Modeling and simulation of silicon epitaxial growth in Siemens CVD reactor

Siemens CVD reactor is an important chemical device for the production of polysilicon. The chemical and physical phenomenon involved in the reactor is very complex. Understanding the multispecies thermal fluid transport and its interaction with the gas/surface reactions is crucial for an optimal design and operation of the reactor. In the present paper, a mathematical model was constructed to describe the fluid dynamics, the heat and mass transfer and the reaction kinetics of the epitaxial growth process in industrial CVD reactors. A modified reaction kinetics model was used to represent the gas phase and surface reactions. The kinetics model was validated using the published experimental data obtained in a temperature range similar to the industrial CVD processes of silicon productions. The epitaxial growth of silicon in a Siemens reactor was simulated using commercial Computational Fluid Dynamics (CFD) software ANSYS FLUENT. The distributions of gas velocity, temperature and species concentrations in the reactor were predicted numerically. Based on the numerical simulation results, a sensitivity analysis was carried out to determine the key factors influencing 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, the growth rate of silicon is determined by the transport of gas species. When the rods׳ diameter increases to 80 mm, 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, the rates of surface reactions become the control factor of deposition rate of Si.