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High-precision free-form surface mirrors are required for synchrotron radiation facilities in the scientific field and semiconductor lithography systems in the industrial field. Previously, we developed a nano-profiler with the goal of achieving a measurement accuracy of 30 nm. The nano-profiler scanned and measured the slope angle of the surface to be measured with laser light and calculated the shape from the angle information. By driving the optical head and surface to be measured with four rotation axes and one translation axis, the surface could be scanned while keeping the optical path length constant. Although the rotation axis was controlled by a high-precision rotary encoder, pitching and yawing errors occurred in the translation axis. In this study, we attempt to eliminate the error of pitching and yawing from the conventional measurement operation of four axes of rotation and one axis of translation to the drive of only four axes of rotation. If the translation drive is eliminated, the optical path length will not be constant, and the sensitivity of the light-receiving element will change. Therefore, we propose a new method to calibrate the sensitivity of the receiving element and perform a comparative measurement with the conventional measurement method. Comparing the measured shapes obtained by both measurement results, it was found that the shapes had a maximum peak to valley difference of 6.2 nm. Thus, the proposed novel measurement method allows a significant reduction in pitching and yawing errors. [ABSTRACT FROM AUTHOR]

Improving the optical performance and functions of mirrors and lenses requires manufacturing pattern shapes such as those of microlens arrays. In this context, various measuring devices have been developed to accurately measure the depth of shapes with a microscopic interferometer. However, with an interferometer, the number of pixels of a light-receiving element, such as a charge-coupled device, is limited; furthermore, when measuring a pattern shape, the measurement field of view becomes narrow. Thus, measuring a wide range of shapes is not possible. By contrast, if the device can arbitrarily increase the number of measurement points, such as in the case of a three-dimensional measuring machine, in principle, a pattern shape can be measured, while ensuring the measurement capability for a wide range of shapes; however, in this case, the measurement time increases. A nano-profiler previously developed by the authors can measure the shape and slope angle distribution of a surface with a laser beam. In this study, the measurement program was changed to realize continuous high-speed scanning at 1 kHz, and the number of measurement points was increased to verify the compatibility between fine pattern shape measurements and diverse shape measurements. The results measured by the nano-profiler were compared with those obtained using microscopic and Fizeau-type interferometers, which can measure the pattern and overall shapes, respectively. In comparison, the difference in pattern depth and overall shape was 2.1 and 2.9 nm PV, respectively. [ABSTRACT FROM AUTHOR]

Unlike interferometers that obtain data from the entire sample, three-dimensional (3D) measuring instruments acquire data from multiple points. A nano-profiler measures slopes at different points on the surface to determine the sample shape, while a coordinate measuring machine (CMM) utilizes contact or non-contact height displacement probes for taking measurements. Therefore, the 3D measurement time increases if the area to be measured is wide. This leads to a reduced measurement accuracy owing to environmental changes. To reduce the 3D measurement time, a nano-profiler that rotates measured objects at a constant velocity and quickly scans each measurement point by following a spiral trajectory was designed. The developed nano-profiler measures angular distribution instead of height distribution. This makes it possible to reduce the drive error during rotation. Compared to an interferometer, the measurement time was reduced from 163 to 17 min with the nano-profiler and a 10 nm peak-to-valley difference was achieved. The slope measurement with spiral scanning was confirmed to be a quick and accurate shape measurement technique that can be used while manufacturing high-precision optical components. [ABSTRACT FROM AUTHOR]

We developed a nano-profiler to determine the shape from slope distribution data for highly accurate free-form surface shape measurement; for example, high-precision optical systems are required in the x-ray and semiconductor fields. An accuracy of ±0.2 µrad is required to achieve a shape measurement accuracy of 30 nm. The angle of the rotary stage is controlled by the rotary encoder, and the calibration curve of the rotary encoder is guaranteed by the national standard machine. However, the error associated with assembling the rotary encoder to the device is not included in the national standard machine's calibration data. Therefore, we propose a method that combines self-calibration with six encoder heads and calibration with a national standard machine. Using this method reduces the extent of calibration by the national standard machine and minimizes the influence of the assembly error. Furthermore, to verify whether the calibration in the proposed method is appropriate, a new encoder for evaluation was installed and evaluated. The results revealed that the influence of the assembly error was reduced to the minimum, and the difference in the calibration between the encoder for evaluation and the national standard machine was 0.027 µrad. [ABSTRACT FROM AUTHOR]

