Biasing of Electrical Potential for Enhancement of Magnetic Czochralski Crystal Growth
Original Publication Date: 1987-Feb-01
Included in the Prior Art Database: 2005-Feb-02
One drawback of Czochralski growth in an axial magnetic field is that the lack of advective transport near the growth surface results in a nonuniform radial distribution of boron dopant. Offering an alternate electrical pathway in parallel with the Hartmann layer changes the flow near the growth interface somewhat and in a favorable way: the boron isopleths assume a less vertical orientation. Damping of the main convective eddies is not significantly affected. A biasing potential gives the crystal grower some control of this. The electrode in the melt should be of an appropriately durable material, e.g., molybdenum, and should be placed on the crucible bottom at the axis of symmetry to avoid introducing azimuthal variation of crystal properties. The lead should be sheathed in fused silica tubing.