JPH0352408B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention provides Si _l Cl 2l+ ₂ from higher chlorinated silicon represented by the general formula SikCl _2k+2 (k is an integer of 2 or more).
(l is an integer of 1 or more such as l〓k). In recent years, with the development of the electronics industry, the demand for silicon for semiconductors such as polycrystalline silicon or amorphous silicon has increased rapidly. Chlorinated silicon Si _l Cl _2l+2 () (integer n≧1) represented by the formula () has recently become particularly important as a raw material for producing silicon for semiconductors. Of course, these can be thermally decomposed as they are to produce amorphous silicon etc. (Belgian Patent Specification No. 889523), but they can be further reduced to form polysilane represented by the formula (), Si _o H _{2o +2} ( ) (an integer where n≧1) This is usually thermally decomposed to produce silicon for semiconductors. However, polysilanes, especially disilane Si ₂ H ₆
When forming an amorphous silicon film by thermal decomposition or glow discharge decomposition, the deposition rate of the film formed on the substrate is much higher than that of monosilane _SiH4 , and the film has excellent electrical properties. It is expected that demand will increase significantly in the future as a raw material for semiconductors for solar cells and photosensitive drums (Japanese Unexamined Patent Publication No. 83929/1983). Conventionally, methods for producing chlorinated silicon, such as hexachlorodisilane itself, are well known, and are usually made by chlorinating particles of an alloy of metal and silicon, such as calcium silicon, magnesium silicon, or ferrosilicon, at high temperatures, or by chlorinating silicon particles themselves. This is done by chlorination at high temperatures (US Pat. No. 2,602,728, US Pat. No. 2,621,111). However, in this case, it is difficult to selectively produce only the target chlorinated silicon, such as hexachlorodisilane, and usually a considerable amount of silicon tetrachloride (n = 1 in general formula ()) in addition to hexachlorodisilane is difficult to produce. , octachlorotrisilane (also n=3) and higher chlorides (hereinafter, those with n≧3 are simply referred to as higher chlorides)
It was inevitable that there would be a considerable amount of side effects. In particular, the production of large amounts of higher chlorides higher than octachlorotrisilane not only reduces the yield of the target hexachlorodisilane, but also makes disposal difficult and impairs operational safety. (The higher chloride easily forms a white solid that can ignite on impact in the presence of water.) Conventionally, regarding higher chlorinated silicon, for example, a disproportionation reaction as shown in the following formula is known. (J.Inorg.Nucl.Chem.)
vol 26 ． p409−444 (1964)). ) 4Si ₂ Cl ₆ →Si ₅ Cl ₁₂ +3SiCl ₄ ) 5Si ₂ Cl ₆ →Si ₆ Cl ₁₄・SiCl ₄ +3SiCl ₄ (→Si ₆ Cl ₁₄ +4SiCl ₄ ) ) 3Si ₃ Cl ₈ →Si ₅ Cl ₁₂ +2Si ₂ Cl ₆ ) 15Si ₃ Cl ₈ →6Si ₆ Cl ₁₄・SiCl ₄ +3SiCl ₄ (→6Si ₆ Cl ₁₄ +9SiCl ₄ ) All of the above reactions use N(CH ₃ ) ₃ as a catalyst,
This is a low-temperature liquid phase reaction that uses amines such as (CH ₃ ) ₃ N·HCl and (CH ₃ ) ₃ N·BCl ₃ . Therefore, by using the above reaction, for example, unnecessary octachlorotrisilane Si ₃ Cl ₈ can be converted into useful hexachlorodisilane.
It should be possible to convert it into Si ₂ Cl ₆ or silicon tetrachloride SiCl ₄ . However, the above-mentioned disproportionation reaction using an amine catalyst has the disadvantage that the conversion rate is low and that the amine compound serving as the catalyst must be separated and removed from the product liquid. As a result of intensive studies in view of the above points, the present inventors have unexpectedly found that higher chlorinated silicon can be converted into other desired chlorinated silicon by heat-treating it in a gaseous state at high temperature in the absence of a catalyst. They discovered that it is possible to do this, and completed the present invention. That is, the present invention uses higher chlorinated silicon represented by the general formula () Si _k Cl _2k+2 () (k is an integer of 2 or more) as a raw material, and heats it alone or in the presence of a diluent at 200°C. 1000
Heat treatment at ℃ to convert at least a part of it into another chlorinated silicon different from () represented by the general formula () Si _l Cl _2l+2 () (l is l〓k, an integer of 1 or more) Chlorinated silicon Si _l characterized by
It consists in a method for producing Cl _2l+2 . The present invention will be explained in detail below. The higher chlorinated silicon that is the raw material in the present invention is represented by the general formula () Si _k Cl _2k+2 () (k is an integer of 2 or more), and includes, for example, hexachlorodisilane, octachlorotrisilane, decachlorotetra Examples include silane. Of course, these can be obtained by any method, but for example, as mentioned above, particles of alloys of metal and silicon, such as calcium silicon, magnesium silicon, or ferrosilicon, are chlorinated at high temperature. or from the product obtained by chlorinating the silicon particles themselves at high temperatures, the desired chlorinated silicon, e.g.
