| 摘要 |
PURPOSE:To enable alignment marks to be aligned with specified positions by driving the first element conforming to the relative slip amount by a method wherein a reference mark made on the main body side and alignment mark made on the first element such as a reticle are lighted through by using incoherent light in the direction reverse to the direction of projection light. CONSTITUTION:A mercury lamp is used for a light source. A g beam (b) is selected from the beams emitted from the mercury lamp to lead the beam into a main body through the intermediary of an optical fiber 3. The fiber 3 is fixed to enter the beam into an optical system irradiating a main body side reticle alignment mark (main body side RA mark) upward. The main body side RA mark and a reticle side RA mark existing at specified gap are lighted through by using this beam so that images of respective RA marks are formed on a CCD or an image sensing tube. Any detected image is fed to a computer to be image-processed for detecting relative slips of respective RA marks. The data are transmitted to a reticle stage driving system to correct the slips for making alignment of the reticle with the main body. Through these procedures, even if the gaps between the main body side RA mark and the reticle side RA mark fluctuate, the RA marks are not subjected to any interference to assure the stable signal output due to incoherent illuminating beam.
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