Browsing by Issue Date, starting with "2002-04-15"

Now showing 1 - 20 of 74747

A method to characterize the dielectric and interfacial properties of metal-insulator-semiconductor structures by microwave measurement
(2002-04-15)
Lue, HT
;
Tseng, TY
;
Huang, GW
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We have developed a method to investigate the dielectric and interfacial properties of gate dielectric thin films by microwave measurement. Ba0.5Sr0.5TiO3 (BST) thin films were deposited on 10 Omega cm (normal) and 10 k Omega cm [high-resistivity, (HR)] silicon substrates at the same time by rf magnetron sputtering. For the BST/HR-silicon, coplanar waveguides (CPW) were fabricated and measured at microwave frequencies with thru-reflect-line calibration while capacitance (C-V) measurements were carried out for BST/normal silicon. From the phase change of CPW transmission line and the maximum capacitance in C-V measurement, the dielectric constants of both the BST thin film and interface layer can be determined. Furthermore, the behaviors of insertion loss versus bias voltage were investigated. The results indicate that our method can provide useful information to study the dielectric and interfacial properties of metal-insulator-semiconductor structures. (C) 2002 American Institute of Physics.
虎頭
(2002-04-20)
管管
An analysis of the combined effects of organic toxicants
(2002-04-22)
Chen, CY
;
Lu, CL
;
環境工程研究所
;
Institute of Environmental Engineering
This paper presents a basic database for the joint actions of 44 binary mixtures of various organic toxicants on Escherichia coli. The multiple toxicity behaviors observed from the E. coli organisms were analyzed and compared with previous works based on the Microtox tests, The two kinds of tests produced quite different responses, in terms of the joint action mode and the sum of toxic units, to various organic mixtures. However, detailed analyses with the considerations of the chemical's mechanisms of toxicity and the slope of toxicant's dose-response curve have revealed several general criteria for the prediction of combined effects of organic toxicants. First, for both reactive and non-reactive toxicants, either additive or less than additive (antagonistic) joint actions will be observed for chemicals of the same mechanism of toxicity. Second, the mixture of reactive toxicants with different mechanisms is the only category of organic mixtures associated with frequent observations of synergism. Third, greater-than-additive (synergistic) effects are inherently associated with toxicants having flat dose-response curves. Less than additive effects are, however, mainly related to a chemical's display steep close-response curves. Model analyses indicate that the observed synergistic effects are due to response addition or response multiplication joint actions. Hence, most of the synergistic joint actions are non-interactive in nature and are governed by the dose-response relationships of individual toxicants. (C) 2002 Elsevier Science B.V. All rights reserved.
Miscibility, melting, and crystallization of poly(trimethylene terephthalate)/poly(ether imide) blends
(2002-04-25)
Huang, JM
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
Miscibility, melting, and crystallization behaviors of solution-blended poly trimethylene terephthalate) (PTT)/poly(ether imide) (PEI) blends ha,e been investigated using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and polarized light microscopy (PLM). These blends show a single and composition-dependent glass transition temperatures over the entire composition range, implying that these blends are fully miscible in the amorphous region. The enthalpy of the middle endotherm melting of the primary crystallization decreases with increasing PEI content in the blend. Recrystallization of PTT during heating scan in DSC is either retarded or fully inhibited by the presence of PEI. In nonisothermal crystallization, the depression of crystallization temperature of PTT also depends on the blend composition and cooling rate; the presence of PEI decreases the PTT segments migrating to the crystallite-melt interface, The effects of temperature and PEI content on the spherulite growth rate of PTT were evaluated by PLM. The spherulite growth rate decreases with the, increase of the PEI content, implying that it is a thermodynamically dominant process. Both thermodynamic and kinetic factors cause total inhibition of PTT crystallization at higher PEI content in the blend. (C) 2002 John Wiley Sons, Inc.
Time requirement for rapid-mixing in coagulation
(2002-04-25)
Kan, CC
;
Huang, CP
;
Pan, JRS
;
環境工程研究所
;
Institute of Environmental Engineering
Mechanisms of coagulation have been widely investigated by many researchers. Little is understood about the critical role of rapid-mixing in water treatment. In this study, a photometric dispersion analyzer (PDA) was employed to monitor clay coagulation by alum and polymeric aluminum chloride (PACl). The effect of rapid-mixing time on particle removal was studied. A standard jar test was performed to determine the degree of destabilization of particles. Maximum ratio outputs of PDA measurements were inversely related to residual turbidities. Adequate rapid-mixing times evaluated from both PDA and mixing tests were close to each other. Studies of coagulation mechanisms at various rapid-mixing times indicated that mixing time had significant impact on charge neutralization and sweep coagulation. The difference in residual turbidity can be attributed to the characteristics of microflocs. The rise in residual turbidity in sweep coagulation suggested the breakage of microflocs. (C) 2002 Elsevier Science B.V. All rights reserved.
