Illumination method and system having a first optical element at a position optically conjugate with an object and a second optical element closer to the object and on a pupil plane of the system

摘要

An illumination system for illuminating an object, such as a system for detecting an alignment mark on a semiconductor wafer. The system includes a light source and an illumination optical system for directing light from the light source toward an object to be illuminated. A first optical element, which preferably is a hologram, is provided in a portion of the light path of the illumination optical system at a position optically conjugate with the object and has a function of amplitude-dividing the light and deflecting a divided light ray. A second optical element, which also preferably is a hologram, is provided in a portion of the light path that is closer to the object as compared to the first optical element and is disposed on a pupil plane of the illumination optical system. The second optical element also has a function of amplitude-dividing the light and deflecting a divided light ray.