JPH04139014A - Production of silicon carbide - Google Patents

Abstract

PURPOSE:To easily obtain high-purity silicon carbide powder, particles and films excellent in crystallinity by supplying hydrocarbon-contg. gas to a reaction chamber in which a solid Si is disposed and heating both of them simultaneously to cause CVD reaction. CONSTITUTION:A hydrocarbon-contg. gas 3 is introduced into a reaction chamber 2 in which a solid Si 5 (on a holder 6) as the source material is disposed. Decomposition of the supplied gas 3 (with a filament 8) and heating of the solid Si 5 (with a heater 7) are performed simultaneously to precipitate silicon carbide in vapor phase.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for producing silicon carbide suitable for producing granular or film-like silicon carbide.

(Conventional technology) Silicon carbide is an artificial mineral that is not produced naturally, and has been used mainly as an abrasive material since ancient times.
It is widely used in firebricks and high-temperature heating elements due to its properties such as wear resistance and high strength. In recent years, high-density sintered silicon carbide materials have excellent high-temperature strength, so their application to structures that are used at high temperatures of 1,500° C. or higher has been studied, and some have even been put into practical use. In addition, silicon carbide is an IV-V material with a wide electrical band gap.
It is known as a Group I compound semiconductor, and research and development is also underway on light-emitting diodes and high-temperature diodes using single crystals. Furthermore, recently, a new silicon carbide sintered body that combines the inherent high thermal conductivity and electrical insulation properties of silicon carbide crystals has been developed and put into practical use as a heat dissipation substrate for semiconductors.

There are various methods for producing silicon carbide, which are roughly classified into the following four methods. In other words, ■ Powdered silicon (S
A method of directly reacting t) with carbon (C), ■ A method of utilizing the reduction reaction of silicon dioxide (S102) with C, ■
A hydride of Si, such as silane (S l m H2m+z
) gas or Si chloride such as silicon tetrachloride (SiC14)
A method of reacting a gas with a hydrocarbon such as propane (03H8) gas or methane (CH4) gas in the gas phase;
H3-CCHs CHs -). ) is synthesized and fired to produce silicon carbide. These methods are appropriately used depending on the use of the silicon carbide described above. For example, method (2) is widely used to produce a large amount of powder for obtaining abrasive materials and sintered bodies. Method (2) is famous as a method for producing silicon carbide fibers.

In addition, method (2) is mainly used for forming thin films on the surfaces of substrates or fibers, and for synthesizing high-purity single crystals, and is usually called CVD (chemical vapor deposition). In this method, solid silicon carbide is obtained by applying energy to the silicon carbide using various methods to cause various chemical reactions. This method has the following advantages: depending on the conditions that cause the chemical reaction, not only powders and grains but also films can be obtained; grains and films can be formed at a temperature lower than the melting point of silicon carbide; It also has features such as being able to form a film with a uniform thickness and being able to obtain highly pure silicon carbide by controlling the purity of the raw material gas.

By the way, in the synthesis of silicon carbide by CVD, Si-containing gases such as the aforementioned S ta H2m+2.5iC14, C-containing gases such as C3H8C2H4CH4, S
i (CH3) Si such as C13(CHi)4si
A gas containing C and C is often used. In any of these cases, the characteristic is that Si is supplied to the reaction system as Si hydride gas or chloride gas.

The CVD method, which has these characteristics, is suitable as a method for forming a silicon carbide film on a substrate as described above, but film formation is generally carried out at a high temperature of 1000°C or higher, and the substrate Depending on the material, the film may crack due to a difference in thermal expansion coefficient, or the film may peel off from the substrate due to insufficient adhesion to the substrate. In addition, when producing silicon carbide powder by the CVD method, the particle size distribution is narrow, and the particle size is 0.01 to 0.000% by controlling the production conditions.
It has the characteristic that ultrafine powder consisting of particles of 1 μm can be easily obtained. That is, the conventional method for producing silicon carbide by CVD is suitable for obtaining fine powder in the submicron range. However, it is not necessarily suitable for obtaining coarse particles. Furthermore, there is a desire for silicon carbide that has even better crystallinity than silicon carbide produced by CVD.

(Problems to be Solved by the Invention) As described above, there are various methods for producing silicon carbide, and each method is used to take advantage of the characteristics of each method depending on the application. However, a method has not yet been established that can easily obtain highly purified silicon carbide powder, particles, and films with excellent crystallinity, and can also reliably obtain a healthy film.

This invention was made in consideration of such circumstances, and
It is an object of the present invention to provide a method for producing silicon carbide that can easily obtain high-purity silicon carbide powder, granules, and σ film with excellent crystallinity, and can also reliably obtain a healthy film.

