A method and apparatus measure properties of two layers of a damascene structure (e.g. a silicon wafer during fabrication), and use the two measurements to identify a location as having voids. The two measurements may be used in any manner, e.g. compared to one another, and voids are deemed to be present...http://www.google.fr/patents/US7301619?utm_source=gb-gplus-shareBrevet US7301619 - Evaluating a multi-layered structure for voids
