Concave and Convex Structures for Advanced 3-D NAND Flash Memory Technology

We investigated the program and reliability characteristics of convex and concave structures for advanced 3-D NAND flash memory. The program characteristics of the convex structure included confined trapped charge distribution due to the concentration of the electric field in the word line (WL) region, leading to better characteristics than the conventional structure. On the other hand, the electric field of the concave structure was dispersed, and intercell trapped charge in the spacer region occurred, which led to degradation of the program performance. The convex structure had improved interference characteristics due to the confined trapped charge distribution, and the concave structure had an improvement in the read disturbance.