Reporter 447, 21 February 2000

Crystal clear way to the self-assembly 3D computer chip

The computer truly came of age in the 1990s but the next decade could see progress grind to a halt. The trusty silicon chip can only handle so much information and the race is on to develop an alternative for the new generation of 'supercomputers'. Like the Manhattan developers who reached for the sky in the face of spiralling land costs, university chemists believe the answer could lie in the third dimension...

The future in a test tube: Professor Richard Bushby’s work could eventually revolutionise the way computer chips are produced.

The circuits printed onto silicon chips at the heart of computers drive everything from video recorders to satellites. The more elements that can be squeezed onto each chip, the smaller, the faster and more powerful computers become. Space on the chips is limited, however, and no matter how many extra circuits the engineers try to cram in, there is a brick wall ahead.

Into the third dimension: Prof Bushby with photographic images of a liquid crystal sample

Stacking the silicon chips on top of each other could boost computing power a thousand-fold but wiring a pile of chips together is a real problem. Conventional wires would be far too small to be manipulated into the precise positions needed to join up the relevant components.

University chemistry researchers are launching a project that could complete a world-first and connect microchips in 3D. Instead of pre-fabricating wires and carefully placing them into position they plan to ‘grow’ the connections from one layer to another like high-tech artificial ivy.

We now have the molecular machinery, said researcher Richard Bushby, to bring about a revolution in super-computing.

The research team has perfected a method for placing layers of unique conductive molecules between the computer chips. The molecules naturally form thin wiry strands, which researchers will use to bring the chips into electrical contact; thus creating the world’s first true 3D computer circuit.

Close examination: PhD student Owen Lozman views liquid crystal samples through a polarising microscope

Molecules that ‘magically’ form themselves into wires may sound fantastic but such self-assembly happens all the time in nature. Membranes in living cells, for example, are made up of molecules that were previously floating around in water, but ‘knew’ to form together into layers, just as a child’s brain develops its own inter-connecting wires - the neural networks.

How this self-assembly happens is now understood and researchers in the SOMS (Self-Organising Molecular Systems) Centre are beginning to design molecules that can copy it.

The disc-shaped liquid crystals created and patented by Professor Bushby and Professor Neville Boden form themselves into stacks like piles of dinner plates. Each plate has a central core made of conducting carbon surrounded by a rim of insulating hydrocarbon assembling into perfect molecular wires.

"We’re confident we can use the wires to join up the chip circuitry vertically, which has never been done before," said Professor Bushby. This will pave the way for a new generation of computers

The research is being carried out jointly with University College London, the University of Strathclyde and universities in France and the Netherlands, through a £1.5m award from the Fifth Framework programme.

The team will initially assess the electrical properties and reliability of four different molecular wire technologies, together with how closely spaced the layers need to be to enable information to be passed between them.

The researchers are targeting a developmental system that will emulate the three-dimensional structure and function of the human retina and visual cortex. "The system we are aiming for will incorporate, for the first time, high image resolution, computer power and fault-tolerance in a small package," said Professor Bushby.

"The kind of molecular computing technologies currently being researched are likely to be limited to two dimensions and to be very error prone. Our project concentrates on one highly innovative way to harness the possibilities of the third dimension."

The University researchers are now just a few months into their three-year project, and Prof Bushby points out their work is "still at the futuristic stage."

It will be around a decade until the 3D microchips find their way onto the market.

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