Inline electrical yield versus optical inspection: Correlations, connections and disconnections

In the state of the art development of chip manufacturing (FinFet technology for example) both optical inspection and inline electrical test are deployed to monitor and facilitate the process development. While optical inspection provides critical process evaluation at the sector inline electrical test (ILT) at M1 provides the information of process impact on the electrical signal, which ultimately is the indication of device operation and performance. It is always tempting but not trivial to compare the optical inspection result (defect density) with the in-line electrical test result (yield) in a quantitative way. Nuances in doing such correlation between the inspection and electrical yield are discussed. In the scenario where a correlation could not be established, ranking the different inspections in terms of yield impact is another source to provide feedback to the process development. To build such yield impact Pareto three different algorithms for counting the sector contribution to the electrical fail are compared.