Browsing by Author "Chao, Tien Sheng"

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A carbon nanotube field effect transistor with tunable conduction-type by electrostatic effects
(2006-07-01)
Chen, Bae-Horng
;
Wei, Jeng-Hua
;
Lo, Po-Yuan
;
Wang, Hung-Hsiang
;
Lai, Ming-Jinn
In this paper, we report a conduction-type-tunable carbon nanotube field effect transistor (CNT-FET) with double-gate structure (DG CNT-FET). In this study, a specially designed narrow top-gate is created to modulate the energy band in the middle region of a single CNT. In the proposed DG device structure, the top-gate and bottom-gate biases exhibit independent modulation behaviors. Depending on whether a positive or negative bias is applied to the top-gate, the CNT-FET can be operated in either n- or p-type conduction. Energy band diagram conducive to the physical mechanisms of the proposed DG CNT-FET device structure is proposed. Based on the proposed hypothesis, ambipolar CNT-FETs can indeed be converted to n- or p-type-like behaviors. (c) 2006 Elsevier Ltd. All rights reserved.
Carrier transportation mechanism of the TaN/HfO(2)/IL/Si structure with silicon surface fluorine implantation
(2008-07-01)
Wu, Woei Cherng
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Lai, Chao-Sung
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Wang, Tzu-Ming
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Wang, Jer-Chyi
;
Hsu, Chih Wei
In this paper, the current transportation mechanism of HfO(2) gate dielectrics with a TaN metal gate and silicon surface fluorine implantation is investigated. Based on the experimental results of the temperature dependence of gate leakage current and Fowler-Nordheim tunneling characteristics at 77 K, we have extracted the current transport mechanisms and energy band diagrams for TaN/HfO(2)/IL/Si structures with fluorine incorporation, respectively. In particular, we have obtained the following physical quantities: 1) fluorinated and as-deposited interfacial layer (IL)/Si barrier heights (or conduction band offsets) at 3.2 and 2.7 eV; 2) TaN/fluorinated and as-deposited HfO(2) barrier heights at 2.6 and 1.9 eV; and 3) effective trapping levels at 1.25 eV (under both gate and substrate injections) below the HIM conduction band and at 1.04 eV (under gate injection) and 1.11 eV (under substrate injection) below the HfO(2) conduction band, which contributes to Frenkel-Poole conduction.
Current transport mechanism for HfO2 gate dielectrics with fluorine incorporation
(2008)
Wu, Woei Cherng
;
Lai, Chao Sung
;
Wang, Tzu Ming
;
Wang, Jer Chyi
;
Hsu, Chih Wei
In this article, the current transport mechanism of fluorinated HfO2 gate dielectrics is investigated. Based on the experimental results of the temperature dependence of gate leakage current and Fowler-Nordheim tunneling characteristics at 77 K, we have extracted the energy band diagrams and current transport mechanisms for TaN/HfOF/fluorinated-interfacial layer (IL)/Si structures. In particular, we have obtained the following quantities that will be useful for modeling and simulation: (i) fluorinated IL/Si barrier height (or conduction band offset): 3.2 eV; (ii) TaN/HfOF barrier height: 2.6 eV; and (iii) trap levels at 1.3 eV (under both gate and substrate injections) below the HfOF conduction band which contributes to Frenkel-Poole conduction. (C) 2007 The Electrochemical Society.
High-performance HfO2 gate dielectrics fluorinated by postdeposition CF4 plasma treatment
(2007)
Wu, Woei Cherng
;
Lai, Chao Sung
;
Wang, Jer Chyi
;
Chen, Jian Hao
;
Ma, Ming Wen
The superior characteristics of fluorinated HfO2 gate dielectrics were investigated. Fluorine was incorporated into HfO2 thin film by postdeposition CF4 plasma treatment to form fluorinated HfO2 gate dielectrics. Secondary-ion mass spectroscopy results showed that there was a significant incorporation of fluorine atoms at the TaN/HfO2 and HfO2/Si interface. Improvement of the gate leakage current, breakdown voltage, capacitance-voltage hysteresis, and charge trapping characteristics was observed in the fluorinated HfO2 gate dielectrics, with no increase of interfacial layer thickness. A physical model is presented to explain the improvement of hysteresis and the elimination of charge trapping. These results indicate that the fluorinated HfO2 gate dielectrics appear to be useful technology for future ultrathin gate dielectrics. (C) 2007 The Electrochemical Society.
