JPH0343204B2 - - Google Patents

Description

Detailed Description of the Invention The present invention relates to a method for producing higher chlorinated silicon by chlorinating silicon particles or silicon alloy particles (hereinafter referred to as metal particles). The present invention relates to a method for continuously producing higher chlorinated silicon using a series of reactors that are arranged so that they can be switched and used in series, depending on the degree of chlorination of metal particles.

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.

Higher chlorinated silicon represented by the formula (), SinCl _2o+2 (n≧2) (), 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. (Belgium Patent Specification No. 889523), but they can be further reduced to form polysilane represented by the formula (), SinH _2o+2 (n≧ 2) () This is usually thermally decomposed to produce silicon for semiconductors.

Thus, polysilanes such as disilane Si ₂ H ₆
When an amorphous silicon film is formed 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. Demand is expected to increase significantly in the future as a raw material for semiconductors for solar cells (Journal of American Chemical Society (JACS) 69, 2692 (1947), JP-A-Sho). 56−
Publication No. 83929).

The method for producing higher chlorinated silicon SinCl _2o+2 (n≧2) itself is known and is usually carried out by chlorinating silicon particles or silicon alloy particles at high temperatures, or by chlorinating silicon particles themselves at high temperatures. (U.S. Patent Nos. 2,602,728 and 2,621,111).

Naturally, the above reaction is a solid-gas reaction, so the reactor for carrying out the reaction is
Fluidized bed reactors or fixed bed reactors are usually employed. Continuous operation is possible when using the former fluidized bed reactor, but the fine powdered chlorides such as calcium chloride, magnesium chloride, iron chloride, etc. that are produced as by-products are the target substance (higher chlorine). Since it flows out of the reactor together with silicon chloride, it is difficult to separate them, and there are drawbacks such as line blockage due to the by-product chloride fine particles.

On the other hand, when the latter fixed bed reactor is used, there is no such drawback, and the volume efficiency of the reactor is reduced due to the accumulation expansion caused by the fine powder by-product chloride remaining in the reactor, and the The fixed bed reactor is considered to be a more practical device for industrial use because the operation itself is relatively easy to carry out, except for the fact that it is a batch-wise operation.

However, when such a fixed bed reactor is adopted, it is necessary to almost completely chlorinate the charged metal particles forming the fixed bed, especially for economic reasons. When the amount of chlorine fed into the fixed bed made of metal particles is increased in order to chlorinate the metal particles, the metal particles are sufficiently chlorinated, but the amount of chlorine that flows out of the reactor unreacted increases, making it difficult to separate and recover. become. That is, since unreacted chlorine dissolves in the condensate of the produced higher chlorinated silicon, it is required to separate and recover the unreacted chlorine from the condensate and circulate it to the reaction system for reuse. If an attempt is made to allow the chlorination reaction to proceed completely, there is a major problem in that the amount of unreacted chlorine that must be separated and recovered increases rapidly, especially in the latter half to the final stage of the reaction when the chlorination reaction rate decreases.

As mentioned above, in the conventional fixed bed reactor, (1) when trying to almost completely react the charged metal particles, the amount of unreacted chlorine increases rapidly, and the load for separating and recovering it becomes extremely large; 2) On the other hand, if the amount of chlorine supplied is reduced, the amount of unreacted metal particles increases dramatically, which is a contradictory problem, and it has been difficult to satisfy both of these problems at the same time.

The present invention has been made to solve these problems, and its gist is as follows: (1) A fixed layer is formed using silicon particles or silicon alloy particles (hereinafter referred to as metal particles), and chlorine is sent to the fixed layer. In the method for producing higher chlorinated silicon represented by the general formula () SinCl _2o+2 () (n is an integer of 2 or more), the fixed layer is A plurality of at least three or more fixed bed reactors A, B, C, . are connected in series as the first stage and B as the second stage to form a reaction system for the first stage cycle, and the first stage reactor A is used as the main reaction zone to react until the charged metal particles are almost completely chlorinated. At the same time, during this time, the second stage reactor B is used as an auxiliary reaction zone so that the unreacted chlorine gas discharged from A and supplied to B is almost completely reacted in this zone, and the process of the second stage cycle is completed. The above B is used as the first stage, and the other fresh reactor C is used as the second stage to form a reaction system for the first stage cycle. The process of the first stage cycle is completed by performing the same process as in the first stage cycle except that C is operated as an auxiliary reaction zone. , the above cycle is repeated while the reactors A, B, ... in which the metal particles have been completely chlorinated are appropriately refilled with fresh metal particles to form fresh fixed bed reactors A, B, ... A method for producing higher chlorinated silicon, characterized by the following.

