JPH0543393A - Method for preparing carbon material - Google Patents

Abstract

PURPOSE:To improve film-forming rate of a carbon material including diamond or a diamond material and enable film formation at a low temperature. CONSTITUTION:Adamantane, diadamantane, triadamantane, 1-adamantanol or 2-adamantanol which is an adamantane compound having OH group or adamantane compound containing a halogen atom in a molecule is used as a starting raw material and gas including fluorine, carbon tetrafluoride, chlorine or carbon tetrachloride, halide gas or hydrogen is used as a reaction auxiliary material.

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 carbon material containing diamond or a diamond material, and in particular, a diamond is produced by using a sublimable substance adamantane, diamantane, triamantane or an adamantane compound as a raw material gas containing carbon. The present invention relates to a reaction gas used when producing a carbon material or a diamond material containing the same.

The present invention relates to a carbon material containing diamond or a method for producing a carbon material aiming at improving the film formation rate of the diamond material.

The present invention relates to low temperature film formation of a carbon material containing diamond or a diamond material.

[0004]

2. Description of the Related Art Conventionally, a hot filament CVD (chemical vapor deposition) method has been most widely used as a method for forming a carbon material containing diamond or a diamond material by using a chemical vapor deposition method. The method is, for example, as shown in FIG. 1, in which a reactive gas is introduced into a quartz reaction tube 1 through a gas inlet 2 and an electric current is applied to a filament 3 made of metal tungsten (or tantalum) to make the filament 1500 ° C.
The substrate 4 is heated by heating to 3000 ° C. to emit thermoelectrons.
To 400 ℃ ~ 1300 ℃. It is a method of forming a carbon material containing diamond or a diamond material on a substrate by a chemical reaction. At this time, the pressure in the reaction vessel is 1 ~
Maintained at 350 Torr. Therefore, the thermal CVD method is a cheap and easy method.

As another carbon material containing diamond or a method for forming a diamond material, microwave plasma C is used.
There is a VD method. In this method, as shown in FIG. 2, for example, a quartz reaction tube 1 is inserted into a part of a microwave waveguide 6, a reaction gas is introduced from the upper portion of the quartz reaction tube, and vacuum exhaust is performed from the lower portion. 2.45 GHz is the most commonly used microwave oscillation frequency. The pressure in the reaction vessel is maintained at 10 to 200 Torr.

As a method of forming a carbon material containing diamond and a diamond material by utilizing the interaction between a microwave and a magnetic field, MCR (Mixed Cyclotron Resonanc) is a phenomenon that occurs when the reaction pressure is higher than 0.1 Torr.
There is a magnetic field microwave plasma CVD method using e) and an ECR plasma CVD method using ECR (Electron Cyclotron Resonance) which is a phenomenon that occurs when the reaction pressure is as low as 0.1 Torr or less.

FIG. 3 shows a schematic view of an apparatus used in the magnetic field microwave plasma CVD method. Utilizing the interaction between the magnetic field generated by the magnetic field coil 7 and the microwave introduced from the microwave waveguide 6 into the reaction chamber, the reactive gas introduced from the gas introduction port 2 is efficiently excited and diamond is deposited on the substrate 4. A carbon material or a diamond material containing is formed. The substrate 4 is externally controlled by heating the substrate holding plate. The stray electric field 8 can also be applied to the substrate 4. As the reaction gas, a gas such as methane, carbon monoxide, ethylene, methanol or ethanol, which is usually a gas or liquid hydrocarbon diluted with hydrogen, is used. Moreover, a gas to which a small amount of water, carbon dioxide, or oxygen is added is also used.

The shape of the apparatus used in the ECR plasma CVD method is almost the same as that of the magnetic field microwave CVD apparatus, but since the reaction pressure is as low as 0.1 Torr or less, the plasma spreads wider than the magnetic field microwave CVD method. Area film formation is possible. Therefore, most ECR plasma CVD apparatuses are of the depot down type, as shown in FIG. In the magnetic field microwave CVD apparatus as shown in FIG. 3, it is very inefficient to form a film over a large area inevitably due to the problems of mass and operability of the reaction chamber. Generally, the reaction gas is introduced through the gas introduction port 2, but a method in which the diluent gas is introduced through the gas introduction port 2 and the source gas is introduced through the gas introduction port 9 or the gas introduction port 10 is also used. Hydrogen is used as the diluent gas, and methane, acetylene, carbon monoxide, carbon dioxide, and the like, which are usually present as a gas, are used as the raw material gas, and methanol, ethanol, which is very rarely present as a liquid, are used. Acetone or the like is used. The uniformity of the film thickness and film quality of the carbon material containing diamond or the diamond material on the substrate 4 may be improved by rotating the substrate holder.

