JP2016141604A - Production method of nanocarbon base material and nanocarbon base material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a nanocarbon base material which has selectively grown nanocarbons without substantial damage in the thickness direction of an SiC substrate and which is applicable to an SiC power device, and to provide the nanocarbon base material which has the selectively grown nanocarbons without substantial damage in the thickness direction of the SiC substrate and which is applicable to the SiC power device.SOLUTION: A production method of a nanocarbon base material 30 in which nanocarbons 20 are formed in a nanocarbon formation region 10b on an SiC substrate 10 comprises: a step of forming a mask layer 16, including sequentially laminated release layer 12 and heat-resistant layer 14, and demarcating the nanocarbon formation region 10b of the SiC substrate 10 with at least the heat-resistant layer 14 on the SiC substrate 10; a step of forming the nanocarbons 20 in the nanocarbon formation region 10b by heating the SiC substrate 10 with the mask layer 16 formed thereon and removing Si from the nanocarbon formation region 10b; and a step of removing the mask layer 16 from the surface of the SiC substrate 10.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a nanocarbon substrate and a nanocarbon substrate.

  Conventionally known methods of synthesizing nanocarbons such as carbon nanotubes (hereinafter referred to as CNT) include arc discharge, laser evaporation, and CVD. Recently, a so-called SiC surface decomposition method has been proposed in which a SiC substrate is heated in a vacuum at a high temperature to remove silicon (Si) atoms from the substrate, and nanocarbon is obtained from the remaining carbon (C) atoms. It has been reported that the surface of the SiC crystal is changed to a Si removal layer by the SiC surface decomposition method, and a nanotube film composed of a large number of CNTs oriented in the thickness direction is obtained in this SiC removal layer (for example, patents) Reference 1).

When heating in vacuum in the SiC surface decomposition method, a predetermined region on the surface of the SiC substrate is covered with a mask to protect the region from which Si atoms are removed. As a result, nanocarbon selectively grows on the exposed portion of the SiC substrate surface, so that a patterned nanocarbon film is obtained in the thickness direction of the SiC substrate between the front surface and the back surface of the SiC substrate. For example, it has been reported that a patterned CNT film is formed using a Si ₃ N ₄ film as a mask (for example, Non-Patent Document 1). Further, it has been reported that a pattern of a CNT film is formed by protecting a predetermined region on the surface of the SiC wafer with a carbon film (C film) and suppressing a CNT growth region (for example, non-patent literature). 2).

Japanese Patent No. 3183845

Michiko Kusunoki et al., “Patterned Carbon Nanotube Films Formed by Surface Decomposition of SiC Wafers”, Jpn. J. Appl. Phys. Vol. 42 (2003) pp.L1486-1488 Z. Goknur Cambaz et al., “Nanocatalytic synthesis of carbon nanotubes, graphene and graphite on SiC”, Carbon, 46 (2008), p.841-849

  A nanocarbon film such as a CNT film formed and patterned in the thickness direction of the SiC substrate can be used as an electrode or the like in a SiC power device. In order to apply to such a use, a nanocarbon substrate from which the mask on the surface of the SiC substrate is removed without damaging the selectively grown nanocarbon is required.

In order to selectively grow nanocarbon and obtain a patterned nanocarbon film in the thickness direction of the SiC substrate, a Si ₃ N ₄ film and a C film are used as a mask. Each of the Si ₃ N ₄ film and the C film has resistance capable of protecting the SiC substrate from high-temperature heating in a vacuum. However, the inventors have found that these films are difficult to selectively remove from the SiC substrate surface without damaging the nanocarbon.

For example, in order to remove the Si ₃ N ₄ film from the SiC substrate surface, a treatment with a relatively high concentration of phosphoric acid is required. This phosphoric acid is expected to cause considerable damage to nanocarbon. On the other hand, the C film cannot be selectively removed with respect to nanocarbon. When the C film as a mask is to be removed from the surface of the SiC substrate, the nanocarbon selectively grown in a predetermined region of the SiC substrate is also removed. For this reason, a patterned nanocarbon film cannot be obtained.

  Therefore, the present invention provides a method for producing a nanocarbon base material that has selectively grown nanocarbon that is substantially undamaged in the thickness direction of the SiC substrate and can be applied to a SiC power device, and a substantially grown nanocarbon. An object of the present invention is to provide a nanocarbon substrate that has nanocarbons that are not damaged in the thickness direction of the SiC substrate and can be applied to SiC power devices.

