Kiyoto Inomata

Open air deposition of SiO2 film from a cold plasma torch of tetramethoxysilane‐H2‐Ar system

A rf plasma beam was generated in the stream of atmospheric pressure argon to be exhausted from a cylindrical nozzle into air. The temperature measurements indicate a nonequilibrium low temperature nature of this plasma. By using this cold plasma torch, films were deposited on the substrates placed in air at growth rates higher than 100 A/s by feeding tetramethoxysilane into the plasma. Fourier transform infrared spectroscopy and x‐ray photoelectron spectroscopy revealed that the films were essentially SiO2 and their structures and properties could be improved by admixing hydrogen in the plasma. The SiO2 films deposited at a rate of 120 A/s from Si(OCH3)4‐H2‐Ar plasma had surfaces as smooth and hard as Corning 7059 glass.

Open air photoresist ashing by a cold plasma torch: Catalytic effect of cathode material

A beam plasma was generated and exhausted into air by applying rf voltage to the atmospheric pressure argon flowing through a cylindrical gap between a needle cathode and a grounded cylindrical anode whose surface was covered with an insulator. This torch‐type plasma with gas and electron temperatures of 240 °C (44.2 meV) and 1.0 eV, respectively, has been verified to be useful for ashing a photoresist without using a pumping system. High rate (≥1.2 μm/min) photoresist ashing was achieved by using Ar plasma containing a small amount of oxygen. Also reported are optical emission analysis of plasma and analyses of ashed Si surface by scanning electron microscopy. Fourier transform infrared spectroscopy, electron microprobe analysis, and x‐ray photoelectron spectroscopy. The use of the Pt cathode was found to provide not only a better ashed surface but also a higher ashing rate than the use of the stainless‐steel cathode.

Production of Fullerenes by Low Temperature Plasma Chemical Vaper Deposition under Atmospheric Pressure

A gas phase reactor developed for generating homogenous low temperature plasma under atmospheric pressure was found to provide a new method for producing fullerenes by a plasma chemical vapor deposition (CVD) process. Into an afterglow region of atmospheric pressure Ar–He mixed gas plasma, an aromatic hydrocarbon was introduced and decomposed into black soot under appropriate reaction conditions. A benzene solution of the soot showed two clear HPLC peaks with retention times corresponding well to those of C60 and C70. The formation of C60 was further confirmed by UV spectroscopy.

Plasma Chemical Vapor Deposition of SiO2 on Air‐Exposed Surfaces by Cold Plasma Torch

A compact size, cold plasma torch developed for open air material processing has been applied to SiO 2 film deposition on various substrates. Under atmospheric pressure, homogenous nonequilibrium low temperature plasma was generated by an RF (13.56 MHz) excitation of helium or argon in a capacitively coupled cylindrical type reactor with the grounded anode shielded with a dielectric material. By using this cold plasma torch, SiO 2 films have been deposited on substrates exposed to air at a temperature of 200°C or below by feeding tetramethoxysilane (TMOS) or tetraethoxysilane (TEOS) into the plasma. The characterization of films by Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, and scanning electron microscopy revealed that the films were essentially SiO 2 . The mixing of hydrogen in the plasma was found quite effective for reducing the carbon contamination and improving the film quality. The step coverage behavior of SiO 2 films was also investigated using trenched Si substrates, and it differed markedly depending on the source gas of films.

Open-air silicon etching by H2–He–CH4 flowing cold plasma

Atmospheric pressure reactive plasma has been generated by RF excitation of a downstream flowing mixture of hydrogen, helium and methane. The plasma was characterized by Langmuir probe and optical emission spectroscopy (OES). The hydrogen plasma beam emerging from the hollow tungsten cathode has been applied to single crystal silicon wafer in open air. The etched wafer has been studied by FE-SEM and stylus machine. Silicon etching rates exceeding 280 A/min have been achieved. Furthermore, pertaining to diamond film deposition, it is elucidated that at high pressures, atomic hydrogen cannot only etch non-diamond phases of carbon but can also etch the Si substrate itself.