JPS62202897A - Production of diamond - Google Patents

Abstract

PURPOSE:To produce diamond having improved adhesivity to a substrate and smoothness, by introducing a reaction gas containing an organic compound into a reaction vessel containing a substrate having the surface on which a metal vapor is deposited and decomposing the reaction gas. CONSTITUTION:A substrate 5 having the surface on which vapor of a metal, e.g. selenium, is deposited in the form of islands having <=5,000Angstrom diameter and/or a film having <=1mum film thickness is held by a substrate holder 4 in a reaction vessel 1 and heated to >=400 deg.C by a heat source 6. A reaction gas prepared by blending an organic compound, e.g. methane, with H2 at 0.001-1.0 volume ratio is introduced from a gas inlet 2 into the vessel 1 to keep the pressure in the vessel 1 at 10<2>-10<4>Torr. A current is simultaneously passed through a heating filament 7 to increase the temperature thereof and the reaction gas is decomposed to grow diamond on the substrate 5.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) 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 excellent characteristics,
Wear-resistant coating on jigs and tools to protect solar cells! ! film,
Research is underway to develop applications for optical lenses and heat sinks for semiconductor components. However, natural diamonds are produced in small quantities and are extremely expensive, so they cannot be used as industrial materials.

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, and it is difficult to manufacture a film, so that the useful properties of diamond cannot be 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 hydrogen and an organic compound such as methane, ethylene, acetylene, or acetone onto the surface of a heated substrate, and pyrolyzing and activating the mixed gas using the thermal energy of a hot filament close to the substrate. This method generates seeds 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. Thermionic electrons are emitted from a hot filament and irradiated onto the substrate while diamond is grown on the substrate (A).

Sawabe and T, I nuzuka:
Appl, Phys, Lett.

Vol, 46 (1985), l), 146-147
).

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 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 substrate surface in the early stage of growth is small, resulting in problems such as formation of a diamond thin film, adhesion between diamond and substrate, smoothness of the diamond film surface, and growth rate of the diamond film. In this respect, it was not necessarily satisfactory. 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 the diamond coating peeling off and shortening the tool life, or causing damage to sliding parts. Even if an attempt was made to improve the sliding characteristics by coating the surface with diamond, there was a problem that the sliding characteristics could not be improved due to the poor smoothness of diamond.

(Problems to be Solved by the Invention) The present invention was made to solve the above-mentioned problems, and uses a vapor phase growth method at low temperature and low pressure to prevent precipitation on the substrate surface during the initial stage of growth. It is an object of the present invention to provide a method that can increase the number density of diamond nuclei and produce diamond with good adhesion to a substrate, smoothness, etc., and a very thin diamond film.

[Structure of the invention]

(Means for Solving the Problems) The diamond manufacturing method of the present invention includes installing a substrate in a reaction vessel, introducing a reaction gas containing an organic compound into the reaction vessel, and decomposing the reaction gas. A method for manufacturing diamond in which diamond is grown on a substrate by using a substrate having a metal vapor-deposited on the surface. 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) is essentially amorphous (may contain crystalline) II structure, transparent and 4000Hv
It contains diamond-like carbon (diaa+ond-like carbon) having hardness and electrical insulation properties of the above.

To carry out the method of the present invention, a substrate with a metal vapor-deposited on its surface is prepared in advance, and this is placed in a reaction vessel, and then one of the three methods described above, namely, chemical vapor deposition, electron beam irradiation, and chemical vapor deposition, is applied. A phase growth method or a plasma chemical vapor deposition method may be applied.

First, the material of the base material constituting the base body is not particularly limited, although various single metals, alloys, ceramics, glass, or composite materials can be used. The type of gold a to be deposited on the surface of this base material is also not particularly limited. Note that in the present invention, metal is not limited to metal in the narrow sense, but also includes semimetals such as metal silicon and selenium. Furthermore, two or more types of metals may be deposited. Methods for producing a substrate by depositing metal on the surface of the substrate include physical vapor deposition methods such as vacuum evaporation method, molecular beam epitaxial method, sputtering method, ionization vapor deposition method, and ion blating method, and chemical vapor deposition method (
CVD method), MOCVD method, plasma chemical vapor deposition method (plasma CVD method), and other chemical vapor deposition methods. The metal on the surface of the base material is preferably in the form of an island with a diameter of 5000 Å or less, a film with a thickness of 1 m or less, or a mixture thereof. This is because if the state of the metal deviates from the above range, the number density of diamond nuclei that will be formed later becomes extremely small.

The substrate thus obtained is placed in a reaction vessel in which the three vapor phase growth methods described above are performed. After introducing a reactive gas into the reaction vessel, diamond is grown on the substrate by chemical vapor deposition, electron beam irradiation chemical vapor deposition, or plasma chemical vapor deposition. The reaction gas must contain an organic compound as a diamond source.