[Structure of the Invention] (Means and Effects for Solving the Problems) A method for producing silicon carbide according to the present invention includes supplying a gas containing hydrocarbons into a reaction vessel provided with solid Si as a raw material, The method is characterized in that silicon carbide is deposited in a vapor phase by simultaneously decomposing the supplied gas and heating the solid St.

The inventors provided Si in a solid state in a reaction vessel,
By heating this Si and causing a so-called CVD reaction that decomposes the carbon source gas by electric discharge, heating, etc., silicon carbide with excellent crystallinity grows on the Si or on the substrate placed near it. I found out. This invention was made based on such knowledge.

St provided in the reaction vessel serves as a raw material for producing silicon carbide by CVD. Therefore, this Si may be in any form as long as it can react with the decomposed carbon source gas. That is, it can take various forms such as powder, granules, lumps, and plates. However, for the purpose of depositing silicon carbide on Si, SL serves as a raw material for SiC and also as a base.

A gas containing hydrocarbons is used as a raw material for C, which is the other element constituting silicon carbide. Thereby, silicon carbide with good crystallinity can be grown. Here, gases containing hydrocarbons include methane (CH4), ethane (C2H, ), propane (C3H8), ethylene (
C2H4), hydrocarbon gas itself such as acetylene (C2H2), or acetone (CHs COCHi),
Methyl alcohol (CH30H), ethyl alcohol (C2H,OH), propyl alcohol (CiH70
H) Butyl alcohol (C4H90H) Refers to an organic compound containing a hydrocarbon group such as acetaldehyde (C)l, CHO), and one or more of these can be used. These carbon source gases become carbon species such as C5CH%CH2, CH3 by decomposition,
It can be considered that these chemical species play an important role in the above CVD reaction.

In addition, in the present invention, B, AI, Ga, In, and TI are produced by supplying the following gases to the reaction vessel and reacting them together with the above gases.

Silicon carbide containing one or more elements among N, P, As, Sb, Bi, etc. can be produced. That is, B, AlGa, In, Tl, N as single gases
, P, As, Sb, Bi.

B2 Hb, Ba Hro, B2 as compound gas
0s, CH3BCI□, (CHiAIBr2)2, (CH3)2AICI.

[(CH3) s A l co 2 ,
Ga 2 H6, (CH3)s Ga, (CH3)2
GaBH4, (CHi)s I n, (CH3)i
T1. NH3, PHi, ASH3, N2 H4,
P209, CH-iAsBr2, CH3As
H2, (CHs) s A s s (CHi)
3B 1% (C2H5) 3B is S bH
s, CI CH2SbCl, CHI 5bH2, (CH
l) One or more of sSb and the like are used as a reactive gas. Here, B, AI, Ga.

Single substances such as In, Tl, P, As, Sb, and Bi are used after being gasified by resistance heating, electron beam heating, or the like. Further, for example, [(CM))s A 1]2 is a liquid at room temperature, but since it is volatile, it is used after being vaporized by heating.

Further, for example, B 2 Hb is a gas at room temperature, so it is used as is. The amount of gas containing the above elements to be supplied to the reaction vessel is not particularly limited, as it depends on the desired doping amount, the type of gas, the method of heating and decomposing the gas, etc.
- For installation, the atomic ratio of (impurities) / (carbon) is 10-5 ~
A range of 10-2 is preferred.

The base material for depositing silicon carbide is not particularly limited as long as it has a melting point equal to or higher than the temperature of the reaction atmosphere of the CVD reaction. The substrate as the base material is S
It may be installed near i or downstream of the flow of gas reacted on Si. When the precipitation reaction is short-term, silicon carbide grows as independent particles on the substrate, and silicon carbide powder can be obtained by collecting the particles.

When the precipitation reaction is carried out for a long time, the precipitated silicon carbide particles fuse and coalesce to form a uniform film and grow.

In addition, when using Si itself as a raw material installed in a reaction vessel as a base, silicon carbide particles,
Since a film can be formed, a bonded body of Si and silicon carbide can be obtained. In this case, since silicon carbide is generated by a chemical reaction on the Si surface, the bond between Si and silicon carbide is strong, and therefore a bonded body with excellent adhesion can be obtained.

Note that when single-crystal 81 is used as the raw material Si, silicon carbide can be epitaxially grown on single-crystal Si by appropriately adjusting conditions, and single-crystal silicon carbide can be obtained.

Next, the precipitation reaction of silicon carbide will be explained.

