Fluorescence correlation spectroscopy (FCS) is used to study additive-abrasive particle interactions in chemical-mechanical planarization (CMP) slurries. FCS provides quantitative determinations of the binding between additives and abrasive particles by characterizing the competitive adsorption of the additive and a fluorescent probe molecule, Alexa fluor 546 (A546) at the surface of a silica abrasive particle. Analysis of the adsorption of benzotriazole (BTA) on colloidal silica confirms the displacement of A546 by added BTA. However, glycine enhances the adsorption of A546 by colloidal silica. FCS is also shown to be a sensitive technique for detecting differences in the surface chemistry between different types of colloidal silica abrasive particles used in CMP processes.

Additive-abrasive interactions in chemical-mechanical planarization (CMP) slurries are investigated using fluorescence correlation spectroscopy (FCS). The FCS technique provides quantitative determinations of the interaction between additives and abrasive particles by characterizing the competitive adsorption of the additive and a fluorescent probe molecule by an abrasive particle. Adsorption of the CMP additives glycine and benzotriazole (BTA) on precipitated and sol-gel colloidal silica abrasives are characterized. Significant differences in the fluorescent probe’s adsorption to the different silica abrasives in the presence of the additives suggest surface chemistry differences between the different types of silica. Extensions of the analysis of FCS data are proposed for improving the quantitative determination of the competitive adsorption of fluorescent probe dyes and CMP additives on abrasive particles.

Fluorescence correlation spectroscopy (FCS) is shown to be an effective characterization tool in the analysis of silica abrasives used in CMP slurries. Tagging of silica particles via non-covalent adsorption of a highly fluorescent dye is the key step in applying the technique to these materials. FCS is shown to have ample analytical sensitivity to detect and analyze the smallest fraction (< 20 nm) of an abrasive silica dispersion. Fractionation of abrasive silica dispersions using preparative ultracentrifugation allows a direct comparison of FCS and dynamic light scattering (DLS) methods for sizing particles with diameters less than 20 nm in the dispersion. The sensitivity of FCS measurements of this type exceeded the sensitivity of DLS determinations in this size range. Non-covalent adsorption of a fluorescent dye by the silica particle enables the characterization of adsorption behaviors of CMP slurry additives, such as benzotriazole (BTA) and amino acids, on abrasive silica particles. Different adsorption behaviors are observed and the use of one specific fluorescent dye, Rhodamine 110, afforded a determination of a quantitative isotherm for dye adsorption. Future applications of the FCS method for sizing abrasive nano-particles and adsorption isotherm analysis of other CMP abrasives, such as alumina and ceria, are proposed.

Particle size distribution (PSD) analysis of colloidal silica abrasives employed in chemical-mechanical planarization slurries is demonstrated using fluorescence correlation spectroscopy (FCS). FCS allows a quantitative determination of the PSD for a dispersion of abrasive silica particles through fluorescence measurements of a dye, Rhodamine 110 (R110), adsorbed to the particles. Analysis of the autocorrelation function (ACF) of the fluorescence intensity fluctuations from R110-dyed silica confirms the presence of the adsorbed dye on the particles. Application of the method of histograms to the ACF yields a detailed analysis of the shape of the PSD for silica particle dispersions. FCS is shown to reliably measure the hydrodynamic diameter of silica particles less than 20 nm in mean size, and at particle concentrations which are too dilute for PSD analysis using a widely applied method for this purpose, dynamic light scattering.