JPH0417891B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention is based on the general formula SiH _x F _4-x (where x=1 to 3
(an integer of ). More specifically, the present invention relates to an improved method for producing partially fluorinated silanes using a balogen exchange method. Partially fluorinated silane has recently attracted attention as a material and gas for forming fluorinated amorphous silicon thin films. (Prior art and problems to be solved by the invention) As a method for producing partially fluorinated silanes, the so-called halogen exchange method involves fluorinating a corresponding partially chlorinated silane with a fluorinating agent that is a metal fluoride. The law is known. Known fluorinating agents used in this case include SbF ₃ , AsF ₃ , TiF ₄ , SnF ₄ , CuF ₂ and ZnF ₂ . A common method for reacting these solid fluorinating agents with partially chlorinated silanes is to bring the fluorinating agent into contact with gaseous or liquid partially chlorinated silanes. However, this method has the disadvantage that the reaction yield is low, side reaction products are likely to be produced, and the purity of the partially fluorinated silane obtained is low. A method is also known in which a fluorinating agent is suspended in a solvent such as ether or pentane and reacted with a partially chlorinated silane (Japanese Patent Application Laid-Open No. 167693/1983). however,
Although this method improves the reaction yield considerably compared to the above method, it is not in a satisfactory state for industrial practical use, and in terms of quality, it is not possible to completely replace chlorine with fluorine in the product. Decomposition products such as intermediates (chlorofluorosilanes), silicon tetrafluoride (SiF ₄ ), and monosilane (SiH ₄ ) are present.
There was a problem that the purity of the product was reduced. In addition, the present inventors previously invented and filed a patent application for a method for producing fluorosilanes in which a fluorinating agent is suspended in anisole and the reaction is carried out (Japanese Patent Application Laid-Open No. 151016/1983). This method uses SiHF ₃ , SiH ₂ F ₂ ,
It is very effective in producing partially fluorinated silanes such as SiH ₃ F, and products can be obtained in high yield and purity. However, the only drawback of this method is that the solvent, anisole, is relatively expensive;
An even cheaper solvent was desired. (Means and effects for solving the problems) In view of the above problems, the present inventors have conducted extensive studies on a method for producing partially fluorinated silane that has a high reaction yield, high purity, and is inexpensive. As a result, if a partially chlorinated silane is fluorinated using a specific solvent and the fluorinating agent is suspended in this solvent,
The inventors have discovered that the above object can be achieved and have completed the present invention. That is, the present invention produces a corresponding partially fluorinated silane by reacting a partially chlorinated silane represented by the general formula SiH _x Cl _4-x (where x = an integer of 1 to 3) with a fluorinating agent. In the method of
The fluorinating agent is suspended in a solvent having high solubility for the partially chlorinated silane and the metal chloride produced by the reaction, and then the fluorinating agent and the partially chlorinated silane are reacted. A method for producing a partially fluorinated silane, in particular a method for producing a partially fluorinated silane, in which the solvent is an alkyl chloride represented by the general formula CnH _2o+1 Cl (where n = an integer of 3 to 8), benzene, toluene, xylene, ethylbenzene, or chlorobenzene. This method uses one or more types. The present invention will be explained in more detail. The fluorinating agents used in the present invention include antimony trifluoride (SbF ₃ ), arsenic trifluoride (AsF ₃ ),
Titanium tetrafluoride (TiF ₃ ), tin tetrafluoride (SnF ₄ ),
Conventionally known fluorinating agents such as metal fluorides such as copper fluoride (CuF ₂ ) and zinc fluoride (ZnF ₂ ) can be used, but ZnF ₂ is preferred from the viewpoint of cost and ease of handling.
It is preferable to use Partially chlorinated silanes and partially fluorinated silanes are
Since both have the property of being easily hydrolyzed in the presence of water, it is necessary to sufficiently remove water from the solvent and fluorinating agent used in the reaction as well as the reaction equipment. For example, fluorinating agents should be used at 200%
