Via chains for defect localization

摘要

Method form via chain and serpentine/comb test structures in kerf areas of a wafer. The via chain test structures comprise a first via chain and a second via chain in a first kerf area. The via chain test structures are formed such that geometrically shaped portions of the first via chain and geometrically shaped portions of the second via chain alternate along the length of the first kerf area. The methods perform relatively low (first) magnification testing to identify a defective geometrically shaped portion that contains a defective via structure. The methods then perform relatively high (second) magnification testing only within the defective geometrically shaped portion. The first magnification testing is performed at a lower magnification relative to the second magnification testing.