Total-Ionizing-Dose Effects on Threshold Voltage Distribution of 64-Layer 3D NAND Memories

We measure total-ionizing-dose (TID) induced threshold voltage $\left(V_{t}\right)$ loss of a commercial 64-layer triple-level-cell (TLC) 3D NAND memory using user-mode commands. Our experiments show that V
t
distributions closely follow Gaussian distributions. At increasing TID, the distributions shift toward lower average values and the distribution widths widen. We calculate exact cell V
t
shifts from the pre-irradiation conditions at different TID values. We find that $V_{t} \operatorname{loss}\left(\Delta V_{t}\right)$ distributions also follow Gaussian distributions. We also find that $\Delta V_{t}$ values strongly depend on the cell programmed states.