| 摘要 |
PURPOSE:To prevent diffraction light intensity from being largely influenced by fine fluctuation of a gap to enable stable detection of difference in position of a mask and a wafer by a method wherein the vicinity of a linear diffraction grid of a wafer mark is processed to be uneven. CONSTITUTION:When laser beam 6 is irradiated to a linear Fresnel zone plate(LFZP) 3, the laser beam 6 forms a spot on a wafer 2 surface where it is focused. At this time the beam is irradiated from a vertical direction in the vicinity of zero-order light which passed through the LFZP 3 and reflected diffraction light on the rear of the LFZP 3, but since diffraction light 5 has been formed in the vicinity of the linear diffraction grid 4, little zero-order reflected light is generated and the reflected light may not pass through the LFZP 3 again. Therefore without multiple interference generated between a mask 1 and a wafer 2 due to reflection diffraction light intensity slowly changed with respect to fluctuation in a gap between the mask 1 and the wafer 2. Stable detection of difference in positions can thus be performed. |
