Numerical analysis of Oxygen control during growth of Czochralski silicon single crystals
In the present work, a set of 2D global furnace simulations accounting for oxygen dissolution and transport have been used to predict Oi content along the produced Silicon crystal. It is shown that Oi content is sensitive to several growth parameters (melt level, crucible rotation, etc.). Results indicate Oxygen tends to increase at the end of the crystal due to a combination of weakening of turbulence and planar velocity in addition to decrease of the melt free surface. Crucible rotation is the most influencing parameter at low melt level. Argon gas pressure and flow have a limited impact at low melt level.
Development of oxygen transport model in Czochralski growth of silicon crystals
Oxygen is one of the most important impurities in Czochralski (Cz)-grown silicon crystals. The precise control of oxygen concentration in growing crystal, both in radial and in axial directions, is required to obtain silicon wafers with necessary electronic properties. A modified numerical model of oxygen transport as a way of prediction of oxygen concentration in growing Si crystals is described in this paper. Test calculations for the updated model were performed for a Cz setup with a small crucible diameter and weak turbulent melt flow. The calculated oxygen profile along the crystallization front is compared with available experimental data. 2-D and 3-D calculation results have evaluated the number of finite volumes in 3-D grid, required for precise description of oxygen transport in the small growth system.
Fundamental study of crystal/melt interface shape change in Czochralski crystal growth
The crystal/melt interface shape is an important factor in determining the crystal quality during crystal growth. To determine the evolution of the interface shape, the relative temperature gradient function Sv(R) is used as a criterion. This function can be derived from careful analysis of the energy balance at the crystal/melt interface. Some results are presented based on the simplified model of crystal conduction and the Czochralski bulk flow model where the crystal pulling rate is set to zero at a certain crystal length and the growth system is in a steady state.