ALIGNMENT OPTICAL SYSTEM

摘要

PURPOSE:To always obtain a stable misalignment detecting signal regardless of the magnitude of reflectance on a wafer surface by inclining a misalignment detecting light beam in a direction orthogonally crossed with a misalignment detecting direction so that the light beam is made incident and providing an aperture for cutting multiple reflected light on a mask. CONSTITUTION:A beam projecting optical system is inclined in the direction perpendicular to the misalignment detecting direction so as to make the beam 1 obliquely incident and the aperture which can cut the multiple interference light between the mask 3 and the wafer 4 is provided on a mark. When the misalignment detecting beam 1 inclined by an angle alpha is made incident just on the aperture which opens to the mask 3 placed close to the wafer 4, the light exiting to the outside from the aperture of width alpha again after being reflected on the surface of the wafer becomes very little. Thus, gap dependent component included in the light obtained through the aperture can be made very little.