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

Abstract

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 Vt distributions closely follow Gaussian distributions. At increasing TID, the distributions shift toward lower average values and the distribution widths widen. We calculate exact cell Vt 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.