JP2682943B2 - Diamond thin film and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diamond thin film having a utility value in applications such as sliding and friction and abrasion resistant members such as tools and the field of electronic parts, and a method for producing the same.

[0002]

2. Description of the Related Art At present, methods of vapor phase synthesizing diamond on a substrate other than diamond are roughly classified into four methods, filament CVD, plasma CVD, plasma jet CVD and flame method. Then, as the diamond synthesis conditions common to these methods, 1) supply of a raw material gas that always contains carbon and hydrogen, 2) the presence of some active means other than temperature, 3) appropriate substrate temperature conditions (500-1)
000 ° C.), 4) Selection of a substrate that does not graphitize diamond, and the like.

Now, taking diamond synthesis by direct current plasma jet CVD as an example, in this method, a discharge gas (argon, hydrogen gas) supplied to a plasma torch in a vacuum chamber is turned into plasma by direct current arc discharge, and a cooling substrate is obtained. A diamond thin film is formed on the substrate by jetting it as a plasma jet on top and mixing it with the discharge gas or supplying the reaction gas (hydrocarbon, hydrogen gas) separately from the discharge gas from the direction intersecting the plasma flame. . That is, the hydrocarbon supplied as a carbon source is rapidly heated to a high temperature in the plasma flame region (arc discharge region) and decomposed to be ejected as a plasma jet, which collides with the substrate and loses energy. Is crystallized as (for example, Japanese Patent Publication No. 4-495).
20).

However, in all cases, not all carbon (C) constituting the hydrocarbon is deposited as diamond, but a considerable amount of components are deposited as amorphous carbon or graphite. On the other hand, the hydrogen gas mixed with the hydrocarbon is also dissociated into atomic hydrogen, which serves to reduce amorphous carbon and graphite to remove them as a gas. When the substrate temperature is low or the film formation rate is increased, amorphous carbon or graphite is likely to be deposited, and in spot irradiation film formation, the central portion has high diamond quality, but the peripheral portion has so-called so-called It is known that non-diamond materials such as diamond-like carbon, amorphous carbon, and graphite are considerably contained.

[0005]

By the way, when a diamond thin film is formed by vapor phase synthesis, the concentration of hydrocarbon (methane) supplied as a carbon source to the plasma flame region depends on the quality of the film formed on the substrate. It is known to have a great impact. That is, when gas phase synthesis is performed by changing the ratio of the mixed gas (hydrocarbon + hydrogen) mixed with the discharge gas or supplied separately to the discharge gas, the crystallinity is generally low in the region of low hydrocarbon concentration. It has been reported that a diamond thin film with good quality can be obtained, and a thin film of microcrystalline diamond can be obtained in a region having a high hydrocarbon concentration (Japanese Patent Laid-Open No. 63-307196).

However, simply hydrocarbon (methane) /
In reality, it is not possible to obtain a sufficient diamond thin film formed on the substrate simply by controlling the mixing ratio of hydrogen. That is, if priority is given only to the precipitation (nucleation) and growth of only diamond, a low proportion of hydrocarbons may be aimed at. At that time, the film due to internal stress (compression) due to the high automorphism of diamond crystals. Peeling, film cracking, and unevenness of the surface appear remarkably, so that it is difficult to obtain a material having good adhesion to the substrate. On the other hand, if the proportion of hydrocarbons is high, the content of amorphous carbon and graphite is increased, and deterioration of the diamond film quality is unavoidable.

If the crystallinity is to be pursued, the precipitated diamond is in the range of ultrafine particles (single crystal, etc.), but considering the requirements as a film, the degree of vacuum is at least equal to or higher than the sputtered film (10). (Minus cube torr or less) is required, which causes problems in both film forming speed and equipment.

As described above, at present, it is difficult to combine a diamond thin film having good crystallinity and to secure a sufficient adhesive strength with the interface of the underlayer, so that it is resistant to sliding on tools and other members. A diamond thin film formed by vapor phase synthesis has not been widely used as a dynamic or abrasion resistant film or a protective film.

The present invention overcomes the above technical problems,
The purpose of the present invention is to provide a diamond thin film having excellent crystallinity and excellent adhesion to a substrate together with its manufacturing method. Further, a few application examples utilizing this novel diamond thin film will be presented below. Is.

