JPH0688773B2 - Method for producing hexachlorodisilane - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing hexachlorodisilane.

More specifically, it relates to a method for obtaining hexachlorodisilane by subjecting chloropolysilane (Si _n Cl _{2n + 2} , n ≧ 3) to chlorinolysis and lowering.

2. Description of the Related Art In recent years, with the development of the electronics industry, the demand for silicon for semiconductors such as polycrystalline silicon or amorphous silicon has rapidly increased. Trichlorosilane, silicon tetrachloride, and monosilane are mainly used as raw materials for the production of silicon for semiconductors. On the other hand, utilization of higher chlorinated silicon has been developed, for example, production of amorphous silicon or polycrystalline silicon by thermal decomposition of SinCl _{2n + 2} (n is a number of 2 or more) (Belgium Patent No. 889523), and further hexachlorodisilane. Production of disilane by reduction (Journal of the Chemical Physics (J.Chem.Phy
s.) vol.22, P939 (1954)), (Journal of Inorganic and Nuclea Chemistry (J.Inorg.Nu
cl.Chem.) vol.25, P307 (1963)) and the like.

When disilane Si ₂ H ₆ is used to form an amorphous silicon film by chemical vapor decomposition (CVD) or glow discharge decomposition (GD), the deposition rate of the film formed on the substrate is higher than that of monosilane SiH _4. Is much larger, and the film has advantages such as excellent electrical characteristics, and it is expected that there will be a significant increase in demand as a raw material for semiconductors for solar cells in the future (JP-A-56-83929). .

Conventionally, hexachlorodisilane has been obtained by chlorinating silicon or a silicon alloy with chlorine. However, in this case, since a considerable amount of silicon tetrachloride and higher chlorides than octachlorotrisilane are unavoidably produced as a by-product, the yield of the target hexachlorodisilane is low. Further, although it is possible to treat the higher chloride as it is with alkaline water or the like and discard it, in that case, there is a drawback that the production cost is increased because a disposal treatment facility is provided.

Furthermore, higher chlorides higher than octachlorotrisilane are
A by-product solid, which is presumed to be a silico-oxalic system, is easily formed.However, since the solid is a substance that is extremely sensitive to heat or shock, it is extremely ignited and burned violently even with a slight shock. Since it is a dangerous and troublesome substance, it has a big safety problem.

Problems to be Solved by the Invention When chlorinating a metal-silicon alloy or silicon to obtain hexachlorodisilane, chloropolysilane (Si _n Cl
When chlorinating and decomposing _{2n + 2} n ≧ 3), it was difficult to eliminate clogging troubles in the equipment, maintain high operation and obtain hexachlorodisilane in high yield.

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted extensive studies to solve the above problems, and completed the present invention.

That is, the method for producing hexachlorodisilane according to the present invention is carried out at a reaction temperature of 250 to 450 ° C. in order to produce hexachlorodisilane by lowering chloropolysilane (Si _n Cl _{2n + 2} , n ≧ 3) with chlorine in a fluidized bed. Characterized by using inert particles as a fluid medium under the conditions, using silicon tetrachloride vapor as a fluid gas, and introducing chlorine into a fluidized bed separately from the silicon tetrachloride vapor which is a fluid gas for chlorination. Is a method for producing hexachlorodisilane.

DESCRIPTION OF THE DRAWINGS The present invention will be described with reference to the drawings.

FIG. 1 shows an example of a method for producing hexachlorodisilane according to the present invention.

Silicon tetrachloride is introduced through a pipe and supplied to the evaporator. Here, the entire amount of silicon tetrachloride is evaporated to form steam. The silicon tetrachloride vapor is introduced from the lower part of the fluidized bed through a dispersion plate through a pipe.

The fluidized bed is filled with 60 mesh pass alumina, and is controlled at 350 ° C. by a heat transfer heater.

Chloropolysilane (Si _n Cl _{2n + 2} , n ≧ 3), which is a raw material, and chlorine are separately introduced into the bed from the lower part of the side surface of the fluidized bed by piping.

