Cell-State-Distribution-Assisted Threshold Voltage Detector for NAND Flash Memory
Cell-State-Distribution-Assisted Threshold Voltage Detector for NAND Flash Memory
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用于 NAND 闪存的单元状态分布辅助阈值电压检测器
DOI：
10.1109/lcomm.2019.2900677
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Fang Yi
中科院分区：
文献类型：
--
作者：
Fan Zhengqin;Cai Guofa;Han Guojun;Liu Wenjie;Fang Yi
工艺微缩以及多级单元技术极大地提高了NAND闪存的存储密度。不幸的是，高密度闪存受到严重噪声的影响，导致其性能急剧恶化。在这封信中，我们提出了一种单元状态分布辅助阈值电压检测（CSD-TVD）来优化读取参考电压。具体来说，所提出的检测方法利用重叠区域的每个子窗口内的多个单元的变化来检测电压偏移并分析其分布。然后，将电压偏移分布的平均值视为最佳电压偏移，用于提高读取参考电压的精度。基于保留特性，我们还构思了一种新型低延迟（LL）CSD-TVD，以减少 CSD-TVD 的检测范围。实验结果表明，所提出的 CSD-TVD 和 LL-CSD-TVD 比最先进的保留优化读取（ROR）和非均匀检测方法实现了更好的错误性能。此外，相对于 CSD-TVD 和 ROR，LL-CSD-TVD 显着降低了读取延迟。
The process scaling as well as the multi-level cell technology greatly increase the storage density of NAND flash memory. Unfortunately, the high-density flash memory suffers from severe noise such that its performance will be dramatically deteriorated. In this letter, we propose a cell-state-distribution-assisted threshold voltage detection (CSD-TVD) to optimize read reference voltages. Specifically, the proposed detection method exploits the variation of a number of cells within each sub-window of the overlap region to detect the voltage shift and analyze its distribution. Afterward, the mean of the voltage-shift distribution is viewed as the optimal voltage shift, which is used to boost the accuracy of the read reference voltage. Based on the retention characteristics, we also conceive a novel low-latency (LL) CSD-TVD to reduce the detection range of the CSD-TVD. The experimental results demonstrate that the proposed CSD-TVD and LL-CSD-TVD achieve better error performance than the state-of-the-art retention-optimized-reading (ROR) and nonuniform detection methods. In addition, the LL-CSD-TVD significantly reduces the read latency with respect to the CSD-TVD and ROR.