| 摘要 |
PURPOSE:To effect an accurate positioning with simple constitution even for a wafer in which position detection in LAS method alignment system is difficult. CONSTITUTION:Diffracted lights L1(+1) and L2(+1) are casted on a grating mark 19X on a wafer 18, a heterodyne beam LC consisting of + or - primary diffracted light from the grating mark 19X is detected by a photoelectrodetector 25C, an envelope line signal SCE is detected by an envelope line detection system 26 from the beat signal SC output from the photoelectrodetector 25C, and the coordinates of the middle point of the envelope line signal SCE is obtained to roughly perform alignment. Then the phase of the beat SC is detected by using a phase detection system 15 to effect fine alignment. |
