JPS63210010A - Production of carbon - Google Patents

Abstract

PURPOSE:To obtain a carbonaceous material contg. nitrogen and having superior strength when a reactive gas made of carbide as starting material is brought into a plasma vapor phase reaction with microwaves to produce the carbonaceous material, by adding hydrogen and nitrogen (compd.) to the reactive gas. CONSTITUTION:A substrate 10 is set in the plasma generating space 1 of a microwave plasma CVD device and the space 1 is evacuated by a pump. A gas 6 such as Ar or hydrogen is introduced into the space 1, microwaves are projected from a microwave generator 4 and a magnetic field is applied from magnets 5, 5' to generate high density plasma. A gas 7 contg. a reactive gas made of carbide such as acetylene, hydrogen and a small amt. of nitrogen or a nitrogen compd. such as ammonia is then introduced into the reaction system and brought into a plasma vapor phase reaction under 0.1-300Torr pressure to form a carbon-base body contg. nitrogen such as a diamond film on the substrate 10.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention causes a plasma gas phase reaction by applying a microwave electric field, and generates a solid object mainly composed of hard carbon, preferably diamond particles or the like. The present invention relates to a method for forming a film that is

[Conventional technology]

Conventionally, as a means for forming a thin film, ECR (electron cyclotron resonance) conditions, that is, I x 10-' to l x 10-'
Electron Cyclotron Resonance (ECR) is a process in which carbon active species are created at a low pressure with a large mean free path sufficient for at least one electron to make one revolution under torr conditions, and a film is formed using the divergent magnetic field. ) is known.

[Conventional problems]

However, carbon produced under such low pressure tends to have an amorphous structure, making it completely impossible to grow diamond in the vapor phase. In addition, it has been impossible to bring the hardness of diamonds produced by this vapor phase method closer to those of diamonds that exist in nature.

For this reason, there has been a strong demand for microcrystalline guyamorado (single crystal carbon) produced by the vapor phase method to have sufficient hardness to be used as an abrasive.

Furthermore, even if we try to form a film at a high pressure of so-called 0, 1 to 300 torr, especially 3 torr or more, which is not the area where such ECR exists, no plasma is generated and it is impossible to use high-density plasma. It had been. It was previously considered impossible to form a crystalline film under such high pressure. However, the inventor of the present invention
It is possible to create high-density plasma even at high pressures such as rr, and such plasma is not ECR but a new mode (
We discovered that this is called "hybrid resonance" here. In addition, by mixing nitride gases such as ammonia and nitrogen with carbide gases under such high pressure, diamonds made by conventional gas phase methods have a 30%
It has been found that hardness can be as strong as ~20 oz.

[Means to solve the problem]

In the present invention, a carbide gas to which nitrogen or ammonia is added together with hydrogen is heated to a pressure of 0.1 to 300 torr, preferably 3 torr.
High pressure of ~3Qtorr creates high-density plasma,
The method involves forming an object mainly composed of carbon to which nitrogen is added, preferably diamond grains or a coating.

These objects to be formed are arranged in the hybrid resonance space or a space apart from the hybrid resonance space that maintains an active state, and the reaction product is coated on the surface of the object. For this purpose,
An object having a surface to be formed is disposed in or near a region where the electric field strength of microwave power is maximum. In addition, in order to generate and sustain high-density plasma at a high pressure of 0.1 to 300 torr, the space containing the column is first heated with lX
ECR (
(electron cyclotron resonance). Introduce a gas at 1 x 10-I to 3 x 10” torr, preferably 3
The plasma state is maintained and changed to a high space pressure of ~30 torr, and the concentration of product gas per unit space in this space is 102 ~
Make the concentration about 10' times higher. This makes it possible to form a film whose main component is carbon, which is a material that can decompose or react only under such high pressure.

For example, diamond, i-carbon (diamond or carbon coating with microcrystalline grains).

In such a case, diamond tends to selectively grow at the edges of the convex portions of the substrate having irregularities.

The formation mechanism of this diamond-containing carbon film leaves behind the components (e.g., crystalline parts) in the dense parts of the film that are being formed during the film formation process, and allows them to grow selectively there. For example, the amorphous portion) is removed using hydrogen plasma, that is, etching is performed. The purpose is to form a film having crystallinity on at least a portion of the formed film.

That is, the present invention adds the force of a magnetic field to the plasma CVD method using microwaves, and uses the interaction between the electric field and the magnetic field of the microwaves. However, lXl0-'~IX10
- ECR (electron cyclotron resonance) conditions effective at 'torr are not used. The present invention moves this plasma state to a high pressure region of 0.1 to 300 torr, and this
The coating is formed using high-density, high-energy plasma at a high pressure of rr. Utilizing the high energy state in the hybrid resonance space, for example, a large amount of activated carbon can be generated to produce films with excellent reproducibility, uniform thickness, and homogeneous properties, such as diamond and i-carbon films. This enabled the formation of

Furthermore, since the strength of the applied magnetic field can be changed arbitrarily, it is possible to set resonance conditions not only for electrons but also for specific ions.

