Tour’s group isn’t the only one exploring three-dimensional memory. IBM’s Stuart Parkin is developing so-called racetrack memory that stores data by altering the magnetic properties of nanowires deposited on silicon. And chip manufacturer SanDisk is developing a three-dimensional memory that uses vertically stacked arrays of diodes.
In the coming years, it will be increasingly important to develop three-dimensional memory, says Tour. “If you’re not in the 3-D memory business in five years, you’re not going to be in the memory business.”
The work has gotten the attention of industry forecasters. “The concept is interesting and potentially promising,” says Victor Zhirnov of the Semiconductor Research Corporation. He notes, though, that it’s still too early to give the technology a full endorsement, as the underlying mechanism of the memory is not yet clear.
Nonetheless, performance of the early prototypes of graphitic memory is promising, says Tour. The cells can be written to and read from at speeds comparable to today’s flash memory. And the voltages that are required to operate them are lower than those required for flash.
In addition, the technology could extend beyond memory to another part of the electronics industry that builds chips called field-programmable gate arrays (FPGAs). These chips are reconfigurable for different tasks, from controlling radios to crunching numbers, but today’s FPGAs are limited in the number of times they can be reconfigured. If the components between layers in FPGAs were connected using graphitic pillars or strips, says Tour, then they could be almost infinitely rewritable.
The Rice University researchers have partnered with startup NuPGA, a company that will use the graphite technology to make FGPAs. In addition, Tour says, an unnamed company supports the memory work. Tour suspects that it could take at least eight years to turn the prototypes into products, because of the need to ensure reliability and optimize the manufacturing process.