| 摘要 |
PURPOSE:To perform an accurate alignment by projecting a mark on a reticle on a mark on a wafer with coherent lights having two frequencies different from an exposure light wavelength, and guiding rediffracted light to a photodetector to detect a beat signal. CONSTITUTION:Coherent alignment lights 10 having two frequencies from a light source 4 is incident to a polarizing optical element 13 through an alignment mark 5 on a reticle 1. The element 13 passes only one of the lights and projects it on an alignment mark 6 on a wafer 2 through a correcting optical system 9 and a projecting lens 3. Then, a diffracted light 11 is guided to a photodetector 14 by a totally reflecting mirror 12 through a space filtering optical system 7 to detect a beat signal. The phase information of the signal is examined to detect positional deviation of the wafer 2 to the reticle 1, thereby performing an accurate alignment by operating the wafer 2 and the reticle 1 based on the detected amount. |