Additionally, in addition to the configuration of the present invention, after generating high-density plasma by the interaction between microwaves and a magnetic field, if high energy is continued until it reaches the object surface, the maximum microwave electric field Carbon atoms excited to a high-energy state exist even in a region 0.5 to 10 cm away from the high-density plasma generation region (a position where the active state of the reactive gas can be maintained), and diamond and carbon atoms exist in a larger space. It is possible to form an i-carbon film.

In the present invention, a cylindrical column is disposed in such a space, a film-forming object is disposed within the column, and a film is formed on the surface of the column.

Examples will be shown below to further explain the present invention.

〔Example〕

FIG. 1 shows a microwave plasma CVD apparatus capable of applying a magnetic field used in the present invention.

In the figure, this device includes a plasma generation space (1) that can be maintained in a reduced pressure state, an auxiliary space (2), electromagnets (5) and (5') that generate magnetic fields, their power source (25), and a microwave oscillator ( 4), a turbo molecular pump (8), a rotary pump (14), and a pressure adjustment valve (11) that constitute the exhaust system.

Substrate holder (10°), film forming object (10), microwave introduction window (15), gas system (6), (7)
, water cooling system (18), (18').

It consists of a halogen lamp (20), a reflecting mirror (21), and a heating space (3).

First, the thin film forming object (10) is placed on the substrate holder (10''), and the plasma generation space (10) is opened from the gate valve (16).
). This substrate holder (10°) was made of quartz so as not to disturb the microwave and magnetic field as much as possible.

As part of the fabrication process, the entire structure was first assembled using a turbo molecular pump (
8), I x 10-'tor by rotary pump
Evacuate to below r. Next, a non-product gas (a gas that does not constitute a post-decomposition reaction body) such as argon, helium, or hydrogen (6) is introduced into the plasma generation region (1) through the 303 CCM gas system (7), and the pressure is increased to l x 1
0-'torr. Microwaves with a frequency of 2.45 GHz and a strength of 500 W are applied from the outside. A magnetic field of about 2 Gauss is applied from magnets (5) and (5') to generate high-density plasma in the plasma generation space (1). From this high-density plasma region, high-energy non-product gas or electrons reach the surface of the object (IO) on the substrate holder (10'') and clean the surface.

Next, a product gas (
gas constituting the post-decomposition/reaction body) such as carbide gas (
Acetylene (CJg), ethylene (C2H, ) or methane (C114, etc.) is introduced at a flow rate of 305 CCH. At this time, the hydrocarbon is diluted with hydrogen to a sufficiently thin concentration of O11 to 5χ.In addition, the method of the present invention uses a nitride gas such as ammonia (Nl13) or nitrogen (N8) at a concentration of 0.1% compared to the hydrocarbon gas. It was added at a concentration ratio of ~5χ.

Then, while maintaining the already generated plasma state, the pressure in the space is changed to lXl0-' to 3X10'' torr, preferably 3 to 30 torr, for example 10 torr.By increasing the pressure in this space, the pressure per unit space is increased. The concentration of the product gas can be increased and the film growth rate can be increased. Carbon atoms excited with high energy are generated and heated to 800 to 1000°C by the heater (20), and the object on the substrate holder (10') (10)
This carbon is deposited on top to form a diamond or i-carbon film with a grain size of 0.1-100μ.

In Figure 1, the magnetic field consists of two ring-shaped magnets (5),
A Helmholtz coil method using (5') was adopted.

Furthermore, FIG. 2 shows the results of examining the strength of the electric and magnetic fields for the space (30) divided into four parts.

In FIG. 2 (A), the horizontal axis (X-axis) is the horizontal direction of the space (30) (reactive gas release direction), and the vertical axis (R-axis)
indicates the diameter direction of the magnet. The curves in the drawings indicate equipotential surfaces of the magnetic field. The number shown on the line indicates the strength of the magnetic field obtained when the magnet (5) is about 2000 Gauss. By adjusting the strength of the magnet (5), the space (100) (875 Gauss ± 18
(within 5 Gauss), it is possible to make the strength of the magnetic field approximately uniform over a large area over a wide area of the formation surface of the substrate. The drawing shows an isomagnetic scene, in particular the line (26) at 875
It is an isomagnetic scene that produces the conditions for Gaussian resonance.

