New entrants into NAND flash memory, one of the fastest growing areas of the semiconductor industry, could be enabled by the announcement of a new memory process by UMC, the Taiwanese silicon foundry.
UMC has announced an NROM-type process used for NAND flash as an alternative to the floating gate CMOS process typically used by NAND flash leaders such as Toshiba, SanDisk and Samsung.
“UMC has been working on flash technology for many years for several customers’ flash products, including commodity flash as well as embedded flash/EEPROM,” said Joe Ko, vice-president of the specialty technology division at UMC.
UMC calls the process SONOS (silicon oxide nitride oxide semiconductor). It is another name for the nitride trapping site storage technology called MNOS (metal nitride oxide semiconductor) which is developed by Saifun of Israel under the name NROM, and which is used by Spansion and Infineon to make NAND flash memory which they respectively call Mirrorbit and TwinFlash.
Last year Cypress Semiconductor licensed a SONOS process from the Colorado company Simtek.
UMC has made its first SONOS product, a 256Mbit, 0.18µm chip, for a Taiwanese semiconductor company called Solid State System. According to UMC, the chip boasts cost-competitive manufacturing, lower power consumption, and equivalent programme/erase performance and reliability compared to conventional NAND flash.
NROM has traditionally lagged in delivering the same density level as floating gate CMOS, although Saifun recently announced a 4bit-per-cell NROM technology which would solve that.
“As we move this current product line to volume production, we are also working with UMC to develop high capacity SONOS memory products on advanced process technology,” said Cheng Liou, vice-president of Solid State System.
Assuming UMC’s SONOS process scales reasonably well, a 65nm process could deliver a NAND flash product in the multi-Gbit density range which is in line with current leading edge NAND flash memories.
www.umc.com