Calibrated scanning force microscope with capabilities in the subnanometre range

This paper refers to quantitative scanning force microscopy (SFM) and dimensional measurement being traceable to metrological standards. The traceability to the unit of length is achieved by calibration of several thousands of selected and sufficiently defined reference positions within the three-dimensional measuring range by three miniature laser interferometers and their output signals at distances of λ/2 (λ corresponds to the wavelength of the He/Ne laser radiation). The expanded uncertainty U of the laser interferometer output signals is estimated to be ≤1 nm. The results reported here refer to the reduction of uncertainty in the subnanometre range by comparisons of measured periods of one-dimensional sinusoidal gratings using optical diffractometry with expanded uncertainties ≤0.1 nm, as well as SFM with an uncertainty originally estimated to be 1 nm. The goal is to reduce as far as possible the uncertainty of the SFM measurement results, e.g. the thickness of films or the pitch of gratings. The present state of work allows to estimate an expanded uncertainty of <0.4 nm and it is hoped to reach a value near the picometre range. The practical goal is to apply this microscopy to evaluations (calibrations) of dimensional parameters of objects in the semiconductor technology and other dimensional micro- and nanostructures.