JPH0952795A - Production of carbon thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a process for production capable of obtain a carbon thin film having the characteristics more approximate to the characteristics of diamond by sputtering. SOLUTION: Sputtering is executed by interposing an auxiliary means consisting of Pt, Ni, Si, Mo, Cu or the alloy thereof between a substrate, for example, a magnetic tape 5 made to travel inline and a graphite target 6. More preferably, the auxiliary means is a Pt wire or Ni wire placed on this target 6.

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 For example, as a necessary condition for the protective layer of the magnetic tape, it is necessary to have high hardness in order to improve durability (still durability), but at the same time, such a protective layer can be formed as thin as possible. It is also necessary to minimize output reduction due to spacing loss.
Table 1 compares diamond, DLC and graphite for some properties. It will be easily understood that as the protective layer of the magnetic tape, a film closer to diamond can realize a thin film having sufficient hardness.

[0003]

[Table 1]

By the way, 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. Reported that DLC thin films can be obtained in argon plasma by DC magnetron sputtering using graphite as a target (N. Savvides, B. Window: J. Vac. Sci. Tech., A.
3 (6), p. 2386 (1985). In addition, Mitani et al. Reported that a method called plasma injection CVD was used to introduce a source gas into a plasma chamber and form a high frequency plasma to form a protective film for a vapor deposition tape for video (Riki Mitani et al., Electronic Materials 1989 August issue, pages 79-83).

[0005]

When forming a DLC thin film by a sputtering method, graphite is used as a target. However, the DLC thin film thus obtained 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 hardness is not sufficient, and it is satisfactory as a protective layer for a magnetic tape, for example. It wasn't possible. Therefore, various attempts have been made to obtain a desired DLC thin film by selecting sputtering conditions. For example, H ₂ and CH ₄ are mixed in an argon gas atmosphere to enhance the ion assist effect to etch the graphite component in the deposited thin film. An object of the present invention is to provide a method capable of producing a carbon thin film closer to diamond by a simpler method without the need of flowing H ₂ or CH ₄ .

[0006]

According to the present invention, in a method for producing a carbon thin film on a substrate by sputtering, Pt, Ni, Si, Mo, Cu, or an alloy thereof is formed between the substrate and the target. Auxiliary means are interposed. It has been found that a carbon thin film closer to diamond can be obtained by carrying out sputtering with such an auxiliary means interposed, as will be apparent from the examples described later. This is probably the Pt, Ni, Si,
It is considered that this is because the carbon atoms constituting graphite are changed from SP ² type to SP ³ type by the catalytic action of Mo, Cu, or their alloys, but the detailed mechanism is not clear.

Pt or Ni is preferred as an auxiliary means,
Besides, those made of Si, Mo, Cu, or alloys thereof are also effective in the present invention.

As an auxiliary means made of Pt or Ni, Pt wire or Ni wire is convenient, but it is needless to say that it is not limited to these forms. When using Pt or Ni wires, the purpose can be achieved by simply placing them on a graphite target. The sputtering method is also not particularly limited, but from the viewpoint of power control, D
C sputtering is preferable to RF sputtering, and magnetron sputtering is preferable in order to avoid the rise in substrate temperature and efficiently maintain the plasma for processing. The substrate is also not particularly limited, and any substrate may be used as long as it is used for a purpose in which it is desirable to use a carbon thin film as a protective film or the like. For example, when forming a DLC thin film as a protective layer of a magnetic tape according to the present invention, the substrate may be a magnetic recording medium that runs inline.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 schematically shows an example of an apparatus that can be used for carrying out the manufacturing method of the present invention. This apparatus uses a magnetic tape 5 that is run inline in a vacuum chamber 1 from an unwinding roll 2 to a winding roll 3 via a cooling can roll 4 as a substrate, and uses the magnetic tape 5 as a substrate.
It is for forming a carbon thin film, that is, a DLC thin film, as a protective layer on the magnetic layer formed in the above.

The magnetic tape 5 will be briefly described. It comprises a base film and a magnetic layer formed on the base film by, for example, electron beam evaporation. The base film is preferably made of polyethylene terephthalate and has a thickness of about 3 to 50 μm. Further, the magnetic layer is a ferromagnetic metal material used in the production of a normal metal thin film type magnetic recording medium, for example, a ferromagnetic metal such as Co, Ni, Fe,
Alternatively, these alloys may be formed into a film with a thickness of about 1000 to 3000Å, and may have a single-layer structure or a multi-layer structure. Further, on the surface opposite to the magnetic layer, a back coat layer formed by applying a coating material or vapor-depositing a metal or a semimetal can be provided to have a thickness of about 0.05 to 1.0 μm.

A graphite target 6 is placed below the cooling can roll 4 as a sputtering target, and a magnet 7 for forming a magnetron is placed below the graphite target 6 to form a cathode. A DC power supply 9 is connected between the anode 8 around the cathode and a DC voltage of, for example, about 300 to 500 V is applied. Above the target 6, a gas nozzle 10 for introducing a gas for plasma formation, for example, argon.
Is installed. According to the present invention, as shown in FIG. 2, a wire 11 made of Pt or Ni is arranged as an auxiliary means between the target 6 and the substrate, in this example, on the target 6. With this configuration, for example, argon gas is introduced from the gas nozzle 10, a voltage is applied between the cathode and the anode to generate plasma, and sputtering is performed on the running magnetic tape 5, whereby a carbon thin film closer to diamond is deposited. You can The magnet 7
Can be configured as either a balanced magnetron or a non-balanced magnetron.

