JPS62138395A - Preparation of diamond film - Google Patents

Abstract

PURPOSE:To facilitate generation of nuclei at the initial stage of generation of diamond and to increase the rate of growth of diamond film in the stage of forming diamond film on the surface of a sustrate by the CVD process by dispersing previously fine particles having SP<3> bond uniformly on the surface of the substrate. CONSTITUTION:Fine particles having SP<3> bonds are dispersed uniformly on the surface of a substrate for forming diamond film by coating volatile org. liquid contg. fine particles having SP<3> bonds dispersed therein, etc. The substrate is then heated at 500-1,300 deg.C. A gaseous mixture consisting of hydrocarbon and H2 is introduced, and diamond film is prepd. by depositing diamond on the substrate by the thermal decomposition of the hydrocarbon. By this method, generation of nuclei in the initial stage of formation of diamond is caused within a short time generating uniform and high density nuclei. Thus, the rate of growth of the film is increased and dense diamond film having uniform thickness suitable as covering of surface of cutting tools can be formed with sufficient efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a method for manufacturing a diamond film, and more particularly, to a method for manufacturing a diamond film that can increase the nucleation density and grow the diamond film at high speed.

(Prior art) In recent years, diamond has come to be synthesized under ultra-high pressure and ultra-high temperature using expensive equipment. Chemical vapor phase synthesis is being researched to efficiently synthesize diamonds and to meet a wide range of applications.

This chemical vapor phase synthesis method introduces a mixed gas of hydrocarbons and hydrogen into a reaction tank, and heats the hydrocarbons by thermally decomposing them using electron beam irradiation, high frequency waves, microwaves, etc. to generate plasma. This method involves depositing diamond on a substrate.

(Problems to be Solved by the Invention) When depositing diamond on a smooth substrate surface by such a chemical vapor phase synthesis method, it is necessary to initially generate nuclei on the substrate surface.

However, according to the conventional method, it is difficult to set the conditions for this nucleation process, it takes time, and the density of the generated nuclei is low and non-uniform, so the thickness of the film is small at the stage of growing into a film. There are disadvantages in that it tends to be non-uniform and it is difficult to obtain a dense film, the film strength decreases, and when used in cutting tools etc., there are problems such as short life.

(Objective of the Invention) The present invention aims to solve the above-mentioned problems, and specifically, it is an object of the present invention to solve the above-mentioned problems. The purpose of this invention is to provide a manufacturing method for increasing the growth rate and obtaining a uniform and dense diamond film.

(Means for solving the problem) That is, according to the present invention, a mixed gas of hydrocarbon and hydrogen is
A method for producing a diamond film in which diamond is deposited on a substrate surface heated to 00 to 1300° C. by thermal decomposition of hydrocarbons, in which fine particles having sp' bonds are uniformly dispersed on the substrate surface. Accordingly, the above-mentioned problems can be solved.

The present invention will be explained in detail below.

The chemical vapor deposition method for diamond uses hydrocarbon and hydrogen as a mixed gas.The activated hydrogen decomposes the hydrocarbon gas and selectively deposits carbon with sp3 bonds on the substrate surface. Has characteristics.

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 that are thermally 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 are generated, as shown in FIG. 1(b), diamonds 3 are precipitated around the generated nuclei 2 and grow in a so-called island shape. If further growth progresses, the first
As shown in Figure (c), adjacent islands overlap and eventually form a film.

In the above process, the nucleation process shown in FIG. 1(a) is difficult to set conditions and is extremely susceptible to the surface condition of the substrate, so nucleation tends to vary and the film becomes non-uniform. easy. Although the mechanism of this nucleation has not yet been clarified, one of the factors is the interaction between ions or electrons in the plasma and the substrate.

The present invention is based on the novel finding that when fine powder having sp' bonds exists on the surface of a substrate at the initial stage of diamond production, diamond is efficiently generated around the fine powder.

