Abstract The constant size reduction of the elementary structures in integrated circuits (ICs) and their increasing complexity pushes laser probing techniques to their limits. For old technologies these techniques were powerful tools in defects detection and internal analysis, but now the major limitations of the laser spot size implies the understanding of the complex information contained in the reflected beam when it covers an area of multiple elementary structures. Knowing the contribution of each elementary structure covered by the laser spot in the reflected laser beam is the key to have a good analysis and interpretation of the probed area. In this paper we will expose the different parameters that modify the intensity of a laser beam and the contribution of a basic structure covered by a big laser spot size as well as the systematic approach we have built to deal with this challenging reflected laser probe signal from multiple elementary substructures in very deep submicron technologies.