KR100721090B1 - Separation Process of Boron Compounds in Chlorosilanes and Composition for Evaporating Chlorosilanes - Google Patents

Abstract

The present invention relates to a method for separating boron compounds in chlorosilanes, wherein a boron compound-containing chlorosilane is made to act on a fluorine element-containing salt to adsorb the boron compound to the fluorine element-containing salt.

According to the present invention, it is possible to remove or concentrate a trace amount of boron in chlorosilanes at low cost without any special device in the process by a very simple operation. In addition, as high-resistance products can be supplied in silicon single crystals, high-quality high-voltage thyristors (silicon controlled rectifiers) can be reliably supplied and doping of impurity elements increases the range of conventional grades.

Boron compounds, chlorosilanes, fluorine element-containing salts, silicones, chlorosilanes evaporation compositions

Description

Separation Process of Boron Compounds in Chlorosilanes and Composition for Evaporating Chlorosilanes

The present invention provides a method for separating boron compounds in chlorosilanes capable of removing trace amounts of boron compounds in chlorosilanes or concentrating the boron compounds at low cost without special equipment in the process by very simple operation, and for evaporating chlorosilanes. It relates to a composition.

The electrical resistance which directly determines the characteristics of silicon as a device is determined in accordance with the amounts of donor elements (group 5B elements such as P and As) and acceptor elements (group 3B elements such as B and A1) contained in the silicon single crystal. It is controlled.

By the way, as a method for producing a silicon single crystal, a method of performing chemical vapor phase growth using chlorosilanes on a silicon single crystal and growing a single crystal of silicon is known, but chlorosilanes are usually produced in the manufacturing process, especially raw metal silicon. Boron from the back is incorporated into the thousands of ppb in the form of boron chloride and the like (mainly BC1 ₃ ). Therefore, when the chlorosilanes are evaporated and supplied to the silicon single crystal, boron chloride is also evaporated and supplied at the same time, so that the boron is incorporated into the obtained silicon single crystal, thereby lowering the electrical resistance of the silicon single crystal.

In this case, elements other than boron are relatively easily removed, but boron, which is a doping element that affects electrical properties when a silicon single crystal is produced, cannot be sufficiently removed from chlorosilanes by a distillation method or an adsorbent method.

For example, when boron is removed by distillation, the effect is effective up to% order, and it is difficult to remove pp levels as well as ppb.

In addition, there is a method of distillative separation from chlorosilanes by adding and reacting a derivatization reagent using the reactivity of boron, but this method has a low derivatization efficiency and is often difficult to separate from the derivatization reagent and the reaction product. For this reason, a method of heating and refluxing to increase reactivity to increase derivatization efficiency has been proposed. However, a method of repeatedly deriving a low derivatization effect and finally having a low derivatization effect has been repeatedly performed. Therefore, in silicon single crystals, high voltage silistors (sensor controlled rectifiers), sensors, etc., which are high resistance products of 10, OO Ω-cm, are required to have a boron concentration of 0.1 ppb or less. Could not be applied.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is a method for separating boron compounds in chlorosilanes that can remove a trace amount of boron compounds in chlorosilanes or concentrate the boron compounds at low cost even without a special device in the process by a very simple operation. And an object for evaporating chlorosilanes.

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining in order to achieve the said objective, the present inventors discovered that chlorosilane containing a trace amount of a boron chloride, for example by the method which makes fluorine element containing salt which is a solid state adsorption agent to normal gas phase or liquid chlorosilanes at normal temperature. By adding a fluorine element-containing salt to the chlorosilane, the chlorosilane to be evaporated is substantially free of boron chloride in the evaporated chlorosilane, and boron chloride is concentrated in the evaporation residue. The present invention has been found to be able to remove traces of boron in chlorosilanes at low cost or to separate and concentrate boron from chlorosilanes, thereby completing the present invention.

Therefore, the present invention,

(1) A boron compound-containing chlorosilane is reacted with a fluorine element-containing salt such as NaF, KF, CaF ₂ , MgF ₂ , NH ₄ F, BaF ₂ , triphenyltin fluoride, or tributyltin fluoride to react the boron compound with the above-mentioned. A separation method of a boron compound in chlorosilanes, which is adsorbed to a fluorine element-containing salt,

(2) After adding a fluorine-containing salt such as NaF, KF, CaF ₂ , MgF ₂ , NH ₄ F, BaF ₂ , triphenyltin fluoride, or tributyltin fluoride to the boron compound-containing chlorosilanes, the chlorosilanes were added. Separation method of boron compound in chlorosilanes characterized by evaporating,

(3) produced by adding fluorine-containing salts such as NaF, KF, CaF ₂ , MgF ₂ , NH ₄ F, BaF ₂ , triphenyltin fluoride, or tributyltin fluoride to boron compound-containing chlorosilanes; It provides a composition for evaporating chlorosilanes.

