Synthesis and Characterization of Silica Nanoparticles

Currently there are several models discussed to describe the formation of monodispersed silica particles. Monodisperse colloidal silica was prepared from tetraethoxysilane in mixture of ammonia, water and ethanol. Chemical system reaction permits the controlled growth of silica nanoparticles and subsequent condition of silicic acid in alcoholic solution. The molar ratio of NH4OH, C2H5OH and H2O has a significant effect on particle size and specific surface area of silica particles. The nature of particles was evaluated using X-ray diffraction, energy dispersive spectroscopy (EDS) and BET. The morphology of particles were determined by scanning electron microscopy (SEM) and transmission electron microscopy(TEM).

Preparation of Inks with Monodisperse Colloidal Silica and their Self-Assembly in a Ink-Jet Printed Droplet

Semispherical self assemblies of colloids have been fabricated on a substrate using inkjet printing with an ink of submicron-sized monodisperse silica particles. Colloidal silica has been prepared by Stöber process. The shape and monodispersity of the synthesized colloidal particles were observed by scanning electron microscopy (SEM) and laser light scattering particle analyzer. Simple test patterns on various substrates (silicon wafer, Cu foil, and Mylar film) were printed with commercial HP printer. It was found that the uniformity and spatial extent of the self-assembled colloidal silica within a dot were significantly influenced by the contact angle between ink and substrates. Ink droplets printed on the hydrophobic Mylar film maintain a higher contact angle as compared to the hydrophilic substrates such as Si wafer. Slower evaporation and high capillary stress exerted on the ink droplet allow hemispherical colloidal aggregates with an ordered internal structure on Mylar film.

Ta/low-κ CMP with Colloidal Silica Particles

Low-κ/Cu interconnect integration achievement is one of the key issues for the future sub-100 nm technologies. Nowadays, no definitive integration scheme has been reported. Low-κ integration is especially difficult because the trench/via etching and CMP processes can damage its properties. In the present work, we present results on different materials that could be used in such integration. We focused our study on the barrier (Ta/TaN) and on a low-κ material (dense and porous), that is a spin-on-dielectric (SOD) of the methylsilsesquioxane (MSQ) type. CMP slurries were made from monodisperse colloidal silica particles. In a first approach, the slurries compositions mainly differed by their pH and abrasive characteristics. The particle size ranged from 12 to 80 nm, with a pH varying between 2 and 11. The sensitivity of the Ta/TaN and low-κ removal rates will also be reported. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) of the different films were carried out in order to evaluate the impact of CMP on their surface quality. Measurements did not show any surface degradation or/and scratches, and no delamination has been observed. Post-CMP κ value measurements have been carried out to highlight possible damage on the low-ê dielectric materials.