Silicon wafer and method of manufacturing the same

1. A silicon wafer having a nitrogen concentration which is from ≧5×10 14 atoms/cm 3 to ≦1×10 16 atoms/cm 3 , a carbon concentration which is from ≧1×10 15 atoms/cm 3 to ≦8.1×10 15 atoms/cm 3 , and containing BMDs having an octahedral shape, wherein BMDs located at a position below the silicon wafer surface at a depth of less than 20 μm and having a diagonal length of 200 nm or more are present in a concentration of ≦2×10 9 /cm 3 , and BMDs located at a depth of more than 50 μm from the wafer surface and having a diagonal length of ≧10 nm to ≦50 nm are present in a concentration of ≧1×10 12 /cm 3 .

2. A method of manufacturing a silicon wafer, containing BMDs having an octahedral shape, wherein BMDs located at a position below the silicon wafer surface at a depth of less than 20 μm and having a diagonal length of 200 nm or more are present in a concentration of ≦2×10 9 /cm 3 , and BMDs located at a depth of more than 50 μm from the wafer surface and having a diagonal length of ≧10 nm to ≦50 nm are present in a concentration of ≧1×10 12 /cm 3 , comprising:

supplying a wafer substrate having a nitrogen concentration of ≧5×10 14 atoms/cm 3 to ≦1×10 16 atoms/cm 3 , and a carbon concentration of ≧1×10 15 atoms/cm 3 to ≦3×10 16 atoms/cm 3 ,

heat treating the wafer substrate by a treatment comprising at least the following steps, in the order given:

(A) a low-temperature heat treatment in a temperature range of ≧650° to ≦750° C. for a time of ≧30 minutes to ≦5 hours;

(B) a heat treatment which increases the temperature in a temperature range of up to 850° C. at a heating rate of ≧0.5° C./minute to ≦2° C./minute;

(C) a cooling and extracting step of decreasing the furnace temperature at a cooling rate of ≧1° C./minute to ≦10° C./minute after step (B), and extracting the wafer from the furnace when the temperature of the furnace is ≧600° C. to ≦750° C., and cooling the wafer to a room temperature; and

(D) a high-temperature heat treatment wherein the furnace is set to ≧600° C. to ≦750° C. after step (C), inserting the wafer into the furnace, raising the temperature of the furnace in the temperature range of ≦1100° C. at a heating rate of ≧5° C./minute to ≦10° C./minute, raising the temperature in the temperature range of ≧1100° C. to ≦1250° C. at a heating rate of ≧1° C./minute to ≦2° C./minute, and holding the wafer at a temperature of ≧1000° C. to ≦1250° C. to provide a diffusion length of inter-lattice oxygen of 50 μm or more.

3. A method of manufacturing a silicon wafer containing BMDs having an octahedral shape, wherein BMDs located at a position below the silicon wafer surface at a depth of less than 20 μm and having a diagonal length of 200 nm or more are present in a concentration of ≦2×10 9 /cm 3 , and BMDs located at a depth of more than 50 μm from the wafer surface and having a diagonal length of ≧10 nm to ≦50 nm are present in a concentration of ≧1×10 12 /cm 3 , comprising:

supplying a wafer substrate having a nitrogen concentration of ≧5×10 14 atoms/cm 3 to ≦1×10 16 atoms/cm 3 , a carbon concentration of ≧1×10 15 atoms/cm 3 to ≦3×10 16 atoms/cm 3 or less,

heat treating the wafer substrate by a heat treatment comprising at least the following steps in the order given:

(A) a low-temperature heat treatment in a temperature range of ≧650° C. to ≦750° C. for a time of ≧30 minutes to ≦5 hours;

(B) a heat treatment which increases the temperature in a temperature range of up to 850° C. at a heating rate of ≧0.5° C./minute to ≦2° C./minute; and

(C) a high-temperature heat treatment wherein heating to less than 1100° C. is performed at a heating rate of ≧5° C./minute to ≦10° C./minute, and in a temperature range of ≧1100° C. to ≦1250° C. at a heating rate of ≧1° C./minute to ≦2° C./minute, and holding the wafer at a temperature of ≧1000° C. to ≦1250° C. to provide a diffusion length of inter-lattice oxygen of 50 μm or more.

4. The method of claim 2, wherein the wafer substrate has an interstitial oxygen concentration of 8.0·10 17 atoms/cm 3 to 9.5·10 17 atoms/cm 3 .

5. The method of claim 2, wherein the carbon concentration is from 1·10 15 atoms/cm 3 to 2·10 16 atoms/cm 3 .

6. The method of claim 4, wherein the carbon concentration is from 1·10 15 atoms/cm3 to 2·10 16 atoms/cm 3 .

7. The method of claim 3, wherein the wafer substrate has an interstitial oxygen concentration of 8.0·10 17 atoms/cm 3 to 9.5·10 17 atoms/cm 3 .

8. The method of claim 3, wherein the wafer substrate has an interstitial oxygen concentration of 8.0·10 17 atoms/cm 3 to 9.5·10 17 atoms/cm 3 .

9. The method of claim 7, wherein the carbon concentration is from 1·10 15 atoms/cm 3 to 2.10 16 atoms/cm 3 .