Process variation during tunnel window formation and its impact on the reliability performance of FLOTOX EEPROM devices

Abstract

Process variation in the buffered oxide etch (BOE) duration during tunnel window formation can cause floating-gate tunnel-oxide (FLOTOX) electrically erasable and programmable read-only memory (EEPROM) devices to exhibit enhanced window closure effect during write/erase endurance tests. Electrical and physical characterisation of devices with insufficient BOE duration indicated the presence of a poor quality or "crabby" oxide region (exhibiting enhanced electron trapping) remaining after tunnel window formation before tunnel oxide growth.