Design, testing and precision control of a novel long-stroke flexure micropositioning system

This paper presents a systematic modeling and control methodology for a two-dimensional flexure beam-based servo stage supporting micro/nano manipulations Compared with conventional mechatronic systems, such systems have major control challenges including cross-axis coupling, dynamical uncertainties, as well as input saturations, which may have adverse effects on system performance unless effectively eliminated A novel disturbance observer-based adaptive backstepping-like control approach is developed for high precision servo manipulation purposes, which effectively accommodates model uncertainties and coupling dynamics An auxiliary system is also introduced, on top of the proposed control scheme, to compensate the input saturations The proposed control architecture is deployed on a customized-designed nano manipulating system featured with a flexure beam structure and voice coil actuators (VCA) Real time experiments on various manipulating tasks, such as trajectory/contour tracking, demonstrate precision errors of less than 1%

A disturbance observer-based adaptive control approach for flexure beam nano manipulators

Recent interest in high-precision positioning stages with large travel ranges has sparked renewed attention to the development of voice coil motors (VCMs). Due to their large output force, VCMs can actuate more complicated flexure structures, eliminate rail friction, and improve positioning speed. The VCM structure is both compact and flexible; hence, it is convenient to design VCMs for a variety of stage structures. Furthermore, VCMs combined with other actuators are able to achieve large travel ranges with high precision. In this paper, we summarize the principles and control methods of a typical VCM, and we analyze its properties, including thrust force, acceleration, and response time. We then present recent research on high-precision VCM positioning stages with large travel ranges.

Contributed Review: Application of voice coil motors in high-precision positioning stages with large travel ranges

Band alignment of amorphous Ge2Sb2Te5 and various substrates was obtained using high-resolution x-ray photoelectron spectroscopy. The valence band offset of Ge2Sb2Te5 on various complementary-metal-oxide-semiconductor (CMOS) materials, i.e., Si, SiO2, HfO2, Si3N4 and NiSi, were investigated with the aid of the core level, valence band, and energy loss spectra. Energy band lineups of Ge2Sb2Te5 on these materials were thus determined which can be used as for phase change memory device engineering and integration with CMOS technology.

Band alignment between amorphous Ge2Sb2Te5 and prevalent complementary-metal-oxide-semiconductor materials

In micromanufacturing and nanomanufacturing in the semiconductor and flat panel display industry, many kinds of positioning system that have a large working area, high speed, and high accuracy are required. In this paper, the design of a mechanically decoupled dual servo (MDDS) stage is proposed and presented. The stage consists of a coarse stage actuated by a linear motor and a fine stage actuated by a voice coil motor. The two stages are required to be developed independently, if possible, to save lead time and ensure the security of trade secrets; therefore, the MDDS stage is designed according to a modular design approach. A dual servo tracking controller is introduced for the MDDS by appending a fine controller to a conventional coarse controller. Despite the modular design without mechanical coupling, a reaction force between the fine stage and coarse stage is generated by the magnetic coupling that is detrimental to positioning and tracking. Therefore, a simple compensator that reduces the effect of the reaction force is also presented. Simulations and experiments are performed to evaluate the performance of the MDDS stage.

Dual Servo Stage Without Mechanical Coupling for Process of Manufacture and Inspection of Flat Panel Displays Via Modular Design Approach

The disk rotation speed of optical disk drives (ODD) has been increasing rapidly to achieve high data transfer rates. High servo bandwidths for focusing and tracking actuator are required to follow dynamic disturbance by high rotation speed in ODD. However, the servo bandwidth is significantly limited by some vibration modes which are induced by the flexibility of the moving part. In this work, the vibration modes affecting the bandwidth of actuators are shifted to high frequency range and suppressed by modifying the FE model which is used to analyze the motion of the actuator. Some local dimensions of the lens holder, which is included in the moving part, are selected as design variables to increase the stiffness without changing the material properties. Selected modal frequencies of the moving part are raised about 10%, while the performances of actuator such as DC and AC sensitivities are hardly affected by the modification.

Improvement of dynamic characteristics for optical pickup actuator using sensitivity analysis

The precision positioning system for semiconductor lithography requires a robust structural design to obtain enough control bandwidth and an efficient actuator with fast access time. In this article, a three-axis stage is proposed as a fine stage of a dual stage for the precision positioning. Its actuators are voice coil motors (VCMs) whose coil windings are mounted on the coarse stage and its magnets are on the fine stage. Between the fine and coarse stages, there is no mechanical connection but only magnetic coupling. The eight pairs of magnets and four coil windings are arrayed symmetrically. The three-axis stage's dynamic characteristics are improved by enhancing the actuating force and modifying its own structure using finite-element analysis in order to meet its requirements of high bandwidth and large forces. The actuating force is strengthened by modifying each VCM's magnetic circuit. The structure is designed to be robust by using design of experiment (DOE) as well. The modified stage is ...

Robust design of a novel three-axis fine stage for precision positioning in lithography

In an examination of the chemical structures of the AlOx∕Co90Fe10 interface, we confirmed that thermal treatment affects the redistribution of oxygen at the interface and that this leads to an increase in the tunneling barrier height of magnetic tunnel junctions The as-deposited Al oxide barrier with a thickness of ∼13A was oxygen-deficient AlOx, but most of it turned into Al2O3, the thermodynamically stable stoichiometric phase, through annealing This enrichment of oxygen is likely responsible for the observed improvement The near-edge x-ray absorption fine structure spectra of Co and Fe proved the fact that after bonding with Co and Fe in the underlying CoFe layer, the oxygen diffused back into the barrier and thereby enriched the barrier to the point where it mostly consisted of Al2O3 Our results confirm that controlling the chemical structures at the interface is a key to modify the properties of magnetic tunnel junctions

The redistribution of oxygen at AlOx∕CoFe interface of magnetic tunnel junctions through thermal treatment

We confirmed that the improvement in properties of magnetic tunnel junctions prepared by radical oxidation after thermal treatment was mostly resulted from the redistribution of oxygen at the AlOx/Co_(90)Fe_(10) interface. The as-deposited Al oxide barrier was oxygen-deficient but most of it re-oxidized into Al₂O₃, the thermodynamically stable stoichiometric phase, through thermal treatment. As a result, the effective barrier height was increased from 1.52 eV to 2.27 eV. On the other hand, the effective barrier width was decreased from 8.2 Å to 7.5 Å. X-ray absorption spectra of Fe and Co clearly showed that the oxygen in the CoFe layer diffused back into the Al barrier and thereby enriched the barrier to close to a stoichiometirc Al₂O₃ phase. The oxygen bonded with Co and Fe diffused back by 6.8 Å and 4.5 Å after thermal treatment, respectively. Our results confirm that controlling the chemical structures of the interface is important to improve the properties of magnetic tunnel junctions.

Effect of Thermal Treatment on AIO x /Co 90 Fe 10 Interface of Magnetic Tunnel Junctions Prepared by Radical Oxidation

To study the carrier reduction pathway for quantum dots (QDs), we have measured carrier lifetimes and photoluminescence spectra both at 10 K and at higher temperatures. We found that the carriers captured in QDs are robust and are not lost to nearby defects, even at elevated temperature, and that the lower emission efficiency of QDs with defects compared to the corresponding defect-free QDs is due to the capture of carriers to defects before entering into the QDs.

Carrier capture before entering into a semiconductor quantum dot as a dominant pathway for the reduction of emission efficiency

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