Bi3.25La0.75Ti3O12 thin films on ultrathin Al2O3 buffered Si for ferroelectric memory application
(2002-04-29)
Chen, SY
;
Sun, CL
;
Chen, SB
;
Chin, A
;
材料科學與工程學系
We have investigated the physical and electrical properties of Bi3.25La0.75Ti3O12 (BLT) thin films on Pt/Ti/SiO2/Si and on Al2O3(6 nm)/Si, which are used for one-transistor-one-capacitor and one-transistor ferroelectric memory, respectively. The BLT thin films on both substrates show good capacitance-voltage characteristics and the same threshold voltage shift of 1.6 V at applied +/-10 V bias. However, the leakage current of BLT on Al2O3/Si at -100 kV/cm is two orders of magnitude lower than that on Pt. The comparable memory characteristics and much reduced leakage current of BLT on Al2O3/Si are the strong advantages as compared with BLT on Pt because it is directly related to switching energy and device scaling down. (C) 2002 American Institute of Physics.
Parallel distance transforms on a linear array architecture
(2002-04-30)
Chia, TL
;
Wang, KB
;
Chen, Z
;
Lou, DC
;
資訊科學與工程研究所
Distance transformation (DT) has been widely used for image matching and shape analysis. In this paper, a parallel algorithm for computing distance transformation is presented. First, it is shown that the algorithm has an execution time of 6N - 4 cycles, for an N x N image using a parallel architecture that requires [N/2] parallel processors. By doing so, the real time requirement is fulfilled and its execution time is independent of the image contents. In addition, a partition method is developed to process an image when the parallel architecture has a fixed number of processing elements (PEs); say two or more. The total execution time for an N x N image by employing a fixed number of PEs is 2[N-2/M + 2(M - 1)], when M is the fixed number of PEs. (C) 2002 Elsevier Science B.V. All rights reserved.
Consistent quantization of noncommutative D-brane in non-constant B field background
(2002-04-30)
Lee, JC
;
電子物理學系
;
Department of Electrophysics
We perform the consistent quantization of open string D-brane in non-constant NS-NS closed string B field background by directly imposing the worldsheet conformal symmetry. In addition to the previous noncommutative D-brane coordinates quantization with constant noncommutative paxameter theta, we obtain a set of constraints on the B field which can be interpreted as a quantum consistent deformation of a curved noncommutative D-brane.
Optimum design for a thermally stable multifinger power transistor
(2002-05-01)
Liao, CH
;
Lee, CP
;
Wang, NL
;
Lin, B
;
電子工程學系及電子研究所
The thermal stability of multifinger bipolar transistors has been analyzed theoretically. Coupled equations are solved to study the onset of instability and its dependence on the distributions of ballasting resistors. Analytical expressions were derived for the emitter ballasting distribution for optimum stable operation. Compared to conventional methods with uniform ballasting, the optimized design can significantly increase the stable operating current of the transistor. An absolutely stable operating condition is also derived. At this condition, the device never becomes unstable.
Locating free positions in LR(k) grammars
(2002-05-01)
Ouyang, ST
;
Wu, PC
;
Wang, FJ
;
資訊工程學系
;
Department of Computer Science
LR(k) is the most general category of linear-time parsing. Before a symbol is recognized in LR parsing, it is difficult to invoke the semantic action associated with the symbol. Adding semantic actions to an LR(k) grammar may result in a non-LR(k) grammar. There are two straightforward approaches adopted by practitioners of parser generators. The first approach is to delay all semantic actions until the whole parse tree is constructed. The second is to add semantic actions to the grammar by chance. This paper presents an efficient algorithm for finding positions (called free positions) that can freely put semantic actions into an LR(k) grammar. The speedups of our method range from 2.23 to 15.50 times for the eight tested grammars.
