Junichi Uchikoshi

Feasibility Study on Ultimate Accuracy in Microcutting Using Molecular Dynamics Simulation

Using molecular dynamics computer simulation, the feasibility is analyzed or, nanometric or an ultimate machining accuracy attainable in microcutting of free machining work materials under perfect motion of a machine tool. Based on the analysis, the micro process of chip and surface generation can be well understood from the atomistic point of view. The minimum thickness of cut, that is a measure of the accuracy attainable, can be expected to be about 1 nm or less, that is, 1/20 to 1/10 of the edge radius of a realistic fine cutting edge available. Tile ultimate roughness and depth of deformed layer of work surface is estimated to be about 0.5 and 5.0 nm, respectively. The quality of work-surface of aluminum is worse than that Of Copper. These results suggest that the ultraprecision metal cutting the machining accuracy of which is at least 1 nm is feasible.

Structure of Micromachined Surface Simulated by Molecular Dynamics Analysis

Using molecular dynamics computer simulation, a feasibility study is made for the quest of ultimate quality of machined surface attainable in diamond microcutting of cooper with a fine cutting edge under hypothetically perfect machine motion. Based on the analyses, the surface generation process and microstructure of worksurface are well understood from atomistic point of view. In cutting of monocrystalline cooper, the worksurface which is free from residual distortion can be obtained and ultimate surface roughness is estimated to be less than 1 nm. In cutting of polycrystalline cooper, nanometrically distorted layer inevitably remains on worksurface. However, the ultimate surface roughness is estimated to be at the same level as that of monocrystalline copper.

Metal-assisted chemical etching of Ge(100) surfaces in water toward nanoscale patterning

We propose the metal-assisted chemical etching of Ge surfaces in water mediated by dissolved oxygen molecules (O2). First, we demonstrate that Ge surfaces around deposited metallic particles (Ag and Pt) are preferentially etched in water. When a Ge(100) surface is used, most etch pits are in the shape of inverted pyramids. The mechanism of this anisotropic etching is proposed to be the enhanced formation of soluble oxide (GeO2) around metals by the catalytic activity of metallic particles, reducing dissolved O2 in water to H2O molecules. Secondly, we apply this metal-assisted chemical etching to the nanoscale patterning of Ge in water using a cantilever probe in an atomic force microscopy setup. We investigate the dependences of probe material, dissolved oxygen concentration, and pressing force in water on the etched depth of Ge(100) surfaces. We find that the enhanced etching of Ge surfaces occurs only when both a metal-coated probe and saturated-dissolved-oxygen water are used. In this study, we present the possibility of a novel lithography method for Ge in which neither chemical solutions nor resist resins are needed.

Molecular dynamics analysis on microstructure of diamond-turned surfaces

By the use of molecular dynamics computer simulation, a feasibility study is made for the quest of ultimate quality of machined surface attainable in diamond microturning of copper and aluminum with a fine cutting edge under hypothetically perfect machine motion. Based on the analyses, the surface generation process and microstructure of worksurface are well understood from atomistic point of view. In cutting of monocrystalline copper, the worksurface which has nearly perfect lattice structure can be obtained and ultimate surface roughness is estimated to be less than 1 nm. The quality of worksurface of aluminum is worse than that of copper, especially machined by the cutting edge with large radius. In cutting of polycrystalline copper, nanometric distorted layer inevitably remains on worksurface. However, the ultimate surface roughness is estimated to be at the same level as that of monocrystalline copper.

Profile measurement of concave spherical mirror and a flat mirror using a high-speed nanoprofiler

Ultraprecise aspheric mirrors that offer nanofocusing and high coherence are indispensable for developing third-generation synchrotron radiation and X-ray free-electron laser sources. In industry, the extreme ultraviolet (wavelength: 13.5 nm) lithography used for high-accuracy aspheric mirrors is a promising technology for fabricating semiconductor devices. In addition, ultraprecise mirrors with a radius of curvature of less than 10 mm are needed in many digital video instruments. We developed a new type of nanoprofiler that traces the normal vector of a mirrors surface. The principle of our measuring method is that the normal vector at each point on the surface is determined by making the incident light beam on the mirror surface and the reflected beam at that point coincide, using two sets of two pairs of goniometers and one linear stage. From the acquired normal vectors and their coordinates, the three-dimensional shape is calculated by a reconstruction algorithm. The characteristics of the measuring method are as follows: the profiler uses the straightness of laser light without using a reference surface. Surfaces of any shape can be measured, and there is no limit on the aperture size. We calibrated this nanoprofiler by considering the system error resulting from the assembly error and encoder scale error, and evaluated the performance at the nanometer scale. We suppressed the effect of random errors by maintaining the temperature in a constant-temperature room within ±0.01°C. We measured a concave spherical mirror with a radius of curvature of 400 mm and a flat mirror and compared the results with those obtained using a Fizeau interferometer. The profiles of the mirrors were consistent within the range of system errors.

