface is covered with the graphite layer 20 can be formed by appropriately controlling the film thickness of the catalytic metal film 38 (film thickness of the Co film) and the film formation temperature.

  Table 1 shows the results of investigating the relationship between the film thickness and deposition temperature of the Co film constituting the catalytic metal film 38 and the structure formed thereby. Note that the thickness of the TiN film constituting the catalytic metal film 38 was constant at 5 nm.

表１中、「ＣＮＴ」はカーボンナノチューブのみが成長されたものを、「グラファイト／ＣＮＴ」は上面にグラファイトが形成されたカーボンナノチューブが形成されたものを、それぞれ示している。

In Table 1, “CNT” indicates that carbon nanotubes are grown only, and “graphite / CNT” indicates that carbon nanotubes having graphite formed on the upper surface are formed.

  As shown in Table 1, the upper surface is covered with the graphite layer by setting the film thickness of the Co film in the range of 2.1 nm to 3.6 nm and the film formation temperature in the range of 450 ° C. to 510 ° C. A carbon nanotube layer could be formed. When the inventors of the present application examined in more detail, the Co film thickness was set to 2.0 nm to 7.0 nm, and growth was performed at a film formation temperature of 350 ° C. to 560 ° C., so that the upper surface was a graphite layer. It was found that a carbon nanotube layer covered with can be formed.

  In addition, the thickness of the formed graphite layer can also be controlled by the thickness of the Co film and the film forming temperature. A graphite layer can be formed, a graphite layer having a thickness of 18 nm can be formed when the thickness of the Co film is 2.6 nm, and a thickness of 30 nm can be formed when the thickness of the Co film is 3.6 nm. A graphite layer could be formed. Further, when the film forming temperature was 450 ° C. and the Co film thickness was 3.6 nm, a graphite layer having a thickness of 20 nm could be formed.

  Although the mechanism by which the carbon nanotube layer 18 whose upper surface is covered with the graphite layer 20 is not clear, the inventors of the present application infer as follows.

  In the present embodiment, the growth of the carbon nanotube layer 18 is performed at a lower temperature than the growth of the carbon nanotube bundle 12. For this reason, in the initial growth process, the Co film of the catalytic metal film 38 is not sufficiently aggregated, and it is considered that graphite is uniformly grown on the catalytic metal film 38. Thereafter, the growth of the carbon nanotubes is started together with the aggregation of the Co film, and as a result, the carbon nanotube layer 18 whose upper surface is covered with the graphite layer 20 is considered to be formed.

  When the carbon nanotube layer 18 whose upper surface is covered with the graphite layer 20 is formed, the graphite layer 20 is formed in about 1 second in the initial stage of growth. The thickness of the carbon nanotube layer 18 (the length of the carbon nanotube) can be arbitrarily controlled by the growth time.

  Next, when the carbon nanotube sheet having the structure shown in FIG. 7 is formed, the steps shown in FIGS. 8C to 9A are repeated as many times as necessary, and the carbon nanotube layer 18 and the graphite layer are repeated. A stack of 20 and a predetermined number of layers are stacked.

  Unlike the carbon nanotube bundle 12, the upper surface of the graphite layer 20 is formed in a planar shape, so that the catalytic metal film 38 can be deposited thereon. As a result, the carbon nanotube layer 18 and the graphite layer 20 can be repeatedly grown.

  Next, in the same manner as in the method of manufacturing the carbon nanotube sheet according to the first embodiment, the region between the carbon nanotube bundles 12, the space between the carbon nanotubes, and the filling layer 16 embedded in the graphite layer are formed (FIG. 9B). .

  Next, in the same manner as in the method of manufacturing the carbon nanotube sheet according to the first embodiment, the carbon nanotube bundle 12, the carbon nanotube layer 18, the graphite layer 20, and the resin layer 16 are peeled from the substrate 30 to obtain the carbon nanotube sheet 10 (FIG. 9 (c)).

  Thus, according to the present embodiment, after forming a plurality of carbon nanotube bundles spaced apart from each other on the substrate, a filling layer is formed by filling the filler and holding the carbon nanotube bundle. The shape change of the carbon nanotube bundle can be prevented. Thereby, it is possible to easily form a carbon nanotube sheet in which the carbon nanotube bundles are oriented in the film thickness direction of the sheet. Moreover, since both ends of the carbon nanotube bundle can be exposed from the filling layer, the thermal conductivity and electrical conductivity with respect to the adherend can be improved.

  In addition, since a laminate of the carbon nanotube layer and the graphite layer is formed in the gap between the carbon nanotube bundles so as to be connected to the carbon nanotube bundle, the thermal conductivity and the electric conductivity in the direction parallel to the surface of the sheet are formed. Can also be improved.

[Third Embodiment]
A semiconductor device and a manufacturing method thereof according to the third embodiment of the present invention will be described with reference to FIGS.

  FIG. 10 is a schematic cross-sectional view showing the structure of the semiconductor device according to the present embodiment, and FIGS. 11 to 13 are process cross-sectional views showing the method for manufacturing the semiconductor device according to the present embodiment.

  First, the structure of the semiconductor device according to the present embodiment will be explained with reference to FIG.

A wiring layer 42 is formed on the substrate 40. An interlayer insulating film 44 is formed in a region on the substrate 40 other than the region where the wiring layer 42 is formed. A via wiring 64 made of a bundle of carbon nanotubes is formed on one end of the wiring layer 42 via a TiN film 52. A wiring layer 66 made of graphite and connected to the via wiring 64 is formed on the via wiring 64. A TiO ₂ film 56 is formed on the wiring layer 42 and the interlayer insulating film 44 in the formation region of the wiring layer 66 excluding the formation region of the via wiring 64. An interlayer insulating film 68 is formed around the via wiring 64 and the wiring layer 66. A via wiring 72 made of a bundle of carbon nanotubes is formed on one end of the wiring layer 66 via a TiN film 70. A wiring layer 74 made of graphite and connected to the via wiring 72 is formed on the via wiring 72. A TiO ₂ film is formed on the interlayer insulating film 68 in the formation region of the wiring layer 74 excluding the formation region of the via wiring 72. An interlayer insulating film 76 is formed around the via wiring 72 and the wiring layer 74.

