Molecular dynamics simulations of Ar~(+)-induced transport of fluorine through fluorocarbon films

摘要

Recent experimental studies of fluorocarbon (FC) plasmas etching various substrates suggest that ions will transport initially bound fluorine (F) through overlying FC films, thereby defluorinating these films and inducing fluorination reaction with the underlying substrate material. Simulations of thermal CF_(2) on Si with simultaneous bombardment by energetic Ar~(+) demonstrate this defluorination phenomenon, showing that F is separated from adsorbed CF_(2) and mixed into the underlying Si, initiating etching. Additionally, this creates dangling bonds on the surface where CF_(2) may adsorb. Thus, our simulations show that F and C uptake is enhanced by energetic rare gas ion impact, the number of Si-F bonds is greatly increased, and the resultant Si etch rate is higher than expected from physical sputtering alone. The results are compared to experimental measurements made under similar conditions, and the mechanisms of ion-induced F transport are identified.