JPH07233475A - Method for forming diamond-like thin film - Google Patents

Abstract

(57) [Summary] [Structure] An arc discharge plasma is generated in the first vacuum chamber 1, the arc discharge plasma is guided to the second vacuum chamber 2, and the arc discharge plasma 5 is introduced in the second vacuum chamber 2. A diamond-like thin film forming raw material gas is supplied to the substrate to excite and decompose the raw material gas to form a diamond-like thin film on the substrate. [Effect] It becomes possible to efficiently form a high-quality diamond-like thin film having a uniform film thickness on a large-area substrate at high speed.

Description

Detailed Description of the Invention

[0001]

The present invention relates to scratch resistance, high permeability,
The present invention relates to a method for forming a diamond-shaped thin film, which is expected to have various applications as a thin film having high thermal conductivity.

[0002]

2. Description of the Related Art Conventionally, as thin films having scratch resistance, diamond thin films and c-BN films have been applied as overcoat films for various jigs and tools, and films for improving scratch resistance of various substrates. Research has been done. Among them, the diamond-like thin film has chemical and thermal stability,
It has been mainly used for such purposes.

As a method for depositing a diamond-like thin film, various CVD methods using a hydrocarbon-based gas as a starting material as a gas material can be mentioned. For example, as a method using non-equilibrium (low temperature) plasma,
Known are a normal p-CVD method (see FIG. 2), a method of generating ECR plasma by applying microwaves in a magnetic field satisfying ECR conditions, a microwave plasma method using a commercial frequency of 2.45 GHz, and the like. There is. These methods are
In this method, the source gas is excited and decomposed by the plasma generated by each method.

Further, as a method of supplying a similar source gas and depositing a diamond-like thin film by a thermal decomposition process, a method of thermally decomposing the source gas with a hot filament installed in the vicinity of the substrate and depositing a desired film, A thermal CVD method or the like using only a usual thermal decomposition reaction has been reported. on the other hand,
As the PVD method, a film forming method using ions is mainly used, and an ion beam vapor deposition method, an ion beam sputtering method and the like are known. Further, Japanese Patent Application Laid-Open No. 2-73962 describes a thin film forming method by a CVD process using high efficiency sheet plasma.

[0005]

However, the conventional p-
When non-equilibrium plasma such as CVD method or ECRCVD method is used, or in the case of thermal CVD method, a film having good film quality can be deposited, but the film formation speed is slow and the film is stably formed on a large-area substrate. There is a problem that a good thin film cannot be deposited. For this reason, there is a problem in terms of mass productivity, which is an obstacle to cost reduction. Further, even when the PVD method is used, there is a problem that it is difficult to increase the area of the ion source used to improve the reactivity of the source gas.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. Arc discharge plasma is generated in a first vacuum chamber, and the arc discharge plasma is generated in a second vacuum chamber. A diamond-like thin film, characterized in that a diamond-like thin film-forming raw material gas is supplied into the arc discharge plasma in a second vacuum chamber to excite and decompose the raw material gas to form a diamond-like thin film on a substrate. The present invention provides a method for forming the same.

FIG. 1 is a schematic sectional view of an example of an apparatus for carrying out the method for forming a diamond-like thin film of the present invention. In FIG. 1, 1 is a first vacuum chamber, 2 is a second vacuum chamber, 3
Is a substrate for forming a diamond thin film, 4 is a substrate holder, 5 is a plasma flow, 6 is a plasma gun, 7 is an anode, 10 is a partition valve between the first vacuum chamber and the second vacuum chamber, Reference numeral 11 is a coil for forming a magnetic field for guiding the plasma generated in the first vacuum chamber to the second vacuum chamber.

In the present invention, arc discharge plasma means
It refers to plasma generated by high-current, low-voltage discharge of several tens to several hundred amperes and several tens to 100 volts in a reduced pressure atmosphere. As a specific configuration of the plasma gun 6 used for generating such plasma, one that can generate an arc discharge plasma flow by causing an arc discharge with the anode 7 arranged facing the gun portion is preferable. In particular, a composite cathode type plasma gun, a pressure gradient type plasma gun, or a combination of both is desirable (see Vol. 25, No. 10).

