JP7022512B2 - Cyclohexasilane with low halogen element content - Google Patents

Description

The present invention relates to cyclic hydrides having a low halogen element content.

Silicon films are used in solar cells, semiconductors, and the like. As a method for producing a silicon film, a vapor deposition film forming method (CVD method) using monosilane as a raw material is widely used. Further, as another method for producing the silicon film, a CVD method using a cyclic silane compound represented by the general formula (SiH ₂ ) n (n = 4, 5, or 6) as a raw material (Patent Document 1), cyclohexaci. A CVD method using orchids as a raw material (Patent Document 2), a method of forming a solution layer containing cyclopentasilane or cyclohexasilane as a solute on a substrate, and producing polysilane by photopolymerization have been reported (Patent Document 3). ing.

As a method for producing a cyclic hydride silane, Patent Document 4 describes that a cyclization reaction of halosilane is carried out in the presence of a specific coordinating compound to obtain a cyclic halogenated silane neutral complex, which is then reduced. Thereby, a method for producing a cyclic hydride silane is disclosed.

Japanese Unexamined Patent Publication No. 60-26664 Special Table 2013-537705 Gazette Japanese Unexamined Patent Publication No. 2013-187261 Japanese Unexamined Patent Publication No. 2015-134755

By the way, it has been found this time that when the cyclic hydrogenated silane contains a halogen element, the purity is lowered by cleaving the Si—Si bond or polymerizing by cleaving the Si—Si bond during storage. Such a decrease in purity could be grasped from the calibration curve purity measured by using a gas chromatograph.

The present invention has been made by paying attention to the above circumstances, and an object of the present invention is to suppress a decrease in purity due to cleavage of a Si—Si bond or the like during storage, and a ring having excellent storage stability. The purpose is to provide silane hydride.

The cyclic hydrogenated silane according to the present invention, which has solved the above problems, is represented by the following formula (1) and has a gist that the halogen element content is 100 ppm or less (including 0 ppm) on a mass basis. In the following formula (1), n is 3 to 8.
(SiH ₂ ) _n ... (1)

The halogen element may be, for example, chlorine. The cyclic hydrogenated silane may be, for example, cyclohexasilane in which n in the formula (1) is 6.

Since the cyclic hydride content of the cyclic hydride of the present invention is reduced to 100 ppm or less on a mass basis, it is suppressed that the purity is lowered due to the cleavage of Si—Si bond during storage, and the storage stability is improved. Can be improved.

The cyclic hydrogenated silane of the present invention is represented by the following formula (1), and the content of the halogen element as an impurity is 100 ppm or less (including 0 ppm) on a mass basis. In the following formula (1), n is 3 to 8. By reducing the halogen element content to the above range, the storage stability of the cyclic hydride can be improved. Further, the cyclic hydrogenated silane is stored in, for example, a stainless steel container and used as a raw material for semiconductors and the like. However, if the cyclic hydride contains a halogen element, the storage container and the semiconductor element may corrode or the semiconductor film may be corroded. Electrical properties (eg, mobility, etc.) deteriorate. However, by reducing the halogen element content to the above range, even if the cyclic hydride silane is stored in a stainless steel container or used as a raw material for semiconductors, it is less likely to corrode. The electrical characteristics of the semiconductor film can be improved.
(SiH ₂ ) _n ... (1)

The halogen elements are fluorine, chlorine, bromine and iodine, and in particular, chlorine.

The cyclic hydride has n of 3 to 8 in the above formula (1), and specifically, cyclotrisilane, cyclotetrasilane, cyclopentasilane, cyclohexasilane, cycloheptasilane, cyclooctasilane and the like. Cyclic hydrogen having a branched silyl group such as cyclic hydride without a branched silyl group, silylcyclotrisilane, silylcyclotetrasilane, silylcyclopentasilane, silylcyclohexasilane, silylcycloheptasilane Examples thereof include silane hydride, and cyclic hydrides having no branched silyl group are preferable. Among the cyclic hydrogenated silanes, cyclohexasilane having n of 6 in the above formula (1) is useful.

The halogen element content in the cyclic hydride is preferably 50 ppm or less, more preferably 30 ppm or less, and particularly preferably 20 ppm or less on a mass basis. The lower limit is, on a mass basis, 0 ppb is most preferable, but it may be about 1 ppb or about 3 ppb.

The purity of the cyclic hydrogenated silane of the present invention is, for example, preferably 95% or more, more preferably 97% or more, and particularly preferably 98% or more. The purity of the cyclic hydride can be measured using, for example, a gas chromatograph.

The cyclic hydrogenated silane of the present invention can be obtained from cyclic hydrides obtained by various methods by reducing the halogen element content by an appropriate method. The method for producing the cyclic hydride silane itself before the halogen element content is reduced is not particularly limited, and various known production methods can be adopted, but preferably, the cyclic halosilane obtained by cyclizing the halosilane can be obtained. The method of reduction is adopted.

Examples of the halosilane (halogenated silane) include dihalosilanes such as dichlorosilane, dibromosilane, diiodosilane, and difluorosilane; trihalosilanes such as trichlorosilane, tribromosilane, triiodosilane, and trifluorosilane; tetrachlorosilane and tetrabromo. Tetrahalosilanes such as silane, tetraiodosilane, and tetrafluorosilane; and the like can be used. Among these, trihalosilane is preferable, and trichlorosilane is particularly preferable.

The method for cyclizing the halosilane is not particularly limited, but for example, the method (A) or (B) below is preferable.
(A) A method for obtaining a cyclic halosilane salt, which comprises a step of contacting a halosilane (halogenated monosilane) with a phosphonium salt and / or an ammonium salt [hereinafter, may be referred to as method A].
(B) A method for obtaining a cyclic halosilane neutral complex, which comprises a step of contacting halosilane with at least one compound selected from the group consisting of the following (I) and (II) [hereinafter, may be referred to as method B]. be].

(I) A compound represented as XR _n [hereinafter, may be referred to as compound I]. When X is P or P = O, n = 3, and R represents the same or different substituted or unsubstituted alkyl or aryl group. When X is S, S = O, O, n = 2, and R represents the same or different substituted or unsubstituted alkyl or aryl group. When X is CN, n = 1, and R represents a substituted or unsubstituted alkyl group or aryl group. However, the number of amino groups in XR _n is 0 or 1.

