Erbium implants improve chips

A method that more efficiently lets silicon emit light could help create a new generation of computer processors and faster telecommunications.

Manchester University researchers and Qinetiq are working on a technique that uses ion beams to implant rare earth atoms, known as erbium, into silicon.

These atoms let silicon emit light, which it cannot do naturally, and open up the possibility to develop computer chips that transmit information by light instead of electrical signals.

'It would increase the rate of transferred information by a magnitude and enable chips to keep up with Moore's law,' said physicist Matthew Halsall, the principal investigator of the Manchester research team.

Chip makers and research teams around the world have demonstrated a similar ability over the last decade to implant rare earth atoms into silicon using ion beams. What makes Halsall's method different is the ability to reduce the amount rare earth atoms cluster in the silicon.

'We believe our process prevents or reduces clustering so we can get more rare earth in the silicon,' he explained. 'We believe silicon with more rare earth will last longer.' Halsall said the use of rare earth atoms for lighting is well tested.

'People have used rare earth atoms in oxides in insulators for things like fluorescent displays and laser amplifiers, which are now common technologies,' he added. 'We're now trying to apply that technology to a different field and miniaturise it onto silicon.'

Others working on light-emitting silicon have avoided the use of rare earth material. Surrey University spin-out Si-Light Technologies, for example, believes the natural defects of silicon can be manipulated to emit light and make efficient LEDs.

'The defect engineering LEDs work well at reduced temperatures but don't have the efficiency at high temperatures,' claimed Halsall.

He explained that only the rare earth approach ensures the light emitted from the silicon is the wavelength needed for current telecommunications.

'With defect engineering, the emission is not at 1.5 microns. The rare earth approach makes things easier when you're trying to integrate it into existing technologies.'

There have already been developments in light-emitting silicon technology, but Halsall said no company has successfully rolled out the technology on a mass scale.

Halsall's team at Manchester University hopes to commercialise its light-emitting silicon-making process through a spin-out company in the next few years.

Qinetiq's electronic-materials processing division is helping the researchers develop the technique for mass production. Halsall said Qinetiq is likely to attain intellectual property related to these processes and later market it to industry.

'We are restricting ourselves to processes one would find inside a standard silicon foundry,' he said.

Halsall said an ion beam system for implanting rare earth atoms into silicon can be easily integrated into current chip manufacturing processes. The researchers, however, are still deciding at what stage of silicon-chip fabrication to include the implantation process.

Siobhan Wagner