Abstract: High purity tetrafluorohydrazine is synthesized by reacting NF.sub.3 with silicon at an elevated temperature. The reaction occurs only periodically and at a low concentration of NF.sub.3. Immediate cooling of the reaction material produces tetrafluorohydrazine and SiF.sub.4. Alkaline hydrolysis removes substantially all impurities. Tetrafluorohydrazine is further recovered by cryogenic trapping from the remaining impurities.

Abstract: What is disclosed is a method for treating a reaction residue from the preparation of organochlorosilanes or chlorosilanes from the reaction of metallic silicon with a chlorinated hydrocarbon or hydrogen chloride, said method comprising (A) combining the reaction residue with water, and (B) granulating the mixture of water and silicon from (A).

Abstract: The invention relates to the selective and stepwise reduction of polyhalosilanes by reacting at room temperature or below with alkyltin hydrides without the use of free radical intermediates. Alkyltin hydrides selectively and stepwise reduce the Si--Br, Si--Cl, or Si--I bonds while leaving intact any Si--F bonds. When two or more different halogens are present on the polyhalosilane, the halogen with the highest atomic weight is preferentially reduced.

Abstract: The invention relates to the selective and sequential reduction of halodisilanes by reacting these compounds at room temperature or below with trialkyltin hydrides or dialkyltin dihydrides without the use of free radical intermediates. The alkyltin hydrides selectively and sequentially reduce the Si-Cl, Si-Br or Si-I bonds while leaving intact the Si-Si and Si-F bonds present.

Abstract: A method is disclosed for increasing the fluosilicic acid (FSA) recovered from a wet process phosphoric acid manufacturing process. The filtrate obtained by washing a filter cake is pumped to a stripper and reacted with H.sub.2 SO.sub.4 to converting the dissolved FSA to gaseous SiF.sub.4. A defoamer is added to the acid-filtrate mixture to reduce the foam produced by the reaction and increase the amount of gaseous SiF.sub.4 recovered from the reaction. The gaseous SiF.sub.4 is recovered from the acid-filtrate reaction mixture and converted to FSA for commercial use.

Abstract: A method for the selective removal of boron halides and other Lewis acid-type impurities from silicon halides is disclosed. Treatment of contaminated silicon halides with siloxanes, which react with the impurities, allow the distillation of silicon halide which is virtually free from contamination within extremely low limits of detectability.

Abstract: Process and apparatus for producing low cost, high purity solar grade silicon ingots in single crystal or quasi single crystal ingot form in a substantially continuous operation in a two stage reactor starting with sodium fluosilicate and a metal more electropositive than silicon (preferably sodium) in separate compartments having easy vapor transport therebetween and thermally decomposing the sodium fluosilicate to cause formation of substantially pure silicon and a metal fluoride which may be continuously separated in the melt and silicon may be directly and continuously cast from the melt.

Abstract: Process for producing low cost, high purity solar grade Si wherein a reduction reaction, preferably the reduction of SiF.sub.4, by an alkali metal (Na preferred) is carried out inside a reaction chamber. The chamber wall and bottom surfaces are configured so as to facilitate the continuous separation of the products of reaction (Si and NaF) and removal of the molten salt by discharging the salt through one or more ports at the bottom of the reaction chamber. Such process is especially useful where it is desirable to discharge the reaction salt products from the reactor and retain silicon within the chamber for later removal.

Abstract: Method for treating waste slurries containing solid impurities, e.g. in the form of metal chlorides, and silicon tetrachloride and trichlorosilane by evaporation and separation techniques to recover more of the silicon tetrachloride and trichlorosilane.

Abstract: Disclosed is a process for the cleavage of chlorosiloxanes in the gas phase at temperatures between 350 and 1450.degree. C. to form chlorosilanes and silicon dioxide as reaction products. The claimed process is preferably performed in the presence of metallic silicon or ferrosilicon. The procedure can be combined with the large-scale technical production of chlorosilanes by the chlorination or hydrochlorination of silicon. The inventive process makes it possible to perform the chlorination or hydrochlorination of silicon with the formation of chlorosilanes in an increased yield while reducing the formation of by-products.

Abstract: Chlorosilanes contaminated with boron-containing impurities can be purified by passing the chlorosilane vapor through a silica fixed bed. Normally the boron level in trichlorosilane is reduced by about 90-99+% by the use of this process. The capacities of the silica columns for the purification of trichlorosilane generally are in the range of 1500-2000 pounds trichlorosilane per pound of silica. The purified chlorosilane is particularly well suited for the production of polycrystalline silicon. Polycrystalline silicon containing 0.03 ppba (parts per billion atomic) has been prepared from trichlorosilane purified with this process.

