JPH01257198A - Method for coating diamond-like carbon film - Google Patents

Abstract

PURPOSE:To prevent generation of a layer adsorbed with reaction gas on the surface of a carbon film in a process for coating a diamond-like carbon film synthesized in vapor phase under a low pressure by allowing the reaction gas to contact with a substrate for a specified time, then stopping the supply of the reaction gas and keeping a degree of vacuum in the vessel at <=a specified value. CONSTITUTION:A substrate (e.g. silicon, magnetic recording medium) is disposed in a high vacuum vessel, and a reaction gas consisting of a C-source gas (e.g. CO, methane) and a dilution gas (e.g. H2) are allowed to contact with said substrate for a specified time after exciting the reaction gas to form thus a diamond-like carbon film on the surface of the substrate. The supply of the reaction gas is stopped immediately thereafter, and the reaction gas in the reaction chamber is evacuated with a vacuum pump to keep a degree of vacuum in the reaction chamber at <=10<-4>Torr. Then, the temp. in the vessel is reduced to room temp., thus, a substrate coated with a diamond-like carbon film is obtd. By the above method, generation of a layer adsorbed with the reaction gas on a carbon film is prevented.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method of coating a diamond-like carbon film, and more particularly to a method of coating a diamond-like carbon film that prevents substantial formation of a reactive gas adsorption layer on the surface. .

(Prior art) Diamond-like carbon films have been used in cutting tools because of their excellent mechanical strength (hardness), high thermal conductivity, high transparency, high refractive index, chemical resistance, abrasion resistance, and solid lubricity. ,
It is expected that it will be used as a coating material for base materials in various fields such as audio parts, optical parts, magnetic recording media, and electronic materials.

In particular, it is promising for use as a top coat film for magnetic recording media, such as magnetic disks, which require mechanical strength (hardness) and wear resistance.

(Problems to be Solved by the Invention) Therefore, the present inventors applied a magnetic material to the base material of a magnetic recording medium, and then formed a diamond-like carbon film thereon by a known method. When used as a magnetic recording medium, various problems occurred, such as the head of the magnetic disk not floating and the head and magnetic disk sticking together, increasing the coefficient of friction, and deposits on the head. I couldn't.

(Means for Solving the Problem) As a result of intensive research in view of the above problems, the present inventors have found that:
It was found that a reactive gas adsorption layer was formed on the surface of the diamond-like carbon film, and this adsorption layer deteriorated the characteristics of the magnetic disk.

Therefore, the present inventors completed the present invention in order to prevent the formation of a reactive gas adsorption layer on the surface of the diamond-like carbon film.

That is, the invention according to claim 1 of the present application for solving the above problem is to bring a substrate placed in a high vacuum container into contact with a reaction gas to form a diamond-like carbon film on the surface of the substrate, and then to cool the substrate. In the method of coating the surface of a substrate with a diamond-like carbon film, after the reaction gas is brought into contact with the substrate for a predetermined time, the supply of the reaction gas is stopped and the degree of vacuum in the container is reduced to 10-4 Torr.
This is a diamond-like carbon film coating method characterized by maintaining the following.

The invention as set forth in claim 2 of the present application provides that in the method for coating a diamond-like carbon film as set forth in claim 1, instead of maintaining the degree of vacuum in the container at 10-4 Torr or less, the reaction gas in the container is This is a method for coating a diamond-like carbon film, which is characterized in that stirring is performed using an active gas, hydrogen gas and/or nitrogen gas.

In both of the inventions of claims 1 and 2, if a magnetic recording medium is particularly selected as the substrate (claim 3), a diamond-like carbon film magnetic recording medium with particularly excellent running characteristics can be manufactured. I can do it.

(Detailed Description of the Invention) (1) Substrate The substrate used in the low-pressure vapor phase diamond-like carbon film coating method of the present invention includes metals such as silicon, tungsten, and molybdenum, alloys such as stainless steel, tantalum silicon, and molybdenum carbide. Examples include inorganic ceramics such as , tungsten carbide, alumina, diamond, spinel, silicon carbide, and silicone, glasses such as quartz glass, crystals of inorganic compounds such as sodium chloride and potassium chloride, and plastics such as polycarbonate.

Among these, silicon and glass are preferred because they have excellent adhesion to the substrate.

