As the development of technology nodes proceeds to 7 nm node, chemical mechanical polishing (CMP) slurries for shallow trench isolation (STI) and the dependent supporting technological parameters cannot fully meet the technical requirements. Higher goals are put forward for the polished surface qualities and the removal selectivity control. In this work, attention is given to studying the STI CMP process by introducing various ionic surfactants in ceria slurries, aiming to control removal rates, removal selectivity, as well as surface qualities after CMP process. The findings of ball milling and subsiding tests were used as a starting point for choosing the effective ionic surfactants, searching the minimal delamination phenomenon with the best dispersibility and stability by experimental comparison. It can be found that Piperazine with a benzene ring and its short-chain derivatives (2-methylpiperazine) have a higher probability to bind to ceria particles, thus limiting sedimentation phenomenon and improving dispersibility for polishing slurries. The impact of two surfactants on removal rates, removal selectivity and surface characteristics were next investigated in polishing trials at various pH levels. Depth of scratches on polished wafers and corresponding surface roughness, as well as morphology of ceria abrasive particles were characterized, respectively. Furthermore, action mechanisms of selected ionic surfactants in ceria slurries have been revealed by solid-liquid interface adsorption characterization, thermogravimetric analysis and zeta potential tests.