  As described above, in the semiconductor device according to the present embodiment, the via wiring (for example, the via wiring 64) that connects the lower wiring layer (for example, the wiring layer 42) and the upper layer wiring (for example, the wiring layer 66) is constituted by the carbon nanotube bundle. Yes. In addition, a wiring layer (for example, the wiring layer 66) connected to a via wiring (for example, the via wiring 64) made of carbon nanotube bundles is formed of a graphite layer.

  By forming the wiring layer and the via wiring with graphite and carbon nanotubes having a low resistance value, the wiring resistance can be greatly reduced. As a result, the semiconductor device can be operated at high speed and the power consumption can be reduced.

  Next, the method for fabricating the semiconductor device according to the present embodiment will be explained with reference to FIGS.

  It is assumed that a wiring layer 42 and an interlayer insulating film 44 are formed on the substrate 40 (FIG. 11A). The wiring layer 42 and the interlayer insulating film 44 are formed by a normal semiconductor device manufacturing process. The substrate 40 includes not only a semiconductor substrate itself such as a silicon substrate, but also a semiconductor substrate on which an element such as a transistor and one or more wiring layers are formed. An example of the material of the wiring layer 42 is copper. In this case, tantalum or the like for preventing copper diffusion is deposited on the bottom of the via.

  On this substrate 40, a photoresist film 48 that exposes a region where a via part for connecting the upper wiring layer to the wiring layer 42 is exposed and covers the other region is formed by photolithography.

  Next, a TiN film 50 having a thickness of about 1 to 20 nm, for example, 5 nm, and a Co film 52 having a thickness of about 2 to 3 nm, for example, 2.1 nm are sequentially deposited by sputtering, for example, from a Co / TiN laminated structure. A catalytic metal film is formed (FIG. 11B). The catalytic metal film may be formed by an electron beam evaporation method, a CVD method, an MBE method, or the like.

  Note that instead of selectively forming the catalytic metal film by the lift-off method as described above, the catalytic metal film may be formed on the entire surface and then patterned using photolithography and ion milling. Other patterning methods include EB (electron beam) exposure, but there is no particular limitation.

  Next, the TiN film 50 and the Co film 52 on the photoresist film 48 are lifted off together with the photoresist film 48, and a catalytic metal film having a laminated structure of the Co film 52 / TiN film 50 is selectively formed in a region where a via portion is to be formed. It remains (FIG. 11 (c)).

  Next, an area where the upper wiring layer connected to the wiring layer 42 is to be formed by photolithography, excluding the area where the via metal film formed of the Co film 52 / TiN film 50 is formed is excluded. A photoresist film 54 that is exposed and covers other regions is formed.

Next, a TiO ₂ film 56 having a thickness of about 1 to ₂₀ nm, for example, 5 nm, and a Co film 58 having a thickness of about 3 to 7 nm, for example, 4.5 nm are sequentially deposited by sputtering, for example, and a Co / TiO ₂ layer is laminated. A catalytic metal film having a structure is formed (FIG. 12A).

Note that the TiO ₂ film 56 different from the TiN film 50 used in the via part formation planned region is used as the base film of the catalyst metal film formed in the wiring layer formation planned region excluding the via part formation planned region. This is because the base film (TiN film 50, TiO ₂ film 56) of the catalyst metal film remains even after the wiring layer is formed. That is, in the via portion formation planned region, it is necessary to use the conductive TiN film 50 in order to ensure electrical connection with the underlying wiring layer 42. This is because if the conductive film is formed of a TiN film or the like, there is a risk of short-circuiting with another wiring layer via the TiN film 50. From this point of view, it is desirable to form an insulating base film such as a TiO ₂ film in the wiring layer formation scheduled region excluding the via part formation scheduled region. In the case where there is no possibility of short circuit between the wiring layers, a conductive base film may be formed in the same manner as the via portion formation scheduled region.

Next, the TiO ₂ film 56 and the Co film 58 on the photoresist film 54 are lifted off together with the photoresist film 54, and the Co film 58 / TiO ₂ film 56 is laminated in the wiring layer formation planned area excluding the via part formation planned area. The resulting catalytic metal film is selectively left (FIG. 12B).

Next, carbon nanotubes and graphite are grown by, for example, a thermal CVD method using the catalytic metal film as a catalyst. The growth conditions at this time are, for example, that the source gas is a mixed gas of acetylene and argon (partial pressure ratio 1: 9), the total gas pressure in the film forming chamber is 1 kPa, and the temperature is 450 ° C. In the via portion formation planned area in which the catalytic metal film of the film 54 is formed, a via wiring 64 made of a carbon nanotube bundle is formed, and in the wiring layer formation scheduled area in which the Co film 58 / TiO ₂ film 56 is formed, A wiring layer 66 made of a graphite layer extending on the via wiring 64 is formed apart from the TiO ₂ film 56 (FIG. 12C). Carbon nanotubes and graphite may be formed by a hot filament CVD method, a remote plasma CVD method, or the like.

  The Co films 52 and 58 become fine particles during the growth process of carbon nanotubes and graphite and are taken into the carbon nanotubes or graphite.

The structures formed on the catalytic metal film made of the Co film 52 / TiN film 54 and the catalytic metal film made of the Co film 58 / TiO ₂ film 56 are different because of the growth rate due to the difference in the thickness of the Co film. This is because of the difference.

