JPH0623437B2 - Method for producing carbon and boron nitride - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention is directed to a solid body containing carbon and boron nitride containing nitrogen and boron as a main component, in which a plasma gas phase reaction is caused by applying microwaves, particularly particles. Alternatively, the present invention relates to a method of forming a film containing the same.

[Conventional technology]

Conventionally, as a means for forming a thin film, under the ECR (electron cyclotron resonance) condition, that is, under the condition of 1 × 10 ⁻³ to 1 × 10 ⁻⁵ torr, the mean free path which is sufficient for at least one round of electrons is large, that is, low. A method using electron cyclotron resonance is known in which active species of carbon are produced by pressure and the divergent magnetic field is used to form a film.

[Conventional problems]

However, carbon produced at such a low pressure tends to have an amorphous structure, and vapor phase growth of diamond was completely impossible.

In addition, coating on superhard metals such as WC (tungsten carbide) has not been possible with conventional carbon-only films.

For this reason, it gives microcrystalline diamond (a single crystal of carbon) produced by the vapor phase method sufficient hardness to be used as an abrasive or coating material, and firmly adheres to cemented carbide. There was a strong demand for the coating to be applied.

Further, until now, even if a film was formed at a high pressure of 1 to 760 torr, especially 10 torr or more, which is not such an ECR existence region, plasma was not generated and it was considered impossible to use high density plasma. . In particular, it has been considered impossible to form a film having crystallinity at such a high pressure. However, the inventor of the present invention is capable of producing a high density plasma even at a high pressure of 1 to 760 torr, preferably 3 to 100 torr, and that such plasma is a new mode (here, referred to as "hybrid resonance") rather than ECR. Found.

Further, at such a high pressure, a carbide gas is mixed with a nitride gas such as ammonia, nitrogen fluoride, or nitrogen, and B ₂ H ₆ or BF ₃ which is a boride gas. It has been found that in addition to having a hardness as strong as 30 to 200%, it can be coated on a cemented carbide metal in close contact with it.

[Means to solve the problem]

The present invention is a nitrogen or ammonia and diborane (B ₂ H ₆₎ or carbide gas boron trifluoride (BF ₃₎ was added together with hydrogen 1~760torr preferably allowed high density plasma at a pressure of 3 ～100Torr, It is intended to form a mixed body or a multi-layer body containing carbon and boron nitride to which nitrogen and boron are added as a main component (both have a component ratio of 90% or more in total), preferably a crystal grain or a coating film.

These objects to be formed are arranged in the hybrid resonance space or a space apart from the object which holds an active state, and the reaction products are coated on the surface of the object. For this purpose
An object having a surface to be formed is arranged in or near a region where the electric field strength of microwave power is maximized. Moreover, since the high-density plasma is generated and maintained at a high pressure of 1 to 760 torr, the concentration of the product gas in this space per unit space is about 10 ² to 10 ⁵ times higher than that of the conventional ECR CVD method. Adjust the concentration. Then, it becomes possible to form a film containing carbon and boron nitride, which are materials that can be decomposed or reacted only at such a high pressure, as main components. For example, diamond, i-carbon (diamond or carbon coating having fine crystal grains). At this time, first, a boron nitride film or a film containing the same as the main component may be formed on the ratio forming surface, and carbon or a multi-layered film containing carbon as the main component may be formed thereon.

The film formation mechanism of the carbon film containing diamond containing nitrogen and boron as the main components leaves the constituents (for example, crystal parts) of the dense part of the film being formed in the film formation process and selectively grows there. At the very least, the structure of the rough portion (for example, the amorphous portion) is removed by hydrogen or oxygen plasmatized, that is, etching is performed. Then, a film having crystallinity is formed on at least a part of the formed film.

Hereinafter, the present invention will be described with reference to examples.