Optimal biorthogonal transform for colored noise suppression with subband Wiener filtering
(2002-05-01)
Phoong, SM
;
Lin, YP
;
電控工程研究所
;
Institute of Electrical and Control Engineering
It is well-known that the Karhunen-Loeve transform (KLT) is optimal for white noise suppression. Recently, Akkarakaran and Vaidyanathan showed that for the case of colored noise, if both the noise and signal have a common KLT, then the KLT is optimal for subband noise suppression. In this paper, we will derive the optimal transform (not restricting to the class of unitary transforms) for the noise suppression problem when the signal and noise have arbitrary spectrum.
Improvements on the duality based method used in solving optimal power flow problems
(2002-05-01)
Lin, CH
;
Lin, SY
;
Lin, SS
;
電控工程研究所
;
Institute of Electrical and Control Engineering
To improve the previously developed dual-type (DT) method used in solving optimal power flow (OPF) problems with large number of thermal-limit constraints, we propose two new techniques in this paper. The first one is a graph-method based decomposition technique which can decompose the large-dimension projection problem, caused by the large number of thermal-limit constraints, into several independent medium-dimension projection subproblems at the expense of slight increment of the dual problem's dimension. The second technique is an active-set strategy based DT method which can solve the medium-dimension projection subproblems efficiently. We have used the DT method embedded with these two new techniques in solving numerous OPF's with large number of thermal-limit constraints. The test results show that the proposed techniques are very efficient and effectively improve the DT method for handling large number of thermal-limit constraints.
Varying appearance speed problem in system modeling and a solution via rate independent memory
(2002-05-01)
Wei, JD
;
Sun, CT
;
資訊工程學系
;
Department of Computer Science
Conventional system models such as the finite impulse response (FIR.) model, autoregressive external input (ARX) model, time delay neural network (TDNN), and recurrent neural network (RNN) depend on short-term memory when modeling a discrete time system. However, short-term memory can be inefficient with a varying appearance speed of I/O data. This inefficiency is referred to herein as the Varying Appearance Speed Problem (VASP) and demonstrated by analyzing impulse and frequency responses. Simulation results indicate that the varying appearance speed leads to asymmetrical cycles. Unable to prevent the memory effect from extensively disturbing the next output cycle, conventional models simulate the systems inaccurately. A solution using rate independent memory is then proposed. Only concerned with the previous extreme inputs, rate independent memory differs from short-term memory and potentially prevents a system model from the impact of varying appearance speeds. To demonstrate the VASP and verify the proposed model, this study conducts three experiments, i.e. (a) learning random step trajectories of circular and trefoil shapes, (b) modeling the relationship between the economic leading and coincident indexes, (c) simulating the connection between the ground-water level and land subsidence. In contrast to conventional models, the model presented here performs better in terms of mean square errors.
Effect of pulse frequency on leveling and resistivity of copper coatings
(2002-05-01)
Chen, CF
;
Lin, KC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Pulse-and DC-plated copper films on wafers were investigated with respect to their applicability as advanced interconnect materials. Pulse frequency was varied to determine its influence on the topography, grain size, and electrical resistivity of electroplated copper films. Morphology and scanning electron microscopy (SEM) studies were conducted on these samples. Smooth and dense coatings were obtained at the optimal frequency of 100 Hz, which displayed the smallest electrical resistance. The leveling capacity of submicron features was also optimized at this frequency.
Distortionless pulse-train propagation in a nonlinear photonic bandgap structure doped uniformly with inhomogeneously broadening two-level atoms
(2002-05-01)
Tseng, HY
;
Chi, S
;
光電工程學系
;
Department of Photonics
The pulse propagation in a one-dimensional nonlinear photonic bandgap (PBG) structure doped uniformly with inhomogeneously broadening two-level atoms is investigated. The Maxwell-Bloch equations describing pulse propagation in such a uniformly doped PBG structure are derived first and further reduced to effective nonlinear coupled-mode equations. An exact analytic pulse-train solution to these effective coupled-mode equations is obtained. Such a distortionless pulse-train solution is given by sinusoidal functions with a DC background and a modulated phase. Numerical examples of the distortionless pulse train in a silica-based PBG structure doped uniformly with Lorentzian line-shape two-level atoms are shown.