  The method for producing a nanocarbon substrate according to the present invention is a method for producing a nanocarbon substrate in which nanocarbon is formed in a nanocarbon formation region on a SiC substrate, and is sequentially laminated on the SiC substrate. A step of forming a mask layer that defines the nanocarbon formation region of the SiC substrate by at least the heat resistant layer, and heating the SiC substrate on which the mask layer is formed, Removing Si from the nanocarbon forming region to form nanocarbon in the nanocarbon forming region; and removing the mask layer from the surface of the SiC substrate.

  The nanocarbon substrate according to the present invention is a nanocarbon substrate in which nanocarbon is formed in a nanocarbon formation region on a SiC substrate, and the SiC substrate includes a nanocarbon non-formation region and the nanocarbon non-formation region. The nanocarbon is grown in the thickness direction of the SiC substrate from the bottom surface of the nanocarbon formation region, and the G band and the D band in the Raman spectrum. And the peak intensity ratio (G / D ratio) is 0.6 or more.

  According to the present invention, a mask layer having a heat-resistant layer is provided on an SiC substrate (hereinafter, also simply referred to as a substrate), and a region of the substrate covered with the mask layer is protected, while the nano layer not covered with the mask layer is provided. In the carbon formation region, nanocarbon is formed in the thickness direction of the substrate between the front surface and the back surface of the substrate. The mask layer includes a release layer and a heat-resistant layer that are sequentially stacked. Since the release layer exists between the substrate and the heat resistant layer, the mask layer having the heat resistant layer is easily removed from the substrate. This makes it possible to produce a nanocarbon base material that is selectively grown and has substantially no damage in the thickness direction of the substrate and can be applied to a SiC power device.

It is sectional drawing explaining the structure of the nanocarbon base material of this invention. It is sectional drawing which shows the manufacturing method of the nanocarbon base material concerning 1st Embodiment of this invention in steps, FIG. 2A is the step which formed the peeling layer on the SiC substrate, FIG. 2B is a peeling layer, a heat-resistant layer, FIG. 2C is a diagram showing a stage in which nanocarbon is formed on the SiC substrate, and FIG. 2D is a diagram showing a stage in which the mask layer is removed from the SiC substrate surface. It is an electron micrograph before heat processing of the SiC substrate which has a peeling layer and a heat-resistant layer. It is an electron micrograph after the heat processing of the SiC substrate shown in FIG. It is an electron micrograph of the nanocarbon base material obtained by removing a peeling layer from the SiC substrate shown in FIG. It is a Raman spectrum acquired about the nanocarbon base material of this invention. FIGS. 7A and 7B are cross-sectional views illustrating a method for manufacturing a nanocarbon substrate according to a second embodiment of the present invention in stages, in which FIG. 7A shows a stage in which a sacrificial layer is formed on the SiC substrate surface, and FIG. FIG. 7C shows a stage in which the sacrificial layer is removed and a mask layer is obtained on the surface of the SiC substrate, FIG. 7D shows a stage in which nanocarbon is formed on the SiC substrate, and FIG. 7E shows a mask layer. It is a figure which shows the step which removed from the SiC substrate surface.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

1. First embodiment (overall configuration)
A nanocarbon substrate according to a first embodiment of the present invention will be described with reference to FIG.

  As shown in FIG. 1, the nanocarbon base material 30 of the present invention includes CNTs 20 as nanocarbons formed in a nanocarbon formation region 10 b of the SiC substrate 10. In the nanocarbon base material 30 of the present invention, the CNTs 20 are selectively formed in a predetermined region (nanocarbon forming region 10b) on the surface of the SiC substrate 10.

  The SiC substrate 10 includes a nanocarbon non-forming region 10a and a nanocarbon forming region 10b that is recessed from the surface of the nanocarbon non-forming region 10a. In the nanocarbon forming region 10b in which the CNTs 20 are formed, Si is removed from the SiC substrate 10, so that the nanocarbon forming region 10b is recessed from the surface of the nanocarbon non-forming region 10a. In the nanocarbon base material 30 of the present invention, the CNT 20 is grown in the thickness direction of the SiC substrate 10 from the bottom surface 11 of the nanocarbon formation region 10b between the front surface and the back surface of the SiC substrate 10. The bottom surface 11 of the nanocarbon formation region 10b on which the CNT 20 is growing is the (000-1) plane (C plane) of the SiC substrate 10.