As shown in the second embodiment, the conditions for performing growth using a Co film having a film thickness of 2.1 nm or 4.5 nm as a catalyst at the film formation temperature are as follows. This is a condition for growing carbon nanotubes. However, the growth rate of carbon nanotubes in the region where the Co film with a thickness of 4.5 nm is formed is significantly slower than the growth rate of carbon nanotubes in the region where the Co film with a thickness of 2.1 nm is formed. After the wiring layer 66 made of a layer is formed, the growth of carbon nanotubes on the catalytic metal film made of the Co film 52 / TiN film 54 becomes dominant. As a result, as the carbon nanotubes grow on the catalytic metal film made of the Co film 52 / TiN film 54, the entire graphite layer in the wiring layer formation scheduled region is lifted, and the catalytic metal made of the Co film 58 / TiO ₂ film 56 Carbon nanotubes no longer grow on the film. As a result, the via wiring 64 and the wiring layer 66 as shown in FIG. 12C are formed.

  Table 2 shows the lengths of the carbon nanotubes formed when the Co film thickness and the carbon nanotube growth conditions are changed.

表２に示すように、カーボンナノチューブの成長レートは、いずれの成長温度の場合にも、Ｃｏ膜厚が厚いほどに小さくなっている。したがって、ビア配線形成領域及び配線層形成領域に堆積するＣｏ膜の膜厚を適宜設定することにより、カーボンナノチューブ束よりなるビア配線と、グラファイト層よりなる配線層とを同時に形成することができる。

As shown in Table 2, the growth rate of carbon nanotubes decreases as the Co film thickness increases at any growth temperature. Therefore, by appropriately setting the film thickness of the Co film deposited in the via wiring formation region and the wiring layer formation region, the via wiring made of the carbon nanotube bundle and the wiring layer made of the graphite layer can be formed simultaneously.

  Next, an interlayer insulating film 68 that covers the wiring layer 66 is formed on the substrate 40 on which the wiring layer 66 is formed, for example, by spin coating or CVD (FIG. 13A).

  Next, the surface of the interlayer insulating film 68 is polished by CMP, for example, until the surface of the wiring layer 66 is exposed (FIG. 13B).

  Next, the steps shown in FIGS. 11B to 13A are repeated as necessary, and via wirings 72 electrically connected to the wiring layer 66 via the TiN film 70 are formed above the wiring layer 66. A wiring layer 74, an interlayer insulating film 76, and the like are formed (FIG. 13C).

  Thus, according to the present embodiment, a via wiring made of a carbon nanotube bundle and a wiring layer made of a graphite layer connected to the via wiring can be formed. Thereby, the electrical resistance of the via wiring and the wiring layer can be greatly reduced, and the characteristics of the semiconductor device can be improved. In addition, since the via wiring made of the carbon nanotube bundle and the wiring layer made of the graphite layer can be formed at the same time, the wiring structure can be formed without significantly changing the manufacturing process. Thereby, the increase in manufacturing cost can be prevented.

[Fourth Embodiment]
A semiconductor device and a manufacturing method thereof according to the fourth embodiment of the present invention will be described with reference to FIGS.

  FIG. 14 is a schematic cross-sectional view showing the structure of the semiconductor device according to the present embodiment, and FIGS. 15 to 17 are process cross-sectional views showing the method for manufacturing the semiconductor device according to the present embodiment.

  First, the structure of the semiconductor device according to the present embodiment will be explained with reference to FIG.

  A wiring layer 42 is formed on the substrate 40. An interlayer insulating film 44 is formed on the substrate 40 on which the wiring layer 42 is formed. A contact hole 46 reaching the wiring layer 42 is formed in the interlayer insulating film 44. A via wiring 64 made of a bundle of carbon nanotubes is formed on the wiring layer 42 in the contact hole 46 via the TiN film 50. A wiring layer 84 connected to the via wiring 64 is formed on the via wiring 64. The wiring layer 84 includes a graphite layer 66a formed on the via wiring 64, a graphite layer 66b formed on the interlayer insulating film via the TiN film 66, and a TiC film 82 formed on the graphite layers 66a and 66b. And have.

  As described above, in the semiconductor device according to the present embodiment, the via wiring (for example, the via wiring 64) that connects the lower wiring layer (for example, the wiring layer 42) and the upper layer wiring (for example, the wiring layer 84) is constituted by the carbon nanotube bundle. Yes. In addition, a wiring layer (for example, the wiring layer 84) connected to a via wiring (for example, the via wiring 64) made of a carbon nanotube bundle is composed of graphite layers 66a and 66b and a TiC film 82.

  By forming the wiring layer and the via wiring with graphite and carbon nanotubes having a low resistance value, the wiring resistance can be greatly reduced. As a result, the semiconductor device can be operated at high speed and the power consumption can be reduced.

  The TiC film 82 formed on the graphite layers 66a and 66b is for ensuring electrical connection between the graphite layers 66a and 66b. The graphite layer 66a and the graphite layer 66b are grown separately from different bases, and although formed in adjacent regions, it is conceivable that sufficient electrical connection cannot be ensured. The TiC film 82 is formed in consideration of such a case, and is not necessarily formed if the electrical connection between the graphite layer 66a and the graphite layer 66b is sufficient.

  Next, the method for fabricating the semiconductor device according to the present embodiment will be explained with reference to FIGS.

  It is assumed that a wiring layer 42 and an interlayer insulating film 44 covering the wiring layer 42 are formed on the substrate 40 (FIG. 15A). The substrate 40 includes not only a semiconductor substrate itself such as a silicon substrate, but also a semiconductor substrate on which an element such as a transistor and one or more wiring layers are formed.

