KR101949542B1 - Methods and systems for producing silane - Google Patents

Abstract

Methods and systems for the preparation of silanes using electrolysis to regenerate reactive components are described. The method and system may be substantially closed loop with respect to halogens, alkali metals or alkaline earth metals and / or hydrogen.

Description

METHODS AND SYSTEMS FOR PRODUCING SILANE FIELD OF THE INVENTION [0001]

Field of the present disclosure relates to methods of making silanes, and in particular to methods involving the use of electrolysis to regenerate reactive components. Some specific embodiments relate to a process wherein the preparation of the silane is substantially " closed-loop " with respect to halogens and / or alkali metals or alkaline earth metals.

Silanes are multipurpose compounds with numerous industrial applications. In the semiconductor industry, silanes can be used for deposition of epitaxial silicon layers on semiconductor wafers and for the production of polycrystalline silicon. Polycrystalline silicon is an essential raw material that is used in the manufacture of various products, for example, integrated circuits and photovoltaic cells (i.e., solar cells), which can be produced by pyrolysis on silicon particles of silane in a fluidized bed reactor to be.

Silanes can be prepared by reacting silicon tetrafluoride with an alkali metal or alkaline earth metal aluminum hydride such as sodium aluminum tetrahydride, as disclosed in U.S. Patent No. 4,632,816, which is incorporated herein by reference for all relevant and consistent purposes. . ≪ / RTI > The method is characterized by high energy efficiency; The cost of starting materials can adversely affect the economy of this system.

Alternatively, the silane can be used for all related and consistent purposes, as described in Mueller et al. quot ;, which is a so-called " process " in which the silicon for metallurgy reacts with hydrogen and silicon tetrachloride to form trichlorosilane, as disclosed in " Development and Economic Evaluation of a Reactive Distillation Process for Silane Production, Quot; Union Carbide Process ". The trichlorosilane subsequently undergoes a series of disproportionation and distillation steps to produce the silane end product. The method requires a large number of mass recycle streams to increase operating costs as well as initial equipment costs.

Thus, there is a continuing need for economical methods for producing silanes and for methods that are closed-loop for certain materials used in the manufacturing process. There is also a need for a system for performing such a method that includes a substantially closed loop system.

One aspect of the disclosure is directed to a process for preparing a silane from an alkali metal or alkaline earth metal halide salt source. The method comprises electrolysis of an alkali metal or alkaline earth metal halide salt to produce a metallic alkali or alkaline earth metal and a halogen gas. The metallic alkali metal or alkaline earth metal is contacted with hydrogen to produce an alkali metal or alkaline earth metal hydride. A halogenated silicon feed gas containing at least one halosilane selected from the group consisting of silicon tetra halide, trihalosilane, dihalosilane and monohalosilane is reacted with a halogen gas and (1) silicon to produce silicon tetra halide And (2) hydrogen generating hydrogen halide, wherein hydrogen halide is further contacted with silicon to produce a mixture containing silicon tetra halide and trihalosilane. The halogenated feed gas is contacted with an alkali metal or alkaline earth metal hydride to produce a silane and an alkali metal or alkaline earth metal halide salt.

Another aspect of the disclosure is directed to a method of making a silane in a substantially closed loop system for an alkali metal or alkaline earth metal. The halogenated silicon feed gas is contacted with an alkali metal or alkaline earth metal hydride to produce a silane and an alkali metal or alkaline earth metal halide salt. Halide salts are electrolyzed to produce metallic alkaline or alkaline earth metals and halogen gases. The metallic alkali metal or alkaline earth metal is contacted with hydrogen to produce an alkali metal or alkaline earth metal hydride. The alkali metal or alkaline earth metal hydride produced by the contacting of the metallic alkali or alkaline earth metal and hydrogen is contacted with a halogenated silicon feed gas to produce a silane and an alkali metal or alkaline earth metal halide salt.

Another aspect of the disclosure is directed to a method of making a silane in a substantially closed loop system for a halogen. A halogenated silicon feed gas containing at least one halosilane selected from the group consisting of silicon tetra halides, trihalosilanes, dihalosilanes and monohalosilanes is contacted with an alkali metal or alkaline earth metal hydride to form silane and alkali Metal or alkaline earth metal halide salt. Halide salts are electrolyzed to produce metallic alkaline or alkaline earth metals and halogen gases. A halogenated silicon feed gas containing at least one halosilane selected from the group consisting of silicon tetra halide, trihalosilane, dihalosilane and monohalosilane is reacted with a halogen gas and (1) silicon to produce silicon tetra halide And (2) hydrogen generating hydrogen halide, wherein hydrogen halide is further contacted with silicon to produce a mixture comprising silicon tetra halide and trihalosilane. The halogenated silicon feed gas is contacted with an alkali metal or alkaline earth metal hydride to produce a silane and an alkali metal or alkaline earth metal halide salt.

In yet another aspect of the present disclosure, a method of making a closed loop of polycrystalline silicon includes providing a halogenated < RTI ID = 0.0 > Wherein the silicon feed gas is contacted with an alkali metal or alkaline earth metal hydride to produce a silane and an alkali metal or alkaline earth metal halide salt. The silane is pyrolyzed to produce polycrystalline silicon and hydrogen. Halide salts are electrolyzed to produce metallic alkaline or alkaline earth metals and halogen gases. A halogenated silicon feed gas containing at least one halosilane selected from the group consisting of silicon tetra halides, trihalosilanes, dihalosilanes and monohalosilanes is produced by electrolysis of an alkali metal or alkaline earth metal halide Wherein the hydrogen halide is further contacted with silicon to form a silicon tetra halide and a trihalo halide, wherein the halogen halide is produced by contacting at least one of halogen gas and silicon producing (1) silicon tetra halide and (2) hydrogen generating hydrogen halide, Silane. ≪ / RTI > The metallic alkali metal or alkaline earth metal is contacted with hydrogen generated from pyrolysis of the silane to produce an alkali metal or alkaline earth metal hydride. The halogenated silicon feed gas produced by the contact of a halogen gas or hydrogen halide with silicon is contacted with an alkali metal or alkaline earth metal hydride produced by the contact of a metallic alkali metal or alkaline earth metal with hydrogen to form silane and an alkali metal or alkaline earth metal hydride, To produce a ground metal halide salt.

