JPH06280019A - Production of thin film of diamond-like carbon - Google Patents

Abstract

PURPOSE:To stably produce a diamond-like-carbon thin film of high quality having uniform particle size by forming a diamond-like-carbon base film on the surface of a substrate by electron cyclotron resonance method, then exciting a gas containing C and H2, and bringing the gas into contact with the carbon base film. CONSTITUTION:A base body 7 is disposed in a vacuum chamber 1 and then the chamber is evacuated. After heating the base body 7 with a heater 11, a source gas containing C and H2 such as methane and ethane and a mixture gas of rare gas such as He and Ar are introduced to the chamber through gas inlet tubes 13 and 14. A magnetic field of specified intensity is applied by a magnetic coil 6, while microwaves of specified frequency are introduced from the microwave oscillator 4 through an inlet 5 to the vacuum chamber 1. The gas such as methane is excited to change into a plasma state, in which carbon-contg. active seeds are brought into contact with the base body 7 to form a base layer comprising diamond-state carbon by electron cyclotron resonance method. Further, by exciting a gas containing C and H2 such as methane and bringing the gas into contact with the substrate, a high quality diamond-like carbon thin film is formed.

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 diamond-like carbon thin film used as a coating for decoration, tools, electronic devices and the like.

[0002]

2. Description of the Related Art Diamond-like carbon thin films have excellent physical properties and are being widely used as a coating material for decoration, tools, electronic devices and the like. Conventionally, as a method for producing a diamond-like carbon thin film, heat C has been used.
VD method, plasma CVD method, ion beam method, ion plating method and the like are known. For example, JP-A-58
-91100 discloses a method of forming a diamond-like carbon thin film by a thermal CVD method using a carbon-containing gas and a hydrogen gas, and JP-A-64-31974 discloses that a carbon-containing gas and a hydrogen-containing gas are not included. A method of forming a film by a plasma CVD method using an active gas is described. Also,
Recently, Japanese Patent Application Laid-Open No. 63-83271 describes a method of forming a film by an electron cyclotron resonance method using a hydrogen gas and a carbon-containing gas.

In Japanese Patent Laid-Open No. 9736/1993, a mixed gas containing a carbon-containing gas and a rare gas, or a mixed gas containing a carbon-containing gas, a hydrogen gas and a rare gas is used to perform an electron cyclotron resonance method. A method of filming is described.

However, the diamond-like carbon thin film obtained by the above method has a non-uniform diamond crystal grain size, and is difficult to use as an electronic material or an optical material.

As a countermeasure against this, Japanese Patent Laid-Open No. 3-278463
In the publication, in order to form diamond particles having a uniform particle size, fine irregularities are formed on a base material, which is then infiltrated and vibrated in a solution containing diamond powder, and further irradiated with an argon beam to generate a nucleus. A method for selectively forming a diamond crystal having a uniform grain size by controlling the generation position is disclosed. However, this method
There is a drawback that the manufacturing process becomes complicated.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above drawbacks, and an object thereof is to provide a method for producing a high quality diamond-like carbon thin film having a uniform grain size in a simple process. To do.

[0007]

The method for producing a diamond-like carbon thin film of the present invention is a method in which a mixed gas consisting of a gas containing carbon and hydrogen and a rare gas is excited by an electron cyclotron resonance method to form an underlayer. A gas containing carbon and hydrogen is excited and brought into contact with the underlayer.

The mixed gas used in the present invention comprises a gas containing carbon and hydrogen and a rare gas.

As the gas containing carbon and hydrogen,
For example, alkane-based gases such as methane, ethane, propane, butane, pentane, and hexane; alkene-based gases such as ethylene, propylene, butene, and pentene; alkadiene-based gases such as pentadiene and butadiene; acetylene, methylacetylene, and the like. Alkyne-based gases; aromatic hydrocarbon-based gases such as benzene, toluene, xylene, indene, naphthalene, phenanthrene; cycloalkane-based gases such as cyclopropane and cyclohexane; cycloalkene-based gases such as cyclopentene and cyclohexene; methano -Alcohol-based gases such as alcohol and ethanol;
Ketone-based gases such as acetone and methyl ethyl ketone; aldehyde-based gases such as methanal and ethanal. These gases may be used alone,
Two or more kinds may be used in combination.

As the gas containing carbon and hydrogen other than the above, a mixed gas of the above gases and hydrogen gas; a gas composed only of carbon and oxygen such as carbon monoxide gas and carbon dioxide gas and the above gas Mixed gas with a gas; mixed gas of hydrogen gas and a gas composed only of carbon and oxygen, such as carbon monoxide gas and carbon dioxide gas. further,
Oxygen gas or water vapor may be added to the gas containing carbon and hydrogen.

