Numerical Simulation Of Czochralski Crystal Growth And Its Model Experiment

Czochralski technique has been widely adopted for growing large diameter single crystals used in electronic and optical device. The quality of the crystal is dependent on the spatial uniformity of solute and impurities, numbers of defects in its crystallographic structure which is influenced by the interactions of hydrodynamics, heat transfer, interface phenomena, and dopant transport in the melt. Because of high temperature of growth system, opaque of crystal and melt, and sometimes poisonous and errosive of the melt and the vapor, It is very difficult to measure the heat transfer and flow structure of the melt. Therefore, it is practical important to use the numerical method to predict the influence of various operational parameters on crystal growth. This dissertation concerned with (1) the establishment of Czochralski bulk flow model, cylindrical crystal model and their numerical method. and the control volume finite difference method based on the boundary fitted curve line coordinate for the coupling model of whole system; (2)introduction of the relative temperature gradient function Sv(R) , which is used to determine the evolution of crystal / melt interface shape, because the shape of the crystal / melt interface during crystal growth is an important factor in determining the crystal quality. From the result of integrated Czochralski dynamic model analyses, It show that one of the factors that cause the inversion of interface shape from convex to concave is the decrease of heat flux flow interface to crystal in the central region of the crystal as the increase of the thermal resistance of crystal, or the increase of the thermal radiation from the surrounding to the melt / crystal / ambient tri—junction. (3) the influence of rotation of crystal and crucible on meridional flow of melt which is studied with and without buoyancy induced convection in the melt. It is found that the natural convection can be suppressed by means of the rotation of crystal due to occurrence of the secondary flow which is opposite to that of the natural convection, while the suppression of the natural convection in the melt by rotation of crucible is due to the centrifugal field introduced. It is found that the Corioli/s force is not the main factor for suppressing the natural convection in the melt. (4) the striation which is formed during the...