NIST-traceable calibration of CD-SEM magnification using a 100-nm pitch standard

This paper is a practical guide to the calibration of magnification of a CD-SEM using a pitch standard. It answers two fundamental metrology questions: 1) how many individual pitch measurements should one take in order to estimate the average pitch of the sample with a specified uncertainty and with a specified confidence level?, and 2) when is it appropriate to recalibrate the instrument following the measurement of the standard? In answering these questions, this paper identifies Cost of Ownership (CoO) elements of the calibration process and outlines best engineering practices for the calibration procedure. The discussion is then extended to the case of tool matching and calibration of not just a single measurement tool, but an entire measurement system comprised of several measurement tools all matched to each other. Finally, this paper discusses the problem of hydrocarbon contamination in a CD-SEM, which limits the number of times that a certain location on the standard can be used for calibration, and presents a methodology to determine how often the measurement location should be changed.