Impact of edge encroachment on programming and erasing gate current in NAND-type flash memory

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

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


The edge encroachment of tunnel oxide is experimentally found to degrade the FowlerNordheim (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.

Original languageEnglish
Article number5737873
Pages (from-to)1257-1263
Number of pages7
JournalIEEE Transactions on Electron Devices
Issue number4
StatePublished - 1 Apr 2011


  • Edge encroachment
  • FowlerNordheim (FN) tunneling
  • NAND-type Flash
  • gate current
  • tunnel oxide

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