JPS62275092A - Production of diamond - Google Patents

Abstract

PURPOSE:To rapidly produce diamond having superior characteristics in the form of a thin film or the like by placing a heating element near the outlet of a reactive gas introducing pipe and applying voltage between the pipe and the heating element so as to increase the numerical density of diamond nuclei deposited on the surface of a substrate. CONSTITUTION:A substrate holder 7 is placed at the center of the lower part of a reactor 1 and a substrate 8 is set on the holder 7. A reactive gas introducing pipe 2 is put in the reactor 1 from the peripheral part of the bottom and a gaseous org. compound is introduced. A heating element 4 is placed near the outlet of the pipe 2 and voltage is applied between the heating element 4 and the pipe 2 from an AC power source 5 connected to them. By this method, the numerical density of diamond unclei deposited on the surface of the substrate 8 in the early stage of growth is increased, so high purity diamond having satisfactory adhesion to the substrate 8 or a very thin diamond film can be produced at a high speed.

Description

[Detailed description of the invention] 3. Detailed description of the invention [Purpose of the invention] (Field of use in business a) TECHNICAL FIELD The present invention relates to improvements in diamond manufacturing methods.

(Prior art) Diamond has the highest hardness and thermal conductivity among currently known substances, and also has extremely high modulus of elasticity, compressive strength, and electrical insulation, and is transparent and chemically resistant. It is a stable substance. Therefore, taking advantage of its immersed characteristics,
Research is being conducted into the development of applications such as wear-resistant coatings for jigs and tools, protective films for large FIa'R ponds, optical lenses, and heat sinks for semiconductor components. However, natural diamonds cannot be used as industrial materials because they are rare and extremely expensive.

For this reason, research on the production of artificial diamonds is actively being conducted, but artificial diamonds manufactured by conventional methods under high temperature and high pressure are also expensive and have little usefulness as industrial materials. Moreover, both natural diamonds and artificial diamonds generally have a lumpy or granular shape, making it difficult to produce a film.
Diamond's useful properties are not fully utilized.

For this reason, research has recently been actively conducted to produce diamonds by vapor phase growth at low temperatures and low pressures. The following three methods are known as the main methods.

The first method involves introducing a gas mixture of specific compounds such as methane, ethylene, acetylene, or acetone and hydrogen onto the surface of a heated substrate, and thermally decomposing the gas mixture using the thermal energy of a hot filament close to the substrate. This method generates active species and grows diamonds on the surface of the substrate (Special Publication No. 1983).
-27753, Asahi Shimbun morning edition, January 1, 1986).

The second method is an improvement on the first method, and in addition to the first method, a voltage is applied between the base and the hot filament so that the base has a positive potential and the hot filament has a negative potential. In this method, diamond is grown on a substrate while emitting hot electrons from a hot filament and irradiating them onto the substrate (Japanese Patent Laid-Open No. 60-221395).

The third method is to decompose raw material organic compound gas in plasma to generate active species and grow diamond on a substrate (JP-A-58-135117, JP-A-59-
3098 etc.).

Since all of these methods are carried out at relatively low temperatures and low pressures, they can be realized with relatively small equipment and are industrially advantageous.

However, in any of the above methods, the number density of diamond nuclei precipitated on the surface of the substrate in the early stage of growth is small, and the formation of a diamond thin film, the adhesion between the diamond and the substrate, the growth rate of the diamond film, etc. are not necessarily satisfactory. It wasn't a kimono.

For this reason, for example, even if diamond is coated on the surface of a tool due to its excellent hardness, the adhesion between the diamond and the substrate is poor, resulting in problems such as the diamond coating peeling off and the tool life being shortened. was there.

In addition to these problems, the first and second methods have the problem that only heat-resistant substrates can be used because the surface of the substrate becomes high temperature due to the thermal energy from the hot filament close to the substrate. . Also, in the third method,
There is a problem in that material components around the substrate are taken into the plasma and the diamond is contaminated.

(Problems to be Solved by the Invention) The present invention has been made to eliminate the above-mentioned problems, and uses a vapor phase growth method at low temperature and low pressure, without abnormally heating the substrate surface. The purpose is to increase the number density of diamond nuclei precipitated on the surface of a substrate in the early stage of growth, and to provide a method that can produce high-purity diamond or very thin diamond thin films with good adhesion to the substrate at high speed. shall be.