(II) At least one heterocyclic compound selected from the group consisting of substituted or unsubstituted heterocyclic compounds containing N, O, S or P having an unshared electron pair in the ring [hereinafter referred to as compound II]. There is]. However, the number of tertiary amino groups as substituents of the heterocyclic compound is 0 or 1.

First, the above method A will be described.

The phosphonium salt is preferably a quaternary phosphonium salt, and a salt represented by the following formula (11) is preferably mentioned. In the following formula (11), R ¹ to R ⁴ may be different from each other, but it is preferable that they are all the same group.

Further, the ammonium salt is preferably a quaternary ammonium salt, and a salt represented by the following formula (12) is preferably mentioned. In the following formula (12), R ⁵ to R ⁸ may be different from each other, but it is preferable that they are all the same group.

In the above formula (11) and the above formula (12), R ¹ to R ⁴ and R ⁵ to R ⁸ independently represent a hydrogen atom, an alkyl group, and an aryl group, ^and A- represents a monovalent anion. ..

The alkyl groups of R ¹ to R ⁴ and R ⁵ to R ⁸ include carbons such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group and cyclohexyl group. Alkyl groups having the number 1 to 16 are preferably mentioned, and alkyl groups having 1 to 8 carbon atoms are more preferable.

As the aryl group of R ¹ to R ⁴ and R ⁵ to R ⁸ , an aryl group having 6 to 18 carbon atoms such as a phenyl group and a naphthyl group is preferable, and an aryl group having 6 to 12 carbon atoms is more preferable.

The R ¹ to R ⁴ and R ⁵ to R ⁸ are preferably an alkyl group or an aryl group, more preferably an aryl group. If R ¹ to R ⁴ and R ⁵ to R ⁸ are aryl groups, as will be described later, when the salt of the cyclic halosilane is produced, the salt of the cyclic halosilane is precipitated and formed in the reaction solution to form the cyclic halosilane. It becomes easy to obtain the salt with high purity. Also, for the same reason, it is preferable to use a phosphonium salt rather than an ammonium salt.

In the above formulas (11) and (12), the monovalent anion represented by A- includes halide ions (for example, ^{Cl- ,} Br- ^, I- ^, etc.) and borate ions (for example, BF ^4- ). , Phylogen-based anions (eg, PF ^6- ) and the like. Among these, halogenated ions are preferable from the viewpoint of easy availability, more preferably ^Cl- , Br-, I- ^{, and} particularly preferably ^{Cl- ,} Br-.

Either one of the phosphonium salt and the ammonium salt may be used, or both may be used. As the phosphonium salt, only one kind may be used, or two or more kinds may be used in combination. Only one type of ammonium salt may be used, or two or more types may be used in combination.

The amount of the phosphonium salt and / or ammonium salt used (the total amount used when two or more kinds are used) is preferably 0.01 mol or more, more preferably 0.05 mol or more, still more preferably 0.05 mol or more with respect to 1 mol of halosilane. It is 0.08 mol or more, preferably 1.0 mol or less, more preferably 0.7 mol or less, still more preferably 0.5 mol or less. When the amount of the phosphonium salt and / or the ammonium salt used is in the above range, the yield of the cyclic halosilane salt tends to be improved.

The above method A is preferably performed in the presence of a chelated ligand such as a polyether, a polythioether, or a polydentate phosphine. By carrying out the cyclization coupling reaction in the presence of a chelate-type ligand, a salt of cyclic halosilane can be efficiently produced. Further, the number of hydrogens and the composition ratio in the obtained cyclic halosilane can be adjusted by appropriately selecting the type of chelate-type ligand to be used.

Examples of the polyether include 1,1-dimethoxyethane, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-dipropoxyetane, 1,2-diisopropoxyetane, 1,2. -Dibutoxyethane, 1,2-diphenoxyethane, 1,3-dimethoxypropane, 1,3-diethoxypropane, 1,3-dipropoxypropane, 1,3-diisopropoxypropane, 1,3-di Butoxypropane, 1,3-diphenoxypropane, 1,4-dimethoxybutane, 1,4-diethoxybutane, 1,4-dipropoxybutane, 1,4-diisopropoxybutane, 1,4-dibutoxybutane , 1,4-Dialkenyl alkanes such as diphenoxybutane and the like. Among these, 1,2-dimethoxyethane is particularly preferable.

Examples of the polythioether include those in which the oxygen atom of the above-exemplified polyether is replaced with a sulfur atom.

Examples of the polydentate phosphin include 1,2-bis (dimethylphosphino) ethane, 1,2-bis (diethylphosphino) ethane, 1,2-bis (dipropylphosphino) ethane, 1,2-. Bis (dibutylphosphino) ethane, 1,2-bis (diphenylphosphino) ethane, 1,3-bis (dimethylphosphino) propane, 1,3-bis (diethylphosphino) propane, 1,3-bis ( Dipropylphosphino) propane, 1,3-bis (dibutylphosphino) propane, 1,3-bis (diphenylphosphino) propane, 1,4-bis (dimethylphosphino) butane, 1,4-bis (diethyl) Bis (dialkylphosphino) alkanes such as phosphino) butane, 1,4-bis (dipropylphosphino) butane, 1,4-bis (dibutylphosphino) butane, 1,4-bis (diphenylphosphino) butane, etc. And bis (diarylphosphino) alkanes. Among these, 1,2-bis (diphenylphosphino) ethane is particularly preferable.

The amount of the chelate-type ligand used may be appropriately set, and for example, it is preferably 0.01 mol or more, more preferably 0.05 mol or more, still more preferably 0.1 mol or more, and more preferably 0.1 mol or more with respect to 1 mol of halosilane. Is 50 mol or less, more preferably 40 mol or less, still more preferably 30 mol or less.

The salt of the cyclic halosilane obtained by the above method A is preferably represented by the following formula (13), for example.

