Browsing by Issue Date, starting with "2000-10-01"

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Migration-adsorption mechanism of metallic impurities out of chemically amplified photoresist onto silicon-based substrates
(2000-10-01)
Yang, CC
;
Ko, FH
;
Wang, MY
;
Wang, TK
;
Wu, SC
The radioactive tracer technique was applied to investigate the migration and adsorption behaviors of metallic impurities (i.e., Ba, Cs, Zn, and Mn) out of chemically amplified photoresist onto silicon-based underlying substrates. Two important process parameters, i.e., baking temperatures and substrate types (e.g., bare silicon, polysilicon, oxide, and nitride) were evaluated. Our results indicated that the transition metals (Zn and Mn) have lower migration ratios than alkali metal (Cs) and alkaline earth metal (Ba), irrespective of the substrate types and baking temperatures. The transition metals form stable complexes with the coexisting solvents and/or hydrolysis species in the photoresist layer. The size of the metal complex, the drag force in solvent evaporation, and the baking process were found to have significant effects on impurity migration. A new model, together with the metal migration in the chemically amplified photoresist and the subsequent adsorption onto the underlying substrate, was proposed to explain the pathway of the metal migration. This model could explain the migration ratios of metallic impurities out of the photoresist layer onto the substrate surface. (C) 2000 The Electrochemical Society. S0013-4651(00)01-026-0. All rights reserved.
Feedback median filter for robust preprocessing of glint noise
(2000-10-01)
Chang, DC
;
Wu, WR
;
電信工程研究所
;
Institute of Communications Engineering
Glint noise may arise in a target tracking system. The non-Gaussian behavior of glint noise can severely degrade the tracking performance, Measurement preprocessing at the front-end of the tracker is an effective method to reduce glint noise. The preprocessor proposed by Hewer, Martin, and Zeh, which used the computationally intensive M-estimator, may not be suitable for practical implementation. An alternative method employing the median filter is studied here. The median tilter is well known for its simplicity and robustness. However, the efficiency of the median biter can be seriously degraded if input samples are not identically distributed. This is what we may encounter in the tracking problem. A feedback median filter is then proposed to overcome this impediment without substantially increasing complexity. Simulations show that the new preprocessor can greatly improve tracking performance in the glint noise environment.
Temperature and annealing effects on photoluminescence spectra of (InAs)(1)/(GaP)(2) superlattices grown by solid-source molecular beam epitaxy
(2000-10-01)
Cheng, YC
;
Chi, S
;
Chou, ST
;
Huang, KF
;
電子物理學系
Anomalous variation of photoluminescence (PL) wavelengths with temperature was observed in (InAs)(1)/(GaP)(2) short-period-superlattice (SPS) quantum wells grown by solid-source molecular beam epitaxy with different phosphorus and arsenic cracker temperatures. We believed that the anomalous PL behavior could be attributed to the multi-axial strain effect existed at the abrupt InAs and GaP interfaces in the SPS structure. After rapid thermal anneal (RTA) treatment, the anomalous PL spectra in the low temperature region disappeared but the high temperature PL characteristics remained, which revealed the thermal stability of the (InAs)(1)/(GaP)(2) quantum well structures and its potential in replacing InGaAsP quaternary.
Parallel synchronous and asynchronous space-decomposition algorithms for large-scale minimization problems
(2000-10-01)
Liu, CS
;
Tseng, CH
;
機械工程學系
;
Department of Mechanical Engineering
Three parallel space-decomposition minimization (PSDM) algorithms, based on the parallel variable transformation (PVT) and the parallel gradient distribution (PGD) algorithms (O.L. Mangasarian, SIMA Journal on Control and Optimization, vol. 33, no. 6, pp. 1916-1925.), are presented for solving convex or nonconvex unconstrained minimization problems. The PSDM algorithms decompose the variable space into subspaces and distribute these decomposed subproblems among parallel processors. It is shown that if all decomposed subproblems are uncoupled of each other, they can be solved independently. Otherwise, the parallel algorithms presented in this paper can be used. Numerical experiments show that these parallel algorithms can save processor time, particularly for medium and large-scale problems. Up to six parallel processors are connected by Ethernet networks to solve four large-scale minimization problems. The results are compared with those obtained by using sequential algorithms run on a single processor. An application of the PSDM algorithms to the training of multilayer Adaptive Linear Neurons (Madaline) and a new parallel architecture for such parallel training are also presented.
