| 摘要 |
PROBLEM TO BE SOLVED: To form an oxygen deposit in a sufficient density for gettering, before a wafer is put into a device process by specifying the cooling rate in a cooling process of the wafer, after formation of an epitaxial film. SOLUTION: Since an oxygen deposit is not formed in density adequate for gettering at the very beginning of a device process, the characteristics of a silicon wafer on which an epitaxial film is to be formed are limited to such that a resistivity is 1Ω.cm or larger, the carbon concentration is (0.1-0.5)×10<16> atoms/cm<13> (new ASTM method), and the oxygen concentration is (10-18)×10<17> atoms/cm<3> (old ASTM method). After a silicon epitaxial film on the surface of the silicon wafer has been formed, the silicon wafer is cooled at a cooling rate of 800-100 deg.C/minute, or lower, preferably 80 deg.C/minute or lower in a temperature range of 800-400 deg.C, in a wafer cooling process. The concentration of the oxygen deposit is 5×10<4> /cm<2> or higher, which is measured by an optical microscope after defect selective etching (Wright liquid) is conducted.
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