[Configuration of the Invention (Means for Solving the Problems)] The diamond manufacturing method of the present invention includes: installing a substrate in a reaction vessel; and introducing a reaction gas into the reaction vessel through at least one inlet. , in growing diamond on the substrate by decomposing the reaction gas, at least one heating element is disposed close to the at least one inlet, and between the corresponding inlet and the heating element; It is characterized by applying a voltage to. In addition, in the present invention, diamond is not limited to cases where the entire structure is completely composed of diamond, but cases where non-diamond components such as graphite or amorphous carbon are mixed together with diamond, or where carbon is the main component (somewhat). (may contain hydrogen)
Diamond-like carbon has an essentially amorphous (may include crystalline) structure, is transparent, has a hardness of 4000 Hv or more, and has electrical insulation properties.
arbon) shall be included.

In carrying out the method of the present invention, first, a substrate is placed in a reaction vessel used in a normal vapor phase growth method. Substrate materials include various single metals, alloys, ceramics,
Glass, artefacts, or composite materials thereof may be used, but are not particularly limited.

A substrate with low heat resistance may also be used.

Next, a reaction gas is introduced into the reaction vessel through at least one inlet. The reactive gas must contain at least an organic compound as a diamond source. The organic compound may be one that produces carbon, which is a constituent element of diamond, by the method of the present invention;
Those with relatively low molecular numbers are preferred, specifically methane, ethane, propane, ethylene, acetylene, butadiene,
Examples include hydrocarbons such as benzene, acetone, methanol, ethanol, and acetaldehyde.

Furthermore, it is effective to mix a predetermined amount of hydrogen into the reaction gas because it increases the diamond precipitation rate and improves the properties of the diamond formed. The appropriate amount of hydrogen to be mixed is not particularly limited as it also depends on other reaction conditions, but for example, the volume ratio of (organic compound)/'
(Hydrogen) is preferably in the range of 0.001 to 1.0. This is because active hydrogen, which is excited and decomposed and generated, accelerates the excitation and decomposition of organic compounds and reacts with non-diamond components such as by-product graphite and amorphous carbon to remove them. This is to be done. Further, in addition to these reactive gases, an inert gas such as Ar or He may be introduced.

In addition, boron, aluminum, gallium,
Diamond having semiconductor properties can be produced by containing at least one of indium or thallium or a compound thereof, or nitrogen, phosphorus, arsenic, antimony, or bismuth or a compound thereof.

Note that the gas pressure inside the reaction container varies depending on the composition of the reaction gas, and is not particularly limited, but for example,
A range of 10'4 Torr is preferred.

Further, the substrate itself may or may not be heated, but heating is effective because it increases the growth rate of diamond and provides good properties. In particular, it is desirable to heat the substrate to 400° C. or higher because this not only reduces the amount of non-diamond components in the diamond but also improves the adhesion between the diamond and the substrate.

When using a reactive gas consisting of two or more types of substances, such as a combination of an organic compound and hydrogen,
These two or more types of reaction gases may be introduced into the reaction vessel through separate introduction ports, or may be introduced through the same introduction port.

Subsequently, at least one heating element disposed close to the at least one inlet is heated, and a voltage is applied between the corresponding inlet and the heating element. As a result, excitation and decomposition of the reactive gas occur frequently, and diamond grows on the substrate.

The heating temperature of the heating element is not particularly limited as it depends on reaction conditions such as reaction gas components and reaction gas pressure, but it is 400°C or higher for excitation and decomposition of organic compounds, and 400°C or higher for excitation and decomposition of hydrogen. For excitation and decomposition of organic compounds and hydrogen, a temperature of 1100°C or higher is desirable.

The applied voltage has an effect whether it is direct current or alternating current, and both may be superimposed. There are two methods: one in which discharge occurs between the inlet and the heating element when voltage is applied, and one in which it does not occur.
There is a street. In the former case, the growth rate of diamond is high, and in the latter case, the purity of diamond is high, so they can be selected depending on the purpose and use. In addition, when applying a DC voltage, the inlet should be placed at a positive potential.
If the heating element is set to a negative potential, it becomes easier for the heating element to emit thermoelectrons, so the effect can be obtained with a small DC voltage.