Performance improvement of CoTiO3 high-k dielectrics with nitrogen incorporation
(2007)
Chen, Jian Hao
;
Huang, Tzung Bin
;
Wu, Xiaohua
;
Landheer, Dolf
;
Lei, Tan Fu
In this paper, three approaches to incorporating nitrogen in CoTiO3 high-k dielectric films, ion implantation of N-2(+), ion implantation of N+, and N2O plasma treatment have been investigated for the new CoTiO3 high-k dielectrics. All three methods reduced the leakage currents and improved the breakdown characteristics but the N2O-plasma treatment produced the best-behaved C-V curves, when compared to the untreated control samples. (c) 2006 The Electrochemical Society.
Prospect of cobalt-mix-tetraethoxysilane method on localized lateral growth of carbon nanotubes for both p- and n-type field effect transistors
(2006-09-01)
Chen, Bae-Horng
;
Lin, Horng-Chih
;
Huang, Tiao-Yuan
;
Wei, Jeng-Hua
;
Hwang, Chien-Liang
To apply carbon nanotubes (CNTs) to nanoelectronics, researchers must effectively control the placement and manipulation of massive numbers of CNTs. In this work, we demonstrate a precise growth of single-walled carbon nanotubes (SWNT) on preassigned locations with only cobalt as catalyst. This is in contrast to the laborious and time-consuming physical manipulation of numerous nanotubes one at a time used in the conventional approach. Laterally grown CNTs were accomplished in preassigned areas using an integrated circuit compatible process in this study. In order to synthesize SWNT as the channel of a field effect transistor (FET), the cobalt-mix-tetraethoxysilane (CMT) solution and catalytic chemical vapor deposition were used. The CMT solution has the unique property of well dispersing the cobalt catalyst and uniformly embedding it in predetermined locations after the CMT solution has solidified. Our results show that laterally grown bundled-CNTs could be formed in atmospheric chemical vapor deposit ion with ethanol, by properly controlling the temperature of process, the process time, and the hydrogen reduction time. Since our bundled-CNTs were exposed to the air, all the as-grown CNT-FETs we manufactured exhibit p-type characteristics. Furthermore, we also demonstrate air-stable n-type CNT-FETs successfully without resorting to any additional and complicated annealing process by simply depositing a silicon nitride film on the as-grown p-type devices by plasma enhanced (PECVD) at 390 degrees C. The use of prepatterned catalyst islands, CVD method, and flexibility of simultaneously manufacturing both n- and p-type CNT-FETs may open a new era for applications of CNT-based nanoelectronics. (c) 2006 American Vacuum Society.
Suppression of interfacial reaction for HfO2 on silicon by pre-CF4 plasma treatment
(2006-08-14)
Lai, Chao Sung
;
Wu, Woei Cherng
;
Chao, Tien Sheng
;
Chen, Jian Hao
;
Wang, Jer Chyi
In this letter, the effects of pre-CF4 plasma treatment on Si for sputtered HfO2 gate dielectrics are investigated. The significant fluorine was incorporated at the HfO2/Si substrate interface for a sample with the CF4 plasma pretreatment. The Hf silicide was suppressed and Hf-F bonding was observed for the CF4 plasma pretreated sample. Compared with the as-deposited sample, the effective oxide thickness was much reduced for the pre-CF4 plasma treated sample due to the elimination of the interfacial layer between HfO2 and Si substrate. These improved characteristics of the HfO2 gate dielectrics can be explained in terms of the fluorine atoms blocking oxygen diffusion through the HfO2 film into the Si substrate. (c) 2006 American Institute of Physics.