According to a first embodiment of the invention, a first and second reticle are used to form layers using a photolithographic process. The first and second reticles each include a grating positioned so that when the reticles are printed, the two gratings will at least partially overlap each other. The...http://www.google.de/patents/US7349105?utm_source=gb-gplus-sharePatent US7349105 - Method and apparatus for measuring alignment of layers in photolithographic processes
