Browsing by Author "Hwang, GJ"

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An effective approach for test-sheet composition with large-scale item banks
(2006-02-01)
Hwang, GJ
;
Lin, BMT
;
Lin, TL
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
A well-constructed test sheet not only helps the instructor evaluate the learning status of the students, but also facilitates the diagnosis of the problems embedded in the students' learning process. This paper addresses the problem of selecting proper test items to compose a test sheet that conforms to such assessment requirements as average difficulty degree, average discrimination degree, length of test time, number of test items, and specified distribution of concept weights. A mixed integer programming model is proposed to formulate the problem of selecting a set of test items that best fit the multiple assessment requirements. As the problem is a generalization of the knapsack problem, which is known to be Xg-hard in the literature, computational challenge hinders the development of efficient solution methods. Seeking approximate solutions in an acceptable time is a viable alternative. In this paper, we propose two heuristic algorithms, based upon iterative adjustment, for finding quality approximate solutions. Extensive experiments are also conducted to assess the performances of different solution methods. Statistics from a series of computational experiments indicate that our proposed algorithms can produce near-optimum combinations of the test items subject to the specified requirements in a reasonable time. (c) 2004 Elsevier Ltd. All rights reserved.
Comparison of characteristics and integration of copper diffusion-barrier dielectrics
(2006-03-01)
Wang, TC
;
Cheng, YL
;
Wang, YL
;
Hsieh, TE
;
Hwang, GJ
The characteristics of various copper (Cu) barrier layers, including SiN, SiCN, and SiCO, were investigated in this work. Carbon-based barrier films (SiCN and SiCO) improved the dielectric constant and line-to-line capacitance, but led to sacrifice in film deposition rate, diffusion-barrier performance, and adhesion strength to Cu in comparison with SiN films. In addition, SiN and SiCO films showed the superior electromigration (EM) performance and stress-induced void migration (SM) performance, respectively. Furthermore, the reliability results of SM and EM are strongly related to the barrier film stress characteristics and the adhesion strength between Cu layers. Therefore, optimization of the barrier layer stress and the enhancement of the interfacial condition between Cu and barrier films are crucial to significantly improve reliability. (c) 2005 Elsevier B.V. All rights reserved.
CoSix thermal stability on narrow-width polysilicon resistors
(2006-01-01)
Chen, YM
;
Tu, GC
;
Wang, YL
;
Hwang, GJ
;
Lo, CY
In this study, the thermal stability of polysilicon lines with various widths and different dopant types in 90-nm processes is investigated. The thermal behavior of silicides formed on N+ polyresistors and P+ polyresistors is very different. The worst thermal stability is found on the narrower N+ polyresistors, while an abnormal thermal behavior is observed on P+ polyresistors. This anomalous thermal-stability change with different drawn linewidths of P+ polyresistors is related to the C Grain-size distribution and the actual polyresistor linewidth. Also, it is interesting to find that the voids formed in P+ polyresistors lead to a stepped increase in sheet resistance. (c) 2006 American Vactatin Society.
Effect of deposition temperature and oxygen flow rate on properties of low dielectric constant SiCOH film prepared by plasma enhanced chemical vapor deposition using diethoxymethylsilane
(2006-02-24)
Cheng, YL
;
Wang, YL
;
Hwang, GJ
;
O'Neill, ML
;
Karwacki, EJ
Low dielectric constant (Low-k) films (SiCOH) were deposited from diethoxymethylsiliane [DEMS; SiH(CH3) (OC2H5)(2)] which has two ethoxy groups along with one methyl group attached to the silicon atoms. The deposited films have been characterized for different oxygen flows, ranging from 50 to 250 standard cubic centimeters per minute (seem). The growth rate is increased with the increasing oxygen (O-2) flow. The absorbance spectrum of Fourier transform infrared spectroscopy shows that the frequency of Si-O stretching vibration mode in the SiCOH film is shifted to a higher wave number with the increase of oxygen flow. It is deduced that the oxygen does not participate in a simple oxidative mechanism, and has no apparent impact on the methyl content even if the relative Si-O content of the deposited films is up to an O-2/DEMS flow rate ratio of 1:1. Also, the refractive index is decreased with increasing the oxygen flow and slightly increased with the deposition temperature. The dielectric constant of the SiCOH is investigated between 2.7 and 3.2, depending on the deposition temperature and O-2/DEMS flow rate ratio, which is lower than that of the current OSG films (k=2.9-3.3). SiCOH films deposited with DEMS only exhibit higher mechanical hardness and lower leakage current than those deposited with both DEMS and oxygen. (c) 2005 Elsevier B.V. All rights reserved.