Furthermore, a magnetic recording medium formed by depositing a magnetic recording material on a support can also be used as a substrate in the present invention. When a diamond-like carbon film is coated on the magnetic layer of a magnetic recording medium, this diamond-like carbon film acts as a protective film, preventing the magnetic head from adhering to the magnetic head and reducing the coefficient of friction. It is possible to prevent deposits such as magnetic powder from adhering to the surface.

Here, a known hard disk can be used as the magnetic recording medium. More specifically, the magnetic recording medium, which is an octet disk, is manufactured by depositing a magnetic material such as cobalt on a support plate made of metal such as aluminum or heat-resistant hard synthetic resin such as polycarbonate by electron beam evaporation, sputtering, or ion blating. It can be obtained by forming by means such as.

(1) Reactive gas The reactive gas used in the method of the present invention is mainly a mixed gas of a carbon source gas and a diluent gas.

Examples of the carbon source gas include paraffinic hydrocarbons such as methane, ethane, propane, and butane, olefinic hydrocarbons such as ethylene, propylene, and butylene, and acetylene hydrocarbons such as acetylene and arylene. Hydrogen, diolefinic hydrocarbons such as butadiene, alicyclic hydrocarbons such as cyclopropane, cyclotutane, cyclopentane, and cyclohexane, and aromatic hydrocarbons such as cyclobutadiene, benzene, toluene, xylene, 3 and naphthalene, etc. -carbohydrogen compounds, ketones such as acetone, diethyl ketone, and benzophenone, alcohols such as methanol and ethanol, -
carbon oxide and oxygen-containing organic compounds such as carbon dioxide;
and nitrogen-containing organic compounds such as amines such as trimethylamine and triethylamine.

In addition, although not a single substance, Class 4 hazardous materials stipulated in the Fire Service Act; Class 1 petroleum such as gasoline, Class 2 petroleum such as kerosene, turpentine, ginger oil, and pine oil, and Class 3 hazardous materials such as heavy oil. Petroleum oils, gear oil, cylinder oil, and other quaternary petroleum oils can also be used. It is also possible to use a mixture of the various carbon compounds mentioned above.

Among these carbon source gases, preferred are paraffinic hydrocarbons such as methane, ethane, and propane, acetone,
These include ketones such as benzophenone, amines such as trimethylamine and triethylamine, carbon dioxide gas, and carbon oxide.

In forming the diamond-like carbon film, a diluting gas can be used together with the carbon source gas.

Examples of the diluting gas include hydrogen gas: inert gases such as argon gas, neon gas, xenon gas, and nitrogen gas.

These may be used alone or in combination of two or more.

Among these, when hydrogen gas is used, plasma is formed by high frequency or microwave irradiation in the plasma CVD method, and atomic hydrogen is formed by heat or discharge in the CVD method.

This atomic hydrogen has the effect of removing graphite-structured carbon that is deposited at the same time as the diamond-like carbon film is deposited.

The inert gas is particularly used in a sputtering method.

When an ion vapor deposition method or an ion beam vapor deposition method is employed, it is used in combination with a carbon source gas consisting of the paraffinic hydrocarbon compound, the oxygen-containing organic compound, and/or the nitrogen-containing organic compound, and is used in the discharge space. It has the effect of ionizing carbon by knocking out carbon atoms by ionizing.

Furthermore, when a high frequency plasma CVD method, a direct current plasma CVD method, or a microwave plasma CVD method is employed, it has the effect of stabilizing the discharge.

When using the diluent gas, the mixing ratio with the carbon source gas is a molar ratio of carbon source gas/diluent gas, which is usually 0.
．． It is 1/100 or more. This mixing ratio is 0.1/100
If it is less than 1, the deposition rate of the diamond-like carbon film becomes slow or the diamond-like carbon film does not precipitate.

(3) Excitation amount of carbon source gas per unit work The excitation means for the carbon source gas used in the low pressure vapor phase diamond-like carbon film coating method of the present invention is as follows:
For example, CVD (chemical vapor deposition) methods such as DC plasma CVD method, high frequency CVD method, microwave CVD method, thermal filament method, and chemical transport method, sputtering method, and PVD (physical vapor deposition) method using ion beam, etc. Conventionally known methods can be used.

1.1 To excite the carbon source gas, a reaction usually proceeds under the following conditions, and a diamond-like carbon film is formed.

