Browsing by Issue Date, starting with "2001-05-15"

Now showing 1 - 20 of 76520

Activation of p-type GaN in a pure oxygen ambient
(2001-05-15)
Wen, TC
;
Lee, SC
;
Lee, WI
;
Chen, TY
;
Chan, SH
In this study, we activated p-type GaN in a pure oxygen ambient by rapid thermal annealing. The sheet resistance of p-type GaN was greatly reduced from > 10(7) Omega/square to 7.06 x 10(4) Omega/square after annealing in oxygen ambient at 500 degreesC, The photoluminescence intensity of blue emission increased by one order of magnitude compared to the as-grown sample. Moreover, the sheet resistance of p-type GaN annealed in pure oxygen ambient is lower than that of p-type GaN annealed in nitrogen ambient. The carrier concentrations of the samples annealed in oxygen ambient are higher than those annealed in nitrogen ambient. The better activation of p-type GaN in oxygen ambient is due to the higher activity of oxygen than that of nitrogen. Oxygen would remove hydrogen that passivates Ma atoms by forming H2O at a lower temperature.
Optoelectronic delayed-feedback and chaos in quantum-well laser diodes
(2001-05-15)
Juang, C
;
Huang, CC
;
Hwang, TM
;
Juang, J
;
Lin, WW
Electronic-controlled route to chaos in a quantum-well laser diode is carried out by a delayed-feedback technique. By introducing an extra delayed-feedback control term cS(n)(t - tau), chaotic light output can be achieved at relatively low bias and small modulation depth. Bifurcation diagram, Poincare map, and Lyapunov exponents suggests quasi-periodicity route to chaos. (C) 2001 Elsevier Science B.V. All rights reserved.
A total standard WIP estimation method for wafer fabrication
(2001-05-16)
Lin, YH
;
Lee, CE
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
The standard work-in-process (WIP) level in a wafer fabrication factory is an important parameter which can be properly used to trigger the decision of when to release specific wafer lots. There are many WIP-based release control policies which have been proven to be effective for wafer fabrication manufacturing, few methods have been proposed to find the suitable WIP-level as a parameter for these release policies. This paper proposes a queueing network-based algorithm to determine the total standard WIP level so that the Fixed-WIP release algorithm to determine the total standard WIP level so that the Fixed-WIP release control policy can apply. A numerical example is provided to elaborate the algorithm. A simulation model of a real-world wafer fabrication factory in Taiwan is built and analyzed. Results of simulation experiment indicate that under the Fixed-WIP control policy, the total standard WIP level estimated from this study achieves a target throughput rate while keeping the corresponding cycle time relatively low. Results also demonstrate that the queueing network-based algorithm is a very useful method to determine the standard WIP level efficiently. (C) 2001 Elsevier Science B.V. All rights reserved.
Differences in curing behavior of cocured and IPN materials
(2001-05-16)
Lin, MS
;
Chiu, CC
;
應用化學系
;
Department of Applied Chemistry
This study addressed the blending and cocuring of resole and epoxy, using NaOH and 4,4'-diaminodiphenylmethane as curing agents. IR band shifts regarding the molecular interactions were investigated with FTIR. Exothermic peak shifts during cocuring reactions were studied with dynamic DSC. Viscosity increases were measured with a Brookfield LVT viscometer at 100 degreesC. The dynamic mechanical properties of the cocured samples were investigated using rheometric dynamic spectroscopy (RDS). Experimental results revealed that the molecular interactions between resole and epoxy resulted in good compatibility as shown by the single damping peak in the RDS curve and the single glass transition for each cocured sample. Also apparent were accelerated curing rates, leading to shifts of the exothermic peaks to lower temperature and faster viscosity increases. Nevertheless, enhanced gel fractions and increased glass-transition temperatures (T-g) of the samples were generally observed for this cocured system. The average molecular weight between crosslinked points calculated for the cocured materials also showed much less than the two components. These curing behaviors were quite different from those of the Interpenetrating Polymer Network (IPN) materials, which usually indicated lowered gel fractions, decreased T-g, and higher average molecular weight between crosslinkings than for components. (C) 2001 John Wiley & Sons, Inc.
