Low defect density silicon

A single crystal silicon ingot having 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 and a radius extending from the central axis to the circumferential edge, the single crystal silicon ingot being characterized in that after the ingot is grown and cooled from the solidification temperature, the constant diameter portion contains an axially symmetric region which is substantially free of agglomerated intrinsic point defects wherein the axially symmetric region extends radially inwardly from a 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 about 30% the length of the radius of the constant diameter portion, and has a length as measured along the central axis of at least about 20% the length of the constant diameter portion of the ingot.

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 and a radius extending from the central axis to the circumferential edge, 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 a growth velocity, v, and an instantaneous axial temperature gradient, G0, of the crystal during the growth of the constant diameter portion of the ingot to cause the formation of an axially symmetrical segment which, upon cooling of the ingot from the solidification temperature, 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 about 30% the length of the radius of the ingot, and has a length as measured along the central axis of at least about 20% the length of the constant diameter portion of the ingot.

A process for growing a single crystal silicon ingot, the single crystal silicon ingot being characterized in that, after the ingot is grown from a silicon melt and cooled from the solidification temperature in accordance with the Czochralski method, a constant diameter portion of the ingot contains an axially symmetric region which is substantially free of agglomerated intrinsic point defects, the process comprising

• controlling a growth velocity, v, and an instantaneous axial temperature gradient, G0, such that a ratio v/G0 ranges in value from about 0.6 to about 1.5 times the critical value of v/G0.

A process for growing a single crystal silicon ingot, the single crystal silicon ingot being characterized in that, after the ingot is grown from a silicon melt and cooled from the solidification temperature in accordance with the Czochralski method, a constant diameter portion of the ingot contains an axially symmetric segment which is substantially free of agglomerated intrinsic point defects, the process comprising

• controlling a growth velocity, v, and an instantaneous axial temperature gradient, G0, such that a ratio v/G0 ranges in value from about 0.6 to about 1.5 times the critical value of v/G0;
• and
• controlling a cooling rate within a temperature range of about 1400° C. to about 800° C., such that the rate ranges from about 0.2° C./minute to about 1.5 ° C./minute.