JP2587636B2 - Diamond synthesis method and equipment - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for synthesizing a diamond, and more particularly to a method of transporting a substance by a chemical reaction and diffusion. And a method and apparatus for synthesizing diamond.

[Conventional technology]

Conventionally, as an apparatus for synthesizing diamond by a chemical transport method, an apparatus shown in FIG. 5 has been proposed. In this apparatus, the pressure inside the reaction vessel 41 is reduced by vacuum cocks 42 and 43 and a vacuum pump (not shown).

Hydrogen plasma is formed by the electrodes 44A and 44B connected to the high frequency power supply 44, and activated hydrogen ｛H ⁺ , H ^* (hydrogen radical)
CH _n ⁺ (n = 1, 2, 3,) is formed by a surface reaction between the material な_る and the raw material 45 composed of a carbon-containing compound, and carbon (C) is supplied into the gas phase by diffusion of the compound. The film-shaped or granular diamond is synthesized on the substrate 49 on the susceptor 50 heated through the heating coil 48.

On the other hand, an example of a hydrogen gas sputtering method, which is one of the physical transport methods that do not use the above-described chemical transport for the raw material introduction and the raw material transport used in the industrial process, will be described with reference to FIG. In FIG. 6, an exhaust port 52 is provided in a reaction vessel 51.
From the cathode 58 and the anode 60 via a high-frequency power supply 55 and a condenser 56.
Is applied in between. In this state, H ₂ gas is introduced from the gas inlet 54.

Hydrogen plasma is formed by the H ₂ gas, and H ⁺ in the hydrogen plasma collides with a target (graphite or amorphous carbon) 59 on a magnet 57 disposed at a tip of a pipe 53 into which cooling water is introduced. SP ³ rich DLC film which is defined on a molecular orbital method by reaction at the same time carbon and hydrogen ions out strike carbon from the target 59 (Diamond Like carbon
A film) is obtained and deposited on the substrate 61 to obtain a film-like or granular diamond.

[Problems to be solved by the invention]

However, in the case of diamond synthesis by the chemical transport method shown in FIG. 5, (1) carbon is formed in the gas phase in the reaction vessel 41 by ions and radicals generated by a surface reaction between activated hydrogen and a raw material containing carbon. Since the carbon is supplied, the amount of carbon supplied is limited, and therefore, the film forming rate is restricted. (2) If the carbon concentration in the gas phase during the film forming reaction is excessive, graphite is deposited on the substrate 49. When it is easily deposited on the surface and the carbon concentration in the gas phase is low, the film formation rate is too low even if diamond is formed. As described above, in the conventional method of synthesizing diamond by the chemical transport method, a system for controlling the supply of the raw material to the activated gas phase is not sufficiently considered.

On the other hand, in the case of diamond synthesis by physical transport shown in FIG. 6, (1) the raw material gas flow rate in the reaction vessel 51 is larger than that of chemical transport, so that the reaction rate of the raw material is lower than that of chemical transport. . (2) Since the flow rate of the source gas is large, the chemical reaction in the reaction vessel 51 is difficult to be uniform, so that the thickness and quality (composition) of the formed film are also difficult to be uniform. In the case of diamond synthesis by a physical transport method other than sputtering, there is also a problem that a large amount of raw material is introduced into the reaction vessel due to a low reaction rate of the raw material, and the raw material is wasted.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a method and apparatus for synthesizing a diamond in which the control of the carbon concentration in the gas phase is easy, the optimum diamond synthesis is possible, and the reaction rate is high. It is in.

[Means for solving the problem]

In order to achieve the above object, the present invention generates activated hydrogen by heating a plasma or a filament, and performs a surface reaction between the activated hydrogen and a raw material containing carbon and a positive ion present in the activated hydrogen. Accelerated by an electric field, CH _n ^* generated by reactive sputtering of the raw material containing carbon ^.
A radical represented by (n = 1, 2, 3, 4) and
The ion represented by CH _n ⁺ (n = 1, 2, 3) is chemically transported onto the substrate to produce a diamond layer on the substrate surface.

[Action]

H ^{+ in} activated hydrogen generated by activation of hydrogen gas
By accelerating the ions with an electric field and colliding them with a raw material containing carbon, the carbon concentration in the gas phase increases.

Then, at the time of sputtering, CH _n ^* (n = 1, 2, 3,...) By a surface reaction between incident H ⁺ ions and a raw material containing carbon.
4) and CH _n ⁺ (n = 1, 2, 3), and at the same time, the carbon atoms (C) and radicals (C ^* ) in the gas phase are more active than the carbon atoms in the raw material. Easily reacts with activated hydrogen to form CH _n ^* (n = 1, 2, 3, 4) and CH _n ⁺ (n
= 1, 2, 3).

At this time, by controlling the acceleration voltage of the positively charged particles, it becomes possible to control the carbon atom concentration and the carbon atom amount in the raw material, and the film thickness, particle diameter, and composition of the product can be made uniform, and the material other than diamond can be obtained. Generation can be suppressed.

