JP3190100B2 - Carbon material production equipment - Google Patents

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 more particularly to a method for improving a film formation speed and simplifying a film formation process by omitting a pretreatment step of a substrate.

[0002]

2. Description of the Related Art Due to its attractive properties such as high hardness and high thermal conductivity, diamond has been actively studied in various fields such as cutting tools and semiconductor materials. Material.

[0003] At present, there are roughly two methods for producing such a method. One is a method for obtaining a single crystal diamond under a high pressure, and the other is a method for forming a diamond thin film from a gas phase under a low pressure. is there.

[0004] We have been studying the latter method in order to use a diamond film as a device or as a coating material. For example, as a method of forming a diamond-containing carbon material or a diamond material using thermal energy in a vapor phase growth method, a hot filament CV is used.
There is a D (chemical vapor deposition) method. The method comprises applying a current to a filament made of metal tungsten (or tantalum), heating the filament to 1500 to 3000 ° C., and heating the substrate to 400 to 1300 ° C. by emitting thermoelectrons. The gas is pyrolyzed by contact heating,
This is a method of forming a carbon material containing diamond or a diamond material on a substrate.

[0005] However, in the above method, the vapor pressure of the filament material is inevitably increased, so that there is a high possibility that the film is contaminated. In addition, there is a disadvantage that the life of the filament is shortened, the frequency of replacement is increased, and the change over time, uniformity per batch, and reproducibility are poor.

The present invention relates to a process for generating plasma using mainly the energy of an electromagnetic field, forming active species, and forming a film therefrom instead of using the above-described thermal energy. Uniformity when considering industrial applications,
This is because a process that has high reproducibility is required. As a process using such a plasma, there are a microwave plasma CVD method and a magnetic field plasma CVD method which are performed at a relatively low pressure, and there are DC plasma, arc plasma, combustion flame in a high pressure (near atmospheric pressure) region. And the like. As described above, the low-pressure process is further divided into a film formed in a low-pressure (100 torr or less) region and a film formed in a medium-low-pressure (100 torr to atmospheric pressure) region. The present invention relates to the former low pressure plasma CVD method. In the method, a microwave is introduced into a reaction tube,
It has a structure in which evacuation is performed while introducing a reaction gas, and the reaction gas is excited to form active species to form a film. The most frequently used microwave oscillation frequency is 2.45 GHz. The pressure in the reactor is maintained at 10-200 Torr.

[0007] The method of forming a plasma using a microwave further utilizes the interaction of the microwave and the magnetic field depending on the conditions, and uses a mixed cyclotron resonance (MCR), a phenomenon that occurs when the reaction pressure is higher than 0.1 Torr. The magnetic field microwave plasma CVD method used and the reaction pressure
EC, a phenomenon that occurs when the pressure is very low, less than 0.1 Torr
There is an ECR plasma CVD method using R (Electron Cyclotron Resonance) and the like.

[0008]

[Problems to be solved by the invention]

One of the problems in the diamond film formation in such a plasma CVD method is the problem of the film formation speed. In a conventional vacuum process, the concentration of the reactive gas is low, so that the film forming speed is inevitably reduced. . That is, in the vacuum process, the film formation rate is how efficiently the active species can be formed and the film can be formed.

Another problem is that the pre-processing of the substrate is troublesome. Briefly showing the pretreatment, for example, when a Si wafer is used as a substrate, ultrasonic treatment is performed in alcohol in which diamond powder is dispersed before film formation.
With this step, reproducibility or uniformity of each batch becomes a problem as well as troublesome film formation. However, if this pretreatment is omitted, the generation of nuclei becomes extremely slow at the stage of nucleation at the initial stage of film formation, and film formation is not smooth. A process that balances these was desired.

Further, there is a problem that the substrate temperature during film formation is lowered. This is because it is difficult to form a composite device with a conventional device (especially, a Si-based device) when a film formation with a high substrate temperature enters a manufacturing process.

