An advanced multiblock solution procedure and its application to silicon tube growth by EFG technique

摘要

The Edge-defined Film-fed Growth (EFG) is a widely used technique for the growth of polycrystalline silicon from its melt in the form of ribbon and hollow cylinders. The current octagonal tube growth technique has been modified successfully to produce 50 cm diameter circular tube for photovoltaic application by ASE Americas, Inc. A comprehensive growth model has been developed that accounts for conduction, convection and radiation heat transfer in the growth system, electromagnetic heating, and solidification. To improve the efficiency and accuracy of the model, two sets of grid system have been employed. A single structured grid system is used to calculate the magnetic potential field generated by radio-frequency induction heater, and a non-matching multi-block grid system to solve the temperature field with fine grids in the vicinity of the die-tip and silicon tube. Two sets of grid system overlap each other. A multi-block solution procedure has been developed satisfying the flux conservation at the block interfaces. The new solution procedure is used to simulate the existing octagonal silicon tube growth. The results obtained by different solvers, e.g., TDMA, CGSTAB, BiCGSTAB, SIP solver, are compared. It is evident that the CPU time is reduced dramatically if a fast solver, such as SIP or multigrid method, is used in the multi-block system.