Browsing by Author "Li, Chi-Wei"

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Characterization and modeling of trap number and creation time distributions under negative-bias-temperature stress
(2012-08-20)
Chiu, Jung-Piao
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Li, Chi-Wei
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Wang, Tahui
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
Individual trapped charge creations and a trap number in p-type metal-oxide-semiconductor field effect transistors (pMOSFETs) under negative bias temperature instability (NBTI) stress are investigated. We find that the characteristic times of a trapped charge creation scatter over several decades of time in small area pMOSFETs, which is attributed to an activation energy distribution in the reaction-diffusion (RD) model of NBTI. We develop a statistical model by combining the RD model with an extracted activation energy distribution to calculate a threshold voltage shift distribution at different NBTI stress times. Our model agrees with measured results very well. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4748108]
Fuzzy PDFF-IIR controller for PMSM drive systems
(2011-08-01)
Cheng, Stone
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Li, Chi-Wei
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機械工程學系
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Department of Mechanical Engineering
Pseudo-derivative feedback with feed-forward gain (PDFF) combines the advantages of proportional-integral (PI) and pseudo-derivative feedback (PDF) controllers. However. PDFF responds more slowly to a command than does PI. To increase the speed of response of the PDFF controller, this work presents a PDFF with moving average errors control. A low-pass IIR filter path for errors compensation that accelerates the slow response is added to a PDFF control loop. A fuzzy inferencer is utilized to adjust the feed-forward gain and integral gain of the PDFF controller to allow closed-loop poles of the transfer function to be properly placed to improve load torque disturbance rejection capability. Simulated and experimental results reveal that the response and load disturbance rejection ability of the fuzzy PDFF-IIR controller are better than those of the traditional PDFF controller. (C) 2011 Elsevier Ltd. All rights reserved.
Statistical Characterization and Modeling of the Temporal Evolutions of Delta V-t Distribution in NBTI Recovery in Nanometer MOSFETs
(2013-03-01)
Chiu, Jung-Piao
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Liu, Yu-Heng
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Hsieh, Hung-Da
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Li, Chi-Wei
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Chen, Min-Cheng
NBTI trapped charge characteristics and recovery mechanisms are examined by a statistical study of individual trapped charge emissions in nanoscale HfSiON/metal gate pMOSFETs. We measure individual trapped charge emission times in NBTI recovery in a large number of devices. The characteristic time distributions of the first three emitted holes are obtained. The distributions can be well modeled by using a thermally-assisted tunnel (ThAT) detrapping model. NBTI trapped charge energy and spatial distributions and its activation energy distribution in the ThAT model are discussed and extracted. Based on the ThAT model and measured result of single-charge induced V-t shifts, we develop a statistical NBTI recovery Delta V-t evolution model. Our model can well reproduce the temporal evolutions of a Delta V-t distribution in a number of NBTI stressed nanometer MOSFETs in relaxation.
V-t Retention Distribution Tail in a Multitime-Program MLC SONOS Memory Due to a Random-Program-Charge-Induced Current-Path Percolation Effect
(2012-05-01)
Chung, Yueh-Ting
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Huang, Tzu-I
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Li, Chi-Wei
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Chou, You-Liang
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Chiu, Jung-Piao
A V-t 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 Delta V-t in NOR-type SONOS multilevel cells (MLCs). Our measurement shows the following: 1) A single-charge-lossinduced Delta V-t 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 V-t level in an MLC SONOS. In addition, we measure a V-t retention distribution in a 512-Mb MTP SONOS memory and observe a significant V-t retention tail. A numerical V-t retention distribution model including the percolation effect and a Poisson-distribution-based multiple-charge-loss model is developed. Our model agrees with the measured V-t retention distribution in a 512-Mb SONOS well. The observed V-t tail is realized mainly due to the percolation effect.