Patent ID: 6689209
Filing Date: 2004-02-10
Classification: A61K,C30B

Abstract:
A process for the preparation of a silicon single crystal in which molten silicon is solidified onto a crystal in accordance with the Czochralski method to form an ingot having a central axis, a seed-cone, an end-cone, a constant diameter portion between the seed-cone and the end-cone having a lateral surface, and a radius extending from the central axis to the lateral surface, the process comprising:forming a region within the constant diameter portion in which vacancies are the predominant intrinsic point defect; heating the lateral surface of the ingot to a temperature in excess of the temperature of the region to cause an inward flux of silicon self interstitial atoms into the region from the heated surface which reduces the concentration of vacancies in the region; and. maintaining the temperature of the region in excess of the temperature, TA, at which agglomeration of vacancy point defects into agglomerated defects occurs during the period of time between the formation of the region and the influx of the silicon self-interstitial atoms from the lateral surface, wherein the length of the lateral surface, as measured in the axial direction, which is coincidentally heated to a temperature in excess of the temperature of the region to cause an inward flux of silicon self interstitial atoms into the region from the heated surface is no greater than about 50% of the axial length of the constant diameter portion of the ingot.