Ultrahigh-speed etching of organic films using microwave-excited nonequilibrium atmospheric-pressure plasma

Abstract

An ultrahigh etch rate (24μm∕min at 155°C and 0.3mm∕min at 325°C) of an organic film was successfully achieved using a microwave-excited nonequilibrium atmospheric-pressure plasma source employing He and O2 gases. This has the potential to be applied to various kinds of fabrication of structures for microelectromechanical systems and bionanotechnology. A stable glow discharge was realized between the narrow gap (200μm) electrodes covered with a dielectric film in atmospheric pressure. The etching characteristics were investigated by changing the O2 flow rate and the distance of the substrate from the electrode. In order to clarify the ultrahigh etching mechanism, in situ diagnostic methods, including two-dimensional imaging of optical emissions in the plasma with an intensified charge-coupled device camera, electron-density evaluation using the Stark-broadened profile of the hydrogen Balmer beta line in optical emission spectroscopy, and two dimensional spatial distribution of ozone density measured with ultraviolet absorption spectroscopy, have been performed. It was found that O atoms were the dominant etching species for ultrahigh-speed etching of the organic film, and the effect of ozone on the etching process was negligible.