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

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.