Extreme Short-Channel Effect on RTS and Inverse Scaling Behavior: Source–Drain Implantation Effect in 25-nm nand Flash Memory

In 25-nm NAND Flash memory, source-drain implantation conditions significantly affect random telegraph signal (RTS). In this extremely short gate length regime, RTS is proportional to the effective gate length (L_eff) which exhibits an “inverse scaling effect.” Process simulation reveals that the laterally straggled and diffused As atoms from source/drain are sufficient to change the effective boron concentration even in the center of the channel which changes macroscale potential profile for the short-channel effect but also changes RTS by modulating random discrete dopant (RDD) effect. This result continues up to 10 000 program/erase cycles which indicates that the defect generation rate for RTS is not changed under the relevant doping conditions. Modeling of the source-drain dopant distribution must include atomistic simulation for accurate prediction of the RDD effect in NAND Flash memory below 30 nm.