JP6630415B2 - High purity cyclohexasilane - Google Patents

Description

  The present invention relates to a high-purity hydrogenated silane compound (particularly cyclohexasilane).

  As a method for synthesizing a hydrogenated silane compound represented by cyclohexasilane, a long-known method using diphenyldichlorosilane as a raw material and undergoing a cyclization, halogenation and reduction step (Hengge method, Non-Patent Document 1) Alternatively, a method of synthesizing and reducing a dianion complex using trichlorosilane and polyamine as raw materials (Patent Document 1), a method of reacting halosilane with an ammonium salt to obtain a cyclic silane intermediate, and reducing the cyclic silane intermediate ( It is known that it can be synthesized in Patent Document 2) and the like.

Japanese Patent No. 4519955 JP 2013-95697 A

Angew. Chem. Int. Ed. Engl., 1977, 16, 403.

  The above-mentioned hydrogenated silane compound has a high possibility of being used in the semiconductor field and the battery field, and it is necessary to prepare a high-purity product by purification.However, a method of purifying the hydrogenated silane compound has not been known so far. .

  Therefore, an object of the present invention is to provide a high-purity hydrogenated silane compound applicable to the semiconductor field and the battery field.

  The present invention, which has solved the above problems, relates to a high-purity cyclohexasilane having a metal element content of 0.01 to 100 ppb. In this case, the content of sodium is preferably 0.01 to 100 ppb.

Further, the production method of the present invention is a method for obtaining a high-purity hydrogenated silane compound having a metal element content of 0.01 to 100 ppb from a hydrogenated silane compound containing impurities, the method comprising: Is the following formula (1)
(SiH ₂ ) _n ... (1)
(In the formula (1), n is 3 to 6.)
Or the following equation (2)
_{Si m H 2m + 2 ... (} 2)
(In the formula (2), m is 3 to 6.)
And characterized in that at least two or more distillation steps under different conditions are performed.

  It is preferable to perform a first distillation step by any of short-stroke distillation, thin-film distillation, and molecular distillation and a second distillation step in a distillation column. The first distillation step is performed at 25 to 80 ° C., and the second distillation step is performed. It is also a preferable embodiment to carry out the reaction at a temperature higher than that of the first distillation step and at 50 to 100 ° C. Further, performing the first distillation step at 3 kPa to 10 Pa is also a preferred embodiment of the method of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the content of the metal element was small, and the high-purity cyclohexasilane which could suppress generation | occurrence | production of the polymer of cyclohexasilane even after long-term storage was able to be provided.

  The present inventors have studied the pressure range and temperature range in which the purification efficiency of crude cyclohexasilane is improved, and decided to distill the crude cyclohexasilane under an absolute pressure of at least 2 kPa or less. A specific distillation apparatus suitable for controlling such a temperature in a specific range or further distilling in a low pressure region (for example, a medium vacuum region of 0.1 to 100 Pa to a high vacuum region of 0.00001 to 0.1 Pa). A method for producing the adopted cyclohexasilane was found, and a patent application was filed (Japanese Patent Application No. 2012-281489).

  Then, the present inventors have studied for the purpose of producing a hydrogenated silane compound having a higher purity than cyclohexasilane obtained by the above method with a good yield. As a result, distillation under different conditions is performed twice or more. Thus, the impurities in the obtained hydrogenated silane compound were successfully reduced. Hereinafter, the present invention will be described.

[High-purity hydrogenated silane compound, especially cyclohexasilane]
The high-purity hydrogenated silane compound of the present invention is characterized in that the content of a metal element as an impurity is 0.01 to 100 ppb (by mass). As a result of producing the hydrogenated silane compound by a production method employing a purification method described later, the metal element could be reduced to the above range. By reducing the metal element to the above range, an increase in the amount of the polymer component when the hydrogenated silane compound is stored for a long period of time could be suppressed. Examples of the metal element include those derived from a reducing agent or a reaction raw material such as aluminum, sodium, potassium, lithium, iron, calcium, magnesium, titanium, chromium, and copper. Among them, a high-purity hydrogenated silane compound in which sodium is reduced to 0.01 to 100 ppb is preferable. This is because sodium is a metal element that is highly likely to be mixed irrespective of the production method and process, and it is industrially useful to reduce sodium.

