| 摘要 |
PURPOSE:To perform positioning with high precision by a method wherein light is entered aslant in double diffraction gratings, and discrepancy of the relative positions is detected from results obtained from the operatinal process of diffracted light intensities of the same degree of positive and negative. CONSTITUTION:The direction of coherent light emitted from a laser beam source 1 is changed by a plane mirror 15 and a spherical mirror 16, and light thereof is entered aslant to the same point of a mask 4. Light entered to a mask mark 5 on the mask 4 is reflected by a wafer mark 8 on a wafer 7, and passes the mask mark 5 again. Because both the marks are consisting of transmission type diffraction gratings, light passed the mark 5 is made to diffracted light, diffracted light of the first degree of positive and negative are reflected by spherical mirrors 17, 18, and are entered into photoelectric converters 12, 13. A substraction process or an addition process is performed by a signal process control part 14 to light intensities obtained by the converters 12, 13, and a signal corresponding to discrepancy of the positions is obtained. When a transfer table 6 is driven conforming to the signal thereof, positioning of high precision can be performed. |
