Patent ID: 7329888

Claim:
A lithographic projection apparatus, comprising: an illumination system adapted to provide illumination radiation; a substrate stage assembly adapted to be disposed in a path of said illumination radiation; a reticle stage assembly arranged in said path of said illumination radiation between said illumination system and said substrate stage assembly; a projection system arranged between said reticle stage assembly and said substrate stage assembly; and an alignment system arranged proximate at least one of said substrate stage assembly and said reticle stage assembly, wherein said alignment system comprises: a source of alignment radiation; a detection system comprising a first detector channel and a second detector channel; and a position determining unit in communication with said detection system, wherein said position determining unit is constructed to process information from said first and second detector channels in a combination to determine an alignment grid for a work piece based on detection of an alignment mark on a work piece via each of said first and second detector channels.