Effects of plasma treatment in the tungsten process for chemical vapor deposition titanium nitride barrier film beyond nanometer technology
(2006-03-01)
Chen, KW
;
Wang, YL
;
Chang, L
;
Li, FY
;
Hwang, GJ
As the device shrunk to 100 nm, the CVD TiN barrier filling would be limited by the process window of contact for both step coverage and plasma treatment. This limitation not only affects the step coverage capability but also poses a challenge to the treatment of the organic film with the small contact hole. In this study, we investigated whether the plasma treatment of the TiN film barrier influences the subsequent tungsten deposition and causes the change of the gapfilling behavior. After the different RF plasma treatment, we found that the resistivity and impurity level of the thin TiN film can influence not only the contact resistance and uniformity, but also the product yield. The over-treatment contacts were found with porous voids in the poor tungsten deposition during the contact filling even after CMP polishing. The resistances of under-treatment contacts would be determined by the impurity level of TiN films. Hence, the optimized TiN deposition and treatment would be critical to the contact resistance and yield performance. (c) 2005 Elsevier B.V. All rights reserved.
Features of the magnetic field of a rectangular combined function bending magnet
(1996-07-01)
Hwang, CS
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Chang, CH
;
Hwang, GJ
;
Uen, TM
;
Tseng, PK
Magnetic field features of the combined function bending magnet with dipole and quadrupole field components are essential for the successful operation of the electron beam trajectory. These fields also dominate the photon beam quality, The vertical magnetic field B-y(X,Y) calculation is performed by a computer code ''MAGNET'' at the magnet center ( s=0 ). Those results are compared with the 2-D field measurement by the Hall probe mapping system. Also detailed survey has been made of the harmonic field strength and the main features of the fundamental integrated strength, effective length, magnetic symmetry, tilt of the pole face, offset of the field center and the fringe field. The end shims that compensate for the strong end negative sextupole field to increase the good field region for the entire integrated strength are discussed. An important physical feature of this combined function bending magnet is the constant ratio of dipole and quadrupole strength integral Bds/integral Gds which is expressed as a function of excitation current in the energy range 0.6 to 1.5 GeV.
Heat, moisture and chemical resistance on low dielectric constant (low-k) film using diethoxymethylsilane (DEMS) prepared by plasma enhanced chemical vapor deposition
(2006-02-24)
Cheng, YL
;
Wang, YL
;
Lan, JK
;
Hwang, GJ
;
O'Neil, ML
Resistance of low dielectric constant (low-k) dielectrics, deposited using Diethoxymethylsilane (DEMS) precursor and helium (He) carrier gas with or without oxygen (O-2) reaction gas, against heat, moisture stress and chemical treatment is clarified. The low dielectric constant organosilicate glass (OSG) films deposited using DEMS and O-2 is shown to be the most reliable: the dielectric constant are stable even after a heating test at 700 degrees C and a pressure cooker test (PCT) for 168 h. This stability is high enough to ensure the low-k properties throughout fabricating multilevel interconnects and long-term reliability after the fabrication. This is due to the stability of Si-CH3 bonds and more Si-C-Si- bonds, which has high degree of cross-linking. However, the degradation of the dielectric constant occurs after O-2 plasma ashing process. The nitrogen plasma treatment is proposed to prevent the damage from O-2 attack in the low-k films deposited using DEMS precursor. (c) 2005 Elsevier B.V. All rights reserved.
High-selectivity damascene chemical mechanical polishing
(2006-03-01)
Chiu, SY
;
Wang, YL
;
Liu, CP
;
Chang, SC
;
Hwang, GJ
In this study, multi-step chemical mechanical polishing (CMP) with different copper removal rates and polishing pads is used to eliminate topography efficiently and to reduce micro-scratches on copper films. In colloidal-silica-based slurry, the polishing behaviors of copper, tantalum and silicon dioxide are found to relate to that kind of alkaline additives. The size of cations from alkaline additives influences the zeta potential of slurries, so as to vary the material removal rate. The addition of small-sized K+ from KOH provides high removal selectivity of tantalum/copper and oxide/copper, so as to benefit the reduction of copper dishing. (c) 2005 Elsevier B.V All rights reserved.
