| 摘要 |
PROBLEM TO BE SOLVED: To detect the amount of defocusing of a mark on a workpiece, without using a light beam having a wavelength range larger than that for position detection. SOLUTION: A focus measuring slit 50 is irradiated by a focus measuring light beam (FL) with a specified polarized characteristic. The image of the focus measuring slit 50 is projected in the vicinity of or directly onto a wafer mark 7. The flux of light(FL) reflected from a wafer(W) is conducted onto the side of a pupil separation member 44 with the use of a polarized beam splitter 18. A defocus amount of the wafer mark 7 is detected from the sidewise dislocation of an image of the focus measuring slit 50 formed by separated light beams 53 and 54, and the defocus amount is compensated. The wafer mark 7 is irradiated with a flux of light (AL) with polarized characteristics different from that of the flux of light(FL) and the same wavelength range as the flux of light(FL). The light beam (AL) is conducted to the side of an image-pickup element 20, using the polarized beam splitter 18 to detect the position of the wafer mark 7. |
