Atomistic simulation of Cu-Ta thin film deposition and other phenomena

Tantalum (Ta) is a metal with good properties to act as a diffusion barrier material in computer chips, where it should prevent the mixing of Cu into Si and SiO. The deposition of thin Cu films onto various Ta substrates has been studied through molecular dynamics simulations, using either empirical EAM potentials or Density Functional Theory (DFT). The influence of the crystal structure, orientation, surface roughness, and temperature of the Ta substrate on the development of the Cu microstructure has been investigated. One of the Ta crystal structures, the complex b-Ta structure with its five inequivalent atomic positions, has also been investigated in detail. DFT calculations are widely applicable and have been applied to three subjects other than Cu/Ta modeling: 1) investigating if the interaction between N interstitials and separate alloy atoms in steels can explain the discrepancy between results of a model by Sun and Bell and experimental data (this turned out not to be the case). 2) investigating if there is an energetic driving force for trapping alloy atoms in Al in interstitial configurations (this did turn out to be the case, trapping energies can be as high as 2 eV). 3) creating a database of energies of Si structures for fitting empirical Si potential parameters.Applied Science