〔Example〕

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

In this figure, this device has a plasma generation space (1) that can be maintained under reduced pressure, an auxiliary space (2), an electromagnet (5) that generates a magnetic field,
(5 ') and its power supply (25), microwave oscillator (4), turbo molecular pump (17) that constitutes the exhaust system, rotary pump
(14), pressure control valve (11), (15), substrate holder (10 '), film forming object (10), microwave introduction window (15), gas system (6),
(7), (8), water cooling system (18), (18 '), halogen lamp (20), reflecting mirror (21), heating space (3).

First, the thin film forming object (10) is placed on the substrate holder (10 ') and is placed in the plasma generation space (1) from the gate valve (16). This substrate holder (10 ') was made of stainless steel so as not to disturb the microwave and magnetic field as much as possible.

As a manufacturing process, first of all, these are turbo molecular pumps (1
7) Evacuate to 1 × 10 ^-6 torr or less with a rotary pump. Next, a non-product gas (a gas that does not form a solid after the decomposition reaction), such as hydrogen (6), is introduced into the plasma generation region (1) through the 300SCCM gas system (7), and a microwave of 2.45GHz frequency is applied from the outside to 1KW. Add with strength. A magnetic field of about 2K Gauss is applied from the magnets (5) and (5 ') to generate high-density plasma in the plasma generation space (1). Non-product gases or electrons with higher energy than this high density plasma region reach the surface of the object (10) on the substrate holder (10 ') and clean the surface.

Next, in this reaction system, hydrogen (6) and gas systems (7) and (8) are used to produce a product gas (a gas that forms a solid after decomposition / reaction) such as a carbide gas (acetylene (C ₂ H ₂ ), ethylene (C ₂ H ₄ ), methyl alcohol (CH ₃ OH), ethyl alcohol (C ₂ H ₅ OH) or methane
(CH ₄ ) etc.) is introduced at a flow rate of 30 SCCM. At this time, the hydrocarbon was diluted with hydrogen to a sufficiently thin concentration of 0.1 to 5%. In addition to this, the method of the present invention uses ammonia (NH ₃ ) or nitrogen (N ₂ )
Nitride gas like (7) and diborane (BF ₃ )
Equal amounts (B / N = 1/1) were added from (8). And BF ₃
The sum with NH ₃ was added at a concentration ratio of 1 to 50% compared to the hydrocarbon gas. Then, the pressure of the space is 1 to 7.6 × 10 ² torr, while maintaining the already generated plasma state,
10 to 100 torr For example, the pressure is changed to 30 torr. By increasing the pressure in this space, the concentration of the product gas per unit space can be increased and the film growth rate can be increased. Then, carbon atoms, boron atoms, and nitrogen atoms excited by high energy are generated, and the substrate holder (1) heated to 800 to 1000 ° C. by the heater (20) and plasma energy
0 ') Boron nitride is formed on the upper body (10) by depositing or admixing the carbon mixed with nitrogen and boron.

In Fig. 1, the magnetic field consists of two ring-shaped magnets (5),
The Helmholtz coil method using (5 ') is adopted. Furthermore, Fig. 2 shows the results of examining the electric and magnetic field strengths in the space (30) divided into four.

In FIG. 2 (A), the horizontal axis (X axis) is the horizontal direction of the space (30) (reactive gas discharge direction), and the vertical axis (R axis) is the diameter direction of the magnet. The curves in the drawings show the isomagnetic surface of the magnetic field. And the number shown on the line shows the strength of the magnetic field obtained when the magnet (5) is about 2000 gauss. magnet
By adjusting the strength of (5), the magnetic field strength can be made approximately uniform over a large area of the substrate formation surface in a large area in the space (100) (within 875 Gauss ± 185 Gauss) where the electrode and magnetic field interact. Can be made. The drawing shows the isofields, in particular the line (26) which produces the condition of resonance at which 875 Gauss.

As shown in Fig. 2 (B), the space (100) in which this resonance condition occurs is the region where the electric field is maximum. Second
The horizontal axis of the figure (B) shows the flowing direction of the reactive gas as in the case of the second figure (A), and the vertical axis shows the strength of the electric field (electric field strength).

Needless to say, when a doughnut-shaped film is formed.

