Impact of Edge Encroachment on Programming and Erasing Gate Current in nand -Type Flash Memory

Author

Liang, Ting ; Shih, Chun-Hsing ; Chang, Wei ; Luo, Yan-Xiang ; Huang, Ming-Kun ; Chien, Nguyen Dang ; Wu, Wen-Fa ; Wu, Sau-Mou ; Lien, Chenhsin ; Shirota, Riichiro ; Huang, Chiu-Tsung ; Lu, Su ; Wang, Alex

Author_Institution

Nat. Tsing Hua Univ., Hsinchu, Taiwan

Volume

58

Issue

4

fYear

2011

fDate

4/1/2011 12:00:00 AM

Firstpage

1257

Lastpage

1263

Abstract

The edge encroachment of tunnel oxide is experimentally found to degrade the Fowler-Nordheim (FN) tunneling gate current of NAND-type Flash cells. This work elucidates the impact of edge encroachment on FN tunneling current for use in programming and erasing operations. The fringing field effect and tunnel oxide with trapezoidal edge are considered in the determination of physical gate current in which a conformal-mapping method is used to estimate the contribution of the fringing fields. These analytical results are confirmed using 2-D device simulations and experimental measurements. The results show that the overlapped encroachment causes an exponential degradation of intrinsic FN tunneling current. Preventing the encroachment of lateral edges resulting from overall tunnel-oxide enlargement is critical to ensuring normal programming and erasing speeds in future NAND-type Flash cells.

Keywords

flash memories; logic gates; tunnelling; 2D device simulation; FN tunneling gate current; Fowler-Nordheim tunneling gate current; NAND-type flash memory; conformal-mapping method; erasing gate current; fringing field effect; programming trapezoidal edge encroachment; tunnel oxide; Analytical models; Capacitors; Current measurement; Image edge detection; Logic gates; Programming; Tunneling; Edge encroachment; Fowler–Nordheim (FN) tunneling; gate current; nand-type Flash; tunnel oxide;

fLanguage

English

Journal_Title

Electron Devices, IEEE Transactions on

Publisher

ieee

ISSN

0018-9383

Type

jour

DOI

10.1109/TED.2011.2105492

Filename

5737873