In the above formula (13), X ¹ and X ² each independently represent a halogen atom, L represents an anionic ligand, and p represents an integer of -2 to 0 as the valence of the ligand L. , K represents a counter cation, q represents an integer of 0 to 2 as the valence of the counter cation K, n represents an integer of 0 to 5, a, b and c are integers of 0 or more and “2n + 6” or less. (However, a + b + c = 2n + 6, and a and c are not 0 at the same time), d is an integer of 0 to 3 (however, a and d are not 0 at the same time), and e is an integer of 0 to 3 (provided that it is not 0 at the same time). , D + e = 3), m is 1 to 2, s represents an integer of 1 or more, and t represents an integer of 1 or more.

The salt of the cyclic halosilane may be made into a free cyclic halosilane by contacting it with Lewis acid and reacting it. The free cyclic halosilane means, for example, a non-complex type cyclic halosilane such as Si ₅ Cl ₁₀ or Si ₆ Cl ₁₂ . Specifically, when a salt of cyclic halosilane is brought into contact with Lewis acid, Lewis acid acts electrochomically on the anionic ligand contained in the salt of cyclic halosilane, and anionic coordination is performed from the salt of cyclic halosilane. As the offspring are withdrawn, the counter cation is liberated to give the corresponding free cyclic halosilane.

The type of Lewis acid is not particularly limited, but it is preferable to use a metal halide. Examples of the metal halide include metal chloride, metal bromide, and metal iodide, but it is preferable to use metal chloride from the viewpoint of reactivity and ease of control of the reaction. The metal elements constituting the metal halide include Group 13 elements such as boron, aluminum, gallium, indium and tarium, Group 11 elements such as copper, silver and gold, Group 4 elements such as titanium and zirconium, iron and zinc. Examples include calcium. Specific examples of the Lewis acid include boron halides such as boron trifluoride, boron trichloride and boron tribromide; aluminum halides such as aluminum chloride and aluminum bromide; halogenation of gallium chloride and gallium bromide. Gallium; Indium halide such as indium chloride and indium bromide; Talium halide such as tallium chloride and talium bromide; Copper halide such as copper chloride and copper bromide; Silver halide such as silver chloride and silver bromide; Halogenated gold such as gold chloride and gold bromide; Titanium halide such as titanium chloride and titanium bromide; Halogenated zirconium such as zirconium chloride and zirconium bromide; Iron halide such as iron chloride and iron bromide; Zinc chloride , Halogenated zinc such as zinc bromide; calcium halide, calcium halide such as calcium bromide; and the like.

The amount of the Lewis acid used may be appropriately adjusted according to the reactivity between the salt of the cyclic halosilane and the Lewis acid, and is preferably 0.5 mol or more, more preferably 0.5 mol or more, with respect to 1 mol of the salt of the cyclic halosilane, for example. It is 1.5 mol or more, preferably 20 mol or less, and more preferably 10 mol or less.

The reaction between the cyclic halosilane salt and Lewis acid is preferably carried out in a solvent or a dispersion medium (these are simply referred to as a solvent). Examples of the solvent (reaction solvent) used in the reaction include hydrocarbon solvents such as hexane and toluene; ether solvents such as diethyl ether, tetrahydrofuran, cyclopentyl methyl ether, diisopropyl ether and methyl tertiary butyl ether. Only one kind of these organic solvents may be used, or two or more kinds thereof may be used in combination. The reaction solvent is preferably purified by distillation, dehydration or the like before the reaction in order to remove water and dissolved oxygen contained therein.

The reaction temperature at the time of reacting the above cyclic halosilane salt with Lewis acid may be appropriately adjusted according to the reactivity, but for example, it is preferably −80 ° C. or higher, more preferably −50 ° C. or higher, still more preferable. Is −30 ° C. or higher, preferably 200 ° C. or lower, more preferably 150 ° C. or lower, still more preferably 100 ° C. or lower.

Next, the above method B will be described.

In XR _n of the above compound I, X coordinates with the cyclic halosilane to form a cyclic halosilane neutral complex. When X is P or P = O, X is trivalent and n, which indicates the number of R, is 3. R represents the same or different substituted or unsubstituted alkyl or aryl group. More preferably, R is a substituted or unsubstituted aryl group. When R is an alkyl group, it may be a linear, branched or cyclic alkyl group, and may be a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group or a cyclohexyl. Alkyl groups having 1 to 16 carbon atoms such as groups are preferably mentioned. When R is an aryl group, an aryl group having about 6 to 18 carbon atoms such as a phenyl group and a naphthyl group is preferably mentioned.

In XR _n of the above compound I, even when X is N, X coordinates with the cyclic halosilane to form a cyclic halosilane neutral complex. However, the number of amino groups in XR _n is 1. When X is N, X is trivalent and n, which indicates the number of R, is 3. R represents the same or different substituted or unsubstituted alkyl or aryl group. R is more preferably a substituted or unsubstituted alkyl group. When R is an alkyl group, a linear, branched or cyclic alkyl group is mentioned, and an alkyl group having 1 to 16 carbon atoms is preferable, and an alkyl group having 1 to 16 carbon atoms such as a methyl group, an ethyl group, a propyl group and a butyl group is preferable. The alkyl group of 4 is more preferable, and the alkyl group having 1 to 3 carbon atoms is further preferable. When R is an aryl group, an aryl group having about 6 to 18 carbon atoms such as a phenyl group and a naphthyl group is preferably mentioned.

In XR _n when X is P and P = O or when X is N, the substituents that the alkyl group may have include an alkoxy group, an amino group, a cyano group, a carbonyl group and a sulfonyl group. Examples of the substituent which the aryl group may have include an alkoxy group, an amino group, a cyano group, a carbonyl group, a sulfonyl group and the like. Examples of the amino group include a dimethylamino group and a diethylamino group, but the number of amino groups is one or less in XR ₃ , and the purpose is to exclude tertiary polyamines. The three Rs may be the same or different.

When the above X is S, S = O, O, X is divalent and n indicating the number of R is 2. R has the same meaning as R when X is P, P = O, and is a substituted or unsubstituted alkyl group or aryl group. More preferably, R is a substituted or unsubstituted aryl group. Further, when X is CN, X is monovalent and n indicating the number of R is 1. Again, R has the same meaning as R when X is P, P = O, and is a substituted or unsubstituted alkyl or aryl group. More preferably, R is a substituted or unsubstituted aryl group.

