JPS6325296A - Production of diamond - Google Patents

Abstract

PURPOSE:To readily obtain homogeneous diamond at a constant growth rate, by introducing an organic compound-containing reaction gas into a reaction vessel having a substrate and heating element of a specific shape which is rigid to deformation stress and provided in the vicinity of the substrate and thermally decomposing the reaction gas. CONSTITUTION:A heating element 7 of an optional cross-sectional shape having a continuous surface elongating in the direction parallel to a substrate without causing deformation even in use for a long period is prepared by using a simple substance metal, e.g. W, Mo, Nb, Ta, Hf, etc., or alloy thereof, ceramics, e.g. TiC, ZrC, HfC, SiC, TiN, etc., or composite material thereof. A substrate 5 is held on a substrate holder 4 provided in the horizontal direction in the lower part of the reaction vessel 1 having a gas inlet 2 and gas outlet 3 on the bottom surface and a mixed gas of an organic compound, e.g. acetone or methane, and H2 is introduced from the gas inlet 2, heated to, e.g. about 1,000 deg.C, by a heating source 6 below the substrate 5 and the above-mentioned heating element 7 placed above in the vicinity of the substrate 5 in the horizontal direction and thermally decomposed to form active species and homogeneously grow diamond on the surface of the substrate 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a diamond manufacturing apparatus, and particularly to an apparatus for manufacturing homogeneous diamond by improving a heating element.

(Prior art) Among currently known materials, diamond has the highest hardness and thermal conductivity, and also has extremely high modulus of elasticity, compressive strength, and electrical insulation, and is transparent and chemically insulating. It is also a stable substance. Therefore, research is underway to utilize its excellent properties to develop applications such as wear-resistant coatings for jigs and tools, protective films for solar cells, 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 using conventional methods under high temperature and high pressure are also expensive and have little utility 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 carried out to produce diamonds by vapor phase growth by decomposing the reactive gas containing the right front compound by heating it with a heating element at low temperature and atmospheric pressure. .

If this low-temperature, low-pressure method can be used, industrial benefits can be expected, such as making the device relatively smaller.

↑The key method is to apply methane to the surface of the heated substrate.
A mixed gas of an organic compound such as ethylene, acetylene, or acetone and hydrogen is introduced, and a hot filament (heating body) provided close to the substrate is heated to 1000°C or higher.
A method is known in which the thermal energy is used to thermally decompose a mixed gas to generate active species and grow diamonds on the surface of the substrate (Special Publication No. 59-27753, Proceedings of the 33rd Joint Conference on Applied Physics). 1p-ZD-6, 1986).

In addition, in order to further improve the diamond growth rate, film quality, and adhesion to the substrate, we have improved the above method.
There is also a known method of growing diamond on a substrate by applying a voltage of about 150 V to the hot filament so that it has a negative potential, emitting thermionic electrons from the hot filament, and irradiating them onto the substrate. 6O-221395).

In addition to these methods, methods using hot filaments are known, such as JP-A-58-156594 and JP-A-60-186499.

In the above method, a coiled filament made of a high melting point metal such as MOLWlTa has conventionally been used as the heating filament.

However, in any of the above methods, the coiled hot filament becomes deformed as the coiled hot filament becomes more droopy (sag) over time of use. For example, when a coiled hot filament is arranged horizontally, the temperature at the center is the highest and it tends to sag due to its own weight. Furthermore, when a coiled hot filament is placed vertically, it deforms so that the upper part extends from the center and the lower part contracts. Such deformation often becomes a problem in coiled heating bodies made of tungsten wire, for example, at temperatures above about 2000°C, but the degree of deformation is determined by the shape constant of the coil, that is, the diameter, pitch, coil diameter, coil length, etc. Depends on. Furthermore, when a reactive gas containing an organic compound is present in the surroundings, the deformation may be accelerated due to the reaction between the coiled hot filament and the reactive gas.

The above-described deformation of the coiled heating element has had an adverse effect on the growth rate, uniformity, etc. of diamond. This problem becomes a fatal weakness, especially when homogeneous diamond-like pus is grown on a substrate over a wide area.

(Problems to be Solved by the Invention) The present invention has been made to solve the above-mentioned problems, and is capable of producing homogeneous diamonds on a substrate without causing deformation of the heating element even when used for a long time. The purpose is to provide diamond manufacturing equipment suitable for manufacturing.

[Structure of the Invention] (Means for Solving the Problems) The diamond manufacturing apparatus of the present invention includes a substrate and a heating body disposed in the vicinity of the substrate in a reaction vessel, and a reaction vessel containing an organic compound. In the apparatus for forming diamond on the surface of the substrate by introducing gas and thermally decomposing it, the heating body has a shape having a continuous surface such as a linear shape or a plate shape extending in a direction parallel to the substrate. This is a characteristic feature.

