Ion Beam Deposition of Ruthenium for Interconnect Applications in a Direct Metal Etch Approach

Metals like ruthenium with low bulk resistivity and electronic mean free path are the most promising candidates for post-copper interconnects. Ion beam deposition has the highest sputter energy and simultaneously fine-control of deposition energetics that enables metal thin films with ideal microstructures–large grains and preferred orientations. Ruthenium thin films deposited by ion beam deposition on 300mm wafers show large grained fully (0001) aligned microstructures presaging low-resistivity. Ion beam deposition achieves lower resistivity compared to approaches using conventional deposition and optimized annealing. Patterning of the IBD Ru films was accomplished using a direct metal approach to form metal lines of 9nm CD (nominal) and metal pitch (MP) 18nm-26nm. Electrical testing of the IBD Ru lines shows tighter line distribution and twelve percent lower line resistivity at same cross-sectional area, compared with wires made by a conventional plasma vapor deposition approach. These results establish the combination of ion beam deposition and semi-damascene direct metal etch as a very promising approach towards low-resistivity interconnects for the next generation of integrated devices.