IBM Group Claims Phase-Change Breakthroughs

By Colleen Taylor -- Electronic News, 12/11/2006

Scientists from IBM, Macronix and Qimonda today announced joint research results that they said pave the way for phase-change memory, a new type of non-volatile computer memory the researchers claim is set to succeed flash memory.

The researchers, who first teamed up for phase-change research in May of 2005, said they have designed, built and demonstrated a prototype phase-change memory device that switched more than 500 times faster than flash while using less than one-half the power to write data into a cell. The device's cross-section is a minuscule 3nm-by-20nm in size, far smaller than flash can be built today, according to the scientists.

"These results dramatically demonstrate that phase-change memory has a very bright future," Dr. T. C. Chen, VP of science and technology at IBM Research, said in a statement. "Many expect flash memory to encounter significant scaling limitations in the near future. Today we unveil a new phase-change memory material that has high performance even in an extremely small volume."

The researchers said the new material is a "complex semiconductor alloy" created at IBM's Almaden Research Center in San Jose, Calif. The material's phase is set by the amplitude and duration of an electrical pulse that heats the material. When heated to a temperature just above melting, the alloy's energized atoms move around into random arrangements. Suddenly stopping the electrical pulse freezes the atoms into a random, amorphous phase. Turning the pulse off more gradually, over about 10 nanoseconds, allows enough time for the atoms to rearrange themselves back into the well-ordered crystalline phase they "prefer," according to the scientists.

The new memory material is a germanium-antimony alloy (GeSb) to which small amounts of other elements have been added to enhance its properties, the researchers said. A patent has been filed covering the composition of the new material.

More technical details of this research will be presented this week at the Institute of Electronics and Electrical Engineer's (IEEE's) 2006 International Electron Devices Meeting (IEDM) in San Francisco.