JPH06135711A - Production of silicon carbide film - Google Patents

Abstract

PURPOSE:To form a silicon carbide film having high crystallinity on a low heat-resistant substrate by activating a reactive gas consisting of silicon halide having a molecular structure with dipole moment and carbon halide and then effecting the chemical reaction in a atmospheric pressure gaseous phase. CONSTITUTION:As the source material, silicon halide having a molecular structure with dipole moment and carbon halide compd. are used. In the production of silicon carbide film by chemical reaction in a atmospheric pressure gaseous phase, the reactive gas containing the material described above is activated at 800-1100 deg.C. This activated reactive gas is introduced to the substrate placed in 140-250 deg.C atmosphere or maintained at 140-250 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon carbide film used as a coating film for extending the life of a cutting tool and improving the machinability, as a surface protective film, and as a part of a semiconductor element or its body. The present invention relates to a method of manufacturing at low temperature.

[0002]

2. Description of the Related Art Conventionally, a raw material gas used for forming a silicon carbide film by a chemical vapor deposition method (hereinafter referred to as a CVD method) is a silicon hydride gas such as silane or disilane and a hydrocarbon such as methane or ethane. And S with hydrogen gas mixture
Si-C using i-C-H system, silicon chloride gas (mainly liquid at normal temperature and pressure) such as silicon tetrachloride and disilicon hexachloride, and mixed gas of hydrocarbon and hydrogen such as methane and ethane Those based on the -Cl-H system are known.

In particular, various methods for producing a silicon carbide film using a hydrocarbon gas are known. As a method for forming the silicon carbide film from the vapor phase, there are a thermal CVD method and a plasma CVD method.
Method, optical CVD method, or the like is used.

In particular, the thermal CVD method can form a film of crystalline silicon carbide (mainly polycrystalline silicon carbide) that grows in bulk, and is often used as a coating method for cutting tools and the like. Here, the crystalline silicon carbide film refers to a silicon carbide film having crystallinity, and includes a microcrystalline state, a polycrystalline state, a microcrystalline state without a clear grain boundary, a polycrystalline state, and It refers to a silicon carbide film having a crystalline state in which a microcrystalline structure and a polycrystalline structure are mixed in an amorphous structure.

Most of the silicon carbide film synthesized by the plasma CVD method has an amorphous structure and is generally used as an electronic material for a part of a semiconductor element or a semiconductor element body. Even by the plasma CVD method, by heating the substrate to 800 ° C. or higher,
It is known that a crystalline silicon carbide film having a microcrystalline state can be obtained, but the film forming rate is 4Å / s, which is extremely small, and the film quality is not good. Furthermore, it is known that when a silicon carbide film is formed by using the photo-CVD method, it becomes an amorphous film containing hydrogen in the film.

[Problems of Prior Art] When bulk crystalline silicon carbide is obtained as described above, it is effective to use the thermal CVD method. However, when the thermal CVD method is used, a necessary atmosphere is required. Since the temperature is more than one thousand and several hundred degrees Celsius, the substrate material that can be used for film formation is naturally limited due to the heat resistance of the substrate. On the other hand, although it is possible to form a film at a relatively low temperature by the plasma CVD method and the photo CVD method, the synthesized silicon carbide film is uniformly amorphous and an attempt is made to obtain a crystalline carbide film. That was virtually impossible.

Further, in order to obtain high productivity, it has been required to operate the device at a temperature as low as possible.

A method of using a hydrocarbon gas as a raw material for obtaining a silicon carbide film is well known, but when the hydrocarbon gas (CH ₄ ) becomes a radical (for example, a CH ₃ radical), it becomes flat. However, a crystalline silicon carbide film of high quality could not be obtained. In particular, in order to obtain a film with enhanced crystallinity, the substrate or the atmosphere must be heated to a high temperature, so that there is a problem that the film cannot be formed on a heat-sensitive substance. Further, in this case, since the temperature of the substrate is set to a high temperature, there is a high possibility that the film will be peeled off after the film formation on the substrate whose coefficient of thermal expansion is extremely different from that of silicon carbide.

