High-precision Stage Research Articles

Attitude Control Method for High-Precision Stage by Compensating for Nonlinearity and Coupling Arising from Euler's Equation and Coordinate Rotation

Attitude Control Method for High-Precision Stage by Compensating for Nonlinearity and Coupling Arising from Euler's Equation and Coordinate Rotation

Design and control of a single-stage dual-actuator system for high-precision manufacturing

This paper proposes a design for the linear state feedback control of the dual-actuator system, which is a dual-input single-output system for the high-precision manufacturing stage. The proposed control prevents saturation or reduces the unnecessary movement of the piezoelectric (PZT) actuator at the transient response by tracking the error between the estimated and actual positions of the coarse-actuator system at each control sample. Also, a new mechanism of the single-stage dual actuator is introduced. The axes of the stepper motor and the PZT actuator are co-axial. The coupling effects between the stepper motor and the PZT actuator are considered. Both the simulation and experiment results show that the proposed algorithm successfully prevents unwanted motions of the PZT actuator at the transient response. The experiment results show that the settling time and overshoot were enhanced by 45.7 and 95.9 %, respectively, for the proposed algorithm when the reference distance was 10 μm, which exceeds the stroke of the PZT actuator.

UV NIL공정에서 액적의 양과 도포방법에 따른 기포형성 연구

최근 나노임프린트 리소그래피 공정이 마이크로/나노 스케일의 소자 개발에 있어서 경제적으로 대량 생산할 수 있는 기술로 주목 받고 있다. 최근 나노임프린트 기술은 공정의 고속화 및 대면적화를 통한 대량생산 기술로의 전환을 목표로 하고 있다. 자외선경화 방식의 나노임프린트의 경우 상온 및 저압의 장점과 함께 비진공 환경에서 공정이 가능하다면 진공챔버 및 고압 스테이지 등과 같은 고가의 장비가 필요 없게 됨으로써 설비비용을 낮추고 공정시간을 단축하는데 큰 기여를 할 수 있다. 그러나 비진공 환경에서는 기포결함이 종종 발생하게 된다. 본 연구에서는 비진공 환경에서의 자외선경화 방식의 나노임프린트 공정 중 레지스트의 액적도포 방법에 따른 기포형성을 연구하였다. 액적의 양과 액적의 수를 달리하여 도포한 레지스트에 대하여 충전 후 기포결함 발생을 분석하였다. Nanoimprint lithography (NIL) is an emerging technology enabling cost-effective and high-throughput nanofabrication. Recently, the major trends of NIL are high throughput and large area patterning. UV curable type NIL (UV NIL) can be performed at room temperature and low pressure. And one advantage of UV NIL is that it does not need vacuum, which greatly simplifies tool construction, so that vacuum oprated high-precision stages and a large vacuum chamber are no longer needed. However, one key issue in non-vacuum environment is air bubble formation problem. Namely, can the air bubbles be completely removed from the resist. In this paper, the air bubbles formation by the method of droplet application in UV NIL with non-vacuum environment are experimentally studied. The effects of the volume of droplet and the number of dispensing points on air bubble formation are investigated.

Self-tuning in master–slave synchronization of high-precision stage systems

For synchronization of high-precision stage systems, in particular the synchronization between a wafer and a reticle stage system of a wafer scanner, a master–slave controller design is presented. The design consists of a synchronization controller based on FIR filters and a data-driven self-tuning approach is used to find the coefficients of these filters. In the context of Lur'e systems, i.e.the reticle stage slave system has a variable gain controller with saturation nonlinearity, a part of the gradients needed for self-tuning is obtained from reconstruction using closed-loop nonlinear models. The remaining part is given by sampled data obtained primarily from time-series measurements. Performance with the synchronization controller is shown to be bounded by a waterbed effect: low-frequency suppression comes at the price of high-frequency amplification. For the considered Lur'e stage systems the ability of the self-tuning to induce improved tracking is discussed in view of this waterbed effect for either simulation results or experimental results.