The surface structure of the hydrogen-saturated Si(110) surfaces after wet cleaning is studied on an atomic scale by means of scanning tunneling microscopy. When a surface oxide layer is stripped using a HF-containing solution, the surface consists of nanometer-scaled terraces and atomic steps along various directions. Coupled monohydride lines are formed inside a small terrace, as predicted by infrared spectra. The Si(110) surface after subsequent rinsing for a short period is occupied by a long terrace along the [110] direction in which the ideal 1×1 structure is formed. Atomic arrangements around step edges are determined in detail based on atomic images and first-principles calculations. A ridge-shaped structure is observed after excess rinsing with water, and infrared spectra indicate that the slope is composed of (111) microfacets. From these results, we present the mechanism underlying the formation of the hydrogen-terminated Si(110) surfaces during wet cleaning processes. [ABSTRACT FROM AUTHOR]

Atomic arrangements of the hydrogen-terminated Si(001) surface after wet cleaning are investigated by scanning tunneling microscopy and by first-principles calculations. The hydrogen-terminated Si(001) surface after dilute HF cleaning is atomically rough with a structure of terraces and steps. In addition, it is confirmed that 1 × 1 dihydride structures are formed inside the terraces. First-principles calculations reveal that the maxima of the local density of states string parallel to the Si-H direction on the 1 × 1 dihydride structure, which makes it possible to determine the atomic arrangement of the observed atomic images. When the surface after HF cleaning is subsequently rinsed with ultrapure water, rows emerge along the 〈110〉 direction. Atomic images show that the rows are mainly formed by a 2 × 1 unit cell. To elucidate the atomic structure of the 2 × 1 unit cell, it is proposed that every other row of the ideal 1 × 1 dihydride surface is preferentially etched with ultrapure water. Total energy calculations are performed based on the first principles of quantum mechanics, which justify the proposed etching mechanism of the Si(001) surface with ultrapure water. [ABSTRACT FROM AUTHOR]

Thermal oxidation (TO) and abrasive polishing were combined for atomic-scale planarization of 4H-SiC. It was found that the oxide/SiC interface was atomically flat regardless of the thickness of the oxide. The specimen prepared by TO was dipped in HF solution to remove the oxide. However, owing to the residual silicon oxycarbide (Si-C-O), the step/terrace structure of 4H-SiC could not be observed. Nanoindentation tests revealed that the hardness of Si-C-O was much lower than that of SiC. A thermally oxidized SiC surface was polished using CeO2 abrasives, which resulted in an atomically flat surface with a well-ordered two-bilayer step/terrace structure. [ABSTRACT FROM AUTHOR]

To improve the thickness uniformity of thin quartz crystal wafer, a new machining process that utilizes an atmospheric pressure plasma was developed. In an atmospheric pressure plasma process, since the kinetic energy of ions that impinge to the wafer surface is small and the density of the reactive species is large, high-efficiency machining without damage is realized, and the thickness distribution is corrected by numerically controlled scanning of the quartz wafer to the localized high-density plasma. By using our developed machining process, the thickness distribution of an AT cut wafer was improved from 174 nm [peak to valley (p-v)] to 67 nm (p-v) within 94 s. Since there are no unwanted spurious modes in the machined quartz wafer, it was proved that the developed machining method has a high machining efficiency without any damage. [ABSTRACT FROM AUTHOR]

In this study, we designed, fabricated, and evaluated a hard x-ray focusing mirror having an ideally focused beam with a full width at half maximum in the intensity profile of 36 nm at an x-ray energy of 15 keV. The designed elliptically curved shape was fabricated by a computer-controlled fabrication system using plasma chemical vaporization machining and elastic emission machining, on the basis of surface profiles accurately measured by combining microstitching interferometry with relative angle determinable stitching interferometry. A platinum-coated surface was employed for hard x-ray focusing with a large numerical aperture. Line-focusing tests on the fabricated elliptical mirror are carried out at the 1-km-long beamline of SPring-8. A full width at half maximum of 40 nm was achieved in the focused beam intensity profile under the best focus conditions. [ABSTRACT FROM AUTHOR]

Metrology plays an important role in surface figuring with subnanometer accuracy. We have developed relative angle determinable stitching interferometry for the surface figuring of elliptical mirrors, in order to realize hard x-ray nanofocusing. In a stitching system, stitching angles are determined not by the general method using a common area between neighboring shots, but by the new method using the mirror’s tilt angles measured at times when profile data are acquired. The high measurement accuracy of approximately 4 nm (peak-to-valley) was achieved in the measurement of a cylindrical surface having the same curvature as the elliptically designed shape to enable hard x-ray nanofocusing. [ABSTRACT FROM AUTHOR]

