Kan Nakayama

Linear interpolation of periodic error in a heterodyne laser interferometer at subnanometer levels (dimension measurement)

Heterodyne laser interferometry and its accuracy at subnanometer levels are discussed. The simplest optical nonpolarization heterodyne interferometer is tested experimentally to understand and reduce fringe distortion. An accuracy of 0.1 nm for the 633-nm He-Ne laser interferometer is achieved. >

Interferometric measurements of the diameters of a single‐crystal silicon sphere

A new interferometer has been developed for the accurate determination of the density of a silicon crystal, in which a single‐crystal silicon sphere of nearly perfect geometry is placed in a Fabry–Perot etalon of accurately known plate distance, and the diameters are obtained by measuring the two gaps between the etalon and the adjacent surface of the sphere. A new method is used to measure the sum of the length of the two gaps by scanning the etalon against the sphere. Two wavelengths, 633 nm from a frequency‐stabilized He–Ne laser and 441 nm from a free‐running He–Cd laser, are used to determine the order of interference by applying the method of exact fractions. The diameter of about 94 mm has been measured with a resolution of 0.5 nm. Diameter measurements from uniformly distributed directions have shown that the mean diameter has been determined with a standard deviation of 8.6 nm, corresponding to 0.28 ppm in the volume determination. The total uncertainty of the volume is estimated to be 0.34 ppm. ...

Micropattern measurement with an atomic force microscope

The atomic force microscope (AFM) can profile both the surfaces of conductors and insulators with nanometer resolution. One of the most promising applications of the AFM is micropattern measurement of semiconductor devices such as linewidth. An AFM with high precision positioning stages using monolithic, parallel spring mechanisms with flexture hinges has been applied to the measurement of nonconducting surfaces. The X‐Y scanner is equipped with the two‐dimensional optical interferometer to measure displacements of the scanner. The sensing lever is a microfabricated V‐shaped Si3N4 cantilever with a tip made using electron beam deposition. Distortion‐free images of a polycarbonate compact disk nonconducting surfaces with details around the pits have been successfully obtained.

Progress in the measurement of lattice spacing d(220) of silicon

X-ray and optical interferometry is applied to the measurement of silicon lattice spacing. The previously reported standard deviation 0.16/spl times/10/sup -6/ has been reduced to 0.05/spl times/10/sup -6/. The d(220) is 192015.593(0.01) fm after correction of lattice strain by carbon and oxygen.

A New Optical Interferometer for Absolute Measurement of Linear Displacement in the Subnanometer Range

A new optical interferometer system for the absolute determination of lattice constant of a crystal is designed and constructed. It can measure linear displacement accurately within the range of 94% of a period of the interference fringes with long term fluctuation of 50 pm for 14 hours and short term fluctuation of 30 pm. Its high visibility, compact and simple structure will allow various applications to precision measurement of dimension in both scientific and industrial fields.

Linewidth Measurement by a New Scanning Tunneling Microscope

We have developed a new STM using monolithic parallel spring mechanisms with fiexture hinges. The STM is equipped with a two-dimensional optical interferometer to calibrate the motion of the scanner with subnanometer accuracy in real time. Distortion-free images of a grating pattern have successfully been observed.

Precision Physical Measurements and Nanometrology

Precision measurements at the National Research Laboratory of Metrology used to determine fundamental constants and to test physical theory are described: they are related to the determination of silicon lattice spacing; the magnetic flux quantum; and a search for the fifth force. Equipment and techniques for nanometrology are described in terms of the nanoscale, nanoguide and nanodrive, all of which have immediate applications in advanced technology. An example is introduced which demonstrates the power of the scanning tunnelling microscope (STM) in nanometrology.

Accurate determination of the density of a crystal silicon sphere

For an independent determination of the Avogadro constant, the density of a 1-kg crystal silicon sphere was determined by direct measurements of its mass and volume. A scanning-type interferometer was used to measure the diameters, and the volume was calculated from the mean of uniformly distributed diameters. The sphere was weighted using a balance for the prototype kilogram at the National Research Laboratory of Metrology (NRLM), and the mass was determined accurately by direct measurements of the buoyancy force acting on the sphere. The total uncertainty of the density is estimated to be 0.34 ppm. Effects of a thin oxide layer and impurities on the density of a pure crystal are evaluated. >

Development of an ultrahigh vacuum atomic force microscope for investigations of semiconductor surfaces

A new atomic force microscope (AFM) adapted for ultrahigh vacuum operation is described. This AFM utilizes the optical beam deflection method to detect the cantilever displacement. Both the laser diode and the photodiode sensor are contained within the vacuum chamber. An inchworm motor mechanism is used for the tip–sample approach. Up to eight cantilevers are stored in the chamber and can be used without breaking vacuum. The vacuum system is equipped with a sample heater, an evaporation cell, a gas inlet valve, and a low‐energy electron diffraction system, for observing semiconductor surfaces. Imaging of a graphite surface and a clean Si (111) surface with step structures have been obtained.

Vertical displacement determination of a levitated superconducting mass

The determination of the vertical displacement of the center of gravity of a levitated superconducting body in the National Research Laboratory of Metrology (NRLM) superconducting magnetic levitation project, which is aimed at establishing a new definition of the unit of mass based on the fundamental constants, is discussed. The translation displacement (three degrees of freedom) and the attitude change (three degrees of freedom) of the measuring point, which is the optical center of the cube corner prism O/sub C/ of the floating body, are measured using a newly developed optical measuring system. To determine the vertical displacement of the center of gravity of the floating body G/sub C/ the relative position of G/sub C/ with respect to O/sub C/ is required, which is determined using the energy relation between the electromagnetic energy and the gravitational potential energy under levitating conditions.