JPH0331788B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for forming a carbon film having excellent conductivity.

[Prior Art] Conventionally, the common method for obtaining conductive carbon films is the thermal decomposition method (for example, Otani et al., "Fundamentals of Carbonization Engineering", 1980, published by Ohm Publishing).

This method decomposes hydrocarbons by heating the reaction system in an atmosphere of raw material aliphatic or aromatic hydrocarbon gas such as methane, ethane, propane, or benzene, and forms a carbon film on the substrate. It is something to do.

A typical carbon film obtained by this method has an electrical conductivity at room temperature of about 70 S/cm when heat-treated at 1000°C, and about 0.2 S/cm when heat-treated at 600°C.

In addition, recently, as a method for obtaining conductive carbon films,
The plasma CVD method is attracting attention (for example, Y. Onuma, Y. Kato, M. Nakao, H. Matsushima; Japanese Journal of Applied Physics, 22(5), 888 (1983),
Or J. Shioya, naughty. Matsubara, S. Murakami, Synthetic Metals, 14,
113 (1986)).

In this method, plasma polymerization is performed using high-frequency discharge in the above-mentioned hydrocarbon gas atmosphere to generate a carbon film on a substrate. In the case of base material temperature, it is quite high at around 1000S/cm, but 800℃
The conductivity is about 50S/cm at 600°C, and about 0.3S/cm at 600°C, which is not much different from the conductivity of carbon films made by thermal decomposition.

[Problems to be solved by the invention] In the conventional method, the minimum synthesis temperature required to obtain a carbon film with an electrical conductivity of 50 S/cm or more is about 900°C in the thermal decomposition method, but in the plasma CVD method, the minimum synthesis temperature is about 900°C. In this case, a high temperature of about 800℃ is required. For this reason, there has been a problem that the types of materials that can be used as base materials and the fields of application are limited.

In other words, it has been impossible to use a material that deforms at high temperatures or a material whose inherent properties change as a base material.

In view of the problems of the prior art described above, the present invention provides a method for obtaining a carbon film having excellent conductivity even at a synthesis temperature of less than 900°C.

[Means for Solving the Problems] This invention solves the problems of the conventional technology by employing an ion beam method to form a carbon film. A method for forming a conductive carbon film is characterized in that the conductive carbon film is formed by a cluster ion beam method on a base material heated to a temperature of 400°C or more and less than 900°C using hydrogen as a raw material.

The hydrocarbons used as raw materials in this invention include:
For example, saturated aliphatic compounds such as methane, ethane, propane, unsaturated aliphatic compounds such as alkenes and alkynes, benzene, naphthalene, anthracene,
Aromatic compounds such as pyrene are used.

As the base material used in this invention, Fe,
Metal materials such as Ni and Al, intermetallic compound materials such as GaAs and InP, metal oxide materials such as SiO ₂ , Al ₂ O ₃ , and TiO ₂ , carbon-based materials such as graphite, diamond thin film, and carbon fiber, NaCl , KBr, and other alkali halide crystalline materials.

As the ion beam method adopted in this invention, for example, an apparatus as shown in Fig. 1 is used (Usui H., Yamada I., Takagi T.; Journal of Vacuum Science and Technology, A4(1), 52).
(1986)).

In FIG. 1, 1 is a chamber, and within the chamber 1 is provided a crucible 3 into which a raw material 2 is introduced. The raw material, hydrocarbon, is in chamber 1.
The raw material is introduced into the crucible 3 from a raw material introduction system 4 provided outside the chamber 1 through a raw material introduction pipe 5 inside the chamber 1 . A nozzle 6 for injecting the raw material is provided on the wall of the crucible 3 on the opposite side of the raw material introduction pipe 5, and a base material setting table 8 on which a base material 7 is set is provided in the direction facing the nozzle 6. There is.

In this apparatus, a crucible 3 is surrounded by a graphite heater 9 for heating the crucible, and a heat shield plate 10 and a cooling jacket 11 are provided around the outer periphery of the graphite heater 9. Between the nozzle 6 and the base material 7, there is an electron-emitting filament 1 that ionizes the injected raw material.
2. An ion accelerating electrode 13 for accelerating the generated ions toward the substrate, and a shutter 14 are provided in this order. The electron emitting filament 12 is arranged so as to emit electrons from three sides to the ejected raw material beam 15, and the electron emitting filament 12
An electron accelerating electrode (grid) 16 is provided between the material beam 15 and the material beam 15 .

A heater 1 for heating the base material 7 is installed around the base material 7.
7 and a heat shield plate 18 provided outside of the heater 17 to prevent heat from dissipating from the heater 17.

In this device, 19 is a cooling water inlet, 20 is an oil rotary pump, and 21 is an oil diffusion pump.

[Operation] When this apparatus is used, the formation of a conductive carbon film in the present invention is performed as follows.

The quartz base material is set on the base material installation stand inside the chamber 1, and the oil rotary pump 20 is installed inside the chamber 1.
The pressure is reduced to, for example, 1 to 2 x 10 ^-6 mmHg by a pressure reducing device comprising an oil diffusion pump 21 and an oil diffusion pump 21. Next, the nozzle 6 of the crucible 3 into which the raw material was introduced
The raw material is spouted out. At this time, if the raw material is easily volatile like benzene, it is not necessary to particularly heat the crucible 3, but for example, in the case of pyrene which is solid at room temperature, it is heated to 100 to 200°C. In addition, a particularly good carbon film can be obtained if the raw material vapor is made into clusters or aggregates.

