Abstract: A method and apparatus generate a measured data set by: (i) providing a probe tip at a selected height from a doped region of a substrate, (ii) applying a probing signal to the probe tip, (iii) measuring a characteristic of an electrical interaction between the probe tip and the doped region of the substrate, and (iv) repeating steps (i) through (iii) for a plurality of different selected heights. A plurality of reference data sets are provided characterizing the electrical interaction between the probe tip and the doped region of the substrate as a function of height between the probe tip and the doped region of the substrate. Each data set corresponds to a different dopant density. The measured data set is compared to the plurality of reference data sets and based on the comparison, the dopant density of the doped region of the substrate is determined.