  Next, a contact hole 46 reaching the wiring layer 42 is formed in the interlayer insulating film 44 by photolithography and dry etching (FIG. 15B).

  Next, a photoresist film 48 that exposes the formation region of the contact hole 46 and covers the other region is formed on the interlayer insulating film 44 by photolithography. Note that the photoresist film 48 may be the photoresist film used for forming the contact hole 46.

  Next, a TiN film 50 having a film thickness of about 1 to 20 nm, for example, 5 nm, and a Co film 52 having a film thickness of about 2 to 3 nm, for example, 2.6 nm are sequentially deposited by sputtering, for example, from a Co / TiN stacked structure. A catalytic metal film is formed (FIG. 11C). The catalytic metal film may be formed by an electron beam evaporation method, a CVD method, an MBE method, or the like.

  Next, the TiN film 50 and the Co film 52 on the photoresist film 48 are lifted off together with the photoresist film 48, and a catalytic metal film having a laminated structure of the Co film 52 / TiN film 50 is formed on the wiring layer 42 in the contact hole 46. It is selectively left (FIG. 16 (a)).

  Next, a photolithography is performed to form a photoresist film 54 that exposes a region where the upper wiring layer connected to the wiring layer 42 is to be formed, except the region where the contact hole 46 is formed, and covers the other regions.

  Next, a TiN film 60 having a film thickness of about 1 to 20 nm, for example, 5 nm, and a Co film 62 having a film thickness of about 3 to 7 nm, for example, 4.5 nm are sequentially deposited by sputtering, for example, from a Co / TiN laminated structure. A catalytic metal film is formed (FIG. 16B).

  Next, the TiN film 60 and the Co film 62 on the photoresist film 54 are lifted off together with the photoresist film 54, and a wiring layer formation scheduled area excluding the contact hole 46 formation area is formed from the Co film 62 / TiN film 60 laminated structure. The resulting catalyst metal film is selectively left (FIG. 16C).

  Next, carbon nanotubes and graphite are grown by, for example, a thermal CVD method using the catalytic metal film as a catalyst. The growth conditions at this time are, for example, that the source gas is a mixed gas of acetylene and argon (partial pressure ratio 1: 9), the total gas pressure in the film forming chamber is 1 kPa, and the temperature is 450 ° C. A via wiring 64 made of a bundle of carbon nanotubes whose upper surface is covered with a graphite layer 66a is formed in the region where the catalytic metal film of the film 54 is formed, and a Co film 62 / TiN film 60 is formed. A graphite layer 66b is formed in the wiring layer formation scheduled region (FIG. 17A). Carbon nanotubes and graphite may be formed by a hot filament CVD method, a remote plasma CVD method, or the like.

  The Co films 52 and 62 are finely divided during the growth process of carbon nanotubes and graphite, and are taken into the carbon nanotubes or graphite.

  The structures formed on the catalytic metal film made of the Co film 52 / TiN film 54 and the catalytic metal film made of the Co film 62 / TiN film 60 are different because of the growth rate due to the difference in the thickness of the Co film. This is because the difference has an effect.

  As shown in the second embodiment, the conditions for performing growth using a Co film having a film thickness of 2.6 nm or 4.5 nm as a catalyst at the above film formation temperature are such that the upper surface is covered with a graphite layer in any case. This is a condition for growing carbon nanotubes. However, the growth rate of carbon nanotubes in the region where the Co film having a thickness of 4.5 nm is formed is significantly slower than the growth rate of carbon nanotubes in the region where the Co film having a thickness of 2.6 nm is formed. While the via wiring 64 made of the carbon nanotube bundle is formed under the layer 66a, the carbon nanotube bundle is hardly grown under the graphite layer 66b. As a result, via wiring 64 and graphite layers 66a and 66b as shown in FIG. 17A are formed.

  Next, a photoresist film 78 is formed by photolithography to expose the wiring layer formation planned region (formation region of the graphite layers 66a and 66b) and cover the other regions.

  Next, a Ti film 80 of, eg, a 50 nm-thickness is deposited by, eg, sputtering (FIG. 17B).

  Next, the Ti film 80 on the photoresist film 78 is lifted off together with the photoresist film 78, and the Ti film 80 is selectively left on the graphite layers 66 a and 66 b in the wiring layer formation scheduled region.

  Next, for example, heat treatment is performed at 450 ° C. for 10 minutes to react the Ti film 80 with the upper portions of the graphite layers 66a and 66b, thereby forming a TiC (titanium carbide) film 82 on the surfaces of the graphite layers 66a and 66b. TiC is formed only by deposition by sputtering, but the formation of TiC is promoted by performing this heat treatment. Thus, the wiring layer 84 composed of the graphite layers 66a and 66b and the TiC film 82 is formed (FIG. 17C).

  Thus, according to the present embodiment, a via wiring made of a carbon nanotube bundle and a wiring layer made of a graphite layer connected to the via wiring can be formed. Thereby, the electrical resistance of the via wiring and the wiring layer can be greatly reduced, and the characteristics of the semiconductor device can be improved. In addition, since the via wiring made of the carbon nanotube bundle and the wiring layer made of the graphite layer can be formed at the same time, the wiring structure can be formed without significantly changing the manufacturing process. Thereby, the increase in manufacturing cost can be prevented.

[Fifth Embodiment]
An electronic apparatus according to a fifth embodiment of the present invention will be described with reference to FIG.

  FIG. 18 is a schematic cross-sectional view showing the structure of the electronic apparatus according to the present embodiment.

  In the present embodiment, an electronic device in which the carbon nanotube sheet according to the first or second embodiment is applied as a vertical wiring sheet will be described.

  A semiconductor element 106 such as a CPU is mounted on the circuit board 100 such as a multilayer wiring board. The semiconductor element 106 is electrically connected to the circuit board 100 via the solder bumps 102, and an underfill 104 is filled between the circuit board 100 and the semiconductor element 106.

