At its annual Imec Technology Forum USA in San Francisco, imec reports on the potential of using ruthenium (Ru) as a disruptive interconnect material for 3nm and beyond technology nodes.
 
High-aspect ratio Ru lines were shown to outperform conventional Cu metallization in two different implementation scenarios, i.e., (1) in buried power rail applications, and (2) as interconnects for advanced memory and logic applications by using subtractive metal etch. 
 
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 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.
 
“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,” said Zsolt Tokei, distinguished member of the technical staff at imec.
 
“Our work proves that subtractive metal etch – which was used in the past for integrating Al interconnects – can be a valid alternative to the damascene implementation of Ru,” Tokei added. “The integration scheme has a strong downscaling potential, and can be considered for advanced memory and logic applications.”
 
Besides Ru, other pure metals, as well as graphene, binary and ternary compounds were found to potentially provide long-term material pipeline for interconnects.