Low Resistivity Tungsten and Ruthenium through Textural Control Using Ion Beam Deposition

Low resistivity metal wiring and interconnects are increasingly challenged by size-dependent effects with downscaling for the next generation back end of line (BEOL) requirements. Ruthenium is considered a strong candidate although it has challenges. However, tungsten wiring is well established, widely used in DRAM, and is relatively easier to integrate. We demonstrate the novel use of ion beam deposition (IBD) to control the microstructural features, such as phase, texture, and grain size distribution of W and Ru thin films. Using IBD to drive highly selective microstructures, we have demonstrated low resistivities of <11 μΩ-cm for <20nm thick as-deposited (0001) oriented Ru and <9 μΩ-cm for <20nm thick as-deposited (110) oriented α-W. IBD deposition of W yielding epitaxial-like textured α-110 thin films was identified as showing favorable resistivity scaling. We propose the IBD of highly oriented (110) α-W as a lower cost, easily integrable solution for next generation wiring.