| 摘要 |
PROBLEM TO BE SOLVED: To prevent measurement accuracy from being deteriorated due to electric noise or the like, by calculating an intersection angle of laser beams with using a phase difference of photoelectric signals corresponding to an intensity of as diffraction light from a diffraction grating on a substrate. SOLUTION: A laser beam from a laser light source 1 is split at 3 to P, S polarization beams to reach a polarization beam splitter(PBS) 19. Two S polarization beams reflected at the PBS 19 are photoelectrically converted by a photoelectric detector 23, whereby a photoelectric signal SR is output. Meanwhile, two P polarization beams passing the PBS 19 penetrate a PBS 27 and are sent onto a wafer mark WM with an intersection angleθ. A diffraction light BTL of the±first order (interference light) generated from the wafer mark WM is reflected at 27 and received by a photoelectric converter 31, whereby a photoelectric signals SD corresponding to an intensity of the light is output. The photoelectric signals SD, SR are input to a phase detector 32 and a phase differenceΔψof waveforms of the signals on the basis of the photoelectric signal SR is obtained. A positional shiftΔX on the wafer mark WM is calculated from the phase differenceΔψ.
|
