Investigation of Retention Characteristics in a Triple-level Charge Trap 3D NAND Flash Memory

Abstract

In this paper, the long term data retention characteristics consisting of three main charge loss mechanisms, detrap, trap-assisted tunneling (TAT), and lateral migration (LM), are investigated in charge trap (CT) 3D NAND flash memory. Three mechanisms were completely separated through experiment design, and each activation energy (E <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</inf> ) was extracted with Arrhenius model well. The detrap mechanism shows the largest E <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</inf> , followed by LM and TAT mechanisms. It is interesting that the contribution rate (CR) of each mechanism is related to time-constant (τ) in the early part of bake time, and depends on the final charge loss in the latter part of bake time. It is inferred that the retention bottleneck is low program level state at high temperature and is high program level state at low temperature. TAT mechanism dominates the final charge loss regardless of temperature region and program level state. In addition, an effective method is proposed to suppress the LM effect.