The organic compound may be one that produces carbon, which is a constituent element of diamond, by various vapor phase growth methods, but those with a relatively low molecular number are preferable, and specifically, methane, ethane, propane, ethylene, Hydrocarbons such as acetylene, butadiene, and benzene, acetone, methanol, ethanol, and acetaldehyde can be mentioned. 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) -
The range of o,ooi to 1,0 is preferable. This is because the active hydrogen that is excited, decomposed, and generated promotes the excitation and decomposition of organic compounds, and is presumed to react with by-product non-diamond components such as graphite and amorphous carbon to remove them. This is for the purpose of

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' 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 non-diamond components but also improves the adhesion between the diamond and the substrate.

(Function) According to the method of the present invention as described above, when the organic compound in the reaction gas decomposes into active chemical species, which are sequentially deposited on the surface of the substrate to form diamond, islands are formed on the substrate in advance. Since the metal is deposited in the form of a shape or a film, the number density of diamond nuclei deposited on the surface of the substrate increases. It is presumed that this is because crystal defects and residual stress occur in the metal deposited on the surface of the base material, which favorably affects the precipitation of diamond nuclei. As a result, it is possible to form a diamond film at a much faster growth rate than before, and the adhesion between the diamond and the substrate and the smoothness of the diamond surface can also be improved, making it possible to form extremely thin diamond films. You can also get it.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

Example 1 First, a molybdenum plate was used as a base material, and gold with an average particle diameter of 200 was formed in the form of islands on the surface of the base material by vacuum evaporation to produce a base body.

Diamond was then grown on the substrate by chemical vapor deposition using the reaction apparatus shown schematically in FIG. 1. In FIG. 1, a gas port 2 and a gas outlet 3 are provided at the bottom of a reaction vessel 1. A substrate holder 4 is provided at the lower part of the reaction vessel 1. The substrate 5 obtained as described above is held on this substrate holder 4, and a heating device for heating the substrate 5 is provided below the substrate holder 4. A source 6 is provided. Furthermore, a hot filament 7 is provided above the base body 5 in close proximity to the base body 5 to heat the reaction gas.

Using the above reaction apparatus, first, the substrate 5 placed on the substrate holder 4 was heated with the heat source 6 and maintained at 750°C. Next, from the gas population 2, 40! It is introduced at a flow rate of d/win, and is exhausted from the gas outlet 3 to make the inside of the reaction vessel 1 about 4.
It was maintained at 0 Torr.

Next, the temperature of the hot filament 7 was raised to 1900°C and maintained.

When this state continued for 15 minutes, 7.5 x 108 pieces/
Diamond nuclei with an average number density of α2 were formed.

The reaction was further continued, and after a total reaction time of 4 hours, a diamond film with an average thickness of 5 uIIt was obtained.

Regarding the obtained film, the smoothness of the film surface and the adhesion to the substrate were measured and evaluated. In addition, the smoothness of the film surface is determined according to JIS
Evaluation was made by measuring the maximum height (Rwax) using the method specified in 80601. In addition, the adhesion was evaluated based on the adhesive force of the film to the substrate using the indentation method (Thin Solid Films, Vol. 79 (
1981), D, 91).

As a result, RIlla× was 0.3 tan, indicating excellent surface smoothness. Furthermore, the adhesion force obtained by the indentation method also showed a large value.

As Comparative Example 1, a diamond was produced under exactly the same conditions as above using the base material itself made of a molybdenum plate as the base body. In this case, the average number density of diamond nuclei after 15 minutes was 6.3 x 10' pieces/aR2, and the average film thickness after 4 hours was 3-. Moreover, RlaX is 0.9-,
The adhesion force also showed a small value.

Furthermore, the average film thickness immediately after the diamond transitioned from granular to continuous film was smaller in Example 1 than in Comparative Example 1.

Example 2 First, a silicon wafer was used as a base material, and an average film thickness of 0.2 l1m was deposited on the surface of the base material by ion blating method.
A metal silicon film was formed to prepare a substrate.

Then, diamond was grown on the substrate by electron beam irradiation chemical vapor deposition using the reaction apparatus shown in the schematic diagram of FIG. 2. Note that in FIG. 2, the same members as in FIG. 1 are designated by the same numbers and their explanations will be omitted. The reaction apparatus shown in FIG. 2 is similar to the reaction apparatus shown in FIG. It has a structure.

Using the reaction apparatus described above, first, the substrate 5 obtained as described above placed on the substrate holder 4 was heated with a heat source 6 and maintained at 550°C. Next, from gas population 2 to reaction vessel 1
A mixed gas of ethane and hydrogen (volume ratio 1:50) was added to
The inside of the reaction vessel 1 was maintained at about 30 Torr by introducing the gas at a flow rate of 50 ne/akin and exhausting from the gas outlet 3.

