Chemicals on CDs may make for ultra-dense flash memory chips

London, July 17 : A California-based company has shown that the chemicals that allow CDs and DVDs to be rewritten by laser beams can pave the way for a future generation of ultra-dense flash memory chips, which can prevent data loss even when the power is turned off.

Greg Atwood and his colleagues at Numonyx-a spinoff from Intel-have revealed that flash memory is at the heart of most of today's popular gadgets like mobile phones, music players, and digital cameras that do not lose software, photos, texts, music, etc. even upon being switched off.

They say that flash memory does so by storing binary data in the form of electric charge in a capacitor/transistor combination.

The researchers say that most flash memory transistors these days are about 65 nanometres wide, with the next generation set for 45 nm.

"But serious issues will begin to arise when dimensions get below 20 nanometres due to the retention of electric charge in the flash transistor," New Scientist magazine quoted Atwood as warning.

The researchers say that once the flash memory transistors become 20 nanometres wide, their use would significantly reduce the number of times they can be written and erased.

Giving future flash a long lifetime and more storage capacity would require a new non-volatile storage mechanism, they add.

Numonyx experts say that, in a CD or DVD, heat from a laser beam is used to make a glassy coating of GST (an alloy of tellurium, antimony and germanium) switch between disordered and crystalline states.

They say that each state is set by the rate at which the laser allows the substance to cool, and that each state has a different reflectivity that allows it to store digital 0s and 1s in an easily readable way.

The researchers say that changes to the material's state and reflectivity can be created through electrical heating as well as laser light, and that GST can be read using electricity too, because each state has unique resistance.

Utilising these properties, the researchers have created a new microchip memory cell wherein blob of GST sits atop a simple resistor.

Different current pulses applied to the resistor heat the blob and change its state, and a second, much lower (non-heating) current can sense the blob's resistance.

The Phase Change Memory (PCM) appears to work reliably, say the researchers.

Numonyx, which has built a 128-megabit flash memory, is presently allowing unnamed gadget makers to assess its potential.

Atwood is upbeat that it is the answer to making ever-denser flash.

"We believe PCM offers new scaling possibilities. You can change and stably hold the phase states in GST cell sizes down to 5 nanometres and below," he says.

He has even revealed that it can be written to at least one million times.

Malcolm Penn, an analyst with Future Horizons, a UK-based microchip market researcher, says Numonyx will have its work cut out proving PCM's viability.

"We don't see the classic field-effect transistor running out of steam for at least 10 years. While it's true that some materials are misbehaving, new materials are always coming along to fix things," he says. "It's going to be cost, not technology, that will be the driving factor. That's the bottom line Numonyx has to address."

A report on the new study has been published in the journal Science.

ANI