JPS62202898A - Production of diamond film - Google Patents

Abstract

PURPOSE:To increase the nucleation density and produce a homogeneous and dense diamond film, by introducing a mixed gas of a hydrocarbon and H2 into a reaction vessel containing a substrate having uniformly dotted metal (compound) and activating the hydrocarbon. CONSTITUTION:A metal, e.g. Ti, or a compound thereof, e.g. TiB2, having >=800 deg.C melting point is uniformly dotted on the surface of a substrate in forming a film to give 10<5>-10<11> particles having 0.005-5mum particle size/cm<2>. The resultant substrate is then placed in a reaction vessel and a mixed gas of a hydrocarbon gas, e.g. CH4, C2H2, C2H4, etc., and H2 gas at 0.005-0.15 mixing ratio is introduced into the reaction vessel. The substrate is then heated at 500-1,300 deg.C and plasma is simultaneously generated by irradiation with electron rays, high frequency, microwaves, etc., to activate the hydrocarbon and form the aimed diamond film on the substrate.

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 been synthesized under ultra-high pressure and ultra-high temperature using expensive equipment. Chemical vapor phase synthesis is being researched in order to respond to a wider range of applications and to efficiently synthesize diamond.

In this chemical vapor phase synthesis method, a mixed gas of hydrocarbons and hydrogen is introduced into a reaction tank, and plasma is generated using electron beam irradiation, high frequency waves, microwaves, etc. to activate the hydrocarbons and generate plasma. In this method, diamond is deposited on a heated substrate.

(Problems to be Solved by the Invention) When depositing diamond on a smooth substrate surface using 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 Problems) That is, according to the present invention, a substrate on which metals or metal compounds thereof are uniformly dotted is placed in a reaction tank, and the substrate is
After heating the substrate to 1300°C, a mixed gas of hydrocarbon and hydrogen is introduced into the reaction tank and the hydrocarbon is activated to form a diamond film on the surface of the substrate. A manufacturing method is provided.

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 SP'' bonds on the substrate surface. It has the following 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), hydrocarbons are thermally decomposed, and among the excited carbon atoms, only sp'' bonded atoms are deposited as diamond 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 growth continues, the first
As shown in Figure (c), adjacent islands overlap and eventually form a diamond film 3. In the above-mentioned 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.
Nucleation tends to vary, and the film tends to be non-uniform. 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 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. .

Various discussions have been made regarding the mechanism of diamond vapor phase synthesis. Among them, the substrate is diamond or CBN.
It is known that diamond is easily formed when the crystal structure is the same or very similar to that of diamond. Further, since diamond generation differs depending on the type of substrate even under the same CvD conditions, it is expected that the surface condition of the substrate greatly contributes to diamond generation, especially nucleation.

The conditions for the reaction mechanism on the substrate surface are: ■ Hydrocarbon gas decomposition and hydrogen abstraction reaction ■ Freezing of sp' crystal ■ sp
'Three types of removal (etching) of substances other than crystals are considered, and these reactions involve the chemical species of hydrocarbon ions, hydrogen ions, and hydrogen radical electrons. Here, when the above-mentioned metal or metal compound is dotted on the surface of the substrate as a nucleating agent, an electric field is generated between the substrate and the nucleating agent due to the difference in electrical conductivity, dielectric constant, etc. It is thought that the interaction of electrons with the substrate surface is significant around the nucleating agent. This was confirmed by the fact that the substrate surrounding the nucleating agent, such as Si, was etched particularly strongly under the etching conditions. It is thought that this difference in interaction greatly contributes to diamond nucleation.

In other words, the presence of the nucleating agent greatly intensifies the plasma around the nucleating agent, and due to the reaction (2), the decomposition of hydrocarbon gas becomes active and carbon is precipitated, and at the same time, the sp' crystal (2) freezes and diamonds are formed. generated. At the initial stage of carbon precipitation, the electric field is strong, so the decomposition rate of (1) is fast, and SP2 crystals (graphite) are formed. This is because at the early stage of nucleation, the decomposition rate of hydrocarbon gas is rapid around the nucleating agent, and the precipitation rate of sp'' crystals exceeds the etching rate of , the electric field becomes weaker because the difference in electrical conductivity or dielectric constant between the carbon generation site and its surroundings becomes smaller.At this time, the decomposition of hydrocarbon gas due to the reaction (■) is suppressed, and the reaction (■) causes sp' Since materials other than crystals, such as sp'' crystals, are sufficiently etched, only SP3 crystals eventually grow and grow as diamonds.

At this time, if the decomposition rate of hydrocarbons in (2) is higher than the etching rate in (2), SPz crystals tend to remain and become graphitized. The rate of decomposition is also highly dependent on the size and amount of the nucleating agent.

For this reason, as a nucleating agent, at the initial stage, there is a difference in electrical conductivity between it and the substrate, and it has a melting point higher than the surface temperature of the substrate during diamond formation.
It is important to have a size large enough to not be erased by etching in the reaction.

