Since 2004 standards for calibration of critical dimension atomic force microscope (CD-AFM) tip width have been available both commercially and through national metrology institutes (NMIs) - such as the National Institute of Standards and Technology (NIST) in the United States. There have been inter-laboratory and inter-method comparisons performed on such samples, but less attention has been paid to the long-term stability of standards and monitoring for damage, wear, or contamination. Using three different CD-AFM instruments, we have tested the consistency and long-term stability of two independent reference calibrations for CD-AFM tip width. Both of these tip width calibrations were based on independently implemented transmission electron microscope (TEM) reference measurements. There were circumstances in which damage occurred or samples needed to be cleaned. Nevertheless, our results show agreement within the uncertainties and stability over a period exceeding 10 years.

Keywords: CD-AFM; linewidth metrology; standards; traceability.