[0009]

However, the raw material gas currently used has a limit in the film forming rate of the carbon material containing diamond or the diamond material. The film forming rate depends on the film forming method, but at present when a new film forming method cannot be found, it is necessary to improve the film forming rate by optimizing the film forming conditions. For example, a magnetic field microwave CV utilizing the interaction between the above magnetic field and microwave.
The film formation rate is 1 μm / hr or less in the D method, and 0.3 μm / hr or less in the ECR plasma CVD method.
However, there are many conditions that can be changed during film formation,
Moreover, since the conditions cannot be changed independently of each other, optimization is difficult.

It is also desired to be able to produce a carbon material or diamond material containing diamond at a low temperature on a heat-sensitive substance such as a low melting point metal. Further, in film formation at a high temperature, the carbon material containing diamond or the diamond material may be cracked by cooling when the sample is taken out, which may cause peeling.

[0011]

[Means for Solving the Problem] In order to improve the film formation rate, the type of reaction gas may be considered. In the past, a gaseous or liquid reaction gas was often used as the type of starting material, but if a solid with a cubic structure having the same SP ³ hybrid orbital as a diamond structure is sublimed and used as a reaction gas, It can be expected to improve the film speed and further the film quality. Therefore, it is an adamantane, diamantane, triamantane, adamantane compound having an OH group 1
It is preferable to use an organic compound having a diamond structure in its molecular structure, such as -adamantanol, 2-adamantanol, or an adamantane compound containing a halogen atom in the molecule.

The basic skeleton of diamond is created by dissociating the hydrogen atom, OH group or halogen atom existing on the outermost side of the molecule having the adamantane structure from the molecule. Then, by adding a reaction auxiliary material most suitable for dissociating hydrogen atoms, OH groups or halogen atoms existing on the outermost side, it becomes easy to form a basic skeleton of diamond.
Therefore, hydrogen atoms or O
Fluorine, which is easily bonded to the H group or halogen atom,
A gas containing a halogen atom such as carbon tetrafluoride, chlorine or carbon tetrachloride, a halide gas, hydrogen or the like can be appropriately selected according to the starting material containing carbon. By adding this reaction auxiliary material, the film formation rate can be improved and low temperature film formation can be performed.

Further, in the plasma CVD method, which has been conventionally used in a carbon material containing diamond or a method for producing a diamond material, even the basic skeleton of diamond generated by strong plasma energy is further dissociated to form carbon. May become atomic. With this, the effect of using an organic compound having a diamond structure in the molecular structure cannot be obtained. Therefore, when exciting the starting material for reaction, it is desired that the excitation is performed by a gentle method. For example, it is possible to use light as the excitation method. That is, the production of a carbon material containing diamond or a diamond material by an optical CVD apparatus. In this case, the halogen compound of adamantane is effective because it is easily excited by ultraviolet light. Similarly, a starting material containing carbon is appropriately selected from adamantane, diamantane, triamantane, 1-adamantanol, 2-adamantanol which is an adamantane compound having an OH group, or an adamantane compound having a halogen atom in the molecule. It is also effective to use, as a reaction auxiliary material, a gas containing a halogen atom such as activated fluorine, carbon tetrafluoride, chlorine, carbon tetrachloride, a halide gas, or hydrogen as a reaction auxiliary material. is there.

[0014]

【Example】

"Example 1" In this experiment, a carbon material containing diamond or a diamond material was deposited using the magnetic field microwave plasma CVD apparatus shown in FIG. In this method, a film can be formed at 1 Torr or less, which is an advantageous method because adamantane is easily sublimated. The film forming conditions are shown below. The substrate used was a φ100 mm Si wafer. Adamantane 10 scc as starting material for reaction
m, and 100 sccm of fluorine was used as a gas for supporting the reaction.
At this time, adamantane is a solid in a normal state at room temperature and normal pressure, but since it is a highly sublimable solid, it is necessary to devise it to send it to the substrate as a gas. That is, when solid adamantane is put into a test tube and the inside of the test tube is evacuated, adamantane sublimes and becomes a gas, but it becomes a gas containing not only adamantane but a large amount of atmospheric components (nitrogen, oxygen, etc.). Will end up. Therefore, since the sublimation of adamantane can be suppressed by cooling the test tube with liquid nitrogen during vacuum exhaust, the test tube must be cooled with liquid nitrogen in order to exhaust the atmosphere. The reaction pressure is
2.0 × 10 ^-1 Torr, substrate temperature 350 ℃, processing time 1hr,
Microwave (2.45GHz) output 1kW, maximum magnetic field strength 2kg
auss. The film thickness was measured by placing a dummy Si wafer for masking on the Si wafer at the time of film formation, and measuring the level difference between the part where the film was formed and the part where the film was not formed by the mask.

