006_EETE

EETE SEPTEMBER 2012

NEWS & TECHNOLOGY Investigating nano-electro-mechanical relay-based computing By Julien Happich A consortium led by iBm has been awarded €2.44m by the realised with platinum silicide and gold. european commission to investigate nano-electro-mechanical so far, several functioning microscale switches have been relay based computing for ultra-low power computing appli- demonstrated with various footprints, showing “on” resistances cations. the goal within the nemiAc project (nano-electro- in the order of 5kohm. the target within the project is to achieve mechanical integration And computation) is to build the world’s a device footprint of 3μm×3μm, a mechanical latency of 50ns first ever miniaturised electro-mechanical relay based proces- with an operating voltage of 5V, and a reliability of 10 billion sor. switching cycles. nano-electro-mechanical (nem) relays have practically zero leakage, an abrupt turn-on transient and a high on-current, and using this 3-terminal relay as a primitive, digital logic can can also be integrated with cmos at the die or wafer level. this makes them prom- ising candidates for digital logic imple- mentation in ultra-low power applications, explains dinesh Pamunuwa, lecturer in nanotechnology in the engineering department of the lancaster university and also in charge of the project’s com- munication. “Building a functioning nem relay based processor, one would go the full circle, effectively using electro-mechanical switches as the basic building block some 200 years after Babbage proposed his original fully mechanical calculator contin- ues Pamunuwa. several research initiatives have been pursuing nem relay based logic, and many innovative relay architectures have been proposed that realise logic function- ality in widely different ways, ranging from combining a basic 3-terminal switching SEM image of a 15.5-μm-long curved cantilever switch. element in the manner of mosFets to multi-terminal relays and multiple-valued logic implementations. be realised by adopting a complementary style approach, with pull-up and pull-down networks connecting the output to Vdd However the main stumbling block in this technology is or ground. Both networks are required as the relay can only be limited switching cycles due to contact material failure. stic- configured to pass a ‘0’ or ‘1’ depending on whether the com- tion caused by surface forces, and material transfer is the main mon source terminal (beam) is grounded or connected to Vdd, cause. the relay architecture is also key in ensuring structural as nem relays are ambipolar, and the actuation depends on the reliability and ensuring scalability. nem relays that operate on voltage difference between the gate and beam. multiple voltage levels to realise complex logic functionality, require multiple contacts to be made and have complex timing A design library of combinational and sequential gates will sequences are generally not conducive to manufacturability and be constructed using circuit architectures that are tailored to repeatability. the nem relay characteristics. For example, one way to take the approach to be explored within nemiAc - www.nemiac. advantage of the ohmic contact and relatively low output im- eu - is based on an in-plane curved cantilever architecture pro- pedance is to have a higher fan-out than would be possible with posed by IBM that optimises the electrostatic field distribution minimum-sized CMOS devices. The intended final demonstrator and beam stiffness and allows miniaturisation. is a 4-bit microprocessor with a reliability of 1 million switching the inclined cantilever design also prevents the beam land- cycles. ing on the gate due to the different angles of motion of the drain researchers from several universities and labs are taking electrode and the beam. the relay is fabricated using a sacri- part in this project, including from the university of Bristol and ficial layer, which ensures precise control of the air gap, with the university of lancaster (uK), from iBm research in Zurich uniformity throughout the length of the beam. and from the nanoelectronic device laboratory (nanolab) of it also makes possible air gaps smaller than the lithographi- École Polytechnique Fédérale de lausanne (switzerland), from cally defined limit, which in turn allows precise control of the st microelectronics in Agrate (italy), and from the KtH royal electric fields and reduced footprints. In this case, the contact is institute of technology, stockholm (sweden). 6 Electronic Engineering Times Europe September 2012 www.electronics-eetimes.com


EETE SEPTEMBER 2012
To see the actual publication please follow the link above