In another aspect of the present disclosure, a system for producing silanes in a substantially closed-loop process includes a vessel in which an alkali metal or alkaline earth metal halide salt is electrolyzed to produce a metallic alkali metal or alkaline earth metal and a halogen gas. The system comprises (1) a silicon tetrahalide and (2) at least one of a silicon tetrahalide and a silicon tetrachloride by reaction of silicon and (1) a halogen gas released from a vessel and (2) ) Trihalosilane. ≪ / RTI > The system comprises a hydride reactor in which hydrogen reacts with the metallic alkali or alkaline earth metal released from the vessel to produce an alkali metal or alkaline earth metal hydride. The system comprises a silane reactor in which at least one of (1) a silicon tetra halide and (2) a trihalosilane reacts with an alkali metal or alkaline earth metal hydride to produce a silane and an alkali metal or alkaline earth metal halide salt.

The features specified in connection with the above-mentioned aspects of the present disclosure are variously improved. Additional features may also be included in the above-mentioned aspects of the present disclosure. These improvements and additional features may be present individually or in any combination. For example, various features discussed below in connection with any of the illustrated embodiments of the present disclosure may be included alone or in any combination in any of the aspects described above in this disclosure.

1 is a schematic diagram of a silane manufacturing system comprising electrolysis of a halide salt according to an embodiment of the present disclosure;
Figure 2 is a cross-sectional view of a Down's cell suitable for electrolysis of a halide salt;
Figure 3 is a schematic diagram of a halogenated silicon feed gas production system containing silicon tetra halide and trihalosilane;
Figure 4 is a schematic view of a substantially closed loop system for producing silanes, in accordance with an embodiment of the present disclosure;
5 is a schematic diagram of a substantially closed loop system for making polycrystalline silicon, in accordance with an embodiment of the present disclosure;
Corresponding reference characters denote corresponding members throughout the drawings.

The method of the present disclosure regenerates the reactive component using electrolysis in a silane manufacturing process. Electrolysis allows the silane manufacturing process to be essentially a closed loop system for certain compounds used in the system, such as halogens (e.g. chlorine) and / or alkali metals or alkaline earth metals (e. G. Sodium) . As used herein, the expression " substantially closed loop method " or " substantially closed loop system " means that for the compound the system or method is not recovered by the system or method unless the compound is a closed loop as an impurity, (E. G., Less than about 5% of the total circulating in the system, as will be described below in more detail, the amount of compound being supplemented) To a system or a system that does not supply it.

In one or more embodiments of this disclosure, the silane is produced by electrolysis of an alkali metal or alkaline earth metal halide salt that produces a metallic alkali or alkaline earth metal and a halogen gas. The metallic alkali metal or alkaline earth metal reacts with hydrogen to produce hydride and the halogen gas reacts with silicon (and in some embodiments, additionally hydrogen) to form silicon tetrahalide and, in some embodiments, trihalosilane To produce a halogenated silicon feed gas. The feed gas reacts to produce silanes and halide salts. In embodiments where the process is a substantially closed loop for at least one of the alkali metal or alkaline earth metal and the halogen gas, the halide salt byproduct is recycled by electrolysis of a halide salt that produces a metallic alkali or alkaline earth metal and a halogen gas.

Silane  Use of electrolysis to make

Referring now to Figure 1, a halide salt 3 is introduced into a vessel 4, where the halide salt is electrolyzed to form a halide gas (e.g., Cl ₂ ) and a metal (e.g., a metallic alkali metal or an alkali Earth metal). As used herein, " halide salts " contain alkali or alkaline earth metals and halogens. The halide salt may have the formula MX _y wherein M is an alkali or alkaline earth metal, X is halogen, y is 1 when M is an alkali metal, and 2 when M is an alkaline earth metal. The alkali metal or alkaline earth metal of the halide salt (also recirculated in the closed loop system in certain embodiments described below) may be selected from the group consisting of lithium, sodium, potassium, magnesium, barium, calcium, and mixtures thereof. The halogen may be selected from fluorine, chlorine, bromine, iodine, and mixtures thereof. Considering the wide availability of sodium chloride and the fact that sodium chloride can be more easily separated into its constituent parts (e.g., chloride gas and sodium metal) compared to other halide salts, sodium is the preferred alkali metal or alkaline earth metal Chloride is the preferred halogen. In this regard, it will be appreciated that in embodiments wherein the method and system of making silane are closed loop to alkali metal or alkaline earth metal, as described below, any alkali metal or alkaline earth metal may be used and any halogen may be used .

One suitable vessel 4 in which the halide salt is electrolyzed is a downs cell. An example of a Downsell is shown in FIG. 2 and is generally referred to by the reference numeral " 20 ". The downshell 20 contains therein at least one halide salt 15 and contains an anode 14 and a cathode 16. [ The anode 14 can be made of, for example, carbon (e.g., graphite), and the cathode 16 can be made of, for example, steel or iron. At the anode 14, the chloride ion is oxidized to form a halogen gas (e.g., Cl ₂ ). In the cathode 16, alkali metal or alkaline earth metal ions are reduced to form a metallic alkali metal or alkaline earth metal. In this connection, it should be understood that the term " metallic " as used herein refers to an alkali metal or alkaline earth metal with zero oxidation number. The formed halogen gas and the metallic alkali or alkaline earth metal are separated by the separator 19. The separator 19 may be a screen or a gauze made of steel or iron. In this regard, it should be understood that electrolysis cells other than downs cells, such as the electrolysis cells disclosed in U.S. Patent No. 5,904,821, incorporated herein by reference for all relevant and consistent purposes, may be used.