In order to obtain a product with a high yield, it is preferable to completely dehydrate the product by heat treatment at ℃ for about 4 hours. As the solvent used in the present invention, it is necessary to use a solvent that has low solubility for the fluorinating agent and partially fluorinated silane, and high solubility for partially chlorinated silane and the metal chloride produced by the reaction. There is. The solubility of the fluorinating agent or metal chloride produced by the reaction can be determined by dissolving these in a solvent to saturation and measuring the amount of metal ions in the solvent, or by measuring the amount of the fluorinating agent or metal chloride dissolved in this solvent. This can be determined by extracting it with water and measuring the fluorine ions or chlorine ions. The solubility of partially chlorinated silanes or partially fluorinated silanes in solvents can be measured by dissolving them in the solvent to a saturation level, then adding water to fix it as silica, and quantifying the silicon content. However, it can also be determined using solubility parameters. That is, a solvent whose solubility parameter is close to that of partially chlorinated silane and far from that of partially fluorinated silane, specifically, one whose solubility parameter is around 9, satisfies the above conditions and is preferable. Specific solvents that meet the above two conditions include alkyl chlorides represented by the general formula CnH _2o+1 Cl (where n = an integer of 3 to 8), Hensen, toluene, xylene, ethylbenzene, chlorobenzene, etc. It will be done. Specific examples of alkyl chloride include n-propyl chloride, isopropyl chloride, n-butyl chloride, isobutyl chloride, and s-chloride.
Butyl, t-butyl chloride, n-pentyl chloride, n-hexyl chloride, etc. can be mentioned. Xylene has three isomers: ortho, meta, and para, and any one of them may be used, or a mixture thereof may be used. In the present invention, it is not clear why good results can be obtained by using the above-mentioned solvents, but this is probably due to the following reasons. In other words, the reaction is considered to be a solid-liquid reaction between the partially chlorinated silane dissolved in the solvent and the solid fluorinating agent, but the solvent dissolves the metal chloride generated on the surface of the fluorinating agent by the reaction. However, it is thought that the reason for this is that the surface of the fluorinating agent is kept active at all times, and that the solvent disperses the heat generated by the reaction to prevent the reaction temperature from rising. Therefore, from that point of view,
The slurry concentration of the fluorinating agent suspended in the solvent is preferably low, and in practical terms is about 5% by weight (hereinafter simply referred to as %), or at most about 50%. The reaction temperature is determined in consideration of the reactivity of halogen exchange or the thermal stability of the partially fluorinated silane produced, but it is usually carried out at -10 to 40°C. If the reaction temperature is too high, side reaction products are likely to be produced, thus reducing the purity of the product. Conversely, if the reaction temperature is too low, the reaction rate of the halogen exchange reaction will decrease. (Examples) Hereinafter, the present invention will be specifically explained using Examples and Comparative Examples. Example 1 100 g of zinc fluoride (ZnF ₂ ) that had been dehydrated at 200°C for 4 hours was placed in a glass flask equipped with a stirrer (No. 1) equipped with a reflux condenser.
ml of n-butyl chloride (n-C ₆ H ₉ Cl). After the lid of the flask was completely sealed, the flask was immersed in an ice water bath to maintain the reaction temperature at 0° C., and a refrigerant was passed through a reflux condenser to prevent evaporation of n-butyl chloride as a solvent. Next, after sufficiently replacing the inside of the system with nitrogen gas,
Add 0.5g/silane trichloride (SiHCl ₃ ) while stirring.
Feed a total of 50g into the flask at a speed of min.
After the feed was completed, the reaction was continued for an additional 2 hours. During the reaction, add 50ml of nitrogen gas as a carrier gas.
It was fed into the flask at a flow rate of min. The reaction product gas and carrier gas generated from the flask were collected in a liquid nitrogen trap after removing impurities in a dry ice-acetone trap. Furthermore, the inside of the liquid nitrogen trap was evacuated using a vacuum pump to remove the nitrogen gas used as a carrier gas. The amount recovered was 28g (yield 88%), which was IR
It was identified as silane trifluoride (SiHF ₃ ) from the absorption chart. In addition, this trifluorosilane can be used in gaseous form.
When the chlorine concentration in trifluorosilane gas was measured after being aerated into the HF aqueous solution, it was found to be only 110 ppm.
The purity of the product was very high. Examples 2-4 In exactly the same manner as in Example 1, except that the solvents shown in Table 1 were used instead of n-butyl chloride,
Trifluorosilane was manufactured. The results are shown in Table 1, and in all cases, high yield and high purity products were obtained.