The rare gas is a gas containing an element belonging to Group 0 of the periodic table, and examples thereof include helium, argon, neon and xenon. These rare gases may be used alone or in combination of two or more. When the rare gas is mixed, the plasma electron density increases, so that the diamond-like carbon thin film deposition rate tends to increase.

The mixing amount of the rare gas in the above mixed gas is appropriately determined depending on the kind of the mixed gas, the film forming pressure and the like. However, if the amount is excessive or too small, the obtained thin film becomes graphite and the diamond-like carbon thin film Since the film forming rate decreases, it is preferably 20 to 90 vol% in the mixed gas.

The mixed amount of the gas containing carbon and hydrogen in the mixed gas is preferably 10 to 80 vol% in the mixed gas.

Regarding the hydrogen gas, the mixing amount in the mixed gas is appropriately determined depending on the kind of the mixed gas used, the film forming pressure, etc., and the mixing amount is not particularly limited.

Examples of the base material used in the present invention include metals such as silicon, aluminum, titanium, molybdenum and tungsten, alloys of these metals, oxides, nitrides and carbides of various metals, glass, ceramics and plastics. The shape is not particularly limited, and examples thereof include a plate shape, a linear shape, and a pipe shape.

When high adhesion between the base material and the diamond-like carbon thin film is required, a cleaning treatment such as cleaning for degreasing and dehydrating the above base material; inert gas such as argon in a vacuum vessel. Known pretreatment such as plasma treatment is preferably performed.

When the base material has a clean surface, the base layer can be easily formed, so that pretreatment of the base material with diamond abrasive grains for forming diamond nuclei is not always necessary.

The mixed gas is excited by the electron cyclotron resonance method to form an underlayer on the base material.

FIG. 1 is a schematic sectional view showing an example of an apparatus used for forming an underlayer. In FIG. 1, reference numeral 1 is a vacuum container, and the vacuum container 1 is a plasma generating chamber 2 and a film forming chamber 3.
It consists of At the center of the side surface of the plasma generation chamber 2,
A microwave oscillator 4 is connected to the plasma generation chamber 2 by a microwave introduction tube 5, and a magnetic field coil 6 is provided around the plasma generation chamber 2 and the microwave introduction tube 5.

On the other hand, in the vacuum container, the base material 7 is made so that the surface of the base material 7 on which the base layer is formed faces the microwave introducing tube 5.
A holding tool 8 for holding is installed. further,
The holder 8 is connected to a DC bias power source 9 for applying a DC bias to the base material 7 by a conductive wire.

The holder 8 is connected to a cooling liquid circulator (not shown) for the case of forming a film at a temperature of about 200 ° C. or lower, and the cooling liquid 10 can be circulated inside. . A heating device 11 is provided for the case of forming a film at about 200 ° C. or higher. Further, the holder 8 is provided with a thermocouple 12 for measuring the temperature of the back surface of the base material.

Two gas introduction pipes 13 and 14 for introducing a mixed gas are connected to the plasma generation chamber 2, and the gas introduction pipe 13 is provided at a position near the holder 8. The wall surface of the film forming chamber 3 is provided with an exhaust port 15 connected to an exhaust device (not shown) for adjusting the pressure inside the vacuum container 1.

The method of forming the underlayer by the above apparatus will be described below. First, after the base material 7 is set in the vacuum container 1 by the holder 8, the inside of the vacuum container 1 is set to a high vacuum. The pressure in the vacuum container 1 at this time is preferably 10 ⁻⁴ Torr or less in order to eliminate the influence on the film formation due to the residual of other impurity gas.

Next, the base material 7 is set to a predetermined temperature. The substrate 7 is held by a holder 8 provided with the cooling device and the heating device 11, and the temperature thereof is from room temperature to 1000.
It is controlled to a predetermined temperature in the range of ° C. When the underlayer is formed at a low temperature of 200 ° C. or less, which has a small thermal influence on the base material 7, the temperature of the base material 7 is set by controlling the temperature of the holding tool 8 in contact therewith. In this case, the base material 7 is set to a temperature of plasma or lower via the holder 8.

In this case, the temperature control method of the holder 8 may be a method of circulating a liquid or a gas having a predetermined temperature inside the holder 8, a method of heating wire, an electric heating, or the like. Since it has a temperature of ℃ or more, in order to keep the film forming temperature of the underlayer at 200 ℃ or less, a liquid circulation system with a large heat capacity is preferable, and at least 2
It is necessary to keep the temperature below 00 ° C.

