SAN FRANCISCO—(BUSINESS WIRE)—December 10, 2006— Scientists from IBM, Macronix and Qimonda today announced joint research results that give a major boost to a new type of computer memory with the potential to be the successor to flash memory chips, which are widely used in computers and consumer electronics like digital cameras and portable music players.
The advancement heralds future success for "phase-change" memory,
which appears to be much faster and can be scaled to dimensions
smaller than flash - enabling future generations of high-density
"non-volatile" memory devices as well as more powerful electronics.
Non-volatile memories do not require electrical power to retain their
information. By combining non-volatility with good performance and
reliability, this phase-change technology may also enable a path
toward a universal memory for mobile applications.
Working together at IBM Research labs on both U.S. coasts, the
scientists 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 3 by 20 nanometers in size,
far smaller than flash can be built today and equivalent to the
industry's chip-making capabilities targeted for 2015. This new result
shows that unlike flash, phase-change memory technology can improve as
it gets smaller with Moore's Law advancements.
"These results dramatically demonstrate that phase-change memory
has a very bright future," said Dr. T. C. Chen, Vice President,
Science & Technology, IBM Research. "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. This should ultimately lead to
phase-change memories that will be very attractive for many
The new material is a complex semiconductor alloy created in an
exhaustive search conducted at IBM's Almaden Research Center in San
Jose, Calif. It was designed with the help of mathematical simulations
specifically for use in phase-change memory cells.
"Emerging memory technologies, like phase-change memory, are
important elements of Qimonda's advanced memory development," said Dr.
Wilhelm Beinvogl, Senior Vice President, Technical Innovation, Qimonda
AG. "We have demonstrated the potential of the phase-change memory
technology on very small dimensions laying out a scalability path.
Thus phase-change memories have the clear potential to play an
important role in future memory systems."
The 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
(Paper 30.3: "Ultra-Thin Phase-Change Bridge Memory Device Using GeSb"
by Y.C. Chen et al. Wednesday morning, December 13.) This paper was
also one of only five to be chosen for the "Highlights of 2006 IEDM"
session at the IEEE's International Solid-State Circuits Conference,
which will be held in San Francisco in February 2007.
"Macronix has dedicated to developing non-volatile memories since
it is formed," added Miin Wu, Chairman and President of Macronix. "The
recognition from IEDM and ISSCC proves that our collaborative efforts
with IBM and Qimonda have achieved continuous success in phase-change
memory technology. Besides the phase-change memory technology
breakthrough, we have also been developing the new NAND Flash
technology, BE-SONOS, as a solution for the data storage application.
We are committed to always providing our customers with high
performance, advanced non-volatile memories solutions."
A computer memory cell stores information -- a digital "zero" or
"one" -- in a structure that can be rapidly switched between two
readily discernible states. Most memories today are based on the
presence or absence of electrical charge contained in a tiny confined
region of the cell. The fastest and most economical memory designs -
SRAM and DRAM, respectively - use inherently leaky memory cells, so
they must be powered continuously and, in case of DRAM, refreshed
frequently as well. These "volatile" memories lose their stored
information whenever their power supply is interrupted.
Most flash memory used today has a "floating gate" charge-storing
cell that is designed not to leak. As a result, flash retains its
stored data and requires power only to read, write or erase
information. This "non-volatile" characteristic makes flash memory
popular in battery-powered portable electronics. Non-volatile data
retention would also be a big advantage in general computer
applications, but writing data onto flash memory is thousands of times
slower than DRAM or SRAM. Also, flash memory cells degrade and become
unreliable after being rewritten about 100,000 times. This is not a
problem in many consumer uses, but is another show-stopper for using
flash in applications that must be frequently rewritten, such as
computer main memories or the buffer memories in networks or storage
systems. A third concern for flash's future is that it may become
extremely difficult to keep its current cell design non-volatile as
Moore's Law shrinks its minimum feature sizes below 45 nanometers.
The IBM/Macronix/Qimonda joint project's phase-change memory
achievement is important because it demonstrates a new non-volatile
phase-change material that can switch more than 500 times faster than
flash memory, with less than one-half the power consumption, and, most
significantly, achieves these desirable properties when scaled down to
at least the 22-nanometer node, two chip-processing generations beyond
floating-gate flash's predicted brick wall.
At the heart of phase-change memory is a tiny chunk of a
semiconductor alloy that can be changed rapidly between an ordered,
crystalline phase having lower electrical resistance to a disordered,
amorphous phase with much higher electrical resistance. Because no
electrical power is required to maintain either phase of the material,
phase-change memory is non-volatile.
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.
The new memory material is a germanium-antimony alloy (GeSb) to
which small amounts of other elements have been added (doped) to
enhance its properties. Simulation studies enabled the researchers to
fine-tune and optimize the material's properties and to study the
details of its crystallization behavior. A patent has been filed
covering the composition of the new material.
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