| 摘要 |
PURPOSE:To reduce the effect of reflected rays from an objective optical system, and thereby detect a position for alignment with high accuracy. CONSTITUTION:A laser beam LB from a laser beam source 1 is radiated on a wafer mark WM through those such as a cylindrical lens 2, a field stop 3, a second objective lens 4, a light transmitter receiver separation prism 5 composed of a polarized beam splitter, a first objective lens 7, a 1/4 wave length plate 6, a mirror 16 and a projection optical system 8. Diffracted light is incident on photodetectors 13A and 13B through those such as a projection optical system 8, the mirror 16, the 1/4 wave length plate 6, the first objective lens 7, and the light transmitter receiver separation prism 5. Reflected rays 15 from the first objective lens 7 transmit the light transmitter receiver separation prism 5 so as to be returned to the laser beam source 1 side. |