  As the high-purity hydrogenated silane compound of the present invention, since cyclohexasilane is particularly useful, a high-purity cyclohexasilane having a metal element (preferably sodium) content of 0.01 to 100 ppb is included. . In addition, even if the metal element is very small, cyclohexasilane which is mixed can be said to be a high-purity cyclohexasilane composition, and the above content is the content in the cyclohexasilane composition. You can also. In the following description, as for the content of the metal element and the content of the polymer, the term “composition” may be omitted, but it means “content in the composition”.

  In the high-purity cyclohexasilane, each content of aluminum, sodium, potassium, lithium, iron, calcium, magnesium, titanium, chromium, and copper is preferably reduced to 10 ppb or less, more preferably 5 ppb or less, It is more preferably at most 2 ppb, particularly preferably at most 1 ppb. The lower limit is most preferably zero (ND), but because it is technically difficult, the lower limit is preferably about 0.01 ppb.

  The high-purity cyclohexasilane of the present invention has a low polymer component content by the method described below. Specifically, in cyclohexasilane, the content of the polymer component is preferably 0 to 5000 ppm (by mass), more preferably 0 to 1000 ppm, still more preferably 0 to 500 ppm, and particularly preferably 0 to 100 ppm. , Most preferably 0 (ND).

  The high-purity cyclohexasilane of the present invention has excellent storage stability due to the small content of the metal element and the polymer component. For example, in a container made of metal and having an inner wall coated with a resin material such as a fluororesin, the amount of increase in the polymer when stored at 25 ° C. for 30 days under a nitrogen atmosphere is preferably 0 to 5000 ppm. And more preferably 0 to 1000 ppm, further preferably 0 to 500 ppm, particularly preferably 0 to 100 ppm, and most preferably 0 (ND). Further, the content of the polymer itself when stored at 25 ° C. for 30 days under a nitrogen atmosphere is also preferably 0 to 5000 ppm, more preferably 0 to 1000 ppm, still more preferably 0 to 500 ppm, and particularly preferably 0 to 100 ppm. , Most preferably 0 (ND).

The high-purity cyclohexasilane of the present invention can be produced by the production method of the present invention described later. However, the high-purity hydrogenated silane compound produced by the production method of the present invention may contain other hydrogenated silane compounds in addition to cyclohexasilane, and these hydrogenated silane compounds are represented by the following formula: (1)
(SiH ₂ ) _n ... (1)
(In the formula (1), n is 3 to 6.)
Or the following equation (2)
_{Si m H 2m + 2 ... (} 2)
(In the formula (2), m is 3 to 6.)
Is represented by In the following description, the term “hydrogenated silane compound” or “high-purity hydrogenated silane compound” includes the compounds represented by the above (1) and (2).

  Examples of the cyclic silane compound represented by the formula (1) include cyclotrisilane, cyclotetrasilane, cyclopentasilane, silylcyclopentasilane, and cyclohexasilane, and a chain silane represented by the formula (2). Examples of the compound include trisilane, tetrasilane, isotetrasilane, pentasilane, neopentasilane, isopentasilane, hexasilane and the like. Substitutes in which these hydrogens are substituted with an alkyl group, an aryl group, or the like may be used. Of these, cyclic silane compounds are preferred, and cyclohexasilane, which is particularly susceptible to polymerization, can suppress the production of a polymer during the purification step by applying the production method of the present invention, and can significantly improve the purification yield. , And the effect of reducing the metal element is likely to appear.

[First distillation step]
The hydrogenated silane compound obtained through the reduction step contains, as impurities, a polymer component of the hydrogenated silane compound (particularly in the case of a cyclic silane compound) of several percent to several tens percent, and a metal element derived from a reducing agent. Since several hundreds to several thousand ppm are contained, if the hydrogenated silane compound (especially cyclohexasilane) containing such impurities is suddenly distilled at a high temperature, the amount of the polymer of the hydrogenated silane compound further increases. Was found. This is because the polymer component or metal element of the hydrogenated silane compound contained in the hydrogenated silane compound as an impurity promotes the polymerization of the hydrogenated silane compound during vacuum distillation performed in a high-temperature distillation tower or the like. It is thought that this is because it has a function as a polymerization accelerator. The polymer refers to a dimer of the target hydrogenated silane compound and a multimer thereof.

