Browsing by Issue Date, starting with "1999-04-01"

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Time-resolved photoluminescence study of InGaAs/GaAs quantum wells on (111)B GaAs substrates
(1999-04-01)
Tsai, FY
;
Lee, CP
;
Shen, JX
;
Oka, Y
;
Cheng, HH
The exciton dynamics in In0.15Ga0.85As/GaAs quantum wells grown on (111)B and (100)GaAs substrates are studied by the time-resolved photoluminescence (PL). We have found that the piezoelectric fields in (111)B samples affect the transient behavior of PL spectra. Compared with the reference (100) samples, we have confirmed that the piezoelectric effect induces slower exciton relaxation in (111)B strained quantum wells. (C) 1999 Elsevier Science Ltd. All rights reserved.
A novel technology to form air gap for ULSI application
(1999-04-01)
Chang, KM
;
Yang, JY
;
Chen, LW
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this letter, we develop a novel process to fill the interline space with air (dielectric constant = 1). A silicon wafer, whose face is downward, patterned with metal lines, is placed on the top of another silicon wafer coated with dry polyimide. Hydrogen silsesquioxanes (HSQ), FOx-16, is diluted and trickled through the slit between the metal lines and the polyimide. Then the HSQ forms an ultrathin liquid layer on the dry polyimide and contacts with the top of the metal lines. After the liquid HSQ becomes dry, the air gap is formed, The dry polyimide has good adhesion to silicon substrate but not to the dry FOx-16, so we can separate the polyimide from the dry FOx-16 and get the air gap. The liquid property of HSQ and its high selective adsorption between the metal lines and the polyimide are utilized to form the air gap.
Effective improvement on barrier capability of chemical vapor deposited WSix using N-2 plasma treatment
(1999-04-01)
Wang, MT
;
Lin, YC
;
Wang, CC
;
Chen, MC
;
電子工程學系及電子研究所
This work studies the thermal stability of Cu/WSx/p(+)-n and Cu/WSiN/WSix/p(+)-n diodes in which the WSix barrier layers were deposited by chemical vapor deposition to a thickness of about 50 nm using SiH4/WF6 chemistry with the SiH4/WF6 flow rates of 6/2 seem, while the WSiN layers were formed by in situ N-2 plasma treatment on the chemically vapor deposited WSix (CVD-WSix) surfaces. Without N-2 plasma treatment, the thermal stability of Cu/WSix (50 nm)/p(+)-n junction diodes was found to reach 500 degrees C; with N-2 plasma treatment, the resultant Cu/WSiN/WSix (50 nm)/p(+)-n junction diodes were able to retain integrity of electrical characteristics up to at least 600 degrees C. Failure mechanism of the WSiN/WSix bilayer in the Cu/WSiN/WSix/Si structure was closely related to the WSix/Si interface reaction and the tungsten silicide formation of the WSix layer. Thus, barrier capability of the WSiN/WSix bilayer can be further improved by suppressing the WSix/Si interface reaction and the silicidation of the WSix layer. The thermal stability of Cu/barrier/p(+)-n diodes was further raised to 650 degrees C by using a multilayer barrier structure of WSiN/Si-x (50 nm)/WSiN/WSix (10 nm) or a WSiN/WSiy (y > 1) barrier We conclude that the post-CVD-WSix treatment with in situ N-2 plasma is a simple, practical, and efficient method of improving the WSix-based barrier capability for Cu metallization. (C) 1999 The Electrochemical Society. S0013-4651(97)09-073-9. All rights reserved.
Optimum multicast of multimedia streams
(1999-04-01)
Wang, CF
;
Lai, BR
;
Jan, RH
;
資訊工程學系
;
Department of Computer Science
In a VOD system, multicast is a preferred method for saving network bandwidth. That is, customers requesting the same video program over a small time interval can be arranged in a multicast tree (group), and then the video server sends a video stream via this tree to customers. In this research, we considered how to arrange a set of multicast trees such that the number of customers served is maximized and the link capacity constraint is maintained. For a directed acyclic graph (DAG), we proposed a branch-and-bound algorithm to solve this problem and the solution method is illustrated by example. Next, we extended the algorithm to find an approximate solution for a general graph case. It is shown, through simulations on randomly generated graphs that the solution for our approximation method is very close to the optimal solution. (C) 1999 Elsevier Science Ltd. All rights reserved.