[0010]

DISCLOSURE OF THE INVENTION A diamond thin film newly provided by the present invention is a diamond thin film synthesized on a substrate by plasma CVD, and single crystal diamond microcrystals are coated with an amorphous hydrocarbon. The fine particles are deposited as fine particles, and the coating layer is deposited as a film to form a film.

In order to form a diamond thin film having good crystallinity and high adhesion by plasma CVD, it is preferable to deposit microcrystalline diamond on the substrate. To do so, the hydrocarbon concentration (hydrocarbon / hydrogen) of the reaction gas supplied to the plasma flame as a synthesis condition.
Is set to a high ratio to suppress the growth of diamond crystals deposited on the substrate, and at the same time suppress the growth of amorphous carbon or graphite during that time.

By the way, in the vapor phase synthesis of a diamond thin film, as described above, it plays a role of suppressing the growth of amorphous carbon by reducing non-diamond materials such as diamond-like carbon, amorphous carbon and graphite. Although the presence of atomic hydrogen has been expected from the past, according to the research and experiment results of the present inventor, under the synthesis condition in which the hydrocarbon in the raw material gas is set to a high ratio, it is not It has been clarified that hydrogenation of crystalline carbon or graphite produces amorphous hydrogenated carbon or amorphous hydrocarbon such as polyacetylene. The amorphous hydrocarbons produced in the vapor phase are uniquely deposited on the substrate in a mixed manner so as to take in the diamond crystallites while suppressing the growth of the diamond crystallites deposited on the substrate. It is newly confirmed to have the property.

That is, a high-concentration active species suitable for nucleating diamond microcrystals in the vapor phase or on the substrate, a vapor phase having an energy content, and a high-concentration hydrogen suitable for producing amorphous hydrogen carbon. Direct contact with the substrate surface by contacting with the gas phase (presumed to be hydrogen attached to a tungling bond of amorphous carbon or graphite) instantaneously (in a thermodynamically non-equilibrium state). Alternatively, it is possible to deposit fine particles composed mainly of diamond microcrystals in a high density state by vapor phase growth via an intermediate substance. The deposited layer formed in this way is a high-density deposition, the internal stress is relaxed, so that it has excellent adhesion to the substrate and the film is dense due to epitaxial growth made of microcrystals. Is. The fact that this deposit is a mixture of microcrystalline diamond and amorphous hydrocarbon (amorphous hydrogenated carbon)
It is confirmed by the results of X-ray diffraction, transmission electron microscope observation, Raman spectroscopic analysis and hardness measurement.

FIG. 1A schematically shows the structure of the above-mentioned diamond thin film, in which a deposition layer (diamond thin film) 2 in which microcrystalline diamond and amorphous hydrocarbon are mixed is formed on a substrate 1. Has been done. In this deposited layer 2, as shown in FIG. 1B, microcrystalline diamond 3 composed of one or a plurality of single crystals covered with amorphous hydrogenated carbon 4 is granularly coated with amorphous hydrogenated carbon 4. The particles 5 are deposited as fine particles 5, and the fine particles 5 are densely deposited with the amorphous hydrogenated carbons 4 forming a coating layer with each other as a binder. This sedimentary layer has a mesh-like cell structure macroscopically. A whisker-like structure of the amorphous hydrogenated carbon 4 is considered to be formed in the growth process in which atomic hydrogen in the vapor phase reacts with the amorphous carbon to deposit the hydrogenated carbon 4 on the surface of the fine particles 5. The presence of 6 is occasionally seen.

For reference, FIG. 6 shows an example of a structural image of a diamond thin film for comparison. Here, (A) shows an image example of a conventional thin film in which graphite and diamond are mixed, and (B) shows a thin film of diamond formed on a substrate according to the present invention and an amorphous hydrocarbon surrounding the diamond. An example image is shown.

Thus, in the diamond thin film containing the amorphous hydrocarbons, the one having excellent crystallinity, which is composed mainly of single crystal microcrystalline diamond, is obtained, and the amorphous hydrocarbons are deposited at a high density using the binder. As a result, excellent characteristics can be obtained for the adhesion to the substrate.

