Process for growing defect-free silicon wherein the grown silicon is cooled in a separate chamber
AssigneeMEMC Electronic Materials, Inc.
InventorsRobert J. Falster, Harold W. Korb
Life of this patent
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Abstract
A process for growing single crystal silicon ingots of which portions are substantially free of agglomerated intrinsic point defects. An ingot is grown generally in accordance with the Czochralski method. A first portion of the ingot cools to a temperature which is less than a temperature TA at which agglomeration of intrinsic point defects in the ingot occurs during the time the ingot is being grown, while a second portion remains at a temperature above TA. The second portion of the ingot is subsequently maintained at a temperature above TA to produce a portion which is substantially free of agglomerated intrinsic point defects.
Claims15
A process for growing a single crystal silicon ingot, the ingot being grown from a silicon melt in accordance with the Czochralski method in a crystal puller comprising a lower growth chamber and an upper pulling chamber, the process comprising:
- growing the silicon ingot in the growth chamber;
- cooling a first portion of the ingot to a temperature less than a temperature of agglomeration, TA, while maintaining a second portion of the ingot at a temperature greater than TA during the growth of the ingot, wherein the temperature of agglomeration is the temperature at which the agglomeration of intrinsic point defects occurs;
- transferring the grown ingot to the pulling chamber;
- and,
- maintaining a temperature profile in the pulling chamber such that the temperature of the cooled first portion of the ingot does not exceed about 1200° C. and the second portion of the ingot is maintained at a temperature greater than TA for a period of time selected to permit out diffusion of intrinsic point defects to reduce the concentration of intrinsic point defects such that the second portion of the ingot is substantially free of agglomerated intrinsic point defects upon being cooled to a temperature less than TA.
Dependencies are inferred from the claim text.