The resulting metallic alkali or alkaline earth metal has a lower concentration than the halide salt, which causes such alkali metal or alkaline earth metal to rise in the cell. The halogen gas also rises and both the halogen gas 18 and the metallic alkali metal or alkaline earth metal 17 are removed from the downsell. A second alkali metal or alkaline earth metal salt is added to the downshell to form a eutectic mixture and suppress the melting point of the electrolyzed halide salt to melt and melt the halide salt or to maintain the halide salt in the molten state Energy costs can be reduced. For example, when sodium chloride is electrolyzed in the downshell 20, a certain amount of calcium chloride, aluminum chloride or sodium carbonate can be added to suppress the melting point of sodium chloride. For example, a mixture containing 53.2 mol% of calcium chloride and 46.8 mol% of sodium chloride has a melting point of 494 DEG C, while the melting point of sodium chloride alone is 801 DEG C, and an exemplary mixture containing 23.1 mol% of sodium carbonate and 76.9 mol% Lt; RTI ID = 0.0 > 634 C. < / RTI > Preferably, the alkali metal or alkaline earth metal of the second salt is the same as or less than the alkali or alkaline earth metal of the halide salt so as not to affect the reduction of the alkali or alkaline earth metal of the halide salt.

Referring again to FIG. 1, a halogen gas 18 is introduced into the halogenation reactor 8, wherein a halogen gas is contacted with the silicon 6 to form a halogenated supply containing silicon tetra halide (e.g., SiCl ₄ ) Water gas 21 is generated. The reaction is described as follows.

Si + 2X ₂ ? SiX ₄ (1)

The source of silicon 6 may be silicon for metallurgy; It should be understood that other sources of silicon may be used, such as sand (i.e., SiO ₂ ), quartz, chief, diatomaceous earth, silicate minerals, fluorosilicates, and mixtures thereof. In this regard, as used herein, " contacting " of two or more reactive compounds generally results in the reaction of the components, and the terms " contact " and " reaction " It should be understood that these terms and their derivatives should not be construed as limiting.

As an alternative to direct reaction with silicon, the halogen gas 18 can be hydrogen halide in the hydrogen halide burner 25 (synonyms hydrogen halide " oven " or " furnace & (HX) by reacting with hydrogen halide (28). The hydrogen halide 26 is reacted with the silicon 6 according to the reaction shown below in the halogenation reactor 8 to form a halogenated silicon feed gas 21 'containing trihalosilane and silicon tetrahalide .

Si + 3HX? SiHX ₃ + H ₂ (2)

_{Si + 4HX → SiX 4 + 2H} 2 (3)

The molar ratio of the silicon tetrahalide to the trihalosilane in the halogenated silicon feed gas 21 'may be varied, and in various embodiments from about 1: 7 to about 1: 2 or from about 1: 6 to about 1: 3 . In this regard, it should be appreciated that the reaction of silicon 6 with hydrogen halide 26 may also produce an unlimited amount of dihalosilane and / or monohalosilane.

In certain embodiments, halogen gas 18 reacts with hydrogen 28 to form hydrogen halide and then reacts with silicon to form a mixture comprising trihalosilane and silicon tetra halide (Figure 3) (Figure 1), because the silane is prepared from the trihalosilane rather than the silicon tetrahalide as shown in the following reaction 5-6ii because it uses less hydride. In addition, direct halogenation reactions may require higher temperatures than the reaction of hydrogen halide with silicon and may be more difficult to control.

The source of hydrogen 28 may be selected from the sources described below with respect to hydrogen feed 31. [ Optionally, the source of hydrogen 28 may be hydrogen separated from the recycled hydrogen or halogenated silicon feed gas 21 'along with the halogenated feed gas 21'. Hydrogen may be separated from the halogenated silicon feed gas 21 'by use of a vapor-liquid separator (not shown). Examples of such vapor-liquid separators include those in which the pressure and / or temperature of the incoming gas is reduced such that a low boiling point gas (e.g., silicon tetra halide and / or trihalosilane) is condensed to form a high boiling point gas (e.g., Hydrogen). ≪ / RTI > Suitable containers include containers commonly referred to in the art as " knock-out drums ". Optionally, the vessel may be cooled to facilitate separation of the gas. Alternatively, the hydrogen may be separated by one or more distillation columns.

As an alternative to the subsequent reaction of hydrogen halide with silicon in a halogenation reactor after the reaction of hydrogen with halogen in a halogenated hydrogen burner as shown in Figure 3, hydrogen gas, halogen gas and silicon react in one vessel To produce a mixture comprising silane and silicon tetra halide. In this regard, although the preparation of hydrogen halide is generally described in the context of anhydrous hydrogen halide gas, in some embodiments it is reacted with silicon in a manner known to those skilled in the art to produce a mixture comprising trihalosilane and silicon tetrahalide It should be appreciated that aqueous hydrogen halides and especially aqueous HF that can be produced can be produced. Further in this regard, although the reaction product of hydrogen halide and silicon has been described as a mixture comprising trihalosilane and silicon tetra halide, the reaction parameters include silicon tetra halide and only trace amounts of trihalosilane 5 vol% or less than about 1 vol%) or to produce trihalosilanes with minor amounts of silicon tetra halide (e.g., less than about 5 vol% or less than about 1 vol%) You should know.

The halogenation reactor 8 can operate as a fluidized bed floating in a gas into which silicon is introduced (e.g., halogen 18 (FIG. 1) or hydrogen halide 26 (FIG. 3)). The halogenation reactor 8 can operate at room temperature (e.g., about 20 캜), particularly when fluorine is selected as the halogen. More generally, the reactor is heated to a temperature of at least about 20 ° C, at least about 75 ° C, at least about 150 ° C, at least about 250 ° C, at least about 500 ° C, at least about 750 ° C, About < RTI ID = 0.0 > 20 C < / RTI > to about 1200 C, from about 250 C to about 1200 C, or from about 500 C to about 1200 C). Reactor 8 can operate at pressures greater than about 1 bar, greater than about 3 bar, or greater than about 6 bar (e.g., from about 1 bar to about 8 bar or from about 3 bar to about 8 bar).

