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*** Contender For Next Generation Memory *** I believe this company was previously called Avanti Corporation. Here is a recent article from Scientific American that explains the context of the technology: sciam.com ______________________________________________________________________ The magnetic RAM teams have divided along scientific lines to pursue three distinct approaches. Of these, the most mature and thoroughly studied is based on a principle discovered only 10 years ago: a phenomenon called giant magnetoresistance (or GMR), in which a magnetic field changes the electrical resistance of a thin metal film by up to 6 percent. Honeywell has exploited this effect in experimental chips that contain more than one million bits, according to James Daughton, president of Nonvolatile Electronics in Eden Prairie, Minn. Unfortunately, GMR devices consume so much current that their transistors burn out if shrunk to the submicron sizes that market economics demand. But a group led by Saied Tehrani at Motorola's research center in Tempe, Ariz., believes it has found a way around this problem with a device called, for historical reasons, a pseudo-spin valve. The design roughly doubles the strength of the GMR effect, alleviating the need for such high power. Tehrani reported in November that his team has successfully built eight-by-eight-bit arrays on top of standard transistor circuitry, which allowed them to write and read each memory cell independently. IBM researchers lead the assault on the second front, devices that exploit electron tunneling through a thin insulator, although Motorola is working on such chips as well. The faint tunneling current varies by as much as 30 percent, depending on whether the fields of two neighboring magnets are aligned or opposite. In March a team of IBM engineers led by William J. Gallagher and Stuart S. P. Parkin announced that it had constructed arrays of 14 bits from such tunnel junctions, as they are known. They have demonstrated bits that are as small as 200 nanometers wide and that switch in five nanoseconds or less, Gallagher reports. Manufacturing masses of tunnel junctions may be tricky, however. The device is exquisitely sensitive to the depth of its thinnest layer, a plane of aluminum just 0.7 nanometer--about four atoms--thick. Any pinholes in that spread can short-out the memory cell. Moreover, both pseudo-spin valves and tunnel junctions develop flaws at temperatures above 300 degrees Celsius. Chip fabrication lines routinely run 100 degrees hotter. Those uncertainties may leave an opening for a third approach that has less money behind it, but more history. Edwin Hall discovered 120 years ago that a current moving through a thin film is deflected to one side by a magnet. Lienau's "magram" device exploits this effect, as does a similar design of Johnson's called a Hall effect hybrid memory. Theoretically, both designs should be easier to manufacture than spin valves or tunnel junctions. They tolerate heat well. And Johnson notes that his design requires only half as many etching steps as DRAMs. Moreover, "unlike all other memories, [magram] can be deposited on glass--perhaps even plastic--instead of single-crystal silicon," Sadwick claims as he shows, during a visit by Scientific American, a glass slide covered in gold wires leading to a one-millimeter-square array of Hall effect sensors. That versatility should allow the memory to be cheap even if it cannot shrink to the submicron cell sizes of its competitors, he argues. With single cells already working, Sadwick says, "I see no reason why we can't get eight-bit commercial samples this year." Johnson, meanwhile, has turned over his design to Honeywell, which has built one-micron test devices on gallium arsenide. "They can write bits in eight nanoseconds," he reports. The next generation, he says, will be smaller, faster and made atop silicon, the industry standard for microchips. --W. Wayt Gibbs in Salt Lake City | ||||||||||||
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