Semiconductors and Components

Micron's Phase-Change Memory under Review

14 October 2013

Micron Technology Inc. is going through a process of defining its future strategy for phase-change memory (PCM).

While a company spokesman said via email that Micron remains committed to PCM, a reference to a process of strategy definition in the same email calls into question whether Micron will scale PCM to 20-nm class production and beyond 1-Gbit memory capacity.

"Micron remains focused on continued PCM innovation," the spokesman said.

PCM is a non-volatile memory that has been pioneered commercially by Micron but with little apparent success. PCM uses a change of material phase, from crystalline to amorphous in thin layer of chalcogenide material to produce resistance change. This is used as the basis of a non-volatile memory device.

Micron has offered a couple of 90-nm 128-Mbit PCM devices for several years and in 2012 claimed it was shipping a 45-nm 1-Gbit device in high volume to Nokia for use in the Asha mobile phone. However, this still leaves PCM behind NAND flash memory in scaling and capacity. NAND flash is in production from multiple companies, including Micron, at nodes below 20-nm.

Close observers of the memory technology developments have pointed out that the 1-Gbit PCM is no longer referenced as a product on Micron's website, although the 128-Gbit serial- and parallel-access PCMs are still listed. This has led to speculation that Micron could be about to abandon PCM.

It is also notable that, although one paper scheduled for presentation at the upcoming International Electron Devices Meeting (IEDM) references 45-nm, 1-Gbit PCM, it does in the context of a discussion of erratic data retention due to crystallization variability. The authors of paper 21.7 claim to be able to stabilize retention by altering the programming conditions, according to the IEDM advanced program.

The spokesperson wrote: "The company is currently in the process of integrating a vast array of mobile IP as a result of the Elpida acquisition and is defining future strategy for PCM and a host of other products. As this process is completed, additional information will be shared."

When challenged that as Micron's future strategy for PCM is undefined it could potentially include the abandonment of PCM, the spokesperson said: "Micron simply is not ready to publicly share details related to future plans the company is working on right now. This includes scaling and definition details."

Micron is not the only the company with PCM experience. STMicroelectronics NV shared research on PCM with Intel and combined with Intel to form a joint venture Numonyx NV. Micron inherited the PCM capability when it acquired Numonyx in May 2010. Samsung has made an 8-Gbit PCM chip using a 20nm-class process that it was due to present at the 2012 International Solid-State Circuits Conference and in the same year SK Hynix and IBM announced joint development on PCM as a "storage-class" memory.

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