Common-path heterodyne interferometric detection scheme for measuring wavelength shift
(1999-04-01)
Lee, JY
;
Su, DC
;
光電工程學系
;
Department of Photonics
When a linearly polarized light passes through a uniaxial crystal, small wavelength shifts will introduce phase difference variations between s- and p-polarizations, These phase difference variations can be measured accurately by heterodyne interferometry. Based on these facts, a common-path heterodyne interferometric detection scheme for measuring wavelength shift is proposed. This scheme has the advantages of both common-path interferometry and heterodyne interferometry. (C) 1999 Elsevier Science B.V. All rights reserved.
Leakage current reduction of chemical-vapor-deposited Ta2O5 films on rugged polycrystalline silicon electrode for dynamic random access memory application
(1999-04-01)
Lin, M
;
Chang, CY
;
Huang, TY
;
Shieh, WY
;
電子工程學系及電子研究所
In this paper we describe the electrical and physical characterizations of Ta2O5 films on rapid thermal nitrided (RTN) rugged polycrystalline silicon electrodes for 256 M dynamic random access memory (DRAM) application. To overcome the higher leakage on Ta2O5 films with rugged poly-Si bottom electrodes, we have successfully employed a light oxidation on rugged poly-Si grains for improving the acute angle of surface morphology, and a post-treatment with rapid thermal nitridation of N2O on Ta2O5 films to reduce the leakage. In addition, a RTN pre-treatment is also applied to prevent rugged poly-Si oxidation during a Ta2O5 film deposition that compromises the effective Ta2O5 thickness. Our results show that Ta2O5 film with an effective thickness of 1.4 nm (physical thickness=10 nm) and a low leakage current density of less than 1 X 10(-8) A/cm(2), suitable for 256 M DRAM application, can be achieved. Our results also show that while a light oxidation on rugged poly-Si grains could improve the acute angle between the rugged poly-Si and its congruent amorphous silicon sub-layer, over oxidation on rugged poly-Si grains could degrade the leakage current and the time dependent dielectric breakdown (TDDB) characteristics of the stacked capacitor.
Collision efficiencies of algae and kaolin in depth filter: The effect of surface properties of particles
(1999-04-01)
Huang, CP
;
Pan, JRS
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Huang, SH
;
環境工程研究所
;
Institute of Environmental Engineering
Column filtration experiments with 2 mm-Phi glass beads were conducted to investigate the behavior of colloids during filtration. Algae and kaolin were used as model particles, while the chemical system was altered by changing the electrolyte concentration and pH. The collision efficiencies from the interaction between colloids and the filter medium were calculated with a semi-empirical approach of the single sphere model and clean-bed filtration theory. The experimental results indicate that ionic strength enhance the removal efficiencies for both algae and kaolin particles significantly. The removal efficiency of the filter for algae decreased with the increase in pH for up to pH 6. No significant change was observed beyond pH 6. Removal efficiencies for kaolin decreased with an increase in pH. It is concluded that collision efficiencies are sensitive to ion strength and pH. (C) 1999 Elsevier Science Ltd. All rights reserved.
A novel transient simulation for 3-D multilevel interconnections on complex topography
(1999-04-01)
Hou, HM
;
Sheen, CS
;
Wu, CY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
An efficient method is presented to model the transient characteristics of distributed resistor-capacitor of ULSI multilevel interconnections on complex topography, in which the reformulation of the boundary-element method (BEM) and the Pade-via-Lanczos (PVL) algorithm associated with multilayer Green's function can avoid the redundant works on both volume mesh and transient analysis associated with the finite-difference method. An adaptive multilayer Green's function is adopted to investigate several cases that have revealed interesting physical mechanisms in charge transfer between conductors on multilayer topography. To improve the timing analysis efficiency of the finite-difference method, the dominant poles are obtained by introducing the PVL algorithm for model-ol der reduction. Hence, it is easy to calculate the transient characteristics of both parallel conductors and complicated configurations such as crossing lines, corners, contacts, multilayers, and their combinations.