As specific examples of the above-mentioned compound I, X such as triphenylphosphine (PPh ₃ ), triphenylphosphine oxide (Ph ₃ P = O), tris (4-methoxyphenyl) phosphine (P (MeOPh) ₃ ) is P or Examples thereof include compounds having P = O; compounds having X of S = O such as dimethyl sulfoxide; compounds having X of CN such as p-tolunitrile (also referred to as p-methylbenzonitrile).

The heterocyclic compound (Compound II) of (II) above needs to have an unshared electron pair in the ring, and the unshared electron pair is coordinated to the cyclic halosilane to be neutral to the cyclic halosilane. Form a complex. Examples of such a heterocyclic compound include one or more substituted or unsubstituted heterocyclic compounds containing N, O, S or P having a lone pair in the ring. The substituent which the heterocyclic compound may have is the same as the substituent which may have when R is an aryl group. Examples of the heterocyclic compound include pyridines, imidazoles, pyrazoles, oxazoles, thiazoles, imidazolines, pyrazines, thiophenes, furans and the like. Specific examples include N, N-dimethyl-4-aminopyridine, tetrahydrothiophene, tetrahydrofuran and the like.

Of the above compounds I and II, the compound which is liquid at the reaction temperature can also serve as a solvent.

The amounts of the above-mentioned compound I and the above-mentioned compound II to be used may be appropriately determined, and the above-mentioned compound may be used, for example, 0.1 to 50 mol, preferably 0.5 to 3 mol, with respect to 6 mol of halosilane.

The cyclic halosilane neutral complex obtained by the above method B is formed of 3 to 8 (preferably 5 or 6, particularly 6) silicon atoms of the halosilane used as a raw material, and has a ring in which silicon atoms are connected. It is a complex containing, and can be represented by the general formula [Y] _l [Si _m Z _{2m-a Ha} ]. In the above general formula, Y is the compound I or the compound II, Z represents the same or different halogen atom of Cl, Br, I, F, l is 1 or 2, m is 3. -8, preferably 5 or 6, particularly preferably 6, a is 0 to 2 m-1, preferably 0 to m.

The cyclization reaction of halosilane in the above methods A and B is preferably carried out by adding a tertiary amine. Hydrochloric acid produced by adding a tertiary amine can be neutralized.

Examples of the tertiary amine used in the cyclization reaction include triethylamine, tripropylamine, tributylamine, trioctylamine, triisobutylamine, triisopentylamine, diethylmethylamine, diisopropylethylamine (DIPEA), and dimethylbutylamine. , Dimethyl-2-ethylhexylamine, diisopropyl-2-ethylhexylamine, methyldioctylamine and the like are preferably mentioned.

As the tertiary amine, one kind may be used, or two or more kinds may be used in combination. In addition, tertiary amines include those that coordinate to cyclic halosilanes. For example, amines that are not relatively bulky and have high symmetry, such as diethylmethylamine and triethylamine, are coordinated relatively efficiently. It is thought that. However, since the yield of the cyclic halosilane neutral complex tends to be low only with the tertiary amine represented by XR _n of the compound I, it is preferable to use the compound I other than the tertiary amine in combination.

The tertiary amine is preferably 0.5 to 4 mol with respect to 1 mol of halosilane, and is particularly preferably the same mol.

In the present invention, although not limited, it is preferable not to use a tertiary polyamine having two or more carbon atoms and three or more amino groups. When the above tertiary polyamine is used, a salt of cyclic halosilane containing silicon as a counter cation is generated, and silane gas is generated during storage or reduction reaction, which is not preferable from the viewpoint of safety.

The cyclization reaction of the halosilane in the above methods A and B can be carried out in an organic solvent, if necessary. As the organic solvent, a solvent that does not interfere with the cyclization reaction is preferable, and for example, a hydrocarbon solvent (for example, hexane, heptane, benzene, toluene, etc.) and a halogenated hydrocarbon solvent (for example, chloroform, dichloromethane, 1, 2-Dichloroethane, etc.), ether solvents (eg, diethyl ether, tetrahydrofuran, cyclopentylmethyl ether, diisopropyl ether, methyl tertiary butyl ether, etc.), acetonitrile and other aprotonic polar solvents are preferable. Among these, chlorinated hydrocarbon solvents such as chloroform, dichloromethane and 1,2-dichloroethane are preferable, and 1,2-dichloroethane is particularly preferable. In addition, these organic solvents may use 1 type or may use 2 or more types in combination.

The amount of the organic solvent used is not particularly limited, but it is usually preferable to adjust the concentration of halosilane to be 0.5 to 10 mol / L, more preferably 0.8 to 8 mol / L, still more preferable. The concentration is 1 to 5 mol / L.

The reaction temperature in the cyclization reaction can be appropriately set according to the reactivity, and is, for example, about 0 to 120 ° C., preferably about 15 to 70 ° C. It is also recommended that the cyclization reaction be carried out in an atmosphere of an inert gas such as nitrogen.

After the cyclization reaction, it is preferable to include a step of washing the reaction solution containing the cyclic halosilane with a non-halogen solvent. That is, when the cyclization reaction is completed, a solution or dispersion of cyclic halosilane (salt of cyclic halosilane, free cyclic halosilane, cyclic halosilane neutral complex, etc.) is produced. This may be concentrated or filtered, and the obtained solid may be purified by washing with, for example, a halogen solvent such as chloroform, dichloromethane or 1,2-dichloroethane or a non-halogen solvent such as acetonitrile or hexane. By including the step of washing the cyclic halosilane with a non-halogen solvent, the content of the halogen element contained in the cyclic hydride tends to be significantly reduced.

Prior to cleaning with the non-halogen solvent, it is preferable to include a step of cleaning with a halogen solvent. The amine hydrochloride can be removed by washing with a halogen solvent, and the halogen solvent can be removed by washing with a non-halogen solvent.

The cleaning using the halogen solvent and the cleaning using the non-halogen solvent may be performed once or twice or more.