In recent years, it has been reported that a blue light emitting device was produced by using a single crystal silicon carbide to make a successful pn junction. However, since it is difficult to obtain a single crystal silicon carbide, a very expensive material is used. Has become. Therefore, research has been conducted on forming a pn junction from thin film silicon carbide, but the present situation is that a crystalline silicon carbide film having a good film quality that can be used as an electronic device has not been formed.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to obtain a method for producing a silicon carbide film which can form a highly crystalline silicon carbide film on a substrate having low heat resistance. Another object of the present invention is to obtain an inexpensive method for manufacturing a silicon carbide film having high productivity without using a conventional apparatus having a complicated vacuum exhaust system.

[0011]

The present invention is a method for producing a silicon carbide film from a material containing silicon and a material containing carbon by a chemical reaction in a vapor phase at atmospheric pressure, wherein halogen is used as the material containing silicon. Using a compound, a material containing a halogen compound as a carbon-containing material and having a molecular structure having a dipole moment, and forming a silicon carbide film by a chemical reaction of a reactive gas composed of these materials in an atmospheric pressure gas phase When activating, the reactive gas containing the material is activated at a temperature of 800 ° C. to 1100 ° C., and the activated reactive gas is heated to a space at a temperature of 140 ° C. to 250 ° C. or 140 ° C. The main constitution is to lead to the surface of a substrate kept at ˜250 ° C. and form a silicon carbide film having a Si—C bond on the substrate.

The formation of a silicon carbide film by a chemical reaction in the atmospheric pressure vapor phase means that the silicon carbide film is produced by a vapor phase chemical reaction (generally referred to as CVD) in the atmospheric pressure without depressurization. Is meant.

The halogen compound is used because it can easily decompose and react even at normal pressure.

The molecular structure having a dipole moment is a molecular structure in which an electric charge is biased when viewed as a single molecule. As a molecular structure having such a dipole moment, the structure of H ₂ O molecule can be mentioned as a general example.

The reason why a material having a molecular structure having a dipole moment is used as a raw material is that attention is paid to its high reactivity, and the high reactivity has been proved by experiments.

CHF ₃ , CClF ₃ , and CH ₃ F can be used as a material having a molecular structure having a dipole moment and containing carbon as a halogen compound.

In the present invention, it is necessary that both the material containing carbon and the material containing silicon be a halogen compound. However, as a material containing silicon, a molecule alone does not have a dipole moment (that is, a bias of the charge). No) SiCl ₄ or SiF ₄ can be used.

A space or 15 in which the reactive gas is activated at a temperature of 800 ° C. to 1100 ° C. and the activated reactive gas is heated to an ambient temperature of 150 ° C. to 250 ° C.
Lead to the substrate surface kept at 0 ° C-250 ° C substrate temperature,
A silicon carbide film is formed on a substrate by means of a halogen compound and a reactive gas having a dipole moment (including a vaporized liquid material) at 800 ° C or higher.
It can be easily activated under atmospheric pressure at a temperature of 1100 ° C., and the activated reactive substrate is heated at 140 ° C. to 25 ° C.
Substrate installed under 0 ° C atmosphere or 140 ° C to 25 ° C
It is based on the experimental result that a good quality crystalline silicon carbide can be obtained by introducing the crystalline silicon carbide onto a substrate kept at a temperature of 0 ° C.

In this case, the activation of the reactive substrate is 1000
Although it is possible to use the temperature of ℃ or less, it has been confirmed that the film cannot be formed at 800 ℃ or less due to insufficient activation. Further, when the activated reactive gas is introduced onto the substrate having a temperature gradient, when the ambient temperature is 140 ° C. or lower, the active species disappears and the desired crystalline silicon carbide film cannot be obtained. It has also been experimentally confirmed that a crystalline silicon carbide film cannot be obtained by the above.

The temperature for activating the reactive gas is set to 1100.
However, if the temperature is higher than this, the activation proceeds too much and the film quality is adversely affected. However, when a material which is a halogen compound and has a molecular structure having a dipole moment is used, it is 1000 ° C. or lower, preferably 95 ° C. or lower.
Since an activation temperature of 0 ° C. or lower is sufficient, it can be said that a high temperature of 1000 ° C. or higher is unnecessary in view of productivity.

