| 摘要 |
PROBLEM TO BE SOLVED: To make it possible to detect position with high accuracy by subjecting the position of an alignment mark in accordance with the position information of an alignment mark image to phase difference detection. SOLUTION: A command is sent via a keyboard 26 to a driving system 32 and a phase plate 30 is inserted into a prescribed position in the optical path between a half prism 6 and a second objective lens 11. The insertion position of the phase plate 30 is between the image side face of a first objective lens and the prescribed position where the zero order diffracted light and±1st order diffracted light from a wafer mark WM overlap substantially each other. As to the mark having the low difference in level, a command is sent to a driving system 28 via the keyboard 26 to insert an aperture diaphragm 27 for illumination into the optical path nearer the alignment mark side (wafer W side) than the exit end of a light guide 4. A main control system 25 outputs a stage control signal to a stage control system 24 in accordance with the position information of the wafer mark WM from a signal processing system 18. This stage control system 24 executes alignment by driving an X-Y stage 23.
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