In this regard, the halogenated silicon feed stream 21 shown in FIG. 1 and the halogenated silicon feed stream 21 'shown in FIG. 3 may be a halosilane other than silicon tetra halide or trihalosilane, By weight of monohalosilane and / or dihalosilane. In addition, the halogenated silicon feed stream 21 or the halogenated silicon feed stream 21 'may be introduced into a disproportionation system (not shown) to produce a quantity of trihalosilane, dihalosilane and / To produce silane. As used herein, " halogenated silicon feed gas " includes any gas containing any amount of at least one halosilane (i.e., silicon tetrahalide, trihalosilane, dihalosilane, or monohalosilane) And includes both gases that have not been introduced into the disproportionation system and gases that have been introduced into the disproportionation system.

Referring again to FIG. 1, a halogenated silicon feed stream 21 (or a halogenated silicon feed stream 21 'as in FIG. 3) is introduced into the silane reactor 30 to produce silane 35. Before being introduced to the silane reactor 30, the halogenated silicon feed gas 21 (or the feed gas 21 'containing both the silicon tetra halide and the trihalosilane) may contain impurities such as aluminum halide or iron halide (For example, AlCl ₃ and / or FeCl ₃ if the halide is chlorine) and / or silicon polymer (eg, Si _n Cl _m polymer if the halide is chlorine). These impurities can be removed by cooling the gas to precipitate impurities from the system. The precipitated impurities can be removed by introducing the gas into a particulate separator, such as a bag filter or a cyclonic separator. The halogenated silicon feed gas 21 (or the silicon tetra halide and / or trihalosilane mixture 21 ') is heated to about 200 < 0 > C to precipitate impurities (e.g., metal halide and / Or less than about 125 占 폚 (e.g., from about 100 占 폚 to about 200 占 폚 or from about 125 占 폚 to about 175 占 폚) as in other embodiments. The gas may be cooled by heat exchange with cooling water or cooling oil in the heat exchanger and / or the cooling device. After the impurity removal, the halogenated silicon feed gas 21 (or the silicon tetra halide and / or trihalosilane mixture 21 ') may contain less than 10 vol% impurities (i.e., compounds other than halosilanes) (For example, from 0.001% by volume to about 10% by volume or from about 0.001% by volume to about 1% by volume) of impurities (for example, less than about 1% by volume, less than about 1% by volume, less than about 0.1% .

The metallic alkali or alkaline earth metal 17 produced as the electrolysis product is introduced into the hydride reactor 9. A certain amount of hydrogen (31) is also introduced into the hydride reactor (9). The reaction between a metallic alkali metal or alkaline earth metal and hydrogen produces an alkali metal or alkaline earth metal hydride (32) as shown by the following reaction.

(2 / y) M + H ₂ ? (2 / y) MH _y (4)

In the above reaction formula, y is 1 when M is an alkali metal and 2 when M is an alkaline earth metal. For example, when M is Na, the reaction proceeds as follows.

_{2Na + H 2 → 2NaH (4i} )

When M is Ca, the reaction proceeds as follows.

Ca + H ₂ ? CaH ₂ (4ii)

Reaction 4 can occur in the presence of a solvent in the hydride reactor (9). Suitable solvents include various hydrocarbon compounds such as toluene, dimethyl ether, diglyme and ionic liquids such as NaAlCl ₄ . NaAlCl In embodiments wherein ₄ is used, the hydride reactor 9 can contain an electrode. When the supply of alkali metal or alkaline earth metal hydride is depleted, the electrode is energized and hydride compounds can be regenerated so that H ₂ reacts with sodium (including a certain amount of Na from NaAlCl ₄ ). In embodiments where NaAlCl ₄ is used as a solvent, other ionic compounds may be added to form a eutectic mixture, as disclosed in U.S. Patent No. 6,482,381, which is incorporated herein by reference for all related and consistent purposes.

The hydride reactor 9 can be a stirred tank reactor, to which a quantity of solvent (not shown) and a metallic alkali or alkaline earth metal 17 are added. Hydrogen 31 may form bubbles through the reaction mixture to form an alkali metal or alkaline earth metal hydride 32 in a batch or semi-continuous or continuous process. Suitable sources of hydrogen 31 include commercially available hydrogen or hydrogen obtained from another process stream. For example, hydrogen can be separated from the trihalosilane and silicon tetrahalide mixture 21 'in embodiments where hydrogen halide is reacted with silicon (e.g., the vapor-liquid separator described above). Optionally or additionally, hydrogen released from the silane during the downstream production of polycrystalline silicon may be used. The amount of solvent, hydrogen (31) and metallic alkali metal or alkaline earth metal (17) added to the reactor (9) is such that the weight ratio of hydride to solvent in reactor (9) is at least about 1:20, About 1: 10 or more, about 1: 5 or more, about 1: 3 or more, about 2: 3 or more, or about 1: 1 or more (for example, about 1:20 to about 1: 2: 3).

In one or more embodiments, the reaction mixture in reactor 9 is mixed well using, for example, one or more relatively high-speed agitating mixers having one or more impellers. The relatively high rate of agitation is such that hydrogen is well dispersed throughout the reaction mixture to maximize the rate of dissolution of the hydrogen and any solid alkali or alkaline earth metal hydrogens such that the liquid alkali or alkaline earth metal is continuously available for reaction with the dissolved hydrogen The rides are sheared from metallic alkaline or alkaline earth metals. In this regard, without being bound by any particular theory, the mass transfer in the hydride reactor is dependent on the liquid transverse resistance and the volumetric gas-liquid mass transfer coefficient (K _L a _G ) is in the range of about 100 to about 1000000 s ^-1 , more typically from about 1,000 to about 10,000 s ^-1 . It should be noted that the specific volumetric gas-liquid mass transfer coefficient (K _L a _G ) may vary depending on the particular hydride and solvent selected for use in reactor (9). The value can be readily determined by one of ordinary skill in the art according to known methodologies (e. G., The measurement of hydrogen utilization as a function of time).

