Browsing by Issue Date, starting with "1997-10-21"

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k-path partitions in trees
(1997-10-21)
Yan, JH
;
Chang, GJ
;
Hedetniemi, SM
;
Hedetniemi, ST
;
應用數學系
For a fixed positive integer k, the k-path partition problem is to partition the vertex set of a graph into the smallest number of paths such that each path has at most k vertices. The 2-path partition problem is equivalent to the edge-cover problem. This paper presents a linear-time algorithm for the k-path partition problem in trees. The algorithm is applicable to the problem of finding the minimum number of message originators necessary to broadcast a message to all vertices in a tree network in one or two time units.
Suppression of optical beat interference using synchronised CDMA technique and in-band clipping carrier
(1997-10-23)
Wang, BH
;
Hsiao, CC
;
Way, WI
;
電信工程研究所
;
Institute of Communications Engineering
The authors propose adding a coherent in-band clipping carrier to a previously demonstrated Walsh-code-based synchronised CDMA (S-CDMA) technique to further suppress the optical beat interference (OBI). Experimental results showed thar a negligible system power penalty can be achieved even when the OBI-induced intensity noise was as high as -90.9dB/Hz. In addition, a large system dynamic range of 10dB can tx obtained to relax the tight power control requirement on S-CDMA signals.
Dielectric characteristics of doped Ba1-xSrxTiO3 at the paraelectric state
(1997-10-30)
Liou, JW
;
Chiou, BS
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Ba1-xSrxTiO3 (x=0 to 1) ferroelectric ceramics doped with 1.0 mol.% MgO and 0.05 mol.% MnO2 were prepared with a rate-controlled sintering profile. The lattice constant of this BST system decreases as the strontium molar fraction increases. This is due to the smaller Sr2+ ionic radius than that of Ba2+. The temperature dependence of the dielectric constant is measured at 10 kHz. A linear relation of the Curie temperature of the BST system to the Sr fraction for x less than or equal to 0.75 is observed. When this reaction is fitted to a modified Curie-Weiss law, two parameters, the critical exponent and the diffuseness parameter, which represent the order of transition broadening, can be calculated. From the values of these two parameters, it is suggested that the physical meanings of these two parameters are correlated to each other. The transition broadening is greatest for x = 0.5 owing to the most composition fluctuation. Dipole relaxation of the composition with x = 0.25 is observed at frequencies above 1 MHz. On the basis of Cole-Cole analysis, a low frequency relaxation due to dopants Mn4+ at below 50 kHz is observed. (C) 1997 Elsevier Science S.A.
Chemical mechanical polishing for selective CVD-W
(1997-10-30)
Wang, MT
;
Yeh, WK
;
Tsai, MS
;
Tseng, WT
;
Chang, TC
This work investigates chemical mechanical polishing (CMP) for W-filled contact holes, vias, and trenches by selective chemical vapor deposition. A novel process that combines the CMP technique with selective chemical vapor deposition of tungsten (CVD-W) was employed to remove nail heads due to overgrowth and W-particles on the surface of dielectric due to selectivity loss. The overfilled nail heads and the selectivity loss can be completely removed with very low down-pressure (3 psi) in a very short polishing time (30 s). This indicates that the novel process is very promising for ULSI multilevel interconnection application. The removal rate selectivities of W to thermal oxide, PECVD-TEOS, and BPSG were found to be 47:1, 30:1 and 15:1, respectively, while the selectivities of W to the barrier metals of TiW, Ti and Ta were determined to be 0.6:1, 6:1 and 28:1, respectively. (C) 1997 Elsevier Science S.A.
Chemical mechanical polishing for selective CVD-W
(1997-10-30)
Wang, MT
;
Yeh, WK
;
Tsai, MS
;
Tseng, WT
;
Chang, TC
This work investigates chemical mechanical polishing (CMP) for W-filled contact holes, vias, and trenches by selective chemical vapor deposition. A novel process that combines the CMP technique with selective chemical vapor deposition of tungsten (CVD-W) was employed to remove nail heads due to overgrowth and W-particles on the surface of dielectric due to selectivity loss. The overfilled nail heads and the selectivity loss can be completely removed with very low down-pressure (3 psi) in a very short polishing time (30 s). This indicates that the novel process is very promising for ULSI multilevel interconnection application. The removal rate selectivities of W to thermal oxide, PECVD-TEOS, and BPSG were found to be 47:1, 30:1 and 15:1, respectively, while the selectivities of W to the barrier metals of TiW, Ti and Ta were determined to be 0.6:1, 6:1 and 28:1, respectively. (C) 1997 Elsevier Science S.A.