  Therefore, in the present invention, it is a main object of the first distillation step to quickly remove impurities (particularly, polymer components) without increasing the amount of the polymer. Therefore, the temperature of the first distillation step is preferably performed at 25 to 80 ° C. If the temperature is too low, not only the evaporation rate is slow, but also the temperature of the condenser must be lowered to ensure that the vaporized hydrogenated silane compound is condensed, and the solid hydrogenated silane compound adheres to the condenser. And the line may be blocked. If the temperature of the condenser is raised to such an extent that the solid hydrogenated silane compound does not precipitate, the temperature difference between the evaporator and the condenser becomes smaller, the amount of the non-condensed hydrogenated silane compound increases, and the distillation yield deteriorates. On the other hand, if the heating temperature of the hydrogenated silane compound is too high, the polymerization proceeds, the amount of the polymer increases in the first distillation step, and the amount of the polymer in the subsequent second distillation step also increases, which is not preferable. . The temperature of the first distillation step is more preferably 30 to 70 ° C, still more preferably 35 to 65 ° C, and particularly preferably 40 to 60 ° C.

  The crude hydrogenated silane compound introduced into the first distillation step may be a solution dissolved in a solvent. At this time, the concentration of the unpurified hydrogenated silane compound in the solution is preferably from 50 to 100% by mass from the viewpoint of distillation efficiency. When the synthesis reaction of the hydrogenated silane compound, which is a stage prior to the distillation, is performed in a reaction solvent, the solvent may be removed and concentrated in advance so that the concentration is within the above-mentioned range.

In the first distillation step, the point is not to increase the amount of the polymer of the hydrogenated silane compound. Therefore, instead of distillation in the distillation column, select a distillation method using a distillation apparatus in which heat history is not easily applied in a short time. Is preferred. For example, a short-path distillation apparatus, a thin-film distillation apparatus, a molecular distillation apparatus, and the like. According to a strict definition, molecular distillation is performed under a high vacuum (for example, about 10 ^-1 Pa to 10 ^-5 Pa), and the distance between the evaporation surface and the condensation surface is shorter than the mean free path of the vapor molecule. In the present specification, the term “molecular distillation” is used in the art to mean molecular distillation, that is, performed under a high vacuum (for example, about 10 ⁻¹ Pa to about 10 ⁻⁵ Pa). As long as the distance between the evaporating surface and the condensing surface is larger than the mean free path of the vapor molecule, it is used. According to such molecular distillation, ideally, all vapor molecules that have evaporated do not collide with other vapor molecules or wall surfaces until they reach the aggregation surface from the evaporation surface, and all the molecules remain in the condenser. Agglomerated. However, the degree of vacuum is too high to implement on a large scale.

On the other hand, a short-path distillation apparatus is an improvement of a molecular distillation apparatus that is slightly difficult on a large scale, and is performed under a medium vacuum (for example, about 10 ² Pa to 10 ⁻¹ Pa), and the evaporation surface and the condensation surface are vaporized. It is characterized in that it is located relative to a position near the level of the mean free path of the molecule. The thin film distillation apparatus is operated under a low vacuum to a medium vacuum (for example, about 3 × 10 ³ Pa to 10 ⁻¹ Pa, preferably about 10 ³ Pa to 10 ⁻¹ Pa), and the condenser is disposed outside the evaporator. And is different from a short stroke distillation apparatus.

  In the present invention, the first distillation step is preferably performed at a reduced pressure (absolute pressure) of 3 kPa or less, more preferably 1 kPa or less, further preferably 500 Pa or less, particularly preferably 200 Pa or less. This is because if the pressure in the first distillation step is too high, the hydrogenated silane compound may be subjected to heat history and the amount of polymer may be increased. The degree of reduction in the degree of pressure reduction in the first distillation step is not particularly limited, but is preferably 1 Pa or more, more preferably 10 Pa or more, in actual operation.

