Ryuji Miyagawa

Ion-beam modification of TiO2 film to multilayered photocatalyst

We report a dry process to produce a multilayered TiO2 film which has the rutile phase on an anatase substrate, for highly activated photocatalysis. Ar ion beam irradiation changes the anatase surface into rutile at 500°C, which is less than the crystallization temperature of rutile from anatase (600°C). The ion beam modification makes it possible to form rutile thin film on anatase. The multilayered structure should be a promising photocatalyst, theoretically.

Detection of Supersonic Waves Emitted from Anomalous Arc Discharge in Plasma Processing Equipment

We report, for the first time, a new method of monitoring anomalous arc discharge in plasma processing equipment by detecting supersonic waves emitted at a discharge site. The supersonic wave is detected with an acoustic transducer attached to the outside surface of a plasma chamber. It is demonstrated that the method can detect anomalous discharge both in direct-current (DC) and radio-frequency (RF) plasma equipment. The results suggest that the method can find the location of anomalous discharge sites in the processing chamber.

Micro Arc Monitoring by Detecting Charge Build-Up on Glass Surface of Viewing Port due to Plasma Dispersion in Plasma Processing Equipment

We report a new method of monitoring micro arc discharge in plasma processing equipment in which we detect the change in wall potential at the inner surface of the glass of the viewing port. The change in the wall potential is detected through a transparent indium–tin–oxide (ITO) film electrode adhered to the outside surface of the glass of the viewing port. It is demonstrated that by means of this method, we can detect micro arc discharge both in direct-current (DC) and radio-frequency (RF) plasma processing equipment. The results indicate that the method is useful for monitoring the occurrence of micro arc discharge presenting a very easy-to-use tool. The results also suggest that the method is useful for monitoring the state of RF plasma.

Oxidation of TiN thin films in an ion-beam-assisted deposition process

Abstract Surface vacancies stimulated by ions play a major role in the oxidation of TiN thin films deposited by a sequential ion-beam-assisted process. A possibility of substitution of N atoms just below the Ti vacant sites at the growing surface is suggested. A method for reducing the oxygen contamination by adjusting both the beam voltage and the current in the ion-assisting techniques is also presented.

Model of coating and drying process for flat polymer film fabrication

The coating procedure of polymer solutions by the scanning technique is developed for LSI technologies at the next generation, where a polymer solution as resists and inter-layer dielectric films is coated on a flat substrate, and then only the solvent is vaporized and removed, and finally the thin film is remaining there. In case of applying to the photo-lithography process, scan coating and its drying processes work together for astonishing flatness in 1% fluctuation range. When the coated polymer solution is dried under reduced pressure or vacuum, the thickness distribution of the resultant film should be accurately prospected and controlled by parameters. The film thickness is generally thicker at the edge and thinner inside from there than the average thickness. A typical thickness profile of a resist film is shown in Figure 1 . The phenomena are always observed, but have not been analyzed numerically. In this paper, we report a numerical model of the drying process of liquid film including polymers and give the essential parameters to the coating and drying processes. The parameters are focused on a vaporization rate, diffusion coefficients, coated solution thickness and intrinsic viscosity, which were calculated by simplified dynamical models of Langmuirs vaporization rate equation and Einstein relation at complex polymer solutions.

An experiment for developing a micro-crack alert system for large thin mirror

We have a plan to install a micro-crack alert system for the primary mirror of Subaru Telescope based on the monitoring of the acoustic emission from any incident events. We report the results of our preliminary experiment for characterizing the acoustic properties of actual Subaru primary mirror. The attenuation of acoustic wave was confirmed to be small enough to allow detection of such events at any locations of the mirror. The position of incident events that might lead to the generation of possible micro-cracks can be identified within less than 3 cm accuracy by placing seven acoustic sensors along the circumference of the primary mirror.