That is, by uniformly dispersing fine powder having sp3 bonds on the substrate surface in advance, initial nucleation is facilitated, and as a result, uniform diamond nuclei can be generated on the substrate surface, and the film itself is also uniform. It can be made into a dense structure.

The present inventors consider the reason for this phenomenon as follows. If there is a difference in electrical conductivity between the substrate and the powder, the interaction between the ions or electrons present in the plasma and the substrate will
It is thought that only the part where fine powder exists has a specific level compared to the surrounding area, and it is thought that this difference in correlation effect greatly contributes to the formation of diamond. Moreover, since it has SP' bonds, it can exist without disappearing even under conditions where the diamond formation mechanism etches precipitates other than sp3 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 phosphorous boride (BP).

Among these, diamond, c-BN, and β-5iC 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 with a good dispersion state.

The amount of coating at this time varies somewhat depending on the fine powder used, but the coating is performed within a range of about 10' to 101 pieces/d of fine powder. If the coating amount is too small, the film will tend to become uneven and it will be difficult to generate nuclei, while if it is too large, it will form as an intermediate layer between the diamond and the substrate, which may have a negative effect on the adhesion between the diamond and the substrate. be.

According to the present invention, the substrate on which the fine powder has been dispersed as described above is placed in a reaction tank, and then the substrate is cut.

A mixed gas of a hydrocarbon gas such as CzHz, CJn, or CzHb and hydrogen gas is introduced. Then, the substrate is heated to a temperature of 500 to 1300 degrees, and plasma is generated by electron beam irradiation, high frequency, microwave, or the like.

In addition, the mixing ratio of hydrocarbon and hydrogen (C, H-/H2)
is 0.005 to 0.15, especially 0.01 to 0.05
is set to

The invention is illustrated by the following example.

Example Using silicon as a substrate, the surface treatment shown in Table 1 was performed, and a diamond film was provided by microwave plasma CVD under the following conditions.

Microwave output 400W Pressure 25Torr CIIa/L 3/100 hours
1 hr At that time, a fine powder having an sp' bond shown in Table 1 was applied to the surface of the substrate, and then a film was formed.

After 1 hour of film formation, the state of nucleation was observed using a microscope.

The occupancy rate of diamond on the substrate surface was also determined, and this value was used as a guideline for the growth rate from the nucleus to the film.

As is clear from Table 1, in sample No. 2, in which no treatment was applied to the substrate surface as in the past, almost no nuclei were observed even after one hour of diamond formation, and it was also noticeable in No. 1, which was simply scratched. There were no nuclear outbreaks. On the other hand, in samples K3 to K9 of the present invention, diamond nucleation was observed in each of the applied fine powders, and diamond and c-BN systems were particularly good, and by increasing the amount of applied nucleation, diamond nucleation was observed. A film was formed by the generation of time.

Also, in β-3iC (t'h8), diamond, c-
Although not as good as BN, good nucleation was observed.

(Effects of the Invention) As described above, the manufacturing method of the present invention provides sp” on the substrate surface.
By uniformly dispersing fine powder with bonds, the initial nucleation during diamond formation can be made uniform and denser in a short time, thereby speeding up film growth and creating a dense diamond film with a uniform thickness. can be obtained.

Such a diamond film can be used as a surface coating of a cutting tool to extend its life, and can also be used as a heat sink to provide excellent thermal conductivity.

[Brief explanation of drawings]

FIGS. 1A to 1C are diagrams showing the process of forming a diamond film. 1 ・ ・ ・ Base material 2...Fine powder 3...Diamond core

Claims (1)

[Claims] (1) Mixed gas of hydrocarbon and hydrogen at 500 to 130
In a method for producing a diamond film, in which diamond is deposited on the substrate surface heated to 0°C by thermal decomposition of hydrocarbons, fine particles having SP^3 bonds are uniformly dispersed on the substrate surface. Characteristic method for producing diamond film.