[Background of Invention] In the previous studies by the inventors, if a halogen (fluorine / chlorine) gas or a halogen (fluorine / chlorine / bromine / iodine) compound, preferably a fluorine-based gas is used as a reaction gas, It has been clarified that it is possible to lower the temperature of the substrate atmosphere and to produce a silicon carbide film having good film quality.

The difference in film quality due to the use of halogen-based gas is considered to be due to the following reason. That is, a hydrogen compound that has been conventionally used as a carbon source (eg, methane)
The carbon radicals generated from the above do not have the four-coordinate (just like a three-dimensional pyramid) that is found in diamond, but easily take the three-coordinate (planar) like graphite as its form. In the case of a halogen compound (for example, carbon tetrafluoride or carbon tetrachloride), it is considered that the above four coordination type (that is, diamond type) is adopted.
According to this idea, it is possible to easily synthesize a material having a diamond type crystal structure by using a halogen compound as a starting material.

The crystal structure of silicon carbide can be classified into two types, that is, an α type which is a crystal structure corresponding to the structure of hexagonal diamond and a β type which is a crystal structure corresponding to the structure of cubic diamond. In both of them, carbon atoms and silicon atoms are bonded in a one-to-one composition ratio in a four-coordinated form. From this, it is concluded that a silicon carbide thin film exhibiting good crystallinity can be produced by using a source gas that can supply carbon radicals and silicon radicals in a tetracoordinated form.

By the way, although silicon tetrachloride has already been used as a raw material gas for silicon carbide, this was made by roughly considering reaction kinetics, and was made from the above crystallographic viewpoint. It should be noted that not. That is, it is clear from the discussion so far that the carbon source gas must be the halogen compound gas at the same time as the silicon source gas. Further, in the above reaction kinetic consideration, an example in which silicon tetrachloride and carbon tetrachloride are combined as a source gas has been reported. In this reaction system, it seems that the above-mentioned crystallographic conditions are satisfied, but there is a problem that a high temperature of about 1700 ° C. is necessary as a reaction temperature. From the above consideration, it is concluded that the selection regarding the kind of the halogen compound as the carbon source is also important.

According to our research, it cannot be said that the radical formation energy when using a gas of a tetracoordinate monomolecular such as carbon tetrafluoride and carbon tetrachloride is not necessarily low, and it is a halogen compound and a molecule. It has become clear that a silicon carbide film with excellent crystallinity can be produced at a lower temperature and normal pressure only by using a gas having a slightly uneven structure balance, that is, a gas having an uneven charge distribution. It was In this case, the most preferable result could be obtained when CHF ₃ was used as the carbon source gas. As described above, it was found that the use of the halogen compound as the reaction gas enables the film formation at a low temperature and atmospheric pressure, and as a result, the film forming apparatus can be simplified.

In the film formation of the silicon carbide film which has been attempted so far, it is necessary to apply a high reaction energy as described above, and thus it is necessary to simply operate a large-scale apparatus. By using the reaction gas system as described above, it is not necessary to prepare a large-scale vacuum device and the application of a gas flow device under normal pressure is sufficient, and the film forming device is greatly simplified as compared with the conventional method. . However, measures against halogen-based gas (processing equipment, etc.) must be thoroughly examined.

In the film forming apparatus used in the course of research prior to the invention, a temperature gradient was set for the reaction tube using an electric furnace. Then, the substrate is installed at an ambient temperature of about 200 ° C., and the gas is passed from the high temperature region of 900 ° C. to the low temperature region at a certain flow rate so that the gas activated in the high temperature region is transferred onto the substrate. It was possible to form a silicon carbide thin film mainly composed of β type. Further, by developing the method, a high temperature gas activation area and a low temperature area of about 200 ° C. where the substrate is installed are prepared, and the gas is passed from the high temperature area to the low temperature area at a certain flow rate in the same manner as the above method. It was confirmed that the silicon carbide film could be formed even by using the method of activating the gas.

The important condition here is the flow velocity of the raw material gas. The reactive species activated in the high temperature region have a lifetime of active species that maintains the energy required to form a film having a crystalline structure in the low temperature portion. That is, if it is possible to select a raw material gas having a low temperature necessary to generate active species, and to select a combination of flow velocities that allows the active species to reach a low temperature region before the life of the active species is exhausted, It is possible to lower the film forming temperature and thus to simplify the reactor.

