5. Discussions

5.1 Discussions of observed practices

Overall, the results of this comparison of measurement of the characteristic properties of standard gratings before/after calibration are close to the expected results: an improvement in measurement accuracy has been observed. Indeed, the discrepancies observed between the values measured by the participants and the reference values are largely reduced after calibration, both for grating pitch by SEM or AFM and for step height by AFM. This comparison showed that most of the participants' equipment was not calibrated and/or their users were not familiar with calibration procedures. It is also worth noting that 20% of the measurements were provided even though they did not comply with the protocol. The results associated with these measurements are...