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.

Developing an Efficient Forward Design Method for Co Post-CMP Cleaning Formulations Based on Nanoparticle Removal Mechanisms

“…Typically, the manufacturing process of Co contact plugs and interconnects comprises etching trenches into dielectric layers, depositing diffusion barrier layers (titanium/titanium nitride, Ti/TiN) and wiring metals (Co) from bottom to top, followed by the removal of overburden materials utilizing chemical mechanical polishing (CMP), which is the most effective technique to realize the local and global planarization of wafer surfaces . One of the most common slurries for Co is composed of colloidal silica (SiO 2 ) as abrasive particles, accompanied by an oxidizer, a complexing agent, a corrosion inhibitor, plus one or more of a long list of additives. − Inevitably, the Co surfaces after the CMP process have to contend with a significant number of defects that include remaining SiO 2 particles, polishing debris, organic residues, severe corrosion, and scratches, which both can easily produce pores and holes in the following lithography and ion implantation steps, leading to short circuits . As a result, there is a need for the indispensable post-CMP cleaning process prior to any further step to minimize these contaminations and then ensure high yield and quality of circuits …”

Effect of Novel pH Regulators on Copper film Chemical Mechanical Polishing for Ruthenium-Based Copper Interconnect under Weak Alkalinity Conditions

“…Based on the above research results, it was found that compared to inorganic bases, mixing organic alkalis with inorganic bases as regulators can greatly improve the stability of slurry, and also have a significant impact on polishing efficiency and surface quality after polishing. L. Zhang et al 26 investigated at low concentrations, that diethanolamine (DEA) could be able to accelerate the polishing process via its auxiliary complexing effect, obtaining higher removal rates. X. Lin et al 27 found that 2-amino-2-methyl-1-propanol (AMP) not only has the function of regulating and stabilizing pH values but also has the function of dispersing abrasives and surfactants.…”