(Example of the invention)

In the diamond synthesis method of the present invention, a carbon material is sputtered. Allotropes of carbon (eg, graphite, amorphous carbon) can be used as the raw material containing carbon, and paraffinic hydrocarbons can be used as the hydrocarbon. However, by simple hydrogen sputtering of these carbon-containing raw materials, an amorphous carbon or DLC film containing graphite is formed on the substrate surface. The reason is that carbon reacts with hydrogen to form CH _n (n = 1, 2, 3,
This is because the reaction of 4) is not sufficiently completed.

According to the present invention, when sputtering a carbon material, an activated hydrogen atmosphere (for example, containing 5 vo 1% or more of activated hydrogen) is formed by means of heating by plasma or filament, as in the case of the chemical transport method, A cathode is disposed on the side of the carbon-containing material so that the H ⁺ ions therein can be used for sputtering of the carbon-containing material, and positively charged particles collide with the carbon-containing material.

In the present invention, nuclides ΔC, CH _n , H ^{* in the} gas phase are determined by mass spectrometry, emission intensity analysis using a spectrum analyzer, or the like ^.
(Hydrogen radical), by measuring the relative amount of H ⁺ (hydrogen ions)}, the atomic C and C ^* of the amount in the gas phase with minimal, positive used in sputtering to increase the CH _n Concentration Charged particles ｛H ⁺ , CH _n ⁺ (n = 1, 2, 3, etc.)
It can be controlled by adjusting the equal acceleration voltage.

Hereinafter, embodiments of the device of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view showing an embodiment of the apparatus of the present invention.

In this diamond synthesizing apparatus, a vacuum cock 2 is provided at one end of a reaction vessel 1, a vacuum cock 3 is provided at the other end of the reaction vessel 1, and a pipe provided with the vacuum cock 3 is provided. Is connected to a vacuum pump 4.

In the reaction vessel 1, high-frequency electrodes 6A and 6B connected to a high-frequency power supply 5 are arranged to face each other. Further, a positive charged particle acceleration anode 8A connected to the DC power supply 7 and arranged on the inner side of the container with respect to the high-frequency electrode 6A, and a positive charged particle acceleration connected to the DC power supply 7 and used also as the high-frequency electrode 6B. A use cathode 8B is provided. Then, a raw material 9 containing carbon is placed on the positive charged particle acceleration cathode 8B.

A substrate heating susceptor 13 that can be heated by the heating coil 11 is installed in the reaction vessel 1 located on the vacuum cock 3 side from the electrode arrangement area.
12 are located.

The inner wall of the quartz reaction vessel 1 is coated with a carbon film in order to prevent contamination of SiO ₂ by sputtering due to plasma generated in the vessel.

Next, the operation of the diamond synthesizing apparatus configured as described above will be described.

Inside the reaction vessel 1 are vacuum cocks 2, 3 and a vacuum pump 4.
Thereby, for example, a vacuum state of about 10 ⁻³ Torr is obtained as an initial vacuum, and hydrogen gas is introduced into the reaction vessel 1.
In the reaction vessel 1, a voltage is applied between the high-frequency electrodes 6A and 6B, whereby a hydrogen plasma 10 is formed.

The H ⁺ ions in the hydrogen plasma 10 form CH _n ^* (n = 1, 2, 3, 4) and CH _n ⁺ (n = 1, 2, 3) by a surface reaction with the carbon-containing raw material 9. I do. The positive ions are accelerated by an electric field formed by a positive charged particle acceleration anode 8A and a positive charged particle acceleration cathode 8B connected to a DC power supply 7, and collide with a carbon-containing raw material 9.
By this collision, carbon is knocked out of the raw material 9, and carbon atoms (C) and radicals are interposed in the gas phase. The carbon atom (C) and the carbon radical are highly activated and react with activated hydrogen to react with CH _n ^* (n = 1, 2, 3, 4) and CH
_n ⁺ (n = 1, 2, 3) is formed. The CH _n ^* (n = 1, 2, 3, 4) and CH _n ⁺ (n =
1, 2 and 3) move to the substrate 12 side on the susceptor 13 heated by the chemical transport via the heating coil 11 and adhere to the substrate 12 in a diamond shape.

FIG. 2 is a schematic sectional view showing another embodiment of the apparatus of the present invention.

2 differs from the device shown in FIG. 1 in that a high-frequency electrode 6A connected to a high-frequency power source 5 in FIG.
6B is omitted, and a filament 14 is provided instead, and heat generated by the filament 14 is used instead of high-frequency plasma as a source of activated hydrogen.

In the apparatus shown in FIG. 2, it is desirable that the filament 14 is heated to 500 ° C. or more in order to form activated hydrogen. In the present invention, activated hydrogen can be formed by both high-frequency plasma and heating by a filament.