  It is preferable that all of the above-mentioned distillation apparatuses use a thin-film evaporator. The thin-film evaporator forms a thin film of an evaporation raw material on an evaporation surface and supplies heat to evaporate. Examples of the evaporator having the evaporating surface include a plate-like body (for example, a rectangular plate, a disk, or the like), a tubular body, a bottomed container, and the like. The surface of the plate-like body, the inner surface of the tubular body Alternatively, the outer surface, the inner surface of the container, or the like may be the evaporation surface. From the viewpoint of thinning and evaporating the evaporation raw material, an evaporator such as a plate-like body or a cylindrical body is preferable. By thinning and evaporating, even if the boiling point of the evaporating material is not reached, the evaporation of the evaporating material can be promoted and the purification efficiency can be increased. In addition, the heat history of the evaporating material can be suppressed by suppressing the bubbling and boiling of the evaporating material. Can be kept small. When the evaporator is a plate-like body or a cylindrical body, a forced thinning means may be provided. As the forced thinning means, for example, a wiper element that operates along the surface of the plate-like body, or the inner or outer surface of the cylindrical body, or a forced rotating means that can generate a centrifugal force by rotating a disk or a cylindrical body Etc. can be used. When a plate-like body or a cylindrical body is provided with a wiper element or a forced rotation means as a forced thinning means, a wiper type thin film evaporator or a centrifugal thin film evaporator is obtained. In addition, even if it is a plate-like body or a cylindrical body which does not have a forced thinning means, if the evaporation surface is arranged vertically and the evaporation raw material is allowed to flow little by little from the upper part, it becomes a falling thin film evaporator. . Particularly preferred are a centrifugal thin film evaporator and a falling thin film evaporator.

  In a molecular distillation apparatus or a short-path distillation apparatus, a condenser is disposed inside an evaporator. In the thin-film distillation apparatus, the condenser is arranged outside the evaporator. In any case, the condenser is provided with a condensing surface for cooling the vapor molecules in contact with the vapor molecules evaporated in the evaporator. In a short-stroke distillation apparatus, the condensation surface of the condenser is arranged opposite to the evaporation surface of the evaporator. In the molecular distillation apparatus as well, it is preferable that the evaporation surface and the condensation surface are arranged opposite to each other, but the present invention is not limited to this, and various arrangements can be made within a range applicable to molecular distillation. As a distillation apparatus in which the evaporation surface and the condensation surface are disposed opposite to each other in the device, for example, the distillation device has a double-pipe structure including an outer cylinder and an inner cylinder, and the inner surface of the outer cylinder is formed as an evaporation surface or a condensation surface. And an outer surface of the inner cylinder as a condensing surface or an evaporating surface. When the evaporating surface and the condensing surface are opposed to each other, the area of the condensing surface is preferably equal to or more than the area of the evaporating surface.

  Although the arrangement of the condenser is different between the molecular distillation apparatus and the short-path distillation apparatus and the thin-film distillation apparatus as described above, these distillation apparatuses are preferably a centrifugal thin-film distillation apparatus, a concentric tube-type distillation apparatus, and a ryebolt. It is classified into a mixed thin film distillation device, a falling film distillation device, and the like.

  The thickness of the thin film formed on the evaporation surface of the thin film evaporator may be appropriately set in consideration of the evaporation rate and the like, but is preferably 10 to 100 μm, more preferably 20 to 90 μm, and still more preferably. Is 30 to 80 μm. In addition, since the evaporation area is determined by the scale of the apparatus, it may be appropriately selected according to the amount of the hydrogenated silane compound to be evaporated.

  In the first distillation step, the evaporated hydrogenated silane compound is preferably condensed at -5C to 30C. The condensation temperature is more preferably -2 ° C to 20 ° C, still more preferably 0 ° C to 15 ° C. When the condensation temperature is within this range, it is possible to maintain good workability without causing the hydrogenated silane compound to be solidified and blocking the inside of the apparatus.

  In the present invention, a series of operations relating to the first distillation step (specifically, operations from charging a hydrogenated silane compound before purification to taking out a condensate of the first distillation) are exposed to the air. It is preferred to do without. For example, the container for the hydrogenated silane compound before purification, the distillation apparatus (evaporator, condenser, etc.), and the container for the condensate of the first distillation are all contained in one explosion-proof booth. The inside may be controlled to an atmosphere of an inert gas such as nitrogen, etc., or the preparation of the liquid before purification, the transfer of the gas after the distillation, and the removal of condensate, etc., may be performed by pressure feeding with an inert gas such as a nitrogen gas. Alternatively, distillation may be performed in a closed device to prevent exposure to the atmosphere.

In the first distillation step, the polymer component in the condensate of the first distillation can be reduced to almost zero, and the metal element can be reduced to about several to several tens of ppm or less, depending on the distillation apparatus and distillation conditions employed. preferable. The quantification of the polymer component can be performed by ¹ H-NMR, and the quantification of the metal element can be performed by ICP or ICP-MS.