In many embodiments of the present disclosure, the hydride reactor 9 is operated under high pressure conditions, such as at least about 50 bar, at least about 125 bar, at least about 200 bar, at least about 275 bar, From about 50 bar to about 350 bar or from about 50 bar to about 200 bar). The hydride reactor 9 is operated at a temperature lower than the thermal decomposition of the alkali metal or alkaline earth metal halide, such as below about 160 占 폚, below about 145 占 폚, or below about 130 占 폚 (e.g., about 120 占 폚 to about 160 占 폚) Can operate.

The alkali metal or alkaline earth metal hydride (32) is typically a solid in an organic solvent. A slurry containing an alkali metal or alkaline earth metal hydride (32) suspended in a solvent may be introduced into the silane reactor (30) to produce the silane (35). In this regard, in another particular embodiment of the present disclosure, an alkali metal or alkaline earth metal hydride (32) can be introduced into the silane reactor (30) as a solid or caked solid containing a smaller amount of solvent You should know. The alkali metal or alkaline earth metal can be separated from the solvent by centrifugation or filtration or any other suitable method available to those skilled in the art. In this regard, it should be understood that solvents other than organic solvents (e.g., NaAlCl ₄ ) may be used without limitation.

As described above, the silicon tetra halide and the alkali metal or alkaline earth metal hydride from the halogenated silicon feed gas 21 (or the mixture 21 'comprising silicon tetra halide and trihalosilane as in FIG. 3) (32) is introduced into the silane reactor (30) to produce silane (35) and halide salt (37) according to the reaction shown below.

(4 / y) MH _y + SiX ₄ ? (4 / y) MX _y + SiH ₄ (5)

_{3MH y + ySiHX 3 → 3MX y} + ySiH 4 (6)

In the above reaction formula, y is 1 when M is an alkali metal and 2 when M is an alkaline earth metal. For example, when M is Na and X is Cl, the reaction proceeds as follows.

_{4NaH + SiCl 4 → 4NaCl + SiH} 4 (5i)

3NaH + SiHCl ₃ ? 3NaCl + SiH ₄ (6i)

When M is Ba and X is Cl, the reaction proceeds as follows.

2BaH ₂ + SiCl ₄ ? 2BaCl ₂ + SiH ₄ (5ii)

3BaH ₂ + 2SiHCl ₃ ? 3BaCl ₂ + 2SiH ₄ (6ii)

The silane reactor 30 may be a stirred tank reactor (e.g., an impeller agitation type). The alkali or alkaline earth metal hydride 32 added to the reactor 30 is suspended in a certain amount of solvent (e.g., toluene) (e.g., by reaction of the alkali metal or alkaline earth metal with hydrogen) . The silicon tetra halide and / or trihalosilane (31) may form bubbles through the hydride slurry, and preferably in a countercurrent relationship. The weight ratio of hydride (32) added to the reactor (30) to the amount of solvent added to the reactor is at least about 1:20, and in yet another embodiment at least about 1:10 or at least about 1: 5 1: 20 to about 1: 5 or about 1: 20 to about 2: 10). The silicon tetra halide and the trihalosilane from the silicon tetra halide or halogenated silicon feed gas 21 '(FIG. 3) from the halogenated silicon feed gas 21 (FIG. 1) are added to the hydride 32 Can be added at substantial stoichiometric ratios, and such molar ratios are shown in reactions 5 to 6ii above.

A certain amount of a catalyst such as triethylaluminum, various Lewis acids or trace alkali metals (e.g., impurity Lewis acids such as metal chlorides) may be added to the reactor 30. These catalysts can lower the temperature at which reactions 5 and 6 achieve sufficient conversion and reduce the amount of heat input into the system. In embodiments where the catalyst is not used, the reactor 30 may operate at a temperature of about 120 캜 or higher (e.g., about 120 캜 to about 225 캜 or about 140 캜 to about 200 캜); In embodiments wherein the catalyst is used, the reactor 30 is operated at relatively low temperatures of about 30 캜 or higher (e.g., from about 30 캜 to about 125 캜, from about 40 캜 to about 100 캜, or from about 40 캜 to about 80 캜) can do. The average residence time of the material added to the reactor 30 can be from about 5 minutes to about 60 minutes.

The silane gas 35 can be relatively pure (e.g., containing less than about 5 vol% or less than about 2 vol% of compounds other than silane). After the silane gas 35 has been removed from the reactor 30, the silane gas 35 may be applied for further processing. For example, silane (35) can be used to remove impurities as disclosed in U.S. Patent No. 5,211,931, U.S. Patent No. 4,554,141, or U.S. Patent No. 5,206,004, each of which is incorporated herein by reference for all relevant and consistent purposes. May be introduced into one or more distillation columns and / or molecular sieves or purified by other known methods available to those skilled in the art (e.g., to remove compounds such as boron halides or phosphorus halides).

The silane gas 35 may be used in the manufacture of polycrystalline silicon (e.g., granular or agglomerated polycrystalline silicon) or may be used to produce one or more epitaxial layers on a silicon wafer. The silane gas may be stored and / or transported prior to use, as will be appreciated by those skilled in the art.

The reaction of the silicon tetra halide in an alkali metal or alkaline earth metal hydride with a halogenated silicon feed gas 21 (or a mixture 21 'comprising a trihalosilane and a silicon tetra halide) can be carried out in the presence of an alkali metal or alkaline earth metal To produce the halide salt (37). Halide salt 37 can be dissolved in a solvent (e. G., Toluene) in an embodiment where a solvent is used and more typically suspended. The halide salt (37) may be commercially available separately from the solvent or may be recycled as further described below.

