On the hot-zone design of Czochralski silicon growth for photovoltaic applications

Several hot-zone designs are presented for Czochralski photovoltaic silicon growth. Without sacrificing the crystal quality, a significant reduction of power and argon consumption was achieved, while the pulling rate was significantly increased. More importantly, the oxygen content in the grown crystals was greatly reduced leading to longer minority lifetime. The degradation rate of the graphite elements was greatly reduced as well. The design reported here included the radiation shield (molybdenum and graphite with different coatings), additional side and bottom insulations (graphite and graphite felt), and a top side insulation. Good agreement was found between computer modeling and experimental measurements in the power consumption and a reference temperature near the heater. Furthermore, the effect of the hot-zone design on the interface concavity is discussed through computer simulation.