JPH0959760A - Production of carbon thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a DLC thin film having high hardness at a high rate at the time of forming a carbon thin film on a substrate by sputtering by using a target prepared by mixing graphite and diamond and producing plasma with high-frequency discharge. SOLUTION: A substrate 2 is supported by a water-cooled holder 3 in a gas chamber 1 and grounded through a variable resistor. A target 4 is opposed to the substrate 2, supported by a water-cooled RF electrode and connected to an RF power source 6 through a matching circuit 5, and the RF electrode is surrounded with a grounded shield 8. A mixture of graphite and diamond is used for the target 4, the chamber 1 is evacuated, and gaseous Ar is introduced to a specified pressure. A high-frequency wave is impressed from the power source 6 to produce plasma, and the target 4 is sputtered. An appropriate DLC thin film is formed on the substrate 2 in this way at a high rate.

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 carbon thin film, and more particularly to diamond-like carbon (D
LC) thin film manufacturing method.

[0002]

2. Description of the Related Art A DLC thin film is an amorphous carbon thin film in which graphite bonds and diamond bonds coexist, and because of its excellent characteristics regarding hardness and sliding, various kinds of DLC thin films such as a magnetic layer protective film of a magnetic recording medium are used. It is attracting attention as a protective film and others for

As a method for forming a DLC thin film, there are high frequency sputtering, plasma CVD method and the like. For example
Savvides et al. Used graphite as a target,
It has been reported that DLC thin films can be obtained in argon plasma by DC magnetron sputtering (N. S.
avvides, B. Window: J. Vac. Sci. Tech., A3 (6), p.2
386 (1985). In addition, Mitani et al. Reported that a method called plasma injection CVD was used to introduce a raw material gas into a plasma chamber to form a high frequency plasma to form a protective film for a vapor deposition tape for video (Riki Mitani et al.
Electronic Materials, August 1989, pp. 79-83).

[0004]

When a DLC thin film is formed by the conventional sputtering method, graphite is used as a target. However, the DLC thin film obtained by this has a strong graphite bonding property and a small diamond component, that is, the ratio of SP ³ / SP ² is not so large that the strength is weak. Therefore, various attempts have been made to obtain a desired DLC thin film by selecting sputtering conditions. For example, H ₂ is mixed in an argon gas atmosphere to enhance the ion assist effect, and the graphite component in the deposited thin film is etched.

However, with such a method, DL
If an attempt is made to increase the hardness of C, there is a problem that the film is likely to peel off as the hardness increases. Then, the subject of this invention is providing the manufacturing method of a carbon thin film which does not have such a problem.

[0006]

According to the present invention, a method for producing a carbon thin film by sputtering is characterized in that graphite is mixed with diamond to form a target, and plasma is generated by high frequency discharge. A thin film formed by sputtering is formed by depositing atoms emitted from a target on a substrate, and its properties depend on the state of the atoms when they reach the substrate, various energies received after deposition, etc. The state of the atom when it reaches is also dominated by phenomena on the target and collisional scattering in the space in which the atom flies. As a result of earnest research, the inventors of the present invention have found that an excellent carbon thin film can be obtained by using a mixture of graphite and diamond as a target and combining the conditions of generating plasma by high frequency discharge. .

The target used in the present invention is
A mixture of graphite and diamond, usually artificial diamond, is used. Such a target can be obtained by, for example, mixing graphite powder with artificial diamond powder and press-molding. Alternatively, artificial diamond having an appropriate grain size may be hardened to an appropriate size and scattered on a normal graphite target for use. Such a target is also included in the concept of “mixing” in the present invention.

According to the present invention, there is no limitation on the mixing ratio of graphite and diamond. That is, in the present invention,
If even a small amount of diamond is present, the carbon bond of the obtained carbon thin film will be strong. And this trend is
It increases as the mixing ratio of diamond increases. Therefore, it suffices that diamond is mixed in the graphite target and that it is sputtered together with graphite. The addition amount depends on the required characteristics (hardness, etc.).
Is a factor determined by the trade-off between cost and cost. However, if the ratio of diamond is too large, the film forming speed is sacrificed, so in general, it is often carried out in the range where the surface area ratio of diamond in the target is 5 to 80%.