The reaction gas reduced in the fluidized bed is discharged to the outside of the bed through a pipe.

Examples of chloropolysilane used in the present invention include octachlorotrisilane (Si ₃ Cl ₈ ), decachlorotetrasilane (Si ₄ Cl ₁₀ ), dodecachloropentasilane (Si ₅ Cl ₁₂ ),
There are tetradecachlorohexasilane (Si ₆ Cl ₁₄ ) and the like, and these can be used alone or as a mixture.

In the present invention, when the reaction temperature is less than 250 ° C., the decomposition rate of chloropolysilane (Si _n Cl _{2n + 2} , n ≧ 3) is low and the production efficiency is poor, and when it exceeds 450 ° C., the decomposition rate is high but the target hexachlorodisilane. Selection rate is poor. Also, when introducing silicon tetrachloride and chlorine used for the fluidized gas into the fluidized bed, if they are mixed and introduced first, the silicon tetrachloride is decomposed, and a phenomenon of blocking the fluidized gas dispersion plate of the fluidized bed occurs, By introducing them separately into the fluidized bed, the trouble of clogging can be avoided. In addition, the use of inert particles such as alumina as the fluidizing medium allows the chloropolysilane (Si _n Cl 2
_{Even if 2n + 2} , n ≧ 3) is the residual liquid in the kettle, it is possible to operate without blocking the reactor.

Effects By carrying out the method of the present invention, it is possible to produce useful hexachlorodisilane from chloropolysilane, which is difficult to handle without any use, and is industrially extremely valuable.

Example-1 A fluidized bed having a diameter of 40 mm and a height of 500 mm is filled with 150 cc of 100 mesh to 250 mesh of alumina, and 12.0 kg / hr of silicon tetrachloride is preheated to 350 ° C. through an evaporator and introduced into the lower part of the fluidized bed. On the other hand, chlorine is 100 Nl / h through the pipe with an inner diameter of 8 mm from the side of the fluidized bed.
Supply. Further, 3.0 kg of octachlorotrisilane was supplied per hour from separate pipes having an inner diameter of 8 mm provided on the side surface of the fluidized bed. The reaction temperature in the fluidized bed was heated by an electric heater from the side of the fluidized bed so as to keep it at 350 ° C. After 4 hours, when the operation seems to have reached a steady state, the reactor outlet gas was condensed in a condenser, and 12.7 kg of silicon tetrachloride, 1.1 kg of hexachlorodisilane, and 1.4 kg of octachlorotrisilane were obtained every hour. .

Example-2 Under exactly the same conditions as in Example-1, mixed octachlorotrisilane 63%, decachlorotetrasilane 21% and other higher order chloropolysilane 16% mixed chloropolysilane of 3.0% per hour instead of octachlorotrisilane. When it was supplied to the fluidized bed and the fluidized bed outlet gas was condensed, 12.9 kg / hour of silicon tetrachloride,
0.8 kg hexachlorodisilane 1.3 kg octachlorotrisilane, 0.1 kg other chloropolysilane were obtained.

Comparative Example-1 The fluidized bed of Example-1 was mixed with chlorine tetrachloride and chlorine discharged from the evaporator, the temperature was kept at 350 ° C., and the mixture was introduced into the reactor. After a lapse of time, the operation was obstructed and the operation had to be stopped.

[Brief description of drawings]

FIG. 1 is a flow sheet showing an example of the method for producing hexachlorodisilane of the present invention.

Claims (1)

[Claims] 1. A method for producing hexachlorodisilane by lowering chloropolysilane (Si _n Cl _{2n + 2} , n ≧ 3) with chlorine in a fluidized bed to produce hexachlorodisilane at a reaction temperature of 250 to 450 ° C.
Hexachloro characterized in that inert particles are used as a fluid medium, silicon tetrachloride vapor is used as a fluid gas, and chlorine is independently introduced into the fluidized bed separately from the fluid gas silicon tetrachloride vapor to be chlorinated. Method for producing disilane.