That is, the temperature of the substrate surface cannot be determined in general since it varies depending on the excitation means of the carbon source gas, the measurement location, etc., but when high-frequency plasma CVD is employed, it is usually between room temperature and 1.000°C. , preferably room temperature to 4
00'' C. If the surface temperature of the substrate exceeds t, ooo C., the amount of graphite, which is non-diamond-like carbon, increases, so it is preferable to avoid this.

The reaction pressure is 10-6 to 103 torr, preferably 1
0-' to 10" jorr.Reaction pressure is 1O-8
When the temperature is lower than torr, the deposition rate of the diamond-like carbon film becomes slow. On the other hand, even if it is made higher than 103 torr, the desired effect cannot be achieved.

In addition, when employing the high frequency plasma CVD method, it is desirable that the high frequency power used for excitation is normally 2 kW or less. Even if the power exceeds 2 kW, the desired effect cannot be obtained, so it is desirable to avoid this.

(4) Cooling The most important thing in the diamond-like carbon film coating method of the present invention is that after forming a diamond-like carbon film on the substrate over a predetermined period of time, the supply of the reaction gas is stopped and the reaction is carried out in the reaction vessel. The goal is to ensure that no gas remains.

This is because if the reaction gas remains in the reaction vessel for any length of time, the reaction gas will be adsorbed onto the surface of the produced diamond-like carbon film, forming a reaction gas adsorption layer.

Since this reactive gas adsorption layer deteriorates various physical properties of the coated diamond-like carbon film, it is necessary to prevent the formation of such a reactive gas adsorption layer.

Therefore, in the present invention, the formation of the reaction gas adsorption layer is prevented by employing at least one of the following two means.

k-masu (Claim 1) First, after stopping the supply of the reaction gas, the pressure inside the container is reduced to a high vacuum state of 10-4 Torr or less, preferably 10-4 Torr or less,
This prevents reactive gases from being adsorbed onto the diamond-like carbon film.

To reduce the above pressure, pressure reduction pumps such as oil diffusion pumps, turbomolecular pumps, and Talaiobon pumps can be used to rapidly (
For example, the degree of vacuum is achieved within about 0 to 60 seconds after the supply of raw material gas is stopped.

) is desirable.

Spooner (Claim 2) Second, in order to quickly discharge the reaction gas in the reaction container from the reaction container after stopping the supply of reaction gas, an inert gas such as helium, neon, argon, xenon, etc. Alternatively, it is carried out by rapidly introducing and replacing hydrogen or nitrogen gas.

In order to quickly eliminate the reaction gas, the replacement gas may be introduced after once creating a high vacuum state.

These gases are preferably the same as hydrogen in the mixed reaction gas or the inert gas used as the carrier gas.

Cooling is generally below 30°C, preferably to room temperature.

(5) Coating product The coating product thus formed has a diamond-like carbon film formed on its surface, and the diamond-like carbon film is as described above, and a reactive gas adsorption layer is formed on its surface. Therefore, the surface of the diamond-like carbon film has high mechanical strength, especially hardness, and is excellent in chemical stability, wear resistance, and solid lubricity. Due to this, the substrate with diamond-like carbon film is suitably used as a material in various technical fields. Therefore, according to the method of the present invention in which a magnetic recording medium is specifically selected as the substrate, adhesion of the head of the magnetic disk is prevented when reading and writing information, the coefficient of friction is small, and moreover, the head slider is free from adhesion such as magnetic powder. A diamond-like carbon film magnetic recording medium without adhesion can be obtained.

(Example) In order to more specifically explain the method of coating a diamond-like carbon film of the present invention, examples are given below.

(Example 1) As a non-magnetic metal base layer (supporting body) with a thickness of 1 mm and 91 mm,
An aluminum alloy substrate (about 1.5-1 mm thick, 6 inches in outer diameter) on which a magnetic layer was formed was used, and cobalt as a ferromagnetic metal was deposited on the surface of the substrate by electron beam evaporation.

The conditions for electron beam evaporation were as follows.