Effects of corrosion environments on the surface finishing of copper chemical mechanical polishing
(1997-10-31)
Wang, MT
;
Tsai, MS
;
Liu, C
;
Tseng, WT
;
Chang, TC
Copper chemical mechanical polishing (Cu-CMP) was investigated using slurries containing alumina abrasive and various types and concentrations of oxidizer, as well as benezotriazole (BTA) additive. We found that the corrosion rate of copper film decreases with increasing BTA concentration in 3 vol.% HNO3 solution, but the passivation effect of BTA saturates as the concentration reaches about 0.01 M. On the other hand, a small amount of H2O2 in H2O2/XJFW8099 slurry enhances the corrosion rate dramatically, while abundance of H2O2 in the slurry suppresses the corrosion reaction effectively. The polishing rate and its non-uniformity decrease with increasing volume ratio of H2O2 in H2O2/XJEW8099 slurry. A very smooth surface with a removal rate of 363.0 nm/min was obtained using the slurry of 1/1 ratio. Depletion of H2O2 in the slurry can result in more abrasive residuals as well as a rougher surface; the surface roughness increases from 0.3 to 9.9 nm as the H2O2/XJFW8099 ratio decreases from 1/1 to 1/4. Our results indicate that the corrosion rate, polishing rate and surface roughness of copper films are sensitively dependent on the type and concentration of oxidizer as well as the BTA additive. (C) 1997 Elsevier Science S.A.
Stabilizing dielectric constant of fluorine-doped SiO2 film by N2O and NH3 plasma post-treatment
(1997-10-31)
Mei, YJ
;
Chang, TC
;
Chang, SJ
;
Pan, FM
;
Chen, MSK
Fluorine doped oxide (SiO2-xFx) films have been found to exhibit a low dielectric constant. However, the critical issue about SiO2-xFx is its low resistance to moisture which causes the dielectric constant of the film to increase with time. In this work, N2O and NH3 plasma post treatments are applied to as-deposited SiO2-xFx films. It has been observed that NH3 plasma post-treatments of SiO2-xFx are quite efficient at blocking moisture. The dielectric constant and stress values of the SiO2-xFx films after the N2O and NH3 plasma post-treatments are very stable. The disadvantage of N2O plasma post-treatment is that the dielectric constant of the SiO2-xFx film increases from 3.21 to 3.6 due to fluorine desorption from the SiO2-xFx network. On the other hand, NH3 plasma post-treatment is more efficient at blocking moisture and keeping the low dielectric constant unchanged due to surface nitridation of the SiO2-xFx film. (C) 1997 Elsevier Science S.A.
Preparation of a novel target material for carbon nitride film deposition
(1997-10-31)
Lu, TR
;
Kuo, CT
;
Chen, TM
;
材料科學與工程學系
;
應用化學系
To increase the nitrogen content and the degree of crystallinity in carbon nitride films by film deposition techniques (i.e. sputtering, laser ablation etc.), a novel target material composed of carbon nitride has been prepared by UV photo-assisted synthesis. The intention is to replace the traditional graphite target with this material. This synthesis involves photo-chemical reaction of sodium amide and chloroform as carbon and nitrogen sources, respectively, followed by high temperature sintering under flowing nitrogen. Elemental analyses indicate the presence of C, N and H in the target material with a nitrogen to carbon ratio of 0.23. Infrared spectroscopy shows a mixture of sp(3) and sp(2) carbon and sp(2) nitrogen in the sintered powder. Six diffraction peaks attributable to alpha-C3N4 were observed in XRD pattern. Grains of similar to 0.3 pm in diameter in an extended network were also observed in the SEM micrographs. The sintered carbon nitride powder is stable up to 800 degrees C. (C) 1997 Elsevier Science S.A.
