Total Ionizing Dose Effects in 3-D NAND Flash Memories

The effects of total ionizing dose on 3-D flash memories irradiated with gamma rays are investigated. The evolution and shape of threshold voltage distributions are studied versus dose for floating gate cell NAND arrays with vertical-channel architecture. The dependence of total dose effects on the logic level stored in the cells, the underlying mechanisms, and the raw bit errors induced by gamma-rays are discussed. The results are then compared with planar NAND and NOR flash technologies, in terms of threshold voltage shifts and bit error rates, showing improvements over previous generations due to the new cell structure.