Friday, May 08, 2009

"CHIPS: Nanocrystals revolutionize flash memory at Freescale "

For over 15 years Freescale has been using polysilicon floating gates for its embedded flash memories, but about five years ago the company realized that polysilicon gates were going to be subject to process uniformity woes beyond the 90 nanometer node. Now after extensive nanocrystalline process development, Freescale will begin switching all its embedded flash memories to the new nanocrystal architecture. Look for microcontrollers using the nanocrystal flash memories by the second half of 2009. R.C.J.

Freescale Semiconductor will use silicon nanocrystal thin-films for floating gates— in place of today's polysilicon floating gates—to move embedded flash to advanced processing nodes. Freescale claims reliability as the motivation when describing its switchover to nanocrystals from both the split-gate and single-transistor (1-T) flash architectures it uses today. Freescale built prototype nanocrystal memory devices in 2005, and over the past four years has also experimented with using nitride charge traps as an alternative means of isolating charge and thus tolerating defects at advanced nodes. Because the nanocrystalline film does not have to be cut into gates, it reduces the number of mask layers needed thus lowering costs. A standard CMOS line can be used too, simplifying the processing, and costs, further.