$V_{t}$ Retention Distribution Tail in a Multitime-Program MLC SONOS Memory Due to a Random-Program-Charge-Induced Current-Path Percolation Effect

Author

Chung, Yueh-Ting ; Huang, Tzu-I ; Li, Chi-Wei ; Chou, You-Liang ; Chiu, Jung-Piao ; Wang, Tahui ; Lee, M.Y. ; Chen, Kuang-Chao ; Lu, Chih-Yuan

Author_Institution

Dept. of Electron. Eng., Nat. Chiao Tung Univ., Hsinchu, Taiwan

Volume

59

Issue

5

fYear

2012

fDate

5/1/2012 12:00:00 AM

Firstpage

1371

Lastpage

1376

Abstract

A Vt retention distribution tail in a multitime-program (MTP) silicon-oxide-nitride-oxide-silicon (SONOS) memory is investigated. We characterize a single-program-charge-loss-induced ΔVt in NOR-type SONOS multilevel cells (MLCs). Our measurement shows the following: 1) A single-charge-loss-induced ΔVt exhibits an exponential distribution in magnitudes, which is attributed to a random-program-charge-induced current-path percolation effect, and 2) the standard deviation of the exponential distribution depends on the program-charge density and increases with a program Vt level in an MLC SONOS. In addition, we measure a Vt retention distribution in a 512-Mb MTP SONOS memory and observe a significant Vt retention tail. A numerical Vt retention distribution model including the percolation effect and a Poisson-distribution-based multiple-charge-loss model is developed. Our model agrees with the measured Vt retention distribution in a 512-Mb SONOS well. The observed Vt tail is realized mainly due to the percolation effect.

Keywords

Poisson distribution; elemental semiconductors; exponential distribution; flash memories; integrated circuit modelling; nitrogen compounds; numerical analysis; percolation; silicon; silicon compounds; NOR-type SONOS multilevel cells; Poisson-distribution-based multiple-charge-loss model; SiO-NO-Si; exponential distribution; multitime-program MLC SONOS memory; numerical voltage retention distribution model; program-charge density; random-program-charge-induced current-path percolation effect; silicon-oxide-nitride-oxide-silicon flash memory; single-program-charge-loss-induced voltage; standard deviation; storage capacity 512 Mbit; voltage retention distribution tail; Current measurement; Educational institutions; Flash memory; Logic gates; Loss measurement; Numerical models; SONOS devices; $V_{t}$ retention distribution; Model; percolation; silicon–oxide–nitride–oxide–silicon (SONOS);

fLanguage

English

Journal_Title

Electron Devices, IEEE Transactions on

Publisher

ieee

ISSN

0018-9383

Type

jour

DOI

10.1109/TED.2012.2188531

Filename

6175940