Increase in the Adsorption Density of Anionic Molecules on Ceria for Defect-Free STI CMP

Abstract

We have investigated the adsorption density of anionic molecules on a ceria surface and its effect on suppressing defects on the SiO(2) films during shallow trench isolation (STI) chemical mechanical planarization (CMP). Intermolecular vacancies in poly(methyl methacrylate) (PMMA) caused by ionic repulsive forces between its carboxyl groups provide adsorption sites on the ceria surface for 3-hydroxypentanedioic acid-3-carboxylic acid (hydrogen citrate), which has a molecular length of 8.39 angstrom. This allows for an increase in adsorption density. The coadsorption of PMMA and hydrogen citrate on the ceria surface leads to an increase in negative charge at the ceria particle-water interface and provides repulsive forces between the ceria particle and the SiO(2) surface. Ceria slurry prepared with the coadsorption of PMMA and hydrogen citrate shows a suppression of remaining particles (90.9%) and microscratches (100%) on the SiO(2) film, resulting from a decrease in the adhesion force of ceria particles on the SiO(2) film. This effect was analyzed by force measurement using atomic force microscopy.