Browsing by Author "Chen, Chuan-Li"

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A Statistical Model for the Headed and Tail Distributions of Random Telegraph Signal Magnitudes in Nanoscale MOSFETs
(2014-07-01)
Chen, Ming-Jer
;
Tu, Kong-Chiang
;
Wang, Huan-Hsiung
;
Chen, Chuan-Li
;
Lai, Shiou-Yi
Trapping-detrapping of a single electron via an individual trap in metal-oxide-semiconductor field-effect transistor (MOSFET) gate dielectric constitutes two-level random telegraph signals. Recent 3-D technology computer-aided design (TCAD) simulations, on an individual MOSFET, revealed that with the position of the trap as a random variable, resulting random telegraph signals relative magnitude Delta I-d/I-d in the subthreshold current at low drain voltage can have two distinct distributions: a headed one for a percolation-free channel and a tail one for a percolative channel. The latter may be effectively treated by a literature formula: (Delta I-d/I-d) = (I-loc/I-d)(2), where I-loc is the local current around the trap. In this paper, we show how to make this formula practically useful. First, we conduct 3-D TCAD simulations on a 35 x 35-nm(2) channel to provide Delta I-d/I-d for a few positions of the trap. This leads to a new statistical model in closed form, which can reproduce headed distributions. Straightforwardly, key criteria are drawn from the model, which can act as guidelines for the adequate use of the I-loc/I-d formula. Extension to threshold voltage shift counterparts, from subthreshold through transition to inversion, is successfully achieved. Importantly, use of the model may overcome the drawbacks of the statistical experiment or simulation in the field.
Criteria for Plasmon-Enhanced Electron Drag in Si Metal-Oxide-Semiconductor Devices
(2015-03-01)
Chen, Ming-Jer
;
Hsieh, Shang-Hsun
;
Liao, Yu-Chiao
;
Chen, Chuan-Li
;
Tsai, Ming-Fu
Plasmons in the highly doped source and drain regions of silicon field-effect transistors can strongly drag channel electrons via long-range collective Coulomb interactions and cause deteriorations in overall device performances. To examine such interactions, two different methods have been published: 1) sophisticated device simulations and 2) carefully calibrated experiments. To provide a more transparent understanding, we propose a third method in terms of two criteria: 1) one for the occurrence of the plasmon resonance and 2) the other for the strength of the plasmons. The former is determined based on our published dragged mobility data due to the interface plasmons and the bulk plasmons in gate. The latter makes use of our more recently experimentally extracted potential fluctuations due to plasmons in crystalline silicon. The effects of the temperature on the criteria are considered. It is a straightforward task to confirm that for a channel density larger than approximately 5 x 10(12) cm(-2), the source and drain plasmons act as key limiters in silicon device scaling. Therefore, the underlying device physics, modeling, simulations, experimental analyses, and data interpretation may be inaccurate if the limiting factors are not incorporated.
Plasmon-enhanced phonon and ionized impurity scattering in doped silicon
(2015-07-28)
Chen, Ming-Jer
;
Hsieh, Shang-Hsun
;
Chen, Chuan-Li
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Historically, two microscopic electron scattering calculation methods have been used to fit macroscopic electron mobility data in n-type silicon. The first method was performed using a static system that included long-range electron-plasmon scattering; however, the well-known Born approximation fails in this case when dealing with electron-impurity scattering. In the second method, sophisticated numerical simulations were developed around plasmon-excited potential fluctuations and successfully reproduced the mobility data at room temperature. In this paper, we propose a third method as an alternative to the first method. First, using a fluctuating system, which was characterized on the basis of our recently experimentally extracted plasmon-excited potential fluctuations, the microscopic calculations reveal enhanced short-range scattering of electrons by phonons and ionized impurities due to increased electron temperature and increased screening length, respectively. The increased hot electron population makes the Born approximation hold, which eases the overall calculation task substantially. Then, we return to the static system while incorporating plasmon-enhanced impurity scattering. The resulting macroscopic electron mobility shows fairly good agreement with data over wide ranges of temperatures (200-400 K) and doping concentrations (10(15) -10(20) cm(-3)). Application of the proposed method to strained silicon is also demonstrated. (C) 2015 AIP Publishing LLC.
Plasmons-Enhanced Minority-Carrier Injection as a Measure of Potential Fluctuations in Heavily Doped Silicon
(2014-07-01)
Chen, Ming-Jer
;
Chen, Chuan-Li
;
Hsieh, Shang-Hsun
;
Chang, Li-Ming
;
電子工程學系及電子研究所
Well-known apparent electrical silicon bandgap narrowing in a heavily doped region of a bipolar transistor is observed by means of an enhanced minority-carrier injection experiment. In the region of interest, plasmons-induced potential fluctuations are existent in nature and hence constitute the origin of apparent bandgap narrowing. In this letter, we extract the underlying potential fluctuations directly from the enhanced minority-carrier injection experiment published in the literature. The core of the extraction lies in a combination of the two existing theoretical frameworks. First, the Gaussian distribution can serve as a good approximation of potential fluctuations. Second, no change can be made in the real bandgap between fluctuating conduction-and valence-band edges. Extracted potential fluctuations come from plasmons, as verified by our published temperature dependences of plasmons limited mobility in the inversion layer of MOSFETs as well as theoretical calculation results on bulk silicon. More importantly, this letter can deliver potential applications in the modeling and simulation area of nanoscale FETs (MOSFETs, FinFETs, and so forth) and bulk semiconductors.
Probing Long-Range Coulomb Interactions in Nanoscale MOSFETs
(2013-12-01)
Chen, Ming-Jer
;
Chang, Li-Ming
;
Wei, Sih-Yun
;
Chen, Wan-Li
;
Yeh, Ting-Hsien
We have recently experimentally probed long-range Coulomb interactions due to plasmons in polysilicon gate of long-channel (1 mu m) MOSFETs. In this letter, we further probe those due to plasmons in the highly doped source and drain. Test vehicles include four more samples from the same manufacturing process but with small channel lengths (down to 33 nm). I-V's of devices are measured at two drain voltages of 0.05 and 1 V, in a temperature range of 292-380 K. Inverse modeling technique is applied to furnish calibrated doping profiles. The inversion layer electron effective mobility is thereby extracted, showing a decreasing trend with decreasing channel length. Such differences reflect more additional scatterers in the shorter devices. Mobility components limited by these additional scatterers are assessed using Matthiessen's rule. From the extracted temperature dependencies, we infer that the strength of source/drain plasmons increases with decreasing channel length. The errors of Matthiessen's rule are adequately dealt with. Corroborative evidence is given as well.