Fabrication of commercial integrated circuits depends critically on the physical and chemical properties of the abrasive slurry particles used to polish silicon wafer surfaces via chemical-mechanical planarization (CMP) to near-atomic flatness. The particle size distribution (PSD) of the abrasive particles is a key factor in the CMP process due to its connection with polishing efficiency and defect creation on wafers during polishing. In this presentation the utility of a single-molecule spectroscopic technique, fluorescence correlation spectroscopy (FCS), in this application is described. FCS stands out among PSD analysis methods based on its sensitivity to particles with hydrodynamic diameters in the sub-10 nm size range. Characterization of abrasive particles of smaller size in CMP slurries has become a requirement as the feature sizes of integrated circuits steadily decrease according to Moore’s law. The use of FCS in conjunction with a complementary technique, particle tracking using the Viewsizer 3000 multi-laser Nanoparticle Tracking Analysis (m NTA), is described as an approach to meet this challenge.