Process for preparing defect free silicon crystals which allows for variability in process conditions

A process for growing a single crystal silicon ingot having a central axis, a seed-cone, an end-cone, a constant diameter portion between the seed-cone and the end-cone, and an ingot segment which comprises a fraction of the constant diameter portion and which is substantially free of agglomerated intrinsic point defects, the process comprising:

• Allowing the ratio v/G0 to vary as a function of the length of the ingot segment as the ingot is grown, with v/G0 being allowed to vary between a minimum value, (v/G0)min, and a maximum value, (v/G0)max, where v is the growth velocity and G0 is the average axial temperature gradient between the temperature of solidification and about 1300° C. at the central axis, with (v/G0)min being no more than about 95% of (v/G0)max;
• and,
• cooling the ingot segment from the temperature of solidification to a temperature between about 1050° C. and about 900° C. over a dwell time, tdw, which is sufficient to prevent the formation of agglomerated intrinsic point defects within the segment.