An atomistic simulator for thin film deposition in three dimensions

We describe an atomistic simulator for thin film deposition in three dimensions (ADEPT). The simulator is designed to bridge the atomic and mesoscopic length scales by using efficient algorithms, including an option to speed up surface diffusion using events with multiple diffusion hops. Sputtered particles are inserted and assigned ballistic trajectories with angular distributions appropriate for magnetron sputtering. Atoms on the surface of the film execute surface diffusion hops with rates that depend on the local configuration, and are consistent with microscopic reversibility. The potential energies are chosen to match information obtained from a database of first principles and molecular dynamics (MD) calculations. Efficient computation is accomplished by selecting atoms with probabilities that are proportional to their hop rates. A first implementation of grain boundary effects is accomplished by including an orientation variable with each occupied site. Energies and mobilities are assigned to atoms in grain boundaries using values obtained from MD. In this article we describe simulations of the deposition of aluminum. The film atoms occupy face centered cubic lattice sites of a single crystal. Three-dimensional films deposited on vias and trenches up to 0.05 mm in size have been simulated. We discuss these films in the context of step coverage issues, and scaling to macroscopic sizes. Texture development is discussed in the light of simulations showing anisotropic crystal growth. Future versions of ADEPT will include a more complete model of grain development in thin films. [S0021-8979(98)04118- 8].