JP7069473B2 - Method for producing high-purity boron trichloride - Google Patents

Description

The present invention relates to a method for producing high-purity boron trichloride. The high-purity boron trichloride obtained in the present invention is a compound useful as, for example, a dry etching gas for aluminum wiring.

Conventionally, as a method for producing high-purity boron trichloride, for example, boron trichloride containing 50 ppm of phosgene and 2 ppm of chlorine is brought into contact with coconut-based activated carbon (silicon content 0.12%) from which water has been removed at 200 ° C. , A method for producing high-purity boron trichloride having phosgene of 0.1 ppm or less and chlorine of 2 ppm or less by adsorbing chlorine on activated carbon is known (see, for example, Patent Document 1).

Further, by reacting phosgene with boron trichloride containing 87.5% by mass and 10% by mass of chlorine with carbon tetraboride (boron carbide), and then distilling and purifying, the high boiling point compound is removed. , A method for producing high-purity boron trichloride having a phosgene content of less than 0.2 mass ppm and a chlorine content of less than 1.0 mass ppm is known (see, for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 10-265216 Japanese Unexamined Patent Publication No. 2013-144644

In the method of Patent Document 1, the water content in the activated carbon must be removed in advance, and the activated carbon needs to contain a certain amount of silicon.

In the method of Patent Document 2, although the amount of phosgene and chlorine can be reduced by reacting boron trichloride with boron carbide, trace components in boron trichloride and boron carbide, such as metal components and surface oxides, can be reduced. There was a possibility that boron trichloride would be decomposed to generate chlorine due to the reaction with the above (verified in Comparative Example 1).

An object of the present invention is to provide a method for producing high-purity boron trichloride in which chlorine is reduced by solving the above-mentioned problems and by a simple method.

An object of the present invention is a method for producing high-purity boron trichloride, which comprises contacting boron trichloride, which may contain chlorine, with a mixture of boron carbide and activated carbon at 350 ° C to 800 ° C. Will be solved by.

According to the present invention, high-purity boron trichloride can be produced from crude boron trichloride containing chlorine.

It is a schematic diagram of the reaction tube produced in Comparative Examples 1 and 2. It is a schematic diagram of the reaction tube produced in Examples 1 to 3.

In the method for producing high-purity boron trichloride according to the present invention, boron trichloride, which may contain chlorine, and a mixture of boron carbide and activated carbon are brought into contact with each other at 350 ° C. to 800 ° C. to bring them into contact with each other at 350 ° C. to 800 ° C. to obtain high-purity boron trichloride. Produces boron. Therefore, high-purity boron trichloride can be suitably produced.

In the present invention, boron trichloride, which may contain chlorine, is brought into contact with a mixture of boron carbide and activated carbon. At this time, since boron trichloride comes into contact with boron carbide in the mixture, there is a possibility that it will be decomposed by a reaction with a metal component, a surface oxide, or the like to generate chlorine.

On the other hand, a part of chlorine generated by the decomposition of boron trichloride is converted into boron trichloride by reacting with boron carbide in the mixture. Unreacted chlorine is treated and removed by activated carbon in the mixture.

In this way, even if boron trichloride contains chlorine from the beginning, even if chlorine is generated by the contact between boron trichloride and boron carbide, chlorine comes into contact with the activated carbon in the mixture, so that the chlorine concentration Is reduced. Therefore, high-purity boron trichloride can be efficiently produced.

In an industrial scale production method, phosgene may be contained in boron trichloride which may contain chlorine, and the phosgene comes into contact with boron carbide at a high temperature (350 ° C. to 800 ° C.). As a result, it is reversibly decomposed into carbon monoxide and chlorine (COCl ₂ → CO + Cl ₂ ). Here, the generated chlorine is treated and removed by activated carbon.

In the present invention, it is presumed that the treatment / removal of chlorine by these activated carbons is performed at a high temperature at which adsorption does not occur, and therefore is not simply due to adsorption by activated carbon.

[Boron trichloride that may contain chlorine]
In the present invention, "boron trichloride which may contain chlorine" is boron trichloride which contains chlorine or whose chlorine concentration is below the detection limit. Boron trichloride, which may contain chlorine, may be diluted with an inert gas such as nitrogen gas.

[Coarse Boron Trichloride]
The "crude boron trichloride" used in the present invention is boron trichloride containing impurities such as chlorine, and more specifically, boron trichloride containing chlorine from the beginning or contact between boron trichloride and boron carbide. Boron trichloride containing chlorine produced by. The crude boron trichloride may be diluted with an inert gas such as nitrogen gas.