  In the nanocarbon substrate 30 of the present invention, the CNT 20 formed in the nanocarbon formation region 10b has a peak intensity ratio (G / D ratio) between the G band and the D band in the Raman spectrum of 0.6 or more. The height h of the CNT 20 depends on conditions for growth, but is generally about 3 to 500 nm, for example, about 200 nm. The height of the CNT 20 can be confirmed by observation with a transmission electron microscope (TEM). The CNT 20 selectively formed in the nanocarbon formation region 10b can be referred to as a patterned CNT film. It is confirmed by an atomic force microscope (AFM) that the surface roughness of the patterned CNT film is about 5 nm.

(Production method)
The manufacturing method of the nanocarbon base material which concerns on 1st Embodiment of this invention is demonstrated with reference to FIG.

  In the method for manufacturing the nanocarbon substrate 30 according to the first embodiment, first, as shown in FIG. 2A, the release layer 12 is formed on the entire surface of the SiC substrate 10. Next, as shown in FIG. 2B, a heat-resistant layer 14 is formed in a predetermined region of the release layer 12, and a mask layer 16 having a laminated structure of the release layer 12 and the heat-resistant layer 14 is formed on the nanocarbon non-formation region 10a. As a result, the nanocarbon forming region 10 b of the SiC substrate 10 is defined by the heat-resistant layer 14. Thereafter, the SiC substrate 10 having the mask layer 16 is heated to remove the release layer 12 on the nanocarbon forming region 10b of the SiC substrate 10 as shown in FIG. 2C, and the nanocarbon forming region 10b of the SiC substrate 10 is removed. CNT20 as nanocarbon is formed. Finally, the mask layer 16 is removed from the surface of the SiC substrate 10 to expose the non-carbon-forming region 10a, and the CNT 20 is selectively grown on the nano-carbon forming region 10b of the SiC substrate 10 as shown in FIG. 2D. The nanocarbon substrate 30 of the present invention is obtained.

  Each step shown in FIGS. 2A to 2D will be described in detail below.

  First, as shown in FIG. 2A, a release layer 12 is formed on the entire (000-1) plane (C plane) of SiC substrate 10. The SiC constituting the SiC substrate 10 is not particularly limited, and examples thereof include 4H—SiC and 6H—SiC.

The release layer 12 is formed of a metal oxide that is soluble in a specific liquid. The specific liquid is a liquid that does not substantially damage the CNT 20 formed in the nanocarbon formation region 10b of the SiC substrate 10 in a later step. In the present specification, the fact that CNTs are not substantially damaged means that the CNT Raman shift (G / D ratio, peak wavenumber, full width at half maximum) does not change, that is, the amount of CNT defects is not increased. That means. Examples of the metal oxide used for forming the release layer 12 include ZnO, Ga ₂ O ₃ , Y ₂ O ₃ , ZrO ₂ , and HfO ₃ . The method for forming the release layer 12 is not particularly limited. If release layer 12 having a predetermined thickness can be formed on the entire surface of SiC substrate 10, release layer 12 can be formed by any method. For example, when forming the peeling layer 12 using ZnO, the liquid phase method using arbitrary materials is employable.

  The thickness of the release layer 12 formed here is preferably about 1 to 3 μm. If the release layer 12 has a thickness of about 1 to 3 μm, the SiC substrate that is not covered with the heat-resistant layer 14 does not substantially change in the portion covered with the heat-resistant layer 14 when heated. A portion of the ten nanocarbon forming regions 10b can be removed.

  As shown in FIG. 2B, a heat-resistant layer 14 is formed in a predetermined region on the release layer 12 formed on the entire surface of the SiC substrate 10. The release layer 12 and the heat-resistant layer 14 that are sequentially stacked constitute a mask layer 16 in the non-carbon-formed region 10a. Nanocarbon formation region 10b of SiC substrate 10 is defined by heat-resistant layer 14 on mask layer 16.

  The heat-resistant layer 14 is formed of a high melting point material that can protect the SiC substrate 10 from heating. By being covered with the heat resistant layer 14, the underlying release layer 12 is also protected from heating. The high melting point material used for forming the heat-resistant layer 14 can be selected from the group consisting of C, W, Ta, Re, and Os, for example. For example, the C layer as the heat-resistant layer 14 is formed by depositing C in a predetermined region of the release layer 12 by, for example, a focused ion beam (FIB) to form the heat-resistant layer 14, thereby forming the nanocarbon of the SiC substrate 10. Region 10b can be defined.

