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We synthesized carbon nanowalls (CNWs) using radical injection plasma-enhanced chemical vapor deposition. The initial growth process of CNWs was investigated with and without O2 gas addition to a C2F6 capacitively coupled plasma with H radical injection. In the case of the CNW synthesis without the addition of O2 gas, scanning electron microscopy (SEM), transmission electron microscopy, x-ray photoelectron spectroscopy (XPS), and Raman spectroscopy revealed that a 10-nm-thick interface layer composed of nanoislands was formed on a Si substrate approximately 1 min prior to CNW formation. In contrast, with O2 gas addition, SEM and XPS revealed that an interface layer was not formed and that CNWs were grown directly from nanoislands. Moreover, Raman spectroscopy suggested that the interface layer was composed of amorphous carbon and that O2 gas addition during CNW growth is effective for achieving a high graphitization of CNWs. Therefore, O2 gas addition has the effect of reducing the amorphicity and disorder of CNWs and controlling CNW nucleation. [ABSTRACT FROM AUTHOR]

Atomic radicals such as hydrogen (H) and oxygen (O) play important roles in process plasmas. In a previous study, we developed a system for measuring the absolute density of H, O, nitrogen, and carbon atoms in plasmas using vacuum ultraviolet absorption spectroscopy (VUVAS) with a compact light source using an atmospheric pressure microplasma [microdischarge hollow cathode lamp (MHCL)]. In this study, we developed a monitoring probe for atomic radicals employing the VUVAS with the MHCL. The probe size was 2.7 mm in diameter. Using this probe, only a single port needs to be accessed for radical density measurements. We successfully measured the spatial distribution of the absolute densities of H and O atomic radicals in a radical-based plasma processing system by moving the probe along the radial direction of the chamber. This probe allows convenient analysis of atomic radical densities to be carried out for any type of process plasma at any time. We refer to this probe as a ubiquitous monitoring probe for atomic radicals. [ABSTRACT FROM AUTHOR]

A low energy NB source, which consisted of a surface wave plasma (SWP) source and two large diameter carbon electrodes, was developed for damageless etching of ultralarge-scale integrated devices. Ion beams were extracted from the SWP using two carbon electrodes, accelerated and injected to the process chamber, and then neutralized without energy loss by a charge exchange reaction. The energy distribution functions of an Ar ion beam and an Ar atom beam was observed using a quadrupole mass spectroscope equipped with an energy analyzer. The energy of the Ar ion beam and the Ar atom beam was controlled by the acceleration voltage. N2 ion and N ion beams were also extracted from a nitrogen plasma source. The intensity ratio of the N ion beam to the N2 ion beam was 5:9, indicating that N ions were efficiently generated in the nitrogen SWP. The N2 ion and N ion beams were changed to N2 molecule and N atom beams, respectively, through a charge exchange reaction without energy loss. The energy of these beams was controlled by the acceleration voltage and was in the region less of than 100 eV. When the acceleration voltage is higher than 40 V, not only the primary peaks due to the N2 ion beam or N ion beam were observed but also a low energy second peak was observed in the energy distribution. The energy of the low energy second peak was controlled by the acceleration voltage. It was concluded that the low energy second peak corresponds to the N2 molecule ion beam and the N ion beam, which is extracted from the second plasma generated in the space between the two carbon electrodes. [ABSTRACT FROM AUTHOR]

An ultrahigh etch rate (24 μm/min at 155 °C and 0.3 mm/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 (200 μm) 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. [ABSTRACT FROM AUTHOR]

An ultrahigh etch rate (14 μm/min) of SiO2 and a high selectivity of SiO2/Si over 200 were achieved using a microwave-excited nonequilibrium atmospheric pressure plasma source employing He, NF3, and H2O gases, which have been developed for application to microelectromechanical systems and other bionanotechnology fields. In order to clarify the etching mechanism, two diagnostic methods have been performed: (1) imaging of plasma emission with an intensified charge-coupled device camera, and (2) absorption measurements using Fourier transform infrared spectroscopy. The etching characteristics are discussed in relation to the spatial distributions of the species involved. The etch rate depended considerably on the distance between the plasma and the substrate. Some radicals generated from the feed gases reached the substrate directly, while other radicals recombined into different species, which reached the substrate. An abundance of HF molecules were produced through a reaction between radicals generated by the atmospheric pressure discharge of NF3 and H2O. From these measurements, it has been found that the HF molecules generated played a role in producing the high etch rate of SiO2 and high etch selectivity of SiO2/Si. [ABSTRACT FROM AUTHOR]

Etching of a SiO2 film [Boro-phospho silicate glass (BPSG)] has been performed in a continuous-wave microwave-excited nonequilibrium atmospheric pressure plasma using a microgap discharge. A NF3/He gas mixture with added H2O was employed as the feed gas. An ultrahigh etch rate for SiO2 (BPSG) of 14 μm/min and an ultrahigh selectivity over Si(SiO2/Si) of 200 was obtained. A mechanism for the selective etching is proposed based on results obtained using Fourier transform infrared spectroscopy and spatially imaged optical emission spectroscopy with an intensified charge-coupled device camera. This process could offer a breakthrough for ultrahigh-speed, damage-free micromachining of SiO2 in microelectromechanical system devices. [ABSTRACT FROM AUTHOR]