First, a gas containing the above-mentioned hydrocarbon as a carbon source is supplied to a reaction vessel in which Si as a raw material is installed. In this case, it is preferable to introduce hydrogen gas into the container together with the carbon source gas. This is because hydrogen gas has the role of a carrier gas for introducing the carbon source gas into the reaction vessel, and also has the effect of promoting the precipitation of silicon carbide by the action of hydrogen atoms generated by decomposition. Although the mixing ratio of carbon source gas and hydrogen gas is not particularly limited,
The preferable range varies depending on the type of carbon source gas.

However, generally (carbon source gas)/(hydrogen gas) -0,
It is preferable to set it as the range of 001-1.0. When using methane gas as a carbon source gas, (methane gas)
/(Hydrogen gas)-〇, silicon carbide with the best crystallinity can be grown in the range of 001 to 0.003.

Although heating of Si is necessary to cause the CVD reaction, the heating method is not particularly limited.

The heating temperature for Si is preferably in the range of 900 to 1400°C in order to precipitate silicon carbide with good crystallinity at a high precipitation rate. Note that the upper limit of 1400°C is
This takes into account the melting point of

Simultaneously with such heating of the Si, a decomposition reaction of the carbon source gas or the mixed gas of the carbon source gas and hydrogen gas supplied onto the Si is induced. The method of inducing the decomposition reaction is not particularly limited, and any method may be used as long as it can provide sufficient energy to decompose the gas using heat, electrons, light, or the like. In other words, methods commonly used in CVD reactions, such as a method that utilizes thermal decomposition using a hot filament (hot filament CVD), provide an electrode to which a positive potential is applied and conduct electrons to decompose and decompose gas. A method of promoting excitation (electron impact CVD), a method using plasma using microwave discharge or direct current discharge (plasma CVD), a method using laser irradiation (laser CVD), etc. can be applied.

Although the reaction pressure is a condition deeply related to the growth rate of silicon carbide, the appropriate range changes depending on other conditions, so it is not limited to a specific range. Generally, higher pressure increases the growth rate due to higher carbon concentration contributing to the reaction. In order to grow silicon carbide with good crystallinity,
It is necessary to set an appropriate pressure according to the method of synthesis reaction, for example, in the case of plasma CVD, the pressure
A range of 0 Torr is desirable.

In the reaction vessel, it is preferable to supply the carbon source gas or mixed gas at an appropriate flow rate and to discharge the gas in the vessel according to the flow rate to form a certain amount of gas flow.

This replenishes the raw material gas consumed by the reaction, and removes unnecessary gas components generated by the reaction (gas components that do not contribute to the growth of silicon carbide or are inconvenient for the growth of silicon carbide) out of the reaction vessel. Can be discharged. The gas flow rate in this case is appropriately determined depending on the synthesis method and the scale of the synthesis apparatus, and is not particularly limited.

Decomposition of carbon source gas in the gas phase for the precipitation of silicon carbide
The conditions for controlling the excitation and precipitation reaction on the substrate are not particularly limited, and the reaction conditions may be set according to each of the above-mentioned synthesis methods. For example, in the hot filament method, it is desirable to heat the filament to 2000° C. or higher. Also,
CVD using DC discharge requires a region on the arc discharge side compared to regular glow discharge. It is preferable to set it to a value equal to or higher than the voltage.

According to the present invention, as described above, solid Si is used as the Si source.
Using this method, silicon carbide powder, grains, and films with good crystallinity can be easily produced by a completely new method of generating CVD. In particular, by using solid Si itself as a raw material, a joined body of St and silicon carbide in which Si and silicon carbide are strongly bonded can be formed in a granular or film-like form. In addition, by using high purity carbon source gas and solid Si, high purity silicon carbide can be obtained.

(Example) Examples of the present invention will be described below.

Example 1 Silicon carbide was manufactured using the vapor phase growth apparatus shown in FIG. This vapor phase growth apparatus 1 includes a reaction vessel 2 made of quartz glass.
It is equipped with The reaction vessel 2 includes a gas supply port 3 connected to a gas supply device (not shown) for supplying raw material gas into the reaction vessel 2, and an exhaust device (not shown) for discharging unnecessary gas generated by the reaction. A discharge port 4 connected to a pipe (not shown) is provided. Furthermore, a molybdenum holder 6 for fixing the Si substrate 5 is disposed within the reaction vessel 2. A heater 7 is provided below the holder 6 to heat the Si substrate 5 and adjust the temperature to a predetermined temperature by being supplied with power from a power source (not shown). moreover,
A filament 8 made of tantalum is provided above the holder 6 to decompose the carbon source gas introduced into the reaction vessel 2 as a raw material gas. This filament 8
is fixed to a power supply jig 9 made of molybdenum, and is supplied with power via this power supply jig 9 from a power supply (not shown).

Silicon carbide was produced using such an apparatus according to the following procedure.