[Second distillation step]
In the second distillation step, vacuum distillation is performed in a known distillation column. By the first distillation, the polymer component of the hydrogenated silane compound, which is considered to promote the polymerization of the hydrogenated silane compound, is reduced to almost zero, and the metal element is reduced to about several to several tens of ppm. Even if the second distillation step is performed at a higher temperature than the first distillation step, there is no possibility that the amount of the polymer component of the hydrogenated silane compound increases. Therefore, the second distillation step can be performed at 50 to 100 ° C. (preferably higher than the temperature employed in the first distillation step). The temperature is more preferably 60 to 90 ° C, and still more preferably 70 to 85 ° C.

  The second distillation step is preferably performed at a reduced pressure (absolute pressure) of 5 kPa or less, more preferably 2 kPa or less, further preferably 1 kPa or less, particularly preferably 200 Pa or less. If the pressure in the second distillation step is too high, the polymer component of the hydrogenated silane compound may be reduced in the first distillation step, but may be newly formed in the second distillation step. The lower limit of the degree of reduced pressure in the second distillation step is not particularly limited, but is preferably 5 Pa or more, more preferably 10 Pa or more, in actual operation.

  In the purified hydrogenated silane compound after the second distillation step, the polymer component of the hydrogenated silane compound is preferably reduced to zero (ND) and the metal element (total amount) is preferably reduced to 100 ppb or less. The metal element in the purified (high-purity) hydrogenated silane compound is more preferably 50 ppb or less, further preferably 20 ppb or less, and particularly preferably 10 ppb or less. The lower limit is most preferably zero (ND), but because it is technically difficult, the lower limit is preferably about 0.01 ppb. Furthermore, the content of each of aluminum, sodium, potassium, lithium, iron, calcium, magnesium, titanium, chromium, and copper is preferably reduced to 10 ppb or less, more preferably 5 ppb or less, and still more preferably 2 ppb or less. Particularly preferred is 1 ppb or less. The lower limit is most preferably zero (ND), but because it is technically difficult, the lower limit is preferably about 0.01 ppb. A silicon film formed using a hydrogenated silane compound in which the content of these metal elements is higher than the above range is not preferable because it has low mobility and causes deterioration in performance when used as a semiconductor. Further, when the metal element is chromium or copper, it is not particularly preferable.

[When the distillation step is performed three or more times]
In the present invention, the polymer component of the hydrogenated silane compound in the purified hydrogenated silane compound is reduced to zero (ND) by performing the second distillation step following the first distillation step described above. Since the metal element can be reduced to 100 ppb or less, there is no need to perform further distillation, but if necessary, a distillation step performed under the same conditions as the first distillation step between the first distillation step and the second distillation step Alternatively, a further distillation step or the like after the second distillation step may be performed.

[Other purification methods]
In addition, purification methods other than distillation include washing of the product with water, an organic solvent, and a mixed solvent thereof, oxidizing agent treatment in which the product is brought into contact with an oxidizing agent, adsorption purification method, reprecipitation method, liquid separation extraction A conventionally known purification method such as a purification method, a recrystallization method, a crystallization method, purification by chromatography or the like may be combined.

[Unpurified hydrogenated silane compound]
In the present invention, the method for synthesizing the unpurified hydrogenated silane compound to be subjected to the first distillation step is not particularly limited, and a known synthesis method can be appropriately employed. For example, when the hydrogenated silane compound is cyclohexasilane, diphenyldichlorosilane is used as a raw material, cyclization is performed using an alkali metal, a 6-membered ring is isolated, and contacted with hydrochloric acid gas in the presence of aluminum chloride to form a solution on silicon. Of the resulting cyclohexasilane, and then contacting the resulting cyclohexasilane halide with a metal hydride such as lithium aluminum hydride to reduce the resulting reaction mixture to crude cyclohexasilane (crude cyclohexasilane). ) Can be used. Further, a method described in Synthesis Example 2 described below, which is found by the present inventors, that is, a method in which a halosilane compound such as trichlorosilane is cyclized in the presence of phosphine, and the obtained cyclohexasilane halide is reduced. Can be used as crude cyclohexasilane.

  In addition, for example, in a preferred embodiment of the present invention, since the first distillation step is performed under a vacuum of 3 kPa or less, the unpurified hydrogenated silane compound to be subjected to the first distillation step desirably has a low content of light boiling components. It is preferable that light-boiling components such as a solvent are removed in advance before being subjected to the first distillation step. Specifically, for example, the solvent may be distilled off under normal pressure or a reduced pressure of more than 2 kPa.

