IBM Dips Chips To Cut Power

Optical image of a typical ionic liquid (IL) gated device with a droplet of IL on top of the gate electrode and the oxide channel.

IBM announced this week that it has developed a way to manufacture both logic and memory that relies on a small drop of “ionic liquid” to flip oxides back and forth between an insulating and conductive state without the need to constantly draw power. In theory, that means both memory and logic built using those techniques could dramatically save power.

IBM described the advance in the journal Science, and also published a summary of its results to its Website.

The central idea is to eliminate as much power as possible as it moves through a semiconductor. Doing so by flipping an insulator to a conducting metal has been done before, IBM researchers told eWEEK, but not to the point that the resulting device was stable. Previous techniques have included changing the temperature or applying external stress, “both of which do not lend themselves to device applications,” IBM said.

IBM’s solution is to use a bit of “ionic liquid” to flip the state. IBM researchers applied a positively charged ionic liquid electrolyte to an insulating oxide material—vanadium dioxide—and successfully converted the material to a metallic state. The material held its metallic state until a negatively charged ionic liquid electrolyte was applied in order to convert it back to its original, insulating state.

Microprocessors and memory using IBM’s techniques could be used to store and transport data in a more efficient, event-driven manner instead of requiring the state of the devices to be maintained by constant electrical currents, IBM said.

A loose analogy would be to compare IBM’s technology to the sort of electronic ink used in the black-and-white versions of the Kindle and other e-readers. There, an electrical charge can be applied to the tiny microcapsules that contain the “ink,” hiding or displaying them to render a page of text. Like IBM’s solution, the e-ink doesn’t require a constant charge; power only needs to be applied to re-render or “flip” the page.

In any event, IBM’s technique could conceivably be applied to both mobile devices as well as power-hungry data centers. IBM touted its solution as one answer to the limits of CMOS devices, which will eventually require new techniques both to be manufactured and continue to conserve power. IBM’s POWER chips, of course, don’t exactly run cool.

Within CMOS, the three key scaling factors are the thickness of the insulator between the gate and the underlying silicon; the channel length; and the power-supply voltage that, when applied to the gate, turns the transistor on. It’s the latter factor that IBM’s technology is trying to eliminate.

“Our ability to understand and control matter at atomic scale dimensions allows us to engineer new materials and devices that operate on entirely different principles than the silicon based information technologies of today,” Stuart Parkin, an IBM Fellow at IBM Research, wrote in a statement. “Going beyond today’s charge-based devices to those that use miniscule ionic currents to reversibly control the state of matter has the potential for new types of mobile devices. Using these devices and concepts in novel three-dimensional architectures could prevent the information technology industry from hitting a technology brick wall.”

IBM has also previously disclosed materials breakthroughs such as “silicon nanophotonics” could boost optical networks and ultimately speed up the data center.

While IBM dismissed the other solutions as impractical, however, it’s still not clear how dipping a chip within ionic liquid would be an improvement. Could the entire chip run immersed in this liquid? If so, how would it affect the transfer of heat? How much does the ionic liquid cost to manufacture, and how much needs to be used? Such questions may have to wait for the future to answer.


Image: IBM

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