Investigation of beryllium implanted P-type GaN
(2001-05-22)
Yu, CC
;
Chu, CF
;
Tsai, JY
;
Wang, SC
;
光電工程學系
We report the preliminary results of beryllium implanted into P-type GaN and the effects on the characteristic of Mg-doped P-GaN. These samples were implanted with Be ions were implanted with two different energies of 50 and 150 keV at two different doses of similar to 10(13) and 10(14) cm(-2) at room temperature. Surface morphology and photoluminescence measurements are presented. (C) 2001 Elsevier Science B.V. All rights reserved.
High etching rate of GaN films by KrF excimer laser
(2001-05-22)
Chu, CF
;
Lee, CK
;
Yu, CC
;
Wang, YK
;
Tasi, JY
A study of laser processing of gallium nitride (GaN) material is reported. A pulsed KrF excimer laser at 248 nm with 20-nsec pulse width and 1 Hz repetition rate is used to etch the GaN film. We establish the material etching parameters under different environmental conditions. By changing the pulsed energy at constant pulse numbers, ablation of GaN surface was observed at threshold laser fluence about 0.3 J cm(-2). Laser etching increase with reducing environment pressure. Al 1.0 J cm (-2) laser fluence, the etching fate is about 35 nm per pulse at atmosphere pressure and increases to 60 nm per pulse at low pressure. The etched depth also increases with increasing laser fluence. The surface morphology of the etched surface was also investigated. (C) 2001 Elsevier Science B.V. All rights reserved.
敲門
(2001-05-29)
管管
Polymer-based self-lubricating material
(2001-05-31)
Shiao, SJ
;
Fu, WS
;
Tuo, CL
;
Cheng, UI
;
應用化學系
A low-friction coefficient material with color based on proper selection of polar conditions of pigment and liquid lubricant was developed. Bush-type bearings were made from poly oxymethylene reinforced with inorganic fillers, including polar compounds of white carbon and glass powder, and nonpolar compounds of carbon black and graphite. The fillers were coated with different levels of titanate, and with polar lubricants such as cetyl alcohol and palmitic acid, and nonpolar lubricants of motor oil, and paraffin. The frictional properties at constant velocity and at constant loading, and the relationships between materials polarity are discussed. An excellent self-lubricating material of frictional coefficient less than 0.02 was obtained. That is superior to the most current commercial products claiming mu = 0.05 similar to 0.06. (C) 2001 John Wiley & Sons, Inc.
Wafer rework strategies at the photolithography stage
(2001-06-01)
Sha, DY
;
Hsieh, LF
;
Chen, KJ
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Defective wafers are often seen during the semiconductor manufacturing process. Technically, there is no known remedy for a defective wafer. However, at the photolithography phase of semiconductor manufacturing, the defective wafers can be reworked to reduce the manufacturing cost significantly. In this paper, when comparing the three rework strategies that were proposed by Zargar, we pinpoint the disadvantages of each and offer two other strategies. We assess the advantages and disadvantages of the five rework strategies of each reworked batch according to total cycle time, the quantity of work-in-process, each machine's utilization rate, the utilization rate of photolithography, and the average length of queues for photolithography. Through simulations and statistics, the fifth strategy is shown to be superior to the first four and most suitable for wafer manufacturing. Significance: At the photolithography stage, the processing relation between lot and lot should be considered. Thus, how to schedule reworking in order to reduce the effect on waiting lots is a crucial issue for wafer manufacturing management.
Managing and sharing collaborative files through WWW
(2001-06-01)
Sheu, RK
;
Chang, YS
;
Yuan, SM
;
資訊工程學系
;
Department of Computer Science
The increasing complexity and geographical separation of design data, tools and teams have demanded for a collaborative and distributed management environment. In this paper, we present a practical system, the CFMS, which is designed to manage collaborative files on WWW. Wherever remote developers are, they can navigate the evolutions and relationships between target files, check in and check out them conveniently on web browsers using CFMS. The capabilities of CFMS include the two-level navigation mechanism for version selection, the relationship model that conceptually manages the relationships between physical files as well as the prefix-based naming scheme that can uniquely identify requested objects. (C) 2001 Elsevier Science B.V. All rights reserved.
Termination detection protocols for mobile distributed systems
(2001-06-01)
Tseng, YC
;
Tan, CC
;
資訊工程學系
;
Department of Computer Science
This paper studies a fundamental problem, the termination defection problem, in distributed systems. Under a wireless network environment, we show how to handle the host mobility and disconnection problems. in particular, when some distributed processes are temporarily disconnected, we show how to capture a weakly terminated state where silence has been reached only by those currently connected processes. A user may desire to know such a state to tell whether the mobile distributed system is still running or is silent because some processes are disconnected. Our protocol tries to exploit the network hierarchy by combining two existing protocols together. It employs the weight-throwing scheme [9], [16], [21] on the wired network side, and the diffusion-based scheme [5], [13] on each wireless cell. Such a hybrid protocol can better pave the gaps of computation and communication capability between static and mobile hosts, thus more scalable to larger distributed systems. Analysis and simulation results are also presented.