The space (100) that produces this resonance condition is designed to be a region where the electric field is maximum, as shown in FIG. 2(B). The horizontal axis of FIG. 2(B) indicates the direction in which the reactive gas flows, as in FIG. 2(^), and the vertical axis indicates the strength of the electric field (electric field strength).

Of course, if a donut-shaped coating is to be formed, this may be used.

There is also a region on the opposite side of the origin symmetrical to region (100) where the electric field is maximum and the magnetic field is constant over a wide region. When there is no need to heat the substrate, film formation in such a space is also effective. However, it is difficult to find a way to perform heating without disturbing the microwave electric field.

As a result, considering the ease of loading and unloading the substrate and the ease of heating, the area (100) in Figure 2 (^) is the most industrially mass-producible of the three areas in order to obtain a uniform and homogeneous coating. Estimated to be in an excellent location. .

As a result, in the present invention, when the substrate (10) is disposed in the area (100), if this substrate is circular, the radius is 100.
It became possible to uniformly and homogeneously form a film with a radius of up to 50 m5.

To make the area even larger, for example, the frequency should be set to 2.45 GH to make the film thickness the same (to make the film thickness uniform) over an area four times as large as this.
By setting 1,225GIIz instead of z, the diameter of this space (toward the right in FIG. 2(A)) can be doubled.

FIG. 3 is a diagram of equal magnetic fields and equal electric fields of the magnetic field (A) and electric field (B) in a circular space at the position of the substrate (10) in FIG. 2. FIG. As is clear from FIG. 3(B), the electric field can reach a maximum of 25 V/m.

For comparison, a thin film was formed under the same conditions without applying a magnetic field. The thin film formed on the substrate at that time was a graphite film.

When we took an electron beam diffraction image of the thin film formed in this example, we found diamond (single crystal grain) spots along with a halo pattern unique to amorphous. -It was a carbon film. As the microwave power was further increased and the formation progressed, the halo pattern gradually disappeared, and at 700 mm or more, the film became a film in which more diamond structures were mixed.

〔effect〕

The present invention can form diamond grains or films by diluting hydrocarbons mixed with nitride gas with hydrogen, and at the same time can prevent lattice defects in the diamond from progressing due to adjacent and external stress. Therefore, nitrogen is added to this. The nitrogen was then added at the same time as the diamond was formed, with ammonia or nitrogen added to a concentration of 0.1 to 5x compared to the hydrocarbon. Then, this ammonia or nitrogen becomes plasma, and nitrogen can be mixed into the formed diamond grains at a ratio of 0.01 to 1% by weight.

In order to compare the presence or absence of nitrogen and the amount of nitrogen in these carbon particles,
It is made into an abrasive material and the polishing work is done from outside. As a result of conducting an indirect strength test on microcrystalline diamond hardness, it was found that the reduction in polishing effect was more than twice that of the case without this addition (i.e., it prevented the diamond grains from becoming finer due to wear). I was able to do so.

As a result, the practicality of the material as a hard material such as diamond grains could be greatly improved.

The method of the present invention uses nitrogen, which is closest in the periodic table, to improve the hardness of diamond. However, if it is possible to prevent lattice defects from progressing due to local forces, boron (B), aluminum (AI), phosphorus (P), or a part of these and nitrogen can be used in an amount of 0.001 to 1. It is effective to mix it in a proportion of % by weight to form a diamond mixture.

Furthermore, in the method of the present invention, the addition of nitrogen is replaced by ammonia (M
HI) or nitrogen (N2). But No2゜N
O, N13 may also be used.

Also, in the drawings, the gas was made to flow from the side to the right. However, it may be from the left side to the right side, from the top to the bottom, or from the bottom to the top.

[Brief explanation of the drawing]

FIG. 1 schematically shows a microwave CvD apparatus using magnetic field/electric field interaction used in the present invention. FIG. 2 shows the magnetic field and electric field characteristics by computer simulation. Figure 3 shows the characteristics of the magnetic field and electric field at a position where the electric field and magnetic field interact. 1... Plasma generation space 4... Microwave oscillator 5.5'... External magnetic field generator 8... Turbo molecular pump 10... Film forming object or substrate 10'...
・Substrate holder 20...Halogen lamp 21...Reflector

Claims (1)

[Claims] Using microwaves with a frequency of 1,500 MHz or more,
A plasma gas phase reaction method for producing an object mainly composed of carbon from a reactive gas of carbide, wherein hydrogen and nitrogen or a compound of nitrogen are simultaneously added to the reactive gas to produce an object mainly composed of carbon mixed with nitrogen. A carbon production method characterized by producing an object. 2. In claim 1, by applying a magnetic field in addition to microwaves at the same time and using the interaction of the electric field and the magnetic field, the main component is carbon containing diamond containing nitrogen in a pressure range of 0.1 to 300 torr. A carbon production method characterized by producing an object.