Bayesian wavelet shrinkage for nonparametric mixed-effects models
(2000-10-01)
Huang, SY
;
Lu, HHS
;
統計學研究所
;
Institute of Statistics
The main purpose of this article is to study the wavelet shrinkage method from a Bayesian viewpoint. Nonparametric mixed-effects models are proposed and used for interpretation of the Bayesian structure. Bayes and empirical Bayes estimation are discussed. The latter is shown to have the Gauss-Markov type optimality (i.e., BLUP), to be equivalent to a method of regularization estimator (MORE), and to be minimax in a certain class. Characterization of prior and posterior regularity is discussed. The smoothness of posterior estimators is controlled via prior parameters. Computational issues including the use of generalized cross validation are discussed, and examples are presented.
Photo-induced liquid crystal alignment with discotic films
(2000-10-01)
Wu, LH
;
Lee, WC
;
Hsu, CS
;
Wu, ST
;
應用化學系
Photo-induced liquid crystal alignment using cross-linked discotic compounds was demonstrated. These discotic compounds exhibit good solubility in common organic solvents, 60 degreesC processing temperature and excellent thermal stability. A linearly polarized long wave ultraviolet light (lambda = 350 nm) was used to initiate the cross-linking process which, in turn, induces liquid crystal alignment on the discotic film surface. The polarity of discotic compounds plays an important role in affecting the pretilt angle of the liquid crystal alignment. A pretilt angle of 1 +/- 0.4 degrees was obtained using single exposure at oblique angle. Potential application of this new photo-alignment film for low temperature poly-silicon thin-film-transistor liquid crystal display is foreseeable.
Chinese dialect identification using segmental and prosodic features
(2000-10-01)
Chang, WW
;
Tsai, WH
;
電信工程研究所
;
Institute of Communications Engineering
Several approaches to Chinese dialect identification based on segmental and prosodic features of speech are described in this paper. When using segmental information only, the system performs phonotactic analysis after speech utterances have been tokenized into sequences of broad phonetic classes. The second scheme comprises prosodic models which are trained to capture tone sequence information for individual dialects. Also proposed is a novel approach that examines differences between Chinese dialects at broad phonetic and prosodic levels. These algorithms were evaluated via a multispeaker read-speech mode. Simulation results indicate that the combined use of Segmental and prosodic features allows the proposed system to discriminate among three major Chinese dialects spoken in Taiwan with 93.0% accuracy. (C) 2000 Acoustical Society of America. [S0001-4966(oo)03410-X].
Effect of the trapping laser linewidth on the atom number in a magneto-optical trap
(2000-10-01)
Chen, YC
;
Lin, WB
;
Hsue, HC
;
Hsu, L
;
Yu, IA
We have experimentally studied the effect of the trapping laser linewidth on the number of capped atoms in a magneto-optical trap (MOT). Our data show that a significant number of the atoms can still be trapped in the MOT, even when the trapping laser linewidth is larger than the natural linewidth of the excited state of the driving transition.
Using inverse modeling to estimate the incident heat flux required to achieve temperature uniformity across a circular disk
(2000-10-01)
Lin, S
;
Chu, HS
;
機械工程學系
;
Department of Mechanical Engineering
This article presents a systematic inverse modeling analysis for estimating the incident heat flux required to achieve temperature uniformity across a circular disk during thermal processing. A one-dimensional thermal model, temperature-dependent thermal properties of silicon, and a future-time algorithm of inverse heat transfer method are used. Vertical and lateral edge-heat compensations on the perimeter are discussed. The required edge-heat compensations for maintaining uniform temperature across 100-mm-diameter (0.6-min-thick), 150-mm-diameter (0.675-mm-thick), 200-mm-diameter (0.725-mm-thick), and 300-mm-diameter (0.775-mm-thick) silicon disks are evaluated intuitively using inverse modeling. Our numerical results show that temperature uniformity can be efficiently achieved using inverse modeling. The resulting maximum temperature differences in our present study were only 0.279, 0.583, 0.989, and 0.178 degreesC across 100-, 150-, 200- and 300-mm-diameter disks, respectively.
Identification of material constants of composite laminates using measured strains
(2000-10-01)
Kam, TY
;
Lin, CH
;
Wang, WT
;
機械工程學系
;
Department of Mechanical Engineering
A method for nondestructive evaluation of material constants of composite laminates is presented. An error function is established to measure the differences between the theoretically and experimentally predicted strains. The identification of the the material constants is formulated as a constrained minimization problem in which the material constants are determined to make the error function a global minimum. A global minimization method, together with an appropriate bounding technique for constraining the variations of the material constants, are used to solve the above minimization problem. The applications of the proposed method are demonstrated by means of several examples on the material constants identification of laminated composite cylindrical pressure vessels. [S0094-4289(00)02704-3].
