Deteriorated Non-Linear Interference in 3D NAND Cell With Word-Line Pitch Scaling Due to the Incapability to Turn on Non-Gate-Controlled Region

For 3D NAND memory, with continuous word line (WL) pitch scaling, deteriorated WL interference and the impact on triple-level cell (TLC) operation window are anticipated. However, as the WL pitch is scaled from 63nm to 50nm, the enormous Vt window losses induced by significantly deteriorated WL interference are found. With scaled WL pitch, the non-linear WL interference behavior of 3D NAND with increasing programmed Vt of neighboring aggressor cell occurs earlier, which leads to unacceptable TLC window losses. The non-linear behavior is due to insufficient gate overdrive on aggressor cell, and the reduction of gate overdrive originates from the weakly-inverted channel locating at non-gate-controlled region. With the two adjacent gates getting closer, the fringing E-field from aggressor cell gets weaker, failing to fully turn on the non-gate-controlled channel. It then increases the effective Vt of aggressor cell, leading to the early insufficient gate overdrive issue and anomalous WL interference deterioration.