Melt motion in a Czochralski crystal puller with an axial magnetic field: isothermal motion

Abstract

A magnetic field suppresses turbulence and thermal convection in a Czochralski crystal puller. The amounts and distributions of dopants and oxygen in the crystal are determined by the motion of the molten silicon during crystal growth. This paper presents analytical solutions for the melt motion in a Czochralski puller with a strong, uniform, axial magnetic field. The relatively small electrical conductivity of the crystal plays a key role in determining the flow. Certain combinations of crystal and crucible rotation rates lead to flow patterns with a large volume of almost stagnant fluid under most of the crystal face. The values of these rotation rates depend on the magnetic field strength.