Location awareness in ad hoc wireless mobile networks
(2001-06-01)
Tseng, YC
;
Wu, SL
;
Liao, WH
;
Chao, CM
;
交大名義發表
Networks composed of dynamically repositioning mobile hosts require location awareness to provide new geographic services and to maximize routing efficiency and quality of service.
Magnetoresistance anomaly in DyFeCo thin films
(2001-06-01)
Wu, JC
;
Wu, CS
;
Wu, TH
;
Chen, BM
;
Shieh, HPD
Microstructured rare-earth-transition-metal DyFeCo films have been investigated using magnetoresistance and extraordinary Hall-effect measurements. The Hall loops reveal variation of coercive fields depending on the linewidth and the composition of the films. The magnetoresistance curves, with changes up to as high as 1.3%, show positive/negative magnetoresistance peaks centered on the coercive fields depending on the linewidth of the films only. The variation of the coercivity can be attributed to the magnetic moment canting between the Dy and FeCo subcomponents and the existence of the diverged magnetization on the edges, and the anomalous magnetoresistance peaks observed are discussed with the existing theories. (C) 2001 American Institute of Physics.
Biological elimination of H2S and NH3 from wastegases by biofilter packed with immobilized heterotrophic bacteria
(2001-06-01)
Chung, YC
;
Huang, CP
;
Tseng, CP
;
環境工程研究所
;
生物科技學系
Biotreatment of various ratios of H2S and NH3 gas mixtures was studied using the biofilters, packed with co-immobilized cells (Arthrobacter oxydans CH8 for NH3 and Pseudomonas putida CH11 for H2S). Extensive tests to determine removal characteristics, removal efficiency, removal kinetics, and pressure drops of the biofilters were performed. To estimate the largest allowable inlet concentration, a prediction model was also employed. Greater than 95% and 90% removal efficiencies were observed for NH3 and H2S, respectively, irrespective of the ratios of H2S and NH3 gas mixtures. The results showed that H2S removal of the biofilter was significantly affected by high inlet concentrations of H2S and NH3. As high H2S concentration was an inhibitory substrate for the growth of heterotrophic sulfur-oxidizing bacteria, the activity of H2S oxidation was thus inhibited. In the case of high NH3 concentration, the poor H2S removal efficiency might be attributed to the acidification of the biofilter. The phenomenon was caused by acidic metabolite accumulation of NH3. Through kinetic analysis, the presence of NH3 did not hinder the NH3 removal, but a high H2S concentration would result in low removal efficiency, Conversely, H2S of adequate concentrations would favor the removal of incoming NH3. The results also indicated that maximum inlet concentrations (model-estimated) agreed well with the experimental values for space velocities of 50-150 h(-1). Hence, the results would be used as the guideline for the design and operation of biofilters. (C) 2001 Elsevier Science Ltd. All rights reserved.
Backside copper metallization of GaAs MESFETs using TaN as the diffusion barrier
(2001-06-01)
Chen, CY
;
Chang, EY
;
Chang, L
;
Chen, SH
;
材料科學與工程學系
Backside copper metallization of GaAs MESFETs using TaN as the diffusion barrier was studied. A thin TaN layer of 40 nm was sputtered on the GaAs substrate before copper firm metallization. As judged from the data of X-ray diffraction (XRD), Anger electron spectroscopy (AES), and cross-sectional transmission electron microscopy (TEM), the Cu/TaN films with GaAs were very stable without interfacial interaction up to 550 OC annealing, The copper metallized MESFETs were thermally stressed at 300 degreesC, The devices showed very little change in the device characteristics (<3 %) after thermal stress, and the changes of the electrical parameters and RF characteristics of the devices after thermal stress were of the same order as those devices without Cu metallization, These results show that TaN is a good diffusion barrier for Cu in GaAs devices and the Cu/TaN films can be used for the backside copper metallization of GaAs MESFETs.
