| 摘要 |
PROBLEM TO BE SOLVED: To provide an apparatus for alignment wherein beat signal obtained from a reticle mark is not affected, even by precisely adjusting the difference in interference fringe of two wavelengths, and by adjusting difference of interfer ence fringe on a wafer, when alignment is performed by heterodyne interference method, using two wavelengths of light. SOLUTION: Reticle mark and wafer mark are illuminated by two color lights of laser light sources 11, 12. Wavelength components of the laser light source 11, included in diffraction light from the reticle mark, are guided to a photoelectric detecting element 30, and two color diffraction lights from the wafer mark are guided to a photoelectric detecting element 31. Beat signals SR, SW are then obtained from the photoelectric detecting elements 30, 31 respectively. The phase difference between the beat signals SR and SW when the laser light source 11 is imaginary turned off is obtained, on the basis of information about the beat signal SW when the laser light source 12 is turned off, and information of the beat signal SW when both the laser light sources 11, 12 is turned in. Difference in the interference fringe is adjusted, based on the phase difference obtained. |