[0012] Intervention of impurities in the film, especially hydrogen, around the grain boundaries is also an important problem when considering the application of diamond films to various directions. Despite mechanically affecting the strength and energy gap of thin films and electronic materials mechanically, methods for controlling the impurity concentration during film formation have not yet been clarified. .

[0013]

SUMMARY OF THE INVENTION The process of the present invention solves the above problems. In the present invention, attention has been paid to using halogenated hydrocarbons as a material gas as such means.

Recently, Patterson et al. Of Rice reported that CF ₄
It is reported that lower temperatures can be achieved than conventional methane systems when using raw materials such as methane and hydrogen or CS ₂ and fluorine. They discuss the formation and stability of solid carbon from simple thermodynamic considerations of solid carbon formation. Specifically, during solid carbon formation, the change in free energy when removing all side chains and the like from the raw material is observed.When the change in free energy at 1000 ° C. is compared, that of methane alone is − 4.5KJ / mo
While no more than the l, while that of making the solid carbon from the CF ₄ and hydrogen orders of magnitude and -340.0KJ / mol greater, therefore that there is a possibility that the deposition of the diamond is easily performed.

However, in their consideration, the consideration of the activation energy is completely absent, and it is not enough to discuss the reactivity with free energy alone. Graphite is also formed, but their considerations were easy and their modeling was inadequate. Their consideration, of course, is thermal energy and cannot be adapted to the plasma state. However, we anticipated that the use of halogenated hydrocarbons would lead to the efficient formation of effective active species even in plasma. That's it.

[0016] That is, specifically, CF4, CHF_Three, CH_Two
F_TwoSuch as halogenated hydrocarbons and hydrogen, or as required
Using a gas to which an inert gas has been added as a raw material gas
In the plasma CVD apparatus, the pretreatment of the substrate is omitted and the ratio is reduced.
Relatively high speed (2 to several times compared to using conventional materials)
Carbon material containing diamond at the above film forming rate) or
It is possible to form a thin film made of diamond material
To adjust the concentration of the halogenated hydrocarbon
Can adjust the impurity concentration in the film centering on hydrogen
It was found that it was.

We believe this is due to the efficient formation of effective active species in the plasma from halogenated hydrocarbons mixed with hydrogen. Although it is speculation, unlike the Patterson model, we think that the action of diradical may be strong in the plasma.
This is because diradical may cause an insertion reaction between CH bonds.

According to our method, the substrate temperature can be reduced. As described later, the diamond peak could be observed even at a low substrate temperature of 100 ° C. to 200 ° C. It is considered that this is because active species necessary for film formation are formed efficiently.

We have also confirmed that simultaneous implantation of hydrogen and halogen into diamond is possible in the present invention. Such implantation of a different element may be effective for device fabrication together with the above-described impurity concentration adjustment.

When a diamond thin film is produced by the method of the present invention, hydrogen halides such as hydrogen fluoride are generated as by-products. It is substantially difficult to use the quartz or stainless steel used in the above. Therefore, as a material of the chamber, a material having relatively low reactivity with hydrogen fluoride or the like and functioning as a structural material at a high temperature, specifically, a ceramic material such as alumina, sapphire, or SiC, and an oxidation-resistant material such as Monel. A metallic material was used. Among these, with respect to SiC, when a material coated by CVD from above the sintered body was used, the concentration of impurities in the resulting film was low, and was very excellent.

The substrate used in connection with the present invention also has the above-mentioned restrictions on the material, and the substrate used is, for example, Si, sapphire, alumina, monel, tungsten carbide, and other oxidation-resistant metal materials.
Hereinafter, the present invention will be described in more detail with reference to Examples.