Next, the temperature of the hot filament 7 was raised to 1950° C. and maintained therein, and a voltage of 150 V was applied between the substrate holder 4 and the hot filament 7 using the DC power supply 8 . As a result,
A thermoelectron beam with a current density of 15 mA/α2 was irradiated from the hot filament 7 in the direction of the substrate 5.

When this state continued for 15 minutes, 7.1 x 103 pieces1
Diamond nuclei with an average number density of 0R2 were formed. Further, after 4 hours, a diamond film with an average thickness of 10 - was obtained.

Regarding the obtained film, the smoothness of the film surface and the adhesion to the substrate were measured and evaluated in the same manner as in Example 1 above, and it was found that Rwa
x was 0.2 tan, and the adhesion force also showed a large value.

As Comparative Example 2, diamond was produced under exactly the same conditions as above using the silicon wafer base material itself as the base. In this case, the average number density of diamond nuclei after 15 minutes was 2.5×10S/cm, and the average film thickness after 2.4 hours was 8 diamond nuclei. Also, Rmax is 0.7 tan,
The adhesion force also showed a small value.

Furthermore, the average film thickness immediately after the diamond transitioned from granular to continuous film was smaller in Example 2 than in Comparative Example 2.

Example 3 First, using quartz glass as a base material, a molybdenum film having an average thickness of 0.5 mm was formed on the surface of the base material by sputtering to produce a base body.

Diamond was then grown on the substrate by microwave plasma chemical vapor deposition using the reaction apparatus shown in the schematic diagram of FIG. 3. In FIG. 3, members having the same functions as the members of the reaction apparatus shown in FIG. 1 are given the same numbers and will be explained. In FIG. 3, a gas outlet 2 is provided on the top surface of the reaction vessel 1, and a gas outlet 3 is provided on the bottom surface. Further, a substrate holder 4 is provided in the center of the reaction vessel 1, and the substrate 5 obtained as described above is held on this substrate holder 4. Furthermore, a waveguide 9 is provided on the side surface of the reaction container 1, and microwaves generated by a microwave oscillator (not shown) are transmitted through the waveguide 9.
The plasma is guided to the base 5 through the plasma and generates plasma.

Using the above reaction apparatus, first, 100% of a mixed gas of methane and hydrogen (volume ratio 1:10) is introduced into the reaction vessel 1 from the gas inlet 2.
The inside of the reaction vessel 1 was maintained at about 3 Torr by introducing at a flow rate of 0 d/min and exhausting from the waste outlet 3. Then 2
Plasma was generated around the base 5 using microwaves of 450 MHz, and this state was maintained.

When this state continued for 15 minutes, 1.8 x 107 pieces/
Diamond nuclei with an average number density of Cl12 were formed. Also, after 4 hours, the average film thickness was 3II! An IL diamond film was obtained.

Regarding the obtained film, the smoothness of the film surface and the adhesion to the substrate were measured and evaluated in the same manner as in Example 1 above.

As a result, RlaX was 1.0 tan, and the adhesion force also showed a relatively large value.

As Comparative Example 3, diamond was produced using the quartz glass substrate itself as a substrate under exactly the same conditions as above.

In this case, the average number density of diamond nuclei after 15 minutes is 4
, 6 x 106 pieces/cm Average film thickness after 2.4 hours is 2.5
I was captivated. Furthermore, RmaX was 1 and 2 tan, and the adhesion force also showed a relatively small value.

Furthermore, the average film thickness in Example 3 was smaller than in Comparative Example 3 immediately after the diamond transitioned from granular to continuous film.

In Example 3, a plasma chemical vapor deposition method using microwaves was described, but similar results can be obtained with other plasma chemical vapor deposition methods using high frequency waves, direct current glow discharge, or the like.

〔Effect of the invention〕

As detailed above, according to the method of the present invention, the number density of diamond nuclei precipitated on the substrate surface can be increased,
As a result, it is extremely useful industrially, as thin-film diamonds with excellent various properties can be obtained quickly.

[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. DESCRIPTION OF SYMBOLS 1... Reaction container, 2... Gas inlet, 3... Gas outlet, 4... Substrate holder, 5... Substrate, 6... Heat source, 7... Hot filament, 8... ...DC power supply, 9.
...Waveguide. Applicant's representative Patent attorney Takehiko Suzue No. 1 ;: Figure 2 Figure 3

Claims (3)

[Claims] (1) A diamond manufacturing method in which a substrate is placed in a reaction vessel, a reactive gas containing an organic compound is introduced into the reaction vessel, and the reactive gas is decomposed to grow diamond on the substrate. A method for producing diamond, characterized by using a substrate on which a metal is vapor-deposited. (2) A method for manufacturing diamond according to claim 1, characterized in that a substrate is used on which a metal island having a diameter of 5000 Å or less is deposited. (3) A method for producing diamond according to claim 1, characterized in that a substrate is used, on the surface of which a metal film having a thickness of 1 μm or less is deposited.