JPH0558782A - Device for vapor phase synthesis of diamond and method therefor - Google Patents

Abstract

PURPOSE:To attain high speed synthesis and enlargement of synthetic region by providing a pair of electrodes for generation of arc discharge between a plasma generator and a substrate holder in a device for vapor phase synthesis of diamond. CONSTITUTION:After the substrate 16 is fixed to the back side of the substrate holder 4 and the vacuum chamber 1 is evacuated to about 0.6Pa by the exhauster 9, an electric discharge gas (for example, argon gas) is fed between the anode 10 and cathod 11 of the plasma generator 2 from the gas introducing pipe 12 and arc discharge is generated by the power source 13 for ignition and hydrogen gas is added from the gas introducing pipe 12. Further, about 150A current from the constant current D.C. power source 14 is supplied between the electrodes to bring out the plasma jet 17 and the raw gas of diamond (for example, methane gas) is supplied from the gas introducing pipe 3 (pressure in the chamber is about 8000Pa). Then, when the plasma 17 is passed through between the electrodes 5, arc discharge is generated in an orthogonal direction to the plasma by supplying about 600V from the constant current D.C. power source 15. Next, the substrate 16 is irradiated for 30min until the substrate becomes 900 deg.C while closing to the plasma generator 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for synthesizing diamond in a vapor phase at high speed and in a wide range by using a plasma jet generated by arc discharge.

[0002]

2. Description of the Related Art The diamond vapor phase synthesis method under low pressure includes hot filament method, electron impact CVD method, direct current plasma CVD method, microwave plasma CVD method, magnetic field microwave plasma CVD method, combustion flame method, plasma jet. There is a CVD method or the like. Among these various synthesizing methods, the plasma jet CVD method has a feature that diamond can be synthesized at a high speed of several hundred μm / h by utilizing thermal plasma in a high temperature state of several thousand degrees.

That is, the plasma jet CVD method is a method of generating a plasma jet by arc discharge in a plasma generator and irradiating the substrate on a substrate holder having a cooling mechanism with the plasma jet to synthesize a diamond film. At that time, arc generation can be obtained by direct-current discharge or high-frequency discharge, but direct-current arc discharge is often used because of its simple structure, low cost, and easy generation of thermal plasma.

On the other hand, research on synthesizing diamond by direct current arc discharge using a plasma generator having an anode with a circular center hole and a cathode located at the center of the anode has been carried out by Fujitsu Laboratories [Kurihara et al. Academic Meeting of the Physical Society of Japan (1
987) 18p-T-3] and Seiichiro Matsumoto et al. Of the Institute for Inorganic Materials [Ceramics, Vol. 24, No. 5, P.I. 41
6 (1989)] and the like are known.

[0005]

Problem to be Solved by the Invention Plasma jet CV
The high-speed synthesis in the D method can be obtained by generating a high density of active species that contribute to diamond synthesis by using a plasma jet in a high temperature state of several thousand degrees generated by arc discharge. However, in the above-mentioned conventional method, there is a method of introducing an organic compound gas, which is a raw material of diamond, into the inside of the plasma generator, or a method of supplying it to the plasma jet from the vicinity of the plasma jet outlet outside the plasma generator. However, there were the following problems.

(1) When an active organic compound gas as a raw material of diamond is introduced into the plasma generator,
The dissociated carbon adheres to the anode surface to make the discharge unstable, make the discharge difficult to occur, or adhere to the plasma jet ejection port to disturb the shape of the plasma jet.

(2) When the source gas of diamond is supplied to the plasma jet from the vicinity of the plasma jet outlet outside the plasma generator, the source gas is introduced into the plasma generator in order to accelerate the decomposition of the source gas. Greater power must be supplied to the plasma jet.

3) The synthetic range of the obtained diamond is
It is small because it depends on the shape of the plasma jet.

Accordingly, it is an object of the present invention to provide a diamond synthesizing apparatus and a synthesizing method capable of obtaining stable arc discharge, efficiently decomposing diamond raw material gas to synthesize diamond at a high speed, and further expanding the diamond synthesizing region. It is in.

