Intel and ST start phase-change trials

It's a memory technology that has taken 30 years to get off the round and it is still not ready to go on the open market. But Intel and STMicroelectronics have reached the point where they can start sending to customers early samples of phase-change memory (PCM) parts.

Intel and ST claimed their new memory, a 128Mb device tagged 'Alverstone' first described at the VLSI Technology Symposium in the summer of 2006, provides fast read and write speeds at lower power than conventional flash and allows for individual bits to be altered, unlike flash which demands that entire blocks of memory be written in one go.

Alverstone is a 128Mb device built on 90nm and is intended to let customers making cellphones and other embedded portable devices evaluate PCM features. With a cell size, the PCM memory is slightly less dense than a NOR flash memory built on an equivalent process: pointing to a die size of around 35mm2. However, ST is now making NOR flash parts on the more advanced 65nm process which cuts the die size further and they support multi-level cell operation.

At this week's International Solid States Circuits Conference (ISSCC), the companies described the first demonstrable high-density, multi-level cell (MLC) large memory device using PCM technology, potentially doubling the capacity per memory cell.

The technology devised for Alverstone is primarily for standalone use as the process steps are very different to those used to make regular CMOS logic. The Alverstone uses a vertical bipolar transistor rather than the CMOS control transistor employed by most other memory technologies.

"This is the most significant non-volatile memory advancement in 40 years," said Ed Doller, chief technology officer-designate of Numonyx, the name given to the Intel and ST joint venture set up to manufacture flash and, possibly, the phase-change memory. "There have been plenty of attempts to find and develop new non-volatile memory technologies, yet of all the concepts, PCM provides the most compelling solution and Intel and STMicroelectronics are delivering PCM into the hands of customers today. This is an important milestone for the industry and for our companies."

Intel and ST use technology licensed from Ovonyx, a company that has attempted to commercialise PCM for close to 30 years. However, the technology has been dogged with reliability and manufacturing problems. Other vendors are experimenting with PCM using alternative approaches. NXP, for example, has an experimental PCM technology derived from work at former parent Philips on rewriteable optical disks.

Image: Cross-section of the Alverston memory cell as shown at the 2006 VLSI Technology Symposium

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