Attachment of CeO2 and SiO2 for Chemical Mechanical Polishing: Theory and Experiments

Abstract

Interactions of finely dispersed abrasive particles in chemical mechanical planarization (CMP) slurries play a vital role in determining the polishing performance. In this study, coupled influence of hydrodynamic and colloidal interactions on the attachment of nanosized ceria (CeO2) particles to a silica (SiO2) surface is investigated. Deposition rates of ceria nanoparticles on silica sensor are determined using quartz crystal microbalance with dissipation monitoring (QCM-D) as a model system and compared with theoretical transport models under the influence of colloidal interactions. It is found that the deposition of ceria nanoparticles on silica is highly dependent on the solution pH, fluid velocity, and concentration of ceria particles in the solution. The system is shown to exhibit considerably different behaviors at acidic and basic pH conditions. More specifically, stronger attachment occurs at neutral pH conditions than at acidic or basic conditions. The concentration of particles is also shown to affect the interaction of ceria with silica in a complex way which is not necessarily predictable by the simplified theories of colloidal interactions. More specifically, increasing ceria bulk concentration within some ranges results in decreasing the initial deposition rate.