Browsing by Author "Yeh, Ta-Ching"

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Asymmetric Gate Capacitance and High Frequency Characteristic Fluctuations in 16 nm Bulk MOSFETs Due to Random Distribution of Discrete Dopants
(2008)
Li, Yiming
;
Hwang, Chih-Hong
;
Yeh, Ta-Ching
;
電信工程研究所
;
Institute of Communications Engineering
Characteristic fluctuation dependence on discrete dopant for 16nm SOI FinFETs at different temperature
(2007)
Li, Yiming
;
Hwang, Chih-Hong
;
Yu, Shao-Ming
;
Huang, Hsuan-Ming
;
Yeh, Ta-Ching
In this paper, we numerically study the discrete-dopant-induced characteristic fluctuations in 16nnn silicon-on-insulator (SOI) FinFETs. For devices under different temperature condition, discrete dopants are statistically generated and positioned into the three-dimensional channel region to examine associated carrier transportation characteristics, concurrently capturing "dopant concentration variation" and "dopant position fluctuation". Electrical characteristics' fluctuations are growing worse when the substrate temperature increases, the standard deviation of threshold voltage increases 1.75 times when substrate temperature increases from 300K to 400K for example. This "atomistic" device simulation technique is computationally cost-effective and provides us an insight into the problem of discrete-dopant-induced fluctuation and the relation between the fluctuation and thermal effect.
Comprehensive Examination of Threshold Voltage Fluctuations in Nanoscale Planar MOSFET and Bulk FinFET Devices
(2008)
Hwang, Chih-Hong
;
Cheng, Hui-Wen
;
Yeh, Ta-Ching
;
Li, Tien-Yeh
;
Huang, Hsuan-Ming
Intrinsic fluctuations on device characteristics, such as the threshold voltage (V(th)) fluctuation is crucial in determining the behavior of nanoscale semiconductor devices. In this paper, the dependency of process-variation and random-dopant-induced Vth fluctuation on the gate oxide thickness scaling in 16 nm metal-oxide-semiconductor field effect transistors (MOSFETs) is investigated. Fluctuations of the threshold voltage for the studied planar MOSFETs with equivalent oxide thicknesses (EOT) from 1.2 nm to 0.2 nm (e.g., SiO(2) for the 1.2 and 0.8 nm EOTs, Al(2)O(3) for the 0.4 nm EOT and HfO(2) for the 0.2 nm EOT) are then for the first time compared with the results of 16nm bulk fin-typed filed effect transistors (FinFETs), which is one of the promising candidates for next generation semiconductor devices. An experimentally validated simulation is conducted to investigate the fluctuation property. Result of this study confirms the suppression of Vth fluctuations with the gate oxide thickness scaling (using high-kappa dielectric). It's found that the immunity of the planar MOSFET against fluctuation suffers from nature of structural limitations. Bulk FinFETs alleviate the challenges of device's scaling and have potential in the nanoelectronics application.
Discrete Dopant Induced Characteristic Fluctuations in 16nm Multiple-Gate SOI Devices
(2007)
Li, Yiming
;
Hwang, Chih-Hong
;
Huang, Hsuan-Ming
;
Yeh, Ta-Ching
;
電信工程研究所
Emission Efficiency Dependence on the Tilted Angle of Nanogaps in Surface Conduction Electron-Emitter
(2008)
Li, Yiming
;
Kuo, Yi-Ting
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Cheng, Hui-Wen
;
Yeh, Ta-Ching
;
Lo, Hsiang-Yu
In this work, the emission efficiency of the novel surface conduction electron-emitter corresponding to tilted angles (0) of the driving electrode is studied numerically. Due to the small angle, the emitter apex becomes significant and induces large electric field. The large electric field then attracts more particles into vacuum and then increases the emission current. However, the structure of the driving electrode limits the electron trajectory while the angle decreases, and it reflects the portion of collected current by the anode decreases and makes a drop in emission efficiency. It shows there is the highest emission efficiency (about 37%) under an optimum angle theta = 60 degrees. The result provides an insight into the relation between emission efficiency and emitter apex.
Morphology effect on field emission property of carbon nanotube emitters in triode structure
(2008)
Cheng, Hui-Wen
;
Yeh, Ta-Ching
;
Kuo, Yi-Ting
;
Li, Yiming
;
Lin, Chen-Chun
In this work, process variation on the field emission property of the fabricated field emission (FE) triode arrays with carbon nanotubes (CNTs) as the field emitters are explored. To fabricate the FE triode structure, nanoporous anodic aluminum oxide (AAO) thin layer was first prepared on the Si substrate, followed by the growth of vertically aligned carbon nanotubes in AAO pore channels by electron cyclotron resonance chemical vapor deposition. The SiO2 dielectric and Al gate electrode layers required for the triode structure were directly deposited on the CNTs. Reactive ion and wet etches were then used to open the FE area in the triode. We employ the finite difference time domain particle-in-cell method to calculate the structure FE properly, where the results are calibrated with the collected FE current of the fabricated samples. The FE current Of Structure is then examined with respect to different shape, random height and angle of the CNT emitters. For symmetric shapes, like circle and square, the emission beam has been more focusing than triangle and trapezoid. The electric field of random height of CNTs is stronger than that of random angle. It is implied that the vertical CNTs has better FE property. Having the symmetric shape and vertical CNTs in triode Structure benefits the FE sources for advanced flat display technologies.
Reduction of Discrete-Dopant-Induced High-Frequency Characteristic Fluctuations in Nanoscale CMOS Circuit
(2008)
Li, Yiming
;
Hwang, Chih-Hong
;
Yeh, Ta-Ching
;
Huang, Hsuan-Ming
;
Li, Tien-Yeh
As the dimension of semiconductor device shrunk into nanoscale, characteristic fluctuation is more pronounced, and become crucial for circuit design. Diverse approaches have been reported to investigate and suppress the random-dopant-induced fluctuations in devices. However, attention is seldom drawn to the existence of high-frequency characteristic fluctuations of active device. In this paper, intrinsic high-frequency characteristic fluctuations of the nanoscale MOSFET circuit induced by random dopants are intensively explored using an experimentally validated simulation methodology, where fluctuation suppression technique is further examined. The circuit gain, the 3db bandwidth and the unity-gain bandwidth of the tested circuit are estimated concurrently capturing the discrete-dopant-number-and discrete-dopant-position-induced fluctuations. This study provides an insight into discrete-dopant-induced intrinsic high-frequency characteristic fluctuations and examines the potential fluctuation suppression technique for nanoscale transistor circuit.
Three-dimensional simulation of field emission triode structure using carbon-nanotube emitters
(2008-09-01)
Li, Yiming
;
Yeh, Ta-Ching
;
電信工程研究所
;
Institute of Communications Engineering
Field emission (FE) triode arrays with the anodic aluminum oxide (AAO) template carbon nanotubes (CNTs) as the field emitters are successfully fabricated and analyzed. Both the experimental measurement and numerical calculation are conducted to examine the electron conduction properties of AAO-CNTs. Using a three-dimensional finite-difference time-domain particle-in-cell method, a set of Maxwell equations and Lorentz equation is solved self-consistently, where the FE current is computed with Fowler-Nordheim equation. We explore the FE characteristics of AAO-CNTs in the triode structure. After calibration with the measured data, we study the evolution of current density and the convergence of the electron beams on anode plate with different gate voltages, anode heights, and SiO2 thickness. The current density and focus performance maintain a trade-off relationship, where a larger current density accompanies more divergent electron beam.