The Alchemy of NAND
August 10, 2011, Flash Memory Summit, Santa Clara, CA—Glen Hawk from Micron Technology described NANDs increasing role in information gathering, search, storage, and retrieval. The various uses for NAND have changed the way we look at data.
Alchemy has been much maligned over the centuries, because some of its early proponents, rather than just try to transform materials, proposed changing lead to gold. Some of the early alchemists discovered elements like zinc, phosphorous, and many others. In fact, the early alchemists developed the foundations for modern chemistry and physics.
In the same way, NAND is changing the functions of storage as everything in our lives becomes digital. Between 2000 and ’10, the world generated 25.7 exabytes of data. Forecasts are the we will generate 57.8 EB in the next two years and data growth will outstrip the gains available from Moore’s Law. The industry needs to find ways to increase production and device storage capacity.
What is the importance of NAND to changing, innovating, and enabling new functions? Cloud computing wouldn’t exist. Video for portable devices couldn’t work without reliable, low cost media storage. Efficient data centers for data mining and analytics need performance-driven storage that other technologies cannot support. Flash has enabled innovation in all these areas.
The challenge is that further scaling and increased integration are getting harder. Optimizing performance for the 20 nm process generation needs new solutions to meet the requirements for reliability and data integrity. Integrating EDD provides one step towards a fully managed solution and is working in eMMC devices. A full system-level solution would have fully integrated subsystem functions to look like a HDD but with increased performance and with a PCIe interface.
Another area for change is to make vertical storage cells that can be stacked. The existing architectures are still flat and scaling makes parameter optimization harder, because the number of electrons is too small. A 3-D structure uses a vertical element to make rings of storage to make use of older processes while increasing bit density and getting higher speed and lower system noise. Using a large ring of silicon for storage changes the detection from 20 electrons/bit to 20k electrons per ring, a much easier task.
A 3-d structure offers a number of benefits: relaxed design rules for the older processes, reduced die size, increased integration of logic and RAM, and reduced delays and noise. All together, this change increases capacity while reducing total cost and cost per bit.
Other technologies have promise. Micron is working on phase-change RAM, which is likely to be an intermediary step between NAND and DRAM, but won’t displace either one. Other technologies are in various stages of R&D, but most are not likely to be available for practical volumes for at least another decade.
