Nitrogen doped and vacancy dominated silicon ingot and thermally treated wafer formed therefrom having radially uniformly distributed oxygen precipitation density and size
Nitrogen-doped CZ silicon crystal ingots and wafers sliced therefrom are disclosed that provide for post epitaxial thermally treated wafers having oxygen precipitate density and size that are substantially uniformly distributed radially and exhibit the lack of a significant edge effect. Methods for producing such CZ silicon crystal ingots are also provided by controlling the pull rate from molten silicon, the temperature gradient and the nitrogen concentration. Methods for simulating the radial bulk micro defect size distribution, radial bulk micro defect density distribution and oxygen precipitation density distribution of post epitaxial thermally treated wafers sliced from nitrogen-doped CZ silicon crystals are also provided.
1. A method of producing a nitrogen-doped CZ silicon crystal ingot, the method comprising:
pulling the silicon crystal ingot from molten silicon at a pull rate of from 0.85 mm per minute to about 1.5 mm per minute during growth of a substantially constant diameter region of the silicon crystal ingot thereby forming the nitrogen-doped CZ silicon crystal ingot, wherein the nitrogen-doped CZ silicon crystal ingot has a surface temperature gradient of from about 10° K per cm to about 35° K per cm at an average crystal surface temperature of from about 1300° C. to about 1415° C., and wherein the silicon crystal ingot has a nitrogen concentration of from about 1*10 13 atoms per cm 3 to about 1*10 15 atoms per cm 3 ;
wherein a wafer sliced from the nitrogen-doped CZ silicon crystal ingot is vacancy dominated and further wherein thermally treated at 780° C. for 3 hours and then at 1000° C. for 16 hours is characterized by:
(1) an edge band in a region extending from about 1000 μm to the edge of said wafer and to the edge of said wafer wherein the edge band comprises oxygen precipitates having an average diameter of from about 30 nm to about 100 nm and an oxygen precipitation density of from about 1*10 8 atoms per cm 3 to about 1*10 10 atoms per cm 3 ,
(2) an increase in radial bulk micro defect size in a region extending from the center of said wafer to the edge of said wafer of less than about 20%, or
(3) an increase in radial bulk micro defect density in a region extending from the center of said wafer to the edge of said wafer of less than about 200%.
2. The method of claim 1 wherein the pull rate is from about 1.1 mm per minute to about 1.5 mm per minute.
3. The method of claim 1 wherein the nitrogen-doped CZ silicon crystal ingot has a surface temperature gradient of from about 10° K per cm to about 25° K per cm at an average crystal surface temperature of from about 1300° C. to about 1415° C.
4. The method of claim 1 wherein said wafer is characterized by an increase in radial bulk micro defect size in a region extending from about 10 mm to the edge of said wafer and to the edge of said wafer of less than about 15%.
5. The method of claim 1 wherein said wafer is characterized by an increase in radial bulk micro defect density in a region extending from about 10 mm to the edge of said wafer to the edge of said wafer of less than about 100%.
6. The method of claim 1 wherein the edge band comprises oxygen precipitates having an average diameter of from about 80 nm to about 90 nm and an oxygen precipitation density of from about 1*10 8 atoms per cm 3 to about 1*10 10 atoms per cm 3 .
7. The method of claim 1 wherein the edge band comprises voids having an average radius of from about 1 nm to about 50 nm.
8. The method of claim 1 wherein the nitrogen-doped CZ silicon crystal ingot has a diameter of about 300 mm.
9. The method of claim 1 wherein the nitrogen concentration is from about 3*10 13 nitrogen atoms per cm 3 to about 2*10 14 nitrogen atoms per cm 3 .
10. The method of claim 1 wherein the nitrogen concentration is from about 1*10 14 nitrogen atoms per cm 3 to about 1*10 15 nitrogen atoms per cm 3 .