[Table] Examples 5-6 Silane trifluoride was produced in exactly the same manner as in Example 1, except that the reaction temperature was maintained at the temperature shown in Table 2. The results are shown in Table 2, and in all cases high yield and high purity products were obtained.

[Table] Comparative Example 1 100 g of zinc fluoride (ZnF ₂ ) was packed into a glass column with an inner diameter of 30 mm, and dehydrated at 200° C. for 4 hours under a nitrogen gas flow. After that, the temperature of the column is
Add trichlorosilane to this column while maintaining it at 60°C.
A total of 50 g was fed at a rate of 0.5 g/min. still,
Silane trichloride was fed as a carrier gas by bubbling nitrogen gas into liquid silane trichloride at a flow rate of 50 ml/min. The reaction product gas and carrier gas were collected in a liquid nitrogen trap after removing impurities in a dry ice-acetone trap. Furthermore, the inside of the liquid nitrogen trap was evacuated using a vacuum pump to remove the nitrogen gas used as a carrier gas. The recovered substance was identified as trifluorosilane from the IR chart, but the amount recovered was small at 13g, and the yield was low at 41%. In addition, the obtained trifluorosilane was aerated into an HF aqueous solution in the same manner as in Example 1, and then the chlorine concentration was measured, and it was found to be 1.52%.
The results showed that the purity was very high and the purity was low. Comparative Examples 2 to 4 Silane trifluorides were produced in exactly the same manner as in Example 6, except that the solvents shown in Table 3 were used instead of n-butyl chloride. The results are shown in Table 3, and the yield and purity were both very low.
Furthermore, when acetonitrile was used as the solvent, the yield was better than other methods, but as a result of IR analysis of the product, it was found that a considerable amount of silicon tetrafluoride (SiF ₄ ) was mixed in. Therefore, the purity was low.

【table】

[Table] _Example 7 Silane difluoride (SiH _{2 F 2} ) was manufactured. Product yield is 30g (yield 89
%), which was identified as silane difluoride from the IR adsorption chart. Furthermore, when this silane difluoride was absorbed in gaseous form into an HF aqueous solution and the chlorine concentration in the gas was measured, it was only 150 ppm, indicating that the purity of the product was extremely high. (Effects of the Invention) As explained in detail above, the present invention uses a fluorinating agent suspended in a solvent to produce a partially fluorinated silane through a fluorination reaction using a halogen exchange method. However, according to the method of the present invention, the fluorination reaction is completely carried out under mild conditions, so the amount of by-products produced is extremely small, and therefore the fluorination reaction is completely carried out under mild conditions. A highly purified product that is extremely suitable as a material for amorphous silicon thin films can be obtained. In addition, the reaction yield is very high and the cost of the solvent is low, making efficient production possible.

Claims (1)

[Claims] 1 General formula SiH _x Cl _4-x (where x = an integer from 1 to 3)
In a method for producing a corresponding partially fluorinated silane by reacting a partially chlorinated silane represented by the formula with a fluorinating agent, the partially chlorinated silane has low solubility in the fluorinating agent and the partially fluorinated silane, and and partial fluorination, which is characterized by suspending a fluorinating agent in a solvent that has high solubility for the metal chloride produced by the reaction, and then reacting the fluorinating agent with a partially chlorinated silane. Method of manufacturing silane. 2 The solvent has the general formula CnH _2o+1 Cl (where n = 3 to 8
alkyl chloride, benzene,
The method according to claim 1, wherein one or more of toluene, xylene, ethylbenzene, and chlorobenzene is used.