JPS58110494A - Synthesizing method for diamond - Google Patents

Abstract

PURPOSE:To synthesize granular or filmlike diamond stably by introducing a gaseous mixture of gaseous H2 passed through the inside of microwave nonpolar discharge and hydrocarbon into the surface of a substrate heated to specific temps. and thermally decomposing the hydrocarbon. CONSTITUTION:After a reacting system is evacuated to 0.05-400Torr by driving an evacuating device 6, the gaseous H2 in a supply device 2 is passed through the inside of the microwave nonpolar discharge generated from a waveguide 4 by a microwave oscillator 3 to grow H in an excited state or atomic state. The H is mixed with hydrocarbon (e.g.; methane) supplied from a supply device 1 and the mixture is introduced into a reacting chamber 5, where the mixture is supplied onto the surface of a substrate 7 on a susceptor 9 heated to 300- 1,300 deg.C by a resistance heating furnace 9, whereby the hydrocarbon in the excited state is thermally decomposed and diamond is deposited. Thus the control of nucleus forming speed is facilitated and the granular or filmlike diamond is synthesized easily.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for synthesizing diamond by chemical vapor deposition method K.

For some time now, the following method has been known as a diamond synthesis method using vapor phase precipitation method K.

1》 Heat the hydrocarbon and introduce it into the nine substrate surface,
] A chemical vapor deposition method in which diamond is precipitated by thermal decomposition with one energy to generate free carbon.

2》 Combining arc discharge and sputtering technology,
An ion/beam method that generates a positive carbon ion beam, accelerates it, focuses it, and causes it to collide with the substrate surface to deposit diamond.

3. A chemical process in which a direct current discharge is generated between the electrodes, and the high-energy electrons during the discharge are used to release the chemical bonds of hydrocarbons, simultaneously generating carbon atoms in the K excited state, and depositing diamonds on the substrate surface. Vapor phase deposition method.

4) Graphite. A substrate and hydrogen gas are sealed, graphite is placed in a high-temperature area and the substrate is placed in a low-temperature area, and the hydrogen gas is thermally or electrically discharged to generate atomic hydrogen. There are chemical transport methods that precipitate diamonds.

The chemical vapor deposition method in 1) above is performed under reduced pressure at ttoo Pcm.
:'p. "; Plate...1゛1 Heat hydrocarbons on the surface of the substrate heated to a temperature below sj+l
TI1l to form a diamond layer, j〆-4.
11. Extremely stable graphite. Analysis of non-diamond carbon is unavoidable.

These inhibit diamond formation. Therefore, by periodically introducing the precipitation operation, oxygen gas, and hydrogen gas,
It is necessary to repeat the operation to remove graphite and non-diamond carbon deposited on the substrate surface. Further, there are drawbacks such as slow deposition rate and the substrate being limited to diamond κ.

1"゜"""""""'゛"゜" 1゛Advantages of being able to deposit diamond on the noodle surface ◇The equipment that generates the carbon positive ion beam and its focusing device are expensive, and the discharge life is short. There are drawbacks such as K incorporation into the precipitated diamond lattice by atoms of the inert gas used subsequently.

In the method described in 3 above, in which plasma is generated periodically to combine with diamond in synchronization with the introduction of the reactant gas, it is difficult to maintain the plasma density uniformly throughout the area. be. Due to this non-uniform density, there is a drawback that κ non-diamond carbon other than diamond is precipitated.

't: The chemical transport method described in note 4) is a sealed tube method, which uses monocarbohydrate produced by the reaction between a gate and atomic hydrogen in a sealed tube, which makes continuous operation difficult. It is. It also has the disadvantage that synthesis conditions such as the concentration of reaction gas, its ratio, and heating temperature cannot be varied independently.

The method of the present invention is intended to improve the drawbacks of the conventional method described above, and the concentration of the reactant gas. It is easy to change the synthesis conditions such as the ratio, heating temperature, and power of the reaction system, and it is possible to stably synthesize diamond or film diamond on the surface of the substrate. This is what we provide.

The present invention is a mixed gas in which hydrogen gas is passed through a microwave non-polar electric discharge and mixed with hydrocarbons. The above object is achieved by a method in which diamond is precipitated by thermal decomposition of excited hydrocarbons by introducing a gas into the surface of the substrate heated to 300-/300''CK.

The principle of the method of the present invention is as follows: The temperature at which graphite is thermodynamically stable. To synthesize diamond using pressure. It is necessary for k to satisfy the following conditions: 9 carbon atoms must be separated individually, these carbon atoms must be in an excited state K, and this excited state must last until the diamond nucleus is formed. It is.

In addition, free carbon generated during the thermal separation of hydrocarbons is also used. In order to grow diamonds, it is necessary to supply free carbon PK with sufficient reaction energy to produce the ``combination seed'' of the diamond.

KO V'"゜"'""゛"""' After passing through a polar discharge, it is mixed with a hydrocarbon, 1. After mixing a hydrocarbon and hydrogen gas, it is passed through a microwave non-polar discharge. Hydrocarbons in an excited state.Hydrogen in an excited state or an atomic state is produced.This excited hydrocarbon is heated and thermally decomposed on the surface of the substrate, and the surface of the excited state is sufficient to cause sp S bonds to the free carbon atoms that are produced. Provides the reaction energy.Hydrogen in the excited state and in the atomic state is responsible for the growth of graphite and non-diamond carbon.
princess. It reacts with Kuken which has 4 bonds, and converts this into & , . , converts into carbon dioxide, or produces hydrocarbons, and acts to clean the surface on which diamonds grow.