Catalytic behavior of metallic particles in anisotropic etching of Ge(100) surfaces in water mediated by dissolved oxygen

The authors demonstrate that Ge(100) surfaces containing metallic particles are etched anisotropically in water. This originates from the catalytic reduction of dissolved oxygen (O2) in water to water molecules (H2O) on the metallic particles, which is followed by the enhanced oxidation of Ge around the particles. The soluble nature of Ge oxide (GeO2) in water promotes the formation of inverted pyramidal etch pits composed of (111) microfacets. On the basis of the results, the authors propose strategies for avoiding unwanted surface roughening during the wet cleaning of Ge.

Photoetching of Silicon by N-Fluoropyridinium Salt

A photoetching method with -fluoropyridinium salts is proposed in this study. Si is etched by applying -fluoropyridinium salts to its surface and exposing the surface to light. The etched surface that uses liquid -fluoropyridinium salts is smoother than when solid -fluoropyridinium salts are used. The etching depth increases with exposure time. H-terminated hydrophobic Si is easier to etch than OH-terminated hydrophilic Si. is produced by photoetching. This suggests that -fluoropiridinium salts receive excited electrons from Si and supply Si with active F species.

Straightness measurement using laser beam straight datum

Using the direction stabilized laser beam as a physical straight datum, instead of the tangible reference surface, a method is proposed for the measurement of an error motion of a slide table and/or surface profile of mechanical components. A specially designed 2D position sensor/compensator for laser beam center is developed combining a quadrant photo-diode (QPD) position sensor for beam center and the piezo-compensator which compensates the beam shift from the center of QPD. By the use the sensor/compensator proposed, the positional and angular fluctuations of laser beam path is evaluated with nanometric resolution. Combining the sensor with the piezo-driven mirror compensator, the directional stabilizer for the laser beam is also designed in the same manner as the sensor/compensator. The stabilized He-Ne laser beam can be used as the metrological datum of straightness within the accuracy of 2 X 10 -8 rad. By mounting the position sensor/compensator on a slide table, the carriage with working distance of 1 m is so designed and built as to move straight along the stabilized laser beam. The carriage can be used as a mechanical straight datum with the accuracy equivalent to the laser beam stability.

Development of surface gradient integrated profiler - Precise coordinate determination of normal vector measured points by self-calibration method and new data analysis from normal vector to surface profile -

A new ultra-precision profiler has been developed to measure items such as asymmetric and aspheric profiles. In the current study, the normal vectors at each point on the surface are determined by a reflected light beam that returns along exactly the same path as the incident beam. The surface gradients at each point are calculated from the normal vector, and the surface profile is obtained by integrating the gradient. At a previous meeting, we reported that normal vector measured points with submicron accuracy can be determined by a self-calibration method. In this paper, the self-calibration method has been tested and shown to have the capability for surface profile measurement accuracy of nanometer order, using a concave mirror with a radius curvature of 2000 mm. The precise surface profile obtained from a measured normal vector has been studied as a new data analysis method that applies Fourier series expansion with the least-square method. Future development will include the following: the elimination of error propagation due to data analysis from normal vector to surface profile, unique determination of profile from normal vector, and enabling random measuring position of normal vector on the mirror.

Absolute Line Profile Measurements of Silicon Plane Mirrors by Near-Infrared Interferometry

Absolute line profiles of three silicon plane mirrors were measured by the three-flat method using a near-infrared interferometer. The interferometer was constructed using a near-infrared laser diode with 1310 nm wavelength light, to which the silicon plane mirror is transparent. The maximum height difference in the absolute line profiles is less than 8.9 nm and the rms value of height difference is less than 2.0 nm for a measured line of 12.7 mm. The near-infrared interferometer is useful for measuring a set of line profiles at the height difference level to calculate the absolute flatness of silicon plane mirrors.