Optimization of laser machining process for the preparation of photomasks, and its application to microsystems fabrication

Conventional photolithography normally utilizes a photomask for patterning light onto a chemical resist film. Therefore, the accuracy of microfabrication is highly dependent on the accuracy of the photomasks. Fabrication of hard masks involves the use of expensive laser pattern generators and other sophisticated machines using very high-precision stages and the necessary control instrumentation; therefore, an inexpensive strategy is highly necessary for laboratory-level fabrication. As this technology is primarily based on raster scanning of a laser beam, the mask making as such becomes a low-throughput process. A strategy of high-throughput manufacturing of hard masks with laser micromachining using a one-step exposure process of a chromated glass slide through a micromachined aluminum shadow mask is proposed. The features that are finally embedded in the mask are highly demagnified and well focused. Optimization of the laser machining process is carried out by considering all processing parameters. The features are characterized using an optical microscope, a scanning electron microscope, and a self-developed image analysis code. Geometrical methods are used to estimate the average edge roughness and feature size. We have also validated the usage of these masks by performing microfabrication on films made of photoresist.

Can cancer registries show whether treatment is contributing to survival increases for melanoma of the skin at a population level?

It is uncertain whether survival increases from melanoma recorded by some population registries include a treatment effect. The US Surveillance, Epidemiology and End Results (SEER) programme has good data quality control, large numbers of cases enabling high statistical precision and summary stage plus thickness, which we consider to be a best-case population registry scenario to investigate potential for a treatment effect. We have investigated SEER data to indicate whether survivals increases are fully attributable to earlier diagnosis and other non-treatment factors. Through relative survival regression, the effects of diagnostic period on 5-year excess mortality were investigated, adjusting for socio-demographic factors, lesion sub-site, histology, thickness and stage at diagnosis in 1990-2009 (n = 99 690 cases). The reduction in excess mortality (95% confidence interval) between 1990-1999 and 2000-2009 was 31 (20-41)% for localised melanoma, 18 (12-22)% for regional melanoma and 3 (-5-10)% for melanomas with distant spread. Younger age was predictive of a greater percentage reduction. Treatment benefits are inferred from the higher survivals in 2000-2009 but uncertainty remains due to incomplete data to adjust for non-treatment factors and a lack of treatment data. Registries should use new information systems to collect more complete data on stage, other prognostic indicators, co-morbidities and treatment, to provide more definitive and detailed information on population effects of cancer control.

Neutron tomography of particulate filters: a non-destructive investigation tool for applied and industrial research

This research describes the development and implementation of high-fidelity neutron imaging and the associated analysis of the images. This advanced capability allows the non-destructive, non-invasive imaging of particulate filters (PFs) and how the deposition of particulate and catalytic washcoat occurs within the filter. The majority of the efforts described here were performed at the High Flux Isotope Reactor (HFIR) CG-1D neutron imaging beamline at Oak Ridge National Laboratory; the current spatial resolution is approximately 50μm. The sample holder is equipped with a high-precision rotation stage that allows 3D imaging (i.e., computed tomography) of the sample when combined with computerized reconstruction tools. What enables the neutron-based image is the ability of some elements to absorb or scatter neutrons where other elements allow the neutron to pass through them with negligible interaction. Of particular interest in this study is the scattering of neutrons by hydrogen-containing molecules, such as hydrocarbons (HCs) and/or water, which are adsorbed to the surface of soot, ash and catalytic washcoat. Even so, the interactions with this adsorbed water/HC is low and computational techniques were required to enhance the contrast, primarily a modified simultaneous iterative reconstruction technique (SIRT). This effort describes the following systems: particulate randomly distributed in a PF, ash deposition in PFs, a catalyzed washcoat layer in a PF, and three particulate loadings in a SiC PF.

