Kensho Sahira

A numerical study on oxygen transport in silicon melt in a double-crucible method

Abstract Oxygen transport in the silicon melt in the double-crucible method was simulated by using the k -ϵ turbulent flow model. The high eddy diffusivity of oxygen calculated from the eddy dynamic viscosity is postulated in the present model. In the mechanisms found in the simulation, the small distance between the hot inner crucible and the melt/crystal interface was the most dominant reason for the increase of the oxygen concentration in the case of the double-crucible method.

A new technique for controlling the dopant concentration in the double-crucible method

Abstract A new doping procedure for keeping the dopant concentration of the crystal constant in a continuous Czochralski method, using a double-walled crucible, is proposed. In this method the initial concentrations in the inner and the outer crucibles are set to be equal. Therefore, the equalizing phenomena of the concentrations between the two crucibles in the initial stage do not have to be considered. The strategy for doping control in this new method is analyzed using a one-dimensional mathematical model.

A Numerical Study of the Influence of Feeding Polycrystalline Silicon Granules on Melt Temperature in the Continuous Czochralski Process

Abstract Temperature change was simulated using a solid body rotating melt model when solid polycrystalline silicon granules were supplied to a melt in a double-crucible method. Only heat conduction was considered in the analysis. The influence of the crucible rotation rates and of the initial temperature of the supplied silicon was investigated systematically and quantitatively. The influence of the crucible rotation rate was stronger than expected, which suggests that the crucible rotation rate cannot be lowered too much because of the possibility of the melt solidifying between the inner and outer crucibles.