Atomic-Level Material Removal Mechanisms of Si(110) Chemical Mechanical Polishing: Insights from ReaxFF Reactive Molecular Dynamics Simulations.

Reactive molecular dynamics (ReaxFF) simulations are performed to explore the atomistic mechanism of chemical mechanical polishing (CMP) processes on a Si(110) surface polished with an a-SiO2 particle. The Si surface is oxidized by reacting with water before the CMP process, and the O atoms of the oxidized Si surface mainly exist in the form of Si-O- dangling bonds and Si-O-Si bonds. In the CMP process, the insertion of O atoms into the surface, the formation of interfacial Si-O-Si and Si-Si bridge bonds, and the adsorption of H atoms on the surface-saturated Si atoms can all cause the surface bond breakage and even the Si atomic removal. The contributions of the four different kinds of tribochemical wear mechanisms to the surface wear decrease in turn and are much larger than that of mechanical wear. The results indicate that the material removal in the actual Si CMP process is the combined results of multiple atomic-level wear mechanisms. Furthermore, we find that the oxide layer of the Si surface plays an important role in the surface wear mainly by providing O atoms to insert into the surface, rather than by providing additional reaction pathways to form interfacial Si-O-Si bridge bonds. This work provides new and further insights into the process and mechanism of silicon removal during CMP.