Low defect density, self-interstitial dominated silicon

摘要

The present invention relates to a process for growing a single crystal silicon ingot in which the ingot comprises a central axis, a seed-cone, an end-cone and a constant diameter portion between the seed-cone and the end-cone having a circumferential edge, a radius extending from the central axis to the circumferential edge and a diameter of greater than 200 mm 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 (i) a growth velocity, v, (ii) an average axial temperature gradient, G₀, during the growth of the constant diameter portion of the crystal over the temperature range from solidification to a temperature of no less than 1325 °C, such that a ratio v/G₀ ranges in value from 0.5 to 2.5 times the critical value of v/G₀ and (iii) the cooling rate of the crystal, such that the crystal cools from the solidification temperature to 1,050 °C over a period of at least about 5 hours, to cause the formation of an axially symmetrical region which is substantially free of agglomerated intrinsic point defects, wherein the axially symmetric region extends inwardly from the circumferential edge of the ingot, has a width as measured from the circumferential edge radially toward the central axis of the ingot which is at least 30% the length of the radius of the ingot, and has a length as measured along the central axis of at least 20% the length of the constant diameter portion of the ingot, wherein the control of G₀ comprises controlling heat transfer at the melt/solid interface.