In the experiment conducted under the above conditions, the film thickness is about 7
was μm. That is, the film forming rate is about 7 μm / h
A result of r was obtained.

By the way, it is necessary to check whether the actually formed film is a carbon material containing diamond or a diamond material. Therefore, the film quality was evaluated by Raman spectroscopy. Fig. 5 shows the results of measuring the film quality of the film formed on the central part of the φ100 mm Si wafer by Raman spectroscopy. 1550cm broad peak of the amorphous carbon material in the vicinity of ^-1 is present, but it is possible to confirm the sharp peak of diamond in 1332 cm ^-1. It is a carbon material that contains a considerable amount of diamond components. That is,
It may be considered that the diamond material is deposited. The sensitivity of Raman spectroscopy is sharp for amorphous carbon but not so much for diamond, which is a difference in peak intensity.

By increasing the microwave output, the film formation rate tends to increase, but the film quality is deteriorated. This means that by increasing the microwave output, the decomposition of adamantane proceeds, the skeleton having the diamond structure collapses, carbon dissociates, and the non-diamond component easily grows.

In an experiment using a fluorine compound of adamantane as a starting material, when fluorine and hydrogen or hydrogen alone was used as a reaction auxiliary material, the film formation rate was about 7 μm / hr, which was almost the same as the above. This experiment shows that using adamantane as the source gas is equivalent to the effect of dissociating hydrogen with fluorine. This is because both are in agreement in that HF is generated. Further, it was confirmed that when a fluorine compound of adamantane was used as a starting material and fluorine was used as a gas for dissociating fluorine and hydrogen, the film formation rate was increased to 8 μm / hr. This indicates that the F ₂ generation by the bonding of the fluorine atoms allows the fluorine atom abstraction reaction to occur more smoothly than the HF generation.

Example 2 In this experiment, the hot filament CVD apparatus shown in FIG. 6 was used. The basic structure is almost the same as that of the conventional hot filament CVD apparatus shown in FIG. 1, but the gas introduction method is slightly changed. The reaction auxiliary material is activated by the hot filament, but the organic compound having the diamond structure inside, which is the starting material, has a structure that is hard to be activated. That is, basically, the reaction auxiliary material is introduced from 11 and the starting material gas is introduced from 12. The film forming conditions are shown below. The substrate used was 10 mm × 10 mm silicon. The substrate is preliminarily subjected to ultrasonic cleaning to obtain a particle size.
The surface is scratched with 30-40 μm diamond powder. The average substrate temperature was kept at 90 ° C. by cooling the substrate with cooling water. The filament temperature was maintained at 1500 ° C by adjusting the filament current. The distance between the filament and the substrate was 10 mm, and the substrate temperature could be set to the set temperature. The raw material gas inlet was set 3 mm from the substrate. The reaction pressure is 10 Torr. The starting material gas used was 10 sccm of adamantane, and 100 sccm of fluorine was used as a gas for assisting the reaction. For comparison, an experiment was also conducted with 100 sccm of hydrogen. At this time, Adamantane has a sublimation point of about 1 at 10 Torr.
Since it is 00 ° C, quartz reaction tube 1 and adamantane inlet
12 was heated to about 100 ° C.

When the film formation rate was measured by the step difference from the dummy Si wafer, it was possible to obtain a film formation rate of 10 μm / hr, which is more than twice the film formation rate when hydrogen is conventionally used. The film quality was evaluated by Raman spectroscopy. The results are shown in Fig. 7.
It was found that there was almost no broad peak of the amorphous carbon material around 1550 cm ^-1 and the diamond material had good film quality.