Highly chlorinated silicon having a higher boiling point than silicon tetrachloride, hexachlorodisilane, etc. separated by means such as distillation can be preferably used. Further, it goes without saying that the higher chlorinated silicon may be used alone or as a mixture. The present invention uses the above-mentioned higher chlorinated silicon as a raw material, and uses it alone or in the presence of a diluent to
Another chlorinated silicon different from (), which is heat treated at ℃ to 1000℃ and at least a part thereof is expressed by the general formula () Si _l Cl _2l+2 () (l is l〓k, an integer of 1 or more) This will transform it into If the heat treatment temperature is less than 200°C, almost no conversion of higher chlorinated silicon will take place, and if it exceeds 1000°C, chlorine gas and metallic silicon will be generated due to the decomposition of higher chlorinated silicon, which is undesirable. . If the heating temperature is within the above range, the higher the heating temperature, the higher the conversion production rate to silicon tetrachloride SiCl ₄ , while the lower the heating temperature, the higher chlorinated silicon increases. When the purpose is to produce silicon, the temperature is preferably 300°C to 700°C. In particular, when producing hexachlorodisilane Si ₂ Cl ₆ from octachlorotrisilane Si ₃ Cl ₈ with good yield, the temperature is preferably 400°C to 600°C. The structure of the converter for carrying out the present invention is such that the heating treatment operation of the raw material gas can be carried out effectively, and it is equipped with cooling and/or heating means, so that the treatment temperature (reaction temperature) can be adjusted to the desired temperature. Any type, such as a tube type or a stirred bed type, may be used as long as it can be controlled within a certain range. Note that the heating means is not particularly limited, and electric heating, a heating medium such as diphenyl, or the like may be used. For example, in the case of a tubular reactor, this is an empty column (empty tube).
It may be used as it is, or it is preferable to fill it with a filler such as α-alumina beads, Raschig rings, Burl saddle rings, etc. to make the heat exchange operation more effective. In an embodiment of carrying out the reaction of the present invention, the raw material higher chlorinated silicon (which is usually liquid or solid at room temperature) may be preheated to about the conversion temperature using a preheater or the like and then supplied to the converter. Alternatively, the higher chlorinated silicon may be supplied as a liquid to a converter maintained at a high temperature, and the heating and conversion reaction of the higher chlorinated silicon may occur in the converter. Since the above conversion reaction is an exothermic reaction, it is necessary to supply a certain amount of heat, especially at the beginning of the reaction. Therefore, the converter may be of a self-heat exchange type, and the raw high-grade chlorinated silicon liquid and the raw high-temperature gas are brought into direct contact through the converter tube wall, and heat recovery may be performed or preferably cooling may be performed. Silicon tetrachloride as a diluent may be sprayed into the converter, or the raw material high grade chlorinated silicon may be diluted with silicon tetrachloride etc. beforehand and supplied to the converter (in this case, the diluent may be sprayed into the converter). It also has the effect of improving the fluidity of higher chlorinated silicon and making it easier to handle). In addition, other diluents that are inert to the reaction system, such as chlorofluorocarbons, methylene chloride, and silicone oil, can also be used. Further, in order to keep the reaction rate within a controllable range and accurately control the reaction heat, the above conversion reaction may be carried out in an atmosphere of an inert gas such as helium, neon, argon, xenon, nitrogen, or the like. Note that the conversion reaction rate is very fast, so it takes 1 second to
The conversion reaction is completed in a reaction time of about 100 seconds (in the case of a continuous flow reaction, the average residence time based on the empty column). After the reaction is completed, the generated gas, which has been converted into chlorinated silicon different from the raw material high chlorinated silicon, is a composition consisting of various chlorinated silicones including the desired chlorinated silicon (including the unreacted raw material high chlorinated silicon). The desired chlorinated silicon can be easily recovered by condensing it and separating it by distillation. According to the present invention, chlorinated silicon such as silicon tetrachloride and/or desired higher chlorinated silicon can be produced using higher chlorinated silicon as a raw material much more easily and with higher yield than when using known methods. Is possible. In addition, the higher chlorinated silicones that are part of the conversion product polymerize and deactivate each other,
It becomes a substance that is safe to handle (for example, a pot residue component in the examples described later) and can be easily disposed of. Hereinafter, the present invention will be specifically explained with reference to Examples. Example 1 A 100 mmφ*980 mm quartz glass tube filled with α-alumina beads with an average particle size of 5 mm was used as a converter, and the temperature was set in advance at 500°C. The raw material, high chlorinated silicon Si ₃ Cl ₈ 2.7Kg, is used as a diluent.