  Due to the heating performed in a later step, a part of the metal oxide forming the heat-resistant layer 14 may sublimate, and the thickness of the heat-resistant layer 14 may decrease. When the thickness becomes too small, the heat-resistant layer 14 cannot sufficiently perform the function of protecting the peeling layer 12 and the SiC substrate 10 thereunder. The heat-resistant layer 14 having a thickness of 100 nm or more does not disappear completely even when it is subjected to a heat treatment at 1600 ° C. for 1 hour, for example. If the heat-resistant layer 14 has a thickness of 100 nm or more, the thickness necessary to protect the underlying release layer 12 and the SiC substrate 10 can be maintained during the heat treatment. Even if the heat-resistant layer 14 is formed to be excessively thick, a special effect is not obtained. If the thickness of the heat-resistant layer 14 is about 300 nm at the maximum, the underlying peeling layer 12 and the SiC substrate 10 can be protected during heat treatment at 1600 ° C. for 1 hour.

  As shown in FIG. 2B, in the SiC substrate 10, the surface of the nanocarbon formation region 10 b is covered with the release layer 12. On the other hand, the nanocarbon non-formation region 10a excluding the nanocarbon formation region 10b is covered with a mask layer 16 having a laminated structure of the release layer 12 and the heat-resistant layer 14.

By heating SiC substrate 10 having mask layer 16, nanocarbon forming region 10 b of SiC substrate 10 is exposed as shown in FIG. 2C, and CNT 20 as nanocarbon is formed from bottom surface 11 of nanocarbon forming region 10 b. Is done. The pressure at this time can be in the range of about 10 ⁻⁶ to 10 ⁻¹ Pa, and the heating temperature can be about 1400 to 1700 ° C. The heating time can be appropriately set according to the pressure range and the heating temperature, but is generally about 5 minutes to 3 hours.

  The heating can be performed, for example, by irradiating the SiC substrate 10 having the mask layer 16 with a continuously oscillated YAG laser beam. The YAG laser beam can be applied to the substantially central portion of the nanocarbon forming region 10b of the SiC substrate 10 with an area of about φ0.2 to 3 mm, for example.

For example, by heating at 1 × 10 ⁻² Pa or less and 1600 ° C. for 1 hour, the metal oxide forming the release layer 12 is sublimated on the nanocarbon formation region 10 b of the SiC substrate 10. The release layer 12 in this portion is removed. At this time, the portion of the release layer 12 covered with the heat resistant layer 14 does not substantially change. In the nanocarbon formation region 10b of the SiC substrate 10 exposed by removing the release layer 12, SiC is decomposed and Si is removed. The CNT 20 shown in FIG. 2C is formed from the surface of the SiC substrate 10 to the inside as the removal of Si proceeds. Since it is formed in this way, CNTs 20 with excellent linearity can be obtained at a high density in the nanocarbon formation region 10b.

  Thereafter, the mask layer 16 is selectively removed from the SiC substrate 10 to expose the surface of the nanocarbon non-formation region 10a of the SiC substrate 10 as shown in FIG. 2D. Mask layer 16 can be easily removed from the surface of SiC substrate 10 by dissolving release layer 12. In order to dissolve the release layer 12, a liquid that does not substantially damage the CNT 20 is used. For example, the ZnO layer as the release layer 12 can be dissolved by treatment with 1 to 35% HCl solution for 1 second to 3 hours. Thus, the nanocarbon substrate 30 of the present invention can be obtained by selectively removing the mask layer 16 from the surface of the SiC substrate 10 and selectively growing the CNTs 20 on the SiC substrate 10.

(Function and effect)
In the method for manufacturing the nanocarbon substrate 30 according to the present embodiment, the nanocarbon non-formation region 10a of the SiC substrate 10 is protected by the mask layer 16 and heated. Thereby, the CNT 20 is selectively grown in the nanocarbon forming region 10b of the SiC substrate 10. The mask layer 16 that protects the nanocarbon non-formation region 10a of the SiC substrate 10 has a laminated structure of a lower release layer 12 and an upper heat-resistant layer 14, and the upper heat-resistant layer 14 protects the SiC substrate 10 from heating. It is formed using a high melting point material.

  On the other hand, the lower release layer 12 is formed of a metal oxide soluble in a liquid that does not substantially damage the CNT 20. The metal oxide used here does not combine with SiC constituting the substrate 10 even when heated. Therefore, according to the method of the first embodiment, the heat-resistant layer 14 is separated from the SiC substrate 10 by the release layer 12 until the mask layer 16 including the heat-resistant layer 14 is removed from the surface of the SiC substrate 10. . As described above, the material forming the release layer 12 is soluble in a liquid that does not substantially damage the selectively grown CNT 20. For this reason, after the CNT 20 is formed, the mask layer 16 including the heat-resistant layer 14 can be removed without substantially damaging the CNT 20 by dissolving the release layer 12 with a predetermined liquid.

