Flow instability of molten Si during Czochralski (CZ) Si crystal growth has been studied utilizing a 3D heat- and mass-transfer model together with global heat- and mass-transfer calculation. It is found that the phase transition from an axisymmetric to a non-axisymmetric mode of the flow occurs depending critically on the growth parameters, such as temperature distribution, crucible as well as crystal rotation rates. In order to prevent the non-axisymmetric instability, low crucible rotation and large temperature difference between the crucible and the crystal are found to be desired. These tendencies are well characterized by the thermal Rossby number and the Taylor number, which represent the relative strengths of Coriolis force to buoyancy force and inertial force. The calculated results are compared and discussed with the experimental observation obtained for the same growth condition.
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