JP3246780B2 - Method and apparatus for forming hard carbon film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for forming a hard carbon film by plasma chemical vapor deposition (hereinafter abbreviated as plasma CVD) in an atmosphere containing a hydrocarbon gas. The present invention relates to a method and an apparatus for forming a hard carbon film having excellent quality and productivity.

[0002]

2. Description of the Related Art A hard carbon film is an ultra-hard carbon film commonly called i-carbon, which has been studied in the UK since the late 1970's. However, it is considered to have a bonding state similar to that of amorphous silicon. In addition, its physical properties are similar to those of diamond, and its properties (high hardness, wear resistance, lubricity, insulation, chemical resistance) protect it from tools and other machines and electronic parts. Or, application to functional devices is expected. The main method of forming this film is a gas phase synthesis method in which a hydrocarbon-based gas is plasma-decomposed.
(DC) method.

[0003]

However, each of the conventional methods has advantages and disadvantages, and there has been a problem that a truly productive method and apparatus have not been realized yet. That is, in the RF system, a hard carbon film is formed by applying RF power to a base material, pulling hydrocarbon-based ions using a self-bias voltage generated there, and colliding with the base material. Therefore, when the substrate area increases, a very large RF power is required to obtain a constant self-bias voltage. Further, since RF power is applied to the base material, factors such as the base material shape, the distance between the base materials, and the degree of processing vacuum are complicatedly entangled with each other, so that a partial arc discharge easily occurs. As a countermeasure, a certain distance between the base materials is required, and the number of processed pieces per batch is reduced. Further, since the introduction of high RF power leads to the cause of arc discharge, the RF system as a production system is naturally limited, and a system for solving this problem has not yet been proposed. Similarly, DC
In this method, too, hydrocarbon ions formed in the ion generation chamber are made to collide with the substrate to which a negative DC voltage is applied to form a hard carbon film. For this reason, it is necessary to rotate the substrate in order to form a three-dimensional film on the substrate. Further, the hydrocarbon ions formed in the ion generating chamber are apt to form particles by a gas phase reaction while moving in the plasma to the base material. At present, there are still many problems such as a significant decrease in film quality such as electrical characteristics.

[0004] In order to solve this problem, an object of the present invention is to propose a method for forming a hard carbon film excellent in film quality and productivity and to provide a forming apparatus.

[0005]

In order to achieve the above object, the present invention provides an initial plasma generating means for generating plasma in a vacuum chamber and a method for decomposing a hydrocarbon gas introduced around a substrate. And a plasma forming means around the substrate for forming a hard carbon film by accelerating and colliding with the substrate.

[0006]

In order to form a hard carbon film by a gas phase synthesis method, it is necessary to form a plasma. For this purpose, plasma is first generated in a vacuum chamber by an initial plasma generating means. The smaller the input power, the better, because it is to generate plasma and not to promote the decomposition of hydrocarbon gas. By doing so, a gas phase reaction such as particle formation in a high plasma density as in a conventional DC type ion generation chamber can be suppressed as much as possible. As the initial plasma generation method, a thermionic discharge method in which electrons emitted by heating the filament collides with gas molecules, a high-frequency discharge method in which gas ions are trapped by applying a high frequency, and the like can be used. By applying a negative DC bias voltage to the substrate while the initial plasma is generated in the vacuum chamber, a plasma having a density and energy corresponding to the applied voltage is easily formed around the substrate. Usually, this plasma is set to have a higher density than the plasma formed by the initial plasma generating means. Here, the hydrocarbon-based gas is decomposed and ionic species are generated.
The collision causes a hard carbon film to be formed efficiently. Furthermore, since the plasma is three-dimensionally covered around the base material, there is no film-forming directivity and very excellent throwing power is exhibited. As a result, a hard carbon film excellent in productivity without deterioration of film quality can be obtained.

[0007]

Embodiment 1 An embodiment according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view illustrating a method and an apparatus for forming a hard carbon film according to the present invention. Trigger for generating initial plasma in vacuum chamber 1
A coil-shaped electrode 2 as an electrode is provided, and is connected to a high-frequency power supply via a matching box outside the vacuum chamber. On the other hand, the substrate 3 is placed on a cathode electrode 4, and the electrode is externally connected to a DC power supply so that a negative bias voltage is applied. Further, the structure is such that hydrocarbon-based gas can be introduced from outside through the gas inlet 5.