  Thus, by the method of the first embodiment, the nanocarbon base material 30 of the present invention having the CNT 20 that is selectively grown and substantially free of damage in the thickness direction of the SiC substrate 10 can be obtained.

  Below, the specific example which manufactured the nanocarbon base material 30 with the method shown in FIG. 2 is shown. First, the peeling layer 12 and the heat-resistant layer 14 were formed on the surface of the SiC substrate 10, and the nanocarbon forming region 10b of the SiC substrate 10 was defined as shown in FIG. 2B. As release layer 12, a ZnO layer (2.4 μm thick) was formed on the entire C surface of SiC substrate 10 by a liquid phase method. As the heat-resistant layer 14, a C layer having a predetermined thickness was formed in a predetermined region of the release layer 12 by FIB. An electron micrograph of SiC substrate 10 provided with release layer 12 and heat-resistant layer 14 in this way is shown in FIG.

As shown in FIG. 3, heat-resistant layers 14 _c1 , 14 _c2 , 14 _c3 , 14 _c4 , 14 _c6 , and 14 _c9 are provided in predetermined regions of the release layer 12 that covers the entire surface of the SiC substrate 10. The thicknesses of the heat-resistant layers 14 _c1 , 14 _c2 , 14 _c3 , 14 _c4 , 14 _c6 , and 14 _c9 are 100 nm, 200 mn, 300 nm, 400 nm, 600 nm, and 900 nm, respectively. In FIG. 3, the region where the release layer 12 is exposed corresponds to the nanocarbon formation region 10 b of the SiC substrate 10. The region where the heat-resistant layers 14 _c1 , 14 _c2 , 14 _c3 , 14 _c4 , 14 _c6 , and 14 _c9 are provided on the release layer 12 corresponds to the nanocarbon non-formation region 10 a of the SiC substrate 10.

The SiC substrate 10 having the heat-resistant layer 14 formed on the release layer 12 in this manner is subjected to a heat treatment of 10 ⁻² Pa or less and 1600 ° C. for 1 hour, and as shown in FIG. 2C, the nanocarbon forming region 10b Then, CNT20 as nanocarbon was formed. An electron micrograph of the SiC substrate 10 after the heat treatment is shown in FIG.

As shown in FIG. 4, after the heat treatment, the release layer 12 does not exist in the nanocarbon formation region 10b, and the CNT 20 is confirmed in this region. Although there is a loss in part, the heat-resistant layers 14 _c1 , 14 _c2 , 14 _c3 , 14 _c4 , 14 _c6 , and 14 _c9 remain after the heat treatment, and the nanocarbon non-formation region 10 a of the SiC substrate 10 is removed from the heat treatment. Presumed protected.

After the CNT 20 is formed, it is treated with a 3% HCl solution for 3 seconds to dissolve the ZnO layer as the peeling layer 12 and remove the heat-resistant layers 14 _c1 , 14 _c2 , 14 _c3 , 14 _c4 , 14 _c6 , 14 _c9 Then, as shown in FIG. 2D, the surface of the nanocarbon non-formation region 10a of the SiC substrate 10 was exposed. FIG. 5 shows an electron micrograph of the nanocarbon substrate 30 thus obtained. The regions protected by the heat-resistant layers 14 _c1 , 14 _c2 , 14 _c3 , 14 _c4 , 14 _c6 , and 14 _c9 are the nanocarbon non-formation regions 10 a ₁ , 10 a ₂ , 10 a ₃ , 10 a ₄ , 10 a ₆ , and 10 a _{9, respectively.} As shown in FIG. If the heat-resistant layer remains after the heat treatment, the presence of SiC in these non-nanocarbon-forming regions 10a ₁ , 10a ₂ , 10a ₃ , 10a ₄ , 10a ₆ , 10a ₉ is protected from the heat treatment. Was confirmed.

A Raman spectrum of the CNT 20 thus formed is shown as a curve c _{0 in} FIG. In FIG. 6, a curve c ₁ is a result obtained for the non-carbon-forming region 10a ₁ provided with a C layer having a thickness of 100 nm as the heat resistant layer 14 _c1 , and a curve c ₃ is a thickness of 300 nm as the heat resistant layer 14 _c3 . the results obtained for the nano-carbon non-formation region 10a ₃ having a C layer. Curves a and b are shown for reference. Specifically, a curve a is a Raman spectrum of CNT formed on a SiC substrate by performing the same heat treatment as described above without forming a mask layer, and a curve b is a Raman spectrum of the SiC substrate before the heat treatment. is there.