[High-purity hydrogenated silane compound not limited to cyclohexasilane]
According to the production method of the present invention, a polymer component of a hydrogenated silane compound is not contained (ND) in a high purification yield of usually 80% or more, more preferably 90% or more, and a metal element (particularly sodium) ) Is reduced to the range of 0.01 to 100 ppb, so that a high-purity hydrogenated silane compound can be obtained. In particular, cyclohexasilane can easily proceed with the polymerization reaction when the amount of the metal element increases, but by setting the content of the metal element within the above range, it is possible to suppress the progress of the polymerization reaction and to store the metal element stably. Become. Cyclohexasilane is superior to lower-order hydrogenated silane compounds in that the growth rate during film formation is high, and has high utility.

  As described above, the high-purity hydrogenated silane compound of the present invention has a low content of the polymer component. Specifically, in the hydrogenated silane compound, the content of the polymer component is preferably 0 to 5000 ppm, more preferably 0 to 1000 ppm, still more preferably 0 to 500 ppm, particularly preferably 0 to 100 ppm, and most preferably. Is 0 (ND).

  The high-purity hydrogenated silane compound of the present invention has excellent storage stability due to the small content of the metal element and the polymer component. For example, in a container made of metal and having an inner wall coated with a resin material such as a fluororesin, the amount of increase in the polymer when stored at 25 ° C. for 30 days under a nitrogen atmosphere is preferably 0 to 5000 ppm. And more preferably 0 to 1000 ppm, further preferably 0 to 500 ppm, particularly preferably 0 to 100 ppm, and most preferably 0 (ND). Further, the content of the polymer itself when stored at 25 ° C. for 30 days under a nitrogen atmosphere is also preferably 0 to 5000 ppm, more preferably 0 to 1000 ppm, still more preferably 0 to 500 ppm, and particularly preferably 0 to 100 ppm. , Most preferably 0 (ND).

  The high-purity hydrogenated silane compound of the present invention is useful, for example, as a silicon raw material used for solar cells, semiconductors, and the like.

  Hereinafter, the present invention will be described more specifically with reference to Examples. However, the present invention is not limited to the following Examples, and may be appropriately modified within a range that can be adapted to the purpose of the preceding and the following. It is of course possible to carry out them, and all of them are included in the technical scope of the present invention.

The purity (yield) of cyclohexasilane is analyzed by a gas chromatograph ("GC2014" manufactured by Shimadzu Corporation) equipped with a capillary column ("DB-1MS" manufactured by J & W SCIENTIFIC; 0.25 mm x 50 m). I asked.
The amount of the metal component was measured by ICP-MS (“Agilent 7700S” manufactured by Agilent Technologies) in a state of being diluted 500 times with 5% by mass of diluted nitric acid.

The presence of a polymer of cyclohexasilane is determined by using ¹ H-NMR (“Unity plus 400” manufactured by Varian) whether a broad peak is observed at 3 to 4 ppm (TMS standard) in heavy benzene. And, when observed, quantified from the integral ratio of the peak.

Synthesis Example 1
The cyclohexasilane was synthesized by the method described in Angew. Chem. Int. Ed. Engl., 1977, 16, 403. Table 1 shows the amount of the polymer and the amount of the metal element in the unpurified cyclohexasilane. In Table 1,% is% by mass, and ppm and ppb are based on mass.

Example 1
The first distillation step of the cyclohexasilane obtained in Synthesis Example 1 was performed using a short-path distillation apparatus (KDL1 type, manufactured by U.I.C., Germany) obtained from Fintech. The evaporation area of the KDL1 short stroke distillation apparatus is 0.017 m ² . The degree of pressure reduction in the first distillation step was 100 Pa, the heating temperature was 40 ° C., and the temperature of the condenser was 5 ° C. The feed rate of the crude cyclohexasilane was 1.5 g / min.
Table 1 shows the yield in the first distillation step, the amount of the polymer in the obtained cyclohexasilane, and the amount of the metal element.

