JPH07100857B2 - Carbon film forming method and apparatus - Google Patents

Description

The present invention relates to a method and apparatus for forming a hard carbon film on the surface of a substrate.

[Background of the Invention]

It is known that methane decomposes by the energy of glow discharge of which hydrocarbon gas to deposit a hard coating called diamond-like carbon or i-carbon under some conditions. This hard carbon film has features such as high electrical insulation, high infrared transmittance, high refractive index, high wear resistance, and low friction coefficient, and various applications can be considered. In particular, if attention is paid to high wear resistance, it can be used as a protective coating layer for magnetic heads, magnetic disks, optical lenses, cemented carbide tools, and the like.

If such a hard carbon coating can be deposited economically on the surface of a film-like substrate, it will be used as a wear-resistant protective layer for magnetic tapes, floppy disks and the like.

The conventional method of forming a hard carbon film has a disadvantage when applied to a film-shaped substrate. That is, in order to form a hard carbon film, a method of forming a film while irradiating the surface of a substrate with high-energy ions, or a method of forming a film while heating the substrate to 600 ° C. or higher has been adopted. As an example of the former, JP-A-58-55319 discloses a method of depositing carbon while irradiating a substrate with hydrogen ions, and JP-A-59-35092 discloses applying a DC bias voltage to the substrate. A method of accelerating and applying ions to the surface of a substrate is disclosed. However, when a film is formed on the insulating film base material, it is impossible to apply a bias voltage to the base material, and when irradiated with ions, abnormal discharge occurs due to the accumulation of electric charges or the film quality is deteriorated. Will not be stable. On the other hand, in the case of the latter method of heating a substrate, in many cases, the film is made of an organic polymer material and lacks heat resistance, and therefore cannot be applied.

As an alternative coating method, high-frequency plasma is preferably used to form a hard carbon coating on the insulating substrate without causing charge-up. Literature (L. Holland and SM
Ojha, Thin Solid Films, Volume 38, L17 (1976))
It has been shown that when a hydrocarbon gas is decomposed by a high frequency bipolar discharge, a hard carbon film is formed on the high frequency application side electrode, as described in 1. In high-frequency plasma, positive and negative charges flowing into the base material are neutralized during one cycle of voltage oscillation, so there is no risk of charge-up.

However, there are various problems in applying the high frequency plasma method as it is to a film-shaped substrate. That is, for continuous treatment of a film-shaped substrate, a method in which the film is wound around the side surface of a cylindrical rotary drum, and the substrate is wound in synchronism with the rotation of the rotary drum, and is treated in a part of the rotary drum. However, when a high-frequency voltage is applied to the rotating drum, 1) a high voltage is applied to the rotating body, which complicates the mechanism.

2) There is a possibility that unnecessary discharge may occur because high voltage is applied to parts other than the processed part of the rotary drum.

3) When a metal thin film is provided on the film with a magnetic tape or the like, the metal thin film itself must be at a high voltage, but for that reason, the feeding and winding mechanism also has a high voltage, and the insulation method becomes complicated. There was a problem.

[Object of the Invention] The present invention solves the above problems and provides a carbon film forming method and apparatus for easily forming a hard carbon film called diamond-like carbon or i-carbon on the surface of a substrate by using high frequency plasma. It is intended to be provided.

[Outline of Invention]

The method for forming a carbon film of the present invention comprises a first grounded first container.
A substrate is placed on the electrode of, the inside of the container is evacuated, and the container is filled with a gas containing hydrocarbon, and the area of the first electrode that is exposed to plasma is larger than that of the first electrode. And a high-frequency voltage is applied to the second electrode located on the base material side of the first electrode to form a carbon coating film on the base material.

Further, the carbon film forming apparatus of the present invention includes a container, a vacuum evacuation mechanism that evacuates the container, a first electrode that is grounded, is located in the container, and that arranges a base material, and the first electrode. A second electrode that has a larger plasma contact area than the first electrode plasma contact area, is located on the substrate side of the first electrode, and is located in the container;
A high-frequency voltage applying mechanism for applying a high-frequency voltage to the electrodes of
A carbon film forming apparatus, comprising: a reaction gas supply mechanism for supplying a gas containing hydrocarbon to the container.

Example of Invention

One embodiment of the present invention will be described in detail below. First, the apparatus will be described with reference to FIG. In the figure, the present apparatus includes a vacuum chamber 1 and a vacuum exhaust mechanism 2 for exhausting the vacuum chamber 1,
It is composed of a film feeding mechanism, a plasma processing chamber 3, a high frequency voltage applying mechanism 4, and a reactive gas applying mechanism 5. The film feeding mechanism includes a feeding roll 7 for feeding the film 6, a rotary electrode 8, a winding roll 9, a guide roll 10 for stabilizing the film tension and preventing the generation of wrinkles, and a power mechanism and a rotation speed adjusting mechanism for rotating them. Become. The plasma processing chamber 3 is provided with a counter electrode 11, a reactive gas introduction port 12 and an exhaust port 13. In order to uniformly introduce the reactive gas into the processing chamber 3, for example, as shown in FIG. 2, it is preferable to make a large number of small holes 14 in the counter electrode 11 and blow out the gas from there. The rotating electrode 8 and the counter electrode 11 are preferably water-cooled in order to prevent temperature rise due to heat generated by plasma.

The rotary electrode 8 is grounded together with the vacuum chamber 1.

The area of the counter electrode 11 is sufficiently larger than the area of the plasma hitting the rotating electrode 8.

A method for forming a film in the above apparatus will be described below.