When adamantane and fluorine are simultaneously introduced from 11 source gas introduction ports, the film formation rate becomes as high as 12 μm / hr, but the film quality is deteriorated and almost no sharp peak of diamond at 1332 cm ⁻¹ is observed. ..

When a fluoride of adamantane is used as the starting material gas and fluorine is used as the reaction auxiliary gas, the film formation rate is increased.
It was 15 μm / hr, and the result of Raman spectroscopy was almost in agreement with that of FIG. 7, showing that a good diamond material was obtained. This is the same as that described in Example 1, and in the case of fluorine as the reaction auxiliary gas, F ₂ generated by the bonding of fluorine atoms to each other facilitates a smoother reaction of withdrawing fluorine atoms than generation of HF. Is shown.
That is, if the adamantane compound contains halogen, it is understood that the most effective effect can be expected by using the halogen gas as the reaction auxiliary gas. Further, it can be seen that the produced film is also a carbon material containing only diamond component.

[Example 3] In this experiment, a carbon material containing diamond or a diamond material was deposited using an optical CVD apparatus. In this experiment, ultraviolet light from a mercury lamp was used as an energy source for activating the reaction material. UV light decomposes and activates halogen gas, but hardly dissociates carbon bonds, so using decomposed and activated halogen gas, adamantane, diamantane,
It is most suitable for dissociating hydrogen or a halogen atom present in triamantane, 1-adamantanol which is an adamantane compound having an OH group, 2-adamantanol, or an adamantane compound having a halogen atom in the molecule. The film forming conditions are shown below. The gases are mixed and introduced from one gas introduction port. As raw material gas, 10 sccm of adamantane and 100 sccm of chlorine were mixed. Chlorine was used because fluorine gas may corrode the glass. The reaction pressure was 1 × 10 ^-2 Torr. Substrate temperature was 40-50 ° C as measured by thermocouple. About 20 UV light source lamps and substrates
mm. A φ2 inch Si wafer was used as the substrate.

As a result of film formation, the film formation rate was 12 μm / hr. Further, the Raman spectrum of the film formation result is not very good as the film quality because the peak at 1332 cm ⁻¹ of diamond becomes weak as shown in FIG.

[0025]

EFFECTS OF THE INVENTION By using the present invention, the film formation rate of a carbon material containing diamond or a diamond material can be adjusted to adamantane, diamantane, triamantane, 1-adamantanol, 2-adamantan which is an adamantane compound having an OH group. 2 when using atanol or an adamantane compound containing a halogen atom in the molecule
I was able to triple it. Moreover, it has become possible to form a diamond material at a lower temperature than before, that is, at 100 ° C to 400 ° C. In particular, it has become possible to form a diamond film even at room temperature by using light.

[Brief description of drawings]

FIG. 1 is a schematic view of a hot filament CVD apparatus.

FIG. 2 is a schematic view of a microwave CVD apparatus.

FIG. 3 is a schematic view of a magnetic field microwave CVD apparatus.

FIG. 4 is a schematic diagram of an ECR plasma CVD apparatus.

FIG. 5 is a Raman spectrum of a diamond material formed by using a magnetic field microwave CVD apparatus.

FIG. 6 is a schematic view of a hot filament CVD apparatus used in this experiment.

FIG. 7 is a Raman spectrum of a diamond material formed by using a hot filament CVD apparatus.

FIG. 8 is a Raman spectrum of a diamond material formed using an optical CVD device.

[Explanation of symbols]

 1 Quartz Reaction Tube 2, 9, 10 Gas Inlet 3 Filament 4 Substrate 5 Exhaust 6 Microwave Waveguide 7 Magnetic Field Coil 8 Floating Potential 11 Dissociation Gas Inlet 12 Raw Material Gas Inlet

Claims (2)

[Claims] 1. A method for producing a carbon material containing diamond by a chemical vapor deposition method or a diamond material, wherein adamantane, diamantane, triamantane, and an adamantane compound having an OH group are used as a material containing carbon atoms in a starting material for reaction. 1-adamantanol, 2-adamantanol, or an adamantane compound containing a halogen atom in the molecule is appropriately selected and used, and halogen such as fluorine, carbon tetrafluoride, chlorine, carbon tetrachloride, etc. is used as a reaction auxiliary material. A method for producing a carbon material, which is used by appropriately selecting from a gas containing atoms or hydrogen. 2. The method for producing a carbon material containing diamond according to claim 1, or the method for producing a diamond material, wherein the temperature of the substrate is 400 ° C. or lower.