As a condition for obtaining the diamond thin film according to the present invention, as described above, a high-concentration radical and a high-concentration hydrogen vapor phase are brought into contact with each other thermodynamically in a nonequilibrium state in the plasma vapor phase. Is important, but such a synthesis condition can be created by the DC plasma jet method described above.

FIG. 4 shows an outline of a DC plasma jet CVD apparatus adopted by the present inventor to form the above diamond thin film on a substrate. That is, inside the vacuum chamber b exhausted by the exhaust device a, the tungsten cathode d
And a plasma torch c in which a cylindrical anode e concentrically surrounding the same is provided and a gas passage f is formed between both electrodes, and a substrate g set in a water cooling holder h are arranged to face each other, and the gas passage of the plasma torch c is arranged. While supplying a discharge gas to f, a direct current is applied to generate an arc between both electrodes to inject a plasma flame i onto the opposing water-cooled substrate g, and at the same time, intersect with the plasma flame i from the gas introduction pipe j inserted in the vacuum chamber b The raw material gas is supplied from the direction to form the diamond thin film on the substrate g.

Here, the conditions for uniformly depositing a diamond thin film in which microcrystalline diamond and amorphous hydrocarbon are mixed are listed as follows. A mixed gas of hydrogen and argon (helium) is used as the plasma gas supplied from the gas passage f of the plasma torch c (hydrogen: 10 to 50 l / min, argon: 10 to 50).
l / min). As the reaction gas, a mixed gas of methane and hydrogen, in which the hydrocarbon concentration is set to a high ratio and a total excess hydrogen gas with hydrogen contained in the plasma gas (discharge gas) is used (methane / hydrogen 5 ~ 20vol%: 1-20l / mi
n). That is, the hydrogen contained in the reaction gas, together with the hydrogen contained in the plasma gas, deposits diamond on the substrate g and simultaneously produces non-diamond amorphous carbon or graphite in the amorphous hydrocarbon. The necessary and sufficient amount is supplied. The reaction gas is supplied from the direction intersecting the plasma flame i through the gas introduction pipe j. At this time, the gas introduction pipe j
It is preferable to mount a quartz tube k for enclosing the reaction gas around the plasma flame i at the tip of the. As shown in FIG. 5, the quartz tube k is provided with an arc-conducting hole 1 at a jet flow position in the arc jet i. It has been experimentally confirmed that when this quartz tube k is attached, the collision, reaction, and quenching action of the reaction gas with respect to the jet i are promoted to form a more uniform and wider diamond thin film on the substrate g. There is. The supply position of the reaction gas is adjusted between the upstream side and the downstream side of the plasma flame i or the position directly above the substrate g.
In addition, the lower the temperature of the raw material gas, the better, and the material is precooled if necessary. The substrate g is set in the water-cooled holder h and controlled at an appropriate temperature. Further, in order to carry out a multi-layer film formation on the substrate g and to enable a peripheral surface film to be formed on the base material of the cylindrical body, the water-cooled holder h is provided with a drive means for advancing and retracting and / or rotating operation. Is desirable. The film formation rate is controlled by the synthesis conditions, and is usually adjusted in the range of 1 to 10 μm / min. The suitable speed in view of the ratio of good crystallinity of microcrystalline diamond and amorphous hydrogenated carbon as a binder is 1 to 3 μm.
/ min. The total pressure of the vacuum chamber b is 50 to 20.
0 Torr.

The preferable film forming conditions for forming the diamond thin film in which the microcrystalline diamond and the amorphous hydrocarbon according to the present invention are mixed are as described above. Whether or not the diamond thin film can be formed by plasma CVD other than the DC plasma jet method is
At this stage, it has not yet been confirmed experimentally. Therefore, in the present invention, the application of the high-frequency plasma jet method, the optical arc plasma jet method, the microwave plasma jet method, etc. other than the direct current plasma jet method is not particularly excluded.

Next, a few application examples using the above diamond thin film will be described. A diamond thin film in which microcrystalline diamond and amorphous hydrocarbon are mixed can be used as it is as a protective film for tools, etc. because of its excellent diamond crystallinity and adhesion to the substrate, but as a binder for microcrystalline diamond. It is experimentally confirmed that the mixed amorphous hydrocarbons are thermally sensitive, and as can be seen from the production process, they are decomposed and gasified by re-irradiation with hydrogen plasma.

