Variations of Vt retention loss in a SONOS flash memory due to a current-path percolation effect

Y. L. Chou, Y. T. Chung, Ta-Hui Wang, S. H. Ku, N. K. Zou, Vincent Chen, W. P. Lu, K. C. Chen, Chih Yuan Lu

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Discrete nitride program charge loss in a small-area SONOS Flash memory cell during retention is observed. Our measurement shows that a retention V t of a programmed SONOS cell exhibits a stepwise evolution with retention time. Individual single-program charge-loss-induced threshold voltage shifts (Δ Vt) are characterized. We find the following: 1) The magnitude of Δ Vt exhibits an exponential distribution, which is believed due to a current-path percolation effect caused by random program charges and substrate dopants, and 2) program-state Vt retention loss has large variations in different cells and P/E cycles due to the percolation effect. We develop a Monte Carlo analysis to take into account the distribution of Δ Vt and a tunneling front model to study the spread of a retention Vt distribution in a SONOS Flash memory.

Original languageEnglish
Article number5723684
Pages (from-to)458-460
Number of pages3
JournalIEEE Electron Device Letters
Issue number4
StatePublished - 1 Apr 2011


  • Percolation
  • retention loss
  • single-program charge

Fingerprint Dive into the research topics of 'Variations of V<sub>t</sub> retention loss in a SONOS flash memory due to a current-path percolation effect'. Together they form a unique fingerprint.

Cite this