Abstract: A process for the production of silicon comprising reacting a gaseous silicon compound of the formula SiH.sub.n X.sub.4-n, wherein X is halogen and n is 0 to 3, with aluminum in solid state. The resulting silicon can be highly pure and will have the particle size of the aluminum feed, making it especially useful for production of solar cells.

Abstract: High-purity metals are obtained by reducing the respective halides with reducing metals in the vapor phase in two or three stages, said reducing metals having greater halogen affinity than that of the metals to be reduced.

Abstract: Highly purified starting materials for the production of silicon suitable for fabrication of solar cells are produced via the carbo-thermal reduction process. A carbon-containing material with impurities therein, either by itself or admixed with glass bodies, which are attained from a melt of quartz sand and glass-forming additives formed into a fiber form and pulverized, is converted into a granulate form with the aid of a bonding agent. The resultant granulates are contacted with a hot inorganic acid, such as 3N HCl at about 90.degree. C., to extract substantially all impurities from the granulates, which can be in pellet or tablet form. The resultant purified pellets are then directly charged into an electrical arc furnace to yield solar-quality silicon. With this process, highly purified SiO.sub.2 and highly purified carbon are produced in a simple and cheap manner. The impurity level for boron, phosphorus and transition metal in these starting materials is less than about 10 ppm.

Abstract: A process to reduce SiO.sub.2 to produce Si, includes the steps:(a) reacting SiO.sub.2 with a saturated hydrocarbon at elevated temperature in a retort, to produce molten Si, and gases including SiO, CO, H.sub.2 and H.sub.2 O,(b) removing such gases from the retort and separating SiO in a first stream and CO, H.sub.2 O and H.sub.2 in a second stream,(c) combusting the second stream to produce heat, and(d) utilizing such heat to aid the reaction in the retort.

Abstract: Pure silicon is obtained in a semicontinuous process by reducing quartz sand with aluminum in a slag medium based on alkaline earth metal silicates. The slag serves thereby simultaneously as a solvent for the aluminum oxide that forms and as an extraction medium for impurities that occur. The silicon formed separates out of the silicate slag and can be separated off. The aluminum oxide produced by the reduction can be separated from the slag and used for recovery of reusable aluminum.

Abstract: A process for preparing high purity silicon metal from Na.sub.2 SiF.sub.6 (sodium fluosilicate). The sodium fluosilicate is heated to decomposition temperature to form NaF, which retains most of the impurities, and gaseous SiF.sub.4. The SiF.sub.4 is then reduced by the bomb reduction method using a reductant having a low packing density.

Abstract: A process and apparatus for thermally decomposing silicon containing gas for deposition on fluidized nucleating silicon seed particles is disclosed.Silicon seed particles are produced in a secondary fluidized reactor by thermal decomposition of a silicon containing gas. The thermally produced silicon seed particles are then introduced into a primary fluidized bed reactor to form a fludized bed. Silicon containing gas is introduced into the primary reactor where it is thermally decomposed and deposited on the fluidized silicon seed particles. Silicon seed particles having the desired amount of thermally decomposed silicon product thereon are removed from the primary fluidized reactor as ultra pure silicon product.An apparatus for carrying out this process is also disclosed.

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 by jetting a spray of reactants into a reaction chamber at a rate and temperature which causes the reaction to take place far enough away from the entry region to avoid plugging of reactants at the entry region and wherein separation in the melt is carried out continuously from the reaction and the Si can be cast directly from the melt.

Abstract: Silicon is manufactured from powdered material containing silica by injecting this, optionally together with a reducing agent, into a gas plasma with the help of a carrier gas. Thereafter the silica material thus heated, together with the reducing agent if any and the energy-rich plasma gas, is introduced in a reaction chamber surrounded by solid reducing agent in lump form, so that the silica is caused to melt and is reduced to liquid silicon.

Abstract: A process for the production of silicon or ferrosilicon by reduction of silicon oxide, optionally in the presence of iron or iron oxide, using a carbonaceous reducing agent, in a reduction furnace.

