International comparison of depth-setting standards

Measurements of depth-setting standards, carried out at nine national metrology laboratories within the framework of EUROMET project No. 301, are compared. The objects used for this comparison take the form of chromium-coated silicon substrates with rectangular grooves of 0,1 mm and 0,01 mm width and nominal depths from 30 nm to 3200 nm. For the calibration several stylus instruments, and interference microscopes based on different measuring principles, were used. The comparison shows that the participating laboratories are able, in general, to determine the groove depth with uncertainties ranging from a few nanometres for a groove of 30 nm nominal depth to some tens of nanometres for a groove of 3200 nm. At 3200 nm the scatter of measurements between the participants is characterized by a standard deviation of 40 nm, a value considered unsatisfactory for calibrations at a primary level.