On the cooling rates of large-diameter silicon crystals

Abstract

A theoretical study has been carried out on the cooling rates of silicon crystals, with diameters between 50 and 100 mm, from 650 °C to room temperature under natural and forced convection conditions. Experimental results are described for a 75‐mm‐diam crystal, again in both natural and forced convection conditions, and are seen to agree well with the theoretical predictions. The significance of the results is discussed in terms of actual changes in donor concentration of a Czochralski‐grown crystal, after ’’annealing’’ at 650 °C, and it is concluded that ’’annealing’’ of ingots may not be sufficient for close‐tolerance materials and reheating of slices may be necessary.