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Precision alignment between layers
Overlay measurement is a critical task in semiconductor manufacturing, as yield-efficient production requires precise alignment between layers. As wafer geometries continue to shrink, measurement systems are increasingly challenged to meet accuracy and repeatability requirements expressed in single-digit nanometers. Micro-Metric systems are based on a robust metrology platform that provides the stability necessary for this application. These systems create intensity profiles of the selected overlay pattern in X and Y directions. Any two pairs of features in the intensity profile can be selected as measurement targets. The center of symmetry of each pair of targets is determined, and the differences between the locations of the two centers in each direction are compared to produce overlay measurements. This technique minimizes errors due to low contrast, unsharp or irregular edges, and corner rounding.
In addition to linewidth and overlay dimensions, the Micro-Metric system also measures contacts, butting error, centroid position, angled lines, and circle diameter in semiconductor applications.
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