In the present invention, boron in the chlorosilanes is mainly present as BC1 ₃ , for example, when NaF is acted on chlorosilanes, BC1 ₃ is considered to form a complex such as NaF and BC1 ₃ -NaF in chlorosilanes. do. In this case, chlorosilanes are nonpolar solvents and do not participate in the added NaF.

Therefore, the combination of B (1S ² 2S ² 2P) and C1 (1S ² 2S ² 2P ⁶ 3S ² 3P ⁵ ) triatoms is that three SP ² hybrid orbits of B (1S ² 2S ² PX ² PY) are C1. When NaF is added to each of the 3P orbitals of fluorine ions, fluorine ions (1S ² 2S ² 2P ⁵ ) are more reactive than chlorine ions and have smaller ionic radii, resulting in less steric hindrance and interaction. , Adsorption reaction occurs.

It was confirmed from the following fact that this reaction was not a substitution reaction but an addition reaction caused by the formation of a complex such as BC1 ₃ -NaF.

That is, after NaF was added to chlorosilanes and chlorosilanes were completely evaporated off by heating, the boron concentration in the residue (NaF) was measured by the methylene blue method. At this time, if a substitution reaction was taking place, BF ₃ would have been produced and evaporated clearly at the time of evaporation because the boiling point was -10 ° C., but the results showed the same values as the boron concentrations that existed before the start of the experiment.

Hereinafter, the present invention will be described in more detail.

The separation method of the boron compound in the chlorosilanes of the present invention is a chlorosilane containing a trace amount of boron compounds such as boron chloride mainly present as BC1 ₃ , usually 0.1 ppb to 1% by weight, in particular 0.1 ppb to 10 ppm. Fluorine element-containing salts are caused to react.

Dichlorosilane, trichlorosilane, tetrachlorosilane, etc. are mentioned as chlorosilanes in this invention.

Examples of the fluorine element-containing salts include an electrolyte substance, and specifically, NaF, KF, CaF ₂ , MgF ₂ , NH ₄ F, BaF ₂ , triphenyltin fluoride, or tributyltin fluoride.

The addition amount of these fluorine element-containing salts is not particularly related to the boron concentration present in the chlorosilanes, but is preferably a molar ratio stoichiometric ratio of 1: 1 with the boron concentration, and may be added in excess.

In this invention, the method of removing the boron compound in chlorosilanes can be performed by adding fluorine element containing salts to chlorosilanes, stirring lightly at normal temperature, and slowly evaporating chlorosilanes. Fluorine element-containing salts which are adsorbents can be easily recovered by filtration or distillation (single-shot distillation is sufficient).

In addition, since the boron compound in the chlorosilanes can be adsorbed by filling a cylindrical container with an fluorine element-containing salt as an adsorbent and passing the chlorosilanes, the recovery operation of the adsorbent is unnecessary when such a method is employed.

In addition, when fluorine element-containing salts are added to chlorosilanes and there is a contaminant caused by boron until the chlorosilanes are actually used, fluorine element-containing salts may be present in the container as it is. Chlorosilanes can be used by single distillation.

The composition in which fluorine element-containing salts are added to the chlorosilanes of the present invention can be used for evaporating chlorosilanes, for example, to grow silicon single crystals by a conventional method. As a result, the boron compound is not accompanied by a high-resistance silicon single crystal that does not substantially contain boron.

Further, according to the present invention, since the boron compound is concentrated by adsorption on fluorine element-containing salts, for example, the boron concentration in the ultra trace concentration region which has not been reached in the conventional quantitative analysis can be reliably quantified. .

Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not limited to the following Example. In addition, since the description that a boron concentration is "0.1 ppb or less" in an Example can be concentrated permanently by the method of this invention, if the concentration ratio is increased, the minimum will fall, but it is "0.1 ppb or less" as one part of a compartment. It is.

<Example 1>

To 50 g of trichlorosilane having BC1 ₃ of 100 ppm, 1 ppm, 10 ppb, and 0.1 ppb as the boron concentration, about 20 mg of NaF (product of Wako Pure Chemical Industries, Ltd.) was added and stirred gently at room temperature. Trichlorosilane (manufactured by Shin-Etsu Chemical Co., Ltd.) was slowly evaporated to measure the boron concentration in each NaF residue (in terms of sample solution) and the boron concentration in the effluent. The results are shown in Table 1.

Boron Concentration in Trichlorosilane Boron concentration in NaF residue Boron concentration in the effluent  100 ppm  100 ppm 0.1 ppb or less               1 ppm             1 ppm 0.1 ppb or less              10 ppb            10 ppb 0.1 ppb or less             0.1 ppb           0.1 ppb 0.1 ppb or less

<Example 2>

Various fluorine-containing salts (manufactured by Wako Pure Chemical Industries, Ltd.) were added to 50 g of tetrachlorosilane having a boron concentration of 10 ppb, and gently stirred at room temperature, followed by slowly stirring with tetrachlorosilane (Shin-Etsu Chemical Co., Ltd.) ) Product) was evaporated to measure the boron concentration (in terms of sample solution) and the boron concentration in the effluent. The results are shown in Table 2.