Silane  substantial Closed loop  Manufacturing method

The method described above can be included in a method for producing a substantially closed loop of silane. The process may be a closed loop for alkali metals or alkaline earth metals and / or halogens. Referring now to FIG. 4, halide salt 37 may be separated from the solvent by use of separator 40. Separator 40 may be an evaporator or other suitable equipment, such as a crystallizer, a filter and / or a gravity-based separator (e.g., a centrifuge) may be used with or in place of the evaporator. Suitable evaporators include wiped-film evaporators. After separation, the dried halide salt can be heated (e.g., up to 500 ° C) to remove trace amounts of solvent.

The solvent 43 may be condensed and reintroduced into the hydride reactor 9 and / or the silane reactor 30. The separated halide salt (3) is used as a feed (3) for electrolysis, whereby the alkali metal or alkaline earth metal and / or halide is substantially recirculated through the system.

In this regard, the actual closed-loop method shown in Figure 4 may be modified to include a halogenated hydrogen burner 25 that produces a gas 21 'containing silicon tetra halide and trihalosilane as in Figure 3 You should know.

As shown in Figure 4, the method does not involve an alkali metal or alkaline earth metal or halogen (i. E., Alone or as an alkali metal or alkaline earth metal or halogen containing compound) anywhere in the injection stream (6, 31) And is substantially a closed loop for the alkali metal or alkaline earth metal and halogen in that the alkali metal or alkaline earth metal and halogen are not removed by the effluent stream 35. In this connection it is to be understood that alkali metals or alkaline earth metals and / or halogens may be removed from the system as impurities or included in the purge stream and supplied to the system or process as a supplemental stream. Any supplement of alkali metal or alkaline earth metal and / or halogen may be achieved by addition of the compound containing each element to the system, and in certain embodiments, by the respective halide salt itself. In various embodiments, the amount of alkali metal or alkaline earth metal and / or halogen gas (which may be added as an alkali metal or alkaline earth metal salt) supplemented to the system is less than about 5% of the total circulating amount in the system, (E.g., from about 0.5% to about 5%) of the total circulation in the system.

In some embodiments of the present disclosure, the system and method may be substantially closed loop with respect to hydrogen. For example, as shown in FIG. 5, the silane 35 from the silane reactor 30 is preferably selected from the group consisting of trace silanes, carbon compounds, trace metals and any dopant boron, May be introduced into the polycrystalline reactor 50 after purification (e. G., Purification by cryogenic activated carbon adsorbent) to remove < / RTI > The polycrystalline reactor 50 may be a fluidized phase (e.g., granular polycrystalline silicon production) or a Siemens reactor (e.g., agglomerated polycrystalline silicon production) ≪ / RTI > Silane is pyrolyzed according to the following reaction to produce polycrystalline silicon.

SiH ₄ ? Si + 2H ₂ (7)

The silane can be further processed before being added to the polycrystalline reactor 50, for example, various purification steps as described above. The reaction product of the reactor 50 comprises polycrystalline silicon 52 and hydrogen 31. As shown in FIG. 5, hydrogen 31 is introduced into the hydride reactor 9. Hydrogen 31 can be further processed by separation and purification (e. G., Distillation) of silicon dust before introduction into hydride reactor 9. As shown in FIG. 5, the only input into the system is silicon 6, and the only emission is polycrystalline silicon 52. The system is substantially a closed loop with respect to hydrogen in that hydrogen is solely removed as an impurity or as a purge stream (not shown) and is also solely added as a supplemental stream (not shown).

Silane  substantial Closed loop  Manufacturing System

The process of the present invention can be carried out in a system for producing silanes, for example, any of the systems illustrated in FIGS. The system may be substantially closed loop for at least one of halogen, alkali metal or alkaline earth metal and hydrogen.

Referring to FIG. 1, the system may include a vessel 4 (e.g., a downsell) in which a halide salt is electrolyzed to produce a metallic alkali or alkaline earth metal and a halogen gas. The halogen gas is transferred from the silicon reservoir to the halogenation reactor 8 by means of a conveying device (1) by a halogenated hydrogen burner 25 (FIG. 3) which reacts with hydrogen to produce hydrogen halide To a halogenation reactor (8) which produces a silicon tetrahalide. In the embodiment where the halogen gas reacts to produce hydrogen halide, the hydrogen halide can then be carried to the halogenation reactor 8 by a carrier apparatus to produce a mixture comprising silicon tetra halide and trihalosilane. Any silicon tetra halide and / or trihalosilane gas produced is carried to the silane reactor 30 by a conveyor.

The system also includes a hydride reactor 9 (e.g., a stirred tank reactor). A metallic alkali metal or alkaline earth metal is carried from the vessel to the hydride reactor (9) by means of a conveying device. Hydrogen gas is also carried to the hydride reactor 9 by the conveying device and reacts with the metallic alkali or alkaline earth metal to produce an alkali metal or alkaline earth metal hydride. The system includes a silane reactor 30 (e.g., a stirred tank reactor) in which the hydride (any solvent, if present) is carried by the conveyor. The hydride is reacted with a silicon tetra halide and / or a trihalosilane gas in the silane reactor 30, optionally in the presence of a solvent to form a halide salt.

In various embodiments, as shown in FIG. 4, the solvent and halide salt may be conveyed to a separator 40 for separating the solvent from the halide salt by the conveying device. The solvent may be conveyed to the hydride reactor 9 by a conveying device and the halide salt may be recycled by the conveying device to form a vessel 4 (FIG. 1) so as to complete a substantially closed loop system for halogens and alkali metals or alkaline earth metals. For example, a downs cell).

In many additional embodiments, the system also includes a polycrystalline reactor 50, which may be a Siemens type reactor or a fluidized bed reactor. The silane is carried from the silane reactor (30) to the polycrystalline reactor (50) by the delivery apparatus to produce hydrogen and polycrystalline silicon. Hydrogen may be carried from the polycrystalline reactor 50 to the hydride reactor 9 by a carrier so that hydrogen can be recycled to complete a substantially closed loop system for hydrogen.