Improvement of ultra-thin 3.3 nm thick oxide for co-salicide process using NF3 annealed poly-gate
(1999-04-01)
Chang, TY
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Lei, TF
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Chao, TS
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Huang, CT
;
Chen, SK
To get high quality ultra-thin oxide is very important and difficult for IC industry now. Using NF3 annealed poly-Si gate to improve gate oxide integrity is described. However, reducing fate, source and drain parasitic resistance with gate lengths down to 0.2 mu m is another key point. Co-salicide process can successfully reduce the gate resistance even for a gate length of 0.075 mu m. Although, Co-salicide process has a leakage problem. Using NF3 annealing to prevent Co diffusing into gate oxide is described too. Results show that the optimal NF3 annealing significantly improves electrical characteristics of ultra-thin oxide and Co-salicide process in terms of leakage current and breakdown field, as compared to the samples without NF3 annealing.
Fuzzy neural network approach for 2-D direction finding in multipath environments
(1999-04-01)
Ma, CW
;
Teng, CC
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電控工程研究所
;
Institute of Electrical and Control Engineering
A fuzzy neural network (FNN) approach for estimating the two-dimensional (2-D) direction of a radiating source in coherent multipath environments via a 2-D passive sensor array is presented. Outputs of the array are preprocessed by a judiciously constructed reference-point preprocessing scheme to produce proper inputs for an FNN. The FNN then uses these preprocessed outputs to produce the estimate of the source direction. Since the preprocessed outputs preserve enough information about the source direction and the FNN maps the preprocessed outputs into the source direction with high accuracy, the FNN approach exhibits good estimation performance. By computer simulations, it is found that the FNN approach drastically outperforms the spatial smoothing 2-D MUSIC algorithm.
Exact solution of the Ginzburg-Landau equation for the upper critical field of a d(x2-y2) superconductor
(1999-04-01)
Dai, MC
;
Yang, TJ
;
Ting, CS
;
電子物理學系
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Department of Electrophysics
A d(x2-y2) superconductor is modeled as the superconducting layers in the a-b plane, whose coupling in the c direction is approximated by the effective mass, within the Ginzburg-Landau theory. In this work, this model is applied to the system where the, coherence length along the c direction is greater than the layer spacing. Based on our model, we calculate the upper critical field in a magnetic field lying in a-e plane and tilted by an angle from the c axis. According to our results, the curvature of H-c2(T) is upward, and the slope - dH(c2)(T)/dT depends on the angle between the c axis and the external field. The most interesting feature is that the ratio of the c-direction parameter related to the effective mass to the n-b plane parameter connected with the effective mass can influence H-c2. As the rafio is decreased, H-c2. becomes increased. We also find that there is no admixture of s-wave component in the critical regime and believe that the upward curvature of the H-c2(T) is the characteristic property of a d-wave superconductor. [S0163-1829(99)01914-1].
Active feedback microstrip leaky wave antenna-synthesiser design with suppressed back lobe radiation
(1999-04-01)
Shih, YC
;
Chen, SK
;
Hu, CC
;
Jou, CF
;
傳播研究所
The design of an active leaky-wave antenna which integrates the antenna with a feedback synthesiser is introduced. The measurement result shows that the antenna has very low back lobe radiation compared with that of traditional single-terminal feeding leaky-wave antennas. Single frequency measurement shows that the radiated power differmce between the main beam and back lobe is >15 dB at 8.2 GHz For the designed feedback synthesiser antenna, the measured radiated power difference between the main beam and back lobe is >15dB at 9.25 GHz, and the scanning angle is similar to 5 degrees as the synthesiser frequency sweeps from 9.25 to 9.37 GHz.
