Patent ID: 7519448

Claim:
A method for detecting a notch as a detection site for alignment formed on a peripheral edge of a semiconductor wafer having a protective sheet joined thereto, thereby determining a handling position of the semiconductor wafer, the method comprising: a first irradiation step of irradiating the peripheral edge of the semiconductor wafer having the protective sheet joined thereto with light from a light source; a light receiving step of detecting the light from the light source through first detection means provided so as to be opposite to the light source with the semiconductor wafer interposed therebetween in a state that the peripheral edge of the semiconductor wafer is irradiated with the light from the light source; a center determination step of subjecting, to coordinate transformation, the position of the light detected by the first detection means along the peripheral edge of the semiconductor wafer, calculating a distance between coordinates of a point determined on a plane of the semiconductor wafer and each coordinates of the peripheral edge of the semiconductor wafer, and determining center coordinates based on a variation amount of a collection of the obtained distance data; a second irradiation step of irradiating the peripheral edge of the semiconductor wafer with light from a light source; a reflection light detection step of detecting light reflected from the semiconductor wafer through second detection means in a state that the peripheral edge of the semiconductor wafer is irradiated with the light from the light source by relatively moving a pair of the light source and the first detection means and the semiconductor wafer in such a manner that the pair of the light source and the first detection means rotates about a center axis of the semiconductor wafer; and a detection site determination step of determining a position of the notch based on a variation in intensity of the reflection light detected by the second detection means.