  A heat spreader 110 for diffusing heat from the semiconductor element 106 is formed on the semiconductor element 106 so as to cover the semiconductor element 106. A carbon nanotube sheet 108 according to the first or second embodiment is formed between the semiconductor element 106 and the heat spreader 110. The carbon nanotube sheet 108 is disposed so that the graphite layer 14 or the carbon nanotube layer 18 is located on the semiconductor element 106 side which is a heat generation source (see FIGS. 1 and 6).

  On the heat spreader 110, a heat sink 114 for radiating heat transmitted to the heat spreader 110 is formed. A carbon nanotube sheet 112 of the present invention is formed between the heat spreader 110 and the heat sink 114.

  As described above, in the electronic apparatus according to the present embodiment, between the semiconductor element 106 and the heat spreader 110 and between the heat spreader 110 and the heat sink 114, that is, between the heat generating portion and the heat radiating portion, according to the first or second embodiment. Carbon nanotube sheets 108 and 112 are provided, respectively.

  As described above, in the carbon nanotube sheet according to the first or second embodiment, the carbon nanotube bundles 12 are oriented perpendicular to the film surface of the sheet, and in the meantime, the carbon nanotube sheet has a layered structure parallel to the film surface of the sheet. A graphite layer 14 made of graphite is formed, and the thermal conductivity in the perpendicular direction and the horizontal direction is extremely high.

  Therefore, by using the carbon nanotube sheet of the present invention as a heat conductive sheet formed between the semiconductor element 106 and the heat spreader 110 and between the heat spreader 110 and the heat sink 114, heat generated from the semiconductor element 106 can be efficiently obtained. The heat spreader 110 and the heat sink 114 can be transmitted in the vertical direction while spreading in the horizontal direction, and the heat dissipation efficiency can be improved. Thereby, the reliability of an electronic device can be improved.

  Thus, according to the present embodiment, the carbon nanotube bundles are oriented with respect to the film surface of the sheet between the semiconductor element and the heat spreader and between the heat spreader and the heat sink, and between the carbon nanotube bundles, the sheet Since the carbon nanotube sheet of the first or second embodiment in which the graphite layer made of graphite having a layered structure parallel to the film surface is formed is disposed, the thermal conductivity between them can be greatly improved. . Thereby, the thermal radiation efficiency of the heat | fever emitted from a semiconductor element can be improved, and the reliability of an electronic device can be improved.

[Sixth Embodiment]
An electronic apparatus according to a sixth embodiment of the present invention will be described with reference to FIG.

  FIG. 19 is a schematic cross-sectional view showing the structure of the electronic apparatus according to the present embodiment.

  In the present embodiment, an electronic device in which the carbon nanotube sheet according to the first and second embodiments is applied as a heat conductive sheet that also serves as a conductive sheet will be described.

  As shown in FIG. 19, a high power amplifier (HPA) 120 used in a radio communication base station or the like is incorporated in a package 122 and joined to a heat sink 124 on the back surface of the package 122. Heat generated from the high-power amplifier 120 is radiated to the heat sink 124 through the back surface of the package 122. At the same time, the package 122 is also used as an electrical ground (ground plane), and needs to be electrically connected to the heat sink 124. For this reason, it is necessary to use a good conductor for electricity and heat for joining the package 122 and the heat sink 124.

  Therefore, as shown in FIG. 19, the package 122 and the heat sink 124 are electrically connected by using the carbon nanotube sheet 126 according to the first or second embodiment at the joint between the package 122 and the heat sink 124. Can do. In addition, heat generated from the high-power amplifier 120 can be efficiently transmitted to the heat sink 124, and heat dissipation efficiency can be improved. Thereby, the reliability of an electronic device can be improved.

  Thus, according to the present embodiment, the carbon nanotube bundle is oriented with respect to the film surface of the sheet between the package of the high-power amplifier and the heat sink, and the film surface of the sheet is interposed between the carbon nanotube bundles. Since the carbon nanotube sheet of the first or second embodiment in which the graphite layer made of graphite having a parallel layered structure is formed, the thermal conductivity between them can be greatly improved. Thereby, the thermal radiation efficiency of the heat | fever emitted from a semiconductor element can be improved, and the reliability of an electronic device can be improved. Further, the high-power amplifier and a heat sink as a ground can be electrically connected.

[Modified Embodiment]
The present invention is not limited to the above embodiment, and various modifications can be made.

  For example, in the above-described embodiment, an example of a sheet-like structure and a semiconductor device using carbon nanotubes has been described. However, the present invention is widely applied to a sheet-like structure and a semiconductor device using a linear structure made of a carbon element. Can be applied. Examples of the linear structure made of carbon elements include carbon nanowires, carbon rods, and carbon fibers in addition to carbon nanotubes. These linear structures are the same as the carbon nanotubes except that their sizes are different. The present invention can also be applied to a sheet-like structure or a semiconductor device using these linear structures.

  In addition, the constituent materials and manufacturing conditions described in the above embodiment are not limited to the descriptions, and can be appropriately changed according to the purpose and the like.

  Further, the purpose of using the carbon nanotube sheet of the present invention is not limited to that described in the above embodiment. The carbon nanotube sheet of the present invention includes, for example, a CPU heat dissipation sheet, a radio communication base station high output amplifier, a radio communication terminal high output amplifier, an electric vehicle high output switch, a server, a personal computer, etc. Application to is possible. Moreover, it is applicable to a vertical wiring sheet and various applications using the same by utilizing the high allowable current density characteristics of carbon nanotubes.