After the DLC thin film is formed as a protective layer on the magnetic tape 5 in this manner, a top coat layer made of an appropriate lubricant may be further formed. This is formed, for example, by applying a fluorine-based lubricant in the air or spraying it on the magnetic layer in a vacuum. The thickness of the top coat layer is 5
It is about 50Å. When a back coat layer is provided, a top coat layer can be formed on it.

[0013]

【Example】

Example 1 A magnetic tape was manufactured by forming a film of cobalt on a PET film having a thickness of 6.5 μm by oblique vapor deposition to a thickness of 2000 liters.
This magnetic tape has Hc = 1600 Oe, Br / Bs = 0.84, Bs = 5
It was 900G. Using the apparatus of FIG. 1, this magnetic tape was used as the magnetic tape 5, and a graphite target 6 was used to form a DLC thin film by DC magnetron sputtering. 28 SCCM of argon gas from the gas nozzle 10
And the chamber 1 had a vacuum degree of 4.2 × 10 ⁻³ Torr. The output of sputtering was 3 kW, and the running speed of the magnetic tape 5 was 1.5 m / min. Also on the target 6,
As shown in Fig. 2, connect a Pt wire with a length of 20 cm and a diameter of 0.5 mm to 1
I arranged five. The thickness of the DLC thin film measured by a step meter was 80Å. Raman spectroscopic analysis was performed on the obtained tape. The results are shown in FIG.

Example 2 In Example 1, instead of the Pt wire, a length of 15 cm and a diameter of 0.
Ten 5 mm Ni wires were arranged. A DLC thin film was formed under the same conditions as in Example 1 except for the above. The thickness of the DLC thin film measured by a step meter was 80Å.

Comparative Example 1 A DLC thin film was formed under the same conditions as in Example 1 except that the Pt line was removed in Example 1. The thickness of the DLC thin film measured by the step meter was still 80Å. Raman spectroscopic analysis was performed on the obtained tape. FIG. 4 shows the results.

Regarding the magnetic recording media obtained in the above Examples and Comparative Examples, carbon black having an average particle size of 40 nm and 80 nm was used in a ratio of 2: 1 on the side opposite to the surface of the PET film on which the magnetic layer was formed. The back coat paint, which is mixed and dispersed in a binder resin of urethane resin and vinyl chloride resin, is applied by a die coating method to a dry film thickness of 0.5 μm and dried to form a back coat layer. Was formed. Further, a protective layer made of diamond-like carbon (DLC) was formed on the magnetic layer by ECR plasma method to a thickness of about 100Å. Next, perfluoropolyether (FOMBLIN AM2001, manufactured by Montecatini)
Is a fluorine-based inert liquid (Fluorinert FC-77, manufactured by Sumitomo 3M Limited) diluted and dispersed to a concentration of 0.05% by weight, and the coating is die-coated on the magnetic layer to a dry film thickness of 20Å. Was applied and dried at 105 ° C. to form a lubricating layer. The obtained product was cut to a width of 8 mm and loaded into a cassette to obtain a high band 8 mm cassette tape. With respect to these tapes, the still durability was examined by using a deck obtained by modifying a commercially available high band 8 mm VTR. As the still durability, the output reduction at 7 MHz after still for 10 hours was used as a standard. Table 2 shows the results.

[0017]

[Table 2]

[0018]

As is clear from the results shown in Table 2, the DLC thin film obtained by the method of the present invention is superior in hardness to the DLC thin film obtained by the conventional method. Thus, it became possible to obtain a carbon thin film close to diamond by sputtering. Also, as can be seen from FIGS. 3 and 4, D obtained by the present invention
A Raman spectroscopic analysis of the LC thin film reveals a shoulder near 1400 cm ⁻¹ , and a DLC thin film closer to diamond is obtained as compared with the case of forming a carbon thin film without the present invention.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a sputtering apparatus that can be used for carrying out the manufacturing method of the present invention.

2 is a simplified plan view of the target portion of FIG. 1. FIG.

FIG. 3 is a graph showing a Raman spectroscopic analysis result obtained for the magnetic tape obtained in Example 1.

FIG. 4 is a graph showing the Raman spectroscopic analysis results obtained for the magnetic tape obtained in Comparative Example 1.

[Explanation of symbols]

 1 Vacuum chamber 2 Unwinding roll 3 Winding roll 4 Cooling can roll 5 Magnetic tape 6 Target 7 Magnet 8 Anode 9 Power supply 10 Gas nozzle 11 Pt wire or Ni wire

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C23C 14/56 C23C 14/56 E G11B 5/84 7303-5D G11B 5/84 B (72) Invention Researcher Junko Ishikawa 2606, Akabane, Kai-cho, Haga-gun, Tochigi Prefecture Kao Corporation Stock Research Institute

Claims (4)

[Claims] 1. A method for producing a carbon thin film on a substrate by sputtering, wherein Pt,
A method for producing a carbon thin film, characterized in that sputtering is performed with an auxiliary means made of Ni, Si, Mo, Cu, or an alloy thereof interposed. 2. The manufacturing method according to claim 1, wherein the auxiliary means is a Pt wire or a Ni wire placed on the target. 3. The manufacturing method according to claim 1, wherein the sputtering is DC magnetron sputtering. 4. The manufacturing method according to claim 1, wherein the substrate is a magnetic recording medium which is run inline.