Abstract: Silicon tetrachloride, hydrogen and metallurgical silicon are reacted at about 400.degree.-600.degree. C. and at pressures in excess of 100 psi, and specifically from about 300 up to about 600 psi to form di- and trichlorosilane that is subjected to disproportionation in the presence of an anion exchange resin to form high purity silane. By-product and unreacted materials are recycled, with metallurgical silicon and hydrogen being essentially the only consumed feed materials. The silane product may be further purified, as by means of activated carbon or cryogenic distillation, and decomposed in a fluid bed or free space reactor to form high purity polycrystalline silicon and by-product hydrogen which can be recycled for further use. The process results in simplified waste disposal operations and enhances the overall conversion of metallurgical grade silicon to silane and high purity silicon for solar cell and semiconductor silicon applications.

Abstract: The process of disproportionation of chlorosilanes in the presence of a dried catalyst which is dried by heating up to 200.degree. C. under vacuum starting from a water-containing anion exchange cross-linked resin matrix containing as a functional group and said resin matrix stable at temperatures up to about 200.degree. C. without separation of the functional group from the resin matrix to produce the disproportionated product of high purity, semiconductor grade, without any contamination from the catalyst.

Abstract: There is disclosed a redistribution catalyst which is the reaction product of a quaternary ammonium halide salt or tertiary amine, and an inorganic carrier having surface hydroxyl groups, such as silica, zeolite, clays, and silicone resins. The catalyst is useful for the disproportionation of chlorosilicon hydrides to dichlorosilane and silane at reaction conditions including a temperature from 0.degree. to 200.degree. C., in liquid or vapor phase with a pressure from 0.1 to 10 atmospheres.

Abstract: A chlorosilane disproportionation catalyst comprising a tertiary amine of the formula: ##STR1## where each R represents an aliphatic hydrocarbon group and the sum of carbon atoms in the three aliphatic hydrocarbon groups as R is 12 or more, and a tertiary amine hydrochloride of the formula: ##STR2## where R is as defined above.

Abstract: Silane, well adopted as a source of semiconductor/photovoltaic grade silicon, is facilely prepared from methyldichlorosilane and trichlorosilane and/or tetrachlorosilane by, (A) in a first step catalytically redistributing methyldichlorosilane with trichlorosilane or tetrachlorosilane, or admixture thereof, to form methyltrichlorosilane and dichlorosilane, and separating dichlorosilane from the resulting reaction medium, and (B) in a second step, catalytically disproportionating the dichlorosilane thus separated to form silane and trichlorosilane, and thence recovering silane thus formed and optionally recycling trichlorosilane to said step (A).

Abstract: The invention relates to the preparation of silicon tetrachloride by reacting material containing SiO.sub.2 with chlorine in the presence of carbon and metal halides and especially chlorides of the fifth main or subsidiary group of the Periodic Table at temperatures in the range of from 500.degree. to 1200.degree. C. The material containing SiO.sub.2 has a BET surface area of at least 0.1 m.sup.2 /g and the carbon has a BET surface area of at least 0.5 m.sup.2 /g.

Abstract: Irradiation of a siloxane derives SiO at low temperatures and forms the basis for a closed cycle reforming the siloxane that decomposes water to produce H.sub.2 and O.sub.

Abstract: Chlorosilanes with an enhanced hydrogen content are selectively produced in the direct reaction of silicon with hydrogen chloride at elevated temperatures by treating the silicon with a source of oxygen during the process. A process is also provided for producing selectively trichlorosilane by reacting hydrogen chloride with a fluidized bed of silicon particles and treating the silicon particles with the source of oxygen.

Abstract: An improved process is disclosed for the high pressure plasma hydrogenation of silicon tetrachloride. Hydrogen and silicon tetrachloride are reacted in the presence of a high pressure plasma and further in the presence of a boron catalyst to form trichlorosilane and dichlorosilane. By adding the boron catalyst the overall conversion efficiency is increased and the dichlorosilane content in the reaction effluent is increased.

