Effect of Lateral Charge Diffusion on Retention Characteristics of 3D NAND Flash Cells

• Published in: IEEE electron device letters 2021-08, Vol.42 (8), p.1148-1151
• Main Authors: Yoo, Ho-Nam, Choi, Bongsik, Back, Jong-Won, Kang, Ho-Jung, Kwon, Eunmee, Chung, Sungyong, Bae, Jong-Ho, Park, Byung-Gook, Lee, Jong-Ho
• Format: Article
• Language: English
• Subjects: 3-D NAND flash memory; charge loss mechanisms; data retention reliability; Diffusion effects; Flash memories; Logic gates; Retention; Temperature; Temperature measurement; Three-dimensional displays; threshold voltage (Vth) instabilities; Time measurement
• ISSN: 0741-3106; 1558-0563
• DOI: 10.1109/LED.2021.3088851

Retention characteristics of 3D NAND Flash cells are investigated at various temperatures ( {T} ) depending on the degree of program and erase. The \Delta {V}_{\text {th}} for each condition is compared to understand the degradation of the retention characteristics attributable to vertical loss and/or lateral diffusion. In addition, the relationship between Program/Erase (PE) window (PGM {V}_{\text {th}} - Erase {V}_{\text {th}} ) and \Delta {V}_{\text {th}} are analyzed. In the case when PGM {V}_{\text {th}} is the same, the \Delta {V}_{\text {th}} decreases as the PE window decreases. At temperatures below 150 °C, \Delta {V}_{\text {th}} and PE window show linear relationship, and as PE window decreases, \Delta {V}_{\text {th}} also decreases to 0. On the other hand, at 250 °C, \Delta {V}_{\text {th}} has a non-zero value even if PE window decreases to 0, thus has a non-linear relationship. The measurement results show that the lateral diffusion has a great influence on the short-term retention of 3D NAND flash cells.