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October 30, 2007

Programmable-metallization-cell (PMC) memory, or nano-ionic memory could start replacing flash memory in 18 months

A new type of memory technology could lead to thumb drives or digital-camera memory cards that store a terabyte of information--more than most hard drives hold today. The first examples of the new technology, which could also slash energy consumption by more than 99 percent, could be on the market within 18 months

UPDATE:I have more details on the PMC memory in a new article.

The new type of memory, called programmable-metallization-cell (PMC) memory, or nano-ionic memory, has been under development at the University of Arizona and at companies such as Sony and IBM. Nano-ionic memory is significantly faster than flash memory, and the speed of some experimental cells has rivaled that of DRAM, which is orders of magnitude faster than flash.

The memory could also prove easy to make. Recently, the Arizona group published work demonstrating that nano-ionic memory can be made from materials conventionally used in computer memory chips and microprocessors. That could make it easier to integrate with existing technologies, and it would mean less retooling at factories, which would appeal to manufacturers.

Another reason that ionic memory is attractive is that it uses extremely low voltages, so it could consume as little as a thousandth as much energy as flash memory. In theory, it could also achieve much higher storage densities--bits of information per unit of surface area--than current technologies can.

Each memory cell consists of a solid electrolyte sandwiched between two metal electrodes. The electrolyte is a glasslike material that contains metal ions. Ordinarily, the electrolyte resists the flow of electrons. But when a voltage is applied to the electrodes, electrons bind to the metal ions, forming metal atoms that cluster together. These atoms form a virus-sized filament that bridges the electrodes, providing a path along which electrical current can flow. Reversing the voltage causes the wire to "dissolve," Kozicki says. The highly resistive state of the electrolyte and the other, low-resistance, state can be used to represent zeroes and ones. Because the metal filament stays in place until it's erased, nano-ionic memory is nonvolatile, meaning that it doesn't require energy to hold on to information, just to read it or write it.

William Gallagher, a senior manager for exploratory nonvolatile-memory research at IBM Research, says that nano-ionic memory is one of several promising next-generation memory technologies. These include MRAM, which stores information using magnetic fields, and phase-change memory, which stores information in a way similar to that used to store bits on DVDs. Gallagher says that ionic memory's competitors have a head start on it. MRAM chips are already sold for some special applications, such as devices that will be exposed to harsh environments. But MRAM may also prove better for high-speed memory applications than as a replacement for flash, so it may not compete directly with nano-ionic memory. Samsung, however, could be selling a phase-change-based flash-replacement memory within a year.

Still, nano-ionic memory may not be far behind. A few companies have licensed nano-ionic-memory technology developed at the University of Arizona. These include Qimonda, based in Germany; Micron Technologies, based in Boise, ID; and a Bay Area stealth-mode startup. The startup is well on the way to producing its first memory devices, which Kozicki says could be available within 18 months. These first chips, however, won't rival hard drives in memory density, he says.

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