Abstract: A process for producing trichlorosilane and equipment for practicing that process are disclosed. The process is a two stage process which combines the reaction of silicon tetrachloride and hydrogen with silicon with the reaction of hydrogen chloride with silicon. In one embodiment of the invention a two stage reactor is provided with a first stage heated to a temperature of about 500.degree.-700.degree. C. and a second stage maintained at a temperature of about 300.degree.-350.degree. C. Each of the first and second stages of the reactor are charged with silicon particles. A mixture comprising hydrogen and silicon tetrachloride are flowed through the silicon particles in the heated first stage to cause a partial hydrogenation of the silicon tetrachloride. The effluent from the first stage includes trichlorosilane and unreacted hydrogen and silicon tetrachloride. Hydrogen chloride is added to this effluent and the mixture of gases are passed through the silicon particles in the second stage of the reactor.

Abstract: A battery of special burners, each adapted for the treatment of a particular range of waste material formed during the conversion of metallurgical grade silicon to high purity silane and silicon, is accompanied by a series arrangement of filters to recover fumed silica by-product and a scrubber to recover muriatic acid as another by-product. All of the wastes are processed, during normal and plant upset waste load conditions, to produce useful by-products in an environmentally acceptable manner rather than waste materials having associated handling and disposal problems.

Abstract: A method for separating chlorosilanes from a gaseous mixture which additionally contains hydrogen and hydrogen chloride by washing the gaseous mixture with saturated hydrochloric acid is disclosed. The resulting chlorosilane hydrolysis products can remain in the hydrochloric acid serving as washing liquid, without interfering with the purifying action. The suspended hydrolysis products are easily filtrable, and can be periodically separated from the hydrochloric acid. In a preferred embodiment, the hydrochloric acid is recirculated and injected into the gas stream being washed.

Abstract: A method for the selective removal of phosphorus and other Lewis base-type impurities from chlorosilane solutions with selected transition metal compounds which react with the impurities and allow subsequent distillation of chlorosilane which is virtually free from contamination within extremely low limits of detectability.

Abstract: SiF.sub.4 gas containing oxygen-containing silicofluoride(s) typified by (SiF.sub.3).sub.2 O as impurity can be refined to extremely high purity by making the SiF.sub.4 gas contact with HF in the presence of a liquid medium having strong affinity for water such as sulfuric acid or phosphoric acid. By reaction with HF, the impurity such as (SiF.sub.3).sub.2 O is converted to SiF.sub.4, while the liquid medium absorbs water formed by the reaction to thereby prevent a reverse reaction between SiF.sub.4 and H.sub.2 O to form (SiF.sub.3).sub.2 O.

Abstract: An agitated bed operation in production of trichlorosilane and silicon tetrachloride from metallic silicon or metallic-silicon-containing solid materials and hydrogen chloride is disclosed. In the new agitated bed operation in a tower type reactor, defects and disadvantages of the conventional fixed bed operation and conventional fluidized bed operation are eliminated.

Abstract: A process is disclosed for the purification of trichlorosilane and other silicon source materials. Trace impurities of boron and phosphorous are removed from trichlorosilane or dichlorosilane by reacting small amounts of oxygen with the trichlorosilane or dichlorosilane at a temperature between about 60.degree. C. and 300.degree. C. The oxygen reacts with the Si--H bond in HSiCl.sub.3 or H.sub.2 SiCl.sub.2 to form a "SiOH" species which in turn complexes impurities such as BCl.sub.3 or PCl.sub.3 present in the chlorosilane. Purification of the chlorosilane is then easily accomplished during a subsequent distillation step which separates the purified chlorosilane from the less volatile complexed boron or phosphorous compounds.

Abstract: The dismutation/redistribution of halogenosilanes into silane is carried out by contacting at least one halogenosilane comprising at least one Si-H function with a compound comprising at least one .alpha.-oxoamine group, then by contacting the products of such reaction with a compound also comprising at least one .alpha.-oxoamine group, to selectively dissolve all products of reaction except for the silane therein, and then separating the desired silane therefrom.

Abstract: Polyvinyl cyclic tertiary amine hydrocarbons having nitrogen in the ring as catalysts for chlorosilane disproportionation. The catalysts are suitable for continuous flow processes redistributing any one or more of SiHCl.sub.3, SiH.sub.2 Cl.sub.2, and SiH.sub.3 Cl.

