SOI is a single crystal thin silicon film isolated by an insulating layer or a fully insulating substrate. SOI has many structural advantages and SOI material can be used in many applications. ZMR is a process for obtaining SOI structure by the recrystallization of a polycrystalline layer on an insulator using focused heat source. The focused heat source raises the local temperature of the polysilicon film above the melting point. Then the molten zone formed solidifies laterally as the heat source is scanning over the wafer.
The major issues in ZMR process have been the origin of defects such as subboundaries. Heat transfer plays a critical role during ZMR. The temperature profiles of the silicon film during ZMR process have been shown to play a major role in the crystal growth. The formed crystal quality is dependent on the morphology of the solidifying liquid/solid interface and the width of molten zone.
In this thesis, the two-dimensional pseudo-steady-state ZMR model has been developed in which the conduction of solid, liquid silicon and $SiO_2$, the convection in molten zone and the radiation are included. Numerical solutions from the model include flow field in the molten zone, temperature field in the full SOI structure and the location of solid/liquid interface in the silicon thin film and silicon substrate.
The finite element method is used for discretization of partial differential equations of the mathematical model. The formed nonlinear algebraic equations set is linearized by the Newton-Raphson iteration scheme. The set of linear algebraic equations is solved using the frontal solver. The solutions of field variables and interface location and shapes are obtained simultaneously.
We can conclude that the one-dimensional assumption which has been used by many other researchers is almost valid but nonplanar melt/solid interface shape necessiates the use of higher dimensional model.
The effects of the various system parameter are investigated. As the upper lamp peak intensity is increased, $\theta_max$, $\psi_max$ and the molten zone width are increased linearly. The increase of the upper lamp peak intensity flattens the interface especially in the silicon substrate. As the scanning speed is increased, the symmetry of the temperature field is broken. The curvature of the right-hand side interface in the molten zone of the silicon substrate is increased and that of the left-hand is decreased. The emissivities of the liquid and solid silicon depend on the capping oxide thickness. Its effect on temperature and flow field makes $\theta_max$, $\psi_max$ and molten zone width to have the maximum value. As the Biot number is increased, the curvature of the interface is increased due to the increase of the heat loss on the top and bottom side.