Hereinafter, the constituent elements of the present invention will be explained in detail.

The target substance of the present invention, higher chlorinated silicon, is a compound represented by the following general formula () SinCl _2o+2 () (n≧2), and examples of desirable ones include hexachlorodisilane, octachlorodisilane, These include chlorotrisilane, decachlorotetrasilane, etc., and hexachlorodisilane is particularly preferred.

Under normal reaction conditions, these are obtained as a mixture, so the desired higher chlorinated silicon, such as hexachlorodisilane, is separated and used by means such as distillation. Note that, depending on the application, it is of course possible to use the mixture as it is. Tetrachloromonosilane (silicon tetrachloride) is also usually mixed as a by-product, but it can be easily separated by distillation.

As the raw metal particles used in the present invention, silicon or silicon alloy can be used, but
When silicon particles are used, the reaction temperature must be higher and the amount of higher chlorinated silicon produced is also smaller, so calcium silicide, magnesium silicide, iron silicide, etc. are used except in special cases. It is advantageous to use silicon alloy particles of

Such metal particles such as calcium silicide are usually preferably used in the form of sand grains with a specific gravity of 1.5 to 8 and a particle size of about 5 to 200 mesh, but if the particles are large, they may be crushed to an appropriate particle size. It is desirable to use the

The chlorination reaction temperature is 300 to 500°C when silicon particles are used as raw metal particles;
When using a silicon alloy, a temperature of about 150 to 350°C is used.

In order to improve the yield of higher chlorinated silicon, it is also preferable to supply chlorine to the reactor together with a diluent such as silicon tetrachloride.

The reactor used in the present invention is one in which at least three or more fixed bed reactors A, B, C, etc. each having a fixed bed formed of metal particles are arranged so as to be mutually switchable. . The number of reactors is 3 or more, preferably 3 to 6, but is of course not particularly limited. Further, although any conventional type of reactor can be used, it is preferable to use one that allows easy filling of metal particles and removal of reaction residues.

Examples of the method of arranging the reactor and the method of operating the reactor according to the present invention will be specifically explained below based on the drawings.

Figure 1 shows the case where three reactors A, B, and C are used, and A, B, and C are all fixed bed reactors of the same type, with the fixed bed formed by fresh metal particles. . Reactors A, B, and C each include a pipe line 1 and a plurality of valves 10, 20, 30,
..., 150 constitute a network as shown. As is clear from the figure, by opening and closing the valves appropriately, two arbitrary reactors are selected and connected in series to create a reaction system A→B, B.
→C, C→A can be formed (here, the arrow → indicates the flow direction of chlorine gas, for example, A→
B indicates that gas leaves reactor A and then enters B. In addition to the above, the opposite B→A, C→B, A
It is easy to see that the above network is constructed in such a way that it is possible to form a reaction system in which →C, but since the explanation would be complicated, it will not be discussed here).

First, select two fresh reactors A and B,
Valve 30, 40, 70, 100, 110, 1
By opening valves 30 and 140 and closing all other valves, a reaction system of a first stage cycle (A→B) in which A is connected in series with A as a first stage and B as a second stage is formed. Using the reaction system of the first stage cycle, chlorine is sent to the reactor to carry out the chlorination reaction, but the chlorination reaction mainly proceeds in reactor A, and the chlorination reaction in reactor B , by unreacted chlorine gas passed through reactor A. In this case, the reaction temperature,
By appropriately setting reaction conditions such as chlorine gas flow rate, chlorine gas concentration, and residence time, reactor B
It is also possible to reduce the amount of unreacted chlorine that passes unreacted to almost zero, and during this time, the overall production rate of reaction products (the total amount produced in reactors A and B) can be kept approximately constant. can be retained. As described above, in the first stage cycle, the first stage reactor A is used as the main reaction zone and the charged metal particles are reacted until almost completely chlorinated, and during this time, the second stage reactor B is used as the auxiliary reaction zone. This allows the unreacted chlorine gas discharged from A and supplied to B to be almost completely reacted in this zone.

Thus, at a stage when the charged metal particles in reactor A are almost completely chlorinated (therefore, in reactor B
The stage of the first stage cycle is completed at the stage where the charged metal particles still remain largely unreacted, and the next cycle is started.

Subsequently select reactor B and fresh reactor C, and close valves 10, 40, 50, 80, 9.
By opening valves 0, 110, 120, and 140 and closing all other valves,
A second stage cycle reaction system (B→C) is formed in which stage C is connected in series with stage C as the second stage.

