The standard technique for tracing circuits onto silicon chips is hitting its physical limits.

Computer chips of the future could be printed, just like books or banknotes. A new laser-stamping technique could one day produce computer chips smaller, faster and more cheaply than today's chemical-etching technology.

Since 1965, the number of transistors on a chip have, as Gordon Moore predicted¹, doubled every 18 months. Now photolithography, the standard technique for tracing circuits onto silicon chips, is hitting its physical limits.

A totally new approach to chip making could put the industry back on track. "Plain old mechanical printing may be the solution," says Fabian Pease, an electrical engineer at Stanford University in California.

With a transparent quartz die and a laser pulse, Stephen Chou and colleagues at Princeton University in New Jersey imprint features only 10 millionths of a millimeter (10 nanometers) wide onto a silicon wafer¹. The best photolithography can reproduce features about 130 nanometers wide.

When the laser light is fired into the die butted against the silicon wafer, it liquefies the surface of the silicon for a fraction of a second and the dies sinks in. The die is then pulled away. The whole process takes just 250 nanoseconds - nearly a million times faster than the blink of an eye.

"According to Moore's law we are taking things 20 years ahead of the current technology," says Chou, who derived the technique from a similar, larger-scale method used to print compact discs. With resolution this high it should, in principle, be possible to cram 100 times more transistors on a chip, he explains.

Chou's technique could work out far cheaper than photolithograpy. It takes fewer steps and the equipment should cost less, he says. Whether it will replace photolithograpy anytime soon remains to be seen.

The team has printed details onto silicon and its relative, polysilicon - both crucial chip components. But there are many other compounds sandwiched into integrated circuits, which must also be patterned in the minutest detail, Pease points out.

If not laser stamping, then some form of chip-printing technology will be the future manufacturing standard says Pease. "It gives an unsurpassed combination of speed and resolution and isn't limited by physical laws." 

California

• References

  1. Moore, G.E.Cramming more components onto integrated circuits. Electronics 38, 114 - 117 (1965).
  2. Chou, S. Y., Keimel, C. & Gu, J. Ultrafast and direct imprint of nanostructures in silicon. Nature 417, 835 - 837 (2002). | Article | ISI | ChemPort |