Modelling analysis and experiments of polycrystalline silicon directional solidification in an annular heating field

Abstract

Abstract As a solution to the low convection strength of the Bridgman method and the convection control difficulties of the electromagnetic induction melting method, a novel, large directional solidification device with annular heaters arranged above the crucible is designed. The inhomogeneous heating field causes differences in melt density, intensifies controllable natural convection and accelerates the moving of impurities from the solid–liquid interface to the surface of the melt, thereby improving purification efficiency and reducing energy consumption. Although the temperature field is inhomogeneous, vertical crystal growth can still be achieved. Mathematical analytic modelling is used to explain the principle, and the feasibility is verified by experiments. The results show that high-quality and large bulk silicon ingot (1 m × 1 m × 0.45 m) can be produced at an average solidification rate of 3.68 μm s−1.