The Role of Diethanolamine on Chemical Mechanical Polishing in Alkaline Glycine-Based Slurries for Cobalt Interconnects

Abstract

Cobalt (Co) and its low resistivity, superior adhesion property, and void-free seamless fill ability, pledge to transform the landscape of integrated circuits in many areas, especially in interconnects and logic contacts. Chemical mechanical polishing (CMP), which can realize local and global planarization, has been recognized as one of the indispensable manufacturing approaches for the fabrication of multilevel metal interconnection structures. The present work introduces diethanolamine (DEA) into our alkaline glycine-based slurries for Co CMP process. The action mechanism of DEA on Co CMP process in glycine-based slurries at pH 8.1 has been clearly revealed by various approaches, including polishing and static etching experiments, X-ray photoelectron spectroscopy survey, electrochemical analysis, as well as adsorption isotherm calculation. At low concentrations, DEA could be able to accelerate the polishing process via its auxiliary complexing effect, obtaining higher removal rates and larger corrosion current densities. Some pitting corrosion could appear on Co surfaces due to the production of Co-glycine complex as well as the auxiliary complexing process, making rougher surface qualities. On the other hand, when the DEA concentration increased to a certain level, it could play a role of corrosion inhibitor, protecting Co surfaces by forming a stable passive layer and moderating material removal rates, removal selectivity, and surface roughness.