US Patent 7311775 Method for heat-treating silicon wafer and silicon wafer

This method for heat-treating a silicon wafer includes: a step of subjecting a silicon wafer to a high-temperature heat treatment in an ambient gas atmosphere of hydrogen gas, argon gas or a mixture thereof; and a step of lowering a temperature at a rate of 2° C./min or less in a nitrogen-gas-containing ambient atmosphere in a portion or all of a process of lowering a temperature to a wafer removal temperature following said high-temperature heat treatment. This silicon wafer has a defect-free layer which is formed by a high-temperature heat treatment and is included in a surface thereof, wherein an average iron concentration in said surface is 1×1010 atoms/cm3 or less.