Control of Melt Flow and Oxygen Distribution Using Traveling Magnetic Field during Directional Solidification of Silicon Ingots

Traveling magnetic field (TMF) is a potential method to control the melt flow and impurity transport during the directional solidification (DS) of silicon ingots. We numerically study the control mechanism of a downward and an upward TMF with different frequencies on the silicon melt flow and oxygen distribution in the DS process. Model experiment of generation and measurement of a TMF is first carried out to validate the magnetic field computing program. Then, the TMF frequency is varied to study its influence on the direction and magnitude of Lorentz force, pattern and intensity of silicon melt flow, and distribution of oxygen impurity. Results show that the downward TMF with large frequency can induce local melt flow above the melt-crystal interface and block the oxygen transport from the dominant flow to the interface. The upward TMF with small frequency and large amplitude can induce thoroughly upward melt flow along the crucible side wall and take the oxygen far away from the melt-crystal interface, which is better for reducing the oxygen content in the silicon melt and ingots.