IBM has shown that a revolutionary new type of computer memory—one
that combines the large capacity of traditional hard disks with the
speed and robustness of flash memory—can be made with standard
chip-making tools.
Memory milestone: These nanowires are part of a prototype chip
for a novel form of data storage that could fit more information into a
smaller space than today’s technology.
The work is important because the cost and complexity of
manufacturing fundamentally new computer components can often derail
their development.
IBM researchers first described their vision for "racetrack" computer memory
in 2008. Today, at the International Electronic Devices Meeting in
Washington, D.C., they unveiled the first prototype that combines on one
chip all the components racetrack memory needs to read, store, and
write data. The chip was fabricated using standard semiconductor
manufacturing tools.
Racetrack memory stores data on nanoscale metal wires. Bits of
information—digital 1s and 0s—are represented by magnetic stripes in
those nanowires, which are created by controlling the magnetic
orientation of different parts of the wire.
Writing data involves inserting a new magnetic stripe into a nanowire
by applying current to it; reading data involves moving the stripes
along the nanowire past a device able to detect the boundaries between
stripes.
Earlier demonstrations of the technology employed nanowires on a
silicon wafer in a specialized research machine, with other components
of the memory attached separately. "All the circuits were separate from
the chip with the nanowires on," says Stuart Parkin,
who first conceived of racetrack memory and leads IBM's research on the
technology at its research lab in Almaden, California. "Now we've been
able to make the first integrated version with everything on one piece
of silicon."
The new racetrack prototype was made at IBM's labs in Yorktown, New
York, using a manufacturing technique known as CMOS, which is widely
used to make processors and various semiconductor components. This
proves that it should be feasible to make racetrack memory commercially,
says Parkin, although much refinement is still needed.
The nickel-iron nanowires at the heart of the prototype were made by
depositing a complete layer of metal onto an area of the wafer, and then
etching away material to leave the nanowires behind.
The wires are approximately 10 micrometers long, 150 nanometers wide,
and 20 nanometers thick. One end of each nanowire is connected to
circuits that deliver pulses of electrons with carefully controlled
quantum-mechanical "spin" to write data into the nanowire as magnetic
stripes. The other end of each nanowire has additional layers patterned
on top that can read out data by detecting the boundaries between
stripes when they move past.
Dafiné Ravelosona, an experimental physicist at the Institute of Fundamental Electronics in Orsay, France, leads a European collaboration
working on its own version of racetrack memory. He says IBM's latest
results are a crucial step along the road to commercialization for the
technology. "It's a nice demonstration that shows it's possible to make
this kind of memory using CMOS," he says.
However, Ravelosona adds that the IBM work doesn't yet demonstrate
all of the key components that make racetrack memory desirable. "They
have only demonstrated that it is possible to move a single bit in each
nanowire," he explains.
Much of the promise of the technology lies in the potential to store
many bits—using many magnetic stripes—in a single tiny nanowire, to
achieve very dense data storage. Ravelosona suggests that the material
used to make the nanowires in the new IBM device lacks the right
magnetic properties to allow that.
Parkin says that the intention wasn't to target density but adds,
"We're focusing on exactly this question." His group is currently
working on how to fit as many magnetic stripes as possible into a
nanowire and has begun experiments that suggest that wires made from a
different type of material may do better.
The nickel-iron alloy of the integrated prototype is what's known as
a soft magnetic material, because it can be easily magnetized and
demagnetized by an external magnetic field. Parkin is also experimenting
with hard magnetic materials, which get their magnetic properties from
their tightly fixed crystalline structure and as a result are not easily
demagnetized.
"Using this different material, we have discovered we can move the
domain walls [between magnetic stripes] very fast and that they are much
smaller and stronger than in the soft magnetic material used in the
integrated devices," says Parkin.
That means not only that it should be easier to put many stripes into
one nanowire, but also that nanowires fabricated with less precision
will still work, which should make fabrication easier. "I call this
racetrack 2.0," he says.
By Tom Simonite
From Technology Review
0 comments:
Post a Comment