[0010]

The above object is to provide a pair of electrodes capable of generating a pair of arc discharges between a plasma generator and a substrate holder after or simultaneously with decomposition of a diamond raw material gas supplied by a plasma jet. This is achieved by applying a DC voltage in the direction orthogonal to the jet and superimposing the ionizing action of the arc discharge generated between the electrodes when the plasma jet passes between the electrodes.

[0011]

[Function] When synthesizing diamond, the substrate temperature is 500 to 1
The growth rate can be increased by setting the temperature to 100 ° C. and supplying a large number of excited species such as atomic hydrogen and methyl groups generated in the gas phase to the substrate surface.

Therefore, when a pair of electrodes capable of generating an arc discharge is installed in the vicinity of the substrate as in the present invention, the diamond raw material gas which has not been decomposed by the heat of the plasma jet and the excited species which have already been dissociated and formed are further excited. Can be promoted, the density of active species that contributes to diamond synthesis reaching the substrate can be increased, and the diamond synthesis rate can be improved. Furthermore, since the discharge space by the arc is formed and the active species are distributed in a wide range, the synthetic area of diamond can be expanded.

[0013]

The present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a vertical cross-sectional view showing an embodiment of the present invention. A gas introduction for supplying a plasma generator 2 into a vacuum chamber 1 and an organic compound gas as a raw material of diamond connected to the plasma generator 2. A tube 3, a water-cooled structure, a substrate holder 4 that can rotate and move freely in vertical and horizontal directions, an arc discharge generation electrode 5 installed between the plasma generator 2 and the substrate holder 4, a current introduction terminal 6, 7, a vacuum gauge 8 and an exhaust device 9 are attached.

The plasma generator 2 comprises an anode 10 made of oxygen-free copper and having a circular center hole, a cathode 11 made of tungsten containing thorium and a gas introduction tube 12 located at the center of the anode 10, and arc discharge is generated. An ignition power source 13 and a plasma jet drawing constant current DC power source 14 are connected in parallel. A constant current DC power supply 15 is connected to the arc discharge generating electrode 5, and the distance between the electrodes is set to 20 mm. The vacuum chamber 1, the substrate holder 4, the anode 10 and the cathode 11 are water-cooled so that the generated plasma jet does not melt or release gas.

In FIG. 1, the substrate holder 4 has a size of 15 × 15.
× A tungsten substrate 16 having a thickness of 1 mm is coated and fixed on the back side with silver paste, and the inside of the vacuum chamber 1 is evacuated by the exhaust device 9 until the reading of the vacuum gauge 8 becomes 0.6 Pa, and then the gas introduction tube. Argon gas as a discharge gas from 12 was made to flow between the anode 10 and the cathode 11 of the plasma generator ² at a pressure of 1.5 kg / cm ² and a flow rate of 15 l / min, and an arc discharge was generated by the ignition power source 13 to introduce the gas. Tube 12
More hydrogen gas pressure 1.5kg / cm ² , flow rate 2l / m
added in. Further, a constant current DC power supply 14 applies a current of 150 A between the electrodes to draw out a plasma jet 17, and a methane gas, which is a raw material of diamond, is supplied from the gas introduction pipe 3 at a pressure of 0.5 kg / cm ² and a flow rate of 0.075 l / m.
It was supplied to the plasma jet 17 in. The pressure in the vacuum chamber 1 at this time was 8000 Pa. Then, when the plasma jet 17 passes between the arc discharge generating electrodes 5, a DC voltage of 6 is generated by the constant current DC power supply 15.
It was applied to 00 V to generate arc discharge in a direction orthogonal to the plasma jet. Further, the movable substrate holder 4 brought the substrate 16 close to the plasma generator 2 until the substrate temperature of the substrate 16 reached 950 ° C., and irradiated for 30 minutes.

Methane gas which is a raw material of diamond is
It is dissociated by the heat of the plasma jet 17 and becomes an excited species such as a methyl group that contributes to diamond synthesis. By using the above device, when passing through the electrode 5,
The arc discharge generated in the direction orthogonal to the traveling direction of the plasma jet 17 promotes decomposition of undissociated methane and further activation of excited species. At this time, by bringing the electrode 5 close to the substrate and shortening the reaching distance to the substrate, active species having a short life can effectively act on the growth of diamond. Also,
Since the discharge space is created by the arc generated in the vicinity of the substrate, the distribution of the active species acts in a direction that spreads and the diamond synthesis region can be expanded.

