Research Projects

Thin metallic films of Cu, Ni, Ag, Au, Sn, and W deposited on Si substrates are a crucial component of modern microelectronic devices and enable the revolution in information technology. However, the underlying plastic deformation mechanisms in thin films are not fully understood due to a complex interplay between microstructure, micro-mechanics, and thin film processing routes. Despite numerous investigations, there is a large discrepancy between model predictions and experiments. Balk et al. observed that flow stress increased with a decrease in film thickness, but below a critical film thickness of ~400nm, flow stress reached a plateau. A constrained diffusion creep model was proposed to explain lower flow stress in unpassivated Cu thin films, but predictions based on the diffusional and thermally activated dislocation glide model do not agree with the experiments. Some studies highlight the importance of Coble creep in thin films, even at room temperature. The effect of grain size on creep behavior is not well studied due to difficulty in controlling grain size independent of film thickness. This study aims to understand this knowledge gap using novel sample processing and real-time stress measurement during in-situ annealing. A combination of experimental stress measurements and constitutive modeling will help develop deformation mechanism maps for thin films.