JPS63274692A - Synthesis of diamond - Google Patents

Abstract

PURPOSE:To improve deposition velocity of diamond and to simplify prepn. of raw material gas by using a gaseous mixture contg. H2 and >=a specified vol.% CO as gaseous raw material. CONSTITUTION:Diamond is deposited on a substrate by allowing a gaseous mixture contg. H2 and >=1vol.% CO after exciting the gaseous mixture to contact with the substrate. If the content of CO in the gaseous mixture is <1vol.%, diamond is not formed or the deposition velocity is extremely small even if it is formed. A means for obtg. said gaseous raw material contg. C in the excited state is, for example, plasma CVD process, sputtering process, ionized vapor deposition process, ion beam vapor deposition process, hot filament process, chemical transfer process, etc.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for synthesizing diamond, and more specifically, it can be widely used in various protective films, optical materials, electronic materials, chemical industrial materials, etc. This invention relates to a diamond synthesis method that efficiently deposits diamonds at a high speed.

[Conventional technology and its problems 1 Diamond synthesis technology has been making remarkable progress in recent years, and so far, the plasma CvD method, which produces hard carbon on the substrate surface by plasma decomposition of hydrocarbons, and the plasma CVD method, which uses asymmetric chemical reaction, CVD methods such as chemical transport methods to obtain a hard carbon film on the substrate surface using hot cathode P! Various synthesis techniques have become known, such as ionization vaporization using a G gun, cold cathode PIG gun, or sputter gun.

By the way, the methods that have been proposed so far use hydrocarbons or a mixed gas of hydrocarbons and hydrogen as the raw material (Japanese Patent Application Laid-open No. 58-91100, Japanese Patent Application Laid-Open No. 58-11).
No. 0494, JP-A-58-135117.

JP-A-59-83732, JP-A-80-1030
99, etc.), these methods have been reported to have a slow diamond deposition rate.

Therefore, in order to improve the diamond deposition rate, a method has been proposed that uses a raw material gas containing carbon monoxide in a mixed gas of hydrocarbon and hydrogen (Japanese Patent Laid-Open No. 110-191097). (see official bulletin).

However, the method described in the above publication requires carbon monoxide to be newly added to the raw material gas used in the conventional method, which complicates the preparation of the raw material gas and makes the operation complicated. There is an obvious problem. Furthermore, according to the above-mentioned publication, if the content of carbon monoxide added to the hydrocarbon is increased to more than 61%, the oxygen content in the artificial diamond deposited on the surface of the substrate becomes too high, causing the crystal structure of the diamond to change. There is a serious drawback that it becomes damaged.

Therefore, there is still a strong need for a method for synthesizing diamond with an intact crystal structure that is easy to operate, has a high deposition rate, and has excellent production efficiency.

[Objective of the Invention J] An object of the present invention is to meet the above-mentioned request and to
VD method, microwave plasma CvD method, hot filament)
No matter which method is used, such as CVD, chemical transport, ionization vapor deposition, or ion beam vapor deposition, the deposition rate is fast, and the operations required to prepare the raw material gas are extremely simple, resulting in excellent production efficiency. . An object of the present invention is to provide a method for synthesizing diamond without disordering the crystal structure.

[Means for achieving the above purpose]

In order to achieve the above object, the inventor has made extensive studies and found that when a mixed gas of carbon monoxide gas and hydrogen gas is used as a raw material, it is surprisingly possible to This invention was achieved by discovering that diamonds can be produced without the use of hydrocarbons, and that diamonds can be synthesized more efficiently at a faster deposition rate than when hydrocarbons are used.

That is, the outline of this invention is that carbon monoxide and hydrogen are
This method of synthesizing diamond is characterized in that a gas obtained by exciting a mixed gas containing hydrogen gas is brought into contact with a substrate at a ratio of hydrogen gas equal to or higher than the working volume.

The carbon monoxide to be used is not particularly limited,
For example, sufficiently purified generator gas or water gas obtained by thermally reacting coal, coke, etc. with air or steam can be used.

There are no particular restrictions on the hydrogen to be used, for example, gasification of petroleum, metamorphosis of natural gas, water gas, etc., electrolysis of water, reaction of iron and steam.

Thoroughly refine what is obtained through complete gasification of coal, etc.
can be used.

In the method of this invention, carbon monoxide and the hydrogen are used as the lX material gas, and the content of the carbon monoxide gas is 1% by volume.
Diamond is deposited on the substrate by bringing the gas obtained by exciting the mixed gas contained above into contact with the substrate at a ratio of preferably 3% by volume or more, more preferably 5% by volume or more.

If the content of hydrogen gas in the mixed gas is less than 1% by volume, diamonds may not survive, or even if diamonds are formed, their deposition rate is extremely low.

