Patent ID: 7799655

Claim:
A method for evaluating a bonded wafer formed by directly bonding a wafer for active layer and a wafer for support substrate without an insulating film and thinning the wafer for active layer, which comprises steps of removing native oxide from a surface of an active layer in the bonded wafer, subjecting the bonded wafer to an etching with an etching liquid having an etching rate to a material constituting the wafer faster than that to an oxide of the material to remove at least a whole of the active layer, and detecting island-shaped oxides exposed by the etching, in which the etching is carried out so as to satisfy a relation of T≦X≦T+500 nm wherein T is a thickness of the active layer (nm) and X is an etching depth (nm) to detect the number and size of the island-shaped oxides.