Enhancing Ceria Slurry Performance for Shallow Trench Isolation Chemical Mechanical Polishing through Non-Ionic Surfactant Addition

Abstract

Abstract Chemical mechanical polishing (CMP) is a committed step in the manufacturing of integrated circuits, especially in the fabrication process of shallow trench isolation (STI) structures. Ceria (CeO2) slurry is widely used in the STI CMP process, while it is vulnerable to causing surface defects owing to particle agglomeration, such as scratches and abrasive residues. Furthermore, CeO2 slurry faces the challenge of low polishing removal selectivity between silicon dioxide (SiO2) and silicon nitride (Si3N4) surfaces. In this study, we investigated the effects of various non-ionic surfactants and different pH levels in CeO2 based slurries on material removal rates, removal selectivity, and surface qualities of polished wafers. Two of the studied non-ionic surfactants that make CeO2 slurries disperse better were selected through sedimentation experiments, which were polyethylpyrrolidone (PVP-K30) and polyethylene glycol, respectively. Subsequently, polishing experiments and atomic force microscopy characterization tests were conducted to illustrate the effects of the selected surfactants at different pH conditions. To further explore the underlying mechanism, the reaction of surfactants on SiO2 and Si3N4 wafers was explained using surface adsorption tests, thermogravimetry experiments, zeta potential measurements, and chemical valence bond structure analysis. As a result, it can be concluded that the performance of ceria slurries used in STI CMP process can be improved by the addition of non-ionic surfactant PVP-K30.