Abstract: Improved yields of monohydrogentrihalosilanes are achieved by contacting the residual silicon obtained from the preparation of organohalosilanes by a metal-catalyzed direct process by contacting the residual silicon simultaneously with gaseous hydrogen halide and with gaseous alkyl halide to form a residual silicon contact mass; selecting a temperature between about 200.degree. C. and about 350.degree. C. at which alkylation of the silicon contact mass in inhibited and at which hydrohalogenation of the silicon contact mass occurs; and heating the silicon contact mass at the selected temperature. The silicon reacts with the gaseous alkyl halide and the gaseous hydrogen halide at the selected temperature to produce improved yields of the monohydrogentrihalosilane.

Abstract: A process is disclosed for the purification of trichlorosilane and other silicon source materials. Trace impurities of boron and phosphorous are removed from trichlorosilane by reacting small amounts of oxygen with the trichlorosilane at a temperature between about 170.degree. and 300.degree. C. The oxygen reacts with the Si--H bond in HSiCl.sub.3 to form a "SiOH" species which in turn complexes impurities such as BCl.sub.3 or PCl.sub.3 present in the trichlorosilane. Purification of the trichlorosilane is then easily accomplished during a subsequent distillation step which separates the purified trichlorosilane from the less volatile complexed boron or phosphorous compounds.

Abstract: Tri- and dichlorosilanes formed by hydrogenation in the course of the reaction of metallurgical silicon, hydrogen and recycle silicon tetrachloride are employed as feed into a separation column arrangement of sequential separation columns and redistribution reactors which processes the feed into ultrahigh purity silane and recycle silicon tetrachloride. A slip stream is removed from the bottom of two sequential columns and added to the recycle silicon tetrachloride process stream causing impurities in the slip streams to be subjected to reactions in the hydrogenation step whereby waste materials can be formed and readily separated.

Abstract: Polycrystalline silicon is produced by a high pressure plasma process. A silicon halide or halosilane is reacted with hydrogen in the presence of a high pressure plasma to deposit silicon on a heated substrate. The effluent from this reaction is collected, the silicon-bearing compounds separated out, and re-introduced to the deposition reaction. The initial silicon bearing compound can be inexpensive silicon tetrachloride. Maximum utilization of all silicon bearing reaction products maximizes polycrystalline silicon production efficiency.

Abstract: An economical, low temperature, closed loop, thermal decomposition process is provided for producing a controllable mixture of heterogeneously and homogeneously nucleated ultrahigh purity polycrystalline silicon suitable for use in the manufacture of semiconductor devices and photovoltaic solar cells.

Abstract: A method is disclosed for the plasma hydrogenation of silicon tetrachloride. A high pressure plasma is utilized to effect a reaction of hydrogen and silicon tetrachloride to form trichlorosilane and other hydrogenated silicon chlorides.

Abstract: Hydrogen containing chlorosilanes, preferably trichlorosilanes, are prepared by reacting silicon tetrachloride with hydrogen at a temperature of 600.degree.-1200.degree. C. with a SiCl.sub.4 /H.sub.2 mixture having a molar composition between 1:1 and 1:50 in equilibrium with SiHCl.sub.3 and HCl and suddenly quenching the mixture to below 300.degree. C.

Abstract: Dry granular silicon acid, an organic polyol and a silicon tetrahalide are mixed simultaneously to produce an organic halosilicon acid resinous product.

Abstract: Hydrogen containing chlorosilanes, preferably trichlorosilanes, are prepared by reacting silicon tetrachloride with hydrogen at a temperature of 600.degree.-1200.degree. C. with a SiCl.sub.4 /H.sub.2 mixture having a molar composition between 1:1 and 1:50 in equilibrium with SiHCl.sub.3 and HCl and suddenly quenching the mixture to below 300.degree. C.

Abstract: A process for producing semiconductor grade silicon. Metallurgical grade silicon, silicon dioxide, and silicon tetrafluoride are chemically combined at an elevated temperature to form silicon difluoride gas. The silicon difluoride gas is then polymerized, preferably in a two-step process. An initial small quantity of silicon difluoride polymers is formed at a first temperature. This initial polymerization removes most of the impurities that were present in the original metallurgical grade silicon and which were transported by the silicon difluoride gas. The bulk of the remaining silicon difluoride gas is then polymerized at a second, lower temperature. These polymers are substantially free from all impurities. The pure silicon difluoride polymers are then thermally decomposed at temperatures below 400.degree. C. to form binary silicon fluoride homologues. The homologues can be distilled for even higher purity, or can be used or stored as formed.