In this embodiment, first, after evacuating the vacuum chamber 1, benzene gas was introduced from the gas inlet 5 so that the gas pressure became 5 × 10 ⁻³ Torr. Thereafter, high-frequency power of 100 W was applied to the coiled electrode 2 to form plasma in the vacuum chamber. At this time, high-frequency power is efficiently transmitted to the coil-shaped electrode 2 and contributes to plasma generation by performing impedance matching in the matching box so as to minimize the load impedance inside the vacuum chamber. This operation is effective in a wide vacuum range.
Next, by applying -3 KV to the cathode electrode 4, a plasma having a higher density than the initial plasma was formed around the cathode electrode 4 and the base material 3. At this time, stainless steel was used as the material of the substrate 3. Under this condition, the benzene gas is decomposed in the plasma around the cathode electrode 4 and the substrate 3, and the ions generated as a result collide with energy, so that three-dimensional A hard carbon film was deposited.

The Vickers hardness of the hard carbon film obtained under the above conditions is 3000 (kg / mm ² ) or more.
Analysis results such as X-ray diffraction, RHEED, Raman spectroscopy and Fourier transform infrared absorption spectroscopy (FT-IR) showed that the film had an amorphous structure and contained hydrogen in the film.

As a comparative sample for confirming the effect of the embodiment of the present invention, a hard carbon film was formed on the same stainless steel substrate as used in the present embodiment by the conventional RF method or DC method. , Film quality and productivity. FIG. 3 is a schematic sectional view of an apparatus showing a conventional RF system. As in the present embodiment, a vacuum chamber 21, a gas inlet 25, a cathode electrode 24, and a base material 23 are provided. In this case, high-frequency power is applied to the base material 23 via the cathode electrode 24. Has been turned on. FIG. 4 is a schematic sectional view of an apparatus showing a conventional DC system. A cathode electrode 34, a substrate 33, and a gas inlet 35 are arranged in the vacuum chamber 31. The ion generating chamber has a filament electrode 36 and an anode electrode 37,
The ions formed in this portion are directed to the substrate 33 with directivity.
The substrate is usually rotated because of the structure for irradiating the substrate. Further, in the conventional DC system, the filament electrode and the base material are arranged to face each other for directivity of ions.

Here, the evaluation of the film quality was made based on the number of particles of φ100 μm or more on the surface of the hard carbon film formed on the stainless steel substrate. For productivity, we estimated the quantity of processing in the same space. In the conventional DC method, the substrate is required to rotate relative to the filament electrode due to the directivity of ions. In the conventional RF method, there is a limitation on the input power and the arrangement of the substrate caused by the need for measures against arc discharge. Consideration has been given to the reduction in processing volume due to restrictions on the amount of processing. The results are shown in Table 1, and it can be seen that in this example, both film quality and productivity are compatible.

[0012]

[Table 1]

[0013]

Embodiment 2 A filament electrode 12 is provided as a trigger electrode for generating an initial plasma in a vacuum chamber 11, and is connected to an AC power supply outside the vacuum chamber.
As in the first embodiment, a cathode electrode 14, a substrate 13, and a gas inlet 15 are provided. In this embodiment, the first embodiment
After introducing benzene gas in the same manner as in
The flow of 10 A through the cell 2 generated thermoelectrons, which collided with benzene gas in the vacuum chamber to generate weak initial plasma. Next, minus 3 is applied to the cathode electrode 14.
A voltage higher than the initial plasma was formed around the cathode electrode 14 and the base material 13 by applying a voltage of KV, and then the voltage application to the filament electrode 12 was stopped. Through such a procedure, the plasma formed around the base material 13 is maintained only by the DC bias voltage applied to the base material thereafter, and the film formation process is proceeding. The film formation process was performed sufficiently stably by setting the bias voltage value and the like.
The DC bias voltage value is determined in advance from the correlation with the hard carbon film characteristics obtained from the value.

