Total Ionizing Dose Effects in 3-D NAND Replacement Gate Flash Memory Cells

Total ionizing dose effects in 3D NAND Flash memories with replacement gate technology are evaluated. Threshold voltage shifts and bit error rates in devices exposed to X rays are studied, focusing on the response of replacement gate cells. The structure of the memory array, the cell geometry and architecture, and the materials impacting on the radiation susceptibility are discussed together with the underlying mechanisms. The results are compared with 3D NAND Flash memory cells with floating gate technology in terms of threshold voltage shifts, dependence on program pattern, and error rate, showing differences, mainly resulting from voltage level optimization choices.