Effect of water-cooled jacket on the oxygen transport during the Czochralski silicon crystal growth process

Abstract

Nowadays, the water-cooled jacket is widely used in the large industrial Czochralski (Cz) furnace to enhance the pulling rate of the monocrystalline silicon crystal for solar cells. It is an efficient tool to increase productivity and reduce the production cost of the photovoltaic industry. However, the water-cooled jacket would affect the oxygen concentration of the grown silicon crystals. In this study, a two-dimensional numerical model was used to investigate the influence of the water-cooled jacket on the heat and oxygen transport in the silicon melt during the crystal growth process. The results demonstrate that the water-cooled jacket significantly enhances the heat loss from the melt-crystal and melt-gas interfaces, resulting in a larger temperature difference and stronger buoyancy convection in the melt, compared to the case without water-cooled jacket. The strong buoyancy convection causes the higher turbulent viscosity in the melt. Consequently, the oxygen transport in the melt is strengthened. By using the water-cooled jacket, the oxygen concentration in the grown crystals was increased by about 2.6 ppma at the crystal length of 400 mm. The simulation results agree reasonably with the experimental data.