In the curve a, the CNT G-band peak is confirmed near 1590 cm ⁻¹ , and the CNT D-band peak is confirmed near 1300 cm ⁻¹ . In this case, the peak intensity ratio (G / D ratio) between the G band and the D band is about 0.9. Generally, it is known that the higher the G / D ratio in the Raman spectrum, the higher the quality of nanocarbons such as CNTs with less damage. If the G / D ratio is 0.6 or more, it can be said that the CNT has substantially no damage.

When the G / D ratio is 0.5 or less, the CNT has damage. For example, after the CNT with _{the Si} 3 _{N 4} film as a mask is selectively grown on the SiC substrate, a _{the Si} 3 _{N 4} film on the SiC substrate is removed by phosphoric acid, in the Raman spectrum obtained for CNT on SiC substrate Has a G / D ratio of 0.5 or less.

In the curve c ₀ , similarly to the curve a, a CNT G-band peak is confirmed near 1590 cm ⁻¹ , and a CNT D-band peak is confirmed near 1300 cm ⁻¹ . The peak intensity ratio (G / D ratio) between the G band and the D band is about 0.9. Since the G / D ratio in the Raman spectrum is 0.6 or more, it can be seen that the CNT 20 obtained here has substantially no damage.

A curve b shown for the SiC substrate before the heat treatment shows a SiC peak in the vicinity of 1500 to 1900 cm ⁻¹ . The peak of the CNT G band (near 1590 cm ⁻¹ ) and the peak of the CNT D band (near 1300 cm ⁻¹ ) are not confirmed in the curve b.

Curve _{c 1,} also in the curves _{c 3,} similar to the curve b, which appears is SiC peak near 1500~1900cm ^-1, G-band peak (1590 cm near ^-1) of CNT, and CNT of D band peak ( 1300 cm- ¹ vicinity) is not confirmed.

Since the shapes of the curves c ₁ and c ₃ are the same as the shape of the curve b, it is possible to protect the SiC substrate 10 from the heat treatment by providing the heat-resistant layer 14 and to avoid the decomposition of SiC in this region. Recognize. When the C layer is formed as the heat-resistant layer 14 as described above, it has also been confirmed that the SiC substrate 10 thereunder can be protected almost certainly if the thickness of the C layer is 100 nm or more.

2. Second Embodiment The nanocarbon substrate 30 as described above can also be manufactured by the method according to the second embodiment. The manufacturing method of the nanocarbon base material 30 which concerns on 2nd Embodiment is demonstrated with reference to FIG.

(Production method)
In the method for manufacturing the nanocarbon substrate 30 according to the second embodiment, first, as shown in FIG. 7A, the sacrificial layer 22 is formed on the surface of the nanocarbon formation region 10 b of the SiC substrate 10. Next, as shown in FIG. 7B, a release layer 24 and a heat-resistant layer 26 are sequentially formed on the surface of the sacrificial layer 22 and the SiC substrate 10. Thereafter, the sacrificial layer 22 is removed to obtain a mask layer 28 having a laminated structure of the peeling layer 24 and the heat-resistant layer 26 as shown in FIG. 7C on the nanocarbon non-formation region 10a. A nanocarbon forming region 10b of the SiC substrate 10 is defined. Further, SiC substrate 10 having mask layer 28 is heated to form CNTs 20 as nanocarbons in nanocarbon formation region 10b of SiC substrate 10 as shown in FIG. 7D. Finally, the mask layer 28 is removed from the surface of the SiC substrate 10 to expose the nanocarbon non-formation region 10a, and the CNT 20 is selectively grown on the nanocarbon formation region 10b of the SiC substrate 10 as shown in FIG. 7E. An inventive nanocarbon substrate 30 is obtained.

  In the above-described first embodiment, the peeling layer 12 on the surface of the nanocarbon forming region 10b of the SiC substrate 10 is removed by heating to expose the nanocarbon forming region 10b. However, in the second embodiment, The surface of the nanocarbon forming region 10b is already exposed during heating. Except for this difference, the method for producing a nanocarbon substrate according to the second embodiment is basically the same as the method for producing a nanocarbon substrate according to the first embodiment.

  Each step shown in FIGS. 7A to 7E will be described in detail below.

