JPS603002B2 - Production method of trichlorosilane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for industrially producing trichlorosilane from silicon tetrachloride.

Silicon for semiconductors is mainly produced by reacting trichlorosilane with hydrogen and depositing silicon on a silicon plate heated by electricity, but in this silicon precipitation reaction, about 60% silicon tetrachloride is produced as a by-product, and trichlorosilane is This is the main cause of decreasing the yield from silane to silicon.

On the other hand, it is not impossible to produce silicon for semiconductors from silicon tetrachloride using a similar method, but this method is rarely used industrially because the reaction rate is slow and the reaction rate is low.

Therefore, various methods for converting silicon tetrachloride into trichlorosilane have been researched, and many of them have been patented.
There are very few methods with a conversion rate of over 50%, and even those that do require harsh operating conditions, so no satisfactory method that can be implemented on an industrial scale has been established. Conventionally, the production of trichlorosilane using silicon tetrachloride as a raw material has mostly been studied in the temperature range of 500 to 1100°C in an externally heated reaction tube, as seen in Hakama Sekisho 48-47500. This temperature range was chosen because there are corrosive gases such as silicon tetrachloride, trichlorosilane, and hydrogen chloride, so there is no material that can withstand higher temperatures than this, and at temperatures above 1100 qo, the produced trichlorosilane The reason is that this is not advantageous because precipitation from silane to silicon begins.

Previously, the present inventors discovered a method that enabled the reaction to occur at higher temperatures, established a method for producing trichlorosilane from silicon tetrachloride that was industrially satisfactory, and filed a patent application. .

(Mochikan Kaikyu-97996). The method uses a method that has never been used before, in which a mixed gas of silicon tetrachloride and hydrogen is blown onto the heating element. It was found that no precipitation occurred. Moreover, since the heating method is internal heating rather than external heating, the problem of corrosion of the reaction vessel is solved, and if the reaction conditions are appropriately set, the conversion rate of silicon tetrachloride to trichlorosilane can be increased to about 60%. It is possible to increase the The conversion rate referred to herein is 10 times the quotient obtained by dividing the number of moles of trichlorosilane produced by the number of moles of silicon tetrachloride used. Until then, it was thought that in the temperature range of 1,100 to 1,600 qo, the silicon precipitation reaction would be more dominant than the conversion to trichlorosilane, but by adopting a new method of blowing a reaction gas onto a heating element, it was possible to reduce the heat generation. It is possible to constantly react in the vicinity of the body and to have only gas present, so that the reaction from silicon tetrachloride to trichlorosilane proceeds quickly, and the trichlorosilane produced is immediately removed from the exothermic part. It is thought that the result is that the precipitation reaction from trichlorosilane to silicon does not occur. Since the heating method is internally heated, there is no need to expose the reactor walls to high temperatures, so the invention avoids the problem of reactor corrosion.

Therefore, it is now possible to use a stainless steel reaction vessel with external water cooling, which was not possible with conventional methods.
It became possible to manufacture devices on an industrial scale. The temperature of the heating element is preferably within a temperature range of 1,100 to 1,600.

If the temperature of the heating element is lower than 1,100 mm, the conversion rate to trichlorosilane will drop significantly, and even if the temperature is higher than 160,000 mm, the conversion rate will remain almost constant at about 57%, and even if the temperature is increased beyond that, the conversion rate will decrease. It does not increase, only the fin radiation energy increases, so it is technically meaningless. In order to produce trichlorosilane at a high conversion rate, generally the flow rate of the feed gas consisting of a mixture of silicon tetrachloride and hydrogen increases;
Preferably, the temperature of the heating element is increased.

The molar ratio of hydrogen to silicon tetrahydride in the V feed gas stream also affects the conversion of trichlorosilane, and when this molar ratio is less than 4, generally satisfactory conversion rates are often not obtained.