In the present invention, a high frequency power source is used as a power source for sputtering. When a DC power source is used, the discharge becomes unstable due to the difference in conductivity between graphite and diamond, and the sputtering becomes nonuniform, so that the desired carbon film cannot be obtained. However, by generating plasma by high-frequency discharge, uniform and stable sputtering can be performed, and a DLC thin film can be suitably formed. The range of high frequencies used is 5
It is about 20MHz. The frequency is typically 13.56MHz and the output impedance is 50Ω.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 schematically shows an apparatus which can be used for carrying out the present invention. In the gas chamber 1,
A substrate 2 on which a thin film is formed is supported by a water-cooled holder 3 and is grounded via a variable resistor. Substrate 2
The target 4 arranged opposite to is supported by an RF electrode 5 which is also water cooled, and the RF electrode 5 is a matching circuit 6
It is connected to the RF power source 7 via. The periphery of the RF electrode 5 is covered with a ground potential shield 8. The gas chamber 1 is evacuated via an exhaust system such as an oil diffusion pump or a cryopump. The required degree of vacuum is usually on the order of 10 ^-5 to 10 ^-7 Torr. On the other hand, a gas can be introduced into the gas chamber 1 by a gas introduction system connected to an argon gas source or the like. According to the invention, the target 4 is made of a mixture of graphite and diamond.

[0011]

【Example】

Example 1 A carbon thin film was formed using a Si glass substrate as the substrate 2 using the apparatus shown in FIG. As target 4,
On a 5 inch x 8 inch, 6 mm thick graphite plate,
An artificial diamond having a diameter of about 3 to 6 μm, which was solidified into a cubic shape with a side of about 1 cm, was scattered at a surface area ratio of about 20%.

The inside of the gas chamber 1 was evacuated to about 1 × 10 ^-6 Torr, and argon gas was introduced at a flow rate of 1.3 Pa. Target voltage is -2000V, substrate voltage is -35V
And the substrate temperature was maintained between 50 and 300 ° C. A high frequency of 3.75 MHz was applied from the RF power source 6 to perform sputtering to form a carbon thin film having a thickness of 500 Å.

Comparative Example 1 The same apparatus as in Example 1 was used. Sputtering was performed under the same conditions as in Example 1 except that the target 4 was changed to only graphite to form a carbon thin film having a thickness of 500 Å.

Comparative Example 2 The same apparatus as in Example 1 was used. As the target 4, an artificial diamond having a size of 5 inches × 8 inches and a thickness of 6 mm was used, and sputtering was performed under the same conditions as in Example 1 except for the above to obtain a carbon thin film having a thickness of 500 Å.

COMPARATIVE EXAMPLE 3 A magnet array is arranged on the back side of the target and D is used as a power source.
DC magnetron discharge was performed using a C power supply at an argon gas pressure of 4 mmTorr and an output of 3 kW. The same target as in Example 1 was used as the target. A carbon thin film with a thickness of 500Å was obtained.

For the carbon thin films obtained in Examples and Comparative Examples, the film forming rate and the micro Vickers hardness are shown in Table 1.
Summarized in The Raman spectra of these carbon thin films are shown in FIG. An argon laser (5145Å) was used as the excitation laser.

[0017]

[Table 1]

As is apparent from FIG. 2, in Example 1 and Comparative Example 2, a peak due to diamond is found near 1330 cm ^-1 . Also, the hardness is sufficient, and it is suitable D
It can be seen that an LC thin film is obtained. Such a protective film is extremely effective as a protective layer in a magnetic recording medium such as a magnetic tape. However, as seen in Comparative Example 2, when the target made entirely of artificial diamond was used, the hardness was the same as in Example 1 despite the decrease in the film formation rate, and the cost was also taken into consideration. This is not preferable.

In the case of Comparative Example 1, no peak around 1330 cm ^-1 is seen, but only a broad peak due to graphite is seen around 1580 cm ^-1 . In the case of Comparative Example 3 as well, 1330 cm ⁻¹ due to diamond bonding
No peaks in the vicinity are observed. It is considered that this is because the diamond bond was not generated due to the nonuniform sputtering. Further, the bonding between the film and the substrate was good in both Examples and Comparative Examples, and no film peeling was observed.

[0020]

As described above, according to the present invention, a suitable DLC thin film having a diamond bond can be manufactured with an excellent film forming rate and hardness. The carbon thin film thus obtained can be used in various fields as a protective film and the like.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of an apparatus that can be used to carry out the method of the present invention.

FIG. 2 is a graph showing Raman spectra of carbon thin films obtained in Examples and Comparative Examples.

[Explanation of symbols]

 1 Gas Chamber 2 Substrate 3 Holder 4 Target 5 RF Electrode 6 Matching Circuit 7 RF Power Supply 8 Shield

Claims (1)

[Claims] 1. A method of producing a carbon thin film by a method of producing a carbon thin film by sputtering, which comprises mixing graphite with diamond to form a target and generating plasma by high-frequency discharge.