The substrate is not particularly limited, and includes, for example, metals such as silicon, aluminum, titanium, tungsten, molybdenum, cobalt, and chromium, oxides, nitrides, and carbides thereof, alloys thereof, Al203-Fl! system, TiC-11i system, Tie-Go system and 84 C-
Both Fe-based cermets and various ceramics can be used.

As a means for exciting the raw material gas to obtain the raw material gas containing carbon in an excited state, for example, plasma CVD is used.
Conventionally known methods can be used, such as a vacuum deposition method, a vacuum deposition method, an ionization deposition method, an ion beam deposition method, a thermal filament method, and a chemical transport method.

When the plasma CVD method is used, the hydrogen is irradiated with Takaoka waves or microwaves (thus forming a plasma), and the hydrogen is heated by CVD methods such as the chemical transport method and the hot filament method.
When using the method, the hydrogen forms atomic hydrogen by heat or electric discharge.

This atomic hydrogen has the effect of removing carbon in the graphite structure that is deposited at the same time as the diamond is deposited.

In the method of this invention, an inert gas can also be used as a carrier for the raw material gas.

Specific examples of the inert gas include argon gas, neon gas, helium gas, xenon gas, and nitrogen gas.

These may be used alone or in combination of two or more.

In the method of this invention, the reaction proceeds under the following conditions, and diamond is deposited on the 1& plate.

That is, since the temperature of the surface of the substrate varies depending on the excitation means of the source gas, it cannot be determined generally, but for example, when using the plasma CVD method,
Usually 400℃~1000℃, preferably 450℃~9
The temperature is 50°C. If this temperature is lower than 400℃,
Diamond deposition rate may be slow or excited carbon may not be produced. On the other hand, if the temperature is higher than too°C, the diamond deposited on the substrate may be etched away, and no improvement in the deposition rate may be observed.

The reaction pressure is usually 101 to 103 torr, preferably 1 to 800 torr, and the reaction pressure is 10 torr.
When it is lower than art, the diamond deposition rate becomes slow or diamond does not precipitate. On the other hand, even if it is made higher than 1(l torr), a corresponding effect cannot be obtained.

The diamond that can be obtained by the method of the present invention can be used, for example, to protect the surface of cutting tools! Various types of protection i1m such as l
, optical materials, electronic materials, chemical industrial materials, etc.

[Effect of the invention] According to this invention, a high frequency plasma CVD method.

Microwave plasma CVD method, FA filament CVD
Diamond can be synthesized at a high deposition rate using a mixed gas of carbon monoxide and hydrogen as a raw material, regardless of the method used, such as the chemical transport method, ionization vapor deposition method, or ion beam vapor deposition method. Therefore, (1) Unlike when using hydrocarbons, the preparation of raw material gas does not become complicated or the operations become complicated.

(2) Excellent production efficiency.

(3) It is possible to provide an industrially advantageous method for synthesizing diamond, which has the effect of not causing disorder in the crystal structure of diamond.

[Example] Next, Examples and Comparative Examples of the present invention will be shown to further specifically explain the present invention.

(Example 1) A microwave power source with a frequency of 2.45G
It was set to 0W.

Next, carbon monoxide was introduced into the reaction chamber at a flow rate of 5 mcc, and hydrogen was introduced at a flow rate of 115 mcc, and diamond was synthesized for 1 hour by microwave plasma CVD.
A deposit with a thickness of 10 #Lm was obtained on the substrate controlled at the above temperature. Note that a silicon wafer was used as the substrate.

When the obtained deposit was subjected to Raman spectroscopic analysis, a peak attributed to diamond was observed near 1333c+++-1 in the Raman scattering spectrum, confirming that it was diamond without impurities.

(Comparative example 1) In Example 1, instead of carbon monoxide.

Diamond was synthesized in the same manner as in Example 1 except that methane gas was used.

As a result, a deposit with a thickness of only 1.0 pm was obtained, and the deposition rate was lowered to 1/1O compared to Example 1.

(Example 2) In Example 1, WC-Go (Co amount 12
%), and the substrate temperature was 800°C and the pressure was 40°C.
torr, carbon monoxide flow rate of 130 sccm, and hydrogen flow rate of 70 x cm, the reaction was carried out for 1 hour to synthesize diamond, and a deposit with a thickness of 6 m was obtained on the substrate.

When the obtained deposit was subjected to Raman spectroscopic analysis, a peak attributed to diamond was observed near 1333 cm-1 in the Raman scattering spectrum.

It was confirmed that the diamond was free of impurities.