SiCl ₄ diluted to 6.3Kg using a metering pump.
The material was supplied to the converter at a rate of 0.15 kg/min, and the conversion reaction was carried out for 60 minutes under an argon gas atmosphere. Note that the average residence time based on the sky tower was 8 seconds. The produced gas was cooled to about 0°C, and 9.0 kg of produced condensate was collected. Next, the resulting condensate was simply distilled under normal pressure.
6.4Kg of SiCl ₄ was obtained, and further under reduced pressure (125
2.1Kg of Si ₂ Cl ₆ by simple distillation at
0.1 kg of pot residue containing 0.2 kg of Si ₃ Cl ₈ and 0.2 kg of Si ₄ Cl ₁₀ was obtained. In other words, 71% (based on Si atoms) of the raw material Si ₃ Cl ₈
This means that it was converted and recovered to Si ₂ Cl ₆ . Comparative Example 1 A 200ml round bottom flask equipped with a stirrer was used as a converter, and the raw material high grade chlorinated silicon was added to it.
24 g of Si ₃ Cl ₈ was charged. Next, the converter was cooled to -196°C in a liquid nitrogen bath, the system was evacuated, and a small amount of trimethylamine (about 1 ml) was injected in gaseous form as a catalyst. The temperature of the converter was raised to room temperature, and after leaving it for 3 hours, the contents of the converter were distilled under reduced pressure (several mmHg). The distillate gas was cooled to about 0° C. and the resulting condensate containing 11.5 g of Si ₂ Cl ₆ was collected. In addition, 12.5 g of white crystalline material was obtained as residue from the pot. The yield of the obtained Si ₂ Cl ₆ relative to the charged Si ₃ Cl ₈ was 44%.
(based on Si atoms). Example 2 An experiment similar to Example 1 was conducted except that the conversion temperature was 400°C. The results are shown in Table 1. Example 3 In Example 1, Si ₃ Cl ₈ 1.9 was used as the charging raw material.
Kg and Si ₅ Cl ₁₂ or more higher chlorinated silicon mixture 0.7Kg
The same experiment as in Example 1 was conducted except that a mixed solution was used in which SiCl ₄ (108 g as Si) was diluted with 0.63 Kg of SiCl 4 as a diluent. The results are shown in Table 1. Example 4 An experiment similar to Example 3 was conducted except that the reaction temperature was 400°C. The results are shown in Table 1. 【table】

Claims (1)

[Claims] 1. Higher chlorinated silicon represented by the general formula () SikCl _2k+2 (k is an integer of 2 or more) () is used as a raw material, and it is heated at 200°C to 1000°C alone or in the presence of a diluent.
Heat treated at ℃ and at least a part of it converted into the general formula () Si _l Cl _2l+2 (l is an integer of 1 or more such that l≠k)
Chlorinated silicon Si _l characterized by being converted into another chlorinated silicon different from () represented by ()
Method for producing Cl _2l+2 . 2. The method according to claim 1, wherein the chlorinated silicon Si _l Cl _2l+2 is SiCl ₄ . 3. The method according to claim 2, wherein the chlorinated silicon Si _l Cl _2l+2 is obtained as a chlorinated silicon composition containing SiCl ₄ . 4. The method according to claim 1, wherein the chlorinated silicon Si _l Cl _2l+2 is Si ₂ Cl ₆ . 5. The method according to claim 4, wherein the chlorinated silicon Si _l Cl _2l+2 is obtained as a chlorinated silicon composition containing Si ₂ Cl ₆ . 6. The method according to any one of claims 1 to 5, wherein the raw material higher chlorinated silicon SikCl _2k+2 is Si ₃ Cl ₈ . 7. The method according to claim 6, wherein the raw material higher chlorinated silicon SikCl _2k+2 is a higher chlorinated silicon composition containing Si ₃ Cl ₈ .