To do this, the pressure inside chamber 1 must be
It is recommended to set it to 1/10 ² of the pressure of .

Electron emitting filament 12 and electron accelerating electrode 16
When, for example, several tens to hundreds of V is applied between them, electrons are emitted toward the raw material beam 15, and the raw material is ionized.

The ionized raw material is accelerated toward the base material by the ion accelerating electrode 13. Base material 7 is 400 in advance
Heated to a temperature above ℃ but below 900℃.

By the above method, a carbon film with excellent conductivity is formed on the surface of the base material at a relatively low temperature.

[Examples] Example 1 A quartz substrate (thickness 1 mm, surface optically polished) was used as a base material, set in a substrate holder in the chamber of the apparatus shown in FIG. 1, and heated to 850°C.
Next, benzene as a raw material was introduced into the chamber through a nozzle, and ion beam evaporation was performed under the following conditions to obtain a uniform dark brown carbon film with good adhesion to the substrate on the substrate.

Pressure of raw material benzene: 5.0×10 ^-5 mmHg (base pressure: 2.0×10 ^-6 mmHg) Electron emission filament current: 30A Electron acceleration voltage: 500V Ion acceleration voltage: 2kV Distance between nozzle and substrate: 15cm Synthesis time: 2hr Obtained The carbon film obtained had a film thickness of about 0.40 μm and an electrical conductivity of 150 S/cm at room temperature.

Example 2 Using benzene as a raw material, ion beam evaporation was performed on a quartz substrate heated to 800° C. under the same conditions as in Example 1 to obtain a dark brown carbon film.

This carbon film had a film thickness of about 0.50 μm and an electrical conductivity of 120 S/cm at room temperature.

Example 3 Using benzene as a raw material, ion beam evaporation was performed on a quartz substrate heated to 600° C. under the same conditions as in Example 1 to obtain a dark brown carbon film.

This carbon film had a film thickness of about 0.60 μm and an electrical conductivity of 70 S/cm at room temperature.

Comparative Example 1 Using benzene as a raw material, thermal decomposition was performed on a quartz substrate heated to 850° C. under the following conditions to obtain a yellow-brown carbon film on the substrate.

Pressure of raw material benzene: 5.0×10 ^-5 mmHg (base pressure: 2.0×10 ^-6 mmHg) Distance between nozzle and substrate: 15 cm Synthesis time: 2 hr The obtained carbon film has a film thickness of about 0.07 μm and an electrical conductivity at room temperature. was 9.0S/cm.

Comparative Example 2 Using benzene as a raw material, thermal decomposition was performed on a quartz substrate heated to 800° C. under the same conditions as in Comparative Example 1 to obtain a yellowish brown carbon film on the substrate.

The obtained carbon film had a film thickness of about 0.08 μm and an electrical conductivity of 4.2 S/cm at room temperature.

Comparative Example 3 Using benzene as a raw material, thermal decomposition was performed on a quartz substrate heated to 600° C. under the same conditions as in Comparative Example 1 to obtain a yellow-brown carbon film on the substrate.

This carbon film had a thickness of about 0.90 μm and an electrical conductivity of 0.12 S/cm at room temperature.

Comparative Example 4 Using benzene as a raw material, plasma CVD was performed on a quartz substrate heated to 850°C under the following conditions.
A carbon film with metallic luster was obtained.

Pressure of raw material benzene: 1 mmHg Plasma output: 40 W (13.56 MHz) Synthesis time: 2 hr This carbon film had a thickness of about 9.5 μm and an electrical conductivity of 170 S/cm at room temperature.

Comparative Example 5 Using benzene as a raw material, plasma was applied to a quartz substrate heated to 800°C under the same conditions as Comparative Example 4.
CVD was performed to obtain a silver-gray carbon film.

This carbon film had a thickness of about 12.0 μm and an electrical conductivity of 53 S/cm at room temperature.

Comparative Example 6 Using benzene as a raw material, plasma was applied to a quartz substrate heated to 600°C under the same conditions as Comparative Example 4.
CVD was performed to obtain a gray carbon film.

This carbon film had a thickness of about 16.0 μm and an electrical conductivity of 0.3 S/cm at room temperature.

FIG. 2 shows the relationship between the synthesis temperature and the electrical conductivity at room temperature of carbon films synthesized by the various methods described above.

[Effects of the Invention] According to this invention, as can be seen from Figure 2, high conductivity can be achieved even when the temperature of the base material is 400°C or more and less than 900°C, which is lower than the conventional pyrolysis method or plasma CVD method. It is possible to obtain a carbon film with high properties.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view schematically showing an apparatus for the ion beam method employed in the present invention, and FIG. 2 is a graph showing the relationship between the synthesis temperature and the electrical conductivity at room temperature of carbon films synthesized by various methods. 1...chamber, 2...raw material, 3...crucible,
6... Nozzle, 7... Base material, 12... Electron emission filament, 13... Ion accelerating electrode, 15...
Raw material beam, 16... electron accelerating electrode, 17... heater for heating the substrate.

Claims (1)

[Claims] 1. A conductive carbon film characterized in that a conductive carbon film is formed by a cluster ion beam method on a base material heated to a temperature of 400°C or more and less than 900°C using a hydrocarbon as a raw material. How to form a film. 2. The method for forming a conductive carbon film according to claim 1, wherein the substrate temperature is 600°C or more and 800°C or less. 3. The method for forming a conductive carbon film according to claim 1, wherein the hydrocarbon is an aromatic hydrocarbon. 4. The method for forming a conductive carbon film according to claim 3, wherein the aromatic hydrocarbon is benzene.