Fabrication and characterization of spherical polycrystalline diamond emitter arrays
(1997-10-31)
Chen, CF
;
Huang, WH
;
材料科學與工程學系
;
Department of Materials Science and Engineering
In this work, a high density of spherical polycrystalline diamond field emitter arrays (SPD-FEAs) were fabricated, using microwave plasma chemical vapor deposition (MPCVD) method. Results obtained from the current-voltage (I-e-V-a) characteristics indicate that the impurities heavily influence electron emission. In addition, the emissions current of the phosphorus-doped SDP-FEAs appears to be 25 times lar er than the boron-doped and 120 times larger than the undoped SPD-FEAs. (C) 1997 Elsevier Science S.A.
Characterization of TiN film grown by low-pressure-chemical-vapor-deposition
(1997-10-31)
Mei, YJ
;
Chang, TC
;
Hu, JC
;
Chen, LJ
;
Yang, YL
Conformal TiN films were deposited by thermal low-pressure-chemical-vapor-deposition (LPCVD) in a rotating disk reactor, using TiCl4 and NH3 with N-2 as a dilution gas. TiN plug with 0.05 mu m contact size was achieved. No void formation was observed in the TiN plug. The result demonstrated that LPCVD-TiN can be used to fill very small contact holes. The excellent step coverage and uniformity resulted from a surface-reaction-rate-limited deposition. The resistivity of TiN film was reduced to 133 mu Omega cm by in-situ NH3 plasma post-treatment. The concentration of chlorine in the TiN him was measured to be less than 2 atomic % (at.%) by Auger electron spectroscope measurement. For Al deposited on TiN, the Al orientation was found to be dependent on the deposition method of Al film, but not on the underlying TiN orientation. (C) 1997 Elsevier Science S.A.
Effects of underlying films on the chemical-mechanical polishing for shallow trench isolation technology
(1997-10-31)
Wang, YL
;
Liu, C
;
Feng, MS
;
Dun, JW
;
Chou, KS
The effects of underlying films on the chemical-mechanical polishing (CMP) removal rate have been studied and characterized. A model for the underlying film mechanical properties such as hardness and Young's modulus, relating to the polishing removal rate was proposed. In addition, a modified shallow trench isolation (STI) process with a thin nitride overcoat has been suggested to eliminate the dishing and oxide remaining on nitride issues. Furthermore, in order to minimize the residual particles and metallic contamination, a modified multi-chemical spray-cleaning process provided for the post-STI CMP cleaning was also studied. (C) 1997 Elsevier Science S.A.
Chemical-mechanical polishing of low-dielectric-constant spin-on-glasses: film chemistries, slurry formulation and polish selectivity
(1997-10-31)
Wang, YL
;
Liu, C
;
Chang, ST
;
Tsai, MS
;
Feng, MS
Alkyl siloxane-based low-dielectric-constant (low-k) spin-on-glass (SOG) thin films with varying amounts of organic content were subjected to polishing experiments using silica-and ZrO2-based slurries with a variety of additives, As the amount of organic content in SOG increases, the chemical-mechanical polishing (CMP) removal rate decreases with silica-based potassium hydroxide-added slurry. On the other hand, zirconia-based slurry resulted in higher removal rates for both SOG (>400 nm/min) and thermal oxide and an adjustment in polish selectivity (related to thermal oxide) ranging from 1.2 to 9.1 can be achieved by adding various amounts of tetra-alkyl substituted ammonium hydroxide. Post-CMP materials characterization by Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) shows the chemical stability and CMP compatibility of SOG thin films. (C) 1997 Elsevier Science S.A.
