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

Abstract

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 (Leff) 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.