Here, the composite cathode type plasma gun has a coil-shaped or pipe-shaped auxiliary electrode made of a refractory metal having a small heat capacity such as tungsten, tantalum, molybdenum, and a main cathode made of lanthanum boride. The initial discharge is concentrated on the auxiliary electrode, the main cathode is heated by using it, and the main cathode performs arc discharge as the final cathode. When the auxiliary electrode reaches a high temperature of 2500 ° C. or higher, The main cathode is 1500-1800 before it affects the life.
It has an advantage that it is heated to 0 ° C. and becomes capable of emitting a large electron flow, and further temperature rise of the auxiliary cathode is avoided.

In the pressure gradient type plasma gun, an intermediate electrode is interposed between the cathode and the anode, and the cathode region is set to 1 Torr.
On the other hand, on the other hand, the discharge is carried out while maintaining the anode region at about 10 ⁻³ Torr, and there is no damage to the cathode due to the ion backflow from the anode region, and the discharge electron is compared to the discharge type without the intermediate electrode. The gas efficiency of the carrier gas for creating the flow is remarkably high, and there is an advantage that a large current discharge is possible.

Therefore, if the plasma gun is constructed by combining the above-mentioned composite cathode type plasma gun and pressure gradient type plasma gun, the above-mentioned advantages can be obtained at the same time. Therefore, the plasma gun used in the present invention can be obtained. As desirable. Further, as the discharge gas to be introduced into the plasma gun for generating plasma, from the viewpoint of discharge efficiency, hydrogen gas, rare gas, or a mixed gas of both can be used. Since it is important to supply a large amount of hydrogen in the process of forming the thin film, it is preferable to use only hydrogen gas or a mixed gas of hydrogen gas and a rare gas as the discharge gas.

Further, by forming the plasma flow drawn from the first vacuum chamber into a sheet and forming a film, a film having a good film thickness distribution can be formed. The sheet forming means at this time may be any one that deforms the plasma flow generated by the plasma gun. Specifically, it is configured to form a magnetic field that crushes the plasma flow from both sides with a magnet, a coil, or the like. It is desirable to do.

Further, the plasma gun may be attached to any part of the film forming vacuum chamber (that is, the second vacuum chamber), but in consideration of the workability of exchanging the plasma gun, the outside of the film forming vacuum chamber is considered. It is desirable that the plasma gun be detachably attached via the partition valve 10.

The increase in area, which is one of the problems of the prior art, can be dealt with by arranging a plurality of plasma guns adjacent to each other on the same plane and simultaneously forming sheet plasma on the same plane.

The source gas may be any gas containing a starting material for forming the main skeleton of the diamond-like thin film, and examples thereof include a compound of carbon and hydrogen (for example, methane-based hydrocarbon, Ethylene hydrocarbons,
Chain compounds such as acetylene hydrocarbons), compounds of carbon, hydrogen and oxygen (various alcohols, compounds having characteristic groups containing oxygen such as carbonyl groups (eg ketones)), carbon and hydrogen And a compound of nitrogen (a compound containing a characteristic group containing nitrogen such as an amino group), a compound of carbon, hydrogen, oxygen and nitrogen (a compound containing a characteristic group containing nitrogen and a characteristic group containing oxygen (for example, ammonium carboxylate) (Salt etc.)), etc., but are not particularly limited thereto.

In the present invention, "diamond-like thin film"
And "a diamond-like thin film having polycrystallinity",
It includes both "a diamond-like thin film having low crystallinity". These films can be formed according to film forming conditions such as film forming temperature and the amount of active hydrogen supplied.

"Diamond-like thin film having polycrystallinity"
Most of the carbon atoms that compose it are sp3 bonds, and have a rough surface texture peculiar to diamond. Raman measurement shows that sp is at 1333 cm ^-1 .
Only a sharp (small half width) peak derived from 3 bonds is observed.

On the other hand, the "diamond-like thin film having low crystallinity" is a film in which sp3 bonds and sp2 bonds of carbon constituting the film are randomly mixed and which does not have a layered structure like graphite. Sp3 binding and sp2 in general
Diamond-like carbon with a bond ratio of about 1: 9 (Diam
ond like carbon (DLC) film,
It also includes what is called an amorphous diamond film, which is said to have a higher proportion of sp3 bonds. In Raman measurement, a very broad (large half-value width) peak centered at 1333 cm ⁻¹ derived from sp3 binding is observed, but it is observed overlapping with a broader peak with higher intensity derived from sp2 binding. Therefore, it is difficult to discuss the difference between the sp2 binding state and the sp3 binding state in the membrane. Therefore, when the carbon (1s) core electron excitation spectrum is evaluated by energy loss spectroscopy (EELS), three relatively blunt peaks are observed from the loss energy of 280 eV to around 300 eV, and sp2 and sp3 bonds are mixed. You can confirm that. 280e derived from π electron
The peak near V is considerably smaller than that in the case of graphite having a large amount of π electrons, which makes it possible to distinguish it from graphite.