We established an efficient ultraprecise figuring process in which numerically controlled plasma chemical vaporization machining (NC-PCVM) and numerically controlled elastic emission machining (NC-EEM) are utilized serially. Intensity images of the x rays reflected by total reflection mirrors greatly fluctuate with respect to the figure error of spatial wavelength ranging from submillimeter to 10 mm. In NC-PCVM, figure errors for spatial wavelength range longer than 10 mm are removed efficiently by using the rotary electrode, and the spatial wavelength close to 1 mm can be corrected by using the pipe electrode. The residual figure error for the spatial wavelength close to 0.1 mm is finally removed by EEM. In this article, we describe the ultraprecise figuring process utilizing the NC-PCVM. Two elliptical mirrors for a Kirkpatrick–Baez (KB) microfocusing unit were manufactured by NC-PCVM using the rotary electrode and the pipe electrode in combination, and a figure accuracy higher than 3 nm (p–v) was achieved for the spatial wavelength range longer than 1 mm. The focusing properties of the two mirrors were evaluated at BL29XUL of SPring-8, and line focusing widths of 0.12 and 0.2 μm (full width at half maximum) were achieved at 15 keV. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A new stitching interferometry based on a microscopic interferometer having peak-to-valley height accuracy of subnanometer order and lateral resolution higher than 20 μm was developed to measure surface figures of large-size x-ray mirror optics. Cumulative errors of the stitching angle in a long spatial wavelength range were effectively reduced to be 1×10[sup -7] rad levels using another interferometer having a large cross section in the optical cavity. Some optical performances of ultraprecise x-ray mirrors, such as submicrofocused beam profile, were wave optically calculated from the measured surface figure profiles and observed at the 1 km long beamline (BL29XUL) of SPring-8. Observed and wave optically calculated results were in good agreement with a high degree of accuracy. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A high current ion system for surface modification has been developed. It consists of a liquid metal ion source, a focusing lens system, deflection plates, a mass separator, and a deceleration electrode system. It can produce a high purity metal ion beam with an energy in the range of 10 eV to 10 keV and ion current up to 20 μA in a vacuum as low as 10-9 Torr. [ABSTRACT FROM AUTHOR]

A lens system for a large current liquid metal ion source has been designed by a numerical computer simulation method. As a computed result, the lens system can focus an ion beam having an emission angle of 60° to a beam having a radius of 1.8 mm at 1 m from the ion source. Following the simulated result, the lens system was constructed and tested. When the total ion current extracted from the ion source was less than 10 μA, more than 95% of the total ion was focused to a beam with a radius of about 2 mm at 1 m from the ion source, which agreed well with the computer simulation result. When the total ion current became more than 10 μA, the minimum radius of the focused ion beam at 1 m from the ion source gradually increased with it. However, even if the total ion current was more than 50 μA, almost 80% of it could be obtained on a 1×1 cm2 target at 1 m from the ion source. [ABSTRACT FROM AUTHOR]

Atomically resolved scanning tunneling microscopy observations are performed on hydrogen-terminated Si(110) surfaces after wet cleaning. When a Si(110) wafer is dipped into dilute HF-containing solution, the surface is constructed by piling small terraces and steps. When the sample is consequently rinsed with ultrapure water, some characteristic features such as a zig–zag chain inside a terrace, a single row at step edges and an isolated zig–zag chain on a terrace are clearly observed, and their atomic arrangements are determined. Excessive rinsing, however, creates the ridge-shaped structure of nanometer height, which is explained by anisotropic etching by OH- ions in water. [ABSTRACT FROM AUTHOR]

A correction to the article "Atomic-scale planarization of 4H-SiC (0001) by combination of thermal oxidation and abrasive polishing" that was published in the October 31, 2013 issue is presented.

Atomic structures of hydrogen-terminated Si(001) surfaces after HF cleaning are investigated by scanning tunneling microscopy. It is revealed that the surface is macroscopically rough but is composed of terraces and steps. Inside a terrace, 1x1 structures are formed. This corresponds to the ideal 1x1 dihydride structure. The step edges run along the <110> direction. On the other hand, the 1x1 dihydride structure disappears when the surface is subsequently rinsed with ultrapure water, because every other dihydride row of the ideal 1x1 structure is preferentially etched in ultrapure water. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Scanning tunneling microscopy observations are performed on a H-terminated Si(001) surface treated with HF solutions and ultrapure water with very low dissolved oxygen and total organic carbon contents. Over a large area, row structures are observed in [110] and [11¯0] directions. Pyramidal-shaped etch pits are also observed, which are caused by anisotropic etching by OH ions. Detailed images clearly show 2×1 periodic structures. It is suggested that every other row of the ideally dihydride 1×1 surface is etched preferentially by OH ions. This explains the mechanism by which the smallest etch pits are formed. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]