NRAM

NRAM

(NanoRAM) A non-volatile, random access memory technology from Nantero, Inc., Woburn, MA (www.nantero.com) that is being developed to initially replace flash memory and ultimately DRAM and SRAM memories. NRAM uses carbon nanotubes for the bit cells, and the 0 or 1 is determined by the tube's physical state: up with high resistance, or down and grounded.

NRAM is expected to be faster and denser than DRAM and also very scalable; able to handle 5 nm bit cells whenever CMOS fabrication advances to that level. It is also very stable in its 0 or 1 state. Using standard CMOS fabrication facilities, Nantero has licensed NRAM to companies with commercial production expected in the 2009-2010 time frame. See future memory chips.

Spin Coat the Tubes onto the Wafer
Making NRAM cells is quite fascinating. A solution of purified carbon nanotubes is placed onto a wafer with predefined round electrodes and spun at centrifugal force to spread the fluid. The tubes wind up in random polarizations, spread evenly across the wafer and over the electrodes. Subsequent steps remove the extraneous tubes and add the interconnects. Each electrode with its carbon tubes becomes a memory cell (see below).

The Bits Are Nanotubes

An NRAM 0 or 1 bit is determined by whether the tubes are straight up or bent down. Changing the charge on the electrode changes the data state (0 or 1) by attracting or repelling the positively charged nanotube. When straight up, the tubes have high resistance; when bent down, they have low resistance. The distance between up and down is 1/10,000 of a human hair.

Making the NRAM Cells

Only two cells are shown here to illustrate the concept; however, billions of cells are created on a wafer, and many, many more tubes land over each electrode.