On the opposite side of the region (100) with respect to its origin symmetry, there is a region where the electric field is maximum and the magnetic field is constant over a wide region. When it is not necessary to heat the substrate, forming a film in such a space is also effective. However, it is difficult to obtain a means for heating without disturbing the electric field of the microwave.

As a result, in consideration of the ease of loading / unloading the substrate and heating, the area (100) in Fig. 2 (A) is the most industrially mass-producible among the three areas in order to obtain a uniform and homogeneous film. It is estimated that the location is excellent. .

As a result, according to the present invention, when the substrate (10) is arranged in the region (100), if the substrate is circular, it is possible to form a uniform and uniform film with a size up to a radius of 100 mm, preferably up to a radius of 50 mm. Became.

To make the area even larger, for example, in order to obtain the same uniform film thickness in this 4 times area, if the frequency is set to 1.225 GHz instead of 2.45 GHz, the diameter of this space (R in Fig. 2 (A))
Direction) can be doubled.

FIG. 3 is a drawing of the magnetic field (A) and the electric field (B) in the circular space at the position of the substrate (10) in FIG. It is clear from Fig. 3 (B) that the electric field can reach up to 25 KV / 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 an electron diffraction image of the thin film formed in this example was taken, spots of polycrystalline boron nitride and crystalline carbon, that is, diamond (single crystal grain) were observed, and a composite film of boron nitride and diamond was formed. Was becoming. Furthermore, as the microwave power was increased from 1 KW to 5 KW, the structure of the formed film became a film in which more diamond structure was mixed.

〔effect〕

According to the present invention, a diamond grain or film is formed by diluting a hydrocarbon mixed with a boride gas and a nitride gas with hydrogen. In this way, it is possible to prevent the lattice defects in the diamond from advancing due to stresses from the proximity and the outside. By forming a coating film containing carbon or boron nitride as a main component on a cemented carbide metal such as tungsten carbide using boron nitride as a binder, it has become possible to improve the adhesion and the hardness as a cutting tool.

In the present invention, one of the reactive gases is a fluoride such as BF ₃
Alternatively, by using NF ₃ , fluorine is generated during plasma formation. This fluorine was effective in etching dirt on the surface to be formed.

The method of the present invention used the closest nitrogen and boron in the periodic table to improve the hardness of diamond. However, at the same time as preventing lattice defects from progressing due to local force,
If it is possible to improve the adhesion on the cemented carbide surface, mix aluminum (Al) and phosphorus (P) in a ratio of 0.001 to 1% by weight to form a mixture of diamond and boron nitride or a multilayer film. Is valid.

In the method of the present invention, the nitride is ammonia (NH ₃ ),
Nitrogen fluoride (NF ₃ ) or nitrogen (N ₂ ) was used. But NO ₂ , N
O, N ₂ O may be used.

[Brief description of drawings]

FIG. 1 shows an outline of a microwave CVD apparatus using a magnetic field / electric field interaction used in the present invention. FIG. 2 shows the magnetic field and electric field characteristics by computer simulation. FIG. 3 shows the characteristics of the magnetic field and the electric field at the position where the electric field-magnetic field interaction is caused. 1 ... Plasma generation space 4 ... Microwave oscillator 5,5 '... External magnetic field generator 17 ... Turbo molecular pump 10 ... Object or substrate for film formation 10' ... Substrate holder 20 ... Halogen lamp 21 ... … Reflector 100 …… The space that becomes the maximum electric field

Claims (2)

[Claims] 1. A plasma gas phase reaction method for producing an object containing carbon and boron nitride as main components by using a microwave, wherein a carbide gas, hydrogen and nitrogen or a nitrogen compound gas and a boride gas are simultaneously produced. A method for producing carbon and boron nitride, which comprises introducing and introducing an object containing carbon and boron nitride mixed with nitrogen and boron as main components. 2. The method according to claim 1, wherein a magnetic field is simultaneously applied in addition to the microwave, and the diamond containing nitrogen and boron is used in the pressure range of 1 to 760 torr by using the interaction between the electric field and the magnetic field. A method for producing carbon and boron nitride, which comprises producing an object mainly composed of carbon and boron nitride.