Motorola Unveils Developments in Successors to Floating-Gate Flash Memory
Papers at Industry Workshop Outline Progress in New Non-Volatile Memory Techniques: SONOS and Silicon Nanocrystals
AUSTIN, Texas, Feb. 11 /PRNewswire-FirstCall/ -- Motorola will present several technical breakthroughs in embedded non-volatile memory technology at the 2003 IEEE Non-Volatile Semiconductor Memory Workshop, Monterey California, February 16-20, 2003. Motorola's research on an advanced class of memory techniques, called thin-film storage, could help the industry find a successor to floating gate-based flash memory, which many believe will not scale to smaller geometries. The advances to be discussed could lead to smaller, more reliable, more powerful and more power-efficient memories. Researchers with Motorola's Semiconductor Products Sector will give four papers on silicon-oxide-nitride-oxide-silicon (SONOS) and silicon nanocrystal memories covering modeling, programming, and local charge storage.
Floating gate-based embedded flash is the workhorse of embedded non-volatile memories. Manufacturers widely use it in applications such as automobiles, appliances, consumer electronics, wireless devices and industrial controls. Flash technology allows manufacturers to re-program microcontrollers several times in the development cycle. This flexibility makes it easy to adjust to fast-changing market demands or correct software problems remotely in the field. However, as the industry begins manufacturing at smaller geometries -- 90nm and smaller -- manufacturing floating gate-based flash becomes impractical. At those dimensions, the chip area spent on the 9-12V high voltage transistors needed to write and erase the flash becomes too expensive. Engineers can't reduce the high voltage in floating-gate based flash without compromising reliability, at the risk of memory failures and loss of data.
"In order to meet the future needs of our customers, Motorola focuses on both evolutionary and revolutionary approaches to non-volatile memory," said Rick Sivan, vice president and director of Motorola's Embedded Memory Center. "SONOS and Silicon nanocrystals are evolutionary memory techniques. They enable further write/erase voltage scaling. Already, some manufacturers are replacing floating-gate flash in certain market segments today. Both of these memories offer reduced power consumption and improved performance over flash memory. They have the added benefit of being simple to manufacture."
Motorola is also an industry leader in magnetoresistive random access memory (MRAM). MRAM has the potential to be a truly revolutionary memory technology, combining the best attributes of the three major memory types onto a "single" chip -- the density of eDRAM, the speed of eSRAM and the non-volatility of flash.
About Thin-Film Storage
Thin-film storage non-volatile memory works by placing the charge storage sites storing the memory bits between two insulating oxide layers beneath a polysilicon gate. SONOS is a technique that uses traps in silicon nitride. Silicon nanocrystal structures consist of small 50-angstrom diameter spheres of silicon -- 10,000 times smaller than a human hair. Motorola has created a technique for depositing these nanocrystals using traditional equipment. The advantage of thin film storage is that the nitride traps or nanocrystals are engineered to hold the charge and prevent lateral movement to other storage sites. This increases reliability because a single oxide defect does not lead to complete charge loss as in a conventional floating gate.
A key issue with today's flash technologies is the lack of reliability of the very thin silicon dioxide layers. This prohibits reducing the terminal voltage of the transistors supporting flash write and erase operations below 9 to 12V. As a result, small bitcells require a large overhead in peripheral circuitry. The key breakthrough to be discussed in the workshop papers is the enabling of voltage scaling towards 6V, reducing size of the memory device, and reducing its power consumption while improving its performance. Motorola evaluates storing charge in both nitride layers as well as nanocrystals to identify the most reliable technology for the demanding industrial and automotive markets.
Motorola's papers at the NVM Workshop include:
- "Warm Carrier Programming of Si Nanocrystalline Memories"
- "Local Charge Storage in Silicon Nanocrystalline Memories"
- "An Embedded 90nm SONOS flash EEPROM Utilizing Hot Electron Injection
Programming and 2-sided Hot Hole Injection Erase"
- "Validation of a Predictive SONOS Model"
For more information about the NVM Workshop visit http://ewh.ieee.org/soc/eds/nvsmw/ .
About Motorola Semiconductors
As the world's #1 producer of embedded processors, Motorola's Semiconductor Products Sector creates DigitalDNA(TM) system-on-chip solutions for a connected world. Our strong focus on wireless communications and networking enables customers to develop smarter, simpler, safer and synchronized products for the person, work team, home and automobile. Motorola's worldwide semiconductor sales were $4.8 billion (USD) in 2002. For more information please visit http://www.motorola.com/semiconductors .
About Motorola
Motorola, Inc. (NYSE: MOT) is a global leader in providing integrated communications and embedded electronic solutions. Sales in 2002 were $26.7 billion. Motorola is a global corporate citizen dedicated to ethical business practices and pioneering important technologies that make things smarter and life better for people, honored traditions that began when the company was founded 75 years ago this year. For more information, please visit: http://www.motorola.com .
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http://ewh.ieee.org/soc/eds/nvsmw
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