Browsing by Author "Lee, TC"

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A general invariance principle for nonlinear time-varying systems and its applications
(2001-12-01)
Lee, TC
;
Liaw, DC
;
Chen, BS
;
電控工程研究所
;
Institute of Electrical and Control Engineering
A general invariance principle, from the output-to-state point of view, is proposed for the dynamical analysis of nonlinear time-varying systems. This is achieved by the construction of a simple and intuitive criterion using integral inequality of the output function and modified detectability conditions. The proposed scheme can be viewed as an extension of the integral invariance principle (Byrnes and Martin, 1995) for time-invariant systems to time-varying systems. Such extension is nontrivial and can be used in various research areas such as adaptive control, tracking control and the control of driftless systems. An application to global tracking control of four-wheeled mobile robots is given to demonstrate the feasibility and validity of the proposed approach.
A method to characterize n(+)-polysilicon/oxide interface traps in ultrathin oxides
(2001-06-01)
Chang, KM
;
Chung, YH
;
Lee, TC
;
Sun, YL
;
電子工程學系及電子研究所
In this study, a new method to characterize the n(+)-polysilicon/oxide interface trap state by measuring the gate voltage-gate leakage current (Vg-Jg) characteristics under the low electric field is developed. These traps are neutral and consist of the fast and slow trap states located near the Fermi level of the n(+)-polyoxide. We use the first order rate equation to characterize the relationship between the gate leakage current and the gate voltage sweep rate. A simple formula to characterize the detrapping behavior of the slow trap states with the detrapping time constant was derived. It is important to find that the smaller detrapping time constant observed in a thinner oxide (2.5 nm) is due to the field enhanced detrapping effect. (C) 2001 The Electrochemical Society.
Adaptive tracking control of nonholonomic mobile robots by computed torque
(2003-07-01)
Lee, TC
;
Lee, CH
;
Teng, CC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
A computed torque controller for a dynamic model of nonholonomic mobile robots with bounded external disturbance is proposed to treat the adaptive tracking control problem using the separated design method. A velocity controller is first designed for the kinematic steering system to make the tracking error approaching to zero asympotically. Then, a computed torque controller is designed such that the true mobile robot velocity converges to the desired velocity controller. In each step, the controllers are designed independently, and this will simplify the design of controllers. A novel stability analysis involving the estimation of some differential inequalities is also given to guarantee the stability of the closed-loop system. Moreover, the regulation problem and the tracking problem will be treated using the proposed controller. In particular, the mobile robots can globally follow any path such as a straight-line, a circle and the path approaching to the origin. Furthermore, the problems of back-into-garage parking and the parallel parking problem can also be solved using the proposed controller. Some interesting simulation results are given to illustrate the effectiveness of the proposed tracking control law.
Characteristics of N2O-grown polyoxide by the recrystallized-polysilicon method
(1998-12-01)
Chang, KM
;
Lee, TC
;
Sun, YL
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This work proposes a new method for growing the polyoxide and investigates its characteristics. Thin amorphous silicon was deposited on the first polysilicon and then recrystallized at 600 degrees C for 24 h to form a new polysilicon. The N2O-grown polyoxide formed by this method has a higher conduction current and better stress endurance than those of the conventional polyoxide. The higher quality polyoxide, as measured by lower gate voltage shift and larger charge-to-breakdown (Q(bd)), is due to the smooth polyoxide/polysilicon interface which increases the stress endurance under high fields. (C) 1998 The Electrochemical Society. S1099-0062(98)06-105-7. All rights reserved.
Comparison of the characteristics of polyoxides grown by thermal, rapid thermal oxidation, and tetraethylorthosilicate deposition methods
(1999-10-01)
Chang, KM
;
Lee, TC
;
Sun, YL
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The characteristics of polyoxides grown by different methods in order to find the best way of growing high qualities of polyoxide were investigated in this work. Thermal, rapid thermal oxidation (RTO), and tetraethylorthosilicate (TEOS) deposition methods were used to grow the polyoxides. RTO provided a smoother interface of polyoxide/polysilicon than that of thermal furnace method. TEOS deposition method resulted in a smooth polyoxide/poly-1 interface due to no polysilicon consumption. The polyoxide grown by thermal method had the worst characteristics, while the post-deposition RTO method had the best qualities (low leakage current, high breakdown electric field, low voltage shift, and high charge-to-breakdown). The high qualities of polyoxide grown by post-deposition RTO method were due to the smooth polyoside/poly-1 interface and less electron trapping.