The structure of the present invention is based on the above experimental results and consideration of the experimental results. Further, if a silicide material which is a halogen compound as the silicon source material and has a molecular structure having a dipole moment is used, it is possible to obtain a crystalline silicon carbide film which is dense and has good crystallinity and a high film formation rate. it can. A material having a molecular structure having such a dipole moment and containing silicon which is a halogen compound is SiHBr.
₃ and SiHCl ₃ . Since these raw materials are liquids at room temperature and pressure, it is necessary to vaporize them before use. Hereinafter, the present invention will be described in more detail based on examples.

[0030]

【Example】

[Embodiment 1] This embodiment relates to a preliminary experiment conducted for confirming the optimum temperature of the atmosphere near the substrate when the silicon carbide film is formed using the structure of the present invention.

In this embodiment, the thermal CVD shown in FIG.
This is an example in which a silicon carbide film is manufactured using an apparatus. This apparatus is a kind of so-called hot wall type thermal CVD apparatus. In this embodiment, a temperature gradient of 900 ° C. to room temperature is applied to the horizontally arranged furnace core tube 1 by using the electric furnace 2 and a cooling fan (for supplying gas from the direction in in the figure). It was set over a length of 30 cm from the dotted line portion indicated by aa ′ in FIG. As the substrate, the substrate 3 was placed over a portion where a temperature gradient from 900 ° C. to room temperature was present as shown in FIG. The temperature (ambient temperature) was measured with a thermocouple.

The core tube material should be carefully examined from the viewpoint of the corrosive environment such as HF gas which may be generated during the reaction, heat resistance and mechanical strength. Leave room for selection depending on conditions. For example SU
The stainless steel material such as S316 may be frequently replaced, or a ceramic material such as sintered silicon carbide or silicon nitride may be used. In this embodiment, Inconel 625 is used among nickel alloy tubes having high corrosion resistance and high mechanical strength.
The dimensions of the core tube are an outer diameter of 32 mm, an inner diameter of 27 mm, and a length of 1 m.

As the substrate 3, Monel 400 (nickel alloy) having a width of 8 mm and a length of 400 mm is placed inside the reactor core tube so that the tip is located at the center of the electric furnace (on the dotted line indicated by aa 'in FIG. 1). I put it in. The reason why the substrate 3 is installed inside the furnace tube 1 in this manner is to clarify the difference in the film formation state depending on the ambient temperature. That is, the temperature of the atmosphere in which the substrate is placed decreases as the distance from the electric furnace 2 increases.

As a material for forming the silicon carbide film, both a silicon source gas and a carbon source gas are halogen compounds, and those having a dipole moment and having a slightly unbalanced molecular structure are preferable. In this embodiment, carbon is used. Only the source gas was a reactive gas with a molecular structure having a dipole moment.

Specifically, SiCl ₄ is used as a silicon source gas.
CHF ₃ was used as a carbon source gas, and they were introduced together with hydrogen gas into the inside of the reactor core tube where the temperature gradient was set. The gas composition is SiCl ₄ : CHF ₃ : H ₂ from 1.7 to
A ratio of 2: 0.8 to 1: 7, preferably 1.85: 0.9: 7 is suitable. However, this gas ratio largely changes depending on the gas species, heating temperature, length of temperature gradient, and cross-sectional flow velocity of gas described later, but at least the hydrogen gas for promoting dissociation / activation of the silicon source / carbon source gas The proportion must be large.

As described above, it has been clarified that the cross-sectional flow velocity is a very important condition for determining the film quality, which is related to the lifetime and the reaching distance of the active species. Here, the cross-sectional flow velocity must be sufficiently examined from the above-mentioned temperature gradient setting distance and the maximum temperature of the temperature gradient. From some preliminary experiments, it was revealed that the cross-sectional flow velocity condition of 1 to 8 cm / s is suitable, and therefore the cross-sectional flow velocity was set to 4 cm / s in this example.
At this time, the total flow rate of the reaction gas is 1500 ccm. The reaction pressure was fixed at 760 Torr, that is, atmospheric pressure using a pressure controller. The reaction time was 4 hours.
The obtained sample is XRD for film crystallinity and XPS for carbon /
The composition ratio of silicon was analyzed for impurities in the film by SIMS.

