Patent ID: 7927957

Claim:
A method for producing a bonded silicon wafer comprising implanting oxygen ions from one-side face of a silicon wafer for active layer with a substrate oxygen concentration of 10×10 17 /cm 3 to 18×10 17 /cm 3 (old ASTM conversion) sliced so as to have such a wafer face that an inclination angle θ (compound angle) with respect to a face perpendicular to <100> orientation or <110> orientation of a silicon single crystal ingot is 0°<θ≦0.15° to form an oxygen ion implanted layer at a given depth position from the one-side face of the silicon wafer for active layer; bonding the one-side face of the silicon wafer for active layer to one-side face of a silicon wafer for support to form a silicon wafer composite; heat-treating (a first heat treatment step) the silicon wafer composite to strengthen the bonding and to convert the oxygen ion implanted layer into an inner SiO 2 layer; exposing the inner SiO 2 layer from other face of the silicon wafer for active layer in the silicon wafer composite; removing the inner SiO 2 layer; and planarizing and polishing a surface of the silicon wafer composite after the removal of the inner SiO 2 layer or subjecting the silicon wafer composite to a heat treatment in a reducing atmosphere (a second heat treatment step) to improve a flatness of the silicon wafer composite.