  First, as shown in FIG. 7A, a sacrificial layer 22 is formed on the nanocarbon formation region 10 b of the SiC substrate 10. The sacrificial layer 22 is removed in a later step in order to form a mask layer 28 that defines the nanocarbon formation region 10b. For these applications, the sacrificial layer 22 is formed with a thickness equal to or greater than the mask layer 28 to be obtained. For example, the sacrificial layer 22 can be formed with a thickness of about 5 μm. As the sacrificial layer 22, for example, a resist pattern formed by a general method using an arbitrary resist material can be used.

  Next, as shown in FIG. 7B, a release layer 24 and a heat-resistant layer 26 are sequentially formed on the entire surface of the SiC substrate 10 on which the sacrificial layer 22 is formed. The release layer 24 and the heat-resistant layer 26 can be formed with the same thickness using the materials described in the first embodiment. However, in the second embodiment, the release layer 24 and the heat-resistant layer 26 are formed at a temperature at which the sacrificial layer 22 is not damaged. In the manufacturing method of the second embodiment, the formation temperature of the release layer 24 and the heat-resistant layer 26 is lower than that of the first embodiment, and can be set as appropriate according to the material of the sacrificial layer 22.

  In the second embodiment, an ion beam sputtering method, a resistance heating vapor deposition method, an electron beam vapor deposition method, or the like can be employed to form the release layer 24 and the heat resistant layer 26. When a ZnO layer is formed as the release layer 24, it may be deposited by the same liquid phase method as in the first embodiment.

  After the release layer 24 and the heat resistant layer 26 are sequentially formed, the sacrificial layer 22 is removed together with portions of the release layer 24 and the heat resistant layer 26 on the sacrificial layer 22. The sacrificial layer 22 can be removed by dissolving with an organic solvent, for example. As a result, as shown in FIG. 7C, a mask layer 28 composed of the portions where the release layer 24 and the heat-resistant layer 26 are left is formed on the surface of the nanocarbon non-formation region 10 a of the SiC substrate 10. The mask layer 28 defines the nanocarbon forming region 10b of the SiC substrate 10.

  Next, SiC substrate 10 on which mask layer 28 is formed is heated. The conditions at this time can be the same as those in the first embodiment. By performing the heat treatment, in the Si removal region 10a of the SiC substrate 10, SiC is decomposed and Si is removed. The CNT 20 shown in FIG. 7D is formed from the surface of the SiC substrate 10 to the inside as the removal of Si proceeds.

  In the subsequent steps, the mask layer 28 is removed from the surface of the SiC substrate 10 by dissolving the release layer 12 in the same manner as in the first embodiment, and the nanocarbon non-formation region 10a is exposed. In this way, the nanocarbon substrate 30 of the present invention in which the CNTs 20 are selectively grown on the SiC substrate 10 as shown in FIG. 7E can be obtained.

(Function and effect)
In the method according to the second embodiment, similarly to the first embodiment, the nanocarbon non-formation region 10a of the SiC substrate 10 is protected by the mask layer 28 and heated to form the CNT 20 on the nanocarbon formation region 10b of the SiC substrate 10. Select to grow. The mask layer 28 in the second embodiment has a laminated structure of a release layer 24 and a heat-resistant layer 26 as in the first embodiment, and the release layer 24 and the heat-resistant layer 26 are the same materials as in the first embodiment. Since this is used, the same effect as in the first embodiment can be obtained.

  The mask layer 28 in the method according to the second embodiment is formed in a predetermined region of the SiC substrate 10 using the sacrificial layer 22. Since the sacrificial layer 22 exists, the mask layer 28 including the release layer 24 and the heat-resistant layer 26 is generally formed at a low temperature. In the mask layer 28, not only the heat resistant layer 26 but also the release layer 24 is patterned. Such a method according to the second embodiment is advantageous in that no impurities are attached to the selectively grown CNTs 20.

  Thus, by the method of the second embodiment, the nanocarbon substrate 30 of the present invention having the CNTs 20 that are selectively grown and substantially free of damage in the thickness direction of the SiC substrate 10 can be obtained.

3. The present invention is not limited to the above-described embodiment, and can be appropriately changed within the scope of the gist of the present invention. In the first embodiment, the heat resistant layer 14 is formed in a predetermined region of the release layer 12 using FIB to define the nanocarbon forming region 10b of the SiC substrate 10, but the heat resistant layer 14 is formed by another method. May be. For example, the nanocarbon forming region 10b of the SiC substrate 10 can be defined by forming the heat-resistant layer 14 on the entire surface of the release layer 12 by resistance heating vapor deposition or the like and patterning the same.

