| 摘要 |
PURPOSE:To reduce a measurement error due to air fluctuations by comparing the signal from a 1st photodetecting means with the signal from a 2nd photodetecting means and finding the position shift of a substrate. CONSTITUTION:A laser light source 1 is provided so as to generate two beams for alignment and the laser beam from the light source 1 is converted by an optical transmission system BTU into two linear polarized light beams which have a specific frequency difference. The two beams cross each other even on a wafer W at a specific angle and if a diffraction grating mark is present in this cross lighted area, interference beat light is generated vertically. A photoelectric element 19X is the 1st photodetecting means and a photoelectric element 24X is the 2nd photodetecting means. The signal DSWx from the photoelectric element 19X and the signal DR1X from the photoelectric element 24X are inputted to a phase difference detection part ALC in a main control system MSC to measure the phase difference between both the signals and information on the position shift quantity corresponding to the phase difference is sent to a stage controller STC and used to control a motor MT1. |
