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AssigneeGlobalWafers Co., Ltd.
InventorsZheng Lu, Gaurab Samanta, Tse-Wei Lu, Feng-Chien Tsai
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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.
A nitrogen-doped CZ silicon crystal ingot, the ingot having a diameter of from about 150 mm to about 450 mm and having a nitrogen concentration of from 1*1014 nitrogen atoms per cm3 to about 1*1015 nitrogen atoms per cm3, wherein a wafer sliced from the nitrogen-doped CZ silicon crystal ingot and thermally treated at 780° C. for 3 hours and then at 1000° C. for 16 hours is characterized by having an edge band in a region extending from about 4000 μm from the edge of said wafer to the edge of said wafer, wherein the bulk micro defect density of the edge band region differs from the remainder of the wafer by no more than 200% and 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 20%, and further wherein the edge band of the wafer sliced from the nitrogen-doped CZ silicon crystal ingot and thermally treated at 780° C. for 3 hours and then at 1000° C. for 16 hours is characterized by oxygen precipitates having an average diameter from about 80 nm to about 90 nm and an oxygen precipitate density of 1*108 per cm3 to about 1*1010 per cm3.
A nitrogen-doped CZ silicon crystal ingot having a diameter of about 300 mm and having a nitrogen concentration of from 1*1014 nitrogen atoms per cm3 to about 1*1015 nitrogen atoms per cm3, wherein a wafer sliced from the nitrogen-doped CZ silicon crystal ingot comprises a front surface, a back surface, a central plane between the front and back surfaces, a circumferential edge joining the front and back surface, a central axis perpendicular to the central plane, a bulk layer which comprises the region of the wafer between the central plane and front surface, and further wherein the wafer sliced from the nitrogen-doped CZ silicon crystal ingot that is thermally treated at 780° C. for 3 hours and then at 1000° C. for 16 hours is characterized by bulk micro defects having an average diameter from about 80 nm to about 90 nm from the central axis of the wafer to the circumferential edge of the wafer, wherein the average diameter decreases by about 6% from the central axis of the wafer to the circumferential edge of the wafer and is further characterized by a bulk micro defect density of 1*109 per cm3 to about 1*1010 per cm3 from the center of the wafer to the edge of the wafer, wherein the bulk micro defect density decreases by about 6% from the central axis of the to the circumferential edge of the wafer.
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