Fujitsu Semiconductor Limited and Mie Fujitsu Semiconductor Limited have reached an agreement with US-based Nantero, Inc. to license that company's technology for NRAM, non-volatile RAM using carbon nanotubes, and to conduct joint development towards releasing a product based.
Three companies are aiming to develop a product using NRAM non-volatile RAM that achieves several 1000 times faster rewrites and many thousands of times more rewrite cycles than embedded flash memory, making it potentially capable of replacing DRAM with non-volatile memory. Fujitsu Semiconductor plans to develop an NRAM-embedded custom LSI product by the end of 2018, with the goal of expanding the product line-up into stand-alone NRAM product after that. Mie Fujitsu Semiconductor, which is a pure-play foundry, plans to offer NRAM-based technology to its foundry customers.
According to Nantero, the company that invented NRAM, seven fabrication plants in various parts of the world experimented with the new memory last year. And other as-yet unannounced chipmakers are already ramping up production behind the scenes.
Fujitsu plans to initially manufacture the NRAM using a 55-nanometer (nm) process, which refers to the size of the transistors used to store bits of data. At that size, the initial memory modules will only be able to store megabytes of data. However, the company also plans a next-generation 40nm-process NRAM version, according to Greg Schmergel, CEO of Nantero.
Initially, NRAM products will likely be aimed at the data center and servers. But over time they could find their way into the consumer market -- and even into mobile devices. Because it uses power in zeptojoules and requires no data clean-up operations in the background, as NAND flash does, NRAM could extend the battery life of a mobile device in standby mode for months, Schmergel said.
Currenty, NRAM can be produced for about half the cost of DRAM, Schmergel said, adding that with greater densities production costs will also shrink -- just as they have for the NAND flash industry.
One big advantage NRAM has over traditional flash memory is its endurance. Flash memory can only sustain a finite number of program/erase (P/E) cycles. The best NAND flash, with error correction code and wear-leveling software, can withstand about 100,000 P/E cycles.
Carbon nanotubes are strong -- very strong. In fact, they're 50 times stronger than steel, and they're only 1/50,000th the size a human hair. Because of carbon nanotubes' strength, NRAM has far greater write endurance compared to NAND flash; the program/erase (P/E) cycles it can endure are practically infinite, according to Schmergel.
NRAM has been tested by Nantero to withstand 1012 P/E cycles and 1015 read cycles, Schmergel said.
While it could some day replace NAND flash, for now, Nantero and its fabrication partners are focused on producing NRAM as a replacement to DRAM because of its cost, which is about half that of traditional memory.
Another advantage is that NRAM is being built using the DDR4 specification interface, so it could sport up to 3.2 billion data transfers per second or 2,400 Mbps -- more than twice as fast as NAND flash.
Another advantage is that NRAM is resistant to extreme heat. It can withstand up to 300 degrees Celsius.
NRAM is made up of an interlocking fabric matrix of carbon nanotubes that can either be touching or slightly separated. Each NRAM "cell" or transistor is made up by a network of the carbon nanotubes that exist between two metal electrodes. The memory acts the same way as other resistive non-volatile RAM technologies.
Carbon nanotubes that are not in contact with each other are in the high resistance state that represents the "off" or "0" state. When the carbon nanotube contact each other, they take on the low-resistance state of "on" or "1."