Recent advances of the metrological AFM at INRIM

Traceable dimensional measurements of step-height and lateral standards, patterned surfaces, and particles at the nanoscale need of calibrated instruments such as the metrological AFMs. These instruments have onboard capacitive sensors or interferometers to control the relative tip-sample movements. Interferometers provide a direct traceability to the unit of length, at the cost of more complex set-ups. A new interferometer set-up has been developed to monitor tip-sample z-displacements of the instrument in use at INRIM. The interferometer is made of a compact and symmetric arrangement of the optics to fit available room and minimize the metrology loop. Preliminary results are reported together with the analysis of the main error sources of z-displacement measurements.