-o: 2 In the method of the present invention, microwave non-polar discharge was employed in order to sustain stable discharge. In the case of DC discharge, electrodes are used, so it is difficult to generate a discharge continuously for a long time because the electrodes will be damaged.

Kawamata is a constant source of electricity with a beast wave frequency of several megahertz or less. ! U
．． I+-1J (7) 1ka. , 4O, ,I, Shep polar discharge can reduce the pressure dependence of the system. be.

The mixing ratio of hydrocarbon and hydrogen gas in the mixed gas used can be varied over a wide range, but from the viewpoint of preventing precipitation of graphite and non-diamond carbon, it is desirable that the upper limit is 70 or less. Approximately O to synthesize granular diamond
．． In order to precipitate expanded diamond, it is desirable that the value be less than 0.

In the group 1f, the precipitated diamond is transferred to graphite VC*'d.
The temperature is preferably 300-/300'C, since it is necessary to prevent the phenomenon of thermal decomposition and cause thermal decomposition on the surface of the hydrocarbon 121 substrate. Particularly preferred is SOO~/000''C.

The pressure inside the tube that generates non-polar electric discharge is kept at 0.0 to maintain stable discharge. A range of OJ-1100 Torr is good.

? -2. ．． 1. Since the method of the present invention is an open-tube method, the mixing ratio of hydrocarbons and raw materials is very low. Gas flow rate, base temperature
>Adjust the direction of the microwave oscillator in the furnace 1゛t,;y′ field=! mi::. Therefore, it is an excited state hydrocarbon. hydrogen. Since the amount of hydrogen produced in the atomic state can be independently controlled, it is easy to control the degree of hydrogen formation.

If you control the speed of this S shape, it will be K second granular diamond. Alternatively, film-like diamond can be easily combined with κ.

Next, the embodiments of the apparatus for carrying out the method of the present invention are shown in FIG. 1 and FIG. Figure 1 shows hydrogen gas passing through a microwave non-electrode discharge with 9'=. ``@l. It is a method of mixing with hydrocarbon gas. 11 "This is a method of passing through a non-polar discharge. Figure 7. In the first figure, /Vi hydrocarbon gas supply device, ``H'' hydrogen gas supply device, 3Fi microwave oscillator, ``Wave guide'', and sVi reaction chamber. , B is an exhaust device. A support stand l for supporting a substrate 7 is installed in the deposition chamber 5, and in FIG. 7, a 1k frame is heated in a resistance heating furnace 9. In FIG. An infrared concentrated irradiation furnace that focuses the light emitted from a halogen lamp/σ heating is performed./λ, 13
, /l is a cock that adjusts the flow rate of hydrogen gas, 1, 1 hydrocarbon gas and the pressure inside the device. /5 is an exhaust port.

After installing the substrate 7 on the support inside the reaction chamber S, the exhaust device t
Activate to reduce the pressure inside the device, and at the same time,
/3 and /da are adjusted to maintain the hydrogen gas flow rate and the pressure inside the device at predetermined values. Next, the substrate is maintained at a predetermined temperature using a resistance heating furnace.

In the case of an infrared concentrated irradiation furnace, the substrate temperature is controlled by adjusting the current flowing through the halogen lamp. Next, the microwave oscillator is activated to generate i-microwave non-polar electric discharge, and hydrocarbon gas whose flow rate is adjusted in advance by K% is introduced.

Example t Molybdenum is used as a substrate, and meta/gas and hydrogen gas are used as reaction gases. Activate the exhaust system to reduce the pressure in the reaction system. Next, κ hydrogen gas is supplied at a flow rate of 100 cc/min, and the cocks /2 and /J are adjusted to maintain the pressure in the reaction system. Adjust Storr IIC. A microphone single-wave oscillator K generates a non-polar electric current. Next, 11. gf900
``On the cllc?'' 5, 2, 1 Gas is supplied at a flow rate of α per minute, mixed with the hydrogen gas that has passed through the non-polar electrode discharge, and introduced onto the heated substrate.3
Time-long precipitation was performed to obtain a diamond precipitated layer with a thickness of about K/μm on the surface of the substrate.

Example 2 A silicon wafer is used as a substrate, and methane gas and hydrogen gas are used as reaction gases. Activate the exhaust system to reduce the pressure of the reaction system. Next K hydrogen gas, hydrocarbon gas each per minute/Q
When supplied with Q ee , /J cc , κi . ”
・ , , 77 , . −
(,Iyln, 't'/'@ILr・Hi bond 0" egg ゜゜'.-7 rr. Next, set the base temperature to 700
As well as causing the CK to rise, the microwave oscillator generated a slight chargeless discharge. Deposition was carried out for 3 hours, and diamond particles of about micrometer size were deposited on the substrate surface.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of a synthesis apparatus for carrying out the method of the present invention. 1/... Hydrocarbon gas supply device, 3... Hydrogen gas supply station, 3... Microwave oscillator, 1 l-1 Hiro... Wave guide, S... Reaction chamber, ゛World 5... Exhaust system, 7... Board,!・・・
- Support stand, 9...Heating furnace, /θ...Infrared concentrated irradiation furnace, //...Halogen lamp. /J,
/3, /l...cock s /j...exhaust port. -5861

Claims (1)

[Scope of Claims] t Hydrogen gas is passed through a microwave non-electrode discharge and a mixed gas mixed with a hydrocarbon is passed through a microwave non-electrode discharge. A diamond synthesis method characterized by introducing a mixed gas of 300~/JOO"CK onto the surface of a heated substrate to precipitate diamond through thermal decomposition of hydrocarbons. 2. Combination of hydrocarbons and hydrogen gas. Mixing ratio is ioo~o.o.
oi.