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.
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
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 applications."
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
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.