[0022]

【Example】

Example 1 First, an example of microwave CVD will be described below. . We performed plasma CVD using a CF ₄ + hydrogen system as a material. The film forming conditions are shown. The pressure in the chamber is 1 to 100 torr, preferably about 40 torr. The CF ₄ concentration is adjusted to 10% or less, preferably 2-3% by hydrogen dilution. From the results of the Raman measurement of the film, it was confirmed that the film quality was improved when the CF ₄ concentration was lowered. However, when the concentration was low, the film formation rate was slow, and in our apparatus, 2-3% was appropriate. Met.
The substrate temperature was set between 600 ° C and 900 ° C. According to Raman measurement of the formed film, the film quality was good at a substrate temperature of about 800 to 820 ° C. Alumina was used as the material of the chamber in consideration of the resistance to halogen.

The microwave plasma C used in this experiment
FIG. 1 shows the configuration of the VD experimental apparatus. Basically, it is an ordinary microwave plasma CVD method, and microwaves are introduced into the chamber from the window 5. The microwave output is 1
00 to 800 W. Usually, it operates at 400 to 600 W. The substrate used was Si, alumina and monel. Here, a region 3 in FIG. 1 shows a plasma distribution when the substrate 4 and the substrate holder 9 are not arranged. (It should be noted that the plasma distribution when the substrate is placed is different from the plasma 3 in the figure.) The substrate was placed at position 6 or position 7. When the substrate was far away from the substrate, as in position 8, no film formation was seen. The deposition rate was about 2-3 μm / hour.
After the film formation time of 4 hours was completed, the film was taken out of the chamber and subjected to Raman spectroscopy. The results shown in FIG. 2, for example, were obtained. A diamond peak is seen around 1332 cm ^-1 . This is a film on the Si substrate arranged at position 6 in FIG. 1, but similar peaks were observed on other Monel and alumina substrates. There was a broad peak at around 1500 cm ^-1 which is considered to be an amorphous carbon material, but a sharp diamond peak was observed at 1332 cm ^-1 . Even if the laser output was changed, it was confirmed that the peak position did not shift, and this peak was identified as diamond. The sensitivity of Raman spectroscopy is sharp for amorphous carbon, but not so high for diamond, which may be due to the difference in peak intensity.

When plasma emission analysis was performed at the time of film formation, radicals such as CF ₃ and CF ₂ were found, but none of carbon completely dissociated from CF ₄ or CF radicals were found. This indicates that active species that are particularly effective for film formation exist in correlation with the power of microwaves and the like. Actually, the latter plasma, in which the radical peak is strong, could form only a substance having poor film quality.

FIG. 3 shows the results of Raman measurement of the film in which the Si substrate was arranged at the position 7 in FIG. Although the film quality was rather poor, a diamond peak was also observed.

Although it has been previously shown that the substrate temperature can be lowered according to our method, specifically, the substrate temperature 100
The substrate temperature dependency was examined in the range of from 900C to 900C.
Since the substrate temperature has a heating effect by plasma, cooling by water cooling is performed. The substrate temperature is measured by installing a thermocouple on the back side of the substrate. A film having a substrate temperature of 400 ° C. or higher was formed at a position 6 in FIG. 1 and a film having a substrate temperature lower than that was formed at a position 7 in FIG. When the formed film was subjected to Raman measurement, the peak of diamond could be confirmed even at a substrate temperature of 100 ° C. or 200 ° C., although it was weak.

Further, we performed SIMS analysis on the film formed at a substrate temperature of 750 ° C. The results showed that changing the concentration of the halogenated hydrocarbon changed the concentration of halogen and hydrogen taken into the film. Specifically, it was shown that the concentration of halogen and hydrogen in the film was increased by increasing the concentration of halogenated hydrocarbon. That is, according to the method of the present invention, the concentrations of halogen and hydrogen in the film could be controlled. Thus, the possibility of manufacturing an electronic device using diamond or a carbon material containing diamond may be sufficiently high.