Degree of vacuum: 10-4 Torr Temperature of substrate: 300°C Thickness = 1,000 people coach-in 7 Next, this cobalt evaporated substrate was placed in a reaction chamber, and the conditions were that the substrate temperature was 200°C and the pressure in the reaction chamber was 10-1 torr. Below, by setting the output of a high-frequency power supply with a frequency of 1:1.56 MHz to 120 W, a mixed reaction gas of 205 CCJ of methane gas and hydrogen gas ZO5ee- was excited as the carbon source gas flow rate supplied into the reaction chamber. The obtained excited gas was brought into contact with the substrate for 20 minutes.

A diamond-like carbon film was formed on the substrate whose temperature was controlled as above.

Immediately after the formation of the diamond-like carbon film on one side of the roof, the supply of the mixed reaction gas of methane gas and hydrogen gas is stopped, and
The reaction gas inside the reaction chamber is discharged to the outside of the reaction system using a turbo molecular pump to reduce the pressure inside the reaction chamber by 2×1 within 60 seconds.
The pressure was reduced to O-6 Torr.

Then, 30 minutes after reaching the above pressure, the temperature inside the reaction chamber was cooled to room temperature to obtain an aluminum alloy substrate coated with a tire cent-shaped carbon film.

Silver was evaporated to a thickness of 100 mm on the obtained aluminum alloy substrate coated with a diamond-like carbon film, and the coating surface was evaluated by Raman spectroscopy (5ER3 method). As a result, it was found that a surface adsorption layer due to reactive gas was formed. estimated to be attributable to 1,400, 1,600c
A very small spectrum near m-' did not appear, indicating that no surface adsorption layer was formed by the reactive gas on the surface of the coated diamond-like carbon film.

Further, after using the aluminum alloy substrate coated with the diamond-like carbon film as a magnetic disk, a head floating test and a contact start/stop test (C3S test) were conducted to test whether it could be applied as a magnetic disk. The results are shown in Table 1.

(The following is a blank space) Table 1 (Comparative Example 1) After the coating in Example 1 was completed, the reaction gas was supplied without stopping the supply of the reaction gas of methane gas and hydrogen gas and without reducing the pressure inside the reaction chamber. The same method as in Example 1 was carried out except that the temperature inside the reaction chamber was lowered to room temperature.

The results obtained are shown below.

The coating surface of the obtained diamond-like carbon film-coated aluminum alloy substrate was evaluated in the same manner as in Example 1, and the coating surface was 1,400.1.600 cm-'.
The appearance of a small spectrum in the vicinity revealed that a surface adsorption layer was formed by the reactive gas on the surface of the coated diamond-like carbon film.

Further, using the diamond-like carbon film-coated aluminum alloy substrate, a test was conducted in the same manner as in Example 1 to determine whether it could be used as a magnetic disk.

The results obtained are listed in Table 1 together with Example 1.

(Effects of the Invention) According to the diamond-like carbon film coating method of the present invention, it is possible to substantially prevent the formation of a reactive gas adsorption layer on the surface of the formed diamond-like carbon film.

As a result, the surface coated with the diamond-like carbon film exhibits the inherent properties of diamond-like carbon, such as high hardness, wear resistance, solid lubricity, mechanical strength, and chemical stability. be able to.

Therefore, various members coated with a diamond-like carbon film by the method of the present invention can be effectively utilized as materials in a wide range of technical fields requiring the above characteristics.

In particular, when a magnetic recording medium is selected as the substrate in the present invention, a diamond-like carbon film material has excellent characteristics such that the head of the magnetic disk floats, has a small coefficient of friction, and does not allow deposits to adhere to the head slider. It is possible to manufacture magnetic recording media.

Claims (3)

[Claims] (1) Bringing a reactive gas into contact with a substrate placed in a high vacuum container to generate a diamond-like carbon film on the substrate surface,
In the method of coating the surface of the substrate with a diamond-like carbon film by cooling, after the reaction gas is brought into contact with the substrate for a predetermined period of time, the supply of the reaction gas is stopped and the degree of vacuum in the container is reduced to 10^- A diamond-like carbon film coating method characterized by maintaining the temperature below ^4 Torr. (2) In the diamond-like carbon film coating method according to claim 1, the degree of vacuum in the container is set to 10^-^.
A method for coating a diamond-like carbon film, characterized in that instead of maintaining the temperature at 4 Torr or less, the reaction gas in the container is replaced with an inert gas, hydrogen gas and/or nitrogen gas. (3) The method for coating a diamond-like carbon film according to claim 1 or 2, wherein the substrate is a magnetic recording medium.