Furthermore, in the above explanation, ■substrate installation, ■reactant gas introduction,
Although the case has been described in which the operations are performed in the order of (1) substrate heating, (2) heating of the heating element, and voltage application, the order is not limited to this, and for example, the order of (1) and (2) may be reversed.

(Operation) According to the method of the present invention as described above, the organic compound in the reaction gas is excited and decomposed to become active chemical species, which are successively deposited on the surface of the substrate to form diamond. At this time, since the heating body is placed close to the inlet and not placed close to the base, abnormal heating of the surface of the base can be prevented. Moreover, the probability of excitation and decomposition of the reaction gas is greatly improved due to the cooperative action of the heating element and the applied voltage, so that the number density of diamond nuclei increases. As a result, film-like diamond can be formed at a much faster growth rate than in the past, and the adhesion between the diamond and the substrate can also be improved. Furthermore, since no plasma is generated, contamination of the diamond by plasma components can be prevented.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
3 to 3 are schematic diagrams of the reactor used in the examples of the present invention. First, these reaction devices will be explained. In addition, in FIGS. 2 and 3, the same members as in FIG. 1 are given the same numbers and their explanations will be omitted.

In FIG. 1, an inlet 2 is inserted from the peripheral edge of the bottom surface of a reaction container 1, and an exhaust port 3 is provided on the top surface of the reaction container 1. A heating body 4 is arranged near the introduction port 2, and an AC power source 5 is connected between the introduction port 2 and the heating body 4. Further, a substrate holder 7 is provided at the center of the lower part of the reaction vessel 1, and a substrate 8 is held on this substrate holder 7. Note that a heating source (not shown) for heating the substrate 8 is provided at the bottom of the substrate holder 7 . Then, only the organic compound gas (C source) is introduced into the reaction vessel 1 through the introduction port 2 .

The reactor shown in FIG. 2 is similar to the reactor shown in FIG. 1 except that a DC power supply 6 is connected between the inlet 2 and the heating element 4 so that the inlet 2 has a positive potential. It has a structure. Then, an organic compound gas (C source) and hydrogen gas (H2) are introduced into the reaction vessel 1 from an inlet 2.

In the reaction apparatus shown in FIG. 3, an inlet 2' is inserted into the reaction vessel 1 from the peripheral edge of the bottom at a position symmetrical to the inlet 2, and a heating element 4' is also arranged near the inlet 2'. The reactor has the same structure as the reactor shown in FIG. 1, except that a DC voltage [6] is connected between the port 2- and the heating element 4' so that the inlet 2- has a positive potential. In the reaction vessel 1,
Organic compound gas (C source) flows from the inlet 2 to the inlet 2'
Hydrogen gas (H2) is introduced from each.

Example 1 Using the reaction apparatus shown in FIG. 1, diamond was produced in the following manner. First, molybdenum is placed on the substrate holder 7 as the substrate 8, and heated with a heating source (not shown).
It was maintained at 50°C. Next, acetone was introduced into the reaction vessel 1 from the inlet 2 at a flow rate of 40+e/1n, and the inside of the reaction vessel 1 was maintained at about 4 Q TOrr by exhausting from the exhaust port 3. Next, the temperature of the heating body 4 was raised to 1300° C. and maintained, and an AC voltage of 1 kV, 60)-12 was applied between the inlet 2 and the heating body 4 from the AC power supply 5.

When this state continued for 15 minutes, 8X1
Diamond nuclei were formed with an average number density of 0"/2. The reaction was continued, and after a total reaction time of 1 hour, a diamond film with an average thickness of 1 tan was obtained, and a total reaction time of 4 hours. Afterwards, a diamond film with an average thickness of 3 mm was obtained.

The adhesion of the obtained film to the substrate was evaluated using the indentation method based on the strength of the film's adhesion to the substrate.<T
h1n 5olid Fills, Vol, 7
9 (1981), p. 91). As a result, the adhesion force showed a large value.

Note that good results similar to those described above were also obtained when a material with low heat resistance, such as aluminum or GaAS, was used as the substrate 8.