The cyclic halosilane can be obtained as a high-purity solid by purification. However, if desired, it can also be obtained as a composition containing a cyclic halosilane containing impurities. The composition containing the cyclic halosilane preferably contains 80% by mass or more of the cyclic halosilane, more preferably 90% by mass or more, still more preferably 95% by mass or more. The upper limit is, for example, 99.99% by mass. Examples of the impurities include a solvent, the residue of the compound I or the compound II, a decomposition product of cyclic halosilane, a halosilane polymer, and the like. The content of the impurities in the composition containing the cyclic halosilane is preferably 20% by mass or less, more preferably 10% by mass or less, further preferably 5% by mass or less, and the lower limit is, for example, 0.01% by mass. %.

Cyclic hydride can be produced by including a step (reduction step) of reducing the cyclic halosilane (salt of cyclic halosilane, free cyclic halosilane, cyclic halosilane neutral complex, etc.). The reduction step is preferably carried out in the presence of a reducing agent.

The reducing agent that can be used in the reduction step is not particularly limited, but it is preferable to use one or more selected from the group consisting of an aluminum-based reducing agent and a boron-based reducing agent. Examples of the aluminum-based reducing agent include lithium aluminum hydride (LiAlH ₄ ; LAH), diisobutylaluminum hydride (DIBAL), and bis (2-methoxyethoxy) aluminum sodium hydride [“Red-Al” (Sigma Aldrich). Metal hydrides such as [registered trademark)] and the like can be mentioned. Examples of the boron-based reducing agent include metal hydrides such as sodium borohydride and lithium triethylborohydride, diborane and the like, and it is preferable to use metal hydrides. One type of reducing agent may be used, or two or more types may be used in combination.

The amount of the reducing agent used in the reducing step may be appropriately set, and for example, the equivalent of hydride in the reducing agent to one silicon-halogen bond of cyclic halosilane is preferably at least 0.9 equivalent or more. The amount of the reducing agent used is more preferably 1.0 to 50 equivalents, still more preferably 1.0 to 30 equivalents, particularly preferably 1.0 to 15 equivalents, and most preferably 1.0 to 2 equivalents. If the amount of the reducing agent used is too large, the post-treatment takes time and the productivity tends to decrease. On the other hand, if the amount of the reducing agent used is too small, the halogen remains unreduced and the yield tends to decrease.

In the reduction step, a Lewis acid catalyst may be used in combination with the reducing agent as a reducing aid. As the Lewis acid catalyst, chlorides such as aluminum chloride, titanium chloride, zinc chloride, tin chloride and iron chloride; bromides such as aluminum bromide, titanium bromide, zinc bromide, tin bromide and iron bromide; iodide Iodides such as aluminum, titanium iodide, zinc iodide, tin iodide, iron iodide; fluorides such as aluminum fluoride, titanium fluoride, zinc fluoride, tin fluoride, iron fluoride; Examples include metal compounds. These may be used alone or in combination of two or more.

The reaction in the reduction step can be carried out in the presence of an organic solvent, if necessary. Examples of the organic solvent include hydrocarbon solvents such as hexane and toluene; ether solvents such as diethyl ether, tetrahydrofuran, cyclopentyl methyl ether, diisopropyl ether and methyl tertiary butyl ether; and the like. One type of these organic solvents may be used, or two or more types may be used in combination. Further, the organic solvent solution obtained when producing the cyclic halosilane may be used as it is as the organic solvent solution in the reduction step, or the organic solvent is distilled off from the organic solvent solution containing the cyclic halosilane to obtain a new solution. The reduction step may be carried out by adding an organic solvent. The organic solvent used in the reaction in the reduction step is preferably purified by distillation, dehydration or the like before the reaction in order to remove water and dissolved oxygen contained therein.

The amount of the organic solvent used in the reduction reaction is preferably adjusted so that the concentration of cyclic halosilane is 0.01 to 1 mol / L, more preferably 0.02 to 0.7 mol / L, and even more preferably 0.02 to 0.7 mol / L. It is 0.03 to 0.5 mol / L. By carrying out the reaction in the above range, the content of the halogen element contained in the cyclic hydride tends to be remarkably reduced.

The reduction can be carried out by contacting the cyclic halosilane with the reducing agent. When the cyclic halosilane is brought into contact with the reducing agent, it is preferable to bring them into contact with each other in the presence of a solvent. To bring the cyclic halosilane into contact with the reducing agent in the presence of a solvent, for example, (a) the reducing agent is added as it is to the solution or dispersion of the cyclic halosilane, and (b) the cyclic halosilane is reduced to the solution or dispersion. A mixing procedure such as adding a solution or dispersion in which the agent is dissolved or dispersed in a solvent, or (c) adding the cyclic halosilane and the reducing agent to the solvent simultaneously or sequentially may be adopted. Of these, the aspect (b) above is particularly preferable.

Further, when the cyclic halosilane is brought into contact with the reducing agent, it is preferable to drop at least one of the cyclic halosilane solution or dispersion and the reducing agent solution or dispersion into the reaction system for reduction. By dropping one or both of the cyclic halosilane and the reducing agent in this way, the heat generated by the reduction reaction can be controlled by the dropping speed, etc. The effect that leads to improvement can be obtained.

When one or both of the cyclic halosilane and the reducing agent are added dropwise, there are the following three embodiments. That is, A) a solution or dispersion of cyclic halosilane is charged in the reactor, and the solution or dispersion of the reducing agent is dropped onto the solution, B) the solution or dispersion of the reducing agent is charged in the reactor. A mode in which a solution or dispersion of cyclic halosilane is dropped onto the solution, and a mode in which the solution or dispersion of cyclic halosilane and a solution or dispersion of a reducing agent are simultaneously or sequentially dropped into the reactor. Among these, the aspect of A) above is preferable.

When one or both of the cyclic halosilane and the reducing agent are added dropwise in the manners A) to C) above, the concentration of the cyclic halosilane solution or dispersion is preferably 0.01 mol / L or more, more preferably 0.02 mol / L. It is L or more, more preferably 0.04 mol / L or more, and particularly preferably 0.05 mol / L or more. If the concentration of cyclic halosilane is too low, the amount of solvent that must be distilled off when isolating the desired product increases, which tends to reduce productivity. On the other hand, the upper limit of the concentration of the cyclic halosilane solution or dispersion is preferably 1 mol / L or less, more preferably 0.8 mol / L or less, still more preferably 0.5 mol / L or less.

