CONCLUSIONCONCLUSIONIn summary, this chapter reviewed briefly the fundamentals of metrology and in-line AFM. Comparing to optical techniques and SEM, AFM is a much younger technique; however, it had a rapid growth to the level that it is recognized as an in-line RMS. With AFM's continuous growth, its role is being expanded from an RMS to a reliable metrology workhorse for profile and surface roughness measurement especially in CMP applications. It is also going to play a significant role as the in-line RMS for both CD metrology and hybrid metrology. Although AFM has been known for its tip wear and low throughput, the latest developments on non-contact mode imaging and the latest level of automation address those limitations. The literature on in-line AFM are still very limited to the knowledge of this author.