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High resolution and energy filtering TEM study of interfacial structure and reaction in advanced materials processing
(1998-04-10)
Chang, HL
;
Chang, L
;
Chen, FR
;
Kai, JJ
;
Tzou, E
High resolution TEM becomes more powerful when coupled with a Gatan imaging filler (GIF). It gives both structural and compositional information simultaneously with subnanometer and nanometer resolution. respectively. By means of these combined techniques, the failure mechanism of diffusion barrier layers in IC devices, having the structure of Al-1%Si-0.5%CuiTiNITi/Si substrate, was investigated. In non-oxygen stuffed samples thermally stressed at 550 degrees C for 1 h serious Al spikes below contacts were observed where metal layer Ti also reacted with Si substrate to form C49-TiSi2 and was consumed completely. TiN and Al become unstable due to high temperature thermal stress and reacted into TiAl3 and AlN. Decomposition of TiN degraded the function of the barrier layer, and so a diffusion path at the weakest point of the contact corner was opened for metal Al alloy to diffuse through the barrier layer and to form a spike below the TiN layer. We also showed that the oxygen-stuffing processes after each TiN/Ti deposition enhances the barrier capability against Al/Si diffusion in thermal stress. It was found that Ti and TiN were oxidized to form titanium oxide which reacted with the Al alloy. As a result, Al2O3 and TiAl3 were found above the TiN layer. Therefore, it is concluded that oxidation during oxygen-stuffing processes provides a means to inhibit diffusion in thermal stress processes, and maintains integrity of the stack structure. (C) 1998 Acta Metallurgica Inc.
Using a weight-assessing model to identify route choice criteria and information effects
(2001-03-01)
Chen, TY
;
Chang, HL
;
Tzeng, GH
;
運輸與物流管理系註：原交通所+運管所
;
Department of Transportation and Logistics Management
Shortest-path (minimum travel time) routing has been adopted over the past few decades. However, many studies have shown that a driver's route and the shortest path differ widely in significant ways, and that most drivers use several criteria in selecting their routes. Since route choice criteria have been the subject of controversy, this study develops an individual behavioral-based mechanism for exploring the crucial criteria affecting drivers' route-selection decisions. On the basis of the weight-assessing model and the habitual domain theory, this study presents the dynamic change of route choice criteria according to their dynamic weights. Furthermore, the effects of information on drivers' route-formulating behaviors are investigated as well in order to provide some valuable suggestions for implementing Advanced Traveler Information Systems (ATIS) in the future. An empirical study in Taipei City was conducted to show the feasibility and applicability of our proposed method and the empirical results indicate excellent performance in practice. (C) 2001 Elsevier Science Ltd. All rights reserved.
Analytical model for design criteria of passively Q-switched laser
(2001-03-01)
Chen, YF
;
Lan, YP
;
Chang, HL
;
電子物理學系
;
光電工程學系
A general and straightforward model was developed for the design of passively Q-switched lasers. With the second-threshold criterion and using a numerically fitting procedure, the output pulse energy was expressed as an analytical function of the initial transmission of the saturable absorber and the reflectivity of the output coupler. An analytical expression for the optimal output reflectivity was also obtained for maximizing the output pulse energy of a passively Q-switched laser with a given initial transmission of the saturable absorber. Excellent agreement was studied between the present results and detailed theoretical computations. A Nd:YAG laser with Cr4+:YAG as a saturable absorber was performed to illustrate the use of the present model.
