Graphene, the one-atom-thick gauze of carbon atoms resembling chicken wire first isolated in 2004, continues to find new and wondrous applications. It has already been used to create the world’s smallest transistor and now researchers at the Georgia Institute of Technology have experimentally demonstrated the potential for graphene to replace copper for interconnects in future generations of integrated circuits.
Interconnects are tiny wires that are used to connect transistors and other devices on integrated circuits. As copper interconnects are made narrower and narrower, their resistivity increases – nearly doubling as the interconnect sizes shrink to 30 nanometers. Interconnects at a scale of 20 nanometers could happen in the next five years, but since the increased resistance of copper interconnects at that scale could offset performance increases, higher density wouldn’t produce faster integrated circuits without other improvements.
The Georgia Tech team’s experiments demonstrated that the performance of graphene nanowire interconnects on the scale of 20 nanometers is comparable to even the most optimistic projections for copper interconnects at that scale. And because the comparisons were between non-optimized graphene and optimistic estimates for copper, the results suggest that performance of the new material will ultimately surpass that of the traditional interconnect material.
“Under real-world conditions, our graphene interconnects probably already out-perform copper at this size scale,” says Raghunath Murali, a research engineer in Georgia Tech’s Microelectronics Research Center and the School of Electrical and Computer Engineering.
Beyond resistivity improvement, graphene interconnects would offer higher electron mobility, better thermal conductivity, higher mechanical strength and reduced capacitance coupling between adjacent wires.
Because graphene can be patterned using conventional microelectronics processes, the transition from copper could be made without integrating a new manufacturing technique into circuit fabrication.
“We are optimistic about being able to use graphene in manufactured systems because researchers can already grow layers of it in the lab,” Murali noted. “There will be challenges in integrating graphene with silicon, but those will be overcome. Except for using a different material, everything we would need to produce graphene interconnects is already well known and established.”
This means that replacing copper interconnects with graphene could help extend the long run of performance improvements for silicon-based integrated circuit technology to keep apace with Moore’s Law.
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