High Bit Cost Scalability and Reliable Cell Characteristics for 7th Generation 1Tb 4Bit/Cell 3D-NAND Flash.

The continuous increase of total number of word-line (WL) layers and the reduction of unit cell size make it difficult to implement quad-level cell (QLC) in 3D-NAND flash. In this paper, we introduce several technological breakthroughs to realize QLC with high performance and reliability for $7^{\mathrm{th}}$ generation 3D-NAND (7 ^th QLC). By introducing advanced technologies, the QLC reliability is enhanced by 74% compared to before the improvement, which is equivalent the previous generation QLC 3D-NAND with 92-layer (5 ^th QLC). Furthermore, the average performance is 25% increased and bit density is doubled compare to $5^{\mathrm{th}}$ QLC.