A Novel Read Scheme for Read Disturbance Suppression in 3D NAND Flash Memory

Abstract

A new read scheme is proposed to suppress read disturbance in unselected strings of three-dimensional (3D) vertical channel flash memories. This new scheme decreases the channel potential difference between select word-line (WL) and adjacent WL by more than 20% and the read disturb due to hot carrier injection in adjacent WL of selected WL is suppressed effectively by about 95%. Meanwhile, boosted channel potential during read operation has been preserved to improve soft programming read disturbance by more than 85% in non-adjacent unselected memory cells, owing to the reduced electric field across tunnel oxide. Compared with the conventional scheme, the proposed scheme leads to a significant improvement in read disturbance characteristics with a shorter read period as well as a simplified waveform of read operation.