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2010 | Book

Angle Sensor for Measurement of Surface Slope and Tilt Motion Read chapter Read first chapter

Precision Nanometrology

Sensors and Measuring Systems for Nanomanufacturing

Author: Wei Gao

Publisher: Springer London

Book Series : Springer Series in Advanced Manufacturing

Part of: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik"

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About this book

Precision Nanometrology describes the new field of precision nanometrology, which plays an important part in nanoscale manufacturing of semiconductors, optical elements, precision parts and similar items. It pays particular attention to the measurement of surface forms of precision workpieces and to stage motions of precision machines. The first half of the book is dedicated to the description of optical sensors for the measurement of angle and displacement, which are fundamental quantities for precision nanometrology. The second half presents a number of scanning-type measuring systems for surface forms and stage motions. The systems discussed include: • error separation algorithms and systems for measurement of straightness and roundness, • the measurement of micro-aspherics, • systems based on scanning probe microscopy, and • scanning image-sensor systems. Precision Nanometrology presents the fundamental and practical technologies of precision nanometrology with a helpful selection of algorithms, instruments and experimental data. It will be beneficial for researchers, engineers and postgraduate students involved in precision engineering, nanotechnology and manufacturing.

Table of Contents

Frontmatter
1. Angle Sensor for Measurement of Surface Slope and Tilt Motion
Abstract
Angle is one of the most fundamental quantities for precision nanometrology. Angle sensors based on the principle of autocollimation, which are conventionally called autocollimators, can accurately measure small tilt angles of a light-reflecting flat surface [1]. Autocollimators have a long history of being used in metrology laboratories for calibration of angle standards, such as polygons, rotary index tables and angle gage blocks. They are also traditionally used in machine shops for surface profile measurements of straightedges, machine tool guideways, precision surface plates, as well as for measurement of tilt error motions of translational stages [2].
2. Laser Autocollimator for Measurement of Multi-axis Tilt Motion
Abstract
Precision stages used in nanomanufacturing, including linear stages and rotary stages, have multi-axis tilt error motions. For a linear stage, the tilt error motions are referred to as the pitch, yaw and roll error motions, which cause unexpected Abbe errors [1, 2]. It is necessary to measure the tilt error motions by using angle sensors for evaluation and compensation of Abbe errors. Conventionally, the measurement of pitch and yaw angles is carried out by an autocollimator using a filament lamp as the light source and a CCD image sensor as the light position detector. As described in Chapter 1, conventional autocollimators, which are large in size and slow in measurement speed, are not suited for dynamic measurement of stage tilt error motions. In addition, the conventional autocollimator cannot detect the roll error motion, which is defined as the angular displacement about the normal axis of the target plane reflector, because no light spot displacement can be generated on the light position detector with respect to the roll error motion.
3. Surface Encoder for Measurement of In-plane Motion
Abstract
Precision planar motion (XY) stages are widely used in machine tools, photolithography equipment and measuring instruments for nanomanufacturing [1–4]. Measurement of the in-plane motions is essential for evaluation of stage performance and/or for feedback control of the stage. In addition to the position information, tilt motions are also important measurement parameters.
4. Grating Encoder for Measurement of In-plane and Out-of-plane Motion
Abstract
In nanomanufacturing, it is necessary to generate not only XY in-plane motions but also Z-directional out-of-plane motions [1]. A lot of stages employed for generation of both in-plane and out-of-plane motions require large strokes in the XY-axes and a relatively small stroke in the Z-axis. Displacement measurement along the three-axes with nanometric resolution is essential for precision positioning of such a stage. Three-axis displacement measurement can be realized by combining a surface encoder described in Chapter 3 for measurement of the translational motion in the XY-plane and a short-range displacement sensor for measurement in the Z-axis. Compared with laser interferometers, the combination of the surface encoder and the displacement sensor are more thermally stable and less expensive, which are important for practical use. However, it is difficult for the two sensors to measure the same point, resulting in large Abbe errors. The difference in the sensor type also causes difficulties in the stage controlling system. It is thus desired to improve the surface encoder from XY in-plane measurement to three-axis in-plane (XY) and out-of-plane (Z) measurement.