When the film produced by the above-mentioned synthesizing apparatus and synthesizing method was analyzed by Raman spectroscopy, a sharp Raman spectrum of diamond was obtained at a position of 1333 cm to ¹ and the synthesis of diamond was confirmed. The film thickness was 50 μm (synthesis speed 100 μm / h), and the film was synthesized on the entire surface of the substrate.

On the other hand, when no arc discharge is generated in the arc discharge generating electrode 5 under the synthesizing conditions according to this embodiment, the synthesizing speed is 20 μm / h and the film size is 10 m in diameter.
It was m.

In this embodiment, the constant current DC power supply 15 connected to the arc discharge generating electrode 5 has a power output of 600 W. However, by using a power supply with a large output, the effect of the present invention is further enhanced. be able to. In that case, it is necessary to prevent the melting due to heat generation by cooling the structure of the electrode 5 with water.

FIG. 2 shows another embodiment of the present invention. The apparatus configuration is almost the same as that of the apparatus used in the above embodiment, but in this embodiment, a DC voltage was applied to the diamond raw material gas supply gas introduction tube to generate arc discharge.

In the vacuum chamber 1, a plasma generator 2,
A water-cooled substrate holder 4, which is rotatable and freely movable in vertical and horizontal directions, is located between the plasma generator 2 and the substrate holder 4, and has a hollow cylindrical shape of molybdenum (high melting point metal) through an insulating insulator 18. An arc discharge generating electrode 5 manufactured by the company is connected, and a gas introduction pipe 3 for supplying an organic compound gas as a raw material of diamond, current introduction terminals 6, 7, a vacuum gauge 8 and an exhaust device 9 are attached. The plasma generator 2 is an anode 1 with a circular center hole made of oxygen-free copper.
0, a cathode 11 made of tungsten containing thorium located in the center of the anode 10 and a gas introduction tube 12, and an ignition power supply 13 for generating an arc discharge and a constant current DC power supply 14 for drawing a plasma jet are connected in parallel. Has been done. Further, a constant current DC power supply 15 is connected to the arc discharge generation electrode 5, and the inter-electrode distance is set to 20 mm. The vacuum chamber 1, the substrate holder 4,
The anode 10 and the cathode 11 are water-cooled so that the generated plasma jet does not melt or emit gas due to the heat of the generated plasma jet.

In FIG. 2, the substrate holder 4 is provided with 15 × 15.
× A tungsten substrate 16 having a thickness of 1 mm is coated and fixed on the back side with silver paste, and the inside of the vacuum chamber 1 is evacuated by the exhaust device 9 until the reading of the vacuum gauge 8 becomes 0.6 Pa, and then the gas introduction tube. Argon gas as a discharge gas from 12 was made to flow between the anode 10 and the cathode 11 of the plasma generator ² at a pressure of 1.5 kg / cm ² and a flow rate of 15 l / min, and an arc discharge was generated by the ignition power source 13 to generate hydrogen gas. Pressure 1.
It was added at 5 kg / cm ² and a flow rate of 2 l / min. Further, a constant current DC power supply 14 applies a current of 150 A between the electrodes to draw out a plasma jet 17, and a methane gas, which is a raw material of diamond, is supplied from the gas introduction pipe 3 at a pressure of 0.5 kg /
It was supplied to the plasma jet 17 at cm ² and a flow rate of 0.075 l / min. At this time, the pressure in the vacuum chamber is 80
It was 00 Pa. Then, when the plasma jet 17 passed through the arc discharge generation electrode 5, a DC voltage of 600 V was applied to the arc discharge generation electrode 5 by the constant current DC power supply 15 to generate arc discharge. Further, the movable substrate holder 4 brought the substrate 16 close to the plasma generator 2 until the substrate temperature of the substrate 16 reached 950 ° C., and irradiated for 20 minutes.

When the produced film was analyzed by Raman spectroscopy, a sharp Raman spectrum of diamond was obtained at a position of 1333 cm- ¹ and it was confirmed that diamond was synthesized. The film thickness was 30 μm (synthesis speed 90 μm / h), and it was synthesized on the entire surface of the substrate.

