Patent ID: 8311771

Claim:
An inspection method of an SOI wafer including, using an optical inspection apparatus having a light source for irradiating light having a wavelength band of a visible light wavelength or more to irradiate the light from the light source to a surface of the SOI wafer having an SOI layer formed on a buried insulator layer, and detecting reflected-light from the SOI wafer to find defects caused by changes due to an increase and a decrease in a film thickness of the SOI layer on the surface of the SOI wafer, the method comprising at least the steps of: calculating a profile P1 showing wavelength dependency of reflectance with respect to the light having a wavelength band of a visible light wavelength or more, in the SOI wafer to be inspected; calculating a profile P2 showing wavelength dependency of reflectance with respect to the light having a wavelength band of a visible light wavelength or more, in an SOI wafer having a film thickness of the SOI layer thicker or thinner than that of the SOI wafer to be inspected by a predetermined thickness t [nm]; calculating a profile P3 (=P2−P1) of a difference between the calculated profiles P1 and P2, or a profile P4 (=(P2−P1)/P1) of a change ratio of the calculated profiles P1 and P2, to select a wavelength λ or a wavelength band in close vicinity of a maximum peak wavelength λ M within the calculated profiles P3 or P4; irradiating light having the selected wavelength λ or wavelength band to the surface of the SOI wafer to be inspected, to detect the reflected-light from the SOI wafer; and finding a place of a peak generated by an increase in reflection intensity of the detected reflected-light, as the defect caused by the change in the film thickness of the SOI layer on the surface of the SOI wafer.