Application of Fluorescence Correlation Spectroscopy in the Characterization of Particle Size Distributions of Colloidal Silica Abrasives Used in Chemical-Mechanical Planarization

Abstract

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.

Characterization of Particle Size and Surface Adsorption for SiO2Abrasives Used in Chemical Mechanical Planarization via Fluorescence Correlation Spectroscopy

“…20 In the present study, the analytical capabilities of one particular single-molecule spectroscopic technique, fluorescence correlation spectroscopy (FCS), 18 are highlighted for colloidal silica dispersions used in CMP processes. This work expands on previously reported preliminary FCS findings for this class of slurries [21][22][23] and identifies future areas of application of the technique for CMP slurry characterization.…”

“…Preliminary FCS studies have demonstrated that the copper CMP additives BTA and glycine interact with the surface of a precipitated silica abrasive (d H = 115 ± 1 nm). [21][22][23] As shown in Figure 6, the degree of A546 adsorption was reduced by BTA in silica-dye mixtures. Separate FCS studies confirmed that de-sorption of A546 was not due to a more favorable binding interaction between A546 and BTA in solution.…”

Fluorescence Correlation Spectroscopic Studies of Particle Properties for Colloidal Ceria Abrasives Used in Chemical-Mechanical Planarization

“…The characterization of physical properties for colloidal CMP abrasives has been achieved using a host of analytical techniques (3)(4)(5)(6). One method in particular, fluorescence correlation spectroscopy (FCS), has been demonstrated in the analysis of both the surface chemistry and particle diameter distribution of nano-sized silica CMP abrasives (7)(8)(9). In the present study, the capabilities of the FCS technique in the analysis of the physical properties of colloidal ceria CMP abrasives are described.…”