Example 1 In the apparatus shown in FIG. 1, graphite (average particle size: 6 μm, manufactured by Nippon Graphite Shoji) was used as the raw material 9, and H ₂ (purity: 99.999% or more) was used as an introduced gas. The operating conditions are as shown in Table 1.

As a result, a thin film adhered to the Si substrate 12 at a film formation rate of 20 μm / h. According to X-ray diffraction, this film was found to have the same peak as diamond, as shown in FIG. In addition, it was found by Raman spectroscopy that the diamond was diamond as shown in FIG. In the same manner, a 0.5 mm square film was sampled, and the film quality was measured. Raman spectroscopic analysis revealed that each film was a diamond-like film and did not contain amorphous carbon or graphite.

Example 2 Tungsten (with an outer diameter of 0.
1 mm) and heated to 1,000 ° C. under the same conditions as shown in Table 1. Under these conditions, the same results as in Example 1 were obtained.

In this case, it is considered that the same result as in the first embodiment was produced due to the generation of activated hydrogen due to the heating of hydrogen by the filament 14.

Conventional Example 1 A diamond synthesis apparatus shown in FIG. 5 was used under the operating conditions shown in Table 2. These operating conditions are different from those in Table 1 in that activated hydrogen is not accelerated by an electric field.

As a result, although the product on the substrate 49 was a single diamond, it was found that the film formation rate was about 1/10 of that of the first embodiment.

Conventional Example 2 A diamond synthesizer shown in FIG. 6 was used under the operating conditions shown in Table 3. The operating conditions are as follows:
00V, which is larger than that of the first embodiment.

As a result, it was found that the product on the substrate 61 had an amorphous carbon film.

〔The invention's effect〕

As described above, according to the present invention, the introduction amount of the raw material into the gas phase by sputtering increases, the CH ⁺ concentration generated by the reaction with H ⁺ ions increases, and at the same time, the reaction rate of activated hydrogen increases. Carbon in the gas phase (ions and radicals)
, The film formation rate is increased as compared with the chemical transport method, and amorphous carbon is not generated as in the case of simple hydrogen sputtering. Therefore, a desired diamond can be synthesized at a high film forming rate.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of the apparatus of the present invention,
FIG. 2 is a schematic sectional view showing another embodiment of the apparatus of the present invention, FIG. 3 is a graph showing an example of X-ray diffraction in the embodiment, and FIG. 4 is an example of Raman spectroscopic analysis in the embodiment. FIG. 5 is a schematic sectional view showing a conventional diamond synthesizing apparatus by a chemical transport method, and FIG. 6 is a schematic sectional view showing a conventional diamond synthesizing apparatus by a physical transport method. 1 ... Reaction vessel, 2, 3 ... Vacuum cock, 4 ... Vacuum pump, 5 ... High frequency power supply, 6A, 6B ... High frequency electrode, 7 ...
... DC power supply, 8A ... Positive charged particle acceleration anode, 8B ... Positive charged particle acceleration cathode, 9 ... Raw material (carbon-containing), 10 ...
Hydrogen plasma, 11 ... heating coil, 12 ... substrate, 13 ...
... susceptor, 14 ... filament.

Claims (7)

(57) [Claims] 1. A surface reaction between activated hydrogen generated by activation of hydrogen gas and a raw material containing carbon, and a positive ion existing in the activated hydrogen is accelerated by an electric field to react the raw material containing carbon. CH generated by sputtering
_A radical represented by _n ^* (n = 1, 2, 3, 4) and an ion represented by CH _n ⁺ (n = 1, 2, 3) are chemically transported onto the substrate, and a diamond layer is formed on the substrate surface. And a diamond synthesis method. 2. The diamond synthesis method according to claim 1, wherein said hydrogen gas is activated by plasma. 3. The diamond synthesizing method according to claim 1, wherein said hydrogen gas is activated by a heating means capable of heating to a temperature necessary for activating the hydrogen gas. . 4. The method according to claim 1, wherein said positive ion is CH _n ⁺ (n = 1, 2, 3)
And a diamond synthesis method according to claim 1, wherein H ⁺ is used. 5. The diamond synthesizing method according to claim 1, wherein said carbon-containing raw material is at least one kind of allotrope of carbon or hydrocarbon. 6. The method according to claim 6, wherein CH _n (n =
0, 1, 2, 3, 4) measuring the concentration, and controlling the accelerating voltage for sputtering so as to reduce the concentration of carbon radicals and carbon ions in the hydrogen gas based on the measured value. The method for synthesizing diamond according to claim (1). 7. A means for generating activated hydrogen by activating hydrogen gas in a reaction vessel which can be maintained in a vacuum state, and a DC power supply at both ends of an intervening region of the activated hydrogen generated by the means. A source containing carbon was placed on the cathode side with the connected anode and cathode, and a substrate for forming a diamond-like layer in a reaction vessel separated from the intervening region of the activated hydrogen was placed. Characteristic diamond synthesizer.