Graphene could out-perform copper as on-chip interconnects, claims the Georgia Institute of Technology.
"As you make copper interconnects narrower and narrower, the resistivity increases as the true nanoscale properties of the material become apparent," said Georgia research engineer Raghunath Murali. "Our experimental demonstration of graphene nanowire interconnects on the scale of 20nm shows that their performance is comparable to even the most optimistic projections for copper interconnects. Under real-world conditions, our graphene interconnects probably already out-perform copper at this scale."
Murali explained the problem with copper: "Resistivity is normally a property inherent to the material and independent of the dimension. But as you get into the nanometre-scale domain, the grain size of the copper become important and conductance is affected by scattering at grain boundaries and at the side walls. These add up to increased resistivity, which nearly doubles as the interconnect sizes shrink to 30 nanometres."
Beyond resistivity, said the university, graphene interconnects would offer higher electron mobility, better thermal conductivity, higher mechanical strength and reduced capacitance between adjacent wires.
Murali and collaborators used graphene flaked from graphite - the highest performance form of graphene available.
They patterned it to form parallel ribbons from 18 to 52nm wide, each with four contacts.
Nothing was done to enhance conductivity.
"Even graphene samples of moderate quality show excellent properties," said Murali. "We are not using very high levels of optimisation or especially clean processes. With our straightforward processing, we are getting graphene interconnects that are essentially comparable to copper. If we do this more optimally, the performance should surpass copper."
See the three pictures below:
Fig. 1 Raghunath Murali (left) and graduate student Kevin Brenner are shown with a test station used to study the properties of graphene
Fig 2. A graphene material sample that was tested for its properties is shown against an image in a test station.
Fig 3. This scanning electron microscope image shows graphene nanoribbons that are 22 nanometres wide between the middle electrode pair.
