Patent ID: 8399341

Claim:
A method for heat treating a silicon wafer comprising the steps of: producing a silicon single crystal ingot grown by Czochralski process; slicing the silicon single crystal ingot into plural silicon wafers; performing a first heat treatment process on the silicon wafer while introducing a first gas including a rare gas, the first heat treatment comprising: rapidly heating the silicon wafer to a first temperature range of 1300° C. or higher and the melting point of silicon or lower at a first heating rate; keeping the silicon wafer at the first temperature; rapidly cooling the silicon wafer to a second temperature range of 400° C. or higher and 800° C. or lower at a first cooling rate; and keeping the silicon wafer at the second temperature; and performing a second heat treatment process on the silicon wafer while stopping introducing the first gas and instead, introducing a second gas including an oxygen gas in an amount of 20 vol. % or more and 100 vol. % or less; the second heat treatment comprising: further keeping the silicon wafer at the second temperature; rapidly heating the silicon wafer from the second temperature to a third temperature range of 1250° C. or higher and the melting point of silicon or lower at a second heating rate; keeping the silicon wafer at the third temperature; and rapidly cooling the silicon wafer from the third temperature at a second cooling rate.