The diamond-like thin film formed by the present invention has a high hardness and can be applied to various hard coats. However, the diamond-like thin film having polycrystallinity has a haze because the surface is rough, and may not be suitable for substrates such as glass, lenses, and plastics that require transparency. Can be used for hard coat. The diamond-like thin film having low crystallinity can be used in applications where transparency is required.

The substrate for forming the diamond-like thin film by the method of the present invention is not particularly limited to various semiconductor substrates, transparent insulating substrates such as glass, long plastic films and the like.

In the method of the present invention, since arc discharge plasma having a high plasma density is used, a large amount of active hydrogen can be supplied, and the bonding between these and the film surface (C-C, C-).
When a diamond-like thin film is formed from the gas phase by reaction with H), carbon bonds (sp2) having a graphite structure formed simultaneously with the diamond-like thin film are easily decomposed and removed, and film formation It becomes possible to open double bonds and the like existing on the surface and the like. In addition, the amount of hydrogen supplied to the growth surface of the film can be controlled by controlling the arc discharge plasma, which makes it possible to form diamond thin films separately.

When a mixture of carbon and fluorine is used as the raw material gas, active fluorine inhibits the formation of a growth re-surface layer (amorphous layer) which inhibits crystal growth, and has polycrystallinity. It becomes easy to form a diamond-like thin film. Further, in forming both the diamond-like thin film having polycrystalline property and the diamond-like thin film having low crystallinity,
The film formation temperature can be reduced by adding fluorine, which
It is possible to form a film even at a low film forming temperature of about 100 ° C., and it is possible to form a diamond-like thin film even on a substrate having low heat resistance such as plastic, and when a diamond-like thin film is to be formed on a large-area substrate. The substrate heating mechanism and the like can be simplified in structure, and the cost of the apparatus can be reduced.

Therefore, when forming a diamond-like thin film having polycrystallinity, it is preferable that the flow rate of the gas containing the compound of carbon and fluorine in the source gas is 50% or less. This is because if it is more than 50%, the etching reaction of the film may proceed and the film formation rate may be slowed.

On the other hand, when forming a diamond-like thin film having low crystallinity, it is preferable that the flow rate of the gas containing the compound of carbon and fluorine in the source gas is 10% or less. This is because if it is more than 10%, a diamond-like thin film having polycrystallinity tends to be easily formed.

The compound of carbon and fluorine is not particularly limited as long as it can supply active fluorine, and various fluorinated methanes (such as tetrafluoromethane) and fluorinated ethylenes can be used.

[0026]

The arc discharge plasma used in the present invention has a plasma density of about 50 to 100 times higher than that of the conventional glow discharge type / ECR discharge type plasma, and the ionization degree of gas is several tens of percent. Plasma with very high ion density, electron density, and neutral active species concentration can be realized. Most of the raw material gas supplied for this purpose contributes to thin film formation. In the conventional p-CVD method, the film forming rate was about several angstroms / sec. It is possible to easily realize a film forming rate of not less than / sec. Therefore, according to the method of the present invention, it becomes possible to deposit a high-quality diamond-like thin film on a large-area substrate at a high speed as compared with the conventional method.

Further, in such arc discharge plasma,
Most of the hydrogen gas supplied for generating plasma is in a highly reactive ion, neutral active state or atomic state, and it is possible to control the growth process of various thin films.

[0028]

【Example】

[Embodiment 1] An embodiment of the present invention will be described below with reference to FIG. 1 is a first for generating plasma
2 is a second vacuum chamber in which a raw material gas is supplied and a plasma flow introduced from the first vacuum chamber excites / decomposes the film to form a thin film. A partition valve 10 is provided between the first vacuum chamber 1 and the second vacuum chamber 2 for facilitating the replacement work of the plasma gun portion.

The substrate 3 (glass plate in this embodiment) on which a diamond-like thin film is to be formed is placed on a substrate holder 4 having a heater for heating the substrate. The plasma flow 5 is guided parallel to the substrate from the first vacuum chamber side toward the facing anode 7, and in the present embodiment, the flow direction of the source gas is orthogonal to the plasma flow. Is supplied from a gas supply pipe (not shown) arranged in such a manner. A magnet (not shown) for deforming the plasma flow into a sheet shape is arranged outside the vacuum chamber so that a magnetic field for crushing the plasma flow from both sides can be formed.

