REDUCED COHERENCE SYMMETRIC GRAZING INCIDENCE DIFFERENTIAL INTERFEROMETER

摘要

A system for inspecting specimens such as semiconductor wafers is provided. The system provides scanning of dual-sided specimens (111) using a diffraction grating (153) that widens and passes nth order (n > 0) wave fronts to the specimen surface and a reflective surface (154,155) for each channel of the light beam. Two channels and two reflective surfaces are preferably employed, and the wavefronts are combined using a second diffraction grating (156) and passed to a camera system (159a,b) having a desired aspect ratio.