JP2798907B2 - Method of making diamond coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a diamond film suitable for use as a sliding surface material, a working tool material, a semiconductor substrate, a heat sink material and the like.

[0002]

2. Description of the Related Art Diamond has excellent characteristics such as hardness, coefficient of thermal expansion, thermal conductivity, refractive index, elastic modulus, transparency, and high insulation. In recent years, this diamond coating has
It is used as a sliding surface material, a processing tool material, a semiconductor substrate, and a heat sink material, or is attracting attention as a material for these materials. The future demand for media (heat sinks) is very high. However, at present, sufficient composition and performance cannot be obtained as compared with natural diamond for use as a semiconductor substrate, and a large single crystal film has not been successfully produced. Absent. On the other hand, some heat sink materials and the like have been put into practical use.

[0003] In a conventional method for producing a diamond film, an organic gas (a gas such as methane or ethane) is mixed in a high-speed plasma flow of a mixture of an inert gas (such as helium or argon) and hydrogen. Introduce and decompose the organic gas to make the contained carbon into a radical (unstable high-energy state in which atoms are extremely susceptible to reaction), and to react and deposit on the substrate to produce diamond. (CVD method). However, at present, the composition is not completely obtained, and it is a mixture of diamond, diamond-like carbon (DLC), and free carbon. That is, in the above conventional method, since hydrogen is used, a substance in which carbon and hydrogen are bonded (DLC, etc.)
It is considered difficult to remove the diamond, and complete diamond production cannot be expected. Therefore, realizing the reactive precipitation of diamond in a system containing no hydrogen is a prerequisite for obtaining a compositionally complete product.

[0004]

DISCLOSURE OF THE INVENTION The present inventors have developed a method of producing a diamond film using a methane and hydrogen as raw materials (CVD method), which is currently the mainstream, and completely separates a carbon film containing no hydrogen. We have intensively investigated a method for producing a film using only a reaction system, and as a result, have confirmed that the method can be realized as described in detail below. The present invention is based on such knowledge, and therefore, the basic technical problem of the present invention is to realize the production of diamond in a system containing no hydrogen, and to provide a route for producing complete diamond. Is to open. Another technical problem of the present invention is to minimize the possibility of containing impurities other than carbon by using a carbon ultrafine powder produced in an inert gas and not exposed to the atmosphere. It is an object of the present invention to provide a method for producing a diamond film which enables a complete diamond film to be produced.

[0005]

According to the present invention, there is provided a method for producing a diamond film, comprising the steps of introducing ultrafine carbon powder into a high-speed plasma flow of an inert gas using a plasma gun. The carbon is decomposed into radicals, and the carbon is reacted and deposited as a diamond film on a substrate (PVD method). In a preferred embodiment of the above method, an ultrafine carbon powder having a particle size of 0.5 to 10 nm is produced by a sublimation method using a high-power CO ₂ laser in an inert gas atmosphere under reduced pressure, and introduced by a plasma gun. To be used as ultrafine carbon powder.

According to the method for producing a diamond film of the present invention described above, as is apparent from the examples described later, diamond is produced in a system containing no hydrogen and using only an inert gas and carbon. Has been realized.
This opens the way for the production of perfect diamonds. According to the above method, since diamond is produced in a production system using carbon ultrafine powder which is produced in an inert gas and is not exposed to the atmosphere and contains no hydrogen, impurities other than carbon are contained. It is possible to make the diamond coating as complete as possible with extremely low possibility.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing a diamond film of the present invention is a new method which can be called a high voltage DC plasma coating method (PVD method) using ultrafine carbon powder as a raw material, and more specifically. Introducing ultrafine carbon powder using a plasma gun into a high-speed plasma flow of an inert gas consisting of helium or argon, the fine carbon particles are decomposed, become radicals, and the carbon atoms become unstable. The state becomes a high energy state, and is reactively deposited as a diamond film on the substrate, that is, a diamond film by DC plasma coating is generated. It is necessary that the inert gas does not contain hydrogen.

The ultrafine carbon powder used in the above method is
Ultrafine powder having a particle size of 0.5 to 10 nm is desirably obtained by a sublimation method using a high-output CO ₂ laser in an inert gas atmosphere such as helium or argon under reduced pressure (10 to 500 torr). Ultrafine powder of carbon produced by exposing to air or containing no impurities other than carbon can be used. In order to introduce the ultrafine powder into the high-speed plasma flow of the inert gas, it is necessary to use a plasma gun that enables this, and it is difficult to introduce the carbon powder with a conventional gun.