5. Scanning Multi-probe System for Measurement of Roundness
Abstract
Roundness is one of the most fundamental geometries of precision workpieces. Most of the round-shaped precision workpieces are manufactured by a turning process, in which a spindle is employed to rotate the workpiece. The out-of-roundness of the workpiece is basically determined by the error motion of the spindle. Measurement of the workpiece roundness error and the spindle error is an essential task for assurance of the manufacturing accuracy.
6. Scanning Error Separation System for Measurement of Straightness
Abstract
The straightness is another fundamental geometric parameter of precision workpieces. The straightness of a workpiece surface can be measured by scanning a displacement sensor or a slope sensor over the workpiece surface by a linear stage (slide). Because the axis of motion of the linear stage functions as the reference for the measurement, any out-of-straightness error motion of the slide will cause a measurement error. Because the out-of-straightness error of a precision linear slide (slide error) is typical on the order of 100 nm over a 100 mm moving stroke [1], it is necessary to separate the error motion for precision nanometrology of the workpiece straightness. The influence of the straightness error of a straightedge surface, which is employed as the reference for measurement of slide error, should also be removed.
Similar to the roundness measurement described in Chapter 5, error separation can be carried out by the multi-sensor method and the reversal method. This chapter provides solutions to some key issues inherent in conventional error separation methods for measurement of workpiece straightness and slide error.
7. Scanning Micro-stylus System for Measurement of Micro-aspherics
Abstract
Aspheric micro-lenses are key components in medical endoscopes for diagnosis and surgery of internal organs [1, 2]. The diameter of the micro-lens is less than 1 mm for fitting into the thin endoscope tube. The aspheric surface of the lens makes it possible to improve the imaging performance of the endoscope while reducing the number of optical elements. To obtain clear and high-quality endoscopic images, it is necessary to employ micro-lenses with high surface form accuracy and good surface finish.
8. Large Area Scanning Probe Microscope for Micro-textured Surfaces
Abstract
Large area three-dimensional (3D) micro-structured surfaces can be found in holograms, diffractive optical elements (DOEs) and anti-reflective films, etc. [1]. A large number of the surfaces are composed of periodical micro-structures with a small structure width (in the X- and Y-directions) from several microns to several tens microns. Most of the surfaces are required to be fabricated accurately over an area lager than several millimeters.
9. Automatic Alignment Scanning Probe Microscope System for Measurement of 3D Nanostructures
Abstract
Nanostructures with dimensions on the order of 1 to 100 nm represented by the nanoedge of a single point diamond cutting tool can be made by nanomanufacturing. The diamond cutting tool is used in ultra-precision cutting to fabricate precision workpieces [1–5]. As shown in Figure 9.1, the tool has a very sharp edge with a radius on the order of 10 to 100 nm. The micro/nanowear of the tool edge poses a large problem because it influences the quality of the machined surface [6]. Diamond cutting has also been used to generate three-dimensional (3D) micro-structured surfaces. In such cases, the fabrication accuracy is influenced not only by the tool edge sharpness, but also by the local 3D profile of the tool edge [7]. Therefore, it is important to conduct precision nanometrology of the edge wear as well as the 3D edge profile.
10. Scanning Image-sensor System for Measurement of Micro-dimensions
Abstract
Measurement of micro-dimensions such as length, depth, width and radius of the nanomanufactured micro-structures is an important task for precision nanometrology. Some of the micro-structures are made on the workpiece over a long stroke and the measurement of the micro-dimension must be made over the entire stroke. In such cases, it requires the measurement system to have fast enough measuring speed.
Backmatter
Metadata
Title
Precision Nanometrology
Author
Wei Gao
Copyright Year
2010
Publisher
Springer London
Electronic ISBN
978-1-84996-254-4
Print ISBN
978-1-84996-253-7
DOI
https://doi.org/10.1007/978-1-84996-254-4