JP2570409B2 - Purification method of chloropolysilane - Google Patents

Description

The present invention relates to a method for purifying a higher chloropolysilane represented by the general formula Si _n Cl _{2n + 2} (n ≧ 2).

Chloropolysilane has recently gained importance as a raw material for producing semiconductor silicon.

Chloropolysilane can be directly thermally decomposed into epitaxial silicon or the like, but is also used as a silica source for optical communication having a high germanium doping rate. Further, chloropolysilane is further reduced to silane represented by Si _n H _{2n + 2} (n ≧ 2), which is used as a raw material for producing semiconductor silicon and amorphous silicon by thermal decomposition or the like. For example, when disilane Si ₂ H ₆ is used to form an amorphous silicon film by thermal decomposition or glow discharge decomposition, monosilane SiH ₄
In comparison with the above, the deposition rate of a film formed on a substrate is much higher, and the film has advantages such as excellent electrical characteristics. Have been.

[Conventional technology and problems]

Chloropolysilane heats silicide particles such as calcium silicon, magnesium silicon, or ferrosilicon or metal silicon particles and sends chlorine gas.
It is produced by chlorinating them. The chloropolysilane obtained by this method contains a large amount of impurities due to the raw materials and equipment used, and therefore must be rectified in order to be used as a semiconductor material. And rectification was repeated.

[Knowledge on problem solving]

The present inventors have pursued a simple and efficient method for purifying chloropolysilane, and as a result, have found that when chloropolysilane is brought into contact with activated carbon, impurities are efficiently removed.

〔The invention's effect〕

The present invention provides a method for purifying chloropolysilane, comprising contacting chloropolysilane represented by the general formula Si _n Cl _{2n + 2} (n ≧ 2) with activated carbon to remove impurities in the liquid.

The impurities to be removed in the present invention are B, P, Al, Fe, Co, Mn, C
r, Cu, Mg, Ti, V, C.

Chloropolysilane is Si ₂ Cl ₆ , Si ₃ Cl ₈ , Si ₄ Cl ₁₀ , etc. Is a series of homologues whose skeleton is the bond of In the present invention, the chloropolysilane may be in a state where the above homologues are individually separated, or may be a mixture of two or more of these dimers, trimers and the like. Further, it may contain by-product SiCl ₄ .

As the activated carbon used in the present invention, commercially available one can be used, and the shape thereof may be any shape such as a granular shape, a powdery shape, a fibrous shape, a sheet shape, and a honeycomb shape.

In order to contact chloropolysilane with activated carbon, the activated carbon to be used is packed in a layer in a column, and chloropolysilane is passed through the layered portion. Or any of these methods, such as a method of using these methods in combination. The temperature of the chloropolysilane at this time is preferably in the range of room temperature to 100 ° C. If the temperature is lower than room temperature, cooling equipment is required. If the temperature is higher than 100 ° C., the adsorption capacity of activated carbon is reduced and the efficiency of removal is reduced. The liquid supply speed is 0.5 SV.
A range of ~ 10 is preferred. The activated carbon to which the impurities have been adsorbed can be reused by treating it with hydrochloric acid, hydrofluoric acid, caustic soda, etc., and drying it.

The chloropolysilane from which impurities have been removed by the activated carbon treatment may be used as a product as it is, or the purity may be further increased by further distillation.

〔The invention's effect〕

According to the purification method of the present invention, impurities such as B, P, Al, Fe, Co, Mn, Cr, Cu, Mg, Ti, V, and C can be separated from chloropolychlorosilane with good selectivity. High-purity chloropolychlorosilane can be produced.

Further, in the present invention, since the contact treatment between activated carbon and chloropolysilane is performed, the treatment operation is extremely simple, and the purification process in the existing chloropolysilane production is greatly simplified.

〔Example〕

Example 1 A well-dried activated carbon (Kuraray Chemical P .; Kuraray Coal P
W), room temperature Si ₂ Cl ₆ , Si
₃ Cl ₈ , Si ₄ Cl ₁₀ , and their mixtures were fed at a feed rate of 0.1 to 2 l / h.
The liquid was supplied at an r / SV ratio of [liquid flow rate (m ³ ) / filled volume (m ³ )] of 0.5 to 10.

After passing through the column, the content of impurities in the chloropolysilane discharged from the column was analyzed. Table 2 shows the results.

As is clear from Table 2, the impurities of B, P, Al, Fe, Co, Mn, Cr, Cu, Mg, Ti, V, and C were separated at a high removal rate over a very wide range of SV ratio. ing.

Example 2 Instead of petroleum coke-based activated carbon (Kuraray Coal PW) used in Example 1, activated carbon of palm, wood chip, or coal coke was used and the SV ratio was fixed at 2, except that the SV ratio was fixed at 2. Activated carbon treatment was performed in the same manner, and the effect of removing impurities from each of the above chloropolysilanes for each type of activated carbon was examined.Both activated carbon treatments showed that B, 0.0001 ppm or less, P, 0.001 ppm Below, Al, Fe, C
o, Mn, Cr, Cu, Mg, Ti, V and C
It was 0.1 ppm or less. As is clear from these results, the treatment method of the present invention can achieve a high impurity removal effect even when the type of activated carbon is changed.

Example 3 The SV ratio was fixed at 2 and the temperature of chloropolysilane was 20, 50,
Activated carbon treatment was performed in the same manner as in Example 1 except that the temperature was set to 100 ° C., and the effect of removing impurities from the chloropolysilane at each liquid temperature was examined. Table 3 shows the results. As is clear from the above results, the treatment method of the present invention achieves a high impurity removing effect in any of the above.

Claims (1)

(57) [Claims] 1. A method for purifying chloropolysilane, comprising contacting chloropolysilane represented by the general formula Si _n Cl _{2n + 2} (n ≧ 2) with activated carbon to remove impurities in the liquid.