Method of analyzing a probe tip deflection signal of a scanning probe microscopy system

A method of analyzing a probe tip deflection signal of a scanning probe microscopy system, for determining a location coordinate of a sidewall structure present on or in a sidewall of a surface feature, the surface feature being present on a surface of a substrate,

• wherein the system comprises at least one probe head comprising a probe including a probe tip arranged on a cantilever, the probe head being configured for scanning the probe tip along one or more directions parallel to the substrate surface, the probe head comprising an actuator for applying a periodic motion to the probe tip during said scanning, and a tip position detector for providing a probe tip deflection signal indicative of a deviation of an actual position of the probe tip from a reference position along a z-direction transverse to the substrate surface, the method comprising:
• obtaining, at a first scan position on the substrate surface, a first plurality of samples of the probe tip deflection signal over time at one or more positions of the probe tip along the z-direction during at least one first cycle of the periodic motion, for providing a signal profile at the first scan position using the first plurality of samples;
• identifying the signal profile to be associated with a grazing impact of the probe tip on the sidewall;
• detecting, in a slope of the signal profile which is associated with a probe tip motion in a z-direction towards the substrate surface, one or more variations in the slope, wherein the variations comprise local maxima or minima;
• associating at least one of the variations with an interaction between the probe tip and the sidewall structure during the probe tip motion, and obtaining a z-position of the probe tip at the at least one variation;
• and
• providing, as the location coordinate of the sidewall structure, the obtained z-position at the at least one variation.