Advanced techniques for contact module development

We describe the application of an advanced SEM-based inspection tool (a KLA 2702 "SEMSpec") during contact module process development. SEMSpec image contrast is derived from surface voltage variations and is particularly well suited to identifying electrical defects within contact chains. Results are presented from a study in which the SEMSpec was effectively used to identify unfilled and partially filled tungsten contacts, many of which were not detectable by standard optical or conventional SEM inspection. SEMSpec images are compared with conventional SEM micrographs (topdown and after FIB cuts). Contrast mechanisms are discussed.