Application of heat treatment and dispersive strengthening concept in interlayer deposition to enhance diamond film adherence
(1997-10-31)
Lin, CR
;
Kuo, CT
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Chang, RM
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材料科學與工程學系
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Department of Materials Science and Engineering
Two different deposition processes were carried out to enhance adherence of diamond films on WC + 3 similar to 5%Co substrate with Ti-Si as the interlayer. One process can be called two-step diamond deposition process. Another process can be called interlayer heat treatment process. Diamond films were deposited by a microwave plasma chemical vapor deposition system. Ti and Si interlayer are deposited by DC sputter and an E-gun, respectively. Film morphologies, interface structure and film qualify were examined by SEM, XRD, Auger electron spectroscopy and Raman spectroscopy. The residual stresses and adhesion strengths of the films were determined by Raman spectroscopy and indentation adhesion testing, respectively. Comparing the regular one-step diamond deposition process with the present two different new processes, the average dP/dX values, which are a measure of the adherence of the film, are 354 kgf/mm, 494 kgf/mm and 787 kgf/mm, respectively. In other words, the interlayer heat treatment process gives the best film adherence on average. For the two-step diamond deposition process, the interlayer thickness and the percent diamond surface coverage of the first diamond deposition step are the main parameters, and there exists an optimum Ti thickness and percent diamond coverage for the best film adherence. The main contribution to better film adherence is not a large difference in residual stress, but is due to the following reasons. The interlayer heat treatment can transform amorphous Si to polycrystalline Si, and may form strong TiC and SiC bonding. The polycrystalline Si and the diamond particles from the first diamond deposition step can be an effective seeds to enhance diamond nucleation. Published by Elsevier Science S.A.
Effects of volume fraction of reinforcement on tensile and creep properties of in-situ TiB/Ti MMC
(1997-11-01)
Tsang, HT
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Chao, CG
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Ma, CY
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材料科學與工程學系
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Department of Materials Science and Engineering
The TEOS CVD oxide deposited on phosphorus in situ doped polysilicon with rapid thermal annealing
(1997-11-01)
Kao, CH
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Lai, CS
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Lee, CL
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交大名義發表
;
電子工程學系及電子研究所
A TEOS oxide deposited on the phosphorus in situ doped polysilicon annealed with RTA is shown to have good electrical characteristics such as a high breakdown field (>12 MV/cm), especially for the positive bias, and a large Qbd (26 Coul/cm(2)). The improvement is believed to be due to the relatively smooth surface of the in situ doped polysilicon and the reduction of the trapping density by RTA.
An enhanced zero-one optimal path set selection method
(1997-11-01)
Chung, CG
;
Lee, JG
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交大名義發表
;
資訊工程學系
;
National Chiao Tung University
One issue in structural program testing is how to select a mimimal set of test paths to meet certain test requirements. This is referred to as the optimal path set selection problem. The previously proposed zero-one optimal path set selection method is a generalized method that can be applied to most coverage criteria. However, the major drawback of this method is that for a large program the computation may take ten or more hours because the computation is exponentially proportional to the number of candidate paths and proportional to the number of components to be covered. To alleviate the drawback, this paper enhances the method by (1) defining five reduction rules, and (2) reusing previously selected path sets to reduce both the number of candidate paths and the number of components to be covered. Since both the number of candidate paths and the number of components to be covered are reduced, the computation time can be greatly reduced. In addition, an efficient approach to handling infeasible paths is proposed. An evaluation of the enhanced zero-one method, the original zero-one method, and a greedy method is executed and the result is presented. (C) 1997 Elsevier Science Inc.
An ART-based fuzzy adaptive learning control network
(1997-11-01)
Lin, CJ
;
Lin, CT
;
交大名義發表
;
電控工程研究所
;
National Chiao Tung University
This paper addresses the structure and an associated on-line learning algorithm of a feedforward multilayered connectionist network for realizing the basic elements and functions of a traditional fuzzy logic controller. The proposed fuzzy adaptive learning control network (FALCON) can be contrasted with the traditional fuzzy logic control systems in their network structure and learning ability. An on-line structure/parameter learning algorithm called FALCON-ART is proposed for constructing the FALCON dynamically. It combines the backpropagation learning scheme for parameter learning and the fuzzy ART algorithm for structure learning. The FALCON-ART has some important features. First of all, it partitions the input state space and output control space using irregular fuzzy hyperboxes according to the distribution of training data. In many existing fuzzy or neural fuzzy control systems, the input and output spaces are always partitioned into ''grids.'' As the number of input/output variables increases, the number of partitioned grids will grow combinatorially. To avoid the problem of combinatorial growing of partitioned grids in some complex systems, the FALCON-ART partitions the input/output spaces in a flexible way based on the distribution of training data. Second, the FALCON-ART can create and train the FALCON in a highly autonomous way. In its initial form, there is no membership function, fuzzy partition, and fuzzy logic rule. They are created and begin to grow as the first training pattern arrives. Thus, the users need not give it any a priori knowledge or even any initial information on these. More notably, the FALCON-ART can on-line partition the input/output spaces, tune membership functions, find proper fuzzy logic rules, and annihilate redundant rules dynamically upon receiving online incoming training data. Computer simulations have been conducted to illustrate the performance and applicability of the proposed system.