Suitable delivery devices are conventional and well known in the art. Suitable conveying devices for the delivery of gases include, for example, compressors or blowers, and suitable conveying devices for the delivery of solids include, for example, a drag, screw, belt and pneumatic conveyor . In this regard, the use of the term " carrier device " in this context is not intended to mean direct delivery of a system from one unit to another, but merely refers to any number of indirect transfer members and / Lt; RTI ID = 0.0 > from one unit to another. ≪ / RTI > For example, after a material from one unit is conveyed to an additional processing unit (e.g., a purifier unit or a storage unit used to provide a buffer between successive or batch processes) . In the above example, each delivery unit comprising the intermediate processing facility itself may be considered to be a " delivery device ", and the expression " delivery device " should not be construed in a limiting sense.

Preferably, all the equipment used in the silane manufacturing system is corrosion resistant in an environment that is used in the system and involves exposure to the resulting compound. Suitable constituent materials are conventional and well known in the art of this disclosure and include, for example, carbon steels, stainless steels, MONEL alloys, INCONEL alloys, HASTELLOY alloys, nickel and non- for example, it includes quartz (i.e., glass), and fluorinated polymers such as TEFLON (TEFLON), kelp (KEL-F), Viton (VITON), knife grease (KALREZ) and ill Ras (AFLAS).

Without departing from the scope of the present disclosure, it is to be understood that the above-described methods and systems may include more than any of the mentioned units (e.g., reactors and / or separation units) / RTI > and / or < / RTI > simultaneously. In addition, it should be understood that the method and system described are exemplary and that the method and system may include additional units that perform additional functions without limitation.

When introducing elements of the present disclosure or its preferred embodiment (s), the articles "a", "an", "the" and "the" are intended to mean that there is more than one element. The terms "comprising", "including" and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

As various changes may be made in the apparatus and method without departing from the scope of the present disclosure, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Claims (95)

