Melt motion in a Czochralski puller with a weak transverse magnetic field

Abstract

The melt motion in a Czochralski silicon crystal puller with a uniform transverse magnetic field is intrinsically three-dimensional. When the magnetic field is relatively weak, the motion consists of an axisymmetric base solution, plus two perturbations which behave as sin 2θ and cos 2θ, neglecting terms which are proportional to the fourth power of the magnetic field strength. A 700 G magnetic field stabilizes a melt motion which is unsteady without a magnetic field. As the strength of the magnetic field increases, the magnitudes of the axial and radial velocities increase to maxima at some field strength above 1000 G. This contrasts with an axial magnetic field for which the axial and radial velocities always decrease as the field strength increases. We estimate that 1500 G is the maximum field strength for which our weak-field asymptotic solution is valid. © 1990.