A quantitative study on removal mechanism for single atomic layer removal in Cu chemical mechanical polishing based on ReaxFF MD simulations

Abstract

Atomic-scale controllable removal is very vital for achieving atomic accuracy non-destructive surface in the whole frequency domain, especially in the manufacturing process of advanced chips in the post-Moore era. The prerequisites for achieving the purpose are to ascertain atomic-scale removal mechanisms and their contributions to single atomic layer removal. In this work, we quantitatively investigate the atomic-scale removal mechanism in different polishing slurries (including H₂O, H₂O₂, or glycine) during Cu CMP via ReaxFF molecular dynamics simulation. It shows that Cu atom can be removed via: OH adsorption, bond chain stretching, pure shearing, H₂O adsorption, and interfacial bond stretching in pure H₂O, OH adsorption and bond chain stretching in pure H₂O₂, as well as glycine adsorption, bond chain stretching, interfacial bond stretching, and pure shearing in pure glycine. Their contributions to material removal decrease in turn under each simulation condition. In aqueous glycine with/without H₂O₂ and aqueous H₂O₂ with/without glycine, glycine and/or OH adsorption dominate Cu atomic removal, H₂O adsorption, bond chain stretching, pure shearing, and interfacial bond stretching play indispensable roles in material removal, and the occurrence of these Cu atomic removal behaviors and their contributions to material removal as well as Cu removal rate are closely dependent on the composition of polishing slurry. This work provides not only chemical and tribochemical insight into Cu atomic removal mechanism in CMP, but also a theoretical guidance for designing Cu CMP slurry.