It is desirable that the hydrogen/silicon tetrachloride molar ratio is as high as possible from the viewpoint of conversion rate, but if silicon tetrachloride is the species that increases this ratio (and therefore the trichlorosilane product).
Considering dilution, reaction efficiency, and ease of separation and recovery of the product, the upper limit of the above molar ratio is 19 degrees.
An apparatus for carrying out the method of the invention comprises hydrogen, silicon tetrachloride,
A heating element made of a material inert to trichlorosilane and hydrogen chloride, such as graphite, silicon, silicon carbide, etc., is provided so that electricity can be applied from the outside, and the inlet for the reaction gas is connected to the heating element. Let Sekiguchi,
A discharge port for generated gas is separately provided at an appropriate position.

Since it is a very simple device, those skilled in the art can freely design it according to the desired production scale. The method of heating the heating element can also be arbitrarily selected from direct current heating, high frequency conductive heating, and the like. Silicon tetrachloride vapor mixed with a hydrogen stream can be fed into this device. According to the method of the invention, when a mixture of hydrogen and silicon tetrachloride is blown onto the heating element as described above, trichlorosilane is produced and hydrogen chloride is produced as a by-product.

Therefore, the generated gas discharged from the outlet is 2 days, SIC1
Contains 4, SiHC13, and HCI. From this mixture, Si
To isolate HC13, first, SiHC1 was
3 and SIC14 were liquefied and separated from Day 2 and HCI, and SjHC13 was fractionated by precision distillation of the liquid. As a result of conducting research on the method of the present invention, the present inventors have found that, rather than supplying silicon tetrachloride and hydrogen simultaneously near the heating element, only silicon tetrachloride is supplied near the heating element.
They discovered that the yield of trichlorosilane is better when the hydrogen is supplied at a distance from the hydrogen a little further away, and that the yield drops again when the hydrogen is supplied too far away, and the present invention was completed based on this finding.

According to the present invention, silicon tetrachloride and hydrogen have a concentration of 1100 to 16
A method for producing trichlorosilane comprising spraying it onto a heating element at 00°C, characterized in that silicon tetrachloride is deposited near the heating element and hydrogen is deposited at a position further away from the heating element. is provided.

In the method of the present invention, it is convenient to use a double tube in which the inner tube protrudes from the outer tube, and to supply silicon tetrachloride and hydrogen from foreign sources through the inner tube. At that time, the ratio of the distance from the heating element to the entrance of the outer pipe (hydrogen supply position) to the distance from the heating element to the entrance of the inner pipe (silicon tetrachloride supply position) is 2 to 10, and The value obtained by dividing the silicon tetrachloride gas supply linear velocity expressed by the arc in terms of 0°C by the distance from the heating element to the closed part of the inner tube (silicon tetrachloride polishing groove position) expressed by the arc is 5 to 50. It is preferable that The above ratio is 2
If it is less than 10, there is no point in supplying silicon tetrachloride and hydrogen separately, and if it exceeds 10, contact between the reactants will be insufficient and the reaction will not proceed. If the distance from the heating element to the inner pipe entrance (silicon tetrachloride supply general position) is greater than 1'5 of the silicon tetrachloride supply linear velocity expressed in ground/second, the effect of SIC frog air being blown onto the heating element surface will decrease. is weak, 1/
If it is less than 5 degrees, the spraying effect will be too strong and SIC14 will be wasted. From an equilibrium relationship, the higher the molar ratio per day for the supply of SIC14, the higher the conversion rate can be, but it is 1/3 to 12
It is overall advantageous to supply at a rate of

Although it is not completely clear why the method of the present invention is advantageous, silicon tetrachloride is
IC14 → SIC120 CI2
{11, dichlorosilylene (SIC12) and chlorine (this reaction occurs at higher temperatures than other reactions), the latter is hydrogen and 20CI2 → 2HCI
{21 becomes hydrogen chloride (this reaction progresses relatively quickly), which leads to the above SIC12 and SIC
It is believed that trichlorosilane is produced by the reaction of 120HCI→SiHC13'3' (this reaction tends to occur at lower temperatures than '1').

