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ST advances PCM foray with NVM-embedded MCUs

Posted: 21 May 2013 ?? ?Print Version ?Bookmark and Share

Keywords:non-volatile memory? PCM? embedded? MCUs?

STMicroelectronics will include phase-change memory (PCM) in the form of an optional integrated non-volatile memory in its microcontrollers. The technology is currently being prototyped at the 90nm manufacturing node, according to ST technology chief Jean-Marc Chery.

Although the embedded PCM technology will be offered to customers in 2014, ST's main motivation is to prepare for the introduction of a 28nm PCM process that will be prototyped in 2016 or 2017, Chery said. PCM would replace NOR flash memory for MCUs, which is not expected to scale beyond the 40nm node, Chery adds.

ST is currently ready for production with a 55nm embedded flash process for MCUs based on a one-transistor NOR memory element. The company is also developing a 40nm NOR-based embedded flash process for automotive applications.

"We continue to invest in PCM because it is fully compatible with the 28nm HKMG CMOS process," Chery told analysts. Chery told EE Times that while the initial embedded PCM introduction would be subject to thermal limitations the company is making progress on finding ternary mixes of elements that would have improved performance at high temperature.

Chery explained that the 90nm PCM MCUs would be offered for general-purpose and secure applications but not automotive applications and that the 28nm PCM embedded non-volatile memory would serve all three application sectors.

Phase-change memory is non-volatile and based on changing the material phase and electrical resistance of a chalcogenide layer by the use of electrical heating. It has been touted as possible replacement for both flash memory and DRAM, but the technology has been in research for decades and now faces numerous competitor technologies.

For phase-change memory the typical germanium, antimony, tellurium element ratio is 2:2:5, but this has the disadvantage of a relatively low melting point. This manifests itself in the problem that pre-programmed memories could be erased during soldering onto a printed circuit board. Although in-system programming can get around this problem the temperature limitation it can also impact the ability to guarantee 10-year retention at elevated temperatures.

ST began work on phase-change memory in 2000 and joined forces on research with Intel. In 2005, ST and Intel and agreed to codevelop a 90nm PCM technology. In 2008, ST and Intel combined their discrete memory businesses to form the Numonyx joint venture which was subsequently bought by Micron Technology. Micron is offering stand-alone 128Mbit phase-change memory at 90nm and a 1Gbit device at 45nm.

- Peter Clarke
??EE Times

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