In this embodiment, the rotary electrode 8 is used as a ground electrode, and a high frequency voltage of 100 KHz or 100 MHz is applied to the counter electrode 11 facing the rotary electrode 8 to hold plasma of hydrocarbon or a mixed gas of hydrocarbon and hydrogen, and to ground electrode. A carbon film is formed on the surface of the upper film-shaped substrate (rotary electrode 8). The greatest feature of the present invention is that the area of the counter electrode 11 is equal to that of the rotating electrode 8.
This is because the area of the (ground-side electrode) to be processed was made sufficiently larger. In the high frequency discharge in the above frequency range, the moving speed of electrons is significantly higher than the moving speed of positive ions, so that the sheath voltage drop caused by the effective area ratio of the two electrodes changes, and the voltage drop of the electrode having a small area increases. However, the above-mentioned effective area is the area of the portion in contact with plasma. Therefore, by making the area of the counter electrode 11 in contact with the plasma sufficiently larger than the area of the processed portion of the rotating electrode 8 (ground side electrode), the plasma potential becomes higher than that of the surface of the processed portion, resulting in high energy. It is possible to create a situation in which the ions of the above flow into the surface of the portion to be treated, and a hard carbon film is formed.

It is preferable that the effective area ratio of the portion to be processed (ground side electrode) of the rotary electrode 8 and the counter electrode 11 is at least 1: 3, and preferably 1: 5 or more. Further, the amplitude of the high frequency voltage is preferably 1 KV or more.

The following gases or vapors are used as the hydrocarbon, for example.

1) Saturated aliphatic hydrocarbons such as methane, ethane, propane and butane 2) Unsaturated aliphatic hydrocarbons such as ethylene, acetylene, propene, butene and butadiene 3) Aromatic hydrocarbons such as benzene, naphthalene, toluene and ethylbenzene The formed hard carbon film is a carbon film having an amorphous structure in which an amorphous or microcrystalline portion containing hydrogen atoms is mixed, and is a hard film having a Vickers hardness of 1000 or more and hard to wear.

Next, the case where the method for forming a hard carbon film according to the present invention is actually applied to the step of forming a protective film on a vapor-deposited magnetic tape will be described as an example.

In the apparatus shown in FIG. 1, a substrate having a Co / Ni alloy magnetic thin film having a thickness of 0.1 μm deposited on one side of a polyester film having a thickness of 10 μm was set. Then, the vacuum chamber 1 and the processing chamber 3 are 1 ×
After pre-evacuating to less than 10 ^-3 Pa, benzene vapor is introduced at a constant flow rate and the exhaust speed is adjusted to adjust the pressure in the processing chamber 3 to 0.05.
Hold on to Torr. Next, while feeding the film at a speed of 5 m / min, a high frequency voltage of 13.56 MHz and a voltage amplitude of 2 KV was applied to the counter electrode 11 to generate plasma. As a result of continuous treatment for 3 hours, a hard carbon film having a thickness of 200Å was uniformly formed on the entire surface of the film having a length of 900 m. No abnormal discharge was observed during the treatment. When the magnetic tape subjected to the above treatment was slit into a width of 8 mm and applied to a VTR playback device, tape sticking and running instability did not occur, and the tape life was greatly improved compared to before treatment.

FIG. 3 shows another embodiment, which is an example of an apparatus in which a plurality of processing chambers are arranged on a rotary drum to improve the processing speed.
In this type of equipment, a multi-layered film is formed by changing the processing conditions in each processing chamber or the type of reactive gas, or the structure of a specific processing chamber is changed to perform other processing such as plasma cleaning, etching, sputtering, or vapor deposition. It is also possible to perform simultaneously with the formation of the carbon film. When a high voltage is applied to the rotary electrode 8, the above multi-functionality is not exhibited. Therefore, this multi-functionality is also a side effect of the present invention by grounding the rotary electrode 8.

〔The invention's effect〕

As described in detail above, according to the present invention, the first electrode is grounded and the high frequency voltage is applied to the second electrode to hold the plasma. Therefore, when the high frequency voltage is applied to the first electrode We were able to eliminate the mechanical problems, the occurrence of unnecessary discharge, and the insulation problems.

In addition, the area of the second electrode is more than the area of the first electrode exposed to the plasma.
Since the area where the plasma of the electrode hits the plasma is made large, it is possible to create a situation in which high-energy ions flow into the area of the portion to be processed, and it is possible to easily form a hard carbon film.

[Brief description of drawings]

FIG. 1 is an embodiment of the present invention and is an overall configuration diagram of a carbon film forming apparatus. FIG. 2 is a partial configuration diagram of the counter electrode portion. FIG. 3 is an overall configuration diagram showing another embodiment of the present invention. 7 ... Delivery roller 8 ... Rotating electrode 9 ... Winding roll 11 ... Opposing electrode

Claims (2)

[Claims] 1. A base material is placed on a grounded first electrode in a container, the interior of the container is evacuated, and a gas containing hydrocarbon is filled in the container. A high-frequency voltage is applied to a second electrode that has a larger plasma contact area than the plasma and is located on the base material side of the first electrode to form a carbon film on the base material. And a method for forming a carbon film. 2. A container, a vacuum evacuation mechanism for evacuating the container, a first electrode which is grounded and is located in the container for disposing a substrate, and a plasma of the first electrode. A high frequency voltage is applied to the second electrode, which has a larger plasma contact area than the contact area, is located on the base material side of the first electrode, and is located in the container. A carbon film forming apparatus comprising: a high frequency voltage applying mechanism; and a reaction gas supply mechanism for supplying a gas containing hydrocarbon to the container.