One of the most significant challenges for technology characterization and failure analysis is to keep instrumentation and techniques in step with the development of technology itself. Not only are dimensions shrinking and new materials being employed, but the rate of change is increasing. According to the 1999International Technology Roadmap for Semiconductors, “The number and difficulty of the technical challenges continue to increase as technology moves forward.”1It could be argued that technology cannot be developed without appropriate analytical techniques; nevertheless while much effort is being directed at materials and processes, only a small proportion is being directed at analysis. Whereas previous versions of the Semiconductor Industry Association roadmap contained a small number of implicit references to characterization and analysis, the 1999 ITRS contains many explicit references. It is clear that characterization is now woven through the roadmap, and technology developers in all areas appreciate the fact that new instrumentation and techniques will be required to sustain the rate of development the semiconductor industry has seen in recent years. Late in 1999, a subcommittee of the Sematech Product Analysis Forum (PAF) reviewed the ITRS and identified a “top-ten” list of challenges which the failure analysis community will face as present technologies are extended and future technologies are developed. This paper discusses the PAF top-ten list of challenges, which is based primarily on the Difficult Challenges tables from each ITRS working group. Eight of the top-ten are challenges of significant technical magnitude; only two could be considered non-technical in nature. Most of these challenges cut across several working group areas and could be considered common threads in the roadmap, ranging from fault simulation and modeling to imaging small features, from electrical defect isolation to deprocessing. While evolutionary changes can be anticipated fairly easily, revolutionary changes require large multi-faceted research efforts. Each of the ten challenges will be discussed in the context of the roadmap, and specific needs in each area will be given. ©2001 American Institute of Physics.