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.
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.