The lower limit of the temperature at the time of dropping (specifically, the temperature of the solution or dispersion for dropping) is preferably −198 ° C. or higher, more preferably −160 ° C. or higher, still more preferably −100 ° C. or higher. The upper limit of the temperature at the time of dropping is preferably + 150 ° C. or lower, more preferably + 100 ° C. or lower, still more preferably + 80 ° C. or lower, and particularly preferably + 40 ° C. or lower. The temperature of the reaction vessel (reaction temperature) may be appropriately set according to the type of cyclic halosilane or reducing agent, and the lower limit is usually preferably −198 ° C. or higher, more preferably −160 ° C. or higher. More preferably, it is −100 ° C. or higher. The upper limit of the temperature of the reaction vessel (reaction solution) is preferably + 150 ° C. or lower, more preferably + 100 ° C. or lower, still more preferably + 80 ° C. or lower, and particularly preferably + 40 ° C. or lower. When the reaction temperature is low, decomposition and polymerization of intermediate products and target products can be suppressed, so that the yield is improved. The reaction time may be appropriately determined depending on the degree of progress of the reaction, and is usually 10 minutes or more and 72 hours or less, preferably 1 hour or more and 48 hours or less, and more preferably 2 hours or more and 24 hours or less.

If the purpose is to reduce the halogen element content in the cyclic hydrogenated silane, raising the reaction temperature is also a method for reducing the halogen element content. In this case, it is recommended that the reaction temperature be, for example, −60 ° C. or higher, preferably −50 ° C. or higher.

As an example, a scheme example using trichlorosilane as the halosilane, triphenylphosphine (PPh ₃ ) as the compound I, and N, N-diisopropylethylamine (DIPEA) as the tertiary amine in the above method B is shown below.

When trichlorosilane is used as a starting material and the compound I is triphenylphosphine (PPh ₃ ), a complex containing a 6-membered ring dodecachlorocyclohexasilane (dodecachlorocyclohexasilane and triphenylphosphine) is usually used as in the above scheme. Is a coordinated neutral complex ([PPh ₃ ] ₂ [Si ₆ Cl ₁₂ ])). Since this cyclic halosilane neutral complex contains no silicon atom other than the silicon atom forming the ring structure, silane gas or organic monosilane is not generated during reduction, alkylation or arylation, or even if it is generated, its amount is low. It can be suppressed.

The yield and yield of the cyclic halosilane neutral complex generated in this cyclization reaction can be calculated by using the methylation reaction represented by the following scheme in which the complex reacts quantitatively.

As a method for reducing a cyclic halosilane neutral complex (for example, [PPh ₃ ] ₂ [Si ₆ Cl ₁₂ ]) to obtain a cyclic hydrogenated silane (for example, cyclohexasilane), for example, LiAlH ₄ is used as a reducing agent. If so, it is represented by the following scheme.

Hereinafter, a plurality of halogen element content reduction methods including the above methods will be presented, and it is recommended to combine these methods as appropriate with reference to the achievement level of halogen element removal. That is, if the halogen element content cannot be reduced to the target amount by one method, a plurality of methods may be combined to reduce the halogen element content to the target amount.

The reduction reaction is usually preferably carried out in an atmosphere of an inert gas such as nitrogen gas or argon gas.

The cyclic hydrogenated silane produced in the reduction reaction is isolated by, for example, solid-liquid separation of a solid (impurities such as by-produced salts) from the reaction solution obtained after the reduction, and then distillation of the solvent under reduced pressure. do.

The above-mentioned solid-liquid separation method can be preferably adopted because of its simple filtration, but is not limited to this, and for example, a known solid-liquid separation method such as centrifugation or decantation can be appropriately adopted.

As a method for reducing the halogen element content in the cyclic hydrogenated silane, as described above, in addition to the method of washing the cyclic halosilane obtained by the reduction reaction with a non-halogen solvent, the above solid-liquid separation is performed. At least twice. That is, it is preferable to include a step of performing solid-liquid separation at least twice after reducing the cyclic halosilane. For example, after the liquid containing cyclic hydride and the solid are once solid-liquid separated (first separation), the liquid containing cyclic hydride is preferably concentrated and a hydrocarbon solvent (hexane or the like) is used as a diluting solvent. After the addition, the solid preferably concentrated and precipitated may be separated again (second separation), and the operation from the first separation to the second separation may be repeated as necessary. After the first separation, solvent dilution, concentration, and solid-liquid separation are more preferably performed once or more, and may be repeated a plurality of times. By performing the solid-liquid separation at least twice in this way, the halogen contained in the by-produced salt or the like can be removed, and the halogen element content in the cyclic hydride can be reduced. The solid-liquid separation may be performed twice or three times or more. The number of times of the solid-liquid separation is not particularly limited, but in consideration of productivity, the upper limit is about 5 times or less.

Next, the solution containing the cyclic hydride obtained by the solid-liquid separation is concentrated as necessary, and then the concentrated cyclic hydride is distilled. This distillation is preferably vacuum distillation. The method of distillation under reduced pressure is not particularly limited, and the distillation may be carried out using a known distillation column. The above distillation is preferably carried out by dividing the fraction into a plurality of fractions, and among the obtained fractions, only an appropriate fraction may be selected in consideration of the halogen element content.

In particular, as one method for reducing the content of the halogen element in the cyclic hydride silane, the distillation (particularly vacuum distillation) may be performed twice or more. For example, a solution containing cyclic hydride silane is distilled under reduced pressure to recover a fraction having an appropriate halogen element content (first distillation), and then the recovered fraction is distilled again under reduced pressure to have an appropriate halogen element content. The distillate may be recovered (second distillation), and if necessary, the second distillation may be repeated.

When the vacuum distillation is performed twice or more, the liquid temperature (internal temperature) in the previous vacuum distillation is preferably 25 to 80 ° C, more preferably 30 to 70 ° C, and later in the vacuum distillation. The liquid temperature (internal temperature) is preferably 20 to 75 ° C, more preferably 30 to 65 ° C. The liquid temperature in the previous vacuum distillation and the liquid temperature in the subsequent vacuum distillation may be the same.

