JPS63166798A - Production of diamond film - Google Patents

Abstract

PURPOSE:To obtain a dense diamond film having an uniform thickness, by introducing a given gas onto a substrate having homogeneously dispersed fine particles having SP<3> bonds and depositing diamond. CONSTITUTION:Fine particles having SP<3> bonds are homogeneously dispersed on the surface of a substrate. A gas for forming diamond containing at least hydrogen atoms, carbon atoms and oxygen atoms is introduced onto the sub strate. The above-mentioned substrate is then heated at 500-1,300 deg.C to disperse the afore-mentioned gas for forming the diamond. Thereby the aimed dense diamond film having a uniform thickness is formed on the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a diamond film, and more particularly to a method of manufacturing a diamond film that increases the nucleation density and grows the diamond film at high speed.

[Prior art]

In recent years, diamonds have been synthesized using expensive equipment under extremely high pressure and high temperatures. Chemical vapor phase synthesis is being researched to efficiently synthesize diamonds for a wide range of applications.

In this chemical vapor phase synthesis method, a mixed gas of hydrocarbons and hydrogen is generally introduced into a reaction tank and heated by thermally decomposing the hydrocarbons using electron beam irradiation, high frequency waves, microwaves, etc. to generate plasma. This method involves depositing diamond on a substrate, but since the deposition rate is extremely slow, attempts have been made to deposit fine nuclei on the substrate at the beginning of the film forming process.

[Problem that the invention seeks to solve]

However, according to the conventional method, it is difficult to set the conditions for this nucleation process, and the density of the generated nuclei is low and non-uniform, so the thickness of the film tends to become non-uniform at the stage of growing into a film. It has the disadvantage that it is difficult to obtain a film, which reduces the film strength, and when used in cutting tools, etc., there are problems such as a shortened service life.

Moreover, since it takes time from the nucleation process to the film formation process, it is difficult to mass-produce diamond-coated members.

[Purpose of the invention]

The present invention aims to solve the above-mentioned problems. Specifically, the present invention accelerates the growth rate of diamond by generating diamond nuclei in a short time and at high density during the initial nucleation process. The purpose of this invention is to provide a manufacturing method for obtaining a uniform and dense diamond film.

Another object of the present invention is to provide a method for manufacturing a diamond film with excellent mass productivity, which can improve the diamond precipitation rate from the nucleation process to the film formation process.

[Means for solving problems]

The present inventors solved the above problems by conducting intensive research and found that the diamond-forming gas contains a small amount of hydrogen atoms, carbon atoms, and oxygen atoms, and that sp 3 bonds are formed on the substrate on which a diamond film can be formed. The present invention was developed based on the finding that by uniformly dispersing fine particles having a nucleation process, the generation of nuclei in the nucleation process can be made faster and more dense.

The present invention will be explained in detail below.

The chemical vapor deposition method for diamond uses a carbon source and a diamond-forming gas containing hydrogen, and its mechanism is to decompose it and selectively deposit carbon with SP3 bonds on the substrate surface. .

Therefore, the process of forming a diamond film on the substrate surface is shown in FIGS. 1(a) to 1(c). In the early stage, Figure 1 (
As shown in a), among the carbon atoms decomposed and brought into an excited state, only those SP3-bonded are precipitated as nuclei 2 on the surface of the substrate 1.

Next, when a certain amount of nuclei 2 are generated, diamond 3 is precipitated around the generated nuclei 2 as shown in FIG. 1(b), and grows in a so-called island shape. If further growth progresses, the first
As shown in Figure (c), adjacent islands overlap to eventually form a film.

The present invention is based on the novel finding that by uniformly dotting the surface of a substrate with metal or its metal compound at the initial stage of the diamond film formation process, diamond can be efficiently formed around the substrate surface. .

That is, by uniformly dispersing fine powder having sp'' bonds on the substrate surface in advance, initial nucleation can be facilitated, and as a result, uniform diamond nuclei can be generated on the substrate surface. .

The present inventors consider the reason for this phenomenon as follows. If there is a difference in electrical conductivity between the substrate and the fine powder, it is thought that the interaction of ions or electrons present in the plasma with the substrate is at a specific level only in the area where the fine powder exists compared to the surrounding area. It is thought that this difference in correlation effects greatly contributes to the formation of diamonds. Furthermore, since it has sP3 bonds, it can exist without disappearing even under conditions where the diamond formation mechanism etch precipitates other than SP'' bonds.

The fine powder having sp3 bonds used in the present invention includes diamond, cubic boron nitride (c-BN),
Cubic silicon carbide (β-3iC), aluminum nitride (
c-AIN) and phosphorus boride (BP).

Among these, diamond, c-BN, and β-3iC are preferable.

The particle size of these fine powders is preferably in the range of 0.05 to 5 μm in view of the thickness of the film formed on the substrate.

Means for uniformly dispersing this fine powder on the substrate surface include dispersing it in a volatile organic liquid such as oil, water, or alcohol as a medium and applying it to the substrate, as well as dispersion plating, spray coating, or adding a surfactant. It may be possible to apply the coating in a well-dispersed state.

The amount of coating at this time varies somewhat depending on the fine powder used, but it should be applied within a range of approximately 10' to 10 pieces/cm' of fine powder. If the amount of coating is small, the film tends to become uneven, and the formation of nuclei. On the other hand, if the amount is too large, an intermediate layer may be formed between the diamond and the substrate, which may adversely affect the adhesion between the diamond and the substrate.

