Abstract: On the basis of selecting the temperature, initial molar ratio of H2 to SiHCl3 and total pressure close to the practical production conditions, the residual amount of SiHCl3 and the yield of byproduct SiCl4 in the Siemens system for the production of semiconductor grade Si were calculated. The diagrams of the residual amount of SiHCl3 and the yield of byproduct SiCl4 versus the selected conditions were plotted respectively. With the help of these thermodynamic diagrams, the influence of the temperature, initial molar ratio of H2 to SiHCl3 and total pressure on the thermodynamic behaviors of SiHCl3 and SiCl4 were discussed. The results show that when the total pressure and initial molar ratio of H2 to SiHCl3 are kept constant, the residual amount of SiHCl3 is inversely proportional to the temperature, and the yield of SiCl4 increases firstly, then decreases with increasing temperature. When the temperature and total pressure are kept constant, the yield of SiCl4 decreases with increase in initial molar ratio of H2 to SiHCl3, but in regard to SiHCl3, its residual amount is in inverse proportion to the initial molar ratio of H2 to SiHCl3. When the temperature and initial molar ratio of H2 to SiHCl3 were held constant, the residual amount of SiHCl3 decreases with decreasing total pressure, and for SiCl4, its yield first increases, and then decreases.

Key words: SiHCl3; SiCl4; Siemens system; thermodynamic behavior