The influence of the calcination time on the physical properties of synthesized ceria particles and their subsequent influence on shallow trench isolation (STI) chemical mechanical planarization (CMP) process performance were investigated. Two different kinds of ceria particles were synthesized by a solid-state displacement method which utilized calcination times of 4 and 6 hours. After the mechanical milling process, both the crystallinity and particle size distribution of the synthesized ceria particles were found to be markedly different between particles formed with different calcination times. Due to incomplete calcination, the ceria particles synthesized with a 4-hour calcination time had a smaller crystallite size than the particles synthesized for 6 hours. This smaller crystallite size ultimately resulted in large agglomerated particles. The differences in the characteristics of the ceria particles further translated into great discrepancies between the STI CMP performances of the ceria slurries made from the two types of particles.

The preparation of microsized uniform silica particles by the hydrolysis and condensation of concentrated tetraethylorthosilicate (TEOS) solutions has been studied in various solvent systems (methanol and ethanol with various long-chain alcohols). Ammonium hydroxide was used not only to initiate hydrolysis and condensation of TEOS, but also to provide the particles with a negative, stabilizing surface charge. Long-chain alcohol was introduced to control the hydrolysis/condensation rate and to reduce the polarity of the system (modified seed growth), as well as to stabilize large particles. To prepare large particles with good uniformity, the solvent composition is important because it determines the stability of both small oligomers and grown particles. The concentration of small seed particles suspended in a solvent and the amount of monomer are also found to be important process parameters in controlling the size and morphology of microspheres. No salt was added to change the surface potential of silica particles. Monodispersed spherical silica particles over 2 μm could be obtained. Moreover, a turbidity experiment showed that the silica growth and nucleation proceeded mainly through the reaction of small oligomers rather than monomeric species.