Epitaxial Ru Nanowire\non Single-Crystalline Graphene\nfor Advanced Interconnect Application

In\nthis work, we study epitaxial Ru metallic nanowire on graphene\nas a model material for future interconnect applications. We first\ngrew epitaxial Ru ultrathin film on single-crystalline, monolayer\ngraphene on SiO<sub>2</sub> substrate. We demonstrated fabrication\nof epitaxial Ru nanowires on graphene using high-resolution H-SiQ\nebeam lithography and reaction ion etching techniques. The epitaxial\nRu nanowires were prepared using O<sub>2</sub>/Cl<sub>2</sub> dry\netching chemistry with ebeam patterned H-SiQ as the etching mask on\npregrown Ru thin film. We created epitaxial Ru nanowires with a line\nheight down to 7 nm and a line width down to 26 nm. Electron backscatter\ndiffraction characterization confirms that the epitaxial Ru nanowires\nmaintain a single-crystalline structure. Focused ion beam milling\nreveals the rectangular shape of the nanowire cross sections. We measured\nthe electrical resistivity of Ru nanowires fabricated on both graphene\nand bare SiO<sub>2</sub> substrates with line widths ranging from\n∼26 nm to ∼200 nm and line height ranging from ∼7\nnm to ∼19 nm. We confirmed that epitaxial Ru nanowires grown\non graphene have significantly lower resistivity (∼13% to ∼38%\nreductions) than polycrystalline Ru nanowires grown on bare SiO<sub>2</sub> substrate with similar cross-section areas which is due to\nbetter crystalline quality and reduced electron grain boundary scattering.