The liquid used in the circulation system is a liquid that has been heated or cooled to a predetermined temperature, such as water, ethylene glycol (antifreeze liquid), alcohols, and liquid nitrogen, liquid helium, etc. when the temperature is further lowered. Is mentioned.

When the underlayer is formed at a high temperature of 200 ° C. or higher, the method for raising the temperature of the base material is to control the heating device 11 of the holder 8 for holding the base material 7 by heating the heating device 11 based on heat. Examples include a method of irradiating the material 7.

Next, the mixed gas is introduced into the vacuum container 1 and adjusted to a predetermined pressure. The lower the pressure, the lower the film formation rate, and the higher the pressure, the lower the quality of the diamond-like carbon thin film obtained. Therefore, the pressure is preferably 1 × 10 ^{−4 to} 50 Torr, more preferably 1 × 10 ^{−2 to} 10 Torr.

The method of introducing the mixed gas is not particularly limited, and the mixed gas may be introduced all at once through the introduction pipes 13 or 14, or the mixed gas is constituted using the introduction pipes 13 and 14. The component gases may be introduced individually. However, when the latter introduction method is adopted, it is preferable to introduce the gas containing carbon through the introduction pipe 13 near the base material 7.

Next, a magnetic field having a predetermined magnetic field strength is applied by the magnetic field coil 6, and a microwave having a predetermined frequency is generated by the microwave oscillator 4, and the microwave is passed through the microwave introduction tube 5 and quartz. It is introduced into the vacuum container 1 through the window 16.

The gas containing carbon and hydrogen introduced into the vacuum vessel 1 is excited into a plasma state, and the carbon-containing active species come into contact with the base material 7, whereby the diamond-like carbon thin film on the base material 7 is formed. A base layer (not shown) is formed.

The above-mentioned predetermined magnetic field strength and frequency are not particularly limited, but it is preferable that the predetermined magnetic field strength and frequency satisfy the conditions required for electron cyclotron resonance. This condition means that the cyclotron frequency of an electron in a constant magnetic field and the microwave frequency match, and for example, when the microwave frequency is 2.45 GHz, the magnetic field strength is 875.
Gauss. At this time, in order to form a uniform film, it is preferable to apply a DC bias to the substrate 7, and the DC bias value is preferably -5 to 200V.

The underlayer is preferably in the form of a thin film, and the film thickness is not particularly limited, but is preferably 0.01 μm or more.

The diamond-like carbon thin film is composed of diamond-like carbon microcrystals, and has a crystallite diameter of 1
It is preferably 00 Å or less. The crystallite diameter varies depending on conditions such as film forming pressure, mixed gas type and its mixing ratio, and film forming temperature. For example, when the film forming temperature becomes lower, the crystallite diameter tends to become smaller.

In the manufacturing method of the present invention, one or more diamond-like carbon thin films are formed on the underlayer formed by the above method.

As the gas used for forming the carbon thin film, the gas containing carbon and hydrogen is used.

As a means for exciting the gas containing carbon and hydrogen, a method conventionally used for synthesizing diamond, for example, a method of decomposing plasma by applying direct current; a method of decomposing plasma by microwave discharge ;
A method of plasma decomposition by the electron cyclotron resonance method; a method of thermally decomposing by hot filament heating and the like can be mentioned, but the electron cyclotron resonance method is preferable from the viewpoint of productivity and adhesion, and according to the method of forming the underlayer A diamond-like carbon thin film is formed.

[0038]

[Properties and identification of film]

(1) Properties of Film The surface grain of the film obtained by a scanning electron microscope was observed to evaluate the crystal grain size. (2) Identification of film The binding energy of the film obtained by X-ray electron spectroscopy was 0.
The valence band spectrum in the range of ˜30 eV was measured, and FIG.
As shown in the valence band spectrum of IIb type natural diamond shown in (4), the presence or absence of peaks peculiar to diamond at 14 eV and 18 eV was confirmed to identify that the obtained film was a diamond-like carbon thin film. Incidentally, in the valence band spectrum of graphite, as shown in FIG. 3, peaks at 14 eV and 18 eV are not confirmed.

(Example 1) In the apparatus shown in FIG.
The stainless steel holder 8 in the vacuum container 1 is not pre-treated with diamond abrasive grains and has a diameter of 4 inches and a thickness of 20.
The Si substrate 7 of 0 μm is installed, and the inside of the vacuum container 1 is set to 1 × 10.
After reducing the pressure to ⁻⁵ Torr, the heating device 11 was heated to 500 ° C.