In the above embodiment, as the catalytic metal film having the base film, although the layered structure of the Co film / TiN film and Co film / TiO ₂ film, the catalytic metal film is not limited thereto. For example, in the case of using a hydrocarbon-based source gas, in the case of using Co, Ni, and Fe as the catalyst species, Ti, TiN, TiO _x , TiSi, Ta, Tan, Zr, Hf, and V are used as the base film. , Nb, W, etc. can be applied. When Fe is used as the catalyst species, Al, Al ₂ O ₃ can also be used as the base film. In the case of using an alcohol source gas, Mo or the like can be applied as a base film in the case of using Co as a catalyst species.

  In addition, the structures of the semiconductor devices shown in the third and fourth embodiments and the electronic devices shown in the fifth and sixth embodiments and the manufacturing methods thereof are typical examples. Correction is possible.

  The sheet-like structure according to the present invention is excellent not only in thermal conductivity and electrical conductivity in a direction perpendicular to the sheet surface, but also in thermal conductivity and electrical conductivity in a direction parallel to the sheet surface. Yes. Therefore, the sheet-like structure of the present invention can be expected to be applied to electronic devices as a high-performance heat conductive sheet or conductive sheet. In addition, the semiconductor device according to the present invention includes a via wiring having a low resistance value and a wiring connected to the via wiring, and can be expected to be applied to a high-performance semiconductor device.

The present invention relates to a method for growing a carbon structure , a sheet-like structure, and a method for manufacturing a semiconductor device .

The objective of this invention is providing the manufacturing method of the sheet-like structure excellent in the heat conductivity and electroconductivity not only in the direction perpendicular | vertical to the surface of a sheet | seat but in a direction parallel to the surface of a sheet | seat. Another object of the present invention is to provide a method of manufacturing a semiconductor equipment comprising a lateral interconnection layer of low resistance is connected to a low resistance via interconnect and this.

FIG. 1 is a plan view and a schematic sectional view showing the structure of a carbon nanotube sheet according to a first embodiment of the present invention. FIG. 2 is a plan view showing the shape of a carbon nanotube bundle in the carbon nanotube sheet according to the first embodiment of the present invention. FIG. 3 is a schematic cross-sectional view showing the structure of the carbon nanotube sheet according to the first embodiment of the present invention. FIG. 4 is a process cross-sectional view (part 1) illustrating the method of manufacturing the carbon nanotube sheet according to the first embodiment of the present invention. FIG. 5 is a process cross-sectional view (part 2) illustrating the method of manufacturing the carbon nanotube sheet according to the first embodiment of the present invention. FIG. 6 is a plan view and a schematic sectional view showing the structure of the carbon nanotube sheet according to the second embodiment of the present invention. FIG. 7 is a schematic cross-sectional view showing the structure of a carbon nanotube sheet according to a modification of the second embodiment of the present invention. FIG. 8 is a process cross-sectional view (Part 1 ) showing the method of manufacturing the carbon nanotube sheet according to the second embodiment of the present invention. Figure 9 is a process cross-sectional views showing a second method of manufacturing the carbon nanotube sheet according to the embodiment forms state of the present invention (Part 2). FIG. 10 is a schematic cross-sectional view showing the structure of the semiconductor device according to the third embodiment of the present invention. FIG. 11 is a process cross-sectional view (No. 1) illustrating the method for manufacturing the semiconductor device according to the third embodiment of the invention. FIG. 12 is a process cross-sectional view (No. 2 ) showing the method for manufacturing the semiconductor device according to the third embodiment of the invention. FIG. 13 is a process cross-sectional view (No. 3 ) showing the method for manufacturing the semiconductor device according to the third embodiment of the invention. FIG. 14 is a schematic cross-sectional view showing the structure of the semiconductor device according to the fourth embodiment of the present invention. FIG. 15 is a process cross-sectional view (No. 1) illustrating the method for manufacturing the semiconductor device according to the fourth embodiment of the invention. FIG. 16 is a process cross-sectional view (part 2) illustrating the method for manufacturing the semiconductor device according to the fourth embodiment of the invention. FIG. 17 is a process cross-sectional view (No. 3) illustrating the method for manufacturing the semiconductor device according to the fourth embodiment of the invention. FIG. 18 is a schematic cross-sectional view showing the structure of an electronic device according to the fifth embodiment of the present invention. FIG. 19 is a perspective view showing the structure of an electronic device according to the sixth embodiment of the present invention.

Then, the catalytic metal film 32b on the photoresist film 34, lifted off together with the photoresist film 34, on the catalytic metal film 32 a of the forming region of the graphite layer 14, thereby selectively leave the catalytic metal film 32b. As a result, a catalytic metal film 32a made of an Fe film having a film thickness of 2.5 nm is formed in a region where the carbon nanotube bundle 12 is to be formed, and an area where the graphite layer 14 is to be formed is made of an Fe film having a thickness of 100 nm. Catalyst metal films 32a and 32b are formed (FIG. 4C).

The filling layer 16 may be formed by immersing the substrate 30 in a filler solution (so-called dip method). Also in this case, a change in the shape of the carbon nanotube bundle can be prevented by the gap provided between the carbon nanotube bundles 12.

Next, the carbon nanotube bundle 12, the graphite layer 14, and the filling layer 16 are peeled from the substrate 30 to obtain the carbon nanotube sheet 10 (FIG. 5C).

As described above, according to the present embodiment, after forming a plurality of carbon nanotube bundles spaced apart from each other on the substrate, a filling layer is formed by filling the filler and holding the carbon nanotube bundle . In this case, the shape change of the carbon nanotube bundle can be prevented. Thereby, it is possible to easily form a carbon nanotube sheet in which the carbon nanotube bundles are oriented in the film thickness direction of the sheet. Moreover, since both ends of the carbon nanotube bundle can be exposed from the filling layer, the thermal conductivity and electrical conductivity with respect to the adherend can be improved.

