JPS6321295A - Production of diamond in gaseous phase - Google Patents

Abstract

PURPOSE:To enhance the gaseous-phase deposition rate and purity of diamond by adding a specified formation assistant into a gaseous mixture, and thermally decomposing the formation assistant before the gaseous mixture is activated when the gaseous mixture consisting of hydrocarbons and hydrogen is activated and diamond is synthesized on a substrate with use of the activated gas. CONSTITUTION:The gaseous mixture consisting of hydrocarbons and hydrogen is activated by the thermoelectrons radiated from a hot filament or plasma discharge, and diamond is produced on the substrate heated by the activated gas. In this case, the formation assistant consisting of the salt of a carboxylic acid contg. sp carbon and a high-valency metal is added to the gaseous mixture, and the formation assistant is thermally decomposed immediately before the gaseous mixture is activated. The thermal decomposition temp. of the formation assistant is preferably controlled to 50-300 deg.C. Lead tetracetate, manganese triacetate, cobalt triacetate, etc., can be exemplified as the formation assistant.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for producing diamond in a vapor phase, and more particularly, to a method for producing a diamond in a vapor phase by improving the activation process of a mixed gas consisting of hydrocarbon and hydrogen. .

[Prior Art] Recently, various attempts have been made to synthesize diamond in a vapor phase using a low-pressure method. According to this method, it is possible to form a diamond film on a base material, and it is possible to produce a high-performance material that has the properties of diamond, such as high hardness, high electrical insulation, and high thermal conductivity. It is expected that such fields of application will expand into a wide range of fields, including the field of metal materials such as high-hardness cutting tools, the field of electronic materials such as VLSI substrates, and the nuclear industry field such as plasma reaction walls.

By the way, conventional diamond vapor phase synthesis methods include, for example, the microwave plasma method using methane as a carbon source disclosed in JP-A-60-54995, and JP-A-58-9.
The hot filament method disclosed in Japanese Patent Publication No. 1100 and the ion sputtering method disclosed in Japanese Patent Application Laid-open No. 10394/1982 are known.

[Problems to be Solved by the Invention] However, in the microwave plasma method disclosed in JP-A-60-54995, the vapor phase deposition rate of diamond is extremely low at 1 μm/hr to 2 μm/hr. The hot filament method disclosed in JP-A No. 58-91100 and the ion sputtering method disclosed in JP-A-53-10394 not only have a low vapor phase deposition rate of diamond, but also produce graphite and hydrogen together with diamond. This produces amorphous carbon containing amorphous carbon. As described above, it has been extremely difficult to industrially produce diamonds using conventional methods.

The present invention has been made to solve the above-mentioned conventional problems, and aims to provide a method for producing high-purity diamond in a vapor phase, which has a high vapor phase deposition rate and does not contain amorphous carbon or the like. It is.

[Means for Solving the Problems] The present invention activates a mixed gas consisting of hydrocarbon and hydrogen by thermionic radiation or plasma discharge from a hot filament, and deposits the mixture on a substrate heated by the activated gas. In the method for manufacturing diamond, S is added to the mixed gas.
A method for producing diamond in a vapor phase, which comprises adding a production aid consisting of a high-valent transition metal salt of a carboxylic acid containing P3 carbon, and thermally decomposing the production aid immediately before activating the mixed gas. It is.

The plasma discharge described above can be generated by a high frequency plasma method or a microwave plasma method.

The high-valent transition metal salt of a carboxylic acid containing an SP3 carbon generates a radical containing an SP3 skeleton such as a methyl radical by thermal decomposition, and at the same time generates CO2, N2, etc. Such high-valent transition metal salts of carboxylic acids include:
For example, lead tetraacetate, tetra(2,2-dimethylpropionic acid)
Lead (TV) carboxylates such as lead, lead tetra(adamantylcarboxylate), manganese (DI) carboxylates such as manganese triacetate, manganese tri(2,2 dimethylpropionic acid), manganese tri(adamantylcarboxylate), etc. , cobalt triacetate, cobalt tri(2,2 dimethylpropion M), cobalt tri(adamantylcarboxylic acid), etc.
II) carboxylic acid salts and the like. In addition, metal salts with different carboxylic acids can also be used. The amount of the production aid made of a high-valent transition metal salt of carboxylic acid added to the mixed gas is desirably 0.1 to 100 in molar ratio to the hydrocarbon in the mixed gas. The reason for this is that if the aperture of the formation aid is less than 0.1, it becomes difficult to sufficiently increase the diamond precipitation rate, whereas if the amount of the formation aid exceeds 100, the amount of oxygen in the diamond There is a risk that there will be more.

