Enhancing 3D NAND flash endurance via thermal annealing: A step towards everlasting SSDs

NAND flash memory has finite endurance, fundamentally constrained by the increasing defect density in the tunnel oxide [1]. The typical endurance for single-level cell (SLC) NAND is around $10^{5}$ cycles, whereas triple-level cell (TLC) NAND endures only $10^{3}$ cycles. This endurance limitation poses challenges for the seamless integration of NAND into future compute-intensive applications and necessitates the periodic replacement of solid-state drives (SSDs) in data centers. Thermal annealing is a well-known technique for repairing degraded flash memory cells and extending their endurance [1], [2]. While previous studies have explored its effects on 2D NAND [3], research on 3D NAND remains limited. This work provides a comprehensive analysis of the impact of thermal annealing on the state of memory cells in 64-layer 3D NAND flash memories, offering new insights into its effectiveness as an endurance recovery strategy. Our findings indicate that annealing NAND cells in the programmed state significantly enhances their endurance compared to annealing them in the erased state. This approach holds great promises for extending the lifespan of flash cells, potentially paving the way for everlasting storage solutions.