Abstract: A process for manufacturing (very high purity) solare voltaic cell grade silicon involving the steps of reacting impure silicon tetrachloride with a lower molecular weight alcohol (e.g. ethanol) to form a silicon alkoxide (e.g. tetraethyl silicate) and then isolating a pure silicon alkoxide by filtration and fractional distillation. The purified silicon alkoxide can then be chemically reduced by reacting with a metal (e.g. Na) thus recovering high purity elemental silicon. The reaction byproducts (e.g. HCl and NaOR) can be used to regenerate the alcohol and resulting salt (e.g. NaCl) can be subjected to electrolysis to recover the metal and the halogen, thus leading to an overall process with total recycle of byproducts.

Abstract: An improved means and method for extracting polycrystalline silicon from silicon source gases is provided wherein seed particles and source gases are reacted in a rising particle reaction chamber in which the gas velocity is sufficient to entrain and eject all seed particles smaller than a predetermined size while those which have grown to a larger size fall through the rising gas stream and are extracted from the base of the reactor. Those seed particles which are ejected from the reaction column are separated from the spent gases and fall back into a concentric reservoir. A first gas not containing any silicon is supplied to a nozzle within the reservoir and creates a first gas-particle mixture which is injected into an auxiliary mixing chamber, where it is further mixed with a high velocity lifting gas which includes the source gases. The lifting and source gas-particle mixture is swept through the reactor where silicon deposits on the seed particles.

Abstract: A cyclic, ideally continuous, process for producing titanium which employs the reduction of titanium fluorides by potassium or sodium, or mixtures thereof, to result in titanium particles in molten alkali metal fluoride, which after separation said alkali metal fluoride is combined with a molten ferrous metal to evolve the alkali metal to be recycled from alkali metal iron fluoride that is then combined with a titanium dioxide containing mineral, ideally ilmenite, to evolve titanium tetrafluoride which is recycled. The process may be employed to produce other metals, especially aluminum, silicon and zirconium.

Abstract: In the production of silicon articles at an elevated temperature, a stream comprising a controlled mixture of an oxygen-containing first gas and a second gas is admitted to the processing chamber. The first gas is one which partially dissociates under the conditions in the chamber to form both oxygen and the second gas. The second gas is one which is not harmful to silicon at the conditions in the chamber. Substantially equilibrium conditions are established in the chamber so that the dissociation of the first gas to oxygen occurs reversibly. The partial pressure of oxygen (P.sub.O.sbsb.2) is sensed in the chamber during processing of the article. In response to the P.sub.O.sbsb.2 level, the ratio of the rates of flow of the oxygen-containing gas and the second gas is adjusted so as to maintain the P.sub.O.sbsb.2 at a level less than about 10.sup.-6 atmosphere, and usually no greater than about 10.sup.

Abstract: There is disclosed a process for preparing ultra pure silicon from metallurgical grade silicon, which comprises (a) continuously passing powdered and acid-leached metallurgical grade silicon through an induction plasma; (b) quenching said treated particles whereby upon solidification of the molten particles, a portion of the impurities therein migrates to the surface of the granules obtained; (c) acid-leaching the surface impurities of the granules obtained in step (b); and (d) after drying the granules obtained, repeating steps (a), (b) and (c) until a silicon of the desired purity is obtained.

Abstract: A method of producing silicon comprising producing a plasma in a gas flow laden with at least one silicon compound so that the silicon compound is reduced or decomposed to silicon and transporting the silicon which may have reacted with other material if present in the plasma and reaction products out of the plasma in the gas flow.

Abstract: A process for producing silicon in which a reaction mixture consisting, on the one hand, of hot-pressed briquettes of silicon dioxide (quartz) and carbon and, on the other hand, of granular quartz are introduced into an electric furnace and reacted so that silicon carbide is produced from the agglomerates and the silicon carbide then reacts with the quartz which fuses from the granular quartz to produce elemental silicon.

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: Pure silicon is obtained in a cyclic process by reducing quartz sand with aluminum; the finely divided quartz is dissolved in an aluminum sulphide slag and is reduced by molten aluminum. The molten aluminum also serves as a solvent for the elemental silicon which crystallizes out and precipitates as the temperature falls. Aluminum oxide formed during the reduction is extracted from the slag and passed on for melt electrolysis in order to recover the aluminum.

Abstract: A method for purifying silicon which employes an electrolytic step using a metal fluoride electrolysis to generate silicon fluoride followed by a chemical reaction step which produces elemental silicon in a highly pure form.