Boron trichloride can be produced, for example, by reacting boron oxide carried on activated carbon with chlorine. In the case of producing boron trichloride on an industrial scale, unreacted residual chlorine is mixed in boron trichloride, or phosgene produced as a by-product is mixed in boron trichloride, resulting in crude boron trichloride. There is. In an industrial scale production method, the amount of phosgen mixed is usually 50% by mass to 900% by mass, and the amount of chlorine mixed is 2% by mass or more.

[Boron Carbide]
As the boron carbide used in the present invention, for example, commercially available boron carbide can be used. Here, as the boron carbide, granular one having a particle size of 1 mm to 4 mm is preferably used.

[Activated carbon]
As the activated carbon used in the present invention, for example, a commercially available one can be used. Here, as the activated carbon, granular carbon having a particle size of 2 mm to 100 mm is preferably used.

[Volume ratio of boron carbide to activated carbon in the mixture of boron carbide and activated carbon]
The volume ratio of boron carbide to activated carbon (volume of boron carbide / volume of activated carbon) in the mixture of boron carbide and activated carbon in the present invention is preferably 0.1 / 1 to 50/1, and more preferably 0. It is 25/1 to 20/1.

[Contact conditions]
In the present invention, for example, after the reactor is filled with a mixture of boron carbide and activated carbon, boron trichloride, which may contain chlorine, is supplied from the upper part of the reactor. By reacting boron trichloride, which may contain chlorine, with a mixture of boron carbide and activated carbon in contact with each other, high-purity boron trichloride with reduced chlorine can be obtained.

(Contact time)
The contact time between boron trichloride, which may contain chlorine under the above contact conditions, and the mixture of boron carbide and activated carbon is preferably 1 second to 200 seconds, more preferably 10 seconds to 50 seconds. ..

(Contact temperature and reaction pressure)
The contact temperature between boron trichloride, which may contain chlorine, and the mixture of boron carbide and activated carbon is preferably 350 ° C. to 800 ° C., more preferably 400 ° C. to 800 ° C., and the reaction pressure is particularly high. Not limited.

Next, the present invention will be specifically described with reference to examples, but the scope of the present invention is not limited thereto.

Comparative Example 1 (contact between boron carbide and boron trichloride)
As shown in FIG. 1, a cylindrical quartz reaction tube 1 having a length of 700 mm and an inner diameter of φ38 mm was filled with 45 ml of boron carbide. After heating the reaction tube to 600 ° C. under the flow of nitrogen gas, the reaction was switched from nitrogen gas to boron trichloride gas (chlorine concentration: less than the detection limit (less than 0.1 mass ppm)). The flow rate of boron trichloride gas was 28.6 sccm. The contact time between the boron trichloride gas and boron carbide was 31 seconds.

As a result of measuring the chlorine concentration at the outlet of the reaction tube over time, 7.7 mass ppm of chlorine, which is considered to be generated due to the decomposition of boron trichloride, was confirmed after 2.5 hours.

Example 1 (contact of a mixture of boron carbide and activated carbon with boron trichloride)
As shown in FIG. 2, a mixture of boron carbide and activated carbon (boron carbide 45 ml / activated carbon 18 ml (volume of boron carbide / volume of activated carbon = 2.) was placed in a cylindrical quartz reaction tube 1 having a length of 700 mm and an inner diameter of φ38 mm. 5/1)) was filled. The particle size of boron carbide was 3 mm to 5 mm. The particle size of the activated carbon was 3 mm to 8 mm. After heating the reaction tube to 600 ° C. under the flow of nitrogen gas, the reaction was switched from nitrogen gas to boron trichloride gas (chlorine concentration: less than the detection limit (less than 0.1 mass ppm)). The flow rate of boron trichloride gas was 28.6 sccm. The contact time between the boron trichloride gas and the mixture of boron carbide and activated carbon was 43 seconds.

As a result of measuring the chlorine concentration at the outlet of the reaction tube over time, the chlorine concentration was below the detection limit (less than 0.1 mass ppm) in every hour from 1 hour to 5 hours later, and boron trichloride. It was confirmed that substantially all the chlorine generated from boron carbide was removed.

