A new 40-nm SONOS structure based on backside trapping for nanoscale memories

Silicon-on-nothing (SON) devices have been analyzed for the first time in view of nanoscaled nonvolatile memories (NVM) applications. Two reliable steady states have been demonstrated using backside charge trapping in the nitride layer under the channel as a memory effect in a 40-nm gate-length pMOS silicon-oxide-nitride-oxide-silicon device realized with SON technology. Low voltages (∼3 V) are required for memory operations and a threshold voltage memory window superior to 0.5 V can be achieved. Charge loss mechanism is analyzed and very promising data retention behavior is demonstrated at 125°C. This architecture, with a storage node localized under the channel, is exactly the same device that can operate as a high-performance transistor at low voltages and as an NVM cell at higher voltage ranges. A total compatibility between logic and the embedded NVM process is thus insured. In view of high-density memories, the feasibility of 2-bit storage in a longer SON device is also demonstrated.