The following are (1) differences in film quality due to differences in carbon source gas species, (2) differences in film quality due to differences in temperature gradient, (3) differences in film quality due to differences in cross-sectional flow velocity in the reaction tube, A comparative example for examining the above three points will be shown. The comparison results will be collectively described later.

Comparative Example 1 In this comparative example, in order to confirm the effect of selecting a carbon source gas species, that is, the effect of using a material having a molecular structure having a dipole moment, CF ₄ was used instead of CHF _3. The results of film formation were compared using the same temperature gradient and cross-sectional flow velocity as in Example 1. The evaluation method of the obtained sample is the same as in Example 1.

[Comparative Example 2] In this comparative example, in order to compare the temperature gradient, the carbon source gas species selection and the cross-sectional flow velocity were the same as in Example 1, and the following two experiments were conducted. 1. The length of the temperature gradient was fixed at 30 cm, and the temperature for activating the reactive gas was set to 950 ° C. and 850 ° C. for two types of film formation. 2. Fix the temperature to activate the reaction gas at 900 ℃,
The temperature gradient length was 45 cm. The evaluation method of the obtained sample is the same as in Example 1.

[Comparative Example 3] In this comparative example, in order to compare the cross-sectional flow velocities, the carbon source gas species selection and the temperature gradient were the same as in Example 1, and the following two experiments were conducted. 1. The raw material gas ratio was fixed to that of Example 1, and the total flow rate was 2200.
The film was formed with a ccm (cross-sectional flow velocity of about 6.4 cm 3 / s). 2. The raw material gas ratio was fixed to that of Example 1, and the total flow rate was 1000.
The film was formed with a ccm (cross-sectional flow velocity of about 2.9 cm 3 / s). The evaluation method of the obtained sample is the same as in Example 1.

The results of Example 1 and Comparative Examples 1 to 3 are summarized below. First, the evaluation results of the sample obtained in Example 1 will be described. Although it is reported that a silicon carbide film produced by a thermal CVD method at a high pressure (atmospheric pressure or a pressure near atmospheric pressure) generally has a cone-shaped surface, the silicon carbide film produced in Example 1 has When the surface was observed by an electron microscope, the atmosphere was about 300 to 90.
Film-like deposits were observed on the substrate at the temperature of ℃.
In particular, it was found that a thin film having a pyramid-shaped surface was formed at a temperature of 250 to 140 ° C. In addition, from the result of XRD (X-ray diffraction) in the same portion, it was confirmed to be a polycrystalline thin film of β-type silicon carbide. On the other hand, the impurity concentration in the film was measured by SIMS, but fluorine was not confirmed at all, and hydrogen was only detected on the surface. XP
The carbon / silicon composition ratio measured by S (X-ray photoelectron spectroscopy) was 0.98, which was very close to the stoichiometric composition. From the result of the film thickness measurement using the stylus type step film thickness meter, it was found that the film thickness was about 8000Å on the substrate at the atmosphere temperature of 180 ° C. From this, it was found that the film forming rate was 0.2 μm / hour. Again 300
It was found that the film formation rate decreased extremely as it moved to a high temperature part above ℃ (however, the crystallinity could not be evaluated sufficiently). Further, in the extremely low temperature portion, there was a tendency to become powder of silicon carbide.

With respect to the results obtained in Example 1 above, in the same evaluation conducted on the sample obtained in Comparative Example 1,
2000Å ~ 1μ in the same temperature range as in Example 1
m deposits were confirmed, but α ・ β over the entire temperature range
No polycrystalline silicon carbide thin film was formed. X
From the results of RD, it was confirmed that, although some α / β-type silicon carbide peaks were weak at some measurement points, most of them were amorphous silicon thin films. Further, in the SIMS measurement, fluorine was not confirmed at all, but hydrogen was detected in the entire depth direction of the film. XPS
The carbon / silicon composition ratio measured in 1. was 0.04. This is probably because CF ₄ is significantly less dissociated than CHF ₃ . From the above, the superiority of using a material that is a halogen compound and has a molecular structure having a dipole moment as a carbon source material was confirmed.

