Decreasing linewidth in electronics packages leads to structures that haven to be described atomistically. Currently copper is among the most interesting materials in electronics due to its electrical and thermal properties. We have developed interatomic potentials to model interfaces in copper metallization. Currently an embedded-atom method potential for a Cu-Ta system and a modified embedded-atom method potential for a Ta-Si system are available. We have used the molecular dynamics method with these potentials to study the energy and microstructure. of several low-index Cu-Ta and Ta-Si interfaces. Yield stress of the Cu-Ta system is correlated with the energy of the interface. In addition, more realistic Cu-Ta interfaces are generated by depositing copper atoms on, a tantalum surface and tantalum atoms on copper surfaces. Tantalum atoms are seen to mix on copper surfaces, while copper atoms stay on tantalum surfaces. We discuss this with bonding energy arguments.