Carbon Nanotube Transistors to Break 10nm LevelLigo George
It is extremely challenging to scale bulk silicon transistors, when the lengths are close to 15nm. 3D Transistor design and Silicon-On-Insulator (SOI) devices are getting more attention to improve the scalability of silicon technology. Carbon Nanotube Transistors have been treated as a possible replacement for silicon transistors, but the question is that, ‘Can CNT transistors can offer better performance over silicon at sub-10 nm lengths?’. Now the experimental results from IBM Research are indicating that the answer is ‘Yes’.
There are various opinions in the nanoelectronics community about Carbon Nano Tube transistors, that they can able to maintain their impressive performance at extremely scaled levels.Some peoples says that the very low effective mass of the carriers will cause tunnelling and breakdown the device around 15nm, this opinion was supported by some theoretical studies. While others remain convinced that the the ultra thin body of single walled Carbon Nano Tubes would allow excellent transistor behaviour even down to 10nm range.
The above picture show the schematics of a sub 10nm Carbon Nanotube Transistor. Although CNT transistors were treated as a best replacement for silicon technology, there is only limited theoretical work and no experimental reports on how CNT will perform in sub 10nm levels. The findings by a team of IBM researchers, scientists from ETH Zurich’s Integrated Systems Laboratory and Purdue University says that CNT can replace silicon effectively. To observe the behaviour of transistor in different scaling, they fabricated several devices with different channel lengths ( between 320nm and 9nm ) on the same CNT. They use same nanotube for all channel lengths because the energy band gap for a CNT is inversely proportional to the diameter, thus a small change in band gap will affect in performance. They found that the previous theory was not accurate for these devices and are due to lack of complete understanding about the transport of carriers.
The 10nm scaled CNT transistor provides low voltage operation that is superior to any other scaled devices and have superb switching behavior in the off-state and clear current saturation at a low drain-source bias of approximately 250 mV in the on-state.
These results of the research will trigger more and more researches about CNT transistors and the main challenge to this was funding. We can hope that these positive results will inspire funding agencies to give funds and makes this technology into a reality.