JPS616199A - Process and apparatus for synthesizing diamond in gaseous phase - Google Patents

Abstract

PURPOSE:To synthesize diamond in the gaseous phase at low temp. with high speed by decomposing and exciting a gaseous mixture consisting of hydrocarbon and H2 in the discharge of high frequency or microwave and irradiating generated plasma with ultraviolet rays or visible rays. CONSTITUTION:After setting a substrate 1 having the surface cleaned by chemical etching on a susceptor 2, the inside of a quartz reaction tube 4 is evacuated 5 to 10<-6>Torr. Then, simultaneously inside of a vacuum vessel 6 is replaced with N2 7 or evacuated 10 to 10<-6>Torr. Then, after evacuating the inside of the reaction tube 4 previously, the substrate 1 is heated to a specified temp. by a halogen lamp 12 and hydrocarbon 13 and H2 14 are introduced into the reaction tube 4, and high frequency is impressed using a high frequency oscillator 17. After generating plasma by this method the light from a generator 20 of ultraviolet rays or visible rays is irradiated, and reaction is carried out for a specified time. As the result, a diamond film is formed on the substrate at low temp. with high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method and apparatus for depositing diamond on a substrate from a gas phase.

(Prior art and its problems) Several methods have been used to synthesize diamond by thermal decomposition of carbon compound gas. For example, in the method described in JP-A-47-42286, diamond ridge crystal powder is placed in a catalyst heater using hydrogen gas as a carrier gas, and the particle size of diamond single crystal can be increased using the following reaction. It reveals something.

CnH2n+2-) C (diamond) + H2 (however, n≦5) Generally, in the case of a diamond gas phase threat, the precipitation of amorphous carbon and graphite other than diamond prevents the subsequent precipitation of diamond.

It states that by the action of a catalytic heater such as platinum or palladium, it can be removed by the following reaction on diamond.

C (amorphous carbon or gelaphite) +'2H, →C
H4 However, in order to grow the evening diamond,
It has the disadvantage of requiring a diamond seed crystal. That is, there is a drawback that diamond cannot be deposited on a substrate made of other materials.

Furthermore, it has the disadvantage that the diamond seed crystal must be maintained at a high GAr. Furthermore, it has the disadvantage that in addition to the process of synthesizing diamond, a process of removing eutectoid non-diamond carbon must be performed.

There are also other methods, such as the Japanese Journal of Applied Physics published in 1982.
panese Journal o(Applied
Physics) Volume 21, No. L, page 183 n
Urabun describes a method in which methane gas is heated in contact with a tungsten heater heated to approximately 20°C (10°C) using hydrogen as a carrier gas, thermally decomposed, and diamond is deposited on a silicon, molybdenum, or quartz glass substrate. I'm being discouraged.

This method is an excellent method in that it allows diamond to be precipitated on materials other than diamond, but since the heater in the tungsten is heated to a high temperature of about 2 (100°C), the tungsten itself The vapor pressure also increases, causing problems such as being consumed in a short period of time and evaporated tungsten adhering to the diamond surface.Also, once heated, the tungsten heater is unable to react due to the interaction between tungsten and carbon and the absorption of gas molecules. Because of this, it becomes extremely brittle and easily susceptible to drunkenness, so the tungsten war heel must be changed frequently, and it cannot be worn for long periods of time.
It is difficult to decide whether to do so. In addition, changes over time in the tungsten heater cause fluctuations in the thermal decomposition of the reactant gas, and it is the inner fan that uniformly deposits A-shaped diamond over a wide area. Furthermore, diamond has a high degree of precipitation unevenness, which has the disadvantage that its practical use is limited.

An example of a diamond vapor phase synthesis method using microwave discharge is the method described in Japanese Patent Laid-Open No. 110494/1983. That is, after hydrogen gas is passed through a microwave electrodeless discharge, a mixed gas mixed with a hydrocarbon, or a mixed gas of a hydrocarbon and hydrogen passed through a microwave electrodeless discharge, is The diamond is introduced into the surface of the substrate heated to 1300° C., and diamond is precipitated from the heat of the excited hydrocarbon.

However, this method uses only thermal energy to thermally decompose excited hydrocarbons on the substrate, and has the disadvantage of having to be heated to the temperature of a rose pot in order to obtain sufficient energy. There is.

