Engineered porous and coated silica particulates for CMP applications

The aim of this study has been to synthesize the microporous silica spheres and to coat as-synthesized SiO₂ with CeO₂ for CMP applications. First, spherical microporous silica powders with a narrow size distribution have been prepared by a precipitation technique involving the hydrolysis reaction of a silicon alkoxide in ethanol. The interparticle microporosity has been created by adsorption of an organic compound (glycerol) as the porogen. The presence of glycerol during the synthesis affects considerably the precipitation mechanism and its effect on the particle size will be discussed. The synthesis of silica microporous spheres of narrow size distribution yielded the preparation, by varying particle size and porosity, of a wide range of aqueous silica slurries. The influence of particle size, particle size distribution, porosity and particle concentration will be discussed in chemical mechanical polishing applications. Although silica particles show large plastic deformation than the bulk material, very good glass polishing rates are obtained due to the plastic deformation of the silica layer during CMP. Silica particles are suitable candidates for application in CMP because silica can be directly precipitated as monodispersed spheres, their narrow size distribution being an important requirement in CMP applications. Secondly, as-synthesized silica particles were coated with the cerium dioxide particles having hexagonal shape, which were precipitated by decomposition from the cerium precursors. For this study, three coating processes were introduced to investigate the best coating parameters. Improvements in CMP of glass were also obtained by coating silica particles with cerium oxide nanoparticles.