Method and system for producing diamonds

Abstract

[Problem] To provide a method and a system for producing large diamonds at a low cost by using different types of substrates. [Solution] The present invention is characterized by comprising: a step for obtaining a carbon film substrate by forming a carbon film on the surface of a substrate; a step for forming a reactive carbon species in a gas phase by irradiating the carbon film substrate with a reactive hydrogen species in a state in which a negative bias voltage is applied thereto, and forming, on the substrate, diamond growth nuclei necessary for growing diamonds; and a step for epitaxially growing diamonds using a CVD device.

Description

Diamond manufacturing method and manufacturing system

[0001] The present invention relates to a method for producing diamond by epitaxially growing diamond on a substrate, and more particularly to a method for producing diamond using a heteroepitaxial growth method and a manufacturing system therefor.

[0002] To widely utilize diamonds in power semiconductors, heat sinks, and other applications, lower-cost manufacturing technologies are essential, and there is a demand for obtaining large diamonds using dissimilar substrates. Known methods for growing diamonds on dissimilar substrates include physically forming diamond nanoparticles that serve as diamond growth nuclei on the substrate, and the BEN (Bias Enhanced Nucleation) method, which applies a negative bias voltage to the substrate and generates plasma in a mixed gas of methane and hydrogen to form diamond growth nuclei. However, these conventional methods make it difficult to use large-diameter substrates.

[0003] For example, Patent Document 1 describes a method in which amorphous and microcrystalline carbon films are formed by catalytic CVD, the amorphous component is annealed and removed with hydrogen-based active species, and then a diamond thin film is formed by catalytic CVD. However, this method requires a catalyst, and the annealing and vapor phase growth must be repeated to form a thick film. Patent Document 2 describes forming a carbon-containing thin film on the surface of a substrate and then performing ion beam treatment to form initial diamond nuclei, but because it is a beam treatment, it cannot be used for a wide range of applications.

[0004] Japanese Unexamined Patent Publication No. 2002-293687 Japanese Unexamined Patent Publication No. 7-97295

[0005] The present invention aims to provide a method and system for manufacturing large diamonds at low cost using dissimilar substrates.

[0006] The present invention provides a method for producing diamond, comprising the steps of: forming a carbon film on the surface of a substrate to obtain a carbon film substrate; forming carbon active species in the gas phase by irradiating the carbon film substrate with a hydrogen active species while applying a negative bias voltage, thereby forming diamond growth nuclei necessary for diamond growth on the substrate; and epitaxially growing diamond using a CVD apparatus.

[0007] The present invention is characterized by having a carbon film pre-formed on the surface of a substrate. When a negative bias voltage is applied to the carbon film substrate and hydrogen-activated species are supplied, for example under reduced pressure, these hydrogen-activated species are accelerated to irradiate the carbon film. At this time, etching occurs on the carbon film due to the hydrogen-activated species, and carbon-activated species are formed in the gas phase. Furthermore, diamond growth nuclei necessary for diamond growth are formed on the substrate by these carbon-activated species. Subsequently, diamond can be grown in the gas phase using known plasma CVD or thermal filament CVD.

[0008] In this invention, a hydrogen-active species refers to a reactive species such as hydrogen ions or hydrogen radicals generated by applying a DC discharge or high-frequency discharge to hydrogen gas. Here, the high-frequency discharge may be a microwave plasma using microwaves as the high frequency. In this invention, the reactive species are derived solely from hydrogen, either from hydrogen gas or a mixed gas of hydrogen gas and an inert gas. In this respect, it differs from conventional BEN treatment of a mixed gas of methane and hydrogen.

[0009] The present invention is characterized by the fact that a carbon film is pre-formed on the surface of the substrate, and there are no limitations on the means by which the carbon film is formed on the surface of the substrate. For example, the carbon film may be formed by transferring a carbon material to the surface of the substrate, or by depositing carbon on the surface of the substrate by vacuum deposition or chemical deposition. When using such a method, the substrate can be made of Ir, Si, Ni, Cu, Pt, Fe, Co, W, Ti, Mo, SiC, MgO, Al ２ O ３ ,GeO ２ , Ga ２ O ３It may be YSZ, GaN, AlN, or an alloy thereof.

[0010] In the present invention, when forming a carbon film on the surface of a substrate, it may be formed by CVD on the surface of the substrate, or by lowering the temperature after solid-solving carbon in the substrate. The substrate for this purpose preferably has a cubic surface, and more preferably contains solid-solved carbon, and is preferably made of Fe, Ni, Pt, Co, Ti, Mo, W, Cu, or an alloy thereof.