Furthermore, the energy range given to the reaction residue by microwave radiation is wide, and there is a drawback that it is not possible to selectively give only the single or close to single-l energy necessary for diamond synthesis.

A diamond vapor phase sweetening method using high-frequency discharge is described, for example, in 7"Rossidainx International ψion Engineering-Concres (Procedings o) published in 1983.
International Ion Engine
The method described on page 1137 of ``Eering Congress'' is rather effective. That is, a mixed gas of methane and hydrogen is subjected to high-frequency discharge at a pressure of 10-1500 Pascals, and diamond-like carbon is deposited on a substrate heated to 700-900°C.

However, when the substrate temperature is low, mainly amorphous carbon is precipitated. That is.

It has the disadvantage that diamond cannot be synthesized at low temperatures.

Furthermore, the range of energy applied to one reaction gas is wide, which has the disadvantage that precipitation of non-diamond carbon cannot be completely prevented.

(Object of the present invention) The object of the invention is to eliminate such conventional drawbacks,
An object of the present invention is to provide a diamond vapor phase synthesis method and apparatus for synthesizing diamond alone at low temperatures and high speeds.

(Structure of the Invention) That is, 1. The present invention is a diamond vapor phase synthesis method in which a mixed gas of hydrocarbon and hydrogen is decomposed and excited in high frequency or microwave discharge to deposit diamond on a substrate. or a diamond vapor phase synthesis method characterized by irradiating with visible light;
and a reaction tube that is connected to a gas supply section and a vacuum exhaust system and in which a substrate can be placed, and a substrate heating means.

In a diamond vapor phase synthesis apparatus equipped with an ultraviolet or visible light irradiation light source and a plasma generation coil or electrode, the ultraviolet or visible light irradiation light source and the plasma generation coil or electrode are located outside the reaction tube and in a vacuum or Make sure it is installed in a nitrogen atmosphere! This is a diamond vapor phase synthesis device with special features.

(Detailed Description of Configuration) The present invention solves the problems of the prior art by adopting the above-described configuration.

Generally, to synthesize diamond from a gas phase, a vapor of a carbon compound is used as a carbon source. However,
The process of Tiemone precipitation from the gas phase requires artificial manipulations to stabilize the thermodynamically metastable phase. It is obvious that if free carbon atoms are obtained only from thermal decomposition of reaction residue, non-diamond carbon will be deposited on the 5-substrate. Furthermore, even in methods using plasma, the internal energy range of the plasma is wide, and it is obvious that non-diamond carbon will precipitate from a range outside the conditions for diamond carbon to precipitate. Therefore, if conditions are created to precipitate diamond carbon in a plasma manner, a single diamond can be synthesized. In the conventional technology, diamond carbon is synthesized on the substrate surface by applying thermal energy, but if the energy of ultraviolet or visible light is used instead of this thermal energy, the substrate temperature can be lowered. Ru. Furthermore, by irradiating the plasma with ultraviolet rays or visible light, the distribution of plasma species, such as radical species and ion species, can be changed, making it possible to control plasma species that tend to deposit diamond carbon.

The angle of irradiation of ultraviolet or visible light (this can be done from above the substrate or from the side of the substrate, but rather than irradiating only one reactive gas molecule or plasma species), the power of irradiating photons onto the substrate surface is more effective than irradiating light onto the substrate surface. It is preferable to irradiate the light from above the substrate because it can be expected to lower the temperature.

As the irradiation position of ultraviolet or visible light, after irradiation with high frequency or microwave number after-claw light,
Although a method of introducing the reaction scum into the substrate may be considered, after irradiation, the internal energy of the reaction scum changes and control is difficult (because of this, it is preferable to irradiate light from above the I&M substrate.

The substrate temperature is oTbm from room temperature to 1000°C.

If the temperature can be lowered from above the Amakawa River, it is desirable to keep it below 800 degrees Celsius.

As a substrate heating method, internal heater heating, lamp heating, high frequency induction heating, etc. can be considered, but lamp heating is preferable because of ease of control. The substrate may be an insulator, a semiconductor, or a conductor. By placing the ultraviolet or visible light irradiation section and the plasma generation section in a nitrogen atmosphere or vacuum and separating them outside the reaction chamber, it is possible to control the yield due to noise generated from the plasma, and to eliminate the difficulty of the light irradiation section 41J + wholesale. Furthermore, it is possible to increase the light transmittance and the reactivity between the reactive gas and photons.

