TCSE: A Target Cell States Elimination Coding Strategy for Highly Reliable Data Storage Based on 3-D NAND Flash Memory

With the wide application of NAND flash storage systems in read-intensive memory, the corresponding reliability enhancement strategies for mitigating read disturb become the focus of investigations in recent years. The prior investigations have reported the strategies based on data modulation and verified their effectiveness in mitigating retention loss. The most significant advantage of these strategies is that they can often achieve significant reliability enhancement effect with great read performance, since they are usually based on asymmetric coding. This feature means that they have the potential to be ideal reliability enhancement strategies for read-intensive memory applications. To propose a universal and highly reliable data storage strategy, this article first observes the error modes at the cell-state level under the reliability stresses of retention loss and read disturb with floating-gate (FG) 3-D triple-level (TLC) NAND flash, and then proposes a target cell states elimination (TCSE) coding strategy for further restraining bit errors. In addition, this article for the first time reports the extra bit errors generated in the decoding process of the storage strategies based on data modulation, and defines the concept of transfer factor (TF) for evaluation. By using the proposed TCSE, the experimental results show that the overall bit error rate (BER) can be reduced by 80%-90% on average, compared with the raw random data pattern.