Substrate-triggered ESD clamp devices for use in power-rail ESD clamp circuits
(2002-05-01)
Ker, MD
;
Chen, TY
;
Wu, CY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Ne electrostatic discharge (ESD) clamp devices for using in power-rail ESD clamp circuits with the substrate-triggered technique ire proposed to improve ESD level in a limited silicon area. The parasitic n-p-n and p-n-p bipolar junction transistors (BJTs) in the CMOS devices ire used to form the substrate-triggered devices Cor ESD protection. Four substrate-triggered de-ices are proposed and investigated in this work, which are named as the substrate-triggered lateral BJT, the substrate-triggered vertical BJT, the substrate-triggered double BJT and the double-triggered double BJT. An RC-based ESD-detection Circuit Is used to generate the triggering Current to turn on the proposed substrate-triggered devices. In order to trigger on the parasitic bipolar transistors more effectively, the symmetric multiple-cell square-type layout method is used to realize these substrate-triggered devices. The power-rail ESD clamp circuits, with such substrate-triggered devices have been fabricated in a 0.6-mum CMOS process. Experimental results have shown that the substrate-triggered device with double-BJT Structure can provide 200%, higher ESD robustness in per silicon area, as compared to the NMOS with the traditional gate-driven design, (C) 2002 Elsevier Science Ltd. All rights reserved.
A neural-network approach for semiconductor wafer post-sawing inspection
(2002-05-01)
Su, CT
;
Yang, T
;
Ke, CM
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Semiconductor wafer post-sawing requires full inspection to assure defect-free outgoing dies. A defect problem is usually identified through visual judgment by the aid of a scanning electron microscope. By this means, potential misjudgment may be introduced into the inspection process due to human fatigue. In addition, the full inspection process can incur significant personnel costs. This research proposed a neural-network approach for semiconductor wafer post-sawing inspection. Three types of neural networks: backpropagation, radial basis function network, and learning vector quantization, were proposed and tested. The inspection time by the proposed approach was less than one second per die, which is efficient enough for a practical application purpose. The pros and cons for the proposed methodology in comparison with two other inspection methods, visual inspection and feature extraction inspection, are discussed. Empirical results showed promise for the proposed approach to solve real-world applications. Finally, we proposed a neural-network-based automatic inspection system framework as future research opportunities.
An explicit model for a quantum channel in 2DEG
(2002-05-01)
Fedirko, VA
;
Chen, MH
;
Chiu, CC
;
Chen, SF
;
Wu, KH
A two-parametric model for a channel in a two-dimensional electron gas (2DEG) is proposed which allows for the explicit analytical solution for the problem of quantum electron transport through the constriction. Conductance step smearing appears naturally and a simple criterion for the step occurrence in terms of channel parameters is given. (C) 2002 Elsevier Science Ltd. All rights reserved.
A 0.99 mu A operating current Li-ion battery protection IC
(2002-05-01)
Shyu, YS
;
Wu, JC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A lithium-ion (Li-ion) battery protection IC with an average current of 0.99 muA (at a battery voltage of 3.6 V) and a standby current (after detecting over-discharge) less than 0.01 muA is presented. This low power performance is achieved via a power-on duty-cycle technique. The protection circuit samples the voltage of the battery periodically and powers down during the rest of time. This Li-ion battery protector provides overcharge, over-discharge, excess-current and short circuits protection. This protection IC was implemented in a 0.6-mum CMOS technology and the active area is 880 mum x 780 mum.
Nonlinear effects of energy band structures on optical transitions in quantum dots
(2002-05-01)
Wu, CC
;
Lin, CJ
;
應用數學系
;
電子工程學系及電子研究所
;
Department of Applied Mathematics
The quantum theory of nonlinear effects for optical transitions of electrons in quasi-zero dimensional (Q0D) quantum dots fabricated from n-type III-V compound semiconductor materials such as n-type GaAs has been studied due to the nonparabolicity of energy band structures. We use the effective mass approximation for carriers in the quantum dots. Most realistic quantum dot systems contain the box with a thickness c and the lateral width (a, b). Using the time-independent perturbation theory, the first order correction of the eigenfunctions and eigenvalues for the system has been calculated. And the free-carrier absorption coefficient may be calculated for Q0D quantum dots from n-type GaAs where the polar optical phonon scattering is dominant. Our results show that the free-carrier absorption coefficient in Q0D quantum dots increases quite rapidly with increasing temperature in the region of low temperatures. When temperatures are larger than 100 K, the free-carrier absorption coefficient increases slowly with temperature. This shows that the nonlinear property of energy band structures due to the nonparabolicity plays an important role in low temperatures. The discussion about the dot size effect of the quantum confinement region in n-type GaAs quantum dots has also been given. (C) 2002 Published by Elsevier Science B.V.