| 摘要 |
PURPOSE:To accurately measure a space between a mask and a wafer even when a relative displacement is generated in mask and wafer detecting means by measuring diffracted light generated by physical optical elements provided in a measuring system and a correcting system. CONSTITUTION:The light beam 1a of a measuring system is diffracted by an optical element 4a, a diffraction grating, on a mask 2 and further diffracted by a light emitting optical element 5a. Light reflected by a wafer 3 is diffracted by the light emitting optical element 5a. Refracted light 61 (62) is led to photosensitive means 8a and a space between the mask 2 and the wafer 3 is calculated from the position of the photosensitive means 8a. The light beam 1b of a correcting system is diffracted by an optical element 4b on the mask 2. Diffracted light 22 is led to photosensitive means 8b and a light beam 25 diffracted by an optical element 5b is incident on photosensitive means 8c. When an angle between, for instance, detecting means and the mask 2 relatively changes, a space between the light beams 61, 62 and the light beam 22 is substituted into a prescribed equation whereby the space can be calculated without being affected by variation factors. |
