Measuring inter-layer edge placement error with SEM contours

Abstract

For advanced technology nodes, the patterning of integrated circuits requires not only a very good control of critical dimensions but also a very accurate control of the alignment between layers. These two factors combine to define the metric of inter-layer edge placement error (EPE) that quantifies the quality of the pattern placement critical for yield. In this work, we consider the inter-layer EPE between a contact layer with respect to a poly layer measured with SEM contours. Inter-layer EPE was measured across wafer for various critical features to assess the importance of dimensional and overlay variability. Area of overlap between contact and poly as well as contact centroid distribution were considered to further characterize the interaction between poly and contact patterns.