Chlorine is introduced into the reaction system of the second stage cycle to carry out a chlorination reaction in the same way, but in this case, reactor B is used as the main reaction zone to remove unreacted metal particles remaining in the first stage cycle. is preferentially reacted, and reactor C is operated as an auxiliary reaction zone, and the unreacted chlorine that has passed unreacted through reactor B is used to advance the reaction. Thus, in the first cycle,
Similar to the second stage cycle, the first stage reactor B is used as the main reaction zone and the charged metal particles are reacted until almost completely chlorinated, and during this time, the second stage reactor B is used as the auxiliary reaction zone and the metal particles are discharged from B. The unreacted chlorine gas supplied to C is almost completely reacted in this zone.

Also during this time, the solid reaction residue in reactor A is removed and refilled with fresh metal particles to form a fresh fixed bed reactor ready for the next reaction cycle.

After the chlorination of metal particles in reactor B is completed, the reaction system of the first stage cycle (C→A) is completed by reactor C containing unreacted metal particles and fresh reactor A that has been refilled. It is formed. That is, valves 10, 20, 50, 60, 10
Open valves 0, 120, and 150, and close all other valves. Reactor C is used as the main reaction zone to preferentially chlorinate the unreacted metal particles remaining in the reactor, and reactor A is used as the auxiliary reaction zone to completely react the unreacted chlorine gas leaving C. This is the same as each cycle above.

Thereafter, by repeating each cycle in the same manner, the reaction is allowed to proceed continuously in a steady state.

The generated gas consisting of higher chlorinated silicon is led to a condenser 160 where it is cooled and condensed, and further separated into each higher chlorinated silicon by a distiller.

The above explanation has been given for the case of three reactors, but the number of reactors and the method of arranging them can be implemented by making appropriate design changes other than the format illustrated in Fig. 1. It goes without saying that the technical scope of the present invention is not limited to the format shown in FIG.

According to the present invention, even in a fixed bed reactor, substantially continuous operation is possible in the same way as in a fluidized bed reactor, so that the operating efficiency can be greatly improved. Furthermore, although it is possible to cause the metal particles charged in the reactor to react almost completely, it is possible to reduce the amount of unreacted chlorine gas that is ultimately entrained in the generated gas to almost zero. Therefore, a remarkable effect can be achieved in that there is no need to separate and recover unreacted chlorine gas.

The present invention will be explained below with reference to Examples.

Example 1 Using three fixed bed reactors arranged as shown in FIG. 1, calcium silicide was chlorinated to produce higher chlorinated silicon.

Three cylindrical reactors made of Pyrex (trademark) glass with the same shape (hereinafter abbreviated as A, B, and C, each having dimensions of 130 mmφ*377 mm L and a capacity of 5000 cm ³ ) were placed in a net as shown in Figure 1. Commercially available calcium silicide (manufactured by Japan Heavy Chemical Industry Co., Ltd., 48 to 200 mesh, Si content 61
(% by weight) was filled into A, B, and C under an argon atmosphere to form a fixed bed reactor having a bed height of 40 mmH.

Valve 30, 40, 70, 100, 110, 1
30 and 140 were opened, and all other valves were closed to form a reaction system (A→B) for the first stage cycle. Set the temperature of reactors A and B to 200℃,
Chlorine gas (manufactured by Tsurumi Soda Co., Ltd., purity 98% by weight, flow rate 2.5/min) was entrained in argon (flow rate 2/min) and supplied in the order of A→B to carry out a chlorination reaction for 7 hours.

After 7 hours of reaction, the flow rate of unreacted chlorine gas passing through the valve 110 was 0.01/min, and the Si content in the reaction residue of reactor A (i.e., the amount of unreacted Si) was about 39 g, which was due to conversion. This corresponded to a rate of 89%.

Next, valves 10, 40, 50, 80, 90,
110, 120, and 140, and close all other valves.
→C) was formed.

The temperature of reactors B and C was set at 200°C, and the chlorination reaction was carried out for 7 hours under the same chlorination conditions as in the first stage cycle. During this time, the reaction residue in reactor A was taken out and newly added calcium silicide 600
g was refilled to form a fresh fixed bed and ready for the next reaction cycle.

After 7 hours of reaction, the flow rate of unreacted chlorine gas passing through the valve 120 was 0.01/min, and the Si content in the reaction residue of reactor B (i.e., the amount of unreacted Si) was about 35 g, which was due to conversion. The rate was equivalent to 90%.

Next, valves 10, 20, 50, 60, 10
0, 120, and 150, and close all other valves, the reaction system of the first stage cycle (C→
A) was formed.