Further, in 1. of Comparative Example 2, the maximum temperature of the temperature gradient (the temperature for activating the reactive gas) which is the part for activating the reactive substrate is set to either 950 ° C or 850 ° C. Even in the case, a large difference was observed in the amount of adhesion of the film or powder and the physical properties as compared with the case where the maximum temperature was 900 ° C. That is, in the case of the maximum temperature of 950 ° C., the deposition of powder which seems to be graphite was recognized on the substrate at the place where the ambient temperature was 800 ° C. to 650 ° C., and crystalline silicon carbide was not obtained. This is probably because the activation of CHF ₃ is extremely advanced. 700 ° C
Although it was in the form of a thin film below, it was found from the analysis results of XRD and SIMS that both the powder and the thin film contained silicon, fluorine and hydrogen.

When the maximum temperature was 850 ° C., no graphite was observed in the high temperature portion as in the case of 950 ° C. However, a crystalline silicon carbide thin film cannot be obtained here either,
A deposit having crystalline silicon carbide scattered in an amorphous structure was observed at 550 ° C to 400 ° C. In addition, the amorphous silicon thin film whose fluorine is detected by SIMS analysis is 400
It was confirmed in the range of ° C to room temperature. 1. of Comparative Example 2 above. From the results, it is concluded that a temperature around 900 ° C. is optimum for activating CHF ₃ as a carbide gas that has a dipole moment and is a halogen compound.

Comparative Example 2-2 was conducted under the experimental conditions of a maximum temperature of 900 ° C. and a temperature gradient length of 45 cm. Amorphous silicon carbide showed XRD at a temperature of 300 ° C. to room temperature.
Was confirmed from the XPS results. Probably, the lifetime of the active species reaches its limit by the time the temperature of the substrate is reached where an appropriate active species rearrangement energy is supplied, and the energy for forming crystalline silicon carbide cannot be maintained on the substrate surface. Are likely to be formed.

In the comparison of the cross-sectional flow velocities of Comparative Example 3, the following results were obtained. First, the total flow rate of raw material gas is 2200 ccm
A thin film mixed with β-type silicon carbide and an amorphous substance was obtained by film formation (cross-sectional flow velocity: about 6.4 cm 3 / s). Identification of this amorphous substance is difficult. It seems that it is amorphous silicon, but SIM seems to contain a lot of carbon. Next, the total flow rate of raw material gas is 1000 ccm (cross-sectional flow velocity is about 2.9 c
In the film formation of m / s), an extremely thin silicon carbide of 500 Å was confirmed at the portion of 650 to 400 ° C. at the thickest part, but the structure could not be identified.

The above experimental results, especially Example 1 and Comparative Example 1
It is concluded from the result of 1. of Comparative Example 2 that: CHF ₃ which is a halogen compound and has a dipole moment is used as a carbon source gas, and SiCl ₄ which is a halogen compound is used as a silicon source gas. This mixed substrate is activated at an ambient temperature of 900 ° C. ~
By introducing the activated mixed gas into the space having an ambient temperature of 250 ° C., good quality crystalline silicon carbide can be produced on the substrate placed in the space.

[Example 2] From the results of Example 1 and Comparative Examples 1 to 3 described above, a linear temperature gradient is not necessarily obtained in this Example by selecting appropriate reaction gas activation temperature and substrate temperature. This is an example of producing a silicon carbide film by using the improved hot wall type thermal CVD apparatus shown in FIG. 2 on the assumption that it is not necessary to stick.

By using the film forming apparatus as in this embodiment, it is possible to easily form a large area film of silicon carbide. There are various types of CVD devices that can be used, such as those using a hot filament and plasma, but for large-area film formation, for example, devising the rotation mechanism of the substrate stage and achieving uniform heat and plasma heating. , A rather difficult device is necessary. On the other hand, when a film is formed using a halogen-based gas as in the present invention, the necessary active species can be obtained by simple electric furnace heating, and if the substrate heating is made uniform, a sufficiently large area film can be formed. Can handle.