[0024]

As described above, according to the present invention, since a highly reactive organic compound gas is not introduced into the plasma generator, stable arc discharge can be obtained in the plasma generator.

Further, due to the arc discharge of the arc discharge generating electrode provided between the plasma generator and the substrate holder, the diamond raw material gas is further activated in the vicinity of the substrate, and the active species contributing to diamond synthesis. Will be promoted, resulting in an increased synthesis rate.
In particular, active species having a short life can be used more effectively than before for the growth of diamond. Furthermore,
Since the active species generation space can be formed in the vicinity of the substrate by arc discharge, the synthetic area can be made wider than before.
In addition, among the atomic hydrogen generated in the plasma generator, the hydrogen atoms that recombine by the time they reach the substrate and become hydrogen molecules can be dissociated again into atomic states, and become diamond impurities. It also has the effect of increasing the removal rate of amorphous carbon and improving the quality of diamond produced.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the present invention.

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

[Explanation of symbols]

1 is a vacuum chamber, 2 is a plasma generator, 3 is a diamond raw material gas introduction tube, 4 is a cold substrate holder, 5 is an electrode for generating an arc discharge, 6 and 7 are current introduction terminals, and 8 is a vacuum gauge.
Reference numeral 9 is an exhaust device, 10 is an anode, 11 is a cathode, 12 is a gas introduction tube, 13 is a power source for ignition, 14 and 15 are constant current DC power sources, 16 is a tungsten substrate, 17 is a plasma jet, and 18 is an insulator. is there.

Claims (4)

[Claims] 1. A plasma generator having an anode having a circular center hole and a cathode positioned at the center of the anode to generate an arc discharge, and a gas introduction pipe connected to the plasma generator for supplying a diamond source gas. Diamond plasma phase consisting of a plasma jet drawing power supply, two arc discharge generating power supplies, a water-cooled substrate holder that can rotate and move freely in vertical and horizontal directions, a vacuum chamber equipped with a vacuum gauge and an exhaust device In the synthesizer, a pair of arc discharge generating electrodes is provided between the plasma generator and the substrate holder, the diamond vapor phase synthesizer. 2. A plasma generator having an anode having a circular center hole and a cathode positioned at the center of the anode to generate an arc discharge, a plasma jet drawing power source, two arc discharge generating power sources, and a water cooling structure. In a diamond vapor phase synthesizing apparatus comprising a substrate holder that can rotate and move freely in vertical and horizontal directions, a vacuum chamber equipped with a vacuum gauge and an exhaust device, an insulating insulator is provided between the plasma generator and the substrate holder. A diamond vapor phase synthesizing device comprising a pair of gas feed pipes for supplying a diamond raw material gas, which are connected to electrodes for arc discharge generation via the above. 3. A mixed gas of an inert gas and hydrogen gas or hydrogen gas is supplied between an anode and a cathode of a plasma generator, arc discharge is generated between the electrodes, and the gas is decomposed into thermal plasma. A plasma jet is jetted, a diamond source gas is supplied to the plasma jet from a gas introduction tube attached to the plasma generator, and a voltage is applied to an arc discharge generation electrode installed vertically below the gas introduction tube. A diamond film is formed by applying an arc discharge when the plasma jet passes between the electrodes, ionizing the plasma jet, and then irradiating the optimal plasma jet on the substrate surface attached to the water-cooled substrate holder. A method for vapor phase synthesis of diamond, characterized in that the vapor phase growth is performed. 4. A mixed gas of an inert gas and hydrogen gas or hydrogen gas is supplied between an anode and a cathode of a plasma generator, arc discharge is generated between the electrodes, and the gas is decomposed into thermal plasma. A plasma jet was made to be jetted, and a diamond raw material gas was supplied to the plasma jet from a pair of gas introduction pipes installed to face each other between the plasma generator and the substrate holder and connected to the gas introduction pipe. A voltage is applied to the electrodes for arc discharge generation, arc discharge is generated when the plasma jet passes between the electrodes, and after the plasma jet is ionized, the optimum plasma jet on the substrate surface attached to the water-cooled substrate holder A method for vapor-phase synthesis of diamond, characterized in that a diamond film is vapor-phase grown by irradiating a diamond.