Projection exposure apparatus

摘要

A projection exposure apparatus employs light in two different wavelength bands for exposure of a photosensitive substrate and for alignment of the substrate with a mask, respectively. The mask has a window through which alignment light is passed to an alignment mark on the substrate and has a shield for preventing illumination of the alignment mark by exposure light. In one embodiment the position of the shield relative to the window is determined by magnification chromatic aberration of a projection optical system with regard to the alignment light. In another embodiment the path of the alignment light through the window is inclined relative to a line perpendicular to the mask and passes through a pupil of the projection optical system at a point deviated from the center of the pupil. In another embodiment a mark on the mask and a mark on the substrate are illuminated with light beams incident on the marks from different directions and forming interference fringes to provide optical information that is utilized to align the mask and the substrate.