Automated ICF Capsule Characterization Using Confocal Surface Profilometry

Capsule ablators are precision hollow spheres used in inertial confinement fusion targets used in high-peak-power laser systems such as the National Ignition Facility. These capsules have high surface-quality requirements, and hence a full surface microscopic mapping system has been developed to characterize them. The capsule-fill-tube-assembly mapping system combines a confocal surface-profiling microscope with a nine-axis, high-precision stage system to provide quantitative three-dimensional data over the entire surface of each capsule prior to assembly into the final target. The system measures the individual volumes of features on the capsule surface that are 7.5 μm3 and larger with an accuracy of ±10%. The positional accuracy is better than 0.25 deg (1σ), or [approximately]5 μm linearly. The data acquisition and image processing are all highly automated in order to keep pace with throughput demands. The system consists of four primary subsystems: the positioning system, the confocal microscope, the automated acquisition code, and the image processing and data management software.

Proposal of Position Reconstruction with Polynomial Fitting Approach for Precise Motion Control

Optical encoders are extensively used for position measurements in motion control systems. The inherent quantization feature of encoders limits the control performance in many applications. This paper shows a way to reconstruct the smooth position signal from the quantized measurements. The method uses a polynomial fitting approach where the degree of polynomial is automatically selected via a convex optimization method. In addition, the information of the plant is exploited by combining an observer. The effectiveness of the proposed method is verified by simulations and experiments using a high-precision linear stage.

Uncertainty investigation of grating interferometry in six degree-of-freedom motion error measurements

An uncertainty analysis of grating interferometry in six degree-of-freedom (DOF) motion error measurements in a linear stage is presented. Six-DOF refers to the translational and rotational motion of a rigid body in a three-dimensional space. The optical measurement method and sensor were constructed and applied to the ballscrew-driven stage for validation. With a single traversal of the stage along the X direction, the optical sensor measured the motion in high resolution along each axis: less than 0.03 arcsec, 20 nm, and 0.4 nm for the rotational, Y and Z directions, and X direction, respectively. A laser interferometer and autocollimator were used for comparison. In conjunction with a performance evaluation for the proposed optical sensor, the measurement uncertainty (k=1) was estimated from the error sources, which included installation error, optics error, electronics error, environmental effects, and motion-induced error (with the exception of the driving axis). Under a given experimental condition, the environmental error is a major error source for the X direction, the optics error strongly affects the Y and Z directions, and environmental effects affect the three rotational directions. Furthermore, the motion error in the high precision stage is less sensitive to the measurement error, but it has to be taken into account in case of a general-purpose stage.

High Precision Modeling and Identification of the Near Transition Sliding Friction in a Mechanical Stage

Mechanical stages are common but very important tools to all the fields in the modern world. However, with the increasing demand for high-precision stage capability, it is found that the frictional characteristics play a more vital role for the stage motion and are worth of a careful investigation. Therefore, the problem of dynamic behavior and parameter identification for the sliding friction in a normal mechanical stage system operated in long range is studied in this paper, especially for the near transition regime between the presliding and sliding friction behaviors. A dynamic model and its corresponding identification method are proposed such that all the system parameters can identified from the derived relationships in a systematical way. The results show that the proposed method indeed works effectively with the experimental data regardless the complex composition and unevenly distributed contact conditions of the actual stage system.

Design and performance of a combined secondary ion mass spectrometry-scanning probe microscopy instrument for high sensitivity and high-resolution elemental three-dimensional analysis

State-of-the-art secondary ion mass spectrometry (SIMS) instruments allow producing 3D chemical mappings with excellent sensitivity and spatial resolution. Several important artifacts however arise from the fact that SIMS 3D mapping does not take into account the surface topography of the sample. In order to correct these artifacts, we have integrated a specially developed scanning probe microscopy (SPM) system into a commercial Cameca NanoSIMS 50 instrument. This new SPM module, which was designed as a DN200CF flange-mounted bolt-on accessory, includes a new high-precision sample stage, a scanner with a range of 100 μm in x and y direction, and a dedicated SPM head which can be operated in the atomic force microscopy (AFM) and Kelvin probe force microscopy modes. Topographical information gained from AFM measurements taken before, during, and after SIMS analysis as well as the SIMS data are automatically compiled into an accurate 3D reconstruction using the software program "SARINA," which was developed for this first combined SIMS-SPM instrument. The achievable lateral resolutions are 6 nm in the SPM mode and 45 nm in the SIMS mode. Elemental 3D images obtained with our integrated SIMS-SPM instrument on Al/Cu and polystyrene/poly(methyl methacrylate) samples demonstrate the advantages of the combined SIMS-SPM approach.