When the vacuum distillation is performed twice or more, the first vacuum distillation is preferably performed at 5 to 400 Pa, more preferably 10 to 300 Pa, and the subsequent vacuum distillation is preferably performed at 5 to 300 Pa, more preferably 10 It is better to do it at ~ 200 Pa. The pressure in the previous vacuum distillation and the pressure in the subsequent vacuum distillation may be the same.

The vacuum distillation may be carried out in a batch manner in order to separate impurities having a higher boiling point and impurities having a lower boiling point than the cyclic hydrogenated silane and to reduce the halogen element content in the cyclic hydride silane.

A compound in which a part of hydrogen of the cyclic hydrogenated silane is substituted with —SiH ₃ (for example, silylcyclopentasilane) may be contained, for example, in an amount of 10 ppb or more on a mass basis. The upper limit is, for example, preferably 1% or less on a mass basis.

As described above, the halogen element content of the cyclic hydrogenated silane obtained by vacuum distillation is reduced to 100 ppm or less. Therefore, since the decrease in purity due to the breaking of the Si—Si bond during storage is suppressed, the storage stability can be improved, and the container corrosion resistance and the semiconductor electrical characteristics can also be improved.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited by the following examples, and the present invention shall be carried out with modifications to the extent that it can be adapted to the above-mentioned and the purposes described below. Of course, they are all possible, and they are all included in the technical scope of the present invention.

In Experiment 1 below, bis (triphenylphosphine) dodecachlorocyclohexasilane which is a cyclic halosilane is produced, and in Experiment 2 below, the bis (triphenylphosphine) dodecachlorocyclohexasilane obtained in Experiment 1 is used and cyclic. Cyclohexasilane, which is a hydrogenated silane, was produced. In Experiment 3 below, the amount of halogen elements contained in the cyclohexasilane obtained in Experiment 2 was measured. In Experiment 4 below, among the cyclohexasilanes obtained in Experiment 2, the storage stability of the cyclohexasilane fraction 4 obtained as the present distilled product was evaluated.

(1) Experiment 1 (Production of cyclic halosilane)
After replacing the inside of a 4-necked flask having a capacity of 3 L equipped with a thermometer, a condenser, a dropping funnel, and a stirrer with nitrogen gas, 155 g (0.591 mol) of triphenylphosphine as the above-mentioned compound I was added to the flask. 458 g (3.54 mol) of diisopropylethylamine was added as a tertiary amine, and 1789 g (18.2 mol) of 1,2-dichloroethane was added as a solvent.

Subsequently, 481 g (3.54 mol) of trichlorosilane as halosilane was slowly added dropwise from the dropping funnel under the condition of 25 ° C. while stirring the solution in the flask. After completion of the dropping, the mixture was stirred as it was for 2 hours, and then heated and stirred at 60 ° C. for 8 hours to carry out a cyclization coupling reaction to obtain a uniform reaction solution. The obtained reaction solution was concentrated, 7200 g of chloroform was added, the mixture was stirred and washed at room temperature for 1 hour, filtered, and the filtered residue was dried under reduced pressure to obtain a crude white solid product.

Next, 5 times the amount of hexane was added to the obtained white solid (crude product), stirred at room temperature for 24 hours, washed, and then filtered. The obtained filtered residue was washed with hexane and filtered again in the same procedure as above, and the obtained filtered residue was dried under reduced pressure to obtain a cyclic halosilane neutral complex [bis (triphenylphosphine) dodecachloro. A refined product of cyclohexasilane, [Ph ₃ P] ₂ [Si ₆ Cl ₁₂ ]] was obtained. All the steps from washing to drying were performed in a nitrogen atmosphere.

When the components contained in the obtained refined product were analyzed by a gas chromatograph (“GC2014” manufactured by Shimadzu Corporation), 1% by mass of chloroform and 1% by mass of an amine salt (amine hydrochloride) were contained as halogenated hydrocarbons. rice field.

(2) Experiment 2 (Production of cyclic hydride)
Under a nitrogen atmosphere, 1099 g of the purified product of the cyclic halosilane neutral complex obtained in the same manner as in Experiment 1 above and 5281 g of diethyl ether were placed in a flask having a capacity of 10 L, and the mixture was stirred at −40 ° C. To this, 2004 g of a 1M diethyl ether solution of LiAlH ₄ was added dropwise from the dropping funnel. The equivalent of hydride in the reducing agent to one silicon-halogen bond of the cyclic halosilane neutral complex is 1.01 equivalent. After completion of the dropping, the mixture was stirred at −40 ° C. for 3 hours to carry out a reduction reaction (reduction step). After stirring for 3 hours, the reaction solution was heated to room temperature, and then solid-liquid separation (first separation) was performed by decantation under a nitrogen atmosphere, and diethyl ether was distilled off under reduced pressure from 6350 g of the obtained liquid content. After concentrating until the liquid volume reached 1100 g, 3455 g of dehydrated hexane was added. Then, the remaining diethyl ether and hexane were distilled off again under reduced pressure, concentrated until the liquid volume reached 1180 g, and then solid-liquid separation (second separation) was performed by filtration to remove the precipitated solid. The solvent was further distilled off from the obtained filtrate, concentrated to a liquid volume of 420 g, and then filtered to obtain 169 g of a crude product of cyclohexasilane which is a cyclic hydrogenated silane as a filtrate. The above operation was performed in two batches to produce a total of 426 g of a crude cyclohexasilane product.

Next, the obtained crude product of cyclohexasilane was distilled under reduced pressure. The vacuum distillation was carried out under the conditions of an internal liquid temperature of 42 to 55 ° C. and a pressure of 130 to 200 Pa, and the fraction was 5 (fractions 1 to 5). The crude product of cyclohexasilane obtained by vacuum distillation weighs 118 g in total, and the GC purity (yield) of each fraction is determined by the capillary column (“DB-1MS” manufactured by J & W SCIENTIFIC, 0.25 mm × 50 m). Was measured by the area percentage method using a gas chromatograph (“GC2014” manufactured by Shimadzu Corporation) equipped with the above. As a result, the GC purity of the crude distilled product of cyclohexasilane was 96.4 to 98.9 area%.