The temperature of reactors C and A was set at 200°C, and the chlorination reaction was carried out for 7 hours under the same chlorination conditions as in the first stage cycle. Also, during this time, the reaction residue in reactor B was taken out and fresh calcium silicide 600
g was refilled to form a fresh fixed bed and ready for the next reaction cycle.

After 7 hours of reaction, the flow rate of unreacted chlorine gas passing through the valve 100 was 0.01/min, and the Si content in the reaction residue in reactor B (i.e., the amount of unreacted Si) was about 36 g, which was due to conversion. The rate was equivalent to 90%.

Thereafter, chlorination reactions were repeated in the same manner for 7 hours each using three reaction systems: A→B, B→C, and C→A. Finally, the calcium silicide remaining in reactor A was reacted for 5 hours under the same reaction conditions, and the reaction was stopped.

Throughout the entire reaction, about 17.9 kg of product liquid was collected by cooling the product gas to about 0°C. The silicon content in the product liquid was 139 mol, which is a yield of 89%.
(Based on Si atom charge). Next, the product liquid was subjected to simple distillation at normal pressure to obtain 4.8 kg of SiCl ₄ , and further simple distillation was performed under reduced pressure (125 mmHg) to obtain 4.8 kg of Si ₂ Cl ₆ and 4.6 kg of Si ₃ Cl ₈ . Pot residue 6.3
Got Kg.

Comparative Example 1 Using one reactor identical to that used in Example 1, the chlorination reaction was carried out for 7 hours. The amount of calcium silicide charged was 600 g, and the chlorination reaction conditions were a reaction temperature of 200°C, an argon flow rate of 2/min, and a chlorine flow rate of 2.5/min.

The chlorine flow rate at the reactor outlet increased rapidly with the passage of reaction time, and after 0.5 hours of reaction time, the chlorine flow rate increased to 4.
The flow rates of unreacted chlorine gas after hours and 7 hours are 0.1/min, 0.5/min, and 2.4
/min.

In addition, the product liquid obtained by this reaction was 1.4
Kg, and the silicon content in the product liquid is 11.3mol
This corresponds to a yield of 87% (based on Si atoms charged). Next, by distilling and separating the product liquid in the same manner as in Example 1, 0.37Kg of SiC ₄ , 0.54Kg of Si ₂ Cl ₆ and
0.4 kg of pot residue containing 0.3 kg of Si ₃ Cl ₈ was obtained.

[Brief explanation of drawings]

FIG. 1 is a flow sheet diagram schematically showing an example of a method for arranging a fixed bed reactor for carrying out the present invention.

Claims (1)

[Claims] 1. By forming a fixed layer of silicon particles or silicon alloy particles (hereinafter referred to as metal particles) and introducing chlorine into the fixed layer to cause a solid-gas reaction and chlorination, the general formula ( ) SinCl _2o+2 () (n is an integer of 2 or more) In the method for producing higher chlorinated silicon represented by B, C, ... are arranged so that they can be switched between each other, and first, at least two of them, fresh reactors A and B, are connected in series with A as the first stage and B as the second stage. form the reaction system of the cycle,
The first stage reactor A is used as the main reaction zone and the charged metal particles are reacted until almost completely chlorinated, and during this time, the second stage reactor B is used as the auxiliary reaction zone and the unreacted metal particles are discharged from A and supplied to B. The stage cycle is completed so that the chlorine gas is almost completely reacted in the zone, and then the above B is connected in series as the first stage and another fresh reactor C as the second stage. A stage cycle reaction system is formed, with B serving as the main reaction zone to preferentially react the metal particles remaining unreacted in the stage cycle to completely chlorinate them, while C serving as the auxiliary reaction zone. The process of the first stage cycle is completed by performing the same operation process as the first stage cycle, and the reactors A, B, etc., in which the metal particles have been completely chlorinated, are refilled with fresh metal particles as appropriate to freshen them. A method for producing higher chlorinated silicon, which comprises repeating the above cycle while using fixed bed reactors A, B, . . . . 2. The method according to claim 1, wherein the silicon alloy is calcium silicide, iron silicide or magnesium silicide. 3. The method according to claim 1 or 2, wherein the higher chlorinated silicon is hexachlorodisilane (n=2). 4. The method according to claim 1 or 2, wherein the higher chlorinated silicon is octachlorotrisilane (n=3). 5. The method according to claim 1 or 2, wherein the higher chlorinated silicon is obtained as a composition containing hexachlorodisilane (n=2). 6. The method according to any one of claims 1 to 6, which uses three reactors A, B, and C.