Homogeneous increase in oxygen concentration in Czochralski silicon crystals by a cusp magnetic field

Abstract

The oxygen concentration in Czochralski (CZ) silicon crystals is increased and homogenized along the growth axes by applying an axially symmetric cusp magnetic field. The orthogonal components of the cusp magnetic field are independently changed on the melt free surface and at the melt-crucible interface where oxygen evaporation and dissolution takes place, respectively. The concentration at a large solidified fraction of 0.6 is increased by slightly reducing the oxygen evaporation rate to 14.1 × 10 17 atoms/cm 3, 35% more than that with no magnetic field. The axial distribution is homogenized with a decrease in the dissolution area and an increase in the reduced dissolution rate. A reduction in the evaporation rate, confirmed by weighing the SiO flakes, is an advantage for stable dislocation-free crystal growths over conventional oxygen-homogenizing techniques using increased oxygen dissolution rates.