[0011] The diamond manufacturing system according to the present invention is characterized by comprising: means for forming a carbon film on the surface of a substrate to obtain a carbon film substrate; means for applying a negative bias voltage to the carbon film substrate; means for supplying only hydrogen or a mixture of hydrogen and an inert gas under reduced pressure; means for forming carbon active species in the gas phase and forming diamond growth nuclei necessary for diamond growth on the substrate; and means for supplying a carbon source using hydrogen gas as a carrier under reduced pressure to epitaxially grow diamond. Herein, each of the means described above may be a separate device, or one or more devices in which some or all of them are programmed and controlled.

[0012] In this invention, since a carbon film is formed on the surface of the substrate, the density of carbon near the substrate surface during diamond production is improved, and a high density of diamond growth nuclei can be formed. Furthermore, by irradiating only hydrogen-active species onto the carbon film, a uniform diamond growth nucleus can be formed in advance, making it easier and less expensive to increase the size of the diamond when growing it in the vapor phase.

[0013] This diagram illustrates the diamond manufacturing process according to the present invention. It shows the Raman spectra of a carbon film (a) and diamond (b) when HOPG (High Oriented Pyrolytic Graphite) is transferred onto the surface of a substrate. It also shows the Raman spectra of a carbon film (a) and diamond (b) when a carbon film is deposited onto the surface of a substrate. Furthermore, it shows the Raman spectra of a carbon film (a) and diamond (b) when a carbon film is formed on the surface of a substrate by CVD. Finally, it shows the Raman spectra of a carbon film (a) and diamond (b) when carbon is dissolved in a solid solution on the surface of a substrate, and then the temperature is lowered to form a carbon film. The Raman spectra for CVD using a substrate without a carbon film on its surface are also shown. (a) is the Raman spectrum before CVD, and (b) is the Raman spectrum after CVD.

[0014] The diamond manufacturing process according to the present invention is explained in the schematic diagram shown in Figure 1. (a) shows the state in which a carbon film is formed on the surface of the substrate. (b) shows hydrogen (H) under reduced pressure. ２ (c) shows the process of supplying gas and performing microwave plasma processing. (c) shows the state in which a negative bias voltage is applied to the substrate side in this state. As a result, hydrogen-active species etch the surface of the carbon film, and carbon-active species such as CHx ions are released into the gas phase, which are formed on the substrate surface as diamond growth nuclei that serve as the source for vapor phase diamond growth. This state is shown in (d). Next, as shown in (e) and (f), when a carbon source such as methane is supplied with hydrogen as a carrier gas under reduced pressure, diamond is grown in the vapor phase by microwave plasma CVD (MPCVD).

[0015] Next, we will describe some examples. <Example 1> Using a carbon film substrate on which HOPG was transferred to the surface of a Ni substrate, a negative bias voltage was applied to the substrate side using an MPCVD apparatus to form diamond growth nuclei on the surface (hereinafter referred to as bias treatment). ・Input power 700W ・Pressure 10kPa ・Hydrogen flow rate 50sccm ・Applied voltage -450V ・Treatment time 3 minutes The Raman spectrum of this result is shown in Figure 2(a). 1575cm² －１A graphite peak is observed nearby. Next, diamond was vapor-grown using MPCVD under the following conditions: - Input power: 800 W - Pressure: 10 kPa - Hydrogen flow rate: 100 sccm with a methane concentration of 2% - Processing time: 5 hours The Raman spectrum of the vapor-grown film obtained by this treatment is shown in Fig. 2(b). 1330 cm －１ A diamond peak is confirmed nearby, indicating that diamond has been formed.

[0016] <Example 2> After forming a carbon film on the surface of a Ni substrate by vapor deposition, bias treatment was performed in the same manner as in Example 1 to form diamond growth nuclei, and then vapor diamond growth was carried out. The Raman spectra of this test sample are shown in Figs. 3(a) and 3(b). Fig. 3(a) shows the Raman spectrum of the deposited carbon film, with a G band at around 1575 cm －１ and a peak of amorphous carbon at the D band around 1350 cm －１ After the subsequent vapor growth treatment, as shown in Fig. 3(b), a diamond peak (around 1330 cm －１ ) was confirmed.