A more preferable amount of the production aid added to the mixed gas is in a molar ratio of 1 to 10 relative to the hydrocarbon.

In the diamond vapor phase manufacturing method of the present invention, conventional manufacturing equipment can be used as is. However, it is necessary to incorporate a member that thermally decomposes the organic production aid immediately before activating the mixed gas consisting of hydrocarbon and hydrogen. As such a vapor phase production apparatus, for example, one shown in FIG. 1 or FIG. 2 can be used. In FIG. 2, the same members as those in FIG. 1 are designated by the same reference numerals, and the explanation thereof will be omitted.

That is, 1 in FIG. 1 is a vacuum chamber. A base plate 3 supported by a support rod 2 is disposed within the chamber 1 . A thermal decomposition reaction chamber 4 is disposed above the chamber 1, and a dish-shaped container 6 containing a production aid 5 is disposed within the reaction chamber 4. Further, an electric furnace 7 is arranged around the outer periphery of the reaction chamber 4 . Reference numeral 8 in the figure represents a mixed gas introduction tube that penetrates the chamber 1 and is inserted into the reaction chamber 4. The chamber 1 and the reaction chamber 4 are connected to each other by a pipe 9
The gas in the reaction chamber 4 is supplied to the chamber 1 through the reactor chamber 4 . A filament 10 is arranged near the lower end of the pipe 9 in the chamber 1 . Further, an exhaust pipe 11 is provided near the bottom of the chamber 1.

Note that 12 in the figure is a substrate (base material) installed on the base plate 3.

The gas phase production apparatus shown in FIG. 2 has a structure in which a waveguide 14 to which a plunger 13 is attached is provided on the side wall of a vacuum chamber 1.

The thermal decomposition temperature of the above-mentioned organic production aid varies depending on the type of production aid, but is preferably about 50 to 300°C. The reason for this is that if the thermal decomposition temperature is lower than 50°C, the decomposition rate will be low, making it difficult to sufficiently improve the diamond precipitation rate;
If the temperature exceeds 0°C, not only no further improvement in the diamond precipitation rate will be observed, but also an undesirable decomposition reaction may occur depending on the type of formation aid.

[Function] According to the present invention, a production aid consisting of a high-valent transition metal salt of a carboxylic acid containing SP3 carbon is added to a mixed gas consisting of a hydrocarbon and hydrogen, and the production aid is added to the mixed gas. By thermally decomposing it just before activation, the
Diamond can be grown on a heated substrate at a precipitation rate of /hr or more, and high purity diamond containing no graphite or amorphous carbon can be obtained.

The effect of such a production aid is unknown, but radicals, carbon oxide, and carbon dioxide generated by thermal decomposition of the production aid (high-valent transition metal salt of carboxylic acid containing SP3 carbon) may be involved. It is thought that the

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 and 2 described above.

Example 1 First, 2 g of lead tetraacetate as the production aid 5 was stored in the dish-shaped container 6 of the reaction chamber 4 of the gas phase production apparatus shown in FIG. A tryr tungsten substrate 12 was installed. Subsequently, after heating the substrate 12 and heating the reaction chamber 4 using the electric furnace 7, a mixed gas consisting of methane and hydrogen gas is introduced from the mixed gas introduction pipe 8 while evacuating the inside of the vacuum chamber 1 through the exhaust pipe 11. The mixed gas is supplied into the chamber 1 through the pipe 9 along with the pyrolysis gas of lead tetraacetate, and the substrate 1 is supplied into the reaction chamber 4 .
Diamond was deposited on the substrate 12 by passing filaments 10 arranged at a distance of 30° to 2°. Note that the conditions at this time are as follows. Board 1
Temperature of 2: 700°C, thermal decomposition temperature of lead tetraacetate in electric furnace 7: 100°C, degree of vacuum in chamber 1: 30tO
rr, molar ratio composition of methane and hydrogen gas constituting the mixed gas: 0.01:1, supply amount of mixed gas: 50SCCM,
Temperature of filament 10; 2000°C1 reaction time;
The duration is 60 minutes.