Direct observation of long-term durability of superconductivity in YBa2Cu3O7-Ag2O composites
(2003-10-01)
Lin, JJ
;
Lin, YH
;
Huang, SM
;
Lee, TC
;
Chen, TM
We report direct observation of long-term durability of superconductivity of several YBa2Cu3O7-Ag2O composites that were first prepared and studied almost fourteen years ago [J. J. Lin et al.: Jpn. J. Appl. Phys. 29 (1990) 497]. Remeasurements performed recently on both resistances and magnetizations indicate a sharp critical transition temperature at 91 K. We also find that such long-term environmental stability of high-temperature superconductivity can only be achieved in YBa2Cu3O7 with Ag2O addition, but not with pure Ag addition.
Electrical characteristics of polyoxide prepared by N-2 preannealing
(2000-01-01)
Chang, KM
;
Lee, TC
;
Wang, JY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper reports on the electrical characteristics of polyoxide with preoxidation N-2 annealing in a rapid thermal annealing system. By treating the polysilicon film before oxidation, the obtained polyoxide has the desired relative characteristics, i.e., a higher breakdown electric field, a smaller voltage shift, and larger charge-to-breakdown. This improvement is due to the reduction of defects, such as microtwins, inside the grain. (C) 1999 The Electrochemical Society. S1099-0062(99)08-054-2. All rights reserved.
Fast parking control of mobile robots: A motion planning approach with experimental validation
(2004-09-01)
Lee, TC
;
Tsai, CY
;
Song, KT
;
電控工程研究所
;
Institute of Electrical and Control Engineering
This paper presents a solution to the general parking problem of nonholonomic mobile robots based on motion planning and tracking controller design. A new global tracking controller is first proposed to achieve global uniformly asymptotic stability and local exponential convergence. The parking problem is then transformed into a tracking one by adding a redesigned virtual trajectory to the original trajectory, thus guaranteeing practical stability with exponential convergence. Further improvement in parking performance is obtained through. linearization and pole-placement methods. One feature of our approach is that fast convergence in parking and tracking can be treated at the same time without switching between two controllers. Moreover, a tuning function is used to enhance parking performance. With the proposed framework, various tracking controllers given in the literature can be adopted to handle parking problems. The effectiveness of the proposed methods is verified by several interesting experiments including parallel parking and back-into-garage parking.
Improved reliability of HfO2/SiON gate stack by fluorine incorporation
(2006-04-01)
Lu, WT
;
Chiein, CH
;
Lan, WT
;
Lee, TC
;
Lehnen, P
Effects of fluorine (F) incorporation on the reliabilities of pMOSFETs with HfO2/SiON gate stacks have been studied. In this letter, fluorine was incorporated during the source/drain implant step and was diffused into the gate stacks during subsequent dopant activation. The authors found that F introduction only negligibly affects the fundamental electrical properties of the transistors, such as threshold voltage V-th, subthreshold swing, gate leakage current, and equivalent oxide thickness. In contrast, reduced generation rates in interface states and charge trapping under constant voltage stress and bias temperature stress were observed for the fluorine-incorporated split. Moreover, the authors demonstrated for the first time that F incorporation could strengthen the immunity against plasma charging damage.
Improvements on electrical characteristics of p-channel metal-oxide-semiconductor field effect transistors with HfO(2) gate stacks by post deposition N(2)O plasma treatment
(2005-11-01)
Lu, WT
;
Chien, CH
;
Lan, WT
;
Lee, TC
;
Yang, MJ
In this work, we found that employing a post deposition N(2)O plasma treatment following the deposition of HfO(2) film can effectively improve the electrical characteristics of p-type channel metal-oxide-semiconductor field-effect transistors (pMOSFETs) with a HfO(2) gate stack in terms of lower gate leakage current, lower interface state density, superior subthreshold swing, higher normalized transconductance and enhanced driving current even though it had led to a slightly higher equivalent oxide thickness (EOT) value of the HfO(2) gate stack by around 0.3 nm. In order to clarify the attributes of the improvements, we used charge pumping (CP) measurement to analyze the densities of interface states and bulk traps in the HfO(2) gate stacks. The improvements are then ascribed to the higher interface quality offered by the post deposition N(2)O plasma treatment. Moreover, we found that to more accurately estimate the bulk traps from the CP measurement, the leakage should be taken into account especially at low frequencies. Finally, it was found that the levels of the bulk traps and interface states can be reduced by the N(2)O plasma treatment, which also helps significantly eliminate the degradation of the gate stack during the subsequent voltage stress.
Improvements on electrical characteristics of p-channel metal-oxide-semiconductor field effect transistors with HfO2 gate stacks by post deposition N2O plasma treatment
(2005-11-01)
Lu, WT
;
Chien, CH
;
Lan, WT
;
Lee, TC
;
Yang, MJ
In this work, we found that employing a post deposition N2O plasma treatment following the deposition of HfO2 film can effectively improve the electrical characteristics of p-type channel metal-oxide-semiconductor field-effect transistors (pMOSFETs) with a HfO2 gate stack in terms of lower gate leakage current, lower interface state density, superior subthreshold swing, higher normalized transconductance and enhanced driving current even though it had led to a slightly higher equivalent oxide thickness (EOT) value of the HfO2 gate stack by around 0.3 nm. In order to clarify the attributes of the improvements, we used charge pumping (CP) measurement to analyze the densities of interface states and bulk traps in the HfO2 gate stacks. The improvements are then ascribed to the higher interface quality offered by the post deposition N2O plasma treatment. Moreover, we found that to more accurately estimate the bulk traps from the CP measurement, the leakage should be taken into account especially at low frequencies. Finally, it was found that the levels of the bulk traps and interface states can be reduced by the N2O plasma treatment, which also helps significantly eliminate the degradation of the gate stack during the subsequent voltage stress.
Influence of sheet resistance on N2O-grown polyoxide
(2000-04-01)
Chang, KM
;
Lee, TC
;
Liu, SH
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The influence of sheet resistance on polyoxide was explored in this paper. Polyoxides were grown on polysilicon with different sheet resistances (30-150 Omega/cm(2)). It was found that as the sheet resistance increased from 30 Omega/cm(2) to 50 Omega/cm(2) the characteristics of polyoxide was improved with higher breakdown electric field and higher charge-to-breakdown. However, as the sheet resistance continued to increase (> 110 Omega/cm(2)), the characteristics of polyoxide became worse again. This phenomenon is explained by phosphorus concentration incorporated into polyoxide. Phosphorus concentration helps to form a smoother polyoxide/polysilicon interface. Thus, the characteristics of polyoxide with high sheet resistance (>110 Omega/cm(2)) was worse than that of polyoxide with low sheet resistance due to a rough polyoxide interface. However, too much. phosphorus incorporated into polyoxide degrades the quality of polyoxide. So the characteristics of polyoxide with low sheet resistance (<50 Omega/cm(2)) became worse again. Consequently, high quality of polyoxide should he grown on the polysilicon with middle sheet resistance (50-110 Omega/cm(2)).
Low temperature electrical transport properties of RuO2 and IrO2 single crystals
(2004-11-17)
Lin, JJ
;
Huang, SM
;
Lin, YH
;
Lee, TC
;
Liu, H
We have systematically measured the electrical transport properties of several RuO2 and IrO2 single crystals over a wide temperature range from 300 K down to 0.3 K to study the conduction mechanisms in these oxides. Our measured resistivities are in close agreement with the recent band-theory calculations for these materials. The characteristic temperatures for the acoustic-mode and optical-mode phonons are determined. Our measured magnetoresistances are positive and follow the Kohler rule, indicating that the transport properties of these oxides exhibit normal behaviour as described by the Boltzmann equation. In contrast, we do not find any signature of superconductivity down to 0.3 K, though the band-theory calculations predict a superconducting transition temperature of similar to5 K. Magnetization measurements suggest a very low level of paramagnetic impurities in our crystals.
Observation of a crossover of the inelastic electron scattering in Sc100-xAgx thick films
(2003-08-15)
Lee, TC
;
Lin, JJ
;
Chang, SF
;
電子物理學系
;
物理研究所
We have made a series of thick Sc films doped with different amounts of Ag, which results in a systematic decrease in the resistivities, i.e., disorder, of the films. From measurements of the low-field magnetoresistances and comparison with three-dimensional weak-localization theoretical predictions, the electron dephasing times are extracted in every film. We find a crossover of the inelastic electron process from the critical electron-electron scattering to the electron-phonon scattering as the disorder decreases and the system progressively moves away from the Anderson localization.
Reliable control of nonlinear systems
(2000-04-01)
Liang, YW
;
Liaw, DC
;
Lee, TC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
In this paper, we extend Veillette's results (1995) to the study of reliable linear-quadratic regulator problem for nonlinear systems. This is achieved by employing the Hamilton-Jacobi inequality in the nonlinear case instead of algebraic Riccati equation in the linear one. The proposed state-feedback controllers are shown to be able to tolerate the outage of actuators within a prespecified subset of actuators. Both the pain margins of guaranteeing system stability and retaining a performance bound are estimated.
The effect of the growth temperature on polyoxide by rapid thermal processing
(2001-03-01)
Chang, KM
;
Lee, TC
;
Sun, YL
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A rapid thermal oxynitridation process using N2O gas as the oxidant has been developed. Due to a smoother polyoxide/polysilicon interface, polyoxide grown by rapid thermal processing has better reliability than that of polyoxide grown by a conventional furnace. Moreover, in order to explore the effects of growth temperature on polyoxides, polyoxides were grown at different temperatures in this study. From this work, we find that polyoxide grown at low temperatures has better reliability than polyoxides grown at high temperature and exhibits improved characteristics such as higher breakdown electric field, less gate voltage shift, and larger charger-to-breakdown.
The relaxation phenomena of positive charges in thin gate oxide during Fowler-Nordheim tunneling stress
(1998-08-01)
Chang, KM
;
Li, CH
;
Wang, SW
;
Yeh, TH
;
Yang, JY
In this study, new relaxation phenomena of positive charges in gate oxide with Fowler-Nordheim (FN) constant current injections have been investigated and characterized. It was found that the magnitudes of applied gate voltage shifts (Delta V-FN) during FN injections, after positive charges relaxed or discharged, have a logarithmic dependence with the relaxation time for both injection polarities, The results can derive the relationship of transient discharging currents, that flow through the oxides after removal of the stress voltage, with the relaxation time. We have shown that the current has a lit dependence for both injection polarities which can be also derived from the tunneling front model. The effects of oxide fields (lower than the necessary voltage for FN tunneling) and wafer temperatures (373 and 423 K) for the relaxation of positive charges are also studied.
Thickness and stress polarity effects on the reliability of the low thermal budget polyoixdes
(2001-10-01)
Chang, KM
;
Chung, YH
;
Chen, HY
;
Lee, TC
;
Sun, YL
In this paper, the thickness and the stress polarity effects on the reliability of the low thermal budget polyoxides are investigated. The polyoxides are prepared by two methods: the low-temperature tetraethylorthosilicate (TEOS) polyoxide deposition and in the rapid thermal chamber in N2O ambient (RTN2O). It is observed that the thinner TEOS polyoxides exhibit higher charge to breakdown (Q(bd)) and larger stress polarity effect than those of the thicker TEOS polyoxides. However, for the RTN2O grown polyoxides from 8.5 nm to 12.9 run, they have the similar values of the Qbd and the stress polarity effects, The nitrogen atoms incorporated in the RTN2O grown polyoxides may be the reason to this less thickness dependence of the Q(bd). Higher barrier height is also observed for the RTN2O grown polyoxides than that of the deposited TEOS polyoxide to obtain a lower tunneling current under a fixed electric field.
Tracking control of mobile robots without constraint on velocities
(2001-09-01)
Lee, CH
;
Lee, TC
;
Teng, CC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
A general tracking control problem for mobile robots is proposed and solved using the backstepping technique. A global result is given for the kinematic steering system to make the tracking error approaching to zero asymptotically. Based on our efforts, the proposed controller can solve both the tracking problem and the regulation problem of mobile robots. In particular, mobile robots can now globally follow any differentiable with bounded velocities path such as a straight line, a circle and the path approaching to the origin using the proposed controller. Moreover, the problem of back-into-garage parking is also solved by our approach. Some interesting simulation results are given to illustrate the effectiveness of the proposed tracking control laws.
Tracking control of unicycle-modeled mobile robots using a saturation feedback controller
(2001-03-01)
Lee, TC
;
Song, KT
;
Lee, CH
;
Teng, CC
;
電機資訊學士班
The tracking control problem with saturation constraint for a class of unicycle-modeled mobile robots is formulated and solved using the backstepping technique and the idea from the LaSalle's invariance principle. A global result is presented in which several constraints on the linear and the angular velocities of the mobile robot from recent literature are dropped. The proposed controller can simultaneously solve both the tracking and regulation problems of a unicycle-modeled mobile robot. With the proposed control laws, the robot can globally follow any path specified by a straight line, a circle or a path approaching the origin using a single controller. As demonstrated, the circular and parallel parking control problem are solved using the proposed controller. Computer simulations are presented which confirm the effectiveness of the proposed tracking control law Practical experimental results validate the simulations.