Hot-Carrier Injection-Induced Disturb and Improvement Methods in 3D NAND Flash Memory

We investigate a hot-carrier injection-induced program disturb in a 3D NAND flash memory. As there exist specific coding patterns, a “down-coupling” region and a “pre-charge” regions are formed during program-verify and the following program phases, respectively, in the inhibit cell strings. A high heating field is built nearby the PGM wordline. Hot carriers may inject into the inhibit cells as Vpgm is applied. Soft ramp-down and pre-turn-on schemes are proposed to mitigate this disturb.