First, a Si disk with a diameter of 15 m5 was placed as the Si substrate 5 in the holder 6 inside the reaction vessel 2. Next, after evacuating the inside of the reaction vessel 2 to 10-' Torr, the filament 8 was
Methane/hydrogen volume ratio 0.1 while heating to 200°C
/99.9 mixed gas at a pressure of 60 Torr and a flow rate of 1
While flowing into the reaction vessel 2 at a rate of 50 cc/min, Si
The temperature of the filament 8 side of the base 5 was maintained at 1000°C. Note that at this time, the heater 7 was used as an auxiliary heating source for adjusting the temperature of the Si substrate 5. In this way, a CVD reaction was allowed to occur, and this reaction was continued for 10 hours. Thereafter, the supply of gas and the heating by the filament 8 and heater 7 were stopped.

When the Si substrate 5 was taken out and observed under a scanning electron microscope, it was confirmed that a -like film consisting of particles with a uniform diameter of 0.5 μm was formed over the entire surface. Next, this sample was forcibly broken along the thickness direction, and its cross section was observed with a scanning electron microscope, and as a result, it was confirmed that the film thickness was about 1 μm. On the other hand, when an X-ray diffraction test was conducted on this film, the diffraction peak was sharp, and the pattern and peak intensity ratio matched the powder X-ray diffraction data of β-type silicon carbide. From these reasons, S
It was confirmed that the film formed on the i-substrate was a polycrystalline film made of β-type silicon carbide particles with excellent crystallinity.

In addition, when the reaction was carried out under the same conditions as above except that ethane, propane, ethylene, acetylene, acetone, methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, and acetaldehyde were used as the carbon source gas, methane gas was Silicon carbide was produced as in the case.

Example 2 In this example, silicon carbide was manufactured using a vapor phase growth apparatus 11 shown in FIG. 2, which is similar to the apparatus used in Example 1. Second
In the figure, the same parts as in FIG. 1 are given the same reference numerals, and their explanation will be omitted. In this device, an average particle diameter of 40 mm is placed in the reaction vessel 2 on the upstream side of the gas flow, that is, on the gas supply port 3 side.
A silicon carbide container 13 charged with μm Si powder 12 is installed. On the downstream side of the gas flow of this container 13, Si
A molybdenum holder 15 for fixing the substrate 14 is provided, and a heating heater 1 is provided below this holder 15.
6 is provided.

Silicon carbide was produced using such an apparatus according to the following procedure.

First, a disk-shaped Si substrate 14 with a diameter of 15 mm was placed in a holder 15 inside the reaction container 2 . Next, reaction container 2
After exhausting the inside to 10-'Torr, set the filament 8 to 22
While heating to 00℃, the volume ratio of methane/hydrogen is 0.1/
99.9 mixed gas at a pressure of 60 Torr and a flow rate of 30
The flow was conducted into the reaction vessel 2 at a rate of 0 cc/min, and the temperature of the filament 8 side of the Si powder 12 was maintained at 1200°C. Further, the surface temperature of the Si substrate 14 was maintained at 950° C. by heating with the heater 16 . In this way, CVD
A reaction was allowed to occur and continued for 10 hours. Thereafter, the supply of gas and the heating by the filament 8 and heater 7.16 were stopped.

When the surface of the Si substrate 14 was observed with a scanning electron microscope and an X-ray diffraction test was performed, it was found that approximately 0.
．． It was confirmed that a film made of particles with a uniform particle size of 2 μm was formed, and that this film was a polycrystalline β-type silicon carbide film with excellent crystallinity. Furthermore, when X-ray diffraction was performed on the powder in the silicon carbide container 13 after the reaction, diffraction peaks of silicon carbide and Si were observed, confirming that a composite powder of silicon carbide and St was produced. Ta.

[Effects of the Invention] According to the present invention, it is possible to easily obtain silicon carbide powder, granules, and films of high purity with excellent crystallinity, and to produce silicon carbide in which a healthy film can be reliably obtained. method can be provided.

[Brief explanation of drawings]

1 and 2 are cross-sectional views showing a vapor phase growth apparatus for producing silicon carbide according to the present invention. 1.11; Vapor phase growth apparatus, 2; Reaction vessel, 5; Si substrate, 6, 15; Holder 7, 16; Heater 8; Filament, 12; Si powder, 14 HSi substrate applicant's agent Patent attorney Takehiko Suzue No. 1 Figure 2

Claims (1)

[Claims] A gas containing a hydrocarbon is supplied into a reaction vessel provided with solid Si as a raw material, and silicon carbide is precipitated in a vapor phase by simultaneously decomposing the supplied gas and heating the solid Si. A method for producing silicon carbide.