The film obtained in this example was evaluated according to the same evaluation criteria as in Example 1. At this time, the conventional DC type film in Example 1 was used as a comparative sample. As a result, the number of particles was almost 0, and a significant improvement in film quality was recognized as compared with the conventional method. Although there are still many unclear points about the particle generation mechanism, the formation of an unnecessarily high plasma density region due to excessive electron emission as in the conventional DC method is a result of the interaction of ions, radicals, electrons, and the like. It is considered that the gas phase reaction is promoted as a result, and as a result, the generation of particles is increased and the film quality is deteriorated. Therefore, a device for suppressing the plasma density to a certain set value or less outside the film formation region is considered. Seems necessary.
However, it is possible to introduce an anode electrode which is conventionally used in the DC method in order to increase the film formation rate in a condition where particles do not occur. Furthermore, compared to the conventional DC method, according to the present embodiment, since there is no ion directivity, the filament electrode and the substrate do not necessarily have to be opposed to each other. And the same effect as in Example 1 was confirmed for the number of processed base materials.

In this embodiment, the hard carbon film is formed directly on the stainless steel substrate. However, the present invention can be applied to the case where the adhesion strength is further increased by introducing an intermediate layer. In addition, benzene was used as the hydrocarbon-based gas, but other hydrocarbon-based gases such as methane and ethane, fluorocarbon-based gases, or a mixed gas thereof may be used. Also,
The processing conditions such as the degree of processing vacuum and the DC bias voltage are also variable without being limited to the present embodiment, but the DC bias voltage is determined from the correlation with the characteristics of the hard carbon film.
A range of 1 KV to -7 KV is desirable. Further, although filament heating is used as a thermionic excitation method as an initial plasma generation means, other means such as a hollow cathode method may be used. Although stainless steel was used as the base material, any material such as SK material can be applied. As specific application examples, appearance quality and surface roughness of watch parts, loom parts, knitting parts, etc. are regarded as important. This is particularly effective for certain fields.

[0016]

As is apparent from the above description, according to the method and apparatus for forming a hard carbon film of the present invention, the hard carbon film has excellent wear resistance and low coefficient of friction. Film quality sufficient to take advantage of the features can be realized in an unprecedented productivity.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a plasma CVD apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view of a plasma CVD apparatus according to another embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view of a conventional plasma CVD apparatus in an RF system.

FIG. 4 is a schematic sectional view of a conventional DC type plasma CVD apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum tank 2 Coiled electrode 3 Base material 4 Cathode electrode 5 Gas inlet 11 Vacuum tank 12 Filament electrode 13 Base material 14 Cathode electrode 15 Gas inlet 21 Vacuum tank 23 Base material 24 Cathode electrode 25 Gas inlet 31 Vacuum tank 33 Base material 34 Cathode electrode 35 Gas inlet 36 Filament electrode 37 Anode electrode

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 16/00-16/56 C01B 31/02 C23C 14/00-14/58 C30B 29/04 H01L 21 / 205 H05H 1/46 B01J 19/08

Claims (5)

(57) [Claims] A cathode for applying a DC voltage to a substrate.
A hydrocarbon-based gas is introduced into a vacuum chamber using a plasma CVD apparatus in which a cathode electrode and a trigger electrode configured to be driven independently of the cathode electrode are arranged in a vacuum chamber. After that, a voltage is applied to the trigger electrode to generate an initial plasma in the vacuum chamber, and then a negative DC bias voltage is applied to the cathode electrode to generate a plasma having a higher density than the initial plasma around the substrate. Forming a hard carbon film on the surface of the substrate by accelerating the decomposition of the hydrocarbon-based gas in the plasma. 2. The method for forming a hard carbon film according to claim 1, wherein the application of the voltage to the trigger electrode is stopped after forming a plasma having a density higher than the initial plasma around the substrate. . 3. A means for introducing a gas into a vacuum chamber, a cathode electrode capable of applying a DC voltage to a substrate, and a cathode electrode for generating an initial plasma, which can be driven independently. An apparatus for forming a hard carbon film, comprising: a trigger electrode configured as described above. 4. An initial plasma generating means comprises a high-frequency power source, a coiled electrode, and a matching box for maximizing power transmission between the two, and an impedance for minimizing a load impedance inside the vacuum chamber. 4. The apparatus for forming a hard carbon film according to claim 3, wherein the apparatus is a high-frequency excitation type plasma generating means configured to be capable of dance matching. 5. An initial plasma generating means comprising an AC power supply and a filament electrode, and configured to emit electrons into a gas phase by heating the filament electrode. 4. The apparatus for forming a hard carbon film according to claim 3, wherein: