Browsing by Author "Wang, WT"

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A novel laser-processed self-aligned gate-overlapped LDD poly-Si TFT
(2002-03-01)
Lin, CW
;
Tseng, CH
;
Chang, TK
;
Lin, CW
;
Wang, WT
A novel process for fabricating self-aligned gate-overlapped LDD (SAGOLDD) poly-Si thin film transistors (TFTs) was demonstrated. Laser Irradiation for dopant activation was performed from the backside of the quartz wafer. The graded LDD structure was naturally formed under the gate edges due to the lateral diffusion of the dapants during the laser activation. In comparison with the conventional laser-processed self-aligned poly-Si TFTs, the SAGOLDD poly-Si TFTs exhibited lower leakage current, suppressed kink effect, and higher reliability. Moreover, the proposed process was simple and very suitable for low-temperature process.
An investigation of bias temperature instability in hydrogenated low-temperature polycrystalline silicon thin film transistors
(2002-09-01)
Lin, CW
;
Tseng, CH
;
Chang, TK
;
Chang, YH
;
Chu, FT
The instability mechanisms of the hydrogenated n-channel low-temperature polycrystalline silicon thin film transistors under on-state stress were investigated with various bias stress conditions and device channel widths. It was found that hot carrier degradation which originated from a high drain electric field and self-heating during high current operation were the two dominant mechanisms responsible for device degradation. An electrically reversible depassivation/passivation phenomenon was also found in devices under high current stress. but not in those under hot carrier stress. It was inferred that the self-heating effect would accelerate the bond breakage and diffusion of hydrogen ions, thus enhancing the rate of depassivation/passivation. Moreover. when the Current in the hot carrier stress mode was sufficiently high. self-heating became the dominant degradation mechanism and hot carrier degradation phenomenon was also suppressed for devices with large channel width, Meanwhile, the electrically reversible depassivation/passivation phenomenon also occurred in this case.
Determination of elastic constants of composite laminates using measured natural frequencies
(2000)
Wang, WT
;
Kam, TY
;
機械工程學系
;
Department of Mechanical Engineering
The identification of material elastic constants of laminated composite plates using measured natural frequencies is studied. The first three natural frequencies of the lower resonant modes of the laminated composite plates were extracted from the modal testing data of the plates. The finite element method is used to perform the modal analysis of the laminated composite plates. An error function is established to measure the differences between the experimentally and theoretically predicted natural frequencies of the laminated composite plates. The identification of the material elastic constants of the laminated composite plates is formulated as a constrained minimization problem in which the elastic constants are determined by making the error function a global minimum. Test results of a number of laminated composite plates are used to illustrate the feasibility and applications of the proposed method.
Elastic constants identification of shear deformable laminated composite plates
(2001-11-01)
Wang, WT
;
Kam, TY
;
機械工程學系
;
Department of Mechanical Engineering
A constrained minimization method is presented for the identification of elastic constants of shear deformable laminated composite plates. Strains and/or displacements obtained from static testing of laminated composite plates are used in the proposed method to identify the elastic constants of the plates. In the identification process, the trial elastic constants of a laminated composite plate are used in a finite-element analysis to predict the strains and displacements of the plate. An error function is established to measure the differences between the experimental and theoretical predictions of strains and/or displacements. A constrained minimization technique is used to minimize the error function and update the trial elastic constants. The best estimates of the elastic constants of the plate are then determined by subsequently reducing the size of the feasible region of the elastic constants and making the error function a global minimum. The accuracy and applications of the proposed method are demonstrated by means of a number of examples. A sensitivity analysis is also performed to study the effects of variations of experimental data on the accuracy of the identified elastic constants.
External failure pressure of a frangible laminated composite canister cover
(1999-12-01)
Kam, TY
;
Wu, JH
;
Wang, WT
;
機械工程學系
;
Department of Mechanical Engineering
The static failure strength of a frangible laminated composite canister cover subjected to uniform external pressure is studied via both theoretical and experimental approaches. The frangible canister cover, which is fabricated with four plate-like laminated composite parts, which is designed in such a way that it will fail in a predetermined pattern when subjected to an impulsive internal pressure and its external Failure pressure is much higher than its internal failure pressure. The stress distribution in the canister cover is determined using the finite element method and the failure of the cover identified on the basis of an appropriate failure criterion. A number of laminated composite canister covers were fabricated and subjected to static external pressure testing. The failure modes of the frangible covers are studied and the experimental results are used to verify the theoretical predictions. Close agreements between the experimental and theoretical results have been observed. The present study shows that the design of frangible covers with external failure pressure much higher than the internal failure pressure can be achieved. (C) 2000 Elsevier Science Ltd. All rights reserved.
Fabrication of low-temperature poly-Si thin film transistors with self-aligned graded lightly doped drain structure
(2002-01-01)
Cheng, HC
;
Lin, CW
;
Cheng, LJ
;
Tseng, CH
;
Chang, TK
A novel approach for fabricating low-temperature poly-Si (LTPS) thin film transistors (TFTs) with self-aligned graded lightly doped drain (LDD) structure was demonstrated. The self-aligned graded LDD structure was formed by side-etching the Al gate under the photoresist followed by excimer laser irradiation for dopant activation and lateral diffusion. The graded LDD poly-Si TFTs exhibited low-leakage-current characteristics without significantly sacrificing driving capability due to the graded dopant distribution in the LDD regions, in which the drain electric field could be reduced. The leakage current of 1 mum graded LDD UPS TFTs at Vds = 5 V and Vgs = -10 V could reach below 1 pA/mum, and the on/off current ratio at Vds = 5 V exceeded 10(7). (C) 2001 The Electrochemical Society.
Failure analysis of a frangible laminated composite canister cover
(1999)
Wu, JH
;
Wang, WT
;
Kam, TY
;
機械工程學系
;
Department of Mechanical Engineering
The static burst strength of a frangible laminated composite canister cover subjected to uniform pressure is studied via both theoretical and experimental approaches. The frangible canister cover, which is fabricated with four plate-like laminated composite parts, is designed to fail in a predetermined pattern. The stress distribution in the canister cover is determined using the finite element method and the failure of the cover is identified on the basis of a failure criterion. A number of laminated composite canister covers were fabricated and subjected to static burst pressure testing. The failure modes of the frangible covers are studied and the experimental results are used to verify the theoretical predictions. Close agreements between the experimental and theoretical results have been observed. The canister covers that had been tested did fail in accordance with the predetermined pattern.
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].
Level shifters for high-speed 1-v to 3.3-v interfaces in a 0.13-mu m Cu-Interconnection/Low-k CMOS technology
(2001)
Wang, WT
;
Ker, MD
;
Chiang, MC
;
Chen, CH
;
電子工程學系及電子研究所
Level shifters for 1.0-V to 3.3-V high-speed interfaces are proposed. Level-up shifter uses zero-Vt 3.3-V NMOSs as voltage clamps to protect 1.0-V NMOS switches from high voltage stress across the gate oxide. Level-down shifter uses 3.3-V NMOSs as both pull-up and pull-down devices with supply voltage of 1.0-V and gate voltage swing from 0-V to 3.3-V. The zero-Vt NMOS is a standard MOSFET device in a 0.13-mum CMOS process without adding extra mask or process step to realize it. Level-up transition from 0.9-V to 3.6-V takes only 1 ns in time, and the level-down transition has no minimum core voltage limitation. These circuits do not consume static DC power, therefore they are very suitable for low-power and high-speed interfaces in the deep sub-quarter-micron CMOS technologies.
Material characterization off laminated composite plates via static testing
(2000-12-01)
Wang, WT
;
Kam, TY
;
機械工程學系
;
Department of Mechanical Engineering
A minimization method for material characterization of laminated composite plates using static test results is presented. Mechanical responses such as strains and displacements are measured from the static tests of the laminated composite plates. The finite element method is used to analyse the deformation of the laminated composite plates. An error function is established to measure the differences between the experimental and theoretical mechanical responses of the laminated composite plates. The identification of the material elastic constants of the laminated composite plates is formulated as a constrained minimization problem in which the elastic constants are determined by making the error function a global minimum. A number of examples are given to illustrate the feasibility and applications of the proposed method. (C) 2000 Elsevier Science Ltd. All rights reserved.