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🏛️國立陽明交通大學機構典藏

Author: search.filters.author.Wang, TahuiSubject: search.filters.subject.SONOS

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Now showing 1 - 5 of 5
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    Variations of V-t Retention Loss in a SONOS Flash Memory Due to a Current-Path Percolation Effect
    (2011-04-01)
    Chou, Y. L.
    ;
    Chung, Y. T.
    ;
    Wang, Tahui
    ;
    Ku, S. H.
    ;
    Zou, N. K.
    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 (Delta V-t) are characterized. We find the following: 1) The magnitude of Delta V-t 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 V-t 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 Delta V-t and a tunneling front model to study the spread of a retention V-t distribution in a SONOS Flash memory.
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    Electric Field Induced Nitride Trapped Charge Lateral Migration in a SONOS Flash Memory
    (2017-01)
    Liu, Yu-Heng
    ;
    Jiang, Cheng-Min
    ;
    Chen, Wei-Chun
    ;
    Wang, Tahui
    ;
    Tsai, Wen-Jer
    We investigated electric field-induced trapped electron lateralmigration in a SONOS flash cell. The threshold voltage shift (Delta V-t) andgate-induceddrain leakage(GIDL) current were measured to monitor nitride electron movement in retention. We applied different voltages to the gate and the source/drain in retention to vary the vertical and lateral electric fields. Our study shows that: 1) GIDL current can be used tomonitor trapped charge lateralmigration and 2) nitride charge lateral migration exhibits strong dependence on the lateral electric field. Based on measured temperature and field dependence, a nitride trapped charge emission process via thermally assisted tunneling is proposed for electron lateral migration. The emission rates of thermally assisted tunneling, direct trap-to-band tunneling and Frenkel-Poole emission were compared.
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    Item type:Item,
    Electric Field Induced Nitride Trapped Charge Lateral Migration in a SONOS Flash Memory
    (2017-01)
    Liu, Yu-Heng
    ;
    Jiang, Cheng-Min
    ;
    Chen, Wei-Chun
    ;
    Wang, Tahui
    ;
    Tsai, Wen-Jer
    We investigated electric field-induced trapped electron lateralmigration in a SONOS flash cell. The threshold voltage shift (Delta V-t) andgate-induceddrain leakage(GIDL) current were measured to monitor nitride electron movement in retention. We applied different voltages to the gate and the source/drain in retention to vary the vertical and lateral electric fields. Our study shows that: 1) GIDL current can be used tomonitor trapped charge lateralmigration and 2) nitride charge lateral migration exhibits strong dependence on the lateral electric field. Based on measured temperature and field dependence, a nitride trapped charge emission process via thermally assisted tunneling is proposed for electron lateral migration. The emission rates of thermally assisted tunneling, direct trap-to-band tunneling and Frenkel-Poole emission were compared.
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    A Novel Hot-Electron Programming Method in a Buried Diffusion Bit-Line SONOS Memory by Utilizing Nonequilibrium Charge Transport
    (2009-02-01)
    Wang, Tahui
    ;
    Tang, Chun-Jung
    ;
    Li, C. -W.
    ;
    Lee, Chih Hsiung
    ;
    Ou, T. -F
    We propose a new hot-electron programming method with a low drain-to-source voltage in a buried-diffusion (BD) bit-line SONOS memory array. In this method, channel electrons are preaccelerated in a cell preceding a program cell. For a small bit-line width, some energetic electrons will traverse an n(+) BD region and enter a program cell with residual energy due to nonequilibrium transport. Our measurement result shows that this residual energy can significantly enhance hot-electron programming efficiency even at a V(ds) of 2.5 V. The concept of this method is verified by means of a Monte Carlo analysis. Our study shows that this method is more effective as a bit-line width reduces.
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    Program Trapped-Charge Effect on Random Telegraph-Noise Amplitude in a Planar SONOS Flash Memory Cell
    (2009-11-01)
    Ma, H. C.
    ;
    Chou, Y. L.
    ;
    Chiu, J. P.
    ;
    Wang, Tahui
    ;
    Ku, S. H.
    Program-charge effects in a SONOS Flash cell on the amplitude of random telegraph noise (RTN) are investigated. We measure RTN in 45 planar SONOS cells and 40 floating-gate (FG) cells in erase state and program state, respectively. We find that a SONOS cell has a wide spread in RTN amplitudes after programming, while an FG cell has identical RTN amplitudes in erase and program states at the same read-current level. A 3-D atomistic simulation is performed to calculate RTN amplitudes. Our result shows that the wide spread of program-state RTN amplitudes in a SONOS cell is attributed to a current-path-percolation effect caused by random discrete nitride charges.