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

摘要

Ab initio molecular dynamics simulations based on density functional theory were used to probe the interactions of O(1~D) and O(3~P) radicals on trimethylcyclictrisiloxane (TMCTS) and aminated TMCTS (TMCTS-NH_2)-a model system for vicinal and aminated organosilicate glass (OSG) low-k dielectric materials. The roles of triplet, O(3~P), and singlet, O(1~D), interactions were investigated, as well as the directional and energetic dependence of the plasma on the product species. O(1~D) attack resulted in the development of complex bonding states including Si-CH_3O and Si-O-NH_2. In contrast the O(3~P) bombardment resulted in the removal of H, CH_3, C_2HO or OH~- from the TMCTS molecule. In the amine terminated model OSG molecule, TMCTS-NH_2, H and OH~- groups were removed but the Si-NH_2 bond remained stable over the energy range 0.1-5.0 eV for all but one of the directions investigated. Therefore, the Si-NH_2 bond is shown to be significantly more stable than the Si-CH_3 and is resistant to changes in bombardment angles and energies. The data explains recent experimental results demonstrating enhanced resistance of aminated OSG films to O_2 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.