JP2762561B2 - Method of synthesizing diamond film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a method for synthesizing a diamond film by a plasma jet, with the object of forming a diamond film having excellent hardness. When a mixed gas of a hydrocarbon gas and a hydrogen gas is supplied between the provided anode and cathode, a plasma jet of carbon is generated by arc discharge, and when forming a diamond film on a substrate to be processed, the plasma A method for synthesizing a diamond film is constituted by adding any element powder of tungsten, molybdenum, silicon and titanium capable of forming a hard carbide by combining with a non-diamond carbon component in a jet.

[Industrial applications]

The present invention relates to a method for synthesizing a diamond film having excellent hardness.

Diamond is an allotrope of carbon (C), exhibits a so-called diamond structure, has a hardness of 10,000 kg / mm ^2, and has a thermal conductivity of 2000 W / mK, which is much better than other substances.

Therefore, various uses have been developed utilizing this characteristic.

In other words, by utilizing the high thermal conductivity, heat sinks (Heat-sin
Attention has been paid to the constituent material of k).

In addition, it is considered to be used for drill blades and cutting tools by utilizing its high hardness, and it is used by coating these tools made of high-hardness sintered alloy such as tungsten carbide (WC). Have been tried to.

[Conventional technology]

As described above, it has been attempted to coat diamond on a tool by utilizing its high hardness.

Now, a high-pressure synthesis method and a low-pressure synthesis method are known as diamond synthesis methods.

Here, the high-pressure synthesis method is a method suitable for growing a single crystal having a relatively large size, but has a problem that the apparatus is large-scale, the growth rate is extremely slow, and the cost is high. .

On the other hand, low-pressure synthesis methods such as microwave plasma chemical vapor deposition and electron beam irradiation chemical vapor deposition are known, and the growth rate is significantly higher than the former, and microcrystals are deposited on the substrate to be processed. The feature is that the film can be formed in the form of

The inventors have succeeded in chemical vapor deposition (abbreviated CVD growth) of a diamond film using a plasma jet chemical vapor deposition apparatus (abbreviated plasma jet CVD apparatus) as shown in FIG.

Now, the configuration and operation of this device will be briefly described as follows.

A metal plate 1 such as copper (Cu) that does not form a carbide is placed on a mounting table 3 that is water-cooled with cooling water 2.

Here, an anode 6 and a cathode 7 for forming a plasma jet 5 are provided at an upper portion of the reaction chamber 4, a raw material gas 8 is supplied therebetween, and a powder is formed for enabling a metal layer to be formed. A supply pipe 9 opens at the tip of the anode 6.

In addition, there is a DC power supply 10 connecting the anode 6 and the cathode 7, and an exhaust port 11 is provided below the reaction chamber 4.

In order to carry out CVD growth of diamond, a mixed gas of hydrogen (H ₂ ) and a hydrocarbon, for example, methane (CH ₄ ) is supplied as a source gas 8 into the reaction chamber 4 from between the anode 6 and the cathode 7. The evacuation system is operated to evacuate from the exhaust port 11, and arc discharge is performed between the positive and negative electrodes while the inside of the reaction chamber 4 is maintained at a low vacuum.
When the source gas 8 is decomposed into plasma by this heat, the plasma jet 5 containing carbon plasma hits the metal plate 1, and the diamond film 13 made of microcrystals grows on the metal plate 1.

In order to grow a mixed film of metal and diamond, metal powder may be supplied into the arc discharge 12 through a powder supply pipe 9. To grow only a metal film, H ₂ is used as a source gas 8. The metal powder may be supplied into the arc discharge 12 through the powder supply pipe 9.

Thus, when the CVD apparatus as shown in FIG. 1 is used, not only the diamond film 13 but also a metal film or a mixed film of metal and diamond can be formed.

The reason why a diamond film grows by plasma jet CVD is that hydrocarbons such as CH ₄ are rapidly heated to a high temperature in an arc discharge region to be decomposed and ejected as a plasma jet. And loses energy by colliding with it, and crystallizes as diamond.

However, at this time, all carbon (C) constituting hydrocarbons
Does not become diamond, but a considerable amount of components is deposited on the metal plate as amorphous carbon or graphite. However, as a raw material gas 8, hydrogen (H ₂ ) gas mixed with hydrocarbons makes amorphous gas. Non-diamond components consisting of high quality carbon or graphite are reduced to hydrocarbons such as CH ₄ , C ₂ H _6, etc. and removed as gas.

However, in reality, the removal action by H ₂ gas is not perfect, and these non-diamond components are detected in most diamond films formed by the plasma jet CVD method, which causes a decrease in hardness.

