A non-volatile memory technology which is denser, faster and more cost-effective than conventional flash memory technology is closer to production, due to the continued efforts of Freescale Semiconductor to optimize the properties of silicon nanocrystals. Freescale has manufactured the world's first 24-megabit (Mbit) memory array based on silicon nanocrystals, a major step toward replacing conventional floating gate-based flash memories.
The 24-Mbit memory array technology was manufactured at Freescale's Austin Technology & Manufacturing Center using 90-nanometer (nm) CMOS bulk technology. The production of a working 24-Mbit memory device requires that silicon nanocrystals be deposited with excellent uniformity and integration approaches that keep the nanocrystal properties intact during subsequent processing. In successfully achieving this, Freescale has overcome major challenges to introducing this technology into production.
Silicon nanocrystal memories are part of an advanced class of memory technologies called thin-film storage. They are more scaleable than conventional floating gate-based flash technology, as their tunnel oxide thickness can be reduced without impacting data retention. The charge is stored on isolated nanocrystals and is lost only from those few nanocrystals that align with defects in the tunnel oxide - while the same defects would result in significant charge loss from a conventional floating gate. A thinner tunnel oxide permits lower-voltage operation, substantially reducing the memory module area needed to generate the bit-cell programming voltages, and allowing for significant wafer processing simplifications and manufacturing cost reductions. The combination of higher bit density and reduced cost translates to lower cost per bit to embed silicon nanocrystal memories. Freescale expects significant reductions in cost per bit of silicon nanocrystal thin-film storage memories.
Posted: Nov 28,2005 by Ron Mertens