Design and Modeling of a Large-Range Modular XYZ Compliant Parallel Manipulator Using Identical Spatial Modules

To meet the need for large-range high-precision motion stages, a design methodology of XYZ compliant parallel manipulators (CPMs) is introduced at first. A spatial double four-beam module and a compliant P (prismatic) joint, composed of two spatial double four-beam modules, are then proposed. Starting from a 3-PPPR (R: revolute) translational parallel manipulator, a large-range modular XYZ CPM with identical spatial modules is constructed using the proposed design approach. Normalized analytical models for the large-range modular XYZ CPM are further presented. As a case study, a modular XYZ CPM with a motion range of 10 mm × 10 mm × 10 mm along the positive X-, Y-, and Z-axes is presented in detail, covering the geometrical parameter determination, performance characteristics analysis, buckling check, and actuation force check. The analytical models are compared with the finite element analysis (FEA) models. Finally, the dynamics consideration, manufacturability, and merits are discussed. It is shown that the proposed large-range modular XYZ CPM has the following main merits compared with existing designs: (1) large range of motion up to 20 mm × 20 mm × 20 mm and (2) reduced number of design parameters through the use of identical spatial modules, although the manufacturability is a challenging issue.

Research on Load-Bearing Characteristics of Precision Air-Bearing Rotary Stage

Air-bearing is a core component of air-bearing rotary stage. The weakness that the air-bearing has the low load capacity and stiffness has been concerned about by domestic and foreign scholars. So how to improve the load capacity and stiffness has become a serious problem. In order to improve the load capacity and stiffness of the air-bearing rotary stage, in this paper, we improved structure of Zhang Wenjie and others’ high-precision direct-drive air-bearing rotary stage. The gas film of air-bearing has been meshed by GAMBIT software, and we use FLUENT software to obtain the carrying capacity features of the gas film. Finally, the structural static force of the precision air-bearing rotary stage will be analyzed by ANSYS software. The analysis results show that: the structural design of the precision air-bearing rotary stage is reasonable, and this structure can provide a larger range of loads. Even in heavy load conditions, a larger deformation will not occur any more. It has a good practical value, and also can be widely used in high precision equipments.

A High-Precision Dual-Servo Stage Using Halbach Linear Active Magnetic Bearings

In this paper, a high-precision dual-servo stage with a magnetically levitated fine stage is described. For magnetic levitation, a Halbach linear active magnetic bearing (HLAMB) is used. The HLAMB has two functions: gravity compensation and actively control of vertical motion. To implement these functions, the HLAMB utilizes permanent magnet arrays and Lorentz coils. The fine stage has positioning capabilities with 6 DOF due to four HLAMBs and four voice coil motors (VCM). The HLAMBs control out-of-plane motions, and the VCM control in-plane motions. The fine stage achieves high-precision position feedback using laser interferometers and capacitive sensors. The coarse stage has an H-type structure that can carry the fine stage 300 mm by 300 mm along the x - and y-axes. Positioning and scanning performances are verified by the experimental results. It has ±10 and ±15 nm in-position stability in the x- and y-axes, respectively. At the scan with 10 mm/s constant velocity, ±1 nm mean tracking error and 4.7 nm jitter were obtained.