In the present invention, diamond is not limited to cases where the entire structure is completely composed of diamond, but also cases where some non-diamond components such as graphite or amorphous carbon are mixed together with diamond, or cases where carbon is the main component ( Diamond-like carbon (which may contain some hydrogen) has an essentially amorphous (may contain crystalline) structure and has a hardness of 4000 Hv or more and electrical insulation properties.
carbon).

The heating body used in the present invention may have any cross-sectional shape as long as it has a continuous surface extending in a direction parallel to the base.

One or more heating bodies may be used.

In addition, the material of the heating body can be various single metals, alloys,
Examples include ceramics, glass, and composite materials thereof, and are not particularly limited. Specifically, W, Mo, Nb, T
a, Hf, LaB5, TiC1ZrC, HfC, Mo
C, NbC, S 1C1T i N, ZrN, HfN,
NbN, UO2W cermet, Ba-0-W, etc. can be mentioned.

(Function) According to the above-mentioned diamond manufacturing apparatus, the heating body has a shape with a continuous surface extending in a direction parallel to the base body, so unlike the conventional coil-shaped one, it is rigid against deformation stress. and can maintain its shape for a long time. Therefore, the homogeneity of the diamond film formed on the substrate is less likely to be adversely affected.

Note that the heating element may undergo creep deformation when used for a long time, so especially when used for a long time, it is desirable to apply an appropriate tensile stress in the long axis direction of the heating element to suppress deformation. Furthermore, in order to improve the uniformity of diamond grown on the substrate, the relative position of the substrate and the heating element may be changed over time.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. In addition, in the following examples, a diamond manufacturing apparatus having a configuration as shown in FIGS. 1 to 6 was used.

In FIG. 1, a gas inlet 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, and a substrate 5 is held horizontally on this substrate holder 4. A heat source 6 for heating the substrate 5 is provided below the substrate holder 4. ing. Further, above the base 5, a heating body 7 is provided in the vicinity of the base 5 in a horizontal direction to heat the reaction gas.

The device shown in FIG. 2 has the same construction as the device shown in FIG. 1, except that tensile stress (indicated by arrows) is applied in the long sleeve direction of the heating element 7.

The apparatus shown in FIG. 3 differs from the apparatus shown in FIG. 1 in that the substrate holder 4, the substrate 5, the heating source 6, and the heating body 7 are all arranged in the vertical direction.

The apparatus shown in FIG. 4 is the same as that shown in FIG. 1 except that a DC power source 8 is connected between the substrate holder 4 and the heating element 7 so that the substrate holder 4 has a positive potential and the heating element 7 has a negative potential. It has a similar configuration to the device.

In the apparatus shown in FIG. 5, a rod-shaped base 5 is vertically arranged in a reaction vessel 1, and four heating elements 7, . ...is provided. Note that the base body 5 is directly heated by applying electricity.

Further, a DC power source (not shown) is connected between the base 5 and the heating body 7 so that the base 5 has a positive potential and the heating body 7 has a negative potential.

In the apparatus shown in FIG. 6, a rod-shaped base 5 is arranged horizontally in a reaction vessel 1, and a heating element 7 is provided so as to be parallel to the longitudinal direction of the rod-shaped base 5. . Note that the base body 5 is designed to rotate.

Further, in the diamond manufacturing apparatus shown in FIGS. 1 to 6, tt=(7): As the heating body 7, those having various shapes shown in FIGS. 7 to 15 are used.

Example 1 The device shown in FIG.
．． A heating element 7 made of a tungsten wire with a length of 30#l was attached, and diamond was grown by chemical vapor deposition under the following conditions. First, a silicon carbide disk having a diameter of 20 m and a thickness of 2 m+ was placed on the substrate holder 4 as the substrate 5, and heated with the heat source 6 and maintained at 750°C.

Next, a mixed gas of methane and hydrogen (mixing ratio 1:100) was introduced into the reaction vessel 1 from the gas inlet 2 and exhausted from the gas outlet 3 to maintain the inside of the reaction vessel 1 at about 50 Torr.

Next, the temperature of the heating element 7 was raised to 1850°C.

The shape of the heating element 7 made of this tungsten wire was almost stable during use, and even after 20 hours of use, the heating element 7 was hardly deformed and maintained its shape before use. In addition, the growth rate of diamond is almost constant and stable, and 20
After a period of time, a uniform diamond film with a thickness of about 12 pn had been formed on the silicon carbide substrate.