The reaction tube 21 of the apparatus (shown in FIG. 2) in this embodiment uses Inconel 625 from the viewpoint of corrosive environment, heat resistance and mechanical strength as in Embodiment 1.
It has a cylindrical shape with an outer diameter of 80 mm, an inner diameter of 70 mm, and a length of 500 mm. However, the size of this reactor is
It changes depending on the selection of a heating device such as a filament (not shown) for heating the substrate or the like. The substrate 23 is the substrate holder 2
Held at 4. Further, the substrate holder 24 has a built-in filament for heating the substrate.

The composition ratio of the raw material gas was the same as in Example 1. However, the total flow rate was 2000 ccm. This resulted in a cross-sectional flow velocity of 0.86 cm / sec. As described above, in the apparatus of this embodiment, activation of the reaction gas and setting of the substrate temperature are performed separately. That is, first, the reaction gas is activated from the outside by an electric furnace 22 installed outside the reaction tube 21, and the temperature of the substrate 23 is set (set at 180 ° C.) by heating with a filament provided in the substrate holder 24. went. The central position of the electric furnace 22 was installed at a distance of about 200 mm from the gas supply port, and the central temperature was 900 ° C. In this embodiment, a hot wall type apparatus using an electric furnace is used, but if the setting of the flow rate is examined, a hot filament may be inserted into the gas flow to activate the raw material gas.

As the sample, the same as in Example 1 was used Monel 400.
It was used as 2 mm x 42 mm and 8 mm thick. Preliminary experiments confirmed that the substrate was only kept warm by the filament and not heated by the electric furnace except by the gas flow. In the first embodiment, the temperature of the atmosphere in which the substrate is placed is measured, but in the present embodiment, the substrate can be heated independently, and if a thermocouple is provided in the holder 24, the substrate can be heated. Since the temperature can be measured accurately, the substrate temperature can be easily set. This is important when using a reaction gas as a raw material for which the substrate temperature must be delicately set.

The composition and flow rate of the reaction gas were the same as in Example 1. The reaction gas introduced from the high temperature side is activated when passing through the electric furnace portion and reaches the Monel substrate kept at 180 ° C. The reaction pressure was fixed at 760 Torr as in Example 1, and the reaction time was 4 hours.

With respect to the obtained sample, the crystallinity of the film was evaluated by XRD and the impurities in the film were evaluated by SIMS in the same manner as in Example 1. From XRD, it was confirmed to be a polycrystalline silicon carbide thin film having a β-type structure. The SIMS measurement results were completely the same as in Example 1. Moreover, when the surface uniformity of the obtained sample was confirmed by a stylus profilometer, it was almost uniform except for a slightly thinned portion (at least about 2400 Å at the periphery) of the substrate (7800). ~ 8000
Å). From this, it can be said that the method of this example is the most suitable method for obtaining a large-area crystalline silicon carbide coating film.
Further, if the activation of the raw material gas and the uniform setting of the substrate temperature are carried out by examining the heating method and the heating apparatus, it is possible to further increase the processing area.

Although the temperature of the substrate is set in this embodiment, the temperature of the atmosphere near the substrate may be set independently of the temperature for heating the reactive gas.

[Embodiment 3] In this embodiment, in order to form a crystalline silicon carbide film, both a material containing silicon and a material containing carbon are halogen compounds and have a molecular structure having a dipole moment. This is an example of the material.

In this example, SiHC was used as a raw material for forming a silicon carbide film by using the apparatus shown in Example 2.
This is an example using l ₃ and CH ₃ F. Except for the raw materials, the same as in Example 2, but since SiHCl ₃ is a liquid material, it was vaporized by heating and used.

When the silicon carbide film obtained in this example was measured by the same measuring method as in the case of example 2, it was found that the silicon carbide film having worse crystallinity than the silicon carbide film obtained in example 2 was obtained. However, it was confirmed that crystalline silicon carbide was obtained. The film quality of the crystalline silicon carbide film obtained in this example was inferior to that of the crystalline silicon carbide film obtained in example 2 because the manufacturing conditions were the same as those in example 2. Seem. Therefore, SiHCl ₃
It is considered that the film quality can be further improved if the optimum conditions can be set for CH and CH ₃ F.

In the above examples, only a silicon carbide film was produced, but if it is desired to impart P or N type conductivity for use in a semiconductor device, B is used.
₂ H ₆ or PH ₃ may be added to the atmosphere in an amount of about 1 to 5%.

