Atomistic Models of Sputter Deposition: Application to Thin Films for Interconnects

Metal lines for electrical connections in Si devices are deposited in the form of blanket films of conducting metals, generally Al or Cu. These films are separated by insulating layers of materials such as SiO sub 2, and etched or polished back to provide the required connecting lines. Barrier layer films are deposited between the insulator and the conducting metal films to prevent in-diffusion or reaction between the metal and insulating layers, and ultimately to protect the electrically active Si regions. We discuss the application of atomistic modeling techniques to the sputter deposition of these films. Modeling based on Monte Carlo simulations is employed to predict film microstructure evolution, e.g., texture development, intergranular porosity, and grain size distributions. Molecular dynamics and first principles calculations provide atomic interaction energies, grain boundary properties, and diffusion barriers for use in the Monte Carlo model. These simulations encompass the wide range of materials properties and morphologies that are exhibited by these films, and facilitate the selection of processes that will optimize the film properties.