Comparison for modern microscopes at research laboratories (Nordic-nano1: 1D-gratings)

NMIs are arranging a comparison measurement for modern microscope (AFM.SEM) users at universities, research institutes and companies in Estonia, Finland, Norway and Sweden. The comparison samples are 1-D gratings with nominal pitches of 300 nm and 700 nm.

Final Report 2013-01-10

The national metrology institutes — the Centre for Metrology and Accreditation (MIKES, FI), Technical Research Institute of Sweden (SP, SE), Justervesenet (JV, NO), and Metrosert (EE) —organized comparison measurement Nordic-nano1 for scanning electron microscopes (SEM)  and atomic force microscopes (AFM) in 2010 - 2011. The purpose of the comparison was to study measurement capabilities at universities and research institutes and to get information about the calibration of their instruments. Twenty-five laboratories participated in the comparison. The participants obtained information about the accuracy of their instruments and their measurement capability. The comparison samples were 1-D gratings with nominally 300 nm and 700 nm pitches. The reference value was measured with the MIKES laser diffractometre [3]. 

The comparison shows that the measurement capabilities of the laboratories vary significantly. For a nominally 300 nm grating, 19 results out of 36 differed from the reference value by more than the estimated uncertainty, and three results did not have an uncertainty estimate. For nominally 700 nm samples, 15 results out of 39 differed more than the estimated uncertainty and four did not have an uncertainty estimate. The largest deviations were approximately 20 % for both grating types.

Strong correlation of relative deviations of the results of individual instruments for both nominally 300 nm and 700 nm gratings show that a simple scale factor calibration would have corrected a large part of the deviations from the reference values (See figure 1). The accuracy of the uncertainty estimates varied between the laboratories, and for some laboratories the appropriateness of the calibration procedures could be considered.