Mechanisms of oxygen plasma damage of amine and methyl terminated organosilicate low-k dielectrics from ab initio molecular dynamics simulations

Abstract

Ab initio molecular dynamics simulations based on density functional theory were used to probe the interactions of O(1D) and O(3P) radicals on trimethylcyclictrisiloxane (TMCTS) and aminated TMCTS (TMCTS-NH2)—a model system for vicinal and aminated organosilicate glass (OSG) low-k dielectric materials. The roles of triplet, O(3P), and singlet, O(1D), interactions were investigated, as well as the directional and energetic dependence of the plasma on the product species. O(1D) attack resulted in the development of complex bonding states including Si–CH3O and Si–O–NH2. In contrast the O(3P) bombardment resulted in the removal of H, CH3, C2HO or OH− from the TMCTS molecule. In the amine terminated model OSG molecule, TMCTS-NH2, H and OH–groups were removed but the Si–NH2 bond remained stable over the energy range 0.1–5.0 eV for all but one of the directions investigated. Therefore, the Si–NH2 bond is shown to be significantly more stable than the Si–CH3 and is resistant to changes in bombardment angles and energies. The data explains recent experimental results demonstrating enhanced resistance of aminated OSG films to O2 plasma-induced carbon loss, and suggest that these methods can provide a predictive tool for understanding plasma damage in OSG films with both terminal and methyl carbon species.