From the first vacuum chamber side, a 1: 1 mixed gas of argon gas and hydrogen gas was flowed at 70 sccm to generate arc discharge plasma. Further, by using the magnetic field of the coil arranged outside the vacuum chamber and the magnetic field of the above-mentioned magnet, this plasma flow was transformed into a substantially sheet shape and introduced into the second vacuum chamber. After the plasma flow was stabilized, the flow rate ratio of methane gas and tetrafluoromethane gas was 66:33 from the source gas supply pipe.
To supply a film.

After film formation at a substrate temperature of 400 ° C. for 10 minutes, the substrate was taken out and the film thickness was measured with a stylus type film thickness meter.
It was confirmed that a 600 nm film was formed. At the same time, the analysis by Raman spectroscopy revealed that sp
Very strong 1333 cm that is thought to be due to 3 bonds
Only the ^-1 peak was observed, which indicated that a diamond-like thin film having polycrystallinity was formed.

[Example 2] Next, the film formation was performed under the same conditions except that the flow rate of the tetrafluoromethane gas in the raw material gas was changed. In each case, a diamond-like thin film having polycrystallinity was formed. The results are shown in Table 1.

[Embodiment 3] The same apparatus as in Embodiment 1 was used to perform discharge with the same discharge gas composition, and then methane gas and methane tetrafluoride gas were supplied from the raw material gas supply pipe at a flow rate ratio of 95: 5. Then, a film was formed on the plastic film. After film formation at a substrate temperature of 100 ° C. for 10 minutes, the substrate was taken out and the film thickness was measured with a stylus type film thickness meter.
It was confirmed that a film of m was formed.

At the same time, when analyzed by Raman spectroscopy, 1333, which is considered to be caused by sp3 bond
Only a very broad peak centered at cm ^-1 was observed. Therefore, energy loss spectroscopy (EE
When the carbon (1s) core electron excitation spectrum was evaluated by LS), the loss energy was 280 eV to 30
Three relatively dull peaks were observed near 0 eV, and sp
It was found that a diamond-like thin film with low crystallinity in which 2 and sp3 bonds were mixed was formed.

[0035]

[Table 1]

[0036]

As described above, according to the method of the present invention, arc discharge plasma is used to form a thin film on a substrate with the reactivity of the source gas in the gas phase being enhanced. As a result, it becomes possible to form a high-quality diamond-like thin film with a uniform film thickness on a large-area substrate at high speed and efficiently as compared with the conventional method.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an example of an apparatus for performing the method of the present invention.

FIG. 2 is a schematic sectional view of a conventional plasma CVD apparatus.

[Explanation of symbols]

 1: First vacuum chamber 2: Second vacuum chamber 3: Substrate 4: Substrate holder 5: Plasma flow 6: Plasma gun 7: Anode 10: Partition valve 11: Coil

Claims (6)

[Claims] 1. An arc discharge plasma is generated in a first vacuum chamber, the arc discharge plasma is guided to a second vacuum chamber, and a diamond-shaped thin film forming raw material gas is introduced into the arc discharge plasma in the second vacuum chamber. A method for forming a diamond-like thin film, which comprises supplying the raw material gas to excite and decompose it to form a diamond-like thin film on a substrate. 2. The method for forming a diamond thin film according to claim 1, wherein the source gas contains at least one kind of gas composed of a compound of carbon and fluorine. 3. The diamond-like thin film according to claim 2, wherein a diamond-like thin film having a polycrystallinity is formed by setting a flow rate ratio of a gas containing a compound of carbon and fluorine in the raw material gas to 50% or less. Forming method. 4. The diamond-like thin film according to claim 2, wherein the diamond-like thin film having low crystallinity is formed by setting the flow rate of the gas containing a compound of carbon and fluorine in the raw material gas to 10% or less. Method. 5. The discharge gas used for generating plasma in the first vacuum chamber is only hydrogen gas or a mixed gas of hydrogen gas and rare gas.
4. The method for forming a diamond-like thin film according to any one of 4 above. 6. The diamond-shaped thin film according to claim 1, wherein the diamond-shaped thin film is formed in a state in which the arc discharge plasma generated in the first vacuum chamber is deformed into a sheet shape. Forming method.