In a diamond production experiment using discharge plasma without using a high-speed plasma flow, the highest quality diamond film is obtained, but there is a problem that the film growth is extremely slow (about 1/1000). However, there is difficulty in its practical use. In addition, it is considered that it is difficult to use ultrafine carbon powder in the method using the discharge plasma. On the other hand, in the PVD method using the powder as in the present invention, a diamond film can be formed in a short time so that there is no problem in practical use.

[0010]

Next, an example of a method for producing a diamond film according to the present invention will be described. The method of the present invention used for the preparation of the diamond coating is by high voltage DC plasma coating using ultrafine carbon powder as a raw material,
Specifically, ultrafine carbon powder having a particle size of about 0.5 to 10 nm was introduced into a high-speed plasma flow of a helium-argon mixed gas containing no hydrogen using a plasma gun. The ultrafine carbon powder was prepared by a sublimation method using a high-output CO ₂ laser under a reduced pressure of helium. Then, a diamond film was successfully formed on a silicon substrate by high-voltage DC plasma coating using the ultrafine carbon powder.

The results of a comparative study of the diamond coating of the above example formed by the DC plasma coating method of ultrafine carbon powder and the diamond coating of the comparative example formed by the ordinary CVD method are described below with reference to the drawings. I do. FIG. 1 shows a Raman spectrum of ordinary carbon. The peak at 1584 cm ^{-1 in} the figure is a peak attributable to graphite, and the peak at 1357 cm ^{-1 is} a peak attributable to amorphous carbon. FIG.
Shows the Raman spectrum of natural diamond. The peak at 1333 cm ^{-1 in} the figure is a peak due to diamond.

FIG. 3 shows a conventional method including hydrogen (CVD).
FIG. 4 is a Raman spectrum of the diamond film formed in the embodiment of the present invention by the PVD method, and FIG. 5 is a Raman spectrum of the diamond film formed by the PVD method. 1 shows X-ray diffraction patterns of an example diamond coating and a coating obtained by the PVD method of the present invention.

From FIGS. 3 to 5, the film obtained by the conventional CVD method is a mixture of diamond, amorphous carbon, and diamond-like carbon (DLC), whereas the film obtained by the embodiment of the present invention is obtained. The resulting coating can be considered to be a mixture of diamond, amorphous carbon, and graphite. In both coatings, a diamond peak is observed, and in the example of the present invention, a graphite peak is also observed, but a diamond-like carbon (DLC) peak due to hydrogen is not observed.
Therefore, in the example of the present invention, as in the comparative example, although it was not successful in the production of a perfect diamond, it was demonstrated that the production of a diamond coating could be carried out in a hydrogen-free system. The path to the production of a perfect diamond was opened.

[0014]

As is evident from the above detailed description, the method for producing a diamond film of the present invention realizes the production of diamond in a system containing no hydrogen, and complete production of diamond. Could open the way for. Further, according to the method of the present invention, by using ultrafine carbon powder produced in an inert gas and not exposed to the atmosphere, the possibility of containing impurities other than carbon is extremely reduced, and as much as possible. It is possible to obtain a method for producing a diamond coating that enables complete production of a diamond coating.

[Brief description of the drawings]

FIG. 1 is a diagram of Raman spectrum of ordinary carbon.

FIG. 2 is a Raman spectrum diagram of a natural diamond.

FIG. 3 is a Raman spectrum diagram of diamond obtained by a conventional method containing hydrogen (CVD method).

FIG. 4 is a Raman spectrum diagram of diamond produced by the method of the present invention (PVD method).

FIG. 5 is a diagram showing X-ray diffraction patterns of coating films obtained by a comparative example according to a conventional method and an example according to the method of the present invention.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yuji Kawakami 1-2-2 Namiki, Tsukuba, Ibaraki Pref. Machinery and Technology Research Institute, Institute of Industrial Science and Technology (72) Inventor Kazuhiro Setoguchi 516 Yokota, Sanmu-cho, Sanmu-gun, Chiba Vacuum Examiner, Yoichi Gotani, Metallurgy Co., Ltd. (56) References JP-A-7-118852 (JP, A) JP-A-7-233475 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB Name) C30B 29/04 C23C 14/06

Claims (2)

(57) [Claims] An ultra-fine powder of carbon is introduced into a high-speed plasma flow of an inert gas using a plasma gun to decompose and convert the carbon into a radical and to form a diamond coating on a substrate. Characteristic method of producing diamond coating. 2. A particle size of 0.5 to 10 by a sublimation method using a high-power CO ₂ laser in an inert gas atmosphere under reduced pressure.
The method for producing a diamond film according to claim 1, wherein an ultrafine powder of carbon having a diameter of nm is produced and used as ultrafine powder of carbon introduced by a plasma gun.