Next, the crude distilled products of cyclohexasilane obtained from the fractions 1 to 5 were collected into one and distilled again under reduced pressure. The vacuum distillation was carried out under the conditions of an internal liquid temperature of 39 to 50 ° C. and a pressure of 63 to 130 Pa, and the fraction was 5 (fractions 1 to 5).

The total amount of the main distilled product of cyclohexasilane obtained by vacuum distillation was 106 g, and the GC purity of each fraction was measured under the same conditions as the crude product of cyclohexasilane. As a result, the GC purity of this distilled product of cyclohexasilane was 98.3 to 99.6 area%.

(3) Experiment 3 (Amount of halogen element contained in cyclic hydride)
After pretreating the crude cyclohexasilane product and the present distilled product obtained in Experiment 2, the amount of halogen element was measured by an ion chromatograph device. For the amount of halogen element, the amount of chlorine was measured.

The above pretreatment was performed by the following procedure. First, 100 μL of cyclohexasilane was placed in a PFA container having a capacity of 20 mL in a glove box under a nitrogen atmosphere. Next, 1000 μL of unheated distilled isopropyl alcohol (IPA) was added. Next, 1000 μL of unheated distilled dimethylaminoethanol was added, and then the lid was lightly closed and allowed to stand overnight to inactivate. After allowing to stand overnight, the mixture was diluted 15-fold with ultrapure water and allowed to stand overnight to complete the pretreatment. The amount of chlorine contained in each fraction of the pretreated cyclohexasilane was measured with an ion chromatograph device (manufactured by DIONEX, "ICS-2000"). The measurement results are shown in Table 1 below.

(4) Experiment 4 (storage stability of cyclic hydride)
Of the present distilled products of cyclohexasilane shown in Table 1 above, the GC purity of the fraction 4 was measured by the area percentage method and the calibration curve method using the above gas chromatograph. Since the area percentage method cannot correctly analyze and evaluate the polymer component that is not vaporized by the gas chromatograph, in this example, the area percentage method and the calibration curve method are used for evaluation. The same measurement was performed after 2 months, and the storage stability was evaluated. In the calibration curve method, mesitylene was used as an internal standard substance, and the purity of the calibration curve was measured. As the cyclohexasilane used for preparing the calibration curve, the present distilled product having a GC purity of 98% or more obtained by the area percentage method obtained in another experiment was used, and the GC measured by the area percentage method of the present distilled product used was used. A calibration curve was prepared by correcting with purity. As a result, the GC purity was 99.6 area% by the area percentage method and 99.6% by the calibration curve method.

Next, the fraction 4 was placed in a stainless steel (SUS) pressure-resistant container in a glove box under a nitrogen atmosphere and stored at room temperature (20 ° C.). After 2 months, the GC purity of the fraction 4 was measured in the same manner by the area percentage method and the calibration curve method. As a result, the GC purity was 99.0 area% by the area percentage method and 99.5% by the calibration curve method.

As is clear from Table 1 above, according to the present invention, both the crude distilled product obtained by performing vacuum distillation once and the distilled product obtained by performing vacuum distillation twice have a halogen element content. Cyclohexasilane of 100 ppm or less was obtained.

Further, as is clear from the result of (4) above, the cyclohexasilane obtained in the present invention had good storage stability. It is considered that this cyclohexasilane can improve the corrosion resistance of the container and the electrical characteristics of the semiconductor.

(5) Experiment 5 (Comparative example)
Same as Experiment 2 except that the second separation is not performed using the purified product of the cyclic halosilane neutral complex [bis (triphenylphosphine) dodecachlorocyclohexasilane] obtained in the same manner as in Experiment 1. The present distilled product of cyclohexasilane was produced under the conditions. Specifically, 906 g of the purified product of the cyclic halosilane neutral complex and 4320 g of diethyl ether were placed in the flask and stirred, and 1649 g of the above diethyl ether solution was added dropwise thereto. After completion of the dropping, the mixture was stirred to carry out a reduction reaction. After stirring, the reaction solution was heated to room temperature, solid-liquid separated (first separation) by decantation, diethyl ether was distilled off from the obtained liquid content of 5372 g under reduced pressure, and the solution was concentrated until the liquid volume reached 950 g. After that, 3000 g of dehydrated hexane was added. Then, the remaining diethyl ether and hexane were distilled off and concentrated, and then 255 g of a crude product of cyclohexasilane, which is a cyclic hydrogenated silane, was obtained without solid-liquid separation (second separation).

Next, the obtained crude cyclohexasilane product was distilled under reduced pressure twice in the same manner as in Experiment 2 above to obtain the present distilled product of cyclohexasilane. The first vacuum distillation was carried out under the conditions of an internal liquid temperature of 45 to 80 ° C. and a pressure of 100 to 170 Pa, and the second vacuum distillation was carried out under the conditions of an internal liquid temperature of 40 to 75 ° C. and a pressure of 70 to 170 Pa.

The GC purity of each distillate of the obtained distilled product of cyclohexasilane was measured under the above conditions. As a result, the GC purity was 98.1 to 98.9 area%.

Further, of the obtained distilled product of cyclohexasilane, the amount of chlorine contained in cyclohexasilane after pretreating the fraction 4 (GC purity is 98.9 area%) under the conditions shown in Experiment 3 above. Was measured. As a result, the amount of chlorine in the fraction 4 was 346 ppm.

Next, under the same conditions as in Experiment 4, the GC purity of the fraction 4 of the obtained distilled product of cyclohexasilane was measured by the area percentage method and the calibration curve method, and the storage stability was evaluated. As a result, among the distilled products, the GC purity of the fraction 4 was 98.9 area% by the area percentage method and 98.3% by the calibration curve method. At the time of 2 months, the GC purity was 98.0 area% by the area percentage method and 96.3% by the calibration curve method.

Claims (2)

The halogen element content is 100 ppm or less (including 0 ppm) on a mass basis.
A cyclohexasilane represented by the following formula (1), which is characterized by having a purity of 95% or more .
(SiH ₂ ) _n ... (1)
[In equation (1), n is 6 . ] The cyclohexasilane according to claim 1, wherein the halogen element is chlorine.