The goal of this work is to give a clear physical comprehension of the charge loss mechanisms of SANOS (Si/Al2O3/Si3N4/SiO2/Si) memories. Retention at room and high temperature is investigated on different samples through experiments and theoretical modeling. We argue that at room temperature, the charge loss essentially results from the tunneling of the electrons trapped at the nitride interface, and the retention life time increases with the nitride thickness. On the contrary, at high temperature, the trapped charges in the nitride volume quickly redistribute, thanks to the thermal emission process, and they migrate to the nitride interface. Indeed, this result suggests that thin-nitride thicknesses in SANOS devices allow keeping a fast program/erase speed without degrading the retention at high temperature.
