Fujitsu to use carbon nanotubes as heatsinks for semiconductors

Tokyo (Japan) - Fujitsu today said that it has successfully developed carbon-nanotube-based heatsinks for semiconductors such as memory and microprocessors. According to the company, carbon nanotubes can effectively amplify signals and dissipate heat simultaneously.

Carbon nanotubes, pure carbon cylinders often only 2 nm in diameter, keep emerging as one of the most promising scaling technologies across the semiconductor industry. Considered to be a future replacement of today's transistor technology in devices such as memory cells and microprocessors, Fujitsu believes that carbon nanotubes (CNT) also hold the potential to become a new and more efficient resource for building heatsinks. According to the company, CNTs have not only shown unusual strong structures and electrical conductivity, but also thermal characteristics that are superior to the metals used today.

The company said that the challenges for new heatsink technologies have surfaced especially in mobile communications, where an increasing demand for higher power and higher frequencies in amplifiers in mobile phone base stations is apparent. "Because high power transistors, the output source for high-performance amplifiers, generate high levels of heat, heat dissipation is extremely important," Fujitsu stated. "Conventionally, heat was dissipated through the use of what is known as the 'face-up structure', in which a high power transistor chip would be connected directly dice-bonded to the package and the heat would escape through the chip."

At higher frequencies, amplifiers using the face-up structure suffer from reduced amplification, which results in inductance from the metal wire, through which the electrical current flows from the electrode of the transistor chip to the electrode of the package. According to Fujitsu, CNTs now have proven to be more efficient than conventional metal bumps as connectors between the chip electrode and the package electrode to dissipate heat generated by transistors.

The technology demonstrated today at the IEEE International Electron Devices Meeting (IEDM) in Washington, D.C. outlined a process to grow CNTs with a vertical length of 15 micrometers or more and connect them to Fujitsu's chip architecture. The company claims that the CNTs can reduce ground inductance by more than 50 percent - which then enables a substantial increase in performance and amplification - "at least 2 decibels at frequencies of 5 GHz or greater" - according to Fujitsu.