Edge detection and edge-preserved compression for error-diffused images
(1997-11-01)
Han, WY
;
Lin, JC
;
資訊工程學系
;
Department of Computer Science
In this paper, a new approach to edge detection and image compression of bilevel error-diffused images is proposed. The proposed approach is directly applied to the error-diffused images without any inverse halftoning technique. The main idea behind the proposed edge detection method is to compute the consistency value of each pixel of the error-diffused image, and the computed values are then clustered into two classes to obtain the desired edges. Here, the consistency value is a function of the mass center and geometric center of the window; more precisely, it represents the possibility that the area covered by the window can be uniform. As for compression, each error-diffused input image is compressed by dividing the image into non-overlapping blocks with size 8x8, then each highly-consistent block is encoded by its average illumination, and each lowly-consistent block is transmitted directly using the original bitmap. The threshold to distinguish these two kinds of blocks is automatically calculated based on the compression rate required by the users. The complexity of our compression technique is low, and this fast method can be used in real-time application. (C) 1997 Elsevier Science Ltd. All rights reserved.
Observation and computation of vortex and/or reverse flow development in mixed convection of air in a slightly inclined rectangular duct
(1997-11-01)
Lin, WL
;
Lin, TF
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
Combined pow visualization and conjugated numerical heat transfer analysis were carried out to study the axial evolution of the buoyancy induced secondary vortex and reverse pow in a mixed convective air pow through a bottom heated, slightly inclined rectangular duct. Results were obtained for the Grashof number Gr ranging from 1.6 x 10(3) to 2.8 x 10(5), inclined angle phi from -20 deg to 26 deg and the Reynolds number Re below 102 covering the steady and time dependent flows. For the buoyancy-opposing case, at a certain critical buoyancy-to-inertia ratio depending on the Re and phi both the experimental and numerical results clearly showed the generation of the longitudinal vortex rolls in the entry half of the duct and a slender reverse pow zone was induced near the exit end of the duct. At a higher buoyancy-to-inertia ratio the stronger reverse flow moves upstream and is in a time periodic snaking motion which is considered to result from the Kelvin-Helmholtz instability associated with the two counter flow streams, namely, the downstream moving longitudinal vortex rolls and the upstream moving reverse flow. Through the viscous shearing effects the strong snaking reverse flow induces a number of eddies moving along it and the longitudinal rolls are pushed towards the duct sides. This strong interaction between the vortex flow and reverse pow leads to an earlier transition to turbulence. A correlation equation was proposed for the penetration length of the reverse flow. However for buoyancy-assisting pow no reverse flow is induced and the longitudinal vortex rolls prevail for the buoyancy-to-inertia ratio up to 2.8 X 10(5). Significant conjugated heat transfer effects were noted from the numerical results.
Four-wave mixing between a soliton and noise in a system with large amplifier spacing
(1997-11-01)
Chi, S
;
Kao, CY
;
Wen, S
;
光電工程學系
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Department of Photonics
Depletion of soliton energy by four-wave mixing between a soliton and amplifier noise in a system with 100-km amplifier spacing is studied. Dispersion exponentially decreasing fiber is used as transmission fiber. Improvement of the system by the use of a sliding-frequency filter to reduce noise power and the depletion of soliton energy is shown. The system can be further improved by compensation for depleted soliton energy. (C) 1997 Optical Society of America.