Disclosed is a method of determining an overlay error between two layers of a multiple layer sample. For a plurality of periodic targets that each have a first structure formed from a first layer and a second structure formed from a second layer of the sample, an optical system is employed to thereby...http://www.google.de/patents/US20040233442?utm_source=gb-gplus-sharePatent US20040233442 - Apparatus and methods for detecting overlay errors using scatterometry
