Investigation of sensitivity improvement on passive voltage contrast for defect isolation

With the increasing complexity of process technology, device features are now down to the deep-submicron range and the number of metal layers has increased to as many as 9 layers. At the same time, failure analysis (FA) has become significantly more difficult especially fault localization. Many localization tools such as EMMI (combined with Mercury Cadmium Telluride detector), LIVA, TIVA, SEI, OBIRCH, OBIC... etc. are not always precise enough by themselves to pin point defects. However, combining these techniques with layout tracing and passive voltage contrast (PVC) can improve the accuracy of defect isolation and increase the FA hit rate greatly. Passive voltage contrast in SEM or FIB is a well-known technique to identify leaky poly and open nodes (contacts via). However, conventional PVC cannot easily discern problems caused by higher resistance or implant induced faulty nodes. This work describes how to use different techniques, such as increasing emission current, increasing objective aperture, applying stage bias and thinning the substrate from the backside to improve the sensitivity of passive voltage contrast to localize defects. (C) 2002 Elsevier Science Ltd. All rights reserved.