JPS6065796A - Hard carbon film and its production - Google Patents

Abstract

PURPOSE:To obtain a carbon film having excellent hardness, lubricity, abrasion resistance, etc., by forming a hard carbon film composed of a mixed crystal of hexagonal diamond and graphite on a substrate using C2H4 plasma. CONSTITUTION:The substrate 2 for forming a hard carbon film, a filament 4 and an electrode 3 for maintaining plasma discharge are arranged in a vacuum bell jar 1. The bell jar 1 is evacuated to high vacuum, and fed with C2H4 gas or a mixture of C2H4 gas and H2 gas through the inlet pipe 8. The filament 4 is heated with the DC source 15, and the electrode 3 for maintaining plasma discharge is charged to positive potential by the DC source 14 to generate C2H4 plasma between the electrode 3 and the filament 4. At the same time, the substrate 2 is charged to a negative potential by the high-voltage source 13 to produce a hard carbon film composed of a mixed crystal of hexagonal diamond and graphite on the substrate 2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hard carbon film and a method for producing the same, which has a hardness as high as 1%, as well as excellent lubricity, wear resistance, and chemical resistance. The present invention relates to a hard carbon film that has the same characteristics and that allows easy formation of fine battens, and a method for manufacturing the same.

For example, in order to further improve the wear resistance and lubricity of the materials of the sliding parts and cutting tools of mechanical parts, the surfaces of the parts are treated with hard films or solid lubricant films. This f! Traditionally, TiN and T are used as hard films for Iig products.
iC, B4C, 8rC, Si3N4.

Materials such as Aj203 have been coated on the surface of parts by methods such as sputtering, ion derating, and chemical vapor deposition (hereinafter referred to as rCVDJ).

However, even if a hard film is formed on the sliding parts of mechanical parts or the surface of cutting tools using this method,
Since these hard films do not have lubricity, adhesion occurs during use, and stress is concentrated, resulting in peeling at the base-film interface.

In addition, attempts have been made to use solid lubricant films for mechanical parts and cutting tools, but if the lubricant film is made thinner in order to achieve higher precision, it has the disadvantage of causing film breakage and shortening the lifespan. ,
If the film is made thicker, a decrease in accuracy due to wear becomes a problem.

Further, these hard films and solid lubricant films usually do not necessarily have high chemical resistance, so they cannot be used for parts and tools that are used in a highly corrosive chemical atmosphere.

Car d? is a coating material with high hardness, excellent wear resistance, lubricity, and chemical resistance. The membrane is known as

For example, the academic journal “Journal of Physics” published by the American Physical Society
Op Applied Physics (Journal o
Ion beam evaporation method published in Applied Physics) J Vol. 42 (published in 1971), p. 2953, Published in the 29th Applied Physics Lecture Proceedings 1a-E-4J of the Japan Society of Applied Physics. Ionized vapor deposition, Proceedings of the 29th Japan Society of Applied Physics 1a-
The low pressure CVD method described in "E-5" is known.

In the above ion beam evaporation method, C+ ions are generated by sputtering from a solid source in an ionization chamber, and then drawn out by applying an electric field to a separation chamber (iE vacuum of 10-6 Torr or higher) to form a carpin film on a substrate. to form. In this method, in order to avoid contamination of the C+ ion beam with impurities, it is necessary to adopt a complicated structure such as making all parts such as electrodes in the ionization chamber carbon. Further, in order to neutralize the positive charges on the carbon surface, a high frequency is fully applied to the substrate. For this reason, ions with a constant kinetic energy cannot be obtained, and stable film characteristics cannot be obtained.

In the ionization deposition method, a magnetic field generated inside a cylindrical magnetic circuit causes thermoelectrons to move in a zykroid to completely ionize the source gas, and C+ and t-on are controlled by a negative voltage applied to the substrate and a grid installed near the substrate. , carbon film is applied. In this method, since the ionization rate is high, positive charges tend to accumulate on the film surface during film formation, which tends to cause dielectric breakdown. In order to completely prevent dielectric breakdown, the grid controls the amount of ions that enter the substrate. However, due to the provision of the grid, the grid material is blown up and mixed into the film. Further, there are other problems such as non-uniformity in film thickness in the shadow areas of the grid.

The Karzan-jitsu formed using the two methods described above is extremely hard and consists of amorphous carbon, cubic diamond (hereinafter simply referred to as "cubic diamond"), or microcrystals containing a mixture of these. ing. Therefore, although the carbon films obtained by these methods have high wear resistance, they have the disadvantage of lacking lubricity.