As Comparative Example 1, using the apparatus shown in FIG. 1, a coil length of 30 am was prepared by winding a tungsten wire with a diameter of 0.1 layer m instead of the heating body 7 shown in FIG. 7 used in Example 1.
Diamond was grown under the same conditions as in Example 1, except that a coiled heating element with a coil diameter of 1.5M and a winding pitch of 1.5 mm was used.

This coiled heating element was gradually deformed and the growth rate of diamond was unstable. After 20 hours, this coiled heating element was greatly deformed, and the average thickness of the obtained diamond film was about 12 mm, which was the same as in Example 1.
The film thickness was non-uniform, with a maximum S summary of 22,11111 and a minimum film thickness of approximately 2 tones.

Example 2 A heating element 7 made of a square molybdenum wire with a side length of 0.2 m and a length of 80 m++ having a square cross-sectional shape as shown in FIG. 10 was attached to the apparatus shown in FIG. Diamonds were grown under the following conditions. first,
A base 5 with a side length of 50 am and a thickness of 5 a is placed on the base holder 4.
A #I tantalum square plate was installed, heated with heat source 6, and maintained at 650°C. Next, from the gas inlet 2 to the reaction vessel 1
A mixed gas of ethane and hydrogen (mixing ratio 1:200) is introduced into the reaction vessel 1, and is exhausted from the gas outlet 3 until the inside of the reaction vessel 1 is heated to approximately 30%.
It was maintained at Torr. Next, the heating element 7 is heated to 2000°C.
At the same time, the temperature of the heating element 7 is increased to 0.1 kMa++2
A tensile stress of . Then, the heating body 7 was reciprocated in a direction perpendicular to the long axis direction and parallel to the surface of the base 5 at a driving speed of 2 mm/win1 and a driving distance of ±251 M.

The shape of the heating element 7 made of this square molybdenum wire was almost stable during use, and even after 30 hours of use, the heating element 7 was hardly deformed and maintained its shape before use. In addition, the growth rate of diamond is almost constant and stable, and 30%
After a period of time, a uniform diamond film with a film thickness of 17yR was formed on the tantalum substrate.

As Comparative Example 2, the apparatus shown in FIG. 2 was used, and instead of the heating body 7 shown in FIG. 10 used in Example 2, a side length of 0.2 was used.
Coil length 80a, coil diameter 2.0111II, winding pitch 1.5 made by winding tart molybdenum square wire.
Diamond was grown under the same conditions as in Example 2 except that a coiled heating element was used.

This coiled heating element was gradually deformed and the growth rate of diamond was unstable. After 30 hours, this coiled heating element was greatly deformed, and the average thickness of the obtained diamond film was about 13-1, with large variations in film thickness depending on the location on the substrate.

Embodiment 3 The apparatus shown in FIG. 3 was provided with long side lengths of 0, 2, . , short side length 0.1M, length 60#
A heating element 7 made of a Ta square wire with a TaC layer formed on its surface was attached, and diamond was grown by chemical vapor deposition under the following conditions. First, an aluminum oxide disk with a diameter of 25 + 1111 mm and a thickness of 4 layers was placed as the substrate 5 on the substrate holder 4, and heated with heating ff16 to 70
It was kept at 0°C. Next, a mixed gas of acetone and hydrogen (mixing ratio 1 near 5) was introduced into the reaction vessel 1 from the gas outlet 2, and the mixture was exhausted from the gas outlet 3, and the inside of the reaction vessel 1 was poured into the reaction vessel 1 with a ladle of 100T.
It was maintained at orr. Next, the temperature of the heating element 7 was raised to 2200°C.

The shape of the heating element 7 made of a Ta square wire with a TaC layer formed on its surface is almost stable during use, and there is almost no deformation of the heating element 7 even after 50 hours of use. I kept it. In addition, the growth rate of diamond is almost constant and stable, and after 50 hours, diamond grows on the aluminum oxide substrate! A uniform diamond film with a thickness of about 30 mm was formed.

As Comparative Example 3, the apparatus shown in FIG. 3 was used, and instead of the heating body 7 shown in FIG. 11 used in Example 3, the long side length was 0.
A coil-shaped heating body with a coil length of 60 mm, a coil diameter of 1.0111, and a winding pitch of 2.0 m was used, which was made by winding a Ta square wire with TaCff formed on the surface, with a short side length of 0.1 aa+ and a coil length of 60 mm. Diamond was grown under the same conditions as in Example 3 except for the above.

This coiled heating element was gradually deformed and the growth rate of diamond was unstable. After 50 hours, this coiled heating element was greatly deformed, and although the obtained diamond film had an average film thickness of about 30 mm, which was almost the same as that of Example 3, the film thickness was uneven, and the diamond film was uneven on the substrate. There were also parts that were not covered with the diamond film.

