| Siemens CVD is an important technology for the production of polysilicon. The chemical and physical phenomenon involved in the Siemens CVD reactor includes turbulent gas flow, convective and radiation heat transfer, gaseous reactions containing a great amount of immediate products, and surface depositions and the crystal growth of silicon. In the present thesis, a comprehensive mathematical model was constructed to describe the fluid dynamics, the heat and mass transfer and the reaction kinetics of the silicon growth process in industrial Siemens CVD reactors.The single-pass conversion of SiHCl3 (TCS) in the growth of Si from SiHCl3 in H2 is low. Suitable process parameters are crucial for a high productivity of Si. Based on the minimization of Gibbs free energy, numerical simulations with different reacting temperatures, operating pressures and inlet gas species ratios were carried out. The results show that 1400 K,0.3 MPa and 2.8:1 inlet  and SiHCl3 mole ratio give a high conversion of SiHCl3 and low concentrations of by-products.Complex gas phase and surface reactions were involved in a Siemens CVD reactor. The growth rates of Si were numerically predicted using different reaction kinetic models by CHEMKIN software. A modified reaction kinetic model (ho-modified) was proposed to represent the gas phase and surface reactions. The kinetics model was verified by the published experimental data obtained in a temperature range similar to the industrial CVD processes of silicon productions.The Chemkin can only be used in the simulations of simple reactors. Further validation of the modified reaction kinetic model (ho-modified) was performed using Ansys Fluent which is comprehensively used in the simulation of turbulent-reaction system. By comparing with the results from Chemkin computations, Ansys Fluent was proved suitable for the prediction of the silicon deposition rates. The realizable k-ε model, eddy-dissipation conception (EDC) model, discrete ordinates (DO) radiation model and detailed gas phase/surface reaction kinetic model (ho-modified) are suitable for the modeling of turbulent reacting flow of an industrial Siemens CVD reactor.Coupled with detailed reaction mechanisms, the epitaxial growth of silicon in a Siemens reactor was simulated by Computational Fluid Dynamics (CFD) method. Based on the numerical simulation results, a sensitivity analysis was carried out to determine the key influencing factors of the growth rate in industrial CVD reactors. Under the conditions of fixed heating power applied to three different rod diameters of 50 mm,80 mm and 100 mm, the simulated results show, when the rods’diameter is 50 mm, the surface temperature is high and the gas temperature is low, and the growth rate of silicon is determined by the transport of gas species. When the rods’diameter is 80 mm, and the averaged surface temperature decreases to 1361 K, the surface reaction rate and transport of gas species control the growth rate of Si together. When the rods’ diameter is 100 mm, the surface temperature decreases further, and the rates of surface reactions become the control factor of deposition rate of Si.The surface-to-surface (S2S) radiation model was used to model the radiation exchange in an enclosure of gray-diffuse surfaces. The heat loss in a Siemens CVD reactor was numerically predicted by the model. The averaged heat loss of a single rod decreases with the increase of rods’ number, but the trends of change is relatively flat with rods’ number. Synthesizes the cost of equipment manufactures, the energy saving is increasingly limited with increasing rods’ number.
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