Example 2 (Contact between a mixture of boron carbide and activated carbon and crude boron trichloride (containing chlorine))
As shown in FIG. 2, a mixture of boron carbide and activated carbon (boron carbide 40 ml / activated carbon 5 ml (volume of boron carbide / volume of activated carbon = 8 /) is placed in a cylindrical quartz reaction tube 1 having a length of 700 mm and an inner diameter of φ38 mm. 1)) was filled. The particle size of boron carbide was 3 mm to 5 mm. The particle size of the activated carbon was 3 mm to 8 mm. After heating the reaction tube to 600 ° C under the flow of nitrogen gas, from nitrogen gas to nitrogen gas containing boron trichloride gas (chlorine concentration: less than the detection limit (less than 0.1 mass ppm)) and 2000 mass ppm of chlorine. I switched. The flow rates of boron trichloride gas and nitrogen gas containing 2000 mass ppm chlorine were set to 25 sccm and 0.5 sccm, respectively (in a mixed gas containing boron trichloride gas and 2000 mass ppm chlorine (crude boron trichloride gas). Chlorine concentration: 40 mass ppm). The contact time between the boron trichloride gas and the mixture of boron carbide and activated carbon was 35 seconds.

As a result of measuring the chlorine concentration at the outlet of the reaction tube over time, the chlorine concentration was below the detection limit (less than 0.1 mass ppm) at any of 6 hours, 12 hours, 18 hours, and 24 hours. , It was confirmed that substantially all the chlorine generated from boron trichloride and boron carbide was removed.

Comparative Example 2 (contact between boron carbide and boron trichloride)
As shown in FIG. 1, a cylindrical quartz reaction tube 1 having a length of 700 mm and an inner diameter of φ38 mm was filled with 45 ml of boron carbide. After heating the reaction tube to 800 ° C. under the flow of nitrogen gas, the reaction was switched from nitrogen gas to boron trichloride gas (below the detection limit (less than 0.1 mass ppm)). The flow rate of boron trichloride gas was 28.6 sccm. The contact time between the boron trichloride gas and boron carbide was 31 seconds.
As a result of measuring the chlorine concentration at the outlet of the reaction tube over time, it was confirmed that 54 mass ppm of chlorine, which was considered to be generated due to the decomposition of boron trichloride, was produced after 1 hour, and 120 mass ppm of chlorine was further 3 hours later. Was confirmed.

Example 3 (contact of a mixture of boron carbide and activated carbon with boron trichloride)
As shown in FIG. 2, a mixture of boron carbide and activated carbon (boron carbide 45 ml / activated carbon 18 ml (volume of boron carbide / volume of activated carbon = 2.) was placed in a cylindrical quartz reaction tube 1 having a length of 700 mm and an inner diameter of φ38 mm. 5/1)) was filled. The particle size of boron carbide was 3 mm to 5 mm. The particle size of the activated carbon was 3 mm to 8 mm. After heating the reaction tube to 800 ° C. under the flow of nitrogen gas, the reaction was switched from nitrogen gas to boron trichloride gas (below the detection limit (less than 0.1 mass ppm)). The flow rate of boron trichloride gas was 28.6 sccm. The contact time between the boron trichloride gas and the mixture of boron carbide and activated carbon was 43 seconds.

As a result of measuring the chlorine concentration at the outlet of the reaction tube over time, chlorine was not detected after 20 minutes, and only 1.1 mass ppm of chlorine was detected after 4 hours.

From the above results, it was confirmed that a large amount of chlorine was generated at the outlet when boron carbide was used, but when a mixture of boron carbide and activated carbon was used, it was below the detection limit at 600 ° C to 800 ° C. Only 1.1 mass ppm of chlorine was detected at the maximum from (less than 0.1 mass ppm).

INDUSTRIAL APPLICABILITY According to the present invention, a method for producing high-purity boron trichloride can be provided.

1 Quartz reaction tube

Claims (5)

A method for producing high-purity boron trichloride, which comprises contacting boron trichloride, which may contain chlorine, with a mixture of boron carbide and activated carbon at 350 ° C to 800 ° C. The method for producing high-purity boron trichloride according to claim 1, wherein the contact time between boron trichloride, which may contain chlorine, and a mixture of boron carbide and activated carbon is 1 second to 200 seconds. The method for producing high-purity boron trichloride according to claim 1 or 2, wherein the activated carbon is granular with a particle size of 2 mm to 100 mm. The method for producing high-purity boron trichloride according to any one of claims 1 to 3, wherein the boron carbide is granular with a particle size of 1 mm to 4 mm. In any one of claims 1 to 4, the volume ratio of boron carbide to activated carbon (volume of boron carbide / volume of activated carbon) in the mixture of boron carbide and activated carbon is 0.1 / 1 to 50/1. The method for producing high-purity boron trichloride according to the above.

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