Therefore, according to the present invention, it is necessary that the metal and metal oxide serving as the nucleating agent have a melting point of 800° C. or higher, especially 1000° C. or higher during film formation, and furthermore, the particle size thereof must be 0.0° C. or higher.
05 μm to 5 p m s, particularly 0.05 p m to 1 IJI11. Melting point is 800℃
If it is lower, it will melt on the substrate surface and will not function as a nucleating agent or will be etched. Particle size is o, oo
If it is smaller than sμ, it will easily disappear due to etching,
If it is larger than 5 μm, the nucleation efficiency is poor and the adhesion after film formation is poor.

Further, it is important to scatter the nucleating agent on the substrate surface in an appropriate amount. That is, if the amount of nucleation is large, the decomposition rate of the above-mentioned (2) becomes too high, and graphite tends to precipitate, or if it exists uniformly, no difference in interaction occurs, and it does not function as a nucleating agent. Therefore, according to the present invention, it is approximately 10' to 10' although it varies somewhat depending on the material used.
It is desirable to scatter the particles within a range of 1/aa.

In the present invention, the metal or metal compound dotted on the substrate when arranging the substrate includes Ti in the periodic table.
, Zr, IVa group of Hf, Va group of V, Nb, Ta,
Cr, Mo, - Vla group + Mn etc. a group, Fe,
Single metals selected from group Ⅰ such as Co and Ni, or complexes thereof, and metal compounds such as CrCl3+FeC1
Chlorides such as z+CoC1, NiC1+FeC1, F
Sulfides such as eS and CrS, TiBz.

Borides such as TaBzJJz+NtB, Ti5iz, V
Silicides such as Siz+CrSi*+MoS iz, T
tC+ LCz+ TaC+ Cr5Cz+ MnC+
Carbide such as NiC, TiN+ TaN, CrN, F
Nitride such as ezN, Tto! , Zr0z+V! O1
+ WO3, Mn0z+ F'ezO=, oxides such as NiO, sulfates such as KFe(SO4-)z, FrCa
Examples include metal-containing organic substances such as HsOw, which either have a melting point of 800°C or higher by themselves, or are reduced by the atmosphere during film formation, and remain on the substrate as a carbide, for example, as a compound with a melting point of 800°C or higher. Those that do are selected.

This nucleating agent can be dotted on the substrate surface by dispersing it in a volatile organic liquid such as oil, water, or alcohol as a medium and applying it to the substrate, or by dispersion plating, spray coating, or adding a surfactant. In addition to being coated in a good condition, it is also possible to form a thin film on the surface of the substrate using a thin film technique such as PVD or CVD, and then scatter it using an etching technique.

According to the present invention, a substrate dotted with a nucleating agent as described above is placed in a reaction tank, and CHa, CJz.

A mixed gas of a hydrocarbon gas such as C2H* or CJi and hydrogen gas is introduced. And the base is 500 to 1300
At the same time, plasma is generated by electron beam irradiation, high frequency waves, microwaves, etc.

In addition, the mixing ratio of hydrocarbon and hydrogen (C, H-/Hz)
is 0.005 to 0.15, especially 0. Ol~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 carried out, and a diamond film was formed by microwave plasma CVD under the following conditions.

Microwave output: 400 Torrc Pressure: 25 Torrc1. /H
z 3/100 hours
1 hr At that time, the metal powder or metal compound powder 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.

Also, find the occupancy rate of diamond on the substrate surface,
This value was used as a guideline for the growth rate from the nucleus to the membrane. The results are shown in Table 1.

As is clear from Table 1, when no nucleating agent remains, the occupancy rate is only 5% even after one hour, whereas the method of the present invention can reliably improve the nucleation rate. As a result, we were able to increase the occupancy rate to over 20%, and in some cases over 90%.

Further, similar experiments were conducted using a 5iJ4 sintered body and a SiC sintered body as substrates, and almost the same results were obtained.

(Effects of the Invention) As described above, the method for manufacturing a diamond film of the present invention uniformizes the initial nucleation during diamond formation in a short time by dotting the surface of the substrate with metal powder or a metal compound in advance. The diamond film can be densified, thereby speeding up film growth and obtaining a dense diamond film with a uniform thickness.

Such a diamond film can be used as a surface coating of a cutting tool to extend the life of the tool1, and can also be used as a heat sink to provide excellent thermal conductivity.

[Brief explanation of drawings]

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

Claims (3)

[Claims] (1) Place a substrate uniformly dotted with metal or its metal compound in a reaction tank and heat the substrate to 500 to 1300°C.
1. A method for producing a diamond film, which comprises heating the substrate to a temperature of 100.degree. C., and then introducing a mixed gas of hydrocarbon and hydrogen into the reaction tank and activating the hydrocarbon to form a diamond film on the surface of the substrate. (2) The method for producing a diamond film according to claim 1, wherein the metal or metal compound is dotted on the substrate as a metal or metal compound having a melting point of 800° C. or higher during film formation. (3) The metal or metal compound has a concentration of 0.00 at the time of film formation.
A method for producing a diamond film according to claim 1 or 2, wherein the diamond film is scattered on the surface of the substrate as particles or films of 5 to 5 μm.