Investigation of Inhibited Channel Potential of 3D NAND Flash Memory According to Word-Line Location

Abstract

Natural local self-boosting (NLSB) was analyzed according to the location of a selected word-line (WL) where potential boosting occurs. When the same pattern occurred, it was found that the top cells (WL11 through WL15) and bottom cells (WL0 through WL4) have identically symmetrical potential boosting. In addition, in the region of the middle cells (WL6 through WL10), a slight change in the potential boosting was also almost the same. In the 3D NAND, where there was a dummy WL (DWL), the NLSB for the edge WL changed as the pattern of the DWL changed. The DWL did not affect the NLSB of the main cell, regardless of the pattern. Therefore, the high potential of the edge WL could reduce the potential difference between the main cell and the edge WL using the DWL.

A Novel Program Scheme for Z-Interference Improvement in 3D NAND Flash Memory

“…For z-interference improvement, several works have aimed to decrease the channel barrier with operation schemes, but most studies have focused on the adjustment of the neighboring cells' Vread during the read operation [9][10][11]16,20]. Other researchers have studied schemes of non-selected cells' Vpass to improve the device characteristics during programming in 3D NAND flash, such as cell Vpass disturbance and PGM disturbance [21,22], but they have not clearly focused on the analysis of the influence of the adjacent cells' WLn ± 1 Vpass on z-interference during programming. Additionally, there is no study on the components and formation factors of WLn (victim) channel barrier increase that arises during WLn + 1 (aggressor) pattern programming.…”

A Review of Cell Operation Algorithm for 3D NAND Flash Memory

“…Third, since it is difficult to remove electrons in the polysilicon channel during the pre-charge operation due to the grain boundary trap [14,15], achieving high channel potential in boosting mode is very challenging. Fourth, when large channel potential difference between adjacent WLs is applied in the end of programming loop [16], the electron/hole pair generated via the trap-assisted band-to-band tunneling (BTBT) mechanism reduces the channel boosting potential [17,18]. Fifth, due to the floating body characteristics of 3D NAND, a negative down-coupling phenomenon occurs during the falling of the verify pulse of the selected and the unselected WLs [19], aggravating the deterioration of the hot carrier injection (HCI) program disturb [20].…”

Channel Potential of Bandgap-Engineered Tunneling Oxide (BE-TOX) in Inhibited 3D NAND Flash Memory Strings

“…However, the current structure constitutes multiple strings that are extensively used; there exists an inhibited string that does not proceed with program operation. Analysis of the inhibited string is necessary because the channel is not directly connected to the body and can thus easily flow into a floating state, causing various phenomena [12][13][14][15]. Therefore, the analysis of the inhibited channel is as important as that of the selected string.…”