| 摘要 |
PURPOSE:To improve exposing accuracy by utilizing interference fringes having two wavelengths with light having two kinds of wavelengths different from exposure wavelength to fit a pattern projection optical system as alignment light to measure the deviation in the position in the height and cross directions between a mask and a wafer. CONSTITUTION:A mask mark 11 is placed on a point A and the alignment light having Doppler-shifted wavelengths lambda1, lambda1+DELTAlambda is made incident as luminous flux having spherical waves to condense on an incident pupil of a projection lens 20 by using an acoustic optical modulator. Here, diffracted light of zero-order, + or - first-order,... is generated from the mask mark 11 and the first-order diffracted light is projected on two points B and C on the wafer 30 through the projection lens 20 with positional information of the mark 11 of the point A. Wafer marks 31b and 31c with the same grating shape are formed on the above positions of points B and C and moire patterns are produced on the marks and the light again diffracted is led by a mirror 41, etc., and detected by a detector 42. The relative deviation in the position of the height directional position can be measured by carrying out prescribed signal processing by a signal processing circuit 43 based on an output signal of the above-mentioned detector 42. |
