Carbon Nanotubes and RAM?

When most people think of RAM they probably aren’t thinking of these tiny carbon nano-structures, but Fujitsu Semiconductor Limited has had other ideas.

Recently they announced that they plan to bring their newly developed carbon nanotube based RAM chips (NRAM) to market in the form of DDR4 by the end of 2018. Data transfer rates to and from this chip are expected to be at least 100x faster than traditional flash storage and on par with silicon based DRAM ~5GB/s typically.


The carbon nanotube crystalline structure, it is very hard to draw by hand but can be visualised easily here in rotating gif form.

Why compare it with flash memory and what does this mean for consumers?
Until they hit the market it’s unlikely that anyone can say how people will benefit from this RAM compared with DRAM, but looking at the non-volatile memory express (NVME) standard for computer storage shows that NRAM sits somewhere between traditional RAM and NAND.
NVME has super-fast transfer speeds, like RAM, but keeps information when not powered, like NAND, which makes it good competition for newer RAM and NAND devices.

Other non-volatile RAM has been manufactured by Fujitsu, Ferro-Electric RAM (FRAM), since the 90s but that has not seen widespread success in desktop class computers due to scaling issues in capacity and demand. Like NRAM this FRAM has super endurance, an impressive rating for 1012 read/write cycles, making it far more robust than NAND. These two types of RAM also consume very little or no power when they’re not in use making them ideal for smaller devices like phones and tablets.

Another challenge facing the platform is in their manufacturing process.
Most modern silicon RAM is made using layers upon layers of circuitry to create the desired capacities but NRAM and FRAM are both currently manufactured in single layer chips. Combining this with the process techniques at 55nm and comparing it with Samsung VNAND memory being manufactured at 40nm means that there is still a lot of work needing to be done to increase the capacities to useful amounts, like gigabytes.

Until the price of these carbon powered chips comes down in price and capacity goes up there isn’t much reason yet to switch over to NRAM, but with plans to add multi-layer chips in the near future it will be worth keeping an eye on this fascinating technology.



BY Andy Elsegood

Melbourne University Electrical Engineering Club


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