Injection-locked coupled microstrip leaky-mode antenna array
(2000-10-01)
Hu, CN
;
Tzuang, CKC
;
電信工程研究所
;
Institute of Communications Engineering
The paper presents a novel design for an injection-locked microstrip leaky-mode antenna array. It demonstrates that the coupling parameters can be obtained numerically, leading to the analysis of the steady-state phase relationships of the coupled oscillators based on Van der Pol equations for determining the excitation signals of the array. In particular, it applies the coupled-mode approach to investigating the clear and considerable mutual coupling effect on the radiation characteristics of the microstrip leaky-mode array. This, in turn, produces a very efficient and accurate assessment of the radiation far-field patterns. Finally, a proof-of-concept design using a two-element injection-locked microstrip leaky-mode array is presented for experimental verification, showing excellent agreement between theoretical data and measured results.
Characterization and reliability of lightly-doped-drain polysilicon thin-film transistors with oxide sidewall spacer formed by one-step selective liquid phase deposition
(2000-10-01)
Shih, PS
;
Chang, TC
;
Huang, TY
;
Yeh, CF
;
Chang, CY
We have proposed and successfully demonstrated a novel process for fabricating a lightly doped drain (LDD) polysilicon thin-film transistor (poly-Si TFT). The oxide sidewall spacer in the new process is formed by a simple one-step selective liquid phase deposition (LPD) at 23 degreesC. In contrast with conventional methods, this new process does not require an additional photolithographic step for defining the non-self-aligned offset gate, or the deposition of an oxide layer and subsequent etch-back to form the: self-aligned sidewall spacer. Devices fabricated by the new process have a lower leakage current and a better ON/OFF current ratio, compared with non-LDD control devices. The new device also shows excellent current saturation characteristics at high bias and better has hot-carrier endurance. Since the apparatus used for LPD oxide deposition is simple and inexpensive, the new process appears to be promising for future high-performance poly-Si TFT fabrication.
A new LDA-based face recognition system which can solve the small sample size problem
(2000-10-01)
Chen, LF
;
Liao, HYM
;
Ko, MT
;
Lin, JC
;
Yu, GJ
A new LDA-based face recognition system is presented in this papal. Linear discriminant analysis (LDA) is one of the most popular linear projection techniques for feature extraction. The major drawback of applying LDA is that it may encounter the small sample size problem. In this paper, we propose a new LDA-based technique which can solve the small sample size problem. We also prove that the most expressive vectors derived ill the null space of the within-class scatter matrix using principal component analysis (PCA) are equal to the optimal discriminant vectors derived in the: original space using LDA. The experimental results show that the new LDA process improves the performance of a face recognition system significantly. (C) 2000 Pattern Recognition Society. Published by Elsevier Science Ltd. All rights reserved.
Surface roughness measurement on microchannels by atomic force microscopy using a bent tapered fiber probe
(2000-10-01)
Chen, SH
;
Lin, HN
;
Yang, CR
;
電子物理學系
;
Department of Electrophysics
We demonstrate a high-resolution and nondestructive surface roughness measurement on microchannels by atomic force microscopy with the use of a bent tapered optical fiber probe. The probe was fabricated by a combination of laser heating-pulling and electric arc bending. Microchannels with a width of 41.5 mu m and a height of 31.9 mu m were fabricated on polycarbonate by excimer laser ablation and the resultant roughness was measured to be 4.8 nm. (C) 2000 American Institute of Physics. [S0034-6748(00)00210-0].
Estimation of Kendall's tau under censoring
(2000-10-01)
Wang, WJ
;
Wells, MT
;
統計學研究所
;
Institute of Statistics
We study nonparametric estimation of Kendall's tau, tau, for bivariate censored data. Previous estimators of tau, proposed by Brown, Hollander and Korwar (1974), Weier and Basu (1980) and Oakes (1982), fail to be consistent when marginals are dependent. Here we express tau as an integral functional of the bivariate survival function and construct a natural estimator via the von Mises functional approach. This does not necessarily yield a consistent estimator since tail region information on the survival curve may not be identifiable due to right censoring. To assess the magnitude of the inconsistency we propose some estimable bounds on tau. It is shown that estimates of the bounds shrink to provide consistency if the largest observations on both marginal coordinates are uncensored and satisfy certain regularity conditions. The bounds depend on the sample size, on censoring rates and, in particular, on the estimated probability of the unknown tail region. We also discuss using the bootstrap method for variance estimation and bias correction. Two illustrative data examples are analyzed, as well as some simulation results.