Estimation of moving vehicle locations using wheel shape information in single 2-D lateral vehicle images by 3-D computer vision techniques
(1999-04-01)
Lai, CC
;
Tsai, WH
;
資訊工程學系
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Department of Computer Science
an approach to the estimation of moving lateral vehicle locations for driving assistance using wheel shape information in single 2-D vehicle images by 3-D computer vision techniques is proposed. The location scheme is supposed to be performed on a vehicle with a camera mounted on the front bumper. An analytical solution is applied to estimate locations of the lateral vehicle. Firstly, the rear wheel shape of a lateral vehicle moving in a nearby lane is imaged. By using the Hough transform, the projected wheel shape, which is an ellipse, is detected. Secondly. the equation of the detected ellipse is used to infer the orientation angle of the lateral vehicle with respect to the camera view direction. Finally, the center of the ellipse shape is used to determine the relative position of the lateral vehicle with respect to the camera lens center, Moreover, an edge-point verification algorithm is utilized to extract the ellipse shape more precisely in the image processing stage. Both computer simulated and real images are tested and good experimental results show the effectiveness of the proposed approach for estimating lateral vehicle locations. The results are useful for driving assistance and vehicle collision avoidance and are discussed in detail. (C) 1999 Elsevier Science Ltd. All rights reserved.
A stage approach for industrial technology development and implementation - the case of Taiwan's computer industry
(1999-04-01)
Chang, PL
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Hsu, CW
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Tsai, CT
;
管理科學系
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Department of Management Science
The objective of this paper is to study how government-supported R&D institutes cooperate with the industrial sector to assist industrial technology development in developing countries. By investigating the case of the computer industry in Taiwan, the authors suggest a stage approach for industrial technology development. This approach emphasizes the implementation of technology, that is, R&D institutes should help industry to truly absorb and apply technology to improve their products or services to upgrade their overall industrial competitiveness. For developing countries, the key problems of industrial technology development are not only gaining technology but also implementing that technology in their own industrial context, This paper suggests that R&D institutes should closely coordinate with industry during the R&D procedures to make different technology implementation strategies at different developmental stages. The approach is based on three stages which respectively represent industrial technology capabilities at weak, medium or strong levels. Five strategies are discussed. To link the implementation strategies and the R&D procedures there are three critical factors to consider: commercialization capability; market timing; and industrial technology requirements. This approach shows how R&D institutes can effectively help industrial technology to develop step-by-step, thus upgrading technological capability and fostering overall industrial growth. (C) 1999 Elsevier Science Ltd. All rights reserved.
A new I-V model considering the impact-ionization effect initiated by the DIGBL current for the intrinsic n-channel poly-Si TFT's
(1999-04-01)
Chen, HL
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Wu, CY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Considering the impact-ionization mechanism occurring in the high drain-bias (V-DS) regime, a new I-V model considering the impact-ionization effect initiated by the drain-induced-grain-barrier-lowering (DIGBL) current has been established for the intrinsic n-channel poly-Si TFT, The simulation results with considering the developed impact-ionization current model are in excellent agreement with the experimental output characteristics of the intrinsic n-channel poly-Si TFT with the mask-gate length ranging from 5 mu m to 40 mu m. In resolving the physical parameters and their underlying operation mechanisms including the grain-barrier height, DIGBL current, and impact-ionization current, the developed I-V model will be beneficial to further understand the underlying physics of the intrinsic poky-Si TFT.
Implementation of a variable D-H parameter model for robot calibration using an FCMAC learning algorithm
(1999-04-01)
Young, KY
;
Chen, JJ
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電控工程研究所
;
Institute of Electrical and Control Engineering
Current robot calibration schemes usually employ calibration models with constant error parameters. Consequently, they are inevitably subject to a certain degree of locality, i.e., the calibrated error parameters (CEPs) will produce the desired accuracy only in certain regions of the robot workspace. To deal with the locality phenomenon, CEPs that vary in different regions of the robot workspace may be more appropriate. Hence, we propose a variable D-H (Denavit and Hartenberg) parameter model to formulate variations of CEPs. An FCMAC (Fuzzy Cerebellar Model Articulation Controller) learning algorithm is used to implement the proposed variable D-K parameter model. Simulations and experiments that verify the effectiveness of the proposed calibration scheme based on the variable D-H parameter model are described.
