Patent ID: 6312516
Filing Date: 2001-11-06
Classification: C30B

Abstract:
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/G.sub.0 to vary as a function of the length of the ingot segment as the ingot is grown, with v/G.sub.0 being allowed to vary between a minimum value, (v/G.sub.0).sub.min, and a maximum value, (v/G.sub.0).sub.max, where v is the growth velocity and G.sub.0 is the average axial temperature gradient between the temperature of solidification and about 1300.degree. C. at the central axis, with (v/G.sub.0).sub.min being no more than about 95% of (v/G.sub.0).sub.max ; and,cooling the ingot segment from the temperature of solidification to a temperature between about 1050.degree. C. and about 900.degree. C. over a dwell time, t.sub.dw, which is sufficient to prevent the formation of agglomerated intrinsic point defects within the segment.