A simple and inexpensive air pump can work as a safe and effective oxygen blender.

No abstract

Oxygen content in the pure Silicon crystal is inevitable because of the significant rate of corrosion of the crucible walls at high temperature. Precise control of oxygen concentration in the crystal is possible only by manipulating underlying flow characteristics of the melt. Thermo-fluidics in this process are extremely complex and responsible for non-uniform oxygen striations. This work is focused to understand the melt flow complexities and its influence on oxygen distribution near the crystallization front. A global model which accounts for hardware configuration is considered for this purpose. The melt flow characteristics are investigated to study the effect of crystal and crucible rotations in absence and presence of the electromagnetic fields (EMs). Our simulation results show that strong buoyancy driven flow interaction generates non-uniformity in oxygen concentration near the edge of the crystal in the absence of magnetic field. Application of external field facilitates more pumping of melt underneath the crystal that prevents stratification of oxygen near the edge.

Czochralski Growth of Silicon Crystal (Cz) is extensively used for single crystal manufacturing and most of the Silicon wafers are manufactured by this process. Melt flow in large crucibles, used for growth of large diameter (300mm) crystal, is turbulent in nature. In this study, we present a model for simulating Czochralski crystal growth process for 300mm crystal. This study is mainly focused on effect of crucible rotation on flow and temperature profiles in the melt. Two-dimensional axisymmetric model was used for this purpose which accounts for generated turbulence, heat/ mass transfer with phase change. Investigations show that flow pattern in co-rotation below the crystal is totally opposite that of counter-rotation. Centrifugal force is dominant due to crystal and crucible rotation, which creates vertical upwards or downward flow below the crystal, depending upon the co-rotation or counter rotation. With increase in pull rate, depth of the predicted interface in the melt was also found to be increased. Simulated results will be helpful for optimization of process parameters to achieve better quality of crystals.