Select Device Disturb Phenomenon in TANOS NAND Flash Memories

Author

Melde, Thomas ; Beug, Marc Florian ; Bach, Lars ; Tilke, Armin Thomas ; Knoefler, Roman ; Bewersdorff-Sarlette, Ulrike ; Beyer, Volkhard ; Czernohorsky, Malte ; Paul, Jan ; Mikolajick, Thomas

Author_Institution

Qimonda GmbH & Co. OHG, Dresden

Volume

30

Issue

5

fYear

2009

fDate

5/1/2009 12:00:00 AM

Firstpage

568

Lastpage

570

Abstract

This letter investigates a new select device disturb phenomenon in TANOS NAND flash memories. Since NAND string select devices contain the same charge trap (CT) stack as the memory cells, they are, in principle, programmable. We observe a select threshold voltage increase during cycling of the cell array. This disturb is caused by electron injection from the outermost wordline into the CT layer of the select devices under the erase condition. The increasing select threshold voltage leads to a reduced string current and, finally, to read fails of the NAND string. The mechanism is evaluated by means of electrical measurements and field simulations. Several options to overcome this issue are proposed.

Keywords

NAND circuits; flash memories; NAND string select devices; TANOS NAND flash memories; charge trap stack; electron injection; select device disturb phenomenon; Degradation; Electric variables measurement; Electron traps; Nonvolatile memory; Performance evaluation; Semiconductor device measurement; Silicon; Testing; Threshold voltage; NAND; Charge trap (CT); cycling; disturb; erase; nonvolatile memory devices; select device;

fLanguage

English

Journal_Title

Electron Device Letters, IEEE

Publisher

ieee

ISSN

0741-3106

Type

jour

DOI

10.1109/LED.2009.2017497

Filename

4850270