Therefore, by utilizing this characteristic, firstly, the following diamond thin film can be presented.
That is, single-crystal diamond microcrystals are deposited as fine particles coated with amorphous hydrocarbon, and the coating film is used as a binder to heat the diamond thin film deposited in a film shape by oil temperature or by hydrogen plasma irradiation. Then, the amorphous hydrocarbon coating layer is melted and decomposed, and fine particles of only microcrystalline diamond are deposited on the substrate. Then, a saturated or fatty acid or its derivative or a higher alcohol or its derivative, for example, is infiltrated into the gaps of the diamond microcrystals as a lubricant or a protective agent by an infiltration method, a spray method, an evaporation method or the like to form diamond microcrystals on the substrate. A protective film is formed by coating.

FIG. 2A schematically shows the protective film thus obtained. As shown in FIG. 2B, the microcrystalline diamond scattered and deposited on the substrate 1 is enlarged. The lubricant or protective agent 8 penetrates into the gap 3 to form a strong protective film 7. If the microcrystalline diamond 3 is covered with the protective film 7, a wide range of applications or fields of use will be developed, as disclosed in JP-A-4-37695 and JP-A-4-47525.

Secondly, the following diamond multilayer thin film can be presented. That is, single-crystal diamond microcrystals are deposited as fine particles coated with amorphous hydrocarbons, and when a diamond thin film deposited in a film form using the coating layer as a binder is irradiated with hydrogen plasma, the amorphous hydrocarbon coatings are covered. The layer is vaporized and decomposed so that only fine particles of microcrystalline diamond are exposed on the substrate. In this state, by utilizing the seed crystal element of diamond, as described in Japanese Patent Laid-Open No. 63-307196, the synthesis conditions are changed, and specifically, the hydrocarbon concentration is set to a low ratio. Then, when diamond having high crystallinity is subjected to vapor phase synthesis, a diamond multilayer thin film is formed in which the second layer made of the highly oriented diamond film is formed on the first layer made of microcrystalline diamond.

FIG. 3 schematically shows the structure of the multi-layered thin film thus obtained. The crystal plane (220) is formed on the first layer 9 made of microcrystalline diamond by using the first layer 9 as a buffer layer. The second layer 10 made of a highly crystalline diamond film having a preferential coordination is formed to have a flat surface.

Further, the diamond thin film formed on the substrate according to the present invention is manufactured by high temperature and high pressure synthesis in recent years, and its usefulness for diamond tools is sought out, paying attention to its good crystallinity. It can also be applied to the production of cluster diamonds. That is, when a diamond thin film is formed on a substrate to which a release agent or the like is applied in advance and then peeled or crushed by an appropriate means or the like, single crystal diamond microcrystals coated with amorphous hydrocarbon are individually separated. The separated fine particles are obtained and can be used as cemented abrasive grains as they are or after decomposing and removing the hydrocarbon coating layer if necessary.

[0027]

EFFECT OF THE INVENTION In the diamond thin film provided by the present invention, single crystal diamond microcrystals are deposited as fine particles coated with amorphous hydrocarbon, and the coating layer is used as a binder to form a film. Therefore, it has excellent characteristics of diamond crystallinity and adhesion to the substrate, and can be used as a protective film for tools and the like. Then, by using microcrystalline diamond obtained by decomposing and removing amorphous hydrocarbons mixed in this diamond thin film as an underlayer, diamond coated with a protective film having utility value in various applications and fields. It is possible to form a thin film and a diamond multi-layered thin film on which a highly crystalline diamond film having orientation is formed, and further, it has a technical value that can be applied as a new manufacturing method of cluster diamond. Will be things.

[0028]

EXAMPLES DC plasma jet C shown in FIGS. 4 and 5
Using a VD apparatus, a diamond thin film was formed on the carbide base (K01) under the following conditions.

