| 摘要 |
PURPOSE: To obtain an alignment device of heterodyne interference system wherein two beams of light of different colors are controlled in fringe deviation keeping signals from a reticule mark unchanged when the position of a wafer mark is detected through the two colored beams. CONSTITUTION: A reticule mark and a wafer mark are illuminated with two beams of light of different colors emitted from laser beam sources 11 and 12. The diffracted light from the reticule mark and the diffracted light from the wafer mark are detected by photodetectors 30 and 31 respectively. The photodetector 30 detects only the diffracted light of the light source 11 through a color filter 29 and outputs a reticule beat signals SR, and the photodetector 31 detects the diffracted two colored light beams and outputs a wafer beat signal SW. The phase difference between the signals SR and SW when the second laser beam source 12 is turned on and the first laser beam source 11 is reduced to 1/10 in output is added to another phase difference between the signals SR and SW when the second laser beam source 12 is turned OFF. |