Fluoride-containing salts Amount (mg) Boron concentration in the residue Boron concentration in the effluent NaF 20 10 ppb 0.1 ppb or less KF 30  9 ppb 0.1 ppb or less CaF ₂ 40 10 ppb 0.1 ppb or less MgF ₂ 30  8 ppb 0.1 ppb or less NH ₄ F 20 10 ppb 0.1 ppb or less BaF ₂ 80 11 ppb 0.1 ppb or less Triphenyl fluoride       180  9 ppb 0.1 ppb or less Tributyl fluoride       130 10 ppb 0.1 ppb or less

<Example 3>

To 50 kg of dichlorosilane (manufactured by Shin-Etsu Chemical Co., Ltd.), 20 g of NaF (manufactured by Wako Pure Chemical Industries, Ltd.) was added, and after stirring at room temperature, the mixture was heated and vaporized, mixed with hydrogen, and heated to about 120 ° C. The chemical vapor phase growth was carried out by heating to a silicon single crystal phase to grow a single crystal of silicon. ·

The resistance value of the single crystal portion obtained at this time was -12,000 Ω-cm.

<Example 4>

To 50 kg of trichlorosilane (manufactured by Shin-Etsu Chemical Co., Ltd.), 20 g of NaF (manufactured by Wako Pure Chemical Industries, Ltd.) was added, stirred at room temperature, and then vaporized by heating, mixed with hydrogen, and about 1200 ° C. The chemical vapor phase growth was carried out by heating to a silicon single crystal phase to grow a single crystal of silicon.

The resistance value of the single crystal part obtained at this time was -11, OOOO-cm.

Example 5

To 50 kg of tetrachlorosilane (manufactured by Shin-Etsu Chemical Co., Ltd.), 20 g of NaF (manufactured by Wako Pure Chemical Industries, Ltd.) was added, stirred at room temperature, heated and vaporized, mixed with hydrogen, and about 1200 ° C. The chemical vapor phase growth was carried out by heating to a silicon single crystal phase to grow a single crystal of silicon.

The resistance value of the single crystal portion obtained at this time was -15,000 Ω-cm.

<Example 6>

To 50 g of tetrachlorosilane (manufactured by Shin-Etsu Chemical Co., Ltd.), 20 mg of NaF (manufactured by Wako Pure Chemical Industries, Ltd.) was added, stirred at room temperature, heated to vaporize tetrachlorosilane, and each residue Boron in water was quantified by methylene blue.

In addition, to confirm the accuracy, a known amount of boron was added and quantified.

object Boron concentration Tetrachlorosilane 0.1 or less Tetrachlorosilane + 0.1 ppb Boron equivalent 0.1 NaF residue 0.1 or less

Comparative Example 1

The boron concentration in the residue and in the effluent was measured in the same manner as in Example 1 except that 20 mg of NaC1 (manufactured by Wako Pure Chemical Industries, Ltd.) and NaBr (manufactured by Wako Pure Chemical Industries Ltd.) were respectively added instead of NaF. It was. The results are shown in Table 4.

Boron concentration in the residue Boron concentration in the effluent NaCl 0 ppb 20 ppb NaBr 0 ppb 10 ppb

Comparative Example 2

The resistance value of the single crystal portion of silicon obtained in the same manner as in Example 3 except that NaC1 (made by Wako Pure Chemical Industries, Ltd.) was used instead of NaF was 10 Ω-cm.

According to the present invention, it is possible to remove or concentrate a trace amount of boron in chlorosilanes at a low cost without any special device in the process by a very simple operation. In addition, as high-resistance products can be supplied in silicon single crystals, high-quality high-voltage thyristors (silicon controlled rectifiers) can be reliably supplied, and the range of conventional grades is increased by doping of impurity elements. In addition, since there was no conventional method for removing trace boron as in the present invention, in order to synthesize chlorosilanes for electronics, it was necessary to carefully select and use metal silicon having a very low boron concentration. Silicon became available.

Claims (3)

The boron compound-containing chlorosilanes are reacted with a fluorine-containing salt such as NaF, KF, CaF ₂ , MgF ₂ , NH ₄ F, BaF ₂ , triphenyltin fluoride, or tributyltin fluoride, thereby containing the fluorine-containing fluorine element. A method for separating a boron compound in chlorosilanes, which is adsorbed to a salt. After adding a fluorine-containing salt such as NaF, KF, CaF ₂ , MgF ₂ , NH ₄ F, BaF ₂ , triphenyltin fluoride or tributyltin fluoride to the boron compound-containing chlorosilanes, evaporating the chlorosilanes A separation method of boron compounds in chlorosilanes. Chlorosilanes produced by adding fluorine-containing salts such as NaF, KF, CaF ₂ , MgF ₂ , NH ₄ F, BaF ₂ , triphenyltin fluoride or tributyltin fluoride to boron compound-containing chlorosilanes Evaporation composition.