Example 4 A heating element 7 made of a molybdenum tube having the shape shown in FIG. 13 and having an outer diameter of 2 am, an inner diameter of 1 JII, and a length of 30 am was installed in the apparatus shown in FIG. Diamonds were grown under these conditions. First, place the substrate 5 on the substrate holder 4 with a diameter of 15111% and a thickness of 1 ml.
A silicon wafer of
It was kept at ℃. Next, a mixed gas of ethane and hydrogen (combined ratio 1:400) is introduced into the reaction vessel 1 from the gas outlet 2, and is exhausted from the gas outlet 3, so that the inside of the reaction vessel 1 is heated to about 30 T.
It was maintained at orr. Next, the temperature of the heating element 7 was raised to 1800°C. At the same time, a voltage of 130 V was applied between the substrate holder 4 and the heating element 7 using a DC voltage 3!8 so that the substrate holder 4 had a positive potential. As a result, an electron beam with an average electron density of 25 mA/cm2 was irradiated from the heating body 7 toward the substrate 5.

The shape of the heating element 7 made of this molybdenum tube was almost stable during use, and even after 20 hours of use, the heating element 7 was hardly deformed and maintained its shape before use. In addition, the growth rate of diamond is almost constant and stable, and 201
After 1 hour, a film thickness of 40μIR was deposited on the silicon wafer substrate.
A uniform diamond film was formed.

As Comparative Example 4, the i position shown in FIG. 4 was used, and instead of the heating body 7 shown in FIG. 13 used in Example 4, a diameter of 2,
Coil length 30m, coil diameter 5xts, winding pitch 6jll made by winding a molybdenum tube with an inner diameter of 111I+
Diamond was grown under the same conditions as in Example 4 except that a coiled heating element of 1 was used.

This coiled heating element was gradually deformed and the growth rate of diamond was unstable. After 20 hours, this coiled heating element was greatly deformed, and the average thickness of the obtained diamond film was about 35 mm, with large variations in film thickness depending on the location on the substrate.

Example 5 The apparatus shown in FIG.
．． Four heating elements 7 made of tungsten wire each having a length of 1 am and a length of 30 aw were attached, and diamond was grown by chemical vapor deposition under the following conditions.

First, a rod-shaped molybdenum base 5 is directly heated with electricity.
The temperature was maintained at 00°C. Next, a mixed gas of acetone and hydrogen (mixing ratio 1:50) is introduced into the reaction vessel 1 from the gas inlet 2, and is exhausted from the gas outlet 3, so that the inside of the reaction vessel 1 is
It was maintained at Torr. Next, the heating elements 7, . . .
The temperature was raised to 50°C. At the same time, the base 5 is
A voltage of i oov was applied between the substrate 5 and the heating body 7, so that the substrate 5 had a positive potential and the heating body 7, . . . had a negative potential. As a result, an average of 1
An electron beam with an electron density of 5 mA/cts 2 was irradiated.

The shape of the heating element 7 made of this tungsten wire is almost stable during use, and even after 40 hours of use, the heating element 7 shows almost no deformation (it maintains its shape before use). The speed is almost constant and stable, 40
After a period of time, a film with a thickness of 100-
A uniform diamond film was formed.

It should be noted that when the diamond manufacturing apparatus shown in FIG.
It was confirmed that a uniform diamond film could be formed on the substrate even when a material other than that used in No. 5 was used.

[Effects of the Invention] As detailed above, according to the diamond manufacturing apparatus of the present invention, a uniform diamond film can be manufactured at a nearly constant growth rate, and a diamond film can be easily manufactured over a wide area. It has extremely great industrial value.

[Brief explanation of the drawing]

1 to 6 are configuration diagrams of a diamond manufacturing apparatus according to the present invention, and FIGS. 7 to 15 are perspective views of a heating body used in the diamond manufacturing apparatus of the present invention. DESCRIPTION OF SYMBOLS 1... Reaction container, 2... Gas inlet, 3... Gas outlet, 4... Substrate holder, 5... Substrate, 6... Heating source, 7... Heating body, 8... ...DC power supply. Applicant's representative Patent attorney Takehiko Suzue Figure 5 Figure 6 Figure 7 Figure 8 Figure 10 Figure 11C Figure 9 Figure 4 Figure 12 Figure 15

Claims (1)

[Claims] In the apparatus for forming diamond on the surface of the substrate by arranging a substrate and a heating body in the vicinity of the substrate in a reaction container, and introducing a reaction gas containing an organic compound into the reaction container and thermally decomposing it, A diamond manufacturing device characterized in that the heating body has a shape having a continuous surface extending in a direction parallel to the base body.