Modeling Thermal Gas Dynamic Processes of the Production of Silicon from Its Halides
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ling Thermal Gas Dynamic Processes of the Production of Silicon from Its Halides L. V. Shabarovaa, *, A. D. Plekhovicha, A. M. Kut’ina, P. G. Sennikova, and R. A. Korneva a
Devyatykh Institute of Chemistry of High-Purity Substances, Russian Academy of Sciences, Nizhny Novgorod, 603950 Russia *e-mail: [email protected] Received February 7, 2019; revised February 7, 2020; accepted February 14, 2020
Abstract—A procedure was developed to model the gas-dynamic and thermal conditions of the production of powdered silicon from silicon tetrachloride and tetrafluoride in a high-frequency induction plasma chemical reactor. The model includes a description of the turbulent flow of a mixture of ideal viscous compressible gases while taking into account the induction heating of the gas by conduction, convection, and radiation, as well as taking into account the effect of the electromagnetic force on plasma motion. The powdered particles form according to the results of the thermodynamic calculations, and the particle distribution in the flow is described by the diffusion mechanism. The results of modeling the conversion of volatile silicon chloride and fluoride in a swirl-stabilized high-frequency induction plasmatron are presented. Keywords: computational experiment, ideal gas, thermodynamics, electromagnetic field, diffusion, silicon DOI: 10.1134/S0040579520040260
INTRODUCTION Silicon halides SiX4 (X = Cl, F) are the main participants of various process chains for the production of high-purity silicon. Silicon tetrachloride is a major byproduct in silicon production by hydrogen reduction of trichlorosilane [1], silane production by trichlorosilane disproportionation [2], and hexachlorodisilane synthesis [3]. The impurity content of silicon tetrachloride is at the purity level of the initial trichlorosilane. Therefore, converting this high-purity byproduct to either chlorosilanes or silicon itself is an important problem [1]. Plasma chemical methods of hydrogenation of silicon tetrachloride are particularly promising for this purpose. In early patents, the hydrogenation of silicon tetrachloride was performed in a radio frequency of (13.56 MHz) discharge [4, 5] and in an arc discharge (12.5 kW) in a hydrogen plasma [6]. A method was developed to produce trichlorosilane in a direct-current discharge in an argon–hydrogen plasma [7]. The decomposition of silicon tetrachloride to form elemental silicon in a microwave discharge was studied [8–10]. The use of low-frequency (880 kHz) plasma for the deposition of thin silicon films from SiCl4 was tested [11]. A high growth rate and degree of nanocrystallinity were reached. Overall, though, despite numerous studies of the reduction of silicon tetrachloride in discharges of various types, a plasmatron with process characteris-
tics suitable for industrial use has not yet been designed. Silicon tetrafluoride SiF4, a structural analog of silicon tetrachloride, contains the maximum amount (27%) of silicon and is therefore promising for silicon production; this is all the more so as S
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