CONTRAST ENHANCEMENT FOR LITHOGRAPHY ALIGNMENT MARK RECOGNITION

摘要

A system and method for providing contrast for determining an edge in alignment systems, in accordance with the present invention, includes propagating light for irradiating an alignment mark and a background portion surrounding the alignment mark of a semiconductor wafer (804). Wavelengths of the propagated light are modulated (806), and reflectance of the wavelength-modulated light is measured for the alignment mark and for the background portion (808). A largest change between the reflectance of the alignment mark and the reflectance of the background portion is determined such that a position where the largest reflectance change occurs indicates an edge of the alignment mark (810).