[Embodiment 2] In this embodiment, an example is shown in which the material gas of Embodiment 1 is changed. That is, the raw material is CHF ₃
, And hydrogen and CHF ₃ in order to lower the concentration of helium. The parameters were set such that the CHF ₃ concentration was 5 to 0.5%, the substrate temperature was 750 ° C. to 820 ° C., and the film formation time was 4 hours. The substrate uses Monel. The other devices used in the experiment are the same as those in the first embodiment.

In both cases where the reaction gas contained He, and where He was not contained, a peak due to diamond was clearly confirmed from the result of Raman spectroscopy. Here, paying attention to the film forming speed, the film forming speed is two to several times faster when CHF ₃ is used than when CF ₄ is used. (However, when He was added, the film formation rate was almost the same as that of CF _4. ) Specifically, when CF ₄ was used at a concentration of 2%, the film formation rate was 2.5 to 3 μm / hour. When CHF ₃ was used, it was ₃ to 8 μm / hour. That is, in our apparatus, CHF ₃ was more suitable for diamond film formation in the plasma CVD method. When a conventional material such as methane was used, the film formation rate was 0.5 to 1 μm, and it is understood that the use of the halogenated hydrocarbon contributes to the improvement of the film formation rate.

Example 3 In this experiment, Example 1 was used.
An example in which the raw materials are changed in the process of (1) is shown. That is,
CHCl ₃ , hydrogen and He were used as raw materials. In Examples 1 and 2, the raw materials were all gases at room temperature, so there was no problem. However, since the raw materials were liquid at room temperature, an experiment was performed using a vaporizer. Since hydrogen chloride is inevitably generated during film formation, an alumina tube is used for the chamber. Substrate temperature is 700-8
The test was performed under the conditions of 00 ° C. and a deposition time of 8 hours. The other devices used in the experiment are the same as those in the first embodiment.

When the obtained thin film was measured by Raman spectroscopy, a very clear peak due to diamond was confirmed. Regarding film thickness, CHF ₃ concentration 2
%, Which was clearly thicker than the result, and confirmed that the depot was rising.

Embodiment 4 In this embodiment, an example in which a film is formed by a magnetic field microwave plasma CVD method will be described. The above method is effective for forming a large-area thin film, and it is possible to form a film on a wafer of at least 4 inches and 6 inches or more. Although it corresponds to the microwave plasma method, it is also characterized in that a film having excellent film quality can be formed as compared with RF plasma or the like. FIG. 4 shows a schematic diagram of the apparatus used in this example. By utilizing the interaction between the magnetic field generated by the magnetic field coil and the microwave introduced into the reaction chamber from the microwave waveguide, the reactive gas flowing from the gas inlet 2 is efficiently excited, and carbon containing diamond is deposited on the substrate 4. Form material or diamond material. Substrate 4
Is externally controlled by heating the substrate holding plate. Further, a floating electric field 13 can be applied to the substrate 4. Usually, when diamond is formed, a gas such as methane, carbon monoxide, ethylene, methanol, or ethanol or a gas obtained by diluting a liquid hydrocarbon with hydrogen is used as a reaction gas, and water, carbon dioxide, and oxygen are also used as a reaction gas. A small amount of added gas may be used. We used CF ₄ and hydrogen as source gases. Some parameters for the film formation are as follows: the degree of vacuum is 0.02 to 5 torr.
r preferably 0.1 to 2 torr, substrate temperature 700 to 800
C. and a microwave output of 1 to 5 kW. The substrates used were Si, Monel and WC. At position 6, a film was formed. The inner wall of the chamber was coated with SiC. The magnetic field was 200-2000 Gauss. When the optimum conditions were determined from Raman measurements with our device, the magnetic field was suitably 800 to 900 gauss. At this time, the film forming speed was 3 μm / hour. Film formation was performed for 4 hours with a magnetic field of 850 gauss and a CF ₄ concentration of 3%, and the film was subjected to Raman measurement. As a result, a diamond peak and an amorphous component peak were observed. Then CF ₄
Was further reduced for a further 4 hours at a concentration of 1.5%, and the Raman peak of the formed film became clearer. From this, it is expected that the concentration of CF ₄ at the time of film formation also greatly affects the film quality in this embodiment.