At the time when the reaction {1} is completed, in the high temperature region (near 1 in Figure 1 mentioned below), SI
C12 probably exists sufficiently stably and coexists without reacting even if hydrogen is present. [Reaction 2- is (2 in Figure 1)
(near)) If the gas moves relatively quickly, SI
The temperature reaches a temperature range (near 3 in FIG. 1) where C12 and HCI can react, and reaction 3' occurs. Considering this, the advantages of the method of the present invention can be well explained. However, if the difference between the distance from the heating surface to the inner tube and the distance to the outer tube is too large, S
Recombination of IC12 occurs to generate SIC14 and Si, which are deactivated. (However, it should be understood that the positions of 1, 2, and 3 in Fig. 1 are only a rough idea, and may vary greatly depending on the equipment and operating conditions.) Next, referring to the drawings, examples will be explained. This will be explained in detail.

The equipment used is shown in the accompanying drawings. In the accompanying drawings, a stainless steel double tube consisting of an inner tube 1 and an outer tube 2 faces the surface of a graphite heating element 3.

In the examples, the inner diameter of the inner tube is 6.4 mm to 19.1 mm, and the inner diameter of the outer tube is 14.9 mm to 30.7 mm. The relative positions of the inner tube, the outer tube, and the surface of the heating element can be changed. For convenience, the distance from the surface of the heating element to the outer pipe entrance is designated as A, and the distance to the inner pipe closing end is designated as B. The device is housed in a stainless steel container as described in the Description of the Prior Art section. Example 1 This was heated to 110 mm using a graphite heating element.

B is 20mm and A is 45mm, and silicon tetrachloride is sprayed at 110mm from the inner diameter 12.7 candle tube, and the inner diameter is 23mm.
．． Hydrogen was supplied from the outer tube of the port at a rate of 160 m/min.
(Hydrogen/silicon tetrachloride molar ratio: 11). The product gas mixture was collected by suction and analyzed by gas chromatography.

The amount of trichlorosilane produced was 46 ta'min, and the conversion rate was 48%. In this case, A/B = 2.250°C equivalent silicon tetrachloride Kusokusha linear velocity x 318 Urimatsu'SeCx
/B 9 Example 2 A heating element made of graphite coated with silicon was used to heat the graphite to 1300 pm.

B is 8mm and A is 45mm, silicon tetrachloride is sprayed at 110 ta'min from the inner pipe on the inner diameter 12.7 side, and the inner diameter is 23mm.
．． Hydrogen was supplied from nine outer tubes at a rate of 160 solutes/min. (Hydrogen/silicon tetrachloride molar ratio: 11). The product gas mixture was collected by suction and analyzed by gas chromatography.

The amount of trichlorosilane produced was 52 units/min, and the conversion rate was
The score was 55%. In this case A/B=5. Total 0°C equivalent silicon tetrachloride linear velocity x Ni18'SeCx
/B=22.5 Example 3 This was heated to 1400° C. using a graphite heating element.

B was set to 25 mm, A was set to 55 mm, and silicon tetrachloride was sprayed at a rate of 55 mm/min from the inner tube with an inner diameter of 64 mm.
．． Hydrogen was supplied from a nine-walled outer tube at a rate of 80 mm/min (hydrogen/silicon tetrachloride molar ratio: 11). Analysis of the produced gas mixture by gas chromatography revealed that the amount of trichlorosilane produced was 27 ta'min, and the conversion rate was 56%. In this case, A/B: 2. 20°C equivalent silicon tetrachloride joint linear velocity x Ni37'SeCx/B
=14.8 Example 4 This was heated to 140 mm using a graphite heating element.