When vapor phase deposition was carried out under the above conditions, a diamond film with an average thickness of 13 μm could be formed on the surface of the substrate 12.

Furthermore, it was confirmed from Raman spectrum and X-ray diffraction analysis that this diamond was equivalent to natural diamond. On the other hand, for comparison, when diamond was vapor-phase deposited under the same conditions except that lead tetraacetate was not added, the average thickness of the diamond film was 1.5 μm.

Example 2 Diamond was vapor-phase deposited under the same conditions as in Example 1 except that manganese triacetate was used instead of lead tetraacetate and the thermal decomposition temperature was set at 80°C. A diamond film of 10 μm could be formed.

Example 3 First, 4 g of lead tetraacetate as the production aid 5 was placed in the container 6 of the reaction chamber 4 of the gas phase production apparatus shown in FIG. A silicon wafer of 110 m x 1 was placed. Next, after heating the silicon wafer and heating the reaction chamber 4 with the electric furnace 7, while exhausting the inside of the vacuum chamber 1 with the exhaust pipe 11,
A mixed gas consisting of methane and hydrogen gas is supplied into the reaction chamber 4 from the mixed gas introduction pipe 8, and the mixed gas is passed through the pipe 9 together with the pyrolysis gas of lead tetraacetate to generate plasma discharge by microwaves from the waveguide 14. Diamond was deposited on the wafer by supplying it into the chamber 1. Note that the conditions at this time are as follows.

Temperature of silicon wafer: 700°C, thermal decomposition temperature of V4 vinegar M lead in electric furnace 7: 100°C, degree of vacuum in chamber 1:
100 torr, molar ratio composition of methane and hydrogen gas constituting the mixed gas: 0.01:1, supply of the mixed gas m
: 100 SCCM, microwave from waveguide 14:
2.45GHz, power output 500W, reaction time; 60
It is a minute.

When vapor phase deposition was carried out under the above conditions, an extremely thick diamond film with an average thickness of 15 μm could be formed on the surface of a silicon wafer. In addition, when this diamond was subjected to a Flyman spectrum and an X-ray diffraction analysis, it was found that 133
A sharp peak was observed at 5 Cm-1, and it was confirmed to be diamond.

Example 4 Diamond was vapor-phase deposited under the same conditions as in Example 3, except that cobalt triacetate was used instead of lead quadrate and the thermal decomposition temperature was set at 80°C. A diamond film with a thickness of 8 μm could be formed.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to easily and inexpensively produce high-purity diamond that has a high vapor phase deposition rate and does not contain amorphous carbon, and as a result, it is possible to produce a high-hardness cutting tool. It has remarkable effects, such as being able to be effectively used in the field of metal materials such as, electronic materials such as VLSI substrates, and the nuclear industry field such as plasma reaction walls.

[Brief explanation of the drawing]

FIGS. 1 and 2 are schematic diagrams showing a vapor phase production apparatus used for vapor phase production of diamond according to the present invention, respectively. 1... Vacuum chamber, 4... Pyrolysis reaction chamber, 5...
- Generation aid, 7... Electric furnace, 8... Mixed gas introduction pipe, 1°... Filament, 12... Substrate, 14...
・Waveguide. Applicant's representative Patent attorney Takehiko Suzue 1st day 2nd day

Claims (2)

[Claims] (1) In a method of activating a mixed gas consisting of hydrocarbon and hydrogen by thermionic radiation or plasma discharge from a hot filament, and manufacturing diamond on a substrate heated by the activated gas, the mixed gas SP inside
Vapor phase production of diamond, characterized by adding a production aid consisting of a high-valent transition metal salt of a carboxylic acid containing ^3 carbon, and thermally decomposing the production aid immediately before activating the mixed gas. Method. (2) The method for producing diamond in a vapor phase according to claim 1, characterized in that the production aid is thermally decomposed at a temperature of 50 to 300°C.