Patent ID: 7431765

Claim:
A process for growing a single crystal silicon ingot in which the ingot comprises a central axis, a seed-cone, a tail end, and a constant diameter portion between the seed-cone and the tail end having a lateral surface and a radius extending from the central axis to the lateral surface, the ingot being grown from a silicon melt and then cooled from the solidification temperature in accordance with the Czochralski method, the process comprising: controlling a growth velocity, v, and an average axial temperature gradient, G 0 , during the growth of the constant diameter portion of the crystal to form a segment which is axially symmetric about the central axis in which crystal lattice vacancies are the predominant intrinsic point defect, the segment having a radial width of at least about 25% of the radius; and, cooling the ingot to form in the axially symmetric segment agglomerated vacancy defects and a residual concentration of crystal lattice vacancy intrinsic point defects, wherein the agglomerated vacancy defects have an average radius of less than about 70 nm and an average void density of greater than 1×10 7 cm −3 , and the concentration of residual crystal lattice vacancy intrinsic point defects is less than the threshold concentration at which uncontrolled oxygen precipitation occurs upon subjecting the cooled segment to an oxygen precipitation heat treatment.