Intel, Numonyx make breakthrough in phase-change memory

Computerworld - Intel Corp. and Numonyx B.V. announced a breakthrough in the development of phase-change memory (PCM) today that has the potential to allow developers to stack multiple layers of PCM arrays in a single die, thereby greatly increasing the density of the nonvolatile memory medium.

Calling the discovery a "milestone" in phase-change memory development, the researchers said they have so far only been able to build a single-layer, 64Mbit chip with the potential for other 64Mbit arrays to be stacked along with it.

Greg Atwood, a senior technology fellow at Numonyx, said the breakthrough in stackable PCM, which is being called PCM-stackable (PCMS), has the potential to create products that can replace DRAM, NOR and NAND flash memory because it will have better bandwidth, greater density and a cost per gigabyte of capacity comparable with today's solid state disk (SSD) drive products.

One layer of the PCMS array. The memory cell stack, including rows and columns, is shown sandwiched between metal layers.

"We believe it enables the possibility of combining the functionality and performance of phase-change memory with more NAND-like cost structure," Atwood said. "And, it's of particular interest given the challenges the existing non-volatile memory technologies are facing over the next decade as well as the continued expansion of [PCM] usage."

The two companies have been working on development of PCM products since 2000, and a stackable PCM product since 2002. Al Fazio, an Intel fellow and director of memory technology development, said it's not unusual for a new memory type to take as many as 10 years to develop.

Atwood said that because the stacking breakthrough builds on top of PCM, a technology already in production, "it's a leading candidate amongst the various stackable memory concepts, most of which have no basis in a proven technology."

Other non-volatile memories in development include graphite memory, and race track memory.

Atwood added that Intel and Numonyx have no current time line for bringing PCMS products to market.

Phase-change memory is made up of a glass-like material called chalcogenide that can be switched between a crystalline and random state using low-voltage electricity.

Current NAND flash memory lithography technology resides at the 32-nanometer level. Future roadmaps scale NAND flash to 20 nanometers, but physical limitations present a barrier to creating anything more dense than that.

PCM, however, currently has the ability to scale to 5 nanometers in size, and the potential of even greater densities, Fazio said.