During its annual Imec Technology Forum USA (ITFUSA) at SEMICON West 2018 in San Francisco, Imec announced a breakthrough on the potential use of ruthenium (Ru) as a disruptive interconnect material for 3 nm and beyond technology nodes.
Using two different implementations as a proof of concept, Imec researchers used high-aspect-ratio Ru lines in buried power rail applications, and as interconnects for advanced memory and logic applications. In both scenarios, Ru wires outperformed conventional copper (Cu) metallization
(Left) Subtractive etch of Ru: At 12 nm CD high aspect ratio of 3 and 5 meet resistance targets. (Right) Buried Ru rails: After high T anneal significant resistivity decrease was demonstrated. Source: Imec
“Due to an increasing resistance-capacitance delay and rising reliability concerns, the use of dual-damascene Cu as a process flow for back-end-of-line interconnect fabrication has become questionable beyond the 5nm technology node. To maintain the scaling paths, imec has therefore been pioneering and pipelining the potential replacement of this conventional Cu technology. Interconnects based on Ru are a promising candidate, because of their resistance to oxidation, high melting point, low bulk resistivity, and the ability to build barrier-less interconnect modules,” says Zsolt Tokei, distinguished member of the technical staff at Imec. “For more than five years, imec has been systematically investigated this disruptive alternative, from the fundamentals to module level implementation. The results have recently come to the point of strong industrial interest,” he adds.
Besides Ru, other pure metals, as well as graphene, binary and ternary compounds were found to potentially provide a long-term material pipeline for interconnects.
