Carbon nanotubes' material cost is now a negligible in overall chip cost, making memory-based on carbon nanotubes more compelling than ever. Including NRAM.
Demand for a new generation of memory that combines high speed and nonvolatility, as well as scalability below 5nm, is now stronger than ever. After years of development and testing, carbon nanotubes (CNTs) have proven to be the most suitable material for to deliver fast, high-density, low-power memory.
And CNTs are no longer only found in research labs. A number of production fabs have been quietly and successfully using CNTs without issues. Not only have CNTs been proven to work on leading-edge CMOS fabrication lines with no new tools or processes required, the cost of the CNT material on a per-chip basis for memory has been reduced by more than 10X also in the last two years alone. This means the CNT material cost is now negligible with respect to chip cost, making the value proposition of CNT memory more compelling than ever.
In fact, the potential for CNTs to be used anywhere silicon is used is significant, and a number of devices can be fabricated beginning with nonvolatile random access memory (NRAM), as well as sensors, transistors and interconnects.
Discovered in 1991 by Sumio Iijima of NEC Corp., CNTs are strong and elastic cylinders of carbon atoms that resemble a tube of rolled-up chicken wire. They are members of the fullerene family and have amazing properties, including the ability to conduct electricity as well as copper, while also being stronger than steel and as hard as a diamond. One CNT is just 1/50,000th the diameter of a human hair, half the density of aluminum, and has better thermal and electrical conductivity properties than any other material scientists are aware of today.
CNTs are strong and elastic cylinders of carbon atoms that resemble a tube of rolled-up chicken wire
Key to the success of moving CNTs from the research lab and into production CMOS fabs has been the availability of CNT material that meets the specifications for use in even leading-edge fabs (with less than 1ppb of any metals), making contamination a non-issue. In fact, this CNT material can be easily spin-coated on wafers using existing coat tools, and patterned using existing lithography and etch tools.
The first core CNT-based technology being readied for commercialization with multiple partner companies today is NRAM. The CNT memory process has already been installed in multiple production fabs and is currently being designed into innovative new electronic products that require increased storage, low power consumption, high speed, reliability, and high endurance.
NRAM has several characteristics that make it ideal as the next-generation technology for both standalone and embedded usage, including:
- CMOS compatible: Can be fabricated in standard CMOS fabs with no new equipment needed
- Limitless scalability: Can scale below 5nm in the future
- High endurance: Proven to operate for orders of magnitude more cycles than flash
- Faster read and write: Same as DRAM, 100s of times faster than NAND
- High reliability: Will retain memory for >1,000 years at 85 degrees Celsius or more than 10 years at 300 degrees Celsius
- Low power: Essentially zero in standby mode, 160x lower write energy per bit than NAND flash
- Low cost: Simple structure, can be 3D multi-layer and multi-level cell (MLC)
The combination of NRAM’s DRAM-like speed and nonvolatility provides substantial opportunities for new designs and architectures, and likely even new devices, for electronics companies. NRAM can be used in a range of products, including consumer devices such as PCs, laptops, smartphones, and tablets, as well as enterprise systems such as networking hardware, storage arrays, and numerous other applications. It is also ideal for government and military usage and high-temperature, high- reliability applications, among others.
Product development projects are in process today for both standalone NRAM and embedded NRAM. Standalone NRAM is being sought for three purposes: for DRAM replacement, for NAND flash replacement, and for applications neither DRAM nor NAND flash can address. In the embedded memory space, there is ongoing work on using embedded NRAM to replace embedded non-volatile memory, including embedded flash or embedded RAM – either SRAM or DRAM.
Over the past decade, researchers in many companies and universities have identified numerous highly promising devices that can be made with CNTs—and by transferring CNTs from lab to fab, mass production has now become a possibility. The first volume application we will see CNTs used for is NRAM, but as the industry continues leveraging the power and versatility of CNTs, we can expect to see this material used in a variety of new applications.
Greg Schmergel is co-founder and CEO of Nantero.
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