Patent ID: 8741740

Claim:
A method for manufacturing an SOI substrate, comprising: forming a first insulating film over a bond substrate; irradiating the bond substrate with hydrogen ions through the first insulating film to form an embrittled layer in the bond substrate; attaching the bond substrate to a base substrate with the first insulating film interposed therebetween; forming a semiconductor film over the base substrate by separating the bond substrate along the embrittled layer; performing a first planarization treatment by etching a surface of the semiconductor film, whereby a natural oxide film and crystal defects on the surface of the semiconductor film are removed; and performing a second planarization treatment by irradiating the semiconductor film with laser light, whereby crystallinity of the semiconductor film is recovered, wherein an acceleration voltage of the hydrogen ions is greater than or equal to 10 kV and less than or equal to 200 kV at the step of irradiating the bond substrate, wherein a dose of the hydrogen ions is greater than or equal to 2.2×10 16 ions/cm 2 and less than or equal to 3.0×10 16 ions/cm 2 , and wherein 2.2×10 16 ions/cm 2 is a dose 2.2 times as high as a minimal dose of hydrogen ions for separating the bond substrate and 3.0×10 16 ions/cm 2 is a dose 3.0 times as high as a minimal dose of hydrogen ions for separating the bond substrate.