SILICON CRYSTAL-GROWTH IN A CUSP MAGNETIC-FIELD

Czochralski silicon crystal growth in the presence of an axially symmetric cusp magnetic field is reported for the first time. The free surface of the melt is centered between two superconducting coils. Oxygen concentration in the crystal is shown to be successfully controlled from 1×1018 to 2×1017 atoms/cm3 by increasing the cusp magnetic field strength up to 3500 Oe at the center of the bottom melt-silica crucible interface, while keeping the crystal rotation constant at 30 rpm and keeping the crucible rotation constant at -10 rpm. Both oxygen and dopant distributions are homogenized by the magnetic field. The good crystal homogeneity results because there is no need to change the crystal and crucible rotations adequately to control the oxygen concentration, in contrast to the previous use of a transverse or vertical magnetic field in which extreme changes in the crucible or crystal rotation rate are required.