Vacancy, dominsated, defect-free silicon
View Patent ↗The present invention relates to a process for growing a single crystal silicon. The process including controlling a growth velocity, v, and an average axial temperature gradient, G 0 , during the growth of the constant diameter portion of the crystal over the temperature range from solidification to a temperature of no less than about 1325° C., to cause the formation of a first axially symmetrical region in which vacancies, upon cooling of the ingot from the solidification temperature, are the predominant intrinsic point defect and which is substantially free of agglomerated intrinsic point defects, wherein the first axially symmetric region has a width of at least about 50% of the radius of the constant diameter portion of the ingot.
1. 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 average axial temperature gradient, G 0 , during the growth of the constant diameter portion of the crystal over the temperature range from solidification to a temperature of no less than about 1325° C., to cause the formation of a first axially symmetrical region in which vacancies, upon cooling of the ingot from the solidification temperature, are the predominant intrinsic point defect and which is substantially free of agglomerated intrinsic point defects wherein the first axially symmetric region has a width of at least about 50% of the radius of the constant diameter portion of the ingot.
2. The process of claim 1 wherein the first axially symmetric region has a length which is at least about 40% the length of the constant diameter portion of the ingot.
3. The process of claim 2 wherein the ingot comprises a second axially symmetric region which is concentric with said first axially symmetric region, the second axially symmetric region containing self-interstitial atoms as the predominant intrinsic point defect and being substantially free of agglomerated silicon self-interstitial intrinsic point defects.
4. The process of claim 1 wherein the first axially symmetric region has a length which is at least about 80% the length of the constant diameter portion of the ingot.
5. The process of claim 4 wherein the ingot comprises a second axially symmetric region which is concentric with said first axially symmetric region, the second axially symmetric region containing self-interstitial atoms as the predominant intrinsic point defect and being substantially free of agglomerated silicon self-interstitial intrinsic point defects.
6. The process of claim 1 wherein the first axially symmetric region has a width which is at least about 80% the length of the radius of the constant diameter portion of the ingot.
7. The process of claim 6 wherein the first axially symmetric region has a length which is at least about 40% the length of the constant diameter portion of the ingot.
8. The process of claim 7 wherein the ingot comprises a second axially symmetric region which is concentric with said first axially symmetric region, the second axially symmetric region containing self-interstitial atoms as the predominant intrinsic point defect and being substantially free of agglomerated silicon self-interstitial intrinsic point defects.
9. The process of claim 6 wherein the first axially symmetric region has a length which is at least about 80% the length of the constant diameter portion of the ingot.
10. The process of claim 9 wherein the ingot comprises a second axially symmetric region which is concentric with said first axially symmetric region, the second axially symmetric region containing self-interstitial atoms as the predominant intrinsic point defect and being substantially free of agglomerated silicon self-interstitial intrinsic point defects.
11. The process of claim 1 wherein the first axially symmetric region has a width which is about equal to the radius of the constant diameter portion of the ingot.
12. The process of claim 11 wherein the first axially symmetric region has a length which is at least about 20% the length of the constant diameter portion of the ingot.
13. The process of claim 11 wherein the first axially symmetric region has a length which is at least about 40% the length of the constant diameter portion of the ingot.