Abstract: Relatively pure Si (having less than about 1 ppm of detrimental impurities therein) is obtained from ordinary quartz sand by uniformly admixing such sand with suitable glass-forming materials, such as boron oxide and alkali-metal carbonates or oxides, melting such admixture to form a glass, annealing the glass so as to obtain a phase separation comprised of an SiO.sub.2 -- rich phase and an impurity-rich phase, extracting the impurity-rich phase via strong acid, such as nitric acid, washing and drying the remaining glass and reducing such glass with carbon-containing compounds, such as graphite, sucrose, starch, etc., in an electric arc. The so-obtained relatively pure silicon is suitable for fabrication into semiconductor components, such as solar cells.

Abstract: A process for the production of silicon or ferrosilicon by reduction of silicon oxide, optionally in the presence of iron oxide, by means of a carbonaceous reducing agent in a reduction furnace. The furnace operation is simplified and the yield is increased by making the supply of energy and the supply of silicon oxide, respectively, independent of each other and by adjusting the ratio between them in such a manner that the gases leaving the furnace have a silicon monoxide content below 10 mole percent. A controlled supply of at least a part of the silicon oxide to the hotter parts of the furnace can be used as a means of making the supply of energy and the supply of silicon oxide reciprocally adjustable.

Abstract: A method and related apparatus are provided for producing on a semi-continuous basis polycrystalline silicon and melt replenishment for a crystal growth crucible. The silicon is deposited in low density form on the inner walls of a multi-walled reaction chamber by delivering gaseous HSiCL.sub.3, SiH.sub.4, or the like, and reducing gas if needed, through the chamber which is heated to the reaction temperature of the feed gas. After a certain amount of silicon has been produced, the chamber temperature is raised sufficiently to melt down the silicon which is then used to replenish a crystal growth crucible. The operations are then cyclically repeated.The apparatus includes a reaction chamber having a multi-walled configuration to maximize the interior surface area on which the silicon is deposited. A drain trap such as a U-shaped tube, or the like, is connected to the bottom of the reaction chamber and provided with heating elements.

Abstract: Method of deposition of silicon in fine crystalline form upon a substrate from a silicon-containing reaction gas which includes, at a set mole ratio of the reaction gas and throughput selected for the deposition process, setting the deposition rate-determining temperature of the substrate, at the beginning of deposition, at a temperature lower than optimal temperature for deposition of silicon thereon, maintaining the lower than optimal temperature during a first deposition phase, thereafter raising the temperature of the substrate to the optimal temperature while maintaining the other parameters determining the rate of deposition, and maintaining the optimal temperature for the remainder of the deposition.

Abstract: Silica is reduced in a direct arc reactor by activated carbon or carbon black having relatively low boron (B) and phosphorus (P) contents to produce silicon having similarly low B and P contents and suitable for use in photovoltaic cells for converting solar energy directly to electrical energy.

Abstract: The invention relates to a method and device for producing polycrystalline silicon. The method consists in particular in purifying a bath of molten silicon which contains impurities by bubbling a mixture of chlorine and oxygen and in progressively crystallizing the purified silicon in a receptacle (22) which is moved vertically downwards in a vertical gradient of temperatures which increase towards the top. Application to manufacturing solar photocells.

Abstract: A process for converting silicon intermediates to high purity silicon by an arc heater characterized by the steps of preliminarily reacting gaseous silicon intermediate, such as a silicon halide, with a metal reductant, such as sodium, to form preliminary reaction products including small solid silicon particles and droplets of salt of the metal reductant, at temperatures below the boiling point of the metal reductant, subsequently heating the reaction products to temperatures above said boiling point in an arc heater chamber to convert the reaction products to droplets of silicon to merge and form larger silicon droplets, and thereafter separating the mixture of silicon droplets and salt vapor.

Abstract: Thin layers of polycrystalline silicon are formed atop a metal substrate, by reducing a gaseous silicon containing compound with metallic zinc, in liquid state, and in the presence of at least one other metal which is also in liquid state, same being either tin, lead, gold, silver, antimony and/or bismuth. The reaction is conducted under conditions such that the zinc compound product of reduction is also in gaseous state.

Abstract: The present invention relates to the production of high purity solar grade silicon from common rice hulls. A unique process for material purification and reduction includes leaching the rice hulls in acid followed by treatment with high purity water, coking the acid-cleaned hulls in a non-oxidizing ambient, compensating the carbon or silica content of the coked hulls to obtain a desired carbon to silica ratio and reducing the silica to produce high purity silicon.