An example of an apparatus used in the present invention and a manufacturing process will be described below using one drawing.

Figures 1 to 4 schematically show the experimental apparatus used in this experiment. Figure 1 shows an apparatus in which the high frequency discharge from the coil 21 is of the 116 conductive coupling type, and the afterclaw plasma is applied to the substrate. FIG. 2 shows an apparatus for introducing Acta-Claw plasma of microwave discharge from a wave kite 19 to a substrate. Figure 3 shows how the high-frequency discharge is capacitively coupled and the substrate is brought into contact with the IM plasma by applying a voltage between the two electrodes 22 installed on the outside of the reaction tube 4 (hereinafter referred to as ``4''). It's exposed.

Figure 4 shows a high-frequency discharge with capacitive coupling and two links n.
This shows a device in which a high frequency wave is applied between the plasma and the substrate is directly placed in the plasma region.

Actually, * was carried out mainly using the apparatus shown in FIG. 1, but the manufacturing process is the same even if the apparatus shown in FIGS. 1 to 4 is used.

In Figs. 1 to 4, after a substrate 1 whose surface has been cleaned by chemical etching is placed on a SiC-coated graphite susceptor 2, the inside of a quartz reaction tube 4 is preliminarily pumped to 10"'' torr by a vacuum evacuation system 3. Vacuum. Exhaust gas is exhausted from the exhaust port 5. At the same time, the inside of the (stainless steel) vacuum chamber 6 is replaced with N2 by opening the cocks 8 and 9 from the cylinder 7, or the cocks 8 and 9 are closed and the inside of the vacuum chamber halo is evacuated to 10-6 Torr using the vacuum exhaust system 10. do. The exhaust residue is exhausted from the exhaust port 11.

The inside of the vacuum chamber 6 was changed to Nt it or evacuated in order to efficiently introduce ultraviolet rays into the quartz reaction tube 4. After the interior of the quartz reaction y4 was preliminarily vacuumed, the substrate 1 on the susceptor 2 was heated to a predetermined temperature using the Haloken lamp 12. Hydrocarbons and hydrogen, which are reaction gases, were introduced into the quartz reaction tube 4 by opening the pipes 15 and 16 from the hydrocarbon cylinder 13 and the hydrogen pipe 14, and the pressure was adjusted to a predetermined pressure by the evacuation system 3. In the device shown in FIG. 1.3.4, a high frequency is applied from a flat frequency oscillator 17, and in the device shown in FIG. 2, a microwave is oscillated by a microwave oscillator 18.
Microwaves were introduced into the quartz reaction tube 4 through the waveguide 19 . After the plasma was generated, light was irradiated by an ultraviolet light or visible light generator 20 to cause a reaction for a predetermined time.

(Example 1) Experiment 1 shown in Fig. 1 shows an example using the system.The experimental conditions were: phosphorus on the substrate, methane on the hydrocarbon, a methane flow rate of lω per minute, a hydrogen flow rate of 100 marks per minute, Set the board temperature to 2
00℃, pressure 1 torr, station frequency 13.56
The reaction was carried out by irradiating ultraviolet rays for 3 hours using a low pressure mercury lamp with an output of 4-600'vV at MHz.

The deposited film had a rough texture, and when the surface was observed using a scanning Seiko microscope, no irregularities were observed and the surface flatness C1 was good. When observed with a transmission electron microscope, a Debye ring was obtained from the first diffraction pattern that matched the lattice spacing of the diamond. From one bright field image.

This film turned out to be made up of several tens of particles. When aluminum is deposited to form a M■S structure and the 1M low resistivity is measured, it is almost constant over the entire substrate, about 101
It was found that the resistivity was very high, 40. 4 thickness is approximately 20 μm, and the growth rate is approximately 7 μ7 per hour.
It was n. The hardness was approximately 800% Hv.

(Example 2) An example using the experimental apparatus shown in FIG. 2 will be described. The actual conditions are: quartz glass for the substrate, propane for the hydrocarbon, propane flow rate at 1/min, hydrogen flow rate at 200Ω/min, substrate temperature at 1000G, pressure at 5 Torr, and microwave frequency at 2.
．． 5 GH2, 600 W light was reacted by irradiating ultraviolet light for 3 hours using a microwave UV light source.