On the development of a computer-assisted testing system with genetic test sheet-generating approach
(2005-11-01)
Hwang, GJ
;
Lin, BMT
;
Tseng, HH
;
Lin, TL
;
資訊管理與財務金融系註：原資管所+財金所
Since the last decade, computer-assisted testing has proven to be an efficient and effective way to evaluating students' learning status such that proper tutoring strategies can be adopted to improve-their learning performance. A good test will not only help the instructor evaluate the learning status of the students, but also facilitate the diagnosis of the problems embedded in the students' learning process. One of the most important and challenging issues in conducting a good test is the construction of test sheets that can meet various assessment requirements. A previous study has indicated that selecting test items to best fit multiple assessment requirements can be formulated as a mixed integer programming model. The problem is known to be NP-hard in the literature and, hence, computational challenges hinder the development of efficient solution methods. As a sequel, we instead seek quality approximate solutions in a reasonable time. Two approximation methods based upon a genetic approach are developed. Statistics from a series of computational experiments indicate that our approach is able to efficiently generate near-optimal combinations of test items that satisfy the specified requirements or constraints.
On the equivalence between magnetic-field-induced phase transitions in the integer quantum Hall effect
(2003-04-01)
Huang, CF
;
Chang, YH
;
Cheng, HH
;
Yang, ZP
;
Wang, SY
Magnetic-field-induced phase transitions in the two-dimensional electron system in a AlGaAs/InGaAs/GaAs heterostructure are studied. Two kinds of magnetic-field-induced phase transitions, plateau-plateau (P-P) and insulator-quantum Hall conductor (I-QH) transitions, are observed in the integer quantum Hall effect regime at high magnetic fields. In the P-P transition, both the semicircle law and the universality of critical conductivities are broken and we do not observe the universal scaling. However, the P-P transition can still be mapped to the I-QH transition by the Landau-level addition transformation, and as the temperature decreases the critical points of these two transitions appear at the same temperature. Our observations indicate that the equivalence between P-P and I-QH transitions can be found by the suitable analysis even when some expected universal properties are invalid. (C) 2003 Elsevier Science Ltd. All rights reserved.
The construction of a 9-pole prototype for SRRC U-10 undulator
(1996-07-01)
Chang, CH
;
Chang, LH
;
Chen, HH
;
Fan, TC
;
Hwang, CS
A 9-pole undulator prototype with a magnetic period length of 10 cm was designed and constructed to examine the mechanical and magnetic field performance. The hybrid permanent magnet structure was optimized by using 2D ''PANDIRA'' and 3D ''TOSCA'' magnetostatic codes. A half period magnet model was also fabricated to verify the magnetic Period length field strength on-axis and the transverse field roll-off within 0.1 % in the good field region of +/- 10 mm at a minimum gap of 22 mm. The end pole configurations, as equipped with either two tunable permanent magnetic rotators or steering coil correctors were designed for minimizing the deviation of the magnetic field strength integrals. The magnet structures were mounted bn a 2 meter long C-frame support structure in which the gap could be moved in parallel and phase motion. The field characteristics, and measurement results between the adjustable gap undulator (AGO) and the hybrid adjustable phase undulator (APU) were also presented.
Three electrodes touch-mode capacitive pressure sensor
(1998-12-01)
Chang, KM
;
Hwang, GJ
;
Hsien, YL
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A three-electrode capacitive pressure sensor for touch-mode operation with sensitivity of 0.030 pF/kPa (or 10.4 mV/kPa using CP-10 C/V converter circuit) in the pressure range of 170-280 kPa is presented with theoretical explanation of experimental results. A special ring structure is designed to integrate a sensing capacitor and a reference capacitor into the same cavity to partially cancel out the temperature effect. A third electrode is included to eliminate two-level connections without reducing its pressure sensitivity. The sensor offers the advantages of simple fabrication processes, planar connections, as well as high sensitivity, near-linear output, and large over-range pressure.