By John Keller
MANASSAS, Va. - Two of the nation’s most prominent manufacturers of radiation-hardened semiconductors are putting the finishing touches on technologies their officials believe will lead to the next generation of solid-state nonvolatile memory devices.
Nonvolatile memory retains its data even after losing power, unlike conventional static random access memory (SRAM) and dynamic random access memory (DRAM) chips.
Scientists from the two companies-the BAE Systems Semiconductor Technology Center in Manassas, Va., and the Honeywell Inc. Space Systems-Plymouth in Plymouth, Minn.-are moving along separate paths toward what they hope will be a fundamental improvement in nonvolatile computer memory.
BAE Systems scientists are pursuing what they call C-RAM, which is short for chalcogenide random-access memory. C-RAM uses an alloy of three materials that BAE licensed from ECD Ovonics in Rochester Hills, Mich., explains Gino Manzo, director of BAE’s Semiconductor Technology Center.
The alloy enables designers to program a charge to the device to either low resistance-also called an amorphous state-or high resistance-also called a crystalline state. “High or low resistance in a memory cell results in a stored one or zero,” Manzo explains. “The resistor does not change when you power the device up or down. It is a unique approach, and something we have been working on for quite some time.”
The BAE Systems C-RAM technology is in early prototypes, and officials plan to start selling the technology in 2006. The most promising applications include “anywhere you want mass nonvolatile storage, such as on processor boards,” Manzo says. The technology is applicable anywhere that designers now use volatile SRAM.
The C-RAM technology in the future also may yield reprogrammable logic for field-programmable gate arrays. “If you make a programmable resistor, you can make reprogrammable logic,” Manzo says. “We could do on-orbit changes in states, which could lead to reprogrammable computing.”
Meanwhile, scientists at Honeywell Space Systems-Plymouth are looking at nonvolatile memory from a different perspective. Honeywell is looking into M-RAM technology, or magnetoresistive random-access memory.
“M-RAM is a true-zero-power memory. Data will remain, and the readout is nondestructive, so in the process of reading you don’t destroy the memory,” says Alan Hurst, microelectronics sales manager at Honeywell Space Systems-Plymouth (formerly known as Honeywell Solid State).
Honeywell officials intend their M-RAM devices to replace plated wire memory, an obsolescent form of nonvolatile memory that Honeywell stopped making back in 1994 when planners anticipated that M-RAM could be a viable replacement.
Honeywell’s work on M-RAM technology began in 1984 at government urging to create a new generation of nonvolatile memory for the U.S. Navy Trident D5 submarine-launched nuclear missile.
M-RAM is designed for strategic radiation hardness levels of at least 1 megarad of total-dose radiation exposure.
Honeywell’s M-RAM work evolved in 2001 to a partnership with Motorola Semiconductor, which now has become Freescale Semiconductor in Austin, Texas. Honeywell is looking to Freescale’s commercial-grade chip fab to manufacture M-RAM memory chips for commercial applications.
Honeywell with its rad-hard line in Minnesota will manufacture hardened versions for military and aerospace applications.