Properties of Si-C-N films prepared on Si substrate using cobalt interfacial layers
(2001-11-01)
Chang, HL
;
Kuo, CT
;
材料科學與工程學系
;
Department of Materials Science and Engineering
A microwave plasma chemical vapor deposition (MPCVD) process was successfully used to synthesize Si-C-N films. The film properties were tuned by deposition parameters and engineering interfacial Co layers on Si substrates. The films were deposited by using CH4, N-2, and additional solid Si columns as raw material sources. The films were characterized by scanning electron microscopy (SEM) for film morphologies, X-ray photo-emission spectroscopy (XPS) and cathodoluminescence (CL) spectroscopy for bonding structure and band gap analyses. The results show that the application of Co interlayer can have the following effects: (1) it can change film morphology from (100) preferred orientation to become pyramidal structure, and the band gap from 2.93 to 4.00 eV; (2) it may possess the additional Si(2p)-Si bonding in the films. By adding additional Si source, the atomic ratio of Si:C:N can change significantly with the decrease in carbon content of films, the film structure may vary from amorphous to crystalline and possess additional C(1s)=N bonding (or N(1s)=C bonding). In summary, the composition, morphology, bonding and crystal structures of Si-C-N films have been successfully demonstrated to be manipulated through applications of Co interlayer and additional Si source. (C) 2001 Elsevier Science B.V. All rights reserved.
Effects of substrate pretreatments and catalyst applications on Si-C-N films and nanotube formations
(2001-12-01)
Chang, HL
;
Kuo, CT
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The Si-C-N films were synthesized on Si substrates by a microwave plasma chemical vapor deposition (MPCVD) system with CH4, H-2 and N-2 as the source gases. Metal coating on Si columns were placed around the specimen and acted as catalyst and additional source of Si. Some of the Si substrates were mechanically polished or chemically etched with HF-KIO3-H2O solutions to obtain different surface roughness before film depositions. Effects of the substrate pretreatment and the action of catalysts on surface morphologies, compositions, band structure, field emission of the films were examined. Nanotubes or nanowires structures were found for films deposited on no-treatment substrate using Fe, Co and Pt catalysts. However, chemical etching substrate can enhance formation of crystals and film nucleation with or without the addition of catalyst. This was the first work to demonstrate the possibility of fabricating the Si-C-N nanotubes through use of the catalysts and by controlling the deposition conditions by MPCVD. Under the present deposition conditions and by using Fe catalyst, the lowest turn-on voltage of the films can be as low as 1.3 V/mum, while the corresponding emission current density at field strength of 20 V/mum can go beyond 2000 muA/cm(2).
Using fuzzy measures and habitual domains to analyze the public attitude and apply to the gas taxi policy
(2002-02-16)
Chen, TY
;
Chang, HL
;
Tzeng, GH
;
運輸與物流管理系註：原交通所+運管所
;
Department of Transportation and Logistics Management
Public acceptance and support are the crucial keys for implementing public policies successfully. Thus, the understanding of public acceptance or rejection towards the policy, as well as the important attributes of concern, could be very helpful to implementing the policy. However, most conventional attitude models could not approximate people's subjective evaluation process exactly by virtue of the additivity and independence assumptions. Additionally, people's decision behavior is deeply affected by their existing habits. Since habitual domains exist in the decision process, if the government can change or extend people's habitual thinking in favor of the public policy, the policy will receive satisfactory acceptance. Therefore, this study uses the habitual domain theory to analyze the public's attitude towards public policies. Furthermore, general fuzzy measures and fuzzy integrals, which require only boundary conditions and monotonicity, are also applied to develop a public attitude analysis model. An empirical study on the compress natural gas (CNG) taxi policy in Taipei City is conducted to show the applicability of the proposed model. The empirical results indicate that there are significant differences between the public's concern and governmental publicity, and some valuable strategies are suggested to the government. (C) 2002 Elsevier Science B.V. All rights reserved.