Solid-state NMR study of cyclo-olefin copolymer (COC)
(2000-10-01)
Huang, WJ
;
Chang, FC
;
Chu, PPJ
;
應用化學系
;
Department of Applied Chemistry
In this article, we have applied solid-state C-13 NMR techniques, cross-polarization/magic-angle spinning (CP/MAS), and single-pulse C-13 NMR to characterize the NE conformation of the cyclo-olefin copolymer. The copolymers containing higher NE contents produce more NE blocks according to C-13 CP/MAS spectral analysis. In addition, NB-dyad-based conformations are able to induce peak splitting in the region of 49-52 ppm. (C) 2000 John Wiley & Sons, Inc.
A new method for constructing fuzzy decision trees and generating fuzzy classification rules from training examples
(2000-10-01)
Chen, SM
;
Lin, SY
;
資訊工程學系
;
Department of Computer Science
This paper presents a new method for constructing fuzzy decision trees and generating fuzzy classification rules from training instances using compound analysis techniques. The proposed method call generate simpler fuzzy classification rules and has a better classification accuracy rate than the existing method. Furthermore. the proposed method generated less fuzzy classification rules.
Electronic compensation for nonideal spatial light modulator characteristics
(2000-10-01)
Budgett, DM
;
Sharp, JH
;
Tang, PC
;
Young, RCD
;
Scott, BF
Compensation for spatial light modulator device imperfections can be achieved using digital electronics. Optical computing applications, requiring accurate phase or amplitude modulation, can then make use of low-cost, enhanced devices. Using electronic compensation, corrections can be made for a nonsquare aspect ratio in the aperture window and a nonlinear phase response-which may also be nonuniform over the aperture. The corrections for these imperfections are implemented using low-cost field programmable gate arrays. This technology enables real-time compensation and is easily adapted to suit a wide range of display devices. The performance enhancement is demonstrated using a popular Seiko-Epson liquid crystal television display operating as a phase modulating spatial light modulator. These developments greatly extend the utility of readily available, inexpensive, spatial light modulators. (C) 2000 Society of Photo-Optical instrumentation Engineers. [S0091-3286(00)02509-5].
Turnaround phenomenon of threshold voltage shifts in amorphous silicon thin film transistors under negative bias stress
(2000-10-01)
Huang, CY
;
Tsai, JW
;
Teng, TH
;
Yang, CJ
;
Cheng, HC
The turnaround phenomenon of threshold voltage shifts is investigated in thin film transistors (TFTs) with different defect densities of hydrogenated amorphous silicon (a-Si:H) films and compositions of SiNx. It was found that TFTs with high-defect-density a-Si:H films and N-rich SiNx gate exhibit the turnaround phenomenon while TFTs with other conditions of a-Si:H and SiNx films do not. Results reveal that the turnaround phenomenon is greatly influenced by charge traps in SiNx and state creation in the a-Si:H layer. When state creation is dominant at low bias stress, the turnaround phenomenon occurs. In contrast, if charge trapping is dominant at low bias stress, the turnaround phenomenon does not occur.
Postexposure delay effect on linewidth variation in base added chemically amplified resist
(2000-10-01)
Ku, CY
;
Shieh, JM
;
Chiou, TB
;
Lin, HK
;
Lei, TF
To elucidate the linewidth variation caused by postexposure delay (PED) in resist films, the distribution of photogenerated acid, the role of additional base component, and the affect of exposure energy were investigated in tert-butoxycarbonyl protected-type chemically amplified positive deep ultraviolet resist. The resist system included an N-methyl pyrrolidone organic base which was evaluated via KrF excimer laser lithography. Using various line-and-space patterns formed with a KrF scanner, this work also investigated the change of linewidth caused by the delay time between exposure and postexposure bake. Experimental results indicate that the linewidth broadened immediately following exposure and became a constant value rather than continuously expanding for various pattern sizes. Based on the mechanism of neutralizing organic base and photogenerated acid, a model was established to describe the linewidth according to FED time. Moreover, the effect of exposure energy on linewidth variation was investigated to not only assess the influence of exposure energy but also clarify the relationship between linewidth broadening and delay rime. Experimental analysis demonstrates that the exposure latitude and depth of focus can be improved by employing FED. (C) 2000 The Electrochemical Society. S0013-4651(99)09-090-4. All rights reserved.