Projection optical apparatus and a photographic mask therefor

摘要

A projection optical apparatus used for projecting a pattern in the photolithographic operation for semiconductor device fabrication and a photographic mask used with the apparatus. In the projection optical apparatus, the reflected light from the pattern of a mask is utilized in place of the transmitted light through the pattern of the mask for the purpose of projecting the pattern. For this purpose, the projection optical apparatus includes illuminating optical means for projecting an illuminating light to the pattern of the mask and light guide means for directing the illuminating light reflected by the pattern of the mask to a projection optical system. A mask adapted for use with the apparatus contains a pattern composed of two opaque areas which are different in reflectance from each other.