Electron Phonon Coupling in Metallic Superlattices

Superlattices offer potential improvement in microelectronic transistor design as diffusion barriers between the silicon active layer and copper interconnects. While these materials provide a novel path forward in terms of electronic and atomic transport, more work must be done to understand potential thermal bottlenecks that could arise from their use in transistors. A major source of thermal buildup in microelectronic devices is the interaction between electrons and the surrounding atomic species in the form of electron-phonon coupling. In this project we explore the coupling between electrons and phonons as heat carriers in conductive multilayer superlattices of copper with tantalum, tungsten, and tantalum nitride. We use time domain thermoreflectance measurements and the two temperature thermal model to better understand the relationship between the electron phonon coupling in these materials and the physical parameters of the system. A greater understanding of this relationship will allow for greater control of the thermal properties of transistors, hopefully leading to increased thermal efficiency in microelectronics.