  Subsequently, a second distillation step of the cyclohexasilane obtained in the first distillation step was performed. The second distillation step is performed using a general vacuum distillation apparatus made of glass (eg, an eggplant flask, a connecting pipe, a distillation connecting pipe (three-pronged), a cooling pipe, and a receiver), at a reduced pressure of 800 Pa, a heating temperature of 80 ° C., and a cooling unit. Distillation was performed at 5 ° C. The yield in the second distillation step was 95% by mass, and the total yield in the first and second distillation steps was 89% by mass. Table 1 shows the amounts of polymer and metal element in the obtained purified cyclohexasilane.

  Further, the obtained purified cyclohexasilane was stored at 25 ° C. for 30 days in a nitrogen atmosphere. When the presence of the polymer component in the cyclohexasilane after storage was confirmed, no polymer component was recognized.

Comparative Example The cyclohexasilane obtained in Synthesis Example 1 was distilled under the same distillation conditions with the same vacuum distillation apparatus as in the second distillation step without performing the first distillation step. The yield was 60% by mass, and it is considered that a considerable amount of cyclohexasilane was converted into a polymer. However, the polymer was not vaporized and could not be detected. Table 1 shows the amounts of metal elements in the obtained purified cyclohexasilane. When purified cyclohexasilane was stored for 30 days in the same manner as in Example 1, it was confirmed that 2% by mass of the polymer component was produced. It was found that in order to maintain the purity of the hydrogenated silane compound at a high level even during long-term storage, it is necessary to reduce the amount of metal elements to a high degree.

Synthesis Example 2
After replacing the inside of a 3 L four-necked flask equipped with a thermometer, a condenser, a dropping funnel and a stirring device with nitrogen gas, 129 g (0.49 mol) of triphenylphosphine as phosphine and 382 g of diisopropylethylamine (2. 95 mol) and 1.2 L of 1,2-dichloroethane as a solvent. Subsequently, 400 g (2.95 mol) of trichlorosilane as a halosilane compound was slowly dropped from the dropping funnel at 25 ° C. while stirring the solution in the flask. After completion of the dropwise addition, the mixture was reacted by heating and stirring at 60 ° C. for 6 hours. The obtained reaction solution was concentrated and washed to obtain a nonionic dodecachlorocyclohexasilane-containing compound ([Ph ₃ P] ₂ [Si ₆ Cl ₁₂ ]) as a white solid.

  In a 100 mL two-necked flask equipped with a dropping funnel and a stirrer, 2.44 g of the obtained white solid (2.18 mmol of dodecachlorocyclohexasilane-containing compound) was placed and dried under reduced pressure. Next, after the inside of the flask was replaced with argon gas, 30 mL of cyclopentyl methyl ether was added as a solvent. Subsequently, while stirring the suspension in the flask, 10 mL of a diethyl ether solution of lithium aluminum hydride (concentration: about 1.0 mol / L) as a reducing agent was gradually dropped from the dropping funnel under the condition of −20 ° C. Then, the mixture was reacted by stirring at -20 ° C for 5 hours. After the reaction, the reaction solution was filtered under a nitrogen gas atmosphere to remove generated salts. The solvent was distilled off from the obtained filtrate under reduced pressure to obtain a colorless transparent liquid crude cyclohexasilane.

Example 2
Using the crude cyclohexasilane obtained in Synthesis Example 2 above, the first distillation step and the second distillation step were performed in the same manner as in Example 1 to obtain purified cyclohexasilane.
The purified cyclohexasilane obtained was stored at 25 ° C. for 30 days under a nitrogen atmosphere, and the presence of the polymer component in the cyclohexasilane after storage was confirmed. As a result, no polymer component was recognized.

  The present invention has provided high-purity cyclohexasilane having a small amount of impurities such as a metal element and a polymer. Further, the method of the present invention can efficiently and easily produce high-purity hydrogenated silane compounds such as high-purity cyclohexasilane. The high-purity hydrogenated silane compound of the present invention is suitably used as a silicon raw material in applications such as solar cells and semiconductors.

Claims (4)

  A high-purity cyclohexasilane having a metal element content of 0.01 to 100 ppb and a polymer component content of 0 to 5000 ppm (by mass).   High-purity cyclohexasilane having a sodium content of 0.01 to 100 ppb and a polymer component content of 0 to 5000 ppm (by mass).   High purity cyclohexasilane having a chromium content of 0.01 to 10 ppb and a polymer component content of 0 to 5000 ppm (by mass).   High-purity cyclohexasilane having a potassium content of 0.01 to 10 ppb and a polymer component content of 0 to 5000 ppm (by mass).