Film forming conditions Plasma gas: hydrogen + argon (hydrogen: 20 l / min, argon: 25 l / min) Reaction gas: methane / hydrogen 10 vol% mixed gas: 10
l / min Chamber total pressure: 120 torr (16 Pa) Arc current: 40 A Arc voltage: 80 V Arc distance: 35 mm (between nozzle and substrate) Substrate temperature: 800 ° C. (1073 K) Holder: Horizontal reciprocating drive 10 mm / sec

Experimental Results FIG. 8 shows a TEM image (high resolution transmission electron micrograph) of the diamond thin film obtained on the substrate, FIG. 9 is an SEM image of the film surface, and FIG. 10 is a diamond microscopic image appearing in FIG. The selected area electron diffraction image of a crystal is shown. From these structural photographs and the Raman spectrum of the precipitates, the thin film formed on the substrate is shown schematically in FIG. 1, and the single crystal diamond microcrystals are fine particles coated with amorphous hydrocarbons. It is confirmed that it is deposited and deposited in the form of a film using the coating layer as a binder.

Next, the diamond thin film formed on the above substrate was subjected to a friction and wear test using a reciprocating sliding tester under the condition of no lubrication in the air, and the results are shown in FIG. For comparison, FIG. 7 also shows the characteristics of the TiN film and the polycrystalline diamond film formed with the methane concentration different from that of the example. According to this result, in the thin film in which the microcrystalline diamond according to the present invention is deposited as fine particles coated with amorphous hydrocarbon, not only the TiN film but also the polycrystalline diamond film in which only diamond is deposited on the substrate Outstanding friction and wear properties were obtained and no scratches were observed on the surface after the test. It is considered that such excellent properties are largely attributable to the amorphous hydrocarbon coating film as the binder. It was confirmed that the amorphous hydrocarbon in the thin film was sufficiently stable even by frictional wear, and could be directly applied to applications such as tools.

[Brief description of the drawings]

FIG. 1 schematically shows the structure of a diamond thin film according to the basic invention, (A) is a sectional view of the diamond thin film, and (B) is a partially enlarged view thereof.

2A and 2B schematically show the structure of a diamond thin film according to an applied invention, where FIG. 2A is a sectional view of the diamond thin film and FIG. 2B is a partially enlarged view thereof.

FIG. 3 is a sectional view schematically showing a structure of a diamond thin film according to an applied invention.

FIG. 4 is an explanatory diagram showing an outline of a DC plasma jet CVD apparatus.

FIG. 5 (A) is an enlarged view of an essential part of FIG. 4 at the time of reaction,
(B) is a plan view of the quartz tube.

FIG. 6 shows a structural image example of a diamond thin film,
(A) is a conventional thin film in which graphite and diamond are mixed,
(B) shows a thin film made of diamond formed on a substrate according to the present invention and an amorphous hydrocarbon surrounding the diamond.

FIG. 7 is a diagram showing a result of a friction and wear test of a diamond thin film formed in an example.

FIG. 8 is an electron micrograph of a diamond thin film formed in an example.

FIG. 9 is an electron micrograph of a diamond thin film formed in an example.

FIG. 10 is a photograph showing an electron diffraction image of a diamond thin film formed in an example.

[Explanation of symbols]

 1 Substrate 2 Deposition Layer (Diamond Thin Film) 3 Microcrystalline Diamond 4 Amorphous Hydrogenated Carbon 5 Fine Particles 6 Whiskers 7 Protective Film 8 Lubrication or Protective Agent 9 First Layer (Microcrystalline Diamond) 10 Second Layer (Highly Oriented Diamond) )

Claims (3)

(57) [Claims] 1. A diamond thin film synthesized on a substrate by plasma CVD, wherein single-crystal diamond microcrystals are deposited as fine particles coated with amorphous hydrocarbon, and the coating layer is used as a binder to form a film. A diamond thin film characterized by being deposited. 2. A discharge gas containing hydrogen gas and an inert gas, which is supplied to a plasma torch, is turned into plasma by a direct current arc discharge and jetted as a plasma jet onto a cooling substrate, and an excessive amount of gas is supplied from a direction intersecting the plasma flame. A method for producing a diamond thin film, which comprises supplying a reaction gas containing hydrogen gas to form a diamond thin film on a substrate. 3. The diamond thin film according to claim 1 is heated or irradiated with hydrogen plasma to melt and decompose the amorphous hydrocarbon coating layer, and then a lubricant or protective agent is allowed to penetrate into the gaps between the diamond microcrystals. A method for producing a featured diamond thin film.