In the low-pressure CVD method, the furnace temperature is raised to 700°C to 1,100°C, and a tungsten filament heated to nearly 2,000°C is placed near the substrate (:'2H4 and H
A mixed gas of 2 is introduced to completely form cubic diamond on the substrate. In this method, the substrate is heated to a high temperature, so there are restrictions on the substrate material.The material produced by this method contains a mixture of cubic diamond and amorphous carbon, and the film formed on the substrate is smooth. A complete film is not formed.

As mentioned above, the carbon film formed by the conventional carbon film manufacturing method is a film made of amorphous carbon or cubic diamond microcrystals, and although it has high hardness, it has no lubricity. .

When trying to use it for sliding parts of mechanical parts and cutting tools, there was a problem with lubricity.

In view of these circumstances, the inventors of the present invention have repeatedly studied the carpin film, which has excellent hardness, lubricity, wear resistance, and chemical resistance. hardness and abrasion resistance of
The present invention was established based on the knowledge that it is possible to form an ideal carbon film by combining the properties of excellent workability and corrosion resistance with graphite's properties of durability and stability against chemicals. I was able to do that.

That is, the present invention has high hardness and m1m properties.

The purpose of this invention is to provide a carbon film with excellent wear resistance and corrosion resistance, and a method for producing the same, and is characterized by being a hard carbon film made of a mixed crystal of hexagonal diamond and graphite. Moreover, this hard carbon film serves as a carbon film forming member and a thermionic emission means.

In a vacuum atmosphere in which a plasma sustaining electrode is placed, C2H
, gas and H2 or an inert gas, or a mixture of both of them, or only C2H4 gas is introduced to generate plasma between the thermionic emission means and the plasma sustaining electrode, and at the same time, a negative charge is applied to the carbon film forming member. A hard carbon film made of a hexagonal diamond and graphite mixed crystal is produced by applying a high voltage to completely generate a carmen film made of a hexagonal diamond and graphite mixed crystal on the carbon film forming member. It is something.

Hereinafter, the content of the present invention will be specifically explained based on Examples.

FIG. 1 shows a schematic diagram of an apparatus used for coating a substrate with a hard carbon film according to the present invention.

This device includes a vacuum belljar 1, substrates 2 for forming a hard carbon film arranged in order in the vertical direction of the belljar 1, electrodes 3 for maintaining plasma discharge. A filament 4 is provided as a thermionic emission means], and a substrate holder 5 is provided as required. A shutter 6 is disposed between the holder 5 and the discharge sustaining electrode 3, and a permanent magnet 7 is disposed below the filament 4.

The vacuum belljar 1 is equipped with gas introduction pipes 8 and 9 that connect to a BzH4 gas source and a Yayariya gas source (not shown). is provided. Further, below the bell jar 1, an exhaust pipe 12 is provided which is connected to an exhaust device (not shown).

Further, the substrate 2 is connected to a high voltage power source 13 outside the belljar 1, and is configured to supply a negative high voltage to the substrate 2 supported on the holder 5.

The discharge sustaining electrode 3 is connected to a DC power source 14 outside the bell jar, and the positive voltage supplied from the power source 14 causes the electrode 3 to be connected to a DC power source 14 outside the bell jar.
It has the function of generating plasma between the filament 4 and the connected filament 4.

The shutter 6 has a function of opening or closing C, H, and plasma reaching the surface of the substrate 2 by opening and closing operations.

Further, the permanent magnet 7 is arranged so as to apply a magnetic field at the same time as the electric field applied between the discharge sustaining electrode 3 and the filament 4, and the electrons are moved along this magnetic field and introduced into the bell jar 1. This serves to increase the number of collisions with the c, H, and r particles, thereby increasing the ionization rate.

A hard carbon film is formed on a carbon film forming substrate using the above apparatus according to the following process.

The carbon film forming substrate 2 is placed on the holder 5 inside the Makabe bell jar 1, and the inside of the vacuum bell jar 1 is evacuated to 5XIQTorr or higher.

Next, the flow rate adjustment valve lli is opened, and the introduction pipe 19 is opened.
: The krlf gas is introduced into the full vacuum bell jar through the gas, and the gas pressure is set to f 10-8 Torr.

Next, a current is sent from the DC power supply 15 to the filament 4 to heat it, and at the same time, from the DC power supply #14 to the discharge sustaining electrode 3.
Then, a positive voltage (50 to 100 V) is applied to generate M gas plasma between the filament 4 and the filament 4.

In this state, a negative high voltage (-1 to -3 kV) is applied to the substrate 2 from the high-voltage electric M13, and Ar+ ions are used to clean the substrate for 10 to 30 minutes, thereby completing the entire substrate cleaning as pretreatment.

