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Transistors a Thousand Times Faster

Towards Terahertz Electronic Components

The goal of the European project Nanotera1, a collaboration among the Institute of Electronics, Microelectronics and Nanotechnology (IEMN)2,the Catholic University of Louvain (Belgium), and the University of Salamanca in Spain, is in one sense simple: multiply the frequency of electronic components by a factor of a thousand. The project's chosen strategy for reaching frequencies of a terahertz (1012Hz) is first to master ballistic nanodevices for semiconductors, in hopes later on of taking some big steps forward in wide-band networks and mobile telephones.

Vue 3D


3D view of a T-shaped ballistic nanodevice

Microprocessor clock rates have increased at a dizzying rate in recent years. Still, at several gigahertz, they are a hundred thousand times slower than the frequency at which optic technologies turn. As a first stage in getting electronic devices back into the race with optical ones, researchers in the project Nanotera, led by the IEMN, are working to develop components capable of operating at a frequency of one terahertz (1012 Hz or 1,000 gigahertz).

“One of the first benefits to be reaped by making this leap will be fibre optic transmission at 160 gigabits per second instead of current rates of 40”, explains Alain Cappy, director of IEMN and coordinator of the project. The signal passing through a fibre optic cable is considerably slowed down by the various switches and electronic amplifiers which line its path. Another winner would be the portable telephone user, whose phone would be considerably simplified by not having to shift frequencies from component to component.

Vue au microscope


An electron microscopy image of a Y-shaped ballistic nanodevice

Ballistic nanodevices for semi-conductors are the cornerstone of the much faster components Nanotera scientists hope to build. In these devices, electrons encounter no obstacle and are simply accelerated by the electric field. “It's as if the electrons are particles” says Alain Cappy, “following a straight-line trajectory.” In a conventional semiconductor, on the other hand, electrons are subject to electromagnetic interactions which make for an erratic and therefore slower course.

The hitch is that electrons only have ballistic properties over very short distances, a few nanometers, while current photolithographic techniques for printing circuits is obviously limited to distances greater than the wavelength of the radiation used in the process. The IEMN recently acquired a latest generation LEICA e-beam lithography system which by replacing light beams with electrons is able to carve details down to ten nanometers.

Using this tool, the team has produced a first batch of a hundred components of different sorts. Tiny T- and Y-shaped components like these will serve to build the transistors and other devices that have yet to be designed. If the three-year project goes according to schedule, the end of 2004 will see the first terahertz components shipped to the electronics industry.




Alain Cappy
Institut d'électronique et de microélectronique du Nord (IEMN)

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