Physical and electrical characteristics of F- and C-doped low dielectric constant chemical vapor deposited oxides
(2001-06-01)
Wu, ZC
;
Shiung, ZW
;
Chiang, CC
;
Wu, WH
;
Chen, MC
This work compares the physical and electrical properties of two species of inorganic low dielectric constant (low-k) chemical vapor deposited (CVD) oxides, F-doped fluorinated silicate glass (FSG, k = 3.5) and C-doped organosilicate glass (OSG, k = 2.9). Experimental results indicate that FSG has a higher thermal stability >600 degreesC! than OSG (500 degreesC), based on the results of thermal annealing for 30 min in an N-2 ambient. The degradation of the low-k property in OSG is mainly due to the thermal decomposition of methyl (-CH3) groups at temperatures above 500 degreesC. For the Cu gated oxide-sandwiched low-k dielectric metal-insulator-semiconductor (MIS) capacitors, Cu penetration was observed in both FSG and OSG after the MIS capacitors were bias-temperature stressed at 250 and 150 degreesC, respectively, with an effective applied field of 0.8 MV/cm. Specifically, Cu appeared to drift more readily in OSG than in FSG, presumably because OSG has a more porous and less dense structure than FSG. The Cu permeation can be impeded by a thin nitride (SiN) barrier layer. (C) 2001 The Electrochemical Society.
The distributed program reliability analysis on ring-type topologies
(2001-06-01)
Lin, MS
;
Chang, MS
;
Chen, DJ
;
Ku, KL
;
資訊科學與工程研究所
Distributed computing system (DCS) has become very popular for its high fault-tolerance, potential for parallel processing, and better reliability performance. One of the important issues in the design of the DCS is the reliability performance. Distributed program reliability (DPR) is addressed to obtain this reliability measure, In this paper, we propose a polynomial-time algorithm for computing the DPR of ring topology and show that solving the DPR problem on a ring of trees topology is NP-hard. (C) 2001 Elsevier Science Ltd. All rights reserved.
斧斤
(2001-06-01)
管管
Physical and electrical characteristics of methylsilane- and trimethylsilane-doped low dielectric constant chemical vapor deposited oxides
(2001-06-01)
Wu, ZC
;
Shiung, ZW
;
Chiang, CC
;
Wu, WH
;
Chen, MC
This work investigates the physical and electrical properties of two species of inorganic C-doped low dielectric constant (low-k) chemical vapor deposited (CVD) organosilicate glasses (OSGs, alpha -SiCO:H). They are both deposited by plasma-enhanced CVD (PECVD) processes using methylsilane [(CH3)SiH3, 1 MS]- and trimethylsilane [(CH3)(3)SiH, 3 MS]-based gases as the reagents, and are designated as OSG1 and OSG2, respectively. Experimental results indicate that the thermal stability temperature of OSG1 is 500 degreesC, while that of OSG2 is 600 degreesC, based on the results of thermal annealing for 30 min in an N-2 ambient. The deterioration of the low-k property in OSG1 is predominately due to the thermal decomposition at temperatures above 500 degreesC of methyl (-CH3) groups, which are introduced to lower the density and polarizability of OSGs. For the Cu-gated oxide-sandwiched low-k dielectric metal-insulator-semiconductor (MIS) capacitors, Cu permeation was observed in both OSG1 and OSG2 after the MIS capacitors were bias-temperature stressed at 150 degreesC with an effective applied field of 0.8 MV/cm. Moreover, Cu appeared to drift more readily in OSG1 than in OSG2, presumably because OSG1 has a more porous and less cross-linked structure than OSG2. The Cu penetration can be mitigated by a thin nitride dielectric barrier. (C) 2001 The Electrochemical Society.
A detailed study of non-uniform quantum well infrared photodetectors
(2001-06-01)
Wang, SY
;
Chin, YC
;
Lee, CP
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A non-uniform quantum well infrared photodetector (NUQWIP) structure is studied. By changing the doping concentration and barrier width of each quantum well, the electric field distribution can be tailored. Different transition types of NUQWIPs were fabricated. Suppressed dark current is obtained for all the NUQWIPs. The NUQWIPs show excellent performance compared with conventional uniform structures. The dark current is about an order of magnitude lower and the background limited temperature increases for 6 degrees. The electric field distribution within the structure is calculated to explain the results and characteristics of the NUQWIPs. The NUQWIP is found to be advantageous for the low cutoff energy detectors using B-C transitions. (C) 2001 Published by Elsevier Science B.V.