[0017] <Example 3> A carbon film was formed on the surface of a Ni substrate using MPCVD. - Input power: 880 W - Pressure: 10 kPa - Hydrogen flow rate: 50 sccm - Methane concentration: 6% - Processing time: 3 minutes The Raman spectrum of the obtained substrate surface is shown in Fig. 4(a). In this case as well, a graphite peak was observed around 1575 cm －１ as in Example 1. Next, the Raman spectrum of the surface obtained by performing bias treatment and MPCVD under the same conditions as in Example 1 is shown in Fig. 4(b). In this case as well, a diamond peak was confirmed around 1330 cm －１ .

[0018] <Example 4> Carbon was dissolved in a Ni substrate. • Input power: 860W • Pressure: 10kPa • Hydrogen flow rate: 50sccm • Methane concentration: 10% • Processing time: 3 minutes. Afterward, the microwave output was reduced to 760W to lower the substrate temperature by 200°C, and a carbon film was formed on the substrate surface. Next, a diamond growth nucleus was formed using the same bias treatment as in Example 1, followed by vapor-phase diamond growth treatment. The Raman spectrum of the carbon film substrate in this case is shown in Figure 5(a), with a graphite peak (1575cm²). －１ (Near) was observed, and after vapor phase growth, the diamond peak (1330 cm) was observed as shown in Figure 5(b). －１ (Nearby) was confirmed.

[0019] <Comparative Example 1> Figure 6 shows the Raman spectrum obtained by applying a negative bias voltage and performing MPCVD on a Ni substrate in the same manner as in Example 1, without forming a carbon film. As shown in Figure 6(a), no peak of carbon film was observed after bias treatment, and as shown in Figure 6(b), no diamond was formed by MPCVD.

[0020] From the above experiments, it was confirmed that by pre-forming a carbon film on the surface of the substrate, diamond formation was achieved through subsequent bias treatment and MPCVD.

[0021] In this invention, a uniformly high-density diamond growth nucleus can be formed, making it possible to increase the size of the diamond.

Claims

1. A method for producing diamond, comprising the steps of: forming a carbon film on the surface of a substrate to obtain a carbon film substrate; forming carbon active species in the gas phase by irradiating the carbon film substrate with a hydrogen active species while applying a negative bias voltage, thereby forming diamond growth nuclei necessary for diamond growth on the substrate; and epitaxially growing diamond using a CVD apparatus.

2. The method for manufacturing a diamond according to claim 1, characterized in that the carbon film is obtained by transferring a carbon material onto the surface of a substrate.

3. The method for producing diamond according to claim 1, characterized in that the carbon film is deposited on the surface of the substrate.

4. The method for manufacturing diamond according to claim 1, characterized in that the carbon film is formed on the surface of the substrate by CVD.

5. The method for producing a diamond according to claim 1, characterized in that the carbon film is formed by dissolving carbon in a substrate and then lowering the temperature.

6. The method for producing diamond according to any one of claims 1 to 5, characterized in that the hydrogen-active species is generated by supplying only hydrogen or a mixed gas of hydrogen and an inert gas, and performing a direct current discharge or high-frequency discharge.

7. The method for producing diamond according to claim 6, characterized in that the hydrogen-active species is generated by microwave plasma.

8. The substrate has a surface made of Ir, Si, Ni, Cu, Pt, Fe, Co, W, Ti, Mo, SiC, MgO, Al ２ O ３ ,GeO ２ , Ga ２ O ３ A method for producing a diamond according to any one of claims 1 to 5, characterized in that the diamond is one of YSZ, GaN, AlN, or an alloy thereof.

9. The method for manufacturing diamond according to any one of claims 1 to 5, characterized in that the substrate has a cubic surface.

10. The method for producing diamond according to any one of claims 1 to 5, characterized in that the substrate has a surface in which carbon is solidly dissolved and is made of Fe, Ni, Pt, Co, Ti, Mo, W, Cu or an alloy thereof.

11. A diamond manufacturing system characterized by comprising: means for forming a carbon film on the surface of a substrate to obtain a carbon film substrate; means for applying a negative bias voltage to the carbon film substrate; means for supplying only hydrogen or a mixture of hydrogen and an inert gas under reduced pressure; means for forming carbon-activated species in the gas phase and forming diamond growth nuclei necessary for diamond growth on the substrate; and means for supplying a carbon source using hydrogen gas as a carrier under reduced pressure to epitaxially grow diamond.

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