Microstructural Optimization of Tungsten for Low Resistivity Using Ion Beam Deposition

As feature sizes shrink with each integration node, wire and interconnect resistivity in the back end of the line increasingly becomes a challenge due to size dependent effects. Microstructural control of metal thin films is critical for accessing the lowest resistivities alongside materials choice. In this paper, we describe depositing a metal material onto a substrate via ion beam deposition with assist in a process chamber at a temperature of at least 250°C to produce ultra-low resistivity metal films. Ion beam deposited thin tungsten films were grown with large and highly oriented α(110) grains having a resistivity less than 9 μΩ-cm and thickness less than 300 Å, with no discernable β-phase, presaging benefits for memory and logic applications using tungsten for wiring.