By John McHale
ALBUQUERQUE, N.M. - Scientists at the U.S. Air Force Phillips Laboratory Space Technology directorate at Kirtland Air Force Base, N. M., are manipulating protons to fabricate a low-power solid-state memory that is non-volatile and radiation hardened.
The new device runs on 2 or 3 volts of electricity, compared to flash memory that needs about 15 volts, says Karel Vanheusden, a member of a team of scientists at Phillips. Non-volatile memory retains its data when its source of electricity shuts off.
Vanheusden was part of a nearby Sandia National Laboratories research team that recently discovered how to fabricate non-volatile memory chips through the use of protons.
"When computer chips are made, wandering atoms sometimes stick in one of the chip`s layers. These atoms may later move through a chip`s transistor, causing it to fail," he explains. "At Sandia, we found a way to deliberately plant similar atoms in a chip during fabrication and learned how to control them. Our atoms don`t move around during a power loss and will store information that can be later recalled once electricity is restored."
Their technology uses mobile protons around the gate oxides in the Metal Oxide Silicon Field Effects Transistor (MOSFET), Vanheusden says. He and his scientists can turn the MOSFET on and off with protons, which protects it from memory loss. To shut the MOSFET off they conduct the protons away; to turn it on they shoot the protons towads the array, he says.
Scientists implant protons in the transistor through a fusion process, but due to the intense heat needed for fusion, some protons become uncontrollable, Vanheusden notes. This becomes a problem when the technology moves from the lab to the fabrication line and the technology is made to wafer scale.
"We need to get the heat temperatures down before moving to the fabrication line, or the uncontrollable protons will make the assembly task near impossible for the scientists working on the line," Vanheusden warns. "The difficulty with the fabrication line is there are about 100 different design steps in producing the chip that cannot conflict, or else the process has to start all over again."
Because the proton-based non-volatile chips process information at a much slower rate than conventional technology, they will probably never replace those used today in desktop systems. Instead, they will be valuable back-up devices - especially in space applications - to save the most recent data input from being lost.
Once developed, Vanheusden predicts the proton solution for solid-state memory will become more popular than flash memory in all systems due to its inexpensive design process and lower power consumption.
The radiation hardening of the protons came as a surprise, says Vanheusden. "We were radiating all the protons and expected them to lose electrons and fail, but to our surprise they did not. We still don`t know why."
It would be the first form of non-volatile memory to withstand radiation, he says. More tests still need to be done, but the Phillips scientist predicts the new technology will be a boon to the space industry by extending the life of satellites. Flash memory and the other forms of solid state memory are not radiation-hardened, says Vanheusden.
