Abstract
Deposition and re-sputtering of Ni-Ti thin films by magnetron sputtering was simulated using a multi-scale modeling approach. The sputtering of Ni and Ti targets and the transport of sputtered Ni and Ti atoms through the background gas were simulated using a Monte-Carlo approach, while the deposition of the sputtered atom onto the film surface was analyzed using molecular dynamics. The interaction of Ar+ ions with the deposited film under the influence of substrate bias was also simulated using a Monte-Carlo approach. The distribution of sputtered atoms over the substrate and the fraction of total sputtered atoms from Ni and Ti targets that reached the substrate were calculated for an off centred target which made an angle of 30° with the substrate. The effects of target voltage and gas temperature on the distribution of sputtered atom over substrate were studied with the help of the aforesaid simulations. It was observed that with increasing target voltage, the fraction of sputtered atoms reaching the substrate was increased slightly for a pure Ni target, while it showed very little change for a pure Ti target. With increasing gas temperature, the value for the same decreased initially, but increased beyond a critical temperature. The velocities of incident Ni and Ti atoms on the substrate were calculated and it was found that no intrinsic re-sputtering could take place for a Ni0.5Ti0.5 thin film under the simulated conditions. The fraction of deposited atoms that were re-sputtered by Ar+ ions under varying substrate bias was also calculated and was found to increase substantially with the increase in the magnitude of the substrate bias voltage. Finally, the stability of crystalline and amorphous Ni and Ti were estimated on the basis of fraction of atoms re-sputtered using a classical molecular dynamics approach.