After sputter cleaning is completed, the flow rate control valve 10 is opened, and the introduction pipe 8? I: C into vacuum bell jar 1 through
Add 4 tons of 2H4 gas and set the gas pressure to 2io-3Torr ~
Set around 10-” Torr.

Next, according to the same procedure as in the case of sputtering with Ar gas, a negative high voltage (-0, 2 to -3 , 5kV),
By opening the shutter 6, a hard carbon film made of a hexagonal diamond and graphite mixed crystal can be formed on the substrate 2.

The hard carbon film thus formed was analyzed by total X+W diffraction and electron beam diffraction, and the results are shown in FIGS. 2 and 3. however,@! The substrate used for forming the carbon film was a (100)81 wafer. Moreover, the X-ray used for X-ray diffraction was a line for Cu-.

Figure 2 is an X-ray diffraction diagram of a hard carbon film formed on a (100)81 wafer, where the horizontal axis is the diffraction angle (2θ).
is shown in degrees, and the vertical axis shows the intensity in arbitrary units (arb, un
it). -1, The curve a in Figure 2 shows the diffraction 'ffMk of the (101) plane of graphite, and the curve is the diffraction line from the (102) plane of hexagonal diamond.
This shows that the hard carbine film formed is composed of hexagonal diamond and graphite.

FIG. 3 is an electron diffraction photograph of the hard carbine film. In this electron diffraction method, only a ring-shaped diffraction pattern appears, without a halo pattern indicating the presence of amorphous material. This shows that the formed hard carbon film is a mixed crystal, and it is clear from FIGS. 2 and 3 that the hard carbon film is a mixed crystal of hexagonal diamond and graphite. On the other hand, conventional carbon films are not mixed crystals, but merely contain a mixture of cubic diamond and amorphous carbon.

In addition, when the substrate on which the hard carbon film is formed is a metal or an insulator, the results of X-ray diffraction of the carpin film formed on the substrate show that carbon, hexagonal diamond, and hexagonal diamond differ depending on the substrate material. The plane orientation of graphite is different. But regardless of the differences in the board Toga, the generated car day? The film is composed of a mixed crystal of hexagonal diamond and graphite.
It was a high quality carbon film.

In addition, when the above-mentioned carbon film consisting of a mixed crystal of hexagonal diamond and graphite is generated, if all the I■2 gas is added, the amount of H+ ion springs increases relatively, so that the carbon deposited on the IB plate in an unstable form is removed as a hydrocarbon, improving the crystallinity of the hard carbon film. Furthermore, when an inert gas such as Ar is added, the discharge is stabilized, but due to the impact effect of the inert gas ions.9. The crystallinity of the produced hard carbine film is improved.

In addition, if all permanent magnets 7 are installed to apply a full magnetic field in parallel to the electric field applied between the discharge sustaining electrode 3 and the filament 4, the electrons will move along the magnetic field and collide with the C2H4 gas particles. As the number of times increases, the ionization rate of the gas particles increases. Therefore, the load on the filament 4 is reduced and its lifespan is extended.

In the above-mentioned method for producing a hard carbine film, the filament 4 is made red hot to cause it to emit thermionic electrons, and the discharged electrons are attracted to the positively charged discharge sustaining electrode 3, thereby generating total plasma. Because of this (D), hot electrons are constantly supplied to the plasma from the red-hot filament 4, resulting in an excess of electrons.However, the ionization rate with this method is small, on the order of 10-5. In addition to the fact that the positive charge accumulated by ions such as
Since neutralization by electrons occurs during film formation, damage to the film due to charge-up can be prevented. Further, when the substrate 2 is an insulating substrate, the surface potential of the insulating substrate becomes negative due to secondary electrons generated by ion bombardment on the holder 5. Therefore, a hard carbon film can be formed on the insulating substrate with the same strong adhesion as on the conductive substrate.

FIG. 4 shows the relationship between the product of the applied voltage to the substrate and the ion current versus the internal stress (in the carbon film) when a hard carbon film is formed on the St substrate by the above method. In FIG. 4, the horizontal axis indicates the product of the substrate applied voltage and the ion current; for example, when the substrate applied voltage is 1 kV and the substrate current is 10 mA,
? , if you get it.

The energy flowing into the board is 1 kV x 10 mA
■・A. In other words, the horizontal axis represents the amount of energy supplied by ion bombardment during the deposition of the hard carbon film.
It is expressed as i:v-A. The # axis represents the internal stress or compression in the hard carbon film of the substrate, which can be controlled by the energy provided by the ions during hard carbon film deposition.