[Problems to be solved by the invention]

As noted earlier, diamond has a hardness of 10,000 kg / c
From big and m ^2, it has been attracting attention as various tools呑coating material, in the diamond film obtained by the plasma jet CVD method is amorphous carbon or graphite is mixed, thereby the hardness is not sufficient This is the problem, and the solution is the challenge.

[Means for solving the problem]

The object is to supply a mixed gas of a hydrocarbon gas and a hydrogen gas between an anode and a cathode provided in the reaction chamber while evacuating the reaction chamber by an exhaust system, and to perform a plasma jet of carbon by arc discharge. When a diamond film is formed on a substrate to be processed by a plasma jet chemical vapor deposition method of generating a tungsten, tungsten capable of forming a hard carbide by combining with a non-diamond carbon component in the plasma jet, The problem can be solved by a method of synthesizing a diamond film to which any one of elemental powders of molybdenum, silicon and titanium is added.

[Action]

In the present invention, when a diamond film is formed by using the plasma jet CVD apparatus shown in FIG. 1, a powder such as W, Mo, Si, or Ti capable of forming a hard carbide is added from a powder supply pipe to form an amorphous carbon. Tungsten carbide (WC, hardness 2200 kg / m
m ² ), molybdenum carbide (Mo ₂ C, hardness 1800 kg / mm ² ), silicon carbide (SiC, hardness 2300 kg / mm ² ), titanium carbide (TiC, hardness 3
000 kg / mm ² ).

That is, since carbon such as amorphous carbon and graphite is activated in terms of energy as compared with diamond, it selectively binds to radicals of a metal element in a plasma state to form hard carbide.

Thus, the present invention in growing the diamond film using the mixed gas of hydrocarbon and H ₂ gas such as CH ₄ as a source gas by plasma jet CVD method, sufficient reduction and removal action of the H ₂ gas is The hardness is improved by changing non-diamond components, which are mixed in a small amount in the polycrystalline diamond film, into hard carbide without being performed.

〔Example〕

Using the CVD apparatus shown in FIG.
Was used in which 8% was added.

Here, as the supply conditions of the raw material gas 8, the flow rate of hydrogen (H ₂ ) gas is 10 to 50 / min, and the flow rate of methane (CH ₄ ) gas is
The powder is supplied while changing in the range of 0.05 to 1 / min.
It was supplied at a rate of 01 to 0.1 cc / hour.

Next, the conditions under which CVD growth is possible are as follows.
kPa ~ 10kPa, arc current value is 10 ~ 70A and arc voltage value is
It is in the range of 50-150V.

FIG. 2 shows a Raman spectrum 14 of a film obtained by supplying W as an additive and a Raman spectrum 15 of a film without an additive. As can be seen from FIG. A broad peak of amorphous carbon is observed at around 1500 cm ^-1 .

On the other hand, the spectrum 14 of the film obtained by supplying W
^-1 diamond sharp peak can be observed and 1500cm
The peak of amorphous carbon near ^-1 is very low.

It was confirmed from the Raman spectroscopy that the diamond film thus synthesized contained very little non-diamond components.

The hardness of the diamond film thus formed was about 10,000 kg / mm ^2, which was close to that of natural diamond.

The conditions for forming the diamond film were the same when the carbide was formed by supplying each of Mo, Si and Ti from the powder supply pipe 9 as the metal powder, and was similar to the case of the WC formation. A diamond film with hardness was obtained.

〔The invention's effect〕

According to the present invention, it is easy to synthesize a diamond film having a small amount of non-diamond components such as amorphous carbon and graphite. By implementing the present invention, a diamond tool can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a plasma jet CVD apparatus used in the present invention, and FIG. 2 is a Raman spectrum distribution diagram. In the figure, 4 is a reaction chamber, 5 is a plasma jet, 6 is an anode, 7 is a cathode, 8 is a raw material gas, 9 is a powder supply pipe, 12 is an arc discharge, and 13 is a diamond film.

Claims (1)

(57) [Claims] A reaction system comprising a reaction chamber and a mixed gas of a hydrocarbon gas and a hydrogen gas supplied between an anode and a cathode provided in the reaction chamber while evacuating the reaction chamber by an evacuation system. When a diamond film is formed on a substrate to be processed by a plasma jet chemical vapor deposition method that generates a jet, tungsten capable of forming a hard carbide by combining with a non-diamond carbon component in the plasma jet is used. A method for synthesizing a diamond film, comprising adding an elemental powder of any one selected from the group consisting of molybdenum, silicon, and titanium.