JPH03218917A - Production of boron trichloride - Google Patents

Abstract

PURPOSE:To synthesize boron trichloride in high yield by continuously supplying aluminum trichloride and boron trichloride in a gas state to promote the reaction. CONSTITUTION:For example, an aluminum chloride generator 2 is charged with metal aluminum blocks and preheated at 200-400 deg.C with a heater 1. A vapor phase reactor 5 made of Ni, comprising a tubular hollow tower is preheated at 200-400 deg.C, while a separator 7 is cooled with air and a cooler 8 is cooled with a coolant. Boron trichloride is continuously synthesized by supplying predetermined amts. of chlorine and boron trifluoride to the generator 2 and the reactor 5, respectively. The reaction of vapor phase AlCl3 and vapor phase BF3 proceeds very fast with the stoichiometric mixing proportion at a temp. higher than the temp. at which AlCl3 can exist in a vapor phase, and the reaction completely terminates in a few seconds. Production of AlF3 in a powdery state affects nothing on the process of the reaction. AlF3 is stable under about 800 deg.C which is the sublimation temp. and can be easily separated from the vapor phase reaction system. Moreover, AlF3 shows no reactivity when mixed with the liquid phase of AlCl3 produced by cooling, and can be separated by distillation of AlCl3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing highly pure boron trichloride, which is used as an etching agent for semiconductor processes and as a raw material for producing boron perfluoride.

[Prior art]

Conventionally, the following method has been known for producing boron trichloride.

(1) For example, US Pat. No. 3,019,089 or 302
5138, in which a mixture of boron trioxide and carbon is reacted with chlorine at 500°C or higher.

(2) For example, as described in Japanese Patent Publication No. 58-57368, a method in which boric acid is adsorbed on activated carbon and then reacted with chlorine at a high temperature.

(3) For example, the reaction between an alkaline earth metal boride and hydrogen chloride as described in Japanese Patent Publication No. 51-39198.

(4) J. Eight meters. Chem. Soc.
．． , 6 201 2 5 7N (
1940) and Inorganic Synthes
A method of reacting solid aluminum halide with boron trifluoride at sublimation temperature, as described in Volume 3, pages 27-30 of ES. However, in this method, the halogens are chlorine and bromine.

Methods (1) and (2) are synthetic methods using boron oxide, carbon, and chlorine, and the reaction temperature is generally 1000 to 13
00°C, and even in the improved method
It is 0 to 800°C. The materials of the reaction system must withstand harsh conditions such as high temperatures and chlorine corrosion. Furthermore, this method cannot avoid the generation of chlorine-based impurities such as phosgene (COClz).

This phosgene differs in boiling point from boron trichloride by only 4°C and cannot be removed by distillation.

Method (3) is difficult to synthesize and uses expensive alkaline earth borides, so it cannot be applied to industrial manufacturing methods.

Method (4) uses aluminum trihalide with its M. This is a method in which boron trihalide is obtained by heating to a temperature at Fahrenheit temperature and reacting with boron trihalide.

In this method, 0.5 mol of aluminum trichloride is sublimed and reacted with 2 mol of boron trifluoride, which is in large excess over the reaction equivalent, and the yield per aluminum trichloride is 8.
Although boron trichloride is obtained at 0%, the yield per boron trifluoride is extremely low at 20%. Using this method requires equipment to recover or remove unreacted boron trifluoride. However, boron trifluoride is an extremely difficult gas to collect, and boron fluoride ions in the collection liquid are difficult to react with calcium ions, requiring special chemical treatment for wastewater treatment.

Due to the problems mentioned above, this reaction has not been used as an industrial method for producing boron trichloride to this day. As a result of a detailed study of this reaction from various aspects, the inventors have found that the reason why it is not used in industrial production methods is as follows. In other words, since aluminum trichloride exists as a solid phase in the same reactor as boron trifluoride, the reaction proceeds on the sublimation surface, and the generated aluminum fluoride coats the solid surface, causing a reaction reaction. To prevent continuation.

[Problem to be solved by the invention]

The purpose of the present invention is to develop a manufacturing method and apparatus for synthesizing boron trichloride in high yield by continuously supplying aluminum trichloride and boron trifluoride in a gas phase to advance the reaction.

[Means for Solving the Problems] The present inventors continuously supply and react solid or molten aluminum with chlorine, hydrogen chloride, and/or a chlorine compound that reacts with aluminum, thereby reducing the amount of gas in the generator. By using a new principle of synthesizing aluminum chloride or heating and sublimating aluminum trichloride to generate gaseous aluminum trichloride, which is reacted with trifluoride and boron in a gas phase reactor. , it was revealed that the above-mentioned obstacles could be completely solved, and the invention was completed.