For example, the energy given by ions '150
When V・AVC is applied, #hill of compression of internal stress is 10
It can be reduced to Kf/rLa. In this manner, by controlling the amount of ion bombardment during hard carbon film deposition, internal stress can be controlled and peeling from the substrate can be prevented.

For substrates that are difficult to form compounds with carbon and difficult to obtain the adhesion of the hard carbon film, after sputter cleaning with Ar gas, open the flow rate control valve 11 for gas introduction, and open the introduction pipe. 9. Introduce S+H4 gas into the vacuum belljar 1 throughout the entire process, and place Sie, 2,000
After being deposited to a thickness of about A, the St@@ may be used as an intermediate film to ensure the adhesion of the hard carbon film.

In addition, when using the Tl substrate 2 whose material is very easily oxidized, after removing the surface oxide film by sputter cleaning with Ar gas, generate N2 plasma, and use the N2 plasma to nitride the surface. FM'f: Effective in increasing the adhesion of hard carbon films while stabilizing the surface condition. For example, on a TI source substrate, plasma is generated in an atmosphere with an Ar gas pressure of 10-3 Torr, and the entire surface of the substrate is cleaned by Ar+ ions by sputtering for 10 to 30 minutes. After that, N2 gas' (i=10
-3 Torr level, and perform surface nitriding treatment using N+ ions for a total of 10 to 30 minutes to form Illi nitride on the substrate surface, and then form a hard carton film.
A hard carbon film with strong adhesion can be formed.

The hard carbon film formed on the substrate by the manufacturing method of the present invention is: (1) By changing the film formation conditions, the hardness of the carbon film can be freely controlled. For example, C2H4 gas pressure k8 X 10-8Torr: C2)14 fJ
'y-flow 20 cc h: Discharge sustaining electrode ゛1 current 0.2 A constant, and the voltage applied to the substrate -
When changing the voltage to 0.5kV, -2,OkV, -2.5kV, the hardness of the obtained hard carbon film is 2,070
゜2.630, 3,300. In this way, the hardness of the hard carbon film formed on the substrate can be freely controlled by changing the film formation conditions.

■ This hard carbon film contains graphite, so it has a self-lubricating effect.

For example, if a load of 11'9 is applied to a steel ball with a diameter of 5 gourds,
When measuring the sliding friction coefficient, stainless steel has a coefficient of 0.25 - quartz has a coefficient of 0.3 or more, while hard carbon film has a coefficient of 0.25 - 0.3 for quartz.
It is 15. This is due to the graphite in the hard carbon film.

(2) Furthermore, this hard carbon film exhibits extremely excellent corrosion resistance against strong acid solutions such as sulfuric acid aqueous solution and hydrofluoric acid aqueous solution, and strong alkaline solutions such as caustic potassium aqueous solution.

(2) Furthermore, since this hard carbon film is used as CzH4 in the synthetic glaze, its purity is very high, and it can be easily processed using a reactive etch technique using oxygen, and is excellent in workability.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the apparatus used in the method for producing a hard carbon film of the present invention, and Fig. 2 is a schematic diagram of a hard carbon film produced according to the method for producing a hard carbon film according to the present invention.
Linear diffraction &S diagram, Figure 3 is an electron diffraction photograph of a hard carpin film produced by the hard carbon film manufacturing method of the present invention, and Figure 4 is a substrate of the hard carpin film produced by the hard carbon film manufacturing method of the present invention. FIG. 3 is a characteristic diagram showing the relationship between the product of applied voltage and ion current versus internal stress. In the drawing. 1 is a vacuum bell jar. 2 is a substrate (member for carbon film formation), 3 is an electrode for maintaining plasma discharge, 4 is a filament (thermionic emission means), 8.9 is a gas introduction tube, 10.11 is a flow rate control valve, 13 is a high pressure 14 is a DC power source; 15 is a power source. Fig. 1

Claims (2)

[Claims] (1) A hard carbon film characterized by being composed of a hexagonal mixed crystal of diamond and graphite. (2) A carbon film forming member, a thermionic emission means,
A plasma discharge sustaining electrode is placed in a vacuum atmosphere, and a mixture of C2H4 gas, H2, or an inert gas, or a mixture of both, is further placed in the vacuum atmosphere.
After introducing the gas, plasma gold is generated in the space between the thermionic emission means and the plasma discharge sustaining electrode, and a negative high voltage is applied to the Cargon film forming member. A method for producing a hard carbon film, which is characterized in that a hard carbon film consisting of a mixed crystal of macrogonal diamond and graphite is entirely formed.