New serial architecture for the Berlekamp-Massey algorithm
(1999-04-01)
Chang, HC
;
Shung, CB
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We propose a new efficient serial architecture to implement the Berlekamp-Massey algorithm, which is frequently used in BCH and Reed-Solomon decoders, An inversionless Berlekamp-Massey algorithm is adopted which not only eliminates the finite-field inverter but also introduces additional parallelism, We discover a clever scheduling of three finite-field multipliers to implement the algorithm very efficiently, Compared to a previously proposed serial Berlekamp-Massey architecture, our technique significantly reduces the latency.
Temperature control of rapid thermal processing system using adaptive fuzzy network
(1999-04-01)
Lin, CT
;
Juang, CF
;
Huang, JC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Temperature control of a rapid thermal processing (RTP) system using a proposed self-constructing adaptive fuzzy inference network (SCAFIN) is presented in this paper. First, the physical modeling of a RTP system is done. An integrated model is given for the components that make up a RTP system. These components are the lamp power dynamics, ray-tracing model, and the wafer thermal dynamic model. The models for the components are integrated in a numerical code to give a computer simulation of the complete RTP system. The simulation can be used to investigate the interaction of the furnace, lamp contour, and the control system. Then a direct inverse control scheme using the proposed SCAFIN is adopted to control the temperature of the RTP system. The SCAFIN is inherently a modified TSK-type fuzzy rule-based model possessing neural network's learning ability. There are no rules initially in the SCAFIN. They are created and adapted as on-line learning proceeds via simultaneous structure and parameter identification. Simulation results show that the control approach is able to track a temporally varying temperature trajectory and maintain the uniformity of the spatial temperature distribution of the wafer in the RTP system simultaneously. (C) 1999 Elsevier Science B.V. All rights reserved.
2D C-tree spatial representation for iconic image
(1999-04-01)
Hsu, FJ
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Lee, SY
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Lin, BS
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資訊科學與工程研究所
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Institute of Computer Science and Engineering
The 2D string approaches provide a natural way of constructing iconic indexing for images. The 2D C-string representation with an efficient cutting mechanism is more characteristic of spatial knowledge and efficient in the representation of iconic images. However, the computation of object ranks in a 2D C-string might make the inference of spatial reasoning somewhat complicated. This shortcoming is overcome by the 2D C-tree representation. The 2D C-tree not only keeps the comprehensive spatial knowledge in the original 2D C-string, but also the ordered labeled tree is more suitable for spatial reasoning and image retrieval. The spatial knowledge can be derived directly from the inference rules embedded in the characteristic structure of the 2D C-tree representation. (C) 1999 Academic Press.
Heat transfer enhancement by a multilobe vortex generator in internally finned tubes
(1999-04-01)
Tsui, YY
;
Leu, SW
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機械工程學系
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Department of Mechanical Engineering
A three-dimensional computational method is employed to study the flow and heat transfer in internally finned tubes with a multilobe vortex generator inserted. Governing equations are discretized using the finite volume method The irregular lobe geometry is treated using curvilinear nonstaggered grids. The linear interpolation method is adopted to calculate face velocities. The results show that secondary flows induced by the lobes are transformed to become axial vortices downstream of the vortex generator. As a consequence of the transport by the vortex flow, the core flow is moved to the fins and the tube wall, while the wall flow moves to the core. In this way, both heat transfer and flow mixing are enhanced. When the fin height is increased the axial vortex is more restricted in the centerline region, and the strength of the vortex flow, represented by circulation, is decreased. In turn, the total pressure loss is also decreased However, the heat transfer increases with fin height. Consequently, efficiency is greatly promoted.