[Structure and Function of the Invention] The present invention is a new manufacturing method for synthesizing boron trichloride by subjecting gaseous aluminum trichloride and boron trifluoride to a continuous gas phase reaction.

That is, the reaction between vapor phase aluminum trichloride and vapor phase boron trifluoride occurs at a stoichiometric mixing ratio (equimolar composition) and at a temperature at which aluminum trichloride exists as a gas phase (180°C).
), it has been found that the reaction is extremely rapid and complete reaction occurs within seconds.

The fact that aluminum fluoride is produced in powder form as a reaction product does not impede the progress of the reaction. Aluminum fluoride is a compound that sublimes at temperatures above about 800°C, but it is a stable compound at temperatures below that and can be easily separated from the gas phase reaction system, and can also be mixed into the cooled liquefied phase of aluminum trichloride that is produced. However, it has no reactivity and can be completely separated by distillation of aluminum trichloride.

Conventionally, the method of sublimating solid aluminum trichloride and reacting with boron trifluoride in the same reactor is essentially a solid-phase surface reaction, and the produced aluminum fluoride inhibits the solid-phase surface reaction, so sublimation Compared to the use of a large excess of boron trifluoride, which necessitates extremely low feed rates and boron trifluoride feed rates, and which results in low yields, the gas phase synthesis principle of the present invention is completely reactive. This is a game-changer.

To give an example of a specific method, when solid aluminum heated to 180 to 700°C is reacted with chlorine, hydrogen chloride, and/or a chlorine compound that reacts with aluminum, aluminum trichloride is easily continuously produced at a reaction rate of almost 100%. It is generated as a gas. In the present invention, not only gaseous aluminum trichloride is produced by the above method and used as it is, but also solid aluminum chloride previously produced by a conventional method is used in the following manner. You can also do that. That is, solid aluminum trichloride is separately sublimated to become a gas. This is the mode of using this. To explain in more detail, when using aluminum chloride by sublimation,
By heating and continuously sublimating in a container dedicated to sublimation, and then introducing gaseous aluminum chloride into a reaction container with boron trifluoride and boron heptaide? Manufacture boron chloride. By separating sublimation and reaction in this way, aluminum fluoride, which is a reaction product with boron trifluoride, is not produced on aluminum chloride, so the reaction proceeds continuously without being inhibited. That is, l: AIcL+ (gas) 10BF3 (gas)
] Since it uses a gas phase reaction method, the content of impurities is extremely small, and unlike conventional production methods using carbon materials, phosgene is not produced as a by-product.

The chlorine compound that reacts with aluminum used in the present invention is CCI. , C2C]. ,C2C]6,CIF
3, SiHzCIz, SiHC]3, SiC14, etc. Even in this case, CO is difficult to separate from BCI because no oxygen is involved throughout the reaction system.
There is no contamination of CI■.

Typical equipment for carrying out the method of the present invention is as follows:
As shown in Figure 1. That is, the heater (1), the generator (2
), chlorine inlet pipe (3) and aluminum trichloride outlet pipe (
4) Aluminum trichloride generator, gas phase reactor for aluminum trichloride, trifluoride, and boron trifluoride (5), boron trifluoride inlet tube (6), and aluminum trifluoride separator (7) This is a boron trichloride production device consisting of a combination of a reaction device consisting of a boron trichloride cooler (8) and a boron trichloride cooler (8). (9
) is a boron trichloride receiver. In this apparatus, a column (GO) filled with aluminum solid can be provided in the aluminum trichloride outflow pipe (4). As a result, even if unreacted chlorine remains due to the reaction between aluminum and chlorine, this remaining chlorine reacts with aluminum to become aluminum trichloride, and can be completely converted to aluminum trichloride.

Further, in the case of sublimating solid aluminum chloride in the present invention, aluminum trichloride may be heated and evaporated in the reactor (2) in the apparatus shown in FIG.

〔Example〕

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

However, the manufacturing equipment used was that shown in Figure 1.

Example 1 Metal aluminum lump (
Fill the container with about 50g of chunks) and preheat to 200-400°C using a heater (1). The gas phase reactor (5) manufactured by Ninowo Ru is 2
It consists of a tubular column with an inner diameter of 52.5 mm and a length of 400 mm, which is preheated to 00 to 400°C. The aluminum fluoride separator (7) is air-cooled, and the cooler (8) is heated with a refrigerant of -15 to
It is cooled to -25°C. As a result of continuously synthesizing boron trichloride by supplying chlorine to the generator (2) and boron trifluoride to the gas phase reactor (5) using flow rate controllers, the synthesis conditions shown in Table 1 were met. Boron trichloride was synthesized with corresponding yield.

