| 摘要 |
PROBLEM TO BE SOLVED: To align an object to be inspected with high accuracy be reducing the position detecting error caused by the asymmetry of a diffraction grating- like mark. SOLUTION: Two luminous fluxes L03 and 30 having different frequencies are made incident to the diffraction grating-like mark WM formed on a wafer at prescribed incident angles and the±3rd order diffracted light generated from the mark WM is detected by means of a photoelectric detector 33. Then, two luminous fluxes L04 and L40 having different frequencies are made incident on the mark WM at prescribed incident angles which are different from those of the luminous fluxes L03 and L30 and the±4th order diffracted light generated from the mark WM is detected by means of the photoelectric detector 33. The alignment of the wafer is performed by correcting the position detecting error caused by the asymmetry of the cross-sectional shape of the mark WM based on beat signals respectively obtained upon detecting the±3rd order and±quaternary diffracted light rays. |
