Early retention or initial threshold voltage shift (IVS) is one of the key reliability challenges in charge trapping memory (CTM) based 3D NAND flash. Re-program scheme was introduced in quad-level-cell (QLC) NAND (Shibata et al., 2007, Lee et al., 2018, Shibata et al., 2019, and Khakifirooz et al., 2021), and the IVS improvement by re-program scheme was reported. In this work, it is found that re-program can suppress ~81% of IVS in 3D NAND, which is much more significant than that of 2D NAND ~50% (Chen et al., 2010). The mechanisms of IVS improvement by re-program scheme in 3D NAND are investigated. Both vertical de-trapping in the BE-tunneling oxide and charge lateral migration (LM) in the charge-trap layer are suppressed in re-program. Re-program is effective in vertical de-trapping suppression both in checker-board pattern (C/P) and solid-board pattern (S/P) cases, and is effective in LM suppression only in C/P case. Furthermore, the LM improvement by re-program scheme is more pronounced with gate length (Lg) and inter-gate space (Ls) scaling down, showing potential in the reliability improvement of advanced 3D NAND technologies.

中文翻译：

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基于电荷陷阱的 3D NAND 闪存重编程方案研究


早期保留或初始阈值电压偏移 (IVS) 是基于电荷捕获存储器 (CTM) 的 3D NAND 闪存的关键可靠性挑战之一。四层单元 (QLC) NAND 中引入了重新编程方案（Shibata 等人，2007 年；Lee 等人，2018 年；Shibata 等人，2019 年；Khakifirooz 等人，2021 年），以及 IVS据报道，通过重新编程计划进行了改进。在这项工作中，发现重新编程可以抑制 3D NAND 中约 81% 的 IVS，这比 2D NAND 约 50% 的 IVS 显着得多（Chen 等人，2010）。研究了 3D NAND 中通过重新编程方案改进 IVS 的机制。 BE隧道氧化物中的垂直去捕获和电荷捕获层中的电荷横向迁移（LM）在重新编程中都被抑制。重新编程对于棋盘图案（C/P）和实心板图案（S/P）情况下的垂直去陷印抑制都有效，并且仅在C/P情况下对于LM抑制有效。此外，随着栅极长度 (Lg) 和栅极间距 (Ls) 的缩小，通过重新编程方案实现的 LM 改进更加明显，显示出先进 3D NAND 技术可靠性改进的潜力。