A process for preparing a silane from a source of an alkali metal or alkaline earth metal halide salt,
Electrolyzing an alkali metal or alkaline earth metal halide salt to produce a metallic alkali or alkaline earth metal and halogen gas;
Said metallic alkali or alkaline earth metal being in contact with hydrogen to produce an alkali metal or alkaline earth metal hydride;
The halogen gas
(1) silicon to produce silicon tetra halide; And
(2) Hydrogen to generate hydrogen halide - The hydrogen halide further contacts with silicon to produce a mixture comprising silicon tetra halide and trihalosilane,
To produce a halogenated silicon feed gas comprising at least one halosilane selected from the group consisting of silicon tetra halides, trihalosilanes, dihalosilanes, and monohalosilanes; And
Contacting the halogenated silicon feed gas with the alkali metal or alkaline earth metal hydride to produce a silane and an alkali metal or alkaline earth metal halide salt, the halogenated silicon feed gas comprising the halogenated silicon feed gas and the halogenated silicon feed gas, Introduced into the disproportionation system prior to contact with an alkali metal or alkaline earth metal hydride -
≪ / RTI > A process for preparing a silane from a source of an alkali metal or alkaline earth metal halide salt,
Electrolyzing an alkali metal or alkaline earth metal halide salt to produce a metallic alkali or alkaline earth metal and halogen gas;
Said metallic alkali or alkaline earth metal being contacted with hydrogen in a solvent to produce an alkali metal or alkaline earth metal hydride;
The halogen gas
(1) silicon to produce silicon tetra halide; And
(2) Hydrogen to generate hydrogen halide - The hydrogen halide further contacts with silicon to produce a mixture comprising silicon tetra halide and trihalosilane,
To produce a halogenated silicon feed gas comprising at least one halosilane selected from the group consisting of silicon tetra halides, trihalosilanes, dihalosilanes, and monohalosilanes; And
Contacting said halogenated silicon feed gas with said alkali metal or alkaline earth metal hydride to produce silane and an alkali metal or alkaline earth metal hydride salt
≪ / RTI > The method of claim 2, wherein said solvent is selected from toluene, dimethyl ether, diglyme (diglyme), NaAlCl _4, and mixtures thereof. The method of claim 2, wherein the method of contacting with said alkali metal or alkaline earth metal hydride, toluene, dimethyl ether, diglyme, NaAlCl ₄ and the halogenated silicon feed gas in a solvent selected from the group consisting of a mixture thereof. 3. The method of claim 2, wherein the consumed solvent comprising the halide salt and the solvent is produced upon contact of the alkali metal or alkaline earth metal hydride with the halogenated silicon feed gas, And recovering the solvent by separation of the solvent. The process according to claim 1 or 2, wherein the halide salt is selected from the group consisting of
Introducing the salt into a vessel comprising a cathode, an anode, and a separator disposed between the cathode and the anode;
Applying a current to the cathode and the anode to produce a halogen gas and a metallic alkali or alkaline earth metal;
Halogen gas and a metallic alkali or alkaline earth metal from the vessel. CLAIMS What is claimed is: 1. A method of making a silane in a substantially closed loop system for an alkali metal or alkaline earth metal,
Contacting a halogenated silicon feed gas with an alkali metal or alkaline earth metal hydride to produce a silane and an alkali metal or alkaline earth metal halide salt wherein the halogenated silicon feed gas is contacted with the halogenated silicon feed gas and the alkali metal Or introduced into the disproportionation system prior to contact of the alkaline earth metal hydride;
Electrolyzing the halide salt to produce a metallic alkali metal or alkaline earth metal and a halogen gas;
Contacting the metallic alkali or alkaline earth metal with hydrogen to produce an alkali metal or alkaline earth metal hydride; And
Contacting the alkali metal or alkaline earth metal hydride produced by the contacting of the metallic alkali or alkaline earth metal with hydrogen with the halogenated silicon feed gas to form silane and an alkali metal or alkaline earth metal halide salt
≪ / RTI > CLAIMS What is claimed is: 1. A method of making a silane in a substantially closed loop system for an alkali metal or alkaline earth metal,
Contacting the halogenated silicon feed gas with an alkali metal or alkaline earth metal hydride to produce silane and an alkali metal or alkaline earth metal halide salt;
Electrolyzing the halide salt to produce a metallic alkali metal or alkaline earth metal and a halogen gas;
Contacting the metallic alkali or alkaline earth metal with hydrogen in a solvent to produce an alkali metal or alkaline earth metal hydride; And
Contacting the alkali metal or alkaline earth metal hydride produced by the contacting of the metallic alkali or alkaline earth metal with hydrogen with the halogenated silicon feed gas to form silane and an alkali metal or alkaline earth metal halide salt;
≪ / RTI > 9. The method of claim 8 wherein said metallic alkali or alkaline earth metal is added to a reaction vessel comprising said solvent to form a reaction mixture and hydrogen gas forms bubbles through said reaction mixture. A method of making a silane in a substantially closed loop system for a halogen,
A halogenated silicon feed gas comprising at least one halosilane selected from the group consisting of silicon tetra halide, trihalosilane, dihalosilane and monohalosilane is contacted with an alkali metal or alkaline earth metal hydride to form silane and alkali Producing a metal or alkaline earth metal halide salt;
Electrolyzing the halide salt to produce a metallic alkali metal or alkaline earth metal and a halogen gas;
The halogen gas
(1) silicon to produce silicon tetra halide; And
(2) Hydrogen to generate hydrogen halide - The hydrogen halide further contacts with silicon to produce a mixture comprising silicon tetra halide and trihalosilane,
To produce a halogenated silicon feed gas comprising at least one halosilane selected from the group consisting of silicon tetra halides, trihalosilanes, dihalosilanes, and monohalosilanes; And
Contacting said halogenated silicon feed gas with an alkali metal or alkaline earth metal hydride to produce silane and an alkali metal or alkaline earth metal halide salt, said halogenated silicon feed gas comprising said halogenated silicon feed gas and said alkali Introduced into the disproportionation system prior to contact of the metal or alkaline earth metal hydride -
≪ / RTI > A method for producing a closed loop of polycrystalline silicon,
A halogenated silicon feed gas comprising at least one halosilane selected from the group consisting of silicon tetra halide, trihalosilane, dihalosilane and monohalosilane is contacted with an alkali metal or alkaline earth metal hydride to form silane and alkali Producing a metal or alkaline earth metal halide salt;
Pyrolyzing the silane to produce polycrystalline silicon and hydrogen;
Electrolyzing the halide salt to produce a metallic alkali metal or alkaline earth metal and a halogen gas;
The halogen gas produced by electrolysis of the alkali metal or alkaline earth metal halide and
(1) silicon to produce silicon tetra halide; And
(2) Hydrogen to generate hydrogen halide - The hydrogen halide further contacts with silicon to produce a mixture comprising silicon tetra halide and trihalosilane,
To produce a halogenated silicon feed gas comprising at least one halosilane selected from the group consisting of silicon tetra halides, trihalosilanes, dihalosilanes, and monohalosilanes;
Contacting said metallic alkali or alkaline earth metal with hydrogen generated from pyrolysis of silane to produce an alkali metal or alkaline earth metal hydride; And
Contacting said halogenated silicon feed gas produced by contact of a halogen gas or hydrogen halide with silicon with said alkali metal or alkaline earth metal hydride produced by contacting said metallic alkali metal or alkaline earth metal with hydrogen to form silane and alkali Step of producing a metal or alkaline earth metal halide salt
/ RTI > A system for producing silane in a substantially closed loop process,
A container for electrolyzing an alkali metal or alkaline earth metal halide salt to produce a metallic alkali metal or alkaline earth metal and a halogen gas;
With silicon
(1) halogen gas emitted from the vessel; And
(2) hydrogen halide produced by the contact of the halogen gas discharged from the container with hydrogen
By one or more of the reactions
(1) a silicon tetrahalide, and
(2) trihalosilane
A halogenating reaction unit for producing at least one of the halogenating reactants;
A hydride reactor in which hydrogen reacts with a metallic alkali metal or alkaline earth metal released from the vessel to produce an alkali metal or alkaline earth metal hydride, the hydride reactor being characterized in that the hydrogen is a reaction mixture containing a solvent and a metallic alkali metal or alkaline earth metal A tank reactor in the form of an agitated tank for forming bubbles through the liquid to produce an alkali metal or alkaline earth metal hydride suspended in the solvent; And
A silane reactor in which at least one of (1) silicon tetra halide and (2) trihalosilane reacts with the alkali metal or alkaline earth metal hydride to produce silane and an alkali metal or alkaline earth metal halide salt
/ RTI > A system for producing silane in a substantially closed loop process,
A container for electrolyzing an alkali metal or alkaline earth metal halide salt to produce a metallic alkali metal or alkaline earth metal and a halogen gas;
With silicon
(1) halogen gas emitted from the vessel; And
(2) hydrogen halide produced by the contact of the halogen gas discharged from the container with hydrogen
By one or more of the reactions
(1) a silicon tetrahalide, and
(2) trihalosilane
A halogenating reaction unit for producing at least one of the halogenating reactants;
A disproportionation system that produces monohalosilane or dihalosilane from at least one of (1) silicon tetra halide and (2) trihalosilane;
A hydride reactor in which the metallic alkali or alkaline earth metal released from the vessel reacts with hydrogen to produce an alkali metal or alkaline earth metal hydride; And
A silane reactor in which at least one of (1) silicon tetra halide and (2) trihalosilane reacts with an alkali metal or alkaline earth metal hydride to produce silane and an alkali metal or alkaline earth metal halide salt
/ RTI > 14. The method of claim 12 or 13, wherein the silane reactor is a halogenated silicon feed comprising at least one halosilane selected from the group consisting of silicon tetra halide, trihalosilane, dihalosilane, and monohalosilane Wherein the gas is a stirred tank reactor that forms bubbles through a reaction mixture containing a solvent and an alkali metal or alkaline earth metal hydride dispersed in the solvent and wherein the alkali metal or alkaline earth metal halide salt is dissolved or suspended in the solvent Lt; / RTI > 15. The system of claim 14, comprising a separator for separating said solvent and said alkali metal or alkaline earth metal halide salt. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete

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