System for obtaining semiconductor-suitable silicon from quartz sand by chemical processing and crystallization

Abstract

A system for producing semiconductor-suitable silicon from quartz sand, characterized in that: • quartz sand is first cleaned, pulverized, and pressed into a shaped body; • the pressed quartz sand is reacted to form crude silicon in a reduction process with the addition of carbon; • the crude silicon is then converted to trichlorosilane by reaction with hydrogen chloride, and this is purified by distillation; • the purified trichlorosilane is decomposed to high-purity polysilicon in the presence of hydrogen; and • the polysilicon is finally converted to single-crystal silicon by crystallization (Czochralski or float-zone process), which is used for the production of wafers.

Description

Technical field: The invention relates to semiconductor technology, in particular a system for producing high-purity silicon from quartz sand, which serves as a starting material for the manufacture of wafers and integrated circuits. State of the art: It is known that quartz sand (SiO2) is used as a raw material for the production of silicon. Existing systems include carbon-thermal reduction, chemical purification via trichlorosilane, and single-crystal pulling (Czochralski or float zone). However, these processes are sometimes costly, energy-intensive, and only feasible in highly specialized industrial facilities. The core of the invention: The present invention proposes a simplified and combinable system in which quartz sand is first cleaned, pulverized, and pressed to obtain a homogeneous starting form. This is followed by reduction to crude silicon, chemical purification via gas-phase reactions (trichlorosilane intermediate), and finally crystallization to high-purity silicon. By combining pressing and sintering techniques with conventional chemical gas purification, the material flow is optimized. At the same time, the pressed SI02 can also be used as an optical substrate, so that the process chain produces both semiconductor silicon and photonic substrates from the same raw material. Technical design of the system: 1. Raw material preparation • Quartz sand is washed, dried, and freed from metal oxides, salts, and organic residues. • The sand is mechanically pulverized and compacted in press molds. • Optional: Color or marking additives for identifying material batches. 2. Reduction • A pressed SiO₂ body is heated in an electric arc or induction furnace with the addition of carbon. • Reaction: SiO₂ + 2C → Si + 2CO↑ SiO₂ + 2C → Si + 2CO↑ SiO₂ + 2C → Si + CO↑ • Result: Crude silicon with 98-99% purity. 3. Chemical Purification • Reaction of the crude silicon with hydrogen chloride (HCl) at elevated temperature • Formation of trichlorosilane (SiHCl₃). • Distillation of the trichlorosilane → separation of impurities. • Decomposition of the pure trichlorosilane with hydrogen → high-purity polysilicon, purity 9N, i.e., 99.999999999%. 4. Crystallization • Conversion of polysilicon to single-crystal silicon by: • Czochralski process: crystal pulling from the melt.• Float-zone process: local zone melting to displace impurities. • Result: silicon ingot (single crystal). 5. Wafer fabrication • Sawing the ingots into wafers • Lapping, grinding, and polishing. • Wafers as a base material for semiconductor chips or photonics integration. Advantages of the invention: • Use of a cost-effective and abundant raw material (quartz sand). • Combination of pressing processes (homogeneous starting material) and gas-phase purification (highest purity). • Possibility of producing both semiconductors and optical substrates from a single process chain. • Potential for more sustainable and resource-efficient silicon production.

Claims

A system for producing semiconductor-suitable silicon from quartz sand, characterized in that: • quartz sand is first cleaned, pulverized, and pressed into a shaped body; • the pressed quartz sand is reacted to form crude silicon in a reduction process with the addition of carbon; • the crude silicon is subsequently converted to trichlorosilane by reaction with hydrogen chloride, and this is purified by distillation; • the purified trichlorosilane is decomposed to high-purity polysilicon in the presence of hydrogen; and • the polysilicon is finally converted to single-crystal silicon by crystallization (Czochralski or float-zone process), which is used for the production of wafers. System according to claim 1, characterized in that the pressed quartz sand is additionally provided with additives that enable marking or optical identification of the material batches. System according to claim 1 or 2, characterized in that the carbon monoxide (CO) produced during the reduction process is captured and used as a by-product for energy generation. System according to one of claims 1-3, characterized in that the pressed quartz sand body is additionally used as an optically conductive substrate by being converted to high-purity glass (fused silica). System according to one of claims 1-4, characterized in that both electronic wafers made of silicon and optical substrates for photonic components are produced from the same process chain. System according to one of claims 1-5, characterized in that the float-zone method is used specifically for the crystallization of the polysilicon in order to obtain particularly high-purity single crystals for power electronics. System according to one of claims 1-6, characterized in that the molded bodies used in pressing and sintering are used directly as a substrate for the subsequent deposition of silicon thin films.

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