Further, in the case where the release layer 12 is formed using ZnO, it has been described that the release layer 12 is dissolved using an HCl solution and the mask layer 16 is removed. However, depending on the type of material forming the release layer 12 The liquid used for dissolution and removal may be appropriately selected. For example, the release layer 12 formed using Ga ₂ O ₃ can be dissolved with an acid such as HCl or a base such as NaOH. The release layer 12 formed using Y ₂ O ₃ , ZrO ₂ , or HfO ₂ can be dissolved with HF.

  Furthermore, in the above-described embodiment, a case has been described in which a SiC substrate in which a predetermined region is protected by a mask layer is heated to remove Si from the C-plane side of the SiC substrate, thereby selectively growing CNTs as nanocarbon. When a predetermined region of the (0001) surface (Si surface) of the SiC substrate is protected by a similar mask layer, graphene can be selectively grown as nanocarbon.

When graphene is selectively grown, heating can be performed in a wider temperature range than when CNT is formed. Specifically, the heating temperature can be 1100 to 1600 ° C., for example, 1400 ° C. In addition, the pressure at which graphene is selectively grown can be approximately the same as that in the case of CNT, but may be heated under atmospheric pressure. When graphene is selectively grown, a pressure range of about 10 ⁻⁶ to 10 ⁶ Pa can be applied.

  By using the method of the present invention, it is also possible to obtain a nanocarbon substrate having selectively grown graphene having substantially no damage in the thickness direction of the SiC substrate.

DESCRIPTION OF SYMBOLS 10 SiC substrate 10a Nanocarbon non-formation area | region 10b Nanocarbon formation area | region 12, 24 Release layer 14,26 Heat-resistant layer 16,28 Mask layer 20 CNT (nanocarbon)
22 Sacrificial layer 30 Nanocarbon substrate

Claims (8)

A method for producing a nanocarbon substrate in which nanocarbon is formed in a nanocarbon forming region on a SiC substrate,
Forming a mask layer that includes a release layer and a heat-resistant layer sequentially laminated on the SiC substrate, and at least the heat-resistant layer delimits the nanocarbon formation region of the SiC substrate;
Heating the SiC substrate on which the mask layer is formed, and removing Si from the nanocarbon forming region, thereby forming nanocarbon in the nanocarbon forming region;
And a step of removing the mask layer from the surface of the SiC substrate. The mask layer is
Forming the release layer over the entire surface of the SiC substrate;
Except on the nanocarbon formation region, the surface of the release layer is covered with the heat-resistant layer,
The method for producing a nanocarbon substrate according to claim 1, wherein the release layer on the nanocarbon forming region is removed by the heating. The mask layer is
Forming a sacrificial layer on the surface of the nanocarbon forming region;
Sequentially forming the release layer and the heat-resistant layer on the surface of the sacrificial layer and the SiC substrate;
The method for producing a nanocarbon substrate according to claim 1, wherein the sacrificial layer is formed by removing the sacrificial layer together with the release layer and the heat-resistant layer on the sacrificial layer. The release layer is formed of a metal oxide soluble in a liquid that does not substantially damage the nanocarbon,
The method for producing a nanocarbon substrate according to any one of claims 1 to 3, wherein the mask layer including the heat-resistant layer is removed by dissolving the release layer with the liquid. The metal _{oxide, ZnO, Ga 2 O 3,} Y 2 O 3, ZrO 2, and a manufacturing method of the nano-carbon substrate according to claim 4, characterized in that it is selected from HfO _3.   The said heat-resistant layer is formed with the high melting-point material which can protect the said SiC substrate from the said heating in the process in which nanocarbon is formed in the said nanocarbon formation area, The any one of Claims 1-5 characterized by the above-mentioned. Method for producing a nanocarbon substrate.   The method for producing a nanocarbon substrate according to claim 6, wherein the high melting point material is selected from C, W, Ta, Re, and Os. A nanocarbon base material in which nanocarbon is formed in a nanocarbon forming region on a SiC substrate,
The SiC substrate includes a nanocarbon non-forming region, and the nanocarbon forming region recessed from the surface of the nanocarbon non-forming region,
The nanocarbon grows in the thickness direction of the SiC substrate from the bottom surface of the nanocarbon formation region, and the peak intensity ratio (G / D ratio) between the G band and the D band in the Raman spectrum is 0.6 or more. A nanocarbon substrate characterized by the above.

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