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.
Effects of crystal rotation rate on the melt–crystal interface of a CZ-Si crystal growth in a transverse magnetic field
Abstract A series of computations were carried out to study the effect of crystal rotation rate on the melt–crystal interface shape and temperature gradient at the interface during CZ-Si crystal growth in a transverse magnetic field (TMCZ). A three-dimensional (3D) global model was used in this study. It was found that the interface deflection changes from non-uniformity in the azimuthal direction to an axisymmetric distribution with increasing crystal rotation rate. The mechanism of this effect is mainly attributed to the spatial fluctuations of local growth rate, which is derived as a function of crystal rotation rate and non-uniformity of interface deflection in the azimuthal direction. It contributes to the formation of the shape of the melt–crystal interface through the heat release of solidification at the melt–crystal interface. Even though the melt–crystal interface shape is nearly axisymmetric at a high crystal rotation rate, local growth rate fluctuations are still noticeable and play an important role in the characteristics of heat transfer and impurity segregation at the melt–crystal interface.