| 摘要 |
PURPOSE:To enable the wafer position to be detected simultaneously with light beams having two or more different wavelength, by applying these light beams to the same region of a registering pattern on the wafer and by providing a light sensor exclusively for each of the light beams. CONSTITUTION:The detection light beams having different wavelength, after reflected from a sample, do not form an image in the surface of an original pattern because of chromatic aberration of a projection lens 3 but form a very large luminous flux (as represented by dotted lines) which passes the original pattern 2 and a beam splitter 11. The luminous flux is then reflected by a reflecting mirror 13 and forms an on-wafe pattern at the position 14 over the original pattern 2. Therefore, if the reference pattern 5 on the original pattern is provided only by a small aperture 5', it cannot allow sufficient light for detection to pass through the original pattern. If the reference pattern is provided by two apertures, however, sufficient light for detection can transmit the original pattern 2 and be applied to a magnifying optical system 6'. Accordingly, the pattern position at the image forming position 14 can be obtained with the use of a pattern detector 7'. |
