| 摘要 |
PURPOSE:To generate a fringe which flows with beat frequency and to irradiate an alignment mark with fringe light so as to be accurately detect a position by synthesizing the monochromatic light of two wavelengths, which are a little different, with the specified difference between optical paths. CONSTITUTION:When reflected light from respective beam irradiation systems to the same fringe beam is made incident on photodetectors 50 and 51, photoelectric signals phi1 and phi2 in accordance with the intensity of the reflected light are outputted. A phase difference between the photoelectric signals phi1 and phi2 is detected by a signal processing circuit 52 so as to obtain relative positional deviation value between a wafer 20 and a reticle 21. The alignment marks of the wafer 20 and the reticle 21 are respectively irradiated with the P polarization component and the S polarization component of the same fringe beam and the position information of the wafer 20 and the reticle 21 is detected from the phase difference of the reflected light. |
