Researchers from the University of California at Berkeley and Intel claim to have made a breakthrough in the cooling of microchips, using a combination of carbon nanotubes and organic molecules to create a highly efficient connection between a chip and its heatsink.
Research carried out by Intel and Berkeley scientists has developed a means of adhering carbon nanotubes to metal, promising a major improvement in cooling efficiency for future semiconductors.
Dealing with heat is a serious issue facing the semiconductor industry. As chips get faster and smaller, you find yourself having to sink large amounts of heat from ever-shrinking components. Previous research had suggested that carbon nanotubes could work as a highly efficient conduit for this heat, but the challenge lay in finding a method for getting the heat across to the nanotubes in the first place.
'The thermal conductivity of carbon nanotubes exceeds that of diamond or any other natural material but because carbon nanotubes are so chemically stable, their chemical interactions with most other materials are relatively weak, which makes for high thermal interface resistance,
' explained Frank Ogletree, a physicist at Berkeley Lab's Materials Sciences Division and leader of the study - meaning where the highly-efficient nanotubes meet the device to be cooled is unfortunately inefficient. 'Intel came to the Molecular Foundry wanting to improve the performance of carbon nanotubes in devices. Working with Nachiket Raravikar and Ravi Prasher, who were both Intel engineers when the project was initiated, we were able to increase and strengthen the contact between carbon nanotubes and the surfaces of other materials. This reduces thermal resistance and substantially improves heat transport efficiency.
The new method works by using organic molecules to form strong covalent bonds between the carbon nanotubes and metal surfaces - the molecular equivalent of using thermal paste between a heatsink and a processor - and has impressive results: compared to previous methods, the new system allows for a six-fold increase in heat flow from the metal to the nanotubes. As an added bonus, the method uses nothing more than gas vapour or low-temperature liquid chemistry - meaning it can easily be integrated into the production process of modern chips.
Despite this, the team hasn't finished: in testing, the process was found to connect only a small portion of the nanotubes to the metal surface; in future, it's hoped that the density of contacts can be improved to further boost the efficiency of heat transfer.
The team's work is to be published in the journal Nature Communications
. Thus far, Intel has not indicated whether it plans to commercialise the technology in the near future.