Patent ID: 6950188

Claim:
A system for aligning a wafer in an exposure apparatus, said system comprising: a holder adapted to hold a wafer, wherein said wafer includes a plurality of alignment marks and wherein said holder is adapted to move in a direction perpendicular to the surface of said wafer; a coarse alignment system; a fine alignment system having a higher precision than said coarse alignment system, wherein said fine alignment system includes a plurality of optical detectors, and wherein each of said optical detectors is positioned to detect a corresponding alignment mark of said alignment marks on said wafer; and an alignment processor connected to and controlling said optical detectors and said holder, wherein said optical detectors are controlled by said alignment processor to simultaneously detect said alignment marks, and wherein said optical detectors are controlled by said alignment processor to simultaneously detect said alignment marks multiple times while said holder moves said wafer in said direction perpendicular to said surface of said wafer.