Abstract: In the production of elemental silicon by chemical vapor deposition on a particulate seed bed, the continuous generation of seed particles for use or recycle is achieved by the maintenance of a separate, subsidiary reaction zone at a temperature which favors breakage of product particles; while a higher temperature, favorable for deposition, is maintained in the principal reaction zone. The separate reaction zones may be established in separate reactors, or in a single reactor.

Abstract: A combined method for purifying silicon and growing single crystals. A multiple step process is disclosed by which metallurgical grade silicon is purified and converted into a high quality monocrystalline silicon ingot. Each of the steps in the process is designed to remove specific impurities and thus improve the electrical quality of the silicon material. First, the insoluble slag and high segregation coefficient impurities are removed. Soluble impurities are then removed by a reactive gas step, and by a liquid-liquid extraction step using reactive metallic oxides or an oxide solvent. The remaining impurities are removed by segregation during freezing by pulling an ingot from a portion of the molten metallurgical grade silicon. The ingot so formed is then used to charge a second crystal puller. One or more of the previous purifying steps can then be repeated for the charge of the second crystal puller and an ingot of improved purity can be pulled from the melt of the second puller.

Abstract: A liquid reactant injector assembly especially suited for the injection of liquid reactant into a high temperature metal reductant vapor and carrier gas stream for the production of metal is disclosed. The assembly is especially adapted for the continuous production of high purity silicon by the reduction of SiCl.sub.4 with sodium. The assembly includes a refractory-lined, hollow, metal shell having a plurality, suitably ten, equally-spaced, concentric, radially directed ports provided in the shell and wall. A hydraulic, atomizing type, spray nozzle is sealingly mounted in each of the ports recessed from the inner wall surface.

Abstract: The method and apparatus for producing liquid silicon of high purity and for casting silicon. Hydrogen and a hydrogenated silane in gaseous state are mixed, preferably with a source of a small amount of oxygen, in a heated chamber producing the liquid silicon, with the exhaust gases bubbling out of the melt under a baffle. The chamber for the melt of liquid silicon preferably is lined with silicon dioxide. The liquid silicon may be used in making high purity vitreous silica and may be used in making castings of silicon. In making castings, the liquid silicon is accumulated in a second chamber and is periodically drawn from the second chamber into a third chamber which contains the mold for the casting.

Abstract: A process for the production of high purity polycrystalline silicon from a mixture of silicon tetrachloride and trichlorosilane. Such a mixture can be used for the rapid deposition of polycrystalline silicon while, at the same time, producing an excess of trichlorosilane in exhaust gases from the reaction. The process permits the modification of the reactor design for the economical and energy conscious production of polycrystalline silicon.

Abstract: A sodium storage and injection system for delivering atomized liquid sodium to a chemical reactor employed in the production of solar grade silicon. The system is adapted to accommodate start-up, shut-down, normal and emergency operations and is characterized by a jacketed injection nozzle adapted to atomize liquefied sodium and a supply circuit connected to the nozzle for delivering thereto liquefied sodium comprising a plurality of replaceable sodium containment vessels, a pump interposed between the vessels and the nozzle, and a pressurizing circuit including a source of inert gas connected with the vessels for maintaining the sodium under pressure.

Abstract: The disclosure relates to formation of polycrystalline silicon by the fluid bed process wherein seed crystals of silicon are entered into the reactor from the bottom thereof and by means of a pressurized feed, the product being removed from the reactor through a tube entering the reactor at its bottommost portion. The removed product passes through a closed line by gravity into a closed vessel, the vessel being movable to a crystal puller apparatus without handling or exposure. The closed line is also tapped, as desired, to remove product on-line for test during operation so that the system can be immediately shut down when improper product is detected without excessive loss of pure polycrystalline silicon. The polycrystalline silicon is fed from the transfer vessel to a melt from which crystals are to be pulled via an intermediate reservoir. The silicon is transferred from the vessel to the reservoir under pressure to prevent contamination thereof.

Abstract: A method of manufacturing high-purity silicon rods by subjecting a silicon compound to pyrolysis on a plurality of rod-shaped high-purity silicon carrier members which have been red-heated by directly passing an electric current therethrough thereby depositing high-purity silicon thereon, characterized in that monosilane supplied into a pyrolysis container is subjected to pyrolysis or thermal decomposition on said red-heated carrier members while insulating the radiant heat between said red-heated carrier members along the overall length thereof.