3D elemental distribution images in biological samples by XRFµCT

An X-ray transmission microtomography (CT) system combined with an X-ray fluorescence microtomography (XRFµCT) system was implemented in the Brazilian Synchrotron Light Laboratory (LNLS), Campinas, Brazil. The aim of this work was to determine the elemental distribution in biological samples (breast, prostate and lung samples) in order to verify the concentration of some elements correlated with characteristics and pathology of each tissue observed by the transmission CT. The experiments were performed at the X-ray fluorescence beamline (D09B-XRF) of the Brazilian Synchrotron Light Laboratory, Campinas, Brazil. A quasi-monochromatic beam produced by a multilayer monochromator was used as an incident beam. The sample was placed on a high-precision goniometer and translation stages that allow rotating as well as translating it perpendicularly to the beam. The fluorescence photons were collected with an energy dispersive HPGe detector placed at 90° to the incident beam, while transmitted photons were detected with a fast Na(Tl) scintillation counter placed behind the sample on the beam path. The CT images were reconstructed using a filtered-back projection algorithm and the XRFµCT images were reconstructed using a filtered-back projection algorithm with absorption corrections. The 3D images were reconstructed using the 3D-DOCTOR software. Results from the 3D visualization showed that the distribution of iron, copper and zinc is different and heterogeneous from the analyzed samples. Copyright © 2011 John Wiley & Sons, Ltd.

Robust Control of a High-precision Positioning Stage Using an Integrated H∞ and QFT Controller

A new three-axis high precision stage is developed in this article, which consists of an X-Y moving platform and a rotational stage on the top of the platform. Piezoelectric actuators embedded in the flexure hinge are utilized to drive the stage and the displacements are measured by laser displacement sensors. To facilitate the design of the device, dynamic models are developed using the Lagrangian approach. The natural frequency of the system is analyzed and compared with the finite element model. Due to the installation and fabrication errors, it is found that the dynamics of the X-Y moving platform is coupled. To achieve better performance, the H∞ controller for the MIMO system is developed first to eliminate the coupling effects. Variable payloads are considered in the design process to achieve system robustness. Then, the H∞ controller is then reshaped using the QFT. The noise and control efforts are reduced significantly after applying the QFT technique. The results demonstrate that the coupling between the X-Y axes can be reduced with the integrated H∞ and QFT controller. Moreover, the settling time and positioning accuracy for a 10-µm step input are less than 0.1 s and 0.3 µm, respectively.

Design and control of a long-traveling nano-positioning stage

Abstract In this paper, a Dual-Axis Long-Traveling Nano-Positioning Stage (DALTNPS) is presented. In order to extend the traveling and increase the accuracy, the two sorts of stages, a traditional ball-screw stage and a three-degrees-of-freedom (3-DOF) piezo-stage, were composed. The traditional ball-screw stage which is composed of two guide-ways and a ball-screw at each axis is a long-travel stage, and the 3-DOF piezo-stage, which is composed of three piezoelectric actuators and four translation–rotation mechanisms, is a high precision stage. In addition, a 3-DOF measuring system and a PID controller are composed of a 3-DOF closed-loop controller and applied to implement the DALTNPS. The measuring system which is composed of two laser interferometers and two plane mirrors is a 3-DOF optical measuring system. Thus, the position at the x and y axes and the rotation around the z axis can be obtained and they are the responses of DALTNPS. Finally, the experiment results evidence that the DALTNPS is characterized by long-travel, high linear accuracy, high rotation accuracy, high contouring accuracy and high motion speed.

Application of Perfect Tracking Control to Large-Scale High-Precision Stage

In the positioning system of the large-scale high-precision stage, the primary resonance mode appears in low frequency, though large-scale high-precision stages are used in industrial fields. In recent years, our research group has applied the perfect tracking control (PTC) method which can design the perfect inverse system of the plant to a large-scale high-precision stage to improve the control performance. Moreover, a synchronous position control based on PTC method is proposed as application to several stages. In early sections, the application of the PTC method to a large-scale stage is introduced. In latter sections, the application to synchronous position control is introduced.

Real-time phase-only color holographic video display system using LED illumination

A real-time full-color phase-only holographic display system generates holograms of 3D objects. The system includes a 3D object formed by voxels, an internet-based transmission capability that transmits the object information to the server, a real-time hologram generation unit, and a holographic display unit with incoherent illumination. The server calculates three phase holograms for RGB components using multiple GPUs. The resultant phase holograms are saved into an RGB bitmap image and loaded to the phase-only spatial light modulators (SLMs). SLMs are illuminated uniformly by LEDs, and reconstructed waves are aligned and overlapped by using high precision optics and stages. Experimental results are satisfactory.