JP2734556B2 - Method for producing amorphous carbon film - Google Patents

Description

The present invention relates to a method for producing an amorphous carbon film,
In particular, the present invention relates to a method for producing a transparent and high-hardness amorphous carbon film, which is effective for various surface protective films and the like.

[Prior Art] Conventionally, it has been known that an amorphous carbon film has no grain boundaries, is chemically stable, and has a high hardness, and has been applied to various surface protective films.

Conventionally, as a method for producing an amorphous carbon film, a sputtering method using a graphite as a target and discharging a rare gas such as argon (for example, N. Savvides and B. Windo)
w, J. Vac. Sci. Technol. A3 (6), pp2386, 1985) and various hydrocarbons such as methane as raw material gas, decompose the gas by generating glow discharge (~ 10Pa) under reduced pressure. Plasma CVD method for adhesion to a substrate (for example, Yamaguchi et al., Showa 62
Spring Proceedings of the Society of Applied Chemistry, p.349) was known.

[Problems to be Solved by the Invention] A method for producing an amorphous carbon film in which a graphite target is sputtered by an argon discharge involves a method in which a large-area substrate is placed on a transport cart and continuously passed through a film forming chamber. The method can be adopted, and mass production is excellent. It also has the advantage of realizing uniform film quality and film thickness distribution over a large area, but has the serious problem that the resulting film is opaque to the visible range, which limits the range of application as a protective film. There was a point.

On the other hand, an amorphous carbon film obtained by the plasma CVD method contains hydrogen in the film and can be transparent in the visible region.However, in order to increase the hardness of the film, a negative bias voltage must be applied to the substrate. A method such as application of a voltage is required, and there is a problem that it is difficult to form a film continuously on a large-area substrate or a film on an insulating substrate. In addition, since the glow discharge is a glow discharge at a relatively high pressure, it is a film forming mechanism that decomposes the raw material gas and adheres to the substrate, resulting in non-uniform discharge and non-uniform distribution of film growth species due to gas decomposition. Therefore, it is difficult to form a film with a uniform film thickness and film quality distribution on a large-area substrate.

Means for Solving the Problems The present invention has been made to solve the above-mentioned conventional problems, and is directed to a method of manufacturing an amorphous carbon film on a substrate by sputtering using a graphite target. The sputtering is performed by magnetron sputtering in a mixed gas atmosphere of hydrogen and argon gas.

In general, in carbon sputtering, rare gas ions such as argon collide with a graphite target and carbon atoms fly out, and this adheres to the substrate.For example, when the atmosphere gas is pure argon, the film formed is black. It becomes an amorphous carbon film.

In this sputtering, using a magnetron sputtering method in which a magnetic field is applied to the target electrode, when hydrogen gas is present in the atmosphere, the electron density near the cathode increases, and the density of activated hydrogen atoms in the plasma increases. This is taken into the carbon film formed on the substrate to form a transparent film. Hydrogen atoms are also effective in regasifying the graphite component of the formed carbon.

When ordinary RF and DC sputtering methods are used, the ionization rate of the atmospheric gas is lower than that of magnetron sputtering, so the density of activated hydrogen atoms is low and hydrogen atoms cannot be sufficiently incorporated into the carbon film. Is not efficiently performed, and a transparent carbon film cannot be obtained.

As rare gases used for sputtering, argon,
A rare gas such as helium can be exemplified. Among them, argon gas is preferable because it is inexpensive and the sputtering rate can be increased.

In magnetron sputtering, stable discharge can be maintained under low gas pressure, and the kinetic energy of each atom or ion of carbon, argon, and hydrogen flying on the film formation surface increases, and as a result, the hardness of the carbon film increases. growing.

Sputtering under a low gas pressure is effective in activating hydrogen atoms in the plasma. In order to ensure sufficient reactivity and hardness of hydrogen and carbon, the total pressure during sputtering must be 3 Pa or less, especially 1
Pa or less is desirable.

Also, the volume mixing ratio of hydrogen and argon is desirably 0.5 to 50%. At a hydrogen gas concentration of 0.5% or less, it is difficult to obtain a sufficiently transparent film. At a hydrogen gas concentration of 50% or more, the structure of the amorphous carbon film formed is dominated by a polyene structure, and the hardness is liable to be significantly reduced.

[Operation] According to the present invention, since magnetron sputtering using a mixed gas of argon and hydrogen as an atmospheric gas is used, discharge with a high electron density at a low gas pressure becomes possible.
Activation of hydrogen atoms and an increase in kinetic energy of particles flying to the substrate occur, and hydrogen is taken into the film to form a transparent hard amorphous carbon film.

Embodiment FIG. 1 is a schematic view of a magnetron sputtering apparatus used for carrying out the present invention.

A magnetic field can be applied to the electrode by a magnet attached to the target electrode. Magnetic flux density is 1000Gaus
s.

The introduced atmosphere gas is a mixed gas of argon and hydrogen having a hydrogen concentration of 10% by volume, and the gas pressure is 1 Pa. The input power was 700W. A glass plate was used as the substrate, and the substrate was heated to 150 ° C. in order to increase the adhesion to the carbon film.

FIG. 2 shows a transmission spectrum of the amorphous carbon film formed under the conditions of the present invention.

FIG. 2 shows that the amorphous carbon film formed according to the present invention is a transparent film in the visible region. The energy gap was 1.98 eV. The hardness of the obtained film was as ^{high as} about 700 kgf / mm ^{2 in} Vickers hardness.

[Effect of the Invention] As described above, according to the present invention, a hard amorphous carbon film transparent and visible in the visible region can be obtained by magnetron sputtering of a graphite target using a mixed gas of argon and hydrogen as an atmosphere gas.

The transparent and hard amorphous carbon film obtained by the present invention is useful as a protective film for a magneto-optical recording film, a protective film for a magnetic recording film, a protective film for various optical products, and various other surface protective films.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus used in the present invention, and FIG. 2 is a view showing a transmission spectrum of an amorphous carbon film formed in the embodiment.

Claims (1)

(57) [Claims] In a method for producing an amorphous carbon film on a substrate by sputtering using a graphite target, the sputtering is performed by magnetron sputtering in a mixed gas atmosphere of hydrogen and argon gas, and the total pressure during sputtering is controlled. Is less than 1 Pa, and the volume mixing ratio of hydrogen and argon gas (H ₂ / H ₂ + A
A method for producing a hard amorphous carbon film for a magnetic recording medium which is transparent in the visible region and has a Vickers hardness of 700 kgf / mm ² or more by introducing hydrogen into the film by setting r) to a mixed gas atmosphere of 0.5 to 50%.