Growth mechanism and properties of the large area well-aligned carbon nano-structures deposited by microwave plasma electron cyclotron resonance chemical vapor deposition
(2002-03-01)
Lin, CH
;
Chang, HL
;
Tsai, MH
;
Kuo, CT
;
材料科學與工程學系
Large area (4-inch diameter) well-aligned carbon nano-structures on Si substrate were successfully synthesized by using a catalyst-assisted microwave plasma electron cyclotron resonance chemical vapor deposition (ECR-CVD) system with CH4 as source gas. The catalysts include Fe, Co and Ni. The catalysts and the deposited nano-structures were characterized by scanning electron microscopy (SEM) transmission electron microscopy (TEM), Raman and field emission I-V measurements. Effects of process parameters on morphologies, structures and properties of the nano-structures were examined. The results show that the deposited nano-structures can include normal nano-tubes, split catalyst nano-tubes, seaweed-like nano-sheets and carbon film, depending mainly on substrate temperature and bias, catalyst materials and their application methods. Deposition mechanisms for different nano-structures, especially, the unique split catalyst nano-tubes and seaweed-like nano-sheets, were proposed. The differences in oxidation resistance and field emission proper-ties between different nano-structures will be compared and discussed. (C) 2002 Elsevier Science B.V. All rights reserved.
Field emission, structure, cathodoluminescence and formation studies of carbon and Si-C-N nanotubes
(2002-03-01)
Chang, HL
;
Lin, CH
;
Kuo, CT
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Catalyst growth carbon and Si-C-N nanotubes have been synthesized successfully by microwave plasma chemical vapor deposition (MPCVD) method using CH4 + H-2 or CH4 + N-2 as gas sources, Si columns as additional Si solid sources, and Fe, Fe-Y, Co-Ni as catalysts. Nanotubes consisting of Si, C and N were made under process gases of CH4 + N-2, and with or without additional Si columns. Well-aligned and nested nanotubes were observed dependent on the catalyst materials. Besides, Si-C-N nanotubes were observed as bamboo-Eke structure. The as-grown nanotubes were purified in an air furnace to investigate their CL signal shift for potential application involving blue light emission. The field emission results indicate that the emission current densities can be above 10 mA/cm(2) at 10 V/mum, and aligned nanotubes belong to better current stability at a constant electric field than nested nanotubes. Nanotubes with a low I-D/I-G ratio (=0.23) via Raman analysis are achieved. The mechanisms of formation for carbon nanotubes and Si-C-N nanotubes are also discussed. (C) 2002 Elsevier Science B.V. All rights reserved.
Effect of silane flowing time on W volcano and plug formation
(2002-05-01)
Chang, HL
;
Juang, FL
;
Kuo, CT
;
交大名義發表
;
National Chiao Tung University
W volcano is one of the defects in semiconductor devices. The presence of defects causes metal line bridges and thus device malfunction. The decomposition of SiH4 gas into Si atoms as nucleation sites is crucial for W film deposition. Here, we investigate the phenomenon in which the flowing time of SiH4 gas appears to dominate both W volcano formation and the degree of W film filling in a hole; the density of W volcanoes is increased with an increase of SiH4 flowing time. The volcano-free process and step-coverage of a W plug with various SiH4 flowing times are evaluated, and a formation mechanism is also proposed.
Forming silicon carbon nitride crystals and silicon carbon nitride nanotubes by microwave plasma-enhanced chemical vapor deposition
(2002-06-17)
Chang, HL
;
Hsu, CM
;
Kuo, CT
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Catalyst-assisted silicon carbon nitride (SiCN) nanotubes and SiCN crystals are prepared. The SiCN nanotubes and SiCN crystals are formed by gaseous sources of CH4/N-2/H-2 and CH4/N-2, respectively, and using solid Si columns arranged symmetrically around the specimen as additional Si sources. The formation of the tubular structure is related to the ambient of process that includes H-2 gas, which is considered to delay the action of the so-called catalyst poisons and keep the tube end open during growth. Analysis shows that the SiCN crystals exhibit tetragonal or hexagonal shapes with sizes of about several microns, and multibonding structures. In contrast, the SiCN tubes are randomly orientated with various diameters, and graphitelike structure. The growth mechanisms of SiCN crystals and SiCN nanotubes are discussed. (C) 2002 American Institute of Physics.

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