Browsing by Author "Chung, Y. T."

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A Comparative Study of NBTI and RTN Amplitude Distributions in High-kappa Gate Dielectric pMOSFETs
(2012-02-01)
Chiu, J. P.
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Chung, Y. T.
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Wang, Tahui
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Chen, Min-Cheng
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Lu, C. Y.
Random telegraph noise (RTN) and negative bias temperature (NBT) stress-induced threshold voltage (V-t) fluctuations in high-kappa gate dielectric and metal-gate pMOSFETs are investigated. We measured RTN amplitude distributions before and after NBT stress. RTN in poststressed devices exhibits a broader amplitude distribution than the prestress one. In addition, we trace a single trapped charge-induced Delta V-t in NBT stress and find that the average Delta V-t is significantly larger than a Delta V(t)caused by RTN. A 3-D atomistic simulation is performed to compare a single-charge-induced Delta V-t by RTN and NBTI. In our simulation, the probability distribution of a NBT trapped charge in the channel is calculated from the reaction-diffusion model. Our simulation confirms that the NBT-induced Delta V-t indeed has a larger distribution tail than RTN due to a current-path percolation effect.
Investigation of Factors Affecting SET-Disturb Failure Time in a Resistive Switching Memory
(2016)
Su, P. C.
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Chung, Y. T.
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Chen, M. C.
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Wang, Tahui
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電子工程學系及電子研究所
Factors affecting SET-disturb failure time (tau(f)) in a tungsten oxide resistive switching memory including SET/RESET cycling stress, resistance window in operation and SET-disturb voltage are investigated. A SET-disturb failure time in high resistance state (HRS) may degrade by orders of magnitude in a post-cycling cell. The degradation is attributed to the formation of a current percolation path of cycling stress-generated traps. A one-dimensional percolation model is proposed for the tau(f) degradation. The dependence of tau(f) on resistance window in operation is characterized. We find that tau(f) is greatly affected by the current level of LRS. The strong LRS dependence of tf is attributed to a small Weibull slope of tau(f). In addition, we perform statistical characterizations of tau(f) at different SET-disturb voltages. A relationship between tau(f) and a SET-disturb voltage in a stressed cell is given.
Investigation of Random Telegraph Noise Amplitudes in Hafnium Oxide Resistive Memory Devices
(2014-01-01)
Chung, Y. T.
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Liu, Y. H.
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Su, P. C.
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Cheng, Y. H.
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Wang, Tahui
Statistical characterization of two-level random telegraph noise (RTN) amplitude distribution in a hafnium oxide resistive memory has been performed. We find that two-level RTN in HRS exhibits a large amplitude distribution tail, as compared to LRS. To investigate an RTN trap position in a hafnium oxide film, we measure the dependence of electron capture and emission times of RTN on applied read voltage. A correlation between an RTN trap position and RTN amplitude is found. A quasi-two-dimensional RTN amplitude simulation based on trap-assisted electron sequential tunneling is developed. Our study shows that RTN traps in a rupture region of a hafnium oxide film are responsible for an RTN large-amplitude tail in HRS mostly.
Variations of V(t) Retention Loss in a SONOS Flash Memory Due to a Current-Path Percolation Effect
(2011-04-01)
Chou, Y. L.
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Chung, Y. T.
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Wang, Tahui
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Ku, S. H.
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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.
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.