Then, the gas flow rate was set to 40 sccm of methanol gas and 140 sccm of argon gas respectively, and the mixed gas was introduced into the vacuum vessel 1 through the gas introduction pipe 14 to a pressure of 0.1 Torr, and the frequency was changed to 2.4.
While applying a microwave of 5 GHz, 1.2 kW and a magnetic field of 2.2 kGauss and applying a DC bias of 30 V for 15 minutes to form a film, a 0.05 μm-thick underlayer made of 70 Å crystallites was formed. Formed. The magnetic field strength near the surface of the base material at this time was 875 Gauss.

Next, a film having a thickness of 0.6 μm was obtained by performing film formation for 4 hours under the same film forming conditions as the formation of the underlayer, except that the argon gas was replaced with hydrogen gas. The obtained thin film was evaluated by the above method (1).
Crystals having a uniform (111) face of diamond having a grain size of about 1 μm were confirmed. Further, as a result of evaluating the obtained thin film by the method (2), valence band spectra peculiar to diamond having peaks at 14 eV and 18 eV were confirmed.

(Example 2) In Example 1, as a pretreatment with known diamond abrasive grains, an average particle size of 20 to 4 was used.
Film formation was performed in the same manner as in Example 1 except that a Si base material that was ultrasonically treated for 30 minutes in an ethanol dispersion liquid in which 0 μm diamond abrasive grains were dispersed was used. The obtained thin film was evaluated in the same manner as in Example 1, and as a result, the result was about 0.
It was confirmed that a film composed of a uniform crystal having a particle size of 1 μm was formed on the entire surface of the base material.
A valence band spectrum peculiar to diamond having peaks at V and 18 eV was confirmed.

(Embodiment 3) On the underlayer formed in the same manner as in Embodiment 1, a conventional microwave plasma CVD method was used to mix a gas of CO gas of 10 sccm and hydrogen gas of 90 sccm to obtain a pressure of 30 Torr and a temperature of 850. 4 at ℃
Film formation was performed for a time to form a thin film having a thickness of 0.1 μm. The obtained thin film was evaluated in the same manner as in Example 1. As a result, it was confirmed that a film composed of uniform crystals having a grain size of about 0.5 μm was formed on the entire surface of the substrate, and X-ray electron In the spectroscopy, valence band spectra peculiar to diamond having peaks at 14 eV and 18 eV were confirmed.

Comparative Example 1 Film formation was carried out for 4 hours in the same manner as in Example 1 except that the underlayer was not formed. As a result of evaluating the obtained thin film in the same manner as in Example 1, it was confirmed that irregular crystals having a particle size of 0.1 μm or less were formed on the substrate.

Comparative Example 2 Film formation was carried out for 4 hours in the same manner as in Example 2 except that the underlayer was not formed. The obtained thin film was evaluated in the same manner as in Example 1. As a result, a film in which crystals having irregular grain sizes of 0.1 μm or less were entangled with each other was confirmed.
A valence band spectrum peculiar to diamond having peaks at eV and 18 eV was confirmed.

[0046]

Since the method for producing a diamond-like carbon thin film of the present invention is as described above, it is possible to form a diamond-like carbon thin film having a uniform grain size, and the obtained diamond-like carbon thin film is for decoration. It can be used as a coating for tools, electronic devices, etc., and can be suitably used for a wide range of applications such as optical materials, electronic materials, and chemical industrial materials.

[0047]

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of an apparatus used in the manufacturing method of the present invention.

FIG. 2 is a valence band spectrum obtained by X-ray electron spectroscopy of type IIb natural diamond.

FIG. 3 is a valence band spectrum obtained by X-ray electron spectroscopy of graphite.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum container 2 Plasma generation chamber 3 Film-forming chamber 4 Microwave oscillator 5 Microwave introduction pipe 6 Magnetic field coil 7 Base material 8 Holding device 9 DC bias power supply 10 Cooling liquid 11 Heating device 12 Thermocouple 13, 14 Gas introduction pipe 15 Exhaust Mouth 16 Quartz window

Claims (1)

[Claims] 1. A mixed gas composed of a gas containing carbon and hydrogen and a rare gas is excited by an electron cyclotron resonance method and brought into contact with a base material to form a base layer composed of a diamond-like carbon film on the base material. Then, a method for producing a diamond-like carbon thin film is characterized in that a gas containing carbon and hydrogen is excited and brought into contact with the underlayer to form a film.