Abstract: Trichlorosilane or silicon tetrachloride is prepared by reacting metallic uminum-containing silicon in a reaction zone with hydrogen chloride or chlorine at a temperature between about 260.degree. and about 1200.degree. C, the reaction gas is then cooled to 40.degree. to 130.degree. in a cooling zone through which the velocity of flow is maintained at between 3 and 30 meters per second, and finally filtered.

Abstract: Dry granular hydrated silica is mixed with silicon tetrahalides, and they react chemically to produce a mixture of halosilicon acids.

Abstract: An improved method is provided for converting metallurgical grade silicon to semiconductor grade silicon, by first reacting the impure silicon with silicon tetrahalide to form a mixture of halosilanes, separating and purifying the trihalosilane, and then depositing semiconductor grade silicon by reacting the trihalosilane. The tetrahalide produced as a by-product of the deposition step is recycled to react with additional impure silicon. Improved trihalosilane yields from reacting silicon with the tetrahalide are achieved by adding hydrogen as a reactant, and by immediate quenching of the effluent with HCl. Such improved yields permit the complete system to be internally balanced so that the net production of by-products can be reduced to zero.

Abstract: Process for the disproportionation of a chlorosilicon hydride which comprises contacting it with an ion exchange resin containing tertiary amino or quaternary ammonium group bonded therein. There is described a cyclic process in which a fixed bed of the resin may be employed.

Abstract: Halogenosilanes and halogenogermanes which are contaminated by a boron-coining impurity are purified by treatment with an effective amount of a hydrated metal oxide or a hydrated silicate containing from about 3 to about 8% by weight of water, and then distilling the treated halogenosilane or halogenogermane at a temperature about 3.degree. to about 15.degree. C above its boiling temperature, and at atmosphere pressure.

Abstract: A balanced closed cycle silicon refinery has been developed for producing electronic silicon from industrial grade silicon. Impurities comprising approximately 1% of the industrial grade silicon are removed during the refinery process to produce the purified silicon, while only a relatively small percentage of make-up chemicals are added to the system. In the refinery, hydrogen chloride is reacted with the impure silicon in a halide reactor to provide trichlorosilane and silicon tetrachloride and hydrogen. The trichlorosilane and/or silicon tetrachloride are purified to remove the impurities, and then reacted with the hydrogen from the halide reactor in a fluidized bed reactor to produce the purified silicon and an effluent comprised of unreacted trichlorosilane, silicon tetrachloride, hydrogen, and the by-product hydrogen chloride.

Abstract: A process is provided for the low cost, high volume production of polycrystalline high purity silicon by a vapor phase reduction of a halosilane, with hydrogen, the resulting polycrystalline silicon being particularly suited for use in the production of single crystal silicon for the manufacture of semiconductor devices, solar cells, and the like.

Abstract: The present invention relates to a process for preparing high yields of hydrosilanes by reacting methylchloropolysilanes with hydrogen gas under pressure at a temperature of from about 25.degree. C to about 350.degree. C in the presence of a copper catalyst. Useful copper catalysts include copper metal, copper salts, and complexes of copper salts with organic ligands.

Abstract: Anhydrous hydrogen fluoride is produced from fluorosilicic acid by its decomposition with sulphuric acid in an improved process. Fluorosilicic acid of high concentration 40-50%, free of suspended silica is decomposed while being heated up to its boiling temperature with partial conversion into gaseous state. Earlier in the process evolved gaseous fluorine compounds which are desiccated by means of sulphuric acid and then separated by hydrogen fluoride absorption in a circulating liquid consisting of sulphuric acid and fluorosulphonic acid. Later hydrogen fluoride is distilled from this liquid and liquefied.

Abstract: A process for preparing hydrogenosilanes by hydrogenating disilanes, especially halogenated disilanes, under relatively mild reaction conditions is disclosed. The hydrogenation is effected in the presence of a catalytic system containing an aprotic compound and a nickel catalyst which consists essentially of finely divided nickel and is obtained by preliminary or in situ reduction of a nickel compound.

Abstract: An improvement in a process for preparing silicon tetrachloride or silicon trichloride wherein elemental silicon is contacted with hydrogen chloride in a fluidized bed, the improvement residing in carrying out the process in the presence of an iron compound, which iron compound is present in an amount such that when calculated as iron, the iron content is 10 to 43 weight percent based on the weight of the total solids in the fluidized bed, at a temperature in the range of 260.degree.-600.degree. C, preferably in the absence of an inert gas.