[Embodiment 5] In this embodiment, an attempt was made to adjust the hydrogen concentration in the film by using the microwave plasma CVD apparatus used in Embodiment 1. Our study showed that the concentration of hydrogen in the film varied with the supply of halogenated hydrocarbons. Therefore, in this example, an experiment was conducted to investigate the specific effect. The film forming conditions are as follows.
The reaction gas used was a CF ₄ + hydrogen system, and the pressure in the chamber was 40 Torr. The substrate was made of Si and heated to 800 ° C. to form a film.

The concentration of CF ₄ is set to 10% or less, 2.5%,
For three points of 5.0% and 7.4%, film formation and measurement of hydrogen concentration in the film by SIMS were performed. As a result, 1.
0 × 10 ²¹ , 1.5 × 10 ²¹ , 1.7 × 10 ²¹ (atoms / c
m ³ ), the concentration of CF _{4 in} the reaction gas 2.
The hydrogen concentration changes in the order of 5% <5.0% <7.4%,
That is, it was found that the hydrogen concentration in the film could be changed by changing the concentration of the halogenated hydrocarbon.

Although this tendency could not be quantitatively evaluated, similar results were obtained for the concentrations of fluorine and silicon. By examining other conditions with a focus on the change in the concentration of the halogenated hydrocarbon, it is considered that the impurity content in the film can be controlled.

[0036]

As described above, in the above-mentioned plasma CVD, a film-forming step without pre-treatment is established and a film-forming speed is improved. This is due to the fact that it is possible to efficiently generate active species involved in film growth by using halogenated hydrocarbons as materials and fabricating equipment to make it possible, And a value several times higher than the conventional film forming rate was obtained.
In addition, it has been clarified that the impurity concentration in the diamond thin film can be adjusted based on the adjustment of the addition amount of the halogenated hydrocarbon.

Thus, the present invention is considered to be a very useful industrial patent.

[Brief description of the drawings]

FIG. 1 shows a microwave plasma CVD apparatus used in the present invention.

FIG. 2 shows an example of a result of a Raman spectrum of a film formed according to the present invention.

FIG. 3 shows an example of a result of a Raman spectrum of a film formed according to the present invention.

FIG. 4 is a magnetic field microwave plasma C used in the present invention.
1 shows a VD device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction chamber 2 Gas inlet 3 Plasma area 4 Substrate 5 Window 6 Position 7 Position 8 Position 9 Substrate holder 10 Waveguide 11 Exhaust 12 Magnetic field generating coil 13 Floating electric field generator

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A 1-298095 (JP, A) JP-A 62-278193 (JP, A) JP-A 62-278192 (JP, A) 198479 (JP, A) JP-A-59-30709 (JP, A) JP-A-62-180072 (JP, A) JP-A-2-30125 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) C23C 16/00-16/56 C30B 29/04 H01L 21/205 H01L 21/3065 H01L 21/31

Claims (3)

(57) [Claims] 1. A containing halogenated hydrocarbons and hydrogen into a reaction chamber
Supplying a non-reactive gas, a carbon material manufacturing apparatus for manufacturing a carbon material or a diamond material comprising a diamond <br/> Monde by plasma CVD, the inner wall surface of said reaction chamber
A carbon material producing apparatus comprising SiC . 2. A reaction gas containing a halogenated hydrocarbon, hydrogen and a rare gas is supplied to a reaction chamber , and the reaction gas is supplied by a plasma CVD method.
Carbon material production apparatus A carbon material manufacturing apparatus for manufacturing a carbon material or a diamond material, the inner wall surface of said reaction chamber, characterized in that it consists of SiC containing diamond Te. 3. The plasma C according to claim 1, wherein
VD method, the carbon material manufacturing apparatus which is a microwave plasma CVD method or a magnetic field microwave plasma CVD method.