Pure-play foundry United Microelectronics Corp. has taken a license to apply SONOS (Silicon Oxide Nitride Oxide Silicon) embedded flash memory and its application to 40nm manufacturing process technology from Cypress Semiconductor Corp. And its use as non-volatile memory at UMC for a 28nm process appears to be on the roadmap.
Only 7 months ago UMC (Hsinchu, Taiwan) was licensing the technology for its 55nm node (see UMC Licenses Embedded Flash IP from Cypress) and according to Cypress (San Jose, Calif.) the technology has the ability to scale to the 28nm node.
The SONOS technology uses charge trapping at the nitride surface to store electrons rather than conducting floating gate. Although SONOS had some issues with regard to data retention at higher temperatures and higher programming voltages, many of those issues have been addressed for established nodes and the technology can deliver a non-volatile memory cell that is easier to integrate into CMOS logic design flow. This is because SONOS requires fewer additional mask layers to insert into a standard CMOS process – only need five additional masks at 40nm compared to a minimum of 12 needed for floating–gate flash memory technologies, Cypress said.
SONOS typically delivers 10 years of data retention at 85 degrees C and 100,000 program/erase endurance cycles. UMC intends to use the embedded NVM in applications for the Internet of Things, wearables and microcontrollers and other logic dominated ICs.
This is the third time UMC has licensed the SONOS memory in the last three years having done so at 55nm in 2014 and 65nm in 2013, which suggests UMC's next move would be to apply the technology at the 28nm node. So far has not been deployed commercially at the 28nm node.
Nonetheless, according to a technical paper from Cypress, SONOS cells have been successfully fabricated using a 28nm poly-SiON baseline process at a foundry and show acceptable threshold voltages and program/erase window. Given the history of cooperation between the two companies that foundry is likely to also be UMC.
"The 40-nm SONOS process is embedded in an ultra-low power process technology and other 40-nm variants. It will benefit a broad range of UMC's customers looking to develop smart, power-efficient products for the Internet of Things and wearable electronics markets," said Sam Geha, vice president of the technology and intellectual property business unit at Cypress.
Cypress is in the process of merging with Spansion Inc., a deal announced in December 2014.
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