Kohji Inagaki

Plasma CVM (Chemical Vaporization Machining) : An Ultra Precision Machining Technique Using High-pressure Reactive Plasma

Conventional machining processes, such as turning, grinding, or lapping, are still applied for many materials including functional ones. But these processes give rise to deformed layers which means that the machined surfaces cannot perform original functions. In order to avoid this, plasma CVM has been developed. Plasma CVM is a chemical machining method utilizing radical reaction. In plasma CVM, high density radicals are generated in plasma under atmospheric pressure, so that the removal rate is very high (>or=200 mu m min-1 for Si) and is equivalent to mechanical machining methods. In this paper, basic concepts and some applications of plasma CVM will be introduced.

Development of a scanning near-field optical microscope with a probe consisting of a small spherical protrusion

Abstract The probe of the scanning near-field optical microscope (SNOM) is a dielectric sphere 500 nm in diameter on a transparent substrate. The probe sphere is illuminated by evanescent waves which are formed by the incidence of a HeNe laser with the wavelength of 632.8 nm under the condition of total internal reflection. The light from the probe is collected by a conventional microscope through the substrate. The detected light intensity varies markedly when a sample is brought into the near-field around the probe. The variation of the detected light intensity in the near-field depends on the complex index of refraction of samples; the smaller the real part of the refractive index, the more marked the increase of the detected light intensity. This result is explained through the use of an electric dipole model for the electromagnetic interaction between the probe and sample. The vertical and lateral resolutions of about 1 nm and 10 nm, respectively, are obtained for a standard sample which is prepared by vacuum evaporation of metal.

Plasma CVM (Chemical Vaporization Machining): – A Chemical Machining Method With Equal Performances to Conventional Mechanical Methods from the Sense of Removal Rates and Spatial Resolutions –

Conventional machining processes, such as turning, grinding, or lapping are still applied for many materials including functional ones. But those processes are accompanied with deformed layer, so that machined surfaces can not perform original functions. In order to avoid such points, Plasma CVM has been developed. Plasma CVM is a chemical machining method utilizing radical reaction. In Plasma CVM, high density radicals are generated in the plasma under the atmospheric pressure, so that removal rate is very high(ex. > 200μm/min for Si), and it is equal to mechanical machining methods. In this paper, basic concepts and some applications of Plasma CVM will be introduced.

Chemical etching of silicon carbide in pure water by using platinum catalyst

Chemical etching of SiC was found to proceed in pure water with the assistance of a Pt catalyst. A 4H-SiC (0001) wafer was placed and slid on a polishing pad in pure water, on which a thin Pt film was deposited to give a catalytic nature. Etching of the wafer surface was observed to remove protrusions preferentially by interacting with the Pt film more frequently, thus flattening the surface. In the case of an on-axis wafer, a crystallographically ordered surface was obtained with a straight step-and-terrace structure, the height of which corresponds to that of an atomic bilayer of Si and C. The etching rate depended upon the electrochemical potential of Pt. The vicinal surface was observed at the potential at which the Pt surface was bare. The primary etching mechanism was hydrolysis with the assistance of a Pt catalyst. This method can, therefore, be used as an environmentally friendly and sustainable technology.

Study on the mechanism of platinum-assisted hydrofluoric acid etching of SiC using density functional theory calculations

Hydrofluoric acid (HF) etching of the SiC surface assisted by Pt as a catalyst is investigated using density functional theory. Etching is initiated by the dissociative adsorption of HF on step-edge Si, forming a five-fold coordinated Si moiety as a metastable state. This is followed by breaking of the Si–C back-bond by a H-transfer process. The gross activation barrier strongly correlates with the stability of the metastable state and is reduced by the formation of Pt–O chemical bonds, leading to an enhancement of the etching reaction.

Measurement and calculation of the differential reflectance spectrum of hydrogen-terminated silicon surfaces having different crystal orientations

The differential reflectance spectrum between the (001) and the (111) hydrogen-terminated Si surfaces without native oxidation is investigated. Careful measurements using developed apparatus and an ultra-clean process are performed. The measured spectrum is compared with the reported one (Chongsawangvirod and Irene 1991 J. Electrochem. Soc. 138 1748-52), and is shown to be roughly identical even though a native oxidation effect exists. The theoretical calculation based on density-functional theory (DFT) and local density approximation (LDA) is also performed. The peak positions in the calculated and the measured spectra are in good accordance with each other, while the magnitudes of the peaks are in relatively worse agreement. Although the inclusion of advanced approximations would provide more accurate results, a qualitative reproduction is achieved in this study as well. It is concluded that the origin of the spectrum is mainly in the deformation of the bulk states induced by surface perturbation.