Next, the carbon nanotube bundle 12, the carbon nanotube layer 18, the graphite layer 20, and the filling layer 16 are peeled off from the substrate 30 in the same manner as in the carbon nanotube sheet manufacturing method according to the first embodiment to obtain the carbon nanotube sheet 10 (FIG. 9 (c)).

As described above, according to the present embodiment, after forming a plurality of carbon nanotube bundles spaced apart from each other on the substrate, a filling layer is formed by filling the filler and holding the carbon nanotube bundle . In this case, the shape change of the carbon nanotube bundle can be prevented. Thereby, it is possible to easily form a carbon nanotube sheet in which the carbon nanotube bundles are oriented in the film thickness direction of the sheet. Moreover, since both ends of the carbon nanotube bundle can be exposed from the filling layer, the thermal conductivity and electrical conductivity with respect to the adherend can be improved.

A wiring layer 42 is formed on the substrate 40. An interlayer insulating film 44 is formed in a region on the substrate 40 other than the region where the wiring layer 42 is formed. On one end portion of the wiring layer 42, a via interconnection 64 made of bundles of carbon nanotubes via the TiN film 5 0 is formed. A wiring layer 66 made of graphite and connected to the via wiring 64 is formed on the via wiring 64. A TiO ₂ film 56 is formed on the wiring layer 42 and the interlayer insulating film 44 in the formation region of the wiring layer 66 excluding the formation region of the via wiring 64. An interlayer insulating film 68 is formed around the via wiring 64 and the wiring layer 66. A via wiring 72 made of a bundle of carbon nanotubes is formed on one end of the wiring layer 66 via a TiN film 70. A wiring layer 74 made of graphite and connected to the via wiring 72 is formed on the via wiring 72. A TiO ₂ film is formed on the interlayer insulating film 68 in the formation region of the wiring layer 74 excluding the formation region of the via wiring 72. An interlayer insulating film 76 is formed around the via wiring 72 and the wiring layer 74.

Next, carbon nanotubes and graphite are grown by, for example, a thermal CVD method using the catalytic metal film as a catalyst. The growth conditions at this time are, for example, that the source gas is a mixed gas of acetylene and argon (partial pressure ratio 1: 9), the total gas pressure in the film forming chamber is 1 kPa, and the temperature is 450 ° C. film 5 0 catalytic metal film is formed via portion formation regions of the formed via wiring 64 made of the carbon nanotube bundles, the Co film 58 / TiO ₂ film 56 is formed a wiring layer formation region is Then, a wiring layer 66 made of a graphite layer extending on the via wiring 64 is formed apart from the TiO ₂ film 56 (FIG. 12C). Carbon nanotubes and graphite may be formed by a hot filament CVD method, a remote plasma CVD method, or the like.

The Co film 52 / TiN film 5 0 made of the catalytic metal film and the Co film 58 / TiO ₂ film 56 is formed in the on the catalyst metal film of the structure is different, the growth due to the difference in film thickness of the Co film This is because of the difference in rate.

As shown in the second embodiment, the conditions for performing growth using a Co film having a film thickness of 2.1 nm or 4.5 nm as a catalyst at the film formation temperature are as follows. This is a condition for growing carbon nanotubes. However, the growth rate of carbon nanotubes in the region where the Co film with a thickness of 4.5 nm is formed is significantly slower than the growth rate of carbon nanotubes in the region where the Co film with a thickness of 2.1 nm is formed. after the wiring layer 66 made of a layer has been formed, the growth of the carbon nanotubes in the catalytic metal film of Co film 52 / TiN film 5 0 becomes dominant. As a result, the growth of carbon nanotubes on the catalyst metal film of Co film 52 / TiN film 5 0, the entire graphite layer in the interconnection layer forming region is lifted, the catalyst consisting of Co film 58 / TiO ₂ film 56 Carbon nanotubes no longer grow on the metal film. As a result, the via wiring 64 and the wiring layer 66 as shown in FIG. 12C are formed.

Next, carbon nanotubes and graphite are grown by, for example, a thermal CVD method using the catalytic metal film as a catalyst. The growth conditions at this time are, for example, that the source gas is a mixed gas of acetylene and argon (partial pressure ratio 1: 9), the total gas pressure in the film forming chamber is 1 kPa, and the temperature is 450 ° C. the via portion forming region in which the catalytic metal film is formed of a film 5 0, the upper surface via interconnection 64 made of carbon nanotube bundles covered by the graphite layer 66a is formed, Co film 62 / TiN film 60 is formed In the planned wiring layer formation region, a graphite layer 66b is formed (FIG. 17A). Carbon nanotubes and graphite may be formed by a hot filament CVD method, a remote plasma CVD method, or the like.

Co film 52 / TiN film 5 0 made of the catalytic metal film on the Co film 62 / TiN film consisting of 60 catalytic metal film on the structure to be formed in is different from the growth rate due to the difference in film thickness of the Co film This is because of the difference.

In the present embodiment, an electronic device in which the carbon nanotube sheet according to the first or second embodiment is applied as a heat conductive sheet will be described.

On the heat spreader 110, a heat sink 114 for radiating heat transmitted to the heat spreader 110 is formed. A carbon nanotube sheet 112 according to the first or second embodiment is formed between the heat spreader 110 and the heat sink 114.

Therefore, the carbon nanotube sheet according to the first or second embodiment is emitted from the semiconductor element 106 by using it as a heat conductive sheet formed between the semiconductor element 106 and the heat spreader 110 and between the heat spreader 110 and the heat sink 114. The heat spread can be transmitted to the heat spreader 110 and the heat sink 114 in the vertical direction while spreading the heat efficiently in the horizontal direction, and the heat radiation efficiency can be improved. Thereby, the reliability of an electronic device can be improved.

