An investigation of the deposition of ceria on silica by quartz crystal microbalance: Observations on the effect of many body interactions

Interaction of ceria and silica is important in a wide variety of applications such as Chemical Mechanical
Polish (CMP). In this work, a Quartz Crystal Microbalance (QCM) and mathematical modeling and simulations are used to investigate the dynamics of the attachment of ceria and silica under different flow rate,
colloid concentration and pH conditions. The well-known DLVO forces of interaction were successfully
used to distinguish between favorable and unfavorable conditions for the attachment of ceria and silica,
and to develop a cleaning procedure to obtain reproducible data when using QCM for studying charged
particles. The use of the optimized cleaning procedure as well as careful selection of the experimental
conditions such as flow rate and concentration led to the important experimental observation that deposition of ceria particles onto silica surface is affected by many body particle–particle interactions in the
bulk that can hinder the ability of the ceria particles to successfully attach to the silica surface. These
experimental results could not be predicted by using a convection-diffusion-migration model which
incorporates a single particle-surface DLVO interaction energy but ignores particle–particle interactions
in the bulk. This is an important finding that permits the determination of the proper conditions for
applications such as CMP and post CMP cleaning