B is 1 block, A is 78 ridges, and silicon tetrachloride is sprayed at a rate of 608 mm/min from an inner diameter 19.1 tube, and hydrogen is sprayed at a rate of 40 mm/min from an outer tube with an inner diameter of 30.7 mm. Supplied in proportion. (Hydrogen/silicon tetrachloride molar ratio: 1/2). Analysis of the generated gas mixture by gas chromatography revealed that the amount of trichlorosilane produced was 132 evenings/min;
The conversion rate was 25%. In this case A/B=7.50℃
Converted silicon tetrachloride supply linear velocity x339 ratio S'SeCx
/B=39.0 Example 5 A heating element made of graphite coated with silicon was used to heat the graphite to 1400°C.

B is 25 arcs, A is 55 arcs, and silicon tetrachloride is sprayed at a rate of 80 m/min from an inner tube with an inner diameter of 9.5 mm.
Hydrogen was supplied from an outer tube with an inner diameter of 184 ribs at a rate of 80 min/min (hydrogen/silicon tetrachloride molar ratio: 7.5). Analysis of the generated gas mixture by gas chromatography revealed that the amount of trichlorosilane produced was 1/min and the conversion rate was 60%.

In this case, A/B 2.20°C equivalent silicon tetrachloride linear velocity x 28Q/SeCx/B=11.2 Example 6 This was heated to 1600°C using a graphite heating element.

B was set to 3 ratio, A was set to 6°, silicon tetrachloride was sprayed at a rate of 55 mm/min from the inner tube with an inner diameter of 64 mm, and hydrogen was sprayed at a rate of 80 mm/min from the outer tube with an inner diameter of 14.9 mm. Supply hydrogen/silicon tetrachloride molar ratio: 11). When the generated gas mixture was analyzed by gas chromatography, it was found that the amount of trichlorosilane produced was 26 min/min, and the G conversion rate was 1%, the same as in the case of 1400 qo.

A/B=2.17 0°C equivalent silicon tetrachloride feeding groove linear velocity x mi 370m/S
eCx/B=12.3 According to the method of the present invention, it is possible to increase the conversion rate of trichlorosilane to silicon tetrachloride to a maximum of about 65%, which could be increased to about 60% in the previous method.

This is a major improvement industrially. Some of the above examples have a conversion rate of about 25%, but the efficiency of the manufacturing method is not evaluated solely by the conversion rate of silicon tetrachloride, but also by the ratio of 2/SIC14 in Tosonsha Gas. It is important to find an economically advantageous point by comprehensively considering the recovery rate of halosilane, utility costs, etc. In this sense, the method of the present invention has the following advantages compared to the invention of Tokukan Sho 53-197996. It is advantageous in that a higher yield can be obtained at the same factory cost under each load condition.

[Brief explanation of the drawing]

The accompanying drawings illustrate the concept of the apparatus used in the method of the invention.

Claims (1)

[Claims] 1. A method for producing trichlorosilane, which comprises blowing silicon tetrachloride and hydrogen onto a heating element at 1,100 to 1,600°C, the silicon tetrachloride being supplied near the heating element, and the hydrogen being emitted from the heating element. A method characterized in that it is supplied to a remote location. 2. The method according to claim 1, characterized in that the distance from the heating element to the hydrogen supply position is 2 to 10 times the distance from the heating element to the silicon tetrachloride supply position. . 3. The method according to claim 1, characterized in that a double tube in which the inner tube protrudes from the outer tube is used, and silicon tetrachloride is supplied from the inner tube and hydrogen is supplied from the outer tube. Method. 4. The method according to claim 3, characterized in that the distance from the heating element to the opening of the outer tube is 2 to 10 times the distance from the heating element to the opening of the inner tube. how to. 5. The method according to any one of claims 1 to 4, wherein the distance from the heating element to the silicon tetrachloride supply port is cm.
1/5 to 1/50 of the silicon tetrachloride supply rate expressed in cm per second converted to 0°C.
A method characterized by: 6. A method according to any one of claims 1 to 5, wherein the molar ratio of hydrogen to silicon tetrachloride is 1.
/3 to 12.