Russell D. Young

Light Scattering from Manufactured Surfaces

We present an evaluation of light scattering theories and experimental techniques for measuring the roughness of manufactured surfaces. Our goal was to define the ultimate capabilities and regions of validity of these methods for deducing surface microtopography. Available theories are evaluated in terms of a heuristic interpretation of direct electromagnetic scattering from surfaces. Experimental methods using specular reflectance, total integrated scatter, angular scattering distribution, and speckle are reviewed in terms of their spatial-bandwidth sampling of surface wavelengths and their roughness amplitude sensitivity and accuracy. Graphs in a slope/relative-wavelength space are used to intercompare the regions of validity of theories, regions of applicability for experimental methods and regions occupied by typical manufactured surfaces. A relatively unknown theory, valid for light scattering from many typical manufactured surfaces but previously unused for this purpose, is briefly described.

Condensation of Tungsten on Tungsten in Atomic Detail: Observation with the Field‐Ion Microscope

Tungsten has been condensed onto a clean tungsten point in a field‐ion microscope held at liquid‐nitrogen and liquid‐hydrogen temperatures. Stepwise field evaporation has been employed to observe the structure of the deposit in atomic detail. The first layer of deposited tungsten atoms above the substrate appears to contain one‐fourth to one‐third vacancies. A brief discussion is given of the possibility of extending the range of specimens observable in the field‐ion microscope by employing a shadowing technique which would leave a highly detailed imprint of the specimen on the emitter surface. It is concluded that the imperfect first layer of deposited tungsten observed in these studies would reduce the fidelity with which the details of the specimen could be observed for high‐resolution microscopy.

Key-Note-PapersLight Scattering from Manufactured Surfaces†

We present an evaluation of light scattering theories and experimental techniques for measuring the roughness of manufactured surfaces. Our goal was to define the ultimate capabilities and regions of validity of these methods for deducing surface microtopography. Available theories are evaluated in terms of a heuristic interpretation of direct electromagnetic scattering from surfaces. Experimental methods using specular reflectance, total integrated scatter, angular scattering distribution, and speckle are reviewed in terms of their spatial-bandwidth sampling of surface wavelengths and their roughness amplitude sensitivity and accuracy. Graphs in a slope/relative-wavelength space are used to intercompare the regions of validity of theories, regions of applicability for experimental methods and regions occupied by typical manufactured surfaces. A relatively unknown theory, valid for light scattering from many typical manufactured surfaces but previously unused for this purpose, is briefly described.

Field Emission Ultramicrometer

A simple, contact free, ultrasensitive distance and displacement measuring instrument has been investigated. Experiments demonstrate that the instrument is capable of operating at spacings as small as a few hundred angstroms. Calculations indicate that distances of 10−3 to 10−6 cm and less can be reproduced to within about one part in 105. With suitable calibration, distance measurements in the 10−3 to 10−6 cm range can be expected to have accuracies limited only by available calibration techniques. The instrument would be most useful as a null or differential distance measuring device. It has the unusual property that resolution improves over several orders of magnitude as the null or measurement point is approached. Since the instrument contains no optical or mechanical lever systems, or delicately balanced bridges, it has inherent long term stability. Proposed applications include: (1) measurement of ball and hole diameters (contact free), (2) differential thermal expansion cell, (3) mechanical vibrati...

In-Process and On-Line Measurement of Surface Finish

Future trends In surface finish measurement for manufacturing are discussed. It is expected that optical techniques will be used increasingly for measurements of surface roughness and of other parameters as well because these techniques are inherently fast and three-dimensional. Four optical techniques are discussed and evaluated. Stylus techniques, however, will continue to play an important role in research and metrology. Statistical methods for the three dimensional characterization of surfaces are briefly reviewed.

Long‐range scanning for scanning tunneling microscopy

We report a scanning tunneling microscope (STM) with 500 μm×500 μm field of view. It departs from past designs in that a long‐range X‐Y stage carries the specimen and scans while the STM head is held stationary. The STM head is capable of scanning with a range of 8 μm. Combining the capability of tip scanning and X‐Y stage scanning yields a wide dynamic range and has useful applications for measuring optical surfaces.

Para‐flex stage for microtopographic mapping

The design and performance of a high‐precision X–Y stage which uses a unique type of flexure pivots is described. Performance achieved with a symmetrical arrangement of four arm/pivots for each axis is such that pitch, roll, and yaw is less than one arcsecond for 1×1‐mm stage motion. Vertical vibration during stage motion is less than 2.5 nm peak to valley, with the major limitation being insufficient decoupling from the drive mechanism. Also described is the application of the stage for performing microtopographic mapping with a stylus transducer.

Comparison Of Linewidth Measurements On An Sem/Interferometer System And An Optical Linewidth-Measuring Microscope

In the current linewidth-measurement program at the National Bureau of Standards, the primary measurement of micrometer-wide lines on black-chromium artifacts is made with an interferometer located in a scanning electron microscope (SEM). The data output consists of a line-image profile from the electron detector and a fringe pattern from the interferometer. A correlation between edge location and fringe location is made for both line edges to give the linewidth in units of the wavelength of a He-Ne laser. A model has been developed to describe the interaction of the electrons with the material line and thereby relate a threshold value on the SEM image profile to a selected point on the material line. An optical linewidth-measuring microscope is used to transfer the primary measurements to secondary measurement artifacts; these artifacts will be used to transfer the linewidth measurements to the integrated-circuit industry. Linewidth measurements from the SEM/interferometer system and the optical linewidth-measuring microscope are compared, and the level of measurement uncertainty for each system is discussed.

Field Desorption of Thorium from a Field‐Evaporated Tungsten Surface

The field‐desorption of thorium from a thermally smoothed tungsten substrate has previously been investigated in the temperature range between 300° and 1090°K. The present work extends these measurements to 77°K and includes desorption from a field‐evaporated surface as well as a thermally smoothed surface. For both types of surfaces at 77°K the desorption field strength was found to be 263×106 V/cm±10%.