Example 1 except that the AC power source 5 is not used as Comparative Example 1
The experiment was conducted under similar conditions. In this case, the average number density of the diamond group after 15 minutes is 5.9 x 10S pieces/α2
Met. Further, even after a reaction time of 4 hours, hardly any film was formed, and only diamond particles with an average particle size of 0.5.11111 were formed.

Example 1 except that the heating body 4 is not heated as Comparative Example 2
The experiment was conducted under similar conditions. In this case, no diamonds were formed even after a reaction time of 4 hours.

Example 2 Using the reaction apparatus shown in FIG. 2, diamond was produced in the following manner. First, silicon was placed as the base 8 on the base holder 7, and heated with a heating source (not shown) for 50 minutes.
It was kept at 0°C. Next, a mixed gas of ethane and hydrogen (the volume ratio of ethane and hydrogen is 1
:50) was introduced at a flow rate of 150 m/1 n, and the inside of the reaction vessel 1 was maintained at about 10 Torr by exhausting from the exhaust port 3.

Next, the temperature of the heating element 4 is raised to 1600° C. and maintained, and a DC power source 6 is used to heat the inlet 2 and the heating element 4 at a temperature of 300° C. so that the inlet 2 is at a positive potential and the heating element 4 is at a negative potential.
A DC voltage of (3) was applied.

When this state continued for 5 minutes, 8.5X
"A diamond group with an average number density of 1Q10 pieces/c!R2 was formed. Also, after a total reaction time of 15 minutes, a diamond film with an average film thickness of 0.5 tan was obtained, and a total reaction time of 4 hours. A diamond film with an average film thickness of 7p was subsequently obtained.The obtained anti-node showed great adhesion.

Note that good results similar to those described above were also obtained when a material with low heat resistance, such as aluminum or GaAS, was used as the substrate 8.

Direct current as comparative example 3! An experiment was conducted under the same conditions as in Example 2, except that 1116 was not used. In this case, the average number density of the diamond group after 5 minutes is 4.8×10'/υ
It was 2. Moreover, no film was formed even after a reaction time of 4 hours, and only diamond particles with an average particle size of 0.4 AIM were formed.

Example 2 except that the heating body 4 is not heated as Comparative Example 4
The experiment was conducted under similar conditions. In this case, no diamonds were formed even after a reaction time of 4 hours.

Example 3 Using the reaction apparatus shown in FIG. 3, diamond was produced in the following manner. First, aluminum nitride was placed as the base 8 on the base holder 7, and heated with a heat source (not shown) and maintained at 600°C.

Next, methane was introduced into the reaction vessel 1 from the inlet 2 at a rate of 1 d/mi.
At a flow rate of n, hydrogen is supplied from the inlet 2' at 100af/min.
The inside of the reaction vessel 1 was maintained at approximately ITorr by being evacuated from the exhaust port 3. Next, the temperature of the heating element 4 close to the methane inlet 2 was raised to 900° C. and maintained, and an AC voltage of 500 V and 100 Hz was applied between the inlet 2 and the heating element 4 using AC 1 g A3. At the same time, the heating element 4' close to the hydrogen inlet 2' is
While raising the temperature to 800°C and maintaining it, a DC power source 6 applies 100V DC between the inlet 2- and the heating element 4' so that the inlet 2'' has a positive potential and the heating element 4- has a negative potential. A voltage was applied.

When this state continued for 5 minutes, 1.3
A diamond group with an average number density of xlo'' III/α2 was formed. Also, after a total reaction time of 15 minutes, a diamond film with an average thickness of 0.6- was obtained, and after a total reaction time of 4 hours, A diamond film with an average thickness of 1 os was obtained.The obtained film showed great adhesion.

Note that good results similar to those described above were also obtained when a material with low heat resistance, such as aluminum or GaAs, was used as the substrate 8.

As Comparative Example 5, an experiment was conducted under the same conditions as in Example 3, except that AC 1[5 and DC power source 6 were not used. In this case, the average number density of the diamond family after 5 minutes is 6,5x1
It was 0S pieces/ClI2. After a reaction time of 15 minutes, the diamond had not yet grown into a film. After a reaction time of 4 hours, a diamond family film with an average thickness of 2-2 was obtained, but the adhesion was small.