Abstract: A semiconductor material, such as elemental silicon, is deposited on heated rod-shaped mandrels from a reactive gas stream capable of pyrolytically depositing silicon wherein the gas stream is regulated in such a manner that the silicon deposition rate remains constant per cubic centimeter of mandrel surface throughout the deposition process.

Abstract: A method of manufacturing high-purity silicon rods having a uniform sectional shape by thermally decomposing monosilane on a plurality of rod-shaped silicon carrier members which have been red-heated by directly passing an electric current therethrough, said silicon carrier members being thermally insulated from one another, characterized in that monosilane is supplied into a pyrolysis container through multi-stage monosilane supply ports located in parallel with the axes of said silicon carrier members held vertically within the pyrolysis container, and that the amount of supply of monosilane through the upper supply ports is increased as compared with that through the lower supply ports in response to the increase of the diameter of each of said silicon rods.

Abstract: A process for producing high purity silicon characterized by the employment of an electric arc heater into which a silicon halide is injected together with a metal reductant such as an alkali metal or an alkaline-earth metal which are reacted together by projecting them tangentially into a reaction chamber to cause the formation of liquid silicon and a gaseous metal halide salt which are separated in a suitable manner such as centrifugally or by condensation.

Abstract: An improved process for the production of pure, elemental semiconductor material, especially silicon, of the type wherein the semiconductor material is produced by decomposition from the gaseous phase, is provided, which includes the initial step of maintaining a melt of the semiconductor material at a temperature of up to a maximum of 200.degree. C above the melting point of the material. Thereafter, at least a gaseous, decomposable compound of the semiconductor material is introduced into the melt, under a pressure of about 0.01 to 30 bar, to produce a pure, elemental semiconductor material in liquid form.

Abstract: A semiconductor material, such as elemental silicon, is deposited on heated rod-shaped mandrels from a reactive gas stream capable of pyrolytically depositing silicon wherein the gas stream is regulated in such a manner that the silicon deposition rate remains constant per cubic centimeter of mandrel surface throughout the deposition process.

Abstract: Epitaxial and diffusion-type planar diodes and solar cells utilize low-cost refined metallurgical silicon substrates having a substantially higher impurity content than conventional high-cost, high purity semiconductor grade silicon. The epitaxial type products have an n-on-p-on-p substrate configuration, while the diffusion-type products have pentavalent impurities diffused therein to form a p-n junction in the low cost silicon substrate. One embodiment employs a multigrained refined metallurgical silicon (RMS) prepared by precipitating essentially iron-free silicon platelets from a solution of metallurgical grade silicon in molten aluminum, melting said refined platelets, in contact with a silica slag and pulling silicon boules from a melt of said refined metallurgical silicon (RMS).

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: A process for converting silicon intermediates to high purity silicon by an arc heater characterized by the thermal reduction of one of several potential purified silicon intermediate compounds using an arc heater as the reduction energy source and using hydrogen as the reductant.

Abstract: A method for the production of single crystal silicon characterized by the steps of feeding into an arc heater a quantity of uncontaminated silicon halide to react with hydrogen or a metal reductant, such as sodium, to produce reaction products including liquid silicon and a gaseous salt of the reductant, depositing the liquid silicon on a downwardly inclined surface, and attaching a single seed crystal of silicon to the liquid silicon and withdrawing the single seed crystal from the liquid silicon so as to propagate a large single crystal.

Abstract: A process for producing high purity silicon characterized by the employment of an electric arc heater into which a silicon halide is injected together with a metal reductant such as an alkali metal or an alkaline-earth metal which are reacted together by projecting them tangentially into a reaction chamber to cause the formation of liquid silicon and a gaseous metal halide salt which are separated in a suitable manner such as centrifugally or by condensation.

Abstract: A method for doping solar grade silicon characterized by the steps of feeding into an arc heated gas stream a quantity of a metal reductant such as an alkali metal or an alkaline-earth metal and also feeding into the stream a quantity of a silicon halide and of a corresponding halide of a doping agent such as arsenic to react with the metal reductant to produce reaction products including a salt of a metal reductant and a mixture of liquid silicon and doping agent, and separating the mixture from the salt of the metal reductant.

Abstract: A process for the production of high purity silicon characterized by the employment of an electric arc heater in which a silicon halide is reacted with hydrogen to produce liquid silicon and gaseous co-products.

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.