According to the present invention, a substrate on which a nucleating agent as described above has been dispersed is placed in a reaction tank, and a diamond-forming gas containing at least hydrogen atoms, carbon atoms, and oxygen atoms is introduced. Then, the board is 500 to 13
While heating to a temperature of 00°C, plasma is generated by electron beam irradiation, high frequency, microwave, etc.

The diamond-forming gas used is a combination of hydrogen, hydrocarbon, oxygen-containing gas, and oxygen-containing organic gas. Hydrocarbons include methane, ethane, propane,
Saturated chain hydrocarbons such as butane, ethylene, propylene,
Examples include unsaturated chain hydrocarbons such as acetylene and allene, alicyclic hydrocarbons such as cyclopropane, cyclobutane and cyclopenkune, and aromatic hydrocarbons such as benzene, toluene and xylene. Among these, hydrocarbons that are gaseous at room temperature are particularly desirable from the viewpoint of handling.

The oxygen-containing gas used is 0□, co, co
Carbide such as □, nitride such as No, No□, Neo, or H
Triatomic molecules such as hydrides such as 2O, Hooz, etc., and oxygen compounds such as triatomic molecules or West atomic molecules can be used.

In addition, oxygen-containing organic compounds include alcohols such as methanol, ethanol, propatool, butanol, methyl ether, ethyl ether, ethyl methyl ether, methyl propyl ether, ethyl propyl ether,
Phenol ethers, acetals, ethers of cyclic ethers (ethylene oxide, dioxane, etc.), acetone, binacolin, mesityl oxide, aromatic ketones (acetophenone, benzophenone, etc.), diketones, ketones such as cyclic ketones, formaldehyde, acetaldehyde, Aldehydes such as butyraldehyde and aromatic aldehydes (benzaldehyde, etc.), organic acids such as formic acid, acetic acid, propionic acid, succinic acid, butyric acid, oxalic acid, tartaric acid, stearic acid, methyl acetate, ethyl acetate, propyl acetate, butyl acetate and dihydric alcohols such as ethylene glycol, triethylene glycol, and diethylene glycol. Methanol, ethanol, propatool, butanol, methyl alcohol, ethyl ether, ethyl methyl ether, methyl propyl ether, ethyl propyl ether, acetone, formaldehyde, acetaldehyde, butyraldehyde, formic acid, acetic acid, methyl acetate, ethyl acetate, propyl acetate, Butyl acetate etc. are preferable.

It is also possible to partially replace hydrogen with an inert gas such as argon or helium.

It is desirable that the ratio and flow rate of gas components of these diamond-generating gases be set within a predetermined range. That is,
The total number of hydrogen atoms introduced into the system as a diamond-generating gas per unit time is (H), and the total number of carbon atoms is (C
), and when the total number of oxygen atoms is (0), by setting the gas components and their flow rates to satisfy the following formula % formula % (), nucleation is performed efficiently and the reaction up to the film formation process. It is possible to promote the progress of the process and also improve the strength of the film itself.

Further, the temperature of the substrate on which the diamond film is formed and the gas pressure during film formation are preferably set within predetermined ranges.

According to experiments conducted by the present inventors, the temperature of the base material was set at 400 to 14
00°C and gas pressure 10-”100 Torr.
It is desirable to set it within the range of r.

The means for forming a diamond film in the present invention is classified by the means for decomposing the diamond-forming gas, and includes a high-frequency heating plasma CVD method, a microwave plasma CVD method,
In addition to plasma CVD methods such as ECR plasma CVD method, CVD method using electron beam irradiation, hot filament CVD method, etc. are employed.

The invention is illustrated by the following example.

The surface treatments shown in Table 1 were carried out using Si, SiC sintered bodies, and Si3Ng sintered bodies as example substrates.

Table 1 Next, place the substrate sample obtained in Table 1 in a reaction tank,
Based on the microwave plasma CVD method, diamond forming gases shown in Table 2 were introduced at various flow rates, and a diamond film was formed under the conditions of a microwave output of 400 W and a pressure of 25 Torr.

During this film-forming process, the state of nucleation on the substrate surface was observed using a microscope after 1 hour had elapsed. The occupancy rate of diamond on the substrate surface was also determined.

Finally, the diamond film was formed for 4 hours, and the film thickness at that point was measured.

The results are shown in Table 2.

As is clear from Table 1, 11111. Almost no nuclei were generated after one hour on the St substrate to which the N112 nucleating agent was not applied or to which the St substrate was simply scratched. The other samples of the present invention from 11h3 to 15 all produced good nucleation, and the film formation rate was 3°5 μm/hr.
It was bigger than that.

〔Effect of the invention〕

As described above, the method for manufacturing a diamond film of the present invention involves uniformly dispersing fine powder having SP3 bonds on the initial substrate surface, and introducing a diamond-forming gas containing at least hydrogen atoms, carbon atoms, and oxygen atoms into the substrate. death,
By decomposing the gas to precipitate diamond, initial nucleation during diamond formation can be efficiently uniformized and densified in a short time. Thereby, film growth can be accelerated and a dense diamond film with a uniform thickness can be obtained. Such a diamond film has improved film strength, can be used as a surface coating for cutting tools to extend its life, and can also be used as a heat sink to provide excellent thermal conductivity.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(c) are diagrams for explaining the process of forming a diamond film. 1...Substrate 2...Fine powder 3...Diamond core

Claims (1)

[Claims] A substrate on which fine particles having SP^3 bonds are uniformly dispersed is placed in a reaction tank, and a diamond-forming gas containing at least hydrogen atoms, carbon atoms, and oxygen atoms is introduced into the reaction tank, and the substrate is 500 to 130
A method for producing a diamond film, comprising heating to 0° C. to decompose the reaction gas and deposit diamond on the substrate.