Application of double crucible in Cz Si crystal growth

摘要

Numerical modeling of melt flow, heat transfer and impurity (phosphorus) diffusion in the double crucible of a "Redmet-90M" Cz puller was carried out in an application to a 200 mm diameter Si single crystal growth. The double crucible consists of two coaxial crucibles having different sizes: 490 mm (external) and 300 mm (internal) inner diameters. The bottom of the internal crucible has a central hole of D_o = 6 and 12 mm diameter for melt inflow from the external crucible. During crystal pulling the granulated Si was added in the external crucible and a melt of the internal crucible was doped by phosphorus. Three-dimensional features of a rotating melt flow affecting heat transfer and impurity diffusion in the internal crucible were analyzed. In particular, the melt precession and thermal asymmetry near the liquid-solid interface (LSI) in the internal crucible are discussed. It is shown that a significant phosphorus losses caused by its evaporation from a melt surface may be compensated by additional phosphorus doping in the internal crucible.