(Comparative Example 2) In Example 2, methane gas and carbon monoxide were used instead of carbon monoxide, and the flow rate of methane gas was 5 sccm.
Diamond was synthesized in the same manner as in Example 2 except that the amount of carbon monoxide was 3 sccm.

As a result, only a deposit with a thickness of 3 days was obtained.

The sedimentation rate was 1/2 compared to that of Example 2.

(Example 3) In Example 1, a silicon substrate was used, the microwave output was set to 400 W, the substrate temperature was set to 800°C, the pressure was set to 40 torr, and the flow rate of carbon monoxide was set to 80 sc.
Diamond was synthesized in the same manner as in Example 1, except that the reaction was carried out for 1 hour under conditions where the hydrogen flow rate was 20 gcc, and a deposit with a thickness of 12 μm was obtained on the substrate.

When the obtained deposit was subjected to Raman spectroscopic analysis, a peak attributed to diamond was observed near 1333 cm-' in the Raman scattering spectrum, confirming that it was diamond without impurities.

(Comparative Example 3) In Example 3, the carbon monoxide method was changed to 0°5sc.
Diamond was synthesized in the same manner as in Example 3, except that the flow rate of hydrogen was changed to 100+cc.

As a result, even after one hour of reaction, the surface procedure of the substrate was not corrected. December 9, 1988 Patent Application No. 109193 of 1988 2 Title of Invention Method for Synthesizing Diamond 3 Relationship with the Amendment Person Case Patent Applicant address: 3-1-1 Marunouchi, Chiyoda-ku, Tokyo Name: Idemitsu Petrochemical Co., Ltd. Representative: Mutsumi Suigo 4 Iinuflno (Address: 3rd floor, Central Nishi-Shinjuku, 8-9-5 Nishi-Shinjuku, Shinjuku-ku, Tokyo Name: Patent attorney Specialist (8759) Naoki Fukumura 5 Date of amendment order None: spontaneous 6 Number of inventions increased by amendment 07 Target of amendment Column 8 of “Detailed explanation of the invention” of specification 1tJ
Contents of amendment (1) "Hydrogen gas" described in page 4, line 12 and page 5, line 13 of the specification is corrected to "carbon monoxide."

(2) The phrase “can be used” on page 4, lines 19 to 20 of the specification can be replaced with “r”, zinc oxide,
It is obtained by decomposing methanol in the presence of a silica catalyst containing zinc oxide and chromium oxide, zinc oxide and iron oxide, zinc oxide and magnesium oxide, zinc oxide, copper oxide, and chromium oxide, or it is filled in a cylinder. Ichihara's carbon monoxide gas can be used. ”.

(3) It is possible to use the material described in the fifth line of page 5 of the specification. methanol in the presence of a silica catalyst supporting lead oxide, zinc oxide and chromium oxide, zinc oxide and iron oxide, lead oxide and magnesium oxide, zinc oxide, copper oxide, chromium oxide, etc. The product obtained by decomposing can be used. ”.

(Insert the following statement between lines 16 and 17 on page 5 of the 0 specification.

Note: The mixed gas can be obtained by mixing the carbon monoxide and hydrogen at the predetermined mixing ratio.Methanol is obtained by decomposing methanol in the presence of the silica catalyst. When using generated gas, the generated gas is usually a mixture of carbon monoxide and hydrogen, so
In order to obtain a mixed gas in the present invention, carbon monoxide or hydrogen may be further added to the generated gas. Note that using this generated gas reduces the danger of using commercially available carbon monoxide gas. can be avoided. (5) "The raw material gas" described in the fifth line of page 6 of the specification is corrected to "mixed gas."

(6) “Raw material gas” stated in line 6 of the specification shall be amended to “gas”.

(7) Add the following statement after the 12th line of the 12th page of the specification.

[(Example 4) In Example 1, carbon monoxide was flowed into one reaction chamber bt5s
ccm and hydrogen at mi95 gccm, a product gas containing carbon monoxide and hydrogen obtained by decomposing methanol in the presence of a silica catalyst was introduced at a flow rate of 50 gccm.
and hydrogen were introduced at a flow rate of 50scc (Co/Hy
'Amount ratio of B = 14/86) was carried out in the same manner as in Example 1 above.

As a result, a deposit with a thickness of 5 Bm was obtained.

When the deposit was subjected to Raman spectroscopic analysis, a peak attributed to diamond was observed near 1333 cm-' in the Raman scattering spectrum, and it was confirmed that the deposit was diamond free of impurities. "that's all

Claims (1)

[Claims] (1) A diamond synthesis method characterized by bringing a substrate into contact with a gas obtained by exciting a mixed gas containing carbon monoxide and hydrogen at a ratio of carbon monoxide of 1% by volume or more. .