The deposited film was brownish, but had good surface flatness. Using a transmission germination microscope, the film was found to be a diamond film made up of dozens of particles. The growth rate was about 41 μm in 3 hours, which was about 14 μm per hour.The hardness was measured at about 70 μm.
It was 00Hv.

(Example 3) As six experimental conditions showing an example using the experimental apparatus shown in Fig. 3, the substrate is a molybdenum plate, the hydrocarbon is acetylene, the acetylene flow rate is g-cc per minute, the hydrogen flow rate is 200 g-cc per minute, The substrate temperature was 300° C., the pressure was 5 Torr, the radio frequency was 400 KHz, the output was soow, and a xenon lamp was used for light, and ultraviolet light and visible light were irradiated. After reacting for 3 hours, a 20 μm precipitate was obtained on the substrate. The growth rate was about 7 μm per hour, and the precipitate was identified by a transmission electron microscope to be diamond. Bright-field images revealed that this film was composed of several dozen particles. The hardness was measured to be approximately 50 (lOHv).

(Example 4) A low pressure water lamp (I.=9Q mW, 2537
A), the inside of the vacuum chamber is filled with air, N, 1 atm,
N.

10 Torr, vacuum (10-' Torr), and measuring the illuminance at the substrate position, we find that vacuum (ssmw) - N2'lO Torr (8 QmW), N, 1 atm (50 mW), and air (3
By creating a nitrogen or vacuum atmosphere inside the vacuum chamber, we were able to increase the illuminance and increase the probability of collision between the reactant gas and photons.

(Effects of the Present Invention) According to the present invention, a complete diamond film can be deposited on a substrate. The growth rate of conventional technology is 1 to 2 μ/hour.
m, but the maximum was about 6μ7n.

According to the present invention, diamond can be synthesized several times faster and at lower temperatures. The crystal structure of the synthesized film matched that of diamond, and it exhibited high hardness and high insulation properties.

The present invention achieves low-temperature synthesis and high growth rate of a diamond film, and is extremely useful in a wide range of industrial applications such as wear-resistant coach ink materials and heat dissipating substrates for IC substrates.

In the apparatus of the present invention, the ultraviolet or OT visual ray irradiation section and the plasma generation section are set in a nitrogen or vacuum atmosphere.

By having a separate structure outside the reaction chamber, noise from the plasma is minimized, making the device easier to operate, increasing light transmittance, and reducing the probability of collision between photons and reactant gas. did it. Comparing the illumination intensity when the atmosphere was air and when the atmosphere was vacuum, the illumination intensity was about three times higher in the case of vacuum than in the case of air.

[Brief explanation of the drawing]

Figures 1 to 4 (1. Soft diagram of the apparatus directly used in the method of the present invention. 1. Substrate, 2. SiC coachic graphite.
Susceptor, 3 Vacuum exhaust system, 4 Ishigu\reaction layer, 5
Exhaust 1'j, 6-A whole chamber, 7.N. To the phone, 8 cock, 9 cock, IO...A'2 Exhaust system, 11 JilFm port, +2 Haloken lamp, 13 Hydrocarbon to the phone, [4 hydrogen cylinder, 15 cock, IO conc, 17. Can Zhou He Home Expansion Device, 18 Fikro Wave Death Tetsu 5.19 Wave Kite, 20 Ultraviolet Light F, V Ishiroe Vision Irradiation Weight, 21 Coil, 22-
+4L pole, dairy Ritz. Agent 7.・””・Part 1)” Hara Mamoru (Less)

Claims (2)

[Claims] (1) In the diamond vapor phase synthesis method in which a mixed gas of hydrocarbon and hydrogen is decomposed and excited in high frequency or microwave discharge to deposit diamond on a substrate, the generated plasma is irradiated with ultraviolet rays or visible light. A distinctive method of diamond vapor phase synthesis. (2) A reaction tube that is connected to a gas supply section and a vacuum exhaust system and in which a substrate can be installed, a substrate heating means, an ultraviolet or visible light irradiation light source, and a coil or electrode for plasma generation. A diamond vapor phase synthesis apparatus characterized in that an ultraviolet or visible light irradiation light source and a coil or electrode for plasma generation are installed outside the reaction tube in a vacuum or in a nitrogen atmosphere. Device.