As Comparative Example 6, an experiment was conducted under the same conditions as in Example 3, except that heating element 4.4- was not heated.

In this case, very little diamond was formed even after a reaction time of 4 hours.

Although the reactor shown in FIG. 9 uses an AC'R source 5, a DC N source may also be used. Conversely, although the reaction apparatus shown in FIG. 2 uses a DC power source 6, an AC power source may also be used. Furthermore, although both the AC power source 5 and the DC power source 6 are used in the reaction apparatus shown in FIG. 3, both may be replaced, or only the AC power source or only the DC power source may be used.

Furthermore, not only the reaction apparatus shown in FIGS. 1 to 3, but also the reaction II shown in FIG. 4 or 5, for example, may be used. Note that in FIG. 4 or 5, the same members as in FIG. 1 are given the same numbers and their explanations will be omitted.

The reaction device shown in FIG. 4 has the same configuration as the reaction device shown in FIG. are doing. Then, into the nuclear power plant vessel 1, an organic compound gas (CI>) is introduced through an inlet 2, and a hydrogen gas (H2) is introduced through an inlet 2'.

In the reaction apparatus shown in FIG. 5, an inlet 2- is inserted into the reaction vessel 1 from the peripheral edge of the bottom at a position symmetrical to the inlet 2, and a heating element 4 is provided adjacent to the inlet 2. A power source for applying voltage between the two is not provided, and a heating element 4' is arranged near the inlet 2- to connect the inlet 2' and the heating element 4-.
The reactor has the same structure as the reactor shown in FIG. 1, except that a DC power supply 6 is connected between the reactor and the inlet 2' so that the inlet 2' has a positive potential. In the reaction vessel 1, there is an inlet 2.
An organic compound gas (Cat) is introduced from the inlet 2', and hydrogen gas (H2) is introduced from the inlet 2'.

In addition to these, various modifications can be considered for the reaction apparatus used in the method of the present invention.

[Effects of the Invention] As detailed above, according to the method of the present invention, it is possible to increase the number density of diamond nuclei precipitated on the surface of the substrate without any problem even if a substrate with low heat resistance is used, and as a result, various effects can be achieved. It is extremely useful industrially, as it allows rapid production of thin film diamonds with excellent properties.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram of a reaction apparatus for forming diamond used in Example 1 of the present invention, and Figure 2 is a schematic diagram of a reaction apparatus for forming diamond used in Example 2 of the present invention. FIG. 3 is a schematic diagram of a reaction apparatus for forming diamond used in Example 3 of the present invention, and FIGS. 4 and 5 are each used in other examples of the present invention. FIG. 1 is a schematic diagram of a reaction apparatus for forming diamond. DESCRIPTION OF SYMBOLS 1... Reaction container, 2.2'... Inlet, 3... Exhaust port, 4.4-... Heating body, 5... AC its, 6
. . . DC power supply, 7. Base holder, 8. Base. Applicant's agent Patent attorney Takehiko Suzue Figure 2

Claims (5)

[Claims] (1) A substrate is installed in a reaction vessel, a reaction gas is introduced into the reaction vessel from at least one inlet, and the reaction gas is decomposed to grow diamond on the substrate. 1. A method for manufacturing diamond, which comprises arranging at least one heating element in the vicinity of one inlet and applying a voltage between the corresponding inlet and the heating element. (2) A reaction gas containing an organic compound is introduced into the reaction vessel through at least one inlet, a heating element is placed close to this inlet, and a voltage is applied between the inlet and the heating element. A method for producing diamond according to claim 1, characterized in that: (3) A reaction gas containing an organic compound and hydrogen is introduced into the reaction vessel through at least one inlet, a heating element is placed close to this inlet, and a voltage is applied between the inlet and the heating element. 2. A method for manufacturing diamond according to claim 1, characterized in that: (4) A reaction gas containing an organic compound and a reaction gas containing hydrogen are introduced into the reaction vessel through at least two inlets, respectively, and a heating element is placed close to at least one of the inlets. 2. The method for manufacturing diamond according to claim 1, wherein a voltage is applied between the inlet and the heating body. (5) A method for manufacturing diamond according to any one of claims 1 to 4, characterized in that a voltage is applied so that the inlet has a positive potential and the heating body has a negative potential.