Silicon wafer, and manufacturing method and heat treatment method of the same

A heat treatment method of a silicon wafer for rendering said silicon wafer to exhibit an IG effect, in which said silicon wafer comprises a mixed domain of [PV] and [PI] and has an oxygen concentration of 0.8×1018 to 1.4×1018 atoms/cm3 (old ASTM),

• where [PI] is a domain neighboring with a domain [I] dominated by interstitial silicon point defects, is classified into a perfect domain [P] including no agglomerates of point defects, and has a concentration of interstitial silicon lower than the lowest concentration of interstitial silicon capable of forming interstitial dislocations, and
• where [PV] is a domain neighboring with a domain [V] dominated by vacancy point defects, is classified into said perfect domain [P], and has a concentration of vacancies equal to or lower than a concentration of vacancies capable of forming COP's or FPD's,
• said method comprising the steps of:
• conducting a first step heat treatment for heating said silicon wafer in an atmosphere of nitrogen, hydrogen, oxygen, mixture of nitrogen and argon, mixture of hydrogen and argon or a mixture of oxygen and argon from a room temperature up to 1,150° C. to 1,200° C. at a temperature elevating speed of 10° C./second to 150° C./second, and for holding said silicon wafer at temperatures of 1,150° C. to 1,200° C. for 0 to 30 seconds;
• and
• subsequently conducting a second step heat treatment for rapidly heating said silicon wafer in a hydrogen gas or in an atmosphere including a hydrogen gas from a room temperature up to temperatures of 1,100° C. to 1,250° C. at a temperature elevating speed of 3° C./minute to 100° C./second, and for holding said silicon wafer for 1 minute to 2 hours.