Particularities of the thermal and oxygen concentration instabilities in a Czochralski process for solar silicon growth

A previous presented numerical model was used to study the time behavior particularities of temperature and oxygen concentration in a Czochralski (Cz) growth process of 200 mm diameter silicon single crystals for photovoltaic applications. First, some important model issues have been addressed: the dependence of the nu-merical results on the refinement level of the grid and on the model for oxygen equilibrium concentration at the melt-crucible interface. Then a parametrical study have been performed to study how the pulling rate and the rotation rate of the crucible influence the fluctuations of temperature and oxygen concentration near the crys-tallization interface. The numerical simulations have revealed that the temperature oscillations are closer to a normal distribution than the oxygen concentration, which is closer to a skewed left distribution.Both the increase of crucible rotation rate and pull speed has an effect of "pushing to the left": the histogram of temperature fluctuations tends from a skewed right distribution to a normal distribution with the increase of the pull speed and crucible rotation values while the oxygen concentration is more skewed to the left. As a general conclusion, the numerical simulations have shown that the oxygen concentration is more sensitive to the crucible rotation than the temperature field, while the pull speed has a stronger effect on temperature oscillations than on the oxygen concentration oscillations.