Effect of a radiation shield on melt/crystal interface shape and pull rate of silicon CZ puller.

Abstract

For a silicon CZcrystal puller, the effect of an annular radiation shield on the temperature profile in the melt and crystal and on the shape of the melt/crystal interface was studied theoretically by use of the finite element analysis based on the conduction-dominated model. It was found that a radiation shield of an appropriate shape and located at an optimumposition in the furnace can make the interface shape less convex to the crystal and can reduce the input power to the furnace at all stages of crystal growth in comparison with operation without a shield. Also, use of a radiation shield increases the pull rate, i.e. the productivity of the CZ puller, because the axial temperature gradient near the melt/crystal interface becomes steeper.