Graphene-copper sandwich to shrink electronics

A graphene-copper-graphene ‘sandwich’ strongly enhances the heat-conducting properties of copper and could further help in the downscaling of electronics.

University of California researchers found that adding a layer of graphene, a one-atom thick material with highly desirable electrical, thermal and mechanical properties, on each side of a copper film increased heat-conducting properties up to 24%.

“This enhancement of copper’s ability to conduct heat could become important in the development of hybrid copper-graphene interconnects for electronic chips that continue to get smaller and smaller,” said Alexander A Balandin, a professor of electrical engineering at the Bourns College of Engineering at the University of California, Riverside. The project was led by Balandin and Konstantin S Novoselov, a professor of physics at the University of Manchester in the United Kingdom.

Whether the heat-conducting properties of copper would improve by layering it with graphene is an important question because copper is the material used for semiconductor interconnects in modern computer chips. Copper replaced aluminium because of its better electrical conductivity.

Downscaling the size of transistors and interconnects and increasing the number of transistors on computer chips has put an enormous strain on copper’s interconnect performance, to the point where there is little room for further improvement. For that reason there is a strong motivation to develop hybrid interconnect structures that can better conduct electrical current and heat.

After examining the grain sizes in copper before and after adding graphene, the researcher found that chemical vapour deposition of graphene conducted at high temperature stimulates grain size growth in copper films. The larger grain sizes in copper coated with graphene results in better heat conduction.

Additionally, the researchers found that the heat conduction improvement from adding graphene was more pronounced in thinner copper films. This is significant because the enhancement should further improve as future copper interconnects scale down to the nanometres range, which is 1/1000th of the micrometre range.

The work at UC Riverside on this project was supported by the National Science Foundation and by STARnet Center for Function Accelerated nanoMaterial Engineering (FAME), a Semiconductor Research Corporation (SRC) program sponsored by Microelectronics Advanced Research Corporation (MARCO) and Defense Advanced Research Projects Agency (DARPA).