Example 2 An aluminum chloride generator (2) is installed on a load cell (continuous weight detection), and solid aluminum chloride is filled therein. Electric heating method (heating through constant current to external heating and internal heater) or infrared heating method (generating P, (
A quartz window plate is provided at 21, and aluminum chloride is continuously sublimed by either heating by irradiation with an infrared lamp.

The sublimated aluminum chloride is introduced into a gas phase reactor (5) and reacted with boron trifluoride in a gas phase. Boron trichloride was continuously synthesized using a flow rate controller, with a fixed amount of supply being made to correspond to the depletion rate of aluminum chloride. The results are shown in Table 2.

Example 3 Using the continuous synthesis apparatus of Example 1, CCI4 or SiCl4 was continuously supplied in the gas phase instead of chlorine to the aluminum chloride generator {2}, and reacted with metal aluminum to generate aluminum chloride, Other conditions were the same as in Example 1 for synthesis.

CCI. , SiC14 gas was supplied by external heating of the filled cylinders. The results are shown in Table 3.

Comparative Example 1 A large excess (4 times equivalent amount) of boron trifluoride was introduced according to the simultaneous sublimation and reaction method (method of prior art 4) in which the aluminum chloride sublimator and the boron trifluoride reactor were not separated. We synthesized boron trichloride. 1 reactor! It is made of a glass container with a 0.5P enlargement on the top of the round bottom %'l flask, and the flask and enlargement have an inner diameter of 30I.
III1 is connected by a glass tube with a length of 250 mm, and the boron trifluoride inlet tube is located in the center of the 1 L round bottom flask. The results are shown in Table 4.

(E) The reaction yield according to the synthesis method described in Prior Art (4) is 80% based on AIC]3, BP. 20 for standard
It is reported that %. As shown in Comparative Example above, the results were in good agreement with the values described in the literature.

Comparative Example 2 In a simultaneous sublimation and reaction method, synthesis was performed by continuously supplying BF in an amount equal to the amount of AICIi charged at a constant flow rate.

The reactor is BP! 100 with an inlet! The reactor has 201 heating cavities above it. AICI3 powder was charged into a reactor, and synthesis was performed by continuously introducing an equal amount of Bh into AICI3 while externally heating the reactor. The superficial velocity in this reaction vessel is extremely small, 0.04 to 0.2 cm/sec. As described above, even if the BF supply rate is kept extremely low, the yield is low. The results are shown in Table 5.

〔Effect of the invention〕

By the method of the present invention, highly pure boron trichloride can be produced extremely easily and with good yield, and as a result, boron trichloride can be supplied to various industries at low cost and in high purity. Originally, boron trichloride is an important chemical material related to the development of new industries such as semiconductor industry and optical-related industry.
In the SI process, it is used as a dry ethosing agent for aluminum and other metals in the microfabrication circuit wiring process, and it is also important as a constituent material of PBN crucibles used in the process of pulling silicon single crystals and other chemical semiconductor crystals. Furthermore, there is growing demand for it as a refractive index control doubant in optical fibers and solar cells, and its use is also expanding to other boron nitride molded product raw materials.

Therefore, the method of the present invention definitely contributes to the development of such diverse applications, and its industrial effects are significant.

[Brief explanation of drawings]

FIG. 1 shows an example of an apparatus used in carrying out the method of the present invention. 5 ... Heater ... Generator ... Chlorine introduction pipe ... Aluminum trichloride outflow pipe ... Gas phase reactor 6 ... Boron trifluoride introduction pipe 7 ... Separator 8. ...Cooler 9...Receiver 10...Column (and above)

Claims (1)

[Claims] (1) Boron trichloride is synthesized by continuously supplying gaseous aluminum trichloride and boron trifluoride to a gas phase reactor and reacting them. Production method. (2) By continuously supplying gaseous aluminum trichloride produced by the reaction of aluminum with chlorine and/or chlorine compounds to a gas phase reactor, and reacting with continuously supplied boron trifluoride. A method for producing boron trichloride, which comprises synthesizing boron trichloride. (3) Claim 1, characterized in that the chlorine compound is a chlorine compound that reacts with hydrogen chloride and/or aluminum.
The method for producing boron trichloride as described in . (4) Production of boron trichloride, characterized in that boron trichloride is synthesized by continuously sublimating solid aluminum chloride, continuously supplying it to a gas phase reactor, and reacting it with boron trifluoride. Method.