Impact of Self-Heating Effect on the Retention of 3-D NAND Flash Memory

The three-dimensional (3-D) NAND flash memory technology has been considered as a promising candidate for future memory solutions, because it overcomes the scaling limitation and reliability issues faced by conventional planar memory. Even though 3-D NAND flash memory structures have many merits, self-heating effect is aggravated seriously due to the poor thermal conductivity of some of the materials in nanoscale used in 3-D NAND fabrication and gate-all-around (GAA) geometry. In this work, the local temperatures in a 3-D NAND flash memory with different operation modes are evaluated. The average temperature can be heated to 400K for the 48-layer stacked cells during the continuous PAGE READ operation. The self-heating effect will cause severe degradation of retention due to the thermal enhanced charge diffusion along the 3-D NAND vertical structure. The impact of self-heating effect on the retention of a string of three cells is simulated by electro-thermal simulation, and three different programmed patterns are considered. The most severe retention degradation by up to 1.6V of the 5.6V programmed voltage after 10(7)s retention time. The results can be useful to the design and optimization for the new generation of 3-D NAND flash memory.