FIG. 19 is a perspective view illustrating the structure of the electronic apparatus according to the present embodiment.

Claims (20)

A plurality of linear structure bundles, each including a linear structure composed of a plurality of carbon elements arranged with a first gap between each other, and arranged with a second gap larger than the first gap;
A graphite layer formed in a region between the plurality of linear structure bundles and connected to the plurality of linear structure bundles;
A sheet-like structure, comprising: the plurality of linear structure bundles and a filler layer that holds the graphite layer, the filler being filled in the first gap and the second gap. In the sheet-like structure according to claim 1,
A linear structure formed in the region between a plurality of the linear structure bundles, including a plurality of linear structures made of carbon element, wherein one end side of the plurality of linear structures is connected to the graphite layer A sheet-like structure further comprising a layer. In the sheet-like structure according to claim 2,
A plurality of the linear structure layers and a plurality of the graphite layers;
The linear structure layer and the graphite layer are alternately laminated. A sheet-like structure characterized by the above. In the sheet-like structure according to any one of claims 1 to 3,
Each of the plurality of linear structures constituting the plurality of linear structure bundles is oriented in the film thickness direction of the filling layer. In the sheet-like structure according to any one of claims 1 to 4,
The said graphite layer has a layered structure parallel to the surface direction of the said packed bed. The sheet-like structure characterized by the above-mentioned. In the sheet-like structure according to any one of claims 1 to 5,
Both end portions of the plurality of linear structure bundles are exposed on the surface. In the sheet-like structure according to any one of claims 1 to 6,
One surface of the said graphite layer is exposed to the surface. The sheet-like structure characterized by the above-mentioned. A first wiring layer formed on the semiconductor substrate;
Consisting of a bundle of linear structures including a plurality of linear structures made of carbon elements, and via wiring connected to the first wiring layer;
An insulating film formed on the semiconductor substrate excluding the via wiring formation region so as to cover the first wiring layer;
And a second wiring layer having a graphite layer formed on the via wiring and the insulating film. Forming a first catalytic metal film on a first region of the substrate;
Forming a second catalytic metal film different from the first catalytic metal film on a second region adjacent to the first region of the substrate;
Selectively forming a first carbon structure having a plurality of linear structures composed of carbon elements on the first region using the first catalytic metal film as a catalyst;
And a step of selectively forming a second carbon structure having a graphite layer on the second region by using the second catalytic metal film as a catalyst. . The method for growing a carbon structure according to claim 9,
A method of growing a carbon structure, wherein the step of forming the first carbon structure and the step of forming the second carbon structure are performed simultaneously. In the method for growing a carbon structure according to claim 10 or 11,
In the step of forming the first catalytic metal film, the first catalytic metal film having an Fe film with a film thickness of 0.3 to 10 nm is formed,
In the step of forming the second catalytic metal film, the second catalytic metal film having an Fe film with a film thickness of 10 nm to 200 nm is formed. The method for growing a carbon structure according to claim 9,
The step of forming the second catalytic metal film is performed after the step of forming the first carbon structure and before the step of forming the second carbon structure. Growth method. The method for growing a carbon structure according to claim 12,
In the step of forming the second carbon structure, the second carbon structure in which the graphite layer is formed on an upper surface of a plurality of linear structure layers made of carbon element is formed. Structure growth method. The method for growing a carbon structure according to claim 13,
After the step of forming the second catalytic metal film, the step of forming the second catalytic metal film and the step of forming the second carbon structure are further repeated, and in the second region, A method of growing a carbon structure, comprising: forming a laminate of the second carbon structure. The method for growing a carbon structure according to any one of claims 12 to 14,
In the step of forming the first catalytic metal film, the first catalytic metal film having an Fe film with a film thickness of 0.3 nm to 10 nm is formed,
In the step of forming the second catalytic metal film, the second catalytic metal film having a Co film having a film thickness of 2.0 nm to 7.0 nm is formed. The method for growing a carbon structure according to any one of claims 12 to 15,
In the step of forming the second carbon structure, the second carbon structure is formed at a temperature of 450 to 510 ° C. A step of forming the first carbon structure and the second carbon structure on the substrate by the carbon structure growth method according to any one of claims 9 to 16. When,
Filling the first carbon structure and the second carbon structure with a filler, and forming a filler layer made of the filler;
And a step of removing the substrate. A method for manufacturing a sheet-like structure. The carbon element growth method according to any one of claims 9 to 11, wherein the first catalytic metal film is used as a catalyst to form a carbon element on the first region of the substrate. Forming a first carbon structure having a plurality of linear structures and a first graphite layer formed on the linear structure, and simultaneously forming the first carbon structure on the second region of the substrate. And forming a second carbon structure having a second graphite layer using the second catalytic metal film as a catalyst,
A method of manufacturing a semiconductor device, comprising: forming a via wiring composed of the plurality of linear structures; and a wiring layer having the first graphite layer and the second graphite layer. In the manufacturing method of the semiconductor device according to claim 18,
In the step of forming the first carbon structure and the second carbon structure, a growth rate of a linear structure made of a carbon element on the first catalyst metal film, and the second catalyst metal film A method of manufacturing a semiconductor device, wherein the first carbon structure and the second carbon structure are separately made using a difference in growth rate of the linear structure made of carbon element above . In the method for manufacturing a semiconductor device according to claim 18 or 19,
In the step of forming the first catalytic metal film, the first catalytic metal film having a first Co film having a film thickness of 2.0 nm to 7.0 nm is formed.
In the step of forming the second catalytic metal film, the second catalytic metal film having a second Co film having a thickness of 2.0 nm to 7.0 nm and thicker than the first Co film is formed. A method for manufacturing a semiconductor device, comprising: forming a semiconductor device.

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