Although hydrogen is used as the diluent gas or the carrier gas in the above embodiments, a halogen gas, a halogen compound gas, or an inert gas such as helium or argon may be used in addition to hydrogen. It is possible.

[0061]

EFFECT OF THE INVENTION A reactive gas composed of a material containing silicon, which is a halogen compound, and a material containing carbon, which is a halogen compound and has a molecular structure having a dipole moment, which is the constitution of the present invention, is heated at 800 ° C. 1100 ° C., preferably activated at an ambient temperature of 850 ° C. to 950 ° C.
A high-quality crystalline silicon carbide thin film containing few impurities, which is conventionally difficult to synthesize, is formed on a substrate placed at an ambient temperature of 40 ° C. to 250 ° C. or a substrate kept at a substrate temperature of 140 ° C. to 250 ° C. High-speed film formation was possible. Moreover, since film formation can be performed at atmospheric pressure, it was possible to obtain industrial utility that a very simple device is required. Moreover, it became possible to form a film at a high speed, which is unusual for a film forming experiment on a different type of substrate.

Particularly, if the type shown in the second embodiment is developed, it is possible to form a large-area polycrystalline silicon carbide thin film. In this case, heat the reactive gas to 900 ° C. and
It suffices to hold the substrate at around 0 ° C. and blow heated gas (active species) onto the substrate at an appropriate rate. Of course, the conditions should be selected depending on the type of gas and the type of substrate, but the present invention is fully applicable.

Furthermore, when the structure of the present invention is used, the ambient temperature or the substrate temperature at the substrate installation location is 140 ° C. to 25 ° C.
Since the temperature may be 0 ° C., a crystalline silicon carbide film can be formed on the surface of a metal, a semiconductor, an insulator, etc., as long as it has a heat resistance of about 150 ° C. or higher. this is,
When the crystalline silicon carbide film is used for protecting the surface or improving wear resistance, the range of applications is greatly expanded. Also,
Since the heat resistance of the substrate can be lowered, when a light emitting element using a crystalline silicon carbide film is to be manufactured,
It is possible to obtain the usefulness that a glass substrate or an organic resin substrate can be used. Needless to say, the base material can be a cutting tool or an object requiring wear resistance.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a thermal CVD apparatus used in Example 1.

FIG. 2 is a schematic view of a thermal CVD apparatus used in Example 2.

[Explanation of symbols]

 1 Reaction Tube 2 Electric Furnace 3 Substrate 21 Reactor 22 Electric Furnace 23 Substrate 24 Substrate Holder

Claims (4)

[Claims] 1. A method for producing a silicon carbide film from a material containing silicon and a material containing carbon by a chemical reaction in an atmospheric pressure gas phase, wherein the material containing silicon is a halogen compound and the material containing carbon. Is a halogen compound and has a molecular structure having a dipole moment. When a silicon carbide film is produced by a chemical reaction in a gas phase at atmospheric pressure, a reactive gas containing the above material is activated at a temperature of 800 to 1100 ° C. And the activated reactive gas is introduced into a space where the temperature of the reactive gas reaches a temperature of 140 ° C. to 250 ° C., and a silicon carbide film is formed on a substrate placed in the space. Method for manufacturing silicon film. 2. The method for manufacturing a silicon carbide film according to claim 3, wherein at least one of CHF ₃ , CClF ₃ , and CH ₃ F is selected and used as the carbon-containing material. 3. A method for producing a silicon carbide film from a material containing silicon and a material containing carbon by a chemical reaction in a gas phase at atmospheric pressure, wherein the material containing silicon is a halogen compound and the material containing carbon. Is a halogen compound and has a molecular structure having a dipole moment. When a silicon carbide film is produced by a chemical reaction in a gas phase at atmospheric pressure, a reactive gas containing the above material is activated at a temperature of 800 to 1100 ° C. A method for producing a silicon carbide film, which comprises converting the activated reactive gas to a substrate surface having a substrate temperature of 140 ° C. to 250 ° C. to form a silicon carbide film on the substrate surface. 4. The method for producing a silicon carbide film according to claim 3, wherein at least one of CHF ₃ , CClF ₃ and CH ₃ F is selected and used as the carbon-containing material.