Impact of String Pattern on the Threshold-Voltage Spread of Program-Inhibited Cell in NAND Flash

Yung Yueh Chiu; Minoru Aoki; Masaru Yano; Riichiro Shirota

doi:10.1109/JEDS.2016.2565820

Impact of String Pattern on the Threshold-Voltage Spread of Program-Inhibited Cell in NAND Flash

Yung Yueh Chiu^*, Minoru Aoki, Masaru Yano, Riichiro Shirota

^*Corresponding author for this work

Department of Electrical and Computer Engineering

Research output: Contribution to journal › Article › peer-review

3 Scopus citations

Abstract

An anomalous threshold-voltage (V _t ) spread of the program-inhibited cell is investigated for the first time in NAND flash memory. The program disturb characteristics are studied by applying the program-inhibited stress on the Nth cell of the unselected bitline with various string patterns for the 0th to (N-1)th cell, using the global self-boosting method. Distinguishing features of the variance of the number of injected electrons (σ _n ² ) into the floating gate are observed. The variance is proportional to the mean value of injected electrons (n) times 10. The other is proportional to n times 20 and occurs only when the (N-1)th cell is programmed in a high V _t level and the other cells are in the erased state. A 3-D TCAD simulation reveals that the former case is attributed to Fowler-Nordheim tunneling from the insufficiently boosting channel, and the latter is explained by hot-electron injection owing to the strong lateral electric field between the Nth and (N-1)th cells.

Original language	English
Article number	7467394
Pages (from-to)	174-178
Number of pages	5
Journal	IEEE Journal of the Electron Devices Society
Volume	4
Issue number	4
DOIs	https://doi.org/10.1109/JEDS.2016.2565820
State	Published - 1 Jul 2016

Keywords

Fowler-Nordheim (FN) tunneling
NAND flash memory
hot-carrier injection (HCI)
program disturb

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title = "Impact of String Pattern on the Threshold-Voltage Spread of Program-Inhibited Cell in NAND Flash",

abstract = " An anomalous threshold-voltage (V t ) spread of the program-inhibited cell is investigated for the first time in NAND flash memory. The program disturb characteristics are studied by applying the program-inhibited stress on the Nth cell of the unselected bitline with various string patterns for the 0th to (N-1)th cell, using the global self-boosting method. Distinguishing features of the variance of the number of injected electrons (σ n 2 ) into the floating gate are observed. The variance is proportional to the mean value of injected electrons (n) times 10. The other is proportional to n times 20 and occurs only when the (N-1)th cell is programmed in a high V t level and the other cells are in the erased state. A 3-D TCAD simulation reveals that the former case is attributed to Fowler-Nordheim tunneling from the insufficiently boosting channel, and the latter is explained by hot-electron injection owing to the strong lateral electric field between the Nth and (N-1)th cells. ",

keywords = "Fowler-Nordheim (FN) tunneling, NAND flash memory, hot-carrier injection (HCI), program disturb",

author = "Chiu, {Yung Yueh} and Minoru Aoki and Masaru Yano and Riichiro Shirota",

year = "2016",

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doi = "10.1109/JEDS.2016.2565820",

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AU - Chiu, Yung Yueh

AU - Aoki, Minoru

AU - Yano, Masaru

AU - Shirota, Riichiro

PY - 2016/7/1

Y1 - 2016/7/1

N2 - An anomalous threshold-voltage (V t ) spread of the program-inhibited cell is investigated for the first time in NAND flash memory. The program disturb characteristics are studied by applying the program-inhibited stress on the Nth cell of the unselected bitline with various string patterns for the 0th to (N-1)th cell, using the global self-boosting method. Distinguishing features of the variance of the number of injected electrons (σ n 2 ) into the floating gate are observed. The variance is proportional to the mean value of injected electrons (n) times 10. The other is proportional to n times 20 and occurs only when the (N-1)th cell is programmed in a high V t level and the other cells are in the erased state. A 3-D TCAD simulation reveals that the former case is attributed to Fowler-Nordheim tunneling from the insufficiently boosting channel, and the latter is explained by hot-electron injection owing to the strong lateral electric field between the Nth and (N-1)th cells.

AB - An anomalous threshold-voltage (V t ) spread of the program-inhibited cell is investigated for the first time in NAND flash memory. The program disturb characteristics are studied by applying the program-inhibited stress on the Nth cell of the unselected bitline with various string patterns for the 0th to (N-1)th cell, using the global self-boosting method. Distinguishing features of the variance of the number of injected electrons (σ n 2 ) into the floating gate are observed. The variance is proportional to the mean value of injected electrons (n) times 10. The other is proportional to n times 20 and occurs only when the (N-1)th cell is programmed in a high V t level and the other cells are in the erased state. A 3-D TCAD simulation reveals that the former case is attributed to Fowler-Nordheim tunneling from the insufficiently boosting channel, and the latter is explained by hot-electron injection owing to the strong lateral electric field between the Nth and (N-1)th cells.

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